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1

Customer-based discrimination against major league baseball players: Additional evidence from All-star ballots  

Microsoft Academic Search

This paper extends the analysis of [Hanssen, A., Andersen, T., 1999. Has discrimination lessened over time? A test using baseball's All-star vote. Economic Inquiry 37, 326–352] using All-star votes from 1990 through 2000 to investigate customer-based discrimination in Major League Baseball (MLB). The previous findings of no evidence of customer-based racial discrimination against minority players are confirmed. However, the evidence

Craig A. Depken II; Jon M. Ford

2006-01-01

2

All-stars adjustment method for the reduction of meridian and astrolabe catalogues  

Microsoft Academic Search

We present an all-stars adjustment method for the reduction of preliminary meridian and astrolabe catalogues. After correcting for precession, nutation, aberration and proper motion, all the observed times are reduced to those relative to the mean positions at one chosen day near the beginning of the year using stars common to different observing days as links, so finding directly the

Yu Fan; Min-Hui Du; Wei Mao; Yu-Di Zhou; Yao Zhang

1989-01-01

3

Sodium laser guide star results at the Lick Observatory  

SciTech Connect

Results of return signal level and guide star spot size for a sodium laser guide star recently installed at the Lick Observatory are presented. Operational characteristics of frequency stability, amplitude stability, and pointing accuracy are discussed.

Friedman, H.; Erbert, G.; Kuklo, T. [and others

1995-10-01

4

Measurements of the Lick Observatory Sodium Laser Guide Star  

SciTech Connect

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

Gavel, D. T., LLNL

1998-03-01

5

Performance of laser guide star adaptive optics at Lick Observatory  

SciTech Connect

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

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

1995-07-19

6

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

SciTech Connect

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

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

1995-11-08

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

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

E-print Network

We present FEROS--Lick/SDSS, an empirical database of Lick/SDSS spectral indices of FGK stars to be used in population synthesis projects for discriminating different stellar populations within the integrated light of galaxies and globular clusters. From about 2500 FEROS stellar spectra obtained from the ESO Science Archive Facility we computed line--strength indices for 1085 non--supergiant stars with atmospheric parameter estimates from the AMBRE project. Two samples of 312 {\\it dwarfs} and of 83 {\\it subgiants} with solar chemical composition and no significant $\\alpha$--element abundance enhancement are used to compare their observational indices with the predictions of the Lick/SDSS library of synthetic indices. In general, the synthetic library reproduces very well the behaviour of observational indices as a function of temperature, but in the case of low temperature ($T_{\\rm eff}$ $\\lesssim $5000\\,K) dwarfs; low temperature subgiants are not numerous enough to derive any conclusion. Several possible ca...

Franchini, M; Di Marcantonio, P; Malagnini, M L; Chavez, M

2014-01-01

9

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

10

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

11

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

12

Documentation for the Machine-Readable Version of the Lick Saturn-Voyager Reference Star Catalogue.  

National Technical Information Service (NTIS)

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 ...

W. H. Warren

1982-01-01

13

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

14

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

SciTech Connect

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

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

2012-09-01

15

Calibrating GMOS Spectra to the Lick/IDS Index System  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

16

ALLStars: Overcoming Multi-Survey Selection Bias using Crowd-Sourced Active Learning  

NASA Astrophysics Data System (ADS)

Developing a multi-survey time-series classifier presents several challenges. One problem is overcoming the sample selection bias which arises when the instruments or observing cadences differ between the training and testing datasets. In this case, the probabilistic distributions characterizing the sources in the training survey dataset differ from the source distributions in the other survey, resulting in poor results when a classifier is naively applied. To resolve this, we have developed the ALLStars active learning framework which allows us to bootstrap a classifier onto a new survey using a small set of optimally chosen sources which are then presented to users for manual classification. Several iterations of this crowd-sourcing process results in a significantly improved classifier. Using this procedure, we have built a variable star light-curve classifier using OGLE, Hipparcos, and ASAS survey data.

Starr, D. L.; Richards, J. W.; Brink, H.; Miller, A. A.; Bloom, J. S.; Butler, N. R.; James, J. B.; Long, J. P.

2012-09-01

17

Performance of adaptive optics at Lick Observatory  

NASA Astrophysics Data System (ADS)

A prototype adaptive optics system has been developed at Lawrence Livermore National Laboratory for use at Lick Observatory. This system is based on an ITEK 69-actuator continuous-surface deformable mirror, a Kodak fast-framing intensified CCD camera, and a Mercury VME board containing four Intel i860 processors. The system has been tested using natural reference stars on the 40-inch Nickel telescope at Lick Observatory yielding up to a factor of 10 increase in image peak intensity and a factor of 6 reduction in image full width at half maximum. These results are consistent with theoretical expectations.

Olivier, Scot S.; An, Jong; Avicola, Kenneth; Bissinger, Horst D.; Brase, James M.; Friedman, Herbert W.; Gavel, Donald T.; Johansson, Erik M.; Max, Claire E.; Waltjen, Kenneth E.; Fisher, William A.; Bradford, William

1994-05-01

18

Performance of adaptive optics at Lick Observatory  

Microsoft Academic Search

A prototype adaptive optics system has been developed at Lawrence Livermore National Laboratory for use at Lick Observatory. This system is based on an ITEK 69-actuator continuous-surface deformable mirror, a Kodak fast-framing intensified CCD camera, and a Mercury VME board containing four Intel i860 processors. The system has been tested using natural reference stars on the 40-inch Nickel telescope at

Scot S. Olivier; Jong An; Kenneth Avicola; Horst D. Bissinger; James M. Brase; Herbert W. Friedman; Donald T. Gavel; Erik M. Johansson; Claire E. Max; Kenneth E. Waltjen; William A. Fisher; William Bradford

1994-01-01

19

Performance of adaptive optics at Lick Observatory  

SciTech Connect

A prototype adaptive optics system has been developed at Lawrence Livermore National Laboratory (LLNL) for use at Lick Observatory. This system is based on an ITEX 69-actuator continuous-surface deformable mirror, a Kodak fast-framing intensified CCD camera, and a Mercury VME board containing four Intel i860 processors. The system has been tested using natural reference stars on the 40-inch Nickel telescope at Lick Observatory yielding up to a factor of 10 increase in image peak intensity and a factor of 6 reduction in image full width at half maximum (FWHM). These results are consistent with theoretical expectations. In order to improve performance, the intensified CCD camera will be replaced by a high-quantum-efficiency low-noise fast CCD camera built for LLNL by Adaptive Optics Associates using a chip developed by Lincoln Laboratory, and the 69-actuator deformable mirror will be replaced by a 127-actuator deformable mirror developed at LLNL. With these upgrades, the system should perform well in median seeing conditions on the 120-inch Shane telescope for observing wavelengths longer than {approximately}1 {mu}m and using natural reference stars brighter than m{sub R} {approximately} 10 or using the laser currently being developed at LLNL for use at Lick Observatory to generate a sodium-layer reference star.

Olivier, S.S.; An, J.; Avicola, K. [Lawrence Livermore National Lab., CA (United States)] [and others

1994-03-01

20

Rise and fall of stars: Investigating the evolution of star status in professional team sports  

Microsoft Academic Search

This article describes an empirical study of the rise and fall of star athletes, using data from the National Basketball Association (NBA) from 1987 to 2008. We measure star status by the number and share of all-star votes, and we apply both Tobit regression and hazard models to investigate the determining factors for star status. We find that the attainment

Yupin Yang; Mengze Shi

21

Progress with the lick adaptive optics system  

SciTech Connect

Progress and results of observations with the Lick Observatory Laser Guide Star Adaptive Optics System are presented. This system is optimized for diffraction-limited imaging in the near infrared, 1-2 micron wavelength bands. We describe our development efforts in a number of component areas including, a redesign of the optical bench layout, the commissioning of a new infrared science camera, and improvements to the software and user interface. There is also an ongoing effort to characterize the system performance with both natural and laser guide stars and to fold this data into a refined system model. Such a model can be used to help plan future observations, for example, predicting the point-spread function as a function of seeing and guide star magnitude.

Gavel, D T; Olivier, S S; Bauman, B; Max, C E; Macintosh, B

2000-03-01

22

Adaptive Optics Performance at Lick and Keck Observatory  

Microsoft Academic Search

The performance of an adaptive optics system developed for the 40 inch Nickel and 120 inch Shane telescopes at Lick Observatory is discussed. The system is based on a 69 actuator continuous-surface deformable mirror and a Hartmann wavefront sensor equipped with a commercial intensified CCD fast-framing camera. Results from tests of this adaptive optics system using natural reference stars on

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

1993-01-01

23

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

24

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

25

IRCAL : The infrared camera for adaptive optics at Lick Observatory  

E-print Network

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

Lloyd, James P.

