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1

MHL ALL-STARS SELECTION PROCESS  

Microsoft Academic Search

5. The VP in charge of All-Star selection (or the League President) will initiate contact with each team's coach. The selection process will be conducted as follows: a. Each team will submit players to participate on the All-Star team. Final All- star team composition will be based on team standings from the seeding weekends to make up the 18 player

Omaha Mavericks

2009-01-01

2

Measurements of the Lick Observatory Sodium Laser Guide Star  

SciTech Connect

The Lick Observatory guide star laser has provided a beacon sufficient to close the adaptive optics loop and produce corrected images during runs in 1996 and 1997. This report summarizes measurements of the wavefront quality of the outgoing beam, photoreturn signal from the sodium beacon, and radiance distribution of the guide star on the sky, and follows with an analysis of the impact of the laser on adaptive optics system performance.

Gavel, D. T., LLNL

1998-03-01

3

Lick Saturn-Voyager Reference Star Catalogue (Klemola+, 1979)  

NASA Astrophysics Data System (ADS)

The Lick Saturn-Voyager Reference Star Catalogue was prepared for purposes of determining up-to-date, reasonably accurate, equatorial coordinates for reference stars in a band of sky against which cameras of the Voyager spacecraft were aligned for observations in the region of Saturn during the flyby. The requirements were a surface density of about three reference stars per observation frame of 24 sq.arcmin of the cameras - somewhat greater that the SAO (Smithsonian Astrophsyical Observatory Staff 1966) and the AGK3 (Dieckvoss et al. 1975) densities - and a positional accuracy +/- 0.5". Visual magnitudes were also required. The completed catalog contains 4551 stars in the right ascension range 12h 40min to 14h 12min, declination zones +02deg. to -09deg. Mean errors of the positions, as derived from least squares solutions against the Perth 70 Catalogue (Hoeg and von der Heide 1976), are about 0.25"; however, individual residuals for some bright and excessively faint stars are as high as 0.5" to 1.0". The accidental error of one measurement, as deduced from a tabular histogram given in the original catalog publication (referenced below), is about 0.09". Apparent photographic and visual magnitudes were derived from iris photometer measurements, visual magnitude being approximated from a derived color-index relation using UBV stars selected from the USNO photoelectric catalog (Blanco et al. 1968) and extended with Perth 70 stars. The resulting magnitudes appear to have mean errors of at least 0.2mag - 0.3mag for the brighter stars (visual magnitude < 10mag) and uncertainties can be as much as 0.5mag for the fainter stars. The magnitudes are considered to be only approximate, especially on the faint end, because of a lack of photoelectric standards there. For additional information concerning the observations and reductions, the original publication (available from A. R. Klemola) should be consulted. (1 data file).

Klemola, A. R.; Taraji, H.; Ocampo, A.

1995-05-01

4

Performance of laser guide star adaptive optics at Lick Observatory  

SciTech Connect

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.

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

1995-07-19

5

Lick Jupiter-Voyager Reference Star Catalogue (Klemola+ 1978)  

NASA Astrophysics Data System (ADS)

The catalog was prepared for purposes of determining up-to-date, reasonably accurate equatorial coordinates for reference stars in a band of sky against which cameras of the Voyager spacecraft were aligned for observations of Jovian satellites during the Jupiter flyby. The catalog contains accurate equatorial coordinates for equinox 1950.0, epoch 1978.27, photographic and visual magnitudes, AGK3 identifications and proper motions for 4983 stars. All of the reference stars are in the range 6h00m to 8h04m in right ascension (1950), declination zones +16 to +23 degrees, and 8h31m to 8h57m, zones +08 to +14 degrees. Mean errors of the positions are about 0.4 second of arc. Introduction The Lick Jupiter-Voyager Reference Star Catalogue. Klemola et al. (1978) was prepared for purposes of determining up-to-date, reasonably accurate, equatorial coordinates for reference stars in a band of sky against which cameras of the Voyager spacecraft were aligned for observations of Jovian satellites during the Jupiter flyby. The requirements were a surface density of three to four reference stars per observation frame of 24 sq. arcmin. of the cameras - somewhat greater than that provided by the AGK3 catalog (Dieckvoss et al. 1975) - and a positional accuracy approximately 0.5. Visual magnitudes were also required. The completed catalog contains 4983 stars in the right ascension ranges 6h00m to 8h04m, declination zones +16 deg. to +23 deg., and 8h31m to 8h57m, declination zones +08 deg. to +14 deg.. Mean errors of the positions, as derived from least squares solutions against the AGK3 reference stars, are about 0.4"; however, individual residuals are fairly numerous in the range 0.6" to 0.8" with some in the range 1.0" to 1.3" The accidental error of one measurement, as deduced from a tabular histogram given in the original catalog publication (referenced below), is about 0.11". Apparent photographic and visual magnitudes were derived from iris photometer measurements, m(v). being approximated from a derived color-index relation using the AGK3 reference stars. The resulting magnitudes appear to have mean errors of at least 0.2 mag while very blue and very red stars (C.I..le.0 mag, and C.I..ge.1.5, respectively) are less certain. The magnitudes are considered to be only approximate (residuals of approximately 0.5 mag are fairly common). For additional information concerning the observations and reductions, the original publication (available from A. R. Klemola) should be consulted. A copy of this document should be transmitted to any recipient of the machine-readable catalog. (1 data file).

Klemola, A. R.; Morabito, L.

1996-04-01

6

NASA ALLSTAR Project  

NASA Technical Reports Server (NTRS)

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 29th, 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.

Levy, Cesar; Ebadian, M. A.

1998-01-01

7

Cartoon All-Stars to the Rescue. Joint Hearing before the Senate Committee on the Judiciary and the House Committee on the Judiciary on An Entertaining Way of Enlightening Children about the Dangers of Substance Abuse. One Hundred First Congress, Second Session.  

ERIC Educational Resources Information Center

This document presents witness testimony and supplemental materials from a Congressional hearing called to examine Cartoon All-Stars to the Rescue, a cartoon designed to teach children about the danger of substance abuse. Opening statements are included by Senator Joseph Biden, Jr., chairman of the Senate Judiciary Committee, and by Senators Strom…

Congress of the U.S., Washington, DC. House Committee on the Judiciary.

8

Lick slit spectra of thirty-eight objective prism quasar candidates and low metallicity halo stars  

NASA Technical Reports Server (NTRS)

Lick Observatory slit spectra of 38 objects which were claimed to have pronounced UV excess and emission lines are presented. Eleven QSOs, four galaxies at z of about 0.1, 22 stars, and one unidentified object with a low S/N spectrum were found. Of 11 objects which Zhan and Chen (1987, 1989) suggested were QSO with z(prism) not greater than 2.8; eight are QSOs. Six of the QSOs show absorption systems, including Q0000+027A with a relatively strong associated C IV absorption system, and Q0008+008 with a damped Ly-alpha system with an H I column density of 10 exp 21/sq cm. The equivalent widths of the Ca II K line, the G band, and the Balmer lines in 10 stars with the best spectra are measured, and metallicities are derived. Seven of them are in the range -2.5 to -1.7, while the others are less metal-poor.

Tytler, David; Fan, Xiao-Ming; Junkkarinen, Vesa T.; Cohen, Ross D.

1993-01-01

9

The FEROS-Lick/SDSS observational data base of spectral indices of FGK stars for stellar population studies  

NASA Astrophysics Data System (ADS)

We present FEROS-Lick/SDSS, an empirical data base of Lick/SDSS spectral indices of FGK stars to be used in population synthesis projects for discriminating different stellar populations within the integrated light of galaxies and globular clusters. From about 2500 FEROS stellar spectra obtained from the European Southern Observatory Science Archive Facility, we computed line-strength indices for 1085 non-supergiant stars with atmospheric parameter estimates from the AMBRE project. Two samples of 312 dwarfs and of 83 subgiants with solar chemical composition and no significant ?-element abundance enhancement are used to compare their observational indices with the predictions of the Lick/SDSS library of synthetic indices. In general, the synthetic library reproduces very well the behaviour of observational indices as a function of temperature, but in the case of low-temperature (Teff ? 5000 K) dwarfs; low-temperature subgiants are not numerous enough to derive any conclusion. Several possible causes of the disagreement are discussed and promising theoretical improvements are presented.

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

2014-07-01

10

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

SciTech Connect

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.

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

11

THE LICK-CARNEGIE SURVEY: A NEW TWO-PLANET SYSTEM AROUND THE STAR HD 207832  

SciTech Connect

Keck/HIRES precision radial velocities of HD 207832 indicate the presence of two Jovian-type planetary companions in Keplerian orbits around this G star. The planets have minimum masses of Msin i = 0.56 M{sub Jup} and 0.73 M{sub Jup}, with orbital periods of {approx}162 and {approx}1156 days, and eccentricities of 0.13 and 0.27, respectively. Stroemgren b and y photometry reveals a clear stellar rotation signature of the host star with a period of 17.8 days, well separated from the period of the radial velocity variations, reinforcing their Keplerian origin. The values of the semimajor axes of the planets suggest that these objects have migrated from the region of giant planet formation to closer orbits. In order to examine the possibility of the existence of additional (small) planets in the system, we studied the orbital stability of hypothetical terrestrial-sized objects in the region between the two planets and interior to the orbit of the inner body. Results indicated that stable orbits exist only in a small region interior to planet b. However, the current observational data offer no evidence for the existence of additional objects in this system.

Haghighipour, Nader [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States); Butler, R. Paul [Department of Terrestrial Magnetism, Carnegie Institute of Washington, Washington, DC 20015 (United States); Rivera, Eugenio J.; Vogt, Steven S. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Henry, Gregory W. [Center of Excellence in Information Systems, Tennessee State University, Nashville, TN 37209 (United States)

2012-09-01

12

The LickX spectra  

NASA Astrophysics Data System (ADS)

Context. Collections of stellar spectra, often called stellar libraries, are useful in a variety of applications in the field of stellar populations. Aims: This is an attempt to improve the much-used Lick library of stellar spectra by removing jitter from the wavelength scale via cross-correlation, and calling the result the LickX library. Methods: Each spectrum was cross-correlated with a template spectrum and a new wavelength solution sought. Low-order polynomials were fit to adjust the old scale to a new fit. Indices were measured, new standard star averages found, and adjusted averages derived for the program stars. Results: The greatest gains in accuracy are expected for the fainter stars and stars of extreme surface temperatures; the bright K giant standard stars in LickX have the same uncertainties as Lick. The spectra and a table of index measurements in which repeated measurements are averaged are made available electronically. Individual stellar spectra, in FITS files, and the ascii catalog of absorption feature index strengths 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/561/A36

Worthey, G.; Danilet, A. B.; Faber, S. M.

2014-01-01

13

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

NASA Technical Reports Server (NTRS)

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.

Levy, Cesar; Ebadian M. A.

1998-01-01

14

Calibrating GMOS Spectra to the Lick/IDS Index System  

NASA Astrophysics Data System (ADS)

We present preliminary results on the calibration of Gemini GMOS spectra to the Lick line index system. The Lick system of spectral line indices is one of the most commonly used methods of determining ages and metallicities of unresolved (integrated light) spectral populations. However, care must be taken to calibrate the measured indices to the standard system before making comparisons with models. The calibration of the Lick/IDS system is complicated because the original Lick spectra were not flux calibrated, so there are usually systematic effects due to differences in continuum shape. In addition, the spectra must be broadened to the Lick spectral resolution. Proper calibration involves observing many of the original Lick/IDS standard stars and deriving offsets to the standard system. The indices of the standard stars must bracket the expected indices of the science targets, so many stars may be needed if a wide range of metallicities or ages is expected. We have observed several dozen Lick standard stars with GMOS North and South on the Gemini telescopes and we present details on the data reduction and the initial calibration to the Lick system. 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 Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina).

Miller, Bryan W.; Trancho, G.; Puzia, T.

2009-12-01

15

Lick Saturn-Voyager reference star catalogue (Klemola, Taraji, and Ocampo 1979): Documentation for the machine-readable version  

NASA Technical Reports Server (NTRS)

The machine readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The catalog contains accurate equatorial coordinates for 4551 stars in a band of sky against which cameras of the Voyager spacecraft were pointed for observations in the region of Saturn during the flyby. All of the reference stars are in the range 12(exp h) 40(exp m) to 14(exp h) 12(exp m) in right ascension (1950) and +02 to -09 degs in declination. Mean errors of the positions are about 0.25 sec.

Warren, Wayne H., Jr.

1990-01-01

16

Lick Jupiter-Voyager reference star catalogue (Klemola, Morabito, and Taraji 1978): Documentation for the machine-readable version  

NASA Technical Reports Server (NTRS)

The machine-readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The catalog contains accurate equatorial coordinates for 4983 stars in a band of sky against which cameras of the Voyager spacecraft were pointed for observations in the region of Jupiter during the flyby. All of the reference stars are in the range 6 hr 00 min to 8 hr 04 min in right ascension (1950), declination zones +16 to +23 degrees, and 8 hr to 31 min to 8 hr 57 min, zones +08 to +14 degrees. Mean errors of the positions are about 0.4 sec.

Warren, Wayne H., Jr.

1990-01-01

17

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

NASA Technical Reports Server (NTRS)

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.

Levy, Cesar; Ebadian, M. A.

1998-01-01

18

New optical design of adaptive optics system at Lick Observatory  

SciTech Connect

We present the requirements, design, and resulting new layout for the laser guide star/natural guide star (LGUNGS) adaptive optics (AO) system on the 3-meter Shane telescope at Lick Observatory. This layout transforms our engineering prototype into a stable, reliable, maintainable end-user-oriented system, suitable for use as a facility instrument. Important new features include convenient calibration using proven phase-shifting diffraction interferometer or phase-diversity techniques'; a new wavefront sensor design that uses the science path's f/28.5 parabola; improved field stop mechanics for better Rayleigh- scatter rejection in LGS mode and better guide-star selection NGS mode; high-sensitivity, wide-field acquisition camera; and significant improvements in adjustment motorization and optomechanical stability. Keywords: Adaptive optics, Lick Observatory, laser guide-star, natural guide-star, phase-shifting diffraction interferometer, phase-diversity, optical design, Bravais lens

Bauman, B J; Freeze, G J; Gavel, D T; Keahi, K K; Kuklo, T C; Lopes, S K; Newman, M J; Olivier, S S; Waltjen, K E

1999-07-22

19

Campus Technology Innovators Awards 2011: Technology All-Stars  

ERIC Educational Resources Information Center

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…

Lloyd, Meg; Raths, David

2011-01-01

20

The Twenty-five Year Lick Planet Search  

NASA Astrophysics Data System (ADS)

The Lick Planet Search program began in 1987 when the first spectrum of ? Ceti was taken with an iodine cell and the Hamilton Spectrograph. Upgrades to the instrument improved the Doppler precision from about 10 m s-1 in 1992 to about 3 m s-1 in 1995. The project detected dozens of exoplanets with orbital periods ranging from a few days to several years. The Lick survey identified the first planet in an eccentric orbit (70 Virginis) and the first multi-planet system around a normal main sequence star (Upsilon Andromedae). These discoveries advanced our understanding of planet formation and orbital migration. Data from this project helped to quantify a correlation between host star metallicity and the occurrence rate of gas giant planets. The program also served as a test bed for innovation with testing of a tip-tilt system at the Coudé focus and fiber scrambler designs to stabilize illumination of the spectrometer optics. The Lick Planet Search with the Hamilton Spectrograph effectively ended when a heater malfunction compromised the integrity of the iodine cell. Here, we present more than 14,000 velocities for 386 stars that were surveyed between 1987 and 2011. Based on observations obtained at the Lick Observatory, which is operated by the University of California.

Fischer, Debra A.; Marcy, Geoffrey W.; Spronck, Julien F. P.

2014-01-01

21

THE LICK-CARNEGIE EXOPLANET SURVEY: A SATURN-MASS PLANET IN THE HABITABLE ZONE OF THE NEARBY M4V STAR HIP 57050  

SciTech Connect

Precision radial velocities (RV) from Keck/HIRES reveal a Saturn-mass planet orbiting the nearby M4V star HIP 57050. The planet has a minimum mass of Msin i {approx} 0.3 M{sub J}, an orbital period of 41.4 days, and an orbital eccentricity of 0.31. V-band photometry reveals a clear stellar rotation signature of the host star with a period of 98 days, well separated from the period of the RV variations and reinforcing a Keplerian origin for the observed velocity variations. The orbital period of this planet corresponds to an orbit in the habitable zone of HIP 57050, with an expected planetary temperature of {approx}230 K. The star has a metallicity of [Fe/H] = 0.32 {+-} 0.06 dex, of order twice solar and among the highest metallicity stars in the immediate solar neighborhood. This newly discovered planet provides further support that the well-known planet-metallicity correlation for F, G, and K stars also extends down into the M-dwarf regime. The a priori geometric probability for transits of this planet is only about 1%. However, the expected eclipse depth is {approx}7%, considerably larger than that yet observed for any transiting planet. Though long on the odds, such a transit is worth pursuing as it would allow for high quality studies of the atmosphere via transmission spectroscopy with Hubble Space Telescope. At the expected planetary effective temperature, the atmosphere may contain water clouds.

Haghighipour, Nader [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States); Vogt, Steven S.; Rivera, Eugenio J.; Laughlin, Greg; Meschiari, Stefano [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Paul Butler, R. [Department of Terrestrial Magnetism, Carnegie Institute of Washington, Washington, DC 20015 (United States); Henry, Gregory W. [Center of Excellence in Information Systems, Tennessee State University, Nashville, TN 37209 (United States)

2010-05-20

22

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.

23

Graduate Astronomy Education in the Early Days of Lick Observatory.  

ERIC Educational Resources Information Center

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)

Osterbrock, Donald E.

1980-01-01

24

[Is being licked by dogs not dirty?].  

PubMed

Being licked by pet dogs is frequently a common advice in articles for the uninitiated. An overview is given about the special antibacterial and wound healing properties of human and canine saliva. New developments in the human area are presumably assigned to dog saliva. Because of the presence of a quite different mouth flora including various potential zoonotic pathogens, it is strictly not advised to let dogs lick the wounds or face of the human. PMID:23025205

Overgaauw, Paul; van Knapen, Frans

2012-09-01

25

Decreased Firing of Striatal Neurons Related to Licking During Acquisition and Overtraining of a Licking Task  

PubMed Central

Neurons that fire in relation to licking, in the ventral part of the dorsolateral striatum (DLS), were studied during acquisition and performance of a licking task in rats for 14 sessions (2 hours/day). Task learning was indicated by fewer errors of omission of licking and improved movement efficiency (i.e., shorter lick duration) over sessions. Number of licks did not change over sessions. Overtraining did not result in habit formation, as indicated by similar reduction of licking responses following devaluation by satiety in both early and late sessions. Twenty-nine lick neurons recorded and tracked over sessions exhibited a significant linear decrease in average firing rate across all neurons over sessions, correlating with concurrent declines in lick duration. Individually, most neurons (86%) exhibited decreased firing rates, while a small proportion (14%) exhibited increased firing rates, during lick movements that were matched over sessions. Reward manipulations did not alter firing patterns over sessions. Aside from the absence of habit formation, striatal processing during unconditioned movements (i.e., licking) was characterized by high activity of movement-related neurons during early performance and decreased activity of the same neurons during overtraining, similar to our previous report of head movement neurons during acquired, skilled, instrumental head movements that ultimately became habitual (Tang et al., 2007). Decreased activity in DLS neurons may reflect a common neural mechanism underlying improvement in movement efficiency with overtraining. Nonetheless, the decreased striatal firing in relation to a movement that did not become habitual demonstrates that not all DLS changes reflect habit formation.

Tang, Chris C.; Root, David H.; Duke, Dawn C.; Zhu, Yun; Teixeria, Kate; Ma, Sisi; Barker, David J.; West, Mark O.

2011-01-01

26

Making star teams out of star players.  

PubMed

Top talent is an invaluable asset: In highly specialized or creative work, for instance, "A" players are likely to be six times as productive as "B" players. So when your company has a crucial strategic project, why not multiply all that firepower and have a team of your best performers tackle it? Yet many companies hesitate to do this, believing that all-star teams don't work: Big egos will get in the way. The stars won't be able to work with one another. They'll drive the team Leader crazy. Mankins, Bird, and Root of Bain & Company believe it's time to set aside that thinking. They have seen all-star teams do extraordinary work. But there is a right way and a wrong way to organize them. Before you can even begin to assemble such a team, you need to have the right talent management practices, so you hire and develop the best people and know what they're capable of. You have to give the team appropriate incentives and leaders and support staffers who are stars in their own right. And projects that are ill-defined or small scale are not for all-star teams. Use them only for critical missions, and make sure their objectives are clear. Even with the right setup, things can still go wrong. The wise executive will take steps to manage egos, prune non-team-players, and prevent average coworkers from feeling completely undervalued. She will also invest a lot of time in choosing the right team Leader and will ask members for lots of feedback to monitor how that leader is doing. PMID:23390743

Mankins, Michael; Bird, Alan; Root, James

2013-01-01

27

ECAC Announces 2009 Division III New England Women's Soccer All-Stars  

Microsoft Academic Search

This year's first team forward selections put up impressive numbers, with two players eclipsing the 60-point plateau. Lesley's Jodi Fralick led the charge with 32 goals and four assists for 68 points. The senior led her squad to an undefeated conference record, and an ECAC Championship berth. MCLA's Jess Tietgans was not far behind, tallying 30 goals and four assists

Lindsay DeStefano

2009-01-01

28

Adaptive Optics System Design and Operation at Lick Observatory  

NASA Astrophysics Data System (ADS)

An adaptive optics system developed for the 40 inch Nickel and 120 inch Shane telescopes at Lick Observatory is described. The adaptive optics system design is based on a 69 actuator continuous-surface deformable mirror and a Hartmann wavefront sensor equipped with a commercial intensified CCD fast-framing camera. The system has been tested at the Cassegrain focus of the 40 inch Nickel telescope where the subaperture diameter is 12 cm. The subaperture slope and mirror control calculations are performed on a four processor single board computer controlled by a Unix workstation. This configuration is capable of up to 1 KHz frame rates. The optical configuration of the system and its interface to the telescope is described. Details of the control system design, operation, and user interface are given. Initial test results emphasizing control system operations of this adaptive optics system using natural reference stars on the 40 inch Nickel telescope are presented. The initial test results are compared to predictions from analyses and simulations. Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Olivier, S. S.; Max, C. E.; Avicola, K.; Bissinger, H. D.; Brase, J. M.; Friedman, H. W.; Gavel, D. T.; Salmon, J. T.; Waltjen, K. E.

1993-12-01

29

Development of a Flood-Warning System and Flood-Inundation Mapping in Licking County, Ohio.  

National Technical Information Service (NTIS)

Digital flood-inundation maps for selected reaches of South Fork Licking River, Raccoon Creek, North Fork Licking River, and the Licking River in Licking County, Ohio, were created by the U.S. Geological Survey (USGS), in cooperation with the Ohio Departm...

C. J. Ostheimer

2012-01-01

30

CCD Data Acquisition Systems at Lick and Keck Observatories.  

National Technical Information Service (NTIS)

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 consider...

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

1992-01-01

31

Fiber Scrambling for High-Resolution Spectrographs. I. Lick Observatory  

NASA Astrophysics Data System (ADS)

In this article, we report all results obtained with a fiber scrambler on the Hamilton spectrograph at Lick Observatory. We demonstrate an improvement in the stability of the instrumental profile using this fiber scrambler. Additionally, we present data obtained with a double scrambler that further improves the stability of the instrument by a factor 2. These results show that errors related to the coupling between the telescope and the spectrograph are the dominant source of instrumental profile variability at Lick Observatory. In particular, we show a strong correlation between instrumental profile variations and hour angle, most likely due to pointing-dependent illumination of the spectrograph optics.

Spronck, Julien F. P.; Fischer, Debra A.; Kaplan, Zachary A.; Schwab, Christian; Szymkowiak, Andrew

2013-05-01

32

77 FR 55796 - Sand Lick Fork Watershed Restoration Project; Daniel Boone National Forest, KY  

Federal Register 2010, 2011, 2012, 2013

...Forest Service Sand Lick Fork Watershed Restoration Project; Daniel Boone National Forest...SUMMARY: The Sand Lick Fork Watershed Restoration Project involves activities to improve...wells, removing abandoned flow lines, restoration of stream channels and associated...

2012-09-11

33

Science, religion, and the fossils at Big Bone Lick  

Microsoft Academic Search

In 1739, Baron de Longueiul, a pioneer explorer of the Ohio River Valley, discovered a spectacular phenomenon: in an area surrounding a salt spring in northern Kentucky, the physical remains of extinct Pleistocene mammals protruded from the ground. The site soon became known as Big Bone Lick and attracted the attention of both American and European scientists. The idea of

Thomas D. Matijasic

1987-01-01

34

75 FR 9530 - FM TABLE OF ALLOTMENTS, French Lick, Indiana, and Irvington, Kentucky.  

Federal Register 2010, 2011, 2012, 2013

...RM-11412] FM TABLE OF ALLOTMENTS, French Lick, Indiana, and Irvington, Kentucky...modifies the license of Station WFLQ(FM), French Lick, Indiana, to specify operation...the licensee of Station WFLQ(FM), French Lick, Indiana, to show cause why...

2010-03-03

35

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

SciTech Connect

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.

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

36

Effects of shifts in sucrose and saccharine concentrations on licking behavior in the rat  

Microsoft Academic Search

4 experiments studied the effects of shifts in concentration of liquid reinforcers on licking behavior of 92 adult rats. Depressed performance (relative to control groups) accompanied a shift of 32-4% sucrose solutions, but no shift in saccharine concentrations. Various bases for this disparity were investigated, including type and levels of deprivation. Depression in licking results from shifts in sucrose concentration,

John R. Vogel; Peter J. Mikulka; Norman E. Spear

1968-01-01

37

Stars  

NASA Astrophysics Data System (ADS)

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.

Capelato, Hugo Vicente

1999-01-01

38

Archaeological Reconnaissance Survey and Salvage Excavation in the Salt Lick Recreation Area.  

National Technical Information Service (NTIS)

An archaeological reconnaissance and survey of the Salt Lick Recreational Area, a U.S. Army Corps of Engineers project adjacent to the Cordell Hull Reservoir/Cumberland River in Jackson County, (north central) Tennessee, has documented nine prehistoric si...

D. B. Ball

1979-01-01

39

Feeding Urea Through Surface Licking in the Growing Buffalo (Bos bubalis) Calves  

Microsoft Academic Search

Kaur, S. and Kakkar, V.K. 1995. Feeding urea through surface licking in the growing buffalo (Bos bubalis) calves. J. Appl. Anim Res., 8: 129–136A new device, called portable feeder with revolving surface, for the gradual intake of urea-molasses mixture, was compared with urea-molasses-mineral block (uromin-lick) and urea containing concentrate mixture in Murrah buffalo calves. The different groups of calves were

Sukhvir Kaur; V. K. Kakkar

1995-01-01

40

Is rat-dam licking behavior regulated by pups’ preputial gland secretion?  

Microsoft Academic Search

Anogenital licking (AGL) is crucial for pups’ survival; nonlicked pups cannot defecate, and they die. A cotton swab impregnated\\u000a with anogenital smears was investigated and the odorous testbox containing it was sniffed by virgins and adult males as well\\u000a as by dams. When the pups’ heads were rubbed with anogenital smears and the perineal area cleaned, the dams licked only

I. Brouette-lahlou; E. Vernet-Maury; J. Chanel

1991-01-01

41

Head Rubbing and Licking Reinforce Social Bonds in a Group of Captive African Lions, Panthera leo  

PubMed Central

Many social animals have a species-specific repertoire of affiliative behaviours that characterise individualised relationships within a group. To date, however, quantitative studies on intragroup affiliative behaviours in social carnivores have been limited. Here, we investigated the social functions of the two most commonly observed affiliative behaviours in captive African lions (Panthera leo): head rubbing and licking. We conducted behavioural observations on a captive group of lions composed of 7 males and 14 females, and tested hypotheses regarding three social functions: tension reduction, social bonding, and social status expression. Disproportionately frequent male–male and female-to-male head rubbing was observed, while more than 95% of all licking interactions occurred in female–female dyads. In accordance with the social bond hypothesis, and in disagreement with the social status expression hypothesis, both head rubbing and licking interactions were reciprocal. After controlling for spatial association, the dyadic frequency of head rubbing was negatively correlated with age difference while licking was positively correlated with relatedness. Group reunion after daily separation did not affect the frequencies of the affiliative behaviours, which was in disagreement with the predictions from the tension reduction hypothesis. These results support the social bond hypothesis for the functions of head rubbing and licking. Different patterns of affiliative behaviour between the sexes may reflect differences in the relationship quality in each sex or the differential predisposition to licking due to its original function in offspring care.

Matoba, Tomoyuki; Kutsukake, Nobuyuki; Hasegawa, Toshikazu

2013-01-01

42

Licking-induced Synchrony in the Taste-Reward Circuit Improves Cue Discrimination during Learning  

PubMed Central

Animals learn which foods to ingest and which to avoid. Despite many studies, the electrophysiological correlates underlying this behavior at the gustatory-reward circuit level remain poorly understood. For this reason, we measured the simultaneous electrical activity of neuronal ensembles in the orbitofrontal cortex, insular cortex, amygdala and nucleus accumbens while rats licked for taste-cues and learned to perform a taste-discrimination Go/No-Go task. This study revealed that rhythmic licking entrains the activity in all these brain regions, suggesting that animal's licking acts as an “internal clock signal” against which single spikes can be synchronized. That is, as animals learned a Go/No-Go task there were increases in the number of licking coherent neurons as well as synchronous spiking between neuron pairs from different brain regions. Moreover, a subpopulation of gustatory cue-selective neurons that fired in synchrony with licking exhibited a greater ability to discriminate among tastants than nonsynchronized neurons. This effect was seen in all four recorded areas and increased markedly after learning, particularly after the cue was delivered and before the animals made a movement to obtain an appetitive or aversive tastant. Overall, these results show that throughout a large segment of the taste-reward circuit, appetitive and aversive associative learning improves spike-timing precision, suggesting that proficiency in solving a taste discrimination Go/No-Go task requires licking-induced neural ensemble synchronous activity.

Gutierrez, Ranier; Simon, Sidney A.; Nicolelis, Miguel A. L.

2010-01-01

43

Photometric light curves for ten rapidly rotating stars in Alpha Persei, the Pleiades, and the field  

NASA Technical Reports Server (NTRS)

We present the results from a photometric monitoring program of ten rapidly rotating stars observed during 1991 using the FLWO 48-in. telescope. Brightness variations for an additional six cluster stars observed with the Lick 40-in. telescope are also given. The periods and light curves for seven Alpha Persei members, two Pleiades members, and one naked T Tauri field star are reported.

Prosser, Charles F.; Schild, Rudolph E.; Stauffer, John R.; Jones, Burton F.

1993-01-01

44

A USB 2.0 computer interface for the UCO/Lick CCD cameras  

NASA Astrophysics Data System (ADS)

The new UCO/Lick Observatory CCD camera uses a 200 MHz fiber optic cable to transmit image data and an RS232 serial line for low speed bidirectional command and control. Increasingly RS232 is a legacy interface supported on fewer computers. The fiber optic cable requires either a custom interface board that is plugged into the mainboard of the image acquisition computer to accept the fiber directly or an interface converter that translates the fiber data onto a widely used standard interface. We present here a simple USB 2.0 interface for the UCO/Lick camera. A single USB cable connects to the image acquisition computer and the camera's RS232 serial and fiber optic cables plug into the USB interface. Since most computers now support USB 2.0 the Lick interface makes it possible to use the camera on essentially any modern computer that has the supporting software. No hardware modifications or additions to the computer are needed. The necessary device driver software has been written for the Linux operating system which is now widely used at Lick Observatory. The complete data acquisition software for the Lick CCD camera is running on a variety of PC style computers as well as an HP laptop.

Wei, Mingzhi; Stover, Richard J.

2004-09-01

45

Taste coding in the nucleus of the solitary tract of the awake, freely licking rat.  

PubMed

It is becoming increasingly clear that the brain processes sensory stimuli differently according to whether they are passively or actively acquired, and these differences can be seen early in the sensory pathway. In the nucleus of the solitary tract (NTS), the first relay in the central gustatory neuraxis, a rich variety of sensory inputs generated by active licking converge. Here, we show that taste responses in the NTS reflect these interactions. Experiments consisted of recordings of taste-related activity in the NTS of awake rats as they freely licked exemplars of the five basic taste qualities (sweet, sour, salty, bitter, umami). Nearly all taste-responsive cells were broadly tuned across taste qualities. A subset responded to taste with long latencies (>1.0 s), suggesting the activation of extraoral chemoreceptors. Analyses of the temporal characteristics of taste responses showed that spike timing conveyed significantly more information than spike count alone in almost one-half of NTS cells, as in anesthetized rats, but with less information per cell. In addition to taste-responsive cells, the NTS contains cells that synchronize with licks. Since the lick pattern per se can convey information, these cells may collaborate with taste-responsive cells to identify taste quality. Other cells become silent during licking. These latter "antilick" cells show a surge in firing rate predicting the beginning and signaling the end of a lick bout. Collectively, the data reveal a complex array of cell types in the NTS, only a portion of which include taste-responsive cells, which work together to acquire sensory information. PMID:22855799

Roussin, Andre T; D'Agostino, Alexandra E; Fooden, Andrew M; Victor, Jonathan D; Di Lorenzo, Patricia M

2012-08-01

46

Keepers of the double stars  

NASA Astrophysics Data System (ADS)

Astronomers have long tracked double stars in efforts to find those that are gravitationally-bound binaries and then to determine their orbits. Early catalogues by the Herschels, Struves, and others began with their own discoveries. In 1906 court reporter and amateur astronomer Sherburne Wesley Burnham published a massive double star catalogue containing data from many observers on more than 13,000 systems. Lick Observatory astronomer Robert Grant Aitken produced a much larger catalogue in 1932 and coordinated with Robert Innes of Johannesburg, who catalogued the southern systems. Aitken maintained and expanded Burnham's records of observations on handwritten file cards, and eventually turned them over to the Lick Observatory, where astrometrist Hamilton Jeffers further expanded the collection and put all the observations on punched cards. With the aid of Frances M. "Rete" Greeby he made two catalogues: an Index Catalogue with basic data about each star, and a complete catalogue of observations, with one observation per punched card. He enlisted Willem van den Bos of Johannesburg to add southern stars, and together they published the Index Catalogue of Visual Double Stars, 1961.0. As Jeffers approached retirement he became greatly concerned about the disposition of the catalogues. He wanted to be replaced by another "double star man," but Lick Director Albert E. Whitford had the new 120-inch reflector, the world's second largest telescope, and he wanted to pursue modern astrophysics instead. Jeffers was vociferously opposed to turning over the card files to another institution, and especially against their coming under the control of Kaj Strand of the United States Naval Observatory. In the end the USNO got the files and has maintained the records ever since, first under Charles Worley, and, since 1997, under Brian Mason. Now called the Washington Double Star Catalog (WDS), it is completely online and currently contains more than 1,200,000 measures of more than 125,000 star systems.

Tenn, Joseph S.

2013-03-01

47

THE LICK-CARNEGIE SURVEY: FOUR NEW EXOPLANET CANDIDATES  

SciTech Connect

We present new precise HIRES radial velocity (RV) data sets of five nearby stars obtained at Keck Observatory. HD 31253, HD 218566, HD 177830, HD 99492, and HD 74156 are host stars of spectral classes F through K and show RV variations consistent with new or additional planetary companions in Keplerian motion. The orbital parameters of the candidate planets in the five planetary systems span minimum masses of M sin i = 27.43 M{sub +} to 8.28 M{sub J}, periods of 17.05-4696.95 days and eccentricities ranging from circular to extremely eccentric (e {approx} 0.63). The fifth star, HD 74156, was known to have both a 52 day and a 2500 day planet, and was claimed to also harbor a third planet at 336 days, in apparent support of the 'Packed Planetary System' hypothesis. Our greatly expanded data set for HD 74156 provides strong confirmation of both the 52 day and 2500 day planets, but strongly contradicts the existence of a 336 day planet, and offers no significant evidence for any other planets in the system.

Meschiari, Stefano; Laughlin, Gregory; Vogt, Steven S.; Rivera, Eugenio J. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Butler, R. Paul [Department of Terrestrial Magnetism, Carnegie Institute of Washington, Washington, DC 20015 (United States); Haghighipour, Nader [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States); Jalowiczor, Peter

2011-02-01

48

Paleontologic investigations at Big Bone Lick State Park, Kentucky: A preliminary report  

USGS Publications Warehouse

The Big Bone Lick area in Kentucky, the first widely known collecting locality for vertebrate fossils in North America, is being investigated for further faunal and geologic evidence. Mammal bones, ranging in age from Wisconsin (Tazewell?) to Recent, were recovered in 1962 from four different faunal zones in two terrace fills.

Schultz, C. B.; Tanner, L. G.; Whitmore, Jr. , F. C.; Ray, L. L.; Crawford, E. C.

1963-01-01

49

A USB 2.0 computer interface for the UCO\\/Lick CCD cameras  

Microsoft Academic Search

The new UCO\\/Lick Observatory CCD camera uses a 200 MHz fiber optic cable to transmit image data and an RS232 serial line for low speed bidirectional command and control. Increasingly RS232 is a legacy interface supported on fewer computers. The fiber optic cable requires either a custom interface board that is plugged into the mainboard of the image acquisition computer

Mingzhi Wei; Richard J. Stover

2004-01-01

50

The Globular Cluster System of NGC 5128: Combining Broad-Band Color and Lick Index Analysis  

NASA Astrophysics Data System (ADS)

We present a mathematically advanced method for the determination of age and metallicity of individual members of globular cluster systems (CGSs) in galaxies by combining all the information inherent in broad-band color and Lick index measurements, and we present first results of our analysis of the GCS of the early type galaxy NGC 5128.

