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Sample records for debris disks exozodiacal

  1. The Kuiper Belt, Exozodiacal Dust, Debris Disks: It's All About Collisions

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc

    2010-01-01

    Debris disks around other stars, like the disks around Fomalhaut, Vega, and Epsilon Eridani, are often described as more massive versions of the Kuiper Belt. But for a long time, it's been hard to test this notion, because grain-grain collisions dominate the grain lifetimes and we lacked the tools to model the effect of collisions on the appearance of the disks. I'll describe a new breakthrough that has allowed us to make 3-D models of collisions in debris disks and exozodiacal clouds for the first time, and I'll show the latest supercomputer simulations of these systems, illustrating the effects of planets and collisions in sculpting these disks. These models will be the key to interpreting debris disk images from HST, Herschel, SOFIA, JWST, and ALMA, as well as understanding the exozodiacal dust backgrounds for direct imaging of exo-Earths.

  2. Hot Exozodiacal Dust Disks, their Detection and Variability, as Measured with Long-Baseline Optical Interferometry.

    NASA Astrophysics Data System (ADS)

    Scott, Nicholas Jon

    2016-01-01

    Near-infrared long-baseline optical interferometry has provided the first unambiguous resolved detections of hot dust around main sequence stars (Absil et al. 2006). This showed that an unexpectedly dense population of (sub)micrometer dust grains close exists to their sublimation temperature of approximately 1400K. A later survey (Absil et al. 2013) revealed that these "hot exozodiacal disks" are relatively common around spectral type A-K stars. Current models of circumstellar debris disks suggest that in the inner region, within 1 AU, of the disk the timescale for complete removal of submicron dust is on the order of a few years (Wyatt 2008). The presence of dust close to the star is surprising because most cold debris belts detected are collisionally dominated. Mutual collisions grind the dust down to the size where radiation pressure pushes the dust out before Poynting-Robertson drag has a chance to pull the dust inward. Competing models exist to explain the persistence of this dust; some of which suggest that dust production is a punctuated and chaotic process fueled by asteroid collisions and comet infall that would show variability on timescales of a few years.High precision long-baseline interferometry observations in the K-band with the FLUOR (Fiber Linked Unit for Optical Recombination) beam combiner at the CHARA (Center for High Angular Resolution Astronomy) Array provided the data for these exozodiacal dust detections. This original instrument has undergone upgrades as part of JouFLU (Jouvence of FLUOR) project. The new instrument has been used to expand the original survey and to re-observe stars from the previous exozodiacal disk survey to search for predicted variations in the detected disks. We have found evidence that for some systems the amount of circumstellar flux from these previously detected exozodiacal disks, or exozodis, has varied greatly. The flux from some exozodis has increased, others decreased, and for a few the amount has remained

  3. The exo-zodiacal disk mapper

    NASA Technical Reports Server (NTRS)

    Petro, Larry; Bely, P.; Burg, R.; Wade, L.; Beichman, C.; Gay, J.; Baudoz, P.; Rabbia, Y.; Perrin, J. M.

    1998-01-01

    Zodiacal dust around neighboring stars could obscure the signal of terrestrial planets observed with the Terrestrial Planet Finder (TPF) if that dust is similar to that in the Solar System. Unfortunately, little is known about the presence, or frequency of occurrence of zodiacal dust around stars and so the relevance of zodiacal dust to the design of the TPF, or to the TPF mission, is unknown. It is likely that direct observation of zodiacal dust disks will be necessary to confidently determine the characteristics of individual systems. A survey of a large number of stars in the solar neighborhood that could be candidates for observation with TPF should be undertaken. We present a concept for a space mission to undertake a sensitive, large-scale survey capable of characterizing solar-system-like zodiacal dust around 400 stars within 20 pc of the Sun.

  4. DIAGNOSING CIRCUMSTELLAR DEBRIS DISKS

    SciTech Connect

    Hahn, Joseph M.

    2010-08-20

    A numerical model of a circumstellar debris disk is developed and applied to observations of the circumstellar dust orbiting {beta} Pictoris. The model accounts for the rates at which dust is produced by collisions among unseen planetesimals, and the rate at which dust grains are destroyed due to collisions. The model also accounts for the effects of radiation pressure, which is the dominant perturbation on the disk's smaller but abundant dust grains. Solving the resulting system of rate equations then provides the dust abundances versus grain size and dust abundances over time. Those solutions also provide the dust grains' collisional lifetime versus grain size, and the debris disk's optical depth and surface brightness versus distance from the star. Comparison to observations then yields estimates of the unseen planetesimal disk's radius, and the rate at which the disk sheds mass due to planetesimal grinding. The model can also be used to measure or else constrain the dust grain's physical and optical properties, such as the dust grains' strength, their light-scattering asymmetry parameter, and the grains' efficiency of light scattering Q{sub s}. The model is then applied to optical observations of the edge-on dust disk orbiting {beta} Pictoris, and good agreement is achieved when the unseen planetesimal disk is broad, with 75 {approx}< r {approx}< 150 AU. If it is assumed that the dust grains are bright like Saturn's icy rings (Q{sub s} = 0.7), then the cross section of dust in the disk is A{sub d} {approx_equal} 2 x 10{sup 20} km{sup 2} and its mass is M{sub d} {approx_equal} 11 lunar masses. In this case, the planetesimal disk's dust-production rate is quite heavy, M-dot {sub d{approx}}9 M {sub +} Myr{sup -1}, implying that there is or was a substantial amount of planetesimal mass there, at least 110 Earth masses. If the dust grains are darker than assumed, then the planetesimal disk's mass-loss rate and its total mass are heavier. In fact, the apparent dearth

  5. Probing the terrestrial regions of planetary systems: warm debris disks with emission features

    SciTech Connect

    Ballering, Nicholas P.; Rieke, George H.; Gáspár, András

    2014-09-20

    Observations of debris disks allow for the study of planetary systems, even where planets have not been detected. However, debris disks are often only characterized by unresolved infrared excesses that resemble featureless blackbodies, and the location of the emitting dust is uncertain due to a degeneracy with the dust grain properties. Here, we characterize the Spitzer Infrared Spectrograph spectra of 22 debris disks exhibiting 10 μm silicate emission features. Such features arise from small warm dust grains, and their presence can significantly constrain the orbital location of the emitting debris. We find that these features can be explained by the presence of an additional dust component in the terrestrial zones of the planetary systems, i.e., an exozodiacal belt. Aside from possessing exozodiacal dust, these debris disks are not particularly unique; their minimum grain sizes are consistent with the blowout sizes of their systems, and their brightnesses are comparable to those of featureless warm debris disks. These disks are in systems of a range of ages, though the older systems with features are found only around A-type stars. The features in young systems may be signatures of terrestrial planet formation. Analyzing the spectra of unresolved debris disks with emission features may be one of the simplest and most accessible ways to study the terrestrial regions of planetary systems.

  6. Imaging the inner regions of debris disks with near-infrared interferometry

    NASA Astrophysics Data System (ADS)

    Defrère, D.; Absil, O.; Augereau, J. C.; di Folco, E.; Coudé du Foresto, V.; Le Bouquin, J. B.; Mérand, A.; Mollier, B.

    2011-10-01

    Most debris disks resolved so far show extended structures located at tens to hundreds AU from the host star, and are more analogous to our solar system's dusty Kuiper belt than to the ˜AU-scale zodiacal disk inside our solar system's asteroid belt. Over the last few years however, a few hot debris disks have been detected around a handful of main sequence stars thanks to the advance of infrared interferometry. The grain populations derived from these observations are quite intriguing, as they point towards very high dust replenishment rates, high cometary activity or major collisional events. In this talk, we review the ongoing efforts to detect bright exozodiacal disks with precision near-infrared interferometry in both hemispheres with CHARA/FLUOR and VLTI/PIONIER. We discuss preliminary statistical trends on the occurrence of bright exozodi around nearby main sequence stars and show how this information could be used to constrain the global architecture and evolution of debris disks.

  7. Near Infrared Characterization of Hot Exo-Zodiacal Disks around Nearby Stars

    NASA Astrophysics Data System (ADS)

    Mennesson, Bertrand

    Debris disks found around main sequence stars are the remnants of planetary formation. The outer colder parts of these disks, analogous to our solar system Kuiper belt, were first detected via their mid/far infrared excess emission, and then abundantly imaged at visible to sub-millimeter wavelengths. Structures and asymmetries in spatially resolved debris disks have been used to infer the presence of yet unseen planets. The power of this technique was recently demonstrated with the direct imaging of massive planets at the inner edge of warped extended dust disks previously detected around Fomalhaut and beta Pic. Conversely, very little is known about the warmer dust component of debris disks, similar to the zodiacal dust of the inner solar system. A few hot disks have been found by Spitzer around mature stars via excess emission at 24 microns. But surprisingly, the majority of hot debris disk detections has come from the ground, where near infrared interferometric observations have recently revealed small (~1%) resolved excesses around a dozen nearby main sequence stars. The dust grains forming in these bright "exozodi disks" or dust belts are located within a few AU of their parent star. They are thought to be produced by the evaporation of comets or by collisions between larger rocky bodies, as in the solar zodiacal disk. Many of the detected disks are however much hotter (1000-1500K) and more massive than the zodiacal cloud. Their grain populations should be rapidly expelled from the inner planetary system by radiation pressure, which indicates inordinate replenishment rates. In practice, the steady state collisional grinding of a massive asteroid belt cannot be at the origin of these dust populations. They are most likely produced by isolated catastrophic events (e.g., major asteroid collision, break-up of a massive comet), or by major dynamical perturbations such as the Falling Evaporating Bodies (FEB) phenomenon in the beta Pic inner disk or the Late Heavy

  8. Lightcurves of Extreme Debris Disks

    NASA Astrophysics Data System (ADS)

    Rieke, George; Meng, Huan; Su, Kate

    2012-12-01

    We have recently discovered that some planetary debris disks with extreme fractional luminosities are variable on the timescale of a few years. This behavior opens a new possibility to understand planet building. Two of the known variable disks are around solar-like stars in the age range of 30 to 100+ Myr, which is the expected era of the final stages of terrestrial planet building. Such variability can be attributed to violent collisions (up to ones on the scale of the Moon-forming event between the proto-Earth and another proto-planet). The collisional cascades that are the aftermaths of these events can produce large clouds of tiny dust grains, possibly even condensed from silica vapor. A Spitzer pilot program has obtained the lightcurve of such a debris disk and caught two minor outbursts. Here we propose to continue the lightcurve monitoring with higher sampling rates and to expand it to more disks. The proposed time domain observations are a new dimension of debris disk studies that can bring unique insight to their evolution, providing important constraints on the collisional and dynamical models of terrestrial planet formation.

  9. Protoplanetary and Debris Disk Morphologies

    NASA Astrophysics Data System (ADS)

    Lomax, Jamie R.; Wisniewski, John P.; Grady, Carol A.; McElwain, Michael W.; Hashimoto, Jun; Donaldson, Jessica; Debes, John H.; Malumuth, Eliot; Roberge, Aki; Weinberger, Alycia J.; SEEDS Team

    2016-01-01

    The types of planets that form around other stars are highly dependent on their natal disk conditions. Therefore, the composition, morphology, and distribution of material in protoplanetary and debris disks are important for planet formation. Here we present the results of studies of two disk systems: AB Aur and AU Mic.The circumstellar disk around the Herbig Ae star AB Aur has many interesting features, including spirals, asymmetries, and non-uniformities. However, comparatively little is known about the envelope surrounding the system. Recent work by Tang et al (2012) has suggested that the observed spiral armss may not in fact be in the disk, but instead are due to areas of increased density in the envelope and projection effects. Using Monte Carlo modeling, we find that it is unlikely that the envelope holds enough material to be responsible for such features and that it is more plausible that they form from disk material. Given the likelihood that gravitational perturbations from planets cause the observed spiral morphology, we use archival H band observations of AB Aur with a baseline of 5.5 years to determine the locations of possible planets.The AU Mic debris disk also has many interesting morphological features. Because its disk is edge on, the system is an ideal candidate for color studies using coronagraphic spectroscopy. Spectra of the system were taken by placing a HST/STIS long slit parallel to and overlapping the disk while blocking out the central star with an occulting fiducial bar. Color gradients may reveal the chemical processing that is occuring within the disk. In addition, it may trace the potential composition and architecture of any planetary bodies in the system because collisional break up of planetesimals produces the observed dust in the system. We present the resulting optical reflected spectra (5200 to 10,200 angstroms) from this procedure at several disk locations. We find that the disk is bluest at the innermost locations of the

  10. Circumstellar Debris Disks and SIRTF

    NASA Astrophysics Data System (ADS)

    Backman, D. E.

    2000-05-01

    At least 15% of nearby main sequence stars are found to have far-IR excesses representing thermal emission from optically thin dust clouds. Famous prototypes of this class of objects include the Vega and beta Pictoris systems. Because destruction times for observed grains are much shorter than the system ages, the dust is known to be ``2nd generation" material released recently from hypothetical asteroid or comet parent bodies and not primordial grains persisting since system formation. The best local analogs to the main sequence debris disk systems are the inner solar system's zodiacal dust cloud and a presumed dust component of the Kuiper Belt. Planetary masses are probably required to drive planetesimals into shattering collisions and star-grazing orbits that produce dust, thus debris disks may allow inference of presence and location of planets. SIRTF will give us much-improved understanding of the frequency of debris disks around field main sequence stars, as well as the amount, size and composition of dust grains versus stellar age. This will help place our solar system into context of evolution of planetary material around normal stars.

  11. Debris Disks Around Nearby Young M Dwarfs

    NASA Astrophysics Data System (ADS)

    Liu, Michael

    2006-07-01

    We propose to obtain HST/ACS F606W coronagraphic imaging of two young {10-50 Myr}, nearby {25-55 pc} M dwarfs to resolve their debris disks in scattered light. Little is known about debris disks around M dwarfs, as very few examples are known and only one, the AU Mic debris disk, has been spatially resolved thus far. IR/sub-mm photometry of our targets indicate large quantities of exceptionally cold dust, comparable to the prototype AU Mic system, and make them excellent candidates for resolved studies with physical resolutions of 1-2 AU. HST/ACS provides an excellent capability for detection of disks in scattered light. Modeling the disk images will allow us to quantify the radial and vertical structure and to search for disk sub-structure, a potential probe of the planet formation process in these young systems. Our program can expand the census of young resolved debris disks, of which very few are currently known. M dwarfs have been largely over-looked in myriad imaging searches: our program will complement the many current programs focusing on the higher-mass AFGK stars. Because our targets belong to nearby young moving groups with known resolved disks around higher mass stars, a key potential outcome of our program is comparative study of coeval debris disks over a range of stellar masses.

  12. Circumstellar Debris Disks: Diagnosing the Unseen Perturber

    NASA Astrophysics Data System (ADS)

    Nesvold, Erika R.; Naoz, Smadar; Vican, Laura; Farr, Will M.

    2016-07-01

    The first indication of the presence of a circumstellar debris disk is usually the detection of excess infrared emission from the population of small dust grains orbiting the star. This dust is short-lived, requiring continual replenishment, and indicating that the disk must be excited by an unseen perturber. Previous theoretical studies have demonstrated that an eccentric planet orbiting interior to the disk will stir the larger bodies in the belt and produce dust via interparticle collisions. However, motivated by recent observations, we explore another possible mechanism for heating a debris disk: a stellar-mass perturber orbiting exterior to and inclined to the disk and exciting the disk particles’ eccentricities and inclinations via the Kozai–Lidov mechanism. We explore the consequences of an exterior perturber on the evolution of a debris disk using secular analysis and collisional N-body simulations. We demonstrate that a Kozai–Lidov excited disk can generate a dust disk via collisions and we compare the results of the Kozai–Lidov excited disk with a simulated disk perturbed by an interior eccentric planet. Finally, we propose two observational tests of a dust disk that can distinguish whether the dust was produced by an exterior brown dwarf or stellar companion or an interior eccentric planet.

  13. Circumstellar Debris Disks: Diagnosing the Unseen Perturber

    NASA Astrophysics Data System (ADS)

    Nesvold, Erika R.; Naoz, Smadar; Vican, Laura; Farr, Will M.

    2016-07-01

    The first indication of the presence of a circumstellar debris disk is usually the detection of excess infrared emission from the population of small dust grains orbiting the star. This dust is short-lived, requiring continual replenishment, and indicating that the disk must be excited by an unseen perturber. Previous theoretical studies have demonstrated that an eccentric planet orbiting interior to the disk will stir the larger bodies in the belt and produce dust via interparticle collisions. However, motivated by recent observations, we explore another possible mechanism for heating a debris disk: a stellar-mass perturber orbiting exterior to and inclined to the disk and exciting the disk particles’ eccentricities and inclinations via the Kozai-Lidov mechanism. We explore the consequences of an exterior perturber on the evolution of a debris disk using secular analysis and collisional N-body simulations. We demonstrate that a Kozai-Lidov excited disk can generate a dust disk via collisions and we compare the results of the Kozai-Lidov excited disk with a simulated disk perturbed by an interior eccentric planet. Finally, we propose two observational tests of a dust disk that can distinguish whether the dust was produced by an exterior brown dwarf or stellar companion or an interior eccentric planet.

  14. Patterns In Debris Disks: No Planets Required?

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc

    2012-01-01

    Debris disks like those around Fomalhaut and Beta Pictoris show striking dust patterns often attributed to hidden exoplanets. These patterns have been crucial for constraining the masses and orbits of these planets. But adding a bit of gas to our models of debris disks--too little gas to detect--seems to alter this interpretation. Small amounts of gas lead to new dynamical instabilities that may mimic the narrow eccentric rings and other structures planets would create in a gas-free disk. Can we still use dust patterns to find hidden exoplanets?

  15. MOLECULAR GAS IN YOUNG DEBRIS DISKS

    SciTech Connect

    Moor, A.; Abraham, P.; Kiss, Cs.; Juhasz, A.; Kospal, A.; Pascucci, I.; Apai, D.; Henning, Th.; Csengeri, T.; Grady, C.

    2011-10-10

    Gas-rich primordial disks and tenuous gas-poor debris disks are usually considered as two distinct evolutionary phases of the circumstellar matter. Interestingly, the debris disk around the young main-sequence star 49 Ceti possesses a substantial amount of molecular gas and possibly represents the missing link between the two phases. Motivated to understand the evolution of the gas component in circumstellar disks via finding more 49 Ceti-like systems, we carried out a CO J = 3-2 survey with the Atacama Pathfinder EXperiment, targeting 20 infrared-luminous debris disks. These systems fill the gap between primordial and old tenuous debris disks in terms of fractional luminosity. Here we report on the discovery of a second 49 Ceti-like disk around the 30 Myr old A3-type star HD21997, a member of the Columba Association. This system was also detected in the CO(2-1) transition, and the reliable age determination makes it an even clearer example of an old gas-bearing disk than 49 Ceti. While the fractional luminosities of HD21997 and 49 Ceti are not particularly high, these objects seem to harbor the most extended disks within our sample. The double-peaked profiles of HD21997 were reproduced by a Keplerian disk model combined with the LIME radiative transfer code. Based on their similarities, 49 Ceti and HD21997 may be the first representatives of a so far undefined new class of relatively old ({approx}>8 Myr), gaseous dust disks. From our results, neither primordial origin nor steady secondary production from icy planetesimals can unequivocally explain the presence of CO gas in the disk of HD21997.

  16. Molecular Gas in Young Debris Disks

    NASA Technical Reports Server (NTRS)

    Moor, A.; Abraham, P.; Juhasz, A.; Kiss, Cs.; Pascucci, I.; Kospal, A.; Apai, D.; Henning, T.; Csengeri, T.; Grady, C.

    2011-01-01

    Gas-rich primordial disks and tenuous gas-poor debris disks are usually considered as two distinct evolutionary phases of the circumstellar matter. Interestingly, the debris disk around the young main-sequence star 49 Ceti possesses a substantial amount of molecular gas and possibly represents the missing link between the two phases. Motivated to understand the evolution of the gas component in circumstellar disks via finding more 49 Ceti-like systems, we carried out a CO J = 3-2 survey with the Atacama Pathfinder EXperiment, targeting 20 infrared-luminous debris disks. These systems fill the gap between primordial and old tenuous debris disks in terms of fractional luminosity. Here we report on the discovery of a second 49 Ceti-like disk around the 30 Myr old A3-type star HD21997, a member of the Columba Association. This system was also detected in the CO(2-1) transition, and the reliable age determination makes it an even clearer example of an old gas-bearing disk than 49 Ceti. While the fractional luminosities of HD21997 and 49 Ceti are not particularly high, these objects seem to harbor the most extended disks within our sample. The double-peaked profiles of HD21997 were reproduced by a Keplerian disk model combined with the LIME radiative transfer code. Based on their similarities, 49 Ceti and HD21997 may be the first representatives of a so far undefined new class of relatively old > or approx.8 Myr), gaseous dust disks. From our results, neither primordia1 origin nor steady secondary production from icy planetesima1s can unequivocally explain the presence of CO gas in the disk ofHD21997.

  17. Secular Planetary Perturbations in Circumstellar Debris Disks

    NASA Astrophysics Data System (ADS)

    Hahn, Joseph M.; Capobianco, C.

    2006-12-01

    Circumstellar debris disks are likely the by-product of collisions among unseen planetesimals. Planetesimals are also the seeds of planets, so it is reasonable to expect that some debris disks might also harbor planets. In fact several such disks, like those orbiting beta Pictoris, Fomalhaut, etc., do appear to be perturbed by unseen planets orbiting within. The signatures of planetary perturbations include: central gaps, warps, and radial offsets in the disk's surface brightness. By modeling the disturbances observed in a circumstellar dust disk, one can then measure or constrain the masses and orbits of the planets that may be lurking within. Of particular interest here are the warps and radial offsets seen in such disks, since these features can be due to secular planetary perturbations (Mouillet et al 1997, Wyatt et al 1999). Secular perturbations are the slowly varying gravitational perturbations that can excite orbital eccentricities and inclinations in a disk, and can also drive a slow orbital precession. Note that a dust grain's motion is completely analytic when suffering secular perturbations (Murray & Dermott 1999), which allows us to rapidly generate a synthetic image of a simulated disk as would be seen in scattered starlight or via thermal emission. And because this model is quite fast, our model can rapidly scan a rather large parameter space in order to determine the planetary configuration that may be responsible for the disk's perturbed appearance. We have applied this dust-disk model to Hubble observations of the β Pictoris dust-disk (from Heap et al 2000), and will report on the planets that may be responsible for the warp seen in this edge-on disk. We will also apply the model to optical and IR observations of debris disks at Fomalhaut, AU Microscopii, and others, with additional results to be reported at conference time.

  18. Signposts of Multiple Planets in Debris Disks

    NASA Astrophysics Data System (ADS)

    Su, Kate Y. L.; Rieke, G. H.

    2014-01-01

    We review the nearby debris disk structures revealed by multi-wavelength images from Spitzer and Herschel, and complemented with detailed spectral energy distribution modeling. Similar to the definition of habitable zones around stars, debris disk structures should be identified and characterized in terms of dust temperatures rather than physical distances so that the heating power of different spectral type of stars is taken into account and common features in disks can be discussed and compared directly. Common features, such as warm (~150 K) dust belts near the water-ice line and cold (~50 K) Kuiper-belt analogs, give rise to our emerging understanding of the levels of order in debris disk structures and illuminate various processes about the formation and evolution of exoplanetary systems. In light of the disk structures in the debris disk twins (Vega and Fomalhaut), and the current limits on the masses of planetary objects, we suggest that the large gap between the warm and cold dust belts is the best signpost for multiple (low-mass) planets beyond the water-ice line.

  19. Searching For Planets in "Holey Debris Disks"

    NASA Astrophysics Data System (ADS)

    Meshkat, Tiffany; Bailey, Vanessa P.; Su, Kate Y. L.; Kenworthy, Matthew A.; Mamajek, Eric E.; Hinz, Philip; Smith, Paul S.

    2015-01-01

    Directly imaging planets provides a unique opportunity to study young planets in the context of their formation and evolution. It examines the underlying semi-major axis exoplanet distribution and enables the characterization of the planet itself with spectroscopic examination of its emergent flux. However, only a handful of planets have been directly imaged, and thus the stars best suited for planet imaging are still a subject of debate. The "Holey Debris Disk" project was created in order to help determine if debris disks with gaps are signposts for planets. These gaps may be dynamically caused by planets accreting the debris material as they form. We present the results from our survey with VLT/NACO and the apodized phase plate coronagraph. We demonstrate that these disks with holes are good targets for directly detecting planets with the discovery of a planet around two of our targets, HD 95086 and HD 106906, at L'-band. Our non-detection of HD 95086 b in H-band demonstrates the importance of thermal infrared observations. The detected planets shepherd the outer cool debris belt. The relatively dust-free gap in these disks implies the presence of one or more closer-in planets. We discuss our new constraints on planets around other targets in our survey as well as disk properties of these targets and describe how future instruments will find the inner planets.

  20. Modeling collisions in circumstellar debris disks

    NASA Astrophysics Data System (ADS)

    Nesvold, Erika

    2015-10-01

    Observations of resolved debris disks show a spectacular variety of features and asymmetries, including inner cavities and gaps, inclined secondary disks or warps, and eccentric, sharp-edged rings. Embedded exoplanets could create many of these features via gravitational perturbations, which sculpt the disk directly and by generating planetesimal collisions. In this thesis, I present the Superparticle Model/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in 3-D, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. I show that SMACK is stable to numerical viscosity and numerical heating over 107 yr, and that it can reproduce analytic models of disk evolution. As an example of the algorithm's capabilities, I use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit and demonstrate that differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring. To demonstrate SMACK's utility in studying debris disk physics, I apply SMACK to simulate a planet on a circular orbit near a ring of planetesimals that are experiencing destructive collisions. Previous simulations of a planet opening a gap in a collisionless debris disk have found that the width of the gap scales as the planet mass to the 2/7th power (alpha = 2/7). I find that gap sizes in a collisional disk still obey a power law scaling with planet mass, but that the index alpha of the power law depends on the age of the system t relative to the collisional timescale t coll of the disk by alpha = 0.32(t/ tcoll)-0.04, with inferred planet masses up to five times smaller than those predicted by the classical gap law. The increased gap sizes likely stem from the interaction between collisions and the mean motion

  1. A Primer on Unifying Debris Disk Morphologies

    NASA Astrophysics Data System (ADS)

    Lee, Eve J.; Chiang, Eugene

    2016-08-01

    A “minimum model” for debris disks consists of a narrow ring of parent bodies, secularly forced by a single planet on a possibly eccentric orbit, colliding to produce dust grains that are perturbed by stellar radiation pressure. We demonstrate how this minimum model can reproduce a wide variety of disk morphologies imaged in scattered starlight. Five broad categories of disk shape can be captured: “rings,” “needles,” “ships-and-wakes,” “bars,” and “moths (a.k.a. fans),” depending on the viewing geometry. Moths can also sport “double wings.” We explain the origin of morphological features from first principles, exploring the dependence on planet eccentricity, disk inclination dispersion, and the parent body orbital phases at which dust grains are born. A key determinant in disk appearance is the degree to which dust grain orbits are apsidally aligned. Our study of a simple steady-state (secularly relaxed) disk should serve as a reference for more detailed models tailored to individual systems. We use the intuition gained from our guidebook of disk morphologies to interpret, informally, the images of a number of real-world debris disks. These interpretations suggest that the farthest reaches of planetary systems are perturbed by eccentric planets, possibly just a few Earth masses each.

  2. Characterization of WISE Debris Disk Stars

    NASA Astrophysics Data System (ADS)

    Padgett, Deborah; Liu, Wilson; Morales, Farisa

    2013-02-01

    We propose to acquire low dispersion spectra with the SOAR Goodman Spectrograph of new debris disk stars identified from the Wide-field Infrared Survey Explorer (WISE survey of the entire sky. Despite many targeted surveys for stellar disks in the solar neighborhood by Spitzer Space Telescope, the census of disks remains incomplete at mid-IR sensitivity levels better than the IRAS limits. The improved sensitivity and spatial resolution of the all-sky WISE survey for debris disks (Padgett et al., submitted) has recently improved this situation, identifying Hipparcos and Tycho stars with mid-infrared excess out to distances of 120 pc. With the SOAR spectrograph we will characterize the new candidate debris disk stars in the southern sky, providing a uniform set of stellar classifications and information on a range of spectroscopic activity indicators related to stellar age. These data will help to constrain the stellar properties of an important new set of solar neighbors with evidence of planetary systems.

  3. The connection between inner and outer debris disks probed by infrared interferometry

    NASA Astrophysics Data System (ADS)

    Absil, O.; Defrère, D.; Mollier, B.; Di Folco, E.; Augereau, J.-C.; Coudé du Foresto, V.; Le Bouquin, J.-B.; Mérand, A.

    2012-03-01

    The far-infrared surveys of nearby main sequence stars performed since the launch of IRAS have shown that a significant fraction of main sequence stars are surrounded by cold dust populations. These surveys are now culminating with the the DUNES and DEBRIS key projects of the Herschel Space Observatory, which is more sensitive than ever and is able to detect cold dust populations with densities similar to that of the solar system Kuiper belt. However, little is known about the occurence of warm dust populations, the equivalent of our zodiacal cloud. Since 2005, high-precision infrared interferometers have opened a new way to directly resolve these exozodiacal dust populations. Interferometric observations enable to reach dynamic ranges (larger than 100:1) that are generally not achievable with classical spectro-photometric observations. We are currently carrying out a survey to characterise the hot dust populations around main sequence stars. The first results of this survey, performed on the CHARA array with the FLUOR instrument, will be presented in this talk. The results are based on a magnitude-limited sample of stars surrounded by cold dust and on an equivalent sample of stars showing no cold dust emission. The statistics for the occurence of bright exozodiacal disks will be presented, and compared with the Spitzer and Herschel results. The possible (dynamical) connections between the two populations will be discussed. We will also review the results obtained by other interferometers and discuss the on-going projects.

  4. Reading the Signatures of Extrasolar Planets in Debris Disks

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc J.

    2009-01-01

    An extrasolar planet sculpts the famous debris dish around Fomalhaut; probably ma ny other debris disks contain planets that we could locate if only we could better recognize their signatures in the dust that surrounds them. But the interaction between planets and debris disks involves both orbital resonances and collisions among grains and rocks in the disks --- difficult processes to model simultanemus]y. I will describe new 3-D models of debris disk dynamics that incorporate both collisions and resonant trapping of dust for the first time, allowing us to decode debris disk images and read the signatures of the planets they contain.

  5. Zodiac II: Debris Disk Imaging Potential

    NASA Technical Reports Server (NTRS)

    Traub Wesley; Bryden, Geoff; Stapelfeldt, Karl; Chen, Pin; Trauger, John

    2011-01-01

    Zodiac II is a proposed coronagraph on a balloon-borne platform, for the purpose of observing debris disks around nearby stars. Zodiac II will have a 1.2-m diameter telescope mounted in a balloon-borne gondola capable of arcsecond quality pointing, and with the capability to make long-duration (several week) flights. Zodiac II will have a coronagraph able to make images of debris disks, meaning that its scattered light speckles will be at or below an average contrast level of about 10(exp -7) in three narrow (7 percent) bands centered on the V band, and one broad (20%) one at I band. We will discuss the potential science to be done with Zodiac II.

  6. Cometary grains in the HD 32297 debris disk

    NASA Astrophysics Data System (ADS)

    Yang, Y.-G.; Li, Aigen

    2016-07-01

    HD 32297 is a young A-type star with a bright edge-on debris disk. The dust thermal emission spectral energy distribution and scattered starlight spectrum are simultaneously modeled in terms of porous cometary grains. Our modeling suggests that, similar to the solar system, the debris disk around HD 32297 may have an inner warm ring and an outer cold disk which are seen in other young debris disks as well.

  7. A near-infrared interferometric survey of debris-disk stars. IV. An unbiased sample of 92 southern stars observed in H band with VLTI/PIONIER

    NASA Astrophysics Data System (ADS)

    Ertel, S.; Absil, O.; Defrère, D.; Le Bouquin, J.-B.; Augereau, J.-C.; Marion, L.; Blind, N.; Bonsor, A.; Bryden, G.; Lebreton, J.; Milli, J.

    2014-10-01

    Context. Detecting and characterizing circumstellar dust is a way to study the architecture and evolution of planetary systems. Cold dust in debris disks only traces the outer regions. Warm and hot exozodiacal dust needs to be studied in order to trace regions close to the habitable zone. Aims: We aim to determine the prevalence and to constrain the properties of hot exozodiacal dust around nearby main-sequence stars. Methods: We searched a magnitude-limited (H ≤ 5) sample of 92 stars for bright exozodiacal dust using our VLTI visitor instrument PIONIER in the H band. We derived statistics of the detection rate with respect to parameters, such as the stellar spectral type and age or the presence of a debris disk in the outer regions of the systems. We derived more robust statistics by combining our sample with the results from our CHARA/FLUOR survey in the K band. In addition, our spectrally dispersed data allowed us to put constraints on the emission mechanism and the dust properties in the detected systems. Results: We find an overall detection rate of bright exozodiacal dust in the H band of 11% (9 out of 85 targets) and three tentative detections. The detection rate decreases from early type to late type stars and increases with the age of the host star. We do not confirm the tentative correlation between the presence of cold and hot dust found in our earlier analysis of the FLUOR sample alone. Our spectrally dispersed data suggest that either the dust is extremely hot or the emission is dominated by the scattered light in most cases. The implications of our results for the target selection of future terrestrial planet-finding missions using direct imaging are discussed. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program IDs 089.C-0365 and 090.C-0526.Appendix A and Table 1 are available in electronic form at http://www.aanda.org

  8. Collisional Cascade in a Debris Disk from an External Perturber

    NASA Astrophysics Data System (ADS)

    Nesvold, Erika; Naoz, Smadar; Vican, Laura; Zuckerman, Benjamin; Holmbeck, Erika

    2015-11-01

    The study of circumstellar debris disks has often been coupled with the study of planet formation. A thermally warm debris disk (~300 K) may indicate the presence of an exoplanet orbiting within and stirring the disk. However, there is another possible mechanism for heating a debris disk: an external stellar-mass perturber exciting the eccentricities and inclinations of the particles in a disk.We explore the consequences of an external perturber on the evolution of a debris disk. The perturber excites the eccentricities of the particles in the disk via the Kozai-Lidov mechanism, triggering a collisional cascade among the planetesimals. These collisions produce smaller dust grains and damp the particles’ larger eccentricities.We present the results of our study of a such a disk using secular analysis and collisional N-body simulations. We will discuss the connections to observations of warm disks and the implications for planet formation.

  9. From IRAS Excesses to Debris Disks

    NASA Astrophysics Data System (ADS)

    Backman, D.; Lagrange, A.-M.

    2014-09-01

    Noted only as a shell star prior to 1984, beta Pictoris was originally observed in the first months of the IRAS mission as a comparison object for Vega. When Fred Gillett presented spectral energy distributions of Vega, Fomalhaut, beta Pictoris, and epsilon Eridani at the Protostars and Planets II conference, the news was relayed quickly to Brad Smith and Rich Terrile who were observing at Las Campanas with a coronagraph. Our understanding that beta Pictoris and other debris disks are clear evidence of maturing planetary systems solidified over the following 15 years with analyses of IRAS & ISO data coupled with spectroscopic observations of Falling Evaporating Bodies.

  10. THE TRANSIT LIGHT CURVE OF AN EXOZODIACAL DUST CLOUD

    SciTech Connect

    Stark, Christopher C.

    2011-10-15

    Planets embedded within debris disks gravitationally perturb nearby dust and can create clumpy, azimuthally asymmetric circumstellar ring structures that rotate in lock with the planet. The Earth creates one such structure in the solar zodiacal dust cloud. In an edge-on system, the dust 'clumps' periodically pass in front of the star as the planet orbits, occulting and forward-scattering starlight. In this paper, we predict the shape and magnitude of the corresponding transit signal. To do so, we model the dust distributions of collisional, steady-state exozodiacal clouds perturbed by planetary companions. We examine disks with dusty ring structures formed by the planet's resonant trapping of in-spiraling dust for a range of planet masses and semi-major axes, dust properties, and disk masses. We synthesize edge-on images of these models and calculate the transit signatures of the resonant ring structures. The transit light curves created by dusty resonant ring structures typically exhibit two broad transit minima that lead and trail the planetary transit. We find that Jupiter-mass planets embedded within disks hundreds of times denser than our zodiacal cloud can create resonant ring structures with transit depths up to {approx}10{sup -4}, possibly detectable with Kepler. Resonant rings produced by planets more or less massive than Jupiter produce smaller transit depths. Observations of these transit signals may provide upper limits on the degree of asymmetry in exozodiacal clouds.

  11. THE COLLISIONAL EVOLUTION OF DEBRIS DISKS

    SciTech Connect

    Gaspar, Andras; Rieke, George H.; Balog, Zoltan E-mail: grieke@as.arizona.edu

    2013-05-01

    We explore the collisional decay of disk mass and infrared emission in debris disks. With models, we show that the rate of the decay varies throughout the evolution of the disks, increasing its rate up to a certain point, which is followed by a leveling off to a slower value. The total disk mass falls off {proportional_to}t {sup -0.35} at its fastest point (where t is time) for our reference model, while the dust mass and its proxy-the infrared excess emission-fades significantly faster ({proportional_to}t {sup -0.8}). These later level off to a decay rate of M{sub tot}(t){proportional_to}t {sup -0.08} and M{sub dust}(t) or L{sub ir}(t){proportional_to}t {sup -0.6}. This is slower than the {proportional_to}t {sup -1} decay given for all three system parameters by traditional analytic models. We also compile an extensive catalog of Spitzer and Herschel 24, 70, and 100 {mu}m observations. Assuming a log-normal distribution of initial disk masses, we generate model population decay curves for the fraction of stars harboring debris disks detected at 24 {mu}m. We also model the distribution of measured excesses at the far-IR wavelengths (70-100 {mu}m) at certain age regimes. We show general agreement at 24 {mu}m between the decay of our numerical collisional population synthesis model and observations up to a Gyr. We associate offsets above a Gyr to stochastic events in a few select systems. We cannot fit the decay in the far-infrared convincingly with grain strength properties appropriate for silicates, but those of water ice give fits more consistent with the observations (other relatively weak grain materials would presumably also be successful). The oldest disks have a higher incidence of large excesses than predicted by the model; again, a plausible explanation is very late phases of high dynamical activity around a small number of stars. Finally, we constrain the variables of our numerical model by comparing the evolutionary trends generated from the exploration

  12. Zodiac II: Debris Disk Science from a Balloon

    NASA Technical Reports Server (NTRS)

    Bryden, Geoffrey; Traub, Wesley; Roberts, Lewis C., Jr.; Bruno, Robin; Unwin, Stephen; Backovsky, Stan; Brugarolas, Paul; Chakrabarti, Supriya; Chen, Pin; Hillenbrand, Lynne; Krist, John; Lillie, Charles; Macintosh, Bruce; Mawet, Dimitri; Mennesson, Bertrand; Moody, Dwight; Rey, Justin; Stapelfeldt, Karl; Stuchlik, David; Trauger, John; Vasisht, Gautam

    2011-01-01

    Zodiac II is a proposed balloon-borne science investigation of debris disks around nearby stars. Debris disks are analogs of the Asteroid Belt (mainly rocky) and Kuiper Belt (mainly icy) in our Solar System. Zodiac II will measure the size, shape, brightness, and color of a statistically significant sample of disks. These measurements will enable us to probe these fundamental questions: what do debris disks tell us about the evolution of planetary systems; how are debris disks produced; how are debris disks shaped by planets; what materials are debris disks made of; how much dust do debris disks make as they grind down; and how long do debris disks live? In addition, Zodiac II will observe hot, young exoplanets as targets of opportunity. The Zodiac II instrument is a 1.1-m diameter SiC (Silicone carbide) telescope and an imaging coronagraph on a gondola carried by a stratospheric balloon. Its data product is a set of images of each targeted debris disk in four broad visible-wavelength bands. Zodiac II will address its science questions by taking high-resolution, multi-wavelength images of the debris disks around tens of nearby stars. Mid-latitude flights are considered: overnight test flights in the US followed by half-global flights in the Southern Hemisphere. These longer flights are required to fully explore the set of known debris disks accessible only to Zodiac II. On these targets, it will be 100 times more sensitive than the Hubble Space Telescope's Advanced Camera for Surveys (HST/ACS); no existing telescope can match the Zodiac II contrast and resolution performance. A second objective of Zodiac II is to use the near-space environment to raise the Technology Readiness Level (TRL) of SiC mirrors, internal coronagraphs, deformable mirrors, and wavefront sensing and control, all potentially needed for a future space-based telescope for high-contrast exoplanet imaging.

  13. Zodiac II: Debris Disk Science from a Balloon

    NASA Technical Reports Server (NTRS)

    Bryden, Geoffrey; Traub, Wesley; Roberts, Lewis C., Jr.; Bruno, Robin; Unwin, Stephen; Backovsky, Stan; Brugarolas, Paul; Chakrabarti, Supriya; Chen, Pin; Hillenbrand, Lynne; Krist, John; Lillie, Charles; Macintosh, Bruce; Mawet, Dimitri; Mennesson, Bertrand; Moody, Dwight; Rahman, Zahidul; Rey, Justin; Stapelfeldt, Karl; Stuchlik, David; Trauger, John; Vasisht, Gautam

    2011-01-01

    Zodiac II is a proposed balloon-borne science investigation of debris disks around nearby stars. Debris disks are analogs of the Asteroid Belt (mainly rocky) and Kuiper Belt (mainly icy) in our Solar System. Zodiac II will measure the size, shape, brightness, and color of a statistically significant sample of disks. These measurements will enable us to probe these fundamental questions: what do debris disks tell us about the evolution of planetary systems; how are debris disks produced; how are debris disks shaped by planets; what materials are debris disks made of; how much dust do debris disks make sa they grind down; and how long do debris disks live? In addition, Zodiac II will observe hot, young exoplanets as targets of opportunity. The Zodiac II instrument is a 1.1-m diameter SiC telescope and an imaging coronagraph on a gondola carried by a stratospheric balloon. Its data product is a set of images of each targeted debris disk in four broad visible wavelength bands. Zodiac II will address its science questions by taking high-resolution, multi-wavelength images of the debris disks around tens of nearby stars. Mid-latitude flights are considered: overnight test flights within the United States followed by half-global flights in the Southern Hemisphere. These longer flights are required to fully explore the set of known debris disks accessible only to Zodiac II. On these targets, it will be 100 times more sensitive than the Hubble Space Telescope's Advanced Camera for Surveys (HST/ACS); no existing telescope can match the Zodiac II contrast and resolution performance. A second objective of Zodiac II is to use the near-space environment to raise the Technology Readiness Level (TRL) of SiC mirrors, internal coronagraphs, deformable mirrors, and wavefront sensing and control, all potentially needed for a future space-based telescope for high-contrast exoplanet imaging.

  14. Constraints on Exoplanet System Architectures from Debris Disks

    NASA Astrophysics Data System (ADS)

    Jang-Condell, Hannah; Chen, Christine H.; Mittal, Tushar; Nesvold, Erika; Kuchner, Marc J.; Manoj, P.; Watson, Dan; Lisse, Carey M.

    2015-12-01

    Debris disks are dusty disks around main sequence stars. Terrestrial planets may be forming in young debris disks with ages <100 Myr. Planets in debris disks dynamically sculpt the dust in these systems. Thus, the spatial structure of debris disks could be an indicator of where planets have formed. We present an analysis of several members of the Scorpius-Centaurus OB Association (Sco Cen) that host both debris disks and planets, including HD 95086, HD 106906, and HD 133803. These objects are about 15-17 Myr old. The thermal emission from the debris disks constrains the locations of the dust. The dust is typically interior to the directly imaged planets in the systems. If additional planets reside in these systems, their locations are constrained by the positions of the dust belts. Many debris disk systems in Sco Cen appear to be two-belt systems. The gap between the belts in each system is a likely location for additional planets. The detection of planets in debris disk systems provide clues about the planet formation process, giving insights into where, when and how planets form.

  15. Modeling the η Corvi debris disk from the sub-AU scale to its outermost regions

    NASA Astrophysics Data System (ADS)

    Lebreton, J.; Beichman, C. A.; Bryden, G.; Defrère, D.; Mennesson, Bertr; Millan-Gabet, R.

    2014-03-01

    Dusty debris disks surrounding main sequence stars are thought to be analogues to thepopulations of small bodies of the Solar System (asteroids, comets/icy bodies and dust grains), however with often much higher masses and associated dust production rates. Mecanisms such as massive collisions or LHB-like events must therefore be invoked to justify their existence. This is especially striking for the nearby F2V star η Corvi that shows a very strong mid- and far-infrared excess despite an estimated age of ~1.4 Gyr (Lisse et al. 2012, Wyatt et al. 2005). We present new observations of the η Crv debris disk obtained in the far-infrared with Herschel/PACS and SPIRE and in the mid-infrared with the Keck Interferometer Nuller (Millan-Gabet et al. 2011). The Herschel/PACS images at 70, 100 and 160 μm reveal a well resolved belt of cold material at ~130 AU, as well as an unresolved component in the innermost parts of the system. This warmer counterpart is resolved in the mid-infrared as a strong null excess originating from within the ~2x4 AU field-of-view of the interferometer, which is reminiscent of the architecture of the Fomalhaut debris disk (Mennesson et al. 2012, Lebreton et al. 2013). The signature of warm silicate dust is also very clear in Spitzer/IRS high-resolution spectra (Chen et al. 2006) at intermediate wavelengths (10-35 μm). We undertake to establish a consistent model of the debris disk from the sub-AU scale to its outermost regions using the GRaTer radiative transfer code (Augereau et al. 1999a, Lebreton et al. 2013) by adjusting simultaneously the interferometric nulls, the resolved Herschel images and the spectro-photometric data against a large parameter space. Our analysis providesaccurate estimates of the fundamental parameters of the disk: its surface density profile, grain size distribution and mass, making it possible to unveil the origin of the dust and the relation between the cold (~50 K) Kuiper-like belt and the warm (~500 K) exo-zodiacal

  16. Warm Circumstellar Debris Disks: Dynamical Excitation by Massive External Perturbers?

    NASA Astrophysics Data System (ADS)

    Nesvold, Erika; Naoz, Smadar; Vican, Laura; Vican, Laura; Zuckerman, Ben M.; Holmbeck, Erika

    2016-01-01

    Observations of circumstellar debris disks have revealed that a subset of this population are warm disks (~300 K). A dynamically excited disk may indicate the presence of an exoplanet orbiting within and stirring the disk. However, observations suggest another possible mechanism for heating a debris disk: an external stellar-mass perturber exciting the eccentricities and inclinations of the particles in a disk.We explore the consequences of an external perturber on the evolution of a debris disk using secular analysis and collisional N-body simulations. The perturber excites the eccentricities of the particles in the disk via the Kozai-Lidov mechanism, triggering a collisional cascade among the planetesimals. These collisions produce smaller dust grains and damp the particles' larger eccentricities.We present the results of our study and discuss the connections to observations of warm disks and the implications for planet formation.

  17. Sharp Eccentric Rings in Planetless Hydrodynamical Models of Debris Disks

    NASA Technical Reports Server (NTRS)

    Lyra, W.; Kuchner, M. J.

    2013-01-01

    Exoplanets are often associated with disks of dust and debris, analogs of the Kuiper Belt in our solar system. These "debris disks" show a variety of non-trivial structures attributed to planetary perturbations and utilized to constrain the properties of the planets. However, analyses of these systems have largely ignored the fact that, increasingly, debris disks are found to contain small quantities of gas, a component all debris disks should contain at some level. Several debris disks have been measured with a dust-to-gas ratio around unity where the effect of hydrodynamics on the structure of the disk cannot be ignored. Here we report that dust-gas interactions can produce some of the key patterns seen in debris disks that were previously attributed to planets. Through linear and nonlinear modeling of the hydrodynamical problem, we find that a robust clumping instability exists in this configuration, organizing the dust into narrow, eccentric rings, similar to the Fomalhaut debris disk. The hypothesis that these disks might contain planets, though thrilling, is not necessarily required to explain these systems.

  18. A Debris Disk Case Study: 49 Ceti with Herschel

    NASA Technical Reports Server (NTRS)

    Roberge, Aki

    2011-01-01

    Gas-poor debris disks represent a fundamentally different class of circumstellar disk than gas-rich protoplanetary disks. Their gas probably originates from the same source as the dust, i.e. planetesimal destruction, but the low gas densities make it difficult to detect. So far, Herschel has detected far-IR gas emission from one debris disk, Beta Pictoris. Here I discuss a well-known debris disk system in the GASPS survey, 49 Ceti. It serves as a case study for modeling low-density gas in optically thin disks. The dust disk appears to be spatially resolved at 70 um. Most interestingly, there appears to be a hint of ClI 158 urn emission at the roughly 2 sigma level. Preliminary modeling suggests that reconciling the sub-mm CO emission from this system with the weak or non-existent far-IR atomic lines may require an unusual chemical composition in the gas of this disk.

  19. Featured Image: Hubble's New Views of Debris Disks

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-09-01

    The Hubble image of a second circumstellar debris disk, HD 207917, and its best-fit model.This is a new deep observation made by Hubbles Space Telescope Imaging Spectrograph of the tilted debris disk surrounding the star HD 207129. In a recent study led by Glenn Schneider (Seward Observatory, University of Arizona), three known, nearby circumstellar disks were imaged by Hubble in order to gain a better understanding of the disks ring-like structure. The three central stars of these disks are all G-type solar analogs, and the debris rings bear many similarities to our own Kuiper belt. Imaging of debris disks like these can help us to learn more about how solar systems form around stars like our own. For more information, check out the paper below!CitationGlenn Schneider et al 2016 AJ 152 64. doi:10.3847/0004-6256/152/3/64

  20. DEBRIS DISKS IN KEPLER EXOPLANET SYSTEMS

    SciTech Connect

    Lawler, S. M.; Gladman, B.

    2012-06-10

    The Kepler mission recently identified 997 systems hosting candidate extrasolar planets, many of which are super-Earths. Realizing these planetary systems are candidates to host extrasolar asteroid belts, we use mid-infrared data from the Wide-field Infrared Survey Explorer (WISE) to search for emission from dust in these systems. We find excesses around eight stars, indicating the presence of warm to hot dust ({approx}100-500 K), corresponding to orbital distances of 0.1-10 AU for these solar-type stars. The strongest detection, KOI 1099, demands {approx}500 K dust interior to the orbit of its exoplanet candidate. One star, KOI 904, may host very hot dust ({approx}1200 K, corresponding to 0.02 AU). Although the fraction of these exoplanet-bearing stars with detectable warm excesses ({approx}3%) is similar to that found by Spitzer surveys of solar-type field stars, the excesses detectable in the WISE data have much higher fractional luminosities (L{sub dust}/L{sub *}) than most known debris disks, implying that the fraction with debris disks of comparable luminosity may actually be significantly higher. It is difficult to explain the presence of dust so close to the host stars, generally corresponding to dust rings at radii <0.3 AU; both the collisional and Poynting-Robertson drag timescales to remove dust from the system are hundreds of years or less at these distances. Assuming a steady state for these systems implies large mass consumption rates with these short removal timescales, meaning that the dust production mechanism in these systems must almost certainly be episodic in nature.

  1. Search for cold debris disks around M-dwarfs

    NASA Astrophysics Data System (ADS)

    Lestrade, J.-F.; Wyatt, M. C.; Bertoldi, F.; Dent, W. R. F.; Menten, K. M.

    2006-12-01

    Debris disks are believed to be related to planetesimals left over around stars after planet formation has ceased. The frequency of debris disks around M-dwarfs which account for 70% of the stars in the Galaxy is unknown while constrains have already been found for A- to K-type stars. We have searched for cold debris disks around 32 field M-dwarfs by conducting observations at λ = 850~μm with the SCUBA bolometer array camera at the JCMT and at λ = 1.2 mm with the MAMBO array at the IRAM 30-m telescopes. This is the first survey of a large sample of M-dwarfs conducted to provide statistical constraints on debris disks around this type of stars. We have detected a new debris disk around the M0.5 dwarf GJ 842.2 at λ = 850~μm, providing evidence for cold dust at large distance from this star (~300 AU). By combining the results of our survey with the ones of Liu et al. (2004), we estimate for the first time the detection rate of cold debris disks around field M-dwarfs with ages between 20 and 200 Myr. This detection rate is 13+6-8% and is consistent with the detection rate of cold debris disks (9-23%) around A- to K-type main sequence stars of the same age. This is an indication that cold disks may be equally prevalent across stellar spectral types.

  2. Detecting Exoplanets with the New Worlds Observer: The Problem of Exozodiacal Dust

    NASA Technical Reports Server (NTRS)

    Roberge, A.; Noecker, M. C.; Glassman, T. M.; Oakley, P.; Turnbull, M. C.

    2009-01-01

    Dust coming from asteroids and comets will strongly affect direct imaging and characterization of terrestrial planets in the Habitable Zones of nearby stars. Such dust in the Solar System is called the zodiacal dust (or 'zodi' for short). Higher levels of similar dust are seen around many nearby stars, confined in disks called debris disks. Future high-contrast images of an Earth-like exoplanet will very likely be background-limited by light scattered of both the local Solar System zodi and the circumstellar dust in the extrasolar system (the exozodiacal dust). Clumps in the exozodiacal dust, which are expected in planet-hosting systems, may also be a source of confusion. Here we discuss the problems associated with imaging an Earth-like planet in the presence of unknown levels of exozodiacal dust. Basic formulae for the exoplanet imaging exposure time as function of star, exoplanet, zodi, exozodi, and telescope parameters will be presented. To examine the behavior of these formulae, we apply them to the New Worlds Observer (NWO) mission. NWO is a proposed 4-meter UV/optical/near-IR telescope, with a free flying starshade to suppress the light from a nearby star and achieve the high contrast needed for detection and characterization of a terrestrial planet in the star's Habitable Zone. We find that NWO can accomplish its science goals even if exozodiacal dust levels are typically much higher than the Solar System zodi level. Finally, we highlight a few additional problems relating to exozodiacal dust that have yet to be solved.

  3. Optical polarization of solar type stars with debris disks

    NASA Astrophysics Data System (ADS)

    García, L.; Gómez, M.

    2015-04-01

    We report optical aperture polarimetry for 34 southern hemisphere main-sequence stars with debris disks, in addition to 54 stars without evidence of disk. These sets of stars are combined with another set of 109 stars from the northern hemisphere, obtained from the literature, to build two samples of 51 and 97 solar-type stars with and without debris disks. The distributions of polarization values for the samples with and without disks show no significant statistical difference, within the precision of our observations. However, we identify a sub-sample of 9 stars (d≲ 50 pc) with disks that have polarization levels above the median for the sample with disk, and that are not appropriately reproduced by Serkowski's interstellar law. These stars are candidates to have intrinsic polarization. In this case the debris disks in these stars may be populated by small dust with sizes of ≍0.1μm.

  4. DUSTY DISKS AROUND WHITE DWARFS. I. ORIGIN OF DEBRIS DISKS

    SciTech Connect

    Dong Ruobing; Wang Yan; Lin, D. N. C.; Liu, X.-W. E-mail: yuw123@psu.ed E-mail: liuxw@bac.pku.edu.c

    2010-06-01

    A significant fraction of the mature FGK stars have cool dusty disks at least an order of magnitude brighter than the solar system's outer zodiacal light. Since such dusts must be continually replenished, they are generally assumed to be the collisional fragments of residual planetesimals analogous to the Kuiper-Belt objects. At least 10% of solar-type stars also bear gas giant planets. The fraction of stars with known gas giants or detectable debris disks (or both) appears to increase with the stellar mass. Here, we examine the dynamical evolution of systems of long-period gas giant planets and residual planetesimals as their host stars evolve off the main sequence, lose mass, and form planetary nebula around remnant white dwarf cores. The orbits of distant gas giant planets and super-km-size planetesimals expand adiabatically. During the most intense asymptotic giant branch mass-loss phase, sub-meter-size particles migrate toward their host stars due to the strong hydrodynamical drag by the intense stellar wind. Along their migration paths, gas giant planets capture and sweep up sub-km-size planetesimals onto their mean-motion resonances. These planetesimals also acquire modest eccentricities which are determined by the mass of the perturbing planets, and the rate and speed of stellar mass loss. The swept-up planetesimals undergo disruptive collisions which lead to the production of grains with an extended size range. The radiation drag on these particles is ineffective against the planets' resonant barrier and they form 30-50 AU size rings which can effectively reprocess the stellar irradiation in the form of FIR continuum. We identify the recently discovered dust ring around the white dwarf WD 2226-210 at the center of the Helix nebula as a prototype of such disks and suggest such rings may be common.

  5. Debris disks: seeing dust, thinking of planetesimals and planets

    NASA Astrophysics Data System (ADS)

    Krivov, Alexander V.

    2010-05-01

    Debris disks are optically thin, almost gas-free dusty disks observed around a significant fraction of main-sequence stars older than about 10 Myr. Since the circumstellar dust is short-lived, the very existence of these disks is considered as evidence that dust-producing planetesimals are still present in mature systems, in which planets have formed - or failed to form - a long time ago. It is inferred that these planetesimals orbit their host stars at asteroid to Kuiper-belt distances and continually supply fresh dust through mutual collisions. This review outlines observational techniques and results on debris disks, summarizes their essential physics and theoretical models, and then places them into the general context of planetary systems, uncovering interrelations between the disks, dust parent bodies, and planets. It is shown that debris disks can serve as tracers of planetesimals and planets and shed light on the planetesimal and planet formation processes that operated in these systems in the past.

  6. The Correlation between Metallicity and Debris Disk Mass

    NASA Astrophysics Data System (ADS)

    Gáspár, András; Rieke, George H.; Ballering, Nicholas

    2016-08-01

    We find that the initial dust masses in planetary debris disks are correlated with the metallicities of their central stars. We compiled a large sample of systems, including Spitzer, the Herschel DUNES and DEBRIS surveys, and WISE debris disk candidates. We also merged 33 metallicity catalogs to provide homogeneous [Fe/H] and {σ }[{Fe/{{H}}]} values. We analyzed this merged sample, including 222 detected disks (74 warm and 148 cold) around a total of 187 systems (some with multiple components) and 440 disks with only upper limits (125 warm and 315 cold) around a total of 360 systems. The disk dust masses at a common early evolutionary point in time were determined using our numerical disk evolutionary code, evolving a unique model for each of the 662 disks backward to an age of 1 Myr. We find that disk-bearing stars seldom have metallicities less than {{[Fe/H]}}=-0.2 and that the distribution of warm component masses lacks examples with large mass around stars of low metallicity ({{[Fe/H]}}\\lt -0.085). Previous efforts to find a correlation have been largely unsuccessful; the primary improvements supporting our result are (1) basing the study on dust masses, not just infrared excess detections; (2) including upper limits on dust mass in a quantitative way; (3) accounting for the evolution of debris disk excesses as systems age; (4) accounting fully for the range of uncertainties in metallicity measurements; and (5) having a statistically large enough sample.

  7. Probing Nearby Planetary Systems by Debris Disk Imaging

    NASA Technical Reports Server (NTRS)

    Stapelfeldt, Karl

    2011-01-01

    Many main-sequence stars possess tenuous circumstellar dust clouds believed to trace extrasolar analogs of the Sun's asteroidand Kuiper Belts. While most of these "debris disks" are known only from far-infrared photometry, a growing number of them are now spatially resolved. In this talk, I'll review what is currently known about the structure of debris disks. Using images from the Hubble, Spitzer, and Herschel Space Telescopes, I will show how modeling of these resolved systems can place strong constraints on dust particle properties in the disks. Some of the disks show disturbed structures suggestive of planetary perturbations: specific cases will be discussed where directly-imaged exoplanets are clearly affecting debris disk structure. I'll conclude with thoughts on the future of high contrast exoplanet imaging.

  8. Gas in Protoplanetary and Debris Disks: Insights from UV Spectroscopy

    NASA Technical Reports Server (NTRS)

    Roberge, Aki

    2008-01-01

    Over the last two decades, observations of protoplanetary and debris disks have played an important role in the new field of extrasolar planetary studies. Many are familiar with the extensive work on the cold circumstellar dust present in these disks done using infrared and sub-millimeter photometry and spectroscopy. However. UV spectroscopy has made some unique contributions by probing the elusive but vital gas component in protoplanetary and debris disks. In this talk, I will outline our picture of the evolution of protoplanetary disks and discuss the importance of the gas component. New insights obtained from UV spectroscopy will be highlighted, as well as some new puzzles. Finally, I will touch on upcoming studies of gas in protoplanetary and debris disks, some at UV wavelengths, some at far-IR and sub-mm wavelengths.

  9. Millimeter Resolved Observations of the HD 181327 Debris Disk

    NASA Astrophysics Data System (ADS)

    Steele, Amy

    2016-01-01

    The presence of debris disks around young main sequence stars hints at the structure of hidden planetary systems, with any deviations from axisymmetry pointing toward interactions among planetesimals. HD 181327 is a ~24 Myr old F5.5 member of the Beta Pic Moving Group that hosts an extremely bright debris disk (L_IR/L_\\star = 0.25%) of dust continuously generated through the collisional erosion of a circumstellar ring of planetesimals at 90 AU. An HST STIS observation of the HD 181327 disk provided tentative evidence for the recent collisional destruction of a Pluto mass object. Spatially resolved millimeter wavelength observations are crucial to investigate this scenario, characterize the structure of the dust disk, and characterize the gravitationally interacting grains. We present ALMA observations at ~1 arcsec resolution and investigate the azimuthal variations in the HD 181327 debris disk at 1.25 mm.

  10. A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective

    NASA Astrophysics Data System (ADS)

    Silverberg, Steven M.; Kuchner, Marc J.; Wisniewski, John P.; Gagné, Jonathan; Bans, Alissa S.; Bhattacharjee, Shambo; Currie, Thayne R.; Debes, John R.; Biggs, Joseph R.; Bosch, Milton; Doll, Katharina; Durantini-Luca, Hugo A.; Enachioaie, Alexandru; Griffith, Philip, Sr.; Hyogo, Michiharu; Piñiero, Fernanda; Disk Detective Collaboration

    2016-10-01

    We used the Disk Detective citizen science project and the BANYAN II Bayesian analysis tool to identify a new candidate member of a nearby young association with infrared excess. WISE J080822.18-644357.3, an M5.5-type debris disk system with significant excess at both 12 and 22 μm, is a likely member (∼ 90 % BANYAN II probability) of the ∼45 Myr old Carina association. Since this would be the oldest M dwarf debris disk detected in a moving group, this discovery could be an important constraint on our understanding of M dwarf debris disk evolution.

  11. Debris Disks as Tracers of Nearby Planetary Systems

    NASA Technical Reports Server (NTRS)

    Stapelfeldt, Karl

    2012-01-01

    Many main-sequence stars possess tenuous circumstellar dust clouds believed to trace extrasolar analogs of the Sun's asteroid and Kuiper Belts. While most of these "debris disks" are known only from far-infrared photometry, dozens are now spatially resolved. In this talk, I'll review the observed structural properties of debris disks as revealed by imaging with the Hubble, Spitzer, and Herschel Space Telescopes. I will show how modeling of the far-infrared spectral energy distributions of resolved disks can be used to constrain their dust particle sizes and albedos. I will review cases of disks whose substructures suggest planetary perturbations, including a newly-discovered eccentric ring system. I'll conclude with thoughts on the potential of upcoming and proposed facilities to resolve similar structures around a greatly expanded sample of nearby debris systems.

  12. Modeling of debris disks in Single and Binary stars

    NASA Astrophysics Data System (ADS)

    García, L.; Gómez, M.

    2016-04-01

    Infrared space observatories such as Spitzer and Herschel have allowed the detection of likely analogs to the Kuiper Belt in single as well as binary systems. The aim of this work is to characterize debris disks in single and binary stars and to identify features shared by the disks in both types of systems, as well as possible differences. We compiled a sample of 25 single and 14 binary stars (ages > 100 Myr) with flux measurements at λ >100 μm and evidence of infrared excesses attributed to the presence of debris disks. Then, we constructed and modeled the observed spectral energy distributions (SEDs), and compared the parameters of the disks of both samples. Both types of disks are relatively free of dust in the inner region (< 3-5 AU) and extend beyond 100 AU. No significant differences in the mass and dust size distributions of both samples are found.

  13. The Transient State of the HD 106906 Circumstellar Debris Disk

    NASA Astrophysics Data System (ADS)

    Nesvold, Erika; Naoz, Smadar

    2016-10-01

    The HD 106906 system poses a challenge for dynamical modelers. The system harbors an extremely distant planetary-mass companion at a projected distance of ~650 au, and a nearly edge-on, asymmetric debris ring oriented ~20° in position angle from the external planet. We show that the gravitational perturbations from the planet excite a collisional cascade in the disk, and we suggest that the observed asymmetric morphology is a result of a transient phase in the disk's evolution. The observed geometry of the system and the morphology of the disk allow us to constrain the current orbital parameters of the system. We also generalize this work and discuss how our model of an external companion perturbing a debris disk could be used to understand disk morphologies in other systems.

  14. Five steps in the evolution from protoplanetary to debris disk

    NASA Astrophysics Data System (ADS)

    Wyatt, M. C.; Panić, O.; Kennedy, G. M.; Matrà, L.

    2015-06-01

    The protoplanetary disks seen around Herbig Ae stars eventually dissipate leaving just a tenuous debris disk, comprised of planetesimals and the dust derived from them, as well as possibly gas and planets. This paper uses the properties of the youngest (10-20 Myr) A star debris disks to consider the transition from protoplanetary to debris disk. It is argued that the physical distinction between these two classes should rest on the presence of primordial gas in sufficient quantities to dominate the motion of small dust grains (rather than on the secondary nature of the dust or its level of stirring). This motivates an observational classification based on the dust emission spectrum which is empirically defined so that A star debris disks require fractional excesses <3 at 12 μm and <2000 at 70 μm. We also propose that a useful hypothesis to test is that the planet and planetesimal systems seen on the main sequence are already in place during the protoplanetary disk phase, but are obscured or overwhelmed by the rest of the disk. This may be only weakly true if the architecture of the planetary system continues to change until frozen at the epoch of disk dispersal, or completely false if planets and planetesimals form during the relatively short dispersal phase. Five steps in the transition are discussed: (i) the well-known carving of an inner hole to form a transition disk; (ii) depletion of mm-sized dust in the outer disk, where it is noted that it is of critical importance to ascertain whether this mass ends up in larger planetesimals or is collisionally depleted; (iii) final clearing of inner regions, where it is noted that multiple debris-like mechanisms exist to replenish moderate levels of hot dust at later phases, and that these likely also operate in protoplanetary disks; (iv) disappearance of the gas, noting the recent discoveries of both primordial and secondary gas in debris disks which highlight our ignorance in this area and its impending enlightenment

  15. A Collisional Algorithm for Modeling Circumstellar Debris Disks

    NASA Technical Reports Server (NTRS)

    Nesvold, Erika; Kuchner, Marc

    2011-01-01

    Many planetary systems harbor circumstellar disks of dust and planetesimals thought to be debris left over from planet formation. These debris disks exhibit a range of morphological features which can arise from the gravitational perturbations of planets. Accurate models of these features, accounting for the interactions of the particles in a disk with each other and with whatever planets they contain, can act as signposts for planets in debris disks that otherwise could not be detected. Such models can also constrain the planet's mass and orbital parameters. Current models for many disks consider the gravitational and radiative effects of the star and planets on the disk, but neglect the morphological consequences of collisional interactions between the planetesimals. Many observed disk features are not satisfactorily explained by the current generation of models. I am developing a new kind of debris disk model that considers both the gravitational shaping of the disk by planets and the inelastic collisions between particles. I will use a hybrid N-body integrator to numerically solve the equations of motion for the particles and planets in the disk. To include the collisional effects, I begin with an algorithm that tests for collisions at each step of the orbit integration and readjusts the velocities of colliding particles. I am adapting this algorithm to the problem at hand by allowing each particle to represent a "swarm" of planetesimals with a range of masses. When the algorithm detects an encounter between swarms, two or three swarms are produced to approximate the range of possible trajectories of the daughter planetesimals. Here I present preliminary results from my collisional algorithm.

  16. Detection Of Exocomets Within Edge-on Debris Disks

    NASA Astrophysics Data System (ADS)

    Montgomery, Sharon Lynn; Welsh, B.

    2011-01-01

    The youngest circumstellar debris disks in orbit around main sequence stars are thought to represent the last stage in the formation of a planetary system. Dust and gas continues to be replenished in these systems when planetesimals reach sizes of around 2000 km. Dynamical instabilities can "stir" the population of smaller planetesimals such that they undergo violent dust-generating collisions with each other. The same instabilities may send comets on highly eccentric orbits toward the star in these debris disk systems. Four stars, including the protypical debris disk star Beta Pic, have already been shown to exhibit short-term (i.e., night-to-night) variability in Ca II, which is widely believed to be due to infalling evaporating bodies (FEBs or exocomets). We have collected moderately high-resolution spectra of ten young, A-type, rapidly-rotating stars with excess infrared continuum emission using the Cassegrain-Echelle spectrograph of the 2.1m Otto Struve Telescope. Here, we report the detection of two new gas disk systems with short-term variability in CaII: 5 Vul and 49 Cet. While the circumstellar disks of both stars have been previously described in the literature, this is the first report of night-to-night variability within the debris disk gas. Velocity arguments have allowed us to place some constraints on the dynamics of the absorbing gas.

  17. New Debris Disks in Nearby Young Moving Groups

    NASA Astrophysics Data System (ADS)

    Moór, A.; Kóspál, Á.; Ábrahám, P.; Balog, Z.; Csengeri, T.; Henning, Th.; Juhász, A.; Kiss, Cs.

    2016-08-01

    A significant fraction of nearby young moving group members harbor circumstellar debris dust disks. Due to their proximity and youth, these disks are attractive targets for studying the early evolution of debris dust and planetesimal belts. Here we present 70 and 160 μm observations of 31 systems in the β Pic moving group, and in the Tucana-Horologium, Columba, Carina, and Argus associations, using the Herschel Space Observatory. None of these stars were observed at far-infrared wavelengths before. Our Herschel measurements were complemented by photometry from the WISE satellite for the whole sample, and by submillimeter/millimeter continuum data for one source, HD 48370. We identified six stars with infrared excess, four of them are new discoveries. By combining our new findings with results from the literature, we examined the incidence and general characteristics of debris disks around Sun-like members of the selected groups. With their dust temperatures of <45 K the newly identified disks around HD 38397, HD 48370, HD 160305, and BD-20 951 represent the coldest population within this sample. For HD 38397 and HD 48370, the emission is resolved in the 70 μm Photodetector Array Camera and Spectrograph images, the estimated radius of these disks is ˜90 au. Together with the well-known disk around HD 61005, these three systems represent the highest mass end of the known debris disk population around young G-type members of the selected groups. In terms of dust content, they resemble the hypothesized debris disk of the ancient solar system.

  18. New Debris Disks in Nearby Young Moving Groups

    NASA Astrophysics Data System (ADS)

    Moór, A.; Kóspál, Á.; Ábrahám, P.; Balog, Z.; Csengeri, T.; Henning, Th.; Juhász, A.; Kiss, Cs.

    2016-08-01

    A significant fraction of nearby young moving group members harbor circumstellar debris dust disks. Due to their proximity and youth, these disks are attractive targets for studying the early evolution of debris dust and planetesimal belts. Here we present 70 and 160 μm observations of 31 systems in the β Pic moving group, and in the Tucana–Horologium, Columba, Carina, and Argus associations, using the Herschel Space Observatory. None of these stars were observed at far-infrared wavelengths before. Our Herschel measurements were complemented by photometry from the WISE satellite for the whole sample, and by submillimeter/millimeter continuum data for one source, HD 48370. We identified six stars with infrared excess, four of them are new discoveries. By combining our new findings with results from the literature, we examined the incidence and general characteristics of debris disks around Sun-like members of the selected groups. With their dust temperatures of <45 K the newly identified disks around HD 38397, HD 48370, HD 160305, and BD-20 951 represent the coldest population within this sample. For HD 38397 and HD 48370, the emission is resolved in the 70 μm Photodetector Array Camera and Spectrograph images, the estimated radius of these disks is ˜90 au. Together with the well-known disk around HD 61005, these three systems represent the highest mass end of the known debris disk population around young G-type members of the selected groups. In terms of dust content, they resemble the hypothesized debris disk of the ancient solar system.

  19. Debris Disks around White Dwarfs: The DAZ Connection

    NASA Astrophysics Data System (ADS)

    Kilic, Mukremin; von Hippel, Ted; Leggett, S. K.; Winget, D. E.

    2006-07-01

    We present near-infrared spectroscopic observations of 20 previously known DAZ white dwarfs obtained at the NASA Infrared Telescope Facility. Two of these white dwarfs (G29-38 and GD 362) are known to display significant K-band excesses due to circumstellar debris disks. Here we report the discovery of excess K-band radiation from another DAZ white dwarf, WD 0408-041 (GD 56). Using spectroscopic observations, we show that the excess radiation cannot be explained by a stellar or substellar companion, and is likely to be caused by a warm debris disk. Our observations strengthen the connection between the debris disk phenomena and the observed metal abundances in cool DAZ white dwarfs. However, we do not find any excess infrared emission from the most metal rich DAZs with Teff=16,000-20,000 K. This suggests that the metal abundances in warmer DAZ white dwarfs may require another explanation.

  20. PLANETESIMALS IN DEBRIS DISKS OF SUN-LIKE STARS

    SciTech Connect

    Shannon, Andrew; Wu Yanqin

    2011-09-20

    Observations of dusty debris disks can be used to test theories of planetesimal coagulation. Planetesimals of sizes up to a couple of thousand kilometers are embedded in these disks and their mutual collisions generate the small dust grains that are observed. The dust luminosities, when combined with information on the dust spatial extent and the system age, can be used to infer initial masses in the planetesimal belts. Carrying out such a procedure for a sample of debris disks around Sun-like stars, we reach the following two conclusions. First, if we assume that colliding planetesimals satisfy a primordial size spectrum of the form dn/ds{proportional_to}s{sup -q}, observed disks strongly favor a value of q between 3.5 and 4, while both current theoretical expectations and statistics of Kuiper belt objects favor a somewhat larger value. Second, number densities of planetesimals are two to three orders of magnitude higher in detected disks than in the Kuiper belt, for comparably sized objects. This is a surprise for the coagulation models. It would require a similar increase in the disk surface density over that of the Minimum Mass Solar Nebula, which is unreasonable. Both of our conclusions are driven by the need to explain the presence of bright debris disks at a few gigayears of age.

  1. Constraining Collisional Models of Planetesimals in Debris Disks

    NASA Astrophysics Data System (ADS)

    MacGregor, Meredith A.; Wilner, David J.; Hughes, A. Meredith; Steele, Amy; Ricci, Luca; Andrews, Sean M.; Chandler, Claire J.; Tahli Maddison, Sarah

    2016-01-01

    Debris disks around main-sequence stars are produced by the ongoing collisional erosion of planetesimals, analogous to Kuiper Belt Objects (KBOs) or comets in our own Solar System. Observations of these dusty belts offer a window into the physical and dynamical properties of planetesimals in extrasolar systems through the size distribution of dust grains. In particular, the millimeter/radio spectral index of thermal dust emission encodes information on the grain size distribution that can be used to test proposed collisional models of planetesimals. We have made sensitive Jansky Very Large Array (JVLA) observations of a sample of 7 nearby debris disks at 9 mm and combine these with archival Australia Telescope Compact Array (ATCA) observations of 8 additional debris disks at 7 mm. Using measurements at (sub)millimeter wavelengths from the literature, we place tight constraints on the millimeter spectral indices and thus grain size distributions of this sample of debris disks. Our analysis gives a weighted mean for the slope of the power-law grain distribution that is close to the classical prediction for a steady-state collisional cascade (q=3.5), but not consistent with the steeper distributions predicted by recent models that include more complex fragmentation processes. To interpret this result, we explore the effects of material strengths, velocity distributions, and small-size cutoffs on the steady-state grain size distribution.

  2. The Dynamical Structure of HR 8799's Inner Debris Disk.

    PubMed

    Contro, B; Wittenmyer, Robert A; Horner, J; Marshall, Jonathan P

    2015-06-01

    The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar system where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanetary dynamics and debris disk-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disk remains unknown. This leaves a significant question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using UNSW Australia's Katana supercomputing facility to follow the dynamical evolution of a model inner disk comprising 300,298 particles for a period of 60 Ma. These simulations have enabled the characterisation of the extent and structure of the inner disk in detail, and will in future allow us to provide a first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet (s) in the inner system. PMID:25862330

  3. The Dynamical Structure of HR 8799's Inner Debris Disk.

    PubMed

    Contro, B; Wittenmyer, Robert A; Horner, J; Marshall, Jonathan P

    2015-06-01

    The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar system where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanetary dynamics and debris disk-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disk remains unknown. This leaves a significant question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using UNSW Australia's Katana supercomputing facility to follow the dynamical evolution of a model inner disk comprising 300,298 particles for a period of 60 Ma. These simulations have enabled the characterisation of the extent and structure of the inner disk in detail, and will in future allow us to provide a first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet (s) in the inner system.

