Science.gov

Sample records for actively creating stars

  1. Creating physics stars

    NASA Astrophysics Data System (ADS)

    Banks, Michael

    2013-07-01

    Korea has begun an ambitious 5bn plan to create 50 new institutes dedicated to fundamental research. Michael Banks meets physicist Se-Jung Oh, president of the Institute for Basic Science, to find out more.

  2. Dead Star Creates Celestial Havoc

    NASA Technical Reports Server (NTRS)

    2006-01-01

    A star's spectacular death in the constellation Taurus was observed on Earth as the supernova of 1054 A.D. Now, almost a thousand years later, a superdense neutron star left behind by the stellar death is spewing out a blizzard of extremely high-energy particles into the expanding debris field known as the Crab Nebula.

    This composite image uses data from three of NASA's Great Observatories. The Chandra X-ray image is shown in light blue, the Hubble Space Telescope optical images are in green and dark blue, and the Spitzer Space Telescope's infrared image is in red. The size of the X-ray image is smaller than the others because ultrahigh-energy X-ray emitting electrons radiate away their energy more quickly than the lower-energy electrons emitting optical and infrared light. The neutron star, which has the mass equivalent to the sun crammed into a rapidly spinning ball of neutrons twelve miles across, is the bright white dot in the center of the image.

  3. Dying star creates sculpture of gas and dust

    NASA Astrophysics Data System (ADS)

    2004-09-01

    Sculpture of gas and dust hi-res Size hi-res: 125 Kb Credits: ESA, NASA, HEIC and The Hubble Heritage Team (STScI/AURA) Dying star creates sculpture of gas and dust The so-called Cat's Eye Nebula, formally catalogued NGC 6543 and seen here in this detailed view from the NASA/ESA Hubble Space Telescope, is one of the most complex planetary nebulae ever seen in space. A planetary nebula forms when Sun-like stars gently eject their outer gaseous layers to form bright nebulae with amazing twisted shapes. Hubble first revealed NGC 6543's surprisingly intricate structures including concentric gas shells, jets of high-speed gas and unusual shock-induced knots of gas in 1994. This new image, taken with Hubble's Advanced Camera for Surveys (ACS), reveals the full beauty of a bull's-eye pattern of eleven or more concentric rings, or shells, around the Cat’s Eye. Each ‘ring’ is actually the edge of a spherical bubble seen projected onto the sky - which is why it appears bright along its outer edge. High resolution version (JPG format) 125 Kb High resolution version (TIFF format) 2569 Kb Acknowledgment: R. Corradi (Isaac Newton Group of Telescopes, Spain) and Z. Tsvetanov (NASA). Sculpture of gas and dust hi-res Size hi-res: 287 Kb Credits: Nordic Optical Telescope and Romano Corradi (Isaac Newton Group of Telescopes, Spain) Dying star creates sculpture of gas and dust An enormous but extremely faint halo of gaseous material surrounds the Cat’s Eye Nebula and is over three light-years across. Some planetary nebulae been found to have halos like this one, likely formed of material ejected during earlier active episodes in the star's evolution - most likely some 50 000 to 90 000 years ago. This image was taken by Romano Corradi with the Nordic Optical Telescope on La Palma in the Canary Islands. The image is constructed from two narrow-band exposures showing oxygen atoms (1800 seconds, in blue) and nitrogen atoms (1800 seconds, in red). High resolution version (JPG

  4. Activity Cycles in Stars

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.

    2009-01-01

    Starspots and stellar activity can be detected in other stars using high precision photometric and spectrometric measurements. These observations have provided some surprises (starspots at the poles - sunspots are rarely seen poleward of 40 degrees) but more importantly they reveal behaviors that constrain our models of solar-stellar magnetic dynamos. The observations reveal variations in cycle characteristics that depend upon the stellar structure, convection zone dynamics, and rotation rate. In general, the more rapidly rotating stars are more active. However, for stars like the Sun, some are found to be inactive while nearly identical stars are found to be very active indicating that periods like the Sun's Maunder Minimum (an inactive period from 1645 to 1715) are characteristic of Sun-like stars.

  5. Creating activity schedules using Microsoft Powerpoint.

    PubMed Central

    Rehfeldt, Ruth Anne; Kinney, Elisabeth M; Root, Shannon; Stromer, Robert

    2004-01-01

    We describe how PowerPoint presentation software can be used to create computer activity schedules to teach individuals with special needs. Presented are the steps involved in creating activity schedules with close-ended and open-ended activities, and for preparing schedules that include photos, sounds, text, and videos that can be used to occasion an individual's engagement in a variety of learning activities. PMID:15154226

  6. Pharmacists' Stellar experience can create Five-Star Success.

    PubMed

    Kaldy, Joanne

    2014-12-01

    The evolving health care system has put an increasing emphasis on balancing quality, outcomes, and costs. As part of this evolution, the Centers for Medicare & Medicaid Services (CMS) is using a Five-Star Quality Rating System to evaluate the quality of care provided by Medicare Advantage and Part D prescription drug plans. At the same time, drug plans are using a Five-Star system to rate pharmacies, which contribute to the CMS ratings of nursing facilities. More than ever, pharmacists can play a significant role in helping facilities, plans, and even pharmacies achieve the highest possible ratings and maintain those standards over time.

  7. The magnetic activity sunlike stars.

    PubMed

    Vaughan, A H

    1984-08-24

    Sunspots, flares, and the myriad time-varying "events" observable in the Sun-the only star whose surface we can examine in detail-are testimony that the Sun is a magnetically variable or active star. Its magnetic field, carried into interplanetary space by the solar wind, produces observable changes in Earth's magnetosphere and variations in the flux of galactic cosmic-ray particles incident upon Earth's upper atmosphere. Centuries of observation have enabled solar scientists to recognize that the Sun's magnetism exists and varies in a globally organized pattern that is somehow coupled to the Sun's rotation. Within the past decade O. C. Wilson demonstrated that analogs of solar activity exist and can be studied in many other dwarf stars. From the continuing study, knowledge of the precise rates of rotation of the stars under investigation is being gained for the first time. The results are expected to increase our understanding of the origin of solar activity and stellar activity in general.

  8. The Chemical Composition of the Active Stars

    NASA Astrophysics Data System (ADS)

    Glazunova, L. V.

    The comparison of the results of the studies of the active stars' chemical composition obtained by different authors has been performed. It was concluded that the difference between the abundances of some elements in active and inactive stars becomes significant (> 3σ) only for the active stars with high chromospheric activity (lgR'HK > -4). This is the case primarily for the light elements, namely Li, Na and Al, as well as heavy elements with Z > 30.

  9. Improving fold activation of small transcription activating RNAs (STARs) with rational RNA engineering strategies.

    PubMed

    Meyer, Sarai; Chappell, James; Sankar, Sitara; Chew, Rebecca; Lucks, Julius B

    2016-01-01

    Regulatory RNAs have become integral components of the synthetic biology and bioengineering toolbox for controlling gene expression. We recently expanded this toolbox by creating small transcription activating RNAs (STARs) that act by disrupting the formation of a target transcriptional terminator hairpin placed upstream of a gene. While STARs are a promising addition to the repertoire of RNA regulators, much work remains to be done to optimize the fold activation of these systems. Here we apply rational RNA engineering strategies to improve the fold activation of two STAR regulators. We demonstrate that a combination of promoter strength tuning and multiple RNA engineering strategies can improve fold activation from 5.4-fold to 13.4-fold for a STAR regulator derived from the pbuE riboswitch terminator. We then validate the generality of our approach and show that these same strategies improve fold activation from 2.1-fold to 14.6-fold for an unrelated STAR regulator, opening the door to creating a range of additional STARs to use in a broad array of biotechnologies. We also establish that the optimizations preserve the orthogonality of these STARs between themselves and a set of RNA transcriptional repressors, enabling these optimized STARs to be used in sophisticated circuits.

  10. Chromospheric Activity in Cool Stars: Open Questions

    NASA Astrophysics Data System (ADS)

    Schröder, K.-P.; Schmitt, J. H. M. M.

    2013-04-01

    Despite a wealth of observational insight into chromospheric physics obtained in the past decades, a number of fundamental questions remain to be answered. On some of them we seem to make progress, others are motivation for ongoing research: is there a well-defined “zero-point” of magnetic stellar activity, and by which heating processes is the basal chromospheric flux created? Or: how did the Sun look like during the Maunder Minimum, and when is the next one due? And are activity cycles of cool giants caused by a solar-type dynamo, despite a very different internal structure? What makes magnetic stellar activity be still (or again?) at work in such very evolved stars — should not all angular momentum have been consumed? To find some answers, the Hamburg Robotic Telescope, equipped with a high-resolution (20,000) spectrograph, will start regular operation at its final site in Guanajuato, central Mexico, this year (2012), in part to resume the legendary Mt. Wilson stellar activity monitoring project.

  11. Metallicity gradients and newly created star-forming systems in interacting galaxies

    NASA Astrophysics Data System (ADS)

    Mendes de Oliveira, Claudia L.

    2015-08-01

    Interactions play an extremely important role in the evolution of galaxies, changing their morphologies and kinematics. Galaxy collisions may result in the formation of intergalactic star-forming objects, such as HII regions, young clusters and/or tidal dwarf galaxies. Several studies have found a wealth of newly created objects in interacting systems. We will exemplify the problems and challenges in this field and will describe observations of the interacting group NGC 6845, which contains four bright galaxies, two of which have extended tidal tails. We obtained Gemini/GMOS spectra for 28 of the regions located in the galaxies and in the tails. All regions in the latter are star-forming objects according to their line ratios, with ages younger than 10 Myr. A super luminous star forming complex is found in the brightest member of the group, NGC 6845A. Its luminosity reveals a star formation density of 0.19 solar masses, per year, per kpc^2, suggesting that this object is a localized starburst. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. We speculate that the observed metallicity gradient may be related to one or more of the following mechanisms: (1) interaction induced inflow of fresh gas to the galaxy center, as seen in simulations, which is expected to dilute the metallicity of the central burst, (2) the formation of young metal-rich star forming regions in the tidal tails, which were born out of enriched gas expelled from the central regions of the system during the interaction and (3) the incremental growth of metals accumulated over time, due to the successful generations of star forming regions along the tails. Finally we will describe our plans to do a search for such objects on Halpha images that will soon be available for 17.5k degrees of the sky, with the A-PLUS survey.

  12. An activity catalogue of southern stars

    NASA Astrophysics Data System (ADS)

    Jenkins, J. S.; Jones, H. R. A.; Tinney, C. G.; Butler, R. P.; McCarthy, C.; Marcy, G. W.; Pinfield, D. J.; Carter, B. D.; Penny, A. J.

    2006-10-01

    We have acquired high-resolution echelle spectra of 225 F6-M5 type stars in the Southern hemisphere. The stars are targets or candidates to be targets for the Anglo-Australian Planet Search. CaII H& K line cores were used to derive activity indices for all of these objects. The indices were converted to the Mt. Wilson system of measurements and logR'HK values determined. A number of these stars had no previously derived activity indices. In addition, we have also included the stars from Tinney et al. using our Mt. Wilson calibration. The radial-velocity instability (also known as jitter) level was determined for all 21 planet-host stars in our data set. We find the jitter to be at a level considerably below the radial-velocity signatures in all but one of these systems. 19 stars from our sample were found to be active (logR'HK > -4.5) and thus have high levels of jitter. Radial-velocity analysis for planetary companions to these stars should proceed with caution.

  13. Magnetism and activity of planet hosting stars

    NASA Astrophysics Data System (ADS)

    Wright, Jason T.; Miller, Brendan P.

    The magnetic activity levels of planet host stars may differ from that of stars not known to host planets in several ways. Hot Jupiters may induce activity in their hosts through magnetic interactions, or through tidal interactions by affecting their host's rotation or convection. Measurements of photospheric, chromospheric, or coronal activity might then be abnormally high or low compared to control stars that do not host hot Jupiters, or might be modulated at the planet's orbital period. Such detections are complicated by the small amplitude of the expected signal, by the fact that the signals may be transient, and by the difficulty of constructing control samples due to exoplanet detection biases and the uncertainty of field star ages. We review these issues, and discuss avenues for future progress in the field.

  14. [Creating optimal hygienic conditions for students' activities].

    PubMed

    Grebniak, N P

    1990-05-01

    Optimization of the preparation of school-children for the working activity may be presented as a model consisting of 4 blocks. Socially significant functions are system-forming factors of this model, i.e. the functions of an organism with which successful implementation of the major types of activities is associated. System approach to the management of schoolchildren's activities based on the dynamic control of socially significant functions and on selective influence on external and internal factors with the help of prophylactic and corrective activities make it possible to maintain its hygienic optimization.

  15. Creating Futures Activity Cards and Teacher Guide.

    ERIC Educational Resources Information Center

    Klenzman, Elizabeth; Taylor, Paula

    Teachers can use these learning activities to teach about the future in elementary and secondary social studies, science, math, language arts, and arts courses. The purpose of the activities is to help students practice creative-thinking skills, investigate problems relevant to their personal futures, experience the concept of change, and evaluate…

  16. PASS: Creating Physically Active School Systems

    ERIC Educational Resources Information Center

    Ciotto, Carol M.; Fede, Marybeth H.

    2014-01-01

    PASS, a Physically Active School System, is a program by which school districts and schools utilize opportunities for school-based physical activity that enhance overall fitness and cognition, which can be broken down into four integral parts consisting of connecting, communicating, collaborating, and cooperating. There needs to be an…

  17. Chandra Reveals a Compact Nebula Created by a Shooting Neutron Star

    NASA Astrophysics Data System (ADS)

    2000-06-01

    In one of its most bizarre images yet, NASA's Chandra X-ray Observatory shows the details of a compact nebula that resembles a gigantic cosmic crossbow. The nebula, located in the Vela supernova remnant, is created as a rapidly rotating neutron star, or pulsar, spins out rings and jets of high-energy particles while shooting through space. "What is fascinating is that the jets from the pulsar are directed exactly along the direction of the pulsar's motion," said Dr. George Pavlov of Penn State University, University Park today at the 196th national meeting of the American Astronomical Society in Rochester, New York. "The southern jet looks like a rocket exhaust!" The X-ray jet can be traced all the way in to the neutron star, and an inner ring is seen for the first time. This ring is thought to represent a shock wave due to matter rushing away from the neutron star. More focused flows at the neutron star's polar regions produce jets of particles that blast away at near the speed of light. Pavlov explained that shortly after the star exploded, jets with unequal thrust along the poles of the neutron star could have accelerated it like a rocket. The neutron star is enveloped in a cloud of high-energy particles emitting X rays as they spiral around magnetic field lines. This cloud, or nebula, is embedded in a much larger cloud produced by the supernova and has a swept-back, cometary shape because of its motion through the larger cloud. The dramatic bow-like structure at the leading edge of the nebula is perpendicular to the jets and has the appearance of a cosmic crossbow with the jets as the arrows. This bow and the smaller one inside it, are thought to be the near edges of tilted rings of X-ray emission from high-energy particles produced by the central neutron star. The neutron star-ring-jet system, which resulted from an explosion in the constellation Vela ten thousand or more years ago, is similar to the remarkable structure observed by Chandra in the Crab Nebula

  18. Line profile asymmetries in chromospherically active stars

    NASA Technical Reports Server (NTRS)

    Dempsey, Robert C.; Bopp, Bernard W.; Strassmeier, Klaus G.; Granados, Arno F.; Henry, Gregory W.; Hall, Douglas S.

    1992-01-01

    A powerful, new probe of chromospheric activity, cross-correlation, has been developed and applied to a variety of stars. In this particular application, an entire CCD spectrum of an active star is correlated with the spectrum of a narrow-line, inactive star of similar spectral type and luminosity class. Using a number of strong lines in this manner enables the detection of absorption profile asymmetries at moderate resolution (lambda/Delta lambda about 40,000) and S/N 150:1. This technique has been applied to 14 systems mostly RS CVn's, with 10 not greater than nu sin i not greater than 50 km/s and P not less than 7 d. Distortions were detected for the first time in five systems: Sigma Gem, IM Peg, GX Lib, UV Crb, and Zeta And. Detailed modeling, incorporating both spectral line profiles and broad-band photometry, is applied to Sigma Gem. Profile asymmetries for this star are fitted by two high-latitude spots covering 5 percent of the stellar surface. The derived spot temperature of 3400 K is lower than found in previous studies. In addition, two well-known systems have been studied: HD 199178 and V711 Tau. Polar spots are found on both.

  19. Chromospherically active stars. I - HD 136905

    NASA Technical Reports Server (NTRS)

    Fekel, F. C.; Hall, D. S.; Africano, J. L.; Gillies, K.; Quigley, R.

    1985-01-01

    The variable star HD 136905, recently designated GX Librae, is a chromospherically active K1 III single-lined spectroscopic binary with a period of 11.1345 days. It has moderate strength Ca II H and K and ultraviolet emission features, while H-alpha is strongly in absorption. The inclination of the system is 58 + or - 17 deg and the unseen secondary is most likely a G or K dwarf. The v sin i of the primary, 32 + or - 2 km/s, results in a minimum radius of 7.0 + or - 0.4 solar radii. Since the star fills a substantial fracture of its Roche lab, the double-peaked limit curve seen by photometric observers is predominantly ellipsoidal in nature. Both the photometry and the spectroscopy yield values for the period and the time of conjunction that are identical within their uncertainties.

  20. STAR FORMATION ACTIVITY IN CLASH BRIGHTEST CLUSTER GALAXIES

    SciTech Connect

    Fogarty, Kevin; Postman, Marc; Connor, Thomas; Donahue, Megan; Moustakas, John

    2015-11-10

    The CLASH X-ray selected sample of 20 galaxy clusters contains 10 brightest cluster galaxies (BCGs) that exhibit significant (>5σ) extinction-corrected star formation rates (SFRs). Star formation activity is inferred from photometric estimates of UV and Hα+[N ii] emission in knots and filaments detected in CLASH Hubble Space Telescope ACS and WFC3 observations. UV-derived SFRs in these BCGs span two orders of magnitude, including two with a SFR ≳ 100 M{sub ⊙} yr{sup −1}. These measurements are supplemented with [O ii], [O iii], and Hβ fluxes measured from spectra obtained with the SOAR telescope. We confirm that photoionization from ongoing star formation powers the line emission nebulae in these BCGs, although in many BCGs there is also evidence of a LINER-like contribution to the line emission. Coupling these data with Chandra X-ray measurements, we infer that the star formation occurs exclusively in low-entropy cluster cores and exhibits a correlation with gas properties related to cooling. We also perform an in-depth study of the starburst history of the BCG in the cluster RXJ1532.9+3021, and create 2D maps of stellar properties on scales down to ∼350 pc. These maps reveal evidence for an ongoing burst occurring in elongated filaments, generally on ∼0.5–1.0 Gyr timescales, although some filaments are consistent with much younger (≲100 Myr) burst timescales and may be correlated with recent activity from the active galactic nucleus. The relationship between BCG SFRs and the surrounding intracluster medium gas properties provide new support for the process of feedback-regulated cooling in galaxy clusters and is consistent with recent theoretical predictions.

  1. Chromospheric Activity in Pre-Main-Sequence Stars

    NASA Astrophysics Data System (ADS)

    Simon, Theodore

    IUE observations of solar-type stars show a decline of chromospheric and TR emission with age. For main-sequence stars older than 100 million yr, this decay is exponential from a plateau defined by the youngest stars. At an age of ~1 million yr, the pre-main-sequence T Tauri stars have UV emission line fluxes some 2 orders of magnitude above the plateau for mainsequence stars. This suggests that chromospheric activity in the T Tauri stars falls to the levels of the older stars by a separate decay scheme. The decline in pre-mainsequence activity may be caused by the evolutionary shallowing of the convection zone, while on the main-sequence it is due to the star's spindown. This hypothesis needs confirmation, but relatively few T Tauri stars have been observed by IUE. Since the majority of the T Tauri stars thus far observed are probably more massive than the Sun, it may be inappropriate to compare their UV emission with that of the older I Mo dwarf stars. We propose here to observe the ultraviolet chromospheric and TR lines of pre-main-sequence stars we believe to be of ~1 M(sun). We have chosen a sample of low-luminosity M-type T Tauri stars from the T-associations in Lupus; if evolutionary tracks have any validity, a large fraction of those stars should be close to 1 M(sun)in mass. In order to place the stars more accurately on the H-R diagram and to determine their rotation rates (for comparison with the mainsequence stars), we plan concurrent visual spectroscopy and visual-infrared photometry.

  2. Observational evidence for enhanced magnetic activity of superflare stars.

    PubMed

    Karoff, Christoffer; Knudsen, Mads Faurschou; De Cat, Peter; Bonanno, Alfio; Fogtmann-Schulz, Alexandra; Fu, Jianning; Frasca, Antonio; Inceoglu, Fadil; Olsen, Jesper; Zhang, Yong; Hou, Yonghui; Wang, Yuefei; Shi, Jianrong; Zhang, Wei

    2016-03-24

    Superflares are large explosive events on stellar surfaces one to six orders-of-magnitude larger than the largest flares observed on the Sun throughout the space age. Due to the huge amount of energy released in these superflares, it has been speculated if the underlying mechanism is the same as for solar flares, which are caused by magnetic reconnection in the solar corona. Here, we analyse observations made with the LAMOST telescope of 5,648 solar-like stars, including 48 superflare stars. These observations show that superflare stars are generally characterized by larger chromospheric emissions than other stars, including the Sun. However, superflare stars with activity levels lower than, or comparable to, the Sun do exist, suggesting that solar flares and superflares most likely share the same origin. The very large ensemble of solar-like stars included in this study enables detailed and robust estimates of the relation between chromospheric activity and the occurrence of superflares.

  3. Observational evidence for enhanced magnetic activity of superflare stars

    PubMed Central

    Karoff, Christoffer; Knudsen, Mads Faurschou; De Cat, Peter; Bonanno, Alfio; Fogtmann-Schulz, Alexandra; Fu, Jianning; Frasca, Antonio; Inceoglu, Fadil; Olsen, Jesper; Zhang, Yong; Hou, Yonghui; Wang, Yuefei; Shi, Jianrong; Zhang, Wei

    2016-01-01

    Superflares are large explosive events on stellar surfaces one to six orders-of-magnitude larger than the largest flares observed on the Sun throughout the space age. Due to the huge amount of energy released in these superflares, it has been speculated if the underlying mechanism is the same as for solar flares, which are caused by magnetic reconnection in the solar corona. Here, we analyse observations made with the LAMOST telescope of 5,648 solar-like stars, including 48 superflare stars. These observations show that superflare stars are generally characterized by larger chromospheric emissions than other stars, including the Sun. However, superflare stars with activity levels lower than, or comparable to, the Sun do exist, suggesting that solar flares and superflares most likely share the same origin. The very large ensemble of solar-like stars included in this study enables detailed and robust estimates of the relation between chromospheric activity and the occurrence of superflares. PMID:27009381

  4. Star Formation Activity in CLASH Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Fogarty, Kevin; Postman, Marc; Connor, Thomas; Donahue, Megan; Moustakas, John

    2015-11-01

    The CLASH X-ray selected sample of 20 galaxy clusters contains 10 brightest cluster galaxies (BCGs) that exhibit significant (>5σ) extinction-corrected star formation rates (SFRs). Star formation activity is inferred from photometric estimates of UV and Hα+[N ii] emission in knots and filaments detected in CLASH Hubble Space Telescope ACS and WFC3 observations. UV-derived SFRs in these BCGs span two orders of magnitude, including two with a SFR ≳ 100 M⊙ yr-1. These measurements are supplemented with [O ii], [O iii], and Hβ fluxes measured from spectra obtained with the SOAR telescope. We confirm that photoionization from ongoing star formation powers the line emission nebulae in these BCGs, although in many BCGs there is also evidence of a LINER-like contribution to the line emission. Coupling these data with Chandra X-ray measurements, we infer that the star formation occurs exclusively in low-entropy cluster cores and exhibits a correlation with gas properties related to cooling. We also perform an in-depth study of the starburst history of the BCG in the cluster RXJ1532.9+3021, and create 2D maps of stellar properties on scales down to ˜350 pc. These maps reveal evidence for an ongoing burst occurring in elongated filaments, generally on ˜0.5-1.0 Gyr timescales, although some filaments are consistent with much younger (≲100 Myr) burst timescales and may be correlated with recent activity from the active galactic nucleus. The relationship between BCG SFRs and the surrounding intracluster medium gas properties provide new support for the process of feedback-regulated cooling in galaxy clusters and is consistent with recent theoretical predictions. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel

  5. Stars Over Mauna Kea: Creating an IYA Supplement in Your Local Newspaper

    NASA Astrophysics Data System (ADS)

    Harvey, J.

    2010-08-01

    Gemini Observatory's Public Information and Outreach Office along with other observatories on Mauna Kea produced a newspaper "tabloid" or special edition supplement on astronomy, specifically related to IYA (see figures 1 and 2). In addition, we contracted with the local newspaper to have an IYA website on their webpage. In the first six months the website had over 840,000 hits with over 5,000 downloads of the Stars Over Mauna Kea publication! As a general astronomy supplement the concept has proven extremely successful.

  6. Nearby Galaxy is a Hotbed of Star Birth Activity

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This new image taken with NASA's Hubble Space Telescope (HST) is of the nearby dwarf galaxy NGC 1569. This galaxy is a hotbed of vigorous star birth activity which blows huge bubbles that riddle its main body. The bubble structure is sculpted by the galactic super-winds and outflows caused by a colossal input of energy from collective supernova explosions that are linked with a massive episode of star birth. The bubbles seen in this image are made of hydrogen gas that glows when hit by the fierce wind and radiation from hot young stars and is racked by supernova shocks. Its 'star factories' are also manufacturing brilliant blue star clusters. NGC 1569 had a sudden onset of star birth about 25 million years ago, which subsided about the time the very earliest human ancestors appeared on Earth. The Marshall Space Flight Center had responsibility for the design, development, and construction of the HST.

  7. General Model for Light Curves of Chromospherically Active Binary Stars

    NASA Astrophysics Data System (ADS)

    Jetsu, L.; Henry, G. W.; Lehtinen, J.

    2017-04-01

    The starspots on the surface of many chromospherically active binary stars concentrate on long-lived active longitudes separated by 180°. Shifts in activity between these two longitudes, the “flip-flop” events, have been observed in single stars like FK Comae and binary stars like σ Geminorum. Recently, interferometry has revealed that ellipticity may at least partly explain the flip-flop events in σ Geminorum. This idea was supported by the double-peaked shape of the long-term mean light curve of this star. Here we show that the long-term mean light curves of 14 chromospherically active binaries follow a general model that explains the connection between orbital motion, changes in starspot distribution, ellipticity, and flip-flop events. Surface differential rotation is probably weak in these stars, because the interference of two constant period waves may explain the observed light curve changes. These two constant periods are the active longitude period ({P}{act}) and the orbital period ({P}{orb}). We also show how to apply the same model to single stars, where only the value of P act is known. Finally, we present a tentative interference hypothesis about the origin of magnetic fields in all spectral types of stars. The CPS results are available electronically at the Vizier database.

  8. Understanding Activity Cycles of Solar Type Stars with Kepler

    NASA Astrophysics Data System (ADS)

    Tovar, Guadalupe; Montet, Benjamin; Johnson, John A.

    2017-01-01

    As the era of exploring new worlds and systems advances we seek to answer the question: How common is our Sun? There is considerable evidence about the recurring activity cycles of our Sun but very little is known about the activity cycles of other stars. By calibrating the full frame images from the original Kepler mission that were taken once a month over the course of four years, we are able to do relative photometry on roughly 5 million stars. By building a model of the pixel response function we were able to achieve 0.8% precision photometry. We identify 50,000 solar type stars based on magnitude, surface gravity, and temperature cuts. We observe the relative increase and decrease in brightness of the stars indicating signs of activity cycles similar to our Sun. We continue to explore how a data driven pixel response function model could improve our precision to 0.1% photometry measurements.

  9. Magnetism and Activity of Planet-Hosting Stars

    NASA Astrophysics Data System (ADS)

    Wright, Jason Thomas; Miller, Brendan

    2015-08-01

    The magnetic activity levels of planet host stars may differ from that of stars not known to host planets in several ways. Hot jupiters may induce activity in their hosts through magnetic interactions, or through tidal interactions by affecting their host's rotation or convection. Measurements of photospheric, chromospheric, or coronal activity might then be abnormally abnormally high or low compared to control stars that do not host hot Jupiters, or might be modulated at the planet's orbital period. Such detections are complicated by the small amplitude of the expected signal, by the fact that the signals may be transient, and by the difficulty of constructing control samples due to exoplanet deteciton biases and the uncertainty of field star ages. I will review these issues, and discuss avenues for future progress in the field.

  10. Spectroscopic observations of active solar-analog stars with high X-ray luminosity, as a proxy of superflare stars

    NASA Astrophysics Data System (ADS)

    Notsu, Yuta; Honda, Satoshi; Maehara, Hiroyuki; Notsu, Shota; Namekata, Kosuke; Nogami, Daisaku; Shibata, Kazunari

    2017-02-01

    Recent studies of solar-type superflare stars have suggested that even old slowly rotating stars similar to the Sun can have large starspots and superflares. We conducted high-dispersion spectroscopy of 49 nearby solar-analog stars (G-type main-sequence stars with Teff ≈ 5600-6000 K) identified as ROSAT soft X-ray sources, which are not binary stars from previous studies. We expected that these stars could be used as a proxy of bright solar-analog superflare stars, since superflare stars are expected to show strong X-ray luminosity. More than half (37) of the 49 target stars show no evidence of binarity, and their atmospheric parameters (temperature, surface gravity, and metallicity) are within the range of ordinary solar-analog stars. We measured the intensity of Ca II 8542 and Hα lines, which are good indicators of the stellar chromospheric activity. The intensity of these lines indicates that all the target stars have large starspots. We also measured v sin i (projected rotational velocity) and lithium abundance for the target stars. Li abundance is a key to understanding the evolution of the stellar convection zone, which reflects the stellar age, mass and rotational history. We confirmed that many of the target stars rapidly rotate and have high Li abundance, compared with the Sun, as suggested by many previous studies. There are, however, also some target stars that rotate slowly (v sin i = 2-3 km s-1) and have low Li abundance like the Sun. These results support that old and slowly rotating stars similar to the Sun could have high activity levels and large starspots. This is consistent with the results of our previous studies of solar-type superflare stars. In the future, it is important to conduct long-term monitoring observations of these active solar-analog stars in order to investigate detailed properties of large starspots from the viewpoint of stellar dynamo theory.

  11. The Suppression of Star Formation by Powerful Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Dwek, E.

    2012-01-01

    The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight corre1ation between the mass of the black hole and the mas. of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming ga1axies are usually dust-obscured and are brightest at infrared and submillimeter wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(exp 44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expe11ing the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.

  12. The suppression of star formation by powerful active galactic nuclei.

    PubMed

    Page, M J; Symeonidis, M; Vieira, J D; Altieri, B; Amblard, A; Arumugam, V; Aussel, H; Babbedge, T; Blain, A; Bock, J; Boselli, A; Buat, V; Castro-Rodríguez, N; Cava, A; Chanial, P; Clements, D L; Conley, A; Conversi, L; Cooray, A; Dowell, C D; Dubois, E N; Dunlop, J S; Dwek, E; Dye, S; Eales, S; Elbaz, D; Farrah, D; Fox, M; Franceschini, A; Gear, W; Glenn, J; Griffin, M; Halpern, M; Hatziminaoglou, E; Ibar, E; Isaak, K; Ivison, R J; Lagache, G; Levenson, L; Lu, N; Madden, S; Maffei, B; Mainetti, G; Marchetti, L; Nguyen, H T; O'Halloran, B; Oliver, S J; Omont, A; Panuzzo, P; Papageorgiou, A; Pearson, C P; Pérez-Fournon, I; Pohlen, M; Rawlings, J I; Rigopoulou, D; Riguccini, L; Rizzo, D; Rodighiero, G; Roseboom, I G; Rowan-Robinson, M; Sánchez Portal, M; Schulz, B; Scott, D; Seymour, N; Shupe, D L; Smith, A J; Stevens, J A; Trichas, M; Tugwell, K E; Vaccari, M; Valtchanov, I; Viero, M; Vigroux, L; Wang, L; Ward, R; Wright, G; Xu, C K; Zemcov, M

    2012-05-09

    The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expelling the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.

  13. Drama Activities for K-6 Students: Creating Classroom Spirit

    ERIC Educational Resources Information Center

    Polsky, Milton E.; Schindel, Dorothy Napp; Tabone, Carmine

    2006-01-01

    In this book, the authors provide dramatic strategies accompanied by age-appropriate stories and poems from around the world that address such issues as sharing, caring, cooperation, consequences, and bullying in order to create a positive classroom environment. The students' enactments take them to different lands around the globe, back into…

  14. Monitoring the activity of the Be star OT Geminorum

    NASA Astrophysics Data System (ADS)

    Arellano Ferro, A.; Sareyan, J. P.; Avila, J. J.; Gonzalez, F.; Dumont, M.; Geos

    1998-02-01

    Observations obtained in 1995-1996 of the Be star OT Geminorum are reported and show that in october 1995 the star reached a very active phase with large variations around a bright plateau, a phase of activity we have also distinguished in previous observations dating from 1960. The time scales involved are discussed and suggest that the violent variations of the activity propagate very quickly on the whole surface of the star or on a huge portion of it. No likely pulsation periods were found. The assumption that the detected activity is due to the effects of an hypothetical companion leads to conclude that such companion could not be detected by the present interferometric techniques. Partly based on observations obtained at the La Luz Observatory of the University of Guanajuato, Mexico.

  15. Stellar model chromospheres. IX - Chromospheric activity in dwarf stars

    NASA Technical Reports Server (NTRS)

    Kelch, W. L.; Worden, S. P.; Linsky, J. L.

    1979-01-01

    High-resolution Ca II K line profiles are used to model the upper photospheres and lower chromospheres of eight main-sequence stars ranging in spectral type from F0 to M0 and exhibiting different degrees of chromospheric activity. The model chromospheres are studied as a function of spectral type and activity for stars of similar spectral type in order to obtain evidence of enhanced nonradiative heating in the upper-photospheric models and in the ratio of minimum temperature at the base of the chromosphere to effective temperature, a correlation between activity and temperature in the lower chromospheres, and a correlation of the width at the base of the K-line emission core and at the K2 features with activity. Chromospheric radiative losses are estimated for the modelled stars and other previously analyzed main-sequence stars. The results obtained strengthen the argument that dMe flare stars exhibit fundamentally solar-type activity but on an increased scale.

  16. Activity-rotation relations for lower main sequence stars

    NASA Astrophysics Data System (ADS)

    Dobson-Hockey, Andrea Kay

    It was known for some time that stellar rotation and activity are related, both for chromospheric activity and control activity. Younger, more rapidly rotating stars of a given spectral type generally show higher levels of activity than do older, more slowly rotating stars. On the Sun acitivity is distinctly related to magnetic fields. This leads to the suggestion that activity, at least in solar-type stars, is traceable to a magnetic dynamo which results from the interaction of rotation and differential rotation with convection. The more efficient the coriolis forces are at introducing helicity into convective motions, the more the magnetic field will be amplified and the more activity that is expected. The precise nature of the relationship between magnetic fields, rotation, and activity remains to be well-defined. It is the purpose to examine the relationship between activity and rotation in order to better define and express such a relation (or relations). To meet this goal, a comprehensive sample of stars was collected from the published literature having two or more of the following: chromospheric Ca II, H, and K emission indices; coronal soft X-ray illumination; rotation rates; and where possible, ages. It is seen that the use of normalized activity units and Rossby number generally improves the correlation between activity and rotation. The use of the convective turnover time further permits a possible explanation for the distribution of stars in an activity-color diagram. A large and homogeneous data set permits better definition of previously examined functional dependencies such as the time decay of activity and the relationship between chromospheric and coronal activity indicators.

  17. Rapid rotation and mixing in active OB stars - Physical processes

    NASA Astrophysics Data System (ADS)

    Zahn, Jean-Paul

    2011-07-01

    In the standard description of stellar interiors, O and B stars possess a thoroughly mixed convective core surrounded by a stable radiative envelope in which no mixing occurs. But as is well known, this model disagrees strongly with the spectroscopic diagnostic of these stars, which reveals the presence at their surface of chemical elements that have been synthesized in the core. Hence the radiation zone must be the seat of some mild mixing mechanisms. The most likely to operate there are linked with the rotation: these are the shear instabilites triggered by the differential rotation, and the meridional circulation caused by the changes in the rotation profile accompanying the non-homologous evolution of the star. In addition to these hydrodynamical processes, magnetic stresses may play an important role in active stars, which host a magnetic field. These physical processes will be critically examined, together with some others that have been suggested.

  18. AN ULTRAVIOLET INVESTIGATION OF ACTIVITY ON EXOPLANET HOST STARS

    SciTech Connect

    Shkolnik, Evgenya L.

    2013-03-20

    Using the far-UV (FUV) and near-UV (NUV) photometry from the NASA Galaxy Evolution Explorer (GALEX), we searched for evidence of increased stellar activity due to tidal and/or magnetic star-planet interactions (SPI) in the 272 known FGK planetary hosts observed by GALEX. With the increased sensitivity of GALEX, we are able probe systems with lower activity levels and at larger distances than what has been done to date with X-ray satellites. We compared samples of stars with close-in planets (a < 0.1 AU) to those with far-out planets (a > 0.5 AU) and looked for correlations of excess activity with other system parameters. This statistical investigation found no clear correlations with a, M{sub p} , or M{sub p} /a, in contrast to some X-ray and Ca II studies. However, there is tentative evidence (at a level of 1.8{sigma}) that stars with radial-velocity-(RV)-detected close-in planets are more FUV-active than stars with far-out planets, in agreement with several published X-ray and Ca II results. The case is strengthened to a level of significance to 2.3{sigma} when transit-detected close-in planets are included. This is most likely because the RV-selected sample of stars is significantly less active than the field population of comparable stars, while the transit-selected sample is similarly active. Given the factor of 2-3 scatter in fractional FUV luminosity for a given stellar effective temperature, it is necessary to conduct a time-resolved study of the planet hosts in order to better characterize their UV variability and generate a firmer statistical result.

  19. The role of mitochondrial fusion and StAR phosphorylation in the regulation of StAR activity and steroidogenesis.

    PubMed

    Castillo, Ana F; Orlando, Ulises; Helfenberger, Katia E; Poderoso, Cecilia; Podesta, Ernesto J

    2015-06-15

    The steroidogenic acute regulatory (StAR) protein regulates the rate-limiting step in steroidogenesis, i.e. the delivery of cholesterol from the outer (OMM) to the inner (IMM) mitochondrial membrane. StAR is a 37-kDa protein with an N-terminal mitochondrial targeting sequence that is cleaved off during mitochondrial import to yield 30-kDa intramitochondrial StAR. StAR acts exclusively on the OMM and its activity is proportional to how long it remains on the OMM. However, the precise fashion and the molecular mechanism in which StAR remains on the OMM have not been elucidated yet. In this work we will discuss the role of mitochondrial fusion and StAR phosphorylation by the extracellular signal-regulated kinases 1/2 (ERK1/2) as part of the mechanism that regulates StAR retention on the OMM and activity.

  20. SWP Echelle Spectra of Chromospherically Active Dwarf Stars

    NASA Astrophysics Data System (ADS)

    Ayres, Thomas R.

    High resolution spectra of the 1150-2000 A region are enormously valuable for probing outer- atmosphere structure in cool stars. For example, such data can be used to separate blends, identify individual emission components in short-period binary systems, determine intensity ratios in close multiplets, estimate reliable emission strengths of lines superimposed on bright stellar continua, and test for the presence or absence of stellar winds at 105 K temperatures. These possibilities are not practical with IUE low-dispersion spectra. However, one must pay a steep-price to obtain useable high-dispersion IUE spectra and the additional dimension of diagnostic information, namely only a handful of the brightest UV sources are accessible even with shift-long exposures. We propose below an observing program to obtain echelle spectra of chromospherically active dwarf stars in the 1150-2000 A shortwavelength region. This program is intended to explore a particular class of objects that heretofore have not been observed at high dispersion with the SWP camera. Futhermore, this program complements previous SWP echelle studies by our group at the University of Colorado of quiet-chromosphere dwarf stars (alpha Cen A, alpha Cen B), active giants (alpha Aur A, lambda And, beta Dra), and the extreme case of the very active RS CVn-type system HR 1099. As described below, highdispersion spectra of these targets have provided a critical interpretive dimension that was lacking in previous low-dispersion studies. However, several fundamental questions have been raised in the course of our exploratory SWP work on what, in practice, are two distinct classes of chromospheric stars: the quiet dwarfs and the active giants. We feel that many of these questions can be answered by bridging the interpretive gap with a careful study of the active dwarfs. Our recent experience with shift-long SWP echelle exposures of chromospheric emission stars has suggested that our previous estimates of

  1. Opportunities to Create Active Learning Techniques in the Classroom

    ERIC Educational Resources Information Center

    Camacho, Danielle J.; Legare, Jill M.

    2015-01-01

    The purpose of this article is to contribute to the growing body of research that focuses on active learning techniques. Active learning techniques require students to consider a given set of information, analyze, process, and prepare to restate what has been learned--all strategies are confirmed to improve higher order thinking skills. Active…

  2. The Evolution of Star Formation Activity in Cluster Galaxies Over 0.15 < z < 1.5

    NASA Astrophysics Data System (ADS)

    Wagner, Cory R.

    In this thesis, we explore 7.5 billion years of evolution in cluster galaxy star formation activity using a sample of 11 high-redshift (1 < z < 1.5) clusters from the IRAC Shallow Cluster Survey, and 25 low-redshift (0.15 < z < 1) clusters from The Cluster Lensing And Supernova survey with Hubble. We compare cluster galaxy star formation to that of the field over 0.15 < z < 1.5 using 8000 galaxies from the UltraVISTA survey. Mid-infrared star formation rates are measured using Spitzer 24 mum data for isolated high-redshift galaxies. We calculate rest-frame ultraviolet star formation rates for low-redshift cluster members using Hubble Space Telescope observations. Using publically available mid-infrared and ultraviolet data for our field sample, we empirically derive scaling relations to adjust low-redshift cluster galaxy ultraviolet star formation rates to mid-infrared levels. We classify cluster galaxy morphology by visual inspection, and use quantitatively measured morphologies for field galaxies. Cluster late-type galaxies at z > 1 show enhanced star formation activity relative to the field, and account for nearly 90% of the overall star formation activity in high-redshift clusters. While high-redshift early-type galaxies are substantially quenched relative to cluster late-types, they still contribute 13% of the total cluster star formation activity. With early-type fractions increasing from 34 to 56% from z 1.5 → 1.16, we find that new cluster early-type galaxies are likely being formed around z 1.4. The fraction of early-type galaxies that are star-forming drops from 29 to 11% over this period, yet their specific star formation rates are roughly constant. These factors suggest that the events that created these new galaxies, possibly mergers, were both recent and gas-rich. With typical coverages of 50% of z < 1 cluster virial radii, we can only probe the cores of low-redshift clusters. We find that in this regime, the star formation activity of cluster

  3. Rotation, differential rotation, and gyrochronology of active Kepler stars

    NASA Astrophysics Data System (ADS)

    Reinhold, Timo; Gizon, Laurent

    2015-11-01

    Context. In addition to the discovery of hundreds of exoplanets, the high-precision photometry from the CoRoT and Kepler satellites has led to measurements of surface rotation periods for tens of thousands of stars, which can potentially be used to infer stellar ages via gyrochronology. Aims: Our main goal is to derive ages of thousands of field stars using consistent rotation period measurements derived by different methods. Multiple rotation periods are interpreted as surface differential rotation (DR). We study the dependence of DR with rotation period and effective temperature. Methods: We reanalyze a previously studied sample of 24 124 Kepler stars using different approaches based on the Lomb-Scargle periodogram. Each quarter (Q1-Q14) is treated individually using a prewhitening approach. Additionally, the full time series and their different segments are analyzed. Results: For more than 18 500 stars our results are consistent with the rotation periods from McQuillan et al. (2014, ApJS, 211, 24). Of these, more than 12 300 stars show multiple significant peaks, which we interpret as DR. Dependencies of the DR with rotation period and effective temperature could be confirmed, e.g., the relative DR increases with rotation period. Gyrochronology ages between 100 Myr and 10 Gyr were derived for more than 17 000 stars using different gyrochronology relations, most of them with uncertainties dominated by period variations. We find a bimodal age distribution for Teff between 3200-4700 K. The derived ages reveal an empirical activity-age relation using photometric variability as stellar activity proxy. Additionally, we found 1079 stars with extremely stable (mostly short) periods. Half of these periods may be associated with rotation stabilized by non-eclipsing companions, the other half might be due to pulsations. Conclusions: The derived gyrochronology ages are well constrained since more than ~93.0% of the stars seem to be younger than the Sun where calibration is

  4. Activity-rotation relations for lower main-sequence stars

    SciTech Connect

    Dobson-Hockey, A.K.

    1987-01-01

    It has been known for some time that stellar rotation and activity are related, both for chromospheric activity (e.g., Noyes et al. 1984) and coronal activity (e.g., Pallavicini et al. 1981; Maggio et al. 1987). Younger, more rapidly rotating stars of a given spectral type generally show higher levels of activity than do older, more slowly rotating stars. On the Sun, activity is distinctly related to magnetic fields. This leads to the suggestion that activity, at least in solar-type stars, is traceable to a magnetic dynamo which results from the interaction of rotation and differential rotation with convection. The more efficient the coriolis forces are at introducing helicity into convective motions, the more the magnetic field will be amplified and the more activity we may expect to see. The precise nature of the relationship between magnetic fields, rotation, and activity remains to be well-defined. This thesis examines the relationship between activity (both chromospheric and coronal) and rotation in order to better define and express such a relation (or relations).

  5. Rotation and differential rotation of active Kepler stars

    NASA Astrophysics Data System (ADS)

    Reinhold, Timo; Reiners, Ansgar; Basri, Gibor

    2013-12-01

    Context. The Kepler space telescope monitors more than 160 000 stars with an unprecedented precision providing the opportunity to study the rotation of thousands of stars. Aims: We present rotation periods for thousands of active stars in the Kepler field derived from Q3 data. In most cases a second period close to the rotation period was detected that we interpreted as surface differential rotation (DR). We show how the absolute and relative shear (ΔΩ and α = ΔΩ/Ω, respectively) correlate with rotation period and effective temperature. Methods: Active stars were selected from the whole sample using the range of the variability amplitude. To detect different periods in the light curves we used the Lomb-Scargle periodogram in a pre-whitening approach to achieve parameters for a global sine fit. The most dominant periods from the fit were associated to different surface rotation periods. Our purely mathematical approach is capable of detecting different periods but cannot distinguish between the physical origins of periodicity. We ascribe the existence of different periods to DR, but spot evolution could also play a role. Because of the large number of stars the period errors are estimated statistically. We thus cannot exclude the existence of false positives among our periods. Results: In our sample of 40 661 active stars we found 24 124 rotation periods P1 between 0.5 and 45 days, with a mean of ⟨P1⟩ = 16.3 days. The distribution of stars with 0.5 < B - V < 1.0 and ages derived from angular momentum evolution that are younger than 300 Myr is consistent with a constant star-formation rate; the detection among older stars is incomplete probably because of our active sample selection. A second period P2 within ±30% of the rotation period P1 was found in 18 616 stars (77.2%). Attributing these two periods to DR we found that for active stars other than the Sun the relative shear α increases with rotation period, and slightly decreases with effective

  6. The young active star SAO 51891 (V383 Lacertae)

    NASA Astrophysics Data System (ADS)

    Biazzo, K.; Frasca, A.; Marilli, E.; Covino, E.; Alcalã, J. M.; Ćakirli, Ö.; Klutsch, A.; Meyer, M. R.

    2009-05-01

    Aims: The aim of this work is to investigate the surface inhomogeneities of a young, late-type star, SAO 51891, at different atmospheric levels, from the photosphere to the upper chromosphere, analyzing contemporaneous optical high-resolution spectra and broad-band photometry. Methods: The full spectral range of FOCES@CAHA (R ≃ 40 000) is used to perform the spectral classification and to determine the rotational and radial velocities. The lithium abundance is measured to obtain an age estimate. The {BVRIJHK}s photometric bands are used to construct the spectral energy distribution (SED). The variations in the observed BV fluxes and effective temperature are used to infer the presence of photospheric spots and observe their behavior over time. The chromospheric activity is studied applying the spectral subtraction technique to Hα, Ca ii H & K, Hɛ, and Ca ii IRT lines. Results: We find SAO 51891 to be a young K0-1V star with a lithium abundance close to the Pleiades upper envelope, confirming its youth ( 100 Myr), which is also inferred from its kinematical membership of the Local Association. No infrared excess is detected from analysis of its SED, limiting the amount of remaining circumstellar dust. We detect a rotational modulation of the luminosity, effective temperature, Ca ii H & K, Hɛ, and Ca ii IRT total fluxes. A simple spot model with two main active regions, about 240 K cooler than the surrounding photosphere, fits the observed light and temperature curves very well. The small-amplitude radial velocity variations are also well reproduced by our spot model. The anti-correlation of light curves and chromospheric diagnostics indicates chromospheric plages spatially associated with the spots. The largest modulation amplitude is observed for the Hɛ flux suggesting that this line is very sensitive to the presence of chromospheric plages. Conclusions: SAO 51891 is a young active star, lacking significant amounts of circumstellar dust or any evidence of low

  7. Chromospherically active stars. 6: Giants with compact hot companions and the barium star scenario

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Henry, Gregory W.; Busby, Michael R.; Eitter, Joseph J.

    1993-01-01

    We have determined spectroscopic orbits for three chromospherically active giants that have hot compact companions. They are HD 160538 (K0 III + wd, P = 904 days), HD 165141 (G8 III + wd, P approximately 5200 days), and HD 185510 (K0 III + sdB, P = 20.6619 days). By fitting an IUE spectrum with theoretical models, we find the white dwarf companion of HD 165141 has a temperature of about 35000 K. Spectral types and rotational velocities have been determined for the three giants and distances have been estimated. These three systems and 39 Ceti are compared with the barium star mass-transfer scenario. The long-period mild barium giant HD 165141 as well as HD 185510 and 39 Ceti, which have relatively short periods and normal abundance giants, appear to be consistent with this scenario. The last binary, HD 160538, a system with apparently near solar abundances, a white dwarf companion, and orbital characteristics similar to many barium stars, demonstrates that the existence of a white-dwarf companion is insufficient to produce a barium star. The paucity of systems with confirmed white-dwarf companions makes abundance analyses of HD 160538 and HD 165141 of great value in examining the role of metallicity in barium star formation.

  8. Chromospherically active stars. 11: Giant with compact hot companions and the barium star scenario

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Henry, Gregory W.; Busby, Michael R.; Eitter, Joseph J.

    1993-01-01

    We have determined spectroscopic orbits for three chromsopherically active giants that have hot compact companions. They are HD 160538 (KO III + wd, P = 904 days), HD 165141 (G8 III + wd, P approximately 5200 days), and HD 185510 (KO III + sdB, P = 20.6619 days). By fitting an IUE spectrum with theoretical models, we find the white dwarf companion of HD 165141 has a temperature of about 35,000 K. Spectral types and rotational velocities have been determined for the three giants and distances have been estimated. These three systems and 39 Ceti are compared with the barium star mass-transfer scenario. The long-period mild barium giant HD 165141 as well as HD 185510 and 39 Ceti, which have relatively short periods and normal abundance giants, appear to be consistent with this scenario. The last binary, HD 160538, a system with apparently near solar abundances, a white dwarf companion, and orbital characteristics similar to many barium stars, demonstrates that the existence of a white dwarf companion is insufficient to produce a barium star. The paucity of systems with confirmed white dwarf companions makes abundance analyses of HD 160538 and HD 165141 of great value in examining the role of metallicity in barium star formation.

  9. Creating Chicago History: Making Outreach Craft Activities Meaningful

    ERIC Educational Resources Information Center

    Karp, Madeline

    2012-01-01

    When it comes to having a traveling outreach activity for a museum, a craft can seem like the perfect solution. It can seemingly be all things at once--educational, quick and fun. But, if poorly constructed, crafts can also have serious fallbacks. Using the Chicago History Museum and the Millennium Park Family Fun Festival as a case study, this…

  10. Creating Activating Events for Transformative Learning in a Prison Classroom

    ERIC Educational Resources Information Center

    Keen, Cheryl H.; Woods, Robert

    2016-01-01

    In this article, we interpreted, in light of Mezirow's theory of transformative learning, interviews with 13 educators regarding their work with marginalized adult learners in prisons in the northeastern United States. Transformative learning may have been aided by the educators' response to unplanned activating events, humor, and respect, and…

  11. Coronal Diagnostics of Intermediate Activity Star XI Boo A

    NASA Technical Reports Server (NTRS)

    Drake, Jeremy

    2005-01-01

    The analysis of Xi Boo A proved difficult to adapt to our line-by-line approach because of the strong wings of the RGS instrumental profile, as has been detailed in earlier reports. While progress was also delayed because of problems in using SAS v4, we succeeded in the past year or so to bring the analysis to conclusion. Abundances have been derived using both EPIC and RGS data, confirming earlier EUVE findings of a mild solar-like FIP effect, though with some evidence of a turn-up in abundances of elements with higher FIP. Plasma densities appear normal for a moderately active stellar corona. Xi Boo A nicely bridges the gap between the very active stars and stars like the Sun, and it indeed does appear that these are the stars in which the solar-like FIP effects begins to change to the "inverse FIP" type of effect seen in the very active stars. Probing this divide was the main goal of the proposal. These results are in the process of being prepared for publication, though we have not decided the target journal as yet.

  12. NUCLEAR ACTIVITY IS MORE PREVALENT IN STAR-FORMING GALAXIES

    SciTech Connect

    Rosario, D. J.; Lutz, D.; Berta, S.; Popesso, P.; Genzel, R.; Saintonge, A.; Tacconi, L.; Wuyts, S. E-mail: lutz@mpe.mpg.de E-mail: popesso@mpe.mpg.de E-mail: amelie@mpe.mpg.de E-mail: swuyts@mpe.mpg.de; and others

    2013-07-01

    We explore the question of whether low and moderate luminosity active galactic nuclei (AGNs) are preferentially found in galaxies that are undergoing a transition from active star formation (SF) to quiescence. This notion has been suggested by studies of the UV-optical colors of AGN hosts, which find them to be common among galaxies in the so-called Green Valley, a region of galaxy color space believed to be composed mostly of galaxies undergoing SF quenching. Combining the deepest current X-ray and Herschel/PACS far-infrared (FIR) observations of the two Chandra Deep Fields with redshifts, stellar masses, and rest-frame photometry derived from the extensive and uniform multi-wavelength data in these fields, we compare the rest-frame U - V color distributions and star formation rate distributions of AGNs and carefully constructed samples of inactive control galaxies. The UV-to-optical colors of AGNs are consistent with equally massive inactive galaxies at redshifts out to z {approx} 2, but we show that such colors are poor tracers of SF. While the FIR distributions of both star-forming AGNs and star-forming inactive galaxies are statistically similar, we show that AGNs are preferentially found in star-forming host galaxies, or, in other words, AGNs are less likely to be found in weakly star-forming or quenched galaxies. We postulate that, among X-ray-selected AGNs of low and moderate accretion luminosities, the supply of cold gas primarily determines the accretion rate distribution of the nuclear black holes.

  13. Solar activity: The Sun as an X-ray star

    NASA Technical Reports Server (NTRS)

    Golub, L.

    1981-01-01

    The existence and constant activity of the Sun's outer atmosphere are thought to be due to the continual emergence of magnetic fields from the Solar interior and the stressing of these fields at or near the surface layers of the Sun. The structure and activity of the corona are thus symptomatic of the underlying magnetic dynamo and the existence of an outer turbulent convective zone on the Sun. A sufficient condition for the existence of coronal activity on other stars would be the existence of a magnetic dynamo and an outer convective zone. The theoretical relationship between magnetic fields and coronal activity can be tested by Solar observations, for which the individual loop structures can be resolved. A number of parameters however, which enter into the alternative theoretical formulations remain fixed in all Solar observations. To determine whether these are truly parameters of the theory observations need to be extended to nearby stars on which suitable conditions may occur.

  14. Quenching of the star formation activity in cluster galaxies

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Roehlly, Y.; Fossati, M.; Buat, V.; Boissier, S.; Boquien, M.; Burgarella, D.; Ciesla, L.; Gavazzi, G.; Serra, P.

    2016-11-01

    We study the star formation quenching mechanism in cluster galaxies by fitting the spectral energy distribution (SED) of the Herschel Reference Survey, a complete volume-limited K-band-selected sample of nearby galaxies including objects in different density regions, from the core of the Virgo cluster to the general field. The SEDs of the target galaxies were fitted using the CIGALE SED modelling code. The truncated activity of cluster galaxies was parametrised using a specific star formation history with two free parameters, the quenching age QA and the quenching factor QF. These two parameters are crucial for the identification of the quenching mechanism, which acts on long timescales when starvation processes are at work, but is rapid and efficient when ram pressure occurs. To be sensitive to an abrupt and recent variation of the star formation activity, we combined twenty photometric bands in the UV to far-infrared in a new way with three age-sensitive Balmer line absorption indices extracted from available medium-resolution (R 1000) integrated spectroscopy and with Hα narrow-band imaging data. The use of a truncated star formation history significantly increases the quality of the fit in HI-deficient galaxies of the sample, that is to say, in those objects whose atomic gas content has been removed during the interaction with the hostile cluster environment. The typical quenching age of the perturbed late-type galaxies is QA ≲ 300 Myr whenever the activity of star formation is reduced by 50% < QF ≤ 80% and QA ≲ 500 Myr for QF > 80%, while that of the quiescent early-type objects is QA ≃ 1-3 Gyr. The fraction of late-type galaxies with a star formation activity reduced by QF > 80% and with an HI-deficiency parameter HI-def > 0.4 drops by a factor of 5 from the inner half virial radius of the Virgo cluster (R/Rvir < 0.5), where the hot diffuse X-ray emitting gas of the cluster is located, to the outer regions (R/Rvir > 4). The efficient quenching of the

  15. MAGNETIC ACTIVITY CYCLES IN THE EXOPLANET HOST STAR {epsilon} ERIDANI

    SciTech Connect

    Metcalfe, T. S.; Mathur, S.; Buccino, A. P.; Mauas, P. J. D.; Petrucci, R.; Brown, B. P.; Soderblom, D. R.; Henry, T. J.; Hall, J. C.; Basu, S.

    2013-02-01

    The active K2 dwarf {epsilon} Eri has been extensively characterized both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3-year magnetic activity cycle in {epsilon} Eri originally reported by Hatzes and coworkers, and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3-year and 13-year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3-year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95 {+-} 0.03 years and 12.7 {+-} 0.3 years, which, by analogy with the solar case, suggests a revised identification of the dynamo mechanisms that are responsible for the so-called 'active' and 'inactive' sequences as proposed by Boehm-Vitense. Finally, based on the observed properties of {epsilon} Eri, we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.

  16. The Life Cycles of Stars: An Information & Activity Booklet Grades K-8, 1997-1998. Star-Child--A Learning Center for Young Astronomers.

    ERIC Educational Resources Information Center

    Truelove, Elizabeth; Dejoie, Joyce

    This booklet contains information and activities on the life cycle of stars. Materials can be adapted for kindergarten through grade 8 classrooms. Background information on massive stars and medium stars and activities with subjects such as star life, constellation shapes, nebula terminology, astronomical distances, and pulsars is included. The 12…

  17. Optical studies of X-ray peculiar chromosphereically active stars

    NASA Astrophysics Data System (ADS)

    Pandey, J. C.

    2006-02-01

    A multiwavelength study of the late-type active stars, selected on the basis of their X-ray and radio luminosities is presented in this thesis. For FR Cnc, a photometric period 0.8267 +/- 0.0004 d has been established. The strong variation in the phase and amplitude of the FR Cnc light curves when folded on this period implies the presence of evolving and migrating spots or spot groups on its surface. A photometric period of 18.802 +/- 0.074 has been discovered in the star HD 81032. The shape and amplitude of the photometric light curves of FR Cnc, HD 81032, HD 95559 and LO Peg are observed to be changing from one epoch to another. The change in the amplitude is mainly due to a change in the minimum of the light curve, and this May be due to a change in the spot coverage. This indicates that photometric variability is due to the presence of dark spots on the surface of active star. Two groups of spots are identified for FR Cnc and LO Peg. The spots are found to migrate, and migration periods of 0.97 year and 0.93 year are determined from the 4 years of data. A migration period of 1.12 years for one group of spots in LO Peg is also determined. Formation of a new group of spots in the star HD 95559 was also seen during our observations. A single large group of spots is found to migrate, and a migration period of 7.32 +/- 0.04 years is determined for HD 81032. The stars FR Cnc, HD 81032, HD 160934 and LO Peg are seen to be redder at the light minimum and we interpret this is due to the relatively cooler temperature of the darker regions present in the visible hemisphere. We find the lack of color-brightness correlation in the star HD 95559 and this May be due to the presence of bright faculae and plages like regions accompanied by dark spots in any one component of the this binary system. The optical spectroscopy of FR Cnc and HD 81032 carried out during 2002-2003, reveals the presence of strong and variable Ca II H and K, Halpha and Hbeta emission features indicative

  18. ACTIVITY ON THE M STAR OF QS Vir

    SciTech Connect

    Ribeiro, T.; Baptista, R.; Kafka, S.; Tappert, C.

    2010-03-15

    We report analysis of VRIJH photometry and phase-resolved optical spectroscopy of the eclipsing DA white dwarf (WD) plus dMe dwarf binary QS Vir. Modeling of the photometric data yields an inclination of i = 74.9 {+-} 0.6 and a mass ratio of q = M {sub 2}/M {sub 1} = 0.50 {+-} 0.05. Our Doppler maps indicate the presence of material in the Roche lobe of the WD, at a location near the M star, likely due to accretion from the stellar wind of the M star (as opposed to Roche-lobe overflow accretion). We also constructed images of the brightness distribution of the M star at different epochs which reveal the location of two stable active regions. Doppler tomography shows that the majority of the hydrogen and Ca II H and K emission originates on the active M dwarf, likely distributed in two preferred activity longitudes, similar to active regions on BY Dra and FK Comae systems.

  19. The optical flares of active star II Pegasi in 2005

    NASA Astrophysics Data System (ADS)

    Gu, Shenghong; Kim, Kang Min; Lee, Byeong-Cheol

    2015-08-01

    We observed the active star II Peg using high-resolution spectrographs of 2.16m telescope at Xinglong station of NAOC and 1.8m telescope at BOAO of KASI from November to December, 2005. By means of spectral subtraction technique, the chromospheric activities of II Peg are analyzed at several activity indicators, including CaII IRT, Hα, NaI D1D2 and HeI D3 lines. The results demonstrate that the magnetic activity of II Peg is very strong, and its chromospheric activities show rotational modulations which imply there are active regions in its chromosphere. Two flare events were hunted during the observations, which were identified by HeI D3 line emission above the continuum. The first flare was happened in November 2005, the second one in December 2005, and they were located in different hemisphere of the star. This may indicate the evolution of active regions. Considering the photospheric spot activities, the possible origin of the detected flares is discussed.

  20. 77 FR 46089 - Agency Information Collection Activities; Proposed Collection; Comment Request; EPA's ENERGY STAR...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-02

    ... Information Collection Activities; Proposed Collection; Comment Request; EPA's ENERGY STAR Program in the... this action are participants in EPA's ENERGY STAR Program in the Commercial and Industrial Sectors. Title: Information Collection Activities Associated with EPA's ENERGY STAR Program in the Commercial...

  1. Comparison of the Motivational Climates Created during Multi-Activity Instruction and Sport Education

    ERIC Educational Resources Information Center

    Parker, Mitchum B.; Curtner-Smith, Matthew D.

    2014-01-01

    Previous research has suggested that sport education (SE) may be a superior curriculum model to multi-activity (MA) teaching because its pedagogies and structures create a task-involving motivational climate. The purpose of this study was to describe and compare the objective motivational climates teachers create within the MA and SE models.…

  2. Co-creating Emotionally Safe Environments at Camp: Training Staff To Facilitate Adventure Activities.

    ERIC Educational Resources Information Center

    Brownlee, Matt; Yerkes, Rita

    2003-01-01

    An emotionally safe environment helps campers participate in adventure activities. Staff development tips for creating a safe environment include using cooperative goal setting; using parallel training processes; developing working lesson plans that outline facilitation techniques for creating emotionally safe environments; and using co-created…

  3. Time-Resolved Spectroscopy of Active Binary Stars

    NASA Technical Reports Server (NTRS)

    Brown, Alexander

    2000-01-01

    This NASA grant covered EUVE observing and data analysis programs during EUVE Cycle 5 GO observing. The research involved a single Guest Observer project 97-EUVE-061 "Time-Resolved Spectroscopy of Active Binary Stars". The grant provided funding that covered 1.25 months of the PI's salary. The activities undertaken included observation planning and data analysis (both temporal and spectral). This project was awarded 910 ksec of observing time to study seven active binary stars, all but one of which were actually observed. Lambda-And was observed on 1997 Jul 30 - Aug 3 and Aug 7-14 for a total of 297 ksec; these observations showed two large complex flares that were analyzed by Osten & Brown (1999). AR Psc, observed for 350 ksec on 1997 Aug 27 - Sep 13, showed only relatively small flares that were also discussed by Osten & Brown (1999). EUVE observations of El Eri were obtained on 1994 August 24-28, simultaneous with ASCA X-ray spectra. Four flares were detected by EUVE with one of these also observed simultaneously, by ASCA. The other three EUVE observations were of the stars BY Dra (1997 Sep 22-28), V478 Lyr (1998 May 18-27), and sigma Gem (1998 Dec 10-22). The first two stars showed a few small flares. The sigma Gem data shows a beautiful complete flare with a factor of ten peak brightness compared to quiescence. The flare rise and almost all the decay phase are observed. Unfortunately no observations in other spectral regions were obtained for these stars. Analysis of the lambda-And and AR Psc observations is complete and the results were published in Osten & Brown (1999). Analysis of the BY Dra, V478 Lyr and sigma Gem EUVE data is complete and will be published in Osten (2000, in prep.). The El Eri EUV analysis is also completed and the simultaneous EUV/X-ray study will be published in Osten et al. (2000, in prep.). Both these latter papers will be submitted in summer 2000. All these results will form part of Rachel Osten's PhD thesis.

  4. The Activity of Weak-Lined T Tauri Stars

    NASA Astrophysics Data System (ADS)

    Welty, Alan D.; Ramsey, Lawrence W.

    1995-03-01

    We have conducted intensive spectroscopic observing campaigns on several weak-lined and classical T Tauri stars (WTTS, CTTS). The data were obtained with the Penn State Fiber Optic Echelle spectrograph in three observing runs at the KPNO 2.1m telescope. We wish to understand the phenomenology of stellar and circumstellar activity of our targets, and to quantify the activity where possible. Here we present results for our WTTS targets, V410 Tau in particular. The first step in our analysis is to determine the spectral type of each target by fitting a grid of standard star spectra to the target star spectra. Byproducts of this process are values for radial and projected rotational velocities and veiling for each observation. We find no veiling (from Hβ to Hα ) in any of our targets. Results for V410 Tau are dramatic. The photospheric temperature distribution (recently Doppler imaged by Strassmeier, Welty, & Rice 1994 and Hatzes 1995) causes line profile variations which cause apparent radial velocity changes. The amplitude of this variability is 500 times the Sun's orbital motion due to Jupiter. Although this is an extreme case, it serves to illustrate the point that radial velocity searches for low mass companions, especially planets, must take stellar activity into account. Three of our other WTTS targets show similar radial velocity variation. We also feature flare observations of V410 Tau. One event was observed rising and declining during one observing night. Its total duration was about 15 hours. It released ~ 10(35) erg in optical line emission. He D_3 radial velocities enable us to locate the flare with respect to features in the Doppler images. Our results suggest that V410 Tau has entered a state of relatively high activity after a decline indicated by various observations made during the 1980s. We will also be pleased to discuss results on our CTTS targets with interested parties.

  5. Activity and Brightness Variations of Sun-Like Stars

    NASA Astrophysics Data System (ADS)

    Hall, Jeffrey C.

    2015-08-01

    Long-term observations of variations in Sun-like stars now span a half century. The Mount Wilson Observatory (MWO) HK Project operated from 1966 to 2003, and the Lowell Observatory Solar-Stellar Spectrograph (SSS) project has operated since 1994; together these programs provide a record of chromospheric activity over multiple stellar cycles for more than 100 stars of V < ~7.5. Long-term photometric monitoring of Sun-like stars, including many of the MWO and SSS targets, began in the early 1980s and continues today at the Fairborn Observatory south of Tucson. I will review progress to date in combining and interpreting the spectrosopic and photometric data sets, including some new results from the most recent years of SSS and Fairborn data. I will also review where deficiencies remain in reconciling and combining the major data sets, and will discuss efforts presently underway to remedy this and provide a long-term record for the benefit of the community.

  6. Chromospherically active stars. X - Spectroscopy and photometry of HD 212280

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Browning, Jared C.; Henry, Gregory W.; Morton, Mary D.; Hall, Douglas S.

    1993-01-01

    The system HD 212280 is a chromospherically active double lined spectroscopic binary with an orbital period of 45.284 days and an eccentricity of 0.50. The spectrum is composite with spectral types of G8 IV and F5-8 V for the components. An estimated inclination of 78 +/- 8 deg results in masses of 1.7 and 1.4 solar mass for the G subgiant and mid-F star, respectively. The distance to the system is estimated to be 112 pc. Photometric observations obtained between 1987 November and 1992 June reveal that HD 212280 is a newly identified variable star with a V amplitude of about 0.15 mag and a mean period of 29.46 days. Our V data were divided into 11 sets and in all but one case two spots were required to fit the data. Lifetimes of 650 days and a minimum of 1350 days have been determined for two of the four spots. The differential rotation coefficient of 0.05 is relatively small. The age of the system is about 1.9 X 10 exp 9 yrs. The G subgiant is rotating slower than pseudosynchronously while the F-type star is rotating faster.

  7. Making Connections: Language Activities for Creating Interpersonal Tolerance in the Classroom

    ERIC Educational Resources Information Center

    Renaud, Susan; Tannenbaum, Elizabeth

    2013-01-01

    Using communicative activities with learners from diverse cultures can create excitement and empathy while promoting the acquisition of English. This article offers ESL/EFL activities that foster interpersonal tolerance among students who have experienced intergroup conflict. The activities are based on the idea that there are four levels of…

  8. Synthetic activity indicators for M-type dwarf stars

    NASA Astrophysics Data System (ADS)

    Wedemeyer, Sven; Ludwig, Hans-Günter; Hauschildt, Peter; De Gennaro Aquino, Ivan

    2015-08-01

    Our understanding of the Sun has been substantially progressed owing to the advances in high-resolution observations during the last decades. These observations guided the development of numerical simulation codes for stellar atmospheres towards unprecedented levels of realism and complexity. Such 3D radiation magnetohydrodynamic (RMHD) codes can be applied and adapted to cooler stars. Here, we present a set of time-dependent 3D RMHD simulations for dwarf stars of spectral type M (representative of AD Leo). "M-dwarfs" are the most abundant stars in our galaxy and known to exhibit mega-flares. Comparisons of M-dwarf models with the Sun as fundamental reference case reveal differences and similarities, which lead to important insights into the structure and dynamics of quiescent "background" atmospheres. The models, which extend from the upper convection zone into the chromosphere, have different initial magnetic field strengths (up to 500G) and topologies, representing regions with different activity levels. The 3D model atmospheres are characterized by a very dynamic and intermittent structure on small spatial and temporal scales, final field strengths reaching a few kG and a wealth of physical processes, which by nature cannot be described by means of 1D static model atmospheres.Synthetic observables, i.e. spectra and intensity images, are calculated by using these models as input for detailed radiative transfer calculations and can be combined into synthetic full stellar disks, thus simulating spatially unresolved observations of M-dwarfs. The considered diagnostics, like, e.g., Halpha, Ca II lines, or the continuum intensity from UV to millimeter wavelengths, sample various properties of the dynamics, thermal and magnetic structure of the photosphere and the chromosphere and thus provide measures of stellar activity, which can be compared to observations. The complicated magnetic field structure and its imprint in synthetic diagnostics may have important

  9. Influence of FFA Activities on Critical Thinking Skills in Texas Three-Star FFA Chapters

    ERIC Educational Resources Information Center

    Latham, Lindsey; Rayfield, John; Moore, Lori L.

