Sample records for allstars star lick

  1. Performance of laser guide star adaptive optics at Lick Observatory

    SciTech Connect

    Olivier, S.S.; An, J.; Avicola, K. [and others

    1995-07-19

    A sodium-layer laser guide star adaptive optics system has been developed at Lawrence Livermore National Laboratory (LLNL) for use on the 3-meter Shane telescope at Lick Observatory. The system is based on a 127-actuator continuous-surface deformable mirror, a Hartmann wavefront sensor equipped with a fast-framing low-noise CCD camera, and a pulsed solid-state-pumped dye laser tuned to the atomic sodium resonance line at 589 nm. The adaptive optics system has been tested on the Shane telescope using natural reference stars yielding up to a factor of 12 increase in image peak intensity and a factor of 6.5 reduction in image full width at half maximum (FWHM). The results are consistent with theoretical expectations. The laser guide star system has been installed and operated on the Shane telescope yielding a beam with 22 W average power at 589 nm. Based on experimental data, this laser should generate an 8th magnitude guide star at this site, and the integrated laser guide star adaptive optics system should produce images with Strehl ratios of 0.4 at 2.2 {mu}m in median seeing and 0.7 at 2.2 {mu}m in good seeing.

  2. Observations of quasar hosts with the Lick Observatory Sodium Laser Guide Star Adaptive Optics system

    Microsoft Academic Search

    E. L. Gates; M. Lacy; S. E. Ridgway; W. H. de Vries

    2004-01-01

    We report on early results of a campaign to study the hosts of quasars from the Sloan Digital Sky Survey using the sodium laser guide star (LGS) adaptive optics (AO) system at Lick Observatory. Two quasars at z<1 were observed in H band using a sodium laser beacon to perform the AO corrections and a faint natural guide star for

  3. Initial results from the Lick Observatory Laser Guide Star Adaptive Optics System

    SciTech Connect

    Olivier, S.S.; An, J.; Avicola, K. [and others

    1995-11-08

    A prototype adaptive optics system has been installed and tested on the 3 m Shane telescope at Lick Observatory. The adaptive optics system performance, using bright natural guide stars, is consistent with expectations based on theory. A sodium-layer laser guide star system has also been installed and tested on the Shane telescope. Operating at 15 W, the laser system produces a 9th magnitude guide star with seeing-limited size at 589 nm. Using the laser guide star, the adaptive optics system has reduced the wavefront phase variance on scales above 50 cm by a factor of 4. These results represent the first continuous wavefront phase correction using a sodium-layer laser guide star. Assuming tip-tilt is removed using a natural guide star, the measured control loop performance should produce images with a Strehl ratio of 0.4 at 2.2 {mu}m in 1 arc second seeing. Additional calibration procedures must be implemented in order to achieve these results with the prototype Lick adaptive optics system.

  4. Magnetic Activity–related Radial Velocity Variations in Cool Stars: First Results from the Lick Extrasolar Planet Survey

    Microsoft Academic Search

    Steven H. Saar; R. Paul Butler; Geoffrey W. Marcy

    1998-01-01

    The discovery of the radial velocity ( ) signatures of planets around several solar-like stars highlights the v rimportance of exploring the sources of variations intrinsic to the stars themselves. We study the stars in the v rLick planetary survey for variations related to stellar activity: the rotation of starspots and convective inhomv rogeneities and their temporal evolution. We study

  5. First significant image improvement from a sodium-layer laser guide star adaptive optics system at Lick Observatory

    SciTech Connect

    Olivier, S.S.; Max, C.E.; Friedman, H.W.; An, J.; Avicola, K.; Beeman, B.V.; Bissinger, H.D.; Brase, J.M.; Erbert, G.V.; Gavel, D.T.; Kanz, K.; Macintosh, B.; Neeb, K.P.; Waltjen, K.E.

    1997-07-14

    Atmospheric turbulence severely limits the resolution of ground-based telescopes. Adaptive optics can correct for the aberrations caused by the atmosphere, but requires a bright wavefront reference source in close angular proximity to the object being imaged. Since natural reference stars of the necessary brightness are relatively rare, methods of generating artificial reference beacons have been under active investigation for more than a decade. In this paper, we report the first significant image improvement achieved using a sodium-layer laser guide star as a wavefront reference for a high- order adaptive optics system. An artificial beacon was created by resonant scattering from atomic sodium in the mesosphere, at an altitude of 95 km. Using this laser guide star, an adaptive optics system on the 3 m Shane Telescope at Lick Observatory produced a factor of 2.4 increase in peak intensity and a factor of 2 decrease in full width at half maximum of a stellar image, compared with image motion compensation alone. The Strehl ratio when using the laser guide star as the reference was 65% of that obtained with a natural guide star, and the image full widths at half maximum were identical, 0.3 arc sec, using either the laser or the natural guide star. This sodium-layer laser guide star technique holds great promise for the world`s largest telescopes. 24 refs., 4 figs., 1 tab.

  6. VizieR Online Data Catalog: Lick indicies for FGK stars (Franchini+, 2014)

    NASA Astrophysics Data System (ADS)

    Franchini, M.; Morossi, C.; Marcantonio, P. D.; Malagnini, M. L.; Chavez, M.

    2015-02-01

    The stars observed by FEROS and studied by the AMBRE project (Worley et al., 2012A&A...542A..48W) constitute an ideal working data set for our purposes since they include a large number of non-supergiant FGK stars with individual estimates of Teff, log g, [M/H], and ?-to-iron ratio ([alpha/Fe]). We searched the European Southern Observatory (ESO) Science Archive Facility and retrieved, through the FEROS/HARPS pipeline processed data Query Form, all the public available spectra of FGK stars with AMBRE atmospheric parameter values in the following ranges: 38003.5, and global metallicity [M/H]>-3.0. A list of 1085 stars, corresponding to 2511 available spectra, was obtained. Since AMBRE provides individual estimates of stellar parameters derived from each spectrum, we computed for 202 stars with more than one observed spectrum average atmospheric parameter values. In any case, the dispersion of values for the same object resulted to be less than the external errors associated with AMBRE results. (1 data file).

  7. VizieR Online Data Catalog: Lick indices for 51 stars (Sansom+, 2013)

    NASA Astrophysics Data System (ADS)

    Sansom, A. E.; de Castro Milone, A.; Vazdekis, A.; Sanchez-Blazquez, P.

    2014-09-01

    A method that is widely used to analyse stellar populations in galaxies is to apply the theoretically derived responses of stellar spectra and line indices to element abundance variations, which are hereafter referred to as response functions. These are applied in a differential way, to base models, in order to generate spectra or indices with different abundance patterns. In this paper, sets of such response functions for three different stellar evolutionary stages are tested with new empirical [Mg/Fe] abundance data for the medium-resolution Isaac Newton Telescope library of empirical spectra (MILES). Recent theoretical models and observations are used to investigate the effects of [Fe/H], [Mg/H] and overall [Z/H] on spectra, via ratios of spectra for similar stars. The global effects of changes in abundance patterns are investigated empirically through direct comparisons of similar stars from MILES, highlighting the impact of abundance effects in the blue part of the spectrum, particularly for lower temperature stars. It is found that the relative behaviour of iron-sensitive line indices are generally well predicted by response functions, whereas Balmer line indices are not. Other indices tend to show large scatter about the predicted mean relations. Implications for element abundance and age studies in stellar populations are discussed and ways forward are suggested to improve the match with the behaviour of spectra and line-strength indices observed in real stars. (1 data file).

  8. Old stellar populations. 5: Absorption feature indices for the complete LICK/IDS sample of stars

    NASA Technical Reports Server (NTRS)

    Worthey, Guy; Faber, S. M.; Gonzalez, J. Jesus; Burstein, D.

    1994-01-01

    Twenty-one optical absorption features, 11 of which have been previously defined, are automatically measured in a sample of 460 stars. Following Gorgas et al., the indices are summarized in fitting functions that give index strengths as functions of stellar temperature, gravity, and (Fe/H). This project was carried out with the purpose of predicting index strengths in the integrated light of stellar populations of different ages and metallicities, but the data should be valuable for stellar studies in the Galaxy as well. Several of the new indices appear to be promising indicators of metallicity for old stellar populations. A complete list of index data and atmospheric parameters is available in computer-readable form.

  9. NASA Allstar Project Aeronautics Learning Laboratory for Science,Technology, and Research (Allstar)

    NASA Technical Reports Server (NTRS)

    Levy, Cesar; Ebadian M. A.

    1998-01-01

    We finished the material development of Level 1, Level 2 and most of Level 3. We created three new galleries, one of streaming videos enabling the user to select his/her appropriate speed of Internet connectivity for better performance. The second gallery on NASA's X-series aircraft and the third is on F-series aircraft. We also completed the placement and activation of all thirteen kiosks. We added one more kiosk over the number suggested in the proposal at Baker Aviation High School - a Dade County Public School for special aviation programs. We felt that the goals of this school matched ALLSTAR's goals and that the placement of the kiosk would better help the local students become interested in the Aviation and Aeronautics field. We continue to work on the development of our "Teacher Resource Guide to ALLSTAR material" in which we tied our material into the national and Florida State standards. We finished the Florida Sunshine State standards, getting positive feedback from local and other educators who use the material on a regular basis. We had another successful workshop on October 29', 1997. We introduced the ALLSTAR website and kiosk to about twenty science and history teachers from Dade County Public Schools (DCPS). Most teachers were from middle schools, although we had some from elementary schools also. We provided several demonstrations of the ALLSTAR material to local schools in the Dade County Public Schools (DCPS) system. We used the ALLSTAR material with FIU's summer immersion program for FLAME students. This program includes a high number of minority students interested in science and engineering. We also presented the material at National Science Teachers Association (NSTA) and National Congress on Aviation and Space Education (NCASE) conferences and will be presenting the material at the Southeast Florida Aviation Consortium (SEFAC). We provided two on-site workshops in the NSTA conference with total attended of about 70 teachers. The BBS was converted to an on-line discussion forum with a unique section on Blacks in Aviation. Prime Technologies coordinated with NASA LARC and the Teacher Resource Centers (TRCs) for scale-up of ALLSTAR and performed live demonstrations of the software in schools and at conventions.

  10. Lick Northern Proper Motion Program: NPM1 Catalog

    Microsoft Academic Search

    R. B. Hanson; A. R. Klemola; B. F. Jones

    1994-01-01

    The Lick Northern Proper Motion (NPM) program measures absolute proper motions, positions, and photographic photometry for ~ 300,000 stars with 8 <= B <= 18 in 1,246 6deg times 6deg fields covering the sky north of declination -23deg . Each NPM field was photographed with the Lick 51 cm Carnegie double astrograph at two epochs between 1947 and 1988. The

  11. Aeronautics Learning Laboratory for Science, Technology, and Research (ALLSTAR)

    NASA Technical Reports Server (NTRS)

    Levy, Cesar; Ebadian, M. A.

    1998-01-01

    We finished the material development of Level 1, Level 2 and most of Level 3. We created three new galleries, one of streaming videos enabling the user to select his/her appropriate speed of Internet connectivity for better performance. The second gallery on NASA's X-series aircraft and the third is on F-series aircraft. We also completed the placement and activation of all thirteen kiosks. We added one more kiosk over the number suggested in the proposal at Baker Aviation High School - a Dade County Public School for special aviation programs. We felt that the goals of this school matched ALLSTAR's goals and that the placement of the kiosk would better help the local students become interested in the Aviation and Aeronautics field. We continue to work on the development of our "Teacher Resource Guide to ALLSTAR material" in which we tied our material into the national and Florida State standards. We finished the Florida Sunshine State standards, getting positive feedback from local and other educators who use the material on a regular basis. We had another successful workshop on October 29 th, 1997. We introduced the ALLSTAR website and kiosk to about twenty science and history teachers from Dade County Public Schools (DCPS). Most teachers were from middle schools, although we had some from elementary schools also. We provided several demonstrations of the ALLSTAR material to local schools in the Dade County Public Schools (DCPS) system. We used the ALLSTAR material with FIU's summer immersion program for FLAME students. This program includes a high number of minority students interested in science and engineering. We also presented the material at National Science Teachers Association (NSTA) and National Congress on Aviation and Space Education (NCASE) conferences and will be presenting the material at the Southeast Florida Aviation Consortium (SEFAC). We provided two on-site workshops in the NSTA conference with total attended of about 70 teachers. The BBS was converted to an on-line discussion forum with a unique section on Blacks in Aviation, Prime Technologies coordinated with NASA LaRC and the Teacher Resource Centers (TRCs) for scale-up of ALLSTAR and performed live demonstrations of the software in schools and at conventions.

  12. Beware of dogs licking ears.

    PubMed

    Godey, B; Morandi, X; Bourdinière, J; Heurtin, C

    1999-10-01

    A patient with right-sided chronic purulent otorrhoea developed meningitis due to Pasteurella multocida transmitted by a dog that frequently licked his ear. We suggest that patients with a perforated tympanic membrane should avoid being licked on their ears by animals. PMID:10520644

  13. Lick Galaxy Correlation Function Revised

    E-print Network

    M. Plionis; S. Borgani

    1994-01-21

    We re-estimate the angular 2-point galaxy correlation function from the Lick galaxy catalogue. We argue that the large-scale gradients observed in the Lick catalogue are dominated by real clustering and therefore they should not be subtracted prior to the estimation of the 2-p correlation function. We find that if no such correction is introduced the galaxy correlations are perfectly consistent with the those found in the APM survey. Thus, the long standing discrepancy between the Lick and APM angular correlations is lifted.

  14. Campus Technology Innovators Awards 2011: Technology All-Stars

    ERIC Educational Resources Information Center

    Lloyd, Meg; Raths, David

    2011-01-01

    Out of a total of 393 entries for the 2011 Campus Technology Innovators award, 10 winners rose to the top in six categories: (1) Leadership, Governance, and Policy; (2) Teaching and Learning; (3) Student Systems and Services; (4) Administrative Systems; (5) IT Infrastructure and Systems; and (6) Education Futurists. These innovative IT leaders…

  15. Lick Observatory Records Digital Archive

    NSDL National Science Digital Library

    Located on the summit of Mount Hamilton in the Diablo Mountain Range, the Lick Observatory is a tremendous astronomical facility. This digital collection from the University of California-Santa Cruz offers up some of the records culled from this facility's history. Here visitors can find historical photographs that document life at the Observatory, along with images of telescopes, lenses, and some of the prominent scientists who have worked there. All told, there are 1,365 images here. First-time visitors will want to start with images of the "Great Lick Refractor," the 36-inch lens that has been part of many astronomical discoveries at the Observatory. Users can focus their search by looking around by date, subject, or geographical location.

  16. First significant image improvement from a sodium-layer laser guide star adaptive optics system at Lick Observatory [3126-29

    Microsoft Academic Search

    S. S. Olivier; C. E. Max; H. W. Friedman; J. R. An; K. Avicola; B. V. Beeman; H. D. Bissinger; J. M. Brase; G. V. Erbert; D. T. Gavel; K. Kanz; B. Macintosh; K. P. Neeb; K. E. Waltjen

    1997-01-01

    Atmospheric turbulence severely limits the resolution of ground-based telescopes. Adaptive optics can correct for the aberrations caused by the atmosphere, but requires a bright wavefront reference source in close angular proximity to the object being imaged. Since natural reference stars of the necessary brightness are relatively rare, methods of generating artificial reference beacons have been under active investigation for more

  17. Graduate Astronomy Education in the Early Days of Lick Observatory.

    ERIC Educational Resources Information Center

    Osterbrock, Donald E.

    1980-01-01

    Discusses Lick Observatory's (University of California) early graduate students and graduate program in astronomy. The history of the Lick Observatory and famous astronomy professors and astronomers associated with the Lick Observatory are also discussed. (DS)

  18. The Lick/SDSS Library. I. Synthetic Index Definition and Calibration

    NASA Astrophysics Data System (ADS)

    Franchini, M.; Morossi, C.; Di Marcantonio, P.; Malagnini, M. L.; Chavez, M.

    2010-08-01

    A new synthetic library of spectral feature indices, Lick/Sloan Digital Sky Survey (SDSS), for stellar population studies is presented. Lick/SDSS is computed from synthetic spectra with resolving power R = 1800 to fully exploit the content of the spectroscopic SDSS-DR7 stellar database. The Lick/SDSS system is based on the Lick/IDS one complemented with a UV index in the wavelength region of Ca II H and K lines. The system is well suited to study ?-element abundances in F, G, and K stars. The reliability of synthetic indices in reproducing the behaviors of observational ones with effective temperature, surface gravity, overall metallicity, and ?-element abundances is tested by using empirical stellar libraries (ELODIE, INDO-U.S., and MILES) and the SDSS-DR7 spectroscopic database. The importance of using the same temperature scale in comparing theoretical and observational indices is discussed. The full consistency between Lick/SDSS and observational indices derived from the above mentioned stellar libraries is assessed. The comparison with indices computed from SDSS-DR7 spectra evidences good consistency for "dwarf" stars and significant disagreement for "giant" stars due to systematic overestimation of the stellar T eff by the SEGUE Stellar Parameter Pipeline.

  19. The automated planet finder at Lick Observatory

    NASA Astrophysics Data System (ADS)

    Radovan, Matt V.; Lanclos, Kyle; Holden, Bradford P.; Kibrick, Robert I.; Allen, S. L.; Deich, William T. S.; Rivera, Eugenio; Burt, Jennifer; Fulton, Benjamin; Butler, Paul; Vogt, Steven S.

    2014-07-01

    By July 2014, the Automated Planet Finder (APF) at Lick Observatory on Mount Hamilton will have completed its first year of operation. This facility combines a modern 2.4m computer-controlled telescope with a flexible development environment that enables efficient use of the Levy Spectrometer for high cadence observations. The Levy provides both sub-meter per second radial velocity precision and high efficiency, with a peak total system throughput of 24%. The modern telescope combined with efficient spectrometer routinely yields over 100 observations of 40 stars in a single night, each of which has velocity errors of 0.7 to 1.4 meters per second, all with typical seeing of < 1 arc second full-width-half-maximum (FWHM). The whole observing process is automated using a common application programming interface (API) for inter-process communication which allows scripting to be done in a variety of languages (Python, Tcl, bash, csh, etc.) The flexibility and ease-of-use of the common API allowed the science teams to be directly involved in the automation of the observing process, ensuring that the facility met their requirements. Since November 2013, the APF has been routinely conducting autonomous observations without human intervention.

  20. Cerebellar cortical output encodes temporal aspects of rhythmic licking movements and is necessary for normal licking frequency

    PubMed Central

    Bryant, Jerí L.; Boughter, John D.; Gong, Suzhen; LeDoux, Mark S.; Heck, Detlef H.

    2015-01-01

    Rodents consume water by performing stereotypic, rhythmic licking movements which are believed to be controlled by brainstem pattern-generating circuits. Previous work has shown that synchronized population activity of inferior olive neurons was phase locked to the licking rhythm in rats, suggesting a cerebellar involvement in temporal aspects of licking behavior. However, what role the cerebellum has in licking behavior and whether licking is represented in the high frequency simple spike output of Purkinje cells remains unknown. We recorded Purkinje cell simple and complex spike activity in awake mice during licking and determined the behavioral consequences of loss of cerebellar function. Mouse cerebellar cortex contained a multifaceted representation of licking behavior encoded in the simple spike activities of Purkinje cells distributed across Crus I, Crus II and lobus simplex of the right cerebellar hemisphere. Lick-related Purkinje cell simple spike activity was modulated rhythmically, phase-locked to the lick rhythm, or non-rhythmically. A subpopulation of lick-related Purkinje cells differentially represented lick interval duration in their simple spike activity. Surgical removal of the cerebellum or temporary pharmacological inactivation of the cerebellar nuclei significantly slowed the licking frequency. Fluid licking was also less efficient in mice with impaired cerebellar function, indicated by a significant decline in the volume per lick fluid intake. The gross licking movement appeared unaffected. Our results suggest a cerebellar role in modulating the frequency of the central pattern generating circuits controlling fluid licking and in the fine coordination of licking, while contributing little to the coordination of the gross licking movement. PMID:20597972

  1. Lick Observatory Optical SETI: targeted search and new directions.

    PubMed

    Stone, R P S; Wright, S A; Drake, F; Muñoz, M; Treffers, R; Werthimer, D

    2005-10-01

    Lick Observatory's Optical SETI (search for extraterrestrial intelligence) program has been in regular operation for 4.5 years. We have observed 4,605 stars of spectral types F-M within 200 light-years of Earth. Occasionally, we have appended objects of special interest, such as stars with known planetary systems. We have observed 14 candidate signals ("triple coincidences"), all but one of which are explained by transient local difficulties. Additional observations of the remaining candidate have failed to confirm arriving pulse events. We now plan to proceed in a more economical manner by operating in an unattended drift scan mode. Between operational and equipment modifications, efficiency will more than double. PMID:16225433

  2. IRCAL : The infrared camera for adaptive optics at Lick Observatory

    E-print Network

    Lloyd, James P.

    IRCAL : The infrared camera for adaptive optics at Lick Observatory James P. Lloyd a , Michael C Optics at Lick (IRCAL). IRCAL is a 1­2.5 micron camera optimised for use with the LLNL Lick adaptive for obtaining high dynamic range images afforded by adaptive optics, coronagraphic masks, and a cross

  3. Patterns of mineral lick visitation by spider monkeys and howler monkeys in Amazonia: are licks perceived as risky areas?

    PubMed

    Link, Andres; Galvis, Nelson; Fleming, Erin; Di Fiore, Anthony

    2011-04-01

    Mineral licks--also known as "salados," "saladeros," or "collpas"--are specific sites in tropical and temperate ecosystems where a large diversity of mammals and birds come regularly to feed on soil. Although the reasons for vertebrate geophagy are not completely understood, animals are argued to obtain a variety of nutritional and health benefits from the ingestion of soil at mineral licks. We studied the temporal patterns of mineral lick use by white-bellied spider monkey (Ateles belzebuth) and red howler monkey (Alouatta seniculus) in a lowland rain forest in Amazonian Ecuador. Using camera and video traps at four different mineral licks, combined with behavioral follows of one group of spider monkeys, we documented rates of mineral lick visitation by both primate species and the relative frequency and intensity of mineral lick use by spider monkeys. On the basis of 1,612 days and 888 nights of mineral lick monitoring, we found that A. belzebuth and A. seniculus both visit mineral licks frequently throughout the year (on average ?14% of days for both species), and mineral lick visitation was influenced by short-term environmental conditions (e.g. sunny and dry weather). For spider monkeys, the area surrounding the lick was also the most frequently and most intensively used region within the group's home range. The fact that spider monkeys spent long periods at the lick area before coming to the ground to obtain soil, and the fact that both species visited the lick preferentially during dry sunny conditions (when predator detectability is presumed to be relatively high) and visited simultaneously more often than expected by chance, together suggest that licks are indeed perceived as risky areas by these primates. We suggest that howler and spider monkeys employ behavioral strategies aimed at minimizing the probability of predation while visiting the forest floor at risky mineral lick sites. PMID:21328597

  4. Licking Microstructure Reveals Rapid Attenuation of Neophobia

    PubMed Central

    Monk, Kevin J.; Rubin, Benjamin D.

    2014-01-01

    Many animals hesitate when initially consuming a novel food and increase their consumption of that food between the first and second sessions of access—a process termed attenuation of neophobia (AN). AN has received attention as a model of learning and memory; it has been suggested that plasticity resulting from an association of the novel tastant with “safe outcome” results in a change in the neural response to the tastant during the second session, such that consumption increases. Most studies have reported that AN emerges only an hour or more after the end of the first exposure to the tastant, consistent with what is known of learning-related plasticity. But these studies have typically measured consumption, rather than real-time behavior, and thus the possibility exists that a more rapidly developing AN remains to be discovered. Here, we tested this possibility, examining both consumption and individual lick times in a novel variant of a brief-access task (BAT). When quantified in terms of consumption, data from the BAT accorded well with the results of a classic one-bottle task—both revealed neophobia/AN specific to higher concentrations (for instance, 28mM) of saccharin. An analysis of licking microstructure, however, additionally revealed a real-time correlate of neophobia—an explicit tendency, similarly specific for 28-mM saccharin, to cut short the initial bout of licks in a single trial (compared with water). This relative hesitancy (i.e., the shortness of the first lick bout to 28-mM saccharin compared with water) that constitutes neophobia not only disappeared between sessions but also gradually declined in magnitude across session 1. These data demonstrate that the BAT accurately measures AN, and that aspects of AN—and the processes underlying familiarization—begin within minutes of the very first taste. PMID:24363269

  5. Conceptual design for a user-friendly adaptive optics system at Lick Observatory

    SciTech Connect

    Bissinger, H.D.; Olivier, S.; Max, C.

    1996-03-08

    In this paper, we present a conceptual design for a general-purpose adaptive optics system, usable with all Cassegrain facility instruments on the 3 meter Shane telescope at the University of California`s Lick Observatory located on Mt. Hamilton near San Jose, California. The overall design goal for this system is to take the sodium-layer laser guide star adaptive optics technology out of the demonstration stage and to build a user-friendly astronomical tool. The emphasis will be on ease of calibration, improved stability and operational simplicity in order to allow the system to be run routinely by observatory staff. A prototype adaptive optics system and a 20 watt sodium-layer laser guide star system have already been built at Lawrence Livermore National Laboratory for use at Lick Observatory. The design presented in this paper is for a next- generation adaptive optics system that extends the capabilities of the prototype system into the visible with more degrees of freedom. When coupled with a laser guide star system that is upgraded to a power matching the new adaptive optics system, the combined system will produce diffraction-limited images for near-IR cameras. Atmospheric correction at wavelengths of 0.6-1 mm will significantly increase the throughput of the most heavily used facility instrument at Lick, the Kast Spectrograph, and will allow it to operate with smaller slit widths and deeper limiting magnitudes. 8 refs., 2 figs.

  6. APF - The Lick Observatory Automated Planet Finder

    E-print Network

    Vogt, Steven S; Kibrick, Robert; Butler, R Paul; Alcott, Barry; Allen, Steve; Arriagada, Pamela; Bolte, Mike; Burt, Jennifer; Cabak, Jerry; Chloros, Kostas; Cowley, David; Deich, William; Dupraw, Brian; Earthman, Wayne; Epps, Harland; Faber, Sandra; Fischer, Debra; Gates, Elinor; Hilyard, David; Holden, Brad; Johnston, Ken; Keiser, Sandy; Kanto, Dick; Katsuki, Myra; Laiterman, Lee; Lanclos, Kyle; Laughlin, Greg; Lewis, Jeff; Lockwood, Chris; Lynam, Paul; Marcy, Geoffrey; McLean, Maureen; Miller, Joe; Misch, Tony; Peck, Michael; Pfister, Terry; Phillips, Andrew; Rivera, Eugenio; Sandford, Dale; Saylor, Mike; Stover, Richard; Thompson, Matthew; Walp, Bernie; Ward, James; Wareham, John; Wei, Mingzhi; Wright, Chris

    2014-01-01

    The Automated Planet Finder (APF) is a facility purpose-built for the discovery and characterization of extrasolar planets through high-cadence Doppler velocimetry of the reflex barycentric accelerations of their host stars. Located atop Mt. Hamilton, the APF facility consists of a 2.4-m telescope and its Levy spectrometer, an optical echelle spectrometer optimized for precision Doppler velocimetry. APF features a fixed format spectral range from 374 nm - 970 nm, and delivers a "Throughput" (resolution * slit width product) of 114,000 arc-seconds, with spectral resolutions up to 150,000. Overall system efficiency (fraction of photons incident on the primary mirror that are detected by the science CCD) on blaze at 560 nm in planet-hunting mode is 15%. First-light tests on the RV standard stars HD 185144 and HD 9407 demonstrate sub-meter per second precision (RMS per observation) held over a 3-month period. This paper reviews the basic features of the telescope, dome, and spectrometer, and gives a brief summary...

  7. Observations of quasar hosts with adaptive optics at Lick Observatory

    E-print Network

    Mark Lacy; Elinor L. Gates; Susan E. Ridgway; Wim de Vries; Gabriela Canalizo; James P. Lloyd; James R. Graham

    2002-09-05

    We present near-infrared H-band observations of the hosts of three z~1 quasars from the Sloan Digital Sky Survey made with the adaptive optics system at Lick Observatory. We derive a PSF for each quasar and model the host plus quasar nucleus to obtain magnitudes and approximate scale sizes for the host galaxies. We find our recovered host galaxies are similar to those found for z~1 quasars observed with the Hubble Space Telescope. They also have, with one interesting exception, black hole mass estimates from their bulge luminosities which are consistent with those from emission-line widths. We thus demonstrate that adaptive optics can be successfully used for the quantitative study of quasar host galaxies, with the caveat that better PSF calibration will be needed for studies of the hosts of significantly brighter or higher redshift quasars with the Lick system.

  8. HOMESTEAD, LAKE FORK, AND LICK CREEK ROADLESS AREAS, OREGON.

    USGS Publications Warehouse

    Evans, James G.; Conyac, Martin D.

    1984-01-01

    A mineral survey concluded that the Homestead, Lake Fork and Lick Creek Roadless Area, Oregon offer little promise for the occurrence of mineral or energy resources in the bedrock. Probable mineral-resource potential is assigned to the west and north parts of the Lake Fork Roadless Area, where gold resources may occur in glacial deposits and alluvium transported into this area from sources outside the roadless area to the west.

  9. High lick rate is maintained throughout spontaneous liquid meals in freely feeding rats.

    PubMed

    Rushing, P A; Houpt, T A; Henderson, R P; Gibbs, J

    1997-11-01

    To investigate the microstructure of spontaneous meals in freely feeding rats, 16 adult male Sprague Dawley rats were housed individually in custom-designed lickometer cages and maintained on a milk diet. Licks were recorded over 23 h at millisecond accuracy via a computer-controlled lickometer. Analysis of lick data revealed an average of about 12 discrete meals/day occurring mainly during the dark phase. The most striking feature of both dark and light meals was the maintenance of a high initial rate of licking until an abrupt decline at the end of the meal. This pattern of licking is very different from the exponential decay of lick rate reported in scheduled test meals of palatable solutions. Thus, the microstructure of licking for meals is affected in an apparently fundamental way by whether a meal is scheduled or spontaneous, suggesting a basic difference in the underlying physiologic controls. PMID:9333217

  10. FIVE PLANETS AND AN INDEPENDENT CONFIRMATION OF HD 196885Ab FROM LICK OBSERVATORY

    SciTech Connect

    Fischer, Debra; Isaacson, Howard; Giguere, Matt; McCarthy, Chris [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132 (United States); Driscoll, Peter [Department of Earth and Planetary Science, Johns Hopkins University, Baltimore, MD (United States); Marcy, Geoffrey W.; Howard, Andrew; Peek, Katherine [Department of Astronomy, University of California, Berkeley, Berkeley, CA (United States); Valenti, Jeff [Space Telescope Science Institute, Baltimore, MD (United States); Wright, Jason T. [Cornell University, Ithaca, NY (United States); Henry, Gregory W. [Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box 9501, Nashville, TN 37209 (United States); Johnson, John Asher, E-mail: fischer@stars.sfsu.ed [NSF Astronomy and Astrophysics Postdoctoral Fellow, Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)

    2009-10-01

    We present time series Doppler data from Lick Observatory that reveal the presence of long-period planetary companions orbiting nearby stars. The typical eccentricity of these massive planets are greater than the mean eccentricity of known exoplanets. HD 30562b has Msin i = 1.29 M {sub Jup}, with semimajor axis of 2.3 AU and eccentricity 0.76. The host star has a spectral type F8V and is metal rich. HD 86264b has Msin i = 7.0 M {sub Jup}, a {sub rel} = 2.86 AU, an eccentricity e = 0.7 and orbits a metal-rich, F7V star. HD 87883b has Msin i = 1.78 M {sub Jup}, a {sub rel} = 3.6 AU, e = 0.53 and orbits a metal-rich K0V star. HD 89307b has Msin i = 1.78 M {sub Jup}, a {sub rel} = 3.3 AU, e = 0.24 and orbits a G0V star with slightly subsolar metallicity. HD 148427b has Msin i = 0.96 M {sub Jup}, a {sub rel} = 0.93 AU, eccentricity of 0.16 and orbits a metal rich K0 subgiant. We also present velocities for a planet orbiting the F8V metal-rich binary star, HD 196885A. The planet has Msin i = 2.58 M {sub Jup}, a {sub rel} = 2.37 AU, and orbital eccentricity of 0.48, in agreement with the independent discovery by Correia et al.

  11. Lick Observatory charge-coupled-device data acquisition system

    NASA Technical Reports Server (NTRS)

    Robinson, L. B.; Stover, R. J.; Osborne, J.; Miller, J. S.; Vogt, S. S.

    1987-01-01

    The Lick Observatory CCD data acquisition system is described, with some observational results to illustrate the system capability. The electronics for the CCD are subdivided into those attached to the dewar, a 'smart' controller near the dewar, and a computer connected by serial link to the smart controller. Software for the controller is in assembler code, while the software for data acquisition and on-line analysis is written in C and uses the UNIX operating system. The computers and controllers are programmed to recognize and operate several different types of CCD. Three separate instruments that use the CCDs are described briefly, together with examples of the data they produce.

  12. Adaptive optics at Lick Observatory: System architecture and operations

    SciTech Connect

    Brase, J.M.; An, J.; Avicola, K. [and others

    1994-03-01

    We will describe an adaptive optics system developed for the 1 meter Nickel and 3 meter Shane telescopes at Lick Observatory. Observing wavelengths will be in the visible for the 1 meter telescope and in the near IR on the 3 meter. The adaptive optics system design is based on a 69 actuator continuous surface deformable mirror and a Hartmann wavefront sensor equipped with an intensified CCD framing camera. The system has been tested at the Cassegrain focus of the 1 meter telescope where the subaperture size is 12.5 cm. The wavefront control calculations are performed on a four processor single board computer controlled by a Unix-based system. We will describe the optical system and give details of the wavefront control system design. We will present predictions of the system performance and initial test results.

  13. Lick-trading by rats: on the substitutability of dry, water, and saccharin tubes.

    PubMed

    Allison, J; Moore, K E

    1985-03-01

    Thirsty rats licked two metal tubes: a water tube paired with another water tube, with saccharin, or with a dry tube. For each pair, a multipoint baseline function was measured by offering free access to one tube throughout each session, and free or restricted access to the other. The three resulting baseline functions showed the members of each pair to be mutual substitutes: When access to either tube was restricted, the rats made more licks at the other. A linear function identified the two water tubes as perfect substitutes. Convex functions identified the members of the saccharin-water and the dry-water pair as imperfect substitutes. Each pair was also tested under several reciprocal fixed-ratio schedules that required instrumental licking of either tube for contingent access to the other. The resulting schedule functions showed the members of each pair to be perfect substitutes: Water licks decreased linearly as licks at the other water tube, the saccharin, or the dry tube increased, in agreement with a conservation model of instrumental performance. Baseline and schedule functions, indistinguishable in the water-water pair, indicated a schedule facilitation of dry-tube licking in the dry-water pair and of water-tube licking in the saccharin-water pair. PMID:3998658

  14. CCD data acquisition systems at Lick and Keck Observatories

    NASA Technical Reports Server (NTRS)

    Kibrick, R. I.; Stover, R. J.; Conrad, A. R.

    1992-01-01

    This paper will describe and compare two distinct but related CCD data acquisition systems (DAS) currently under development at Lick and Keck Observatories. Although these two systems have a number of major architectural differences, they share a considerable amount of common hardware and software. Both of these new systems build on a large body of proven software that is the foundation of the existing CCD DAS currently in use at Lick Observatory. Both will provide support for reading up to four on-chip amplifiers per CCD and/or reading out mosaics of CCD chips. In addition, they will provide the capability for interactive, real-time adjustment of CCD waveforms for engineering purposes. Each of these two systems is composed of three major subsystems: (1) an instrument computer and its software; (2) a data capture computer and its software; and (3) a CCD/dewar controller and its software. The instrument computer is a Unix workstation, and the functions it provides include user interfaces, the interactive real-time display of CCD images, and the recording of image and FITS header data to disk and/or tape. The data capture computer is responsible for the packaging and high-speed transfer of the CCD pixel data stream into a bulk RAM, and the subsequent transfer of this data to the instrument computer. The CCD/dewar controller generates the waveforms for clocking the CCD, digitizes the pixel data, and transmits it via high-speed link to the data capture computer. It is also responsible for monitoring and controlling the dewar temperature and cryogen levels. Given the number of different types of processors and high-speed data links employed in both systems, a major emphasis of this paper will be on the various forms of interprocessor communications utilized for data transfer and distributed process synchronization.

  15. Constraints on Type IIn Supernova Progenitor Outbursts from the Lick Observatory Supernova Search

    E-print Network

    Bilinski, Christopher; Li, Weidong; Williams, G Grant; Zheng, WeiKang; Filippenko, Alexei V

    2015-01-01

    We searched through roughly 12 years of archival survey data acquired by the Katzman Automatic Imaging Telescope (KAIT) as part of the Lick Observatory Supernova Search (LOSS) in order to detect or place limits on possible progenitor outbursts of Type IIn supernovae (SNe~IIn). The KAIT database contains multiple pre-SN images for 5 SNe~IIn (plus one ambiguous case of a SN IIn/imposter) within 50 Mpc. No progenitor outbursts are found using the false discovery rate (FDR) statistical method in any of our targets. Instead, we derive limiting magnitudes (LMs) at the locations of the SNe. These limiting magnitudes (typically reaching $m_R \\approx 19.5\\,\\mathrm{mag}$) are compared to outbursts of SN 2009ip and $\\eta$ Car, plus additional simulated outbursts. We find that the data for SN 1999el and SN 2003dv are of sufficient quality to rule out events $\\sim40$ days before the main peak caused by initially faint SNe from blue supergiant (BSG) precursor stars, as in the cases of SN 2009ip and SN 2010mc. These SNe~IIn...

  16. Rocky Planets Around Cool Stars A Marie Curie Initial Training Network

    E-print Network

    Pinfield, David J.

    #12;RoPACS Degenarate companion and extrasolar planets L/ T dwarfs White dwarfs Planet host stars Gliese Coralie Hipparcos HARPS Keck and Lick T and L dwarf candidates White Dwarfs Outline #12;RoPACS Ultracool dwarfs

  17. ALLSTAR Network: FIU

    NSDL National Science Digital Library

    The Aeronautics Learning Laboratory for Science, Technology, and Research is a highly acclaimed educational site that covers many aspects of aeronautics. Funded in part by NASA and Raytheon, the Web site has material suitable for middle school, high school, and beginning college students. Further, there are three main sections -- aeronautics history, careers and education in aerospace, and principles of aeronautics. Each of the modules has several chapters that focus on specific concepts, such as aircraft propulsion and rocket performance. Multimedia visualizations, videos, and audio clips add to the learning experience.

  18. Effects of Adrenoceptor Agents on Apomorphine-Induced Licking Behavior in Rats

    Microsoft Academic Search

    Mohammad-Reza Zarrindast; Soheila Fazli-Tabaei; Saeed Semnanian; Yaghoub Fathollahi; Seyed Hossein Yahyavi

    2000-01-01

    In the present study, intraperitoneal (IP) administration of the dopaminergic receptor agonist apomorphine (0.1, 0.25, and 0.5 mg\\/kg) induced a dose-dependent licking in rats. The intraperitoneal injection of the ?1?adrenoceptor agonist phenylephrine (1–8 mg\\/kg) but not the ?2-adrenoceptor agonist clonidine (0.025–0.05 mg\\/kg) decreased licking induced by apomorphine. The ?-adrenoceptor antagonists prazosin, phenoxybenzamine, and yohimbine also reduced the apomorphine response significantly.

  19. Snapshot Metallicity Estimate of Resolved Stellar Systems Through Lick Fe5270 Diagnostic

    NASA Astrophysics Data System (ADS)

    Buzzoni, A.; Bertone, E.; Chavez, M.

    2009-10-01

    We outline a new method to derive a "snapshot" metallicity estimate of stellar systems (providing one resolves at least the brightest part of the color-magnitude diagram) on the basis of low-resolution (i.e., 6-8 Å FWHM) spectroscopy of a small stellar sample. Our method relies on the Fe5270 Lick index measurements and takes advantage of the special behavior of this spectral feature that reaches its maximum strength among the ubiquitous component of K-type giants. This makes the Fe5270max estimate a robust and model-independent tracer of cluster [Fe/H], being particularly insensitive to the age of the stellar population. A comparison of the Fe5270max distribution derived from globular and open clusters, as well as from the field giant population in the Galaxy disk, confirms a tight correlation of the index maximum versus cluster [Fe/H] over the entire metallicity range for a stellar population with [Fe/H] gsim-2.0. Relying on a theoretical calibration of the feature, we trust to infer effectively cluster metallicity within a typical uncertainty of 0.1-0.2 dex, depending on red giant branch (RGB) luminosity sampling of the observations. A handful of stars (5-10 objects) is required for the method to be applied, with low-metallicity stellar populations more easily managed, being Fe5270max located within the few brightest RGB stars of the system. In any case, we show that even the observation of a coarse stellar set would allow us to place a confident lower limit on cluster metallicity.

  20. EPS Prize Lecture. Licking and liking: the assessment of hedonic responses in rodents.

    PubMed

    Dwyer, Dominic M

    2012-01-01

    Affective processes are a key determinant of behaviour: At its simplest, liked stimuli are approached while disliked stimuli are avoided. Although assessing hedonic responses in nonverbal animals can be difficult, one relatively tractable approach relies on detailed analyses of rodents' consummatory behaviour. Rodents typically produce rhythmic sets of licks that can be grouped into clusters on the basis of the intervals between licks. The mean number of licks in a cluster (cluster size) is directly related to the concentration of palatable and unpalatable solutions. These relationships suggest that lick cluster size might be a useful index of an animal's hedonic reaction to the solution being consumed. I begin by reviewing studies of conditioned flavour preference and aversion that support the idea that lick cluster size can provide useful information about rats' hedonic reactions. I then describe how this methodology has been used to address previously intractable issues in the investigation of contrast effects as well as revealing an analogue of effort justification effects that, in humans, are commonly explained in terms of cognitive dissonance reduction. Finally, I consider how lick analysis might provide information about hedonic responses in animal models of human psychiatric disorders. In all these cases, how an animal did something was particularly informative about why it was doing it. PMID:22404646

  1. Constraints on Type IIn supernova progenitor outbursts from the Lick Observatory Supernova Search

    NASA Astrophysics Data System (ADS)

    Bilinski, Christopher; Smith, Nathan; Li, Weidong; Williams, G. Grant; Zheng, WeiKang; Filippenko, Alexei V.

    2015-06-01

    We searched through roughly 12 years of archival survey data acquired by the Katzman Automatic Imaging Telescope (KAIT) as part of the Lick Observatory Supernova Search in order to detect or place limits on possible progenitor outbursts of Type IIn supernovae (SNe IIn). The KAIT data base contains multiple pre-SN images for five SNe IIn (plus one ambiguous case of an SN IIn/imposter) within 50 Mpc. No progenitor outbursts are found using the false discovery rate statistical method in any of our targets. Instead, we derive limiting magnitudes (LMs) at the locations of the SNe. These LMs (typically reaching mR ? 19.5 mag) are compared to outbursts of SN 2009ip and ? Car, plus additional simulated outbursts. We find that the data for SN 1999el and SN 2003dv are of sufficient quality to rule out events ˜40 d before the main peak caused by initially faint SNe from blue supergiant precursor stars, as in the cases of SN 2009ip and SN 2010mc. These SNe IIn may thus have arisen from red supergiant progenitors, or they may have had a more rapid onset of circumstellar matter interaction. We also estimate the probability of detecting at least one outburst in our data set to be ?60% for each type of the example outbursts, so the lack of any detections suggests that such outbursts are either typically less luminous (intrinsically or owing to dust) than ˜-13 mag, or not very common among SNe IIn within a few years prior to explosion.

  2. Stars

    NASA Astrophysics Data System (ADS)

    Capelato, Hugo Vicente

    1999-01-01

    We will begin our study with a more or less superficial inspection of the "forest" of stars that we see in the skies. The first thing we notice is that, as sources of light, they are much weaker than the Sun. Second, their apparent colors vary; from a bluish-white in most of them to a reddish-yellow, which is rarer. There is also a third aspect, though it is not very obvious to the naked eye: most of the stars group themselves in small families of two, three or more members. A good example is the Alpha Centauri, the closest star to us, which, in fact, is a triple system of stars. Another is the group of 7 stars that make up the Pleiades, which will be discussed later on. In fact, almost half of the stars are double systems with only two members, called binary stars. Most of these double stars, though together, are separated by several astronomical units (one astronomical unit, AU, is the distance from Earth to the sun: see Chapter 1), and revolve around each other over periods of several years. And yet the revolutions of some binary stars, separated by much smaller distances, occur in only a few hours! These stars are so close to each other that they can share enveloping material. Often this exchange occurs in a somewhat violent manner. Local explosions may occur, expelling matter away from the system. In other binary systems, where one of the components is a very compact, dense star, companion material flows more calmly, making up a light disk around the compact star.

  3. Stars

    NSDL National Science Digital Library

    Roberta Johnson

    2000-07-01

    This section of the Windows to the Universe web site provides information and images about stars including star statistics, and a star gallery. Windows to the Universe is a user-friendly learning system pertaining to the Earth and Space sciences. The objective of this project is to develop an innovative and engaging web site that spans the Earth and Space sciences and includes a rich array of documents, including images, movies, animations, and data sets that explore the Earth and Space sciences and the historical and cultural ties between science, exploration and the human experience. Links at the top of each page allow users to navigate between beginner, intermediate and advanced levels.

  4. APF-The Lick Observatory Automated Planet Finder

    NASA Astrophysics Data System (ADS)

    Vogt, Steven S.; Radovan, Matthew; Kibrick, Robert; Butler, R. Paul; Alcott, Barry; Allen, Steve; Arriagada, Pamela; Bolte, Mike; Burt, Jennifer; Cabak, Jerry; Chloros, Kostas; Cowley, David; Deich, William; Dupraw, Brian; Earthman, Wayne; Epps, Harland; Faber, Sandra; Fischer, Debra; Gates, Elinor; Hilyard, David; Holden, Brad; Johnston, Ken; Keiser, Sandy; Kanto, Dick; Katsuki, Myra; Laiterman, Lee; Lanclos, Kyle; Laughlin, Greg; Lewis, Jeff; Lockwood, Chris; Lynam, Paul; Marcy, Geoffrey; McLean, Maureen; Miller, Joe; Misch, Tony; Peck, Michael; Pfister, Terry; Phillips, Andrew; Rivera, Eugenio; Sandford, Dale; Saylor, Mike; Stover, Richard; Thompson, Matthew; Walp, Bernie; Ward, James; Wareham, John; Wei, Mingzhi; Wright, Chris

    2014-04-01

    The Automated Planet Finder (APF) is a facility purpose-built for the discovery and characterization of extrasolar planets through high-cadence Doppler velocimetry of the reflex barycentric accelerations of their host stars. Located atop Mount Hamilton, the APF facility consists of a 2.4 m telescope and its Levy spectrometer, an optical echelle spectrometer optimized for precision Doppler velocimetry. APF features a fixed-format spectral range from 374-970 nm, and delivers a "throughput" (resolution × slit width product) of 114,000?, with spectral resolutions up to 150,000. Overall system efficiency (fraction of photons incident on the primary mirror that are detected by the science CCD) on blaze at 560 nm in planet-hunting mode is 15%. First-light tests on the radial-velocity (RV) standard stars HD 185144 and HD 9407 demonstrate sub-meter-per-second precision (rms per observation) held over a 3 month period. This paper reviews the basic features of the telescope, dome, and spectrometer, and gives a brief summary of first-light performance.

  5. Ground-based detectability of terrestrial and Jovian extrasolar planets: observations of CM Draconis at Lick Observatory

    NASA Technical Reports Server (NTRS)

    Doyle, L. R.; Dunham, E. T.; Deeg, H. J.; Blue, J. E.; Jenkins, J. M.

    1996-01-01

    The detection of terrestrial-sized extrasolar planets from the ground has been thought to be virtually impossible due to atmospheric scintillation limits. However, we show that this is not the case especially selected (but nevertheless main sequence) stars, namely small eclipsing binaries. For the smallest of these systems, CM Draconis, several months to a few years of photometric observations with 1-m-class telescopes will be sufficient to detect the transits of any short-period planets of sizes > or = 1.5 Earth radii (RE), using cross-correlation analysis with moderately good photometry. Somewhat larger telescopes will be needed to extend this detectability to terrestrial planets in larger eclipsing binary systems. (We arbitrarily define "terrestrial planets" herein as those whose disc areas are closer to that of Earth's than Neptune's i.e., less than about 2.78 RE.) As a "spin-off" of such observations, we will also be able to detect the presence of Jovian-mass planets without transits using the timing of the eclipse minima. Eclipse minima will drift in time as the binary system is offset by a sufficiently massive planet (i.e., one Jupiter mass) about the binary/giant-planet barycenter, causing a periodic variation in the light travel time to the observer. We present here an outline of present observations taking place at the University of California Lick Observatory using the Crossley 0.9-m telescope in collaboration with other observatories (in South Korea, Crete, France, Canary Islands, and New York) to detect or constrain the existence of terrestrial planets around main sequence eclipsing binary star systems, starting with CM Draconis. We demonstrate the applicability of photometric data to the general detection of gas giant planets via eclipse minima timings in many other small-mass eclipsing binary systems as well.

  6. Licking behaviour induces partial anthelmintic efficacy of ivermectin pour-on formulation in untreated cattle

    E-print Network

    Paris-Sud XI, Université de

    in untreated cattle 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Alain Bousquet-Mélou a,d, *, Philippe Jacquiet b 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 Licking behaviour in cattle has been reported between cattle on the reduction in the faecal egg count (FEC) after pour- on administration in a group

  7. Progress with Adaptive Optics Testbeds at the UCO\\/Lick Observatory Laboratory for Adaptive Optics

    Microsoft Academic Search

    Donald Gavel

    2007-01-01

    We report on experimental results with adaptive optics testbeds at the UCO\\/Lick Observatory. One testbed is dedicated to high contrast AO imaging and is a prototype for a ground-based extrasolar planet imager. The second testbed is dedicated to developing concepts and architectures for multi-laser guidestar tomography in wide-field AO applications. Concurrent with the testbed experiments we are evaluating the new

  8. Sodium Laser Guide Star Adaptive Optics Imaging Polarimetry of Herbig Ae\\/Be Stars

    Microsoft Academic Search

    M D Perrin; J R Graham; J P Lloyd; P Kalas; E L Gates; D T Gavel; D M Pennington; C E Max

    2004-01-01

    The future of high-resolution ground-based optical and infrared astronomy requires the successful implementation of laser guide star adaptive optics systems. We present the first science results from the Lick Observatory sodium beacon laser guide star system. By coupling this system to a near-infrared (J;H;Ks bands) dual-channel imaging polarimeter, we achieve very high sensitivity to light scattered in the circumstellar enviroment

  9. Nearby supernova rates from the Lick Observatory Supernova Search - IV. A recovery method for the delay-time distribution

    NASA Astrophysics Data System (ADS)

    Maoz, Dan; Mannucci, Filippo; Li, Weidong; Filippenko, Alexei V.; Della Valle, Massimo; Panagia, Nino

    2011-04-01

    Recovery of the supernova (SN) delay-time distribution (DTD) - the SN rate versus time that would follow a hypothetical brief burst of star formation - can shed light on SN progenitors and physics, as well as on the time-scales of chemical enrichment. Previous attempts to reconstruct the DTD have been based either on comparison of mean SN rates versus redshift to cosmic star-formation history (SFH), or on the comparison of SN rates among galaxies with different mean ages. Here, we present an approach to recover the SN DTD that avoids the averaging and loss of information of other schemes. We compare the SFHs of individual galaxies to the numbers of SNe discovered by a survey in each galaxy (generally zero, sometimes one SN, rarely a few). We apply the method to a subsample of 3505 galaxies, hosting 82 type-Ia SNe (SNe Ia) and 119 core-collapse supernovae (CC SNe), from the Lick Observatory Supernova Search (LOSS), that have SFHs reconstructed from Sloan Digital Sky Survey (SDSS) spectra. We find a >2? SN Ia DTD signal in our shortest-delay, 'prompt' bin at <420 Myr. We identify and study a systematic error, due to the limited aperture of the SDSS spectroscopic fibres, that causes some of the prompt signal to leak to the later bins of the DTD. After accounting for this systematic error, we demonstrate that a prompt SN Ia contribution is required by the data at the >99 per cent confidence level. We further find a 4? indication of SNe Ia that are 'delayed' by >2.4 Gyr. Thus, the data support the existence of both prompt and delayed SNe Ia. We measure the time integral over the SN DTD. For CC SNe we find a total yield of 0.010 ± 0.002 SNe per M? formed, in excellent agreement with expectations, if all stars more massive than 8 M? lead to visible SN explosions. This argues against scenarios in which the minimum mass for core-collapse SNe is ?10 M?, or in which a significant fraction of massive stars collapse without an accompanying explosion. For SNe Ia, the time-integrated yield is 0.0023 ± 0.0006 SNe per M? formed, most of them with delays <2.4 Gyr. Finally, we show the robust performance of the method on simulated samples, and demonstrate that its application to already existing SN samples, such as the full LOSS sample, but with complete and unbiased SFH estimates for the survey galaxies, could provide an accurate and detailed measurement of the SN Ia DTD.

  10. Stellar population models of Lick indices with variable element abundance ratios

    Microsoft Academic Search

    Daniel Thomas; Claudia Maraston; Ralf Bender

    2003-01-01

    We provide the whole set of Lick indices from CN1 to TiO2 in the wavelength range 4000 <~<~lambda<~ 6500 Å of simple stellar population models with, for the first time, variable element abundance ratios, [alpha\\/Fe ]= 0.0, 0.3, 0.5, [alpha\\/Ca ]=-0.1, 0.0, 0.2, 0.5 and [alpha\\/N]=-0.5, 0.0. The models cover ages between 1 and 15 Gyr, metallicities between 1\\/200 and

  11. VizieR Online Data Catalog: Lick AGN monitoring 2011: light curves (Barth+, 2015)

    NASA Astrophysics Data System (ADS)

    Barth, A. J.; Bennert, V. N.; Canalizo, G.; Filippenko, A. V.; Gates, E. L.; Greene, J. E.; Li, W.; Malkan, M. A.; Pancoast, A.; Sand, D. J.; Stern, D.; Treu, T.; Woo, J.-H.; Assef, R. J.; Bae, H.-J.; Brewer, B. J.; Cenko, S. B.; Clubb, K. I.; Cooper, M. C.; Diamond-Stanic, A. M.; Hiner, K. D.; Honig, S. F.; Hsiao, E.; Kandrashoff, M. T.; Lazarova, M. S.; Nierenberg, A. M.; Rex, J.; Silverman, J. M.; Tollerud, E. J.; Walsh, J. L.

    2015-05-01

    This project was allocated 69 nights at the Lick 3m Shane telescope, distributed between 2011 March 27 and June 13. Observations were conducted using the Kast double spectrograph (3440-5515Å on the blue side and 5410-8200Å on the red side). In order to extend our light curves for two AGNs, we also requested additional observations from other observers using the Kast spectrograph: Mrk 50 from 2011 January through March, and Zw 229-015 in June and July. For Zw 229-015, three additional observations were taken 20-23 days after the end of our main campaign. See section 3. (2 data files).

  12. The Michigan Binary Star Program

    NASA Astrophysics Data System (ADS)

    Lindner, Rudi P.

    2007-07-01

    At the end of the nineteenth century, William J. Hussey and Robert G. Aitken, both at Lick Observatory, began a systematic search for unrecorded binary stars with the aid of the 12" and 36" refracting telescopes at Lick Observatory. Aitken's work (and book on binary stars) are well known, Hussey's contributions less so. In 1905 Hussey, a Michigan engineering graduate, returned to direct the Ann Arbor astronomy program, and immediately he began to design new instrumentation for the study of binary stars and to train potential observers. For a time, he spent six months a year at the La Plata Observatory, where he discovered a number of new pairs and decided upon a major southern hemisphere campaign. He spent a decade obtaining the lenses for a large refractor, through the vicissitudes of war and depression. Finally, he obtained a site in South Africa, a 26" refractor, and a small corps of observers, but he died in London en route to fulfill his dream. His right hand man, Richard Rossiter, established the observatory and spent the next thirty years discovering and measuring binary stars: his personal total is a record for the field. This talk is an account of the methods, results, and utility of the extraordinary binary star factory in the veldt.

