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1

4-H All-Star Constitution (Revised 3-22-14)  

E-print Network

4-H All-Star Constitution (Revised 3-22-14) ARTICLE I - Name The organization shall be known as the Virginia Chapter of 4-H All Stars and shall be associated with the 4-H Program of Virginia Cooperative Extension of Virginia

Liskiewicz, Maciej

2

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

Microsoft Academic Search

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

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

1995-01-01

3

Taylor's Multiple Talent Teaching Approach: All-Star Instruction in Practice.  

ERIC Educational Resources Information Center

The article describes the application of C. Taylor's multiple talent teaching approach in an Alberta sixth-grade class. The model is described graphically in the form of a star with the center being academic learning and the five points noting the aspects of communicating, decision making, forecasting, creating, and planning. (DB)

Warkentin, Irwin E.; Millar, Garnet W.

1985-01-01

4

OPEN A W L OPEN B W L OPEN C W L 220 All-Stars 5 0 The Broskis 4 0 4th Floor Bigler Girls 4 1  

E-print Network

OPEN A W L OPEN B W L OPEN C W L 220 All-Stars 5 0 The Broskis 4 0 4th Floor Bigler Girls 4 1 Team Sons of Pitches 3 2 Underage Blockers 0 4 Unnatural Selection 2 3 The Cannoneers 2 3 Hastings 3 Ballers

Yener, Aylin

5

Combined Lick-Voyager Reference Star Catalogue (Dunham 1986)  

Microsoft Academic Search

The catalogue contains accurate equatorial coordinates for stars in several bands of sky against which cameras of Voyager spacecraft were pointed for observations in the regions of Jupiter, Saturn, Uranus and Neptune during the flyby. This catalogue is compiled by combining the four reference star catalogues for Voyager mission: Uranus-Voyager Reference Star Catalogue Klemola A.R., Owen Jr. W.M. Neptune-Voyager Reference

D. W. Dunham

1995-01-01

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

VizieR Online Data Catalog: 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

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

Documentation for the machine-readable version of the lick Saturn-Voyager Reference Star Catalogue  

Microsoft Academic Search

The machine-readable version of the catalog is described. The catalog was prepared in order to determine 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. Tape contents and characteristics are described and a sample listing presented.

W. H. Warren Jr.

1982-01-01

12

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

13

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

14

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

15

GMOS Calibration to the Lick Index System  

NASA Astrophysics Data System (ADS)

In studies of unresolved stellar populations, age and metallicity are often the two most sought after quantities of interest. By comparing the stellar absorption features of unresolved systems to those of the Lick standard stars, ages and metallicities of the underlying stellar populations can be determined. However, care must be taken in calibrating spectra to the Lick system, as the original Lick spectra were not flux calibrated. In order to properly calibrate unresolved spectra, it is necessary to observe many of the original Lick standard stars and derive offsets to the standard system. This project has collected and reduced all available Lick observations performed with the Gemini Multi-Object Spectrograph (GMOS). In addition, a new online database is being developed, in which the derived offsets and reduced spectra will eventually be available for download.

Mirocha, Jordan; Miller, B.; Trancho, G.

2010-01-01

16

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

17

Carbon and nitrogen abundances in old, very metal-poor stars A reprise based on the low-resolution Lick survey  

NASA Astrophysics Data System (ADS)

A summary is given of the carbon and nitrogen abundances found in the Lick survey of nearly 300 old, very metal-poor stars (Fe/H of less than -1.3). The survey consists of population samples drawn from various stellar subsystems of the Galaxy as well as different stages of stellar evolution. The question of whether a systematic pattern of carbon depletion and nitrogen enhancement emerges within the data was examined and three conclusions were made: (1) the average value of (C + N)/Fe lies within narrow limits for all stellar subsystems, suggesting that the large nitrogen enhancement found in many evolved metal-poor stars is the result of interior C and N mixing; (2) the degree of carbon depletion and corresponding nitrogen enhancement is much larger than predicted by classical evolutionary theory; and (3) the extensive CN processing that occurs in evolved metal-poor stars proceeds further in some stellar subsystems than in others. This is particularly true of the most metal-poor halo field giants vis-a-vis giants in M15 and M92.

Langer, G. E.; Kraft, R. P.

1984-05-01

18

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

Microsoft Academic Search

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

Wayne H. Warren Jr.

1990-01-01

19

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

20

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

21

Atmospheric Turbulence Characteristics Inferred from Optical Measurements at Lick Observatory  

Microsoft Academic Search

This thesis used images of stars and wavefront sensor measurements taken at Lick Observatory on Mt. Hamilton, California by the Laser Guide Star Project of Lawrence Livermore National Laboratory over the period from February, 1993 to March, 1995. The observations were a part of the development of an adaptive optics system to be used on the Shane 120 inch telescope

Lawrence William Bradford

1996-01-01

22

Lick Galaxy Correlation Function Revised  

E-print Network

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

M. Plionis; S. Borgani

1994-01-21

23

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

24

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

25

The Licking County Writing Project.  

ERIC Educational Resources Information Center

The 24 articles in this special journal resulted from the Licking County (Ohio) Writing Project. The articles provide information about the following: (1) how to motivate students and teachers, (2) prewriting activities, (3) lightening the teacher's grading load, (4) the uses of conferences, (5) sustained silent reading, (6) traditional techniques…

Davis, James E., Ed.; Davis, Hazel K., Ed.

1982-01-01

26

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

27

CCD use at Lick Observatory  

NASA Technical Reports Server (NTRS)

The CCD detector and data handling system in regular use at Lick Observatory are described. A grism system has been installed on the automated Cassegrain spectrograph at the Shane 3-meter telescope. A very compact CCD cooling system has been developed using a commercial gas expansion refrigerator; the dewar is a cylinder 15 cm in diameter and 6 cm high. The data acquisition computer, an LSI 11/23 with 256 kbyte RAM, 160 Mbyte Winchester disk, and color video display, provides for FITS format magnetic tape storage as well as preliminary analysis of images and spectra. The 3-meter telescope spectrographic system uses a 500 x 500 pixel thinned CCD. Design information and operational experience for these detector systems are presented along with some results to illustrate the quality of the data being obtained and the current limitations of the CCD detectors and data system.

Lauer, T. R.; Miller, J. S.; Osborne, C. S.; Robinson, L. B.; Stover, R. J.

1984-01-01

28

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

29

The automated planet finder at Lick Observatory  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

30

[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

31

Lick Observatory Optical SETI: targeted search and new directions.  

PubMed

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

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

2005-10-01

32

Operant control of the pattern of licking in rats.  

PubMed

In an attempt to slow down the highly regular rate of licking by instrumental conditioning, 10 rats were trained to obtain their daily ration of water in an apparatus equipped with a retractable drinking spout. Termination of a photoelectrically monitored lick started a computer controlled delay during which the spout was made inaccesible. The subsequent return of the spout was either permanent or limited to a time window (D or W conditions). The cycle was reset by each lick. With stationary spout, the interlick intervals (ILIs) were around 210 +/- 16 ms (median and interquartile range). The spout return was gradually delayed during 22 sessions from 140 to 260 ms and limited to a 260-340 ms window during 11 sessions. A session consisted of 512 licks with stationary spout followed by 7 X 512 licks under D or W conditions. Two rats were able to smoothly adjust to the limited spout availability by increasing median ILI to 290 ms. Four rats generated bimodal ILI distributions indicating gradual reduction of tongue protrusion to an undetected lick followed by abrupt increase of lick amplitude. Three rats increased the median ILI to 260 ms and the interquartile range to 80-150 ms. The above changes of lick pattern allowed the rats to attain tongue-spout contact in 41 to 89% licks. It is concluded that the rats can substantially slow down their lick rate provided that they receive feedback information about the failure or success of each lick. PMID:3987844

Hernandez-Mesa, N; Mamedov, Z; Bures, J

1985-01-01

33

Analysing globular cluster observations. Models and analysis tools for Lick/IDS indices  

NASA Astrophysics Data System (ADS)

We have extended our evolutionary synthesis code, galev, to include Lick/IDS absorption-line indices for both simple and composite stellar population models (star clusters and galaxies), using polynomial fitting functions. We present a mathematically advanced Lick index analysis tool (LINO) for the determination of the ages and metallicities of globular clusters (CGs). An extensive grid of galev models for the evolution of star clusters at various metallicities over a Hubble time is compared to observed sets of Lick indices of varying completeness and precision. A dedicated ?^2-minimisation procedure selects the best model including 1 ? uncertainties on age and metallicity. We discuss the age and metallicity sensitivities of individual indices and show that these sensitivities themselves depend on age and metallicity; thus, we extend Worthey's (1994) concept of a "metallicity sensitivity parameter" for an old stellar population at solar metallicity to younger clusters of different metallicities. We find that indices at low metallicity are generally more age sensitive than at high metallicity. Our aim is to provide a robust and reliable tool for the interpretation of star-cluster spectra becoming available from 10 m class telescopes in a large variety of galaxies - metal-rich & metal-poor, starburst, post-burst, and dynamically young. We test our analysis tool using observations from various authors for Galactic and M 31 GCs, for which reliable age and metallicity determinations are available in the literature, and discuss to what extent the observational availability of various subsets of Lick indices affects the results. For M 31 GCs, we discuss the influence of non-solar abundance ratios on our results. All models are accessible from our website, http://www.astro.physik.uni-goettingen.de/~galev/

Lilly, T.; Alvensleben, U. Fritze-V.

2006-10-01

34

Atmospheric Turbulence Characteristics Inferred from Optical Measurements at Lick Observatory  

NASA Astrophysics Data System (ADS)

This thesis used images of stars and wavefront sensor measurements taken at Lick Observatory on Mt. Hamilton, California by the Laser Guide Star Project of Lawrence Livermore National Laboratory over the period from February, 1993 to March, 1995. The observations were a part of the development of an adaptive optics system to be used on the Shane 120 inch telescope at Lick. Speckle images were made with a CCD camera operating with a fast shutter. For wavefront measurements, a tip-tilt tracking and control loop was used to correct for tip-tilt at a point in the optical train ahead of a Shack-Hartmann lenslet array. The latter measured slopes of the tip-tilt corrected wavefront at each subaperture. Output from the wavefront sensor was used for wavefront reconstruction and subsequent driving of a deformable mirror. Long exposure images were interleaved with wavefront measurements using the same CCD camera used for speckle imaging. Characterization of the atmospheric turbulence affecting image quality is an important aspect of the design of adaptive optics systems. This thesis looked at observed correlations across the telescope aperture, correlations between points in the field of view, and temporal correlations of signals. The measurements yielded functions that can be fit to model functions parameterized by a few variables that depend on the Kolmogorov model of turbulence and upon the altitude dependence of the strength of turbulence C_n^2. The parameters of interest included the value of the spatial coherence length as given by Fried's r_0, the isoplanatic angle theta_0 and the atmospheric coherence time tau_0. Analysis included testing of two models that permit calculation of a vertical distribution of turbulence from readily available data on temperatures, pressures and wind velocities, That data is routinely gathered by National Weather Service radiosondes. The models make some suppositions about how the vertical gradients of those quantities can be related to turbulence strength. The vertical profiles so generated have much greater resolution than any model constructed from an inversion of the parameters used in fitting the optical data. These detailed profiles were used to calculate r_0, theta_0 and tau_0. Those values were then compared with experimental data. In general, agreement with experiment was poor, possibly due to the presence of low altitude turbulence not well accounted for by the models. (SECTION: Dissertation Summaries)

Bradford, Lawrence William

1996-04-01

35

Fiber scrambling for high-resolution spectrographs. I. Lick Observatory  

E-print Network

In this paper, 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; Kaplan, Zachary A; Schwab, Christian; Szymkowiak, Andrew

2013-01-01

36

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

Federal Register 2010, 2011, 2012, 2013, 2014

...AGRICULTURE Forest Service Sand Lick Fork Watershed Restoration Project; Daniel Boone National...SUMMARY: The Sand Lick Fork Watershed Restoration Project involves activities...in part, to manage and/ or restore watersheds to ensure water quality supports...

2012-09-11

37

APF - The Lick Observatory Automated Planet Finder  

E-print Network

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

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

2014-01-01

38

Geochemistry of mineral licks at Loskop Dam Nature Reserve, Mpumalanga, South Africa.  

PubMed

Although numerous hypotheses have been proposed to explain geophagy, the primary driver of this behaviour remains elusive. Supplementation of scarce nutrients is one commonly cited explanation. We examined the element concentration of three licks relative to adjacent topsoils to infer the possible reasons for geophagy at Loskop Dam Nature Reserve. Lick samples had greater concentrations of B, Co, Zn, Se, Mo and Mn (Loskop Main Lick); Cu (Klopperskloof Lick); and Na (Klopperskloof Lick and Rhenosterhoek Lick) than those of adjacent topsoil. We suggest that supplementation with all or some of these nutrients is a likely driver of geophagy in this fenced reserve, with different licks providing herbivores with different suites of nutrients. PMID:20473705

Stephenson, J D; Mills, A; Eksteen, J J; Milewski, A V; Myburgh, J G

2011-02-01

39

VizieR Online Data Catalog: Lick NPM2 Catalog Preliminary Version (Hanson+ 2002)  

NASA Astrophysics Data System (ADS)

The NPM2 Catalog is the second part of the Lick Northern Proper Motion (NPM) program to measure absolute proper motions, on an inertial system defined by some 50,000 faint galaxies, for nearly 400,000 stars over a blue apparent magnitude range from 8 to 18. There are 1246 6x6degree fields in the NPM survey (to declination -23°). The NPM2 Catalog covers the 28% of the northern sky lying near the plane of the the Milky Way and contains some 230,000 stars in the 347 NPM fields remaining after the 1993 NPM1 Catalog (149,000 stars in 899 fields away from the Milky Way). Each NPM field was photographed with the 51 cm Carnegie Double Astrograph at two epochs between 1947 and 1988. The mean first and second epochs are 1950 and 1977; the average epoch difference is 27 years. The first-epoch plates were taken in the blue only; both blue and yellow plates were taken at the second epoch. For NPM2, the plates were scanned by the Precision Measuring Machine (PMM) at the US Naval Observatory, Flagstaff. From the PMM scans, some 120,000 faint (B>14) stars were chosen anonymously for the NPM astrometric reductions and for statistical studies of stellar motions. In addition, the NPM2 catalog contains some 80,000 bright (B<14) positional reference stars, mostly from the Tycho-2 Catalogue, and some 35,000 stars chosen for astronomical interest from Klemola's "Lick Input Catalog of Special Stars" (ICSS). Details of the NPM2 star selection, data reductions, and catalog compilation will be presented in a paper being prepared for the Astronomical Journal. The present version (September 2002) of the NPM2 Catalog contains 196,639 stars from 295 of the 347 NPM2 fields (85%). The remaining 52 fields, in the Summer Milky Way from -02 to -23°, are now being processed, and will be added to the catalog in 2003. Together with the NPM1 Catalog (J2000 version at http://www.ucolick.org/~npm/NPM1/) the NPM2 Catalog completes the Lick Northern Proper Motion program after more than a half-century of work by three generations of Lick Observatory astronomers. The NPM2 catalog gives J2000 positions computed for the catalog epoch 2000, and is in the form of 108 one-degree declination zone files (e.g. z+83n) from +83 to -23°. Following the convention of the NPM1 catalog, each NPM2 star has an NPM2 "name" (e.g. +83.0001) reflecting the declination zone and a running number in right ascension order within the zone. Each star's entry includes the absolute proper motion and blue (B) magnitude. For 98.5% of the stars the B-V color is also given. Other data given for each star are: the original mean epoch, a stellar class code, the number of NPM fields on which the star was measured, and discrepancy flags for proper motion, and photometry. Tycho-2 numbers are given for the primary positional reference stars (40% of NPM2); for these stars the Tycho B,V photometry, transformed to Johnson B and B-V, is listed in preference to the NPM2 photographic photometry. ACRS and Hipparcos numbers are also given for NPM2 stars selected from those catalogs. The RMS errors of the NPM2 absolute proper motions are about 0.6"/centy (6mas/yr) in each coordinate, comparable to the NPM1 errors. The RMS position errors at the NPM2 catalog epoch 2000 average about 0.2" (200mas) in each coordinate, due mostly to the accumulated proper motion error from original plate epochs (average 1968) to 2000. The pure positional errors at the original epochs average 0.08" (80mas) in each coordinate. The RMS errors for the NPM photographic photometry average about 0.18mag in B, and 0.20mag in B-V. We thank the National Science Foundation for its long-term support of the NPM program. The NPM2 phase was supported by NSF grants AST-9530632 and AST-9988105. We thank the Yale Southern Proper Motion group (W. van Altena, I. Platais, and T. Girard) for their help in developing software to process the PMM plate scans. (1 data file).

Hanson, R. B.; Klemola, A. R.; Jones, B. F.; Monet, D. G.

2002-09-01

40

VizieR Online Data Catalog: The LickX Spectra library (Worthey+, 2014)  

NASA Astrophysics Data System (ADS)

Table2 lists spectral index measurements from the stellar spectral library that forms the basis of the Lick index system. Each star was cross-correlated with a template spectrum to improve the wavelength scale, removing most of the wavelength jitter from the original library, and some mistakes in names of objects were corrected. This collection of FITS files is a reworked version of the stellar spectral library that forms the basis of the Lick index system. Each star was cross-correlated with a template spectrum to improve the wavelength scale, removing most of the wavelength jitter from the original library, and some mistakes in names of objects were corrected. New FITS header Keywords give updated wavelength scale: WCRVAL is the wavelength of the first pixel in angstroms WCDELT is the dispersion in angstroms per pixel Occasionally wavelength limit information is include with keywords WLIMIT1 the wavelength in angstroms of the first reliable blue-end pixel WLIMIT2 the wavelength in angstroms of the first reliable red-end pixel Note that the old, unimproved wavelength scale is still present, using the standard keywords CRVAL and CDELT, and users are cautioned that those keywords are included only for historical reference and should not be used as the wavelength scale for scientific applications. The binary data parts of the files are 2048 pixels x 1 pixel in size. The file names are in time order and are of the form sdrXXNNMM, where XX = the number of the observing run NN = the "tape number" MM = the "scan number" Some observing runs have no data and are missing. The tape and scan numbers refer to the original PDP-11 data storage system and are no longer relevant except that the final series of integers remains in time-sequence order when alphabetized. There are 1043 FITS files, each containing one spectrum. (3 data files).

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

2013-11-01

41

Observations of quasar hosts with adaptive optics at Lick Observatory  

E-print Network

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

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

2002-09-05

42

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

USGS Publications Warehouse

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

Evans, James G.; Conyac, Martin D.

1984-01-01

43

Attempt to modify rate and duration of licking in rats by operant conditioning.  

PubMed

Lick-rate in rats is said to be constant for a given animal, despite variations of internal and external stimuli. On the other hand, small changes can be observed due to changes in the construction of the licking device. However, variations do not exceed 20%. In an attempt to gain operant control over the ILI (interlick interval - the time between two lick-onsets) the delivery of reinforcement (20 ?l water) was made dependent on the emission of ILIs of a predetermined length longer than during baseline licking. It could be observed that rats could not shift the peak of their ILI distribution within the reinforced range but - to increase the number of reinforcements - they increased the scatter of the ILI distribution or developed a "harmonic" peak at double ILI length. When the animals were forced in a second experiment to prolong the lick-duration (time of tongue-spout contact) to obtain water, they failed if the restriction from the drinking spout made a closer approach impossible. It is argued that the ability to obtain reinforcement under both schedules is due to postural changes of the animal. The mechanisms controlling licking seem to be relatively constant, which allows good coordination with other behaviours which have to be performed during drinking, such as breathing and swallowing. It can be concluded that the amount of water consumed by rats is controlled by the length of time spent in licking and not by changing the lick-rate. PMID:24923849

Welzl, H

1976-12-01

44

The Lick AGN Monitoring Project 2. Photometric Light Curves  

NASA Astrophysics Data System (ADS)

The Lick AGN Monitoring Project (LAMP) targeted 13 nearby Seyfert 1 galaxies with the intent of measuring the masses of their central black holes using reverberation mapping. In conjunction with the spectroscopic monitoring, we obtained broad-band B and V imaging observations on most nights between the months of February and May 2008. The sample of 13 objects was divided between four telescopes: the 30-inch Katzman Automatic Imaging Telescope (KAIT), the 2-meter Multicolor Active Galactic Nuclei Monitoring (MAGNUM) telescope, the Palomar 60-inch telescope, and the 32-inch Tenagra II telescope. In this talk, we will discuss the observational methods, the photometric measurements, the resultant light curves, and the variability characteristics of each object.

Walsh, Jonell; LAMP Collaboration

2009-01-01

45

Adaptive optics at Lick Observatory: System architecture and operations  

SciTech Connect

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

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

1994-03-01

46

New tools for the tracing of ancient starbursts: Analysing globular cluster systems using Lick indices  

NASA Astrophysics Data System (ADS)

We present mathematically advanced tools for the determination of age, metallicity, and mass of old Globular Clusters (CGs) using both broad-band colors and spectral indices, and we present their application to the Globular Cluster Systems (GCSs) of elliptical galaxies. Since one of the most intriguing questions of today's astronomy aims at the evolutionary connection between (young) violently interacting galaxies at high-redshift and the (old) elliptical galaxies we observe nearby, it is necessary to reveal the possibly violent star-formation history of these old galaxies. By means of evolutionary synthesis models, we can show that, using the integrated light of a galaxy's (composite) stellar content alone, it is impossible to date (and, actually, to identify) even very strong starbursts if these events took place more than two or three Gyr ago. However, since large and violent starbursts are associated with the formation of GCs, GCSs are very good tracers of the most violent starburst events in the history of their host galaxies. Using our well-established Göttingen SED (Spectral Energy Distribution) analysis tool, we can reveal the age, metallicity, mass (and possibly extinction) of GCs by comparing the observations with an extensive grid of SSP model colors. This is done in a statistically advanced and reasonable way, including their 1 ? uncertainties. However, since for all colors the evolution slows down considerably at ages older than about 8 Gyr, even with several passbands and a long wavelength base line, the results are severely uncertain for old clusters. Therefore, we incorporated empirical calibrations for Lick indices in our models and developed a Lick indices analysis tool that works in the same way as the SED analysis tool described above. We compare the theoretical possibilities and limitations of both methods as well as their results for the example of the cD galaxy NGC 1399, for which both multi-color observations and, for a subsample of clusters, spectral indices are available, and address implications for the nature and origin of the observed bimodal color distribution.

Lilly, T.; Fritze-v. Alvensleben, U.; de Grijs, R.

2005-05-01

47

Conditioned lick behavior and evoked responses using whisker twitches in head restrained rats  

PubMed Central

To examine whisker barrel evoked response potentials in chronically implanted rats during behavioral learning with very fast response times, rats must be calm while immobilized with their head restrained. We quantified their behaviors during training with an ethogram and measured each individual animals’ progress over the training period. Once calm under restraint, rats were conditioned to differentiate between a reward and control whisker twitch, then provide a lick response when presented with the correct stimulus, rewarded by a drop of water. Rats produced the correct licking response (after reward whisker twitch), and learned not to lick after a control whisker was twitched. By implementing a high density 64 channel electrocorticogram (ECoG) electrode array, we mapped the barrel field of the somatosensory cortex with high spatial and temporal resolution during conditioned lick behaviors. In agreement with previous reports, we observe a larger evoked response after training, probably related to mechanisms of cortical plasticity. PMID:18718491

Topchiy, Irina A.; Wood, Rachael M.; Peterson, BreeAnne; Navas, Jinna A.; Rojas, Manuel J.; Rector, David M.

2008-01-01

48

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. PMID:20053910

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

2010-01-01

49

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. PMID:24023806

Matoba, Tomoyuki; Kutsukake, Nobuyuki; Hasegawa, Toshikazu

2013-01-01

50

The Fine Temporal Structure of the Rat Licking Pattern: What Causes the Variabiliy in the Interlick Intervals and How is it Affected by the Drinking Solution?  

PubMed Central

Licking is a repetitive behavior controlled by a central pattern generator. Even though interlick intervals (ILIs) within bursts of licks are considered fairly regular, the conditions that affect their variability are unknown. We analyzed the licking pattern in rats that licked water, 10% sucrose solution, or 10% ethanol solution, in 90-min recording sessions after 4h of water deprivation. The histograms of ILIs indicate that licking typically occurred at a preferred ILI of about 130?140ms with evidence of bimodal or multimodal distributions due to occasional licking failures. We found that the longer the pause between bursts of licks, the shorter was the first ILI of the burst. When bursts of licks were preceded by a pause >4 s, the ILI was the shortest (~110ms) at the beginning of the burst, and then it increased rapidly in the first few licks and slowly in subsequent licks. Interestingly, the first ILI of a burst of licks was not significantly different when licking any of the 3 solutions, but subsequent licks exhibited a temporal pattern characteristic of each solution. The rapid deceleration in intraburst licking rate was due to an increase from ~27ms to ~56ms in the tongue-spout contact duration while the intercontact interval was only slightly changed (80?90ms). Therefore, the contact duration seems to be the major factor that increases the variability in the ILIs and could be another means for the rat to adjust the amount of fluid ingested in each individual lick. PMID:23902635

2013-01-01

51

The fine temporal structure of the rat licking pattern: what causes the variabiliy in the interlick intervals and how is it affected by the drinking solution?  