Lilly, Thomas; Fritze-v. Alvensleben, Uta; de Grijs, Richard

51

Licking for taste solutions by potassium-deprived rats: specificity and mechanisms.  

PubMed

There has been little work on the specificity and mechanisms underlying the appetite of potassium (K(+)) deprived rats, and there are conflicting results. To investigate the contribution of oral factors to changes in intake induced by K(+) deficiency, we conducted two experiments using 20-s "brief access" tests. In Experiment 1, K(+)-deprived rats licked less for water than did replete rats. After adjusting for this difference, K(+)-deprived rats exhibited increased licking for 100 mM CaCl(2), 100 mM MgCl(2), and 100 mM FeCl(2) compared with K(+)-replete rats. In Experiment 2, which used larger rats, the K(+)-deprived and replete groups licked equally for water, 500 mM Na.Gluconate, 350 mM KCl, 500 mM KHCO(3), and 1 mM quinine.HCl, but the K(+)-deprived rats licked more for 500 mM KCl, 500 mM CsCl, and 500 mM NaCl than did the replete rats. Licking was unaffected by addition to NaCl of 200 muM amiloride, an epithelial Na(+) channel (ENaC) blocker, or 100 muM ruthenium red, a vanilloid receptor 1 (VR-1) antagonist, or by addition to KCl of 50 muM 4-aminopyridine, a K(+) channel blocker. These findings suggest that K(+)-deprivation produces a non-specific appetite that is guided by oral factors. We found no evidence that this response was mediated by ENaC, VR-1, or K(+) channels in taste receptor cells. PMID:18255104

Guenthner, C J; McCaughey, S A; Tordoff, M G; Baird, J P

2008-03-18

52

The Eclipse Expeditions of the Lick Observatory and the Beginnings of Astrophysics in the United States  

NASA Astrophysics Data System (ADS)

During the years 1898 to 1932, Lick Observatory organized a remarkable series of 17 solar eclipse expeditions, all the more remarkable because Lick astronomers evidenced no enduring interest in solar physics. The science of these expeditions involved three issues of major significance during the development of astrophysics during the first three decades of the twentieth century: (1) testing of General Relativity; (2) non-LTE in extended atmospheres and gaseous nebulae; (3) role of magnetic fields in the sun. The expeditions made major contributions to the first two topics. Even though W.W. Campbell, the director of Lick, had extensive contact with George Ellery Hale, who had measured the magnetic fields of sunspots at Mt. Wilson, Lick astronomers missed the clues concerning the importance of magnetic fields in the corona. Campbell's measurement of the deflection of starlight at the eclipse of 1922 was his major achievement of the many eclipse expeditions. He had approached that test of General Relativity with considerable distrust of Einstein's theory and considered Eddington's 1919 results to be suspect. It is to Campbell's great credit that the results published jointly with Trumpler confirmed the predictions of Einstein with higher precision than Eddington had achieved. Donald Menzel joined the staff of Lick Observatory in 1926 as their first astrophysicist. Osterbrock describes him as a ``stranger in a strange land.'' He was given the analysis of the eclipse flash spectra. This work, published in 1931, represents the beginning of the astrophysical study of chromospheres and laid the foundation for the quantitative analysis of extended atmospheres and gaseous nebula.

Malville, J. McKim; Pearson, John

2012-09-01

53

APF-The Lick Observatory Automated Planet Finder  

NASA Astrophysics Data System (ADS)

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.

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

54

ShaneAO: an enhanced adaptive optics and IR imaging system for the Lick Observatory 3-meter telescope  

NASA Astrophysics Data System (ADS)

The Lick Observatory 3-meter telescope has a history of serving as a testbed for innovative adaptive optics techniques. In 1996, it became one of the first astronomical observatories to employ laser guide star (LGS) adaptive optics as a facility instrument available to the astronomy community. Work on a second-generation LGS adaptive optics system, ShaneAO, is well underway, with plans to deploy on telescope in 2013. In this paper we discuss key design features and implementation plans for the ShaneAO adaptive optics system. Once again, the Shane 3-m will host a number of new techniques and technologies vital to the development of future adaptive optics systems on larger telescopes. Included is a woofer-tweeter based wavefront correction system incorporating a voice-coil actuated, low spatial and temporal bandwidth, high stroke deformable mirror in conjunction with a high order, high bandwidth MEMs deformable mirror. The existing dye laser, in operation since 1996, will be replaced with a fiber laser recently developed at Lawrence Livermore National Laboratories. The system will also incorporate a high-sensitivity, high bandwidth wavefront sensor camera. Enhanced IR performance will be achieved by replacing the existing PICNIC infrared array with an Hawaii 2RG. The updated ShaneAO system will provide opportunities to test predictive control algorithms for adaptive optics. Capabilities for astronomical spectroscopy, polarimetry, and visible-light adaptive optical astronomy will be supported.

Kupke, Renate; Gavel, Donald; Roskosi, Constance; Cabak, Gerald; Cowley, David; Dillon, Daren; Gates, Elinor L.; McGurk, Rosalie; Norton, Andrew; Peck, Michael; Ratliff, Christopher; Reinig, Marco

2012-07-01

55

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

PubMed

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. PMID:11539351

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

1996-06-25

56

Licking behaviour and environmental contamination arising from pour-on ivermectin for cattle  

Microsoft Academic Search

Pour-on formulations of endectocides are extensively used to treat and control systemic parasitic diseases in cattle, worldwide. The purpose of the present study was to investigate the influence of the natural licking behaviour of cattle on the plasma and faecal disposition of topically administered ivermectin. Twelve Holstein cattle were given one single intravenous (i.v.) (200 ?g\\/kg) and topical (500 ?g\\/kg)

Ce Line M. Laffont; Michel Alvinerie; Alain Bousquet-Mélou; Pierre-Louis Toutain

2001-01-01

57

Hippocampal neuronal responses during signaled licking of gustatory stimuli in different contexts.  

PubMed

Neuroanatomical studies suggest that hippocampal formation (HF) receives information from all sensory modalities including taste via the parahippocampal cortices. To date, however, no neurophysiological study has reported that HF neurons encode taste information. In the present study, we recorded CA1 HF neurons from freely behaving rats during performance of a visually-guided licking task in two different triangular chambers. When a cue lamp came on, the rats were required to press a bar to trigger a tube to protrude into the chambers for 3 s. During this period, the rats could lick one of six sapid solutions: [0.1M NaCl (salty), 0.3M sucrose (sweet), 0.01 M citric acid (sour), 0.0001 M quinine HCl (bitter), 0.01 M monosodium L-glutamate (MSG, umami), and a mixture of MSG and 0.001 M disodium-5'-inosinate (IMP) (MSG+IMP)], and distilled water. Of a total 285 pyramidal and interneurons, the activity of 173 was correlated with at least one of the events in the task-illumination of cue lamps, bar pressing, or licking the solution. Of these, 137 neurons responded during licking, and responses of 62 of these cells were greater to sapid solutions than to water (taste neurons). Multivariate analyses of the taste neurons suggested that, in the HF, taste quality might be encoded based on hedonic value. Furthermore, the activity of most taste neurons was chamber-specific. These results implicate the HF in guiding appetitive behaviors such as conditioned place preference. PMID:20087892

Ho, Anh Son; Hori, Etsuro; Nguyen, Phuong Hong Thi; Urakawa, Susumu; Kondoh, Takashi; Torii, Kunio; Ono, Taketoshi; Nishijo, Hisao

2011-05-01

58

Take Me Out to the Ballgame: How the East-west Classic All-Star Game Affected the African American Community of the Midwest  

Microsoft Academic Search

Thirty years ago only baseball aficionados and some African Americans were very familiar with the existence of the all-black Negro League baseball teams. Since then, the general public has been made more and more aware of these teams and their histories. Surely, though, these teams had more importance for the black community than to simply represent a \\

Trisha L. Bucholz

2004-01-01

59

A robust method for the analysis of integrated spectra from globular clusters using Lick indices  

NASA Astrophysics Data System (ADS)

We define a method for the analysis of the integrated spectra of extragalactic globular clusters that provides more reliable measures of the age, metallicity and ?-element abundance ratio than have so far been achieved. The method involves the simultaneous fitting of up to 25 Lick indices in a ?2 fitting technique that maximizes the use of the available data. Here we compare three sets of single stellar population (SSP) models of Lick indices to the high signal-to-noise, integrated spectra of 20 Galactic globular clusters. The ages, [Fe/H] and ?-element abundance ratios derived from the SSP models are compared with the results of resolved stellar population studies from the literature. We find good consistency with the published values, with an agreement of better than 0.1 dex in all three derived parameters. The technique allows the identification of abundance ratio anomalies, such as the known nitrogen overabundance in Galactic globular clusters, and the presence of anomalous horizontal branch morphologies. It also minimizes the impact on the derived parameters of imperfect calibration to the Lick system, and reduction errors in general. The method defined in this paper is therefore robust with respect to many of the difficulties that plague the application of SSP models in general. Consequently, it is well suited to the study of extragalactic globular cluster systems.

Proctor, Robert N.; Forbes, Duncan A.; Beasley, Michael A.

2004-12-01

60

Online correction of licking-induced brain motion during two-photon imaging with a tunable lens.  

PubMed

Two-photon calcium imaging in awake, head-fixed animals enables the measurement of neuronal activity during behaviour. Often, licking for the retrieval of water reward is used as a measurable report of the animal's decision during reward-driven behaviour. However, licking behaviour can induce severe motion artifacts that interfere with two-photon imaging of cellular activity. Here, we describe a simple method for the online correction of licking-induced focus shifts for two-photon calcium imaging of neocortical neurons in the head-fixed mouse. We found that licking causes a stereotyped drop of neocortical tissue, shifting neurons up to 20 ?m out of focus. Based on the measurement of licking with a piezo film sensor, we developed a feedback model, which provides a corrective signal for fast optical focus adjustments with an electrically tunable lens. Using online correction with this feedback model, we demonstrate a reduction of licking-related focus changes below 3 ?m, minimizing motion artifact contamination of cellular calcium signals. Focus correction with a tunable lens is a simple and effective method to improve the ability to monitor neuronal activity during reward-based behaviour. PMID:23940380

Chen, Jerry L; Pfäffli, Oliver A; Voigt, Fabian F; Margolis, David J; Helmchen, Fritjof

2013-10-01

61

The effect of self-licking behavior on pharmacokinetics of eprinomectin and clinical efficacy against Psoroptes cuniculi in topically administered rabbits.  

PubMed

Ear mange mite Psoroptes cuniculi, one of the predominant parasites in rabbits, can cause considerable weight loss, low favorable fee conversion rates, and meningitis. The present experiment was to investigate the difference of plasma disposition and the variation of clinical efficacy under the effect of animal self-licking behavior in topically administered rabbits. Ten rabbits for pharmacokinetic study in two groups (the self-licking and the nonlicking)were topically administered with 1 mg kg(-1) of eprinomectin. In the self-licking group, rabbits were allowed to self-lick freely, while, to prevent self-licking, each animal in the non-licking group was fitted with a pet collar. Compared to the non-licking group, self-licking behavior contributed to an extremely significant shorter half-life of absorption (14.85+/-2.79 h in licking group vs.29.44+/-7.81 h in non-licking group, p<0.01) and an extremely significant higher C(max) value for eprinomectin (21.95+/-5.36 h in licking group vs. 6.98+/-0.72 ng ml(-1) in non-licking group, p<0.01) in plasma disposition. An extremely significantly shorter mean residence time (50.72+/-3.45 h) in self-licking group was also determined compared with the value obtained in non-licking group (106.66+/-7.39 h; p<0.01). Clinical efficacy study of eprinomectin was examined in rabbits naturally infested with P. cuniculi which were randomly allocated in three groups: the self-licking, the non-licking, and control groups. All rabbits in the self-licking and the non-licking groups were treated with topical eprinomectin at a single dose of 2 mg kg(-1) (day 0). Topical eprinomection led to a complete parasitological recovery in both treated groups on day 14 and remained free of live mites and clinical lesions from day 21 to the end of the study period (day 35). PMID:20069313

Wen, Huiqiang; Pan, Baoliang; Wang, Fangfei; Yang, Zhenzhong; Wang, Zhujun; Liu, Shuai; Wang, Ming

2010-02-01

62

Hamilton Jeffers and the Double Star Catalogues  

NASA Astrophysics Data System (ADS)

Astronomers have long tracked double stars in efforts to find those that are gravitationally-bound binaries and then to determine their orbits. Court reporter and amateur astronomer Shelburne Wesley Burnham (1838-1921) published a massive double star catalogue containing more than 13,000 systems in 1906. The next keeper of the double stars was Lick Observatory astronomer Robert Grant Aitken (1864-1951), who produced a much larger catalogue in 1932. Aitken maintained and expanded Burnham’s records of observations on handwritten file cards, eventually turning them over to Lick Observatory astrometrist Hamilton Moore Jeffers (1893-1976). Jeffers further expanded the collection and put all the observations on punched cards. With the aid of Frances M. "Rete" Greeby (1921-2002), he made two catalogues: an Index Catalogue with basic data about each star, and a complete catalogue of observations, with one observation per punched card. He enlisted Willem van den Bos of Johannesburg to add southern stars, and they published the Index Catalogue of Visual Double Stars, 1961.0. As Jeffers approached retirement he became greatly concerned about the disposition of the catalogues. He wanted to be replaced by another "double star man," but Lick Director Albert E. Whitford (1905-2002) had the new 120-inch reflector, the world’s second largest telescope, and he wanted to pursue modern astrophysics instead. Jeffers was vociferously opposed to turning over the card files to another institution, and especially against their coming under the control of Kaj Strand of the U.S. Naval Observatory. In the end the USNO got the files and has maintained the records ever since, first under Charles Worley (1935-1997), and, since 1997, under Brian Mason. Now called the Washington Double Star Catalog (WDS), it is completely online and currently contains more than 1,000,000 measures of more than 100,000 pairs.

Tenn, Joseph S.

2013-01-01

63

Early Photographs of the Distant Sierra Nevada Mountains Taken from Lick Observatory  

NASA Astrophysics Data System (ADS)

During World War I, a group of American chemists, physicists and astronomers developed processes for greatly increasing the infrared sensitivity of photographic emulsions, for long-distance reconnaissance from airplanes or the ground. After the war Lick Observatory astronomers, beginning with C.D. Shane and Mary Lea Heger, used long-focal-length astronomical cameras and these hypersensitization methods to photograph the distant Sierra Nevada range, including Yosemite Valley and Half Dome, nearly one hundred miles away across the Central Valley of California. These pictures, widely exhibited and admired, strengthened links between astronomers, the Eastman Kodak Company and the public.

Osterbrock, Donald E.

2006-12-01

64

Frequency of maternal licking and grooming correlates negatively with vulnerability to cocaine and alcohol use in rats  

PubMed Central

Because licking and grooming behavior of dams with pups can influence some behaviors of pups when they are adults, we tested if licking and grooming scores in a maternal separation protocol correlated with cocaine or ethanol self-administration in the pups as adults. The protocol produced litters that were separated from dams for 0 (MS0), 15 (MS15) or 180 (MS180) min, and a nonhandled (NH) group as well. Self-administration of both drugs as shown in earlier studies was lowest in the MS15 group, highest in the NH group and intermediate in the other groups. Licking and grooming scores correlated negatively with drug intake and suggests that maternal care of pups can influence drug use in pups when they are adults.

Francis, D.D.; Kuhar, M.J.

2008-01-01

65

Antinociceptive interaction between benfotiamine and resveratrol in capsaicin-induced licking.  

PubMed

In an attempt to provide more direct evidence concerning the possible antinociceptive effect of resveratrol-benfotiamine combination on neurogenic pain, we investigated whether resveratrol and benfotiamine administered alone or in combination decrease capsaicin induced nociception in mice. Before testing, the animals were placed individually in transparent glass cylinders, 20 cm in diameter, serving as observation chambers. After the adaptation period, 20 microL of capsaicin (1.6 microg/paw) were injected under the skin of the dorsal of the right hind paw. Animals were observed individually for 5 min after capsaicin injection. The amount of time spent licking the injected paw was timed with a chronometer and was considered as indicative of nociception. Animals were pretreated with resveratrol (56.2-177 mg/kg, i.p.), benfotiamine (100-1000 mg/kg, p.o.) and their combinations (11:1, 22:2, 44:4; 88:8 mg/kg benfotiamine:resveratrol). It was observed that resveratrol (ED50 = 104 +/- 8.2 mg/kg) was able to produce more important decrement of capsaicin-induced licking than benfotiamine (ED50 = 529.4 +/- 85.2 mg/kg). In addition, a synergistic interaction was observed between benfotiamine and resveratrol, suggesting that this combination could be useful in neurogenic nociception. PMID:22128427

Montiel-Ruiz, Rosa Mariana; Reyes-García, Gerardo; Flores-Murrieta, Francisco; Déciga-Campos, Myrna

2009-01-01

66

Searching for Planets Around other Stars  

NASA Technical Reports Server (NTRS)

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.

1998-01-01

67

New binary stars (19th series) discovered at Nice  

NASA Astrophysics Data System (ADS)

A total of 209 measurements of 100 visual binaries discovered in observations with the 50-cm refractor at the Observatoire de Nice between April 1983 and October 1984 are presented in a table. The format is the same as that used in the Lick Observatory index catalog (Jeffers and van den Bos, 1963), and the present list brings the total number of binaries discovered at Nice to 2250, from observations of 109,004 stars.

Couteau, P.

1985-05-01

68

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

Microsoft Academic Search

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,

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

1999-01-01

69

Robert G. Aitken and His ADS: Double Star Oberver, Cataloguer, Statistician, and Observatory Director  

NASA Astrophysics Data System (ADS)

Robert G. Aitken was a dynamical astronomer of the old school, a long-time visual double star observer. He was born in 1864 in Jackson, California, a small town in the Gold Country midway between Yosemite and Sacramento. His education at Williams College under Truman Safford; his early teaching career at Livermore College and the University of the Pacific; his simultaneous graduate reading course in mathematics; and his becoming a professional astronomer under the tutelage of Edward S. Holden and Edward E. Barnard at Lick Observatory will be described. Aitken made a systematic survey of the entire sky north of -30 degrees for double stars, joined by William J. Hussey for a time. It produced important new information on binary and multiple stars and their orbits. His book The Binary Stars and his New General Catalogue of Double Stars (ADS) were his monuments. Aitken was associate director of Lick Observatory from 1923 until 1930, while W. W. Campbell was simultaneously director and president of the University of California. Then Aitken was director himself from 1930 until he retired in 1935 and moved to Berkeley, where he continued writing until his death in 1951. Aitken was editor of the PASP for 51 years. He hoped that Gerard P. Kuiper would succeed him as the double star observer at Lick Observatory, but that was not to be. Aitken at various times held every office in the ASP, and was vice president, then president, of the AAS.

Osterbrock, D. E.

2000-05-01

70

BINARIES AMONG DEBRIS DISK STARS  

SciTech Connect

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 discovered a previously unknown M-star companion to HD 1051 at a projected separation of 628 AU. We found that 25% {+-} 4% of our debris disk systems are binary or triple star systems, substantially less than the expected {approx}50%. The period distribution for these suggests a relative lack of systems with 1-100 AU separations. Only a few systems have blackbody disk radii 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.

Rodriguez, David R.; Zuckerman, B., E-mail: drodrigu@das.uchile.cl [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

2012-02-01

71

A Movie of the 1882 Transit of Venus Assembled from Plates Taken at Lick Observatory by David P. Todd  

NASA Astrophysics Data System (ADS)

We present a series of 141 photographic plates of the 1882 Transit of Venus, taken by David P. Todd at Lick Observatory. To our knowledge, the plates - which were recently rediscovered on Mount Hamilton - are by far the most complete photographic record of the transit. We also present the plates in the form of a high-resolution time-lapse movie, showing nearly all of the more than four hours of the transit visible from Mount Hamilton. The movie is notable for making visible an event that no living person has seen, but that has been lying dormant in the Lick archive for 120 years. The series also has a place of importance in the history of photography, and especially in the then-emerging art of chronophotography, the serial recording of a moving event.

Misch, A.; Sheehan, W.

2004-12-01

72

Stability Analysis of the Planetary System Orbiting Upsilon Andromedae. 2; Simulations Using New Lick Observatory Fits  

NASA Technical Reports Server (NTRS)

We present results of long-term numerical orbital integrations designed to test the stability of the three-planet system orbiting upsilon Andromedae and short-term integrations to test whether mutual perturbations among the planets can be used to determine planetary masses. Our initial conditions are based on recent fits to the radial velocity data obtained by the planet search group at Lick Observatory. The new fits result in significantly more stable systems than did the initially announced planetary parameters. Our integrations using the 2000 February parameters show that if the system is nearly planar, then it is stable for at least 100 Myr for m(sub f) = 1/sin i less than or = 4. In some stable systems, the eccentricity of the inner planet experiences large oscillations. The relative periastra of the outer two planets' orbits librate about 0 deg. in most of the stable systems; if future observations imply that the periastron longitudes of these planets are very closely aligned at the present epoch, dynamical simulations may provide precise estimates for the masses and orbital inclinations of these two planets.

Lissauer, Jack J.; Rivera, Eugenio J.; DeVincenzi, Donald (Technical Monitor)

2001-01-01

73

Precise Doppler Monitoring of Barnard's Star  

NASA Astrophysics Data System (ADS)

We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the second nearest star system to Earth, obtained from Lick and Keck Observatories during the 25 years between 1987 and 2012. The early precision was 20 m s-1 but was 2 m s-1 during the last 8 years, constituting the most extensive and sensitive search for Doppler signatures of planets around this stellar neighbor. We carefully analyze the 136 Keck radial velocities spanning 8 years by first applying a periodogram analysis to search for nearly circular orbits. We find no significant periodic Doppler signals with amplitudes above ~2 m s-1, setting firm upper limits on the minimum mass (Msin i) of any planets with orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for circular orbits, we determine that planetary companions to Barnard's Star with masses above 2 M ? and periods below 10 days would have been detected. Planets with periods up to 2 years and masses above 10 M ? (0.03 M Jup) are also ruled out. A similar analysis allowing for eccentric orbits yields comparable mass limits. The habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger, save for face-on orbits. Previous claims of planets around the star by van de Kamp are strongly refuted. The radial velocity of Barnard's Star increases with time at 4.515 ± 0.002 m s-1 yr-1, consistent with the predicted geometrical effect, secular acceleration, that exchanges transverse for radial components of velocity. Based on observations made at Keck Observatory and Lick Observatory.

Choi, Jieun; McCarthy, Chris; Marcy, Geoffrey W.; Howard, Andrew W.; Fischer, Debra A.; Johnson, John A.; Isaacson, Howard; Wright, Jason T.

2013-02-01

74

Measurement of the reaeration coefficients of the North Fork Licking River at Utica, Ohio by radioactive tracers  

USGS Publications Warehouse

Reaeration coefficients of the North Fork Licking River at Utica, Ohio were measured by the radioactive-tracer method. The tests were conducted on a 2.1-mile reach on September 23 and October 7, 1981, during low-flow conditions. Krypton-85 gas and tritium were the radioopactive tracers, which were used in conjunction with rhodamine-WT dye. The reaertion coefficients determined on September 23 were 3.09 days-1 (subreach 1-2) and 3.32 days-1 (subreach 2-3). On October 7, the values were 2.04 days -1 and 2.23 days-1 respectively.

Hren, Janet

1983-01-01

75

Spectroscopic Observations of Nearby Low Mass Stars  

NASA Astrophysics Data System (ADS)

Young low-mass stars are known to be bright in X-ray and UV due to a high level of magnetic activity. By cross-correlating the GALEX Catalog with the WISE and 2MASS Point Source Catalogs, we have identified more than 2,000 stars whose UV excesses suggest ages in the 10-100 Myr range. We used the Shane 3-m telescope at Lick Observatory on Mount Hamilton, California to observe some of these 2,000 stars spectroscopically. We measured the equivalent width of lithium at 6708 A absorption and H-alpha emission lines. Out of a total of 122 stars observed with the Kast grating spectrometer, we find that roughly 10% have strong lithium absorption features. The high percentage of stars with lithium present is further evidence of the importance of UV emission as a youth indicator for low-mass stars. In addition, we used high-resolution spectra obtained with the Hamilton echelle spectrograph to determine radial velocities for several UV-bright stars. These radial velocities will be useful for the calculation of Galactic UVW space velocities for determination of possible moving group membership. This work is supported by NASA Astrophysics Data Analysis Program award NNX12AH37G to RIT and UCLA and Chilean FONDECYT grant 3130520 to Universidad de Chile. This submission presents work for the GALNYSS project and should be linked to abstracts submitted by David Rodriguez, Laura Vican, and Joel Kastner.

Vican, Laura; Zuckerman, B. M.; Rodriguez, D.

2014-01-01

76

Licking and c-fos expression in the dorsal horn of the spinal cord after the formalin test.  

PubMed

We investigated whether c-fos expression in the dorsal horn is affected by licking in the formalin test. Thirty adult Sprague-Dawley rats were divided into 5 groups of 6 rats each: a free condition control (Free Cont) group, formalin test under free condition (Free F-test) group, scrub stimulation under free condition (Free Scrub) group, restrained condition control (Restricted Cont) group, and formalin test under restrained condition (Restricted F-test) group. Animals in the three free condition groups and two restricted groups were put in a clear plastic chamber and a restraining chamber, respectively. Ten percent formalin was injected into the left rear paw in the Free and Restricted F-test groups. Animals in the Free Scrub group were scrubbed on the left rear paw with a wet cotton swab. The Free Cont, Restricted Cont, and Free Scrub groups showed little c-fos expression. The number of c-fos positive cells in the ipsilateral surface dorsal horn of the Restricted F-test group was significantly less than that of the Free F-test group (P < 0.05). The results indicated that the licking action increased c-fos expression of the lumbar dorsal horn in the formalin test. PMID:16492833

Fukuda, Taeko; Watanabe, Kazuhiro; Hisano, Setsuji; Toyooka, Hidenori

2006-03-01

77

Radial Velocity Variations of K Giant Stars  

NASA Astrophysics Data System (ADS)

We have observed a sample of 182 K giants at Lick Observatory over the past 2.5 years, using the Hamilton Spectrograph in conjunction with the Iodine Cell. This yields radial velocities with precisions of about 5-7 m/s. The stars in our sample have been selected from the Hipparcos Catalogue and are believed to be bona-fide single stars. Two thirds of the stars show radial velocity dispersions of less than about 50 m/s, with a peak at about 20 m/s. Some stars show short-term variations on the order of days that seem to be rather random, whereas other stars show long-term trends of the order of years. The radial velocity curves of some of the stars suggest periodic variations with periods of the order of 1-2 years, which could be due either to non-radial pulsations or the rotational modulation of surface features. We find that redder K giants in general show larger radial velocity variations, whereas we do not find a clear correlation between radial velocity variations and photometric variability.

Mitchell, D. S.; Frink, S.; Quirrenbach, A.; Fischer, D. A.

2001-12-01

78

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

NASA Astrophysics Data System (ADS)

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).

Osterbrock, D. E.

2002-12-01

79

A PRELIMINARY APPRAISAL OF THE BIOLOGICAL INTEGRITY OF THE EAST FORK WHITE LICK CREEK IN THE WEST FORK WHITE RIVER WATERSHED USING FISH COMMUNITY ASSESSMENT  

Microsoft Academic Search

A biological community assessment conducted during July 1997 in response to requests by IDEM's Permits and Modeling Sections in the Office of Water Management to assess potential or existing impacts that may have occurred or may now be occurring in the East Fork White Lick Creek Basin due to run-off of deicing agents used at the Indianapolis International Airport (IIAP).

James R. Stahl; Thomas P. Simon; Eric O. Edberg

1997-01-01

80

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

PubMed

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

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

2014-04-01

81

T1R2 and T1R3 subunits are individually unnecessary for normal affective licking responses to polycose: implications for saccharide taste receptors in mice  

PubMed Central

The T1R2 and T1R3 proteins are expressed in taste receptor cells and form a heterodimer binding with compounds described as sweet by humans. We examined whether Polycose taste might be mediated through this heterodimer by testing T1R2 knockout (KO) and T1R3 KO mice and their wild-type (WT) littermate controls in a series of brief-access taste tests (25-min sessions with 5-s trials). Sucrose, Na-saccharin, and Polycose were each tested for three consecutive sessions with order of presentation varied among subgroups in a Latin-Square manner. Both KO groups displayed blunted licking responses and initiated significantly fewer trials of sucrose and Na-saccharin across a range of concentrations. KO mice tested after Polycose exposure demonstrated some degree of concentration-dependent licking of sucrose, likely attributable to learning related to prior postingestive experience. These results are consistent with prior findings in the literature, implicating the T1R2+3 heterodimer as the principal taste receptor for sweet-tasting ligands, and also provide support for the potential of postingestive experience to influence responding in the KO mice. In contrast, T1R2 KO and T1R3 KO mice displayed concentration-dependent licking responses to Polycose that tracked those of their WT controls and in some cases licked midrange concentrations more; the number of Polycose trials initiated overall did not differ between KO and WT mice. Thus, the T1R2 and T1R3 proteins are individually unnecessary for normal concentration-dependent licking of Polycose to be expressed in a brief-access test. Whether at least one of these T1R protein subunits is necessary for normal Polycose responsiveness remains untested. Alternatively, there may be a novel taste receptor(s) that mediates polysaccharide taste.

Treesukosol, Yada; Blonde, Ginger D.; Spector, Alan C.

2009-01-01

82

Spectral energy distribution /119 - 685 nm/ in 16 shell stars and a tentative model for accreting Be stars  

NASA Technical Reports Server (NTRS)

IUE low-dispersion spectra and spectral scans made with the Lick Observatory IDS scanners have been combined for 16 shell stars. Eleven objects can be represented by Kurucz (1979) model atmospheres, although some of them display strong shell-type line spectra. Five among them are known binaries. The six remaining objects display complex spectra. A model involving continuum and line radiation from a hydrogen cloud surrounding the accreting component is proposed. A generalization of this model with optically thick segments of the cloud promises to explain even more exotic objects such as beta Lyrae, W Serpentis and possibly epsilon Aurigae.

Plavec, M. J.; Dobias, J. J.; Weiland, J. L.; Stone, R. P. S.

1982-01-01

83

A Precision Velocity Study of Photometrically Stable Stars in the Cepheid Instability Strip  

NASA Astrophysics Data System (ADS)

Results of a precision Doppler velocity survey of 15 stars that lie in or near the Cepheid instability strip are presented. Previous studies have shown that these stars are photometrically stable. Long-term radial velocity precision of 15 m s-1 has been achieved with the use of an iodine absorption cell and a high-resolution cross-dispersed echelle spectrometer. The stars show a variety of behavior from stability (at the level of 30 m s-1) to variability from 50 m s-1 to a few km s-1. Periodograms of many of the program stars show significant peaks at 50-80 days that are not associated with radial pulsation. Previously undetected binary companions have been found around two of the stars. Line profiles are compared to ? Cep. Based on observations obtained at Lick Observatory, operated by the University of California.

Butler, R. Paul

1998-02-01

84

The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad-line Region in Mrk 50  

NASA Astrophysics Data System (ADS)

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 ± 10 deg above the plane. We also constrain the inclination angle to be 9+7 -5 deg, close to face-on. Finally, the black hole mass of Mrk 50 is inferred to be log10(M BH/M ?) = 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 with the commonly adopted mean value of 0.74 based on aligning the M BH-?* 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.

Pancoast, Anna; Brewer, Brendon J.; 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.; Hönig, 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

2012-07-01

85

Star Formation  

NASA Astrophysics Data System (ADS)

Stars are one of the most important constituents of the Universe, and understanding their formation is crucial to many areas of astrophysics. Stars form from dense molecular gas, and they tend not to form in isolation. Stars often form in binary and multiple systems, and these systems tend to form in clusters with 102-105 members. Stars also form with a wide range of masses, from substellar brown dwarfs with masses < 0. 1 M ? to massive stars > 100 M ?, and wherever stars form the distribution of their masses seems always to be the same. This chapter will review our current understanding of star formation from cold gas to young star clusters.

Goodwin, Simon

86

Strange stars  

Microsoft Academic Search

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

Charles Alcock; Edward Farhi; Angela Olinto

1986-01-01

87

Strange stars  

NASA Technical Reports Server (NTRS)

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.

Alcock, Charles; Farhi, Edward; Olinto, Angela

1986-01-01

88

Be Stars  

NASA Astrophysics Data System (ADS)

A Be star (pronounced `bee-ee' star) is a non-supergiant B-type star whose spectrum displays or has displayed one or more Balmer lines in emission and Be is the notation for the spectral classification of such a star (see also CLASSIFICATION OF STELLAR SPECTRA). `Classical' Be stars are believed to have acquired the circumstellar (CS) material that produces the Balmer emission through ejection of...

Peters, G.; Murdin, P.

2000-11-01

89

Stars and Star Myths.  

ERIC Educational Resources Information Center

Myths and tales from around the world about constellations and facts about stars in the constellations are presented. Most of the stories are from Greek and Roman mythology; however, a few Chinese, Japanese, Polynesian, Arabian, Jewish, and American Indian tales are also included. Following an introduction, myths are presented for the following 32…

Eason, Oliver

90

PRECISE DOPPLER MONITORING OF BARNARD'S STAR  

SciTech Connect

We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the second nearest star system to Earth, obtained from Lick and Keck Observatories during the 25 years between 1987 and 2012. The early precision was 20 m s{sup -1} but was 2 m s{sup -1} during the last 8 years, constituting the most extensive and sensitive search for Doppler signatures of planets around this stellar neighbor. We carefully analyze the 136 Keck radial velocities spanning 8 years by first applying a periodogram analysis to search for nearly circular orbits. We find no significant periodic Doppler signals with amplitudes above {approx}2 m s{sup -1}, setting firm upper limits on the minimum mass (Msin i) of any planets with orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for circular orbits, we determine that planetary companions to Barnard's Star with masses above 2 M {sub Circled-Plus} and periods below 10 days would have been detected. Planets with periods up to 2 years and masses above 10 M {sub Circled-Plus} (0.03 M {sub Jup}) are also ruled out. A similar analysis allowing for eccentric orbits yields comparable mass limits. The habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger, save for face-on orbits. Previous claims of planets around the star by van de Kamp are strongly refuted. The radial velocity of Barnard's Star increases with time at 4.515 {+-} 0.002 m s{sup -1} yr{sup -1}, consistent with the predicted geometrical effect, secular acceleration, that exchanges transverse for radial components of velocity.

Choi, Jieun; Marcy, Geoffrey W.; Howard, Andrew W.; Isaacson, Howard [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)] [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); McCarthy, Chris [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132 (United States)] [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132 (United States); Fischer, Debra A. [Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States)] [Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States); Johnson, John A. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)] [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Wright, Jason T., E-mail: jieun_eb@berkeley.edu [Department of Astronomy, The Pennsylvania State University, University Park, PA 16802 (United States)

2013-02-20

91

Absolute Spectrophotometry of 237 Open Cluster Stars  

NASA Astrophysics Data System (ADS)

We present absolute spectrophotometry of 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M 39. The observations were taken using the Wampler single-channel scanner (Wampler 1966) on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. 21 bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwiths ranging from 32Angstroms to 64 Angstroms. Data are standardized to the Hayes--Latham (1975) system. Our measurements are compared to filter colors on the Johnson BV, Stromgren ubvy, and Geneva U V B_1 B_2 V_1 G systems, as well as to spectrophotometry of a few stars published by Gunn, Stryker & Tinsley and in the Spectrophotometric Standards Catalog (Adelman; as distributed by the NSSDC). Both internal and external comparisons to the filter systems indicate a formal statistical accuracy per bandpass of 0.01 to 0.02 mag, with apparent larger ( ~ 0.03 mag) differences in absolute calibration between this data set and existing spectrophotometry. These data will comprise part of the spectrophotometry that will be used to calibrate the Beijing-Arizona-Taipei-Connecticut Color Survey of the Sky (see separate paper by Burstein et al. at this meeting).

Clampitt, L.; Burstein, D.

1994-12-01

92

The Washington Visual Double Star Catalog (Mason+ 2001-2010)  

NASA Astrophysics Data System (ADS)

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).

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

2010-11-01

93

The Washington Visual Double Star Catalog (Mason+ 2001-2012)  

NASA Astrophysics Data System (ADS)

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).

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

2012-11-01

94

The Washington Visual Double Star Catalog (Mason+ 2001-2010)  

NASA Astrophysics Data System (ADS)

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).

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

2009-10-01

95

The Washington Visual Double Star Catalog (Mason+ 2001-2011)  

NASA Astrophysics Data System (ADS)

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).

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

2011-11-01

96

The Washington Visual Double Star Catalog (Mason+ 2001-2013)  

NASA Astrophysics Data System (ADS)

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).

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

2013-11-01

97

The Washington Visual Double Star Catalog (Mason+ 2001-2014)  

NASA Astrophysics Data System (ADS)

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).