26

Geology of the Lick Observatory Quadrangle, California  

Microsoft Academic Search

The Lick Observatory 7.5-minute quadrangle exposes evidence of geologic events that range from subduction of Mesozoic Franciscan Complex, through accumulation of marine Miocene porcellanite and clastics, to the development of the San Andreas fault system and deformation within it. The active Calaveras fault zone, with its linear valleys and subparallel strike-slip strands, transects the quadrangle and, northwest of San Filipe

Benjamin M. Page

1999-01-01

27

University of Toronto Scarborough, Department of Athletics and Recreation UNIVERSITY ALL-STAR CAMPS for KiDs  

E-print Network

Camper Pick-Up 4:30 - 6:00 pm Extended Care Only What to Bring? Come in play clothes, running shoes with a light coloured hat, sunscreen, snack and an athletic type water bottle (with name on it, dress comfortably for sporting activities. Remember: If you are not taking advantage of our meal plan

Boonstra, Rudy

28

ECOLOGICAL IMPORTANCE OF LICKS TO FOUR UNGULATE SPECIES IN NORTH-CENTRAL BRITISH COLUMBIA  

E-print Network

ECOLOGICAL IMPORTANCE OF LICKS TO FOUR UNGULATE SPECIES IN NORTH-CENTRAL BRITISH COLUMBIA by Jeremy) THE UNIVERSITY OF NORTHERN BRITISH COLUMBIA June 2004 © Jeremy B. Ayotte, 2004 #12;ii ABSTRACT Elemental at two wet licks and three dry licks in the Tuchodi watershed, north-central British Columbia. Three

Bolch, Tobias

29

CCD Data Acquisition Systems at Lick and Keck Observatories  

Microsoft Academic Search

This paper describes the evolution of the existing CCD Data Acquisition System (DAS) at Lick Observatory, and its influence on the design of the CCD DAS currently under development for Keck Observatory. Tradeoffs between various types of interfaces between instrument computers and CCD controllers are also explored.

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

1993-01-01

30

Proposed Multiconjugate Adaptive Optics Experiment at Lick Observatory  

SciTech Connect

While the theory behind design of multiconjugate adaptive optics (MCAO) systems is growing, there is still a paucity of experience building and testing such instruments. We propose using the Lick adaptive optics (AO) system as a basis for demonstrating the feasibility/workability of MCAO systems, testing underlying assumptions, and experimenting with different approaches to solving MCAO system issues.

Bauman, B J; Gavel, D T; Flath, L M; Hurd, R L; Max, C E; Olivier, S S

2001-08-15

31

Characterization of the Lick adaptive optics point spread function  

Microsoft Academic Search

We have investigated both the temporal and spatial structure of the point spread function (PSF) produced by the Lick Observatory adaptive optics (AO) system using the FastSub readout mode of the IRCAL camera using short-exposure images with exposure times of 22ms at a frame rate of ~ 20Hz suitable for \\

Szymon Gladyszab; Julian C. Christou; Michael Redfern

2006-01-01

32

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

33

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

SciTech Connect

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

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

2009-10-01

34

Remote observing with the Nickel Telescope at Lick Observatory  

NASA Astrophysics Data System (ADS)

We describe a project to enable remote observing on the Nickel 1-meter Telescope at Lick Observatory. The purpose was to increase the subscription rate and create more economical means for graduate- and undergraduate students to observe with this telescope. The Nickel Telescope resides in a 125 year old dome on Mount Hamilton. Remote observers may work from any of the University of California (UC) remote observing facilities that have been created to support remote work at both Keck Observatory and Lick Observatory. The project included hardware and software upgrades to enable computer control of all equipment that must be operated by the astronomer; a remote observing architecture that is closely modeled on UCO/Lick's work to implement remote observing between UC campuses and Keck Observatory; new policies to ensure safety of Observatory staff and equipment, while ensuring that the telescope subsystems would be suitably configured for remote use; and new software to enforce the safety-related policies. The results increased the subscription rate from a few nights per month to nearly full subscription, and has spurred the installation of remote observing sites at more UC campuses. Thanks to the increased automation and computer control, local observing has also benefitted and is more efficient. Remote observing is now being implemented for the Shane 3- meter telescope.

Grigsby, Bryant; Chloros, Konstantinos; Gates, John; Deich, William T. S.; Gates, Elinor; Kibrick, Robert

2008-07-01

35

The Lick AGN Monitoring Project 1. Introduction, Goals, and Observations  

NASA Astrophysics Data System (ADS)

Reverberation mapping has been the most powerful tool for measurement of the structure of AGN broad-line regions and measurement of the masses of black holes in broad-lined active galaxies, and it provides the fundamental calibration for secondary techniques used to estimate black hole masses in distant AGNs. The sample of galaxies having high-quality reverberation data has only increased slowly in recent years, however, because of the logistical difficulty of carrying out the long observing campaigns necessary to measure emission-line and continuum variability in AGNs. In order to expand the sample of nearby AGNs having reverberation data, especially in the low-mass regime, we designed and carried out the Lick AGN Monitoring Project. We selected a sample of 13 nearby Seyfert 1 galaxies having expected H-beta lag times of 3-14 days, and expected black hole masses between 10^6 and 3*10^7 solar masses. Our spectroscopic monitoring campaign consisted of 64 mostly-consecutive nights on the Lick 3-meter Shane telescope in Spring 2008; this represents the largest allocation of nights to a single observing program in a single semester at Lick. Imaging observations were also obtained for photometric monitoring of continuum variability during the campaign. In this contribution, we will describe the survey goals, sample selection, and observational strategy for the reverberation campaign.

Barth, Aaron J.; LAMP Collaboration

2009-01-01

36

ALLSTAR Network: FIU  

NSDL National Science Digital Library

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

1995-01-01

37

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

38

Nutrition or detoxification: why bats visit mineral licks of the Amazonian rainforest.  

PubMed

Many animals in the tropics of Africa, Asia and South America regularly visit so-called salt or mineral licks to consume clay or drink clay-saturated water. Whether this behavior is used to supplement diets with locally limited nutrients or to buffer the effects of toxic secondary plant compounds remains unclear. In the Amazonian rainforest, pregnant and lactating bats are frequently observed and captured at mineral licks. We measured the nitrogen isotope ratio in wing tissue of omnivorous short-tailed fruit bats, Carollia perspicillata, and in an obligate fruit-eating bat, Artibeus obscurus, captured at mineral licks and at control sites in the rainforest. Carollia perspicillata with a plant-dominated diet were more often captured at mineral licks than individuals with an insect-dominated diet, although insects were more mineral depleted than fruits. In contrast, nitrogen isotope ratios of A. obscurus did not differ between individuals captured at mineral lick versus control sites. We conclude that pregnant and lactating fruit-eating bats do not visit mineral licks principally for minerals, but instead to buffer the effects of secondary plant compounds that they ingest in large quantities during periods of high energy demand. These findings have potential implications for the role of mineral licks for mammals in general, including humans. PMID:18431492

Voigt, Christian C; Capps, Krista A; Dechmann, Dina K N; Michener, Robert H; Kunz, Thomas H

2008-01-01

39

SNAPSHOT METALLICITY ESTIMATE OF RESOLVED STELLAR SYSTEMS THROUGH LICK Fe5270 DIAGNOSTIC  

SciTech Connect

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

Buzzoni, A. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna (Italy); Bertone, E.; Chavez, M., E-mail: alberto.buzzoni@oabo.inaf.i [INAOE-Instituto Nacional de AstrofIsica Optica y Electronica, Luis Enrique Erro 1, 72840 Tonantzintla, Puebla (Mexico)

2009-10-01

40

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

PubMed

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

2009-01-30

41

Coal handling\\/The Licking River Terminal: a showcase in coal handling  

Microsoft Academic Search

Oglebay Norton Co.'s new Licking River Terminal near Cincinnati is moving low-sulfur Kentucky coal onto barge fleets plying the Ohio River to serve electric power generating stations. The Louisville and Nashville Railroad hauls coal some 250 to 300 mi from the Harlan and the Hazard coalfields to the DeCoursey yard three miles from the Licking River Terminal, delivering the coal

Yewell

1978-01-01

42

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

43

Head rubbing and licking reinforce social bonds in a group of captive African lions, Panthera leo.  

PubMed

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

44

IV nicotine self-administration in rats using the consummatory operant licking response.  

PubMed

Nicotine self-administered by tobacco smoking or chewing is very addictive in humans. Rat models have been developed in which nicotine is self-administered IV by the rats pressing a lever. However the reinforcing value of nicotine is much less in these models than the addictiveness of human tobacco use would indicate. The IV nicotine self-administration operant lever press model does not fully capture important aspects of tobacco use in humans. Conditioned oral consumption actions of smoking or chewing tobacco may play important roles in tobacco addiction. Neural circuitry underlying essential food consummatory responses may facilitate consummatory aspects of tobacco intake. To capture this motor consummatory aspect of tobacco addiction in the rat model of nicotine self-administration, we have developed a method of using a licking response instead of a lever press to self-administer IV nicotine. Sprague-Dawley rats were trained to lick one of two waterspouts for IV nicotine (0.03mg/kg/infusion). With the licking response rats self-administered stable nicotine levels throughout 24 sessions (45min each) of testing. The number of total licks/session significantly increased in a linear fashion over that period. The number of licks/infusion was substantial, rising steadily with training to an average of over 100 licks/infusion. Including the consummatory motor act with nicotine self-administration could help better model the compulsive aspects of tobacco addiction in humans. PMID:20804779

Levin, Edward D; Hampton, Dawn; Rose, Jed E

2010-12-01

45

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

46

Keepers of the double stars  

NASA Astrophysics Data System (ADS)

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

Tenn, Joseph S.

2013-03-01

47

Localization of the central rhythm generator involved in spontaneous consummatory licking in rats: functional ablation and electrical brain stimulation studies.  