PubMed

Licking is a repetitive behavior controlled by a central pattern generator. Even though interlick intervals (ILIs) within bursts of licks are considered fairly regular, the conditions that affect their variability are unknown. We analyzed the licking pattern in rats that licked water, 10% sucrose solution, or 10% ethanol solution, in 90-min recording sessions after 4h of water deprivation. The histograms of ILIs indicate that licking typically occurred at a preferred ILI of about 130-140ms with evidence of bimodal or multimodal distributions due to occasional licking failures. We found that the longer the pause between bursts of licks, the shorter was the first ILI of the burst. When bursts of licks were preceded by a pause >4 s, the ILI was the shortest (~110ms) at the beginning of the burst, and then it increased rapidly in the first few licks and slowly in subsequent licks. Interestingly, the first ILI of a burst of licks was not significantly different when licking any of the 3 solutions, but subsequent licks exhibited a temporal pattern characteristic of each solution. The rapid deceleration in intraburst licking rate was due to an increase from ~27ms to ~56ms in the tongue-spout contact duration while the intercontact interval was only slightly changed (80-90ms). Therefore, the contact duration seems to be the major factor that increases the variability in the ILIs and could be another means for the rat to adjust the amount of fluid ingested in each individual lick. PMID:23902635

Lin, Xiong Bin; Pierce, Dwight R; Light, Kim Edward; Hayar, Abdallah

2013-10-01

52

Externally Dispersed Interferometry with the Lick Observatory Echelle Spectrograph  

NASA Astrophysics Data System (ADS)

We demonstrate stellar and solar measurements of full-bandwidth echelle spectra using an externally dispersed interferometer (EDI). Spectral resolution of ~120k has been obtained using the ~60k resolution CAT facility at the Lick Observatory. The EDI is a series combination of a fixed delay interferometer and a grating spectrograph that increases the spectrograph's effective resolution by factors of 2 to 3. EDI uses a heterodyning effect to shift the input spectrum's high spectral resolution information to lower spatial frequencies that are less sensitive to the resolution limit caused by the spectrograph slit size and by the Nyquist limit of the detector. The resolution-boosted spectra is obtained by numerically reversing the heterodyning effect and combining these data with the ordinary spectrum simultaneously acquired within the EDI data. The interferometer fringes imprinted on the spectrum are exactly periodic in frequency space and acts as a fiducial net that uniformly covers the entire echelle bandwidth. Instrumental distortions that deviate the stellar signal also deviate these fiducial fringes, so the measurement, in comparison to a classical echelle data, is extremely robust to beam profile errors. Our method uses a uniform-phase interferometer fringe at the spectrograph entrance slit. Therefore the spectrograph may use either a 2d-echelle or slit-imaging format. The EDI has applications in Doppler radial velocimetry and high resolution spectroscopy. Work was partially supported by CalSpace/Lockheed, and NASA SARA research grants NAG5-9091 and NAG5-3051. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Erskine, D. J.; Edelstein, J.

2002-12-01

53

Taste Coding in the Nucleus of the Solitary Tract of the Awake, Freely Licking Rat  

PubMed Central

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 extra-oral chemoreceptors. Analyses of the temporal characteristics of taste responses showed that spike timing conveyed significantly more information than spike count alone in almost 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 “anti-lick” 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.

2012-01-01

54

C57BL/6J and DBA/2J mice vary in lick rate and ingestive microstructure.  

PubMed

Fluid licking in mice is an example of a rhythmic behavior thought to be under the control of a central pattern generator. Inbred strains of mice have been shown to differ in mean or modal interlick interval (ILI) duration, suggesting a genetic-based variation. We investigated water licking in the commonly used inbred strains C57BL/6J (B6) and DBA/2J (D2), using a commercially available contact lickometer. Results from 20-min test sessions indicated that D2 mice lick at a faster rate than B6 mice (10.6 licks/s vs. 8.5 licks/s), based on analysis of the distribution of short-duration ILIs (50-160 ms). This strain difference was independent of sex, extent of water deprivation or total number of licks. D2 mice also displayed a faster lick rate when the strains were tested with a series of brief (5 s) trials. However, when ingestion over the entire 20-min session was analyzed, it was evident that D2 mice had an overall slower rate of ingestion than B6 mice. This was because of the tendency for D2 mice to have more very long pauses (>30 s) between sequences of licking bursts. Overall, it appeared that D2 mice licked more efficiently, ingesting more rapidly during excursions to the spout that were fewer and farther between. PMID:17212649

Boughter, J D; Baird, J-P; Bryant, J; St John, S J; Heck, D

2007-10-01

55

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

56

Polyphase speleogenesis in Lick Creek Cave, Little Belt Mountains, Montana, USA  

Microsoft Academic Search

Lick Creek Cave in northern Montana (USA) is hosted in limestones of the Lower Carboniferous Madison Group near Tiger Butte, an Eocene quartz–syenite porphyry intrusive dome. The cave is located within the zone of contact metamorphism of the dome, which crops out ?300m from the cave entrance. The cave consists of two genetically distinct cave systems separated by a fracture

Kevin L. Carrière; Hans G. Machel; John C. Hopkins

2010-01-01

57

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

58

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

NASA Astrophysics Data System (ADS)

We report on experimental results with adaptive optics testbeds at the UCO/Lick Observatory. One testbed is dedicated to high contrast AO imaging and is a prototype for a ground-based extrasolar planet imager. The second testbed is dedicated to developing concepts and architectures for multi-laser guidestar tomography in wide-field AO applications. Concurrent with the testbed experiments we are evaluating the new components and key technologies applicable to the next generation of AO systems including MEMS deformable mirrors, high speed low noise detectors, wavefront sensing methods, and fast wavefront control processors. The high contrast testbed has achieved its contrast goal of better than 10^-6 in a 5 to 15 lambda/d region around the central star, the "discovery region," using a 1024 actuator MEMS deformable mirror correcting typical atmospheric aberrations. A new section of the testbed has been added recently which will contain an advanced concept apodized pupil Lyot coronagraph for which some initial results will be attained in time for this conference. We now progressing with the design phase of the Gemini Planet Imager instrument for which we are developing a 4096 actuator MEMS device. The Multi-guidestar Tomography testbed has been configured to analyze MCAO and MOAO architectures under consideration for the Keck and proposed Thirty Meter Telescope AO systems. These configurations will consist of from 5 to 9 laser guidestars spread out on a field of between 2 and 5 arcminutes diameter. Testbed results are clearly showing the extension of the high-Strehl correction field out to these wide fields, which are much larger than the isoplanatic angle. As part of this project, we have developed high-speed tomography algorithms for efficient minimum-variance estimation and control of wavefronts. We have also scoped and prototyped the specialized compute hardware necessary to implement them in real-time. In the component development area we are investigating the use of MEMS deformable mirrors for open-loop control of wavefronts. This will enable the multi-object AO (MOAO) configuration that is suited to simultaneous multi-object spectroscopy, an architecture that multiplies the efficiency of science observing on large telescopes. Since the actuation of MEMS deformable mirrors is based on a very repeatable and low hysteresis electrostatic deflection process, they show great promise for this their use in this approach. Present go-to accuracies have been demonstrated to on the order of 15nm rms. MEMS are also small and lower in cost than current generation piezo actuator DMs, which implies that they have potential for additional applications throughout the AO optical system. We are investigating applications in the high-order wavefront and tip/tilt sensors.

Gavel, D.

59

Salt licks do not increase local densities of the deer ked, Lipoptena cervi, an abundant ectoparasite of cervids.  

PubMed

The deer ked, Lipoptena cervi (Diptera: Hippoboscidae), is a common ectoparasite of the moose, Alces alces (Artiodactyla: Cervidae). Salt licks are widely used to manipulate moose movements to prevent damage to saplings and traffic accidents. They may cause moose to gather in small areas, which could create aggregates of deer ked pupae as the parasite is a short-distance flyer and its dispersion depends on its hosts. We investigated whether the population density of flying deer keds could be influenced by manipulating salt licks and how environmental variables affect parasite density. Densities were estimated in 40 experimental sites with four treatments (no salt licks, introduced salt licks, removed salt licks, permanent salt licks) in September during 2007-2010. Forest edges, mixed forests on mineral soil and coniferous forests on peat soil were the habitats with high numbers of parasites. The manipulation of salt licks seemed to be ineffective in reducing the density of deer keds as the only factor to show statistical significance with parasite numbers in the mixed-model analysis was year of determination. Annual deer ked densities correlated with the abundance of moose in the region. Moreover, high spring and summer temperatures seemed to increase the numbers of flying imagos. PMID:24131141

Paakkonen, T; Nieminen, P; Roininen, H; Mustonen, A-M

2014-09-01

60

The Lick AGN Monitoring Project 2011: New Velocity-Resolved Reverberation-Mapping Results  

NASA Astrophysics Data System (ADS)

The Lick AGN Monitoring Project 2011 observing campaign was carried out over the course of 11 weeks in Spring 2011 using spectroscopic data from the Lick 3-m telescope and imaging data from several queue-scheduled telescopes. Here we present new reverberation-mapping measurements for four nearby Seyfert galaxies: Arp 151, Mrk 279, Mrk 1511, and NGC 4593. We will describe the imaging and spectroscopic observing campaigns, light curve measurements, and broad-line reverberation lag measurements. Velocity-resolved reverberation lags can encode important clues to the kinematic structure of the broad-line region, and we will present new measurements of velocity-dependent H-beta lags in our sample.

Barth, Aaron J.; Pancoast, A.; LAMP2011 Collaboration

2013-01-01

61

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

Microsoft Academic Search

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

Donald Gavel

2007-01-01

62

MULTIPLICITY AMONG WIDELY SEPARATED BROWN DWARF COMPANIONS TO NEARBY STARS: GLIESE 337CD  

E-print Network

MULTIPLICITY AMONG WIDELY SEPARATED BROWN DWARF COMPANIONS TO NEARBY STARS: GLIESE 337CD Adam J March 13 ABSTRACT We present Lick Natural Guide Star Adaptive Optics observations of the L8 brown dwarf and metallicity. From a compilation of all known widely separated (k100 AU) stellar­ brown dwarf multiple systems

Burgasser, Adam J.

63

Mineral licks: motivational factors for visitation and accompanying disease risk at communal use sites of elk and deer.  

PubMed

Free-ranging cervids acquire most of their essential minerals through forage consumption, though occasionally seek other sources to account for seasonal mineral deficiencies. Mineral sources occur as natural geological deposits (i.e., licks) or as anthropogenic mineral supplements. In both scenarios, these sources commonly serve as focal sites for visitation. We monitored 11 licks in Rocky Mountain National Park, north-central Colorado, using trail cameras to quantify daily visitation indices (DVI) and soil consumption indices (SCI) for Rocky Mountain elk (Cervus elaphus) and mule deer (Odocoileus hemionus) during summer 2006 and documented elk, mule deer, and moose (Alces alces) visiting licks. Additionally, soil samples were collected, and mineral concentrations were compared to discern levels that explain rates of visitation. Relationships between response variables; DVI and SCI, and explanatory variables; elevation class, moisture class, period of study, and concentrations of minerals were examined. We found that DVI and SCI were greatest at two wet, low-elevation licks exhibiting relatively high concentrations of manganese and sodium. Because cervids are known to seek Na from soils, we suggest our observed association of Mn with DVI and SCI was a likely consequence of deer and elk seeking supplemental dietary Na. Additionally, highly utilized licks such as these provide an area of concentrated cervid occupation and interaction, thus increasing risk for environmental transmission of infectious pathogens such as chronic wasting disease, which has been shown to be shed in the saliva, urine, and feces of infected cervids. PMID:24711146

Lavelle, Michael J; Phillips, Gregory E; Fischer, Justin W; Burke, Patrick W; Seward, Nathan W; Stahl, Randal S; Nichols, Tracy A; Wunder, Bruce A; VerCauteren, Kurt C

2014-12-01

64

A radial velocity spectrometer for the Automated Planet Finder Telescope at Lick Observatory  

NASA Astrophysics Data System (ADS)

The Ken and Gloria Levy Spectrometer is being constructed at the Instrument Development Laboratory (Technical Facilities) of UCO/ Lick Observatory for use on the 2.4 meter Automated Planet Finder Telescope at Mt. Hamilton. The mechanical design of the instrument has been optimized for precision Doppler measurements. A key component of the design is the space-frame structure that contains passive thermal compensation. Determinate hexapod structures are used to mount the collimator, prism, and echelle grating. In this paper we describe the instrument mechanical design and some features that will help it detect rocky planets in the habitable zone.

Radovan, Matthew V.; Cabak, Gerald F.; Laiterman, Lee H.; Lockwood, Christopher T.; Vogt, Steven S.

2010-07-01

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

FIRST, a fibered aperture masking instrument: Results of the Lick observing campaign  

NASA Astrophysics Data System (ADS)

FIRST is a prototype instrument aimed at achieving high dynamic range and angular resolution in ground-based images at visible wavelengths near the diffraction limit. FIRST utilizes an aperture masking-like technique that makes use of single-mode fibers and pupil remapping to maximize the area of the telescope mirror in use. While located at Lick observatory in 2011 and 2012, FIRST observed 25 binary systems with the Shane 3m telescope, with separations ranging from 20 to 200 mas, comparable to the 50 mas diffraction limit for our central wavelength. Huby et al. (2013) has reported results for the Capella system that established the utility of FIRST for characterizing stellar binaries using the directly measured spectral flux ratio. Using an improved data analysis pipeline, we obtained closure phase measurements for a majority of the targets observed at Lick, and derived angular separations and spectral flux ratios. From the spectral flux ratios we obtained spectra for the companions over at least 600-850 nm with R~300. Finally, by obtaining results for many binary systems we have better constrained the current performance of FIRST, which has an exciting future ahead at its current location behind SCExAO at the Subaru 8.2 m telescope, where it will eventually become available for general use by the astronomical community.

Bordwell, Baylee; Duchene, Gaspard; Huby, Elsa; Goebel, Sean; Marchis, Franck; Perrin, Guy; Lacour, Sylvestre; Kotani, Takayuki; Gates, Elinor L.; Choquet, Elodie

2015-01-01

67

Rat psychomotor vigilance task with fast response times using a conditioned lick behavior  

PubMed Central

Investigations into the physiological mechanisms of sleep control require an animal psychomotor vigilance task (PVT) with fast response times (<300ms). Rats provide a good PVT model since whisker stimulation produces a rapid and robust cortical evoked response, and animals can be trained to lick following stimulation. Our prior experiments used deprivation-based approaches to maximize motivation for operant conditioned responses. However, deprivation can influence physiological and neurobehavioral effects. In order to maintain motivation without water deprivation, we conditioned rats for immobilization and head restraint, then trained them to lick for a 10% sucrose solution in response to whisker stimulation. After approximately 8 training sessions, animals produced greater than 80% correct hits to the stimulus. Over the course of training, reaction times became faster and correct hits increased. Performance in the PVT was examined after 3, 6 and 12 hours of sleep deprivation achieved by gentle handling. A significant decrease in percent correct hits occurred following 6 and 12 hours of sleep deprivation and reaction times increased significantly following 12 hours of sleep deprivation. While behaviorally the animals appeared to be awake, we observed significant increases in EEG delta power prior to misses. The rat PVT with fast response times allows investigation of sleep deprivation effects, time on task and pharmacological agents. Fast response times also allow closer parallel studies to ongoing human protocols. PMID:20696188

Walker, Jennifer L.; Walker, Brendan M.; Fuentes, Fernanda Monjaraz; Rector, David M.

2010-01-01

68

The Michigan Binary Star Program  

NASA Astrophysics Data System (ADS)

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

Lindner, Rudi P.

2007-07-01

69

Results of the Lick Observatory Supernova Search Follow-up Photometry Program: BVRI Light Curves of 165 Type Ia Supernovae  

Microsoft Academic Search

We present BVRI light curves of 165 Type Ia supernovae (SNe Ia) from the Lick Observatory Supernova Search follow-up photometry program from 1998 through 2008. Our light curves are typically well sampled (cadence of 3-4 days) with an average of 21 photometry epochs. We describe our monitoring campaign and the photometry reduction pipeline that we have developed. Comparing our data

Mohan Ganeshalingam; Weidong Li; Alexei V. Filippenko; Carmen Anderson; Griffin Foster; Elinor L. Gates; Christopher V. Griffith; Bryant J. Grigsby; Niels Joubert; Joel Leja; Thomas B. Lowe; Brent Macomber; Tyler Pritchard; Patrick Thrasher; Dustin Winslow

2010-01-01

70

Greater Superficial Petrosal Nerve Transection in Rats does not Change Unconditioned Licking Responses to Putatively Sweet Taste Stimuli  

Microsoft Academic Search

The greater superficial petrosal nerve (GSP), innervating taste buds in the palate, is known to be exceptionally responsive to sucrose, especially compared with the responsiveness of the chorda tympani nerve (CT). However, whereas transection of the CT (CTX) alone has little or no effect on unconditioned licking responses to many ''sweet'' stimuli, the impact of GSP transection (GSPX) alone is

Enshe Jiang; Ginger Blonde; Mircea Garcea; Alan C. Spector

2008-01-01

71

Linoleic and Oleic Acids Alter the Licking Responses to Sweet, Salt, Sour, and Bitter Tastants in Rats  

Microsoft Academic Search

The free fatty acids (FFAs), linoleic and oleic acids, commonly found in dietary fats can be detected by rats on the basis of gus- tatory cues following conditioned taste aversion pairings. FFAs depolarize the membrane potential of isolated rat taste receptor cells by inhibiting delayed rectifying potassium channels. This study examined the licking response of rats to sweet, salt, sour,

David W. Pittman; Caroline E. Labban; Abigail A. Anderson; Hayley E. O'Connor

2006-01-01

72

Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations  

NASA Astrophysics Data System (ADS)

We present a new set of model predictions for 16 Lick absorption line indices from H? through Fe5335 and UBV colors for single stellar populations with ages ranging between 1 and 15 Gyr, [Fe/H] ranging from -1.3 to +0.3, and variable abundance ratios. The models are based on accurate stellar parameters for the Jones library stars and a new set of fitting functions describing the behavior of line indices as a function of effective temperature, surface gravity, and iron abundance. The abundances of several key elements in the library stars have been obtained from the literature in order to characterize the abundance pattern of the stellar library, thus allowing us to produce model predictions for any set of abundance ratios desired. We develop a method to estimate mean ages and abundances of iron, carbon, nitrogen, magnesium, and calcium that explores the sensitivity of the various indices modeled to those parameters. The models are compared to high-S/N data for Galactic clusters spanning the range of ages, metallicities, and abundance patterns of interest. Essentially all line indices are matched when the known cluster parameters are adopted as input. Comparing the models to high-quality data for galaxies in the nearby universe, we reproduce previous results regarding the enhancement of light elements and the spread in the mean luminosity-weighted ages of early-type galaxies. When the results from the analysis of blue and red indices are contrasted, we find good consistency in the [Fe/H] that is inferred from different Fe indices. Applying our method to estimate mean ages and abundances from stacked SDSS spectra of early-type galaxies brighter than L*, we find mean luminosity-weighed ages of the order of ~8 Gyr and iron abundances slightly below solar. Abundance ratios, [X/Fe], tend to be higher than solar and are positively correlated with galaxy luminosity. Of all elements, nitrogen is the more strongly correlated with galaxy luminosity, which seems to indicate secondary nitrogen enrichment. If that interpretation is correct, this result may impose a lower limit of 50-200 Myr to the timescale of star formation in early-type galaxies. Unlike clusters, galaxies show a systematic effect whereby higher order, bluer, Balmer lines yield younger ages than H?. This age discrepancy is stronger for lower luminosity galaxies. We examine four possible scenarios to explain this trend. Contamination of the bluer indices by a metal-poor stellar population with a blue horizontal branch cannot account for the data. Blue stragglers and abundance-ratio effects cannot be ruled out, as they can potentially satisfy the data, even though this can only be achieved by resorting to extreme conditions, such as extremely high [O/Fe] or specific blue-straggler frequencies. The most likely explanation is the presence of small amounts of a young/intermediate-age stellar population component. We simulate this effect by producing two-component models and show that they provide a reasonably good match to the data when the mass fraction of the young component is typically a few percent. If confirmed, this result implies star formation has been extended in early-type galaxies, and more so in less massive galaxies, which seems to lend support to the ``downsizing'' scenario. Moreover, it implies that stellar population synthesis models are capable of constraining not only the mean ages of stellar populations in galaxies, but also their age spread.

Schiavon, Ricardo P.

2007-07-01

73

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

PubMed

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

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

2014-10-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

75

Catalog of spectral and luminosity classes of 6037 stars in the direction of the Galactic anticenter  

NASA Astrophysics Data System (ADS)

A catalog of the spectral and luminosity classes of 6037 stars is presented which has been compiled on the basis of the plan of the Abatumani Astrophysical Observatory for the mass MK classification of stars, taking peculiarities into account. The stars in the catalog are arranged in the order of increasing right ascension; they are numbered according to the zones corresponding to 1-deg declination. The catalog is provided with suitable search charts reproduced from the Lick Atlas.

Chargeishvili, Ketevan B.

76

Laser guide star measurements at Lawrence Livermore National Laboratory  

SciTech Connect

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

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

1993-02-01

77

The Selective Serotonin Reuptake Inhibitor Paroxetine Does Not Alter Consummatory Concentration-Dependent Licking of Prototypical Taste Stimuli by Rats  

PubMed Central

Serotonin and the 5HT1A receptor are expressed in a subset of taste receptor cells, and the 5HT3 receptor is expressed on afferent fibers innervating taste buds. Exogenous administration of the selective serotonin reuptake inhibitor, paroxetine, has been shown to increase taste sensitivity to stimuli described by humans as sweet and bitter. Serotonergic agonists also decrease food and fluid intake, and it is possible that modulations of serotonin may alter taste-based hedonic responsiveness; alternatively, or in combination, serotonin may interact with physiological state to impact ingestive behavior. In this study, the unconditioned licking of prototypical taste stimuli by rats in brief-access taste tests was assessed following paroxetine administration (0.3–10 mg/kg intraperitoneal). We also measured sucrose licking by rats in different deprivation states after paroxetine (5 mg/kg). In neither experiment did we find any evidence of an effect of paroxetine on licking relative to water to any of the taste stimuli in the brief-access test at doses that decreased food intake. However, in some conditions, paroxetine decreased trials initiated to tastants. Therefore, a systemic increase in serotonin via paroxetine administration can decrease appetitive behavior in brief-access tests but is insufficient to alter taste-guided consummatory behavior. PMID:21422376

Spector, Alan C.

2011-01-01

78

A one-dimensional, steady-state, dissolved-oxygen model and waste-load assimilation study for Little and Big Lick creeks, Blackford and Delaware counties, Indiana  

USGS Publications Warehouse

A digital computer model was used to predict alternatives for future waste loadings on Little Lick and Big Lick Creeks, Blackford and Delaware Counties, IN, that would be compatible with Indiana stream water-quality standards defined for two critical hydrologic conditions, summer and winter low flows. The model parameters included atmospheric reaeration, carbonaceous and nitrogenous biochemical-oxygen demand, and benthic-oxygen demand. The model was calibrated with data collected during three water-quality surveys at low flow. During these surveys, in-stream dissolved-oxygen concentrations averaged less than 3 mg/L, well below the State minimum requirement of 5.0 mg/L. The model indicated that these low concentrations were caused by high waste loadings, lack of dilution, low reaeration, and benthic-oxygen demand. The summer waste-assimilation study assumed that future reductions in discharge loadings would decrease carbonaceous and benthic decay and increase nitrogenous decay. This study indicated that projected effluent waste loads that would provide acceptable in-stream dissolved-oxygen concentrations are highly dependent on rates of nitrification. Ammonia toxicity became the limiting water-quality criterion at low nitrification rates. The winter waste-assimilation study indicated that projected dissolved-oxygen concentrations in Little Lick and Big Lick Creeks did not fall below the State standard. Owing to a lack of dilution, however, ammonia-nitrogen concentrations would violate in-stream toxicity standards in both Little Lick and Big Lick Creeks. (USGS)

Peters, James G.; Crawford, Charles G.; Wilber, William G.

1980-01-01

79

Role of pups' ultrasonic calls in a particular maternal behavior in Wistar rat: pups' anogenital licking.  

PubMed

Stimuli from pups maintain maternal behavior in the postpartum period. Olfactory cues are strongly involved in a particular component of maternal behavior: anogenital licking (MAGL). In addition to the olfactive stimulus, ultrasonic calls from pups are critical in ensuring pup survival. Pups emit vocalizations in distress situations. In a first experiment, pups' calls are recorded around MAGL sequences. In 2 out of 3 cases these calls appear to induce MAGL behavior from the dam with preputialectomised pups as well as with intact pups, but preputialectomised pups alone call again at the end of MAGL sequences. In a second experiment, ultrasonic calls from pups emitted just before AGL sequences were recorded and played back to dams in a glass-dish selection test. Whatever the pups' treatment (preputialectomised or sham), dams showed the specific ingestive behavior towards filter paper impregnated with dodecyl propionate (DP) when auditory cues (pups' ultrasonic calls) and olfactory cues (DP) were combined. The coordination of pups' ultrasonic calls and anogenital odor in MAGL behavior is discussed, ultrasonic calls might be an inducing factor and DP the regulating factor. PMID:1449642

Brouette-Lahlou, I; Vernet-Maury, E; Vigouroux, M

1992-09-28

80

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

NASA Astrophysics Data System (ADS)

The Lick AGN Monitoring Project 2011 observing campaign was carried out over the course of 11 weeks in spring 2011. Here we present the first results from this program, a measurement of the broad-line reverberation lag in the Seyfert 1 galaxy Mrk 50. Combining our data with supplemental observations obtained prior to the start of the main observing campaign, our data set covers a total duration of 4.5 months. During this time, Mrk 50 was highly variable, exhibiting a maximum variability amplitude of a factor of ~4 in the U-band continuum and a factor of ~2 in the H? line. Using standard cross-correlation techniques, we find that H? and H? lag the V-band continuum by ?cen = 10.64+0.82 - 0.93 and 8.43+1.30 - 1.28 days, respectively, while the lag of He II ?4686 is unresolved. The H? line exhibits a symmetric velocity-resolved reverberation signature with shorter lags in the high-velocity wings than in the line core, consistent with an origin in a broad-line region (BLR) dominated by orbital motion rather than infall or outflow. Assuming a virial normalization factor of f = 5.25, the virial estimate of the black hole mass is (3.2 ± 0.5) × 107 M ?. These observations demonstrate that Mrk 50 is among the most promising nearby active galaxies for detailed investigations of BLR structure and dynamics.

Barth, Aaron J.; Pancoast, Anna; Thorman, Shawn J.; Bennert, Vardha N.; Sand, David J.; Li, Weidong; Canalizo, Gabriela; Filippenko, Alexei V.; Gates, Elinor L.; Greene, Jenny E.; Malkan, Matthew A.; Stern, Daniel; Treu, Tommaso; Woo, Jong-Hak; Assef, Roberto J.; Bae, Hyun-Jin; Brewer, Brendon J.; 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; Tollerud, Erik J.; Walsh, Jonelle L.; Walters, Richard; da Silva, Robert L.; Fumagalli, Michele; Gregg, Michael D.; Harris, Chelsea E.; Hsiao, Eric Y.; Lee, Jeffrey; Lopez, Liliana; Rex, Jacob; Suzuki, Nao; Trump, Jonathan R.; Tytler, David; Worseck, Gábor; Yesuf, Hassen M.