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

2014-02-01

98

Massive binary stars as a probe of massive star formation  

NASA Astrophysics Data System (ADS)

Massive stars are among the largest and most influential objects we know of on a sub-galactic scale. Binary systems, composed of at least one of these stars, may be responsible for several types of phenomena, including type Ib/c supernovae, short and long gamma ray bursts, high-velocity runaway O and B-type stars, and the density of the parent star clusters. Our understanding of these stars has met with limited success, especially in the area of their formation. Current formation theories rely on the accumulated statistics of massive binary systems that are limited because of their sample size or the inhomogeneous environments from which the statistics are collected. The purpose of this work is to provide a higher-level analysis of close massive binary characteristics using the radial velocity information of 113 massive stars (B3 and earlier) and binary orbital properties for the 19 known close massive binaries in the Cygnus OB2 Association. This work provides an analysis using the largest amount of massive star and binary information ever compiled for an O-star rich cluster like Cygnus OB2, and compliments other O-star binary studies such as NGC 6231, NGC 2244, and NGC 6611. I first report the discovery of 73 new O or B-type stars and 13 new massive binaries by this survey. This work involved the use of 75 successful nights of spectroscopic observation at the Wyoming Infrared Observatory in addition to observations obtained using the Hydra multi-object spectrograph at WIYN, the HIRES echelle spectrograph at KECK, and the Hamilton spectrograph at LICK. I use these data to estimate the spectrophotometric distance to the cluster and to measure the mean systemic velocity and the one-sided velocity dispersion of the cluster. Finally, I compare these data to a series of Monte Carlo models, the results of which indicate that the binary fraction of the cluster is 57 +/- 5% and that the indices for the power law distributions, describing the log of the periods, mass-ratios, and eccentricities, are --0.2 +/- 0.3, 0.3 +/- 0.3, and --0.8 +/- 0.3 respectively (or not consistent with a simple power law distribution). The observed distributions indicate a preference for short period systems with nearly circular orbits and companions that are not likely drawn from a standard initial mass function, as would be expected from random pairing. An interesting and unexpected result is that the period distribution is inconsistent with a standard power-law slope stemming mainly from an excess of periods between 3 and 5 days and an absence of periods between 7 and 14 days. One possible explanation of this phenomenon is that the binary systems with periods from 7--14 days are migrating to periods of 3--5 days. In addition, the binary distribution here is not consistent with previous suggestions in the literature that 45% of OB binaries are members of twin systems (mass ratio near 1).

Kiminki, Daniel C.

2010-10-01

99

STAR Publications  

Cancer.gov

STAR Publications The following citations are of reports that have been published in the scientific literature concerning the Study of Tamoxifen and Raloxifene (STAR). The citations are listed in reverse chronological order.

100

STAR System.  

ERIC Educational Resources Information Center

The STAR System is a developmental guidance approach to be used with elementary school children in the 5th or 6th grades. Two basic purposes underlie STAR: to increase learning potential and to enhance personal growth and development. STAR refers to 4 basic skills: sensory, thinking, adapting, and revising. Major components of the 4 skills are:…

Doverspike, James E.

101

The Evolving Mixture of Barium Isotopes in Milky Way Halo Stars  

NASA Astrophysics Data System (ADS)

Heavy metals in stars form through one of two types of neutron capture processes: the rapid r-process or slower s-process. The fraction of odd and even barium isotopes in stars can indicate which process predominantly contributed to a star’s heavy metals, since odd barium isotopes predominantly form through the r-process and even barium isotopes through the s-process. The “stellar model” predicts that older stars contain comparable amounts of odd and even barium isotopes, while the “classical model” states that they almost exclusively contain odd isotopes. This study investigated these competing models by analyzing high-resolution spectra of twelve Milky Way stars. These spectra were analyzed for the first time in this study. To quantify r- and s-process enrichment, we measured the odd barium isotope fraction in the stars by fitting models to the stars’ spectra. Generating models involved measuring the stars’ Doppler shift, resolution, and barium abundance. To reduce error margins we optimized resolution and barium abundance measurements by enhancing existing techniques through several rounds of revisions. Our results support the stellar model of heavy metal enrichment, and our proposed optimizations will enable future researchers to obtain a deeper understanding of chemical enrichment in the Universe. This research was supported by the Science Internship Program at the University of California Santa Cruz, Lick Observatory, and the National Science Foundation.

Choudhury, Zareen; Kirby, E. N.; Guhathakurta, P.

2014-01-01

102

Applications of Precision Doppler Velocity Measurements in Variable Star Studies  

NASA Astrophysics Data System (ADS)

Techniques developed over the last 10 years have improved the precision of Doppler velocity measurements by more than two orders of magnitude. While most of this work has centered on the discovery of extrasolar planets, a number of applications have been developed for the study of variable stars. Work carried out with the Lick Observatory Iodine absorption cell has resulted in the direct detection of velocity gradients in Cepheid photospheres, the first precision comparison of Doppler velocities in the visible and near IR, and a 6 year survey of photometrically non-variable supergiants in and about the Cepheid instability strip. Most of the photometric non-variables show Doppler velocity variations of 50 to 1,000 m/s and periods of 40 to 250 days. In addition, the Lick Planet Survey has shown that slowly rotating solar-type stars are intrinsically stable to at least 3 m/s. The Keck Iodine absorption cell has been used for search for solar-type oscillations in the bright K1 dwarf star 107 Psc. A precision of 2 m/s was obtained on a six hour data string of 200 observations. The detection threshold was 55 cm/s over the expected oscillation frequency window. We did not detect any oscillations at this level. In comparison, the solar 5 minute oscillation has an amplitude of 0.23 m/s, thus this technique is already within a factor of two of achieving the necessary detection threshold. The Lick Observatory precision Doppler technique makes use of a fast echelle spectrograph at resolution of R=62,000 and a large format CCD which acquires the entire visible and near IR spectrum in each exposure. Starlight is sent through an iodine absorption cell placed at the spectrometer entrance slit. The resulting superimposed iodine lines provide a fiducial wavelength scale against which to measure radial velocity shifts. The shapes of iodine lines convey the PSF of the spectrometer to account for changes in spectrometer optics and illumination on all time scales.

Butler, R. P.

103

The Lick-Carnegie Exoplanet Survey: Gliese 687 b—A Neptune-mass Planet Orbiting a Nearby Red Dwarf  

NASA Astrophysics Data System (ADS)

Precision radial velocities from the Automated Planet Finder (APF) and Keck/HIRES reveal an Msin (i) = 18 ± 2 M ? planet orbiting the nearby M3V star GJ 687. This planet has an orbital period P = 38.14 days and a low orbital eccentricity. Our Strömgren b and y photometry of the host star suggests a stellar rotation signature with a period of P = 60 days. The star is somewhat chromospherically active, with a spot filling factor estimated to be several percent. The rotationally induced 60 day signal, however, is well separated from the period of the radial velocity variations, instilling confidence in the interpretation of a Keplerian origin for the observed velocity variations. Although GJ 687 b produces relatively little specific interest in connection with its individual properties, a compelling case can be argued that it is worthy of remark as an eminently typical, yet at a distance of 4.52 pc, a very nearby representative of the galactic planetary census. The detection of GJ 687 b indicates that the APF telescope is well suited to the discovery of low-mass planets orbiting low-mass stars in the as yet relatively un-surveyed region of the sky near the north celestial pole.

Burt, Jennifer; Vogt, Steven S.; Butler, R. Paul; Hanson, Russell; Meschiari, Stefano; Rivera, Eugenio J.; Henry, Gregory W.; Laughlin, Gregory

2014-07-01

104

Stationary Star  

NSDL National Science Digital Library

This is an activity about star movement due to the Earth's rotation. Learners will utilize the Sky Tonight online program to find the star that appears stationary in our night sky. They will then draw conclusions about the Earthâs rotation based on the position changes of certain stars. This activity requires the use of a computer with Internet access. This activity is Sky Tonight Activity 2 in a larger resource, Space Update.

105

Neutron Stars  

NASA Technical Reports Server (NTRS)

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.

Cottam, J.

2007-01-01

106

Star Images, Star Performances (College Course File).  

ERIC Educational Resources Information Center

Describes a course that focuses attention on the position of the actor, especially the star actor, in cinematic and television signification. Divides the course into three sections: "The Star System,""Stars as Images," and "Star Performance." (RS)

Butler, Jeremy G.

1990-01-01

107

Star Formation in Early-type galaxies (Longhetti+ 1998)  

NASA Astrophysics Data System (ADS)

The paper is the first of a series (Longhetti et al., 1998A&AS..130..267L, 1998b (Paper III) in press) dedicated to the study of the star formation history in early-type galaxies which show fine structures and/or interaction signatures. It presents nuclear line-strength indices for a sample composed of 21 shell galaxies, from the Malin & Carter (1983ApJ...274..534M) southern survey, and 30 members of isolated interacting pairs, from the Reduzzi & Rampazzo (1995ApL....30....1R) catalogue, located in low density environments. The spectral range covers 3700Å4200Å) indices defined by the Lick Group. Measures have been transformed into the Lick-IDS ``standard'' system. The procedure has been tested on a set of 5 elliptical galaxies selected from the Gonzalez (1993, Ph.D. thesis) sample. We derive also three blue (?<4200) indices, namely {DELTA}(4000Å) defined by Hamilton (1985ApJ...297..371H), H+K(CaII) and Hdelta/FeI defined by Rose (1984AJ.....89.1238R, 1985AJ.....90.1927R). Blue indices are correlated to the age of the last starburst occurred in a galaxy (Leonardi & Rose, 1996AJ....111..182L). The indices determination, the estimate of the measurement errors and the correction for the galaxies velocity dispersions are discussed in detail. In the Appendix A we present the indices for a set of hot stars (T>10000K) which may be used for extending, toward high temperatures, Worthey (1992, Ph.D. Thesis) fitting functions. (12 data files).

Longhetti, M.; Rampazzo, R.; Bressan, A.; Chiosi, C.

1998-03-01

108

Photometric Observations of 6000 Stars in the Cygnus Field  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

109

Neutron stars  

NASA Astrophysics Data System (ADS)

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.

Lattimer, James M.

2014-05-01

110

Symbiotic stars  

NASA Technical Reports Server (NTRS)

The physical characteristics of symbiotic star systems are discussed, based on a review of recent observational data. A model of a symbiotic star system is presented which illustrates how a cool red-giant star is embedded in a nebula whose atoms are ionized by the energetic radiation from its hot compact companion. UV outbursts from symbiotic systems are explained by two principal models: an accretion-disk-outburst model which describes how material expelled from the tenuous envelope of the red giant forms an inwardly-spiralling disk around the hot companion, and a thermonuclear-outburst model in which the companion is specifically a white dwarf which superheats the material expelled from the red giant to the point where thermonuclear reactions occur and radiation is emitted. It is suspected that the evolutionary course of binary systems is predetermined by the initial mass and angular momentum of the gas cloud within which binary stars are born. Since red giants and Mira variables are thought to be stars with a mass of one or two solar mass, it is believed that the original cloud from which a symbiotic system is formed can consist of no more than a few solar masses of gas.

Kafatos, M.; Michalitsianos, A. G.

1984-01-01

111

Barnard’s Star: Planets or Pretense  

NASA Astrophysics Data System (ADS)

Barnard’s Star remains popular with planet hunters because it is not only an extremely near, high proper motion star, but also the object of early planet-detection claims. In 1963, van de Kamp explained perturbations in its proper motion by the presence of a planet. In 1969, he produced another single-planet solution and a two-planet solution to the astrometric wobbles detected. At least 19 studies have failed to confirm his results using a range of techniques, including radial velocity, direct imaging, and speckle interferometry. However, most of them lacked the sensitivity to detect the planets he described, including astrometric studies at the McCormick and Naval Observatories. However, radial-velocity monitoring of Barnard’s Star at Lick and Keck Observatories from 1987 through 2012 appears to have ruled out such planets. Based upon observations made at the Sproul Observatory between 1916 and 1962, van de Kamp claimed that Barnard’s Star had a planet with about 1.6 times the mass of Jupiter and an orbital period of 24 years. After accounting for instrumentation effects that might have been partially responsible for his initial results, he continued to assert that this red dwarf had two planets. In his 1982 analysis of ~20,000 exposures collected between 1938 and 1981, he calculated that two planets with 0.7- and 0.5-Jupiter masses in 12- and 20-year orbits, respectively, orbited the second-closest stellar system to our own. Starting in 1995, the dramatic successes of radial velocity searches for extrasolar planets drove van de Kamp’s unsubstantiated claims from popular consciousness. Although many low-mass stellar companions were discovered through astrometry, the technique has been less successful for planets: “The Extrasolar Planets Encyclopaedia” identifies one such discovery out of the 997 planets listed on 2013 September 23. Although Barnard’s Star has lost its pretensions to hosting the first extrasolar planets known, its intrinsic properties will keep it under observation. NSF grant AST 98-20711, Litton Marine Systems, Levinson Fund, University of Virginia, Hampden-Sydney College, and US Naval Observatory supported this research.

Bartlett, Jennifer L.; Ianna, P. A.

2014-01-01

112

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

SciTech Connect

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.

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

113

Chameleon stars  

SciTech Connect

We consider a gravitating spherically symmetric configuration consisting of a scalar field nonminimally coupled to ordinary matter in the form of a perfect fluid. For this system we find static, regular, asymptotically flat solutions for both relativistic and nonrelativistic cases. It is shown that the presence of the nonminimal interaction leads to substantial changes both in the radial matter distribution of the star and in the star's total mass. A simple stability test indicates that, for the choice of parameters used in the paper, the solutions are unstable.

Dzhunushaliev, Vladimir [Institute for Basic Research, Eurasian National University, Astana, 010008 (Kazakhstan); Institute of Physicotechnical Problems and Material Science of the NAS of the Kyrgyz Republic, 265 a, Chui Street, Bishkek, 720071 (Kyrgyzstan); Folomeev, Vladimir [Institute of Physicotechnical Problems and Material Science of the NAS of the Kyrgyz Republic, 265 a, Chui Street, Bishkek, 720071 (Kyrgyzstan); Singleton, Douglas [Institute for Basic Research, Eurasian National University, Astana, 010008 (Kazakhstan); Physics Department, CSU Fresno, Fresno, California 93740-8031 (United States)

2011-10-15

114

14 CFR 91.145 - Management of aircraft operations in the vicinity of aerial demonstrations and major sporting...  

Code of Federal Regulations, 2010 CFR

...Roses Football Game; (6) World Cup Soccer; (7) Major League Baseball All-Star Game; (8) World Series; (9) Kodak Albuquerque International Balloon Fiesta; (10) Sandia Classic Hang Gliding Competition; (11) Indianapolis 500...

2009-01-01

115

14 CFR 91.145 - Management of aircraft operations in the vicinity of aerial demonstrations and major sporting...  

Code of Federal Regulations, 2010 CFR

...Roses Football Game; (6) World Cup Soccer; (7) Major League Baseball All-Star Game; (8) World Series; (9) Kodak Albuquerque International Balloon Fiesta; (10) Sandia Classic Hang Gliding Competition; (11) Indianapolis 500...

2010-01-01

116

14 CFR 91.145 - Management of aircraft operations in the vicinity of aerial demonstrations and major sporting...  

...Team (Golden Knights); (4) Summer/Winter Olympic Games; (5) Annual Tournament of Roses Football Game; (6) World Cup Soccer; (7) Major League Baseball All-Star Game; (8) World Series; (9) Kodak Albuquerque...

2014-01-01

117

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. ...

2010-04-15

118

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.

119

Converting neutron stars into strange stars  

NASA Technical Reports Server (NTRS)

If strange matter is formed in the interior of a neutron star, it will convert the entire neutron star into a strange star. The proposed mechanisms are reviewed for strange matter seeding and the possible strange matter contamination of neutron star progenitors. The conversion process that follows seeding and the recent calculations of the conversion timescale are discussed.

Olinto, A. V.

1991-01-01

120

RW Tauri as a weak W Serpentis star  

NASA Technical Reports Server (NTRS)

Observations of the short-period eclipsing binary RW Tau made with the LWR and SWP cameras of the IUE satellite and with the ITS scanner at the 3-m Shane telescope of the Lick Observatory in August and October, 1982, are reported and analyzed. At total eclipse, weak excess continuous radiation in the LWR range and emission lines at Si IV (1), C IV (1), Al III (1), Fe III (34), and Mg II (1) in the SWP range were detected. These findings are similar to those for W Ser-type binaries such as U Cep. The parameters of the system are estimated using a bilinearly interpolated atmospheric model of the type developed by Kurucz (1979): primary-star T(eff) = 11,750 K, log g = 4.2, cool-component spectral type = K0 III, E(B-V) color excess = 0.14 mag, system distance = 270 pc. The implications of these findings for proposed models of the W Ser binaries are discussed, and the observation of a possible distant optical companion star 45 arcsec from RW Tau is reported.

Plavec, M. J.; Dobias, J. J.

1983-01-01

121

Spectroscopic variations in the T Tauri star RW Aurigae  

NASA Astrophysics Data System (ADS)

Echelle spectra of the extreme T Tauri star RW Aurigae have been taken during ninety-one nights, over six years by G. Basri at Lick Observatory. Current models predict that the H? and Ca 2 lines form in different temperature regions of the star; simultaneous monitoring of these lines will therefore provide some constraints to the models of T Tauri systems. In order to better see the changes in the emission lines, we have made movies of the profile variations of the H? and Ca 2 lines. Strings of data were used in which successive observations were separated by no more than three days. The data were interpolated onto a constant time step of 0.1 days. The movies make it possible to identify times when these two lines were in phase with each other, out of phase, and quiescent. It appears that the two emission lines are not wholly disconnected from one another even though current models imply that they are. As part of our search for possible connections between H? and Ca 2, we have attempted a power spectrum analysis of the individual spectra and the changes of the spectra over time. Such connections will provide specific constraints on the line formation mechanisms as well as on the line emitting region.

Lauer, J. L.; Kuhi, L. V.

1997-12-01

122

The origin of S0s in clusters: evidence from the bulge and disc star formation histories  

NASA Astrophysics Data System (ADS)

The individual star formation histories of bulges and discs of lenticular (S0) galaxies can provide information on the processes involved in the quenching of their star formation and subsequent transformation from spirals. In order to study this transformation in dense environments, we have decomposed long-slit spectroscopic observations of a sample of 21 S0s from the Virgo Cluster to produce one-dimensional spectra representing purely the bulge and disc light for each galaxy. Analysis of the Lick indices within these spectra reveals that the bulges contain consistently younger and more metal-rich stellar populations than their surrounding discs, implying that the final episode of star formation within S0s occurs in their central regions. Analysis of the ?-element abundances in these components further presents a picture in which the final episode of star formation in the bulge is fuelled using gas that has previously been chemically enriched in the disc, indicating the sequence of events in the transformation of these galaxies. Systems in which star formation in the disc was spread over a longer period contain bulges in which the final episode of star formation occurred more recently, as one might expect for an approximately coeval population in which the transformation from spiral to S0 occurred at different times. With data of this quality and the new analysis method deployed here, we can begin to describe this process in a quantitative manner for the first time.

Johnston, Evelyn J.; Aragón-Salamanca, Alfonso; Merrifield, Michael R.

2014-06-01

123

THE FREQUENCY OF HOT JUPITERS ORBITING NEARBY SOLAR-TYPE STARS  

SciTech Connect

We determine the fraction of F, G, and K dwarfs in the solar neighborhood hosting hot Jupiters as measured by the California Planet Survey from the Lick and Keck planet searches. We find the rate to be 1.2% {+-} 0.38%, which is consistent with the rate reported by Mayor et al. from the HARPS and CORALIE radial velocity (RV) surveys. These numbers are more than double the rate reported by Howard et al. for Kepler stars and the rate of Gould et al. from the OGLE-III transit search; however, due to small number statistics these differences are of only marginal statistical significance. We explore some of the difficulties in estimating this rate from the existing RV data sets and comparing RV rates to rates from other techniques.

Wright, J. T. [Department of Astronomy, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Marcy, G. W.; Howard, A. W. [Department of Astronomy, University of California, Berkeley, CA, 94720-3411 (United States); Johnson, John Asher; Morton, T. D. [Department of Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA, 91125 (United States); Fischer, D. A., E-mail: jtwright@astro.psu.edu [Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States)

2012-07-10

124

DB Pulsating Stars  

NASA Astrophysics Data System (ADS)

Pulsating WHITE DWARF stars with nearly pure helium atmospheres exist in a narrow temperature range near 25 000 K. At this writing, there are eight of these stars known. Collectively, they go by two names: the V777 Her stars, named after the VARIABLE STAR designation of the first known star in the class, and the more informative name, the DBV stars. The name DBV follows the standard convention fo...

Winget, D.; Murdin, P.

2000-11-01

125

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

PubMed Central

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.

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

2005-01-01

126

Star Search  

NSDL National Science Digital Library

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.

Science, American A.

2009-01-01

127

O stars and Wolf-Rayet stars  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

128

Lifestyles of the Stars.  

ERIC Educational Resources Information Center

Some general information on stars is provided in this National Aeronautics and Space Administration pamphlet. Topic areas briefly discussed are: (1) the birth of a star; (2) main sequence stars; (3) red giants; (4) white dwarfs; (5) neutron stars; (6) supernovae; (7) pulsars; and (8) black holes. (JN)

National Aeronautics and Space Administration, Cocoa Beach, FL. John F. Kennedy Space Center.

129

StarHeads  

NSDL National Science Digital Library

StarHeads, the last product of the Star*s Family is now available at the Centre de Donnees astronomiques de Strasbourg (CDS). StarHeads gives access to about 400 individual pages of astronomers and space scientists, and this figure is rapidly growing. Forms based browser is required.

130

Overexpression of neuropeptide Y in the dorsomedial hypothalamus increases trial initiation but does not significantly alter concentration-dependent licking to sucrose in a brief-access taste test.  

PubMed

Evidence in the literature raises the possibility that alterations in neuropeptide Y (NPY) in the dorsomedial hypothalamus (DMH) may contribute to hyperphagia leading to body weight gain. Previously, we have shown that compared to AAVGFP controls, adeno-associated virus (AAV)-mediated overexpression of NPY in the DMH of lean rats resulted in significantly higher body weight gain that was attributed to increased food intake, and this was further exacerbated by a high-fat diet. Here, we tested AAVNPY and AAVGFP control rats in a brief-access taste procedure (10-s trials, 30-min sessions) to an array of sucrose concentrations under ad libitum and partial food and water access conditions. The test allows for some segregation of the behavioral components by providing a measure of trial initiation (appetitive) and unconditioned licks at each concentration (consummatory). Consistent with previous findings suggesting that NPY has a primary effect on appetitive function, overexpression of DMH NPY did not significantly alter concentration-dependent licking response to sucrose but when tested in a non-restricted food and water schedule, AAVNPY rats initiated significantly more sucrose trials compared to AAVGFP controls in a brief-access taste test. PMID:23313404

Treesukosol, Yada; Bi, Sheng; Moran, Timothy H

2013-02-17

131

Overexpression of neuropeptide Y in the dorsomedial hypothalamus increases trial initiation but does not significantly alter concentration-dependent licking to sucrose in a brief-access taste test  

PubMed Central

Evidence in the literature raises the possibility that alterations in neuropeptide Y (NPY) in the dorsomedial hypothalamus (DMH) may contribute to hyperphagia leading to body weight gain. Previously, we have shown that compared to AAVGFP controls, adeno-associated virus (AAV)-mediated overexpression of NPY in the DMH of lean rats resulted in significantly higher body weight gain that was attributed to increased food intake, and this was further exacerbated by a high-fat diet. Here, we tested AAVNPY and AAVGFP control rats in a brief-access taste procedure (10-s trials, 30-min sessions) to an array of sucrose concentrations under ad libitum and partial food and water access conditions. The test allows for some segregation of the behavioral components by providing a measure of trial initiation (appetitive) and unconditioned licks at each concentration (consummatory). Consistent with previous findings suggesting that NPY has a primary effect on appetitive function, overexpression of DMH NPY did not significantly alter concentration-dependent licking response to sucrose but when tested in a non-restricted food and water schedule, AAVNPY rats initiated significantly more sucrose trials compared to AAVGFP controls in a brief-access taste test.

Treesukosol, Yada; Bi, Sheng; Moran, Timothy H.

2013-01-01

132

Influence of Departures from LTE on Oxygen Abundance Determination in the Atmospheres of A - K stars  

NASA Astrophysics Data System (ADS)

Solar oxygen abundance is a key parameter for the studies of solar physics. Oxygen abundances of cool stars with different metallicities are important for understanding the galactic chemical evolution. We present non-LTE calculations for O I with the classical plane-parallel (1D) model atmospheres for a set of stellar parameters corresponding to stars of spectral types from A to K. Non-LTE leads to strengthening the O I lines, and the difference between the non-LTE and LTE abundances (non-LTE correction) is negative. The departures from LTE grow toward higher effective temperature and lower surface gravity. In the entire temperature range and log g = 4, the non-LTE correction does not exceed 0.05 dex in absolute value for lines of O I in the visible spectral range. The non-LTE corrections are significantly larger for the infrared O I 7771-5, 8446 Å lines and reach an order of magnitude for A-type stars. To differentiate the effects of inelastic collisions with electrons and neutral hydrogen atoms on the statistical equilibrium (SE) of O I, we derived the oxygen abundance for the five well studied A-type stars. For each star, non-LTE largely removes the difference between the infrared and visible lines found in LTE. In the case of cool stars (Sun and Procyon), inelastic collisions with H I affect the SE of O I, and agreement between the abundances from different lines is achieved when using the Drawin's formalism for collisional rates calculations. The solar mean oxygen abundance from the six lines is ? = 8.74 +/- 0.05, when using the MAFAGS-OS solar model atmosphere and ? = 8.78 +/- 0.03, when applying the 3D corrections taken from the literature. The non-LTE abundances of oxygen are derived for the sample of cool dwarfs with various metallicities on high-resolution spectra observed in the Lick observatory.

Sitnova, Tatyana; Mashonkina, Lyudmila; Zhao, Gang; Ryabchikova, Tatiana; Pakhomov, Yury

2014-01-01

133

Herschel's Star Gages  

NSDL National Science Digital Library

The EJS Herschel's Star Gages Model illustrates William Herschel's methods of "star gages" by which he attempted to map out the shape of our galaxy in 1785. Herschel's star gages (sic) relied on two important assumptions: that Herschel's telescope (his "large 20 foot" with an 18.5 inch aperture) could see to the ends of the galaxy, and that within the galactic system stars are distributed uniformly. If the first assumption holds then the stars seen in the telescope all lie within a conical region of space with the apex at the telescope and the base at the edge of the galaxy. If the second assumption holds then the number of stars seen in the telescope is proportional to the volume of this cone. Since the volume of the cone is proportional to the cube of its height, the distance to the galactic edge in any direction is proportional to the cube root of the number of stars seen in that direction. This simulation allows the user to use Herschel's method of star gages to map out the shape of an artificial "star system" for which Herschel's assumptions are valid. One window shows the view through a telescope, with a slider to change the telescopes direction (around a single fixed axis). Another window shows a 3D view of the star system, showing either all of the stars in the system or only those stars visible through the telescope. A third window shows a plot of the star gages. Plotting star gages for many different directions maps out a cross-section of the star system. An optional slider allows the user to decrease the distance to at which stars are no longer visible, and a menu allows the user to select a star system in which the stars are not distributed uniformly. These options let the user explore how violations of Herschel's two fundamental assumptions invalidate his star gage method.

Timberlake, Todd

2011-05-28

134

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

SciTech Connect

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.

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

135

Wolf-Rayet stars  

NASA Technical Reports Server (NTRS)

The properties and evolutionary status of WR stars are examined, reviewing the results of recent observational and theoretical investigations. Topics discussed include spectral types and line strengths, magnitudes and colors, intrinsic variability, IR and radio observations, X-ray observations, the Galactic distribution of WR stars, WR stars in other galaxies, and WR binaries. Consideration is given to the inferred masses, composition, and stellar winds of WR stars; model atmospheres; WR stars and the Galactic environment; and WR stars as a phase of stellar evolution. Diagrams, graphs, and tables of numerical data are provided.

Abbott, David C.; Conti, Peter S.

1987-01-01

136

LGS-AO: the making of a star for astronomy.  

NASA Astrophysics Data System (ADS)

For astronomers, it all started in 1985 when Foy and Labeyrie (1985, A&A, 152, L29)published the concept of creating a laser guide star (LGS) in the mesospheric layer of the atmosphere to extend the use of adaptive optics (AO) to a much larger fraction of the astronomical sky. Shortly thereafter, the first sodium wavelength laser beam was propagated from Mauna Kea to validate the LGS concept (Thompson & Gardner 1987, Nature, 328, 229). In 1991, the results from the research undertaken by the U.S. Dept. of Defence were published in the open literature (Fugate et al. 1991, Nature, 353, 144). Experiments were subsequently performed at a number of Observatories (Apache Point, MMT, Calar Alto & Lick) resulting in one operational LGS-AO facility on the Lick 3-m telescope (Max et al. 1997, Science, 277, 1649). Today, Keck II LGS-AO, the first operational LGS-AO facility on an 8-10-m class telescope, is paving a new road for astronomical science by providing very high angular resolution (FWHMs of 50-60 mas with Strehls of 20-35% at K) over half of the sky. AO-corrected imagers and spectrographs at Keck and elsewhere will soon be used by a wider community of astronomers to complement and frequently surpass the observations obtained from space. We will present a review and a discussion of this powerful new instrumentation: the exciting scientific showcases and the challenges for combining complicated dynamic systems into productive, reliable and user-friendly instrumentation. We will provide an update on the forthcoming LGSAO intruments at other major observatories. We will report on the image quality performance, as well as on-sky observing efficiency, for the Keck II system (Wizinowich et al. 2005, PASP, submitted). As many astronomers plan for "AO all-the-time" on large and extremely large telescope, this talk will provide some information and lessons learned for how to best prepare for the bright LGS-AO future.

Le Mignant, D.

2005-12-01

137

AN ULTRAVIOLET SPECTROSCOPIC ATLAS OF LOCAL STARBURSTS AND STAR-FORMING GALAXIES: THE LEGACY OF FOS AND GHRS  

SciTech Connect

We present 46 rest-frame ultraviolet (UV) spectra of 28 local starburst and star-forming galaxies which were observed with the Faint Object Spectrograph (FOS) and the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) at a spectral resolution of a few 100 km s{sup -1}. We compare the HST spectra with lower resolution International Ultraviolet Explorer (IUE) spectra of the same galaxies and find systematic differences: the bright star clusters targeted in HST's {approx}1'' apertures provide about 15% of the starburst luminosity traced by IUE's 10'' x 20'' aperture; they are bluer and have stronger stellar-wind features suggesting that the HST apertures have preferentially been placed on the youngest areas of the burst. In contrast, lines arising from the interstellar medium (ISM) show similar equivalent widths in both the large and small aperture observations, suggesting similar ISM properties from larger to smaller scales. In order to quantify the UV spectral morphology of star-forming galaxies, we created a set of UV line indices similar to the standard optical Lick indices. We discuss the relation between the UV spectral morphology and the properties of the galaxy host. We present our atlas of FOS and GHRS spectra both in print and online. The data set is useful as a baseline for comparisons with observations of the rest-frame UV spectra of star-forming galaxies at high redshift.

Leitherer, Claus [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Tremonti, Christy A. [Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter St., Madison, WI 53706 (United States); Heckman, Timothy M. [Department of Physics and Astronomy, Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Calzetti, Daniela, E-mail: leitherer@stsci.edu, E-mail: tremonti@astro.wisc.edu, E-mail: heckman@pha.jhu.edu, E-mail: calzetti@astro.umass.edu [Department of Astronomy, University of Massachusetts, LGRT-B 524, Amherst, MA 01003 (United States)

2011-02-15

138

An Ultraviolet Spectroscopic Atlas of Local Starbursts and Star-forming Galaxies: The Legacy of FOS and GHRS  

NASA Astrophysics Data System (ADS)

We present 46 rest-frame ultraviolet (UV) spectra of 28 local starburst and star-forming galaxies which were observed with the Faint Object Spectrograph (FOS) and the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) at a spectral resolution of a few 100 km s-1. We compare the HST spectra with lower resolution International Ultraviolet Explorer (IUE) spectra of the same galaxies and find systematic differences: the bright star clusters targeted in HST's ~1'' apertures provide about 15% of the starburst luminosity traced by IUE's 10'' × 20'' aperture; they are bluer and have stronger stellar-wind features suggesting that the HST apertures have preferentially been placed on the youngest areas of the burst. In contrast, lines arising from the interstellar medium (ISM) show similar equivalent widths in both the large and small aperture observations, suggesting similar ISM properties from larger to smaller scales. In order to quantify the UV spectral morphology of star-forming galaxies, we created a set of UV line indices similar to the standard optical Lick indices. We discuss the relation between the UV spectral morphology and the properties of the galaxy host. We present our atlas of FOS and GHRS spectra both in print and online. The data set is useful as a baseline for comparisons with observations of the rest-frame UV spectra of star-forming galaxies at high redshift.

Leitherer, Claus; Tremonti, Christy A.; Heckman, Timothy M.; Calzetti, Daniela

2011-02-01

139

Star Formation in Galaxies  

NASA Technical Reports Server (NTRS)

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.

1987-01-01

140

Open Star Clusters  

NSDL National Science Digital Library

This site offers information about the formation of star clusters, the pleiades, how to calculate star cluster distances, and much more. There are also some great images that techers can use on this website.

2005-02-11

141

'Polaris, Mark Kummerfeldt's Star, and My Star.'  

ERIC Educational Resources Information Center

In most astronomy courses, descriptions of stars and constellations reveal the western European origins of the astronomers who named them. However, it is suggested that a study of non-western views be incorporated into astronomy curricula. Descriptions of various stars and constellations from different cultures and instructional strategies are…

McLure, John W.

1984-01-01

142

Southern Cool Stars Misclassified as Carbon Stars  

NASA Astrophysics Data System (ADS)

We report a list of 24 red stars classified as carbon stars by one author. Close examination of them on near-IR objective-prism plates reveals that they are of M type or earlier. Three are variable in the ASAS-3 Catalog.

MacConnell, D. J.

2006-01-01

143

A star tracking algorithm suitable for star sensor  

NASA Astrophysics Data System (ADS)

The sufficient attitude knowledge including location of recognized stars in star image can be obtained with Lost-in-Space case. In order to make use of the sufficient attitude knowledge, the star sensor may work in star tracking case. To achieve this, a star tracking algorithm is proposed in this paper. The previous location of recognized stars in star image may be used to obtain location of observed star in proper region of current star image with the star tracking algorithm. The simulations and real sky experiment results show that the star tracking algorithm proposed in this paper not only improves update rate of star sensor, but also avoids fault star pattern recognition. Finally, a star sensor featuring star tracking algorithm proposed in this paper was for on-orbit demonstration.

Li, Baohua; Zhang, Yingchun; Li, Huayi; Wang, Changhong

2007-03-01

144

Star formation history of early-type galaxies in low density environments. I. Nuclear line-strength indices  

NASA Astrophysics Data System (ADS)

This paper is the first of a series \\cite[(Longhetti et al. 1997a,b)]{lon97} dedicated to the study of the star formation history in early-type galaxies which show fine structures and/or signatures of interaction. It presents nuclear line-strength indices for a sample composed of 21 shell galaxies, from the \\cite[Malin & Carter (1983)]{mal83} southern survey, and 30 members of isolated interacting pairs, from the \\cite[Reduzzi & Rampazzo (1995)]{red95} catalogue, located in low density environments. The spectral range covers 3700 Angstroms < lambda < 5700 Angstroms at 2.1 Angstroms FWHM resolution. We measure 16 red (lambda > 4200 Angstroms) indices defined by the Lick Group. Measures have been transformed into the Lick-IDS ``standard'' system. The procedure has been tested on a set of 5 elliptical galaxies selected from the \\cite[Gonzalez (1993)]{gon93} sample. We derive also three blue (lambda < 4200) indices, namely Delta (4000 Angstroms) defined by \\cite[Hamilton (1985)]{ham85}, H+K(CaII) and Hdelta /FeI defined by \\cite[Rose (1984, 1985)]{ros84}. Blue indices are correlated to the age of the last starburst occurred in a galaxy \\cite[(Leonardi & Rose 1996)]{leo96}. The determination of these indices, the estimate of the measurement errors and the correction for the galaxies velocity dispersions are discussed in detail. In the Appendix A we present the indices for a set of hot stars (T> 10000 K) which may be used for extending W92 fitting functions toward high temperatures. Based on observations obtained at ESO, La Silla, Chile. Tables 1-8 are also available in electronic form at CDS and Tables 9-15 are only available in electronic form at CDS: via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

Longhetti, M.; Rampazzo, R.; Bressan, A.; Chiosi, C.

1998-06-01

145

Spectroscopy of be stars  

NASA Astrophysics Data System (ADS)

This chapter describes non supergiant B-type stars that show emission lines, called Be stars. The emission is caused by the presence of a circumstellar decretion disk. Many physical phenomena are thought to be involved in these stars, such as rapid rotation, pulsations and magnetic fields, and give rise to variations. Spectroscopy is used as a diagnostic tool to study Be stars, by professional astronomers as well as by amateurs.

Neiner, C.

2011-04-01

146

Chromospheres of Coronal Stars  

NASA Technical Reports Server (NTRS)

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

Linsky, Jeffrey L.; Wood, Brian E.

1996-01-01

147

Supernova Star Maps  

NSDL National Science Digital Library

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.

Pacific, Astronomical S.

2008-01-01

148

Star Field Simulator.  

National Technical Information Service (NTIS)

A Star Field Simulator has been developed to serve as a source of radiation for the ASTRO Star Tracker. The star tracker and simulator are components of a motion compensation test facility located at Marshall Space Flight Center in Huntsville, Alabama. Pr...

1985-01-01

149

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.

2007-06-12

150

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.

151

America's Star Libraries  

ERIC Educational Resources Information Center

"Library Journal"'s new national rating of public libraries, the "LJ" Index of Public Library Service, identifies 256 "star" libraries. It rates 7,115 public libraries. The top libraries in each group get five, four, or three Michelin guide-like stars. All included libraries, stars or not, can use their scores to learn from their peers and improve…

Lyons, Ray; Lance, Keith Curry

2009-01-01

152

Strange Quark Star Crusts  

SciTech Connect

If strange quark matter is absolutely stable, some neutron stars may be strange quark stars. Strange quark stars are usually assumed to have a simple liquid surface. We show that if the surface tension of droplets of quark matter in the vacuum is sufficiently small, droplets of quark matter on the surface of a strange quark star may form a solid crust on top of the strange quark star. This solid crust can significantly modify the predictions for the photon emission for the surface in an observable way.