  13. The lick-index calibration of the Gemini multi-object spectrographs

    SciTech Connect

    Puzia, Thomas H. [Department of Astronomy and Astrophysics, Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Macul, Santiago (Chile); Miller, Bryan W.; Trancho, Gelys [Gemini Observatory, Casilla 603, La Serena (Chile); Basarab, Brett [Middlebury College, Middlebury, VT 05753 (United States); Mirocha, Jordan T. [Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Butler, Karen, E-mail: tpuzia@astro.puc.cl, E-mail: bmiller@gemini.edu [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

    2013-06-01

    We present the calibration of the spectroscopic Lick/IDS standard line-index system for measurements obtained with the Gemini Multi-Object Spectrographs known as GMOS-North and GMOS-South. We provide linear correction functions for each of the 25 standard Lick line indices for the B600 grism and two instrumental setups, one with 0.''5 slit width and 1 × 1 CCD pixel binning (corresponding to ?2.5 Å spectral resolution) and the other with 0.''75 slit width and 2 × 2 binning (?4 Å). We find small and well-defined correction terms for the set of Balmer indices H?, H? {sub A}, and H? {sub A} along with the metallicity sensitive indices Fe5015, Fe5270, Fe5335, Fe5406, Mg{sub 2}, and Mgb that are widely used for stellar population diagnostics of distant stellar systems. We find other indices that sample molecular absorption bands, such as TiO{sub 1} and TiO{sub 2}, with very wide wavelength coverage or indices that sample very weak molecular and atomic absorption features, such as Mg{sub 1}, as well as indices with particularly narrow passband definitions, such as Fe4384, Ca4455, Fe4531, Ca4227, and Fe5782, which are less robustly calibrated. These indices should be used with caution.

  14. IV nicotine self-administration in rats using a consummatory operant licking response: sensitivity to serotonergic, glutaminergic and histaminergic drugs.

    PubMed

    Cousins, Vanessa; Rose, Jed E; Levin, Edward D

    2014-10-01

    Tobacco smoking is characterized by repeated self-administration of nicotine by placing the cigarette in the mouth. The repeated hand-to-mouth self-administration is essentially a consummatory act. We recently developed a paradigm in which rats lick one of two spouts to trigger intravenous (IV) delivery of nicotine, which combines a consummatory act with rapid delivery of nicotine to model the act of tobacco smoking. We have found that rats will lick hundreds of times per nicotine infusion. In the current study, using the operant licking nicotine self-administration model with young adult Sprague-Dawley rats (0.03mg/kg/infusion of nicotine), we tested the effect of antagonists of H1 histamine receptors pyrilamine, serotonin (5HT) type 2 receptors ketanserin and N-methyl-d-aspartate (NMDA) glutamate receptors with d-cycloserine as well as an agonist of 5HT2c receptors lorcaserin, in dose ranges that we have found in previous studies to significantly reduce IV nicotine self-administration with the operant lever press operand. The H1 antagonist pyrilamine significantly reduced operant licking for nicotine self-administration. Pyrilamine caused significant reductions in the operant licking paradigm at lower doses (10 and 20mg/kg) than those we previously observed to affect responding in the operant lever press paradigm. In contrast, the 5HT2A and C antagonist ketanserin did not show an effect of reducing nicotine self-administration in the same dose range we had found in a previous study to significantly reduce operant lever press nicotine self-administration. The 5HT2C agonist lorcaserin significantly decreased nicotine self-administration in the licking paradigm at the same dose threshold as with lever press responding. The NMDA glutamate partial agonist d-cycloserine did not produce any change in nicotine self-administration with the licking operand, in contrast to its effect on the classic lever-pressing task. The rat model incorporating consummatory aspects of tobacco addiction can provide distinct and potentially more relevant information concerning possible new avenues of treatment to combat tobacco addiction. PMID:24953434

  15. ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory

    E-print Network

    Gavel, Donald; Dillon, Daren; Norton, Andrew; Ratliff, Chris; Cabak, Jerry; Phillips, Andrew; Rockosi, Connie; McGurk, Rosalie; Srinath, Srikar; Peck, Michael; Deich, William; Lanclos, Kyle; Gates, John; Saylor, Michael; Ward, Jim; Pfister, Terry

    2014-01-01

    A new high-order adaptive optics system is now being commissioned at the Lick Observatory Shane 3-meter telescope in California. This system uses a high return efficiency sodium beacon and a combination of low and high-order deformable mirrors to achieve diffraction-limited imaging over a wide spectrum of infrared science wavelengths covering 0.8 to 2.2 microns. We present the design performance goals and the first on-sky test results. We discuss several innovations that make this system a pathfinder for next generation AO systems. These include a unique woofer-tweeter control that provides full dynamic range correction from tip/tilt to 16 cycles, variable pupil sampling wavefront sensor, new enhanced silver coatings developed at UC Observatories that improve science and LGS throughput, and tight mechanical rigidity that enables a multi-hour diffraction- limited exposure in LGS mode for faint object spectroscopy science.

  16. Laser guide star measurements at Lawrence Livermore National Laboratory

    SciTech Connect

    Friedman, H.; Avicola, K.; Bissinger, H.; Brase, J.; Duff, J.; Gavel, D.; Horton, J.; Max, C.; Olivier, S.; Rapp, D.; Salmon, T.; Smauley, D.; Waltjen, K.

    1993-02-01

    Recent studies from the Laser Guide Star Project at Lawrence Livermore National Laboratory are presented. Photometry of the return signal has shown that the photon return is approximately 10 photons/cm{sup 2}ms at the pupil of the receiving telescope in agreement with a detailed model of the sodium interaction. Wavefronts of the laser guide star have also been measured with a Shack-Hartmann technique and power spectra have been shown to agree with those of nearby natural stars. Plans for closed loop demonstrations using the laser guide star at LLNL and nearby Lick Observatory are discussed.

  17. A novel automated method for measuring the effect of analgesics on formalin-evoked licking behavior in rats.

    PubMed

    Sakiyama, Yojiro; Sujaku, Tetsujo; Furuta, Akihiro

    2008-01-30

    The behavioral assessment of pain is essential for the analysis of pain mechanisms and the evaluation of analgesic drugs. The formalin test is one of such methods widely used as a model of injury-induced pain in rodents. This test is manually demanding and the recording of results is left to the subjectivity of the experimenters. Thus we developed a novel automated method to estimate the pharmacological response in formalin-induced licking behavior in rats using a multicolor detection technique. Two color markers were preliminarily applied to rats-yellow dye on the mouth and fluorescent green tape on the right hind paw. Behaviors of the animals were recorded from both above and below the subject, by a dual-view digital video camera system. After injection with formalin into the hind paw, rats exhibited a biphasic display of licking behavior. Licking time was measured by the sum of frames where the distance between these markers was less than an appropriate threshold of distance (TD). The split-plot analysis of variance demonstrated that the sum of squares of differences in licking time between manual and automated measurement was minimized when TD = 20mm. In addition, frames in which moving velocity of these markers is less than 2.5mm/s was neglected for calculation in order to eliminate sedative effect on the recorded data. On these conditions, subcutaneous administration of morphine in rats dose-dependently decreased formalin-elicited nociceptive responses. These results suggest that under optimal conditions the automated technique when applied to pharmacological studies are more reliable and efficient than if they are manually recorded. PMID:17881061

  18. Odor-taste convergence in the nucleus of the solitary tract of the awake freely licking rat.

    PubMed

    Escanilla, Olga D; Victor, Jonathan D; Di Lorenzo, Patricia M

    2015-04-22

    Flavor is produced by the integration of taste, olfaction, texture, and temperature, currently thought to occur in the cortex. However, previous work has shown that brainstem taste-related nuclei also respond to multisensory inputs. Here, we test the hypothesis that taste and olfaction interact in the nucleus of the solitary tract (NTS; the first neural relay in the central gustatory pathway) in awake, freely licking rats. Electrophysiological recordings of taste and taste + odor responses were conducted in an experimental chamber following surgical electrode implantation and recovery. Tastants (0.1 m NaCl, 0.1 m sucrose, 0.01 m citric acid, and 0.0001 m quinine) were delivered for five consecutive licks interspersed with five licks of artificial saliva rinse delivered on a VR5 schedule. Odorants were n-amyl acetate (banana), acetic acid (vinegar), octanoic acid (rancid), and phenylethyl alcohol (floral). For each cell, metric space analyses were used to quantify the information conveyed by spike count, by the rate envelope, and by individual spike timing. Results revealed diverse effects of odorants on taste-response magnitude and latency across cells. Importantly, NTS cells were more competent at discriminating taste + odor stimuli versus tastants presented alone for all taste qualities using both rate and temporal coding. The strong interaction of odorants and tastants at the NTS underscores its role as the initial node in the neural circuit that controls food identification and ingestion. PMID:25904782

  19. Searching for Planets Around other Stars

    NASA Technical Reports Server (NTRS)

    1998-01-01

    In this colloquim presentation, Professor of Astronomy, Geoffrey Marcy discusses the discovery of planets orbiting other stars. Using the Doppler shift caused by stellar wobble that is caused by nearby planetary mass, astronomers have been able to infer the existence of Jupiter-sized planets around other stars. Using a special spectrometer at Lick Observatory, the wobble of several stars have been traced over the years required to generate an accurate pattern required to infer the stellar wobble. Professor Marcy, discusses the findings of planets around 47 Ursae Majoris, 16 Cygni B, 51 Pegasus, and 56 Rho 1 Cne. In the case of 56 Rho 1 Cne the planet appears to be close to the star, within 1.5 astronomical units. The observations from the smaller Lick Observatory will be augmented by new observations from the larger telescope at the Kek observatory. This move will allow observations of smaller planets, as opposed to the massive planets thus far discovered. The astronomers also hope to observe smaller stars with the Kek data. Future spaceborne observations will allow the discovery of even smaller planets. A spaceborne interferometer is in the planning stages, and an even larger observatory, called the Terrestrial Planet Finder, is hoped for. Professor Marcy shows artists' renderings of two of the planets thus far discovered. He also briefly discusses planetary formation and shows slides of both observations from the Orion Nebula and models of stellar system formation.

  20. The lick AGN monitoring project 2011: Fe II reverberation from the outer broad-line region

    SciTech Connect

    Barth, Aaron J.; Cooper, Michael C. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697-4575 (United States); Pancoast, Anna; Treu, Tommaso [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Bennert, Vardha N. [Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 (United States); Brewer, Brendon J. [Department of Statistics, The University of Auckland, Private Bag 92019, Auckland 1142 (New Zealand); Canalizo, Gabriela [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Filippenko, Alexei V.; Li, Weidong; Cenko, S. Bradley; Clubb, Kelsey I. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Gates, Elinor L. [Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Sand, David J. [Texas Tech University, Physics Department, Box 41051, Lubbock, TX 79409-1051 (United States); Stern, Daniel; Assef, Roberto J. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Boulevard, Pasadena, CA 91109 (United States); Woo, Jong-Hak [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Bae, Hyun-Jin [Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749 (Korea, Republic of); Buehler, Tabitha, E-mail: barth@uci.edu [Department of Physics and Astronomy, N283 ESC, Brigham Young University, Provo, UT 84602-4360 (United States); and others

    2013-06-01

    The prominent broad Fe II emission blends in the spectra of active galactic nuclei have been shown to vary in response to continuum variations, but past attempts to measure the reverberation lag time of the optical Fe II lines have met with only limited success. Here we report the detection of Fe II reverberation in two Seyfert 1 galaxies, NGC 4593 and Mrk 1511, based on data from a program carried out at Lick Observatory in Spring 2011. Light curves for emission lines including H? and Fe II were measured by applying a fitting routine to decompose the spectra into several continuum and emission-line components, and we use cross-correlation techniques to determine the reverberation lags of the emission lines relative to V-band light curves. In both cases, the measured lag (?{sub cen}) of Fe II is longer than that of H?, although the inferred lags are somewhat sensitive to the choice of Fe II template used in the fit. For spectral decompositions done using the Fe II template of Véron-Cetty et al., we find ?{sub cen}(Fe II)/?{sub cen}(H?) = 1.9 ± 0.6 in NGC 4593 and 1.5 ± 0.3 in Mrk 1511. The detection of highly correlated variations between Fe II and continuum emission demonstrates that the Fe II emission in these galaxies originates in photoionized gas, located predominantly in the outer portion of the broad-line region.

  1. THE LICK AGN MONITORING PROJECT: ALTERNATE ROUTES TO A BROAD-LINE REGION RADIUS

    SciTech Connect

    Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Hood, Carol E.; Barth, Aaron J.; Bentz, Misty C.; Walsh, Jonelle L. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697-4575 (United States); Bennert, Vardha N.; Treu, Tommaso [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Gates, Elinor [Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States); Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90024 (United States); Woo, Jong-Hak [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul, Korea, 151-742 (Korea, Republic of)

    2010-11-01

    It is now possible to estimate black hole (BH) masses across cosmic time, using broad emission lines in active galaxies. This technique informs our views of how galaxies and their central BHs coevolve. Unfortunately, there are many outstanding uncertainties associated with these 'virial' mass estimates. One of these comes from using the accretion luminosity to infer a size for the broad-line region (BLR). Incorporating the new sample of low-luminosity active galaxies from our recent monitoring campaign at Lick Observatory, we recalibrate the radius-luminosity relation with tracers of the accretion luminosity other than the optical continuum. We find that the radius of the BLR scales as the square root of the X-ray and H{beta} luminosities, in agreement with recent optical studies. On the other hand, the scaling appears to be marginally steeper with narrow-line luminosities. This is consistent with a previously observed decrease in the ratio of narrow-line to X-ray luminosity with increasing total luminosity. The radius of the BLR correlates most tightly with H{beta} luminosity, while the X-ray and narrow-line relations both have comparable scatter of a factor of 2. These correlations provide useful alternative virial BH masses in objects with no detectable optical/UV continuum emission, such as high-redshift galaxies with broad emission lines, radio-loud objects, or local active galaxies with galaxy-dominated continua.

  2. The Lick AGN Monitoring Project 2011: Fe II Reverberation from the Outer Broad-Line Region

    E-print Network

    Barth, Aaron J; Bennert, Vardha N; Brewer, Brendon J; Canalizo, Gabriela; Filippenko, Alexei V; Gates, Elinor L; Greene, Jenny E; Li, Weidong; Malkan, Matthew A; Sand, David J; Stern, Daniel; Treu, Tommaso; Woo, Jong-Hak; Assef, Roberto J; Bae, Hyun-Jin; Buehler, Tabitha; Cenko, S Bradley; Clubb, Kelsey I; Cooper, Michael C; Diamond-Stanic, Aleksandar M; Hoenig, Sebastian F; Joner, Michael D; Laney, C David; Lazarova, Mariana S; Nierenberg, A M; Silverman, Jeffrey M; Tollerud, Erik J; Walsh, Jonelle L

    2013-01-01

    The prominent broad Fe II emission blends in the spectra of active galactic nuclei have been shown to vary in response to continuum variations, but past attempts to measure the reverberation lag time of the optical Fe II lines have met with only limited success. Here we report the detection of Fe II reverberation in two Seyfert 1 galaxies, NGC 4593 and Mrk 1511, based on data from a program carried out at Lick Observatory in Spring 2011. Light curves for emission lines including H-beta and Fe II were measured by applying a fitting routine to decompose the spectra into several continuum and emission-line components, and we use cross-correlation techniques to determine the reverberation lags of the emission lines relative to V-band light curves. In both cases the measured lag (t_cen) of Fe II is longer than that of H-beta, although the inferred lags are somewhat sensitive to the choice of Fe II template used in the fit. For spectral decompositions done using the Fe II template of Veron-Cetty et al. (2004), we f...

  3. The Lick AGN Monitoring Project 2011: Reverberation Mapping of Markarian 50

    E-print Network

    Barth, A J; Thorman, S J; Bennert, V N; Sand, D J; Li, W; Canalizo, G; Filippenko, A V; Gates, E L; Greene, J E; Malkan, M A; Stern, D; Treu, T; Woo, J -H; Assef, R J; Bae, H -J; Brewer, B J; Buehler, T; Cenko, S B; Clubb, K I; Cooper, M C; Diamond-Stanic, A M; Hiner, K D; Hoenig, S F; Joner, M D; Kandrashoff, M T; Laney, C D; Lazarova, M S; Nierenberg, A M; Park, D; Silverman, J M; Son, D; Sonnenfeld, A; Tollerud, E J; Walsh, J L; Walters, R; da Silva, R L; Fumagalli, M; Gregg, M D; Harris, C E; Hsiao, E Y; Lee, J; Lopez, L; Rex, J; Suzuki, N; Trump, J R; Tytler, D; Worseck, G; Yesuf, H M

    2011-01-01

    The Lick AGN Monitoring Project 2011 observing campaign was carried out over the course of 11 weeks in Spring 2011. Here we present the first results from this program, a measurement of the broad-line reverberation lag in the Seyfert 1 galaxy Mrk 50. Combining our data with supplemental observations obtained prior to the start of the main observing campaign, our dataset covers a total duration of 4.5 months. During this time, Mrk 50 was highly variable, exhibiting a maximum variability amplitude of a factor of 4 in the U-band continuum and a factor of 2 in the H-beta line. Using standard cross-correlation techniques, we find that H-beta and H-gamma lag the V-band continuum by tau_cen = 10.64(-0.93,+0.82) and 8.43(-1.28,+1.30) days, respectively, while the lag of He II 4686 is unresolved. The H-beta line exhibits a symmetric velocity-resolved reverberation signature with shorter lags in the high-velocity wings than in the line core, consistent with an origin in a broad-line region dominated by orbital motion r...

  4. The Lick AGN Monitoring Project: Alternate Routes to a Broad-line Region Radius

    E-print Network

    Greene, Jenny E; Barth, Aaron J; Bennert, Vardha N; Bentz, Misty C; Filippenko, Alexei V; Gates, Elinor; Malkan, Matthew A; Treu, Tommaso; Walsh, Jonelle L; Woo, Jong-Hak

    2010-01-01

    It is now possible to estimate black hole masses across cosmic time, using broad emission lines in active galaxies. This technique informs our views of how galaxies and their central black holes coevolve. Unfortunately, there are many outstanding uncertainties associated with these "virial" mass estimates. One of these comes from using the accretion luminosity to infer a size for the broad-line region. Incorporating the new sample of low-luminosity active galaxies from our recent monitoring campaign at Lick Observatory, we recalibrate the radius-luminosity relation with tracers of the accretion luminosity other than the optical continuum. We find that the radius of the broad-line region scales as the square root of the X-ray and Hbeta luminosities, in agreement with recent optical studies. On the other hand, the scaling appears to be marginally steeper with narrow-line luminosities. This is consistent with a previously observed decrease in the ratio of narrow-line to X-ray luminosity with increasing total lum...

  5. The Lick AGN Monitoring Project: Photometric Light Curves and Optical Variability Characteristics

    E-print Network

    Walsh, Jonelle L; Bentz, Misty C; Barth, Aaron J; Baliber, Nairn; Li, Weidong; Stern, Daniel; Bennert, Vardha Nicola; Brown, Timothy M; Canalizo, Gabriela; Filippenko, Alexei V; Gates, Elinor L; Greene, Jenny E; Malkan, Matthew A; Sakata, Yu; Street, Rachel A; Treu, Tommaso; Woo, Jong-Hak; Yoshii, Yuzuru

    2009-01-01

    The Lick AGN Monitoring Project targeted 13 nearby Seyfert 1 galaxies with the intent of measuring the masses of their central black holes using reverberation mapping. The sample includes 12 galaxies selected to have black holes with masses roughly in the range 10^6-10^7 solar masses, as well as the well-studied AGN NGC 5548. In conjunction with a spectroscopic monitoring campaign, we obtained broad-band B and V images on most nights from 2008 February through 2008 May. The imaging observations were carried out by four telescopes: the 0.76-m Katzman Automatic Imaging Telescope (KAIT), the 2-m Multicolor Active Galactic Nuclei Monitoring (MAGNUM) telescope, the Palomar 60-in (1.5-m) telescope, and the 0.80-m Tenagra II telescope. Having well-sampled light curves over the course of a few months is useful for obtaining the broad-line reverberation lag and black hole mass, and also allows us to examine the characteristics of the continuum variability. In this paper, we discuss the observational methods and the ph...

  6. The Lick AGN Monitoring Project: Recalibrating Single-Epoch Virial Black Hole Mass Estimates

    E-print Network

    Park, Daeseong; Treu, Tommaso; Barth, Aaron J; Bentz, Misty C; Bennert, Vardha N; Canalizo, Gabriela; Filippenko, Alexei V; Gates, Elinor; Greene, Jenny E; Malkan, Matthew A; Walsh, Jonelle

    2011-01-01

    We investigate the calibration and uncertainties of black hole mass estimates based on the single-epoch (SE) method, using homogeneous and high-quality multi-epoch spectra obtained by the Lick Active Galactic Nucleus (AGN) Monitoring Project for 9 local Seyfert 1 galaxies with black hole masses < 10^8 M_sun. By decomposing the spectra into their AGN and stellar components, we study the variability of the single-epoch Hbeta line width (full width at half-maximum intensity, FWHM_Hbeta; or dispersion, sigma_Hbeta) and of the AGN continuum luminosity at 5100A (L_5100). From the distribution of the "virial products" (~ FWHM_Hbeta^2 L_5100^0.5 or sigma_Hbeta^2 L_5100^0.5) measured from SE spectra, we estimate the uncertainty due to the combined variability as ~ 0.05 dex (12%). This is subdominant with respect to the total uncertainty in SE mass estimates, which is dominated by uncertainties in the size-luminosity relation and virial coefficient, and is estimated to be ~ 0.46 dex (factor of ~ 3). By comparing the...

  7. The Lick AGN Monitoring Project: Reverberation Mapping of Optical Hydrogen and Helium Recombination Lines

    E-print Network

    Bentz, Misty C; Barth, Aaron J; Yoshii, Yuzuru; Woo, Jong-Hak; Wang, Xiaofeng; Treu, Tommaso; Thornton, Carol E; Street, Rachel A; Steele, Thea N; Silverman, Jeffrey M; Serduke, Frank J D; Sakata, Yu; Minezaki, Takeo; Malkan, Matthew A; Li, Weidong; Lee, Nicholas; Hiner, Kyle D; Hidas, Marton G; Greene, Jenny E; Gates, Elinor L; Ganeshalingam, Mohan; Filippenko, Alexei V; Canalizo, Gabriela; Bennert, Vardha Nicola; Baliber, Nairn

    2010-01-01

    We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range ~10^6-10^7M_sun and also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to allow for a time lag to be measured between the continuum fluctuations and the response to these fluctuations in the broad Hbeta emission, which we have previously reported. We present here the light curves for the Halpha, Hgamma, HeII 4686, and HeI 5876 emission lines and the time lags for the emission-line responses relative to changes in the continuum flux. Combining each emission-line time lag with the measured width of the line in the variable part of the spectrum, we determine a virial mass of the central supermassive black hole fro...

  8. The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad Line Region in Mrk 50

    E-print Network

    Pancoast, Anna; Treu, Tommaso; Barth, Aaron J; Bennert, Vardha N; Canalizo, Gabriela; Filippenko, Alexei V; Gates, Elinor L; Greene, Jenny E; Li, Weidong; Malkan, Matthew A; Sand, David J; Stern, Daniel; Woo, Jong-Hak; Assef, Roberto J; Bae, Hyun-Jin; Buehler, Tabitha; Cenko, S Bradley; Clubb, Kelsey I; Cooper, Michael C; Diamond-Stanic, Aleksandar M; Hiner, Kyle D; Hoenig, Sebastian F; Joner, Michael D; Kandrashoff, Michael T; Laney, C David; Lazarova, Mariana S; Nierenberg, A M; Park, Dawoo; Silverman, Jeffrey M; Son, Donghoon; Sonnenfeld, Alessandro; Thorman, Shawn J; Tollerud, Erik J; Walsh, Jonelle L; Walters, Richard

    2012-01-01

    We present dynamical modeling of the broad line region (BLR) in the Seyfert 1 galaxy Mrk 50 using reverberation mapping data taken as part of the Lick AGN Monitoring Project (LAMP) 2011. We model the reverberation mapping data directly, constraining the geometry and kinematics of the BLR, as well as deriving a black hole mass estimate that does not depend on a normalizing factor or virial coefficient. We find that the geometry of the BLR in Mrk 50 is a nearly face-on thick disk, with a mean radius of 9.6(+1.2,-0.9) light days, a width of the BLR of 6.9(+1.2,-1.1) light days, and a disk opening angle of 25\\pm10 degrees above the plane. We also constrain the inclination angle to be 9(+7,-5) degrees, close to face-on. Finally, the black hole mass of Mrk 50 is inferred to be log10(M(BH)/Msun) = 7.57(+0.44,-0.27). By comparison to the virial black hole mass estimate from traditional reverberation mapping analysis, we find the normalizing constant (virial coefficient) to be log10(f) = 0.78(+0.44,-0.27), consistent ...

  9. Modelling reverberation mapping data - II. Dynamical modelling of the Lick AGN Monitoring Project 2008 data set

    NASA Astrophysics Data System (ADS)

    Pancoast, Anna; Brewer, Brendon J.; Treu, Tommaso; Park, Daeseong; Barth, Aaron J.; Bentz, Misty C.; Woo, Jong-Hak

    2014-12-01

    We present dynamical modelling of the broad-line region (BLR) for a sample of five Seyfert 1 galaxies using reverberation mapping data taken by the Lick AGN Monitoring Project in 2008. By modelling the AGN continuum light curve and H? line profiles directly, we are able to constrain the geometry and kinematics of the BLR and make a measurement of the black hole mass that does not depend upon the virial factor, f, needed in traditional reverberation mapping analysis. We find that the geometry of the BLR is generally a thick disc viewed close to face-on. While the H? emission is found to come preferentially from the far side of the BLR, the mean size of the BLR is consistent with the lags measured with cross-correlation analysis. The BLR kinematics are found to be consistent with either inflowing motions or elliptical orbits, often with some combination of the two. We measure black hole masses of log _{10}(M_ BH/M_{odot })=6.62^{+0.10}_{-0.13} for Arp 151, 7.42^{+0.26}_{-0.27} for Mrk 1310, 7.59^{+0.24}_{-0.21} for NGC 5548, 6.37^{+0.21}_{-0.16} for NGC 6814, and 6.99^{+0.32}_{-0.25} for SBS 1116+583A. The f factors measured individually for each AGN are found to correlate with inclination angle, although not with M BH, L5100, or FWHM/? of the emission line profile.

  10. Quaternary chronostratigraphy and stable isotope paleoecology of Big Bone Lick, Kentucky, USA

    NASA Astrophysics Data System (ADS)

    Tankersley, Kenneth Barnett; Murari, Madhav Krishna; Crowley, Brooke E.; Owen, Lewis A.; Storrs, Glenn W.; Mortensen, Litsa

    2015-05-01

    Big Bone Lick (BBL) in northern Kentucky, USA has been a critical geologic site in the historical development of North American Quaternary vertebrate paleontology since the 1700s. Sedimentology, geoarcheology, paleontology, accelerator mass spectrometry radiocarbon and optically stimulated luminescence dating, and stable carbon and nitrogen isotope analyses were undertaken to develop a chronostratigraphy and history of erosion and deposition for the site to provide a foundation for understanding taphonomy, and species extinction and adaptation to periods of climatic and environmental change. Three geomorphic surfaces are recognized at BBL representing significant periods of floodplain aggradation since the last glacial maximum (26.5-19 ka) dating to the Oldest Dryas (Tazewell, 25-19 ka), the Older Dryas (Cary, 14-12 ka), and late Holocene (5 ka to the present). Unconformities suggest significant periods of degradation during the transitions from cold and dry to warm and moist climates from the Oldest Dryas (Tazewell) to Bølling Oscillation, from the Older Dryas (Cary) to the Allerød, and from the Younger Dryas (Valders) to the Holocene Climatic Optimum. Increased anthropogenic activities since ~ 5 ka may have increased soil upland erosion and floodplain aggradation. Stable isotopes demonstrate that the landscape has been dominated by C3 vegetation since the last glacial maximum.

  11. Star-to-Star Abundance Variations among Bright Giants in the Mildly Metal-poor Globular Cluster M4

    Microsoft Academic Search

    Inese I. Ivans; Christopher Sneden; Robert P. Kraft; Nicholas B. Suntzeff; Verne V. Smith; G. Edward Langer; Jon P. Fulbright

    1999-01-01

    We present a chemical composition analysis of 36 giants in the nearby mildly metal-poor (=-1.18) ``CN-bimodal'' globular cluster M4. The stars were observed at the Lick and McDonald Observatories using high-resolution échelle spectrographs and at the Cerro Tololo Inter-American Observatory using the multiobject spectrometer. Confronted with a cluster having interstellar extinction that is large and variable across the cluster face,

  12. LGS Polarimetry and Integral Field Spectroscopy of Herbig Ae/Be Stars

    NASA Astrophysics Data System (ADS)

    Perrin, M. D.; Graham, J. R.; Kalas, P.

    2005-12-01

    The combination of LGS AO polarimetry at Lick and LGS AO imaging spectroscopy at Keck provides a unique and powerful view of the dusty circumstellar environments of young stars. We describe our imaging polarimetric survey of Herbig Ae/Be stars, conducted with the Lick Observatory AO system in both natural and laser guide star modes. Laser guide star AO is needed to observe the complete population of HAEBEs: even though these young, massive stars are intrinsically bright, many (particularly the youngest) are very embedded and thus faint. The laser guide star system at Lick allows us to observe essentially all northern hemisphere HAEBEs at the high resolution afforded by adaptive optics, while differential polarimetry provides high sensitivity to light scattered by circumstellar dust. Using the Lick LGS system, we have resolved circumstellar dust around eight HAEBEs (LkHa 198, LkHa 233, V376 Cas, VY Mon, LkHa 225, Parsamian 21, Parsamian 22, & V645 Cyg), plus a similar number of objects in NGS mode. The revealed dust structures variously include face-on and edge-on disks, extended circumstellar envelopes, bipolar outflow cavities, and tidal streamers between binary stars. In addition, we have recently observed several of these targets using Keck LGS AO and OSIRIS, the new integral field spectrograph, to search for outflows traced by near-IR [FeII] emission lines. These observations will enable us to test proposed models for jet launching and collimation around HAEBEs. Parsamian 21 and LkHa 233 both display [FeII] emission on subarcsecond scales, in the case of LkHa 233 taking the form of a narrowly collimated jet which can be traced to within 0.1 arcsec of the central source. This work has been supported by the NSF Center for Adaptive Optics and the NASA Michelson Fellowship Program.

  13. Image improvement from a sodium-layer laser guide star adaptive optics system

    SciTech Connect

    Max, C. E., LLNL

    1997-06-01

    A sodium-layer laser guide star beacon with high-order adaptive optics at Lick Observatory produced a factor of 2.4 intensity increase and a factor of 2 decrease in full width at half maximum for an astronomical point source, compared with image motion compensation alone. Image full widths at half maximum were identical for laser and natural guide stars (0.3 arc seconds). The Strehl ratio with the laser guide star was 65% of that with a natural guide star. This technique should allow ground-based telescopes to attain the diffraction limit, by correcting for atmospheric distortions.

  14. Binaries Among Debris Disk Stars

    NASA Astrophysics Data System (ADS)

    Rodriguez, David R.; Zuckerman, B.

    2012-01-01

    We have gathered a sample of 112 main-sequence stars with known debris disks. We collected published information and performed adaptive optics observations at Lick Observatory to determine if these debris disks are associated with binary or multiple stars. We discover a previously unknown M-star companion to HIP 1185 at a projected separation of 628 AU. We find that 25% of our debris disk systems are binary or triple star systems, substantially less than the expected 50%. The period distribution for these suggests a relative lack of systems with 1-100 AU separations. Only a few systems have blackbody disk sizes comparable to the binary/triple separation. Together, these two characteristics suggest that binaries with intermediate separations of 1-100 AU readily clear out their disks. We find that the fractional disk luminosity, as a proxy for disk mass, is generally lower for multiple systems than for single stars at any given age. Hence, for a binary to possess a disk or form planets it must either be a very widely separated binary with disk particles orbiting a single star or it must be a small separation binary with a circumbinary disk. This research was supported in part by NASA grants to UCLA.

  15. Laser Guide Star Adaptive Optics Polarimetry of Three Herbig Ae/Be Stars

    NASA Astrophysics Data System (ADS)

    Perrin, M. D.; Gavel, D. T.; Gates, E. L.; Graham, J. R.; Kalas, P.; Larwood, J. D.; Lloyd, J. P.; Max, C. E.; Pennington, D. M.

    2003-12-01

    We have obtained high spatial resolution near-IR imaging polarimetry of several Herbig Ae/Be stars using the Laser Guide Star adaptive optics (AO) system at Lick Observatory. We present here our observations of three of these objects: LkH? 198, LkH? 225, and LkH? 233. Herbig Ae/Be stars are young intermediate-mass stars, whose detailed nature is not as well understood as that of the lower-mass T Tauri stars. AO polarimetry enables us to probe circumstellar dust and outflows at high spatial resolution and dynamic range; the use of the Lick Observatory/LLNL laser guide star system enables observations of these distant and heavily visually extincted targets which could not otherwise be observed with AO. We find a bipolar structure ˜ 10 arcsec in extent oriented north-south surrounding LkH? 198, perpendicular to a dark lane suggestive of an edge-on circumstellar disk. The infrared companion 6 arcsec north illuminates nebulosity oriented in the NW-SE direction and may be the best candidate for driving CO outflow in the region. The two stellar components of the binary LkH? 225 show complex circumstellar structures that resemble tidal arms. Our polarimetric observations establish that the material is illuminated in scattered light from LkHa 225 and is thus physically associated with the binary. The observed morphology may be explained by tidal interactions between circumstellar disks during a close encounter of these stars. LkH? 233 presents a narrow, unpolarized lane separating its characteristic X-shaped reflection nebulosity. This dark lane is oriented perpendicular to a jet and the bipolar cavity and may represent an optically thick circumstellar disk that blocks our direct view of the star at wavelengths shorter than 2.2 micron. This work has been supported by the NSF Center for Adaptive Optics.

  16. Four Big-Telescope Planetary Astronomers of the 1920's at Mount Wilson, Yerkes, and Lick Observatories

    NASA Astrophysics Data System (ADS)

    Osterbrock, D. E.

    2002-12-01

    Contrary to current mythology, many professional astronomers tried to do planetary research before World War II, as Ronald Doel and I have previously emphasized. Their difficulty was that once the known planets had been studied with the biggest and best telescopes, spectrographs, and radiometers there was little more they could do until some new instrumental development came along, and these were rare in those years. Two astronomers who observed planets in the 1920's were Frank Ross, of the Yerkes Observatory faculty, with the Mount Wilson 60- and 100-inch telescopes, and William H. Wright, at Lick, with its 36-inch Crossley reflector, which he considered a big telescope. Both were keenly interested in photographic emulsions (Ross had been a research physicist at the Eastman Kodak Laboratory), and when fast new panchromatic films and plates became available in the 1920's they quickly applied them to photographing the planets. Robert J. Trumpler, also at Lick, used its 36-inch refractor in a combination of photographic (in the yellow and red spectral regions) and visual observing to map and describe Martian surface features. All three of them began planetary observing at the close opposition of Mars in 1924; they were all mainline scientists who ultimately were elected to the National Academy of Sciences. All three of them were doing descriptive work, seeing what was there, and none of them had any theoretical ideas to check or disprove. Francis G. Pease, more of a telescope designer and engineer at Mount Wilson, also used its 60- and 100-inch reflectors, chiefly to take photographs of the planets for illustrations in books and magazines. They all used fine-grain photographic plates, but seeing was a problem they could not overcome. Examples of their planetary photographs, papers, and letters will be posted. Ross and Trumpler dropped out of planetary astronomy after 1928, but Wright and Pease continued in it for many years. An interesting sidelight is that Gerard P. Kuiper, as a young postdoc at Lick, co-authored his first planetary paper in English with Wright (on Mars).

  17. Liquid Feed Passage Route into Stomach Compartments, Influence of Abomasal Infusions on Plasma Glucose, and Supplementation of Dry Rations with Liquid Feeds from Lick-Wheel Feeders1

    Microsoft Academic Search

    L. H. Whitlow; S. P. Marshall; H. H. Van Horn; J. R. Flores

    1976-01-01

    Passage route into stomach compart- ments of liquid feeds containing a marker was studied by feeding a liquid supple- ment and molasses from a lick-wheel feeder and by infusing the liquid supple- ment into the reticulorumen 30 rain prior to sampling contents of the reticuloru- men and abomasum and 4 h prior to sampling blood for plasma glucose. Re- covery

  18. Image improvement from a sodium-layer laser guide star adaptive optics system

    Microsoft Academic Search

    C. E. Max; S. S. Olivier; H. W. Friedman

    1997-01-01

    A sodium-layer laser guide star beacon with high-order adaptive optics at Lick Observatory (Mount Hamilton, California) produced a factor of 2.4 intensity increase and a factor of 2 decrease in full width at half maximum for an astronomical point source, compared with image motion compensation alone. The image full widths at half maximum were identical for laser and natural guide

  19. Taste coding in the parabrachial nucleus of the pons in awake, freely licking rats and comparison with the nucleus of the solitary tract.

    PubMed

    Weiss, Michael S; Victor, Jonathan D; Di Lorenzo, Patricia M

    2014-04-01

    In the rodent, the parabrachial nucleus of the pons (PbN) receives information about taste directly from the nucleus of the solitary tract (NTS). Here we examined how information about taste quality (sweet, sour, salty, and bitter) is conveyed in the PbN of awake, freely licking rats, with a focus on how this information is transformed from the incoming NTS signals. Awake rats with electrodes in the PbN had free access to a lick spout that delivered taste stimuli (5 consecutive licks; 100 mM NaCl, 10 mM citric acid, 0.01 mM quinine HCl, or 100 mM sucrose and water) or water (as a rinse) on a variable-ratio schedule. To assess temporal coding, a family of metrics that quantifies the similarity of two spike trains in terms of spike count and spike timing was used. PbN neurons (n = 49) were generally broadly tuned across taste qualities with variable response latencies. Some PbN neurons were quiescent during lick bouts, and others, some taste responsive, showed time-locked firing to the lick pattern. Compared with NTS neurons, spike timing played a larger role in signaling taste in the first 2 s of the response, contributing significantly in 78% (38/49) of PbN cells compared with 45% of NTS cells. Also, information from temporal coding increased at a faster rate as the response unfolded over time in PbN compared with NTS. Collectively, these data suggest that taste-related information from NTS converges in the PbN to enable a subset of PbN cells to carry a larger information load. PMID:24381029

  20. Commissioning ShARCS: the Shane adaptive optics infrared camera-spectrograph for the Lick Observatory Shane 3-m telescope

    NASA Astrophysics Data System (ADS)

    McGurk, Rosalie; Rockosi, Constance; Gavel, Donald; Kupke, Renate; Peck, Michael; Pfister, Terry; Ward, Jim; Deich, William; Gates, John; Gates, Elinor; Alcott, Barry; Cowley, David; Dillon, Daren; Lanclos, Kyle; Sandford, Dale; Saylor, Mike; Srinath, Srikar; Weiss, Jason; Norton, Andrew

    2014-07-01

    We describe the design and first-light early science performance of the Shane Adaptive optics infraRed Camera- Spectrograph (ShARCS) on Lick Observatory's 3-m Shane telescope. Designed to work with the new ShaneAO adaptive optics system, ShARCS is capable of high-efficiency, diffraction-limited imaging and low-dispersion grism spectroscopy in J, H, and K-bands. ShARCS uses a HAWAII-2RG infrared detector, giving high quantum efficiency (<80%) and Nyquist sampling the diffraction limit in all three wavelength bands. The ShARCS instrument is also equipped for linear polarimetry and is sensitive down to 650 nm to support future visible-light adaptive optics capability. We report on the early science data taken during commissioning.

  1. Sodium Laser Guide Star Adaptive Optics Imaging Polarimetry of Herbig Ae/Be Stars

    SciTech Connect

    Perrin, M D; Graham, J R; Lloyd, J P; Kalas, P; Gates, E L; Gavel, D T; Pennington, D M; Max, C E

    2004-01-08

    The future of high-resolution ground-based optical and infrared astronomy requires the successful implementation of laser guide star adaptive optics systems. We present the first science results from the Lick Observatory sodium beacon laser guide star system. By coupling this system to a near-infrared (J;H;Ks bands) dual-channel imaging polarimeter, we achieve very high sensitivity to light scattered in the circumstellar enviroment of Herbig Ae/Be stars on scales of 100-300 AU. Observations of LkH{alpha} 198 reveal a highly polarized, biconical nebula 10 arcseconds in diameter (6000 AU) . We also observe a polarized jet-like feature associated with the deeply embedded source LkH{alpha} 198-IR. The star LkH{alpha} 233 presents a narrow, unpolarized dark lane dividing its characteristic butterfly-shaped polarized reflection nebulosity. This linear structure is oriented perpendicular to an optical jet and bipolar cavity and is consistent with the presence of an optically thick circumstellar disk blocking our direct view of the star. These data suggest that the evolutionary picture developed for the lower-mass T Tauri stars is also relevant to the Herbig Ae/Be stars and demonstrate the ability of laser guide star adaptive optics systems to obtain scientific results competitive with natural guide star adaptive optics or space-based telescopes.

  2. Chromospheric Activity in nearby Planet Search Stars

    NASA Astrophysics Data System (ADS)

    Isaacson, Howard T.

    2009-01-01

    We present the stellar chromospheric activity measurements of 2000 F, G, K and M type stars. Observations of high resolution spectra were collected from August 2004 to the present at the Lick and Keck Observatories as part of the California Planet Search program. The Keck observations were taken after the CCD upgrade on HIRES in August 2004. Measurements of emission flux in the cores of the Calcium H and K absorption lines are converted to the standard metric of S-values as established by Mt. Wilson observatory. In addition to time series S-values, we include values found directly from the S-value including stellar rotation period, and age. An activity thresh hold has been established which establishes a limit to our ability to detect planets as a function of activity. This threshold defines the level of jitter in a star.

  3. A NEW CEMP-s RR LYRAE STAR

    SciTech Connect

    Kinman, T. D.; Beers, Timothy C. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Aoki, Wako [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Brown, Warren R. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-08-10

    We show that SDSS J170733.93+585059.7 (hereafter SDSS J1707+58), previously identified by Aoki and collaborators as a carbon-enhanced metal-poor star (with s-process-element enhancements, CEMP-s), on the assumption that it is a main-sequence turnoff star, is the RR Lyrae star VIII-14 identified by the Lick Astrograph Survey. Revised abundances for SDSS J1707+58 are [Fe/H] = -2.92, [C/Fe] = +2.79, and [Ba/Fe] = +2.83. It is thus one of the most metal-poor RR Lyrae stars known, and has more extreme [C/Fe] and [Ba/Fe] than the only other RR Lyrae star known to have a CEMP-s spectrum (TY Gru). Both stars are Oosterhoff II stars with prograde kinematics, in contrast to stars with [C/Fe] < + 0.7, such as KP Cyg and UY CrB, which are disk stars. Twelve other RR Lyrae stars with [C/Fe] {>=}+0.7 are presented as CEMP candidates for further study.

  4. The Search for Possible Stellar Companions of DEBRIS Candidate Stars: An Update

    NASA Astrophysics Data System (ADS)

    Butner, Harold M.; Saikin, A.; Leisure, G. S.; Wolfe, C. A.; Tom, H.; Duchene, G.; Rodriguez, D.; DEBRIS Team

    2012-01-01

    Among the key projects of the ESO Herschel mission is a survey that searches for evidence of associated debris disks among nearby main sequence stars. The DEBRIS sample covers nearly 450 stars ranging from spectral type A0 through late M-stars. To model properly the far-infrared results, it is important to know whether the candidate stars have companions or not. To this end, we have undertaken a survey of nearly 300 of the DEBRIS stars that are visible from the northern hemisphere using the Shane 3-meter telescope at Lick Observatory. Our observations are done in the J, H, and K bands with the Shane adaptive optics system and the Lick Observatory IRCAL (a near-infrared IR camera). These observations allow us to look for previously undetected companions in the DEBRIS sample, down to possible separations as small as a few AU between the primary and companion. We present our current results for nearly 200 stars and discuss future planned observations.

  5. First Results from the Lick AGN Monitoring Project: The Mass of the Black Hole in Arp 151

    E-print Network

    Bentz, Misty C; Barth, Aaron J; Baliber, Nairn; Bennert, Nicola; Canalizo, Gabriela; Filippenko, Alexei V; Ganeshalingam, Mohan; Gates, Elinor L; Greene, Jenny E; Hidas, Marton G; Hiner, Kyle D; Lee, Nicholas; Li, Weidong; Malkan, Matthew A; Minezaki, Takeo; Serduke, Frank J D; Shiode, Joshua H; Silverman, Jeffrey M; Steele, Thea N; Stern, Daniel; Street, Rachel A; Thornton, Carol E; Treu, Tommaso; Wang, Xiaofeng; Woo, Jong-Hak; Yoshii, Yuzuru

    2008-01-01

    We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 13 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range ~10^6-10^7 M_sun. We present here the first results from this project -- the mass of the central black hole in Arp 151. Strong variability throughout the campaign led to an exceptionally clean Hbeta lag measurement in this object of 4.25(+0.68/-0.66) days in the observed frame. Coupled with the width of the Hbeta emission line in the variable spectrum, we determine a black hole mass of (7.1 +/- 1.2)x10^6 M_sun, assuming the Onken et al. normalization for reverberation-based virial masses. We also find velocity-resolved lag information within the Hbeta emission line which clearly shows infalling gas in the Hbeta-emitting region. Further detailed analysis may lead to a full model of the geometry and kinematics of broad line region gas around the central black hole...

  6. The Lick AGN Monitoring Project: Broad-Line Region Radii and Black Hole Masses from Reverberation Mapping of Hbeta

    E-print Network

    Bentz, Misty C; Barth, Aaron J; Baliber, Nairn; Bennert, Nicola; Canalizo, Gabriela; Filippenko, Alexei V; Ganeshalingam, Mohan; Gates, Elinor L; Greene, Jenny E; Hidas, Marton G; Hiner, Kyle D; Lee, Nicholas; Li, Weidong; Malkan, Matthew A; Minezaki, Takeo; Sakata, Yu; Serduke, Frank J D; Silverman, Jeffrey M; Steele, Thea N; Stern, Daniel; Street, Rachel A; Thornton, Carol E; Treu, Tommaso; Wang, Xiaofeng; Woo, Jong-Hak; Yoshii, Yuzuru

    2009-01-01

    We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range ~10^6-10^7 M_sun and also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to allow for a time lag to be measured between the continuum fluctuations and the response to these fluctuations in the broad Hbeta emission. We present here the light curves for the objects in this sample and the subsequent Hbeta time lags for the nine objects where these measurements were possible. The Hbeta lag time is directly related to the size of the broad-line region, and by combining the lag time with the measured width of the Hbeta emission line in the variable part of the spectrum, we determine the virial mass of the central supe...

  7. THE LICK AGN MONITORING PROJECT 2011: DYNAMICAL MODELING OF THE BROAD-LINE REGION IN Mrk 50

    SciTech Connect

    Pancoast, Anna; Brewer, Brendon J.; Treu, Tommaso; Bennert, Vardha N.; Sand, David J. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Barth, Aaron J.; Cooper, Michael C. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697-4575 (United States); Canalizo, Gabriela [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Filippenko, Alexei V.; Li, Weidong; Cenko, S. Bradley; Clubb, Kelsey I. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Gates, Elinor L. [Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Stern, Daniel; Assef, Roberto J. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Boulevard, Pasadena, CA 91109 (United States); Woo, Jong-Hak [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Bae, Hyun-Jin [Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749 (Korea, Republic of); Buehler, Tabitha, E-mail: pancoast@physics.ucsb.edu [Department of Physics and Astronomy, N283 ESC, Brigham Young University, Provo, UT 84602-4360 (United States); and others

    2012-07-20

    We present dynamical modeling of the broad-line region (BLR) in the Seyfert 1 galaxy Mrk 50 using reverberation mapping data taken as part of the Lick AGN Monitoring Project (LAMP) 2011. We model the reverberation mapping data directly, constraining the geometry and kinematics of the BLR, as well as deriving a black hole mass estimate that does not depend on a normalizing factor or virial coefficient. We find that the geometry of the BLR in Mrk 50 is a nearly face-on thick disk, with a mean radius of 9.6{sup +1.2}{sub -0.9} light days, a width of the BLR of 6.9{sup +1.2}{sub -1.1} light days, and a disk opening angle of 25 {+-} 10 deg above the plane. We also constrain the inclination angle to be 9{sup +7}{sub -5} deg, close to face-on. Finally, the black hole mass of Mrk 50 is inferred to be log{sub 10}(M{sub BH}/M{sub Sun }) = 7.57{sup +0.44}{sub -0.27}. By comparison to the virial black hole mass estimate from traditional reverberation mapping analysis, we find the normalizing constant (virial coefficient) to be log{sub 10} f = 0.78{sup +0.44}{sub -0.27}, consistent with the commonly adopted mean value of 0.74 based on aligning the M{sub BH}-{sigma}* relation for active galactic nuclei and quiescent galaxies. While our dynamical model includes the possibility of a net inflow or outflow in the BLR, we cannot distinguish between these two scenarios.

  8. THE LICK AGN MONITORING PROJECT: THE M {sub BH}-{sigma}{sub *} RELATION FOR REVERBERATION-MAPPED ACTIVE GALAXIES

    SciTech Connect

    Woo, Jong-Hak [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Treu, Tommaso; Bennert, Vardha N. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Barth, Aaron J.; Walsh, Jonelle L.; Bentz, Misty C. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697-4575 (United States); Wright, Shelley A.; Filippenko, Alexei V.; Li, Weidong [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Martini, Paul [Department of Astronomy, and Center for Cosmology and Astroparticle Physics, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Canalizo, Gabriela [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Gates, Elinor [Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States); Greene, Jenny [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Malkan, Matthew A. [Department of Physics, University of California, Los Angeles, CA 90024 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, MS 169-527, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Minezaki, Takeo, E-mail: woo@astro.snu.ac.k [Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)

    2010-06-10

    To investigate the black hole mass versus stellar velocity dispersion (M {sub BH}-{sigma}{sub *}) relation of active galaxies, we measured the velocity dispersions of a sample of local Seyfert 1 galaxies, for which we have recently determined black hole masses using reverberation mapping. For most objects, stellar velocity dispersions were measured from high signal-to-noise ratio optical spectra centered on the Ca II triplet region ({approx}8500 A), obtained at the Keck, Palomar, and Lick Observatories. For two objects, in which the Ca II triplet region was contaminated by nuclear emission, the measurement was based on high-quality H-band spectra obtained with the OH-Suppressing Infrared Imaging Spectrograph at the Keck-II telescope. Combining our new measurements with data from the literature, we assemble a sample of 24 active galaxies with stellar velocity dispersions and reverberation-based black hole mass measurements in the range of black hole mass 10{sup 6} < M {sub BH}/M {sub sun} < 10{sup 9}. We use this sample to obtain reverberation-mapping constraints on the slope and intrinsic scatter of the M {sub BH}-{sigma}{sub *} relation of active galaxies. Assuming a constant virial coefficient f for the reverberation-mapping black hole masses, we find a slope {beta} = 3.55 {+-} 0.60 and the intrinsic scatter {sigma}{sub int} = 0.43 {+-} 0.08 dex in the relation log(M {sub BH}/M {sub sun}) = {alpha} + {beta} log({sigma}{sub *}/200 km s{sup -1}), which are consistent with those found for quiescent galaxies. We derive an updated value of the virial coefficient f by finding the value which places the reverberation masses in best agreement with the M {sub BH}-{sigma}{sub *} relation of quiescent galaxies; using the quiescent M {sub BH}-{sigma}{sub *} relation determined by Gueltekin et al., we find log f = 0.72{sup +0.09} {sub -0.10} with an intrinsic scatter of 0.44 {+-} 0.07 dex. No strong correlations between f and parameters connected to the physics of accretion (such as the Eddington ratio or line-shape measurements) are found. The uncertainty of the virial coefficient remains one of the main sources of the uncertainty in black hole mass determinations using reverberation mapping, and therefore also in single-epoch spectroscopic estimates of black hole masses in active galaxies.

  9. Laser guide star adaptive optics imaging polarimetry of Herbig Ae/Be stars

    NASA Astrophysics Data System (ADS)

    Perrin, Marshall D.; Graham, James R.; Kalas, Paul; Lloyd, James P.; Max, Claire E.; Gavel, Donald T.; Pennington, Deanna M.; Gates, Elinor L.

    2004-10-01

    Current and future large telescopes depend critically on laser guide star adaptive optics (LGS AO) to achieve their scientific goals. However, there are still relatively few scientific results reported from existing LGS AO systems. We present some of the first science results from the Lick Observatory sodium beacon LGS AO system. We achieve high sensitivity to light scattered in the circumstellar enviroment of Herbig Ae/Be stars on scales of 100-200 AU by coupling the LGS AO system to a near-infrared (J,H,Ks bands) dual channel imaging polarimeter. We describe the design, implementation, and performance of this instrument. The dominant noise source near bright stars in AO images is a "seeing halo" of uncorrected speckles, and since these speckles are unpolarized, dual-channel polarimetry achieves a significant contrast gain. Our observations reveal a wide range of morphologies, including bipolar nebulosities with and without outflow-evacuated cavities and disk-mediated interaction among members of a binary. These data suggest that the evolutionary picture developed for the lower-mass T Tauri stars is also relevant to the Herbig Ae/Be stars, and demonstrate the ability of LGS AO systems to enhance the scientific capabilities of even modest sized telescopes.

  10. Image improvement from a sodium-layer laser guide star adaptive optics system

    SciTech Connect

    Max, C.E.; Olivier, S.S.; Friedman, H.W. [Lawrence Livermore National Lab., CA (United States)] [and others] [Lawrence Livermore National Lab., CA (United States); and others

    1997-09-12

    A sodium-layer laser guide star beacon with high-order adaptive optics at Lick Observatory (Mount Hamilton, California) produced a factor of 2.4 intensity increase and a factor of 2 decrease in full width at half maximum for an astronomical point source, compared with image motion compensation alone. The image full widths at half maximum were identical for laser and natural guide stars (0.3 arc second). The Strehl ratio with the laser guide star was 65 percent of that with a natural guide star. This technique should allow ground-based telescopes to attain the diffraction limit, by correcting for atmospheric distortions. 21 refs., 4 figs., 1 tab.

  11. Commissioning ShARCS: the Shane Adaptive optics infraRed Camera-Spectrograph for the Lick Observatory 3-m telescope

    E-print Network

    McGurk, Rosalie; Gavel, Donald; Kupke, Renate; Peck, Michael; Pfister, Terry; Ward, Jim; Deich, William; Gates, John; Gates, Elinor; Alcott, Barry; Cowley, David; Dillon, Daren; Lanclos, Kyle; Sandford, Dale; Saylor, Mike; Srinath, Srikar; Weiss, Jason; Norton, Andrew

    2014-01-01

    We describe the design and first-light early science performance of the Shane Adaptive optics infraRed Camera-Spectrograph (ShARCS) on Lick Observatory's 3-m Shane telescope. Designed to work with the new ShaneAO adaptive optics system, ShARCS is capable of high-efficiency, diffraction-limited imaging and low-dispersion grism spectroscopy in J, H, and K-bands. ShARCS uses a HAWAII-2RG infrared detector, giving high quantum efficiency (>80%) and Nyquist sampling the diffraction limit in all three wavelength bands. The ShARCS instrument is also equipped for linear polarimetry and is sensitive down to 650 nm to support future visible-light adaptive optics capability. We report on the early science data taken during commissioning.

  12. Uncoupling of complex regulatory patterning during evolution of larval development in echinoderms

    E-print Network

    Yankura, Kristen A; Martik, Megan L; Jennings, Charlotte K; Hinman, Veronica F

    2010-01-01

    cloned sea star orthologs and performed WMISH and FISH. CKJcloned sea star orthologs and performed WMISH and FISH. Allstar animal pole domain as demonstrated by a two-probe fluores- cence in situ hybridization (FISH)

  13. 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.

  14. Variable Stars Pulsating Stars: periodic

    E-print Network

    Basu, Shantanu

    Variable Stars · Pulsating Stars: periodic expansion and contraction, e.g., Cepheids, RR Lyrae increases . Why? #12;Pulsating Stars Cepheid variables: giant stars, very luminous Type II Cepheids: lower Z's · Catacylsmic and Eruptive Variables: sudden large changes, e.g., novae and supernovae · Others: changes

  15. 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.