2011-12-01

81

Identifying Young, Nearby Stars  

NASA Technical Reports Server (NTRS)

Young stars have certain characteristics, e.g., high atmospheric abundance of lithium and chromospheric activity, fast rotation, distinctive space motion and strong X-ray flux compared to that of older main sequence stars. We have selected a list of candidate young (<100Myr) and nearby (<60pc) stars based on their space motion and/or strong X-ray flux. To determine space motion of a star, one needs to know its coordinates (RA, DEC), proper motion, distance, and radial velocity. The Hipparcos and Tycho catalogues provide all this information except radial velocities. We anticipate eventually searching approx. 1000 nearby stars for signs of extreme youth. Future studies of the young stars so identified will help clarify the formation of planetary systems for times between 10 and 100 million years. Certainly, the final output of this study will be a very useful resource, especially for adaptive optics and space based searches for Jupiter-mass planets and dusty proto-planetary disks. We have begun spectroscopic observations in January, 2001 with the 2.3 m telescope at Siding Spring Observatory (SSO) in New South Wales, Australia. These spectra will be used to determine radial velocities and other youth indicators such as Li 6708A absorption strength and Hydrogen Balmer line intensity. Additional observations of southern hemisphere stars from SSO are scheduled in April and northern hemisphere observations will take place in May and July at the Lick Observatory of the University of California. AT SSO, to date, we have observed about 100 stars with a high resolution spectrometer (echelle) and about 50 stars with a medium spectral resolution spectrometer (the "DBS"). About 20% of these stars turn out to be young stars. Among these, two especially noteworthy stars appear to be the closest T-Tauri stars ever identified. Interestingly, these stars share the same space motions as that of a very famous star with a dusty circumstellar disk--beta Pictoris. This new finding better constrains the age of beta Pictoris to be approx. 10 Myr.

Webb, Rich; Song, Inseok; Zuckerman, Ben; Bessell, Mike

2001-01-01

82

A low-cost solution to measure mouse licking in an electrophysiological setup with a standard analog-to-digital converter  

PubMed Central

Licking behavior in rodents is widely used to determine fluid consumption in various behavioral contexts and is a typical example of rhythmic movement controlled by internal pattern-generating mechanisms. The measurement of licking behavior by commercially available instruments is based on either tongue protrusion interrupting a light beam or on an electrical signal generated by the tongue touching a metal spout. We report here that licking behavior can be measured with high temporal precision by simply connecting a metal sipper tube to the input of a standard analog/digital (A/D) converter and connecting the animal to ground (via a metal cage floor). The signal produced by a single lick consists of a 100–800 mV dc voltage step, which reflects the metal-to-water junction potential and persists for the duration of the tongue–spout contact. This method does not produce any significant electrical artifacts and can be combined with electrophysiological measurements of single unit activity from neurons involved in the control of the licking behavior. PMID:16364450

Hayar, Abdallah; Bryant, Jeri L.; Boughter, John D.; Heck, Detlef H.

2008-01-01

83

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

84

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

85

Baker's Dozen "Greatest Hits" by UC Astronomers at UCO Facilities (Keck/Lick) Greatest Hits Faculty UC Campus UCO Facility International/World-Class Prizes  

E-print Network

) **Davis UCB Keck **Gruber Prize (for Galaxy/Cosmology Theory) Coil UCSD Keck Cooper UCI Keck 7. First Astronomy Telescope using Laser Technology to Remove the Blur of Our Atmosphere Max/Gavel LLNL/UCSC/UCO Lick 9. First Pictures of Multiple Planets in a "Solar System" beyond our Own Macintosh LLNL Keck 10

86

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

87

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

SciTech Connect

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

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

2004-01-08

88

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

89

Reconstructing the Star Formation Histories of Galaxies  

E-print Network

We present a methodological study to find out how far back and to what precision star formation histories of galaxies can be reconstructed from CMDs, from integrated spectra and Lick indices, and from integrated multi-band photometry. Our evolutionary synthesis models GALEV allow to describe the evolution of galaxies in terms of all three approaches and we have assumed typical observational uncertainties for each of them and then investigated to what extent and accuracy different star formation histories can be discriminated. For a field in the LMC bar region with both a deep CMD from HST observations and a trailing slit spectrum across exactly the same field of view we could test our modelling results against real data.

Uta Fritze; Thomas Lilly

2007-01-15

90

To join Friends of Lick Observatory by mail, please complete this membership application and return with either your credit card number and signature or a check made payable to UCSC Foundation (with FoLO in  

E-print Network

with either your credit card number and signature or a check made payable to UCSC Foundation (with Fo donation, please enter that amount here: ________ Check or Credit card number ___________________ Country_________________ Quasar Circle -- $2500 James Lick Society -- $5000 Contact phone number

91

Effects of haloperidol and clozapine on tongue dynamics during licking in CD1, BALB\\/c and C57BL\\/6 mice  

Microsoft Academic Search

Rationale: In an initial effort to describe how genetic background influences the differential motor effects of haloperidol, a drug\\u000a with high extrapyramidal side effect (EPS) liability, and clozapine, an antipsychotic low in EPS, both drugs were studied\\u000a in inbred strains of mice (BALB\\/c and C57BL\\/6) previously shown to have differential sensitivities to haloperidol. Objectives: Behavioral differences in lick dynamics for

Guanghui Wang; Stephen C. Fowler

1999-01-01

92

RESULTS OF THE LICK OBSERVATORY SUPERNOVA SEARCH FOLLOW-UP PHOTOMETRY PROGRAM: BVRI LIGHT CURVES OF 165 TYPE Ia SUPERNOVAE  

SciTech Connect

We present BVRI light curves of 165 Type Ia supernovae (SNe Ia) from the Lick Observatory Supernova Search follow-up photometry program from 1998 through 2008. Our light curves are typically well sampled (cadence of 3-4 days) with an average of 21 photometry epochs. We describe our monitoring campaign and the photometry reduction pipeline that we have developed. Comparing our data set to that of Hicken et al., with which we have 69 overlapping supernovae (SNe), we find that as an ensemble the photometry is consistent, with only small overall systematic differences, although individual SNe may differ by as much as 0.1 mag, and occasionally even more. Such disagreement in specific cases can have significant implications for combining future large data sets. We present an analysis of our light curves which includes template fits of light-curve shape parameters useful for calibrating SNe Ia as distance indicators. Assuming the B - V color of SNe Ia at 35 days past maximum light can be presented as the convolution of an intrinsic Gaussian component and a decaying exponential attributed to host-galaxy reddening, we derive an intrinsic scatter of {sigma} = 0.076 {+-} 0.019 mag, consistent with the Lira-Phillips law. This is the first of two papers, the second of which will present a cosmological analysis of the data presented herein.

Ganeshalingam, Mohan; Li Weidong; Filippenko, Alexei V.; Anderson, Carmen; Foster, Griffin; Griffith, Christopher V.; Joubert, Niels; Leja, Joel; Macomber, Brent; Pritchard, Tyler; Thrasher, Patrick; Winslow, Dustin [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Gates, Elinor L.; Grigsby, Bryant J.; Lowe, Thomas B. [Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States)

2010-10-15

93

Xenon in Mercury-Manganese Stars  

E-print Network

Previous studies of elemental abundances in Mercury-Manganese (HgMn) stars have occasionally reported the presence of lines of the ionized rare noble gas Xe II, especially in a few of the hottest stars with Teff ~ 13000--15000 K. A new study of this element has been undertaken using observations from Lick Observatory's Hamilton Echelle Spectrograph. In this work, the spectrum synthesis program UCLSYN has been used to undertake abundance analysis assuming LTE. We find that in the Smith & Dworetsky sample of HgMn stars, Xe is vastly over-abundant in 21 of 22 HgMn stars studied, by factors of 3.1--4.8 dex. There does not appear to be a significant correlation of Xe abundance with Teff. A comparison sample of normal late B stars shows no sign of Xe II lines that could be detected, consistent with the expected weakness of lines at normal abundance. The main reason for the previous lack of widespread detection in HgMn stars is probably due to the strongest lines being at longer wavelengths than the photographic blue. The lines used in this work were 4603.03A, 4844.33A and 5292.22A.

M. M. Dworetsky; J. L. Persaud; K. Patel

2008-01-16

94

A NEW CEMP-s RR LYRAE STAR  

SciTech Connect

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

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

2012-08-10

95

Performance of MEMS-based visible-light adaptive optics at Lick Observatory: closed- and open-loop control  

NASA Astrophysics Data System (ADS)

At the University of California's Lick Observatory, we have implemented an on-sky testbed for next-generation adaptive optics (AO) technologies. The Visible-Light Laser Guidestar Experiments instrument (ViLLaGEs) includes visible-light AO, a micro-electro-mechanical-systems (MEMS) deformable mirror, and open-loop control of said MEMS on the 1-meter Nickel telescope at Mt. Hamilton. (Open-loop in this sense refers to the MEMS being separated optically from the wavefront sensing path; the MEMS is still included in the control loop.) Future upgrades include predictive control with wind estimation and pyramid wavefront sensing. Our unique optical layout allows the wavefronts along the open- and closed-loop paths to be measured simultaneously, facilitating comparison between the two control methods. In this paper we evaluate the performance of ViLLaGEs in openand closed-loop control, finding that both control methods give equivalent Strehl ratios of up to ~ 7% in I-band and similar rejection of temporal power. Therefore, we find that open-loop control of MEMS on-sky is as effective as closed-loop control. Furthermore, after operating the system for three years, we find MEMS technology to function well in the observatory environment. We construct an error budget for the system, accounting for 130 nm of wavefront error out of 190 nm error in the science-camera PSFs. We find that the dominant known term is internal static error, and that the known contributions to the error budget from open-loop control (MEMS model, position repeatability, hysteresis, and WFS linearity) are negligible.

Morzinski, Katie; Johnson, Luke C.; Gavel, Donald T.; Grigsby, Bryant; Dillon, Daren; Reinig, Marc; Macintosh, Bruce A.

2010-07-01

96

WEATHER, p. 2 Volume 133, Number 7 Tuesday, February 26, 2013  

E-print Network

, p. 4 NbA All-STAR WEEkEND From the "Shooting Stars" to the All-Star game sports, p. 12 THE p Tip said gunman was after Reif in retaliation for Swartz death, alerts to students delayed By Joanna L. Rafael Reif and school staff in retaliation for the death of Aaron Swartz. It is unclear how long

97

The Selective Serotonin Reuptake Inhibitor Paroxetine Decreases Breakpoint of Rats Engaging in a Progressive Ratio Licking Task for Sucrose and Quinine Solutions  

PubMed Central

Increased serotonergic activity has been shown to reduce motivation to ingest, which may involve, in part, gustatory processes. Here, we examined the effect of paroxetine, a selective serotonin reuptake inhibitor, on appetitive responding for a preferred and an avoided taste solution using a progressive ratio (PR) task in which licking was employed as the operant. Male Sprague-Dawley rats (n = 8/taste stimulus) were trained to respond for a concentration series of sucrose or quinine on fixed and PR schedules of reinforcement. Performance for sucrose was assessed while the rats were partially food- and water-restricted and nondeprived, and performance for water and quinine was assessed while the rats were water-deprived. Then, the rats were injected with vehicle (10% dimethyl sulfoxide, 1mL/kg intraperitoneal [ip], ?1h) or paroxetine (5mg/kg), and their responding on a PR schedule for sucrose measured when the rats were nondeprived or for water and quinine when the rats were water-deprived. Paroxetine decreased breakpoint, which was defined as the number of operant (e.g., dry) licks in the final reinforced ratio, for water, quinine, and sucrose. This demonstrates that a general systemic increase in serotonergic activity decreases the appetitive-based responses to both preferred and nonpreferred fluids under different deprivation states. PMID:23254343

2013-01-01

98

Identifying Very Metal-Rich Stars with Low-Resolution Spectra: Finding Planet-Search Targets  

E-print Network

We present empirical calibrations that estimate stellar metallicity, effective temperature and surface gravity as a function of Lick/IDS indices. These calibrations have been derived from a training set of 261 stars for which (1) high-precision measurements of [Fe/H], T_eff and log g have been made using spectral-synthesis analysis of HIRES spectra, and (2) Lick indices have also been measured. Our [Fe/H] calibration, which has precision 0.07 dex, has identified a number of bright (V < 9) metal-rich stars which are now being screened for hot Jupiter-type planets. Using the Yonsei-Yale stellar models, we show that the calibrations provide distance estimates accurate to 20% for nearby stars. This paper outlines the second tier of the screening of planet-search targets by the N2K Consortium, a project designed to identify the stars most likely to harbor extrasolar planets. Discoveries by the N2K Consortium include the transiting hot Saturn HD 149026 b (Sato et al. 2005, astro-ph/0507009) and HD 88133 b (Fischer et al. 2005). See Ammons et al. (2005, In Press) for a description of the first tier of N2K metallicity screening, calibrations using broadband photometry.

Sarah E. Robinson; Jay Strader; S. Mark Ammons; Gregory Laughlin; Debra Fischer

2005-10-05

99

The catalog of spectral and luminosity classes of 6037 stars in the direction of the Galaxy anticenter.  

NASA Astrophysics Data System (ADS)

The catalogue contains 558 objects with peculiarities in the spectrum Ap, Am, Ba II and composite spectrum stars, 86 emission stars, O, B, M and objects with H?-emission as well as 453 M and 36 C-stars. A limiting apparent magnitude in V for the stars in question is 12m 5 and for M 15m0. The stars in the catalogue are arranged in the order of increasing right ascension. They are numbered according to the zones corresponding to one degree declination. The catalogue is provided with suitable searching charts reproduced from the Lick Atlas. The reference system on the charts refers to the epoch of 1950 and is plotted according to the SAO catalogue.

Chargejshvili, K. B.

100

A Search for Binary Stars at Low Metallicity  

E-print Network

We present initial results measuring the companion fraction of metal-poor stars ([Fe/H]$<-$2.0). We are employing the Lick Observatory planet-finding system to make high-precision Doppler observations of these objects. The binary fraction of metal-poor stars provides important constraints on star formation in the early Galaxy (Carney et al. 2003). Although it has been shown that a majority of solar metallicity stars are in binaries, it is not clear if this is the case for metal-poor stars. Is there a metallicity floor below which binary systems do not form or become rare? To test this we are determining binary fractions at metallicities below [Fe/H]$=-2.0$. Our measurments are not as precise as the planet finders', but we are still finding errors of only 50 to 300 m/s, depending on the signal-to-noise of a spectrum and stellar atmosphere of the star. At this precision we can be much more complete than previous studies in our search for stellar companions.

David K. Lai; Sara Lucatello; Michael Bolte; Debra A. Fischer; Jennifer A. Johnson

2007-08-30

101

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

E-print Network

Precision radial velocities from the Automated Planet Finder and Keck/HIRES reveal an M*sin(i) =18 +/- 2 Earth mass planet orbiting the nearby M3V star GJ 687. This planet has an orbital period, P = 38.14 days, and a low orbital eccentricity. Our Stromgren 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 687b 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 687b indicates that the APF...

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

2014-01-01

102

Van Gogh's Starry Nights, Lincoln's Moon, Shakespeare's Stars, and More: Tales of Astronomy in Art, History, and Literature  

NASA Astrophysics Data System (ADS)

How do astronomical methods make it possible to calculate dates and times for Vincent van Gogh's night-sky paintings? Why is there a blood-red sky in Edvard Munch's The Scream? How can the 18.6-year cycle of the lunar nodes and the Moon's declination on the night of August 29-30, 1857, explain a long-standing mystery about Abraham Lincoln's honesty in the murder case known as the almanac trial? Why is a bright star described in Act 1, Scene 1, of Hamlet? There is a long tradition of astronomical methods employed to analyze works of art, to understand historical events, and to elucidate passages in literature. Both Edmond Halley and George Biddell Airy calculated lunar phases and tide tables in attempts to determine the landing beach where Julius Caesar invaded Britain in 55 B.C. Henry Norris Russell computed configurations of Jupiter and Saturn to determine a date for a 14th-century celestial event mentioned in Chaucer's Troilus and Criseyde. In this tradition, our Texas State group has published a series of articles in Sky & Telescope over the last two decades, applying astronomy to art, history, and literature. Don Osterbrock worked with us 3 years ago when my students and I calculated dates for moonrise photographs taken by Ansel Adams in Yosemite National Park. The peaks of the Sierra Nevada crest in Yosemite are more than 125 miles from Lick Observatory, but the mountains can become visible from Lick on clear winter days and were photographed from there on early infrared-sensitive plates during the 1920s and 1930s. As we tested our topographic software by identifying the peaks that appear in the Lick plates, it was a pleasure to come to know Don, a former director of Lick Observatory and the person in whose honor this talk is dedicated.

Olson, Donald W.

2009-01-01

103

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

104

The StarScan Plate Measuring Machine: Overview and Calibrations  

NASA Astrophysics Data System (ADS)

The StarScan machine at the U.S. Naval Observatory (USNO) completed measuring photographic astrograph plates to allow determination of proper motions for the USNO CCD Astrograph Catalog (UCAC) program. All applicable 1940 AGK2 plates, about 2200 Hamburg Zone Astrograph plates, 900 Black Birch (USNO Twin Astrograph) plates, and 300 Lick Astrograph plates have been measured. StarScan comprises a CCD camera, a telecentric lens, an air-bearing granite table, stepper motor screws, and Heidenhain scales to operate in a step-stare mode. The repeatability of StarScan measures is about 0.2 ?m. The CCD mapping as well as the global table coordinate system has been calibrated using a special dot calibration plate and the overall accuracy of StarScan y data is derived to be 0.5 ?m. Application to real photographic plate data shows that position information of at least 0.65 ?m accuracy can be extracted from coarse-grain 103a-type emulsion astrometric plates. Transformations between "direct" and "reverse" measures of fine-grain emulsion plate measures are obtained on the 0.3 ?m level per well-exposed stellar image and coordinate, a level that is at the limit of the StarScan machine.

Zacharias, N.; Winter, L.; Holdenried, E. R.; de Cuyper, J.-P.; Rafferty, T. J.; Wycoff, G. L.

2008-05-01

105

Integrated Spectroscopy of Bulge Globular Clusters and Fields I. The Data Base and Comparison of Individual Lick Indices in Clusters and Bulge  

E-print Network

We present a comprehensive spectroscopic study of the integrated light of metal-rich Galactic globular clusters and the stellar population in the Galactic bulge. We measure line indices which are defined by the Lick standard system and compare index strengths of the clusters and Galactic bulge. Both metal-rich globular clusters and the bulge are similar in most of the indices, except for the CN index. We find a significant enhancement in the CN/ index ratio in metal-rich globular clusters compared with the Galactic bulge. The mean iron index of the two metal-rich globular clusters NGC 6528 and NGC 6553 is comparable with the mean iron index of the bulge. Index ratios such as Mgb/, Mg2/, Ca4227/, and TiO/, are comparable in both stellar population indicating similar enhancements in individual elements which are traced by the indices. From the globular cluster data we fully empirically calibrate several metallicity-sensitive indices as a function of [Fe/H] and find tightest correlations for the Mg2 index and the composite [MgFe] index. We find that all indices show a similar behavior with galactocentric radius, except for the Balmer series, which show a large scatter at all radii. However, the scatter is entirely consistent with the cluster-to-cluster variations in the horizontal branch morphology.

Thomas H. Puzia; Roberto P. Saglia; Markus Kissler-Patig; Claudia Maraston; Laura Greggio; Alvio Renzini; Sergio Ortolani

2002-09-12

106

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

E-print Network

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

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

2014-01-01

107

THE LICK-CARNEGIE EXOPLANET SURVEY: A URANUS-MASS FOURTH PLANET FOR GJ 876 IN AN EXTRASOLAR LAPLACE CONFIGURATION  

SciTech Connect

Continued radial velocity (RV) monitoring of the nearby M4V red dwarf star GJ 876 with Keck/High Resolution Echelle Spectrograph has revealed the presence of a Uranus-mass fourth planetary companion in the system. The new planet has a mean period of P{sub e} = 126.6 days (over the 12.6-year baseline of the RV observations), and a minimum mass of m{sub e} sin i{sub e} = 12.9 {+-} 1.7 M {sub +}. The detection of the new planet has been enabled by significant improvements to our RV data set for GJ 876. The data have been augmented by 36 new high-precision measurements taken over the past five years. In addition, the precision of all of the Doppler measurements have been significantly improved by the incorporation of a high signal-to-noise template spectrum for GJ 876 into the analysis pipeline. Implementation of the new template spectrum improves the internal rms errors for the velocity measurements taken during 1998-2005 from 4.1 m s{sup -1} to 2.5 m s{sup -1}. Self-consistent, N-body fits to the RV data set show that the four-planet system has an invariable plane with an inclination relative to the plane of the sky of i = 59.{sup 0}5. The fit is not significantly improved by the introduction of a mutual inclination between the planets 'b' and 'c', but the new data do confirm a non-zero eccentricity, e{sub d} = 0.207 {+-} 0.055 for the innermost planet, 'd'. In our best-fit coplanar model, the mass of the new component is m{sub e} = 14.6 {+-} 1.7 M {sub +}. Our best-fitting model places the new planet in a three-body resonance with the previously known giant planets (which have mean periods of P{sub c} = 30.4 and P{sub b} = 61.1 days). The critical argument, {psi}{sub Laplace} = {lambda} {sub c} - 3{lambda} {sub b} + 2{lambda} {sub e}, for the Laplace resonance librates with an amplitude of {Delta}{psi}{sub Laplace} = 40{sup 0} {+-} 13{sup 0} about {psi}{sub Laplace} = 0{sup 0}. Numerical integration indicates that the four-planet system is stable for at least a billion years (at least for the coplanar cases). This resonant configuration of three giant planets orbiting an M dwarf primary differs from the well-known Laplace configuration of the three inner Galilean satellites of Jupiter, which are executing very small librations about {psi}{sub Laplace} = 180{sup 0} and which never experience triple conjunctions. The GJ 876 system, by contrast, comes close to a triple conjunction between the outer three planets once per every orbit of the outer planet, 'e'.

Rivera, Eugenio J.; Laughlin, Gregory; Vogt, Steven S.; Meschiari, Stefano [UCO/Lick Observatory, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Butler, R. Paul [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington DC, 20015-1305 (United States); Haghighipour, Nader, E-mail: rivera@ucolick.or [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Monoa, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

2010-08-10

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

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.

110

Sea Stars  

NSDL National Science Digital Library

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

2012-07-28

111

Scintillating Stars  

NSDL National Science Digital Library

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

Riddle, Bob

2003-02-01

112

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

113

Lucky Star  

NSDL National Science Digital Library

Watch this video from Cyberchase and then play the Lucky Star game! The Lucky Star game show the will ask you math-related questions and give you four possible answers to choose from. Your goal is to answer the questions correctly and score as many points as you can. You can score points during two different rounds: the pick-a-star round and the lightning round. During the pick-a-star round you have as much time as you want to answer the questions. During the lightning round you have to think fast in order to earn the points. Good luck!

2008-01-01

114

Finding Habitable Planets Around the Nearest Stars  

NASA Astrophysics Data System (ADS)

The discovery of the first 700 extrasolar planets have had a profound impact on science and society. The 2000 Decadal Survey of Astronomy & Astrophysics cites the discovery of extrasolar planets as the most important advance of the previous decade. The 2010 Decadal Survey cites extrasolar planets as one of the three pillars of modern astrophysics, and explicitly states that the discovery of potentially habitable planets around nearby stars is the highest priority for the next decade. Most of the planets that have been discovered orbiting nearby stars are massive gas giants found with Doppler velocity systems that have achieved 3 to 10 m/s. This first generation of exoplanets had amplitudes of 50 m/s or more, and could be detected with sparse sampling. Terrestrial mass and super-earth planets in habitable 1 AU orbits around G dwarfs have Doppler amplitudes of less than 0.5 m/s, and are currently undetectable. Due to their lower mass and brightness, the habitable liquid water zone around M dwarfs is at 0.1 to 0.2 AU, with corresponding Doppler velocity amplitudes of 2 to 5 m/s. These planets are typically in multiple planet systems in which several planets have similar amplitudes, leading to complex Doppler velocity signals. These planets can be detected with high cadence observations that achieve state-of-the-art precision of 1 m/s. While M dwarfs constitute 70% of the nearest stars, they are significantly fainter than nearby G & K dwarfs, and require large telescopes to reach 1 m/s precision. We have built the first American Doppler velocity system that produces 1 m/s precision. The Planet Finding Spectrometer (PFS) on Magellan has been custom built for precision velocity measurements. Compared to HIRES on Keck, PFS is mechanically and thermally stabilized, has triple the throughput, operates at higher resolution, and had 50% greater sampling. PFS on Magellan is slightly faster than HIRES on Keck in spite of the difference in aperture, 6.5-m vs 10-m. We are currently receiving ~50 nights per year on Magellan/PFS to target the nearest M dwarfs with high cadence observations. Over the next 3 years we will survey the nearest 200 M dwarfs with sufficient precision and cadence to detect terrestrial mass and super- earth planets in the habitable zone of these stars. After just two high cadence observing runs we already have candidates. Over the past quarter century our planet surveys, initially at Lick and later at Keck and the AAT, have had a broad societal and scientific impact, including the discovery of half of the known planets orbiting nearby stars. Our work has been credited with providing the motivation for the new disciplines of astrobiology and extrasolar planet studies. All the Iodine precision velocity systems in the world are based on our original system on the Lick 3-m (Butler et al. 1996). For us the PFS/Magellan system is the culmination of 25 years of work, leading to the detection of potentially habitable planets.

Butler, R.

115

Star Life  

NSDL National Science Digital Library

Visitors to this site can follow the life cycle of a star, beginning with its formation from matter exploded outward by the Big Bang, followed by its expansion into a red giant as nuclear "fuel" is consumed, and ending with its "death" in a supernova, after which it becomes a neutron star or black hole.

116

VizieR Online Data Catalog: 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.

2015-02-01

117

VizieR Online Data Catalog: 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.