PubMed Central

Localization of the central rhythm generator (CRG) of spontaneous consummatory licking was studied in freely moving rats by microinjection of tetrodotoxin (TTX) into the pontine reticular formation. Maximum suppression of spontaneous water consumption was elicited by TTX (1 ng) blockade of the oral part of the nucleus reticularis gigantocellularis (NRG), whereas TTX injections into more caudal or rostral locations caused significantly weaker disruption of drinking. To verify the assumption that TTX blocked the proper CRG of licking rather than some relay in its output, spontaneously drinking thirsty rats were intracranially stimulated via electrodes chronically implanted into the oral part of the NRG. Lick-synchronized stimulation (a 100-ms train of 0.1-ms-wide rectangular pulses at 100 Hz and 25-150 microA) applied during continuous licking (after eight regular consecutive licks) caused a phase shift of licks emitted after stimulus delivery. The results suggest that the stimulation has reset the CRG of licking without changing its frequency. The reset-inducing threshold current was lowest during the tongue retraction and highest during the tongue protrusion period of the lick cycle. It is concluded that the CRG of licking is located in the oral part of NRG. PMID:8622936

Brozek, G; Zhuravin, I A; Megirian, D; Bures, J

1996-01-01

48

Three Instruments in Four Years: The UCO/Lick Data-Driven Toolkit  

NASA Astrophysics Data System (ADS)

A panoply of new software tools has accompanied the rapid instrument construction schedule at UCO/Lick Observatory (PFCAM to Lick in 1997, ESI to Keck in 1999, DEIMOS to Keck in 2000). These Tcl/Tk-based tools maintain and interact with a relational database of instrument characteristics. They assist software design, generate thousands of lines of code, documentation, and configuration files, facilitate motor-control calibration, permit fully-automated remote testing and evaluation of performance, aid user-interface design, produce diagrams, and serve as a communications nexus between software and hardware teams. The toolkit has greatly reduced the amount of effort required from many UCO/Lick technicians, and has set new standards for quality and performance of the resulting instruments. We present here an overview of these tools and their outputs.

Allen, S. L.; Clarke, D. A.

49

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

50

Reconstruction of a nonhealing lick granuloma in a dog using a phalangeal fillet technique.  

PubMed

A 6.5-year-old, castrated male Dalmatian was presented with a 3-month history of a chronic, nonhealing wound related to a previously excised lick granuloma. Reconstruction of the wound on the lateral metatarsal region was achieved using a phalangeal fillet technique, without digital pad transposition. The skin flap healed successfully with very good cosmetic and functional results. PMID:17823479

Demetriou, Jackie L; Shales, Christopher J; Hamilton, Michael H; Sissener, Thomas R

2007-01-01

51

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

USGS Publications Warehouse

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

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

1963-01-01

52

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

53

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

NASA Astrophysics Data System (ADS)

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

Malville, J. McKim; Pearson, John

2012-09-01

54

Hamilton Jeffers and the Double Star Catalogues  

NASA Astrophysics Data System (ADS)

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

Tenn, Joseph S.

2013-01-01

55

APF-The Lick Observatory Automated Planet Finder  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

56

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

Microsoft Academic Search

Because licking and grooming behavior of dams with pups can influence some behaviors of pups when they are adults, we tested if licking and grooming scores in a maternal separation protocol correlated with cocaine or ethanol self-administration in the pups as adults. The protocol produced litters that were separated from dams for 0 (MS0), 15 (MS15) or 180 (MS180) min,

D. D. Francis; M. J. Kuhar

2008-01-01

57

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

58

Diversity,distribution, and abundance of ground dwelling spiders at Lick Creek Park, College Station, Texas  

E-print Network

DIVERSITY, DISTRIBUTION, AND ABUNDANCE OF GROUND DWELLING SPIDERS AT LICK CREEK PARK, COLLEGE STATION, TEXAS A Thesis by TAKESHA YVONNE HENDERSON Submitted to the Office of Graduate Studies of Texas A&M University in partial... by TAKESHA YVONNE HENDERSON Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair of Committee, Marvin Harris Committee...

Henderson, Takesha Yvonne

2009-06-02

59

Stability Analysis of the Planetary System Orbiting upsilo Andromedae. II. Simulations Using New Lick Observatory Fits  

Microsoft Academic Search

We present results of long-term numerical orbital integrations designed to test the stability of the three-planet system orbiting upsilo Andromedae and short-term integrations to test whether mutual perturbations among the planets can be used to determine planetary masses. Our initial conditions are based on recent fits to the radial velocity data obtained by the planet search group at Lick Observatory.

Jack J. Lissauer; Eugenio J. Rivera

2001-01-01

60

VIRIS: A Visual-Infrared Imaging System for the Lick Observatory 1-M Telescope  

E-print Network

We describe a system in use at the Lick Observatory 1-m Nickel telescope for near-simultaneous imaging at optical and near-infrared wavelengths. The combined availability of a CCD and a NICMOS-3 camera makes the system well-suited for photometric monitoring from 0.5-2.2 microns of a variety of astrophysical objects. Our science program thus far has concentrated on studying variability trends in young stellar objects.

James R. Graham; Lynne A. Hillenbrand; Anthony A. Misch

1998-02-20

61

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

PubMed Central

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

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

2013-01-01

62

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

63

Searching for Planets Around other Stars  

NASA Technical Reports Server (NTRS)

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

1998-01-01

64

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

65

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

66

Gender, culture, and astrophysical fieldwork: Elizabeth Campbell and the Lick Observatory-Crocker eclipse expeditions.  

NASA Astrophysics Data System (ADS)

The article is organized as follows. It begins with an overview of women in nineteenth-century American science. It then describes the culture of mountaintop observatories and life on Mount Hamilton. Elizabeth Campbell's unique role in the Crocker-Lick expeditions drew upon her equally unique role in the observatory, and also on the meaning given to women's work in general on the mountain. The bulk of the article focuses on the Campbells and their expeditions to India in 1898, Spain in 1905, and the South Pacific in 1908. The third section compares the Lick Observatory expeditions to those conducted by David Todd of Amherst College. Todd's wife, Mabel Loomis Todd, went into the field several times with her husband, but her place in the field was radically different from Elizabeth Campbell's, a difference that can be ascribed to a combination of local culture and personality. Finally, it compares American expeditions to British expeditions of the period, to see what the absence of British women on expeditions can tell us about the way national scientific styles and cultures affected gender roles in science.

Pang, A. S.-K.

67

Characterization of hind paw licking and lifting to noxious radiant heat in the rat with and without chronic inflammation  

Microsoft Academic Search

The paw withdrawal latency to thermal radiant heat stimuli is a widely used nociceptive measure to study hyperalgesic mechanisms. In the present study, in addition to the paw withdrawal latency, two behavioral components of pain behaviors, paw licking and paw lifting have been characterized and quantified. The thermal stimuli were successively applied to the plantar surface of the rat hind

Bopaiah Pooviah Cheppudira

2006-01-01

68

The helium abundances in HgMn and normal stars  

E-print Network

The parameter-free model of diffusion in the atmospheres of HgMn stars (Michaud 1986; Michaud et al 1979) predicts that helium should sink below the He II ionization zone in order that diffusion of other elements may take place, and that all HgMn stars should have deficits of helium in their photospheres, with a minimum deficit of 0.3 dex. In this study, the Smith & Dworetsky (1993) sample of HgMn stars and normal comparison stars is examined, and the helium abundances determined by spectrum synthesis using echelle spectra taken at Lick Observatory and the AAT. The prediction is confirmed; all HgMn stars are deficient in He by as much as 1.5 dex. Also, two HgMn stars, HR7361 and HR7664, show clear evidence of helium stratification.

M. M. Dworetsky

2004-07-26

69

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

SciTech Connect

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

Max, C. E., LLNL

1997-06-01

70

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

E-print Network

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

2014-01-01

71

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

72

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

73

THE LICK AGN MONITORING PROJECT: PHOTOMETRIC LIGHT CURVES AND OPTICAL VARIABILITY CHARACTERISTICS  

SciTech Connect

The Lick AGN Monitoring Project targeted 13 nearby Seyfert 1 galaxies with the intent of measuring the masses of their central black holes using reverberation mapping. The sample includes 12 galaxies selected to have black holes with masses roughly in the range 10{sup 6}-10{sup 7} M {sub sun}, as well as the well-studied active galactic nucleus (AGN) NGC 5548. In conjunction with a spectroscopic monitoring campaign, we obtained broadband B and V images on most nights from 2008 February through 2008 May. The imaging observations were carried out by four telescopes: the 0.76 m Katzman Automatic Imaging Telescope, the 2 m Multicolor Active Galactic Nuclei Monitoring telescope, the Palomar 60 inch (1.5 m) telescope, and the 0.80 m Tenagra II telescope. Having well-sampled light curves over the course of a few months is useful for obtaining the broad-line reverberation lag and black hole mass, and also allows us to examine the characteristics of the continuum variability. In this paper, we discuss the observational methods and the photometric measurements, and present the AGN continuum light curves. We measure various variability characteristics of each of the light curves. We do not detect any evidence for a time lag between the B- and V-band variations, and we do not find significant color variations for the AGNs in our sample.