    2015-01-01

    The purpose of this study was to determine the relationship of FFA activities on critical thinking skills of Texas FFA members in three-star FFA chapters. This descriptive study was conducted in eight purposively selected three-star FFA chapters throughout Texas. Three-star chapters are those chapters who have emerged as outstanding programs…

  10. Long-Term Starspot Activity of Some Chromospherically Active Rs CVn and BY Dra Stars

    NASA Astrophysics Data System (ADS)

    Kozhevnikova, Alla; Ilya, Alekseev

    2016-10-01

    We present results of our long-term photometric observations of a sample of 15 chromospherically active BY Dra and RS CVn-type stars. Observations were carried out at a 70-cm telescope and multichannel photometer of Kourovka Astronomical Observatory of Ural Federal University and at a 1.25-m telescope of Crimean Astrophysical Observatory from 2003 to 2015 in Johnson B, V, R, I bands. We also use the previously published photometric data for all these stars to find the meaning of historical star's brightness, that we assume as a brightness of unspotted photosphere. Using a renewed zonal spot model for spotted stellar photospheres we determined spot parameters for all observational seasons, as our as published ones, that were spanning almost over 45 years for some stars (e.g. CG Cyg, WY Cnc, EV Lac, V 1396 Cyg). It is shown that the spots were located at low and middle latitudes up to 58 deg., are cooler than the surrounding photosphere by 200 - 2000 K according to the spectral class. The spotted area varied from season to season, comprising 13%-47% of the surface area of the star. Almost half of the stars display drifts of their spots towards the equator and poles during certain time intervals; however, the speeds of the spots' latitude drifts are lower than the analogous speeds for sunspots, by factors of 1.5-4, on average. Activity cycles lasting from 5 to 40 years have been determined or confirmed for majority of the studied stars. As a rule, cycles are expressed in synchronous variations of spot areas, spot latitudes and average photometric star's brightness.

  11. EXPLORING THE CONNECTION BETWEEN STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN THE LOCAL UNIVERSE

    SciTech Connect

    LaMassa, Stephanie M.; Heckman, T. M.; Ptak, A.; Schiminovich, D.; Bertincourt, B.; O'Dowd, M.

    2012-10-10

    We study a combined sample of 264 star-forming, 51 composite, and 73 active galaxies using optical spectra from the Sloan Digital Sky Survey (SDSS) and mid-infrared (mid-IR) spectra from the Spitzer Infrared Spectrograph. We examine optical and mid-IR spectroscopic diagnostics that probe the amount of star formation and relative energetic contributions from star formation and an active galactic nucleus (AGN). Overall we find good agreement between optical and mid-IR diagnostics. Misclassifications of galaxies based on the SDSS spectra are rare despite the presence of dust obscuration. The luminosity of the [Ne II] 12.8 {mu}m emission line is well correlated with the star formation rate measured from the SDSS spectra, and this holds for the star-forming, composite, and AGN-dominated systems. AGNs show a clear excess of [Ne III] 15.6 {mu}m emission relative to star-forming and composite systems. We find good qualitative agreement between various parameters that probe the relative contributions of the AGN and star formation, including the mid-IR spectral slope, the ratio of the [Ne V] 14.3 {mu}m to [Ne II] {mu}m 12.8 fluxes, the equivalent widths of the 7.7 {mu}m, 11.3 {mu}m, and 17 {mu}m polycyclic aromatic hydrocarbon (PAH) features, and the optical 'D' parameter which measures the distance at which a source lies from the locus of star-forming galaxies in the optical BPT emission-line diagnostic diagram. We also consider the behavior of the three individual PAH features by examining how their flux ratios depend upon the degree of AGN dominance. We find that the PAH 11.3 {mu}m feature is significantly suppressed in the most AGN-dominated systems.

  12. ACTIVITY ANALYSES FOR SOLAR-TYPE STARS OBSERVED WITH KEPLER. I. PROXIES OF MAGNETIC ACTIVITY

    SciTech Connect

    He, Han; Wang, Huaning; Yun, Duo

    2015-11-15

    Light curves of solar-type stars often show gradual fluctuations due to rotational modulation by magnetic features (starspots and faculae) on stellar surfaces. Two quantitative measures of modulated light curves are employed as the proxies of magnetic activity for solar-type stars observed with Kepler telescope. The first is named autocorrelation index i{sub AC}, which describes the degree of periodicity of the light curve; the second is the effective fluctuation range of the light curve R{sub eff}, which reflects the depth of rotational modulation. The two measures are complementary and depict different aspects of magnetic activities on solar-type stars. By using the two proxies i{sub AC} and R{sub eff}, we analyzed activity properties of two carefully selected solar-type stars observed with Kepler (Kepler ID: 9766237 and 10864581), which have distinct rotational periods (14.7 versus 6.0 days). We also applied the two measures to the Sun for a comparative study. The result shows that both the measures can reveal cyclic activity variations (referred to as i{sub AC}-cycle and R{sub eff}-cycle) on the two Kepler stars and the Sun. For the Kepler star with the faster rotation rate, i{sub AC}-cycle and R{sub eff}-cycle are in the same phase, while for the Sun (slower rotator), they are in the opposite phase. By comparing the solar light curve with simultaneous photospheric magnetograms, it is identified that the magnetic feature that causes the periodic light curve during solar minima is the faculae of the enhanced network region, which can also be a candidate of magnetic features that dominate the periodic light curves on the two Kepler stars.

  13. Chromospheric activity and rotation of FGK stars in the solar neighbourhood: characterizing possible exoplanetary system host stars

    NASA Astrophysics Data System (ADS)

    Martínez-Arnáiz, Raquel M.

    2011-06-01

    This dissertation has investigated the chromospheric activity and rotation of nearby cool stars, which can potentially host exoplanetary systems. 1. High-resolution echelle spectra have been obtained for 565 nearby (d ≤ 25 pc) cool (spectral types F to M) stars. The observations were taken using high resolution echelle optical spectrographs. The observations were designed to ensure a spectral coverage including all the optical magnetic activity indicator lines: from the Ca II H & K lines to the Ca II IRT, including all the Balmer lines Hα, Hβ, Hγ, Hδ, and H?. This fact has ensured a simultaneous analysis of the magnetic activity using different diagnostics. The spectral coverage of the spectra has also permitted a precise analysis of the stellar properties as well as rotational and radial velocities. 2. The suitability of the stars as targets in exoplanetary search surveys has been analysed using the results obtained in the spectroscopic survey. Using the measured chromospheric activity in the optical spectrum, activity-induced RV jitter has been calculated for the active stars in the sample. Although the intrinsic variability of stellar activity makes it impossible to directly subtract the computed values from the RV signal, it provides an estimation of the activity-related noise. Therefore, this values can be used to set the minimum detectable mass for a planet orbiting the star or to determine the minimal amplitude variation that could indicate the existence of a planet. The compilation of the activity, rotation and predicted activity-induced RV jitter build up into a catalogue that determines the suitability of the stars as targets in exoplanet search surveys. 3. The relationship between pairs of excess surface flux in different activity diagnostics has been analysed using the results from the spectroscopic survey. The results show a clear correlation between the activity measured in different optical indicators. This fact confirms previous findings and

  14. Activity on the classical T Tauri star BP Tauri.

    NASA Astrophysics Data System (ADS)

    Gullbring, E.; Barwig, H.; Chen, P. S.; Gahm, G. F.; Bao, M. X.

    1996-03-01

    We have made a detailed investigation of the short-term variability in optical light (UBVRI) of the classical T Tauri star BP Tauri. Photometric data (in UBVRI) were collected from Wendelstein Observatory, Germany in 1991, 1992 and 1993 with time-resolutions down to 1sec and, from binning, fluctuations with total amplitudes down to a few milli-magnitudes could be resolved. Additional observations (in UBV) were collected in China. The total time of monitoring amounts to 135 hours. The normal state of BP Tau is that it stays completely constant in brightness in all bands, or shows only very slow and smooth changes during a night, to the limit of detection. Brightenings, events, occurred on time-scales from 0.6hours to a few hours but none of these reached a total amplitude >0.3mag in U. As a rule these events do not have the characteristic flare profile as in the lightcurves of stellar surface flares. The total optical energies of the events are a few times 10^35^erg, with a relatively small spread. The energy distributions at peak flux can be represented by black-body radiation. However, the inferred temperature is very low, 7000-8000K, and not significantly different from that derived for the background veiling. Hence, the events on BP Tau are very different from normal stellar flares. From power analysis of the time series, we conclude that there is no power indicating frequent and short lasting phenomena, like surface flares. In particular there is no signal in the U band. Such flares would have been expected to be numerous in this high-sensitivity survey, however, if BP Tau had a magnetic surface activity comparable to that of ordinary flare stars. Also, there is no tail in the distribution of events towards smaller amplitudes and shorter durations. We show that the events of BP Tau are consistent with inhomogeneous mass infall from magnetically controlled accretion between a circumstellar disk and a hot spot at the star. To account for the constancy in

  15. Dynamo action and magnetic activity of the giant star Pollux

    NASA Astrophysics Data System (ADS)

    Brun, Allan Sacha; Palacios, Ana

    2015-08-01

    Recent spectropolarimetric observations of the giant star Pollux have revealed that it possesses a weak global magnetic field of the order of a Gauss. Using 3-D nonlinear MHD simulations performed with the ASH code we study the source of this global magnetic field in this slowly rotating giant star (Omega*=Omega_sun/20). We find that the extended convective envelope is able to generate a multi-scales magnetic field reaching of the order of 10% of the kinetic energy contained in the envelope. This global field acts such as to suppress the strong differential rotation present in the purely hydrodynamical progenitor simulation. When filtering the large scale magnetic field components (dipole, quadrupole) we find magnetic field of the order of a few Gauss, hence in qualitative agreeement with observations. Our study confirms that such slowly rotating convective giants are likely to possess global magnetic field maintained through contemporaneous dynamo action and not as the vestige of their past main sequence activity.

  16. Active Spacecraft Potential Control: Results From the Double Star Project

    NASA Astrophysics Data System (ADS)

    Torkar, K.; Fazakerley, A.; Steiger, W.

    2006-10-01

    The ion emitter instrument "active spacecraft potential control" (ASPOC) has been used successfully in several magnetospheric missions including the European Space Agency Cluster Project. An improved version has been developed for the equatorial spacecraft of the Chinese-European Double Star mission (TC-1) launched in December 2003. The modifications include a new design of the ion emitter modules. As a result, higher currents than in previous missions can be achieved. The main objective of the investigation is the reduction of positive spacecraft potential in order to minimize perturbations to the plasma measurements onboard, in particular to the plasma electron instrument PEACE. These data show an almost complete suppression of photoelectrons when ASPOC is emitting at 30- to 50-muA beam current. The angular distribution of the electrons in the presence of the ion beam is investigated in detail. The measurement of ambient electron distributions is highly improved.

  17. Creating Classrooms of and for Activism at the Intersections of Class, Race, Ethnicity, Gender, and Disability

    ERIC Educational Resources Information Center

    Nishida, Akemi; Fine, Michelle

    2014-01-01

    In this article the authors describe pedagogy which rests on commitments to solidarity, activism, and intersectional understandings of personhood and social (in)justices. The authors seek to create accessible classrooms where our many selves and critical consciousness can be in (dis)comforting conversation with one another. Then, they hope to…

  18. Creating Healthy Active Minds for Personal Success (CHAMPS) in Middle School

    ERIC Educational Resources Information Center

    Shawley, Jessica

    2016-01-01

    The purpose of this article is to provide support for middle school physical education programs that meet the developmental needs of students while providing for student choice. With its health and physical education program called Creating Healthy Active Minds for Personal Success (CHAMPS), Moscow Middle School is striving to cultivate student…

  19. Stellar activity of planetary host star HD 189 733

    NASA Astrophysics Data System (ADS)

    Boisse, I.; Moutou, C.; Vidal-Madjar, A.; Bouchy, F.; Pont, F.; Hébrard, G.; Bonfils, X.; Croll, B.; Delfosse, X.; Desort, M.; Forveille, T.; Lagrange, A.-M.; Loeillet, B.; Lovis, C.; Matthews, J. M.; Mayor, M.; Pepe, F.; Perrier, C.; Queloz, D.; Rowe, J. F.; Santos, N. C.; Ségransan, D.; Udry, S.

    2009-03-01

    Aims: Extra-solar planet search programs require high-precision velocity measurements. They need to determine how to differentiate between radial-velocity variations due to Doppler motion and the noise induced by stellar activity. Methods: We monitored the active K2V star HD 189 733 and its transiting planetary companion, which has a 2.2-day orbital period. We used the high-resolution spectograph SOPHIE mounted on the 1.93-m telescope at the Observatoire de Haute-Provence to obtain 55 spectra of HD 189 733 over nearly two months. We refined the HD 189 733b orbit parameters and placed limits on both the eccentricity and long-term velocity gradient. After subtracting the orbital motion of the planet, we compared the variability in spectroscopic activity indices with the evolution in the radial-velocity residuals and the shape of spectral lines. Results: The radial velocity, the spectral-line profile, and the activity indices measured in He I (5875.62 Å), Hα (6562.81 Å), and both of the Ca II H&K lines (3968.47 Å and 3933.66 Å, respectively) exhibit a periodicity close to the stellar-rotation period and the correlations between them are consistent with a spotted stellar surface in rotation. We used these correlations to correct for the radial-velocity jitter due to stellar activity. This results in achieving high precision in measuring the orbital parameters, with a semi-amplitude K = 200.56 ± 0.88 m s-1 and a derived planet mass of MP = 1.13 ± 0.03 M_Jup. Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE Consortium (program 07A.PNP.CONS).

  20. Stars and Planets: A New Set of Middle School Activities

    NASA Technical Reports Server (NTRS)

    Urquhart, M. L.

    2002-01-01

    A set of lesson plans for grades 6-8 which deal with the sizes and distances of stars and planets using a scale factor of 1 to 10 billion, the life cycle of stars, and the search for planets beyond the solar system. Additional information is contained in the original extended abstract.

  1. Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter

    NASA Astrophysics Data System (ADS)

    Martínez-Arnáiz, R.; Maldonado, J.; Montes, D.; Eiroa, C.; Montesinos, B.

    2010-09-01

    Context. Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles, and their perturbations alter the line centroids creating a radial velocity jitter that might “contaminate” the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims: We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d ≤ 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e., Ca ii H & K lines, to others that hold noteworthy advantages. Methods: We used high resolution (~50 000) echelle optical spectra. Standard data reduction was performed using the IRAF echelle package. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. We measured the equivalent widths of the chromospheric emission lines in the subtracted spectrum and transformed them into fluxes by applying empirical equivalent width and flux relationships. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R'_HK index. Results: We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity

  2. Pattern formation for active particles on optically created ordered and disordered substrates (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Reichhardt, Charles M.; Ray, Dipanjan; Reichhardt, Cynthia J.

    2015-08-01

    There has been tremendous growth in the field of active matter, where the individual particles that comprise the system are self-driven. Examples of this class of system include biological systems such as swimming bacteria and crawling cells. More recently, non-biological swimmers have been created using colloidal Janus particles that undergo chemical reactions on one side to produce self-propulsion. These active matter systems exhibit a wide variety of behaviors that are absent in systems undergoing purely thermal fluctuations, such as transitions from uniform liquids to clusters or living crystals, pushing objects around, ratchet effects, and phase separation in mixtures of active and passive particles. Here we examine the collective effects of active matter disks in the presence of static or dynamic substrates. For colloids, such substrates could be created optically in the form of periodic, random, or quasiperiodic patterns. For thermal particles, increasing the temperature generally increases the diffusion or mobility of the particles when they move over a random or periodic substrates. We find that when the particles are active, increasing the activity can increase the mobility for smaller run lengths but decrease the mobility at large run lengths. Additionally we find that at large run lengths on a structured substrate, a variety of novel active crystalline states can form such as stripes, squares and triangular patterns.

  3. Creating a Physical Activity Self-Report Form for Youth Using Rasch Methodology.

    PubMed

    DiStefano, Christine; Pate, Russell; McIver, Kerry; Dowda, Marsha; Beets, Michael; Murrie, Dale

    2016-01-01

    Measurement of youth's physical activity levels is recommended to ensure that children are meeting recommended activity guidelines. This article describes the creation of an instrument to measure youth's levels of physical activity, where a strong test validation perspective (Benson, 1998) was followed to create the scale. The development process involved a mixed-method (qualitative followed by quantitative) framework. First, focus groups were conducted, where results informed item creation. Next, three alternative forms were created with different response formats to measure childrens' frequency of participation in various physical activities and intensity of participation. Lastly, a sample of over 500 middle school children was obtained, where three different response scales were investigated. The optimal scale considered measurement of physical activity using a three-point Likert frequency; intensity of activity participation did not strongly contribute to the measurement of children's activity levels. The final version form is thought to be acceptable for use with children in surveillance and large-group studies, as well as in smaller sample applications.

  4. Creating a Physical Activity Self-Report Form for Youth Using Rasch Methodology

    PubMed Central

    DiStefano, Christine; Pate, Russell; McIver, Kerry; Dowda, Marsha; Beets, Michael; Murrie, Dale

    2016-01-01

    Measurement of youth’s physical activity levels is recommended to ensure that children are meeting recommended activity guidelines. This article describes the creation of an instrument to measure youth’s levels of physical activity, where a strong test validation perspective (Benson, 1998) was followed to create the scale. The development process involved a mixed-method (qualitative followed by quantitative) framework. First, focus groups were conducted where results informed item creation. Next, three alternative forms were created with different response formats to measure children’s’ frequency of participation in various physical activities and intensity of participation. Lastly, a sample of over 500 middle school children was obtained where three different response scales were investigated. The optimal scale considered measurement of physical activity using a three-point Likert frequency; intensity of activity participation did not strongly contribute to the measurement of children’s activity levels. The final version form is thought to be acceptable for use with children in surveillance and large-group studies, as well as in smaller sample applications. PMID:28009580

  5. A Novel Approach for Creating Activity-Aware Applications in a Hospital Environment

    NASA Astrophysics Data System (ADS)

    Bardram, Jakob E.

    Context-aware and activity-aware computing has been proposed as a way to adapt the computer to the user’s ongoing activity. However, deductively moving from physical context - like location - to establishing human activity has proved difficult. This paper proposes a novel approach to activity-aware computing. Instead of inferring activities, this approach enables the user to explicitly model their activity, and then use sensor-based events to create, manage, and use these computational activities adjusted to a specific context. This approach was crafted through a user-centered design process in collaboration with a hospital department. We propose three strategies for activity-awareness: context-based activity matching, context-based activity creation, and context-based activity adaptation. We present the implementation of these strategies and present an experimental evaluation of them. The experiments demonstrate that rather than considering context as information, context can be a relational property that links ’real-world activities’ with their ’computational activities’.

  6. Can persuasive messages encourage individuals to create action plans for physical activity?

    PubMed

    Sweet, Shane N; Brawley, Lawrence R; Hatchell, Alexandra; Gainforth, Heather L; Latimer-Cheung, Amy E

    2014-08-01

    Given the positive influence of action planning on physical activity, persuasive messages could be designed to promote action planning. The purpose of this paper was to test action planning messages in two studies. Participants were allocated to one of two message groups, reading either a physical activity only or physical activity plus action planning message (Study 1) and either a gain-framed or loss-framed action planning message (Study 2). The percent of individuals who created an action plan and the quality of the plans were evaluated. In Study 1, individuals in the physical activity plus action planning group created as many action plans as the physical activity only group, but their plans were higher quality. In Study 2, Week 2 differences between the gain- and loss-framed message groups were found for action planning. To our knowledge, these studies were the first to investigate message-induced action planning as a behavior. More research is needed to optimize these messages.

  7. Exploring the optical contrast effect in strong atomic lines for exoplanets transiting active stars

    NASA Astrophysics Data System (ADS)

    Cauley, Paul W.; Redfield, Seth

    2017-01-01

    Transmission spectroscopy is a powerful tool for detecting and characterizing planetary atmospheres. Non-photospheric features on the stellar disk, however, can contaminate the planetary signal: during transit the observed spectrum is weighted towards the features not currently being occulted by the planet. This contrast effect can mimic absorption in the planetary atmosphere for strong atomic lines such as Na I, Ca II, and the hydrogen Balmer lines. While the contrast effect is negligible for quiet stars, contributions to the transmission signal from active stellar surfaces can produce ~1% changes in the line core. It is therefore critical that these contrast signals be differentiated from true absorption features in the planetary atmosphere. Here we present our work on simulating the contrast effect for an active stellar surface. We discuss the particular case of HD 189733 b, a well-studied hot Jupiter orbiting an active K-dwarf, due to the plethora of atomic absorption signals reported in its atmosphere.Specifically, we focus on Hα to address recent suggestions that the measured in-transit signals are a result of stellar activity. In the contrast model we include center-to-limb variations and calculate limb darkening parameters as a function of wavelength across the line of interest. The model includes contributions to the spectrum from spots, faculae and plages, filaments, and the bare stellar photosphere. Stellar rotation is also included. We find that it is very difficult to reproduce the measured in-transit Hα signals for reasonable active region parameters. In addition, it is difficult to create an in-transit contrast signature that lasts for the duration of the transit unless the planet is crossing an active latitudinal belt and is always obscuring active regions. This suggests that the Hα measurements arise predominantly in the planetary atmosphere. However, the contrast effect likely contributes to these signals. Furthermore, our results could be

  8. Stellar activity and the rotation of Hyades stars

    SciTech Connect

    Radick, R.R.; Baliunas, S.L.

    1987-12-01

    New measurements of rotation periods for Hyades stars, which were obtained from re-analysis of Mount Wilson Observatory Ca II H-K emission flux measurements, are reported. The existence of systematic, color-dependent discrepancies between the measured rotation periods for Hyades stars and those predicted by the Rossby relation as originally calibrated by Noyes et al. 1984 has led to a re-examination of the form of the relationship between chromospheric emission, rotation, and color.

  9. CKI isoforms α and ε regulate Star-PAP target messages by controlling Star-PAP poly(A) polymerase activity and phosphoinositide stimulation.

    PubMed

    Laishram, Rakesh S; Barlow, Christy A; Anderson, Richard A

    2011-10-01

    Star-PAP is a non-canonical, nuclear poly(A) polymerase (PAP) that is regulated by the lipid signaling molecule phosphatidylinositol 4,5 bisphosphate (PI4,5P(2)), and is required for the expression of a select set of mRNAs. It was previously reported that a PI4,5P(2) sensitive CKI isoform, CKIα associates with and phosphorylates Star-PAP in its catalytic domain. Here, we show that the oxidative stress-induced by tBHQ treatment stimulates the CKI mediated phosphorylation of Star-PAP, which is critical for both its polyadenylation activity and stimulation by PI4,5P(2). CKI activity was required for the expression and efficient 3'-end processing of its target mRNAs in vivo as well as the polyadenylation activity of Star-PAP in vitro. Specific CKI activity inhibitors (IC261 and CKI7) block in vivo Star-PAP activity, but the knockdown of CKIα did not equivalently inhibit the expression of Star-PAP targets. We show that in addition to CKIα, Star-PAP associates with another CKI isoform, CKIε in the Star-PAP complex that phosphorylates Star-PAP and complements the loss of CKIα. Knockdown of both CKI isoforms (α and ε) resulted in the loss of expression and the 3'-end processing of Star-PAP targets similar to the CKI activity inhibitors. Our results demonstrate that CKI isoforms α and ε modulate Star-PAP activity and regulates Star-PAP target messages.

  10. Neuroblastoma Arginase Activity Creates an Immunosuppressive Microenvironment That Impairs Autologous and Engineered Immunity.

    PubMed

    Mussai, Francis; Egan, Sharon; Hunter, Stuart; Webber, Hannah; Fisher, Jonathan; Wheat, Rachel; McConville, Carmel; Sbirkov, Yordan; Wheeler, Kate; Bendle, Gavin; Petrie, Kevin; Anderson, John; Chesler, Louis; De Santo, Carmela

    2015-08-01

    Neuroblastoma is the most common extracranial solid tumor of childhood, and survival remains poor for patients with advanced disease. Novel immune therapies are currently in development, but clinical outcomes have not matched preclinical results. Here, we describe key mechanisms in which neuroblastoma inhibits the immune response. We show that murine and human neuroblastoma tumor cells suppress T-cell proliferation through increased arginase activity. Arginase II is the predominant isoform expressed and creates an arginine-deplete local and systemic microenvironment. Neuroblastoma arginase activity results in inhibition of myeloid cell activation and suppression of bone marrow CD34(+) progenitor proliferation. Finally, we demonstrate that the arginase activity of neuroblastoma impairs NY-ESO-1-specific T-cell receptor and GD2-specific chimeric antigen receptor-engineered T-cell proliferation and cytotoxicity. High arginase II expression correlates with poor survival for patients with neuroblastoma. The results support the hypothesis that neuroblastoma creates an arginase-dependent immunosuppressive microenvironment in both the tumor and blood that leads to impaired immunosurveillance and suboptimal efficacy of immunotherapeutic approaches.

  11. Bar Effects on Central Star Formation and Active Galactic Nucleus Activity

    NASA Astrophysics Data System (ADS)

    Oh, Seulhee; Oh, Kyuseok; Yi, Sukyoung K.

    2012-01-01

    Galactic bars are often suspected to be channels of gas inflow to the galactic center and to trigger central star formation and active galactic nucleus (AGN) activity. However, the current status on this issue based on empirical studies is unsettling, especially regarding AGNs. We investigate this question based on the Sloan Digital Sky Survey Data Release 7. From the nearby (0.01 < z < 0.05) bright (M r < -19) database, we have constructed a sample of 6658 relatively face-on late-type galaxies through visual inspection. We found 36% of them to have a bar. Bars are found to be more common in galaxies with earlier morphology. This makes sample selection critical. Parameter-based selections would miss a large fraction of barred galaxies of early morphology. Bar effects on star formation or AGNs are difficult to understand properly because multiple factors (bar frequency, stellar mass, black hole mass, gas contents, etc.) seem to contribute to them in intricate manners. In the hope of breaking these degeneracies, we inspect bar effects for fixed galaxy properties. Bar effects on central star formation seem higher in redder galaxies. Bar effects on AGNs on the other hand are higher in bluer and less massive galaxies. These effects seem more pronounced with increasing bar length. We discuss possible implications in terms of gas contents, bar strength, bar evolution, fueling timescale, and the dynamical role of supermassive black hole.

  12. High dispersion spectroscopy of solar-type superflare stars. II. Stellar rotation, starspots, and chromospheric activities

    NASA Astrophysics Data System (ADS)

    Notsu, Yuta; Honda, Satoshi; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Nogami, Daisaku; Shibata, Kazunari

    2015-06-01

    We conducted high dispersion spectroscopic observations of 50 superflare stars with Subaru/HDS. These 50 stars were selected from the solar-type superflare stars that we had discovered from the Kepler data. More than half (34 stars) of these 50 target superflare stars show no evidence of binarity, and we estimated stellar parameters of these 34 stars in our previous study (Notsu et al. 2015, PASJ, 67, 32). According to our previous studies using Kepler data, superflare stars show quasi-periodic brightness variations whose amplitude (0.1%-10%) is much larger than that of the solar brightness variations (0.01%-0.1%) caused by the existence of sunspots on the rotating solar surface. In this study, we investigated whether these quasi-periodic brightness variations of superflare stars are explained by the rotation of a star with fairly large starspots, by using stellar parameters derived in Paper I. First, we confirmed that the value of the projected rotational velocity, v sin i, is consistent with the rotational velocity estimated from the period of the brightness variation. Next, we measured the intensity of Ca II infrared triplet lines and Hα line, good indicators of the stellar chromospheric activity, and compared them with other stellar properties. The intensity of Ca II infrared triplet lines indicates that the mean magnetic field strength () of the target superflare stars can be higher than that of the Sun. A correlation between the amplitude of the brightness variation and the intensity of Ca II triplet line was found. All the targets expected to have large starspots because of their large amplitude of the brightness variation show high chromospheric activities compared to the Sun. These results support the idea that the brightness variation of superflare stars is due to the rotation with large starspots.

  13. Mixing of quantum states: A new route to creating optical activity.

    PubMed

    Baimuratov, Anvar S; Tepliakov, Nikita V; Gun'ko, Yurii K; Baranov, Alexander V; Fedorov, Anatoly V; Rukhlenko, Ivan D

    2016-12-01

    The ability to induce optical activity in nanoparticles and dynamically control its strength is of great practical importance due to potential applications in various areas, including biochemistry, toxicology, and pharmaceutical science. Here we propose a new method of creating optical activity in originally achiral quantum nanostructures based on the mixing of their energy states of different parities. The mixing can be achieved by selective excitation of specific states or via perturbing all the states in a controllable fashion. We analyze the general features of the so produced optical activity and elucidate the conditions required to realize the total dissymmetry of optical response. The proposed approach is applicable to a broad variety of real systems that can be used to advance chiroptical devices and methods.

  14. Chromospherically Active Stars in the RAVE Survey. II. Young Dwarfs in the Solar Neighborhood

    NASA Astrophysics Data System (ADS)

    Žerjal, M.; Zwitter, T.; Matijevič, G.; Grebel, E. K.; Kordopatis, G.; Munari, U.; Seabroke, G.; Steinmetz, M.; Wojno, J.; Bienaymé, O.; Bland-Hawthorn, J.; Conrad, C.; Freeman, K. C.; Gibson, B. K.; Gilmore, G.; Kunder, A.; Navarro, J.; Parker, Q. A.; Reid, W.; Siviero, A.; Watson, F. G.; Wyse, R. F. G.

    2017-01-01

    A large sample of over 38,000 chromospherically active candidate solar-like stars and cooler dwarfs from the RAVE survey is addressed in this paper. An improved activity identification with respect to the previous study was introduced to build a catalog of field stars in the solar neighborhood with an excess emission flux in the calcium infrared triplet wavelength region. The central result of this work is the calibration of the age–activity relation for main-sequence dwarfs in a range from a few 10 {Myr} up to a few Gyr. It enabled an order of magnitude age estimation of the entire active sample. Almost 15,000 stars are shown to be younger than 1 {Gyr} and ∼2000 younger than 100 {Myr}. The young age of the most active stars is confirmed by their position off the main sequence in the J ‑ K versus {N}{UV}-V diagram showing strong ultraviolet excess, mid-infrared excess in the J ‑ K versus {W}1-{W}2 diagram, and very cool temperatures (J-K> 0.7). They overlap with the reference pre-main-sequence RAVE stars often displaying X-ray emission. The activity level increasing with the color reveals their different nature from the solar-like stars and probably represents an underlying dynamo-generating magnetic fields in cool stars. Of the RAVE objects from DR5, 50% are found in the TGAS catalog and supplemented with accurate parallaxes and proper motions by Gaia. This makes the database of a large number of young stars in a combination with RAVE’s radial velocities directly useful as a tracer of the very recent large-scale star formation history in the solar neighborhood. The data are available online in the Vizier database.

  15. Processing sleep data created with the Drosophila Activity Monitoring (DAM) System.

    PubMed

    Pfeiffenberger, Cory; Lear, Bridget C; Keegan, Kevin P; Allada, Ravi

    2010-11-01

    Adult behavioral assays have been used with great success in Drosophila melanogaster to identify circadian rhythm genes. In particular, the locomotor activity assay can identify altered behavior patterns over the course of several days in small populations, or even individual flies. Sleep is a highly conserved behavior that is required for optimal performance and, in many cases, life of an organism. Drosophila demonstrate a behavioral state that shows traits consistent with sleep: periods of relative behavioral immobility that coincide with an increased arousal threshold after ~5 min of inactivity, regulated by circadian and homeostatic mechanisms. However, because flies do not produce brain waves recordable by electroencephalography, sleep researchers use behavior-based paradigms to infer when a fly is asleep, as opposed to awake but immobile. Data on Drosophila activity can be collected using an automated monitoring system to provide insight into sleep duration, consolidation, and latency, as well as sleep deprivation and rebound. This protocol details the use of Counting Macro, an Excel-based program, to process data created with the Drosophila Activity Monitoring (DAM) System from TriKinetics for sleep analyses. Specifically, it details the steps necessary to convert the raw data created by the DAM System into sleep duration and consolidation data, broken down into the light (L), dark (D), light:dark cycling (LD), and constant darkness (DD) phases of a behavior experiment.

  16. XUV-driven mass loss from extrasolar giant planets orbiting active stars

    NASA Astrophysics Data System (ADS)

    Chadney, J. M.; Galand, M.; Unruh, Y. C.; Koskinen, T. T.; Sanz-Forcada, J.

    2015-04-01

    Upper atmospheres of Hot Jupiters are subject to extreme radiation conditions that can result in rapid atmospheric escape. The composition and structure of the upper atmospheres of these planets are affected by the high-energy spectrum of the host star. This emission depends on stellar type and age, which are thus important factors in understanding the behaviour of exoplanetary atmospheres. In this study, we focus on Extrasolar Giant Planets (EPGs) orbiting K and M dwarf stars. XUV spectra for three different stars - ɛ Eridani, AD Leonis and AU Microscopii - are constructed using a coronal model. Neutral density and temperature profiles in the upper atmosphere of hypothetical EGPs orbiting these stars are then obtained from a fluid model, incorporating atmospheric chemistry and taking atmospheric escape into account. We find that a simple scaling based solely on the host star's X-ray emission gives large errors in mass loss rates from planetary atmospheres and so we have derived a new method to scale the EUV regions of the solar spectrum based upon stellar X-ray emission. This new method produces an outcome in terms of the planet's neutral upper atmosphere very similar to that obtained using a detailed coronal model of the host star. Our results indicate that in planets subjected to radiation from active stars, the transition from Jeans escape to a regime of hydrodynamic escape at the top of the atmosphere occurs at larger orbital distances than for planets around low activity stars (such as the Sun).

  17. Chromospheric activity and ages of solar-type stars

    SciTech Connect

    Barry, D.C.; Cromwell, R.H.; Hege, E.K.

    1987-04-01

    Observations of 15 solar-type stars in the intermediate-age open cluster NGC 752 are reported. A lower resolution analog of the Mount Wilson S index is shown to yield absolute chromospheric surface flux values for these stars with about 60 percent of the sensitivity of the Mount Wilson system. Absolute chromospheric surface fluxes of solar-type stars in eight clusters ranging from 10 million yrs to six billion or more years in age are presented. Two heuristic forms are shown to fit the data about equally well, with no indication of a discontinuity at intermediate ages. These relations can yield chromospheric ages for any G-type dwarf or subgiant with a Mount Wilson S index. The usefulness of this lower resolution approach for studies of chemical and dynamical evolution of the Galaxy as well as of the stellar birth rate is pointed out. 24 references.

  18. Potent inhibition by star fruit of human cytochrome P450 3A (CYP3A) activity.

    PubMed

    Hidaka, Muneaki; Fujita, Ken-ichi; Ogikubo, Tetsuya; Yamasaki, Keishi; Iwakiri, Tomomi; Okumura, Manabu; Kodama, Hirofumi; Arimori, Kazuhiko

    2004-06-01

    There has been very limited information on the capacities of tropical fruits to inhibit human cytochrome P450 3A (CYP3A) activity. Thus, the inhibitory effects of tropical fruits on midazolam 1'-hydroxylase activity of CYP3A in human liver microsomes were evaluated. Eight tropical fruits such as common papaw, dragon fruit, kiwi fruit, mango, passion fruit, pomegranate, rambutan, and star fruit were tested. We also examined the inhibition of CYP3A activity by grapefruit (white) and Valencia orange as controls. The juice of star fruit showed the most potent inhibition of CYP3A. The addition of a star fruit juice (5.0%, v/v) resulted in the almost complete inhibition of midazolam 1'-hydroxylase activity (residual activity of 0.1%). In the case of grape-fruit, the residual activity was 14.7%. The inhibition depended on the amount of fruit juice added to the incubation mixture (0.2-6.0%, v/v). The elongation of the preincubation period of a juice from star fruit (1.25 or 2.5%, v/v) with the microsomal fraction did not alter the CYP3A inhibition, suggesting that the star fruit did not contain a mechanism-based inhibitor. Thus, we discovered filtered extracts of star fruit juice to be inhibitors of human CYP3A activity in vitro.

  19. Hormonal activation of a kinase cascade localized at the mitochondria is required for StAR protein activity.

    PubMed

    Poderoso, Cecilia; Maloberti, Paula; Duarte, Alejandra; Neuman, Isabel; Paz, Cristina; Cornejo Maciel, Fabiana; Podesta, Ernesto J

    2009-03-05

    It is known that ERK1/2 and MEK1/2 participate in the regulation of Star gene transcription. However, their role in StAR protein post-transcriptional regulation is not described yet. In this study we analyzed the relationship between the MAPK cascade and StAR protein phosphorylation and function. We have demonstrated that (a) steroidogenesis in MA-10 Leydig cells depends on the specific of ERK1/2 activation at the mitochondria; (b) ERK1/2 phosphorylation is driven by mitochondrial PKA and constitutive MEK1/2 in this organelle; (c) active ERK1/2 interacts with StAR protein, leads to StAR protein phosphorylation at Ser(232) only in the presence of cholesterol; (d) directed mutagenesis of Ser(232) (S232A) inhibited in vitro StAR protein phosphorylation by ERK1; (e) transient transfection of MA-10 cells with StAR S232A cDNA markedly reduced the yield of progesterone production. We show that StAR protein is a substrate of ERK1/2, and that mitochondrial ERK1/2 is part of a multimeric complex that regulates cholesterol transport.

  20. A New Active Stage of the Symbiotic Star CH Cygni

    NASA Astrophysics Data System (ADS)

    Iijima, Takashi

    2017-03-01

    The spectral variation of the symbiotic star CH Cygni has been monitored at Asiago Astrophysical Observatory using the 1.22m Galileo telescope. Recently, P Cygni type high velocity absorption components appeared on the H I Balmer lines, which were not seen in early December 2016.

  1. Comparative Analysis of the Activity Cycles of the Atmospheres of the Sun and of Stars of the Solar-Type

    NASA Astrophysics Data System (ADS)

    Bruevich, E. A.; Bruevich, V. V.; Shimanovskaya, E. V.

    2016-03-01

    The atmospheric activity of the sun and of stars of the solar-type is analyzed using observations from the HK-project at the Mount Wilson Observatory, California, and the Carnegie Planet Search Program at the Keck and Lick Observatories, as well as from the Magellan Planet Search Program at the Las Campanas Observatory. It is shown that a cyclical activity of the stars that is analogous to the 11-year solar activity cycle occurs in stars of spectral classes F, G, and K and is more pronounced in stars of class K. A comparative analysis of the solar-type stars with different levels of chromospheric and coronal activity confirms that the sun is one of the stars with a comparatively low level of atmospheric activity and that these stars have a minimal level of coronal emission and minimal variations in the fluxes of photospheric radiation.

  2. CHROMOSPHERICALLY ACTIVE STARS IN THE RADIAL VELOCITY EXPERIMENT (RAVE) SURVEY. I. THE CATALOG

    SciTech Connect

    Žerjal, M.; Zwitter, T.; Matijevič, G.; Strassmeier, K. G.; Siviero, A.; Steinmetz, M.; Bienaymé, O.; Bland-Hawthorn, J.; Boeche, C.; Grebel, E. K.; Freeman, K. C.; Kordopatis, G.; Munari, U.; Navarro, J. F.; Parker, Q. A.; Reid, W.; Seabroke, G.; Wyse, R. F. G.

    2013-10-20

    RAVE, the unbiased magnitude limited survey of southern sky stars, contained 456,676 medium-resolution spectra at the time of our analysis. Spectra cover the Ca II infrared triplet (IRT) range, which is a known indicator of chromospheric activity. Our previous work classified all spectra using locally linear embedding. It identified 53,347 cases with a suggested emission component in calcium lines. Here, we use a spectral subtraction technique to measure the properties of this emission. Synthetic templates are replaced by the observed spectra of non-active stars to bypass the difficult computations of non-local thermal equilibrium profiles of the line cores and stellar parameter dependence. We derive both the equivalent width of the excess emission for each calcium line on a 5 Å wide interval and their sum EW{sub IRT} for ∼44,000 candidate active dwarf stars with signal-to-noise ratio >20, with no cuts on the basis of the source of their emission flux. From these, ∼14,000 show a detectable chromospheric flux with at least a 2σ confidence level. Our set of active stars vastly enlarges previously known samples. Atmospheric parameters and, in some cases, radial velocities of active stars derived from automatic pipelines suffer from systematic shifts due to their shallower calcium lines. We re-estimate the effective temperature, metallicity, and radial velocities for candidate active stars. The overall distribution of activity levels shows a bimodal shape, with the first peak coinciding with non-active stars and the second with the pre-main-sequence cases. The catalog will be made publicly available with the next RAVE public data releases.

  3. Building inhabitant feedback: Creating a reflective practice for environmental design using activity theory

    NASA Astrophysics Data System (ADS)

    Cunningham, Dara Suzanne

    The way buildings are designed now, there is little feedback from use involved in the design process. Attempts to correct this problem have been made in the form of Post Occupancy Evaluations (POEs) for 50-years but have largely failed. POEs are the accepted method for environmental designers to collect feedback about buildings in use. They are infrequently conducted, after the building is built, in a one-time only evaluation, and not funded as part of the build process. Other products receive feedback about the design in use from online critiques. Online critiques could provide a platform for feedback from actors engaged with buildings in use for environmental designers to utilize in developing reflective design rationale to avoid adverse consequences in future designs or correct consequences in past and current designs. Since buildings constitute such a large part of the human environment, it's important to research the effects of buildings on their inhabitants. In order for environmental designers to act on feedback from situated use, designers need to have access to that feedback and all actors interacting with the building design need to have an easy, inexpensive, and accessible method to submit feedback. These needs can be addressed by utilizing modern networked and mobile computing to collect and access building feedback. The analysis presented in this dissertation is informed by a thorough evaluation of the theory of reflective practice, activity theory, environmental design, and cognitive science research. From this analysis, I developed the following contributions. First, I expanded Schon's reflective practice by combining his theory with a modified version of activity theory, using activity theory to enrich reflective practice and create Reflective Activity Systems Theory (RAST), which provides a new framework to develop design rationale based on feedback from use and a focus on the activity. Second, I suggest the design of an activity information system

  4. Community design and policies for free-range children: creating environments that support routine physical activity.

    PubMed

    Fenton, Mark

    2012-02-01

    Growing concern over childhood obesity has prompted a focus on underlying epidemics of physical inactivity and poor nutrition. Regarding the former, there is increasing understanding that behavior change promotion alone has not increased population physical activity levels and that an ecological approach is necessary. Therefore, the public health profession has moved beyond traditional behavior change campaigns toward a growing focus on altering policies and the built environment to create settings that support increases in routine, not just exercise or leisure time, physical activity among children. A survey of the literature suggests four broad factors that define settings where routine physical activity, especially active transportation, is more likely to occur: • a compact variety of land uses, with a mix of destinations in close proximity; • a comprehensive network of bicycle, pedestrian, and transit facilities; • inviting and functional site designs for pedestrians, cyclists, and transit users; • safety and access for users of all ages, incomes, abilities and disabilities. Although these principles are increasingly accepted as beneficial, not just to health but to a community's economic, environmental, and social well-being, many contemporary ordinances and development practices undermine these outcomes. Therefore, five specific policy and intervention approaches are recommended to guide communities to these outcomes: 1. zoning and development policies to protect open space, contain sprawl, and focus investment toward thriving, mixed downtowns and village centers; 2. Complete Streets policies, which require roadways that are safe and functional for pedestrians, bicyclists, and transit users, as well as motor vehicles; 3. a transportation- (not just recreation-) oriented trail network; 4. creation of bicycle- and transit-friendly infrastructure and incentive policies; 5. development of policy-based Safe Routes to School interventions. This proposed

  5. Schools and Obesity Prevention: Creating School Environments and Policies to Promote Healthy Eating and Physical Activity

    PubMed Central

    Story, Mary; Nanney, Marilyn S; Schwartz, Marlene B

    2009-01-01

    Context: Research consistently shows that the majority of American children do not consume diets that meet the recommendations of the Dietary Guidelines for Americans, nor do they achieve adequate levels of daily physical activity. As a result, more children are overweight today than at any other time in U.S. history. Schools offer many opportunities to develop strategies to prevent obesity by creating environments in which children eat healthfully and engage regularly in physical activity. Methods: This article discusses the role of schools in obesity prevention efforts. Current issues in schools' food and physical activity environments are examined, as well as federal, state, and local policies related to food and physical activity standards in schools. The article is organized around four key areas: (1) school food environments and policies, (2) school physical activity environments and policies, (3) school body mass index measurements, and (4) school wellness policies. Recommendations for accelerating change also are addressed. Findings: The article found that (1) competitive foods (foods sold outside of federally reimbursed school meals) are widely available in schools, especially secondary schools. Studies have related the availability of snacks and drinks sold in schools to students' high intake of total calories, soft drinks, total fat and saturated fat, and lower intake of fruits and vegetables; (2) physical activity can be added to the school curriculum without academic consequences and also can offer physical, emotional, and social benefits. Policy leadership has come predominantly from the districts, then the states, and, to a much lesser extent, the federal government; (3) few studies have examined the effectiveness or impact of school-based BMI measurement programs; and (4) early comparative analyses of local school wellness policies suggest that the strongest policies are found in larger school districts and districts with a greater number of

  6. Stellar Activity and the Rotation of Hyades Stars

    DTIC Science & Technology

    1987-12-01

    emnission (RH~t ) Is plotted ag.,rr-t Ros-sb% numiber -- the rotation period scaled by the convective turnover time scale The solid curve is the riresir...also be relieved by a moudification to the shape ot thre scaling funiction r,) as shown in Fig Ic The solid curve is the meant irlation obitained by...pre’dicted period, scaled by observed period) for -22 Hyvades stars (b,) Normalized Call H-K emision ass a f nction or Rossby number The solid curve is. the

  7. Neural activities in V1 create the bottom-up saliency map of natural scenes.

    PubMed

    Chen, Cheng; Zhang, Xilin; Wang, Yizhou; Zhou, Tiangang; Fang, Fang

    2016-06-01

    A saliency map is the bottom-up contribution to the deployment of exogenous attention. It, as well as its underlying neural mechanism, is hard to identify because of the influence of top-down signals. A recent study showed that neural activities in V1 could create a bottom-up saliency map (Zhang et al. in Neuron 73(1):183-192, 2012). In this paper, we tested whether their conclusion can generalize to complex natural scenes. In order to avoid top-down influences, each image was presented with a low contrast for only 50 ms and was followed by a high contrast mask, which rendered the whole image invisible to participants (confirmed by a forced-choice test). The Posner cueing paradigm was adopted to measure the spatial cueing effect (i.e., saliency) by an orientation discrimination task. A positive cueing effect was found, and the magnitude of the cueing effect was consistent with the saliency prediction of a computational saliency model. In a following fMRI experiment, we used the same masked natural scenes as stimuli and measured BOLD signals responding to the predicted salient region (relative to the background). We found that the BOLD signal in V1, but not in other cortical areas, could well predict the cueing effect. These results suggest that the bottom-up saliency map of natural scenes could be created in V1, providing further evidence for the V1 saliency theory (Li in Trends Cogn Sci 6(1):9-16, 2002).

  8. Examining How Activity Shapes Students' Interactions While Creating Representations in Early Elementary Science

    NASA Astrophysics Data System (ADS)

    Danish, Joshua Adam; Saleh, Asmalina

    2014-09-01

    It is common practice in elementary science classrooms to have students create representations, such as drawings, as a way of exploring new content. While numerous studies suggest the benefits of representation in science, the majority focus on specific, canonical representations, such as graphs. Few offer insight or guidance regarding how teachers might effectively incorporate ad hoc, non-normative student-generated representations in their curricula. This study addresses this gap by detailing the relationship between two designed activities-one that supported more open-ended engagement with referents and the other that promoted a synthesis of referents-and the representational products that students generated as a result. We present data from a mixed age classroom (ages 6-9, N = 32) as students depicted their understanding of loggerhead sea turtles. Findings indicate that students performed better when working alone in the open condition and in collaborative dyads in the synthesize condition. These results suggest that it is necessary to unpack how mediating factors (such as students' cooperative strategies, facilitator feedback and materials used) align, to support or inhibit students' representational activities.

  9. Radial velocity measurements of the chromospherically-active stars (2): HD 28591 = V492 Per

    NASA Technical Reports Server (NTRS)

    Dadonas, V.; Sperauskas, J.; Fekel, F. C.; Morton, M. D.

    1994-01-01

    From two sets of the spectroscopic observations covering a ten year period we have obtained 59 radial velocities of the chromospherically-active star HD 28591 = V492 Per. It is a G9III single-lined spectroscopic binary with a period of 21.2910 days and a circular orbit. The upsilon sin i of 24.6 km/sec, results in a minimum radius 10.3 solar radii. We estimate a distance of 165 +/- 40 pc and an orbital inclination of 65 +/- 25 degrees. The secondary is probably a mid to late-type K dwarf. The star is brighter than the limiting magnitude of the Bright Star Catalogue. The mean photometric and the orbital periods are identical within their uncertainties. Since the star fills a significant fraction of its Roche lobe, about 62%, the photometric light curve may be the result of starspots and a modest ellipticity effect.

  10. Activity and cold spots on the surface of G-type superflare stars

    NASA Astrophysics Data System (ADS)

    Savanov, I. S.

    2015-07-01

    Based on the high precision photometric observations of the Kepler space telescope, we have investigated the properties of the active regions (cold spots) on the surface of 279 stars of the spectral class G, for which 1547 superflares with energies in the range of 1033-1036 erg have been revealed. The main conclusion of our study is the quantitative estimation of the increased surface spottedness of superflare stars, which indicates enhancedmagnetic activity of these objects. The increased spottedness on the surfaces of the studied stars was confirmed based on two independent estimations of stellar brightness variations. In addition, it was concluded that superflare stars do not stand out in the common dataset of differential rotation parameters. Based on the data considered, no correlation was found of the spottedness parameters or the differential rotation parameters with the characteristics of these objects—their Rossby numbers and superflare energy. Additionally, the correlation between the superflare energy and the inverse Rossby number was considered. None of these comparisons gave an indication for the presence of any obvious correlation. The results of the analysis of five stars with a few dozen flares registered indicate that for the same star whereas spottedness S variations are small, significant changes in the superflare energy can be achieved. On the example of KIC 10422252, we show that at sixfold S variations, the flare energy varies by orders of magnitude at any given S value.

  11. The Evolution of Cyclic Activity of the Sun in the Context of Physical Processes on Late-Type Stars

    NASA Astrophysics Data System (ADS)

    Katsova, Maria M.

    Features of the solar cycle in the context of stellar activity are investigated. We discovered reliably differential rotation in chromospheres of some stars and presented the first stellar butterfly diagrams. These stars possess less regular variability and do not demonstrate excellent cycles. This is the first evidence for differences of the solar activity from processes on stars with Excellent cycles. We compare indices of the chromospheric activity of the Sun with that for above 1,300 northern and southern stars whose activity revealed during planet search programs. We argue the matter pro and con for two possible ways of an evolution of activity from a contraction phase to 10Gyrs. When a young star brakes down, the chromospheric and the coronal activity weaken synchronously. The solar-like activity of the most main sequence F and early G stars does evolve by this path. The activity of the later stars from G5 to K7 after a definite level evolves by another way: the chromospheric activity diminishes up to the solar level, while coronae stay stronger than the solar one. Two possible paths of the evolution of activity are associated with the different depth of the convective zone of these stars. Physically this means that the relative input of small- and large-scale of magnetic fields differs for F-G and K stars.

  12. X-ray spectral diagnostics of activity in massive stars

    NASA Astrophysics Data System (ADS)

    Cohen, David H.; Wollman, Emma E.; Leutenegger, Maurice A.

    2011-07-01

    X-rays give direct evidence of instabilities, time-variable structure, and shock heating in the winds of O stars. The observed broad X-ray emission lines provide information about the kinematics of shock-heated wind plasma, enabling us to test wind-shock models. And their shapes provide information about wind absorption, and thus about the wind mass-loss rates. Mass-loss rates determined from X-ray line profiles are not sensitive to density-squared clumping effects, and indicate mass-loss rate reductions of factors of 3 to 6 over traditional diagnostics that suffer from density-squared effects. Broad-band X-ray spectral energy distributions also provide mass-loss rate information via soft X-ray absorption signatures. In some cases, the degree of wind absorption is so high, that the hardening of the X-ray SED can be quite significant. We discuss these results as applied to the early O stars ζ Pup (O4 If), 9 Sgr (O4 V((f))), and HD 93129A (O2 If*).

  13. Ultraviolet and X-ray Activity and Flaring on Low-Mass Exoplanet Host Stars

    NASA Astrophysics Data System (ADS)

    France, Kevin; Parke Loyd, R. O.; Brown, Alexander

    2015-08-01

    The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. High-energy photons (X-ray to NUV) from these stars regulate the atmospheric temperature profiles and photochemistry on orbiting planets, influencing the production of potential “biomarker” gases. We present results from the MUSCLES Treasury Survey, an ongoing study of time-resolved UV and X-ray spectroscopy of nearby M and K dwarf exoplanet host stars. This program uses contemporaneous Hubble Space Telescope and Chandra (or XMM) observations to characterize the time variability of the energetic radiation field incident on the habitable zones planetary systems at d < 15 pc. We find that all exoplanet host stars observed to date exhibit significant levels of chromospheric and transition region UV emission. M dwarf exoplanet host stars display 30 - 2000% UV emission line amplitude variations on timescales of minutes-to-hours. The relative flare/quiescent UV flux amplitudes on old (age > 1 Gyr) planet-hosting M dwarfs are comparable to active flare stars (e.g., AD Leo), despite their lack of flare activity at visible wavelengths. We also detect similar UV flare behavior on a subset of our K dwarf exoplanet host stars. We conclude that strong flares and stochastic variability are common, even on “optically inactive” M dwarfs hosting planetary systems. These results argue that the traditional assumption of weak UV fields and low flare rates on older low-mass stars needs to be revised.

  14. Exploring the Connection Between Star Formation and AGN Activity in the Local Universe

    NASA Technical Reports Server (NTRS)

    LaMassa, Stephanie M.; Heckman. T. M.; Ptak, Andrew; Schiminovich, D.; O'Dowd, M.; Bertincourt, B.

    2012-01-01

    We study a combined sample of 264 star-forming, 51 composite, and 73 active galaxies using optical spectra from SDSS and mid-infrared (mid-IR) spectra from the Spitzer Infrared Spectrograph. We examine optical and mid-IR spectroscopic diagnostics that probe the amount of star formation and relative energetic con- tributions from star formation and an active galactic nucleus (AGN). Overall we find good agreement between optical and mid-IR diagnostics. Misclassifications of galaxies based on the SDSS spectra are rare despite the presence of dust obscuration. The luminosity of the [NeII] 12.8 micron emission-line is well correlated with the star formation rate (SFR) measured from the SDSS spectra, and this holds for the star forming, composite, and AGN-dominated systems. AGN show a clear excess of [NeIII] 15.6 micron emission relative to star forming and composite systems. We find good qualitative agreement between various parameters that probe the relative contributions of the AGN and star formation, including: the mid-IR spectral slope, the ratio of the [NeV] 14.3 micron to [NeII] micron 12.8 fluxes, the equivalent widths of the 7.7, 11.3, and 17 micron PAH features, and the optical "D" parameter which measures the distance a source lies from the locus of star forming galaxies in the optical BPT emission-line diagnostic diagram. We also consider the behavior of the three individual PAH features by examining how their flux ratios depend upon the degree of AGN-dominance. We find that the PAH 11.3 micron feature is significantly suppressed in the most AGN-dominated systems.

  15. Examining the Flicker-Jitter Relation of K2 stars: the Dependence on Chromospheric Activity

    NASA Astrophysics Data System (ADS)

    Luhn, Jacob K.; Bastien, Fabienne A.; Wright, Jason

    2017-01-01

    Recently, Bastien et al. (2014) have shown that short timescale photometric variations from high-precision Kepler light curves, coined "flicker", can be linked to radial velocity (RV) noise, or "jitter", in chromospherically inactive stars. Observations of the sun show invariance in flicker over its 11-year activity cycle. Therefore, we seek to examine how well the relation holds for more active stars. Here we explore the relation between photometric flicker and RV jitter by extending the sample to stars observed by the recent K2 mission for which data have been released (Campaigns 0-8). The initial Kepler sample included 12 stars with surface gravities 3 < log(g) < 4.5, effective temperatures 4900 < Teff < 5900, and chromospheric activity -5.3 < log(R'HK) < -5.0. Our sample includes over 50 stars across a slightly wider range of surface gravities (2.5 < log(g) < 5), effective temperatures (4700 < Teff < 6100), and much larger range of chromospheric activity (-5.4 < log(R'HK) < -4.1). Additionally, we provide an empirical estimate for RV jitter based on the photometric flicker. Finally, we discuss the implications of this result on future RV follow-up for TESS and other future telescopes which will produce high-precision light curves.

  16. The onset of chromospheric activity among the A- and F- type stars

    NASA Technical Reports Server (NTRS)

    Simon, Theodore; Landsman, Wayne

    1987-01-01

    IUE observations of C II lambda1335 and C IV lambda1549 and ground-based observations of He I lambda5876 have previously discovered intense levels of chromospheric activity among early F type stars. Virtually all F dwarfs show stronger chromospheric and transition region emission than do the cooler and more deeply convective dwarf stars like the Sun. The IUE spectra and those of He lambda5876 place the onset of stellar activity along the main sequence near a color B - V = 0.28, which corresponds approximately to spectral type FO and an effective temperature of 7300 K. However, existing X-ray observations of A and F stars suggest that coronal activity may reach a peak blueward of this high temperature boundary at B - V = 0.28 before vanishing among the early and mid A-type stars. Discussed are preliminary results of a new effort to refine the location of the high temperature boundary to chromospheric activity among A- and F- type stars, making use of low dispersion short-wavelength spectra from the IUE archives from which the strengths of C IV, C II, and Lyman alpha emission have been measured.

  17. CHROMOSPHERIC ACTIVITY AND JITTER MEASUREMENTS FOR 2630 STARS ON THE CALIFORNIA PLANET SEARCH

    SciTech Connect

    Isaacson, Howard; Fischer, Debra E-mail: debra.fischer@yale.ed

    2010-12-10

    We present time series measurements of chromospheric activity for more than 2600 main-sequence and subgiant stars on the California Planet Search (CPS) program with spectral types ranging from about F5V to M4V for main-sequence stars and from G0IV to about K5IV for subgiants. The large data set of more than 44,000 spectra allows us to identify an empirical baseline floor for chromospheric activity as a function of color and height above the main sequence. We define {Delta}S as an excess in emission in the Ca II H and K lines above the baseline activity floor and define radial velocity jitter as a function of {Delta}S and B - V for main-sequence and subgiant stars. Although the jitter for any individual star can always exceed the baseline level, we find that K dwarfs have the lowest level of jitter. The lack of correlation between observed jitter and chromospheric activity in K dwarfs suggests that the observed jitter is dominated by instrumental or analysis errors and not astrophysical noise sources. Thus, given the long-term precision for the CPS program, radial velocities are not correlated with astrophysical noise for chromospherically quiet K dwarf stars, making these stars particularly well suited for the highest precision Doppler surveys. Chromospherically quiet F and G dwarfs and subgiants exhibit higher baseline levels of astrophysical jitter than K dwarfs. Despite the fact that the rms in Doppler velocities is correlated with the mean chromospheric activity, it is rare to see one-to-one correlations between the individual time series activity and Doppler measurements, diminishing the prospects for correcting activity-induced velocity variations in F and G dwarfs.

  18. Change in the activity character of the coronae of low-mass stars of various spectral types

    NASA Astrophysics Data System (ADS)

    Nizamov, B. A.; Katsova, M. M.; Livshits, M. A.

    2017-03-01

    We study the dependence of the coronal activity index on the stellar rotation velocity. This question has been considered previously for 824 late-type stars on the basis of a consolidated catalogue of soft X-ray fluxes. We carry out a more refined analysis separately for G, K, and M dwarfs. Two modes of activity are clearly identified in them. The first is the saturation mode, is characteristic of young stars, and is virtually independent of their rotation. The second refers to the solar-type activity whose level strongly depends on the rotation period. We show that the transition from one mode to the other occurs at rotation periods of 1.1, 3.3, and 7.2 days for stars of spectral types G2, K4, and M3, respectively. In light of the discovery of superflares on G and K stars from the Kepler spacecraft, the question arises as to what distinguishes these objects from the remaining active late-type stars. We analyze the positions of superflare stars relative to the remaining stars observed by Kepler on the "amplitude of rotational brightness modulation (ARM)—rotation period" diagram. The ARM reflects the relative spots area on a star and characterizes the activity level in the entire atmosphere. G and K superflare stars are shown to be basically rapidly rotating young objects, but some of them belong to the stars with the solar type of activity.

  19. Results from the Nearby Stars (NStars) Program: Chromospheric Activity in a Sample of Nearby Solar Analogs

    NASA Astrophysics Data System (ADS)

    Corbally, Christopher J.; J., S.; Gray, R. O.

    2010-01-01

    Since the year 2000, our institutions have been engaged in a study of the nearby dwarf and giant stars earlier than spectral type M0 in the Hipparcos catalog and within 40 parsecs of the Sun (3600 stars). This study has used classification-resolution spectra to provide new, precise spectral types and basic physical parameters (effective temperature, surface gravity and metallicity). In addition, we are providing measures of the chromospheric activity for these stars. Results so far have been published in Gray et al. (2003, 2006). Here we outline the continuation of this study to which recent improvements have been made. These are both to the estimation of chromospheric activity, now closer to the Mount Wilson system, and to the derivation of stellar parameters through use of Kurucz's newer, Atlas12 atmospheric models. For a limited, improved sample, activity and evolutionary age are compared.

  20. Creating a Star: The Science of Fusion--Fusion Power Would Not Contribute to Global Warming, Acid Rain, or Other Forms of Air Pollution, nor Would It Create Long-Lived Radioactive Waste

    ERIC Educational Resources Information Center

    Baird, Stephen L.

    2005-01-01

    Fusion is the process that powers the sun and the stars. Since the 1950s, scientists and engineers in the United States and around the world have been conducting fusion research in pursuit of the creation of a new energy source for our planet and to further our understanding and control of plasma, the fourth state of matter that dominates the…

  1. Dissecting galaxies: spatial and spectral separation of emission excited by star formation and AGN activity

    NASA Astrophysics Data System (ADS)

    Davies, Rebecca L.; Groves, Brent; Kewley, Lisa J.; Dopita, Michael A.; Hampton, Elise J.; Shastri, Prajval; Scharwächter, Julia; Sutherland, Ralph; Kharb, Preeti; Bhatt, Harish; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stéphanie; Srivastava, Shweta

    2016-10-01

    The optical spectra of Seyfert galaxies are often dominated by emission lines excited by both star formation and active galactic nucleus (AGN) activity. Standard calibrations (such as for the star formation rate) are not applicable to such composite (mixed) spectra. In this paper, we describe how integral field data can be used to spectrally and spatially separate emission associated with star formation from emission associated with accretion on to an AGN. We demonstrate our method using integral field data for two AGN host galaxies (NGC 5728 and NGC 7679) from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). The spectra of NGC 5728 and NGC 7679 form clear sequences of AGN fraction on standard emission line ratio diagnostic diagrams. We show that the emission line luminosities of the majority (>85 per cent) of spectra along each AGN fraction sequence can be reproduced by linear superpositions of the emission line luminosities of one AGN dominated spectrum and one star formation dominated spectrum. We separate the Hα, Hβ, [N II]λ6583, [S II]λλ6716, 6731, [O III]λ5007 and [O II]λλ3726, 3729 luminosities of every spaxel into contributions from star formation and AGN activity. The decomposed emission line images are used to derive the star formation rates and AGN bolometric luminosities for NGC 5728 and NGC 7679. Our calculated values are mostly consistent with independent estimates from data at other wavelengths. The recovered star-forming and AGN components also have distinct spatial distributions which trace structures seen in high-resolution imaging of the galaxies, providing independent confirmation that our decomposition has been successful.

  2. A Cluster Of Activities On Coma From The Hubble Space Telescope, StarDate, And McDonald Observatory

    NASA Astrophysics Data System (ADS)

    Hemenway, Mary Kay; Jogee, S.; Fricke, K.; Preston, S.

    2011-01-01

    With a goal of providing a vast audience of students, teachers, the general public, and Spanish-speakers with activities to learn about research on the Coma cluster of galaxies based on the HST ACS Treasury survey of Coma, McDonald Observatory used a many-faceted approach. Since this research offered an unprecedented legacy dataset, part of the challenge was to convey the importance of this project to a diverse audience. The methodology was to create different products for different (overlapping) audiences. Five radio programs were produced in English and Spanish for distribution on over 500 radio stations in the US and Mexico with a listening audience of over 2 million; in addition to the radio listeners, there were over 13,000 downloads of the English scripts and almost 6000 of the Spanish. Images were prepared for use in the StarDate Online Astronomy Picture of the Week, for ViewSpace (used in museums), and for the StarDate/Universo Teacher Guide. A high-school level activity on the Coma Cluster was prepared and distributed both on-line and in an upgraded printed version of the StarDate/Universo Teacher Guide. This guide has been distributed to over 1700 teachers nationally. A YouTube video about careers and research in astronomy using the Coma cluster as an example was produced. Just as the activities were varied, so were the evaluation methods. This material is based upon work supported by the National Aeronautics and Space Administration under Grant/Contract/Agreement No. HST-EO-10861.35-A issued through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  3. Chromospherically active stars. II - HD 82558, a young single BY Draconis variable

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Bopp, Bernard W.; Africano, John L.; Goodrich, Bret D.; Palmer, Leigh Hunter

    1986-01-01

    It is presently noted that the HD 82558 chromospherically active star is a young and rapidly rotating K2 V single BY Draconis variable with very strong far-UV emission features and an H-alpha line filled to the continuum level by emission. HD 82558 has constant velocity and is not a member of the Hyades Supercluster. Its light curve behavior, which appears to have been stable for several hundred rotation cycles, is reminiscent of that of the young, rapidly rotating, single K V variable H II 1883 in the Pleiades; this stability may be characteristic of young, single, chromospherically active stars.

  4. Magnetic cycles of Sun-like stars with different levels of coronal and chromospheric activity — comparison with the Sun

    NASA Astrophysics Data System (ADS)

    Shimanovskaya, Elena; Bruevich, Vasiliy; Bruevich, Elena

    2016-09-01

    The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from the HK-project at the Mount Wilson Observatory, the California and Carnegie Planet Search Program at the Keck and Lick Observatories and the Magellan Planet Search Program at the Las Campanas Observatory. We show that for stars of F, G and K spectral classes, the cyclic activity, similar to the 11-yr solar cycle, is different: it becomes more prominent in K-stars. Comparative study of Sun-like stars with different levels of chromospheric and coronal activity confirms that the Sun belongs to stars with a low level of chromospheric activity and stands apart among these stars by its minimum level of coronal radiation and minimum level of variations in photospheric flux.

  5. The Life Cycles of Stars: An Information and Activity Booklet, Grades 9-12, 1997-1998. Imagine the Universe! Probing the Structure & Evaluation of the Cosmos.

    ERIC Educational Resources Information Center

    Whitlock, Laura A.; Granger, Kara C.

    This booklet contains information and activities on the life cycle of stars. Materials can be adapted for grade 9 through grade 12 classrooms. Background information about star birth and life, black dwarfs, supernovae, white dwarfs, neutron stars, black holes, and the electromagnetic spectrum is included. The seven activities focus on star mass,…

  6. CHROMOSPHERIC ACTIVITY OF SOUTHERN STARS FROM THE MAGELLAN PLANET SEARCH PROGRAM

    SciTech Connect

    Arriagada, Pamela

    2011-06-10

    I present chromospheric-activity measurements of {approx}670 F, G, K, and M main-sequence stars in the Southern Hemisphere, from {approx}8000 archival high-resolution echelle spectra taken at Las Campanas Observatory since 2004. These stars were targets from the Old Magellan Planet Search, and are now potential targets for the New Magellan Planet Search that will look for rocky and habitable planets. Activity indices (S values) are derived from Ca II H and K line cores and then converted to the Mount Wilson system. From these measurements, chromospheric (log R'{sub HK}) indices are derived, which are then used as indicators of the level of radial-velocity jitter, age, and rotation periods these stars present.

  7. Chromospheric Activity of Southern Stars from the Magellan Planet Search Program

    NASA Astrophysics Data System (ADS)

    Arriagada, Pamela

    2011-06-01

    I present chromospheric-activity measurements of ~670 F, G, K, and M main-sequence stars in the Southern Hemisphere, from ~8000 archival high-resolution echelle spectra taken at Las Campanas Observatory since 2004. These stars were targets from the Old Magellan Planet Search, and are now potential targets for the New Magellan Planet Search that will look for rocky and habitable planets. Activity indices (S values) are derived from Ca II H and K line cores and then converted to the Mount Wilson system. From these measurements, chromospheric (log R'HK) indices are derived, which are then used as indicators of the level of radial-velocity jitter, age, and rotation periods these stars present. Based on observations obtained with the Magellan Telescopes, operated by the Carnegie Institution, Harvard University, University of Michigan, University of Arizona, and the Massachusetts Institute of Technology.

  8. Simultaneous Broadband Observations of jet-dominated active galaxies with NuSTAR

    NASA Astrophysics Data System (ADS)

    Furniss, Amy

    2014-08-01

    The exceptionally energetic particle populations at work within powerful relativistic jets associated with active galaxies make these sources natural targets for the NuSTAR hard X-ray instrument. This space-based satellite can observe their emission between 3 and 70 keV with unprecedented sensitivity. This emission is likely due to the synchrotron process, and particles responsible for the hard X-ray emission are also expected to produce gamma-rays via inverse Compton process observed by instruments such as Fermi Large Area Telescope, VERITAS, MAGIC and HESS. Since the launch of NuSTAR, the instrument has led simultaneous broadband campaigns on multiple gamma-ray emitting jetted active galaxies. NuSTAR was able to observe Mrk 421 during unprecedented low and high states, as well as variability in Mrk 501 consistent with a magnetic reconnection event. Additionally, the extreme blazar 1ES 0229+200 was observed with NuSTAR, together with ground based gamma-ray instruments, providing the first complete picture of the broadband emission. These invaluable observations of BL Lac-type objects were supplemented with NuSTAR observations of the exceptionally variable flat spectrum radio quasar 3C 279, observed during the highest gamma-ray state yet observed by the Fermi LAT instrument. We will share the results from these multiwavelength campaigns, with particular emphasis on the implications for the study of the most relativistic particle populations at work within the Universe.

  9. A connection between star formation activity and cosmic rays in the starburst galaxy M82.

    PubMed

    2009-12-10

    Although Galactic cosmic rays (protons and nuclei) are widely believed to be mainly accelerated by the winds and supernovae of massive stars, definitive evidence of this origin remains elusive nearly a century after their discovery. The active regions of starburst galaxies have exceptionally high rates of star formation, and their large size-more than 50 times the diameter of similar Galactic regions-uniquely enables reliable calorimetric measurements of their potentially high cosmic-ray density. The cosmic rays produced in the formation, life and death of massive stars in these regions are expected to produce diffuse gamma-ray emission through interactions with interstellar gas and radiation. M82, the prototype small starburst galaxy, is predicted to be the brightest starburst galaxy in terms of gamma-ray emission. Here we report the detection of >700-GeV gamma-rays from M82. From these data we determine a cosmic-ray density of 250 eV cm(-3) in the starburst core, which is about 500 times the average Galactic density. This links cosmic-ray acceleration to star formation activity, and suggests that supernovae and massive-star winds are the dominant accelerators.

  10. A CORRELATION BETWEEN HOST STAR ACTIVITY AND PLANET MASS FOR CLOSE-IN EXTRASOLAR PLANETS?

    SciTech Connect

    Poppenhaeger, K.; Schmitt, J. H. M. M.

    2011-07-01

    The activity levels of stars are influenced by several stellar properties, such as stellar rotation, spectral type, and the presence of stellar companions. Analogous to binaries, planetary companions are also thought to be able to cause higher activity levels in their host stars, although at lower levels. Especially in X-rays, such influences are hard to detect because coronae of cool stars exhibit a considerable amount of intrinsic variability. Recently, a correlation between the mass of close-in exoplanets and their host star's X-ray luminosity has been detected, based on archival X-ray data from the ROSAT All-Sky Survey. This finding has been interpreted as evidence for star-planet interactions. We show in our analysis that this correlation is caused by selection effects due to the flux limit of the X-ray data used and due to the intrinsic planet detectability of the radial velocity method, and thus does not trace possible planet-induced effects. We also show that the correlation is not present in a corresponding complete sample derived from combined XMM-Newton and ROSAT data.

  11. LITHIUM ABUNDANCE IN SOLAR-TYPE STARS WITH LOW CHROMOSPHERIC ACTIVITY: APPLICATION TO THE SEARCH FOR MAUNDER MINIMUM ANALOGS

    SciTech Connect

    Lubin, Dan; Tytler, David; Kirkman, David

    2010-06-10

    We use measurements of lithium abundance to examine the evolutionary history of stars frequently believed to be in a Maunder minimum (MM) state due to their low chromospheric activity. In a sample whose main-sequence membership has been verified using Hipparcos parallax data, we find that stars with very low chromospheric activity log R'{sub HK} {<=} -5.0 have substantially depleted lithium compared with the full sample, with half of these lithium abundances lying more than one standard deviation below the sample mean for their range of color index. One interpretation is that these stars are near the end of their main-sequence lifetime, and therefore their low activity does not necessarily signify a transient MM state in a solar-age star. Conversely, using information in published activity time series for some stars, and combined lithium and activity measurements from the Ursa Major moving group and M67, we find limited evidence that a low-activity star having lithium abundance in the normal range for its color index may be a viable MM candidate. Thus, lithium abundance, which can be readily observed or even retrieved from some of the spectroscopic data collected by recent planet-search surveys, may have value for expanding and refining the program star lists for long-term MM searches. Finally, we find that the use of Hipparcos parallax data to ascertain main-sequence membership sharpens the distinction in sample-mean lithium abundance between stars with planet detections and comparison stars.