2014-11-01

118

VizieR Online Data Catalog: 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

119

VizieR Online Data Catalog: 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

120

Exploding star  

NASA Astrophysics Data System (ADS)

Three astronomers report that the star Eta Carinae, 100 times more massive than the sun, is nearing its life expectancy and will explode sometime in the next 10,000 years. Until now, astronomers have been unable to discern whether the star was in the process of being born, was a middle-aged star with an unusual outflow of material, or an aged star about to explode.The huge star is coming to the end of what is considered a normal lifetime—about 2 million years—for a star of its size, according to Kris Davidson at the University of Minnesota, Nolan R. Walborn (presently at the Goddard Space Flight Center) of Cerro Tololo Inter-American Observatory, and Theodore R. Gull at Goddard. When Eta Carinae explodes, the astronomers report, it could emit more light than all the hundreds of billions of other stars in the galaxy for weeks. The expected explosion, or supernova, could produce a bright point of light that would be visible in broad daylight, they add.

121

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

122

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

123

Classifying stars  

NSDL National Science Digital Library

You will be able to describe the H-R diagram and explain how astronomers use it. The most important characteristics for classifying stars are: a) Color b) Temperature c) Size d) Composition e) Brightness The classification scheme that we currently use is the H-R diagram which is in the Earth Science Reference Tables (ESRT). The H-R diagram groups stars by surface temperature compared to their luminosity. 1)Today you will be reading a short tutorial ...

B, Mr.

2007-11-10

124

Tycho's Star  

NASA Astrophysics Data System (ADS)

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

Murdin, P.

2000-11-01

125

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. PMID:23313404

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

2013-01-01

126

STARS no star on Kauai  

SciTech Connect

The island of Kuai, home to the Pacific Missile Range Facility, is preparing for the first of a series of Star Wars rocket launches expected to begin early this year. The Strategic Defense Initiative plans 40 launches of the Stategic Target System (STARS) over a 10-year period. The focus of the tests appears to be weapons and sensors designed to combat multiple-warhead ICBMs, which will be banned under the START II Treaty that was signed in January. The focus of this article is to express the dubious value of testing the STARS at a time when their application will not be an anticipated problem.

Jones, M.

1993-04-01

127

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

Code of Federal Regulations, 2013 CFR

...States Army Parachute 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...

2013-01-01

128

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

Code of Federal Regulations, 2011 CFR

...States Army Parachute 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...

2011-01-01

129

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

Code of Federal Regulations, 2010 CFR

...States Army Parachute 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...

2010-01-01

130

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

Code of Federal Regulations, 2012 CFR

...States Army Parachute 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...

2012-01-01

131

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

Code of Federal Regulations, 2014 CFR

...States Army Parachute 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...

2014-01-01

132

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

133

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

134

Investigating the star formation histories of the brightest cluster galaxies  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

135

VizieR Online Data Catalog: 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

136

Energy Star  

E-print Network

ENERGY STAR ENERGY TARGETS ESL-KT-12-10-08 CATEE 2012: Clean Air Through Energy Efficiency Conference, Galveston, TX, October 9-11, 2012 POP QUIZ!!!! What is EUI?? Energy Use Intensity Do you know the EUI and any of the buildings you designed... Efficiency Conference, Galveston, TX, October 9-11, 2012 The CFLs in an ENERGY STAR qualified light fixture only need to be changed once every 8 years on average, compared with an annual ladder-climb for incandescent light bulbs. 6 CONSIDERING TIME...

Reihl, K.; Tullos, A.

2012-01-01

137

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

E-print Network

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

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

2007-11-28

138

Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity  

NASA Astrophysics Data System (ADS)

Context. We have obtained precise radial velocities for a sample of 373 G and K type giants at Lick Observatory regularly over more than 12 years. Planets have been identified around 15 of these giant stars, and an additional 20 giant stars host planet candidates. Aims: We are interested in the occurrence rate of substellar companions around giant stars as a function of stellar mass and metallicity. We probe the stellar mass range from approximately 1 to beyond 3 M?, which is not being explored by main-sequence samples. Methods: We fit the giant planet occurrence rate as a function of stellar mass and metallicity with a Gaussian and an exponential distribution, respectively. Results: We find strong evidence for a planet-metallicity correlation among the secure planet hosts of our giant star sample, in agreement with the one for main-sequence stars. However, the planet-metallicity correlation is absent for our sample of planet candidates, raising the suspicion that a good fraction of them might indeed not be planets despite clear periodicities in the radial velocities. Consistent with the literature results for subgiants, the giant planet occurrence rate increases in the stellar mass interval from 1 to 1.9 M?. However, there is a maximum at a stellar mass of 1.9+ 0.1-0.5 M?, and the occurrence rate drops rapidly for masses larger than 2.5-3.0 M?. We do not find any planets around stars more massive than 2.7 M?, although there are 113 stars with masses between 2.7 and 5 M? in our sample (corresponding to a giant planet occurrence rate smaller than 1.6% at 68.3% confidence in that stellar mass bin). We also show that this result is not a selection effect related to the planet detectability being a function of the stellar mass. Conclusions: We conclude that giant planet formation or inward migration is suppressed around higher mass stars, possibly because of faster disk depletion coupled with a longer migration timescale. Based on observations collected at Lick Observatory, University of California.Table 3 is 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/574/A116

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

2015-02-01

139

Star Power  

ScienceCinema

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

None

2014-11-18

140

Star Power  

NSDL National Science Digital Library

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

Twin Cities Public Television

2010-01-01

141

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. ...

142

Star Power  

SciTech Connect

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

None

2014-10-17

143

STAR Highlights  

E-print Network

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

Hiroshi Masui; for the STAR Collaboration

2011-06-29

144

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.

145

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

146

Star formation and the ages of stars  

NASA Astrophysics Data System (ADS)

In this contribution we illustrate how the knowledge of the ages of stars is important to constrain star formation processes. We focus on two specific cases: star formation around the supermassive black hole at the center of the Galaxy and triggered star formation on the borders of Hii regions.

Martins, F.

2014-11-01

147

Stars : the end of a star  

NSDL National Science Digital Library

What happens during the death of a star? This activity page, part of an interactive laboratory series for grades 8-12, introduces students to the final processes of stars. Here students read about low-mass, medium-mass, and massive stars. Low-mass stars produce white dwarfs. A pop-up window describes how white dwarfs form. Medium-mass stars produce neutron stars and supernova. Pop-up information explains the supernova process. Massive stars undergo carbon burning. An interactive lab activity presents students the opportunity to predict temperature, pressure, and gravity changes that occur during carbon fusion. In a final lab activity, students compare initial star size with the type of death that occurs. Activity questions about star death are provided for each star size and are recordable and printable. Copyright 2005 Eisenhower National Clearinghouse

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

2003-01-01

148

Triggered Star Formation by Massive Stars  

NASA Astrophysics Data System (ADS)

We present our diagnosis of the role that massive stars play in the formation of low- and intermediate-mass stars in OB associations (the ? Ori region, Ori OB1, and Lac OB1 associations). We find that the classical T Tauri stars and Herbig Ae/Be stars tend to line up between luminous O stars and bright-rimmed or comet-shaped clouds; the closer to a cloud the progressively younger they are. Our positional and chronological study lends support to the validity of the radiation-driven implosion mechanism, where the Lyman continuum photons from a luminous O star create expanding ionization fronts to evaporate and compress nearby clouds into bright-rimmed or comet-shaped clouds. Implosive pressure then causes dense clumps to collapse, prompting the formation of low-mass stars on the cloud surface (i.e., the bright rim) and intermediate-mass stars somewhat deeper in the cloud. These stars are a signpost of current star formation; no young stars are seen leading the ionization fronts further into the cloud. Young stars in bright-rimmed or comet-shaped clouds are likely to have been formed by triggering, which would result in an age spread of several megayears between the member stars or star groups formed in the sequence.

Lee, Hsu-Tai; Chen, W. P.

2007-03-01

149

Triggered Star Formation by Massive Stars  

E-print Network

We present our diagnosis of the role that massive stars play in the formation of low- and intermediate-mass stars in OB associations (the Lambda Ori region, Ori OB1, and Lac OB1 associations). We find that the classical T Tauri stars and Herbig Ae/Be stars tend to line up between luminous O stars and bright-rimmed or comet-shaped clouds; the closer to a cloud the progressively younger they are. Our positional and chronological study lends support to the validity of the radiation-driven implosion mechanism, where the Lyman continuum photons from a luminous O star create expanding ionization fronts to evaporate and compress nearby clouds into bright-rimmed or comet-shaped clouds. Implosive pressure then causes dense clumps to collapse, prompting the formation of low-mass stars on the cloud surface (i.e., the bright rim) and intermediate-mass stars somewhat deeper in the cloud. These stars are a signpost of current star formation; no young stars are seen leading the ionization fronts further into the cloud. Young stars in bright-rimmed or comet-shaped clouds are likely to have been formed by triggering, which would result in an age spread of several megayears between the member stars or star groups formed in the sequence.

Hsu-Tai Lee; W. P. Chen

2009-02-03

150

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

E-print Network

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

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

2007-01-01

151

Binary stars.  

PubMed

Most stars in the solar neighborhood are either double or multiple systems. They provide a unique opportunity to measure stellar masses and radii and to study many interesting and important phenomena. The best candidates for black holes are compact massive components of two x-ray binaries: Cygnus X-1 and LMC X-3. The binary radio pulsar PSR 1913 + 16 provides the best available evidence for gravitational radiation. Accretion disks and jets observed in close binaries offer a very good testing ground for models of active galactic nuclei and quasars. PMID:17749544

Paczynacuteski, B

1984-07-20

152

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

153

Carlsberg Meridian Catalogue, La Palma. Number 9. Observations of positions of stars and planets, May 1984 to March 1995 including extinction and meteorological data.  

NASA Astrophysics Data System (ADS)

This catalogue (CMC9) contains 141593 positions and magnitudes of 138603 stars north of declination -40°, 117559 proper motions, and 19585 positions and magnitudes of 97 Solar System objects obtained with the Carlsberg Automatic Meridian Circle on La Palma during the period May 1984 to March 1995. CMC9 includes CMC1 to CMC8; i.e. it comprises all the observations made since the instrument began operation on La Palma. The positions of the stars are for the epoch of observation and the equinox J2000.0, and are referred to the new International Celestial Reference Frame. The original version of the catalogue with positions referred to a smoothed version of the FK5 is also given. The limiting magnitude is V = 15.4. The catalogue mainly comprises observations and proper motions for the following programmes: 36000 International Reference Stars, 30000 faint reference stars in a global net, 18000 reference stars in the fields of radio sources, 17000 stars in the Lick Northern Proper Motion catalogue, 5000 reference stars for calibration of Schmidt plates, 2600 stars in the Gliese catalogue of nearby stars, 5000 stars in nearby OB associations, 10500 F-type stars within 100 pc, 9000 G-type d&g, K-type g stars within 300 pc, 2200 unbiased sample of K/M-type d stars, 2200 reference stars near Veron-Cetty galaxies, 1050 variable stars (12 - 14 mag) in GCVS, 800 stars (11 - 14 mag) with pm > 0?-3/yr ion NLTT, and several smaller programmes mainly aimed at galactic kinematics. Positions and magnitudes of 8 novae and 7 supernovae which occurred in the years 1991 to 1995 are included. The catalogue also contains observations of the following Solar System objects: Callisto, Ganymede, Rhea, Titan, Iapetus, Hyperion, Uranus, Oberon, Neptune, Pluto and 87 minor planets. The mean error of a catalogue position in the zenith is 0?-09 in right ascension and declination in CMC4-5-6, improving to 0?-06 in CMC7-9. The accuracy in magnitude is 0.05 mag throughout. The mean error of the proper motions, derived by combining the position in this catalogue with those at earlier epochs, is typically in the range 0?-003 to 0?-004 per year. Cross-references are given to DM, AGK, SAO, HD and the double star catalogues ADS and WDS. The catalogue also contains 12216 mean annual observed positions of the FK5 stars used to transfer the instrumental system to the FK5 frame. A compilation of all the meteorological data collected in the years 1984 - 1995 is appended.

154

Carlsberg Meridian Catalogues, La Palma. Numbers 1 - 11, 1999. Observations of positions of stars and planets, May 1984 to May 1998 including extinction and meteorological data.  

NASA Astrophysics Data System (ADS)

This composite catalogue contains 180812 positions and magnitudes of 176591 stars north of declination -40°, 155005 proper motions, and 25848 positions and magnitudes of 184 Solar System objects obtained with the Carlsberg Automatic Meridian Circle on La Palma during the period May 1984 to May 1998. It includes CMC1 - 11; i.e. it comprises all the observations made with the moving-slit micrometer since the instrument began operation on La Palma. The positions of the stars are for the epoch of observation and the equinox J2000.0, and are referred to the new International Celestial Reference Frame. The limiting magnitude is V = 15.4. The catalogue mainly comprises observations and proper motions for the following programmes: 36000 International Reference Stars, 30000 faint reference stars in a global net, 18000 reference stars in the fields of radio sources, 17000 stars in the Lick Northern Proper Motion catalogue, 5000 reference stars for calibration of Schmidt plates, 2600 stars in the Gliese catalogue of nearby stars, 5000 stars in nearby OB associations, 10500 F-type stars within 100 pc, 9000 G-type d&g, K-type g stars within 300 pc, 2200 unbiased sample of K/M-typed stars, 19400 reference stars near Veron-Cetty galaxies, 4700 variable stars (12 - 14 mag) in GCVS, 12400 stars (11 - 14 mag) with pm > 0?-18/yr in NLTT, and several smaller programmes mainly aimed at galactic kinematics. Positions and magnitudes of 12 novae and 8 supernovae which occurred in the years 1991 to 1998 are included. The catalogue also contains observations of the following Solar System objects: Callisto, Ganymede, Rhea, Titan, Iapetus, Hyperion, Uranus, Oberon, Neptune, Pluto and 173 minor planets and comet P/Wild 2. The mean error of a catalogue position in the zenith is 0-09 in right ascension and declination in CMC1 - 6, improving to 0-06 in CMC7 - 11. The accuracy in magnitude is 0.05 mag in CMC1 - 10, improving to 0.03 mag in CMC11. The mean error of the proper motions, derived by combining the position in this catalogue with those at earlier epochs, is typically in the range 0??003 to 0??004 per year. Cross-references are given to DM, AGK, SAO, HD and the Washington Double Star catalogues. The catalogue also contains 12216 mean annual observed positions of the FK5 stars used to transfer the instrumental system to the FK5 frame in the years 1984 - 1995. A compilation of all the meteorological data collected in the years 1984 - 1998, including the atmospheric extinction, is appended.

155

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

156

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

157

Massive Stars in Transition  

E-print Network

We discuss the various post-main sequence phases of massive stars, focusing on Wolf-Rayet stars, Luminous Blue Variables, plus connections with other early-type and late-type supergiants. End states for massive stars are also investigated, emphasising connections between Supernovae originating from core-collapse massive stars and Gamma Ray Bursts.

Paul A. Crowther

2003-05-08

158

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.

159

Counting Your Lucky Stars  

NSDL National Science Digital Library

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

Ricles, Shannon; Hatok, Tim; Taylor, Berlina

2013-01-30

160

Star Clusters Sterrenstelsels & Kosmos  

E-print Network

Star Clusters Sterrenstelsels & Kosmos deel 2 1 #12;Types of star clusters 2 #12;Open or Galactic Clusters · "Open" or Galactic clusters are low mass, relatively small (~10 pc diameter) clusters of stars in the Galactic disk containing stars · The Pleiades cluster is a good example of an open cluster

Weijgaert, Rien van de

161

Egyptian "Star Clocks"  

NASA Astrophysics Data System (ADS)

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

Symons, Sarah

162

Neutron Stars and NuSTAR  

NASA Astrophysics Data System (ADS)

My thesis centers around the study of neutron stars, especially those in massive binary systems. To this end, it has two distinct components: the observational study of neutron stars in massive binaries with a goal of measuring neutron star masses and participation in NuSTAR, the first imaging hard X-ray mission, one that is extremely well suited to the study of massive binaries and compact objects in our Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing high energy X-ray telescope to orbit. NuSTAR has an order-of-magnitude better angular resolution and has two orders of magnitude higher sensitivity than any currently orbiting hard X-ray telescope. I worked to develop, calibrate, and test CdZnTe detectors for NuSTAR. I describe the CdZnTe detectors in comprehensive detail here - from readout procedures to data analysis. Detailed calibration of detectors is necessary for analyzing astrophysical source data obtained by the NuSTAR. I discuss the design and implementation of an automated setup for calibrating flight detectors, followed by calibration procedures and results. Neutron stars are an excellent probe of fundamental physics. The maximum mass of a neutron star can put stringent constraints on the equation of state of matter at extreme pressures and densities. From an astrophysical perspective, there are several open questions in our understanding of neutron stars. What are the birth masses of neutron stars? How do they change in binary evolution? Are there multiple mechanisms for the formation of neutron stars? Measuring masses of neutron stars helps answer these questions. Neutron stars in high-mass X-ray binaries have masses close to their birth mass, providing an opportunity to disentangle the role of "nature" and "nurture" in the observed mass distributions. In 2006, masses had been measured for only six such objects, but this small sample showed the greatest diversity in masses among all classes of neutron star binaries. Intrigued by this diversity - which points to diverse birth masses - we undertook a systematic survey to measure the masses of neutron stars in nine high-mass X-ray binaries. In this thesis, I present results from this ongoing project. While neutron stars formed the primary focus of my work, I also explored other topics in compact objects. Appendix A describes the discovery and complete characterization of a 1RXS J173006.4+033813, a polar cataclysmic variable. Appendix B describes the discovery of a diamond planet orbiting a millisecond pulsar, and our search for its optical counterpart.

Bhalerao, Varun

2012-05-01

163

Stellar population and the origin of intra-cluster stars around brightest cluster galaxies: the case of NGC 3311  

NASA Astrophysics Data System (ADS)

Context. We investigate the stellar population and the origin of diffuse light around brightest cluster galaxies. Aims: We study the stellar population of the dynamically hot stellar halo of NGC 3311, the brightest galaxy in the Hydra I cluster, and that of photometric substructures in the diffuse light to constrain the origin of these components. Methods: We analyze absorption lines in medium-resolution, long-slit spectra in the wavelength range 4800-5800 Å obtained with FORS2 at the Very Large Telescope. We measure the equivalent width of Lick indices out to 20 kpc from the center of NGC 3311 and fit them with stellar population models that account for the [?/Fe] overabundance. Results: Stars in the dynamically hot halo of NGC 3311 are old (age >13 Gyr), metal-poor ([Z/H] ~ -0.35), and alpha-enhanced ([?/Fe] ~ 0.48). Together with the high velocity dispersion, these measurements indicate that the stars in the halo were accreted from the outskirts of other early-type galaxies, with a possible contribution from dwarf galaxies. We identify a region in the halo of NGC 3311 associated with a photometric substructure where the stellar population is even more metal-poor ([Z/H] ~ -0.73). In this region, our measurements are consistent with a composite stellar population superposed along the line of sight, consisting of stars from the dynamically hot halo of NGC 3311 and stars stripped from dwarf galaxies. The latter component contributes ?28% to the local surface brightness. Conclusions: The build-up of diffuse light around NGC 3311 is on-going. Based on the observed stellar population properties, the dominant part of these stars may have come from the outskirts of bright early-type galaxies, while stars from stripped dwarf galaxies are presently being added. Based on observations collected at the European Southern Observatory for the program 082.A-0255(A).

Coccato, L.; Gerhard, O.; Arnaboldi, M.; Ventimiglia, G.

2011-09-01

164

ASPECTOS HISTOLÓGICOS DA PELE DA REGIÃO ANOGENITAL DE GATOS DOMÉSTICOS À LUZ DO COMPORTAMENTO DE LAMBEDURA ANOGENITAL DO NEONATO EXIBIDO PELA MÃE Histological characterization of domestic cat anogenital region in the light of neonatal anogenital licking behavior exhibited by mother Aspectos histológicos de la piel de la región ano genital de gatos domésticos a la luz del comportamiento de lamedura ano genital del neonato demostrado por la madre  

Microsoft Academic Search

Domestic cat neonates, as well as the ones of the vison and ferret, do not eliminated voluntarily (Defecation and urination), being the behavior of elimination controlled during the first weeks after the birth by the anogenital reflex. In the absence of anogenital licking, the neonate dependents of this behavior die due the complications associates with no defecation and urination. Based

Carlos Gabriel Almeida; Ticiana SILVA; Franco Pereira; Marcos Renato Franzosi

165

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

166

Astronomy: A Star Party  

NSDL National Science Digital Library

This lesson is designed to teach students about the functions of a telescope, the daylight uses of a telescope, the parts of the telescope, and to identify and view certain stars and planets during a star party at night.

167

Astrophysics: Stars fight back  

NASA Astrophysics Data System (ADS)

Galaxies contain fewer stars than predicted. The discovery of a massive galactic outflow of molecular gas in a compact galaxy, which forms stars 100 times faster than the Milky Way, may help to explain why. See Letter p.68

Hopkins, Philip F.

2014-12-01

168

Stars in Nutrition & Cancer  

Cancer.gov

Stars in Nutrition & Cancer Soy and Cancer: Wish You Were Young Again Star Speaker Stephen Barnes, PhD Professor, Department of Pharmacology and Toxicology University of Alabama Birmingham Birmingham, Alabama Meeting Date Monday, October 04, 2010

169

Dublin, 11.09.2011 Star FormationStar FormationStar FormationStar Formation  

E-print Network

Dublin, 11.09.2011 Star FormationStar FormationStar FormationStar Formation An observational viewJ. Rowles, G. IoannidisJ. Rowles, G. Ioannidis #12;Dublin, 11.09.2011 Layout of the talkLayout of the talk on UWISH2 data #12;Dublin, 11.09.2011 GMCsGMCsGMCsGMCs Gravity and Turbulence dominate (maybe B

Froebrich, Dirk

170

Dibaryons in neutron stars  

NASA Technical Reports Server (NTRS)

The effects are studied of H-dibaryons on the structure of neutron stars. It was found that H particles could be present in neutron stars for a wide range of dibaryon masses. The appearance of dibaryons softens the equations of state, lowers the maximum neutron star mass, and affects the transport properties of dense matter. The parameter space is constrained for dibaryons by requiring that a 1.44 solar mass neutron star be gravitationally stable.

Olinto, Angela V.; Haensel, Pawel; Frieman, Joshua A.

1991-01-01

171

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.

172

Van Maanen's Star  

NASA Astrophysics Data System (ADS)

This star in the constellation of Pisces, although faint, is of much importance as it is the nearest readily observable white dwarf—a class of star of considerable significance in studies of stellar evolution. The white dwarfs Sirius B and Procyon B are both closer, but their proximity to their much brighter companions makes them very difficult to study as individual stars....

Murdin, P.

2000-11-01

173

White Dwarf Stars  

Microsoft Academic Search

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

Steven Kawaler; Michael Dahlstrom

2000-01-01

174

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.

2009-12-08

175

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.

Astronomical Society of the Pacific

2008-01-01

176

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

177

Star formation Simon Goodwin  

E-print Network

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

Crowther, Paul

178

Analyzing Star Trails  

NSDL National Science Digital Library

In this activity, students examine a photograph of the night sky and answer questions about their observations. The picture, taken by a high school student in upstate New York, offers insight into the Earth's rotation, apparent star motion, the location of Polaris (the North Star), circumpolar constellations, and pointer stars.

Steve Kluge

179

Moores School of Music University of Houston 120 School of Music Bldg. Houston, TX 77204-4017 Phone: (713) 743-3009 Fax: (713) 743-3166 www.uh.edu/music  

E-print Network

, The Forest Battle from Star Wars Pryor: Phenomenal Polka Sousa: The Aviators Free Admission Friday, October, Eddie Lewis & Living Rhythms, and the Houston Professional Musician's Union All-Star Big Band featuring Tonight Show trumpet star Bobby Shew. Also, Mr. Fulgham will be directing The Maria Williams Big Band

Azevedo, Ricardo

180

Massive stars and star clusters in the Antennae galaxies  

E-print Network

Large numbers of young stars are formed in merging galaxies, such as the Antennae galaxies. Most of these stars are formed in compact star clusters (i.e., super star clusters), which have been the focus of a large number of studies. However, an increasing number of projects are beginning to focus on the individual stars as well. In this contribution, we examine a few results relevant to the triggering of star and star cluster formation; ask what fraction of stars form in the field rather than in clusters; and begin to explore the demographics of both the massive stars and star clusters in the Antennae. 1.

C. Whitmore

2006-01-01

181

Massive stars and star clusters in the Antennae galaxies  

E-print Network

Large numbers of young stars are formed in merging galaxies, such as the Antennae galaxies. Most of these stars are formed in compact star clusters (i.e., super star clusters), which have been the focus of a large number of studies. However, an increasing number of projects are beginning to focus on the individual stars as well. In this contribution, we examine a few results relevant to the triggering of star and star cluster formation; ask what fraction of stars form in the field rather than in clusters; and begin to explore the demographics of both the massive stars and star clusters in the Antennae.

Bradley C. Whitmore

2006-12-22

182

Stars and Constellations  

NSDL National Science Digital Library

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

Kaler, James, B.

183

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.

Dave Bock

1999-01-21

184

Magnetic chemically peculiar stars  

E-print Network

Chemically peculiar (CP) stars are main-sequence A and B stars with abnormally strong or weak lines for certain elements. They generally have magnetic fields and all observables tend to vary with the same period. Chemically peculiar stars provide a wealth of information; they are natural atomic and magnetic laboratories. After a brief historical overview, we discuss the general properties of the magnetic fields in CP stars, describe the oblique rotator model, explain the dependence of the magnetic field strength on the rotation, and concentrate at the end on HgMn stars.