  16. Swimming with ShARCS: Comparison of On-sky Sensitivity With Model Predictions for ShaneAO on the Lick Observatory 3-meter Telescope

    E-print Network

    Srinath, Srikar; Rockosi, Constance; Kupke, Renate; Gavel, Donald; Cabak, Gerald; Cowley, David; Peck, Michael; Ratliff, Christopher; Gates, Elinor; Peck, Michael; Dillon, Daren; Norton, Andrew; Reining, Marc

    2014-01-01

    The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (ShARCS - Shane Adaptive optics infraRed Camera and Spectrograph) and dual-deformable mirror adaptive optics (AO) system (ShaneAO). We present first-light measurements of imaging sensitivity in the Ks band. We compare measured results to predicted signal-to-noise ratio and magnitude limits from modeling the emissivity and throughput of ShaneAO and ShARCS. The model was validated by comparing its results to the Keck telescope adaptive optics system model and then by estimating the sky background and limiting magnitudes for IRCAL, the previous infra-red detector on the Shane telescope, and comparing to measured, published results. We predict that the ShaneAO system will measure lower sky backgrounds and achieve 20\\% higher throughput across the $JHK$ bands despite having more optical surfaces than the current system. It will enable imaging of fainter objects (by 1-2 magnitudes) and will be faster to reach a fiducial ...

  17. Swimming with ShARCS: comparison of on-sky sensitivity with model predictions for ShaneAO on the Lick Observatory 3-meter telescope

    NASA Astrophysics Data System (ADS)

    Srinath, Srikar; McGurk, Rosalie; Rockosi, Constance; Kupke, Renate; Gavel, Donald; Cabak, Gerald; Cowley, David; Peck, Michael; Ratliff, Christopher; Gates, Elinor; Dillon, Daren; Norton, Andrew; Reining, Marc

    2014-08-01

    The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (ShARCS - Shane Adaptive optics infraRed Camera and Spectrograph) and dual-deformable mirror adaptive optics (AO) system (ShaneAO). We present first-light measurements of imaging sensitivity in the Ks band. We compare mea- sured results to predicted signal-to-noise ratio and magnitude limits from modeling the emissivity and throughput of ShaneAO and ShARCS. The model was validated by comparing its results to the Keck telescope adaptive optics system model and then by estimating the sky background and limiting magnitudes for IRCAL, the pre- vious infra-red detector on the Shane telescope, and comparing to measured, published results. We predict that the ShaneAO system will measure lower sky backgrounds and achieve 20% higher throughput across the JHK bands despite having more optical surfaces than the current system. It will enable imaging of fainter objects (by 1-2 magnitudes) and will be faster to reach a fiducial signal-to-noise ratio by a factor of 10-13. We highlight the improvements in performance over the previous AO system and its camera, IRCAL.

  18. 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.

  19. An Astrometric Companion to the Nearby Metal-Poor, Low-Mass Star LHS 1589

    NASA Astrophysics Data System (ADS)

    Lépine, Sébastien; Rich, R. Michael; Shara, Michael M.; Cruz, Kelle L.; Skemer, Andrew

    2007-10-01

    We report the discovery of a companion to the high proper motion star LHS 1589, a nearby high-velocity, low-mass subdwarf. The companion (LHS 1589B) is located 0.224''+/-0.004'' to the southwest of the primary (LHS 1589A), and is 0.5 mag fainter than the primary in the Ks band. The pair was resolved with the IRCAL infrared camera at Lick Observatory, operating with the Laser Guide Star Adaptive Optics system. A low-resolution spectrum of the unresolved pair obtained at the MDM observatory shows the source to be consistent with a cool subdwarf of spectral subtype sdK7.5. A photometric distance estimate places the metal-poor system at a distance d=81+/-18 pc from the Sun. We also measure a radial velocity Vrad=67+/-8 km s-1, which, together with the proper motion and estimated distance, suggests that the pair is roaming the inner Galactic halo on a highly eccentric orbit. With a projected orbital separation s=18.1+/-4.8 AU, and a crude estimate of the system's total mass, we estimate the orbital period of the system to be in the range 75 yr stars. Based on observations performed with the Laser Guide Star Adaptive Optics system at the Lick Observatory, operated by the University of California system. Based on observations conducted at the MDM observatory, operated jointly by the University of Michigan, Dartmouth College, the Ohio State University, Columbia University, and the University of Ohio.

  20. Hadron star models. [neutron stars

    NASA Technical Reports Server (NTRS)

    Cohen, J. M.; Boerner, G.

    1974-01-01

    The properties of fully relativistic rotating hadron star models are discussed using models based on recently developed equations of state. All of these stable neutron star models are bound with binding energies as high as about 25%. During hadron star formation, much of this energy will be released. The consequences, resulting from the release of this energy, are examined.

  1. Characterizing the Adaptive Optics Off-Axis Point-Spread Function. II. Methods for Use in Laser Guide Star Observations

    E-print Network

    E. Steinbring; S. M. Faber; B. A. Macintosh; D. Gavel; E. L. Gates

    2005-05-10

    Most current astronomical adaptive optics (AO) systems rely on the availability of a bright star to measure the distortion of the incoming wavefront. Replacing the guide star with an artificial laser beacon alleviates this dependency on bright stars and therefore increases sky coverage, but it does not eliminate another serious problem for AO observations. This is the issue of PSF variation with time and field position near the guide star. In fact, because a natural guide star is still necessary for correction of the low-order phase error, characterization of laser guide star (LGS) AO PSF spatial variation is more complicated than for a natural guide star alone. We discuss six methods for characterizing LGS AO PSF variation that can potentially improve the determination of the PSF away from the laser spot, that is, off-axis. Calibration images of dense star fields are used to determine the change in PSF variation with field position. This is augmented by AO system telemetry and simple computer simulations to determine a more accurate off-axis PSF. We report on tests of the methods using the laser AO system on the Lick Observatory Shane Telescope. [Abstract truncated.

  2. Photometric Observations of 6000 Stars in the Cygnus Field

    NASA Technical Reports Server (NTRS)

    Borucki, W.; Caldwell, D.; Koch, D.; Jenkins, J.; Ninkov, Z.

    1999-01-01

    A small photometer to detect transits by extrasolar planets has been assembled and is being tested at Lick Observatory on Mt. Hamilton, California. The Vulcan photometer is constructed from a 30 cm focal length, F/2.5 AeroEktar reconnaissance lens and Photometrics PXL16800 CCD camera. A spectral filter is used to confine the pass band from 480 to 763 mn. It simultaneously monitors 6000 stars brighter than 12th magnitude within a single star field in the galactic plane. When the data are folded and phased to discover low amplitude transits, the relative precision of one-hour samples is about 1 part per thousand (10 x l0(exp -3)) for many of the brighter stars. This precision is sufficient to find jovian-size planets orbiting solar-like stars, which have signal amplitudes from 5 to 30 x l0(exp -3) depending on the inflation of the planet and the size of the star. Based on the frequency of giant inner-planets discovered by Doppler-velocity method, one or two planets should be detectable in a rich star field. The goal of the observations is to obtain the sizes of giant extrasolar planets in short-period orbits and to combine these with masses determined from Doppler velocity measurements to determine the densities of these planets. A further goal is to compare the measured planetary diameters with those predicted from theoretical models. From August 10 through September 30 of 1998, a forty nine square degree field in the Cygnus constellation centered at RA and DEC of 19 hr 47 min, +36 deg 55 min was observed. Useful data were obtained on twenty-nine nights. Nearly fifty stars showed some evidence of transits with periods between 0.3 and 8 days. Most had amplitudes too large to be associated with planetary transits. However, several stars showed low amplitude transits. The data for several transits of each of these two stars have been folded and been folded into 30 minute periods. Only Cygl433 shows any evidence of a flattened bottom that is expected when a small object transits a much larger primary. However when high-resolution spectra were obtained for both stars, the stars were found to be double-lined binaries so similar in size as to have indistinguishable transit depths. The low amplitude of the transits is explained if the stellar orbital planes are tipped approximately 5 degrees from the line of sight causing both binaries to show grazing transits. The two absorption lines, due to the H(sub beta) feature in each star, are apparent and indicate the presence of a binary system with similar components.

  3. THE MANGANESE MERCURY STAR ?1 BOOTIS

    PubMed Central

    Montgomery, John Wm.; Aller, Lawrence H.

    1969-01-01

    High-dispersion plates secured with the Coudé spectrograph of the Lick 120 inch telescope have been used to analyze the peculiar A star ?1 Bootis. Spectral-energy distribution measurements are combined with line-intensity data for iron and manganese in two stages of ionization to obtain a fit with model atmospheres for Teff = 13,000°K and log g = 4. The influence of adopted T and g on the derived abundances is discussed. Although C, O, Mg, Si, Ti, Cr, and Fe appear to have nearly normal (i.e., solar) abundances, strontium appears to be enhanced in abundance by an order of magnitude, and scandium is about 50 times overabundant, while manganese and yttrium appear to be two orders of magnitude overabundant. If the identification of gallium is correct, this element is overabundant by a factor approaching 100,000; while if ?3983.90 is to be attributed to HgII, as Bidelman suggests, the overabundance of this element is many orders of magnitude. PMID:16578698

  4. Sea Stars

    NSDL National Science Digital Library

    2012-07-28

    At first glance, starfish, more properly called sea stars, aren’t doing much of anything. In this video, Jonathan’s investigations reveal a slow-motion predator that hunts and attacks its prey. Traveling the world, Jonathan investigates sea stars from the tropics to the Antarctic and uses time-lapse photography to reveal an amazing complexity to the world of the sea star. Please see the accompanying study guide for educational objectives and discussion points.

  5. The effect of footwear and surface conditions on spinal contour and flexibility with constrained standing 

    E-print Network

    Stephenson, Donya Ann

    1995-01-01

    Two studies were conducted to determine the effects on the spinal column, flexibility and the level of discomfort people experience as a result of standing using Converse[] All-Star athletic shoes on six different industrial floor surfaces and four...

  6. Scintillating Stars

    NSDL National Science Digital Library

    Bob Riddle

    2003-02-01

    Often, a bright planet that is visible over the horizon will be mistaken for a star. Some believe they can tell the difference between a star and a planet because stars twinkle, or scintillate , and planets do not. In actuality however, both will twinkle because any light that passes through our atmosphere, whether it be reflected from a planet or generated by a star, will be interfered with by the atmospheric elements. This month's column sheds light on this "scintillating" subject and engages students in a research activity that revolves around the question: Is Pluto a planet?

  7. Neutron Stars

    NASA Technical Reports Server (NTRS)

    Cottam, J.

    2007-01-01

    Neutron stars were discovered almost 40 years ago, and yet many of their most fundamental properties remain mysteries. There have been many attempts to measure the mass and radius of a neutron star and thereby constrain the equation of state of the dense nuclear matter at their cores. These have been complicated by unknown parameters such as the source distance and burning fractions. A clean, straightforward way to access the neutron star parameters is with high-resolution spectroscopy. I will present the results of searches for gravitationally red-shifted absorption lines from the neutron star atmosphere using XMM-Newton and Chandra.

  8. VizieR Online Data Catalog: The Washington Visual Double Star Catalog (Mason+ 2001-2014)

    NASA Astrophysics Data System (ADS)

    Mason, B. D.; Wycoff, G. L.; Hartkopf, W. I.; Douglass, G. G.; Worley, C. E.

    2015-07-01

    The Washington Visual Double Star Catalog (WDS) is the successor to the Index Catalogue of Visual Double Stars, 1961.0 (IDS; Jeffers and van den Bos, Publ. Lick Obs. 21). Three earlier double star catalogs in XXth century, those by Burnham (BDS, 1906, "General Catalogue of Double Stars within 121 degrees of the North Pole", Carnegie Institution of Washington), Innes (SDS, 1927, "Southern Double Star Catalogue -19 to -90 degrees", Union Observatory, Johannesburg, South Africa), and Aitken (ADS, 1932 "New General Catalogue of Double Stars within 121 degrees of the North Pole", Carnegie Institution of Washington), each covered only a portion of the sky. Both the IDS and the WDS cover the entire sky, and the WDS is intended to contain all known visual double stars for which at least one differential measure has been published. The WDS is continually updated as published data become available. Prior to this, three major updates have been published (Worley and Douglass 1984, "Washington Visual Double Star Catalog, 1984.0", U.S. Naval Observatory, Washington; Worley and Douglass 1997A&AS..125..523W, Cat. I/237; Mason, Wycoff, Hartkopf, Douglass and Worley 2001AJ....122.3466M; and Mason et al. 2006.5). The Washington Double Star Catalog (WDS) has seen numerous changes since the last major release of the catalog. The application of many techniques and considerable industry over the past few years has yielded significant gains in both the number of systems and the number of measures. Is is maintained by the US Naval Observatory, and represents the world's principal database of astrometric double and multiple star information. The WDS contains positions (J2000), discoverer designations, epochs, position angles, separations, magnitudes, spectral types, proper motions, and, when available, Durchmusterung numbers and notes for the components of the systems. (3 data files).

  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. PMID:17836594

  10. Star Journey

    NSDL National Science Digital Library

    Carolyn Anderson

    This National Geographic web-site contains information about the Hubble Space Telescope (HST) along with a star chart and facts about objects in the night sky. The HST section contains details about the building and structure of the HST, how it captures light, positioning the HST to targets, instruments used to record and measure infrared through UV wavelengths, how the HST is powered and communicates with the Earth. Star Attractions discusses properties of constellations, the Milky Way galaxy, other galaxies, star clusters and nebulae. This information is then put together on the National Geographic Star Chart. This chart contains maps of the heavens for the northern and southern hemispheres. The chart contains constellation names, location of stars and other objects, and links to HST images of various galaxies and objects on the chart with names and detailed descriptions. There is an image index to find HST images from the site, details about chart symbol meanings, and links for more information.

  11. Star dust.

    PubMed

    Ney, E P

    1977-02-11

    Infrared astronomy has shown that certain classes of stars are abundant producers of refractory grains, which condense in their atmospheres and are blown into interstellar space by the radiation pressure of these stars. Metallic silicates of the kind that produce terrestrial planets are injected by the oxygen-rich stars and carbon and its refractories by carbon stars. Much of the interstellar dust may be produced by this mechanism. A number of "infrared stars" are completely surrounded by their own dust, and a few of these exhibit a unique morphology that suggests the formation of a planetary system or a stage in the evolution of a planetary nebula. Certain novae also condense grains, which are blown out in their shells. In our own solar system, comets are found to contain the same silicates that are present elsewhere in the galaxy, suggesting that these constituents were present in the primeval solar nebula. PMID:17732279

  12. RETIRED A STARS AND THEIR COMPANIONS. III. COMPARING THE MASS-PERIOD DISTRIBUTIONS OF PLANETS AROUND A-TYPE STARS AND SUN-LIKE STARS

    SciTech Connect

    Bowler, Brendan P.; Johnson, John Asher; Liu, Michael C. [Institute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Marcy, Geoffrey W.; Peek, Kathryn M. G. [Department of Astronomy, University of California, MS 3411, Berkeley, CA 94720-3411 (United States); Henry, Gregory W. [Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box 9501, Nashville, TN 37209 (United States); Fischer, Debra A.; Clubb, Kelsey I. [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132 (United States); Reffert, Sabine; Schwab, Christian [ZAH-Landessternwarte, Koenigstuhl 12, 69117 Heidelberg (Germany); Lowe, Thomas B., E-mail: bpbowler@ifa.hawaii.ed [UCO/Lick Observatory, Santa Cruz, CA 95064 (United States)

    2010-01-20

    We present an analysis of approx5 years of Lick Observatory radial velocity measurements targeting a uniform sample of 31 intermediate-mass (IM) subgiants (1.5 approx< M{sub *}/M{sub sun}approx< 2.0) with the goal of measuring the occurrence rate of Jovian planets around (evolved) A-type stars and comparing the distributions of their orbital and physical characteristics to those of planets around Sun-like stars. We provide updated orbital solutions incorporating new radial velocity measurements for five known planet-hosting stars in our sample; uncertainties in the fitted parameters are assessed using a Markov-Chain Monte Carlo method. The frequency of Jovian planets interior to 3 AU is 26{sup +9}{sub -8}%, which is significantly higher than the 5%-10% frequency observed around solar-mass stars. The median detection threshold for our sample includes minimum masses down to left brace0.2, 0.3, 0.5, 0.6, 1.3right brace M{sub Jup} within left brace0.1, 0.3, 0.6, 1.0, 3.0right brace AU. To compare the properties of planets around IM stars to those around solar-mass stars we synthesize a population of planets based on the parametric relationship dN propor to M {sup a}lpha P {sup b}eta dlnMdlnP, the observed planet frequency, and the detection limits we derived. We find that the values of alpha and beta for planets around solar-type stars from Cumming et al. fail to reproduce the observed properties of planets in our sample at the 4sigma level, even when accounting for the different planet occurrence rates. Thus, the properties of planets around A stars are markedly different than those around Sun-like stars, suggesting that only a small (approx50%) increase in stellar mass has a large influence on the formation and orbital evolution of planets.

  13. Effects of supplementary urea-minerals lick block on the kinetics of fibre digestion, nutrient digestibility and nitrogen utilization of low quality roughages.

    PubMed

    Wu, Yue-ming; Hu, Wei-lian; Liu, Jian-xin

    2005-08-01

    Three yearling lambs with a rumen cannula were used to investigate the effects of supplementation with an urea-minerals lick block (ULB) on the kinetics of ruminal fibre digestion, nutrient digestibility and nitrogen (N) utilization of rice straw (RS), ammonia bicarbonate (AB)treated RS (ABRS) and hay prepared from natural pasture. The digestibility of dry matter and organic matter of RS increased by 13.1% and 12.7% (P<0.05) when the diet was supplemented with ULB, and approached to that of ABRS, indicating that the effect of ULB on digestibility of RS is similar to that of AB treatment. The digestibility of ABRS was slightly improved by the ULB feeding. Nitrogen retention was highest in lambs fed on ABRS alone, followed by hay with ULB, and was lowest in animals fed on RS with ULB. However, both the amount and proportion of N retention to N intake were enhanced by ULB supplementation to lambs fed on hay. The proportion of N retained to N digested decreased due to ULB supplementation to lambs fed on RS or ABRS. Supplementing ULB did not greatly influence the rumen degradation of either dry matter or crude protein in each of the three diets. RS and hay had similar values in the potential extent of digestion (PED) and digestion rate of PED (kd) of fibrous materials, but the discrete lag time for RS was lower than that for hay. The AB treatment significantly increased the PED (P<0.05) and kd (P<0.05) of RS. Neither the PED nor kd for RS and ABRS was influenced by ULB supplementation, but the kd for hay significantly increased due to ULB. The lag time for hay was also shortened by the ULB feeding. The ULB improved the digestion of fibre in the rumen of lambs fed on low quality roughage. It is inferred that while ULB is effective in increasing nutrient digestibility of low quality roughages by improving ruminal fibre digestion. A synchronized supply of N and energy to rumen microbes should be considered to improve the efficiency of N utilization when the basal diet is ammoniated straw. PMID:16052713

  14. An infrared coronagraphic search for substellar companions to young nearby stars

    NASA Astrophysics Data System (ADS)

    McCarthy, Chris

    2001-08-01

    This dissertation presents a comprehensive infrared coronagraphic search for substellar companions to stars. The research consists of: (1) a 102 star infrared survey using the Keck telescope, capable of detecting extrasolar brown dwarfs and planets typically more massive than 10 MJupiter , orbiting between about 75 and 300 AU, (2) a 178 star infrared survey at Steward and Lick Observatories, with optical followup from Keck Observatory, capable of detecting companions with masses greater than 30 MJupiter, orbiting between about 120 to 1200 AU and (3) a 24 star survey of two very young stellar associations TW Hydrae and MBM 12, capable of detecting companions down to 2 MJupiter, between about 25 and 1000 AU. These searches are the first to place limits on the frequency of massive planets orbiting beyond 75 AU, and the most sensitive to encompass such a large number of stars. This research resulted in the discovery of one brown dwarf companion, zero planets and 23 double stars. The frequency of brown dwarf companions to G, K & M stars orbiting between 75 and 300 AU is measured to be 1 +/- 1%, the most precise measurement of this quantity to date. The frequency of massive (>30MJupiter) brown dwarf companions is found to be 0.6% +/- 0.6%. The frequency of giant planet companions with masses between 5 and 10 MJupiter orbiting between 75 and 300 AU is measured here for the first time to be no more than 3%. Taken together with results of other searches encompassing a wide range of orbital separations, this research implies that objects with masses between 12 and 75 MJupiter form very rarely as companions to stars. Theories of star formation which could explain these data are only now beginning to emerge.

  15. Stars equilibrium

    NSDL National Science Digital Library

    University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

    2003-01-01

    What causes the fusion reaction in a star's core? This activity page, part of an interactive laboratory series for grades 8-12, introduces students to processes inside a star. Students read about the equilibrium process in a star, in which outward gas pressure equals inward gravitational pressure. Then, an interactive lab activity offers students the opportunity to predict temperature, pressure, and gravity changes that occur during equilibrium. The chemical reactions of the fusion process are presented, and more specific detailed reactions are available in a pop-up box. Student practice quizzes about the equilibrium process and pressure and gravity interactions inside the star are included, as are answers. Copyright 2005 Eisenhower National Clearinghouse

  16. Neutron stars

    NASA Astrophysics Data System (ADS)

    Lattimer, James M.

    2014-05-01

    Neutron stars are laboratories for dense matter and gravitational physics. Observations of neutron stars from sources such as radio pulsars, low-mass X-ray binaries, X-ray bursts and thermally-emitting neutron stars are setting bounds to neutron star masses, radii, rotation rates, temperatures and ages. Mass measurements constrain the equation of state at the highest densities and set firm bounds to the highest possible density of cold matter. Radii constrain the equation of state in the vicinity of the nuclear saturation density and yield information about the density dependence of the nuclear symmetry energy. Laboratory measurements and theoretical studies of pure neutron matter are in remarkable agreement with observational bounds.

  17. Tycho's Star

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A supernova remnant in Cassiopeia, 7.7° north of ? Cas, which suddenly appeared as a brilliant naked-eye star in November 1572 and reached a maximum apparent magnitude of -3.5. Until its disappearance 16 months later, it was extensively studied by the Danish astronomer Tycho Brahe (1546-1601), who described its early appearance as follows: `Initially, the new star was brighter than any other fixe...

  18. Tycho's Star

    Microsoft Academic Search

    P. Murdin

    2000-01-01

    A supernova remnant in Cassiopeia, 7.7° north of alpha Cas, which suddenly appeared as a brilliant naked-eye star in November 1572 and reached a maximum apparent magnitude of -3.5. Until its disappearance 16 months later, it was extensively studied by the Danish astronomer Tycho Brahe (1546-1601), who described its early appearance as follows: `Initially, the new star was brighter than

  19. Investigating the star formation histories of the brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Groenewald, D. N.; Loubser, S. I.

    2014-10-01

    This article is devoted to the study of the central stellar populations of the brightest cluster galaxies (BCGs). High signal-to-noise ratio, long-slit spectra for a sample of 39 galaxies were fitted against two stellar population models, Pegase.HR (P.HR) and Vazdekis/MILES, to determine the star formation histories of the galaxies using full spectrum fitting, to investigate, in particular, whether a single stellar population (SSP) or composite stellar population model provides the better description. Monte Carlo simulations and ?2 maps were used to check the reliability of the solutions. The ages and [Fe/H] were (i) compared with those derived with the Lick indices and (ii) tested against the internal galaxy properties (the velocity dispersions and absolute K-band magnitudes) and the properties of the host cluster environment (X-ray temperatures, luminosities, offsets and the presence of cooling flows (CFs)), to determine whether any statistically significant correlations existed. The results indicate that 79 per cent of the BCG sample could be represented by an SSP fit, while the remaining 21 per cent likely experienced more than one star formation epoch. The correlations showed that the BCGs hosted in CF clusters are generally found closer to the centre of the clusters, while the BCGs in non-CF clusters are generally found further away. The main results suggested that at least some of the galaxies in the BCG sample had a more complex star formation history than first assumed and that the presence of CFs in the clusters could account for some, but not all, of the star formation activity of BCGs.

  20. Retired A Stars and Their Companions II: Jovian planets orbiting kappa Coronae Borealis and HD167042

    E-print Network

    John A. Johnson; Geoffrey W. Marcy; Debra A. Fischer; Jason T. Wright; Sabine Reffert; Julia M. Kregenow; Peter K. G. Williams; Kathryn M. G. Peek

    2007-11-28

    We report precise Doppler measurements of two evolved stars, kappa CrB (HD142091) and HD 167042, obtained at Lick Observatory as part of our search for planets orbiting intermediate-mass subgiants. Periodic variations in the radial velocities of both stars reveal the presence of substellar orbital companions. These two stars are notably massive with stellar masses of 1.80 Msun and 1.64 Msun, indicating that they are former A-type dwarfs that have evolved off of the main sequence and are now K-type subgiants. The planet orbiting kappa CrB has a minimum mass Msini = 1.8 Mjup, eccentricity e = 0.146 and a 1208 day period, corresponding to a semimajor axis of 2.7 AU. The planet around HD167042 has a minimum mass Msini = 1.7 Mjup and a 412.6 day orbit, corresponding to a semimajor axis of 1.3 AU. The eccentricity of HD167042b is consistent with circular (e = 0.027+/-0.04), adding to the rare class of known exoplanets in long-period, circular orbits similar to the Solar System gas giants. Like all of the planets previously discovered around evolved A stars, kappa CrBb and HD167042b orbit beyond 0.8 AU.

  1. Energy Star 

    E-print Network

    Reihl, K.; Tullos, A.

    2012-01-01

    to design, track, and report energy use of projects ESL-KT-12-10-08 CATEE 2012: Clean Air Through Energy Efficiency Conference, Galveston, TX, October 9-11, 2012 Source: 2006 Lunch & Learn Workshop. ?Energy Star ? New Building Design.? Karen P. Butler.... US Environmental Protection Agency. ESL-KT-12-10-08 CATEE 2012: Clean Air Through Energy Efficiency Conference, Galveston, TX, October 9-11, 2012 Source: 2006 Lunch & Learn Workshop. ?Energy Star ? New Building Design.? Karen P. Butler. US...

  2. Star struck

    NASA Astrophysics Data System (ADS)

    Closer to home, astronomers using the Hubble Space Telescope recently took a close-up photograph of the red supergiant star Betelgeuse, providing astronomers with their first direct look at the surface of a star besides the Sun.Andrea Dupree of the Harvard-Smithsonian Center for Astrophysics and Ronald Gilliland of the Space Telescope Science Institute presented pictures of Betelgeuse revealing an extended atmosphere and a surface marked by a bright spot more than 10 Earths wide and as much as 2000 K warmer than the rest of the surface.

  3. Characterizing the Adaptive Optics Off-Axis Point-Spread Function - I: A Semi-Empirical Method for Use in Natural-Guide-Star Observations

    E-print Network

    E. Steinbring; S. M. Faber; S. Hinkley; B. A. Macintosh; D. Gavel; E. L. Gates; Julian C. Christou; M. Le Louarn; L. M. Raschke; Scott A. Severson; F. Rigaut; David Crampton; J. P. Lloyd; James R. Graham

    2002-07-12

    Even though the technology of adaptive optics (AO) is rapidly maturing, calibration of the resulting images remains a major challenge. The AO point-spread function (PSF) changes quickly both in time and position on the sky. In a typical observation the star used for guiding will be separated from the scientific target by 10" to 30". This is sufficient separation to render images of the guide star by themselves nearly useless in characterizing the PSF at the off-axis target position. A semi-empirical technique is described that improves the determination of the AO off-axis PSF. The method uses calibration images of dense star fields to determine the change in PSF with field position. It then uses this information to correct contemporaneous images of the guide star to produce a PSF that is more accurate for both the target position and the time of a scientific observation. We report on tests of the method using natural-guide-star AO systems on the Canada-France-Hawaii Telescope and Lick Observatory Shane Telescope, augmented by simple atmospheric computer simulations. At 25" off-axis, predicting the PSF full width at half maximum using only information about the guide star results in an error of 60%. Using an image of a dense star field lowers this error to 33%, and our method, which also folds in information about the on-axis PSF, further decreases the error to 19%.

  4. STAR Highlights

    E-print Network

    Hiroshi Masui; for the STAR Collaboration

    2011-06-29

    We report selected results from STAR collaboration at RHIC, focusing on jet-hadron and jet-like correlations, quarkonium suppression and collectivity, di-electron spectrum in both p+p and Au+Au, and higher moments of net-protons as well as azimuthal anisotropy from RHIC Beam Energy Scan program.

  5. Star Power

    ScienceCinema

    None

    2014-11-18

    The U.S. Department of Energy's Princeton Plasma Physics Laboratory has released ''Star Power,'' a new informational video that uses dramatic and beautiful images and thought-provoking interviews to highlight the importance of the Laboratory's research into magnetic fusion.

  6. Star Power

    NSDL National Science Digital Library

    Twin Cities Public Television

    2010-01-01

    In this activity, learners create a star show and discover how they can prevent light pollution. Using simple materials, learners first design constellation boxes. Next, learners use their constellation boxes and desk lamps to explore how city lights impact the visibility of constellations. Finally, learners design shields to reduce light pollution and increase the visibility of constellations.

  7. Brittle Star

    USGS Multimedia Gallery

    A tiny brittle star (the central disc is smaller than a dime) clings to the branches of a soft coral in a sample bucket brought into the shipboard laboratory from a submersible dive. This creature makes its home on the deep, dark ocean floor. ...

  8. Star Power

    SciTech Connect

    None

    2014-10-17

    The U.S. Department of Energy's Princeton Plasma Physics Laboratory has released ''Star Power,'' a new informational video that uses dramatic and beautiful images and thought-provoking interviews to highlight the importance of the Laboratory's research into magnetic fusion.

  9. Precise Radial Velocities of Giant Stars VII. Occurrence Rate of Giant Extrasolar Planets as a Function of Mass and Metallicity

    E-print Network

    Reffert, Sabine; Quirrenbach, Andreas; Trifonov, Trifon; Künstler, Andreas

    2014-01-01

    (abridged) We have obtained precise radial velocities for a sample of 373 G and K type giants at Lick Observatory regularly over more than 12 years. Planets have been identified around 15 giant stars; an additional 20 giant stars host planet candidates. We investigate the occurrence rate of substellar companions around giant stars as a function of stellar mass and metallicity. We probe the stellar mass range from about 1 to beyond 3 M_Sun, which is not being explored by main-sequence samples. We fit the giant planet occurrence rate as a function of stellar mass and metallicity with a Gaussian and an exponential distribution, respectively. We find strong evidence for a planet-metallicity correlation among the secure planet hosts of our giant star sample, in agreement with the one for main-sequence stars. However, the planet-metallicity correlation is absent for our sample of planet candidates, raising the suspicion that a good fraction of them might indeed not be planets. Consistent with the results obtained b...

  10. Extensive Lesions in the Gustatory Cortex in the Rat Do Not Disrupt the Retention of a Presurgically Conditioned Taste Aversion and Do Not Impair Unconditioned Concentration-Dependent Licking of Sucrose and Quinine

    PubMed Central

    2014-01-01

    Although damage to gustatory cortex (GC) in the rat has been reported to severely impair, if not eliminate, retention of a presurgically conditioned taste aversion (CTA), it has equivocal effects on taste preference as measured by intake tests. Because intake tests can be influenced by nongustatory (e.g., postingestive) factors, we employed the brief-access taste test to assess the effects of ibotenic acid–induced lesions targeting the GC on unconditioned licking to a sucrose and then a quinine concentration series in a specialized lickometer. As a functional lesion assessment, a presurgical CTA to 0.1M NaCl was established in thirsty rats by following 15-min intake with intraperitoneal administration of either LiCl (or NaCl for control) on 2 occasions. Both conditioned sham-operated (SHAM) rats and rats with histologically confirmed extensive damage to the GC (GCX) avoided a NaCl concentration series relative to unconditioned controls in a postsurgical brief-access CTA test, with no difference between the surgical groups in their responses to NaCl or similar concentrations of KCl. GCX rats also did not differ from SHAM rats in the EC50 of concentration–response functions for sucrose or quinine. Clearly, the critical cortical area required for the retention of a presurgical CTA falls outside of the extensive area of damage, which was well centered within the conventionally defined gustatory zone of the insular cortex. The absence of an effect on unconditioned responsiveness to sucrose and quinine suggests that the damaged region is also unnecessary for the normal expression of affective licking responses to tastants. PMID:24226296

  11. Spectroscopy: Star Light, Star Bright

    NSDL National Science Digital Library

    This is a student reading about the different types of spectra: continuous, absorption, and emission. Learners will read about the differences between each and see graphical representations of each. This activity is from the Stanford Solar Center's All About the Sun: Sun and Stars activity guide for Grades 5-8 and can also accompany the Stanford Solar Center's Build Your Own Spectroscope activity.

  12. Energy Star

    E-print Network

    Reihl, K.; Tullos, A.

    2012-01-01

    ENERGY STAR ENERGY TARGETS ESL-KT-12-10-08 CATEE 2012: Clean Air Through Energy Efficiency Conference, Galveston, TX, October 9-11, 2012 POP QUIZ!!!! What is EUI?? Energy Use Intensity Do you know the EUI and any of the buildings you designed... submit anytime before earn utility bills ? Project Types ? Commercial buildings (office, schools, hotels, banks, courthouses, warehouses, big box retail, etc.) ? Target Finder ? Achieve an EPA rating of 75 or greater ? Submit two documents 1...

  13. Christmas star.

    NASA Astrophysics Data System (ADS)

    Bia?a, J.

    There are continuous attempts to identify the legendary Christmas Star with a real astronomical event accompanying the birth of Jesus from Nazareth. Unfortunately, the date of birth is difficult to establish on the basis of historical records with better accuracy than a few years. During that period a number of peculiar astronomical events were observed and it seem to be impossible to identify the right one unambiguously.

  14. Retired A Stars and Their Companions II: Jovian planets orbiting kappa Coronae Borealis and HD167042

    E-print Network

    Johnson, John A; Fischer, Debra A; Wright, Jason T; Reffert, Sabine; Kregenow, Julia M; Williams, Peter K G; Peek, Kathryn M G

    2007-01-01

    We report precise Doppler measurements of two evolved stars, kappa CrB (HD142091) and HD 167042, obtained at Lick Observatory as part of our search for planets orbiting intermediate-mass subgiants. Periodic variations in the radial velocities of both stars reveal the presence of substellar orbital companions. These two stars are notably massive with stellar masses of 1.80 Msun and 1.64 Msun, indicating that they are former A-type dwarfs that have evolved off of the main sequence and are now K-type subgiants. The planet orbiting kappa CrB has a minimum mass Msini = 1.8 Mjup, eccentricity e = 0.146 and a 1208 day period, corresponding to a semimajor axis of 2.7 AU. The planet around HD167042 has a minimum mass Msini = 1.7 Mjup and a 412.6 day orbit, corresponding to a semimajor axis of 1.3 AU. The eccentricity of HD167042b is consistent with circular (e = 0.027+/-0.04), adding to the rare class of known exoplanets in long-period, circular orbits similar to the Solar System gas giants. Like all of the planets pr...

  15. CHEMICAL ABUNDANCE ANTICORRELATIONS IN GLOBULAR CLUSTER STARS: THE EFFECT ON CLUSTER INTEGRATED SPECTRA

    SciTech Connect

    Coelho, P. [Nucleo de Astrofisica Teorica, Universidade Cruzeiro do Sul, R. Galvao Bueno 868, Liberdade, 01506-000, Sao Paulo (Brazil); Percival, S. M.; Salaris, M., E-mail: paula.coelho@cruzeirodosul.edu.br, E-mail: smp@astro.livjm.ac.uk, E-mail: ms@astro.livjm.ac.uk [Astrophysics Research Institute, Liverpool John Moores University, 12 Quays House, Birkenhead, CH41 1LD (United Kingdom)

    2011-06-10

    It is widely accepted that individual Galactic globular clusters harbor two coeval generations of stars, the first one born with the 'standard' {alpha}-enhanced metal mixture observed in field halo objects and the second one characterized by an anticorrelated CNONa abundance pattern overimposed on the first generation, {alpha}-enhanced metal mixture. We have investigated with appropriate stellar population synthesis models how this second generation of stars affects the integrated spectrum of a typical metal-rich Galactic globular cluster, like 47 Tuc, focusing our analysis on the widely used Lick-type indices. We find that the only indices appreciably affected by the abundance anticorrelations are Ca4227, G4300, CN{sub 1}, CN{sub 2}, and NaD. The age-sensitive Balmer line, Fe line, and the [MgFe] indices widely used to determine age, Fe, and total metallicity of extragalactic systems are largely insensitive to the second generation population. Enhanced He in second generation stars affects also the Balmer line indices of the integrated spectra, through the change of the turnoff temperature and-with the assumption that the mass-loss history of both stellar generations is the same-the horizontal branch morphology of the underlying isochrones.

  16. 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. PMID:17749544

  17. Star Search

    NSDL National Science Digital Library

    2012-04-02

    In this online activity, learners can test their skills at finding constellations in the northern hemisphere's night sky. Learners can choose during which season to look, and then look for four constellations in that season. The simulation shows a simple representation of the night sky with key stars highlighted. Use this as a practice before going outside or just to give learners an idea of the difficulties involved in identifying constellations. When learners set up a free account at Kinetic City, they can answer bonus questions at the end of the activity as a quick assessment. As a larger assessment, learners can complete the Smart Attack game after they've completed several activities.

  18. O stars and Wolf-Rayet stars

    NASA Technical Reports Server (NTRS)

    Conti, Peter S.; Underhill, Anne B.; Jordan, Stuart (editor); Thomas, Richard (editor)

    1988-01-01

    Basic information is given about O and Wolf-Rayet stars indicating how these stars are defined and what their chief observable properties are. Part 2 of the volume discussed four related themes pertaining to the hottest and most luminous stars. Presented are: an observational overview of the spectroscopic classification and extrinsic properties of O and Wolf-Rayet stars; the intrinsic parameters of luminosity, effective temperature, mass, and composition of the stars, and a discussion of their viability; stellar wind properties; and the related issues concerning the efforts of stellar radiation and wind on the immediate interstellar environment are presented.

  19. Counting Your Lucky Stars

    NSDL National Science Digital Library

    Shannon Ricles

    2013-01-30

    In this activity, learners sample a star field to estimate the number of stars in the universe. This activity simulates how astronomers use sampling instead of census (counting) to more easily collect data in space. Learners predict, count, approximate, and average the number of stars in a Star Field Sheet.

  20. RR Lyrae Stars

    NASA Astrophysics Data System (ADS)

    Smith, Horace A.

    2004-09-01

    Preface; 1. Introduction; 2. The absolute magnitude of the RR Lyrae stars; 3. RR Lyrae stars in globular clusters; 4. RR Lyrae stars of the galactic field; 5. Period changes, the Blanzhko effect, and the double mode pulsation; 6. RR Lyrae stars beyond the Milky Way; Glossary of symbols; Short list of journal abbreviations; References; Index.

  1. Discovery of a Nearly Edge-On Disk around the Young Fe Star PDS 453

    NASA Astrophysics Data System (ADS)

    Perrin, Marshall D.; Schnieder, G.; Duchene, G.; Hines, D.; Pinte, C.; Fitzgerald, M.; Wisniewski, J.; HST GO 11155 Team

    2010-01-01

    We present the first spatially-resolved imaging of a protoplanetary disk around PDS 453, a young F2e star intermediate in mass between T Tauri and Herbig Ae stars. Using Lick AO polarimetry and HST NICMOS coronagraphic imaging and polarimetry, we spatially resolve the disk in scattered light from 1-2 microns, achieving an angular resolution of 0.15" and an inner working angle of 0.3" (20 and 40 AU respectively, for an assumed distance of 140 pc). In addition we present spatially-unresolved Gemini T-ReCS mid-IR photometry. Our high-contrast imaging reveals a highly inclined disk (i ~ 80 degrees) with a radius of 220 AU and a sharp outer edge, potentially due to flyby truncation by a nearby candidate stellar companion. Fitting radiative transfer disk models simultaneously to the imaging and SED allows determination of key disk properties as well as constraints on the nature of the scattering dust grains.

  2. IntrAst2 (Petrovay) Variable stars VARIABLE STARS

    E-print Network

    Petrovay, Kristóf

    ) A variable star is what is listed in GCVS or VSX GCVS: General Catalogue of Variable Stars; http (version 4.2, 47 811 stars). AAVSO VSX: International Variable Star Index http://www.aavso.org/vsx (AAVSO

  3. A high angular resolution survey of circumstellar dust around Herbig Ae/Be stars

    NASA Astrophysics Data System (ADS)

    Perrin, Marshall Dimsey

    This thesis presents the development of a sensitive near-infrared differential imaging polarimeter, and its subsequent use, combined with mid infrared imaging, to survey circumstellar dust around 110 Herbig Ae/Be stars. Planets are born in dusty circumstellar disks around young stars. By imaging such disks we can learn about the environment and physical processes that assemble planets from primordial dust and gas. But these observations are challenging on account of the high angular resolution and high dynamic range necessary to detect the disk's faint reflected light against a far brighter background of stellar light. One powerful method for obtaining the necessary contrast is the use of differential polarimetry to separate polarized dust-scattered light from unpolarized starlight. For this reason, I have developed a differential polarimetry mode for IRCAL, the adaptive optics science camera at Lick Observatory, which uses a YLF Wollaston prism beamsplitter to attenuate 98-99% of stellar light. I describe this instrument, summarize the data reduction and image analysis algorithms employed, and discuss lessons learned for future high-contrast imaging systems. A second strategy for high contrast science is to obtain observations at mid-infrared wavelengths, where dust is bright and stellar light is comparatively faint. These two techniques are complementary, respectively probing scattered and thermal light, and their multiwavelength combination can help constrain numerical models of circumstellar disks and envelopes. I have obtained near-IR adaptive optics imaging polarimetry and mid-IR imaging of a large sample of Herbig Ae/Be stars; 110 targets were observed with AO polarimetry and 61 with mid-IR imaging. Of these stars, 40 are found to have extended polarized nebulosity arising from scattered light. The dust geometry is highly variable, ranging from circumstellar disks to envelopes split by bipolar outflow cavities to complex arcs and lanes of dust spiraling around and between stars. I present detailed studies of a subset of these objects, including laser guide star AO observations of disks and envelopes around the stars LkHalpha 198 and LkHalpha 233; the discovery of the first resolved edge-on circumstellar disk around a Herbig Ae/Be star, PDS 144 N; and integral field spectroscopy of a narrowly collimated bipolar outflow from LkHalpha 233. I conclude by discussing future prospects for advances in the studies of circumstellar disks with the coming generation of high contrast instruments.

  4. Intrinsically variable stars

    NASA Technical Reports Server (NTRS)

    Bohm-Vitense, Erika; Querci, Monique

    1987-01-01

    The characteristics of intrinsically variable stars are examined, reviewing the results of observations obtained with the IUE satellite since its launch in 1978. Selected data on both medium-spectral-class pulsating stars (Delta Cep stars, W Vir stars, and related groups) and late-type variables (M, S, and C giants and supergiants) are presented in spectra, graphs, and tables and described in detail. Topics addressed include the calibration of the the period-luminosity relation, Cepheid distance determination, checking stellar evolution theory by the giant companions of Cepheids, Cepheid masses, the importance of the hydrogen convection zone in Cepheids, temperature and abundance estimates for Population II pulsating stars, mass loss in Population II Cepheids, SWP and LWP images of cold giants and supergiants, temporal variations in the UV lines of cold stars, C-rich cold stars, and cold stars with highly ionized emission lines.

  5. Star Formation in Galaxies

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Topics addressed include: star formation; galactic infrared emission; molecular clouds; OB star luminosity; dust grains; IRAS observations; galactic disks; stellar formation in Magellanic clouds; irregular galaxies; spiral galaxies; starbursts; morphology of galactic centers; and far-infrared observations.

  6. Lone Star Trail 

    E-print Network

    Unknown

    2011-09-05

    The Energy Star performance rating system for buildings has achieved widespread adoption in the building sector as a standard benchmark for energy performance. In 2011, the U.S. EPA released an updated technical methodology for its Energy Star...

  7. Theory of star formation

    E-print Network

    McKee, Christopher F.; Ostriker, Eve C.

    2007-01-01

    the star is at rest in a medium of ?nite temperature. Today,by the star. The outer-disk temperature is not much largerstars, are more subject to fragmentation (Kratter & Matzner, 2006). At temperatures

  8. QCD in Neutron Stars and Strange Stars

    SciTech Connect

    Weber, Fridolin [Department of Physics, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1233 (United States); Negreiros, Rodrigo [FIAS, Goethe University, Ruth Moufang Str 1, 60438 Frankfurt (Germany)

    2011-05-24

    This paper provides an overview of the possible role of Quantum Chromo Dynamics (QCD) for neutron stars and strange stars. The fundamental degrees of freedom of QCD are quarks, which may exist as unconfined (color superconducting) particles in the cores of neutron stars. There is also the theoretical possibility that a significantly large number of up, down, and strange quarks may settle down in a new state of matter known as strange quark matter, which, by hypothesis, could be more stable than even the most stable atomic nucleus, {sup 56}Fe. In the latter case new classes of self-bound, color superconducting objects, ranging from strange quark nuggets to strange quark stars, should exist. The properties of such objects will be reviewed along with the possible existence of deconfined quarks in neutron stars. Implications for observational astrophysics are pointed out.

  9. Star formation Simon Goodwin

    E-print Network

    Crowther, Paul

    Star formation Simon Goodwin Dept Physics & Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK. s.goodwin@sheffield.ac.uk 1 Abstract Stars are one of the most important consituents of the Universe, and understanding their formation is crucial to many areas of astrophysics. Stars form from dense

  10. White Dwarf Stars

    Microsoft Academic Search

    Steven Kawaler; Michael Dahlstrom

    2000-01-01

    A white dwarf is a very dense star: The earth-sized remains of a Sun-like star that has burned all of its nuclear fuel. Although it's unable to carry out the workaday activities of a living star, a white dwarf is still an interesting object to astronomers. For one thing, white dwarfs experience \\

  11. The MONS Star Trackers

    E-print Network

    Timothy R. Bedding; Hans Kjeldsen

    2000-03-17

    The MONS satellite will have two Star Trackers to sense the spacecraft attitude, and we plan to use them as scientific instruments to perform high-precision photometry of thousands of stars. We briefly describe the current plans for the Star Trackers and their expected capabilities.

  12. Supernova Star Maps

    NSDL National Science Digital Library

    2012-12-26

    This fun astronomy activity allows learners to experience finding stars in the night sky that will eventually go supernova. This activity is perfect for a star party outdoors. The PDF contains step-by-step instructions, photos, presentation tips, ready-to-print star maps, and links to background information.

  13. Life Cycles of Stars

    NSDL National Science Digital Library

    This Powerpoint presentation inroduces younger students to the life cycles of stars. Topics include stellar nurseries, types of stars, supernovae, the fates of stars of either high or low mass, and the creation of heavier elements by continued fusion of successively heavier elements.

  14. Spots on Am stars

    E-print Network

    Balona, L A; Abedigamba, O P; Ripepi, V; Smalley, B

    2015-01-01

    We investigate the light variations of 15 Am stars using four years of high-precision photometry from the Kepler spacecraft and an additional 14 Am stars from the K2 Campaign 0 field. We find that most of the Am stars in the Kepler field have light curves characteristic of rotational modulation due to star spots. Of the 29 Am stars observed, 12 are {\\delta} Scuti variables and one is a {\\gamma} Doradus star. One star is an eclipsing binary and another was found to be a binary from time-delay measurements. Two Am stars show evidence for flares which are unlikely to be due to a cool companion. The fact that 10 out of 29 Am stars are rotational variables and that some may even flare strongly suggests that Am stars possess significant magnetic fields. This is contrary to the current understanding that the enhanced metallicity in these stars is due to diffusion in the absence of a magnetic field. The fact that so many stars are {\\delta} Scuti variables is also at odds with the prediction of diffusion theory. We su...

  15. Main Sequence Stars

    NSDL National Science Digital Library

    This website from the Australian Telescope Outreach and Education group provides a thorough introduction to the life and death of stars. The website uses text, diagrams, and images to help explain how stars evolve. Highlights include a discussion of stellar fusion reactions and also a straightforward calculation of the lifetime of a star.

  16. Star Formation Ralf Klessen

    E-print Network

    Klessen,Ralf

    need to explain dynamic star formation theory gravity vs. turbulence (and all the rest) examples, green radio: blue Star formation in interacting galaxies: (from the Chandra Webpage) #12;(HST. The Trapezium cluster is only visible in the IR and contains about 2000 newly born stars. Orion molecular cloud

  17. Asteroseismology of B stars

    NASA Astrophysics Data System (ADS)

    Thoul, A.

    2009-03-01

    Numerous B stars on the main sequence are found to be variable. These stars have a relatively simple structure, and yet they present some very interesting challenges. It is important to understand these stars before we can expect to be able to understand stars which have a more complicated internal structure. Asteroseismology of B stars has made considerable progress in the last few years, thanks to the observations obtained from large multisite campaigns, and it is now possible to determine global parameters for these stars such as their masses, ages, metallicities, with very high accuracy. Many variable B stars are also observed with the CoRoT space mission, and statistical studies may become possible in the near future. Detailed studies of the oscillation spectra of ? Cephei stars have already allowed to put some limits on the overshooting parameter, and this overshooting parameter is found to vary from one star to the next. Some ? Cephei stars are found to present differential rotation in their envelopes, while others are compatible with solid body rotation. Some B stars present nitrogen enhancement, even though they are very slow rotators. The instability strips of B stars differ depending on the composition and the opacity tables adopted. Microscopic diffusion and radiative accelerations could produce an accumulation of iron-group elements in some layers of these stars. Hybrid pulsators, showing both ? Cephei and SPB pulsations have been observed. Some of the best observed stars have pulsation spectra which still cannot be reproduced by modelling. Here I review the present status of the observations and of the modelling of ? Cephei stars, emphasizing both the successes reached and the questions and problems which remain open today.

  18. Stars and Constellations

    NSDL National Science Digital Library

    Kaler, James, B.

    This site from Jim Kaler, a Professor of Astronomy at the University of Illinois, is geared toward amateur and budding astronomers. Kaler offers detailed but non-technical descriptions of selected stars and a link to a photo of their respective constellations. Another section of the site, The Natures of Stars, consists of basic overviews of key concepts. The star descriptions are interesting to beginner and avid starwatchers alike, but the photos would benefit perhaps from superimposed arrows or other finding aids. The Stars site grows by one celestial body each week: the Star of the Week from Kaler's other site, Skylights.

  19. Ponderable soliton stars

    NASA Technical Reports Server (NTRS)

    Chiu, Hong-Yee

    1990-01-01

    The theory of Lee and Pang (1987), who obtained solutions for soliton stars composed of zero-temperature fermions and bosons, is applied here to quark soliton stars. Model soliton stars based on a simple physical model of the proton are computed, and the properties of the solitons are discussed, including the important problem of the existence of a limiting mass and thus the possible formation of black holes of primordial origin. It is shown that there is a definite mass limit for ponderable soliton stars, so that during cooling a soliton star might reach a stage beyond which no equilibrium configuration exists and the soliton star probably will collapse to become a black hole. The radiation of ponderable soliton stars may alter the short-wavelength character of the cosmic background radiation, and may be observed as highly redshifted objects at z of about 100,000.

  20. Ponderable soliton stars

    NASA Astrophysics Data System (ADS)

    Chiu, Hong-Yee

    1990-12-01

    The theory of Lee and Pang (1987), who obtained solutions for soliton stars composed of zero-temperature fermions and bosons, is applied here to quark soliton stars. Model soliton stars based on a simple physical model of the proton are computed, and the properties of the solitons are discussed, including the important problem of the existence of a limiting mass and thus the possible formation of black holes of primordial origin. It is shown that there is a definite mass limit for ponderable soliton stars, so that during cooling a soliton star might reach a stage beyond which no equilibrium configuration exists and the soliton star probably will collapse to become a black hole. The radiation of ponderable soliton stars may alter the short-wavelength character of the cosmic background radiation, and may be observed as highly redshifted objects at z of about 100,000.

  1. Dynamical Analysis of the 6:1 Resonance of the Brown Dwarfs Orbiting the K Giant Star ? Ophiuchi

    NASA Astrophysics Data System (ADS)

    Lee, Man Hoi; Trifonov, Trifon; Quirrenbach, Andreas; Reffert, Sabine

    2015-05-01

    The K giant star ? Oph has two brown dwarf companions (with minimum masses of about 22 and 25 times the mass of Jupiter), whose orbital periods are about 530 and 3200 days and close to 6:1 in ratio. We present a dynamical analysis of this system, using 150 precise radial velocities obtained at the Lick Observatory in combination with data already available in the literature. We investigate a large set of orbital fits by applying systematic ?2 grid-search techniques coupled with self-consistent dynamical fitting. We find that the brown dwarfs are indeed locked in an aligned 6:1 resonant configuration, with all six mean-motion resonance angles librating around 0°, but the inclination of the orbits is poorly constrained. As with resonant planet pairs, the brown dwarfs in this system were most likely captured into resonance through disk-induced convergent migration. Thus the ? Oph system shows that brown dwarfs can form like planets in disks around stars.This work is supported in part by Hong Kong RGC grant HKU 7024/13P.

  2. THE SOLAR NEIGHBORHOOD. XXVI. AP Col: THE CLOSEST (8.4 pc) PRE-MAIN-SEQUENCE STAR

    SciTech Connect

    Riedel, Adric R.; Henry, Todd J.; Jao, Wei-Chun [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302-4106 (United States); Murphy, Simon J. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Melis, Carl [Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093-0424 (United States); Subasavage, John P., E-mail: riedel@chara.gsu.edu, E-mail: thenry@chara.gsu.edu, E-mail: jao@chara.gsu.edu, E-mail: murphysj@mso.anu.edu.au, E-mail: cmelis@ucsd.edu, E-mail: jsubasavage@ctio.noao.edu [Cerro Tololo Inter-American Observatory, La Serena (Chile)

    2011-10-15

    We present the results of a multi-technique investigation of the M4.5Ve flare star AP Col, which we discover to be the nearest pre-main-sequence star. These include astrometric data from the CTIO 0.9 m, from which we derive a proper motion of 342.0 {+-} 0.5 mas yr{sup -1}, a trigonometric parallax of 119.21 {+-} 0.98 mas (8.39 {+-} 0.07 pc), and photometry and photometric variability at optical wavelengths. We also provide spectroscopic data, including radial velocity (22.4 {+-} 0.3 km s{sup -1}), lithium equivalent width (EW) (0.28 {+-} 0.02 A), H{alpha} EW (-6.0 to -35 A), vsin i (11 {+-} 1 km s{sup -1}), and gravity indicators from the Siding Spring 2.3 m WiFeS, Lick 3 m Hamilton echelle, and Keck-I HIRES echelle spectrographs. The combined observations demonstrate that AP Col is the closer of only two known systems within 10 pc of the Sun younger than 100 Myr. Given its space motion and apparent age of 12-50 Myr, AP Col is likely a member of the recently proposed {approx}40 Myr old Argus/IC 2391 Association.

  3. The Power of a Planet Population: Kepler's Super-Earth Compositions, Mass-Radius Relation, and Host Star Multiplicity

    NASA Astrophysics Data System (ADS)

    Wolfgang, Angie

    2015-01-01

    The Kepler Mission has found thousands of planetary candidates with radii between 1 and 4 times that of Earth. These planets have no analogues in our Solar System, providing an unprecedented opportunity to assess planet formation and evolution processes for an entirely new planetary population. By coupling theoretical work with sophisticated statistical modeling, we place quantitative constraints on the distribution of physically relevant properties, such as planet compositions, while accurately incorporating the large uncertainties and biases in the Kepler data. We first apply this framework to the composition distribution of Kepler's sub-Neptunes: assuming an internal structure consisting of a rocky core with a hydrogen and helium envelope, we find that these envelopes are most likely to be ~ 1% of these planets' total mass with an intrinsic scatter of ± 0.5 dex. Our results do not produce a one-to-one relationship between super-Earth masses and radii. Accordingly, we derive a probability density function that incorporates the intrinsic scatter in planetary masses at a given radius, which provides dynamical studies a more appropriate means to map Kepler radii to masses. Finally, we present first results from our campaign to detect stellar companions to Kepler super-Earth host stars using the laser guide star adaptive optics systems at Lick Observatory, and discuss implications for the orbital evolution of this entirely new class of planets.