Steiner, Andrew W. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States)

2007-02-27

153

Neutron Star Collision  

NSDL National Science Digital Library

Systems of orbiting neutron stars are born when the cores of two old stars collapse in supernova explosions. Neutron stars have the mass of our Sun but are the size of a city, so dense that boundaries between atoms disappear. Einsteins theory of general relativity predicts that the orbit shrinks from ripples of space-time called gravitational waves. After about 1 billion simulation years, the two neutron stars closely circle each other at 60,000 revolutions per minute. The stars finally merge in a few milliseconds, sending out a burst of gravitational waves.

Bock, Dave; Shalf, John; Swesty, Doug; Calder, Alan; Wang, Ed

1999-01-21

154

Ponderable soliton stars  

NASA Technical Reports Server (NTRS)

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.

Chiu, Hong-Yee

1990-01-01

155

Metallicity and Ionization Balance in a Very Metal-Poor Galactic Halo Turnoff Star  

NASA Astrophysics Data System (ADS)

We have derived the iron metallicity of the very metal-poor main-sequence turnoff star HD 84937, using many Fe I and Fe II transitions over the largest wavelength range to date, 2300-7500A. The high resolution spectra for this work were taken with the Lick 3.0m Hamilton, the Magellan MIKE, and the Hubble Space Telescope STIS echelle spectrographs. From a standard LTE analysis, we derive metallicities for HD 84937 from both Fe I and Fe II lines that are consistent with literature values, [Fe/H] -2.2. These are the first results in our project to provide new abundances for many Fe-peak elements from their neutral and ionized species using both visible and UV wavelength data. HD 84937 provides a benchmark for assessing the departures from LTE ionization equilibria in cooler, lower gravity very metal-poor stars. This work has been supported by The University of Texas Astronomy Department Cox Undergraduate Excellence Fund to MAA, NSF grants AST-0607708, AST-0908978 to CS and AST-0707447 to JJC, and NASA Grant NNX08AQ09G to JEL.

Alvarez, Matthew; Sneden, C.; Fulbright, J.; Lawler, J. E.; Sobeck, J. S.; Cowan, J. J.

2010-01-01

156

Blue Horizontal-Branch Stars in Old, Metal-rich Stellar Systems  

NASA Astrophysics Data System (ADS)

Twenty years ago, Burstein et al. recognized that the metal-rich globular clusters in the Andromeda galaxy (M31) exhibited anomalously strong Balmer and CN lines compared to Milky Way clusters. They suggested that younger ages might be the cause, unless blue stars above the main-sequence turnoff or on the horizontal branch were uncommonly prominent. Here we test these suggestions by fitting the detailed mid-ultraviolet (2280-3120 Å) and optical (3850-4750 Å) spectra of one moderately metal-rich M31 globular cluster, G1. We explore the effects of a wide range of nonsolar temperatures and abundance ratios, by combining a small set of theoretical stellar spectra, such as those calculated by Peterson, Dorman, & Rood in 2001 using extensively updated atomic line constants. To match the mid-UV fluxes of G1, we find that hot components with Teff>=8000 K must be included. We obtain a very good fit with cool and hot blue horizontal-branch (BHB) stars, but less satisfactory fits for blue straggler stars, those hotter than the main-sequence turnoff. The G1 color-magnitude diagram does show cool BHB stars, and the color of its giant branch supports the metallicity of one-sixth the solar value deduced from the composite spectrum with BHB stars. The turnoff temperature of the best-fit model is consistent with that of turnoff stars in Galactic globular clusters and the field halo, indicating that G1 is comparably old. Because metal-rich cool BHB and extremely blue HB stars have now been found within our own Galaxy-in open clusters, globular clusters, and the field of the bulge-we suggest that these hot HB stars be considered in fitting spectra of metal-rich populations, such as the Andromeda globular clusters, to avoid possible underestimates of their ages. We plan to make the relevant spectral calculations available as part of our Hubble Treasury program. Based on observations with the Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under contract with the National Aeronautics and Space Administration (NASA). Based on observations obtained with the Shane Telescope at Mount Hamilton, UCO/Lick Observatory.

Peterson, Ruth C.; Carney, Bruce W.; Dorman, Ben; Green, Elizabeth M.; Landsman, Wayne; Liebert, James; O'Connell, Robert W.; Rood, Robert T.

2003-05-01

157

PG 1159 Stars  

NASA Astrophysics Data System (ADS)

The PG 1159 stars form a small group of about 30 objects. They are named after the prototype PG 1159-035 (=GW Vir), which was discovered in the Palomar-Green survey. They are hot post-asymptotic giant branch (post-AGB) stars and their location in the HR diagram coincides with the hottest central stars of PLANETARY NEBULAE (CSPN) and the hottest WHITE DWARFS (WD). The most peculiar characteristic ...

Werner, K.; Murdin, P.

2000-11-01

158

Sizing up the stars  

NASA Astrophysics Data System (ADS)

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

Boyajian, Tabetha S.

159

Jars of Stars: Advanced  

NSDL National Science Digital Library

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. Use multiplication to create a close estimate of how many stars are in each jar. The activity guide contains a material list, sample questions to ask, literary connections, extensions, and alignment to local and national standards.

Houston, Children'S M.

2004-01-01

160

Orbiting Binary Stars  

NSDL National Science Digital Library

This simulation demonstrates the path of binary stars' orbit. The user is able to set the masses, orbital separation, orbital eccentricity, the inclination angle to our line of sight, and the angle of the nodes of two orbiting stars. The observed velocities of the two stars, and the Doppler shifted spectral lines are also shown in the upper right box. The site also includes definitions of terms used, instructions on how to use the simulation and a few examples.

Kolena, John

2007-12-11

161

STAR TPC Gas System  

Microsoft Academic Search

The STAR TPC (Time Projection Chamber) Gas System supplies either of two mixtures, P10 (Ar 90% + CH4 10%) or C2H6 50% + He 50%, to the STAR TPC (STAR Project, Brookhaven, USA) at a controlled pressure. This system regulates the pressure and com- position of the gas while monitoring gas temperature, O2 and H2O. A computer data ac- quisition

L. Kotchenda; S. Kozlov; P. Kravtsov; A. Markova; M. Strikhanov; B. Stringfellow; V. Trofimova; R. Wells; H. Wiemand

2002-01-01

162

Neutron star cooling  

Microsoft Academic Search

The impact of nuclear physics theories on cooling of isolated neutron stars\\u000ais analyzed. Physical properties of neutron star matter important for cooling\\u000aare reviewed such as composition, the equation of state, superfluidity of\\u000avarious baryon species, neutrino emission mechanisms. Theoretical results are\\u000acompared with observations of thermal radiation from neutron stars. Current\\u000aconstraints on theoretical models of dense matter,

D. G. Yakovlev; O. Y. Gnedin; M. E. Gusakov; A. D. Kaminker; K. P. Levenfish; A. Y. Potekhin

2005-01-01

163

NASA's Nearby Stars Project  

NASA Astrophysics Data System (ADS)

In 1998, NASA initiated the Nearby Stars Project (NSTARS), which intends to make a vigorous reconnaissance of stars within 20 parsecs of the Sun. The NSTARS goal is to develop a comprehensive observational and theoretical understanding of the nearest stars. Information is being gathered about each star's fundamental characteristics, including: astrometry, luminosity, temperature, optical/infrared spectral energy distribution, age, activity level, metallicity, companions (both stellar and planetary), and quantification of exozodiacal dust, if any. NSTARS currently includes two primary areas of effort, Database and Research. Construction has begun on the Database, which will be web-accessible and provide important high-quality information about the nearest stars. Examples will be shown of prototype "Front" and "Back" pages included in the Database. An important difference between NSTARS and previous nearby star efforts such as the Catalog of Nearby Stars is the presence of a significant, directed, Research effort. NSTARS is supporting observing programs to discover "missing" members of the nearby star sample, and to characterize the population astrometrically, photometrically, and spectroscopically. NSTARS will also impose quality control on data already available. Given the public's clear interest in stars near to the Sun, a third area of effort, Education, is planned once the first two efforts are firmly established. Through the NSTARS Project, a high-quality resource will be available for professional astronomers worldwide, as well as any members of the public who might be interested.

Henry, T. J.; Backman, D. E.; Christensen, R.; Moller, K.; Vacin, E.; West, S.

1998-12-01

164

Star Market Scandal  

NSDL National Science Digital Library

The is one several activities in which students are required to access and analyze actual data from NASA missions, including video interviews with real NASA scientists, to solve a mystery. In this mystery, students explore stars and their properties, investigate the different characteristics of stars, and look for trends and patterns to determine what kinds of stars different companies are buying, and why. During the activity, students analyze a list of stars purchased by each company using tools showing a star's luminosity in infrared, x-ray, and visible ranges of light, and tools that plot the stars in different ways. Star Market can be used as a supplemental learning tool to support the scientific method, understanding the life cycle of stars, and learning about the different reasons scientists study stars. It is one several activities within "Space Mysteries," a series of inquiry-driven, interactive Web explorations. Each Mystery in "Space Mysteries" is designed to teach at least one physical science concept (e.g. interactions of energy and matter, structures and properties of matter, energy, motion, or forces), and is accompanied by materials to be used by classroom teachers.

165

Delta Scuti stars: Theory  

SciTech Connect

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.

Guzik, J.A.

1998-03-01

166

Massive soliton stars  

NASA Technical Reports Server (NTRS)

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.

Chiu, Hong-Yee

1990-01-01

167

Star Trek in the Schools  

ERIC Educational Resources Information Center

Describes specific educational programs for using the Star Trek TV program from kindergarten through college. For each grade level lesson plans, ideas for incorporating Star Trek into future classes, and reports of specific programs utilizing Star Trek are provided. (SL)

Journal of Aerospace Education, 1977

1977-01-01

168

Stars and Flowers, Flowers and Stars  

NASA Astrophysics Data System (ADS)

The author, a graduated from the Bucharest University (1964), actually living and working in Israel, concerns his book to variable stars and flowers, two domains of his interest. The analogies includes double stars, eclipsing double stars, eclipses, Big Bang. The book contains 34 chapters, each of which concerns various relations between astronomy and other sciences and pseudosciences such as Psychology, Religion, Geology, Computers and Astrology (to which the author is not an adherent). A special part of the book is dedicated to archeoastronomy and ethnoastronomy, as well as to history of astronomy. Between the main points of interest of these parts: ancient sanctuaries in Sarmizegetusa (Dacia), Stone Henge(UK) and other. The last chapter of the book is dedicated to flowers. The book is richly illustrated. It is designed for a wide circle of readers.

Minti, Hari

2012-12-01

169

Winds from Cool Stars  

Microsoft Academic Search

The structure of the outer atmospheres of luminous cool stars reveals the evolution of magnetic activity as dynamo heating decreases and atmospheres expand while the stars evolve across the color-magnitude diagram. The relationship between winds and high temperature material can also be investigated. A comprehensive picture of the dynamics of the outer atmospheres is constructed based principally upon recent spectroscopic

A. K. Dupree

2004-01-01

170

The North (Wall) Star  

NSDL National Science Digital Library

Celestial navigation is the art and science of finding one's geographic position by means of astronomical observations, particularly by measuring altitudes of celestial objects â sun, moon, planets or stars. This activity starts with a basic, but very important and useful, celestial measurement: measuring the altitude of Polaris (the North Star) or measuring the latitude.

Integrated Teaching And Learning Program

171

Science through ARts (STAR)  

ERIC Educational Resources Information Center

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…

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

2005-01-01

172

Party with the Stars.  

ERIC Educational Resources Information Center

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)

Blaine, Lloyd

1997-01-01

173

The Violent Neutron Star  

NASA Astrophysics Data System (ADS)

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.

Watts, A. L.

2012-12-01

174

Eclipsing Binary Stars  

NSDL National Science Digital Library

This site offers information about binary stars. There are many complex computations in this website along with other links to help explain the concepts. They are in the form of websites, articles, software, and visuals. Some of the topics include: a simple model for computing light curves, shape of a rotating star, and many more.

2004-07-17

175

Quarkonium at STAR.  

National Technical Information Service (NTIS)

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, ...

T. J. LeCompte

1998-01-01

176

Nebraska STARS: Achieving Results  

ERIC Educational Resources Information Center

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

Roschewski, Pat; Isernhagen, Jody; Dappen, Leon

2006-01-01

177

Neutron star models  

NASA Technical Reports Server (NTRS)

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.

Canuto, V.; Bowers, R. L.

1981-01-01

178

Hyperons in neutron stars  

SciTech Connect

Generalized beta equilibrium involving nucleons, hyperons, and isobars is examined for neutron star matter. The hyperons produce a considerable softening of the equation of state. It is shown that the observed masses of neutron stars can be used to settle a recent controversy concerning the nuclear compressibility. Compressibilities less than 200 MeV are incompatible with observed masses. 7 refs., 9 figs.

Glendenning, N.K.

1986-04-01

179

Lives and Deaths of Stars  

NSDL National Science Digital Library

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.

Strobel, Nick

2009-08-06

180

Variability of carbon stars  

NASA Astrophysics Data System (ADS)

The results of photographic monitoring of carbon stars situated in several regions near the galactic equator, carried out with the Schmidt telescope, are reported. Almost all stars with light range in red passband (0.63 micron) exceeding one magnitude turned out to be long-period variables. About 10 percent of all carbon stars have light range in V passband larger than two magnitudes. In most cases, variations of long-period carbon stars can be regarded as a sum of two components: periodical and secondary. The cycle length of the secondary component is between 2 to 10 cycles of the periodic component. Carbon stars with thick circumstellar dust shells have extremely long (about 600 days) periods and a steep ascending branch of light curve. In the blue-violet radiation of the object CIT 6 = RW LMi, the periodic component of variations is absent, although the light range of the secondary component and short time fluctuations are the largest.

Alksnis, A.

181

Activity Cycles in Stars  

NASA Technical Reports Server (NTRS)

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.

Hathaway, David H.

2009-01-01

182

New Analyses of Star-to-Star Abundance Variations among Bright Giants in the Mildly Metal-poor Globular Cluster M5  

NASA Astrophysics Data System (ADS)

We present a chemical composition analysis of 36 giant stars in the mildly metal-poor (<[Fe/H]>=-1.21) globular cluster M5 (NGC 5904). The analysis makes use of high-resolution data acquired for 25 stars at the Keck I telescope, as well as a reanalysis of the high-resolution spectra for 13 stars acquired for an earlier study at Lick Observatory. We employed two analysis techniques: (1) adopting standard spectroscopic constraints, including setting the surface gravity from the ionization equilibrium of iron, and (2) subsequent to investigating alternative approaches, adopting an analysis consistent with the non-LTE precepts as recently described by Thévenin & Idiart. The abundance ratios we derive for magnesium, silicon, calcium, scandium, titanium, vanadium, nickel, barium, and europium in M5 show no significant abundance variations, and the ratios are comparable to those of halo field stars. However, large variations are seen in the abundances of oxygen, sodium, and aluminum, the elements that are sensitive to proton-capture nucleosynthesis. These variations are well-correlated with the CN band strength index S(3839). Surprisingly, in M5 the dependence of the abundance variations on logg is in the opposite sense to that discovered in M13 by the Lick-Texas group where the relationship provided strong evidence in support of the evolutionary scenario. The present analysis of M5 giants does not necessarily rule out an evolutionary scenario, but it provides no support for it either. In comparing the abundances of M5 and M4 (NGC 6121), another mildly metal-poor (<[Fe/H]>=-1.08) globular cluster, we find that silicon, aluminum, barium, and lanthanum are overabundant in M4 with respect to that seen in M5, confirming and expanding the results of previous studies. In comparing the abundances between these two clusters and others having comparable metallicities, we find that the anticorrelations observed in M5 are similar to those found in more metal-poor clusters, M3, M10, and M13 (<[Fe/H]>=-1.5 to -1.6), whereas the behavior in M4 is more like that of the more metal-rich globular cluster M71 (<[Fe/H]>~-0.8). We conclude that among stars in Galactic globular clusters there is no definitive ``single'' value of [X/Fe] at a given [Fe/H] for at least some ?-capture, odd-Z, and slow neutron-capture process elements, in this case, silicon, aluminum, barium, and lanthanum. Based in part on observations obtained with the W. M. Keck Observatory, which is operated by the California Association for Research in Astronomy, Inc., on behalf of the University of California, the California Institute of Technology, and the National Aeronautics and Space Administration.

Ivans, Inese I.; Kraft, Robert P.; Sneden, Christopher; Smith, Graeme H.; Rich, R. Michael; Shetrone, Matthew

2001-09-01

183

The ? Orionis Star Forming Region  

NASA Astrophysics Data System (ADS)

Around the O8 star ? Orionis is a highly evolved star-forming region, comprising recently formed stars from 0.2 M?Mar to 24 M?Mar and dark clouds actively forming stars, all within a 30-pc radius ring of dust and neutral and molecular hydrogen. The spatial and age distributions of the stars show that originally star formation occurred in an elongated giant molecular cloud, with the most massive stars forming in a dense central core. A supernova is suggested as the mechanism that terminated star formation in that core and formed the surrounding ring. Star formation continues in remnant dark clouds distant from the original core. The local initial mass functions differ significantly across the region, although the global IMF is field-like. Interestingly, the lack of H? emission in stars near ? Ori indicates that the environment of the massive stars was not conducive for the survival of accretion disks.

Mathieu, R. D.

2008-12-01

184

Computational Star Formation (IAU S270)  

NASA Astrophysics Data System (ADS)

1. Historical introduction; 2. Individual star formation: observations; 3. Low-mass star formation: observations; 4. Individual star formation: theory; 5. Formation of clusters: observations; 6. Formation of clusters: theory; 7. Numerical methods: MHD; 8. Numerical methods: radiative dynamics; 9. Local star formation processes; 10. Star formation feedback; 11. Star formation on galactic scales; 12. Special purpose hardware; 13. Computational methods; 14. Radiation diagnostics of star formation; 15. Large scale star formation; 16. Cosmological star formation; 17. Computational star formation: Summary; Index.

Alves, João.; Elmegreen, Bruce G.; Girart, Josep M.; Trimble, Virginia

2011-05-01

185

Hot Subdwarf Stars  

NASA Astrophysics Data System (ADS)

Hot subdwarf stars (sdBs, sdOs) are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. They are found in all Galactic stellar populations and are sufficiently common to account for the UV-upturn of early-type galaxies. About half of the sdBs reside in close binaries; companions are white dwarfs or low-mass main-sequence stars. Binary population-synthesis models explain naturally the actual sdB binary fractions of field and globular cluster stars as well as of He-sdOs if white-dwarf mergers are considered. Hot helium flashes explain the chemical composition of He-sdOs. Asteroseismology of a dozen pulsating sdB stars allowed determination of their masses and detection of a planet to V391 Peg. The discoveries of an sdO star unbound to the Galaxy, potential SN Ia progenitors and probably a hidden population of neutron stars or black hole companions have great impact on astrophysics at large.

Heber, Ulrich

2009-09-01

186

Measuring stars with Gaia  

NASA Astrophysics Data System (ADS)

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.

Thévenin, F.

2013-12-01

187

Variations in surface roughness of seven orthodontic archwires: an SEM-profilometry study  

PubMed Central

Objective The purpose of this study was to evaluate the surface roughness (SR) of 2 types of orthodontic archwires made by 4 different manufacturers. Methods This in vitro experimental study was conducted on 35 specimens of 7 different orthodontic archwires, namely, 1 nickel-titanium (NiTi) archwire each from the manufacturers American Orthodontics, OrthoTechnology, All-Star Orthodontics, and Smart Technology, and 1 stainless steel (SS) archwire each from the manufacturers American Orthodontics, OrthoTechnology, and All-Star Orthodontics. After analyzing the composition of each wire by energy-dispersive X-ray analysis, the SR of each wire was determined by scanning electron microscopy (SEM) and surface profilometry. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests (? < 0.05). Results The average SR of NiTi wires manufactured by Smart Technology, American Orthodontics, OrthoTechnology, and All-Star Orthodontics were 1,289 ± 915 A°, 1,378 ± 372 A°, 2,444 ± 369 A°, and 5,242 ± 2,832 A°, respectively. The average SR of SS wires manufactured by All-Star Orthodontics, OrthoTechnology, and American Orthodontics were 710 ± 210 A°, 1,831 ± 1,156 A°, and 4,018 ± 2,214 A°, respectively. Similar to the results of profilometry, the SEM images showed more defects and cracks on the SS wire made by American Orthodontics and the NiTi wire made by All-Star Orthodontics than others. Conclusions The NiTi wire manufactured by All-Star Orthodontics and the SS wire made by American Orthodontics were the roughest wires.

Rakhshan, Vahid; Pousti, Maryam; Rahimi, Hajir; Shariati, Mahsa; Aghamohamadi, Bahareh

2012-01-01

188

Spectroscopy of ? Doradus stars  

NASA Astrophysics Data System (ADS)

The musician programme at the University of Canterbury has been successfully identifying pulsation modes in many ? Doradus stars using hundreds of ground-based spectroscopic observations. This paper describes some of the successful mode identifications and emerging patterns of the programme. The hybrid ? Doradus/? Scuti star HD 49434 remains an enigma, despite the analysis of more than 1700 multi-site high-resolution spectra. A new result for this star is apparently distinct line-profile variations for the ? Doradus and ? Scuti frequencies.

Brunsden, E.; Pollard, K. R.; Cottrell, P. L.; Wright, D. J.; De Cat, P.; Kilmartin, P. M.

2014-02-01

189

Kepler Star Wheels  

NSDL National Science Digital Library

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.

190

StarDate Online  

NSDL National Science Digital Library

This on-line version of StarDate astronomy magazine provides current viewing information, a sky almanac, Moon phase calculator, sunrise and sunset calculator, planet viewing information, and meteor shower updates. News and Features contains information and details on the latest findings and research in the field of astronomy. Resources contains an image gallery, an astroglossary, and solar system, constellation, and star guides. The Radio section contains past radio programs by date, or searchable by subject. Also available are an archive database of past StarDate articles, and a teacher's section with ideas for teaching astronomy concepts in the classroom.

191

VV Cephei Type Stars  

NASA Astrophysics Data System (ADS)

Three new VV Cephei-type stars were discovered by Barbier (1971). We propose to observe these systems to detect and characterize the continuum of the companion and to investigate emission lines from the cool M star and/or by circumstellar material. One star (BD+63 0003) has been monitored extensively by one of the investigators (EFG) and observations would be scheduled about 6 to 9 months apart to coincide with maximum and minimum light in order to detect any dependence of emission activity or interaction with the hot component on the pulsations of the M supergiant component.

Shaw, J. Scott

1984-07-01

192

Modeling of Be Stars  

NASA Astrophysics Data System (ADS)

Be stars are still a big unknown in respect of origin and geometry of circumstellar disk around a star. The program shellspec is designed to solve a simple radiative transfer along the line of sight in three-dimensional moving media, so it is able to compute synthetic spectrum for our case (a star with a disk). Our goal was to develop an effective method to search in parameter space which can allow us to find a good estimate of physical parameters of the disk.

Šejnová, K.; Votruba, V.; Koubská, P.

2012-12-01

193

A principal component analysis approach to the star formation history of elliptical galaxies in compact groups  

NASA Astrophysics Data System (ADS)

Environmental differences in the stellar populations of early-type galaxies are explored using principal component analysis (PCA), focusing on differences between elliptical galaxies in Hickson Compact Groups (HCGs) and in the field. The method is model-independent and purely relies on variations between the observed spectra. The projections (PC1, PC2) of the observed spectra on the first and second principal components reveal a difference with respect to environment, with a wider range in PC1 and PC2 in the group sample. We define a spectral parameter (? ? 0.36PC1-PC2) which simplifies this result to a single number: field galaxies have a very similar value of ?, whereas HCG galaxies span a wide range in this parameter. The segregation is found regardless of the way the input spectral energy distributions (SEDs) are presented to PCA (i.e. changing the spectral range; using uncalibrated data; subtracting the continuum or masking the SED to include only the Lick spectral regions). Simple models are applied to give physical meaning to the PCs. We obtain a strong correlation between the values of ? and the mass fraction in younger stars, so that some group galaxies present a higher fraction of them, implying a more complex star formation history in groups. Regarding `dynamically related' observables such as a4 or velocity dispersion, we find a correlation with PC3, but not with either PC1 or PC2. PCA is more sensitive than other methods based on a direct analysis of observables such as the structure of the surface brightness profile or the equivalent width of absorption lines. The latter do not reveal any significant variation between field and compact group galaxies. Our results imply that the presence of young stars only amounts to a fraction of a per cent in its contribution to the total variance, reflecting the power of PCA as a tool to extract small variations in the spectra from unresolved stellar populations.

Ferreras, Ignacio; Pasquali, Anna; de Carvalho, Reinaldo R.; de la Rosa, Ignacio G.; Lahav, Ofer

2006-08-01

194

On the conversion of neutron stars into quark stars  

NASA Astrophysics Data System (ADS)

The possible existence of two families of compact stars, neutron stars and quark stars, naturally leads to a scenario in which a conversion process between the two stellar objects occurs with a consequent release of energy of the order of 1053 erg. We discuss recent hydrodynamical simulations of the burning process and neutrino diffusion simulations of cooling of a newly formed strange star. We also briefly discuss this scenario in connection with recent measurements of masses and radii of compact stars.

Pagliara, Giuseppe

2014-03-01

195

The Constellations and their Stars  

NSDL National Science Digital Library

This website is a tutorial on constellations and the stars in them. It offers an alphabetical and monthly listing of the constellations. It also provides a listing of stars, messier objects, and a list of the brightest stars in the sky. The user can also use the website's interactive star chart, Milky Way photos, or helpful links.

Dolan, Chris

2005-05-15

196

Cool luminous stars  

NASA Technical Reports Server (NTRS)

The consequences of magnetic fields for the atmospheres of cool stars are addressed based on IUE and Einstein Observatory observations. Gross atmospheric structure data for cool luminous stars are discussed, and the relevance of the observations for the energy balance and nonradiative heating rates is considered. Data from X-ray fluxes, low dispersion UV spectra, and high dispersion spectra in the region of the Mg II resonance lines are presented. New results on cool star atmospheres provided by high dispersion UV spectra are considered, including those pertaining to spectral line identification, identification of emission components in close binary systems, densities and atmospheric extension, emission line widths, properties of stellar winds as derived from IUE data, and systematic flows of transition region plasma. An explanation for the observed spectra of cool giants and supergiants is proposed in terms of active, quiet, and hybrid stars.

Linsky, J. L.

1982-01-01

197

Winds from cool stars  

NASA Technical Reports Server (NTRS)

Spectral observations of cool stars enable study of the presence and character of winds and the mass loss process in objects with effective temperatures, gravities, and atmospheric compositions which differ from that of the Sun. A wealth of recent spectroscopic measurements from the Hubble Space Telescope, and the Extreme Ultraviolet Explorer complement high resolution ground-based measures in the optical and infrared spectral regions. Such observations when combined with realistic semi-empirical atmospheric modeling allow us to estimate the physical conditions in the atmospheres and winds of many classes of cool stars. Line profiles support turbulent heating and mass motions. In low gravity stars, evidence is found for relatively fast (approximately 200 km s(exp -1)), warm winds with rapid acceleration occurring in the chromosphere. In some cases outflows commensurate with stellar escape velocities are present. Our current understanding of cool star winds will be reviewed including the implications of stellar observations for identification of atmospheric heating and acceleration processes.

Dupree, A. K.

1995-01-01

198

Astrophysics: Twinkling stars  

NASA Astrophysics Data System (ADS)

A correlation between stellar brightness variations and the gravitational acceleration at a star's surface has been observed that allows this acceleration to be measured with a precision of better than 25%. See Letter p.427

Christensen-Dalsgaard, Jørgen

2013-08-01

199

Detector limitations, STAR.  

National Technical Information Service (NTIS)

Every detector has limitations in terms of solid angle, particular technologies chosen, cracks due to mechanical structure, etc. If all of the presently planned parts of STAR (Solenoidal Tracker At RHIC) were in place, these factors would not seriously li...

D. G. Underwood

1998-01-01

200

Women and the Stars.  

ERIC Educational Resources Information Center

Described are the contributions of 15 women astronomers to the modern understanding of the stars. Discussed are early women pioneers, early spectrographic studies, and recent women astronomers. A list of 29 references is included. (CW)

Spradley, Joseph L.

1990-01-01

201

Variable star data online  

NASA Astrophysics Data System (ADS)

Roger Pickard, Andy Wilson and Gary Poyner describe the online database of the British Astronomical Association Variable Star Section, a treasure trove of observations stretching back nearly 125 years.

Pickard, Roger; Wilson, Andy; Poyner, Gary

2012-06-01

202

Which stars have planets?  

NASA Technical Reports Server (NTRS)

The question of predicting which stars have planetary systems is discussed, with special attention given to the work of Nakano (1988), who combined scaling arguments with his theory (Nakano, 1987) of formation of planets in the solar system to estimate planetary growth rates around stars of various masses. It is argued that, in addition to stellar mass, the process of planet formation depends on other parameters, such as angular momentum and collisions. The existence of binary and multiple star systems of varying type demonstrates that angular momentum variations can play a crucial role, while the fact that the solar system has four giant planets and four terrestrial planets is considered to be due to the effects of random impacts and scatterings. It is concluded that, at present, the concept of determining what types of planetary systems are to be expected about stars of varying masses cannot be resolved.

Lissauer, J. J.

1989-01-01

203

Sleeping under the stars  

NASA Astrophysics Data System (ADS)

Sherlock Holmes and Dr. Watson went on a camping trip. As they lay down for the night, Holmes said, “Watson, look up at the sky and tell me what you see.”Watson:“! see millions and millions of stars.”

Zirkel, Jack

204

Planets Around Neutron Stars  

NASA Technical Reports Server (NTRS)

The objective of this proposal was to continue investigations of neutron star planetary systems in an effort to describe and understand their origin, orbital dynamics, basic physical properties and their relationship to planets around normal stars. This research represents an important element of the process of constraining the physics of planet formation around various types of stars. The research goals of this project included long-term timing measurements of the planets pulsar, PSR B1257+12, to search for more planets around it and to study the dynamics of the whole system, and sensitive searches for millisecond pulsars to detect further examples of old, rapidly spinning neutron stars with planetary systems. The instrumentation used in our project included the 305-m Arecibo antenna with the Penn State Pulsar Machine (PSPM), the 100-m Green Bank Telescope with the Berkeley- Caltech Pulsar Machine (BCPM), and the 100-m Effelsberg and 64-m Parkes telescopes equipped with the observatory supplied backend hardware.

Wolszczan, Alexander; Kulkarni, Shrinivas R; Anderson, Stuart B.

2003-01-01

205

Galactic and extragalactic star formation  

SciTech Connect

This book present new technology that allows the linking of the physics of local star forming regions to the global star forming properties of galaxies. Galactic star formation and examination of the processes of formation of nearby stars are addressed. Focus is on bipolar outflows and circumstellar disks. Larger scale phenomena in molecular clouds are then discussed, followed by reviews of star formation across the Milky Way.

Pudritz, R.E. (Minnesota Univ., Minneapolis, MN (USA). Heat Transfer Lab.); Fich, M. (Waterloo Univ., ON (Canada))

1988-01-01

206

SPATIAL ECONOMETRIC STAR MODELS  

Microsoft Academic Search

Spatial regression models incorporating non-stationarity in the regression coefficients are popular. In this paper we propose a family of spatial Smooth Transition AutoRegressive (STAR) models inspired by analogous nonlinear approaches developed in the time series literature. Spatial STAR models constitute a parsimonious, easy-to-estimate approach to modeling nonlinear spatial parameter variation and endogenous detection of spatial regimes. A distinct advantage of

Raymond J. G. M. Florax; Valerien O. Pede; Matthew T. Holt

207

Jars of Stars  

NSDL National Science Digital Library

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.

Houston, Children'S M.

2014-04-07

208

The first stars  

NASA Astrophysics Data System (ADS)

The possible nature of the first generation of stars is considered, using a star of 25 Msolar as an example. General nucleosynthesis and the production of CNO catalysts is examined in detail. The increase in neutron excess and its significance for yields from explosive burning is discussed. An estimate of the ratio of ionizing photons to heavy elements produced is derived, for use in early universe simulations.

Arnett, David

209

Chaotic Star Birth  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] [figure removed for brevity, see original site] Click on the image for Poster VersionClick on the image for IRAS 4B Inset

Located 1,000 light years from Earth in the constellation Perseus, a reflection nebula called NGC 1333 epitomizes the beautiful chaos of a dense group of stars being born. Most of the visible light from the young stars in this region is obscured by the dense, dusty cloud in which they formed. With NASA's Spitzer Space Telescope, scientists can detect the infrared light from these objects. This allows a look through the dust to gain a more detailed understanding of how stars like our sun begin their lives.

The young stars in NGC 1333 do not form a single cluster, but are split between two sub-groups. One group is to the north near the nebula shown as red in the image. The other group is south, where the features shown in yellow and green abound in the densest part of the natal gas cloud. With the sharp infrared eyes of Spitzer, scientists can detect and characterize the warm and dusty disks of material that surround forming stars. By looking for differences in the disk properties between the two subgroups, they hope to find hints of the star and planet formation history of this region.

The knotty yellow-green features located in the lower portion of the image are glowing shock fronts where jets of material, spewed from extremely young embryonic stars, are plowing into the cold, dense gas nearby. The sheer number of separate jets that appear in this region is unprecedented. This leads scientists to believe that by stirring up the cold gas, the jets may contribute to the eventual dispersal of the gas cloud, preventing more stars from forming in NGC 1333.

In contrast, the upper portion of the image is dominated by the infrared light from warm dust, shown as red.

2005-01-01

210

Spectroscopic Binary Stars  

NASA Astrophysics Data System (ADS)

Historically, spectroscopic binary stars were binary systems whose nature was discovered by the changing DOPPLER EFFECT or shift of the spectral lines of one or both of the component stars. The observed Doppler shift is a combination of that produced by the constant RADIAL VELOCITY (i.e. line-of-sight velocity) of the center of mass of the whole system, and the variable shift resulting from the o...

Batten, A.; Murdin, P.

2000-11-01

211

The Neutron Star Census  

NASA Astrophysics Data System (ADS)

The paucity of old isolated accreting neutron stars in ROSAT observations is used to derive a lower limit on the mean velocity of neutron stars at birth. The secular evolution of the population is simulated following the paths of a statistical sample of stars for different values of the initial kick velocity, drawn from an isotropic Gaussian distribution with mean velocity 0<=<=550 km s-1. The spin-down, induced by dipole losses and by the interaction with the ambient medium, is tracked together with the dynamical evolution in the Galactic potential, allowing for the determination of the fraction of stars which are, at present, in each of the four possible stages: ejector, propeller, accretor, and georotator. Taking from the ROSAT All Sky Survey an upper limit of ~10 accreting neutron stars within ~140 pc from the Sun, we infer a lower bound for the mean kick velocity, >~200-300 km s-1, corresponding to a velocity dispersion ?V>~125-190 km s-1. The same conclusion is reached for both a constant magnetic field (B~1012 G) and a magnetic field decaying exponentially with a timescale ~109 yr. Such high velocities are consistent with those derived from radio pulsar observations. Present results, moreover, constrain the fraction of low-velocity stars, which could have escaped pulsar statistics, to less than 1%.

Popov, S. B.; Colpi, M.; Treves, A.; Turolla, R.; Lipunov, V. M.; Prokhorov, M. E.

2000-02-01

212

MMT Hypervelocity Star Survey  

NASA Astrophysics Data System (ADS)

We describe a new survey for unbound hypervelocity stars (HVSs), stars traveling with such extreme velocities that dynamical ejection from a massive black hole is their most likely origin. We investigate the possible contribution of unbound runaway stars, and show that the physical properties of binaries constrain low-mass runaways to bound velocities. We measure radial velocities for HVS candidates with the colors of early A-type and late B-type stars. We report the discovery of six unbound HVSs with velocities and distances exceeding the conservative escape velocity estimate of Kenyon and collaborators. We additionally report four possibly unbound HVSs with velocities and distances exceeding the lower escape velocity estimate of Xue and collaborators. These discoveries increase the number of unbound HVSs by 60%-100%. Other survey objects include 19 newly identified z ~ 2.4 quasars. One of the HVSs may be a horizontal branch star, consistent with the number of evolved HVSs predicted by Galactic center ejection models. Finding more evolved HVSs will one day allow a probe of the low-mass regime of HVSs and will constrain the mass function of stars in the Galactic center.

Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J.

2009-01-01

213

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

SciTech Connect

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.

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

214

Star formation around isolated T Tauri stars?  

NASA Astrophysics Data System (ADS)

The authors want to present their search for young stellar objects around the two isolated T Tau stars TW Hya (Rucinski and Krautter 1983) and CoD -29°8887 (de la Reza et al. 1989). From the known spectroscopic features of these objects, TW Hya is to be classified as a classical T Tau star (CTTS), but it is not associated with a dark cloud region like all other known CTTSs. The same situation turns out for the weak-line T Tau star (WTTS) CoD -29°8887. One possible explanation for their isolated position is that they have formed from small dark clouds or globules, which were later destroyed. The authors carried out two ROSAT PSPC observations pointing at TW Hya and CoD -29°8887 and used a source detection procedure considering all the standard ROSAT energy bands to test this hypothesis. Spectroscopic follow-up observations were made for 24 possible T Tauri candidates, but there are no further low-mass young stellar objects in the vicinity of the two targets. The study shows that the objects are definitely not formed in a cluster at the positions of the objects.

Hoff, W.; Pfau, W.; Henning, T.