  4. The Dynamical Structure of HR 8799's Inner Debris Disk

    NASA Astrophysics Data System (ADS)

    Contro, B.; Wittenmyer, Robert A.; Horner, J.; Marshall, Jonathan P.

    2015-06-01

    The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar system where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanetary dynamics and debris disk-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disk remains unknown. This leaves a significant question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using UNSW Australia's Katana supercomputing facility to follow the dynamical evolution of a model inner disk comprising 300,298 particles for a period of 60 Ma. These simulations have enabled the characterisation of the extent and structure of the inner disk in detail, and will in future allow us to provide a first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet (s) in the inner system.

  5. Resolved imaging of the HR 8799 Debris disk with Herschel

    SciTech Connect

    Matthews, Brenda; Booth, Mark; Broekhoven-Fiene, Hannah; Marois, Christian; Kennedy, Grant; Wyatt, Mark; Sibthorpe, Bruce; Macintosh, Bruce

    2014-01-01

    We present Herschel far-infrared and submillimeter maps of the debris disk associated with the HR 8799 planetary system. We resolve the outer disk emission at 70, 100, 160, and 250 μm and detect the disk at 350 and 500 μm. A smooth model explains the observed disk emission well. We observe no obvious clumps or asymmetries associated with the trapping of planetesimals that is a potential consequence of planetary migration in the system. We estimate that the disk eccentricity must be <0.1. As in previous work by Su et al., we find a disk with three components: a warm inner component and two outer components, a planetesimal belt extending from 100 to 310 AU, with some flexibility (±10 AU) on the inner edge, and the external halo that extends to ∼2000 AU. We measure the disk inclination to be 26° ± 3° from face-on at a position angle of 64° E of N, establishing that the disk is coplanar with the star and planets. The spectral energy distribution of the disk is well fit by blackbody grains whose semi-major axes lie within the planetesimal belt, suggesting an absence of small grains. The wavelength at which the spectrum steepens from blackbody, 47 ± 30 μm, however, is short compared with other A star debris disks, suggesting that there are atypically small grains likely populating the halo. The PACS longer wavelength data yield a lower disk color temperature than do MIPS data (24 and 70 μm), implying two distinct halo dust-grain populations.

  6. Study of Scattered Light from Known Debris Disks

    NASA Technical Reports Server (NTRS)

    Rodriguez, Joseph E.; Weinberger, Alycia J.; Roberge, Aki

    2011-01-01

    Using the Spitzer Space Telescope, a group of edge on debris disks, surrounding main-sequence shell stars have been discovered in the infrared. These disks are of high interest because they not only have dust, but an observed amount of circumstellar gas. HD158352 was an ideal target to try and image the disk because it was one of the closest stars in this group. Using the Hubble Space Telescope's Space Telescope Imaging Spectrograph (STIS), we attempted to take a direct image of the light scattered from the known disk in a broad optical bandpass. Studying these particular type of disks in high detail will allow us to learn more about gas-dust interactions. In particular, this will allow us to learn how the circumstellar gas evolves during the planet-forming phase. Even though it was predicted that the disk should have a magnitude of 20.5 at 3", no disk was seen in any of the optical images. This suggests that the parameters used to predict the brightness of the disk are not what we first anticipated and adjustments to the model must be performed. We also present the blue visible light spectrum of the scattered light from the debris disk surrounding Beta Pictoris. We are analyzing archival observations taken by Heap, using Hubble Space Telescope's STIS instrument. A long slit with a bar was used to occult Beta Pictoris as well as the PSF star. This was done because it is necessary to subtract a PSF observed the same way at the target to detect the disk. It appears that we have detected light from the disk but the work was in progress at the time of the abstract deadline.

  7. Characterization of WISE Debris Disk Stars - 2013B

    NASA Astrophysics Data System (ADS)

    Padgett, Deborah; Liu, Wilson; Morales, Farisa; Stapelfeldt, Karl

    2013-08-01

    We propose to acquire low dispersion spectra with the SOAR Goodman Spectrograph of new debris disk stars identified from the Wide-field Infrared Survey Explorer (WISE survey of the entire sky. Despite many targeted surveys for stellar disks in the solar neighborhood by Spitzer Space Telescope, the census of disks remains incomplete at mid-IR sensitivity levels better than the IRAS limits. The improved sensitivity and spatial resolution of the all-sky WISE survey for debris disks (Padgett et al., submitted) has recently improved this situation, identifying Hipparcos and Tycho stars with mid-infrared excess out to distances of 120 pc. With the SOAR spectrograph we will characterize the new candidate debris disk stars in the southern sky, providing a uniform set of stellar classifications and information on a range of spectroscopic activity indicators related to stellar age. These data will help to constrain the stellar properties of an important new set of solar neighbors with evidence of planetary systems.

  8. Coronagraphic Imaging of Debris Disks from a High Altitude Balloon Platform

    NASA Astrophysics Data System (ADS)

    Unwin, Stephen C.; Traub, W. A.; Trauger, J. T.; Bryden, G.; Stuchlik, D. W.; Lillie, C. F.

    2012-05-01

    Direct imaging of exoplanets orbiting nearby stars is a major observational challenge, demanding high angular resolution and extremely high dynamic range close to the parent star. Such a system could image and characterize the atmospheres of exoplanets, and also observe exozodiacal dust within the exoplanetary system. The ultimate experiment requires a space-based platform, but demonstrating much of the needed technology as well as performing valuable measurements of circumstellar debris disks, can be done from a high-altitude balloon platform. In this paper, we show how progress in key technologies leads to a balloon experiment as a logical future step toward a space mission. The HCIT testbed has shown ultra-high contrast using small optics in a vacuum testbed. A recent ground-based experiment has demonstrated the ability to control three active optics in series - a lightweight controllable primary mirror, and two deformable mirrors - to achieve close to the best wavefront correction possible with large optics in an in-air testbed. We briefly describe the Wallops Arcsecond Pointer (WASP), which has had a very successful first flight, showing the capability of a balloon platform to stably point to the accuracy required for a coronagraph payload experiment. A balloon-borne coronagraph mission would incorporate all of these advances in an instrument that verifies each one in a space-like environment, and enabling forefront science. Such an experiment would be a step toward mitigating the technical risks of a major space-based exoplanet coronagraph. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2012. California Institute of Technology. Government sponsorship acknowledged.

  9. Resolving the Dusty Debris Disk of 49 Ceti

    NASA Astrophysics Data System (ADS)

    Lieman-Sifry, Jesse; Hughes, A. Meredith

    2015-01-01

    Understanding the dispersal of primordial gas and dust from circumstellar disks is necessary for determining the timeline for giant planet formation. While the current assumption is that the gas and dust evolve simultaneously, there are a few systems that defy this paradigm. The nearby A star 49 Ceti, at a distance of 61 pc, hosts one of only a few known circumstellar disks that exhibits the dust qualities of an older debris disk but still displays a substantial mass of molecular gas, a characteristic normally associated with youth. We present Atacama Large Millimeter/Submillimeter Array (ALMA) observations at 850μm and a spatial resolution of 0.47x0.39 arcsec that resolve emission from the dust disk for the first time. To investigate the properties of the dust grains and the morphology of the disk, we simultaneously model the high-resolution ALMA data and the unresolved spectral energy distribution (SED). The detected emission reveals a disk that extends from 1.16±0.12AU to 286±7AU with an increase in surface density at 113±2AU that is viewed at an inclination of 79.6±.4°. The increase in surface density corresponds to the inner radius of the gas disk, hinting that similar mechanisms may be responsible for sculpting the gas and dust disks at this late stage of disk evolution.

  10. Comprehensive Census and Complete Characterization of Nearby Debris Disk Stars

    NASA Astrophysics Data System (ADS)

    Cotten, Tara H.; Song, Inseok

    2016-01-01

    Debris disks are intimately linked to planetary system evolution since the rocky material surrounding the host stars is believed to be due to secondary generation from the collisions of planetesimals. With the conclusion and lack of future large scale infrared excess survey missions, it is time to summarize the history of using excess emission in the infrared as a tracer of debris and exploit all available data as well as provide a comprehensive study of the parameters of these important objects. We have compiled a catalog of infrared excess stars from peer-reviewed articles and performed an extensive search for new debris disks by cross-correlating the Tycho-2 and AllWISE catalogs. This study will conclude following the thorough examination of each debris disk star's parameters obtained through high-resolution spectroscopy at various facilities which is currently ongoing. We will maintain a webpage (www.debrisdisks.org) devoted to these infrared excess sources and provide various resources related to our catalog creation, SED fitting, and data reduction.

  11. Search for cold debris disks around M-dwarfs. II

    NASA Astrophysics Data System (ADS)

    Lestrade, J.-F.; Wyatt, M. C.; Bertoldi, F.; Menten, K. M.; Labaigt, G.

    2009-11-01

    Although 70% of the stars in the Galaxy are M-dwarfs, thermal emission searches for cold debris disks have been conducted mostly for A-type and solar-type stars. We report on new λ=1.2 mm continuum observations of thirty M-dwarfs, using the MAMBO-2 bolometer array camera at the IRAM 30 m telescope. For a statistical analysis, we combine these data with our prior SCUBA and MAMBO-2 observations of 20 other M-dwarfs. Our sample consists of M-dwarfs in moving groups, with relatively young ages, and of nearby M-dwarfs with unknown ages. Only one cold debris disk (GJ842.2) was detected significantly. We compare the implied disk abundance constraints with those found in two comparable submillimeter surveys of 10 to 190 Myr old A- and FGK-type stars. For the 19 youngest (ages less than 200 Myr) M-dwarfs in our sample, we derive a cold disk fraction of 5.3+10.5-5.0%, compared to 15+11.5-11.5% for FGK-stars and 22+33-20% for A-stars. Hence, for this age group, there is an apparent trend of fewer cold disks for later stellar types. Although its statistical significance is marginal, this trend is strengthened by the deeper observations of our M-dwarf sample. We derive a cold disk fraction of <10% for the older (likely a few Gyr) M-dwarfs in our sample. Finally, although inconclusively related to a debris disk, we present the complex millimeter structure found around the position of the M 1.5 dwarf GJ526 in our sample.

  12. GAS EMISSION FROM DEBRIS DISKS AROUND A AND F STARS

    SciTech Connect

    Zagorovsky, Kyryl; Brandeker, Alexis; Wu Yanqin E-mail: alexis@astro.su.s

    2010-09-01

    Gas has been detected in a number of debris disk systems. This gas may have arisen from grain sublimation or grain photodesorption. It interacts with the surrounding dust grains through a number of charge and heat exchanges. Studying the chemical composition and physical state of this gas can therefore reveal much about the dust component in these debris disks. We have produced a new code, ONTARIO, to address gas emission from dusty gas-poor disks around A-F stars. This code computes the gas ionization and thermal balance self-consistently, with particular care taken of heating/cooling mechanisms. Line emission spectra are then produced for each species (up to zinc) by statistical equilibrium calculations of the atomic/ionic energy levels. For parameters that resemble the observed {beta} Pictoris gas disk, we find that the gas is primarily heated by photoelectric emission from dust grains, and primarily cooled through the C II 157.7 {mu}m line emission. The gas can be heated to a temperature that is warmer than that of the dust and may in some cases reach temperature for thermal escape. The dominant cooling line, C II 157.7 {mu}m, should be detectable by Herschel in these disks, while the O I 63.2 {mu}m line will be too faint. We also study the dependence of the cooling line fluxes on a variety of disk parameters, in light of the much improved sensitivity to thermal line emission in the mid/far-infrared and at submillimeter wavelengths provided by, in particular, Herschel, SOFIA, and ALMA. These new instruments will yield much new information about dusty debris disks.

  13. Mass and Temperature of the TWA 7 Debris Disk

    NASA Astrophysics Data System (ADS)

    Matthews, Brenda C.; Kalas, Paul G.; Wyatt, Mark C.

    2007-07-01

    We present photometric detections of dust emission at 850 and 450 μm around the pre-main-sequence M1 dwarf TWA 7 using the SCUBA camera on the James Clerk Maxwell Telescope. These data confirm the presence of a cold dust disk around TWA 7, a member of the TW Hydrae Association (TWA). Based on the 850 μm flux, we estimate the mass of the disk to be 18 Mlunar (0.2 M⊕) assuming a mass opacity of 1.7 cm2 g-1 with a temperature of 45 K. This makes the TWA 7 disk (d=55 pc) an order of magnitude more massive than the disk reported around AU Microscopii (GL 803), the closest (9.9 pc) debris disk detected around an M dwarf. This is consistent with TWA 7 being slightly younger than AU Mic. We find that the mid-IR and submillimeter data require the disk to be comprised of dust at a range of temperatures. A model in which the dust is at a single radius from the star, with a range of temperatures according to grain size, is as effective at fitting the emission spectrum as a model in which the dust is of uniform size, but has a range of temperatures according to distance. We discuss this disk in the context of known disks in the TWA and around low-mass stars; a comparison of masses of disks in the TWA reveals no trend in mass or evolutionary state (gas-rich vs. debris) as a function of spectral type.

  14. HIGH SPATIAL RESOLUTION IMAGING OF THERMAL EMISSION FROM DEBRIS DISKS

    SciTech Connect

    Moerchen, Margaret M.; Telesco, Charles M.; Packham, Christopher

    2010-11-10

    We have obtained subarcsecond mid-IR images of a sample of debris disks within 100 pc. For our sample of 19 A-type debris disk candidates chosen for their IR excess, we have resolved, for the first time, five sources plus the previously resolved disk around HD 141569. Two other sources in our sample have been ruled out as debris disks since the time of sample selection. Three of the six resolved sources have inferred radii of 1-4 AU (HD 38678, HD 71155, and HD 181869), and one source has an inferred radius {approx}10-30 AU (HD 141569). Among the resolved sources with detections of excess IR emission, HD 71155 appears to be comparable in size (r {approx} 2 AU) to the solar system's asteroid belt, thus joining {zeta} Lep (HD 38678, reported previously) to comprise the only two resolved sources of that class. Two additional sources (HD 95418 and HD 139006) show spatial extents that imply disk radii of {approx}1-3 AU, although the excess IR fluxes are not formally detected with better than 2{sigma} significance. For the unresolved sources, the upper limits on the maximum radii of mid-IR disk emission are in the range {approx}1-20 AU, four of which are comparable in radius to the asteroid belt. We have compared the global color temperatures of the dust to that expected for the dust in radiative equilibrium at the distances corresponding to the observed sizes or limits on the sizes. In most cases, the temperatures estimated via these two methods are comparable, and therefore, we see a generally consistent picture of the inferred morphology and the global mid-IR emission. Finally, while our sample size is not statistically significant, we note that the older sources (>200 Myr) host much warmer dust (T {approx}> 400 K) than younger sources (in the tens of Myr).

  15. Does the debris disk around HD 32297 contain cometary grains?

    SciTech Connect

    Rodigas, Timothy J.; Hinz, Philip M.; Bailey, Vanessa; Defrere, Denis; Leisenring, Jarron; Schneider, Glenn; Skemer, Andrew J.; Vaitheeswaran, Vidhya; Debes, John H.; Mamajek, Eric E.; Pecaut, Mark J.; Currie, Thayne; De Rosa, Robert J.; Ward-Duong, Kimberly; Hill, John M.; Skrutskie, Michael

    2014-03-01

    We present an adaptive optics imaging detection of the HD 32297 debris disk at L' (3.8 μm) obtained with the LBTI/LMIRcam infrared instrument at the Large Binocular Telescope. The disk is detected at signal-to-noise ratio per resolution element ∼3-7.5 from ∼0.''3 to 1.''1 (30-120 AU). The disk at L' is bowed, as was seen at shorter wavelengths. This likely indicates that the disk is not perfectly edge-on and contains highly forward-scattering grains. Interior to ∼50 AU, the surface brightness at L' rises sharply on both sides of the disk, which was also previously seen at Ks band. This evidence together points to the disk containing a second inner component located at ≲50 AU. Comparing the color of the outer (50 disk at L' with archival Hubble Space Telescope/NICMOS images of the disk at 1-2 μm allows us to test the recently proposed cometary grains model of Donaldson et al. We find that the model fails to match this disk's surface brightness and spectrum simultaneously (reduced chi-square = 17.9). When we modify the density distribution of the model disk, we obtain a better overall fit (reduced chi-square = 2.87). The best fit to all of the data is a pure water ice model (reduced chi-square = 1.06), but additional resolved imaging at 3.1 μm is necessary to constrain how much (if any) water ice exists in the disk, which can then help refine the originally proposed cometary grains model.

  16. Gap Clearing by Planets in a Collisional Debris Disk

    NASA Astrophysics Data System (ADS)

    Nesvold, Erika R.; Kuchner, Marc J.

    2015-01-01

    We apply our 3D debris disk model, SMACK, to simulate a planet on a circular orbit near a ring of planetesimals that are experiencing destructive collisions. Previous simulations of a planet opening a gap in a collisionless debris disk have found that the width of the gap scales as the planet mass to the 2/7th power (α = 2/7). We find that gap sizes in a collisional disk still obey a power law scaling with planet mass, but that the index α of the power law depends on the age of the system t relative to the collisional timescale t coll of the disk by α = 0.32(t/t coll)-0.04, with inferred planet masses up to five times smaller than those predicted by the classical gap law. The increased gap sizes likely stem from the interaction between collisions and the mean motion resonances near the chaotic zone. We investigate the effects of the initial eccentricity distribution of the disk particles and find a negligible effect on the gap size at Jovian planet masses, since collisions tend to erase memory of the initial particle eccentricity distributions. Finally, we find that the presence of Trojan analogs is a potentially powerful diagnostic of planets in the mass range ~1-10 M Jup. We apply our model to place new upper limits on planets around Fomalhaut, HR 4796 A, HD 202628, HD 181327, and β Pictoris.

  17. GAP CLEARING BY PLANETS IN A COLLISIONAL DEBRIS DISK

    SciTech Connect

    Nesvold, Erika R.; Kuchner, Marc J. E-mail: Marc.Kuchner@nasa.gov

    2015-01-10

    We apply our 3D debris disk model, SMACK, to simulate a planet on a circular orbit near a ring of planetesimals that are experiencing destructive collisions. Previous simulations of a planet opening a gap in a collisionless debris disk have found that the width of the gap scales as the planet mass to the 2/7th power (α = 2/7). We find that gap sizes in a collisional disk still obey a power law scaling with planet mass, but that the index α of the power law depends on the age of the system t relative to the collisional timescale t {sub coll} of the disk by α = 0.32(t/t {sub coll}){sup –0.04}, with inferred planet masses up to five times smaller than those predicted by the classical gap law. The increased gap sizes likely stem from the interaction between collisions and the mean motion resonances near the chaotic zone. We investigate the effects of the initial eccentricity distribution of the disk particles and find a negligible effect on the gap size at Jovian planet masses, since collisions tend to erase memory of the initial particle eccentricity distributions. Finally, we find that the presence of Trojan analogs is a potentially powerful diagnostic of planets in the mass range ∼1-10 M {sub Jup}. We apply our model to place new upper limits on planets around Fomalhaut, HR 4796 A, HD 202628, HD 181327, and β Pictoris.

  18. A New Millimeter Look at the HD 15115 Debris Disk

    NASA Astrophysics Data System (ADS)

    MacGregor, Meredith A.; Wilner, David J.; Andrews, Sean M.; Hughes, A. M

    2014-06-01

    We have used the Submillimeter Array (SMA) to make 1.3 millimeter observations of the debris disk surrounding HD 15115, an F-type star located in the 12 Myr-old beta Pictoris moving group. This nearly edge-on debris disk (the "Blue Needle") has been previously well-resolved in optical scattered light and displays an extreme asymmetry. Unlike scattered light that reflects tiny grains that are blown out by stellar radiation and swept by the interstellar medium, the thermal emission from large grains that dominate at millimeter wavelengths closely traces the locations of the dust-producing parent planetesimals. The SMA observations reveal a circumstellar belt of dust emission. We characterize the millimeter emission using Markov Chain Monte Carlo methods to fit parametric models directly to the visibilities and place limits on departures from axisymmetry.

  19. Modeling the PAH Emission Spectra of Protoplanetary and Debris Disks

    NASA Astrophysics Data System (ADS)

    Li, Aigen; Lunine, J. I.

    2006-05-01

    The 3.3, 6.2, 7.7, 8.6 and 11.3 micron emission features of polycyclic aromatic hydrocarbon (PAH) molecules have been detected in protoplanetary disks around Herbig Ae/Be stars and T Tauri stars and in debris disks around main-sequence stars. PAHs play an important role in the thermal budget and chemistry of the gas in the disk, by providing photoelectrons for heating the gas and large surface areas for chemical reactions. Stochastically heated by a single UV/visible photon, the PAH emission is spatially more extended than large grains and therefore, the disks can be more easily resolved at the PAH emission bands. We propose to model the PAH emission spectra of protoplanetary and debris disks obtained by Spitzer and ISO. We will first calculate the temperature probability distribution functions dP/dT for both neutral and ionized PAHs of a wide range of sizes, at a wide range of radial distances (from the central star) in disks illuminated by stars of a wide range of spectral types. By modeling the PAH emission of dust disks, we will be able (1) to derive the abundance, size and spatial distributions of PAHs; (2) to derive the PAH photoelectric heating rates which dominate the gas heating in the disk surface layers; and (3) to see how the abundance and properties of the PAHs vary among disks at different evolutionary stages and illuminated by stars of different parameters (e.g. luminosity, spectral type). This program will create a web-based ``library'' of the temperature distribution functions dP/dT of PAHs (and their emission spectra and photoelectric heating rates) as a function of size, charge state, and radial distance in disks illuminated by stars of different spectral types. This library, a useful tool for interpreting the PAH emission features of dust disks obtained by Spitzer and for understanding the disk chemistry, will be made publicly available by April 2007 via the WWW at http://www.missouri.edu/~lia/.

  20. Disk Radii and Grain Sizes in Herschel-resolved Debris Disks

    NASA Astrophysics Data System (ADS)

    Pawellek, Nicole; Krivov, Alexander V.; Marshall, Jonathan P.; Montesinos, Benjamin; Ábrahám, Péter; Moór, Attila; Bryden, Geoffrey; Eiroa, Carlos

    2014-09-01

    The radii of debris disks and the sizes of their dust grains are important tracers of the planetesimal formation mechanisms and physical processes operating in these systems. Here we use a representative sample of 34 debris disks resolved in various Herschel Space Observatory (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) programs to constrain the disk radii and the size distribution of their dust. While we modeled disks with both warm and cold components, and identified warm inner disks around about two-thirds of the stars, we focus our analysis only on the cold outer disks, i.e., Kuiper-belt analogs. We derive the disk radii from the resolved images and find a large dispersion for host stars of any spectral class, but no significant trend with the stellar luminosity. This argues against ice lines as a dominant player in setting the debris disk sizes, since the ice line location varies with the luminosity of the central star. Fixing the disk radii to those inferred from the resolved images, we model the spectral energy distribution to determine the dust temperature and the grain size distribution for each target. While the dust temperature systematically increases toward earlier spectral types, the ratio of the dust temperature to the blackbody temperature at the disk radius decreases with the stellar luminosity. This is explained by a clear trend of typical sizes increasing toward more luminous stars. The typical grain sizes are compared to the radiation pressure blowout limit s blow that is proportional to the stellar luminosity-to-mass ratio and thus also increases toward earlier spectral classes. The grain sizes in the disks of G- to A-stars are inferred to be several times s blow at all stellar luminosities, in agreement with collisional models of debris disks. The sizes, measured in the units of s blow, appear to decrease with the luminosity

  1. Disk radii and grain sizes in Herschel-resolved debris disks

    SciTech Connect

    Pawellek, Nicole; Krivov, Alexander V.; Marshall, Jonathan P.; Montesinos, Benjamin; Ábrahám, Péter; Moór, Attila; Bryden, Geoffrey; Eiroa, Carlos

    2014-09-01

    The radii of debris disks and the sizes of their dust grains are important tracers of the planetesimal formation mechanisms and physical processes operating in these systems. Here we use a representative sample of 34 debris disks resolved in various Herschel Space Observatory (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) programs to constrain the disk radii and the size distribution of their dust. While we modeled disks with both warm and cold components, and identified warm inner disks around about two-thirds of the stars, we focus our analysis only on the cold outer disks, i.e., Kuiper-belt analogs. We derive the disk radii from the resolved images and find a large dispersion for host stars of any spectral class, but no significant trend with the stellar luminosity. This argues against ice lines as a dominant player in setting the debris disk sizes, since the ice line location varies with the luminosity of the central star. Fixing the disk radii to those inferred from the resolved images, we model the spectral energy distribution to determine the dust temperature and the grain size distribution for each target. While the dust temperature systematically increases toward earlier spectral types, the ratio of the dust temperature to the blackbody temperature at the disk radius decreases with the stellar luminosity. This is explained by a clear trend of typical sizes increasing toward more luminous stars. The typical grain sizes are compared to the radiation pressure blowout limit s {sub blow} that is proportional to the stellar luminosity-to-mass ratio and thus also increases toward earlier spectral classes. The grain sizes in the disks of G- to A-stars are inferred to be several times s {sub blow} at all stellar luminosities, in agreement with collisional models of debris disks. The sizes, measured in the units of s {sub blow}, appear to decrease

  2. An ATCA Survey of Debris Disks at 7 Millimeters

    NASA Astrophysics Data System (ADS)

    Ricci, L.; Maddison, S. T.; Wilner, D.; MacGregor, M. A.; Ubach, C.; Carpenter, J. M.; Testi, L.

    2015-11-01

    We present Australia Telescope Compact Array continuum observations at a wavelength of 6.8 mm of five debris disks: β Pictoris, q1 Eridani, HD 107146, HD 181327, and HD 95086. These observations provide the detection at the longest wavelengths obtained to date for all these debris disks. By combining our 6.8 mm data with previous detections at shorter sub-millimeter/millimeter wavelengths we measure the long wavelength spectral index of these sources. We then use previous estimates for the temperature of the emitting dust to derive the spectral index of the dust emissivity. Under the assumption that all the detected flux comes from dust only, we constrain the slope of the solid size distribution, assumed to be a power-law. The values that we infer for the slope of the size distribution range between about 3.36 and 3.50. We compare our findings with the case of the Fomalhaut debris disk and use these results to test the predictions of collisional cascades of planetesimal belts.

  3. Searching for debris disks around seven radio pulsars

    SciTech Connect

    Wang, Zhongxiang; Wang, Xuebing; Ng, C.-Y.; Li, Aigen; Kaplan, David L.

    2014-10-01

    We report on our searches for debris disks around seven relatively nearby radio pulsars, which are isolated sources that were carefully selected as targets on the basis of our deep K{sub s} -band imaging survey. The K{sub s} images obtained with the 6.5 m Baade Magellan Telescope at Las Campanas Observatory are analyzed together with the Spitzer/IRAC images at 4.5 and 8.0 μm and the WISE images at 3.4, 4.6, 12, and 22 μm. No infrared counterparts of these pulsars are found, with flux upper limits of ∼μJy at near-infrared (λ < 10 μm) and ∼10-1000 μJy at mid-infrared wavelengths (λ > 10 μm). The results of this search are discussed in terms of the efficiency of converting the pulsar spin-down energy to thermal energy and X-ray heating of debris disks, with a comparison made of the two magnetars 4U 0142+61 and 1E 2259+586, which are suggested to harbor a debris disk.

  4. Hole-y Debris Disks, Batman! Where are the planets?

    NASA Astrophysics Data System (ADS)

    Bailey, V.; Meshkat, T.; Hinz, P.; Kenworthy, M.; Su, K. Y. L.

    2014-03-01

    Giant planets at wide separations are rare and direct imaging surveys are resource-intensive, so a cheaper marker for the presence of giant planets is desirable. One intriguing possibility is to use the effect of planets on their host stars' debris disks. Theoretical studies indicate giant planets can gravitationally carve sharp boundaries and gaps in their disks; this has been seen for HR 8799, β Pic, and tentatively for HD 95086 (Su et al. 2009, Lagrange et al. 2010, Moor et al. 2013). If more broadly demonstrated, this link could help guide target selection for next generation direct imaging surveys. Using Spitzer MIPS/IRS spectral energy distributions (SEDs), we identify several dozen systems with two-component and/or large inner cavity disks (aka Hole-y Debris Disks). With LBT/LBTI, VLT/NaCo, GeminiS/NICI, MMT/Clio and Magellan/Clio, we survey a subset these SEDselected targets (~20). In contrast to previous disk-selected planet surveys (e.g.: Janson et al. 2013, Wahhaj et al. 2013) we image primarily in the thermal IR (L'-band), where planet-to-star contrast is more favorable and background contaminants less numerous. Thus far, two of our survey targets host planet-mass companions, both of which were discovered in L'-band after they were unrecognized or undetectable in H-band. For each system in our sample set, we will investigate whether the known companions and/or companions below our detection threshold could be responsible for the disk architecture. Ultimately, we will increase our effective sample size by incorporating detection limits from surveys that have independently targeted some of our systems of interest. In this way we will refine the conditions under which disk SED-based target selection is likely to be useful and valid.

  5. Constraints on Planetesimal Collision Models in Debris Disks

    NASA Astrophysics Data System (ADS)

    MacGregor, Meredith A.; Wilner, David J.; Chandler, Claire; Ricci, Luca; Maddison, Sarah T.; Cranmer, Steven R.; Andrews, Sean M.; Hughes, A. Meredith; Steele, Amy

    2016-06-01

    Observations of debris disks offer a window into the physical and dynamical properties of planetesimals in extrasolar systems through the size distribution of dust grains. In particular, the millimeter spectral index of thermal dust emission encodes information on the grain size distribution. We have made new VLA observations of a sample of seven nearby debris disks at 9 mm, with 3\\prime\\prime resolution and ˜5 μJy beam-1rms. We combine these with archival ATCA observations of eight additional debris disks observed at 7 mm, together with up-to-date observations of all disks at (sub)millimeter wavelengths from the literature, to place tight constraints on the millimeter spectral indices and thus grain size distributions. The analysis gives a weighted mean for the slope of the power-law grain size distribution, n(a)\\propto {a}-q, of < q> =3.36+/- 0.02, with a possible trend of decreasing q for later spectral type stars. We compare our results to a range of theoretical models of collisional cascades, from the standard self-similar, steady-state size distribution (q = 3.5) to solutions that incorporate more realistic physics such as alternative velocity distributions and material strengths, the possibility of a cutoff at small dust sizes from radiation pressure, and results from detailed dynamical calculations of specific disks. Such effects can lead to size distributions consistent with the data, and plausibly the observed scatter in spectral indices. For the AU Mic system, the VLA observations show clear evidence of a highly variable stellar emission component; this stellar activity obviates the need to invoke the presence of an asteroid belt to explain the previously reported compact millimeter source in this system.

  6. Debris Disks Among the Shell Stars: Insights from Spitzer

    NASA Technical Reports Server (NTRS)

    Roberge, Aki; Weinberger, Alycia; Teske, Johanna

    2008-01-01

    Shell stars are a class of early-type stars that show narrow absorption lines in their spectra that appear to arise from circumstellar class. This observationally defined class contains a variety of objects, including evolved stars and classical Be stars. However, some of the main sequence shell stars harbor debris disks and younger protoplanetary disks, though this aspect of the class has been largely overlooked. We surveyed a set of main sequence stars for cool dust using Spitzer MIPS and found four additional systems with IR excesses at both 24 and 70 microns. This indicates that the stars have both circumstellar gas and dust, and are likely to be edge-on debris disks. Our estimate of the disk fraction among nearby main sequence shell stars is 48% +/- 14%. We discuss here the nature of the shell stars and present preliminary results from ground-based optical spectra of the survey target stars. We will also outline our planned studies aimed at further characterization of the shell star class.

  7. Drag-o-llision Models of Extrasolar Planets in Debris Disks

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc

    2009-01-01

    An extrasolar planet sculpts the famous debris disk around Fomalhaut; probably many other debris disks contain planets that we could locate if only we could better recognize their signatures in the dust that surrounds them. But the interaction between planets and debris disks involves both orbital resonances and collisions among grains and rocks in the disks---difficult processes to model simultaneously. The author describes new 3-D models of debris disk dynamics, Drag-o-llision models, that incorporate both collisions and resonant trapping of dust for the first time. The author also discusses the implications of these models for coronagraphic imaging with Gemini and other telescopes.

  8. IMAGING DISCOVERY OF THE DEBRIS DISK AROUND HIP 79977

    SciTech Connect

    Thalmann, C.; Dominik, C.; Janson, M.; Brandt, T. D.; Knapp, G. R.; Buenzli, E.; Wisniewski, J. P.; Carson, J.; McElwain, M. W.; Currie, T.; Moro-Martin, A.; Abe, L.; Brandner, W.; Feldt, M.; Goto, M.; Hashimoto, J.; and others

    2013-02-01

    We present Subaru/HiCIAO H-band high-contrast images of the debris disk around HIP 79977, whose presence was recently inferred from an infrared excess. Our images resolve the disk for the first time, allowing characterization of its shape, size, and dust grain properties. We use angular differential imaging (ADI) to reveal the disk geometry in unpolarized light out to a radius of {approx}2'', as well as polarized differential imaging to measure the degree of scattering polarization out to {approx}1.''5. In order to strike a favorable balance between suppression of the stellar halo and conservation of disk flux, we explore the application of principal component analysis to both ADI and reference star subtraction. This allows accurate forward modeling of the effects of data reduction on simulated disk images, and thus direct comparison with the imaged disk. The resulting best-fit values and well-fitting intervals for the model parameters are a surface brightness power-law slope of S{sub out} = -3.2[ - 3.6, -2.9], an inclination of i = 84 Degree-Sign [81 Degree-Sign , 86 Degree-Sign ], a high Henyey-Greenstein forward-scattering parameter of g = 0.45[0.35, 0.60], and a non-significant disk-star offset of u = 3.0[ - 1.5, 7.5] AU = 24[ - 13, 61] mas along the line of nodes. Furthermore, the tangential linear polarization along the disk rises from {approx}10% at 0.''5 to {approx}45% at 1.''5. These measurements paint a consistent picture of a disk of dust grains produced by collisional cascades and blown out to larger radii by stellar radiation pressure.

  9. HUBBLE SPACE TELESCOPE OBSERVATIONS OF THE HD 202628 DEBRIS DISK

    SciTech Connect

    Krist, John E.; Bryden, Geoffrey; Stapelfeldt, Karl R.; Plavchan, Peter

    2012-08-15

    A ring-shaped debris disk around the G2V star HD 202628 (d = 24.4 pc) was imaged in scattered light at visible wavelengths using the coronagraphic mode of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The ring is inclined by {approx}64 Degree-Sign from face-on, based on the apparent major/minor axis ratio, with the major axis aligned along P.A. = 130 Degree-Sign . It has inner and outer radii (>50% maximum surface brightness) of 139 AU and 193 AU in the northwest ansae and 161 AU and 223 AU in the southeast ({Delta}r/r Almost-Equal-To 0.4). The maximum visible radial extent is {approx}254 AU. With mean surface brightness of V Almost-Equal-To 24 mag arcsec{sup -2}, this is the faintest debris disk observed to date in reflected light. The center of the ring appears offset from the star by {approx}28 AU (deprojected). An ellipse fit to the inner edge has an eccentricity of 0.18 and a = 158 AU. This offset, along with the relatively sharp inner edge of the ring, suggests the influence of a planetary-mass companion. There is a strong similarity with the debris ring around Fomalhaut, though HD 202628 is a more mature star with an estimated age of about 2 Gyr. We also provide surface brightness limits for nine other stars in our study with strong Spitzer excesses around which no debris disks were detected in scattered light (HD 377, HD 7590, HD 38858, HD 45184, HD 73350, HD 135599, HD 145229, HD 187897, and HD 201219).

  10. Hubble Space Telescope Observations of the HD 202628 Debris Disk

    NASA Technical Reports Server (NTRS)

    Krist, John E.; Stapelfeldt, Karl R.; Bryden, Geoffrey; Plavchan, Peter

    2012-01-01

    A ring-shaped debris disk around the G2V star HD 202628 (d = 24.4 pc) was imaged in scattered light at visible wavelengths using the coronagraphic mode of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The ring is inclined by approx.64deg from face-on, based on the apparent major/minor axis ratio, with the major axis aligned along PA = 130deg. It has inner and outer radii (> 50% maximum surface brightness) of 139 AU and 193 AU in the northwest ansae and 161 AU and 223 AU in the southeast ((Delta)r/r approx. = 0.4). The maximum visible radial extent is approx. 254 AU. With a mean surface brightnesses of V approx. = 24 mag arcsec.(sup -2), this is the faintest debris disk observed to date in reflected light. The center of the ring appears offset from the star by approx.28 AU (deprojected). An ellipse fit to the inner edge has an eccentricity of 0.18 and a = 158 AU. This offset, along with the relatively sharp inner edge of the ring, suggests the influence of a planetary-mass companion. There is a strong similarity with the debris ring around Fomalhaut, though HD 202628 is a more mature star with an estimated age of about 2 Gyr. We also provide surface brightness limits for nine other stars in our study with strong Spitzer excesses around which no debris disks were detected in scattered light (HD 377, HD 7590, HD 38858, HD 45184, HD 73350, HD 135599, HD 145229, HD 187897, and HD 201219).

  11. Debris Disks in Aggregate: Using Hubble Space Telescope Coronagraphic Imagery to Understand the Scattered-Light Disk Detection Rate

    NASA Technical Reports Server (NTRS)

    Grady, Carol A.

    2011-01-01

    Despite more than a decade of coronagraphic imaging of debris disk candidate stars, only 16 have been imaged in scattered light. Since imaged disks provide our best insight into processes which sculpt disks, and can provide signposts of the presence of giant planets at distances which would elude radial velocity and transit surveys, we need to understand under what conditions we detect the disks in scattered light, how these disks differ from the majority of debris disks, and how to increase the yield of disks which are imaged with 0.1" angular resolution. In this talk, I will review what we have learned from a shallow HSTINICMOS NIR survey of debris disks, and present first results from our on-going HST /STIS optical imaging of bright scattered-light disks.

  12. NEW DEBRIS DISK CANDIDATES AROUND 49 NEARBY STARS

    SciTech Connect

    Koerner, D. W.; Kim, S.; Trilling, D. E.; Larson, H.; Cotera, A.; Stapelfeldt, K. R.; Wahhaj, Z.; Fajardo-Acosta, S.; Padgett, D.; Backman, D.

    2010-02-10

    We present 49 new candidate debris disks that were detected around nearby stars with the Spitzer Space Telescope using the Multiband Imaging Photometer (MIPS) at 24 {mu}m (MIPS24) and 70 {mu}m (MIPS70). The survey sample was composed of stars within 25 pc of the Sun that were not previously observed by any other MIPS survey. Only stars with V < 9 were selected, corresponding to spectral types earlier than M0. MIPS24 integration times were chosen to detect the stellar photosphere at 10{sigma} levels or better. MIPS70 observations were designed to detect excess infrared emission from any star in the MIPS70 sample with a disk as luminous at that around {epsilon} Eridani. The resulting sample included over 436 nearby stars that were observed with both MIPS24 and MIPS70, plus an additional 198 observed only with MIPS24. Debris disk candidates were defined as targets where excess emission was detected at 3{sigma} levels or greater, and the ratio of observed flux density to expected photosphere emission was three standard deviations or more above the mean value for the sample. The detection rate implied by the resulting 29 MIPS24 candidates is 4.6%. A detection rate of 4.8% is implied by 21 MIPS70 candidates. The distribution of spectral types for stars identified as candidates resembles that of the general sample and yields strong evidence that debris-disk occurrence does not decrease for K dwarfs. Modeling of non-uniform sensitivity in the sample is required to interpret quantitative estimates of the overall detection frequency and will be presented in a future work.

  13. THE DEBRIS DISK AROUND {gamma} DORADUS RESOLVED WITH HERSCHEL

    SciTech Connect

    Broekhoven-Fiene, Hannah; Matthews, Brenda C.; Booth, Mark; Kavelaars, J. J.; Koning, Alice; Kennedy, Grant M.; Wyatt, Mark C.; Sibthorpe, Bruce; Lawler, Samantha M.; Qi, Chenruo; Su, Kate Y. L.; Rieke, George H.; Wilner, David J.; Greaves, Jane S.

    2013-01-01

    We present observations of the debris disk around {gamma} Doradus, an F1V star, from the Herschel Key Programme DEBRIS (Disc Emission via Bias-free Reconnaissance in the Infrared/Submillimetre). The disk is well resolved at 70, 100, and 160 {mu}m, resolved along its major axis at 250 {mu}m, detected but not resolved at 350 {mu}m, and confused with a background source at 500 {mu}m. It is one of our best resolved targets and we find it to have a radially broad dust distribution. The modeling of the resolved images cannot distinguish between two configurations: an arrangement of a warm inner ring at several AU (best fit 4 AU) and a cool outer belt extending from {approx}55 to 400 AU or an arrangement of two cool, narrow rings at {approx}70 AU and {approx}190 AU. This suggests that any configuration between these two is also possible. Both models have a total fractional luminosity of {approx}10{sup -5} and are consistent with the disk being aligned with the stellar equator. The inner edge of either possible configuration suggests that the most likely region to find planets in this system would be within {approx}55 AU of the star. A transient event is not needed to explain the warm dust's fractional luminosity.

  14. The Debris Disk around γ Doradus Resolved with Herschel

    NASA Astrophysics Data System (ADS)

    Broekhoven-Fiene, Hannah; Matthews, Brenda C.; Kennedy, Grant M.; Booth, Mark; Sibthorpe, Bruce; Lawler, Samantha M.; Kavelaars, J. J.; Wyatt, Mark C.; Qi, Chenruo; Koning, Alice; Su, Kate Y. L.; Rieke, George H.; Wilner, David J.; Greaves, Jane S.

    2013-01-01

    We present observations of the debris disk around γ Doradus, an F1V star, from the Herschel Key Programme DEBRIS (Disc Emission via Bias-free Reconnaissance in the Infrared/Submillimetre). The disk is well resolved at 70, 100, and 160 μm, resolved along its major axis at 250 μm, detected but not resolved at 350 μm, and confused with a background source at 500 μm. It is one of our best resolved targets and we find it to have a radially broad dust distribution. The modeling of the resolved images cannot distinguish between two configurations: an arrangement of a warm inner ring at several AU (best fit 4 AU) and a cool outer belt extending from ~55 to 400 AU or an arrangement of two cool, narrow rings at ~70 AU and ~190 AU. This suggests that any configuration between these two is also possible. Both models have a total fractional luminosity of ~10-5 and are consistent with the disk being aligned with the stellar equator. The inner edge of either possible configuration suggests that the most likely region to find planets in this system would be within ~55 AU of the star. A transient event is not needed to explain the warm dust's fractional luminosity.

  15. The dynamical structure of the HR8799 inner debris disk

    NASA Astrophysics Data System (ADS)

    Wittenmyer, Robert A.; Contro de Godoy, Bruna; Horner, Jonathan; Marshall, Jonathan P.

    2014-11-01

    The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar System where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanet dynamics and debris disc-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disc remains unknown, leaving a question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using University of New South Wales's Katana supercomputing facility to follow the dynamical evolution of a model inner disc comprising 250,000 particles for a period of 100 million years. These simulations will (1) characterise the extent and structure of the inner disk in detail and (2) provide the first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet(s) in the inner system.

  16. Fomalhaut's Debris Disk and Planet: Constraining the Mass of Formalhaut B from Disk Morphology

    NASA Technical Reports Server (NTRS)

    Chiang, E.; Kite, E.; Kalas, P.; Graham, J. R.; Clampin, M.

    2008-01-01

    Following the optical imaging of exoplanet candidate Fomalhaut b (Fom b), we present a numerical model of how Fomalhaut's debris disk is gravitationally shaped by a single interior planet. The model is simple, adaptable to other debris disks, and can be extended to accommodate multiple planets. If Fom b is the dominant perturber of the belt, then to produce the observed disk morphology it must have a mass M(sub pl) < 3M(sub J), an orbital semimajor axis a(sub pl) > 101.5AU, and an orbital eccentricity e(sub pl) = 0.11 - 0.13. These conclusions are independent of Fom b's photometry. To not disrupt the disk, a greater mass for Fom b demands a smaller orbit farther removed from the disk; thus, future astrometric measurement of Fom b's orbit, combined with our model of planet-disk interaction, can be used to determine the mass more precisely. The inner edge of the debris disk at a approximately equals 133AU lies at the periphery of Fom b's chaotic zone, and the mean disk eccentricity of e approximately equals 0.11 is secularly forced by the planet, supporting predictions made prior to the discovery of Fom b. However, previous mass constraints based on disk morphology rely on several oversimplifications. We explain why our constraint is more reliable. It is based on a global model of the disk that is not restricted to the planet's chaotic zone boundary. Moreover, we screen disk parent bodies for dynamical stability over the system age of approximately 100 Myr, and model them separately from their dust grain progeny; the latter's orbits are strongly affected by radiation pressure and their lifetimes are limited to approximately 0.1 Myr by destructive grain-grain collisions. The single planet model predicts that planet and disk orbits be apsidally aligned. Fomalhaut b's nominal space velocity does not bear this out, but the astrometric uncertainties are difficult to quantify. Even if the apsidal misalignment proves real, our calculated upper mass limit of 3 M(sub J) still

  17. Asteroid Belts in Debris Disk Twins: Vega and Fomalhaut

    NASA Astrophysics Data System (ADS)

    Su, Kate Y.; Rieke, G.

    2013-01-01

    Nearby debris disks have been playing an important role in our understanding the complexity of the underlying planetary architectures (planets, minor bodies and debris) since their first discovery by IRAS through infrared excesses. Among them, the two early-type stars, Vega and Fomalhaut, are similar in terms of mass, age, distance and global disk properties; therefore, they are often referred as “Debris Disk Twins”. Much attention has been focused on their large, cold Kuiper-belt-analog rings because they contain the majority of the left-over planetesimals and fine debris that covers a large surface area, making them readily detectable through infrared and submillimeter observations. We present Spitzer 10-35 μm spectroscopic data centered at both stars, and identify warm, unresolved excess emission in the close vicinity of Vega for the first time. The properties of the warm excess in Vega are further characterized with ancillary photometry in the mid-infrared using data probed area within ~5" diameter from the star and resolved images in the far-infrared and submillimeter wavelengths. The Vega warm excess shares many similar properties with the one found around Fomalhaut. The emission shortward of ~30 μm from both warm components is well described as a blackbody emission of ~170 K, just above the temperature at which water ice sublimates. Interestingly, two other systems, eps Eri and HR 8799, also show such an unresolved warm component using the same approach of combining imaging and mid-infrared spectroscopy. These warm components may be analogous to our asteroid belt, but of far greater mass (fractional luminosity of ~1e-5 - 1e-6). The dust characteristic temperature and tentative detections at submillimeter suggest the warm excess arises from a planetesimal ring placed near the ice line and presumably created by processes occurring near the equivalent location in other debris systems as well. In light of the current detection limits on the planetary

  18. DEBRIS DISKS OF MEMBERS OF THE BLANCO 1 OPEN CLUSTER

    SciTech Connect

    Stauffer, John R.; Noriega-Crespo, Alberto; Rebull, Luisa M.; James, David; Strom, Steven; Wolk, Scott; Carpenter, John M.; Barrado y Navascues, David; Backman, Dana; Cargile, P. A.

    2010-08-20

    We have used the Spitzer Space Telescope to obtain Multiband Imaging Photometer for Spitzer (MIPS) 24 {mu}m photometry for 37 members of the {approx}100 Myr old open cluster Blanco 1. For the brightest 25 of these stars (where we have 3{sigma} uncertainties less than 15%), we find significant mid-IR excesses for eight stars, corresponding to a debris disk detection frequency of about 32%. The stars with excesses include two A stars, four F dwarfs, and two G dwarfs. The most significant linkage between 24 {mu}m excess and any other stellar property for our Blanco 1 sample of stars is with binarity. Blanco 1 members that are photometric binaries show few or no detected 24 {mu}m excesses whereas a quarter of the apparently single Blanco 1 members do have excesses. We have examined the MIPS data for two other clusters of similar age to Blanco 1-NGC 2547 and the Pleiades. The AFGK photometric binary star members of both of these clusters also show a much lower frequency of 24 {mu}m excesses compared to stars that lie near the single-star main sequence. We provide a new determination of the relation between the V - K {sub s} color and K {sub s} - [24] color for main sequence photospheres based on Hyades members observed with MIPS. As a result of our analysis of the Hyades data, we identify three low mass Hyades members as candidates for having debris disks near the MIPS detection limit.

  19. THE FREQUENCY OF DEBRIS DISKS AT WHITE DWARFS

    SciTech Connect

    Barber, Sara D.; Patterson, Adam J.; Kilic, Mukremin; Leggett, S. K.; Dufour, P.; Bloom, J. S.; Starr, D. L.

    2012-11-20

    We present near- and mid-infrared photometry and spectroscopy from PAIRITEL, IRTF, and Spitzer of a metallicity-unbiased sample of 117 cool, hydrogen-atmosphere white dwarfs (WDs) from the Palomar-Green survey and find five with excess radiation in the infrared, translating to a 4.3{sup +2.7} {sub -1.2}% frequency of debris disks. This is slightly higher than, but consistent with the results of previous surveys. Using an initial-final mass relation, we apply this result to the progenitor stars of our sample and conclude that 1-7 M {sub Sun} stars have at least a 4.3% chance of hosting planets; an indirect probe of the intermediate-mass regime eluding conventional exoplanetary detection methods. Alternatively, we interpret this result as a limit on accretion timescales as a fraction of WD cooling ages; WDs accrete debris from several generations of disks for {approx}10 Myr. The average total mass accreted by these stars ranges from that of 200 km asteroids to Ceres-sized objects, indicating that WDs accrete moons and dwarf planets as well as solar system asteroid analogs.

  20. Binary Debris Disks: Follow-on Observations of Spitzer Discoveries

    NASA Astrophysics Data System (ADS)

    Stansberry, John; Haghighipour, Nader; Jensen, Eric; Kortenkamp, Stephen; Mathieu, Robert; Rieke, George; Stapelfeldt, Karl; Su, Katherine; Trilling, David

    2008-03-01

    We have completed a MIPS survey for debris disks in 63 A5-F5 main sequence binary systems having separations of 0 - 500 AU, placing the secondary within the planet-forming zone. All targets were detected at 24um; at 70um we observed 50 of the targets, detecting 50 of those at SNR > 3. A surprising result of the survey is that 18 of those systems (36%) display 70um emission in excess of the photospheres, a rate is larger than that seen for single stars of comparable age. The 9% excess rate we found at 24um is also high by that comparison. To explore this difference, we propose to complete the initial survey at 70um, and to refine the results for the systems that show excess emission. The systems lacking 70um data ~all have separations > 5 AU: completing the sample will balance the larger number of systems with 70um data and separations < 5AU. These data will provide the control sample for an approved MIPS cycle 4 survey of 50 close binaries, provide the link to existing results for single stars, and should turn up ~4 more debris disks. Our estimates for where the dust resides in these disk systems is crude, with typical errors on the distance between the stars and the dust of about one order of magnitude. We also propose to obtain IRS 7-38um spectra of 15 of the systems known to have excesses, and use the spectra to improve these uncertainties significantly. By modeling the shape of the emission spectrum, we will accurately locate the inner-edges of the disks. For circumbinary disks, the location of the inner-edge will provide tests of models for dynamical stability (of the dust parent bodies), and possibly provide evidence of planets on circumbinary orbits (if the inner-edge turns out to be well outside the region where it would be expected to be stable). For circumstellar disks, the location of the inner-edge may be diagnostic of the presence of planets on circumstellar orbits, if it is found to be well-removed from the star.

  1. The decay of debris disks around solar-type stars

    SciTech Connect

    Sierchio, J. M.; Rieke, G. H.; Su, K. Y. L.; Gáspár, Andras

    2014-04-10

    We present a Spitzer MIPS study of the decay of debris disk excesses at 24 and 70 μm for 255 stars of types F4-K2. We have used multiple tests, including consistency between chromospheric and X-ray activity and placement on the H-R diagram, to assign accurate stellar ages. Within this spectral type range, at 24 μm, 13.6% ± 2.8% of the stars younger than 1 Gyr have excesses at the 3σ level or more, whereas none of the older stars do, confirming previous work. At 70 μm, 22.5% ± 3.6% of the younger stars have excesses at ≥3σ significance, whereas only 4.7{sub −2.2}{sup +3.7}% of the older stars do. To characterize the far-infrared behavior of debris disks more robustly, we doubled the sample by including stars from the DEBRIS and DUNES surveys. For the F4-K4 stars in this combined sample, there is only a weak (statistically not significant) trend in the incidence of far-infrared excess with spectral type (detected fractions of 21.9{sub −4.3}{sup +4.8}%, late F; 16.5{sub −3.3}{sup +3.9}%, G; and 16.9{sub −5.0}{sup +6.3}%, early K). Taking this spectral type range together, there is a significant decline between 3 and 4.5 Gyr in the incidence of excesses, with fractional luminosities just under 10{sup –5}. There is an indication that the timescale for decay of infrared excesses varies roughly inversely with the fractional luminosity. This behavior is consistent with theoretical expectations for passive evolution. However, more excesses are detected around the oldest stars than are expected from passive evolution, suggesting that there is late-phase dynamical activity around these stars.

  2. Formation of Sharp Eccentric Rings in Debris Disks with Gas but Without Planets

    NASA Technical Reports Server (NTRS)

    Lyra, W.; Kuchner, M.

    2013-01-01

    'Debris disks' around young stars (analogues of the Kuiper Belt in our Solar System) show a variety of non-trivial structures attributed to planetary perturbations and used to constrain the properties of those planets. However, these analyses have largely ignored the fact that some debris disks are found to contain small quantities of gas, a component that all such disks should contain at some level. Several debris disks have been measured with a dust-to-gas ratio of about unity, at which the effect of hydrodynamics on the structure of the disk cannot be ignored. Here we report linear and nonlinear modelling that shows that dust-gas interactions can produce some of the key patterns attributed to planets. We find a robust clumping instability that organizes the dust into narrow, eccentric rings, similar to the Fomalhaut debris disk. The conclusion that such disks might contain planets is not necessarily required to explain these systems.

  3. Formation of sharp eccentric rings in debris disks with gas but without planets.

    PubMed

    Lyra, W; Kuchner, M

    2013-07-11

    'Debris disks' around young stars (analogues of the Kuiper Belt in our Solar System) show a variety of non-trivial structures attributed to planetary perturbations and used to constrain the properties of those planets. However, these analyses have largely ignored the fact that some debris disks are found to contain small quantities of gas, a component that all such disks should contain at some level. Several debris disks have been measured with a dust-to-gas ratio of about unity, at which the effect of hydrodynamics on the structure of the disk cannot be ignored. Here we report linear and nonlinear modelling that shows that dust-gas interactions can produce some of the key patterns attributed to planets. We find a robust clumping instability that organizes the dust into narrow, eccentric rings, similar to the Fomalhaut debris disk. The conclusion that such disks might contain planets is not necessarily required to explain these systems. PMID:23846656

  4. Formation of sharp eccentric rings in debris disks with gas but without planets.

    PubMed

    Lyra, W; Kuchner, M

    2013-07-11

    'Debris disks' around young stars (analogues of the Kuiper Belt in our Solar System) show a variety of non-trivial structures attributed to planetary perturbations and used to constrain the properties of those planets. However, these analyses have largely ignored the fact that some debris disks are found to contain small quantities of gas, a component that all such disks should contain at some level. Several debris disks have been measured with a dust-to-gas ratio of about unity, at which the effect of hydrodynamics on the structure of the disk cannot be ignored. Here we report linear and nonlinear modelling that shows that dust-gas interactions can produce some of the key patterns attributed to planets. We find a robust clumping instability that organizes the dust into narrow, eccentric rings, similar to the Fomalhaut debris disk. The conclusion that such disks might contain planets is not necessarily required to explain these systems.

  5. Herschel detects oxygen in the β Pictoris debris disk

    NASA Astrophysics Data System (ADS)

    Brandeker, A.; Cataldi, G.; Olofsson, G.; Vandenbussche, B.; Acke, B.; Barlow, M. J.; Blommaert, J. A. D. L.; Cohen, M.; Dent, W. R. F.; Dominik, C.; Di Francesco, J.; Fridlund, M.; Gear, W. K.; Glauser, A. M.; Greaves, J. S.; Harvey, P. M.; Heras, A. M.; Hogerheijde, M. R.; Holland, W. S.; Huygen, R.; Ivison, R. J.; Leeks, S. J.; Lim, T. L.; Liseau, R.; Matthews, B. C.; Pantin, E.; Pilbratt, G. L.; Royer, P.; Sibthorpe, B.; Waelkens, C.; Walker, H. J.

    2016-06-01

    The young star β Pictoris is well known for its dusty debris disk produced through collisional grinding of planetesimals, kilometre-sized bodies in orbit around the star. In addition to dust, small amounts of gas are also known to orbit the star; this gas is likely the result of vaporisation of violently colliding dust grains. The disk is seen edge on and from previous absorption spectroscopy we know that the gas is very rich in carbon relative to other elements. The oxygen content has been more difficult to assess, however, with early estimates finding very little oxygen in the gas at a C/O ratio that is 20 × higher than the cosmic value. A C/O ratio that high is difficult to explain and would have far-reaching consequences for planet formation. Here we report on observations by the far-infrared space telescope Herschel, using PACS, of emission lines from ionised carbon and neutral oxygen. The detected emission from C+ is consistent withthat previously reported observed by the HIFI instrument on Herschel, while the emission from O is hard to explain without assuming a higher density region in the disk, perhaps in the shape of a clump or a dense torus required to sufficiently excite the O atoms. A possible scenario is that the C/O gas is produced by the same process responsible for the CO clump recently observed by the Atacama Large Millimeter/submillimeter Array in the disk and that the redistribution of the gas takes longer than previously assumed. A more detailed estimate of the C/O ratio and the mass of O will have to await better constraints on the C/O gas spatial distribution. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  6. The mid-infrared spectrum of the zodiacal and exozodiacal light

    NASA Astrophysics Data System (ADS)

    Reach, William T.; Morris, Patrick; Boulanger, François; Okumura, Koryo

    2003-08-01

    change such that dust further from the Sun has a weaker silicate feature. To compare the properties of zodiacal dust to dust around other main sequence stars, we reanalyzed the exozodiacal light spectrum for β Pic to derive the shape of its silicate feature. The zodiacal and exozodiacal spectra are very different. The exozodiacal spectra are dominated by cold dust, with emission peaking in the far-infrared, while the zodiacal spectrum peaks around 20 μm. We removed the debris disk continuum from the spectra by fitting a blackbody with a different temperature for each aperture (ranging from 3.7″ to 27″); the resulting silicate spectra for β Pic are identical for all apertures, indicating that the silicate feature arises close to the star. The shape of the silicate feature from β Pic is nearly identical to that derived from the ISO spectrum of 51 Oph; both exozodiacal features are very different from that of the zodiacal light. The exozodiacal features are roughly triangular, peaking at 10.3 μm, while the zodiacal feature is more boxy, indicating a different mineralogy.

  7. Forming Gaps in Debris Disks with Fewer Planets via Planet Migration

    NASA Astrophysics Data System (ADS)

    Morrison, Sarah J.; Kratter, Kaitlin M.

    2016-10-01

    Debris disks across a wide range of ages can possess wide gaps of several AU or more; these gaps have been attributed to the presence of multiple planets. While at least two planets are likely needed for maintaining the edges of such gaps, large gaps may require more than two in more dynamically packed configurations to be able to have cleared material within the gap in the present day. As an alternative to currently packed planets occupying gaps in debris disks, we assess whether planetesimal and dynamical instability-driven planet migration could produce wide gaps with lower mass, fewer planets on relevant timescales to be consistent with the observed properties of debris disk systems. We also discuss implications for the disk properties in which these mechanisms could operate within the broader evolutionary context linking planets, debris disks, and the protoplanetary disks from which they originated.

  8. Predictions for shepherding planets in scattered light images of debris disks

    SciTech Connect

    Rodigas, Timothy J.; Hinz, Philip M.; Malhotra, Renu

    2014-01-01

    Planets can affect debris disk structure by creating gaps, sharp edges, warps, and other potentially observable signatures. However, there is currently no simple way for observers to deduce a disk-shepherding planet's properties from the observed features of the disk. Here we present a single equation that relates a shepherding planet's maximum mass to the debris ring's observed width in scattered light, along with a procedure to estimate the planet's eccentricity and minimum semimajor axis. We accomplish this by performing dynamical N-body simulations of model systems containing a star, a single planet, and an exterior disk of parent bodies and dust grains to determine the resulting debris disk properties over a wide range of input parameters. We find that the relationship between planet mass and debris disk width is linear, with increasing planet mass producing broader debris rings. We apply our methods to five imaged debris rings to constrain the putative planet masses and orbits in each system. Observers can use our empirically derived equation as a guide for future direct imaging searches for planets in debris disk systems. In the fortuitous case of an imaged planet orbiting interior to an imaged disk, the planet's maximum mass can be estimated independent of atmospheric models.

  9. A Study on the Characteristics of the Structure of Vega's Debris Disk

    NASA Astrophysics Data System (ADS)

    Lu, Tao; Ji, Jiang-hui

    2013-10-01

    The clumpy structure in the Vega's debris disk was reported at millimeter wavelengths previously, and attributed to the concentration of dust grains trapped in resonances with a potential high-eccentricity planet. However, current imaging at multi-wavelengths with higher sensitivity indicates that the Vega's debris disk has a smooth structure. But a planet orbiting Vega could not be neglected, and the present-day observations may place a severe constraint on the orbital parameters for the potential planet. Herein, we utilize the modi- fied MERCURY codes to numerically simulate the Vega system, which consists of a debris disk and a planet. In our simulations, the initial inner and outer boundaries of the debris disk are assumed to be 80 AU and 120 AU, respectively. The dust grains in the disk have the sizes from 10 μm to 100 μm, and the nearly coplanar orbits. From the outcomes, we show that the evolution of debris disk is consistent with recent observations, if there is no planet orbiting Vega. However, if Vega owns a planet with a high eccentricity (e.g., e = 0.6), the planet's semi- major axis cannot be larger than 60 AU, otherwise, an aggregation phenomenon will occur in the debris disk due to the existence of the postulated planet. In addition, the 2:1 mean motion resonances may play a significant role in forming the structure of debris disk.

  10. Asteroid Belts in Debris Disk Twins: Vega and Fomalhaut

    NASA Technical Reports Server (NTRS)

    Su, Kate Y. L.; Rieke, George H.; Malhortra, Renu; Stapelfeldt, Karl R.; Hughes, A. Meredith; Bonsor, Amy; Wilner, David J.; Balog, Zoltan; Watson, Dan M.; Werner, Michael W.; Misselt, Karl A.

    2013-01-01

    Vega and Fomalhaut are similar in terms of mass, ages, and global debris disk properties; therefore, they are often referred to as debris disk twins. We present Spitzer 10-35 micrometers spectroscopic data centered at both stars and identify warm, unresolved excess emission in the close vicinity of Vega for the first time. The properties of the warm excess in Vega are further characterized with ancillary photometry in the mid-infrared and resolved images in the far-infrared and submillimeter wavelengths. The Vega warm excess shares many similar properties with the one found around Fomalhaut. The emission shortward of approximately 30 micrometers from both warm components is well described as a blackbody emission of approximately 170 K. Interestingly, two other systems, Eri and HR 8799, also show such an unresolved warm dust using the same approach. These warm components may be analogous to the solar system s zodiacal dust cloud, but of far greater mass (fractional luminosity of approximately 10(exp-5) to 10(exp-6) compared to 10(exp-8) to 10(exp-7). The dust temperature and tentative detections in the submillimeter suggest that the warm excess arises from dust associated with a planetesimal ring located near the water-frost line and presumably created by processes occurring at similar locations in other debris systems as well. We also review the properties of the 2 micrometers hot excess around Vega and Fomalhaut, showing that the dust responsible for the hot excess is not spatially associated with the dust we detected in the warm belt.We suggest it may arise from hot nano grains trapped in the magnetic field of the star. Finally, the separation between the warm and cold belt is rather large with an orbital ratio greater than or approximately 10 in all four systems. In light of the current upper limits on the masses of planetary objects and the large gap, we discuss the possible implications for their underlying planetary architecture and suggest that multiple, low

  11. ASTEROID BELTS IN DEBRIS DISK TWINS: VEGA AND FOMALHAUT

    SciTech Connect

    Su, Kate Y. L.; Rieke, George H.; Misselt, Karl A.; Malhotra, Renu; Stapelfeldt, Karl R.; Hughes, A. Meredith; Bonsor, Amy; Balog, Zoltan; Watson, Dan M.; Werner, Michael W.

    2013-02-15

    Vega and Fomalhaut are similar in terms of mass, ages, and global debris disk properties; therefore, they are often referred to as 'debris disk twins'. We present Spitzer 10-35 {mu}m spectroscopic data centered at both stars and identify warm, unresolved excess emission in the close vicinity of Vega for the first time. The properties of the warm excess in Vega are further characterized with ancillary photometry in the mid-infrared and resolved images in the far-infrared and submillimeter wavelengths. The Vega warm excess shares many similar properties with the one found around Fomalhaut. The emission shortward of {approx}30 {mu}m from both warm components is well described as a blackbody emission of {approx}170 K. Interestingly, two other systems, {epsilon} Eri and HR 8799, also show such an unresolved warm dust using the same approach. These warm components may be analogous to the solar system's zodiacal dust cloud, but of far greater mass (fractional luminosity of {approx}10{sup -5} to 10{sup -6} compared to 10{sup -8} to 10{sup -7}). The dust temperature and tentative detections in the submillimeter suggest that the warm excess arises from dust associated with a planetesimal ring located near the water-frost line and presumably created by processes occurring at similar locations in other debris systems as well. We also review the properties of the 2 {mu}m hot excess around Vega and Fomalhaut, showing that the dust responsible for the hot excess is not spatially associated with the dust we detected in the warm belt. We suggest it may arise from hot nano grains trapped in the magnetic field of the star. Finally, the separation between the warm and cold belt is rather large with an orbital ratio {approx}>10 in all four systems. In light of the current upper limits on the masses of planetary objects and the large gap, we discuss the possible implications for their underlying planetary architecture and suggest that multiple, low-mass planets likely reside between the

  12. Exozodiacal Dust Workshop

    NASA Technical Reports Server (NTRS)

    Backman, D. E. (Editor); Caroff, L. J. (Editor); Sandford, S. A. (Editor); Wooden, D. H. (Editor)

    1998-01-01

    The purpose of the workshop was to understand what effect circumstellar dust clouds will have on NASA's proposed Terrestrial Planet Finder (TPF) mission's ability to search for terrestrial-sized planets orbiting stars in the solar neighborhood. The workshop participants reviewed the properties of TPF, summarized what is known about the local zodiacal cloud and about exozodiacal clouds, and determined what additional knowledge must be obtained to help design TPF for maximum effectiveness within its cost constraint. Recommendations were made for ways to obtain that additional knowledge, at minimum cost. The workshop brought together approximately 70 scientists, from four different countries. The active participants included astronomers involved in the study of the local zodiacal cloud, in the formation of stars and planetary systems, and in the technologies and techniques of ground- and space-based infrared interferometry. During the course of the meeting, 15 invited talks and 20 contributed poster papers were presented, and there were four working sessions. This is a collection of the invited talks, contributed poster papers, and summaries of the working sessions.

  13. A Unique Gas-Rich Debris Disk: Herschel Imaging and Spectroscopy of 49 Ceti

    NASA Technical Reports Server (NTRS)

    Roberge, Aki

    2012-01-01

    Gas-poor debris disks represent a fundamentally different class of circumstellar disk than gas-rich protoplanetary disks. Their gas probably originates from the same source as the dust, i.e. planetesimal destruction, but the low gas densities make it difficult to detect. So far, Herschel has detected far-IR gas emission from only one or two debris disks, Beta Pictoris being one of them. Here we present Herschel GASPS observations of a well-known debris disk system, 49 Ceti. The dust disk is spatially resolved in thermal emission at 70 _m. Most interestingly, weak far-IR gas emission is detected. Preliminary modeling suggests that reconciling the sub-mm CO emission seen from this system with the far-IR gas detection and upper limits requires a low gas-to-dust ratio and possibly an unusual gas composition.

  14. Silica Debris Disk Evidence for Giant Planet Forming Impacts

    NASA Astrophysics Data System (ADS)

    Lisse, C.

    2014-04-01

    Giant impacts are major formation events in the history of our solar system. The final assembly of the planets, as we understand it, had to include massive fast collision events as the planets grew to objects with large escape velocities or in regions of high Keplerian velocities (Chambers 2004; Kenyon & Bromley 2004a,b, 2006; Fegley & Schaefer 2005). These massive impact events should create large amounts of glassy silica material derived from the rapid melting, vaporization, and refreezing of normal silicate rich primitive rocky material. We report here the detection of 4 bright silica-rich debris disks in the Spitzer IRS spectral archive, and the possible identification of 7 others. The stellar types of the system primaries span from A5V to G0V, their ages are 10 - 100 Myr, and the dust is warm, 280 - 480 K, and is located between 1.5 and 6 AU, well inside the systems' terrestrial planet regions. The minimum amount of detected 0.1 - 20 dust mass ranges from 10^21 - 10^23 kg; assuming < 10% dust formation efficiency (Benz 2009, 2011) this implies collisions involving impactors massing at least 10^22 - 10^24 kg, i.e. from Moon to Earth mass. We find possible trends in the mineralogy of the silica, with predominantly amorphous silica found in the 2 younger systems, and crystalline silica in the older systems. We speculate this is due higher velocity impacts found in younger, hotter systems, coupled with the effects of energetic photon annealing of small amorphous silica grains. All of these measures are consistent with the creation of silica rich rubble, or construction debris, during the terrestrial planet formation era of giant impacts.

  15. A Study on the Characteristics of the Structure of Vega's Debris Disk

    NASA Astrophysics Data System (ADS)

    Lu, T.; Ji, J. H.

    2013-03-01

    Clumpy structure in the Vega's debris disk has been previously reported at millimeter wavelengths and attributed to the concentrations of dust grains trapped in resonances with a potential planet. However, current imaging at multi-wavelengths with higher sensitivity is against the former observed structure. The disk is now revealed to have a smooth structure. A planet orbiting Vega could not be neglected,but the present-day observations may place a severe constraint on the orbital parameters for the potential planet. Herein, we utilize modified MERCURY codes to numerically simulate Vega system, consisting of debris disk and a planet. In our simulations, the initial inner and outer boundaries of the debris disk are assumed to be 80~AU and 120~AU, respectively. The radius of dust grains distributes in the range from 10 μm to 100 μm, in nearly coplanar orbits. From the outcomes, we show that the evolution of debris disk is consistent with recent observations, if there is no planet orbiting Vega. However, if Vega owns a planet with a high eccentricity (e.g., e=0.6), the planetary semi-major axis cannot be larger than 60~AU, otherwise, the structure of debris disk will congregate due to the existence of the postulated planet. The 2:1 mean motion resonances may play a significant role in sculpting the debris disk.

  16. COLLISIONAL AND LUMINOSITY EVOLUTION OF A DEBRIS DISK: THE CASE OF HD 12039

    SciTech Connect

    Weidenschilling, S. J.

    2010-10-20

    Extrasolar debris disks that are bright enough to be observed are dense enough to be collision-dominated; i.e., the small grains that produce their infrared excess have collisional lifetimes shorter than their Poynting-Robertson decay times. This paper describes a numerical code for the modeling of such disks, including accretion and gravitational stirring as well as disruptive collisions. A constraint relating the mass of a debris disk and the sizes of the largest embedded bodies to its luminosity is demonstrated. The collisional code is applied to the debris disk around HD 12039, which has been intensively observed by the Spitzer Space Telescope. The evolution in time of the disk's luminosity is computed for a range of initial disk masses and planetesimal sizes. The luminosity at a given age depends on both the initial disk mass and the initial size of the planetesimals. Luminosity decays more rapidly for massive disks due to the combination of collisional depletion of small bodies and their accretion by bodies too large to contribute to dust production. Disks with low initial masses evolve slowly and can maintain their luminosities for {approx} Gyr timescales. This behavior may explain the lack of correlation between stellar metallicity and the abundance of debris disks.

  17. HD 100453: A Link Between Gas-Rich Protoplanetary Disks and Gas-Poor Debris Disks

    NASA Astrophysics Data System (ADS)

    Collins, K. A.; Grady, C. A.; Hamaguchi, K.; Wisniewski, J. P.; Brittain, S.; Sitko, M.; Carpenter, W. J.; Williams, J. P.; Mathews, G. S.; Williger, G. M.; van Boekel, R.; Carmona, A.; Henning, Th.; van den Ancker, M. E.; Meeus, G.; Chen, X. P.; Petre, R.; Woodgate, B. E.

    2009-05-01

    HD 100453 has an IR spectral energy distribution (SED) which can be fit with a power law plus a blackbody. Previous analysis of the SED suggests that the system is a young Herbig Ae star with a gas-rich, flared disk. We reexamine the evolutionary state of the HD 100453 system by refining its age (based on a candidate low-mass companion) and by examining limits on the disk extent, mass accretion rate, and gas content of the disk environment. We confirm that HD 100453B is a common proper motion companion to HD 100453A, with a spectral type of M4.0V-M4.5V, and derive an age of 10 ± 2 Myr. We find no evidence of mass accretion onto the star. Chandra ACIS-S imagery shows that the Herbig Ae star has L x/L bol and an X-ray spectrum similar to nonaccreting β Pic Moving Group early F stars. Moreover, the disk lacks the conspicuous Fe II emission and excess FUV continuum seen in spectra of actively accreting Herbig Ae stars, and from the FUV continuum, we find the accretion rate is < 1.4 × 10-9 M sun yr-1. A sensitive upper limit to the CO J = 3-2 intensity indicates that the gas in the outer disk is likely optically thin. Assuming a [CO]/[H2] abundance of 1 × 10-4 and a depletion factor of 103, we find that the mass of cold molecular gas is less than ~0.33 M J and that the gas-to-dust ratio is no more than ~4:1 in the outer disk. The combination of a high fractional IR excess luminosity, a relatively old age, an absence of accretion signatures, and an absence of detectable circumstellar molecular gas suggests that the HD 100453 system is in an unusual state of evolution between a gas-rich protoplanetary disk and a gas-poor debris disk.

  18. HD 100453: A LINK BETWEEN GAS-RICH PROTOPLANETARY DISKS AND GAS-POOR DEBRIS DISKS

    SciTech Connect

    Collins, K. A.; Williger, G. M.; Grady, C. A. E-mail: williger@physics.louisville.edu

    2009-05-20

    HD 100453 has an IR spectral energy distribution (SED) which can be fit with a power law plus a blackbody. Previous analysis of the SED suggests that the system is a young Herbig Ae star with a gas-rich, flared disk. We reexamine the evolutionary state of the HD 100453 system by refining its age (based on a candidate low-mass companion) and by examining limits on the disk extent, mass accretion rate, and gas content of the disk environment. We confirm that HD 100453B is a common proper motion companion to HD 100453A, with a spectral type of M4.0V-M4.5V, and derive an age of 10 {+-} 2 Myr. We find no evidence of mass accretion onto the star. Chandra ACIS-S imagery shows that the Herbig Ae star has L {sub x}/L {sub bol} and an X-ray spectrum similar to nonaccreting {beta} Pic Moving Group early F stars. Moreover, the disk lacks the conspicuous Fe II emission and excess FUV continuum seen in spectra of actively accreting Herbig Ae stars, and from the FUV continuum, we find the accretion rate is < 1.4 x 10{sup -9} M {sub sun} yr{sup -1}. A sensitive upper limit to the CO J = 3-2 intensity indicates that the gas in the outer disk is likely optically thin. Assuming a [CO]/[H{sub 2}] abundance of 1 x 10{sup -4} and a depletion factor of 10{sup 3}, we find that the mass of cold molecular gas is less than {approx}0.33 M {sub J} and that the gas-to-dust ratio is no more than {approx}4:1 in the outer disk. The combination of a high fractional IR excess luminosity, a relatively old age, an absence of accretion signatures, and an absence of detectable circumstellar molecular gas suggests that the HD 100453 system is in an unusual state of evolution between a gas-rich protoplanetary disk and a gas-poor debris disk.