  12. Vanderbilt University Study Creates New Roadmap for Cellular Activity - Office of Cancer Clinical Proteomics Research

    Cancer.gov

    Scientists studying cellular processes have long sought to measure redox modifications because they provide one of the normal layers of cell control. But redox disruption or oxidative stress at the cellular level can also create a pathway to diseases like

  13. Activities of X-ray binaries accompanied by a neutron star with weak magnetic field: Cir X-1, Aql X-1 and 4U 1608-52

    NASA Astrophysics Data System (ADS)

    Matsuoka, Masaru; Mihara, Tatehiro; Asai, Kazumi

    This paper is presented on X-ray activities of X-ray binaries accompanied by a neutron star with weak magnetic field. Neutron star low mass X-ray binaries (NS-LMXBs) have been well studied so far, but there are still unknown problems concerning activities of outbursts and X-ray spectral features. We can define the soft and hard states which show different spectra created from each disk structure. These states depend on the gas accretion rate causing viscosity change in the disk, whereas we have pointed out an importance of magnetic field in NS-LMXB for X-ray activities (Matsuoka & Asai 2013). Thus, we have obtained decay features occurred by a propeller effect for Aql X-1 and 4U1608-52, and thus, we have defined the propeller effect levels of these sources (Asai et al. 2013). A companion star of Cir X-1 is a star of B5~A0 type, but it has X-ray spectral feature similar to NS-LMXB as well as it produced type I X-ray bursts. A long history over 40 years of X-ray observations has provided that Cir X-1 X-ray intensities have many varieties from continuous variable fluxes with Z-type feature of NS-LMXB to recurrent outburst fluxes with Atoll-type feature on a time scale of years. Recent MAXI observations have revealed a strange sudden decay feature in some outbursts. It is difficult to explain this decay feature by the simple picture which causes by ordinary mechanisms known in NS-LMXB such as a state transition, a propeller effect and a brink due to disk irradiation (Powell et al. 2007). Therefore, we introduced new type of instability of the accretion disk in relation to stellar wind stripping effect (Asai et al. 2014) which may be common to a system consisting of a compact star and an ordinary massive star.

  14. Ca II activity and rotation in F-K evolved stars

    NASA Astrophysics Data System (ADS)

    Pasquini, L.; de Medeiros, J. R.; Girardi, L.

    2000-09-01

    Ca II H and K high resolution observations for 60 evolved stars in the field and in 5 open clusters are presented. From these spectra chromospheric fluxes are derived, and a homogeneous sample of more than 100 giants is built adding data from the literature. In addition, for most stars, rotational velocities were derived from CORAVEL observations. By comparing chromospheric emission in the cluster stars we confirm the results of Pasquini & Brocato (1992): chromospheric activity depends on the stellar effective temperature, and mass, when intermediate mass stars (M ~ 4 Msun) are considered. The Hyades and the Praesepe clump giants show the same level of activity, as expected from stars with similar masses and effective temperatures. A difference of up to 0.4 dex in the chromospheric fluxes among the Hyades giants is recorded and this sets a clear limit to the intrinsic spread of stellar activity in evolved giants. These differences in otherwise very similar stars are likely due to stellar cycles and/or differences in the stellar initial angular momentum. Among the field stars none of the giants with (V-R)o < 0.4 and Ia supergiants observed shows a signature of Ca II activity; this can be due either to the real absence of a chromosphere, but also to other causes which preclude the appearance of Ca II reversal. By analyzing the whole sample we find that chromospheric activity scales linearly with stellar rotational velocity and a high power of stellar effective temperature: F'k ~ Teff7.7 (Vsini)0.9. This result can be interpreted as the effect of two chromospheric components of different nature: one mechanical and one magnetic. Alternatively, by using the Hipparcos parallaxes and evolutionary tracks, we divide the sample according to the stellar masses, and we follow the objects along an evolutionary track. For each range of masses activity can simply be expressed as a function of only one parameter: either the Teff or the angular rotation Omega , with laws F

  15. The evolution of chromospheric activity in middle-aged Sun-like stars

    NASA Astrophysics Data System (ADS)

    Curtis, Jason L.

    2016-01-01

    Ages of stars are difficult to infer because stars change very little during the majority of their lifetimes. However, stars are observed to spin down over time due to magnetic braking, which weakens the magnetic dynamo as well. This spin down has led to a new age dating method called gyrochronology, which has been successfully calibrated for Sun-like stars up to 2.5 Gyr, but is still undetermined at older ages and lower masses. The decay of magnetic activity has also been utilized to empirically calibrate an age relationship at ages less than 600 Myr with nearby young star clusters (e.g. Hyades), and pinned down at 4 Gyr with M67, but the relationship is basically unconstrained at intermediate ages and sub-Solar masses. Advances in observational facilities have brought distant clusters into view, while the discovery of Ruprecht 147 has provided a new benchmark that is the oldest nearby cluster (3 Gyr, 300 pc, Curtis et al. 2013), and which provides a bridge across this historic age gap. I will present new, high quality chromospheric activity data for NGC 752 at 1.5 Gyr and Ruprecht 147 at 3 Gyr. The stars of Ruprecht 147 will demonstrate the typical activity level and variability experienced by the Sun at a time when multicellular life first evolved on Earth. I will also re-evaluate the M67 data by considering contamination by the interstellar medium, with implications for the frequency of Maunder Minima. Finally, I will discuss a new opportunity to investigate stellar spin down and variability in low mass KM dwarfs with the K2 Survey of Ruprecht 147, which will have just concluded in late December 2015.

  16. Star Power: Providing for the Gifted & Talented. Module 5. Enrichment Activities for the Gifted/Talented.

    ERIC Educational Resources Information Center

    Mallis, Jackie; Gilman, Sharlene

    The document presents Module 5, enrichment activities for the gifted/talented, of the Star Power modules developed for school personnel who have an interest in or a need to explore the area of gifted and talented education. It is explained in an introductory section that the modules can be used for independent study, for small group interaction,…

  17. The Chromospheric Activity-Age Relation for M Dwarf Stars in Wide Binary Systems

    NASA Astrophysics Data System (ADS)

    Silvestri, N. M.

    2002-12-01

    We present new chromospheric activity-age relations for M dwarf stars in wide binary systems with white dwarf companions. This study is unique in that we use the cooling age of the white dwarf to determine the age of the M dwarf star in the binary system. Assuming that the members of the gravitationally bound system are coeval, the age of the white dwarf is therefore the age of the M dwarf companion. The colors and magnitudes at which chromospheric activity becomes pervasive (at the ``Hα limit") in M stars have been shown to correlate linearly with log(age) in young (<= 4 Gyr) cluster M dwarfs. We find that M dwarfs in wide binaries older than 4 Gyr depart from this linear relation and are found to have activity at colors and magnitudes both bluer and brighter than predicted by M dwarf cluster relations. Also, activity is present in nearly all cluster M dwarfs above the ``Hα limit", whereas not all binary M dwarfs are found to be active above this limit. These relations differ considerably from the rotationally driven dynamo relation for F, G, and K stars that suggests a different magnetic heating mechanism for M dwarf stars. The new relations extend to ages beyond the oldest ages provided by cluster M dwarf activity-age estimates. However, more work is necessary to decrease the uncertainties in these new relations and extend them to later (>= M5.5) spectral types. This work was supported by the NASA Graduate Researchers Program Grant NGT 200415; A Grant-in-Aid of Research from the National Academy of Sciences administered by Sigma Xi, The Scientific Research Society; NASA Grant Y701296; and NSF Grant AST 0206115.

  18. HerMES: disentangling active galactic nuclei and star formation in the radio source population

    NASA Astrophysics Data System (ADS)

    Rawlings, J. I.; Page, M. J.; Symeonidis, M.; Bock, J.; Cooray, A.; Farrah, D.; Guo, K.; Hatziminaoglou, E.; Ibar, E.; Oliver, S. J.; Roseboom, I. G.; Scott, Douglas; Seymour, N.; Vaccari, M.; Wardlow, J. L.

    2015-10-01

    We separate the extragalactic radio source population above ˜50 μJy into active galactic nuclei (AGN) and star-forming sources. The primary method of our approach is to fit the infrared spectral energy distributions (SEDs), constructed using Spitzer/IRAC (Infrared Array Camera) and Multiband Imaging Photometer for Spitzer (MIPS) and Herschel/SPIRE photometry, of 380 radio sources in the Extended Chandra Deep Field-South. From the fitted SEDs, we determine the relative AGN and star-forming contributions to their infrared emission. With the inclusion of other AGN diagnostics such as X-ray luminosity, Spitzer/IRAC colours, radio spectral index and the ratio of star-forming total infrared flux to k-corrected 1.4 GHz flux density, qIR, we determine whether the radio emission in these sources is powered by star formation or by an AGN. The majority of these radio sources (60 per cent) show the signature of an AGN at some wavelength. Of the sources with AGN signatures, 58 per cent are hybrid systems for which the radio emission is being powered by star formation. This implies that radio sources which have likely been selected on their star formation have a high AGN fraction. Below a 1.4 GHz flux density of 1 mJy, along with finding a strong contribution to the source counts from pure star-forming sources, we find that hybrid sources constitute 20-65 per cent of the sources. This result suggests that hybrid sources have a significant contribution, along with sources that do not host a detectable AGN, to the observed flattening of the source counts at ˜1 mJy for the extragalactic radio source population.

  19. IUE observations of the chromospheric activity-age relation in young solar-type stars

    NASA Technical Reports Server (NTRS)

    Simon, T.; Boesgaard, A. M.

    1982-01-01

    Ultraviolet data obtained with the IUE spacecraft are presented for a dozen solar-type stars in the field. The stars are of spectral type F6 V - G1 V; on the basis of their high Li content, they range in age from 0.1 to 2.8 Gyr. The evolution of transition regions and chromospheric emission with stellar age is studied along with the surface distribution of magnetically active regions as revealed by rotational modulation of UV emission line fluxes.

  20. The host stars of Kepler's habitable exoplanets: superflares, rotation and activity

    NASA Astrophysics Data System (ADS)

    Armstrong, D. J.; Pugh, C. E.; Broomhall, A.-M.; Brown, D. J. A.; Lund, M. N.; Osborn, H. P.; Pollacco, D. L.

    2016-01-01

    We embark on a detailed study of the light curves of Kepler's most Earth-like exoplanet host stars using the full length of Kepler data. We derive rotation periods, photometric activity indices, flaring energies, mass-loss rates, gyrochronological ages, X-ray luminosities and consider implications for the planetary magnetospheres and habitability. Furthermore, we present the detection of superflares in the light curve of Kepler-438, the exoplanet with the highest Earth Similarity Index to date. Kepler-438b orbits at a distance of 0.166 au to its host star, and hence may be susceptible to atmospheric stripping. Our sample is taken from the Habitable Exoplanet Catalogue, and consists of the stars Kepler-22, Kepler-61, Kepler-62, Kepler-174, Kepler-186, Kepler-283, Kepler-296, Kepler-298, Kepler-438, Kepler-440, Kepler-442, Kepler-443 and KOI-4427, between them hosting 15 of the most habitable transiting planets known to date from Kepler.

  1. Differential rotation as a model for starspots in magnetically active stars

    NASA Astrophysics Data System (ADS)

    Agostino, Christopher James; Basri, Gibor S.

    2017-01-01

    The Kepler mission has provided an opportunity to significantly expand our understanding of starspots. We have implemented a MCMC method to determine spot parameters of input light curves using a differential rotation spot model. We generated model light curves and explored parameter space in order to test the reliability of our method in retrieving input parameters and to investigate what constraints on spot parameters can be determined from photometric data. We also applied our method to light curves of magnetically active Kepler stars, using only a few spots. One interesting initial conclusion is that it is often possible to replicate complicated light curves over many rotation periods without the need for any spot evolution on stars with rotation periods less than 20 days. We have also begun investigating to what extent spot evolution is preferred as the alternative model for stellar variability. Of course, it is very likely that real stars exhibit both phenomena.

  2. Recovering planet radial velocity signals in the presence of starspot activity in fully convective stars

    NASA Astrophysics Data System (ADS)

    Barnes, J. R.; Jeffers, S. V.; Anglada-Escudé, G.; Haswell, C. A.; Jones, H. R. A.; Tuomi, M.; Feng, F.; Jenkins, J. S.; Petit, P.

    2017-04-01

    Accounting for stellar activity is a crucial component of the search for ever-smaller planets orbiting stars of all spectral types. We use Doppler imaging methods to demonstrate that starspot-induced radial velocity variability can be effectively reduced for moderately rotating, fully convective stars. Using starspot distributions extrapolated from sunspot observations, we adopt typical M dwarf starspot distributions with low contrast spots to synthesize line profile distortions. The distortions are recovered using maximum entropy regularized fitting and the corresponding stellar radial velocities are measured. The procedure is demonstrated that for a late-M star harbouring an orbiting planet in the habitable zone. The technique is effective for stars with v sin i = 1-10km s-1, reducing the stellar noise contribution by factors of nearly an order of magnitude. With a carefully chosen observing strategy, the technique can be used to determine the stellar rotation period and is robust to uncertainties such as unknown stellar inclination. While demonstrated for late-type M stars, the procedure is applicable to all spectral types.

  3. Antidotal activity of Averrhoa carambola (Star fruit) on fluoride induced toxicity in rats.

    PubMed

    Vasant, Rupal A; Narasimhacharya, A V R L

    2014-06-01

    Consumption of fluoride leads to several physiological disturbances in carbohydrate, lipid and antioxidant metabolisms. Averrhoa carambola L. fruit (Star fruit) is a commonly consumed fruit in tropical countries and is an ingredient in folklore medicines. As the fruits have high polyphenolic and antioxidant contents, the present study was undertaken to investigate the potential of star fruit as a dietary supplement in attenuating the fluoride induced hyperglycemia, hypercholesterolemia and oxidative stress in laboratory rats. A four-week exposure to fluoride caused sustained hyperglycemia, hyperlipidemia and oxidative stress and, when the diet was supplemented with star fruit powder, carbohydrate, lipid and antioxidant profiles were restored significantly. It is surmised that the antihyperglycemic, antihypercholesterolemic and antioxidant activities of star fruit in fluoride exposed rats could be due to the presence of polyphenols, flavonoids, saponins, phytosterols, ascorbic acid and fibers in the fruit, which are all well known regulators of carbohydrate, lipid and antioxidant metabolisms. These findings suggest that star fruit can be used as a dietary supplement in fluoride endemic regions to contain fluoride induced hyperglycemia, hyperlipidemia and oxidative stress.

  4. Antidotal activity of Averrhoa carambola (Star fruit) on fluoride induced toxicity in rats

    PubMed Central

    Vasant, Rupal A.

    2014-01-01

    Consumption of fluoride leads to several physiological disturbances in carbohydrate, lipid and antioxidant metabolisms. Averrhoa carambola L. fruit (Star fruit) is a commonly consumed fruit in tropical countries and is an ingredient in folklore medicines. As the fruits have high polyphenolic and antioxidant contents, the present study was undertaken to investigate the potential of star fruit as a dietary supplement in attenuating the fluoride induced hyperglycemia, hypercholesterolemia and oxidative stress in laboratory rats. A four-week exposure to fluoride caused sustained hyperglycemia, hyperlipidemia and oxidative stress and, when the diet was supplemented with star fruit powder, carbohydrate, lipid and antioxidant profiles were restored significantly. It is surmised that the antihyperglycemic, antihypercholesterolemic and antioxidant activities of star fruit in fluoride exposed rats could be due to the presence of polyphenols, flavonoids, saponins, phytosterols, ascorbic acid and fibers in the fruit, which are all well known regulators of carbohydrate, lipid and antioxidant metabolisms. These findings suggest that star fruit can be used as a dietary supplement in fluoride endemic regions to contain fluoride induced hyperglycemia, hyperlipidemia and oxidative stress. PMID:26109886

  5. Hyper X-ray Flares on Active Stars Detected with MAXI

    NASA Astrophysics Data System (ADS)

    Higa, Masaya; Tsuboi, Yohko; Negoro, Hitoshi; Nakahira, Satoshi; Tomida, Hiroshi; Matsuoka, Masaru; aff002

    2014-08-01

    MAXI started its operation in 2009 August. Owing to its unprecedentedly high sensitivity as an all-sky X-ray monitor and to its capability of real-time data transfer, we have detected 56 strong flares from twenty-one active stars (eleven RS CVn systems, one Algol system, seven dMe stars, one dKe star and one Young Stellar Object). These flares have large X-ray luminosity of 6 × 1030 -5 × 1033 ergs s-1 in the 2-20 keV band. The flares can be thought to be high ends among their own categories. During the flare from AT Mic on 2012 April 18th, one of the largest X-ray luminosities was recorded as a dMe star, 6 × 1032 ergs s-1 in the 2-20 keV band. It is larger than its bolometric luminosity by 4 times. The total energy emitted during the flare is 1036 ergs in the same band. Such total energy can be obtained on large flares from RS CVn system, but not on any other flares from dMe stars. In this proceeding, we report on the present situation in characteristics of hyper X-ray flares on each stellar categories.

  6. Multiwavelength study of the magnetically active T Tauri star HD 283447

    NASA Technical Reports Server (NTRS)

    Feigelson, Eric D.; Welty, Alan D.; Imhoff, Catherine; Hall, Jeffrey C.; Etzel, Paul B.; Phillips, Robert B.; Lonsdale, Colin J.

    1994-01-01

    We observed the luminous T Tauri star HD 283447 = V773 Tauri simultaneously at X-ray, ultraviolet, optical photometric and spectroscopic, and radio wavelengths for several hours on UT 1992 September 11. ROSAT, IUE, Very Large Array (VLA) and an intercontinental Very Long Baseline Interferometry (VLBI) network, and three optical observatories participated in the campaign. The star is known for its unusually high and variable nonthermal radio continuum emission. High levels of soft X-ray and Mg II line emission are discovered, with luminosity L(sub x) = 5.5 x 10(exp 30) ergs/s (0.2 - 2 keV) and L(sub Mg II) = 1 x 10(exp 29) ergs/s, respectively. Optically, the spectrum exhibits rather weak characteristics of `classical' T Tauri stars. A faint, broad emission line component, probably due to a collimated wind or infall, is present. During the campaign, the radio luminosity decreased by a factor of 4, while optical/UV lines and X-ray emission remained strong but constant. The large gyrosynchrotron-emitting regions are therefore decoupled from the chromospheric and coronal emission. Five models for the magnetic geometry around the star are discussed; solar-type activity, dipole magnetosphere, star-disk magnetic coupling, disk magnetic fields, and close binary interaction. The data suggest that two magnetic geometries are simultaneously present: complex multipolar fields like those on the Sun, and a large-scale field possibly associated with the circumstellar disk.

  7. Correlating The Star Formation Histories Of MaNGA Galaxies With Their Past AGN Activity

    NASA Astrophysics Data System (ADS)

    Gonzalez Ortiz, Andrea

    2017-01-01

    We investigate active galactic nuclei (AGN) as a primary mechanism affecting star formation in MaNGA galaxies. Using the Pipe3D code, we modeled the stellar population from MaNGA spectra and derived the star formation histories of 53 AGN host galaxies. We seek to compare the star formation histories of the host galaxies of AGN with the ages of their radio lobes to better understand the role of AGN feedback in the star formation histories of MaNGA galaxies. MaNGA (Mapping Nearby Galaxies at APO) is one of the three core programs in the fourth generation Sloan Digital Sky Survey(SDSS). MaNGA will investigate the internal kinematics of nearly 10,000 local galaxies through dithered observations using fiber integral field units (IFUs) that vary in diameter from 12" (19 fibers) to 32" (127 fibers). In this poster, we present initial results on the star formation histories of MaNGA AGN host galaxies. This work was supported by the SDSS Research Experience for Undergraduates program, which is funded by a grant from Sloan Foundation to the Astrophysical Research Consortium.

  8. Cosmic web and star formation activity in galaxies at z ∼ 1

    SciTech Connect

    Darvish, B.; Mobasher, B.; Sales, L. V.; Sobral, D.; Scoville, N. Z.; Best, P.; Smail, I.

    2014-11-20

    We investigate the role of the delineated cosmic web/filaments on star formation activity by exploring a sample of 425 narrow-band selected Hα emitters, as well as 2846 color-color selected underlying star-forming galaxies for a large-scale structure at z = 0.84 in the COSMOS field from the HiZELS survey. Using the scale-independent Multi-scale Morphology Filter algorithm, we are able to quantitatively describe the density field and disentangle it into its major components: fields, filaments, and clusters. We show that the observed median star formation rate (SFR), stellar mass, specific SFR, the mean SFR-mass relation, and its scatter for both Hα emitters and underlying star-forming galaxies do not strongly depend on different classes of environment, in agreement with previous studies. However, the fraction of Hα emitters varies with environment and is enhanced in filamentary structures at z ∼ 1. We propose mild galaxy-galaxy interactions as the possible physical agent for the elevation of the fraction of Hα star-forming galaxies in filaments. Our results show that filaments are the likely physical environments that are often classed as the 'intermediate' densities and that the cosmic web likely plays a major role in galaxy formation and evolution which has so far been poorly investigated.

  9. Spectral characterization and differential rotation study of active CoRoT stars

    NASA Astrophysics Data System (ADS)

    Nagel, E.; Czesla, S.; Schmitt, J. H. M. M.

    2016-05-01

    The CoRoT space telescope observed nearly 160 000 light curves. Among the most outstanding is that of the young, active planet host star CoRoT-2A. In addition to deep planetary transits, the light curve of CoRoT-2A shows strong rotational variability and a superimposed beating pattern. To study the stars that produce such an intriguing pattern of photometric variability, we identified a sample of eight stars with rotation periods between 0.8 and 11 days and photometric variability amplitudes of up to 7.5%, showing a similar CoRoT light curve. We also obtained high-resolution follow-up spectroscopy with TNG/SARG and carried out a spectral analysis with SME and MOOG. We find that the color dependence of the light curves is consistent with rotational modulation due to starspots and that latitudinal differential rotation provides a viable explanation for the light curves, although starspot evolution is also expected to play an important role. Our MOOG and SME spectral analyses provide consistent results, showing that the targets are dwarf stars with spectral types between F and mid-K. Detectable Li i absorption in four of the targets confirms a low age of 100-400 Myr also deduced from gyrochronology. Our study indicates that the photometric beating phenomenon is likely attributable to differential rotation in fast-rotating stars with outer convection zones.

  10. A maximum entropy approach to detect close-in giant planets around active stars

    NASA Astrophysics Data System (ADS)

    Petit, P.; Donati, J.-F.; Hébrard, E.; Morin, J.; Folsom, C. P.; Böhm, T.; Boisse, I.; Borgniet, S.; Bouvier, J.; Delfosse, X.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Barnes, J. R.

    2015-12-01

    Context. The high spot coverage of young active stars is responsible for distortions of spectral lines that hamper the detection of close-in planets through radial velocity methods. Aims: We aim to progress towards more efficient exoplanet detection around active stars by optimizing the use of Doppler imaging in radial velocity measurements. Methods: We propose a simple method to simultaneously extract a brightness map and a set of orbital parameters through a tomographic inversion technique derived from classical Doppler mapping. Based on the maximum entropy principle, the underlying idea is to determine the set of orbital parameters that minimizes the information content of the resulting Doppler map. We carry out a set of numerical simulations to perform a preliminary assessment of the robustness of our method, using an actual Doppler map of the very active star HR 1099 to produce a realistic synthetic data set for various sets of orbital parameters of a single planet in a circular orbit. Results: Using a simulated time series of 50 line profiles affected by a peak-to-peak activity jitter of 2.5 km s-1, in most cases we are able to recover the radial velocity amplitude, orbital phase, and orbital period of an artificial planet down to a radial velocity semi-amplitude of the order of the radial velocity scatter due to the photon noise alone (about 50 m s-1 in our case). One noticeable exception occurs when the planetary orbit is close to co-rotation, in which case significant biases are observed in the reconstructed radial velocity amplitude, while the orbital period and phase remain robustly recovered. Conclusions: The present method constitutes a very simple way to extract orbital parameters from heavily distorted line profiles of active stars, when more classical radial velocity detection methods generally fail. It is easily adaptable to most existing Doppler imaging codes, paving the way towards a systematic search for close-in planets orbiting young, rapidly

  11. Spatio-temporal activity in real time (STAR): Optimization of regional fMRI feedback

    PubMed Central

    Magland, Jeremy F.; Tjoa, Christopher W.; Childress, Anna Rose

    2011-01-01

    The use of real-time feedback has expanded fMRI from a brain probe to include potential brain interventions with significant therapeutic promise. However, whereas time-averaged blood oxygenation level-dependent (BOLD) signal measurement is usually sufficient for probing a brain state, the real-time (frame-to-frame) BOLD signal is noisy, compromising feedback accuracy. We have developed a new real-time processing technique (STAR) that combines noise-reduction properties of multi-voxel (e.g., whole-brain) techniques with the regional specificity critical for therapeutics. Nineteen subjects were given real-time feedback in a cognitive control task (imagining repetitive motor activity vs. spatial navigation), and were all able to control a visual feedback cursor based on whole-brain neural activity. The STAR technique was evaluated, retrospectively, for five a priori regions of interest in these data, and was shown to provide significantly better (frame-by-frame) classification accuracy than a regional BOLD technique. In addition to regional feedback signals, the output of the STAR technique includes spatio-temporal activity maps (movies) providing insight into brain dynamics. The STAR approach offers an appealing optimization for real-time fMRI applications requiring an anatomically-localized feedback signal. PMID:21232612

  12. Long-term Optical Activity of the Hard X-ray Flaring Star DG CVn

    NASA Astrophysics Data System (ADS)

    Šimon, V.

    2017-04-01

    DG CVn is a young late-type star which displayed an X-ray and optical superflare in 2014. This paper presents an analysis of the long-term activity of this object in the optical band. I used the photographic data from DASCH (Digital Access to a Sky Century @ Harvard). These measurements from the years 1895-1989 cover the blue spectral region. CCD V-band ASAS data were used for several UV Cet-type stars to place the activity of DG CVn in the context of flaring stars. I show that three large brightenings (flares) of DG CVn by more than 1 mag were detected on the DASCH plates. The character of the long-term activity (regarding the histogram of brightness) of DG CVn is compatible with those of flaring stars UV Cet and V371 Ori. The flares brighter than ˜ 0.4 mag represent less than 1 percent of the observed data in all three objects

  13. Activity and age from Kepler and K2 observations of field and cluster stars

    NASA Astrophysics Data System (ADS)

    Soderblom, David R.

    2017-01-01

    Kepler and K2 are providing key insights into activity-related phenomena on late-type stars. Kepler observations showed that highly energetic flares can be seen on many more types of stars than the M dwarfs that have been the traditional focus of flare studies. Some stars similar to the Sun have been seen to exhibit flares with $\\sim10^4$ times the energy of the largest solar flares ever seen, for example. The K2 extension of Kepler has been especially valuable by providing data for several open clusters, including the Pleiades, Praesepe, Hyades, and M67.In this review I will summarize the flaring behavior seen with Kepler and K2, from A stars through Ms and from the pre-main sequence to solar age. The Pleiades and M67 provide useful examples to illustrate what is seen and not seen.Other aspects of Kepler and K2 light curves have been studied as indicators of activity, and some results from that will be presented. Finally, these indicators of activity will be placed into an age context using indicators and measurements of age from Kepler/K2.

  14. A Study of EUV Emission in Active Be Stars in the Canis Major Interstellar Tunnel

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine J.

    Spectroscopic observations are proposed of three active Be stars and one comparison object that are located in the Canis Major tunnel of low interstellar gas density to search for the presence of a 10^5-10^7 K plasma that contemporary theories of disk formation or flare/episodic/ pulsational activity predict. The program stars include kappa CMa (B2IVe, in which flare-type activity has been observed), omega CMa (B2.5Ve, an apparent nonradial pulsator), alpha Col (B7IVe, which has an unusually large C IV absorption for its spectral type), and zeta CMa (B2.5V, a non-emission line B star to be used for comparison). The Be stars are all viewed at low-moderate inclinations to our line-of-sight so that EUV absorption in the wind should be minimized. The strengths of the emission lines He II 304 and 256 and numerous Fe lines in the SW region will be compared with those already observed in epsilon CMa (B2II) and beta CMa (B1II, a beta Cephei radial pulsator) with EUVE. The temperature of the plasma will be determined from the ionization state of the emission lines and the size/location of the emitting region estimated from the widths of these features and any observed modulation with phase in the optical light curve.

  15. NuSTAR X-ray observations of small flares and non-flaring active regions

    NASA Astrophysics Data System (ADS)

    Hannah, I. G.; Grefenstette, B.; Smith, D. M.; Marsh, A.; Glesener, L.; Krucker, S.; Hudson, H. S.; White, S.; Madsen, K.; Caspi, A.; Vogel, J.; Shih, A.

    2015-12-01

    We present imaging spectroscopy of the Sun with the NuSTAR hard X-ray (HXR) telescope, an astrophysics mission that uses focusing optics to directly image X-rays between ~2-80 keV. Although not optimized for solar observations, NuSTAR's high sensitivity can probe previously inaccessible X-ray emission from the Sun - crucial for searching for high temperature and non-thermal emission from "non-flaring" active regions. We present analysis of the first NuSTAR solar observations, that began in late 2014 and continued through 2015. These include using its imaging spectroscopy capabilities to derive the thermal characteristics of several "non-flaring" active regions, providing limits to the high temperature emission. We also show NuSTAR observations of several small microflares that were also observed by Hinode/XRT (in multiple thicker filters sensitive to higher temperatures) and RHESSI. This combination of three separate X-ray telescopes provides a broad observational characterization of active region heating by these very small microflares.

  16. Photometric activity of the Herbig Be star MWC 297 over 25 years

    NASA Astrophysics Data System (ADS)

    Barsunova, O. Yu.; Mel'nikov, S. Yu.; Grinin, V. P.; Katysheva, N. A.; Shugarov, S. Yu.

    2013-02-01

    The photometric behavior of the hot, young Herbig Be starMWC 297 on various time scales is studied using published data, as well as new observations. The series of photometric observations covers about 25 years. Over this time, the star showed low-amplitude (Δ V ≈ 0.3 m ) irregular variabilitymodulated by large-scale cyclic variabilitywith an amplitude close to 0.2 m and a period (or quasi-period) of 5.4±0.1 yr. A detailed seasonal analysis of the data shows that the light curve of MWC 297 displays two types of photometric features: low-amplitude Algol-like fading with an amplitude close to 0.2 m and low-amplitude flares resembling the flares of UV Ceti stars, but being more powerful and having longer durations. The variations of the stellar brightness are accompanied by variations of the B- V and V - R colors: when the brightness decreases, B- V decreases, while V - R increases (the star reddens). The reddening law is close to the standard interstellar reddening law. Although the character of the brightness variability ofMWC 297 resembles the photometric activity of UX Ori type stars, which is due to variations of their circumstellar extinction, its scale is very far from the scales observed for UX Ori stars. It is difficult to reconcile the level of photometric activity with the idea that MWC 297 is observed through its own gas-dust disk viewed almost edge-on, as has been suggested in several studies.

  17. Photometric and Polarimetric Activity of the Herbig Ae Star VX Cas

    NASA Astrophysics Data System (ADS)

    Shakhovskoi, D. N.; Rostopchina, A. N.; Grinin, V. P.; Minikulov, N. Kh.

    2003-04-01

    We present the results of our simultaneous photometric and polarimetric observations of the Herbig Ae/Be star VX Cas acquired in 1987 2001. The star belongs to the UX Ori subtype of young variable stars and exhibits a rather low level of photometric activity: only six Algol-like minima with amplitudes ΔV>1m were recorded in 15 years of observations. Two of these minima, in 1998 and 2001, were the deepest in the history of the star’s photometric studies, with V amplitudes of about 2m. In each case, the dimming was accompanied by an increase in the linear polarization in agreement with the law expected for variable circumstellar extinction. The highest V polarization was about 5%. Observations of VX Cas in the deep minima revealed a turnover of the color tracks, typical of stars of this type and due to an increased contribution from radiation scattered in the circumstellar disk. We separated the observed polarization of VX Cas into interstellar (P is) and intrinsic (P in) components. Their position angles differ by approximately 60°, with P is dominating in the bright state and P in dominating during the deep minima. The competition of these two polarization components leads to changes in both the degree and position angle of the polarization during the star’s brightness variations. Generally speaking, in terms of the behavior of the brightness, color indices, and linear polarization, VX Cas is similar to other UX Ori stars studied by us earlier. A number of episodes of photometric and polarimetric activity suggest that, in their motion along highly eccentric orbits, circumstellar gas and dust clouds can enter the close vicinity of the star (and be disrupted there).

  18. New insight into the relation between star formation activity and dust content in galaxies

    NASA Astrophysics Data System (ADS)

    da Cunha, Elisabete; Eminian, Celine; Charlot, Stéphane; Blaizot, Jérémy

    2010-04-01

    We assemble a sample of 3258 low-redshift galaxies from the Sloan Digital Sky Survey Data Release 6 with complementary photometric observations by the Galaxy Evolution Explorer, the Two Micron All Sky Survey and the Infrared Astronomical Satellite at far-ultraviolet and infrared wavelengths. We use a recent, simple but physically motivated model to interpret the observed spectral energy distributions of the galaxies in this sample in terms of statistical constraints on physical parameters describing the star formation history and dust content. The focus on a subsample of 1658 galaxies with highest signal-to-noise ratio observations enables us to investigate most clearly several strong correlations between various derived physical properties of galaxies. In particular, we find that the typical dust mass Md of a galaxy forming stars at a rate ψ can be estimated remarkably well using the formula over at least three orders of magnitude in both quantities. We also find that the dust-to-stellar mass ratio, the ratio of dust mass to star formation rate and the fraction of dust luminosity contributed by the diffuse interstellar medium (ISM) all correlate strongly with specific star formation rate. A comparison with recent models of chemical and dust evolution of galaxies suggests that these correlations could arise, at least in part, from an evolutionary sequence. As galaxies form stars, their ISM becomes enriched in dust, while the drop in gas supply makes the specific star formation rate decrease. Interestingly, as a result, a young, actively star-forming galaxy with low dust-to-gas ratio may still be highly dusty (in the sense of a high dust-to-stellar mass ratio) because it contains large amounts of interstellar gas. This may be important for the interpretation of the infrared emission from young, gas-rich star-forming galaxies at high redshift. The results presented in this paper should be especially useful to improve the treatment of the ISM properties of galaxies

  19. Examining How Activity Shapes Students' Interactions While Creating Representations in Early Elementary Science

    ERIC Educational Resources Information Center

    Danish, Joshua Adam; Saleh, Asmalina

    2014-01-01

    It is common practice in elementary science classrooms to have students create representations, such as drawings, as a way of exploring new content. While numerous studies suggest the benefits of representation in science, the majority focus on specific, canonical representations, such as graphs. Few offer insight or guidance regarding how…

  20. Hα-activity and ages for stars in the SARG survey

    NASA Astrophysics Data System (ADS)

    Sissa, E.; Gratton, R.; Desidera, S.; Martinez Fiorenzano, A. F.; Bonfanti, A.; Carolo, E.; Vassallo, D.; Claudi, R. U.; Endl, M.; Cosentino, R.

    2016-12-01

    Stellar activity influences radial velocity (RV) measurements and can also mimic the presence of orbiting planets. As part of the search for planets around the components of wide binaries performed with the SARG High Resolution Spectrograph at the TNG, it was discovered that HD 200466A shows strong variation in RV that is well correlated with the activity index based on Hα. We used SARG to study the Hα line variations in each component of the binaries and a few bright stars to test the capability of the Hα index of revealing the rotation period or activity cycle. We also analysed the relations between the average activity level and other physical properties of the stars. We finally tried to reveal signals in the RVs that are due to the activity. At least in some cases the variation in the observed RVs is due to the stellar activity. We confirm that Hα can be used as an activity indicator for solar-type stars and as an age indicator for stars younger than 1.5 Gyr. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.A table of the individual Hα measurements is 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/596/A76

  1. A SPITZER CENSUS OF STAR FORMATION ACTIVITY IN THE PIPE NEBULA

    SciTech Connect

    Forbrich, Jan; Lada, Charles J.; Muench, August A.; Alves, Joao

    2009-10-10

    The Pipe Nebula, a large nearby molecular cloud, lacks obvious signposts of star formation in all but one of more than 130 dust extinction cores that have been identified within it. In order to quantitatively determine the current level of star formation activity in the Pipe Nebula, we analyzed 13 deg{sup 2} of sensitive mid-infrared maps of the entire cloud, obtained with the Multiband Imaging Photometer for Spitzer at wavelengths of 24 mum and 70 mum, to search for candidate young stellar objects (YSOs) in the high-extinction regions. We argue that our search is complete for class I and typical class II YSOs with luminosities of L {sub bol} approx 0.2 L {sub sun} and greater. We find only 18 candidate YSOs in the high-extinction regions of the entire Pipe cloud. Twelve of these sources are previously known members of a small cluster associated with Barnard 59, the largest and most massive dense core in the cloud. With only six candidate class I and class II YSOs detected toward extinction cores outside of this cluster, our findings emphatically confirm the notion of an extremely low level of star formation activity in the Pipe Nebula. The resulting star formation efficiency for the entire cloud mass is only approx0.06%.

  2. Forecasting life: a study of activity cycles in low-mass stars: lessons from long-term stellar light curves.

    PubMed

    Kafka, Stella

    2012-06-01

    Magnetic activity cycles are indirect traces of magnetic fields and can provide an insight on the nature and action of stellar dynamos and stellar magnetic activity. This, in turn, can determine local space weather and activity effects on stellar habitable zones. Using photometric monitoring of low-mass stars, we study the presence and properties of their magnetic activity cycles. We introduce long-term light curves of our sample stars, and discuss the properties of the observed trends, especially at spectral types where stars are fully convective (later than M3).

  3. Monitoring the Stellar Activity of Transit-Hosting Stars II: supporting HST exoplanet atmosphere observations

    NASA Astrophysics Data System (ADS)

    Wilson, Paul Anthony; Evans, Tom; Sing, David K.; Aigrain, Suzanne

    2012-02-01

    We propose to use the CTIO 1.3m telescope with ANDICAM to monitor 5 bright stars that host transiting exoplanets in an effort to characterise their activity. These observations will provide critical ground-based support for our large HST program that has been granted 124 orbits to perform a survey of UV-optical atmospheric transmission spectra for 8 hot Jupiters using the STIS instrument (Cycle 19, Prog 12473, PI D Sing). They are required because active stellar regions inevitably contaminate measured planetary light curves by causing the apparent planet-to-star radius to vary in a wavelength dependent manner. Regular ground-based photometric monitoring performed using the CTIO 1.3m telescope will allow us to determine the spot activity at the time of the HST observations, so that the stellar baseline flux can be accurately normalised for every transit observed, enabling transmission spectra from multiple visits to be combined.

  4. No Sun-like dynamo on the active star ζ Andromedae from starspot asymmetry.

    PubMed

    Roettenbacher, R M; Monnier, J D; Korhonen, H; Aarnio, A N; Baron, F; Che, X; Harmon, R O; Kővári, Zs; Kraus, S; Schaefer, G H; Torres, G; Zhao, M; ten Brummelaar, T A; Sturmann, J; Sturmann, L

    2016-05-12

    Sunspots are cool areas caused by strong surface magnetic fields that inhibit convection. Moreover, strong magnetic fields can alter the average atmospheric structure, degrading our ability to measure stellar masses and ages. Stars that are more active than the Sun have more and stronger dark spots than does the Sun, including on the rotational pole. Doppler imaging, which has so far produced the most detailed images of surface structures on other stars, cannot always distinguish the hemisphere in which the starspots are located, especially in the equatorial region and if the data quality is not optimal. This leads to problems in investigating the north-south distribution of starspot active latitudes (those latitudes with more starspot activity); this distribution is a crucial constraint of dynamo theory. Polar spots, whose existence is inferred from Doppler tomography, could plausibly be observational artefacts. Here we report imaging of the old, magnetically active star ζ Andromedae using long-baseline infrared interferometry. In our data, a dark polar spot is seen in each of two observation epochs, whereas lower-latitude spot structures in both hemispheres do not persist between observations, revealing global starspot asymmetries. The north-south symmetry of active latitudes observed on the Sun is absent on ζ And, which hosts global spot patterns that cannot be produced by solar-type dynamos.

  5. No Sun-like dynamo on the active star ζ Andromedae from starspot asymmetry

    NASA Astrophysics Data System (ADS)

    Roettenbacher, R. M.; Monnier, J. D.; Korhonen, H.; Aarnio, A. N.; Baron, F.; Che, X.; Harmon, R. O.; Kővári, Zs.; Kraus, S.; Schaefer, G. H.; Torres, G.; Zhao, M.; Ten Brummelaar, T. A.; Sturmann, J.; Sturmann, L.

    2016-05-01

    Sunspots are cool areas caused by strong surface magnetic fields that inhibit convection. Moreover, strong magnetic fields can alter the average atmospheric structure, degrading our ability to measure stellar masses and ages. Stars that are more active than the Sun have more and stronger dark spots than does the Sun, including on the rotational pole. Doppler imaging, which has so far produced the most detailed images of surface structures on other stars, cannot always distinguish the hemisphere in which the starspots are located, especially in the equatorial region and if the data quality is not optimal. This leads to problems in investigating the north-south distribution of starspot active latitudes (those latitudes with more starspot activity); this distribution is a crucial constraint of dynamo theory. Polar spots, whose existence is inferred from Doppler tomography, could plausibly be observational artefacts. Here we report imaging of the old, magnetically active star ζ Andromedae using long-baseline infrared interferometry. In our data, a dark polar spot is seen in each of two observation epochs, whereas lower-latitude spot structures in both hemispheres do not persist between observations, revealing global starspot asymmetries. The north-south symmetry of active latitudes observed on the Sun is absent on ζ And, which hosts global spot patterns that cannot be produced by solar-type dynamos.

  6. MID-INFRARED SPECTRAL INDICATORS OF STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN NORMAL GALAXIES

    SciTech Connect

    Treyer, Marie; Martin, Christopher D.; Wyder, Ted; Schiminovich, David; O'Dowd, Matt; Johnson, Benjamin D.; Charlot, Stephane; Heckman, Timothy; Martins, Lucimara; Seibert, Mark; Van der Hulst, J. M.

    2010-08-20

    We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 'normal' and local (z {approx} 0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph as part of the Spitzer-SDSS-GALEX Spectroscopic Survey, which includes multi-wavelength photometry from the ultraviolet to the far-infrared and optical spectroscopy. The continuum and features were extracted using PAHFIT, a decomposition code which we find to yield PAH equivalent widths (EWs) up to {approx}30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low-metallicity galaxies, or ULIRGs), we find significant variations in PAH, continuum, and emission-line properties, and systematic trends between these MIR properties and optically derived physical properties, such as age, metallicity, and radiation field hardness. We revisit the diagnostic diagram relating PAH EWs and [Ne II]12.8 {mu}m/[O IV]25.9 {mu}m line ratios and find it to be in much better agreement with the standard optical SF/AGN classification than when spline decompositions are used, while also potentially revealing obscured AGNs. The luminosity of individual PAH components, of the continuum, and, with poorer statistics, of the neon emission lines and molecular hydrogen lines are found to be tightly correlated to the total infrared (TIR) luminosity, making individual MIR components good gauges of the total dust emission in SF galaxies. Like the TIR luminosity, these individual components can be used to estimate dust attenuation in the UV and in H{alpha} lines based on energy balance arguments. We also propose average scaling relations between these components and dust-corrected, H{alpha}-derived SF rates.

  7. Disentangling Dominance: Obscured AGN Activity versus Star Formation in BPT-Composites

    NASA Astrophysics Data System (ADS)

    Trouille, Laura

    2011-11-01

    Approximately 20% of SDSS emission-line galaxies (ELG) lie in the BPT-comp regime, between the Kauffmann et al. (2003) empirically determined SF-dominated regime and the Kewley et al. (2001) theoretically predicted AGN-dominated regime. BPT-AGN, on the other hand, make up only 11% of the ELG population. Whether to include the significant number of BPT-comp in samples of AGN or samples of star-forming galaxies is an open question and has important implications for galaxy evolution studies, metallicity studies, etc. Using a large pectroscopic sample of GOODS-N and LH galaxies with deep Chandra imaging, we perform an X-ray stacking analysis of BPT-comp. We find the stacked signal to be X-ray hard. This X-ray hardness can be indicative of obscured AGN activity or the presence of HMXBs associated with ongoing star formation. In order to distinguish between these scenarios, we perform an IR stacking analysis using Spitzer 24 micron data. The stacked BPT-comp lies well above the expected value for L_x/L_IR for pure star-forming galaxies; similarly for the X-ray detected BPT-comp. We also find that the BPT-comp lie in the AGN-dominated regime of our new TBT diagnostic, which uses [NeIII]/[OII] versus rest-frame g-z colour to identify AGN and star forming galaxies out to z=1.4. [NeIII], which has a higher ionisation potential than other commonly used forbidden emission lines, appears to foster a more reliable selection of AGN-dominated galaxies. These findings suggest that both the X-ray and optical signal in BPT-comp are dominated by obscured or low accretion rate AGN activity rather than star formation. This is in contrast to claims by previous optical emission-line studies that the signal in BPT-comp is dominated by star-formation activity. Therefore, we recommend that groups carefully consider the impact of excluding or including BPT-comp on the interpretation of their results. For example, for studies involving determining the bolometric contribution from AGN activity

  8. Recent unusual activity in the Be star FY Canis Majoris

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine J.

    1988-08-01

    Unusual activity observed in the circumstelar envelope of FY CMa during April-May, 1987 is reported. Nightly CCD observations from April 16-20 revealed an invariant H-alpha emission feature and a simple absorption profile for He I 6678 with very weak double emission components. Similar observations on May 2, however, showed that the V lobe of the H-alpha feature had increased in strength by 30 percent and that the He I line had developed into a structured inverse P Cygni profile.

  9. Feedback in the local Universe: Relation between star formation and AGN activity in early type galaxies

    NASA Astrophysics Data System (ADS)

    Vaddi, Sravani; O'Dea, Christopher; Baum, Stefi; Jones, Christine; Forman, William; Whitmore, Samantha; Ahmed, Rabeea; Pierce, Katherine; Leary, Sara

    2015-08-01

    Aim: We address the relation between star formation and AGN activity in a large sample of nearby early type (E and S0) galaxies. The redshift range of the galaxies is 0.0002star formation and thus the process of galaxy evolution and formation. Evidence of AGN feedback is found in massive galaxies in galaxy clusters. However, how common AGN feedback is in the local universe and in small scale systems is still not evident.Methods: To answer this question, we carried out a multiple wavelength study of a sample of 231 early type galaxies which were selected to have an apparent K-band magnitude brighter than 13.5 and whose positions correlate with Chandra ACIS-I and ACIS-S sources. The galaxies in the sample are unbiased regarding their star formation and radio source properties. Using the archival observations at radio, IR and UV from VLA, WISE and GALEX respectively, we obtained the radio power, estimate FUV star formation rate (SFR) and other galaxy properties to study AGN activity and ongoing star formation.Results: The relationship between radio power and stellar mass shows that there is an upper envelope of radio power that is a steep function of stellar luminosity. This suggests that less massive galaxies have low radio power while massive galaxies are capable of hosting powerful radio sources. The Radio-MIR relation shows that galaxies with P>=1022 WHz-1 are potential candidates for being AGN. About ~ 7% of the sample show evidence of ongoing star formation with SFR ranging from 10-3 to 1 M⊙yr-1. These are also less massive and radio faint suggesting the absence of active accretion. There is nearly equal fraction of star forming galaxies in radio faint (P<1022 WHz-1) and radio bright galaxies (P>=1022 WHz-1) . Only ~ 5% of the galaxies in our sample have P>=1022 WHz-1 and most of them do not show evidence of bright accretion disks. We see a weak correlation and a dispersion of

  10. Star-formation Activity in the Neighborhood of W-R 1503-160L Star in the Mid-infrared Bubble N46

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Baug, T.; Ojha, D. K.; Janardhan, P.; Ninan, J. P.; Luna, A.; Zinchenko, I.

    2016-07-01

    In order to investigate star-formation (SF) processes in extreme environments, we have carried out a multi-wavelength analysis of the mid-infrared bubble N46, which hosts a WN7 Wolf-Rayet (W-R) star. We have used 13CO line data to trace an expanding shell surrounding the W-R star containing about five condensations within the molecular cloud associated with the bubble. The W-R star is associated with a powerful stellar wind having a mechanical luminosity of ˜4 × 1037 erg s-1. A deviation of the H-band starlight mean polarization angles around the bubble has also been traced, indicating the impact of stellar wind on the surroundings. The Herschel temperature map shows a temperature range of ˜18-24 K toward the five molecular condensations. The photometric analysis reveals that these condensations are associated with the identified clusters of young stellar objects, revealing ongoing SF process. The densest among these five condensations (peak N(H2) ˜9.2 × 1022 cm-2 and A V ˜ 98 mag) is associated with a 6.7 GHz methanol maser, an infrared dark cloud, and the CO outflow, tracing active massive SF within it. At least five compact radio sources (CRSs) are physically linked with the edges of the bubble, and each of them is consistent with the radio spectral class of a B0V-B0.5V-type star. The ages of the individual infrared counterparts of three CRSs (˜1-2 Myr) and a typical age of WN7 W-R star (˜4 Myr) indicate that the SF activities around the bubble are influenced by the feedback of the W-R star.

  11. Heliophysics: Active Stars, their Astrospheres, and Impacts on Planetary Environments

    NASA Astrophysics Data System (ADS)

    Schrijver, C. J.; Bagenal, F.; Sojka, J. J.

    2016-04-01

    Preface; 1. Introduction Carolus J. Schrijver, Frances Bagenal and Jan J. Sojka; 2. Solar explosive activity throughout the evolution of the Solar System Rachel Osten; 3. Astrospheres, stellar winds, and the interstellar medium Brian Wood and Jeffrey L. Linsky; 4. Effects of stellar eruptions throughout astrospheres Ofer Cohen; 5. Characteristics of planetary systems Debra Fischer and Ji Wang; 6. Planetary dynamos: updates and new frontiers Sabine Stanley; 7. Climates of terrestrial planets David Brain; 8. Upper atmospheres of the giant planets Luke Moore, Tom Stallard and Marina Garland; 9. Aeronomy of terrestrial upper atmospheres David E. Siskind and Stephen W. Bougher; 10. Moons, asteroids, and comets interacting with their surroundings Margaret G. Kivelson; 11. Dusty plasmas Mihály Horányi; 12. Energetic-particle environments in the Solar System Norbert Krupp; 13. Heliophysics with radio scintillation and occultation Mario M. Bisi; Appendix 1. Authors and editors; List of illustrations; List of tables; References; Index.

  12. CoRoT-2a Magnetic Activity: Hints for Possible Star-Planet Interaction

    NASA Astrophysics Data System (ADS)

    Pagano, Isabella; Lanza, Antonino F.; Leto, Giuseppe; Messina, Sergio; Barge, Pierre; Baglin, Annie

    2009-09-01

    CoRoT-2a is a young (≈0.5 Gyr) G7V star accompanied by a transiting hot-Jupiter, discovered by the CoRoT satellite (Alonso et al. Astron Astrophys 482:L21, 2008; Bouchy et al. Astron Astrophys 482:L25, 2008). An analysis of its photospheric activity, based on spot modelling techniques previously developed by our group for the analysis of the Sun as a star, shows that the active regions on CoRoT-2a arised within two active longitudes separated by about 180° and rotating with periods of 4.5221 and 4.5543 days, respectively, at epoch of CoRoT observations (112 continous days centered at ≈2007.6). We show that the total spotted area oscillates with a period of about 28.9 days, a value close to 10 times the synodic period of the planet with respect to the active longitude pattern rotating in 4.5221 days. Moreover, the variance of the stellar flux is modulated in phase with the planet orbital period. This suggests a possible star-planet magnetic interaction, a phenomenon already seen in other extrasolar planetary systems hosting hot-Jupiters.

  13. No Evidence for Activity Correlations in the Radial Velocities of Kapteyn’s Star

    NASA Astrophysics Data System (ADS)

    Anglada-Escudé, G.; Tuomi, M.; Arriagada, P.; Zechmeister, M.; Jenkins, J. S.; Ofir, A.; Dreizler, S.; Gerlach, E.; Marvin, C. J.; Reiners, A.; Jeffers, S. V.; Butler, R. Paul; Vogt, S. S.; Amado, P. J.; Rodríguez-López, C.; Berdiñas, Z. M.; Morin, J.; Crane, J. D.; Shectman, S. A.; Díaz, M. R.; Sarmiento, L. F.; Jones, H. R. A.

    2016-10-01

    Stellar activity may induce Doppler variability at the level of a few m s-1 which can then be confused by the Doppler signal of an exoplanet orbiting the star. To first order, linear correlations between radial velocity measurements and activity indices have been proposed to account for any such correlation. The likely presence of two super-Earths orbiting Kapteyn’s star was reported in Anglada-Escudé et al., but this claim was recently challenged by Robertson et al., who argued for evidence of a rotation period (143 days) at three times the orbital period of one of the proposed planets (Kapteyn’s b, P = 48.6 days) and the existence of strong linear correlations between its Doppler signal and activity data. By re-analyzing the data using global statistics and model comparison, we show that such a claim is incorrect given that (1) the choice of a rotation period at 143 days is unjustified, and (2) the presence of linear correlations is not supported by the data. We conclude that the radial velocity signals of Kapteyn’s star remain more simply explained by the presence of two super-Earth candidates orbiting it. We note that analysis of time series of activity indices must be executed with the same care as Doppler time series. We also advocate for the use of global optimization procedures and objective arguments, instead of claims based on residual analyses which are prone to biases and incorrect interpretations.

  14. EUV-driven ionospheres and electron transport on extrasolar giant planets orbiting active stars

    NASA Astrophysics Data System (ADS)

    Chadney, J. M.; Galand, M.; Koskinen, T. T.; Miller, S.; Sanz-Forcada, J.; Unruh, Y. C.; Yelle, R. V.

    2016-03-01

    The composition and structure of the upper atmospheres of extrasolar giant planets (EGPs) are affected by the high-energy spectrum of their host stars from soft X-rays to the extreme ultraviolet (EUV). This emission depends on the activity level of the star, which is primarily determined by its age. In this study, we focus upon EGPs orbiting K- and M-dwarf stars of different ages - ɛ Eridani, AD Leonis, AU Microscopii - and the Sun. X-ray and EUV (XUV) spectra for these stars are constructed using a coronal model. These spectra are used to drive both a thermospheric model and an ionospheric model, providing densities of neutral and ion species. Ionisation - as a result of stellar radiation deposition - is included through photo-ionisation and electron-impact processes. The former is calculated by solving the Lambert-Beer law, while the latter is calculated from a supra-thermal electron transport model. We find that EGP ionospheres at all orbital distances considered (0.1-1 AU) and around all stars selected are dominated by the long-lived H+ ion. In addition, planets with upper atmospheres where H2 is not substantially dissociated (at large orbital distances) have a layer in which H3+ is the major ion at the base of the ionosphere. For fast-rotating planets, densities of short-lived H3+ undergo significant diurnal variations, with the maximum value being driven by the stellar X-ray flux. In contrast, densities of longer-lived H+ show very little day/night variability and the magnitude is driven by the level of stellar EUV flux. The H3+ peak in EGPs with upper atmospheres where H2 is dissociated (orbiting close to their star) under strong stellar illumination is pushed to altitudes below the homopause, where this ion is likely to be destroyed through reactions with heavy species (e.g. hydrocarbons, water). The inclusion of secondary ionisation processes produces significantly enhanced ion and electron densities at altitudes below the main EUV ionisation peak, as

  15. Navigating the Active Learning Swamp: Creating an Inviting Environment for Learning.

    ERIC Educational Resources Information Center

    Johnson, Marie C.; Malinowski, Jon C.

    2001-01-01

    Reports on a survey of faculty members (n=29) asking them to define active learning, to rate how effectively different teaching techniques contribute to active learning, and to list the three teaching techniques they use most frequently. Concludes that active learning requires establishing an environment rather than employing a specific teaching…

  16. Active Learning: Creating Excitement in the Classroom. 1991 ASHE-ERIC Higher Education Reports.

    ERIC Educational Resources Information Center

    Bonwell, Charles C.; Eison, James A.

    This monograph examines the nature of active learning at the higher education level, the empirical research on its use, the common obstacles and barriers that give rise to faculty resistance, and how faculty and staff can implement active learning techniques. A preliminary section defines active learning and looks at the current climate…

  17. Creating the Learning Activities Package. Instructional Improvement Through In-Service.

    ERIC Educational Resources Information Center

    Jobe, Holly; And Others

    This paper describes an in-service course for the design, development, and evaluation of mediated learning activities. Each Learning Activities Package (LAP) has six basic components: concept, rationale, objectives, preassessment, activities, and evaluation. Each of these components is outlined, with emphasis placed on writing objectives…

  18. CONNECTING FLARES AND TRANSIENT MASS-LOSS EVENTS IN MAGNETICALLY ACTIVE STARS

    SciTech Connect

    Osten, Rachel A.; Wolk, Scott J.

    2015-08-10

    We explore the ramification of associating the energetics of extreme magnetic reconnection events with transient mass-loss in a stellar analogy with solar eruptive events. We establish energy partitions relative to the total bolometric radiated flare energy for different observed components of stellar flares and show that there is rough agreement for these values with solar flares. We apply an equipartition between the bolometric radiated flare energy and kinetic energy in an accompanying mass ejection, seen in solar eruptive events and expected from reconnection. This allows an integrated flare rate in a particular waveband to be used to estimate the amount of associated transient mass-loss. This approach is supported by a good correspondence between observational flare signatures on high flaring rate stars and the Sun, which suggests a common physical origin. If the frequent and extreme flares that young solar-like stars and low-mass stars experience are accompanied by transient mass-loss in the form of coronal mass ejections, then the cumulative effect of this mass-loss could be large. We find that for young solar-like stars and active M dwarfs, the total mass lost due to transient magnetic eruptions could have significant impacts on disk evolution, and thus planet formation, and also exoplanet habitability.

  19. The Main Sequences of Star-forming Galaxies and Active Galactic Nuclei at High Redshift

    NASA Astrophysics Data System (ADS)

    Mancuso, C.; Lapi, A.; Shi, J.; Cai, Z.-Y.; Gonzalez-Nuevo, J.; Béthermin, M.; Danese, L.

    2016-12-01

    We provide a novel, unifying physical interpretation on the origin, average shape, scatter, and cosmic evolution for the main sequences of star-forming galaxies and active galactic nuclei (AGNs) at high redshift z≳ 1. We achieve this goal in a model-independent way by exploiting: (i) the redshift-dependent star formation rate functions based on the latest UV/far-IR data from HST/Herschel, and related statistics of strong gravitationally lensed sources; (ii) deterministic evolutionary tracks for the history of star formation and black hole accretion, gauged on a wealth of multiwavelength observations including the observed Eddington ratio distribution. We further validate these ingredients by showing their consistency with the observed galaxy stellar mass functions and AGN bolometric luminosity functions at different redshifts via the continuity equation approach. Our analysis of the main sequence for high-redshift galaxies and AGNs highlights that the present data are consistently interpreted in terms of an in situ coevolution scenario for star formation and black hole accretion, envisaging these as local, time-coordinated processes.

  20. Star Formation and AGN Activity in Luminous and Ultraluminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Kartaltepe, Jeyhan

    2015-08-01

    In the local universe, Ultraluminous Infrared Galaxies (ULIRGs, L_IR > 10^12 L⊙) are all interacting and merging systems. We explore the evolution of the morphological and nuclear properties of (U)LIRGs over cosmic time using a large sample of galaxies from Her- schel observations of the CANDELS fields (including GOODS, COSMOS, and UDS). In particular, we investigate whether the role of galaxy mergers has changed between z ˜ 2 and now using the extensive visual classification catalogs produced by the CANDELS team. The combination of a selection from Herschel, near the peak of IR emission, and rest-frame optical morphologies from CANDELS, provides the ideal comparison to nearby (U)LIRGs. We also use rest-frame optical emission line diagnostics, X-ray luminosity, and MIR colors to separate AGN from star-formation dominated galaxies. We then study the how role of galaxy mergers and the presence of AGN activity correspond to the galaxy’s position in the star formation rate - stellar mass plane. Are galaxies that have specific star formation rates elevated above the main sequence more likely to be mergers? We investigate how AGN identified with different methods correspond to different morphologies and merger stages as well as position on the star formation rate - stellar mass plane.

  1. Flare Activity and Polarization States of White Dwarfs in Binary Star Systems

    NASA Astrophysics Data System (ADS)

    Boneva, D.; Filipov, L.

    2017-03-01

    We investigate flare activity and emission properties of white dwarf binary stars. We apply the polarization as a mechanism to probe the flares and the released resulting radiation. The polarization could appear as patterns in these cases, as it depends mainly on the properties of radiation and geometry of the source. The observational data of MV Lyr and CH Cyg are analysed. A repeated variability in the brightness could affect the degree of polarization. Detectable variations in the polarization parameters of selected binaries for the flares activity period are shown in the result. The analysis may help us to establish more evidence of the close correlation between flares, flow structure transformation around the primary star and polarization parameter variability.

  2. Magnetic activity in the HARPS M dwarf sample. The rotation-activity relationship for very low-mass stars through

    NASA Astrophysics Data System (ADS)

    Astudillo-Defru, N.; Delfosse, X.; Bonfils, X.; Forveille, T.; Lovis, C.; Rameau, J.

    2017-03-01

    Context. Atmospheric magnetic fields in stars with convective envelopes heat stellar chromospheres, and thus increase the observed flux in the Ca ii H and K doublet. Starting with the historical Mount Wilson monitoring program, these two spectral lines have been widely used to trace stellar magnetic activity, and as a proxy for rotation period (Prot) and consequently for stellar age. Monitoring stellar activity has also become essential in filtering out false-positives due to magnetic activity in extra-solar planet surveys. The Ca ii emission is traditionally quantified through the -index, which compares the chromospheric flux in the doublet to the overall bolometric flux of the star. Much work has been done to characterize this index for FGK-dwarfs, but M dwarfs - the most numerous stars of the Galaxy - were left out of these analyses and no calibration of their Ca ii H and K emission to an exists to date. Aims: We set out to characterize the magnetic activity of the low- and very-low-mass stars by providing a calibration of the -index that extends to the realm of M dwarfs, and by evaluating the relationship between and the rotation period. Methods: We calibrated the bolometric and photospheric factors for M dwarfs to properly transform the S-index (which compares the flux in the Ca ii H and K lines to a close spectral continuum) into the . We monitored magnetic activity through the Ca ii H and K emission lines in the HARPS M dwarf sample. Results: The index, like the fractional X-ray luminosity LX/Lbol, shows a saturated correlation with rotation, with saturation setting in around a ten days rotation period. Above that period, slower rotators show weaker Ca ii activity, as expected. Under that period, the index saturates to approximately 10-4. Stellar mass modulates the Ca ii activity, with showing a constant basal activity above 0.6 M⊙ and then decreasing with mass between 0.6 M⊙ and the fully-convective limit of 0.35 M⊙. Short-term variability of the

  3. Coronal temperatures of selected active cool stars as derived from low resolution Einstein observations

    NASA Technical Reports Server (NTRS)

    Vilhu, Osmi; Linsky, Jeffrey L.

    1990-01-01

    Mean coronal temperatures of some active G-K stars were derived from Rev1-processed Einstein-observatory's IPC-spectra. The combined X-ray and transition region emission line data are in rough agreement with static coronal loop models. Although the sample is too small to derive any statistically significant conclusions, it suggests that the mean coronal temperature depends linearly on the inverse Rossby-number, with saturation at short rotation periods.

  4. Star-forming galaxy models: Blending star formation into TREESPH

    NASA Technical Reports Server (NTRS)

    Mihos, J. Christopher; Hernquist, Lars

    1994-01-01

    We have incorporated star-formation algorithms into a hybrid N-body/smoothed particle hydrodynamics code (TREESPH) in order to describe the star forming properties of disk galaxies over timescales of a few billion years. The models employ a Schmidt law of index n approximately 1.5 to calculate star-formation rates, and explicitly include the energy and metallicity feedback into the Interstellar Medium (ISM). Modeling the newly formed stellar population is achieved through the use of hybrid SPH/young star particles which gradually convert from gaseous to collisionless particles, avoiding the computational difficulties involved in creating new particles. The models are shown to reproduce well the star-forming properties of disk galaxies, such as the morphology, rate of star formation, and evolution of the global star-formation rate and disk gas content. As an example of the technique, we model an encounter between a disk galaxy and a small companion which gives rise to a ring galaxy reminiscent of the Cartwheel (AM 0035-35). The primary galaxy in this encounter experiences two phases of star forming activity: an initial period during the expansion of the ring, and a delayed phase as shocked material in the ring falls back into the central regions.

  5. A Method for Measuring Active Region Filling Factors on Solar-Type Stars

    NASA Astrophysics Data System (ADS)

    Giampapa, Mark Steven; Andretta, Vincenzo; Beeck, Benjamin; Reiners, Ansgar; Schussler, Manfred

    2015-04-01

    Radiative diagnostics of “activity” in the Sun and solar-type stars are spatially associated with sites of emergent magnetic flux. The magnetic fields themselves are widely regarded as the surface manifestations of a dynamo mechanism. The further development of both dynamo theory and models of the non-radiative heating of outer stellar atmospheres requires a knowledge of stellar magnetic field properties. In this context, it becomes important to determine the surface distribution, or at least the fractional coverage of, magnetic active regions as one critical constraint for dynamo models. But, while information on the spatial distribution of activity on stellar surfaces can be gathered in some special cases (mostly rapid rotators), such measurements have always been elusive in more solar-like stars. We discuss the challenges and results obtained from a method that relies on the non-linear response of the two principal He I triplet lines (at 1083 nm and 587.6 nm) to infer useful constraints on the fractional area coverage of magnetic active regions on solar-type stars.

  6. Bulges and discs in the local Universe. Linking the galaxy structure to star formation activity

    NASA Astrophysics Data System (ADS)

    Morselli, L.; Popesso, P.; Erfanianfar, G.; Concas, A.

    2017-01-01

    We use a sample built on the SDSS DR7 catalogue and the bulge-disc decomposition of Simard et al. (2011, ApJS, 196, 11) to study how the bulge and disc components contribute to the parent galaxy's star formation activity, by determining its position in the star formation rate (SFR) - stellar mass (M⋆) plane at 0.02 < z < 0.1 and around the main sequence (MS) of star-forming galaxies. For this purpose, we use the bulge and disc colours as proxy for their SFRs, while the total galaxy SFR comes from Hα or D4000. We study the mean galaxy bulge-total mass ratio (B/T) as a function of the residual from the MS (ΔMS) and find that the B/T-ΔMS relation exhibits a parabola-like shape with the peak of the MS corresponding to the lowest B/Ts at any stellar mass. The lower and upper envelope of the MS are populated by galaxies with similar B/T, velocity dispersion and concentration (R90/R50) values. The mean values of such distributions indicate that the majority of the galaxies are characterised by classical bulges and not pseudo-bulges. Bulges above the MS are characterised by blue colours or, when red, by a high level of dust obscuration, thus indicating that in both cases they are actively star forming. When on the MS or below it, bulges are mostly red and dead. At stellar masses above 1010.5M⊙, bulges on the MS or in the green valley tend to be significantly redder than their counterparts in the quiescence region, despite similar levels of dust obscuration. This could be explained with different age or metallicity content, suggesting different evolutionary paths for bulges on the MS and green valley with respect to those in the quiescence region. The disc g-r colour anti-correlates at any mass with the distance from the MS, getting redder when approaching the MS lower envelope and the quiescence region. The anti-correlation flattens as a function of the stellar mass, likely due to a higher level of dust obscuration in massive SF galaxies. We conclude that the

  7. ACTIVE LEARNING TO OVERCOME SAMPLE SELECTION BIAS: APPLICATION TO PHOTOMETRIC VARIABLE STAR CLASSIFICATION

    SciTech Connect

    Richards, Joseph W.; Starr, Dan L.; Miller, Adam A.; Bloom, Joshua S.; Butler, Nathaniel R.; Berian James, J.; Brink, Henrik; Long, James P.; Rice, John

    2012-01-10

    Despite the great promise of machine-learning algorithms to classify and predict astrophysical parameters for the vast numbers of astrophysical sources and transients observed in large-scale surveys, the peculiarities of the training data often manifest as strongly biased predictions on the data of interest. Typically, training sets are derived from historical surveys of brighter, more nearby objects than those from more extensive, deeper surveys (testing data). This sample selection bias can cause catastrophic errors in predictions on the testing data because (1) standard assumptions for machine-learned model selection procedures break down and (2) dense regions of testing space might be completely devoid of training data. We explore possible remedies to sample selection bias, including importance weighting, co-training, and active learning (AL). We argue that AL-where the data whose inclusion in the training set would most improve predictions on the testing set are queried for manual follow-up-is an effective approach and is appropriate for many astronomical applications. For a variable star classification problem on a well-studied set of stars from Hipparcos and Optical Gravitational Lensing Experiment, AL is the optimal method in terms of error rate on the testing data, beating the off-the-shelf classifier by 3.4% and the other proposed methods by at least 3.0%. To aid with manual labeling of variable stars, we developed a Web interface which allows for easy light curve visualization and querying of external databases. Finally, we apply AL to classify variable stars in the All Sky Automated Survey, finding dramatic improvement in our agreement with the ASAS Catalog of Variable Stars, from 65.5% to 79.5%, and a significant increase in the classifier's average confidence for the testing set, from 14.6% to 42.9%, after a few AL iterations.

  8. A Multi-wavelength Study of Star Formation Activity in the S235 Complex

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Ojha, D. K.; Luna, A.; Anandarao, B. G.; Ninan, J. P.; Mallick, K. K.; Mayya, Y. D.

    2016-03-01

    We have carried out an extensive multi-wavelength study to investigate the star formation process in the S235 complex. The S235 complex has a spherelike shell appearance at wavelengths longer than 2 μm and harbors an O9.5V type star approximately at its center. A near-infrared extinction map of the complex traces eight subregions (having AV > 8 mag), and five of them appear to be distributed in an almost regularly spaced manner along the spherelike shell surrounding the ionized emission. This picture is also supported by the integrated 12CO and 13CO intensity maps and by Bolocam 1.1 mm continuum emission. The position-velocity analysis of CO reveals an almost semi-ringlike structure, suggesting an expanding H ii region. We find that the Bolocam clump masses increase as we move away from the location of the ionizing star. This correlation is seen only for those clumps that are distributed near the edges of the shell. Photometric analysis reveals 435 young stellar objects (YSOs), 59% of which are found in clusters. Six subregions (including five located near the edges of the shell) are very well correlated with the dust clumps, CO gas, and YSOs. The average values of Mach numbers derived using NH3 data for three (East 1, East 2, and Central E) out of these six subregions are 2.9, 2.3, and 2.9, indicating these subregions are supersonic. The molecular outflows are detected in these three subregions, further confirming the ongoing star formation activity. Together, all these results are interpreted as observational evidence of positive feedback of a massive star.

  9. A MULTI-WAVELENGTH STUDY OF STAR FORMATION ACTIVITY IN THE S235 COMPLEX

    SciTech Connect

    Dewangan, L. K.; Luna, A.; Mayya, Y. D.; Ojha, D. K.; Ninan, J. P.; Mallick, K. K.; Anandarao, B. G.

    2016-03-01

    We have carried out an extensive multi-wavelength study to investigate the star formation process in the S235 complex. The S235 complex has a spherelike shell appearance at wavelengths longer than 2 μm and harbors an O9.5V type star approximately at its center. A near-infrared extinction map of the complex traces eight subregions (having A{sub V} > 8 mag), and five of them appear to be distributed in an almost regularly spaced manner along the spherelike shell surrounding the ionized emission. This picture is also supported by the integrated {sup 12}CO and {sup 13}CO intensity maps and by Bolocam 1.1 mm continuum emission. The position–velocity analysis of CO reveals an almost semi-ringlike structure, suggesting an expanding H ii region. We find that the Bolocam clump masses increase as we move away from the location of the ionizing star. This correlation is seen only for those clumps that are distributed near the edges of the shell. Photometric analysis reveals 435 young stellar objects (YSOs), 59% of which are found in clusters. Six subregions (including five located near the edges of the shell) are very well correlated with the dust clumps, CO gas, and YSOs. The average values of Mach numbers derived using NH{sub 3} data for three (East 1, East 2, and Central E) out of these six subregions are 2.9, 2.3, and 2.9, indicating these subregions are supersonic. The molecular outflows are detected in these three subregions, further confirming the ongoing star formation activity. Together, all these results are interpreted as observational evidence of positive feedback of a massive star.