1996-02-01

215

A Four-planet System Orbiting The K0V Star HD 141399  

NASA Astrophysics Data System (ADS)

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 yr 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 MJ , 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.

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

2014-06-01

216

Life Cycle of Stars  

NASA Technical Reports Server (NTRS)

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.

1999-01-01

217

Blurred Star Image Processing for Star Sensors under Dynamic Conditions  

PubMed Central

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.

Zhang, Weina; Quan, Wei; Guo, Lei

2012-01-01

218

Blurred star image processing for star sensors under dynamic conditions.  

PubMed

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

Zhang, Weina; Quan, Wei; Guo, Lei

2012-01-01

219

Pre-main sequence stars, emission stars and recent star formation in the Cygnus region  

NASA Astrophysics Data System (ADS)

The recent star formation history in the Cygnus region is studied using 5 clusters (IC 4996, NGC 6910, Berkeley 87, Biurakan 2 and Berkeley 86). The optical data from the literature are combined with the 2MASS data to identify the pre-main sequence (pre-MS) stars as stars with near IR excess. We identified 93 pre-MS stars and 9 stars with H_alpha emission spectra. The identified pre-MS stars are used to estimate the turn-on age of the clusters. The duration of star formation was estimated as the difference between the turn-on and the turn-off age. We find that, NGC 6910 and IC 4996 have been forming stars continuously for the last 6 -- 7 Myr, Berkeley 86 and Biurakan 2 for 5 Myr and Berkeley 87 for the last 2 Myr. This indicates that the Cygnus region has been actively forming stars for the last 7 Myr, depending on the location. Nine emission line stars were identified in 4 clusters, using slit-less spectra (Be 87 - 4 stars; Be 86 - 2 stars, NGC 6910 - 2 stars and IC 4996 - 1 star). The individual spectra were obtained and analysed to estimate stellar as well as disk properties. All the emission stars are in the MS, well below the turn-off, in the core hydrogen burning phase. These stars are likely to be Classical Be (CBe) stars. Thus CBe phenomenon can be found in very young MS stars which are just a few (2--7) Myr old. This is an indication that CBe phenomenon need not be an evolutionary effect.

Bhavya, B.; Mathew, Blesson; Subramaniam, Annapurni

220

Chemical Evolution of Binary Stars  

NASA Astrophysics Data System (ADS)

Energy generation by nuclear fusion is the fundamental process that prevents stars from collapsing under their own gravity. Fusion in the core of a star converts hydrogen to heavier elements from helium to uranium. The signature of this nucleosynthesis is often visible in a single star only for a very short time, for example while the star is a red giant or, in massive stars, when it explodes. Contrarily, in a binary system nuclear-processed matter can captured by a secondary star which remains chemically polluted long after its more massive companion star has evolved and died. By probing old, low-mass stars we gain vital insight into the complex nucleosynthesis that occurred when our Galaxy was much younger than it is today. Stellar evolution itself is also affected by the presence of a companion star. Thermonuclear novae and type Ia supernovae result from mass transfer in binary stars, but big questions still surround the nature of their progenitors. Stars may even merge and one of the challenges for the future of stellar astrophysics is to quantitatively understand what happens in such extreme systems. Binary stars offer unique insights into stellar, galactic and extragalactic astrophysics through their plethora of exciting phenomena. Understanding the chemical evolution of binary stars is thus of high priority in modern astrophysics.

Izzard, R. G.

2013-02-01

221

Polydisperse star polymer solutions  

PubMed

We analyze the effect of polydispersity in the arm number on the effective interactions, structural correlations, and phase behavior of star polymers in a good solvent. The effective interaction potential between two star polymers with different arm numbers is derived using scaling theory. The resulting expression is tested against monomer-resolved molecular dynamics simulations. We find that the theoretical pair potential is in agreement with the simulation data in a much wider polydispersity range than other proposed potentials. We then use this pair potential as an input in a many-body theory to investigate polydispersity effects on the structural correlations and the phase diagram of dense star polymer solutions. In particular, we find that a polydispersity of 10%, which is typical in experimental samples, does not significantly alter previous findings for the phase diagram of monodisperse solutions. PMID:11102050

von Ferber C; Jusufi; Watzlawek; Likos; Lowen

2000-11-01

222

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.

2007-04-13

223

GuideStar  

NSDL National Science Digital Library

Donors and philanthropists can now more easily compare and monitor organizations to which they may contribute, while nonprofit organizations can perhaps spend less of their resources on fundraising. These are the goals of Philanthropic Research, Inc's GuideStar, a clearinghouse of information on more than 600,000 charities and nonprofit organizations. GuideStar hosts a searchable database, a newsletter, employment and volunteer opportunity listings, and valuable articles in addition to lists of links for both donors and nonprofit organizations. Database information includes brief descriptions of the charities/nonprofits and their programs, funding sources, geographic location(s), and income/asset statements. GuideStar derives its information from 990 tax submissions to the IRS as well as directly from the nonprofit organizations themselves.

224

Subdwarf B Star Rotation  

NASA Astrophysics Data System (ADS)

A transfer of angular momentum from the core to envelope is understood to occur in red giants as evolution up the Red Giant Branch proceeds. As a consequence, any subdwarf-B star which had a red giant progenitor may be expected to be a slow rotator; KIC 010139564 could be an object of this kind as it is known to have a long rotation period of 25.6±1.8 days, determined from the rotation splitting of nonradial modes. As rotation splitting of nonradial modes will not be resolved in every case, it is proposed in the present paper that subdwarf-B star rotation periods might be determined from the pulsation amplitude variations of these modes, caused by beating between closely spaced but unresolved rotation splitting. Any successful determination of a substantial number of subdwarf-B star rotation rates could, when linked to progenitor red giant core rotation rates, provide a further constraint on binary population synthesis models.

Lynas-Gray, A.

2014-04-01

225

Computational astrophysics: Pulsating stars  

SciTech Connect

The field of computational astrophysics in pulsating star studies has grown considerably since the advent of the computer. Initially calculations were done on the IBM 704 with 32K of memory and now we use the CRAY YMP computers with considerably more memory. Our early studies were for models of pulsating stars using a 1D Lagrangian hydrodynamic code (SPEC) with radiation diffusion. The radiative transfer was treated in the equilibrium diffusion approximation and the hydrodynamics was done utilizing the approximation of artificial viscosity. The early calculations took many hours of 704 CPU time. Early in 1965 we decided to improve on the usual treatment of the radiative transfer used in our codes by utilizing the method of moments, the so-called variable Eddington approximation. In this approximation the material energy field is uncoupled from the radiation energy field and the angular dependence is introduced through the Eddington factor. A multigroup frequency dependent method may also be applied. The Eddington factor is determined by snapshots of the stars structure utilizing a y-line approximation. The full radiative transfer approximation appears necessary in order to understand the light curves for W Virginia stars and may be important for the light curves of RR Lyrae stars. A detailed radiative transfer method does not appear to be necessary for the understanding of Cepheid light curves. A recent improvement to our models for Pulsating stars is in the use of an adaptive mesh scheme to resolve the sharp features in the nonlinear hydrodynamic structure. From these improved structures, better analysis of the radius, velocity, and light curves could be obtained.

Davis, C.G.

1993-08-01

226

Atmospheres around Neutron Stars  

NASA Astrophysics Data System (ADS)

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.

Fryer, Chris L.; Benz, Willy

1994-12-01

227

American Urban Star Fest  

NASA Astrophysics Data System (ADS)

Over the last couple of decades New York City implemented, and continues to carry out, several schemes of eradicating luminous graffiti. One result has been the gradual recovery of the natural night sky. By 1994 the normal clear sky transparency over Manhattan deepened to fourth magnitude and has been slowly creeping deeper, until in 2002 it is at magnitude 4 to 4.5. In the spring of 1995, during some lazing on a Manhattan rooftop under a sky full of stars, several New York astronomers hatched the idea of letting the whole people celebrate the renewed starry sky. In due course they, through the Amateur Astronomers Association, engaged the New York City Parks Department and the Urban Park Rangers in an evening of quiet picnicking to enjoy the stars in their natural sky. Thus the Urban Star Fest was born. The event thrilled about 3,000 visitors in Central Park's Sheep Meadow on Saturday 30 September 1995. This year's Fest, the eighth in the series demonstrated the City's upper skyline of stars on Saturday 5 October 2002 to about 2,200 enthused visitors. Although the Fest is always noted as cancelable for inclement weather, so far, it has convened every year, with attendance ranging from 4,000 down to a mere 1,000, this latter being under the smoke plume of the World Trade Center in 2001. Despite this swing in attendance, the American Urban Star Fest is America's largest regularly scheduled public astronomy event. Of course, special occasions, like comets or eclipses, can and do attract far larger interest both in the city and elsewhere. The presentation shows the setup and program of the American Urban Star Fest, to illustrate how the general public can actively become aware of the night sky and see for themselves the result of their very own efforts at removing light pollution--and note where improvement is yet to come.

Pazmino, John

2003-12-01

228

Double Neutron Star Systems and Natal Neutron Star Kicks  

Microsoft Academic Search

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

Chris Fryer; Vassiliki Kalogera

1997-01-01

229

Modeling Massive Star Formation  

NASA Astrophysics Data System (ADS)

In this contribution I will discuss how massive star forming cores might compare to their lower mass brethren using insights from theoretical models. Is there such a thing as a truly massive pre-stellar core? Do massive star forming cores grow in mass, or is the core mass fixed when a protostar is formed? What is the role of filaments in forming massive protostellar cores? After I have discussed these theoretical considerations I will then examine how such questions can be tested by observations.

Smith, Rowan

2014-07-01

230

A Star on Earth  

ScienceCinema

At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: create a star on Earth. The National Spherical Torus Experiment (NSTX) is a magnetic fusion device that is used to study the physics principles of spherically shaped plasmas -- hot ionized gases in which, under the right conditions, nuclear fusion will occur. Fusion is the energy source of the sun and all of the stars. Not just limited to theoretical work, the NSTX is enabling cutting-edge research to develop fusion as a future energy source.

Prager, Stewart; Zwicker, Andrew; Hammet, Greg; Tresemer, Kelsey; Diallo, Ahmed

2014-06-06

231

Chaplygin dark star  

SciTech Connect

We study the general properties of a spherically symmetric body described through the generalized Chaplygin equation of state. We conclude that such an object, dubbed generalized Chaplygin dark star, should exist within the context of the generalized Chaplygin gas (GCG) 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.

Bertolami, O.; Paramos, J. [Departamento de Fisica, Instituto Superior Tecnico, Avenida Rovisco Pais 1, 1049-001 Lisbon (Portugal)

2005-12-15

232

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.

233

A Real Shooting Star  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Click on the image for movie of A Real Shooting Star

This artist's animation illustrates a star flying through our galaxy at supersonic speeds, leaving a 13-light-year-long trail of glowing material in its wake. The star, named Mira (pronounced my-rah) after the latin word for 'wonderful,' sheds material that will be recycled into new stars, planets and possibly even life. NASA's Galaxy Evolution Explorer discovered the long trail of material behind Mira during its survey of the entire sky in ultraviolet light.

The animation begins by showing a close-up of Mira -- a red-giant star near the end of its life. Red giants are red in color and extremely bloated; for example, if a red giant were to replace our sun, it would engulf everything out to the orbit of Mars. They constantly blow off gas and dust in the form of stellar winds, supplying the galaxy with molecules, such as oxygen and carbon, that will make their way into new solar systems. Our sun will mature into a red giant in about 5 billion years.

As the animation pulls out, we can see the enormous trail of material deposited behind Mira as it hurls along between the stars. Like a boat traveling through water, a bow shock, or build up of gas, forms ahead of the star in the direction of its motion. Gas in the bow shock is heated and then mixes with the cool hydrogen gas in the wind that is blowing off Mira. This heated hydrogen gas then flows around behind the star, forming a turbulent wake.

Why does the trailing hydrogen gas glow in ultraviolet light? When it is heated, it transitions into a higher-energy state, which then loses energy by emitting ultraviolet light - a process known as fluorescence.

Finally, the artist's rendering gives way to the actual ultraviolet image taken by the Galaxy Evolution Explorer

Mira is located 350 light-years from Earth in the constellation Cetus, otherwise known as the whale. Coincidentally, Mira and its 'whale of a tail' can be found in the tail of the whale constellation.

2007-01-01

234

Neutrinos from neutron stars  

NASA Technical Reports Server (NTRS)

A calculation of the flux of ultra-high energy neutrinos from galactic neutron stars is presented. The calculation is used to determine the number of point sources detectable at the sensitivity threshold of a proposed deep underwater muon and neutrino detector array. The detector array would have a point source detection threshold of about 100 eV/sq cm-sec. Analysis of neutrino luminosities and the number of detectable sources suggests that the deep underwater detector may make a few discoveries. In particular, a suspected neutron star in the Cyg X-3 source seems a promising target for the deep underwater array.

Helfand, D. J.

1979-01-01

235

Tech Stars Scholarship Program  

NSDL National Science Digital Library

Seek grant funding for scholarships that target engineering technology. Unique scholarships and associated benefits will help differentiate your program from others. The Tech Stars program at Florence-Darlington Technical College is a successful example of this strategy. The loan-to-own laptop computer feature of this scholarship program is resulting in higher enrollments and more full-time students in the target majors. Tech Star students must agree to certain guidelines to receive the laptop or awards used for books, tuition or computer technology certification fees.

2009-07-15

236

The most magnetic stars  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

237

Isolating Triggered Star Formation  

SciTech Connect

Galaxy pairs provide a potentially powerful means of studying triggered star formation from galaxy interactions. We use a large cosmological N-body simulation coupled with a well-tested semi-analytic substructure model to demonstrate that the majority of galaxies in close pairs reside within cluster or group-size halos and therefore represent a biased population, poorly suited for direct comparison to 'field' galaxies. Thus, the frequent observation that some types of galaxies in pairs have redder colors than 'field' galaxies is primarily a selection effect. We use our simulations to devise a means to select galaxy pairs that are isolated in their dark matter halos with respect to other massive subhalos (N= 2 halos) and to select a control sample of isolated galaxies (N= 1 halos) for comparison. We then apply these selection criteria to a volume-limited subset of the 2dF Galaxy Redshift Survey with M{sub B,j} {le} -19 and obtain the first clean measure of the typical fraction of galaxies affected by triggered star formation and the average elevation in the star formation rate. We find that 24% (30.5 %) of these L* and sub-L* galaxies in isolated 50 (30) h{sup -1} kpc pairs exhibit star formation that is boosted by a factor of {approx}> 5 above their average past value, while only 10% of isolated galaxies in the control sample show this level of enhancement. Thus, 14% (20 %) of the galaxies in these close pairs show clear triggered star formation. Our orbit models suggest that 12% (16%) of 50 (30) h{sup -1} kpc close pairs that are isolated according to our definition have had a close ({le} 30 h{sup -1} kpc) pass within the last Gyr. Thus, the data are broadly consistent with a scenario in which most or all close passes of isolated pairs result in triggered star formation. The isolation criteria we develop provide a means to constrain star formation and feedback prescriptions in hydrodynamic simulations and a very general method of understanding the importance of triggered star formation in a cosmological context.

Barton, Elizabeth J.; Arnold, Jacob A.; /UC, Irvine; Zentner, Andrew R.; /KICP, Chicago /Chicago U., EFI; Bullock, James S.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC

2007-09-12

238

A Star Is Born  

NSDL National Science Digital Library

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.

Henning, Lee A.

239

Synthetic guide star generation  

DOEpatents

A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

Payne, Stephen A. (Castro Valley, CA) [Castro Valley, CA; Page, Ralph H. (Castro Valley, CA) [Castro Valley, CA; Ebbers, Christopher A. (Livermore, CA) [Livermore, CA; Beach, Raymond J. (Livermore, CA) [Livermore, CA

2008-06-10

240

Finding Planets around other stars  

NASA Video Gallery

Just as the Earth revolves around the sun, our closest star, other planets might orbit the stars you see in the night sky. Think of all the planets in the universe that may be just the right distan...

241

The Death of a Star  

ERIC Educational Resources Information Center

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)

Thorne, Kip S.

1971-01-01

242

Why Do We Study Stars?  

NSDL National Science Digital Library

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.

Imamura, Jim

2005-04-27

243

Neutron Stars as Physics Laboratories  

Microsoft Academic Search

X-ray timing and spectrophotometry of accretion-powered neutron stars have been used to determine or constrain many of the intrinsic properties of these stars, including their masses, radii, magnetic fields, spin frequencies, and internal structure. These measurements have important implications for the evolution of ordinary and neutron stars in binary systems, the supernova process in massive stars, accretion-induced collapse of white

F. K. Lamb

1994-01-01

244

Finding Mars-Sized Planets in Inner Orbits of Other Stars by Photometry  

NASA Technical Reports Server (NTRS)

High precision photometry from a spaceborne telescope has the potential of discovering sub-earth sized inner planets. Model calculations by Wetherill indicate that Mars-sized planets can be expected to form throughout the range of orbits from that of Mercury to Mars. While a transit of an Earth-sized planet causes a 0.084% decrease in brightness from a solar-like star, a transit of a planet as small as Mars causes a flux decrease of only 0.023%. Stellar variability will be the limiting factor for transit measurements. Recent analysis of solar variability from the SOLSTICE experiment shows that much of the variability is in the UV at <400 nm. Combining this result with the total flux variability measured by the ACRIM-1 photometer implies that the Sun has relative amplitude variations of about 0.0007% in the 17-69 pHz bandpass and is presumably typical for solar-like stars. Tests were conducted at Lick Observatory to determine the photometric precision of CCD detectors in the 17-69 pHz bandpass. With frame-by-frame corrections of the image centroids it was found that a precision of 0.001% could be readily achieved, corresponding to a signal to noise ratio of 1.4, provided the telescope aperture was sufficient to keep the statistical noise below 0.0006%. With 24 transits a planet as small as Mars should be reliably detectable. If Wetherill's models are correct in postulating that Mars-like planets are present in Mercury-like orbits, then a six year search should be able to find them.

Borucki, W.; Cullers, K.; Dunham, E.; Koch, D.; Mena-Werth, J.; Cuzzi, Jeffrey N. (Technical Monitor)

1995-01-01

245

Star formation and molecular clouds  

NASA Technical Reports Server (NTRS)

Several differnt stages can be discerned within the star formation process. Star formation can be considered to start when a molecular cloud fragments into many clumps. Many different physical processes are likely to play an important role in star formation, including self-gravity, magnetic fields, rotation, winds, and radiation transport. The current knowledge on some of these processes are reviewed.

Tielens, Alexander G. G. M.

1988-01-01

246

Asteroseismology of Binary Stars  

NASA Astrophysics Data System (ADS)

The study of stellar oscillations, asteroseismology, enables us to draw conclusions on the inner structure of stars; thereby helping improve stellar models. Given that the majority of stars are found in binary or multiple systems, we expect to find many such systems containing pulsators. Binary stars, and in particular eclipsing binaries, play a crucial role in stellar astrophysics. Eclipse shapes, radial velocities, and other geometric properties of orbits are related to the physical properties of the components, such as radius and mass. These properties can, therefore, easily be derived from spectroscopic and photometric observations by simply applying the laws of physics and without relying on any assumptions of stellar-structure models. Hence, the understanding of eclipsing binary systems with pulsating components provide accurate constraints on the input physics for asteroseismic models. We will study nine different eclipsing binary stars containing pulsating components that range in masses from about 2-8 Mo. We will make use of high-precision photometry provided by the Kepler satellite and combine them with high-resolution spectroscopy gathered with the HERMES spectrograph mounted on the Mercator telescope, located on La Palma, Spain. The prospects of this challenging project will be presented and illustrated by the means of a case study.

Schmid, Valentina; Aerts, Conny; Debosscher, Jonas

2013-06-01

247

Colors of Stars  

NSDL National Science Digital Library

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.

Hemenway, Mary K.

2011-01-01

248

StarLogo TNG  

NASA Astrophysics Data System (ADS)

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 builds on the StarLogo tradition of agent-based modeling for students and teachers, with the added features of a graphical programming environment and a three-dimensional (3D) world. The graphical programming environment reduces the learning curve of programming, especially syntax. The 3D graphics make for a more immersive and engaging experience for students, including making it easy to design and program their own video games. Another change to StarLogo TNG is a fundamental restructuring of the virtual machine to make it more transparent. As a result of these changes, classroom use of TNG is expanding to new areas. This chapter is concluded with a description of field tests conducted in middle and high school science classes.

Klopfer, Eric; Scheintaub, Hal; Huang, Wendy; Wendel, Daniel

249

Winds from Cool Stars  

NASA Astrophysics Data System (ADS)

The structure of the outer atmospheres of luminous cool stars reveals the evolution of magnetic activity as dynamo heating decreases and atmospheres expand while the stars evolve across the color-magnitude diagram. The relationship between winds and high temperature material can also be investigated. A comprehensive picture of the dynamics of the outer atmospheres is constructed based principally upon recent spectroscopic evidence from FUSE HST and optical and infrared spectra. In contrast to the solar example winds from cool giant and supergiant stars can exhibit supersonic acceleration in their chromospheres carry away more material and possess temperatures ranging from 10000K to 80000K. Coronal material near 107 K appears confined and does not participate in atmospheric expansion. Empirical relations between atmospheric structure and mass loss will be discussed. For metal deficient stars the discovery of signatures of pulsation may play an important role in driving mass loss. The detection of warm winds in cool giants and supergiants provides the crucial link between the hot fast solar wind with low mass loss and cool slow supergiant winds with substantially larger rates of mass loss.

Dupree, A. K.

2004-01-01

250

Division Iv: Stars  

NASA Astrophysics Data System (ADS)

This Division IV was started on a trial basis at the General Assembly in The Hague 1994 and was formally accepted at the Kyoto General Assembly in 1997. Its broad coverage of ``Stars'' is reflected in its relatively large number of Commissions and so of members (1266 in late 2011). Its kindred Division V, ``Variable Stars'', has the same history of its beginning. The thinking at the time was to achieve some kind of balance between the number of members in each of the 12 Divisions. Amid the current discussion of reorganizing the number of Divisions into a more compact form it seems advisable to make this numerical balance less of an issue than the rationalization of the scientific coverage of each Division, so providing more effective interaction within a particular field of astronomy. After all, every star is variable to a certain degree and such variability is becoming an ever more powerful tool to understand the characteristics of every kind of normal and peculiar star. So we may expect, after hearing the reactions of members, that in the restructuring a single Division will result from the current Divisions IV and V.

Corbally, Christopher; D'Antona, Francesca; Spite, Monique; Asplund, Martin; Charbonnel, Corinne; Docobo, Jose Angel; Gray, Richard O.; Piskunov, Nikolai E.

2012-04-01

251

STAR Enrollment Statistics  

Cancer.gov

For STAR, 184,461 women went through the risk assessment process to determine their eligibility for the trial. Of these women, 96,368 were eligible for the trial because of their increased risk of developing breast cancer. Of those risk-eligible women, 19,747 chose to participate.

252

Magnetic Dynamos and Stars  

SciTech Connect

Djehuty is a code that has been developed over the last five years by the Lawrence Livermore National Laboratory (LLNL), from earlier code designed for programmatic efforts. Operating in a massively parallel environment, Djehuty is able to model entire stars in 3D. The object of this proposal was to continue the effort to introduce magneto-hydrodynamics (MHD) into Djehuty, and investigate new classes of inherently 3D problems involving the structure, evolution and interaction of stars and planets. However, towards the end of the second year we discovered an unexpected physical process of great importance in the evolution of stars. Consequently for the third year we changed direction and concentrated on this process rather than on magnetic fields. Our new process was discovered while testing the code on red-giant stars, at the 'helium flash'. We found that a thin layer was regularly formed which contained a molecular-weight inversion, and which led therefore to Rayleigh-Taylor instability. This in turn led to some deeper-than-expected mixing, which has the property that (a) much {sup 3}He is consumed, and (b) some {sup 13}C is produced. These two properties are closely in accord with what has been observed over the last thirty years in red giants, whereas what was observed was largely in contradiction to what earlier theoretical models predicted. Thus our new 3D models with Djehuty explain a previously-unexplained problem of some thirty years standing.

Eggleton, P P

2007-02-15

253

Physics of the Stars  

ERIC Educational Resources Information Center

Describes how astrophysics can be a do-it-yourself project within a school boy's budget and background, by giving detailed instruction on equipment construction. In addition, this article describes many experiments to undertake, with the equipment, such as determining color temperature, star spectra, chemical composition and others. (BR)

Haig, G. Y.

1974-01-01

254

Bohr Sommerfeld star products  

NASA Astrophysics Data System (ADS)

We relate the Bohr-Sommerfeld conditions to formal deformation quantization of symplectic manifolds by classifying star products adapted to some Lagrangian submanifold L, i.e. products preserving the classical vanishing ideal IL of L up to IL-preserving equivalences.

Carl, Michael

2008-05-01

255

Emmy's Moon and Stars  

NSDL National Science Digital Library

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.

Eberle, Francis; Tugel, Joyce; Keeley, Page

2007-01-01

256

Focus on the Stars.  

ERIC Educational Resources Information Center

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…

Geary, Pat; And Others

257

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.

258

The Summer Stars Program.  

ERIC Educational Resources Information Center

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…

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

1997-01-01

259

The Astounding Stars.  

ERIC Educational Resources Information Center

Studying about stellar constellations provides children with an opportunity to learn about ancient myths and mathematics at the same time. An interdisciplinary teaching unit combines information about myths associated with the zodiac signs and instructions for plotting the coordinates of stars. (PP)

Montgomery, Angela; And Others

1983-01-01

260

Desk Top Stars  

NSDL National Science Digital Library

This module designed for middle school students uses simple, fun experiments to introduce some tools and concepts of astronomers. Students are asked to consider how astronomers answer questions like: How old is the Universe? How far away is a galaxy? What are stars made of? The exercise includes working with a simple spectrometer. This unit may be easily modified for other students.

White, Storn; Therrien, Roy; Baker, Johnathin

261

Supernova induced star formation  

Microsoft Academic Search

The evidence for the triggering of star formation by shocks from expanding supernova shells is examined with special emphasis on the solar system. It is shown that the recently discovered isotopic anomalies, mainly in Ti, can serve as the best signature for this purpose. It is suggested that the discovery of correlated anomalies in Ti, Fe, and Ca will give

S. Ramadurai

1986-01-01

262

Our Star, the Sun  

NSDL National Science Digital Library

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

Hemenway, Mary K.

2000-09-01

263

Neutron Star Mysteries  

NASA Astrophysics Data System (ADS)

Neutron stars provide a unique laboratory in which to explore the nuclear equation of state at high densities. Nevertheless, their interior structure and equation of state have remained a mystery. Recently, a number of advances have been made toward unraveling this mystery. The first direct optical images of a nearby neutron star have been obtained from HST. High quality data for X-ray emission from low-mass X-ray binaries, including observations of nearly coherent oscillations (NCO's) and quasi-periodic oscillations (QPOs) now exist. The existence of a possible absorption feature as well as pulsar light curves and glitches, and studies of soft-gamma repeaters, have all led to significant new constraints on the mass-radius relation and maximum mass of neutron stars. We also discuss how models of supernova explosion dynamics and the associated r-process nucleosynthesis also constrain the nuclear equation of state, along with heavy-ion and monopole resonance data. Recent work on the search for the Friedman-Chandrasekhar-Schutz instability and the effects of internal magnetic fields are also discussed. The overall constraints on the neutron star equation of state are summarized.

Mathews, G. J.; Fragile, P. C.; Suh, I.; Wilson, J. R.

2003-04-01

264

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...

2010-08-12

265

Stabilizing Star Wars  

SciTech Connect

An orderly replacement of offensive with defensive nuclear weapons is part of the defense-protected build-down (DPB) strategy described by Weinberg and Barkenbus. Differing from the administration's Star Wars approach by relying on interceptor missiles rather than costly and unproven lasers and particle beams, the plan also calls for a simultaneous freeze on offensive weapons. (DCK)

Weinberg, A.M.; Barkenbus, J.N.

1984-01-01

266

Circles and Star Polygons.  

ERIC Educational Resources Information Center

Two graphics programs for students in grades six-12 are given. "Circle Through 3 Points" and "Star Polygons." Students gain familiarity with the xy-plane, the radii and centers of circles, and ellipses, while more advanced students learn about parametric equations and using random numbers to produce random shapes. (MNS)

Kimberling, Clark

1985-01-01

267

Reaching for the Stars  

ERIC Educational Resources Information Center

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…

Terry, Dorothy Givens

2012-01-01

268

The STAR Trigger System  

NASA Astrophysics Data System (ADS)

The STAR experiment at RHIC consists primarily of a large cylindrical TPC positioned inside a 0.5 Tesla solenoidal magnet. The beams cross at STAR every 107ns, and the trigger system must examine every crossing to see if an interesting interaction has occured. A system was designed in three parts: (1) three fast trigger detectors, (2) a set of custom, pipelined, digital PC boards to take a first look at the data and trigger the rest of STAR, and (3) two layers of CPUs to perform more detailed analyses and potentially abort the event. The trigger detectors consist of: a barrel of scintillator slats surrounding the TPC, two zero-degree calorimeters, one on either side of STAR, and the TPC endcaps instrumented as multi-wire proportional chambers. The data from these detectors is stored in a tree of Data Storage and Manipulation boards (DSM) that simultaneously analyze the data calculating, for example, the total multiplicity of hits in the scintillator barrel and wire chamber. The results of the DSM calculations go to the Trigger Control Unit (TCU), along with the detector busy status, where the TCU decides whether or not to issue a trigger. The detectors and these custom PC boards will be discussed, and trigger detector results from this year's AuAu run will be presented.

Judd, E.; Crawford, H.; Engelage, J.; Greiner, L.; Milosevich, Z.; Bieser, F.; Marks, K.; Eppley, G.; Adler, C.

2000-10-01

269

Superfluidity in Neutron Stars  

Microsoft Academic Search

MATTER in the interior of a typical neutron star is a mixture of three degenerate interacting quantum liquids-neutrons, protons and electrons, the latter two having a density at most a few per cent that of the neutrons1. The mixture, bounded on the inside by a superdense core of hadrons, muons and so on, and most likely by a solid mantle

Gordon Baym; Christopher Pethick; David Pines

1969-01-01

270

White Dwarf Stars  

NSDL National Science Digital Library

This NASA site provides information about white dwarfs, produced when stars like our Sun exhaust their nuclear fuel and blow off much of their mass. The site contains an explanation of their properties and composition. Additional links include an introductory article, online quiz, cool facts, FAQ, and other resources.

2007-01-26

271

Quarkonium at STAR  

SciTech Connect

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.

LeCompte, T. J.

1998-11-11

272

First Star I See.  

ERIC Educational Resources Information Center

This children's novel tells the story of a young girl with attention deficit disorder (ADD) without hyperactivity and her younger brother who has ADD with hyperactivity. Trying to win a school writing contest on the topic of space and stars helps bright, imaginative Paige Bradley realize that fixing her "focusing knob" will compensate for her ADD.…

Caffrey, Jaye Andras

273

Project Star Cookbook.  

National Technical Information Service (NTIS)

Project STAR (Serving To Advance Rehabilitation) was a three year, tri-agency pilot plan designed to aid the families of diagnosed, adolescent mental retardates in poor and minority communities and to encourage and enable them to become involved in the op...

1974-01-01

274

Chromospheres of Cool Stars.  

National Technical Information Service (NTIS)

Progress in understanding the nature and origin of cool star chromospheres and transition regions since the launch of IUE is reviewed. While previous observations in the visible and UV regions laid the foundations for present work, the nature of the IUE i...

C. Jordan

1986-01-01

275

Halo Star Lithium Depletion  

SciTech Connect

The depletion of lithium during the pre-main-sequence and main-sequence phases of stellar evolution plays a crucial role in the comparison of the predictions of big bang nucleosynthesis with the abundances observed in halo stars. Previous work has indicated a wide range of possible depletion factors, ranging from minimal in standard (nonrotating) stellar models to as much as an order of magnitude in models that include rotational mixing. Recent progress in the study of the angular momentum evolution of low-mass stars permits the construction of theoretical models capable of reproducing the angular momentum evolution of low-mass open cluster stars. The distribution of initial angular momenta can be inferred from stellar rotation data in young open clusters. In this paper we report on the application of these models to the study of lithium depletion in main-sequence halo stars. A range of initial angular momenta produces a range of lithium depletion factors on the main sequence. Using the distribution of initial conditions inferred from young open clusters leads to a well-defined halo lithium plateau with modest scatter and a small population of outliers. The mass-dependent angular momentum loss law inferred from open cluster studies produces a nearly flat plateau, unlike previous models that exhibited a downward curvature for hotter temperatures in the 7Li-Teff plane. The overall depletion factor for the plateau stars is sensitive primarily to the solar initial angular momentum used in the calibration for the mixing diffusion coefficients. Uncertainties remain in the treatment of the internal angular momentum transport in the models, and the potential impact of these uncertainties on our results is discussed. The 6Li/7Li depletion ratio is also examined. We find that the dispersion in the plateau and the 6Li/7Li depletion ratio scale with the absolute 7Li depletion in the plateau, and we use observational data to set bounds on the 7Li depletion in main-sequence halo stars. A maximum of 0.4 dex depletion is set by the observed dispersion and 6Li/7Li depletion ratio, and a minimum of 0.2 dex depletion is required by both the presence of highly overdepleted halo stars and consistency with the solar and open cluster 7Li data. The cosmological implications of these bounds on the primordial abundance of 7Li are discussed. (c) (c) 1999. The American Astronomical Society.

Pinsonneault, M. H.; Walker, T. P.; Steigman, G.; Narayanan, Vijay K.

1999-12-10

276

H-cluster stars  

NASA Astrophysics Data System (ADS)

The study of dense matter at ultrahigh density has a very long history, which is meaningful for us to understand not only cosmic events in extreme circumstances but also fundamental laws of physics. It is well known that the state of cold matter at supranuclear density depends on the non-perturbative nature of quantum chromodynamics (QCD) and is essential for modelling pulsars. A so-called H-cluster matter is proposed in this paper as the nature of dense matter in reality. In compact stars at only a few nuclear densities but low temperature, quarks could be interacting strongly with each other there. That might render quarks grouped in clusters, although the hypothetical quark clusters in cold dense matter have not been confirmed due to the lack of both theoretical and experimental evidence. Motivated by recent lattice QCD simulations of the H-dibaryons (with structure uuddss), we therefore consider here a possible kind of quark clusters, H-clusters, that could emerge inside compact stars during their initial cooling as the dominant components inside (the degree of freedom could then be H-clusters there). Taking into account the in-medium stiffening effect, we find that at baryon densities of compact stars H-cluster matter could be more stable than nuclear matter. We also find that for the H-cluster matter with lattice structure, the equation of state could be so stiff that it would seem to be `superluminal' in the most dense region. However, the real sound speed for H-cluster matter is in fact difficult to calculate, so at this stage we do not put constraints on our model from the usual requirement of causality. We study the stars composed of H-clusters, i.e. H-cluster stars, and derive the dependence of their maximum mass on the in-medium stiffening effect, showing that the maximum mass could be well above 2 M? as observed and that the resultant mass-radius relation fits the measurement of the rapid burster under reasonable parameters. Besides a general understanding of different manifestations of compact stars, we expect further observational and experimental tests for the H-cluster stars in the future.

Lai, X. Y.; Gao, C. Y.; Xu, R. X.

2013-06-01

277

Electrodynamics of neutron stars  

NASA Astrophysics Data System (ADS)

Although the standard model for radio pulsars is a rotating magnetized neutron star and the vast majority (if not all) of pulsars are thought to have appreciable inclination angles between the spin and magnetization axes, most theoretical papers use simplified field models (e.g., aligned spin axis and magnetic dipole axis). Deutsch long ago gave exact (in vacuo) closed expressions for these inclined fields (modulo some typos and oversights), but these expressions were rather clumsy and required extensive hand processing to convert into ordinary functions of radius and angle for the electromagnetic fields. Moreover, these expressions were effectively written down by inspection (no details of the derivations given), which leaves the reader with little physical understanding of where the various electric and magnetic field components come from, particularly near the neutron star surface where many models assume the radio emission is generated. Finally, rather little analysis of what these fields implied was given beyond speculation that they could accelerate cosmic rays. As pulsar models become more sophisticated, it seems important that all researchers use a consistent set of underlying fields, which we hope to present here, as well as understand why these fields are present. It is also interesting to know what happens to charged particles from the star that move in these fields. Close to the star, ambient particles tend to simply /ExB drift around the star with the same rotational velocity as the star itself. But far from the star, charged particles are accelerated away in the wave zone, as was first pointed out by Ostriker and Gunn. We expand their calculations using more general fields and elucidate the particle's dynamics accordingly. Very efficient acceleration is observed even for particles starting at 103 light-cylinder distances. We also stress the effects of a non-zero radial magnetic field. Electrons are accelerated to much higher energies than, say, protons (not to the same energy as when the two cross a fixed potential drop). We pay particular attention to particles accelerated along the spin axis (particles that might be involved in jet formation). An important limitation to the present work is the neglect of collective radiation reaction. Single particle radiation reaction (e.g., Compton scattering of the wave flux) is not an accurate estimate of the forces on a plasma. We are working on remedying this limitation.

Michel, F. C.; Li, H.