  19. A SPITZER INFRARED SPECTROGRAPH STUDY OF DEBRIS DISKS AROUND PLANET-HOST STARS

    SciTech Connect

    Dodson-Robinson, Sarah E.; Beichman, C. A.; Carpenter, John M.; Bryden, Geoffrey

    2011-01-15

    Since giant planets scatter planetesimals within a few tidal radii of their orbits, the locations of existing planetesimal belts indicate regions where giant planet formation failed in bygone protostellar disks. Infrared observations of circumstellar dust produced by colliding planetesimals are therefore powerful probes of the formation histories of known planets. Here we present new Spitzer infrared spectrograph (IRS) spectrophotometry of 111 solar-type stars, including 105 planet hosts. Our observations reveal 11 debris disks, including two previously undetected debris disks orbiting HD 108874 and HD 130322. Combining the 32 {mu}m spectrophotometry with previously published MIPS photometry, we find that the majority of debris disks around solar-type stars have temperatures in the range 60 {approx}< T{sub dust} {approx}< 100 K. Assuming a dust temperature T{sub dust} = 70 K, which is representative of the nine debris disks detected by both IRS and MIPS, debris rings surrounding Sun-like stars orbit between 15 and 240 AU depending on the mean particle size. Our observations imply that the planets detected by radial-velocity searches formed within 240 AU of their parent stars. If any of the debris disks studied here have mostly large, blackbody emitting grains, their companion giant planets must have formed in a narrow region between the ice line and 15 AU.

  20. Debris Disks in the Scorpius–Centaurus OB Association Resolved by ALMA

    NASA Astrophysics Data System (ADS)

    Lieman-Sifry, Jesse; Hughes, A. Meredith; Carpenter, John M.; Gorti, Uma; Hales, Antonio; Flaherty, Kevin M.

    2016-09-01

    We present a CO(2-1) and 1240 μm continuum survey of 23 debris disks with spectral types B9-G1, observed at an angular resolution of 0.″5–1″ with the Atacama Large Millimeter/Submillimeter Array (ALMA). The sample was selected for large infrared excess and age ˜10 Myr, to characterize the prevalence of molecular gas emission in young debris disks. We identify three CO-rich debris disks, plus two additional tentative (3σ) CO detections. Twenty disks were detected in the continuum at the >3σ level. For the 12 disks in the sample that are spatially resolved by our observations, we perform an independent analysis of the interferometric continuum visibilities to constrain the basic dust disk geometry, as well as a simultaneous analysis of the visibilities and broadband spectral energy distribution to constrain the characteristic grain size and disk mass. The gas-rich debris disks exhibit preferentially larger outer radii in their dust disks, and a higher prevalence of characteristic grain sizes smaller than the blowout size. The gas-rich disks do not exhibit preferentially larger dust masses, contrary to expectations for a scenario in which a higher cometary destruction rate would be expected to result in a larger mass of both CO and dust. The three debris disks in our sample with strong CO detections are all around A stars: the conditions in disks around intermediate-mass stars appear to be the most conducive to the survival or formation of CO.

  1. Debris Disks in the Scorpius-Centaurus OB Association Resolved by ALMA

    NASA Astrophysics Data System (ADS)

    Lieman-Sifry, Jesse; Hughes, A. Meredith; Carpenter, John M.; Gorti, Uma; Hales, Antonio; Flaherty, Kevin M.

    2016-09-01

    We present a CO(2-1) and 1240 μm continuum survey of 23 debris disks with spectral types B9-G1, observed at an angular resolution of 0.″5-1″ with the Atacama Large Millimeter/Submillimeter Array (ALMA). The sample was selected for large infrared excess and age ˜10 Myr, to characterize the prevalence of molecular gas emission in young debris disks. We identify three CO-rich debris disks, plus two additional tentative (3σ) CO detections. Twenty disks were detected in the continuum at the >3σ level. For the 12 disks in the sample that are spatially resolved by our observations, we perform an independent analysis of the interferometric continuum visibilities to constrain the basic dust disk geometry, as well as a simultaneous analysis of the visibilities and broadband spectral energy distribution to constrain the characteristic grain size and disk mass. The gas-rich debris disks exhibit preferentially larger outer radii in their dust disks, and a higher prevalence of characteristic grain sizes smaller than the blowout size. The gas-rich disks do not exhibit preferentially larger dust masses, contrary to expectations for a scenario in which a higher cometary destruction rate would be expected to result in a larger mass of both CO and dust. The three debris disks in our sample with strong CO detections are all around A stars: the conditions in disks around intermediate-mass stars appear to be the most conducive to the survival or formation of CO.

  2. OT2_amoor_4: A census of debris disks in nearby young moving groups with Herschel.

    NASA Astrophysics Data System (ADS)

    Moór, A.

    2011-09-01

    Nearly all young stars harbour circumstellar disks, that serve as the reservoir for mass accretion onto the star, and later become the birthplace of planetary systems. After the disappearance of the gas component from the disk a dusty debris disk is formed that is believed to mark the location of the planetesimal belt as well. For outlining the evolution of such debris disks traditionally open clusters and field stars were studied, however we argue that the recently discovered young moving groups are more suitable objects for such analyses, due to their proximity and good coverage of the first 50 Myr period of the planetary system evolution. In this proposal we request 70/160 um Herschel/PACS photometric observations for so-far unobserved moving group members. These observations will provide a complete coverage of all known members within 80 pc of five nearby young moving groups (beta Pic Moving Group, Tucana-Horologium, Carina, Columba, and Argus), in the A to K spectral range. Based on the new observations we will identify new debris disks, characterize the disk population within individual moving groups, and study disk evolution by comparing the groups of different ages. The results will be used to verify predictions of the self-stirring model of the evolution of planetesimal disks. We will also compare the properties of debris disks in groups of the same age, looking for additional 'environmental' parameters that affect disk structure over a whole moving group. Our study will be a significant contribution to the census of debris disks in young moving groups, increasing the number of observed sources by a factor of 1.5. Since Spitzer could perform only a limited census and the so-far approved Herschel programs added very few additional moving group obervations, our programme is expected to have a high legacy value.

  3. Coronagraphic Imaging of Debris Disks from a High Altitude Balloon Platform

    NASA Technical Reports Server (NTRS)

    Unwin, Stephen; Traub, Wesley; Bryden, Geoffrey; Brugarolas, Paul; Chen, Pin; Guyon, Olivier; Hillenbrand, Lynne; Kasdin, Jeremy; Krist, John; Macintosh, Bruce; Mawet, Dimitri; Mennesson, Bertrand; Moody, Dwight; Roberts, Lewis C. Jr; Stapelfeldt, Karl; Stuchlik, David; Trauger, John; Vasisht, Gautam

    2012-01-01

    Debris disks around nearby stars are tracers of the planet formation process, and they are a key element of our understanding of the formation and evolution of extrasolar planetary systems. With multi-color images of a significant number of disks, we can probe important questions: can we learn about planetary system evolution; what materials are the disks made of; and can they reveal the presence of planets? Most disks are known to exist only through their infrared flux excesses as measured by the Spitzer Space Telescope, and through images measured by Herschel. The brightest, most extended disks have been imaged with HST, and a few, such as Fomalhaut, can be observed using ground-based telescopes. But the number of good images is still very small, and there are none of disks with densities as low as the disk associated with the asteroid belt and Edgeworth-Kuiper belt in our own Solar System. Direct imaging of disks is a major observational challenge, demanding high angular resolution and extremely high dynamic range close to the parent star. The ultimate experiment requires a space-based platform, but demonstrating much of the needed technology, mitigating the technical risks of a space-based coronagrap, and performing valuable measurements of circumstellar debris disks, can be done from a high-altitude balloon platform. In this paper we present a balloon-borne telescope experiment based on the Zodiac II design that would undertake compelling studies of a sample of debris disks.

  4. Coronagraphic Imaging of Debris Disks from a High Altitude Balloon Platform

    NASA Technical Reports Server (NTRS)

    Unwin, Stephen; Traub, Wesley; Bryden, Geoffrey; Brugarolas, Paul; Chen, Pin; Guyon, Olivier; Hillenbrand, Lynne; Krist, John; Macintosh, Bruce; Mawet, Dimitri; Mennesson, Bertrand; Moody, Dwight; Roberts, Lewis C., Jr.; Stapelfeldt, Karl; Stuchlik, David; Trauger, John; Vasisht, Gautam

    2012-01-01

    Debris disks around nearby stars are tracers of the planet formation process, and they are a key element of our understanding of the formation and evolution of extrasolar planetary systems. With multi-color images of a significant number of disks, we can probe important questions: can we learn about planetary system evolution; what materials are the disks made of; and can they reveal the presence of planets? Most disks are known to exist only through their infrared flux excesses as measured by the Spitzer Space Telescope, and through images measaured by Herschel. The brightest, most extended disks have been imaged with HST, and a few, such as Fomalhaut, can be observed using ground-based telescopes. But the number of good images is still very small, and there are none of disks with densities as low as the disk associated with the asteroid belt and Edgeworth-Kuiper belt in our own Solar System. Direct imaging of disks is major observational challenge, demanding high angular resolution and extremely high dynamic range close to the parent star. The ultimate experiment requires a space-based platform, but demonstrating much of the needed technology, mitigating the technical risks of a space-based coronagraph, and performing valuable measurements of circumstellar debris disks, can be done from a high-altitude balloon platform. In this paper we present a balloon-borne telescope concept based on the Zodiac II design that could undertake compelling studies of a sample of debris disks.

  5. THE SPITZER INFRARED SPECTROGRAPH DEBRIS DISK CATALOG. I. CONTINUUM ANALYSIS OF UNRESOLVED TARGETS

    SciTech Connect

    Chen, Christine H.; Mittal, Tushar; Kuchner, Marc; Forrest, William J.; Watson, Dan M.; Lisse, Carey M.; Manoj, P.; Sargent, Benjamin A.

    2014-04-01

    During the Spitzer Space Telescope cryogenic mission, Guaranteed Time Observers, Legacy Teams, and General Observers obtained Infrared Spectrograph (IRS) observations of hundreds of debris disk candidates. We calibrated the spectra of 571 candidates, including 64 new IRAS and Multiband Imaging Photometer for Spitzer (MIPS) debris disks candidates, modeled their stellar photospheres, and produced a catalog of excess spectra for unresolved debris disks. For 499 targets with IRS excess but without strong spectral features (and a subset of 420 targets with additional MIPS 70 μm observations), we modeled the IRS (and MIPS data) assuming that the dust thermal emission was well-described using either a one- or two-temperature blackbody model. We calculated the probability for each model and computed the average probability to select among models. We found that the spectral energy distributions for the majority of objects (∼66%) were better described using a two-temperature model with warm (T {sub gr} ∼ 100-500 K) and cold (T {sub gr} ∼ 50-150 K) dust populations analogous to zodiacal and Kuiper Belt dust, suggesting that planetary systems are common in debris disks and zodiacal dust is common around host stars with ages up to ∼1 Gyr. We found that younger stars generally have disks with larger fractional infrared luminosities and higher grain temperatures and that higher-mass stars have disks with higher grain temperatures. We show that the increasing distance of dust around debris disks is inconsistent with self-stirred disk models, expected if these systems possess planets at 30-150 AU. Finally, we illustrate how observations of debris disks may be used to constrain the radial dependence of material in the minimum mass solar nebula.

  6. Gas and Dust in Debris Disks: Clues to the Late Stages of Planet Formation

    NASA Technical Reports Server (NTRS)

    Roberge, Aki

    2012-01-01

    The basic character of debris disks was established soon after their discovery in the mid- 1980's. These disks around nearby main sequence stars are composed of material (mostly dust) produced by collisions and/or evaporation of extrasolar asteroids and comets. However, fundamental observational questions about debris disks remain unanswered. How much material do debris disks typically contain and how does it evolve with time? What is the composition of their dust and gas? Are planets present or forming in the disks? Answers to these questions will provide insights into the late stages of planetary system formation and the origins of terrestrial planet atmospheres. In this talk, I will explain our current understanding of the place of debris disks in the planet formation process. Progress toward addressing the questions given above will be discussed, with emphasis on recent studies of the small but important gas component. Finally, I will outline the implications of debris dust for future efforts to directly image and characterize extrasolar terrestrial planets.

  7. DISCOVERY OF AN EDGE-ON DEBRIS DISK WITH A DUST RING AND AN OUTER DISK WING-TILT ASYMMETRY

    SciTech Connect

    Kasper, Markus; Apai, Dániel; Wagner, Kevin; Robberto, Massimo

    2015-10-20

    Using Very Large Telescope/SPHERE near-infrared dual-band imaging and integral field spectroscopy, we discovered an edge-on debris disk around the 17 Myr old A-type member of the Scorpius–Centaurus OB association HD 110058. The edge-on disk can be traced to about 0.″6 or 65 AU projected separation. In its northern and southern wings, the disk shows at all wavelengths two prominent, bright, and symmetrically placed knots at 0.″3 or 32 AU from the star. We interpret these knots as a ring of planetesimals whose collisions may produce most of the dust observed in the disk. We find no evidence for a bow in the disk, but we identify a pair of symmetric, hooklike features in both wings. Based on similar features in the Beta Pictoris disk, we propose that this wing-tilt asymmetry traces either an outer planetesimal belt that is inclined with respect to the disk midplane or radiation-pressure-driven dust blown out from a yet unseen inner belt that is inclined with respect to the disk midplane. The misaligned inner or outer disk may be a result of interaction with a yet unseen planet. Overall, the disk geometry resembles the nearby disk around Beta Pictoris, albeit seen at smaller radial scales.

  8. The Contribution of Small Body Disruptions to Debris Disks

    NASA Astrophysics Data System (ADS)

    Espy Kehoe, Ashley J.; Kehoe, Thomas James Joseph; Colwell, Joshua E.

    2016-01-01

    We have performed detailed dynamical modeling of the structure of a faint dust band observed in coadded InfraRed Astronomical Satellite data at an ecliptic latitude of 17° that convincingly demonstrates that it is the result of a relatively recent (significantly less than 1 Ma) disruption of an asteroid and is still in the process of forming. We show that young dust bands retain information on the size distribution and cross-sectional area of dust released in the original asteroid disruption, before it is lost to orbital and collisional decay. We find that the Emilkowalski cluster is the source of this partial band and that the dust released in the disruption would correspond to a regolith layer ˜3 m deep on the ˜10 km diameter source body's surface. The dust in this band is described by a cumulative size-distribution inverse power-law index with a lower bound of 2.1 (implying domination of cross- sectional area by small particles) for dust particles with diameters ranging from a few μm up to a few cm. The coadded observations show that the thermal emission of the dust band structure is dominated by large (mm-cm size) particles. We find that dust particle ejection velocities need to be a few times the escape velocity of the Emilkowalski cluster source body to provide a good fit to the inclination dispersion of the observations. We discuss the implications that such a significant release of material, during the disruption of an asteroid, has for the temporal evolution of the structure, composition, and magnitude of the zodiacal cloud. Using the highly sensitive Wide-field Infrared Survey Explorer (WISE) dataset, we can now search for more of these faint signatures of very recent small body disruptions. Starting with the constraints on the amount and size distribution of the dust released in an asteroid catastrophic disruption, we can extrapolate to determine how small body disruptions would appear in extra solar debris disk systems.

  9. NEAR-ULTRAVIOLET AND OPTICAL EFFECTS OF DEBRIS DISKS AROUND WHITE DWARFS

    SciTech Connect

    Zabot, A.; Kanaan, A.; Cid Fernandes, R.

    2009-10-20

    Studies of debris disks around white dwarfs (WDs) have focused on infrared wavelengths because debris disks are much colder than the star and are believed to contribute to the spectrum only at longer wavelengths. Nevertheless, these disks are made of dust grains that absorb and scatter near-UV and optical photons from the WD, leaving a fingerprint that can be used to further constrain disk properties. Our goal is to show that it is possible to detect near-UV and optical effects of debris disks in the star + disk integrated spectrum. We make theoretical calculations and discuss the necessary observational conditions to detect the near-UV and optical effects. We show how these effects can be used to infer the disk mass, composition, optical depth, and inclination relative to the line of sight. If the IR excess is due to a disk, then near-UV and optical effects should be observed in only some systems, not all of them, while for dust shells the effects should be observed in all systems.

  10. The Detectability of Exo-Earths and Super-Earths via Resonant Signatures in Exozodiacal Clouds

    NASA Technical Reports Server (NTRS)

    Stark, Christopher C.; Kuchner, Marc

    2008-01-01

    Directly imaging extrasolar terrestrial planets necessarily means contending with the astrophysical noise of exozodiacal dust and the resonant structures created by these planets in exozodiacal clouds. Using a custom tailored hybrid symplectic integrator we have constructed 120 models of resonant structures created by exo-Earths and super-Earths on circular orbits interacting with collisionless steady-state dust clouds around a Sun-like star. Our models include enough particles to overcome the limitations of previous simulations that were often dominated by a handful of long-lived particles, allowing us to quantitatively study the contrast of the resulting ring structures. We found that in the case of a planet on a circular orbit, for a given star and dust source distribution, the morphology and contrast of the resonant structures depend on only two parameters: planet mass and (square root)ap/Beta, where ap is the planet's semi-major axis and Beta is the ratio of radiation pressure force to gravitational force on a grain. We constructed multiple-grain-size models of 25,000 particles each and showed that in a collisionless cloud, a Dohnanyi crushing law yields a resonant ring whose optical depth is dominated by the largest grains in the distribution, not the smallest. We used these models to estimate the mass of the lowest-mass planet that can be detected through observations of a resonant ring for a variety of assumptions about the dust cloud and the planet's orbit. Our simulations suggest that planets with mass as small as a few times Mars' mass may produce detectable signatures in debris disks at ap greater than or approximately equal to 10 AU.

  11. DIRECT IMAGING OF AN ASYMMETRIC DEBRIS DISK IN THE HD 106906 PLANETARY SYSTEM

    SciTech Connect

    Kalas, Paul G.; Wang, Jason J.; Duchene, Gaspard; Dong, Ruobing; Graham, James R.; Rosa, Robert J. De; Rajan, Abhijith; Patience, Jennifer; Millar-Blanchaer, Maxwell A.; Chilcote, Jeffrey; Chen, Christine; Fitzgerald, Michael P.; Macintosh, Bruce; Murray-Clay, Ruth; Matthews, Brenda; Marois, Christian; Draper, Zachary H.; Lawler, Samantha; Rameau, Julien; Doyon, René; and others

    2015-11-20

    We present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco–Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ∼50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the “needle” morphology seen for the HD 15115 debris disk. The planet candidate is oriented ∼21° away from the position angle of the primary’s debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary’s disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. We show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet.

  12. Direct imaging of an asymmetric debris disk in the HD 106906 planetary system

    SciTech Connect

    Kalas, Paul G.; Rajan, Abhijith; Wang, Jason J.; Millar-Blanchaer, Maxwell A.; Duchene, Gaspard; Chen, Christine; Fitzgerald, Michael P.; Dong, Ruobing; Graham, James R.; Patience, Jennifer; Macintosh, Bruce; Murray-Clay, Ruth; Matthews, Brenda; Rameau, Julien; Marois, Christian; Chilcote, Jeffrey; De Rosa, Robert J.; Doyon, René; Draper, Zachary H.; Lawler, Samantha; Ammons, S. Mark; Arriaga, Pauline; Bulger, Joanna; Cotten, Tara; Follette, Katherine B.; Goodsell, Stephen; Greenbaum, Alexandra; Hibon, Pascale; Hinkley, Sasha; Hung, Li -Wei; Ingraham, Patrick; Lafreniere, David; Larkin, James E.; Long, Douglas; Maire, Jérôme; Marchis, Franck; Metchev, Stan; Morzinski, Katie M.; Nielsen, Eric L.; Oppenheimer, Rebecca; Perrin, Marshall D.; Pueyo, Laurent; Rantakyrö, Fredrik T.; Ruffio, Jean -Baptiste; Saddlemyer, Leslie; Savransky, Dmitry; Schneider, Adam C.; Sivaramakrishnan, Anand; Soummer, Rémi; Song, Inseok; Thomas, Sandrine; Ward-Duong, Kimberly; Wiktorowicz, Sloane J.; Wolff, Schuyler G.

    2015-11-13

    Here, we present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco–Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ~50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the "needle" morphology seen for the HD 15115 debris disk. The planet candidate is oriented ~21° away from the position angle of the primary's debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary's disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. In conclusion, we show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet.

  13. Direct imaging of an asymmetric debris disk in the HD 106906 planetary system

    DOE PAGES

    Kalas, Paul G.; Rajan, Abhijith; Wang, Jason J.; Millar-Blanchaer, Maxwell A.; Duchene, Gaspard; Chen, Christine; Fitzgerald, Michael P.; Dong, Ruobing; Graham, James R.; Patience, Jennifer; et al

    2015-11-13

    Here, we present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco–Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ~50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the "needle" morphologymore » seen for the HD 15115 debris disk. The planet candidate is oriented ~21° away from the position angle of the primary's debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary's disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. In conclusion, we show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet.« less

  14. SMACK: A NEW ALGORITHM FOR MODELING COLLISIONS AND DYNAMICS OF PLANETESIMALS IN DEBRIS DISKS

    SciTech Connect

    Nesvold, Erika R.; Kuchner, Marc J.; Pan, Margaret; Rein, Hanno E-mail: Marc.Kuchner@nasa.gov E-mail: rein@ias.edu

    2013-11-10

    We present the Superparticle-Method/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in three dimensions, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. We show that SMACK is stable to numerical viscosity and numerical heating over 10{sup 7} yr and that it can reproduce analytic models of disk evolution. We use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit. Differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring.

  15. SMACK: A New Algorithm for Modeling Collisions and Dynamics of Planetesimals in Debris Disks

    NASA Technical Reports Server (NTRS)

    Nesvold, Erika Rose; Kuchner, Marc J.; Rein, Hanno; Pan, Margaret

    2013-01-01

    We present the Superparticle Model/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in 3-D, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. We show that SMACK is stable to numerical viscosity and numerical heating over 10(exp 7) yr, and that it can reproduce analytic models of disk evolution. We use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit. Differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring.

  16. METAL ACCRETION ONTO WHITE DWARFS CAUSED BY POYNTING-ROBERTSON DRAG ON THEIR DEBRIS DISKS

    SciTech Connect

    Rafikov, Roman R.

    2011-05-01

    Recent discoveries of compact (sizes {approx}debris disks around more than a dozen metal-rich white dwarfs (WDs) suggest that pollution of these stars with metals may be caused by accretion of high-Z material from the disk. But the mechanism responsible for efficient transfer of mass from a particulate disk to the WD atmosphere has not yet been identified. Here we demonstrate that radiation of the WD can effectively drive accretion of matter through the disk toward the sublimation radius (located at several tens of WD radii), where particles evaporate, feeding a disk of metal gas accreting onto the WD. We show that, contrary to some previous claims, Poynting-Robertson (PR) drag on the debris disk is effective at providing metal accretion rate M-dot{sub PR}{approx}10{sup 8} g s{sup -1} and higher, scaling quadratically with WD effective temperature. We compare our results with observations and show that, as expected, no WD hosting a particulate debris disk shows evidence of metal accretion rate below that produced by the PR drag. Existence of WDs accreting metals at rates significantly higher than M-dot{sub PR} suggests that another mechanism in addition to the PR drag drives accretion of high-Z elements in these systems.

  17. The SEEDS Direct Imaging Survey for Planets and Scattered Dust Emission in Debris Disk Systems

    NASA Technical Reports Server (NTRS)

    Janson, Markus; Brandt, Timothy; Moro-Martin, Amaya; Usuda, Tomonori; Thalmann, Christian; Carson, Joseph C.; Goto, Miwa; Currie, Thayne; McElwain, M. W.; Itoh, Yoichi; Fukagawa, Misato; Crepp, Justin; Kuzuhara, Masayuki; Hashimoto, Jun; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Abe, Lyu; Brandner, Wolfgang; Egner, Sebastian; Fedlt, Markus; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiro; Hayashi, Saeko

    2013-01-01

    Debris disks around young main-sequence stars often have gaps and cavities which for a long time have been interpreted as possibly being caused by planets. In recent years, several giant planet discoveries have been made in systems hosting disks of precisely this nature, further implying that interactions with planets could be a common cause of such disk structures. As part of the SEEDS high-contrast imaging survey, we are surveying a population of debris disk-hosting stars with gaps and cavities implied by their spectral energy distributions, in order to attempt to spatially resolve the disk as well as to detect any planets that may be responsible for the disk structure. Here we report on intermediate results from this survey. Five debris disks have been spatially resolved, and a number of faint point sources have been discovered, most of which have been tested for common proper motion, which in each case has excluded physical companionship with the target stars. From the detection limits of the 50 targets that have been observed, we find that beta Pic b-like planets (approximately 10M(sub jup) planets around G-A-type stars) near the gap edges are less frequent than 15-30%, implying that if giant planets are the dominant cause of these wide (27 AU on average) gaps, they are generally less massive than beta Pic b.

  18. THE SEEDS DIRECT IMAGING SURVEY FOR PLANETS AND SCATTERED DUST EMISSION IN DEBRIS DISK SYSTEMS

    SciTech Connect

    Janson, Markus; Brandt, Timothy D.; Moro-Martin, Amaya; Usuda, Tomonori; Kudo, Tomoyuki; Egner, Sebastian; Thalmann, Christian; Carson, Joseph C.; Goto, Miwa; Currie, Thayne; McElwain, M. W.; Itoh, Yoichi; Fukagawa, Misato; Crepp, Justin; Kuzuhara, Masayuki; Hashimoto, Jun; Kusakabe, Nobuhiko; Abe, Lyu; Brandner, Wolfgang; Feldt, Markus; and others

    2013-08-10

    Debris disks around young main-sequence stars often have gaps and cavities which for a long time have been interpreted as possibly being caused by planets. In recent years, several giant planet discoveries have been made in systems hosting disks of precisely this nature, further implying that interactions with planets could be a common cause of such disk structures. As part of the SEEDS high-contrast imaging survey, we are surveying a population of debris-disk-hosting stars with gaps and cavities implied by their spectral energy distributions, in order to attempt to spatially resolve the disk as well as to detect any planets that may be responsible for the disk structure. Here, we report on intermediate results from this survey. Five debris disks have been spatially resolved, and a number of faint point sources have been discovered, most of which have been tested for common proper motion, which in each case has excluded physical companionship with the target stars. From the detection limits of the 50 targets that have been observed, we find that {beta} Pic b-like planets ({approx}10 M{sub jup} planets around G-A-type stars) near the gap edges are less frequent than 15%-30%, implying that if giant planets are the dominant cause of these wide (27 AU on average) gaps, they are generally less massive than {beta} Pic b.

  19. WARM DEBRIS DISKS PRODUCED BY GIANT IMPACTS DURING TERRESTRIAL PLANET FORMATION

    SciTech Connect

    Genda, H.; Kobayashi, H.; Kokubo, E.

    2015-09-10

    In our solar system, Mars-sized protoplanets frequently collided with each other during the last stage of terrestrial planet formation, called the giant impact stage. Giant impacts eject a large amount of material from the colliding protoplanets into the terrestrial planet region, which may form debris disks with observable infrared excesses. Indeed, tens of warm debris disks around young solar-type stars have been observed. Here we quantitatively estimate the total mass of ejected materials during the giant impact stages. We found that ∼0.4 times the Earth’s mass is ejected in total throughout the giant impact stage. Ejected materials are ground down by collisional cascade until micron-sized grains are blown out by radiation pressure. The depletion timescale of these ejected materials is determined primarily by the mass of the largest body among them. We conducted high-resolution simulations of giant impacts to accurately obtain the mass of the largest ejected body. We then calculated the evolution of the debris disks produced by a series of giant impacts and depleted by collisional cascades to obtain the infrared excess evolution of the debris disks. We found that the infrared excess is almost always higher than the stellar infrared flux throughout the giant impact stage (∼100 Myr) and is sometimes ∼10 times higher immediately after a giant impact. Therefore, giant impact stages would explain the infrared excess from most observed warm debris disks. The observed fraction of stars with warm debris disks indicates that the formation probability of our solar-system-like terrestrial planets is approximately 10%.

  20. A debris disk around an isolated young neutron star.

    PubMed

    Wang, Zhongxiang; Chakrabarty, Deepto; Kaplan, David L

    2006-04-01

    Pulsars are rotating, magnetized neutron stars that are born in supernova explosions following the collapse of the cores of massive stars. If some of the explosion ejecta fails to escape, it may fall back onto the neutron star or it may possess sufficient angular momentum to form a disk. Such 'fallback' is both a general prediction of current supernova models and, if the material pushes the neutron star over its stability limit, a possible mode of black hole formation. Fallback disks could dramatically affect the early evolution of pulsars, yet there are few observational constraints on whether significant fallback occurs or even the actual existence of such disks. Here we report the discovery of mid-infrared emission from a cool disk around an isolated young X-ray pulsar. The disk does not power the pulsar's X-ray emission but is passively illuminated by these X-rays. The estimated mass of the disk is of the order of 10 Earth masses, and its lifetime (> or = 10(6) years) significantly exceeds the spin-down age of the pulsar, supporting a supernova fallback origin. The disk resembles protoplanetary disks seen around ordinary young stars, suggesting the possibility of planet formation around young neutron stars.

  1. A debris disk around an isolated young neutron star.

    PubMed

    Wang, Zhongxiang; Chakrabarty, Deepto; Kaplan, David L

    2006-04-01

    Pulsars are rotating, magnetized neutron stars that are born in supernova explosions following the collapse of the cores of massive stars. If some of the explosion ejecta fails to escape, it may fall back onto the neutron star or it may possess sufficient angular momentum to form a disk. Such 'fallback' is both a general prediction of current supernova models and, if the material pushes the neutron star over its stability limit, a possible mode of black hole formation. Fallback disks could dramatically affect the early evolution of pulsars, yet there are few observational constraints on whether significant fallback occurs or even the actual existence of such disks. Here we report the discovery of mid-infrared emission from a cool disk around an isolated young X-ray pulsar. The disk does not power the pulsar's X-ray emission but is passively illuminated by these X-rays. The estimated mass of the disk is of the order of 10 Earth masses, and its lifetime (> or = 10(6) years) significantly exceeds the spin-down age of the pulsar, supporting a supernova fallback origin. The disk resembles protoplanetary disks seen around ordinary young stars, suggesting the possibility of planet formation around young neutron stars. PMID:16598251

  2. Azimuthal asymmetries in the debris disk around HD 61005. A massive collision of planetesimals?

    NASA Astrophysics Data System (ADS)

    Olofsson, J.; Samland, M.; Avenhaus, H.; Caceres, C.; Henning, Th.; Moór, A.; Milli, J.; Canovas, H.; Quanz, S. P.; Schreiber, M. R.; Augereau, J.-C.; Bayo, A.; Bazzon, A.; Beuzit, J.-L.; Boccaletti, A.; Buenzli, E.; Casassus, S.; Chauvin, G.; Dominik, C.; Desidera, S.; Feldt, M.; Gratton, R.; Janson, M.; Lagrange, A.-M.; Langlois, M.; Lannier, J.; Maire, A.-L.; Mesa, D.; Pinte, C.; Rouan, D.; Salter, G.; Thalmann, C.; Vigan, A.

    2016-06-01

    Context. Debris disks offer valuable insights into the latest stages of circumstellar disk evolution, and can possibly help us to trace the outcomes of planetary formation processes. In the age range 10 to 100 Myr, most of the gas is expected to have been removed from the system, giant planets (if any) must have already been formed, and the formation of terrestrial planets may be on-going. Pluto-sized planetesimals, and their debris released in a collisional cascade, are under their mutual gravitational influence, which may result into non-axisymmetric structures in the debris disk. Aims: High angular resolution observations are required to investigate these effects and constrain the dynamical evolution of debris disks. Furthermore, multi-wavelength observations can provide information about the dust dynamics by probing different grain sizes. Methods: Here we present new VLT/SPHERE and ALMA observations of the debris disk around the 40 Myr-old solar-type star HD 61005. We resolve the disk at unprecedented resolution both in the near-infrared (in scattered and polarized light) and at millimeter wavelengths. We perform a detailed modeling of these observations, including the spectral energy distribution. Results: Thanks to the new observations, we propose a solution for both the radial and azimuthal distribution of the dust grains in the debris disk. We find that the disk has a moderate eccentricity (e ~ 0.1) and that the dust density is two times larger at the pericenter compared to the apocenter. Conclusions: With no giant planets detected in our observations, we investigate alternative explanations besides planet-disk interactions to interpret the inferred disk morphology. We postulate that the morphology of the disk could be the consequence of a massive collision between ~1000 km-sized bodies at ~61 au. If this interpretation holds, it would put stringent constraints on the formation of massive planetesimals at large distances from the star. Based on observations

  3. The Herschel cold debris disks: Confusion with the extragalactic background at 160 μm

    SciTech Connect

    Gáspár, András; Rieke, George H.

    2014-03-20

    The Herschel 'DUst around NEarby Stars' (DUNES) survey has found a number of debris disk candidates that are apparently very cold, with temperatures near 22 K. It has proven difficult to fit their spectral energy distributions with conventional models for debris disks. Given this issue, we carefully examine the alternative explanation that the detections arise from confusion with infrared cirrus and/or background galaxies that are not physically associated with the foreground stars. We find that such an explanation is consistent with all of these detections.

  4. OT2_dpadgett_2: Warm A Star Debris Disks from WISE

    NASA Astrophysics Data System (ADS)

    Padgett, D.

    2011-09-01

    Debris disks trace the collisional breakdown of asteroid and comet parent bodies orbiting nearby main sequence stars. Debris disks are typically cold analogs of our Kuiper belt with emission peaking near 70 microns wavelength. However, a relatively small number of warm disks are known with emission at 22 - 24 microns. These systems are especially interesting because they trace dust in the region likely to host terrestrial planets, where the dust has a short dynamical lifetimes. They also tend to be young systems aged < 1 Gyr. This knowledge of warm debris disks - extrasolar analogs to our solar system's Zodiacal cloud - is based on the 25 year old IRAS survey and observations of selected targets with ISO and Spitzer. The Wide-Field Infrared Survey Explorer (WISE) has recently completed new, sensitive all-sky mapping in the 3.3, 4.6, 12, and 22 micron bands. Association of the WISE sources to Hipparcos and Tycho stars has led to the identification of 61 nearby main sequence A stars with robustly detected warm 22 micron excesses not previously known. To determine whether these systems represent outbursts of asteroidal dust production (such as in the HD 69830 system), or simply the Wien side of emission from a cold outer dust belt, photometry at longer wavelengths is needed. We propose Herschel/PACS 70 and 160 micron photometry of this unbiased sample of new A star debris disks. These data will allow us to fully characterize the dust temperature and infrared luminosity of these systems, allowing them to be understood in the context of other debris disks and disk evolution theory. Herschel OT1 observations of FGKM stars from this survey show a 90% detection rate for 70 micron excess emission. The results from these combined samples will strongly constrain our picture of the collisional history of inner planetary systems.

  5. SEARCHING FOR PLANETS IN HOLEY DEBRIS DISKS WITH THE APODIZING PHASE PLATE

    SciTech Connect

    Meshkat, Tiffany; Kenworthy, Matthew A.; Bailey, Vanessa P.; Su, Kate Y. L.; Hinz, Philip M.; Smith, Paul S.; Mamajek, Eric E.

    2015-02-10

    We present our first results from a high-contrast imaging search for planetary mass companions around stars with gapped debris disks, as inferred from the stars' bright infrared excesses. For the six considered stars, we model the disks' unresolved infrared spectral energy distributions in order to derive the temperature and location of the disk components. With VLT/NaCo Apodizing Phase Plate coronagraphic L'-band imaging, we search for planetary mass companions that may be sculpting the disks. We detect neither disks nor companions in this sample, confirmed by comparing plausible point sources with archival data. In order to calculate our mass sensitivity limit, we revisit the stellar age estimates. One target, HD 17848, at 540 ± 100 Myr old is significantly older than previously estimated. We then discuss our high-contrast imaging results with respect to the disk properties.

  6. Modeling the HD 32297 Debris Disk With Far-Infrared Herschel Data

    NASA Technical Reports Server (NTRS)

    Donaldson, J.K.; Lebreton, J.; Roberge, A.; Augereau, J.-C.; Krivov, A. V.

    2013-01-01

    HD 32297 is a young A-star (approx. 30 Myr) 112 pc away with a bright edge-on debris disk that has been resolved in scattered light. We observed the HD 32297 debris disk in the far-infrared and sub-millimeter with the Herschel Space Observatory PACS and SPIRE instruments, populating the spectral energy distribution (SED) from 63 to 500 micron..We aimed to determine the composition of dust grains in the HD 32297 disk through SED modeling, using geometrical constraints from the resolved imaging to break the degeneracies inherent in SED modeling. We found the best fitting SED model has two components: an outer ring centered around 110 AU, seen in the scattered light images, and an inner disk near the habitable zone of the star. The outer disk appears to be composed of grains>2 micron consisting of silicates, carbonaceous material, and water ice with an abundance ratio of 1:2:3 respectively and 90% porosity. These grains appear consistent with cometary grains, implying the underlying planetesimal population is dominated by comet-like bodies. We also discuss the 3.7 sigma detection of [C ii] emission at 158 micron with the Herschel PACS instrument, making HD 32297 one of only a handful of debris disks with circumstellar gas detected

  7. MODELING THE HD 32297 DEBRIS DISK WITH FAR-INFRARED HERSCHEL DATA

    SciTech Connect

    Donaldson, J. K.; Lebreton, J.; Augereau, J.-C.; Krivov, A. V.

    2013-07-20

    HD 32297 is a young A-star ({approx}30 Myr) 112 pc away with a bright edge-on debris disk that has been resolved in scattered light. We observed the HD 32297 debris disk in the far-infrared and sub-millimeter with the Herschel Space Observatory PACS and SPIRE instruments, populating the spectral energy distribution (SED) from 63 to 500 {mu}m. We aimed to determine the composition of dust grains in the HD 32297 disk through SED modeling, using geometrical constraints from the resolved imaging to break the degeneracies inherent in SED modeling. We found the best fitting SED model has two components: an outer ring centered around 110 AU, seen in the scattered light images, and an inner disk near the habitable zone of the star. The outer disk appears to be composed of grains >2 {mu}m consisting of silicates, carbonaceous material, and water ice with an abundance ratio of 1:2:3 respectively and 90% porosity. These grains appear consistent with cometary grains, implying the underlying planetesimal population is dominated by comet-like bodies. We also discuss the 3.7{sigma} detection of [C II] emission at 158 {mu}m with the Herschel PACS instrument, making HD 32297 one of only a handful of debris disks with circumstellar gas detected.

  8. INNER EDGES OF COMPACT DEBRIS DISKS AROUND METAL-RICH WHITE DWARFS

    SciTech Connect

    Rafikov, Roman R.; Garmilla, Jose A. E-mail: garmilla@astro.princeton.edu

    2012-12-01

    A number of metal-rich white dwarfs (WDs) are known to host compact, dense particle disks, which are thought to be responsible for metal pollution of these stars. In many such systems, the inner radii of disks inferred from their spectra are so close to the WD that particles directly exposed to starlight must be heated above 1500 K and are expected to be unstable against sublimation. To reconcile this expectation with observations, we explore particle sublimation in H-poor debris disks around WDs. We show that because of the high metal vapor pressure the characteristic sublimation temperature in these disks is 300-400 K higher than in their protoplanetary analogs, allowing particles to survive at higher temperatures. We then look at the structure of the inner edges of debris disks and show that they should generically feature superheated inner rims directly exposed to starlight with temperatures reaching 2500-3500 K. Particles migrating through the rim toward the WD (and rapidly sublimating) shield the disk behind them from strong stellar heating, making the survival of solids possible close to the WD. Our model agrees well with observations of WD+disk systems provided that disk particles are composed of Si-rich material such as olivine, and have sizes in the range {approx}0.03-30 cm.

  9. ALMA CONTINUUM OBSERVATIONS OF A 30 Myr OLD GASEOUS DEBRIS DISK AROUND HD 21997

    SciTech Connect

    Moór, A.; Ábrahám, P.; Kiss, Cs.; Gabányi, K.; Juhász, A.; Schmalzl, M.; Kóspál, Á.; Apai, D.; Pascucci, I.; Csengeri, T.; Grady, C.; Henning, Th.; Hughes, A. M.

    2013-11-10

    Circumstellar disks around stars older than 10 Myr are expected to be gas-poor. There are, however, two examples of old (30-40 Myr) debris-like disks containing a detectable amount of cold CO gas. Here we present Atacama Large Millimeter/Submillimeter Array (ALMA) and Herschel Space Observatory observations of one of these disks, around HD 21997, and study the distribution and origin of the dust and its connection to the gas. Our ALMA continuum images at 886 μm clearly resolve a broad ring of emission within a diameter of ∼4.''5, adding HD 21997 to the dozen debris disks resolved at (sub)millimeter wavelengths. Modeling the morphology of the ALMA image with a radiative transfer code suggests inner and outer radii of ∼55 and ∼150 AU, and a dust mass of 0.09 M {sub ⊕}. Our data and modeling hints at an extended cold outskirt of the ring. Comparison with the morphology of the CO gas in the disk reveals an inner dust-free hole where gas nevertheless can be detected. Based on dust grain lifetimes, we propose that the dust content of this gaseous disk is of secondary origin and is produced by planetesimals. Since the gas component is probably primordial, HD 21997 is one of the first known examples of a hybrid circumstellar disk, a thus-far little studied late phase of circumstellar disk evolution.

  10. A DEBRIS disk around the planet hosting M-star GJ 581 spatially resolved with Herschel

    NASA Astrophysics Data System (ADS)

    Lestrade, J.-F.; Matthews, B. C.; Sibthorpe, B.; Kennedy, G. M.; Wyatt, M. C.; Bryden, G.; Greaves, J. S.; Thilliez, E.; Moro-Martín, A.; Booth, M.; Dent, W. R. F.; Duchêne, G.; Harvey, P. M.; Horner, J.; Kalas, P.; Kavelaars, J. J.; Phillips, N. M.; Rodriguez, D. R.; Su, K. Y. L.; Wilner, D. J.

    2012-12-01

    Debris disks have been found primarily around intermediate and solar mass stars (spectral types A-K) but rarely around low mass M-type stars. We have spatially resolved a debris disk around the remarkable M3-type star GJ 581 hosting multiple planets using deep PACS images at 70, 100 and 160 μm as part of the DEBRIS Program on the Herschel Space Observatory. This is the second spatially resolved debris disk found around an M-type star, after the one surrounding the young star AU Mic (12 Myr). However, GJ 581 is much older (2-8 Gyr), and is X-ray quiet in the ROSAT data. We fit an axisymmetric model of the disk to the three PACS images and found that the best fit model is for a disk extending radially from 25 ± 12 AU to more than 60 AU. Such a cold disk is reminiscent of the Kuiper belt but it surrounds a low mass star (0.3 M⊙) and its fractional dust luminosity Ldust/L∗ of ~ 10-4 is much higher. The inclination limits of the disk found in our analysis make the masses of the planets small enough to ensure the long-term stability of the system according to some dynamical simulations. The disk is collisionally dominated down to submicron-sized grains and the dust cannot be expelled from the system by radiation or wind pressures because of the low luminosity and low X-ray luminosity of GJ 581. We suggest that the correlation between low-mass planets and debris disks recently found for G-type stars also applies to M-type stars. Finally, the known planets, of low masses and orbiting within 0.3 AU from the star, cannot dynamically perturb the disk over the age of the star, suggesting that an additional planet exists at larger distance that is stirring the disk to replenish the dust. Herschel in an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation by NASA.

  11. Saturn's G and D Rings Provide Nearly Complete Measured Scattering Phase Functions of Nearby Debris Disks

    NASA Astrophysics Data System (ADS)

    Hedman, Matthew M.; Stark, Christopher C.

    2015-09-01

    The appearance of debris disks around distant stars depends upon the scattering/phase function (SPF) of the material in the disk. However, characterizing the SPFs of these extrasolar debris disks is challenging because only a limited range of scattering angles are visible to Earth-based observers. By contrast, Saturn’s tenuous rings can be observed over a much broader range of geometries, so their SPFs can be much better constrained. Since these rings are composed of small particles released from the surfaces of larger bodies, they are reasonable analogs to debris disks and so their SPFs can provide insights into the plausible scattering properties of debris disks. This work examines two of Saturn’s dusty rings: the G ring (at 167,500 km from Saturn’s center) and the D68 ringlet (at 67,600 km). Using data from the cameras on board the Cassini spacecraft, we are able to estimate the rings’ brightnesses at scattering angles ranging from 170° to 0.°5. We find that both of the rings exhibit extremely strong forward-scattering peaks, but for scattering angles above 60° their brightnesses are nearly constant. These SPFs can be well approximated by a linear combination of three Henyey-Greenstein functions, and are roughly consistent with the SPFs of irregular particles from laboratory measurements. Comparing these data to Fraunhofer and Mie models highlights several challenges involved in extracting information about particle compositions and size distributions from SPFs alone. The SPFs of these rings also indicate that the degree of forward scattering in debris disks may be greatly underestimated.

  12. Signatures of planets in the observable structure of circumstellar debris disks

    NASA Astrophysics Data System (ADS)

    Wyatt, Mark C.

    Recent advances in astronomical instrumentation have led to a vast increase in our knowledge of the environments of nearby stars. In particular, we are now able to image the thermal emission from the disks of dust around main sequence stars that may be the fossil remnants of planetary formation. These observations imply that the distribution of dust in the debris disks is neither smooth nor symmetrical; e.g., mid-infrared images of the disk of dust around the young A0V star HR 4796A show two lobes of emission, one of which may be ~5% brighter than the other. The observed structure of the debris disk in the solar system, i.e., the zodiacal cloud, also contains asymmetries: it has an offset center of symmetry, it is warped, and there is an asymmetric ring of dust co-orbiting with the Earth. Since the zodiacal cloud's asymmetries have been shown to be signatures of the gravitational perturbations of the solar system's planets, it is hoped that it may be possible to indirectly detect extrasolar planetary systems by their signatures in debris disk observations. This dissertation uses the physical processes that affect the evolution of debris material in the solar system to create a generalized model for the evolution of circumstellar debris material. It then shows how planetary perturbations affect that evolution, thereby causing the signatures of planets seen in the structure of the zodiacal cloud. This model can be used to provide a quantitative interpretation of debris disk observations, and the necessary modeling techniques are demonstrated by their application to observations of the HR 4796 disk. As well as determining the large scale structure of the HR 4796 disk, the modeling shows how a small body (>10M⊕) in the HR 4796 system that is on an orbit with an eccentricity larger than 0.02 could be the cause of the observed brightness asymmetry. The modeling also shows that the disk's mid-IR emitting particles are hotter than black body (and therefore small), and

  13. Other Debris Disks: Description and Similarities/Differences with Beta Pictoris Through Scattered-Light Imaging

    NASA Astrophysics Data System (ADS)

    Schneider, G.

    2014-09-01

    Though circumstellar orbiting debris has been inferred from thermal IR excesses around many stars since the initial discovery (from IRAS) and then scattered-light imaging of the Beta Pictoris disk thirty years ago, resolved images that directly inform on the spatial distribution of the disk material have historically proven extremely challenging to obtain. A dozen years lapsed between the Beta Pic disk discovery imaging and that of the second such system then revealed (HR 4796A). To date, two-dozen well-resolved images of circumstellar debris systems have emerged (mostly with space-based coronagraphy) and map their small-particle populations. They allow us to break degeneracies that otherwise conflate disk geometries and grain properties when attempting to model unresolved spatial energy distributions alone. They also provides a wealth of information crucial to better arbitrate between possible particle compositions, and optical/physical properties. They enable discrimination between the architectures of such systems that may contain co-orbiting planets, and between dynamical effects that may influence disk evolution from environmental (extrinsic and intrinsic) forces. Such images have provided unique insights into both the genesis and outcomes of the processes of planetary system formation. Individually, these images have been powerful diagnostically, and insightful interpretively. Collectively they exhibit remarkable diversity in morphologies, architectures, sub-structures and properties that allowed us to inter-compare these systems in the context of our own solar systems debris disk and in light of the benchmark, best studied, exoplanet-hosting debris system: Beta Pic. Herein we briefly review the state of the field regarding these ÓotherÓ disks today, with illustrative examples of today's menagerie, and of what the future may unfold.

  14. STRUCTURE AND EVOLUTION OF DEBRIS DISKS AROUND F-TYPE STARS. I. OBSERVATIONS, DATABASE, AND BASIC EVOLUTIONARY ASPECTS

    SciTech Connect

    Moor, A.; Abraham, P.; Kiss, L. L.; Kiss, Cs.; Pascucci, I.; Apai, D.; Kospal, A.; Csengeri, T.; Henning, Th.; Juhasz, A.; Bayliss, D.; Kovacs, J.; Szalai, T.

    2011-03-15

    Although photometric and spectroscopic surveys with the Spitzer Space Telescope remarkably increased the number of well-studied debris disks around A-type and Sun-like stars, detailed analyses of debris disks around F-type stars remained less frequent. Using the MIPS camera and the Infrared Spectrograph (IRS) spectrograph, we searched for debris dust around 82 F-type stars with Spitzer. We found 27 stars that harbor debris disks, nine of which are new discoveries. The dust distribution around two of our stars, HD 50571 and HD 170773, was found to be marginally extended on the 70 {mu}m MIPS images. Combining the MIPS and IRS measurements with additional infrared and submillimeter data, we achieved excellent spectral coverage for most of our debris systems. We have modeled the excess emission of 22 debris disks using a single temperature dust ring model and of five debris systems with two-temperature models. The latter systems may contain two dust rings around the star. In accordance with the expected trends, the fractional luminosity of the disks declines with time, exhibiting a decay rate consistent with the range of model predictions. We found the distribution of radial dust distances as a function of age to be consistent with the predictions of both the self-stirred and the planetary-stirred disk evolution models. A more comprehensive investigation of the evolution of debris disks around F-type stars, partly based on the presented data set, will be the subject of an upcoming paper.

  15. Herschel's "Cold Debris Disks": Background Galaxies or Quiescent Rims of Planetary Systems?

    NASA Technical Reports Server (NTRS)

    Krivov, A. V.; Eiroa, C.; Loehne, T.; Marshall, J. P.; Montesinos, B.; DelBurgo, C.; Absil, O.; Ardila, D.; Augereau, J.-C.; Bayo, A.; Bryden, G.; Danchi, W.; Ertel, S.; Lebreton, J.; Liseau, R.; Mora, A.; Mustill, A. J.; Mutschke, H.; Neuhaeuser, R.; Pilbratt, G. L.; Roberge, A.; Schmidt, T. O. B.; Stapelfeldt, K. R.; Thebault, Ph.; Vitense, Ch.; White, G. J.; Wolf, S.

    2013-01-01

    Infrared excesses associated with debris disk host stars detected so far peak at wavelengths around approx, 100 micron or shorter. However, 6 out of 31 excess sources studied in the Herschel Open Time Key Programme, DUNES, have been seen to show significant-and in some cases extended-excess emission at 160 micron, which is larger than the 100 micron excess. This excess emission has been attributed to circumstellar dust and has been suggested to stem from debris disks colder than those known previously. Since the excess emission of the cold disk candidates is extremely weak, challenging even the unrivaled sensitivity of Herschel, it is prudent to carefully consider whether some or even all of them may represent unrelated galactic or extragalactic emission, or even instrumental noise. We re-address these issues using several distinct methods and conclude that it is highly unlikely that none of the candidates represents a true circumstellar disk. For true disks, both the dust temperatures inferred from the spectral energy distributions and the disk radii estimated from the images suggest that the dust is nearly as cold as a blackbody. This requires the grains to be larger than approx. 100 micron, even if they are rich in ices or are composed of any other material with a low absorption in the visible. The dearth of small grains is puzzling, since collisional models of debris disks predict that grains of all sizes down to several times the radiation pressure blowout limit should be present. We explore several conceivable scenarios: transport-dominated disks, disks of low dynamical excitation, and disks of unstirred primordial macroscopic grains. Our qualitative analysis and collisional simulations rule out the first two of these scenarios, but show the feasibility of the third one. We show that such disks can indeed survive for gigayears, largely preserving the primordial size distribution. They should be composed of macroscopic solids larger than millimeters, but

  16. Herschel's "Cold Debris Disks": Background Galaxies or Quiescent Rims of Planetary Systems?

    NASA Astrophysics Data System (ADS)

    Krivov, A. V.; Eiroa, C.; Löhne, T.; Marshall, J. P.; Montesinos, B.; del Burgo, C.; Absil, O.; Ardila, D.; Augereau, J.-C.; Bayo, A.; Bryden, G.; Danchi, W.; Ertel, S.; Lebreton, J.; Liseau, R.; Mora, A.; Mustill, A. J.; Mutschke, H.; Neuhäuser, R.; Pilbratt, G. L.; Roberge, A.; Schmidt, T. O. B.; Stapelfeldt, K. R.; Thébault, Ph.; Vitense, Ch.; White, G. J.; Wolf, S.

    2013-07-01

    Infrared excesses associated with debris disk host stars detected so far peak at wavelengths around ~100 μm or shorter. However, 6 out of 31 excess sources studied in the Herschel Open Time Key Programme, DUNES, have been seen to show significant—and in some cases extended—excess emission at 160 μm, which is larger than the 100 μm excess. This excess emission has been attributed to circumstellar dust and has been suggested to stem from debris disks colder than those known previously. Since the excess emission of the cold disk candidates is extremely weak, challenging even the unrivaled sensitivity of Herschel, it is prudent to carefully consider whether some or even all of them may represent unrelated galactic or extragalactic emission, or even instrumental noise. We re-address these issues using several distinct methods and conclude that it is highly unlikely that none of the candidates represents a true circumstellar disk. For true disks, both the dust temperatures inferred from the spectral energy distributions and the disk radii estimated from the images suggest that the dust is nearly as cold as a blackbody. This requires the grains to be larger than ~100 μm, even if they are rich in ices or are composed of any other material with a low absorption in the visible. The dearth of small grains is puzzling, since collisional models of debris disks predict that grains of all sizes down to several times the radiation pressure blowout limit should be present. We explore several conceivable scenarios: transport-dominated disks, disks of low dynamical excitation, and disks of unstirred primordial macroscopic grains. Our qualitative analysis and collisional simulations rule out the first two of these scenarios, but show the feasibility of the third one. We show that such disks can indeed survive for gigayears, largely preserving the primordial size distribution. They should be composed of macroscopic solids larger than millimeters, but smaller than a few

  17. MILLIMETER IMAGING OF THE {beta} PICTORIS DEBRIS DISK: EVIDENCE FOR A PLANETESIMAL BELT

    SciTech Connect

    Wilner, David J.; Andrews, Sean M.; Hughes, A. Meredith

    2011-02-01

    We present observations at 1.3 mm wavelength of the {beta} Pictoris debris disk with beam size 4.''3 x 2.''6 (83 x 50 AU) from the Submillimeter Array. The emission shows two peaks separated by {approx}7'' along the disk plane, which we interpret as a highly inclined dust ring or belt. A simple model constrains the belt center to 94 {+-} 8 AU, close to the prominent break in slope of the optical scattered light. We identify this region as the location of the main reservoir of dust-producing planetesimals in the disk.

  18. HERSCHEL's ''COLD DEBRIS DISKS'': BACKGROUND GALAXIES OR QUIESCENT RIMS OF PLANETARY SYSTEMS?

    SciTech Connect

    Krivov, A. V.; Loehne, T.; Mutschke, H.; Neuhaeuser, R.; Eiroa, C.; Marshall, J. P.; Mustill, A. J.; Montesinos, B.; Del Burgo, C.; Absil, O.; Ardila, D.; Augereau, J.-C.; Ertel, S.; Lebreton, J.; Bryden, G.; Danchi, W.; Liseau, R.; Mora, A.; Pilbratt, G. L. [ESA Astrophysics and Fundamental Physics Missions Division, ESTEC and others

    2013-07-20

    Infrared excesses associated with debris disk host stars detected so far peak at wavelengths around {approx}100 {mu}m or shorter. However, 6 out of 31 excess sources studied in the Herschel Open Time Key Programme, DUNES, have been seen to show significant-and in some cases extended-excess emission at 160 {mu}m, which is larger than the 100 {mu}m excess. This excess emission has been attributed to circumstellar dust and has been suggested to stem from debris disks colder than those known previously. Since the excess emission of the cold disk candidates is extremely weak, challenging even the unrivaled sensitivity of Herschel, it is prudent to carefully consider whether some or even all of them may represent unrelated galactic or extragalactic emission, or even instrumental noise. We re-address these issues using several distinct methods and conclude that it is highly unlikely that none of the candidates represents a true circumstellar disk. For true disks, both the dust temperatures inferred from the spectral energy distributions and the disk radii estimated from the images suggest that the dust is nearly as cold as a blackbody. This requires the grains to be larger than {approx}100 {mu}m, even if they are rich in ices or are composed of any other material with a low absorption in the visible. The dearth of small grains is puzzling, since collisional models of debris disks predict that grains of all sizes down to several times the radiation pressure blowout limit should be present. We explore several conceivable scenarios: transport-dominated disks, disks of low dynamical excitation, and disks of unstirred primordial macroscopic grains. Our qualitative analysis and collisional simulations rule out the first two of these scenarios, but show the feasibility of the third one. We show that such disks can indeed survive for gigayears, largely preserving the primordial size distribution. They should be composed of macroscopic solids larger than millimeters, but smaller

  19. Molecular gas clumps from the destruction of icy bodies in the β Pictoris debris disk.

    PubMed

    Dent, W R F; Wyatt, M C; Roberge, A; Augereau, J-C; Casassus, S; Corder, S; Greaves, J S; de Gregorio-Monsalvo, I; Hales, A; Jackson, A P; Hughes, A Meredith; Lagrange, A-M; Matthews, B; Wilner, D

    2014-03-28

    Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets, and dwarf planets, but is gas also released in such events? Observations at submillimeter wavelengths of the archetypal debris disk around β Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85 astronomical units from the star, in a plane closely aligned with the orbit of the inner planet, β Pictoris b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet or from the remnants of a collision of Mars-mass planets. PMID:24603151

  20. Molecular Gas Clumps from the Destruction of Icy Bodies in the β Pictoris Debris Disk

    NASA Astrophysics Data System (ADS)

    Dent, W. R. F.; Wyatt, M. C.; Roberge, A.; Augereau, J.-C.; Casassus, S.; Corder, S.; Greaves, J. S.; de Gregorio-Monsalvo, I.; Hales, A.; Jackson, A. P.; Hughes, A. Meredith; Lagrange, A.-M.; Matthews, B.; Wilner, D.

    2014-03-01

    Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets, and dwarf planets, but is gas also released in such events? Observations at submillimeter wavelengths of the archetypal debris disk around β Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85 astronomical units from the star, in a plane closely aligned with the orbit of the inner planet, β Pictoris b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet or from the remnants of a collision of Mars-mass planets.

  1. Molecular Gas Clumps from the Destruction of Icy Bodies in the beta Pictoris Debris Disk

    NASA Technical Reports Server (NTRS)

    Dent, W. R. F.; Wyatt, M. C.; Roberge, A.; Augereau, J. -C.; Casassus, S.; Corder, S.; Greaves, J. S.; DeGregorio-Monsalvo, I.; Hales, A.; Jackson, A. P.; Hughes, A. Meredith; Lagrange, A. -M.; Matthews, B.; Wilner, D.

    2014-01-01

    Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets. But is gas also released in such events? Observations at sub-mm wavelengths of the archetypal debris disk around ß Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85 AU from the star, in a plane closely aligned with the orbit of the inner planet, beta Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

  2. What Debris Disks Can Tell Us about the Masses, Orbits, and Compositions of Planets

    NASA Astrophysics Data System (ADS)

    Rodigas, T.

    2014-09-01

    Our solar system contains four gas giant planets that have interacted and shaped the Kuiper Belt since their formation. They have affected its structure and shape and in the process have flung comets and small rocky bodies towards the inner terrestrial planets. Many of these bodies contain organic materials and water ice, the main ingredients required for Earth-like life. Therefore the Kuiper Belt holds clues to the properties of the solar system's planets. In the same way, it is thought that extrasolar debris disks, analogous to the solar system's Kuiper Belt, contain information on nearby planets. In this talk, I will discuss several recent results that relate the properties of debris disks to masses, orbits, and compositions of as-yet undetected planets. First, I will present 3.8 micron LBTI high-contrast adaptive optics (AO) imaging on the bright, edge-on debris disk around HD 32297 (Rodigas et al. 2014b). Combing our high signal-to-noise (S/N) detection with archival images at 1-2 microns, we constrain the composition of the dust grains in the disk. In particular, we test a recently proposed cometary grains model. We find that pure water ice is a better overall fit, suggesting at least one of the key ingredients for life may be present in this system. Second, I will present Magellan AO (MagAO) imaging results on the debris ring around HR 4796A at seven wavelengths from 0.7-4 microns (Rodigas et al. 2014c, in prep.). With such complete wavelength coverage and high S/N detections, we are able to obtain accurate photometry and constrain the composition of the dustÑin particular with regard to organic materials. Finally, I will present a new tool designed specifically for observers and planet hunters. Using a simple equation that depends solely on the width of a debris disk in scattered light, observers can estimate the maximum mass of an interior planet shepherding the disk (Rodigas et al. 2014a). This provides an independent, dynamical check on an imaged planet

  3. Revealing Asymmetries in the HD181327 Debris Disk: A Recent Massive Collision or Interstellar Medium Warping

    NASA Technical Reports Server (NTRS)

    Stark, Christopher C.; Schneider, Glenn; Weinberger, Alycia J.; Debes, John H.; Grady, Carol A.; Jang-Condell, Hannah; Kuchner, Marc J.

    2014-01-01

    New multi-roll coronagraphic images of the HD181327 debris disk obtained using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope reveal the debris ring in its entirety at high signal-to-noise ratio and unprecedented spatial resolution. We present and apply a new multi-roll image processing routine to identify and further remove quasi-static point-spread function-subtraction residuals and quantify systematic uncertainties. We also use a new iterative image deprojection technique to constrain the true disk geometry and aggressively remove any surface brightness asymmetries that can be explained without invoking dust density enhancements/ deficits. The measured empirical scattering phase function for the disk is more forward scattering than previously thought and is not well-fit by a Henyey-Greenstein function. The empirical scattering phase function varies with stellocentric distance, consistent with the expected radiation pressured-induced size segregation exterior to the belt. Within the belt, the empirical scattering phase function contradicts unperturbed debris ring models, suggesting the presence of an unseen planet. The radial profile of the flux density is degenerate with a radially varying scattering phase function; therefore estimates of the ring's true width and edge slope may be highly uncertain.We detect large scale asymmetries in the disk, consistent with either the recent catastrophic disruption of a body with mass greater than 1% the mass of Pluto, or disk warping due to strong interactions with the interstellar medium.

  4. Revealing asymmetries in the HD 181327 debris disk: A recent massive collision or interstellar medium warping

    SciTech Connect

    Stark, Christopher C.; Kuchner, Marc J.; Schneider, Glenn; Weinberger, Alycia J.; Debes, John H.; Grady, Carol A.; Jang-Condell, Hannah

    2014-07-01

    New multi-roll coronagraphic images of the HD 181327 debris disk obtained using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope reveal the debris ring in its entirety at high signal-to-noise ratio and unprecedented spatial resolution. We present and apply a new multi-roll image processing routine to identify and further remove quasi-static point-spread function-subtraction residuals and quantify systematic uncertainties. We also use a new iterative image deprojection technique to constrain the true disk geometry and aggressively remove any surface brightness asymmetries that can be explained without invoking dust density enhancements/deficits. The measured empirical scattering phase function for the disk is more forward scattering than previously thought and is not well-fit by a Henyey-Greenstein function. The empirical scattering phase function varies with stellocentric distance, consistent with the expected radiation pressured-induced size segregation exterior to the belt. Within the belt, the empirical scattering phase function contradicts unperturbed debris ring models, suggesting the presence of an unseen planet. The radial profile of the flux density is degenerate with a radially varying scattering phase function; therefore estimates of the ring's true width and edge slope may be highly uncertain. We detect large scale asymmetries in the disk, consistent with either the recent catastrophic disruption of a body with mass >1% the mass of Pluto, or disk warping due to strong interactions with the interstellar medium.

  5. The debris disk candidates: eleven 24 μm excess stars in the Spitzer SWIRE fields

    NASA Astrophysics Data System (ADS)

    Wu, Hong; Wu, Chao-Jian; Cao, Chen; Wolf, Sebastian; Hu, Jing-Yao

    2012-05-01

    We present the optical to mid-infrared SEDs of 11 debris disk candidates from Spitzer SWIRE fields. All the candidates are selected from SWIRE 24 μm sources matched with both the SDSS star catalog and the 2MASS point source catalog. They show an excess in the mid-infrared at 24 μm (KS—[24]Vega >= 0.44), indicating the presence of a circumstellar dust disk. The observed optical spectra show that they are all late-type main-sequence stars covering the spectral types of FGKM. Their fractional luminosities are well above 5 × 10-5, even up to the high fractional luminosity of 1 × 10-3. The high galactic latitudes of SWIRE fields indicate that most of these candidates could belong to the oldest stars in the thick disk. Our results indicate that high fractional luminosity debris disks could exist in old solar-like star systems, though they are still quite rare. Their discovery at high galactic latitudes also provides an excellent opportunity for further study of the properties and evolution of debris disks in regions of the Galaxy with low densities of ISM, called ISM poor environments.

  6. AU Mic’s Debris Disk Chemistry Revealed Using Spatially Resolved Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lomax, Jamie Renae; Donaldson, Jessica; Debes, John H.; Malumuth, Eliot; Roberge, Aki; Weinberger, Alycia J.; Wisniewski, John P.

    2015-01-01

    We present the first coronagraphic spectroscopy of the AU Mic debris disk system obtained with HST/STIS as part of GO-12512. Spectra of the system were taken by placing a long slit in the disk direction while blocking out the central star with an occulting bar. A naked star of similar spectral type was likewise observed for a PSF subtraction. This procedure results in a two dimensional spectrum as a function of disk position between 5200 and 10,200 angstroms for the system. We use the spectra to determine the cold dust grain composition by characterizing the system's color as a function of radial distance along the disk's midplane. This reveals the dynamical perturbations and chemical processing occurring within the disk and traces the potential composition and architecture of any planetary bodies in the system because the planetesimals that form planets produce the observed dust through collisional break up and evaporation.

  7. Discovery of a Substellar Companion to the Nearby Debris Disk Host HR 2562

    NASA Astrophysics Data System (ADS)

    Konopacky, Quinn M.; Rameau, Julien; Duchêne, Gaspard; Filippazzo, Joseph C.; Giorla Godfrey, Paige A.; Marois, Christian; Nielsen, Eric L.; Pueyo, Laurent; Rafikov, Roman R.; Rice, Emily L.; Wang, Jason J.; Ammons, S. Mark; Bailey, Vanessa P.; Barman, Travis S.; Bulger, Joanna; Bruzzone, Sebastian; Chilcote, Jeffrey K.; Cotten, Tara; Dawson, Rebekah I.; De Rosa, Robert J.; Doyon, René; Esposito, Thomas M.; Fitzgerald, Michael P.; Follette, Katherine B.; Goodsell, Stephen; Graham, James R.; Greenbaum, Alexandra Z.; Hibon, Pascale; Hung, Li-Wei; Ingraham, Patrick; Kalas, Paul; Lafrenière, David; Larkin, James E.; Macintosh, Bruce A.; Maire, Jérôme; Marchis, Franck; Marley, Mark S.; Matthews, Brenda C.; Metchev, Stanimir; Millar-Blanchaer, Maxwell A.; Oppenheimer, Rebecca; Palmer, David W.; Patience, Jenny; Perrin, Marshall D.; Poyneer, Lisa A.; Rajan, Abhijith; Rantakyrö, Fredrik T.; Savransky, Dmitry; Schneider, Adam C.; Sivaramakrishnan, Anand; Song, Inseok; Soummer, Remi; Thomas, Sandrine; Wallace, J. Kent; Ward-Duong, Kimberly; Wiktorowicz, Sloane J.; Wolff, Schuyler G.

    2016-09-01

    We present the discovery of a brown dwarf companion to the debris disk host star HR 2562. This object, discovered with the Gemini Planet Imager (GPI), has a projected separation of 20.3 ± 0.3 au (0\\buildrel{\\prime\\prime}\\over{.} 618+/- 0\\buildrel{\\prime\\prime}\\over{.} 004) from the star. With the high astrometric precision afforded by GPI, we have confirmed, to more than 5σ, the common proper motion of HR 2562B with the star, with only a month-long time baseline between observations. Spectral data in the J-, H-, and K-bands show a morphological similarity to L/T transition objects. We assign a spectral type of L7 ± 3 to HR 2562B and derive a luminosity of log(L {}{bol}/{L}⊙ )=-4.62+/- 0.12, corresponding to a mass of 30 ± 15 {M}{Jup} from evolutionary models at an estimated age of the system of 300-900 Myr. Although the uncertainty in the age of the host star is significant, the spectra and photometry exhibit several indications of youth for HR 2562B. The source has a position angle that is consistent with an orbit in the same plane as the debris disk recently resolved with Herschel. Additionally, it appears to be interior to the debris disk. Though the extent of the inner hole is currently too uncertain to place limits on the mass of HR 2562B, future observations of the disk with higher spatial resolution may be able to provide mass constraints. This is the first brown-dwarf-mass object found to reside in the inner hole of a debris disk, offering the opportunity to search for evidence of formation above the deuterium burning limit in a circumstellar disk.

  8. OT2_dardila_2: PACS Photometry of Transiting-Planet Systems with Warm Debris Disks

    NASA Astrophysics Data System (ADS)

    Ardila, D.

    2011-09-01

    Dust in debris disks is produced by colliding or evaporating planetesimals, the remnant of the planet formation process. Warm dust disks, known by their emission at =<24 mic, are rare (4% of FGK main-sequence stars), and specially interesting because they trace material in the region likely to host terrestrial planets, where the dust has very short dynamical lifetimes. Dust in this region comes from very recent asteroidal collisions, migrating Kuiper Belt planetesimals, or migrating dust. NASA's Kepler mission has just released a list of 1235 candidate transiting planets, and in parallel, the Wide-Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky mapping in the 3.4, 4.6, 12, and 22 micron bands. By cross-identifying the WISE sources with Kepler candidates as well as with other transiting planetary systems we have identified 21 transiting planet hosts with previously unknown warm debris disks. We propose Herschel/PACS 100 and 160 micron photometry of this sample, to determine whether the warm dust in these systems represents stochastic outbursts of local dust production, or simply the Wien side of emission from a cold outer dust belt. These data will allow us to put constraints in the dust temperature and infrared luminosity of these systems, allowing them to be understood in the context of other debris disks and disk evolution theory. This program represents a unique opportunity to exploit the synergy between three great space facilities: Herschel, Kepler, and WISE. The transiting planet sample hosts will remain among the most studied group of stars for the years to come, and our knowledge of their planetary architecture will remain incomplete if we do not understand the characteristics of their debris disks.

  9. Fast-moving features in the debris disk around AU Microscopii.

    PubMed

    Boccaletti, Anthony; Thalmann, Christian; Lagrange, Anne-Marie; Janson, Markus; Augereau, Jean-Charles; Schneider, Glenn; Milli, Julien; Grady, Carol; Debes, John; Langlois, Maud; Mouillet, David; Henning, Thomas; Dominik, Carsten; Maire, Anne-Lise; Beuzit, Jean-Luc; Carson, Joseph; Dohlen, Kjetil; Engler, Natalia; Feldt, Markus; Fusco, Thierry; Ginski, Christian; Girard, Julien H; Hines, Dean; Kasper, Markus; Mawet, Dimitri; Ménard, François; Meyer, Michael R; Moutou, Claire; Olofsson, Johan; Rodigas, Timothy; Sauvage, Jean-Francois; Schlieder, Joshua; Schmid, Hans Martin; Turatto, Massimo; Udry, Stephane; Vakili, Farrokh; Vigan, Arthur; Wahhaj, Zahed; Wisniewski, John

    2015-10-01

    In the 1980s, excess infrared emission was discovered around main-sequence stars; subsequent direct-imaging observations revealed orbiting disks of cold dust to be the source. These 'debris disks' were thought to be by-products of planet formation because they often exhibited morphological and brightness asymmetries that may result from gravitational perturbation by planets. This was proved to be true for the β Pictoris system, in which the known planet generates an observable warp in the disk. The nearby, young, unusually active late-type star AU Microscopii hosts a well-studied edge-on debris disk; earlier observations in the visible and near-infrared found asymmetric localized structures in the form of intensity variations along the midplane of the disk beyond a distance of 20 astronomical units. Here we report high-contrast imaging that reveals a series of five large-scale features in the southeast side of the disk, at projected separations of 10-60 astronomical units, persisting over intervals of 1-4 years. All these features appear to move away from the star at projected speeds of 4-10 kilometres per second, suggesting highly eccentric or unbound trajectories if they are associated with physical entities. The origin, localization, morphology and rapid evolution of these features are difficult to reconcile with current theories.

  10. Fast-moving features in the debris disk around AU Microscopii.

    PubMed

    Boccaletti, Anthony; Thalmann, Christian; Lagrange, Anne-Marie; Janson, Markus; Augereau, Jean-Charles; Schneider, Glenn; Milli, Julien; Grady, Carol; Debes, John; Langlois, Maud; Mouillet, David; Henning, Thomas; Dominik, Carsten; Maire, Anne-Lise; Beuzit, Jean-Luc; Carson, Joseph; Dohlen, Kjetil; Engler, Natalia; Feldt, Markus; Fusco, Thierry; Ginski, Christian; Girard, Julien H; Hines, Dean; Kasper, Markus; Mawet, Dimitri; Ménard, François; Meyer, Michael R; Moutou, Claire; Olofsson, Johan; Rodigas, Timothy; Sauvage, Jean-Francois; Schlieder, Joshua; Schmid, Hans Martin; Turatto, Massimo; Udry, Stephane; Vakili, Farrokh; Vigan, Arthur; Wahhaj, Zahed; Wisniewski, John

    2015-10-01

    In the 1980s, excess infrared emission was discovered around main-sequence stars; subsequent direct-imaging observations revealed orbiting disks of cold dust to be the source. These 'debris disks' were thought to be by-products of planet formation because they often exhibited morphological and brightness asymmetries that may result from gravitational perturbation by planets. This was proved to be true for the β Pictoris system, in which the known planet generates an observable warp in the disk. The nearby, young, unusually active late-type star AU Microscopii hosts a well-studied edge-on debris disk; earlier observations in the visible and near-infrared found asymmetric localized structures in the form of intensity variations along the midplane of the disk beyond a distance of 20 astronomical units. Here we report high-contrast imaging that reveals a series of five large-scale features in the southeast side of the disk, at projected separations of 10-60 astronomical units, persisting over intervals of 1-4 years. All these features appear to move away from the star at projected speeds of 4-10 kilometres per second, suggesting highly eccentric or unbound trajectories if they are associated with physical entities. The origin, localization, morphology and rapid evolution of these features are difficult to reconcile with current theories. PMID:26450055

  11. HERSCHEL PACS OBSERVATIONS AND MODELING OF DEBRIS DISKS IN THE TUCANA-HOROLOGIUM ASSOCIATION

    SciTech Connect

    Donaldson, J. K.; Roberge, A.; Chen, C. H.; Augereau, J.-C.; Menard, F.; Eiroa, C.; Meeus, G.; Krivov, A. V.; Mathews, G. S.; Riviere-Marichalar, P.; Sandell, G.

    2012-07-10

    We present Herschel PACS photometry of 17 B- to M-type stars in the 30 Myr old Tucana-Horologium Association. This work is part of the Herschel Open Time Key Programme 'Gas in Protoplanetary Systems'. 6 of the 17 targets were found to have infrared excesses significantly greater than the expected stellar IR fluxes, including a previously unknown disk around HD30051. These six debris disks were fitted with single-temperature blackbody models to estimate the temperatures and abundances of the dust in the systems. For the five stars that show excess emission in the Herschel PACS photometry and also have Spitzer IRS spectra, we fit the data with models of optically thin debris disks with realistic grain properties in order to better estimate the disk parameters. The model is determined by a set of six parameters: surface density index, grain size distribution index, minimum and maximum grain sizes, and the inner and outer radii of the disk. The best-fitting parameters give us constraints on the geometry of the dust in these systems, as well as lower limits to the total dust masses. The HD105 disk was further constrained by fitting marginally resolved PACS 70 {mu}m imaging.

  12. THE ABSENCE OF COLD DUST AROUND WARM DEBRIS DISK STAR HD 15407A

    SciTech Connect

    Fujiwara, Hideaki; Onaka, Takashi; Takita, Satoshi; Kataza, Hirokazu; Murakami, Hiroshi; Yamashita, Takuya; Fukagawa, Misato; Ishihara, Daisuke

    2012-11-01

    We report Herschel and AKARI photometric observations at far-infrared (FIR) wavelengths of the debris disk around the F3V star HD 15407A, in which the presence of an extremely large amount of warm dust ({approx}500-600 K) has been suggested by mid-infrared (MIR) photometry and spectroscopy. The observed flux densities of the debris disk at 60-160 {mu}m are clearly above the photospheric level of the star, suggesting excess emission at FIR as well as at MIR wavelengths previously reported. The observed FIR excess emission is consistent with the continuum level extrapolated from the MIR excess, suggesting that it originates in the inner warm debris dust and cold dust ({approx}50-130 K) is absent in the outer region of the disk. The absence of cold dust does not support a late-heavy-bombardment-like event as the origin of the large amount of warm debris dust around HD 15047A.