  4. A 4-Planet System Orbiting the K0V Star HD 141399

    E-print Network

    Vogt, Steven S; Rivera, Eugenio J; Kibrick, Robert; Burt, Jennifer; Hanson, Russell; Meschiari, Stefano; Henry, Gregory W; Laughlin, Gregory

    2014-01-01

    We present precision radial velocity (RV) data sets from Keck-HIRES and from Lick Observatory's new Automated Planet Finder Telescope and Levy Spectrometer on Mt. Hamilton that reveal a multiple-planet system orbiting the nearby, slightly evolved, K-type star HD 141399. Our 91 observations over 10.5 years suggest the presence of four planets with orbital periods of 94.35, 202.08, 1070.35, and 3717.35 days and minimum masses of 0.46, 1.36, 1.22, and 0.69 Jupiter masses respectively. The orbital eccentricities of the three inner planets are small, and the phase curves are well sampled. The inner two planets lie just outside the 2:1 resonance, suggesting that the system may have experienced dissipative evolution during the protoplanetary disk phase. The fourth companion is a Jupiter-like planet with a Jupiter-like orbital period. Its orbital eccentricity is consistent with zero, but more data will be required for an accurate eccentricity determination.

  5. Cooling of dense stars

    NASA Technical Reports Server (NTRS)

    Tsuruta, S.

    1972-01-01

    Cooling rates were calculated for neutron stars of about one solar mass and 10 km radius, with magnetic fields from zero to about 10 to the 14th power gauss, for extreme cases of maximum and zero superfluidity. The results show that most pulsars are so cold that thermal ionization of surface atoms would be negligible. Nucleon superfluidity and crystallization of heavy nuclei were treated quantitatively, and more realistic hadron star models were chosen. Cooling rates were calculated for a stable hyperon star near the maximum mass limit, a medium weight neutron star, and a light neutron star with neutron-rich heavy nuclei near the minimum mass limit. Results show that cooling rates are a sensitive function of density. The Crab and Vela pulsars are considered, as well as cooling of a massive white dwarf star.

  6. Sizing up the stars

    NASA Astrophysics Data System (ADS)

    Boyajian, Tabetha S.

    For the main part of this dissertation, I have executed a survey of nearby, main sequence A, F, and G-type stars with the CHARA Array, successfully measuring the angular diameters of forty-four stars to better than 4% accuracy. The results of these observations also yield empirical determinations of stellar linear radii and effective temperatures for the stars observed. In addition, these CHARA-determined temperatures, radii, and luminosities are fit to Yonsei-Yale isochrones to constrain the masses and ages of the stars. These quantities are compared to the results found in Allende Prieto & Lambert (1999), Holmberg et al. (2007), and Takeda (2007), who indirectly determine these same properties by fitting models to observed photometry. I find that for most cases, the models underestimate the radius of the star by ~ 12%, while in turn they overestimate the effective temperature by ~ 1.5-4%, when compared to my directly measured values, with no apparent correlation to the star's metallicity or color index. These overestimated temperatures and underestimated radii in these works appear to cause an additional offset in the star's surface gravity measurements, which consequently yield higher masses and younger ages, in particular for stars with masses greater than ~ 1.3 [Special characters omitted.] . Alternatively, these quantities I measure are also compared to direct measurements from a large sample of eclipsing binary stars in Andersen (1991), and excellent agreement is seen within both data sets. Finally, a multi-parameter solution is found to fit color-temperature-metallicity values of the stars in this sample to provide a new calibration of the effective temperature scale for these types of stars. Published work in the field of stellar interferometry and optical spectroscopy of early-type stars are presented in Appendix D and E, respectively. INDEX WORDS: Interferometry, Infrared, Stellar Astronomy, Fundamental Properties, Effective Temperatures, Stellar Radii

  7. Massive soliton stars

    NASA Technical Reports Server (NTRS)

    Chiu, Hong-Yee

    1990-01-01

    The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of soliton stars. The possibility of primordial creation of soliton stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside soliton stars, the luminosity of soliton stars is not determined by its radiative transfer characteristics, and the surface temperature of soliton stars can be the same as its interior temperature. It is possible that soliton stars are intense X-ray radiators at large distances. Soliton stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside soliton stars during early epochs of the universe. In addition, if soliton stars exist they could assume the role played by massive black holes in galactic centers.

  8. Introduction to neutron stars

    NASA Astrophysics Data System (ADS)

    Lattimer, James M.

    2015-02-01

    Neutron stars contain the densest form of matter in the present universe. General relativity and causality set important constraints to their compactness. In addition, analytic GR solutions are useful in understanding the relationships that exist among the maximum mass, radii, moments of inertia, and tidal Love numbers of neutron stars, all of which are accessible to observation. Some of these relations are independent of the underlying dense matter equation of state, while others are very sensitive to the equation of state. Recent observations of neutron stars from pulsar timing, quiescent X-ray emission from binaries, and Type I X-ray bursts can set important constraints on the structure of neutron stars and the underlying equation of state. In addition, measurements of thermal radiation from neutron stars has uncovered the possible existence of neutron and proton superfluidity/superconductivity in the core of a neutron star, as well as offering powerful evidence that typical neutron stars have significant crusts. These observations impose constraints on the existence of strange quark matter stars, and limit the possibility that abundant deconfined quark matter or hyperons exist in the cores of neutron stars.

  9. Delta Scuti stars: Theory

    SciTech Connect

    Guzik, J.A.

    1998-03-01

    The purpose of asteroseismology is not only to derive the internal structure of individual stars from their observed oscillation frequencies, but also to test and extend one`s understanding of the physics of matter under the extremes of temperature, density, and pressure found in stellar interiors. In this review, the author hopes to point out what one can learn about the Sun by studying {delta} Scuti stars, as well as what one can learn about stars more massive or evolved than the Sun. He discusses some of the difficulties in theoretical approaches to asteroseismology for {delta} Scuti stars, using FG Vir, {delta} Scuti, and CD-24{degree} 7599 as examples.

  10. Massive soliton stars

    NASA Astrophysics Data System (ADS)

    Chiu, Hong-Yee

    1990-05-01

    The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of soliton stars. The possibility of primordial creation of soliton stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside soliton stars, the luminosity of soliton stars is not determined by its radiative transfer characteristics, and the surface temperature of soliton stars can be the same as its interior temperature. It is possible that soliton stars are intense X-ray radiators at large distances. Soliton stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside soliton stars during early epochs of the universe. In addition, if soliton stars exist they could assume the role played by massive black holes in galactic centers.

  11. Combinations of 148 navigation stars and the star tracker

    NASA Technical Reports Server (NTRS)

    Duncan, R.

    1980-01-01

    The angular separation of all star combinations for 148 nav star on the onboard software for space transportation system-3 flight and following missions is presented as well as the separation of each pair that satisfies the viewing constraints of using both star trackers simultaneously. Tables show (1) shuttle star catalog 1980 star position in M 1950 coordinates; (2) two star combination of 148 nav stars; and (3) summary of two star-combinations of the star tracker 5 deg filter. These 148 stars present 10,875 combinations. For the star tracker filters of plus or minus 5 deg, there are 875 combinations. Formalhaut (nav star 26) has the best number of combinations, which is 33.

  12. The Lick Observatory CCD data acquisition system

    NASA Technical Reports Server (NTRS)

    Robinson, L. B.; Stover, R. J.

    1987-01-01

    An evolving system for CCD data acquisition is described. The electronics are subdivided into those attached to the dewar, a 'smart' controller near the dewar, and a computer connected by serial link to the smart controller. Software for the smart controller is in assembler code, while the data acquisition and on-line analysis software is written in 'C' and uses the UNIX operating system.

  13. The Lick Observatory Hamilton Echelle Spectrometer

    Microsoft Academic Search

    Steven S. Vogt

    1987-01-01

    The Hamilton Echelle Spectrometer, installed at the coude focus of the Shane 3-m telescope, is a high-dispersion spectrograph optimized for use with today's largest available CCDs, and for the even larger CCDs expected in the future. It was designed primarily for high-resolution (R = 30,000 to 60,000) wide-bandpass spectroscopy of point-like sources down to a limiting magnitude of about V

  14. Scope on the Skies: Star Light, Star Bright

    NSDL National Science Digital Library

    Bob Riddle

    2009-03-01

    In astronomy, the brightness of a star is described in terms of a star’s magnitude. Stellar magnitude is expressed two different ways, using the terms apparent magnitude and absolute magnitude. For both magnitudes, the numbering scale is the same, with negative numbers being brighter stars and positive numbers being dimmer stars. This month’s column sheds light on the stars and how astronomers measure distances to these celestial objects.

  15. Neutron star models

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Bowers, R. L.

    1981-01-01

    The current state of neutron star structure calculations is reviewed. Uncertainties in the equation of state for matter at and above nuclear density remain. The role of the delta resonance, pion condensates, and quark matter is reviewed. It is found that recent models yield stable neutron star masses which are consistent with observational estimates.

  16. Party with the Stars.

    ERIC Educational Resources Information Center

    Blaine, Lloyd

    1997-01-01

    Describes a Star Party which involves comparing the different colors of the stars, demonstrating how astronomers measure the sky with degrees, determining the cardinal direction, discussing numerous stories that ancient civilizations gave to constellations, exercising science process skills, and using science instruments. (JRH)

  17. Science Through ARts (STAR)

    NASA Technical Reports Server (NTRS)

    Kolecki, Joseph; Petersen, Ruth; Williams, Lawrence

    2002-01-01

    Science Through ARts (STAR) is an educational initiative designed to teach students through a multidisciplinary approach to learning. This presentation describes the STAR pilot project, which will use Mars exploration as the topic to be integrated. Schools from the United Kingdom, Japan, the United States, and possibly eastern Europe are expected to participate in the pilot project.

  18. Lithium in Evolved Stars

    Microsoft Academic Search

    Daniel D. Hiltgen; Christopher Sneden

    1994-01-01

    I. Lithium in F-G Giants at the Rotational Break As a star crosses the Hertzprung Gap, its surface rotational velocity declines abruptly between between spectral types G0 and G3 III. This rotational break must in large part be due to the growth of of the convective envelope and, thus, the star must exhibit a decline of the surface Li abundance.

  19. White dwarf stars

    Microsoft Academic Search

    J. Liebert

    1980-01-01

    Observations and properties of white-dwarf stars are reviewed. Observational constraints are discussed in terms of methods of discovery, selection effects, white dwarfs in binaries and clusters, stellar colors, spectral types, and kinematic properties. The following stellar and atmospheric parameters are examined: astrometric masses and radii; temperatures, radii, and gravities of DA stars; abundances in white dwarfs with helium atmospheres; and

  20. StarLogo TNG

    Microsoft Academic Search

    Eric Klopfer; Hal Scheintaub; Wendy Huang; Daniel Wendel

    2009-01-01

    Computational approaches to science are radically altering the nature of scientific investigatiogn. Yet these computer programs and simulations are sparsely used in science education, and when they are used, they are typically ``canned'' simulations which are black boxes to students. StarLogo The Next Generation (TNG) was developed to make programming of simulations more accessible for students and teachers. StarLogo TNG

  1. Science through ARts (STAR)

    ERIC Educational Resources Information Center

    Densmore, Marycay; Kolecki, Joseph C.; Miller, Allan; Petersen, Ruth; Terrell, Mike

    2005-01-01

    Science Through ARts (STAR) is a free, international, cross-curricular program thematically aligned with "The Vision for Space Exploration," a framework of goals and objectives published by NASA in February 2004. Through the STAR program, students in grades 5 through 12 are encouraged to apply their knowledge in creative ways as they approach a…

  2. The Violent Neutron Star

    NASA Astrophysics Data System (ADS)

    Watts, A. L.

    2012-12-01

    Neutron stars enable us to study both the highest densities and the highest magnetic fields in the known Universe. In this article I review what can be learned about such fundamental physics using magnetar bursts. Both the instability mechanisms that trigger the bursts, and the subsequent dynamical and radiative response of the star, can be used to explore stellar and magnetospheric structure and composition.

  3. Colors of Stars

    NSDL National Science Digital Library

    David Joiner

    The Colors of Stars Lesson studies how we study temperature of objects through the radiation they emit. This lesson has the student compare three stars in Orion (one red, one whitish-blue, one deep blue) and try to determine which is hottest and which is coolest.

  4. Dissolving star cluster candidates

    Microsoft Academic Search

    E. Bica; B. X. Santiago; C. M. Dutra; H. Dottori; M. R. de Oliveira; D. Pavani

    2001-01-01

    We present a list of 34 neglected entries from star cluster catalogues located at relatively high galactic latitudes (|b| > 15deg) which appear to be candidate late stages of star cluster dynamical evolution. Although underpopulated with respect to usual open clusters, they still present a high number density contrast as compared to the galactic field. This was verified by means

  5. Carbon star effective temperatures

    Microsoft Academic Search

    S. T. Ridgway; G. H. Jacoby; R. R. Joyce; D. C. Wells

    1981-01-01

    Possible methods for measuring the effective temperatures of individual carbon stars are discussed. Since calibrations of broad or narrow-band photometric colors is impractical at present, empirical corrections to narrow band color temperatures is the only valid procedure. The effective temperature of the star TW Oph is estimated, based on preliminary reduction of the occultation and associated photometry

  6. Star spot location estimation using Kalman filter for star tracker.

    PubMed

    Liu, Hai-bo; Yang, Jian-kun; Wang, Jiong-qi; Tan, Ji-chun; Li, Xiu-jian

    2011-04-20

    Star pattern recognition and attitude determination accuracy is highly dependent on star spot location accuracy for the star tracker. A star spot location estimation approach with the Kalman filter for a star tracker has been proposed, which consists of three steps. In the proposed approach, the approximate locations of the star spots in successive frames are predicted first; then the measurement star spot locations are achieved by defining a series of small windows around each predictive star spot location. Finally, the star spot locations are updated by the designed Kalman filter. To confirm the proposed star spot location estimation approach, the simulations based on the orbit data of the CHAMP satellite and the real guide star catalog are performed. The simulation results indicate that the proposed approach can filter out noises from the measurements remarkably if the sampling frequency is sufficient. PMID:21509065

  7. Lives and Deaths of Stars

    NSDL National Science Digital Library

    Strobel, Nick

    Stars live for a very long time compared to human lifetimes. Your great, great grandparents saw the same stars as you will see tonight (if it's clear). Our lifetimes are measured in years. Star lifetimes are measured in millions of years. Even though star timescales are enormous, it is possible to know how stars are born, live, and die. This chapter covers the stages a star will go through in its life and how it was figured out. The last part of the chapter will cover the remains of stars, white dwarfs, neutron stars, and the Hollywood favorite: black holes.

  8. Star Formation Thresholds

    NASA Astrophysics Data System (ADS)

    Schaye, Joop

    2008-05-01

    To make predictions for the existence of “dark galaxies”, it is necessary to understand what determines whether a gas cloud will form stars. Star formation thresholds are generally explained in terms of the Toomre criterion for gravitational instability. I contrast this theory with the thermo-gravitational instability hypothesis of Schaye (2004), in which star formation is triggered by the formation of a cold gas phase and which predicts a nearly constant surface density threshold. I argue that although the Toomre analysis is useful for the global stability of disc galaxies, it relies on assumptions that break down in the outer regions, where star formation thresholds are observed. The thermo-gravitational instability hypothesis can account for a number of observed phenomena, some of which were thought to be unrelated to star formation thresholds.

  9. Revised Anatomy of Stars

    E-print Network

    Dubin, M; Dubin, Maurice; Soberman, Robert K.

    1997-01-01

    Stars accrete near invisible hydrogen dominated agglomerates. This population, the `dark matter,' effects the nature of stars. Measurements show plasma streams impacting Earth, planets, Sun and stars. This mass-energy source contradicts nebula collapse model for stars. The visual derived model, to which later discoveries (e.g., fusion) were appended, is confounded and contradicted by new observations. Discovery of a quantity of beryllium 7 (53 day half-life) in the Earth's upper atmosphere, fusion produced, hence from the solar outer zone, proves core fusion wrong. Magnetically pinched plasmas from aggregates impact stars at hundreds of km/s, create impulsive conditions for nuclear explosions below the surface. Disks with planets aid cluster capture. Planets modulate the influx varying fusion, hence luminosity (e.g., solar cycle). This population, with no assumptions or ad hoc physics, explains mysterious phenomena, e.g., luminosity/wind variation, sunspots, high temperature corona, CMEs, etc. Standard explan...

  10. 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.

  11. The Brightest Carbon Stars

    E-print Network

    Cheryl Frost; Robert Cannon; John Lattanzio; Peter Wood; Manuel Forestini

    1997-10-06

    It is currently accepted that Hot-Bottom-Burning (HBB) in intermediate-mass asymptotic giant branch (AGB) stars prevents the formation of C~stars. Nevertheless, we present in this paper the results of some detailed evolutionary calculations which show that even with HBB we obtain C~stars at the highest luminosities reached on the AGB. This is due to mass-loss reducing the envelope mass so that HBB ceases but dredge-up continues. The high mass-loss rate produces an optically thick wind before the star reaches C/O>1. This is consistent with the recent results of van Loon et al. (1997a,b) who find obscured C~stars in the Magellanic Clouds at luminosities up to M_{bol} = -6.8.

  12. Ages of young stars

    E-print Network

    Soderblom, David R; Jeffries, Rob D; Mamajek, Eric E; Naylor, Tim

    2013-01-01

    Determining the sequence of events in the formation of stars and planetary systems and their time-scales is essential for understanding those processes, yet establishing ages is fundamentally difficult because we lack direct indicators. In this review we discuss the age challenge for young stars, specifically those less than ~100 Myr old. Most age determination methods that we discuss are primarily applicable to groups of stars but can be used to estimate the age of individual objects. A reliable age scale is established above 20 Myr from measurement of the Lithium Depletion Boundary (LDB) in young clusters, and consistency is shown between these ages and those from the upper main sequence and the main sequence turn-off -- if modest core convection and rotation is included in the models of higher-mass stars. Other available methods for age estimation include the kinematics of young groups, placing stars in Hertzsprung-Russell diagrams, pulsations and seismology, surface gravity measurement, rotation and activ...

  13. Extreme Horizontal Branch Stars

    E-print Network

    Ulrich Heber

    2008-04-03

    A review is presented on the properties, origin and evolutionary links of hot subluminous stars which are generally believed to be extreme Horizontal Branch stars or closely related objects. Amongst the field stars a large fraction of sdBs are found to reside in close binaries. The companions are predominantly white dwarfs, or low mass main sequence stars. Systems with sufficiently massive WD companions may qualify as SN Ia progenitors. Recently evidence has been found that the masses of some unseen companions might exceed the Chandrasekhar mass, hence they must be neutron stars or black holes. Even a planet has recently been detected orbiting the pulsating sdB star V391 Peg. Quite to the opposite, in globular clusters, only very few sdB binaries are found indicating that the dominant sdB formation processes is different in a dense environment. Binary population synthesis models identify three formation channels, (i) stable Roche lobe overflow, (ii) one or two common envelope ejection phases and (iii) the merger of two helium white dwarfs. The latter channel may explain the properties of the He-enriched sdO stars because their binary fraction is lower than that of the sdBs by a factor of ten or more. Pulsating subluminous B (sdB) stars play an important role for asteroseismology as this technique has already led to mass determinations for a handful of stars. A unique hyper-velocity sdO star moving so fast that it is unbound to the Galaxy has probably been ejected by the super-massive black hole in the Galactic centre. (abridged)

  14. Catch a Star!

    NASA Astrophysics Data System (ADS)

    2006-11-01

    ESO and the European Association for Astronomy Education are launching today the 2007 edition of 'Catch a Star!', their international astronomy competition for school students. Now in its fifth 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. Students are invited to 'become astronomers' and embark on a journey to explore the Universe. ESO PR Photo 42/06 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. For the artistically minded, 'Catch a Star!' also includes an artwork competition, 'Catch a Star Artists'. "'Catch a Star!' offers a unique opportunity for students to learn more about astronomy and about the methods scientists use to discover new things about the Universe", said Douglas Pierce-Price, Education Officer at ESO. In teams, students choose an astronomical topic to study and produce an in-depth report. An important part of the project for 'Catch a Star Researchers' is to think about how ESO's telescopes or a telescope of the future can contribute to their investigations of the subject. As well as the top prize - a trip to one of ESO's observatory sites in Chile - visits to observatories in Germany, Austria and Spain, and many other prizes are also available to 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 chosen with the help of a public online vote. The first editions of 'Catch a Star!' have attracted several hundred entries from more than 25 countries worldwide. Previous winning entries have included "Star clusters and the structure of the Milky Way" (Budapest, Hungary), "Vega" (Acqui Terme, Italy) and "Venus transit" (Lleida, Spain). Some previous winning entries are visible on the Catch a Star! Web site. Detailed entry information can be found on ESO's website, at http://www.eso.org/catchastar/ The deadline for submitting an entry for the 2007 competition is Friday 2 March 2007, 17:00 Central European Time.

  15. Planets of young stars

    E-print Network

    E. W. Guenther; E. Esposito

    2007-01-10

    Since the first massive planet in a short period orbit was discovered, the question arised how such an object could have formed. There are basically two formation scenarios: migration due to planet-disk or planet-planet interaction. Which of the two scenarios is more realistic can be found out by observing short-period planets of stars with an age between 10E7 and 10E8 yrs. The second aim of the survey is to find out how many planets originally formed, and how many of these are destroyed in the first Gyrs: Do most young, close-in planets evaporate, or spiral into the host stars? In here we report on the first results of a radial-velocity search program for planets of young stars which we began in 2004. Using HARPS, we currently monitor 85 stars with ages between 10E7 and 10E8 yrs. We show that the detection of planets of young stars is possible. Up to now, we have identified 3 planet-candidates. Taking this result together with the results of other surveys, we conclude that the frequency of massive-short period planets of young stars is not dramatically higher than that of old stars.

  16. O(He) Stars

    E-print Network

    T. Rauch; E. Reiff; K. Werner; J. W. Kruk

    2008-04-15

    Spectral analyses of H-deficient post-AGB stars have shown that a small group of four extremely hot objects exists which have almost pure He absorption-line spectra in the optical. These are classified as O(He) stars. For their evolution there are two scenarios: They could be the long-sought hot successors of RCrB stars, which have not been identified up to now. If this turns out to be true, then a third post-AGB evolutionary sequence is revealed, which is probably the result of a double-degenerate merging process. An alternative explanation might be that O(He) stars are post early-AGB stars. These depart from the AGB just before they experience their first thermal pulse (TP) which will then occur as a late thermal pulse (LTP). This would be a link to the low-mass He-enriched sdO stars and low-mass, particularly He-rich PG1159 stars.

  17. Measuring stars with Gaia

    NASA Astrophysics Data System (ADS)

    Thévenin, F.

    2013-12-01

    Beyond the extraordinary three dimensional map that Gaia will create for a billion of stars, it will reveal the origin and history of the Milky Way as the major goal. This does not weakness the fantastic impact of Gaia on the stellar physic. It will put constraints on the modeling of stars to an extreme that consequently new input physics will be mandatory to understand a Gaia HR diagram. Stars are formed in populations and evolve as collection of objects revealing important clues on how they formed, what kind of mass function is active during the star formation, how frequent is the star formation, all of this is imprinted in the intrinsic properties of stars that large surveys combined together like Gaia, Kepler, PLATO will revealed. The characterization of stars hosting planets is also a goal of such combination of large surveys and in particular of the measure of distances in the Galaxy. The launch of Gaia is for November of 2013 and the output catalogue is expected for 2020. Then will start the beginning of a new Astrophysics touching so many topics that a new age of astrophysics is then foreseen.

  18. Nucleosynthesis In Binary Stars

    NASA Astrophysics Data System (ADS)

    Izzard, Robert G.

    2004-01-01

    Galactic chemical evolution models require stellar nucleosynthesis yields as input data. Stellar evolution models are used to calculate such yields but do not take into account the fact that many stars are in binaries. The computing time required to explore the binary star parameter space is usually considered to be prohibitively large. Therefore binaries, except for type Ia supernovae and novae which are included in an ad hoc way, are ignored in most Galactic chemical evolution models. In this dissertation synthetic nucleosynthesis models are developed which approximate full stellar evolution models. Cunning methods are employed to model shell burning in low- and intermediate-mass stars while high-mass stars have their surface abundances fitted to their mass. Explosive yields are fitted to published results. The synthetic nucleosynthesis model, with the addition of algorithms to deal with mass transfer in binaries, is coupled to a rapid binary star evolution code. The use of a synthetic model speeds up the calculation of stellar yields by a factor of about 107 and extends the analysis to binary stars. Single- and binary-star yields are calculated for a range of initial mass and separation distributions. A change in the primary or single-star mass distribution is most significant. Changing the secondary mass or separation distribution has a smaller effect. Consideration is then given to variation of the input physics to determine which free parameters are important for the calculation of yields from single and binary stars. It is found that certain parameters are important for some isotopes. Future prospects are then briefly discussed.

  19. Life Products of Stars

    E-print Network

    Aldo M. Serenelli; Masataka Fukugita

    2006-06-27

    We attempt to document complete energetic transactions of stars in their life. We calculate photon and neutrino energies that are produced from stars in their each phase of evolution from 1 to 8 M_sun, using the state-of-the-art stellar evolution code, tracing the evolution continuously from pre-main sequence gravitational contraction to white dwarfs. We also catalogue gravitational and thermal energies and helium, and heavier elements that are stored in stars and those ejected into interstellar space in each evolutionary phase.

  20. Superradiance in stars

    NASA Astrophysics Data System (ADS)

    Cardoso, Vitor; Brito, Richard; Rosa, João L.

    2015-06-01

    It has long been known that dissipation is a crucial ingredient in the superradiant amplification of wave packets off rotating objects. We show that, once appropriate dissipation mechanisms are included, stars are also prone to superradiance and superradiant instabilities. In particular, ultralight dark matter with small interaction cross section with the star material or self-annihilation can trigger a superradiant instability. On long time scales, the instability strips the star of most of its angular momentum. Whether or not new stationary configurations surrounded by scalar condensates exist remains to be seen.

  1. Kepler Star Wheels

    NSDL National Science Digital Library

    2013-07-14

    This is a make-it-yourself planisphere designed to show where Kepler is pointing. Learners can use it to locate exoplanets around stars in the night sky. It comes with two wheels: one with coordinate grid for plotting additional exoplanet stars and one without grid that is easier to read; and two holders for varying latitudes (one for 30°-50° and one for 50°-70°). The product is updated approximately annually to incorporate improvements and any newly discovered planets orbiting naked eye stars.

  2. Hyperons in neutron stars

    NASA Astrophysics Data System (ADS)

    Katayama, Tetsuya; Saito, Koichi

    2015-07-01

    Using the Dirac-Brueckner-Hartree-Fock approach, the properties of neutron-star matter including hyperons are investigated. In the calculation, we consider both time and space components of the vector self-energies of baryons as well as the scalar ones. Furthermore, the effect of negative-energy states of baryons is partly taken into account. We obtain the maximum neutron-star mass of 2.08M?, which is consistent with the recently observed, massive neutron stars. We discuss a universal, repulsive three-body force for hyperons in matter.

  3. Strange nonchaotic stars.

    PubMed

    Lindner, John F; Kohar, Vivek; Kia, Behnam; Hippke, Michael; Learned, John G; Ditto, William L

    2015-02-01

    The unprecedented light curves of the Kepler space telescope document how the brightness of some stars pulsates at primary and secondary frequencies whose ratios are near the golden mean, the most irrational number. A nonlinear dynamical system driven by an irrational ratio of frequencies generically exhibits a strange but nonchaotic attractor. For Kepler's "golden" stars, we present evidence of the first observation of strange nonchaotic dynamics in nature outside the laboratory. This discovery could aid the classification and detailed modeling of variable stars. PMID:25699444

  4. Gamma Cassiopeiae and Be stars

    NASA Astrophysics Data System (ADS)

    Whitehorne, Mary Lou

    1989-10-01

    A brief review of recent literature is presented regarding the complex nature of Be stars. Be stars may represent an extreme example of processes occurring to a much lesser degree in several types of normal stars. The three major spectral phase changes observed in Be stars are demonstrated.

  5. Can Boltzmann Soliton Star Exist?

    NASA Astrophysics Data System (ADS)

    Su, Rukeng; Chen, Xuelei; Pan, Rongshi

    1992-12-01

    The fermion soliton stars suggested by Lee and Pang are extended to finite temperature. The degeneracy temperature TD above which the fermion soliton star will become a Boltzmann soliton star is given. We prove that the Boltzmann soliton star cannot exist, because it is unstable.

  6. Coalescence of compact binary stars with a quark star component

    NASA Astrophysics Data System (ADS)

    Koshy, Sam

    Coalescing compact star binaries are among the most promising sources for the next generation of gravitational detectors. Accurate theoretical waveform templates are required to extract their gravitational wave signal from noisy data and it is expected that about 10 mergers per year (or more) of such binaries will be found by these upcoming detectors. If these binaries tidally lock/synchronize, where synchronization is facilitated by a large viscosity for the stellar fluid, then their inspiral is accelerated. This will result in a phase mismatch between the signal and templates and failure to include these contributions from tidal synchronization can hamper detection. Bildsten and Cutler in 1992 studied tidal synchronization in neutron star-neutron star and black hole-neutron star binaries, and found that the viscosity of the neutron star was too small Here we study the same effect but in binaries with a quark star component. What makes quark stars different from neutron stars is that (a) quark matter can potentially have large viscosities and (b) unlike neutron stars, quark stars do not have a theoretical lower mass limit. These two features imply that quark stars could tidally synchronize under some extreme conditions on certain parameters, unlike neutron stars which never synchronize. Thus, the gravitational wave signal can be used to detect and differentiate quark stars from ordinary neutron stars. One important feature of inspiraling binaries during the final stages of the inspiral is the possibility of mass transfer, which can further alter the expected gravitational wave signal Therefore, we study the conditions necessary for stable mass transfer in the neutron star-quark star binary system and determine that the most likely scenario at this stage is unstable mass transfer from the neutron star to the quark star. Finally, we examine the fate of the binary system after tidal synchronization is achieved. We propose a variational study of tidal synchronization based on the work of Lai et al. in 1994, which accounts for deformations of the component stars of the neutron star-quark star binary. Using a newly devised polytropic equation of state for quark stars, we expect the stars to remain tidally synchronized although more sophisticated numerics will be required to prove this. Our main conclusion is that gravitational waves can discriminate between neutron star-neutron star binaries and neutron star-quark star binaries, but only if one assumes an extreme selection of theoretical parameters. In practice, this distinction may therefore be very difficult to achieve.

  7. The Auger Star Monitor

    NASA Astrophysics Data System (ADS)

    Diaz, Johana; Nitz, David; Fick, Brian

    2006-04-01

    The Auger Star Monitor (ASM) is designed to automatically measure the total vertical atmospheric extinction above the Auger Observatory. The system continually takes wide-field CCD images of the night sky through a Johnson U-Band filter. Photometry is performed on the star images. The change in recorded star brightness as a function of zenith angle is used to obtain values for the integrated density of atmospheric scattering components. The MTU group has installed two ASMs; one at the Southern Observatory atop the Los Leones Fluorescence Detector building and one at the future site of the Northern Observatory in Colorado. Both of these units have been routinely operating during the past year. Much of our effort has turned to developing better data-reduction algorithms and automated software. Significant work has done to perfect the algorithms for image processing, star identification and photometry. Partial results of extinction coefficients obtained by the ASM will be presented.

  8. Stars resembling the Sun

    NASA Astrophysics Data System (ADS)

    Cayrel de Strobel, G.

    This review is primarily directed to the question whether photometric solar analogues remain such when subjected to detailed spectroscopic analyses and interpreted with the help of internal stucture models. In other words, whether the physical parameters: mass, chemical composition, age (determining effective temperature and luminosity), chromospheric activity, equatorial rotation, lithium abundance, velocity fields etc., we derive from the spectral analysis of a photometric solar analogue, are really close to those of the Sun. We start from 109 photometric solar analogues extracted from different authors. The stars selected had to satisfy three conditions: i) their colour index (B-V) must be contained in the interval: ? (B-V) = 0.59-0.69, ii) they must possess a trigonometric parallax, iii) they must have undergone a high resolution detailed spectroscopic analysis. First, this review presents photometric and spectrophotometric researches on solar analogues and recalls the pionneering work on these stars by the late Johannes Hardorp. After a brief discussion on low and high resolution spectroscopic researches, a comparison is made between effective temperatures as obtained, directly, from detailed spectral analyses and those obtained, indirectly, from different photometric relations. An interesting point in this review is the discussion on the tantalilizing value of the (B-V)solar of the Sun, and the presentation of a new reliable value of this index. A short restatement of the kinematic properties of the sample of solar analogues is also made. And, finally, the observational ( T eff, M bol) diagram, obtained with 99 of the initially presented 109 analogues, is compared to a theoretical ( T eff, M bol) diagram. This latter has been constructed with a grid of internal structure models for which, (very important for this investigation), the Sun was used as gauge. In analysing the position, with respect to the Sun, of each star we hoped to find a certain number of stars tightly neighbouring the Sun in mass, chemical composition and state of evolution. The surprising result is that the stars occupy in this HR Diagram a rather extended region around the Sun, many of them seem more evolved and older than the Sun, and only 4 of the evolved stars seem younger. The age of some stars in the sample is also discussed in terms of chromospheric activity and Li-content. Our conclusion is much the same as that contained in previous papers we have written on the subject: in spite of a much larger number of stars, we have not been able to nominate a single star of the sample for a ``perfect good solar twin''. Another aim in beginning, 25 years ago, this search for solar analogues, was to have ready a bunch of stars resembling the Sun and analysed spectroscopically in detail, in order that, when planets hunters of solar type stars, finally would have found such a specimen, we would have been able to immediately compare the physical parameters of this star to those of the Sun. We have been lucky enough: one of the good solar analogues we present herewith, is 51 Pegasi (HD 217014) which, according to the very recent observations by Mayor and Queloz (1995), has a planet orbiting around it. And what is more: two other stars possessing planets: 47 Ursae Majoris (HD 95128) and 70 Virginis (HD 117176), have just been discovered by Marcy and Butler (187th Meeting of the AAS, January 1996). One of them, 47 Ursae Majoris, is also included in the list of photometric solar analogues. The other star, 70 Virginis, has only been included after the ``Planets News'', because the colour index (B-V) of this star is slightly higher than the prescribted limit of the selection, (B-V = 0.71, instead, 0.69). It would have been a pity to leave the third '' planet star out of the competition.

  9. The origin of stars

    NASA Astrophysics Data System (ADS)

    Smith, Michael D.

    Where do stars come from and how do they form? These are profound questions which link the nature of our Universe to the roots of mankind. Yet, until a recent revolution in understanding, the proposed answers have been raw speculation. Now, accompanying penetrating observations, a new picture has come into prominence. This book presents the latest astounding observations and scientific ideas covering star formation, star birth and early development. It encompasses all aspects, from the dramatic stories of individual objects, to the collective influence of entire stellar systems. The very first stars to come into existence and the nurturing of planets are discussed to provide the reader with a comprehensive overview. Presenting background information with only the essential mathematics, this book will appeal to scientists wishing to expand their horizons, students seeking solid foundations, and general readers with enquiring minds.

  10. Cooling of neutron stars

    NASA Technical Reports Server (NTRS)

    Pethick, C. J.

    1992-01-01

    It is at present impossible to predict the interior constitution of neutron stars based on theory and results from laboratory studies. It has been proposed that it is possible to obtain information on neutron star interiors by studying thermal radiation from their surfaces, because neutrino emission rates, and hence the temperature of the central part of a neutron star, depend on the properties of dense matter. The theory predicts that neutron stars cool relatively slowly if their cores are made up of nucleons, and cool faster if the matter is in an exotic state, such as a pion condensate, a kaon condensate, or quark matter. This view has recently been questioned by the discovery of a number of other processes that could lead to copious neutrino emission and rapid cooling.

  11. Strangeness in Neutron Stars

    E-print Network

    Weber, F; Negreiros, R P; Rosenfield, P; Weber, Fridolin; Ho, Alexander; Negreiros, Rodrigo P.; Rosenfield, Philip

    2006-01-01

    It is generally agreed on that the tremendous densities reached in the centers of neutron stars provide a high-pressure environment in which several intriguing particles processes may compete with each other. These range from the generation of hyperons to quark deconfinement to the formation of kaon condensates and H-matter. There are theoretical suggestions of even more exotic processes inside neutron stars, such as the formation of absolutely stable strange quark matter. In the latter event, neutron stars would be largely composed of strange quark matter possibly enveloped in a thin nuclear crust. This paper gives a brief overview of these striking physical possibilities with an emphasis on the role played by strangeness in neutron star matter, which constitutes compressed baryonic matter at ultra-high baryon number density but low temperature which is no accessible to relativistic heavy ion collision experiments.

  12. Strangeness in Neutron Stars

    E-print Network

    Weber, F

    2001-01-01

    It is generally agreed on that the tremendous densities reached in the centers of neutron stars provide a high-pressure environment in which numerous novel particles processes are likely to compete with each other. These processes range from the generation of hyperons to quark deconfinement to the formation of kaon condensates and H-matter. There are theoretical suggestions of even more exotic processes inside neutron stars, such as the formation of absolutely stable strange quark matter, a configuration of matter even more stable than the most stable atomic nucleus, iron. In the latter event, neutron stars would be largely composed of pure quark matter, eventually enveloped in a thin nuclear crust. No matter which physical processes are actually realized inside neutron stars, each one leads to fingerprints, some more pronounced than others though, in the observable stellar quantities. This feature combined with the unprecedented progress in observational astronomy, which allows us to see vistas with remarkab...

  13. Masers and star formation

    E-print Network

    Vincent L. Fish

    2007-04-02

    Recent observational and theoretical advances concerning astronomical masers in star forming regions are reviewed. Major masing species are considered individually and in combination. Key results are summarized with emphasis on present science and future prospects.

  14. Masers and star formation

    Microsoft Academic Search

    Vincent L. Fish

    2007-01-01

    Recent observational and theoretical advances concerning astronomical masers in star forming regions are reviewed. Major masing species are considered individually and in combination. Key results are summarized with emphasis on present science and future prospects.

  15. Soft Physics from STAR

    E-print Network

    Fuqiang Wang

    2005-10-27

    New results on soft hadron distributions and correlations measured with the STAR experiment are presented. Knowledge about the bulk properties of relativistic heavy-ion collisions offered by these results is discussed.

  16. Inside a Star . . .

    ERIC Educational Resources Information Center

    Akerman, Jane; Wentzel, Donat G.

    1973-01-01

    Describes classroom activities to understand the evolution of elements as it occurs in the stars. Activities can be undertaken in groups. Explicit instructions and background materials are included. (PS)

  17. Dissolving star cluster candidates

    E-print Network

    E. Bica; B. X. Santiago; C. M. Dutra; H. Dottori; M. R. de Oliveira; D. Pavani

    2000-11-14

    We present a list of 34 neglected entries from star cluster catalogues located at relatively high galactic latitudes ($|b| >$ 15$^{\\circ}$) which appear to be candidate late stages of star cluster dynamical evolution. Although underpopulated with respect to usual open clusters, they still present a high number density contrast as compared to the galactic field. This was verified by means of (i) predicted model counts from different galactic subsystems in the same direction, and (ii) Guide Star Catalog equal solid angle counts for the object and surrounding fields. This suggests that the objects are physical systems, possibly star clusters in the process of disruption or their fossil remains. The sample will be useful for followup studies in view of verifying their physi cal nature.

  18. Dissolving star cluster candidates

    E-print Network

    Bica, E; Dutra, C M; Dottori, H; De Oliveira, M R; Pavani, D B

    2001-01-01

    We present a list of 34 neglected entries from star cluster catalogues located at relatively high galactic latitudes ($|b| >$ 15$^{\\circ}$) which appear to be candidate late stages of star cluster dynamical evolution. Although underpopulated with respect to usual open clusters, they still present a high number density contrast as compared to the galactic field. This was verified by means of (i) predicted model counts from different galactic subsystems in the same direction, and (ii) Guide Star Catalog equal solid angle counts for the object and surrounding fields. This suggests that the objects are physical systems, possibly star clusters in the process of disruption or their fossil remains. The sample will be useful for followup studies in view of verifying their physi cal nature.

  19. The lambda Bootis stars

    E-print Network

    E. Paunzen

    1998-05-06

    In this article the current knowledge of the group of lambda Bootis stars is reviewed. These metal poor objects are quite outstanding compared to other chemically peculiar stars of the upper main sequence. Up to now no theory has been developed which is able to explain the majority of observational results. This article is mainly focused on the work which needs to be done in the future in order to clarify the lambda Bootis phenomenon.

  20. Matter accreting neutron stars

    SciTech Connect

    Meszaros, P.

    1981-09-01

    Some of the fundamental neutron star parameters, such as the mass and the magnetic field strength, were experimentally determined in accreting neutron star systems. Some of the relevant data and the models used to derive useful information from them, are reviewed concentrating mainly on X-ray pulsars. The latest advances in our understanding of the radiation mechanisms and the transfer in the strongly magnetized polar cap regions are discussed.

  1. Bubbly Little Star

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In this processed Spitzer Space Telescope image, baby star HH 46/47 can be seen blowing two massive 'bubbles.' The star is 1,140 light-years away from Earth.

    The infant star can be seen as a white spot toward the center of the Spitzer image. The two bubbles are shown as hollow elliptical shells of bluish-green material extending from the star. Wisps of green in the image reveal warm molecular hydrogen gas, while the bluish tints are formed by starlight scattered by surrounding dust.

    These bubbles formed when powerful jets of gas, traveling at 200 to 300 kilometers per second, or about 120 to 190 miles per second, smashed into the cosmic cloud of gas and dust that surrounds HH 46/47. The red specks at the end of each bubble show the presence of hot sulfur and iron gas where the star's narrow jets are currently crashing head-on into the cosmic cloud's gas and dust material.

    Whenever astronomers observe a star, or snap a stellar portrait, through the lens of any telescope, they know that what they are seeing is slightly blurred. To clear up the blurring in Spitzer images, astronomers at the Jet Propulsion Laboratory developed an image processing technique for Spitzer called Hi-Res deconvolution.

    This process reduces blurring and makes the image sharper and cleaner, enabling astronomers to see the emissions around forming stars in greater detail. When scientists applied this image processing technique to the Spitzer image of HH 46/47, they were able to see winds from the star and jets of gas that are carving the celestial bubbles.

    This infrared image is a three-color composite, with data at 3.6 microns represented in blue, 4.5 and 5.8 microns shown in green, and 24 microns represented as red.

  2. Star of Bethlehem

    NASA Astrophysics Data System (ADS)

    Hughes, D.; Murdin, P.

    2001-07-01

    The biblical Star of Bethlehem, which heralded the birth of Jesus Christ, is only mentioned in the Gospel of St Matthew 2. The astrologically significant 7 bc triple conjunction of Jupiter and Saturn in the constellation of Pisces is the most likely candidate, although a comet/nova in 5 bc and a comet in 4 bc cannot be ruled out. There is also the possibility that the star was simply fictitious....

  3. Holographic Neutron Stars

    E-print Network

    Jan de Boer; Kyriakos Papadodimas; Erik Verlinde

    2009-07-23

    We construct in the context of the AdS/CFT correspondence degenerate composite operators in the conformal field theory that are holographically dual to degenerate stars in anti de Sitter space. We calculate the effect of the gravitational back-reaction using the Tolman-Oppenheimer-Volkoff equations, and determine the "Chandrasekhar limit" beyond which the star undergoes gravitational collapse towards a black hole.

  4. Jars of Stars

    NSDL National Science Digital Library

    Children's Museum of Houston

    2014-09-19

    This math activity uses stars, jars, and scoops to help learners build their estimation and volume skills. As you play, estimate how many scoops of stars it will take to fill a variety of jars. This activity helps learners estimate, predict, reason, strategize, measure volumes, multiply, divide and practice fractions. The activity guide contains a material list, sample questions to ask, literary connections, extensions, and alignment to local and national standards.

  5. Cold Hybrid Star Properties

    SciTech Connect

    Moshfegh, H. R.; Darehmoradi, M.; Mojarrad, M. Ghazanfari [Department of Physics, University of Tehran, North Kargar, P.O.B 14395-547, Tehran (Iran, Islamic Republic of)

    2011-10-28

    Properties of neutron stars with quark core are investigated. The equation of state of hadronic matter is calculated using Myers and Swiatecki two nucleon interaction within Thomas-Fermi semiclassical approximation (TF). For quark matter we employ The MIT bag model with constant and density dependent bag parameter. With use of the obtained equation of states we have calculated mass-radius relation of such hybrid stars.

  6. The Chaplygin dark star

    E-print Network

    O. Bertolami; J. Paramos

    2005-12-14

    We study the general properties of a spherically symmetric body described through the generalized Chaplygin equation of state. We conclude that such object, dubbed generalized Chaplygin dark star, should exist within the context of the generalized Chaplygin gas model of unification of dark energy and dark matter, and derive expressions for its size and expansion velocity. A criteria for the survival of the perturbations in the GCG background that give origin to the dark star are developed, and its main features are analyzed.

  7. Dark Stars: A Review

    E-print Network

    Katherine Freese; Tanja Rindler-Daller; Douglas Spolyar; Monica Valluri

    2015-01-10

    Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $10^6 M_\\odot$), very bright ($>10^9 L_\\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses DSs existing today but focuses on the early generation of dark stars.

  8. 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.

  9. STAR Facility Tritium Accountancy

    SciTech Connect

    R. J. Pawelko; J. P. Sharpe; B. J. Denny

    2007-09-01

    The Safety and Tritium Applied Research (STAR) facility has been established to provide a laboratory infrastructure for the fusion community to study tritium science associated with the development of safe fusion energy and other technologies. STAR is a radiological facility with an administrative total tritium inventory limit of 1.5g (14,429 Ci) [1]. Research studies with moderate tritium quantities and various radionuclides are performed in STAR. Successful operation of the STAR facility requires the ability to receive, inventory, store, dispense tritium to experiments, and to dispose of tritiated waste while accurately monitoring the tritium inventory in the facility. This paper describes tritium accountancy in the STAR facility. A primary accountancy instrument is the tritium Storage and Assay System (SAS): a system designed to receive, assay, store, and dispense tritium to experiments. Presented are the methods used to calibrate and operate the SAS. Accountancy processes utilizing the Tritium Cleanup System (TCS), and the Stack Tritium Monitoring System (STMS) are also discussed. Also presented are the equations used to quantify the amount of tritium being received into the facility, transferred to experiments, and removed from the facility. Finally, the STAR tritium accountability database is discussed.

  10. STAR facility tritium accountancy

    SciTech Connect

    Pawelko, R. J.; Sharpe, J. P.; Denny, B. J. [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States)

    2008-07-15

    The Safety and Tritium Applied Research (STAR) facility has been established to provide a laboratory infrastructure for the fusion community to study tritium science associated with the development of safe fusion energy and other technologies. STAR is a radiological facility with an administrative total tritium inventory limit of 1.5 g (14,429 Ci) [1]. Research studies with moderate tritium quantities and various radionuclides are performed in STAR. Successful operation of the STAR facility requires the ability to receive, inventory, store, dispense tritium to experiments, and to dispose of tritiated waste while accurately monitoring the tritium inventory in the facility. This paper describes tritium accountancy in the STAR facility. A primary accountancy instrument is the tritium Storage and Assay System (SAS): a system designed to receive, assay, store, and dispense tritium to experiments. Presented are the methods used to calibrate and operate the SAS. Accountancy processes utilizing the Tritium Cleanup System (TCS), and the Stack Tritium Monitoring System (STMS) are also discussed. Also presented are the equations used to quantify the amount of tritium being received into the facility, transferred to experiments, and removed from the facility. Finally, the STAR tritium accountability database is discussed. (authors)

  11. Massive Star Formation

    E-print Network

    Tan, Jonathan C; Caselli, Paola; Fontani, Francesco; Fuente, Asuncion; Krumholz, Mark R; McKee, Christopher F; Stolte, Andrea

    2014-01-01

    The enormous radiative and mechanical luminosities of massive stars impact a vast range of scales and processes, from the reionization of the universe, to the evolution of galaxies, to the regulation of the interstellar medium, to the formation of star clusters, and even to the formation of planets around stars in such clusters. Two main classes of massive star formation theory are under active study, Core Accretion and Competitive Accretion. In Core Accretion, the initial conditions are self-gravitating, centrally concentrated cores that condense with a range of masses from the surrounding, fragmenting clump environment. They then undergo relatively ordered collapse via a central disk to form a single star or a small-N multiple. In this case, the pre-stellar core mass function has a similar form to the stellar initial mass function. In Competitive Accretion, the material that forms a massive star is drawn more chaotically from a wider region of the clump without passing through a phase of being in a massive,...

  12. Appendix 14-C Revised July 2010

    E-print Network

    Swaddle, John

    any camp or clinic advertisement or promotion (e.g., camp brochure, Web site, newspaper or magazine all-star camp held from June 30 to July 2, 2000, the women's basketball coaching staff restricted. The head women's basketball coach initially printed 250 brochures for the camp, which were mailed to 120

  13. DIAA Official Handbook, 2004-2005.

    ERIC Educational Resources Information Center

    Delaware State Department of Education, 2004

    2004-01-01

    This publication details all of the official rules and regulations of the Delaware Interscholastic Athletic Association. Some of the items discussed are: All-Star Contests; Appeal Procedure; Associate Member School; Awards; Conditioning Programs; Investigative Procedure; Non-School Competition; Postgraduates/Higher Institutions; Practice Sessions;…

  14. What Research Tells the Coach About Football.

    ERIC Educational Resources Information Center

    Paige, Roderick R.

    This booklet is designed to make available research findings about football with interpretations for practical application. Chapter 1, "Physical Characteristics of Football Athletes," includes a table comparing the height and weight of National Football League players and All-Star players. Somatotyping and body composition are discussed. In…

  15. A fast star image extraction algorithm for autonomous star sensors

    NASA Astrophysics Data System (ADS)

    Zhu, Xifang; Wu, Feng; Xu, Qingquan

    2012-11-01

    Star sensors have been developed to acquire accurate orientation information in recent decades superior to other attitude measuring instruments. A star camera takes photos of the night sky to obtain star maps. An important step to acquire attitude knowledge is to compare the features of the observed stars in the maps with those of the cataloged stars using star identification algorithms. To calculate centroids of the star images before this step, they are required to be extracted from the star maps in advance. However, some large or ultra large imaging detectors are applied to acquire star maps for star sensors with the development of electronic imaging devices. Therefore, star image extraction occupies more and more portions of the whole attitude measurement period of time. It is required to shorten star image extraction time in order to achieve higher response rate. In this paper, a novel star image extraction algorithm is proposed which fulfill the tasks efficiently. By scanning star map, the pixels brighter than the gray threshold are found and their coordinates and brightness are stored in a cross-linked list. Data of these pixels are linked by pointers, while other pixels are neglected. Therefore, region growing algorithm can be used by choosing the first element in the list as a starting seed. New seeds are founded if the neighboring pixels are brighter than the threshold, and the last seed is deleted from the list. Next search continues until no neighboring pixels are in the list. At that time, one star image is extracted, and its centroid is calculated. Likely, other star images may be extracted, and then the examined seeds are deleted which are never considered again. A new star image search always begins from the first element for avoiding unnecessary scanning. The experiments have proved that for a 1024×1024 star map, the image extraction takes nearly 16 milliseconds. When CMOS APS is utilized to transfer image data, the real-time extraction can be almost achieved.

  16. Life Cycle of Stars

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In this stunning picture of the giant galactic nebula NGC 3603, the crisp resolution of NASA's Hubble Space Telescope captures various stages of the life cycle of stars in one single view. To the upper left of center is the evolved blue supergiant called Sher 25. The star has a unique circumstellar ring of glowing gas that is a galactic twin to the famous ring around the supernova 1987A. The grayish-bluish color of the ring and the bipolar outflows (blobs to the upper right and lower left of the star) indicates the presence of processed (chemically enriched) material. Near the center of the view is a so-called starburst cluster dominated by young, hot Wolf-Rayet stars and early O-type stars. A torrent of ionizing radiation and fast stellar winds from these massive stars has blown a large cavity around the cluster. The most spectacular evidence for the interaction of ionizing radiation with cold molecular-hydrogen cloud material are the giant gaseous pillars to the right of the cluster. These pillars are sculptured by the same physical processes as the famous pillars Hubble photographed in the M16 Eagle Nebula. Dark clouds at the upper right are so-called Bok globules, which are probably in an earlier stage of star formation. To the lower left of the cluster are two compact, tadpole-shaped emission nebulae. Similar structures were found by Hubble in Orion, and have been interpreted as gas and dust evaporation from possibly protoplanetary disks (proplyds). This true-color picture was taken on March 5, 1999 with the Wide Field Planetary Camera 2.

  17. Models of symbiotic stars

    NASA Technical Reports Server (NTRS)

    Friedjung, Michael

    1993-01-01

    One of the most important features of symbiotic stars is the coexistence of a cool spectral component that is apparently very similar to the spectrum of a cool giant, with at least one hot continuum, and emission lines from very different stages of ionization. The cool component dominates the infrared spectrum of S-type symbiotics; it tends to be veiled in this wavelength range by what appears to be excess emission in D-type symbiotics, this excess usually being attributed to circumstellar dust. The hot continuum (or continua) dominates the ultraviolet. X-rays have sometimes also been observed. Another important feature of symbiotic stars that needs to be explained is the variability. Different forms occur, some variability being periodic. This type of variability can, in a few cases, strongly suggest the presence of eclipses of a binary system. One of the most characteristic forms of variability is that characterizing the active phases. This basic form of variation is traditionally associated in the optical with the veiling of the cool spectrum and the disappearance of high-ionization emission lines, the latter progressively appearing (in classical cases, reappearing) later. Such spectral changes recall those of novae, but spectroscopic signatures of the high-ejection velocities observed for novae are not usually detected in symbiotic stars. However, the light curves of the 'symbiotic nova' subclass recall those of novae. We may also mention in this connection that radio observations (or, in a few cases, optical observations) of nebulae indicate ejection from symbiotic stars, with deviations from spherical symmetry. We shall give a historical overview of the proposed models for symbiotic stars and make a critical analysis in the light of the observations of symbiotic stars. We describe the empirical approach to models and use the observational data to diagnose the physical conditions in the symbiotics stars. Finally, we compare the results of this empirical approach with existing models and discuss unresolved problems requiring new observational and theoretical work.