Walsh, Jonelle L.; Bentz, Misty C.; Barth, Aaron J. [Department of Physics and Astronomy, University of California at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4574 (United States); Minezaki, Takeo; Sakata, Yu; Yoshii, Yuzuru [Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Baliber, Nairn; Bennert, Vardha Nicola; Street, Rachel A.; Treu, Tommaso [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Li Weidong; Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, MS 169-527, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Brown, Timothy M. [Las Cumbres Observatory Global Telescope, 6740 Cortona Dr. Ste. 102, Goleta, CA 93117 (United States); Canalizo, Gabriela [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Gates, Elinor L. [Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States); Greene, Jenny E. [Princeton University Observatory, Princeton, NJ 08544 (United States); Malkan, Matthew A.; Woo, Jong-Hak [Department of Physics and Astronomy, University of California, Los Angeles, CA 90024 (United States)], E-mail: jlwalsh@uci.edu

2009-11-01

74

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

SciTech Connect

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

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

2010-11-01

75

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

76

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

E-print Network

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

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

2011-01-01

77

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

78

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

Microsoft Academic Search

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

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

1997-01-01

79

Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants  

Microsoft Academic Search

We report precision Doppler measurements of three intermediate-mass subgiants obtained at Lick and Keck Observatories. All three stars show variability in their radial velocities consistent with planet-mass companions in Keplerian orbits. We find a planet with a minimum mass MPsini=2.5 MJ in a 351.5 day orbit around HD 192699, a planet with a minimum mass of 2.0 MJ in a

John Asher Johnson; Debra A. Fischer; Geoffrey W. Marcy; Jason T. Wright; Peter Driscoll; R. Paul Butler; Saskia Hekker; Sabine Reffert; Steven S. Vogt

2007-01-01

80

The Lick AGN Monitoring Project: Recalibrating Single-epoch Virial Black Hole Mass Estimates  

NASA Astrophysics Data System (ADS)

We investigate the calibration and uncertainties of black hole (BH) mass estimates based on the single-epoch (SE) method, using homogeneous and high-quality multi-epoch spectra obtained by the Lick Active Galactic Nucleus (AGN) Monitoring Project for nine local Seyfert 1 galaxies with BH masses <108 M ?. By decomposing the spectra into their AGNs and stellar components, we study the variability of the SE H? line width (full width at half-maximum intensity, FWHMH? or dispersion, ?H?) and of the AGN continuum luminosity at 5100 Å (L 5100). From the distribution of the "virial products" (vprop FWHMH? 2 L 0.5 5100 or ?H? 2 L 0.5 5100) measured from SE spectra, we estimate the uncertainty due to the combined variability as ~0.05 dex (12%). This is subdominant with respect to the total uncertainty in SE mass estimates, which is dominated by uncertainties in the size-luminosity relation and virial coefficient, and is estimated to be ~0.46 dex (factor of ~3). By comparing the H? line profile of the SE, mean, and root-mean-square (rms) spectra, we find that the H? line is broader in the mean (and SE) spectra than in the rms spectra by ~0.1 dex (25%) for our sample with FWHMH? <3000 km s-1. This result is at variance with larger mass BHs where the difference is typically found to be much less than 0.1 dex. To correct for this systematic difference of the H? line profile, we introduce a line-width dependent virial factor, resulting in a recalibration of SE BH mass estimators for low-mass AGNs.

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

2012-03-01

81

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

82

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...

Dworetsky, M M; Patel, K

2008-01-01

83

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

84

THE LICK AGN MONITORING PROJECT: REVERBERATION MAPPING OF OPTICAL HYDROGEN AND HELIUM RECOMBINATION LINES  

SciTech Connect

We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3 m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range {approx}10{sup 6}-10{sup 7} M{sub sun} and also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to allow for a time lag to be measured between the continuum fluctuations and the response to these fluctuations in the broad H{beta} emission, which we have previously reported. We present here the light curves for the H{alpha}, H{gamma}, He II {lambda}4686, and He I {lambda}5876 emission lines and the time lags for the emission-line responses relative to changes in the continuum flux. Combining each emission-line time lag with the measured width of the line in the variable part of the spectrum, we determine a virial mass of the central supermassive black hole from several independent emission lines. We find that the masses are generally consistent within the uncertainties. The time-lag response as a function of velocity across the Balmer line profiles is examined for six of the AGNs. We find similar responses across all three Balmer lines for Arp 151, which shows a strongly asymmetric profile, and for SBS 1116+583A and NGC 6814, which show a symmetric response about zero velocity. For the other three AGNs, the data quality is somewhat lower and the velocity-resolved time-lag response is less clear. Finally, we compare several trends seen in the data set against the predictions from photoionization calculations as presented by Korista and Goad. We confirm several of their predictions, including an increase in responsivity and a decrease in the mean time lag as the excitation and ionization level for the species increases. Specifically, we find the time lags of the optical recombination lines to have weighted mean ratios of {tau}(H{alpha}):{tau}(H{beta}):{tau}(H{gamma}):{tau}(He I):{tau}(He II) = 1.54:1.00:0.61:0.36:0.25. Further confirmation of photoionization predictions for broad-line gas behavior will require additional monitoring programs for these AGNs while they are in different luminosity states.

Bentz, Misty C.; Walsh, Jonelle L.; Barth, Aaron J.; Thornton, Carol E. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697 (United States); Yoshii, Yuzuru; Sakata, Yu; Minezaki, Takeo [Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Woo, Jong-Hak; Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90024 (United States); Wang, Xiaofeng; Steele, Thea N.; Silverman, Jeffrey M.; Serduke, Frank J. D.; Li, Weidong; Lee, Nicholas [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Treu, Tommaso; Street, Rachel A.; Hidas, Marton G. [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Hiner, Kyle D. [Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521 (United States); Greene, Jenny E., E-mail: mbentz@uci.ed [Princeton University Observatory, Princeton, NJ 08544 (United States)

2010-06-20

85

Manganese Abundances in Cluster and Field Stars  

E-print Network

We have derived Mn abundances for more than 200 stars in 19 globular clusters. In addition, Mn abundance determinations have been made for a comparable number of halo field and disk stars possessing an overlapping range of metallicities and stellar parameters. Our primary data set was comprised of high resolution spectra previously acquired at the McDonald, Lick and Keck Observatories. To enlarge our data pool, we acquired globular and open cluster spectra from several other investigators. Data were analyzed using synthetic spectra of the 6000 \\AA Mn I triplet. Hyperfine structure parameters were included in the synthetic spectra computations. Our analysis shows that for the metallicity range $-0.7>$[Fe/H]$>$$-$2.7 stars of 19 globular clusters have a a mean relative abundance of $$= $-0.37\\pm0.01$ ($\\sigma$ = 0.10), a value in agreement with that of the field stars: $$= $-0.36\\pm0.01$ ($\\sigma$ = 0.08). Despite the 2 orders of magnitude span in metallicity, the $$ ratio remains constant in both stellar populations. Our Mn abundance data indicate that there is no appreciable variation in the relative nucleosynthetic contribution from massive stars that undergo core-collapse supernovae and thus, no significant change of the associated initial mass function in the specified metallicity range.

J. S. Sobeck; I. I. Ivans; J. A. Simmerer; C. Sneden; P. Hoeflich; J. P. Fulbright; R. P. Kraft

2006-04-28

86

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

PubMed

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

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

2006-03-01

87

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

88

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

Microsoft Academic Search

Three yearling lambs with a rumen cannula were used to investigate the effects of supplementation with an urea-minerals lick block (ULB) on the kinetics of ruminal fibre digestion, nutrient digestibility and nitrogen (N) utilization of rice straw (RS), ammonia bicarbonate (AB)-treated RS (ABRS) and hay prepared from natural pasture. The digestibility of dry matter and organic matter of RS increased

WU Yue-ming; HU Wei-lian; LIU Jian-xin

2005-01-01

89

Precise radial velocities of giant stars. V. A brown dwarf and a planet orbiting the K giant stars ? Geminorum and 91 Aquarii  

NASA Astrophysics Data System (ADS)

Aims: We aim to detect and characterize substellar companions to K giant stars to further our knowledge of planet formation and stellar evolution of intermediate-mass stars. Methods: For more than a decade we have used Doppler spectroscopy to acquire high-precision radial velocity measurements of K giant stars. All data for this survey were taken at Lick Observatory. Our survey includes 373 G and K giants. Radial velocity data showing periodic variations were fitted with Keplerian orbits using a ?2 minimization technique. Results: We report the presence of two substellar companions to the K giant stars ? Gem and 91 Aqr. The brown dwarf orbiting ? Gem has an orbital period of 305.5 ± 0.1 days, a minimum mass of 20.6 MJ, and an eccentricity of 0.031 ± 0.009. The planet orbiting 91 Aqr has an orbital period of 181.4 ± 0.1 days, a minimum mass of 3.2 MJ, and an eccentricity of 0.027 ± 0.026. Both companions have exceptionally circular orbits for their orbital distance, as compared to all previously discovered planetary companions. Based on observations collected at Lick Observatory, University of California, and at the European Southern Observatory, Chile, under program IDs 088.D-0132, 089.D-0186, and 090.D-0155.Appendices are available in electronic form at http://www.aanda.org

Mitchell, David S.; Reffert, Sabine; Trifonov, Trifon; Quirrenbach, Andreas; Fischer, Debra A.

2013-07-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

91

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

SciTech Connect

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

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

1997-09-12

92

Stars and Star Myths.  

ERIC Educational Resources Information Center

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

Eason, Oliver

93

PRECISE DOPPLER MONITORING OF BARNARD'S STAR  

SciTech Connect

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

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

2013-02-20

94

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

95

Absolute Spectrophotometry of 237 Open Cluster Stars  

NASA Astrophysics Data System (ADS)

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

Clampitt, L.; Burstein, D.