  13. THE SPITZER INFRARED SPECTROGRAPH DEBRIS DISK CATALOG. II. SILICATE FEATURE ANALYSIS OF UNRESOLVED TARGETS

    SciTech Connect

    Mittal, Tushar; Chen, Christine H.; Jang-Condell, Hannah; Manoj, P.; Sargent, Benjamin A.; Watson, Dan M.; Lisse, Carey M.

    2015-01-10

    During the Spitzer Space Telescope cryogenic mission, astronomers obtained Infrared Spectrograph (IRS) observations of hundreds of debris disk candidates that have been compiled in the Spitzer IRS Debris Disk Catalog. We have discovered 10 and/or 20 μm silicate emission features toward 120 targets in the catalog and modeled the IRS spectra of these sources, consistent with MIPS 70 μm observations, assuming that the grains are composed of silicates (olivine, pyroxene, forsterite, and enstatite) and are located either in a continuous disk with power-law size and surface density distributions or thin rings that are well-characterized using two separate dust grain temperatures. For systems better fit by the continuous disk model, we find that (1) the dust size distribution power-law index is consistent with that expected from a collisional cascade, q = 3.5-4.0, with a large number of values outside this range, and (2) the minimum grain size, a {sub min}, increases with stellar luminosity, L {sub *}, but the dependence of a {sub min} on L {sub *} is weaker than expected from radiation pressure alone. In addition, we also find that (3) the crystalline fraction of dust in debris disks evolves as a function of time with a large dispersion in crystalline fractions for stars of any particular stellar age or mass, (4) the disk inner edge is correlated with host star mass, and (5) there exists substantial variation in the properties of coeval disks in Sco-Cen, indicating that the observed variation is probably due to stochasticity and diversity in planet formation.

  14. VARIATIONS ON DEBRIS DISKS. II. ICY PLANET FORMATION AS A FUNCTION OF THE BULK PROPERTIES AND INITIAL SIZES OF PLANETESIMALS

    SciTech Connect

    Kenyon, Scott J.; Bromley, Benjamin C. E-mail: bromley@physics.utah.ed

    2010-05-15

    We describe comprehensive calculations of the formation of icy planets and debris disks at 30-150 AU around 1-3 M {sub sun} stars. Disks composed of large, strong planetesimals produce more massive planets than disks composed of small, weak planetesimals. The maximum radius of icy planets ranges from {approx}1500 km to 11,500 km. The formation rate of 1000 km objects-{sup P}lutos{sup -}is a useful proxy for the efficiency of icy planet formation. Plutos form more efficiently in massive disks, in disks with small planetesimals, and in disks with a range of planetesimal sizes. Although Plutos form throughout massive disks, Pluto production is usually concentrated in the inner disk. Despite the large number of Plutos produced in many calculations, icy planet formation is inefficient. At the end of the main sequence lifetime of the central star, Plutos contain less than 10% of the initial mass in solid material. This conclusion is independent of the initial mass in the disk or the properties of the planetesimals. Debris disk formation coincides with the formation of planetary systems containing Plutos. As Plutos form, they stir leftover planetesimals to large velocities. A cascade of collisions then grinds the leftovers to dust, forming an observable debris disk. In disks with small ({approx}<1-10 km) planetesimals, collisional cascades produce luminous debris disks with maximum luminosity {approx}10{sup -2} times the stellar luminosity. Disks with larger planetesimals produce debris disks with maximum luminosity {approx}5 x 10{sup -4} (10 km) to 5 x 10{sup -5} (100 km) times the stellar luminosity. Following peak luminosity, the evolution of the debris disk emission is roughly a power law, f {proportional_to} t {sup -n} with n{approx} 0.6-0.8. Observations of debris disks around A-type and G-type stars strongly favor models with small planetesimals. In these models, our predictions for the time evolution and detection frequency of debris disks agree with published

  15. THE DEBRIS DISK OF VEGA: A STEADY-STATE COLLISIONAL CASCADE, NATURALLY

    SciTech Connect

    Mueller, S.; Loehne, T.; Krivov, A. V.

    2010-01-10

    The archetypical debris disk around Vega has been observed intensively over the past 25 years. It has been argued that the resulting photometric data and images may be in contradiction with a standard, steady-state collisional scenario of the disk evolution. In particular, the emission in the mid-infrared (mid-IR) appears to be in excess of what is expected from a 'Kuiper belt' at approx100 AU, which is evident in the submillimeter images and inferred from the majority of photometric points. Here we re-address the question of whether or not the Vega disk observations are compatible with a continuous dust production through a collisional cascade. Instead of seeking a size and spatial distribution of dust that provide the best fit to observations, our approach involves physical modeling of the debris disk 'from the sources'. We assume that dust is maintained by a belt of parent planetesimals, and employ our collisional and radiative transfer codes to consistently model the size and radial distribution of the disk material and then thermal emission of dust. In doing so, we vary a broad set of parameters, including the stellar properties, the exact location, extension, and dynamical excitation of the planetesimal belt, chemical composition of solids, and the collisional prescription. We are able to reproduce the spectral energy distribution in the entire wavelength range from the near-IR to millimeter, as well as the mid-IR and submillimeter radial brightness profiles of the Vega disk. Thus, our results suggest that the Vega disk observations are not in contradiction with a steady-state collisional dust production, and we put important constraints on the disk parameters and physical processes that sustain it. The total disk mass in approx<100 km-sized bodies is estimated to be approx10 Earth masses. Provided that collisional cascade has been operating over much of the Vega age of approx350 Myr, the disk must have lost a few Earth masses of solids during that time. We

  16. Deep MIPS Observations of the IC 348 Nebula: Constraints on the Evolutionary State of Anemic Circumstellar Disks and the Primordial-to-Debris Disk Transition

    NASA Astrophysics Data System (ADS)

    Currie, Thayne; Kenyon, Scott J.

    2009-09-01

    We describe new, deep MIPS photometry and new high signal-to-noise optical spectroscopy of the 2.5 Myr old IC 348 Nebula. To probe the properties of the IC 348 disk population, we combine these data with previous optical/infrared photometry and spectroscopy to identify stars with gas accretion, to examine their mid-IR colors, and to model their spectral energy distributions. IC 348 contains many sources in different evolutionary states, including protostars and stars surrounded by primordial disks, two kinds of transitional disks, and debris disks. Most disks surrounding early/intermediate spectral-type stars (>1.4 M sun at 2.5 Myr) are debris disks; most disks surrounding solar and subsolar-mass stars are primordial disks. At the 1-2 σ level, more massive stars also have a smaller frequency of gas accretion and smaller mid-IR luminosities than lower-mass stars. These trends are suggestive of a stellar mass-dependent evolution of disks, where most disks around high/intermediate-mass stars shed their primordial disks on rapid, 2.5 Myr timescales. The frequency of MIPS-detected transitional disks is ≈15%-35% for stars plausibly more massive than 0.5 M sun. The relative frequency of transitional disks in IC 348 compared to that for 1 Myr old Taurus and 5 Myr old NGC 2362 is consistent with a transition timescale that is a significant fraction of the total primordial disk lifetime.

  17. DEEP MIPS OBSERVATIONS OF THE IC 348 NEBULA: CONSTRAINTS ON THE EVOLUTIONARY STATE OF ANEMIC CIRCUMSTELLAR DISKS AND THE PRIMORDIAL-TO-DEBRIS DISK TRANSITION

    SciTech Connect

    Currie, Thayne; Kenyon, Scott J. E-mail: skenyon@cfa.harvard.edu

    2009-09-15

    We describe new, deep MIPS photometry and new high signal-to-noise optical spectroscopy of the 2.5 Myr old IC 348 Nebula. To probe the properties of the IC 348 disk population, we combine these data with previous optical/infrared photometry and spectroscopy to identify stars with gas accretion, to examine their mid-IR colors, and to model their spectral energy distributions. IC 348 contains many sources in different evolutionary states, including protostars and stars surrounded by primordial disks, two kinds of transitional disks, and debris disks. Most disks surrounding early/intermediate spectral-type stars (>1.4 M {sub sun} at 2.5 Myr) are debris disks; most disks surrounding solar and subsolar-mass stars are primordial disks. At the 1-2 {sigma} level, more massive stars also have a smaller frequency of gas accretion and smaller mid-IR luminosities than lower-mass stars. These trends are suggestive of a stellar mass-dependent evolution of disks, where most disks around high/intermediate-mass stars shed their primordial disks on rapid, 2.5 Myr timescales. The frequency of MIPS-detected transitional disks is {approx}15%-35% for stars plausibly more massive than 0.5 M {sub sun}. The relative frequency of transitional disks in IC 348 compared to that for 1 Myr old Taurus and 5 Myr old NGC 2362 is consistent with a transition timescale that is a significant fraction of the total primordial disk lifetime.

  18. Does the Collapse of a Supramassive Neutron Star Leave a Debris Disk?

    PubMed

    Margalit, Ben; Metzger, Brian D; Beloborodov, Andrei M

    2015-10-23

    One possible channel for black hole formation is the collapse of a rigidly rotating massive neutron star as it loses its angular momentum or gains excessive mass through accretion. It was proposed that part of the neutron star may form a debris disk around the black hole. Such short-lived massive disks could be the sources of powerful jets emitting cosmological gamma-ray bursts. Whether the collapse creates a disk depends on the equation of state of the neutron star. We survey a wide range of equations of states allowed by observations and find that disk formation is unfeasible. We conclude that this channel of black hole formation is incapable of producing powerful jets, and discuss implications for models of gamma-ray bursts. PMID:26551095

  19. RESOLVED MILLIMETER-WAVELENGTH OBSERVATIONS OF DEBRIS DISKS AROUND SOLAR-TYPE STARS

    SciTech Connect

    Steele, Amy; Hughes, A. Meredith; Carpenter, John; Ricarte, Angelo; Andrews, Sean M.; Wilner, David J.; Chiang, Eugene

    2016-01-01

    The presence of debris disks around young main-sequence stars hints at the existence and structure of planetary systems. Millimeter-wavelength observations probe large grains that trace the location of planetesimal belts. The Formation and Evolution of Planetary Systems Spitzer Legacy survey of nearby young solar analogues yielded a sample of five debris disk-hosting stars with millimeter flux suitable for interferometric follow-up. We present observations with the Submillimeter Array (SMA) and the Combined Array for Research in Millimeter-wave Astronomy at ∼2″ resolution that spatially resolve the debris disks around these nearby (d ∼ 50 pc) stars. Two of the five disks (HD 377, HD 8907) are spatially resolved for the first time and one (HD 104860) is resolved at millimeter wavelengths for the first time. We combine our new observations with archival SMA and Atacama Large Millimeter/Submillimeter Array data to enable a uniform analysis of the full five-object sample. We simultaneously model the broadband photometric data and resolved millimeter visibilities to constrain the dust temperatures and disk morphologies, and perform a Markov Chain Monte Carlo analysis to fit for basic structural parameters. We find that the radii and widths of the cold outer belts exhibit properties consistent with scaled-up versions of the Solar System's Kuiper Belt. All the disks exhibit characteristic grain sizes comparable to the blowout size, and all the resolved observations of emission from large dust grains are consistent with an axisymmetric dust distribution to within the uncertainties. These results are consistent with comparable studies carried out at infrared wavelengths.

  20. Resolved Millimeter-wavelength Observations of Debris Disks around Solar-type Stars

    NASA Astrophysics Data System (ADS)

    Steele, Amy; Hughes, A. Meredith; Carpenter, John; Ricarte, Angelo; Andrews, Sean M.; Wilner, David J.; Chiang, Eugene

    2016-01-01

    The presence of debris disks around young main-sequence stars hints at the existence and structure of planetary systems. Millimeter-wavelength observations probe large grains that trace the location of planetesimal belts. The Formation and Evolution of Planetary Systems Spitzer Legacy survey of nearby young solar analogues yielded a sample of five debris disk-hosting stars with millimeter flux suitable for interferometric follow-up. We present observations with the Submillimeter Array (SMA) and the Combined Array for Research in Millimeter-wave Astronomy at ∼2″ resolution that spatially resolve the debris disks around these nearby (d ∼ 50 pc) stars. Two of the five disks (HD 377, HD 8907) are spatially resolved for the first time and one (HD 104860) is resolved at millimeter wavelengths for the first time. We combine our new observations with archival SMA and Atacama Large Millimeter/Submillimeter Array data to enable a uniform analysis of the full five-object sample. We simultaneously model the broadband photometric data and resolved millimeter visibilities to constrain the dust temperatures and disk morphologies, and perform a Markov Chain Monte Carlo analysis to fit for basic structural parameters. We find that the radii and widths of the cold outer belts exhibit properties consistent with scaled-up versions of the Solar System's Kuiper Belt. All the disks exhibit characteristic grain sizes comparable to the blowout size, and all the resolved observations of emission from large dust grains are consistent with an axisymmetric dust distribution to within the uncertainties. These results are consistent with comparable studies carried out at infrared wavelengths.

  1. Gemini Planet Imager Observations of the AU Microscopii Debris Disk: Asymmetries within One Arcsecond

    NASA Astrophysics Data System (ADS)

    Wang, Jason J.; Graham, James R.; Pueyo, Laurent; Nielsen, Eric L.; Millar-Blanchaer, Max; De Rosa, Robert J.; Kalas, Paul; Ammons, S. Mark; Bulger, Joanna; Cardwell, Andrew; Chen, Christine; Chiang, Eugene; Chilcote, Jeffrey K.; Doyon, René; Draper, Zachary H.; Duchêne, Gaspard; Esposito, Thomas M.; Fitzgerald, Michael P.; Goodsell, Stephen J.; Greenbaum, Alexandra Z.; Hartung, Markus; Hibon, Pascale; Hinkley, Sasha; Hung, Li-Wei; Ingraham, Patrick; Larkin, James E.; Macintosh, Bruce; Maire, Jerome; Marchis, Franck; Marois, Christian; Matthews, Brenda C.; Morzinski, Katie M.; Oppenheimer, Rebecca; Patience, Jenny; Perrin, Marshall D.; Rajan, Abhijith; Rantakyrö, Fredrik T.; Sadakuni, Naru; Serio, Andrew; Sivaramakrishnan, Anand; Soummer, Rémi; Thomas, Sandrine; Ward-Duong, Kimberly; Wiktorowicz, Sloane J.; Wolff, Schuyler G.

    2015-10-01

    We present Gemini Planet Imager (GPI) observations of AU Microscopii, a young M dwarf with an edge-on, dusty debris disk. Integral field spectroscopy and broadband imaging polarimetry were obtained during the commissioning of GPI. In our broadband imaging polarimetry observations, we detect the disk only in total intensity and find asymmetries in the morphology of the disk between the southeast (SE) and northwest (NW) sides. The SE side of the disk exhibits a bump at 1″ (10 AU projected separation) that is three times more vertically extended and three times fainter in peak surface brightness than the NW side at similar separations. This part of the disk is also vertically offset by 69 ± 30 mas to the northeast at 1″ when compared to the established disk midplane and is consistent with prior Atacama Large Millimeter/submillimeter Array and Hubble Space Telescope/Space Telescope Imaging Spectrograph observations. We see hints that the SE bump might be a result of detecting a horizontal sliver feature above the main disk that could be the disk backside. Alternatively, when including the morphology of the NW side, where the disk midplane is offset in the opposite direction ∼50 mas between 0.″4 and 1.″2, the asymmetries suggest a warp-like feature. Using our integral field spectroscopy data to search for planets, we are 50% complete for ∼4 MJup planets at 4 AU. We detect a source, resolved only along the disk plane, that could either be a candidate planetary mass companion or a compact clump in the disk.

  2. Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk Around HD 32297

    NASA Technical Reports Server (NTRS)

    Currie, Thayne; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Kuchner, Marc; Jang, Condell, Hannah; Wilner, David; Andrews, Sean; Dahm, Scott; Robitaille,Thomas

    2012-01-01

    We present Keck/NIRC2 K(sub s) band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of r = 0.3 - 2.5" (approx equals 35 - 280 AU). The disk is highly warped to the north and exhibits a complex, "wavy" surface brightness profile interior to r approx equals 110 AU, where the peaks/plateaus in the profiles are shifted between the NE and SW disk lobes. The SW side of the disk is 50 - 100% brighter at r = 35 - 80 AU, and the location of its peak brightness roughly coincides with the disk's mm emission peak. Spectral energy distribution modeling suggests that HD 32297 has at least two dust populations that may originate from two separate belts likely at different locations, possibly at distances coinciding with the surface brightness peaks. A disk model fur a single dust belt including a phase function with two components and a 5 - 10 AU pericenter offset explains the disk's warped structure and reproduces some of the surface brightness profile's shape (e.g. the overall "wavy" profile, the SB peak/plateau shifts) but more poorly reproduces the disk's brightness asymmetry and the profile at wider separations (r > 110 AU). Although there may be a1ternate explanations, agreement between the SW disk brightness peak and disk's peak rom emission is consistent with an overdensity of very small, sub-blowout-sized dust and large, 0.1 - 1 mm-sized grains at approx equal 45 AU tracing the same parent population of planetesimals. New near-IR and submm observations may be able to clarify whether even more complex grain scattering properties or dynamical sculpting by an unseen planet are required to explain HD 32297's disk structure.

  3. Gemini Planet Imager observations of the AU Microscopii debris disk: Asymmetries within one arcsecond

    SciTech Connect

    Wang, Jason J.; Graham, James R.; Pueyo, Laurent; Nielsen, Eric L.; Millar-Blanchaer, Max; De Rosa, Robert J.; Kalas, Paul; Ammons, S. Mark; Bulger, Joanna; Cardwell, Andrew; Chen, Christine; Chiang, Eugene; Chilcote, Jeffrey K.; Doyon, René; Draper, Zachary H.; Duchêne, Gaspard; Fitzgerald, Michael P.; Goodsell, Stephen J.; Greenbaum, Alexandra Z.; Hartung, Markus; Hibon, Pascale; Hinkley, Sasha; Hung, Li -Wei; Ingraham, Patrick; Larkin, James E.; Macintosh, Bruce; Maire, Jerome; Marchis, Franck; Marois, Christian; Matthews, Brenda C.; Morzinski, Katie M.; Oppenheimer, Rebecca; Patience, Jenny; Perrin, Marshall D.; Rajan, Abhijith; Rantakyrö, Fredrik T.; Sadakuni, Naru; Serio, Andrew; Sivaramakrishnan, Anand; Soummer, Rémi; Thomas, Sandrine; Ward-Duong, Kimberly; Wiktorowicz, Sloane J.; Wolff, Schuyler G.

    2015-09-23

    We present Gemini Planet Imager (GPI) observations of AU Microscopii, a young M dwarf with an edge-on, dusty debris disk. Integral field spectroscopy and broadband imaging polarimetry were obtained during the commissioning of GPI. In our broadband imaging polarimetry observations, we detect the disk only in total intensity and find asymmetries in the morphology of the disk between the southeast (SE) and northwest (NW) sides. The SE side of the disk exhibits a bump at 1'' (10 AU projected separation) that is three times more vertically extended and three times fainter in peak surface brightness than the NW side at similar separations. This part of the disk is also vertically offset by 69 ± 30 mas to the northeast at 1'' when compared to the established disk midplane and is consistent with prior Atacama Large Millimeter/submillimeter Array and Hubble Space Telescope/Space Telescope Imaging Spectrograph observations. We see hints that the SE bump might be a result of detecting a horizontal sliver feature above the main disk that could be the disk backside. Alternatively, when including the morphology of the NW side, where the disk midplane is offset in the opposite direction ~50 mas between 0farcs4 and 1farcs2, the asymmetries suggest a warp-like feature. Using our integral field spectroscopy data to search for planets, we are 50% complete for ~4 MJup planets at 4 AU. Lastly, we detect a source, resolved only along the disk plane, that could either be a candidate planetary mass companion or a compact clump in the disk.

  4. Gemini Planet Imager observations of the AU Microscopii debris disk: Asymmetries within one arcsecond

    DOE PAGES

    Wang, Jason J.; Graham, James R.; Pueyo, Laurent; Nielsen, Eric L.; Millar-Blanchaer, Max; De Rosa, Robert J.; Kalas, Paul; Ammons, S. Mark; Bulger, Joanna; Cardwell, Andrew; et al

    2015-09-23

    We present Gemini Planet Imager (GPI) observations of AU Microscopii, a young M dwarf with an edge-on, dusty debris disk. Integral field spectroscopy and broadband imaging polarimetry were obtained during the commissioning of GPI. In our broadband imaging polarimetry observations, we detect the disk only in total intensity and find asymmetries in the morphology of the disk between the southeast (SE) and northwest (NW) sides. The SE side of the disk exhibits a bump at 1'' (10 AU projected separation) that is three times more vertically extended and three times fainter in peak surface brightness than the NW side atmore » similar separations. This part of the disk is also vertically offset by 69 ± 30 mas to the northeast at 1'' when compared to the established disk midplane and is consistent with prior Atacama Large Millimeter/submillimeter Array and Hubble Space Telescope/Space Telescope Imaging Spectrograph observations. We see hints that the SE bump might be a result of detecting a horizontal sliver feature above the main disk that could be the disk backside. Alternatively, when including the morphology of the NW side, where the disk midplane is offset in the opposite direction ~50 mas between 0farcs4 and 1farcs2, the asymmetries suggest a warp-like feature. Using our integral field spectroscopy data to search for planets, we are 50% complete for ~4 MJup planets at 4 AU. Lastly, we detect a source, resolved only along the disk plane, that could either be a candidate planetary mass companion or a compact clump in the disk.« less

  5. KECK/NIRC2 IMAGING OF THE WARPED, ASYMMETRIC DEBRIS DISK AROUND HD 32297

    SciTech Connect

    Currie, Thayne; Kuchner, Marc; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Jang-Condell, Hannah; Wilner, David; Andrews, Sean; Kraus, Adam; Dahm, Scott; Robitaille, Thomas

    2012-09-20

    We present Keck/NIRC2 K{sub s} -band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of r = 0.''3-2.''5 ( Almost-Equal-To 35-280 AU). The disk is highly warped to the north and exhibits a complex, 'wavy' surface brightness (SB) profile interior to r Almost-Equal-To 110 AU, where the peaks/plateaus in the profiles are shifted between the NE and SW disk lobes. The SW side of the disk is 50%-100% brighter at r = 35-80 AU, and the location of its peak brightness roughly coincides with the disk's millimeter (mm) emission peak. Spectral energy distribution modeling suggests that HD 32297 has at least two dust populations that may originate from two separate belts, likely at different locations, possibly at distances coinciding with the SB peaks. A disk model for a single dust belt including a phase function with two components and a 5-10 AU pericenter offset explains the disk's warped structure and reproduces some of the SB profile's shape (e.g., the overall 'wavy' profile, the SB peak/plateau shifts) but more poorly reproduces the disk's brightness asymmetry and the profile at wider separations (r > 110 AU). Although there may be alternate explanations, agreement between the SW disk brightness peak and disk's peak mm emission is consistent with an overdensity of very small, sub-blowout-sized dust and large, 0.1-1 mm sized grains at Almost-Equal-To 45 AU tracing the same parent population of planetesimals. New near-IR and submillimeter observations may be able to clarify whether even more complex grain scattering properties or dynamical sculpting by an unseen planet are required to explain HD 32297's disk structure.

  6. Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk Around HD 32297

    NASA Technical Reports Server (NTRS)

    Currie, Thayne; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Kuchner, Marc; Jang-Condell, Hannah; Wilner, David; Andrews, Sean; Kraus, Adam; Dahm, Scott; Robitaille, Thomas

    2012-01-01

    We present Keck/NIRC2 Ks band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of r = 0.3-2.5 arcse (approx 35-280 AU). The disk is highly warped to the north and exhibits a complex, "wavy" surface brightness profile interior to r approx 110 AU, where the peaks/plateaus in the profiles are shifted between the NE and SW disk lobes. The SW side of the disk is 50 - 100% brighter at r = 35 - 80 AU, and the location of its peak brightness roughly coincides with the disk's mm emission peak. Spectral energy distribution modeling suggests that HD 32297 has at least two dust populations that may originate from two separate belts likely at different locations, possibly at distances coinciding with the surface brightness peaks. A disk model for a single dust belt including a phase function with two components and a 5-10 AU pericenter offset explains the disk's warped structure and reproduces some of the surface brightness profile's shape (e.g. the overall "wavy" profile, the SB peak/plateau shifts) but more poorly reproduces the disk's brightness asymmetry. Although there may be alternate explanations, agreement between the SW disk brightness peak and disk's peak mm emission is consistent with an overdensity of very small, sub-blowout-sized dust and large, 0.1-1 mm-sized grains at approx 45 AU tracing the same parent population of planetesimals. New near-IR and submm observations may be able to clarify whether even more complex grain scattering properties or dynamical sculpting by an unseen planet are required to explain HD 32297's disk structure.

  7. GEMINI PLANET IMAGER OBSERVATIONS OF THE AU MICROSCOPII DEBRIS DISK: ASYMMETRIES WITHIN ONE ARCSECOND

    SciTech Connect

    Wang, Jason J.; Graham, James R.; De Rosa, Robert J.; Kalas, Paul; Chiang, Eugene; Duchêne, Gaspard; Pueyo, Laurent; Chen, Christine; Greenbaum, Alexandra Z.; Nielsen, Eric L.; Millar-Blanchaer, Max; Ammons, S. Mark; Bulger, Joanna; Cardwell, Andrew; Goodsell, Stephen J.; Chilcote, Jeffrey K.; Doyon, René; Draper, Zachary H.; Esposito, Thomas M.; Fitzgerald, Michael P.; and others

    2015-10-01

    We present Gemini Planet Imager (GPI) observations of AU Microscopii, a young M dwarf with an edge-on, dusty debris disk. Integral field spectroscopy and broadband imaging polarimetry were obtained during the commissioning of GPI. In our broadband imaging polarimetry observations, we detect the disk only in total intensity and find asymmetries in the morphology of the disk between the southeast (SE) and northwest (NW) sides. The SE side of the disk exhibits a bump at 1″ (10 AU projected separation) that is three times more vertically extended and three times fainter in peak surface brightness than the NW side at similar separations. This part of the disk is also vertically offset by 69 ± 30 mas to the northeast at 1″ when compared to the established disk midplane and is consistent with prior Atacama Large Millimeter/submillimeter Array and Hubble Space Telescope/Space Telescope Imaging Spectrograph observations. We see hints that the SE bump might be a result of detecting a horizontal sliver feature above the main disk that could be the disk backside. Alternatively, when including the morphology of the NW side, where the disk midplane is offset in the opposite direction ∼50 mas between 0.″4 and 1.″2, the asymmetries suggest a warp-like feature. Using our integral field spectroscopy data to search for planets, we are 50% complete for ∼4 M{sub Jup} planets at 4 AU. We detect a source, resolved only along the disk plane, that could either be a candidate planetary mass companion or a compact clump in the disk.

  8. Searching for Outer Planet Debris Disks/Rings with WISE

    NASA Astrophysics Data System (ADS)

    Skrutskie, M. F.; Masci, F.; Fowler, J.; Cutri, R. M.; Verbiscer, A.; Wright, E. L.

    2011-10-01

    The NASA Wide-Field Infrared Survey Explorer (WISE) imaged the entire celestial sphere at 3.4, 4.6, 12, and 22μm during its 9 month cryogenic survey mission with typical 5-sigma sensitivity for point source detection near the ecliptic of 0.08, 0.11, 1, and 6 mJy (Wright et al. 2010). In addition to the detection of hundreds of millions of stars and galaxies as well as a vast number of known and new asteroids (Mainzer et al. 2011), WISE was sensitive to extended emission from warm dust in the Solar System, for example from zodiacal dust bands and comet debris trails. WISE also scanned all of the superior planets during its mission, encountering them serendipitously during normal Survey operations. This paper presents the result of searches for dust emission originating from irregular satellite impact debris or activity around Jupiter, Saturn, Uranus and Neptune, primarily in the longest wavelength band at 22μm. WISE delivered angular resolution of 6 arcseconds in the three shorterwavelength bands and 12 arcseconds in the band most suited for outer Solar System dust detection at 22μm. Jupiter and Saturn heavily saturate the detectors and scattered light limits the inner radius for analysis. Since WISE acquired its observations over many days, and in some cases weeks, we have constructed deep coadds in the frame of the moving planet rather than using standard WISE Atlas Image Coadds. WISE typically dedicated about 70 sec of observation to each point on the sky near the ecliptic plane, so WISE observations are not nearly as sensitive as those possible with the Spitzer Space Telescope during its cryogenic mission. All of the giant planets were located in a region of the sky scanned in the second half of WISE's all-sky coverage. As a result none of these fields was included in the 57% of the sky covered in the April 2011 WISE Preliminary Data Release. At the time of the WISE Final Data Release, planned for Spring 2012, the individual calibrated "Level 1" frames

  9. The Peculiar Debris Disk of HD 111520 as Resolved by the Gemini Planet Imager

    NASA Astrophysics Data System (ADS)

    Draper, Zachary H.; Duchêne, Gaspard; Millar-Blanchaer, Maxwell A.; Matthews, Brenda C.; Wang, Jason J.; Kalas, Paul; Graham, James R.; Padgett, Deborah; Ammons, S. Mark; Bulger, Joanna; Chen, Christine; Chilcote, Jeffrey K.; Doyon, René; Fitzgerald, Michael P.; Follette, Kate B.; Gerard, Benjamin; Greenbaum, Alexandra Z.; Hibon, Pascale; Hinkley, Sasha; Macintosh, Bruce; Ingraham, Patrick; Lafrenière, David; Marchis, Franck; Marois, Christian; Nielsen, Eric L.; Oppenheimer, Rebecca; Patel, Rahul; Patience, Jenny; Perrin, Marshall; Pueyo, Laurent; Rajan, Abhijith; Rameau, Julien; Sivaramakrishnan, Anand; Vega, David; Ward-Duong, Kimberly; Wolff, Schuyler G.

    2016-08-01

    Using the Gemini Planet Imager, we have resolved the circumstellar debris disk around HD 111520 at a projected range of ˜30–100 AU in both total and polarized H-band intensity. The disk is seen edge-on at a position angle of 165° along the spine of emission. A slight inclination and asymmetric warp are covariant and alter the interpretation of the observed disk emission. We employ three point-spread function subtraction methods to reduce the stellar glare and instrumental artifacts to confirm that there is a roughly 2:1 brightness asymmetry between the NW and SE extension. This specific feature makes HD 111520 the most extreme example of asymmetric debris disks observed in scattered light among similar highly inclined systems, such as HD 15115 and HD 106906. We further identify a tentative localized brightness enhancement and scale height enhancement associated with the disk at ˜40 AU away from the star on the SE extension. We also find that the fractional polarization rises from 10% to 40% from 0.″5 to 0.″8 from the star. The combination of large brightness asymmetry and symmetric polarization fraction leads us to believe that an azimuthal dust density variation is causing the observed asymmetry.

  10. The Peculiar Debris Disk of HD 111520 as Resolved by the Gemini Planet Imager

    NASA Astrophysics Data System (ADS)

    Draper, Zachary H.; Duchêne, Gaspard; Millar-Blanchaer, Maxwell A.; Matthews, Brenda C.; Wang, Jason J.; Kalas, Paul; Graham, James R.; Padgett, Deborah; Ammons, S. Mark; Bulger, Joanna; Chen, Christine; Chilcote, Jeffrey K.; Doyon, René; Fitzgerald, Michael P.; Follette, Kate B.; Gerard, Benjamin; Greenbaum, Alexandra Z.; Hibon, Pascale; Hinkley, Sasha; Macintosh, Bruce; Ingraham, Patrick; Lafrenière, David; Marchis, Franck; Marois, Christian; Nielsen, Eric L.; Oppenheimer, Rebecca; Patel, Rahul; Patience, Jenny; Perrin, Marshall; Pueyo, Laurent; Rajan, Abhijith; Rameau, Julien; Sivaramakrishnan, Anand; Vega, David; Ward-Duong, Kimberly; Wolff, Schuyler G.

    2016-08-01

    Using the Gemini Planet Imager, we have resolved the circumstellar debris disk around HD 111520 at a projected range of ˜30-100 AU in both total and polarized H-band intensity. The disk is seen edge-on at a position angle of 165° along the spine of emission. A slight inclination and asymmetric warp are covariant and alter the interpretation of the observed disk emission. We employ three point-spread function subtraction methods to reduce the stellar glare and instrumental artifacts to confirm that there is a roughly 2:1 brightness asymmetry between the NW and SE extension. This specific feature makes HD 111520 the most extreme example of asymmetric debris disks observed in scattered light among similar highly inclined systems, such as HD 15115 and HD 106906. We further identify a tentative localized brightness enhancement and scale height enhancement associated with the disk at ˜40 AU away from the star on the SE extension. We also find that the fractional polarization rises from 10% to 40% from 0.″5 to 0.″8 from the star. The combination of large brightness asymmetry and symmetric polarization fraction leads us to believe that an azimuthal dust density variation is causing the observed asymmetry.

  11. Detailed models of a sample of debris disks: from Herschel, KIN and Spitzer to the JWST

    NASA Astrophysics Data System (ADS)

    Lebreton, J.; Beichman, C.; Augereau, J. C.

    2014-12-01

    Dusty debris disks surrounding main sequence stars are extrasolar equivalents to the Solar System populations of asteroids, icy bodies and dust grains. Many were observed in thermal emission by Herschel with unprecedented wavelength coverage and spatial resolution, complementing available scattered light images, mid-infrared spectra and interferometric measurements. We present detailed models of the HD 181327 and HD 32297 disks obtained with the GRaTer radiative transfer code and made possible thanks to Herschel. We then focus on the intriguing case of the nearby F2V star η Corvi that shows strong infrared excess despite an estimated age of 1.4 Gyr. We establish a detailed model of its disk from the sub-AU scale to its outermost regions based on observations from the Keck Interferometer Nuller, Herschel and Spitzer. These bright and extended disks will be of prime interest for future observations with the JWST. We finally discuss new debris disks science that will be addressed with the NIRCam and MIRI instruments.

  12. Revealing the structure and dust content of debris disks on solar systems scales with GPI

    NASA Astrophysics Data System (ADS)

    Duchene, Gaspard; Fitzgerald, Michael P.; Kalas, Paul; Graham, James R.; Arriaga, Pauline; Bruzzone, Sebastian; Chen, Christine; Dawson, Rebekah Ilene; Dong, Ruobing; Draper, Zachary; Esposito, Thomas; Follette, Katherine; Hung, Li-Wei; Lawler, Samantha; Metchev, Stanimir; Millar-Blanchaer, Max; Murray-Clay, Ruth; Perrin, Marshall D.; Rameau, Julien; Wang, Jason; Wolff, Schuyler; Macintosh, Bruce; GPIES Team

    2016-01-01

    High contrast scattered light images offer the best prospect to assess the detailed geometry and structure of dusty debris disks. In turn, such images can yield profound insight on the architecture of the underlying planetary system as dust grains respond to the gravitational pull of planetary bodies. A new generation of extreme adaptive optics systems now enables an unprecedented exploration of circumstellar disks on solar system scales. Here we review the new science derived from over a dozen debris disks imaged with the Gemini Planet Imager (GPI) as part of the GPI Exoplanet Survey (GPIES). In addition to its exquisite imaging capability, GPI's polarimetric mode provides invaluable insight on the dust content of each disk, in most cases for the very first time. These early results typically reveal narrow belts of material with evacuated regions roughly 50-100 AU in radius, subtle asymmetries in structure and high degree of linear polarization. We will provide an overview of the disk observations made during the GPIES campaign to date and will discuss in more detail some of the most remarkable systems.This work is supported by grants NSF AST-0909188, -1411868, -1413718; NASA NNX-15AD95G, -14AJ80G, -11AD21G; and the NExSS research network.

  13. Analysis of the Chemical Composition of the Atmospheres of Stars with Debris Disks and Planetary Systems

    NASA Astrophysics Data System (ADS)

    Rojas, M.; Drake, N. A.; Chavero, C.; Pereira, C. B.; Kholtygin, A. F.; Solovyov, D. I.

    2013-12-01

    Spectroscopic studies of seven low mass stars in spectral classes F, G, and K are presented. Four of these (HD 1581, HD 10700, HD 17925, and HD 22484) have debris disks and for two of them (HD 22049 and HD 222582(A + B)) planets are observed. Neither a debris disk nor planets have been observed for one the program stars (HD 20766). High resolution spectral observations of the program stars were made at the 2.2-m telescope of the European Southern Observatory (ESO) during 2008 with the FEROS spectrograph (R = 48000, spectral range 3800-9200 Å). The fundamental parameters of the stars are determined, including effective temperature, acceleration of gravity at the stars' surface, microturbulence velocity, metallicity, and the abundances of volatile and refractory elements in their atmospheres. The positions of all these stars are indicated on a Hertzsprung-Russell diagram.

  14. Debris Disk Variability: Observational Test Bed for Probing Terrestrial Planet Formation

    NASA Astrophysics Data System (ADS)

    Su, Kate; Rieke, George; Jackson, Alan; Gaspar, Andras; Meng, Huan

    2014-12-01

    The newly discovered variable emission by extreme debris disks provides a unique opportunity to learn about asteroid-sized bodies in young exoplanetary systems and to explore planetesimal collisions and their aftermaths during the era of terrestrial planet building. However, the baseline of existing observations is too short to characterize this behavior well. We propose to monitor variations in seven systems where they have already been identified, and to look for them in seven more systems that are likely to behave similarly, selected because their high levels of warm dust point to elevated rates of planetesimal collisions. This program requires 130 hours of observing time and will establish the time-domain study of debris disks as an important heritage of the Spitzer warm mission.

  15. Modeling self-subtraction in angular differential imaging: Application to the HD 32297 debris disk

    SciTech Connect

    Esposito, Thomas M.; Fitzgerald, Michael P.; Graham, James R.; Kalas, Paul

    2014-01-01

    We present a new technique for forward-modeling self-subtraction of spatially extended emission in observations processed with angular differential imaging (ADI) algorithms. High-contrast direct imaging of circumstellar disks is limited by quasi-static speckle noise, and ADI is commonly used to suppress those speckles. However, the application of ADI can result in self-subtraction of the disk signal due to the disk's finite spatial extent. This signal attenuation varies with radial separation and biases measurements of the disk's surface brightness, thereby compromising inferences regarding the physical processes responsible for the dust distribution. To compensate for this attenuation, we forward model the disk structure and compute the form of the self-subtraction function at each separation. As a proof of concept, we apply our method to 1.6 and 2.2 μm Keck adaptive optics NIRC2 scattered-light observations of the HD 32297 debris disk reduced using a variant of the 'locally optimized combination of images' algorithm. We are able to recover disk surface brightness that was otherwise lost to self-subtraction and produce simplified models of the brightness distribution as it appears with and without self-subtraction. From the latter models, we extract radial profiles for the disk's brightness, width, midplane position, and color that are unbiased by self-subtraction. Our analysis of these measurements indicates a break in the brightness profile power law at r ≈ 110 AU and a disk width that increases with separation from the star. We also verify disk curvature that displaces the midplane by up to 30 AU toward the northwest relative to a straight fiducial midplane.

  16. CHEMISTRY OF IMPACT-GENERATED SILICATE MELT-VAPOR DEBRIS DISKS

    SciTech Connect

    Visscher, Channon; Fegley, Bruce Jr.

    2013-04-10

    In the giant impact theory for lunar origin, the Moon forms from material ejected by the impact into an Earth-orbiting disk. Here we report the initial results from a silicate melt-vapor equilibrium chemistry model for such impact-generated planetary debris disks. In order to simulate the chemical behavior of a two-phase (melt+vapor) disk, we calculate the temperature-dependent pressure and chemical composition of vapor in equilibrium with molten silicate from 2000 to 4000 K. We consider the elements O, Na, K, Fe, Si, Mg, Ca, Al, Ti, and Zn for a range of bulk silicate compositions (Earth, Moon, Mars, eucrite parent body, angrites, and ureilites). In general, the disk atmosphere is dominated by Na, Zn, and O{sub 2} at lower temperatures (<3000 K) and SiO, O{sub 2}, and O at higher temperatures. The high-temperature chemistry is consistent for any silicate melt composition, and we thus expect abundant SiO, O{sub 2}, and O to be a common feature of hot, impact-generated debris disks. In addition, the saturated silicate vapor is highly oxidizing, with oxygen fugacity (f{sub O{sub 2}}) values (and hence H{sub 2}O/H{sub 2} and CO{sub 2}/CO ratios) several orders of magnitude higher than those in a solar-composition gas. High f{sub O{sub 2}} values in the disk atmosphere are found for any silicate composition because oxygen is the most abundant element in rock. We thus expect high oxygen fugacity to be a ubiquitous feature of any silicate melt-vapor disk produced via collisions between rocky planets.

  17. FIVE DEBRIS DISKS NEWLY REVEALED IN SCATTERED LIGHT FROM THE HUBBLE SPACE TELESCOPE NICMOS ARCHIVE

    SciTech Connect

    Soummer, Rémi; Perrin, Marshall D.; Pueyo, Laurent; Choquet, Élodie; Chen, Christine; Golimowski, David A.; Brendan Hagan, J.; Moerchen, Margaret; N'Diaye, Mamadou; Wolff, Schuyler; Debes, John; Hines, Dean C.; Mittal, Tushar; Rajan, Abhijith; Schneider, Glenn

    2014-05-10

    We have spatially resolved five debris disks (HD 30447, HD 35841, HD 141943, HD 191089, and HD 202917) for the first time in near-infrared scattered light by reanalyzing archival Hubble Space Telescope (HST)/NICMOS coronagraphic images obtained between 1999 and 2006. One of these disks (HD 202917) was previously resolved at visible wavelengths using the HST/Advanced Camera for Surveys. To obtain these new disk images, we performed advanced point-spread function subtraction based on the Karhunen-Loève Image Projection algorithm on recently reprocessed NICMOS data with improved detector artifact removal (Legacy Archive PSF Library And Circumstellar Environments (LAPLACE) Legacy program). Three of the disks (HD 30447, HD 35841, and HD 141943) appear edge-on, while the other two (HD 191089 and HD 202917) appear inclined. The inclined disks have been sculpted into rings; in particular, the disk around HD 202917 exhibits strong asymmetries. All five host stars are young (8-40 Myr), nearby (40-100 pc) F and G stars, and one (HD 141943) is a close analog to the young Sun during the epoch of terrestrial planet formation. Our discoveries increase the number of debris disks resolved in scattered light from 19 to 23 (a 21% increase). Given their youth, proximity, and brightness (V = 7.2-8.5), these targets are excellent candidates for follow-up investigations of planet formation at visible wavelengths using the HST/Space Telescope Imaging Spectrograph coronagraph, at near-infrared wavelengths with the Gemini Planet Imager and Very Large Telescope/SPHERE, and at thermal infrared wavelengths with the James Webb Space Telescope NIRCam and MIRI coronagraphs.

  18. Five Debris Disks Newly Revealed in Scattered Light from the Hubble Space Telescope NICMOS Archive

    NASA Astrophysics Data System (ADS)

    Soummer, Rémi; Perrin, Marshall D.; Pueyo, Laurent; Choquet, Élodie; Chen, Christine; Golimowski, David A.; Brendan Hagan, J.; Mittal, Tushar; Moerchen, Margaret; N'Diaye, Mamadou; Rajan, Abhijith; Wolff, Schuyler; Debes, John; Hines, Dean C.; Schneider, Glenn

    2014-05-01

    We have spatially resolved five debris disks (HD 30447, HD 35841, HD 141943, HD 191089, and HD 202917) for the first time in near-infrared scattered light by reanalyzing archival Hubble Space Telescope (HST)/NICMOS coronagraphic images obtained between 1999 and 2006. One of these disks (HD 202917) was previously resolved at visible wavelengths using the HST/Advanced Camera for Surveys. To obtain these new disk images, we performed advanced point-spread function subtraction based on the Karhunen-Loève Image Projection algorithm on recently reprocessed NICMOS data with improved detector artifact removal (Legacy Archive PSF Library And Circumstellar Environments (LAPLACE) Legacy program). Three of the disks (HD 30447, HD 35841, and HD 141943) appear edge-on, while the other two (HD 191089 and HD 202917) appear inclined. The inclined disks have been sculpted into rings; in particular, the disk around HD 202917 exhibits strong asymmetries. All five host stars are young (8-40 Myr), nearby (40-100 pc) F and G stars, and one (HD 141943) is a close analog to the young Sun during the epoch of terrestrial planet formation. Our discoveries increase the number of debris disks resolved in scattered light from 19 to 23 (a 21% increase). Given their youth, proximity, and brightness (V = 7.2-8.5), these targets are excellent candidates for follow-up investigations of planet formation at visible wavelengths using the HST/Space Telescope Imaging Spectrograph coronagraph, at near-infrared wavelengths with the Gemini Planet Imager and Very Large Telescope/SPHERE, and at thermal infrared wavelengths with the James Webb Space Telescope NIRCam and MIRI coronagraphs.

  19. CONFIRMING THE PRIMARILY SMOOTH STRUCTURE OF THE VEGA DEBRIS DISK AT MILLIMETER WAVELENGTHS

    SciTech Connect

    Hughes, A. Meredith; Plambeck, Richard; Chiang, Eugene; Wilner, David J.; Andrews, Sean M.; Mason, Brian; Carpenter, John M.; Chiang, Hsin-Fang; Williams, Jonathan P.; Hales, Antonio; Su, Kate; Dicker, Simon; Korngut, Phil; Devlin, Mark

    2012-05-01

    Clumpy structure in the debris disk around Vega has been previously reported at millimeter wavelengths and attributed to concentrations of dust grains trapped in resonances with an unseen planet. However, recent imaging at similar wavelengths with higher sensitivity has disputed the observed structure. We present three new millimeter-wavelength observations that help to resolve the puzzling and contradictory observations. We have observed the Vega system with the Submillimeter Array (SMA) at a wavelength of 880 {mu}m and an angular resolution of 5''; with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at a wavelength of 1.3 mm and an angular resolution of 5''; and with the Green Bank Telescope (GBT) at a wavelength of 3.3 mm and angular resolution of 10''. Despite high sensitivity and short baselines, we do not detect the Vega debris disk in either of the interferometric data sets (SMA and CARMA), which should be sensitive at high significance to clumpy structure based on previously reported observations. We obtain a marginal (3{sigma}) detection of disk emission in the GBT data; the spatial distribution of the emission is not well constrained. We analyze the observations in the context of several different models, demonstrating that the observations are consistent with a smooth, broad, axisymmetric disk with inner radius 20-100 AU and width {approx}> 50 AU. The interferometric data require that at least half of the 860 {mu}m emission detected by previous single-dish observations with the James Clerk Maxwell Telescope be distributed axisymmetrically, ruling out strong contributions from flux concentrations on spatial scales of {approx}<100 AU. These observations support recent results from the Plateau de Bure Interferometer indicating that previous detections of clumpy structure in the Vega debris disk were spurious.

  20. UV Spectroscopy of Star-grazing Comets Within the 49 Ceti Debris Disk

    NASA Astrophysics Data System (ADS)

    Miles, Brittany E.; Roberge, Aki; Welsh, Barry

    2016-06-01

    We present the analysis of time-variable Doppler-shifted absorption features in far-UV spectra of the unusual 49 Ceti debris disk. This nearly edge-on disk is one of the brightest known and is one of the very few containing detectable amounts of circumstellar (CS) gas as well as dust. In our two visits of Hubble Space Telescope STIS spectra, variable absorption features are seen on the wings of lines arising from Cii and Civ but not for any of the other CS absorption lines. Similar variable features have long been seen in spectra of the well-studied β Pictoris debris disk and attributed to the transits of star-grazing comets. We calculated the velocity ranges and apparent column densities of the 49 Cet variable gas, which appears to have been moving at velocities of tens to hundreds of km s-1 relative to the central star. The velocities in the redshifted variable event seen in the second visit show that the maximum distances of the infalling gas at the time of transit were about 0.05-0.2 au from the central star. A preliminary attempt at a composition analysis of the redshifted event suggests that the C/O ratio in the infalling gas is super-solar, as it is in the bulk of the stable disk gas.

  1. Near-infrared imaging of white dwarfs with candidate debris disks

    SciTech Connect

    Wang, Zhongxiang; Tziamtzis, Anestis; Wang, Xuebing

    2014-02-10

    We have carried out JHK{sub s} imaging of 12 white dwarf debris disk candidates from the WIRED Sloan Digital Sky Survey Data Release 7 catalog, aiming to confirm or rule out disks among these sources. On the basis of positional identification and the flux density spectra, we find that seven white dwarfs have excess infrared emission, but mostly at Wide-field Infrared Survey Explorer W1 and W2 bands. Four are due to nearby red objects consistent with background galaxies or very low mass dwarfs, and one exhibits excess emission at JHK{sub s} consistent with an unresolved L0 companion at the correct distance. While our photometry is not inconsistent with all seven excesses arising from disks, the stellar properties are distinct from the known population of debris disk white dwarfs, making the possibility questionable. In order to further investigate the nature of these infrared sources, warm Spitzer imaging is needed, which may help resolve galaxies from the white dwarfs and provide more accurate flux measurements.

  2. Substantial reservoirs of molecular hydrogen in the debris disks around young stars.

    PubMed

    Thi, W F; Blake, G A; van Dishoeck, E F; van Zadelhoff, G J; Horn, J M; Becklin, E E; Mannings, V; Sargent, A I; van Den Ancker, M E; Natta, A

    2001-01-01

    Circumstellar accretion disks transfer matter from molecular clouds to young stars and to the sites of planet formation. The disks observed around pre-main-sequence stars have properties consistent with those expected for the pre-solar nebula from which our own Solar System formed 4.5 Gyr ago. But the 'debris' disks that encircle more than 15% of nearby main-sequence stars appear to have very small amounts of gas, based on observations of the tracer molecule carbon monoxide: these observations have yielded gas/dust ratios much less than 0.1, whereas the interstellar value is about 100 (ref. 9). Here we report observations of the lowest rotational transitions of molecular hydrogen (H2) that reveal large quantities of gas in the debris disks around the stars beta Pictoris, 49 Ceti and HD135344. The gas masses calculated from the data are several hundreds to a thousand times greater than those estimated from the CO observations, and yield gas/dust ratios of the same order as the interstellar value.

  3. Bright debris disk candidates detected with the AKARI/FAR-infrared surveyor

    SciTech Connect

    Liu, Qiong; Wang, Tinggui; Jiang, Peng E-mail: twang@ustc.edu.cn

    2014-07-01

    We cross-correlate the Hipparcos main-sequence star catalog with the AKARI/FIS catalog and identify 136 stars (at >90% reliability) with far-infrared detections in at least one band. After rejecting 57 stars classified as young stellar objects, Be stars and other type stars with known dust disks or with potential contaminations, and 4 stars without infrared excess emission, we obtain a sample of 75 candidate stars with debris disks. Stars in our sample cover spectral types from B to K with most being early types. This represents a unique sample of luminous debris disks that derived uniformly from an all-sky survey with a spatial resolution factor of four better than the previous such survey by IRAS. Moreover, by collecting the infrared photometric data from other public archives, almost three-quarters of them have infrared excesses in more than one band, allowing an estimate of the dust temperatures. We fit the blackbody model to the broadband spectral energy distribution of these stars to derive the statistical distribution of the disk parameters. Four B stars with excesses in four or more bands require a double blackbody model, with the high one around 100 or 200 K and the low one around 40-50 K.

  4. Substantial reservoirs of molecular hydrogen in the debris disks around young stars

    NASA Technical Reports Server (NTRS)

    Thi, W. F.; Blake, G. A.; van Dishoeck, E. F.; van Zadelhoff, G. J.; Horn, J. M.; Becklin, E. E.; Mannings, V.; Sargent, A. I.; van Den Ancker, M. E.; Natta, A.

    2001-01-01

    Circumstellar accretion disks transfer matter from molecular clouds to young stars and to the sites of planet formation. The disks observed around pre-main-sequence stars have properties consistent with those expected for the pre-solar nebula from which our own Solar System formed 4.5 Gyr ago. But the 'debris' disks that encircle more than 15% of nearby main-sequence stars appear to have very small amounts of gas, based on observations of the tracer molecule carbon monoxide: these observations have yielded gas/dust ratios much less than 0.1, whereas the interstellar value is about 100 (ref. 9). Here we report observations of the lowest rotational transitions of molecular hydrogen (H2) that reveal large quantities of gas in the debris disks around the stars beta Pictoris, 49 Ceti and HD135344. The gas masses calculated from the data are several hundreds to a thousand times greater than those estimated from the CO observations, and yield gas/dust ratios of the same order as the interstellar value.

  5. UV Spectroscopy of Star-grazing Comets Within the 49 Ceti Debris Disk

    NASA Astrophysics Data System (ADS)

    Miles, Brittany E.; Roberge, Aki; Welsh, Barry

    2016-06-01

    We present the analysis of time-variable Doppler-shifted absorption features in far-UV spectra of the unusual 49 Ceti debris disk. This nearly edge-on disk is one of the brightest known and is one of the very few containing detectable amounts of circumstellar (CS) gas as well as dust. In our two visits of Hubble Space Telescope STIS spectra, variable absorption features are seen on the wings of lines arising from Cii and Civ but not for any of the other CS absorption lines. Similar variable features have long been seen in spectra of the well-studied β Pictoris debris disk and attributed to the transits of star-grazing comets. We calculated the velocity ranges and apparent column densities of the 49 Cet variable gas, which appears to have been moving at velocities of tens to hundreds of km s‑1 relative to the central star. The velocities in the redshifted variable event seen in the second visit show that the maximum distances of the infalling gas at the time of transit were about 0.05–0.2 au from the central star. A preliminary attempt at a composition analysis of the redshifted event suggests that the C/O ratio in the infalling gas is super-solar, as it is in the bulk of the stable disk gas.

  6. DISCOVERY OF MOLECULAR GAS AROUND HD 131835 IN AN APEX MOLECULAR LINE SURVEY OF BRIGHT DEBRIS DISKS

    SciTech Connect

    Moór, A.; Ábrahám, P.; Kóspál, Á.; Szabó, Gy. M.; Kiss, Cs.; Henning, Th.; Balog, Z.; Juhász, A.; Pascucci, I.; Vavrek, R.; Csengeri, T.; Güsten, R.; Grady, C.

    2015-11-20

    Debris disks are considered to be gas-poor, but recent observations revealed molecular or atomic gas in several 10–40 Myr old systems. We used the APEX and IRAM 30 m radio telescopes to search for CO gas in 20 bright debris disks. In one case, around the 16 Myr old A-type star HD 131835, we discovered a new gas-bearing debris disk, where the CO 3–2 transition was successfully detected. No other individual system exhibited a measurable CO signal. Our Herschel Space Observatory far-infrared images of HD 131835 marginally resolved the disk at both 70 and 100 μm, with a characteristic radius of ∼170 AU. While in stellar properties HD 131835 resembles β Pic, its dust disk properties are similar to those of the most massive young debris disks. With the detection of gas in HD 131835 the number of known debris disks with CO content has increased to four, all of them encircling young (≤40 Myr) A-type stars. Based on statistics within 125 pc, we suggest that the presence of a detectable amount of gas in the most massive debris disks around young A-type stars is a common phenomenon. Our current data cannot conclude on the origin of gas in HD 131835. If the gas is secondary, arising from the disruption of planetesimals, then HD 131835 is a comparably young, and in terms of its disk, more massive analog of the β Pic system. However, it is also possible that this system, similar to HD 21997, possesses a hybrid disk, where the gas material is predominantly primordial, while the dust grains are mostly derived from planetesimals.

  7. Insights into Planet Formation from Debris Disks - II. Giant Impacts in Extrasolar Planetary Systems

    NASA Astrophysics Data System (ADS)

    Wyatt, Mark C.; Jackson, Alan P.

    2016-03-01

    Giant impacts refer to collisions between two objects each of which is massive enough to be considered at least a planetary embryo. The putative collision suffered by the proto-Earth that created the Moon is a prime example, though most Solar System bodies bear signatures of such collisions. Current planet formation models predict that an epoch of giant impacts may be inevitable, and observations of debris around other stars are providing mounting evidence that giant impacts feature in the evolution of many planetary systems. This chapter reviews giant impacts, focussing on what we can learn about planet formation by studying debris around other stars. Giant impact debris evolves through mutual collisions and dynamical interactions with planets. General aspects of this evolution are outlined, noting the importance of the collision-point geometry. The detectability of the debris is discussed using the example of the Moon-forming impact. Such debris could be detectable around another star up to 10 Myr post-impact, but model uncertainties could reduce detectability to a few 100 yr window. Nevertheless the 3 % of young stars with debris at levels expected during terrestrial planet formation provide valuable constraints on formation models; implications for super-Earth formation are also discussed. Variability recently observed in some bright disks promises to illuminate the evolution during the earliest phases when vapour condensates may be optically thick and acutely affected by the collision-point geometry. The outer reaches of planetary systems may also exhibit signatures of giant impacts, such as the clumpy debris structures seen around some stars.

  8. Herschel Observations of Gas and Dust in the Unusual 49 Ceti Debris Disk

    NASA Technical Reports Server (NTRS)

    Roberge, A.; Kamp, I.; Montesinos, B.; Dent, W. R. F.; Meeus, G.; Donaldson, J. K.; Olofsson, J.; Moor, A.; Augereau, J.-C.; Howard, C.; Eiroa, C.; Thi, W.-F.; Ardila, D. R.; Sandell, G.; Woitke, P.

    2013-01-01

    We present far-IR/sub-mm imaging and spectroscopy of 49 Ceti, an unusual circumstellar disk around a nearby young A1V star. The system is famous for showing the dust properties of a debris disk, but the gas properties of a low-mass protoplanetary disk. The data were acquired with the Herschel Space Observatory PACS and SPIRE instruments, largely as part of the “Gas in Protoplanetary Systems” (GASPS) Open Time Key Programme. Disk dust emission is detected in images at 70, 160, 250, 350, and 500 micron; 49 Cet is significantly extended in the 70 micron image, spatially resolving the outer dust disk for the first time. Spectra covering small wavelength ranges centered on eight atomic and molecular emission lines were obtained, including [O i] 63 micron and [C ii] 158 micron. The C ii line was detected at the 5 sigma level—the first detection of atomic emission from the disk. No other emission lines were seen, despite the fact that the Oi line is the brightest one observed in Herschel protoplanetary disk spectra. We present an estimate of the amount of circumstellar atomic gas implied by the C ii emission. The new far-IR/sub-mm data fills in a large gap in the previous spectral energy distribution (SED) of 49 Cet. A simple model of the new SED confirms the two-component structure of the disk: warm inner dust and cold outer dust that produces most of the observed excess. Finally, we discuss preliminary thermochemical modeling of the 49 Cet gas/dust disk and our attempts to match several observational results simultaneously. Although we are not yet successful in doing so, our investigations shed light on the evolutionary status of the 49 Cet gas, which might not be primordial gas but rather secondary gas coming from comets.

  9. VOLATILE-RICH CIRCUMSTELLAR GAS IN THE UNUSUAL 49 CETI DEBRIS DISK

    SciTech Connect

    Roberge, Aki; Grady, Carol A.; Welsh, Barry Y.; Kamp, Inga; Weinberger, Alycia J.

    2014-11-20

    We present Hubble Space Telescope Space Telescope Imaging Spectrograph far-UV spectra of the edge-on disk around 49 Ceti, one of the very few debris disks showing submillimeter CO emission. Many atomic absorption lines are present in the spectra, most of which arise from circumstellar gas lying along the line-of-sight to the central star. We determined the line-of-sight C I column density, estimated the total carbon column density, and set limits on the O I column density. Surprisingly, no line-of-sight CO absorption was seen. We discuss possible explanations for this non-detection, and present preliminary estimates of the carbon abundances in the line-of-sight gas. The C/Fe ratio is much greater than the solar value, suggesting that 49 Cet harbors a volatile-rich gas disk similar to that of β Pictoris.

  10. Searching for Planets in Holey Debris Disks with the Apodizing Phase Plate

    NASA Astrophysics Data System (ADS)

    Meshkat, Tiffany; Bailey, Vanessa P.; Su, Kate Y. L.; Kenworthy, Matthew A.; Mamajek, Eric E.; Hinz, Philip M.; Smith, Paul S.

    2015-02-01

    We present our first results from a high-contrast imaging search for planetary mass companions around stars with gapped debris disks, as inferred from the stars' bright infrared excesses. For the six considered stars, we model the disks' unresolved infrared spectral energy distributions in order to derive the temperature and location of the disk components. With VLT/NaCo Apodizing Phase Plate coronagraphic L'-band imaging, we search for planetary mass companions that may be sculpting the disks. We detect neither disks nor companions in this sample, confirmed by comparing plausible point sources with archival data. In order to calculate our mass sensitivity limit, we revisit the stellar age estimates. One target, HD 17848, at 540 ± 100 Myr old is significantly older than previously estimated. We then discuss our high-contrast imaging results with respect to the disk properties. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile, ESO under program numbers 090.C-0148(A) and 091.C-0457(A)

  11. THE GEMINI PLANET-FINDING CAMPAIGN: THE FREQUENCY OF GIANT PLANETS AROUND DEBRIS DISK STARS

    SciTech Connect

    Wahhaj, Zahed; Liu, Michael C.; Nielsen, Eric L.; Ftaclas, Christ; Chun, Mark; Biller, Beth A.; Hayward, Thomas L.; Thatte, Niranjan; Tecza, Matthias; Shkolnik, Evgenya L.; Kuchner, Marc; Reid, I. Neill; De Gouveia Dal Pino, Elisabete M.; Gregorio-Hetem, Jane; Boss, Alan; Lin, Douglas N. C.; and others

    2013-08-20

    We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. We achieved median H-band contrasts of 12.4 mag at 0.''5 and 14.1 mag at 1'' separation. Follow-up observations of the 66 candidates with projected separation <500 AU show that all of them are background objects. To establish statistical constraints on the underlying giant planet population based on our imaging data, we have developed a new Bayesian formalism that incorporates (1) non-detections, (2) single-epoch candidates, (3) astrometric and (4) photometric information, and (5) the possibility of multiple planets per star to constrain the planet population. Our formalism allows us to include in our analysis the previously known {beta} Pictoris and the HR 8799 planets. Our results show at 95% confidence that <13% of debris disk stars have a {>=}5 M{sub Jup} planet beyond 80 AU, and <21% of debris disk stars have a {>=}3 M{sub Jup} planet outside of 40 AU, based on hot-start evolutionary models. We model the population of directly imaged planets as d {sup 2} N/dMda{proportional_to}m {sup {alpha}} a {sup {beta}}, where m is planet mass and a is orbital semi-major axis (with a maximum value of a{sub max}). We find that {beta} < -0.8 and/or {alpha} > 1.7. Likewise, we find that {beta} < -0.8 and/or a{sub max} < 200 AU. For the case where the planet frequency rises sharply with mass ({alpha} > 1.7), this occurs because all the planets detected to date have masses above 5 M{sub Jup}, but planets of lower mass could easily have been detected by our search. If we ignore the {beta} Pic and HR 8799 planets (should they belong to a rare and distinct group), we find that <20% of debris disk stars have a {>=}3 M{sub Jup} planet beyond 10 AU, and {beta} < -0.8 and/or {alpha} < -1.5. Likewise, {beta} < -0.8 and/or a{sub max} < 125 AU. Our Bayesian constraints are not strong enough to reveal any dependence of the planet

  12. The Exozodiacal Dust Problem for Direct Observations of Exo-Earths

    NASA Astrophysics Data System (ADS)

    Roberge, Aki; Chen, Christine H.; Millan-Gabet, Rafael; Weinberger, Alycia J.; Hinz, Philip M.; Stapelfeldt, Karl R.; Absil, Olivier; Kuchner, Marc J.; Bryden, Geoffrey

    2012-08-01

    Debris dust in the habitable zones of stars—otherwise known as exozodiacal dust—comes from extrasolar asteroids and comets and is thus an expected part of a planetary system. Background flux from the solar system's zodiacal dust and the exozodiacal dust in the target system is likely to be the largest source of astrophysical noise in direct observations of terrestrial planets in the habitable zones of nearby stars. Furthermore, dust structures like clumps, thought to be produced by dynamical interactions with exoplanets, are a possible source of confusion. In this article, we qualitatively assess the primary impact of exozodiacal dust on high-contrast direct imaging at optical wavelengths, such as would be performed with a coronagraph. Then we present the sensitivity of previous, current, and near-term facilities to thermal emission from debris dust at all distances from nearby solar-type stars, as well as our current knowledge of dust levels from recent surveys. Finally, we address the other method of detecting debris dust, through high-contrast imaging in scattered light. This method is currently far less sensitive than thermal emission observations, but provides high spatial resolution for studying dust structures. This article represents the first report of NASA's Exoplanet Exploration Program Analysis Group (ExoPAG).

  13. ALMA OBSERVATIONS OF THE DEBRIS DISK AROUND THE YOUNG SOLAR ANALOG HD 107146

    SciTech Connect

    Ricci, L.; Carpenter, J. M.; Fu, B.; Hughes, A. M.; Corder, S.; Isella, A.

    2015-01-10

    We present the Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations at a wavelength of 1.25 mm of the debris disk surrounding the ∼100 Myr old solar analog HD 107146. The continuum emission extends from about 30 to 150 AU from the central star with a decrease in the surface brightness at intermediate radii. We analyze the ALMA interferometric visibilities using debris disk models with radial profiles for the dust surface density parameterized as (1) a single power law, (2) a single power law with a gap, and (3) a double power law. We find that models with a gap of radial width ∼8 AU at a distance of ∼80 AU from the central star, as well as double power-law models with a dip in the dust surface density at ∼70 AU provide significantly better fits to the ALMA data than single power-law models. We discuss possible scenarios for the origin of the HD 107146 debris disk using models of planetesimal belts in which the formation of Pluto-sized objects trigger disruptive collisions of large bodies, as well as models that consider the interaction of a planetary system with a planetesimal belt and spatial variation of the dust opacity across the disk. If future observations with higher angular resolution and sensitivity confirm the fully depleted gap structure discussed here, a planet with a mass of approximately a few Earth masses in a nearly circular orbit at ∼80 AU from the central star would be a possible explanation for the presence of the gap.

  14. Unraveling the mystery of exozodiacal dust

    NASA Astrophysics Data System (ADS)

    Ertel, Steve; Augereau, Jean-Charles; Thebault, Philippe; Absil, Olivier; Bonsor, Amy; Defrere, Denis; Kral, Quentin; Le Bouquin, Jean-Baptiste; Lebreton, Jeremy; Coude du Foresto, Vincent

    2013-07-01

    Exozodiacal dust clouds are thought to be the extrasolar analogs of the Solar System's zodiacal dust. Studying these systems provides insights in the architecture of the innermost regions of planetary systems, including the habitable zone. Furthermore, the mere presence of the dust may result in major obstacles for direct imaging of earth-like planets. Our EXOZODI project aims to detect and study exozodiacal dust and to explain its origin. We are carrying out the first large, near-infrared interferometric survey in the northern (CHARA/FLUOR) and southern (VLTI/PIONIER) hemisphere. Preliminary results suggest a detection rate of up to 30% around A to K type stars and interesting trends with spectral type and age. In addition to the statistical analysis of our survey results, detailed modeling studies of single systems, modeling of possible dust creation mechanisms and the development of next-generation modeling tools dedicated to address the mystery of exozodiacal dust are main tasks of our project.

  15. HUBBLE SPACE TELESCOPE OPTICAL IMAGING OF THE ERODING DEBRIS DISK HD 61005

    SciTech Connect

    Maness, H. L.; Kalas, P.; Peek, K. M. G.; Chiang, E. I.; Graham, James R.; Scherer, K.; Fitzgerald, M. P.; Hines, D. C.; Schneider, G.; Metchev, S. A.

    2009-12-20

    We present Hubble Space Telescope optical coronagraphic polarization imaging observations of the dusty debris disk HD 61005. The scattered light intensity image and polarization structure reveal a highly inclined disk with a clear asymmetric, swept back component, suggestive of significant interaction with the ambient interstellar medium (ISM). The combination of our new data with the published 1.1 mum discovery image shows that the grains are blue scattering with no strong color gradient as a function of radius, implying predominantly submicron-sized grains. We investigate possible explanations that could account for the observed swept back, asymmetric morphology. Previous work has suggested that HD 61005 may be interacting with a cold, unusually dense interstellar cloud. However, limits on the intervening interstellar gas column density from an optical spectrum of HD 61005 in the Na I D lines render this possibility unlikely. Instead, HD 61005 may be embedded in a more typical warm, low-density cloud that introduces secular perturbations to dust grain orbits. This mechanism can significantly distort the ensemble disk structure within a typical cloud crossing time. For a counterintuitive relative flow direction-parallel to the disk midplane-we find that the structures generated by these distortions can very roughly approximate the HD 61005 morphology. Future observational studies constraining the direction of the relative ISM flow will thus provide an important constraint for future modeling. Independent of the interpretation for HD 61005, we expect that interstellar gas drag likely plays a role in producing asymmetries observed in other debris disk systems, such as HD 15115 and delta Velorum.

  16. A SPITZER SPACE TELESCOPE STUDY OF THE DEBRIS DISKS AROUND FOUR SDSS WHITE DWARFS

    SciTech Connect

    Brinkworth, C. S.; Girven, J. M.; Hoard, D. W.; Gaensicke, B. T.; Marsh, T. R.; Parsons, S. G.; Koester, D.

    2012-05-01

    We present Spitzer Space Telescope data of four isolated white dwarfs that were previously known to harbor circumstellar gaseous disks. Infrared Array Camera photometry shows a significant infrared excess in all of the systems, SDSS0738+1835, SDSS0845+2257, SDSS1043+0855, and SDSS1617+1620, indicative of a dusty extension to those disks. The 4.5 {mu}m excesses seen in SDSS0738, SDSS0845, and SDSS1617 are 7.5, 5.7, and 4.5 times the white dwarf contribution, respectively. In contrast, in SDSS1043, the measured flux density at 4.5 {mu}m is only 1.7 times the white dwarf contribution. We compare the measured IR excesses in the systems to models of geometrically thin, optically thick disks, and find that we are able to match the measured spectral energy distributions to within 3{sigma} of the uncertainties, although disks with unfeasibly hot inner dust temperatures generally provide a better fit than those below the dust sublimation temperature. Possible explanations for the dearth of dust around SDSS1043+0855 are briefly discussed. Including our previous study of SDSS1228+1040, all five white dwarfs with gaseous debris disks have significant amounts of dust around them. It is evident that gas and dust can coexist around these relatively warm, relatively young white dwarfs.

  17. A RESOLVED DEBRIS DISK AROUND THE CANDIDATE PLANET-HOSTING STAR HD 95086

    SciTech Connect

    Moór, A.; Ábrahám, P.; Szabó, Gy. M.; Kiss, Cs.; Kóspál, Á.; Apai, D.; Pascucci, I.; Balog, Z.; Henning, Th.; Csengeri, T.; Grady, C.; Juhász, A.; Szulágyi, J.; Vavrek, R.

    2013-10-01

    Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) A-type star HD 95086. The strong infrared excess of the system indicates that, similar to HR8799, β Pic, and Fomalhaut, the star harbors a circumstellar disk. Aiming to study the structure and gas content of the HD 95086 disk, and to investigate its possible interaction with the newly discovered planet, here we present new optical, infrared, and millimeter observations. We detected no CO emission, excluding the possibility of an evolved gaseous primordial disk. Simple blackbody modeling of the spectral energy distribution suggests the presence of two spatially separate dust belts at radial distances of 6 and 64 AU. Our resolved images obtained with the Herschel Space Observatory reveal a characteristic disk size of ∼6.''0 × 5.''4 (540 × 490 AU) and disk inclination of ∼25°. Assuming the same inclination for the planet candidate's orbit, its reprojected radial distance from the star is 62 AU, very close to the blackbody radius of the outer cold dust ring. The structure of the planetary system at HD 95086 resembles the one around HR8799. Both systems harbor a warm inner dust belt and a broad colder outer disk and giant planet(s) between the two dusty regions. Modeling implies that the candidate planet can dynamically excite the motion of planetesimals even out to 270 AU via their secular perturbation if its orbital eccentricity is larger than about 0.4. Our analysis adds a new example to the three known systems where directly imaged planet(s) and debris disks coexist.

  18. Polarimetry and flux distribution in the debris disk around HD 32297

    NASA Astrophysics Data System (ADS)

    Asensio-Torres, R.; Janson, M.; Hashimoto, J.; Thalmann, C.; Currie, T.; Buenzli, E.; Kudo, T.; Kuzuhara, M.; Kusakabe, N.; Abe, L.; Akiyama, E.; Brandner, W.; Brandt, T. D.; Carson, J.; Egner, S.; Feldt, M.; Goto, M.; Grady, C.; Guyon, O.; Hayano, Y.; Hayashi, M.; Hayashi, S.; Henning, T.; Hodapp, K.; Ishii, M.; Iye, M.; Kandori, R.; Knapp, G.; Kwon, J.; Matsuo, T.; McElwain, M.; Mayama, S.; Miyama, S.; Morino, J.; Moro-Martin, A.; Nishimura, T.; Pyo, T.; Serabyn, E.; Suenaga, T.; Suto, H.; Suzuki, R.; Takahashi, Y.; Takami, M.; Takato, N.; Terada, H.; Turner, E.; Watanabe, M.; Wisniewski, J.; Yamada, T.; Takami, H.; Usuda, T.; Tamura, M.

    2016-09-01

    We present high-contrast angular differential imaging (ADI) observations of the debris disk around HD 32297 in H-band, as well as the first polarimetric images for this system in polarized differential imaging (PDI) mode with Subaru/HICIAO. In ADI, we detect the nearly edge-on disk at ≥5σ levels from ~0.45″ to ~1.7″ (50-192 AU) from the star and recover the spine deviation from the midplane already found in previous works. We also find for the first time imaging and surface brightness (SB) indications for the presence of a gapped structure on both sides of the disk at distances of ~0.75″ (NE side) and ~0.65″ (SW side). Global forward-modelling work delivers a best-fit model disk and well-fitting parameter intervals that essentially match previous results, with high-forward scattering grains and a ring located at 110 AU. However, this single ring model cannot account for the gapped structure seen in our SB profiles. We create simple double ring models and achieve a satisfactory fit with two rings located at 60 and 95 AU, respectively, low-forward scattering grains and very sharp inner slopes. In polarized light we retrieve the disk extending from ~0.25-1.6″, although the central region is quite noisy and high S/N are only found in the range ~0.75-1.2″. The disk is polarized in the azimuthal direction, as expected, and the departure from the midplane is also clearly observed. Evidence for a gapped scenario is not found in the PDI data. We obtain a linear polarization degree of the grains that increases from ~10% at 0.55″ to ~25% at 1.6″. The maximum is found at scattering angles of ~90°, either from the main components of the disk or from dust grains blown out to larger radii.

  19. A Resolved Debris Disk Around the Candidate Planet-hosting Star HD 95086

    NASA Technical Reports Server (NTRS)

    Moor, A.; Abraham, P.; Kospal, A.; Szabo, Gy. M.; Apai, D.; Balog, Z.; Csengeri, T.; Grady, C.; Henning, Th.; Juhasz, J.; Kiss, Cs.; Pasucci, I.; Szulagyi, J.; Vavrek, R.

    2013-01-01

    Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) A-type star HD 95086. The strong infrared excess of the system indicates that, similar to HR8799, Beta Pic, and Fomalhaut, the star harbors a circumstellar disk. Aiming to study the structure and gas content of the HD 95086 disk, and to investigate its possible interaction with the newly discovered planet, here we present new optical, infrared, and millimeter observations. We detected no CO emission, excluding the possibility of an evolved gaseous primordial disk. Simple blackbody modeling of the spectral energy distribution suggests the presence of two spatially separate dust belts at radial distances of 6 and 64 AU. Our resolved images obtained with the Herschel Space Observatory reveal a characteristic disk size of approx. 6.0 × 5.4 (540 × 490 AU) and disk inclination of approx 25 deg. Assuming the same inclination for the planet candidate's orbit, its reprojected radial distance from the star is 62 AU, very close to the blackbody radius of the outer cold dust ring. The structure of the planetary system at HD 95086 resembles the one around HR8799. Both systems harbor a warm inner dust belt and a broad colder outer disk and giant planet(s) between the two dusty regions. Modeling implies that the candidate planet can dynamically excite the motion of planetesimals even out to 270 AU via their secular perturbation if its orbital eccentricity is larger than about 0.4. Our analysis adds a new example to the three known systems where directly imaged planet(s) and debris disks coexist.