  18. Sounds of a Star

    NASA Astrophysics Data System (ADS)

    2001-06-01

    Acoustic Oscillations in Solar-Twin "Alpha Cen A" Observed from La Silla by Swiss Team Summary Sound waves running through a star can help astronomers reveal its inner properties. This particular branch of modern astrophysics is known as "asteroseismology" . In the case of our Sun, the brightest star in the sky, such waves have been observed since some time, and have greatly improved our knowledge about what is going on inside. However, because they are much fainter, it has turned out to be very difficult to detect similar waves in other stars. Nevertheless, tiny oscillations in a solar-twin star have now been unambiguously detected by Swiss astronomers François Bouchy and Fabien Carrier from the Geneva Observatory, using the CORALIE spectrometer on the Swiss 1.2-m Leonard Euler telescope at the ESO La Silla Observatory. This telescope is mostly used for discovering exoplanets (see ESO PR 07/01 ). The star Alpha Centauri A is the nearest star visible to the naked eye, at a distance of a little more than 4 light-years. The new measurements show that it pulsates with a 7-minute cycle, very similar to what is observed in the Sun . Asteroseismology for Sun-like stars is likely to become an important probe of stellar theory in the near future. The state-of-the-art HARPS spectrograph , to be mounted on the ESO 3.6-m telescope at La Silla, will be able to search for oscillations in stars that are 100 times fainter than those for which such demanding observations are possible with CORALIE. PR Photo 23a/01 : Oscillations in a solar-like star (schematic picture). PR Photo 23b/01 : Acoustic spectrum of Alpha Centauri A , as observed with CORALIE. Asteroseismology: listening to the stars ESO PR Photo 23a/01 ESO PR Photo 23a/01 [Preview - JPEG: 357 x 400 pix - 96k] [Normal - JPEG: 713 x 800 pix - 256k] [HiRes - JPEG: 2673 x 3000 pix - 2.1Mb Caption : PR Photo 23a/01 is a graphical representation of resonating acoustic waves in the interior of a solar-like star. Red and blue 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 Centaurus in the southern hemisphere. It is actually

  19. Pulsating Star Mystery Solved

    NASA Astrophysics Data System (ADS)

    2010-11-01

    By discovering the first double star where a pulsating Cepheid variable and another star pass in front of one another, an international team of astronomers has solved a decades-old mystery. The rare alignment of the orbits of the two stars in the double star system has allowed a measurement of the Cepheid mass with unprecedented accuracy. Up to now astronomers had two incompatible theoretical predictions of Cepheid masses. The new result shows that the prediction from stellar pulsation theory is spot on, while the prediction from stellar evolution theory is at odds with the new observations. The new results, from a team led by Grzegorz Pietrzy?ski (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), appear in the 25 November 2010 edition of the journal Nature. Grzegorz Pietrzy?ski introduces this remarkable result: "By using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile, along with other telescopes, we have measured the mass of a Cepheid with an accuracy far greater than any earlier estimates. This new result allows us to immediately see which of the two competing theories predicting the masses of Cepheids is correct." Classical Cepheid Variables, usually called just Cepheids, are unstable stars that are larger and much brighter than the Sun [1]. They expand and contract in a regular way, taking anything from a few days to months to complete the cycle. The time taken to brighten and grow fainter again is longer for stars that are more luminous and shorter for the dimmer ones. This remarkably precise relationship makes the study of Cepheids one of the most effective ways to measure the distances to nearby galaxies and from there to map out the scale of the whole Universe [2]. Unfortunately, despite their importance, Cepheids are not fully understood. Predictions of their masses derived from the theory of pulsating stars are 20-30% less than predictions from the theory of the evolution of stars. This embarrassing discrepancy has been known since the 1960s. To resolve this mystery, astronomers needed to find a double star containing a Cepheid where the orbit happened to be seen edge-on from Earth. In these cases, known as eclipsing binaries, the brightness of the two stars dims as one component passes in front of the other, and again when it passes behind the other star. In such pairs astronomers can determine the masses of the stars to high accuracy [3]. Unfortunately neither Cepheids nor eclipsing binaries are common, so the chance of finding such an unusual pair seemed very low. None are known in the Milky Way. Wolfgang Gieren, another member of the team, takes up the story: "Very recently we actually found the double star system we had hoped for among the stars of the Large Magellanic Cloud. It contains a Cepheid variable star pulsating every 3.8 days. The other star is slightly bigger and cooler, and the two stars orbit each other in 310 days. The true binary nature of the object was immediately confirmed when we observed it with the HARPS spectrograph on La Silla." The observers carefully measured the brightness variations of this rare object, known as OGLE-LMC-CEP0227 [4], as the two stars orbited and passed in front of one another. They also used HARPS and other spectrographs to measure the motions of the stars towards and away from the Earth - both the orbital motion of both stars and the in-and-out motion of the surface of the Cepheid as it swelled and contracted. This very complete and detailed data allowed the observers to determine the orbital motion, sizes and masses of the two stars with very high accuracy - far surpassing what had been done before for a Cepheid. The mass of the Cepheid is now known to about 1% and agrees exactly with predictions from the theory of stellar pulsation. However, the larger mass predicted by stellar evolution theory was shown to be significantly in error. The much-improved mass estimate is only one outcome of this work, and the team hopes to find other examples of these

  20. Holographic Magnetic Star

    E-print Network

    Piyabut Burikham; Tossaporn Chullaphan

    2012-05-16

    A warm fermionic AdS star under a homogeneous magnetic field is explored. We obtain the relativistic Landau levels by using Dirac equation and use the Tolman-Oppenheimer-Volkoff (TOV) equation to study the physical profiles of the star. Bulk properties such as sound speed, adiabatic index, and entropy density within the star are calculated analytically and numerically. Bulk temperature increases the mass limit of the AdS star but external magnetic field has the opposite effect. The results are partially interpreted in terms of the pre-thermalization process of the gauge matter at the AdS boundary after the mass injection. The entropy density is found to demonstrate similar temperature dependence as the magnetic black brane in the AdS in certain limits regardless of the different nature of the bulk and Hawking temperatures. Total entropy of the AdS star is also found to be an increasing function of the bulk temperature and a decreasing function of the magnetic field, similar behaviour to the mass limit. Since both total entropy and mass limit are global quantities, they could provide some hints to the value of entropy and energy of the dual gauge matter before and during the thermalization.

  1. Star Caught Smoking

    NASA Astrophysics Data System (ADS)

    2007-08-01

    VLTI Snapshots Dusty Puff Around Variable Star Using ESO's Very Large Telescope Interferometer, astronomers from France and Brazil have detected a huge cloud of dust around a star. This observation is further evidence for the theory that such stellar puffs are the cause of the repeated extreme dimming of the star. ESO PR Photo 34a/07 ESO PR Photo 34a/07 Dust Cloud in a R CrB Star (Artist's Impression) R Coronae Borealis stars are supergiants exhibiting erratic variability. Named after the first star that showed such behaviour [1], they are more than 50 times larger than our Sun. R Coronae Borealis stars can see their apparent brightness unpredictably decline to a thousandth of their nominal value within a few weeks, with the return to normal light levels being much slower. It has been accepted for decades that such fading could be due to obscuration of the stellar surface by newly formed dusty clouds. This 'Dust Puff Theory' suggests that mass is lost from the R Coronae Borealis (or R CrB for short) star and then moves away until the temperature is low enough for carbon dust to form. If the newly formed dust cloud is located along our line-of-sight, it eclipses the star. As the dust is blown away by the star's strong light, the 'curtain' vanishes and the star reappears. RY Sagittarii is the brightest member in the southern hemisphere of this family of weird stars. Located about 6,000 light-years away towards the constellation of Sagittarius (The Archer), its peculiar nature was discovered in 1895 by famous Dutch astronomer Jacobus Cornelius Kapteyn. In 2004, near-infrared adaptive optics observations made with NACO on ESO's Very Large Telescope allowed astronomers Patrick de Laverny and Djamel Mékarnia to clearly detect the presence of clouds around RY Sagittarii. This was the first direct confirmation of the standard scenario explaining the light variations of R CrB stars by the presence of heterogeneities in their envelope surrounding the star. ESO PR Photo 32e/07 ESO PR Photo 34b/07 Clouds around RY Sagittarii (NACO/VLT) However, the precise place where such dust clouds would form was still unclear. The brightest cloud detected was several hundred stellar radii from the centre, but it had certainly formed much closer. But how much closer? To probe the vicinity of the star, the astronomers then turned to ESO's Very Large Telescope Interferometer. Combining two different pairs of the 8.2-m Unit Telescopes and using the mid-infrared MIDI instrument that allows detecting cold structures, the astronomers explored the inner 110 astronomical units [2] around the star. Given the remoteness of RY Sagittarii, this corresponds to looking at details on a one-euro coin that is about 75 km away! The astronomers found that a huge envelope, about 120 times as big as RY Sagittarii itself, surrounds the supergiant star. But more importantly, the astronomers also found evidence for a dusty cloud lying only about 30 astronomical units away from the star, or 100 times the radius of the star. "This is the closest dusty cloud ever detected around a R CrB-type variable since our first direct detection in 2004," says Patrick de Laverny, leader of the team. "However, it is still detected too far away from the star to distinguish between the different scenarios proposed within the Dust Puff Theory for the possible locations in which the dusty clouds form." If the cloud moves at the speed of 300 km/s, as one can conservatively assume, it was probably ejected more than 6 months before its discovery from deeper inside the envelope. The astronomers are now planning to monitor RY Sagittarii more carefully to shed more light on the evolution of the dusty clouds surrounding it. "Two hundred years after the discovery of the variable nature of R CrB, many aspects of the R CrB phenomenon remain mysterious," concludes de Laverny.

  2. SYSTEMS FOR THE TRANSDISCIPLINARY ADVANCEMENT OF RESEARCH (STAR) http://www.ls.wisc.edu/star/

    E-print Network

    Sheridan, Jennifer

    SYSTEMS FOR THE TRANSDISCIPLINARY ADVANCEMENT OF RESEARCH (STAR) http://www.ls.wisc.edu/star STAR: Organization Development for Transdisciplinary Research STAR (Systems professionals. STAR features opportunities to form ongoing relationships and working

  3. Blurred star image processing for star sensors under dynamic conditions.

    PubMed

    Zhang, Weina; Quan, Wei; Guo, Lei

    2012-01-01

    The precision of star point location is significant to identify the star map and to acquire the aircraft attitude for star sensors. Under dynamic conditions, star images are not only corrupted by various noises, but also blurred due to the angular rate of the star sensor. According to different angular rates under dynamic conditions, a novel method is proposed in this article, which includes a denoising method based on adaptive wavelet threshold and a restoration method based on the large angular rate. The adaptive threshold is adopted for denoising the star image when the angular rate is in the dynamic range. Then, the mathematical model of motion blur is deduced so as to restore the blurred star map due to large angular rate. Simulation results validate the effectiveness of the proposed method, which is suitable for blurred star image processing and practical for attitude determination of satellites under dynamic conditions. PMID:22778666

  4. I-Love relation for incompressible stars and realistic stars

    E-print Network

    T. K. Chan; Atma P. O. Chan; P. T. Leung

    2014-11-26

    In spite of the diversity in the equations of state of nuclear matter, the recently discovered I-Love-Q relations [Yagi and Yunes, Science {\\bf 341}, 365 (2013)], which relate the moment of inertia, tidal Love number (deformability) and the spin-induced quadrupole moment of compact stars, hold for various kinds of realistic neutron stars and quark stars. While the physical origin of such universality is still a current issue, the observation that the I-Love-Q relations of incompressible stars can well approximate those of realistic compact stars hints at a new direction to approach the problem. In this paper, by establishing recursive post-Minkowskian expansion for the moment of inertia and the tidal deformability of incompressible stars, we analytically derive the I-Love relation for incompressible stars and show that the so obtained formula can be used to accurately predict the behavior of realistic compact stars from the Newtonian limit to the maximum mass limit.

  5. General Relativity&Compact Stars

    SciTech Connect

    Glendenning, Norman K.

    2005-08-16

    Compact stars--broadly grouped as neutron stars and white dwarfs--are the ashes of luminous stars. One or the other is the fate that awaits the cores of most stars after a lifetime of tens to thousands of millions of years. Whichever of these objects is formed at the end of the life of a particular luminous star, the compact object will live in many respects unchanged from the state in which it was formed. Neutron stars themselves can take several forms--hyperon, hybrid, or strange quark star. Likewise white dwarfs take different forms though only in the dominant nuclear species. A black hole is probably the fate of the most massive stars, an inaccessible region of spacetime into which the entire star, ashes and all, falls at the end of the luminous phase. Neutron stars are the smallest, densest stars known. Like all stars, neutron stars rotate--some as many as a few hundred times a second. A star rotating at such a rate will experience an enormous centrifugal force that must be balanced by gravity or else it will be ripped apart. The balance of the two forces informs us of the lower limit on the stellar density. Neutron stars are 10{sup 14} times denser than Earth. Some neutron stars are in binary orbit with a companion. Application of orbital mechanics allows an assessment of masses in some cases. The mass of a neutron star is typically 1.5 solar masses. They can therefore infer their radii: about ten kilometers. Into such a small object, the entire mass of our sun and more, is compressed.

  6. Detecting Primordial Stars

    E-print Network

    Nino Panagia

    2004-10-08

    We discuss the expected properties of the first stellar generations in the Universe. We find that it is possible to discern truly primordial populations from the next generation of stars by measuring the metallicity of high-z star forming objects. The very low background of the future James Webb Space Telescope (JWST) will enable it to image and study first-light sources at very high redshifts, whereas its relatively small collecting area limits its capability in obtaining spectra of z~10-15 first-light sources to either the bright end of their luminosity function or to strongly lensed sources. With a suitable investment of observing time JWST will be able to detect individual Population III supernovae, thus identifying the very first stars that formed in the Universe.

  7. Energy Production in Stars

    NSDL National Science Digital Library

    Energy Production in Stars is part of the Astronomy 162: Stars, Galaxies, and Cosmology course offered by the Department of Physics and Astronomy at the University of Tennessee. This section covers the mass-energy relation of special relativity; the curve of binding energy, and its implications for fusion and fission reactions, and stellar energy production; nuclear reactions, and their relation to the Coulomb barrier, and quantum mechanical tunneling; temperature and pressure in stars, including the kinetic theory of gases, ideal gas law, and the Gamow window for charged particle reactions; the proton-proton chain; the carbon-nitrogen-oxygen (CNO) cycle; the triple-alpha process, mass-5 and mass-8 bottlenecks; advanced burning stages; stellar energy transport; and the solar neutrino problem.

  8. The Cambridge Star Atlas

    NASA Astrophysics Data System (ADS)

    Tirion, Wil

    The Cambridge Star Atlas covers the entire sky, both northern and southern latitudes, in an attractive format that is suitable for beginners and experienced astronomical observers. There is a series of monthly sky charts, followed by an atlas of the whole sky, arranged in 20 overlapping charts. Each chart shows stars down to magnitude 6.5, together with about 900 non-stellar objects, such as clusters and galaxies, which can be seen with binoculars or a small telescope. There is a comprehensive map of the Moon's surface, showing craters and other named features. Wil Tirion is the world's foremost artist and designer of astronomical maps. For this edition he has devised improved versions of the monthly charts and added all-sky charts, and the text has been completely revised. In this improved and expanded format, The Cambridge Star Atlas is an ideal reference atlas for sky watchers everywhere.

  9. Star-ND (Multi-Dimensional Star-Identification)

    E-print Network

    Spratling, Benjamin

    2012-07-16

    of DOCTOR OF PHILOSOPHY May 2011 Major Subject: Aerospace Engineering STAR-ND (MULTI-DIMENSIONAL STAR-IDENTIFICATION) A Dissertation by BENJAMIN BARNETT SPRATLING IV Submitted to the Office of Graduate Studies of Texas A... May 2011 Major Subject: Aerospace Engineering iii ABSTRACT Star-ND (Multi-Dimensional Star-Identification). (May 2011) Benjamin Barnett Spratling IV, B.S., Auburn University Chair of Advisory Committee: Dr. Daniele Mortari In order...

  10. Atmospheres around Neutron Stars

    NASA Astrophysics Data System (ADS)

    Fryer, Chris L.; Benz, Willy

    1994-12-01

    Interest in the behavior of atmospheres around neutron stars has grown astronomically in the past few years. Some of this interest arrived in the wake of the explosion of Supernova 1987A and its elusive remnant; spawning renewed interest in a method to insure material ``fall-back'' onto the adolescent neutron star in an effort to transform it into a silent black hole. However, the bulk of the activity with atmospheres around neutron stars is concentrated in stellar models with neutron star, rather than white dwarf, cores; otherwise known as Thorne-Zytkow objects. First a mere seed in the imagination of theorists, Thorne-Zytkow objects have grown into an observational reality with an ever-increasing list of formation scenarios and observational prospects. Unfortunately, the analytic work of Chevalier on supernova fall-back implies that, except for a few cases, the stellar simulations of Thorne-Zytkow objects are missing an important aspect of physics: neutrinos. Neutrino cooling removes the pressure support of these atmospheres, allowing accretion beyond the canonical Eddington rate for these objects. We present here the results of detailed hydrodynamical simulations in one and two dimensions with the additional physical effects of neutrinos, advanced equations of state, and relativity over a range of parameters for our atmosphere including entropy and chemical composition as well as a range in the neutron star size. In agreement with Chevalier, we find, under the current list of formation scenarios, that the creature envisioned by Thorne and Zytkow will not survive the enormous appetite of a neutron star. However, neutrino heating (a physical effect not considered in Chevalier's analysis) can play an important role in creating instabilities in some formation schemes, leading to an expulsion of matter rather than rapid accretion. By placing scrutiny upon the formation methods, we can determine the observational prospects for each.

  11. Kinematics of T Tauri stars in nearby star forming regions.

    NASA Astrophysics Data System (ADS)

    Frink, S.

    1999-02-01

    The kinematics of T Tauri stars in the nearby star forming regions Taurus-Auriga, Chamaeleon, Lupus and Scorpius-Centaurus is studied using proper motions from the Hipparcos, PPM, ACT, TRC and STARNET proper motion catalogues. Especially the STARNET catalogue is very well suited for this purpose as it provides accurate proper motions for about 4.3 million stars, so that a large number of T Tauri stars is included in that catalogue. Where available, Hipparcos parallaxes and radial velocities are combined with the proper motions to calculate space velocities and velocity dispersions. In the Scorpius-Centaurus association, the favourable geometry allows for the determination of kinematical distances. A large fraction of the stars in the samples belongs to the population of weak-line T Tauri stars discovered with the help of the X-ray satellite ROSAT during the last years. In contrast to classical T Tauri stars, which had preferentially been found very close to the densest cores of the cloud material in those star forming regions, weak-line T Tauri stars are distributed over larger regions in space. The kinematic signatures of processes producing such halos of weak-line T Tauri stars should still be visible, and the observed motions of the stars are analyzed in the framework of various star formation scenarios.

  12. Kinematics of T Tauri Stars in nearby Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Frink, Sabine

    The kinematics of T Tauri stars in the nearby star forming regions Taurus-Auriga, Chamaeleon, Lupus and Scorpius-Centaurus is studied using proper motions from the Hipparcos, PPM, ACT, TRC and STARNET proper motion catalogues. Especially the STARNET catalogue is very well suited for this purpose as it provides accurate proper motions for about 4.3 million stars, so that a large number of T Tauri stars is included in that catalogue. Where available, Hipparcos parallaxes and radial velocities are combined with the proper motions to calculate space velocities and velocity dispersions. In the Scorpius-Centaurus association, the favourable geometry allows for the determination of kinematical distances. A large fraction of the stars in the samples belongs to the population of weak-line T Tauri stars discovered with the help of the X-ray satellite ROSAT during the last years. In contrast to classical T Tauri stars, which had preferentially been found very close to the densest cores of the cloud material in those star forming regions, weak-line T Tauri stars are distributed over larger regions in space. The kinematic signatures of processes producing such halos of weak-line T Tauri stars should still be visible, and the observed motions of the stars are analyzed in the framework of various star formation scenarios.

  13. Triggered star formation in the environment of young massive stars

    Microsoft Academic Search

    Matthias Gritschneder; T. Naab; F. Heitsch; A. Burkert

    2007-01-01

    Recent observations with the Spitzer Space Telescope show clear evidence that star formation takes place in the surrounding of young massive O-type stars, which are shaping their environment due to their powerful radiation and stellar winds. In this work we investigate the effect of ionising radiation of massive stars on the ambient interstellar medium (ISM): In particular we want to

  14. Double Neutron Star Systems and Natal Neutron Star Kicks

    Microsoft Academic Search

    Chris Fryer; Vassiliki Kalogera

    1997-01-01

    We study the four double neutron star systems found in the Galactic disk in terms of the orbital characteristics of their immediate progenitors and the natal kicks imparted to neutron stars. Analysis of the effect of the second supernova explosion on the orbital dynamics, combined with recent results from simulations of rapid accretion onto neutron stars, lead us to conclude

  15. The Neutron Star Zoo

    E-print Network

    Harding, Alice K

    2013-01-01

    Neutron stars are a very diverse population, both in their observational and their physical properties. They prefer to radiate most of their energy at X-ray and gamma-ray wavelengths. But whether their emission is powered by rotation, accretion, heat, magnetic fields or nuclear reactions, they are all different species of the same animal whose magnetic field evolution and interior composition remain a mystery. This article will broadly review the properties of inhabitants of the neutron star zoo, with emphasis on their high-energy emission.

  16. Star cluster dynamics.

    PubMed

    Vesperini, Enrico

    2010-02-28

    Dynamical evolution plays a key role in shaping the current properties of star clusters and star cluster systems. A detailed understanding of the effects of evolutionary processes is essential to be able to disentangle the properties that result from dynamical evolution from those imprinted at the time of cluster formation. In this review, I focus my attention on globular clusters, and review the main physical ingredients driving their early and long-term evolution, describe the possible evolutionary routes and show how cluster structure and stellar content are affected by dynamical evolution. PMID:20083508

  17. A Star Is Born

    NSDL National Science Digital Library

    Lee Ann Henning

    This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 9-12. It addresses the question of how astronomers know the evolution of a star without being able to see it happen. Students look at the different stages in the lives of stars, from protostars to red giants and black holes. The lesson includes objectives, materials, procedures, discussion questions, evaluation ideas, performing extensions, suggested readings, and vocabulary. There are videos available to order which complement this lesson, audio vocabulary, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

  18. The DQ Herculis stars

    NASA Astrophysics Data System (ADS)

    Patterson, Joseph

    1994-03-01

    We review the properties of the DQ Herculis stars: cataclysmic variables containing an accreting, magnetic, rapidly rotating white dwarf. These stars are characterized by strong X-ray emission, high-excitation spectra, and very stable optical and X-ray pulsations in their light curves. There is considerable resemblance to their more famous cousins, the AM Herculis stars, but the latter class is additionally characterized by spin-orbit synchronism and the presence of strong circular polarization. We list eighteen stars passing muster as certain or very likely DQ Her stars. The rotational periods range from 33 s to 2.0 hr. Additional periods can result when the rotating searchlight illuminates other structures in the binary. A single hypothesis explains most of the observed properties: magnetically channeled accretion within a truncated disk. Some accretion flow still seems to proceed directly to the magnetosphere, however. The white dwarfs' magnetic moments are in the range 1032 - 1034 G cc, slightly weaker than in AM Her stars but with some probable overlap. The more important reason why DQ Hers have broken synchronism is probably their greater accretion rate and orbital separation. The observed Lx/LV values are surprisingly low for a radially accreting white dwarf, suggesting that most of the accretion energy is not radiated in a strong shock above the magnetic pole. The fluxes can be more satisfactorily explained if most of the radial infall energy manages to bypass the shock and deposit itse lf directly in the white dwarf photosphere, where it should emerge as extreme ultraviolet (EUV) radiation. This also provides an adequate source of ionizing photons to power the high-excitation optical and UV emission lines. This is probably the DQ Her analog to the famous 'soft X-ray excess' in AM Her stars. However, unlike the AM Her case, this radiation has not been directly observed, so the analogy must not (yet) be embraced too firmly. There is some conventional wisdom today which segregates the short-period from the long-period DQ Her stars. But the observational grounds for this distinction are slim, except in one respect: X-ray emission from short-period systems appears to be weaker and softer. This must be due to the shallower depth of the potential well, and/or the greater difficulty the fast rotators have in enforcing radial accretion flow.

  19. The DQ Herculis stars

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph

    1994-01-01

    We review the properties of the DQ Herculis stars: cataclysmic variables containing an accreting, magnetic, rapidly rotating white dwarf. These stars are characterized by strong X-ray emission, high-excitation spectra, and very stable optical and X-ray pulsations in their light curves. There is considerable resemblance to their more famous cousins, the AM Herculis stars, but the latter class is additionally characterized by spin-orbit synchronism and the presence of strong circular polarization. We list eighteen stars passing muster as certain or very likely DQ Her stars. The rotational periods range from 33 s to 2.0 hr. Additional periods can result when the rotating searchlight illuminates other structures in the binary. A single hypothesis explains most of the observed properties: magnetically channeled accretion within a truncated disk. Some accretion flow still seems to proceed directly to the magnetosphere, however. The white dwarfs' magnetic moments are in the range 10(sup 32) - 10(sup 34) G cc, slightly weaker than in AM Her stars but with some probable overlap. The more important reason why DQ Hers have broken synchronism is probably their greater accretion rate and orbital separation. The observed L(sub x)/L(sub V) values are surprisingly low for a radially accreting white dwarf, suggesting that most of the accretion energy is not radiated in a strong shock above the magnetic pole. The fluxes can be more satisfactorily explained if most of the radial infall energy manages to bypass the shock and deposit itse lf directly in the white dwarf photosphere, where it should emerge as extreme ultraviolet (EUV) radiation. This also provides an adequate source of ionizing photons to power the high-excitation optical and UV emission lines. This is probably the DQ Her analog to the famous 'soft X-ray excess' in AM Her stars. However, unlike the AM Her case, this radiation has not been directly observed, so the analogy must not (yet) be embraced too firmly. There is some conventional wisdom today which segregates the short-period from the long-period DQ Her stars. But the observational grounds for this distinction are slim, except in one respect: X-ray emission from short-period systems appears to be weaker and softer. This must be due to the shallower depth of the potential well, and/or the greater difficulty the fast rotators have in enforcing radial accretion flow.

  20. The most magnetic stars

    NASA Astrophysics Data System (ADS)

    Wickramasinghe, Dayal T.; Tout, Christopher A.; Ferrario, Lilia

    2014-01-01

    Observations of magnetic A, B and O stars show that the poloidal magnetic flux per unit mass ?p/M appears to have an upper bound of approximately 10-6.5 G cm2 g-1. A similar upper bound to the total flux per unit mass is found for the magnetic white dwarfs even though the highest magnetic field strengths at their surfaces are much larger. For magnetic A and B stars, there also appears to be a well-defined lower bound below which the incidence of magnetism declines rapidly. According to recent hypotheses, both groups of stars may result from merging stars and owe their strong magnetism to fields generated by a dynamo mechanism as they merge. We postulate a simple dynamo that generates magnetic field from differential rotation. We limit the growth of magnetic fields by the requirement that the poloidal field stabilizes the toroidal and vice versa. While magnetic torques dissipate the differential rotation, toroidal field is generated from poloidal by an ? dynamo. We further suppose that mechanisms that lead to the decay of toroidal field lead to the generation of poloidal. Both poloidal and toroidal fields reach a stable configuration which is independent of the size of small initial seed fields but proportional to the initial differential rotation. We pose the hypothesis that strongly magnetic stars form from the merging of two stellar objects. The highest fields are generated when the merge introduces differential rotation that amounts to critical break-up velocity within the condensed object. Calibration of a simplistic dynamo model with the observed maximum flux per unit mass for main-sequence stars and white dwarfs indicates that about 1.5 × 10-4 of the decaying toroidal flux must appear as poloidal. The highest fields in single white dwarfs are generated when two degenerate cores merge inside a common envelope or when two white dwarfs merge by gravitational-radiation angular momentum loss. Magnetars are the most magnetic neutron stars. Though these are expected to form directly from single stars, their magnetic flux to mass ratio indicates that a similar dynamo, driven by differential rotation acquired at their birth, may also be the source of their strong magnetism.

  1. Sizing Up the Stars

    NSDL National Science Digital Library

    This is an activity about size, distance, and perspective. Learners will observe two objects of the same size placed at different distances, and they will observe two objects of different size placed at varying distances. This concept is then related to how our Sun looks larger than all of the other stars in the sky due to Earth's proximity to it. This activity is from the Stanford Solar Center's All About the Sun: Sun and Stars activity guide for Grades 5-8 and can also accompany the Stanford Solar Center's Build Your Own Spectroscope activity.

  2. 5.NF Origami Stars

    NSDL National Science Digital Library

    2012-11-11

    This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Avery and Megan are cutting paper to make origami stars. They need $\\frac{1}{5}$ of a sheet of paper in order to make each star. If they have 6 sheets ...

  3. The Drifting Star

    NASA Astrophysics Data System (ADS)

    2008-04-01

    By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its temperature is 6150 K, its mass is 1.25 times that of the Sun, and its age is 625 million years. Moreover, the star is found to be more metal-rich than the Sun by about 50%. ESO PR Photo 09b/08 ESO PR Photo 09b/08 Constellations "These results show the power of asteroseismology when using a very precise instrument such as HARPS," says Vauclair. "It also shows that Iota Horologii has the same metal abundance and age as the Hyades cluster and this cannot be a coincidence." The Hyades is an ensemble of stars that is seen with the unaided eye in the Northern constellation Taurus ("The Bull"). This open cluster, located 151 light-years away, contains stars that were formed together 625 million years ago. The star Iota Horologii must have thus formed together with the stars of the Hyades cluster but must have slowly drifted away, being presently more than 130 light-years away from its original birthplace. This is an important result to understand how stars move on the galactic highways of the Milky Way. This also means that the amount of metals present in the star is due to the original cloud from which it formed and not because it engulfed planetary material. "The chicken and egg question of whether the star got planets because it is metal-rich, or whether it is metal-rich because it made planets that were swallowed up is at least answered in one case," says Vauclair. More information The astronomers' study is being published as a Letter to the Editor in Astronomy and Astrophysics ("The exoplanet-host star iota Horologii: an evaporated member of the primordial Hyades cluster", by S. Vauclair et al.). The team is composed of Sylvie Vauclair, Marion Laymand, Gérard Vauclair, Alain Hui Bon Hoa, and Stéphane Charpinet (LATT, Toulouse, France), François Bouchy (IAP, Paris, France), and Michaël Bazot (University of Porto, Portugal).

  4. Exploring Game Performance in the National Basketball Association Using Player Tracking Data.

    PubMed

    Sampaio, Jaime; McGarry, Tim; Calleja-González, Julio; Jiménez Sáiz, Sergio; Schelling I Del Alcázar, Xavi; Balciunas, Mindaugas

    2015-01-01

    Recent player tracking technology provides new information about basketball game performance. The aim of this study was to (i) compare the game performances of all-star and non all-star basketball players from the National Basketball Association (NBA), and (ii) describe the different basketball game performance profiles based on the different game roles. Archival data were obtained from all 2013-2014 regular season games (n = 1230). The variables analyzed included the points per game, minutes played and the game actions recorded by the player tracking system. To accomplish the first aim, the performance per minute of play was analyzed using a descriptive discriminant analysis to identify which variables best predict the all-star and non all-star playing categories. The all-star players showed slower velocities in defense and performed better in elbow touches, defensive rebounds, close touches, close points and pull-up points, possibly due to optimized attention processes that are key for perceiving the required appropriate environmental information. The second aim was addressed using a k-means cluster analysis, with the aim of creating maximal different performance profile groupings. Afterwards, a descriptive discriminant analysis identified which variables best predict the different playing clusters. The results identified different playing profile of performers, particularly related to the game roles of scoring, passing, defensive and all-round game behavior. Coaching staffs may apply this information to different players, while accounting for individual differences and functional variability, to optimize practice planning and, consequently, the game performances of individuals and teams. PMID:26171606

  5. Exploring Game Performance in the National Basketball Association Using Player Tracking Data

    PubMed Central

    Calleja-González, Julio; Jiménez Sáiz, Sergio; Schelling i del Alcázar, Xavi; Balciunas, Mindaugas

    2015-01-01

    Recent player tracking technology provides new information about basketball game performance. The aim of this study was to (i) compare the game performances of all-star and non all-star basketball players from the National Basketball Association (NBA), and (ii) describe the different basketball game performance profiles based on the different game roles. Archival data were obtained from all 2013-2014 regular season games (n = 1230). The variables analyzed included the points per game, minutes played and the game actions recorded by the player tracking system. To accomplish the first aim, the performance per minute of play was analyzed using a descriptive discriminant analysis to identify which variables best predict the all-star and non all-star playing categories. The all-star players showed slower velocities in defense and performed better in elbow touches, defensive rebounds, close touches, close points and pull-up points, possibly due to optimized attention processes that are key for perceiving the required appropriate environmental information. The second aim was addressed using a k-means cluster analysis, with the aim of creating maximal different performance profile groupings. Afterwards, a descriptive discriminant analysis identified which variables best predict the different playing clusters. The results identified different playing profile of performers, particularly related to the game roles of scoring, passing, defensive and all-round game behavior. Coaching staffs may apply this information to different players, while accounting for individual differences and functional variability, to optimize practice planning and, consequently, the game performances of individuals and teams. PMID:26171606

  6. The Death of a Star

    ERIC Educational Resources Information Center

    Thorne, Kip S.

    1971-01-01

    Theories associated with the gravitational collapse of a star into black holes" are described. Suggests that the collapse and compression might go through the stages from white dwarf star to neutron core to black hole." (TS)

  7. Texas LoanSTAR Program

    E-print Network

    Trevino, E.

    2012-01-01

    Texas LoanSTAR Program LoanSTAR Statistics ? Average loan size - $2 million ? Number of loans ? 216 ? Maximum loan size - $5 million ? Minimum loan size ? n/a Public Entities ? K-12 Schools ? Higher Education ? Local Governments ? State...

  8. Why Do We Study Stars?

    NSDL National Science Digital Library

    Imamura, James N. (James Noboru), 1952-

    This presentation overviews solar energy from stars, nucleosynthesis, how other trace elements form, and how studying stars is useful for physicists. These lectures contain pictures, images, graphs, and links to the definitions of astronomical terms all within its text.

  9. Star Formation in Irregular Galaxies.

    ERIC Educational Resources Information Center

    Hunter, Deidre; Wolff, Sidney

    1985-01-01

    Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

  10. Star clusters as diaries of galaxies

    E-print Network

    Th. Maschberger; P. Kroupa

    2007-06-11

    Most if not all stars form in star clusters. Thus the distribution of star clusters preserves the information on the star formation history of a galaxy. Massive clusters form only during episodes of high star formation activity whereas periods of low star formation activity cannot produce them. We present here the method of Maschberger & Kroupa (2007) to derive the star formation history of a galaxy from its star-cluster content.

  11. The Pulsating White Dwarf Stars

    Microsoft Academic Search

    G. Fontaine; P. Brassard

    2008-01-01

    We present a summary of what is currently known about the three distinct families of isolated pulsating white dwarfs. These are the GW Vir stars (He\\/C\\/O-atmosphere stars with Teff ~= 120,000 K), the V777 Her stars (He-atmosphere, Teff ~= 25,000 K), and the ZZ Ceti stars (H-atmosphere, Teff ~= 12,000 K), all showing multiperiodic luminosity variations caused by low-order and

  12. Spectral Modeling Hot Star Winds

    E-print Network

    Cohen, David

    Spectral Modeling of X-Rays from Hot Star Winds Emma Wollman Advisor: David Cohen #12;Hot Stars ·· Short-livedShort-lived (~ 1-10 million yrs)(~ 1-10 million yrs) #12;Stellar Winds · Net momentum · More luminosity !"stronger wind · Mass-loss rate determines the fate of the star #12;X-ray Production

  13. High-gravity central stars

    E-print Network

    Thomas Rauch

    2006-07-11

    NLTE spectral analyses of high-gravity central stars by means of state-of-the-art model atmosphere techniques provide information about the precursor AGB stars. The hydrogen-deficient post-AGB stars allow investigations on the intershell matter which is apparently exhibited at the stellar surface. We summarize recent results from imaging, spectroscopy, and spectropolarimetry.

  14. Massive hybrid stars with strangeness

    NASA Astrophysics Data System (ADS)

    Takatsuka, T.; Hatsuda, T.; Masuda, K.

    2015-10-01

    How massive the hybrid stars could be is discussed by a "3-window model" proposed from a new strategy to construct the equation of state with hadron-quark transition. It is found that hybrid stars have a strong potentiality to generate a large mass compatible with two-solar-mass neutron star observations.

  15. Fluctuation studies in STAR

    E-print Network

    Supriya Das

    2006-12-08

    Study of event by event fluctuations of thermodynamic quantities offer us more insight about the hot and dense matter created in the relativistic heavy ion collisions. In this review the recent results on these studies carried out by the STAR collaboration are presented.

  16. Colors of Stars

    NSDL National Science Digital Library

    Mary Kay Hemenway

    2011-01-01

    In this activity, learners observe colors in the flame of a burning candle to explore connections between matter, light, color and temperature -- basic concepts of matter and energy. Then, learners elaborate on these basic concepts in a new context of astronomy by drawing scale models of stars. This activity involves an open flame; adult supervision is recommended.

  17. Focus on the Stars.

    ERIC Educational Resources Information Center

    Geary, Pat; And Others

    This document consists of a series of astronomy activities for intermediate grade students. It contains three major teaching sections. Teacher Section I deals with stars, constellations, and galaxies and presents a series of demonstrations, discussion topics, readings, and hands-on-activities. Teachers Section II is concerned with a planetarium…

  18. The Summer Stars Program.

    ERIC Educational Resources Information Center

    Cantrell, Mary Lou; Ebdon, Susan Austin; Firlik, Russell; Johnson, Diane; Rearick, Dianne

    1997-01-01

    Designing projects around Gardner's multiple intelligences, a Connecticut school created a one-week summer camp where children can tap into their unique strengths. The Summer Stars program allows children ages 7-12 to choose materials and activities from many topics and to participate in one of three internships involving a discovery museum, a…

  19. Pygmy stars: first pair.

    PubMed

    Zwicky, F

    1966-07-01

    The binary LP 101-15/16 having the proper motion of 1.62 seconds of arc per year has been studied with the prime-focus spectrograph of the 200-inch (508 cm) telescope. Indications are that LP 101-15/16 is the first pair of pygmy stars ever discovered. One of its components, LP 101-16, is probably a blue pygmy star which is at least four magnitudes fainter than the ordinary white dwarfs. Also, two of the Balmer lines in absorption appear to be displaced toward the red by amounts which indicate the existence of an Einstein gravitational red shift corresponding to about 1000 km sec-1. On the other hand LP 101-15 is red and shows an entirely new type of spectrum, which suggests that it may be a first representative of a type of red pygmy star which is 2.5 magnitudes fainter than the M-type dwarf stars of the main sequence. PMID:17730606

  20. Almagest (Ptolemy's Star Catalog)

    Microsoft Academic Search

    C. Ptolemy; K. Manitius

    1995-01-01

    This catalogue is the machine readable version of the star catalogue given by Claudius Ptolemy in his book called usually the Almagest. It is based upon its translation by K. Manitius (ed. B.G. Teubner, Leipzig 1913). The table reproduces the values given in book VII, chapter V, namely Identification, name, longitude, latitude and magnitude. To facilitate its use the following

  1. Neutrinos from Protoneutron Stars

    E-print Network

    S. Reddy; J. Pons; M. Prakash; J. M. Lattimer

    1998-02-24

    We study the diffusive transport of neutrinos in a newly born neutron star to explore its sensitivity to dense matter properties. Energy and lepton number which are trapped during the catastrophic implosion diffuse out on the time scale of a few tens of seconds. Results for different dense matter models are presented.

  2. Our Star, the Sun

    NSDL National Science Digital Library

    Mary Kay Hemenway

    2000-09-01

    Is the word "star" the first idea that leaps into your mind when you think about the sun? Some people think of warm summer days, beaches, or romantic sunsets. Children may think of something round and bright that is out in the daytime and disappears at ni

  3. Reaching for the Stars

    ERIC Educational Resources Information Center

    Terry, Dorothy Givens

    2012-01-01

    Dr. Mae Jemison is the world's first woman astronaut of color who continues to reach for the stars. Jemison was recently successful in leading a team that has secured a $500,000 federal grant to make interstellar space travel a reality. The Dorothy Jemison Foundation for Excellence (named after Jemison's mother) was selected in June by the Defense…

  4. Quarkonium at STAR

    SciTech Connect

    LeCompte, T. J.

    1998-11-11

    The STAR detector is capable of reconstruction the J/{psi} meson in its dielectron decay channel, along with continuum dielectrons from heavy quark decay. The limitation is not instrumental--the ability of the STAR detector to identify electrons--rather, the primary limitation is yield. We expect to reconstruct of order 10,000 events per year in the bin of highest centrality, with perhaps ten times that many integrated over all bins of centrality. This is enough for a rather detailed study of J/{psi} production. The yields for {psi}{prime} and the high p{sub T} {chi} mesons which are in a low enough background region of phase space to permit reconstruction are too small for precision measurements. The only parent of the J/{psi} with a large enough yield for clear observation is the b quark. Even limited to just the J/{psi}, there is a rich physics program available to STAR: the yield provides information on the gluon flux as well as color screening, especially when compared to the open charm and b {r_arrow} J/{psi}X yields. The p{sub T} distribution measures energy loss in a nuclear medium, either by comparison with pp data or across different bins in centrality. The STAR quarkonium program should provide several unique windows into the physics of heavy ion collisions at RHIC.

  5. Deepsea Brittle Star

    USGS Multimedia Gallery

    Collected from more than 1000 feet below the surface of the Gulf of Mexico, this fragile brittle star clings to a soft coral.  These deep-sea coral ecosystems ar biodiversity hot-spots in the deep ocean, but they are also vulnerable to climate change issues such as increased temperature and ocean ac...

  6. Written in the Stars

    E-print Network

    Seager, Sara

    I first really saw the stars when I was 10 years old and on my first camping trip, in Ontario. I remember awakening late one night, stepping outside the tent, and looking up. I was completely stunned by what I saw. ...

  7. Emmy's Moon and Stars

    NSDL National Science Digital Library

    Francis Eberle

    2007-01-01

    The purpose of this assessment probe is to elicit students' ideas about the relative position of common objects seen in the sky. The probe is designed to find out if students recognize how far away the stars are in relation to the Earth and the Moon.

  8. THE STAR OFFLINE FRAMEWORK.

    SciTech Connect

    FINE,V.; FISYAK,Y.; PEREVOZTCHIKOV,V.; WENAUS,T.

    2000-02-07

    The Solenoidal Tracker At RHIC (STAR) is a-large acceptance collider detector, commissioned at Brookhaven National Laboratory in 1999. STAR has developed a software framework supporting simulation, reconstruction and analysis in offline production, interactive physics analysis and online monitoring environments that is well matched both to STAR's present status of transition between Fortran and C++ based software and to STAR's evolution to a fully OO software base. This paper presents the results of two years effort developing a modular C++ framework based on the ROOT package that encompasses both wrapped Fortran components (legacy simulation and reconstruction code) served by IDL-defined data structures, and fully OO components (all physics analysis code) served by a recently developed object model for event data. The framework supports chained components, which can themselves be composite subchains, with components (''makers'') managing ''data sets'' they have created and are responsible for. An St-DataSet class from which data sets and makers inherit allows the construction of hierarchical organizations of components and data, and centralizes almost all system tasks such as data set navigation, I/O, database access, and inter-component communication. This paper will present an overview of this system, now deployed and well exercised in production environments with real and simulated data, and in an active physics analysis development program.

  9. The First Stars

    NSDL National Science Digital Library

    The very first stars in the universe died a long time before astronomers could get a look at them. Billions of years after the last of these first stars expired, telescopes are finally tracking them down. This radio broadcast uncovers new research into how the transition from dark to light came about. After the Big Bang which established time, space and matter, there was a dark age - a stretch of 100 million years which persisted until the first lights appeared. The broadcast explains why the first stars - before the stars and galaxies we know today came into being - are believed to have been phenomenally large protostars with a mass - or weight - around 100 times greater than our own Sun and occupying a vastly greater volume of space. So far, no visual trace of these megastars has been found, but we could be on the threshold of finding it, perhaps with the NGST telescope (Next Generation Space Telescope). The broadcast is 30 minutes in length.

  10. Masers and star formation

    Microsoft Academic Search

    Vincent L. Fish; Jansky Fellow

    2007-01-01

    Recent observational and theoretical advances concerning astronomical masers\\u000ain star forming regions are reviewed. Major masing species are considered\\u000aindividually and in combination. Key results are summarized with emphasis on\\u000apresent science and future prospects.

  11. Formality and Star Products

    Microsoft Academic Search

    Alberto S. Cattaneo; Davide Indelicato

    2004-01-01

    These notes, based on the mini-course given at the PQR2003 Euroschool held in Brussels in 2003, aim to review Kontsevich's formality theorem together with his formula for the star product on a given Poisson manifold. A brief introduction to the employed mathematical tools and physical motivations is also given.

  12. The Double Star mission

    Microsoft Academic Search

    Z. X. Liu; C. P. Escoubet; Z. Pu; H. Laakso; J. K. Shi; C. Shen; M. Hapgood

    2005-01-01

    The Double Star Programme (DSP) was first proposed by China in March, 1997 at the Fragrant Hill Workshop on Space Science, Beijing, organized by the Chinese Academy of Science. It is the first mission in collaboration between China and ESA. The mission is made of two spacecraft to investigate the magnetospheric global processes and their response to the interplanetary disturbances

  13. Dilepton Measurements at STAR

    E-print Network

    F. Geurts

    2013-05-23

    In the study of hot and dense nuclear matter, created in relativistic heavy-ion collisions, dilepton measurements play an essential role. Leptons, when compared to hadrons, have only little interaction with the strongly interacting system. Thus, dileptons provide ideal penetrating probes that allow the study of such a system throughout its space-time evolution. In the low mass range ($M_{ll}3.0$ GeV/$c^2$), dilepton measurements are expected to see contributions from primordial processes involving heavy quarks, and Drell-Yan production. With the introduction of the Time-of-Flight detector, the STAR detector has been able to perform large acceptance, high purity electron identification. In this contribution, we will present STAR's recent dielectron measurements in the low and intermediate mass range for RHIC beam energies ranging between 19.6 and 200 GeV. Compared to electrons, muon measurements have the advantage of reduced bremsstrahlung radiation in the surrounding detector materials. With the upcoming detector upgrades, specifically the muon detector (MTD), STAR will be able to include such measurements in its (di-)lepton studies. We will discuss the future dilepton program at STAR and the physics cases for these upgrades.

  14. Star Cluster Formation and Star Formation: The Role of Environment and Star Formation Efficiencies

    E-print Network

    Uta Fritze

    2008-01-15

    Analyzing global starburst properties in various kinds of starburst and post-starburst galaxies and relating them to the properties of the star cluster populations they form, I explore the conditions for the formation of massive, compact, long-lived star clusters. The aim is to find out whether the relative amount of star formation that goes into star cluster formation as opposed to field star formation, and into the formation of massive long-lived clusters in particular, is universal or scales with star formation rate, burst strength, star formation efficiency, galaxy or gas mass, and whether or not there are special conditions or some threshold for the formation of star clusters that merit to be called globular clusters a few gigayears later.

  15. Spectroscopic Study of Extended Star Clusters in Dwarf Galaxy NGC 6822

    NASA Astrophysics Data System (ADS)

    Hwang, Narae; Park, Hong Soo; Lee, Myung Gyoon; Lim, Sungsoon; Hodge, Paul W.; Kim, Sang Chul; Miller, Bryan; Weisz, Daniel

    2014-03-01

    We present a spectroscopic study of the four extended star clusters (ESCs) in NGC 6822 based on the data obtained with the Gemini Multi-Object Spectrograph on the Gemini-South 8.1 m telescope. The radial velocities derived from the spectra range from -61.2 ± 20.4 km s-1 (for C1) to -115.34 ± 57.9 km s-1 (for C4) and, unlike the intermediate-age carbon stars, they do not display any sign of systematic rotation around NGC 6822. The ages and metallicities derived using the Lick indices show that the ESCs are old (>=8 Gyr) and metal poor ([Fe/H] <~ -1.5). NGC 6822 is found to have both metal poor ([Fe/H] ?-2.0) and metal rich ([Fe/H] ?-0.9) star clusters within 15' (2 kpc) from the center, whereas only metal poor clusters are observed in the outer halo with r >= 20'(2.6 kpc). The kinematics, old ages, and low metallicities of ESCs suggest that ESCs may have accreted into the halo of NGC 6822. Based on the velocity distribution of ESCs, we have determined the total mass and the mass-to-light ratio of NGC 6822: M_{N6822} = 7.5^{+4.5}_{-0.1} \\times 10^{9}\\ M_{\\odot } and (M/L)_{N6822} = 75^{+45}_{-1} (M/L)_{\\odot }. It shows that NGC 6822 is one of the most dark matter dominated dwarf galaxies in the Local Group. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  16. Sodium laser guide star system at Lawrence Livermore National Laboratory: System description and experimental results

    SciTech Connect

    Avicola, K.; Brase, J.; Morris, J. [and others

    1994-03-02

    The architecture and major system components of the sodium-layer kw guide star system at LLNL will be described, and experimental results reported. The subsystems include the laser system, the beam delivery system including a pulse stretcher and beam pointing control, the beam director, and the telescope with its adaptive-optics package. The laser system is one developed for the Atomic Vapor Laser Isotope Separation (AVLIS) Program. This laser system can be configured in various ways in support of the AVLIS program objectives, and was made available to the guide star program at intermittent times on a non-interference basis. The first light transmitted into the sky was in July of 1992, at a power level of 1. 1 kW. The laser pulse width is about 32 ns, and the pulse repetition rate was 26 kHz for the 1. 1 kW configuration and 13 kHz for a 400 W configuration. The laser linewidth is tailored to match the sodium D{sub 2} absorption line, and the laser system has active control of beam pointing and wavefront quality. Because of the short pulse length the sodium transition is saturated and the laser power is not efficiently utilized. For this reason a pulse stretcher was developed, and the results of this effort will be reported. The beam is delivered via an evacuated pipe from the laser building to the guide star site, a distance of about 100 meters, and then launched vertically. A beam director provides the means to track the sky in the full AO system, but was not used in the experiments reported here. The return signal is collected by a 1/2 meter telescope with the AO package. This telescope is located 5 meters from the km launch tube. Smaller packages for photometry, wavefront measurement, and spot image and motion analysis have been used. Although the unavailability of the AVLIS laser precluded a full AO system demonstration, data supporting feasibility and providing input to the system design for a Lick Observatory AO system was obtained.

  17. Halo Star Evolution

    E-print Network

    Brian Chaboyer

    1995-09-08

    In this review, I will discuss a few problems which point to the need for improved stellar evolution models of halo stars. Current stellar evolution models do not match the observed $^7$Li abundance patterns, suggesting that the input physics and/or the assumptions used in constructing the models are in need of revision. It appears that all halo stars have suffered some $^7$Li depletion, implying that the primordial $^7$Li abundance is higher than that presently observed in hot halo stars. Observations of abundances of various elements in globular cluster giant branch stars have suggested for some time now that some form of deep mixing, which is not present in theoretical models, occurs in halo stars. The driving mechanism for this mixing, and its incorporation into stellar models remain one of the key problems in stellar modeling. Current theoretical isochrones are able to provide a good match to observed colour-magnitude diagrams. However, there is some evidence that the theoretical luminosity functions are in disagreement with observations. This is an area which requires further study, as it suggests that the relative main sequence/giant branch lifetimes predicted by the models are incorrect. A discussion of some of the uncertainties involved in determining the ages of globular clusters is presented. The absolute ages of globular clusters provide a lower bound to the age of the universe, and so are of great interest to cosmologists. Unfortunately, present uncertainties in stellar models lead to a rather large range in the inferred ages of globular clusters of 11 -- 18 Gyr.

  18. The Electronic Be Star Newsletter

    NASA Astrophysics Data System (ADS)

    Gies, D. R.

    1995-01-01

    The Be Star Newsletter, a publication of the IAU Working Group on Active B Stars, is now available on-line as an electronic journal. The Be Star Newsletter is a non-refereed electronic and paper journal that is published approximately twice per year. The Newsletter is open to all contributions (observations, theory, or other news) concerning early-type stars and especially hot, near main-sequence stars. The goal of the Newsletter is to foster communication between researchers interested in this field of stellar astronomy.

  19. Hot Stars in Globular Clusters

    E-print Network

    S. Moehler

    1998-12-08

    Blue horizontal branch and UV bright stars in several globular clusters are analysed spectroscopically and the results are compared with predictions of stellar evolutionary theory. We find that the distribution of temperatures and surface gravities of the blue HB stars may be explained by the effects of deep mixing. The masses derived for these stars are too low unless one uses the long distance scale for globular clusters. First results on blue HB stars in metal rich clusters are presented. Analyses of hot UV bright stars in globular clusters uncovered a lack of genuine post-asymptotic giant branch stars which may explain the lack of planetary nebulae in globular clusters seen by Jacoby et al. (1997). Abundance analyses of post-AGB stars in two globular clusters suggest that gas and dust may separate during the AGB phase.

  20. Star Cluster Formation and Feedback

    E-print Network

    Krumholz, Mark R; Arce, Hector G; Dale, James E; Gutermuth, Robert; Klein, Richard I; Li, Zhi-Yun; Nakamura, Fumitaka; Zhang, Qizhou

    2014-01-01

    Stars do not generally form in isolation. Instead, they form in clusters, and in these clustered environments newborn stars can have profound effects on one another and on their parent gas clouds. Feedback from clustered stars is almost certainly responsible for a number of otherwise puzzling facts about star formation: that it is an inefficient process that proceeds slowly when averaged over galactic scales; that most stars disperse from their birth sites and dissolve into the galactic field over timescales $\\ll 1$ Gyr; and that newborn stars follow an initial mass function (IMF) with a distinct peak in the range $0.1 - 1$ $M_\\odot$, rather than an IMF dominated by brown dwarfs. In this review we summarize current observational constraints and theoretical models for the complex interplay between clustered star formation and feedback.

  1. Gaining Insight into Star Formation: Resolved Star Formation Laws

    NASA Astrophysics Data System (ADS)

    Liebst, Kelley; Scowen, Paul A.

    2014-06-01

    Until recently astronomers have used star formation laws to measure the star formation rate and star formation efficiency of galaxies only on global scales because of the poor resolution of available data. What I am now capable of producing is a spatially resolved star formation law that can provide direct insight into the physical processes that govern star formation and assess the short-term nature of bursts of star formation and the longer-term nature of larger-scale events that can dictate the global distribution of stars and the ultimate fate of a galaxy as a whole. I am using exquisite narrowband optical data from a variety of sources, including the Hubble Space Telescope, and Kitt Peak National Observatory, etc., in conjunction with infrared data from the Spitzer Infrared Nearby Galaxy Survey and the Spitzer Local Volume Legacy survey, neutral gas data from The HI Nearby Galaxy Survey, and molecular gas data from the Berkeley-Illinois-Maryland Association Survey of Nearby Galaxies, to provide star formation rates and star formation efficiencies on previously inaccessible small spatial scales across a suite of galaxies that represent a range of star formation environments and scales. My sample includes 18 spiral galaxies ranging from 2.1 to 15.1 Mpc in distance and offers a large range of morphological types (i.e. a large range of star formation environments). I am using these data to test different models of star formation modes under a variety of physical conditions and relate the variations I observe to the known local physical conditions and the associated star formation histories for each locale within each galaxy.This is the heart of the matter - that the nature and evolution of the local physical environment intimately influences how stars can form, how quickly and how massive those stars are allowed to form, and as a result how they shape the local conditions for subsequent star formation. It is this tracking of the stellar ecology that is vital for insight into the star formation process, but also to understand the conditions that can result in star and planet formation, or conversely what conditions prevent this. Such an analysis is only possible with the kind of datasets I am producing.

  2. Metallicity of Vegalike stars

    NASA Astrophysics Data System (ADS)

    Saffe, C.; Gómez, M.; Pintado, O.; González, E.

    We present spectroscopic metallicities of more than 100 candidate Vega-like stars, with BAFGK spectral types, 40 of which have been confirmed by SPITZER. We used more than 400 spectra taken from CASLEO, with the REOSC spectrograph in cross-dispersion mode. The metallicity was derived by two methods. First, we used Kurucz (1992) model atmospheres, together with the measure of Fe lines equivalent widths. Then, we compared observed spectra with a grid of synthetic spectra (Munari et al. 2005), aplying the Downhill method (Gray 2001). We derived solar metallicites (median=-0.15 dex) for the sample of candidate Vega-like stars, independent of the spectral type. FULL TEXT IN SPANISH

  3. The first stars

    NASA Technical Reports Server (NTRS)

    Silk, J.

    1983-01-01

    Primordial clouds are likely to be remarkably uniform over stellar mass-scales in the absence of a pre-existing generation of stars. Thermal instability is found to occur during the collapse of a primordial cloud when the H2 abundance is rising and the H2 optical depth is of order unity. The e-folding rate for fluctuation growth exceeds the free-fall collapse rate by an order of magnitude. Large density fluctuations of mass-scale 0.1 solar mass arise in any collapsing cloud with metallicity not greater than 0.001 of the solar value. Gravitational instability ensures that many of the clumps coagulate to form protostars of masses extending up to the initial Jeans mass when the fluctuations develop, namely 100 solar masses. The primordial IMF should therefore have spanned the mass range from 0.1 to 100 solar masses, but may have been dominated by the more massive stars.

  4. White Dwarf Stars

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Peering deep inside a cluster of several hundred thousand stars, NASA's Hubble Space Telescope has uncovered the oldest burned-out stars in our Milky Way Galaxy, giving astronomers a fresh reading on the age of the universe.

    Located in the globular cluster M4, these small, burned-out stars -- called white dwarfs -- are about 12 to 13 billion years old. By adding the one billion years it took the cluster to form after the Big Bang, astronomers found that the age of the white dwarfs agrees with previous estimates that the universe is 13 to 14 billion years old.