1994-12-01

96

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

97

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

Microsoft Academic Search

Three yearling lambs with a rumen cannula were used to investigate the effects of supplementation with an urea-minerals lick\\u000a block (ULB) on the kinetics of ruminal fibre digestion, nutrient digestibility and nitrogen (N) utilization of rice straw\\u000a (RS), ammonia bicarbonate (AB)-treated RS (ABRS) and hay prepared from natural pasture. The digestibility of dry matter and\\u000a organic matter of RS increased

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

2005-01-01

98

Massive binary stars as a probe of massive star formation  

NASA Astrophysics Data System (ADS)

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

Kiminki, Daniel C.

2010-10-01

99

Maternal licking regulates hippocampal glucocorticoid receptor transcription through a thyroid hormone-serotonin-NGFI-A signalling cascade  

PubMed Central

Variations in parental care direct phenotypic development across many species. Variations in maternal pup licking/grooming (LG) in the rat regulate the development of individual differences in hypothalamic–pituitary–adrenal responses to stress. The adult offspring of mothers that show an increased frequency of pup LG have increased hippocampal glucocorticoid receptor (GR) expression and more modest pituitary–adrenal responses to stress. This parental effect is mediated by the epigenetic programming of a GR exon 1 promoter (exon 17) through the binding of the transcription factor nerve growth factor-inducible factor A (NGFI-A). In this paper, we report that: (i) the association of NGFI-A with the exon 17 GR promoter is dynamically regulated by mother–pup interactions; (ii) this effect is mimicked by artificial tactile stimulation comparable to that provided by pup LG; (iii) that serotonin (5-HT) induces an NGFI-A-dependent increase in GR transcription in hippocampal neurons and NGFI-A overexpression is sufficient for this effect; and (iv) that thyroid hormones and 5-HT are key mediators of the effects of pup LG and tactile stimulation on NGFI-A binding to the exon 17 GR promoter in hippocampus. These findings suggest that pup LG directly activates 5-HT systems to initiate intracellular signalling pathways in the hippocampus that regulate GR transcription. PMID:22826348

Hellstrom, Ian C.; Dhir, Sabine K.; Diorio, Josie C.; Meaney, Michael J.

2012-01-01

100

University Council on Athletics & Recreation REPORT TO SENATE  

E-print Network

, Academic All-Star Ceremony, Special Olympics, OFSSA Basketball Championships); 3. Increase in participation championship banners and 9 team and 31 individual medals; 5. Increase in the number of Academic All-Stars (288) core service teams: Recreation and Sport Clubs; Inter-university Sport; Facility Operations

Graham, Nick

101

75 FR 54191 - Pendency of Request for Exemption From the Bond/Escrow Requirement Relating to the Sale of Assets...  

Federal Register 2010, 2011, 2012, 2013

...Chicago National League Ball Club, LLC AGENCY: Pension...warranted. The legislative history of section 4204 indicates...Chicago National League Ball Club, LLC (the ``Seller...receipts from All-Star games; (ii) radio and television...Division Series, All-Star Games, and (iii)...

2010-09-03

102

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

103

Spectrophotometry of 237 Stars in 7 Open Clusters  

NASA Astrophysics Data System (ADS)

Spectrophotometry is presented for 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M39. The observations were taken by Lee McDonald and David Burstein using the Wampler single-channel scanner on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. Sixteen bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwidths 32Angstroms, 48 Angstroms or 64 Angstroms. Data are standardized to the Hayes-Latham system to mutual accuracy of 0.016 mag per passband. The accuracy of the spectrophotometry is assessed in three ways on a star-by-star basis. First, comparisons are made with previously published spectrophotometry for 19 stars observed in common. Second, (B-V) colors and uvby colors are compared for 236 stars and 221 stars, respectively. Finally, comparsions are made for 200 main sequence stars to the spectral synthesis models of Kurucz, fixing log g = 4.0 and [Fe/H] = 0.0, and only varying effective temperature. The accuracy of tests using uvby colors and the Kurucz models are shown to track each other closely, yielding an accuracy estimate (1 sigma ) of 0.01 mag for the 13 colors formed from bandpasses longward of the Balmer jump, and 0.02 mag for the 3 colors formed from the three bandpasses below the Balmer jump. In contrast, larger scatter is found relative to the previously published spectrophotometry of Bohm-Vitense & Johnson (16 stars in common) and Gunn & Stryker (3 stars). We also show that the scatter in the fits of the spectrophotometric colors and the uvby filter colors is a reasonable way to identify the observations of which specific stars are accurate to 1 sigma , 2 sigma , .... As such, the residuals from both the filter color fits and the Kurucz model fits are tabulated for each star where it was possible to make a comparison, so users of these data can choose stars according to the accuracy of the data that is appropriate to their needs. The very good agreement between the models and these data verifies the accuracy of these data, and also verifies the usefulness of the Kurucz models to define spectrophotometry for stars in this temperature range (>5000 K). These data define accurate spectrophotometry of bright, open cluster stars that can be used as a secondary flux calibration for CCD-based spectrophotometric surveys.

Clampitt, Lori; Burstein, David

1997-08-01

104

Sea Stars  

NSDL National Science Digital Library

At first glance, starfish, more properly called sea stars, arenât doing much of anything. In this video, Jonathanâs 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.

Productions, Jonathan B.

2010-10-06

105

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

106

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

107

Effects of benzodiazepine and GABA antagonists on anticonflict effects of antianxiety drugs injected into the rat amygdala in a water-lick suppression test.  

PubMed

In order to elucidate the role of the amygdala in rat conflict behavior in a water lick suppression test, we examined the effect of lesions of various nuclei of the amygdaloid complex on this behavior. An anticonflict effect was produced by a lesion of the anterior part of central and basolateral amygdala, and lesion to the posterior part of the central amygdala, but not by posterior of the basolateral amygdala or medial amygdala lesions. These results suggest that the amygdala, especially the anterior part of the central and basolateral nuclei, plays an important role in conflicting behavior of rats in the water lick test. In a second experiment, the effects of benzodiazepine- and GABA-antagonists on the anticonflict action of diazepam, zopiclone, and phenobarbital injected into the anterior part of central and basolateral amygdala were examined, also using a water lick suppression test. A dose-dependent anticonflict action was produced by systemic administration as well as by intra-amygdala injection of diazepam, zopiclone, lormetazepam, flurazepam and phenobarbital. The order of potency was lormetazepam greater than zopiclone greater than or equal to diazepam greater than flurazepam greater than or equal to phenobarbital for both routes of injection. The anticonflict effects of diazepam and zopiclone injected into the amygdala were completely reversed by Ro15-1788 and beta-CCM but not by bicuculline, while the anticonflict effect of phenobarbital was reversed by beta-CCM but not by Ro15-1788 or bicuculline. The present results strongly suggest that the anterior nuclei of central and basolateral amygdala are important sites of action of antianxiety drugs, and that an anticonflict action produced by intra-amygdala injection of benzodiazepines or barbiturate is mediated through the different receptor mechanisms. PMID:2567034

Shibata, S; Yamashita, K; Yamamoto, E; Ozaki, T; Ueki, S

1989-01-01

108

A pre-partum lift in ewe nutrition from a high-energy lick or maize or by grazing Lotus uliginosus pasture, increases colostrum production and lamb survival.  

PubMed

This experiment tested the hypothesis that a lift in the nutrition of ewes, before lambing, to increase colostrum production would enhance lamb survival. In all, 261 mature Corriedale ewes, each with a single fetus from a synchronised mating, grazed native pasture to day 130 after mating; at which point they were weighed, condition scored and allocated to graze either native pasture or a pasture dominant with Lotus uliginosus. Five days later (14 days before the expected start of lambing) the ewes were allocated to one of four treatments and fed: (i) native pasture alone, (ii) native pasture plus a commercial high-energy lick, (iii) L. uliginosus pasture alone or (iv) L. uliginosus pasture plus whole maize. The weight, viscosity and concentration of components and immunoglobulin G in the colostrum that had accumulated at parturition, were measured for 10 ewes in each treatment. The lambs that survived to 20 days of age from the 221 ewes that were not milked, were recorded. The ewes supplemented with the lick or maize grain and those that grazed the L. uliginosus pasture alone accumulated two to three times more colostrum at birth than the ewes that grazed native pasture alone (396, 635 and 662 g v. 206 g; P < 0.01). The colostrum from the ewes that grazed only native pasture was more viscous (lower score) than that from the ewes supplemented with the lick or maize grain or the ewes that grazed the L. uliginosus pasture alone (scores of 4.1 v. 6.2, 6.5 and 6.4, P < 0.001) and, not surprisingly, the concentration of lactose in the colostrum of the ewes fed only native pasture was also much lower (1.1% v. 3.0%, 2.8% and 2.6%; P < 0.001)he survival of lambs from the ewes fed only native pasture was less than that of the lambs from ewes fed native pasture plus the commercial lick (81.8% v. 95.5%; P < 0.05) or the L. uliginosus pasture alone (92.4%, P < 0.05), and also tended to be lower than that for lambs born to ewes fed L. uliginosus pasture plus maize (91.8%, P = 0.08). The concentration of glucose in the blood of the lambs from the ewes that grazed only native pasture was lower than that of the other lambs (42.1 v. 60.2 ng/ml, P = 0.012). We conclude that the marked increase in colostrum production associated with the lift in ewe nutrition, just prior to lambing, enhanced lamb survival. PMID:22444848

Banchero, G E; Quintans, G; Lindsay, D R; Milton, J T B

2009-08-01

109

THE LICK AGN MONITORING PROJECT: BROAD-LINE REGION RADII AND BLACK HOLE MASSES FROM REVERBERATION MAPPING OF Hbeta  

SciTech Connect

We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range approx10{sup 6}-10{sup 7} M {sub sun} and also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to allow for a time lag to be measured between the continuum fluctuations and the response to these fluctuations in the broad Hbeta emission. We present here the light curves for all the objects in this sample and the subsequent Hbeta time lags for the nine objects where these measurements were possible. The Hbeta lag time is directly related to the size of the broad-line region (BLR) in AGNs, and by combining the Hbeta lag time with the measured width of the Hbeta emission line in the variable part of the spectrum, we determine the virial mass of the central supermassive black hole in these nine AGNs. The absolute calibration of the black hole masses is based on the normalization derived by Onken et al., which brings the masses determined by reverberation mapping into agreement with the local M {sub BH}-sigma{sub *}relationship for quiescent galaxies. We also examine the time lag response as a function of velocity across the Hbeta line profile for six of the AGNs. The analysis of four leads to rather ambiguous results with relatively flat time lags as a function of velocity. However, SBS 1116+583A exhibits a symmetric time lag response around the line center reminiscent of simple models for circularly orbiting BLR clouds, and Arp 151 shows an asymmetric profile that is most easily explained by a simple gravitational infall model. Further investigation will be necessary to fully understand the constraints placed on the physical models of the BLR by the velocity-resolved response in these objects.