  20. Resolving the multi-temperature debris disk around gamma Doradus with Herschel

    NASA Astrophysics Data System (ADS)

    Broekhoven-Fiene, Hannah

    We present Herschel observations of the debris disk around gamma Doradus (HD 27290, HIP 19893) from the Herschel Key Programme DEBRIS (Disc Emission via Bias-free Reconnaissance in the Infrared/Submillimetre). The disk is well-resolved with PACS at 70, 100 and 160 mum and detected with SPIRE at 250 and 350 mum. The 250 mum image is only resolved along the disk's long axis. The SPIRE 500 mum 3 sigma detection includes a nearby background source. gamma Dor's spectral energy distribution (SED) is sampled in the submillimetre for the first time and modelled with multiple modified-blackbody functions to account for its broad shape. Two approaches are used, both of which reproduce the SED in the same way: a model of two narrow dust rings and a model of an extended, wide dust belt. The former implies the dust rings have temperatures of ˜90 and 40 K, corresponding to blackbody radii of 25 and 135 AU, respectively. The latter model suggests the dust lies in a wide belt extending from 15 to 230 AU. The resolved images, however, show dust extending beyond ˜350 AU. This is consistent with other debris disks whose actual radii are observed to be a factor of 2 - 3 times larger than the blackbody radii. Although it is impossible to determine a preferred model from the SED alone, the resolved images suggest that the dust is located in a smooth continuous belt rather than discrete narrow rings. Both models estimate that the dust mass is 6.7 x 10 -3 M. and that fractional luminosity is 2.5 x 10-5. This amount of dust is within the levels expected from steady state evolution given the age of gamma Doradus and therefore a transient event is not needed to explain the dust mass. No asymmetries that would hint at a planetary body are evident in the disk at Herschel's resolution. However, the constraints placed on the dust's location suggest that the most likely region to find planets is within 20 AU of the star.

  1. Coronagraphic imaging of the submillimeter debris disk of a 200Myr old M-dwarf

    NASA Astrophysics Data System (ADS)

    Lestrade, Jean-Francois

    2006-07-01

    A recent sub-millimeter survey has unambiguously discovered a new debris disk around the M0.5 dwarf GJ842.2 which is 200 Myr old. Reanalysis of the IRAS data has shown that there is also a 25 micron excess toward this star indicating warm dust close to the star. It is also only the second debris disk found among M-dwarfs that constitute 70 % of the stars in the Galaxy. Collisional and Poynting-Roberston timescale arguments indicate that the cold grains detected in the sub-mm are ``primordial'', i.e. original grains from the protoplanetary phase. The disk around GJ842.2 is thus unique in terms of the presence of dust at such a late stage of evolution and presents two conundrums: why did it retain so much primordial dust at large distances, and why does it continue to produce dust close to the star? We propose to conduct high contrast NICMOS coronagraphic imaging of GJ842.2 to determine the spatial distribution of the small reflecting grains and test the various scenarios which might explain the IRAS and sub-mm data e.g.resonant trapping of dust by planets or ``sandblasting'' by interstellar medium grains working more aggressively on a low-luminosity star than on an A-type star like Beta Pic. Also, we would search for an evolutionary sequence between GJ842.2 and the only other M-dwarf with a disk resolved by HST, the 10 Myr old AU Mic system.

  2. Searching for the HR 8799 Debris Disk with HST/STIS

    NASA Astrophysics Data System (ADS)

    Gerard, B.; Lawler, S.; Marois, C.; Tannock, M.; Matthews, B.; Venn, K.

    2016-06-01

    We present a new algorithm for space telescope high contrast imaging of close-to-face-on planetary disks called Optimized Spatially Filtered (OSFi) normalization. This algorithm is used on HR 8799 Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) coronagraphic archival data, showing an over-luminosity after reference star point-spread function (PSF) subtraction that may be from the inner disk and/or planetesimal belt components of this system. The PSF-subtracted radial profiles in two separate epochs from 2011 and 2012 are consistent with one another, and self-subtraction shows no residual in both epochs. We explore a number of possible false-positive scenarios that could explain this residual flux, including telescope breathing, spectral differences between HR 8799 and the reference star, imaging of the known warm inner disk component, OSFi algorithm throughput and consistency with the standard spider normalization HST PSF subtraction technique, and coronagraph misalignment from pointing accuracy. In comparison to another similar STIS data set, we find that the over-luminosity is likely a result of telescope breathing and spectral difference between HR 8799 and the reference star. Thus, assuming a non-detection, we derive upper limits on the HR 8799 dust belt mass in small grains. In this scenario, we find that the flux of these micron-sized dust grains leaving the system due to radiation pressure is small enough to be consistent with measurements of other debris disk halos.

  3. Dust and Polycyclic Aromatic Hydrocarbon in the HD 34700 Debris Disk

    NASA Astrophysics Data System (ADS)

    Seok, Ji Yeon; Li, Aigen

    2015-08-01

    The debris disk around the Vega-type star HD 34700 is detected in dust thermal emission from the near-infrared (IR) to millimeter (mm) and submm wavelength range. Also detected is a distinct set of emission features at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μ {{m}}, which are commonly attributed to polycyclic aromatic hydrocarbon (PAH) molecules. We model the observed dust IR spectral energy distribution (SED) and PAH emission features of the HD 34700 disk in terms of porous dust and astronomical-PAHs. Porous dust together with a mixture of neutral and ionized PAHs closely explains the dust IR SED and PAH emission features observed in the HD 34700 disk. Due to the stellar radiation pressure and Poynting-Robertson drag together with the photodissociation of PAHs, substantial removal of dust and PAHs has occurred in the disk, and continuous replenishment of these materials is required to maintain their current abundances. This implies that these materials are not primitive but secondary products probably originating from mutual collisions among planetesimals, asteroids, and comets.

  4. The AU Mic Debris Disk: Far-infrared and Submillimeter Resolved Imaging

    NASA Astrophysics Data System (ADS)

    Matthews, Brenda C.; Kennedy, Grant; Sibthorpe, Bruce; Holland, Wayne; Booth, Mark; Kalas, Paul; MacGregor, Meredith; Wilner, David; Vandenbussche, Bart; Olofsson, Göran; Blommaert, Joris; Brandeker, Alexis; Dent, W. R. F.; de Vries, Bernard L.; Di Francesco, James; Fridlund, Malcolm; Graham, James R.; Greaves, Jane; Heras, Ana M.; Hogerheijde, Michiel; Ivison, R. J.; Pantin, Eric; Pilbratt, Göran L.

    2015-10-01

    We present far-infrared and submillimeter maps from the Herschel Space Observatory and the James Clerk Maxwell Telescope of the debris disk host star AU Microscopii. Disk emission is detected at 70, 160, 250, 350, 450, 500, and 850 μm. The disk is resolved at 70, 160, and 450 μm. In addition to the planetesimal belt, we detect thermal emission from AU Mic’s halo for the first time. In contrast to the scattered light images, no asymmetries are evident in the disk. The fractional luminosity of the disk is 3.9× {10}-4 and its milimeter-grain dust mass is 0.01 {M}\\oplus (±20%). We create a simple spatial model that reconciles the disk spectral energy distribution as a blackbody of 53 ± 2 K (a composite of 39 and 50 K components) and the presence of small (non-blackbody) grains which populate the extended halo. The best-fit model is consistent with the “birth ring” model explored in earlier works, i.e., an edge-on dust belt extending from 8.8 to 40 AU, but with an additional halo component with an {r}-1.5 surface density profile extending to the limits of sensitivity (140 AU). We confirm that AU Mic does not exert enough radiation force to blow out grains. For stellar mass-loss rates of 10–100 times solar, compact (zero porosity) grains can only be removed if they are very small; consistently with previous work, if the porosity is 0.9, then grains approaching 0.1 μm can be removed via corpuscular forces (i.e., the stellar wind).

  5. The AU Mic Debris Disk: Far-infrared and Submillimeter Resolved Imaging

    NASA Astrophysics Data System (ADS)

    Matthews, Brenda C.; Kennedy, Grant; Sibthorpe, Bruce; Holland, Wayne; Booth, Mark; Kalas, Paul; MacGregor, Meredith; Wilner, David; Vandenbussche, Bart; Olofsson, Göran; Blommaert, Joris; Brandeker, Alexis; Dent, W. R. F.; de Vries, Bernard L.; Di Francesco, James; Fridlund, Malcolm; Graham, James R.; Greaves, Jane; Heras, Ana M.; Hogerheijde, Michiel; Ivison, R. J.; Pantin, Eric; Pilbratt, Göran L.

    2015-10-01

    We present far-infrared and submillimeter maps from the Herschel Space Observatory and the James Clerk Maxwell Telescope of the debris disk host star AU Microscopii. Disk emission is detected at 70, 160, 250, 350, 450, 500, and 850 μm. The disk is resolved at 70, 160, and 450 μm. In addition to the planetesimal belt, we detect thermal emission from AU Mic’s halo for the first time. In contrast to the scattered light images, no asymmetries are evident in the disk. The fractional luminosity of the disk is 3.9× {10}-4 and its milimeter-grain dust mass is 0.01 {M}\\oplus (±20%). We create a simple spatial model that reconciles the disk spectral energy distribution as a blackbody of 53 ± 2 K (a composite of 39 and 50 K components) and the presence of small (non-blackbody) grains which populate the extended halo. The best-fit model is consistent with the “birth ring” model explored in earlier works, i.e., an edge-on dust belt extending from 8.8 to 40 AU, but with an additional halo component with an {r}-1.5 surface density profile extending to the limits of sensitivity (140 AU). We confirm that AU Mic does not exert enough radiation force to blow out grains. For stellar mass-loss rates of 10-100 times solar, compact (zero porosity) grains can only be removed if they are very small; consistently with previous work, if the porosity is 0.9, then grains approaching 0.1 μm can be removed via corpuscular forces (i.e., the stellar wind).

  6. Can Eccentric Debris Disks Be Long-lived? A First Numerical Investigation and Application to Zeta(exp 2) Reticuli

    NASA Technical Reports Server (NTRS)

    Faramaz, V.; Beust, H.; Thebault, P.; Augereau, J.-C.; Bonsor, A.; delBurgo, C.; Ertel, S.; Marshall, J. P.; Milli, J.; Montesinos, B.; Mora, A.; Bryden, G.; Danchi, William C.; Eiroa, C.; White, G. J.; Wolf, S.

    2014-01-01

    Context. Imaging of debris disks has found evidence for both eccentric and offset disks. One hypothesis is that they provide evidence for massive perturbers, for example, planets or binary companions, which sculpt the observed structures. One such disk was recently observed in the far-IR by the Herschel Space Observatory around Zeta2 Reticuli. In contrast with previously reported systems, the disk is significantly eccentric, and the system is several Gyr old. Aims. We aim to investigate the long-term evolution of eccentric structures in debris disks caused by a perturber on an eccentric orbit around the star. We hypothesise that the observed eccentric disk around Zeta2 Reticuli might be evidence of such a scenario. If so, we are able to constrain the mass and orbit of a potential perturber, either a giant planet or a binary companion. Methods. Analytical techniques were used to predict the effects of a perturber on a debris disk. Numerical N-body simulations were used to verify these results and further investigate the observable structures that may be produced by eccentric perturbers. The long-term evolution of the disk geometry was examined, with particular application to the Zeta2 Reticuli system. In addition, synthetic images of the disk were produced for direct comparison with Herschel observations. Results. We show that an eccentric companion can produce both the observed offsets and eccentric disks. These effects are not immediate, and we characterise the timescale required for the disk to develop to an eccentric state (and any spirals to vanish). For Zeta2 Reticuli, we derive limits on the mass and orbit of the companion required to produce the observations. Synthetic images show that the pattern observed around Zeta2 Reticuli can be produced by an eccentric disk seen close to edge-on, and allow us to bring additional constraints on the disk parameters of our model (disk flux and extent). Conclusions. We conclude that eccentric planets or stellar companions

  7. DYNAMICAL HEATING INDUCED BY DWARF PLANETS ON COLD KUIPER BELT–LIKE DEBRIS DISKS

    SciTech Connect

    Muñoz-Gutiérrez, M. A.; Pichardo, B.; Peimbert, A.; Reyes-Ruiz, M.

    2015-10-01

    With the use of long-term numerical simulations, we study the evolution and orbital behavior of cometary nuclei in cold Kuiper belt–like debris disks under the gravitational influence of dwarf planets (DPs); we carry out these simulations with and without the presence of a Neptune-like giant planet. This exploratory study shows that in the absence of a giant planet, 10 DPs are enough to induce strong radial and vertical heating on the orbits of belt particles. On the other hand, the presence of a giant planet close to the debris disk, acts as a stability agent reducing the radial and vertical heating. With enough DPs, even in the presence of a Neptune-like giant planet some radial heating remains; this heating grows steadily, re-filling resonances otherwise empty of cometary nuclei. Specifically for the solar system, this secular process seems to be able to provide material that, through resonant chaotic diffusion, increase the rate of new comets spiraling into the inner planetary system, but only if more than the ∼10 known DP sized objects exist in the trans-Neptunian region.

  8. Fomalhaut b is Probably Not a Planet: Frequent Collisions within the Fomalhaut Debris Disk

    NASA Astrophysics Data System (ADS)

    Lawler, Samantha; Greenstreet, Sarah; Gladman, Brett

    2015-12-01

    Fomalhaut hosts a beautiful debris disk ring and a directly imaged planet candidate, Fomalhaut b, which seems to continually defy expectations. Originally thought to be a Jovian-mass planet constraining the ring, its unexpected spectral properties and highly eccentric, possibly ring-crossing orbit have completely ruled out that possibility. Many theories have been proposed to explain the weird properties of Fomalhaut b, including a large circumplanetary ring, a system of irregular satellites, and a recent small body collision. We expand on the last theory, discussing our collisional probability simulations of the Fomalhaut debris disk, based on the structure of our Kuiper belt, which show the catastrophic disruption rate of d~100 km bodies in the high-eccentricity scattering component is several per decade. This model paints a picture of the Fomalhaut system as having recently (with ~10-100 Myr) experienced a dynamical instability within its planetary system, which scattered a massive number of planetesimals onto large, high-eccentricity orbits similar to that of Fom b. If Fomalhaut b is indeed a dust cloud produced by such a collision, we should soon see another appear, while Fomalhaut b will expand until it is either resolved or becomes too faint to be seen.

  9. Spitzer IRS Spectra of Debris Disks in the Scorpius-Centaurus OB Association

    NASA Astrophysics Data System (ADS)

    Jang-Condell, Hannah; Chen, Christine H.; Mittal, Tushar; Manoj, P.; Watson, Dan; Lisse, Carey M.; Nesvold, Erika; Kuchner, Marc

    2015-08-01

    We analyze spectra obtained with the Spitzer Infrared Spectrograph (IRS) of 110 B-, A-, F-, and G-type stars with optically thin infrared excess in the Scorpius-Centaurus OB association. The ages of these stars range from 11 to 17 Myr. We fit the infrared excesses observed in these sources by Spitzer IRS and the Multiband Imaging Photometer for Spitzer (MIPS) to simple dust models according to Mie theory. We find that nearly all of the objects in our study can be fit by one or two belts of dust. Dust around lower mass stars appears to be closer in than around higher mass stars, particularly for the warm dust component in the two-belt systems, suggesting a mass-dependent evolution of debris disks around young stars. For those objects with stellar companions, all dust distances are consistent with truncation of the debris disk by the binary companion. The gaps between several of the two-belt systems can place limits on the planets that might lie between the belts, potentially constraining the mass and locations of planets that may be forming around these stars.

  10. SPITZER IRS SPECTRA OF DEBRIS DISKS IN THE SCORPIUS–CENTAURUS OB ASSOCIATION

    SciTech Connect

    Jang-Condell, Hannah; Chen, Christine H.; Mittal, Tushar; Lisse, Carey M.; Manoj, P.; Watson, Dan; Nesvold, Erika; Kuchner, Marc

    2015-08-01

    We analyze spectra obtained with the Spitzer Infrared Spectrograph (IRS) of 110 B-, A-, F-, and G-type stars with optically thin infrared excess in the Scorpius–Centaurus OB association. The ages of these stars range from 11 to 17 Myr. We fit the infrared excesses observed in these sources by Spitzer IRS and the Multiband Imaging Photometer for Spitzer (MIPS) to simple dust models according to Mie theory. We find that nearly all of the objects in our study can be fit by one or two belts of dust. Dust around lower mass stars appears to be closer in than around higher mass stars, particularly for the warm dust component in the two-belt systems, suggesting a mass-dependent evolution of debris disks around young stars. For those objects with stellar companions, all dust distances are consistent with truncation of the debris disk by the binary companion. The gaps between several of the two-belt systems can place limits on the planets that might lie between the belts, potentially constraining the mass and locations of planets that may be forming around these stars.

  11. THE TUCANA/HOROLOGIUM, COLUMBA, AB DORADUS, AND ARGUS ASSOCIATIONS: NEW MEMBERS AND DUSTY DEBRIS DISKS

    SciTech Connect

    Zuckerman, B.; Rhee, Joseph H.; Song, Inseok; Bessell, M. S. E-mail: rhee@astro.ucla.edu E-mail: bessell@mso.anu.edu.au

    2011-05-10

    We propose 35 star systems within {approx}70 pc of Earth as newly identified members of nearby young stellar kinematic groups; these identifications include the first A- and late-B-type members of the AB Doradus moving group and field Argus Association. All but one of the 35 systems contain a bright solar- or earlier-type star that should make an excellent target for the next generation of adaptive optics (AO) imaging systems on large telescopes. AO imaging has revealed four massive planets in orbit around the {lambda} Boo star HR 8799. Initially, the planets were of uncertain mass due in large part to the uncertain age of the star. We find that HR 8799 is a likely member of the {approx}30 Myr old Columba Association, implying planet masses {approx}6 times that of Jupiter. We consider Spitzer Space Telescope MIPS photometry of stars in the {approx}30 Myr old Tucana/Horologium and Columba Associations, the {approx}40 Myr old field Argus Association, and the {approx}70 Myr old AB Doradus moving group. The percentage of stars in these young stellar groups that display excess emission above the stellar photosphere at 24 and 70 {mu}m wavelengths-indicative of the presence of a dusty debris disk-is compared with corresponding percentages for members of 11 open clusters and stellar associations with ages between 8 and 750 Myr, thus elucidating the decay of debris disks with time.

  12. Temperature condensation trend in the debris-disk binary system ζ2 Reticuli

    NASA Astrophysics Data System (ADS)

    Saffe, C.; Flores, M.; Jaque Arancibia, M.; Buccino, A.; Jofré, E.

    2016-04-01

    Context. Detailed abundance studies have reported different trends between samples of stars with and without planets, possibly related to the planet formation process. Whether these differences are still present between samples of stars with and without debris disk is still unclear. Aims: We explore condensation temperature Tc trends in the unique binary system ζ1 Ret -ζ2 Ret to determine whether there is a depletion of refractories that could be related to the planet formation process. The star ζ2 Ret hosts a debris disk which was detected by an IR excess and confirmed by direct imaging and numerical simulations, while ζ1 Ret does not present IR excess or planets. These characteristics convert ζ2 Ret in a remarkable system where their binary nature together with the strong similarity of both components allow us, for the first time, to achieve the highest possible abundance precision in this system. Methods: We carried out a high-precision abundance determination in both components of the binary system via a line-by-line, strictly differential approach. First we used the Sun as a reference and then we used ζ2 Ret. The stellar parameters Teff, log g, [Fe/H], and vturb were determined by imposing differential ionization and excitation equilibrium of Fe I and Fe II lines, with an updated version of the program FUNDPAR, together with plane-parallel local thermodynamic equilibrium ATLAS9 model atmospheres and the MOOG code. We then derived detailed abundances of 24 different species with equivalent widths and spectral synthesis with the MOOG program. The chemical patterns were compared with a recently calculated solar-twins Tc trend, and then mutually between both stars of the binary system. The rocky mass of depleted refractory material was estimated according to recent data. Results: The star ζ1 Ret is found to be slightly more metal rich than ζ2 Ret by ~0.02 dex. In the differential calculation of ζ1 Ret using ζ2 Ret as reference, the abundances of the

  13. Insights into Planet Formation from Debris Disks: I. The Solar System as an Archetype for Planetesimal Evolution

    NASA Astrophysics Data System (ADS)

    Matthews, Brenda C.; Kavelaars, JJ

    2016-05-01

    Circumstellar disks have long been regarded as windows into planetary systems. The advent of high sensitivity, high resolution imaging in the submillimeter where both the solid and gas components of disks can be detected opens up new possibilities for understanding the dynamical histories of these systems and therefore, a better ability to place our own solar system, which hosts a highly evolved debris disk, in context. Comparisons of dust masses from protoplanetary and debris disks have revealed a stark downturn in mass in millimeter-sized grains around a stellar age of 10 Myr, ostensibly in the "transition disk" phase, suggesting a period of rapid accretion of such grains onto planetesimals. This rapid formation phase is in keeping with radionucleide studies of Kuiper Belt Objects in the solar system. Importantly, this suggests that any thermal gradients in the gas of disks of this era will be "frozen in" to the planetesimals as they rapidly accrete from the solids and ices in their vicinity. Measurements of radial gradients in thermal tracers such as DHO, DCN and other tracers can therefore provide insight into the nascent solar system's abundances. In studies of dynamical evolution of the solar system, it is tacitly assumed that such abundances can reveal the location of formation for bodies now found in the asteroid belt and Kuiper belt. Similarly, evidence of gas detected from collisional evolution in young debris disks could potentially reveal how rapidly objects have dynamically evolved in those systems, most of which will be significantly younger than the solar system.

  14. The Gemini Planet-finding Campaign: The Frequency Of Giant Planets around Debris Disk Stars

    NASA Astrophysics Data System (ADS)

    Wahhaj, Zahed; Liu, Michael C.; Nielsen, Eric L.; Biller, Beth A.; Hayward, Thomas L.; Close, Laird M.; Males, Jared R.; Skemer, Andrew; Ftaclas, Christ; Chun, Mark; Thatte, Niranjan; Tecza, Matthias; Shkolnik, Evgenya L.; Kuchner, Marc; Reid, I. Neill; de Gouveia Dal Pino, Elisabete M.; Alencar, Silvia H. P.; Gregorio-Hetem, Jane; Boss, Alan; Lin, Douglas N. C.; Toomey, Douglas W.

    2013-08-01

    We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. We achieved median H-band contrasts of 12.4 mag at 0.''5 and 14.1 mag at 1'' separation. Follow-up observations of the 66 candidates with projected separation <500 AU show that all of them are background objects. To establish statistical constraints on the underlying giant planet population based on our imaging data, we have developed a new Bayesian formalism that incorporates (1) non-detections, (2) single-epoch candidates, (3) astrometric and (4) photometric information, and (5) the possibility of multiple planets per star to constrain the planet population. Our formalism allows us to include in our analysis the previously known β Pictoris and the HR 8799 planets. Our results show at 95% confidence that <13% of debris disk stars have a >=5 M Jup planet beyond 80 AU, and <21% of debris disk stars have a >=3 M Jup planet outside of 40 AU, based on hot-start evolutionary models. We model the population of directly imaged planets as d 2 N/dMdavpropm α a β, where m is planet mass and a is orbital semi-major axis (with a maximum value of a max). We find that β < -0.8 and/or α > 1.7. Likewise, we find that β < -0.8 and/or a max < 200 AU. For the case where the planet frequency rises sharply with mass (α > 1.7), this occurs because all the planets detected to date have masses above 5 M Jup, but planets of lower mass could easily have been detected by our search. If we ignore the β Pic and HR 8799 planets (should they belong to a rare and distinct group), we find that <20% of debris disk stars have a >=3 M Jup planet beyond 10 AU, and β < -0.8 and/or α < -1.5. Likewise, β < -0.8 and/or a max < 125 AU. Our Bayesian constraints are not strong enough to reveal any dependence of the planet frequency on stellar host mass. Studies of transition disks have suggested that about 20% of stars are undergoing planet

  15. ON THE UNUSUAL GAS COMPOSITION IN THE {beta} PICTORIS DEBRIS DISK

    SciTech Connect

    Xie, Ji-Wei; Wu, Yanqin; Brandeker, Alexis E-mail: wu@astro.utoronto.ca

    2013-01-10

    The metallic gas associated with the {beta} Pic debris disk is not believed to be primordial, but arises from the destruction of dust grains. Recent observations have shown that carbon and oxygen in this gas are exceptionally overabundant compared to other elements, by some 400 times. We study the origin of this enrichment under two opposing hypotheses: preferential production, where the gas is produced with the observed unusual abundance (as may happen if gas is produced by photodesorption from C/O-rich icy grains), and preferential depletion, where the gas evolves to the observed state from an original solar abundance (if outgassing occurs under high-speed collisions) under a number of dynamical processes. We include in our study the following processes: radiative blowout of metallic elements, dynamical coupling between different species, and viscous accretion onto the star. We find that, if gas viscosity is sufficiently low (the conventional {alpha} parameter {approx}< 10{sup -3}), differential blowout dominates. While gas accumulates gradually in the disks, metallic elements subject to strong radiation forces, such as Na and Fe, deplete more quickly than C and O, naturally leading to the observed overabundance of C and O. On the other hand, if gas viscosity is high ({alpha} {approx}> 10{sup -1}, as expected for this largely ionized disk), gas is continuously produced and viscously accreted toward the star. This removal process does not discriminate between elements so the observed overabundance of C and O has to be explained by a preferential production that strongly favors C and O to other metallic elements. One such candidate is photodesorption off the grains. We compare our calculation against all observed elements ({approx}10) in the gas disk and find a mild preference for the second scenario, based on the abundance of Si alone. If true, {beta} Pic should still be accreting at an observable rate, well after its primordial disk has disappeared.

  16. Probing for Exoplanets Hiding in Dusty Debris Disks: Disk Imaging, Characterization, and Exploration with HST-STIS Multi-roll Coronagraphy

    NASA Technical Reports Server (NTRS)

    Schneider, Glenn; Grady, Carol A.; Hines, Dean C.; Stark, Christopher C.; Debes, John; Carson, Joe; Kuchner, Marc J.; Perrin, Marshall; Weinberger, Alycia; Wisniewski, John P.; Silverstone, Murray D.; Jang-Condell, Hannah; Henning, Thomas; Bruce E. Woodgate; Serabyn, Eugene; Moro-Martin, Amaya; Tamura, Motohide; Hinz, Phillip M.; Rodigas, Timothy J.

    2014-01-01

    Spatially resolved scattered-light images of circumstellar debris in exoplanetary systems constrain the physical properties and orbits of the dust particles in these systems. They also inform on co-orbiting (but unseen) planets, the systemic architectures, and forces perturbing the starlight-scattering circumstellar material. Using HST/STIS broadband optical coronagraphy, we have completed the observational phase of a program to study the spatial distribution of dust in a sample of ten circumstellar debris systems, and one "mature" protoplanetrary disk all with HST pedigree, using PSF-subtracted multi-roll coronagraphy. These observations probe stellocentric distances greater than or equal to 5 AU for the nearest systems, and simultaneously resolve disk substructures well beyond corresponding to the giant planet and Kuiper belt regions within our own Solar System. They also disclose diffuse very low-surface brightness dust at larger stellocentric distances. Herein we present new results inclusive of fainter disks such as HD92945 (F (sub disk) /F (sub star) = 5x10 (sup -5) confirming, and better revealing, the existence of a narrow inner debris ring within a larger diffuse dust disk. Other disks with ring-like sub-structures and significant asymmetries and complex morphologies include: HD181327 for which we posit a spray of ejecta from a recent massive collision in an exo-Kuiper belt; HD61005 suggested to be interacting with the local ISM; HD15115 and HD32297, discussed also in the context of putative environmental interactions. These disks, and HD15745, suggest that debris system evolution cannot be treated in isolation. For AU Mic's edge-on disk we find out-of-plane surface brightness asymmetries at greater than or equal to 5 AU that may implicate the existence of one or more planetary perturbers. Time resolved images of the MP Mus proto-planetary disk provide spatially resolved temporal variability in the disk illumination. These and other new images from our HST

  17. Probing for Exoplanets Hiding in Dusty Debris Disks: Disk Imaging, Characterization, and Exploration with HST/STIS Multi-roll Coronagraphy

    NASA Astrophysics Data System (ADS)

    Schneider, Glenn; Grady, Carol A.; Hines, Dean C.; Stark, Christopher C.; Debes, John H.; Carson, Joe; Kuchner, Marc J.; Perrin, Marshall D.; Weinberger, Alycia J.; Wisniewski, John P.; Silverstone, Murray D.; Jang-Condell, Hannah; Henning, Thomas; Woodgate, Bruce E.; Serabyn, Eugene; Moro-Martin, Amaya; Tamura, Motohide; Hinz, Phillip M.; Rodigas, Timothy J.

    2014-10-01

    Spatially resolved scattered-light images of circumstellar debris in exoplanetary systems constrain the physical properties and orbits of the dust particles in these systems. They also inform on co-orbiting (but unseen) planets, the systemic architectures, and forces perturbing the starlight-scattering circumstellar material. Using Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) broadband optical coronagraphy, we have completed the observational phase of a program to study the spatial distribution of dust in a sample of 10 circumstellar debris systems and 1 "mature" protoplanetrary disk, all with HST pedigree, using point-spread-function-subtracted multi-roll coronagraphy. These observations probe stellocentric distances >=5 AU for the nearest systems, and simultaneously resolve disk substructures well beyond corresponding to the giant planet and Kuiper Belt regions within our own solar system. They also disclose diffuse very low-surface-brightness dust at larger stellocentric distances. Herein we present new results inclusive of fainter disks such as HD 92945 (F disk/F star = 5 × 10-5), confirming, and better revealing, the existence of a narrow inner debris ring within a larger diffuse dust disk. Other disks with ring-like substructures and significant asymmetries and complex morphologies include HD 181327, for which we posit a spray of ejecta from a recent massive collision in an exo-Kuiper Belt; HD 61005, suggested to be interacting with the local interstellar medium; and HD 15115 and HD 32297, also discussed in the context of putative environmental interactions. These disks and HD 15745 suggest that debris system evolution cannot be treated in isolation. For AU Mic's edge-on disk, we find out-of-plane surface brightness asymmetries at >=5 AU that may implicate the existence of one or more planetary perturbers. Time-resolved images of the MP Mus protoplanetary disk provide spatially resolved temporal variability in the disk

  18. Probing for exoplanets hiding in dusty debris disks: Disk imaging, characterization, and exploration with HST/STIS multi-roll coronagraphy

    SciTech Connect

    Schneider, Glenn; Hinz, Phillip M.; Grady, Carol A.; Hines, Dean C.; Debes, John H.; Perrin, Marshall D.; Moro-Martin, Amaya; Stark, Christopher C.; Kuchner, Marc J.; Woodgate, Bruce E.; Weinberger, Alycia J.; Rodigas, Timothy J.; Wisniewski, John P.; Silverstone, Murray D.; Jang-Condell, Hannah; Henning, Thomas; Serabyn, Eugene; Tamura, Motohide

    2014-10-01

    Spatially resolved scattered-light images of circumstellar debris in exoplanetary systems constrain the physical properties and orbits of the dust particles in these systems. They also inform on co-orbiting (but unseen) planets, the systemic architectures, and forces perturbing the starlight-scattering circumstellar material. Using Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) broadband optical coronagraphy, we have completed the observational phase of a program to study the spatial distribution of dust in a sample of 10 circumstellar debris systems and 1 'mature' protoplanetrary disk, all with HST pedigree, using point-spread-function-subtracted multi-roll coronagraphy. These observations probe stellocentric distances ≥5 AU for the nearest systems, and simultaneously resolve disk substructures well beyond corresponding to the giant planet and Kuiper Belt regions within our own solar system. They also disclose diffuse very low-surface-brightness dust at larger stellocentric distances. Herein we present new results inclusive of fainter disks such as HD 92945 (F {sub disk}/F {sub star} = 5 × 10{sup –5}), confirming, and better revealing, the existence of a narrow inner debris ring within a larger diffuse dust disk. Other disks with ring-like substructures and significant asymmetries and complex morphologies include HD 181327, for which we posit a spray of ejecta from a recent massive collision in an exo-Kuiper Belt; HD 61005, suggested to be interacting with the local interstellar medium; and HD 15115 and HD 32297, also discussed in the context of putative environmental interactions. These disks and HD 15745 suggest that debris system evolution cannot be treated in isolation. For AU Mic's edge-on disk, we find out-of-plane surface brightness asymmetries at ≥5 AU that may implicate the existence of one or more planetary perturbers. Time-resolved images of the MP Mus protoplanetary disk provide spatially resolved temporal variability

  19. Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space Telescope around 21 Sun-like Stars

    NASA Astrophysics Data System (ADS)

    Metchev, Stanimir

    2006-07-01

    We propose to use the high-contrast capability of the NICMOS coronagraph to image a sample of newly discovered circumstellar disks associated with Sun-like stars. These systems were identified by their strong thermal infrared {IR} emission with the Spitzer Space Telescope as part of the Spitzer Legacy Science program titled "The Formation and Evolution of Planetary Systems" {FEPS, P.I.: M.Meyer}. Modeling of the thermal excess emission from the spectral energy distributions alone cannot distinguish between narrowly confined high-opacity disks and broadly distributed, low-opacity disks. By resolving light scattered by the circumstellar material, our proposed NICMOS observations can break this degeneracy, thus revealing the conditions under which planet formation processes are occuring or have occured. For three of our IR-excess stars that have known radial-velocity planets, resolved imaging of the circumstellar debris disks may further offer an unprecedented view of planet-disk interactions in an extrasolar planetary system. Even non-detections of the light scattered by the circumstellar material will place strong constraints on the disk geometries, ruling out disk models with high optical depth. Unlike previous disk imaging programs, our program contains a well-defined sample of 1 solar mass stars covering a range of ages from 3 Myr to 3 Gyr, thus allowing us to study the evolution of disks from primordial to debris for the first time. The results from our program will greatly improve our understanding of the architecture of debris disks around Sun-like stars, and will create a morphological context for the existence of our own solar system. This proposal is for a continuation of an approved Cycle 14 program {GO/10527, P.I.: D. Hines}.

  20. Non-LTE spectral models for the gaseous debris-disk component of Ton 345

    NASA Astrophysics Data System (ADS)

    Hartmann, S.; Nagel, T.; Rauch, T.; Werner, K.

    2014-11-01

    Context. For a fraction of single white dwarfs with debris disks, an additional gaseous disk was discovered. Both dust and gas are thought to be created by the disruption of planetary bodies. Aims: The composition of the extrasolar planetary material can directly be analyzed in the gaseous disk component, and the disk dynamics might be accessible by investigating the temporal behavior of the Ca ii infrared emission triplet, hallmark of the gas disk. Methods: We obtained new optical spectra for the first helium-dominated white dwarf for which a gas disk was discovered (Ton 345) and modeled the non-LTE spectra of viscous gas disks composed of carbon, oxygen, magnesium, silicon, sulfur, and calcium with chemical abundances typical for solar system asteroids. Iron and its possible line-blanketing effects on the model structure and spectral energy distribution was still neglected. A set of models with different radii, effective temperatures, and surface densities as well as chondritic and bulk-Earth abundances was computed and compared with the observed line profiles of the Ca ii infrared triplet. Results: Our models suggest that the Ca ii emission stems from a rather narrow gas ring with a radial extent of R = 0.44-0.94 R⊙, a uniform surface density Σ = 0.3 g cm-2, and an effective temperature of Teff ≈ 6000 K. The often assumed chemical mixtures derived from photospheric abundances in polluted white dwarfs - similar to a chondritic or bulk-Earth composition - produce unobserved emission lines in the model and therefore have to be altered. We do not detect any line-profile variability on timescales of hours, but we confirm the long-term trend over the past decade for the red-blue asymmetry of the double-peaked lines. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).

  1. SPITZER OBSERVATIONS OF THE lambda ORIONIS CLUSTER. I. THE FREQUENCY OF YOUNG DEBRIS DISKS AT 5 Myr

    SciTech Connect

    Hernandez, Jesus; Calvet, Nuria; Hartmann, L.; Muzerolle, J.; Gutermuth, R.; Stauffer, J.

    2009-12-10

    We present IRAC/MIPS Spitzer observations of intermediate-mass stars in the 5 Myr old lambda Orionis cluster. In a representative sample of stars earlier than F5 (29 stars), we find a population of nine stars with varying degree of moderate 24 mum excess comparable to those produced by debris disks in older stellar groups. As expected in debris disks systems, those stars do not exhibit emission lines in their optical spectra. We also include in our study the star HD 245185, a known Herbig Ae object which displays excesses in all Spitzer bands and shows emission lines in its spectrum. We compare the disk population in the lambda Orionis cluster with the disk census in other stellar groups studied using similar methods to detect and characterize their disks and spanning a range of ages from 3 Myr to 10 Myr. We find that for stellar groups of 5 Myr or older the observed disk frequency in intermediate-mass stars (with spectral types from late B to early F) is higher than in low-mass stars (with spectral types K and M). This is in contradiction with the observed trend for primordial disk evolution, in which stars with higher stellar masses dissipate their primordial disks faster. At 3 Myr, the observed disk frequency in intermediate-mass stars is still lower than for low-mass stars indicating that second generation dusty disks start to dominate the disk population at 5 Myr for intermediate-mass stars. This result agrees with recent models of evolution of solids in the region of the disk where icy objects form (>30 AU), which suggest that at 5-10 Myr collisions start to produce large amount of dust during the transition from runaway to oligarchic growth (reaching sizes of approx500 km) and then dust production peaks at 10-30 Myr, when objects reach their maximum size (>=1000 km).

  2. SATURN’S G AND D RINGS PROVIDE NEARLY COMPLETE MEASURED SCATTERING PHASE FUNCTIONS OF NEARBY DEBRIS DISKS

    SciTech Connect

    Hedman, Matthew M.; Stark, Christopher C. E-mail: cstark@stsci.edu

    2015-09-20

    The appearance of debris disks around distant stars depends upon the scattering/phase function (SPF) of the material in the disk. However, characterizing the SPFs of these extrasolar debris disks is challenging because only a limited range of scattering angles are visible to Earth-based observers. By contrast, Saturn’s tenuous rings can be observed over a much broader range of geometries, so their SPFs can be much better constrained. Since these rings are composed of small particles released from the surfaces of larger bodies, they are reasonable analogs to debris disks and so their SPFs can provide insights into the plausible scattering properties of debris disks. This work examines two of Saturn’s dusty rings: the G ring (at 167,500 km from Saturn’s center) and the D68 ringlet (at 67,600 km). Using data from the cameras on board the Cassini spacecraft, we are able to estimate the rings’ brightnesses at scattering angles ranging from 170° to 0.°5. We find that both of the rings exhibit extremely strong forward-scattering peaks, but for scattering angles above 60° their brightnesses are nearly constant. These SPFs can be well approximated by a linear combination of three Henyey–Greenstein functions, and are roughly consistent with the SPFs of irregular particles from laboratory measurements. Comparing these data to Fraunhofer and Mie models highlights several challenges involved in extracting information about particle compositions and size distributions from SPFs alone. The SPFs of these rings also indicate that the degree of forward scattering in debris disks may be greatly underestimated.

  3. A peculiar class of debris disks from Herschel/DUNES. A steep fall off in the far infrared

    NASA Astrophysics Data System (ADS)

    Ertel, S.; Wolf, S.; Marshall, J. P.; Eiroa, C.; Augereau, J.-C.; Krivov, A. V.; Löhne, T.; Absil, O.; Ardila, D.; Arévalo, M.; Bayo, A.; Bryden, G.; del Burgo, C.; Greaves, J.; Kennedy, G.; Lebreton, J.; Liseau, R.; Maldonado, J.; Montesinos, B.; Mora, A.; Pilbratt, G. L.; Sanz-Forcada, J.; Stapelfeldt, K.; White, G. J.

    2012-05-01

    Context. The existence of debris disks around old main sequence stars is usually explained by continuous replenishment of small dust grains through collisions from a reservoir of larger objects. Aims: We present photometric data of debris disks around HIP 103389 (HD 199260), HIP 107350 (HN Peg, HD 206860), and HIP 114948 (HD 219482), obtained in the context of our Herschel open time key program DUNES (DUst around NEarby Stars). Methods: We used Herschel/PACS to detect the thermal emission of the three debris disks with a 3σ sensitivity of a few mJy at 100 μm and 160 μm. In addition, we obtained Herschel/PACS photometric data at 70 μm for HIP 103389. These observations are complemented by a large variety of optical to far-infrared photometric data. Two different approaches are applied to reduce the Herschel data to investigate the impact of data reduction on the photometry. We fit analytical models to the available spectral energy distribution (SED) data using the fitting method of simulated thermal annealing as well as a classical grid search method. Results: The SEDs of the three disks potentially exhibit an unusually steep decrease at wavelengths ≥70 μm. We investigate the significance of the peculiar shape of these SEDs and the impact on models of the disks provided it is real. Using grain compositions that have been applied successfully for modeling of many other debris disks, our modeling reveals that such a steep decrease of the SEDs in the long wavelength regime is inconsistent with a power-law exponent of the grain size distribution -3.5 expected from a standard equilibrium collisional cascade. In contrast, a steep grain size distribution or, alternatively an upper grain size in the range of few tens of micrometers are implied. This suggests that a very distinct range of grain sizes would dominate the thermal emission of such disks. However, we demonstrate that the understanding of the data of faint sources obtained with Herschel is still incomplete

  4. A Peculiar Class of Debris Disks from Herschel/DUNES: A Steep Fall Off in the Far Infrared

    NASA Technical Reports Server (NTRS)

    Ertel, S.; Wolf, S.; Marshall, J. P.; Eiroa, C.; Augereau, J. C.; Krivov, A. V.; Lohne, T.; Absil, O.; Ardila, D.; Arevalo, M.; Bayo, A.; Bryden, G.; del Burgo, C.; Greaves, J.; Kennedy, G.; Lebreton, J.; Liseau, R.; Maldonado, J.; Montesinos, B.; Mora, A.; Pilbratt, G. L.; Sanz-Forcada, J.; Stapelfeldt, K.; White, G. J.

    2012-01-01

    Context. The existence of debris disks around old main sequence stars is usually explained by continuous replenishment of small dust grains through collisions from a reservoir of larger objects. Aims. We present photometric data of debris disks around HIP 103389 (HD199260), HIP 100350 (HN Peg, HD206860), and HIP 114948 (HD 219482), obtained in the context of our Herschel Open TIme Key Program DUNES (DUst around NEarby Stars). Methods. We used Herschel/PACS to detect the thermal emission of the three debris disks with a 30 sigma sensitivity of a few mJy at l00 micron and 160 micron. In addition, we obtained Herschel/PACS photometric data at 70 micron for HIP 103389. These observations are complemented by a large variety of optical to far-infrared photometric data. Two different approaches are applied to reduce the Herschel data to investigate the impact of data reduction on the photometry. We fit analytical models to the available spectral energy distribution (SED) data using the fitting method of simulated therma1 annealing as well as a classical grid search method. Results. The SEDs of the three disks potentially exhibit an unusually steep decrease at wavelengths >= 70 micron. We investigate the significance of the peculiar shape of these SEDs and the impact on models of the disks provided it is real. Using grain compositions that have been applied successfully for modeling of many other debris disks, our modeling reveals that such a steep decrease of the SEDs in the long wavelength regime is inconsistent with a power-law exponent of the grain size distribution -3.5 expected from a standard equilibrium collisional cascade. In contrast, a steep grain size distribution or, alternatively an upper grain size in the range of few tens of micrometers are implied. This suggests that a very distinct range of grain sizes would dominate the thermal. emission of such disks. However, we demonstrate that the understanding of the data of faint sources obtained with Herschel is

  5. HD 106906 b: A PLANETARY-MASS COMPANION OUTSIDE A MASSIVE DEBRIS DISK

    SciTech Connect

    Bailey, Vanessa; Reiter, Megan; Morzinski, Katie; Males, Jared; Su, Kate Y. L.; Hinz, Philip M.; Stark, Daniel; Close, Laird M.; Follette, Katherine B.; Rodigas, Timothy; Meshkat, Tiffany; Kenworthy, Matthew; Mamajek, Eric; Briguglio, Runa; Puglisi, Alfio; Xompero, Marco; Weinberger, Alycia J.

    2014-01-01

    We report the discovery of a planetary-mass companion, HD 106906 b, with the new Magellan Adaptive Optics (MagAO) + Clio2 system. The companion is detected with Clio2 in three bands: J, K{sub S} , and L', and lies at a projected separation of 7.''1 (650 AU). It is confirmed to be comoving with its 13 ± 2 Myr F5 host using Hubble Space Telescope Advanced Camera for Surveys astrometry over a time baseline of 8.3 yr. DUSTY and COND evolutionary models predict that the companion's luminosity corresponds to a mass of 11 ± 2 M {sub Jup}, making it one of the most widely separated planetary-mass companions known. We classify its Magellan/Folded-Port InfraRed Echellette J/H/K spectrum as L2.5 ± 1; the triangular H-band morphology suggests an intermediate surface gravity. HD 106906 A, a pre-main-sequence Lower Centaurus Crux member, was initially targeted because it hosts a massive debris disk detected via infrared excess emission in unresolved Spitzer imaging and spectroscopy. The disk emission is best fit by a single component at 95 K, corresponding to an inner edge of 15-20 AU and an outer edge of up to 120 AU. If the companion is on an eccentric (e > 0.65) orbit, it could be interacting with the outer edge of the disk. Close-in, planet-like formation followed by scattering to the current location would likely disrupt the disk and is disfavored. Furthermore, we find no additional companions, though we could detect similar-mass objects at projected separations >35 AU. In situ formation in a binary-star-like process is more probable, although the companion-to-primary mass ratio, at <1%, is unusually small.

  6. Unraveling the Mystery of Exozodiacal Dust

    NASA Astrophysics Data System (ADS)

    Ertel, S.; Augereau, J.-C.; Thébault, P.; Absil, O.; Bonsor, A.; Defrère, D.; Kral, Q.; Le Bouquin, J.-B.; Lebreton, J.; Coudé du Foresto, V.

    2014-01-01

    Exozodiacal dust clouds are thought to be the extrasolar analogs of the Solar System's zodiacal dust. Studying these systems provides insights in the architecture of the innermost regions of planetary systems, including the Habitable Zone. Furthermore, the mere presence of the dust may result in major obstacles for direct imaging of earth-like planets. Our EXOZODI project aims to detect and study exozodiacal dust and to explain its origin. We are carrying out the first large, near-infrared interferometric survey in the northern (CHARA/FLUOR) and southern (VLTI/PIONIER) hemispheres. Preliminary results suggest a detection rate of up to 30% around A to K type stars and interesting trends with spectral type and age. We focus here on presenting the observational work carried out by our team.

  7. ALMA Observations of the Molecular Gas in the Debris Disk of the 30 Myr Old Star HD 21997

    NASA Technical Reports Server (NTRS)

    Kospal, A.; Moor, A.; Juhasz, A.; Abraham, P.; Apai, D.; Csengeri, T.; Grady, C. A.; Henning, Th.; Hughes, A. M.; Kiss, Cs.; Pascucci, I.; Schmalzl, M.

    2013-01-01

    The 30 Myr old A3-type star HD 21997 is one of the two known debris dust disks having a measurable amount of cold molecular gas. With the goal of understanding the physical state, origin, and evolution of the gas in young debris disks, we obtained CO line observations with the Atacama Large Millimeter/submillimeter Array (ALMA). Here, we report on the detection of (12)CO and (13)CO in the J = 2-1 and J = 3-2 transitions and C(18)O in the J = 2-1 line. The gas exhibits a Keplerian velocity curve, one of the few direct measurements of Keplerian rotation in young debris disks. The measured CO brightness distribution could be reproduced by a simple star+disk system, whose parameters are r(sub in) < 26 AU, r(sub out) = 138 +/- 20 AU, Stellar M = 1.8 +0.5/-0.2 Solar M, and i = 32. Deg. 6 +/- 3 deg..1. The total CO mass, as calculated from the optically thin C(18)O line, is about (4-8) ×10(exp -2 ) Solar M, while the CO line ratios suggest a radiation temperature on the order of 6-9 K. Comparing our results with those obtained for the dust component of the HD 21997 disk from ALMA continuum observations by Moor et al., we conclude that comparable amounts of CO gas and dust are present in the disk. Interestingly, the gas and dust in the HD 21997 system are not colocated, indicating a dust-free inner gas disk within 55 AU of the star. We explore two possible scenarios for the origin of the gas. A secondary origin, which involves gas production from colliding or active planetesimals, would require unreasonably high gas production rates and would not explain why the gas and dust are not colocated. We propose that HD 21997 is a hybrid system where secondary debris dust and primordial gas coexist. HD 21997, whose age exceeds both the model predictions for disk clearing and the ages of the oldest T Tauri-like or transitional gas disks in the literature, may be a key object linking the primordial and the debris phases of disk evolution.

  8. ALMA OBSERVATIONS OF THE MOLECULAR GAS IN THE DEBRIS DISK OF THE 30 Myr OLD STAR HD 21997

    SciTech Connect

    Kóspál, Á.; Moór, A.; Ábrahám, P.; Kiss, Cs.; Juhász, A.; Schmalzl, M.; Apai, D.; Csengeri, T.; Grady, C. A.; Henning, Th.; Hughes, A. M.; Pascucci, I.

    2013-10-20

    The 30 Myr old A3-type star HD 21997 is one of the two known debris dust disks having a measurable amount of cold molecular gas. With the goal of understanding the physical state, origin, and evolution of the gas in young debris disks, we obtained CO line observations with the Atacama Large Millimeter/submillimeter Array (ALMA). Here, we report on the detection of {sup 12}CO and {sup 13}CO in the J = 2-1 and J = 3-2 transitions and C{sup 18}O in the J = 2-1 line. The gas exhibits a Keplerian velocity curve, one of the few direct measurements of Keplerian rotation in young debris disks. The measured CO brightness distribution could be reproduced by a simple star+disk system, whose parameters are r{sub in} < 26 AU, r{sub out} = 138 ± 20 AU, M{sub *}=1.8{sup +0.5}{sub -0.2} M{sub ☉}, and i = 32.°6 ± 3.°1. The total CO mass, as calculated from the optically thin C{sup 18}O line, is about (4-8) × 10{sup –2} M{sub ⊕}, while the CO line ratios suggest a radiation temperature on the order of 6-9 K. Comparing our results with those obtained for the dust component of the HD 21997 disk from ALMA continuum observations by Moór et al., we conclude that comparable amounts of CO gas and dust are present in the disk. Interestingly, the gas and dust in the HD 21997 system are not colocated, indicating a dust-free inner gas disk within 55 AU of the star. We explore two possible scenarios for the origin of the gas. A secondary origin, which involves gas production from colliding or active planetesimals, would require unreasonably high gas production rates and would not explain why the gas and dust are not colocated. We propose that HD 21997 is a hybrid system where secondary debris dust and primordial gas coexist. HD 21997, whose age exceeds both the model predictions for disk clearing and the ages of the oldest T Tauri-like or transitional gas disks in the literature, may be a key object linking the primordial and the debris phases of disk evolution.

  9. ALMA Observations of the Molecular Gas in the Debris Disk of the 30 Myr Old Star HD 21997

    NASA Astrophysics Data System (ADS)

    Kóspál, Á.; Moór, A.; Juhász, A.; Ábrahám, P.; Apai, D.; Csengeri, T.; Grady, C. A.; Henning, Th.; Hughes, A. M.; Kiss, Cs.; Pascucci, I.; Schmalzl, M.

    2013-10-01

    The 30 Myr old A3-type star HD 21997 is one of the two known debris dust disks having a measurable amount of cold molecular gas. With the goal of understanding the physical state, origin, and evolution of the gas in young debris disks, we obtained CO line observations with the Atacama Large Millimeter/submillimeter Array (ALMA). Here, we report on the detection of 12CO and 13CO in the J = 2-1 and J = 3-2 transitions and C18O in the J = 2-1 line. The gas exhibits a Keplerian velocity curve, one of the few direct measurements of Keplerian rotation in young debris disks. The measured CO brightness distribution could be reproduced by a simple star+disk system, whose parameters are r in < 26 AU, r out = 138 ± 20 AU, M_*=1.8^{+0.5}_{-0.2} M ⊙, and i = 32.°6 ± 3.°1. The total CO mass, as calculated from the optically thin C18O line, is about (4-8) × 10-2 M ⊕, while the CO line ratios suggest a radiation temperature on the order of 6-9 K. Comparing our results with those obtained for the dust component of the HD 21997 disk from ALMA continuum observations by Moór et al., we conclude that comparable amounts of CO gas and dust are present in the disk. Interestingly, the gas and dust in the HD 21997 system are not colocated, indicating a dust-free inner gas disk within 55 AU of the star. We explore two possible scenarios for the origin of the gas. A secondary origin, which involves gas production from colliding or active planetesimals, would require unreasonably high gas production rates and would not explain why the gas and dust are not colocated. We propose that HD 21997 is a hybrid system where secondary debris dust and primordial gas coexist. HD 21997, whose age exceeds both the model predictions for disk clearing and the ages of the oldest T Tauri-like or transitional gas disks in the literature, may be a key object linking the primordial and the debris phases of disk evolution.

  10. Dynamical Simulations of Extrasolar Planetary Systems with Debris Disks Using a GPU Accelerated N-Body Code

    NASA Astrophysics Data System (ADS)

    Moore, Alexander

    This thesis begins with a description of a hybrid symplectic integrator named QYMSYM which is capable of planetary system simulations. This integrator has been programmed with the Compute Unified Device Architecture (CUDA) language which allows for implementation on Graphics Processing Units (GPUs). With the enhanced compute performance made available by this choice, QYMSYM was used to study the effects debris disks have on the dynamics of the extrasolar planetary systems HR 8799 and KOI-730. The four planet system HR 8799 was chosen because it was known to have relatively small regions of stability in orbital phase space. Using this fact, it can be shown that a simulated debris disk of moderate mass around HR 8799 can easily pull this system out of these regions of stability. In other cases it is possible to migrate the system to a region of stability - although this requires significantly more mass and a degree of fine tuning. These findings suggest that previous studies on the stability of HR 8799 which do not include a debris disk may not accurately report on the size and location of the stable orbital phase space available for the planets. This insight also calls into question the practice of using dynamical simulations to help constrain observed planetary orbital data. Next, by studying the stability of another four planet system, KOI-730, whose planets are in an 8:6:4:3 mean motion resonance, we were additionally able to determine mass constraints on debris disks for KOI-730 like Kepler objects. Noting that planet inclinations increase by a couple of degrees when migrating through a Neptune mass debris disk, and that planet candidates discovered by the Kepler Space Telescope are along the line of site, it is concluded that significant planetary migration did not occur among the Kepler objects. This result indicates that Kepler objects like KOI-730 have relatively small or stable debris disks which did not cause migration of their planets - ruling out late

  11. Radial profiles of the Phoebe ring: A vast debris disk around Saturn

    NASA Astrophysics Data System (ADS)

    Tamayo, Daniel; Markham, Stephen R.; Hedman, Matthew M.; Burns, Joseph A.; Hamilton, Douglas P.

    2016-09-01

    We present observations at optical wavelengths with the Cassini Spacecraft's Imaging Science System of the Phoebe ring, a vast debris disk around Saturn that seems to be collisionally generated by its irregular satellites. The analysis reveals a radial profile from 80-260 Saturn radii (RS) that changes behavior interior to ≈110RS. We attribute this to either the moon Iapetus...sweeping up small particles, or to orbital instabilities that cause the ring to flare up vertically. Our study yields an integrated I/F at 0.635 μm along Saturn's shadow in the Phoebe ring's midplane from 80-250 RS of 2.7-0.3+0.9. We develop an analytical model for the size-dependent secular dynamics of retrograde Phoebe ring grains, and compare this model to the observations. This analysis implies that 1) the "Phoebe" ring is partially sourced by debris from irregular satellites beyond Phoebe's orbit and 2) the scattered light signal is dominated by small grains (≲20 μm in size). If we assume that the Phoebe ring is generated through steady-state micrometeoroid bombardment, this implies a power-law size distribution with index >4, which is unusually steep among Solar System rings. This suggests either a steep size distribution of ejecta when material is initially released, or a subsequent process that preferentially breaks up large grains.

  12. Detection and Characterization of Extrasolar Planets through Mean-motion Resonances. I. Simulations of Hypothetical Debris Disks

    NASA Astrophysics Data System (ADS)

    Tabeshian, Maryam; Wiegert, Paul A.

    2016-02-01

    The gravitational influence of a planet on a nearby disk provides a powerful tool for detecting and studying extrasolar planetary systems. Here we demonstrate that gaps can be opened in dynamically cold debris disks at the mean-motion resonances of an orbiting planet. The gaps are opened away from the orbit of the planet itself, revealing that not all disk gaps need contain a planetary body. These gaps are large and deep enough to be detectable in resolved disk images for a wide range of reasonable disk-planet parameters, though we are not aware of any such gaps detected to date. The gap shape and size are diagnostic of the planet location, eccentricity and mass, and allow one to infer the existence of unseen planets, as well as many important parameters of both seen and unseen planets in these systems. We present expressions to allow the planetary mass and semimajor axis to be calculated from observed gap width and location.

  13. ALMA Observations of the Debris Disk of Solar Analog τ Ceti

    NASA Astrophysics Data System (ADS)

    MacGregor, Meredith A.; Lawler, Samantha M.; Wilner, David J.; Matthews, Brenda C.; Kennedy, Grant M.; Booth, Mark; Di Francesco, James

    2016-09-01

    We present 1.3 mm observations of the Sun-like star τ Ceti with the Atacama Large Millimeter/submillimeter Array that probe angular scales of ∼ 1\\prime\\prime (4 au). This first interferometric image of the τ Ceti system, which hosts both a debris disk and a possible multiplanet system, shows emission from a nearly face-on belt of cold dust with a position angle of 90^\\circ surrounding an unresolved central source at the stellar position. To characterize this emission structure, we fit parametric models to the millimeter visibilities. The resulting best-fit model yields an inner belt edge of {6.2}-4.6+9.8 au, consistent with inferences from lower resolution, far-infrared Herschel observations. While the limited data at sufficiently short baselines preclude us from placing stronger constraints on the belt properties and its relation to the proposed five planet system, the observations do provide a strong lower limit on the fractional width of the belt, {{Δ }}R/R\\gt 0.75 with 99% confidence. This fractional width is more similar to broad disks such as HD 107146 than narrow belts such as the Kuiper Belt and Fomalhaut. The unresolved central source has a higher flux density than the predicted flux of the stellar photosphere at 1.3 mm. Given previous measurements of an excess by a factor of ∼2 at 8.7 mm, this emission is likely due to a hot stellar chromosphere.

  14. OT1_dpadgett_1: PACS Photometry of Nearby Warm Debris Disk Systems from the WISE All-Sky Survey

    NASA Astrophysics Data System (ADS)

    Padgett, D.

    2010-07-01

    Debris disks trace the collisional breakdown of asteroid and comet parent bodies orbiting nearby main sequence stars. They are detectable in ~16% of FGK stars, nearly twice as often in A stars, and are almost unknown around M stars. The debris disks of sunlike stars are typically cold analogs of our Kuiper belt with emission peaking near 70 microns wavelength. However, a relatively small number of warm disks are known with emission at 24 microns. These systems are especially interesting because they trace dust in the region likely to host terrestrial planets, where the dust has a short dynamical lifetimes. They also tend to be young systems aged < 1 Gyr. This knowledge of warm debris disks - extrasolar analogs to our solar system's Zodiacal cloud - is based on the 25 year old IRAS survey and observations of selected targets with ISO and Spitzer. The Wide-Field Infrared Survey Explorer (WISE) has just completed new, sensitive all-sky mapping in the 3.3, 4.6, 12, and 22 micron bands. Association of the WISE sources to Hipparcos and Tycho stars has led to the identification of 99 nearby main sequence stars with robustly detected warm 22 micron excesses not previously known. To determine whether these systems represent outbursts of asteroidal dust production (such as in the HD 69830 system), or simply the Wien side of emission from a cold outer dust belt, photometry at longer wavelengths is needed. We propose Herschel/PACS 70 and 160 micron photometry of this unbiased sample. These data will allow us to fully characterize the dust temperature and infrared luminosity of these systems, allowing them to be understood in the context of other debris disks and disk evolution theory. The sample includes field M stars as close as 12 pc, the first objects of this class seen to have warm dust emission. The results will strongly constrain our picture of the collisional history of inner planetary systems.

  15. Detection of Variable Gaseous Absorption Features in the Debris Disks Around Young A-type Stars

    NASA Astrophysics Data System (ADS)

    Montgomery, Sharon L.; Welsh, Barry Y.

    2012-10-01

    We present medium resolution (R = 60,000) absorption measurements of the interstellar Ca II K line observed towards five nearby A-type stars (49 Ceti, 5 Vul, ι Cyg, 2 And, and HD 223884) suspected of possessing circumstellar gas debris disks. The stars were observed on a nightly basis during a six night observing run on the 2.1-meter Otto Struve telescope at the McDonald Observatory, Texas. We have detected nightly changes in the absorption strength of the Ca II K line observed near the stellar radial velocity in three of the stars (49 Ceti, i Cyg and HD 223884). Such changes in absorption suggest the presence of a circumstellar (atomic) gas disk around these stars. In addition to the absorption changes in the main Ca II K line profile, we have also observed weak transient absorption features that randomly appear at redshifted velocities in the spectra of 49 Ceti, 5 Vul, and 2 And. These absorption features are most probably associated with the presence of falling evaporated bodies (exo-comets) that liberate evaporating gas on their approach to the central star. This now brings the total number of systems in which exocomet activity has been observed at Ca II or Na I wavelengths on a nightly basis to seven (β Pic, HR 10, HD 85905, β Car, 49 Ceti, 5 Vul, and 2 And), with 2 And exhibiting weaker and less frequent changes. All of the disk systems presently known to exhibit either type of short-term variability in Ca II K line absorption are rapidly rotating A-type stars (V sin i > 120 km s-1). Most exhibit mid-IR excesses, and many of them are very young (< 20 Myr), thus supporting the argument that many of them are transitional objects between Herbig Ae and "Vega-like" A-type stars with more tenuous circumstellar disks. No mid-IR excess (due to the presence of a dust disk) has yet been detected around either 2 And or HD 223884, both of which have been classified as λ Boötis-type stars. This may indicate that the observed changes in gas absorption for these two

  16. Models of the η Corvi Debris Disk from the Keck Interferometer, Spitzer, and Herschel

    NASA Astrophysics Data System (ADS)

    Lebreton, J.; Beichman, C.; Bryden, G.; Defrère, D.; Mennesson, B.; Millan-Gabet, R.; Boccaletti, A.

    2016-02-01

    Debris disks are signposts of analogs to small-body populations of the solar system, often, however, with much higher masses and dust production rates. The disk associated with the nearby star η Crv is especially striking, as it shows strong mid- and far-infrared excesses despite an age of ∼1.4 Gyr. We undertake constructing a consistent model of the system that can explain a diverse collection of spatial and spectral data. We analyze Keck Interferometer Nuller measurements and revisit Spitzer and additional spectrophotometric data, as well as resolved Herschel images, to determine the dust spatial distribution in the inner exozodi and in the outer belt. We model in detail the two-component disk and the dust properties from the sub-AU scale to the outermost regions by fitting simultaneously all measurements against a large parameter space. The properties of the cold belt are consistent with a collisional cascade in a reservoir of ice-free planetesimals at 133 AU. It shows marginal evidence for asymmetries along the major axis. KIN enables us to establish that the warm dust consists of a ring that peaks between 0.2 and 0.8 AU. To reconcile this location with the ∼400 K dust temperature, very high albedo dust must be invoked, and a distribution of forsterite grains starting from micron sizes satisfies this criterion, while providing an excellent fit to the spectrum. We discuss additional constraints from the LBTI and near-infrared spectra, and we present predictions of what James Webb Space Telescope can unveil about this unusual object and whether it can detect unseen planets.

  17. The Exozodiacal Dust Problem for Direct Observations of ExoEarths

    NASA Technical Reports Server (NTRS)

    Roberge, Aki; Chen, Christine H.; Millan-Gabet, Rafael; Weinberger, Alycia J.; Hinz, Philip M.; Stapelfeldt, Karl R.; Absil, Olivier; Kuchner, Marc J.; Bryden, Geoffrey

    2012-01-01

    Debris dust in the habitable zones of stars otherwise known as exozodiacal dust comes from extrasolar asteroids and comets and is thus an expected part of a planetary system. Background flux from the Solar Systems zodiacal dust and the exozodiacal dust in the target system is likely to be the largest source of astrophysical noise in direct observations of terrestrial planets in the habitable zones of nearby stars. Furthermore, dust structures like clumps, thought to be produced by dynamical interactions with exoplanets, are a possible source of confusion. In this paper, we qualitatively assess the primary impact of exozodical dust on high-contrast direct imaging at optical wavelengths, such as would be performed with a coronagraph. Then we present the sensitivity of previous, current, and near-term facilities to thermal emission from debris dust at all distances from nearby solar-type stars, as well as our current knowledge of dust levels from recent surveys. Finally, we address the other method of detecting debris dust, through high-contrast imaging in scattered light. This method is currently far less sensitive than thermal emission observations, but provides high spatial resolution for studying dust structures. This paper represents the first report of NASA's Exoplanet Exploration Program Analysis Group (ExoPAG).

  18. Spatially Resolved Imaging of the Two-component η Crv Debris Disk with Herschel

    NASA Astrophysics Data System (ADS)

    Duchêne, G.; Arriaga, P.; Wyatt, M.; Kennedy, G.; Sibthorpe, B.; Lisse, C.; Holland, W.; Wisniewski, J.; Clampin, M.; Kalas, P.; Pinte, C.; Wilner, D.; Booth, M.; Horner, J.; Matthews, B.; Greaves, J.

    2014-04-01

    We present far-infrared and submillimeter images of the η Crv debris disk system obtained with Herschel and SCUBA-2, as well as Hubble Space Telescope visible and near-infrared coronagraphic images. In the 70 μm Herschel image, we clearly separate the thermal emission from the warm and cold belts in the system, find no evidence for a putative dust population located between them, and precisely determine the geometry of the outer belt. We also find marginal evidence for azimuthal asymmetries and a global offset of the outer debris ring relative to the central star. Finally, we place stringent upper limits on the scattered light surface brightness of the outer ring. Using radiative transfer modeling, we find that it is impossible to account for all observed properties of the system under the assumption that both rings contain dust populations with the same properties. While the outer belt is in reasonable agreement with the expectations of steady-state collisional cascade models, albeit with a minimum grain size that is four times larger than the blow-out size, the inner belt appears to contain copious amounts of small dust grains, possibly below the blow-out size. This suggests that the inner belt cannot result from a simple transport of grains from the outer belt and rather supports a more violent phenomenon as its origin. We also find that the emission from the inner belt has not declined over three decades, a much longer timescale than its dynamical timescale, which indicates that the belt is efficiently replenished.

  19. Spatially resolved imaging of the two-component η Crv debris disk with Herschel

    SciTech Connect

    Duchêne, G.; Arriaga, P.; Kalas, P.; Wyatt, M.; Kennedy, G.; Sibthorpe, B.; Lisse, C.; Holland, W.; Wisniewski, J.; Clampin, M.; Pinte, C.; Booth, M.; Horner, J.; Matthews, B.; Greaves, J.

    2014-04-01

    We present far-infrared and submillimeter images of the η Crv debris disk system obtained with Herschel and SCUBA-2, as well as Hubble Space Telescope visible and near-infrared coronagraphic images. In the 70 μm Herschel image, we clearly separate the thermal emission from the warm and cold belts in the system, find no evidence for a putative dust population located between them, and precisely determine the geometry of the outer belt. We also find marginal evidence for azimuthal asymmetries and a global offset of the outer debris ring relative to the central star. Finally, we place stringent upper limits on the scattered light surface brightness of the outer ring. Using radiative transfer modeling, we find that it is impossible to account for all observed properties of the system under the assumption that both rings contain dust populations with the same properties. While the outer belt is in reasonable agreement with the expectations of steady-state collisional cascade models, albeit with a minimum grain size that is four times larger than the blow-out size, the inner belt appears to contain copious amounts of small dust grains, possibly below the blow-out size. This suggests that the inner belt cannot result from a simple transport of grains from the outer belt and rather supports a more violent phenomenon as its origin. We also find that the emission from the inner belt has not declined over three decades, a much longer timescale than its dynamical timescale, which indicates that the belt is efficiently replenished.

  20. Constraints on the Presence of SiO Gas in the Debris Disk of HD172555

    NASA Astrophysics Data System (ADS)

    Wilson, T. L.; Nilsson, R.; Chen, C. H.; Lisse, C. M.; Moerchen, M.; Käufl, H.-U.; Banzatti, A.

    2016-08-01

    We have carried out two sets of observations to quantify the properties of SiO gas in the unusual HD 172555 debris disk: (1) a search for the J = 8-7 rotational transition from the vibrational ground state, carried out with the Atacama Pathfinder EXperiment (APEX) submillimeter telescope and heterodyne receiver at 863 μm and (2) a search at 8.3 μm for the P(17) ro-vibrational transition of gas phase SiO, carried out with the Very Large Telescope (VLT)/VISIR with a resolution, λ/Δλ, of 30,000. The APEX measurement resulted in a 3.3σ detection of an interstellar feature, but only an upper limit to emission at the radial velocity and line width expected from HD 172555. The VLT/VISIR result was also an upper limit. These were used to provide limits for the abundance of gas phase SiO for a range of temperatures. The upper limit from our APEX detection, assuming an 8000 K primary star photospheric excitation, falls more than an order of magnitude below the self-shielding stability threshold derived by Johnson et al. (2012). Our results thus favor a solid-state origin for the 8.3 μm feature seen in the Spitzer IRS spectrum of the circumstellar excess emission and the production of circumstellar O i and Si i by SiO UV photolysis. The implications of these estimates are explored in the framework of models of the HD 172555 circumstellar disk.

  1. MAMBO image of the debris disk around ɛ Eridani: robustness of the azimuthal structure

    NASA Astrophysics Data System (ADS)

    Lestrade, Jean-François; Thilliez, Elodie

    2015-04-01

    The debris disk closest to Earth is the one around the star ɛ Eridani at a distance of 3.2 pc. It is the prime target for detailed studies of a belt of planetesimals left from the early phase of planet formation other than the Kuiper belt. The non-uniform ring-like structure around ɛ Eridani, originally discovered at λ = 850 μm with the bolometer camera SCUBA, could be the signpost of unseen long-period planets interior to the disk that gravitationally interact with it through mean-motion resonances. However, the reliability of the structure at 850 μm, which has been debated, has not been verified with independent observations until now. We present a high signal-to-noise ratio image of this structure at λ = 1.2 mm made with the bolometer camera MAMBO and compare this with the SCUBA image. We have found that three of the four emission clumps (NE, NW, SW) and the two deep hollows to the east and west are at the same positions in the MAMBO and SCUBA images within astrometric uncertainty. The SE clump is at odds, significantly brighter and more extended in the SCUBA than in the MAMBO images, but it is possible that this mismatch is an artifact. We conclude that this degree of positional coincidence provides tentative evidence that the observed structure is robust. In addition, we present the radial brightness profile of our MAMBO image and show that the width of the planetesimal belt around ɛ Eridani is narrower than 22 AU, a more stringent upper limit than determined from previous observations. The corresponding relative width is 0.1 ≤ ΔR/R ≤ 0.4, which is lower than for the Kuiper belt.

  2. Constraints on the Presence of SiO Gas in the Debris Disk of HD172555

    NASA Astrophysics Data System (ADS)

    Wilson, T. L.; Nilsson, R.; Chen, C. H.; Lisse, C. M.; Moerchen, M.; Käufl, H.-U.; Banzatti, A.

    2016-08-01

    We have carried out two sets of observations to quantify the properties of SiO gas in the unusual HD 172555 debris disk: (1) a search for the J = 8–7 rotational transition from the vibrational ground state, carried out with the Atacama Pathfinder EXperiment (APEX) submillimeter telescope and heterodyne receiver at 863 μm and (2) a search at 8.3 μm for the P(17) ro-vibrational transition of gas phase SiO, carried out with the Very Large Telescope (VLT)/VISIR with a resolution, λ/Δλ, of 30,000. The APEX measurement resulted in a 3.3σ detection of an interstellar feature, but only an upper limit to emission at the radial velocity and line width expected from HD 172555. The VLT/VISIR result was also an upper limit. These were used to provide limits for the abundance of gas phase SiO for a range of temperatures. The upper limit from our APEX detection, assuming an 8000 K primary star photospheric excitation, falls more than an order of magnitude below the self-shielding stability threshold derived by Johnson et al. (2012). Our results thus favor a solid-state origin for the 8.3 μm feature seen in the Spitzer IRS spectrum of the circumstellar excess emission and the production of circumstellar O i and Si i by SiO UV photolysis. The implications of these estimates are explored in the framework of models of the HD 172555 circumstellar disk.

  3. ON THE MORPHOLOGY AND CHEMICAL COMPOSITION OF THE HR 4796A DEBRIS DISK

    SciTech Connect

    Rodigas, Timothy J.; Weinberger, Alycia; Stark, Christopher C.; Debes, John H.; Chen, Christine; Hinz, Philip M.; Close, Laird; Smith, Paul S.; Males, Jared R.; Skemer, Andrew J.; Follette, Katherine B.; Morzinski, Katie; Wu, Ya-Lin; Schneider, Glenn; Puglisi, Alfio; Briguglio, Runa; Esposito, Simone; Pinna, Enrico; Riccardi, Armando; Xompero, Marco

    2015-01-10

    We present resolved images of the HR 4796A debris disk using the Magellan adaptive optics system paired with Clio-2 and VisAO. We detect the disk at 0.77 μm, 0.91 μm, 0.99 μm, 2.15 μm, 3.1 μm, 3.3 μm, and 3.8 μm. We find that the deprojected center of the ring is offset from the star by 4.76 ± 1.6 AU and that the deprojected eccentricity is 0.06 ± 0.02, in general agreement with previous studies. We find that the average width of the ring is 14{sub −2}{sup +3}% (11.1{sub −1.6}{sup +2.4} AU), also comparable to previous measurements. Combining our new scattered light data with archival Hubble Space Telescope images at ∼0.5-2 μm, along with previously unpublished Spitzer/MIPS thermal emission data and all other literature thermal data, we set out to constrain the chemical composition of the dust grains. After testing 19 individual root compositions and more than 8400 unique mixtures of these compositions, we find that good fits to the scattered light alone and thermal emission alone are discrepant, suggesting that caution should be exercised if fitting to only one or the other. When we fit to both data sets simultaneously, we find that silicates and organics are generally the most favored, while large abundances of water ice are usually not favored. These results suggest the HR 4796A dust grains are similar to interstellar dust and solar system comets, though improved modeling is necessary to place better constraints on the exact chemical composition of the dust.

  4. Millimeter Emission Structure in the First ALMA Image of the AU Mic Debris Disk

    NASA Astrophysics Data System (ADS)

    MacGregor, Meredith A.; Wilner, David J.; Rosenfeld, Katherine A.; Andrews, Sean M.; Matthews, Brenda; Hughes, A. Meredith; Booth, Mark; Chiang, Eugene; Graham, James R.; Kalas, Paul; Kennedy, Grant; Sibthorpe, Bruce

    2013-01-01

    We present 1.3 mm ALMA Cycle 0 observations of the edge-on debris disk around the nearby, ~10 Myr old, M-type star AU Mic. These observations obtain 0.''6 (6 AU) resolution and reveal two distinct emission components: (1) the previously known dust belt that extends to a radius of 40 AU and (2) a newly recognized central peak that remains unresolved. The cold dust belt of mass ~1 M Moon is resolved in the radial direction with a rising emission profile that peaks sharply at the location of the outer edge of the "birth ring" of planetesimals hypothesized to explain the midplane scattered light gradients. No significant asymmetries are discerned in the structure or position of this dust belt. The central peak identified in the ALMA image is ~6 times brighter than the stellar photosphere, which indicates an additional emission process in the inner regions of the system. Emission from a stellar corona or activity may contribute, but the observations show no signs of temporal variations characteristic of radio-wave flares. We suggest that this central component may be dominated by dust emission from an inner planetesimal belt of mass ~0.01 M Moon, consistent with a lack of emission shortward of 25 μm and a location lsim3 AU from the star. Future millimeter observations can test this assertion, as an inner dust belt should be readily separated from the central star at higher angular resolution.