  10. A Census of Star Formation and Active Galactic Nuclei Populations in Abell 1689

    NASA Astrophysics Data System (ADS)

    Jones, Logan H.; Atlee, David Wesley

    2016-01-01

    A recent survey of low-z galaxy clusters observed a disjunction between X-ray and mid-infrared selected populations of active galactic nuclei (X-ray and IR AGNs) (Atlee+ 2011, ApJ 729, 22.). Here we present an analysis of near-infrared spectroscopic data of star-forming galaxies in cluster Abell 1689 in order to confirm the identity of some of their IR AGN and to provide a check on their reported star formation rates. Our sample consists of 24 objects in Abell 1689. H and K band spectroscopic observations of target objects and standard stars were obtained by David Atlee between 2010 May 17 and 2011 June 6 using the Large Binocular Telescope's LUCI instrument. After undergoing initial reductions, standard stars were corrected for telluric absorption using TelFit (Gullikson+ 2014, AJ, 158, 53). Raw detector counts were converted to physical units using the wavelength-dependent response of the grating and the star's reported H and K band magnitudes to produce conversion factors that fully correct for instrumental effects. Target spectra were flux-calibrated using the airmass-corrected transmission profiles produced by TelFit and the associated H band conversion factor (or the average of the two factors, for nights with two standard stars). Star formation rates were calculated using the SFR-L(Ha) relation reported in Kennicutt (1998), with the measured luminosity of the Pa-a emission line at the luminosity distance of the cluster used as a proxy for L(Ha) (Kennicutt 1998, ARA&A 36, 189; Hummer & Stoney 1987, MNRAS 346, 1055). The line ratios H2 2.121 mm/Brg and [FeII]/Pab were used to classify targets as starburst galaxies, AGNs, or LINERs (Rodriguez-Ardila+ 2005, MNRAS, 364, 1041). Jones was supported by the NOAO/KPNO Research Experience for Undergraduates (REU) Program, which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  11. Create an Adventure Challenge: Using Recess Time to Supplement Physical Activity during the School Day

    ERIC Educational Resources Information Center

    DiGiacinto, Kacey Lynn; Jones, Emily

    2010-01-01

    NASPE recommends children ages 5-12 accumulate at least 60 minutes of moderate to vigorous physical activity each day of the week. With the growing occurrence of obesity in the United States, it is clear that too many of America's youth are not meeting the recommended amount of daily physical activity. Given that America's youth are having…

  12. The hot Jupiter of the magnetically active weak-line T Tauri star V830 Tau

    NASA Astrophysics Data System (ADS)

    Donati, J.-F.; Yu, L.; Moutou, C.; Cameron, A. C.; Malo, L.; Grankin, K.; Hébrard, E.; Hussain, G. A. J.; Vidotto, A. A.; Alencar, S. H. P.; Haywood, R. D.; Bouvier, J.; Petit, P.; Takami, M.; Herczeg, G. J.; Gregory, S. G.; Jardine, M. M.; Morin, J.; MaTYSSE Collaboration

    2017-03-01

    We report results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star V830 Tau and its recently detected newborn close-in giant planet. Our observations, carried out within the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) programme, were spread over 91 d, and involved the ESPaDOnS and Narval spectropolarimeters linked to the 3.6-m Canada-France-Hawaii, the 2-m Bernard Lyot, and the 8-m Gemini-North Telescopes. Using Zeeman-Doppler Imaging, we characterize the surface brightness distributions, magnetic topologies, and surface differential rotation of V830 Tau at the time of our observations, and demonstrate that both distributions evolve with time beyond what is expected from differential rotation. We also report that near the end of our observations, V830 Tau triggered one major flare and two weaker precursors, showing up as enhanced redshifted emission in multiple spectral activity proxies. With three different filtering techniques, we model the radial velocity (RV) activity jitter (of semi-amplitude 1.2 km s-1) that V830 Tau generates, successfully retrieve the 68 ± 11 m s-1 RV planet signal hiding behind the jitter, further confirm the existence of V830 Tau b, and better characterize its orbital parameters. We find that the method based on Gaussian-process regression performs best thanks to its higher ability at modelling not only the activity jitter, but also its temporal evolution over the course of our observations, and succeeds at reproducing our RV data down to an rms precision of 35 m s-1. Our result provides new observational constraints on scenarios of star/planet formation and demonstrates the scientific potential of large-scale searches for close-in giant planets around T Tauri stars.

  13. Modelling the photosphere of active stars for planet detection and characterization

    NASA Astrophysics Data System (ADS)

    Herrero, Enrique; Ribas, Ignasi; Jordi, Carme; Morales, Juan Carlos; Perger, Manuel; Rosich, Albert

    2016-02-01

    Context. Stellar activity patterns are responsible for jitter effects that are observed at different timescales and amplitudes in the measurements obtained from photometric and spectroscopic time series observations. These effects are currently in the focus of many exoplanet search projects, since the lack of a well-defined characterization and correction strategy hampers the detection of the signals associated with small exoplanets. Aims: Accurate simulations of the stellar photosphere based on the most recent available models for main-sequence stars can provide synthetic photometric and spectroscopic time series data. These may help to investigate the relation between activity jitter and stellar parameters when considering different active region patterns. Moreover, jitters can be analysed at different wavelength scales (defined by the passbands of given instruments or space missions) to design strategies to remove or minimize them. Methods: We present the StarSim tool, which is based on a model for a spotted rotating photosphere built from the integration of the spectral contribution of a fine grid of surface elements. The model includes all significant effects affecting the flux intensities and the wavelength of spectral features produced by active regions and planets. The resulting synthetic time series data generated with this simulator were used to characterize the effects of activity jitter in extrasolar planet measurements from photometric and spectroscopic observations. Results: Several cases of synthetic data series for Sun-like stars are presented to illustrate the capabilities of the methodology. A specific application for characterizing and modelling the spectral signature of active regions is considered, showing that the chromatic effects of faculae are dominant for low-temperature contrasts of spots. Synthetic multi-band photometry and radial velocity time series are modelled for HD 189733 by adopting the known system parameters and fitting for the

  14. NREL Team Creates High-Activity, Durable Platinum Extended Surface Catalyst for Fuel Cells (Fact Sheet)

    SciTech Connect

    Not Available

    2011-02-01

    Researchers with NREL's Fuel Cell team showed that platinum can replace copper nanowires in such a way that high-surface-area and high-specific-activity catalysts are produced, potentially allowing for lower-cost catalysts.

  15. Strong variable linear polarization in the cool active star II Peg

    NASA Astrophysics Data System (ADS)

    Rosén, Lisa; Kochukhov, Oleg; Wade, Gregg A.

    2014-08-01

    Magnetic fields of cool active stars are currently studied polarimetrically using only circular polarization observations. This provides limited information about the magnetic field geometry since circular polarization is only sensitive to the line-of-sight component of the magnetic field. Reconstructions of the magnetic field topology will therefore not be completely trustworthy when only circular polarization is used. On the other hand, linear polarization is sensitive to the transverse component of the magnetic field. By including linear polarization in the reconstruction the quality of the reconstructed magnetic map is dramatically improved. For that reason, we wanted to identify cool stars for which linear polarization could be detected at a level sufficient for magnetic imaging. Four active RS CVn binaries, II Peg, HR 1099, IM Peg, and σ Gem were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. Mean polarization profiles in all four Stokes parameters were derived using the multi-line technique of least-squares deconvolution (LSD). Not only was linear polarization successfully detected in all four stars in at least one observation, but also, II Peg showed an extraordinarily strong linear polarization signature throughout all observations. This qualifies II Peg as the first promising target for magnetic Doppler imaging in all four Stokes parameters and, at the same time, suggests that other such targets can possibly be identified.

  16. Neutrino-heated stars and broad-line emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Macdonald, James; Stanev, Todor; Biermann, Peter L.

    1991-01-01

    Nonthermal radiation from active galactic nuclei indicates the presence of highly relativistic particles. The interaction of these high-energy particles with matter and photons gives rise to a flux of high-energy neutrinos. In this paper, the influence of the expected high neutrino fluxes on the structure and evolution of single, main-sequence stars is investigated. Sequences of models of neutrino-heated stars in thermal equilibrium are presented for masses 0.25, 0.5, 0.8, and 1.0 solar mass. In addition, a set of evolutionary sequences for mass 0.5 solar mass have been computed for different assumed values for the incident neutrino energy flux. It is found that winds driven by the heating due to high-energy particles and hard electromagnetic radiation of the outer layers of neutrino-bloated stars may satisfy the requirements of the model of Kazanas (1989) for the broad-line emission clouds in active galactic nuclei.

  17. Electrons precipitation stimulated by plasma jets injection in FLUXUS and NORTH STAR active rocket experiments

    NASA Astrophysics Data System (ADS)

    Gavrilov, B.; Erlandson, R.; Lynch, K.; Meng, C.; Podgorny, I.; Pfaff, R.; Stenbaek-Nielsen, H.; Sobyanin, D.; Zetzer, J.

    In Russian-American active rocket experiments FLUXUS (49? N, 47? E, 1997) and NORTH STAR (70? N, 148? W, 1999) high-velocity plasma jets were injected along and across the geomagnetic field respectively. In the both experiments high- density plasma jets pushed out the magnetic field. Later, when the magnetic field penetrated into the plasma jet, plasma was polarized and E=-VxB/c electric field was registered. As a result, Alfvén waves, carrying the field-aligned currents, propagate along the magnetic field lines. If the current density is rather high, the field-aligned electric fields can appear, and electrons would be accelerated along the magnetic field lines. Electron fluxes with energy from several eV to 2 keV were revealed in the both experiments. During NORTH STAR experiment electron fluxes caused by auroral precipitation were also registered

  18. Active ion emission onboard the Double Star TC-1 spacecraft - results from initial science operations

    NASA Astrophysics Data System (ADS)

    Torkar, K.; Steiger, W.; Narheim, B. T.; Svenes, K.; Fehringer, M.; Escoubet, C. P.; Fazakerley, A. N.; Zhao, H.

    An ion emitter instrument ASPOC (Active Spacecraft Potential Control) belongs to the payload of the Chinese-European Double Star mission (TC-1) launched in December 2003. The instrument is a further development to the ones flown in the Cluster mission. Its objective is a reduction of the spacecraft potential in order to minimise the perturbations to the plasma measurements on board. The operation of the scientific payload began after commissioning in February 2004. Comparisons to Cluster are being made based on data from the first half year of the Double Star mission. The enhanced capabilities of the instrument allow to achieve even lower potentials than on Cluster. Differences to Cluster can also be expected because of the plasma environment at the equatorial orbit of TC-1. The effects of spacecraft potential control on the electron measurements by the instrument PEACE as observed during the first months of science operations are discussed.

  19. Engineering Neprilysin Activity and Specificity to Create a Novel Therapeutic for Alzheimer’s Disease

    PubMed Central

    Webster, Carl I.; Burrell, Matthew; Olsson, Lise-Lotte; Fowler, Susan B.; Digby, Sarah; Sandercock, Alan; Snijder, Arjan; Tebbe, Jan; Haupts, Ulrich; Grudzinska, Joanna; Jermutus, Lutz; Andersson, Christin

    2014-01-01

    Neprilysin is a transmembrane zinc metallopeptidase that degrades a wide range of peptide substrates. It has received attention as a potential therapy for Alzheimer’s disease due to its ability to degrade the peptide amyloid beta. However, its broad range of peptide substrates has the potential to limit its therapeutic use due to degradation of additional peptides substrates that tightly regulate many physiological processes. We sought to generate a soluble version of the ectodomain of neprilysin with improved activity and specificity towards amyloid beta as a potential therapeutic for Alzheimer’s disease. Extensive amino acid substitutions were performed at positions surrounding the active site and inner surface of the enzyme and variants screened for activity on amyloid beta 1–40, 1–42 and a variety of other physiologically relevant peptides. We identified several mutations that modulated and improved both enzyme selectivity and intrinsic activity. Neprilysin variant G399V/G714K displayed an approximately 20-fold improved activity on amyloid beta 1–40 and up to a 3,200-fold reduction in activity on other peptides. Along with the altered peptide substrate specificity, the mutant enzyme produced a markedly altered series of amyloid beta cleavage products compared to the wild-type enzyme. Crystallisation of the mutant enzyme revealed that the amino acid substitutions result in alteration of the shape and size of the pocket containing the active site compared to the wild-type enzyme. The mutant enzyme offers the potential for the more efficient degradation of amyloid beta in vivo as a therapeutic for the treatment of Alzheimer’s disease. PMID:25089527

  20. Competency-based medical education and scholarship: Creating an active academic culture during residency.

    PubMed

    Bourgeois, James A; Hategan, Ana; Azzam, Amin

    2015-10-01

    The competency-based medical education movement has been adopted in several medical education systems across the world. This has the potential to result in a more active involvement of residents in the educational process, inasmuch as scholarship is regarded as a major area of competency. Substantial scholarly activities are well within the reach of motivated residents, especially when faculty members provide sufficient mentoring. These academically empowered residents have the advantage of early experience in the areas of scholarly discovery, integration, application, and teaching. Herein, the authors review the importance of instituting the germinal stages of scholarly productivity in the creation of an active scholarly culture during residency. Clear and consistent institutional and departmental strategies to promote scholarly development during residency are highly encouraged.

  1. Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths

    NASA Astrophysics Data System (ADS)

    Feltre, A.; Charlot, S.; Gutkin, J.

    2016-03-01

    In the context of observations of the rest-frame ultraviolet and optical emission from distant galaxies, we explore the emission-line properties of photoionization models of active and inactive galaxies. Our aim is to identify new line-ratio diagnostics to discriminate between gas photoionization by active galactic nuclei (AGN) and star formation. We use a standard photoionization code to compute the emission from AGN narrow-line regions and compare this with calculations of the nebular emission from star-forming galaxies achieved using the same code. We confirm the appropriateness of widely used optical spectral diagnostics of nuclear activity versus star formation and explore new diagnostics at ultraviolet wavelengths. We find that combinations of a collisionally excited metal line or line multiplet, such as C IV λλ1548, 1551, O III] λλ1661, 1666, N III] λ1750, [Si III] λ1883+Si III] λ1892 and [C III] λ1907+C III] λ1909, with the He II λ1640 recombination line are individually good discriminants of the nature of the ionizing source. Diagrams involving at least three of these lines allow an even more stringent distinction between active and inactive galaxies, as well as valuable constraints on interstellar gas parameters and the shape of the ionizing radiation. Several line ratios involving Ne-based emission lines, such as [Ne IV] λ2424, [Ne III] λ3343 and [Ne V] λ3426, are also good diagnostics of nuclear activity. Our results provide a comprehensive framework to identify the sources of photoionization and physical conditions of the ionized gas from the ultraviolet and optical nebular emission from galaxies. This will be particularly useful to interpret observations of high-redshift galaxies with future facilities, such as the James Webb Space Telescope and extremely large ground-based telescopes.

  2. Creating Trans-Inclusive Schools: Introductory Activities That Enhance the Critical Consciousness of Future Educators

    ERIC Educational Resources Information Center

    De Pedro, Kris Tunac; Jackson, Christopher; Campbell, Erin; Gilley, Jade; Ciarelli, Brock

    2016-01-01

    The Lawrence King murder and other tragedies surrounding transgender youth have prompted a national discussion about the need for schools to be more supportive and inclusive of transgender students. In this multi-authored reflection, the authors describe a series of three introductory activities in an undergraduate educational studies course aimed…

  3. Creating a Cell Map as an Active-Learning Tool in a Biochemistry Course

    ERIC Educational Resources Information Center

    Del Bianco, Cristina

    2010-01-01

    Teaching metabolism to a biochemistry class with diverse academic backgrounds is a challenging task. Often students lack the global perspective that is needed to understand how different metabolic pathways are reciprocally regulated. The classroom activity presented in this article is designed to facilitate the learning of metabolism by having the…

  4. Creating Healthier Afterschool Environments in the Healthy Eating Active Communities Program

    ERIC Educational Resources Information Center

    Hinkle, Arnell J.; Yoshida, Sallie

    2014-01-01

    Afterschool programs in California have the potential to play a major role in obesity prevention given that they serve close to a million low-income children. A five-year initiative called the Healthy Eating Active Communities (HEAC) was funded in 2005 by the California Endowment to demonstrate that disparities related to childhood obesity and…

  5. Stellar magnetic activity and variability of oscillation parameters: An investigation of 24 solar-like stars observed by Kepler

    NASA Astrophysics Data System (ADS)

    Kiefer, René; Schad, Ariane; Davies, Guy; Roth, Markus

    2017-02-01

    Context. The Sun and solar-like stars undergo activity cycles for which the underlying mechanisms are not well understood. The oscillations of the Sun are known to vary with its activity cycle and these changes provide diagnostics on the conditions below the photosphere. Kepler has detected solar-like oscillations in hundreds of stars but as of yet, no widespread detection of signatures of magnetic activity cycles in the oscillation parameters of these stars have been reported. Aims: We analysed the photometric short cadence Kepler time series of a set of 24 solar-like stars, which were observed for at least 960 d each, with the aim to find signatures of stellar magnetic activity in the oscillation parameters. Methods: We analyse the temporal evolution of oscillation parameters by measuring mode frequency shifts, changes in the height of the p-mode envelope, as well as granulation timescales. Results: For 23 of the 24 investigated stars, we find significant frequency shifts in time. We present evidence for magnetic activity in six of these stars. We find that the amplitude of the frequency shifts decreases with stellar age and rotation period. For KIC 8006161 (the most prominent example), we find that frequency shifts are smallest for the lowest and largest for the highest p-mode frequencies, as they are for the Sun. Conclusions: These findings show that magnetic activity can be routinely observed in the oscillation parameters for solar-like stars, which opens up the possibility of placing the solar activity cycle in the context of other stars by asteroseismology.

  6. Active living research: creating and using evidence to support childhood obesity prevention.

    PubMed

    Sallis, James F; Cutter, Carmen L; Lou, Deborah; Spoon, Chad; Wilson, Amanda L; Ding, Ding; Ponkshe, Prabhu; Cervero, Robert; Patrick, Kevin; Schmid, Thomas L; Mignano, Alexandra; Orleans, C Tracy

    2014-02-01

    The second phase of Active Living Research (ALR-2, 2007-2012) focused on advancing the Robert Wood Johnson Foundation (RWJF)'s goal of reversing the childhood obesity epidemic. The mission was to stimulate and support research to identify environmental factors and policies that influence physical activity for children and families to inform effective childhood obesity prevention strategies, with an emphasis on the lower-income and racial/ethnic communities with highest childhood obesity prevalence. The present report describes ALR activities undertaken to accomplish three goals. The first goal-to build an evidence base-was furthered by funding 230 competitive grants to identify and evaluate promising environment and policy changes. More than 300 publications have been produced so far. The second goal-to build an interdisciplinary and diverse field of investigators-was supported through annual conferences and linked journal supplements, academic outreach to multiple disciplines, and grants targeting young investigators and those representing groups historically disadvantaged or underrepresented in RWJF-funded research. The third goal-to use research to inform policy and practice-was advanced through research briefs; webinars; research-translation grants supporting ALR grantees to design communications tailored to decision-maker audiences; active engagement of policymakers and other stakeholders in ALR program meetings and annual conferences; ALR presentations at policy-related meetings; and broad outreach through a widely used website, e-mailed newsletters, and social media. ALR-2 findings and products have contributed to a rapid increase in the evidence base and field of active living research, as documented by an independent program evaluation.

  7. Catch a Star 2008!

    NASA Astrophysics Data System (ADS)

    2007-10-01

    ESO and the European Association for Astronomy Education have just launched the 2008 edition of 'Catch a Star', their international astronomy competition for school students. Now in its sixth year, the competition offers students the chance to win a once-in-a-lifetime trip to ESO's flagship observatory in Chile, as well as many other prizes. CAS logo The competition includes separate categories - 'Catch a Star Researchers' and 'Catch a Star Adventurers' - to ensure that every student, whatever their level, has the chance to enter and win exciting prizes. In teams, students investigate an astronomical topic of their choice and write a report about it. An important part of the project for 'Catch a Star Researchers' is to think about how ESO's telescopes such as the Very Large Telescope (VLT) or future telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Extremely Large Telescope (E-ELT) could contribute to investigations of the topic. Students may also include practical activities such as observations or experiments. For the artistically minded, 'Catch a Star' also offers an artwork competition, 'Catch a Star Artists'. Last year, hundreds of students from across Europe and beyond took part in 'Catch a Star', submitting astronomical projects and artwork. "'Catch a Star' gets students thinking about the wonders of the Universe and the science of astronomy, with a chance of winning great prizes. It's easy to take part, whether by writing about astronomy or creating astronomically inspired artwork," said Douglas Pierce-Price, Education Officer at ESO. As well as the top prize - a trip to ESO's Very Large Telescope in Chile - visits to observatories in Austria and Spain, and many other prizes, can also be won. 'Catch a Star Researchers' winners will be chosen by an international jury, and 'Catch a Star Adventurers' will be awarded further prizes by lottery. Entries for 'Catch a Star Artists' will be displayed on the web and winners

  8. Twinning in fcc lattice creates low-coordinated catalytically active sites in porous gold

    NASA Astrophysics Data System (ADS)

    Krajčí, Marian; Kameoka, Satoshi; Tsai, An-Pang

    2016-08-01

    We describe a new mechanism for creation of catalytically active sites in porous gold. Samples of porous gold prepared by de-alloying Al2Au exhibit a clear correlation between the catalytic reactivity towards CO oxidation and structural defects in the fcc lattice of Au. We have found that on the stepped {211} surfaces quite common twin boundary defects in the bulk structure of porous gold can form long close-packed rows of atoms with the coordination number CN = 6. DFT calculations confirm that on these low-coordinated Au sites dioxygen chemisorbs and CO oxidation can proceed via the Langmuir-Hinshelwood mechanism with the activation energy of 37 kJ/mol or via the CO-OO intermediate with the energy barrier of 19 kJ/mol. The existence of the twins in porous gold is stabilized by the surface energy.

  9. Twinning in fcc lattice creates low-coordinated catalytically active sites in porous gold.

    PubMed

    Krajčí, Marian; Kameoka, Satoshi; Tsai, An-Pang

    2016-08-28

    We describe a new mechanism for creation of catalytically active sites in porous gold. Samples of porous gold prepared by de-alloying Al2Au exhibit a clear correlation between the catalytic reactivity towards CO oxidation and structural defects in the fcc lattice of Au. We have found that on the stepped {211} surfaces quite common twin boundary defects in the bulk structure of porous gold can form long close-packed rows of atoms with the coordination number CN = 6. DFT calculations confirm that on these low-coordinated Au sites dioxygen chemisorbs and CO oxidation can proceed via the Langmuir-Hinshelwood mechanism with the activation energy of 37 kJ/mol or via the CO-OO intermediate with the energy barrier of 19 kJ/mol. The existence of the twins in porous gold is stabilized by the surface energy.

  10. Electrospray deposition in vacuum as method to create functionally active protein immobilization on polymeric substrates.

    PubMed

    Fornari, Enzo; Roberts, Clive J; Temperton, Robert H; O'Shea, James N

    2015-09-01

    We demonstrate in this work the deposition of a large biological molecule (fibronectin) on polymeric substrates in a high vacuum environment using an electrospray deposition system. Fibronectin was deposited and its distribution and structure investigated and retention of function (ability to promote cell adhesion) on return to liquid environment is shown. AFM was used to monitor changes in the morphology of the surface before and after fibronectin deposition, whilst the biological activity of the deposited protein is assessed through a quantitative analysis of the biomolecular adhesion and migration of fibroblast cells to the modified surfaces. For the first time we have demonstrated that using high vacuum electrospray deposition it is possible to deposit large protein molecules on polymeric surfaces whilst maintaining the protein activity. The deposition of biological molecules such as proteins with the retention of their activity onto clean well-controlled surfaces under vacuum condition, offers the possibility for future studies utilizing high resolution vacuum based techniques at the atomic and molecular scale providing a greater understanding of protein-surface interface behaviour of relevance to a wide range of applications such as in sensors, diagnostics and tissue engineering.

  11. Creating Colored Letters: Familial Markers of Grapheme-Color Synesthesia in Parietal Lobe Activation and Structure.

    PubMed

    Colizoli, Olympia; Murre, Jaap M J; Scholte, H Steven; Rouw, Romke

    2017-02-14

    Perception is inherently subjective, and individual differences in phenomenology are well illustrated by the phenomenon of synesthesia (highly specific, consistent, and automatic cross-modal experiences, in which the external stimulus corresponding to the additional sensation is absent). It is unknown why some people develop synesthesia and others do not. In the current study, we tested whether neural markers related to having synesthesia in the family were evident in brain function and structure. Relatives of synesthetes (who did not have any type of synesthesia themselves) and matched controls read specially prepared books with colored letters for several weeks and were scanned before and after reading using magnetic resonance imaging. Effects of acquired letter-color associations were evident in brain activation. Training-related activation (while viewing black letters) in the right angular gyrus of the parietal lobe was directly related to the strength of the learned letter-color associations (behavioral Stroop effect). Within this obtained angular gyrus ROI, the familial trait of synesthesia related to brain activation differences while participants viewed both black and colored letters. Finally, we compared brain structure using voxel-based morphometry and diffusion tensor imaging to test for group differences and training effects. One cluster in the left superior parietal lobe had significantly more coherent white matter in the relatives compared with controls. No evidence for experience-dependent plasticity was obtained. For the first time, we present evidence suggesting that the (nonsynesthete) relatives of grapheme-color synesthetes show atypical grapheme processing as well as increased brain connectivity.

  12. When conditioned responses "fire back": bidirectional cross-activation creates learning opportunities in synesthesia.

    PubMed

    Meier, B; Rothen, N

    2007-07-13

    In grapheme-color synesthesia, the letter "c" printed in black may be experienced as red, but typically the color red does not trigger the experience of the letter "c." Therefore, at the level of subjective experience, cross-activation is usually unidirectional. However, recent evidence from digit-color synesthesia suggests that at an implicit level bidirectional cross-activation can occur. Here we demonstrate that this finding is not restricted to this specific type of synesthesia. We introduce a new method that enables the investigation of bidirectionality in other types of synesthesia. We found that a group of grapheme-color synesthetes, but not a control group, showed a startle in response to a color-inducing grapheme after a startle response was conditioned to the specific corresponding color. These results implicate that when the startle response was associated with the real color an association between shock and the grapheme was also established. By this mechanism (i.e. implicit cross-activation) the conditioned response to the real color generalized to the synesthetic color. We suggest that parietal brain areas are responsible for this neural backfiring.

  13. Hide and Seek: Radial-velocity searches for planets around active stars

    NASA Astrophysics Data System (ADS)

    Haywood, Raphaelle

    2017-01-01

    The ultimate obstacle to determining the masses of small, rocky exoplanets through radial-velocity (RV) monitoring is the intrinsic variability of the host stars themselves. For my PhD, I developed an intuitive and robust data analysis framework in which the activity-induced variations are modelled with a Gaussian process that has the frequency structure of the stellar magnetic activity. This allowed me to determine precise and accurate masses of the planets in the CoRoT-7, Kepler-78 and Kepler-10 systems. In parallel, I explored the physical origin of activity-induced RV variations of our best-known star: the Sun. I conducted the first systematic RV campaign of the Sun seen as an exoplanet host star using the 3.6m/HARPS spectrograph, by observing sunlight reflected off the bright asteroid 4/Vesta. I used images from the Solar Dynamics Observatory to reconstruct the RV signals incurred by individual surface features such as sunspots, faculae and granulation. I found that the activity-induced RV variations are driven by the suppression of convective blueshift arising dominantly from the presence of faculae. I also identified the full-disc magnetic flux as an excellent proxy for activity-induced RV variations.I am now pursuing my solar investigations using Sun-as-a-star RV observations acquired with the new solar telescope feed at HARPS-N. In particular, I am investigating the impact of magnetic surface features on the shapes of the spectral line profiles, rather than on the RVs themselves (which are a single moment of these lines). This work is key to developing physically-driven, better-tailored models for activity-induced RV variations, in preparation for the potentially habitable, Earth-like planets to be discovered and characterised in the coming years with TESS and GMT/G-CLEF.This work was funded by the Science and Technology Facilities Council in the United Kingdom and the John Templeton Foundation.

  14. DISCOVERY OF A 1.6 YEAR MAGNETIC ACTIVITY CYCLE IN THE EXOPLANET HOST STAR {iota} HOROLOGII

    SciTech Connect

    Metcalfe, T. S.; Judge, P. G.; Knoelker, M.; Mathur, S.; Rempel, M.; Basu, S.; Henry, T. J.; Soderblom, D. R.

    2010-11-10

    The Mount Wilson Ca HK survey revealed magnetic activity variations in a large sample of solar-type stars with timescales ranging from 2.5 to 25 years. This broad range of cycle periods is thought to reflect differences in the rotational properties and the depths of the surface convection zones for stars with various masses and ages. In 2007, we initiated a long-term monitoring campaign of Ca II H and K emission for a sample of 57 southern solar-type stars to measure their magnetic activity cycles and their rotational properties when possible. We report the discovery of a 1.6 year magnetic activity cycle in the exoplanet host star {iota} Horologii and obtain an estimate of the rotation period that is consistent with Hyades membership. This is the shortest activity cycle so far measured for a solar-type star and may be related to the short-timescale magnetic variations recently identified in the Sun and HD 49933 from helioseismic and asteroseismic measurements. Future asteroseismic observations of {iota} Hor can be compared to those obtained near the magnetic minimum in 2006 to search for cycle-induced shifts in the oscillation frequencies. If such short activity cycles are common in F stars, then NASA's Kepler mission should observe their effects in many of its long-term asteroseismic targets.

  15. Analysis of Chandra X-ray Spectra of the Young, Active Star AB Dor

    NASA Astrophysics Data System (ADS)

    Linsky, J. L.; Gagne, M.

    2001-05-01

    The early-K dwarf AB Dor is a nearby (15 pc), young (20--30 Myr), rapidly rotating (Prot = 0.514 day) star with saturated X-ray emission (Lx/Lbol ~ 10-3) and cool prominence-like gas extending several stellar radii into its corona. We observed this extensively studied star on 1999 Oct 9 for 60 ks with the high energy transmission grating (HETG/ACIS-S) on Chandra. The rich X-ray spectra contain emission lines of N, O, Ne, Mg, Al, Si, S, Ar, Ca, Fe, and Ni. As is seen in other active stars, the Ne abundance is high and the Fe abundance low compared to solar photospheric abundances, indicating the reverse of the enhanced first ionization potential (FIP) effect seen in the solar corona. The emission measure distribution shows peaks near log T = 6.8 and 7.3, and the helium-like triplets of O VII, Ne IX, and Mg XI indicate electron densities log ne ~ 11.0. We will use these data to infer the size and properties of coronal loops in the stellar corona. We find no noticeable line shifts indicative of a wind or downflows. This GTO Chandra program is supported by NASA through a grant to NIST and the University of Colorado.

  16. Star formation and AGN activity in the most luminous LINERs in the local universe

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Povic, M.; Netzer, H.; Masegosa, J.; Nordon, R.; Pérez, E.; Schoenell, W.

    2017-03-01

    This work presents the properties of 42 objects in the group of the most luminous, highest star formation rate (SFR) low-ionization nuclear emission-line regions (LINERs) at z = 0.04 - 0.11. We obtained long-slit spectroscopy of the nuclear regions for all sources, and FIR data (Herschel and IRAS) for 13 of them.We measured emission-line intensities, extinction, stellar populations, stellar masses, ages, active galactic nuclei (AGN) luminosities, and SFRs. We find considerable differences from other low-redshift LINERs, and general similarity to star-forming galaxies. We confirm the existence of such luminous LINERs in the local universe, after being previously detected at z˜0.3 by Tommasin et al. The median stellar mass of these LINERs corresponds to 6 - 7× 10^{10} M_⊙ which was found in previous works to correspond to the peak of relative growth rate of stellar populations and therefore for the highest SFRs. Other LINERs although showing similar AGN luminosities have lower SFR. We find that most of these sources have LAGN ˜ LSF suggesting co-evolution of black hole and stellarmass. In general, the fraction of local LINERs on the main sequence of star-forming galaxies is related to their AGN luminosity.

  17. Activity and magnetic field structure of the Sun-like planet-hosting star HD 1237

    NASA Astrophysics Data System (ADS)

    Alvarado-Gómez, J. D.; Hussain, G. A. J.; Grunhut, J.; Fares, R.; Donati, J.-F.; Alecian, E.; Kochukhov, O.; Oksala, M.; Morin, J.; Redfield, S.; Cohen, O.; Drake, J. J.; Jardine, M.; Matt, S.; Petit, P.; Walter, F. M.

    2015-10-01

    We analyse the magnetic activity characteristics of the planet-hosting Sun-like star, HD 1237, using HARPS spectro-polarimetric time-series data. We find evidence of rotational modulation of the magnetic longitudinal field measurements that is consistent with our ZDI analysis with a period of 7 days. We investigate the effect of customising the LSD mask to the line depths of the observed spectrum and find that it has a minimal effect on the shape of the extracted Stokes V profile but does result in a small increase in the S/N (~7%). We find that using a Milne-Eddington solution to describe the local line profile provides a better fit to the LSD profiles in this slowly rotating star, which also affects the recovered ZDI field distribution. We also introduce a fit-stopping criterion based on the information content (entropy) of the ZDI map solution set. The recovered magnetic field maps show a strong (+90 G) ring-like azimuthal field distribution and a complex radial field dominating at mid latitudes (~45 degrees). Similar magnetic field maps are recovered from data acquired five months apart. Future work will investigate how this surface magnetic field distribution affeccts the coronal magnetic field and extended environment around this planet-hosting star.

  18. New Insights on Late-A and Early-F Star Activity

    NASA Astrophysics Data System (ADS)

    Freire Ferrero, R.; Catalano, S.; Marilli, E.; Gouttebroze, P.; Talavera, A.; Bruhweiler, F.

    The onset of chromospheric activity in late-A and early-F stars is here discussed. The detection of Ly- emission core in several A and F atars with the IUE satellite, gives evidence for the presence of chromospheric layers in these stars up to B - V = 0m.19 (Marilli et al., 1996). Semiempirical chromospheric models for Altair allowed us (Freire Ferrero et al., 1995) to explain the observed emission profiles taking into account normal H I interstellar (IS) absorption. However, due to the very high rotational velocity, we analysed alternative hypotheses to explain the observed emissions: (1) circumstellar or shell matter; (2) co-rotating expanding optically thin wind. We ruled out these hypotheses because their effects are negligible and as a consequence, this result reinforces the chromospheric origin of the observed Ly- core in Altair. The stars of our sample, having observed Ly- profilies similar to Altair's and similar stellar and IS properties, should reproduce similar chromospheric behaviour. Here we discuss several important questions that are raised by these results.

  19. Star formation and AGN activity in the most luminous LINERs in the local universe

    NASA Astrophysics Data System (ADS)

    Pović, Mirjana; Márquez, Isabel; Netzer, Hagai; Masegosa, Josefa; Nordon, Raanan; Pérez, Enrique; Schoenell, William

    2016-11-01

    This work presents the properties of 42 objects in the group of the most luminous, highest star formation rate (SFR) low-ionization nuclear emission-line regions (LINERs) at z = 0.04-0.11. We obtained long-slit spectroscopy of the nuclear regions for all sources, and FIR data (Herschel and IRAS) for 13 of them. We measured emission-line intensities, extinction, stellar populations, stellar masses, ages, active galactic nuclei (AGN) luminosities, and SFRs. We find considerable differences from other low-redshift LINERs, in terms of extinction, and general similarity to star-forming galaxies. We confirm the existence of such luminous LINERs in the local universe, after being previously detected at z ˜ 0.3 by Tommasin et al. The median stellar mass of these LINERs corresponds to 6-7 × 1010 M⊙ which was found in previous work to correspond to the peak of relative growth rate of stellar populations and therefore for the highest SFRs. Other LINERs although showing similar AGN luminosities have lower SFR. We find that most of these sources have LAGN ˜ LSF suggesting co-evolution of black hole and stellar mass. In general, the fraction of local LINERs on the main sequence of star-forming galaxies is related to their AGN luminosity.

  20. Star formation activity of intermediate redshift cluster galaxies out to the infall regions

    NASA Astrophysics Data System (ADS)

    Gerken, B.; Ziegler, B.; Balogh, M.; Gilbank, D.; Fritz, A.; Jäger, K.

    2004-07-01

    We present a spectroscopic analysis of two galaxy clusters at z≈0.2, out to ˜4 Mpc. The two clusters VMF73 and VMF74 as identified by \\citet{VMFJQH98} were observed with multiple object spectroscopy using MOSCA at the Calar Alto 3.5 m telescope. Both clusters lie in the ROSAT Position Sensitive Proportional Counter field R285 and were selected from the X-ray Dark Cluster Survey \\citep{GBCZ04} that provides optical V- and I-band data. VMF73 and VMF74 are located at respective redshifts of z=0.25 and z=0.18 with velocity dispersions of 671 km s-1 and 442 km s-1, respectively. Both cluster velocity dispersions are consistent with Gaussians. The spectroscopic observations reach out to ˜2.5 virial radii. Line strength measurements of the emission lines Hα and [O II]λ3727 are used to assess the star formation activity of cluster galaxies which show radial and density dependences. The mean and median of both line strength distributions as well as the fraction of star forming galaxies increase with increasing clustercentric distance and decreasing local galaxy density. Except for two galaxies with strong Hα and [O II] emission, all of the cluster galaxies are normal star forming or passive galaxies. Our results are consistent with other studies that show the truncation in star formation occurs far from the cluster centre. Table A.1 is only available in electronic from at http//www.edpsciences.org

  1. STAR FORMATION ACTIVITY IN THE GALACTIC H II COMPLEX S255-S257

    SciTech Connect

    Ojha, D. K.; Ghosh, S. K.; Samal, M. R.; Pandey, A. K.; Sharma, Saurabh; Bhatt, B. C.; Tamura, M.; Mohan, V.; Zinchenko, I.

    2011-09-10

    We present results on the star formation activity of an optically obscured region containing an embedded cluster (S255-IR) and molecular gas between two evolved H II regions, S255 and S257. We have studied the complex using optical and near-infrared (NIR) imaging, optical spectroscopy, and radio continuum mapping at 15 GHz, along with Spitzer-IRAC results. We found that the main exciting sources of the evolved H II regions S255 and S257 and the compact H II regions associated with S255-IR are of O9.5-B3 V nature, consistent with previous observations. Our NIR observations reveal 109 likely young stellar object (YSO) candidates in an area of {approx}4.'9 x 4.'9 centered on S255-IR, which include 69 new YSO candidates. To see the global star formation, we constructed the V - I/V diagram for 51 optically identified IRAC YSOs in an area of {approx}13' x 13' centered on S255-IR. We suggest that these YSOs have an approximate age between 0.1 and 4 Myr, indicating a non-coeval star formation. Using spectral energy distribution models, we constrained physical properties and evolutionary status of 31 and 16 YSO candidates outside and inside the gas ridge, respectively. The models suggest that the sources associated with the gas ridge are younger (mean age {approx}1.2 Myr) than the sources outside the gas ridge (mean age {approx}2.5 Myr). The positions of the young sources inside the gas ridge at the interface of the H II regions S255 and S257 favor a site of induced star formation.

  2. Busy Teachers: A Case of Comparing Online Teacher-Created Activities with the Ready-Made Activity Resource Books

    ERIC Educational Resources Information Center

    Khoshhal, Yasin

    2016-01-01

    With the ever-growing needs for more resources, the lack of concentration on preparing an exclusive activity for a particular classroom can be observed in a large number of educational contexts. The present study investigates the efficiency of ready-made activities for busy teachers. To this end, an activity from the ready-made resource book,…

  3. Liver segmentation with new supervised method to create initial curve for active contour.

    PubMed

    Zareei, Abouzar; Karimi, Abbas

    2016-08-01

    The liver performs a critical task in the human body; therefore, detecting liver diseases and preparing a robust plan for treating them are both crucial. Liver diseases kill nearly 25,000 Americans every year. A variety of image segmentation methods are available to determine the liver's position and to detect possible liver tumors. Among these is the Active Contour Model (ACM), a framework which has proven very sensitive to initial contour delineation and control parameters. In the proposed method based on image energy, we attempted to obtain an initial segmentation close to the liver's boundary, and then implemented an ACM to improve the initial segmentation. The ACM used in this work incorporates gradient vector flow (GVF) and balloon energy in order to overcome ACM limitations, such as local minima entrapment and initial contour dependency. Additionally, in order to adjust active contour control parameters, we applied a genetic algorithm to produce a proper parameter set close to the optimal solution. The pre-processing method has a better ability to segment the liver tissue during a short time with respect to other mentioned methods in this paper. The proposed method was performed using Sliver CT image datasets. The results show high accuracy, precision, sensitivity, specificity and low overlap error, MSD and runtime with few ACM iterations.

  4. Creating experiential learning activities using Web 2.0 tools and technologies: a case study.

    PubMed

    Brixey, Juliana J; Warren, Judith J

    2009-01-01

    Learning is no longer an internal individual activity but occurs through networks and connections. The aim of this project was to teach online health informatics students to use Web 2.0 tools and technologies to form networks and connections through experiential learning assignments. Web 2.0 tools and technologies were evaluated using a criteria checklist prior to implementation for students enrolled in health informatics classes at the University of Kansas School of Nursing. Health informatics students have developed competencies using an instant message service, blogging, concept mapping, social bookmarking, and interacting a virtual environment. In the future, health care professionals will have to work in rapidly changing environments and keep abreast of new innovations and tools, learn to use those tools, and to teach others about the tools.

  5. Creating leptin-like biofunctions by active immunization against chicken leptin receptor in growing chickens.

    PubMed

    Lei, M M; Wu, S Q; Shao, X B; Li, X W; Chen, Z; Ying, S J; Shi, Z D

    2015-01-01

    In this study, immunization against chicken leptin receptor (cLEPR) extracellular domain (ECD) was applied to investigate leptin regulation and LEPR biofunction in growing chicken pullets. A recombinant protein (cLEPR ECD) based on the cLEPR complemenary DNA sequence corresponding to the 582nd to 796th amino acid residues of cLEPR mature peptide was prepared and used as antigen. Immunization against cLEPR ECD in growing chickens increased anti-cLEPR ECD antibody titers in blood, enhanced proportions of phosphorylated janus kinase 2 (JAK2) and served as signal transducer and activator of transcription 3 (STAT3) protein in liver tissue. Chicken live weight gain and abdominal fat mass were significantly decreased (P < 0.05), but feed intake was stimulated by cLEPR ECD immunization (P < 0.05). The treatment also upregulated the gene expression levels of lepR, AMP-activated protein kinase (AMPK), acetyl CoA carboxylase-2 (ACC2), and uncoupling protein 3 (UCP3) in liver, abdominal fat, and breast muscle (P < 0.05) but decreased fasn expression levels (P < 0.01). Apart from that of lepR, the expression of appetite-regulating genes, such as orexigenic genes, agouti-related peptide (AgRP) and neuropeptide Y (NPY), were upregulated (P < 0.01), whereas the anorexigenic gene proopiomelanocortin (POMC) was downregulated in the hypothalamic tissue of cLEPR-immunized pullets (P < 0.01). Blood concentrations of metabolic molecules, such as glucose, triglycerides, and very-low-density lipoprotein, were significantly decreased in cLEPR-immunized pullets but those of cholesterol, high-density lipoprotein, and low-density lipoprotein increased. These results demonstrate that antibodies to membrane proximal cLEPR ECD enhance cLEPR signal transduction, which stimulates metabolism and reduces fat deposition in chickens.

  6. LOCAL LUMINOUS INFRARED GALAXIES. III. CO-EVOLUTION OF BLACK HOLE GROWTH AND STAR FORMATION ACTIVITY?

    SciTech Connect

    Alonso-Herrero, Almudena; Hernan-Caballero, Antonio; Pereira-Santaella, Miguel; Rieke, George H.; Diamond-Stanic, Aleksandar M.; Wang Yiping; Rigopoulou, Dimitra

    2013-03-10

    Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of <78 Mpc). We estimate typical BH masses of 3 Multiplication-Sign 10{sup 7} M{sub Sun} using [Ne III] 15.56 {mu}m and optical [O III] {lambda}5007 gas velocity dispersions and literature stellar velocity dispersions. We find that in a large fraction of local LIRGs, the current SFR is taking place not only in the inner nuclear {approx}1.5 kpc region, as estimated from the nuclear 11.3 {mu}m PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios higher than those of optically selected Seyferts of similar active galactic nucleus (AGN) luminosities. However, the majority of the IR-bright galaxies in the revised-Shapley-Ames Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be higher in local LIRGs with the lowest SFRs. All of this suggests that in local LIRGs there is a distinct IR-bright star-forming phase taking place prior to the bulk of the current BH growth (i.e., AGN phase). The latter is reflected first as a composite and then as a Seyfert, and later as a non-LIRG optically identified Seyfert nucleus with moderate SF in its host galaxy.

  7. Creating connections to life during life-threatening illness: Creative activity experienced by elderly people and occupational therapists

    PubMed Central

    la Cour, Karen; Josephsson, Staffan; Luborsky, Mark

    2014-01-01

    Objective The aim of this study was to discover and characterize components of engagement in creative activity as occupational therapy for elderly people dealing with life-threatening illness, from the perspective of both clients and therapists. Despite a long tradition of use in clinical interventions, key questions remain little addressed concerning how and why people seek these activities and the kinds of benefits that may result. Method Qualitative interviews were conducted with 8 clients and 7 therapists participating in creative workshops using crafts at a nursing home in Sweden. Analysis of the interviews was conducted using a constant comparative method. Findings Engaging in creative activity served as a medium that enabled creation of connections to wider culture and daily life that counters consequences of terminal illness, such as isolation. Creating connections to life was depicted as the core category, carried out in reference to three subcategories: (1) a generous receptive environment identified as the foundation for engaging in creative activity; (2) unfolding creations—an evolving process; (3) reaching beyond for possible meaning horizons. Conclusion The findings suggest that the domain of creative activity can enable the creation of connections to daily life and enlarge the experience of self as an active person, in the face of uncertain life-threatening illness. Ultimately, the features that participants specify can be used to refine and substantiate the use of creative activities in intervention and general healthcare. PMID:16389735

  8. The Role of Memory Activation in Creating False Memories of Encoding Context

    PubMed Central

    Arndt, Jason

    2010-01-01

    Three experiments examined false memory for encoding context by presenting DRM themes (Deese, 1959; Roediger & McDermott, 1995) in usual-looking fonts and testing related, but unstudied, lure items in a font that was shown during encoding. In two of the experiments, testing lure items in the font used to study their associated themes increased false recognition relative to testing lure items in a font that was used to study a different lure's theme. Further, studying a larger number of associates exacerbated the influence of testing lure items in a font used to study their associated themes. Finally, testing lures in a font that was encoded many times, but was not used to present the lures' studied associates, increased lure errors more than testing lures in a font that was encoded relatively fewer times. These results favor the explanation of false recognition offered by global-matching models of recognition memory over the explanations of activation-monitoring theory and fuzzy-trace theory. PMID:20053045

  9. Vitamin C blocks inflammatory platelet-activating factor mimetics created by cigarette smoking.

    PubMed Central

    Lehr, H A; Weyrich, A S; Saetzler, R K; Jurek, A; Arfors, K E; Zimmerman, G A; Prescott, S M; McIntyre, T M

    1997-01-01

    Cigarette smoking within minutes induces leukocyte adhesion to the vascular wall and formation of intravascular leukocyte-platelet aggregates. We find this is inhibited by platelet-activating factor (PAF) receptor antagonists, and correlates with the accumulation of PAF-like mediators in the blood of cigarette smoke-exposed hamsters. These mediators were PAF-like lipids, formed by nonenzymatic oxidative modification of existing phospholipids, that were distinct from biosynthetic PAF. These PAF-like lipids induced isolated human monocytes and platelets to aggregate, which greatly increased their secretion of IL-8 and macrophage inflammatory protein-1alpha. Both events were blocked by a PAF receptor antagonist. Similarly, blocking the PAF receptor in vivo blocked smoke-induced leukocyte aggregation and pavementing along the vascular wall. Dietary supplementation with the antioxidant vitamin C prevented the accumulation of PAF-like lipids, and it prevented cigarette smoke-induced leukocyte adhesion to the vascular wall and formation of leukocyte-platelet aggregates. This is the first in vivo demonstration of inflammatory phospholipid oxidation products and it suggests a molecular mechanism coupling cigarette smoke with rapid inflammatory changes. Inhibition of PAF-like lipid formation and their intravascular sequela by vitamin C suggests a simple dietary means to reduce smoking-related cardiovascular disease. PMID:9153277

  10. Detecting planets around active stars: impact of magnetic fields on radial velocities and line bisectors

    NASA Astrophysics Data System (ADS)

    Hébrard, É. M.; Donati, J.-F.; Delfosse, X.; Morin, J.; Boisse, I.; Moutou, C.; Hébrard, G.

    2014-09-01

    Although technically challenging, detecting Earth-like planets around very low mass stars is in principle accessible to the existing velocimeters of highest radial-velocity (RV) precision. However, low-mass stars being active, they often feature dark spots and magnetic regions at their surfaces generating a noise level in RV curves (called activity jitter) that can severely limit our practical ability at detecting Earth-like planets. Whereas the impact of dark spots on RV data has been extensively studied in the literature, that of magnetic features only received little attention up to now. In this paper, we aim at quantifying the impact of magnetic fields (and the Zeeman broadening they induce) on line profiles, line bisectors and RV data. With a simple model, we quantitatively study the RV signals and bisector distortions that small magnetic regions or global magnetic dipoles can generate, especially at infrared wavelengths where the Zeeman broadening is much larger than that in the visible. We report in particular that the impact of magnetic features on line bisectors can be different from that of cool spots when the rotational broadening is comparable to or larger than the Zeeman broadening; more specifically, we find in this case that the top and bottom sections of the bisectors are anticorrelated, i.e. the opposite behaviour of what is observed for cool spots. We finally suggest new options to show and ultimately filter the impact of the magnetic activity on RV curves.

  11. PHYSICAL PROPERTIES, STAR FORMATION, AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN BALMER BREAK GALAXIES AT 0 < z < 1

    SciTech Connect

    Diaz Tello, J.; Donzelli, C.; Padilla, N.; Fujishiro, N.; Yoshikawa, T.; Hanami, H.; Hatsukade, B.

    2013-07-01

    We present a spectroscopic study with the derivation of the physical properties of 37 Balmer break galaxies, which have the necessary lines to locate them in star-forming-active galactic nuclei (AGNs) diagnostic diagrams. These galaxies span a redshift range from 0.045 to 0.93 and are somewhat less massive than similar samples of previous works. The studied sample has multiwavelength photometric data coverage from the ultraviolet to mid-infrared (MIR) Spitzer bands. We investigate the connection between star formation and AGN activity via optical, mass-excitation (MEx), and MIR diagnostic diagrams. Through optical diagrams, 31 (84%) star-forming galaxies, two (5%) composite galaxies, and three (8%) AGNs were classified, whereas from the MEx diagram only one galaxy was classified as AGN. A total of 19 galaxies have photometry available in all the IRAC/Spitzer bands. Of these, three AGN candidates were not classified as AGN in the optical diagrams, suggesting they are dusty/obscured AGNs, or that nuclear star formation has diluted their contributions. By fitting the spectral energy distribution of the galaxies, we derived the stellar masses, dust reddening E(B - V), ages, and UV star formation rates (SFRs). Furthermore, the relationship between SFR surface density ({Sigma}{sub SFR}) and stellar mass surface density per time unit ({Sigma}{sub M{sub */{tau}}}) as a function of redshift was investigated using the [O II] {lambda}3727, 3729, H{alpha} {lambda}6563 luminosities, which revealed that both quantities are larger for higher redshift galaxies. We also studied the SFR and specific SFR (SSFR) versus stellar mass and color relations, with the more massive galaxies having higher SFR values but lower SSFR values than less massive galaxies. These results are consistent with previous ones showing that, at a given mass, high-redshift galaxies have on average larger SFR and SSFR values than low-redshift galaxies. Finally, bluer galaxies have larger SSFR values than redder

  12. A Closer View of the Radio-FIR Correlation: Disentangling the Contributions of Star Formation and Active Galactic Nucleus Activity

    NASA Astrophysics Data System (ADS)

    Morić, I.; Smolčić, V.; Kimball, A.; Riechers, D. A.; Ivezić, Ž.; Scoville, N.

    2010-11-01

    We extend the Unified Radio Catalog, a catalog of sources detected by various (NVSS, FIRST, WENSS, GB6) radio surveys, and SDSS, to IR wavelengths by matching it to the IRAS Point and Faint Source catalogs. By fitting each NVSS-selected galaxy's NUV-NIR spectral energy distribution (SED) with stellar population synthesis models we add to the catalog star formation rates (SFRs), stellar masses, and attenuations. We further add information about optical emission-line properties for NVSS-selected galaxies with available SDSS spectroscopy. Using an NVSS 20 cm (F 1.4 GHz >~ 2.5 mJy) selected sample, matched to the SDSS spectroscopic ("main" galaxy and quasar) catalogs and IRAS data (0.04 < z <~ 0.2) we perform an in-depth analysis of the radio-FIR correlation for various types of galaxies, separated into (1) quasars, (2) star-forming, (3) composite, (4) Seyfert, (5) LINER, and (6) absorption line galaxies using the standard optical spectroscopic diagnostic tools. We utilize SED-based SFRs to independently quantify the source of radio and FIR emission in our galaxies. Our results show that Seyfert galaxies have FIR/radio ratios lower than, but still within the scatter of, the canonical value due to an additional (likely active galactic nucleus (AGN)) contribution to their radio continuum emission. Furthermore, IR-detected absorption and LINER galaxies are on average strongly dominated by AGN activity in both their FIR and radio emission; however their average FIR/radio ratio is consistent with that expected for star-forming galaxies. In summary, we find that most AGN-containing galaxies in our NVSS-IRAS-SDSS sample have FIR/radio flux ratios indistinguishable from those of the star-forming galaxies that define the radio-FIR correlation. Thus, attempts to separate AGNs from star-forming galaxies by their FIR/radio flux ratios alone can separate only a small fraction of the AGNs, such as the radio-loud quasars. Based on observations with the National Radio Astronomy

  13. Physical Properties, Star Formation, and Active Galactic Nucleus Activity in Balmer Break Galaxies at 0 < z < 1

    NASA Astrophysics Data System (ADS)

    Díaz Tello, J.; Donzelli, C.; Padilla, N.; Fujishiro, N.; Hanami, H.; Yoshikawa, T.; Hatsukade, B.

    2013-07-01

    We present a spectroscopic study with the derivation of the physical properties of 37 Balmer break galaxies, which have the necessary lines to locate them in star-forming-active galactic nuclei (AGNs) diagnostic diagrams. These galaxies span a redshift range from 0.045 to 0.93 and are somewhat less massive than similar samples of previous works. The studied sample has multiwavelength photometric data coverage from the ultraviolet to mid-infrared (MIR) Spitzer bands. We investigate the connection between star formation and AGN activity via optical, mass-excitation (MEx), and MIR diagnostic diagrams. Through optical diagrams, 31 (84%) star-forming galaxies, two (5%) composite galaxies, and three (8%) AGNs were classified, whereas from the MEx diagram only one galaxy was classified as AGN. A total of 19 galaxies have photometry available in all the IRAC/Spitzer bands. Of these, three AGN candidates were not classified as AGN in the optical diagrams, suggesting they are dusty/obscured AGNs, or that nuclear star formation has diluted their contributions. By fitting the spectral energy distribution of the galaxies, we derived the stellar masses, dust reddening E(B - V), ages, and UV star formation rates (SFRs). Furthermore, the relationship between SFR surface density (ΣSFR) and stellar mass surface density per time unit (\\Sigma _{M_{\\ast }/\\tau }) as a function of redshift was investigated using the [O II] λ3727, 3729, Hα λ6563 luminosities, which revealed that both quantities are larger for higher redshift galaxies. We also studied the SFR and specific SFR (SSFR) versus stellar mass and color relations, with the more massive galaxies having higher SFR values but lower SSFR values than less massive galaxies. These results are consistent with previous ones showing that, at a given mass, high-redshift galaxies have on average larger SFR and SSFR values than low-redshift galaxies. Finally, bluer galaxies have larger SSFR values than redder galaxies and for a given

  14. Rotation-Activity-Age Relations For Solar-Type And Cooler Stars

    NASA Astrophysics Data System (ADS)

    Basri, Gibor

    2016-08-01

    The fact that stellar rotation and chromospheric emission are correlated with age was explicitly noted by Wilson (1963) and reinforced by Kraft (1967). Wilson knew that Ca II emission was correlated with surface magnetic field in the Sun. Skumanich (1972) suggested a simple functional for the age-activity relation, and suggested that magnetic braking was the likely reason for the decline in activity. A theory for the rotation-activity connection was elucidated by Noyes et al. (1984), who invoked the Rossby number as important to the stellar dynamo. This calibrated the relation by convection zone depth and turnover time, although it was noted early and recently confirmed that it is not clear whether Rossby number is empirically superior to the rotation period itself in producing a clear rotation-activity relation. In fact, turnover times are hard to properly define, and the Rossby number is itself calibrated to tighten the relations. The number of stars in samples used to study this has increased dramatically, as have the diagnostics available to assess magnetic activity. It remains clear is that there is a strong relationship between magnetic activity and stellar rotation, and that magnetic braking forces both activity and rotation to decrease with age. These relations are also subject to modification as a function of stellar mass. There has recently been a great increase in the number of measured stellar rotation periods, and in the calibration of these relations using star clusters (whose ages can be independently assessed). I will summarize some of the ongoing progress on this topic.

  15. Creating Stimulating Learning and Thinking Using New Models of Activity-Based Learning and Metacognitive-Based Activities

    ERIC Educational Resources Information Center

    Pang, Katherine

    2010-01-01

    The purpose of this paper is to present a novel way to stimulate learning, creativity, and thinking based on a new understanding of activity-based learning (ABL) and two methods for developing metacognitive-based activities for the classroom. ABL, in this model, is based on the premise that teachers are distillers and facilitators of information…

  16. The SpaceInn-SISMA Database: Characterization of a Large Sample of Variable and Active Stars by Means of Harps Spectra

    NASA Astrophysics Data System (ADS)

    Rainer, M.; Poretti, E.; Mistò, A.; Panzera, M. R.; Molinaro, M.; Cepparo, F.; Roth, M.; Michel, E.; Monteiro, M. J. P. F. G.

    2016-12-01

    We created a large database of physical parameters and variability indicators by fully reducing and analyzing the large number of spectra taken to complement the asteroseismic observations of the COnvection, ROtation and planetary Transits (CoRoT) satellite. 7103 spectra of 261 stars obtained with the ESO echelle spectrograph HARPS have been stored in the VO-compliant database Spectroscopic Indicators in a SeisMic Archive (SISMA), along with the CoRoT photometric data of the 72 CoRoT asteroseismic targets. The remaining stars belong to the same variable classes of the CoRoT targets and were observed to better characterize the properties of such classes. Several useful variability indicators (mean line profiles, indices of differential rotation, activity and emission lines) together with v\\sin i and radial-velocity measurements have been extracted from the spectra. The atmospheric parameters {T}{eff},{log}g, and [Fe/H] have been computed following a homogeneous procedure. As a result, we fully characterize a sample of new and known variable stars by computing several spectroscopic indicators, also providing some cases of simultaneous photometry and spectroscopy.

  17. The Evolution of Accretion and Activity Signatures in Young A Stars

    NASA Astrophysics Data System (ADS)

    Williger, G. M.; Grady, C. A.; Hamaguchi, K.; Hubrig, S.; Bouret, J.-C.; Roberge, A.; Sahu, M.; Woodgate, B.; Kimble, R.

    2005-12-01

    FUV spectroscopy obtained with FUSE reveals excess continuum light in 12 lightly reddened Herbig Ae stars, as well as the routine presence of emission in a range of ionization stages sampling material from neutral atomic gas to transition region temperature plasma. The FUV excess light is correlated with the near IR colors of the stars which has previously been noted as a tracer of mass accretion rate. In several cases, sufficient data exist to demonstrate that FUV continuum variability is present and is correlated with changes in the FUV emission lines, particularly red-shifted material. Combining the FUV spectra with disk inclination data, we find that the red-shifted C III 1176 emission is seen for inclinations between 0 and 60 degrees with no dependence upon inclination in that range, as expected for funneled accretion scenarios. The FUV excess light and X-ray luminosity show the same evolutionary trend, dropping gradually over the 1st 10 Myr as long as the star is accreting material from the disk. Centrally-cleared A debris disk systems have X-ray luminosities which are at least 3 orders of magnitude fainter than the Herbig Ae stars, demonstrating that the X-ray emission is related to accretion and not to more conventional stellar activity. Plasma at transition region and chromospheric temperatures persists longer, at least in some systems. Recent magnetic field detections for 5 of the FUSE Herbig Ae stars and Beta Pictoris indicate that magnetic fields with typical field strengths of 50 to several hundred Gauss are present over the entire age range where the accretion signatures are seen. This study is based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985. Data included in this study were obtained under FUSE GO Programs C126, D065, and the FUSE Legacy program E510. HST observations of HD 163296 and HD 104237 were obtained under HST

  18. Star Formation and AGN activity of X-ray selected AGN host galaxies in the Chandra-COSMOS Legacy Survey

    NASA Astrophysics Data System (ADS)

    Suh, Hyewon

    2017-01-01

    One of the ongoing issues for understanding the galaxy formation and evolution is how active galactic nuclei (AGNs) affect the growth of their host galaxies. We investigate the correlations between AGN activity and star formation properties of a large sample of ~3700 X-ray selected AGNs over a wide range of luminosities (42 < log Lx < 45) up to z~5 in the Chandra-COSMOS Legacy Survey. We perform a multi-component modeling from the far-infrared, when available, to the near-UV using AGN emission from the big-blue-bump (for Type 1 AGNs), a nuclear dust torus model, a galaxy model and a starburst component for the spectral energy distributions (SEDs). Through detailed analysis of SEDs, we derive AGN host galaxy properties, such as stellar masses, star formation rates (SFRs), and AGN luminosities. We find that AGN host galaxies have, on average, similar SFRs compared to the normal star-forming main sequence galaxies, suggesting no significant enhancement or quenching of star formation. The average SFR of AGN host galaxies shows a flat distribution in bins of AGN luminosity, consistent with recent ideas that the shorter variability timescale of AGN compared to star formation can lead to a flat relationship between the SFR and black hole accretion rates. Our results suggest that both star formation and nuclear activity in the majority of AGN host galaxies might be driven more by internal secular processes at z<3, implying that they have substantially grown at much earlier epoch.

  19. A THEORY ON THE CONVECTIVE ORIGINS OF ACTIVE LONGITUDES ON SOLAR-LIKE STARS

    SciTech Connect

    Weber, Maria A.; Fan Yuhong; Miesch, Mark S.

    2013-06-20

    Using a thin flux tube model in a rotating spherical shell of turbulent, solar-like convective flows, we find that the distribution of emerging flux tubes in our simulation is inhomogeneous in longitude, with properties similar to those of active longitudes on the Sun and other solar-like stars. The large-scale pattern of flux emergence our simulations produce exhibits preferred longitudinal modes of low order, drift with respect to a fixed reference system, and alignment across the equator at low latitudes between {+-}15 Degree-Sign . We suggest that these active-longitude-like emergence patterns are the result of columnar, rotationally aligned giant cells present in our convection simulation at low latitudes. If giant convecting cells exist in the bulk of the solar convection zone, this phenomenon, along with differential rotation, could in part provide an explanation for the behavior of active longitudes.

  20. Hide and Seek: Radial-Velocity Searches for Planets around Active Stars

    NASA Astrophysics Data System (ADS)

    Haywood, Raphaëlle Dawn

    2015-11-01

    The detection of low-mass extra-solar planets through radial-velocity searches is currently limited by the intrinsic magnetic activity of the host stars. The correlated noise that arises from their natural radial-velocity variability can easily mimic or conceal the orbital signals of super-Earth and Earth-mass extra-solar planets. I developed an intuitive and robust data analysis framework in which the activity-induced variations are modelled with a Gaussian process that has the frequency structure of the photometric variations of the star, thus allowing me to determine precise and reliable planetary masses. I applied this technique to three recently discovered planetary systems: CoRoT-7, Kepler-78 and Kepler-10. I determined the masses of the transiting super-Earth CoRoT-7b and the small Neptune CoRoT-7c to be 4.73 ± 0.95 M⊕ and 13.56 ± 1.08 M⊕, respectively. The density of CoRoT-7b is 6.61 ± 1.72 g.cm-3, which is compatible with a rocky composition. I carried out Bayesian model selection to assess the nature of a previously identified signal at 9 days, and found that it is best interpreted as stellar activity. Despite the high levels of activity of its host star, I determined the mass of the Earth-sized planet Kepler-78b to be 1.76 ± 0.18 M⊕. With a density of 6.2(+1.8:-1.4) g.cm-3, it is also a rocky planet. I found the masses of Kepler-10b and Kepler-10c to be 3.31 ± 0.32 M⊕ and 16.25 ± 3.66 M⊕, respectively. Their densities, of 6.4(+1.1:-0.7) g.cm-3 and 8.1 ± 1.8 g.cm-3, imply that they are both of rocky composition - even the 2 Earth-radius planet Kepler-10c! In parallel, I deepened our understanding of the physical origin of stellar radial-velocity variability through the study of the Sun, which is the only star whose surface can be imaged at high resolution. I found that the full-disc magnetic flux is an excellent proxy for activity-induced radial-velocity variations; this result may become key to breaking the activity barrier in coming

  1. Chromospheric activity and lithium line variations in the spectra of the spotted star LQ Hydrae

    NASA Astrophysics Data System (ADS)

    Flores Soriano, M.; Strassmeier, K. G.; Weber, M.

    2015-03-01

    Context. Although the relationship between lithium abundance in stars and their magnetic activity is commonly accepted, it is still unclear how the different phenomena related to it can increase the amount of Li, reduce its depletion, or be a source of bias for the measurements. Aims: We study the rotational modulation of chromospheric and photospheric parameters of the young, active, single K2 dwarf LQ Hya and their connection with the variability of the Li i 6708 Å line. Methods: A total of 199 high-resolution STELLA spectra and quasi-simultaneous photometry were used to compute effective temperature, gravity, and chromospheric activity indicators such as Hα and Hβ emission, Balmer decrement, and chromospheric electron density, as a function of the rotational phase. The variation of the Li i 6708 Å line was characterized in terms of equivalent width, abundance, and of 6Li/7Li isotopic ratio in the form of line shifts. Results: Photospheric and chromospheric parameters show clear rotational modulation. Effective temperatures and continuum variations reveal a higher concentration of cool spots on the side of the star on which we also detect stronger chromospheric activity. Increased electron densities and the modulation of the He i D3 line suggest that the source of this activity can be a combination of plages and repeated low-intensity flares. The Li line and other temperature-sensitive lines are clearly enhanced by the spots located on the most active side of the star. Li abundances calculated taking into account the temperature variations simultaneously show, although with high dispersion, a small overabundance of this element that correlates well with the surface magnetic activity. In addition, the Li line center is more intensely redshifted than in the other hemisphere, which might be interpreted as a weak enrichment of 6Li. Based on data obtained with the STELLA robotic telescope in Tenerife, an AIP facility jointly operated by AIP and IAC, and the Vienna

  2. DO MOST ACTIVE GALACTIC NUCLEI LIVE IN HIGH STAR FORMATION NUCLEAR CUSPS?

    SciTech Connect

    Mushotzky, Richard F.; Shimizu, T. Taro; Meléndez, Marcio; Koss, Michael

    2014-02-01

    We present early results of the Herschel PACS (70 and 160 μm) and SPIRE (250, 350, and 500 μm) survey of 313 low redshift (z < 0.05), ultra-hard X-ray (14-195 keV) selected active galactic nuclei (AGNs) from the 58 month Swift/Burst Alert Telescope catalog. Selection of AGNs from ultra-hard X-rays avoids bias from obscuration, providing a complete sample of AGNs to study the connection between nuclear activity and star formation in host galaxies. With the high angular resolution of PACS, we find that >35% and >20% of the sources are ''point-like'' at 70 and 160 μm respectively and many more have their flux dominated by a point source located at the nucleus. The inferred star formation rates (SFRs) of 0.1-100 M {sub ☉} yr{sup –1} using the 70 and 160 μm flux densities as SFR indicators are consistent with those inferred from Spitzer Ne II fluxes, but we find that 11.25 μm polycyclic aromatic hydrocarbon data give ∼3× lower SFR. Using GALFIT to measure the size of the far-infrared emitting regions, we determined the SFR surface density (M {sub ☉} yr{sup –1} kpc{sup –2}) for our sample, finding that a significant fraction of these sources exceed the threshold for star formation driven winds (0.1 M {sub ☉} yr{sup –1} kpc{sup –2})

  3. HATS-2b: A transiting extrasolar planet orbiting a K-type star showing starspot activity

    NASA Astrophysics Data System (ADS)

    Mohler-Fischer, M.; Mancini, L.; Hartman, J. D.; Bakos, G. Á.; Penev, K.; Bayliss, D.; Jordán, A.; Csubry, Z.; Zhou, G.; Rabus, M.; Nikolov, N.; Brahm, R.; Espinoza, N.; Buchhave, L. A.; Béky, B.; Suc, V.; Csák, B.; Henning, T.; Wright, D. J.; Tinney, C. G.; Addison, B. C.; Schmidt, B.; Noyes, R. W.; Papp, I.; Lázár, J.; Sári, P.; Conroy, P.

    2013-10-01

    We report the discovery of HATS-2b, the second transiting extrasolar planet detected by the HATSouth survey. HATS-2b is moving on a circular orbit around a V = 13.6 mag, K-type dwarf star (GSC 6665-00236), at a separation of 0.0230 ± 0.0003 AU and with a period of 1.3541 days. The planetary parameters have been robustly determined using a simultaneous fit of the HATSouth, MPG/ESO 2.2 m/GROND, Faulkes Telescope South/Spectral transit photometry, and MPG/ESO 2.2 m/FEROS, Euler 1.2 m/CORALIE, AAT 3.9 m/CYCLOPS radial-velocity measurements. HATS-2b has a mass of 1.37 ± 0.16 MJ, a radius of 1.14 ± 0.03 RJ, and an equilibrium temperature of 1567 ± 30 K. The host star has a mass of 0.88 ± 0.04 M⊙ and a radius of 0.89 ± 0.02 R⊙, and it shows starspot activity. We characterized the stellar activity by analyzing two photometric follow-up transit light curves taken with the GROND instrument, both obtained simultaneously in four optical bands (covering the wavelength range of 3860-9520 Å). The two light curves contain anomalies compatible with starspots on the photosphere of the host star along the same transit chord. Tables of the individual photometric measurements are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/558/A55

  4. Relations Between He I λ10830 Absorption Strength and Stellar Activity Amongst Dwarf Stars

    NASA Astrophysics Data System (ADS)

    Smith, Graeme H.

    2016-11-01

    Correlations are identified between the strength of the λ10830 He I triplet line and the following tracers of stellar activity amongst FGK dwarfs with colours of (B - V) > 0.47: coronal soft X-ray emission, emission in the λ1549 C IV and λ1335 C II lines originating from the transition region, and Ca II H and K emission from the chromosphere. No such correlations are present amongst dwarfs with spectral type earlier than F6. In addition, G and K dwarfs with strong triplet lines show evidence of excess flux in the GALEX FUV band compared to weak-triplet-line dwarfs. The X-ray spectra of late-F, G, and K dwarfs with He I triplets stronger than 160 mÅ have greater values of the ROSAT hardness ratio HR1 than are typical of weak-triplet dwarfs in the same range of spectral type. In other words, dwarfs later than F7V with strong He I triplet lines tend towards harder 0.1-2.0 keV X-ray spectra than weak-triplet dwarfs, although values of HR1 -0.2 to +0.1 can still be encountered amongst a minority of weak-He-triplet stars. As regards, FGK main sequence stars the observational data on the λ10830 triplet line remains sparse. Progress could be made through spectroscopy of high resolution for samples of hundreds of stars, selected on the basis of having other measures of chromospheric and coronal activity available.

  5. STRONG VARIABLE ULTRAVIOLET EMISSION FROM Y GEM: ACCRETION ACTIVITY IN AN ASYMPTOTIC GIANT BRANCH STAR WITH A BINARY COMPANION?

    SciTech Connect

    Sahai, Raghvendra; Neill, James D.; Gil de Paz, Armando; Sanchez Contreras, Carmen

    2011-10-20

    Binarity is believed to dramatically affect the history and geometry of mass loss in asymptotic giant branch (AGB) and post-AGB stars, but observational evidence of binarity is sorely lacking. As part of a project to look for hot binary companions to cool AGB stars using the Galaxy Evolution Explorer archive, we have discovered a late-M star, Y Gem, to be a source of strong and variable UV emission. Y Gem is a prime example of the success of our technique of UV imaging of AGB stars in order to search for binary companions. Y Gem's large and variable UV flux makes it one of the most prominent examples of a late-AGB star with a mass accreting binary companion. The UV emission is most likely due to emission associated with accretion activity and a disk around a main-sequence companion star. The physical mechanism generating the UV emission is extremely energetic, with an integrated luminosity of a few x L{sub sun} at its peak. We also find weak CO J = 2-1 emission from Y Gem with a very narrow line profile (FWHM of 3.4 km s{sup -1}). Such a narrow line is unlikely to arise in an outflow and is consistent with emission from an orbiting, molecular reservoir of radius 300 AU. Y Gem may be the progenitor of the class of post-AGB stars which are binaries and possess disks but no outflows.