Bentz, Misty C.; Walsh, Jonelle L.; Barth, Aaron J. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697 (United States); Baliber, Nairn; Bennert, Vardha Nicola; Greene, Jenny E.; Hidas, Marton G. [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Canalizo, Gabriela; Hiner, Kyle D. [Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521 (United States); Filippenko, Alexei V.; Ganeshalingam, Mohan; Lee, Nicholas; Li, Weidong; Serduke, Frank J. D.; Silverman, Jeffrey M.; Steele, Thea N. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Gates, Elinor L. [Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States); Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90024 (United States); Minezaki, Takeo; Sakata, Yu, E-mail: mbentz@uci.ed [Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)

2009-11-01

110

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

SciTech Connect

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

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

2010-06-10

111

The selective serotonin reuptake inhibitor paroxetine decreases breakpoint of rats engaging in a progressive ratio licking task for sucrose and quinine solutions.  

PubMed

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

Mathes, Clare M; Gregson, Jillian R; Spector, Alan C

2013-03-01

112

Neutron stars  

NASA Astrophysics Data System (ADS)

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

Lattimer, James M.

2014-05-01

113

Stars equilibrium  

NSDL National Science Digital Library

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

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

2003-01-01

114

Star fruit  

Microsoft Academic Search

The carambola or star fruit belongs to the Oxalidaceae family, species Averrhoa carambola. Slices cut in cross-section have the form of a star (Figure 1). It is believed to have originated in Ceylon and the Moluccas\\u000a but it has been cultivated in southeast Asia and Malaysia for many centuries. It is commonly grown in some provinces in southern\\u000a China, in

Miguel M. Neto; Ruither O. Carolino; Norberto P. Lopes; Norberto Garcia-Cairasco

115

Supersolar metallicity in G0-G3 main-sequence stars with V < 15  

NASA Astrophysics Data System (ADS)

The basic stellar atmospheric parameters (effective temperature, surface gravity and global metallicity) were determined simultaneously for a sample of 233 stars, limited in magnitude (V < 15), with spectral types between G0 and G3 and luminosity class V (main sequence). The analysis was based on spectroscopic observations collected at the Observatorio Astrofísico Guillermo Haro and using a set of Lick-like indices defined in the spectral range 3800-4800 Å. An extensive set of indices computed in a grid of theoretical spectra was used as a comparison tool in order to determine the photospheric parameters. The method was validated by matching the results from spectra of the asteroids Vesta and Ceres with the Sun parameters. The main results were as follows: (i) the photospheric parameters were determined for the first time for 213 objects in our sample and (ii) a sample of 20 new super-metal-rich star candidates was found.

López-Valdivia, R.; Bertone, E.; Chávez, M.; Tapia-Schiavon, C.; Hernández-Águila, J. B.; Valdés, J. R.; Chavushyan, V.

2014-11-01

116

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.

117

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

E-print Network

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

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

2005-05-10

118

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.

2014-10-01

119

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

120

The friendly stars  

NASA Astrophysics Data System (ADS)

Describes prominent stars such as Vega, Arcturus, and Antares and means of identifying them, discusses the constellations in which they are located, and explains star names, stellar light, distances between stars, and types of stars.

Martin, Martha Evans

121

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

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

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

E-print Network

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

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

2014-01-01

124

Observations of comet P/Shoemaker-Levy 9 impact on Jupiter from Lick Obseravtory using a high resolution speckle imaging camera  

SciTech Connect

During the week of the impacts of Comet Shoemaker-Levy 9 into Jupiter, we used a speckle imaging camera mounted on the Lick Observatory 3 meter Telescope to record a continuous stream of images of the planet. Because the speckle imaging technique compensates for atmospheric blurring, the resulting images were most likely the highest resolution of any taken from the ground. These images compliment the Hubble Space Telescope data by covering time periods when Hubble was not observing Jupiter. We collected full planet 1024 by 1024 pixel CCD images taken 20 per minute for 4 hours per night over 6 nights July 15 to 22. Only a portion of this raw data has been reduced to high resolution images to date.

Max, C.; Gavel, D.; Johansson, E.; Sherwood, B.; Liu, M.; Bradford, B.

1996-03-15

125

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

126

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

127

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.

Television, Twin C.

2010-01-01

128

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.

129

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

130

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

131

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

NASA Astrophysics Data System (ADS)

We present a chemical composition analysis of 36 giants in the nearby mildly metal-poor (<[Fe/H]>=-1.18) ``CN-bimodal'' globular cluster M4. The stars were observed at the Lick and McDonald Observatories using high-resolution échelle spectrographs and at the Cerro Tololo Inter-American Observatory using the multiobject spectrometer. Confronted with a cluster having interstellar extinction that is large and variable across the cluster face, we combined traditional spectroscopic abundance methods with modifications to the line depth ratio technique pioneered by Gray to determine the atmospheric parameters of our stars. We derive a total-to-selective extinction ratio of 3.4+/-0.4 and an average reddening of 0.33+/-0.01, which is significantly lower than that estimated by using the dust maps made by Schlegel and coworkers. We determine abundance ratios typical of halo field and cluster stars for scandium, titanium, vanadium, nickel, and europium with star-to-star variations in these elements of less than +/-0.1. Silicon, aluminum, barium, and lanthanum are overabundant with respect to what is seen in other globular clusters of similar metallicity. These overabundances confirm the results of an earlier study by Brown & Wallerstein based on a much smaller sample of M4 giants. Superposed on the primordial abundance distribution is evidence for the existence of proton capture synthesis of carbon, oxygen, neon, and magnesium. We recover some of the C, N, O, Na, Mg, and Al abundance swings and correlations found in other more metal-poor globular clusters, but the range of variation is muted. In the case of Mg and Al, this is compatible with the idea that the Al enhancements are derived from the destruction of ^25,26Mg, not ^24Mg. We determine that the C+N+O abundance sum is constant to within the observational errors and agrees with the C+N+O total that might be expected for M4 stars at birth. The asymptotic giant branch (AGB) stars in M4 have C, N, and O abundances that show less evidence for proton capture nucleosynthesis than is found in the less evolved stars of the red giant branch (RGB). Deeply mixed stars of the RGB, subsequent to the helium core flash, might take up residence on the blue end of the horizontal branch and thus fail to evolve back to the AGB, but reasons for skepticism concerning this scenario are noted.

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

1999-09-01

132

Christmas star.  

NASA Astrophysics Data System (ADS)

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

Bia?a, J.

133

Planck stars  

E-print Network

A star that collapses gravitationally can reach a further stage of its life, where quantum-gravitational pressure counteracts weight. The duration of this stage is very short in the star proper time, yielding a bounce, but extremely long seen from the outside, because of the huge gravitational time dilation. Since the onset of quantum-gravitational effects is governed by energy density --not by size-- the star can be much larger than planckian in this phase. The object emerging at the end of the Hawking evaporation of a black hole can can then be larger than planckian by a factor $(m/m_{\\scriptscriptstyle P})^n$, where $m$ is the mass fallen into the hole, $m_{\\scriptscriptstyle P}$ is the Planck mass, and $n$ is positive. The existence of these objects alleviates the black-hole information paradox. More interestingly, these objects could have astrophysical and cosmological interest: they produce a detectable signal, of quantum gravitational origin, around the $10^{-14} cm$ wavelength.

Rovelli, Carlo

2014-01-01

134

Planck stars  

E-print Network

A star that collapses gravitationally can reach a further stage of its life, where quantum-gravitational pressure counteracts weight. The duration of this stage is very short in the star proper time, yielding a bounce, but extremely long seen from the outside, because of the huge gravitational time dilation. Since the onset of quantum-gravitational effects is governed by energy density ---not by size--- the star can be much larger than planckian in this phase. The object emerging at the end of the Hawking evaporation of a black hole can then be larger than planckian by a factor $(m/m_{\\scriptscriptstyle P})^n$, where $m$ is the mass fallen into the hole, $m_{\\scriptscriptstyle P}$ is the Planck mass, and $n$ is positive. We consider arguments for $n=1/3$ and for $n=1$. There is no causality violation or faster-than-light propagation. The existence of these objects alleviates the black-hole information paradox. More interestingly, these objects could have astrophysical and cosmological interest: they produce a detectable signal, of quantum gravitational origin, around the $10^{-14} cm$ wavelength.