  5. MILLIMETER EMISSION STRUCTURE IN THE FIRST ALMA IMAGE OF THE AU Mic DEBRIS DISK

    SciTech Connect

    MacGregor, Meredith A.; Wilner, David J.; Rosenfeld, Katherine A.; Andrews, Sean M.; Matthews, Brenda; Booth, Mark; Hughes, A. Meredith; Chiang, Eugene; Graham, James R.; Kalas, Paul; Kennedy, Grant; Sibthorpe, Bruce

    2013-01-10

    We present 1.3 mm ALMA Cycle 0 observations of the edge-on debris disk around the nearby, {approx}10 Myr old, M-type star AU Mic. These observations obtain 0.''6 (6 AU) resolution and reveal two distinct emission components: (1) the previously known dust belt that extends to a radius of 40 AU and (2) a newly recognized central peak that remains unresolved. The cold dust belt of mass {approx}1 M{sub Moon} is resolved in the radial direction with a rising emission profile that peaks sharply at the location of the outer edge of the 'birth ring' of planetesimals hypothesized to explain the midplane scattered light gradients. No significant asymmetries are discerned in the structure or position of this dust belt. The central peak identified in the ALMA image is {approx}6 times brighter than the stellar photosphere, which indicates an additional emission process in the inner regions of the system. Emission from a stellar corona or activity may contribute, but the observations show no signs of temporal variations characteristic of radio-wave flares. We suggest that this central component may be dominated by dust emission from an inner planetesimal belt of mass {approx}0.01 M{sub Moon}, consistent with a lack of emission shortward of 25 {mu}m and a location {approx}<3 AU from the star. Future millimeter observations can test this assertion, as an inner dust belt should be readily separated from the central star at higher angular resolution.

  6. Potential multi-component structure of the debris disk around HIP 17439 revealed by Herschel/DUNES

    NASA Astrophysics Data System (ADS)

    Ertel, S.; Marshall, J. P.; Augereau, J.-C.; Krivov, A. V.; Löhne, T.; Eiroa, C.; Mora, A.; del Burgo, C.; Montesinos, B.; Bryden, G.; Danchi, W.; Kirchschlager, F.; Liseau, R.; Maldonado, J.; Pilbratt, G. L.; Schüppler, Ch.; Thébault, Ph.; White, G. J.; Wolf, S.

    2014-01-01

    Context. The dust observed in debris disks is produced through collisions of larger bodies left over from the planet/planetesimal formation process. Spatially resolving these disks permits to constrain their architecture and thus that of the underlying planetary/planetesimal system. Aims: Our Herschel open time key program DUNES aims at detecting and characterizing debris disks around nearby, sun-like stars. In addition to the statistical analysis of the data, the detailed study of single objects through spatially resolving the disk and detailed modeling of the data is a main goal of the project. Methods: We obtained the first observations spatially resolving the debris disk around the sun-like star HIP 17439 (HD 23484) using the instruments PACS and SPIRE on board the Herschel Space Observatory. Simultaneous multi-wavelength modeling of these data together with ancillary data from the literature is presented. Results: A standard single component disk model fails to reproduce the major axis radial profiles at 70 μm, 100 μm, and 160 μm simultaneously. Moreover, the best-fit parameters derived from such a model suggest a very broad disk extending from few au up to few hundreds of au from the star with a nearly constant surface density which seems physically unlikely. However, the constraints from both the data and our limited theoretical investigation are not strong enough to completely rule out this model. An alternative, more plausible, and better fitting model of the system consists of two rings of dust at approx. 30 au and 90 au, respectively, while the constraints on the parameters of this model are weak due to its complexity and intrinsic degeneracies. Conclusions: The disk is probably composed of at least two components with different spatial locations (but not necessarily detached), while a single, broad disk is possible, but less likely. The two spatially well-separated rings of dust in our best-fit model suggest the presence of at least one high mass

  7. A Sensitive Identification of Warm Debris Disks in the Solar Neighborhood through Precise Calibration of Saturated WISE Photometry

    NASA Astrophysics Data System (ADS)

    Patel, Rahul I.; Metchev, Stanimir A.; Heinze, Aren

    2014-05-01

    We present a sensitive search for WISE W3 (12 μm) and W4 (22 μm) excesses from warm optically thin dust around Hipparcos main sequence stars within 75 pc from the Sun. We use contemporaneously measured photometry from WISE, remove sources of contamination, and derive and apply corrections to saturated fluxes to attain optimal sensitivity to >10 μm excesses. We use data from the WISE All-Sky Survey Catalog rather than the AllWISE release because we find that its saturated photometry is better behaved, allowing us to detect small excesses even around saturated stars in WISE. Our new discoveries increase by 45% the number of stars with warm dusty excesses and expand the number of known debris disks (with excess at any wavelength) within 75 pc by 29%. We identify 220 Hipparcos debris disk host stars, 108 of which are new detections at any wavelength. We present the first measurement of a 12 μm and/or 22 μm excess for 10 stars with previously known cold (50-100 K) disks. We also find five new stars with small but significant W3 excesses, adding to the small population of known exozodi, and we detect evidence for a W2 excess around HIP 96562 (F2V), indicative of tenuous hot (780 K) dust. As a result of our WISE study, the number of debris disks with known 10-30 μm excesses within 75 pc (379) has now surpassed the number of disks with known >30 μm excesses (289, with 171 in common), even if the latter have been found to have a higher occurrence rate in unbiased samples.

  8. FIRST SCATTERED-LIGHT IMAGE OF THE DEBRIS DISK AROUND HD 131835 WITH THE GEMINI PLANET IMAGER

    SciTech Connect

    Hung, Li-Wei; Arriaga, Pauline; Fitzgerald, Michael P.; Esposito, Thomas M.; Duchêne, Gaspard; Kalas, Paul G.; De Rosa, Robert J.; Graham, James R.; Maire, Jérôme; Chilcote, Jeffrey K.; Marois, Christian; Millar-Blanchaer, Maxwell A.; Bruzzone, Sebastian; Rajan, Abhijith; Pueyo, Laurent; Wolff, Schuyler G.; Chen, Christine H.; Konopacky, Quinn; Ammons, S. Mark; Draper, Zachary H.; and others

    2015-12-10

    We present the first scattered-light image of the debris disk around HD 131835 in the H band using the Gemini Planet Imager. HD 131835 is a ∼15 Myr old A2IV star at a distance of ∼120 pc in the Sco-Cen OB association. We detect the disk only in polarized light and place an upper limit on the peak total intensity. No point sources resembling exoplanets were identified. Compared to its mid-infrared thermal emission,  in scattered light the disk shows similar orientation but different morphology. The scattered-light disk extends from ∼75 to ∼210 AU in the disk plane with roughly flat surface density. Our Monte Carlo radiative transfer model can describe the observations with a model disk composed of a mixture of silicates and amorphous carbon. In addition to the obvious brightness asymmetry due to stronger forward scattering, we discover a weak brightness asymmetry along the major axis, with the northeast side being 1.3 times brighter than the southwest side at a 3σ level.

  9. First scattered-light image of the debris disk around HD 131835 with the Gemini Planet Imager

    DOE PAGES

    Hung, Li -Wei; Duchêne, Gaspard; Arriaga, Pauline; Fitzgerald, Michael P.; Maire, Jérôme; Marois, Christian; Millar-Blanchaer, Maxwell A.; Bruzzone, Sebastian; Rajan, Abhijith; Pueyo, Laurent; et al

    2015-12-09

    Here, we present the first scattered-light image of the debris disk around HD 131835 in the H band using the Gemini Planet Imager. HD 131835 is a ~15 Myr old A2IV star at a distance of ~120 pc in the Sco-Cen OB association. We detect the disk only in polarized light and place an upper limit on the peak total intensity. No point sources resembling exoplanets were identified. Compared to its mid-infrared thermal emission, in scattered light the disk shows similar orientation but different morphology. The scattered-light disk extends from ~75 to ~210 AU in the disk plane with roughlymore » flat surface density. Our Monte Carlo radiative transfer model can describe the observations with a model disk composed of a mixture of silicates and amorphous carbon. In addition to the obvious brightness asymmetry due to stronger forward scattering, we discover a weak brightness asymmetry along the major axis, with the northeast side being 1.3 times brighter than the southwest side at a 3σ level.« less

  10. First scattered-light image of the debris disk around HD 131835 with the Gemini Planet Imager

    SciTech Connect

    Hung, Li -Wei; Duchêne, Gaspard; Arriaga, Pauline; Fitzgerald, Michael P.; Maire, Jérôme; Marois, Christian; Millar-Blanchaer, Maxwell A.; Bruzzone, Sebastian; Rajan, Abhijith; Pueyo, Laurent; Kalas, Paul G.; De Rosa, Robert J.; Graham, James R.; Konopacky, Quinn; Wolff, Schuyler G.; Ammons, S. Mark; Chen, Christine H.; Chilcote, Jeffrey K.; Draper, Zachary H.; Esposito, Thomas M.; Gerard, Benjamin; Goodsell, Stephen; Greenbaum, Alexandra; Hibon, Pascale; Hinkley, Sasha; Macintosh, Bruce; Marchis, Franck; Metchev, Stanimir; Nielsen, Eric L.; Oppenheimer, Rebecca; Patience, Jennifer L.; Perrin, Marshall D.; Rantakyrö, Fredrik T.; Sivaramakrishnan, Anand; Wang, Jason J.; Ward-Duong, Kimberly; Wiktorowicz, Sloane J.

    2015-12-09

    Here, we present the first scattered-light image of the debris disk around HD 131835 in the H band using the Gemini Planet Imager. HD 131835 is a ~15 Myr old A2IV star at a distance of ~120 pc in the Sco-Cen OB association. We detect the disk only in polarized light and place an upper limit on the peak total intensity. No point sources resembling exoplanets were identified. Compared to its mid-infrared thermal emission, in scattered light the disk shows similar orientation but different morphology. The scattered-light disk extends from ~75 to ~210 AU in the disk plane with roughly flat surface density. Our Monte Carlo radiative transfer model can describe the observations with a model disk composed of a mixture of silicates and amorphous carbon. In addition to the obvious brightness asymmetry due to stronger forward scattering, we discover a weak brightness asymmetry along the major axis, with the northeast side being 1.3 times brighter than the southwest side at a 3σ level.

  11. Bringing “The Moth” to Light: A Planet-sculpting Scenario for the HD 61005 Debris Disk

    NASA Astrophysics Data System (ADS)

    Esposito, Thomas M.; Fitzgerald, Michael P.; Graham, James R.; Kalas, Paul; Lee, Eve J.; Chiang, Eugene; Duchêne, Gaspard; Wang, Jason; Millar-Blanchaer, Maxwell A.; Nielsen, Eric; Ammons, S. Mark; Bruzzone, Sebastian; De Rosa, Robert J.; Draper, Zachary H.; Macintosh, Bruce; Marchis, Franck; Metchev, Stanimir A.; Perrin, Marshall; Pueyo, Laurent; Rajan, Abhijith; Rantakyrö, Fredrik T.; Vega, David; Wolff, Schuyler

    2016-10-01

    The HD 61005 debris disk (“The Moth”) stands out from the growing collection of spatially resolved circumstellar disks by virtue of its unusual swept-back morphology, brightness asymmetries, and dust ring offset. Despite several suggestions for the physical mechanisms creating these features, no definitive answer has been found. In this work, we demonstrate the plausibility of a scenario in which the disk material is shaped dynamically by an eccentric, inclined planet. We present new Keck NIRC2 scattered-light angular differential imaging of the disk at 1.2-2.3 μm that further constrains its outer morphology (projected separations of 27-135 au). We also present complementary Gemini Planet Imager 1.6 μm total intensity and polarized light detections that probe down to projected separations less than 10 au. To test our planet-sculpting hypothesis, we employed secular perturbation theory to construct parent body and dust distributions that informed scattered-light models. We found that this method produced models with morphological and photometric features similar to those seen in the data, supporting the premise of a planet-perturbed disk. Briefly, our results indicate a disk parent body population with a semimajor axis of 40-52 au and an interior planet with an eccentricity of at least 0.2. Many permutations of planet mass and semimajor axis are allowed, ranging from an Earth mass at 35 au to a Jupiter mass at 5 au.

  12. First Scattered-light Image of the Debris Disk around HD 131835 with the Gemini Planet Imager

    NASA Astrophysics Data System (ADS)

    Hung, Li-Wei; Duchêne, Gaspard; Arriaga, Pauline; Fitzgerald, Michael P.; Maire, Jérôme; Marois, Christian; Millar-Blanchaer, Maxwell A.; Bruzzone, Sebastian; Rajan, Abhijith; Pueyo, Laurent; Kalas, Paul G.; De Rosa, Robert J.; Graham, James R.; Konopacky, Quinn; Wolff, Schuyler G.; Ammons, S. Mark; Chen, Christine H.; Chilcote, Jeffrey K.; Draper, Zachary H.; Esposito, Thomas M.; Gerard, Benjamin; Goodsell, Stephen; Greenbaum, Alexandra; Hibon, Pascale; Hinkley, Sasha; Macintosh, Bruce; Marchis, Franck; Metchev, Stanimir; Nielsen, Eric L.; Oppenheimer, Rebecca; Patience, Jennifer L.; Perrin, Marshall D.; Rantakyrö, Fredrik T.; Sivaramakrishnan, Anand; Wang, Jason J.; Ward-Duong, Kimberly; Wiktorowicz, Sloane J.

    2015-12-01

    We present the first scattered-light image of the debris disk around HD 131835 in the H band using the Gemini Planet Imager. HD 131835 is a ∼15 Myr old A2IV star at a distance of ∼120 pc in the Sco-Cen OB association. We detect the disk only in polarized light and place an upper limit on the peak total intensity. No point sources resembling exoplanets were identified. Compared to its mid-infrared thermal emission, in scattered light the disk shows similar orientation but different morphology. The scattered-light disk extends from ∼75 to ∼210 AU in the disk plane with roughly flat surface density. Our Monte Carlo radiative transfer model can describe the observations with a model disk composed of a mixture of silicates and amorphous carbon. In addition to the obvious brightness asymmetry due to stronger forward scattering, we discover a weak brightness asymmetry along the major axis, with the northeast side being 1.3 times brighter than the southwest side at a 3σ level.

  13. SILICATE DUST SIZE DISTRIBUTION FROM HYPERVELOCITY COLLISIONS: IMPLICATIONS FOR DUST PRODUCTION IN DEBRIS DISKS

    SciTech Connect

    Takasawa, S.; Nakamura, A. M.; Arakawa, M.; Seto, Y.; Sangen, K.; Setoh, M.; Machii, N.; Kadono, T.; Shigemori, K.; Hironaka, Y.; Fujioka, S.; Sano, T.; Watari, T.; Dohi, K.; Ohno, S.; Maeda, M.; Sakaiya, T.; Otani, K.; Takeuchi, T.

    2011-06-01

    Fragments generated by high-velocity collisions between solid planetary bodies are one of the main sources of new interplanetary dust particles. However, only limited ranges of collision velocity, ejecta size, and target materials have been studied in previous laboratory experiments, and the collision condition that enables the production of dust-sized particles remains unclear. We conducted hypervelocity impact experiments on silicate rocks at relative velocities of 9 to 61 km s{sup -1}, which is beyond the upper limit of previous laboratory studies. Sub-millimeter-diameter aluminum and gold spheres were accelerated by laser ablation and were shot into dunite and basalt targets. We analyzed the surfaces of aerogel blocks deployed near the targets using an electron probe micro analyzer and counted the number of particles that contained the target material. The size distributions of ejecta ranged from five to tens of microns in diameter. The total cross-sectional area of dust-sized ejecta monotonically increased with the projectile kinetic energy, independent of impact velocity, projectile diameter, and projectile and target material compositions. The slopes of the cumulative ejecta-size distributions ranged from -2 to -5. Most of the slopes were steeper than the -2.5 or -2.7 that is expected for a collisional equilibrium distribution in a collision cascade with mass-independent or mass-dependent catastrophic disruption thresholds, respectively. This suggests that the steep dust size-distribution proposed for the debris disk around HD172555 (an A5V star) could be due to a hypervelocity collision.

  14. A Comprehensive Dust Model Applied to the Resolved Beta Pictoris Debris Disk from Optical to Radio Wavelengths

    NASA Astrophysics Data System (ADS)

    Ballering, Nicholas P.; Su, Kate Y. L.; Rieke, George H.; Gáspár, András

    2016-06-01

    We investigate whether varying the dust composition (described by the optical constants) can solve a persistent problem in debris disk modeling—the inability to fit the thermal emission without overpredicting the scattered light. We model five images of the β Pictoris disk: two in scattered light from the Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph at 0.58 μm and HST/Wide Field Camera 3 (WFC 3) at 1.16 μm, and three in thermal emission from Spitzer/Multiband Imaging Photometer for Spitzer (MIPS) at 24 μm, Herschel/PACS at 70 μm, and Atacama Large Millimeter/submillimeter Array at 870 μm. The WFC3 and MIPS data are published here for the first time. We focus our modeling on the outer part of this disk, consisting of a parent body ring and a halo of small grains. First, we confirm that a model using astronomical silicates cannot simultaneously fit the thermal and scattered light data. Next, we use a simple generic function for the optical constants to show that varying the dust composition can improve the fit substantially. Finally, we model the dust as a mixture of the most plausible debris constituents: astronomical silicates, water ice, organic refractory material, and vacuum. We achieve a good fit to all data sets with grains composed predominantly of silicates and organics, while ice and vacuum are, at most, present in small amounts. This composition is similar to one derived from previous work on the HR 4796A disk. Our model also fits the thermal spectral energy distribution, scattered light colors, and high-resolution mid-IR data from T-ReCS for this disk. Additionally, we show that sub-blowout grains are a necessary component of the halo.

  15. A Submillimeter Search of Nearby Young Stars for Cold Dust: Discovery of Debris Disks around Two Low-Mass Stars

    NASA Astrophysics Data System (ADS)

    Liu, Michael C.; Matthews, Brenda C.; Williams, Jonathan P.; Kalas, Paul G.

    2004-06-01

    We present results from a James Clerk Maxwell Telescope/SCUBA 850 μm search for cold dust around eight nearby young stars belonging to the β Pic (t~12 Myr) and the Local Association (t~50 Myr) moving groups. Unlike most past submillimeter studies, our sample was chosen solely on the basis of stellar age. Our observations achieve about an order of magnitude greater sensitivity in dust mass compared to previous work in this age range. We detected two of the three M dwarfs in our sample at 850 μm, GJ 182 and GJ 803 (M*~0.5 Msolar), with inferred dust masses of only ~0.01-0.03 M⊕. GJ 182 may also possess a 25 μm excess, which is indicative of warm dust in the inner few AU of its disk. For GJ 803 (AU Mic; HD 197481), submillimeter mapping finds that the 850 μm emission is unresolved. A nondetection of the CO 3-2 line indicates the system is gas-poor, and the spectral energy distribution suggests the presence of a large inner disk hole (~17AU=1.7" in radius for blackbody grains). These are possible indications that planets at large separations can form around M dwarfs within ~10 Myr. In a companion paper, we confirm the existence of a dust disk around GJ 803 using optical coronagraphic imaging. Given its youthfulness, proximity, and detectability, the GJ 803 disk will be a valuable system for studying disk, and perhaps planet, formation in great detail. Overall, submillimeter measurements of debris disks point to a drop in dust mass by a factor of ~103 within the first ~10 Myr, with the subsequent decline in the masses of submillimeter-detected disks consistent with t-0.5-t-1.

  16. Cometary Dust in the Debris Disks of HD 31648 and HD 163296: Two "Baby" (BETA) Pictoris Stars

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Grady, Carol A.; Lynch, David K.; Russell, Ray W.; Hanner, Martha S.; Hanner, Martha S.

    1999-01-01

    The debris disks surrounding the pre-main-sequence stars HD 31648 and HD 163296 were observed spectroscopically between 3 and 14 microns. Both stars possess a silicate emission feature at 10 microns that resembles that of the star beta Pictoris and those observed in solar system comets. The structure of the band is consistent with a mixture of olivine and pyroxene material, plus an underlying continuum of unspecified origin. The similarity in both size and structure of the silicate band suggests that the material in these systems had a processing history similar to that in our own solar system prior to the time that the grains were incorporated into comets.

  17. Newly Discovered Silicate Features in the Spectra of Young Warm Debris Disks: Probing Terrestrial Regions of Planetary Systems

    NASA Astrophysics Data System (ADS)

    Ballering, N.; Rieke, G.

    2014-03-01

    Terrestrial planets form by the collisional accretion of planetesimals during the first 100 Myr of a system’s lifetime. For most systems, the terrestrial regions are too near their host star to be directly seen with high-contrast imaging (e.g. with HST, MagAO, or LBTI) and too warm to be imaged with submillimeter interferometers (e.g. ALMA). Mid-infrared excess spectra—originating from the thermal emission of the circumstellar dust leftover from these collisions—remain the best data to constrain the properties of the debris in these regions. The spectra of most debris disks are featureless, taking the shape of (modified) blackbodies. Determining the properties of debris disks with featureless spectra is complicated by a degeneracy between the grain size and location (large grains near the star and small grains farther from the star may be indistinguishable). Debris disk spectra that exhibit solid state emission features allow for a more accurate determination of the dust size and location (e.g. Chen et al. 2006; Olofsson et al. 2012). Such features probe small, warm dust grains in the inner regions of these systems where terrestrial planet formation may be proceeding (Lisse et al. 2009). We report here a successful search for such features. We identified our targets with a preliminary search for signs of emission features in the Spitzer IRS spectra of a number of young early type stars known to harbor warm debris disks. We fit to each target a physically-motivated model spectrum consisting of the sum of the stellar photosphere (modeled as a blackbody) and thermal emission from two dust belts. Each belt was defined by 6 parameters: the inner and outer orbital radii (rin and rout), the index of the radial surface density power law (rexp), the minimum and maximum grain sizes (amin and amax), and the index of the grain size distribution power law (aexp). aexp was fixed to -3.65 and amax was fixed to 1000 μm for all models; all other parameters were allowed to

  18. Variations on Debris Disks III. Collisional Cascades and Giant Impacts in the Terrestrial Zones of Solar-type Stars

    NASA Astrophysics Data System (ADS)

    Kenyon, Scott J.; Bromley, Benjamin C.

    2016-01-01

    We analyze two new sets of coagulation calculations for solid particles orbiting within the terrestrial zone of a solar-type star. In models of collisional cascades, numerical simulations demonstrate that the total mass, the mass in 1 mm and smaller particles, and the dust luminosity decline with time more rapidly than predicted by analytic models, \\propto {t}-n with n ≈ 1.1-1.2 instead of 1. Size distributions derived from the numerical calculations follow analytic predictions at r ≲ 0.1 km but are shallower than predicted at larger sizes. In simulations of planet formation, the dust luminosity declines more slowly than in pure collisional cascades, with n ≈ 0.5-0.8 instead of 1.1-1.2. Throughout this decline, giant impacts produce large, observable spikes in dust luminosity that last ˜0.01-0.1 Myr and recur every 1-10 Myr. If most solar-type stars have Earth mass planets with a ≲1-2 AU, observations of debris around 1-100 Myr stars allow interesting tests of theory. Current data preclude theories where terrestrial planets form out of 1000 km or larger planetesimals. Although the observed frequency of debris disks among ≳30 Myr old stars agrees with our calculations, the observed frequency of warm debris among 5-20 Myr old stars is smaller than predicted.

  19. A TREND BETWEEN COLD DEBRIS DISK TEMPERATURE AND STELLAR TYPE: IMPLICATIONS FOR THE FORMATION AND EVOLUTION OF WIDE-ORBIT PLANETS

    SciTech Connect

    Ballering, Nicholas P.; Rieke, George H.; Su, Kate Y. L.; Montiel, Edward

    2013-09-20

    Cold debris disks trace the limits of planet formation or migration in the outer regions of planetary systems, and thus have the potential to answer many of the outstanding questions in wide-orbit planet formation and evolution. We characterized the infrared excess spectral energy distributions of 174 cold debris disks around 546 main-sequence stars observed by both the Spitzer Infrared Spectrograph and the Multiband Imaging Photometer for Spitzer. We found a trend between the temperature of the inner edges of cold debris disks and the stellar type of the stars they orbit. This argues against the importance of strictly temperature-dependent processes (e.g., non-water ice lines) in setting the dimensions of cold debris disks. Also, we found no evidence that delayed stirring causes the trend. The trend may result from outward planet migration that traces the extent of the primordial protoplanetary disk, or it may result from planet formation that halts at an orbital radius limited by the efficiency of core accretion.

  20. Exozodiacal Dust and Direct Imaging of Extrasolar Planets

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc

    2008-01-01

    Direct imaging of extrasolar planets means contending with dust from extrasolar asteroids and comets. This 'exozodiacal dust' creates a structured background light that can easily outshine the light from an exoEarth and confuse a planet-search mission like TPF or TOPS. But exozodiacal dust can be both friend and foe: planets can stir dust clouds into patterns that reveal the presence of the planet and constrain its mass and orbit. I'll describe some recent research on this topic: 3-D dynamical models of dust clouds with planets and searches for exozodiacal dust with the Keck Interferometer. The author also offers a prediction for the typical zodiacal dust background found around solar analogs, based on seafloor sediment data.

  1. Pursuing the planet-debris disk connection: Analysis of upper limits from the Anglo-Australian planet search

    SciTech Connect

    Wittenmyer, Robert A.; Marshall, Jonathan P.

    2015-02-01

    Solid material in protoplanetary disks will suffer one of two fates after the epoch of planet formation; either being bound up into planetary bodies, or remaining in smaller planetesimals to be ground into dust. These end states are identified through detection of sub-stellar companions by periodic radial velocity (or transit) variations of the star, and excess emission at mid- and far-infrared wavelengths, respectively. Since the material that goes into producing the observable outcomes of planet formation is the same, we might expect these components to be related both to each other and their host star. Heretofore, our knowledge of planetary systems around other stars has been strongly limited by instrumental sensitivity. In this work, we combine observations at far-infrared wavelengths by IRAS, Spitzer, and Herschel with limits on planetary companions derived from non-detections in the 16 year Anglo-Australian Planet Search to clarify the architectures of these (potential) planetary systems and search for evidence of correlations between their constituent parts. We find no convincing evidence of such correlations, possibly owing to the dynamical history of the disk systems, or the greater distance of the planet-search targets. Our results place robust limits on the presence of Jupiter analogs which, in concert with the debris disk observations, provides insights on the small-body dynamics of these nearby systems.

  2. Searching for Faint Exozodiacal Disks: Keck Results and LBTI Status

    NASA Astrophysics Data System (ADS)

    Defrère, D.; Hinz, P.; Mennesson, B.; Millan-Gabet, R.; Skemer, A.; Bailey, V.; Rodigas, T. J.

    2014-01-01

    The possible presence of dust in the habitable zone around nearby main-sequence stars is considered as a major hurdle toward the direct imaging of Earth-like extrasolar planets with future dedicated space-based telescopes (e.g., Roberge et al. 2012). In this context, NASA has funded two ground-based mid-infrared nulling interferometers to combine the large apertures available at the Keck Observatory and the Large Binocular Telescope (LBT). In this poster, we present the preliminary results of the extended survey carried out with the Keck Interferometer Nuller (KIN) between 2008 and 2011 and describe the forthcoming LBTI survey.

  3. Massive collisions in debris disks: possible application to the beta Pic disc

    NASA Astrophysics Data System (ADS)

    Kral, Q.; Thébault, P.; Augereau, J.-C.; Boccaletti, A.; Charnoz, S.

    2014-09-01

    The new LIDT-DD code has been used to study massive collisions in debris discs. This new hybrid model is a fully self-consistent code coupling dynamics and collisions to study debris discs (Kral et al. 2013). It models the full complexity of debris discs' physics such as high velocity collisions, radiation-pressure affected orbits, wide range of grains' dynamical behaviour, etc. LIDT-DD can be used on many possible applications. Our first test case concerns the violent breakup of a massive planetesimal such as the ones happening during the late stages of planetary formation or with the biggest bodies in debris belts. We investigate the duration, magnitude and spatial structure of the signature left by such a violent event, as well as its observational detectability. We find that the breakup of a Ceres-sized body creates an asymmetric dust disc that is homogenized, by the coupled action of collisions and dynamics. The luminosity excess in the breakup's aftermath should be detectable by mid-IR photometry, from a 30 pc distance. As for the asymmetric structures, we derive synthetic images for the SPHERE/VLT and MIRI/JWST instruments, showing that they should be clearly visible and resolved from a 10 pc distance. We explain the observational signature of such impacts and give scaling laws to extrapolate our results to different configurations. These first results confirm that our code can be used to study the massive collision scenario to explain some asymmetries in the Beta-Pic disc.

  4. THE MINERALOGY AND STRUCTURE OF THE INNER DEBRIS DISK OF {beta} PICTORIS

    SciTech Connect

    Li Dan; Telesco, Charles M.; Wright, Christopher M.

    2012-11-10

    We observed the edge-on, planet-bearing disk of {beta} Pictoris using T-ReCS at Gemini to clarify and extend previous observations and conclusions about this unique system. Our spectroscopy and spectral modeling of the 10 {mu}m silicate feature constrain the spatial distributions of three representative dust components (0.1 {mu}m/2.0 {mu}m glassy olivine and crystalline forsterite) across the inner 20 AU of the disk. We confirm that the 2.0 {mu}m glassy olivine is strongly peaked in the disk center and that the 0.1 {mu}m glassy olivine does not show this concentration, but rather is double peaked, with the peaks on either side of the star. However, we do not see the strong difference in brightness between those two peaks reported in a previous study. Although the spatial distribution of the 0.1 {mu}m dust is consistent with the scenario of a dust-replenishing planetesimal belt embedded in the disk, we note an alternative interpretation that can explain the spatial distributions of the 0.1 {mu}m and 2.0 {mu}m grains simultaneously and does not require the planetesimal belt. In addition to the spectroscopy, we also obtained a new 11.7 {mu}m image of the {beta} Pic disk. By comparing this image with that acquired in 2003, we confirm the existence and overall shape of the dusty clump at 52 AU in the SW disk. We speculate that the clump's projected spatial displacement of {approx}2.0 AU, a 3.6{sigma} result, between two epochs separated by seven years is due to the Keplerian motion of the clump at an orbital radius of 54.3{sup +2.0} {sub -1.2} AU.

  5. Limits of detection in debris disks around young stars with NaCo/Sparse Aperture Masking observations

    NASA Astrophysics Data System (ADS)

    Gauchet, L.; Lacour, S.

    2014-09-01

    To understand the formation and evolution of solar systems and planets formations in the stars neighbourhood, we need to obtain information of their state at different time of their evolution. Here, we focus on debris disks around young stars aged of ten to few tens of Myr, we analyze NaCo/Sparse Aperture Masking (SAM) observations in the L' band (3.8 μm) of eight objects (beta Pictoris, AU Mic, 49 Ceti, eta Tel, Fomalhaut, G Lupi, HD182327 and HR8799). The aim is to get limits of detection about the mass of the debris orbiting around their stars. The SAM technique consists in transforming a single telescope into a Fizeau interferometer using a non redundant mask inserted in a pupil plane of the instrument. The analysis of the observations was completed with the sparse aperture mode pipeline. Interference fringes are fitted to obtain complex visibilities of the object, then the closure phases are calibrated and evaluated. Finally, a map of the detection limits is obtained as it is related to the closure phases previously estimated. In order to obtain an estimation of the mass corresponding to the luminosity measured with the reduction pipeline we are using theoretical isochrones interpolated into synthetic color tables. The results are maps of detection limits in unit of Jupiter Mass in a range of up to 450 mas around the stars.

  6. SPITZER INFRARED SPECTROGRAPH SPECTROSCOPY OF THE 10 Myr OLD EF Cha DEBRIS DISK: EVIDENCE FOR PHYLLOSILICATE-RICH DUST IN THE TERRESTRIAL ZONE

    SciTech Connect

    Currie, Thayne; Lisse, Carey M.; Sicilia-Aguilar, Aurora; Rieke, George H.; Su, Kate Y. L.

    2011-06-20

    We describe Spitzer Infrared Spectrograph spectroscopic observations of the {approx}10 Myr old star, EF Cha. Compositional modeling of the spectra from 5 {mu}m to 35 {mu}m confirms that it is surrounded by a luminous debris disk with L{sub D} /L{sub *} {approx} 10{sup -3}, containing dust with temperatures between 225 K and 430 K, characteristic of the terrestrial zone. The EF Cha spectrum shows evidence for many solid-state features, unlike most cold, low-luminosity debris disks but like some other 10-20 Myr old luminous, warm debris disks (e.g., HD 113766A). The EF Cha debris disk is unusually rich in a species or combination of species whose emissivities resemble that of finely powdered, laboratory-measured phyllosilicate species (talc, saponite, and smectite), which are likely produced by aqueous alteration of primordial anhydrous rocky materials. The dust and, by inference, the parent bodies of the debris also contain abundant amorphous silicates and metal sulfides, and possibly water ice. The dust's total olivine to the pyroxene ratio of {approx}2 also provides evidence of aqueous alteration. The large mass volume of grains with sizes comparable to or below the radiation blow-out limit implies that planetesimals may be colliding at a rate high enough to yield the emitting dust but not so high as to devolatize the planetesimals via impact processing. Because phyllosilicates are produced by the interactions between anhydrous rock and warm, reactive water, EF Cha's disk is a likely signpost for water delivery to the terrestrial zone of a young planetary system.

  7. CORONAL MASS EJECTIONS AS A MECHANISM FOR PRODUCING IR VARIABILITY IN DEBRIS DISKS

    SciTech Connect

    Osten, Rachel; Livio, Mario; Lubow, Steve; Pringle, J. E.; Soderblom, David; Valenti, Jeff

    2013-03-10

    Motivated by recent observations of short-timescale variations in the infrared emission of circumstellar disks, we propose that coronal mass ejections can remove dust grains on timescales as short as a few days. Continuous monitoring of stellar activity, coupled with infrared observations, can place meaningful constraints on the proposed mechanism.

  8. A SEARCH FOR EXOZODIACAL CLOUDS WITH KEPLER

    SciTech Connect

    Stark, Christopher C.; Boss, Alan P.; Weinberger, Alycia J.; Jackson, Brian K.; Endl, Michael; Cochran, William D.; Johnson, Marshall; Caldwell, Caroline; Agol, Eric; Ford, Eric B.; Hall, Jennifer R.; Ibrahim, Khadeejah A.

    2013-02-20

    Planets embedded within dust disks may drive the formation of large scale clumpy dust structures by trapping dust into resonant orbits. Detection and subsequent modeling of the dust structures would help constrain the mass and orbit of the planet and the disk architecture, give clues to the history of the planetary system, and provide a statistical estimate of disk asymmetry for future exoEarth-imaging missions. Here, we present the first search for these resonant structures in the inner regions of planetary systems by analyzing the light curves of hot Jupiter planetary candidates identified by the Kepler mission. We detect only one candidate disk structure associated with KOI 838.01 at the 3{sigma} confidence level, but subsequent radial velocity measurements reveal that KOI 838.01 is a grazing eclipsing binary and the candidate disk structure is a false positive. Using our null result, we place an upper limit on the frequency of dense exozodi structures created by hot Jupiters. We find that at the 90% confidence level, less than 21% of Kepler hot Jupiters create resonant dust clumps that lead and trail the planet by {approx}90 Degree-Sign with optical depths {approx}> 5 Multiplication-Sign 10{sup -6}, which corresponds to the resonant structure expected for a lone hot Jupiter perturbing a dynamically cold dust disk 50 times as dense as the zodiacal cloud.

  9. A Double Dusty Dilemma - IRAC Flux Changes in Circumbinary Debris Disk

    NASA Astrophysics Data System (ADS)

    Parsons, Steven; Farihi, Jay; Gaensicke, Boris

    2015-10-01

    We have serendipitously discovered the first metal-polluted white dwarf with what appears to be a circumbinary dust disk. Both the atmospheric metals and infrared excess were found by our team a few years ago, but only recently did we (surprisingly!) identify a spectroscopic periodicity of 2.27 hr which unambiguously identifies this peculiar system as a close binary. Most remarkable for this proposal is that the system must be dynamically unstable, as a companion and canonical (flat, opaque) dust disk occupy overlapping orbital regions. We thus strongly suspected the system must be in a state of relatively rapid change, and recent DDT observations confirmed our hypothesis. We now propose to observe the system over a complete binary orbit to further constrain the changes in infrared flux, and to distentangle dust emission variability from any changes induced by the binary orbit itself. Micron-size dust grains should be subject to PR drag within a decade, and imply dust depletion on yearly timescales -- consistent with the DDT data. Our third epoch observations will provide an direct test by searching for a continuing decrease in dust emission. If such a decrease is not confirmed, it would imply the circumbinary dust reservoir is being replenished on yearly timescales.

  10. ζ2 Reticuli, its debris disk, and its lonely stellar companion ζ1 Ret. Different Tc trends for different spectra

    NASA Astrophysics Data System (ADS)

    Adibekyan, V.; Delgado-Mena, E.; Figueira, P.; Sousa, S. G.; Santos, N. C.; Faria, J. P.; González Hernández, J. I.; Israelian, G.; Harutyunyan, G.; Suárez-Andrés, L.; Hakobyan, A. A.

    2016-06-01

    Context. Several studies have reported a correlation between the chemical abundances of stars and condensation temperature (known as Tc trend). Very recently, a strong Tc trend was reported for the ζ Reticuli binary system, which consists of two solar analogs. The observed trend in ζ2 Ret relative to its companion was explained by the presence of a debris disk around ζ2 Ret. Aims: Our goal is to re-evaluate the presence and variability of the Tc trend in the ζ Reticuli system and to understand the impact of the presence of the debris disk on a star. Methods: We used very high-quality spectra of the two stars retrieved from the HARPS archive to derive very precise stellar parameters and chemical abundances. We derived the stellar parameters with the classical (nondifferential) method, while we applied a differential line-by-line analysis to achieve the highest possible precision in abundances, which are fundamental to explore for very tiny differences in the abundances between the stars. Results: We confirm that the abundance difference between ζ2 Ret and ζ1 Ret shows a significant (~2σ) correlation with Tc. However, we also find that the Tc trends depend on the individual spectrum used (even if always of very high quality). In particular, we find significant but varying differences in the abundances of the same star from different individual high-quality spectra. Conclusions: Our results for the ζ Reticuli system show, for example, that nonphysical factors, such as the quality of spectra employed and errors that are not accounted for, can be at the root of the Tc trends for the case of individual spectra. Based on data obtained from the ESO Science Archive Facility under request number vadibekyan204818, vadibekyan204820, and vadibekyan185979.The tables with EWs of the lines and chemical abundances are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A34

  11. Debris Disk Structure and Morphology as Revealed by Aggressive STIS Multi-Roll Coronagraphy: A New Look at Some Old Friends

    NASA Technical Reports Server (NTRS)

    Grady, Carol A; Kuchner, Marc; Woodgate, Bruce E.

    2012-01-01

    We present new imaging results from a well-selected sample of II circumstellar debris disks, all with HST pedigree, using STIS visible-light 6-roll PSF-template subtracted coronagraphy (PSFTSC). These new observations, pushing HST to its highest levels of coronagraphic performance, simultaneously probe both the interior regions of these debris systems, with inner working distances < app 8 AU for half the stars in this sample (corresponding to the giant planet and Kuiper belt regions within our own solar system), and the exterior regions far beyond. These new images enable direct inter-comparison of the architectures of these exoplanetary debris systems in the context of our own Solar System: These observations also permit us, for the first time, to characterize material in these regions at high spatial resolution and identify disk sub-structures that are signposts of planet formation and evolution; in particular, asymmetries and non-uniform debris structures that signal the presence of co-orbiting perturbing planets, and dynamical interactions (e.g., resulting in posited small grain stripping and disk "pollution") with the ISM. We focus here on recently acquired and reduced images of he circumstellar debris systems about: AU Mic (edge-on, and @ 10 pc the closest star in our sample), HD 61005, HD 32297 and HD 15115 (all with morphologies strongly suggestive of ISM wind interactions), HD 181327 & HDI07146 (close to face-on with respectively narrow and broad debris rings), and MP Mus (a "mature" proto-planetary disk hosted by a cTTS). All of our objects were previously observed in the near-IR with inferior spatial resolution and imaging efficacy, but with NICMOS r = 0.3" inner working angle (IWA) comparable to STIS multi-roll coronagraphy. The combination of new optical and existing near-IR imaging can strongly constrain the dust properties, thus enabling an assessment of grain processing and planetesimal populations. These results will directly inform upon the

  12. Does the Presence of Planets Affect the Frequency and Properties of Extrasolar Kuiper Belts? Results from the Herschel Debris and Dunes Surveys

    NASA Astrophysics Data System (ADS)

    Moro-Martín, A.; Marshall, J. P.; Kennedy, G.; Sibthorpe, B.; Matthews, B. C.; Eiroa, C.; Wyatt, M. C.; Lestrade, J.-F.; Maldonado, J.; Rodriguez, D.; Greaves, J. S.; Montesinos, B.; Mora, A.; Booth, M.; Duchêne, G.; Wilner, D.; Horner, J.

    2015-03-01

    The study of the planet-debris disk connection can shed light on the formation and evolution of planetary systems and may help “predict” the presence of planets around stars with certain disk characteristics. In preliminary analyses of subsamples of the Herschel DEBRIS and DUNES surveys, Wyatt et al. and Marshall et al. identified a tentative correlation between debris and the presence of low-mass planets. Here we use the cleanest possible sample out of these Herschel surveys to assess the presence of such a correlation, discarding stars without known ages, with ages \\lt 1 Gyr, and with binary companions \\lt 100 AU to rule out possible correlations due to effects other than planet presence. In our resulting subsample of 204 FGK stars, we do not find evidence that debris disks are more common or more dusty around stars harboring high-mass or low-mass planets compared to a control sample without identified planets. There is no evidence either that the characteristic dust temperature of the debris disks around planet-bearing stars is any different from that in debris disks without identified planets, nor that debris disks are more or less common (or more or less dusty) around stars harboring multiple planets compared to single-planet systems. Diverse dynamical histories may account for the lack of correlations. The data show a correlation between the presence of high-mass planets and stellar metallicity, but no correlation between the presence of low-mass planets or debris and stellar metallicity. Comparing the observed cumulative distribution of fractional luminosity to those expected from a Gaussian distribution in logarithmic scale, we find that a distribution centered on the solar system’s value fits the data well, while one centered at 10 times this value can be rejected. This is of interest in the context of future terrestrial planet detection and characterization because it indicates that there are good prospects for finding a large number of debris

  13. An Interferometric Study of the Fomalhaut Inner Debris Disk. II. Keck Nuller Mid-infrared Observations

    NASA Astrophysics Data System (ADS)

    Mennesson, B.; Absil, O.; Lebreton, J.; Augereau, J.-C.; Serabyn, E.; Colavita, M. M.; Millan-Gabet, R.; Liu, W.; Hinz, P.; Thébault, P.

    2013-02-01

    We report on high-contrast mid-infrared observations of Fomalhaut obtained with the Keck Interferometer Nuller (KIN) showing a small resolved excess over the level expected from the stellar photosphere. The measured null excess has a mean value of 0.35% ± 0.10% between 8 and 11 μm and increases from 8 to 13 μm. Given the small field of view of the instrument, the source of this marginal excess must be contained within 2 AU of Fomalhaut. This result is reminiscent of previous VLTI K-band (sime2μm) observations, which implied the presence of a ~0.88% excess, and argued that thermal emission from hot dusty grains located within 6 AU from Fomalhaut was the most plausible explanation. Using a parametric two-dimensional radiative transfer code and a Bayesian analysis, we examine different dust disk structures to reproduce both the near- and mid-infrared data simultaneously. While not a definitive explanation of the hot excess of Fomalhaut, our model suggests that the most likely inner few AU disk geometry consists of a two-component structure, with two different and spatially distinct grain populations. The 2-11 μm data are consistent with an inner hot ring of very small (sime10-300 nm) carbon-rich grains concentrating around 0.1 AU. The second dust population—inferred from the KIN data at longer mid-infrared wavelengths—consists of larger grains (size of a few microns to a few tens of microns) located further out in a colder region where regular astronomical silicates could survive, with an inner edge around 0.4 AU-1 AU. From a dynamical point of view, the presence of the inner concentration of submicron-sized grains is surprising, as such grains should be expelled from the inner planetary system by radiation pressure within only a few years. This could either point to some inordinate replenishment rates (e.g., many grazing comets coming from an outer reservoir) or to the existence of some braking mechanism preventing the grains from moving out.

  14. THE GRAY NEEDLE: LARGE GRAINS IN THE HD 15115 DEBRIS DISK FROM LBT /PISCES/Ks AND LBTI /LMIRcam/L' ADAPTIVE OPTICS IMAGING

    SciTech Connect

    Rodigas, Timothy J.; Hinz, Philip M.; Vaitheeswaran, Vidhya; Skemer, Andrew J.; Su, Kate Y. L.; Bailey, Vanessa; Schneider, Glenn; Close, Laird; Apai, Daniel; Leisenring, Jarron; Skrutskie, Michael; Mannucci, Filippo; Esposito, Simone; Arcidiacono, Carmelo; Pinna, Enrico; Argomedo, Javier; Agapito, Guido; Bono, Giuseppe; Briguglio, Runa; Boutsia, Kostantina; and others

    2012-06-10

    We present diffraction-limited Ks band and L' adaptive optics images of the edge-on debris disk around the nearby F2 star HD 15115, obtained with a single 8.4 m primary mirror at the Large Binocular Telescope. At the Ks band, the disk is detected at signal-to-noise per resolution element (SNRE) {approx} 3-8 from {approx}1 to 2.''5 (45-113 AU) on the western side and from {approx}1.''2 to 2.''1 (63-90 AU) on the east. At L' the disk is detected at SNRE {approx} 2.5 from {approx}1 to 1.''45 (45-90 AU) on both sides, implying more symmetric disk structure at 3.8 {mu}m. At both wavelengths the disk has a bow-like shape and is offset from the star to the north by a few AU. A surface brightness asymmetry exists between the two sides of the disk at the Ks band, but not at L'. The surface brightness at the Ks band declines inside 1'' ({approx}45 AU), which may be indicative of a gap in the disk near 1''. The Ks - L' disk color, after removal of the stellar color, is mostly gray for both sides of the disk. This suggests that scattered light is coming from large dust grains, with 3-10 {mu}m sized grains on the east side and 1-10 {mu}m dust grains on the west. This may suggest that the west side is composed of smaller dust grains than the east side, which would support the interpretation that the disk is being dynamically affected by interactions with the local interstellar medium.

  15. The gaseous debris disk of the white dwarf SDSS J1228+1040. HST/COS search for far-ultraviolet signatures

    NASA Astrophysics Data System (ADS)

    Hartmann, S.; Nagel, T.; Rauch, T.; Werner, K.

    2016-09-01

    Context. Gaseous and dust debris disks around white dwarfs (WDs) are formed from tidally disrupted planetary bodies. This offers an opportunity to determine the composition of exoplanetary material by measuring element abundances in the accreting WD's atmosphere. A more direct way to do this is through spectral analysis of the disks themselves. Aims: Currently, the number of chemical elements detected through disk emission-lines is smaller than that of species detected through lines in the WD atmospheres. We assess the far-ultraviolet (FUV) spectrum of one well-studied object (SDSS J122859.93+104032.9) to search for disk signatures at wavelengths < 1050 Å, where the broad absorption lines of the Lyman series effectively block the WD photospheric flux. In addition, we investigate the Ca ii infrared triplet (IRT) line profiles to constrain disk geometry and composition. Methods: We performed FUV observations (950-1240 Å) with the Hubble Space Telescope/Cosmic Origins Spectrograph and used archival optical spectra. We compared them with non-local thermodynamic equilibrium model spectra. Results: No disk emission-lines were detected in the FUV spectrum, indicating that the disk effective temperature is Teff ≈ 5000 K. The long-time variability of the Ca ii IRT was reproduced with a precessing disk model of bulk Earth-like composition, having a surface mass density of 0.3 g cm-2 and an extension from 55 to 90 WD radii. The disk has a spiral shape that precesses with a period of approximately 37 years, confirming previous results. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26666.

  16. Relevance of the submillimeter fluxes on the SED modeling of debris disks. (Spanish Title: Importancia de los flujos submilimétricos en el modelado de las SED de discos debris)

    NASA Astrophysics Data System (ADS)

    García, L. H.; Gómez, M.

    The modeling of Spectral Energy Distributions (SEDs) is a generally used method to characterize the so-called debris disks. This technique requires reliable flux measurements in a wide range of wavelengths, including the IR and sub-mm regimes. However, fluxes at wavelengths larger than 100 microns are not always available. In this contribution we investigate how such measurements affect the derived parameters for a sample of 24 stars showing excesses in their SEDs. If the excesses at wavelengths larger than 70 microns exceed those for wavelengths larger than 100 microns, the sets of disks parameters derived from the SED modeling excluding and including fluxes for wavelengths larger than 100 microns roughly agree.

  17. Decoding Debris System Substructures: Imprints of Planets/Planetesimals and Signatures of Extrinsic Influences on Material in Ring-Like Disks

    NASA Astrophysics Data System (ADS)

    Grady, C. A.; Schneider, Glenn; Carson, Joseph; Debes, John H.; Gaspar, Andras; Henning, Thomas; Hines, Dean C.; Hinz, Philip; Jang-Condell, Hannah; Kuchner, Marc J.; Moro-Martin, Amaya; Perrin, Marshall D.; Rodigas, T. J.; Serabyn, Gene; Silverstone, Murray D.; Stark, Christopher C.; Tamura, Motohide; Weinberger, Alycia J.; Wisniewski, John P.; Konishi, Mihoko

    2016-01-01

    How do circumstellar (CS) disks evolve and form planetary systems? Is our solar system's two-component debris disk (DD) typical? Are planets implicated by evidence of dynamical stirring in disks? Are DD architectures correlated with stellar mass? To address these highly-compelling questions of fundamental astrophysical import, we obtained deep follow-up HST/STIS coronagraphic imagery of five intermediate-inclination ring-like DDs. By combining data from two coronagraphic apertures we obtain images with unprecedented clarity, sensitivity, and photometric efficacy. We discover a scattered light counterpart to the dust disk previously seen in the mid-IR only in HD 141569 A interior to the 2 rings previously imaged in scattered light. We also place refined optical limits on planets in that system. For HR 4796 A we detect outer nebulosity extending as far as 10 arc seconds from the star, and compare it with other systems with distant dust. We report on early stages of analysis for our other 3 program stars.

  18. The twofold debris disk around HD 113766 A. Warm and cold dust as seen with VLTI/MIDI and Herschel/PACS

    NASA Astrophysics Data System (ADS)

    Olofsson, J.; Henning, Th.; Nielbock, M.; Augereau, J.-C.; Juhàsz, A.; Oliveira, I.; Absil, O.; Tamanai, A.

    2013-03-01

    Context. Warm debris disks are a sub-sample of the large population of debris disks, and display excess emission in the mid-infrared. Around solar-type stars, very few objects (~2% of all debris disks) show emission features in mid-IR spectroscopic observations that are attributed to small, warm silicate dust grains. The origin of this warm dust could be explained either by a recent catastrophic collision between several bodies or by transport from an outer belt similar to the Kuiper belt in the solar system. Aims: We present and analyze new far-IR Herschel/PACS photometric observations, supplemented by new and archival ground-based data in the mid-IR (VLTI/MIDI and VLT/VISIR), for one of these rare systems: the 10-16 Myr old debris disk around HD 113766 A. We improve an existing model to account for these new observations. Methods: We implemented the contribution of an outer planetesimal belt in the Debra code, and successfully used it to model the spectral energy distribution (SED) as well as complementary observations, notably MIDI data. We better constrain the spatial distribution of the dust and its composition. Results: We underline the limitations of SED modeling and the need for spatially resolved observations. We improve existing models and increase our understanding of the disk around HD 113766 A. We find that the system is best described by an inner disk located within the first AU, well constrained by the MIDI data, and an outer disk located between 9-13 AU. In the inner dust belt, our previous finding of Fe-rich crystalline olivine grains still holds. We do not observe time variability of the emission features over at least an eight-year time span in an environment subjected to strong radiation pressure. Conclusions: The time stability of the emission features indicates that μm-sized dust grains are constantly replenished from the same reservoir, with a possible depletion of sub- μm-sized grains. We suggest that the emission features may arise from

  19. THE SPITZER c2d SURVEY OF WEAK-LINE T TAURI STARS. III. THE TRANSITION FROM PRIMORDIAL DISKS TO DEBRIS DISKS

    SciTech Connect

    Wahhaj, Zahed; Cieza, Lucas; Koerner, David W.; Case, April; Stapelfeldt, Karl R.; Chapman, Nicholas; Padgett, Deborah L.; Brooke, Tim; Keller, James R.; MerIn, Bruno; Evans, Neal J.; Harvey, Paul; Sargent, Anneila; Van Dishoeck, Ewine F.; Allen, Lori; Blake, Geoff; Mundy, Lee; Myers, Philip C.

    2010-12-01

    We present 3.6 to 70 {mu}m Spitzer photometry of 154 weak-line T Tauri stars (WTTSs) in the Chamaeleon, Lupus, Ophiuchus, and Taurus star formation regions, all of which are within 200 pc of the Sun. For a comparative study, we also include 33 classical T Tauri stars which are located in the same star-forming regions. Spitzer sensitivities allow us to robustly detect the photosphere in the IRAC bands (3.6 to 8 {mu}m) and the 24 {mu}m MIPS band. In the 70 {mu}m MIPS band, we are able to detect dust emission brighter than roughly 40 times the photosphere. These observations represent the most sensitive WTTSs survey in the mid- to far-infrared to date and reveal the frequency of outer disks (r = 3-50 AU) around WTTSs. The 70 {mu}m photometry for half the c2d WTTSs sample (the on-cloud objects), which were not included in the earlier papers in this series, those of Padgett et al. and Cieza et al., are presented here for the first time. We find a disk frequency of 19% for on-cloud WTTSs, but just 5% for off-cloud WTTSs, similar to the value reported in the earlier works. WTTSs exhibit spectral energy distributions that are quite diverse, spanning the range from optically thick to optically thin disks. Most disks become more tenuous than L{sub disk}/L{sub *} = 2 x 10{sup -3} in 2 Myr and more tenuous than L{sub disk}/L{sub *} = 5 x 10{sup -4} in 4 Myr.

  20. Detection of exozodiacal dust: a step toward Earth-like planet characterization with infrared interferometry

    NASA Astrophysics Data System (ADS)

    Defrère, Denis

    2009-12-01

    The existence of other habitable worlds and the possible development of life elsewhere in the Universe have been among mankind's fundamental questions for thousands of years. These interrogations about our origins and place in the Universe are today at the dawn of being answered in scientific terms. The key year was 1995 with the discovery of the first extrasolar planet orbiting around a solar-type star. About 400 extrasolar planets are known today and the possibility to identify habitable worlds and even life among them largely contributes to the growing interest about their nature and properties. However, characterizing planetary systems is a very difficult task due to both the huge contrast and the small angular separation between the host stars and their environment. New techniques have emerged during the past decades with the purpose of tackling these fantastic observational challenges. In that context, infrared interferometry is a very promising technique, since it provides the required angular resolution to separate the emission of the star from that of its environment. This dissertation is devoted to the characterization of extrasolar planetary systems using the high angular resolution and dynamic range capabilities of infrared interferometric techniques. The first part of the present work is devoted to the detection with current interferometric facilities of warm dust within the first few astronomical units of massive debris discs around nearby stars. In order to extend the imaging of planetary systems to fainter discs and to extrasolar planets, we investigate in a second step the performance of future space-based nulling interferometers and make a comparison with ground-based projects. Finally, the third part of this work is dedicated to the impact of exozodiacal discs on the performance of future life-searching space missions, the goal being to characterize extrasolar planets with sizes down to that of the Earth.

  1. Sparse aperture masking at the VLT. II. Detection limits for the eight debris disks stars β Pic, AU Mic, 49 Cet, η Tel, Fomalhaut, g Lup, HD 181327 and HR 8799

    NASA Astrophysics Data System (ADS)

    Gauchet, L.; Lacour, S.; Lagrange, A.-M.; Ehrenreich, D.; Bonnefoy, M.; Girard, J. H.; Boccaletti, A.

    2016-10-01

    Context. The formation of planetary systems is a common, yet complex mechanism. Numerous stars have been identified to possess a debris disk, a proto-planetary disk or a planetary system. The understanding of such formation process requires the study of debris disks. These targets are substantial and particularly suitable for optical and infrared observations. Sparse aperture masking (SAM) is a high angular resolution technique strongly contributing to probing the region from 30 to 200 mas around the stars. This area is usually unreachable with classical imaging, and the technique also remains highly competitive compared to vortex coronagraphy. Aims: We aim to study debris disks with aperture masking to probe the close environment of the stars. Our goal is either to find low-mass companions, or to set detection limits. Methods: We observed eight stars presenting debris disks (β Pictoris, AU Microscopii, 49 Ceti, η Telescopii, Fomalhaut, g Lupi, HD 181327, and HR 8799) with SAM technique on the NaCo instrument at the Very Large Telescope (VLT). Results: No close companions were detected using closure phase information under 0.5'' of separation from the parent stars. We obtained magnitude detection limits that we converted to Jupiter masses detection limits using theoretical isochrones from evolutionary models. Conclusions: We derived upper mass limits on the presence of companions in the area of a few times the telescope's diffraction limits around each target star. Based on observations collected at the European Southern Observatory (ESO) during runs 087.C-0450(A), 087.C-0450(B) 087.C-0750(A), 088.C-0358(A).All magnitude detection limits maps are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/595/A31

  2. EXPLORATIONS BEYOND THE SNOW LINE: SPITZER/IRS SPECTRA OF DEBRIS DISKS AROUND SOLAR-TYPE STARS

    SciTech Connect

    Lawler, S. M.; Beichman, C. A.; Ciardi, D. R.; Bryden, G.; Tanner, A. M.; Stapelfeldt, K. R.; Su, K. Y. L.; Lisse, C. M.

    2009-11-01

    We have observed 152 nearby solar-type stars with the Infrared Spectrometer (IRS) on the Spitzer Space Telescope. Including stars that met our criteria but were observed in other surveys, we get an overall success rate for finding excesses in the long-wavelength IRS band (30-34 mum) of 11.8% +- 2.4%. The success rate for excesses in the short-wavelength band (8.5-12 mum) is approx1% including sources from other surveys. For stars with no excess at 8.5-12 mum, the IRS data set 3sigma limits of around 1000 times the level of zodiacal emission present in our solar system, while at 30-34 mum data set limits of around 100 times the level of our solar system. Two stars (HD 40136 and HD 10647) show weak evidence for spectral features; the excess emission in the other systems is featureless. If the emitting material consists of large (10 mum) grains as implied by the lack of spectral features, we find that these grains are typically located at or beyond the snow line, approx1-35 AU from the host stars, with an average distance of 14 +- 6 AU; however, smaller grains could be located at significantly greater distances from the host stars. These distances correspond to dust temperatures in the range approx50-450 K. Several of the disks are well modeled by a single dust temperature, possibly indicative of a ring-like structure. However, a single dust temperature does not match the data for other disks in the sample, implying a distribution of temperatures within these disks. For most stars with excesses, we detect an excess at both IRS and Multiband Imaging Photometer for Spitzer (MIPS) wavelengths. Only three stars in this sample show a MIPS 70 mum excess with no IRS excess, implying that very cold dust is rare around solar-type stars.

  3. Discovery of concentric broken rings at sub-arcsec separations in the HD 141569A gas-rich, debris disk with VLT/SPHERE

    NASA Astrophysics Data System (ADS)

    Perrot, C.; Boccaletti, A.; Pantin, E.; Augereau, J.-C.; Lagrange, A.-M.; Galicher, R.; Maire, A.-L.; Mazoyer, J.; Milli, J.; Rousset, G.; Gratton, R.; Bonnefoy, M.; Brandner, W.; Buenzli, E.; Langlois, M.; Lannier, J.; Mesa, D.; Peretti, S.; Salter, G.; Sissa, E.; Chauvin, G.; Desidera, S.; Feldt, M.; Vigan, A.; Di Folco, E.; Dutrey, A.; Péricaud, J.; Baudoz, P.; Benisty, M.; De Boer, J.; Garufi, A.; Girard, J. H.; Menard, F.; Olofsson, J.; Quanz, S. P.; Mouillet, D.; Christiaens, V.; Casassus, S.; Beuzit, J.-L.; Blanchard, P.; Carle, M.; Fusco, T.; Giro, E.; Hubin, N.; Maurel, D.; Moeller-Nilsson, O.; Sevin, A.; Weber, L.

    2016-05-01

    Context. Transition disks correspond to a short stage between the young protoplanetary phase and older debris phase. Along this evolutionary sequence, the gas component disappears leaving room for a dust-dominated environment where already-formed planets signpost their gravitational perturbations. Aims: We endeavor to study the very inner region of the well-known and complex debris, but still gas-rich disk, around HD 141569A using the exquisite high-contrast capability of SPHERE at the VLT. Recent near-infrared (IR) images suggest a relatively depleted cavity within ~200 au, while former mid-IR data indicate the presence of dust at separations shorter than ~100 au. Methods: We obtained multi-wavelength images in the near-IR in J, H2, H3 and Ks-bands with the IRDIS camera and a 0.95-1.35 μm spectral data cube with the IFS. Data were acquired in pupil-tracking mode, thus allowing for angular differential imaging. Results: We discovered several new structures inside 1'', of which the most prominent is a bright ring with sharp edges (semi-major axis: 0.4'') featuring a strong north-south brightness asymmetry. Other faint structures are also detected from 0.4'' to 1'' in the form of concentric ringlets and at least one spiral arm. Finally, the VISIR data at 8.6 μm suggests the presence of an additional dust population closer in. Besides, we do not detect companions more massive than 1-3 mass of Jupiter. Conclusions: The performance of SPHERE allows us to resolve the extended dust component, which was previously detected at thermal and visible wavelengths, into very complex patterns with strong asymmetries; the nature of these asymmetries remains to be understood. Scenarios involving shepherding by planets or dust-gas interactions will have to be tested against these observations. Based on data collected at the European Southern Observatory, Chile, ESO programs 095.C-0381 and 095.C-0298.

  4. HERSCHEL-RESOLVED OUTER BELTS OF TWO-BELT DEBRIS DISKS AROUND A-TYPE STARS: HD 70313, HD 71722, HD 159492, AND F-TYPE: HD 104860

    SciTech Connect

    Morales, F. Y.; Bryden, G.; Werner, M. W.; Stapelfeldt, K. R.

    2013-10-20

    We present dual-band Herschel/Photodetector Array Camera and Spectrometer imaging for four stars whose spectral energy distributions (SEDs) suggest two-ring disk architectures that mirror that of the asteroid-Kuiper Belt geometry of our own solar system. The Herschel observations at 100 μm spatially resolve the cold/outer-dust component for each star-disk system for the first time, finding evidence of planetesimals at >100 AU, i.e., a larger size than assumed from a simple blackbody fit to the SED. By breaking the degeneracy between the grain properties and the dust's radial location, the resolved images help constrain the dust grain-size distribution for each system. Three of the observed stars are A-type and one solar-type. On the basis of the combined Spitzer/IRS+MIPS (5-70 μm), the Herschel/PACS (100 and 160 μm) dataset, and under the assumption of idealized spherical grains, we find that the cold/outer belts of the three A-type stars are well fit with a mixed ice/rock composition rather than pure rocky grains, while the debris around the solar-type star is consistent with either rock or ice/rock grains. For the solar-type star HD 104860, we find that the minimum grain size is larger than expected from the threshold set by radiative blowout. The A-type stars HD 71722 and HD 159492, on the other hand, require minimum grain sizes that are smaller than blowout for inner- and outer-ring populations. In the absence of spectral features for ice, we find that the behavior of the continuum can help constrain the composition of the grains (of icy nature and not pure rocky material) given the Herschel-resolved locations of the cold/outer-dust belts.

  5. CONSTRAINING THE EXOZODIACAL LUMINOSITY FUNCTION OF MAIN-SEQUENCE STARS: COMPLETE RESULTS FROM THE KECK NULLER MID-INFRARED SURVEYS

    SciTech Connect

    Mennesson, B.; Serabyn, E.; Colavita, M. M.; Bryden, G.; Doré, O.; Traub, W.; Millan-Gabet, R.; Absil, O.; Wyatt, M.; Danchi, W.; Kuchner, M.; Stapelfeldt, K.; Defrère, D.; Hinz, P.; Ragland, S.; Scott, N.; Woillez, J.

    2014-12-20

    Forty-seven nearby main-sequence stars were surveyed with the Keck Interferometer mid-infrared Nulling instrument (KIN) between 2008 and 2011, searching for faint resolved emission from exozodiacal dust. Observations of a subset of the sample have already been reported, focusing essentially on stars with no previously known dust. Here we extend this previous analysis to the whole KIN sample, including 22 more stars with known near- and/or far-infrared excesses. In addition to an analysis similar to that of the first paper of this series, which was restricted to the 8-9 μm spectral region, we present measurements obtained in all 10 spectral channels covering the 8-13 μm instrumental bandwidth. Based on the 8-9 μm data alone, which provide the highest signal-to-noise measurements, only one star shows a large excess imputable to dust emission (η Crv), while four more show a significant (>3σ) excess: β Leo, β UMa, ζ Lep, and γ Oph. Overall, excesses detected by KIN are more frequent around A-type stars than later spectral types. A statistical analysis of the measurements further indicates that stars with known far-infrared (λ ≥ 70 μm) excesses have higher exozodiacal emission levels than stars with no previous indication of a cold outer disk. This statistical trend is observed regardless of spectral type and points to a dynamical connection between the inner (zodi-like) and outer (Kuiper-Belt-like) dust populations. The measured levels for such stars are clustering close to the KIN detection limit of a few hundred zodis and are indeed consistent with those expected from a population of dust that migrated in from the outer belt by Poynting-Robertson drag. Conversely, no significant mid-infrared excess is found around sources with previously reported near-infrared resolved excesses, which typically have levels of the order of 1% over the photospheric flux. If dust emission is really at play in these near-infrared detections, the absence of a strong mid

  6. Constraining the Exozodiacal Luminosity Function of Main-sequence Stars: Complete Results from the Keck Nuller Mid-infrared Surveys

    NASA Astrophysics Data System (ADS)

    Mennesson, B.; Millan-Gabet, R.; Serabyn, E.; Colavita, M. M.; Absil, O.; Bryden, G.; Wyatt, M.; Danchi, W.; Defrère, D.; Doré, O.; Hinz, P.; Kuchner, M.; Ragland, S.; Scott, N.; Stapelfeldt, K.; Traub, W.; Woillez, J.

    2014-12-01

    Forty-seven nearby main-sequence stars were surveyed with the Keck Interferometer mid-infrared Nulling instrument (KIN) between 2008 and 2011, searching for faint resolved emission from exozodiacal dust. Observations of a subset of the sample have already been reported, focusing essentially on stars with no previously known dust. Here we extend this previous analysis to the whole KIN sample, including 22 more stars with known near- and/or far-infrared excesses. In addition to an analysis similar to that of the first paper of this series, which was restricted to the 8-9 μm spectral region, we present measurements obtained in all 10 spectral channels covering the 8-13 μm instrumental bandwidth. Based on the 8-9 μm data alone, which provide the highest signal-to-noise measurements, only one star shows a large excess imputable to dust emission (η Crv), while four more show a significant (>3σ) excess: β Leo, β UMa, ζ Lep, and γ Oph. Overall, excesses detected by KIN are more frequent around A-type stars than later spectral types. A statistical analysis of the measurements further indicates that stars with known far-infrared (λ >= 70 μm) excesses have higher exozodiacal emission levels than stars with no previous indication of a cold outer disk. This statistical trend is observed regardless of spectral type and points to a dynamical connection between the inner (zodi-like) and outer (Kuiper-Belt-like) dust populations. The measured levels for such stars are clustering close to the KIN detection limit of a few hundred zodis and are indeed consistent with those expected from a population of dust that migrated in from the outer belt by Poynting-Robertson drag. Conversely, no significant mid-infrared excess is found around sources with previously reported near-infrared resolved excesses, which typically have levels of the order of 1% over the photospheric flux. If dust emission is really at play in these near-infrared detections, the absence of a strong mid

  7. Herschel-resolved Outer Belts of Two-belt Debris Disks around A-type Stars: HD 70313, HD 71722, HD 159492, and F-type: HD 104860

    NASA Astrophysics Data System (ADS)

    Morales, F. Y.; Bryden, G.; Werner, M. W.; Stapelfeldt, K. R.

    2013-10-01

    We present dual-band Herschel/Photodetector Array Camera and Spectrometer imaging for four stars whose spectral energy distributions (SEDs) suggest two-ring disk architectures that mirror that of the asteroid-Kuiper Belt geometry of our own solar system. The Herschel observations at 100 μm spatially resolve the cold/outer-dust component for each star-disk system for the first time, finding evidence of planetesimals at >100 AU, i.e., a larger size than assumed from a simple blackbody fit to the SED. By breaking the degeneracy between the grain properties and the dust's radial location, the resolved images help constrain the dust grain-size distribution for each system. Three of the observed stars are A-type and one solar-type. On the basis of the combined Spitzer/IRS+MIPS (5-70 μm), the Herschel/PACS (100 and 160 μm) dataset, and under the assumption of idealized spherical grains, we find that the cold/outer belts of the three A-type stars are well fit with a mixed ice/rock composition rather than pure rocky grains, while the debris around the solar-type star is consistent with either rock or ice/rock grains. For the solar-type star HD 104860, we find that the minimum grain size is larger than expected from the threshold set by radiative blowout. The A-type stars HD 71722 and HD 159492, on the other hand, require minimum grain sizes that are smaller than blowout for inner- and outer-ring populations. In the absence of spectral features for ice, we find that the behavior of the continuum can help constrain the composition of the grains (of icy nature and not pure rocky material) given the Herschel-resolved locations of the cold/outer-dust belts. Herschel is an ESA space observatory with science instruments provided by European-led principal investigator consortia and with important participation from NASA.

  8. SEARCHING FOR GAS GIANT PLANETS ON SOLAR SYSTEM SCALES: VLT NACO/APP OBSERVATIONS OF THE DEBRIS DISK HOST STARS HD172555 AND HD115892

    SciTech Connect

    Quanz, Sascha P.; Meyer, Michael R.; Kenworthy, Matthew A.; Girard, Julien H. V.; Kasper, Markus

    2011-08-01

    Using the Apodizing Phase Plate (APP) coronagraph of Very Large Telescope/NACO we searched for planetary mass companions around HD115892 and HD172555 in the thermal infrared at 4 {mu}m. Both objects harbor unusually luminous debris disks for their age and it has been suggested that small dust grains were produced recently in transient events (e.g., a collision) in these systems. Such a collision of planetesimals or protoplanets could have been dynamically triggered by yet unseen companions. We did not detect any companions in our images but derived the following detection limits: for both objects we would have detected companions with apparent magnitudes between {approx}13.2 and 14.1 mag at angular separations between 0.''4 and 1.''0 at the 5{sigma} level. For HD115892 we were sensitive to companions with 12.1 mag even at 0.''3. Using theoretical models these magnitudes are converted into mass limits. For HD115892 we would have detected objects with 10-15 M{sub Jup} at angular separations between 0.''4 and 1.''0 (7-18 AU). At 0.''3 ({approx}5.5 AU) the detection limit was {approx}>25 M{sub Jup}. For HD172555 we reached detection limits between 2 and 3 M{sub Jup} at separations between 0.''5 and 1.''0 (15-29 AU). At 0.''4 ({approx}11 AU) the detection limit was {approx}>4 M{sub Jup}. Despite the non-detections, our data demonstrate the unprecedented contrast performance of NACO/APP in the thermal infrared at very small inner working angles and we show that our observations are mostly background limited at separations {approx}>0.''5.

  9. An Unbiased Near-infrared Interferometric Survey for Hot Exozodiacal Dust

    NASA Astrophysics Data System (ADS)

    Ertel, S.; Augereau, J.-C.; Absil, O.; Defrère, D.; Le Bouquin, J.-B.; Marion, L.; Bonsor, A.; Lebreton, J.

    2015-03-01

    Exozodiacal dust is warm or hot dust found in the inner regions of planetary systems orbiting main sequence stars, in or around their habitable zones. The dust can be the most luminous component of extrasolar planetary systems, but predominantly emits in the near- to mid-infrared where it is outshone by the host star. Interferometry provides a unique method of separating this dusty emission from the stellar emission. The visitor instrument PIONIER at the Very Large Telescope Interferometer (VLTI) has been used to search for hot exozodiacal dust around a large sample of nearby main sequence stars. The results of this survey are summarised: 9 out of 85 stars show excess exo- zodiacal emission over the stellar photospheric emission.

  10. Orbital Debris

    NASA Technical Reports Server (NTRS)

    Kessler, D. J. (Compiler); Su, S. Y. (Compiler)

    1985-01-01

    Earth orbital debris issues and recommended future activities are discussed. The workshop addressed the areas of environment definition, hazards to spacecraft, and space object management. It concluded that orbital debris is a potential problem for future space operations. However, before recommending any major efforts to control the environment, more data are required. The most significant required data are on the population of debris smaller than 4 cm in diameter. New damage criteria are also required. When these data are obtained, they can be combined with hypervelocity data to evaluate the hazards to future spacecraft. After these hazards are understood, then techniques to control the environment can be evaluated.

  11. High Resolution Imaging of Circumstellar Disks at Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Wilner, David J.

    2004-01-01

    We summarize progress on our program to use high angular resolution imaging of thermal dust continuum emission at millimeter and submillimeter wavelengths to probe the structure of protoplanetary disks and debris disks around nearby stars.

  12. EXOZODIACAL DUST LEVELS FOR NEARBY MAIN-SEQUENCE STARS: A SURVEY WITH THE KECK INTERFEROMETER NULLER

    SciTech Connect

    Millan-Gabet, R.; Serabyn, E.; Mennesson, B.; Traub, W. A.; Stapelfeldt, K.; Bryden, G.; Colavita, M. M.; Booth, A. J.; Barry, R. K.; Danchi, W. C.; Kuchner, M.; Stark, C. C.; Ragland, S.; Hrynevych, M.; Woillez, J.

    2011-06-10

    The Keck Interferometer Nuller (KIN) was used to survey 25 nearby main-sequence stars in the mid-infrared, in order to assess the prevalence of warm circumstellar (exozodiacal) dust around nearby solar-type stars. The KIN measures circumstellar emission by spatially blocking the star but transmitting the circumstellar flux in a region typically 0.1-4 AU from the star. We find one significant detection ({eta} Crv), two marginal detections ({gamma} Oph and {alpha} Aql), and 22 clear non-detections. Using a model of our own solar system's zodiacal cloud, scaled to the luminosity of each target star, we estimate the equivalent number of target zodis needed to match our observations. Our three zodi detections are {eta} Crv (1250 {+-} 260), {gamma} Oph (200 {+-} 80), and {alpha} Aql (600 {+-} 200), where the uncertainties are 1{sigma}. The 22 non-detected targets have an ensemble weighted average consistent with zero, with an average individual uncertainty of 160 zodis (1{sigma}). These measurements represent the best limits to date on exozodi levels for a sample of nearby main-sequence stars. A statistical analysis of the population of 23 stars not previously known to contain circumstellar dust (excluding {eta} Crv and {gamma} Oph) suggests that, if the measurement errors are uncorrelated (for which we provide evidence) and if these 23 stars are representative of a single class with respect to the level of exozodi brightness, the mean exozodi level for the class is <150 zodis (3{sigma} upper limit, corresponding to 99% confidence under the additional assumption that the measurement errors are Gaussian). We also demonstrate that this conclusion is largely independent of the shape and mean level of the (unknown) true underlying exozodi distribution.

  13. Formation of Planets in a Protoplanetary Disk

    NASA Video Gallery

    The artist conception shows a newly formed star surrounded by a swirling protoplanetary disk of dust and gas. Debris coalesces to create rocky 'planetesimals' that collide and grow to eventually fo...

  14. Planetesimal Disk Microlensing

    NASA Astrophysics Data System (ADS)

    Heng, Kevin; Keeton, Charles R.

    2009-12-01

    Motivated by debris disk studies, we investigate the gravitational microlensing of background starlight by a planetesimal disk around a foreground star. We use dynamical survival models to construct a plausible example of a planetesimal disk and study its microlensing properties using established ideas of microlensing by small bodies. When a solar-type source star passes behind a planetesimal disk, the microlensing light curve may exhibit short-term, low-amplitude residuals caused by planetesimals several orders of magnitude below Earth mass. The minimum planetesimal mass probed depends on the photometric sensitivity and the size of the source star, and is lower when the planetesimal lens is located closer to us. Planetesimal lenses may be found more nearby than stellar lenses because the steepness of the planetesimal mass distribution changes how the microlensing signal depends on the lens/source distance ratio. Microlensing searches for planetesimals require essentially continuous monitoring programs that are already feasible and can potentially set constraints on models of debris disks, the progeny of the supposed extrasolar analogues of Kuiper Belts.

  15. PLANETESIMAL DISK MICROLENSING

    SciTech Connect

    Heng, Kevin; Keeton, Charles R. E-mail: keeton@physics.rutgers.ed

    2009-12-10

    Motivated by debris disk studies, we investigate the gravitational microlensing of background starlight by a planetesimal disk around a foreground star. We use dynamical survival models to construct a plausible example of a planetesimal disk and study its microlensing properties using established ideas of microlensing by small bodies. When a solar-type source star passes behind a planetesimal disk, the microlensing light curve may exhibit short-term, low-amplitude residuals caused by planetesimals several orders of magnitude below Earth mass. The minimum planetesimal mass probed depends on the photometric sensitivity and the size of the source star, and is lower when the planetesimal lens is located closer to us. Planetesimal lenses may be found more nearby than stellar lenses because the steepness of the planetesimal mass distribution changes how the microlensing signal depends on the lens/source distance ratio. Microlensing searches for planetesimals require essentially continuous monitoring programs that are already feasible and can potentially set constraints on models of debris disks, the progeny of the supposed extrasolar analogues of Kuiper Belts.