1999-09-01

278

Weighing the Smallest Stars  

NASA Astrophysics Data System (ADS)

VLT Finds Young, Very Low Mass Objects Are Twice As Heavy As Predicted Summary Thanks to the powerful new high-contrast camera installed at the Very Large Telescope, photos have been obtained of a low-mass companion very close to a star. This has allowed astronomers to measure directly the mass of a young, very low mass object for the first time. The object, more than 100 times fainter than its host star, is still 93 times as massive as Jupiter. And it appears to be almost twice as heavy as theory predicts it to be. This discovery therefore suggests that, due to errors in the models, astronomers may have overestimated the number of young "brown dwarfs" and "free floating" extrasolar planets. PR Photo 03/05: Near-infrared image of AB Doradus A and its companion (NACO SDI/VLT) A winning combination A star can be characterised by many parameters. But one is of uttermost importance: its mass. It is the mass of a star that will decide its fate. It is thus no surprise that astronomers are keen to obtain a precise measure of this parameter. This is however not an easy task, especially for the least massive ones, those at the border between stars and brown dwarf objects. Brown dwarfs, or "failed stars", are objects which are up to 75 times more massive than Jupiter, too small for major nuclear fusion processes to have ignited in its interior. To determine the mass of a star, astronomers generally look at the motion of stars in a binary system. And then apply the same method that allows determining the mass of the Earth, knowing the distance of the Moon and the time it takes for its satellite to complete one full orbit (the so-called "Kepler's Third Law"). In the same way, they have also measured the mass of the Sun by knowing the Earth-Sun distance and the time - one year - it takes our planet to make a tour around the Sun. The problem with low-mass objects is that they are very faint and will often be hidden in the glare of the brighter star they orbit, also when viewed in large telescopes. Astronomers have however found ways to overcome this difficulty. For this, they rely on a combination of a well-considered observational strategy with state-of-the-art instruments. High contrast camera First, astronomers searching for very low mass objects look at young nearby stars because low-mass companion objects will be brightest while they are young, before they contract and cool off. In this particular case, an international team of astronomers [1] led by Laird Close (Steward Observatory, University of Arizona), studied the star AB Doradus A (AB Dor A). This star is located about 48 light-years away and is "only" 50 million years old. Because the position in the sky of AB Dor A "wobbles", due to the gravitational pull of a star-like object, it was believed since the early 1990s that AB Dor A must have a low-mass companion. To photograph this companion and obtain a comprehensive set of data about it, Close and his colleagues used a novel instrument on the European Southern Observatory's Very Large Telescope. This new high-contrast adaptive optics camera, the NACO Simultaneous Differential Imager, or NACO SDI [2], was specifically developed by Laird Close and Rainer Lenzen (Max-Planck-Institute for Astronomy in Heidelberg, Germany) for hunting extrasolar planets. The SDI camera enhances the ability of the VLT and its adaptive optics system to detect faint companions that would normally be lost in the glare of the primary star. A world premiere ESO PR Photo 03/05 ESO PR Photo 03/05 Infrared image of AB Doradus A and its companion [Preview - JPEG: 400 x 406 pix - 99k] [Normal - JPEG: 800 x 812 pix - 235k] Caption: ESO PR Photo 03/05 is an enhanced, false-colour near-infrared image of AB Dor A and C. The faint companion "AB Dor C" - seen as the pink dot at 8 o'clock - is 120 times fainter than its primary star. The tiny separation between A and C, only 0.156 arcsec, is smaller than a one Euro coin seen at 20 km distance. Nevertheless, the new NACO SDI camera was able to

2005-01-01

279

How Big Is That Star?  

NSDL National Science Digital Library

This activity teaches students how to determine the sizes of stars by using simple representations and manipulating the mathematical equations which are illustrated and demonstrated within this lesson. It is important for students to generally comprehend the size, mass, and density of stars. As they complete this lesson, students will be able to explain the relationship between radius and mass among a list of stars, understand how a binary star system's orbit can cause changes in the observed brightness of the system, and determine the diameters of stars by analyzing data and manipulating equations.

280

The Natures of the Stars  

NSDL National Science Digital Library

It is the purpose of this site to provide a deep, non-technical review of stars and their natures for the beginner. This page presents facts about stars as we know them without delving into the details of discovery. A parallel site that explores the spectra of the stars examines how we have learned so much of what is presented here. The two sites are linked, allowing you to go back and forth between them to see how stars are born, live their lives, and die, in the process creating other stars, perhaps other earths, and all that is around us.

Kaler, James

2004-07-16

281

Licking County Community Solar Energy Program  

SciTech Connect

A Community Solar Energy Feasibility Study and Education Program for Central Ohio is described. LEADS Community Action Agency and the Denison University Homestead, with support of federal and university grants, designed and constructed five solar heating systems. Three passive solar greenhouses, one passive trombe wall and one active solar system were retrofitted on local structures between April 1979 and April 1980. Two semesters of community solar education through the Denison Experimental College and one semester through Ohio State University/Newark were coordinated with design, construction and performance of these five solar systems. Community residents received a balanced education including classroom training in solar energy practice. Classes and demonstrations were also conducted for such diverse groups as elementary, junior and senior high schools, senior citizens, mental health organizations, news media, other community action agencies and colleges statewide as well as interested individuals.

Downs, R. (LEADS, Newark, OH); Blynn, R.; Glosser, D.; Homestead, D.

1980-01-01

282

Gaining Insight into Star Formation: Resolved Star Formation Laws  

NASA Astrophysics Data System (ADS)

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.

Liebst, Kelley; Scowen, Paul A.

2014-06-01

283

Dead Star Rumbles  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Composite of Supernova Remnant Cassiopeia A This Spitzer Space Telescope composite shows the supernova remnant Cassiopeia A (white ball) and surrounding clouds of dust (gray, orange and blue). It consists of two processed images taken one year apart. Dust features that have not changed over time appear gray, while those that have changed are colored blue or orange. Blue represents an earlier time and orange, a later time.

These observations illustrate that a blast of light from Cassiopeia A is waltzing outward through the dusty skies. This dance, called an 'infrared echo,' began when the remnant erupted about 50 years ago.

Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion 325 years ago. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. This remnant is located 10,000 light-years away in the northern constellation Cassiopeia.

An infrared echo is created when a star explodes or erupts, flashing light into surrounding clumps of dust. As the light zips through the dust clumps, it heats them up, causing them to glow successively in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. This apparent motion can be seen here by the shift in colored dust clumps.

Echoes are distinct from supernova shockwaves, which are made up material that is swept up and hurled outward by exploding stars.

This infrared echo is the largest ever seen, stretching more than 50 light-years away from Cassiopeia A. If viewed from Earth, the entire movie frame would take up the same amount of space as two full moons.

Hints of an older infrared echo from Cassiopeia A's supernova explosion hundreds of years ago can also be seen.

The earlier Spitzer image was taken on November 30, 2003, and the later, on December 2, 2004.

2005-01-01

284

Bright Be-shell stars  

NASA Astrophysics Data System (ADS)

Echelle observations are presented and discussed for 23 of the 27 known "normal" shell stars brighter than about 6.5 mag. In addition to those typical cases, three stars with known transitions between emission & shell and pure emission line appearance, and three rapidly rotating B stars without records of line emission (Bn stars) are added to the sample. Long-term V/R emission-line variability and central quasi emission bumps (CQEs) in photospheric lines were found in 75% of all normal shell stars. This strongly suggests that the velocity law in most, if not all, disks of Be stars is roughly Keplerian. Both phenomena may occur in the same star but not at the same time. This is in agreement with the previous conclusion that CQEs only form in the presence of negligible line-of-sight velocities while long-term V/R variations are due to non-circular gas particle orbits caused by global disk oscillations. V/R variations associated with binary orbits are much less pronounced. Similarly, phase lags between different lines were detected in long-term V/R variable stars only. A binary fraction of only one-third is too low to support binary hypotheses as an explanation of the Be phenomenon. CQEs detected in 3 out of 19 Bn stars reveal the presence of disk-like equatorial concentrations of matter in B stars without emission lines. Accordingly, there seem to be intermediate cases between disk-free B stars and Be stars. Previous claims of the existence of shell stars with low v sin i could not be confirmed. Shell stars are Be stars viewed equator-on, and their observed rotational velocities are indistinguishable from the equatorial ones which are the same as in Be stars. The mean fraction of the critical rotation velocity is 81±12%. The standard deviation is comparable to, or even less than, the observational uncertainties. Since this would require star-to-star differences to be negligible, which is unrealistic, the correlation between the widths of strong spectral lines and the stellar rotation velocities may be truncated or severely distorted at its extreme end. A number of not previously known facts about individual stars is also reported.

Rivinius, Th.; Štefl, S.; Baade, D.

2006-11-01

285

Rotating massive stars: From first stars to gamma ray bursts  

NASA Astrophysics Data System (ADS)

This article first reviews the basic physics of rotating stars and their evolution. The changes of the mechanical and thermal equilibrium of rotating stars are examined. An important, predicted and observed, effect is that rotating stars are hotter at the poles and cooler at the equator. The mass loss by stellar winds, which are influenced by the anisotropic temperature distribution, is discussed. These anisotropies in the interior are also driving circulation currents, which transports the chemical elements and the angular momentum in stars. Internal differential rotation, if present, creates instabilities and mixing, in particular, the shear mixing, the horizontal turbulence and their interactions. A major check of the model predictions concerns the changes of the surface abundances, which are modified by mass loss in the very massive stars and by rotational mixing in O-type and B-type stars. The observations are shown to confirm the existence of rotational mixing, with much larger effects at lower metallicities. The predictions of stellar models concerning the evolution of the surface velocities, the evolutionary tracks in the Hertzsprung-Russell diagram and lifetimes, the populations of blue, red supergiants and Wolf-Rayet stars, and the progenitors of type Ibc supernovae are discussed. In many aspects, rotating models are shown to provide a much better fit than nonrotating ones. Using the same physical ingredients as those which fit the best observations of stars at near solar metallicities, the consequences of rotating models for the status of Be stars, the progenitors of gamma ray bursts, the evolution of Pop III stars and of very metal-poor stars, the early chemical evolution of galaxies, the origin of the C-enhanced metal poor stars and of the chemical anomalies in globular clusters are explored. Rotation together with mass loss are two key physical ingredients shaping the evolution of massive stars during the whole cosmic history.

Maeder, André; Meynet, Georges

2012-01-01

286

Stars at Gammasphere  

NASA Astrophysics Data System (ADS)

STARS (Silicon Telescope Array for Reaction Studies) is a highly segmented array of particle telescope designed to allow for particle-gamma coincidence measurements in both forward and inverse kinematics at either forward or backward angles using GAMAMSPHERE. Two different arrays of Silicon surface barrier detectors can be employed depending on the configuration of the experiment. The first STARS experiment at GAMMASPHERE took place in April 2002. The ^157Gd(^3He,?)^156Gd reaction at E_? = 45 MeV was used to a) measure level densities and gamma-ray strength functions below the neutron binding energy, and b) to simulate neutron-induced reactions on ^155Gd. Preliminary results from this experiment will be presented. This work was funded by the US Department of Energy under contracts number W-7405-ENG-48 (LLNL), AC03-76SF00098 (LBNL) and the Norwegian Research Council (Oslo).

Bernstein, L. A.; Schiller, A.; Cooper, J. R.; Becker, J. A.; Fallon, P.; Macchiavelli, M. A.; McMahan, M. A.; Guttormsen, M.; Rekstad, J. B.; Siem, S.; Sarantites, D. G.; Sobotka, L. G.; Mitchell, G. E.; Tavukcu, E.

2002-10-01

287

Orthographic star coordinates.  

PubMed

Star coordinates is a popular projection technique from an nD data space to a 2D/3D visualization domain. It is defined by setting n coordinate axes in the visualization domain. Since it generally defines an affine projection, strong distortions can occur: an nD sphere can be mapped to an ellipse of arbitrary size and aspect ratio. We propose to restrict star coordinates to orthographic projections which map an nD sphere of radius r to a 2D circle of radius r. We achieve this by formulating conditions for the coordinate axes to define orthographic projections, and by running a repeated non-linear optimization in the background of every modification of the coordinate axes. This way, we define a number of orthographic interaction concepts as well as orthographic data tour sequences: a scatterplot tour, a principle component tour, and a grand tour. All concepts are illustrated and evaluated with synthetic and real data. PMID:24051828

Lehmann, Dirk J; Theisel, Holger

2013-12-01

288

Dilepton Measurements at STAR  

NASA Astrophysics Data System (ADS)

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 (Mll < 1.1 GeV/c2), the dominant source of dileptons originates from the decay of vector mesons which may see effects from chiral symmetry restoration. In the intermediate mass range (1.1 < Mll < 3.0 GeV/c2), the main contributions to the mass spectrum are expected to originate from the thermal radiation of a quark-gluon plasma as well as the decays of charm mesons. In the high mass range (Mll > 3.0 GeV/c2), 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.

Geurts, Frank; STAR Collaboration

2013-08-01

289

Our Super Star  

NSDL National Science Digital Library

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.

2005-01-01

290

High-luminosity Stars  

NASA Astrophysics Data System (ADS)

The most luminous stars in galaxies are of extraordinary astronomical importance. With the new generation of 10 m class ground-based telescopes and with the large observatories in space such as the HST they can be studied as individuals in galaxies out to 20 Mpc distance including the VIRGO and FORNAX GALAXY CLUSTERS. The quantitative analysis of their spectra yields important information about d...

Kudritzki, R.; Murdin, P.

2000-11-01

291

The faintest stars  

NASA Technical Reports Server (NTRS)

A determination of the luminosity and mass functions is given for field stars at the bottom of the main sequence as the first results from a 320 sq deg survey based on both optical and near-infrared photometry. The luminosity and mass functions are determined with an order of magnitude higher precision than previous studies achieve. No evidence is found for a mass function steepening toward the H-burning limit.

Tinney, C. G.; Mould, J. R.; Ried, I. N.

1992-01-01

292

Neutron Star Cooling  

Microsoft Academic Search

Observation of cooling neutron stars can potentially provide information\\u000aabout the states of matter at supernuclear densities. We review physical\\u000aproperties important for cooling such as neutrino emission processes and\\u000asuperfluidity in the stellar interior, surface envelopes of light elements due\\u000ato accretion of matter and strong surface magnetic fields. The neutrino\\u000aprocesses include the modified Urca process, and the

D. G. Yakovlev; O. Y. Gnedin

2004-01-01

293

Harmonic mappings onto stars  

NASA Astrophysics Data System (ADS)

A general version of the Radó-Kneser-Choquet theorem implies that a piecewise constant sense-preserving mapping of the unit circle onto the vertices of a convex polygon extends to a univalent harmonic mapping of the unit disk onto the polygonal domain. This paper discusses similarly generated harmonic mappings of the disk onto nonconvex polygonal regions in the shape of regular stars. Calculation of the Blaschke product dilatation allows a determination of the exact range of parameters that produce univalent mappings.

Duren, Peter; McDougall, Jane; Schaubroeck, Lisbeth

2005-07-01

294

Star Formation in Lynds 1641  

NASA Astrophysics Data System (ADS)

We conducted an extensive multi-wavelength study of the nearest giant molecular cloud, L1641, with the goal of characterizing its stellar populations. At a distance of approximately 500 pc, L1641 provides an excellent opportunity for studying star formation over the entire range of stellar masses, and the star formation history in a region thought representative of those dominating stellar production in the Milky Way. Our approach combines imaging surveys at optical and infrared wavelengths with spectroscopic surveys at ?? 6000-9000Å to measure stellar luminosities and effective temperatures. Stellar ages and masses are then estimated from comparison of L*, Teff with pre-main sequence evolutionary tracks. The stars for which we have obtained classifiable spectra as well as optical (R,I) and near-infrared and near-infrared (J,H,K) photometry number ~300, and are contained within four regions, each approximately 20' square (2.5 × 2.5 pc). Our 2.25micron images reveal both modest aggregates of several tens of stars and stars distributed at random across the face of the cloud; we find no evidence of rich (N gg 100 stars) clusters. The aggregate members appear to have formed within the past 1 Myr, while the distributed population contains both young stars (t < 1Myr) and stars ranging in age up to 30 Myr. From comparison of the fraction of the youngest stars forming in aggregates and in isolation, we conclude that stars born initially in aggregates comprise 25 - 50% of the total stars formed in L1641. The observed frequency distribution of stellar ages enables a discussion of the star-forming history of the cloud. The L1641 cloud has been producing stars for nearly 30 Myr and over the last 10 Myr, the SFR has been roughly constant. We explore the implications of this result for the ``off-cloud'' spatial distribution of young stars. Finally, we examine the circumstellar disk properties of stars in our spectroscopic sample. The frequency of disks, as inferred from infrared excess emission, is found to be higher for stars less massive than 1 Modot than for more massive stars. We also find that at least six stars in L1641 have apparently retained their accretion disks beyond an age of 3 Myr. The thesis is available on the World Wide Web at: http://decoy.phast.umass.edu/

Allen, Lori E.

1995-11-01

295

Flares on Mira stars?  

NASA Technical Reports Server (NTRS)

Fourteen cases of flares reported on Mira type stars have been collected. These flares typically have an amplitude of over half a magnitude, a rise time of minutes, and a duration of tens of minutes. Nine of the 11 stars represent a normal cross section of the Mira population, while the remaining two are in symbiotic systems (CH Cyg and RX Pup). The flares were observed photographically (five cases), photometrically (three cases), visually (three cases), and with radio telescopes (two cases), while CH Cyg has had flares observed by many techniques. The evidence for the existence of flares on Miras is strong but not definitive. It is possible to hypothesize a variety of background or instrumental effects that could explain all 14 events; however, there is no evidence that suggests the data should be taken at other than face value, and there are good arguments for rejecting the possibility of artifacts. It is felt that the current data warrant systematic observational and theoretical investigation of the possibility of flares on Mira stars.

Schaefer, Bradley E.

1991-01-01

296

STAR Analysis Framework  

NASA Astrophysics Data System (ADS)

The STAR collaboration has developed STAF (STAR Analysis Framework), a distributable data analysis framework based upon the software bus concept and implemented using CORBA-compliant(http://www.omg.org) C++ classes. The extended lifetime of the experiment, the prodigious quantity of data to be handled, and the number of collaborators compel us to pay special attention in software design to the maintainability, upgradability, and scalability of the analysis software for STAR. Object-oriented programming techniques provide a powerful tool for the development and maintenance of complex software systems. The emergence of the CORBA software bus standard from the Object Management Group presents a well-accepted industry standard for combining an OOP approach to software development with a software model distributed over a heterogeneous computer network. We are currently using STAF to develop analysis code on simulated data using the familiar KUIP command-line interface from CERN. We present an overview of the design of STAF, some results from our experience with the software environment, plans for distributing STAF components for event parallel processing, and for upgrading the user interface to a distributed, network-based interface using Java(tm) from Sun Microsystems, Inc.

Olson, D. L.; Tull, C. E.

1996-10-01

297

Multiarm star polymers dynamics  

NASA Astrophysics Data System (ADS)

Multiarm star polymers, consisting of a high number of linear homopolymer arms joined covalently to a central core, represent model soft 'hybrid' spheres encompassing both polymeric (arm) and colloidal (core) character. Due to this topology, the single star has a nonuniform monomer density distribution. In nondilute solutions, a liquid-like ordering occurs as a consequence of the enhanced osmotic pressure that outbalances the entropic stretching of the arms; this type of order persists in the melt as well, due to 'macromolecular excluded volume' effects. The resulting rich dynamic response, which is presented in this review, exhibits signatures of both polymeric and colloidal behaviour. In solution, concentration and number density fluctuations relax via cooperative diffusion, self-diffusion and structural relaxation. In the melt, the viscoelastic terminal relaxation involves arm relaxation (independent of arm number) and structural rearrangements of the stars (strongly dependent on arm number and size). The identification of the relaxation mechanisms in such complex soft spheres provides the necessary ingredients for the molecular design and control of novel composite materials combining properties of polymers and colloids.

Vlassopoulos, Dimitris; Fytas, George; Pakula, Tadeusz; Roovers, Jacques

2001-10-01

298

Heavy Metal Stars  

NASA Astrophysics Data System (ADS)

La Silla Telescope Detects Lots of Lead in Three Distant Binaries Summary Very high abundances of the heavy element Lead have been discovered in three distant stars in the Milky Way Galaxy . This finding strongly supports the long-held view that roughly half of the stable elements heavier than Iron are produced in common stars during a phase towards the end of their life when they burn their Helium - the other half results from supernova explosions. All the Lead contained in each of the three stars weighs about as much as our Moon. The observations show that these "Lead stars" - all members of binary stellar systems - have been more enriched with Lead than with any other chemical element heavier than Iron. This new result is in excellent agreement with predictions by current stellar models about the build-up of heavy elements in stellar interiors. The new observations are reported by a team of Belgian and French astronomers [1] who used the Coude Echelle Spectrometer on the ESO 3.6-m telescope at the La Silla Observatory (Chile). PR Photo 26a/01 : A photo of HD 196944 , one of the "Lead stars". PR Photo 26b/01 : A CES spectrum of HD 196944 . The build-up of heavy elements Astronomers and physicists denote the build-up of heavier elements from lighter ones as " nucleosynthesis ". Only the very lightest elements (Hydrogen, Helium and Lithium [2]) were created at the time of the Big Bang and therefore present in the early universe. All the other heavier elements we now see around us were produced at a later time by nucleosynthesis inside stars. In those "element factories", nuclei of the lighter elements are smashed together whereby they become the nuclei of heavier ones - this process is known as nuclear fusion . In our Sun and similar stars, Hydrogen is being fused into Helium. At some stage, Helium is fused into Carbon, then Oxygen, etc. The fusion process requires positively charged nuclei to move very close to each other before they can unite. But with increasing atomic mass and hence, increasing positive charge of the nuclei, the electric repulsion between the nuclei becomes stronger and stronger. In fact, the fusion process only works up to a certain mass limit, corresponding to the element Iron [2]. All elements that are heavier than Iron cannot be produced via this path. But then, how were those heavy elements we now find on the Earth produced in the first place? From where comes the Zirconium in artificial diamonds, the Barium that colours fireworks, the Tungsten in the filaments in electric bulbs? Which process made the Lead in your car battery? Beyond iron The production of elements heavier than Iron takes place by adding neutrons to the atomic nuclei . These neutral particles do not feel any electrical repulsion from the charged nuclei. They can therefore easily approach them and thereby create heavier nuclei. This is indeed the way the heaviest chemical elements are built up. There are actually two different stellar environments where this process of "neutron capture" can happen. One place where this process occurs is inside very massive stars when they explode as supernovae . In such a dramatic event, the build-up proceeds very rapidly, via the so-called "r-process" ( "r" for rapid ). The AGB stars But not all heavy elements are created in such an explosive way. A second possibility follows a more "peaceful" road. It takes place in rather normal stars, when they burn their Helium towards the end of their lives. In the so-called "s-process" ( "s" for slow ), heavier elements are then produced by a rather gentle addition of neutral neutrons to atomic nuclei. In fact, roughly half of all the elements heavier than Iron are believed to be synthesized by this process during the late evolutionary phases of stars. This process takes place during a specific stage of stellar evolution, known as the "AGB" phase [3]. It occurs just before an old star expels its gaseous envelope into the surrounding interstellar s

2001-08-01

299

Reinvestigating the Lambda Boo Stars  

NASA Astrophysics Data System (ADS)

The peculiar nature of Lambda Bootis was first introduced in 1943. Subsequently, Lambda Boo stars have been slowly recognized as a group of A-type Population I dwarfs that show mild to extreme deficiencies of iron-peak elements, although C, N, O, and S can be near solar. MK classification criteria include broad hydrogen lines, a weak metallic-line spectrum compared to MK standards, coupled with a particularly weak Mg II 4481 line. This intriguing stellar class has recently regained the spotlight because of the directly imaged planets around a confirmed Lambda Boo star-HR 8799 and a probable Lambda Boo star-Beta Pictoris. The possible link between Lambda Boo stars and planet-bearing stars motivates us to study Lambda Boo stars systematically. However, Lambda Boo candidates published in the literature have been selected using widely different criteria. The Lambda Boo class has become somewhat of a "grab bag" for any peculiar A-type stars that didn't fit elsewhere. In order to determine the origin of Lambda Boo stars’ low abundances and to better discriminate between theories explaining the Lambda Boo phenomenon, a refined working definition of Lambda Boo stars is needed. We have re-evaluated all published Lambda Boo candidates and their existing spectra. After applying a consistent set of optical/UV classification criteria, we identified over 60 confirmed and over 20 probable Lambda Boo stars among all stars that have been suggested as Lambda Boo candidates. We are obtaining new observations for those probable Lambda Boo stars. We also have explored the possible link between debris disks and Lambda Boo Stars.

Cheng, Kwang-Ping; Corbally, C. J.; Gray, R. O.; Murphy, S.; Neff, J. E.; Desai, A.; Newsome, I.; Steele, P.

2014-01-01

300

Initial masses of stars changing into Wolf--Rayet stars  

SciTech Connect

It is shown that the spatial distribution and the ratio of populations of massive Wolf--Rayet stars of O and B spectral classes found by P. Conti et al. (1983) are consistent with the statement that components of close binary systems with masses M/sub 1,2/> or approx. =20 M/sub sun/ and all other stars with masses M> or approx. =40 M/sub sun/ become Wolf--Rayet stars.

Tutukov, A.V.; Yungel'son, L.R.

1985-05-01

301

The Dependence of Signal-To-Noise Ratio (S/N) Between Star Brightness and Background on the Filter Used in Images Taken by the Vulcan Photometric Planet Search Camera  

NASA Technical Reports Server (NTRS)

The Vulcan Photometric Planet Search is the ground-based counterpart of Kepler Mission Proposal. The Kepler Proposal calls for the launch of telescope to look intently at a small patch of sky for four year. The mission is designed to look for extra-solar planets that transit sun-like stars. The Kepler Mission should be able to detect Earth-size planets. This goal requires an instrument and software capable of detecting photometric changes of several parts per hundred thousand in the flux of a star. The goal also requires the continuous monitoring of about a hundred thousand stars. The Kepler Mission is a NASA Discovery Class proposal similar in cost to the Lunar Prospector. The Vulcan Search is also a NASA project but based at Lick Observatory. A small wide-field telescope monitors various star fields successively during the year. Dozens of images, each containing tens of thousands of stars, are taken any night that weather permits. The images are then monitored for photometric changes of the order of one part in a thousand. These changes would reveal the transit of an inner-orbit Jupiter-size planet similar to those discovered recently in spectroscopic searches. In order to achieve a one part in one thousand photometric precision even the choice of a filter used in taking an exposure can be critical. The ultimate purpose of an filter is to increase the signal-to-noise ratio (S/N) of one's observation. Ideally, filters reduce the sky glow cause by street lights and, thereby, make the star images more distinct. The higher the S/N, the higher is the chance to observe a transit signal that indicates the presence of a new planet. It is, therefore, important to select the filter that maximizes the S/N.

Mena-Werth, Jose

1998-01-01

302

Steady Advances Against Cystic Fibrosis | NIH MedlinePlus the Magazine  

MedlinePLUS

... old Gunnar Esiason, son of former all-star NFL quarterback and current NFL commentator Boomer Esiason, hasn't let cystic fibrosis ( ... He and his parents—Cheryl Esiason and former NFL quarterback Boomer Esiason—are helping to fund research ...

303

Division IV / Working Group on Massive Stars  

NASA Astrophysics Data System (ADS)

Our Working Group (WG) studies massive, luminous stars, both individually and in resolved and unresolved populations, with historical focus on early-type (OB) stars, A-supergiants, and Wolf-Rayet stars. Our group also studies lower mass stars (e.g., central stars of planetary nebulae and their winds) which display features similar or related to those present in massive stars, and thus may improve our understanding of the physical processes occurring in massive stars. In recent years, massive red supergiants that evolve from hot stars have been included into our activities as well. We emphasize the role of massive stars in other branches of astrophysics, particularly regarding the First Stars, long duration Gamma-Ray bursts, formation of massive stars and their feedback on star formation in general, pulsations of massive stars, and starburst galaxies.

Puls, Joachim; Leitherer, Claus; Owocki, Stan; Crowther, Paul; Hanson, Margaret; Herrero, Artemio; Langer, Norbert; Owocki, Stan; Rauw, Gregor; St-Louis, Nicole; Townsend, Richard

2012-04-01

304

An Introduction to the Sun and Stars  

NASA Astrophysics Data System (ADS)

Introduction; 1. Seeing the Sun; 2. The working Sun; 3. Measuring stars; 4. Comparing stars; 5. The formation of stars; 6. The main sequence life of stars; 7. The life of stars beyond the main sequence; 8. The death of stars; 9. The remnants of stars; Conclusion; Answers and comments; Appendix 1. Useful quantities and units; Appendix 2. Stellar nomenclature; Appendix 3. The 100 closest stars to the Sun; Appendix 4. The 100 brightest stars visible from Earth; Appendix 5. The chemical elements and their abundances; Glossary; Acknowledgements; Index.

Green, Simon F.; Jones, Mark H.

2004-02-01

305

Star formation in elliptical galaxies  

NASA Astrophysics Data System (ADS)

In this paper we anticipate part of the results of a recent study by the Padova group to cast light on the formation and evolution of elliptical galaxies by means of N-body TSPH simulations including star formation, feed-back and chemical evolution. Particular attention is paid here to the case of dwarf spheroidals of the Local Group which, thanks to their proximity and modern ground-based and space instrumentation, can be resolved into single stars so that independent determinations of their age and star formation history can be derived. Dwarf galaxies are known to exhibit complicated histories of star formation ranging from a single very old episode to a series of bursts over most of the Hubble time. By understanding the physical process driving star formation in these objects, we might be able to infer the mechanism governing star formation in more massive elliptical galaxies.

Chiosi, Cesare

306

Upper Atmospheres of Late M Stars  

Microsoft Academic Search

Although the later M stars have colors redder than the warmest N stars and, presumably, lower effective temperatures, their ultraviolet spectra differ considerably. An M star, in low resolution IUE spectra, shows a rather smooth, featureless continuum, while the warmer N stars and coolest R stars show very strong photospheric absorption lines of zero-volt iron-peak elements. These same differences are

Hollis R. Johnson

1985-01-01

307

Space Science in Action: Stars [Videotape].  

ERIC Educational Resources Information Center

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…

1999

308

Radio observations related to star formation  

Microsoft Academic Search

In a brief overview of the basic facts in the field, consideration is given to radio and sub-mm observations related to star formation, and to a possible evolutionary sequence of O and B stars and their protostellar shells. Radio observations related to the formation of single stars and star clusters are then examined with special emphasis on stars less massive

P. G. Mezger; L. F. Smith

1977-01-01

309

Geometric voting algorithm for star trackers  

Microsoft Academic Search

We present an algorithm for recovering the orientation (attitude) of a satellite-based camera. The algorithm matches stars in an image taken with the camera to stars in a star catalogue. The algorithm is based on a geometric voting scheme in which a pair of stars in the catalogue votes for a pair of stars in the image if the angular

Michael Kolomenkin; Sharon Pollak; Ilan Shimshoni; Michael Lindenbaum

2008-01-01

310

Hipparcos variable stars (Adelman+, 2001)  

NASA Astrophysics Data System (ADS)

The data known as the Hipparcos Photometry obtained with the Hipparcos satellite have been investigated to find those stars which are least variable. Such stars are excellent candidates to serve as standards for photometric systems. Their spectral types suggest in which parts of the HR diagrams stars are most constant. In some cases these values strongly indicate that previous ground based studies claiming photometric variability are incorrect or that the level of stellar activity has changed. (1 data file).

Adelman, S. J.

2001-02-01

311

Superfluidity in Neutron Star Matter  

Microsoft Academic Search

The research on the superfluidity of neutron matter can be traced back to Migdal’s observation that neutron stars are good\\u000a candidates for being macroscopic superfluid systems [1]. And, in fact, during more than two decades of neutron-star physics the presence of neutron and proton superfluid phases\\u000a has been invoked to explain the dynamical and thermal evolution of a neutron star.

Umberto Lombardo; Hans-Josef Schulze

2001-01-01

312

QPO Constraints on Neutron Stars  

NASA Technical Reports Server (NTRS)

The kilohertz frequencies of QPOs from accreting neutron star systems imply that they are generated in regions of strong gravity, close to the star. This suggests that observations of the QPOs can be used to constrain the properties of neutron stars themselves, and in particular to inform us about the properties of cold matter beyond nuclear densities. Here we discuss some relatively model-insensitive constraints that emerge from the kilohertz QPOs, as well as recent developments that may hint at phenomena related to unstable circular orbits outside neutron stars.

Miller, M. Coleman

2005-01-01

313

Star formation rates and starbursts  

NASA Astrophysics Data System (ADS)

Understanding star formation rates in galaxies requires understanding both the rate at which molecular clouds form and the efficiency of star formation in these clouds. The efficiency of star formation is probably limited mainly by the destruction of star-forming clouds by ionization, and molecular clouds probably form by a combination of large-scale gravitational instabilities and cloud accretion processes. These hypotheses lead to quantitative predictions that agree well with observational estimates of both the efficiency of star formation and the timescale for converting gas into stars. The predicted timescale depends mainly on the surface density of gas in a galaxy, and the predicted star formation rate per unit area is proportional to the square of the gas surface density, similar to the original Schmidt law. A burst of star formation requires an exceptionally high gas surface density; this results in both a short timescale and a high efficiency for star formation. The gas feeding a starburst must be assembled rapidly into the starburst region, and this requires a violent large-scale disturbance to the interstellar medium in a galaxy, such as that produced by a tidal interaction or merger with another galaxy.

Larson, Richard B.

314

The Spacelab IPS Star Simulator  

NASA Astrophysics Data System (ADS)

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 deg 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 two to eight visual magnitudes. The star size is less than 100 arcsec. The minimum star movement is less than 5 arcsec and the relative position accuracy is approximately 40 arcsec. The purpose of this paper is to describe the IPS Star Simulator design and to provide an operational scenario so others may gain from the approach and possible use of the system.

Wessling, Francis C., III

315

Accretion Onto Magnetic Degenerate Stars  

NASA Technical Reports Server (NTRS)

While the original objectives of this research program included the study of radiative processes in cataclysmic variables and the evolution of neutron star magnetic fields, the scope of the reported research expanded to other related topics as this project developed. This final report therefore describes the results of our research in the following areas: 1) Irradiation-driven mass transfer cycles in cataclysmic variables and low-mass X-ray binaries; 2) Propeller effect and magnetic field decay in isolated old neutron stars; 3) Decay of surface magnetic fields in accreting neutron stars and pulsars; 4) Finite-Difference Hydrodynamic simulations of mass transfer in binary stars.

Frank, Juhan

2000-01-01

316

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.

2011-03-28

317

The Spacelab IPS Star Simulator  

NASA Technical Reports Server (NTRS)

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 deg 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 two to eight visual magnitudes. The star size is less than 100 arcsec. The minimum star movement is less than 5 arcsec and the relative position accuracy is approximately 40 arcsec. The purpose of this paper is to describe the IPS Star Simulator design and to provide an operational scenario so others may gain from the approach and possible use of the system.

Wessling, Francis C., III

1993-01-01

318

The Spacelab IPS Star Simulator  

NASA Technical Reports Server (NTRS)

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.

Wessling, Francis C., III

1993-01-01

319

Optical filtering for star trackers  

NASA Technical Reports Server (NTRS)

The optimization of optical filtering was investigated for tracking faint stars, down to the fifth magnitude. The effective wavelength and bandwidth for tracking pre-selected guide stars are discussed along with the results of an all-electronic tracker with a star tracking photomultiplier, which was tested with a simulated second magnitude star. Tables which give the sum of zodiacal light and galactic background light over the entire sky for intervals of five degrees in declination, and twenty minutes in right ascension are included.

Wilson, R. E.

1973-01-01

320

Binary Star Software for Teaching  

NASA Astrophysics Data System (ADS)

Educational software for Macintosh computers to aid in teaching binary star concepts is now available free from my web site http://www.uark.edu/misc/clacy/BinaryStars/. Four programs are available to teach binary star concepts such as orbital period, orbital phase, eclipsing binary star, dates of minima, semi-major axis, eccentricity, longitude of periastron, orbital inclination, Kepler;s laws, and observing seasons. These programs may be used in a teaching laboratory setting, or for personal use. Both student manuals and instructor manuals are provided.

Lacy, C. H. S.

1998-12-01

321

Star Atlases and Software  

NASA Astrophysics Data System (ADS)

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.

Brazell, Owen; Argyle, R. W.

322

Moon and Stars  

NSDL National Science Digital Library

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.

Science, Lawrence H.

1997-01-01

323

The guide star catalog  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

324

Outside the stars  

NASA Astrophysics Data System (ADS)

Three case studies in the areas of high energy astrophysics, classical cosmology, and astrophysical cosmology and the origin of galaxies are presented. Attention is given to solar neutrinos, solar and stellar seismology, nucleosynthesis of the heavy elements, stellar evolution in globular clusters, and postmain-sequence evolution and mass loss. It is shown how the understanding of the internal structures of the stars is directly related to processes which are of importance in a wide range of different astrophysical disciplines. Determination of the deceleration of the universe from observations of distant galaxies is adressed.

Longair, Malcolm S.

1993-01-01

325

The Death of Stars II: High Mass Stars  

NSDL National Science Digital Library

This article from the Australian Telescope National Facility describes the death of massive stars. It discusses the formation and characteristics of supernovae, hypernovae, neutron stars/pulsars, and black holes. The article includes an animated diagram showing how the pulsar beam is observed from Earth.

2009-06-03

326

Triggered Star Formation Surrounding Wolf-Rayet Star HD 211853  

NASA Astrophysics Data System (ADS)

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 103 cm-3 and kinematic temperature ~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.