Carlo Rovelli; Francesca Vidotto

2014-01-25

135

When Stars Collide  

E-print Network

When two stars collide and merge they form a new star that can stand out against the background population in a starcluster as a blue straggler. In so called collision runaways many stars can merge and may form a very massive star that eventually forms an intermediate mass blackhole. We have performed detailed evolution calculations of merger remnants from collisions between main sequence stars, both for lower mass stars and higher mass stars. These stars can be significantly brighter than ordinary stars of the same mass due to their increased helium abundance. Simplified treatments ignoring this effect give incorrect predictions for the collision product lifetime and evolution in the Hertzsprung-Russell diagram.

E. Glebbeek; O. R. Pols

2007-10-09

136

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

137

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

2005-09-13

138

Star formation - An overview  

NASA Technical Reports Server (NTRS)

Methods for studying star formation are reviewed. Stellar clusters and associations, as well as field stars, provide a fossil record of the star formation process. Regions of current star formation provide a series of snapshots of different epochs of star formation. A simplified picture of individual star formation as it was envisioned in the late 1970s is contrasted with the results of recent observations, in particular the outflow phenomenon.

Evans, N. J., II

1985-01-01

139

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

140

T H E U N I V E R S I T Y O F T E X A S A T A R L I N G T O N November 20, 2008  

E-print Network

in Dallas. "We are going to be involved -- but we have no idea how," said Sue Stevens, senior media games scheduled at the stadium." Professional sporting events like the 2010 NBA All-Star game and Super

Chiao, Jung-Chih

141

2013 GLOS Awards Scholarship Award  

E-print Network

"Heart to Heart" Women's Cardiac Care - Alpha Phi Dartmouth College GLOS Brotherhood/Sisterhood Program Delta Epsilon GLOS Athletic All-star Awards, Sarah Leonard ­ Delta Delta Delta and Cole Sulser- Chi

142

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

...Olympic Games; (5) Annual Tournament of Roses Football Game; (6) World Cup Soccer; (7) Major League Baseball All-Star Game; (8) World Series; (9) Kodak Albuquerque International Balloon Fiesta; (10) Sandia Classic Hang Gliding...

2014-01-01

143

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

144

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

145

On stars and Steiner stars Adrian Dumitrescu  

E-print Network

On stars and Steiner stars Adrian Dumitrescu Csaba D. T´oth Guangwu Xu§ March 9, 2009 Abstract A Steiner star for a set P of n points in Rd connects an arbitrary point in Rd to all points of P, while a star connects one of the points in P to the remaining n - 1 points of P. All connections are realized

Dumitrescu, Adrian

146

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

147

Extragalactic Star Clusters: the Resolved Star Approach  

NASA Astrophysics Data System (ADS)

The physical processes leading to the dissolution of star clusters is a topic barely studied and still not understood. We started a pilot project to develop a new approach to directly detect and study the properties of stellar clusters while they are being destroyed. Our technique currently under development makes use of the exceptional spatial resolution and sensitivity of the ACS camera onboard HST to resolve individual stars in nearby galaxies. PSF stellar photometry and color-magnitude diagrams allows us to separate the most massive stars (more likely to be in clusters) from the star field background. While applying the method to the normal spiral galaxy NGC1313, we found that the method of studying star clusters through resolved stars in nearby galaxies is even more powerful than we first expected. The stellar maps obtained for NGC1313 show that a large fraction of early B-type stars contained in the galaxy are already part of the star field background rather that being in star clusters. Such stars live for 5 to 25 Myr. Since most stars form in clusters, the presence of such massive stars in the field means that they must have left their birthplace very rapidly. It also means that the processes involved in the dissolution of the clusters are extremely efficient. The only plausible explanation for so many young stars to be in the field background is the infant mortality of star clusters. We will present the latest results on the two galaxies NGC 1313 and IC 2475 and discuss the potential of the new approach for studying extragalactic stellar clusters.

Pellerin, Anne; Meyer, M. J.; Jason, H.; Calzetti, D.

2006-12-01

148

IntrAst2 (Petrovay) Variable stars VARIABLE STARS  

E-print Network

IntrAst2 (Petrovay) Variable stars VARIABLE STARS Definitions: (a) Stars displaying brightness variations (in the optical domain) All stars are variables (a matter of sensitivity only). (b) Stars) A variable star is what is listed in GCVS or VSX GCVS: General Catalogue of Variable Stars; http

Petrovay, Kristóf

149

Herschel's Star Gages  

NSDL National Science Digital Library

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

Timberlake, Todd

2011-05-28

150

Ages and Metallicities of the Nuclei and Field Stars of Dwarf Elliptical Galaxies  

NASA Astrophysics Data System (ADS)

We present preliminary ages and metallicities for six nucleated dwarf elliptical galaxies (dE,N) in the Fornax Cluster based on Lick/IDS index measurements and SSP models. Employing IRAF and IDL routines we have successfully extracted high signal-to-noise (S/N >= 30 per Å) Gemini GMOS-S spectra of both galactic nuclei and field star regions. Extracted spectrum have a wavelength range of 3,700 Å to 6,500 Å with a resolution of 4 Å. We fit our data with empirical chemo-evolutionary models to determine radial velocity along with Hb and [MgFe]' line indices. We then compare our measurements to current SSP model predictions by Bruzual & Charlot (2003) to determine age and metallicity. Results suggest that the dE nuclei have intermediate ages ( 5 Gyr) and less than solar metallicities ([Fe/H] <= -0.64dex). Comparing nuclei and dE field star spectra, we find evidence that in general the nuclei have undergone more recent star formation. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: The National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina).

Henderson, Scott; Miller, B. W.; Harris, W.; Lotz, J. M.

2007-12-01

151

Spectroscopic Study of Extended Star Clusters in Dwarf Galaxy NGC 6822  

E-print Network

We present a spectroscopic study of the four extended star clusters (ESCs) in NGC 6822 based on the data obtained with Gemini Multi-Object Spectrograph (GMOS) on the Gemini-South 8.1m telescope. Their radial velocities derived from the spectra range from $-61.2 \\pm 20.4$ km s$^{-1}$ (for C1) to $-115.34 \\pm 57.9$ 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 ($\\geq 8$ Gyr) and metal poor ([Fe/H]$\\lesssim -1.5$). NGC 6822 is found to have both metal poor ([Fe/H]$\\approx -2.0$) and metal rich ([Fe/H]$\\approx -0.9$) star clusters within 15 arcmin (2 kpc) from the center, while only metal poor clusters are observed in the outer halo with $r \\geq 20$ arcmin (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 deter...

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

2014-01-01

152

The Origin of S0s in Clusters: evidence from the bulge and disc star formation histories  

E-print Network

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 $\\alpha$-element abundances in these components further presents a picture in which the final episode of star formation in the bulge is fueled using gas that has previously been chemically enriched in the disc, indicating the sequence of events in the transfo...

Johnston, Evelyn J; Merrifield, Michael R

2014-01-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

154

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.

155

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

156

Open Star Clusters  

NSDL National Science Digital Library

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

2005-02-11

157

Dynamical Young Star Masses  

NASA Astrophysics Data System (ADS)

Mass is a star's most important property, once composition has been established, and determines the entire life trajectory of an object. Only a couple dozen young stars have absolute dynamical mass measurements, and many of those are imprecise. We propose to observe ~17 young close visual binaries in the Taurus star forming region to advance our knowledge of young star masses. We will use NIRSPEC in high-resolution mode behind the adaptive optics system on the Keck II telescope.

Prato, Lisa; Schaefer, Gail; Simon, Michal

2013-08-01

158

Eclipsing Binary Stars  

NSDL National Science Digital Library

Eclipsing Binary Stars model simulates the detection of eclipsing binary stars. In this method, the light curve from the combination of the two stars, and how it changes over time due to each star transiting (or being occulted or eclipsing the other), is observed and then analyzed. In this simulation each star orbits the other in circular motion via Kepler's third law.  When one star passes in front of the other (transits), it blocks part of the starlight of the other star. This decrease in starlight is shown on the graph.  In the simulation the binary star system is shown as seen from Earth (edge on view) and from overhead, but magnified greatly, and with the star sizes not shown to the scale of the orbit. The mass, radius, and temperature of each star can be changed. The simulation uses either simple 3D or Java 3D (if installed) to render the view the stars. If Java 3D is not installed, the simulation defaults to simple 3D using Java. The Eclipsing Binary Stars model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_astronomy_eclipsing_binaries.jar file will run the program if Java is installed.

Belloni, Mario

2010-07-15

159

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

160

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

161

Vega-like stars  

NASA Astrophysics Data System (ADS)

The results on Vega-like stars obtained with ISO are discussed. We find that the incidence of Vega-like disks is approximately 21% on average, with some dependency upon the spectral type. While young stars do more frequently show disks than old stars, there is no clear trend in the amount of dust seen at different ages. We also discuss the discovery of a Vega-like disk associated with ?1Cnc, a star which is know to be orbited by a planet. Finally we show preliminary results on HD 207129, an old G star with a very prominent IR excess.

Dominik, C.; Habing, H. J.; Laureijs, R. J.; Jourdain de Muizon, M.; Bouchet, P.; Heske, A.; Kessler, M. F.; Leech, K.; Metcalfe, L.; Salama, A.; Siebenmorgen, R.; Trams, N. R.

1999-03-01

162

The most luminous stars.  