    The images, including some taken by Hubble's Wide Field and Planetary Camera 2, are available online at

    http://oposite.stsci.edu/pubinfo/pr/2002/10/ or

    http://www.jpl.nasa.gov/images/wfpc .

    The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    In the top panel, a ground-based observatory snapped a panoramic view of the entire cluster, which contains several hundred thousand stars within a volume of 10 to 30 light-years across. The Kitt Peak National Observatory's .9-meter telescope took this picture in March 1995. The box at left indicates the region observed by the Hubble telescope.

    The Hubble telescope studied a small region of the cluster. A section of that region is seen in the picture at bottom left. A sampling of an even smaller region is shown at bottom right. This region is only about one light-year across. In this smaller region, Hubble pinpointed a number of faint white dwarfs. The blue circles indicate the dwarfs. It took nearly eight days of exposure time over a 67-day period to find these extremely faint stars.

    Globular clusters are among the oldest clusters of stars in the universe. The faintest and coolest white dwarfs within globular clusters can yield a globular cluster's age. Earlier Hubble observations showed that the first stars formed less than 1 billion years after the universe's birth in the big bang. So, finding the oldest stars puts astronomers within arm's reach of the universe's age.

    Hubble's Wide Field and Planetary Camera 2 made the observations from January through April 2001. These optical observations were combined to create the above images. Spectral data were also taken. M4 is 7,000 light-years away in the constellation Scorpius.

    The full press release on the latest findings is online at

    http://oposite.stsci.edu/pubinfo/pr/2002/10/pr.html .

    The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract with the Goddard Space Flight Center, Greenbelt, Md. The Hubble Space Telescope is a project of international cooperation between the European Space Agency and NASA. The California Institute of Technology in Pasadena manages JPL for NASA.

  5. Neutron Stars for Undergraduates

    E-print Network

    Richard R. Silbar; Sanjay Reddy

    2003-11-26

    Calculating the structure of white dwarf and neutron stars would be a suitable topic for an undergraduate thesis or an advanced special topics or independent study course. The subject is rich in many different areas of physics accessible to a junior or senior physics major, ranging from thermodynamics to quantum statistics to nuclear physics to special and general relativity. The computations for solving the coupled structure differential equations (both Newtonian and general relativistic) can be done using a symbolic computational package, such as Mathematica. In doing so, the student will develop computational skills and learn how to deal with dimensions. Along the way he or she will also have learned some of the physics of equations of state and of degenerate stars.

  6. Characterizing Hot Star Winds

    NASA Astrophysics Data System (ADS)

    Canizares, Claude

    2014-09-01

    tau CMa is an 09 II star, the brightest in the open cluster NGC 2362. The existing HETG spectrum of 90 ks exposure shows that the O VIII profile is broad, slightly asymmetric and blueshifted, making it look like a classic freely expanding stellar wind. Other lines are not well characterized due to the lower signal. With 300 ks total exposure, we can characterize the line shapes for Si, Mg, Ne, and Fe, thus probing the wind to higher temperatures and nearer the photosphere. We will also obtain better constraints on He-triplet f/i ratios, important for determining the radial location of X-ray formation. The results are important for comparison to stars of different spectral types, ages, and with different wind-formation mechanisms (thick, thin, colliding, or magnetically confined).

  7. The Star Formation Camera

    Microsoft Academic Search

    Paul A. Scowen; Rolf Jansen; Matthew Beasley; Daniela Calzetti; Steven Desch; Alex Fullerton; John Gallagher; Doug Lisman; Steve Macenka; Sangeeta Malhotra; Mark McCaughrean; Shouleh Nikzad; Robert O'Connell; Sally Oey; Deborah Padgett; James Rhoads; Aki Roberge; Oswald Siegmund; Stuart Shaklan; Nathan Smith; Daniel Stern; Jason Tumlinson; Rogier Windhorst; Robert Woodruff

    2009-01-01

    The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV\\/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the

  8. Star in the heart

    PubMed Central

    Krishnamoorthy, K M; Tharakan, J A; Krishnamanohar, S R

    2004-01-01

    In a 50 year old woman, transthoracic echocardiography showed a left atrial mass. Transoesophageal echocardiography delineated its attachment. Additionally, cystic spaces were seen arranged concentrically in the shape of a star in the centre of the tumour. Surgical excision followed. Histopathological examination confirmed myxoma with areas of haemorrhage and necrosis. This case highlights the acoustic property of myxomas in a rare and beautiful manner and emphasises the superior transoesophageal imaging of myxomas. PMID:15084571

  9. Radius of neutron stars

    SciTech Connect

    Meszaros, P.; Riffert, H.

    1987-12-01

    Consideration is given to recent calculations of general relativistic effects in the beaming, spectrum, and pulse properties of accreting neutron stars. Some possible models for X-ray pulsars and QPOs are analyzed, which indicate that current observational and theoretical requirements can be explained with a value of the radius smaller than about two Schwarzschild radii. Concurrent information and calculations on several X-ray burster sources are compatible with this conclusion. 33 references.

  10. StarChild

    NSDL National Science Digital Library

    Whitlock, Laura

    Created by the United States National Aeronautics and Space Administration, StarChild is an online astronomy learning center for elementary and middle school students. Included are materials about the solar system, the Milky Way galaxy, and extra-galactic astronomy. Materials are divided into two different grade levels. Once divided into these two levels, the resource contains information on the solar system, universe, space stuff and a glossary. Translations are also available in German, Italian, Portuguese and Spanish.

  11. Chameleon dark matter stars

    E-print Network

    Folomeev, Vladimir; Dzhunushaliev, Vladimir

    2013-01-01

    We consider static, spherically symmetric equilibrium configurations consisting of interacting dark matter/dark energy and embedded in an external, homogeneous chameleon scalar field. With the coupling function, form of which is taken to meet cosmological observations, we estimate the effect of such a nonminimal coupling on the properties of dark matter compact configurations. We show that the masses and sizes of the resulting chameleon dark matter stars are smaller than those of systems with no field present.

  12. Asymmetric Dark Matter Stars

    E-print Network

    Kouvaris, Chris

    2015-01-01

    We study the possibility of asymmetric dark matter with self-interactions forming compact stable objects. We solve the Tolman-Oppenheimer-Volkoff equation and find the mass-radius relation of such "dark stars", their density profile and their Chandrasekhar mass limit. We consider fermionic asymmetric dark matter with Yukawa-type self-interactions appropriate for solving the well known problems of the collisionless dark matter paradigm. We find that in several cases the relativistic effects are significant.

  13. Our Super Star

    NSDL National Science Digital Library

    2005-01-01

    In this lesson, students use observations, activities, and videos to learn basic facts about the Sun. They will understand that the Sun appears to move in predictable daily patterns, that it is a star and its radiation lights and heats Earth, that night and day are a result of Earth's rotation, and recognize that all planets in our solar system orbit the Sun. They will also test ways to use solar power to bake cookies.

  14. Asteroseismology of Pulsating Stars

    NASA Astrophysics Data System (ADS)

    Joshi, Santosh; Joshi, Yogesh C.

    2015-03-01

    The success of helioseismology is due to its capability of measuring p-mode oscillations in the Sun. This allows us to extract information on the internal structure and rotation of the Sun from the surface to the core. Similarly, asteroseismology is the study of the internal structure of the stars as derived from stellar oscillations. In this review we highlight the progress in the observational asteroseismology, including some basic theoretical aspects. In particular, we discuss our contributions to asteroseismology through the study of chemically peculiar stars under the `Nainital-Cape Survey' project being conducted at ARIES, Nainital, since 1999. This survey aims to detect new rapidly-pulsating Ap (roAp) stars in the northern hemisphere. We also discuss the contribution of ARIES towards the asteroseismic study of the compact pulsating variables. We comment on the future prospects of our project in the light of the new optical 3.6-m telescope to be installed at Devasthal (ARIES). Finally, we present a preliminary optical design of the high-speed imaging photometers for this telescope.

  15. Asteroseismology of Pulsating Stars

    NASA Astrophysics Data System (ADS)

    Joshi, Santosh; Joshi, Yogesh C.

    2015-04-01

    The success of helioseismology is due to its capability of measuring p-mode oscillations in the Sun. This allows us to extract information on the internal structure and rotation of the Sun from the surface to the core. Similarly, asteroseismology is the study of the internal structure of the stars as derived from stellar oscillations. In this review we highlight the progress in the observational asteroseismology, including some basic theoretical aspects. In particular, we discuss our contributions to asteroseismology through the study of chemically peculiar stars under the `Nainital-Cape Survey' project being conducted at ARIES, Nainital, since 1999. This survey aims to detect new rapidly-pulsating Ap (roAp) stars in the northern hemisphere. We also discuss the contribution of ARIES towards the asteroseismic study of the compact pulsating variables. We comment on the future prospects of our project in the light of the new optical 3.6-m telescope to be installed at Devasthal (ARIES). Finally, we present a preliminary optical design of the high-speed imaging photometers for this telescope.

  16. Triggered star formation in the environment of young massive stars

    NASA Astrophysics Data System (ADS)

    Gritschneder, Matthias; Naab, T.; Heitsch, F.; Burkert, A.

    Recent observations with the Spitzer Space Telescope show clear evidence that star formation takes place in the surrounding of young massive O-type stars, which are shaping their environment due to their powerful radiation and stellar winds. In this work we investigate the effect of ionising radiation of massive stars on the ambient interstellar medium (ISM): In particular we want to examine whether the UV-radiation of O-type stars can lead to the observed pillar-like structures and can trigger star formation. We developed a new implementation, based on a parallel Smooth Particle Hydrodynamics code (VINE), that allows an efficient treatment of the effect of ionising radiation from massive stars on their turbulent gaseous environment. Here we present first results at very high resolution. We show that ionising radiation can trigger the collapse of an otherwise stable molecular cloud. The arising structures resemble observed structures (e.g. the pillars of creation in the Eagle Nebula (M16) or the Horsehead Nebula B33). Including the effect of gravitation we find small regions that can be identified as formation places of individual stars. We conclude that ionising radiation from massive stars alone can trigger substantial star formation in molecular clouds.

  17. Triggered Star Formation in the Environment of Young Massive Stars

    E-print Network

    M. Gritschneder; T. Naab; F. Heitsch; A. Burkert

    2006-09-26

    Recent observations with the Spitzer Space Telescope show clear evidence that star formation takes place in the surrounding of young massive O-type stars, which are shaping their environment due to their powerful radiation and stellar winds. In this work we investigate the effect of ionising radiation of massive stars on the ambient interstellar medium (ISM): In particular we want to examine whether the UV-radiation of O-type stars can lead to the observed pillar-like structures and can trigger star formation. We developed a new implementation, based on a parallel Smooth Particle Hydrodynamics code (called IVINE), that allows an efficient treatment of the effect of ionising radiation from massive stars on their turbulent gaseous environment. Here we present first results at very high resolution. We show that ionising radiation can trigger the collapse of an otherwise stable molecular cloud. The arising structures resemble observed structures (e.g. the pillars of creation in the Eagle Nebula (M16) or the Horsehead Nebula B33). Including the effect of gravitation we find small regions that can be identified as formation places of individual stars. We conclude that ionising radiation from massive stars alone can trigger substantial star formation in molecular clouds.

  18. Which Stars Form Black Holes and Neutron Stars?

    E-print Network

    Michael P. Muno

    2006-11-18

    I describe the current state of our knowledge of the mapping between the initial masses of stars and the compact objects -- particularly neutron stars and black holes -- that they produce. Most of that knowledge is theoretical in nature, and relies on uncertain assumptions about mass loss through winds, binary mass transfer, and the amount of mass ejected during a supernovae. Observational constraints on the initial masses of stars that produce neutron stars and black holes is scarce. They fall into three general categories: (1) models of the stars that produced the supernova remnants associated with known compact objects, (2) scenarios through with high mass X-ray binaries were produced, and (3) associations between compact objects and coeval clusters of stars for which the minimum masses of stars that have undergone supernovae are known. I focus on the last category as the most promising in the near term. I describe three highly-magnetized neutron stars that have been associated with progenitors that had initial masses of $>$30\\msun, and evaluate the prospects of finding further associations between star clusters and compact objects.

  19. A Stars in the Pleiades

    NASA Astrophysics Data System (ADS)

    Willson, Lee Anne

    We propose to observe selected A stars in the Pleiades in the long wavelength region at high resolution to search for signatures of mass loss. Mass loss rates sufficiently high to be observable with IUE, and sufficiently high force these stars to evolve down the main sequence, has been suggested by Willson, Bowen and Struck-Marcell (1987). This mass loss is expected to be highest for rapidly rotating stars, and to be somewhat concentrated towards the equatorial zones, so the stars with the largest vsini values are expected to show the strongest P Cygni profiles. We propose to observe 8-10 Pleiades A stars at high resolution, covering the range In spectral subclass and vsini. As these observations will occupy typically 2/3-3/4 of a US1 shift, we also plan to obtain low resolution spectra of as many of the unobserved Pleiades A stars as we can fit Into the remainder of each shift.

  20. Chinese Constellations and Star Maps

    NASA Astrophysics Data System (ADS)

    Sun, Xiaochun

    Star observations can be traced back to as early as the twenty-third century BC in ancient China. By the fifth century BC, the Chinese had named the 28 asterisms that formed the basic reference points for the Chinese equatorial coordinate system. By the first century BC, the Chinese had developed a unique system of constellations that reflected Chinese cosmological ideas with the central theme of the correlation between Heaven and Man. Star charts have been discovered on tomb ceilings dating back to Han times. But most of them are illustrative in their presentation of stars. The Dunhuang star maps from the ninth century, the star maps in the Xin yixiang fa yao of the eleventh century, and the Suzhou Astronomical Planisphere of the thirteenth century are examples of precise star maps from ancient China.

  1. The Constellations and Their Stars

    NSDL National Science Digital Library

    This comprehensive site looks at constellations, stars, the Milky Way, and Messier objects. Constellations are listed alphabetically as well as by month, and data covers star names and Messier objects in the constellation, the meaning of their names, and stories behind the constellation. There are also links to a regular star chart, and an interactive star chart where the constellation can be viewed in a variety of ways. Stars are listed alphabetically or by catalog number, and link to star name, designation, coordinates (declination and right ascension), brightness, and spectral type. There is also a description of known Messier objects, Milky Way photographs, a constellation abbreviation table, a Moon phases demonstration, and references and links for more information.

  2. New Abundansec From Very Old Stars

    E-print Network

    Hansen, T; Christlieb, N; Yong, D; Beers, T C; Andersen, J

    2015-01-01

    Metal-poor stars hold the fossil record of the Galactic chemical evolution and nucleosynthesis processes that took place at the earliest times in the history of our Galaxy. From detailed abundance studies of low mass, extremely metal-poor stars ([Fe/H] capture. The sample includes some of the most metal-poor stars ([Fe/H] capture elements, and also a number of stars enhanced in carbon. The so called CEMP (carbon enhanced metal-poor) stars, these stars make up ~20% of the stars with [Fe/H] < -3, and 80% of the stars with [Fe/H] < -4.5. The progenitors of CEMP stars is still ...

  3. Slowly Rotating Boson Fermion Stars

    E-print Network

    Claudio M G de Sousa; Vanda Silveira

    2001-02-04

    Relativistic prescription is used to study the slow rotation of stars composed by self-gravitating bosons and fermions (fermions may be considered as neutrons). Previous results demand that purely boson stars are unable to display slow rotation, if one uses relativistic prescription with classical scalar fields. In contrast to this, the present work shows that a combined boson-neutron star in its ground-state can rotate. Their structure and stability are analysed under slow rotation approximations.

  4. Two unusual, radially pulsating stars

    NASA Astrophysics Data System (ADS)

    Smolec, Rados?aw

    2014-12-01

    We present the results of pulsation modelling of two unusual radially pulsating stars pds and bep. The former variable is the first BL Her-type star showing the period doubling effect. The second variable is a member of well-detached eclipsing binary system and the first member of a new class of variable stars that mimic RR Lyrae pulsation, but have unusually small masses.

  5. Massive star clusters in galaxies.

    PubMed

    Harris, William E

    2010-02-28

    The ensemble of all star clusters in a galaxy constitutes its star cluster system. In this review, the focus of the discussion is on the ability of star clusters, particularly the systems of old massive globular clusters (GCs), to mark the early evolutionary history of galaxies. I review current themes and key findings in GC research, and highlight some of the outstanding questions that are emerging from recent work. PMID:20083511

  6. Special types of B stars

    NASA Astrophysics Data System (ADS)

    Lesh, J. R.

    The properties of the Beta Cephei stars are examined with emphasis on spectral types, luminosities, periods, and light and velocity variations. Typical members of the group and their position in the observational and theoretical HR diagram are discussed. Those B stars with anomalous spectra (chemically peculiar) are considered including hot subdwarfs, extreme helium, weak helium, strong helium, helium variable, magnetic and mercury-manganese stars.

  7. Fast Star Pattern Recognition Using Spherical Triangles

    E-print Network

    Crassidis, John L.

    Fast Star Pattern Recognition Using Spherical Triangles Craig L. Cole Orbital Sciences Corporation-4400 A current method by which star trackers identify stars is to match the angles between stars within its field of view to angles stored in a catalog. If an angle can be matched to one pair of stars, the attitude

  8. 24 STELLAR REMNANTS White Dwarf Stars

    E-print Network

    Sitko, Michael L.

    1 24 STELLAR REMNANTS White Dwarf Stars The first white dwarf star (Sirius B) was discovered of Sirius A&B X-ray image #12;2 The white dwarf stars are the endpoints of the evolution of low-mass stars numbers of white dwarfs exist. They may be among the most populous stars in the Galaxy, and recent deep

  9. Radial solitary waves in periodic variable stars

    E-print Network

    Fedor V. Prigara

    2006-09-15

    It is shown that the oscillations of brightness in classical Cepheids and other 'pulsating' variable stars are caused rather by the passing of radial solitary waves through the photosphere of a star, than by pulsations of a star. Radial solitary waves also determine the oscillations of brightness in some other types of periodic variable stars ordinary not considered as pulsating stars.

  10. Space Science in Action: Stars [Videotape].

    ERIC Educational Resources Information Center

    1999

    This videotape recording shows students the many ways scientists look at the stars and how they can use what they see to answer questions such as What are stars made of?, How far away are they?, and How old are the stars? Students learn about the life span of stars and the various stages they pass through from protostar to main sequence star to…

  11. Flattest Star Ever Seen

    NASA Astrophysics Data System (ADS)

    2003-06-01

    VLT Interferometer Measurements of Achernar Challenge Stellar Theory Summary To a first approximation, planets and stars are round. Think of the Earth we live on. Think of the Sun, the nearest star, and how it looks in the sky. But if you think more about it, you realize that this is not completely true. Due to its daily rotation, the solid Earth is slightly flattened ("oblate") - its equatorial radius is some 21 km (0.3%) larger than the polar one. Stars are enormous gaseous spheres and some of them are known to rotate quite fast, much faster than the Earth. This would obviously cause such stars to become flattened. But how flat? Recent observations with the VLT Interferometer (VLTI) at the ESO Paranal Observatory have allowed a group of astronomers [1] to obtain by far the most detailed view of the general shape of a fast-spinning hot star, Achernar (Alpha Eridani) , the brightest in the southern constellation Eridanus (The River). They find that Achernar is much flatter than expected - its equatorial radius is more than 50% larger than the polar one! In other words, this star is shaped very much like the well-known spinning-top toy, so popular among young children. The high degree of flattening measured for Achernar - a first in observational astrophysics - now poses an unprecedented challenge for theoretical astrophysics . The effect cannot be reproduced by common models of stellar interiors unless certain phenomena are incorporated, e.g. meridional circulation on the surface ("north-south streams") and non-uniform rotation at different depths inside the star. As this example shows, interferometric techniques will ultimately provide very detailed information about the shapes, surface conditions and interior structure of stars . PR Photo 15a/03 : The VLT Interferometer configuration for the Achernar measurements PR Photo 15b/03 : Achernar's "profile" , as measured by the VLTI. PR Photo 15c/03 : Models of Achernar's spatial shape. VLTI observations of Achernar ESO PR Photo 15a/03 ESO PR Photo 15a/03 [Preview - JPEG: 400 x 502 pix - 40k [Normal - JPEG: 800 x 1004 pix - 216k] Caption :PR Photo 15a/03 shows the configuration of the VLT Interferometer (VLTI) for the measurements of Achernar , described in this press release. The moveable, 40-cm test telescopes were positioned at specific "stations" (E0 + G1; B3 + M0; with baselines of 66 m and 140 m, respectively), allowing contiguous measurements in two nearly perpendicular directions. The two light beams were then sent via the path-compensating VLTI Delay Lines to the VINCI test instrument where they combined to form interferometric fringes. The positions of the four 8.2-m VLT Unit Telescopes are indicated by numbered circles. Test observations with the VLT Interferometer (VLTI) at the Paranal Observatory proceed well [2], and the astronomers have now begun to exploit many of these first measurements for scientific purposes. One spectacular result, just announced, is based on a series of observations of the bright, southern star Achernar (Alpha Eridani; the name is derived from "Al Ahir al Nahr" = "The End of the River"), carried out between September 11 and November 12, 2002. The two 40-cm siderostat test telescopes that served to obtain "First Light" with the VLT Interferometer in March 2001 were also used for these observations. They were placed at selected positions on the VLT Observing Platform at the top of Paranal to provide a "cross-shaped" configuration with two "baselines" of 66 m and 140 m, respectively, at 90° angle, cf. PR Photo 15a/03 . At regular time intervals, the two small telescopes were pointed towards Achernar and the two light beams were directed to a common focus in the VINCI test instrument in the centrally located VLT Interferometric Laboratory. Due to the Earth's rotation during the observations, it was possible to measure the angular size of the star (as seen in the sky) in different directions. Achernar's profile ESO PR Photo 15b/03 ESO PR Photo 15b/03 [

  12. Quark Stars: Features and Findings

    E-print Network

    Prashanth Jaikumar

    2007-01-25

    Under extreme conditions of temperature and/or density, quarks and gluons are expected to undergo a deconfinement phase transition. While this is an ephemeral phenomenon at the ultra-relativistic heavy-ion collider (BNL-RHIC), quark matter may exist naturally in the dense interior of neutron stars. Herein, we present an appraisal of the possible phase structure of dense quark matter inside neutron stars, and the likelihood of its existence given the current status of neutron star observations. We conclude that quark matter inside neutron stars cannot be dismissed as a possibility, although recent observational evidence rules out most soft equations of state.

  13. The Spacelab IPS Star Simulator

    NASA Technical Reports Server (NTRS)

    Wessling, Francis C., III

    1993-01-01

    The cost of doing business in space is very high. If errors occur while in orbit the costs grow and desired scientific data may be corrupted or even lost. The Spacelab Instrument Pointing System (IPS) Star Simulator is a unique test bed that allows star trackers to interface with simulated stars in a laboratory before going into orbit. This hardware-in-the loop testing of equipment on earth increases the probability of success while in space. The IPS Star Simulator provides three fields of view 2.55 x 2.55 degrees each for input into star trackers. The fields of view are produced on three separate monitors. Each monitor has 4096 x 4096 addressable points and can display 50 stars (pixels) maximum at a given time. The pixel refresh rate is 1000 Hz. The spectral output is approximately 550 nm. The available relative visual magnitude range is 2 to 8 visual magnitudes. The star size is less than 100 arc seconds. The minimum star movement is less than 5 arc seconds and the relative position accuracy is approximately 40 arc seconds. The purpose of this paper is to describe the LPS Star Simulator design and to provide an operational scenario so others may gain from the approach and possible use of the system.

  14. Multiple stars: designation, catalogues, statistics

    E-print Network

    A. Tokovinin

    2006-01-23

    Discussion of the designation of multiple-star components leads to a conclusion that, apart from components, we need to designate systems and centers-of-mass. The hierarchy is coded then by simple links to parent. This system is adopted in the multiple star catalogue, now available on-line. A short review of multiple-star statistics is given: the frequency of different multiplicities in the field, periods of spectroscopic sub-systems, relative orbit orientation, empirical stability criterion, and period-period diagram with its possible connection to formation of multiple stars.

  15. The Elements: Forged in Stars

    NSDL National Science Digital Library

    All the stars in the universe, including the Sun, are nuclear furnaces fueled by fusion. Beginning with the fusion of hydrogen and continuing with fusion of successively heavier elements, stars form all the naturally occurring elements heavier than hydrogen and helium. This video segment illustrates the critical role that stars play in creating the elements, and describes the process of nucleosynthesis, in which increasingly heavier elements up through iron are formed, at which point the star collapses and explodes in a supernova, during which elements heavier than iron are created. The segment is three minutes forty-two seconds in length. A background essay and discussion questions are included.

  16. The Uhuru star aspect sensor.

    NASA Technical Reports Server (NTRS)

    Jagoda, N.; Austin, G.; Mickiewicz, S.; Goddard, R.

    1972-01-01

    Description of the star sensor used in the spin-stabilized Uhuru satellite for the purpose of detecting and locating stellar X-ray sources. The star sensor had the capability of detecting fourth-magnitude stars to within 1 arc minute of azimuth and 2 arc minutes of elevation. This was achieved with the aid of a slightly modified 76-mm, f/0.87 Super Farron lens, an 'n' shaped reticle located in the focal plane, and an RCA CF70114F photomultiplier serving as the detection element. The star sensor is composed of three major components - a high-voltage power supply, the photomultiplier, and an amplifier.

  17. Boson star at finite temperature

    E-print Network

    S. Latifah; A. Sulaksono; T. Mart

    2014-12-04

    By using a simple thermodynamical method we confirm the finding of Chavanis and Harko that stable Bose-Einstein condensate stars can form. However, by using a thermodynamically consistent boson equation of state, we obtain a less massive Bose-Einstein condensate star compared to the one predicted by Chavanis and Harko. We also obtain that the maximum mass of a boson star is insensitive to the change of matter temperature. However, the mass of boson star with relatively large radius depends significantly on the temperature of the boson matter.

  18. Hubble Sees a Neutron Star Alone in Space Nearest Known Neutron Star

    E-print Network

    Barnes, Joshua Edward

    Hubble Sees a Neutron Star Alone in Space Nearest Known Neutron Star #12;Birth of a Neutron Star & neutrinos. The birth temperature of a neutron star is ~5×1011 K, but neutrino emission cools it to `only' 106 to 107 K. #12;Sizes of Neutron Stars Google Maps: Oahu #12;Sizes of Neutron Stars Artist

  19. Dielectron Measurements in STAR

    E-print Network

    F. Geurts; for the STAR Collaboration

    2012-08-16

    Ultrarelativistic heavy-ion collisions provide a unique environment to study the properties of strongly interacting matter. Dileptons, which are not affected by the strong interactions, are an ideal penetrating probe. We present the dielectron results for p+p and Au+Au collisions at $\\sqrt{s_\\mathrm{NN}}}$ =200 GeV, as measured by the STAR experiment. We discuss the prospects of dilepton measurements with the near-future detector upgrades, and the recent lower beam energy Au+Au measurements.

  20. Upsilon measurement in STAR

    E-print Network

    Mauro R. Cosentino

    2007-06-06

    We present preliminary results of Upsilon production in p+p collisions at sqrt(s)=200 GeV at central rapidity. This measurement was performed at the STAR experiment through the Upsilon->e^+e^- decay channel. In this manuscript we describe the experimental details, from the development of a specially designed trigger setup to the analysis methods used to discriminate electrons from hadrons. The production cross-section obtained B*{(dsigma/dy)|(y=0)}=91(28)(22) pb is compatible with our expectations based on pQCD calculations.

  1. The guide star catalog

    NASA Technical Reports Server (NTRS)

    Lasker, Barry M.; Jenkner, Helmut; Russell, Jane L.

    1987-01-01

    Part 1 of the catalog presents an astronomical overview of the Guide Star Catalog, together with its history, the properties of its current implementation, and the prospects for enhancement. Part 2 presents the algorithms used in photometric and astrometric calibration of the catalog, as well as the analyses of the related errors. Part 3 presents the current structure and content, as well as future enhancements in this area. An overview of the forthcoming publications is given, both with regard to scientific papers and electronic media.

  2. Supermassive monopole stars

    NASA Technical Reports Server (NTRS)

    Fry, J. N.; Fuller, G. M.

    1984-01-01

    In this paper, the evolution of a superheavy monopole-dominated universe is reexamined; in particular, the evolution of rotation-stabilized monopole-burning 'stars', balancing effects of radiation and annihilation are examined. In contrast to earlier results, it is found that this can lead to complete burning of all poles present in such an object within finite time. If monopoles can be brought within acceptable limits by dynamical processes, an inflationary epoch of the early universe need not be associated with grand unification.

  3. On Magnetized Neutron Stars

    E-print Network

    Luiz L. Lopes; Debora P. Menezes

    2015-03-11

    In this work we review the formalism normally used in the literature about the effects of density-dependent magnetic fields on the properties of neutron stars, expose some ambiguities that arise and propose a way to solve the related problem. Our approach explores more deeply the concept of pressure, yielding the so called chaotic magnetic field formalism for the stress tensor. We also use a different way of introducing a variable magnetic field, which depends on the energy density rather than on the baryonic density, which allows us to build a parameter free model.

  4. Star Atlases and Software

    NASA Astrophysics Data System (ADS)

    Brazell, Owen; Argyle, R. W.

    In the 7 years or so that have passed since the first edition of this book was published perhaps one of the areas that has changed the most has been in the area of charts and software. The realm of the paper chart has pretty much been taken over by software in all its guises. It would perhaps not have been possible to have foreseen 10 years ago that one could look up double stars and their information on your phone as you can do on many of today's smart phones. The popularity of tablets and netbooks also means that much more information is now available in the field that it was before.

  5. Moon and Stars

    NSDL National Science Digital Library

    Lawrence Hall of Science

    1997-01-01

    In this craft activity, learners create a string of cut-out moons and stars. This activity is phrased to encourage a parent and child to look at the Moon every night, and make simple illustrations of what they see, but can be adapted for various groups of learners. When learners have three or four different shapes drawn, they can cut out as many as desired and create a pattern, string them together, and hang them in a special place. Learners create simple patterns at first (A, B, A, B) and move on to more complex patterns as they mature and gain experience.

  6. TRIGGERED STAR FORMATION SURROUNDING WOLF-RAYET STAR HD 211853

    SciTech Connect

    Liu Tie; Wu Yuefang; Zhang Huawei [Department of Astronomy, Peking University, 100871 Beijing (China); Qin Shengli, E-mail: liutiepku@gmail.com [I. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany)

    2012-05-20

    The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 10{sup 3} cm{sup -3} and kinematic temperature {approx}20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed toward core 'A', which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the 'collect and collapse' process functions in this region. The star-forming activities in core 'A' seem to be affected by the 'radiation-driven implosion' process.

  7. Cavitation from bulk viscosity in neutron stars and quark stars

    E-print Network

    Jes Madsen

    2009-09-30

    The bulk viscosity in quark matter is sufficiently high to reduce the effective pressure below the corresponding vapor pressure during density perturbations in neutron stars and strange stars. This leads to mechanical instability where the quark matter breaks apart into fragments comparable to cavitation scenarios discussed for ultra-relativistic heavy-ion collisions. Similar phenomena may take place in kaon-condensed stellar cores. Possible applications to compact star phenomenology include a new mechanism for damping oscillations and instabilities, triggering of phase transitions, changes in gravitational wave signatures of binary star inspiral, and astrophysical formation of strangelets. At a more fundamental level it points to the possible inadequacy of a hydrodynamical treatment of these processes in compact stars.

  8. Wolf-Rayet stars from Very Massive Stars

    NASA Astrophysics Data System (ADS)

    Yusof, Norhasliza

    2015-01-01

    Many studies focused on very massive stars (VMS) within the framework of Pop. III stars, because this is where they were thought to be abundant. In this work, we focus on the evolution of VMS in the local universe following the discovery of VMS in the R136 cluster in the Large Magellanic Cloud (LMC). We computed grids of VMS evolutionary tracks in the range 120-500 M ? with solar, LMC and Small Magellanic Cloud metallicities. All models end their lives as Wolf-Rayet (WR) stars of the WC (or WO) type. We discuss the evolution and fate of VMS around solar metallicity with particular focus on the WR phase. For example, we show that a distinctive feature that may be used to disentangle Wolf-Rayet stars originating from VMS from those originating from lower initial masses is the enhanced abundances of Ne and Mg at the surface of WC stars.

  9. Globular Star Clusters Stas Jevsevar (28030543)

    E-print Network

    ?umer, Slobodan

    Globular Star Clusters Author: Stas Jevsevar (28030543) Mentor: prof. Tomaz Zwitter Abstract In this seminar globular star clusters are represented as very important objects, that have been studied for over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.5 RR Lyrae stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4 Globular

  10. Massive Star Formation in the Galactic Center

    E-print Network

    D. F. Figer

    2008-03-12

    The Galactic center is a hotbed of star formation activity, containing the most massive star formation site and three of the most massive young star clusters in the Galaxy. Given such a rich environment, it contains more stars with initial masses above 100 \\Msun than anywhere else in the Galaxy. This review concerns the young stellar population in the Galactic center, as it relates to massive star formation in the region. The sample includes stars in the three massive stellar clusters, the population of younger stars in the present sites of star formation, the stars surrounding the central black hole, and the bulk of the stars in the field population. The fossil record in the Galactic center suggests that the recently formed massive stars there are present-day examples of similar populations that must have been formed through star formation episodes stretching back to the time period when the Galaxy was forming.

  11. Star Products for Relativistic Quantum Mechanics

    E-print Network

    P. Henselder

    2007-05-24

    The star product formalism has proved to be an alternative formulation for nonrelativistic quantum mechanics. We want introduce here a covariant star product in order to extend the star product formalism to relativistic quantum mechanics in the proper time formulation.

  12. Recovery Ship Freedom Star

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Freedom Star, one of NASA's two solid rocket booster recovery ships, is towing a barge containing the third Space Shuttle Super Lightweight External Tank (SLWT) into Port Canaveral. This SLWT was slated for use to launch the orbiter Discovery on mission STS-95 in October 1998. This first time towing arrangement, part of a cost saving plan by NASA to prudently manage existing resources, began June 12 from the Michoud Assembly Facility in New Orleans where the Shuttle's external tanks were manufactured. The barge was transported up Banana River to the LC-39 turn basin using a conventional tug boat. Previously, NASA relied on an outside contractor to provide external tank towing services at a cost of about $120,000 per trip. The new plan allowed NASA's Space Flight Operations contractor, United Space Alliance (USA), to provide the same service to NASA using the recovery ships during their downtime between Shuttle launches. Studies showed a potential savings of about $50,000 per trip. The cost of the necessary ship modifications would be paid back by the fourteenth tank delivery. The other recovery ship, Liberty Star, also underwent deck strengthening enhancements and had the necessary towing wench installed.

  13. Thermal Evolution of Strange Stars

    E-print Network

    Zhou Xia; Wang Lingzhi; Zhou Aizhi

    2007-09-03

    We investigated the thermal evolution of rotating strange stars with the deconfinement heating due to magnetic braking. We consider the stars consisting of either normal quark matter or color-flavor-locked phase. Combining deconfinement heating with magnetic field decay, we find that the thermal evolution curves are identical to pulsar data.

  14. WhiteStar user's guide

    SciTech Connect

    Ezell, T.F.

    1990-08-01

    The WhiteStar project provides design engineers with needed part design data. WhiteStar encourages the use of preferred parts by providing a user-convenient parts database. This report shows selections the user makes in order to obtain information on a particular part. 15 figs.

  15. Axion emission from neutron stars

    NASA Technical Reports Server (NTRS)

    Iwamoto, N.

    1984-01-01

    It is shown that axion emission from neutron stars is the dominant energy-loss mechanism for a range of values of the Peccei-Quinn symmetry-breaking scale (F) not excluded by previous constraints. This gives the possibility of obtaining a better bound on F from measurements of surface temperature of neutron stars.

  16. Fate of most massive stars

    NASA Astrophysics Data System (ADS)

    Yusof, Norhasliza; Hirschi, Raphael; Kassim, Hasan Abu

    2012-09-01

    The first generations of stars are thought to have been more massive than Pop I stars and therefore some of these are thought to have produced pair creation supernovae (PCSNe) at the end of their life. However, the chemical signature of PCSNe is not observed in extremely metal poor stars (e.g. Umeda and Nomoto 2002) and it raises the following questions: Were stars born less (or more massive) than the mass range expected to lead to the PCSNe? Or was mass loss too strong during the evolution of these stars and prevented them from retaining enough mass to produce PCSNe? The discovery of very massive stars (VMS, M > 100 M ?) in the Milky Way and LMC (Crowther et al. 2010) shows that VMS can form and exist. The observations of PCSN candidates (2006gy & 2007bi) also seems to indicate that such SNe may occur. Mass loss plays a crucial role in the life of VMS since the star will only die as a PCSN if the star retains a high mass throughout its life. In this paper, we shall describe the dependence of VMS evolution on metallicity and present stellar evolution models at various metallicities, including the effects of mass loss and rotation. Based on our models, we will give our predictions concerning the fate of these VMS, either a PCSN or SNIc (possibly GRBs in some cases) as a function of metallicity.

  17. Observing RR Lyrae type stars

    NASA Astrophysics Data System (ADS)

    Skarka, M.; Liska, J.; Dreveny, R.; Auer, R. F.

    2015-02-01

    A current status of an ongoing survey dealing with observation of RR Lyrae type stars is presented. This project, called the Czech RR Lyrae observation project, works in cooperation with amateur observers, and aims to collect precise multicolour photometric data of bright RR Lyrae stars. The first important result was the discovery of the Blazhko effect in CN Cam.

  18. A spectrophotometric catalog of stars

    Microsoft Academic Search

    A. V. Kharitonov; V. M. Tereshchenko; L. N. Kniazeva

    1978-01-01

    The book presents the distribution of energy in spectra of 602 stars expressed as illuminance produced by stars at the earth atmosphere boundary. The Vega spectrum energy distribution is used as the basic standard compiled by averaging data in the 3200-8000 A wavelength range with a mean square accuracy of 4%. The catalog is applicable in astrophysics and geophysics, the

  19. Variable stars: Which Nyquist frequency?

    Microsoft Academic Search

    L. Eyer; P. Bartholdi

    1999-01-01

    In the analysis of variable stars, the problem of sampling is central. This article focusses on the determination of the Nyquist frequency. It is well defined in the case of regular sampling. However, the time series of variable stars observations are generally unevenly sampled. Fourier analysis using the spectral window furnishes some clues about the equivalent Nyquist frequency in the

  20. Dust near luminous ultraviolet stars

    NASA Technical Reports Server (NTRS)

    Henry, Richard C.

    1993-01-01

    This report describes research activities related to the Infrared Astronomical Satellite (IRAS) sky survey. About 745 luminous stars were examined for the presence of interstellar dust heated by a nearby star. The 'cirrus' discovered by IRAS is thermal radiation from interstellar dust at moderate and high galactic latitudes. The IRAS locates the dust which must (at some level) scatter ultraviolet starlight, although it was expected that thermal emission would be found around virtually every star, most stars shown no detectable emission. And the emission found is not uniform. It is not that the star is embedded in 'an interstellar medium', but rather what is found are discrete clouds that are heated by starlight. An exception is the dearth of clouds near the very hottest stars, implying that the very hottest stars play an active role with respect to destroying or substantially modifying the dust clouds over time. The other possibility is simply that the hottest stars are located in regions lacking in dust, which is counter-intuitive. A bibliography of related journal articles is attached.

  1. Rotation of White Dwarf Stars

    NASA Astrophysics Data System (ADS)

    Kawaler, Steven D.

    2015-06-01

    I discuss and consider status of observational determinations of the rotation velocities of white dwarf stars via asteroseismology and spectroscopy. While these observations have important implications on our understanding of the angular momentum evolution of stars in their late stages of evolution, more direct methods are sorely needed to disentangle ambiguities.

  2. Commission 42: Close Binary Stars

    Microsoft Academic Search

    Slavek M. Rucinski; Ignasi Ribas; Alvaro Giménez; Petr Harmanec; Ronald W. Hilditch; Janusz Kaluzny; Panayiotis Niarchos; Birgitta Nordström; Katalin Oláh; Mercedes T. Richards; Colin D. Scarfe; Edward M. Sion; Guillermo Torres; Sonja Vrielmann

    2009-01-01

    Two meetings of interest to close binaries took place during the reporting period: A full day session on short-period binary stars mostly CV's (Milone et al. 2008) during the 2006 AAS Spring meeting in Calgary and the very broadly designed IAU Symposium No. 240 on Binary Stars as Critical Tools and Tests in Contemporary Astrophysics in Prague, 2006, with many

  3. Guide to Stars and Galaxies

    NSDL National Science Digital Library

    Guide to Stars and Galaxies, produced by the Engineering in Astronomy team at the University of Bradford, England, is a multimedia guide to stars and galaxies. The guide has been converted from a popular CD-ROM (with permission), is rich in graphics and audio, and is nicely done.

  4. Exploding Stars with Magnetic Towers

    Microsoft Academic Search

    Dmitri Uzdensky; Andrew MacFadyen

    2005-01-01

    We consider the formation and propagation of a magnetically dominated outflow, similar to Lynden-Bell's ``magnetic tower,'' inside a collapsing star. We calculate the structure of this flow as it burrows through the stellar envelope. The passage of the tower through the star drives a strong bow shock behind which an over-pressured cocoon forms. In turn, the cocoon collimates the tower

  5. Quark stars within relativistic models

    E-print Network

    D. P. Menezes; C. Providencia; D. B. Melrose

    2005-07-22

    Lately, it has been suggested that strange (quark) stars can be responsible for glitches and other observational features of pulsars. Some discussions on whether quark stars, if really exist, are bare or crusted are also a source of controversy in the recent literature. In the present work we use the Nambu-Jona-Lasinio model, known to incorporate chiral symmetry, necessarily present in the QCD formalism, in order to describe quark star properties. We compare our results for the stars and the features of the model with the much simpler model normally used in the description of strange stars, namely the MIT bag model. We also investigate the differences in the stellar properties which arise due to the presence of the crust. We show that the NJL model produces results which are somewhat different as compared with the MIT model.

  6. Grand unification of neutron stars

    PubMed Central

    Kaspi, Victoria M.

    2010-01-01

    The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to isolated neutron stars, from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-Ray Observatory, in celebration of its 10th anniversary. Finally, I describe the current status of efforts at physical “grand unification” of this wealth of observational phenomena, and comment on possibilities for Chandra’s next decade in this field. PMID:20404205

  7. Neutron Stars are Follicly Challenged

    NASA Astrophysics Data System (ADS)

    Yunes, Nicolas; Yagi, Kent; Stein, Leo; Pappas, George; Apostolatos, Theocharis; Kyutoku, Koutarou

    2015-04-01

    Black holes satisfy certain no-hair relations through which all multipole moments of the spacetime can be specified in terms of just a few quantities, like their mass and spin angular momentum. I will describe how neutron stars and quark stars also satisfy similar no-hair relations that are approximately independent of their equation of state. I will show how these results hold for both slowly- and rapidly-rotating stars in full General Relativity, provided the stars are uniformly rotating and uncharged. I will then explain why such relations may be relevant to observations of the pulse profile of hot spots on rotating neutron stars with NICER, as well as how they could be used to test General Relativity with binary pulsar and gravitational wave observations. I acknowledge support from the NSF CAREER Award PHY-1250636.

  8. NAOS -- finding NAOMI guide stars

    NASA Astrophysics Data System (ADS)

    Davenhall, A. C.

    Observations made with the NAOMI adaptive optics system on the William Herschel Telescope (WHT) usually require a guide star located close to the target object being observed. This manual describes how to find such guide stars. It documents the NAOS package whose purpose is precisely to find suitable guide stars and also describes various related items of software. Details of the potential guide stars are produced as tabular lists in text files, finding charts and tables in a format suitable for input into GAIA or CURSA. This document is aimed at astronomers who are planning to observe with the NAOMI adaptive optics system on the WHT and need to find guide stars for their target objects.

  9. OB Stars in Stochastic Regimes

    NASA Astrophysics Data System (ADS)

    Oey, M. S.; Lamb, J. B.; Werk, J. K.; Clarke, C. J.

    2011-06-01

    The highest-mass stars have the lowest frequency in the stellar initial mass function (IMF), and they are also the most easily observed stars. Thus, the counting statistics for OB stars provide important tests for the fundamental nature and quantitative parameters of the IMF. We first examine some local statistics for the stellar upper-mass limit itself. Then, we examine the parameter space and statistics for extremely sparse clusters that contain OB stars, in the SMC. We find that thus far, these locally observed counting statistics are consistent with a constant stellar upper-mass limit. The sparse OB star clusters easily fall within the parameter space of Monte Carlo simulations of cluster populations. If the observed objects are representative of their cluster birth masses, their existence implies that the maximum stellar mass is largely independent of the parent cluster mass.

  10. FLARES ON A Bp STAR

    SciTech Connect

    Mullan, D. J. [Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States)

    2009-09-01

    Two large X-ray flares have been reported from the direction of a magnetic B2p star ({sigma} Ori E). Sanz-Forcada et al. have suggested that the flares did not occur on the B2p star but on a companion of late spectral type. A star which is a candidate for a late-type flare star near {sigma} Ori E has recently been identified by Bouy et al. However, based on the properties of the flares, and based on a recent model of rotating magnetospheres, we argue that, rather than attributing the two flares to a late-type dwarf, it is a viable hypothesis that the flares were magnetic phenomena associated with the rotating magnetosphere of the B2p star itself.

  11. A Swarm of Ancient Stars

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This stellar swarm is M80 (NGC 6093), one of the densest of the 147 known globular star clusters in the Milky Way galaxy. Located about 28,000 light-years from Earth, M80 contains hundreds of thousands of stars, all held together by their mutual gravitational attraction. Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster have the same age (about 15 billion years), but cover a range of stellar masses. Every star visible in this image is either more highly evolved than, or in a few rare cases more massive than, our own Sun. Especially obvious are the bright red giants, which are stars similar to the Sun in mass that are nearing the ends of their lives.

  12. Multiplicity of chemically peculiar stars

    E-print Network

    S. Hubrig; N. Ageorges; M. Schoeller

    2005-10-11

    Recently, with the goal to study multiplicity of chemically peculiar stars, we carried out a survey of 40 stars using diffraction limited near infrared (IR) imaging with NAOS-CONICA (NACO) at the VLT. Here, we announce the detection of 27 near IR companion candidates around 25 late B-type chemically peculiar stars exhibiting strong overabundances of the chemical elements Hg and Mn in their atmospheres. A key point for the understanding of the abundance patterns in these stars may be connected with binarity and multiplicity. It is intriguing that more than half of the sample of HgMn stars studied previously by speckle interferometry and recently using the adaptive optics system NACO belong to multiple systems.

  13. Rotational Evolution of Protoneutron Stars

    E-print Network

    Yefei Yuan; Jeremy S. Heyl

    2003-05-06

    We study the rotational evolution of a protoneutron star with hyperons and nucleons or solely nucleons in its core due to the escape of the trapped neutrinos. It is found that at the early stage of its evolution, the stellar crust contracts significantly, consequently the star spins up. At the late stage, a the protoneutron star with hyperons, it keeps shrinking and spinning up till all the trapped neutrinos escape. Consequently, the distribution of the stellar initial spin periods is skewed toward shorter periods. For a protoneutron star with only nucleons, the expansion of its core dominates, and the stellar rotation slows down. After the neutrinos escape, the range of the spin periods is narrower than the initial one, but the distribution is still nearly uniform. If the hyperonic star is metastable, its rotational frequency accelerates distinguishedly before it collapses to a black hole.

  14. Asteroseismology of Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Huber, Daniel

    Eclipsing binaries have long served as benchmark systems to measure fundamental properties of stars. In recent decades, asteroseismology—the study of stellar pulsations—has emerged as a powerful new tool to study the structure and evolution of stars across the H-R diagram. Pulsating stars in eclipsing binary systems are particularly valuable since fundamental properties such as radii and masses can then be determined using two independent techniques. Furthermore, independently measured properties from binary orbits can be used to improve asteroseismic modelling for pulsating stars in which mode identifications are not straightforward. This chapter provides a review of asteroseismic detections in eclipsing binary stars, with a focus on space-based missions such as CoRoT and Kepler and empirical tests of asteroseismic scaling relations for stochastic (`solar-like') oscillations.

  15. Flares on a Bp Star

    NASA Astrophysics Data System (ADS)

    Mullan, D. J.

    2009-09-01

    Two large X-ray flares have been reported from the direction of a magnetic B2p star (? Ori E). Sanz-Forcada et al. have suggested that the flares did not occur on the B2p star but on a companion of late spectral type. A star which is a candidate for a late-type flare star near ? Ori E has recently been identified by Bouy et al. However, based on the properties of the flares, and based on a recent model of rotating magnetospheres, we argue that, rather than attributing the two flares to a late-type dwarf, it is a viable hypothesis that the flares were magnetic phenomena associated with the rotating magnetosphere of the B2p star itself.

  16. Improved autonomous star identification algorithm

    NASA Astrophysics Data System (ADS)

    Luo, Li-Yan; Xu, Lu-Ping; Zhang, Hua; Sun, Jing-Rong

    2015-06-01

    The log–polar transform (LPT) is introduced into the star identification because of its rotation invariance. An improved autonomous star identification algorithm is proposed in this paper to avoid the circular shift of the feature vector and to reduce the time consumed in the star identification algorithm using LPT. In the proposed algorithm, the star pattern of the same navigation star remains unchanged when the stellar image is rotated, which makes it able to reduce the star identification time. The logarithmic values of the plane distances between the navigation and its neighbor stars are adopted to structure the feature vector of the navigation star, which enhances the robustness of star identification. In addition, some efforts are made to make it able to find the identification result with fewer comparisons, instead of searching the whole feature database. The simulation results demonstrate that the proposed algorithm can effectively accelerate the star identification. Moreover, the recognition rate and robustness by the proposed algorithm are better than those by the LPT algorithm and the modified grid algorithm. Project supported by the National Natural Science Foundation of China (Grant Nos. 61172138 and 61401340), the Open Research Fund of the Academy of Satellite Application, China (Grant No. 2014_CXJJ-DH_12), the Fundamental Research Funds for the Central Universities, China (Grant Nos. JB141303 and 201413B), the Natural Science Basic Research Plan in Shaanxi Province, China (Grant No. 2013JQ8040), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20130203120004), and the Xi’an Science and Technology Plan, China (Grant. No CXY1350(4)).

  17. A synoptic of H-alpha line profile in the T Tauri star SU Aurigae

    NASA Technical Reports Server (NTRS)

    Giampapa, Mark S.; Basri, Gibor S.; Johns, Christopher M.; Imhoff, Catherine

    1993-01-01

    We present a catalog of 106 high spectral resolution observations of the H-alpha line profile in the T Tauri star SU Aurigae, obtained during the period from 1986 October through 1990 November. The spectra were acquired during joint synoptic programs to observe selected T Tauri stars using the Hamilton Echelle Spectrometer of the Lick Observatory and the solar-stellar spectrograph at the McMath telescope of the National Solar Observatory on Kitt Peak. A restricted set of Mg II h and k line profiles was also obtained in a coordinated program involving the International Ultraviolet Explorer (IUE) satellite observatory and the McMath solar-stellar facility. Striking variability is evident on a nightly basis. A key result is that the relative intensity in the blue wing of H-alpha spanning a range of velocities bear -150 km/s is modulated at a period of 2.98 +/- 0.4 days. We identify the 2.98 day period with the rotation period of the star. We also find that the occurrence of the periodic modulation of the mass outflow is episodic and most evident during a 2 week sequence of nightly observations. We find two other intervals where the periodic spectroscopic variability is likely present, although at a lower level of significance at a lower level of significance. The variability is otherwise stochastic in nature. The Mg II resonance lines exhibit clear variability that is most pronounced in the blue wing of the k line. A comparison of the Mg II k line profile with H-alpha profiles obtained nearly simultaneous yields no apparent correlation between the variable features in each line. The profile shapes of the Mg II h and k lines are generally indicative of formation in a wind. An analysis of the principal features that appear in the H-alpha profile set suggests that the line is composed of contributions from an enhanced chromosphere; a relatively slow moving, dense, optically thick component of a stellar wind formed relatively close to the star; and an optically thin, high-velocity, expanding stellar wind located further away from the star. An investigation of possible correlations among the principal features in the series of H-alpha profiles suggests that as the density in the wind increases, the wind may become more unstable to large turbulence. This may lead to a reduction in the wind bulk velocity, thus regulating the mass-loss rate. We also find that the position of the main absorption feature which is always present in the H-alpha profiles is not correlated with its depth, indicating that optical depth and wind velocity are not correlated in the denser portions of the wind.

  18. The first stars: a classification of CEMP-no stars

    E-print Network

    Maeder, Andre

    2015-01-01

    We propose and apply a new classification for the CEMP-no stars, which are "carbon-enhanced metal-poor" stars with no overabundance of s-elements and with [Fe/H] generally inferior or equal to -2.5. This classification is based on the changes in abundances for the elements and isotopes involved in the CNO, Ne-Na, and Mg-Al nuclear cycles. These abundances change very much owing to successive back and forth mixing motions between the He- and H-burning regions in massive stars (the "source stars" responsible for the chemical enrichment of the CEMP-no stars). The wide variety of the ratios [C/Fe], 12C/13C, [N/Fe], [O/Fe], [Na/Fe], [Mg/Fe], [Al/Fe], [Sr/Fe], and [Ba/Fe], which are the main characteristics making the CEMP-no and low s stars so peculiar, is described well in terms of the proposed nucleosynthetic classification. We note that the [(C+N+O)/Fe] ratios significantly increase for lower values of [Fe/H]. The classification of CEMP-no stars and the behavior of [(C+N+O)/Fe] support the presence, in the firs...

  19. Double Neutron Star Systems and Natal Neutron Star Kicks

    E-print Network

    Chris Fryer; Vassiliki Kalogera

    1997-06-03

    We study the four double neutron star systems found in the Galactic disk in terms of the orbital characteristics of their immediate progenitors and the natal kicks imparted to neutron stars. Analysis of the effect of the second supernova explosion on the orbital dynamics, combined with recent results from simulations of rapid accretion onto neutron stars lead us to conclude that the observed systems could not have been formed had the explosion been symmetric. Their formation becomes possible if kicks are imparted to the radio-pulsar companions at birth. We identify the constraints imposed on the immediate progenitors of the observed double neutron stars and calculate the ranges within which their binary characteristics (orbital separations and masses of the exploding stars) are restricted. We also study the dependence of these limits on the magnitude of the kick velocity and the time elapsed since the second explosion. For each of the double neutron stars, we derive a minimum kick magnitude required for their formation, and for the two systems in close orbits we find it to exceed 200km/s. Lower limits are also set to the center-of-mass velocities of double neutron stars, and we find them to be consistent with the current proper motion observations.

  20. Surface abundances of ON stars

    NASA Astrophysics Data System (ADS)

    Martins, F.; Simón-Díaz, S.; Palacios, A.; Howarth, I.; Georgy, C.; Walborn, N. R.; Bouret, J.-C.; Barbá, R.

    2015-06-01

    Context. Massive stars burn hydrogen through the CNO cycle during most of their evolution. When mixing is efficient or when mass transfer in binary systems occurs, chemically processed material is observed at the surface of O and B stars. Aims: ON stars show stronger lines of nitrogen than morphologically normal counterparts. Whether this corresponds to the presence of material processed through the CNO cycle is not known. Our goal is to answer this question. Methods: We performed a spectroscopic analysis of a sample of ON stars with atmosphere models. We determined the fundamental parameters as well as the He, C, N, and O surface abundances. We also measured the projected rotational velocities. We compared the properties of the ON stars to those of normal O stars. Results: We show that ON stars are usually rich in helium. Their CNO surface abundances are fully consistent with predictions of nucleosynthesis. ON stars are more chemically evolved and rotate - on average - faster than normal O stars. Evolutionary models including rotation cannot account for the extreme enrichment observed among ON main sequence stars. Some ON stars are members of binary systems, but others are single stars as indicated by stable radial velocities. Mass transfer is therefore not a simple explanation for the observed chemical properties. Conclusions: We conclude that ON stars show extreme chemical enrichment at their surface, consistent with nucleosynthesis through the CNO cycle. Its origin is not clear at present. Based on observations obtained 1) at the Anglo-Australian Telescope; 2) at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii; 3) at the ESO/La Silla Observatory under programs 081.D-2008, 083.D-0589, 086.D-0997; 4) the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias; 5) the Mercator Telescope, operated on the island of La Palma by the Flemish Community at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Appendices are available in electronic form at http://www.aanda.orgThe reduced spectra 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/578/A109

  1. Multiplicity of Herbig Ae/Be stars

    NASA Astrophysics Data System (ADS)

    Thomas, Sandrine; van der Bliek, Nicole; Brandvig, Ben; Bouvier, Jerome; Rodgers, Bernadette; Doppmann, Greg; Woodward, Chick

    2005-08-01

    Theories on star formation have treated the formation of low mass, intermediate mass and high mass stars distinctly. However it is not at all clear that there is a difference in the formation of these three groups. In fact, as many stars form in clusters, it is very likely that stars of different masses actually form and evolve together. We are conducting a photometric and spectroscopic study of multiples around Herbig Ae/Be (HAEBE) stars, to investigate the nature of the companions. HAEBE stars are PMS stars of intermediate mass, spanning the mass range between low-mass T Tauri stars and high mass stars. Hence, they fill an important parameter space in addressing the question of whether high mass and low-mass stars form the same way. Here we propose to obtain high resolution AO imaging to search for multiples amongst Herbig Ae/Be stars, continuing the work by Bouvier & Corporon (2001).