  16. AGE DETERMINATION FOR 346 NEARBY STARS IN THE HERSCHEL DEBRIS SURVEY

    SciTech Connect

    Vican, Laura

    2012-06-15

    DEBRIS is a flux-limited survey of nearby stars (spectral types A-M) for evidence of debris disks with the Herschel Space Observatory. One goal of the survey is to determine disk incidence as a function of various stellar parameters. Understanding debris disk evolution depends on knowledge of the precise age of stars around which these debris disks are found. However, finding ages for field stars is notoriously difficult. Furthermore, in an unbiased sample like DEBRIS, one is working with stars across many spectral types. This requires a multi-method approach to age determination. In this paper, we outline several methods of age determination broken down by spectral type, including some strengths and limitations of each method. In total, we were able to calculate ages for 263 of 274 F-, G-, and K-type stars, and all 83 A-type stars in the DEBRIS sample.

  17. THE EVOLUTION OF INNER DISK GAS IN TRANSITION DISKS

    SciTech Connect

    Hoadley, K.; France, K.; McJunkin, M.; Alexander, R. D.; Schneider, P. C.

    2015-10-10

    Investigating the molecular gas in the inner regions of protoplanetary disks (PPDs) provides insight into how the molecular disk environment changes during the transition from primordial to debris disk systems. We conduct a small survey of molecular hydrogen (H{sub 2}) fluorescent emission, using 14 well-studied Classical T Tauri stars at two distinct dust disk evolutionary stages, to explore how the structure of the inner molecular disk changes as the optically thick warm dust dissipates. We simulate the observed Hi-Lyman α-pumped H{sub 2} disk fluorescence by creating a 2D radiative transfer model that describes the radial distributions of H{sub 2} emission in the disk atmosphere and compare these to observations from the Hubble Space Telescope. We find the radial distributions that best describe the observed H{sub 2} FUV emission arising in primordial disk targets (full dust disk) are demonstrably different than those of transition disks (little-to-no warm dust observed). For each best-fit model, we estimate inner and outer disk emission boundaries (r{sub in} and r{sub out}), describing where the bulk of the observed H{sub 2} emission arises in each disk, and we examine correlations between these and several observational disk evolution indicators, such as n{sub 13–31}, r{sub in,} {sub CO}, and the mass accretion rate. We find strong, positive correlations between the H{sub 2} radial distributions and the slope of the dust spectral energy distribution, implying the behavior of the molecular disk atmosphere changes as the inner dust clears in evolving PPDs. Overall, we find that H{sub 2} inner radii are ∼4 times larger in transition systems, while the bulk of the H{sub 2} emission originates inside the dust gap radius for all transitional sources.

  18. The Pseudo-Zodi Problem for Edge-On Planetary Systems

    NASA Astrophysics Data System (ADS)

    Stark, Christopher C.; Kuchner, Marc J.; Lincowski, Andrew

    2015-03-01

    Future direct observations of extrasolar Earth-sized planets in the habitable zone (HZ) could be hampered by a worrisome source of noise, starlight-reflecting exozodiacal dust. Mid-infrared surveys are currently underway to constrain the amount of exozodiacal dust in the HZs around nearby stars. However, at visible wavelengths another source of dust, invisible to these surveys, may dominate over exozodiacal dust. For systems observed near edge-on, a cloud of dust with face-on optical depth 10-7 beyond ˜5 AU can mimic the surface brightness of a cloud of exozodiacal dust with equal optical depth if the dust grains are sufficiently forward-scattering. We posit that dust migrating inward from cold debris belts via Poynting-Robertson drag could produce this “pseudo-zodiacal” effect, potentially making it ˜ 50% as common as exozodiacal clouds. We place constraints on the disk radii and scattering phase function required to produce the effect.

  19. Space Shuttle Debris Transport

    NASA Technical Reports Server (NTRS)

    Gomez, Reynaldo J., III

    2010-01-01

    This slide presentation reviews the assessment of debris damage to the Space Shuttle, and the use of computation to assist in the space shuttle applications. The presentation reviews the sources of debris, a mechanism for determining the probability of damaging debris impacting the shuttle, tools used, eliminating potential damaging debris sources, the use of computation to assess while inflight damage, and a chart showing the applications that have been used on increasingly powerful computers simulate the shuttle and the debris transport.

  20. Orbital Debris: A Chronology

    NASA Technical Reports Server (NTRS)

    Portree, Davis S. F. (Editor); Loftus, Joseph P., Jr. (Editor)

    1999-01-01

    This chronology covers the 37-year history of orbital debris concerns. It tracks orbital debris hazard creation, research, observation, experimentation, management, mitigation, protection, and policy. Included are debris-producing, events; U.N. orbital debris treaties, Space Shuttle and space station orbital debris issues; ASAT tests; milestones in theory and modeling; uncontrolled reentries; detection system development; shielding development; geosynchronous debris issues, including reboost policies: returned surfaces studies, seminar papers reports, conferences, and studies; the increasing effect of space activities on astronomy; and growing international awareness of the near-Earth environment.

  1. Herniated Disk

    MedlinePlus

    ... keep them in place. As you age, the disks break down or degenerate. As they do, they lose their cushioning ability. This can lead to pain if the back is stressed. A herniated disk is a disk that ruptures. This allows the ...

  2. Harnessing the Power of the WFIRST-Coronagraph: A Coordinated Plan for Exoplanet and Disk Science

    NASA Astrophysics Data System (ADS)

    Turnbull, Margaret

    We propose to form a WFIRST Coronagraph Science Investigation Team (WFIRST-C SIT) for the purpose of defining the coronagraph scientific performance requirements, designing an exoplanet and debris disk observing program, and developing data analysis techniques including faint source detection and spectral retrieval. Our team will accomplish these tasks by: 1. Providing detailed characterization of the candidate target stars in terms of stellar/substeller companions, circumstellar debris, and astrophysical background in order to inform the final target selection by the community. As part of this effort, we will make a plan for coordination between WFIRST and Large Binocular Telescope Interferometer (LBTI) target selection, to obtain both scattered light and thermal emission observations of exozodiacal dust in the same systems. This will be important precursor science for future exoEarth direct imaging missions. 2. Creating simulated spatial-spectral data cubes representative of what the WFIRST coronagraph may see around the candidate targets, including known and hypothetical exoplanets, dynamically consistent interplanetary dust distributions, and astrophysical background contamination. The code framework to make the high-fidelity input models exists within our team, and we currently have a complete spectral data cube that allows us to generate images at any wavelength between 0.3 microns and 2.5 microns. To generate the simulated datasets for WFIRST, we will make use of instrument simulation tools provided by the coronagraph design team, spanning the range of expected coronagraph performance characteristics. We will also add functionality to these tools, or build our own, as required. 3. Designing and conducting a â€oeblind retrieval challenge― study to distribute these data amongst source detection and spectral modeling teams in the exoplanet and wider astrophysics community. Given the variety of sources expected in each planet-finding field, we expect

  3. Report on orbital debris

    NASA Technical Reports Server (NTRS)

    1989-01-01

    The success of space endeavors depends upon a space environment sufficiently free of debris to enable the safe and dependable operation of spacecraft. An environment overly cluttered with debris would threaten the ability to utilize space for a wide variety of scientific, technological, military, and commercial purposes. Man made space debris (orbital debris) differs from natural meteoroids because it remains in earth orbit during its lifetime and is not transient through the space around the Earth. The orbital debris environment is considered. The space environment is described along with sources of orbital debris. The current national space policy is examined, along with ways to minimize debris generation and ways to survive the debris environment. International efforts, legal issues and commercial regulations are also examined.

  4. Turbomachinery debris remover

    DOEpatents

    Krawiec, Donald F.; Kraf, Robert J.; Houser, Robert J.

    1988-01-01

    An apparatus for removing debris from a turbomachine. The apparatus includes housing and remotely operable viewing and grappling mechanisms for the purpose of locating and removing debris lodged between adjacent blades in a turbomachine.

  5. Debris exhaust system

    DOEpatents

    McBride, D.D.; Bua, D.; Domankevitz, Y.; Nishioka, N.

    1998-06-23

    A debris removal system removes debris from a work site by flowing fluid away from the work site toward the periphery of a structure. The fluid flow can be kept constant around the periphery so that debris is removed evenly. The structure can have a reduced cross section between the fluid inlet and the work site so that the resulting increased fluid velocity works to prevent debris from escaping. 9 figs.

  6. Debris exhaust system

    DOEpatents

    McBride, Donald D.; Bua, Dominic; Domankevitz, Yacov; Nishioka, Norman

    1998-01-01

    A debris removal system removes debris from a work site by flowing fluid away from the work site toward the periphery of a structure. The fluid flow can be kept constant around the periphery so that debris is removed evenly. The structure can have a reduced cross section between the fluid inlet and the work site so that the resulting increased fluid velocity works to prevent debris from escaping.

  7. Optical Disks.

    ERIC Educational Resources Information Center

    Gale, John C.; And Others

    1985-01-01

    This four-article section focuses on information storage capacity of the optical disk covering the information workstation (uses microcomputer, optical disk, compact disc to provide reference information, information content, work product support); use of laser videodisc technology for dissemination of agricultural information; encoding databases…

  8. Supersized Disk (Artist's Concept)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Annotated ImageData Graph

    This illustration compares the size of a gargantuan star and its surrounding dusty disk (top) to that of our solar system. Monstrous disks like this one were discovered around two 'hypergiant' stars by NASA's Spitzer Space Telescope. Astronomers believe these disks might contain the early 'seeds' of planets, or possibly leftover debris from planets that already formed.

    The hypergiant stars, called R 66 and R 126, are located about 170,000 light-years away in our Milky Way's nearest neighbor galaxy, the Large Magellanic Cloud. The stars are about 100 times wider than the sun, or big enough to encompass an orbit equivalent to Earth's. The plump stars are heavy, at 30 and 70 times the mass of the sun, respectively. They are the most massive stars known to sport disks.

    The disks themselves are also bloated, with masses equal to several Jupiters. The disks begin at a distance approximately 120 times greater than that between Earth and the sun, or 120 astronomical units, and terminate at a distance of about 2,500 astronomical units.

    Hypergiant stars are the puffed-up, aging descendants of the most massive class of stars, called 'O' stars. The stars are so massive that their cores ultimately collapse under their own weight, triggering incredible explosions called supernovae. If any planets circled near the stars during one of these blasts, they would most likely be destroyed.

    The orbital distances in this picture are plotted on a logarithmic scale. This means that a given distance shown here represents proportionally larger actual distances as you move to the right. The sun and planets in our solar system have been scaled up in size for better viewing. Little Dust Grains in Giant Stellar Disks The graph above of data from NASA's Spitzer Space Telescope shows the composition of a monstrous disk of what may be planet-forming dust circling the colossal 'hypergiant' star

  9. High Resolution Imaging of Circumstellar Disks at Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Wilner, David J.

    2003-01-01

    Our program uses the techniques of millimeter interferometry to make high resolution observations of dust continuum emission to study the structure of protoplanetary disks and debris disks around nearby stars. Observations of dust emission at these wavelengths are advantageous because the dust emission is generally optically thin and directly proportional to mass, and contrast with stellar photospheres is not a problem. We are using of several observational facilities, including (1) the Very Large Array (VLA) of the National Radio Astronomy Observatories, (2) the Plateau de Bure Interferometer (PdBI) of the Institut de RadioAstronomie Millimetrique, and (3) the Submillimeter Array (SMA), now under construction by the Smithsonian Astrophysical Observatory and Academia Sinica (Taiwan). In the past year, we have accomplished the following (more details below): (1) We continued work on our 'low resolution' VLA survey of disks in Herbig Ae star and binary systems, primarily to identify candidates for higher resolution follow-up. We have submitted a paper for publication on the detailed analysis of the structure of the disk around CQ Tauri; (2) We completed analysis of our PdBI observations of the debris disk around Vega, and we presented these results at (1) the 199th AAS meeting in Washington, DC, and (2) a symposium in memory of Fred Gillett on Debris Disks and the Formation of Planets, in Tucson, AZ; (3) We continue commissioning observations with the SMA, which include the first ever interferometric images in the 850 micron wavelength band, in preparation for eventually imaging debris disks.

  10. Herniated disk

    MedlinePlus

    ... roots. Slipped disks occur more often in middle-aged and older men, usually after strenuous activity. Other ... calm the nerves Muscle relaxants to relieve back spasms LIFESTYLE CHANGES If you are overweight, diet and ...

  11. Disk Detective: Discovery of New Circumstellar Disk Candidates through Citizen Science

    NASA Astrophysics Data System (ADS)

    Kuchner, Marc J.; Silverberg, Steven M.; Bans, Alissa S.; Bhattacharjee, Shambo; Kenyon, Scott J.; Debes, John H.; Currie, Thayne; García, Luciano; Jung, Dawoon; Lintott, Chris; McElwain, Michael; Padgett, Deborah L.; Rebull, Luisa M.; Wisniewski, John P.; Nesvold, Erika; Schawinski, Kevin; Thaller, Michelle L.; Grady, Carol A.; Biggs, Joseph; Bosch, Milton; C̆ernohous, Tadeás̆; Durantini Luca, Hugo A.; Hyogo, Michiharu; Wah, Lily Lau Wan; Piipuu, Art; Piñeiro, Fernanda; the Disk Detective Collaboration

    2016-10-01

    The Disk Detective citizen science project aims to find new stars with 22 μm excess emission from circumstellar dust using data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission. Initial cuts on the AllWISE catalog provide an input catalog of 277,686 sources. Volunteers then view images of each source online in 10 different bands to identify false positives (galaxies, interstellar matter, image artifacts, etc.). Sources that survive this online vetting are followed up with spectroscopy on the FLWO Tillinghast telescope. This approach should allow us to unleash the full potential of WISE for finding new debris disks and protoplanetary disks. We announce a first list of 37 new disk candidates discovered by the project, and we describe our vetting and follow-up process. One of these systems appears to contain the first debris disk discovered around a star with a white dwarf companion: HD 74389. We also report four newly discovered classical Be stars (HD 6612, HD 7406, HD 164137, and HD 218546) and a new detection of 22 μm excess around the previously known debris disk host star HD 22128.

  12. The fate of debris in the Pluto-Charon system

    NASA Astrophysics Data System (ADS)

    Smullen, Rachel; Kratter, Kaitlin M.

    2016-05-01

    Pluto has recently been thrust into the spotlight with the fly-by of New Horizons. This dwarf planet and its moons provide an opportunity to study circumbinary dynamics close to home. We perform N-body simulations of a test-particle disk around the Pluto-Charon binary to study the fate of debris that should result from the formation of the Pluto-Charon binary. We not only investigate the stability and time evolution of debris within the Pluto system, but also track ejected debris to see where it may collect in the solar system. By studying the dynamics of the Pluto-Charon system, we may be able to place constraints on the cratering rates from its natal disk and identify tracers of the formation of this system.

  13. Circumstellar debris and pollution at white dwarf stars

    NASA Astrophysics Data System (ADS)

    Farihi, J.

    2016-04-01

    Circumstellar disks of planetary debris are now known or suspected to closely orbit hundreds of white dwarf stars. To date, both data and theory support disks that are entirely contained within the preceding giant stellar radii, and hence must have been produced during the white dwarf phase. This picture is strengthened by the signature of material falling onto the pristine stellar surfaces; disks are always detected together with atmospheric heavy elements. The physical link between this debris and the white dwarf host abundances enables unique insight into the bulk chemistry of extrasolar planetary systems via their remnants. This review summarizes the body of evidence supporting dynamically active planetary systems at a large fraction of all white dwarfs, the remnants of first generation, main-sequence planetary systems, and hence provide insight into initial conditions as well as long-term dynamics and evolution.

  14. Design of orbital debris shields for oblique hypervelocity impact

    NASA Technical Reports Server (NTRS)

    Fahrenthold, Eric P.

    1994-01-01

    A new impact debris propagation code was written to link CTH simulations of space debris shield perforation to the Lagrangian finite element code DYNA3D, for space structure wall impact simulations. This software (DC3D) simulates debris cloud evolution using a nonlinear elastic-plastic deformable particle dynamics model, and renders computationally tractable the supercomputer simulation of oblique impacts on Whipple shield protected structures. Comparison of three dimensional, oblique impact simulations with experimental data shows good agreement over a range of velocities of interest in the design of orbital debris shielding. Source code developed during this research is provided on the enclosed floppy disk. An abstract based on the work described was submitted to the 1994 Hypervelocity Impact Symposium.

  15. Design of orbital debris shields for oblique hypervelocity impact

    NASA Astrophysics Data System (ADS)

    Fahrenthold, Eric P.

    1994-02-01

    A new impact debris propagation code was written to link CTH simulations of space debris shield perforation to the Lagrangian finite element code DYNA3D, for space structure wall impact simulations. This software (DC3D) simulates debris cloud evolution using a nonlinear elastic-plastic deformable particle dynamics model, and renders computationally tractable the supercomputer simulation of oblique impacts on Whipple shield protected structures. Comparison of three dimensional, oblique impact simulations with experimental data shows good agreement over a range of velocities of interest in the design of orbital debris shielding. Source code developed during this research is provided on the enclosed floppy disk. An abstract based on the work described was submitted to the 1994 Hypervelocity Impact Symposium.

  16. Modeling debris-covered glaciers: response to steady debris deposition

    NASA Astrophysics Data System (ADS)

    Anderson, Leif S.; Anderson, Robert S.

    2016-05-01

    Debris-covered glaciers are common in rapidly eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. If continuous debris cover is present, ablation rates can be significantly reduced leading to increases in glacier length. In order to quantify feedbacks in the debris-glacier-climate system, we developed a 2-D long-valley numerical glacier model that includes englacial and supraglacial debris advection. We ran 120 simulations on a linear bed profile in which a hypothetical steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier terminus. Our model and parameter selections can produce 2-fold increases in glacier length. Debris flux onto the glacier and the relationship between debris thickness and melt rate strongly control glacier length. Debris deposited near the equilibrium-line altitude, where ice discharge is high, results in the greatest glacier extension when other debris-related variables are held constant. Debris deposited near the equilibrium-line altitude re-emerges high in the ablation zone and therefore impacts melt rate over a greater fraction of the glacier surface. Continuous debris cover reduces ice discharge gradients, ice thickness gradients, and velocity gradients relative to initial debris-free glaciers. Debris-forced glacier extension decreases the ratio of accumulation zone to total glacier area (AAR). Our simulations reproduce the "general trends" between debris cover, AARs, and glacier surface velocity patterns from modern debris-covered glaciers. We provide a quantitative, theoretical foundation to interpret the effect of debris cover on the moraine record, and to assess the effects of climate change on debris-covered glaciers.

  17. Is the HD 15115 circumstellar disk really asymmetrical?

    NASA Astrophysics Data System (ADS)

    Mazoyer, J.; Boccaletti, A.; Augereau, J.-C.; Lagrange, A.-M.; Galicher, R.; Baudoz, P.

    2014-09-01

    Similarly to beta Pictoris, HD 15115 is a young and nearby (45.2 pc) star that hosts a debris disk. This debris disk was first imaged in 2007 (Kalas et al., 2007) in visible using HST and in H band using the Keck observatory. The disk appeared edge-on and showed an asymmetry between its west and east parts. This detection was later observed in J band using HST / Nicmos data (Debes et al., 2008) and in Ks and L' using LBT (Rodigas et al. 2012). These observations confirmed the asymmetric nature of HD 15115 debris disk. We present here the results of the analysis of data from the Gemini / NICI archival system from 2009 and 2011 in H and K bands. We use newly developed differential treatment algorithms on these data (ADI, LOCI, KLIP) to subtract the light of the star and image the disk up to 1 arc second (30 AU). From this analysis, we find an inclination of 86 (confirming previous conclusions about HD 15115). We derive the disk position angle and spine and photometry and only find a brightness asymmetry in these elements. We also present evidence of an ring at 2 arc seconds (60 AU), with a rather sharp inner edge, and no sign of an asymmetry. With this radius and inclination, we create disk models (Augereau et al. 1999) and put constraints on the disk parameters, using either the position angle, spine and photometry or forward modeling.

  18. Warm Disks from Giant Impacts

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-10-01

    In the process of searching for exoplanetary systems, weve discovered tens of debris disks close around distant stars that are especially bright in infrared wavelengths. New research suggests that we might be looking at the late stages of terrestrial planet formation in these systems.Forming Terrestrial PlanetsAccording to the widely-accepted formation model for our solar-system, protoplanets the size of Mars formed within a protoplanetary disk around our Sun. Eventually, the depletion of the gas in the disk led the orbits of these protoplanets to become chaotically unstable. Finally, in the giant impact stage, many of the protoplanets collided with each other ultimately leading to the formation of the terrestrial planets and their moons as we know them today.If giant impact stages occur in exoplanetary systems, too leading to the formation of terrestrial exoplanets how would we detect this process? According to a study led by Hidenori Genda of the Tokyo Institute of Technology, we might be already be witnessing this stage in observations of warm debris disks around other stars. To test this, Genda and collaborators model giant impact stages and determine what we would expect to see from a system undergoing this violent evolution.Modeling CollisionsSnapshots of a giant impact in one of the authors simulations. The collision causes roughly 0.05 Earth masses of protoplanetary material to be ejected from the system. Click for a closer look! [Genda et al. 2015]The collaborators run a series of simulations evolving protoplanetary bodies in a solar system. The simulations begin 10 Myr into the lifetime of the solar system, i.e., after the gas from the protoplanetary disk has had time to be cleared and the protoplanetary orbits begin to destabilize. The simulations end when the protoplanets are done smashing into each other and have again settled into stable orbits, typically after ~100 Myr.The authors find that, over an average giant impact stage, the total amount of

  19. SPECS: Orbital debris removal

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The debris problem has reached a stage at which the risk to satellites and spacecraft has become substantial in low Earth orbit (LEO). This research discovered that small particles posed little threat to spacecraft because shielding can effectively prevent these particles from damaging the spacecraft. The research also showed that, even though collision with a large piece of debris could destroy the spacecraft, the large pieces of debris pose little danger because they can be tracked and the spacecraft can be maneuvered away from these pieces. Additionally, there are many current designs to capture and remove large debris particles from the space environment. From this analysis, it was decided to concentrate on the removal of medium-sized orbital debris, that is, those pieces ranging from 1 cm to 50 cm in size. The current design incorporates a transfer vehicle and a netting vehicle to capture the medium-sized debris. The system is based near an operational space station located at 28.5 deg inclination and 400 km altitude. The system uses ground-based tracking to determine the location of a satellite breakup or debris cloud. These data are uploaded to the transfer vehicle, which proceeds to rendezvous with the debris at a lower altitude parking orbit. Next, the netting vehicle is deployed, tracks the targeted debris, and captures it. After expending the available nets, the netting vehicle returns to the transfer vehicle for a new netting module and continues to capture more debris in the target area. Once all the netting modules are expended, the transfer vehicle returns to the space station's orbit where it is resupplied with new netting modules from a space shuttle load. The new modules are launched by the shuttle from the ground and the expended modules are taken back to Earth for removal of the captured debris, refueling, and repacking of the nets. Once the netting modules are refurbished, they are taken back into orbit for reuse. In a typical mission, the

  20. SPECS: Orbital debris removal

    NASA Astrophysics Data System (ADS)

    The debris problem has reached a stage at which the risk to satellites and spacecraft has become substantial in low Earth orbit (LEO). This research discovered that small particles posed little threat to spacecraft because shielding can effectively prevent these particles from damaging the spacecraft. The research also showed that, even though collision with a large piece of debris could destroy the spacecraft, the large pieces of debris pose little danger because they can be tracked and the spacecraft can be maneuvered away from these pieces. Additionally, there are many current designs to capture and remove large debris particles from the space environment. From this analysis, it was decided to concentrate on the removal of medium-sized orbital debris, that is, those pieces ranging from 1 cm to 50 cm in size. The current design incorporates a transfer vehicle and a netting vehicle to capture the medium-sized debris. The system is based near an operational space station located at 28.5 deg inclination and 400 km altitude. The system uses ground-based tracking to determine the location of a satellite breakup or debris cloud. These data are uploaded to the transfer vehicle, which proceeds to rendezvous with the debris at a lower altitude parking orbit. Next, the netting vehicle is deployed, tracks the targeted debris, and captures it. After expending the available nets, the netting vehicle returns to the transfer vehicle for a new netting module and continues to capture more debris in the target area. Once all the netting modules are expended, the transfer vehicle returns to the space station's orbit where it is resupplied with new netting modules from a space shuttle load. The new modules are launched by the shuttle from the ground and the expended modules are taken back to Earth for removal of the captured debris, refueling, and repacking of the nets. Once the netting modules are refurbished, they are taken back into orbit for reuse. In a typical mission, the

  1. Uncovering debris in the Milky Way

    NASA Astrophysics Data System (ADS)

    Ruchti, Gregory R.; Read, Justin; Gaia-ESO Consortium

    2016-01-01

    In our current cosmological model, typical Milky Way mass galaxies should experience many mergers over their lifetimes. We have developed new chemo-dynamical techniques to hunt for accreted stars - the stellar debris from satellite galaxies - in the Milky Way and its disk. We have applied our template to data from the Gaia-ESO Survey - an extraordinary new resource. I will discuss our latest results, including, for the first time, a new signature with which we can directly detect the Milky Way's last major merger some 8-10 billion years ago.

  2. Orbital debris: A technical assessment

    NASA Technical Reports Server (NTRS)

    Gleghorn, George; Asay, James; Atkinson, Dale; Flury, Walter; Johnson, Nicholas; Kessler, Donald; Knowles, Stephen; Rex, Dietrich; Toda, Susumu; Veniaminov, Stanislav

    1995-01-01

    To acquire an unbiased technical assessment of (1) the research needed to better understand the debris environment, (2) the necessity and means of protecting spacecraft against the debris environment, and (3) potential methods of reducing the future debris hazard, NASA asked the National Research Council to form an international committee to examine the orbital debris issue. The committee was asked to draw upon available data and analyses to: characterize the current debris environment, project how this environment might change in the absence of new measures to alleviate debris proliferation, examine ongoing alleviation activities, explore measures to address the problem, and develop recommendations on technical methods to address the problems of debris proliferation.

  3. The Fourier-Kelvin Stellar Interferometer (FKSI): Infrared Detection and Characterization of Exozodiacal Dust to Super-Earths, A Progress Report

    NASA Technical Reports Server (NTRS)

    Danchi, W.

    2010-01-01

    The Fourier-Kelvin Stellar Interferometer (FKSI) is a structurally connected infrared space interferometer with 0.5 m diameter telescopes on a 12.5 m baseline, and is passively cooled to approx.60K. The FKSI operates in the thermal infrared from 3-8 microns in a nulling (or starlight suppressing) mode for the detection and characterization of exoplanets, debris disks, extrasolar zodiacal dust levels. The FKSI will have the highest angular resolution of any infrared space instrument ever made with its nominal resolution of 40 mas at a 5 micron center wavelength. This resolution exceeds that of Spitzer by a factor of 38 and JWST by a factor of 5. The FKSI mission is conceived as a "probe class" or "mid-sized" strategic mission that utilizes technology advances from flagship projects like JWST, SIM, Spitzer, and the technology programs of TPF-I/Darwin. During the past year we began investigating an enhanced version of FKSI with 1-2 m diameter telescopes, passively cooled to 40K, on a 20-m baseline, with a sunshade giving a +/- 45 degree Field-of-Regard. This enhanced design is capable of detecting and characterizing the atmospheres of many 2 Earth-radius super-Earths and a few Earth-twins. We will report progress on the design of the enhanced mission concept and current status of the technologies needed for this mission.

  4. Characterization of Debris from the DebriSat Hypervelocity Test

    NASA Technical Reports Server (NTRS)

    Rivero, M.; Kleespies, J.; Patankar, K.; Fitz-Coy, N.; Liou, J.-C.; Sorge, M.; Huynh, T.; Opiela, J.; Krisko, P.; Cowardin, H.

    2015-01-01

    The DebriSat project is an effort by NASA and the DoD to update the standard break-up model for objects in orbit. The DebriSat object, a 56 kg representative LEO satellite, was subjected to a hypervelocity impact in April 2014. For the hypervelocity test, the representative satellite was suspended within a "soft-catch" arena formed by polyurethane foam panels to minimize the interactions between the debris generated from the hypervelocity impact and the metallic walls of the test chamber. After the impact, the foam panels and debris not caught by the panels were collected and shipped to the University of Florida where the project has now advanced to the debris characterization stage. The characterization effort has been divided into debris collection, measurement, and cataloguing. Debris collection and cataloguing involves the retrieval of debris from the foam panels and cataloguing the debris in a database. Debris collection is a three-step process: removal of loose debris fragments from the surface of the foam panels; X-ray imaging to identify/locate debris fragments embedded within the foam panel; extraction of the embedded debris fragments identified during the X-ray imaging process. As debris fragments are collected, they are catalogued into a database specifically designed for this project. Measurement involves determination of size, mass, shape, material, and other physical properties and well as images of the fragment. Cataloguing involves a assigning a unique identifier for each fragment along with the characterization information.

  5. FIRST-LIGHT LBT NULLING INTERFEROMETRIC OBSERVATIONS: WARM EXOZODIACAL DUST RESOLVED WITHIN A FEW AU OF η Crv

    SciTech Connect

    Defrère, D.; Hinz, P. M.; Skemer, A. J.; Bailey, V. P.; Hoffmann, W. F.; Arbo, P.; Brusa, G.; Downey, E. C.; Durney, O.; Gaspar, A.; Grenz, P.; Kennedy, G. M.; Mennesson, B.; Bryden, G.; Millan-Gabet, R.; Beichman, C.; Danchi, W. C.; Absil, O.; Esposito, S.; Haniff, C.; and others

    2015-01-20

    We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81-12.41 μm) emission around the nearby main-sequence star η Crv (F2V, 1-2 Gyr). The measured source null depth amounts to 4.40% ± 0.35% over a field-of-view of 140 mas in radius (∼2.6 AU for the distance of η Crv) and shows no significant variation over 35° of sky rotation. This relatively low null is unexpected given the total disk to star flux ratio measured by the Spitzer Infrared Spectrograph (IRS; ∼23% across the N' band), suggesting that a significant fraction of the dust lies within the central nulled response of the LBTI (79 mas or 1.4 AU). Modeling of the warm disk shows that it cannot resemble a scaled version of the solar zodiacal cloud unless it is almost perpendicular to the outer disk imaged by Herschel. It is more likely that the inner and outer disks are coplanar and the warm dust is located at a distance of 0.5-1.0 AU, significantly closer than previously predicted by models of the IRS spectrum (∼3 AU). The predicted disk sizes can be reconciled if the warm disk is not centrosymmetric, or if the dust particles are dominated by very small grains. Both possibilities hint that a recent collision has produced much of the dust. Finally, we discuss the implications for the presence of dust for the distance where the insolation is the same as Earth's (2.3 AU)

  6. Space Debris & its Mitigation

    NASA Astrophysics Data System (ADS)

    Kaushal, Sourabh; Arora, Nishant

    2012-07-01

    Space debris has become a growing concern in recent years, since collisions at orbital velocities can be highly damaging to functioning satellites and can also produce even more space debris in the process. Some spacecraft, like the International Space Station, are now armored to deal with this hazard but armor and mitigation measures can be prohibitively costly when trying to protect satellites or human spaceflight vehicles like the shuttle. This paper describes the current orbital debris environment, outline its main sources, and identify mitigation measures to reduce orbital debris growth by controlling these sources. We studied the literature on the topic Space Debris. We have proposed some methods to solve this problem of space debris. We have also highlighted the shortcomings of already proposed methods by space experts and we have proposed some modification in those methods. Some of them can be very effective in the process of mitigation of space debris, but some of them need some modification. Recently proposed methods by space experts are maneuver, shielding of space elevator with the foil, vaporizing or redirecting of space debris back to earth with the help of laser, use of aerogel as a protective layer, construction of large junkyards around international space station, use of electrodynamics tether & the latest method proposed is the use of nano satellites in the clearing of the space debris. Limitations of the already proposed methods are as follows: - Maneuvering can't be the final solution to our problem as it is the act of self-defence. - Shielding can't be done on the parts like solar panels and optical devices. - Vaporizing or redirecting of space debris can affect the human life on earth if it is not done in proper manner. - Aerogel has a threshold limit up to which it can bear (resist) the impact of collision. - Large junkyards can be effective only for large sized debris. In this paper we propose: A. The Use of Nano Tubes by creating a mesh

  7. A New Offset Debris Ring around a Nearby Star Observed with the HST/STIS

    NASA Technical Reports Server (NTRS)

    Krist, John; Stapelfeldt, Karl; Bryden, Geoffrey

    2011-01-01

    We are conducting an HST/STIS coronagraphic imaging study of nearby stars that have Spitzer-measured infrared excesses indicating that they are surrounded by debris disks. Around one of the stars we have imaged a debris ring with a sharp inner edge and extending from about 165 AU to 250 AU. The ring center is offset from the star by -8 AU with a visually estimated intrinsic ellipticity of e-0.1 , suggestive of gravitational perturbation of the disk by a planet, like the Fomalhaut disk. Assuming a neutral disk color, the mean surface brightness of V=22.3 mag/square arcsec makes this the second faintest disk yet imaged in scattered light, second to HD 207129.

  8. Disk filter

    DOEpatents

    Bergman, W.

    1985-01-09

    An electric disk filter provides a high efficiency at high temperature. A hollow outer filter of fibrous stainless steel forms the ground electrode. A refractory filter material is placed between the outer electrode and the inner electrically isolated high voltage electrode. Air flows through the outer filter surfaces through the electrified refractory filter media and between the high voltage electrodes and is removed from a space in the high voltage electrode.

  9. Disk filter

    DOEpatents

    Bergman, Werner

    1986-01-01

    An electric disk filter provides a high efficiency at high temperature. A hollow outer filter of fibrous stainless steel forms the ground electrode. A refractory filter material is placed between the outer electrode and the inner electrically isolated high voltage electrode. Air flows through the outer filter surfaces through the electrified refractory filter media and between the high voltage electrodes and is removed from a space in the high voltage electrode.

  10. Formation of Phobos and Deimos in an extended circum-Martian accretion disk

    NASA Astrophysics Data System (ADS)

    Rosenblatt, Pascal; Charnoz, Sébastien; Dunseath-Terao, Mariko; Dunseath, Kevin; Trinh, Antony

    2015-11-01

    Recent exploration of Phobos by Mars Express has renewed the interest in the origin of the Martian moons, which remains an open issue. New studies have recently focused on accretion of debris in a circum-Martian disk. Craddock (Icarus, 2011) has proposed a scenario of formation of such a disk (about 10-4 to 10-3 % the mass of Mars) from a giant collision occurred early in Mars' history. Rosenblatt and Charnoz (Icarus, 2012) have shown that moonlets can be formed, with Phobos and Deimos masses, in a compact disk close to the planet. Nevertheless, the orbit of these moonlets rapidly recedes back to Mars and the moonlet system vanishes in much less than 1 Gy.Citron at al. (Icarus, 2015) have modeled the formation of a disk of debris resulting from a giant collision but with a larger mass (0.1 % of Mars' mass) than in Craddock (2011). They have shown that most of the disk mass is concentrated close to the planet but a small part can extend beyond the synchronous limit (6 Mars' radii).We study here the accretion of debris in an extended disk, focusing in the edge of this disk where surface density of material is the lowest. However, we take into account the gravitational influence of the more massive bodies formed in the denser part of the disk. Our results highlight the driven mechanisms of accretion in a circum-Martian disk of debris.

  11. Benefits of Active Debris Removal on the LEO Debris Population

    NASA Astrophysics Data System (ADS)

    Maniwa, Kazuaki; Hanada, Toshiya; Kawamoto, Satomi

    Since the launch of Sputnik, orbital debris population continues to increase due to ongoing space activities, on-orbit explosions, and accidental collisions. In the future, a great deal of fragments can be expected to be created by explosions and collisions. In spite of prevention of satellite and rocket upper stage explosions and other mitigation measures, debris population in low Earth orbit may not be stabilized. To better limit the growth of the future debris population, it is necessary to remove the existing debris actively. This paper studies about the effectiveness of active debris removal in low Earth orbit where the collision rate with and between space debris is high. This study does not consider economic problems, but investigates removing debris which may stabilize well the current debris population based on the concept of Japan Aerospace Exploration Agency.

  12. Meteoroid/Debris Shielding

    NASA Technical Reports Server (NTRS)

    Christiansen, Eric L.

    2003-01-01

    This report provides innovative, low-weight shielding solutions for spacecraft and the ballistic limit equations that define the shield's performance in the meteoroid/debris environment. Analyses and hypervelocity impact testing results are described that have been used in developing the shields and equations. Spacecraft shielding design and operational practices described in this report are used to provide effective spacecraft protection from meteoroid and debris impacts. Specific shield applications for the International Space Station (ISS), Space Shuttle Orbiter and the CONTOUR (Comet Nucleus Tour) space probe are provided. Whipple, Multi-Shock and Stuffed Whipple shield applications are described.

  13. The Vela pulsar with an active fallback disk

    SciTech Connect

    Özsükan, Gökçe; Ekşi, K. Yavuz; Hambaryan, Valeri; Neuhäuser, Ralph; Hohle, Markus M.; Ginski, Christian; Werner, Klaus

    2014-11-20

    Fallback disks are expected to form around young neutron stars. The presence of these disks can be revealed by their blackbody spectrum in the infrared, optical, and UV bands. We present a re-reduction of the archival optical and infrared data of the Vela pulsar, together with the existing infrared and UV spectrum of Vela, and model their unpulsed components with the blackbody spectrum of a supernova debris disk. We invoke the quiescent disk solution of Sunyaev and Shakura for the description of the disk in the propeller stage and find the inner radius of the disk to be inside the light cylinder radius. We perform a high-resolution X-ray analysis with XMM-Newton and find a narrow absorption feature at 0.57 keV that can be interpreted as the K {sub α} line of He-like oxygen (O VII). The strength of the line indicates an element over-abundance in our line of sight exceeding the amounts that would be expected from interstellar medium. The spectral feature may originate from the pulsar wind nebula and may be partly caused by the reprocessed X-ray radiation by the fallback disk. We discuss the lower-than-three braking index of Vela as partially due to the contribution of the propeller torques. Our results suggest that the pulsar mechanism can work simultaneously with the propeller processes and that the debris disks can survive the radiation pressure for at least ∼10{sup 4} yr. As Vela is a relatively close object, and a prototypical pulsar, the presence of a disk, if confirmed, may indicate the ubiquity of debris disks around young neutron stars.

  14. Orbital Debris: A Policy Perspective

    NASA Technical Reports Server (NTRS)

    Johnson, Nicholas L.

    2007-01-01

    A viewgraph presentation describing orbital debris from a policy perspective is shown. The contents include: 1) Voyage through near-Earth Space-animation; 2) What is Orbital Debris?; 3) Orbital Debris Detectors and Damage Potential; 4) Hubble Space Telescope; 5) Mir Space Station Solar Array; 6) International Space Station; 7) Space Shuttle; 8) Satellite Explosions; 9) Satellite Collisions; 10) NASA Orbital Debris Mitigation Guidelines; 11) International Space Station Jettison Policy; 12) Controlled/Uncontrolled Satellite Reentries; 13) Return of Space Objects; 14) Orbital Debris and U.S. National Space Policy; 15) U.S Government Policy Strategy; 16) Bankruptcy of the Iridium Satellite System; 17) Inter-Agency Space Debris Coordination Committee (IADC); 18) Orbital Debris at the United Nations; 19) Chinese Anti-satellite System; 20) Future Evolution of Satellite Population; and 21) Challenge of Orbital Debris

  15. In Brief: Marine debris plan

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2008-09-01

    A new U.S. federal interagency report on preventing and reducing marine debris focuses on responses to debris already in the environment, prevention of debris, research and development, and coordination among agencies. The report, released on 22 September, was prepared by 11 federal agencies and is intended to guide the strategies of federal agencies and the Interagency Marine Debris Coordinating Committee. The report is available at http://ocean.ceq.gov/about/docs/SIMOR_IMDCC_Report.pdf.

  16. THE NATURE OF TRANSITION CIRCUMSTELLAR DISKS. II. SOUTHERN MOLECULAR CLOUDS

    SciTech Connect

    Romero, Gisela A.; Schreiber, Matthias R.; Rebassa-Mansergas, Alberto; Cieza, Lucas A.; Merin, Bruno; Smith Castelli, Analia V.; Allen, Lori E.; Morrell, Nidia

    2012-04-10

    Transition disk objects are pre-main-sequence stars with little or no near-IR excess and significant far-IR excess, implying inner opacity holes in their disks. Here we present a multifrequency study of transition disk candidates located in Lupus I, III, IV, V, VI, Corona Australis, and Scorpius. Complementing the information provided by Spitzer with adaptive optics (AO) imaging (NaCo, VLT), submillimeter photometry (APEX), and echelle spectroscopy (Magellan, Du Pont Telescopes), we estimate the multiplicity, disk mass, and accretion rate for each object in our sample in order to identify the mechanism potentially responsible for its inner hole. We find that our transition disks show a rich diversity in their spectral energy distribution morphology, have disk masses ranging from {approx}<1 to 10 M{sub JUP}, and accretion rates ranging from {approx}<10{sup -11} to 10{sup -7.7} M{sub Sun} yr{sup -1}. Of the 17 bona fide transition disks in our sample, three, nine, three, and two objects are consistent with giant planet formation, grain growth, photoevaporation, and debris disks, respectively. Two disks could be circumbinary, which offers tidal truncation as an alternative origin of the inner hole. We find the same heterogeneity of the transition disk population in Lupus III, IV, and Corona Australis as in our previous analysis of transition disks in Ophiuchus while all transition disk candidates selected in Lupus V, VI turned out to be contaminating background asymptotic giant branch stars. All transition disks classified as photoevaporating disks have small disk masses, which indicates that photoevaporation must be less efficient than predicted by most recent models. The three systems that are excellent candidates for harboring giant planets potentially represent invaluable laboratories to study planet formation with the Atacama Large Millimeter/Submillimeter Array.

  17. An MCMC Circumstellar Disks Modeling Tool

    NASA Astrophysics Data System (ADS)

    Wolff, Schuyler; Perrin, Marshall D.; Mazoyer, Johan; Choquet, Elodie; Soummer, Remi; Ren, Bin; Pueyo, Laurent; Debes, John H.; Duchene, Gaspard; Pinte, Christophe; Menard, Francois

    2016-01-01

    We present an enhanced software framework for the Monte Carlo Markov Chain modeling of circumstellar disk observations, including spectral energy distributions and multi wavelength images from a variety of instruments (e.g. GPI, NICI, HST, WFIRST). The goal is to self-consistently and simultaneously fit a wide variety of observables in order to place constraints on the physical properties of a given disk, while also rigorously assessing the uncertainties in the derived properties. This modular code is designed to work with a collection of existing modeling tools, ranging from simple scripts to define the geometry for optically thin debris disks, to full radiative transfer modeling of complex grain structures in protoplanetary disks (using the MCFOST radiative transfer modeling code). The MCMC chain relies on direct chi squared comparison of model images/spectra to observations. We will include a discussion of how best to weight different observations in the modeling of a single disk and how to incorporate forward modeling from PCA PSF subtraction techniques. The code is open source, python, and available from github. Results for several disks at various evolutionary stages will be discussed.

  18. Space debris- ECSL Study

    NASA Astrophysics Data System (ADS)

    Lafferranderie, G.

    2002-01-01

    Despite several attempts and despite the worldwide recognition of the need of attacking it, the space debris legal issues has not been put in the agenda as a separate issue on the agenda of the COPUOS Legal Subcommittee. However for the first time, mention will appear in 2002 but only under item 5 of the Legal Subcommittee: report of activities of international organisations, here the European Centre for Space Law (ECSL). ECSL report will describe the method followed, a questionnaire widely distributed to interested persons and on a personal basis. The questionnaire tries to identify the basic concerns. From the responses received and from also analysis of positions expressed in various colloquia, articles, etc. some directions could be drawn up: do we need a "legal definition" of space debris? For which purposes? Are we in a situation fro presenting now such a legal definition able to cope with the technical evolution of the space object? Which type of legal or technical description "instrument" will be the most appropriate? Etc. One particular question is emerging: the basis of the liability for damages caused in outer space. The author wish is simply to draw the attention on concrete, immediate concerns while identifying also simple ways able to offer a framework to deal with the legal impacts coming from space debris issue. I have envisioned two other subjects that I have abandoned: .

  19. The Evolution of a Planet-Forming Disk (Artist's Concept Animation)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This animation shows the evolution of a planet-forming disk around a star. Initially, the young disk is bright and thick with dust, providing raw materials for building planets. In the first 10 million years or so, gaps appear within the disk as newborn planets coalesce out of the dust, clearing out a path.

    In time, this planetary 'debris disk' thins out as gravitational interactions with numerous planets slowly sweep away the dust. Steady pressure from the starlight and solar winds also blows out the dust. After a few billion years, only a thin ring remains in the outermost reaches of the system, a faint echo of the once-brilliant disk.

    Our own solar system has a similar debris disk -- a ring of comets called the Kuiper Belt. Leftover dust in the inner portion of the solar system is known as 'zodiacal dust.'

    Bright, young disks can be imaged directly by visible-light telescopes, such as NASA's Hubble Space Telescope. Older, fainter debris disks can be detected only by infrared telescopes like NASA's Spitzer Space Telescope, which sense the disks' dim heat.

  20. THE LONG-LIVED DISKS IN THE {eta} CHAMAELEONTIS CLUSTER

    SciTech Connect

    Sicilia-Aguilar, Aurora; Bouwman, Jeroen; Juhasz, Attila; Henning, Thomas; Roccatagliata, Veronica; Lawson, Warrick A.; Acke, Bram; Decin, Leen; Feigelson, Eric D.; Tielens, A. G. G. M.; Meeus, Gwendolyn

    2009-08-20

    We present Infrared Spectrograph spectra and revised Multiband Imaging Photometer photometry for the 18 members of the {eta} Chamaeleontis cluster. Aged 8 Myr, the {eta} Cha cluster is one of the few nearby regions within the 5-10 Myr age range, during which the disk fraction decreases dramatically and giant planet formation must come to an end. For the 15 low-mass members, we measure a disk fraction {approx}50%, high for their 8 Myr age, and four of the eight disks lack near-IR excesses, consistent with the empirical definition of 'transition' disks. Most of the disks are comparable to geometrically flat disks. The comparison with regions of different ages suggests that at least some of the 'transition' disks may represent the normal type of disk around low-mass stars. Therefore, their flattened structure and inner holes may be related to other factors (initial masses of the disk and the star, environment, binarity), rather than to pure time evolution. We analyze the silicate dust in the disk atmosphere, finding moderate crystalline fractions ({approx}10%-30%) and typical grain sizes {approx}1-3 {mu}m, without any characteristic trend in the composition. These results are common to other regions of different ages, suggesting that the initial grain processing occurs very early in the disk lifetime (<1 Myr). Large grain sizes in the disk atmosphere cannot be used as a proxy for age, but are likely related to higher disk turbulence. The dust mineralogy varies between the 8-12 {mu}m and the 20-30 {mu}m features, suggesting high temperature dust processing and little radial mixing. Finally, the analysis of IR and optical data on the B9 star {eta} Cha reveals that it is probably surrounded by a young debris disk with a large inner hole, instead of being a classical Be star.

  1. The Nature of Transition Disks in Nearby Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Cieza, Lucas A.; Schreiber, M. R.; Romero, G. A.; Orellana, M.; Williams, J. P.; Merin, B.

    2011-01-01

    We present an update on our ongoing project to characterize a large sample of Spitzer selected transition disks located in several star-forming regions. Transition objects are pre-main-sequence stars with optically thin inner disks and optically thick outer disks. Different mechanisms have been proposed to explain their inner opacity holes: planet formation, grain growth, photoevaporation, and tidal truncation in tight binaries. These mechanisms, all relevant to disk evolution in general, can be distinguished when disk masses, accretion rates, and multiplicity information are available. We have already completed our study of Ophiuchus objects, presenting the results from Adaptive Optics (AO) imaging, submillimeter photometry, and echelle spectroscopy observations. We are currently working on several other regions, including Taurus-Auriga, Perseus, Serpens, and Lupus. Our results show that transition disks are a very heterogeneous group of objects with a wide range of SED morphologies, disk masses ( < 0.5 to 40 Mjup), and accretion rates (<10E-11 to 10E-7 Msolar/yr). Since the properties of our transition disks point toward distinct processes driving the evolution of each disk, we have been able to identify very strong candidates for the following disk categories: circumbinary disks, grain-growth dominated disks, photoevaporating disks, debris disks, and (giant) planet-forming disks.

  2. Current Issues in Orbital Debris

    NASA Technical Reports Server (NTRS)

    Johnson, Nicholas L.

    2011-01-01

    During the past two decades, great strides have been made in the international community regarding orbital debris mitigation. The majority of space-faring nations have reached a consensus on an initial set of orbital debris mitigation measures. Implementation of and compliance with the IADC and UN space debris mitigation guidelines should remain a high priority. Improvements of the IADC and UN space debris mitigation guidelines should continue as technical consensus permits. The remediation of the near-Earth space environment will require a significant and long-term undertaking.

  3. Microplastic debris in sandhoppers

    NASA Astrophysics Data System (ADS)

    Ugolini, A.; Ungherese, G.; Ciofini, M.; Lapucci, A.; Camaiti, M.

    2013-09-01

    Adults of the sandhopper Talitrus saltator were fed with dry fish food mixed with polyethylene microspheres (diameter 10-45 μm). Observations of homogenized guts revealed the presence of microspheres independently of their dimensions. The gut resident time (GRT) was recorded and most of the microspheres are expelled in 24 h. Microspheres are totally expelled in one week. Preliminary investigations did not show any consequence of microsphere ingestion on the survival capacity in the laboratory. FT-IR analyses carried out on faeces of freshly collected individuals revealed the presence of polyethylene and polypropylene. This confirms that microplastic debris could be swallowed by T. saltator in natural conditions.

  4. Space Debris Hazard Evaluation

    NASA Technical Reports Server (NTRS)

    Davison, Elmer H.; Winslow, Paul C., Jr.

    1961-01-01

    The hazard to space vehicles from natural space debris has been explored. A survey of the available information pertinent to this problem is presented. The hope is that this presentation gives a coherent picture of the knowledge to date in terms of the topic covered. The conclusion reached is that a definite hazard exists but that it can only be poorly assessed on the basis of present information. The need for direct measurement of this hazard is obvious, and some of the problems involved in making these direct measurements have been explored.

  5. Evolution and precession of accretion disk in tidal disruption events

    NASA Astrophysics Data System (ADS)

    Shen, R.-F.; Matzner, C. D.

    2012-12-01

    In a supermassive black hole (BH) tidal disruption event (TDE), the tidally disrupted star feeds the BH via an accretion disk. Most often it is assumed that the accretion rate history, hence the emission light curve, tracks the rate at which new debris mass falls back onto the disk, notably the t-5/3 power law. But this is not the case when the disk evolution due to viscous spreading - the driving force for accretion - is carefully considered. We construct a simple analytical model that comprehensively describes the accretion rate history across 4 different phases of the disk evolution, in the presence of mass fallback and disk wind loss. Accretion rate evolves differently in those phases which are governed by how the disk heat energy is carried away, early on by advection and later by radiation. The accretion rate can decline as steeply as t-5/3 only if copious disk wind loss is present during the early advection-cooled phase. Later, the accretion rate history is t-8/7 or shallower. These have great implications on the TDE flare light curve. A TDE accretion disk is most likely misaligned with the equatorial plane of the spinning BH. Moreover, in the TDE the accretion rate is super- or near-Eddington thus the disk is geometrically thick, for which case the BH's frame dragging effect may cause the disk precess as a solid body, which may manifest itself as quasi-periodic signal in the TDE light curve. Our disk evolution model predicts the disk precession period increases with time, typically as ∝ t. The results are applied to the recently jetted TDE flare Swift transient J1644 + 57 which shows numerous, quasi-periodic dips in its long-term X-ray light curve. As the current TDE sample increases, the identification of the disk precession signature provides a unique way of measuring BH spin and studying BH accretion physics.

  6. DiskDetective.org: Finding Homes for Exoplanets Through Citizen Science

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc J.

    2016-01-01

    The Disk Detective project is scouring the data archive from the WISE all-sky survey to find new debris disks and protoplanetary disks-the dusty dens where exoplanets form and dwell. Volunteers on this citizen science website have already performed 1.6 million classifications, searching a catalog 8x the size of any published WISE survey. We follow up candidates using ground based telescopes in California, Arizona, Chile, Hawaii, and Argentina. We ultimately expect to increase the pool of known debris disks by approx. 400 and triple the solid angle in clusters of young stars examined with WISE, providing a unique new catalog of isolated disk stars, key planet-search targets, and candidate advanced extraterrestrial civilizations. Come to this talk to hear the news about our latest dusty discoveries and the trials and the ecstasy of launching a new citizen science project. Please bring your laptop or smartphone if you like!

  7. Disk Alloy Development

    NASA Technical Reports Server (NTRS)

    Gabb, Tim; Gayda, John; Telesman, Jack

    2001-01-01

    The advanced powder metallurgy disk alloy ME3 was designed using statistical screening and optimization of composition and processing variables in the NASA HSR/EPM disk program to have extended durability at 1150 to 1250 "Fin large disks. Scaled-up disks of this alloy were produced at the conclusion of this program to demonstrate these properties in realistic disk shapes. The objective of the UEET disk program was to assess the mechanical properties of these ME3 disks as functions of temperature, in order to estimate the maximum temperature capabilities of this advanced alloy. Scaled-up disks processed in the HSR/EPM Compressor / Turbine Disk program were sectioned, machined into specimens, and tested in tensile, creep, fatigue, and fatigue crack growth tests by NASA Glenn Research Center, in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. Additional sub-scale disks and blanks were processed and tested to explore the effects of several processing variations on mechanical properties. Scaled-up disks of an advanced regional disk alloy, Alloy 10, were used to evaluate dual microstructure heat treatments. This allowed demonstration of an improved balance of properties in disks with higher strength and fatigue resistance in the bores and higher creep and dwell fatigue crack growth resistance in the rims. Results indicate the baseline ME3 alloy and process has 1300 to 1350 O F temperature capabilities, dependent on detailed disk and engine design property requirements. Chemistry and process enhancements show promise for further increasing temperature capabilities.

  8. Orbital Debris Studies at NASA

    NASA Technical Reports Server (NTRS)

    Stansbery, Gene; Krisko, Paula; Whitlock, Dave

    2007-01-01

    Any discussion of expanding the capabilities of Space Surveillance Networks to include tracking and cataloging smaller objects will require a good understanding of orbital debris. In the current U.S. catalog of over 11,000 objects, more than 50% are classified as "debris" to include fragmentation debris, operational debris, liquid metal coolant, and Westford needles. If the catalog is increased to 100,000 objects by lowering the tracked object size threshold, almost all of the additional objects will be orbital debris. The Orbital Debris Program Office has been characterizing the small orbital debris environment through measurements and modeling for many years. This presentation will specifically discuss two different studies conducted at NASA. The first study was done in 1992 and examined the requirements and produced a conceptual design for a Collision Avoidance Network to protect the Space Station Freedom from centimeter sized orbital debris while minimizing maneuvers. The second study was conducted last year and produced NASA s estimate of the orbital population for the years 2015 and 2030 for objects 2 cm and larger.

  9. Seabirds and floating plastic debris.

    PubMed

    Cadée, Gerhard C

    2002-11-01

    80% of floating plastic debris freshly washed ashore on a Dutch coast showed peckmarks made by birds at sea. They either mistake these debris for cuttlebones or simply test all floating objects. Ingestion of plastic is deleterious for marine organisms. It is urgent to set measures to plastic litter production.

  10. Space debris modeling at NASA

    NASA Astrophysics Data System (ADS)

    Johnson, Nicholas L.

    2001-10-01

    Since the Second European Conference on Space Debris in 1997, the Orbital Debris Program Office at the NASA Johnson Space Center has undertaken a major effort to update and improve the principal software tools employed to model the space debris environment and to evaluate mission risks. NASA's orbital debris engineering model, ORDEM, represents the current and near-term Earth orbital debris population from the largest spacecraft to the smallest debris in a manner which permits spacecraft engineers and experimenters to estimate the frequency and velocity with which a satellite may be struck by debris of different sizes. Using expanded databases and a new program design, ORDEM2000 provides a more accurate environment definition combined with a much broader array of output products in comparison with its predecessor, ORDEM96. Studies of the potential long-term space debris environment are now conducted with EVOVLE 4.0, which incorporates significant advances in debris characterization and breakup modeling. An adjunct to EVOLVE 4.0, GEO EVOLVE has been created to examine debris issues near the geosynchronous orbital regime. In support of NASA Safety Standard (NSS) 1740.14, which establishes debris mitigation guidelines for all NASA space programs, a set of evaluation tools called the Debris Assessment Software (DAS) is specifically designed for program offices to determine whether they are in compliance with NASA debris mitigation guidelines. DAS 1.5 has recently been completed with improved WINDOWS compatibility and graphics functions. DAS 2.0 will incorporate guideline changes in a forthcoming revision to NSS 1740.14. Whereas DAS contains a simplified model to calculate possible risks associated with satellite reentries, NASA's higher fidelity Object Reentry Survival Analysis Tool (ORSAT) has been upgraded to Version 5.0. With the growing awareness of the potential risks posed by uncontrolled satellite reentries to people and property on Earth, the application of

  11. IMAGES OF THE EXTENDED OUTER REGIONS OF THE DEBRIS RING AROUND HR 4796 A

    SciTech Connect

    Thalmann, C.; Dominik, C.; Janson, M.; Buenzli, E.; Brandt, T. D.; Wisniewski, J. P.; Moro-Martin, A.; Schneider, G.; Carson, J.; McElwain, M. W.; Grady, C. A.; Goto, M.; Brandner, W.; Feldt, M.; Abe, L.; Fukue, T.; and others

    2011-12-10

    We present high-contrast images of HR 4796 A taken with Subaru/HiCIAO in the H band, resolving the debris disk in scattered light. The application of specialized angular differential imaging methods allows us to trace the inner edge of the disk with high precision and reveals a pair of 'streamers' extending radially outward from the ansae. Using a simple disk model with a power-law surface brightness profile, we demonstrate that the observed streamers can be understood as part of the smoothly tapered outer boundary of the debris disk, which is most visible at the ansae. Our observations are consistent with the expected result of a narrow planetesimal ring being ground up in a collisional cascade, yielding dust with a wide range of grain sizes. Radiation forces leave large grains in the ring and push smaller grains onto elliptical or even hyperbolic trajectories. We measure and characterize the disk's surface brightness profile, and confirm the previously suspected offset of the disk's center from the star's position along the ring's major axis. Furthermore, we present first evidence for an offset along the minor axis. Such offsets are commonly viewed as signposts for the presence of unseen planets within a disk's cavity. Our images also offer new constraints on the presence of companions down to the planetary mass regime ({approx}9 M{sub Jup} at 0.''5, {approx}3 M{sub Jup} at 1'').

  12. Images of the Extended Outer Regions of the Debris Ring around HR 4796 A

    NASA Technical Reports Server (NTRS)

    Thalmann, C.; Janson, M.; Buenzli, E.; Brandt, T. D.; Wisniewski, J. P.; Moro-Martin, A.; Usuda, T.; Schneider, G.; Carson, J.; McElwain, M. W.; Grady, C. A.; Goto, M.; Abe, L.; Brandner, W.; Dominik, C.; Egner, S.; Feldt, M.; Fukue, T.; Golota, T.; Guyon, O.; Hashimoto, J.; Hayano, Y.; Hayashi, M.; Hayashi, S.; Serabyn, E.

    2012-01-01

    We present high-contrast images of HR 4796 A taken with Subaru/HiCIAO in H-band, resolving the debris disk in scattered light. The application of specialized angular differential imaging methods (ADI) allows us to trace the inner edge of the disk with high precision, and reveals a pair of "streamers" extending radially outwards from the ansae. Using a simple disk model with a power-law surface brightness profile, we demonstrate that the observed streamers can be understood as part of the smoothly tapered outer boundary of the debris disk, which is most visible at the ansae. Our observations are consistent with the expected result of a narrow planetesimal ring being ground up in a collisional cascade, yielding dust with a wide range of grain sizes. Radiation forces leave large grains in the ring and push smaller grains onto elliptical, or even hyperbolic trajectories. We measure and characterize the disk's surface brightness profile, and confirm the previously suspected offset of the disk's center from the star's position along the ring's major axis. Furthermore, we present first evidence for an offset along the minor axis. Such offsets are commonly viewed as signposts for the presence of unseen planets within a disk's cavity. Our images also offer new constraints on the presence of companions down to the planetary mass regime (approx 9 M(sub Jup) at 0".5, approx 3 M(sub Jup) at 1").

  13. An Introduction to Space Debris

    NASA Astrophysics Data System (ADS)

    Wright, David

    2008-04-01

    Space debris is any human-made object in orbit that no longer serves a useful purpose, including defunct satellites, discarded equipment and rocket stages, and fragments from the breakup of satellites and rocket stages. It is a concern because--due to its very high speed in orbit--even relatively small pieces can damage or destroy satellites in a collision. Since debris at high altitudes can stay in orbit for decades or longer, it accumulates as more is produced and the risk of collisions with satellites grows. Since there is currently no effective way to remove large amounts of debris from orbit, controlling the production of debris is essential for preserving the long-term use of space. Today there are 860 active satellites in orbit, supporting a wide range of civil and military uses. The 50 years of space activity since the launch of Sputnik 1 has also resulted in well over half a million pieces of orbiting debris larger than 1 cm in size. There are two main sources of space debris: (1) routine space activity and the accidental breakup of satellites and stages placed in orbit by such activity, and (2) the testing or use of destructive anti-satellite (ASAT) weapons that physically collide with satellites at high speed. The international community is attempting to reduce the first category by developing strict guidelines to limit the debris created as a result of routine space activities. However, the destruction of a single large spy satellite by an ASAT weapon could double the total amount of large debris in low earth orbit, and there are currently no international restrictions on these systems. This talk will give an introduction to what's in space, the origins of space debris, efforts to stem its growth, the threat it poses to satellites in orbit, and the long-term evolution of the debris population.

  14. DEBRIS DISTRIBUTION IN HD 95086—A YOUNG ANALOG OF HR 8799

    SciTech Connect

    Su, Kate Y. L.; Smith, Paul S.; Rieke, George H.; Morrison, Sarah; Malhotra, Renu; Balog, Zoltan

    2015-02-01

    HD 95086 is a young early-type star that hosts (1) a 5 M{sub J} planet at the projected distance of 56 AU revealed by direct imaging, and (2) a prominent debris disk. Here we report the detection of 69 μm crystalline olivine feature from the disk using the Spitzer/MIPS-SED data covering 55-95 μm. Due to the low resolution of the MIPS-SED mode, this feature is not spectrally resolved, but is consistent with the emission from crystalline forsterite contributing ∼5% of the total dust mass. We also present detailed analysis of the disk spectral energy distribution and re-analysis of resolved images obtained by Herschel. Our results suggest that the debris structure around HD 95086 consists of a warm (∼175 K) belt, a cold (∼55 K) disk, and an extended disk halo (up to ∼800 AU), and is very similar to that of HR 8799. We compare the properties of the three debris components, and suggest that HD 95086 is a young analog of HR 8799. We further investigate and constrain single-planet, two-planet, three-planet, and four-planet architectures that can account for the observed debris structure and are compatible with dynamical stability constraints. We find that equal-mass four-planet configurations of geometrically spaced orbits, with each planet of mass ∼ 5 M{sub J} , could maintain the gap between the warm and cold debris belts, and also be just marginally stable for timescales comparable to the age of the system.

  15. VLT imaging of the β Pictoris gas disk

    NASA Astrophysics Data System (ADS)

    Nilsson, R.; Brandeker, A.; Olofsson, G.; Fathi, K.; Thébault, Ph.; Liseau, R.

    2012-08-01

    Context. Circumstellar debris disks older than a few Myr should be largely devoid of primordial gas remaining from the protoplanetary disk phase. Tracing the origin of observed atomic gas in Keplerian rotation in the edge-on debris disk surrounding the ~12 Myr old star β Pictoris requires more detailed information about its spatial distribution than has previously been acquired by limited slit spectroscopy. Especially indications of asymmetries and presence of Ca ii gas at high disk latitudes call for additional investigation to exclude or confirm its connection to observed dust structures or suggested cometary bodies on inclined eccentric orbits. Aims: We set out to recover a complete image of the Fe i and Ca ii gas emission around β Pic by spatially resolved, high-resolution spectroscopic observations to better understand the morphology and origin of the gaseous disk component. Methods: The multiple fiber facility FLAMES/GIRAFFE at the Very Large Telescope (VLT), with the large integral-field-unit ARGUS, was used to obtain spatially resolved optical spectra (from 385.9 to 404.8 nm) in four regions covering the northeast and southwest side of the disk. Emission lines from Fe i (at 386.0 nm) and Ca ii (at 393.4 and 396.8 nm) were mapped and could be used to fit a parametric function for the disk gas distribution, using a gas-ionisation code for gas-poor debris disks. Results: Both Fe i and Ca ii emission are clearly detected, with the former dominating along the disk midplane, and the latter revealing vertically more extended gas. The surface intensity of the Fe i emission is lower but more extended in the northeast (reaching the 210 AU limit of our observations) than in the southwest, while Ca ii shows the opposite asymmetry. The modelled Fe gas disk profile shows a linear increase in scale height with radius, and a vertical profile that suggests dynamical interaction with the dust. We also qualitatively demonstrate that the Ca ii emission profile can be

  16. Implementation of the hazardous debris rule

    SciTech Connect

    Sailer, J.E.

    1993-01-05

    Hazardous debris includes objects contaminated with hazardous waste. Examples of debris include tree stumps, timbers, boulders, tanks, piping, crushed drums, personal protective clothing, etc. Most of the hazardous debris encountered comes from Superfund sites and other facility remediation, although generators and treaters of hazardous waste also generate hazardous debris. Major problems associated with disposal of debris includes: Inappropriateness of many waste treatments to debris; Difficulties in obtaining representative samples; Costs associated with applying waste specific treatments to debris; Subtitle C landfill space was being used for many low hazard debris types. These factors brought about the need for debris treatment technologies and regulations that addressed these issues. The goal of such regulation was to provide treatment to destroy or remove the contamination if possible and, if this is achieved, to dispose of the cleaned debris as a nonhazardous waste. EPA has accomplished this goal through promulgation of the Hazardous Debris Rule, August 18, 1992.

  17. JSC Orbital Debris Website Description

    NASA Astrophysics Data System (ADS)

    Johnson, Nicholas L.

    2006-01-01

    Purpose: The website provides information about the NASA Orbital Debris Program Office at JSC, which is the lead NASA center for orbital debris research. It is recognized world-wide for its leadership in addressing orbital debris issues. The NASA Orbital Debris Program Office has taken the international lead in conducting measurements of the environment and in developing the technical consensus for adopting mitigation measures to protect users of the orbital environment. Work at the center continues with developing an improved understanding of the orbital debris environment and measures that can be taken to control its growth. Major Contents: Orbital Debris research is divided into the following five broad efforts. Each area of research contains specific information as follows: 1) Modeling - NASA scientists continue to develop and upgrade orbital debris models to describe and characterize the current and future debris environment. Evolutionary and engineering models are described in detail. Downloadable items include a document in PDF format and executable software. 2) Measurements - Measurements of near-Earth orbital debris are accomplished by conducting ground-based and space-based observations of the orbital debris environment. The data from these sources provide validation of the environment models and identify the presence of new sources. Radar, optical and surface examinations are described. External links to related topics are provided. 3) Protection - Orbital debris protection involves conducting hypervelocity impact measurements to assess the risk presented by orbital debris to operating spacecraft and developing new materials and new designs to provide better protection from the environment with less weight penalty. The data from this work provides the link between the environment defined by the models and the risk presented by that environment to operating spacecraft and provides recommendations on design and operations procedures to reduce the risk as

  18. THE DISK POPULATION OF THE UPPER SCORPIUS ASSOCIATION

    SciTech Connect

    Luhman, K. L.; Mamajek, E. E.

    2012-10-10

    We present photometry at 3-24 {mu}m for all known members of the Upper Scorpius association ({tau} {approx} 11 Myr) based on all images of these objects obtained with the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer. We have used these data to identify the members that exhibit excess emission from circumstellar disks and estimate the evolutionary stages of these disks. Through this analysis, we have found {approx}50 new candidates for transitional, evolved, and debris disks. The fraction of members harboring inner primordial disks is {approx}< 10% for B-G stars (M > 1.2 M{sub Sun }) and increases with later types to a value of {approx}25% at {approx}>M5 (M {approx}< 0.2 M{sub Sun }), in agreement with the results of previous disk surveys of smaller samples of Upper Sco members. These data indicate that the lifetimes of disks are longer at lower stellar masses and that a significant fraction of disks of low-mass stars survive for at least {approx}10 Myr. Finally, we demonstrate that the distribution of excess sizes in Upper Sco and the much younger Taurus star-forming region ({tau} {approx} 1 Myr) is consistent with the same, brief timescale for clearing of inner disks.

  19. The Structure of the Pre-Lunar Disk

    NASA Astrophysics Data System (ADS)

    Ward, William R.

    2010-10-01

    In the giant impact model of lunar formation (Cameron & Ward 1976), the Earth is surrounded by a debris disk composed primarily of silicate material immediately following the impact event (e.g., Canup 2004). The dynamical evolution of the disk is driven by gravitational instabilities that generate an effective viscosity, causing the disk to spread (Ward & Cameron 1978; Takeda & Ida 2001). A portion of the material expands across the Roche boundary where it can eventually accrete into the Moon, while the remaining material is re-accreted by the Earth. The spreading rate is regulated by the disk's radiation budget through a complex two-phase gas/magna equilibrium state that maintains the radiation temperature near 2000 K (Thompson & Stevenson 1988). The vertical structure of the disk must satisfy the Clausius-Clapeyron phase equilibrium equation as well as equations of hydrostatic and convective equilibrium. The two phase disk has a modified sound speed that depends on the mass fractions of gas versus liquid, and consequently, there is a range of possible structures that depend on these fractions. We will examine under what conditions different disk structures are likely to have prevailed during the early history of the system. The resulting consequences of various disk histories on the dynamics and timing of the Moon's accretion will also be considered. This research is supported by funds from the NASA Lunar Science Institute (NLSI) and from NASA's LASER program.

  20. SEEDS Polarimetric Imagery of the AB Aur Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Wisniewski, John P.; Fukagawa, M.; Grady, C.; Hashimoto, J.; Hodapp, K.; Kudo, T.; Munetake, M.; Okamoto, Y.; Tamura, M.; SEEDS Team

    2011-01-01

    The Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) is a large survey which will be observing roughly 200 protoplanetary and debris disk systems over the next five years using the HiCIAO coronagraph + AO188 system on the Subaru telescope. We present new J-band polarimetric differential imagery of the proto-type Herbig Ae star, AB Aurigae, which diagnoses scattered light from the system between 20 - 540 AU at a resolution of roughly 8 AU. We discuss the morphology we observe in the outer disk region in the context of previous observations of the system, and compare/contrast the morphology in the inner disk region with recent H-band imagery of the system made with HiCIAO (Hashimoto et al 2010). This work was supported in part by NSF grants AST 0802230 and AST 1009314 and the AAS' Chretien International Research Grant.

  1. Understanding Floppy Disks.

    ERIC Educational Resources Information Center

    Valentine, Pamela

    1980-01-01

    The author describes the floppy disk with an analogy to the phonograph record, and discusses the advantages, disadvantages, and capabilities of hard-sectored and soft-sectored floppy disks. She concludes that, at present, the floppy disk will continue to be the primary choice of personal computer manufacturers and their customers. (KC)

  2. 14 CFR 417.211 - Debris analysis.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Debris analysis. 417.211 Section 417.211... TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.211 Debris analysis. (a) General. A flight safety analysis must include a debris analysis. For an orbital or suborbital launch, a debris...

  3. 14 CFR 417.211 - Debris analysis.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Debris analysis. 417.211 Section 417.211... TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.211 Debris analysis. (a) General. A flight safety analysis must include a debris analysis. For an orbital or suborbital launch, a debris...

  4. 14 CFR 417.211 - Debris analysis.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Debris analysis. 417.211 Section 417.211... TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.211 Debris analysis. (a) General. A flight safety analysis must include a debris analysis. For an orbital or suborbital launch, a debris...

  5. 14 CFR 417.211 - Debris analysis.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Debris analysis. 417.211 Section 417.211... TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.211 Debris analysis. (a) General. A flight safety analysis must include a debris analysis. For an orbital or suborbital launch, a debris...

  6. 14 CFR 417.211 - Debris analysis.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 4 2014-01-01 2014-01-01 false Debris analysis. 417.211 Section 417.211... TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.211 Debris analysis. (a) General. A flight safety analysis must include a debris analysis. For an orbital or suborbital launch, a debris...

  7. Floppy disk utility user's guide

    NASA Technical Reports Server (NTRS)

    Akers, J. W.

    1980-01-01

    A floppy disk utility program is described which transfers programs between files on a hard disk and floppy disk. It also copies the data on one floppy disk onto another floppy disk and compares the data. The program operates on the Data General NOVA-4X under the Real Time Disk Operating System. Sample operations are given.

  8. Floppy disk utility user's guide

    NASA Technical Reports Server (NTRS)

    Akers, J. W.

    1981-01-01

    The Floppy Disk Utility Program transfers programs between files on the hard disk and floppy disk. It also copies the data on one floppy disk onto another floppy disk and compares the data. The program operates on the Data General NOVA-4X under the Real Time Disk Operating System (RDOS).

  9. NASA Orbital Debris Baseline Populations

    NASA Technical Reports Server (NTRS)

    Krisko, Paula H.; Vavrin, A. B.

    2013-01-01

    The NASA Orbital Debris Program Office has created high fidelity populations of the debris environment. The populations include objects of 1 cm and larger in Low Earth Orbit through Geosynchronous Transfer Orbit. They were designed for the purpose of assisting debris researchers and sensor developers in planning and testing. This environment is derived directly from the newest ORDEM model populations which include a background derived from LEGEND, as well as specific events such as the Chinese ASAT test, the Iridium 33/Cosmos 2251 accidental collision, the RORSAT sodium-potassium droplet releases, and other miscellaneous events. It is the most realistic ODPO debris population to date. In this paper we present the populations in chart form. We describe derivations of the background population and the specific populations added on. We validate our 1 cm and larger Low Earth Orbit population against SSN, Haystack, and HAX radar measurements.

  10. Modeling transiting circumstellar disks: characterizing the newly discovered eclipsing disk system OGLE LMC-ECL-11893

    SciTech Connect

    Scott, Erin L.; Mamajek, Eric E.; Pecaut, Mark J.; Quillen, Alice C.; Moolekamp, Fred; Bell, Cameron P. M.

    2014-12-10

    We investigate the nature of the unusual eclipsing star OGLE LMC-ECL-11893 (OGLE J05172127-6900558) in the Large Magellanic Cloud recently reported by Dong et al. The eclipse period for this star is 468 days, and the eclipses exhibit a minimum of ∼1.4 mag, preceded by a plateau of ∼0.8 mag. Spectra and optical/IR photometry are consistent with the eclipsed star being a lightly reddened B9III star of inferred age ∼150 Myr and mass ∼4 M {sub ☉}. The disk appears to have an outer radius of ∼0.2 AU with predicted temperatures of ∼1100-1400 K. We model the eclipses as being due to either a transiting geometrically thin dust disk or gaseous accretion disk around a secondary object; the debris disk produces a better fit. We speculate on the origin of such a dense circumstellar dust disk structure orbiting a relatively old low-mass companion, and on the similarities of this system to the previously discovered EE Cep.

  11. HNC IN PROTOPLANETARY DISKS

    SciTech Connect

    Graninger, Dawn; Öberg, Karin I.; Qi, Chunhua; Kastner, Joel

    2015-07-01

    The distributions and abundances of small organics in protoplanetary disks are potentially powerful probes of disk physics and chemistry. HNC is a common probe of dense interstellar regions and the target of this study. We use the Submillimeter Array (SMA) to observe HNC 3–2 toward the protoplanetary disks around the T Tauri star TW Hya and the Herbig Ae star HD 163296. HNC is detected toward both disks, constituting the first spatially resolved observations of HNC in disks. We also present SMA observations of HCN 3–2 and IRAM 30 m observations of HCN and HNC 1–0 toward HD 163296. The disk-averaged HNC/HCN emission ratio is 0.1–0.2 toward both disks. Toward TW Hya, the HNC emission is confined to a ring. The varying HNC abundance in the TW Hya disk demonstrates that HNC chemistry is strongly linked to the disk physical structure. In particular, the inner rim of the HNC ring can be explained by efficient destruction of HNC at elevated temperatures, similar to what is observed in the ISM. However, to realize the full potential of HNC as a disk tracer requires a combination of high SNR spatially resolved observations of HNC and HCN and disk-specific HNC chemical modeling.