  6. RADIO OBSERVATIONS OF THE STAR FORMATION ACTIVITIES IN THE NGC 2024 FIR 4 REGION

    SciTech Connect

    Choi, Minho; Kang, Miju; Lee, Jeong-Eun

    2015-07-15

    Star formation activities in the NGC 2024 FIR 4 region were studied by imaging centimeter continuum sources and water maser sources using several archival data sets from the Very Large Array. The continuum source VLA 9 is elongated in the northwest–southeast direction, consistent with the FIR 4 bipolar outflow axis, and has a flat spectrum in the 6.2–3.6 cm interval. The three water maser spots associated with FIR 4 are also distributed along the outflow axis. One of the spots is located close to VLA 9, and another one is close to an X-ray source. Examinations of the positions of compact objects in this region suggest that the FIR 4 cloud core contains a single low-mass protostar. VLA 9 is the best indicator of the protostellar position. VLA 9 may be a radio thermal jet driven by this protostar, and it is unlikely that FIR 4 contains a high-mass young stellar object (YSO). A methanol 6.7 GHz maser source is located close to VLA 9, at a distance of about 100 AU. The FIR 4 protostar must be responsible for the methanol maser action, which suggests that methanol class II masers are not necessarily excited by high-mass YSOs. Also discussed are properties of other centimeter continuum sources in the field of view and the water masers associated with FIR 6n. Some of the continuum sources are radio thermal jets, and some are magnetically active young stars.

  7. WIDESPREAD AND HIDDEN ACTIVE GALACTIC NUCLEI IN STAR-FORMING GALAXIES AT REDSHIFT >0.3

    SciTech Connect

    Juneau, Stephanie; Bournaud, Frederic; Daddi, Emanuele; Elbaz, David; Alexander, David M.; Mullaney, James R.; Magnelli, Benjamin; Hwang, Ho Seong; Willner, S. P.; Coil, Alison L.; Rosario, David J.; Trump, Jonathan R.; Faber, S. M.; Kocevski, Dale D.; Cooper, Michael C.; Frayer, David T.; and others

    2013-02-20

    We characterize the incidence of active galactic nuclei (AGNs) in 0.3 < z < 1 star-forming galaxies by applying multi-wavelength AGN diagnostics (X-ray, optical, mid-infrared, radio) to a sample of galaxies selected at 70 {mu}m from the Far-Infrared Deep Extragalactic Legacy survey (FIDEL). Given the depth of FIDEL, we detect 'normal' galaxies on the specific star formation rate (sSFR) sequence as well as starbursting systems with elevated sSFR. We find an overall high occurrence of AGN of 37% {+-} 3%, more than twice as high as in previous studies of galaxies with comparable infrared luminosities and redshifts but in good agreement with the AGN fraction of nearby (0.05 < z < 0.1) galaxies of similar infrared luminosities. The more complete census of AGNs comes from using the recently developed Mass-Excitation (MEx) diagnostic diagram. This optical diagnostic is also sensitive to X-ray weak AGNs and X-ray absorbed AGNs, and reveals that absorbed active nuclei reside almost exclusively in infrared-luminous hosts. The fraction of galaxies hosting an AGN appears to be independent of sSFR and remains elevated both on the sSFR sequence and above. In contrast, the fraction of AGNs that are X-ray absorbed increases substantially with increasing sSFR, possibly due to an increased gas fraction and/or gas density in the host galaxies.

  8. Egyptian "Star Clocks"

    NASA Astrophysics Data System (ADS)

    Symons, Sarah

    Diagonal, transit, and Ramesside star clocks are tables of astronomical information occasionally found in ancient Egyptian temples, tombs, and papyri. The tables represent the motions of selected stars (decans and hour stars) throughout the Egyptian civil year. Analysis of star clocks leads to greater understanding of ancient Egyptian constellations, ritual astronomical activities, observational practices, and pharaonic chronology.

  9. Thermally activated post-glitch response of the neutron star inner crust and core. I. Theory

    SciTech Connect

    Link, Bennett

    2014-07-10

    Pinning of superfluid vortices is predicted to prevail throughout much of a neutron star. Based on the idea of Alpar et al., I develop a description of the coupling between the solid and liquid components of a neutron star through thermally activated vortex slippage, and calculate the response to a spin glitch. The treatment begins with a derivation of the vortex velocity from the vorticity equations of motion. The activation energy for vortex slippage is obtained from a detailed study of the mechanics and energetics of vortex motion. I show that the 'linear creep' regime introduced by Alpar et al. and invoked in fits to post-glitch response is not realized for physically reasonable parameters, a conclusion that strongly constrains the physics of a post-glitch response through thermal activation. Moreover, a regime of 'superweak pinning', crucial to the theory of Alpar et al. and its extensions, is probably precluded by thermal fluctuations. The theory given here has a robust conclusion that can be tested by observations: for a glitch in the spin rate of magnitude Δν, pinning introduces a delay in the post-glitch response time. The delay time is t{sub d} = 7(t{sub sd}/10{sup 4} yr)((Δν/ν)/10{sup –6}) d, where t{sub sd} is the spin-down age; t{sub d} is typically weeks for the Vela pulsar and months in older pulsars, and is independent of the details of vortex pinning. Post-glitch response through thermal activation cannot occur more quickly than this timescale. Quicker components of post-glitch response, as have been observed in some pulsars, notably, the Vela pulsar, cannot be due to thermally activated vortex motion but must represent a different process, such as drag on vortices in regions where there is no pinning. I also derive the mutual friction force for a pinned superfluid at finite temperature for use in other studies of neutron star hydrodynamics.

  10. An evolutionary model for collapsing molecular clouds and their star formation activity. II. Mass dependence of the star formation rate

    SciTech Connect

    Zamora-Avilés, Manuel; Vázquez-Semadeni, Enrique

    2014-10-01

    We discuss the evolution and dependence on cloud mass of the star formation rate (SFR) and efficiency (SFE) of star-forming molecular clouds (MCs) within the scenario that clouds are undergoing global collapse and that the SFR is controlled by ionization feedback. We find that low-mass clouds (M {sub max} ≲ 10{sup 4} M {sub ☉}) spend most of their evolution at low SFRs, but end their lives with a mini-burst, reaching a peak SFR ∼10{sup 4} M {sub ☉} Myr{sup –1}, although their time-averaged SFR is only (SFR) ∼ 10{sup 2} M {sub ☉} Myr{sup –1}. The corresponding efficiencies are SFE{sub final} ≲ 60% and (SFE) ≲ 1%. For more massive clouds (M {sub max} ≳ 10{sup 5} M {sub ☉}), the SFR first increases and then reaches a plateau because the clouds are influenced by stellar feedback since earlier in their evolution. As a function of cloud mass, (SFR) and (SFE) are well represented by the fits (SFR) ≈ 100(1 + M {sub max}/1.4 × 10{sup 5} M {sub ☉}){sup 1.68} M {sub ☉} Myr{sup –1} and (SFE) ≈ 0.03(M {sub max}/2.5 × 10{sup 5} M {sub ☉}){sup 0.33}, respectively. Moreover, the SFR of our model clouds follows closely the SFR-dense gas mass relation recently found by Lada et al. during the epoch when their instantaneous SFEs are comparable to those of the clouds considered by those authors. Collectively, a Monte Carlo integration of the model-predicted SFR(M) over a Galactic giant molecular cloud mass spectrum yields values for the total Galactic SFR that are within half an order of magnitude of the relation obtained by Gao and Solomon. Our results support the scenario that star-forming MCs may be in global gravitational collapse and that the low observed values of the SFR and SFE are a result of the interruption of each SF episode, caused primarily by the ionizing feedback from massive stars.

  11. A NEW MULTI-BAND RADIAL VELOCITY TECHNIQUE FOR DETECTING EXOPLANETS AROUND ACTIVE STARS

    SciTech Connect

    Ma Bo; Ge Jian E-mail: jge@astrto.ufl.edu

    2012-05-10

    The radial velocity (RV) technique is one of the most efficient ways of detecting exoplanets. However, large RV jitters induced by starspots on an active star can inhibit detection of any exoplanet present or even lead to a false positive detection. This paper presents a new multi-band RV technique capable of substantially reducing starspot-induced RV jitters from stellar RV measurements to allow efficient and accurate extraction of RV signals caused by exoplanets. It takes full advantage of the correlation of RV jitters at different spectral bands and the independence of exoplanet signals at the corresponding bands. Simulations with a single-spot model and a multi-spot model have been conducted to investigate the RV jitter reduction capability of this method. The results show that this method can reduce the RV jitter amplitude by at least an order of magnitude, allowing detection of weaker exoplanet signals without significantly increasing RV observation time and cadence. This method can greatly reduce the observation time required to detect Earth-like planets around solar type stars with {approx}0.1 m s{sup -1} long term Doppler precision if spot-induced jitter is the dominant astrophysical noise source for RV measurements. This method can work efficiently for RV jitter removal if: (1) all the spots on a target star have approximately the same temperature during RV observations; (2) the RV jitter amplitude changes with wavelength, i.e., the RV jitter amplitude ratio, {alpha}, between two different spectral bands is not close to one; (3) the spot-induced RV jitter dominates the RV measurement error.

  12. Zeeman-Doppler imaging of active young solar-type stars

    NASA Astrophysics Data System (ADS)

    Hackman, T.; Lehtinen, J.; Rosén, L.; Kochukhov, O.; Käpylä, M. J.

    2016-03-01

    Context. By studying young magnetically active late-type stars, i.e. analogues to the young Sun, we can draw conclusions on the evolution of the solar dynamo. Aims: We determine the topology of the surface magnetic field and study the relation between the magnetic field and cool photospheric spots in three young late-type stars. Methods: High-resolution spectropolarimetry of the targets was obtained with the HARPSpol instrument mounted at the ESO 3.6 m telescope. The signal-to-noise ratios of the Stokes IV measurements were boosted by combining the signal from a large number of spectroscopic absorption lines through the least squares deconvolution technique. Surface brightness and magnetic field maps were calculated using the Zeeman-Doppler imaging technique. Results: All three targets show clear signs of magnetic fields and cool spots. Only one of the targets, V1358 Ori, shows evidence of the dominance of non-axisymmetric modes. In two of the targets, the poloidal field is significantly stronger than the toroidal one, indicative of an α2-type dynamo, in which convective turbulence effects dominate over the weak differential rotation. In two of the cases there is a slight anti-correlation between the cool spots and the strength of the radial magnetic field. However, even in these cases the correlation is much weaker than in the case of sunspots. Conclusions: The weak correlation between the measured radial magnetic field and cool spots may indicate a more complex magnetic field structure in the spots or spot groups involving mixed magnetic polarities. Comparison with a previously published magnetic field map shows that on one of the stars, HD 29615, the underlying magnetic field changed its polarity between 2009 and 2013. Based on observations made with the HARPSpol instrument on the ESO 3.6 m telescope at La Silla (Chile), under the program ID 091.D-0836.

  13. Mechanisms for quenching star formation activities in green valley galaxies and its depends on morphologies

    NASA Astrophysics Data System (ADS)

    Kong, Xu; Pan, Zhizheng; Lian, Jianhui

    2015-08-01

    Galaxies are categorized into two main populations, red quiescent galaxies and blue star-forming galaxies. One of the key questions is which physical mechanisms are responsible for quenching star formation activities in blue galaxies and the resulting transformation? In this talk, we present research on the morphologies, spectra, and environments of "green valley" galaxies in the COSMOS field and low redshift "green valley" galaxies in SDSS. Our findings suggest that environmental conditions, most likely starvation and harassment, significantly affect the transformation of M* < 10^10.0 Msun blue galaxies into red galaxies, especially at z < 0.5. Using image from SDSS and GALEX, we analyze the radial ultraviolet-optical color distributions in a sample of low redshift green valley galaxies, and investigate how quenching is processing in a galaxy. The early-type "green valley" galaxies (ETGs) have dramatically different radial NUV-r color distributions compared to late-type "green valley" galaxies (LTGs), most of ETGs have blue cores, nearly all LTGs have uniform color profiles that can be well-interpreted as red bulges plus blue disk components. These results suggest that the LTGs follow a general model by which quenching first occurs in the core regions, and then finally extend to the rest of the galaxy; for ETGs, their star formations are centrally concentrated. Our results can be re-examined and have important implications for the IFU surveys, such as MaNGA and SAMI (2013ApJ...776...14P, 2014ApJ...792L...4P, 2015MNRAS.446.1449L).

  14. VizieR Online Data Catalog: Stellar activity and kinematics of FGK stars (Murgas+, 2013)

    NASA Astrophysics Data System (ADS)

    Murgas, F.; Jenkins, J. S.; Rojo, P.; Jones, H. R. A.; Pinfield, D. J.

    2013-02-01

    We present a compilation of stellar activity catalogs combined with galactic velocity information of 2529 F, G, and K stars. The stellar activity catalogs use in this work are: Jenkins et al. 2011 (Cat. J/A+A/531/A8); Gray et al. 2003 (Cat. J/AJ/126/2048), 2006 (Cat. J/AJ/132/161); Henry et al 1996 (Cat. J/A+A/111/439); Wright et al. 2004 (Cat. J/ApJS/152/261); Duncan et al. (1991ApJS...76..383D, Cat. III/159). The galactic velocities are taken from the Jenkins et al. 2011 (Cat. J/A+A/531/A8) and the Geneva-Copenhaguen Survey (GCS) Nordstrom et al. (2004A&A...418..989N, Cat. V/117). (1 data file).

  15. Chromospherically active stars. 13: HD 30957: A double lined K dwarf binary

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Dadonas, Virgilijus; Sperauskas, Julius; Vaccaro, Todd R.; Patterson, L. Ronald

    1994-01-01

    HD 30957 is a double-lined spectroscopic binary with a period of 44.395 days and a modest eccentricity of 0.09. The spectral types of the components are K2-3 V and K5 V. The measured v sin i for both components is less than or equal to 3 km/s and the orbital inclination is estimated to be 69 deg. The system is relatively nearby with a parallax of 0.025 sec or a distance of 40 pc. Space motions of the system indicate that it does not belong to any of the known moving groups. Absolute surface fluxes of the Ca II H and K lines have been recomputed and indicate only modest chromospheric activity. If the stars are rotating pseudosynchronously, the lack of light variability is consistent with the value of the critical Rossby number for starspot activity.

  16. The Sedentary Time and Activity Reporting Questionnaire (STAR-Q): reliability and validity against doubly labeled water and 7-day activity diaries.

    PubMed

    Csizmadi, Ilona; Neilson, Heather K; Kopciuk, Karen A; Khandwala, Farah; Liu, Andrew; Friedenreich, Christine M; Yasui, Yutaka; Rabasa-Lhoret, Rémi; Bryant, Heather E; Lau, David C W; Robson, Paula J

    2014-08-15

    We determined measurement properties of the Sedentary Time and Activity Reporting Questionnaire (STAR-Q), which was designed to estimate past-month activity energy expenditure (AEE). STAR-Q validity and reliability were assessed in 102 adults in Alberta, Canada (2009-2011), who completed 14-day doubly labeled water (DLW) protocols, 7-day activity diaries on day 15, and the STAR-Q on day 14 and again at 3 and 6 months. Three-month reliability was substantial for total energy expenditure (TEE) and AEE (intraclass correlation coefficients of 0.84 and 0.73, respectively), while 6-month reliability was moderate. STAR-Q-derived TEE and AEE were moderately correlated with DLW estimates (Spearman's ρs of 0.53 and 0.40, respectively; P < 0.001), and on average, the STAR-Q overestimated TEE and AEE (median differences were 367 kcal/day and 293 kcal/day, respectively). Body mass index-, age-, sex-, and season-adjusted concordance correlation coefficients (CCCs) were 0.24 (95% confidence interval (CI): 0.07, 0.36) and 0.21 (95% CI: 0.11, 0.32) for STAR-Q-derived versus DLW-derived TEE and AEE, respectively. Agreement between the diaries and STAR-Q (metabolic equivalent-hours/day) was strongest for occupational sedentary time (adjusted CCC = 0.76, 95% CI: 0.64, 0.85) and overall strenuous activity (adjusted CCC = 0.64, 95% CI: 0.49, 0.76). The STAR-Q demonstrated substantial validity for estimating occupational sedentary time and strenuous activity and fair validity for ranking individuals by AEE.

  17. Photospheric Activity in Selected Be STARS: lambda Eri and gamma Cas

    NASA Technical Reports Server (NTRS)

    Smith, Myron A.

    1994-01-01

    Recent observations of rapid variations in optical He I lines, X-rays, and FUV wavelengths in the prototypical classical Be stars lambda Eri and star gamma Cas hint that the violent processes occur on the surfaces of these stars almost all the time. We suggest that of these phenomena show greater similarities with magnetic flaring than any other process through to occur on stars.

  18. Magnetic activity and differential rotation in the very young star KIC 8429280

    NASA Astrophysics Data System (ADS)

    Frasca, A.; Fröhlich, H.-E.; Bonanno, A.; Catanzaro, G.; Biazzo, K.; Molenda-Żakowicz, J.

    2011-08-01

    Aims: We present a spectroscopic and photometric analysis of the rapid rotator KIC 8429280, discovered by ourselves as a very young star and observed by the NASA Kepler mission, designed to determine its activity level, spot distribution, and differential rotation. Methods: We use ground-based data, such as high-resolution spectroscopy and multicolor broad-band photometry, to derive stellar parameters (vsini, spectral type, Teff, log g, and [Fe/H]), and we adopt a spectral subtraction technique to highlight the strong chromospheric emission in the cores of hydrogen Hα and Ca ii H&K and infrared triplet (IRT) lines. We then fit a robust spot model to the high-precision Kepler photometry spanning 138 days. Model selection and parameter estimation is performed in a Bayesian manner using a Markov chain Monte Carlo method. Results: We find that KIC 8429280 is a cool (K2 V) star with an age of about 50 Myr, based on its lithium content, that has passed its T Tau phase and is spinning up approaching the ZAMS on its radiative track. Its high level of chromospheric activity is clearly indicated by the strong radiative losses in Ca ii H&K and IRT, Hα, and Hβ lines. Furthermore, its Balmer decrement and the flux ratio of Ca ii IRT lines imply that these lines are mainly formed in optically-thick regions similar to solar plages. The analysis of the Kepler data uncovers evidence of at least seven enduring spots. Since the star's inclination is rather high - nearly 70° - the assignment of the spots to either the northern or southern hemisphere is not unambiguous. We find at least three solutions with nearly the same level of residuals. Even in the case of seven spots, the fit is far from being perfect. Owing to the exceptional precision of the Kepler photometry, it is not possible to reach the noise floor without strongly enhancing the degrees of freedom and, consequently, the non-uniqueness of the solution. The distribution of the active regions is such that the spots are

  19. Relativistic jet activity from the tidal disruption of a star by a massive black hole.

    PubMed

    Burrows, D N; Kennea, J A; Ghisellini, G; Mangano, V; Zhang, B; Page, K L; Eracleous, M; Romano, P; Sakamoto, T; Falcone, A D; Osborne, J P; Campana, S; Beardmore, A P; Breeveld, A A; Chester, M M; Corbet, R; Covino, S; Cummings, J R; D'Avanzo, P; D'Elia, V; Esposito, P; Evans, P A; Fugazza, D; Gelbord, J M; Hiroi, K; Holland, S T; Huang, K Y; Im, M; Israel, G; Jeon, Y; Jeon, Y-B; Jun, H D; Kawai, N; Kim, J H; Krimm, H A; Marshall, F E; P Mészáros; Negoro, H; Omodei, N; Park, W-K; Perkins, J S; Sugizaki, M; Sung, H-I; Tagliaferri, G; Troja, E; Ueda, Y; Urata, Y; Usui, R; Antonelli, L A; Barthelmy, S D; Cusumano, G; Giommi, P; Melandri, A; Perri, M; Racusin, J L; Sbarufatti, B; Siegel, M H; Gehrels, N

    2011-08-24

    Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.

  20. A Large Sample of Magnetically-Active Stars Observed With Kepler

    NASA Astrophysics Data System (ADS)

    Wells, Mark; Neff, J. E.; Brown, A.; Ayres, T. R.; Basri, G. S.; Berdyugina, S.; Harper, G.; Hawley, S. L.; Korhonen, H.; Kowalski, A.; Micela, G.; Piskunov, N. E.; Ramsey, L. W.; Saar, S. H.; Walkowicz, L. M.

    2013-01-01

    We have observed about 325 stars in our Kepler Guest Observer programs (Cycles 1 through 4). For most of these targets, we are analyzing extremely high-precision light curves that have been continuously sampled every 30 minutes for up to 3 years. Our sample of candidate magnetically-active stars was selected primarily using GALEX colors. Starspots, pulsations, and variations due to eclipsing and contact binaries combine to produce a rich variety of light curves. We have developed semi-automated procedures to characterize this variability and thus to classify the targets and identify the physical mechanisms that dominate their Kepler light curves. We will describe these procedures and discuss the range of physical properties covered by our final classification scheme. We are using this Kepler database of variability over timescales of minutes to years to provide diagnostics of flares, starspot formation, evolution, migration, and ultimately of stellar cycles in general. This work contains results obtained using the NASA Kepler satellite and from the Apache Point Observatory, the MMT (using NOAO community access time), and the Hobby-Eberly Telescope. Funding is provided by NASA Kepler grants NNX10AC51G, NNX11AC79G, and NNX12AC85G to the University of Colorado, by NSF grant AST-1109695 to the College of Charleston, and by a grant from the South Carolina Space Grant consortium.

  1. Plasma Jet Motion Across the Geomagnetic Field in the ``North Star'' Active Geophysical Experiment

    NASA Astrophysics Data System (ADS)

    Gavrilov, B. G.; Zetzer, J. I.; Podgorny, I. M.; Sobyanin, D. B.; Meng, C.-I.; Erlandson, R. E.; Stenbaek-Nielsen, H. C.; Pfaff, R. F.; Lynch, K. A.

    2003-01-01

    The active geophysical rocket experiment ``North Star'' was carried out in the auroral ionosphere on January 22, 1999, at the Poker Flat Research Range (Alaska, USA) using the American research rocket Black Brant XII with explosive plasma generators on board. Separable modules with scientific equipment were located at distances of from 170 to 1595 m from the plasma source. The experiment continued the series of the Russian-American joint experiments started by the ``Fluxus'' experiment in 1997. Two injections of aluminum plasma across the magnetic field were conducted in the ``North Star'' experiment. They were different, since in the first injection a neutral gas cloud was formed in order to increase the plasma ionization due to the interaction of neutrals of the jet and cloud. The first and second injections were conducted at heights of 360 and 280 km, respectively. The measurements have shown that the charged particle density was two orders of magnitude higher in the experiment with the gas release. The magnetic field in the first injection was completely expelled by the dense plasma of the jet. The displacement of the magnetic field in the second injection was negligible. The plasma jet velocity in both injections decreased gradually due to its interaction with the geomagnetic field. One of the most interesting results of the experiment was the conservation of high plasma density during the propagation of the divergent jet to considerable distances. This fact can be explained by the action of the critical ionization velocity mechanism.

  2. Obscured active galactic nuclei triggered in compact star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Chang, Yu-Yen; Le Floc'h, Emeric; Juneau, Stéphanie; da Cunha, Elisabete; Salvato, Mara; Civano, Francesca; Marchesi, Stefano; Gabor, J. M.; Ilbert, Olivier; Laigle, Clotilde; McCracken, H. J.; Hsieh, Bau-Ching; Capak, Peter

    2017-03-01

    We present a structural study of 182 obscured active galactic nuclei (AGNs) at z ≤ 1.5, selected in the Cosmic Evolution Survey field from their extreme infrared to X-ray luminosity ratio and their negligible emission at optical wavelengths. We fit optical to far-infrared spectral energy distributions and analyse deep Hubble Space Telescope imaging to derive the physical and morphological properties of their host galaxies. We find that such galaxies are more compact than normal star-forming sources at similar redshift and stellar mass, and we show that it is not an observational bias related to the emission of the AGN. Based on the distribution of their UVJ colours, we also argue that this increased compactness is not due to the additional contribution of a passive bulge. We thus postulate that a vast majority of obscured AGNs reside in galaxies undergoing dynamical compaction, similar to processes recently invoked to explain the formation of compact star-forming sources at high redshift.

  3. Regulation to Create Environments Conducive to Physical Activity: Understanding the Barriers and Facilitators at the Australian State Government Level

    PubMed Central

    Shill, Jane; Mavoa, Helen; Crammond, Brad; Loff, Bebe; Peeters, Anna; Lawrence, Mark; Allender, Steven; Sacks, Gary; Swinburn, Boyd A.

    2012-01-01

    Introduction Policy and regulatory interventions aimed at creating environments more conducive to physical activity (PA) are an important component of strategies to improve population levels of PA. However, many potentially effective policies are not being broadly implemented. This study sought to identify potential policy/regulatory interventions targeting PA environments, and barriers/facilitators to their implementation at the Australian state/territory government level. Methods In-depth interviews were conducted with senior representatives from state/territory governments, statutory authorities and non-government organisations (n = 40) to examine participants': 1) suggestions for regulatory interventions to create environments more conducive to PA; 2) support for preselected regulatory interventions derived from a literature review. Thematic and constant comparative analyses were conducted. Results Policy interventions most commonly suggested by participants fell into two areas: 1) urban planning and provision of infrastructure to promote active travel; 2) discouraging the use of private motorised vehicles. Of the eleven preselected interventions presented to participants, interventions relating to walkability/cycling and PA facilities received greatest support. Interventions involving subsidisation (of public transport, PA-equipment) and the provision of more public transport infrastructure received least support. These were perceived as not economically viable or unlikely to increase PA levels. Dominant barriers were: the powerful ‘road lobby’, weaknesses in the planning system and the cost of potential interventions. Facilitators were: the provision of evidence, collaboration across sectors, and synergies with climate change/environment agendas. Conclusion This study points to how difficult it will be to achieve policy change when there is a powerful ‘road lobby’ and government investment prioritises road infrastructure over PA

  4. Inherited activation-inactivation of the star gene in foxes: its bearing on the problem of domestication.

    PubMed

    Belyaev, D K; Ruvinsky, A O; Trut, L N

    1981-01-01

    A frequency of more than 10(-2) of the de novo appearance of piebald spotting (star) was established in silver-black foxes selected for domestic behavior. The star phenotype is determined by the autosomal semidominant gene S. Ten genealogical groups of foxes, in which star arose independently, were analyzed. Of these, the star character is determined by S alleles in at least seven groups. The S gene is located in a linkage group other than the earlier described W (Georgian white) locus. The star gene is incompletely penetrant, but its penetrance is significantly higher in offspring from tame mothers than from aggressive ones, or when S is received from a heterozygous vixen (Ss). There was a notable shortage of homozygous (SS) offspring from Ss X Ss crosses, which cannot be adequately explained by selective embryonic mortality, differential zygotic and gametic death, or transgression of homozygous and heterozygous phenotypes. Some foxes, proven carriers of a homozygous (Ss) genotype, showed the phenotype and mode of inheritance characteristic of heterozygotes (Ss). Presumably, the mechanism responsible of these observations is a heritable functional activation-inactivation of the star gene. Some implications of this concept in terms of destabilizing selection are discussed.

  5. Active optics: variable curvature mirrors for ELT laser guide star refocusing systems

    NASA Astrophysics Data System (ADS)

    Challita, Zalpha; Hugot, Emmanuel; Madec, Fabrice; Ferrari, Marc; Le Mignant, David; Vivès, Sébastien; Cuby, Jean-Gabriel

    2011-10-01

    The future generation of Extremely Large Telescopes will require a complex combination of technologies for adaptive optics (AO) systems assisted by laser guide stars (LGS). In this context, the distance from the LGS spot to the telescope pupil ranges from about 80 to 200 km, depending on the Sodium layer altitude and the elevation of the telescope. This variation leads to a defocusing effect on the LGS wave-front sensor which needs to be compensated. We propose an active mirror able to compensate for this variation, based on an original optical design including this active optics component. This LGS Variable Curvature Mirror (LGS-VCM) is a 120 mm spherical active mirror able to achieve 820 μm deflection sag with an optical quality better than 150 nm RMS, allowing the radius of curvature variation from F/12 to F/2. Based on elasticity theory, the deformation of the metallic mirror is provided by an air pressure applied on a thin meniscus with a variable thickness distribution. In this article, we detail the analytical development leading to the specific geometry of the active component, the results of finite element analysis and the expected performances in terms of surface error versus the range of refocalisation. Three prototypes have been manufactured to compare the real behavior of the mirror and the simulations data. Results obtained on the prototypes are detailed, showing that the deformation of the VCM is very close to the simulation, and leads to a realistic active concept.

  6. A radiation-hardened two transistor memory cell for monolithic active pixel sensors in STAR experiment

    NASA Astrophysics Data System (ADS)

    Wei, X.; Gao, D.; Dorokhov, A.; Hu, Y.

    2011-01-01

    Radiation tolerance of Monolithic Active Pixel Sensors (MAPS) is dramatically decreased when intellectual property (IP) memories are integrated for fast readout application. This paper presents a new solution to improve radiation hardness and avoid latch-up for memory cell design. The tradeoffs among radiation tolerance, area and speed are significantly considered and analyzed. The cell designed in 0.35 μm process satisfies the radiation tolerance requirements of STAR experiment. The cell size is 4.55 × 5.45 μm2. This cell is smaller than the IP memory cell based on the same process and is only 26% of a radiation tolerant 6T SRAM cell used in previous contribution. The write access time of the cell is less than 2 ns, while the read access time is 80 ns.

  7. Chromospheric activity in Delta Scuti stars - The suspected variable Tau Cygni

    NASA Technical Reports Server (NTRS)

    Fracassini, M.; Pasinetti Fracassini, L. E.; Mariani, A.; Pastori, L.; Teays, T. J.

    1991-01-01

    High-resolution IUE spectra of the suspected variable Tau Cyg were obtained to search for a possible variability of the Mg II h, k double-peaked emission. The observations, spanning an interval of about 6.3 h, have shown flux excursions within or just near 15 percent, a value suggested as the detection limit of actual variations with IUE spectra. A variability, difficult to explain, could be present in the ratios Fk2v/Fk2r. The emission fluxes seem to be higher than those of the Delta Scuti variables Rho Pup and Beta Cas. This comparison could give some insights on the possible role of the convection on the pulsational and chromospheric activities of Tau Cyg. A positive correlation between the total emission fluxes and the rotational velocities of these stars was found.

  8. The photometric variability of the chromospherically active binary star HD 80715

    NASA Technical Reports Server (NTRS)

    Strassmeier, Klaus G.; Hooten, James T.; Hall, Douglas S.; Fekel, Francis C.

    1989-01-01

    Differential UBVRI photometry of the double-lined BY Dra system HD 80715 (K3 V + K3 V) obtained in December 1987 is presented. The star is found to be a variable with a full amplitude of 0.06 mag in V and a period similar or equal to the orbital period of 3.804 days. The mechanism of the variability is interpreted as rotational modulation due to dark starspots. In an attempt to detect chromospheric activity, high-resolution CCD spectra were obtained at Ca II H and K and at Fe I 6430 A and Ca I 6439 A, the photospheric lines normally used for Doppler imaging. HD 80715 shows double H and K emission features at a constant flux level for each component.

  9. A Search for Hard X-ray Emission from Active Stars Using CGRO/BATSE

    NASA Astrophysics Data System (ADS)

    White, S. M.; Harmon, B. A.; Lim, J.; Kundu, M. R.

    We report the results of a search for > 20 keV photons from active stars using CGRO/BATSE Earth-occultation observations. Twelve of the "usual suspects" together with 12 "placebo" locations have been analyzed using the BATSE software for occultation analysis developed at NASA/MSFC. There are four detections at the nominal 5sigma level, and eight at the 3sigma level. However the strongest detection (that of AB Dor) shows clear evidence for contamination from the nearby strong source LMC X-4. 18 of the 24 fields yield positive fluxes, indicating a clear bias in the results, and possibly indicating the presence of weak background hard X-ray sources detectable by BATSE in long-term studies.

  10. High Energy Gamma Rays and Neutrinos from Star-forming Activities in the Galactic and Extragalactic Sources

    NASA Astrophysics Data System (ADS)

    Razzaque, Soebur

    2017-01-01

    The origin of the IceCube astrophysical neutrinos is an outstanding question. Star-forming activities which can accelerate particles to very high energies have been suggested as possible origin of these neutrinos. I will present a scenario where a subset of the neutrino events originate from the Galactic center region and Fermi Bubbles, resulting from star-forming activities. Multi-messenger signal in high energy gamma rays and neutrinos can probe this scenario. I will also present an analysis of the statistical association of the star-forming sources in our Galaxy and outside, with astrophysical neutrinos, as well as expected neutrino signal from these sources by fitting gamma-ray data.

  11. SALT observations of the chromospheric activity of transiting planet hosts: mass-loss and star-planet interactions★

    NASA Astrophysics Data System (ADS)

    Staab, D.; Haswell, C. A.; Smith, Gareth D.; Fossati, L.; Barnes, J. R.; Busuttil, R.; Jenkins, J. S.

    2017-04-01

    We measured the chromospheric activity of the four hot Jupiter hosts WASP-43, WASP-51/HAT-P-30, WASP-72 and WASP-103 to search for anomalous values caused by the close-in companions. The Mount Wilson Ca II H & K S-index was calculated for each star using observations taken with the Robert Stobie Spectrograph at the Southern African Large Telescope. The activity level of WASP-43 is anomalously high relative to its age and falls among the highest values of all known main-sequence stars. We found marginal evidence that the activity of WASP-103 is also higher than expected from the system age. We suggest that for WASP-43 and WASP-103 star-planet interactions (SPI) may enhance the Ca II H & K core emission. The activity levels of WASP-51/HAT-P-30 and WASP-72 are anomalously low, with the latter falling below the basal envelope for both main-sequence and evolved stars. This can be attributed to circumstellar absorption due to planetary mass-loss, though absorption in the interstellar medium may contribute. A quarter of known short-period planet hosts exhibit anomalously low activity levels, including systems with hot Jupiters and low-mass companions. Since SPI can elevate and absorption can suppress the observed chromospheric activity of stars with close-in planets, their Ca II H & K activity levels are an unreliable age indicator. Systems where the activity is depressed by absorption from planetary mass-loss are key targets for examining planet compositions through transmission spectroscopy.

  12. Nuclear star formation activity and black hole accretion in nearby Seyfert galaxies

    SciTech Connect

    Esquej, P.; Alonso-Herrero, A.; Hernán-Caballero, A.; González-Martín, O.; Ramos Almeida, C.; Rodríguez Espinosa, J. M.; Roche, P.; Mason, R. E.; Díaz-Santos, T.; Levenson, N. A.; Aretxaga, I.; Packham, C.

    2014-01-01

    Recent theoretical and observational works indicate the presence of a correlation between the star-formation rate (SFR) and active galactic nucleus (AGN) luminosity (and, therefore, the black hole accretion rate, M-dot {sub BH}) of Seyfert galaxies. This suggests a physical connection between the gas-forming stars on kpc scales and the gas on sub-pc scales that is feeding the black hole. We compiled the largest sample of Seyfert galaxies to date with high angular resolution (∼0.''4-0.''8) mid-infrared (8-13 μm) spectroscopy. The sample includes 29 Seyfert galaxies drawn from the AGN Revised Shapley-Ames catalog. At a median distance of 33 Mpc, our data allow us to probe nuclear regions on scales of ∼65 pc (median value). We found no general evidence of suppression of the 11.3 μm polycyclic aromatic hydrocarbon (PAH) emission in the vicinity of these AGN, and we used this feature as a proxy for the SFR. We detected the 11.3 μm PAH feature in the nuclear spectra of 45% of our sample. The derived nuclear SFRs are, on average, five times lower than those measured in circumnuclear regions of 600 pc in size (median value). However, the projected nuclear SFR densities (median value of 22 M {sub ☉} yr{sup –1} kpc{sup –2}) are a factor of 20 higher than those measured on circumnuclear scales. This indicates that the SF activity per unit area in the central ∼65 pc region of Seyfert galaxies is much higher than at larger distances from their nuclei. We studied the connection between the nuclear SFR and M-dot {sub BH} and showed that numerical simulations reproduce our observed relation fairly well.

  13. IMPLICATIONS OF MASS AND ENERGY LOSS DUE TO CORONAL MASS EJECTIONS ON MAGNETICALLY ACTIVE STARS

    SciTech Connect

    Drake, Jeremy J.; Cohen, Ofer; Yashiro, Seiji; Gopalswamy, Nat

    2013-02-20

    Analysis of a database of solar coronal mass ejections (CMEs) and associated flares over the period 1996-2007 finds well-behaved power-law relationships between the 1-8 A flare X-ray fluence and CME mass and kinetic energy. We extrapolate these relationships to lower and higher flare energies to estimate the mass and energy loss due to CMEs from stellar coronae, assuming that the observed X-ray emission of the latter is dominated by flares with a frequency as a function of energy dn/dE = kE {sup -{alpha}}. For solar-like stars at saturated levels of X-ray activity, the implied losses depend fairly weakly on the assumed value of {alpha} and are very large: M-dot {approx}5 Multiplication-Sign 10{sup -10} M{sub sun} yr{sup -1} and E-dot {approx}0.1 L{sub sun}. In order to avoid such large energy requirements, either the relationships between CME mass and speed and flare energy must flatten for X-ray fluence {approx}> 10{sup 31} erg, or the flare-CME association must drop significantly below 1 for more energetic events. If active coronae are dominated by flares, then the total coronal energy budget is likely to be up to an order of magnitude larger than the canonical 10{sup -3} L {sub bol} X-ray saturation threshold. This raises the question of what is the maximum energy a magnetic dynamo can extract from a star? For an energy budget of 1% of L {sub bol}, the CME mass loss rate is about 5 Multiplication-Sign 10{sup -11} M {sub Sun} yr{sup -1}.

  14. Challenges to Understand Stellar Chromospheres and Stellar Activity: The Limit Case of Late-A and Early-F Stars

    NASA Astrophysics Data System (ADS)

    Freire Ferrero, R.; Gouttebroze, P.

    The onset of chromospheric activity appears at late-A and early-F stars where theories predict atmospheres in radiative equilibrium and shallow or non-existent convective zones. The detection of Ly-α emission cores in several A and F stars, first with the IUE satellite and then with the HST, gives evidence for the presence of chromospheric layers in these stars up to B - V = 0. ^m19 (Catalano et al. [CITE]). Semiempirical chromospheric models for Altair allowed us (Freire et al. [CITE]) to explain the observed emission profiles taking into account normal HI IS absorption. However, due to the very high rotational velocity we analyzed alternative hypotheses like the formation of Ly-α emissions into a corotating expanding wind, but we ruled out this alternative because we obtained inconsistent results. In addition, X-ray emission (originated surely in a corona) strengthen the presence of a chromosphere. Here we place the problem of chromospheric activity of late-A and early-F stars in the general context of the formation of over-photospheric stellar layers, comparing them with late-type star and solar cases.

  15. Synthesis and antioxidant activity of star-shape phenolic antioxidants catalyzed by acidic nanocatalyst based on reduced graphene oxide.

    PubMed

    Golestanzadeh, Mohsen; Naeimi, Hossein; Zahraie, Zohreh

    2017-02-01

    Phenolic antioxidants play important role in prevention of oxidation in different industrials. The research objective in the current study was synthesis and evaluate of antioxidant activity of star-shape phenolic antioxidants. The synthetic compounds were prepared in the presence of sulfonated reduced graphene oxide. The antioxidant activity of synthesized compounds was investigated by spectrophotometrically method according to the DPPH assay. Overall, these compounds are potentially important antioxidant and also to limit activity of reactive oxygen species.

  16. Variability of stellar granulation and convective blueshift with spectral type and magnetic activity. I. K and G main sequence stars

    NASA Astrophysics Data System (ADS)

    Meunier, N.; Lagrange, A.-M.; Mbemba Kabuiku, L.; Alex, M.; Mignon, L.; Borgniet, S.

    2017-01-01

    Context. In solar-type stars, the attenuation of convective blueshift by stellar magnetic activity dominates the RV (radial velocity) variations over the low amplitude signal induced by low mass planets. Models of stars that differ from the Sun will require a good knowledge of the attenuation of the convective blueshift to estimate its impact on the variations. Aims: It is therefore crucial to precisely determine not only the amplitude of the convective blueshift for different types of stars, but also the dependence of this convective blueshift on magnetic activity, as these are key factors in our model producing the RV. Methods: We studied a sample of main sequence stars with spectral types from G0 to K2 and focused on their temporally averaged properties: the activity level and a criterion allowing to characterise the amplitude of the convective blueshift. This criterion is derived from the dependence of the convective blueshift with the intensity at the bottom of a large set of selected spectral lines. Results: We find the differential velocity shifts of spectral lines due to convection to depend on the spectral type, the wavelength (this dependence is correlated with the Teff and activity level), and on the activity level. This allows us to quantify the dependence of granulation properties on magnetic activity for stars other than the Sun. We are indeed able to derive a significant dependence of the convective blueshift on activity level for all types of stars. The attenuation factor of the convective blueshift appears to be constant over the considered range of spectral types. We derive a convective blueshift which decreases towards lower temperatures, with a trend in close agreement with models for Teff lower than 5800 K, but with a significantly larger global amplitude. Differences also remain to be examined in detail for larger Teff. We finally compare the observed RV variation amplitudes with those that could be derived from our convective blueshift using

  17. Spectroscopic evidence for an engineered, catalytically active Trp radical that creates the unique reactivity of lignin peroxidase.

    PubMed

    Smith, Andrew T; Doyle, Wendy A; Dorlet, Pierre; Ivancich, Anabella

    2009-09-22

    The surface oxidation site (Trp-171) in lignin peroxidase (LiP) required for the reaction with veratryl alcohol a high-redox-potential (1.4 V) substrate, was engineered into Coprinus cinereus peroxidase (CiP) by introducing a Trp residue into a heme peroxidase that has similar protein fold but lacks this activity. To create the catalytic activity toward veratryl alcohol in CiP, it was necessary to reproduce the Trp site and its negatively charged microenvironment by means of a triple mutation. The resulting D179W+R258E+R272D variant was characterized by multifrequency EPR spectroscopy. The spectra unequivocally showed that a new Trp radical [g values of g(x) = 2.0035(5), g(y) = 2.0027(5), and g(z) = 2.0022(1)] was formed after the [Fe(IV)=O Por(*+)] intermediate, as a result of intramolecular electron transfer between Trp-179 and the porphyrin. Also, the EPR characterization crucially showed that [Fe(IV)=O Trp-179(*)] was the reactive intermediate with veratryl alcohol. Accordingly, our work shows that it is necessary to take into account the physicochemical properties of the radical, fine-tuned by the microenvironment, as well as those of the preceding [Fe(IV)=O Por(*+)] intermediate to engineer a catalytically competent Trp site for a given substrate. Manipulation of the microenvironment of the Trp-171 site in LiP allowed the detection by EPR spectroscopy of the Trp-171(*), for which direct evidence has been missing so far. Our work also highlights the role of Trp residues as tunable redox-active cofactors for enzyme catalysis in the context of peroxidases with a unique reactivity toward recalcitrant substrates that require oxidation potentials not realized at the heme site.

  18. WZ Cephei: A Dynamically Active W UMa-Type Binary Star

    NASA Astrophysics Data System (ADS)

    Jeong, Jang-Hae; Kim, Chun-Hwey

    2011-09-01

    An intensive analysis of 185 timings of WZ Cep, including our new three timings, was made to understand the dynamical picture of this active W UMa-type binary. It was found that the orbital period of the system has complexly varied in two cyclical components superposed on a secularly downward parabola over about 80y. The downward parabola, corresponding to a secular period decrease of -9.d97 × 10-8 y-1, is most probably produced by the action of both angular momentum loss (AML) due to magnetic braking and mass-transfer from the massive primary component to the secondary. The period decrease rate of -6.d72 × 10-8 y-1 due to AML contributes about 67% to the observed period decrease. The mass flow of about 5.16 × 10-8 M⊙ y-1 from the primary to the secondary results the remaining 33% period decrease. Two cyclical components have an 11.y8 period with amplitude of 0.d0054 and a 41.y3 period with amplitude of 0.d0178. It is very interesting that there seems to be exactly in a commensurable 7:2 relation between their mean motions. As the possible causes, two rival interpretations (i.e., light-time effects (LTE) by additional bodies and the Applegate model) were considered. In the LTE interpretation, the minimum masses of 0.30 M⊙ for the shorter period and 0.49 M⊙ for the longer one were calculated. Their contributions to the total light were at most within 2%, if they were assumed to be main-sequence stars. If the LTE explanation is true for the WZ Cep system, the 7:2 relation found between their mean motions would be interpreted as a stable 7:2 orbit resonance produced by a long-term gravitational interaction between two tertiary bodies. In the Applegate model interpretation, the deduced model parameters indicate that the mechanism could work only in the primary star for both of the two period modulations, but could not in the secondary. However, we couldn't find any meaningful relation between the light variation and the period variability from the historical

  19. A SINFONI view of the nuclear activity and circumnuclear star formation in NGC 4303

    NASA Astrophysics Data System (ADS)

    Riffel, Rogemar A.; Colina, L.; Storchi-Bergmann, T.; Piqueras López, J.; Arribas, S.; Riffel, R.; Pastoriza, M.; Sales, Dinalva A.; Dametto, N. Z.; Labiano, A.; Davies, R. I.

    2016-10-01

    We present new maps of emission-line flux distributions and kinematics in both ionized (traced by H I and [Fe II] lines) and molecular (H2) gas of the inner 0.7 × 0.7 kpc2 of the galaxy NGC 4303, with a spatial resolution 40-80 pc and velocity resolution 90-150 km s- 1 obtained from near-IR integral field spectroscopy using the Very Large Telescope instrument SINFONI. The most prominent feature is a 200-250 pc ring of circumnuclear star-forming regions. The emission from ionized and molecular gas shows distinct flux distributions: while the strongest H I and [Fe II] emission comes from regions in the west side of the ring (ages ˜ 4 Myr), the H2 emission is strongest at the nucleus and in the east side of the ring (ages > 10 Myr). We find that regions of enhanced hot H2 emission are anti-correlated with those of enhanced [Fe II] and H I emission, which can be attributed to post-starburst regions that do not have ionizing photons anymore but still are hot enough (≈2000 K) to excite the H2 molecule. The line ratios are consistent with the presence of an active galactic nucleus at the nucleus. The youngest regions have stellar masses in the range 0.3-1.5 × 105 M⊙ and ionized and hot molecular gas masses of ˜0.25-1.2 × 104 M⊙ and ˜2.5-5 M⊙, respectively. The stellar and gas velocity fields show a rotation pattern, with the gas presenting larger velocity amplitudes than the stars, with a deviation observed for the H2 along the nuclear bar, where increased velocity dispersion is also observed, possibly associated with non-circular motions along the bar. The stars in the ring show smaller velocity dispersion than the surroundings, which can be attributed to a cooler dynamics due to their recent formation from cool gas.

  20. "Things to Share and Do" from the Daybreak Star Indian Reader: Classroom Activities for the Middle Grades.

    ERIC Educational Resources Information Center

    Wolfe, Karleen

    Designed for classroom use, the booklet is a collection of the easiest-to-use classroom ideas taken from past issues of the "Daybreak Star Indian Reader," published monthly throughout the school year by the United Indians of All Tribes Foundation. The selection of articles and activities focus primarily on Plains and Northwest Indian cultures,…

  1. Actively targeted delivery of anticancer drug to tumor cells by redox-responsive star-shaped micelles.

    PubMed

    Shi, Chunli; Guo, Xing; Qu, Qianqian; Tang, Zhaomin; Wang, Yi; Zhou, Shaobing

    2014-10-01

    In cancer therapy nanocargos based on star-shaped polymer exhibit unique features such as better stability, smaller size distribution and higher drug capacity in comparison to linear polymeric micelles. In this study, we developed a multifunctional star-shaped micellar system by combination of active targeting ability and redox-responsive behavior. The star-shaped micelles with good stability were self-assembled from four-arm poly(ε-caprolactone)-poly(ethylene glycol) copolymer. The redox-responsive behaviors of these micelles triggered by glutathione were evaluated from the changes of micellar size, morphology and molecular weight. In vitro drug release profiles exhibited that in a stimulated normal physiological environment, the redox-responsive star-shaped micelles could maintain good stability, whereas in a reducing and acid environment similar with that of tumor cells, the encapsulated agent was promptly released. In vitro cellular uptake and subcellular localization of these micelles were further studied with confocal laser scanning microscopy and flow cytometry against the human cervical cancer cell line HeLa. In vivo and ex vivo DOX fluorescence imaging displayed that these FA-functionalized star-shaped micelles possessed much better specificity to target solid tumor. Both the qualitative and quantitative results of the antitumor effect in 4T1 tumor-bearing BALB/c mice demonstrated that these redox-responsive star-shaped micelles have a high therapeutic efficiency to artificial solid tumor. Therefore, the multifunctional star-shaped micelles are a potential platform for targeted anticancer drug delivery.

  2. WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star

    NASA Astrophysics Data System (ADS)

    Delrez, L.; Santerne, A.; Almenara, J.-M.; Anderson, D. R.; Collier-Cameron, A.; Díaz, R. F.; Gillon, M.; Hellier, C.; Jehin, E.; Lendl, M.; Maxted, P. F. L.; Neveu-VanMalle, M.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.; Smalley, B.; Smith, A. M. S.; Triaud, A. H. M. J.; Udry, S.; Van Grootel, V.; West, R. G.

    2016-06-01

    We present the discovery by the WASP-South survey of WASP-121 b, a new remarkable short-period transiting hot Jupiter. The planet has a mass of 1.183_{-0.062}^{+0.064} MJup, a radius of 1.865 ± 0.044 RJup, and transits every 1.274 9255_{-0.000 0025}^{+0.000 0020} days an active F6-type main-sequence star (V = 10.4, 1.353_{-0.079}^{+0.080} M⊙, 1.458 ± 0.030 R⊙, Teff = 6460 ± 140 K). A notable property of WASP-121 b is that its orbital semimajor axis is only ˜1.15 times larger than its Roche limit, which suggests that the planet is close to tidal disruption. Furthermore, its large size and extreme irradiation (˜7.1 109 erg s-1 cm-2) make it an excellent target for atmospheric studies via secondary eclipse observations. Using the TRAnsiting Planets and PlanetesImals Small Telescope, we indeed detect its emission in the z'-band at better than ˜4σ, the measured occultation depth being 603 ± 130 ppm. Finally, from a measurement of the Rossiter-McLaughlin effect with the CORALIE spectrograph, we infer a sky-projected spin-orbit angle of 257.8°_{-5.5°}^{+5.3°}. This result may suggest a significant misalignment between the spin axis of the host star and the orbital plane of the planet. If confirmed, this high misalignment would favour a migration of the planet involving strong dynamical events with a third body.

  3. Determining the Covering Factor of Compton-thick Active Galactic Nuclei with NuSTAR

    NASA Astrophysics Data System (ADS)

    Brightman, M.; Baloković, M.; Stern, D.; Arévalo, P.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Fuerst, F.; Gandhi, P.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Koss, M.; LaMassa, S.; Puccetti, S.; Rivers, E.; Vasudevan, R.; Walton, D. J.; Zhang, W. W.

    2015-05-01

    The covering factor of Compton-thick (CT) obscuring material associated with the torus in active galactic nuclei (AGNs) is at present best understood through the fraction of sources exhibiting CT absorption along the line of sight (NH > 1.5 × 1024 cm-2) in the X-ray band, which reveals the average covering factor. Determining this CT fraction is difficult, however, due to the extreme obscuration. With its spectral coverage at hard X-rays (>10 keV), Nuclear Spectroscopic Telescope Array (NuSTAR) is sensitive to the AGNs covering factor since Compton scattering of X-rays off optically thick material dominates at these energies. We present a spectral analysis of 10 AGNs observed with NuSTAR where the obscuring medium is optically thick to Compton scattering, so-called CT AGNs. We use the torus models of Brightman & Nandra that predict the X-ray spectrum from reprocessing in a torus and include the torus opening angle as a free parameter and aim to determine the covering factor of the CT gas in these sources individually. Across the sample we find mild to heavy CT columns, with NH measured from 1024 to 1026 cm-2, and a wide range of covering factors, where individual measurements range from 0.2 to 0.9. We find that the covering factor, fc, is a strongly decreasing function of the intrinsic 2-10 keV luminosity, LX, where fc = (-0.41 ± 0.13)log10(LX/erg s-1)+18.31 ± 5.33, across more than two orders of magnitude in LX (1041.5-1044 erg s-1). The covering factors measured here agree well with the obscured fraction as a function of LX as determined by studies of local AGNs with LX > 1042.5 erg s-1.

  4. Creating Chemigrams in the Classroom.

    ERIC Educational Resources Information Center

    Guhin, Paula

    2003-01-01

    Describes an art activity in which students create "chemigrams" using exposed photo paper to create designs. Explains that this activity can be used with middle and high school students as an introduction to photography or use of chemicals. (CMK)

  5. Fusion of Active and Passive Microwave Observations to Create AN Essential Climate Variable Data Record on Soil Moisture

    NASA Astrophysics Data System (ADS)

    Wagner, W.; Dorigo, W.; de Jeu, R.; Fernandez, D.; Benveniste, J.; Haas, E.; Ertl, M.

    2012-07-01

    Soil moisture was recently included in the list of Essential Climate Variables (ECVs) that are deemed essential for IPCC (Intergovernmental Panel on Climate Change) and UNFCCC (United Nations Framework Convention on Climate Change) needs and considered feasible for global observation. ECVs data records should be as long, complete and consistent as possible, and in the case of soil moisture this means that the data record shall be based on multiple data sources, including but not limited to active (scatterometer) and passive (radiometer) microwave observations acquired preferably in the low-frequency microwave range. Among the list of sensors that can be used for this task are the C-band scatterometers on board of the ERS and METOP satellites and the multi-frequency radiometers SMMR, SSM/I, TMI, AMSR-E, and Windsat. Together, these sensors already cover a time period of more than 30 years and the question is how can observations acquired by these sensors be merged to create one consistent data record? This paper discusses on a high-level possible approaches for fusing the individual satellite data. It is argued that the best possible approach for the fusion of the different satellite data sets is to merge Level 2 soil moisture data derived from the individual satellite data records. This approach has already been demonstrated within the WACMOS project (http://wacmos.itc.nl/) funded by European Space Agency (ESA) and will be further improved within the Climate Change Initiative (CCI) programme of ESA (http://www.esa-cci.org/).

  6. Symmetry-breaking magnetic fields create a vortex fluid that exhibits a negative viscosity, active wetting, and strong mixing.

    PubMed

    Martin, James E; Solis, Kyle J

    2014-06-14

    There are many areas of science and technology where being able to generate vigorous, noncontact flow would be desirable. We have discovered that three dimensional, time-dependent electric or magnetic fields having key symmetries can be used to generate controlled fluid motion by the continuous injection of energy. Unlike natural convection, this approach does not require a thermal gradient as an energy source, nor does it require gravity, so space applications are feasible. The result is a highly active material we call a vortex fluid. The homogeneous torque density of this fluid enables it to climb walls, induce ballistic droplet motion, and mix vigorously, even in such complex geometries as porous media. This vortex fluid can also exhibit a negative viscosity, which can immeasurably extend the control range of the "smart fluids" used in electro- and magnetorheological devices and can thus significantly increase their performance. Because the applied fields are uniform and modest in strength, vortex fluids of any scale can be created, making applications of any size, from directing microdroplet motion to controlling damping in magnetorheological dampers that protect bridges and buildings from earthquakes, feasible.

  7. Unbiased identification of signal-activated transcription factors by barcoded synthetic tandem repeat promoter screening (BC-STAR-PROM)

    PubMed Central

    Gosselin, Pauline; Rando, Gianpaolo; Fleury-Olela, Fabienne; Schibler, Ueli

    2016-01-01

    The discovery of transcription factors (TFs) controlling pathways in health and disease is of paramount interest. We designed a widely applicable method, dubbed barcorded synthetic tandem repeat promoter screening (BC-STAR-PROM), to identify signal-activated TFs without any a priori knowledge about their properties. The BC-STAR-PROM library consists of ∼3000 luciferase expression vectors, each harboring a promoter (composed of six tandem repeats of synthetic random DNA) and an associated barcode of 20 base pairs (bp) within the 3′ untranslated mRNA region. Together, the promoter sequences encompass >400,000 bp of random DNA, a sequence complexity sufficient to capture most TFs. Cells transfected with the library are exposed to a signal, and the mRNAs that it encodes are counted by next-generation sequencing of the barcodes. This allows the simultaneous activity tracking of each of the ∼3000 synthetic promoters in a single experiment. Here we establish proof of concept for BC-STAR-PROM by applying it to the identification of TFs induced by drugs affecting actin and tubulin cytoskeleton dynamics. BC-STAR-PROM revealed that serum response factor (SRF) is the only immediate early TF induced by both actin polymerization and microtubule depolymerization. Such changes in cytoskeleton dynamics are known to occur during the cell division cycle, and real-time bioluminescence microscopy indeed revealed cell-autonomous SRF–myocardin-related TF (MRTF) activity bouts in proliferating cells. PMID:27601530

  8. Star-shaped ZnO/Ag hybrid nanostructures for enhanced photocatalysis and antibacterial activity

    NASA Astrophysics Data System (ADS)

    Andrade, George R. S.; Nascimento, Cristiane C.; Lima, Zenon M.; Teixeira-Neto, Erico; Costa, Luiz P.; Gimenez, Iara F.

    2017-03-01

    Zinc oxide (ZnO) particles with a star-shaped morphology have been synthesized by a novel and simple room-temperature method and decorated with silver nanoparticles (SNPs) for enhanced photocatalysis and bactericide applications. The presence of thiourea during the precipitation of ZnO in alkaline conditions allowed the control of morphological features (e.g. average size and shape) and the surface functionalization with thiocyanate ions (SCN-). SNPs were deposited into the ZnO surface by a photoreduction method and their sizes could be easily controlled by changing the ZnO/AgNO3 ratio. The presence of SCN- on the semiconductor surface prevents uncontrollable growth of Ag nanoparticles into different morphologies and high degrees of polydispersity. XRD, SEM, TEM, FTIR, UV-vis-NIR and PL were employed for characterizing the structure, morphology and optical properties of the as-obtained pure and hybrid nanostructures. Finally, the hybrid ZnO/Ag particles have shown plasmon-enhanced performance for applications in photocatalysis and antibacterial activity compared to the pure ZnO counterpart. In this work, evaluation of the photodegradation of an aqueous methylene blue solution under UV-A irradiation and the antibacterial activity toward 4 bacterial strains, including Gram-positive bacteria Staphylococcus aureus (ATCC 43300, ATCC 25923 and ATCC 33591) and Gram-negative bacteria Pseudomonas aeruginosa (ATCC 27853).

  9. FUV Spectra of Evolved Late-K and M Stars: Mass Loss Revisited and Stellar Activity

    NASA Technical Reports Server (NTRS)

    Harper, Graham M.

    2002-01-01

    This is the final report for the FUSE Cycle 1 program A100: FUV Spectra of Evolved Late-K and M Stars: Mass Loss revisited and Stellar Activity. Targets alpha TrA (K3 II) and gamma Cru (M3 III) were originally assigned 25 ksec each, to be observed in the medium aperture. Once the in-flight performance and telescope alignment problems were known, the observations were reprogrammed to optimized the scientific return of the program. Alpha TrA was scheduled for 25 ksec observations in both the medium and large apertures. The principle aim of this program was to measure the stellar FUV line and continuum emission, in order to estimate the photoionization radiation field and to determine the level of stellar activity through the fluxes in the collisionally excited high temperature diagnostics: C III 977Angstroms and O VI 1032,1038Angstrom doublet. The medium aperture observations were obtained successfully while the large aperture observations were thought by Johns Hopkins University (JHU)to be lost to satellite problems. There was insufficient signal-to- noise in the medium aperture short wavelength Sic channels to do quantitative science.

  10. Nebraska STARS: Achieving Results

    ERIC Educational Resources Information Center

    Roschewski, Pat; Isernhagen, Jody; Dappen, Leon

    2006-01-01

    In 2000, the state of Nebraska passed legislation requiring the assessment of student performance on content standards, but its requirements were very different from those of any other state. Nebraska created what has come to be known as STARS (School-based Teacher-led Assessment and Reporting System). Under STARS, each of Nebraska's nearly 500…

  11. Magnetically active stars in Taurus-Auriga: Photometric variability and basic physical parameters

    NASA Astrophysics Data System (ADS)

    Grankin, K. N.

    2013-04-01

    We have analyzed homogeneous long-term photometric observations of 28 well-known weakline T Tauri stars (WTTS) and 60 WTTS candidates detected by the ROSAT observatory toward the Taurus-Auriga star-forming region. We show that 22 known WTTS and 39 WTTS candidates exhibit periodic light variations that are attributable to the phenomenon of spotted rotational modulation. The rotation periods of these spotted stars lie within the range from 0.5 to 10 days. Significant differences between the long-term photometric behaviors of known WTTS and WTTS candidates have been found. We have calculated accurate luminosities, radii, masses, and ages for 74 stars. About 33% of the sample of WTTS candidates have ages younger than 10 Myr. The mean distance to 24 WTTS candidates with reliable estimates of their radii is shown to be 143 ± 26 pc. This is in excellent agreement with the adopted distance to the Taurus-Auriga star-forming region.

  12. Activity-brightness Correlations for the Sun and Sun-like Stars

    NASA Astrophysics Data System (ADS)

    Preminger, D. G.; Chapman, G. A.; Cookson, A. M.

    2011-10-01

    We analyze the effect of solar features on the variability of the solar irradiance in three different spectral ranges. Our study is based on two solar-cycles' worth of full-disk photometric images from the San Fernando Observatory, obtained with red, blue, and Ca II K-line filters. For each image we measure the photometric sum, Σ, which is the relative contribution of solar features to the disk-integrated intensity of the image. The photometric sums in the red and blue continuum, Σr and Σb, exhibit similar temporal patterns: they are negatively correlated with solar activity, with strong short-term variability, and weak solar-cycle variability. However, the Ca II K-line photometric sum, ΣK, is positively correlated with solar activity and has strong variations on solar-cycle timescales. We show that we can model the variability of the Sun's bolometric flux as a linear combination of Σr and ΣK. We infer that, over solar-cycle timescales, the variability of the Sun's bolometric irradiance is directly correlated with spectral line variability, but inversely correlated with continuum variability. Our blue and red continuum filters are quite similar to the Strömgren b and y filters used to measure stellar photometric variability. We conclude that active stars whose visible continuum brightness varies inversely with activity, as measured by the Ca HK index, are displaying a pattern that is similar to that of the Sun, i.e., radiative variability in the visible continuum that is spot-dominated.

  13. Polycyclic Aromatic Hydrocarbons in Galaxies at z ~ 0.1: The Effect of Star Formation and Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    O'Dowd, Matthew J.; Schiminovich, David; Johnson, Benjamin D.; Treyer, Marie A.; Martin, Christopher D.; Wyder, Ted K.; Charlot, S.; Heckman, Timothy M.; Martins, Lucimara P.; Seibert, Mark; van der Hulst, J. M.

    2009-11-01

    We present the analysis of the polycyclic aromatic hydrocarbon (PAH) spectra of a sample of 92 typical star-forming galaxies at 0.03 < z < 0.2 observed with the Spitzer intensified Reticon spectrograph (IRS). We compare the relative strengths of PAH emission features with Sloan Digital Sky Survey optical diagnostics to probe the relationship between PAH grain properties and star formation and active galactic nuclei (AGNs) activity. Short-to-long wavelength PAH ratios, and in particular the 7.7 μm-to-11.3 μm feature ratio, are strongly correlated with the star formation diagnostics Dn (4000) and Hα equivalent width, increasing with younger stellar populations. This ratio also shows a significant difference between active and non-active galaxies, with the active galaxies exhibiting weaker 7.7 μm emission. A hard radiation field as measured by [O III]/Hβ and [Ne III]_{15.6 μm}/[Ne II]_{12.8 μm} effects PAH ratios differently depending on whether this field results from starburst activity or an AGN. Our results are consistent with a picture in which larger PAH molecules grow more efficiently in richer media and in which smaller PAH molecules are preferentially destroyed by the AGN.

  14. POLYCYCLIC AROMATIC HYDROCARBONS IN GALAXIES AT z approx 0.1: THE EFFECT OF STAR FORMATION AND ACTIVE GALACTIC NUCLEI

    SciTech Connect

    O'Dowd, Matthew J.; Schiminovich, David; Johnson, Benjamin D.; Treyer, Marie A.; Martin, Christopher D.; Wyder, Ted K.; Charlot, S.; Heckman, Timothy M.; Martins, Lucimara P.; Seibert, Mark; Van der Hulst, J. M.

    2009-11-01

    We present the analysis of the polycyclic aromatic hydrocarbon (PAH) spectra of a sample of 92 typical star-forming galaxies at 0.03 < z < 0.2 observed with the Spitzer intensified Reticon spectrograph (IRS). We compare the relative strengths of PAH emission features with Sloan Digital Sky Survey optical diagnostics to probe the relationship between PAH grain properties and star formation and active galactic nuclei (AGNs) activity. Short-to-long wavelength PAH ratios, and in particular the 7.7 mum-to-11.3 mum feature ratio, are strongly correlated with the star formation diagnostics D{sub n} (4000) and Halpha equivalent width, increasing with younger stellar populations. This ratio also shows a significant difference between active and non-active galaxies, with the active galaxies exhibiting weaker 7.7 mum emission. A hard radiation field as measured by [O{sub III}]/Hbeta and [Ne{sub III}]{sub 15.6m}u{sub m}/[Ne{sub II}]{sub 12.8m}u{sub m} effects PAH ratios differently depending on whether this field results from starburst activity or an AGN. Our results are consistent with a picture in which larger PAH molecules grow more efficiently in richer media and in which smaller PAH molecules are preferentially destroyed by the AGN.

  15. What powers the starburst activity of NGC 1068? Star-driven gravitational instabilities caught in the act

    NASA Astrophysics Data System (ADS)

    Romeo, Alessandro B.; Fathi, Kambiz

    2016-08-01

    We explore the role that gravitational instability plays in NGC 1068, a nearby Seyfert galaxy that exhibits unusually vigorous starburst activity. For this purpose, we use the Romeo-Falstad disc instability diagnostics and data from the BIMA Survey of Nearby Galaxies, the Sloan Digital Sky Survey and the Spectrographic Areal Unit for Research on Optical Nebulae. Our analysis illustrates that NGC 1068 is a gravitationally unstable `monster'. Its starburst disc is subject to unusually powerful instabilities. Several processes, including feedback from the active galactic nucleus and starburst activity, try to quench such instabilities from inside out by depressing the surface density of molecular gas across the central kpc, but they do not succeed. Gravitational instability `wins' because it is driven by the stars via their much higher surface density. In this process, stars and molecular gas are strongly coupled, and it is such a coupling that ultimately triggers local gravitational collapse/fragmentation in the molecular gas.

  16. Magnetic activity and differential rotation in the young Sun-like stars KIC 7985370 and KIC 7765135

    NASA Astrophysics Data System (ADS)

    Fröhlich, H.-E.; Frasca, A.; Catanzaro, G.; Bonanno, A.; Corsaro, E.; Molenda-Żakowicz, J.; Klutsch, A.; Montes, D.

    2012-07-01

    Aims: We present a detailed study of the two Sun-like stars KIC 7985370 and KIC 7765135, to determine their activity level, spot distribution, and differential rotation. Both stars were previously discovered by us to be young stars and were observed by the NASA Kepler mission. Methods: The fundamental stellar parameters (vsini, spectral type, Teff, log g, and [Fe/H]) were derived from optical spectroscopy by comparison with both standard-star and synthetic spectra. The spectra of the targets allowed us to study the chromospheric activity based on the emission in the core of hydrogen Hα and Ca ii infrared triplet (IRT) lines, which was revealed by the subtraction of inactive templates. The high-precision Kepler photometric data spanning over 229 days were then fitted with a robust spot model. Model selection and parameter estimation were performed in a Bayesian manner, using a Markov chain Monte Carlo method. Results: We find that both stars are Sun-like (of G1.5 V spectral type) and have an age of about 100-200 Myr, based on their lithium content and kinematics. Their youth is confirmed by their high level of chromospheric activity, which is comparable to that displayed by the early G-type stars in the Pleiades cluster. The Balmer decrement and flux ratio of their Ca ii-IRT lines suggest that the formation of the core of these lines occurs mainly in optically thick regions that are analogous to solar plages. The spot model applied to the Kepler photometry requires at least seven persistent spots in the case of KIC 7985370 and nine spots in the case of KIC 7765135 to provide a satisfactory fit to the data. The assumption of the longevity of the star spots, whose area is allowed to evolve with time, is at the heart of our spot-modelling approach. On both stars, the surface differential rotation is Sun-like, with the high-latitude spots rotating slower than the low-latitude ones. We found, for both stars, a rather high value of the equator-to-pole differential

  17. Active phenomena in the pre-main sequence Herbig Ae star HD 163296

    NASA Technical Reports Server (NTRS)

    Catala, C.; Praderie, F.; Simon, T.; Talavera, A.; The, P. S.

    1989-01-01

    Observations by IUE of the short-term variability of the Mg II and Ca II resonance lines in the Herbig Ae star HD 163296 are presented. Evidence that these lines show a phenomenon of rotational modulation, similar to the one observed in AB Aur, another Herbig Ae star is found. The variations in the spectrum of HD 163296 are even more conspicuous than in the spectrum of AB Aur. Magnetically structured winds may thus be a widespread phenomenon among the pre-main sequence Herbig Ae/Be stars.

  18. X-ray/microwave relation of different types of active stars

    NASA Technical Reports Server (NTRS)

    Guedel, Manuel; Benz, Arnold O.

    1993-01-01

    Coronal active stars of seven classes between spectral types F and M, single and double, are compared in their quiescent radio and X-ray luminosities L(R) and L(X). We find, largely independent of stellar class, log L(X) is less than about log L(R) + 15.5. This general relation points to an intimate connection between the nonthermal, energetic electrons causing the radio emission and the bulk plasma of the corona responsible for thermal X-rays. The relation, observed over six orders of magnitude, suggests that the heating mechanism necessarily involves particle acceleration. We derive requirements for simple models based on optically thin gyrosynchrotron emission of mildly relativistic electrons and thermal X-rays from the bulk plasma. We discuss the possibility that a portion of the accelerated particles heats the ambient plasma by collisions. More likely, plasma heating and particle acceleration may occur in parallel and in the same process, but at a fixed ratio.

  19. Determining the Covering Factor of Compton-Thick Active Galactic Nuclei with NuSTAR

    NASA Technical Reports Server (NTRS)

    Brightman, M.; Balokovic, M.; Stern, D.; Arevalo, P.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Zhang, W. W.

    2015-01-01

    The covering factor of Compton-thick (CT) obscuring material associated with the torus in active galactic nuclei (AGNs) is at present best understood through the fraction of sources exhibiting CT absorption along the line of sight (N(sub H) greater than 1.5 x 10(exp 24) cm(exp -2)) in the X-ray band, which reveals the average covering factor. Determining this CT fraction is difficult, however, due to the extreme obscuration. With its spectral coverage at hard X-rays (greater than 10 keV), Nuclear Spectroscopic Telescope Array (NuSTAR) is sensitive to the AGNs covering factor since Compton scattering of X-rays off optically thick material dominates at these energies. We present a spectral analysis of 10 AGNs observed with NuSTAR where the obscuring medium is optically thick to Compton scattering, so-called CT AGNs. We use the torus models of Brightman and Nandra that predict the X-ray spectrum from reprocessing in a torus and include the torus opening angle as a free parameter and aim to determine the covering factor of the CT gas in these sources individually. Across the sample we find mild to heavy CT columns, with N(sub H) measured from 10(exp 24) to 10(exp 26) cm(exp -2), and a wide range of covering factors, where individual measurements range from 0.2 to 0.9. We find that the covering factor, f(sub c), is a strongly decreasing function of the intrinsic 2-10 keV luminosity, L(sub X), where f(sub c) = (-0.41 +/- 0.13)log(sub 10)(L(sub X)/erg s(exp -1))+18.31 +/- 5.33, across more than two orders of magnitude in L(sub X) (10(exp 41.5) - 10(exp 44) erg s(exp -1)). The covering factors measured here agree well with the obscured fraction as a function of LX as determined by studies of local AGNs with L(sub X) greater than 10(exp 42.5) erg s(exp -1).