Liu, Tie; Wu, Yuefang; Zhang, Huawei; Qin, Sheng-Li

2012-05-01

327

Hierarchical star formation in M 51: star\\/cluster complexes  

Microsoft Academic Search

We report on a study of young star cluster complexes in the spiral galaxy M 51. Recent studies have confirmed that star clusters do not form in isolation, but instead tend to form in larger groupings or complexes. We use HST broad and narrow band images (from both WFPC2 and ACS), along with BIMA-CO observations to study the properties and

N. Bastian; M. Gieles; Yu. N. Efremov

2005-01-01

328

Al-Sufi's Investigation of Stars, Star Clusters and Nebulae  

NASA Astrophysics Data System (ADS)

The distinguished Arabic astronomer, Al-Sufi (AD 903-986) is justly famous for his Book of the Fixed Stars, an outstanding Medieval treatise on astronomy that was assembled in 964. Developed from Ptolemy's Algamest, but based upon al-Sufi's own stellar observations, the Book of the Fixed Stars has been copied down through the ages, and currently 35 copies are known to exist in various archival repositories around the world. Among other things, this major work contains 55 astronomical tables, plus star charts for 48 constellations. For the first time a long-overdue English translation of this important early work is in active preparation. In this paper we provide biographical material about Al-Sufi and the contents of his Book of the Fixed Stars, before examining his novel stellar magnitude system, and his listing of star clusters and nebulae (including the first-ever mention of the Great Nebula in Andromeda).

Hafez, Ihsan; Stephenson, F. R.; Orchiston, W.

2011-01-01

329

Charged boson stars  

NASA Astrophysics Data System (ADS)

We study time-independent, spherically symmetric, self-gravitating systems minimally coupled to a scalar field with U(1) gauge symmetry: charged boson stars. We find numerical solutions to the Einstein-Maxwell equations coupled to the relativistic Klein-Gordon equation. It is shown that bound stable configurations exist only for values of the coupling constant less than or equal to a certain critical value. The metric coefficients and the relevant physical quantities, such as the total mass and charge, turn out to be, in general, bound functions of the radial coordinate, reaching their maximum values at a critical value of the scalar field at the origin. We discuss the stability problem from both the quantitative and qualitative point of view. We take into account the electromagnetic contribution to the total mass and investigate the stability issue considering the binding energy per particle. We verify the existence of configurations with positive binding energy in which objects that are apparently bound can be unstable against small perturbations, in full analogy with the effect observed in the mass-radius relation of neutron stars.

Pugliese, Daniela; Quevedo, Hernando; Rueda H., Jorge A.; Ruffini, Remo

2013-07-01

330

Multistate boson stars  

SciTech Connect

Motivated by the increasing interest in models which consider scalar fields as viable dark matter candidates, we have constructed a generalization of relativistic boson stars (BS) composed of two coexisting states of the scalar field, the ground state and the first excited state. We have studied the dynamical evolution of these multistate boson stars (MSBS) under radial perturbations, using numerical techniques. We show that stable MSBS can be constructed, when the number of particles in the first excited state, N{sup (2)}, is smaller than the number of particles in the ground state, N{sup (1)}. On the other hand, when N{sup (2)}>N{sup (1)}, the configurations are initially unstable. However, they evolve and settle down into stable configurations. In the stabilization process, the initially ground state is excited and ends in a first excited state, whereas the initially first excited state ends in a ground state. During this process, both states emit scalar field radiation, decreasing their number of particles. This behavior shows that even though BS in the first excited state are intrinsically unstable under finite perturbations, the configuration resulting from the combination of this state with the ground state produces stable objects. Finally we show in a qualitative way, that stable MSBS could be realistic models of dark matter galactic halos, as they produce rotation curves that are flatter at large radii than the rotation curves produced by BS with only one state.

Bernal, A.; Barranco, J. [Max-Planck-Institut fuer Gravitationsphysik, Albert Einstein Institut, 14476 Golm (Germany); Alic, D. [Max-Planck-Institut fuer Gravitationsphysik, Albert Einstein Institut, 14476 Golm (Germany); Department of Physics, Universitat de les Illes Balears, Cra. Valldemossa (Spain); Palenzuela, C. [Max-Planck-Institut fuer Gravitationsphysik, Albert Einstein Institut, 14476 Golm (Germany); Canadian Institute for Theoretical Astrophysics (CITA), Toronto (Canada)

2010-02-15

331

Star TPC at Rhic.  

NASA Astrophysics Data System (ADS)

The construction of a Time Projection Chamber (TPC) for the RHIC collider STAR detector system(J. Harris and the STAR Collaboration, Conceptual Design Report for the Solenoidal Tracker At RHIC PUB-5347), (1992). is more than halfway completed. The TPC will provide tracking to measure heavy ion collisions of Au on Au as well as lighter projectiles including protons on protons. At RHIC, with center of mass energies of 200 GeV/n, it is expected that central collisions will yield 4000 charged particles in the acceptance region of the TPC. The design has been optimized to provide tracking and dE/dx values for the high density of particles with pseudo rapidity in the range of mid ? mid = 0-1.8. The active gas volume of the TPC is a cylinder 4.2 meters long and 4 meters in diameter. Electrons left by the ionizing particles drift to either end of the TPC cylinder where they are read out with multi-wire proportional chambers equipped with continuous array pad readout. There are a total of 140,000 pads, each equipped with low noise electronics which take 512 time sample measurements, thereby providing a full 3D, 70 million pixel representation of the tracks through the gas volume. Both tracking and dE/dx are obtained from the pad signals. We will be reporting on design details, test results and construction progress.

Wieman, Howard

1996-10-01

332

Recovery Ship Freedom Star  

NASA Technical Reports Server (NTRS)

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.

1998-01-01

333

White Dwarf Stars  

NASA Astrophysics Data System (ADS)

White dwarfs are the final stage for more than 95% of all stars. Their population statistics and properties contain a wealth of information about the history of star formation in our galaxy, the ages of stellar systems, and the relation between original mass at birth and that of the final remnant. They are also interesting individually as laboratories for physical conditions not easily reached in terrestrial labs: macroscopic manifestation of the Pauli principle, high densities and pressures, and extremely high magnetic fields. After a brief introduction with some historical milestones the observational status is reviewed: spectroscopic classification, determination of stellar parameters from spectroscopic and photometric observations, effective temperatures, surface gravities, radii, and masses. The next sections deal with the physics of the interior and evolution of white dwarfs, leading to the mass-radius relation and cooling times. Going back closer to the observations again, the physical processes in the outer layers are discussed: gravitational separation, diffusion, radiative levitation, accretion, and convective mixing. This leads to a review of our current understanding of the origin of spectral types and their interrelation. A final section gives brief introductions to topics at the center of current research: white dwarfs in open and globular clusters, debris disks, the origin of accreted metals in the atmospheres, magnetic fields and their origin, variable white dwarfs, and white dwarfs in binaries. This chapter was finished in February 2010 and reflects the status of knowledge at that time.

Koester, Detlev

334

Stars and Planets  

NASA Astrophysics Data System (ADS)

'Estrelas e Planetas' (Stars and Planets) project was developed during the academic year 2009/2010 and was tested on three 3rd grade classes of one school in Quarteira, Portugal. The aim was to encourage the learning of science and the natural and physical phenomena through the construction and manipulation of materials that promote these themes - in this case astronomy. Throughout the project the students built a small book containing three themes of astronomy: differences between stars and planets, the solar system and the phases of the Moon. To each topic was devoted two sessions of about an hour each: the first to teach the theoretical aspects of the theme and the second session to assembly two pages of the book. All materials used (for theoretical sessions and for the construction of the book) and videos of the finished book are available for free use in www.miguelneta.pt/estrelaseplanetas. So far there is only a Portuguese version but soon will be published in English as well. This project won the Excellency Prize 2011 of Casa das Ciências, a portuguese site for teachers supported by the Calouste Gulbenkian Fundation (www.casadasciencias.org).

Neta, Miguel

2014-05-01

335

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

SciTech Connect

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.

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

1994-03-02

336

Infrared observations of Be stars  

NASA Technical Reports Server (NTRS)

IRAS observations of the Be stars and the correlations between the IR excess and the stellar parameters are discussed. The quantitative interpretation of the IR excess is described and interpreted in terms of the characteristics of the circumstellar material. Some of the major problems of the IR studies of Be stars are examined, and possible future studies are addressed.

Lamers, Henny J. G. L. M.

1987-01-01

337

Astronomy: A truly embryonic star  

NASA Astrophysics Data System (ADS)

The discovery of what may be the best example yet of a forming star caught in the moments just before birth provides a missing link in our understanding of how giant gas clouds collapse to form fully fledged stars. See Letter p.83

Clarke, David A.

2012-12-01

338

The Spectral Types of Stars  

NSDL National Science Digital Library

This article outlines the discovery of spectra and stellar spectral classifications. Included are mnemonics of the spectral sequence, what spectra lines can tell astronomers about a star, how temperature and luminosity relate to the Hertzsprung-Russell diagram, and luminosity classifications for stars.

Macrobert, Alan

2004-07-14

339

High Speed Astrometry - Barnard's Star  

NASA Astrophysics Data System (ADS)

FGS POS mode observations of Barnard's Star will be analyzed to detect planetary companions. Whether or not companions are detected, the results from Barnard's Star will be compared to results from Prooxima Cen in an effort to identify all remaining systematic effects produced by HST and/or FGS in both data sets.

Jefferys, William

1995-07-01

340

Axion emission from neutron stars  

NASA Technical Reports Server (NTRS)

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.

Iwamoto, N.

1984-01-01

341

Model atmospheres of Be stars  

Microsoft Academic Search

A solution to the basic equations governing the structure and dynamics of Be star envelopes is considered as remote now as it was five years ago. In fact, the advent of coronae in stellar wind models has made the entire process even more complex. At present the ad hoc models still furnish the best picture of Be stars. Among the

R. Poeckert

1982-01-01

342

A spectrophotometric catalog of stars  

Microsoft Academic Search

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

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

1978-01-01

343

Collapse anisotropy for massive stars  

Microsoft Academic Search

A series of numerical experiments to simulate the evolution of massive binary systems is described. The simulations yielded an estimate of 70-10 km\\/s for the kick velocity of a neutron star following the collapse of a normal star. It is demonstrated that kick velocity can be used as a measure of the mean anisotropy of the entire collapse process. Some

V. G. Kornilov; V. M. Lipunov

1984-01-01

344

Nonradial oscillations of neutron stars  

Microsoft Academic Search

Linear, adiabatic, Newtonian, nonradial pulsation analyses have been performed for finite-temperature neutron star models with a fluid core, solid crust, and thin surface fluid ocean, including the effects of the neutron star crust. The pulsation equations are considered, including the spheroidal and toroidal modes. A local analysis is performed to provide information about the pulsation modes in the short-wavelength limit.

P. N. Mcdermott; H. M. Van Horn; C. J. Hansen

1988-01-01

345

Theory of neutron star magnetospheres  

Microsoft Academic Search

The theory of neutron star magnetospheres is presented with reference to the most important observational data on neutron stars available to date. In particular, attention is given to the nature of pulsars and pulsar properties and statistics; phenomenological models; the aligned rotator and oblique rotator models; the disk models; alternative models; and radio emission models. The discussion also covers winds

F. C. Michel

1991-01-01

346

The Physics of Neutron Stars  

Microsoft Academic Search

Neutron stars are some of the densest manifestations of massive objects in the universe. They are ideal astrophysical laboratories for testing theories of dense matter physics and provide connections among nuclear physics, particle physics, and astrophysics. Neutron stars may exhibit conditions and phenomena not observed elsewhere, such as hyperon-dominated matter, deconfined quark matter, superfluidity and superconductivity with critical temperatures near

J. M. Lattimer; M. Prakash

2004-01-01

347

Comparable Habitable Zones of Stars  

NASA Video Gallery

The habitable zone is the distance from a star where one can have liquid water on the surface of a planet. If a planet is too close to its parent star, it will be too hot and water would have evapo...

348

Stars Get Dizzy After Lunch  

NASA Astrophysics Data System (ADS)

Exoplanet searches have discovered a large number of "hot Jupiters"—high-mass planets orbiting very close to their parent stars in nearly circular orbits. A number of these planets are sufficiently massive and close-in to be significantly affected by tidal dissipation in the parent star, to a degree parameterized by the tidal quality factor Q *. This process speeds up their star's rotation rate while reducing the planet's semimajor axis. In this paper, we investigate the tidal destruction of hot Jupiters. Because the orbital angular momenta of these planets are a significant fraction of their star's rotational angular momenta, they spin up their stars significantly while spiraling to their deaths. Using the Monte Carlo simulation, we predict that for Q * = 106, 3.9 × 10-6 of stars with the Kepler Target Catalog's mass distribution should have a rotation period shorter than 1/3 day (8 hr) due to accreting a planet. Exoplanet surveys such as SuperWASP, HATnet, HATsouth, and KELT have already produced light curves of millions of stars. These two facts suggest that it may be possible to search for tidally destroyed planets by looking for stars with extremely short rotational periods, then looking for remnant planet cores around those candidates, anomalies in the metal distribution, or other signatures of the recent accretion of the planet.

Zhang, Michael; Penev, Kaloyan

2014-06-01

349

Dust near luminous ultraviolet stars  

NASA Technical Reports Server (NTRS)

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.

Henry, Richard C.

1993-01-01

350

Galaxy Collisions and Star Formation  

Microsoft Academic Search

We present a brief overview of some recent observations of colliding galaxies and relevant numerical simulations. These are compared, and details of the locations and history of collision induced star formation are explored, with possible application to star formation at earlier epochs.

Susan A. Lamb; Nathan C. Hearn

2000-01-01

351

Galaxy Collisions and Star Formation  

Microsoft Academic Search

We present a brief overview of some recent observations of colliding galaxies\\u000aand relevant numerical simulations. These are compared, and details of the\\u000alocations and history of collision induced star formation are explored, with\\u000apossible application to star formation at earlier epochs.

Susan A. Lamb; Nathan C. Hearn

2000-01-01

352

Grand unification of neutron stars.  

PubMed

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

Kaspi, Victoria M

2010-04-20

353

Neutron Star Crustal Mass Fractions  

SciTech Connect

We are investigating mass fractions on the crust of a neutron star which would remain after one year of cooling. We use cooling curves corresponding with various densities, or depths, of the neutron star just after its formation. We assume the modified Urca process dominates the energy budget of the outer layers of the star in order to calculate the temperature of the neutron star as a function of time. Using a nuclear reaction network up to technetium, we calculate how the distribution of nuclei quenches at various depths of the neutron star crust. The initial results indicate that {sup 28}Si is the lightest isotope to be optically thick on the surface after one year of cooling.

Hoffman, Kelsey L.; Heyl, Jeremy S. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1 (Canada)

2008-02-27

354

The Diversity of Neutron Stars  

NASA Astrophysics Data System (ADS)

Neutron stars are invaluable tools for exploring stellar death, the physics of ultra-dense matter, and the effects of extremely strong magnetic fields. The observed population of neutron stars is dominated by the >1000 radio pulsars, but there are distinct sub-populations that, while fewer in number, can have significant impact on our understanding of the issues mentioned above. These populations are the nearby, isolated neutron stars discovered by ROSAT, and the central compact objects in supernova remnants. The studies of both of these populations have been greatly accelerated in recent years through observations with the Chandra X-ray Observatory and the XMM-Newton telescope. First, we discuss radio, optical, and X-ray observations of the nearby neutron stars aimed at determining their relation to the Galactic neutron star population and at unraveling their complex physical processes by determining the basic astronomical parameters that define the population---distances, ages, and magnetic fields---the uncertainties in which limit any attempt to derive basic physical parameters for these objects. We conclude that these sources are 1e6 year-old cooling neutron stars with magnetic fields above 1e13 Gauss. Second, we describe the hollow supernova remnant problem: why many of the supernova remnants in the Galaxy have no indication of central neutron stars. We have undertaken an X-ray census of neutron stars in a volume-limited sample of Galactic supernova remnants, and from it conclude that either many supernovae do not produce neutron stars contrary to expectation, or that neutron stars can have a wide range in cooling behavior that makes many sources disappear from the X-ray sky.

Kaplan, David L.

2004-12-01

355

The Ages of Nearby Stars  

NASA Astrophysics Data System (ADS)

Stellar age estimates are necessary to understand the evolution of stars and planetary systems. To date these have not been obtained for most nearby stellar systems. Published values have never been compiled into a single catalog, and rely on techniques that are diverse and of uneven quality. Methods presented in the literature include chromospheric activity, lithium equivalent width, surface gravity, metallicity, space velocity, isochrone fitting, and determination of rotation periods. We compiled published ages for all stars with V < 9 and within 25pc of the Sun in this work. The sample includes stars with spectral types K and earlier. Results with different methods are compared and an observational program is outlined to complete the census of ages for all nearby stars. Comparison and analysis of age estimates from diverse methods indicate that the determination of stellar rotation periods is the best age-dating method for nearby stars. Rotation is better suited to the sample of nearby stars because most lie on the main sequence where other methods are less reliable. Rotation is also a more direct indicator than chromospheric activity, since stellar activity is believed to result from magnetic field activity due to stellar rotation. Only a small fraction of rotation periods are available for stars in the solar neighborhood. The prospects for a complete census are investigated here. Photometric rotation periods for seven stars were measured using the Lowell 31-inch telescope. These rotation periods illustrate the feasibility of carrying out part of the survey with instrumentation available to NAU and Lowell Observatory. Time and instrument requirements for a more complete survey are estimated and used to show that a volume-limited survey of stellar ages for spectral types K and earlier could be carried out in three years for stars within 15pc and six years for stars within 25pc.

Saylor, Dicy Ann

356

Hierarchical star formation in M 51: star/cluster complexes  

NASA Astrophysics Data System (ADS)

We report on a study of young star cluster complexes in the spiral galaxy M 51. Recent studies have confirmed that star clusters do not form in isolation, but instead tend to form in larger groupings or complexes. We use HST broad and narrow band images (from both WFPC2 and ACS), along with BIMA-CO observations to study the properties and investigate the origin of these complexes. We find that the complexes are all young (<10 Myr), have sizes between ~85 and ~240 pc, and have masses between 3-30 × 104~ M?. Unlike that found for isolated young star clusters, we find a strong correlation between the complex mass and radius, namely M? R2.33 ± 0.19. This is similar to that found for giant molecular clouds (GMCs). By comparing the mass-radius relation of GMCs in M 51 to that of the complexes we can estimate the star formation efficiency within the complexes, although this value is heavily dependent on the assumed CO-to-H2 conversion factor. The complexes studied here have the same surface density distribution as individual young star clusters and GMCs. If star formation within the complexes is proportional to the gas density at that point, then the shared mass-radius relation of GMCs and complexes is a natural consequence of their shared density profiles. We briefly discuss possibilities for the lack of a mass-radius relation for young star clusters. We note that many of the complexes show evidence of merging of star clusters in their centres, suggesting that larger star clusters can be produced through the build up of smaller clusters.

Bastian, N.; Gieles, M.; Efremov, Yu. N.; Lamers, H. J. G. L. M.

2005-11-01

357

The Chemical Composition Contrast between M3 and M13 Revisited: New Abundances for 28 Giant Stars in M3  

NASA Astrophysics Data System (ADS)

We report new chemical abundances of 23 bright red giant members of the globular cluster M3, based on high-resolution (R~45,000) spectra obtained with the Keck I telescope. The observations, which involve the use of multislits in the HIRES Keck I spectrograph, are described in detail. Combining these data with a previously reported small sample of M3 giants obtained with the Lick 3 m telescope, we compare metallicities and [X/Fe] ratios for 28 M3 giants with a 35-star sample in the similar-metallicity cluster M13, and with Galactic halo field stars having [Fe/H]<-1. For elements having atomic number A>=A(Si), we derive little difference in [X/Fe] ratios in the M3, M13, or halo field samples. All three groups exhibit C depletion with advancing evolutionary state beginning at the level of the red giant branch ``bump,'' but the overall depletion of about 0.7-0.9 dex seen in the clusters is larger than that associated with the field stars. The behaviors of O, Na, Mg, and Al are distinctively different among the three stellar samples. Field halo giants and subdwarfs have a positive correlation of Na with Mg, as predicted from explosive or hydrostatic carbon burning in Type II supernova sites. Both M3 and M13 show evidence of high-temperature proton-capture synthesis from the ON, NeNa, and MgAl cycles, while there is no evidence for such synthesis among halo field stars. But the degree of such extreme proton-capture synthesis in M3 is smaller than it is in M13: the M3 giants exhibit only modest deficiencies of O and corresponding enhancements of Na, less extreme overabundances of Al, fewer stars with low Mg and correspondingly high Na, and no indication that O depletions are a function of advancing evolutionary state, as has been claimed for M13. We have also considered NGC 6752, for which Mg isotopic abundances have been reported by Yong et al. Giants in NGC 6752 and M13 satisfy the same anticorrelation of O abundances with the ratio (25Mg+26Mg)/24Mg, which measures the relative contribution of rare to abundant isotopes of Mg. This points to a scenario in which these abundance ratios arose in the ejected material of 3-6 Msolar cluster stars, material that was then used to form the atmospheres of the presently evolving low-mass cluster stars. It also suggests that the low oxygen abundance seen among the most evolved M13 giants arose in hot bottom O-to-N processing in these same intermediate-mass cluster stars. Thus, mixing is required by the dependence of some abundance ratios on luminosity, but an earlier nucleosynthesis process in a hotter environment than giants or main-sequence stars is required by the variations previously seen in stars near the main sequence. The nature and the site of the earlier process is constrained but not pinpointed by the observed Mg isotopic ratio. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

Sneden, Christopher; Kraft, Robert P.; Guhathakurta, Puragra; Peterson, Ruth C.; Fulbright, Jon P.

2004-04-01

358

StarFISH: For Inferring Star-formation Histories  

NASA Astrophysics Data System (ADS)

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.

Harris, Jason; Zaritsky, Dennis

2012-04-01

359

Star in the making  

SciTech Connect

As the result of a recent series of high-frequency molecular-line observations, astronomers may have detected the infalling envelope around an embedded radiation source, providing the first direct glimpse at the actual process of star formation. The object in question is known as IRAS 16293-2422 and was initially uncovered in a sky survey by the Infrared Astronomical Satellite. It is in an outlying region of the Ophiuchus dark nebula, near rho Ophiuchi just north of Antares, about 520 light-years away. Using the 12-m-diameter radio telescope of the National Radio Astronomy Observatory at Kitt Peak, emissions from a spectral line of the carbon monosulfide molecule (CS) were observed at a frequency near 245,000 MHz, corresponding to a wavelength of about 1 mm; the asymmetric shape of the emission curve is just what would be expected from a collapsing gas.

Lada, C.J.

1986-10-01

360

Abundances in Przybylski's star  

NASA Astrophysics Data System (ADS)

We have derived abundances for 54 elements in the extreme roAp star HD101065. ESO spectra with a resolution of about 80000, and S/N of 200 or more were employed. The adopted model has Teff=6600K, and log(g)=4.2. Because of the increased line opacity and consequent low gas pressure, convection plays no significant role in the temperature structure. Lighter elemental abundances through the iron group scatter about standard abundance distribution (SAD) (solar) values. Iron and nickel are about one order of magnitude deficient while cobalt is enhanced by 1.5dex. Heavier elements, including the lanthanides, generally follow the solar pattern but enhanced by 3 to 4dex. Odd-Z elements are generally less abundant than their even-Z neighbours. With a few exceptions (e.g. Yb), the abundance pattern among the heavy elements is remarkably coherent, and resembles a displaced solar distribution.

Cowley, C. R.; Ryabchikova, T.; Kupka, F.; Bord, D. J.; Mathys, G.; Bidelman, W. P.

2000-09-01

361

Gaia and variable stars  

NASA Astrophysics Data System (ADS)

The study of variable phenomena (periodic, irregular or transient) provides a unique way to acquire knowledge about objects in our Universe. Currently, we are going through a rapid expansion of time-domain astrophysics. One reason for this expansion is the technological developments materialised in small to medium size observational projects such as HAT, OGLE, Catalina, PTF and upcoming very large projects such as Gaia or LSST. In this article, we are focusing on the ESA cornerstone mission Gaia. This spacecraft will provide astrometric, photometric and spectroscopic measurements for one billion stars. Among the existing and planned multi-epoch projects Gaia is unique because it will provide exquisite astrometric measurements for all objects it observes. We provide a brief overview of the literature concerning this mission and its expected contribution to variability studies.

Eyer, Laurent; Holl, Berry; Mowlavi, Nami

2014-01-01

362

AGB stars & presolar grains  

NASA Astrophysics Data System (ADS)

Among presolar materials recovered in meteorites, abundant SiC and Al2O3 grains of AGB origins were found. They showed records of C, N, O, 26Al and s-element isotopic ratios that proved invaluable in constraining the nucleosynthesis models for AGB stars [1, 2]. In particular, when these ratios are measured in SiC grains, they clearly reveal their prevalent origin in cool AGB circumstellar envelopes and provide information on both the local physics and the conditions at the nucleosynthesis site (the H- and He-burning layers deep inside the structure). Among the properties ascertained for the main part of the SiC data (the so-called mainstream ones), we mention a large range of 14N/15N ratios, extending below the solar value [3], and 12C/13C ratios ? 30. Other classes of grains, instead, display low carbon isotopic ratios (? 10) and a huge dispersion for N isotopes, with cases of large 15N excess. In the same grains, isotopes currently feeded by slow neutron captures reveal the characteristic pattern expected from this process at an efficiency slightly lower than necessary to explain the solar main s-process component. Complementary constraints can be found in oxide grains, especially Al2O3 crystals. Here, the oxygen isotopes and the content in 26Al are of a special importance for clarifying the partial mixing processes that are known to affect evolved low-mass stars. Successes in modeling the data, as well as problems in explaining some of the mentioned isotopic ratios through current nucleosynthesis models are briefly outlined.

Busso, M.; Trippella, O.; Maiorca, E.; Palmerini, S.

2014-05-01

363

Symbiotic star AG Dra  

SciTech Connect

The results are given of photometric (in the system UBVRJHKLM) and spectrophotometric (in the range 3300-7500 A) observations of the symbiotic star AG Dra. Its cold component is a red giant of the spectral class K4-K5 having approximately constant light, ..delta..I less than or equal to 0/sup m/3, which fills its Roche lobe and is apparently on the asymptotic branch of giants. At wavelength 5 ..mu..m there is an infrared excess associated with the emission of a gas envelop with mass M approx. 10/sup -6/ M/sub circle/. The observations of AG Dra showed that with increasing bolometric flux from the hot component its effective temperature decreases. The hot component may be a red dwarf with M approx. 0.4 M/sub circle/ onto whose equatorial regions there is disk accretion of the matter of the cold star at M greater than or equal to 10/sup -4/ M/sub circle//yr. When the accretion rate is enhanced, during an outburst of AG Dra, the stellar wind from the surface of the red dwarf is increased and its effective temperature decreased. The hot component of AG Dra could also be a white dwarf with L greater than or equal to 3 x 10/sup 3/ L/sub circle/ and R/sub eff--/ 0.2 R/sub circle/. The energy source of its outbursts is the gravitational energy of matter accreting at the rate M greater than or equal to 10/sup -5/ M/sub circle//yr. At the times between the outbursts, its luminosity may be determined by the release of energy produced by the burning of a hydrogen layer source on its surface.

Ipatov, A.P.; Yudin, B.F.

1987-05-01

364

Do Massive Stars Have Planets?  

NASA Astrophysics Data System (ADS)

We recently conducted a near- and mid-infrared survey of a sample of 117 DA white dwarfs from the Palomar-Green (PG) survey. The white dwarfs in this sample are decedent from 1-7 solar mass stars; this survey constrained the frequency of planetary systems in the elusive intermediate-mass regime. We found that at least 4.3% of 1-7 Msol stars host planetary systems. However, the mass distribution of our sample is strongly biased toward lower mass white dwarfs, descendants of M < 3 Msol main-sequence stars. To constrain the frequency of dusty disks around massive white dwarfs, and in turn the frequency of planets around their massive progenitor main-sequence stars, we propose to observe 100 massive white dwarfs from the Sloan Digital Sky Survey in the IRAC 4.5 micron band. We restrict our sample to M > 0.8 Msol white dwarfs (> 3 Msol progenitor stars) and Teff = 9500 - 22,500 K. All but one of the known dusty white dwarfs have temperatures in this range, where dust orbiting within the tidal radius of the star will remain solid. However, no previous Spitzer survey has targeted massive WDs in this temperature range, and this unique discovery space remains unexplored. Assuming a similar disk frequency for normal and massive WDs, we are 99.5% confident that our proposed survey of 100 stars will find at least one dusty WD and it will provide stringent constraints on the frequency of planets around massive stars for the first time. This result will provide an important test for the planet formation models around sun-like and higher mass stars.

Barber, Sara; Kilic, Mukremin; Leggett, Sandy

2012-12-01

365

The FUSE Cool Star Survey  

NASA Astrophysics Data System (ADS)

As part of the PI-team program, the FUSE cool star group has surveyed eight coronal, non-coronal, and hybrid stars using the LWRS (30 arcsec × 30 arcsec) aperture, providing full wavelength coverage in the FUSE bandpass. Additional stars are being observed with the MDRS (4 arcsec × 20 arcsec) slit for the team D/H program, primarily to obtain intrinsic Lyman ? profiles. We provide here an overview of the observations to date, with examples of the types of studies currently in progress.

Ake, T. B.; Dupree, A. K.; Linsky, J. L.; FUSE Cool Star Team

2003-10-01

366

Blue Metal-Poor Stars  

NASA Astrophysics Data System (ADS)

A photometric investigation of three blue stars of low iron abundance was conducted during the summer of 2003; the goal was to determine if a periodic variation in brightness exists. The observations were taken with the SARA 0.9m telescope during three nights at the end of June for the stars CS22890-069 and CS22872-062, and data taken during one night in the beginning of July for the star CS22884-065. This project was made possible by the National Science Foundation with grant AST0097616, the Curry Foundation, and the Shodor Foundation.

Cortes, S. R.; King, J. R.

2003-12-01

367

Astrometric Observations of Neutron Stars  

NASA Astrophysics Data System (ADS)

Precision astrometry on neutron stars can yield model-independent distances and velocities to neutron stars. I will review how such measurements are being exploited, for example, to locate neutron star birth sites, establish reference frame ties, model the Galactic electron density distribution, and constrain the astrophysics of supernova explosions. In the short term, systematic surveys and high sensitivity on very long baselines will produce ongoing science dividends from precision astrometry. In the longer term, new technology such as focal plane arrays, new telescopes such as the Square Kilometre Array, and synergy with new instruments such as Gaia, LSST, and GLAST, all hold great promise in an upcoming era of microarcsecond astrometry

Chatterjee, Shami

2009-07-01

368

Neutron star moments of inertia  

NASA Technical Reports Server (NTRS)

An approximation for the moment of inertia of a neutron star in terms of only its mass and radius is presented, and insight into it is obtained by examining the behavior of the relativistic structural equations. The approximation is accurate to approximately 10% for a variety of nuclear equations of state, for all except very low mass stars. It is combined with information about the neutron-star crust to obtain a simple expression (again in terms only of mass and radius) for the fractional moment of inertia of the crust.

Ravenhall, D. G.; Pethick, C. J.

1994-01-01

369

The late stages of evolution of helium star-neutron star binaries and the formation of double neutron star systems  

Microsoft Academic Search

With a view to understanding the formation of double neutron star binaries, we investigate the late stages of evolution of helium stars with masses of 2.8-6.4Msolar in binary systems with a 1.4-Msolar neutron star companion. We found that mass transfer from 2.8- to 3.3-Msolar helium stars (originating from main-sequence stars with masses of 10-12Msolar that underwent case B evolution, or

J. D. M. Dewi; O. R. Pols

2003-01-01

370

Where are the Distant Worlds? Star Maps  

NSDL National Science Digital Library

This activity includes twelve monthly star charts to identify the stars that are visible in the night sky and that are known to have planets around them. The star maps can be used to find constellations and identify stars with extrasolar planets. (Northern Hemisphere only, naked eye)

371

Hipparcos photometry of CP stars (Adelman 1998)  

NASA Astrophysics Data System (ADS)

The Hipparcos photometry of the chemically peculiar main-sequence B, A and F stars are examined for variability. Some non-magnetic CP stars, Mercury-Manganese and metallic-line stars, which according to canonical wisdom should not be variable, may be variable and are identified for further study. Some potentially important magnetic CP stars are noted. (3 data files).

Adelman, S. J.

1998-06-01

372

Stars and Stellar Evolution: the Next Decade  

Microsoft Academic Search

The science frontier for stars and stellar evolution is as close as the Sun and as distant as exploding stars at redshift 8.3. The field includes the Sun as a star, stellar astrophysics, the structure and evolution of single and multiple stars, compact objects, supernovae, gamma-ray bursts, solar neutrinos, and extreme physics on stellar scales. The following 4 questions appear

Roger Chevalier

2011-01-01

373

The STAR experiment's data acquisition system  

Microsoft Academic Search

STAR is one of the major experiments at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, Upton, USA. RHIC together with STAR began commissioning in June 1999 while the first physics data will be gathered after October 1999. STAR will study ultrarelativistic heavy-ion collisions using its large TPC (Time Projection Chamber) in the first months of running. STAR's

J. M. Langgraf; M. J. LeVine; J. M. Nelson; D. Roerich; J. J. Schambach; D. Schmischke; M. W. Schulz; C. Struck; C. R. Consiglio; R. Scheetz; Y. Zhao

1999-01-01

374

The STAR experiment's data acquisition system  

Microsoft Academic Search

STAR is one of the major experiments at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, Upton, USA. RHIC together with STAR began commissioning in June 1999 while the first physics data will be gathered after October 1999. STAR will study ultrarelativistic heavy-ion collisions using its large TPC (time projection chamber) in the first months of running. STAR's

J. M. Landgraf; M. J. LeVine; J. M. Nelson; D. Roerich; J. J. Schambach; D. Schmischke; M. W. Schulz; C. Struck; C. R. Consiglio; R. Scheetz; Y. Zhao

2000-01-01

375

Where Are the Distant Worlds? Star Maps  

NSDL National Science Digital Library

This fun hands-on astronomy activity lets learners use star maps (included) to find constellations and to identify stars with extrasolar planets (Northern Hemisphere only, naked eye). Use this activity at a star party on a dark, clear night. Included in the PDF are activity suggestions, background information, and over 30 pages of printable star maps and planetary postcards.

Pacific, Astronomical S.

2009-01-01

376

Terrestrial planet formation surrounding close binary stars  

Microsoft Academic Search

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

Elisa V. Quintana; Jack J. Lissauer

2006-01-01

377

A Heavy Flavor Tracker for STAR  

SciTech Connect

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

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.; Miller,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

378

The Mineralogy of Dust Around Evolved Stars  

Microsoft Academic Search

Infrared (IR) observations of evolved red giant stars (AGB stars) have shown that many are surrounded by dust envelopes, which are ejected into the interstellar medium and seed the next generation of stars and planets. By studying these one can understand the origins of interstellar and solar system materials. AGB stars fall into two main categories: oxygen-rich and carbon-rich. The

A. K. Speck

1998-01-01

379

A Heavy Flavor Tracker for STAR  

SciTech Connect

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.

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

380

The Stars behind the Curtain  

NASA Astrophysics Data System (ADS)

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

2010-02-01

381

Stromvil Photometry: Peculiar Stars and Anomalous Reddening  

NASA Astrophysics Data System (ADS)

Possibilities of the Stromvil photometric system in identifying peculiar stars of various types are reviewed. The system can identify in the presence of interstellar reddening the following types of peculiar stars: F--G--K--M subdwarfs, G--K--M metal-deficient giants, cool carbon, barium and zirconium stars, chemically peculiar B and A stars, emission-line stars (Be, Ae/Be, WR, T Tauri, etc.), white dwarfs, a fraction of horizontal-branch stars and many types of unresolved binaries. Also, the system can identify stars affected by anomalous interstellar reddening and classify them correctly.

Straizys, V.

382

Multiplicity in 5 Msolar stars  

NASA Astrophysics Data System (ADS)

Binary/multiple status can affect stars at all stages of their lifetimes: evolution onto the main sequence, properties on the main sequence, and subsequent evolution. 5 Msolar stars have provided a wealth of information about the binary properties fairly massive stars. The combination of cool evolved primaries and hot secondaries in Cepheids (geriatric B stars) have yielded detailed information about the distribution of mass ratios. and have also provided a surprisingly high fraction of triple systems. Ground-based radial velocity orbits combined with satellite data from Hubble, FUSE, IUE, and Chandra are needed to provide full information about the systems, including the masses. As a recent example, X-ray observations can identify low mass companions which are young enough to be physical companions. Typically binary status and properties (separation, eccentricity, mass ratio) determine whether any stage of evolution takes an exotic form.

Evans, Nancy Remage

2011-07-01

383

Children's Literature on Neutron Stars  

NASA Astrophysics Data System (ADS)

Children's literature is simple discussion of complicated issues. Neutron stars are discussed in several children's books. Using libraries in Chicago, I will review children's books on neutron stars and compare the literature to literature from scientific discussions of neutron stars on sites like the Chandra site, Hubble Space Telescope site and NASA site. The result will be a discussion of problems and issues involved in discussion of neutron stars. Do children's books leave material out? Do children's books discuss recent observations? Do children's books discuss anything discredited or wrong? How many children's books are in resources like World Cat, the Library of Congress catalog, and the Chicago Public Library catalog? Could children's books be useful to present some of your findings or observations or projects? Children's books are useful for both children and scientist as they present simplified discussion of topics, although sometimes issues are simplified too much.

Struck, James

384

The mysterious SU UMa stars  

SciTech Connect

This paper discusses the characteristics and the source of energy of the explosive stars called cataclysmic variables (CVs), with special attention given to the SU UMa stars, which represent CVs which have disks. In SU UMa binaries, a gas stream from a cool reddish star hits an accretion disk spiraling around a white dwarf. The impact of the stream produces a bright 'hot spot' on the edge of the disk, seen only when the system is quiescent and the disk is relatively dim (during outbursts, the hot spot is swamped by the light of the disk itself). The principal source of energy and light of most CVs is the gravitational potential energy released by matter falling from the dim reddish companion onto the white dwarf. The mechanism involved in the overflow of the reddish star is believed to be magnetic braking. Simulations are presented that explain the SU UMa phenomena and which may be applicable to other high-mass-ratio interacting binaries.