Schöller, Markus

2015-01-01

185

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

186

Stars main sequence  

NSDL National Science Digital Library

What happens during most of a star's life? This activity page, part of an interactive laboratory series for grades 8-12, introduces students to the main sequence phase of a star's existence. This phase is where a star lives out the majority of its life. In an interactive lab activity, students predict the length of the main sequence for four different stars. The predictions can be printed for later evaluation. Students view diagrams that compare the size and color of stars to human lives, and equilibrium within a star is stressed. Finally, students choose between two hypotheses about the length of life of a star. Students write a one- to three-sentence explanation for their hypotheses. The correct answer is provided. Copyright 2005 Eisenhower National Clearinghouse

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

2003-01-01

187

Disks around HAEBE stars  

NASA Astrophysics Data System (ADS)

Do Herbig Ae/Be stars have accretion disks like T Tauri stars? We report the detection of 850 micron continuum emission toward 21 of 33 HAEBE stars in a JCMT mapping and archival survey; more than half the sample was observed at 450 micron as well. Of the detected sources, eight show extended, disk-like dust emission centered on the star. The others are unresolved in our beam, suggesting that the dust envelopes or disks around these stars are less than a few arcsec, similar to the sizes of envelopes and disks seen toward most T Tauri stars. Several of the detected but unresolved stars (e.g., MWC 297, Elias 1, HD 142666) have very flat SEDs in the submillimeter, suggesting the presence of dust with unusual properties or disks with large dust grains or planetesimals. These disks may be on the verge of forming planetary systems. Many HAEBE stars lie in regions of extended dust emission; quite often, however, our maps show that the strongest submillimeter emission originates from younger, optically invisible, heavily embedded sources rather than from the HAEBE stars. Mapping therefore is essential in order to determine whether the submillimeter or far-infrared emission detected in large beam measurements is from a HAEBE star, nearby protostars or merely from the dust cloud in which the star is embedded. In addition to already known cases like R CrA, LkHa 198, and BD+40 4124, where the submillimeter emission is dominated by emission from heavily embedded Class I or Class 0 sources, we find several other regions where the same is true or where the dust emission comes the surrounding PDR/molecular cloud interface, but not from the star itself. Only one star, the extremely distant MWC 300, showed no emission at all in the SCUBA field of view. Guest User, Canadian Astronomy Data Center, which is operated by the Dominion Astrophysical Observatory for the National Research Council of Canada's Herzberg Institute of Astrophysics.

Sandell, G.; Weintraub, D. A.

2002-05-01

188

Activity in F stars  

NASA Technical Reports Server (NTRS)

Measurements of He I 5876 A and IUE measurements of chromospheric and transition region lines in a large sample of F-type stars are presented. The data show that activity is detectable in nearly all early F-type stars and differs in several of its characteristics from that typically seen in cooler stars with slow rotation and fully developed convective zones. The onset of activity occurs near B-V = 0.28, which corresponds approximately to spectral type F0 and T(eff) = 7300 K. There is no correlation between the level of activity and the abundances of lithium and beryllium in F stars hotter than T(eff) = 6600 K. All but one of the stars in the 6600-7300 K temperature interval are active. The levels of activity in these stars are independent of Rossby number.

Wolff, Sidney C.; Boesgaard, Ann Merchant; Simon, Theodore

1986-01-01

189

The First Stars  

NASA Astrophysics Data System (ADS)

The standard cosmological model predicts that the first cosmological objects are formed when the age of the universe is a few hundred million years. Recent theoretical studies and numerical simulations consistently suggest that the first objects are very massive primordial stars. We introduce the key physics and explain why the first stars are thought to be massive, rather than to be low-mass stars. The state-of-the-art simulations include all the relevant atomic and molecular physics to follow the thermal evolution of a prestellar gas cloud to very high ``stellar'' densities. Evolutionary calculations of the primordial stars suggest the formation of massive blackholes in the early universe. Finally, we show the results from high-resolution simulations of star formation in a low-metallicity gas. Vigorous fragmentation is triggered in a star-forming gas cloud at a metallicity of as low as Z = 10-5Zsolar.

Yoshida, Naoki

2010-10-01

190

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

NASA Astrophysics Data System (ADS)

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

Wolfgang, Angie

2015-01-01

191

The Solar Neighborhood. XXVI. AP Col: The Closest (8.4 pc) Pre-Main-Sequence Star  

E-print Network

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 0.9m, from which we derive a proper motion of 342.0+/-0.5 mas yr^-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^-1), lithium Equivalent Width (EW) (0.28+/-0.02 A), H-alpha EW (-6.0 to -35 A), {\\it vsini} (11+/-1 km s^-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 ~40 Myr old Argus/IC 2391 association.

Riedel, Adric R; Henry, Todd J; Melis, Carl; Jao, Wei-Chun; Subasavage, John P; 10.1088/0004-6256/142/4/104

2011-01-01

192

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

193

Strange Nonchaotic Stars  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

194

Star Trek Generations  

NSDL National Science Digital Library

Paramount Pictures and Viacom Online have developed a World Wide Web site to herald the upcoming motion picture Star Trek Generations. The site offers a galaxy of unique Star Trek elements for downloading, including pictures, sounds and a preview of the movie, in addition to behind-the-scenes information. Make sure to give Paramount "Your Input"- all respondents will receive a digital version of the Star Trek Generations movie poster

195

The Lick Observatory image-dissector scanner.  

NASA Technical Reports Server (NTRS)

A scanner that uses an image dissector to scan the output screen of an image tube has proven to be a sensitive and linear detector for faint astronomical spectra. The image-tube phosphor screen acts as a short-term storage element and allows the system to approach the performance of an ideal multichannel photon counter. Pulses resulting from individual photons, emitted from the output phosphor and detected by the image dissector, trigger an amplifier-discriminator and are counted in a 24-bit, 4096-word circulating memory. Aspects of system performance are discussed, giving attention to linearity, dynamic range, sensitivity, stability, and scattered light properties.

Robinson, L. B.; Wampler, E. J.

1972-01-01

196

Cooling of dense stars  

NASA Technical Reports Server (NTRS)

Some recent work on thermal properties of dense stars is described. It is now generally believed that pulsars are rotating, magnetic neutron stars (Gold, 1968). Moreover, theoretical considerations and some observational evidence (such as the speed-ups of the Crab and Vela pulsars) suggest the presence of superfluids in neutron stars. In the earlier cooling calculations the effect of magnetic fields and superfluidity was not taken into account. In the recent work, emphasis was placed on the effect of these new factors, which were expected to reduce cooling rates significantly. The new outcome may prove valuable for the understanding of pulsar and X-ray star problems.

Tsuruta, S.

1974-01-01

197

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

198

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

199

Superfluidity in neutron stars  

NASA Astrophysics Data System (ADS)

Astrophysical evidence is reviewed for the existence of at least three distinct superfluids inside neutron stars from the observed relaxation of the rotation and spin-down rates of the pulsars Vela, Crab, and PSR0525 + 21, following sudden jumps or glitches in these quantities. Theoretical aspects of neutron and proton superfluids in neutron stars and core neutron communication, glitches and post-glitch relaxation, neutron star coupling, and vortex creep theory are discussed. The effects of the superfluid interior in the accreting neutron star X-ray sources are also considered.

Pines, D.; Alpar, M. A.

1985-07-01

200

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.

201

Star-ND (Multi-Dimensional Star-Identification)  

E-print Network

In order to perform star-identification with lower processing requirements, multi-dimensional techniques are implemented in this research as a database search as well as to create star pattern parameters. New star pattern parameters are presented...

Spratling, Benjamin

2012-07-16

202

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. PMID:23112943

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

2012-01-01

203

Extreme horizontal branch stars  

NASA Astrophysics Data System (ADS)

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

Heber, U.

204

GLOBAL STAR FORMATION REVISITED  

SciTech Connect

A general treatment of disk star formation is developed from a dissipative multiphase model, with the dominant dissipation due to cloud collisions. The Schmidt-Kennicutt (SK) law emerges naturally for star-forming disks and starbursts. We predict that there should be an inverse correlation between Tully-Fisher law and SK law residuals. The model is extended to include a multiphase treatment of supernova feedback that leads to a turbulent pressure-regulated generalization of the star formation law and is applicable to gas-rich starbursts. Enhanced pressure, as expected in merger-induced star formation, enhances star formation efficiency. An upper limit is derived for the disk star formation rate in starbursts that depends on the ratio of global ISM to cloud pressures. We extend these considerations to the case where the interstellar gas pressure in the inner galaxy is dominated by outflows from a central active galactic nucleus (AGN). During massive spheroid formation, AGN-driven winds trigger star formation, resulting in enhanced supernova feedback and outflows. The outflows are comparable to the AGN-boosted star formation rate and saturate in the super-Eddington limit. Downsizing of both SMBH and spheroids is a consequence of AGN-driven positive feedback. Bondi accretion feeds the central black hole with a specific accretion rate that is proportional to the black hole mass. AGN-enhanced star formation is mediated by turbulent pressure and relates spheroid star formation rate to black hole accretion rate. The relation between black hole mass and spheroid velocity dispersion has a coefficient (Salpeter time to gas consumption time ratio) that provides an arrow of time. Highly efficient, AGN-boosted star formation can occur at high redshift.

Silk, Joseph [Physics Department, University of Oxford, 1 Keble Road, Oxford OX1 3RH (United Kingdom); Norman, Colin [Physics Department, Johns Hopkins University, 2400 North Charles Street, Baltimore, MD 21218 (United States)], E-mail: silk@astro.ox.ac.uk, E-mail: norman@stsci.edu

2009-07-20

205

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

206

White dwarf stars  

Microsoft Academic Search

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

J. Liebert

1980-01-01

207

Science Through ARts (STAR)  

NASA Technical Reports Server (NTRS)

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

Kolecki, Joseph; Petersen, Ruth; Williams, Lawrence

2002-01-01

208

Colors of Stars  

NSDL National Science Digital Library

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

Joiner, David; The Shodor Education Foundation, Inc.

209

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

210

Planet -Star Plasma Interactions  

E-print Network

Planet - Star Plasma Interactions Philippe Zarka LESIA, Observatoire de Paris/CNRS, Meudon philippe.zarka@obspm.fr References : · Zarka, P., Plasma interactions of exoplanets with their parent star and associated radio emissions, Planet. Space Sci., 55, 598-617, 2007. · Griessmeier, J.-M., P. Zarka and H. Spreeuw, Predicting

Demoulin, Pascal

211

Build Your Own Star  

NSDL National Science Digital Library

This SEED (Schlumberger Excellence in Educational Development) website from Schlumberger provides a simulation of the life-cycle of a star. The user chooses the initial mass and "metal" (non-hydrogen/helium) content, and the site shows how the star evolves and ultimately how it dies. The site also explains "the most famous graph in astronomy," the H-R diagram.

2010-03-08

212

The Birth of Massive Stars and Star Clusters  

E-print Network

In the present-day universe, it appears that most, and perhaps all, massive stars are born in star clusters. It also appears that all star clusters contain stars drawn from an approximately universal initial mass function, so that almost all rich young star clusters contain massive stars. In this review I discuss the physical processes associated with both massive star formation and with star cluster formation. First I summarize the observed properties of star-forming gas clumps, then address the following questions. How do these clumps emerge from giant molecular clouds? In these clustered environments, how do individual stars form and gain mass? Can a forming star cluster be treated as an equilibrium system or is this process too rapid for equilibrium to be established? How does feedback affect the formation process?

Jonathan C. Tan

2005-04-11

213

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

214

The Brightest Carbon Stars  

E-print Network

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

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

1997-10-06

215

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

216

When Stars Blow Up What Stars Explode?  

E-print Network

;Cataclysmic Variables ·Binary star systems incorporating a white dwarf ·Outbursts due to disk instabilities #12;GK Per = Nova Per 1901 #12;Novae Thermonuclear detonations on a white dwarf ·Hydrogen accumulates ·Type Ia: core collapse of a 1.4 M white dwarf o complete detonation of the core - no remnant ·Type II

Walter, Frederick M.

217

lone star healthy streams program The Lone Star Healthy Streams  

E-print Network

lone star healthy streams program The Lone Star Healthy Streams (LSHS) Program provides rural of a Synergistic, Comprehensive Statewide Lone Star Healthy Streams Program. LSHS is incorporating educational) to reduce bacteria runoff. Educational programs are an important part of this strategy. #12;lone star

218

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

219

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

220

Hyperons in neutron stars  

E-print Network

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

Katayama, Tetsuya

2015-01-01

221

Intergalactic Star Formation  

E-print Network

Star formation in interacting systems may take place in various locations, from the dust--enshrouded core of Ultraluminous Infrared Galaxies to more unusual places such as the debris of colliding galaxies expelled into the intergalactic medium. Determining whether star-formation proceeds in the latter environment, far from the parent galaxies, in a similar way as in spiral disks has motivated the multi--wavelength study presented here. We collected VLA/HI, UV/GALEX, optical Halpha and MIR/Spitzer images of a few nearby interacting systems chosen for their prominent "intergalactic" star formation activity. Preliminary results on the spectacular collisional HI ring around NGC 5291 are presented.

Pierre-Alain Duc; Meederic Boquien; Jonathan Braine; Elias Brinks; Ute Lisenfeld; Vassilis Charmandaris

2006-10-13

222

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

223

Finding the Pole Star  

NSDL National Science Digital Library

This lesson plan is part of a high school course on astronomy, Newtonian mechanics and spaceflight and provides a closer look at the pole star and the neighboring constellations, especially the Big Dipper and Cassiopeia. One objective is for the student to know the constellations of the Big Dipper and Cassiopeia, and their use in finding the Pole Star. The student will also realize that other celestial objects - Sun, Moon and planets - share the rotation (and hence rise and set), even though their positions among the stars slowly change.

Stern, David

224

Life Products of Stars  

E-print Network

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

Aldo M. Serenelli; Masataka Fukugita

2006-06-27

225

NASA star simulator  

NASA Technical Reports Server (NTRS)

A star simulator is described which is capable of simulating a field of three or more stars in response to signals from a computer interface. Star magnitude and spectral output can be manipulated and absolute position measurements can be obtained with the system. The simulator is a single axis system which consists of two assemblies: a light source and filter wheel assembly, and a translation stage assembly. The assemblies are self contained on 60.96 x 60.96 cm breadboards and are connected via three fiber optic cables. A summary of operational modes is provided.

1986-01-01

226

Spectroscopy of Massive Stars  

E-print Network

Although rare, massive stars, being the main sources of ionizing radiation, chemical enrichment and mechanical energy in the Galaxy, are the most important objects of the stellar population. This review presents the many different aspects of the main tool used to study these stars, i.e. spectroscopy. The first part consists in an introduction on these objects and their physical properties (mass, wind, evolution, relation with their environment). Next, the spectral behaviour of single massive stars is investigated, in the visible as well as in the X-ray domain. Finally, the last part of this paper deals with massive binaries, especially those exhibiting a colliding wind phenomenon.

Yael Naze

2006-12-06

227

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.

228

Formation History of Stars and Star Clusters in Nearby Galaxies  

E-print Network

Abstract. We present first results from an HST/ACS imaging survey of stars and star clusters in five nearby spiral galaxies. This contribution concentrates on NGC 1313, a highly distorted late-type barred spiral. We compare the field star and cluster formation histories in our three ACS pointings for this galaxy. In one pointing, both the cluster and field star age distributions show clear evidence for a ramp-up in the star formation rate about 10 8 years ago.

A. Vazdekis; R. Peletier; S. S. Larsen; M. D. Mora; J. P. Brodie; T. Richtler

2007-01-01

229

Scope on the Skies: Star light, star bright  

NSDL National Science Digital Library

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

Bob Riddle

2009-03-01

230

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

231

IRAS colors of normal stars  

NASA Technical Reports Server (NTRS)

Using stars from the Bright Star Catalog, supplemented by cool dwarf stars from the Gliese catalog, that were detected by IRAS, the authors define empirically the median intrinsic visual-to-infrared color indices for 'normal' stars as a function of IRAS wavelength, spectral type and luminosity class. Anomalously red stars are discussed. Two otherwise undistinguished F giant stars are found with significant excesses at 12 microns. Be stars differ markedly from nonemission B stars in their V-(12) indices due to contamination of the former by free-free emission. Both B and Be stars show large dispersions in V-(25) colors that are associated with the heating of local, but strictly interstellar, dust clouds by some of the non-emission B stars. The derived sequences of stellar colors are closely approximated by either simple blackbody predictions or by model-atmosphere calculations.

Cohen, Martin; Schwartz, Deborah E.; Chokshi, Arati; Walker, Russell G.

1987-01-01

232

Masers and star formation  

E-print Network

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

Vincent L. Fish

2007-04-02

233

The origin of stars  

NASA Astrophysics Data System (ADS)

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

Smith, Michael D.

234

Cosmology with hypervelocity stars  

SciTech Connect

In the standard cosmological model, the merger remnant of the Milky Way and Andromeda (Milkomeda) will be the only galaxy remaining within our event horizon once the Universe has aged by another factor of ten, ? 10{sup 11} years after the Big Bang. After that time, the only extragalactic sources of light in the observable cosmic volume will be hypervelocity stars being ejected continuously from Milkomeda. Spectroscopic detection of the velocity-distance relation or the evolution in the Doppler shifts of these stars will allow a precise measurement of the vacuum mass density as well as the local matter distribution. Already in the near future, the next generation of large telescopes will allow photometric detection of individual stars out to the edge of the Local Group, and may target the ? 10{sup 5±1} hypervelocity stars that originated in it as cosmological tracers.

Loeb, Abraham, E-mail: aloeb@cfa.harvard.edu [Institute for Theory and Computation, Harvard University, 60 Garden St., Cambridge, MA 02138 (United States)

2011-04-01

235

Guide star probabilities  

NASA Technical Reports Server (NTRS)

Probabilities are calculated for acquiring suitable guide stars (GS) with the fine guidance system (FGS) of the space telescope. A number of the considerations and techniques described are also relevant for other space astronomy missions. The constraints of the FGS are reviewed. The available data on bright star densities are summarized and a previous error in the literature is corrected. Separate analytic and Monte Carlo calculations of the probabilities are described. A simulation of space telescope pointing is carried out using the Weistrop north galactic pole catalog of bright stars. Sufficient information is presented so that the probabilities of acquisition can be estimated as a function of position in the sky. The probability of acquiring suitable guide stars is greatly increased if the FGS can allow an appreciable difference between the (bright) primary GS limiting magnitude and the (fainter) secondary GS limiting magnitude.

Soneira, R. M.; Bahcall, J. N.

1981-01-01

236

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

237

Searching between the stars  

SciTech Connect

The cosmic cycle of birth and death is considered, taking into account the initial big bang, the formation of galaxies and stars, nuclear burning and element formation, and the mixing of supernova material with the rest of the interstellar gas. The interstellar medium as viewed in 1970 is discussed, along with the electromagnetic spectrum, ultraviolet satellite telescopes, detectors for microwaves, X-ray measures from satellites, primordial hydrogen in the galactic disc, clouds of molecular hydrogen, and heavy elements between the stars. A cloud model of the interstellar gas is provided, and a description is presented of the structure of clouds, aspects of cloud evolution, the formation of star groups, and questions regarding the evolution from protostar to star.

Spitzer, L. Jr.

1982-01-01

238

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

239

Soft Physics from STAR  

E-print Network

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

Fuqiang Wang

2005-10-27

240

Alkaline broadening in Stars  

E-print Network

Giving new insight for line broadening theory for atoms with more structure than hydrogen in most stars. Using symbolic software to build precise wave functions corrected for ds;dp quantum defects. The profiles obtained with that approach, have peculiar trends, narrower than hydrogen, all quantum defects used are taken from atomic database topbase. Illustration of stronger effects of ions and electrons on the alkaline profiles, than neutral-neutral collision mechanism. Keywords : Stars: fundamental parameters - Atomic processes - Line: profiles.

De Kertanguy, A

2015-01-01

241

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.

2014-09-19

242

Physics and Star Trek  

NSDL National Science Digital Library

Created and maintained by physicist Jason Hinson, the Physics and Star Trek Web site investigates faster than light travel and subspace physics. Each topic is presented as a mix of factual information along with speculation on the author's part on how these phenomena could or could not work. Although the site consists of much text and few graphics, which may turn away some potential readers, the interesting subject will definitely appeal to hard core Star Trek or physics junkies.

243

Cold Hybrid Star Properties  

SciTech Connect

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

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

2011-10-28

244

Bubbly Little Star  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

2007-01-01

245

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

246

Stars Grouped with ? Car  

NASA Astrophysics Data System (ADS)

The region around the ? Car nebula contains three O associations, which provide examples of very rare objects, including a Wolf-Rayet star and several massive O3 stars. One of the early Chandra ACIS-I images was centered on ? Car, and included the region of Trumpler 16 (of which ? Car is a member), and also some of Trumpler 14. The Chandra image confirms the well known result that O and very early B stars are X-ray sources (Seward and Chlebowski, 1982, ApJ, 256, 530) with LX ~= 10-7 Lbol. In addition, the new Chandra image reveals a population of X-ray sources without O or B spectral type counterparts, which are presumably pre-main sequence stars. Analysis is assisted by reasonable uniformity of the optical extinction across the association. However, X-ray results permit us to confirm extra absorption of soft X-ray flux in two stars which have unusually high optical extinction, and lie near the edge of dust lanes. The energy sensitivity of the ACIS-CCD provides low resolution spectra. We have used these to compare spectra of the stars with different photospheric temperatures, as well as varying stellar wind strengths.

Evans, Nancy Remage; Seward, Fredrick D.

2001-09-01

247

MMT Hypervelocity Star Survey  

E-print Network

We describe a new survey for unbound hypervelocity stars (HVSs), stars traveling with such extreme velocities that dynamical ejection from a massive black hole (MBH) 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 6 unbound HVSs with velocities and distances exceeding the conservative escape velocity estimate of Kenyon and collaborators. We additionally report 4 possibly unbound HVSs with velocities and distances exceeding the lower escape velocity estimate of Xue and collaborators. These discoveries increase the number of known 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.

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

2008-09-15

248

Seeing Stars in Serpens  

NASA Technical Reports Server (NTRS)

Infant stars are glowing gloriously in this infrared image of the Serpens star-forming region, captured by NASA's Spitzer Space Telescope.

The reddish-pink dots are baby stars deeply embedded in the cosmic cloud of gas and dust that collapsed to create it. A dusty disk of cosmic debris, or 'protoplanetary disk,' that may eventually form planets, surrounds the infant stars.

Wisps of green throughout the image indicate the presence of carbon rich molecules called polycyclic aromatic hydrocarbons. On Earth, these molecules can be found on charred barbecue grills and in automobile exhaust. Blue specks sprinkled throughout the image are background stars in our Milky Way galaxy.

The Serpens star-forming region is located approximately 848 light-years away in the Serpens constellation.

The image is a three-channel, false-color composite, where emission at 4.5 microns is blue, emission at 8.0 microns is green, and 24 micron emission is red.

2006-01-01

249

Captured older stars as the reason for apparently prolonged star formation in young star clusters  

E-print Network

The existence of older stars within a young star cluster can be interpreted to imply that star formation occurs on time scales longer than a free-fall time of a pre-cluster cloud core. Here the idea is explored that these older stars are not related to the star formation process forming the young star cluster but rather that the orbits of older field stars are focused by the collapsing pre-cluster cloud core. Two effects appear: The focussing of stellar orbits leads to an enhancement of the density of field stars in the vicinity of the centre of the young star cluster. And due to the time-dependent potential of the forming cluster some of these stars can get bound gravitationally to the cluster. These stars exhibit similar kinematical properties as the newly formed stars and can not be distinguished from them on the basis of radial-velocity or proper-motion surveys. Such contaminations may lead to a wrong apparent star-formation history of a young cluster. In the case of the ONC the theoretical number of gravitationally bound older low-mass field stars agrees with the number of observed older low-mass stars.

Jan Pflamm-Altenburg; Pavel Kroupa

2006-11-16

250

Models of symbiotic stars  

NASA Technical Reports Server (NTRS)

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

Friedjung, Michael

1993-01-01

251

Pulsating Star Mystery Solved  

NASA Astrophysics Data System (ADS)

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

2010-11-01

252

Sounds of a Star  

NASA Astrophysics Data System (ADS)

Acoustic Oscillations in Solar-Twin "Alpha Cen A" Observed from La Silla by Swiss Team Summary Sound waves running through a star can help astronomers reveal its inner properties. This particular branch of modern astrophysics is known as "asteroseismology" . In the case of our Sun, the brightest star in the sky, such waves have been observed since some time, and have greatly improved our knowledge about what is going on inside. However, because they are much fainter, it has turned out to be very difficult to detect similar waves in other stars. Nevertheless, tiny oscillations in a solar-twin star have now been unambiguously detected by Swiss astronomers François Bouchy and Fabien Carrier from the Geneva Observatory, using the CORALIE spectrometer on the Swiss 1.2-m Leonard Euler telescope at the ESO La Silla Observatory. This telescope is mostly used for discovering exoplanets (see ESO PR 07/01 ). The star Alpha Centauri A is the nearest star visible to the naked eye, at a distance of a little more than 4 light-years. The new measurements show that it pulsates with a 7-minute cycle, very similar to what is observed in the Sun . Asteroseismology for Sun-like stars is likely to become an important probe of stellar theory in the near future. The state-of-the-art HARPS spectrograph , to be mounted on the ESO 3.6-m telescope at La Silla, will be able to search for oscillations in stars that are 100 times fainter than those for which such demanding observations are possible with CORALIE. PR Photo 23a/01 : Oscillations in a solar-like star (schematic picture). PR Photo 23b/01 : Acoustic spectrum of Alpha Centauri A , as observed with CORALIE. Asteroseismology: listening to the stars ESO PR Photo 23a/01 ESO PR Photo 23a/01 [Preview - JPEG: 357 x 400 pix - 96k] [Normal - JPEG: 713 x 800 pix - 256k] [HiRes - JPEG: 2673 x 3000 pix - 2.1Mb Caption : PR Photo 23a/01 is a graphical representation of resonating acoustic waves in the interior of a solar-like star. Red and blue colours show element displacements in opposite directions. Geologists monitor how seismic waves generated by earthquakes propagate through the Earth, and thus learn about the inner structure of our planet. The same technique works for stars. The Sun, our nearest star and a typical middle-age member of its class, has been investigated in this way since the 1960's. With "solar seismology" , astronomers have been able to learn much about the inner parts of the star, and not only the outer layers normally visible to the telescopes. In the Sun, heat is bubbling up from the central regions where enormous amount of energy is created by nuclear reactions . In the so-called convective zone , the gas is virtually boiling, and hot gas-bubbles are rising with a speed that is close to that of sound. Much like you can hear when water starts to boil, the turbulent convection in the Sun creates noise . These sound waves then propagate through the solar interior and are reflected on the surface, making it oscillate. This "ringing" is well observed in the Sun, where the amplitude and frequency of the oscillations provide astronomers with plenty of information about the physical conditions in the solar interior. From the Sun to the stars There is every reason to believe that our Sun is a quite normal star of its type. Other stars that are similar to the Sun are therefore likely to pulsate in much the same way as the Sun. The search for such oscillations in other solar-like stars has, however, been a long and difficult one. The problem is simply that the pulsations are tiny, so very great precision is needed in the measurements. However, the last few years have seen considerable progress in asteroseismology, and François Bouchy and Fabien Carrier from the Geneva Observatory have now been able to detect unambiguous acoustic oscillations in the Solar-twin star, Alpha Centauri A. The bright and nearby star Alpha Centauri Alpha Centauri (Alpha Cen) [1] is the brightest star in the constellation Centaurus in the southern hemisphere. It is actually

2001-06-01

253

How star clusters could survive low star formation efficiencies  

E-print Network

After the stars of a new, embedded star cluster have formed they blow the remaining gas out of the cluster. Especially winds of high mass stars and definitely the on-set of the first super novae can remove the residual gas from a cluster. This leads to a very violent mass-loss and leaves the cluster out of virial equilibrium. Standard models predict that the star formation efficiency (SFE) has to be about 33 per cent for sudden (within one crossing-time of the cluster) gas expulsion to retain some of the stars in a bound cluster. If the efficiency is lower the stars of the cluster disperse completely. Recent observations reveal that in strong star bursts star clusters do not form in isolation but in complexes containing dozens and up to several hundred star clusters (super-clusters). By carrying out numerical experiments we demonstrate that in these environments (i.e. the deeper potential of the star cluster complex and the merging process of the star clusters within these super-clusters) the SFEs could be as low as 20 per cent, leaving a gravitationally bound stellar population. We demonstrate that the merging of the first clusters happens faster than the dissolution time therefore enabling more stars to stay bound within the merger object. Such an object resembles the outer Milky Way globular clusters and the faint fuzzy star clusters recently discovered in NGC 1023.