  20. Star formation across galactic environments

    NASA Astrophysics Data System (ADS)

    Young, Jason

    . Complementing this study of normal star-forming galaxies, my study of quasar host galaxies utilizes narrow- and medium-band images of eight Palomar-Green (PG) quasars from the WFPC2 and NICMOS instruments aboard the Hubble Space Telescope. Using images of a point-spread function (PSF) star in the same filters, I subtract the PSF of the quasar from each of the target images. The residual light images clearly show the host galaxies of the respective quasars. The narrow-band images were chosen to be centered on the Hbeta, [O II ], [O III], and Paalpha emission lines, allowing the use of line ratios and luminosities to create extinction and star formation maps. Additionally, I utilize the line-ratio maps to distinguish AGN-powered line emission from star formation powered line emission with line-diagnostic diagrams. I find star formation in each of the eight quasar host galaxies in my study. The bulk star-formation rates are lower than expected, suggesting that quasar host galaxies may be dynamically more advanced than previously believed. Seven of the eight quasar host galaxies in this study have higher-than-typical mass-specific star-formation rates. Additionally, I see evidence of shocked gas, supporting the hypotheses presented in earlier works that suggest that AGN activity quenches star formation in its host galaxy by disrupting its gas reservoir.

  1. Star-disk collisions in active galactic nuclei and the origin of the broad line region

    SciTech Connect

    Zurek, W.H.; Colgate, S.A.; Siemiginowska, A.

    1991-12-05

    Stars of a cluster surrounding the central black hole in an AGN will collide with the accretion disk. For a central black hole of 10{sup 8} M{circle_dot} and a cluster with 10{sup 7} {minus} 10{sup 8} stars within a parsec, one estimates that {approximately}10{sup 4} such collisions will occur per year. Collisions are hypersonic (Mach number M {much_gt} 1). Some of the wake of the star -- the disk material shocked by its passage -- will follow it out of the disk. Such ``star tails`` with the estimated masses {delta}m {approximately} 10{sup 25} {minus} 10{sup 27} g subsequently expand, cool and begin to recombine. We propose that -- when illuminated by the ionizing flux from the central source -- they are likely to be the origin of the observed broad emission lines.

  2. Star-disk collisions in active galactic nuclei and the origin of the broad line region

    SciTech Connect

    Zurek, W.H.; Colgate, S.A. ); Siemiginowska, A. )

    1991-12-05

    Stars of a cluster surrounding the central black hole in an AGN will collide with the accretion disk. For a central black hole of 10{sup 8} M{circle dot} and a cluster with 10{sup 7} {minus} 10{sup 8} stars within a parsec, one estimates that {approximately}10{sup 4} such collisions will occur per year. Collisions are hypersonic (Mach number M {much gt} 1). Some of the wake of the star -- the disk material shocked by its passage -- will follow it out of the disk. Such star tails'' with the estimated masses {delta}m {approximately} 10{sup 25} {minus} 10{sup 27} g subsequently expand, cool and begin to recombine. We propose that -- when illuminated by the ionizing flux from the central source -- they are likely to be the origin of the observed broad emission lines.

  3. A PANCHROMATIC STUDY OF BLAST COUNTERPARTS: TOTAL STAR FORMATION RATE, MORPHOLOGY, ACTIVE GALACTIC NUCLEUS FRACTION, AND STELLAR MASS

    SciTech Connect

    Moncelsi, Lorenzo; Ade, Peter A. R.; Cortese, Luca; Dye, Simon; Eales, Stephen; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Pascale, Enzo; Tucker, Carole; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Scott, Douglas; Wiebe, Donald V.; Devlin, Mark J.; Truch, Matthew D. P.; Netterfield, Calvin B.; Viero, Marco P.

    2011-02-01

    We carry out a multi-wavelength study of individual galaxies detected by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) and identified at other wavelengths, using data spanning the radio to the ultraviolet (UV). We develop a Monte Carlo method to account for flux boosting, source blending, and correlations among bands, which we use to derive deboosted far-infrared (FIR) luminosities for our sample. We estimate total star-formation rates (SFRs) for BLAST counterparts with z {<=} 0.9 by combining their FIR and UV luminosities. Star formation is heavily obscured at L{sub FIR} {approx}> 10{sup 11} L{sub sun}, z {approx}> 0.5, but the contribution from unobscured starlight cannot be neglected at L{sub FIR} {approx}< 10{sup 11} L{sub sun}, z {approx}< 0.25. We assess that about 20% of the galaxies in our sample show indication of a type 1 active galactic nucleus, but their submillimeter emission is mainly due to star formation in the host galaxy. We compute stellar masses for a subset of 92 BLAST counterparts; these are relatively massive objects, with a median mass of {approx}10{sup 11} M{sub sun}, which seem to link the 24 {mu}m and Submillimetre Common-User Bolometer Array (SCUBA) populations, in terms of both stellar mass and star formation activity. The bulk of the BLAST counterparts at z {approx}< 1 appears to be run-of-the-mill star-forming galaxies, typically spiral in shape, with intermediate stellar masses and practically constant specific SFRs. On the other hand, the high-z tail of the BLAST counterparts significantly overlaps with the SCUBA population, in terms of both SFRs and stellar masses, with observed trends of specific SFR that support strong evolution and downsizing.

  4. Chromospheres of Coronal Stars

    NASA Technical Reports Server (NTRS)

    Linsky, Jeffrey L.; Wood, Brian E.

    1996-01-01

    We summarize the main results obtained from the analysis of ultraviolet emission line profiles of coronal late-type stars observed with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope. The excellent GHRS spectra provide new information on magnetohydrodynamic phenomena in the chromospheres and transition regions of these stars. One exciting new result is the discovery of broad components in the transition region lines of active stars that we believe provide evidence for microflare heating in these stars.

  5. Nothing to Hide -- An X-ray Survey of Star Formation Activity in the Pipe Nebula

    NASA Astrophysics Data System (ADS)

    Forbrich, Jan; Posselt, Bettina; Lada, Charles J.; Covey, Kevin

    2009-09-01

    The Pipe Nebula, a large nearby molecular cloud, lacks obvious signposts of star formation in all but one of more than 130 dust extinction cores that have been identified within it. In a recent mid-infrared survey using Spitzer-MIPS to cover 13 square degrees, we have established that the star formation efficiency for the entire cloud is only ˜0.06%. The mid-infrared data are most sensitive for the earliest evolutionary stages of Young Stellar Objects (YSOs), covering class I protostars and typical class II sources (classical T Tauri stars). X-ray observations allow us to extend our survey to constrain any population of classical and weak-line T Tauri stars. In a first step, we use the ROSAT All-Sky Survey to constrain any overall T Tauri star population of the Pipe Nebula. Due to the fact that the Pipe Nebula is at a distance of only 130 pc, the ROSAT survey is already quite sensitive. Assuming a typical level of extinction, the completeness for G- and K-type stars is estimated to be about 50%. Subsequently, we use XMM-Newton observations pointed at three high-extinction regions within the Pipe Nebula to analyze these areas at higher sensitivity. These three regions are Barnard 59, the only core with ongoing star formation, the ``ring'' (i.e., the highest extinction region in the ``bowl'' of the Pipe), and Barnard 68. We additionally analyze the YSOs of Barnard 59 in the radio continuum to constrain high-energy processes. Overall, our results corroborate our previous Spitzer result that the star formation efficiency of the Pipe Nebula is very low.

  6. Star formation and accretion in the circumnuclear disks of active galaxies

    NASA Astrophysics Data System (ADS)

    Wutschik, Stephanie; Schleicher, Dominik R. G.; Palmer, Thomas S.

    2013-12-01

    Aims: We explore the evolution of supermassive black holes (SMBH) centered in a circumnuclear disk (CND) as a function of the mass supply from the host galaxy and considering different star formation laws, which may give rise to a self-regulation via the injection of supernova-driven turbulence. Methods: A system of equations describing star formation, black hole accretion and angular momentum transport in the disk was solved self-consistently for an axisymmetric disk in which the gravitational potential includes contributions from the black hole, the disk and the hosting galaxy. Our model extends the framework provided by Kawakatu & Wada (2008, ApJ, 681, 73), by separately considering the inner and outer part of the disk, and by introducing a potentially non-linear dependence of the star formation rate on the gas surface density and the turbulent velocity. The star formation recipes are calibrated using observational data for NGC 1097, while the accretion model is based on turbulent viscosity as a source of angular momentum transport in a thin viscous accretion disk. Results: We find that current data provide no strong constraint on the star formation recipe, and can in particular not distinguish between models entirely regulated by the surface density, and models including a dependence on the turbulent velocity. The evolution of the black hole mass, on the other hand, strongly depends on the applied star formation law, as well as the mass supply from the host galaxy. We suggest to explore the star formation process in local AGN with high-resolution ALMA observations to break the degeneracy between different star formation models.

  7. The mid-infrared emission of narrow-line active galactic nuclei: Star formation, nuclear activity, and two populations revealed by WISE

    SciTech Connect

    Rosario, David J.; Burtscher, Leonard; Davies, Richard; Genzel, Reinhard; Lutz, Dieter; Tacconi, Linda J.

    2013-12-01

    We explore the nature of the long-wavelength mid-infrared (MIR) emission of a sample of 13,000 local Type II (narrow-line) active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS) using 12 μm and 22 μm photometry from the WISE all-sky survey. In combination with FIRST 1.4 GHz photometry, we show that AGNs divide into two relatively distinct populations or 'branches' in the plane of MIR and radio luminosity. Seyfert galaxies lie almost exclusively on an MIR-bright branch (Branch A), while low-ionization nuclear emission line galaxies (LINERs) are split evenly into Branch A and the MIR-faint Branch B. We devise various tests to constrain the processes that define the branches, including a comparison to the properties of pure star-forming inactive galaxies on the MIR-radio plane. We demonstrate that the total MIR emission of objects on Branch A, including most Seyfert galaxies, is governed primarily by host star formation, with ≈15% of the 22 μm luminosity coming from AGN-heated dust. This implies that ongoing dusty star formation is a general property of Seyfert host galaxies. We show that the 12 μm broadband luminosity of AGNs on Branch A is suppressed with respect to star-forming galaxies, possibly due to the destruction of PAHs or deeper 10 μm Si absorption in AGNs. We uncover a correlation between the MIR luminosity and [O III] λ5007 luminosity in AGNs. This suggests a relationship between the star formation rate and nuclear luminosity in the AGN population, but we caution on the importance of selection effects inherent to such AGN-dominated emission-line galaxies in driving such a correlation. We highlight the MIR-radio plane as a useful tool in comparative studies of star formation and nuclear activity in AGNs.

  8. Constraints on Feedback in the Local Universe: The Relation Between Star Formation and AGN Activity in Early Type Galaxies

    NASA Astrophysics Data System (ADS)

    Vaddi, Sravani; O'Dea, Christopher P.; Baum, Stefi Alison

    2016-01-01

    We address the relation between star formation and AGN activity in a sample of 231 nearby (0.0002 < z < 0.0358) early type galaxies by carrying out a multi-wavelength study using archival observations in the UV, IR and radio. Our results indicate that early type galaxies in the current epoch are rarely powerful AGNs, with P < 1022 WHz-1 for a majority of the galaxies. Only massive galaxies are capable of hosting powerful radio sources while less massive galaxies are hosts to lower radio power sources. Evidence of ongoing star formation is seen in approximately 7% of the sample. The SFR of these galaxies is less than 0.1 M⊙yr-1. They also tend to be radio faint (P < 1022 WHz-1). There is a nearly equal fraction of star forming galaxies in radio faint (P < 1022 WHz-1) and radio bright galaxies (P ≥ 1022 WHz-1) suggesting that both star formation and radio mode feedback are constrained to be very low in our sample. We notice that our galaxy sample and the Brightest Cluster Galaxies (BCGs) follow similar trends in radio power versus SFR. This may be produced if both radio power and SFR are related to stellar mass.

  9. GS34-6+65: A Large Galactic Supershell Originating in an Active Star Formation Region and Extending to the Halo

    NASA Astrophysics Data System (ADS)

    Maciejewski, Witold; Murphy, Edward M.; Lockman, Felix J.; Savage, Blair D.

    1995-03-01

    The Galactic supershell GS34-6+65 (Heiles 1979) was mapped in the H{I}; 21 cm emission line with the NRAO 140 ft radiotelescope. The observations cover galactic longitudes 30(deg) ; to 40(deg) ; and latitudes -1(deg) ; to -15(deg) ; with 10 arcmin spacing in both coordinates. Centered at l=35, b=-5 and v_rad=+56km/s, the supershell consists of an irregular spherical shell about 7(deg) ; in diameter, which reaches 9.5(deg) ; below the galactic plane, and of a well defined, massive cone at low latitudes which connects to the molecular cloud CO[35,44] (Dame et al.1986) through a narrow (20 pc wide) channel of reduced H{I}; emission. On the basis of an investigation of objects near the line of sight to the supershell and information from the galactic rotation curve, we derive a distance of ~ 3.7 kpc, which implies that the shell has a diameter of ~ 450 pc and extends at least 600 pc into the Galactic halo. The distance also indicates that the supershell originates in the Sagittarius arm. The concentration of supernova remnants, star forming regions and H{II}; regions in this direction implies that the supershell is a remnant of multiple supernovae and that strong star formation activity persists in this region of the Galaxy, though the large column density (greater than 10(22) H/cm(2) ) prevents us from seeing the stars. We interpret W48 as a region of star formation induced by a shock wave related to the cone. We consider simple models to take into account geometrical and dynamical effects resulting in observed H{I}; emission at given radial velocity. We estimate the swept up mass in the shell to be 7.3*E(4) Msun ; and the mass in the cone -- 1.3*E(5) Msun ;. The estimated kinetic energy of the supershell, 5.0*E(51) ergs, imposes a minimicrons limit of about 5.0*E(52) ergs on the total energy of the event creating the supershell. REFERENCES: Dame, T. M., Elmegreen, B. G., Cohen, R. S., Thaddeus, P. 1986, Astroph. Journ., 305, 892 Heiles, C. 1979, Astroph. Journ., 229

  10. Activity Of T Tauri Type Stars And Objects Similar To Them

    NASA Astrophysics Data System (ADS)

    Ibryamov, Sunay

    2016-06-01

    The main purpose of the dissertation is on the basis of long-term light curves, to be classified the variability of 28 PMS stars and to be draw conclusions about the physical mechanisms initiating observed changes in their brightness. 22 of the investigated stars are located in the dense molecular cloud L935, known as 'Gulf of Mexico' (NGC 7000/IC 5070), and 6 stars are located in the vicinity of the reflection nebula NGC 7129. The multicolour photometric observations that we present were performed from 1993 to 2015 with the 2-m RCC, the 50/70-cm Schmidt and the 60-cm Cassegrain telescopes of the Rozhen NAO (Bulgaria) and the 1.3-m RC telescope of the Skinakas Observatory (Greece). All frames were taken through a standard Johnson-Cousins set of filters. The studied stars were classified as follows: V752 Cyg, V1539 Cyg, V1716 Cyg, FHO 26, FHO 29, LkHα 186, LkHα 187, LkHα 191, [KW97] 53-17, [KW97] 53-22, [KW97] 53-23, V391 Cep, NGC 7129 S V2 and 2MASS J21403576+6635000 show characteristics for classical T Tauri stars; V1538 Cyg, V1929 Cyg, [KW97] 53-20 and NGC 7129 S V1 are probably weak-line T Tauri stars; LkHα 189 and [KW97] 53-11 show characteristics for both type T Tauri stars and spectral observations are needed for their exact classification; V350 Cep shows indications for EXor and/or FUor-type variability; V521 Cyg, FHO 27, FHO 28 and NGC 7129 S V3 show characteristics for UXor-type variability; V1957 Cyg, V2051 Cyg and [KW97] 53-36 likely are evolved PMS stars or post-T Tauri stars. Periodicity was discovered for 3 of the investigated stars. V1716 Cyg indicates 4.15-day period, V1929 Cyg indicates 0.43-day period and LkHα 189 indicates 2.45-day period.

  11. GOODS-HERSCHEL: SEPARATING HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI AND STAR-FORMING GALAXIES USING INFRARED COLOR DIAGNOSTICS

    SciTech Connect

    Kirkpatrick, Allison; Pope, Alexandra; Charmandaris, Vassilis; Daddi, Emmanuele; Elbaz, David; Pannella, Maurilio; Aussel, Herve; Dasyra, Kalliopi; Leiton, Roger; Scott, Douglas; Magnelli, Benjamin; Popesso, Paola; Altieri, Bruno; Coia, Daniela; Valtchanov, Ivan; Dannerbauer, Helmut; Dickinson, Mark; Kartaltepe, Jeyhan; Magdis, Georgios

    2013-02-15

    We have compiled a large sample of 151 high-redshift (z = 0.5-4) galaxies selected at 24 {mu}m (S {sub 24} > 100 {mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-infrared spectrum into contributions from star formation and activity in the galactic nuclei. In addition, we have a wealth of photometric data from Spitzer IRAC/MIPS and Herschel PACS/SPIRE. We explore how effective different infrared color combinations are at separating our mid-IR spectroscopically determined active galactic nuclei from our star-forming galaxies. We look in depth at existing IRAC color diagnostics, and we explore new color-color diagnostics combining mid-IR, far-IR, and near-IR photometry, since these combinations provide the most detail about the shape of a source's IR spectrum. An added benefit of using a color that combines far-IR and mid-IR photometry is that it is indicative of the power source driving the IR luminosity. For our data set, the optimal color selections are S {sub 250}/S {sub 24} versus S {sub 8}/S {sub 3.6} and S {sub 100}/S {sub 24} versus S {sub 8}/S {sub 3.6}; both diagnostics have {approx}10% contamination rate in the regions occupied primarily by star-forming galaxies and active galactic nuclei, respectively. Based on the low contamination rate, these two new IR color-color diagnostics are ideal for estimating both the mid-IR power source of a galaxy when spectroscopy is unavailable and the dominant power source contributing to the IR luminosity. In the absence of far-IR data, we present color diagnostics using the Wide-field Infrared Survey Explorer mid-IR bands which can efficiently select out high-z (z {approx} 2) star-forming galaxies.

  12. Herschel-ATLAS: the connection between star formation and AGN activity in radio-loud and radio-quiet active galaxies

    NASA Astrophysics Data System (ADS)

    Gürkan, G.; Hardcastle, M. J.; Jarvis, M. J.; Smith, D. J. B.; Bourne, N.; Dunne, L.; Maddox, S.; Ivison, R. J.; Fritz, J.

    2015-10-01

    We examine the relationship between star formation and active galactic nuclei (AGN) activity by constructing matched samples of local (0 < z < 0.6) radio-loud and radio-quiet AGN in the Herschel-Astrophysical Terahertz Large Area Survey fields. Radio-loud AGN are classified as high-excitation and low-excitation radio galaxies using their emission lines and WISE 22-μm luminosity. AGN accretion and jet powers in these active galaxies are traced by [O III] emission-line and radio luminosity, respectively. Star formation rates (SFRs) and specific star formation rates (SSFRs) were derived using Herschel 250-μm luminosity and stellar mass measurements from the Sloan Digital Sky Survey-Max Planck Institute for Astrophysics-John Hopkins University catalogue. In the past, star formation studies of AGN have mostly focused on high-redshift sources to observe the thermal dust emission that peaks in the far-infrared, which limited the samples to powerful objects. However, with Herschel we can expand this to low redshifts. Our stacking analyses show that SFRs and SSFRs of both radio-loud and radio-quiet AGN increase with increasing AGN power but that radio-loud AGN tend to have lower SFR. Additionally, radio-quiet AGN are found to have approximately an order of magnitude higher SSFRs than radio-loud AGN for a given level of AGN power. The difference between the star formation properties of radio-loud and -quiet AGN is also seen in samples matched in stellar mass.

  13. Neutron Stars

    NASA Astrophysics Data System (ADS)

    van den Heuvel, Ed

    Radio pulsars are unique laboratories for a wide range of physics and astrophysics. Understanding how they are created, how they evolve and where we find them in the Galaxy, with or without binary companions, is highly constraining of theories of stellar and binary evolution. Pulsars' relationship with a recently discovered variety of apparently different classes of neutron stars is an interesting modern astrophysical puzzle which we consider in Part I of this review. Radio pulsars are also famous for allowing us to probe the laws of nature at a fundamental level. They act as precise cosmic clocks and, when in a binary system with a companion star, provide indispensable venues for precision tests of gravity. The different applications of radio pulsars for fundamental physics will be discussed in Part II. We finish by making mention of the newly discovered class of astrophysical objects, the Fast Radio Bursts, which may or may not be related to radio pulsars or neutron stars, but which were discovered in observations of the latter.

  14. Creating Active and High-Impact Learning: Moving out of the Classroom with Field-Based Student Consulting Projects

    ERIC Educational Resources Information Center

    Heriot, Kirk C.; Cook, Ronald G.; Matthews, Charles H.; Simpson, Leo

    2007-01-01

    Active learning has attracted considerable attention in higher education in response to concerns about how and what students are learning. Many pedagogies may be categorized as active learning, although most are classroom-based. The authors propose an alternative to "active learning in the classroom", which they characterize as "active learning…

  15. Managing Challenging Behaviors of Dementia in Veterans: Identifying and Changing Activators and Consequences Using STAR-VA.

    PubMed

    Curyto, Kim J; McCurry, Sue M; Luci, Katherine; Karlin, Bradley E; Teri, Linda; Karel, Michele J

    2017-02-01

    One of the most challenging clinical issues for long-term care staff is the management of dementia-related behavioral symptoms. STAR-VA is an interdisciplinary intervention for managing challenging behaviors of Veterans with dementia in Community Living Centers (CLCs) within the U.S. Department of Veterans Affairs. The goals of the current article are to delineate categories of challenging behaviors found in CLCs, the context in which behaviors occurred, and the interventions used by CLC clinical teams when implementing STAR-VA. In 2013, 17 CLC teams completed STAR-VA training, enrolling 71 Veteran participants. Four independent raters identified common assessment and intervention themes for six behavior categories, coding activators, consequences, goal behaviors, and care plans for each category. Successful care plans included staff changes in communication approaches, incorporation of pleasant events into care, and individualized environmental modifications. Findings illustrate the range of interventions that CLC teams may apply as a result of systematic behavioral assessment informing an understanding of activators and consequences of dementia-related behaviors. [Journal of Gerontological Nursing, 43(2), 33-43.].

  16. Star Formation Activity in the Galactic H II Region Sh2-297

    NASA Astrophysics Data System (ADS)

    Mallick, K. K.; Ojha, D. K.; Samal, M. R.; Pandey, A. K.; Bhatt, B. C.; Ghosh, S. K.; Dewangan, L. K.; Tamura, M.

    2012-11-01

    We present a multiwavelength study of the Galactic H II region Sh2-297, located in the Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756 cm-3 and 9.15 × 105 cm-6 pc using the radio continuum observations at 610 and 1280 MHz, and Very Large Array archival data at 1420 MHz. To understand local star formation, we identified the young stellar object (YSO) candidates in a region of area ~7farcm5 × 7farcm5 centered on Sh2-297 using grism slitless spectroscopy (to identify the Hα emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color and color-magnitude (CM) diagrams, giving 50 red sources (H - K > 0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be ~0.1-2 M ⊙ and 0.5-2 Myr using optical (V/V-I) and NIR (J/J-H) CM diagrams. The mean age of the YSOs is found to be ~1 Myr, which is of the order of dynamical age of 1.07 Myr of the H II region. Using the estimated range of visual extinction (1.1-25 mag) from literature and NIR data for the region, spectral energy distribution models have been implemented for selected YSOs which show masses and ages to be consistent with estimated values. The spatial distribution of YSOs shows an evolutionary sequence, suggesting triggered star formation in the region. The star formation seems to have propagated from the ionizing star toward the cold dark cloud LDN1657A located west of Sh2-297.

  17. Heavy Metal Stars

    NASA Astrophysics Data System (ADS)

    2001-08-01

    La Silla Telescope Detects Lots of Lead in Three Distant Binaries Summary Very high abundances of the heavy element Lead have been discovered in three distant stars in the Milky Way Galaxy . This finding strongly supports the long-held view that roughly half of the stable elements heavier than Iron are produced in common stars during a phase towards the end of their life when they burn their Helium - the other half results from supernova explosions. All the Lead contained in each of the three stars weighs about as much as our Moon. The observations show that these "Lead stars" - all members of binary stellar systems - have been more enriched with Lead than with any other chemical element heavier than Iron. This new result is in excellent agreement with predictions by current stellar models about the build-up of heavy elements in stellar interiors. The new observations are reported by a team of Belgian and French astronomers [1] who used the Coude Echelle Spectrometer on the ESO 3.6-m telescope at the La Silla Observatory (Chile). PR Photo 26a/01 : A photo of HD 196944 , one of the "Lead stars". PR Photo 26b/01 : A CES spectrum of HD 196944 . The build-up of heavy elements Astronomers and physicists denote the build-up of heavier elements from lighter ones as " nucleosynthesis ". Only the very lightest elements (Hydrogen, Helium and Lithium [2]) were created at the time of the Big Bang and therefore present in the early universe. All the other heavier elements we now see around us were produced at a later time by nucleosynthesis inside stars. In those "element factories", nuclei of the lighter elements are smashed together whereby they become the nuclei of heavier ones - this process is known as nuclear fusion . In our Sun and similar stars, Hydrogen is being fused into Helium. At some stage, Helium is fused into Carbon, then Oxygen, etc. The fusion process requires positively charged nuclei to move very close to each other before they can unite. But with increasing

  18. Stellar and circumstellar activity of the Be star MU Centauri. I. Line emission outbursts

    NASA Astrophysics Data System (ADS)

    Rivinius, Th.; Baade, D.; Stefl, S.; Stahl, O.; Wolf, B.; Kaufer, A.

    1998-05-01

    With a total of 408 echelle spectra obtained with Heros\\ (Heidelberg Extended Range Optical Spectrograph) during 6 observing runs covering 355 nights in 4 years and the spectral range from 3450 to 8620 Angstroms at a resolving power of 20000, this study is based on one of the most extensive homogeneous observational records of the short-, medium-, and long-term variability of any Be star. One week worth of low-resolution spectra with very high temporal sampling was additionally obtained. Three dense series of very high-resolution low-noise profiles of He Ilambda 6678 observed in 1985-1987 (309 spectra), one of Si Iiilambda {4553}\\ obtained in 1995 (27 spectra) simultaneously to the low-resolution data and several shorter datasets of different observing dates and wavelengths could also be relied upon for verification purposes. The star was found to be in the process of continued gradual recovery of the Hα\\ emitting disk which had been lost from 1977-1989. During the monitoring period numerous line emission outbursts were observed. A detailed generalized pattern of an outburst cycle is derived from observations of different circumstellar lines at times of various levels of emission from the disk. Relative quiescence, precursor, outburst, and subsequent relaxation can be distinguished as the main constituting phases, even though there are distinct differences between different groups of spectral lines. The actual appearance of outbursts depends also quite noticeably on the strength of the already present circumstellar emission. Outbursts are preceded by a significant decline in the peak height of all circumstellar emission lines, which only lasts a few days. The outbursts proper are characterized by the occurrence within 1-3 days of (i) broad emission wings, (ii) rapid cyclic variability of the violet-to-red (V/R) emission peak ratio, (iii) temporary high velocity absorptions, (iv) transient sharp absorption spikes at the edges of photospheric lines, (v) an

  19. Star Clusters within FIRE

    NASA Astrophysics Data System (ADS)

    Perez, Adrianna; Moreno, Jorge; Naiman, Jill; Ramirez-Ruiz, Enrico; Hopkins, Philip F.

    2017-01-01

    In this work, we analyze the environments surrounding star clusters of simulated merging galaxies. Our framework employs Feedback In Realistic Environments (FIRE) model (Hopkins et al., 2014). The FIRE project is a high resolution cosmological simulation that resolves star forming regions and incorporates stellar feedback in a physically realistic way. The project focuses on analyzing the properties of the star clusters formed in merging galaxies. The locations of these star clusters are identified with astrodendro.py, a publicly available dendrogram algorithm. Once star cluster properties are extracted, they will be used to create a sub-grid (smaller than the resolution scale of FIRE) of gas confinement in these clusters. Then, we can examine how the star clusters interact with these available gas reservoirs (either by accreting this mass or blowing it out via feedback), which will determine many properties of the cluster (star formation history, compact object accretion, etc). These simulations will further our understanding of star formation within stellar clusters during galaxy evolution. In the future, we aim to enhance sub-grid prescriptions for feedback specific to processes within star clusters; such as, interaction with stellar winds and gas accretion onto black holes and neutron stars.

  20. Star Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z=5.3

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared OR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multi wavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  1. Star and Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z equals 5.3

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multi wavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  2. Star and Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z=5.3

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  3. Effects of Droplet-Vitrification Cryopreservation Based on Physiological and Antioxidant Enzyme Activities of Brassidium Shooting Star Orchid

    PubMed Central

    Rahmah, Safrina; Ahmad Mubbarakh, Safiah; Soo Ping, Khor

    2015-01-01

    Protocorm-like bodies (PLBs) of Brassidium Shooting Star orchid were successfully cryopreserved using droplet-vitrification method. Vitrification based cryopreservation protocol is comprised of preculture, osmoprotection, cryoprotection, cooling, rewarming, and growth recovery and each and every step contributes to the achievement of successful cryopreservation. In order to reveal the lethal and nonlethal damage produced by cryopreservation, histological observation, scanning electron microscopy (SEM), and biochemical analysis were carried out in both cryopreserved and noncryopreserved PLBs of Brassidium Shooting Star orchid comparing with the control PLBs stock culture. Histological and scanning electron microscopy analyses displayed structural changes in cryopreserved PLBs due to the impact of cryoinjury during exposure to liquid nitrogen. Total soluble protein significantly increased throughout the dehydration process and the highest value was achieved when PLBs were stored in liquid nitrogen. Ascorbate peroxidase (APX) and catalase (CAT) showed the highest enzyme activities in both dehydration and cryostorage treatments indicating that stress level of PLBs was high during these stages. PMID:25861687

  4. The Abundances of Carbon and Nitrogen in the Photospheres of Active B Stars

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine J.

    2011-01-01

    Contemporary models for the structure and evolution of rapidly-rotating OB stars predict a photospheric enrichment of nitrogen due to the mixing of the CNO-processed material from the star's core with the original surface material. The predicted N-enhancement increases as the star approaches its critical rotational velocity. Alternatively the Algol primaries should have N-enriched photospheres if the material currently being transferred is from the mass loser's original core. To test these predictions, the C and N abundances in selected early Be stars and B-type mass gainers in Algol systems have been determined from spectroscopic data obtained with the IUE and FUSE spacecraft. The abundance analyses, carried through with the Hubeny/Lanz NLTE codes TLUSTY/SYNSPEC, were confronted with some challenges that are not encountered in abundance studies of sharp-lined, non-emission B stars including the treatment of shallow, blended rotationally-broadened lines, the appropriate value for the microturbulence parameter, correction for disk emission and possible shell absorption, and latitudinal variation of Teff and log g. The FUV offers an advantage over the optical region as there is far less influence from disk emission and the N lines are intrinsically stronger. Particularly useful are the features of C II 1324 Å, C III 1176 Å, 1247 Å, N I 1243 Å, and N III 1183,84 Å. Be stars with v sin i < 150 km s-1 were chosen to minimize the effect of latitudinal parameter variation. Given the errors it appears that the N abundance in the Be stars is normal. Expected mixing is apparently suppressed, and this study lends no support for Be star models based upon critical rotation. However, expected N-enhancement and a low C abundance are inferred for the B-type primaries in some interacting binaries. GJP is grateful for support from NASA Grants NNX07AH56G (ADP) and NNX07AF89G (FUSE), and the USC WiSE program.

  5. The relationship between star formation activity and galaxy structural properties in CANDELS and a semi-analytic model

    NASA Astrophysics Data System (ADS)

    Brennan, Ryan; Pandya, Viraj; Somerville, Rachel S.; Barro, Guillermo; Bluck, Asa F. L.; Taylor, Edward N.; Wuyts, Stijn; Bell, Eric F.; Dekel, Avishai; Faber, Sandra; Ferguson, Henry C.; Koekemoer, Anton M.; Kurczynski, Peter; McIntosh, Daniel H.; Newman, Jeffrey A.; Primack, Joel

    2017-02-01

    We study the correlation of galaxy structural properties with their location relative to the SFR-M* correlation, also known as the star formation `star-forming main sequence' (SFMS), in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and Galaxy and Mass Assembly Survey and in a semi-analytic model (SAM) of galaxy formation. We first study the distribution of median Sérsic index, effective radius, star formation rate (SFR) density and stellar mass density in the SFR-M* plane. We then define a redshift-dependent main sequence and examine the medians of these quantities as a function of distance from this main sequence, both above (higher SFRs) and below (lower SFRs). Finally, we examine the distributions of distance from the main sequence in bins of these quantities. We find strong correlations between all of these galaxy structural properties and the distance from the SFMS, such that as we move from galaxies above the SFMS to those below it, we see a nearly monotonic trend towards higher median Sérsic index, smaller radius, lower SFR density, and higher stellar density. In the SAM, bulge growth is driven by mergers and disc instabilities, and is accompanied by the growth of a supermassive black hole which can regulate or quench star formation via active galactic nucleus feedback. We find that our model qualitatively reproduces the trends described above, supporting a picture in which black holes and bulges co-evolve, and active galactic nucleus feedback plays a critical role in moving galaxies off of the SFMS.

  6. Active Phenomena in the Pre-main Sequence Star AB AUR

    NASA Technical Reports Server (NTRS)

    Praderie, F.; Simon, T.; Boesgaard, A. M.; Felenbok, P.; Catala, C.; Czarny, J.; Talavera, A.

    1985-01-01

    The Herbig Ae star AB Aur presents short time scale variability in the Mg II and Ca II resonance lines. A qualitative model of the expanding envelope, involving fast and slow streams in a co-rotating structure, is proposed to explain the Mg II spectral variability.

  7. Optical and X-ray studies of chromospherically active stars: FR Cancri, HD 95559 and LO Pegasi

    NASA Technical Reports Server (NTRS)

    Pandey, J. C.; Singh, K. P.; Drake, S. A.; Sagar, R.

    2005-01-01

    We present a multiwavelength study of three chromospherically active stars, namely FR Cnc (= BD +16 degrees 1753), HD 95559 and LO Peg (=BD +22 degrees 4409), including newly obtained optical photometry, (for FR Cnc) low-resolution optical spectroscopy, as well as archival IR and X-ray observations. The BVR photometry carried out during the years 2001 - 2004 has found significant photometric variability to be present in all three stars. For FR Cnc, a photometric period 0.826685 +/- 0.000034 d has been established. The strong variation in the phase and amplitude of the FR Cnc light curves when folded on this period implies the presence of evolving and migrating spots or spot groups on its surface. Two independent spots with migration periods of 0.97 and 0.93 years respectively are inferred. The photometry of HD 95559 suggests the formation of a spot (group) during the interval of our observations. We infer the existence of two independent spots or groups in the photosphere of LO Peg, one of which has a migration period of 1.12 years. The optical spectroscopy of FR Cnc carried out during 2002-2003, reveals the presence of strong and variable Ca I1 H and K, H(sub beta) and H(sub alpha) emission features indicative of high level of chromospheric activity. The value of 5.3 for the ratio of the excess emission in H(sub alpha) to H(sub beta), EH(sub alpha)/EH(sub beta), suggests that the chromospheric emission may arise from an extended off-limb region. We have searched for the presence of color excesses in the near-IR JHK bands of these stars using 2MASS data, but none of them appear to have any significant color excess. We have also analyzed archival X-ray observations of HD 95559 and LO Peg carried out by with the ROSAT observatory. The best fit models to their X-ray spectra imply the presence of two coronal plasma components of differing temperatures and with sub-solar metal abundances. The inferred emission measures and temperatures of these systems are similar to

  8. A single cell level measurement of StAR expression and activity in adrenal cells.

    PubMed

    Lee, Jinwoo; Yamazaki, Takeshi; Dong, Hui; Jefcoate, Colin

    2017-02-05

    The Steroidogenic acute regulatory protein (StAR) directs mitochondrial cholesterol uptake through a C-terminal cholesterol binding domain (CBD) and a 62 amino acid N-terminal regulatory domain (NTD) that contains an import sequence and conserved sites for inner membrane metalloproteases. Deletion of the NTD prevents mitochondrial import while maintaining steroidogenesis but with compromised cholesterol homeostasis. The rapid StAR-mediated cholesterol transfer in adrenal cells depends on concerted mRNA translation, p37 StAR phosphorylation and controlled NTD cleavage. The NTD controls this process with two cAMP-inducible modulators of, respectively, transcription and translation SIK1 and TIS11b/Znf36l1. High-resolution fluorescence in situ hybridization (HR-FISH) of StAR RNA resolves slow RNA splicing at the gene loci in cAMP-induced Y-1 cells and transfer of individual 3.5 kB mRNA molecules to mitochondria. StAR transcription depends on the CREB coactivator CRTC2 and PKA inhibition of the highly inducible suppressor kinase SIK1 and a basal counterpart SIK2. PKA-inducible TIS11b/Znf36l1 binds specifically to highly conserved elements in exon 7 thereby suppressing formation of mRNA and subsequent translation. Co-expression of SIK1, Znf36l1 with 3.5 kB StAR mRNA may limit responses to pulsatile signaling by ACTH while regulating the transition to more prolonged stress.

  9. A hot Jupiter around the very active weak-line T Tauri star TAP 26

    NASA Astrophysics Data System (ADS)

    Yu, L.; Donati, J.-F.; Hébrard, E. M.; Moutou, C.; Malo, L.; Grankin, K.; Hussain, G.; Collier Cameron, A.; Vidotto, A. A.; Baruteau, C.; Alencar, S. H. P.; Bouvier, J.; Petit, P.; Takami, M.; Herczeg, G.; Gregory, S. G.; Jardine, M.; Morin, J.; Ménard, F.; Matysse Collaboration

    2017-01-01

    We report the results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star TAP 26, carried out within the MaTYSSE programme with the ESPaDOnS spectropolarimeter at the 3.6 m Canada-France-Hawaii Telescope. Applying Zeeman-Doppler Imaging to our observations, concentrating in 2015 November and 2016 January and spanning 72 d in total, 16 d in 2015 November and 13 d in 2016 January, we reconstruct surface brightness and magnetic field maps for both epochs and demonstrate that both distributions exhibit temporal evolution not explained by differential rotation alone. We report the detection of a hot Jupiter (hJ) around TAP 26 using three different methods, two using Zeeman-Doppler Imaging (ZDI) and one Gaussian-Process Regression (GPR), with a false-alarm probability smaller than 6 10-4. However, as a result of the aliasing related to the observing window, the orbital period cannot be uniquely determined; the orbital period with highest likelihood is 10.79±0.14 d followed by 8.99±0.09 d. Assuming the most likely period, and that the planet orbits in the stellar equatorial plane, we obtain that the planet has a minimum mass Msin i of 1.66±0.31 MJup and orbits at 0.0968±0.0032 au from its host star. This new detection suggests that disc type II migration is efficient at generating newborn hJs, and that hJs may be more frequent around young T Tauri stars than around mature stars (or that the MaTYSSE sample is biased towards hJ-hosting stars).

  10. A dynamo model of magnetic activity in solar-like stars with different rotational velocities

    SciTech Connect

    Karak, Bidya Binay; Choudhuri, Arnab Rai; Kitchatinov, Leonid L.

    2014-08-10

    We attempt to provide a quantitative theoretical explanation for the observations that Ca II H/K emission and X-ray emission from solar-like stars increase with decreasing Rossby number (i.e., with faster rotation). Assuming that these emissions are caused by magnetic cycles similar to the sunspot cycle, we construct flux transport dynamo models of 1 M{sub ☉} stars rotating with different rotation periods. We first compute the differential rotation and the meridional circulation inside these stars from a mean-field hydrodynamics model. Then these are substituted in our dynamo code to produce periodic solutions. We find that the dimensionless amplitude f{sub m} of the toroidal flux through the star increases with decreasing rotation period. The observational data can be matched if we assume the emissions to go as the power 3-4 of f{sub m}. Assuming that the Babcock-Leighton mechanism saturates with increasing rotation, we can provide an explanation for the observed saturation of emission at low Rossby numbers. The main failure of our model is that it predicts an increase of the magnetic cycle period with increasing rotation rate, which is the opposite of what is found observationally. Much of our calculations are based on the assumption that the magnetic buoyancy makes the magnetic flux tubes rise radially from the bottom of the convection zone. Taking into account the fact that the Coriolis force diverts the magnetic flux tubes to rise parallel to the rotation axis in rapidly rotating stars, the results do not change qualitatively.

  11. DETERMINING THE COVERING FACTOR OF COMPTON-THICK ACTIVE GALACTIC NUCLEI WITH NuSTAR

    SciTech Connect

    Brightman, M.; Baloković, M.; Fuerst, F.; Harrison, F. A.; Stern, D.; Arévalo, P.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Gandhi, P.; Hailey, C. J.; Hickox, R. C.; Koss, M.; LaMassa, S.; and others

    2015-05-20

    The covering factor of Compton-thick (CT) obscuring material associated with the torus in active galactic nuclei (AGNs) is at present best understood through the fraction of sources exhibiting CT absorption along the line of sight (N{sub H} > 1.5 × 10{sup 24} cm{sup −2}) in the X-ray band, which reveals the average covering factor. Determining this CT fraction is difficult, however, due to the extreme obscuration. With its spectral coverage at hard X-rays (>10 keV), Nuclear Spectroscopic Telescope Array (NuSTAR) is sensitive to the AGNs covering factor since Compton scattering of X-rays off optically thick material dominates at these energies. We present a spectral analysis of 10 AGNs observed with NuSTAR where the obscuring medium is optically thick to Compton scattering, so-called CT AGNs. We use the torus models of Brightman and Nandra that predict the X-ray spectrum from reprocessing in a torus and include the torus opening angle as a free parameter and aim to determine the covering factor of the CT gas in these sources individually. Across the sample we find mild to heavy CT columns, with N{sub H} measured from 10{sup 24} to 10{sup 26} cm{sup −2}, and a wide range of covering factors, where individual measurements range from 0.2 to 0.9. We find that the covering factor, f{sub c}, is a strongly decreasing function of the intrinsic 2–10 keV luminosity, L{sub X}, where f{sub c} = (−0.41 ± 0.13)log{sub 10}(L{sub X}/erg s{sup −1})+18.31 ± 5.33, across more than two orders of magnitude in L{sub X} (10{sup 41.5}–10{sup 44} erg s{sup −1}). The covering factors measured here agree well with the obscured fraction as a function of L{sub X} as determined by studies of local AGNs with L{sub X} > 10{sup 42.5} erg s{sup −1}.

  12. Observational analysis of the physical conditions in galactic and extragalactic active star forming regions

    NASA Astrophysics Data System (ADS)

    Kristensen, L. E.

    2007-10-01

    In my thesis observations of near-infrared rovibrational H_2 emission in active star-forming regions are presented and analysed. The main subject of this work concerns new observations of the Orion Molecular Cloud (OMC1) and in particular the BN-KL region. Data consist of images of individual H_2 lines with high spatial resolution obtained both at the Canada-France-Hawaii Telescope and at the ESO Very Large Telescope (VLT). With the high spatial resolution of the VLT it is possible to analyse in detail (down to 60 AU ~ 0.13") individual objects in the region. I have also analysed H_2 and [FeII] emission from outflows in two dark clouds (Bok globules BHR71 and BHR137) and a high excitation blob in the Magellanic Clouds (N159-5). In the latter, data consist of long-slit spectra obtained at the ESO-VLT. In order to facilitate this work I ran a large grid of ~25000 shock models, producing almost 400 Gb of results. These models are state-of-the-art and there is a large number of free parameters which can be adjusted. A big part of my project has been to analyse the results from this grid and make it publically available. Furthermore, as it turned out, not all results are equally reliable and I have had to develop methods for checking the consistency of the wealth of results obtained. But with the model results and a sound knowledge of shock physics it is now relatively straightforward to interpret the H_2 and [FeII] data. The models allow me to predict the large-scale physical conditions in OMC1 such as density, shock velocities, magnetic field strengths, etc. Overall the preshock density is of the order of ~10^5-10^7 cm(-3) and shock velocities are in the interval 10-40 km/s. Another very interesting result is a new method developed for analysing bow shocks observed at high spatial resolution. For one isolated bow shock in OMC1 I predict a shock velocity of 50 km/s and a preshock density of the order of 5x10^5 cm(-3). The 3D velocity has recently been measured to 55 km

  13. Kepler Flares. IV. A Comprehensive Analysis of the Activity of the dM4e Star GJ 1243

    NASA Astrophysics Data System (ADS)

    Silverberg, Steven M.; Kowalski, Adam F.; Davenport, James R. A.; Wisniewski, John P.; Hawley, Suzanne L.; Hilton, Eric J.

    2016-10-01

    We present a comprehensive study of the active dM4e star GJ 1243. We use previous observations and ground-based echelle spectroscopy to determine that GJ 1243 is a member of the Argus association of field stars, suggesting it is ∼ 30{--}50 {{Myr}} old. We analyze 11 months of 1 minute cadence data from Kepler, presenting Kepler flare frequency distributions, as well as determining correlations between flare energy, amplitude, duration, and decay time. We find that the exponent α of the power-law flare energy distribution varies in time, primarily due to completeness of sample and the low frequency of high-energy flares. We also find a deviation from a single power law at high energy. We use ground-based spectroscopic observations that were simultaneous with the Kepler data to provide simultaneous photometric and spectroscopic analysis of three low-energy flares, the lowest-energy dMe flares with detailed spectral analysis to date on any star. The spectroscopic data from these flares extend constraints for radiative hydrodynamic flare models to a lower energy regime than has previously been studied. We use this simultaneous spectroscopy and Kepler photometry to develop approximate conversions from the Kepler bandpass to the traditional U and B bands. This conversion will be a critical factor in comparing any Kepler flare analyses to the canon of previous ground-based flare studies.

  14. Magnetically elevated accretion discs in active galactic nuclei: broad emission-line regions and associated star formation

    NASA Astrophysics Data System (ADS)

    Begelman, Mitchell C.; Silk, Joseph

    2017-01-01

    We propose that the accretion discs fueling active galactic nuclei (AGN) are supported vertically against gravity by a strong toroidal (φ-direction) magnetic field that develops naturally as the result of an accretion disc dynamo. The magnetic pressure elevates most of the gas carrying the accretion flow at R to large heights z ≳ 0.1R and low densities, while leaving a thin dense layer containing most of the mass - but contributing very little accretion - around the equator. We show that such a disc model leads naturally to the formation of a broad emission-line region through thermal instability. Extrapolating to larger radii, we demonstrate that local gravitational instability and associated star formation are strongly suppressed compared to standard disc models for AGN, although star formation in the equatorial zone is predicted for sufficiently high mass supply rates. This new class of accretion disc models thus appears capable of resolving two longstanding puzzles in the theory of AGN fueling: the formation of broad emission-line regions and the suppression of fragmentation thought to inhibit accretion at the required rates. We show that the disc of stars that formed in the Galactic Center a few million years ago could have resulted from an episode of magnetically elevated accretion at ≳ 0.1 of the Eddington limit.

  15. The different origins of magnetic fields and activity in the Hertzsprung gap stars, OU Andromedae and 31 Comae

    NASA Astrophysics Data System (ADS)

    Borisova, A.; Aurière, M.; Petit, P.; Konstantinova-Antova, R.; Charbonnel, C.; Drake, N. A.

    2016-06-01

    Context. When crossing the Hertzsprung gap, intermediate-mass stars develop a convective envelope. Fast rotators on the main sequence, or Ap star descendants, are expected to become magnetic active subgiants during this evolutionary phase. Aims: We compare the surface magnetic fields and activity indicators of two active, fast rotating red giants with similar masses and spectral class but different rotation rates - OU And (Prot = 24.2 d) and 31 Com (Prot = 6.8 d) - to address the question of the origin of their magnetism and high activity. Methods: Observations were carried out with the Narval spectropolarimeter in 2008 and 2013. We used the least-squares deconvolution (LSD) technique to extract Stokes V and I profiles with high signal-to-noise ratio to detect Zeeman signatures of the magnetic field of the stars. We then provide Zeeman-Doppler imaging (ZDI), activity indicators monitoring, and a precise estimation of stellar parameters. We use state-of-the-art stellar evolutionary models, including rotation, to infer the evolutionary status of our giants, as well as their initial rotation velocity on the main sequence, and we interpret our observational results in the light of the theoretical Rossby numbers. Results: The detected magnetic field of OU Andromedae (OU And) is a strong one. Its longitudinal component Bl reaches 40 G and presents an about sinusoidal variation with reversal of the polarity. The magnetic topology of OU And is dominated by large-scale elements and is mainly poloidal with an important dipole component, as well as a significant toroidal component. The detected magnetic field of 31 Comae (31 Com) is weaker, with a magnetic map showing a more complex field geometry, and poloidal and toroidal components of equal contributions. The evolutionary models show that the progenitors of OU And and 31 Com must have been rotating at velocities that correspond to 30 and 53%, respectively, of their critical rotation velocity on the zero age main sequence

  16. Stimulation of StAR expression by cAMP is controlled by inhibition of highly inducible SIK1 via CRTC2, a co-activator of CREB.

    PubMed

    Lee, Jinwoo; Tong, Tiegang; Takemori, Hiroshi; Jefcoate, Colin

    2015-06-15

    In mouse steroidogenic cells the activation of cholesterol metabolism is mediated by steroidogenic acute regulatory protein (StAR). Here, we visualized a coordinated regulation of StAR transcription, splicing and post-transcriptional processing, which are synchronized by salt inducible kinase (SIK1) and CREB-regulated transcription coactivator (CRTC2). To detect primary RNA (pRNA), spliced primary RNA (Sp-RNA) and mRNA in single cells, we generated probe sets by using fluorescence in situ hybridization (FISH). These methods allowed us to address the nature of StAR gene expression and to visualize protein-nucleic acid interactions through direct detection. We show that SIK1 represses StAR expression in Y1 adrenal and MA10 testis cells through inhibition of processing mediated by CRTC2. Digital image analysis matches qPCR analyses of the total cell culture. Evidence is presented for spatially separate accumulation of StAR pRNA and Sp-RNA at the gene loci in the nucleus. These findings establish that cAMP, SIK and CRTC mediate StAR expression through activation of individual StAR gene loci.

  17. Measurement of 56Fe activity produced in inelastic scattering of neutrons created by cosmic muons in an iron shield.

    PubMed

    Krmar, M; Jovančević, N; Nikolić, D

    2012-01-01

    We report on the study of the intensities of several gamma lines emitted after the inelastic scattering of neutrons in (56)Fe. Neutrons were produced via nuclear processes induced by cosmic muons in the 20tons massive iron cube placed at the Earth's surface and used as a passive shield for the HPGe detector. Relative intensities of detected gamma lines are compared with the results collected in the same iron shield by the use of the (252)Cf neutrons. Assessment against the published data from neutron scattering experiments at energies up to 14MeV is also provided. It allowed us to infer the qualitative information about the average energy of muon-created neutrons in the iron shield.

  18. Creating an Environment Conducive to Active and Collaborative Learning: Redesigning Introduction to Sociology at a Large Research University

    ERIC Educational Resources Information Center

    Lo, C. C.; Prohaska, A.

    2011-01-01

    In 2003 a Southeastern research university undertook the redesign of an introductory sociology course in order to improve student success by adding active and collaborative learning activities that gave students greater responsibility for learning. The new "hybrid" course provides most course materials online, requires electronic…

  19. Web-Based Interactive Video Vignettes Create a Personalized Active Learning Classroom for Introducing Big Ideas in Introductory Biology

    ERIC Educational Resources Information Center

    Wright, L. Kate; Newman, Dina L.; Cardinale, Jean A.; Teese, Robert

    2016-01-01

    The typical "flipped classroom" delivers lecture material in video format to students outside of class in order to make space for active learning in class. But why give students passive material at all? We are developing a set of high-quality online educational materials that promote active, hands-on science learning to aid in teaching…

  20. The extremely deep minimum in the IR brightness of the symbiotic star CH Cygni, accompanied by new activity of its hot component

    NASA Astrophysics Data System (ADS)

    Taranova, O. G.; Yudin, B. F.

    1992-04-01

    The results of photometric UBVJHKLMN observations of the symbiotic star CH Cyg are presented. In 1990, an extremely deep minimum was observed in its light curve, accompanied by new activity of the hot component of this binary star. If one considers a sharp decrease in the bolometric luminosity of the red giant (M7III) of CH Cyg by about 40 percent to be impossible, then the significant drop in the star's IR brightness may be connected with the obscuration of the red giant by a dust cloud which absorbs neutrally. In this case, it is required that the optical depth of the dust envelope as a whole decrease by about 30 percent.

  1. Star parties in Mexico, extended to Colombia and China

    NASA Astrophysics Data System (ADS)

    Torres-Peimbert, Silvia; Franco, Jose

    2015-08-01

    Sparked by the enthusiasm of the International Year of Astronomy, a set of simultaneous star parties have been held since 2008 in several cities in Mexico. These star parties have raised big expectations among the population and they have been repeated at least yearly. The activity has increased in size and participating sites. The most recent one took place on November 29th 2014, and it included 55 locations across Mexico as well as 5 in Colombia and one in China. To organize this activity a Mexican National Committee was created formed by several universities, the French Embassy, related industries and astronomical societies. We present more information on this activity.

  2. THE IMPACT OF INTERACTIONS, BARS, BULGES, AND ACTIVE GALACTIC NUCLEI ON STAR FORMATION EFFICIENCY IN LOCAL MASSIVE GALAXIES

    SciTech Connect

    Saintonge, Amelie; Fabello, Silvia; Wang Jing; Catinella, Barbara; Tacconi, Linda J.; Genzel, Reinhard; Gracia-Carpio, Javier; Wuyts, Stijn; Kramer, Carsten; Moran, Sean; Heckman, Timothy M.; Schiminovich, David; Schuster, Karl

    2012-10-20

    Using atomic and molecular gas observations from the GASS and COLD GASS surveys and complementary optical/UV data from the Sloan Digital Sky Survey and the Galaxy Evolution Explorer, we investigate the nature of the variations in the molecular gas depletion time observed across the local massive galaxy population. The large and unbiased COLD GASS sample allows us for the first time to statistically assess the relative importance of galaxy interactions, bar instabilities, morphologies, and the presence of active galactic nuclei (AGNs) in regulating star formation efficiency. We find that both the H{sub 2} mass fraction and depletion time vary as a function of the distance of a galaxy from the main sequence traced by star-forming galaxies in the SFR-M {sub *} plane. The longest gas depletion times are found in below-main-sequence bulge-dominated galaxies ({mu}{sub *} >5 Multiplication-Sign 10{sup 8} M {sub Sun} kpc{sup -2}, C > 2.6) that are either gas-poor (M{sub H{sub 2}}/M {sub *} <1.5%) or else on average less efficient by a factor of {approx}2 than disk-dominated galaxies at converting into stars any cold gas they may have. We find no link between the presence of AGNs and these long depletion times. In the regime where galaxies are disk-dominated and gas-rich, the galaxies undergoing mergers or showing signs of morphological disruptions have the shortest molecular gas depletion times, while those hosting strong stellar bars have only marginally higher global star formation efficiencies as compared to matched control samples. Our interpretation is that the molecular gas depletion time variations are caused by changes in the ratio between the gas mass traced by the CO(1-0) observations and the gas mass in high-density star-forming cores (as traced by observations of, e.g., HCN(1-0)). While interactions, mergers, and bar instabilities can locally increase pressure and raise the ratio of efficiently star-forming gas to CO-detected gas (therefore lowering the CO

  3. Coronal Activity in Low-Mass Pre-Main Sequence Stars: NGC 2264

    NASA Technical Reports Server (NTRS)

    Tebbe, H. J.; Patten, B. M.

    2000-01-01

    We present the preliminary results of an analysis of ROSAT images in the region of the populous young (age approx. 3 Myr) star-forming region NGC 2264. The cluster was imaged with the ROSAT HRI in two sets of pointings -- one set near the central region of the cluster, centered on the star LW Mon, and the other set in the southern part of the cluster, centered near the star V428 Mon, just south of the Cone Nebula. In total 113 unique X-ray sources have been identified in the ROSAT images with signal-to-noise ratios greater than 3. The limiting luminosities (log Lx(ergs/sec)) for 3-sigma detections are estimated to be 30.18, 30.23, and 30.08 for the northern field, southern field, and overlap region between the two fields respectively. Extensive optical photometry, classification spectroscopy, and proper motions, obtained from recent ground-based surveys of this region, were used to identify the most likely optical counterpart to each X-ray source. Although most of our X-ray selected sample appears to be associated with NGC 2264 members, we find that the vast majority of the cluster membership was undetected in the ROSAT HRI survey. The X-ray cumulative luminosity function for solar-mass stars in NGC 2264 shows that most of the low-mass members probably have X-ray luminosities similar to those seen for the X-ray brightest members of older clusters such as IC 2391/IC 2602 (age approx. 50 Myr) and the Pleiades (age approx. 100 Myr). This research was funded in part by the SAO Summer Intern Program and NASA grant NAG5-8120.

  4. Star formation and nuclear activity in the blue early-type galaxy NGC 5373

    NASA Astrophysics Data System (ADS)

    Zaidi, Tayeb; Miller, Brendan P.; Gallo, Elena; Alfvin, Erik; Martinkus, Charlotte; Molter, Edward

    2015-01-01

    We present new optical and X-ray observations of NGC 5373, an isolated star-forming elliptical that has a stellar mass of 7e10 solar and lies at a distance of 175 Mpc. Our B and R band Magellan IMACS imaging substantially improves on SDSS resolution and sensitivity, enabling accurate modeling of the galaxy surface brightness profile. As expected from its mass, NGC 5373 is a core galaxy with a best-fit Sersic profile of n~3.8; no prominent tidal tails or shells are found, although there are slight residual asymmetries. The H-alpha emission in the SDSS spectrum is narrow, and the line ratios confirm a star-forming classification in the BPT diagram, near the transition/composite line. The star formation rate is about 6 solar masses per year, making NGC 5373 an extreme outlier relative to typical local early-type galaxies of similar mass. Our 50 ks Chandra ACIS-S exposure provides a clear detection of a central X-ray source, with a hardness ratio consistent with a power-law photon index of 2.0+/-0.5. The unabsorbed luminosity is Lx = 2e40 erg/s over 0.3-8 keV. Comparison with a MARX simulated point spread function suggests the central source may be extended, for example due to contributions from one or more unresolved high-mass X-ray binaries, as might be present given the high star formation rate. For a black hole of 1.6e8 solar masses as predicted from scaling relations, Lx/Ledd is then around 1e-6 (or potentially lower).

  5. How Stars Form

    NASA Astrophysics Data System (ADS)

    McKee, Christopher F.

    2017-01-01

    Stars are the atoms of the universe. The process by which stars form is at the nexus of astrophysics since they are believed to be responsible for the re-ionization of the universe, they created the heavy elements, they play a central role in the formation and evolution of galaxies, and their formation naturally leads to the formation of planets. Whereas early work on star formation was based on the assumption that it is a quiescent process, it is now believed that turbulence plays a dominant role. In this overview, I shall discuss the evolution of our understanding of how stars form and current ideas about the stellar initial mass function and the rate of star formation.

  6. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion

    NASA Astrophysics Data System (ADS)

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-06-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones.

  7. A CENSUS OF BROAD-LINE ACTIVE GALACTIC NUCLEI IN NEARBY GALAXIES: COEVAL STAR FORMATION AND RAPID BLACK HOLE GROWTH

    SciTech Connect

    Trump, Jonathan R.; Fang, Jerome J.; Faber, S. M.; Koo, David C.; Kocevski, Dale D.

    2013-02-15

    We present the first quantified, statistical map of broad-line active galactic nucleus (AGN) frequency with host galaxy color and stellar mass in nearby (0.01 < z < 0.11) galaxies. Aperture photometry and z-band concentration measurements from the Sloan Digital Sky Survey are used to disentangle AGN and galaxy emission, resulting in estimates of uncontaminated galaxy rest-frame color, luminosity, and stellar mass. Broad-line AGNs are distributed throughout the blue cloud and green valley at a given stellar mass, and are much rarer in quiescent (red sequence) galaxies. This is in contrast to the published host galaxy properties of weaker narrow-line AGNs, indicating that broad-line AGNs occur during a different phase in galaxy evolution. More luminous broad-line AGNs have bluer host galaxies, even at fixed mass, suggesting that the same processes that fuel nuclear activity also efficiently form stars. The data favor processes that simultaneously fuel both star formation activity and rapid supermassive black hole accretion. If AGNs cause feedback on their host galaxies in the nearby universe, the evidence of galaxy-wide quenching must be delayed until after the broad-line AGN phase.

  8. The SEEDS High-Contrast Imaging Survey: Exoplanet and Brown Dwarf Survey for Nearby Young Stars Dated with Gyrochronology and Activity Age Indicators

    NASA Astrophysics Data System (ADS)

    Kuzuhara, Masayuki; Tamura, Motohide; Helminiak, Kris; Mede, Kyle; Brandt, Timothy; Janson, Markus; Kandori, Ryo; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun

    2015-12-01

    The SEEDS campaign has successfully discovered and characterized exoplanets, brown dwarfs, and circumstellar disks since it began in 2009, via the direct imaging technique. The survey has targeted nearby young stars, as well as stars associated to star-forming regions, the Pleiades open cluster, moving groups, and debris disks. We selected the nearby young stars that have been dated with age indicators based on stellar rotation periods (i.e., gyrochronology) and chromoshperic/coronal activities. Of these, nearly 40 were observed, with ages mainly between 100 and 1000 Myr and distances less than 40 pc. Our observations typically attain the contrast of ~6 x 10-6 at 1'' and better than ~1 x 10-6 beyond 2'', enabling us to detect a planetary-mass companion even around such old stars. Indeed, the SEEDS team reported the discovery that the nearby Sun-like star GJ 504 hosts a Jovian companion GJ 504b, which has a mass of 3-8.5 Jupiter masses that is inferred according to the hot-start cooling models and our estimated system age of 100-510 Myr. The remaining observations out of the selected ~40 stars have resulted in no detection of additional planets or brown dwarf companions. Meanwhile, we have newly imaged a low-mass stellar companion orbiting the G-type star HIP 10321, for which the presence of companion was previously announced via radial velocity technique. The astrometry and radial velocity measurements are simultaneously analyzed to determine the orbit, providing constraints on the dynamical mass of both objects and stellar evolution models. Here we summarize our direct imaging observations for the nearby young stars dated with gyrochrolorogy and activity age indicators. Furthermore, we report the analysis for the HIP 10321 system with the imaged low-mass companion.

  9. Magnetic activity in the photosphere of CoRoT-Exo-2a. Active longitudes and short-term spot cycle in a young Sun-like star

    NASA Astrophysics Data System (ADS)

    Lanza, A. F.; Pagano, I.; Leto, G.; Messina, S.; Aigrain, S.; Alonso, R.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Boumier, P.; Collier Cameron, A.; Comparato, M.; Cutispoto, G.; de Medeiros, J. R.; Foing, B.; Kaiser, A.; Moutou, C.; Parihar, P. S.; Silva-Valio, A.; Weiss, W. W.

    2009-01-01

    Context: The space experiment CoRoT has recently detected transits by a hot Jupiter across the disc of an active G7V star (CoRoT-Exo-2a) that can be considered as a good proxy for the Sun at an age of approximately 0.5 Gyr. Aims: We present a spot modelling of the optical variability of the star during 142 days of uninterrupted observations performed by CoRoT with unprecedented photometric precision. Methods: We apply spot modelling approaches previously tested in the case of the Sun by modelling total solar irradiance variations, a good proxy for the optical flux variations of the Sun as a star. The best results in terms of mapping of the surface brightness inhomogeneities are obtained by means of maximum entropy regularized models. To model the light curve of CoRoT-Exo-2a, we take into account the photometric effects of both cool spots and solar-like faculae, adopting solar analogy. Results: Two active longitudes initially on opposite hemispheres are found on the photosphere of CoRoT-Exo-2a with a rotation period of 4.522 ± 0.024 days. Their separation changes by ≈80° during the time span of the observations. From this variation, a relative amplitude of the surface differential rotation lower than ~1 percent is estimated. Individual spots form within the active longitudes and show an angular velocity ~1 percent lower than that of the longitude pattern. The total spotted area shows a cyclic oscillation with a period of 28.9 ± 4.3 days, which is close to 10 times the synodic period of the planet as seen by the rotating active longitudes. We discuss the effects of solar-like faculae on our models, finding indications of a facular contribution to the optical flux variations of CoRoT-Exo-2a being significantly smaller than in the present Sun. Conclusions: The implications of such results for the internal rotation of CoRoT-Exo-2a are discussed, based on solar analogy. A possible magnetic star-planet interaction is suggested by the cyclic variation of the spotted

  10. Calibrating the Age-Rotation-Activity Relation in Low-Mass Stars: Chromospheric and Coronal Activity in the 500 Myr-old M37 Open Cluster

    NASA Astrophysics Data System (ADS)

    Núñez, Alejandro; Agueros, Marcel A.

    2017-01-01

    In low-mass stars, the strength of the magnetic dynamo decreases over time as stars spin down through the loss of angular momentum via magnetized winds. Both coronal X-ray emission and chromospheric Hα emission trace the strength of the changing dynamo and, when combined with rotation periods in a single-aged population, can therefore be used to examine the dependence of magnetic activity on rotation across a range of masses. We observed the 500-Myr-old open cluster M37 with Chandra and Hectospec on the MMT to obtain X-ray and Hα measurements for its low-mass stars. We obtained a sample of ≈280 cluster members with X-ray detections, ≈290 with Hα measurements, and ≈80 with both. This is the largest sample available for analyzing the dependence of coronal and chromospheric emission on rotation for a single-aged population. We used published rotation periods (Prot) to calculate Rossby numbers, Ro = Prot / τ, where τ is the convective turnover time, for all of the known rotators. We also determined the ratios of X-ray and Hα luminosities to bolometric luminosities to minimize mass dependencies when characterizing the rotation-activity relation at 500 Myr. With these data we explored how X-ray and Hα luminosity depend on Ro, and whether the behavior in the unsaturated regime (i.e., when increasing or decreasing Ro changes the measured activity) differ for these two tracers of magnetic activity. Finally, we examine the age-activity relation as measured in the X ray using seven open clusters spanning the age range 6-600 Myr.

  11. Enigma of Runaway Stars Solved

    NASA Astrophysics Data System (ADS)

    1997-01-01

    . In fact, this is one of the most `perfect' bow shocks of parabolic form ever observed around an OB-runaway. Moreover, the orientation of the bow shock indicates that the system is moving towards the north; its origin must therefore lie somewhere south of its present position in the sky. It also turns out that the accordingly deduced path of HD77581 crosses a well-known OB-association with the designation Vel OB1 . At the measured distance of Vel OB1 of about 6000 lightyears, the observed proper motion and radial velocity of HD77581 indicate a space velocity of 90 km/sec. With this velocity, it would have taken HD77581 and its compact companion about 2.5 million years to travel the distance between Vel OB1 and its present position. This corresponds exactly to the expected time that has passed since the supernova explosion of the progenitor star of Vela~X-1, as deduced from the observed properties of the binary system. The puzzle comes together Now everything fits! The observation of a bow shock around the OB star HD77581 and its compact companion Vela X-1 supports the scenario originally proposed by Blaauw to create OB-runaway stars by the supernova explosion of the binary companion. Following back the path of the system resulted in the discovery of the place where it was born and from where it escaped after the violent supernova explosion which produced the neutron star that now manifests itself as the strong X-ray source known as Vela X-1. More information about this research project This research project is described in ESO Preprint no.~1199 and will appear shortly as a Letter to the Editor in `Astrophysical Journal' (ApJ 475, L37-L40). Notes: [1] Professor Adriaan Blaauw is a well-known Dutch astronomer (Leiden and Groningen). He participated very actively in the build-up of ESO in the 1950's and 60's and he was ESO Director General from 1970 - 1974. He is the author of ` ESO's Early History - The European Southern Observatory from concept to reality ' (1991). [2

  12. Creating a Before-School Physical Activity Program: Pre-Service Physical Educators' Experiences and Implications for PETE

    ERIC Educational Resources Information Center

    McMullen, Jaimie; van der Mars, Hans; Jahn, Julie A.

    2014-01-01

    The purpose of this study is to describe the experiences of physical education teacher education (PETE) majors enrolled in an internship course that provided them with authentic experiences promoting and facilitating a before-school physical activity (PA) program and to examine the associated implications for PETE programs within the Comprehensive…

  13. Creating a Safe Climate for Active Learning and Student Engagement: An Example from an Introductory Social Work Module

    ERIC Educational Resources Information Center

    Ni Raghallaigh, M.; Cunniffe, R.

    2013-01-01

    This article explores the experiences of students who participated in a series of seminars that employed active learning methodologies. The study on which the article is based involved two parts. First, students completed a questionnaire after each seminar, resulting in 468 questionnaires. Second, nine students participated in a focus group where…

  14. Creating Readers: Over 1000 Games, Activities, Tongue Twisters, Fingerplays, Songs, and Stories To Get Children Excited about Reading.

    ERIC Educational Resources Information Center

    Schiller, Pam

    Combining the language experience approach and phonics instruction, this guide provides parents and early childhood teachers a comprehensive resource for developing a strong foundation for pre-readers. The guide offers over 1,000 activities, games, fingerplays, songs, tongue-twisters, poems, and stories for the letters of the alphabet to develop a…

  15. SPOON-FEEDING GIANT STARS TO SUPERMASSIVE BLACK HOLES: EPISODIC MASS TRANSFER FROM EVOLVING STARS AND THEIR CONTRIBUTION TO THE QUIESCENT ACTIVITY OF GALACTIC NUCLEI

    SciTech Connect

    MacLeod, Morgan; Ramirez-Ruiz, Enrico; Grady, Sean; Guillochon, James

    2013-11-10

    Stars may be tidally disrupted if, in a single orbit, they are scattered too close to a supermassive black hole (SMBH). Tidal disruption events are thought to power luminous but short-lived accretion episodes that can light up otherwise quiescent SMBHs in transient flares. Here we explore a more gradual process of tidal stripping where stars approach the tidal disruption radius by stellar evolution while in an eccentric orbit. After the onset of mass transfer, these stars episodically transfer mass to the SMBH every pericenter passage, giving rise to low-level flares that repeat on the orbital timescale. Giant stars, in particular, will exhibit a runaway response to mass loss and 'spoon-feed' material to the black hole for tens to hundreds of orbital periods. In contrast to full tidal disruption events, the duty cycle of this feeding mode is of order unity for black holes M{sub bh} ∼> 10{sup 7} M{sub ☉}. This mode of quasi-steady SMBH feeding is competitive with indirect SMBH feeding through stellar winds, and spoon-fed giant stars may play a role in determining the quiescent luminosity of local SMBHs.

  16. OMEGA - OSIRIS Mapping of Emission-line Galaxies in A901/2: II. - Environmental influence on integrated star formation properties and AGN activity

    NASA Astrophysics Data System (ADS)

    Rodríguez del Pino, Bruno; Aragón-Salamanca, Alfonso; Chies-Santos, Ana L.; Weinzirl, Tim; Bamford, Steven P.; Gray, Meghan E.; Böhm, Asmus; Wolf, Christian; Maltby, David T.

    2017-01-01

    We present a study of the star formation and AGN activity for galaxies in the Abell 901/2 multi-cluster system at z ˜ 0.167 as part of the OMEGA survey. Using Tuneable Filter data obtained with the OSIRIS instrument at the GTC we produce spectra covering the Hα and [N II] spectral lines for more than 400 galaxies. Using optical emission-line diagnostics, we identify a significant number of galaxies hosting AGN, which tend to have high masses and a broad range of morphologies. Moreover, within the environmental densities probed by our study, we find no environmental dependence on the fraction of galaxies hosting AGN. The analysis of the integrated Hα emission shows that the specific star formation rates (SSFRs) of a majority of the cluster galaxies are below the field values for a given stellar mass. We interpret this result as evidence for a slow decrease in the star formation activity of star-forming galaxies as they fall into higher-density regions, contrary to some previous studies which suggested a rapid truncation of star formation. We find that most of the intermediate- and high-mass spiral galaxies go through a phase in which their star formation is suppressed but still retain significant star-formation activity. During this phase, these galaxies tend to retain their spiral morphology while their colours become redder. The presence of this type of galaxies in high density regions indicates that the physical mechanism responsible for suppressing star-formation affects mainly the gas component of the galaxies, suggesting that ram-pressure stripping or starvation are potentially responsible.

  17. Hyper-Spectral Synthesis of Active OB Stars Using GLaDoS

    NASA Astrophysics Data System (ADS)

    Hill, N. R.; Townsend, R. H. D.

    2016-11-01

    In recent years there has been considerable interest in using graphics processing units (GPUs) to perform scientific computations that have traditionally been handled by central processing units (CPUs). However, there is one area where the scientific potential of GPUs has been overlooked - computer graphics, the task they were originally designed for. Here we introduce GLaDoS, a hyper-spectral code which leverages the graphics capabilities of GPUs to synthesize spatially and spectrally resolved images of complex stellar systems. We demonstrate how GLaDoS can be applied to calculate observables for various classes of stars including systems with inhomogenous surface temperatures and contact binaries.

  18. A Census of the Class of X-ray Active γ Cas Stars

    NASA Astrophysics Data System (ADS)

    Smith, M. A.; de Oliveira, R. L.; Motch, C.