Charles, P.A. (Royal Greenwich Observatory, La Palma (Spain))

1990-01-01

385

The Nearest Stars (Presidential Address)  

NASA Astrophysics Data System (ADS)

A history of star position measurements, leading to proper motions and parallax measurements is given, with special reference to the southern hemisphere, Alpha Cen and Proxima Cen. The Hipparcos and Gaia satellites are also mentioned.

Glass, I. S.

2013-10-01

386

Coronal Structures in Cool Stars  

NASA Technical Reports Server (NTRS)

Many papers have been published that further elucidate the structure of coronas in cool stars as determined from EUVE, HST, FUSE, Chandra, and XMM-Newton observations. Highlights of these are summarized including publications during this reporting period and presentations.

Oliversen, Ronald (Technical Monitor); Duprec, Andrea K.

2003-01-01

387

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.

2009-05-21

388

Mass loss from carbon stars  

NASA Technical Reports Server (NTRS)

The present consideration of the circumstellar envelopes around carbon stars on the basis of IRAS data indicates that the grains are composed of amorphous carbon rather than graphite, with an extrapolated outflowing material opacity that is large enough for the radiation pressure on the grains to drive the matter to infinity. At least 10 percent of the carbon stars have a mass loss rate that has changed by a factor of 2 during the past 1000 years. The stars that are losing large amounts of mass are generally long period variables. All these results are consistent with a two-step process of mass loss from most of the stars with substantial mass-outflow rates.

Jura, M.

1986-01-01

389

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.

2007-04-01

390

Starspots on Young pms Stars  

NASA Astrophysics Data System (ADS)

Long-term, multiband photometric observations of 8 young PMS stars are used to construct models for their starspots. It is shown that the average density of starspots is up to 40 % of the total surface of a star (V824 Ara), while the difference in temperatures between a quiet photosphere and a spot ranges from 870 K (AB Dor) to 1700-1800 K (PZ Tel, V1321 Ori, V395 Cep). The spots lie at low (2-8°, V343 Nor) and medium (25-61°) latitudes, while the largest latitude of starspots is 16-80°. A cyclical activity that shows up as changes in the total area and average latitude of the starspots is observed in the stars PZ Tel, TY Col, V824 Ara, and AB Dor. A latitudinal drift of the starspots and differential rotation of the star are observed which are analogous to those of the sun.

Alekseev, I. Yu.

2014-06-01

391

The Lives of Binary Stars  

NSDL National Science Digital Library

This site offers information about the history of binary stars, how they form, and their evolution. There are also images and animations provided throughout this tutorial to better describe observations and binary systems.

Dhillon, Vik

2007-02-17

392

Spots on T Tauri stars  

NASA Astrophysics Data System (ADS)

Periodic light curves were recorded for the following 15 T Tauri stars (for nine of which this was the first detection of periodic variability): V 410 Tau, DF Tau, UX Tau A, FK 1, FK 2, WK 2, DN Tau, GW Ori, SY Cha, LH(alpha) 332-20, LH(alpha) 332-21, CoD-33-deg 10685, RY Lup, SR 12, and SR 9. The previously reported periodic variability of the SY Cha and RY Lup stars was confirmed. These periodic variations are thought to result from rotational modulation by a group of spots at the stellar surface. The properties of spots on 11 stars were deduced from extensive light-curve synthesis. In most cases, they were found to be comparable to the properties of spots found on RS CVn stars.

Bouvier, J.; Bertout, C.

1989-02-01

393

Star formation across galactic environments  

NASA Astrophysics Data System (ADS)

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.

Young, Jason

394

Neutron skins and neutron stars  

NASA Astrophysics Data System (ADS)

Background: The neutron skin of a heavy nucleus as well as many neutron-star properties are highly sensitive to the poorly constrained density dependence of the symmetry energy.Purpose: To provide for the first time meaningful theoretical errors and to assess the degree of correlation between the neutron-skin thickness of 208Pb and several neutron-star properties.Methods: A proper covariance analysis based on the predictions of an accurately calibrated relativistic functional “FSUGold” is used to quantify theoretical errors and correlation coefficients.Results: We find correlation coefficients of nearly 1 (or -1) between the neutron-skin thickness of 208Pb and a host of observables of relevance to the structure, dynamics, and composition of neutron stars.Conclusions: We suggest that a follow-up Lead Radius Experiment (PREX) measurement, ideally with a 0.5% accuracy, could significantly constrain the equation of state of neutron-star matter.

Fattoyev, F. J.; Piekarewicz, J.

2012-07-01

395

Quantum Collapse in Quark Stars?  

SciTech Connect

Quark matter is expected to exist in the interior of compact stellar objects as neutron stars or even the more exotic strange stars. Bare strange quark stars and (normal) strange quark-matter stars, those possessing a baryon (electron-supported) crust, are hypothesized as good candidates to explain the properties of a set of peculiar stellar sources. In this presentation, we modify the MIT Bag Model by including the electromagnetic interaction. We also show that this version of the MIT model implies the anisotropy of the Bag pressure due to the presence of the magnetic field. The equations of state of degenerate quarks gases are studied in the presence of ultra strong magnetic fields. The behavior of a system made-up of quarks having (or not) anomalous magnetic moment is reviewed. A structural instability is found, which is related to the anisotropic nature of the pressures in this highly magnetized matter.

Perez Martinez, A.; Perez Rojas, H. [ICIMAF, Calle E esq 15 No. 309 Vedado (Cuba); Mosquera Cuesta, H. J. [Centro Brasileiro de Pesquisas Fisicas, Laboratorio de Cosmologia e Fisica Experimental de Altas Energias, Rua Dr. Xavier Sigaud 150, Urca, CEP 22290-180, Rio de Janeiro (Brazil)

2006-06-19

396

Sleuthing the Isolated Compact Stars  

NASA Astrophysics Data System (ADS)

In the early 1990's, isolated thermally-emitting neutron stars accreting from the interstellar medium were predicted to show up in their thousands in the ROSAT soft X-ray all-sky survey. The glut of sources would provide unprecedented opportunities for probing the equation of state of ultra-dense matter. Only seven objects have been firmly identified to date. The reasons for this discrepency are discussed and recent high resolution X-ray spectroscopic observations of these objects are described. Spectra of the brightest of the isolated neutron star candidates, RX J1856.5-3754, continue to present interpretational difficulties for current neutron star model atmospheres and alternative models are briefly discussed. RX J1856.5-3754 remains a valid quark star candidate.

Drake, J. J.

2004-08-01

397

Are all Trapezium stars magnetic?  

NASA Astrophysics Data System (ADS)

Recent X-ray observations of unprecedented length (10 days) of the Orion Nebula Cluster with the Chandra satellite (the COUP project) have revealed X-ray flares on the light-curves of late-B and A stars, as well as two new cases of rotational modulation, in addition to the already known case of the O7 star ?1 OriC. We show that the X-ray emission of A stars (which have neither deep outer convective zones nor strong UV radiation) when detected must be due to the solar-like magnetic activity of unresolved late-type companions, and that most, if not all, of the O and early B stars of the Trapezium may be magnetized and emit X-rays by magnetically channelled wind shocks.

Montmerle, T.

398

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

NASA Astrophysics Data System (ADS)

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.

Kerrod, Robin

2005-02-01

399

X-Ray Emission From Hybrid Stars  

NASA Astrophysics Data System (ADS)

Hybrid stars are giant stars that exhibit both chromospheric emission features and signatures of mass outflow, and hence provide a link between stars on either side of the ``Coronal Dividing Line". We have obtained long duration ROSAT PSPC exposures of two nearby hybrid stars (alpha TrA and iota Aur), and here, we compare these observations with models of X-ray emission on giant stars.

Kashyap, V.; Rosner, R.; Harnden, F. R., Jr.; Maggio, A.

1993-05-01

400

AGB (asymptotic giant branch): Star evolution  

SciTech Connect

Asymptotic giant branch stars are red supergiant stars of low-to-intermediate mass. This class of stars is of particular interest because many of these stars can have nuclear processed material brought up repeatedly from the deep interior to the surface where it can be observed. A review of recent theoretical and observational work on stars undergoing the asymptotic giant branch phase is presented. 41 refs.

Becker, S.A.

1987-01-01

401

Massive stars in the UV  

Microsoft Academic Search

We emphasize in this paper the importance of the UV range for our knowledge of massive stars and the fundamental role played\\u000a by past and present space-based UV capabilities (IUE, HST, FUSE and others). Based on a review of the work developed in the\\u000a last years and the state of the art situation for quantitative spectroscopy of massive stars, we

F. Najarro; A. Herrero; E. Verdugo

402

STAR Vertex Detector Upgrade Development  

SciTech Connect

We report on the development and prototyping efforts undertaken with the goal of producing a micro-vertex detector for the STAR experiment at the RHIC accelerator at BNL. We present the basic detector requirements and show a sensor development path, conceptual mechanical design candidates and readout architecture. Prototyping and beam test results with current generation MimoSTAR-2 sensors and a readout system featuring FPGA based on-the-fly hit finding and data sparsification are also presented.

Greiner, Leo C.; Matis, Howard S.; Stezelberger, Thorsten; Vu,Chinh Q.; Wieman, Howard; Szelezniak, Michal; Sun, Xiangming

2008-01-28

403

Unified EOS for neutron stars  

NASA Astrophysics Data System (ADS)

The equation of state (EOS) of dense matter is a crucial input for the neutron-star structure calculations. This Fortran code can obtain a "unified EOS" in the many-body calculations based on a single effective nuclear Hamiltonian, and is valid in all regions of the neutron star interior. For unified EOSs, the transitions between the outer crust and the inner crust and between the inner crust and the core are obtained as a result of many-body calculations.

Chamel, Nicolas; Potekhin, Alexander

2014-03-01

404

Heavy flavor production in STAR  

NASA Astrophysics Data System (ADS)

We report on the recent STAR results on heavy flavor production in Au+Au collisions at = 200, 62.4 and 39 GeV. We present the nuclear modification factor and elliptic flow of open charm mesons and electrons from semileptonic decays of heavy flavor hadrons. We also report on new measurements of energy dependence of J/? production. STAR data are compared to theoretical model calculations and physics implications are discussed.

Kiko?a, Daniel; Star Collaboration

2014-05-01

405

Neutron Stars as Physics Laboratories  

NASA Astrophysics Data System (ADS)

X-ray timing and spectrophotometry of accretion-powered neutron stars have been used to determine or constrain many of the intrinsic properties of these stars, including their masses, radii, magnetic fields, spin frequencies, and internal structure. These measurements have important implications for the evolution of ordinary and neutron stars in binary systems, the supernova process in massive stars, accretion-induced collapse of white dwarfs and neutron stars, and the properties of extremely dense matter. High-speed X-ray spectrophotometry has also revealed a variety of phenomena, such as pulse-frequency variations, QPOs, aperiodic X-ray variability, and systematic X-ray brightness and spectral changes that provide valuable information about the structure and dynamics of accretion flows, the interaction of such flows with the magnetic fields and surfaces of neutron stars, and hydrodynamics in the presence of intense radiation and very strong magnetic fields. The X-ray Timing Explorer will have a unique combination of large-area detectors, 2--200 keV energy response, all-sky monitors, microsecond time resolution, sophisticated onboard data processing, high telemetry rates, and unprecedented maneuverability and is expected to produce major advances in these areas of physics and astrophysics. Some of the possible advances will be described.

Lamb, F. K.

1994-12-01

406

Massive Stars: Life and Death  

NASA Astrophysics Data System (ADS)

One of the most powerful tests of stellar evolution theory for massive stars is to observationally establish the causal mapping between different populations of massive stars (e.g., red-supergiants, wolf-rayet stars) and their explosions (e.g., supernovae). This connection has been firmly proven only for a handful of objects, most notably in the case of supernova 1987A in the LMC with its blue-supergiant progenitor star Sk -69 202. However, the progenitors of most supernova types have not been identified directly. I will present two supernova-like transients discovered this year in the nearby galaxies NGC 6946 and NGC 300 for which we have identified the progenitors as dust-enshrouded massive stars in Spitzer images. This new class of luminous transients has progenitors that are extremely rare compared to known massive stellar populations in M33 identified in the mid-infrared. I will discuss the implications of these findings in the context of "low-mass" massive stars (i.e., close to 8 Msun) and connect it to electron-capture supernovae.

Prieto, Jose

2009-01-01

407

Outer atmospheres of late stars  

SciTech Connect

The short-wavelength spectra of the stars UX Ari during flare activity and in the quiet state and RW Aur are analyzed. An independent determination of the electron density made it possible to draw the reliable conclusion from the line intensities that the extent of the transition region between chromosphere and corona is considerably greater for these stars and Capella than for the sun. Two groups of stars are distinguished: 1) rotating red dwarfs; 2) subgiants belonging to systems of the RS C Vn-type and T Tau-type stars. The former are characterized by coronal loops emitting in the x-ray region. The appearance of considerable fluxes in lines of ions with T/sub i/roughly-equal10/sup 5/ /sup 0/K in stars of the latter group without x-ray enhancement is connected with direct heating with T = 10/sup 4/--10/sup 5/ /sup 0/K and with the development of upward-intensifying motions. Such a dynamical model of the outer atmosphere differs considerably from the usually considered outflow of the solar-wind type, efficiently cooling the coronas of stars with low gravity.

Katsova, M.M.

1982-11-01

408

Outflows from Newborn Multiple Stars  

NASA Astrophysics Data System (ADS)

Analysis of a sample of giant Herbig-Haro flow sources shows that 79% - 86% are binaries or higher order multiples. This represents the youngest sample of stars studied so far for binarity. A stellar dynamics jet hypothesis is proposed in which the dynamical decay of triple or multiple systems leads to giant outflow activity. Close triple approaches will cause serious perturbations and probably direct collisions among individual circumstellar disks, with a consequent burst of outflow activity, which can produce giant HH bow shocks. As one component is ejected, the two remaining stars and their small truncated disks form a closer bound pair with high eccentricity. Gas streams from a circumbinary disk feed the stars and this as well as other dynamical effects cause the binary orbit to shrink. As the stellar components gradually spiral towards each other, accretion and outflow becomes cyclic, modulated on an orbital time scale. The resulting HH flows can be read as a fossil record of the evolution of orbital motions of the newly formed binary as it shrinks from a typical separation of 100 AU or more to 10 AU or less. After a triple disintegration event, both components (star and close binary) leave their nascent envelope, and while one component becomes visible as a T Tauri star, the other will be obscured for a while by the envelope and will appear as a bright near-infrared object, thus explaining the socalled IRC binaries which are infrequently found in star forming regions.

Reipurth, Bo

409

Enigma of Runaway Stars Solved  

NASA Astrophysics Data System (ADS)

Supernova Propels Companion Star through Interstellar Space The following success story is a classical illustration of scientific progress through concerted interplay of observation and theory. It concerns a 35-year old mystery which has now been solved by means of exciting observations of a strange double star. An added touch is the successive involvement of astronomers connected to the European Southern Observatory. For many years, astronomers have been puzzled by the fact that, among the thousands of very young, hot and heavy stars which have been observed in the Milky Way, there are some that move with exceptionally high velocities. In some cases, motions well above 100 km/sec, or ten times more than normal for such stars, have been measured. How is this possible? Which mechanism is responsible for the large amounts of energy needed to move such heavy bodies at such high speeds? Could it be that these stars are accelerated during the powerful explosion of a companion star as a supernova? Such a scenario was proposed in 1961 by Adriaan Blaauw [1], but until now, observational proof has been lacking. Now, however, strong supporting evidence for this mechanism has become available from observations obtained at the ESO La Silla observatory. The mysterious runaway stars OB-runaway stars [2] are heavy stars that travel through interstellar space with an anomalously high velocity. They have been known for several decades, but it has always been a problem to explain their high velocities. Although most OB-runaway stars are located at distances of several thousands of lightyears, their high velocity results in a measurable change in position on sky photos taken several years apart. The velocity component in the direction of the Earth can be measured very accurately from a spectrogram. From a combination of such observations, it is possible to measure the space velocity of OB-runaways. Bow shocks reveal runaway stars It has also been found that some OB-runaways display bow shocks of compressed matter, which look very much like the bow wave around a boat crossing the ocean. They are of the same physical nature as a bow shock created by a jet-fighter in the air. The explanation is similar: when an OB-runaway star plows through the interstellar medium (a very thin mixture of gas and dust particles) with supersonic velocity [3], interstellar matter is swept up in a bow shock. Stars of low velocity do not create bow shocks. Thus, the detection of a bow shock around a particular OB star indicates that it must have a supersonic velocity, thereby securely identifying it as a runaway star, even if its velocity has not been measured directly. Runaway stars come from stellar groups When a star's direction of motion in space is known, it is possible to reconstruct its previous path and, even more interestingly, to find the place where the star originally came from. It turns out that the paths of many OB-runaways can be traced back to socalled OB-associations , that is groups of 10 to 100 OB-type stars which are located in the spiral arms of our galaxy. About fifty OB-associations are known in the Milky Way. In fact, the majority of all known OB stars are members of an OB-association. Therefore, it is not very surprising that OB-runaway stars should also originate from OB-associations. This is also how they got their name: at some moment, they apparently left the association in which they were formed. The ejection mechanism But why were the OB-runaway stars kicked out of the OB-association and how did they achieve such high speeds? One possibility is that some OB stars in an OB-association are ejected due to strong gravitational effects at the time of close encounters between the members of the group. Complicated computer simulations show that this is in principle possible. Nevertheless, since many years, most astronomers think that a more likely scenario is that of violent supernova explosions, first proposed in 1961 by Adriaan Blaauw. Stellar evolution theory predicts that all OB stars will end their life in a supernova explosion. The he

1997-01-01

410

STAR FORMATION IN DENSE CLUSTERS  

SciTech Connect

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.

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

411

Flare stars at radio wavelengths  

NASA Technical Reports Server (NTRS)

The radio emission from dMe flare stars is discussed using Very Large Array and Arecibo observations as examples. Active flare stars emit weak, unpolarized, quiescent radio radiation that may be always present. Although thermal bremsstrahlung and/or thermal gyroresonance radiation account for the slowly-varying, quiescent radio radiation of solar active regions, these processes cannot account for the long-wavelength quiescent radiation observed from nearby dMe flare stars. It has been attributed to nonthermal gyrosynchrotron radiation, but some as yet unexplained mechanism must be continually producing the energetic electrons. Long duration, narrow-band radiation is also emitted from some nearby dMe stars at 20 cm wavelength. Such radiation may be attributed to coherent plasma radiation or to coherent electron-cyclotron masers. Impulsive stellar flares exhibit rapid variations that require radio sources that are smaller than the star in size, and high brightness temperatures greater than 10(exp 15) K that are also explained by coherent radiation processes. Quasi-periodic temporal fluctuations suggest pulsations during some radio flares. Evidence for frequency structure and positive or negative frequency drifts during radio flares from dMe stars is also presented.

Lang, Kenneth R.

1990-01-01

412

Flare stars at radio wavelengths  

NASA Technical Reports Server (NTRS)

The radio emission from dMe flare stars is discussed using Very Large Array and Arecibo observations as examples. Active flare stars emit weak, unpolarized, quiescent radio radiation that may be always present. Although thermal bremsstrahlung and/or thermal gyroresonance radiation account for the slowly-varying, quiescent radio radiation of solar active regions, these processes cannot account for the long-wavelength quiescent radiation observed from nearby dMe flare stars. It has been attributed to nonthermal gyrosynchrotron radiation, but some as yet unexplained mechanism must be continually producing the energetic electrons. Long duration, narrow-band radiation is also emitted from some nearby dMe stars at 20 cm wavelength. Such radiation may be attributed to coherent plasma radiation or to coherent electron-cyclotron masers. Impulsive stellar flares exhibit rapid variations that require radio sources that are smaller than the star in size, and high brightness temperatures greater than 10(exp 15) K that are also explained by coherent radiation processes. Quasi-periodic temporal fluctuations suggest pulsations during some radio flares. Evidence for frequency structure and positive or negative frequency drifts during radio flares from dMe stars is also presented.

Lang, Kenneth R.

1989-01-01

413

Limits to Neutron Star Spin  

NASA Astrophysics Data System (ADS)

Over the past decade our understanding of accreting neutron stars has been revolutionized. Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have resulted in the discovery of fast, coherent X-ray intensity oscillations (hereafter, ``burst oscillations'') during thermonuclear X-ray bursts from 13 low mass X-ray binaries (LMXBs). Although many of their detailed properties remain to be fully understood, it is now beyond doubt that these oscillations result from spin modulation of the thermonuclear burst flux from the neutron star surface. In addition, RXTE observations led to the discovery of the first accreting millisecond pulsars, the sample of which now includes six systems, several of which are in extremely compact binary systems with essentially massive planet companions. These millisecond timing phenomena are providing powerful new probes of the formation, evolution and structure of neutron stars. I will describe recent efforts to constrain neutron star structure using detailed modelling of their properties. I will also discuss what the observed distribution of neutron star spin frequencies is telling us about the torques which may act to limit the ultimate spin up of accreting neutron stars.

Strohmayer, Tod

2005-04-01

414

Space Shuttle Star Tracker Challenges  

NASA Technical Reports Server (NTRS)

The space shuttle fleet of avionics was originally designed in the 1970's. Many of the subsystems have been upgraded and replaced, however some original hardware continues to fly. Not only fly, but has proven to be the best design available to perform its designated task. The shuttle star tracker system is currently flying as a mixture of old and new designs, each with a unique purpose to fill for the mission. Orbiter missions have tackled many varied missions in space over the years. As the orbiters began flying to the International Space Station (ISS), new challenges were discovered and overcome as new trusses and modules were added. For the star tracker subsystem, the growing ISS posed an unusual problem, bright light. With two star trackers on board, the 1970's vintage image dissector tube (IDT) star trackers track the ISS, while the new solid state design is used for dim star tracking. This presentation focuses on the challenges and solutions used to ensure star trackers can complete the shuttle missions successfully. Topics include KSC team and industry partner methods used to correct pressurized case failures and track system performance.

Herrera, Linda M.

2010-01-01

415

The sun, our star  

NASA Astrophysics Data System (ADS)

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.

Noyes, R. W.

416

Undercover Stars Among Exoplanet Candidates  

NASA Astrophysics Data System (ADS)

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

2005-03-01

417

VLA observations of dwarf M flare stars and magnetic stars  

NASA Technical Reports Server (NTRS)

The VLA has been used to search for 6 cm emission from 16 nearby dwarf M stars, leading to the detection of only one of them - Gliese 735. The dwarf M flare stars AD Leonis and YZ Canis Minoris were also monitored at 6 cm and 20 cm wavelength in order to study variability. Successive oppositely circularly polarized bursts were detected from AD Leo at 6 cm, suggesting the presence of magnetic fields of both magnetic polarities. An impulsive 20-cm burst from YZ CMi preceded slowly varying 6-cm emission. The VLA was also used, unsuccessfully, to search for 6-cm emission from 13 magnetic Ap stars, all of which exhibit kG magnetic fields. Although the Ap magnetic stars have strong dipolar magnetic fields, the failure to detect gyroresonant radiation suggests that these stars do not have hot, dense coronae. The quiescent microwave emission from GL 735 is probably due to nonthermal radiation, since unusually high (H = 50 kG or greater) surface magnetic fields are inferred under the assumption that the 6-cm radiation is the gyroresonant radiation of thermal electrons.

Willson, R. F.; Lang, K. R.; Foster, P.

1988-01-01

418

Diagnosing the Star Formation Rate in Massive Galactic Star Forming Regions  

NASA Astrophysics Data System (ADS)

In extragalactic studies many different observables are used to trace the star formation history averaged over galaxy or kiloparsec scales. By studying star formation in our Galaxy we are able to resolve individual sources and directly count up the young stars in a star forming complex. The star formation rates that are determined from this method rely on the input assumptions. I will describe how different assumptions and variables alter the derived star formation rate for a sample of massive galactic star forming regions and how these star formation rates compare to those derived using methods developed in the study of external galaxies.

Willis, Sarah; Marengo, Massimo; Smith, Howard Alan; Allen, Lori; Guzman, Andres; Martinez, Rafael

2014-06-01

419

Far-infrared properties of flare stars and dM stars  

NASA Technical Reports Server (NTRS)

Results are reported from a search of the IRAS data base for flare stars and for a control sample of dM stars. At 12 microns, 70-80 percent of both samples have been detected. The K-12 colors of flare stars are significantly different from those of dM stars: for a given K magnitude, a flare star is about 70 percent brighter at 12 microns than a dM star. At 100 microns, 27 percent of the flare stars which are sources at 12 microns have been detected, while none of the comparable dM stars has been detected. Implications for microflaring are discussed.

Mullan, D. J.; Stencel, R. E.; Backman, D. E.

1989-01-01

420

Superflares on Late-Type Stars  

NASA Astrophysics Data System (ADS)

We present the results of an extensive survey of superflares on late-type stars (G, K, and M-type main sequence stars) using the Kepler satellite data. Wefound about 6,800 superflares on late-type stars from the data of about 120,000 stars observed over 500 days. The total bolometric energy of superflares in oursample ranges from 1032 erg to 1036 erg. Our data suggest that the occurrencefrequency of superflares depends on the surface temperature and the rotationperiod of stars. Superflares on M-type stars occur about 10-100 times morefrequently than those on G-type stars. Our results suggest that the average frequency ofsuperflares releasing 1034-1035 erg of energy (100-1,000 times larger than the largestsolar flares) on M-type stars and Sun-like stars is once in 10 years and once in a few thousand years respectively.

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

2014-04-01

421

Observations of O and Of stars.  

NASA Technical Reports Server (NTRS)

Evaluation of spectrograms with a dispersion of 16.2 A/mm covering the spectral range from 3300 to 4900 A obtained for three early O stars and three early Of stars. Detailed line profiles of selected hydrogen and helium lines were obtained, and equivalent widths of nearly all visible lines were measured. Comparison of the spectroscopic properties between Of stars and O stars suggests that Of stars have lower surface gravities than do O stars. Comparison of their photometric properties confirms this suggestion. Hence present temperature scales for O5-O8 stars should not be applied to Of stars until the effect of gravity in determining spectral type has been determined. In addition, the spectra suggest that atmospheric models of Of stars should take into account spherical and hydrodynamic effects.

Heap, S. R.

1971-01-01

422

New distances to RAVE stars  

NASA Astrophysics Data System (ADS)

Probability density functions (pdfs) are determined from new stellar parameters for the distance moduli of stars for which the RAdial Velocity Experiment (RAVE) has obtained spectra with S/N ? 10. Single-Gaussian fits to the pdf in distance modulus suffice for roughly half the stars, with most of the other half having satisfactory two-Gaussian representations. As expected, early-type stars rarely require more than one Gaussian. The expectation value of distance is larger than the distance implied by the expectation of distance modulus; the latter is itself larger than the distance implied by the expectation value of the parallax. Our parallaxes of Hipparcos stars agree well with the values measured by Hipparcos, so the expectation of parallax is the most reliable distance indicator. The latter are improved by taking extinction into account. The effective temperature-absolute magnitude diagram of our stars is significantly improved when these pdfs are used to make the diagram. We use the method of kinematic corrections devised by Schönrich, Binney and Asplund to check for systematic errors for general stars and confirm that the most reliable distance indicator is the expectation of parallax. For cool dwarfs and low-gravity giants, tends to be larger than the true distance by up to 30 per cent. The most satisfactory distances are for dwarfs hotter than 5500 K. We compare our distances to stars in 13 open clusters with cluster distances from the literature and find excellent agreement for the dwarfs and indications that we are overestimating distances to giants, especially in young clusters.

Binney, J.; Burnett, B.; Kordopatis, G.; McMillan, P. J.; Sharma, S.; Zwitter, T.; Bienaymé, O.; Bland-Hawthorn, J.; Steinmetz, M.; Gilmore, G.; Williams, M. E. K.; Navarro, J.; Grebel, E. K.; Helmi, A.; Parker, Q.; Reid, W. A.; Seabroke, G.; Watson, F.; Wyse, R. F. G.

2014-01-01

423

Sequential star formation in Cassiopeia  

NASA Astrophysics Data System (ADS)

Massive stars (M ? 9 M_{?}) are usually formed in OB associations, consisting of one or more not very massive open clusters and a halo of scattered young stars. The study of these open clusters can provide clues about how stellar formation proceeds from the parent molecular clouds. We present first results on a project to understand sequential star formation mechanisms in OB associations. We have chosen associations Cas OB4, Cas OB5 and Cas OB7, close to the Cassiopeia constellation, at l = 110°-125°. Previous determinations of their distance provided very similar values for them all, and placed them on the Perseus Arm. This study aims at improved distance and age determinations using new spectroscopic observations and existing photometry. The goal is to investigate whether the clusters in Cas OB4, Cas OB5 and Cas OB7 are separate entities or can be enclosed in a global common OB association. If associated,we will check for evidence of induced star formation. We preselected about 100 stars from 12 clusters, based on photometric criteria. Long-slit spectra were taken with the Intermediate Dispersion Spectrograph at the Isaac Newton Telescope (2.5 m), located in La Palma's Observatorio del Roque de los Muchachos. We used the R632V grating, to achieve a spectral coverage between 3500 Å and 5500 Å and spectral resolution of 0.90 Å px^{-1}. The observed spectra have been used to determine the spectral type and luminosity class of the sample stars. The spectral classification yields the stellar properties (from calibrations), and will enable the reconstruction of the HR-diagram. We present in this poster newly discovered B-type stars in two selected clusters.

Velasco, S.; García, M.; Negueruela, I.

2013-05-01

424

Formation of hybrid stars from metastable hadronic stars  

NASA Astrophysics Data System (ADS)

We study the consequences of quark matter nucleation in cold hadronic matter employing three relativistic-mean-field models to describe the hadronic phase and the Nambu-Jona-Lasinio (NJL) model for the quark one. We explore the effect of a vector interaction in the NJL Lagrangian and of a phenomenological bag constant on neutron stars metastability. We delineate the region of parameters of the quark phase that allow for the formation of stable hybrid stars with mass compatible with the almost 2M? pulsars PSR J1614-2230 (1.97±0.04M?) and PSR J0348+0432 (2.01±0.04M?). It is shown, however, that not all hybrid star configurations with ˜2M? are populated after nucleation.

Logoteta, Domenico; Providência, Constança; Vidaña, Isaac

2013-11-01

425

Binary star formation: Primary disks and secondary stars1  

NASA Astrophysics Data System (ADS)

Most intermediate mass, pre-main-sequence Herbig Ae/Be stars reside in binary systems. As they are young, the properties of these systems allow us to constrain how they form. We have investigated the formation of Herbig Ae/Be (HAe/Be) stars by assessing the relationship between HAe/Be binary systems and their circumstellar disks. To do this, we use linear spectropolarimetric observations over H? to determine the orientation of circumstellar disks in HAe/Be binaries. We then employ the disk and binary data to investigate the relative orientation of the systems and their disks. We conclude that the orbital planes of HAe/Be binary systems and the disks around their primaries are likely to be co-planar. This is consistent with the notion that these systems, and perhaps massive stars, form via monolithic collapse and disk fragmentation.

Wheelwright, H. E.; Vink, J. S.; Oudmaijer, R. D.; Drew, J. E.

2012-05-01

426

Kepler and the RR Lyrae Stars  

NASA Astrophysics Data System (ADS)

(Abstract only) The spectacular data delivered by NASA's Kepler mission have not only boosted the discovery of planets orbiting other stars, but they have opened a window on the inner workings of the stars themselves. For the study of the RR Lyrae stars, Kepler has provided a breakthrough. To date, over fifty RR Lyrae stars are known in the Kepler field. I will present some of the most interesting results on RR Lyrae stars obtained through Kepler so far. Though high-precision satellite data have led to new insights, amateur observations of these stars remain extremely valuable and can complement the space data.

Kolenberg, K.

2014-06-01

427

Old and new neutron stars  

SciTech Connect

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.

Ruderman, M.

1984-09-01

428

Lithium production in SAGB stars  

NASA Astrophysics Data System (ADS)

We explore the production of and stellar yields of 7Li for a range of mass and metallicity. We test the effect of varying the mass loss rate and well as the mixing length parameter on the production of lithium. There is a short duration of strong enhancement of Lithium in the early AGB phase, before any thermal pulses. Higher mass-loss rate, particularly in the early AGB phase, will result in stronger Li enhancement. In general, metal-poor stars produce less lithium because the mass-loss rates are lower during the Li-rich phase. We also compare the observed abundances of Li-rich stars with our models and discuss possible formation of Li-rich stars through mass transfer from SAGB primary. If a SAGB star is observed before thermal pulses or the SAGB primary evolution truncated before thermal pulses due to binary interactions, then the observed SAGB stars or its companion may be observed as Li-rich but without s-process isotopes.

Lau, Herbert H. B.; Doherty, Carolyn L.; Gil-Pons, Pilar; Lattanzio, John C.

429

Dynamical Evolution of Multiple Stars  

NASA Astrophysics Data System (ADS)

We have modeled the dynamical evolution of small groups of N=3 18 stars in the framework of the gravitational N-body problem, taking into account possible coalescences of stars and the ejection of single and binary stars from the system. The distribution of states is analyzed for a time equal to 300 initial crossing times of the system. The parameters of the binaries and stable triple systems formed, as well as those of ejected single stars, are studied. In most cases, the evolution of the group results in the formation of a binary or stable triple system. The orbital eccentricities of the binaries formed are distributed according to the law f(e)=2e. As a rule, stable triple systems display pronounced hierarchy (the mean ratio of the semimajor axes of the outer and inner binaries is about 20:1). Stars are ejected with velocities from several km/s to several tens of km/s. The results of the modeling are compared with the parameters of observed wide binaries and triple systems.

Rubinov, A. V.; Petrova, A. V.; Orlov, V. V.

2002-11-01

430

Gravitational Lensing by Boson Stars  

NASA Astrophysics Data System (ADS)

Boson stars can be gravitational lenses in a similar way as other astrophysical objects (Dabrowski & Schunck 2000). They can be transparent which allows the light to pass through them and to be gravitationally deflected. We discuss the lens equation for these stars as well as the details of magnification assuming they are on non-cosmological distance from the observer and that their mass is M = 1010M?. We find that there are typically three images of a star. There is one tangential critical curve (Einstein ring) and one radial critical curve for tangential and radial magnification, respectively. The deflection angles for the light moving in the gravitational field of boson stars can be very large (even of the order of degrees) which means that they are very strong relativistic objects. We derive an analytic formula for the lens equation applied for such large deflection angles. Although the large deflection angle images are highly demagnified, their existence in the area of the tangential critical curve may help in observational detection of suitable lenses possessing characteristic features of boson stars which could serve as a direct evidence for scalar fields in the universe...

Schunck, Franz E.; Dabrowski, Mariusz P.

2002-12-01

431

Hot Stars in the Galactic Halo  

NASA Astrophysics Data System (ADS)

Participants; Preface; Foreword; Acknowledgements; Part I. Introductory Papers: 1. What is the galaxy's halo population?; 2. Theoretical properties of horizontal-branch stars; 3. A review of A-type horizontal-branch stars; Part II. Surveys: 4. A progress report on the Edinburgh-Cape object survey; 5. A 300 square degree survey of young stars at high galactic latitudes; 6. The isolation of a new sample of B stars in the halo; 7. A northern catalog of FHB/A stars; 8. Recent progress on a continuing survey of galactic globular clusters for blue stragglers; 9. UV observations with FAUST and the galactic model; 10. Hot stars at the South Galactic Pole; Part III. Clusters: 11. Population II horizontal branches: a photometric study of globular clusters; 12. The period-shift effect in Oosterhoff type II globular clusters; 13. UV photometry of hot stars in omega centauri; 14. Spectroscopic and UBV observations of blue stars at the NGP; 15. Population I horizontal branches: probing the halo-to-disk transition; Part IV. Stars: 16. Very hot subdwarf O stars; 17. Quantitative spectroscopy of the very hot subluminous O-stars: K646, PG1159-035, and KPD0005+5106; 18. Analyzing the helium-rich hot sdO stars in the Palomar Green Survey; 19. Late type companions of hot sd O stars; 20. Hot stars in globular clusters; 21. Faint blue stars from the Hamburg Schmidt Survey; 22. Stellar winds and the evolution of sdB's to sdO's; 23. Halo stars in the Vilnius photometric system; 24. Horizontal branch stars in the geneva photometric system; 25. Zeeman observations of FHB stars and hot subdwarf stars; 26. What does a FHB star's spectrum look like?; 27. A technique for distinguishing FHB stars from A-type stars; 28. eEemental abundances of halo A and interloper stars; 29. The mass of blue horizontal branch stars in the globular cluster NGC6397; 30. IUE observations of blue HB stars in the globular clusters M3 and NGC6752; 31. Metallicities and kinematics of the local RR lyraes: lukewarm stars in the halo; 32. Baade-Wesselink analyses of field vs. cluster RR lyrae variables; 33. The rotation of population II A stars; 34. Horizontal branch stars and possibly related objects; 35. A new group of post-AGB objects - the hot carbon-poor stars; 36. MK classifications of hot stars in the halo 37. Photometry of XX Virginis and V716 Ophiuchi and the period luminosity relations of type II cepheids; 38. Rotation and oxygen line strengths in blue horizontal branch stars; Part V. Miscellaneous: 39. UBV CCd photometry of the halo of M31; 40. Can stars still form in the galactic halo?; 41. The ultraviolet imaging telescope on the Astro -1 and Astro -2 missions; 42. Are analogues of hot subdwarf stars responsible for the UVX phenomenon in galaxy nucleli; 43. A survey for field BHB stars outside the solar circle; 44. Post-AGB A and F supergiants as standard candles; 45. The extended horizontal-branch: a challenge for stellar evolution theory; 46. Astronomical patterns in fractals: the work of A. G. Davis Philip on the Mandelbrot