M. Fellhauer; P. Kroupa

2004-11-29

254

Star Caught Smoking  

NASA Astrophysics Data System (ADS)

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

2007-08-01

255

Ages of Young Stars  

NASA Astrophysics Data System (ADS)

Determining the sequence of events in the formation of stars and planetary systems and their timescales is essential for understanding those processes, yet establishing ages is fundamentally difficult because we lack direct indicators. In this review we discuss the age challenge for young stars, specifically those less than ~100 m.y. old. Most age determination methods that we discuss are primarily applicable to groups of stars but can be used to estimate the age of individual objects. A reliable age scale is established above 20 m.y. from measurement of the lithium depletion boundary (LDB) in young clusters, and consistency is shown between these ages and those from the upper-main-sequence (UMS) and main-sequence (MS) turn-off — if modest core convection and rotation is included in the models of higher-mass stars. Other available methods for age estimation include the kinematics of young groups, placing stars in Hertzsprung-Russell diagrams (HRDs), pulsations and seismology, surface gravity measurement, rotation and activity, and Li abundance. We review each of these methods and present known strengths and weaknesses. Below ~20 m.y., both model-dependent and observational uncertainties grow, the situation is confused by the possibility of age spreads, and no reliable absolute ages yet exist. The lack of absolute age calibration below 20 m.y. should be born in mind when considering the lifetimes of protostellar phases and circumstellar material.

Soderblom, D. R.; Hillenbrand, L. A.; Jeffries, R. D.; Mamajek, E. E.; Naylor, T.

256

Condensate dark matter stars  

SciTech Connect

We investigate the structure and stability properties of compact astrophysical objects that may be formed from the Bose-Einstein condensation of dark matter. Once the critical temperature of a boson gas is less than the critical temperature, a Bose-Einstein Condensation process can always take place during the cosmic history of the universe. Therefore we model the dark matter inside the star as a Bose-Einstein condensate. In the condensate dark matter star model, the dark matter equation of state can be described by a polytropic equation of state, with polytropic index equal to one. We derive the basic general relativistic equations describing the equilibrium structure of the condensate dark matter star with spherically symmetric static geometry. The structure equations of the condensate dark matter stars are studied numerically. The critical mass and radius of the dark matter star are given by M{sub crit} ? 2(l{sub a}/1fm){sup 1/2}(m{sub ?}/1 GeV){sup ?3/2}M{sub s}un and R{sub crit} ? 1.1 × 10{sup 6}(l{sub a}/1 fm){sup 1/2}(m{sub ?}/1 GeV){sup ?3/2} cm respectively, where l{sub a} and m{sub ?} are the scattering length and the mass of dark matter particle, respectively.

Li, X.Y.; Harko, T.; Cheng, K.S., E-mail: lixinyu@hku.hk, E-mail: harko@hkucc.hku.hk, E-mail: hrspksc@hkucc.hku.hk [Department of Physics and Center for Theoretical and Computational Physics, The University of Hong Kong, Pok Fu Lam Road, Hong Kong (China)

2012-06-01

257

Holographic magnetic star  

NASA Astrophysics Data System (ADS)

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

Burikham, Piyabut; Chullaphan, Tossaporn

2012-06-01

258

Dark Stars: A Review  

E-print Network

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

Freese, Katherine; Spolyar, Douglas; Valluri, Monica

2015-01-01

259

Characterizing Retired A Stars  

NASA Astrophysics Data System (ADS)

A complete understanding of the formation and evolution of planetary systems depends on the precise characterization of the planets and their host stars. The stellar mass is particularly important because it might influence the planet occurrence and it is used to constrain the planetary masses, thus providing information about the systems' architectures. Single FGK stars on the main sequence usually have precise masses estimated from evolutionary tracks, but the results of this method for subgiants and giants have recently been called into question. In this work, we describe the ongoing efforts to precisely constrain the the masses of evolved stars using a sample of more than 250 retired A stars as well as some benchmark subgiants and giants. Different input atmospheric parameters (from excitation and ionization equilibria, spectral synthesis, interferometry and photometry) and methods (evolutionary tracks, lithium abundances and asteroseismology) are used to critically evaluate the stellar masses and its uncertainties. Preliminary results are discussed and suggest that current mass determinations for evolved stars do not present any systematic errors.

Ghezzi, Luan; Johnson, John; Dias do Nascimento, José

2015-01-01

260

MMT Hypervelocity Star Survey  

E-print Network

We describe a new survey for unbound hypervelocity stars (HVSs), stars traveling with such extreme velocities that dynamical ejection from a massive black hole (MBH) 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 6 unbound HVSs with velocities and distances exceeding the conservative escape velocity estimate of Kenyon and collaborators. We additionally report 4 possibly unbound HVSs with velocities and distances exceeding the lower escape velocity estimate of Xue and collaborators. These discoveries increase the number of known 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 ...

Brown, Warren R; Kenyon, Scott J

2008-01-01

261

Holographic Magnetic Star  

E-print Network

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

Piyabut Burikham; Tossaporn Chullaphan

2012-05-16

262

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

E-print Network

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

Sheridan, Jennifer

263

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. PMID:22778666

Zhang, Weina; Quan, Wei; Guo, Lei

2012-01-01

264

I-Love relation for incompressible stars and realistic stars  

E-print Network

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

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

2014-11-26

265

Runaway Stars, Hypervelocity Stars, and Radial Velocity Surveys  

E-print Network

Runaway stars ejected from the Galactic disk populate the halo of the Milky Way. To predict the spatial and kinematic properties of runaways, we inject stars into a Galactic potential, compute their trajectories through the Galaxy, and derive simulated catalogs for comparison with observations. Runaways have a flattened spatial distribution, with higher velocity stars at Galactic latitudes less than 30 degrees. Due to their shorter stellar lifetimes, massive runaway stars are more concentrated towards the disk than low mass runaways. Bound (unbound) runaways that reach the halo probably originate from distances of 6--12 kpc (10--15 kpc) from the Galactic center, close to the estimated origin of the unbound runaway star HD 271791. Because runaways are brighter and have smaller velocities than hypervelocity stars (HVSs), radial velocity surveys are unlikely to confuse runaway stars with HVSs. We estimate that at most 1 runaway star contaminates the current sample. We place an upper limit of 2% on the fraction o...

Bromley, Benjamin C; Brown, Warren R; Geller, Margaret J

2009-01-01

266

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

267

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

268

Polydisperse star polymer solutions  

E-print Network

We analyze the effect of polydispersity in the arm number on the effective interactions, structural correlations and the 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.

Christian von Ferber; Arben Jusufi; Martin Watzlawek; Christos N. Likos; Hartmut Lowen

2000-07-31

269

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.

270

Evolution of Protoneutron Stars  

E-print Network

We study the thermal and chemical evolution during the Kelvin-Helmholtz phase of the birth of a neutron star, employing neutrino opacities that are consistently calculated with the underlying equation of state (EOS). Expressions for the diffusion coefficients appropriate for general relativistic neutrino transport in the equilibrium diffusion approximation are derived. The diffusion coefficients are evaluated using a field-theoretical finite temperature EOS that includes the possible presence of hyperons. The variation of the diffusion coefficients is studied as a function of EOS and compositional parameters. We present results from numerical simulations of protoneutron star cooling for internal stellar properties as well as emitted neutrino energies and luminosities. We discuss the influence of the initial stellar model, the total mass, the underlying EOS, and the addition of hyperons on the evolution of the protoneutron star and upon the expected signal in terrestrial detectors.

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

1998-07-03

271

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

272

A search for nearby young stars among the flare stars  

E-print Network

Flare stars were discovered in the late 1940s in the solar vicinity and were named UV Cet-type variables (classical FSs). Among the FSs within 100 pc we search for young stars. For the search we take spectra with sufficient resolution to resolve Lithium at 6707 \\AA and Calcium at 6718 \\AA of all the stars. The real young stars are prime targets for the search of extra-solar planets by direct imaging.

Brigitte König; Ralph Neuhäuser; Valeri Hambaryan

2001-06-11

273

On the efficiency of field star capture by star clusters  

E-print Network

An exciting recent finding regarding scaling relations among globular clusters is the so-called 'blue tilt': clusters of the blue sub-population follow a trend of redder colour with increasing luminosity. In this paper we evaluate to which extent field star capture over a Hubble time may explain the 'blue tilt'. We perform collisional N-body simulations to quantify the amount of field star capture occuring over a Hubble time to star clusters with 10^3 to 10^6 stars. In the simulations we follow the orbits of field stars passing through a star cluster and calculate the energy change that the field stars experience due to gravitational interaction with cluster stars during one passage through the cluster. The capture condition is that their total energy after the passage is smaller than the gravitational potential at the cluster's tidal radius. By folding this with the fly-by rates of field stars with an assumed space density as in the solar neighbourhood and a range of velocity dispersions, we derive estimates on the mass fraction of captured field stars as a function of environment. We find that integrated over a Hubble time, the ratio between captured field stars and total number of clusters stars is very low (star velocity dispersion sigma=15 km/s. This holds for star clusters in the mass range of both open clusters and globular clusters. We furthermore show that tidal friction has a negligible effect on the energy distribution of field stars after interaction with the cluster. We conclude that field star capture is not a probable mechanism for creating the colour-magnitude trend of metal-poor globular clusters.

Steffen Mieske; Holger Baumgardt

2007-09-10

274

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

275

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

276

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

277

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

278

The DQ Herculis stars  

NASA Technical Reports Server (NTRS)

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

Patterson, Joseph

1994-01-01

279

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.

280

5.NF Origami Stars  

NSDL National Science Digital Library

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

281

A Star on Earth  

SciTech Connect

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

2014-03-05

282

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

283

Star Cluster Simulations  

E-print Network

The simulation of rich star clusters presents challenging problems of several kinds, including the design of suitable hardware and software, and numerous theoretical problems in stellar dynamics and stellar physics. Great progress has been made possible in recent years through the widespread use of GRAPE hardware. Simulations are, however, still too small to be applied to real star clusters without scaling. How this is done is partly an issue of stellar dynamics, and it has thrown into focus a number of fundamental theoretical problems in this field.

D. C. Heggie

1997-11-17

284

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

285

GeoSTAR  

NASA Astrophysics Data System (ADS)

The Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR, is a new concept for a microwave atmospheric sounder intended for geostationary satellites such as the GOES weather satellites operated by NOAA. A small but fully functional prototype has recently been developed at the Jet Propulsion Laboratory to demonstrate the feasibility of using aperture synthesis in lieu of the large solid parabolic dish antenna that is required with the conventional approach. Spatial resolution requirements dictate such a large aperture in GEO that the conventional approach has not been feasible, and it is only now with the GeoSTAR approach that a GEO microwave sounder can be contemplated. Others have proposed GEO microwave radiometers that would operate at sub-millimeter wavelengths to circumvent the large-aperture problem, but GeoSTAR is the only viable approach that can provide full sounding capabilities equal to or exceeding those of the AMSU systems now operating on LEO weather satellites and which have had tremendous impact on numerical weather forecasting. GeoSTAR will satisfy a number of important measurement objectives, many of them identified by NOAA as unmet needs in their GOES-R pre-planned product improvements (P3I) lists and others by NASA in their research roadmaps and as discussed in a white paper submitted to the NRC Decadal Survey. The performance of the prototype has been outstanding, and this proof of concept represents a major breakthrough in remote sensing capabilities. The GeoSTAR concept is now at a stage of development where an infusion into space systems can be initiated either on a NASA sponsored research mission or on a NOAA sponsored operational mission. GeoSTAR is an ideal candidate for a joint "research to operations" mission, and that may be the most likely scenario. Additional GeoSTAR related technology development and other risk reduction activities are under way, and a GeoSTAR mission is feasible in the GOES-R/S time frame, 2014-2016. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration.

Lambrigtsen, B.; Gaier, T.; Tanner, A.; Kangaslahti, P.; Brown, S.

2006-12-01

286

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

287

The Drifting Star  

NASA Astrophysics Data System (ADS)

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

2008-04-01

288

Mesopotamian Star Lists  

NASA Astrophysics Data System (ADS)

Sumerian and Akkadian names of stars and constellations occur in cuneiform texts for over 2,000 years, from the third millennium BC down to the death of cuneiform in the early first millennium AD, but no fully comprehensive list was ever compiled in antiquity. Lists of stars and constellations are available in both the lexical tradition and astronomical-astrological tradition of the cuneiform scribes. The longest list in the former is that in the series Urra = hubullu, in the latter, those in Mul-Apin.

Horowitz, Wayne

289

The Austin Energy Star Program  

E-print Network

TEE AUSTTN ENERGY STAR PROGRM DOUGLAS L. SEITER Program Manager Resource Management Department City of Austin The Austin Energy Star Program is an Austin-specific energy rating system implemented in July, 1985. Since the first builders joined...

Seiter, D. L.

1988-01-01

290

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

291

Asteroseismology of white dwarf stars  

E-print Network

Most of low- and intermediate-mass stars that populate the Universe will end their lives as white dwarf stars. These ancient stellar remnants have encrypted inside a precious record of the evolutionary history of the progenitor stars, providing a wealth of information about the evolution of stars, star formation, and the age of a variety of stellar populations, such as our Galaxy and open and globular clusters. While some information like surface chemical composition, temperature and gravity of white dwarfs can be inferred from spectroscopy, the internal structure of these compact stars can be unveiled only by means of asteroseismology, an approach based on the comparison between the observed pulsation periods of variable stars and the periods of appropriate theoretical models. In this communication, we first briefly describe the physical properties of white dwarf stars and the various families of pulsating white dwarfs known up to the present day, and then we present two recent analysis carried out by the La...

Córsico, A H

2014-01-01

292

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

293

Star clusters as diaries of galaxies  

E-print Network

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

Th. Maschberger; P. Kroupa

2007-06-11

294

Binary stars - Formation by fragmentation  

NASA Technical Reports Server (NTRS)

Theories of binary star formation by capture, separate nuclei, fission and fragmentation are compared, assessing the success of theoretical attempts to explain the observed properties of main-sequence binary stars. The theory of formation by fragmentation is examined, discussing the prospects for checking the theory against observations of binary premain-sequence stars. It is concluded that formation by fragmentation is successful at explaining many of the key properties of main-sequence binary stars.

Boss, Alan P.

1988-01-01

295

The Pulsating White Dwarf Stars  

Microsoft Academic Search

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

G. Fontaine; P. Brassard

2008-01-01

296

Radial stability in stratified stars  

E-print Network

We formulate within a generalized distributional approach the treatment of the stability against radial perturbations for both neutral and charged stratified stars in Newtonian and Einstein's gravity. We obtain from this approach the boundary conditions connecting two any phases within a star and underline its relevance for realistic models of compact stars with phase transitions, owing to the modification of the star's set of eigenmodes with respect to the continuous case.

Pereira, Jonas P

2015-01-01

297

Spectral Modeling Hot Star Winds  

E-print Network

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

Cohen, David

298

Massive Hybrid Stars with Strangeness  

E-print Network

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

Tatsuyuki Takatsuka; Tetsuo Hatsuda; Kota Masuda

2014-02-19

299

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

300

The evolution of massive stars  

NASA Technical Reports Server (NTRS)

The hypotheses underlying theoretical studies of the evolution of massive model stars with and without mass loss are summarized. The evolutionary tracks followed by the models across theoretical Hertzsprung-Russell (HR) diagrams are compared with the observed distribution of B stars in an HR diagram. The pulsational properties of models of massive star are also described.

1982-01-01

301

High-gravity central stars  

E-print Network

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

Thomas Rauch

2006-07-11

302

Molecules between the Stars.  

ERIC Educational Resources Information Center

Provides a listing of molecules discovered to date in the vast interstellar clouds of dust and gas. Emphasizes the recent discoveries of organic molecules. Discusses molecular spectral lines, MASERs (microwave amplification by stimulated emission of radiation), molecular clouds, and star birth. (TW)

Verschuur, Gerrit L.

1987-01-01

303

Chemical Compositions of Stars  

NASA Astrophysics Data System (ADS)

In 1835, in a famously inaccurate forecast, the French philosopher Auguste Comte wrote of stars that, `We understand the possibility of determining their shapes, their distances, their sizes and their movements; whereas we would never know how to study by any means their chemical composition…'. At the close of the 20th century the accurate measurement of the abundances of the chemical elements in...

Leckrone, D.; Murdin, P.

2000-11-01

304

RISING STAR THE SCIENCE  

E-print Network

RISING STAR THE SCIENCE OF WINE THINKING ABOUT PHILOSOPHY FISHING FOR A CANCER CURE TEACHING a different picture. Biologists searching for a cancer cure in the genes of a tiny fish; researchers who are studying a tiny striped fish that may yield a cure to the scourge of leukaemia. 13 TEACHING THE TEACHERS

Auckland, University of

305

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

306

Pygmy stars: first pair.  

PubMed

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

Zwicky, F

1966-07-01

307

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

308

Mystery Star 1054  

NASA Astrophysics Data System (ADS)

It all began like any ordinary day. But suddenly, the sky changed with the appearance of a new star. Men and women raised their heads, shaking with fear. The sky should not change, they cried---this must be a sign of the gods! We are doomed: this guest in our sky can only bring plague and disaster.

Nazé, Yaël

2004-07-01

309

Dihedral ‘star’ tensegrity structures  

Microsoft Academic Search

This paper presents conditions for self-equilibrium and super stability of dihedral ‘star’ tensegrity structures, based on their dihedral symmetry. It is demonstrated that the structures are super stable if and only if they have an odd number of struts, and the struts are as close as possible to each other. Numerical investigations show that their prestress stability is sensitive to

J. Y. Zhang; S. D. Guest; R. Connelly; M. Ohsaki

2010-01-01

310

The massive star IMF  

E-print Network

We review our current knowledge on the IMF in nearby environments, massive star forming regions, super star clusters, starbursts and alike objects from studies of integrated light, and discuss the various techniques used to constrain the IMF. In most cases, including UV-optical studies of stellar features and optical-IR analysis of nebular emission, the data is found to be compatible with a "universal" Salpeter-like IMF with a high upper mass cut-off over a large metallicity range. In contrast, near-IR observations of nuclear starbursts and LIRG show indications of a lower M_up and/or a steeper IMF slope, for which no alternate explanation has yet been found. Also, dynamical mass measurements of seven super star clusters provide so far no simple picture of the IMF. Finally we present recent results of a direct stellar probe of the upper end of the IMF in metal-rich HII regions, showing no deficiency of massive stars at high metallicity, and determining a lower limit on M_up of >~ 60--90 Msun.

Daniel Schaerer

2002-08-12

311

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.

312

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

313

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

314

Multipath star switch controller  

NASA Technical Reports Server (NTRS)

Device concept permits parallel computers to scan several commonnetwork-connected data stations at maximum rate. Sequencers leap-frog to bypass ports already being serviced by another computer. Two-path system for 16-port star switch controller is cost effective if added bandwidth or increased reliability is desired. Triple-path system would be cost effective for 32-port controller.

Anderson, T. O.

1980-01-01

315

Isolating Triggered Star Formation  

E-print Network

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 select galaxy pairs that are isolated in their dark matter halos with respect to other massive subhalos (N=2 halos) and 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_Bj ~ 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. 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. (Abridged.)

Elizabeth J. Barton; Jacob A. Arnold; Andrew R. Zentner; James S. Bullock; Risa H. Wechsler

2007-08-21

316

Almagest (Ptolemy's Star Catalog)  

Microsoft Academic Search

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

C. Ptolemy; K. Manitius

1995-01-01

317

Neutrinos from Protoneutron Stars  

E-print Network

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

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

1998-02-24

318

Neutron Star Phenomena  

NASA Technical Reports Server (NTRS)

Various phenomena involving neutron stars are addressed. Electron-positron production in the near magnetosphere of gamma-ray pulsars is discussed along with magnetic field evolution in spun-up and spinning-down pulsars. Glitches and gamma-ray central engines are also discussed.

Ruderman, Malvin

1998-01-01

319

Insight into star death  

SciTech Connect

Nineteen neutrinos, formed in the center of a supernova, became a theorist's dream. They came straight from the heart of supernova 1987A and landed in two big underground tanks of water. Suddenly a new chapter in observational astronomy opened as these two neutrino telescopes gave astronomers their first look ever into the core of a supernova explosion. But the theorists' dream almost turned into a nightmare. Observations of the presupernova star showed conclusively that the star was a blue supergiant, but theorists have long believed only red supergiant stars could explode as supernovae. Do astronomers understand supernovae better now than when supernova 1987A exploded in the Large Magellanic Cloud (LMC) one year ago Yes. The observations of neutrinos spectacularly confirmed a vital aspect of supernova theory. But the observed differences between 1987A and other supernovae have illuminated and advanced our perception of how supernovae form. By working together, observers and theorists are continuing to hone their ideas about how massive stars die and how the subsequent supernovae behave.

Talcott, R.

1988-02-01

320

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

321

Star Trek Physics  

NSDL National Science Digital Library

The authors suggest several ways to catch and hold student interest in physics. One excellent method is to use the television series Star Trek to extend the science curriculum. The beauty of this program is that the writers based their creations

Cole, Lynn; Radhe, Sue E.

2002-03-01

322

The Double Star mission  

Microsoft Academic Search

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

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

2005-01-01

323

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...

324

Fluctuation studies in STAR  

E-print Network

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

Supriya Das

2006-12-08

325

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

E-print Network

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

Uta Fritze

2008-01-15

326

White Dwarf Stars  

NASA Astrophysics Data System (ADS)

White dwarfs are the evolutionary endpoint for nearly 95% of all stars born in our Galaxy, the final stages of evolution of all low- and intermediate mass stars, i.e., main sequence stars with masses below (8.5± 1.5) M_{odot}, depending on metallicity of the progenitor, mass loss and core overshoot. Massive white dwarfs are intrinsically rare objects, tand produce a gap in the determination of the initial vs. final mass relation at the high mass end (e.g. Weidemann 2000 A&A, 363, 647; Kalirai et al. 2008, ApJ, 676, 594; Williams, Bolte & Koester 2009, ApJ, 693, 355). Main sequences stars with higher masses will explode as SNII (Smartt S. 2009 ARA&A, 47, 63), but the limit does depend on the metallicity of the progenitor. Massive white dwarfs are probably SNIa progenitors through accretion or merger. They are rare, being the final product of massive stars (less common) and have smaller radius (less luminous). Kepler et al. 2007 (MNRAS, 375, 1315), Kleinman et al. 2013 (ApJS, 204, 5) estimate only 1-2% white dwarfs have masses above 1 M_{odot}. The final stages of evolution after helium burning are a race between core growth and loss of the H-rich envelope in a stellar wind. When the burning shell is exposed, the star rapidly cools and burning ceases, leaving a white dwarf. As they cool down, the magnetic field freezes in, ranging from a few kilogauss to a gigagauss. Peculiar type Ia SN 2006gz, SN 2007if, SN 2009dc, SN 2003fg suggest progenitors in the range 2.4-2.8 M_{odot}, and Das U. & Mukhopadhyay B. (2012, Phys. Rev. D, 86, 042001) estimate that the Chandrasekhar limit increases to 2.3-2.6 M_{odot} for extremely high magnetic field stars, but differential rotation induced by accretion could also increase it, according to Hachisu I. et al. 2012 (ApJ, 744, 69). García-Berro et al. 2012, ApJ, 749, 25, for example, proposes double degenerate mergers are the progenitors of high-field magnetic white dwarfs. We propose magnetic fields enhance the line broadening in WDs, causing an overestimated surface gravity, and ultimately determine if these magnetic fields are likely developed through the star's own surface convection zone, or inherited from massive Ap/Bp progenitors. We discovered around 20 000 spectroscopic white dwarfs with the Sloan Digital Sky Survey (SDSS), with a corresponding increase in relatively rare varieties of white dwarfs, including the massive ones (Kleinman et al. 2013, ApJS, 204, 5, Kepler et al. 2013, MNRAS, 439, 2934). The mass distributions of the hydrogen-rich (DA) measured from fitting the spectra with model atmospheres calculated using unidimensinal mixing lenght-theory (MLT) shows the average mass (as measured by the surface gravity) increases apparently below 13 000K for DAs (e.g. Bergeron et al. 1991, ApJ, 367, 253; Tremblay et al. 2011, ApJ, 730, 128; Kleinman et al. 2013). Only with the tridimensional (3D) convection calculations of Tremblay et al. 2011 (A&A, 531, L19) and 2013 (A&A, 552, 13; A&A, 557, 7; arXiv 1309.0886) the problem has finally been solved, but the effects of magnetic fields are not included yet in the mass determinations. Pulsating white dwarf stars are used to measure their interior and envelope properties through seismology, and together with the luminosity function of white dwarf stars in clusters and around the Sun are valuable tools for the study of high density physics, and the history of stellar formation.

Kepler, S. O.