  2. StarFISH: For Inferring Star-formation Histories

    NASA Astrophysics Data System (ADS)

    Harris, Jason; Zaritsky, Dennis

    2012-04-01

    StarFISH is a suite of programs designed to determine the star formation history (SFH) of a stellar population, given multicolor stellar photometry and a library of theoretical isochrones. It constructs a library of synthetic color-magnitude diagrams from the isochrones, which includes the effects of extinction, photometric errors and completeness, and binarity. A minimization routine is then used to determine the linear combination of synthetic CMDs that best matches the observed photometry. The set of amplitudes modulating each synthetic CMD describes the star formation history of the observed stellar population.

  3. 23 New Variable Stars

    NASA Astrophysics Data System (ADS)

    Clark, M.

    2014-12-01

    I report the discovery of 23 new variable stars: ten W UMa eclipsing (USNO 1070-0023351, USNO 1023-0051547, USNO 1024-0049987, USNO 1023-0051277, USNO 1289-0181948, USNO1287-0180792, USNO12870-0177514, GSC 01965:01128, USNO 1395-0370184, USNO 1395-0370731); four which may be W UMa eclipsing (USNO 0943-0001247, GSC 05581:00450, USNO 0820-0342790, USNO 1026-0049630); four other eclipsing (GSC 00008:00428, USNO1287-0181263, GSC 00814:00461, GSC 01665:01505); one RR Lyr ((GSC 00540:00848); one that might be an RR Lyr ((GSC 05568:00529); and three others for which the type could not be determined (USNO 1287-0181515, USNO 1288-0184031, USNO 1295-0192642).

  4. Stars Just Got Bigger - A 300 Solar Mass Star Uncovered

    NASA Astrophysics Data System (ADS)

    2010-07-01

    Using a combination of instruments on ESO's Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the Sun, or twice as much as the currently accepted limit of 150 solar masses. The existence of these monsters - millions of times more luminous than the Sun, losing weight through very powerful winds - may provide an answer to the question "how massive can stars be?" A team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, has used ESO's Very Large Telescope (VLT), as well as archival data from the NASA/ESA Hubble Space Telescope, to study two young clusters of stars, NGC 3603 and RMC 136a in detail. NGC 3603 is a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust, located 22 000 light-years away from the Sun (eso1005). RMC 136a (more often known as R136) is another cluster of young, massive and hot stars, which is located inside the Tarantula Nebula, in one of our neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away (eso0613). The team found several stars with surface temperatures over 40 000 degrees, more than seven times hotter than our Sun, and a few tens of times larger and several million times brighter. Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses. The star R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and with a birthweight of as much as 320 times that of the Sun. In NGC 3603, the astronomers could also directly measure the masses of two stars that belong to a double star system [1], as a validation of the models used. The stars A1, B and C in this cluster have estimated masses at birth above or close to 150 solar masses. Very massive stars produce very powerful outflows. "Unlike humans, these stars are born heavy and lose weight as they age," says Paul Crowther. "Being a little over a million years old, the most extreme star R136a1 is already 'middle-aged' and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses." If R136a1 replaced the Sun in our Solar System, it would outshine the Sun by as much as the Sun currently outshines the full Moon. "Its high mass would reduce the length of the Earth's year to three weeks, and it would bathe the Earth in incredibly intense ultraviolet radiation, rendering life on our planet impossible," says Raphael Hirschi from Keele University, who belongs to the team. These super heavyweight stars are extremely rare, forming solely within the densest star clusters. Distinguishing the individual stars - which has now been achieved for the first time - requires the exquisite resolving power of the VLT's infrared instruments [2]. The team also estimated the maximum possible mass for the stars within these clusters and the relative number of the most massive ones. "The smallest stars are limited to more than about eighty times more than Jupiter, below which they are 'failed stars' or brown dwarfs," says team member Olivier Schnurr from the Astrophysikalisches Institut Potsdam. "Our new finding supports the previous view that there is also an upper limit to how big stars can get, although it raises the limit by a factor of two, to about 300 solar masses." Within R136, only four stars weighed more than 150 solar masses at birth, yet they account for nearly half of the wind and radiation power of the entire cluster, comprising approximately 100 000 stars in total. R136a1 alone energises its surroundings by more than a factor of fifty compared to the Orion Nebula cluster, the closest region of massive star formation to Earth. Understanding how high mass stars form is puzzling enough, due to their very short lives and powerful winds, so that the identification of such extreme cases as R136a1 raises the challenge to theorists still fu

  5. Strange-quark-matter stars

    SciTech Connect

    Glendenning, N.K.

    1989-11-01

    We investigate the implications of rapid rotation corresponding to the frequency of the new pulsar reported in the supernovae remnant SN1987A. It places very stringent conditions on the equation of state if the star is assumed to be bound by gravity alone. We find that the central energy density of the star must be greater than 13 times that of nuclear density to be stable against the most optimistic estimate of general relativistic instabilities. This is too high for the matter to consist of individual hadrons. We conclude that it is implausible that the newly discovered pulsar, if its half-millisecond signals are attributable to rotation, is a neutron star. We show that it can be a strange quark star, and that the entire family of strange stars can sustain high rotation if strange matter is stable at an energy density exceeding about 5.4 times that of nuclear matter. We discuss the conversion of a neutron star to strange star, the possible existence of a crust of heavy ions held in suspension by centrifugal and electric forces, the cooling and other features. 34 refs., 10 figs., 1 tab.

  6. Hyperon-Mixed Neutron Stars

    NASA Astrophysics Data System (ADS)

    Takatsuka, T.

    Hyperon mixing in neutron star matter is investigated by the G-matrix-based effective interaction approach under the attention to use the YN and the YY potentials compatible with hypernuclear data and is shown to occur at densities relevant to neutron star cores, together with discussions to clarify the mechanism of hyperon contamination. It is remarked that developed Y-mixed phase causes a dramatic softening of the neutron star equation of state and leads to the serious problem that the resulting maximum mass Mmax for neutron star model contradicts the observed neutron star mass (Mmax Mobs) the threshold densities for ? and ?- are pushed to higher density side, from ˜2?0 to ˜ 4?0 (?0 being the nuclear density). On the basis of a realistic Y-mixed neutron star model, occurrence of Y-superfluidity essential for "hyperon cooling" scenario is studied and both of ?- and ?-- superfluids are shown to be realized with their critical temperatures 108-9 K, meaning that the "hyperon cooling" is a promising candidate for a fast non-standard cooling demanded for some neutron stars with low surface temperature. A comment is given as to the consequence of less attractive ?? interaction suggested by the "NAGARA event" 6??He.

  7. Exoplanets bouncing between binary stars

    NASA Astrophysics Data System (ADS)

    Moeckel, Nickolas; Veras, Dimitri

    2012-05-01

    Exoplanetary systems are found not only among single stars, but also among binaries of widely varying parameters. Binaries with separations of 100-1000 au are prevalent in the solar neighbourhood; at these separations, planet formation around a binary member may largely proceed as if around a single star. During the early dynamical evolution of a planetary system, planet-planet scattering can eject planets from a star's grasp. In a binary, the motion of a planet ejected from one star has effectively entered a restricted three-body system consisting of itself and the two stars, and the equations of motion of the three-body problem will apply as long as the ejected planet remains far from the remaining planets. Depending on its energy, escape from the binary as a whole may be impossible or delayed until the three-body approximation breaks down, and further close interactions with its planetary siblings boost its energy when it passes close to its parent star. Until then, this planet may be able to transition from the space around one star to the other, and chaotically 'bounce' back and forth. In this paper, we directly simulate scattering planetary systems that are around one member of a circular binary, and quantify the frequency of bouncing in scattered planets. We find that a great majority (70-85 per cent) of ejected planets will pass at least once through the space of it's host's binary companion, and depending on the binary parameters about 35-75 per cent will begin bouncing. The time spent bouncing is roughly lognormally distributed with a peak at about 104 yr, with only a small percentage bouncing for more than 1 Myr. This process may perturb and possibly incite instability among existing planets around the companion star. In rare cases, the presence of multiple planets orbiting both stars may cause post-bouncing capture or planetary swapping.

  8. Asteroseismology of EC14026 Stars

    NASA Astrophysics Data System (ADS)

    Charpinet, Stephane; Fontaine, G.; Brassard, P.; Billères, M.

    2001-05-01

    EC14026 stars form a class of pulsating stars which recent discovery originates back to 1997 (Kilkenny et al. 1997, MNRAS, 285,640). These are hot, relatively compact objets belonging to the class of subdwarf B (or sdB) stars and showing rapid multiperiodic (P 80-600 seconds), low amplitude (a few millimags) luminosity variations. These stars are identified to Extended Horizontal Branch (EHB) models, and thus are evolved, low mass (M 0.5 Modot) core helium burning objects (Dorman et al. 1993, ApJ, 415, 596). The theory of EC14026 stars, which origin is anterior to their "observational discovery" (their existence was predicted on these theoretical basis; Charpinet et al. 1996, ApJ, 471, L103), is nowadays in a relatively mature state. The mode driving mechanism identified is a kappa-mechanism caused by the formation, due to microscopic chemical diffusion processes, of a strongly overabundant reservoir of iron in the envelope of these stars. This theory has been remarkably consistent with the rapidly growing amounts of observational data so far, thus opening the way to a potentially very fruitful application of the tools of asteroseismology to probe the structure of these objects. In this context, I will present a method to constrain, with asteroseismology, the stellar parameters of EC14026 stars. This method is based on the construction of large grids of pulsating subdwarf B star models, each model being analysed with a linear nonadiabatic pulsation code, aimed at deriving the most appropriate set of model parameters that can best reproduce the observed periods of a given pulsating sdB star. With this method, fundamental quantities such as the effective temperature, the surface gravity, the total mass, and the mass of the H-rich envelope can be inferred.

  9. Star-ND (Multi-Dimensional Star-Identification) 

    E-print Network

    Spratling, Benjamin

    2012-07-16

    OF TABLES .................................................................................................... xii CHAPTER I INTRODUCTION: SPACECRAFT AUTONOMOUS ATTITUDE DETERMINATION... Page Figure 1 Typical spacecraft autonomous attitude determination process.......................2 Figure 2 Typical star-ID process ....................................................................................3 Figure 3 Field...

  10. Sea Star Succumbing to Sea Star Wasting Disease

    USGS Multimedia Gallery

    Unlike their smiling cartoon brethren on television, since 2013, real-life sea stars have been suffering from a wasting disease epidemic in which they lose limbs and literally disintegrate in a matter of days. ...

  11. Magnetic fields of degenerate stars

    NASA Astrophysics Data System (ADS)

    Chanmugam, G.

    The magnetic fields of degenerate stars are discussed with emphasis on such basic issues as how their magnetic field strengths are determined, their origin, and evolution. The magnetic fields of both white dwarfs and neutron stars are discussed together, and it is speculated that the origin and evolution of their fields may be related. It is also suggested that it may be possible to apply and test models for the evolution of the magnetic fields in neutron stars by using white dwarfs and vice versa.

  12. Variable stars in Stellar Systems

    E-print Network

    Giuseppe Bono; Silvia Petroni; Marcella Marconi

    2002-12-07

    We discuss in detail the pulsation properties of variable stars in globular clusters (GCs) and in Local Group (LG) dwarf galaxies. Data available in the literature strongly support the evidence that we still lack a complete census of variable stars in these stellar systems. This selection bias is even more severe for small-amplitude variables such as Oscillating Blue Stragglers (OBSs) and new exotic groups of variable stars located in crowded cluster regions. The same outcome applies to large-amplitude, long-period variables as well as to RR Lyrae and Anomalous Cepheids in dwarf galaxies.

  13. Soliton stars at finite temperature

    NASA Astrophysics Data System (ADS)

    Cottingham, W. N.; Vinh Mau, R.

    1991-09-01

    We investigate the properties of soliton stars in the Lee-Wick model when a temperature dependence is introduced into this model. It is found that at some critical temperature Tc~100-200 MeV, a first-order phase transition occurs leading to the formation of soliton stars with characteristics similar to those considered by Lee and Pang but with a much smaller mass and size. We study the evolution of these soliton stars with the temperature from the early Universe to the present time.

  14. Violent star and star cluster formation in nearby and distant galaxies

    E-print Network

    Uta Fritze - v. Alvensleben

    2005-09-14

    I present recent observations and analyses of star cluster formation in a wide variety of environments -- from young star clusters and super star clusters in normal actively star-forming spirals and irregulars to starbursting dwarfs and spiral-spiral mergers. Star cluster formation in interacting galaxies can be restricted to central starburst region, extend over the entire body of the merger, or even all along extended tidal structures. I address methods and results for the determination of star cluster ages, metallicities, masses, and sizes and discuss the nature, possible lifetimes and future signatures of these star cluster populations, as well as the relative importance of field star formation vs. star cluster formation.

  15. "Catch a Star !"

    NASA Astrophysics Data System (ADS)

    2002-05-01

    ESO and EAAE Launch Web-based Educational Programme for Europe's Schools Catch a star!... and discover all its secrets! This is the full title of an innovative educational project, launched today by the European Southern Observatory (ESO) and the European Association for Astronomy Education (EAAE). It welcomes all students in Europe's schools to an exciting web-based programme with a competition. It takes place within the context of the EC-sponsored European Week of Science and Technology (EWST) - 2002 . This unique project revolves around a web-based competition and is centred on astronomy. It is specifically conceived to stimulate the interest of young people in various aspects of this well-known field of science, but will also be of interest to the broad public. What is "Catch a Star!" about? [Go to Catch a Star Website] The programme features useful components from the world of research, but it is specifically tailored to (high-)school students. Younger participants are also welcome. Groups of up to four persons (e.g., three students and one teacher) have to select an astronomical object - a bright star, a distant galaxy, a beautiful comet, a planet or a moon in the solar system, or some other celestial body. Like detectives, they must then endeavour to find as much information as possible about "their" object. This information may be about the position and visibility in the sky, the physical and chemical characteristics, particular historical aspects, related mythology and sky lore, etc. They can use any source available, the web, books, newspaper and magazine articles, CDs etc. for this work. The group members must prepare a (short) summarising report about this investigation and "their" object, with their own ideas and conclusions, and send it to ESO (email address: eduinfo@eso.org). A jury, consisting of specialists from ESO and the EAAE, will carefully evaluate these reports. All projects that are found to fulfill the stipulated requirements, including a reasonable degree of scientific correctness, are entered as "registered projects" and will receive a lottery number. The first 1000 participants from the corresponding groups will also get a "Catch a star" T-Shirt by mail. All accepted entries will be listed at the corresponding website and all accepted reports will be displayed soon after the expiry of the deadline for submission on November 1st, 2002 . Winners to be Announced on November 8, 2002 On November 8th, 2002, at the end of the European Week of Science and Technology, the winners will be found by drawing numbers in a lottery. This event will take place at the ESO Headquarters in Garching (Germany) and will be webcast. The First Prize is a free trip for the members of the group to the ESO Paranal Observatory in Chile , the site of the ESO Very Large Telescope (VLT) . The Paranal trip will be realised in any case, but because of age restrictions, it can only be offered to a group in which all participants are 15 years of age or older at the time of the drawing. Younger participants may win an interesting trip within Europe. There will also be other prizes, to be announced later. Starting now The programme starts now and is open for groups of up to three students and one teacher, who must all belong to a school in Europe on November 1, 2002 . This means that only students who did not yet terminate their school studies on this date can participate. No student may participate in more than one group. The programme is administered by the ESO Educational Office , in close collaboration with members of the EAAE, mostly physics teachers. Details about how to register and how to prepare the report about "your" object are available on the web at: http://www.eso.org/public/outreach/eduoff/cas/ About the ESO Educational Office The ESO Educational Office was established in July 2001. It is part of the EPR Department at ESO Headquarters in Garching near Munich. The aim is to provide support of astronomy and astrophysics education, especially at the high-schoo

  16. Fast Star Pattern Recognition Using Planar Triangles

    E-print Network

    Crassidis, John L.

    Fast Star Pattern Recognition Using Planar Triangles Craig L. Cole John L. Crassidis Abstract A new method for star identification based on using planar triangles is developed and compared to a standard angle method approach. The angle method creates angles between stars within the field of view of a star

  17. 27 STELLAR REMNANTS White Dwarf Stars

    E-print Network

    Sitko, Michael L.

    1 27 STELLAR REMNANTS White Dwarf Stars The first white dwarf star (Sirius B) was discovered&B Orbit of Sirius A&B X-ray image The white dwarf stars are the endpoints of the evolution of low), large numbers of white dwarfs exist. They may be among the most populous stars in the Galaxy, and recent

  18. Homogeneous Star Products Louis Boutet de Monvel

    E-print Network

    Boutet de Monvel, Louis

    Homogeneous Star Products Louis Boutet de Monvel Abstract: We give short proofs of results concerning homogeneous star products, of which S. Gutt's star product on the dual of a Lie algebra is a particular case. Keywords: Star-products, linear Poisson brackets. MSC2000: 19L47, 32A25, 58J20, 58J40

  19. Multiple stars: designation, catalogues, A. Tokovinin1

    E-print Network

    Tokovinin, Andrei A.

    Multiple stars: designation, catalogues, statistics A. Tokovinin1 Cerro Tololo Inter of multiple-star components leads to a conclusion that, apart from components, we need to designate systems in the multiple star catalogue, now available on-line. A short review of multiple-star statistics is given

  20. Photometry of 50 suspected variable stars

    Microsoft Academic Search

    James T. Hooten; Douglas S. Hall

    1990-01-01

    Fifty stars have been chosen as suspected variable stars and analyzed for variability. A large portion of this sample are stars that are either proved active chromosphere stars or are candidates for such activity. The photometric data base consists of differential V measurements of the Vanderbilt 16 inch (41 cm) automatic photoelectric telescope and 25 observers at 26 observatories worldwide.

  1. A Heavy Flavor Tracker for STAR

    SciTech Connect

    Xu, Z.; Chen, Y.; Kleinfelder, S.; Koohi, A.; Li, S.; Huang, H.; Tai, A.; Kushpil, V.; Sumbera, M.; Colledani, C.; Dulinski, W.; Himmi,A.; Hu, C.; Shabetai, A.; Szelezniak, M.; Valin, I.; Winter, M.; Surrow,B.; Van Nieuwenhuizen, G.; Bieser, F.; Gareus, R.; Greiner, L.; Lesser,F.; Matis, H.S.; Oldenburg, M.; Ritter, H.G.; Pierpoint, L.; Retiere, F.; Rose, A.; Schweda, K.; Sichtermann, E.; Thomas, J.H.; Wieman, H.; Yamamoto, E.; Kotov, I.

    2005-03-14

    We propose to construct a Heavy Flavor Tracker (HFT) for the STAR experiment at RHIC. The HFT will bring new physics capabilities to STAR and it will significantly enhance the physics capabilities of the STAR detector at central rapidities. The HFT will ensure that STAR will be able to take heavy flavor data at all luminosities attainable throughout the proposed RHIC II era.

  2. Star formation in active dwarf galaxies

    Microsoft Academic Search

    C. M. Telesco

    1986-01-01

    Star formation and the ISM in active dwarf galaxies are studied based on data from the IRAS Point Source Catalog. The dwarf galaxies that show evidence of recent energetic star formation are generally also strong far-infrared emitters; thus, active current star formation is associated with a history of energetic star formation. A fraction of the galaxies considered here have a

  3. X-ray Emission from Massive Stars

    E-print Network

    Cohen, David

    X-ray Emission from Massive Stars David Cohen Department of Physics and Astronomy Swarthmore be related to the production of X-rays on massive stars. If so, massive stars' X-rays are much different than those found our own Sun and other cooler stars like the Sun that produce X-rays via magnetic activity

  4. Photometry of Southern Hemisphere red dwarf stars

    Microsoft Academic Search

    D. Weistrop

    1980-01-01

    Results are presented for a photometric investigation of a spectroscopically selected sample of red dwarf stars in the Southern Hemisphere. Absolute magnitudes and distances for the stars are estimated from broadband red colors. Three stars which may be subluminous are identified, as are several stars which may be within 25 pc. The tangential velocity and velocity dispersion of the sample

  5. The Massive Star Content of NGC 3603

    Microsoft Academic Search

    Nicholas W. Melena; Philip Massey; Nidia I. Morrell; Amanda M. Zangari

    2008-01-01

    We investigate the massive star content of NGC 3603, the closest known giant H II region. We have obtained spectra of 26 stars in the central cluster using the Baade 6.5 m telescope (Magellan I). Of these 26 stars, 16 had no previous spectroscopy. We also obtained photometry of all of the stars with previous or new spectroscopy, primarily using

  6. Terrestrial planet formation surrounding close binary stars

    Microsoft Academic Search

    Elisa V. Quintana; Jack J. Lissauer

    2006-01-01

    Most stars reside in binary\\/multiple star systems; however, previous models of planet formation have studied growth of bodies orbiting an isolated single star. Disk material has been observed around both components of some young close binary star systems. Additionally, it has been shown that if planets form at the right places within such disks, they can remain dynamically stable for

  7. Q-stars at finite temperature

    Microsoft Academic Search

    Ru-Keng Su; Cheng-Gang Su; Rong-Shi Pan

    1992-01-01

    The discussions on Q-stars are extended to finite temperature. We find that below the critical temperature Tc the radius, mass and the frequency of the Q-star will increase with temperature. The critical temperature at which the Q-star will disappear and the epoch in which the Q-star can exist are given.

  8. Scalar soliton star at finite temperature

    Microsoft Academic Search

    Rukeng Su; Rongshi Pan

    1989-01-01

    The discussion on scalar soliton stars are extended to finite temperature. We find that below the critical temperature Tc, the radius, surface width and the mass of the soliton star will increase with temperature. At the critical temperature, the soliton stars disappear. The epoch in which the soliton star can exist is given.

  9. The Stars behind the Curtain

    NASA Astrophysics Data System (ADS)

    2010-02-01

    ESO is releasing a magnificent VLT image of the giant stellar nursery surrounding NGC 3603, in which stars are continuously being born. Embedded in this scenic nebula is one of the most luminous and most compact clusters of young, massive stars in our Milky Way, which therefore serves as an excellent "local" analogue of very active star-forming regions in other galaxies. The cluster also hosts the most massive star to be "weighed" so far. NGC 3603 is a starburst region: a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust. Located 22 000 light-years away from the Sun, it is the closest region of this kind known in our galaxy, providing astronomers with a local test bed for studying intense star formation processes, very common in other galaxies, but hard to observe in detail because of their great distance from us. The nebula owes its shape to the intense light and winds coming from the young, massive stars which lift the curtains of gas and clouds revealing a multitude of glowing suns. The central cluster of stars inside NGC 3603 harbours thousands of stars of all sorts (eso9946): the majority have masses similar to or less than that of our Sun, but most spectacular are several of the very massive stars that are close to the end of their lives. Several blue supergiant stars crowd into a volume of less than a cubic light-year, along with three so-called Wolf-Rayet stars - extremely bright and massive stars that are ejecting vast amounts of material before finishing off in glorious explosions known as supernovae. Using another recent set of observations performed with the SINFONI instrument on ESO's Very Large Telescope (VLT), astronomers have confirmed that one of these stars is about 120 times more massive than our Sun, standing out as the most massive star known so far in the Milky Way [1]. The clouds of NGC 3603 provide us with a family picture of stars in different stages of their life, with gaseous structures that are still growing into stars, newborn stars, adult stars and stars nearing the end of their life. All these stars have roughly the same age, a million years, a blink of an eye compared to our five billion year-old Sun and Solar System. The fact that some of the stars have just started their lives while others are already dying is due to their extraordinary range of masses: high-mass stars, being very bright and hot, burn through their existence much faster than their less massive, fainter and cooler counterparts. The newly released image, obtained with the FORS instrument attached to the VLT at Cerro Paranal, Chile, portrays a wide field around the stellar cluster and reveals the rich texture of the surrounding clouds of gas and dust. Notes [1] The star, NGC 3603-A1, is an eclipsing system of two stars orbiting around each other in 3.77 days. The most massive star has an estimated mass of 116 solar masses, while its companion has a mass of 89 solar masses. More information ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large op

  10. The MACHO Project LMC Variable Star Inventory. X. The R Coronae Borealis Stars

    Microsoft Academic Search

    C. Alcock; R. A. Allsman; D. R. Alves; T. S. Axelrod; A. Becker; D. P. Bennett; Geoffrey C. Clayton; K. H. Cook; N. Dalal; A. J. Drake; K. C. Freeman; M. Geha; K. D. Gordon; K. Griest; D. Kilkenny; S. L. Marshall; D. Minniti; K. A. Misselt; C. A. Nelson; B. A. Peterson; P. Popowski; M. R. Pratt; P. J. Quinn; C. W. Stubbs; W. Sutherland; A. Tomaney; T. Vandehei; D. L. Welch

    2001-01-01

    We report the discovery of eight new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The discovery of these new stars increases the number of known RCB stars in the LMC to thirteen. We have also discovered four stars similar to the Galactic variable DY Per. These stars decline much more

  11. NAAP Variable Star Photometry 1/12 Variable Star Photometry Student Guide

    E-print Network

    Farritor, Shane

    Name: NAAP ­ Variable Star Photometry 1/12 Variable Star Photometry ­ Student Guide Background of Variable Stars and Properties of CCDs. Question 1: The light variation from a variable star is shown in the figure to the right. a) Identify the type of variable star and explain your criteria for classifying

  12. Abundance Signatures in Halo Stars: Clues to Nucleosynthesis in the First Stars

    E-print Network

    Cowan, John

    ; nucleosynthesis: stellar PACS: 32.30;97.10.Tk;97.10.Cv INTRODUCTION Halo stars contain the nucleosyntheticAbundance Signatures in Halo Stars: Clues to Nucleosynthesis in the First Stars John J. Cowan-based telescopes to make extensive studies of Galactic halo stars. These stars contain the nucleosynthesis products

  13. THE ROLE OF HELIUM STARS IN THE FORMATION OF DOUBLE NEUTRON STARS N. Ivanova,1

    E-print Network

    Rasio, Frederic A.

    THE ROLE OF HELIUM STARS IN THE FORMATION OF DOUBLE NEUTRON STARS N. Ivanova,1 K. Belczynski,1,2 V:5 6 M with a 1.4 M neutron star companion to investigate the formation of double neutron star systems phase) leads to the formation of extremely short-period double neutron star systems (with Pd0:1 days

  14. The Neutron Star Zoo

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2014-01-01

    Neutron stars are a very diverse population, both in their observational and their physical properties. They prefer to radiate most of their energy at X-ray and gamma-ray wavelengths. But whether their emission is powered by rotation, accretion, heat, magnetic fields or nuclear reactions, they are all different species of the same animal whose magnetic field evolution and interior composition remain a mystery. This article will broadly review the properties of inhabitants of the neutron star zoo, with emphasis on their high-energy emission. XXX Neutron stars are found in a wide variety of sources, displaying an amazing array of behavior. They can be isolated or in binary systems, accreting, heating, cooling, spinning down, spinning up, pulsing, flaring and bursting. The one property that seems to determine their behavior most strongly is their magnetic field strength, structure and evolution. The hot polar caps, bursts and flares of magnetars are likely due to the rapid decay and twisting of their superstrong magnetic fields, whose very existence requires some kind of early dynamo activity. The intermediate-strength magnetic fields of RPPs determines their spin-down behavior and radiation properties. However, the overlap of the magnetar and RPP populations is not understood at present. Why don't high-field RPPs burst or flare? Why don't lower-field magnetars sometimes behave more like RPPs? INS may be old magnetars whose high fields have decayed, but they do not account for the existence of younger RPPs with magnetar-strength fields. Not only the strength of the magnetic field but also its configuration may be important in making a NS a magnetar or a RPP. Magnetic field decay is a critical link between other NS populations as well. "Decay" of the magnetic field is necessary for normal RPPs to evolve into MSPs through accretion and spin up in LMXBs. Some kind of accretion-driven field reduction is the most likely mechanism, but it is controversial since it is not clear how effective it is or on what timescale a buried field might re-emerge. One piece of evidence in favor of accretion-driven field reduction is the fact that NSs in LMXBs, which are older systems (> 108 yr), have mostly low fields and NSs in HMXBs, which are younger systems (107 - 108 yr), have higher fields. This may be an indication that accretion-driven field reduction or decay has not had enough time to operate in HMXBs but has in LMXBs. However, there does not seem to be any evidence of decaying fields in either the LMXB or HMXB populations; e.g. smaller magnetic fields in older systems. On the other hand, CCOs are very young so if they acquired their low fields through mass fallback accretion, the field submergence would have had to operate on much faster timescales than it apparently does in LMXBs. But as we continue to find new species in the NS zoo, one of these may someday be the "Rosetta Stone" that will give us the clues for solving these puzzles.

  15. THE ORIGIN OF S-STARS AND A YOUNG STELLAR DISK: DISTRIBUTION OF DEBRIS STARS OF A SINKING STAR CLUSTER

    SciTech Connect

    Fujii, M. [Department of Astronomy, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Iwasawa, M.; Makino, J. [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Funato, Y., E-mail: fujii@cfca.j, E-mail: makino@cfca.j, E-mail: iwasawa@cfca.ac.j, E-mail: funato@artcompsci.or [Department of General System Studies, College of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902 (Japan)

    2010-06-10

    Within the distance of 1 pc from the Galactic center (GC), more than 100 young massive stars have been found. The massive stars at 0.1-1 pc from the GC are located in one or two disks, while those within 0.1 pc from the GC, S-stars, have an isotropic distribution. How these stars are formed is not well understood, especially for S-stars. Here, we propose that a young star cluster with an intermediate-mass black hole (IMBH) can form both the disks and S-stars. We performed a fully self-consistent N-body simulation of a star cluster near the GC. Stars that escaped from the tidally disrupted star cluster were carried to the GC due to a 1:1 mean motion resonance with the IMBH formed in the cluster. In the final phase of the evolution, the eccentricity of the IMBH becomes very high. In this phase, stars carried by the 1:1 resonance with the IMBH were dropped from the resonance and their orbits are randomized by a chaotic Kozai mechanism. The mass function of these carried stars is extremely top-heavy within 10''. The surface density distribution of young massive stars has a slope of -1.5 within 10'' from the GC. The distribution of stars in the most central region is isotropic. These characteristics agree well with those of stars observed within 10'' from the GC.

  16. EUVE Observations of Neutron Stars

    E-print Network

    Eric J. Korpela; Stuart Bowyer

    1998-03-04

    We present the results of searches for EUV emission from neutron stars conducted with the EUVE Deep Survey and Scanner Telescopes. To date, 21 fields containing known neutron stars have been observed in the Lexan/Boron (40--190 angstrom) band. Of these, 11 fields were simultaneously observed in the Aluminum/Carbon (160-385 angstrom) band. Five neutron stars which have been detected in the EUV have been reported previously; no new detections have been made in the studies reported here. For those sources not detected, we have used the observations to obtain limits on the spectral flux from the neutron stars in these bands. We provide means to convert these fluxes into intrinsic source fluxes for black-body and power law spectra for varying levels of absorption by the interstellar medium.

  17. Star formation across galactic environments

    NASA Astrophysics Data System (ADS)

    Young, Jason

    I present here parallel investigations of star formation in typical and extreme galaxies. The typical galaxies are selected to be free of active galactic nuclei (AGN), while the extreme galaxies host quasars (the most luminous class of AGN). These two environments are each insightful in their own way; quasars are among the most violent objects in the universe, literally reshaping their host galaxies, while my sample of AGN-free star-forming galaxies ranges from systems larger than the Milky Way to small galaxies which are forming stars at unsustainably high rates. The current paradigm of galaxy formation and evolution suggests that extreme circumstances are key stepping stones in the assembly of galaxies like our Milky Way. To test this paradigm and fully explore its ramifications, this dual approach is needed. My sample of AGN-free galaxies is drawn from the KPNO International Spectroscopic Survey. This Halpha-selected, volume-limited survey was designed to detect star-forming galaxies without a bias toward continuum luminosity. This type of selection ensures that this sample is not biased toward galaxies that are large or nearby. My work studies the KISS galaxies in the mid- and far-infrared using photometry from the IRAC and MIPS instruments aboard the Spitzer Space Telescope. These infrared bands are particularly interesting for star formation studies because the ultraviolet light from young stars is reprocessed into thermal emission in the far-infrared (24mum MIPS) by dust and into vibrational transitions features in the mid-infrared (8.0mum IRAC) by polycyclic aromatic hydrocarbons (PAHs). The work I present here examines the efficiencies of PAH and thermal dust emission as tracers of star-formation rates over a wide range of galactic stellar masses. I find that the efficiency of PAH as a star-formation tracer varies with galactic stellar mass, while thermal dust has a highly variable efficiency that does not systematically depend on galactic stellar mass. 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.

  18. From supernovae to neutron stars

    NASA Astrophysics Data System (ADS)

    Suwa, Yudai

    2014-04-01

    Gravitational collapse, bounce, and explosion of an iron core of an 11.2 M? star are simulated by two-dimensional neutrino-radiation hydrodynamic code. The explosion is driven by the neutrino heating aided by multi-dimensional hydrodynamic effects such as convection. Following the explosion phase, we continue the simulation focusing on the thermal evolution of the protoneutron star up to ˜ 70 s when the crust of the neutron star is formed, using one-dimensional simulation. We find that the crust forms at a high-density region (? ˜ 1014 g cm-3) and it proceeds from inside to outside. This is the first self-consistent simulation that successfully follows from the collapse phase to the protoneutron star cooling phase based on multi-dimensional hydrodynamic simulation.

  19. An onboard star identification algorithm

    NASA Technical Reports Server (NTRS)

    Ha, Kong; Femiano, Michael

    1993-01-01

    The paper presents the autonomous Initial Stellar Acquisition (ISA) algorithm developed for the X-Ray Timing Explorer for prividing the attitude quaternion within the desired accuracy, based on the one-axis attitude knowledge (through the use of the Digital Sun Sensor, CCD Star Trackers, and the onboard star catalog, OSC). Mathematical analysis leads to an accurate measure of the performance of the algorithm as a function of various parameters, such as the probability of a tracked star being in the OSC, the sensor noise level, and the number of stars matched. It is shown that the simplicity, tractability, and robustness of the ISA algorithm, compared to a general three-axis attiude determination algorithm, make it a viable on-board solution.

  20. Is covariant star product unique?

    E-print Network

    Dmitri Vassilevich

    2011-01-24

    We give a nontechnical introduction to the problem of non-uniqueness of star products and describe a covariant resolution of this problem. Some implications (e.g., for noncommutative gravity) and further prospects are discussed.

  1. Boson stars with repulsive selfinteractions

    E-print Network

    Pratik Agnihotri; Juergen Schaffner-Bielich; Igor N. Mishustin

    2009-03-31

    The properties of compact stars made of massive bosons with a repulsive selfinteraction mediated by vector mesons are studied within the mean-field approximation and general relativity. We demonstrate that there exists a scaling property for the mass-radius curve for arbitrary boson masses and interaction strengths which results in an universal mass-radius relation. The radius remains nearly constant for a wide range of compact star masses. The maximum stable mass and radius of boson stars are determined by the interaction strength and scale with the Landau mass and radius. Both, the maximum mass and the corresponding radius increase linearly with the interaction strength so that they can be radically different compared to the other families of boson stars where interactions are ignored.

  2. Cool Stars and Space Weather

    NASA Astrophysics Data System (ADS)

    Vidotto, A. A.; Jardine, M.; Cameron, A. C.; Morin, J.; Villadsen, J.; Saar, S. H.; Alvarado, J.; Cohen, Ofer; Holzwarth, V.; Poppenhaeger, K.; Reville, V.

    2015-01-01

    Stellar flares, winds and coronal mass ejections form the ``space weather''. They are signatures of the magnetic activity of cool stars and, since activity varies with age, mass and rotation, the space weather that extra-solar planets experience can be very different from the one encountered by the solar system planets. How do stellar activity and magnetism influence the space weather of exoplanets orbiting main-sequence stars? How do the environments surrounding exoplanets differ from those around the planets in our own solar system? How can the detailed knowledge acquired by the solar system community be applied in exoplanetary systems? How does space weather affect habitability? These were questions that were addressed in the splinter session ``Cool stars and Space Weather'', that took place on 9 Jun 2014, during the Cool Stars 18 meeting. In this paper, we present a summary of the contributions made to this session.

  3. Failing as a Cool Star

    NSDL National Science Digital Library

    Astrobiology Magazine article published July 14, 2004. At the 13th Cambridge Workshop on "Cool Stars, Stellar Systems, and the Sun," Dr. Kevin L. Luhman (Harvard-Smithsonian Center for Astrophysics) announced the discovery of a unique pair of newborn brown dwarfs in orbit around each other. Brown dwarfs were discovered in the mid-nineties as hybrid stellar objects: too small to ignite as stars, but too big to be planets. To reconcile the classification, astronomers have looked at newborn dwarfs less than a million years old to see if they might have paired up with a larger parent star. If so, some sort of slingshot mass might explain why the cool dwarfs fail to become stars.

  4. Kepler Mission Star Field Lithograph

    NSDL National Science Digital Library

    This two-sided 8in. X 10in. print document depicts the Kepler Mission Field of View imposed upon a star field that includes the constellations Cygnus and Delphinus on the front. A description of the mission, the star selection constraints, the location of the field in the night sky, distances to the stars, and the CCD layout is included on the back. An image on the back also illustrates the distance the field is from the galactic center and the size of the field of view. NASA's Kepler mission is a spaceborne telescope specifically designed to survey our region of the Milky Way galaxy to detect and characterize hundreds of Earth-size and smaller planets in or near the habitable zone. The habitable zone encompasses the distances from a star where liquid water can exist on a planet's surface.

  5. The Star Guide: Learn How To Read the Night Sky Star by Star, 2nd Edition

    NASA Astrophysics Data System (ADS)

    Kerrod, Robin

    2005-02-01

    A thorough revision of the bestselling guide to the night sky - over 100,000 copies sold! The first edition of The Star Guide introduced readers of all ages to the wonders of the night sky. Now comes the highly anticipated revised edition, expertly updated by one of the world's leading writers on astronomy and space. Illustrated throughout in full color, the guide features spectacular new photographs from the Hubble Space Telescope, more than 60 easy-to-use star charts, and an invaluable detachable planisphere. Special sections explain the nature of stars and galaxies and what makes the universe tick.

  6. Superfluid Hydrodynamics in Neutron Stars

    NASA Astrophysics Data System (ADS)

    Mendell, Gregory Allen

    Superfluidity is predicted to exist in neutron stars. Superfluid effects on the dynamics of these stars have not been investigated in depth in the past. In this thesis, superfluid hydrodynamics in neutron stars is developed extensively. It is shown that superfluidity has important effects on the oscillation modes, dissipative properties, and stability of these stars. Very general hydrodynamic equations are derived which describe superfluid mixtures. The fluid equations are coupled to the electromagnetic and gravitational fields. Forces due to the quantized vortices of the superfluids are also included. It is shown that new vorticity-preserving forces can be introduced into the superfluid-mixture equations. The equations are then adapted to describe neutron stars composed primarily of superfluid neutrons, superconducting protons, and degenerate electrons and muons. The set of equations is closed by constructing a model of the total energy density and using it to express the dependent variables in terms of the independent variables. The low-frequency long-wavelength limit of the equations is determined. The results can be used to study superfluid effects on the global oscillations of neutron stars. The equations are generalized further to include dissipative effects. Most important is a form of dissipation known as mutual friction, which occurs only in superfluids. In neutron stars, mutual friction is due to electron scattering off the neutron and proton vortices. An energy functional is constructed which determines the damping time of a mode due to the various forms of dissipation, including mutual friction. Plane-wave solutions are found to the equations. Mutual friction is shown to be the dominant form of dissipation in neutron stars for sufficiently large angular velocities. Gravitational radiation tends to make all rotating stars unstable, while internal dissipation tends to counteract this instability. This, gravitational radiation can limit the maximum angular velocity of neutron stars. The most important conclusion of this thesis is that mutual friction completely suppresses the gravitational-radiation instability in rotating neutron stars cooler than the superfluid-transition temperature.

  7. Studies of subdwarf B stars

    NASA Astrophysics Data System (ADS)

    Reed, Michael David

    Subdwarf B (sdB) stars are horizontal branch stars with thin hydrogen envelopes surrounding a half solar mass helium core. Following their classification in 1966 by Greenstein, little progress was made in understanding these apparently common stars. When pulsators were discovered by Kilkenny et al. (1997), it became plausible that we could explore their interiors through asteroseismology. Our study of four well observed sdB stars, relying on standard stellar models and asteroseismology tools, has produced some new results and pinpointed wide gaps in our understanding of these stars. We are able to identify specific pulsation modes in the coolest pulsating sdB star, Feige48. We then match these modes to a stellar model. We also confirm the work of Kawaler (1999) and his model match for PG1605. We were able to place a firm lower limit to the evolutionary timescale of Feige48 of 31 million years. We also developed new tools for use in the asteroseismology of close binaries. Eclipsing binaries can uniquely identify modes of pulsation, provided the pulsation axis is aligned with the rotation axis. If the tidal force of the companion is stronger than the Coriolis force, the pulsation axis may align with the companion. From simulations, we determined that such a condition will present three signatures in the light curves and temporal spectrum, from which it is possible to uniquely identify pulsation modes. From preliminary data on PG1336, we find strong evidence that this pulsating sdB star in a 2.4 hour binary has a pulsation axis that points towards the companion. Studies of sdB stars represent a rapidly progressing field in stellar astronomy. Through sdB stars, we may hope to constrain nuclear physics by measuring evolution rates driven by helium fusion. Such an understanding will filter down through stellar evolution in an increased understanding of giant branch and white dwarf stars. Subdwarf B stars themselves will place constraints on white dwarf evolution as they will evolve to distinctly lower mass white dwarfs than average.

  8. Hot Strange Stars. III. Stability

    NASA Astrophysics Data System (ADS)

    Hajyan, G. S.; Alaverdyan, A. G.

    2015-06-01

    The stability of hot strange stars (HSS) is studied. It is shown that a static stability criterion can be used to determine the stability of these stars. It is also found that stability is lost after the maximum mass in the mass-central density curves for isothermal series of HSS. These two points are so close that, as a first approximation, the maximum point can be regarded as the point at which the isothermal series of HSS loses stability.

  9. The Zoo of Neutron Stars

    E-print Network

    S. B. Popov

    2007-01-22

    In these lecture notes I briefly discuss the present day situation and new discoveries in astrophysics of neutron stars focusing on isolated objects. The latter include soft gamma repeaters, anomalous X-ray pulsars, central compact objects in supernova remnants, the Magnificent seven, and rotating radio transients. In the last part of the paper I describe available tests of cooling curves of neutron stars and discuss different additional constraints which can help to confront theoretical calculations of cooling with observational data.

  10. The STAR Dilepton Physics Program

    E-print Network

    Frank Geurts

    2012-10-19

    Dileptons provide ideal penetrating probes of the evolution of strongly-interacting matter. With the Time-of-Flight upgrade, STAR is in a unique position to provide large-acceptance dielectron measurements. We discuss preliminary dielectron results for Au+Au collisions at $\\sqrt{s_\\mathrm{NN}}$=19.6 - 200 GeV, and compare to recent model calculations. With upcoming detector upgrades STAR will further improve its dielectron measurements as well as include dimuon measurements.

  11. Student Observation Network: Star Count

    NSDL National Science Digital Library

    In this hands-on activity, students investigate whether people in different parts of the world see the same number of stars. They will learn how to construct a viewing tube, use it to count the stars in random samples of sky, make calculations, and record the data. They will then share their data online with other students from all over the world to find out why differences might occur.

  12. GRBs from the First Stars

    SciTech Connect

    Iocco, Fabio; /Naples U. /KIPAC, Menlo Park

    2007-04-16

    We present an estimate of the Gamma Ray Bursts which should be expected from metal-free, elusive first generation of stars known as PopulationIII (PopIII). We derive the GRB rate from these stars from the Stellar Formation Rate obtained in several Reionization scenarios available in the literature. In all of the analyzed models we find that GRBs from PopIII are subdominant with respect to the ''standard'' (PopII) ones up to z {approx} 10.

  13. Laser Guide Star Operational Issues

    Microsoft Academic Search

    C. E. Max

    2000-01-01

    Introduction Operational Implications for the Laser System Rayleigh Scattering Focus Changes Variations in Sodium Column Density Requirement to Nod the Telescope for Infra-Red Observing Calibration of the Adaptive Optics System for Sodium Laser Guide - Star Operation Types of Internal Calibration Sources Static Calibration Auxiliary Wavefront Sensors Dynamic Calibration (Real-Time Point-Spread-Function Measurements) Safety Considerations Regarding Laser Guide Star Systems Laser

  14. Magnesium Isotopes in Halo Stars

    E-print Network

    Jorge Melendez; Judith G. Cohen

    2007-08-29

    We have determined Mg isotope ratios in halo field dwarfs and giants in the globular cluster M71 based on high S/N high spectral resolution (R = 10$^5$) Keck HIRES spectra. Unlike previous claims of an important contribution from intermediate-mass AGB stars to the Galactic halo, we find that our $^{26}$Mg/$^{24}$Mg ratios can be explained by massive stars.

  15. How Far Are the Stars?

    ERIC Educational Resources Information Center

    Murphy, Edward; Bell, Randy L.

    2005-01-01

    On any night, the stars seen in the sky can be as close to Earth as a few light-years or as distant as a few thousand light-years. Distances this large are hard to comprehend. The stars are so far away that the fastest spacecraft would take tens of thousands of years to reach even the nearest one. Yet, astronomers have been able to accurately…

  16. Soliton stars at finite temperature

    NASA Astrophysics Data System (ADS)

    Cottingham, W. N.; Vinh Mau, R.

    1991-05-01

    We investigate the properties of soliton stars in the Lee-Wick model when a temperature dependence is introduced into this model. It is found that at some critical temperature Tc ~ 100-200 MeV, a first order phase transition occurs leading to the formation of soliton stars with some characteristics similar to those considered by Lee and Pang but with much smaller mass and size. When they cool to their cold configuration their mass ~ 10-6 Msolar.

  17. Soliton stars at finite temperature

    Microsoft Academic Search

    W. N. Cottingham; R. Vinh Mau

    1991-01-01

    We investigate the properties of soliton stars in the Lee-Wick model when a temperature dependence is introduced into this model. It is found that at some critical temperature Tc ~ 100-200 MeV, a first order phase transition occurs leading to the formation of soliton stars with some characteristics similar to those considered by Lee and Pang but with much smaller

  18. Soliton stars at finite temperature

    Microsoft Academic Search

    W. N. Cottingham; R. Vinh Mau

    1991-01-01

    We investigate the properties of soliton stars in the Lee-Wick model when a temperature dependence is introduced into this model. It is found that at some critical temperature {ital T}{sub {ital c}}{similar to}100--200 MeV, a first-order phase transition occurs leading to the formation of soliton stars with characteristics similar to those considered by Lee and Pang but with a much

  19. Soliton stars at finite temperature

    Microsoft Academic Search

    W. N. Cottingham; R. Vinh Mau

    1991-01-01

    We investigate the properties of soliton stars in the Lee-Wick model when a temperature dependence is introduced into this model. It is found that at some critical temperature Tc~100-200 MeV, a first-order phase transition occurs leading to the formation of soliton stars with characteristics similar to those considered by Lee and Pang but with a much smaller mass and size.

  20. Supernovae in the Lives of Stars

    NSDL National Science Digital Library

    2012-12-26

    Many people think the different stages in the life of a star are actually different types of stars, rather than just stages in the life of a single star. In this fun activity learners discover the lifecycle of stars and learn when supernovae happen. This activity can be used indoors or outdoors, before a star party, in a classroom, or at a club meeting. The pdf contains step-by-step instructions, photos, presentation tips, background information, and ready-to-print handouts.

  1. STAR FORMATION IN DENSE CLUSTERS

    SciTech Connect

    Myers, Philip C., E-mail: pmyers@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2011-12-10

    A model of core-clump accretion with equally likely stopping describes star formation in the dense parts of clusters, where models of isolated collapsing cores may not apply. Each core accretes at a constant rate onto its protostar, while the surrounding clump gas accretes as a power of protostar mass. Short accretion flows resemble Shu accretion and make low-mass stars. Long flows resemble reduced Bondi accretion and make massive stars. Accretion stops due to environmental processes of dynamical ejection, gravitational competition, and gas dispersal by stellar feedback, independent of initial core structure. The model matches the field star initial mass function (IMF) from 0.01 to more than 10 solar masses. The core accretion rate and the mean accretion duration set the peak of the IMF, independent of the local Jeans mass. Massive protostars require the longest accretion durations, up to 0.5 Myr. The maximum protostar luminosity in a cluster indicates the mass and age of its oldest protostar. The distribution of protostar luminosities matches those in active star-forming regions if protostars have a constant birthrate but not if their births are coeval. For constant birthrate, the ratio of young stellar objects to protostars indicates the star-forming age of a cluster, typically {approx}1 Myr. The protostar accretion luminosity is typically less than its steady spherical value by a factor of {approx}2, consistent with models of episodic disk accretion.

  2. Kepler Rapidly Rotating Giant Stars

    NASA Astrophysics Data System (ADS)

    Costa, A. D.; Canto Martins, B. L.; Bravo, J. P.; Paz-Chinchón, F.; das Chagas, M. L.; Leão, I. C.; Pereira de Oliveira, G.; Rodrigues da Silva, R.; Roque, S.; de Oliveira, L. L. A.; Freire da Silva, D.; De Medeiros, J. R.

    2015-07-01

    Rapidly rotating giant stars are relatively rare and may represent important stages of stellar evolution, resulting from stellar coalescence of close binary systems or accretion of substellar companions by their hosting stars. In the present Letter, we report 17 giant stars observed in the scope of the Kepler space mission exhibiting rapid rotation behavior. For the first time, the abnormal rotational behavior for this puzzling family of stars is revealed by direct measurements of rotation, namely from photometric rotation period, exhibiting a very short rotation period with values ranging from 13 to 55 days. This finding points to remarkable surface rotation rates, up to 18 times the rotation of the Sun. These giants are combined with six others recently listed in the literature for mid-infrared (IR) diagnostics based on Wide-field Infrared Survey Explorer information, from which a trend for an IR excess is revealed for at least one-half of the stars, but at a level far lower than the dust excess emission shown by planet-bearing main-sequence stars.

  3. Helium in Chemically Peculiar Stars

    E-print Network

    F. Leone

    1998-05-05

    For the purpose of deriving the helium abundances in chemically peculiar stars, the importance of assuming a correct helium abundance has been investigated for determining the effective temperature and gravity of main sequence B-type stars, making full use of the present capability of reproducing their helium lines. Even if the flux distribution of main sequence B-type stars appears to depend only on the effective temperature for any helium abundance, the effective temperature, gravity and helium abundance have to be determined simultaneously by matching the Balmer line profiles. New MULTI NLTE calculations, performed adopting ATLAS9 model atmospheres and updated helium atomic parameters, reproduce most of the observed equivalent widths of neutral helium lines for main sequence B-type stars and they make us confident of the possibility to correctly derive the helium abundance in chemically peculiar stars. An application of previous methods to the helium rich star HD 37017 shows that helium could be stratified in the magnetic pole regions, as expected in the framework of the diffusion theory in the presence of mass loss.

  4. The sun, our star

    NASA Astrophysics Data System (ADS)

    Noyes, R. W.

    Observational data, analytical models, and instrumentation used to study the sun and its evolution are detailed, and attention is given to techniques for converting solar energy to useful power on earth. The star ignited when the mutual gravitational attractions of dust and vapor in a primordial cloud in the Galaxy caused an in-rush of accelerating particles which eventually became dense enough to ignite. The heat grew until inward rushing matter was balanced by outward moving radiative forces. The planets formed from similar debris, and solar radiation is suggested to have triggered the chemical reactions giving rise to life on earth. Visual, spectroscopic, coronagraphic, and UV observations of the sun from the ground and from spacecraft, particularly Skylab, are described, together with features of the solar surface, magnetic field, sunspots, and coronal loops. Models for the processes that occur in the solar interior are explored, as are the causes of solar flares. Attention is given to solar cells, heliostat arrays, wind turbines, and water turbines as means to convert, either directly or indirectly, the earth-bound solar energy to electrical and thermal power. Finally, the life cycle of the sun, about 9 billion yr in duration, is summarized, noting the current status of midlife.

  5. 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.

  6. Stars and Slopes

    NSDL National Science Digital Library

    This activity uses logarithmic plotting to show the power of a straight line in mathematics, science, and engineering. Students will use the slopes of various curves plotted on log-log graph paper to classify stellar objects as binary stars, supernovae, or active galaxies. The data used in this lesson were obtained from X-ray astronomy satellites. It provides an opportunity for students to apply the knowledge of plotting data and obtaining a slope using a log-log coordinate system, determine the line of best fit from a set of data obtained from X-ray astronomy satellites, and discover the relationship between slope and the classification of stellar objects. By displaying the data in a graphic, the relationship of the dependent variable on the independent variable can be seen. The most powerful form of display is when the result is a straight line - which can always be converted quickly into a mathematical equation. This lesson will use both rectangular and logarithmic graphs.

  7. $??$ Interaction and Neutron Stars

    E-print Network

    Yeunhwan Lim; Chang Ho Hyun; Kyujin Kwak; Chang-Hwan Lee

    2014-12-18

    We investigate the effect of the $\\Lambda\\Lambda$ interactions on the bulk properties of neutron star (NS). We employ a few Skyrme-type models and a finite-range force model in order to describe the $\\Lambda \\Lambda$ interactions for the nuclear matter of NS. With the model parameters that reproduce the binding energies of the double-$\\Lambda$ hypernuclei, we calculate the equation of state (EoS) for the matter of NS self-consistently. By solving the Tolman-Oppenheimer-Volkoff equation with the new EoS, we find that the bulk properties of NS, such as mass and radius, strongly depend on the $\\Lambda \\Lambda$ interactions. It has been generally known (as "hyperonization puzzle") that the existence of hyperons in NS matter is not well supported by the recent discovery of the high mass NS ($M_{NS} \\approx 2 M_\\odot$) because hyperons make the EoS soft. However, we find that some of our NS models can predict both the existence of the $\\sim 2 M_\\odot$ NS and the observationally constrained mass-radius relations. Our results indicate that the $\\Lambda \\Lambda$ interactions could provide a clue to this puzzle.

  8. Spectral variability of LBV star V 532 (Romano's star)

    NASA Astrophysics Data System (ADS)

    Sholukhova, O. N.; Fabrika, S. N.; Zharova, A. V.; Valeev, A. F.; Goranskij, V. P.

    2011-04-01

    We present the results of studying the spectral and photometric variability of the luminous blue variable star V532 in M33. The photometric variations are traced from 1960 to 2010, spectral variations - from 1992 to 2009. The star has revealed an absolute maximum of visual brightness (1992-1994, high/cold state) and an absolute minimum (2007-2008, low/hot state) with a brightness difference of ?B ? 2.3 m . The temperature estimates in the absolute maximum and absolute minimum were found to be T ˜ 22000 K and T ˜ 42000 K, respectively. The variability of the spectrum of V532 is fully consistent with the temperature variations in its photosphere, while both permitted and forbidden lines are formed in an extended stellar atmosphere. Broad components of the brightest lines were found, the broadening of these components is due to electron scattering in the wind parts closest to the photosphere. We measured the wind velocity as a difference between the emission and absorption peaks in the PCyg type profiles. The wind velocity clearly depends on the size of the stellar photosphere or on the visual brightness, when brightness declines, the wind velocity increases. In the absolute minimum a kinematic profile of the V532 atmosphere was detected. The wind velocity increases and its temperature declines with distance from the star. In the low/hot state, the spectral type of the star corresponds to WN8.5h, in the high/cold state - to WN11. We studied the evolution of V532 along with the evolution of AGCar and the massive WR binary HD5980 in SMC. During their visual minima, all the three stars perfectly fit with the WNL star sequence by Crowther and Smith (1997). However, when visual brightness increases, all the three stars form a separate sequence. It is possible that this reflects a new property of LBV stars, namely, in the high/cold states they do not pertain to the bona fide WNL stars.