    2016-11-01

    “γ Cas stars” are perhaps the primary contributors to the total hard X-ray flux from Galactic B stars. We review basic properties of 12 suspected or known members of this class. The sample extends out to 6-7 kpc and is finally sufficient to compare such basic properties as spectral type, rotation rate, binarity/Blue Straggler status, Hα lobe structure EWHα, Lx, temperature of the dominant X-ray emitting plasma component (kThot), and ranges in Lx and kThot.

  19. Transcriptional activation of LON Gene by a new form of mitochondrial stress: A role for the nuclear respiratory factor 2 in StAR overload response (SOR).

    PubMed

    Bahat, Assaf; Perlberg, Shira; Melamed-Book, Naomi; Isaac, Sara; Eden, Amir; Lauria, Ines; Langer, Thomas; Orly, Joseph

    2015-06-15

    High output of steroid hormone synthesis in steroidogenic cells of the adrenal cortex and the gonads requires the expression of the steroidogenic acute regulatory protein (StAR) that facilitates cholesterol mobilization to the mitochondrial inner membrane where the CYP11A1/P450scc enzyme complex converts the sterol to the first steroid. Earlier studies have shown that StAR is active while pausing on the cytosolic face of the outer mitochondrial membrane while subsequent import of the protein into the matrix terminates the cholesterol mobilization activity. Consequently, during repeated activity cycles, high level of post-active StAR accumulates in the mitochondrial matrix. To prevent functional damage due to such protein overload effect, StAR is degraded by a sequence of three to four ATP-dependent proteases of the mitochondria protein quality control system, including LON and the m-AAA membranous proteases AFG3L2 and SPG7/paraplegin. Furthermore, StAR expression in both peri-ovulatory ovarian cells, or under ectopic expression in cell line models, results in up to 3-fold enrichment of the mitochondrial proteases and their transcripts. We named this novel form of mitochondrial stress as StAR overload response (SOR). To better understand the SOR mechanism at the transcriptional level we analyzed first the unexplored properties of the proximal promoter of the LON gene. Our findings suggest that the human nuclear respiratory factor 2 (NRF-2), also known as GA binding protein (GABP), is responsible for 88% of the proximal promoter activity, including the observed increase of transcription in the presence of StAR. Further studies are expected to reveal if common transcriptional determinants coordinate the SOR induced transcription of all the genes encoding the SOR proteases.

  20. The Search for Signatures Of Transient Mass Loss in Active Stars

    NASA Astrophysics Data System (ADS)

    Crosley, Michael Kevin; Osten, Rachel A.

    2017-01-01

    In order to understand habitability of exoplanets, we must understand their environments and how their host star shapes them. Stellar eruptive events are an important factor when considering habitability. The lack of experimental evidence necessitates the heavy reliance on solar scaling relationships when determining the impact of stellar eruptive events. Typically, stellar eruptive events cannot be observed in the same manner as solar events. The research we are conducting is proposing a new method for detecting Coronal Mass Ejections (CMEs), which are a type of stellar eruptive event. As CMEs travel through the stellar atmosphere, they are able to produce a Type II radio burst. Observation of Type II radio burst is the best method to identify and categorize CMEs. The LOw Frequency ARray (LOFAR) provides a means for detecting this event. Fifteen hours of observation on YZ Canis Minoris (YZ CMi), a nearby M dwarf flare star, was used to test this method. Ongoing research about jointly observed flares and CMEs is discussed to further expand the methodology. We explore using solar multi-wavelength observations to provide greater constraints on CMEs and further test the applicability of solar scaling relationships. We determine how well the velocity, mass, and CME kinetic energy can be constrained using the types of datasets available to stellar astronomers when compared to direct corona graphic solar observations.

  1. Peculiar objects towards 3FGL J0133.3+5930: an eclipsing Be star and an active galactic nucleus

    NASA Astrophysics Data System (ADS)

    Martí, Josep; Luque-Escamilla, Pedro L.; Paredes, Josep M.; Iwasawa, Kazushi; Galindo, Daniel; Ribó, Marc; Marín-Felip, Víctor

    2017-02-01

    Aims: We aim to contribute to the identification of unassociated gamma-ray sources in the galactic plane to enlarge the currently known population of gamma-ray binaries and related systems, such as radio-emitting X-ray binaries and microquasars. These objects are currently regarded as excellent test beds for the understanding of high-energy phenomena in stellar systems. Methods: Potential targets of study are selected based on cross-identification of the third Fermi Large Area Telescope catalogue with historical catalogues of luminous stars that have often been found as optical counterparts in known cases. Follow-up observations and analysis of multi-wavelength archival data are later used to seek further proofs of association beyond the simple positional agreement. Results: Current results enable us to present here the case of the Fermi source 3FGL J0133.3+5930 where two peculiar objects have been discovered inside its region of uncertainty. One of them is the star TYC 3683-985-1 (LS I +59 79) whose eclipsing binary nature is reported in this work. The other is the X-ray source Swift J0132.9+5932, which we found to be a likely low-power active galactic nucleus at z = 0.1143 ± 0.0002. If this second object is of blazar type, it could easily account for the observed gamma-ray photon flux. However, this is not confirmed at present, thus rendering the star system TYC 3683-985-1 as a still possible alternative counterpart candidate to the Fermi source.

  2. THERMAL AND RADIATIVE ACTIVE GALACTIC NUCLEUS FEEDBACK HAVE A LIMITED IMPACT ON STAR FORMATION IN HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Roos, Orianne; Juneau, Stéphanie; Bournaud, Frédéric; Gabor, Jared M.

    2015-02-10

    The effects of active galactic nuclei (AGNs) on their host galaxies depend on the coupling between the injected energy and the interstellar medium (ISM). Here, we model and quantify the impact of long-range AGN ionizing radiation—in addition to the often considered small-scale energy deposition—on the physical state of the multi-phase ISM of the host galaxy and on its total star formation rate (SFR). We formulate an AGN spectral energy distribution matched with observations, which we use with the radiative transfer (RT) code Cloudy to compute AGN ionization in a simulated high-redshift disk galaxy. We use a high-resolution (∼6 pc) simulation including standard thermal AGN feedback and calculate RT in post-processing. Surprisingly, while these models produce significant AGN-driven outflows, we find that AGN ionizing radiation and heating reduce the SFR by a few percent at most for a quasar luminosity (L {sub bol} = 10{sup 46.5} erg s{sup –1}). Although the circumgalactic gaseous halo can be kept almost entirely ionized by the AGN, most star-forming clouds (n ≳ 10{sup 2} {sup –} {sup 3} cm{sup –3}) and even the reservoirs of cool atomic gas (n ∼ 0.3-10 cm{sup –3})—which are the sites of future star formation (SF; 100-200 Myr), are generally too dense to be significantly affected. Our analysis ignores any absorption from a putative torus, making our results upper limits on the effects of ionizing radiation. Therefore, while the AGN-driven outflows can remove substantial amounts of gas in the long term, the impact of AGN feedback on the SF efficiency in the interstellar gas in high-redshift galaxies is marginal, even when long-range radiative effects are accounted for.

  3. Creating a flipbook as a medium of instruction based on the research on activity test of kencur extract

    NASA Astrophysics Data System (ADS)

    Monika, Icha; Yeni, Laili Fitri; Ariyati, Eka

    2016-02-01

    This research aimed to reveal the validity of the flipbook as a medium of learning for the sub-material of environmental pollution in the tenth grade based on the results of the activity test of kencur (Kaempferia galanga) extract to control the growth of the Fusarium oxysporum fungus. The research consisted of two stages. First, testing the validity of the medium of flipbook through validation by seven assessors and analyzed based on the total average score of all aspects. Second, testing the activity of the kencur extract against the growth of Fusarium oxysporum by using the experimental method with 10 treatments and 3 repetitions which were analyzed using one-way analysis of variance (ANOVA) test. The making of the flipbook medium was done through the stages of analysis for the potential and problems, data collection, design, validation, and revision. The validation analysis on the flipbook received an average score of 3.7 and was valid to a certain extent, so it could be used in the teaching and learning process especially in the sub-material of environmental pollution in the tenth grade of the senior high school.

  4. Activity and cool spots on the surfaces of G-type stars with superflares from observations with the Kepler Space Telescope

    NASA Astrophysics Data System (ADS)

    Savanov, I. S.; Dmitrienko, E. S.

    2015-09-01

    The properties of active regions (cool spots) on the surfaces of 279 G-type stars in which more than 1500 superflares with energies of 1033-1036 erg were detected are analyzed. Diagrams plotting the superflare energy against activity parameters of the stars (the area of their magnetic spots) are considered, and a more extensive study of the activity of two stars with the highest numbers of flares is presented. The range of variation of the superflare energies (up to two orders of magnitude) is realized over the entire interval of rotation periods. It is proposed that the plot of superflare energy vs. rotational period is bimodal. There are probably no appreciable differences in the maximum flare energies for the two groups of objects, which have rotational periods of more than and less than 10 days. Three groups of stars with different surface spottednesses can be distinguished in a plot of superflare energy vs. cool-spot area. The range of variation of the flare energy within a group is roughly the same for these three groups. Most of the points on this diagram lie to the right of the dependence corresponding to B = 3000Gand an inclination i = 90° (the first two groups of objects). It is confirmed that the flare activity is not related directly to circumpolar active regions, since the majority of the points on the diagram lie to the right of the dependence for B = 1000 G and i = 3°. Analysis of stars from the sample, including objects with more than 20 superflares, shows that large variations of the energy (by up to two orders of magnitude) can be reached with small variations of the spottedness parameter S for a single star. Appreciable variability of the spottedness (by factors of five to six) was detected for only two objects from the sample (KIC 10422252 and KIC 11764567). These stars displayed an increase in the flare energy by orders of magnitude for any spottedness level. The activity of KIC 11551430 and KIC 11764567 is analyzed in detail using all

  5. The nuclear receptor NR2F2 activates star expression and steroidogenesis in mouse MA-10 and MLTC-1 Leydig cells.

    PubMed

    Mendoza-Villarroel, Raifish E; Robert, Nicholas M; Martin, Luc J; Brousseau, Catherine; Tremblay, Jacques J

    2014-07-01

    Testosterone production is dependent on cholesterol transport within the mitochondrial matrix, an essential step mediated by a protein complex containing the steroidogenic acute regulatory (STAR) protein. In steroidogenic Leydig cells, Star expression is hormonally regulated and involves several transcription factors. NR2F2 (COUP-TFII) is an orphan nuclear receptor that plays critical roles in cell differentiation and lineage determination. Conditional NR2F2 knockout prior to puberty leads to male infertility due to insufficient testosterone production, suggesting that NR2F2 could positively regulate steroidogenesis and Star expression. In this study we found that NR2F2 is expressed in the nucleus of some peritubular myoid cells and in interstitial cells, mainly in steroidogenically active adult Leydig cells. In MA-10 and MLTC-1 Leydig cells, small interfering RNA (siRNA)-mediated NR2F2 knockdown reduces basal steroid production without affecting hormone responsiveness. Consistent with this, we found that STAR mRNA and protein levels were reduced in NR2F2-depleted MA-10 and MLTC-1 cells. Transient transfections of Leydig cells revealed that a -986 bp mouse Star promoter construct was activated 3-fold by NR2F2. Using 5' progressive deletion constructs, we mapped the NR2F2-responsive element between -131 and -95 bp. This proximal promoter region contains a previously uncharacterized direct repeat 1 (DR1)-like element to which NR2F2 is recruited and directly binds. Mutations in the DR1-like element that prevent NR2F2 binding severely blunted NR2F2-mediated Star promoter activation. These data identify an essential role for the nuclear receptor NR2F2 as a direct activator of Star gene expression in Leydig cells, and thus in the control of steroid hormone biosynthesis.

  6. Engaging stakeholders and target groups in prioritising a public health intervention: the Creating Active School Environments (CASE) online Delphi study

    PubMed Central

    Morton, Katie L; Atkin, Andrew J; Corder, Kirsten; Suhrcke, Marc; Turner, David; van Sluijs, Esther M F

    2017-01-01

    Objectives Stakeholder engagement and public involvement are considered as integral to developing effective public health interventions and is encouraged across all phases of the research cycle. However, limited guidelines and appropriate tools exist to facilitate stakeholder engagement—especially during the intervention prioritisation phase. We present the findings of an online ‘Delphi’ study that engaged stakeholders (including young people) in the process of prioritising secondary school environment-focused interventions that aim to increase physical activity. Setting Web-based data collection using an online Delphi tool enabling participation of geographically diverse stakeholders. Participants 37 stakeholders participated, including young people (age 13–16 years), parents, teachers, public health practitioners, academics and commissioners; 33 participants completed both rounds. Primary and secondary outcome measures Participants were asked to prioritise a (short-listed) selection of school environment-focused interventions (eg, standing desks, outdoor design changes) based on the criteria of ‘reach’, ‘equality’, ‘acceptability’, ‘feasibility’, ‘effectiveness’ and ‘cost’. Participants were also asked to rank the criteria and the effectiveness outcomes (eg, physical activity, academic achievement, school enjoyment) from most to least important. Following feedback along with any new information provided, participants completed round 2 4 weeks later. Results The intervention prioritisation process was feasible to conduct and comments from participants indicated satisfaction with the process. Consensus regarding intervention strategies was achieved among the varied groups of stakeholders, with ‘active lessons’ being the favoured approach. Participants ranked ‘mental health and well-being’ as the most important outcome followed by ‘enjoyment of school’. The most important criteria was ‘effectiveness’, followed by

  7. A Cytosolic STIM2 Preprotein Created by Signal Peptide Inefficiency Activates ORAI1 in a Store-independent Manner*

    PubMed Central

    Graham, Sarah J. L.; Dziadek, Marie A.; Johnstone, Lorna S.

    2011-01-01

    Calcium (Ca2+) influx through the plasma membrane store-operated Ca2+ channel ORAI1 is controlled by Ca2+ sensors of the stromal interaction molecule (STIM) family. STIM1 responds to endoplasmic reticulum (ER) Ca2+ store depletion by redistributing and activating ORAI1 from regions of the ER juxtaposed to the plasma membrane. Unlike STIM1, STIM2 can regulate ORAI1 in a store-dependent and store-independent manner, but the mechanism by which this is achieved is unknown. Here we find that STIM2 is translated from a highly conserved methionine residue and is directed to the ER by an incredibly long 101-amino acid signal peptide. We find that although the majority of the total STIM2 population resides on the ER membrane, a second population escapes ER targeting to accumulate as a full-length preprotein in the cytosol, signal peptide intact. Unlike STIM2, preSTIM2 localizes to the inner leaflet of the plasma membrane where it interacts with ORAI1 to regulate basal Ca2+ concentration and Ca2+-dependent gene transcription in a store-independent manner. Furthermore, a third protein comprising a fragment of the STIM2 signal peptide is released from the ER membrane into the cytosol where it regulates gene transcription in a Ca2+-independent manner. This study establishes a new model for STIM2-mediated regulation of ORAI1 in which two distinct proteins, STIM2 and preSTIM2, control store-dependent and store-independent modes of ORAI1 activation. PMID:21383014

  8. Strange stars

    NASA Technical Reports Server (NTRS)

    Alcock, Charles; Farhi, Edward; Olinto, Angela

    1986-01-01

    Strange matter, a form of quark matter that is postulated to be absolute stable, may be the true ground stage of the hadrons. If this hypothesis is correct, neutron stars may convert to 'strange stars'. The mass-radius relation for strange stars is very different from that of neutron stars; there is no minimum mass, and for mass of 1 solar mass or less, mass is proportional to the cube of the radius. For masses between 1 solar mass and 2 solar masses, the radii of strange stars are about 10 km, as for neutron stars. Strange stars may have an exposed quark surface, which is capable of radiating at rates greatly exceeding the Eddington limit, but has a low emissivity for X-ray photons. The stars may have a thin crust with the same composition as the preneutron drip outer layer of a conventional neutron star crust. Strange stars cool efficiently via neutrino emission.

  9. Creating functional sophistication from simple protein building blocks, exemplified by factor H and the regulators of complement activation.

    PubMed

    Makou, Elisavet; Herbert, Andrew P; Barlow, Paul N

    2015-10-01

    Complement control protein modules (CCPs) occur in numerous functionally diverse extracellular proteins. Also known as short consensus repeats (SCRs) or sushi domains each CCP contains approximately 60 amino acid residues, including four consensus cysteines participating in two disulfide bonds. Varying in length and sequence, CCPs adopt a β-sandwich type fold and have an overall prolate spheroidal shape with N- and C-termini lying close to opposite poles of the long axis. CCP-containing proteins are important as cytokine receptors and in neurotransmission, cell adhesion, blood clotting, extracellular matrix formation, haemoglobin metabolism and development, but CCPs are particularly well represented in the vertebrate complement system. For example, factor H (FH), a key soluble regulator of the alternative pathway of complement activation, is made up entirely from a chain of 20 CCPs joined by short linkers. Collectively, therefore, the 20 CCPs of FH must mediate all its functional capabilities. This is achieved via collaboration and division of labour among these modules. Structural studies have illuminated the dynamic architectures that allow FH and other CCP-rich proteins to perform their biological functions. These are largely the products of a highly varied set of intramolecular interactions between CCPs. The CCP can act as building block, spacer, highly versatile recognition site or dimerization mediator. Tandem CCPs may form composite binding sites or contribute to flexible, rigid or conformationally 'switchable' segments of the parent proteins.

  10. Chromospherically active stars. III - HD 26337 = EI Eri: An RS CVn candidate for the Doppler-imaging technique

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Quigley, Robert; Gillies, Kim; Africano, John L.

    1987-01-01

    Spectroscopic observations of the chromospherically active G5 IV single-lined binary HD 26337 = EI Eri are presented. An orbital period of 1.94722 days is found for the star. It has moderately strong Ca II H and K emission and strong ultraviolet emission features, while H-alpha is a weak absorption feature that is variable in strength. The inclination of the system is 46 + or - 12 deg, and the unseen secondary is probably a late K or early M dwarf. The v sin i of the primary is 50 + or - 3 km/s, resulting in a minimum radius of 1.9 + or - 0.1 solar radius. The star is within the required limits for Doppler imaging. The primary is close to filling its Roche lobe, resulting in a strong constraint that the mass ratio is 2.6 or greater, with a primary mass of at least 1.4 solar mass. The distance to the system is estimated at 75 pc.

  11. TIME VARIABILITY OF EMISSION LINES FOR FOUR ACTIVE T TAURI STARS. I. OCTOBER-DECEMBER IN 2010

    SciTech Connect

    Chou, Mei-Yin; Takami, Michihiro; Karr, Jennifer L.; Shang Hsien; Liu, Hauyu Baobab; Manset, Nadine; Beck, Tracy; Pyo, Tae-Soo; Chen, Wen-Ping; Panwar, Neelam

    2013-04-15

    We present optical spectrophotometric monitoring of four active T Tauri stars (DG Tau, RY Tau, XZ Tau, RW Aur A) at high spectral resolution (R {approx}> 1 Multiplication-Sign 10{sup 4}), to investigate the correlation between time variable mass ejection seen in the jet/wind structure of the driving source and time variable mass accretion probed by optical emission lines. This may allow us to constrain the understanding of the jet/wind launching mechanism, the location of the launching region, and the physical link with magnetospheric mass accretion. In 2010, observations were made at six different epochs to investigate how daily and monthly variability might affect such a study. We perform comparisons between the line profiles we observed and those in the literature over a period of decades and confirm the presence of time variability separate from the daily and monthly variability during our observations. This is so far consistent with the idea that these line profiles have a long-term variability (3-20 yr) related to episodic mass ejection suggested by the structures in the extended flow components. We also investigate the correlations between equivalent widths and between luminosities for different lines. We find that these correlations are consistent with the present paradigm of steady magnetospheric mass accretion and emission line regions that are close to the star.

  12. Stars and Star Myths.

    ERIC Educational Resources Information Center

    Eason, Oliver

    Myths and tales from around the world about constellations and facts about stars in the constellations are presented. Most of the stories are from Greek and Roman mythology; however, a few Chinese, Japanese, Polynesian, Arabian, Jewish, and American Indian tales are also included. Following an introduction, myths are presented for the following 32…

  13. The age-mass-metallicity-activity relation for solar-type stars: comparisons with asteroseismology and the NGC 188 open cluster

    NASA Astrophysics Data System (ADS)

    Lorenzo-Oliveira, D.; Porto de Mello, G. F.; Schiavon, R. P.

    2016-10-01

    Context. The Mount Wilson Ca ii index log(R'_HK) is the accepted standard metric of calibration for the chromospheric activity versus age relation for FGK stars. Recent results claim its inability to discern activity levels, and thus ages, for stars older than ~2 Gyr, which would severely hamper its application to date disk stars older than the Sun. Aims: We present a new activity-age calibration of the Mt. Wilson index that explicitly takes mass and [Fe/H] biases into account; these biases are implicit in samples of stars selected to have precise ages, which have so far not been appreciated. Methods: We show that these selection biases tend to blur the activity-age relation for large age ranges. We calibrate the Mt. Wilson index for a sample of field FGK stars with precise ages, covering a wide range of mass and [Fe/H] , augmented with data from the Pleiades, Hyades, M 67 clusters, and the Ursa Major moving group. Results: We further test the calibration with extensive new Gemini/GMOS log ()R'HK) data of the old, solar [Fe/H] clusters, M 67 and NGC 188. The observed NGC 188 activity level is clearly lower than M 67. We correctly recover the isochronal age of both clusters and establish the viability of deriving usable chromospheric ages for solar-type stars up to at least ~6 Gyr, where average errors are ~0.14 dex provided that we explicitly account for the mass and [Fe/H] dimensions. We test our calibration against asteroseismological ages, finding excellent correlation (ρ = + 0.89). We show that our calibration improves the chromospheric age determination for a wide range of ages, masses, and metallicities in comparison to previous age-activity relations.

  14. Fast Variability in Selected Chromospherically Active Dwarf Stars and Observational Equipment for Their Study

    NASA Astrophysics Data System (ADS)

    Bogdanovski, Rumen G.

    2015-06-01

    The observations of variable stars, especially those which show fast changes in their brightness, require high speed and high precision photometry. In order to study events like low amplitude optical oscillations and small scale fluctuations in the light curves, synchronous observations are required. These observations have to be carried out simultaneously at two or more, preferably distant, sites (Romanyuk et al., 2001), which allows the identification and elimination of artifacts produced by the equipment and the atmospheric interferences. In this way the fine structure of the light curve is revealed with a significant certainty. In order to study these events a new high speed time synchronized photometric system had to be designed, which addresses the requirements of the observations of high frequency subtle phenomena during stellar flares. It provides remote automatedand centralized control of the photometric equipment over a computer network,as well as remotemonitoring. Furthermore, some preliminary data processing can be performed at the time the data is obtained.

  15. Comparison of morphology of active cyclic steps created by turbidity currents on Squamish Delta, British Columbia, Canada with flume experiments

    NASA Astrophysics Data System (ADS)

    Yokokawa, Miwa; Yamamoto, Shinya; Higuchi, Hiroyuki; Hughes Clarke, John E.; Izumi, Norihiro

    2015-04-01

    Upper-flow-regime bedforms, such as cyclic steps and antidunes, have been reported to be formed by turbidity currents. Their formative conditions are, however, not fully understood because of the difficulty of field surveys in the deep sea. Field observations of turbidity currents and seabed topography on the Squamish delta in Howe Sound, British Columbia, Canada have been undertaken which found bedwaves actively migrating in the upstream direction in channels formed on the prodelta slope. Their topography and behavior suggest that they are cyclic steps formed by turbidity currents. Because Squamish delta is as shallow as around 150 m, and easy to access compared with general submarine canyons, it is thought to be one of the best places for studying characteristics of cyclic steps formed by turbidity currents through field observations. In this study, we have analyzed configurations of cyclic steps with the use of data obtained in the field observation of 2011, and compare them with the data from the flume experiments. On the prodelta slope, three major active channels are clearly developed. In addition to the sonar survey, a 600 kHz ADCP was installed in 150m of water just seaward of the termination of the North Channel. In addition, 1200kHz ADCP and 500kHz M3s are suspended from the research vessel in 60 m of water and 300 m distance from the delta edge. We selected images showing large daily differences. The steps move vigorously at the upper 600m parts of the prodelta slope, so that we measured the steps in this area. From the profiles perpendicular to the bedwave crest lines through the center of channels, wavelength and wave height for each step, mean slope were measured on the software for quantitative image analyses manually. Wave steepness for each step was calculated using the wavelength and wave height measured as above. The mean slope ranges from 6.8° ~ 2.7° (more proximal, steeper), mean wavelength and wave heights of steps range from 24.5 to 87.6m

  16. Differential rotation of cool active stars: the case of intermediate rotators

    NASA Astrophysics Data System (ADS)

    Petit, P.; Donati, J.-F.; Collier Cameron, A.

    2002-08-01

    In this paper, we present a new method for measuring the surface differential rotation of cool stars with rotation periods of a few days, for which the sparse phase coverage achievable from single-site observations generally prevents the use of more conventional techniques. The basic idea underlying this new analysis is to obtain the surface differential rotation pattern that minimizes the information content of the reconstructed Doppler image through a simultaneous fit of all available data. Simulations demonstrate that the performance of this new method in the case of cool stars is satisfactory for a variety of observing strategies. Differential rotation parameters can be recovered reliably as long as the total data set spans at least 4 per cent of the time for the equator to lap the pole by approximately one complete cycle. We find in particular that these results hold for potentially complex spot distributions (as long as they include a mixture of low- and high-latitude features), and for various stellar inclination angles and rotation velocities. Such measurements can be obtained from either unpolarized or polarized data sets, provided their signal-to-noise ratio is larger than approximately 500 and 5000 per 2kms-1 spectral bin, respectively. This method should therefore be very useful for investigating differential rotation in a much larger sample of objects than what has been possible up to now, and should hence give us the opportunity of studying how differential rotation reacts to various phenomena operating in stellar convective zones, such as tidal effects or dynamo magnetic field generation.

  17. The Search for Signatures of Transient Mass Loss in Active Stars

    NASA Astrophysics Data System (ADS)

    Crosley, M. K.; Osten, R. A.; Broderick, J. W.; Corbel, S.; Eislöffel, J.; Grießmeier, J.-M.; van Leeuwen, J.; Rowlinson, A.; Zarka, P.; Norman, C.

    2016-10-01

    The habitability of an exoplanet depends on many factors. One such factor is the impact of stellar eruptive events on nearby exoplanets. Currently this is poorly constrained due to heavy reliance on solar scaling relationships and a lack of experimental evidence. Potential impacts of coronal mass ejections (CMEs), which are the large eruption of magnetic field and plasma from a star, are space weather and atmospheric stripping. A method for observing CMEs as they travel though the stellar atmosphere is the type II radio burst, and the new Low Frequency Array (LOFAR) provides a means of detection. We report on 15 hr of observation of YZ Canis Minoris (YZ CMi), a nearby M dwarf flare star, taken in LOFAR’s beam-formed observation mode for the purposes of measuring transient frequency-dependent low-frequency radio emission. The observations utilized the Low Band Antenna (10-90 MHz) or High Band Antenna (110-190 MHz) for five three-hour observation periods. In this data set, there were no confirmed type II events in this frequency range. We explore the range of parameter space for type II bursts constrained by our observations. Assuming the rate of shocks is a lower limit to the rate at which CMEs occur, no detections in a total of 15 hr of observation places a limit of {ν }{type{II}}\\lt 0.0667 shocks/hr ≤ ν CME for YZ CMi due to the stochastic nature of the events and the limits of observational sensitivity. We propose a methodology to interpret jointly observed flares and CMEs which will provide greater constraints to CMEs and test the applicability of solar scaling relations.

  18. Binary stars.

    PubMed

    Paczynacuteski, B

    1984-07-20

    Most stars in the solar neighborhood are either double or multiple systems. They provide a unique opportunity to measure stellar masses and radii and to study many interesting and important phenomena. The best candidates for black holes are compact massive components of two x-ray binaries: Cygnus X-1 and LMC X-3. The binary radio pulsar PSR 1913 + 16 provides the best available evidence for gravitational radiation. Accretion disks and jets observed in close binaries offer a very good testing ground for models of active galactic nuclei and quasars.

  19. CO-DARK Star Formation and Black Hole Activity in 3C 368 at Z = 1.131: Coeval Growth of Stellar and Supermassive Black Hole Masses

    NASA Astrophysics Data System (ADS)

    Lamarche, C.; Stacey, G.; Brisbin, D.; Ferkinhoff, C.; Hailey-Dunsheath, S.; Nikola, T.; Riechers, D.; Sharon, C. E.; Spoon, H.; Vishwas, A.

    2017-02-01

    We present the detection of four far-infrared fine-structure oxygen lines, as well as strong upper limits for the CO(2–1) and [N ii] 205 μm lines, in 3C 368, a well-studied radio-loud galaxy at z = 1.131. These new oxygen lines, taken in conjunction with previously observed neon and carbon fine-structure lines, suggest a powerful active galactic nucleus (AGN), accompanied by vigorous and extended star formation. A starburst dominated by O8 stars, with an age of ∼6.5 Myr, provides a good fit to the fine-structure line data. This estimated age of the starburst makes it nearly concurrent with the latest episode of AGN activity, suggesting a link between the growth of the supermassive black hole and stellar population in this source. We do not detect the CO(2–1) line, down to a level twelve times lower than the expected value for star-forming galaxies. This lack of CO line emission is consistent with recent star formation activity if the star-forming molecular gas has low metallicity, is highly fractionated (such that CO is photodissociated throughout much of the clouds), or is chemically very young (such that CO has not yet had time to form). It is also possible, although we argue it is unlikely, that the ensemble of fine-structure lines is emitted from the region heated by the AGN.

  20. THE ROLE OF GALAXY INTERACTION IN ENVIRONMENTAL DEPENDENCE OF THE STAR FORMATION ACTIVITY AT z {approx_equal} 1.2

    SciTech Connect

    Ideue, Y.; Taniguchi, Y.; Shioya, Y.; Kajisawa, M.; Nagao, T.; Trump, J. R.; Iovino, A.; Koekemoer, A. M.; Le Fevre, O.; Ilbert, O.; Scoville, N. Z.

    2012-03-01

    In order to understand environmental effects on star formation in high-redshift galaxies, we investigate the physical relationships between the star formation activity, stellar mass, and environment for z {approx_equal} 1.2 galaxies in the 2 deg{sup 2} COSMOS field. We estimate star formation using the [O II]{lambda}3727 emission line and environment from the local galaxy density. Our analysis shows that for massive galaxies (M{sub *} {approx}> 10{sup 10} M{sub Sun }), the fraction of [O II] emitters in high-density environments ({Sigma}{sub 10th} {approx}> 3.9 Mpc{sup -2}) is 1.7 {+-} 0.4 times higher than in low-density environments ({Sigma}{sub 10th} {approx}< 1.5 Mpc{sup -2}), while the [O II] emitter fraction does not depend on environment for low-mass M{sub *} {approx}< 10{sup 10} M{sub Sun} galaxies. In order to understand what drives these trends, we investigate the role of companion galaxies in our sample. We find that the fraction of [O II] emitters in galaxies with companions is 2.4 {+-} 0.5 times as high as that in galaxies without companions at M{sub *} {approx}> 10{sup 10} M{sub Sun }. In addition, massive galaxies are more likely to have companions in high-density environments. However, although the number of star-forming galaxies increases for massive galaxies with close companions and in dense environments, the average star formation rate of star-forming galaxies at a given mass is independent of environment and the presence/absence of a close companion. These results suggest that interactions and/or mergers in a high-density environment could induce star formation in massive galaxies at z {approx} 1.2, increasing the fraction of star-forming galaxies with M{sub *} {approx}> 10{sup 10} M{sub Sun }.

  1. Narrow-band Imagery with the Goddard Fabry-Perot: Probing the Epoch of Active Accretion for PMS Stars

    NASA Technical Reports Server (NTRS)

    Woodgate, Bruce E.; Grady, C.; Endres, M.; Williger, G.

    2006-01-01

    The STIS coronagraphic imaging sample of I'MS stars was surveyed with the Goddard Fabry-Perot (GFP) interferometer to determine what fraction of the stars drive jets, whether there is any difference in behavior for a group of intermediate-mass stars as compared with T Tauri stars, and to search for evolutionary effects. Compared to broad band imaging, the FGP achieves an emission-line nebulosity-to-star contrast gain of between 500 and 3000. To date, we have detected jets associated with classical T Tauri stars spanning a factor of 280 in mass accretion rate in approximately 50% of the STIS coronagraphic imaging sample. We also detected jets or Herbig-HARO knots associated with 5 Herbig Ae stars, all younger than 8 Myr, for a detection fraction which is smaller than the T Tauri survey.

  2. Reaching for the Stars.

    ERIC Educational Resources Information Center

    Roper-Davis, Sharon

    1999-01-01

    Describes "Reaching for the Stars," a program which develops teaming and mentoring skills in senior physics students. Phase 1 requires student pairs to design a rocket; Phase 2 pairs seniors with gifted second graders who build the rocket from written instructions; and in Phase 3, pairs of seniors create a children's storybook explaining…

  3. KOI-676: An active star with two transiting planets and a third possible candidate detected with TTV

    NASA Astrophysics Data System (ADS)

    Ioannidis, P.; Schmitt, J.; Avdellidou, C.; von Essen, C.; Eric, A.

    2013-09-01

    We report the detection and characterization of two short period, Neptune sized planets, around the active star KOI-676. The orbital elements of both planets are not the expected ones, as they lead to miscalculation of the stellar parameters. We discuss various scenarios which could cause that discrepancy and we suggest that the reason is most probably the high eccentricities of the orbits. We use the Transit Timing Variations, detected in both planets' O-C diagrams to support our theory, while due to the lack of autocorrelation in their pattern we suggest the existence of a third, more massive, mutual inclined, outer perturber. To clarify our suggestions we use n-body simulations to model the TTVs and check the stability of the system.

  4. ENVIRONMENTAL EFFECTS ON THE STAR FORMATION ACTIVITY IN GALAXIES AT z {approx_equal} 1.2 IN THE COSMOS FIELD

    SciTech Connect

    Ideue, Y.; Nagao, T.; Sasaki, S.; Taniguchi, Y.; Shioya, Y.; Saito, T.; Murayama, T.; Trump, J. R.; Koekemoer, A. M.; Aussel, H.; Ilbert, O.; Sanders, D. B.; McCracken, H.; Mobasher, B.

    2009-08-01

    We investigate the relation between the star formation activity in galaxies and environment at z {approx_equal} 1.2 in the Cosmic Evolution Survey field, using the fraction of [O II] emitters and the local galaxy density. The fraction of [O II] emitters appears to be almost constant over the surface density of galaxies between 0.2 and 10 Mpc{sup -2}. This trend is different from that seen in the local universe where the star formation activity is weaker in higher density regions. To understand this difference between z {approx} 1 and z {approx} 0, we study the fraction of non-isolated galaxies as a function of local galaxy density. We find that the fraction of non-isolated galaxies increases with increasing density. Our results suggest that the star formation in galaxies at z {approx} 1 is triggered by galaxy interaction and/or mergers.

  5. Hysteresis Effect in the Activity Indices of the Atmospheres of the Sun and Solar-Type Stars During the Rising and Falling Phases of Cycles

    NASA Astrophysics Data System (ADS)

    Bruevich, E. A.; Yakunina, G. V.

    2016-09-01

    The hysteresis effect that shows up as a nonunique relationship among the emissions from the photosphere, chromosphere, and corona during the rising and falling phases of solar and stellar activity is analyzed. The following solar indices are analyzed and compared in different phases of the cycle: the radiative flux in the hydrogen Lyman alpha line FLα, radio emission at 10.7 cm F10.7, the sunspot number SSN, the radiative flux in the 530.0 nm green coronal line F530.3, the solar constant TSI, and the relative flux ratio c/w (ratio of the fluxes in the center and in the wings) for the 280 nm Mg II line. In stars with cycles, a hysteresis effect is observed between the CaII chromospheric S-activity index for stars in the Mount Wilson HK project and the photospheric flux Fph for these stars.

  6. MC2: boosted AGN and star formation activity in CIZA J2242.8+5301, a massive post-merger cluster at z = 0.19

    NASA Astrophysics Data System (ADS)

    Sobral, David; Stroe, Andra; Dawson, William A.; Wittman, David; Jee, M. James; Röttgering, Huub; van Weeren, Reinout J.; Brüggen, Marcus

    2015-06-01

    Cluster mergers may play a fundamental role in the formation and evolution of cluster galaxies. Stroe et al. revealed unexpected overdensities of candidate Hα emitters near the ˜1-Mpc-wide shock fronts of the massive (˜2 × 1015 M⊙) `Sausage' merging cluster, CIZA J2242.8+5301. We used the Keck/Deep Imaging Multi-Object Spectrograph and the William Herschel Telescope/AutoFib2+WYFFOS to confirm 83 Hα emitters in and around the merging cluster. We find that cluster star-forming galaxies in the hottest X-ray gas and/or in the cluster subcores (away from the shock fronts) show high [S II]6716/[S II]6761 and high [S II] 6716/Hα, implying very low electron densities (<30 × lower than all other star-forming galaxies outside the cluster) and/or significant contribution from supernovae, respectively. All cluster star-forming galaxies near the cluster centre show evidence of significant outflows (blueshifted Na D ˜200-300 km s-1), likely driven by supernovae. Strong outflows are also found for the cluster Hα active galactic nucleus (AGN). Hα star-forming galaxies in the merging cluster follow the z ˜ 0 mass-metallicity relation, showing systematically higher metallicity (˜0.15-0.2 dex) than Hα emitters outside the cluster (projected R > 2.5 Mpc). This suggests that the shock front may have triggered remaining metal-rich gas which galaxies were able to retain into forming stars. Our observations show that the merger of impressively massive (˜1015 M⊙) clusters can provide the conditions for significant star formation and AGN activity, but, as we witness strong feedback by star-forming galaxies and AGN (and given how massive the merging cluster is), such sources will likely quench in a few 100 Myr.

  7. A search for Wolf-Rayet stars in active star forming regions of low mass galaxies - GR8, NGC 2366, IC 2574, and NGC 1569

    NASA Astrophysics Data System (ADS)

    Drissen, Laurent; Roy, Jean-Rene; Moffat, Anthony F. J.

    1993-10-01

    We report the detection, via narrow-band 4686 A filter imagery, of possible new Wolf-Rayet stars in the most massive giant H II regions of the irregular galaxies NGC 2366 and IC 2574. One stellar knot in the post-starburst galaxy NGC 1569 also appears to contain a weak excess of light at 4686 A. A similar search yielded negative results in the very low mass galaxy GR8. The strongest 4686 A excess is located close to the secondary eastern knot in the core of NGC 2366-I (NGC 2363). If this excess is of stellar origin, about five Wolf-Rayet stars of the luminous late-type can account for the excess emission. Nebular emission wraps around this cluster in the form of a shell. The putative Wolf-Rayet stars appear to be close to the center of the large expanding H II bubble discovered by Roy et al. (1991). A possible nebular origin of the 4686 A excess is also discussed.

  8. Strange Nonchaotic Stars

    NASA Astrophysics Data System (ADS)

    Lindner, John F.; Kohar, Vivek; Kia, Behnam; Hippke, Michael; Learned, John G.; Ditto, William L.

    2015-08-01

    Exploiting the unprecedented capabilities of the planet-hunting Kepler space telescope, which stared at 150 000 stars for four years, we discuss recent evidence that certain stars dim and brighten in complex patterns with fractal features. Such stars pulsate at primary and secondary frequencies whose ratios are near the famous golden mean, the most irrational number. A nonlinear system driven by an irrational ratio of frequencies is generically attracted toward a “strange” behavior that is geometrically fractal without displaying the “butterfly effect” of chaos. Strange nonchaotic attractors have been observed in laboratory experiments and have been hypothesized to describe the electrochemical activity of the brain, but a bluish white star 16 000 light years from Earth in the constellation Lyra may manifest, in the scale-free distribution of its minor frequency components, the first strange nonchaotic attractor observed in the wild. The recognition of stellar strange nonchaotic dynamics may improve the classification of these stars and refine the physical modeling of their interiors. We also discuss nonlinear analysis of other RR Lyrae stars in Kepler field of view and discuss some toy models for modeling these stars.References: 1) Hippke, Michael, et al. "Pulsation period variations in the RRc Lyrae star KIC 5520878." The Astrophysical Journal 798.1 (2015): 42.2) Lindner, John F., et al. "Strange nonchaotic stars." Phys. Rev. Lett. 114, 054101 (2015)

  9. Pulsating Stars

    NASA Astrophysics Data System (ADS)

    Catelan, M.; Smith, H. A.

    2015-03-01

    This book surveys our understanding of stars which change in brightness because they pulsate. Pulsating variable stars are keys to distance scales inside and beyond the Milky Way galaxy. They test our understanding not only of stellar pulsation theory but also of stellar structure and evolution theory. Moreover, pulsating stars are important probes of the formation and evolution of our own and neighboring galaxies. Our understanding of pulsating stars has greatly increased in recent years as large-scale surveys of pulsating stars in the Milky Way and other Local Group galaxies have provided a wealth of new observations and as space-based instruments have studied particular pulsating stars in unprecedented detail.

  10. Curious Variables Experiment (CURVE). RZ LMi - the Most Active SU UMa Star

    NASA Astrophysics Data System (ADS)

    Olech, A.; Wisniewski, M.; Zloczewski, K.; Cook, L. M.; Mularczyk, K.; Kedzierski, P.

    2008-06-01

    We report extensive photometry of the frequently outbursting dwarf nova RZ Leo Minoris. During two seasons of observations we detected 12 superoutbursts and 7 normal outbursts. The V magnitude of the star varied in range from 16.5 mag to 13.9 mag. The superoutbursts occur quite regularly flashing every 19.07(4) days and lasting slightly over 10 days. The average interval between two successive normal outbursts is 4.027(3) days. The mean superhump period observed during the superoutbursts is P_sh=0.059396(4) days (85.530+/-0.006 min). The period of the superhumps was constant except for one superoutburst when it increased with a rate of dot P/P_sh=7.6(1.9)x10^-5. Our observations indicate that RZ LMi enters the stage of permanent superhumps, both in superoutbursts and quiescence. This may indicate that decoupling of thermal and tidal instabilities play important role in ER UMa systems. No periodic light variations which can be connected with orbital period of the binary were seen, thus the mass ratio and evolutionary status of RZ LMi are still unknown.

  11. Upscaling Self-Sustaining Treatment for Active Remediation (STAR): Experimental Study of Scaling Relationships for Smouldering Combustion to Remediate Soil

    NASA Astrophysics Data System (ADS)

    Kinsman, L.; Gerhard, J.; Torero, J.; Scholes, G.; Murray, C.

    2013-12-01

    Self-sustaining Treatment for Active Remediation (STAR) is a relatively new remediation approach for soil contaminated with organic industrial liquids. This technology uses smouldering combustion, a controlled, self-sustaining burning reaction, to destroy nonaqueous phase liquids (NAPLs) and thereby render soil clean. While STAR has been proven at the bench scale, success at industrial scales requires the process to be scaled-up significantly. The objective of this study was to conduct an experimental investigation into how liquid smouldering combustion phenomena scale. A suite of detailed forward smouldering experiments were conducted in short (16 cm dia. x 22 cm high), intermediate (16 cm dia. x 127 cm high), and large (97 cm dia. x 300 cm high; a prototype ex-situ reactor) columns; this represents scaling of up to 530 times based on the volume treated. A range of fuels were investigated, with the majority of experiments conducted using crude oil sludge as well as canola oil as a non-toxic surrogate for hazardous contaminants. To provide directly comparable data sets and to isolate changes in the smouldering reaction which occurred solely due to scaling effects, sand grain size, contaminant type, contaminant concentration and air injection rates were controlled between the experimental scales. Several processes could not be controlled and were identified to be susceptible to changes in scale, including: mobility of the contaminant, heat losses, and buoyant flow effects. For each experiment, the propagation of the smouldering front was recorded using thermocouples and analyzed by way of temperature-time and temperature-distance plots. In combination with the measurement of continuous mass loss and gaseous emissions, these results were used to evaluate the fundamental differences in the way the reaction front propagates through the mixture of sand and fuel across the various scales. Key governing parameters were compared between the small, intermediate, and large

  12. Creating a Health Journal

    MedlinePlus

    ... Health Resources Healthcare Management Working With Your Doctor Creating a Personal Health Journal (Health Diary) Creating a Personal Health Journal (Health Diary) Healthcare ManagementWorking ...

  13. Angiotensin II-induced protein kinase D activates the ATF/CREB family of transcription factors and promotes StAR mRNA expression.

    PubMed

    Olala, Lawrence O; Choudhary, Vivek; Johnson, Maribeth H; Bollag, Wendy B

    2014-07-01

    Aldosterone synthesis is initiated upon the transport of cholesterol from the outer to the inner mitochondrial membrane, where the cholesterol is hydrolyzed to pregnenolone. This process is the rate-limiting step in acute aldosterone production and is mediated by the steroidogenic acute regulatory (StAR) protein. We have previously shown that angiotensin II (AngII) activation of the serine/threonine protein kinase D (PKD) promotes acute aldosterone production in bovine adrenal glomerulosa cells, but the mechanism remains unclear. Thus, the purpose of this study was to determine the downstream signaling effectors of AngII-stimulated PKD activity. Our results demonstrate that overexpression of the constitutively active serine-to-glutamate PKD mutant enhances, whereas the dominant-negative serine-to-alanine PKD mutant inhibits, AngII-induced StAR mRNA expression relative to the vector control. PKD has been shown to phosphorylate members of the activating transcription factor (ATF)/cAMP response element binding protein (CREB) family of leucine zipper transcription factors, which have been shown previously to bind the StAR proximal promoter and induce StAR mRNA expression. In primary glomerulosa cells, AngII induces ATF-2 and CREB phosphorylation in a time-dependent manner. Furthermore, overexpression of the constitutively active PKD mutant enhances the AngII-elicited phosphorylation of ATF-2 and CREB, and the dominant-negative mutant inhibits this response. Furthermore, the constitutively active PKD mutant increases the binding of phosphorylated CREB to the StAR promoter. Thus, these data provide insight into the previously reported role of PKD in AngII-induced acute aldosterone production, providing a mechanism by which PKD may be mediating steroidogenesis in primary bovine adrenal glomerulosa cells.

  14. The Brown Dwarf Eclipsing Binary 2M0535-05: A Case Study for Activity Effects on Physical Properties of Low-Mass Stars and Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    Stassun, K. G.

    2013-02-01

    2M0535-05 is a one-of-a-kind eclipsing binary (EB) comprising two brown dwarfs (BDs), and is an important benchmark for understanding the fundamental properties of BDs and low-mass stars. Because 2M0535-05 presents a peculiar reversal of temperatures with mass (the higher mass, magnetically active BD in the system is cooler than the lower mass companion BD), 2M0535-05 is particularly important as a case study for the effects of magnetic activity on the properties of low-mass objects. Using a large number of low-mass M-dwarfs and EBs in the field, we have developed empirical relations for determining the amount by which the temperatures and radii-and therefore the estimated masses-of low-mass stars and BDs are altered due to chromospheric activity. The relations link the amount by which an active object's temperature is suppressed, and its radius inflated, to the strength of its Hα emission. These relations are found to approximately preserve bolometric luminosity. Applying these relations to 2M0535-05 brings the activity-corrected radii and temperatures of 2M0535-05 into precise agreement with theoretical isochrones for inactive stars. The relations that we present are applicable to BDs and low-mass stars with masses below 0.8 M⊙ and for which the activity, as measured by Hα, is in the range - 4.6 < log LHα/Lbol < -3.3. We discuss implications of this work for determinations of young cluster IMFs, and discuss competing ideas for the physical mechanism by which magnetic fields alter the temperatures and radii of low-mass stars.

  15. Narrow-band Imagery With The Goddard Fabry-Perot: Probing The Epoch Of Active Accretion For PMS Stars

    NASA Astrophysics Data System (ADS)

    Woodgate, Bruce E.; Grady, C.; Endres, M.; Hilton, G.; Williger, G.

    2006-06-01

    Over the past 5 years we surveyed the STIS coronagraphic imaging sample of PMS stars with the Goddard Fabry-Perot (GFP) interferometer at the Apache Point Observatory 3.5m telescope to determine what fraction of the stars drive jets, whether there is any difference in behavior for a group of intermediate-mass stars as compared with T Tauri stars, and to search for evolutionary effects. Compared to broad band imaging, the GFP achieves an emission-line nebulosity-to-star contrast gain of between 500 and 3000, depending upon choice of Fabry-Perot etalon, over a field which is 1.67' in radius. To date, we have detected jets associated with classical T Tauri stars spanning a factor of 280 in mass accretion rate in approximately 50% of the STIS coronagraphic imaging sample. Jets have not been detected in any of the stars with mass accretion rates less than 10$^{-8.5}$ solar masses/year, including objects with IR spectral energy distributions indicating deficits of warm, near-stellar dust. The GFP is also equipped with a simple Lyot coronagraph which allows us to search for similar outflows around brighter objects. To date, we have detected jets or Herbig-Haro knots associated with 5 Herbig Ae stars, all younger than 8 Myr, for a detection fraction which is similar to the T Tauri survey. No jets have been detected for Herbig Ae stars with IR SEDs indicating the presence of central cavities in the disks.

  16. Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819 Tau and V830 Tau

    NASA Astrophysics Data System (ADS)

    Donati, J.-F.; Hébrard, E.; Hussain, G. A. J.; Moutou, C.; Malo, L.; Grankin, K.; Vidotto, A. A.; Alencar, S. H. P.; Gregory, S. G.; Jardine, M. M.; Herczeg, G.; Morin, J.; Fares, R.; Ménard, F.; Bouvier, J.; Delfosse, X.; Doyon, R.; Takami, M.; Figueira, P.; Petit, P.; Boisse, I.; MaTYSSE Collaboration

    2015-11-01

    We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri stars (wTTSs) V819 Tau and V830 Tau within the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) programme, involving the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. At ≃3 Myr, both stars dissipated their discs recently and are interesting objects for probing star and planet formation. Profile distortions and Zeeman signatures are detected in the unpolarized and circularly polarized lines, whose rotational modulation we modelled using tomographic imaging, yielding brightness and magnetic maps for both stars. We find that the large-scale magnetic fields of V819 Tau and V830 Tau are mostly poloidal and can be approximated at large radii by 350-400 G dipoles tilted at ≃30° to the rotation axis. They are significantly weaker than the field of GQ Lup, an accreting classical T Tauri star (cTTS) with similar mass and age which can be used to compare the magnetic properties of wTTSs and cTTSs. The reconstructed brightness maps of both stars include cool spots and warm plages. Surface differential rotation is small, typically ≃4.4 times smaller than on the Sun, in agreement with previous results on wTTSs. Using our Doppler images to model the activity jitter and filter it out from the radial velocity (RV) curves, we obtain RV residuals with dispersions of 0.033 and 0.104 km s-1 for V819 Tau and V830 Tau, respectively. RV residuals suggest that a hot Jupiter may be orbiting V830 Tau, though additional data are needed to confirm this preliminary result. We find no evidence for close-in giant planet around V819 Tau.

  17. Herschel Observed Stripe 82 Quasars and Their Host Galaxies: Connections between AGN Activity and host Galaxy Star Formation

    NASA Astrophysics Data System (ADS)

    Dong, X. Y.; Wu, Xue-Bing

    2016-06-01

    In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high-luminosity quasars with a mean bolometric luminosity of 1046.4 erg s-1. The redshift range of this sample is within z < 4, with a mean value of 1.5 ± 0.78. Because we only selected quasars that have been detected in all three Herschel-SPIRE bands, the quasar sample is complete yet highly biased. Based on the multi-wavelength photometric observation data, we conducted a spectral energy distribution (SED) fitting through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity, far-IR (FIR) luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419 M ⊙ yr-1 and the mean gas mass is ˜1011.3 M ⊙. All of these results point to an IR luminous quasar system. Compared with star formation main sequence (MS) galaxies, at least 80 out of 207 quasars are hosted by starburst galaxies. This supports the statement that luminous AGNs are more likely to be associated with major mergers. The SFR increases with the redshift up to z = 2. It is correlated with the AGN bolometric luminosity, where {L}{{FIR}}\\propto {L}{{Bol}}0.46+/- 0.03. The AGN bolometric luminosity is also correlated with the host galaxy mass and gas mass. Yet the correlation between L FIR and L Bol has higher significant level, implies that the link between AGN accretion and the SFR is more primal. The M BH/M * ratio of our sample is 0.02, higher than the value 0.005 in the local universe. It might indicate an evolutionary trend of the M BH-M * scaling relation.

  18. Properties of galaxy groups in the Sloan Digital Sky Survey - II. Active galactic nucleus feedback and star formation truncation

    NASA Astrophysics Data System (ADS)

    Weinmann, Simone M.; van den Bosch, Frank C.; Yang, Xiaohu; Mo, H. J.; Croton, Darren J.; Moore, Ben

    2006-11-01

    Successfully reproducing the galaxy luminosity function (LF) and the bimodality in the galaxy distribution requires a mechanism that can truncate star formation in massive haloes. Current models of galaxy formation consider two such truncation mechanisms: strangulation, which acts on satellite galaxies, and active galactic nucleus (AGN) feedback, which predominantly affects central galaxies. The efficiencies of these processes set the blue fraction of galaxies, fblue(L, M), as a function of galaxy luminosity, L, and halo mass, M. In this paper, we use a galaxy group catalogue extracted from the Sloan Digital Sky Survey (SDSS) to determine fblue(L, M). To demonstrate the potential power of these data as a benchmark for galaxy formation models, we compare the results to the semi-analytical model for galaxy formation of Croton et al. Although this model accurately fits the global statistics of the galaxy population, as well as the shape of the conditional LF, there are significant discrepancies when the blue fraction of galaxies as a function of mass and luminosity is compared between the observations and the model. In particular, the model predicts (i) too many faint satellites in massive haloes, (ii) a blue fraction of satellites that is much too low, and (iii) a blue fraction of centrals that is too high and with an inverted luminosity dependence. In the same order, we argue that these discrepancies owe to (i) the neglect of tidal stripping in the semi-analytical model, (ii) the oversimplified treatment of strangulation, and (iii) improper modelling of dust extinction and/or AGN feedback. The data presented here will prove useful to test and calibrate future models of galaxy formation and, in particular, to discriminate between various models for AGN feedback and other star formation truncation mechanisms.

  19. Star-forming Activity in the H II Regions Associated with the IRAS 17160-3707 Complex

    NASA Astrophysics Data System (ADS)

    Nandakumar, G.; Veena, V. S.; Vig, S.; Tej, A.; Ghosh, S. K.; Ojha, D. K.

    2016-11-01

    We present a multiwavelength investigation of star formation activity toward the southern H ii regions associated with IRAS 17160-3707, located at a distance of 6.2 kpc with a bolometric luminosity of 8.3 × 105 L ⊙. The ionized gas distribution and dust clumps in the parental molecular cloud are examined in detail using measurements at infrared, submillimeter and radio wavelengths. The radio continuum images at 1280 and 610 MHz obtained using the Giant Metrewave Radio Telescope reveal the presence of multiple compact sources as well as nebulous emission. At submillimeter wavelengths, we identify seven dust clumps and estimate their physical properties such as temperature: 24-30 K, mass: 300-4800 M ⊙ and luminosity: 9-317 × 102 L ⊙ using modified blackbody fits to the spectral energy distributions (SEDs) between 70 and 870 μm. We find 24 young stellar objects (YSOs) in the mid-infrared, with a few of them coincident with the compact radio sources. The SEDs of the YSOs have been fitted by the Robitaille models and the results indicate that those having radio compact sources as counterparts host massive objects in early evolutionary stages with best fit age ≤0.2 Myr. We compare the relative evolutionary stages of clumps using various signposts such as masers, ionized gas, presence of YSOs and infrared nebulosity, and find six massive star-forming clumps and one quiescent clump. Of the former, five are in a relatively advanced stage and one in an earlier stage.

  20. Massive Stars

    NASA Astrophysics Data System (ADS)

    Livio, Mario; Villaver, Eva

    2009-11-01

    Participants; Preface Mario Livio and Eva Villaver; 1. High-mass star formation by gravitational collapse of massive cores M. R. Krumholz; 2. Observations of massive star formation N. A. Patel; 3. Massive star formation in the Galactic center D. F. Figer; 4. An X-ray tour of massive star-forming regions with Chandra L. K. Townsley; 5. Massive stars: feedback effects in the local universe M. S. Oey and C. J. Clarke; 6. The initial mass function in clusters B. G. Elmegreen; 7. Massive stars and star clusters in the Antennae galaxies B. C. Whitmore; 8. On the binarity of Eta Carinae T. R. Gull; 9. Parameters and winds of hot massive stars R. P. Kudritzki and M. A. Urbaneja; 10. Unraveling the Galaxy to find the first stars J. Tumlinson; 11. Optically observable zero-age main-sequence O stars N. R. Walborn; 12. Metallicity-dependent Wolf-Raynet winds P. A. Crowther; 13. Eruptive mass loss in very massive stars and Population III stars N. Smith; 14. From progenitor to afterlife R. A. Chevalier; 15. Pair-production supernovae: theory and observation E. Scannapieco; 16. Cosmic infrared background and Population III: an overview A. Kashlinsky.

  1. Twenty-one-base-pair insertion polymorphism creates an enhancer element and potentiates SLC6A1 GABA transporter promoter activity

    PubMed Central

    Hirunsatit, Rungnapa; George, Elizabeth D.; Lipska, Barbara K.; Elwafi, Hani M.; Sander, Lisa; Yrigollen, Carolyn M.; Gelernter, Joel; Grigorenko, Elena L.; Lappalainen, Jaakko; Mane, Shrikant; Nairn, Angus C.; Kleinman, Joel E.; Simen, Arthur A.

    2009-01-01

    Objective Sodium-dependent and chloride-dependent γ-aminobutyric acid (GABA) transporter 1 (SLC6A1) is the target of a number of drugs of clinical importance and is a major determinant of synaptic GABA concentrations. We resequenced the human SLC6A1 gene previously and discovered a novel 21 bp insertion in the predicted promoter region that creates a second tandem copy of the sequence. Here we sought to determine the functional relevance of this variation. Methods We used reporter assays, mobility shift assays, quantitative PCR, and proteomics methods as well as postmortem expression analysis for this work. Results Reporter assays showed that the insertion allele significantly increases promoter activity in multiple cell lines. The zinc finger transcription factor ZNF148 was found to significantly transactivate the promoter and increase expression when overexpressed but could not account for the differences in activity between the two alleles of the promoter. Copy number of the insertion sequence was associated with exponentially increasing activity of a downstream promoter, suggesting that the insertion sequence has enhancer activity when present in multiple copies. SLC6A1 promoter genotype was found to predict SLC6A1 RNA expression in human postmortem hippocampal samples. These results suggest that the insertion polymorphism leads to increased SLC6A1 promoter activity because, in part, of creation of an enhancer element when present as multiple copies. Genotyping individuals from Tanzania in this study suggested that the insertion allele has its origin in Africa. Conclusion On account of the effect of the insertion on promoter activity, this relatively common polymorphism may prove useful in predicting clinical response to pharmacological modulators of SLC6A1 as well as GABAergic function in individuals of African descent. PMID:19077666

  2. Making Stars … With a Little Help

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-11-01

    Extremely high star formation rates have been observed in galaxies at high redshifts, posing somewhat of a mystery: how are these enormous rates achieved? A team of scientists has proposed that these high rates of star formation could be explained by feedback from active nuclei at the centers of the galaxies.Pressurized BubbleWe believe that star formation occurs in galaxies as a result of gas clumps that collapse under their own gravity, eventually becoming dense enough to launch nuclear fusion. Recently, theres been mounting evidence that the star formation rate is significantly higher in high-redshift galaxies, particularly those with active galactic nuclei (AGN). Could this simply be caused by a higher gas fraction at higher redshifts? Or is it possible that a different mechanism is at work in these galaxies, producing more efficient star formation?A team of authors led by Rebekka Bieri (Paris Institute of Astrophysics) has proposed that this enhanced star formation may be caused by positive feedback from the active nucleus of the galaxy. The team suggests that an outflow from the AGN could create an over-pressurized bubble around the galactic disk that pushes back on the disk, leading to a higher rate of star formation.Simulating a BoostThe authors test this toy model by simulating the scenario. They model a disk galaxy with roughly a tenth of the mass of the Milky Way, which starts in a relaxed state. The galaxy is then evolved either with or without an applied external pressure, representing the isotropic pressure from the bubble created by the AGN outflow. These models are tested in two different scenarios: one where the initial gas fraction is 10%, and one where the initial gas fraction is 50%.Star formation rates for the low-gas-fraction (left) and high-gas-fraction (right) simulated galaxies. The blue lines show the rates without external pressure; the red lines show the rates with external pressure applied. [Bieri et al. 2015]The simulations show that

  3. GLOBAL STAR FORMATION REVISITED

    SciTech Connect

    Silk, Joseph; Norman, Colin E-mail: norman@stsci.edu

    2009-07-20

    A general treatment of disk star formation is developed from a dissipative multiphase model, with the dominant dissipation due to cloud collisions. The Schmidt-Kennicutt (SK) law emerges naturally for star-forming disks and starbursts. We predict that there should be an inverse correlation between Tully-Fisher law and SK law residuals. The model is extended to include a multiphase treatment of supernova feedback that leads to a turbulent pressure-regulated generalization of the star formation law and is applicable to gas-rich starbursts. Enhanced pressure, as expected in merger-induced star formation, enhances star formation efficiency. An upper limit is derived for the disk star formation rate in starbursts that depends on the ratio of global ISM to cloud pressures. We extend these considerations to the case where the interstellar gas pressure in the inner galaxy is dominated by outflows from a central active galactic nucleus (AGN). During massive spheroid formation, AGN-driven winds trigger star formation, resulting in enhanced supernova feedback and outflows. The outflows are comparable to the AGN-boosted star formation rate and saturate in the super-Eddington limit. Downsizing of both SMBH and spheroids is a consequence of AGN-driven positive feedback. Bondi accretion feeds the central black hole with a specific accretion rate that is proportional to the black hole mass. AGN-enhanced star formation is mediated by turbulent pressure and relates spheroid star formation rate to black hole accretion rate. The relation between black hole mass and spheroid velocity dispersion has a coefficient (Salpeter time to gas consumption time ratio) that provides an arrow of time. Highly efficient, AGN-boosted star formation can occur at high redshift.

  4. Phosphorylation of Rap1 by cAMP-dependent Protein Kinase (PKA) Creates a Binding Site for KSR to Sustain ERK Activation by cAMP.

    PubMed

    Takahashi, Maho; Li, Yanping; Dillon, Tara J; Stork, Philip J S

    2017-01-27

    Cyclic adenosine monophosphate (cAMP) is an important mediator of hormonal stimulation of cell growth and differentiation through its activation of the extracellular signal-regulated kinase (ERK) cascade. Two small G proteins, Ras and Rap1 have been proposed to mediate this activation. Using HEK293 cells as a model system, we have recently shown that both Ras and Rap1 are required for cAMP signaling to ERKs. However, cAMP-dependent Ras signaling to ERKs is transient and rapidly terminated by PKA phosphorylation of the Raf isoforms C-Raf and B-Raf. In contrast, cAMP-dependent Rap1 signaling to ERKs and Rap1 is potentiated by PKA. We show that this is due to sustained binding of B-Raf to Rap1. One of the targets of PKA is Rap1 itself, directly phosphorylating Rap1a on serine 180 and Rap1b on serine 179. We show that these phosphorylations create potential binding sites for the adaptor protein 14-3-3 that links Rap1 to the scaffold protein KSR. These results suggest that Rap1 activation of ERKs requires PKA phosphorylation and KSR binding. Because KSR and B-Raf exist as heterodimers within the cell, this binding also brings B-Raf to Rap1, allowing Rap1 to couple to ERKs through B-Raf binding to Rap1 independently of its Ras-binding domain.

  5. NEAR-ULTRAVIOLET ABSORPTION, CHROMOSPHERIC ACTIVITY, AND STAR-PLANET INTERACTIONS IN THE WASP-12 SYSTEM

    SciTech Connect

    Haswell, C. A.; Fossati, L.; Holmes, S.; Kolb, U. C.; Busuttil, R.; Carter, A.; Ayres, T.; France, K.; Froning, C. S.; Street, R. A.; Hebb, L.; Cameron, A. Collier; Enoch, B.; Burwitz, V.; Rodriguez, J.; West, R. G.; Pollacco, D.; Wheatley, P. J. E-mail: l.fossati@open.ac.uk E-mail: leslie.hebb@vanderbilt.edu

    2012-11-20

    Extended gas clouds have been previously detected surrounding the brightest known close-in transiting hot Jupiter exoplanets, HD 209458 b and HD 189733 b; we observed the distant but more extreme close-in hot Jupiter system, WASP-12, with Hubble Space Telescope (HST). Near-UV (NUV) transits up to three times deeper than the optical transit of WASP-12 b reveal extensive diffuse gas, extending well beyond the Roche lobe. The distribution of absorbing gas varies between visits. The deepest NUV transits are at wavelength ranges with strong stellar photospheric absorption, implying that the absorbing gas may have temperature and composition similar to those of the stellar photosphere. Our spectra reveal significantly enhanced absorption (greater than 3{sigma} below the median) at {approx}200 individual wavelengths on each of two HST visits; 65 of these wavelengths are consistent between the two visits, using a strict criterion for velocity matching that excludes matches with velocity shifts exceeding {approx}20 km s{sup -1}. Excess transit depths are robustly detected throughout the inner wings of the Mg II resonance lines independently on both HST visits. We detected absorption in Fe II {lambda}2586, the heaviest species yet detected in an exoplanet transit. The Mg II line cores have zero flux, emission cores exhibited by every other observed star of similar age and spectral type are conspicuously absent. WASP-12 probably produces normal Mg II profiles, but the inner portions of these strong resonance lines are likely affected by extrinsic absorption. The required Mg{sup +} column is an order of magnitude greater than expected from the interstellar medium, though we cannot completely dismiss that possibility. A more plausible source of absorption is gas lost by WASP-12 b. We show that planetary mass loss can produce the required column. Our Visit 2 NUV light curves show evidence for a stellar flare. We show that some of the possible transit detections in resonance

  6. Nano-photo active cellulosic fabric through in situ phytosynthesis of star-like Ag/ZnO nanocomposites: Investigation and optimization of attributes associated with photocatalytic activity.

    PubMed

    Aladpoosh, Razieh; Montazer, Majid

    2016-05-05

    In this study, nano-photo active cellulosic fabric was prepared through in situ phytosynthesis of star-like Ag/ZnO nanocomposites using the ashes of Seidlitzia rosmarinus plants so-called Keliab. This is provided alkali media as a vital condition for synthesis of nanocomposites, further increasing the reduce-ability of cellulosic chains by activation of hydroxyl groups. The intermolecular dehydrolysis of intermediates ions under thermal and alkaline conditions leads to formation of Ag/ZnO heterostructure. Various analytical techniques were employed to confirm Ag/ZnO nanocomposites on the cotton fabric. The surface morphology, crystal phase and chemical structure of the treated fabrics were characterized by field emission and scanning electron microscopy (FE-SEM and SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDX). Moreover, influence of precursors: silver nitrate, zinc acetate and Keliab solution on attributes associated with photocatalytic activities including self-cleaning, whiteness and wettability was investigated via central composite design (CCD). The treated cotton samples exhibited self-cleaning activities through methylene blue degradation under day-light exposure along with improved wettability and whiteness. The prepared sample in optimized conditions showed good antibacterial activities against Staphylococcus aureus and Escherichia coli with enhanced fabric tensile strength.

  7. A Star on Earth

    SciTech Connect

    Prager, Stewart; Zwicker, Andrew; Hammet, Greg; Tresemer, Kelsey; Diallo, Ahmed

    2014-03-05

    At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: create a star on Earth. The National Spherical Torus Experiment (NSTX) is a magnetic fusion device that is used to study the physics principles of spherically shaped plasmas -- hot ionized gases in which, under the right conditions, nuclear fusion will occur. Fusion is the energy source of the sun and all of the stars. Not just limited to theoretical work, the NSTX is enabling cutting-edge research to develop fusion as a future energy source.

  8. A Star on Earth

    ScienceCinema

    Prager, Stewart; Zwicker, Andrew; Hammet, Greg; Tresemer, Kelsey; Diallo, Ahmed

    2016-07-12

    At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: create a star on Earth. The National Spherical Torus Experiment (NSTX) is a magnetic fusion device that is used to study the physics principles of spherically shaped plasmas -- hot ionized gases in which, under the right conditions, nuclear fusion will occur. Fusion is the energy source of the sun and all of the stars. Not just limited to theoretical work, the NSTX is enabling cutting-edge research to develop fusion as a future energy source.

  9. CH Stars and Barium Stars

    NASA Astrophysics Data System (ADS)

    Bond, H.; Sion, E.; Murdin, P.

    2000-11-01

    The classical barium (or `Ba II') stars are RED GIANT STARS whose spectra show strong absorption lines of barium, strontium and certain other heavy elements, as well as strong features due to carbon molecules. Together with the related class of CH stars, the Ba II stars were crucial in establishing the existence of neutron-capture reactions in stellar interiors that are responsible for the synt...

  10. An Enhancement of 160um-derived Star-Formation Rates in Active Galaxies to z = 3.2 with the ZFOURGE Survey

    NASA Astrophysics Data System (ADS)

    Cowley, Michael; Spitler, L.

    2016-08-01

    ZFOURGE is a new imaging survey, which employs unique near-infrared medium- band filters designed to probe galaxy properties over the last 12 billion years. By supplementing the high-quality ZFOURGE galaxy catalogues with data in radio, X- ray, and infrared wavebands, we have studied the complex interplay between AGNs and their host galaxies to a time when the Universe was only 10-15% of its present age. I will report on our study to compare the 160-um derived star-formation rates in active and non-active galaxies and show that AGN hosts, over all redshifts, tend to exhibit an elevated average star-formation activity compared to their non-active counterparts.

  11. Flare And Starspot-Induced Variabilities Of Red Dwarf Stars In The Open Cluster M37: Photometric Study On Stellar Magnetic Activity

    NASA Astrophysics Data System (ADS)

    Chang, Seo-Won; Byun, Yong-Ik; Hartman, Joel D.

    2016-07-01

    We investigate the statistical properties of flare and starspot-induced variabilities of red dwarf stars in the open cluster M37, particularly (1) understanding magnetic activity phenomena that are seen in groups of stars (with the same age and mass) and (2) the correlations among activity indicators. The use of both tracers is particularly useful for statistical studies since it can provide more homogeneous information about their activity behaviors. We recalibrate the archival imaging data of the M37 obtained by one-month observing run with MMT/Megacam camera, i.e., Deep, High-cadence and Long-term monitoring survey. To detect any significant variability from cool objects, forced photometry with our multi-aperture indexing technique is applied to the entire time-series images. In this contributed talk, we present an update on flare and rotational statistics of this cluster and further strong evidences that support the classical age-rotation-activity paradigm.

  12. Seeing Stars in Serpens

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Infant stars are glowing gloriously in this infrared image of the Serpens star-forming region, captured by NASA's Spitzer Space Telescope.

    The reddish-pink dots are baby stars deeply embedded in the cosmic cloud of gas and dust that collapsed to create it. A dusty disk of cosmic debris, or 'protoplanetary disk,' that may eventually form planets, surrounds the infant stars.

    Wisps of green throughout the image indicate the presence of carbon rich molecules called polycyclic aromatic hydrocarbons. On Earth, these molecules can be found on charred barbecue grills and in automobile exhaust. Blue specks sprinkled throughout the image are background stars in our Milky Way galaxy.

    The Serpens star-forming region is located approximately 848 light-years away in the Serpens constellation.

    The image is a three-channel, false-color composite, where emission at 4.5 microns is blue, emission at 8.0 microns is green, and 24 micron emission is red.