2014-10-01

327

Putting A Stars into Context: Evolution, Environment, and Related Stars  

NASA Astrophysics Data System (ADS)

Physical processes such as radiative diffusion, differential gravitational settling, grain accretion, convection, magnetic fields and non-radial pulsations, which play an important role in stars of many different types, are best studied in A-type stars, where they show their most extreme manifestations. New observational results obtained in the past few years and recent theoretical advances allow us for the first time to follow the development of these processes and their evolution throughout the life of the star, before, during and after the main sequence. They also open the possibility to understand better the dependencies of A-star processes on their galactic environment, and the relations of these processes with similar ones in related (mostly hotter) stars. These qualitatively new pieces of information open the possibility of gaining insight into A-star physics from a novel perspective. The meeting discussed the potential of this unprecedented approach, and its implications for our knowledge and understanding of A-type stars.

Mathys, Gautier; Griffin, Elizabeth R.; Kochukhov, Oleg; Monier, Richard; Wahlgren, Glenn M.

2014-11-01

328

Brave New World: A Good News Scenario for Educational Reform.  

ERIC Educational Resources Information Center

A good news scenario about the future of education in the United States includes many things that are already being done and other things that can be dreamed of. One example is the "Awesome All-Stars Academy," a dream of a group of dedicated politicians, administrators, teachers, parents, community members, and students who took seriously their…

Lenaghan, D.

329

What Research Tells the Coach About Football.  

ERIC Educational Resources Information Center

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

Paige, Roderick R.

330

Important Broomball Dates Wednesday, August 24 -Orientation Info Session  

E-print Network

­ Homecoming Broomball Championship Game (after Huskies Hockey) Friday, October 14 - Rink Staff , Referee, January 10 - Ball Drop, 2011-2012 Season Begins Wednesday, February 8 - Skills Competition & All-Star Game. Chocolate will be sizzling in the shack, But oh no! A broomball breaks with a loud crack. A new season

Endres. William J.

331

Neutron stars and quark stars: Two coexisting families of compact stars?  

E-print Network

The mass-radius relation of compact stars is discussed with relation to the presence of quark matter in the core. The existence of a new family of compact stars with quark matter besides white dwarfs and ordinary neutron stars is outlined.

J. Schaffner-Bielich

2006-12-29

332

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

333

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.

334

Spectroscopic Study of Extended Star Clusters in Dwarf Galaxy NGC 6822  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

335

Complexes of stars and complexes of star clusters  

E-print Network

Most star complexes are in fact complexes of stars, clusters and gas clouds; term "star complexes" was introduced as general one disregarding the preferential content of a complex. Generally the high rate of star formation in a complex is accompanied by the high number of bound clusters, including massive ones, what was explained by the high gas pressure in such regions. However, there are also complexes, where clusters seems to be more numerous in relation to stars than in a common complex. The high rate of clusters - but not isolated stars - formation seems to be typical for many isolated bursts of star formation, but deficit of stars might be still explained by the observational selection. The latter cannot, however, explain the complexes or the dwarf galaxies, where the high formation rate of only stars is observed. The possibility of the very fast dissolution of parental clusters just in such regions should itself be explained. Some difference in the physical conditions (turbulence parameters ?) within the initial gas supercloud might be a reason for the high or low stars/clusters number ratio in a complex.

Yuri N. Efremov

2005-12-12

336

Complexes of Stars and Complexes of Star Clusters  

E-print Network

Most star complexes are in fact complexes of stars, clusters and gas clouds; term ”star complexes ” was introduced as general one disregarding the preferential content of a complex. Generally the high rate of star formation in a complex is accompanied by the high number of bound clusters, including massive ones, what was explained by the high gas pressure in such regions. However, there are also complexes, where clusters seems to be more numerous in relation to stars than in a common complex. The high rate of clusters-but not isolated stars- formation seems to be typical for many isolated bursts of star formation, but deficit of stars might be still explained by the observational selection. The latter cannot, however, explain the complexes or the dwarf galaxies, where the high formation rate of only stars is observed. The possibility of the very fast dissolution of parental clusters just in such regions should itself be explained. Some difference in the physical conditions (turbulence parameters first of all) within the initial gas supercloud might be a reason for the high or low stars/clusters number ratio in a complex. 1

unknown authors

2005-01-01

337

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

338

Characterizing Hot Star Winds  

NASA Astrophysics Data System (ADS)

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

Canizares, Claude

2014-09-01

339

White Dwarf Stars  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

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

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

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

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

The full press release on the latest findings is online at

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

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

1999-01-01

340

Evolution of helium stars  

NASA Technical Reports Server (NTRS)

The evolution of helium stars in the mass range from 4 to 15 solar masses has been followed from the initial helium main sequence to the end of carbon burning in the core, with the use of Carson's (1976) radiative opacities. As compared with earlier work based on smaller opacities, the main-sequence band in the H-R diagram is now both wider and cooler than before. If neutrino losses are neglected in the stellar models, the phase of carbon burning in the core occurs in the red-supergiant region; otherwise, it occurs, as it does in the earlier models with or without neutrino emission, close to the helium main sequence. Observational data for Wolf-Rayet stars and R Coronae Borealis variables are found to lend some support to the present models.

Stothers, R.; Chin, C.-W.

1977-01-01

341

Neutron Stars for Undergraduates  

E-print Network

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

Richard R. Silbar; Sanjay Reddy

2003-09-16

342

The first stars  

NASA Technical Reports Server (NTRS)

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

Silk, J.

1983-01-01

343

Shooting Star Experiment  

NASA Technical Reports Server (NTRS)

The Shooting Star Experiment (SSE) is designed to develop and demonstrate the technology required to focus the sun's energy and use the energy for inexpensive space Propulsion Research. Pictured is an engineering model (Pathfinder III) of the Shooting Star Experiment (SSE). This model was used to test and characterize the motion and deformation of the structure caused by thermal effects. In this photograph, alignment targets are being placed on the engineering model so that a theodolite (alignment telescope) could be used to accurately measure the deformation and deflections of the engineering model under extreme conditions, such as the coldness of deep space and the hotness of the sun as well as vacuum. This thermal vacuum test was performed at the X-Ray Calibration Facility because of the size of the test article and the capabilities of the facility to simulate in-orbit conditions

1997-01-01

344

Detector limitations, STAR  

SciTech Connect

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 limit our ability to exploit the spin physics possible in RHIC. What is of greater concern at the moment is the construction schedule for components such as the Electromagnetic Calorimeters, and the limited funding for various levels of triggers.

Underwood, D. G.

1998-07-13

345

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

346

Particle Physics From Stars  

Microsoft Academic Search

Low-mass particles, such as neutrinos, axions, other Nambu-Goldstone bosons, and gravitons, are produced in the hot and dense interior of stars. Therefore, astrophysical arguments constrain the properties of these particles in ways that are often complementary to cosmological arguments and to laboratory experiments. This review provides an update on the most important stellar-evolution limits and discusses them in the context

Georg G. Raffelt

1999-01-01

347

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

348

Polarimetry of binary stars  

E-print Network

Astronomical polarimetry is a powerful technique that can provide physical information sometimes difficult or impossible to obtain by any other type of observation. Almost every class of binary star can benefit from polarimetric observations: pre-main-sequence objects, close or contact binaries, mass-transfer systems, evolved binaries, cataclysmic variables, eclipsing binaries, etc. In these systems, polarimetry can help determine the geometry of the circumstellar or circumbinary matter distribution, yield information on asymmetries and anisotropies, identify obscured sources, map starspots, detect magnetic fields, and establish orbital parameters, to name just a few examples. The orbital inclination in particular is a very important piece of information for a binary system because it can lead to the determination of the components' masses, the fundamental parameter that determines a star's initial structure and subsequent evolution. This review will illustrate the usefulness of polarimetric techniques for the study of binary stars, with examples of results obtained for a variety of binary systems, and an overview of models, including those used to retrieve the orbital inclination.

N. Manset

2005-11-08

349

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

350

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

351

Chemical abundances of T Tauri stars in star forming regions  

NASA Astrophysics Data System (ADS)

Accretion disks of T Tauri stars are commonly assumed to be the site where planets form. At the same time, surveys of old planet-host stars -the end product of planet formation- have shown that gas giant planets preferentially form around metal-rich stars. A critical question, with important implications for our understanding of planet formation, is therefore whether metal-rich T Tauri stars exist. In this context, we have started a project aimed at the determination of the metallicity of T Tauri stars in different star forming regions (SFRs): we present the results of a pilot study focusing on a few members of the Orion Nebula Cluster (ONC) and Sigma and Lambda Orionis clusters.

D'Orazi, V.; Randich, S.; Palla, F.; Flaccomio, E.; Pallavicini, R.; Sacco, G. G.

352

Magnetic fields in star formation: from galaxies to stars  

NASA Astrophysics Data System (ADS)

Magnetic fields are important at every scale in the star formation process: from the dynamics of the ISM in galaxies, to the collapse of turbulent molecular clouds to form stars and in the fragmentation of individual star forming cores. The recent development of a robust algorithm for MHD in the Smoothed Particle Hydrodynamics method has enabled us to perform simulations of star formation including magnetic fields at each of these scales. This paper focusses on three questions in particular: What is the effect of magnetic fields on fragmentation in star forming cores? How do magnetic fields affect the collapse of turbulent molecular clouds to form stars? and: What effect do magnetic fields have on the dynamics of the interstellar medium?

Price, D. J.; Bate, M. R.; Dobbs, C. L.

2009-08-01

353

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

354

Efficiencies of Low-Mass Star and Star Cluster Formation  

Microsoft Academic Search

Using a quantitative model for bipolar outflows driven by hydromagnetic\\u000aprotostellar winds, we calculate the efficiency of star formation assuming that\\u000aavailable gas is either converted into stars or ejected in outflows. We\\u000aestimate the efficiency of a single star formation event in a protostellar\\u000acore, finding 25%-70% for cores with various possible degrees of flattening.\\u000aThe core mass function

Christopher D. Matzner; Christopher F. McKee

2000-01-01

355

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

356

RUNAWAY STARS, HYPERVELOCITY STARS, AND RADIAL VELOCITY SURVEYS  

SciTech Connect

Runaway stars ejected from the Galactic disk populate the halo of the Milky Way. To predict the spatial and kinematic properties of runaways, we inject stars into a Galactic potential, compute their trajectories through the Galaxy, and derive simulated catalogs for comparison with observations. Runaways have a flattened spatial distribution, with higher velocity stars at Galactic latitudes less than 30{sup 0}. Due to their shorter stellar lifetimes, massive runaway stars are more concentrated toward the disk than low mass runaways. Bound (unbound) runaways that reach the halo probably originate from distances of 6-12 kpc (10-15 kpc) from the Galactic center, close to the estimated origin of the unbound runaway star HD 271791. Because runaways are brighter and have smaller velocities than hypervelocity stars (HVSs), radial velocity surveys are unlikely to confuse runaway stars with HVSs. We estimate that at most one runaway star contaminates the current sample. We place an upper limit of 2% on the fraction of A-type main-sequence stars ejected as runaways.

Bromley, Benjamin C. [Department of Physics, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J.; Brown, Warren R.; Geller, Margaret J., E-mail: bromley@physics.utah.ed, E-mail: skenyon@cfa.harvard.ed, E-mail: wbrown@cfa.harvard.ed, E-mail: mgeller@cfa.harvard.ed [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States)

2009-12-01

357

Which Stars Form Black Holes and Neutron Stars?  

E-print Network

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

Michael P. Muno

2006-11-18

358

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

359

The physics of neutron stars.  

PubMed

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 10(10) kelvin, opaqueness to neutrinos, and magnetic fields in excess of 10(13) Gauss. Here, we describe the formation, structure, internal composition, and evolution of neutron stars. Observations that include studies of pulsars in binary systems, thermal emission from isolated neutron stars, glitches from pulsars, and quasi-periodic oscillations from accreting neutron stars provide information about neutron star masses, radii, temperatures, ages, and internal compositions. PMID:15105490

Lattimer, J M; Prakash, M

2004-04-23

360

Star Forming Regions in Cepheus  

NASA Astrophysics Data System (ADS)

The northern Milky Way in the constellation of Cepheus (100° ? l ? 120°; 0° ? b ? 20°) contains several star forming regions. The molecular clouds of the Cepheus Flare region at b > 10°, are sites of low and intermediate mass star formation located between 200 and 450 pc from the Sun. Three nearby OB associations, Cep OB2, Cep OB3, Cep OB4, located at 600--800 pc, are eac= h involved in forming stars, like the well known high mass star forming regio= n S 140 at 900 pc. The reflection nebula NGC 7129 around 1 kpc harbors young, compact clusters of low and intermediate mass stars. The giant star forming complex NGC 7538 and the young open cluster NGC 7380, associated with the Perseus arm, are located at d > 2 kpc.

Kun, M.; Kiss, Z. T.; Balog, Z.

2008-12-01

361

The Constellations and Their Stars  

NSDL National Science Digital Library

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

362

Chinese Constellations and Star Maps  

NASA Astrophysics Data System (ADS)

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

Sun, Xiaochun

363

Spectropolarimetry of hot, luminous stars  

NASA Technical Reports Server (NTRS)

I review polarimetric observations of presumably single, hot luminous stars. The stellar types discussed are OB stars. B(e) supergiants, Luminous Blue Variables (LBV), Wolf-Rayet (W-R) stars, and type II supernovae (SN). It is shown that variable, intrinsic polarization is a common phenomenon in that part of the Hertzsprung-Russell (HR) diagram which these stars occupy. However, much observational work remains to be done before we can answer the most basic, statistical questions about the polarimetric properties of different groups of hot, luminous stars. Insight into the diagnostic power of polarization observations has been gained, but cannot be exploited without detailed models. Thus, while polarimetric observations do tell us that the mass-loss processes of all types of massive stars are time-dependent and anisotropic, the significance that this might have for the accuracy of their stellar parameters and evolutionary paths remains elusive.

Schulte-Ladbeck, Regina E.

1994-01-01

364

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

365

24 STELLAR REMNANTS White Dwarf Stars  

E-print Network

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

Sitko, Michael L.

366

Formation of the First Star Clusters  

E-print Network

Formation of the First Star Clusters Ralf Klessen Zentrum für Astronomie der Universität Heidelberg-Hsu Wang ... many collaborators abroad! #12;First star formation agenda #12;Star cluster formation First of molecular clouds Star cluster formation First star formation Magnetic fields in the primordial universe

Klessen,Ralf

367

Fast Star Pattern Recognition Using Spherical Triangles  

E-print Network

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

Crassidis, John L.

368

Anisotropic charged dark energy star  

E-print Network

As the stars carry electrical charges, we present in this paper a model for charged dark energy star which is singularity free. We take Krori-Barua space time. We assume that the radial pressure exerted on the system due to the presence of dark energy is proportional to the isotropic perfect fluid matter density and the difference between tangential and radial pressure is proportional to the square of the electric field intensity. The solution satisfies the physical conditions inside the star

Kanika Das; Nawsad Ali

2014-02-02

369

The Orion nebula star cluster  

NASA Technical Reports Server (NTRS)

Photography through filters which suppress nebular light reveal a clustering of faint red stars centered on the Trapezium, this evidences a distinct cluster within the larger OB1 association. Stars within about 20 ft of trapezium comprise the Orion Nebula star cluster are considered. Topics discussed re: (1) extinction by dust grains; (2) photometric peculiarities; (3) spectroscopic peculiarities; (4) young variables; (5) the distribution and motion of gas within the cluster.

Panek, R. J.

1982-01-01

370

Mass Determinations of Star Clusters  

E-print Network

Mass determinations are difficult to obtain and still frequently characterised by deceptively large uncertainties. We review below the various mass estimators used for star clusters of all ages and luminosities. We highlight a few recent results related to (i) very massive old star clusters, (ii) the differences and similarities between star clusters and cores of dwarf elliptical galaxies, and (iii) the possible strong biases on mass determination induced by tidal effects.

Georges Meylan

2001-07-03

371

Two unusual, radially pulsating stars  

NASA Astrophysics Data System (ADS)

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

Smolec, Rados?aw

2014-12-01

372

Flattest Star Ever Seen  

NASA Astrophysics Data System (ADS)

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

2003-06-01

373

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.

374

Massive Star Asteroseismology in Action  

NASA Astrophysics Data System (ADS)

After highlighting the principle and power of asteroseismology for stellar physics, we briefly emphasize some recent progress in this research for various types of stars. We give an overview of high-precision high duty-cycle space photometry of OB-type stars. Further, we update the overview of seismic estimates of stellar parameters of OB dwarfs, with specific emphasis on convective core overshoot. We discuss connections between pulsational, rotational, and magnetic variability of massive stars and end with future prospects for asteroseismology of evolved OB stars.

Aerts, Conny

2015-01-01

375

Quark Stars: Features and Findings  

E-print Network

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

Prashanth Jaikumar

2007-01-25

376

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

377

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

378

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

379

The emergence of "super-canonical" stars in R136-type star-burst clusters  

E-print Network

The emergence of "super-canonical" stars in R136-type star-burst clusters Sambaran Banerjee stars in the local universe" (JD2) #12;Super-cluster R136: a magnificent gallery of massive stars cluster in the LMC. Image credit: ESO #12;Observation of "super-canonical" stars in R136Very massive stars

Crowther, Paul

380

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

E-print Network

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

Barnes, Joshua Edward

381

H-cluster stars  

E-print Network

The study of dense matter at ultra-high 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 supra-nuclear density depends on the non-perturbative nature of quantum chromo-dynamics (QCD) and is essential for modeling 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 has 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 are therefore considering 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 most dense region. However, the real sound speed for H-cluster matter is in fact hard to calculate, so at this stage we do not put constraints on our model from the usual requirment of causality.

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

2011-07-05

382

Supercomputing and Ap stars  

E-print Network

Certain problems in the field of stellar atmospheres, polarized radiative transfer and magnetic field diagnostics cannot be addressed by means of traditional sequential programming techniques because CPU times become prohibitive on even the fastest single processor machines when realistic physics and accurate numerical methods are employed. This contribution discusses the question of what kind of supercomputing approach is best suited for the modelling of Ap stars, pointing out the superiority of parallel computing with Ada95 over High Performance Fortran in all of the above-mentioned fields.

Martin J. Stift

1998-05-06

383

Contact binary stars  

NASA Technical Reports Server (NTRS)

Ultraviolet and X-ray surveys of the W Ursae Majoris type stars are reviewed. These systems exhibit extended coronas and transition regions that are confined close to the optically determined surfaces. Correlations of X-ray activity with period or rotational velocity indicate a turn-over or saturation of emission at the short periods or high velocities found in the W UMa-type systems. For a number of systems, ultraviolet emission appears to be anti-correlated with the strength of X-ray emission. These observations are discussed in terms of solar structures, activity, and evolution.

Dupree, A. K.

1983-01-01

384

Chemistry between the stars.  

PubMed

Life--as we know it--is a chemical process, based on water and carbon compounds. Complex organic molecules are made primarily from the biogenic elements--carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur--that formed deep within massive ancient stars. How did these elements travel from their stellar birthplaces across time and space to make up the life-form that is reading these words? In this article, we'll take a look at the chemical processes that set the stage for the origin of life. PMID:11539061

Irvine, W M

1987-01-01

385

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

386

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

387

Dust from AGB stars  

E-print Network

Dust is formed in the expanding atmosphere during late stages of stellar evolution. Dust influences the dynamics and thermodynamics of the stellar atmosphere by its opacity. The dust opacity depends both on the optical properties of the grain material as well as on the amount of dust present. A rich source of information on some mineral phases of dust in AGB stars comes from the study of presolar grains from meteorites. This paper presents a short overview of presolar grains studies and describes how the optical properties of dust grains are obtained in the laboratory.

Anja C. Andersen

2007-02-22

388

Upsilon measurement in STAR  

E-print Network

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

Mauro R. Cosentino

2007-06-06

389

Dielectron Measurements in STAR  

E-print Network

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

F. Geurts; for the STAR Collaboration

2012-08-16

390

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

391

How to Cook a Star: The reason stars shine  

NSDL National Science Digital Library

The site discusses the eraly theories that attempted to explain why the sun shines. By the end of the article the author discusses the process of nuclear fusion in the sun and other stars. At the end of the article there is a link to another articel that discusses what happens when stars run out of hydrogen.

Tung, Brian

2007-01-04

392

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

393

TRIGGERED STAR FORMATION SURROUNDING WOLF-RAYET STAR HD 211853  

SciTech Connect

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

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

2012-05-20

394

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

395

Wolf-Rayet stars from Very Massive Stars  

NASA Astrophysics Data System (ADS)

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

Yusof, Norhasliza

2015-01-01

396

Journey to the Centre of the Star: Various Ways of Finding Star Centers in Star Clustering  

E-print Network

Abstract. The Star algorithm is an effective and efficient algorithm for graph clustering. We propose a series of novel, yet simple, metrics for the selection of Star centers in the Star algorithm and its variants. We empirically study the performance of off-line, standard and extended, and on-line versions of the Star algorithm adapted to the various metrics and show that one of the proposed metrics outperforms all others in both effectiveness and efficiency of clustering. We empirically study the sensitivity of the metrics to the threshold value of the algorithm and show improvement with respect to this aspect too. 1

Derry Tanti Wijaya; Stéphane Bressan

397

Neutron stars as cosmic neutron matter laboratories.  

NASA Astrophysics Data System (ADS)

Recent developments which have radically changed our understanding of the dynamics of neutron star superfluids and the free precession of neutron stars are summarized, and the extent to which neutron stars are cosmic neutron matter laboratories is discussed.

Pines, D.

398

Massive Star Formation in the Galactic Center  

E-print Network

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

D. F. Figer

2008-03-12

399

Globular Star Clusters Stas Jevsevar (28030543)  

E-print Network

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

Â?umer, Slobodan

400

Star Products for Relativistic Quantum Mechanics  

E-print Network

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

P. Henselder

2007-05-24

401

Really Hot Stars  

NASA Astrophysics Data System (ADS)

Spectacular VLT Photos Unveil Mysterious Nebulae Summary Quite a few of the most beautiful objects in the Universe are still shrouded in mystery. Even though most of the nebulae of gas and dust in our vicinity are now rather well understood, there are some which continue to puzzle astronomers. This is the case of a small number of unusual nebulae that appear to be the subject of strong heating - in astronomical terminology, they present an amazingly "high degree of excitation". This is because they contain significant amounts of ions, i.e., atoms that have lost one or more of their electrons. Depending on the atoms involved and the number of electrons lost, this process bears witness to the strength of the radiation or to the impact of energetic particles. But what are the sources of that excitation? Could it be energetic stars or perhaps some kind of exotic objects inside these nebulae? How do these peculiar objects fit into the current picture of universal evolution? New observations of a number of such unusual nebulae have recently been obtained with the Very Large Telescope (VLT) at the ESO Paranal Observatory (Chile). In a dedicated search for the origin of their individual characteristics, a team of astronomers - mostly from the Institute of Astrophysics & Geophysics in Liège (Belgium) [1] - have secured the first detailed, highly revealing images of four highly ionized nebulae in the Magellanic Clouds, two small satellite galaxies of our home galaxy, the Milky Way, only a few hundred thousand light-years away. In three nebulae, they succeeded in identifying the sources of energetic radiation and to eludicate their exceptional properties: some of the hottest, most massive stars ever seen, some of which are double. With masses of more than 20 times that of the Sun and surface temperatures above 90 000 degrees, these stars are truly extreme. PR Photo 09a/03: Nebula around the hot star AB7 in the SMC. PR Photo 09b/03: Nebula near the hot Wolf-Rayet star BAT99-2 in the LMC. PR Photo 09c/03: Nebula near the hot binary star BAT99-49 in the LMC. PR Photo 09d/03: The N44C Nebula in the LMC. Four unique images of highly excited nebulae in the Magellanic Clouds ESO PR Photo 09a/03 ESO PR Photo 09a/03 [Preview - JPEG: 400 x 472 pix - 74k [Normal - JPEG: 800 x 943 pix - 720k] [Full-Res - JPEG: 1200 x 1414 pix - 1.2M] ESO PR Photo 09b/03 ESO PR Photo 09b/03 [Preview - JPEG: 400 x 466 pix - 70k [Normal - JPEG: 800 x 931 pix - 928k] [Full-Res - JPEG: 1200 x 1397 pix - 1.8M] ESO PR Photo 09c/03 ESO PR Photo 09c/03 [Preview - JPEG: 400 x 469 pix - 74k [Normal - JPEG: 800 x 937 pix - 1.1M] [Full-Res - JPEG: 1200 x 1405 pix - 2.2M] ESO PR Photo 09d/03 ESO PR Photo 09d/03 [Preview - JPEG: 400 x 473 pix - 28k [Normal - JPEG: 800 x 945 pix - 368k] [Full-Res - JPEG: 1200 x 1418 pix - 600k] Captions: PR Photo 09a/03 is a reproduction of a "near-true" three-colour composite image of the highly excited nebula around the hot double star AB7 in the Small Magellanic Cloud (SMC), obtained in January 2002 with the FORS1 multi-mode instrument at the 8.2-m VLT MELIPAL telescope at the Paranal Observatory (Chile). It is based on three exposures through narrow-band optical (interference) filters that isolate the light from specific atoms and ions. In this rendering, the blue colour represents the light from singly ionized Helium (He II; wavelength 468.6 nm; exposure time 30 min), green corresponds to doubly ionized oxygen ([O III]; 495.7 + 500.7 nm; 5 min) and red to hydrogen atoms (H; H-alpha line at 656.2 nm; 5 min). Of these three ions, He II is the tracer of high excitation, i.e. the bluest areas of the nebula are the hottest. The sky field measures 400 x 400 arcsec2; the original pixel size on the 2k x 2k CCD is 0.23 arcsec. North is up and east to the left. Before combination, the CCD frames were flat-fielded and cleaned of cosmic-rays. Moreover, the stars in the blue (He II) image were removed in order to provide a clearer view of the surrounding nebular emission. The reproduced brightness is proportional to the squar

2003-04-01

402

Autonomous star tracker performance  

NASA Astrophysics Data System (ADS)

First in NASA's New Frontiers series of missions, the New Horizons spacecraft was successfully launched on January 19, 2006. New Horizons is scheduled to perform a gravity assist at Jupiter on February 28, 2007, arrive at Pluto on July 14, 2015; completing an extended mission to at least one Kuiper Belt Object in subsequent years. The concept of operations requires a star tracker that operates autonomously both in a standard three-axis "staring" mode during operations involving instrument observations and in a spin stabilized mode during cruise operations with nominal rotational rates up to 5 rpm. With the support of the Johns Hopkins University Applied Physics Laboratory, Galileo Avionica redesigned their Autonomous Star Trackers (ASTR) to use time-delayed integration techniques to provide autonomous spacecraft attitude estimates at 10 Hz at spin rates up to 10 rpm. This paper will present the performance of the upgraded ASTR in both inertial stare and spin stabilized modes for the first six months of the mission. In addition, effects of the vehicle motion on performance, effects of stray light and direct Sun blinding on tracking and performance, and unanticipated "features" or characteristics of the ASTRs will be discussed.