  12. Removing orbital debris with lasers

    NASA Astrophysics Data System (ADS)

    Phipps, Claude R.; Baker, Kevin L.; Libby, Stephen B.; Liedahl, Duane A.; Olivier, Scot S.; Pleasance, Lyn D.; Rubenchik, Alexander; Trebes, James E.; Victor George, E.; Marcovici, Bogdan; Reilly, James P.; Valley, Michael T.

    2012-05-01

    Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the use of LEO space is threatened by runaway collision cascading. A problem predicted more than thirty years ago, the threat from debris larger than about 1 cm demands serious attention. A promising proposed solution uses a high power pulsed laser system on the Earth to make plasma jets on the objects, slowing them slightly, and causing them to re-enter and burn up in the atmosphere. In this paper, we reassess this approach in light of recent advances in low-cost, light-weight modular design for large mirrors, calculations of laser-induced orbit changes and in design of repetitive, multi-kilojoules lasers, that build on inertial fusion research. These advances now suggest that laser orbital debris removal (LODR) is the most cost-effective way to mitigate the debris problem. No other solutions have been proposed that address the whole problem of large and small debris. A LODR system will have multiple uses beyond debris removal. International cooperation will be essential for building and operating such a system.

  13. The physics of debris flows

    USGS Publications Warehouse

    Iverson, R.M.

    1997-01-01

    Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ???10 m3 of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate

  14. The physics of debris flows

    NASA Astrophysics Data System (ADS)

    Iverson, Richard M.

    1997-08-01

    Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ˜10 m³ of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate

  15. Optical Observations of Space Debris

    NASA Technical Reports Server (NTRS)

    Seitzer, Patrick; Abercromby, Kira; Rodriquez, Heather; Barker, Edwin S.; Kelecy, Thomas

    2008-01-01

    This viewgraph presentation reviews the use of optical telescopes to observe space debris. .It will present a brief review of how the survey is conducted, and what some of the significant results encompass. The goal is to characterize the population of debris objects at GEO, with emphasis on the faint object population. Because the survey observations extend over a very short arc (5 minutes), a full six parameter orbit can not be determined. Recently we have begun to use a second telescope, the 0.9-m at CTIO, as a chase telescope to do follow-up observations of potential GEO debris candidates found by MODEST. With a long enough sequence of observations, a full six-parameter orbit including eccentricity can be determined. The project has used STK since inception for planning observing sessions based on the distribution of bright cataloged objects and the anti-solar point (to avoid eclipse). Recently, AGI's Orbit Determination Tool Kit (ODTK) has been used to determine orbits, including the effects of solar radiation pressure. Since an unknown fraction of the faint debris at GEO has a high area-to-mass ratio (A/M), the orbits are perturbed significantly by solar radiation. The ODTK analysis results indicate that temporal variations in the solar perturbations, possibly due to debris orientation dynamics, can be estimated in the OD process. Additionally, the best results appear to be achieved when solar forces orthogonal to the object-Sun line are considered. Determining the A/M of individual objects and the distribution of A/M values of a large sample of debris is important to understanding the total population of debris at GEO

  16. Space Debris Environment Remediation Concepts

    NASA Technical Reports Server (NTRS)

    Johnson, Nicholas L.; Klinkrad, Heiner

    2009-01-01

    Long-term projections of the space debris environment indicate that even drastic measures, such as an immediate, complete halt of launch and release activities, will not result in a stable environment of man-made space objects. Collision events between already existing space hardware will within a few decades start to dominate the debris population, and result in a net increase of the space debris population, also in size regimes which may cause further catastrophic collisions. Such a collisional cascading will ultimately lead to a run-away situation ("Kessler syndrome"), with no further possibility of human intervention. The International Academy of Astronautics (IAA) has been investigating the status and the stability of the space debris environment in several studies by first looking into space traffic management possibilities and then investigating means of mitigating the creation of space debris. In an ongoing activity, an IAA study group looks at ways of active space debris environment remediation. In contrast to the former mitigation study, the current activity concentrates on the active removal of small and large objects, such as defunct spacecraft, orbital stages, and mission-related objects, which serve as a latent mass reservoir that fuels initial catastrophic collisions and later collisional cascading. The paper will outline different mass removal concepts, e.g. based on directed energy, tethers (momentum exchange or electrodynamic), aerodynamic drag augmentation, solar sails, auxiliary propulsion units, retarding surfaces, or on-orbit capture. Apart from physical principles of the proposed concepts, their applicability to different orbital regimes, and their effectiveness concerning mass removal efficiency will be analyzed. The IAA activity on space debris environment remediation is a truly international project which involves more than 23 contributing authors from 9 different nations.

  17. Bringing "The Moth" to Light: A Planet-Perturbed Disk Scenario for the HD 61005 System

    NASA Astrophysics Data System (ADS)

    Esposito, Thomas M.; Fitzgerald, Michael P.; Graham, James R.; Kalas, Paul G.; Millar-Blanchaer, Max; Wang, Jason

    2015-12-01

    The HD 61005 debris disk ("The Moth") is notable for its unusual swept-back "wing" morphology, brightness asymmetries, dust ring offset, and a cleared region inside of ~50 AU. Here we present Gemini Planet Imager data that reveal this disk in scattered light down to Jupiter-like separations of <10 AU. Complementary W.M. Keck NIRC2/AO J,H,K imaging shows the disk's outer regions with high angular resolution. Based on these data, we propose a new explanation for the disk's features: that of an unseen planet on an inclined, eccentric orbit perturbing the disk material. To test this scenario, we used secular perturbation theory to construct 3-D dust distributions that informed 2-D scattered-light models, which we then compared with the data via an MCMC analysis. We found that the best-fit models reproduced morphological disk features similar to those observed, indicating that the perturber scenario is plausible for this system.

  18. Hydroplaning and submarine debris flows

    NASA Astrophysics Data System (ADS)

    de Blasio, Fabio V.; Engvik, Lars; Harbitz, Carl B.; ElverhøI, Anders

    2004-01-01

    Examination of submarine clastic deposits along the continental margins reveals the remnants of holocenic or older debris flows with run-out distances up to hundreds of kilometers. Laboratory experiments on subaqueous debris flows, where typically one tenth of a cubic meter of material is dropped down a flume, also show high velocities and long run-out distances compared to subaerial debris flows. Moreover, they show the tendency of the head of the flow to run out ahead of the rest of the body. The experiments reveal the possible clue to the mechanism of long run-out. This mechanism, called hydroplaning, begins as the dynamic pressure at the front of the debris flow becomes of the order of the pressure exerted by the weight of the sediment. In such conditions a layer of water can intrude under the sediment with a lubrication effect and a decrease in the resistance forces between the sediment and the seabed. A physical-mathematical model of hydroplaning is presented and investigated numerically. The model is applied to both laboratory- and field-scale debris flows. Agreement with laboratory experiments makes us confident in the extrapolation of our model to natural flows and shows that long run-out distances can be naturally attained.

  19. Biological response to prosthetic debris

    PubMed Central

    Bitar, Diana; Parvizi, Javad

    2015-01-01

    Joint arthroplasty had revolutionized the outcome of orthopaedic surgery. Extensive and collaborative work of many innovator surgeons had led to the development of durable bearing surfaces, yet no single material is considered absolutely perfect. Generation of wear debris from any part of the prosthesis is unavoidable. Implant loosening secondary to osteolysis is the most common mode of failure of arthroplasty. Osteolysis is the resultant of complex contribution of the generated wear debris and the mechanical instability of the prosthetic components. Roughly speaking, all orthopedic biomaterials may induce a universal biologic host response to generated wear débris with little specific characteristics for each material; but some debris has been shown to be more cytotoxic than others. Prosthetic wear debris induces an extensive biological cascade of adverse cellular responses, where macrophages are the main cellular type involved in this hostile inflammatory process. Macrophages cause osteolysis indirectly by releasing numerous chemotactic inflammatory mediators, and directly by resorbing bone with their membrane microstructures. The bio-reactivity of wear particles depends on two major elements: particle characteristics (size, concentration and composition) and host characteristics. While any particle type may enhance hostile cellular reaction, cytological examination demonstrated that more than 70% of the debris burden is constituted of polyethylene particles. Comprehensive understanding of the intricate process of osteolysis is of utmost importance for future development of therapeutic modalities that may delay or prevent the disease progression. PMID:25793158

  20. Astounding Jumping Disk.

    ERIC Educational Resources Information Center

    Guzdziol, Edward S.

    1991-01-01

    Activities involving concave rubber disks are utilized to illustrate the scientific principles of kinetic and potential energy. Provides teacher instructions and questions related to the activity. (MDH)

  1. Glass rupture disk

    DOEpatents

    Glass, S. Jill; Nicolaysen, Scott D.; Beauchamp, Edwin K.

    2002-01-01

    A frangible rupture disk and mounting apparatus for use in blocking fluid flow, generally in a fluid conducting conduit such as a well casing, a well tubing string or other conduits within subterranean boreholes. The disk can also be utilized in above-surface pipes or tanks where temporary and controllable fluid blockage is required. The frangible rupture disk is made from a pre-stressed glass with controllable rupture properties wherein the strength distribution has a standard deviation less than approximately 5% from the mean strength. The frangible rupture disk has controllable operating pressures and rupture pressures.

  2. THE INNER DISK STRUCTURE, DISK-PLANET INTERACTIONS, AND TEMPORAL EVOLUTION IN THE β PICTORIS SYSTEM: A TWO-EPOCH HST/STIS CORONAGRAPHIC STUDY

    SciTech Connect

    Apai, Dániel; Schneider, Glenn; Grady, Carol A.; Wyatt, Mark C.; Lagrange, Anne-Marie; Kuchner, Marc J.; Stark, Christopher J.; Lubow, Stephen H.

    2015-02-20

    We present deep Hubble Space Telescope/Space Telescope Imaging Spectrograph coronagraphic images of the β Pic debris disk obtained at two epochs separated by 15 yr. The new images and the re-reduction of the 1997 data provide the most sensitive and detailed views of the disk at optical wavelengths as well as the yet smallest inner working angle optical coronagraphic image of the disk. Our observations characterize the large-scale and inner-disk asymmetries and we identify multiple breaks in the disk radial surface brightness profile. We study in detail the radial and vertical disk structure and show that the disk is warped. We explore the disk at the location of the β Pic b super-Jupiter and find that the disk surface brightness slope is continuous between 0.''5 and 2.''0, arguing for no change at the separations where β Pic b orbits. The two epoch images constrain the disk's surface brightness evolution on orbital and radiation pressure blow-out timescales. We place an upper limit of 3% on the disk surface brightness change between 3'' and 5'', including the locations of the disk warp, and the CO and dust clumps. We discuss the new observations in the context of high-resolution multi-wavelength images and divide the disk asymmetries in two groups: axisymmetric and non-axisymmetric. The axisymmetric structures (warp, large-scale butterfly, etc.) are consistent with disk structure models that include interactions of a planetesimal belt and a non-coplanar giant planet. The non-axisymmetric features, however, require a different explanation.

  3. Reprocessing in Luminous Disks

    NASA Astrophysics Data System (ADS)

    Bell, K. R.

    1999-11-01

    We develop and investigate a procedure that accounts for disk reprocessing of photons that originate in the disk itself. Surface temperatures and simple, blackbody spectral energy distributions (SEDs) of protostellar disks are calculated. In disks that flare with radius, reprocessing of stellar photons results in temperature profiles that are not power-law at all radii but are consistently shallower than r-3/4. Including the disk as a radiation source (as in the case of active accretion) along with the stellar source further flattens the temperature profile. Disks that flare strongly near the star and then smoothly curve over and become shadowed at some distance (``decreasing curvature'' disks) exhibit nearly power-law temperature profiles that result in power-law infrared SEDs with slopes in agreement with typical observations of young stellar objects. Disk models in which the photospheric thickness is controlled by the local opacity and in which the temperature decreases with radius naturally have this shape. Uniformly flaring models do not match observations as well; progressively stronger reprocessing at larger radii leads to SEDs that flatten toward the infrared or even have a second peak at the wavelength corresponding (through the Wien law) to the temperature of the outer edge of the disk. In FU Orionis outbursting systems, the dominant source of energy is the inner disk. Reprocessing throughout the disk depends sensitively on the inner disk shape and emitted temperature profile. We show that the thermal instability outburst models of Bell & Lin reproduce trends in the observed SEDs of FU Ori systems with T~r-3/4 in the inner disk (r<~0.25 AU corresponding to λ<~10 μm) and T~r-1/2 in the outer disk. Surface irradiation during outburst and quiescence is compared in the region of planet formation (1-10 AU). The contrast between the two phases is diminished by the importance of the reprocessing of photons from the relatively high mass flux, outer disk (Ṁ=10

  4. Debris Flows and Related Phenomena

    NASA Astrophysics Data System (ADS)

    Ancey, C.

    Torrential floods are a major natural hazard, claiming thousands of lives and millions of dollars in lost property each year in almost all mountain areas on the Earth. After a catastrophic eruption of Mount St. Helen in the USA in May 1980, water from melting snow, torrential rains from the eruption cloud, and water displaced from Spirit Lake mixed with deposited ash and debris to produce very large debris flows and cause extensive damage and loss of life [1]. During the 1985 eruption of Nevado del Ruiz in Colombia, more than 20,000 people perished when a large debris flow triggered by the rapid melting of snow and ice at the volcano summit, swept through the town of Armero [2]. In 1991, the eruption of Pinatubo volcano in the Philippines disperses more than 5 cubic kilometres of volcanic ash into surrounding valleys. Much of that sediment has subsequently been mobilised as debris flows by typhoon rains and has devastated more than 300 square kilometres of agricultural land. Even, in Eur opean countries, recent events that torrential floods may have very destructive effects (Sarno and Quindici in southern Italy in May 1998, where approximately 200 people were killed). The catastrophic character of these floods in mountainous watersheds is a consequence of significant transport of materials associated with water flows. Two limiting flow regimes can be distinguished. Bed load and suspension refer to dilute transport of sediments within water. This means that water is the main agent in the flow dynamics and that the particle concentration does not exceed a few percent. Such flows are typically two-phase flows. In contrast, debris flows are mas s movements of concentrated slurries of water, fine solids, rocks and boulders. As a first approximation, debris flows can be treated as one-phase flows and their flow properties can be studied using classical rheological methods. The study of debris flows is a very exciting albeit immature science, made up of disparate elements

  5. Fomalhaut's Disk And Planet: Constraining The Mass And Orbit Of Fomalhaut-b Using Disk Morphology"

    NASA Astrophysics Data System (ADS)

    Chiang, Eugene; Kite, E.; Kalas, P.; Graham, J. R.; Clampin, M.

    2009-01-01

    We present a numerical model of how Fomalhaut b, the recently imaged exoplanet candidate, shapes Fomalhaut's debris disk. Our model indicates that Fomalhaut b must have a mass less than 3 Jupiter masses. Previous mass constraints based on disk morphology rely on several oversimplifications. We explain why our new constraints on the mass and the orbit of Fomalhaut b are more reliable. They are based on a global model of the disk that is not restricted to the chaotic zone boundary. We screen disk parent bodies, which define Fomalhaut's birth ring, for dynamical stability over the system age. Parent bodies are modelled separately from their dust grain progeny, whose orbits are strongly affected by radiation pressure and whose lifetimes are limited to about 0.1 Myr by destructive grain-grain collisions. Parent bodies are evacuated from mean-motion resonances with Fomalhaut b; these empty resonances are akin to the Kirkwood gaps opened by Jupiter. The belt contains at least 3 Earth masses of solids that are grinding down to dust, their velocity dispersions stirred so strongly by Fomalhaut b that collisions are destructive.

  6. DebriSat Project Update and Planning

    NASA Technical Reports Server (NTRS)

    Sorge, M.; Krisko, P. H.

    2016-01-01

    DebriSat Reporting Topics: DebriSat Fragment Analysis Calendar; Near-term Fragment Extraction Strategy; Fragment Characterization and Database; HVI (High-Velocity Impact) Considerations; Requirements Document.

  7. NASA Orbital Debris Requirements and Best Practices

    NASA Technical Reports Server (NTRS)

    Hull, Scott

    2014-01-01

    Limitation of orbital debris accumulation is an international and national concern, reflectedin NASA debris limitation requirements. These requirements will be reviewed, along with some practices that can be employed to achieve the requirements.

  8. Physical Properties of Supraglacial Debris on Mars

    NASA Astrophysics Data System (ADS)

    Baker, D. M. H.; Carter, L. M.

    2016-09-01

    The thickness and physical properties of surface debris preserving glacial ice in the mid-latitudes of Mars is assessed using crater morphology and radar sounding data. We suggest that this debris layer is much thicker than has been hypothesized.

  9. THE REINCARNATION OF INTERSTELLAR DUST: THE IMPORTANCE OF ORGANIC REFRACTORY MATERIAL IN INFRARED SPECTRA OF COMETARY COMAE AND CIRCUMSTELLAR DISKS

    SciTech Connect

    Kimura, Hiroshi

    2013-09-20

    We consider the reincarnation of interstellar dust to be reborn in protoplanetary disks as aggregates consisting of submicron-sized grains with a crystalline or amorphous silicate core and an organic-rich carbonaceous mantle. We find that infrared spectra of reincarnated interstellar dust reproduce emission peaks at correct wavelengths where the peaks were observed in cometary comae, debris disks, and protoplanetary disks if the volume fraction of organic refractory meets the constraints on elemental abundances. We discuss what we can learn from the infrared spectra of reincarnated interstellar dust in cometary comae and circumstellar disks.

  10. Identification of main-sequence stars with mid-infrared excesses: Frequency of beta Pictoris analogs and transition disk systems

    NASA Astrophysics Data System (ADS)

    Uzpen, Brian Robert

    There is solid evidence of life on only one planet in the Universe: Earth. Since current technologies are not capable of directly observing planets, we must rely on secondary indicators, such as circumstellar disks to detect them. Circumstellar disks are commonplace around pre-main-sequence stars; it is believed these disks are a natural byproduct of star formation where planets can form. The general theoretical evolutionary sequence from the optically thick pre-main-sequence stars (T-Tauri and Herbig AeBe) to optically thin "debris disks", is as follows: After particles grow through condensation, they reach a critical value and form planetary cores; these cores accrete the gas around them and form planets. As the available circumstellar material decreases, the inner disk will develop a hole. Circumstellar material dissipates in the outer disk, while particles collide creating a population of grains that re-radiate stellar energy in the far-IR, a characteristic of debris disks. These debris disks represent a final stage of planet formation. Given that most stars originally have circumstellar disks, it is likely that planetary systems are common. Material similar in temperature to Earth emits primarily at ~10 mm (mid-IR wavelengths). By identifying stars with circumstellar material that emits in the mid-IR, it may be possible to locate Earth-like planetary systems; mid-IR excesses may also be an indicator of disks undergoing clearing processes with inner disk holes of a few AU. The purpose of this work is to identify and characterize a large sample of stellar sources with circumstellar disks that re-radiate energy at mid-IR wavelengths and place them in the greater context of disk evolution and planet formation. To achieve this goal, a large number of stellar sources with mid-IR excesses are identified through wide-area Galactic surveys. Far-IR photometry is utilized to confirm the mid-IR excess in a majority of the newly identified sources. Follow-up optical

  11. A WISE survey of circumstellar disks in Taurus

    SciTech Connect

    Esplin, T. L.; Luhman, K. L.; Mamajek, E. E.

    2014-04-01

    We have compiled photometry at 3.4, 4.6, 12, and 22 μm from the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) for all known members of the Taurus complex of dark clouds. Using these data and photometry from the Spitzer Space Telescope, we have identified members with infrared excess emission from circumstellar disks and have estimated the evolutionary stages of the detected disks, which include 31 new full disks and 16 new candidate transitional, evolved, evolved transitional, and debris disks. We have also used the WISE All-Sky Source Catalog to search for new disk-bearing members of Taurus based on their red infrared colors. Through optical and near-infrared spectroscopy, we have confirmed 26 new members with spectral types of M1-M7. The census of disk-bearing stars in Taurus should now be largely complete for spectral types earlier than ∼M8 (M ≳ 0.03 M {sub ☉}).

  12. Discovery of an Inner Disk Component around HD 141569 A

    NASA Astrophysics Data System (ADS)

    Konishi, Mihoko; Grady, Carol A.; Schneider, Glenn; Shibai, Hiroshi; McElwain, Michael W.; Nesvold, Erika R.; Kuchner, Marc J.; Carson, Joseph; Debes, John. H.; Gaspar, Andras; Henning, Thomas K.; Hines, Dean C.; Hinz, Philip M.; Jang-Condell, Hannah; Moro-Martín, Amaya; Perrin, Marshall; Rodigas, Timothy J.; Serabyn, Eugene; Silverstone, Murray D.; Stark, Christopher C.; Tamura, Motohide; Weinberger, Alycia J.; Wisniewski, John. P.

    2016-02-01

    We report the discovery of a scattering component around the HD 141569 A circumstellar debris system, interior to the previously known inner ring. The discovered inner disk component, obtained in broadband optical light with Hubble Space Telescope/Space Telescope Imaging Spectrograph coronagraphy, was imaged with an inner working angle of 0.″25, and can be traced from 0.″4 (∼46 AU) to 1.″0 (∼116 AU) after deprojection using i = 55°. The inner disk component is seen to forward scatter in a manner similar to the previously known rings, has a pericenter offset of ∼6 AU, and break points where the slope of the surface brightness changes. It also has a spiral arm trailing in the same sense as other spiral arms and arcs seen at larger stellocentric distances. The inner disk spatially overlaps with the previously reported warm gas disk seen in thermal emission. We detect no point sources within 2″ (∼232 AU), in particular in the gap between the inner disk component and the inner ring. Our upper limit of 9 ± 3 MJ is augmented by a new dynamical limit on single planetary mass bodies in the gap between the inner disk component and the inner ring of 1 MJ, which is broadly consistent with previous estimates. Based on data collected by the Hubble Space Telescope, operated by the Space Telescope Science Institute.

  13. Discovery of an Inner Disk Component Around HD 141569 A

    NASA Technical Reports Server (NTRS)

    Konishi, Mihoko; Grady, Carol A.; Schneider, Glenn; Shibai, Hiroshi; McElwain, Michael W.; Nesvold, Erika R.; Kuchner, Marc J.; Carson, Joseph; Debes, John H.; Gaspar, Andras; Serabyn, Eugene

    2016-01-01

    We report the discovery of a scattering component around the HD 141569 A circumstellar debris system, interior to the previously known inner ring. The discovered inner disk component, obtained in broadband optical light with Hubble Space Telescope/Space Telescope Imaging Spectrograph coronagraphy, was imaged with an inner working angle of 0 25 arcseconds, and can be traced from 0 4 seconds (approximately 46 atomic units) to 1.0 arcseconds (approximately 116 atomic units) after deprojection using inclination = 55 degrees. The inner disk component is seen to forward scatter in a manner similar to the previously known rings, has a pericenter offset of approximately 6 atomic units, and break points where the slope of the surface brightness changes. It also has a spiral arm trailing in the same sense as other spiral arms and arcs seen at larger stellocentric distances. The inner disk spatially overlaps with the previously reported warm gas disk seen in thermal emission. We detect no point sources within 2 arcseconds (approximately 232 atomic units), in particular in the gap between the inner disk component and the inner ring. Our upper limit of 9 plus or minus 3 mass Jupiter (M (sub J)) is augmented by a new dynamical limit on single planetary mass bodies in the gap between the inner disk component and the inner ring of 1 mass Jupiter, which is broadly consistent with previous estimates.

  14. UN COPUOS Space Debris Guidelines

    NASA Astrophysics Data System (ADS)

    Portelli, Claudio

    The Space systems today provide growing benefits to enhance the quality of humankind. However as a by product, the orbiting objects inevitably leaves some debris which after 50 years of space activities represent a concern for all space agencies and manufacturers and operators. Since last year no international agreement was in place to mitigate the growing population of space debris objects. The successful result obtained at UN COPUOS in 2007 and available in the OOSA web site, now gives to the public, a set of voluntary international guidelines that could, if adopted by each space fairing Country, help in maintaining the present space environment. More further steps are necessary in the future to define a legal and normative framework. The paper will present the seven established UN Space Debris guidelines as well as examples of the minimum steps to be carried out at national level to enable the UN COPUOS to start the discussion of the legal aspect associated with the space debris issue.

  15. A Passive Nuclear Debris Collector.

    ERIC Educational Resources Information Center

    Griffin, John J.; And Others

    1979-01-01

    Describes a nuclear debris collector which removes trace substances from the lower atmosphere during rainfall. Suggests that the collector could be implemented into courses at various educational levels and could result in developing a network for monitoring the geographical extent of nuclear contamination. (Author/SA)

  16. Simulations of SSLV Ascent and Debris Transport

    NASA Technical Reports Server (NTRS)

    Rogers, Stuart; Aftosmis, Michael; Murman, Scott; Chan, William; Gomez, Ray; Gomez, Ray; Vicker, Darby; Stuart, Phil

    2006-01-01

    A viewgraph presentation on Computational Fluid Dynamic (CFD) Simulation of Space Shuttle Launch Vehicle (SSLV) ascent and debris transport analysis is shown. The topics include: 1) CFD simulations of the Space Shuttle Launch Vehicle ascent; 2) Debris transport analysis; 3) Debris aerodynamic modeling; and 4) Other applications.

  17. Orbital Debris and Future Environment Remediation

    NASA Technical Reports Server (NTRS)

    Liou, Jer-Chyi

    2011-01-01

    This slide presentation is an overview of the historical and current orbital debris environment. Included is information about: Projected growth of the future debris population, The need for active debris removal (ADR), A grand challenge for the 21st century and The forward path

  18. ALMA Observations of HD 141569’s Circumstellar Disk

    NASA Astrophysics Data System (ADS)

    White, J. A.; Boley, A. C.; Hughes, A. M.; Flaherty, K. M.; Ford, E.; Wilner, D.; Corder, S.; Payne, M.

    2016-09-01

    We present ALMA band 7 (345 GHz) continuum and 12CO(J = 3-2) observations of the circumstellar disk surrounding HD 141569. At an age of about 5 Myr, the disk has a complex morphology that may be best interpreted as a nascent debris system with gas. Our 870 μm ALMA continuum observations resolve a dust disk out to approximately 56 au from the star (assuming a distance of 116 pc) with 0.″38 resolution and 0.07 mJy beam-1 sensitivity. We measure a continuum flux density for this inner material of 3.8 ± 0.4 mJy (including calibration uncertainties). The 12CO(3-2) gas is resolved kinematically and spatially from about 30 to 210 au. The integrated 12CO(3-2) line flux density is 15.7 ± 1.6 Jy km s-1. We estimate the mass of the millimeter debris and 12CO(3-2) gas to be ≳0.04 M ⊕ and ˜2 × 10-3 M ⊕, respectively. If the millimeter grains are part of a collisional cascade, then we infer that the inner disk (<50 au) has ˜160 M ⊕ contained within objects less than 50 km in radius, depending on the planetesimal size distribution and density assumptions. Markov Chain Monte Carlo modeling of the system reveals a disk morphology with an inclination of 53.°4 centered around an M = 2.39 M ⊙ host star (Msin(i) = 1.92 M ⊙). We discuss whether the gas in HD 141569's disk may be second generation. If it is, the system can be used to study the clearing stages of planet formation.

  19. Applying Knowledge from Terrestrial Debris-Covered Glaciers to Constrain the Evolution of Martian Debris-Covered Ice

    NASA Astrophysics Data System (ADS)

    Koutnik, M. R.; Pathare, A. V.; Todd, C.; Waddington, E.; Christian, J. E.

    2016-09-01

    We will discuss the application of terrestrial knowledge on debris emplacement, the effects of debris on glacier-surface topography, debris transport by ice flow, deformation of debris-laden ice, and atmosphere-glacier feedbacks to Mars ice.

  20. Photometric Studies of GEO Debris

    NASA Technical Reports Server (NTRS)

    Seitzer, Patrick; Cowardin, Heather M.; Barker, Edwin; Abercromby, Kira J.; Foreman, Gary; Horstman, Matt

    2009-01-01

    The photometric signature of a debris object can be useful in determining what the physical characteristics of a piece of debris are. We report on optical observations in multiple filters of debris at geosynchronous Earth orbit (GEO). Our sample is taken from GEO objects discovered in a survey with the University of Michigan's 0.6-m aperture Schmidt telescope MODEST (for Michigan Orbital DEbris Survey Telescope), and then followed up in real-time with the SMARTS (Small and Medium Aperture Research Telescope System) 0.9-m at CTIO for orbits and photometry. Our goal is to determine 6 parameter orbits and measure colors for all objects fainter than R = 15 th magnitude that are discovered in the MODEST survey. At this magnitude the distribution of observed angular rates changes significantly from that of brighter objects. There are two objectives: 1. Estimate the orbital distribution of objects selected on the basis of two observational criteria: brightness (magnitude) and angular rates. 2. Obtain magnitudes and colors in standard astronomical filters (BVRI) for comparison with reflectance spectra of likely spacecraft materials. What is the faint debris likely to be? In this paper we report on the photometric results. For a sample of 50 objects, more than 90 calibrated sequences of R-B-V-I-R magnitudes have been obtained with the CTIO 0.9-m. For objects that do not show large brightness variations, the colors are largely redder than solar in both B-R and R-I. The width of the color distribution may be intrinsic to the nature of the surfaces, but also could be that we are seeing irregularly shaped objects and measuring the colors at different times with just one telescope. For a smaller sample of objects we have observed with synchronized CCD cameras on the two telescopes. The CTIO 0.9-m observes in B, and MODEST in R. The CCD cameras are electronically linked together so that the start time and duration of observations are the same to better than 50 milliseconds. Thus

  1. Dusty debris clouds around main sequence and post-main sequence stars

    NASA Technical Reports Server (NTRS)

    Zuckerman, B.

    1993-01-01

    During the past decade, infrared observations by IRAS and from the ground have revealed that many stars are orbited by dusty debris disks. Somewhat more indirect arguments indicate that many of these systems also contain asteroids, comets, and/or planets, thereby suggesting that planetary systems may be quite common in the Milky Way. Dust clouds at the main sequence K5 star HD 98800 and the white dwarf Giclas 29-38 are particularly noteworthy and mysterious.

  2. Segregation dynamics in debris flows

    NASA Astrophysics Data System (ADS)

    Hill, K. M.; Fei, M.

    2014-12-01

    Debris flows are massive flows consisting of mixtures of particles of different sizes and interstitial fluids such as water and mud. In sheared mixtures of different-sized (same density) particles, it is well known that larger particles tend to go up (toward the free surface), and the smaller particles, down, commonly referred to as the "Brazil-nut problem" or "kinetic sieving". When kinetic sieving fluxes are combined with advection in flows, they can give rise to a spectacular range of segregation patterns. These segregation / advection dynamics are recognized as playing a role in the coarsening of a debris flow front (its "snout") and the coarsening of the self-formed channel sides or levees. Since particle size distribution influences the flow dynamics including entrainment of bed materials, modeling segregation dynamics in debris flows is important for modeling the debris flows themselves. In sparser systems, the Brazil-nut segregation is well-modeled using kinetic theory applied to dissipative systems, where an underlying assumption involves random, uncorrelated collisions. In denser systems, where kinetic theory breaks down we have recently developed a new mixture model that demonstrates the segregation fluxes are driven by two effects associated with the kinetic stress or granular temperature (the kinetic energy associated with velocity fluctuations): (1) the difference between the partitioning of kinetic and contact stresses among the species in the mixture and (2) a kinetic stress gradient. Both model frameworks involve the temperature gradient as a driving force for segregation, but kinetic theory sends larger particles toward lower temperatures, and our mixture model sends larger particles away from lower temperatures. Which framework works under what conditions appears to depend on correlations in the flow such as those manifested in clusters and force chains. We discuss the application of each theoretical framework to representing segregation dynamics

  3. An optimal trajectory design for debris deorbiting

    NASA Astrophysics Data System (ADS)

    Ouyang, Gaoxiang; Dong, Xin; Li, Xin; Zhang, Yang

    2016-01-01

    The problem of deorbiting debris is studied in this paper. As a feasible measure, a disposable satellite would be launched, attach to debris, and deorbit the space debris using a technology named electrodynamic tether (EDT). In order to deorbit multiple debris as many as possible, a suboptimal but feasible and efficient trajectory set has been designed to allow a deorbiter satellite tour the LEO small bodies per one mission. Finally a simulation given by this paper showed that a 600 kg satellite is capable of deorbiting 6 debris objects in about 230 days.

  4. Detecting debris flows using ground vibrations

    USGS Publications Warehouse

    LaHusen, Richard G.

    1998-01-01

    Debris flows are rapidly flowing mixtures of rock debris, mud, and water that originate on steep slopes. During and following volcanic eruptions, debris flows are among the most destructive and persistent hazards. Debris flows threaten lives and property not only on volcanoes but far downstream in valleys that drain volcanoes where they arrive suddenly and inundate entire valley bottoms. Debris flows can destroy vegetation and structures in their path, including bridges and buildings. Their deposits can cover roads and railways, smother crops, and fill stream channels, thereby reducing their flood-carrying capacity and navigability.

  5. Orbital Debris Research in the United States

    NASA Technical Reports Server (NTRS)

    Stansbery, Gene

    2009-01-01

    The presentation includes information about growth of the satellite population, the U.S. Space Surveillance Network, tracking and catalog maintenance, Haystack and HAX radar observation, Goldstone radar, the Michigan Orbital Debris Survey Telescope (MODEST), spacecraft surface examinations and sample of space shuttle impacts. GEO/LEO observations from Kwajalein Atoll, NASA s Orbital Debris Engineering Model (ORDEM2008), a LEO-to-GEO Environment Debris Model (LEGEND), Debris Assessment Software (DAS) 2.0, the NASA/JSC BUMPER-II meteoroid/debris threat assessment code, satellite reentry risk assessment, optical size and shape determination, work on more complicated fragments, and spectral studies.

  6. Orbiting space debris: Dangers, measurement and mitigation

    NASA Astrophysics Data System (ADS)

    McNutt, Ross T.

    1992-06-01

    Space debris is a growing environmental problem. Accumulation of objects in earth orbit threatens space systems through the possibility of collisions and runaway debris multiplication. The amount of debris in orbit is uncertain due to the lack of information on the population of debris between 1 and 10 centimeters diameter. Collisions with debris even smaller than 1 cm can be catastrophic due to the high orbital velocities involved. Research efforts are under way at NASA, United States Space Command and the Air Force Phillips Laboratory to detect and catalog the debris population in near-earth space. Current international and national laws are inadequate to control the proliferation of space debris. Space debris is a serious problem with large economic, military, technical and diplomatic components. Actions need to be taken now to: determine the full extent of the orbital debris problem; accurately predict the future evolution of the debris population; decide the extent of the debris mitigation procedures required; implement these policies on a global basis via an international treaty. Action must be initiated now, before the loss of critical space systems such as the space shuttle or the space station.

  7. β Pictoris' inner disk in polarized light and new orbital parameters for β Pictoris b

    DOE PAGES

    Millar-Blanchaer, Maxwell A.; Graham, James R.; Pueyo, Laurent; Kalas, Paul; Dawson, Rebekah I.; Wang, Jason; Perrin, Marshall D.; Moon, Dae -Sik; Macintosh, Bruce; Ammons, S. Mark; et al

    2015-09-16

    Here, we present H-band observations of β Pic with the Gemini Planet Imager's (GPI's) polarimetry mode that reveal the debris disk between ~0farcs3 (6 AU) and ~1farcs7 (33 AU), while simultaneously detecting β Pic b. The polarized disk image was fit with a dust density model combined with a Henyey–Greenstein scattering phase function. The best-fit model indicates a disk inclined to the line of sight (more » $$\\phi =85\\buildrel{\\circ}\\over{.} {27}_{-0.19}^{+0.26}$$) with a position angle (PA) $${\\theta }_{\\mathrm{PA}}=30\\buildrel{\\circ}\\over{.} {35}_{-0.28}^{+0.29}$$ (slightly offset from the main outer disk, $${\\theta }_{\\mathrm{PA}}\\approx 29^\\circ $$), that extends from an inner disk radius of $${23.6}_{-0.6}^{+0.9}\\;\\mathrm{AU}$$ to well outside GPI's field of view.« less

  8. The fast debris evolution model

    NASA Astrophysics Data System (ADS)

    Lewis, H. G.; Swinerd, G. G.; Newland, R. J.; Saunders, A.

    2009-09-01

    The 'particles-in-a-box' (PIB) model introduced by Talent [Talent, D.L. Analytic model for orbital debris environmental management. J. Spacecraft Rocket, 29 (4), 508-513, 1992.] removed the need for computer-intensive Monte Carlo simulation to predict the gross characteristics of an evolving debris environment. The PIB model was described using a differential equation that allows the stability of the low Earth orbit (LEO) environment to be tested by a straightforward analysis of the equation's coefficients. As part of an ongoing research effort to investigate more efficient approaches to evolutionary modelling and to develop a suite of educational tools, a new PIB model has been developed. The model, entitled Fast Debris Evolution (FADE), employs a first-order differential equation to describe the rate at which new objects ⩾10 cm are added and removed from the environment. Whilst Talent [Talent, D.L. Analytic model for orbital debris environmental management. J. Spacecraft Rocket, 29 (4), 508-513, 1992.] based the collision theory for the PIB approach on collisions between gas particles and adopted specific values for the parameters of the model from a number of references, the form and coefficients of the FADE model equations can be inferred from the outputs of future projections produced by high-fidelity models, such as the DAMAGE model. The FADE model has been implemented as a client-side, web-based service using JavaScript embedded within a HTML document. Due to the simple nature of the algorithm, FADE can deliver the results of future projections immediately in a graphical format, with complete user-control over key simulation parameters. Historical and future projections for the ⩾10 cm LEO debris environment under a variety of different scenarios are possible, including business as usual, no future launches, post-mission disposal and remediation. A selection of results is presented with comparisons with predictions made using the DAMAGE environment model

  9. Space Tourism: Orbital Debris Considerations

    NASA Astrophysics Data System (ADS)

    Mahmoudian, N.; Shajiee, S.; Moghani, T.; Bahrami, M.

    2002-01-01

    Space activities after a phase of research and development, political competition and national prestige have entered an era of real commercialization. Remote sensing, earth observation, and communication are among the areas in which this growing industry is facing competition and declining government money. A project like International Space Station, which draws from public money, has not only opened a window of real multinational cooperation, but also changed space travel from a mere fantasy into a real world activity. Besides research activities for sending man to moon and Mars and other outer planets, space travel has attracted a considerable attention in recent years in the form of space tourism. Four countries from space fairing nations are actively involved in the development of space tourism. Even, nations which are either in early stages of space technology development or just beginning their space activities, have high ambitions in this area. This is worth noting considering their limited resources. At present, trips to space are available, but limited and expensive. To move beyond this point to generally available trips to orbit and week long stays in LEO, in orbital hotels, some of the required basic transportations, living requirements, and technological developments required for long stay in orbit are already underway. For tourism to develop to a real everyday business, not only the price has to come down to meaningful levels, but also safety considerations should be fully developed to attract travelers' trust. A serious hazard to space activities in general and space tourism in particular is space debris in earth orbit. Orbiting debris are man-made objects left over by space operations, hazardous to space missions. Since the higher density of debris population occurs in low earth orbit, which is also the same orbit of interest to space tourism, a careful attention should be paid to the effect of debris on tourism activities. In this study, after a

  10. Evolution of accretion disks in tidal disruption events

    SciTech Connect

    Shen, Rong-Feng; Matzner, Christopher D. E-mail: matzner@astro.utoronto.ca

    2014-04-01

    During a stellar tidal disruption event (TDE), an accretion disk forms as stellar debris returns to the disruption site and circularizes. Rather than being confined within the circularizing radius, the disk can spread to larger radii to conserve angular momentum. A spreading disk is a source of matter for re-accretion at rates that may exceed the later stellar fallback rate, although a disk wind can suppress its contribution to the central black hole accretion rate. A spreading disk is detectible through a break in the central accretion rate history or, at longer wavelengths, by its own emission. We model the evolution of TDE disk size and accretion rate by accounting for the time-dependent fallback rate, for the influence of wind losses in the early advective stage, and for the possibility of thermal instability for accretion rates intermediate between the advection-dominated and gas-pressure-dominated states. The model provides a dynamic basis for modeling TDE light curves. All or part of a young TDE disk will precess as a solid body because of the Lense-Thirring effect, and precession may manifest itself as a quasi-periodic modulation of the light curve. The precession period increases with time. Applying our results to the jetted TDE candidate Swift J1644+57, whose X-ray light curve shows numerous quasi-periodic dips, we argue that the data best fit a scenario in which a main-sequence star was fully disrupted by an intermediate mass black hole on an orbit significantly inclined from the black hole equator, with the apparent jet shutoff at t = 500 days corresponding to a disk transition from the advective state to the gas-pressure-dominated state.

  11. Ripples in disk galaxies

    NASA Astrophysics Data System (ADS)

    Schweizer, Francois; Seitzer, Patrick

    1988-05-01

    The authors present evidence that ripples ("shells") occur not only in ellipticals, as hitherto believed, but also in disk galaxies of Hubble types S0, S0/Sa, and Sa, and probably even in the Sbc galaxy NGC 3310. This evidence includes the discovery of ripples in the northern disk galaxies NGC 3032, 3619, 4382, 5548 (a Seyfert), and 5739, and in the "diskless S0" NGC 7600. It is argued that these ripples cannot usually have resulted form transient spiral waves or other forced vibrations in the existing disks, but instead consist of extraneous sheet-like matter. The frequent presence of major disk-shaped companions suggests that ripple material may be acquired not only through wholesale mergers, but also through mass transfer from neighbor galaxies.

  12. Hot Accretion Disks Revisited

    NASA Astrophysics Data System (ADS)

    Bjoernsson, Gunnlaugur; Abramowicz, Marek A.; Chen, Xingming; Lasota, Jean-Pierre

    1996-08-01

    All previous studies of hot (Tp 1010-1012 K), optically thin accretion disks have neglected either the presence of e+ e- pairs or advective cooling. Thus all hot disk models constructed previously have not been self-consistent. In this paper we calculate local disk models including pair physics, relevant radiative processes in the hot plasma, and the effect of advective cooling. We use a modification of the Björnsson & Svensson mapping method. We find that the role of e+ e- pairs in the structure of hot, optically thin accretion disks is far less significant than was previously thought. The improved description of the radiation-matter interactions provided in the present paper modify the previously obtained values of the critical parameters characterizing advectively dominated flows.

  13. Gas in Protoplanetary Disks

    NASA Technical Reports Server (NTRS)

    Roberge, Aki

    2008-01-01

    Gas makes up the bulk of the mass in a protoplanetary disk, but it is much more difficult to observe than the smaller dust component. The l ifetime of gas in a disk has far-reaching consequences. including lim iting the time available for giant planet formation and controlling t he migration of planetary bodies of all sizes, from Jupiters to meter-sized planetesimals. Here I will discuss what is known about the gas component of protoplanetary disks, highlighting recent results from i nfrared studies with the Spitzer Space Telescope. Exciting upcoming o pportunities for gas studies will also be discussed. In particular, the first large far-IR survey of gas tracers from young disks will be p erformed using the Herschel Space Observatory, as part of the "Gas in Protoplanetary Systems" (GASPS) Open Time Key Project.

  14. Gas in Protoplanetary Disks

    NASA Technical Reports Server (NTRS)

    Roberge, Aki

    2008-01-01

    Gas makes up the bulk of the mass in a protoplanetary disk, but it is much more difficult to observe than the smaller dust component. The lifetime of gas in a disk has far-reaching consequences, including limiting the time available for giant planet formation and controlling the migration of planetary bodies of all sizes, from Jupiters to meter-sized planetesimals. Here I will discuss what is known about the gas component of protoplanetary disks, highlighting recent results from infrared studies with the Spitzer Space Telescope. Exciting upcoming opportunities for gas studies will also be discussed. In particular, the first large far-IR survey of gas tracers from young disks will be performed using the Herschel Space Observatory, as part of the 'Gas in Protoplanetary Systems' (GASPS) Open Time Key Project.

  15. Organizing Your Hard Disk.

    ERIC Educational Resources Information Center

    Stocker, H. Robert; Hilton, Thomas S. E.

    1991-01-01

    Suggests strategies that make hard disk organization easy and efficient, such as making, changing, and removing directories; grouping files by subject; naming files effectively; backing up efficiently; and using PATH. (JOW)

  16. Comparison of debris flux models

    NASA Astrophysics Data System (ADS)

    Sdunnus, H.; Beltrami, P.; Klinkrad, H.; Matney, M.; Nazarenko, A.; Wegener, P.

    The availability of models to estimate the impact risk from the man-made space debris and the natural meteoroid environment is essential for both, manned and unmanned satellite missions. Various independent tools based on different approaches have been developed in the past years. Due to an increased knowledge of the debris environment and its sources e.g. from improved measurement capabilities, these models could be updated regularly, providing more detailed and more reliable simulations. This paper addresses an in-depth, quantitative comparison of widely distributed debris flux models which were recently updated, namely ESA's MASTER 2001 model, NASA's ORDEM 2000 and the Russian SDPA 2000 model. The comparison was performed in the frame of the work of the 20t h Interagency Debris Coordination (IADC) meeting held in Surrey, UK. ORDEM 2000ORDEM 2000 uses careful empirical estimates of the orbit populations based onthree primary data sources - the US Space Command Catalog, the H ystackaRadar, and the Long Duration Exposure Facility spacecraft returned surfaces.Further data (e.g. HAX and Goldstone radars, impacts on Shuttle windows andradiators, and others) were used to adjust these populations for regions in time,size, and space not covered by the primary data sets. Some interpolation andextrapolation to regions with no data (such as projections into the future) wasprovided by the EVOLVE model. MASTER 2001The ESA MASTER model offers a full three dimensional description of theterrestrial debris distribution reaching from LEO up to the GEO region. Fluxresults relative to an orbiting target or to an inertial volume can be resolved intosource terms, impactor characteristics and orbit, as well as impact velocity anddirection. All relevant debris source terms are considered by the MASTERmodel. For each simulated source, a corresponding debris generation model interms of mass/diameter distribution, additional velocities, and directionalspreading has been developed. A

  17. Protostars and Disks

    NASA Technical Reports Server (NTRS)

    Ho, Paul

    1997-01-01

    The research concentrated on high angular resolution (arc-second scale) studies of molecular cloud cores associated with very young star formation. New ways to study disks and protoplanetary systems were explored. Findings from the areas studied are briefly summarized: (1) molecular clouds; (2) gravitational contraction; (3) jets, winds, and outflows; (4) Circumstellar Disks (5) Extrasolar Planetary Systems. A bibliography of publications and submitted papers produced during the grant period is included.

  18. Planet Forming Protostellar Disks

    NASA Technical Reports Server (NTRS)

    Lubow, Stephen

    1998-01-01

    The project achieved many of its objectives. The main area of investigation was the interaction of young binary stars with surrounding protostellar disks. A secondary objective was the interaction of young planets with their central stars and surrounding disks. The grant funds were used to support visits by coinvestigators and visitors: Pawel Artymowicz, James Pringle, and Gordon Ogilvie. Funds were also used to support travel to meetings by Lubow and to provide partial salary support.

  19. Comparison of space debris estimates

    SciTech Connect

    Canavan, G.H.; Judd, O.P.; Naka, R.F.

    1996-10-01

    Debris is thought to be a hazard to space systems through impact and cascading. The current environment is assessed as not threatening to defense systems. Projected reductions in launch rates to LEO should delay concerns for centuries. There is agreement between AFSPC and NASA analyses on catalogs and collision rates, but not on fragmentation rates. Experiments in the laboratory, field, and space are consistent with AFSPC estimates of the number of fragments per collision. A more careful treatment of growth rates greatly reduces long-term stability issues. Space debris has not been shown to be an issue in coming centuries; thus, it does not appear necessary for the Air Force to take additional steps to mitigate it.

  20. Debris flow study in Malaysia

    NASA Astrophysics Data System (ADS)

    Bahrin Jaafar, Kamal

    2016-04-01

    The phenomenon of debris flow occurs in Malaysia occasionally. The topography of Peningsular Malysia is characterized by the central mountain ranges running from south to north. Several parts of hilly areas with steep slopes, combined with high saturation of soil strata that deliberately increase the pore water pressure underneath the hill slope. As a tropical country Malaysia has very high intensity rainfall which is triggered the landslide. In the study area where the debris flow are bound to occur, there are a few factors that contribute to this phenomenon such as high rainfall intensity, very steep slope which an inclination more than 35 degree and sandy clay soil type which is easily change to liquidity soil. This paper will discuss the study of rainfall, mechanism, modeling and design of mitigation measure to avoid repeated failure in future in same area.

  1. Orbital Debris Observations with WFCAM

    NASA Astrophysics Data System (ADS)

    Kendrick, R.; Mann, B.; Read, M.; Kerr, T.; Irwin, M.; Cross, N.; Bold, M.,; Varricatt, W.; Madsen, G.

    2014-09-01

    The United Kingdom Infrared Telescope has been operating for 35 years on the summit of Mauna Kea as a premier Infrared astronomical facility. In its 35th year the telescope has been turned over to a new operating group consisting of University of Arizona, University of Hawaii and the LM Advanced Technology Center. UKIRT will continue its astronomical mission with a portion of observing time dedicated to orbital debris and Near Earth Object detection and characterization. During the past 10 years the UKIRT Wide Field CAMera (WFCAM) has been performing large area astronomical surveys in the J, H and K bands. The data for these surveys have been reduced by the Cambridge Astronomical Survey Unit in Cambridge, England and archived by the Wide Field Astronomy Unit in Edinburgh, Scotland. During January and February of 2014 the Wide Field CAMera (WFCAM) was used to scan through the geostationary satellite belt detecting operational satellites as well as nearby debris. Accurate photometric and astrometric parameters have been developed by CASU for each of the detections and all data has been archived by WFAU. This paper will present the January and February results of the orbital debris surveys with WFCAM.

  2. Fast, Capacious Disk Memory Device

    NASA Technical Reports Server (NTRS)

    Muller, Ronald M.

    1990-01-01

    Device for recording digital data on, and playing back data from, memory disks has high recording or playback rate and utilizes available recording area more fully. Two disks, each with own reading/writing head, used to record data at same time. Head on disk A operates on one of tracks numbered from outside in; head on disk B operates on track of same number in sequence from inside out. Underlying concept of device applicable to magnetic or optical disks.

  3. Space Shuttle Solid Rocket Booster Debris Assessment

    NASA Technical Reports Server (NTRS)

    Kendall, Kristin; Kanner, Howard; Yu, Weiping

    2006-01-01

    The Space Shuttle Columbia Accident revealed a fundamental problem of the Space Shuttle Program regarding debris. Prior to the tragedy, the Space Shuttle requirement stated that no debris should be liberated that would jeopardize the flight crew and/or mission success. When the accident investigation determined that a large piece of foam debris was the primary cause of the loss of the shuttle and crew, it became apparent that the risk and scope of - damage that could be caused by certain types of debris, especially - ice and foam, were not fully understood. There was no clear understanding of the materials that could become debris, the path the debris might take during flight, the structures the debris might impact or the damage the impact might cause. In addition to supporting the primary NASA and USA goal of returning the Space Shuttle to flight by understanding the SRB debris environment and capability to withstand that environment, the SRB debris assessment project was divided into four primary tasks that were required to be completed to support the RTF goal. These tasks were (1) debris environment definition, (2) impact testing, (3) model correlation and (4) hardware evaluation. Additionally, the project aligned with USA's corporate goals of safety, customer satisfaction, professional development and fiscal accountability.

  4. Probing Terrestrial Planet Formation with Extreme Disk Variability

    NASA Astrophysics Data System (ADS)

    Su, Kate; Rieke, George; Gaspar, Andras; Jackson, Alan

    2016-08-01

    Spitzer has advanced our knowledge about the critical stages of terrestrial planet formation (and in some cases destruction) by discovering young stars orbited by 1.) silica dust emission close to their terrestrial zones indicative of the violent collisions, and 2.) variable disk emission arising from the aftermath of asteroid-size impacts. The variable emission provides a unique opportunity to learn about asteroid-sized bodies in young exoplanetary systems and to explore planetesimal collisions and their aftermaths during the era of terrestrial-planet-building. We propose continued study of debris disk variability, focused in two areas: (1) to provide continuous monitoring of systems where our existing program has discovered substantial variations indicative of major ongoing episodes of planetesimal impacts; and (2) to investigate intensively possible variations in the dust content of systems that show prominent crystalline emission features to establish a link between the two indicators of planet building. Together these objectives will prepare us for the JWST era, when we will again obtain mid-infrared spectra of these systems, and of both higher spectral resolution and signal to noise than has been possible previously. This program will extend the time-domain study of extreme debris disks as an important heritage of the Spitzer warm mission.

  5. Deficiency of molecular hydrogen in the disk of beta Pictoris.

    PubMed

    Lecavelier des Etangs, A; Vidal-Madjar, A; Roberge, A; Feldman, P D; Deleuil, M; André, M; Blair, W P; Bouret, J C; Désert, J M; Ferlet, R; Friedman, S; Hébrard, G; Lemoine, M; Moos, H W

    2001-08-16

    Molecular hydrogen (H2) is by far the most abundant material from which stars, protoplanetary disks and giant planets form, but it is difficult to detect directly. Infrared emission lines from H2 have recently been reported towards beta Pictoris, a star harbouring a young planetary system. This star is surrounded by a dusty 'debris disk' that is continuously replenished either by collisions between asteroidal objects or by evaporation of ices on Chiron-like objects. A gaseous disk has also been inferred from absorption lines in the stellar spectrum. Here we present the far-ultraviolet spectrum of beta Pictoris, in which H2 absorption lines are not seen. This allows us to set a very low upper limit on the column density of H2: N(H2) disk on the direct line of sight. Carbon monoxide (CO) has been seen in absorption against the star, yielding a ratio of CO/H2 > 6 x 10-4. As CO would be destroyed under ambient conditions in about 200 years (refs 9, 11), our result demonstrates that the CO in the disk arises from evaporation of planetesimals.

  6. The Disk and Planets of Solar Analogue τCeti

    NASA Astrophysics Data System (ADS)

    Lawler, S. M.; Francesco, J. Di; Kennedy, G.; Sibthorpe, B.; Booth, M.; Vandenbussche, B.; Matthews, B.; Tuomi, M.

    2015-01-01

    τ Ceti is a nearby, mature star very similar to our Sun, with a massive Kuiper belt analogue tep{Greavesetal2004} and possible multiplanet system tep{Tuomietal2013} that has been compared to our Solar System. We present infrared and submillimeter observations of the debris disk from the Herschel Space Observatory and the James Clerk Maxwell Telescope (JCMT). We find the best model of the disk is a wide annulus ranging from 5-55 AU, inclined from face-on by 30°. tet{Tuomietal2013} report five possible super-Earths tightly nestled inside 1.4 AU, and we model this planetary system and place dynamical constraints on the inner edge of the disk. We find that due to the low masses and fairly circular orbits of the planets, the disk could reach as close to the star as 1.5 AU, with some stable orbits even possible between the two outermost planets. The photometric modelling cannot rule out a disk inner edge as close to the star as 1 AU, though 5-10 AU produces a better fit to the data. Dynamical modelling shows that the 5 planet system is stable with the addition of a Saturn-mass planet on an orbit outside 5 AU, where the Tuomi et al. analysis would not have detected a planet of this mass.

  7. HST AND SPITZER OBSERVATIONS OF THE HD 207129 DEBRIS RING

    SciTech Connect

    Krist, John E.; Stapelfeldt, Karl R.; Bryden, Geoffrey; Rieke, George H.; Su, K. Y. L.; Gaspar, Andras; Chen, Christine C.; Beichman, Charles A.; Hines, Dean C.; Rebull, Luisa M.; Tanner, Angelle; Trilling, David E.; Clampin, Mark

    2010-10-15

    A debris ring around the star HD 207129 (G0V; d = 16.0 pc) has been imaged in scattered visible light with the ACS coronagraph on the Hubble Space Telescope (HST) and in thermal emission using MIPS on the Spitzer Space Telescope at {lambda} = 70 {mu}m (resolved) and 160 {mu}m (unresolved). Spitzer IRS ({lambda} = 7-35 {mu}m) and MIPS ({lambda} = 55-90 {mu}m) spectrographs measured disk emission at {lambda}> 28 {mu}m. In the HST image the disk appears as a {approx}30 AU wide ring with a mean radius of {approx}163 AU and is inclined by 60{sup 0} from pole-on. At 70 {mu}m, it appears partially resolved and is elongated in the same direction and with nearly the same size as seen with HST in scattered light. At 0.6 {mu}m, the ring shows no significant brightness asymmetry, implying little or no forward scattering by its constituent dust. With a mean surface brightness of V = 23.7 mag arcsec{sup -2}, it is the faintest disk imaged to date in scattered light. We model the ring's infrared spectral energy distribution (SED) using a dust population fixed at the location where HST detects the scattered light. The observed SED is well fit by this model, with no requirement for additional unseen debris zones. The firm constraint on the dust radial distance breaks the usual grain size-distance degeneracy that exists in modeling of spatially unresolved disks, and allows us to infer a minimum grain size of {approx}2.8 {mu}m and a dust size distribution power-law spectral index of -3.9. An albedo of {approx}5% is inferred from the integrated brightness of the ring in scattered light. The low-albedo and isotropic scattering properties are inconsistent with Mie theory for astronomical silicates with the inferred grain size and show the need for further modeling using more complex grain shapes or compositions. Brightness limits are also presented for six other main-sequence stars with strong Spitzer excess around which HST detects no circumstellar nebulosity (HD 10472, HD 21997, HD

  8. Radio pulsar disk electrodynamics

    SciTech Connect

    Michel, F.C.

    1983-03-01

    We outline the macroscopic physics of a disk close to an isolated, magnetized, rotating neutron star. It seems likely that such systems are formed from time to time in the universe. The neutron star acts as a Faraday disk dynamo, and the disk acts as both a load and a neutral sheet, permitting the polar cap current to return to the neutron star and also splitting a dipolar magnetic field into two monopolar halves. Michel and Dessler have proposed that such systems are radio pulsars. The dominant energy loss is from the stellar wind torque (giving a deceleration index n = 7/3), and the next contribution is dissipation in the ''auroral'' zones, where the current returns to the star in a sheet about 5 cm thick. The latter is comparable to the observed radio luminosities and is in reasonable accord with the data. The disk itself may be a source of visible radiation comparable to that in pulsed radiofrequency emission. As the pulsar ages, the disk expands and narrows into a ring, the plausible consequence of which could be cessation of pulsed emission at periods of a few seconds.

  9. Evaluating tsunami hazards from debris flows

    USGS Publications Warehouse

    Watts, P.; Walder, J.S.; ,

    2003-01-01

    Debris flows that enter water bodies may have significant kinetic energy, some of which is transferred to water motion or waves that can impact shorelines and structures. The associated hazards depend on the location of the affected area relative to the point at which the debris flow enters the water. Three distinct regions (splash zone, near field, and far field) may be identified. Experiments demonstrate that characteristics of the near field water wave, which is the only coherent wave to emerge from the splash zone, depend primarily on debris flow volume, debris flow submerged time of motion, and water depth at the point where debris flow motion stops. Near field wave characteristics commonly may be used as & proxy source for computational tsunami propagation. This result is used to assess hazards associated with potential debris flows entering a reservoir in the northwestern USA. ?? 2003 Millpress,.

  10. Orbital debris: Technical issues and future directions

    NASA Technical Reports Server (NTRS)

    Potter, Andrew (Editor)

    1992-01-01

    An international conference on orbital debris sponsored jointly by the American Institute of Aeronautics and Astronautics, NASA, and the Department of Defense, was held in Baltimore, Maryland, 16-19 Apr. 1990. Thirty-three papers were presented. The papers were grouped into the areas of measurements, modeling, and implications of orbital debris for space flight. New radar and optical measurements of orbital debris were presented that showed the existence of a large population of small debris. Modeling of potential future environments showed that runaway growth of the debris population from random collisions was a real possibility. New techniques for shielding against orbital debris and methods for removal of satellites from orbit were discussed.

  11. The impact of debris on marine life.

    PubMed

    Gall, S C; Thompson, R C

    2015-03-15

    Marine debris is listed among the major perceived threats to biodiversity, and is cause for particular concern due to its abundance, durability and persistence in the marine environment. An extensive literature search reviewed the current state of knowledge on the effects of marine debris on marine organisms. 340 original publications reported encounters between organisms and marine debris and 693 species. Plastic debris accounted for 92% of encounters between debris and individuals. Numerous direct and indirect consequences were recorded, with the potential for sublethal effects of ingestion an area of considerable uncertainty and concern. Comparison to the IUCN Red List highlighted that at least 17% of species affected by entanglement and ingestion were listed as threatened or near threatened. Hence where marine debris combines with other anthropogenic stressors it may affect populations, trophic interactions and assemblages. PMID:25680883

  12. The Chemistry of Nearby Disks

    NASA Astrophysics Data System (ADS)

    Öberg, Karin I.

    2016-01-01

    The gas and dust rich disks around young stars are the formation sites of planets. Observations of molecular trace species have great potential as probes of the disk structures and volatile compositions that together regulate planet formation. The disk around young star TW Hya has become a template for disk molecular studies due to a combination of proximity, a simple face-on geometry and richness in volatiles. It is unclear, however, how typical the chemistry of the TW disk is. In this proceeding, we review lessons learnt from exploring the TW Hya disk chemistry, focusing on the CO snowline, and on deuterium fractionation chemistry. We compare these results with new ALMA observations toward more distant, younger disks. We find that while all disks have some chemical structures in common, there are also substantial differences between the disks, which may be due to different initial conditions, structural or chemical evolutionary stages, or a combination of all three.

  13. Variations in debris distribution and thickness on Himalayan debris-covered glaciers

    NASA Astrophysics Data System (ADS)

    Gibson, Morgan; Rowan, Ann; Irvine-Fynn, Tristram; Quincey, Duncan; Glasser, Neil

    2016-04-01

    Many Himalayan glaciers are characterised by extensive supraglacial debris coverage; in Nepal 33% of glaciers exhibit a continuous layer of debris covering their ablation areas. The presence of such a debris layer modulates a glacier's response to climatic change. However, the impact of this modulation is poorly constrained due to inadequate quantification of the impact of supraglacial debris on glacier surface energy balance. Few data exist to describe spatial and temporal variations in parameters such as debris thickness, albedo and surface roughness in energy balance calculations. Consequently, improved understanding of how debris affects Himalayan glacier ablation requires the assessment of surface energy balance model sensitivity to spatial and temporal variability in these parameters. Measurements of debris thickness, surface temperature, reflectance and roughness were collected across Khumbu Glacier during the pre- and post-monsoon seasons of 2014 and 2015. The extent of the spatial variation in each of these parameters are currently being incorporated into a point-based glacier surface energy balance model (CMB-RES, Collier et al., 2014, The Cryosphere), applied on a pixel-by-pixel basis to the glacier surface, to ascertain the sensitivity of glacier surface energy balance and ablation values to these debris parameters. A time series of debris thickness maps have been produced for Khumbu Glacier over a 15-year period (2000-2015) using Mihalcea et al.'s (2008, Cold Reg. Sci. Technol.) method, which utilised multi-temporal ASTER thermal imagery and our in situ debris surface temperature and thickness measurements. Change detection between these maps allowed the identification of variations in debris thickness that could be compared to discrete measurements, glacier surface velocity and morphology of the debris-covered area. Debris thickness was found to vary spatially between 0.1 and 4 metres within each debris thickness map, and temporally on the order of 1

  14. Best Mitigation Paths To Effectively Reduce Earth's Orbital Debris

    NASA Technical Reports Server (NTRS)

    Wiegman, Bruce M.

    2009-01-01

    This slide presentation reviews some ways to reduce the problem posed by debris in orbit around the Earth. It reviews the orbital debris environment, the near-term needs to minimize the Kessler syndrome, also known as collisional cascading, a survey of active orbital debris mitigation strategies, the best paths to actively remove orbital debris, and technologies that are required for active debris mitigation.

  15. Premixed direct injection disk

    SciTech Connect

    York, William David; Ziminsky, Willy Steve; Johnson, Thomas Edward; Lacy, Benjamin; Zuo, Baifang; Uhm, Jong Ho

    2013-04-23

    A fuel/air mixing disk for use in a fuel/air mixing combustor assembly is provided. The disk includes a first face, a second face, and at least one fuel plenum disposed therebetween. A plurality of fuel/air mixing tubes extend through the pre-mixing disk, each mixing tube including an outer tube wall extending axially along a tube axis and in fluid communication with the at least one fuel plenum. At least a portion of the plurality of fuel/air mixing tubes further includes at least one fuel injection hole have a fuel injection hole diameter extending through said outer tube wall, the fuel injection hole having an injection angle relative to the tube axis. The invention provides good fuel air mixing with low combustion generated NOx and low flow pressure loss translating to a high gas turbine efficiency, that is durable, and resistant to flame holding and flash back.

  16. Primary dispersal of supraglacial debris and debris cover formation on alpine glaciers

    NASA Astrophysics Data System (ADS)

    Kirkbride, M. P.; Deline, P.

    2009-04-01

    Debris-covered glaciers are receiving increased attention due to the modulation of runoff by supraglacial covers, and to the lake outburst flood hazard at many covered glacier termini. Observed increases in debris cover extents cannot presently be explained in terms of glaciological influences. The supply of englacial debris to the supraglacial zone has previously been understood only in terms of local dispersal due to differential ablation between covered and uncovered ice, for example on medial moraines. Here, we introduce the term primary dispersal to describe the process of migration of the outcrops of angled debris septa across melting, thinning ablation zones. Understanding primary debris dispersal is an essential step to understanding how supraglacial debris cover is controlled by glaciological variables, and hence is sensitive to climatically-induced fluctuation. Three measures of a glacier's ability to evacuate supraglacial debris are outlined: (1) a concentration factor describing the focussing of englacial debris into specific supraglacial mass loads; (2) the rate of migration of a septum outcrop relative to the local ice surface; and (3) a downstream velocity differential between a septum outcrop and the ice surface. (1) and (2) are inversely related, while (3) increases downglacier to explain why slow-moving, thinning ice rapidly becomes debris covered. Data from Glacier d'Estelette (Italian Alps) illustrate primary dispersal processes at a site where debris cover is increasing in common with many other shrinking alpine glaciers. We develop a model of the potential for debris cover formation and growth in different glaciological environments. This explains why glaciers whose termini are obstructed often have steep debris septa feeding debris covers which vary slowly in response to mass balance change. In contrast, at glaciers with gently-dipping debris-bearing foliation, the debris cover extent is sensitive to glaciological change. These findings

  17. Modelling the Huge, Herschel-Resolved Debris Ring around HD 207129

    NASA Technical Reports Server (NTRS)

    Lohne, T.; Augereau, J. C.; Ertel, S.; Marshall, J. P.; Mora, A.; Absil, O.; Stapelfeldt, K.; Thebault, P.; Bayo, A.; del Burgo, C.; Danchi, W.; Krivov, A. V.; Lebreton, J.; Letawe, G.; Magain, P.; Maldonado, J.; Montesinos, B.; Pilbratt, G. L.; White, G. J.; Wolf, S.

    2011-01-01

    Debris disks, which are inferred from the observed infrared excess to be ensembles of dust, rocks. and probably planetesimals, arc common features of stellar systems. As the mechanisms of their fonnation and evolution are linked to those of planetary bodies, they provide valuable infonnation. The few well-resolved debris disks are even more valuable because they can serve as modelling benchmarks and help resolve degeneracies in modelling aspects such as typical grain sizes and distances. Here, we present an analysis of the HD 207129 debris disk, based on its well-covered spectral energy distribution and Herschel/PACS images obtained in the framework of the DUNES (DUst around NEarby Stars) programme. We use an empirical power-law approach to the distribution of dust and we then model the production and removal of dust by means of collisions, direct radiation pressure, and drag forces. The resulting best-fit model contains a total of nearly 10(sup -2) Earth masses in dust, with typical grain sizes in the planetesimal beh ranging from 4 to 7 micrometers. We constrain the dynamical excitation to be low, which results in very long collisional lifetimes and a drag that notably fills the inner gap, especially at 70 micrometers. The radial distribution stretches from well within 100 AU in an unusual, outward-riSing slope towards a rather sharp outer edge at about 170-190 AU. The inner edge is therefore smoother than that reported for Fomalhaut, but the contribution from the extended halo of barely bound grains is similarly small. Both slowly self-stirring and planetary perturbations could potentially have formed and shaped this disk.

  18. Slim accretion disks

    SciTech Connect

    Abramowicz, M.A.; Czerny, B.; Lasota, J.P.; Szuszkiewicz, E.

    1988-09-01

    A new branch of equilibrium solutions for stationary accretion disks around black holes is found. These solutions correspond to moderately super-Eddington accretion rates. The existence of the new branch is a consequence of an additional cooling due to general relativistic Roche lobe overflow and horizontal advection of heat. On an accretion rate versus surface density plane the new branch forms, together with the two standard branches (corresponding to the Shakura-Sunyaev accretion disk models) a characteristically S-shaped curve. This could imply a limit cycle-type behavior for black hole accretion flows with accretion rates close ot the Eddington one. 29 references.

  19. Hot stars with disks

    NASA Astrophysics Data System (ADS)

    Grundstrom, Erika D.

    The evolutionary paths of the massive O and B type stars are often defined by angular momentum transformations that involve circumstellar gas disks. This circumstellar gas is revealed in several kinds of observations, and here I describe a series of investigations of the hydrogen line emission from such disk using detailed studies of five massive binaries and a survey of 128 Be stars. By examining three sets of spectra of the active mass-transfer binary system RY Scuti, I determined masses of 7.1±1.2 [Special characters omitt ed.] for the bright supergiant and 30.0±2.1 [Special characters omitted.] for the massive companion that is hidden by an accretion torus. I also present a cartoon model of the complex mass flows in the system. Using optical spectroscopy and X-ray flux data, I investigated the mass transfer processes in four massive X-ray binaries (a massive B star with mass flowing onto a compact, neutron star companion). The B-supergiant system LS I +65 010 transfers mass via stellar winds. I find the X-ray flux modulates with the orbital period. In the other three X-ray binary systems (LS I +61 303, HDE 245770, and X Per), an outflowing circumstellar disk is responsible for the mass transfer, and in all three systems, the disk appears to be truncated by gravitational interactions with the compact companion. The disk in the microquasar system LS I +61 303 is limited in radius by the periastron separation and an increase in both Ha equivalent width and X-ray flux following periastron may be due to a density wave in the disk induced by tidal forces. Observations of HDE 245770 document what appears to be the regeneration of a circumstellar disk. The disk of X Per appears to have grown to near record proportions and the X-ray flux has dramatically increased. Tidal interaction may generate a spiral density wave in the disk and cause an increase in Ha equivalent width and mass transfer to the compact companion. During the course of the analysis of the X

  20. Giant Planet Formation by Disk Instability in Low Mass Disks?

    NASA Astrophysics Data System (ADS)

    Boss, Alan P.

    2010-12-01

    Forming giant planets by disk instability requires a gaseous disk that is massive enough to become gravitationally unstable and able to cool fast enough for self-gravitating clumps to form and survive. Models with simplified disk cooling have shown the critical importance of the ratio of the cooling to the orbital timescales. Uncertainties about the proper value of this ratio can be sidestepped by including radiative transfer. Three-dimensional radiative hydrodynamics models of a disk with a mass of 0.043 M sun from 4 to 20 AU in orbit around a 1 M sun protostar show that disk instabilities are considerably less successful in producing self-gravitating clumps than in a disk with twice this mass. The results are sensitive to the assumed initial outer disk (To ) temperatures. Models with To = 20 K are able to form a single self-gravitating clump, whereas models with To = 25 K form clumps that are not quite self-gravitating. These models imply that disk instability requires a disk with a mass of at least ~0.043 M sun inside 20 AU in order to form giant planets around solar-mass protostars with realistic disk cooling rates and outer-disk temperatures. Lower mass disks around solar-mass protostars must rely upon core accretion to form inner giant planets.

  1. Small Orbital Debris Mitigation Mission Architecture

    NASA Technical Reports Server (NTRS)

    Wiegmann, Bruce M.

    2011-01-01

    Small orbital debris in LEO (1-10 cm in size) presents a clear and present danger to operational LEO spacecraft. This debris field has dramatically increased (nearly doubled) in recent years following the Chinese ASAT Test in 2007 and the Iridium/Cosmos collision in 2009. Estimates of the number of small debris have grown to 500,000 objects after these two events; previously the population was 300,000 objects. These small, untracked debris objects (appproximately 500,000) outnumber the larger and tracked objects (appproximately 20,000) by a factor 25 to 1. Therefore, the risk of the small untracked debris objects to operational spacecraft is much greater than the risk posed by the larger and tracked LEO debris objects. A recent study by The Aerospace Corporation found that the debris environment will increase the costs of maintaining a constellation of government satellites by 5%, a constellation of large commercial satellites by 11%, and a constellation of factory built satellites by 26% from $7.6 billion to $9.57 billion. Based upon these facts, the NASA Marshall Space Flight Center (MSFC) Advanced Concepts Office (ACO) performed an architecture study on Small Orbital Debris Active Removal (SODAR) using a space-based nonweapons- class laser satellite for LEO debris removal. The goal of the SODAR study was to determine the ability of a space-based laser system to remove the most pieces of debris (1 cm to 10 cm, locations unknown), in the shortest amount of time, with the fewest number of spacecraft. The ESA developed MASTER2005 orbital debris model was used to probabilistically classify the future debris environment including impact velocity, magnitude, and directionality. The study ground rules and assumptions placed the spacecraft into a high inclination Low Earth Orbit at 800 km as an initial reference point. The architecture study results found that a spacecraft with an integrated forward-firing laser is capable of reducing the small orbital debris flux within

  2. Riding a Trail of Debris

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1

    This image taken by NASA's Spitzer Space Telescope shows the comet Encke riding along its pebbly trail of debris (long diagonal line) between the orbits of Mars and Jupiter. This material actually encircles the solar system, following the path of Encke's orbit. Twin jets of material can also be seen shooting away from the comet in the short, fan-shaped emission, spreading horizontally from the comet.

    Encke, which orbits the Sun every 3.3 years, is well traveled. Having exhausted its supply of fine particles, it now leaves a long trail of larger more gravel-like debris, about one millimeter in size or greater. Every October, Earth passes through Encke's wake, resulting in the well-known Taurid meteor shower.

    This image was captured by Spitzer's multiband imaging photometer when Encke was 2.6 times farther away than Earth is from the Sun. It is the best yet mid-infrared view of the comet at this great distance. The data are helping astronomers understand how rotating comets eject particles as they circle the Sun.

  3. Orbital Debris Observations with WFCAM

    NASA Technical Reports Server (NTRS)

    Bold, Matthew; Cross, Nick; Irwin, Mike; Kendrick, Richard; Kerr, Thomas; Lederer, Susan; Mann, Robert; Sutorius, Eckhard

    2014-01-01

    The United Kingdom Infrared Telescope has been operating for 35 years on the summit of Mauna Kea as a premier Infrared astronomical facility. In its 35th year the telescope has been turned over to a new operating group consisting of University of Arizona, University of Hawaii and the LM Advanced Technology Center. UKIRT will continue its astronomical mission with a portion of observing time dedicated to orbital debris and Near Earth Object detection and characterization. During the past 10 years the UKIRT Wide Field CAMera (WFCAM) has been performing large area astronomical surveys in the J, H and K bands. The data for these surveys have been reduced by the Cambridge Astronomical Survey Unit in Cambridge, England and archived by the Wide Field Astronomy Unit in Edinburgh, Scotland. During January and February of 2014 the Wide Field CAMera (WFCAM) was used to scan through the geostationary satellite belt detecting operational satellites as well as nearby debris. Accurate photometric and astrometric parameters have been developed by CASU for each of the detections and all data has been archived by WFAU.

  4. Solar disk sextant

    NASA Technical Reports Server (NTRS)

    Sofia, S.; Chiu, H.-Y.; Maier, E.; Schatten, K. H.; Minott, P.; Endal, A. S.

    1984-01-01

    This paper presents the conceptual design of an instrument, called the solar disk sextant, to be used in space to measure the shape and the size of the sun and their variations. The instrumental parameters required to produce sufficient sensitivity to address the problems of solar oblateness, solar pulsations, and global size changes of climatic importance are given.

  5. Accretion disk coronae

    NASA Technical Reports Server (NTRS)

    White, N. E.;