  13. Activities and Achievements of the Double Star Committee of the Socié té Astronomique de France

    NASA Astrophysics Data System (ADS)

    Agati, Jean-Louis; Caille, Sébastien; Debackère, André; Durand, Pierre; Losse, Florent; Manté, René; Mauroy, Florence; Mauroy, Pascal; Morlet, Guy; Pinlou, Claude; Salaman, Maurice; Soulié, Edgar; Thorel, Yvonne; Thorel, Jean-Claude

    2007-08-01

    In a synthesis article (see ref. below), the double star expert Paul COUTEAU put the work of French pioneers of double stars observation in the perspective of the double star work carried in the world. After Antoine Yvon VILLARCEAU and Camille FLAMMARION, one prominent pioneer of double stars was Robert JONCKHEERE (1888toiles Doubles, Maurice DURUY (1894le with a 40-cm and later a 60-cm telescope at Le Rouret (Alpes1995) had started the measurement of double stars as an amateur. He was granted permission to measure them with the 38-cm of the Paris Observatory and made an impressive number of measures during his long 2006) made double star observations for the book which was then in preparation under the title La revue des constellations. Their measures remained unpublished; but publication of the measures made by Robert SAGOT is in preparation. At about the same time, the neurology professor Jacques LE BEAU (1908toiles doubles visuelles. That book triggered the interest of more amateur astronomers for double stars and indirectly influenced the creation of a group of double star observers which was transformed into the Commission des É toiles Doubles

  14. Chemical Composition and Biological Activity of Star Anise Illicium verum Extracts Against Maize Weevil, Sitophilus zeamais Adults

    PubMed Central

    Wei, Linlin; Hua, Rimao; Li, Maoye; Huang, Yanzhang; Li, Shiguang; He, Yujie; Shen, Zonghai

    2014-01-01

    This study aims to develop eco-friendly botanical pesticides. Dried fruits of star anise (Illicium verum Hook.f. (Austrobaileyales: Schisandraceae)) were extracted with methyl alcohol (MA), ethyl acetate (EA), and petroleum ether (PE) at 25°C. The constituents were determined by gas chromatography-mass spectrometry, and the repellency and contact toxicity of the extracts against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) adults were tested. Fortyfour compounds, whose concentrations were more than 0.2%, were separated and identified from the MA, EA, and PE extracts. The extraction yields of trans-anethole, the most abundant biologically active compound in I. verum, were 9.7%, 7.5%, and 10.1% in the MA, EA, and PE extracts, respectively. Repellency increased with increasing extract dose. The average repellency rate of the extracts against S. zeamais adults peaked at 125.79 μg/cm2 72 hr after treatment. The percentage repellency of the EA extract reached 76.9%, making it a class IV repellent. Contact toxicity assays showed average mortalities of 85.4% (MA), 94.5% (EA), and 91.1% (PE). The EA extract had the lowest median lethal dose, at 21.2 μg/cm2 72 hr after treatment. The results suggest that I. verum fruit extracts and trans-anethole can potentially be developed as a grain protectant to control stored-product insect pests. Other active constituents in the EA extract merit further research. PMID:25368036

  15. Chemical composition and biological activity of star anise Illicium verum extracts against maize weevil, Sitophilus zeamais adults.

    PubMed

    Wei, Linlin; Hua, Rimao; Li, Maoye; Huang, Yanzhang; Li, Shiguang; He, Yujie; Shen, Zonghai

    2014-01-01

    This study aims to develop eco-friendly botanical pesticides. Dried fruits of star anise (Illicium verum Hook.f. (Austrobaileyales: Schisandraceae)) were extracted with methyl alcohol (MA), ethyl acetate (EA), and petroleum ether (PE) at 25°C. The constituents were determined by gas chromatography-mass spectrometry, and the repellency and contact toxicity of the extracts against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) adults were tested. Forty-four compounds, whose concentrations were more than 0.2%, were separated and identified from the MA, EA, and PE extracts. The extraction yields of trans-anethole, the most abundant biologically active compound in I. verum, were 9.7%, 7.5%, and 10.1% in the MA, EA, and PE extracts, respectively. Repellency increased with increasing extract dose. The average repellency rate of the extracts against S. zeamais adults peaked at 125.79 µg/cm(2) 72 hr after treatment. The percentage repellency of the EA extract reached 76.9%, making it a class IV repellent. Contact toxicity assays showed average mortalities of 85.4% (MA), 94.5% (EA), and 91.1% (PE). The EA extract had the lowest median lethal dose, at 21.2 µg/cm(2) 72 hr after treatment. The results suggest that I. verum fruit extracts and trans-anethole can potentially be developed as a grain protectant to control stored-product insect pests. Other active constituents in the EA extract merit further research.

  16. Stellar Dynamical Processes in Massive Star and Star Cluster Formation

    NASA Astrophysics Data System (ADS)

    Tan, Jonathan; Eyer, L.

    2009-01-01

    We study how high precision astrometric measurements by SIM and GAIA of stars involved in dynamical ejection events from star clusters can constrain theories of massive star and star cluster formation. We focus on the Orion Nebula Cluster (ONC). First, we investigate the scientific potential associated with an accurate measurement of the distance and proper motion of Theta 1 Ori C, which is the most massive star in the cluster and was recently involved (about 4000 years ago) in the ejection of a B star: the Becklin-Neugebauer (BN) star. The motion of the BN star has taken it close to a massive protostar, known as source I, where it appears to have influenced the accretion and outflow activity, most likely by a tidal interaction with the accretion disk. An accurate proper motion measurement of Theta 1 Ori C will constrain BN's initial motion, allowing us to search for deflections caused by the gravitational potential of the massive protostar. Second, we search the Hipparcos catalog for candidate runaway stars, i.e. that have been dynamically ejected from the cluster over the course of the last several Myr. SIM and GAIA observations of these stars will be needed to confirm their origin from the ONC. The results of this study will constrain the star cluster formation timescale and the statistics of the population of ejected stars. JCT acknowledges support from from NSF CAREER grant AST-0645412 and a grant from NASA for SIM Science Studies.

  17. Creating new library services through collaboration with resident groups : Aimimg at human resource development and information literacy education in ways only libraries can do : Study on activities of an NPO called Ueda Library Club

    NASA Astrophysics Data System (ADS)

    Morita, Utako

    Creating new library services through collaboration with resident groups : Aimimg at human resource development and information literacy education in ways only libraries can do : Study on activities of an NPO called Ueda Library Club

  18. Astronomy: Minds-on the Universe. Supplemental Teaching Activities for Grades K-8.

    ERIC Educational Resources Information Center

    Marble, Stephen; Fowler, Marilyn, Ed.

    This teachers guide contains activities and materials created to teach astronomy concepts to children from grades K-8. It is organized into four units: (1) Earth and Stars; (2) Spheres and Orbits; (3) Stars and Gravity; and (4) Scales and Measurement. Activities are arranged within each unit around six content topics: (1) Earth; (2) Solar System;…

  19. Starring role of toll-like receptor-4 activation in the gut-liver axis

    PubMed Central

    Carotti, Simone; Guarino, Michele Pier Luca; Vespasiani-Gentilucci, Umberto; Morini, Sergio

    2015-01-01

    Since the introduction of the term “gut-liver axis”, many studies have focused on the functional links of intestinal microbiota, barrier function and immune responses to liver physiology. Intestinal and extra-intestinal diseases alter microbiota composition and lead to dysbiosis, which aggravates impaired intestinal barrier function via increased lipopolysaccharide translocation. The subsequent increased passage of gut-derived product from the intestinal lumen to the organ wall and bloodstream affects gut motility and liver biology. The activation of the toll-like receptor 4 (TLR-4) likely plays a key role in both cases. This review analyzed the most recent literature on the gut-liver axis, with a particular focus on the role of TLR-4 activation. Findings that linked liver disease with dysbiosis are evaluated, and links between dysbiosis and alterations of intestinal permeability and motility are discussed. We also examine the mechanisms of translocated gut bacteria and/or the bacterial product activation of liver inflammation and fibrogenesis via activity on different hepatic cell types. PMID:26600967

  20. The Evolution of Star formation Activity in Cluster Galaxies over 0.15 < z < 1.5

    NASA Astrophysics Data System (ADS)

    Wagner, Cory R.; Courteau, Stéphane; Brodwin, Mark; Stanford, S. A.; Snyder, Gregory F.; Stern, Daniel

    2017-01-01

    We explore 7.5 billion years of evolution in the star formation activity of massive ({M}\\star > {10}10.1 {M}ȯ ) cluster galaxies using a sample of 25 clusters over 0.15< z< 1 from the Cluster Lensing And Supernova survey with Hubble and 11 clusters over 1< z< 1.5 from the IRAC Shallow Cluster Survey. Galaxy morphologies are determined visually using high-resolution Hubble Space Telescope images. Using the spectral energy distribution fitting code Code Investigating GALaxy Emission, we measure star formation rates, stellar masses, and 4000 Å break strengths. The latter are used to separate quiescent and star-forming galaxies (SFGs). From z∼ 1.3 to z∼ 0.2, the specific star formation rate (sSFR) of cluster SFGs and quiescent galaxies decreases by factors of three and four, respectively. Over the same redshift range, the sSFR of the entire cluster population declines by a factor of 11, from 0.48+/- 0.06 {{Gyr}}-1 to 0.043+/- 0.009 {{Gyr}}-1. This strong overall sSFR evolution is driven by the growth of the quiescent population over time; the fraction of quiescent cluster galaxies increases from {28}-19+8 % to {88}-4+5 % over z ∼ 1.3 to 0.2. The majority of the growth occurs at z≳ 0.9, where the quiescent fraction increases by 0.41. While the sSFR of the majority of star-forming cluster galaxies is at the level of the field, a small subset of cluster SFGs have low field-relative star formation activity, suggestive of long-timescale quenching. The large increase in the fraction of quiescent galaxies above z∼ 0.9, coupled with the field-level sSFRs of cluster SFGs, suggests that higher-redshift cluster galaxies are likely being quenched quickly. Assessing those timescales will require more accurate stellar population ages and star formation histories.

  1. A fusion promoter created by a new insertion sequence, IS1490, activates transcription of 2,4,5-trichlorophenoxyacetic acid catabolic genes in Burkholderia cepacia AC1100.

    PubMed Central

    Hübner, A; Hendrickson, W

    1997-01-01

    Transposition and transcriptional activation by insertion sequences in Burkholderia cepacia AC1100 were investigated. Two closely related new elements, IS1413 and IS1490, were identified and characterized. These elements are not highly related to other insertion sequences identified in AC1100 or other B. cepacia isolates. Based on their structures and the sequences of the inverted terminal repeats and the putative transposase protein, the insertion elements (IS elements) are similar to IST2 of Thiobacillus ferrooxidans and several related elements. All the IS elements that have been identified in this strain are found in multiple copies (10 to 40), and they have high-level promoter activity capable of stimulating transcription from a distance up to 500 bp from a target gene. Strain AC1100 was originally isolated after prolonged selection for the ability to utilize the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) as a sole carbon source. Three IS elements are located near the first gene of the 2,4,5-T catabolic pathway, tftA. IS1490 inserted 110 bp upstream of tftA and created a fusion promoter responsible for constitutive transcription of the gene. Our results confirm the hypothesis that IS elements play a central role in transcription of 2,4,5-T genes and likely have stimulated rapid evolution of the metabolic pathway. PMID:9098071

  2. Identification of striated muscle activator of Rho signaling (STARS) as a novel calmodulin target by a newly developed genome-wide screen.

    PubMed

    Furuya, Yusui; Denda, Miwako; Sakane, Kyohei; Ogusu, Tomoko; Takahashi, Sumio; Magari, Masaki; Kanayama, Naoki; Morishita, Ryo; Tokumitsu, Hiroshi

    2016-07-01

    To search for novel target(s) of the Ca(2+)-signaling transducer, calmodulin (CaM), we performed a newly developed genome-wide CaM interaction screening of 19,676 GST-fused proteins expressed in human. We identified striated muscle activator of Rho signaling (STARS) as a novel CaM target and characterized its CaM binding ability and found that the Ca(2+)/CaM complex interacted stoichiometrically with the N-terminal region (Ala13-Gln35) of STARS in vitro as well as in living cells. Mutagenesis studies identified Ile20 and Trp33 as the essential hydrophobic residues in CaM anchoring. Furthermore, the CaM binding deficient mutant (Ile20Ala, Trp33Ala) of STARS further enhanced its stimulatory effect on SRF-dependent transcriptional activation. These results suggest a connection between Ca(2+)-signaling via excitation-contraction coupling and the regulation of STARS-mediated gene expression in muscles.

  3. Creating corporate advantage.

    PubMed

    Collis, D J; Montgomery, C A

    1998-01-01

    What differentiates truly great corporate strategies from the merely adequate? How can executives at the corporate level create tangible advantage for their businesses that makes the whole more than the sum of the parts? This article presents a comprehensive framework for value creation in the multibusiness company. It addresses the most fundamental questions of corporate strategy: What businesses should a company be in? How should it coordinate activities across businesses? What role should the corporate office play? How should the corporation measure and control performance? Through detailed case studies of Tyco International, Sharp, the Newell Company, and Saatchi and Saatchi, the authors demonstrate that the answers to all those questions are driven largely by the nature of a company's special resources--its assets, skills, and capabilities. These range along a continuum from the highly specialized at one end to the very general at the other. A corporation's location on the continuum constrains the set of businesses it should compete in and limits its choices about the design of its organization. Applying the framework, the authors point out the common mistakes that result from misaligned corporate strategies. Companies mistakenly enter businesses based on similarities in products rather than the resources that contribute to competitive advantage in each business. Instead of tailoring organizational structures and systems to the needs of a particular strategy, they create plain-vanilla corporate offices and infrastructures. The company examples demonstrate that one size does not fit all. One can find great corporate strategies all along the continuum.

  4. Outburst Activity Driven by Evolved Pulsating Star in the Symbiotic Binary AG Dra

    NASA Astrophysics Data System (ADS)

    Gális, R.; Hric, L.; Leedjärv, L.

    2015-12-01

    The symbiotic system AG Dra regularly undergoes quiescent and active stages which consist of the series of individual outbursts. The period analysis of new and historical photometric data, as well as radial velocities, confirmed the presence of the two periods. The longer one around ≈ 550 d is related to the orbital motion and the shorter one ≈355 d could be due to pulsation of the cool component of AG Dra.

  5. VizieR Online Data Catalog: Star formation in active and normal galaxies (Tsai+, 2015)

    NASA Astrophysics Data System (ADS)

    Tsai, M.; Hwang, C.-Y.

    2015-11-01

    We selected 104 active galaxies from the lists of Melendez et al. (2010MNRAS.406..493M), Condon et al. 1991 (cat. J/ApJ/378/65), and Ho & Ulvestad 2001 (cat. J/ApJS/133/77). Most of the sources are identified as Active Galactic Nuclei (AGNs), and a few of them are classified as Luminous InfraRed Galaxies (LIRGs). We obtained 3.6 and 8μm infrared images of these galaxies from the Spitzer Archive (http://sha.ipac.caltech.edu/applications/Spitzer/SHA/) and 8GHz images from the VLA archive (http://archive.nrao.edu/archive/archiveimage.html). We also selected a nearby AGN sub-sample containing 21 radio-selected AGNs for further spatial analysis. We selected 25 nearby AGNs exhibiting no detected radio emission in order to compare with the results of the radio-selected sources. For comparison, we also selected normal galaxies with distances less than 15Mpc from the catalog of Tully 1994 (see cat. VII/145). We only selected the galaxies that have Spitzer archive data and are not identified as AGNs in either the Veron-Cetty & Veron 2006 (see cat. VII/258) AGN catalog or in the NED database (http://ned.ipac.caltech.edu/). Our results for the radio-selected and the non-radio-selected active galaxies are listed in Table1, and those for the normal galaxies are listed in Table2. (2 data files).

  6. Further observations of the lambda 10830 He line in stars and their significance as a measure of stellar activity

    NASA Technical Reports Server (NTRS)

    Zirin, H.

    1975-01-01

    Measurements of the lambda 1030 He line in 198 stars are given along with data on other features in that spectral range. Nearly 80% of all G and K stars show some lambda 10830; of these, half are variable and 1/4 show emission. It was confirmed that lambda 10830 is not found in M stars, is weak in F stars, and is particularly strong in close binaries. The line is found in emission in extremely late M and S stars, along with P gamma, but P gamma is not in emission in G and K stars with lambda 10830 emissions. Variable He emission and Ti I emission are found in the RV Tauri variables R Scuti and U Mon. In R Aqr the Fe XIII coronal line lambda 10747 and a line at lambda 11012 which may be singlet He or La II are found, as well as lambda 10830 and P gamma. The nature of coronas or hot chromospheres in the various stars is discussed. It was concluded that the lambda 10830 intensity must be more or less proportional to the energy deposited in the chromosphere corona by non-thermal processes.

  7. Collapsing Enormous Stars

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-09-01

    One of the big puzzles in astrophysics is how supermassive black holes (SMBHs) managed to grow to the large sizes weve observed in the very early universe. In a recent study, a team of researchers examines the possibility that they were formed by the direct collapse of supermassive stars.Formation MysterySMBHs billions of times as massive as the Sun have been observed at a time when the universe was less than a billion years old. But thats not enough time for a stellar-mass black hole to grow to SMBH-size by accreting material so another theory is needed to explain the presence of these monsters so early in the universes history. A new study, led by Tatsuya Matsumoto (Kyoto University, Japan), poses the following question: what if supermassive stars in the early universe collapsed directly into black holes?Previous studies of star formation in the early universe have suggested that, in the hot environment of these primordial times, stars might have been able to build up mass much faster than they can today. This could result in early supermassive stars roughly 100,000 times more massive than the Sun. But if these early stars end their lives by collapsing to become massive black holes in the same way that we believe massive stars can collapse to form stellar-mass black holes today this should result in enormously violent explosions. Matusmoto and collaborators set out to model this process, to determine what we would expect to see when it happens!Energetic BurstsThe authors modeled the supermassive stars prior to collapse and then calculated whether a jet, created as the black hole grows at the center of the collapsing star, would be able to punch out of the stellar envelope. They demonstrated that the process would work much like the widely-accepted collapsar model of massive-star death, in which a jet successfully punches out of a collapsing star, violently releasing energy in the form of a long gamma-ray burst (GRB).Because the length of a long GRB is thought to

  8. Patrol of the short wavelength activity and flares of Sun as star

    NASA Astrophysics Data System (ADS)

    Afanasiev, I.; Avakyan, S.; Leonov, N.; Serova, A.; Voronin, N.

    Monitoring of the spectral range which most affects solar-terrestrial relationship - soft X-ray and extreme UV-radiations allows to solve ? problem of solar activity influence on all aspects of the Sun - Earth ties and to select the most important precursors of solar flares and the solar events related with a flare (such as proton events, high-velocity plasma streams in the solar wind, shock waves, coronal mass ejection and, the most important, the beginning of principal magnetic storms). Solar activity is constantly monitored at present (in the USA) only in two sections of the spectrum of ionizing radiation: <0.8 nm and >115 (119) nm. However, so far there has been no monitoring of the flux in the most geoeffective region of the spectrum (0.8-115 nm) from the entire disk of the sun; this region completely monitors the main part of the ionosphere of the earth and the ionosphere of the other planets of the solar system, including the formation and status of the main ionospheric maxima. This occurs solely because of technical and methodological difficulties in performing the measurements and calibration in this spectral range on spacecraft, because it is necessity to use only windowless optics. At the present the solar the optical - electronic equipment (OEE) is testing and there are plans to launch OEE of Space Solar Patrol (SSP) consisting of solar radiometers and spectrometers at the Russian Module of the International Space Station. So the solving the problem of the permanent monitoring-patrol of ionizing radiation from the full disk of the Sun appears in the main tasks of fundamental scientific studies in space. The results of this monitoring can be contribution in development of simultaneous studies in several sciences, such as: - solar astrophysics (state of all solar atmospheric regions), - meteorology, physics of atmosphere (the influence of solar activity on global changes, climate and weather including the effects of atmo s pheric electricity), - aeronomy

  9. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crighton, Devin; Das, Sudeep; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, Erik D.; Schmitt, Benjamin; Sehgal, Neelima; Sievers, Johnathan; Staggs, Suzanne; Swetz, Daniel; Thornton, Robert; Wollack, Edward

    2014-01-01

    We present a catalogue of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 -1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97 per cent of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogues. When combined with flux densities from the Australia Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, A(sub 148-218), of 3.7 (+0.62 or -0.86), and includes both local galaxies and sources with redshift around 6. Dusty sources with no counterpart in existing catalogues likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  10. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Duenner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, EriK D.; Wollack, Edward

    2013-01-01

    We present a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 GHz and/or 218GHz in the 2008 Southern survey. Flux densities span 14-1700mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two sub-populations: 167 radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogs. When combined with flux densities from the Australian Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148GHz, with the trend continuing to 218GHz. The ACT dust-dominated source population has a median spectral index, alpha(sub 148-218), of 3.7+0.62 or -0.86, and includes both local galaxies and sources with redshifts as great as 5.6. Dusty sources with no counterpart in existing catalogs likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  11. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, Erik D.; Wollack, Edward

    2014-01-01

    We present a catalogue of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 - 1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97 per cent of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogues. When combined with flux densities from the Australia Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, alpha(sub 148-218), of 3.7 +0.62/-0.86), and includes both local galaxies and sources with redshift around 6. Dusty sources with no counterpart in existing catalogues likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  12. The NuSTAR X-ray spectrum of the low-luminosity active galactic nucleus in NGC 7213

    NASA Astrophysics Data System (ADS)

    Ursini, F.; Marinucci, A.; Matt, G.; Bianchi, S.; Tortosa, A.; Stern, D.; Arévalo, P.; Ballantyne, D. R.; Bauer, F. E.; Fabian, A. C.; Harrison, F. A.; Lohfink, A. M.; Reynolds, C. S.; Walton, D. J.

    2015-09-01

    We present an analysis of the 3-79 keV NuSTAR spectrum of the low-luminosity active galactic nucleus NGC 7213. In agreement with past observations, we find a lower limit to the high-energy cut-off of Ec > 140 keV, no evidence for a Compton-reflected continuum and the presence of an iron K α complex, possibly produced in the broad-line region. From the application of the MYTORUS model, we find that the line-emitting material is consistent with the absence of a significant Compton reflection if arising from a Compton-thin torus of gas with a column density of 5.0^{+2.0}_{-1.6}× 10^{23} cm-2. We report variability of the equivalent width of the iron lines on the time-scale of years using archival observations from XMM-Newton, Chandra and Suzaku. This analysis suggests a possible contribution from dusty gas. A fit with a Comptonization model indicates the presence of a hot corona with a temperature kTe > 40 keV and an optical depth τ ≲ 1, assuming a spherical geometry.

  13. An Investigation of the Largest Flares in Active Cool Star Binaries with ALEXIS

    NASA Technical Reports Server (NTRS)

    Stern, Robert A.

    1998-01-01

    After a long delay due to the initial problems with the ALEXIS attitude control, the heroic efforts on the part of the ALEXIS satellite team enabled us to carry out this survey. However, the combination of the higher than expected and variable background in the ALEXIS detectors, and the lower throughput of the ALEXIS telescopes resulted in no convincing detections of large flares from the active binary systems. In addition, vignetting-corrected effective exposure times from the ALEXIS aspect solution were not available prior to the end of this contract; therefore, we were unable to convert upper limits measured in ALEXIS counts to the equivalent.

  14. LANL Activities Supporting Electron Accelerator Production of 99Mo for NorthStar Medical Radioisotopes, LLC

    SciTech Connect

    Dale, Gregory E.; Kelsey, Charles T. IV; Woloshun, Keith A.; Holloway, Michael A.; Olivas, Eric R.; Dalmas, Dale A.; Romero, Frank P.; Hurtle, Kenneth P.

    2012-07-11

    Summary of LANL FY12 Activities are: (1) Preparation, performance, and data analysis for the FY12 accelerator tests at ANL - (a) LANL designed and installed a closed-loop helium target cooling system at ANL for the FY12 accelerator tests, (b) Thermal test was performed on March 27, (c) 24 h production test to follow the accelerator upgrade at ANL; (2) Local target shielding design and OTR/IR recommendations - (a) Target dose rate and activation products were calculated with MCNPX, (b) {sup 206}Pb({gamma},2n){sup 204m}Pb vs {sup 204g}Pb branching ratio unpublished, will measure using the LANL microtron, (c) OTR system nearing final configuration, (d) IR prototype system demonstrated during the recent thermal test at ANL; (3) Target housing lifetime estimation - Target housing material specifications and design to be finalized following the thermal test, lifetime not believed to be an issue; and (4) Target cooling system reliability - Long duration system characterizations will begin following the thermal test.

  15. TESTING DIAGNOSTICS OF NUCLEAR ACTIVITY AND STAR FORMATION IN GALAXIES AT z > 1

    SciTech Connect

    Trump, Jonathan R.; Barro, Guillermo; Koo, David C.; Faber, S. M.; Kocevski, Dale D.; Yan, Renbin; Juneau, Stephanie; McLean, Ian S.; Perez-Gonzalez, Pablo G.; Villar, Victor

    2013-01-20

    We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z {approx} 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [O III]/H{beta} ratio is insufficient as an active galactic nucleus (AGN) indicator at z > 1. For the four X-ray-detected galaxies, the classic diagnostics ([O III]/H{beta} versus [N II]/H{alpha} and [S II]/H{alpha}) remain consistent with X-ray AGN/SF classification. The X-ray data also suggest that 'composite' galaxies (with intermediate AGN/SF classification) host bona fide AGNs. Nearly {approx}2/3 of the z {approx} 1.5 emission-line galaxies have nuclear activity detected by either X-rays or the classic diagnostics. Compared to the X-ray and line ratio classifications, the mass-excitation method remains effective at z > 1, but we show that the color-excitation method requires a new calibration to successfully identify AGNs at these redshifts.

  16. Testing Diagnostics of Nuclear Activity and Star Formation in Galaxies at z > 1

    NASA Astrophysics Data System (ADS)

    Trump, Jonathan R.; Konidaris, Nicholas P.; Barro, Guillermo; Koo, David C.; Kocevski, Dale D.; Juneau, Stéphanie; Weiner, Benjamin J.; Faber, S. M.; McLean, Ian S.; Yan, Renbin; Pérez-González, Pablo G.; Villar, Victor

    2013-01-01

    We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z ~ 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [O III]/Hβ ratio is insufficient as an active galactic nucleus (AGN) indicator at z > 1. For the four X-ray-detected galaxies, the classic diagnostics ([O III]/Hβ versus [N II]/Hα and [S II]/Hα) remain consistent with X-ray AGN/SF classification. The X-ray data also suggest that "composite" galaxies (with intermediate AGN/SF classification) host bona fide AGNs. Nearly ~2/3 of the z ~ 1.5 emission-line galaxies have nuclear activity detected by either X-rays or the classic diagnostics. Compared to the X-ray and line ratio classifications, the mass-excitation method remains effective at z > 1, but we show that the color-excitation method requires a new calibration to successfully identify AGNs at these redshifts. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. Also based on data obtained at the W. M. Keck Observatory, made possible by the generous financial support of the W. M. Keck Foundation and operated as a scientific partnership among Caltech, the University of California, and NASA.

  17. STAR heavy flavor tracker

    NASA Astrophysics Data System (ADS)

    Qiu, Hao

    2014-11-01

    Hadrons containing heavy quarks are a clean probe of the early dynamic evolution of the dense and hot medium created in high-energy nuclear collisions. To explore heavy quark production at RHIC, the Heavy Flavor Tracker (HFT) for the STAR experiment was built and installed in time for RHIC Run 14. The HFT consists of four layers of silicon detectors. The two outermost layers are silicon strip detectors and the two innermost layers are made from state-of-the-art ultra-thin CMOS Monolithic Active Pixel Sensors (MAPS). This is the first application of a CMOS MAPS detector in a collider experiment. The use of thin pixel sensors plus the use of carbon fiber supporting material limits the material budget to be only 0.4% radiation length per pixel detector layer, enabling the reconstruction of low pT heavy flavor hadrons. The status and performance of the HFT in the RHIC 200 GeV Au + Au run in 2014 are reported. Very good detector efficiency, hit residuals and track resolution (DCAs) were observed in the cosmic ray data and in the Au + Au data.

  18. ACTIVE GALACTIC NUCLEUS PAIRS FROM THE SLOAN DIGITAL SKY SURVEY. II. EVIDENCE FOR TIDALLY ENHANCED STAR FORMATION AND BLACK HOLE ACCRETION

    SciTech Connect

    Liu Xin; Shen Yue; Strauss, Michael A.

    2012-01-20

    Active galactic nuclei (AGNs) are occasionally seen in pairs, suggesting that tidal encounters are responsible for the accretion of material by both central supermassive black holes (BHs). In Paper I of this series, we selected a sample of AGN pairs with projected separations r{sub p} < 100 h{sup -1}{sub 70} kpc and velocity offsets <600 km s{sup -1} from the Seventh Data Release of the Sloan Digital Sky Survey and quantified their frequency. In this paper, we address the BH accretion and recent star formation properties in their host galaxies. AGN pairs experience stronger BH accretion, as measured by their [O III] {lambda}5007 luminosities (corrected for contribution from star formation) and Eddington ratios, than do control samples of single AGNs matched in redshift and host-galaxy stellar mass. Their host galaxies have stronger post-starburst activity and younger mean stellar ages, as indicated by stronger H{delta} absorption and smaller 4000 A break in their spectra. The BH accretion and recent star formation in the host galaxies both increase with decreasing projected separation in AGN pairs, for r{sub p} {approx}< 10-30 h{sup -1}{sub 70} kpc. The intensity of BH accretion, the post-starburst strength, and the mean stellar ages are correlated between the two AGNs in a pair. The luminosities and Eddington ratios of AGN pairs are correlated with recent star formation in their host galaxies, with a scaling relation consistent with that observed in single AGNs. Our results suggest that galaxy tidal interactions enhance both BH accretion and host-galaxy star formation in close AGN pairs, even though the majority of low-redshift AGNs are not coincident with on-going interactions.

  19. Lithium and Isotopic Ratio Li6/Li7 in Magnetic roAp Stars as an Indicator of Active Processes

    NASA Astrophysics Data System (ADS)

    Polosukhina, N.; Shavrina, A.; Lyashko, D.; Nesvacil, N.; Drake, N.; Smirnova, M.

    2015-04-01

    The lines of lithium at 6708 Å and 6103 Å are analyzed in high resolution spectra of some sharp-lined and slowly rotating roAp stars. Three spectral synthesis codes— STARSP, ZEEMAN2, and SYNTHM—were used. New lines of rare earth elements (REE) from the DREAM database and the lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. For both lithium lines, the enhanced abundances of lithium in the atmospheres of the stars studied are obtained. The lithium abundance determined from the Li 6103 Å line is higher than that from the Li 6708 Å for all the stars. This may be evidence of vertical lithium stratification, abnormal temperature distribution, or unidentified blending of the 6103 Å line. Our work on two roAp stars, HD 83368 and HD 60435 (Shavrina et al. 2001) provides evidence of an enhanced lithium abundance near the magnetic-field poles. We can expect similar effects in the sharp-lined roAp stars. High lithium abundance for all the stars and the estimates of the 6Li/7Li ratio (0.2-0.5) can be explained by production of Li in the cosmic ray spallation reactions in the interstellar medium where the stars were born, and by preservation of the original 6Li and 7Li by strong magnetic fields of these stars. The values of the 6Li/7Li ratio expected from production by cosmic rays are about 0.5-0.8 (Knauth et al. 2003; Webber et al. 2002). New laboratory and theoretical gf-values for REE lines are necessary in order to refine our estimates of lithium abundances and the isotopic ratio.

  20. Coronal activity in F-, G-, and K-type stars. IV - Evidence for expanding loop geometries in stellar coronae

    NASA Technical Reports Server (NTRS)

    Schrijver, C. J.; Lemen, J. R.; Mewe, R.

    1989-01-01

    A detailed analysis is presented of X-ray spectra of Capella and of Sigma2 CrB. The spectra of both stars are compatible with coronae consisting of two different ensembles of static loops with different maximum temperatures and ratios of the cross sectional areas at the loop top and at the footpoint. The cool (5 MK) loop components in both stars show evidence of relatively strong expansion with height. The hot (30 MK) components appear to expand much less.

  1. Enhanced anticancer activity of DM1-loaded star-shaped folate-core PLA-TPGS nanoparticles

    NASA Astrophysics Data System (ADS)

    Tang, Xiaolong; Liang, Yong; Zhu, Yongqiang; Cai, Shiyu; Sun, Leilei; Chen, Tianyi

    2014-10-01

    The efficient delivery of therapeutic drugs into interested cells is a critical challenge to broad application of nonviral vector systems. In this research, emtansine (DM1)-loaded star-shaped folate-core polylactide- d-α-tocopheryl polyethylene glycol 1000 succinate (FA-PLA-TPGS-DM1) copolymer which demonstrated superior anticancer activity in vitro/ vivo in comparison with linear FA-PLA-TPGS nanoparticles was applied to be a vector of DM1 for FR+ breast cancer therapy. The DM1- or coumarin 6-loaded nanoparticles were fabricated, and then characterized in terms of size, morphology, drug encapsulation efficiency, and in vitro drug release. And the viability of MCF-7/HER2 cells treated with FA-DM1-nanoparticles (NPs) was assessed. Severe combined immunodeficient mice carrying MCF-7/HER2 tumor xenografts were treated in several groups including phosphate-buffered saline control, DM1, DM1-NPs, and FA-DM1-NPs. The antitumor activity was then assessed by survival time and solid tumor volume. All the specimens were prepared for formalin-fixed and paraffin-embedded tissue sections for hematoxylin-eosin staining. The data showed that the FA-DM1-NPs could efficiently deliver DM1 into MCF-7/HER2 cells. The cytotoxicity of DM1 to MCF-7/HER2 cells was significantly increased by FA-DM1-NPs when compared with the control groups. In conclusion, the FA-DM1-NPs offered a considerable potential formulation for FR+ tumor-targeting biotherapy.

  2. De novo-engineered transcription activator-like effector (TALE) hybrid nuclease with novel DNA binding specificity creates double-strand breaks.

    PubMed

    Mahfouz, Magdy M; Li, Lixin; Shamimuzzaman, Md; Wibowo, Anjar; Fang, Xiaoyun; Zhu, Jian-Kang

    2011-02-08

    Site-specific and rare cutting nucleases are valuable tools for genome engineering. The generation of double-strand DNA breaks (DSBs) promotes homologous recombination in eukaryotes and can facilitate gene targeting, additions, deletions, and inactivation. Zinc finger nucleases have been used to generate DSBs and subsequently, for genome editing but with low efficiency and reproducibility. The transcription activator-like family of type III effectors (TALEs) contains a central domain of tandem repeats that could be engineered to bind specific DNA targets. Here, we report the generation of a Hax3-based hybrid TALE nuclease with a user-selected DNA binding specificity. We show that the engineered TALE nuclease can bind to its target sequence in vitro and that the homodimeric TALE nuclease can cleave double-stranded DNA in vitro if the DNA binding sites have the proper spacing and orientation. Transient expression assays in tobacco leaves suggest that the hybrid nuclease creates DSB in its target sequence, which is subsequently repaired by nonhomologous end-joining repair. Taken together, our data show the feasibility of engineering TALE-based hybrid nucleases capable of generating site-specific DSBs and the great potential for site-specific genome modification in plants and eukaryotes in general.

  3. Deepest Image of Exploded Star Uncovers Bipolar Jets

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This spectacular Chandra X-Ray Observatory (CXO) image of the supernova remnant Cassiopeia A is the most detailed image ever made of the remains of an exploded star. The one-million-second image shows a bright outer ring (green) 10 light years in diameter that marks the location of a shock wave generated by the supernova explosion. In the upper left corner is a large jet-like structure that protrudes beyond the shock wave, and a counter-jet can be seen on the lower right. The x-ray spectra show that the jets are rich in silicon atoms, and relatively poor in iron atoms. This indicates that the jets formed soon after the initial explosion of the star, otherwise, the jets should have contained large quantities of iron from the star's central regions. The bright blue areas are composed almost purely of iron gas, which was produced in the central, hottest regions of the star and somehow ejected in a direction almost perpendicular to the jets. The bright source at the center of the image is presumed to be a neutron star created during the supernova. Unlike most others, this neutron star is quiet, faint, and so far shows no evidence of pulsed radiation. A working hypothesis is that the explosion that created Cassiopeia A produced high speed jets similar to, but less energetic than, the hyper nova jets thought to produce gamma-ray bursts. During the explosion, the star may have developed an extremely strong magnetic filed that helped to accelerate the jets and later stifled any pulsar wind activity. CXO project management is the responsibility of NASA's Marshall Space Flight Center in Huntsville, Alabama.

  4. X-ray flux variability of active galactic nuclei observed using NuSTAR

    NASA Astrophysics Data System (ADS)

    Rani, Priyanka; Stalin, C. S.; Rakshit, Suvendu

    2017-04-01

    We present results of a systematic study of flux variability on hourly time-scales in a large sample of active galactic nuclei (AGN) in the 3-79 keV band using data from Nuclear Spectroscopic Telescope Array. Our sample consists of four BL Lac objects (BL Lacs), three flat spectrum radio quasars (FSRQs) 24 Seyfert 1, 42 Seyfert 2 and eight narrow line Seyfert 1 (NLSy1) galaxies. We find that in the 3-79 keV band, about 65 per cent of the sources in our sample show significant variations on hourly time-scales. Using the Mann-Whitney U-test and the Kolmogorov-Smirnov test, we find no difference in the variability behaviour between Seyfert 1 and 2 galaxies. The blazar sources (FSRQs and BL Lacs) in our sample are more variable than Seyfert galaxies that include Seyfert 1 and Seyfert 2 in the soft (3-10 keV), hard (10-79 keV) and total (3-79 keV) bands. NLSy1 galaxies show the highest duty cycle of variability (87 per cent), followed by BL Lacs (82 per cent), Seyfert galaxies (56 per cent) and FSRQs (23 per cent). We obtained flux doubling/halving time in the hard X-ray band less than 10 min in 11 sources. The flux variations between the hard and soft bands in all the sources in our sample are consistent with zero lag.

  5. On the coronae of rapidly rotating stars. IV - Coronal activity in F dwarfs and implications for the onset of the dynamo

    NASA Technical Reports Server (NTRS)

    Walter, F. M.

    1983-01-01

    X-ray observations of 14 early F dwarfs are reported and these stars are used, together with a complete sample from the literature, to examine how the characteristics of coronal X-ray emission vary from dwarfs of spectral type A through G. Evidence for a rotation-activity relation in stars redder than B - V = 0.45 is found. Stellar duplicity and age, except insofar as they influence the rotation rate, do not appear to be important in determining the coronal X-ray flux level in F dwarfs. It is suggested that the appearance of a relation between rotation and activity at B - V = 0.45 indicates the turn-on of a solar-like dynamo. The high X-ray surface fluxes and small variance thereof for dwarfs with B - V = 0.3-0.45 are also discussed.

  6. Pixel response function experimental techniques and analysis of active pixel sensor star cameras

    NASA Astrophysics Data System (ADS)

    Fumo, Patrick; Waldron, Erik; Laine, Juha-Pekka; Evans, Gary

    2015-04-01

    The pixel response function (PRF) of a pixel within a focal plane is defined as the pixel intensity with respect to the position of a point source within the pixel. One of its main applications is in the field of astrometry, which is a branch of astronomy that deals with positioning data of a celestial body for tracking movement or adjusting the attitude of a spacecraft. Complementary metal oxide semiconductor (CMOS) image sensors generally offer better radiation tolerance to protons and heavy ions than CCDs making them ideal candidates for space applications aboard satellites, but like all image sensors they are limited by their spatial frequency response, better known as the modulation transfer function. Having a well-calibrated PRF allows us to eliminate some of the uncertainty in the spatial response of the system providing better resolution and a more accurate centroid estimation. This paper describes the experimental setup for determining the PRF of a CMOS image sensor and analyzes the effect on the oversampled point spread function (PSF) of an image intensifier, as well as the effects due to the wavelength of light used as a point source. It was found that using electron bombarded active pixel sensor (EBAPS) intensification technology had a significant impact on the PRF of the camera being tested as a result of an increase in the amount of carrier diffusion between collection sites generated by the intensification process. Taking the full width at half maximum (FWHM) of the resulting data, it was found that the intensified version of a CMOS camera exhibited a PSF roughly 16.42% larger than its nonintensified counterpart.

  7. OT2_mdickins_1: Herschel+CANDELS: Unraveling the physical processes that regulate star formation and AGN activity in ordinary galaxies at z=2

    NASA Astrophysics Data System (ADS)

    Dickinson, M.

    2011-09-01

    The deepest Herschel surveys have established a distinction between steady "main sequence" star formation, whose rate is closely tied to galaxy mass at a given redshift, and elevated starburst activity in ordinary, L*(IR) galaxies at z > 1.5. They have also shown that supermassive black hole growth occurs mainly through secular processes in these main sequence galaxies, and have revealed otherwise obscured AGN missed by the deepest X-ray surveys. However, the physical processes that trigger starbursts, and the relation between star formation, AGN activity, and the structural properties of galaxies at this peak era of galaxy growth, are far from clear. We propose a survey to address these questions by measuring far-infrared luminosities and star formation rates for a large sample of high redshift galaxies with deep, high-resolution near-infrared imaging from the CANDELS HST WFC3 Treasury program. Herschel PACS and SPIRE observations deep enough to detect 700+ L*(IR) galaxies at z > 1.5 will be obtained for the five CANDELS fields and correlated with the detailed morphological and structural properties that only HST/WFC3 imaging can provide. We will establish whether interactions and mergers drive starburst activity, and examine their relevance for fueling AGN activity. The improved statistics will allow a definitive measure of the space density of L*(IR) galaxies at z=2, a basic (and currently very uncertain) demographic quantity for the history of cosmic star formation. The survey will provide a legacy of targets for detailed investigation with ALMA, tripling (beyond GOODS-South alone) the number of ALMA-accessible fields with the deepest Herschel data.

  8. Star Polymers.

    PubMed

    Ren, Jing M; McKenzie, Thomas G; Fu, Qiang; Wong, Edgar H H; Xu, Jiangtao; An, Zesheng; Shanmugam, Sivaprakash; Davis, Thomas P; Boyer, Cyrille; Qiao, Greg G

    2016-06-22

    Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

  9. Radio stars.

    PubMed

    Hjellming, R M; Wade, C M

    1971-09-17

    Up to the present time six classes of radio stars have been established. The signals are almost always very faint and drastically variable. Hence their discovery has owed as much to serendipity as to the highly sophisticated equipment and techniques that have been used. When the variations are regular, as with the pulsars, this characteristic can be exploited very successfully in the search for new objects as well as in the detailed study of those that are already known. The detection of the most erratically variable radio stars, the flare stars and the x-ray stars, is primarily a matter of luck and patience. In the case of the novas, one at least knows where and oughly when to look for radio emission. A very sensitive interferometer is clearly the best instrument to use in the initial detection of a radio star. The fact that weak background sources are frequently present makes it essential to prove that the position of a radio source agrees with that of a star to within a few arc seconds. The potential of radio astronomy for the study of radio stars will not be realized until more powerful instruments than those that are available today can be utilized. So far, we have been able to see only the most luminous of the radio stars.

  10. The distribution of satellites around massive galaxies at 1 < z < 3 in ZFOURGE/CANDELS: Dependence on star formation activity

    SciTech Connect

    Kawinwanichakij, Lalitwadee; Papovich, Casey; Quadri, Ryan F.; Tran, Kim-Vy H.; Mehrtens, Nicola; Spitler, Lee R.; Cowley, Michael; Kacprzak, Glenn G.; Glazebrook, Karl; Nanayakkara, Themiya; Labbé, Ivo; Straatman, Caroline M. S.; Allen, Rebecca; Davé, Romeel; Dekel, Avishai; Ferguson, Henry C.; Koekemoer, Anton M.; Hartley, W. G.; Koo, David C.; and others

    2014-09-10

    We study the statistical distribution of satellites around star-forming and quiescent central galaxies at 1 < z < 3 using imaging from the FourStar Galaxy Evolution Survey and the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey. The deep near-IR data select satellites down to log (M/M {sub ☉}) > 9 at z < 3. The radial satellite distribution around centrals is consistent with a projected Navarro-Frenk-White profile. Massive quiescent centrals, log (M/M {sub ☉}) > 10.78, have ∼2 times the number of satellites compared to star-forming centrals with a significance of 2.7σ even after accounting for differences in the centrals' stellar-mass distributions. We find no statistical difference in the satellite distributions of intermediate-mass quiescent and star-forming centrals, 10.48 < log (M/M {sub ☉}) < 10.78. Compared to the Guo et al. semi-analytic model, the excess number of satellites indicates that quiescent centrals have halo masses 0.3 dex larger than star-forming centrals, even when the stellar-mass distributions are fixed. We use a simple toy model that relates halo mass and quenching, which roughly reproduces the observed quenched fractions and the differences in halo mass between star-forming and quenched galaxies only if galaxies have a quenching probability that increases with halo mass from ∼0 for log (M{sub h} /M {sub ☉}) ∼ 11 to ∼1 for log (M{sub h} /M {sub ☉}) ∼ 13.5. A single halo-mass quenching threshold is unable to reproduce the quiescent fraction and satellite distribution of centrals. Therefore, while halo quenching may be an important mechanism, it is unlikely to be the only factor driving quenching. It remains unclear why a high fraction of centrals remain star-forming even in relatively massive halos.

  11. Sounds of a Star

    NASA Astrophysics Data System (ADS)

    2001-06-01

    colours show element displacements in opposite directions. Geologists monitor how seismic waves generated by earthquakes propagate through the Earth, and thus learn about the inner structure of our planet. The same technique works for stars. The Sun, our nearest star and a typical middle-age member of its class, has been investigated in this way since the 1960's. With "solar seismology" , astronomers have been able to learn much about the inner parts of the star, and not only the outer layers normally visible to the telescopes. In the Sun, heat is bubbling up from the central regions where enormous amount of energy is created by nuclear reactions . In the so-called convective zone , the gas is virtually boiling, and hot gas-bubbles are rising with a speed that is close to that of sound. Much like you can hear when water starts to boil, the turbulent convection in the Sun creates noise . These sound waves then propagate through the solar interior and are reflected on the surface, making it oscillate. This "ringing" is well observed in the Sun, where the amplitude and frequency of the oscillations provide astronomers with plenty of information about the physical conditions in the solar interior. From the Sun to the stars There is every reason to believe that our Sun is a quite normal star of its type. Other stars that are similar to the Sun are therefore likely to pulsate in much the same way as the Sun. The search for such oscillations in other solar-like stars has, however, been a long and difficult one. The problem is simply that the pulsations are tiny, so very great precision is needed in the measurements. However, the last few years have seen considerable progress in asteroseismology, and François Bouchy and Fabien Carrier from the Geneva Observatory have now been able to detect unambiguous acoustic oscillations in the Solar-twin star, Alpha Centauri A. The bright and nearby star Alpha Centauri Alpha Centauri (Alpha Cen) [1] is the brightest star in the constellation

  12. Star formation activity in spiral galaxy disks and the properties of radio halos: Observational evidence for a direct dependence

    NASA Technical Reports Server (NTRS)

    Dahlem, Michael; Lisenfeld, Ute; Golla, Gotz

    1995-01-01

    In this article we address observationally the questions: how does star formation (SF) in the disks of galaxies lead to the creation of radio halos, and what minimum energy input into the interstellar medium (ISM) is needed to facilitate this? For the investigation we use a sample of five edge-on galaxies exhibiting radio continuum emmission in their halos and enhanced SF spread over large parts of their disks. In a detailed study of the two galaxies in our sample for which we have the best data, NGC 891 and NGC 4631, we show that the radio halos cut off abruptly at galactocentric radii smaller than those of the underlying thin radio disks. Our most important result is that the halo cutoffs are spatially coincident with the radii where the SF activity in the underlying disks drops sharply. The difference in radius of the emission distributions tracing ongoing SF in the disks (IRAS 50 micrometers, H alpha) versus that of the nonthermal radio continuum thin disks (tracing the distribution of cosmic-ray (CR) electrons) is typically a few kpc. This difference in extent is caused by CR diffusion. We have measured the CR diffusion coefficients in the thin disks of both NGC 891 and NGC 4631. For radial diffusion of CR electrons within the galactic disks the values are D(sub r) = 1.1-2.5 x 10 (exp 29) sq cm/s (NGC 4631) and D(sub r) = 1.2 x 10(exp 29) sq cm/s (NGC 891). For motions in the z-direction in areas within the thin disks where no outflows occur, we derive a firm upper limit of D(sub z) less than or equal to 0.2 x 10(exp 28) sq cm/s for NGC 891. The value for NGC 4631 is D(sub z = 1.4 x 10 (exp 28) sq cm/s. The other three galaxies in our sample, NGC 3044, NGC 4666, and NGC 5775 show (at the sensitivity of our data) less extended, more filamentary radio halos. Isolates spurs or filaments of nonthermal radio continuum emission in their halos are traced only above the most actively star-forming regions in the disks. This, in conjuction with the results obtained for

  13. The NuSTAR Extragalactic Surveys: The Number Counts of Active Galactic Nuclei and the Resolved Fraction of the Cosmic X-Ray Background

    NASA Astrophysics Data System (ADS)

    Harrison, F. A.; Aird, J.; Civano, F.; Lansbury, G.; Mullaney, J. R.; Ballantyne, D. R.; Alexander, D. M.; Stern, D.; Ajello, M.; Barret, D.; Bauer, F. E.; Baloković, M.; Brandt, W. N.; Brightman, M.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Del Moro, A.; Forster, K.; Gandhi, P.; Giommi, P.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R. C.; Hornstrup, A.; Kitaguchi, T.; Koglin, J.; Luo, B.; Madsen, K. K.; Mao, P. H.; Miyasaka, H.; Mori, K.; Perri, M.; Pivovaroff, M.; Puccetti, S.; Rana, V.; Treister, E.; Walton, D.; Westergaard, N. J.; Wik, D.; Zappacosta, L.; Zhang, W. W.; Zoglauer, A.

    2016-11-01

    We present the 3-8 keV and 8-24 keV number counts of active galactic nuclei (AGNs) identified in the Nuclear Spectroscopic Telescope Array (NuSTAR) extragalactic surveys. NuSTAR has now resolved 33%-39% of the X-ray background in the 8-24 keV band, directly identifying AGNs with obscuring columns up to ˜ {10}25 {{cm}}-2. In the softer 3-8 keV band the number counts are in general agreement with those measured by XMM-Newton and Chandra over the flux range 5× {10}-15 ≲ S(3-8 keV)/{erg} {{{s}}}-1 {{cm}}-2 ≲ {10}-12 probed by NuSTAR. In the hard 8-24 keV band NuSTAR probes fluxes over the range 2× {10}-14 ≲ S(8-24 keV)/{erg} {{{s}}}-1 {{cm}}-2 ≲ {10}-12, a factor ˜100 fainter than previous measurements. The 8-24 keV number counts match predictions from AGN population synthesis models, directly confirming the existence of a population of obscured and/or hard X-ray sources inferred from the shape of the integrated cosmic X-ray background. The measured NuSTAR counts lie significantly above simple extrapolation with a Euclidian slope to low flux of the Swift/BAT 15-55 keV number counts measured at higher fluxes (S(15-55 keV) ≳ 10-11 {erg} {{{s}}}-1 {{cm}}-2), reflecting the evolution of the AGN population between the Swift/BAT local (z\\lt 0.1) sample and NuSTAR’s z˜ 1 sample. CXB synthesis models, which account for AGN evolution, lie above the Swift/BAT measurements, suggesting that they do not fully capture the evolution of obscured AGNs at low redshifts.

  14. Early science with the large millimeter telescope: exploring the effect of AGN activity on the relationships between molecular gas, dust, and star formation

    SciTech Connect

    Kirkpatrick, Allison; Pope, Alexandra; Calzetti, Daniela; Narayanan, Gopal; Schloerb, F. Peter; Yun, Min S.; Aretxaga, Itziar; Montaña, Alfredo; Vega, Olga; Armus, Lee; Helou, George; Shi, Yong

    2014-12-01

    The molecular gas, H{sub 2}, that fuels star formation in galaxies is difficult to observe directly. As such, the ratio of L {sub IR} to L{sub CO}{sup ′} is an observational estimate of the star formation rate compared with the amount of molecular gas available to form stars, which is related to the star formation efficiency and the inverse of the gas consumption timescale. We test what effect an IR luminous active galactic nucleus (AGN) has on the ratio L{sub IR}/L{sub CO}{sup ′} in a sample of 24 intermediate redshift galaxies from the 5 mJy Unbiased Spitzer Extragalactic Survey (5MUSES). We obtain new CO(1-0) observations with the Redshift Search Receiver on the Large Millimeter Telescope. We diagnose the presence and strength of an AGN using Spitzer IRS spectroscopy. We find that removing the AGN contribution to L{sub IR}{sup tot} results in a mean L{sub IR}{sup SF}/L{sub CO}{sup ′} for our entire sample consistent with the mean L{sub IR}/L{sub CO}{sup ′} derived for a large sample of star forming galaxies from z ∼ 0-3. We also include in our comparison the relative amount of polycyclic aromatic hydrocarbon emission for our sample and a literature sample of local and high-redshift ultra luminous infrared galaxies and find a consistent trend between L{sub 6.2}/L{sub IR}{sup SF} and L{sub IR}{sup SF}/L{sub CO}{sup ′}, such that small dust grain emission decreases with increasing L{sub IR}{sup SF}/L{sub CO}{sup ′} for both local and high-redshift dusty galaxies.

  15. Study on the faint star extraction technology with MEMS gyro aided APS star tracker

    NASA Astrophysics Data System (ADS)

    Xing, Fei; Zhao, Borui; Sun, Ting; Xu, Wei; You, Zheng

    2013-08-01

    Star tracker is the most accurate attitude sensor for satellite. Generally speaking, the higher the accuracy, the fainter the star can be sensed by the star tracker. How to extract the faint star from a star image is becoming a critical technology in dynamic condition for star tracker, especially using the APS (Active Pixels Sensor) detector. A novel APS star tracker with MEMS Gyroscope aided system was proposed in this paper that could extremely improve the detection effect and capability for the faint stars. During the exposure time of star tracker, the trajectory of star projection on the detector maybe occupy more than ten pixels due to the satellite rotation. In this situation, the signal-to-noise ratio will decline sharply, and the traditional star extraction method for faint star will take no effect. As a result, the accuracy of star tracker would decline sharply, even more, couldn't work. Using the MEMS Gyroscope, the track of star projection can be predicated and measured, on the basis of which the deconvolution algorithm could be taken to recover the faint star signal. The accuracy of the star projection centroid could be improved obviously, and the dynamic performance of the star tracker would be improved by a magnitude. Meanwhile, the MEMS gyroscope has not less volume, mass and power consumption, which make it more suitable for the application of APS star tracker.

  16. Modelling the magnetic activity and filtering radial velocity curves of young Suns : the weak-line T Tauri star LkCa 4

    NASA Astrophysics Data System (ADS)

    Donati, J.-F.; Hébrard, E.; Hussain, G.; Moutou, C.; Grankin, K.; Boisse, I.; Morin, J.; Gregory, S. G.; Vidotto, A. A.; Bouvier, J.; Alencar, S. H. P.; Delfosse, X.; Doyon, R.; Takami, M.; Jardine, M. M.; Fares, R.; Cameron, A. C.; Ménard, F.; Dougados, C.; Herczeg, G.; Matysse Collaboration

    2014-11-01

    We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star LkCa 4 within the Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets (MaTYSSE) programme, involving ESPaDOnS at the Canada-France-Hawaii Telescope. Despite an age of only 2 Myr and a similarity with prototypical classical T Tauri stars, LkCa 4 shows no evidence for accretion and probes an interesting transition stage for star and planet formation. Large profile distortions and Zeeman signatures are detected in the unpolarized and circularly polarized lines of LkCa 4 using Least-Squares Deconvolution (LSD), indicating the presence of brightness inhomogeneities and magnetic fields at the surface of LkCa 4. Using tomographic imaging, we reconstruct brightness and magnetic maps of LkCa 4 from sets of unpolarized and circularly polarized LSD profiles. The large-scale field is strong and mainly axisymmetric, featuring a ≃2 kG poloidal component and a ≃1 kG toroidal component encircling the star at equatorial latitudes - the latter making LkCa 4 markedly different from classical T Tauri stars of similar mass and age. The brightness map includes a dark spot overlapping the magnetic pole and a bright region at mid-latitudes - providing a good match to the contemporaneous photometry. We also find that differential rotation at the surface of LkCa 4 is small, typically ≃5.5 times weaker than that of the Sun, and compatible with solid-body rotation. Using our tomographic modelling, we are able to filter out the activity jitter in the radial velocity curve of LkCa 4 (of full amplitude 4.3 km s-1) down to an rms precision of 0.055 km s-1. Looking for hot Jupiters around young Sun-like stars thus appears feasible, even though we find no evidence for such planets around LkCa 4.

  17. MOIRCS DEEP SURVEY. VIII. EVOLUTION OF STAR FORMATION ACTIVITY AS A FUNCTION OF STELLAR MASS IN GALAXIES SINCE z {approx} 3

    SciTech Connect

    Kajisawa, M.; Ichikawa, T.; Yamada, T.; Akiyama, M.; Uchimoto, Y. K.; Yoshikawa, T.; Onodera, M.

    2010-11-01

    We study the evolution of star formation activity of galaxies at 0.5 < z < 3.5 as a function of stellar mass, using very deep NIR data taken with the Multi-Object Infrared Camera and Spectrograph on the Subaru telescope in the GOODS-North region. The NIR imaging data reach K{approx} 23-24 Vega magnitude and they allow us to construct a nearly stellar-mass-limited sample down to {approx}10{sup 9.5-10} M{sub sun} even at z {approx} 3. We estimated star formation rates (SFRs) of the sample with two indicators, namely, the Spitzer/MIPS 24 {mu}m flux and the rest-frame 2800 A luminosity. The SFR distribution at a fixed M{sub star} shifts to higher values with increasing redshift at 0.5 < z < 3.5. More massive galaxies show stronger evolution of SFR at z {approx}> 1. We found galaxies at 2.5 < z < 3.5 show a bimodality in their SSFR distribution, which can be divided into two populations by a constant SSFR of {approx}2 Gyr{sup -1}. Galaxies in the low-SSFR group have SSFRs of {approx}0.5-1.0 Gyr{sup -1}, while the high-SSFR population shows {approx}10 Gyr{sup -1}. The cosmic SFR density (SFRD) is dominated by galaxies with M{sub star} = 10{sup 10-11} M{sub sun} at 0.5 < z < 3.5, while the contribution of massive galaxies with M{sub star} = 10{sup 11-11.5} M{sub sun} shows a strong evolution at z>1 and becomes significant at z {approx} 3, especially in the case with the SFR based on MIPS 24 {mu}m. In galaxies with M{sub star} = 10{sup 10-11.5} M{sub sun}, those with a relatively narrow range of SSFR ({approx}<1 dex) dominates the cosmic SFRD at 0.5 < z < 3.5. The SSFR of galaxies that dominate the SFRD systematically increases with redshift. At 2.5 < z < 3.5, the high-SSFR population, which is relatively small in number, dominates the SFRD. Major star formation in the universe at higher redshift seems to be associated with a more rapid growth of stellar mass of galaxies.

  18. The MIXR sample: AGN activity versus star formation across the cross-correlation of WISE, 3XMM, and FIRST/NVSS

    NASA Astrophysics Data System (ADS)

    Mingo, B.; Watson, M. G.; Rosen, S. R.; Hardcastle, M. J.; Ruiz, A.; Blain, A.; Carrera, F. J.; Mateos, S.; Pineau, F.-X.; Stewart, G. C.

    2016-11-01

    We cross-correlate the largest available mid-infrared (Wide-field Infrared Survey Explorer - WISE), X-ray (3XMM) and radio (Faint Images of the Radio Sky at Twenty centimetres+NRAO VLA Sky Survey) catalogues to define the MIXR sample of AGN and star-forming galaxies. We pre-classify the sources based on their positions on the WISE colour/colour plot, showing that the MIXR triple selection is extremely effective to diagnose the star formation and AGN activity of individual populations, even on a flux/magnitude basis, extending the diagnostics to objects with luminosities and redshifts from SDSS DR12. We recover the radio/mid-IR star formation correlation with great accuracy, and use it to classify our sources, based on their activity, as radio-loud and radio-quiet active galactic nuclei (AGN), low excitation radio galaxies/low ionization nuclear emission line regions, and non-AGN galaxies. These diagnostics can prove extremely useful for large AGN and galaxy samples, and help develop ways to efficiently triage sources when data from the next generation of instruments becomes available. We study bias in detail, and show that while the widely used WISE colour selections for AGN are very successful at cleanly selecting samples of luminous AGN, they miss or misclassify a substantial fraction of AGN at lower luminosities and/or higher redshifts. MIXR also allows us to test the relation between radiative and kinetic (jet) power in radio-loud AGN, for which a tight correlation is expected due to a mutual dependence on accretion. Our results highlight that long-term AGN variability, jet regulation, and other factors affecting the Q/Lbol relation, are introducing a vast amount of scatter in this relation, with dramatic potential consequences on our current understanding of AGN feedback and its effect on star formation.

  19. The ultraviolet and visible light variability of BP Tauri - Possible clues for the origin of T Tauri star activity

    NASA Technical Reports Server (NTRS)

    Simon, Theodore; Vrba, Frederick J.; Herbst, William

    1990-01-01

    BP Tau is a moderate-strength T Tauri star, which has previously been studied photometrically by Vrba et al. (1986, 1989) and shown to have a 7.6-day light cycle. Here, BP Tau was reobserved in order to monitor this star with the IUE satellite. In conjunction with the UV spectroscopy, nearly simultaneous ground-based optical photometry was also obtained. At optical wavelengths, the star was initially found to be varying with a period of 7.6 days. This variability suddenly vanished and was followed by a quiescent state that lasted about 11 days. The star then resumed its variability with a period of about 6.1 days. The UV continuum and most of the UV emission lines appeared to vary in phase with the optical flux. No variations were observed on the very short timescales ranging from several hours to half a day, expected on the basis of axisymmetric, quasi-steady-state accretion disk models of T Tauri stars. However, the nearly week-long variations that were observed may be consistent with a magnetically buffered accretion model, which has been proposed by Uchida and Shibata.

  20. A GALAXY BLAZES WITH STAR FORMATION

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Most galaxies form new stars at a fairly slow rate, but members of a rare class known as 'starburst' galaxies blaze with extremely active star formation. Scientists using NASA's Hubble Space Telescope are perfecting a technique to determine the history of starburst activity in galaxies by using the colors of star clusters. Measuring the clusters' colors yields information about stellar temperatures. Since young stars are blue, and older stars redder, the colors can be related to the ages, somewhat similar to counting the rings in a fallen tree trunk in order to determine the tree's age. The galaxy NGC 3310 is forming clusters of new stars at a prodigious rate. Astronomer Gerhardt Meurer of The Johns Hopkins University leads a team of collaborators who are studying several starburst galaxies, including NGC 3310, which is showcased in this month's Hubble Heritage image. There are several hundred star clusters in NGC 3310, visible in the Heritage image as the bright blue diffuse objects that trace the galaxy's spiral arms. Each of these star clusters represents the formation of up to about a million stars, a process that takes less than 100,000 years. In addition, hundreds of individual young, luminous stars can be seen throughout the galaxy. Once formed, the star clusters become redder with age as the most massive and bluest stars exhaust their fuel and burn out. Measurements in this image of the wide range of cluster colors show that they have ages ranging from about one million up to more than one hundred million years. This suggests that the starburst 'turned on' over 100 million years ago. It may have been triggered when a companion galaxy collided with NGC 3310. These observations may change astronomers' view of starbursts. Starbursts were once thought to be brief episodes, resulting from catastrophic events like a galactic collision. However, the wide range of cluster ages in NGC 3310 suggests that the starbursting can continue for an extended interval, once

  1. Cardiac glycoside ouabain induces activation of ATF-1 and StAR expression by interacting with the α4 isoform of the sodium pump in Sertoli cells.

    PubMed

    Dietze, Raimund; Konrad, Lutz; Shihan, Mazen; Kirch, Ulrike; Scheiner-Bobis, Georgios

    2013-03-01

    Sertoli cells express α1 and α4 isoforms of the catalytic subunit of Na(+),K(+)-ATPase (sodium pump). Our recent findings demonstrated that interactions of the α4 isoform with cardiotonic steroids (CTS) like ouabain induce signaling cascades that resemble the so-called non-classical testosterone pathway characterized by activation of the c-Src/c-Raf/Erk1/2/CREB signaling cascade. Here we investigate a possible physiological significance of the activated cascade. The results obtained in the current investigation show that the ouabain-induced signaling cascade also leads to the activation of the CREB-related activating transcription factor 1 (ATF-1) in the Sertoli cell line 93RS2 in a concentration- and time-dependent manner, as demonstrated by detection of ATF-1 phosphorylated on Ser63 in western blots. The ouabain-activated ATF-1 protein was found to localize to the cell nuclei. The sodium pump α4 isoform mediates this activation, as it is ablated when cells are incubated with siRNA to the α4 isoform. Ouabain also leads to increased expression of steroidogenic acute regulator (StAR) protein, which has been shown to be a downstream consequence of CREB/ATF-1 activation. Taking into consideration that CTS are most likely produced endogenously, the demonstrated induction of StAR expression by ouabain establishes a link between CTS, the α4 isoform of the sodium pump, and steroidogenesis crucial for male fertility and reproduction.

  2. Stellar Activity at the End of the Main Sequence: GHRS Observations of the M8 Ve Star VB 10

    NASA Technical Reports Server (NTRS)

    Linsky, Jeffrey L.; Wood, Brian E.; Brown, Alexander; Giampapa, Mark S.; Ambruster, Carol

    1995-01-01

    We present Goddard High Resolution Spectrograph observations of the M8 Ve star VB 10 (equal to G1 752B), located very near the end of the stellar main sequence, and its dM3.5 binary companion G1 752A. These coeval stars provide a test bed for studying whether the outer atmospheres of stars respond to changes in internal structure as stars become fully convective near mass 0.3 solar mass (about spectral type M5), where the nature of the stellar magnetic dynamo presumably changes, and near the transition from red to brown dwarfs near mass 0.08 solar mass (about spectral type M9), when hydrogen burning ceases at the end of the main sequence. We obtain upper limits for the quiescent emission of VB 10 but observe a transition region spectrum during a large flare, which indicates that some type of magnetic dynamo must be present. Two indirect lines of evidence-scaling from the observed X-ray emission and scaling from a time-resolved flare on AD Leo suggest that the fraction of the stellar bolometric luminosity that heats the transition region of VB 10 outside of obvious flares is comparable to, or larger than, that for G1 752A. This suggests an increase in the magnetic heating rates, as measured by L(sub line)/L(sub bol) ratios, across the radiative/convective core boundary and as stars approach the red/brown dwarf boundary. These results provide new constraints for dynamo models and models of coronal and transition-region heating in late-type stars.

  3. Can Children Really Create Knowledge?

    ERIC Educational Resources Information Center

    Bereiter, Carl; Scardamalia, Marlene

    2010-01-01

    Can children genuinely create new knowledge, as opposed to merely carrying out activities that resemble those of mature scientists and innovators? The answer is yes, provided the comparison is not to works of genius but to standards that prevail in ordinary research communities. One important product of knowledge creation is concepts and tools…

  4. Star Formation in Self-gravitating Disks in Active Galactic Nuclei. II. Episodic Formation of Broad-line Regions

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Min; Du, Pu; Baldwin, Jack A.; Ge, Jun-Qiang; Hu, Chen; Ferland, Gary J.

    2012-02-01

    This is the second in a series of papers discussing the process and effects of star formation in the self-gravitating disk around the supermassive black holes in active galactic nuclei (AGNs). We have previously suggested that warm skins are formed above the star-forming (SF) disk through the diffusion of warm gas driven by supernova explosions. Here we study the evolution of the warm skins when they are exposed to the powerful radiation from the inner part of the accretion disk. The skins initially are heated to the Compton temperature, forming a Compton atmosphere (CAS) whose subsequent evolution is divided into four phases. Phase I is the duration of pure accumulation supplied by the SF disk. During phase II clouds begin to form due to line cooling and sink to the SF disk. Phase III is a period of preventing clouds from sinking to the SF disk through dynamic interaction between clouds and the CAS because of the CAS overdensity driven by continuous injection of warm gas from the SF disk. Finally, phase IV is an inevitable collapse of the entire CAS through line cooling. This CAS evolution drives the episodic appearance of broad-line regions (BLRs). We follow the formation of cold clouds through the thermal instability of the CAS during phases II and III, using linear analysis. Since the clouds are produced inside the CAS, the initial spatial distribution of newly formed clouds and angular momentum naturally follow the CAS dynamics, producing a flattened disk of clouds. The number of clouds in phases II and III can be estimated, as well as the filling factor of clouds in the BLR. Since the cooling function depends on the metallicity, the metallicity gradients that originate in the SF disk give rise to different properties of clouds in different radial regions. We find from the instability analysis that clouds have column density N H <~ 1022 cm-2 in the metal-rich regions whereas they have N H >~ 1022 cm-2 in the metal-poor regions. The metal-rich clouds compose

  5. A multiwavelength photometric census of AGN and star formation activity in the brightest cluster galaxies of X-ray selected clusters

    NASA Astrophysics Data System (ADS)

    Green, T. S.; Edge, A. C.; Stott, J. P.; Ebeling, H.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Metcalfe, N.; Kaiser, N.; Wainscoat, R. J.; Waters, C.

    2016-09-01

    Despite their reputation as being `red and dead', the unique environment inhabited by brightest cluster galaxies (BCGs) can often lead to a self-regulated feedback cycle between radiatively cooling intracluster gas and star formation and active galactic nucleus (AGN) activity in the BCG. However the prevalence of `active' BCGs, and details of the feedback involved, are still uncertain. We have performed an optical, UV and mid-IR photometric analysis of the BCGs in 981 clusters at 0.03 < z < 0.5, selected from the ROSAT All Sky Survey. Using Pan-STARRS PS1 3π, GALEX and WISE survey data we look for BCGs with photometric colours which deviate from that of the bulk population of passive BCGs - indicative of AGN and/or star formation activity within the BCG. We find that whilst the majority of BCGs are consistent with being passive, at least 14 per cent of our BCGs show a significant colour offset from passivity in at least one colour index. And, where available, supplementary spectroscopy reveals the majority of these particular BCGs show strong optical emission lines. On comparing BCG `activity' with the X-ray luminosity of the host cluster, we find that BCGs showing a colour offset are preferentially found in the more X-ray luminous clusters, indicative of the connection between BCG `activity' and the intracluster medium.

  6. Creating alternatives in science.

    PubMed

    Gravagna, Nicole G

    2009-04-01

    Traditional scientist training at the PhD level does not prepare students to be competitive in biotechnology or other non-academic science careers. Some universities have developed biotechnology-relevant doctoral programmes, but most have not. Forming a life science career club makes a statement to university administrators that it is time to rework the curriculum to include biotechnology-relevant training. A career club can supplement traditional PhD training by introducing students to available career choices, help them develop a personal network and teach the business skills that they will need to be competitive in science outside of academia. This paper is an instructional guide designed to help students create a science career club at their own university. These suggestions are based on the experience gained in establishing such a club for the Graduate School at the University of Colorado Denver. We describe the activities that can be offered, the job descriptions for the offices required and potential challenges. With determination, a creative spirit, and the guidance of this paper, students should be able to greatly increase awareness of science career options, and begin building the skills necessary to become competitive in non-academic science.

  7. Creating Heliophysics Concept Maps

    NASA Astrophysics Data System (ADS)

    Ali, N. A.; Peticolas, L. M.; Paglierani, R.; Mendez, B. J.

    2011-12-01

    The Center for Science Education at University of California Berkeley's Space Sciences Laboratory is creating concept maps for Heliophysics and would like to get input from scientists. The purpose of this effort is to identify key concepts related to Heliophysics and map their progression to show how students' understanding of Heliophysics might develop from Kindergarten through higher education. These maps are meant to tie into the AAAS Project 2061 Benchmarks for Scientific Literacy and National Science Education Standards. It is hoped that the results of this effort will be useful for curriculum designers developing Heliophysics-related curriculum materials and classroom teachers using Heliophysics materials. The need for concept maps was identified as a result of product analysis undertaken by the NASA Heliophysics Forum Team. The NASA Science Education and Public Outreach Forums have as two of their goals to improve the characterization of the contents of the Science Mission Directorate and Public Outreach (SMD E/PO) portfolio (Objective 2.1) and assist SMD in addressing gaps in the portfolio of SMD E/PO products and project activities (Objective 2.2). An important part of this effort is receiving feedback from solar scientists regarding the inclusion of key concepts and their progression in the maps. This session will introduce the draft concept maps and elicit feedback from scientists.

  8. America's Star Libraries: Top-Rated Libraries

    ERIC Educational Resources Information Center

    Lance, Keith Curry; Lyons, Ray

    2009-01-01

    "Library Journal"'s national rating of public libraries, the "LJ" Index of Public Library Service 2009, Round 2, identifies 258 "star" libraries. Created by Keith Curry Lance and Ray Lyons and based on 2007 data from the IMLS, it rates 7,268 public libraries. The top libraries in each group get five, four, or three stars. All included libraries,…

  9. A brightness-referenced star identification algorithm for APS star trackers.

    PubMed

    Zhang, Peng; Zhao, Qile; Liu, Jingnan; Liu, Ning

    2014-10-08

    Star trackers are currently the most accurate spacecraft attitude sensors. As a result, they are widely used in remote sensing satellites. Since traditional charge-coupled device (CCD)-based star trackers have a limited sensitivity range and dynamic range, the matching process for a star tracker is typically not very sensitive to star brightness. For active pixel sensor (APS) star trackers, the intensity of an imaged star is valuable information that can be used in star identification process. In this paper an improved brightness referenced star identification algorithm is presented. This algorithm utilizes the k-vector search theory and adds imaged stars' intensities to narrow the search scope and therefore increase the efficiency of the matching process. Based on different imaging conditions (slew, bright bodies, etc.) the developed matching algorithm operates in one of two identification modes: a three-star mode, and a four-star mode. If the reference bright stars (the stars brighter than three magnitude) show up, the algorithm runs the three-star mode and efficiency is further improved. The proposed method was compared with other two distinctive methods the pyramid a