Rogers, Gabe D.; Schwinger, Marsha R.; Kaidy, James T.; Strikwerda, Thomas E.; Casini, Roberto; Landi, Andrea; Bettarini, Rossano; Lorenzini, Stefano

2009-07-01

403

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

404

Rotation of Giant Stars  

E-print Network

The internal rotation of post-main sequence stars is investigated, in response to the convective pumping of angular momentum toward the stellar core, combined with a tight magnetic coupling between core and envelope. The spin evolution is calculated using model stars of initial mass 1, 1.5 and $5\\,M_\\odot$, taking into account mass loss on the giant branches and the partitioning of angular momentum between the outer and inner envelope. We also include the deposition of orbital angular momentum from a sub-stellar companion, as influenced by tidal drag as well as the excitation of orbital eccentricity by a fluctuating gravitational quadrupole moment. A range of angular velocity profiles $\\Omega(r)$ is considered in the deep convective envelope, ranging from solid rotation to constant specific angular momentum. We focus on the backreaction of the Coriolis force on the inward pumping of angular momentum, and the threshold for dynamo action in the inner envelope. Quantitative agreement with measurements of core ro...

Kissin, Yevgeni

2015-01-01

405

Guide to Stars and Galaxies  

NSDL National Science Digital Library

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

406

Thermal Evolution of Strange Stars  

E-print Network

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

Zhou Xia; Wang Lingzhi; Zhou Aizhi

2007-09-03

407

Rotational velocities of B stars  

NASA Astrophysics Data System (ADS)

We measured projected rotational velocities for nearly 1100 B stars with these results. (1) They average substantially less than those published in the Bright Star Catalogue and are about one-quarter of the break-up velocities. (2) For the late B stars the deconvolved distribution in V is bimodal; one lobe consists of rapidly-rotating normal stars and the other lobe of slowly-rotating Ap stars. This is consistent with diffusion theory by Michaud. (3) Using interior models by Bertelli et al. we predicted rotational velocities of giants and found that they agree with observational ones for rigid-body rotation. Combining this with other data, we conclude that if the expansion of post-main sequence stars is a factor of <4, the conservation of angular momentum is by rigid-body rotation but for factors >4, it is in shells. (4) In binaries the primaries have synchronized rotational and orbital motions for periods <2.4 days. For the A stars studied by Abt & Morrell the limit is 5.0 days. (5) In binaries the orbits are circularized for periods <1.5 days and for A star <2.5 days. For binaries of 107.5 - 1010.2yr the maximum circularized period is 0.0016 A0.40 days.

Abt, Helmut A.; Levato, Hugo; Grosso, Monica

408

Fundamental Parameters of Massive Stars  

E-print Network

We discuss the determination of fundamental parameters of `normal' hot, massive OB-type stars, namely temperatures, luminosities, masses, gravities and surface abundances. We also present methods used to derive properties of stellar winds -- mass-loss rates and wind velocities from early-type stars.

Paul A Crowther

2003-05-08

409

Rotation of White Dwarf Stars  

E-print Network

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

Kawaler, Steven D

2014-01-01

410

Physics of Neutron Star Crusts  

E-print Network

The physics of neutron star crusts is vast, involving many different research fields, from nuclear and condensed matter physics to general relativity. This review summarizes the progress, which has been achieved over the last few years, in modeling neutron star crusts, both at the microscopic and macroscopic levels. The confrontation of these theoretical models with observations is also briefly discussed.

N. Chamel; P. Haensel

2008-12-20

411

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

412

Star Wars and gravitational constants  

Microsoft Academic Search

Star Wars takes place in another galaxy in another age and the adventure plays out on ``inhabitable'' planets unknown to us. Yet, it is curious how all the planets and other astronomical bodies of different sizes and compositions that Star Wars characters visit seem to have the same gravitational field at the surface.

Ryan Doherty; JamesAlexRembert; Nathan Boice; Priscilla Laws

1998-01-01

413

A database of AP stars  

NASA Astrophysics Data System (ADS)

A database for 3195 Ap stars, which can be used on an IBM-compatible personal computer, is described. It is essentially based on Renson's general catalogue of Ap and Am stars, but contains much additional information. It operates within the Dbase III Plus system.

Renson, P.; Kobi, D.; North, P.

1991-07-01

414

Magnetic fields in massive stars  

E-print Network

Although indirect evidence for the presence of magnetic fields in high-mass stars is regularly reported in the literature, the detection of these fields remains an extremely challenging observational problem. We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

S. Hubrig

2007-03-09

415

Stars in the Tarantula Nebula  

NASA Technical Reports Server (NTRS)

In the most active starburst region in the local universe lies a cluster of brilliant, massive stars, known to astronomers as Hodge 301. Hodge 301, seen in the lower right hand corner of this image, lives inside the Tarantula Nebula in our galactic neighbor, the Large Magellanic Cloud. This star cluster is not the brightest, or youngest, or most populous star cluster in the Tarantula Nebula, that honor goes to the spectacular R136. In fact, Hodge 301 is almost 10 times older than the young cluster R136. But age has its advantages; many of the stars in Hodge 301 are so old that they have exploded as supernovae. These exploded stars are blasting material out into the surrounding region at speeds of almost 200 miles per second. This high speed ejecta are plowing into the surrounding Tarantula Nebula, shocking and compressing the gas into a multitude of sheets and filaments, seen in the upper left portion of the picture. Hodge 301 contains three red supergiants - stars that are close to the end of their evolution and are about to go supernova, exploding and sending more shocks into the Tarantula. Also present near the center of the image are small, dense gas globules and dust columns where new stars are being formed today, as part of the overall ongoing star formation throughout the Tarantula region.

1999-01-01

416

STARS: A Year in Review  

ERIC Educational Resources Information Center

The Sustainability Tracking, Assessment & Rating System[TM] (STARS) is a program of AASHE, the Association for the Advancement of Sustainability in Higher Education. AASHE is a member-driven organization with a mission to empower higher education to lead the sustainability transformation. STARS was developed by AASHE with input and insight from…

Association for the Advancement of Sustainability in Higher Education, 2011

2011-01-01

417

Mathematics Teaching with the Stars  

ERIC Educational Resources Information Center

The mathematics instructional approaches of effective elementary teachers in urban high- poverty schools were investigated. Approximately 99 urban elementary teachers were administered the Star Teacher Selection Interview; a total of 31 were identified as star teachers. These teachers were then administered the Instructional Practices…

McKinney, Sueanne E.; Bol, Linda; Berube, Clair

2010-01-01

418

Accretion processes in star formation  

Microsoft Academic Search

This volume reviews our current knowledge of the processes governing the formation of stars, from the collapse and fragmentation of cold molecular gas clouds through the formation and evolution of disks which can form planets. It provides an especially timely reference for understanding recent discoveries of extrasolar planets and new direct evidence for protoplanetary disks around young stars. Each topic

Lee Hartmann

1998-01-01

419

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

420

Bag model and quark star  

NASA Astrophysics Data System (ADS)

In this paper, incorporating the property of the vacuum negative pressure, namely, the bag constant, we present a new model of the equation of state (EOS) of quark matter at finite chemical potential and zero temperature. By comparing our EOS with Fraga et al.’s EOS and SQM1 model, one finds that our EOS is softer than Fraga et al.’s EOS and SQM1 model. The reason for this difference is analyzed. With these results we investigate the structure of a quark star. A comparison between our model of the quark star and other models is made. The obtained mass of the quark star is 1.3˜1.66M? and the radius is 9.5˜14Km. One can see that our star’s compactness is smaller than that of the other two models.

Li, Hua; Luo, Xin-Lian; Zong, Hong-Shi

2010-09-01

421

Timing with NuSTAR  

NASA Astrophysics Data System (ADS)

We present an overview of timing studies with NuSTAR. We start from the current status of the NuSTAR timing calibration focusing on three main topics: relative time precision, absolute time precision and dead time correction. Then, we review the use of timing in some interesting scientific results of the mission, including, but not limited to: the timing of rotation-powered pulsars and magnetars, measuring the spin evolution of these neutron stars; the phase-resolved study of cyclotron resonance scattering features (CRSFs) in accreting X-ray pulsars, yielding a measure of the magnetic field close in the accretion column close to the surface; the study of aperiodic variability and quasi-periodic oscillations in several accreting black holes and neutron stars, giving a measure of the relevant time scales around the accreting objects and independent constraints on the spectral models. For the latter, we make use of novel timing techniques specifically adapted to NuSTAR.

Bachetti, Matteo

422

Grand unification of neutron stars  

PubMed Central

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.

2010-01-01

423

Quark stars within relativistic models  

E-print Network

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

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

2005-07-22

424

UBVRI photometry of red stars  

NASA Astrophysics Data System (ADS)

A total of 50 Mira- and SR-type red variable stars were observed by means of the photoelectric photometry UBVRI Kron-Cousins system. In addition, 15 nearby red dwarf stars having spectral subtypes similar to those of Mira stars at maximum were observed in order to show that the conversion of the natural system into the Landolt (1983) standard system can be made for stars as red as the Mira variables, in spite of the shortage of standard late M-type stars. The relationship function and spectral type-color index scale on the Johnson system was converted into the present system. By means of VRI photometry, the spectral subtype can immediately be determined in different phases of the light curve. SR variables have the same color indices and spectral subclasses as Mira variables.

Celis S., L.

1986-03-01

425

Physics of primordial star formation  

NASA Astrophysics Data System (ADS)

The study of primordial star formation has a history of nearly sixty years. It is generally thought that primordial stars are one of the key elements in a broad range of topics in astronomy and cosmology, from Galactic chemical evolution to the formation of super-massive blackholes. We review recent progress in the theory of primordial star formation. The standard theory of cosmic structure formation posits that the present-day rich structure of the Universe developed through gravitational amplification of tiny matter density fluctuations left over from the Big Bang. It has become possible to study primordial star formation rigorously within the framework of the standard cosmological model. We first lay out the key physical processes in a primordial gas. Then, we introduce recent developments in computer simulations. Finally, we discuss prospects for future observations of the first generation of stars.

Yoshida, Naoki

2012-09-01

426

Neutron stars, strange stars, and the nuclear equation of state  

SciTech Connect

This article consists of three parts. In part one we review the present status of dense nuclear matter calculations, and introduce a representative collection of realistic nuclear equations of state which are derived for different assumptions about the physical behavior of dense matter (baryon population, pion condensation,.possible transition of baryon matter to quark matter). In part two we review recently performed non-rotating and rotating compact star calculations performed for these equations of state. The minimum stable rotational periods of compact stars, whose knowledge is of decisive importance for the interpretation of rapidly rotating pulsars, axe determined. For this purpose two different limits on stable rotation are studied: rotation at the general relativistic Kepler period (below which mass shedding at the star`s equator sets in), and, secondly, rotation at the gravitational radiation-reaction instability (at which emission of gravitational waves set in which slows the star down). Part three of this article deals with the properties of hypothetical strange stars. Specifically we investigate the amount of nuclear solid crust that can be carried by a rotating strange star, and answer the question whether such objects can give rise to the observed phenomena of pulsar glitches, which is at the present time the only astrophysical test of the strange-quark-matter hypothesis.

Weber, F.; Glendenning, N.K.

1992-11-02

427

StarGuides Plus  

NASA Astrophysics Data System (ADS)

StarGuides Plus represents the most comprehensive and accurately validated collection of practical data on organizations involved in astronomy, related space sciences and other related fields. This invaluable reference source (and its companion volume, StarBriefs Plus) should be on the reference shelf of every library, organization or individual with any interest in these areas. The coverage includes relevant universities, scientific committees, institutions, associations, societies, agencies, companies, bibliographic services, data centers, museums, dealers, distributors, funding organizations, journals, manufacturers, meteorological services, national norms & standard institutes, parent associations & societies, publishers, software producers & distributors, and so on. Besides astronomy and associated space sciences, related fields such as aeronautics, aeronomy, astronautics, atmospheric sciences, chemistry, communications, computer sciences, data processing, education, electronics, engineering, energetics, environment, geodesy, geophysics, information handling, management, mathematics, meteorology, optics, physics, remote sensing, and so on, are also covered where appropriate. After some thirty years in continuous compilation, verification and updating, StarGuides Plus currently gathers together some 6,000 entries from 100 countries. The information is presented in a clear, uncluttered manner for direct and easy use. For each entry, all practical data are listed: city, postal and electronic-mail addresses, telephone and fax numbers, URLs for WWW access, foundation years, numbers of members and/or numbers of staff, main activities, publications titles (with frequencies, ISS-Numbers and circulations), names and geographical coordinates of observing sites, names of planetariums, awards (prizes and/or distinctions) granted, etc. The entries are listed alphabetically in each country. An exhaustive index gives a breakdown not only by different designations and acronyms, but also by location and major terms in names. Thematic sub-indices are also provided as well as a list of telephone and telefax national codes. In short, almost anyone involved in any way in the fields of astronomy and related space sciences will find invaluable contact and background information in this volume. All entries have been compiled from data supplied by the listed organizations and all data have been independently verified - making this compilation the most accurate and relevant source available. Link: http://www.wkap.nl/prod/b/1-4020-1926-2

Heck, A.

428

23 New Variable Stars  

NASA Astrophysics Data System (ADS)

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

Clark, M.

2014-12-01

429

Nearby Motionless Stars  

NASA Astrophysics Data System (ADS)

Almost 15% of all systems within 25 parsecs should be moving slower than 0.18 arcseconds per year, but traditional proper motion searches for nearby systems will miss them. Apart from USNO-B1, work by Lepine and Deacon, and stars bright enough to be seen by Hipparcos, the proper motion regime is almost completely unexplored. We have made a photometric search of the SuperCOSMOS database (Hambly 2002) to locate new nearby systems. The most promising targets moving slower than 0.18"/yr are being followed up with low resolution spectroscopy, CCD photometry, and trigonometric parallaxes from the CTIOPI program. Our first results have revealed nearby nearly-motionless systems like SCR2049-4012 (9.2 pc, 0.06"/yr), and a large number of apparent binary and young systems (a few perhaps as young as TW Hydra) of great astrophysical interest. This research is supported by NSF grant AST 09-08402

Riedel, Adric R.; Henry, T. J.; White, R. J.; Song, I.; Jensen, E. N.; RECONS

2011-01-01

430

Strangeness production in STAR  

E-print Network

We present a summary of strangeness enhancement results comparing data from Cu+Cu and Au+Au collisions at sqrt(SNN) = 200GeV measured by the STAR experiment. Relative yields in central Cu+Cu data seem to be higher than the equivalent sized peripheral Au+Au collision. In addition, strange particle production from these two systems is compared in terms of a statistical model, applying a Grand-Canonical ensemble and also applying a canonical correlation volume for the strange particles. Thermal fit results from the Grand-Canonical formalism shows little dependence on the system size but, when considering a strange canonical ensemble, strangeness enhancement shows a strong dependency on the correlation volume.

J. Takahashi; R. Derradi de Souza

2008-09-04

431

StarDate Online  

NSDL National Science Digital Library

As the longest-running science feature in the United States, StarDate has covered everything from the Big Dipper to super novas. The program serves as the public education and outreach arm of the University of Texas McDonald Observatory, and is broadcast in both Spanish and English. Visitors can listen to their latest radio program, and there is so much more to take in on this fine site. Amateur astronomers will want to look at their daily "Stargazing Tip" which is featured on the homepage, and then can look at the "Featured Image". After that, it's definitely worthwhile to look more closely into the "Stargazing" section. This section includes weekly tips, a stargazing almanac, a beginner's guide, and tips for viewing the planets and meteors. Finally, educators will want to look at the "Teachers" section, as it features lesson plans and classroom activities.

432

Shooting Star Experiment  

NASA Technical Reports Server (NTRS)

The Shooting Star Experiment (SSE) is designed to develop and demonstrate the technology required to focus the Sun's energy and use the energy for inexpensive space propulsion research. Pictured is an engineering model (Pathfinder III) of SSE and its thermal vacuum test to simulate in-orbit conditions at the X-Ray Calibration Facility at the Marshall Space Flight Center (MSFC). This model was used to test and characterize the motion and deformation of the structure caused by thermal effects. In this photograph, alignment targets are being placed on the engineering model so that a theodolite (alignment telescope) could be used to accurately measure the deformation and deflection of the engineering model under extreme condition, such as the coldness of deep space and the hotness of the Sun, as well as vacuum.

1997-01-01

433

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

434

Stars Just Got Bigger - A 300 Solar Mass Star Uncovered  

NASA Astrophysics Data System (ADS)

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

2010-07-01

435

Cooling Evolution of Hybrid Stars  

E-print Network

The cooling of compact isolated objects for different values of the gravitational mass has been simulated for two alternative assumptions. One is that the interior of the star is purely hadronic and second that the star can have a rather large quark core. It has been shown that within a nonlocal chiral quark model the critical density for a phase transition to color superconducting quark matter under neutron star conditions can be low enough for these phases to occur in compact star configurations with masses below 1.3 M_sun. For a realistic choice of parameters the equation of state (EoS) allows for 2SC quark matter with a large quark gap ~ 100 MeV for u and d quarks of two colors that coexists with normal quark matter within a mixed phase in the hybrid star interior. We argue that, if in the hadronic phase the neutron pairing gap in 3P_2 channel is larger than few keV and the phases with unpaired quarks are allowed, the corresponding hybrid stars would cool too fast. Even in the case of the essentially suppressed 3P_2 neutron gap if free quarks occur for M < 1.3 M_sun, as it follows from our EoS, one could not appropriately describe the neutron star cooling data existing by today. It is suggested to discuss a "2SC+X" phase, as a possibility to have all quarks paired in two-flavor quark matter under neutron star constraints, where the X-gap is of the order of 10 keV - 1 MeV. Density independent gaps do not allow to fit the cooling data. Only the presence of an X-gap that decreases with increase of the density could allow to appropriately fit the data in a similar compact star mass interval to that following from a purely hadronic model.

H. Grigorian

2005-02-28

436

Accreting neutron stars, black holes, and degenerate dwarf stars  

NASA Astrophysics Data System (ADS)

During the past 8 years, extended temporal and broadband spectroscopic studies carried out by X-ray astronomical satellites have led to the identification of specific compact X-ray sources as accreting neutron stars, black holes, and degenerate dwarf stars in close binary systems. Such sources provide a unique opportunity to study matter under extreme conditions not accessible in the terrestrial laboratory. Quantitative theoretical models have been developed which demonstrate that detailed studies of these sources will lead to a greatly increased understanding of dense and superdense hadron matter, hadron superfluidity, high-temperature plasma in superstrong magnetic fields, and physical processes in strong gravitational fields. Through a combination of theory and observation such studies will make possible the determination of the mass, radius, magnetic field, and structure of neutron stars and degenerate dwarf stars and the identification of further candidate black holes, and will contribute appreciably to our understanding of the physics of accretion by compact astronomical objects.

Pines, D.

1980-02-01

437

Sea Star Succumbing to Sea Star Wasting Disease  

USGS Multimedia Gallery

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

438

The Sun: Our Nearest Star  

NASA Technical Reports Server (NTRS)

We have in our celestial backyard, a prime example of a variable star. The Sun, long thought to be "perfect" and unvarying, began to reveal its cycles in the early 1600s as Galileo Galilei and Christoph Scheiner used a telescope to study sunspots. For the past four hundred years, scientists have accumulated data, showing a magnetic cycle that repeats, on average, every eleven (or twenty-two) years. In addition, modern satellites have shown that the energy output at radio and x-ray wavelengths also varies with this cycle. This talk will showcase the Sun as a star and discuss how solar studies may be used to understand other stars.

Adams, M. L.; Six, N. Frank (Technical Monitor)

2002-01-01

439

Neutron stars with dark energy  

NASA Astrophysics Data System (ADS)

After a short review on the possible experimental observations to verify pseudocomplex General Relativity, neutron stars as a particular object of interest are investigated. Dark energy is added to the structure of a neutron star, while for the nuclear part the chiral SU(3) model is used. For the coupling of matter to dark energy a special assumption is made. The consequences are discussed. We show that neutron stars of up to six solar masses are obtained, which already behave similar to a black hole.

Hess, P. O.; Rodríguez, I.; Greiner, W.; Boller, T.

2015-01-01

440

Infrared stars in binary systems  

NASA Technical Reports Server (NTRS)

The peculiar F-type supergiant HD 101584, which has a large and unusual infrared excess, is discussed along with the possibility that the infrared radiation could be accounted for by a cool companion. The peculiar F supergiants 89 Her, v Sgr, and R CrB are also considered as possible binary systems containing an infrared star. It is pointed out that all four of these stars have infrared excesses with characteristics similar to the infrared radiation from several cool objects which are known single stars.

Humphreys, R. M.; Ney, E. P.

1974-01-01

441

Star formation in dwarf galaxies  

NASA Astrophysics Data System (ADS)

In this thesis, we examine the star formation history and stellar feedback effects of dwarf galaxies under the influence of extragalactic ultraviolet radiation, as well as the evolution of residual gas within tidally-limited dwarf galaxies and globular clusters. Previous work has indicated that the background UV flux can easily ionize the gas within typical dwarf galaxies, delaying or even preventing cooling and star formation within them. Many dwarf galaxies within the Local Group are, however, observed to contain multiple generations of stars, the oldest of which formed in the early epochs of cosmic evolution, when the background UV flux was intense. In order to address this paradox, we consider the dynamical evolution of gas in dwarf galaxies using a one-dimensional, spherically symmetric, Lagrangian numerical scheme which also computes the effects of radiative transfer and photoionization. We include in the scheme a physically-motivated star formation recipe and consider the effects of feedback. This scheme allows us to follow the history of the gas and of star formation within dwarf galaxies, as influenced by both external and internal UV radiation. Our results indicate that star formation in the severe environment of dwarf galaxies is a difficult and inefficient process. In potentials with total mass less than a few 106 M? , and velocity dispersion less than a few km s-1 , residual gas is efficiently photoionized by cosmic background UV radiation. For intermediate mass systems, such as the dSphs around the Galaxy, star formation can proceed within early cosmic epochs despite the intense background UV flux. Triggering processes such as merger events, collisions, and tidal disturbance can lead to density enhancements, reducing the recombination timescale, allowing gas to cool and star formation to proceed. However, the star formation and gas retention efficiency may vary widely in galaxies with similar dark matter potentials, because they depend on many factors, such as the baryonic fraction, external perturbation, IMF, and background UV intensity. We suggest that the presence of very old stars in these dwarf galaxies indicates that their initial baryonic to dark matter content was comparable to the cosmic value. This constraint suggests that the initial density fluctuation of baryonic matter may be correlated with that of the dark matter. For the more massive dwarf elliptical galaxies, the star formation efficiency and gas retention rate is much higher. Their mass to light ratio is regulated by star formation feedback, and is expected to be nearly independent of their absolute luminosity. The results of our theoretical models reproduce the observed M/L - Mupsilon correlation. (Abstract shortened by UMI.)

Dong, Shawfeng

442

Doppler Imaging of Ap Stars  

E-print Network

Doppler imaging, a technique which inverts spectral line profile variations of an Ap star into a two-dimensional abundance maps, provides new observational constraints on diffusion mechanism in the presence of a global magnetic field. A programme is presented here with the aim to obtain abundance distributions of at least five elements on each star, in order to study how different diffusion processes act under influence of a stellar magnetic field. The importance of this multi-element approach is demonstrated, by presenting the abundance maps of helium, magnesium, silicon, chromium and iron for the magnetic B9pSi star CU Virginis.

R. Kuschnig

1998-05-06

443

Star polymers in correlated disorder  

E-print Network

We analyze the impact of a porous medium (structural disorder) on the scaling of the partition function of a star polymer immersed in a good solvent. We show that corresponding scaling exponents change if the disorder is long-range-correlated and calculate the exponents in the new universality class. A notable finding is that star and chain polymers react in qualitatively different manner on the presence of disorder: the corresponding scaling exponents increase for chains and decrease for stars. We discuss the physical consequences of this difference.

V. Blavats'ka; C. von Ferber; Yu. Holovatch

2007-11-23

444

Boson star and dark matter  

E-print Network

Bound states of complex scalar fields (boson stars) have long been proposed as possible candidates for the dark matter in the universe. Considerable work has already been done to study various aspects of boson stars. In the present work, assuming a particular anisotropic matter distribution, we solve the Einstein-Klein-Gordon equations with a cosmological constant to obtain bosonic configurations by treating the problem geometrically. The results are then applied to problems covering a wide range of masses and radii of the boson stars and the relevant self interaction parameters are calculated. We compare our results with earlier treatments to show the applicability of the geometrical approach.

R. Sharma; S. Karmakar; S. Mukherjee

2008-12-18

445

Spectrophotometry of three S stars and thirteen carbon N stars  

NASA Astrophysics Data System (ADS)

The absolute energy distributions in the visual spectra (lambdalambda 3200-7600 Angstroms) of 13 N carbon stars and three S stars have been investigated. The spectral resolution of the data is 50 Angstroms and the relative rms error is 2-5%. Our data supplement and extend the Almaty and other spectrophotometric catalogs that are lacking in these types of objects. The results can be compared with model atmospheres and also used in other studies.

Tereshchenko, V. M.

1999-08-01

446

Violent star and star cluster formation in nearby and distant galaxies  

E-print Network

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

Uta Fritze - v. Alvensleben

2005-09-14

447

Nucleosynthesis in AGB Stars John Lattanzio  

E-print Network

Nucleosynthesis in AGB Stars John Lattanzio Dept of Mathematics and Statistics, Monash University of the nucleosynthesis occurring in AGB stars. We the summarise some new calculations of intermediate mass stars which include all thermal pulses until the star is about to leave the AGB, as well as a detailed nucleosynthesis

Lattanzio, John

448

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

449

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

450

The life and death of star clusters  

Microsoft Academic Search

It is generally believed that most stars are born in groups and clusters, rather than in the field. In recent years it has been demonstrated that merging galaxies produce large numbers of young massive star clusters, sometimes called super star clusters. Understanding what triggers the formation of these young massive clusters provides important information about the formation of stars in

B. C. Whitmore

2007-01-01

451