  9. Undercover Stars Among Exoplanet Candidates

    NASA Astrophysics Data System (ADS)

    2005-03-01

    Very Large Telescope Finds Planet-Sized Transiting Star Summary An international team of astronomers have accurately determined the radius and mass of the smallest core-burning star known until now. The observations were performed in March 2004 with the FLAMES multi-fibre spectrograph on the 8.2-m VLT Kueyen telescope at the ESO Paranal Observatory (Chile). They are part of a large programme aimed at measuring accurate radial velocities for sixty stars for which a temporary brightness "dip" has been detected during the OGLE survey. The astronomers find that the dip seen in the light curve of the star known as OGLE-TR-122 is caused by a very small stellar companion, eclipsing this solar-like star once every 7.3 days. This companion is 96 times heavier than planet Jupiter but only 16% larger. It is the first time that direct observations demonstrate that stars less massive than 1/10th of the solar mass are of nearly the same size as giant planets. This fact will obviously have to be taken into account during the current search for transiting exoplanets. In addition, the observations with the Very Large Telescope have led to the discovery of seven new eclipsing binaries, that harbour stars with masses below one-third the mass of the Sun, a real bonanza for the astronomers. PR Photo 06a/05: Brightness "Dip" and Velocity Variations of OGLE-TR-122. PR Photo 06b/05: Properties of Low-Mass Stars and Planets. PR Photo 06c/05: Comparison Between OGLE-TR-122b, Jupiter and the Sun. The OGLE Survey When a planet happens to pass in front of its parent star (as seen from the Earth), it blocks a small fraction of the star's light from our view [1]. These "planetary transits" are of great interest as they allow astronomers to measure in a unique way the mass and the radius of exoplanets. Several surveys are therefore underway which attempt to find these faint signatures of other worlds. One of these programmes is the OGLE survey which was originally devised to detect microlensing events by monitoring the brightness of a very large number of stars over extended time intervals. During the past years, it has also included a search for periodic, very shallow "dips" in the brightness of stars, caused by the regular transit of small orbiting objects (small stars, brown dwarfs [2] or Jupiter-size planets). The OGLE team has since announced 177 "planetary transit candidates" from their survey of several hundred thousand stars in three southern sky fields, one in the direction of the Galactic Centre, another within the Carina constellation and the third within the Centaurus/Musca constellations. The nature of the transiting object can however only be established by subsequent radial-velocity observations of the parent star. The size of the velocity variations (the amplitude) is directly related to the mass of the companion object and therefore allows discrimination between stars and planets as the cause of the observed brightness "dip". A Bonanza of Low-Mass Stars An international team of astronomers [3] has made use of the 8.2-m VLT Kueyen telescope for this work. Profiting from the multiplex capacity of the FLAMES/UVES facility that permits to obtain high-resolution spectra of up to 8 objects simultaneously, they have looked at 60 OGLE transit candidate stars, measuring their radial velocities with an accuracy of about 50 m/s [4]. This ambitious programme has so far resulted in the discovery of five new transiting exoplanets (see, e.g., ESO PR 11/04 for the announcement of two of those). Most of the other transit candidates identified by OGLE have turned out to be eclipsing binaries, that is, in most cases common, small and low-mass stars passing in front of a solar-like star. This additional wealth of data on small and light stars is a real bonanza for the astronomers. Constraining the Relation Between Mass and Radius Low-mass stars are exceptionally interesting objects, also because the physical conditions in their interiors have much in common with those of giant planets, like Jupit

  10. Quadrupole moments of rotating neutron stars and strange stars

    E-print Network

    Urbanec, Martin; Stuchlik, Zdenek

    2013-01-01

    We present results for models of neutron stars and strange stars constructed using the Hartle-Thorne slow-rotation method with a wide range of equations of state, focusing on the values obtained for the angular momentum $J$ and the quadrupole moment $Q$, when the gravitational mass $M$ and the rotational frequency $\\Omega$ are specified. Building on previous work, which showed surprising uniformity in the behaviour of the moment of inertia for neutron-star models constructed with widely-different equations of state, we find similar uniformity for the quadrupole moment. These two quantities, together with the mass, are fundamental for determining the vacuum space-time outside neutron stars. We study particularly the dimensionless combination of parameters $QM/J^2$ (using units for which $c=G=1$). This quantity goes to 1 in the case of a Kerr-metric black hole and deviations away from 1 then characterize the difference between neutron-star and black-hole space-times. It is found that $QM/J^2$ for both neutron s...

  11. Star Formation in IC 348

    NASA Astrophysics Data System (ADS)

    Herbst, W.

    2008-12-01

    A review of work on the small, compact, nearby young cluster IC 348 is given. This region is particularly important because it is well surveyed at a variety of wavelengths and intermediate in nature between dense clusters and loose associations. Its earliest type star is B5 and it contains a few hundred stellar members as well as some brown dwarfs, protostars, Herbig-Haro objects and starless sub-mm cores. The total mass of its components is ˜90 M_?, most of which is in the form of pre-main sequence stars. Perhaps the biggest challenge to work on the cluster is the relatively high and variable extinction (A_v=3D1-7 mag). Studies to date have provided particularly valuable insights into the initial mass function, disk lifetimes, stellar rotation properties, X-ray properties, outflows and substructure of the cluster. Results on the stellar component include the following: 1) the initial mass function matches that for field stars in the stellar and brown dwarf regimes, 2) the fraction of stars with disks is probably normal for the cluster's age, 3) the rotation properties match those of the Orion Nebula Cluster and are significantly different, in the sense of slower rotation, than NGC 2264, 4) the X-ray properties of the stars appear normal for T Tauri stars. There is a ridge of high extinction that lies ˜10 arcmin (0.9 pc in projection) to the southwest of IC 348 and contains about a dozen Class 0 and I protostars as well as some Herbig Haro objects and sub-mm cores. This region, which also contains the "Flying Ghost Nebula" and the well-studied object HH 211, clearly signals that star formation in this part of the Perseus dark clouds is not yet finished. An extensive kinematical study involving both proper motions and radial velocities for the 400 members of the cluster would be most desirable.

  12. Star Formation in Satellite Galaxies

    E-print Network

    C. M. Gutierrez; M. S. Alonso; J. G. Funes; M. B. Ribeiro

    2006-04-14

    We present narrow-band observations of the H$\\alpha$ emission in a sample of 31 satellite orbiting isolated giant spiral galaxies. The sample studied spans the range $-19star formation rates are 0.68 and 3.66 M$_\\sun$ yr$^{-1}$ respectively. Maps of the spatial distribution of ionized gas are presented. The star-forming regions show a rich structure in which frequently discrete complexes are imposed over more diffuse structures. In general, the current star formation rates are smaller that the mean values in the past obtained from the current stellar content; this probably indicates a declining rhythm with time in the generation of new stars. However, the reserve of gas is enough to continue fueling the current levels of star formation activity for at least another Hubble time. Four of the objects (NGC 2718b, NGC 4541e, NGC 5965a$_1$ and NGC 5965a$_2$) with higher current star formation rates show clear signs of interaction with close companions of comparable brightness at projected distances of 25, 20 and 2 kpc respectively. The only two galaxies in our sample that do not show star formation activity are members of these interacting systems, and it is unclear if this is a consequence of intrinsic properties (both are Hubble early types) or if it is related with possible disruption of the external parts due to the interaction. In the case of the pair NGC 2718a-b there are indications of gas transport between both galaxies.

  13. M-type Vega-like stars

    E-print Network

    Inseok Song; A. Weinberger; E. Becklin; B. Zuckerman; C. Chen

    2002-04-15

    We carried out a search for M-type Vega-like stars by correlating the IRAS Faint Source Catalog with Hipparcos selected M-type stars. Three stars with apparent IRAS 25mu excess emission are shown instead to be non-IR-excess stars from ground-based 11.7 and 17.9mu photometry. Two stars previously suggested to have Vega-like mid-IR excess are also shown to be non-excess stars. These results imply that other suggested mid-IR excess stars in the literature may also be false excess stars. Detection threshold bias is apparently responsible for these bogus IR excesses. Sixty micron excess emission from a previously known M-type Vega-like star (GJ 803) is identified again.

  14. 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.

  15. Ancient Guest Stars as harbingers of neutron star formation

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-Ru

    The well-known AD 1006, 1054, 1572, and 1604 were described as "Guest Stars" by Chinese, Japanese and Korean. In most cases, it might thus be possible to expect a Guest Star to be a term for supernova or nova. There are a lot of records concerning ancient Guest Stars in Chinese historical books. Two catalogues were compiled by Xi (1955) and Xi and Bo (1965, 1966) that listed 90 probable novae or supernovae observed between 1400 BC and AD 1700. Clark and Stephenson (1977), Ho (1962) and Kanda (1935) collected more or less similar records. Among all the historical records more than 80% are from China. The discussion presented in this paper is based on them.

  16. Heavy Calcium in CP Stars

    E-print Network

    C. R. Cowley; S. Hubrig; F. Castelli; J. F. Gonzalez; B. Wolff

    2007-03-09

    Large wavelength shifts of infrared triplet lines of Ca II have been observed in the spectra of HgMn and magnetic Ap stars. They have been attributed to the heavy calcium isotopes, including Ca-48. One member of the triplet, $\\lambda$8542, had been either unavailable, or of poor quality in earlier spectra. The present material shows conclusively that the stellar $\\lambda$8542 shifts are consistent with an interpretation in terms of Ca-48. We find no relation between isotopic shifts of the Ca II triplet lines, and those of Hg II $\\lambda$3984. There is a marginal indication that the shifts are {\\it anticorrelated} with the surface field strengths of the magnetic stars. We see sparse evidence for Ca-48 in other chemically peculiar stars, e.g. Am's, metal-poor stars, or chemically peculiar red giants. However, the sample is still very small, and the wavelengths of all three triplet lines, including those in the Sun, show slight positive shifts with respect to terrestrial positions. Some profiles of the Ca II infrared triplet in the magnetic stars show extensive wings beyond a well-defined core. We can obtain reasonable fits to these profiles using a stratified calcium abundance similar to that used by previous workers. There is no indication that either the stratification or the Zeeman effect significantly disturbs the measurement of isotope shifts.

  17. Cepheid Binarity and Star Formation

    NASA Astrophysics Data System (ADS)

    Remage Evans, Nancy

    Classical Cepheids are important for extragalactic distance calibration and star formation studies. A survey the fifty brightest classical Cepheids in our galaxy to search for blue companions will provide the following: An accurate determination of the percentage of Cepheid binaries with companions more massive than 2 MO and with mass ratios as small as M (COMP) / M(cep) - 1/3. This will provide valuable information on star formation for intermediate mass stars in the mass ratio and period ranges poorly sampled by other techniques. An accurate identification of Cepheids with bright companions and hence improved calibrations of temperature, reddening, and luminosity scales. A stringent test of reddening from the visual region for many Cepheids. These results must be determined from a survey of Cepheids in our galaxy since crowding in external galaxies will confuse the detection of physical companions, and orbital radial velocity material will not be available to provide additional information on mass and period distribution. While this survey builds on the 36 Cepheids already observed with IUE, it is vital to observe the 23 other stars on this program in order to obtain unbiased statistics because many of the observations in the archives were made because the stars were suspected of having companions.

  18. Old and new neutron stars

    SciTech Connect

    Ruderman, M.

    1984-09-01

    The youngest known radiopulsar in the rapidly spinning magnetized neutron star which powers the Crab Nebula, the remnant of the historical supernova explosion of 1054 AD. Similar neutron stars are probably born at least every few hundred years, but are less frequent than Galactic supernova explosions. They are initially sources of extreme relativistic electron and/or positron winds (approx.10/sup 38/s/sup -1/ of 10/sup 12/ eV leptons) which greatly decrease as the neutron stars spin down to become mature pulsars. After several million years these neutron stars are no longer observed as radiopulsars, perhaps because of large magnetic field decay. However, a substantial fraction of the 10/sup 8/ old dead pulsars in the Galaxy are the most probable source for the isotropically distributed ..gamma..-ray burst detected several times per week at the earth. Some old neutron stars are spun-up by accretion from companions to be resurrected as rapidly spinning low magnetic field radiopulsars. 52 references, 6 figures, 3 tables.

  19. Chemical Soups Around Cool Stars

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This artist's conception shows a young, hypothetical planet around a cool star. A soupy mix of potentially life-forming chemicals can be seen pooling around the base of the jagged rocks. Observations from NASA's Spitzer Space Telescope hint that planets around cool stars the so-called M-dwarfs and brown dwarfs that are widespread throughout our galaxy might possess a different mix of life-forming, or prebiotic, chemicals than our young Earth.

    Life on our planet is thought to have arisen out of a pond-scum-like mix of chemicals. Some of these chemicals are thought to have come from a planet-forming disk of gas and dust that swirled around our young sun. Meteorites carrying the chemicals might have crash-landed on Earth.

    Astronomers don't know if these same life-generating processes are taking place around stars that are cooler than our sun, but the Spitzer observations show their disk chemistry is different. Spitzer detected a prebiotic molecule, called hydrogen cyanide, in the disks around yellow stars like our sun, but found none around cooler, less massive, reddish stars. Hydrogen cyanide is a carbon-containing, or organic compound. Five hydrogen cyanide molecules can join up to make adenine a chemical element of the DNA molecule found in all living organisms on Earth.

  20. Infrared photometry of O stars

    NASA Technical Reports Server (NTRS)

    Castor, J. I.; Simon, T.

    1983-01-01

    The results of a survey of 50 O stars in the J, H, K, L, and M bands are described. The observations are described, and the fitting of reddening relations to them is discussed. The zero points in the reddening relations are related to the intrinsic colors of the samples of normal stars, and these are compared with theoretical colors. The comparison reveals anomalies at L and M, which are discussed. The residuals for an individual star from the reddening relations are a measure of its infrared excesses, if indeed it has any. How the excesses can be fitted to a stellar wind model to derive a parameter that involves the rate of mass loss in the wind, the stellar radius and temperature, and wind terminal velocity is considered. The results for a number of individual stars are discussed and compared with other mass loss measurements, and it is concluded that no single model is capable of reconciling the IR, UV, radio, and H-alpha observations for the stars.

  1. Magnetic topologies of cool stars

    E-print Network

    J. -F. Donati; M. M. Jardine; P. Petit; J. Morin; J. Bouvier; A. C. Cameron; X. Delfosse; B. Dintrans; W. Dobler; C. Dougados; J. Ferreira; T. Forveille; S. G. Gregory; T. Harries; G. A. J. Hussain; F. Menard; F. Paletou

    2007-02-06

    Stellar magnetic fields can be investigated using several, very complementary approaches. While conventional spectroscopy is capable of estimating the average magnetic strength of potentially complex field configurations thanks to its low sensitivity to the vector properties of the field, spectropolarimetry can be used to map the medium- and large-scale structure of magnetic topologies. In particular, the latter approach allows one to retrieve information about the poloidal and toroidal components of the large-scale dynamo fields in low-mass stars, and thus to investigate the physical processes that produce them. Similarly, this technique can be used to explore how magnetic fields couple young stars to their massive accretion disc and thus to estimate how much mass and angular momentum are transfered to the newly-born low-mass star. We present here the latest results in this field obtained with spectropolarimetry, with special emphasis on the surprising discoveries obtained on very-low mass fully-convective stars and classical T Tauri stars thanks to the ESPaDOnS spectropolarimeter recently installed on the 3.6m Canada-France-Hawaii Telescope.

  2. Magnetic Fields in Stars: Origin and Impact

    NASA Astrophysics Data System (ADS)

    Langer, N.

    2014-08-01

    Various types of magnetic fields occur in stars: small scale fields, large scale fields, and internal toroidal fields. While the latter may be ubiquitous in stars due to differential rotation, small scale fields (spots) may be associated with envelop convection in all low and high mass stars. The stable large scale fields found in only about 10% of intermediate mass and massive stars may be understood as a consequence of dynamical binary interaction, e.g., the merging of two stars in a binary. We relate these ideas to magnetic fields in white dwarfs and neutron stars, and to their role in core-collapse and thermonuclear supernova explosions.

  3. Polarization measurements of Vega-like stars

    E-print Network

    H. C. Bhatt; Manoj P

    2000-09-29

    Optical linear polarization measurements are presented for about 30 Vega-like stars. These are then compared with the polarization observed for normal field stars. A significant fraction of the Vega-like stars are found to show polarization much in excess of that expected to be due to interstellar matter along the line of sight to the star. The excess polarization must be intrinsic to the star, caused by circumstellar scattering material that is distributed in a flattened disk. A correlation between infrared excess and optical polarization is found for the Vega-like stars.

  4. Basic data on hydrogen-deficient stars

    NASA Technical Reports Server (NTRS)

    Drilling, J. S.

    1986-01-01

    The current state of knowledge on the diistribution and motions of various types of hydrogen-deficient stars, and of their positions in the H-R diagram, is reviewed. It is concluded that the extreme helium stars (with the exception of the H-deficient binaries) and cool hydrogen-deficient stars belong to the population of the Galactic nuclear bulge, whereas the intermediate helium stars are young stars of Population I. The helium-rich sdO stars appear to be a local sample which is predominantly Population I.

  5. Neutron star cooling constraints for color superconductivity in hybrid stars

    SciTech Connect

    Popov, S. B. [Sternberg Astronomical Institute, Universitetski pr. 13, RU-119992 Moscow (Russian Federation); Grigorian, H. [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany); Department of Physics, Yerevan State University, 375049 Yerevan (Armenia); Blaschke, D. [Gesellschaft fuer Schwerionenforschung mbH (GSI), D-64291 Darmstadt (Germany); Bogoliubov Laboratory for Theoretical Physics, JINR Dubna, RU-141980 Dubna (Russian Federation)

    2006-08-15

    We apply the recently developed logN-logS test of compact star cooling theories for the first time to hybrid stars with a color superconducting quark matter core. Although there is not yet a microscopically founded superconducting quark matter phase that would fulfill constraints from cooling phenomenology, we explore the hypothetical 2SC+X phase and show that the magnitude and density dependence of the X-gap can be chosen to satisfy a set of tests: temperature-age (T-t), the brightness constraint, logN-logS, and the mass spectrum constraint. The latter test appears as a new conjecture from the present investigation.

  6. The MACHO Project LMC Variable Star Inventory: III. New R Coronae Borealis Stars

    E-print Network

    C. Alcock; R. A. Allsman; D. R. Alves; T. S. Axelrod; A. Becker; D. P. Bennett; G. C. Clayton; K. H. Cook; K. C. Freeman; K. Griest; J. A. Guern; D. Kilkenny; M. J. Lehner; S. L. Marshall; B. A. Peterson; M. R. Pratt; P. J. Quinn; A. W. Rodgers; C. W. Stubbs; W. Sutherland; D. L. Welch

    1996-05-07

    We report the discovery of two new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The identification of both stars has been confirmed spectroscopically. One is a cool RCB star (T_eff about 5000 K) characterized by very strong Swan bands of C_2 and violet bands of CN, and weak or absent Balmer lines, G-band and 12C-13C bands. The second star is an example of a hot RCB star of which only 3 were previously known to exist in the Galaxy and none in the LMC. Its spectrum is characterized by several C II lines in emission. Both stars have shown deep declines of Delta V > 4 mag in brightness. The new stars are significantly fainter at maximum light than the three previously known LMC RCB stars. The amount of reddening toward these stars is somewhat uncertain but both seem to have absolute magnitudes, M_V, about half a magnitude fainter than the other three stars. Estimates of M_Bol find that the hot RCB star lies in the range of the other three stars while the cool RCB star is fainter. The two cool LMC RCB stars are the faintest at M_Bol. The discovery of these two new stars brings to five the number of known RCB stars in the LMC and demonstrates the utility of the MACHO photometric database for the discovery of new RCB stars.

  7. Unexplained Brightening of Unusual Star

    NASA Astrophysics Data System (ADS)

    1997-01-01

    Recent observations with the Hubble Space Telescope (HST) have documented an unexpected and rapid, seven-fold brightening of an unusual double star at the centre of the impressive 47 Tucanae globular cluster in the southern sky. This is the first HST observation of such a rare phenomenon. The astronomers [1] who are involved in this observational program find that this event cannot be explained by any of the common processes known to occur in such stars. The cores of globular clusters Globular clusters are like huge swarms of stars, containing about one million suns, which move around in their common gravitational field. Most galaxies contain globular clusters; around 150 are known within the confines of our Galaxy, the Milky Way. Globular clusters change with time. In particular, at some stage in the life of a globular cluster, its central region will contract whereby the stars there move closer to each other. This phenomenon is referred to as core collapse [2]. Observations with the Hubble Space Telescope (HST) have revealed enormous central densities of the order of 30,000 stars per cubic light-year in clusters with fully collapsed cores; this is to be compared with the stellar density in the solar neighborhood of only 0.003 stars per cubic light-year [3]. Binary stars in globular clusters Binary (i.e., double) stars play an important role in the evolution of globular clusters: they can delay, halt, or even reverse the process of core collapse. In this dense stellar environment, close encounters between passing stars and binaries are relatively frequent. Such events may leave the binary stars more tightly bound, and at the same time speed up the motion of the stars involved, thereby counteracting the contraction of the core. The same close stellar encounters may also produce a diverse progeny of exotic objects. The centers of globular clusters contain blue stragglers (stars that ``look'' younger than they really are), millisecond pulsars (rapidly rotating, very compact objects), both high- and low-luminosity X-ray sources , and cataclysmic variables (double stars whose light `flickers'). The kinds and numbers of these objects in cluster cores constrain the complex and as yet incompletely understood formation channels, most of which involve encounters with binaries. Many of the above exotic objects are strong emitters of ultraviolet light. The globular cluster 47 Tucanae 47 Tucanae is an impressive globular cluster that is visible with the naked eye from the southern hemisphere. It is one of the closest (distance 15,000 lightyears) and heaviest (total mass about 1 million solar masses) in our Galaxy. It contains about 1 million stars and the member stars have been intensively studied for decades. The observed structure of 47 Tucanae indicates that it is now approaching its ultimate fate during a core collapse phase. There are five known low-luminosity X-ray sources in the core of this cluster, eleven millisecond pulsars, many blue stragglers, and a centrally concentrated population of eclipsing binary stars. The observations support the idea that the population of primordial binaries in this cluster has been heavily modified by stellar encounters. The HST observations In late 1996, the group of astronomers obtained time to observe the central area of 47 Tucanae with the Hubble Space Telescope and the second Wide Field and Planetary Camera (WFPC2). During a period of more than 4 hours, a total of 15 CCD exposures were obtained through an ultraviolet filter (transmission near 3000 A), showing the thousands of individual stars in this densely populated region. Caption to ESO PR Photo 03/97 [GIF, 57k] When inspecting this material, it immediately became clear that one of the stars had undergone a substantial brightening in the course of these observations. In fact, its brightness increased by as much as 2.1 magnitudes, that is a factor of seven, in less than one hour; see the photos that accompany this Press Release. By the end of the observations, it had become the brightest star in the core of the cluster. Caption to ESO

  8. Star Cluster Buzzing With Pulsars

    NASA Astrophysics Data System (ADS)

    2005-01-01

    A dense globular star cluster near the center of our Milky Way Galaxy holds a buzzing beehive of rapidly-spinning millisecond pulsars, according to astronomers who discovered 21 new pulsars in the cluster using the National Science Foundation's 100-meter Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The cluster, called Terzan 5, now holds the record for pulsars, with 24, including three known before the GBT observations. Pulsar Diagram Pulsar Diagram: Click on image for more detail. "We hit the jackpot when we looked at this cluster," said Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, VA. "Not only does this cluster have a lot of pulsars -- and we still expect to find more in it -- but the pulsars in it are very interesting. They include at least 13 in binary systems, two of which are eclipsing, and the four fastest-rotating pulsars known in any globular cluster, with the fastest two rotating nearly 600 times per second, roughly as fast as a household blender," Ransom added. Ransom and his colleagues reported their findings to the American Astronomical Society's meeting in San Diego, CA, and in the online journal Science Express. The star cluster's numerous pulsars are expected to yield a bonanza of new information about not only the pulsars themselves, but also about the dense stellar environment in which they reside and probably even about nuclear physics, according to the scientists. For example, preliminary measurements indicate that two of the pulsars are more massive than some theoretical models would allow. "All these exotic pulsars will keep us busy for years to come," said Jason Hessels, a Ph.D student at McGill University in Montreal. Globular clusters are dense agglomerations of up to millions of stars, all of which formed at about the same time. Pulsars are spinning, superdense neutron stars that whirl "lighthouse beams" of radio waves or light around as they spin. A neutron star is what is left after a massive star explodes as a supernova at the end of its life. The pulsars in Terzan 5 are the product of a complex history. The stars in the cluster formed about 10 billion years ago, the astronomers say. Some of the most massive stars in the cluster exploded and left the neutron stars as their remnants after only a few million years. Normally, these neutron stars would no longer be seen as swiftly-rotating pulsars: their spin would have slowed because of the "drag" of their intense magnetic fields until the "lighthouse" effect is no longer observable. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF (Click on image for GBT gallery) However, the dense concentration of stars in the cluster gave new life to the pulsars. In the core of a globular cluster, as many as a million stars may be packed into a volume that would fit easily between the Sun and our nearest neighbor star. In such close quarters, stars can pass near enough to form new binary pairs, split apart such pairs, and binary systems even can trade partners, like an elaborate cosmic square dance. When a neutron star pairs up with a "normal" companion star, its strong gravitational pull can draw material off the companion onto the neutron star. This also transfers some of the companion's spin, or angular momentum, to the neutron star, thereby "recycling" the neutron star into a rapidly-rotating millisecond pulsar. In Terzan 5, all the pulsars discovered are rotating rapidly as a result of this process. Astronomers previously had discovered three pulsars in Terzan 5, some 28,000 light-years distant in the constellation Sagittarius, but suspected there were more. On July 17, 2004, Ransom and his colleagues used the GBT, and, in a 6-hour observation, found 14 new pulsars, the most ever found in a single observation. "This was possible because of the great sensitivity of the GBT and the new capabilities of our backend processor," said Ingrid Stairs, a professor at the Univer

  9. A Sparkling Spray of Stars

    NASA Astrophysics Data System (ADS)

    2008-12-01

    The festive season has arrived for astronomers at the European Southern Observatory (ESO) in the form of this dramatic new image. It shows the swirling gas around the region known as NGC 2264 -- an area of sky that includes the sparkling blue baubles of the Christmas Tree star cluster. Omega Centauri ESO PR Photo 48/08 NGC 2264 and the Christmas Tree cluster NGC 2264 lies about 2600 light-years from Earth in the obscure constellation of Monoceros, the Unicorn, not far from the more familiar figure of Orion, the Hunter. The image shows a region of space about 30 light-years across. William Herschel discovered this fascinating object during his great sky surveys in the late 18th century. He first noticed the bright cluster in January 1784 and the brightest part of the visually more elusive smudge of the glowing gas clouds at Christmas nearly two years later. The cluster is very bright and can easily be seen with binoculars. With a small telescope (whose lenses will turn the view upside down) the stars resemble the glittering lights on a Christmas tree. The dazzling star at the top is even bright enough to be seen with the unaided eye. It is a massive multiple star system that only emerged from the dust and gas a few million years ago. As well as the cluster there are many interesting and curious structures in the gas and dust. At the bottom of the frame, the dark triangular feature is the evocative Cone Nebula, a region of molecular gas flooded by the harsh light of the brightest cluster members. The region to the right of the brightest star has a curious, fur-like texture that has led to the name Fox Fur Nebula. Much of the image appears red because the huge gas clouds are glowing under the intense ultra-violet light coming from the energetic hot young stars. The stars themselves appear blue as they are hotter, younger and more massive than our own Sun. Some of this blue light is scattered by dust, as can be seen occurring in the upper part of the image. This intriguing region is an ideal laboratory for studying how stars form. The entire area shown here is just a small part of a vast cloud of molecular gas that is in the process of forming the next generation of stars. Besides the feast of objects in this picture there are many interesting objects hidden behind the murk of the nebulosity. In the region between the tip of the Cone Nebula and the brightest star at the top of the picture there are several stellar birthing grounds where young stars are forming. There is even evidence of the intense stellar winds from these youthful embryos blasting out from the hidden stars in the making. This picture of NGC 2264, including the Christmas Tree Cluster, was created from images taken with the Wide Field Imager (WFI), a specialised astronomical camera attached to the 2.2-metre Max-Planck Society/ESO telescope at the La Silla observatory in Chile. Located nearly 2400 m above sea level, in the mountains of the Atacama Desert, ESO's La Silla enjoys some of the clearest and darkest skies on the whole planet, making the site ideally suited for studying the farthest depths of the Universe. To make this image, the WFI stared at the cluster for more than ten hours through a series of specialist filters to build up a full colour image of the billowing clouds of fluorescing hydrogen gas.

  10. Elastic deformations of compact stars

    NASA Astrophysics Data System (ADS)

    Andersson, Lars; Beig, Robert; Schmidt, Bernd G.

    2014-09-01

    We prove existence of solutions for an elastic body interacting with itself through its Newtonian gravitational field. Our construction works for configurations near one given by a self-gravitating ball of perfect fluid. We use an implicit function argument. In so doing we have to revisit some classical work in the astrophysical literature concerning linear stability of perfect fluid stars. The results presented here extend previous work by the authors, which was restricted to the astrophysically insignificant situation of configurations near one of vanishing stress. In particular, ‘mountains on neutron stars’, which are made possible by the presence of an elastic crust in neutron stars, can be treated using the techniques developed here.

  11. Barium Stars and Thermohaline Mixing

    SciTech Connect

    Husti, Laura [Dipartimento di Fisica Generale, Universita di Torino, Via Pietro Giuria 1, 10125 Turin (Italy)

    2008-01-24

    Barium stars are formed in binary systems through mass transfer from the carbon and s-element rich primary in the AGB phase, to the secondary star which is in a less evolved evolutionary stage. The mixing of the accreted material from the AGB donor with the envelope of the secondary results in a dilution of the s-element abundances. Dilution in red giants is explained by the occurence of the first dredge up, while in case of dwarfs thermohaline mixing would determine it. A comparison between the theoretical predictions of the AGB stellar models and the spectroscopical observations of a large sample of barium stars has been made. Dilution due to thermohaline mixing was taken into account when searching for best fits of the observational data. The importance of thermohaline mixing in barium dwarfs is discussed.

  12. Spin physics highlights from STAR

    NASA Astrophysics Data System (ADS)

    Gibson, A.

    2015-05-01

    As the world's only polarized proton collider, the Relativistic Heavy Ion Collider (RHIC) at Brookhaven plays an important role in understanding the spin structure of the proton. The STAR detector, with its large acceptance for calorimetry and tracking, has been used to study polarized proton collisions for more than a decade with a range of jet, meson, and boson probes. We will discuss jets, neutral pions, and W bosons as probes of the proton's helicity structure. Here STAR measurements have significant impact on global fits of sea quark polarizations and have provided the first firm evidence of non-zero gluon polarization within the proton. We will discuss W/Z bosons, jets, pions, and pion-jet correlations as probes of the transverse spin structure of the proton, and we will use the example of a proposed dijet measurement with an upgraded STAR detector to peer into the future.

  13. Testing Gravity Theories Using Stars

    E-print Network

    Jeremy Sakstein; Bhuvnesh Jain; Vinu Vikram

    2014-09-12

    Modified theories of gravity have received a renewed interest due to their ability to account for the cosmic acceleration. In order to satisfy the solar system tests of gravity, these theories need to include a screening mechanism that hides the modifications on small scales. One popular and well-studied theory is chameleon gravity. Our own galaxy is necessarily screened, but less dense dwarf galaxies may be unscreened and their constituent stars can exhibit novel features. In particular, unscreened stars are brighter, hotter and more ephemeral than screened stars in our own galaxy. They also pulsate with a shorter period. In this essay, we exploit these new features to constrain chameleon gravity to levels three orders of magnitude lower the previous measurements. These constraints are currently the strongest in the literature.

  14. Microlensing of close binary stars

    NASA Astrophysics Data System (ADS)

    Rattenbury, Nicholas J.

    2009-01-01

    The gravity due to a multiple-mass system has a remarkable gravitational effect: the extreme magnification of background light sources along extended so-called caustic lines. This property has been the channel for some remarkable astrophysical discoveries over the past decade, including the detection and characterization of extrasolar planets, the routine analysis of limb darkening, and, in one case, limits set on the apparent shape of a star several kiloparsec distant. In this paper, we investigate the properties of the microlensing of close binary star systems. We show that in some cases it is possible to detect flux from the Roche lobes of close binary stars. Such observations could constrain models of close binary stellar systems.

  15. Exploding Stars and Stripes

    NASA Astrophysics Data System (ADS)

    2011-03-01

    The discovery of a pattern of X-ray "stripes" in the remains of an exploded star may provide the first direct evidence that a cosmic event can accelerate particles to energies a hundred times higher than achieved by the most powerful particle accelerator on Earth. This result comes from a very long observation of the Tycho supernova remnant with NASA's Chandra X-ray Observatory. It could explain how some of the extremely energetic particles bombarding the Earth, called cosmic rays, are produced. "We've seen lots of intriguing structures in supernova remnants, but we've never seen stripes before," said Kristoffer Eriksen, a postdoctoral researcher at Rutgers University who led the study. "This made us think very hard about what's happening in the blast wave of this powerful explosion." This latest study from Chandra provides support for a theory about how magnetic fields can be dramatically amplified in such blast waves. In this theory, the magnetic fields become highly tangled and the motions of the particles very turbulent near the expanding supernova shock wave at the front edge of the supernova remnant. High-energy charged particles can bounce back and forth across the shock wave repeatedly, gaining energy with each crossing. Theoretical models of the motion of the most energetic particles -- which are mostly protons -- are predicted to leave a messy network of holes and dense walls corresponding to weak and strong regions of magnetic fields, respectively. The X-ray stripes discovered by the Chandra researchers are thought to be regions where the turbulence is greater and the magnetic fields more tangled than surrounding areas, and may be the walls predicted by the theory. Electrons become trapped in these regions and emit X-rays as they spiral around the magnetic field lines. However, the regular and almost periodic pattern of the X-ray stripes was not predicted by the theory. "It was a big surprise to find such a neatly arranged set of stripes," said co-author Jack Hughes, professor of physics and astronomy at Rutgers. "We were not expecting so much order to appear in so much chaos. It could mean that the theory is incomplete, or that there's something else we don't understand." Assuming that the spacing between the X-ray stripes corresponds to the radius of the spiraling motion of the highest energy protons in the supernova remnant, the spacing corresponds to energies about 100 times higher than reached in the Large Hadron Collider. These energies equal the highest energies of cosmic rays thought to be produced in our Galaxy. Because cosmic rays are composed of charged particles, like protons and electrons, their direction of motion changes when they encounter magnetic fields throughout the galaxy. So, the origin of individual cosmic rays detected on Earth cannot be determined. Supernova remnants have long been considered a good candidate for producing the most energetic cosmic rays in our Galaxy. The protons can reach energies that are hundreds of times higher than the highest energy electrons, but since they do not radiate efficiently like the electrons, direct evidence for the acceleration of cosmic ray protons in supernova remnants has been lacking. These results also support the prediction that magnetic fields in interstellar space are greatly amplified in supernova remnants, but the difference between the observed and predicted structures means that other interpretations cannot be ruled out. "We were excited to discover these stripes because they might allow us to directly track, for the first time, the origin of the most energetic particles produced in our galaxy," said Eriksen. "But, we're not claiming victory yet." The Tycho supernova remnant is named for the famous Danish astronomer Tycho Brahe, who reported observing the supernova in 1572. Scientists think the explosion occurred when a white dwarf star grew in mass and exceeded its weight limit, forming a so-called Type Ia supernova. The Tycho remnant is located in the Milky Way, about

  16. Gravity darkening in binary stars

    NASA Astrophysics Data System (ADS)

    Espinosa Lara, F.; Rieutord, M.

    2012-11-01

    Context. Interpretation of light curves of many types of binary stars requires the inclusion of the (cor)relation between surface brightness and local effective gravity. Until recently, this correlation has always been modeled by a power law relating the flux or the effective temperature and the effective gravity, namely Teff ? geff? . Aims: We look for a simple model that can describe the variations of the flux at the surface of stars belonging to a binary system. Methods: This model assumes that the energy flux is a divergence-free vector anti-parallel to the effective gravity. The effective gravity is computed from the Roche model. Results: After explaining in a simple manner the old result of Lucy (1967, Z. Astrophys., 65, 89), which says that ? ~ 0.08 for solar type stars, we first argue that one-dimensional models should no longer be used to evaluate gravity darkening laws. We compute the correlation between log Teff and log geff using a new approach that is valid for synchronous, weakly magnetized, weakly irradiated binaries. We show that this correlation is approximately linear, validating the use of a power law relation between effective temperature and effective gravity as a first approximation. We further show that the exponent ? of this power law is a slowly varying function, which we tabulate, of the mass ratio of the binary star and the Roche lobe filling factor of the stars of the system. The exponent ? remains mostly in the interval [0.20,0.25] if extreme mass ratios are eliminated. Conclusions: For binary stars that are synchronous, weakly magnetized and weakly irradiated, the gravity darkening exponent is well constrained and may be removed from the free parameters of the models.

  17. AN ULTRACOOL STAR'S CANDIDATE PLANET

    SciTech Connect

    Pravdo, Steven H. [Jet Propulsion Laboratory, California Institute of Technology, 306-431, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Shaklan, Stuart B. [Jet Propulsion Laboratory, California Institute of Technology, 301-451, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)], E-mail: spravdo@jpl.nasa.gov, E-mail: stuart.shaklan@jpl.nasa.gov

    2009-07-20

    We report here the discovery of the first planet around an ultracool dwarf star. It is also the first extrasolar giant planet astrometrically discovered around a main-sequence star. The statistical significance of the detection is shown in two ways. First, there is a 2 x 10{sup -8} probability that the astrometric motion fits a parallax-and-proper-motion-only model. Second, periodogram analysis shows a false alarm probability of 3 x 10{sup -5} that the discovered period is randomly generated. The planetary mass is M {sub 2} = 6.4 (+2.6,-3.1) Jupiter-masses (M {sub J}), and the orbital period is P = 0.744 (+0.013,-0.008) yr in the most likely model. In less likely models, companion masses that are higher than the 13 M {sub J} planetary mass limit are ruled out by past radial velocity (RV) measurements unless the system RV is more than twice the current upper limits and the near-periastron orbital phase was never observed. This new planetary system is remarkable, in part, because its star, VB 10, is near the lower mass limit for a star. Our astrometric observations provide a dynamical mass measurement and will in time allow us to confront the theoretical models of formation and evolution of such systems and their members. We thus add to the diversity of planetary systems and to the small number of known M-dwarf planets. Planets such as VB 10b could be the most numerous type of planets because M stars comprise >70% of all stars. To date they have remained hidden since the dominant RV planet-discovery technique is relatively insensitive to these dim, red systems.

  18. Warm Winds of Hybrid Stars

    NASA Astrophysics Data System (ADS)

    Dupree, A. K.; Brickhouse, N. S.

    1998-05-01

    ORFEUS spectra of two hybrid stars alpha Aqr (G2 Ib, HD 209750) and alpha TrA (K2 II, HD 150798), and beta Dra (G2 Ib-IIa, HD 159181) cover the far ultraviolet region lambda lambda 912--1218 with a moderate resolution of ~ 3000. Blue--shifted O VI (lambda 1032) and C III (lambda 977) emission relative to Si III (lambda 1206) is detected in the two hybrid stars, and the markedly narrow resonance line profiles of C III and Si III in the two hybrid objects as compared to the coronal star beta Dra also suggest wind absorption. The observed Doppler shifts could be caused by a warm wind of at least 3x 10(5) K in the hybrid stars with outflows ~ 100--200 km\\ s(-1) . An asymmetric profile of C III in beta Dra might also result from wind absorption, although the acceleration would have to begin at higher temperatures (T ~ 7000 K) in this coronal star as compared to the hybrids. Electron densities determined from C III multiplets in beta Dra and alpha TrA indicate values between 8.3--8.6 dex (cm(-3) ), giving a pressure of ~ 2 x 10(13) cm(-3) K at T ~ 7x 10(4) K. Wind absorption and interstellar extinction must be considered when applying emission line diagnostics in this wavelength region. These observations make the connection between hot and cool winds across the color-magnitude diagram, by demonstrating that intermediate warm winds exist among luminous stars.

  19. Formation of the first stars.

    PubMed

    Bromm, Volker

    2013-11-01

    Understanding the formation of the first stars is one of the frontier topics in modern astrophysics and cosmology. Their emergence signalled the end of the cosmic dark ages, a few hundred million years after the Big Bang, leading to a fundamental transformation of the early Universe through the production of ionizing photons and the initial enrichment with heavy chemical elements. We here review the state of our knowledge, separating the well understood elements of our emerging picture from those where more work is required. Primordial star formation is unique in that its initial conditions can be directly inferred from the ? cold dark matter (?CDM) model of cosmological structure formation. Combined with gas cooling that is mediated via molecular hydrogen, one can robustly identify the regions of primordial star formation, the so-called minihalos, having total masses of ~10(6) M? and collapsing at redshifts z ? 20-30. Within this framework, a number of studies have defined a preliminary standard model, with the main result that the first stars were predominantly massive. This model has recently been modified to include a ubiquitous mode of fragmentation in the protostellar disks, such that the typical outcome of primordial star formation may be the formation of a binary or small multiple stellar system. We will also discuss extensions to this standard picture due to the presence of dynamically significant magnetic fields, of heating from self-annihalating WIMP dark matter, or cosmic rays. We conclude by discussing possible strategies to empirically test our theoretical models. Foremost among them are predictions for the upcoming James Webb space telescope (JWST), to be launched ~2018, and for 'stellar archaeology', which probes the abundance pattern in the oldest, most-metal poor stars in our cosmic neighborhood, thereby constraining the nucleosynthesis inside the first supernovae. PMID:24168986

  20. Formation of the first stars

    NASA Astrophysics Data System (ADS)

    Bromm, Volker

    2013-11-01

    Understanding the formation of the first stars is one of the frontier topics in modern astrophysics and cosmology. Their emergence signalled the end of the cosmic dark ages, a few hundred million years after the Big Bang, leading to a fundamental transformation of the early Universe through the production of ionizing photons and the initial enrichment with heavy chemical elements. We here review the state of our knowledge, separating the well understood elements of our emerging picture from those where more work is required. Primordial star formation is unique in that its initial conditions can be directly inferred from the ? cold dark matter (?CDM) model of cosmological structure formation. Combined with gas cooling that is mediated via molecular hydrogen, one can robustly identify the regions of primordial star formation, the so-called minihalos, having total masses of ˜106 M? and collapsing at redshifts z ? 20-30. Within this framework, a number of studies have defined a preliminary standard model, with the main result that the first stars were predominantly massive. This model has recently been modified to include a ubiquitous mode of fragmentation in the protostellar disks, such that the typical outcome of primordial star formation may be the formation of a binary or small multiple stellar system. We will also discuss extensions to this standard picture due to the presence of dynamically significant magnetic fields, of heating from self-annihalating WIMP dark matter, or cosmic rays. We conclude by discussing possible strategies to empirically test our theoretical models. Foremost among them are predictions for the upcoming James Webb space telescope (JWST), to be launched ˜2018, and for ‘stellar archaeology’, which probes the abundance pattern in the oldest, most-metal poor stars in our cosmic neighborhood, thereby constraining the nucleosynthesis inside the first supernovae.

  1. Star City, Russia Medical Operations

    NASA Technical Reports Server (NTRS)

    Chandler, Michael R.; Senter, Cedric H.; Roden, Sean K.; Gilmore, Stevan; Powers, William E.; Alexander, David J.

    2004-01-01

    Since the beginning of the NASA/Mir missions, NASA has had astronauts in training at the Gagarin Cosmonaut Training Center (GCTC), also known as Star City, with crewmembers currently there to train for the International Space Station missions. Agreements have been reached with all International Partners that allow the crewmember's parent agency to provide a flight surgeon to oversee crewmember health and safety during training away from home. NASA Medical Operations through the Bioastronautics Contract employs flight surgeons to provide medical support for U.S. crewmembers and their support staff. This poster presentation reviews the aspects of NASA medical operations at Star City.

  2. MMAS: Make Me A Star

    NASA Astrophysics Data System (ADS)

    Lombardi, James; Sawyer Warren, Jessica

    2014-12-01

    Make Me A Star (MMAS) quickly generates stellar collision remnants and can be used in combination with realistic dynamical simulations of star clusters that include stellar collisions. The code approximates the merger process (including shock heating, hydrodynamic mixing, mass ejection, and angular momentum transfer) with simple algorithms based on conservation laws and a basic qualitative understanding of the hydrodynamics. These simple models agree very well with those from SPH (smoothed particle hydrodynamics) calculations of stellar collisions, and the subsequent stellar evolution of these models also matches closely that of the more accurate hydrodynamic models.

  3. Towards a realistic axion star

    E-print Network

    J. Barranco; A. Bernal

    2008-08-01

    In this work we estimate the radius and the mass of a self-gravitating system made of axions. The quantum axion field satisfies the Klein-Gordon equation in a curved space-time and the metric components of this space-time are solutions to the Einstein equations with a source term given by the vacuum expectation value of the energy-momentum operator constructed from the axion field. As a first step towards an axion star we consider the up to the sixth term in the axion potential expansion. We found that axion stars would have masses of the order of asteroids and radius of the order of few centimeters.

  4. Nucleosynthesis in red giant stars

    NASA Astrophysics Data System (ADS)

    Mowlavi, Nami

    The production of elements from helium-3 to fluorine in low- and intermediate-mass stars is reviewed and compared to chemical abundances observed at the surface of both red giant branch and asymptotic giant branch stars. It is highlighted that, while the trends predicted by standard models are generally well confirmed, many chemical abundances observed at the surface of red giants require the operation of non-standard mixing in the stellar interior. In addition, chemical abundance predictions from presently available asymptotic giant branch models further suffer from the uncertainties affecting the third dredge-up phenomenon, the source of neutrons and the hot bottom burning process.

  5. Coalescing binary neutron star systems

    NASA Astrophysics Data System (ADS)

    Calder, Alan C.; Swesty, F. Douglas; Wang, Edward Y. M.

    2001-10-01

    We present numerical studies of coalescing neutron star pairs with Newtonian hydrodynamics coupled to the 2.5 Post-Newtonian radiation reaction of Blanchet, Damour, and Schäfer [1]. Our simulations evolve the Euler equations using a modification of the ZEUS 2-D algorithm [2] and use a Fast Fourier Transformation method for solving the Poisson equation for the gravitational and radiation reaction potentials. We find that the radiation reaction produces a significant effect on a neutron star pair when compared to a purely Newtonian simulation. .

  6. Neutron skins and neutron stars

    SciTech Connect

    Piekarewicz, J. [Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States)

    2013-11-07

    The neutron-skin thickness of heavy nuclei provides a fundamental link to the equation of state of neutron-rich matter, and hence to the properties of neutron stars. The Lead Radius Experiment ('PREX') at Jefferson Laboratory has recently provided the first model-independence evidence on the existence of a neutron-rich skin in {sup 208}Pb. In this contribution we examine how the increased accuracy in the determination of neutron skins expected from the commissioning of intense polarized electron beams may impact the physics of neutron stars.

  7. The Twelve Pointed Star Game

    NSDL National Science Digital Library

    NRICH team

    2012-01-01

    In this probability game for two or more players, students determine the possible outcomes and determine their likelihood in order to create a winning strategy. To play this game, players select three numbers from the star (1-12), and then take turns rolling the die and putting a marker on the ray that matches the sum, the player who gets three markers on their number first wins. This resource includes teachers notes with suggestions for introducing the game, discussion questions, support suggestions,and a printable star game board.

  8. Eclipsing Binary Stars from Space

    E-print Network

    H. Bruntt; J. Southworth

    2006-10-18

    We have begun a programme to obtain high-precision photometry of bright detached eclipsing binary (dEB) stars with the Wide field InfraRed Explorer (WIRE) satellite. Due to the small aperture of WIRE only stars brighter than V=6 can be observed. We are collecting data for about a dozen dEB targets and here we present preliminary results for three of them. We have chosen dEBs with primary components of B and early A type. One of our aims is to combine the information from the light curve analyses of the eclipses with asteroseismic information from the analysis of the pulsation of the primary component.

  9. How Hot is That Star

    NSDL National Science Digital Library

    Jim Meunier

    This resource is part of the Science Education Gateway (SEGway) project, funded by NASA, which is a national consortium of scientists, museums, and educators working together to bring the latest science to students, teachers, and the general public. How hot is the Sun? How do scientists know? Students perform guided Web research through several sites on solar astronomy to answer theses questions, and more: how to measure the temperature of any star, and how astronomers use Hertzsprung-Russell (H-R) diagrams to classify stars by temperature and luminosity. This unit is divided into six lessons, and contains feedback from other educators who have used this module.

  10. Nuclear Physics of Neutron Stars

    E-print Network

    J. Piekarewicz

    2009-01-28

    Understanding the equation of state (EOS) of cold nuclear matter, namely, the relation between the pressure and energy density, is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the special role that nuclear physics plays in constraining the EOS of cold baryonic matter and its impact on the properties of neutron stars.

  11. How Far Are the Stars?

    NSDL National Science Digital Library

    Edward Murphy

    2005-02-01

    On any night, the stars seen in the sky can be as close to Earth as a few light-years or as distant as a few thousand light-years. Distances this large are hard to comprehend. In this article, we explore how astronomers measure the distances to stars and learn about the roles of observation and inference in the development of scientific knowledge, a critical aspect of the nature of science. The goal of this article is to help teachers and students develop understandings about the size of the universe and how science can tell us so much about things we cannot observe directly.

  12. Rotational Properties of Massive Stars

    NASA Astrophysics Data System (ADS)

    Penny, Laura

    2013-06-01

    This review summarizes our current observational evidence for the distribution of rotation rates among massive stars. The results from recent campaigns to determine projected rotational velocities for large numbers of OB-type stars are included. Despite the growing database of v sin i values for these objects, several key questions remain. What is the ZAMS distribution of velocities? What effect does stellar density, cluster vs. field, have on the initial rotation rates? How does the ``hidden'' population of former members of binary systems contaminate these samples? And does a lower metallicity result in faster rotation for these objects?

  13. Changes in Athletic Identity Following Team Selection: Self-Protection versus Self-Enhancement

    Microsoft Academic Search

    J. ROBERT GROVE; MAREE FISH; ROBERT C. EKLUND

    2004-01-01

    Self-protection and self-enhancement were investigated in a field study of female athletes who were vying for selection in state all-star teams. Participants completed the Athletic Identity Measurement Scale (AIMS; Brewer, Van Raalte, & Linder, 1993) on three occasions, and changes over time were compared for players who made the team and players who did not make the team. Findings revealed

  14. Strawberry FaEtr2 gene RNAi expression vector construction and genetic transformation

    Microsoft Academic Search

    Chunli Song; Junlian Ma; Xia Tang; Zide Zhang; Zhixia Hou

    2009-01-01

    The short hairpin RNA (shRNA) expression vector of the FaEtr2 gene was constructed by inserting the sense fragment into the constructed antisense vector of FaEtr2 (pBI121-Anti-Etr2) in sense orientation. The constructed RNA interference (RNAi) expression vector was transformed into Agrobacterium fumefeciens LBA4404 and used to infect strawberry leaves. Using in vitro plantlet leaves as explants, the transformation conditions of All-Star

  15. Terrestrial Planet Formation Around Individual Stars Within Binary Star Systems

    E-print Network

    Elisa V. Quintana; Fred C. Adams; Jack J. Lissauer; John E. Chambers

    2007-01-09

    We calculate herein the late stages of terrestrial planet accumulation around a solar type star that has a binary companion with semimajor axis larger than the terrestrial planet region. We perform more than one hundred simulations to survey binary parameter space and to account for sensitive dependence on initial conditions in these dynamical systems. As expected, sufficiently wide binaries leave the planet formation process largely unaffected. As a rough approximation, binary stars with periastron $q_B > 10$ AU have minimal effect on terrestrial planet formation within $\\sim 2$ AU of the primary, whereas binary stars with $q_B \\la$ 5 AU restrict terrestrial planet formation to within $\\sim$ 1 AU of the primary star. Given the observed distribution of binary orbital elements for solar type primaries, we estimate that about 40 -- 50 percent of the binary population is wide enough to allow terrestrial planet formation to take place unimpeded. The large number of simulations allows for us to determine the distribution of results -- the distribution of plausible terrestrial planet systems -- for effectively equivalent starting conditions. We present (rough) distributions for the number of planets, their masses, and their orbital elements.

  16. Probing the Faintest Stars in a Globular Star Cluster

    E-print Network

    Harvey B. Richer; Jay Anderson; James Brewer; Saul Davis; Gregory G. Fahlman; Brad M. S. Hansen; Jarrod Hurley; Jasonjot S. Kalirai; Ivan R. King; David Reitzel; R. Michael Rich; Michael M. Shara; Peter B. Stetson

    2007-02-07

    NGC 6397 is the second closest globular star cluster to the Sun. Using 5 days of time on the Hubble Space Telescope, we have constructed the deepest ever color-magnitude diagram for this cluster. We see a clear truncation in each of its two major stellar sequences. Faint red main sequence stars run out well above our observational limit and near to the theoretical prediction for the lowest mass stars capable of stable hydrogen-burning in their cores. We also see a truncation in the number counts of faint blue stars, namely white dwarfs. This reflects the limit to which the bulk of the white dwarfs can cool over the lifetime of the cluster. There is also a turn towards bluer colors in the least luminous of these objects. This was predicted for the very coolest white dwarfs with hydrogen-rich atmospheres as the formation of H2 causes their atmospheres to become largely opaque to infrared radiation due to collision-induced absorption.

  17. MMT HYPERVELOCITY STAR SURVEY. II. FIVE NEW UNBOUND STARS

    SciTech Connect

    Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J., E-mail: wbrown@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: skenyon@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-05-20

    We present the discovery of five new unbound hypervelocity stars (HVSs) in the outer Milky Way halo. Using a conservative estimate of Galactic escape velocity, our targeted spectroscopic survey has now identified 16 unbound HVSs as well as a comparable number of HVSs ejected on bound trajectories. A Galactic center origin for the HVSs is supported by their unbound velocities, the observed number of unbound stars, their stellar nature, their ejection time distribution, and their Galactic latitude and longitude distribution. Other proposed origins for the unbound HVSs, such as runaway ejections from the disk or dwarf galaxy tidal debris, cannot be reconciled with the observations. An intriguing result is the spatial anisotropy of HVSs on the sky, which possibly reflects an anisotropic potential in the central 10-100 pc region of the Galaxy. Further progress requires measurement of the spatial distribution of HVSs over the southern sky. Our survey also identifies seven B supergiants associated with known star-forming galaxies; the absence of B supergiants elsewhere in the survey implies there are no new star-forming galaxies in our survey footprint to a depth of 1-2 Mpc.

  18. Quark stars: their influence on Astroparticle Physics

    E-print Network

    Sanjay K. Ghosh

    2008-08-12

    We discuss some of the recent developments in the quark star physics along with the consequences of possible hadron to quark phase transition at high density scenario of neutron stars and their implications on the Astroparticle Physics.

  19. White Dwarfs, Neutron Stars and Black Holes

    ERIC Educational Resources Information Center

    Szekeres, P.

    1977-01-01

    The three possible fates of burned-out stars: white dwarfs, neutron stars and black holes, are described in elementary terms. Characteristics of these celestial bodies, as provided by Einstein's work, are described. (CP)

  20. Making Galaxies: One Star at a Time

    SciTech Connect

    Tom Abel

    2006-09-18

    Dr. Tom Abel of Stanford University talks about the entire history of the universe, from the big bang to formation of stars and galaxies. His work uses mathematical models to understand and predict how stars and galaxies initially form.