PubMed

Stars with individual luminosities more than a million times that of the sun are now being studied in a variety of contexts. Observational and theoretical ideas about the most luminous stars have changed greatly in the past few years. They can be observed spectroscopically even in nearby galaxies. They are not very stable; some have had violent outbursts in which large amounts of mass were lost. Because of their instabilities, these stars do not evolve to become red superglants as less luminous stars do. Theoretical scenarios for the evolution of these most massive stars depend on the effects of turbulence and mixing combined with high radition densities. PMID:17801579

Humphreys, R M; Davidson, K

1984-01-20

163

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.

164

Neutron Star Collision  

NSDL National Science Digital Library

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

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

1999-01-21

165

Evolution of variable stars  

SciTech Connect

Throughout the domain of the H R diagram lie groupings of stars whose luminosity varies with time. These variable stars can be classified based on their observed properties into distinct types such as ..beta.. Cephei stars, delta Cephei stars, and Miras, as well as many other categories. The underlying mechanism for the variability is generally felt to be due to four different causes: geometric effects, rotation, eruptive processes, and pulsation. In this review the focus will be on pulsation variables and how the theory of stellar evolution can be used to explain how the various regions of variability on the H R diagram are populated. To this end a generalized discussion of the evolutionary behavior of a massive star, an intermediate mass star, and a low mass star will be presented. 19 refs., 1 fig., 1 tab.

Becker, S.A.

1986-08-01

166

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

167

Ponderable soliton stars  

NASA Astrophysics Data System (ADS)

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

1990-12-01

168

Massive Star and Star Cluster Formation  

E-print Network

I review the status of massive star formation theories: accretion from collapsing, massive, turbulent cores; competitive accretion; and stellar collisions. I conclude the observational and theoretical evidence favors the first of these models. I then discuss: the initial conditions of star cluster formation as traced by infrared dark clouds; the cluster formation timescale; and comparison of the initial cluster mass function in different galactic environments.

Jonathan C. Tan

2006-10-16

169

Massive stars, disks, and clustered star formation  

NASA Astrophysics Data System (ADS)

The formation of an isolated massive star is inherently more complex than the relatively well-understood collapse of an isolated, low-mass star. The dense, clustered environment where massive stars are predominantly found further complicates the picture, and suggests that interactions with other stars may play an important role in the early life of these objects. In this thesis we present the results of numerical hydrodynamic experiments investigating interactions between a massive protostar and its lower-mass cluster siblings. We explore the impact of these interactions on the orientation of disks and outflows, which are potentially observable indications of encounters during the formation of a star. We show that these encounters efficiently form eccentric binary systems, and in clusters similar to Orion they occur frequently enough to contribute to the high multiplicity of massive stars. We suggest that the massive protostar in Cepheus A is currently undergoing a series of interactions, and present simulations tailored to that system. We also apply the numerical techniques used in the massive star investigations to a much lower-mass regime, the formation of planetary systems around Solar- mass stars. We perform a small number of illustrative planet-planet scattering experiments, which have been used to explain the eccentricity distribution of extrasolar planets. We add the complication of a remnant gas disk, and show that this feature has the potential to stabilize the system against strong encounters between planets. We present preliminary simulations of Bondi-Hoyle accretion onto a protoplanetary disk, and consider the impact of the flow on the disk properties as well as the impact of the disk on the accretion flow.

Moeckel, Nickolas Barry

170

Touchstone Stars: Highlights from the Cool Stars 18 Splinter Session  

E-print Network

We present a summary of the splinter session on "touchstone stars" -- stars with directly measured parameters -- that was organized as part of the Cool Stars 18 conference. We discuss several methods to precisely determine cool star properties such as masses and radii from eclipsing binaries, and radii and effective temperatures from interferometry. We highlight recent results in identifying and measuring parameters for touchstone stars, and ongoing efforts to use touchstone stars to determine parameters for other stars. We conclude by comparing the results of touchstone stars with cool star models, noting some unusual patterns in the differences.

Mann, Andrew W; Boyajian, Tabetha; Gaidos, Eric; von Braun, Kaspar; Feiden, Gregory A; Metcalfe, Travis; Swift, Jonathan J; Curtis, Jason L; Deacon, Niall R; Filippazzo, Joseph C; Gillen, Ed; Hejazi, Neda; Newton, Elisabeth R

2014-01-01

171

59Death Stars Our sun is an active star that  

E-print Network

- Suppose that searches for planets orbiting red dwarf stars have studied 1000 stars for a total of 480 % Problem 3 - Suppose that searches for planets orbiting red dwarf stars have studied 1000 stars for a total dwarf stars. To two significant figures, about how long would inhabitants on each planet have to wait

172

Massive Star Generations  

NASA Astrophysics Data System (ADS)

This survey extends and enhances Chandra/ACIS studies of massive stars by sampling both very young O stars ionizing ultracompact HII regions (UCHIIRs) and the aged and evolved massive stars in Young Massive Clusters (YMCs). This will double the Chandra sample of UCHIIRs and provide dozens of X-ray spectra on older massive stars. We combine two new ACIS-I pointings with GTO and archival data to achieve an economical study of W42 and W33, nearby massive star-forming regions <1 Myr old, plus the much older and more distant YMCs Cl 1813-178 and Red Supergiant Cluster 1. These sensitive observations will also document pre-main sequence populations and trace the effects of massive star feedback by mapping diffuse X-rays from supernova remnants and wind-shocked plasma.

Townsley, Leisa

2014-09-01

173

Intelligent star tracker  

NASA Astrophysics Data System (ADS)

Current state-of-the-art commercial star sensors typically weigh 15 pounds, attain 5 to 10 arc-second accuracy, and use roughly 10 watts of power. Unfortunately, the current state-of-the-art commercial star sensors do not meet many of NASA's next-generation spacecraft and instrument needs. Nor do they satisfy Air Force's needs for micro/nano-satellite systems. In an effort to satisfy micro/nano satellite mission needs the Air Force Research Laboratory is developing an intelligent star Tracker, called IntelliStar, which incorporates several novel technologies including Silicon carbide optical housing, MEMs based adaptive optic technologies, smart active pixels, and algebraic coding theory. The design considerations associated with the development of the IntelliStar system are presented along with experimental results which characterize each technologies contribution to overall system performance. In addition to being light weight, the IntelliStar System offers advantages in speed, size, power consumption, and radiation tolerance.

Clark, Natalie

2001-11-01

174

The Theatre of stars  

NASA Astrophysics Data System (ADS)

Planetariums are special instruments in education and didactics of Astronomy and Astrophysics. Since 1930 the Planetarium of Milan, the most important planetarium in Italy, has played a fundamental role in outreach to the public. Italian tradition always preferred didactics in ``live'' lessons. Now technology expands the potential of the star projector and the theatre of stars is a real window on the universe, where you can travel among the stars and galaxies, to reach the boundaries of space and time.

Cavedon, M.; Peri, F.

175

Sizing up the stars  

NASA Astrophysics Data System (ADS)

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

Boyajian, Tabetha S.

176

More lead stars  

NASA Astrophysics Data System (ADS)

The standard model for the operation of the s-process in asymptotic giant branch (AGB) stars predicts that low-metallicity ([Fe/H] <~ -1) AGB stars should exhibit large overabundances of Pb and Bi as compared to other s-elements. The discovery of the first three such ``lead stars'' (defined as stars enriched in s-elements with [Pb/hs] >~ 1, hs being any of Ba, La or Ce) among CH stars has been reported in a previous paper (Van Eck et al. \\cite{VanEck-01}). Five more CH stars (with [Fe/H] ranging from -1.5 to -2.5) are studied in the present paper, and two of them appear to be enriched in lead (with [Pb/Ce] =~ 0.7). The Pb I line at lambda4057 .812 Å is detected and clearly resolved thanks to high-resolution spectra (R = lambda /Delta lambda = 135ts000 ). The abundances for these two stars (HD 198269 and HD 201626) are consistent with the predictions for the s-process operating in low-metallicity AGB stars as a consequence of the ``partial mixing'' of protons below the convective hydrogen envelope. Another two stars (HD 189711 and V Ari) add to a growing number of low-metallicity stars (also including LP 625-44 and LP 706-7, as reported by Aoki et al. \\cite{Aoki2001}) which do not conform to these predictions. Variations on the canonical proton-mixing scenario for the operation of the s-process in low-metallicity stars, that could account for these discrepant stars, are briefly discussed. Based on observations carried out at the European Southern Observatory (La Silla, Chile; Program 65.L-0354) and at the Observatoire de Haute Provence (operated by CNRS, France).

Van Eck, S.; Goriely, S.; Jorissen, A.; Plez, B.

2003-06-01

177

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

178

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

179

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.

180

Massive soliton stars  

NASA Astrophysics Data System (ADS)

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

1990-05-01

181

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

182

Sixquarks in neutron stars  

NASA Astrophysics Data System (ADS)

Neutron star parameters are calculated with regard to the existence of recently discovered sixquarks-narrow dibaryon resonances. It is shown that as compared to the previous calculations, the maximum masses and radii of neutron stars are notably reduced, compact objects of very low masses appear to be stable. It is shown that at the certain stage of the star collapse an instability occurs which leads to the second type Supernova flare. It is also shown that in a certain pressure interval two phases exist: neutron and neutron-sixquark ones, and the first type Supernova flares can be interpreted as a phase transition in the external layers of the neutron stars.

Kuzmin, Yu. V.

183

Combinations of 148 navigation stars and the star tracker  

NASA Technical Reports Server (NTRS)

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

Duncan, R.

1980-01-01

184

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

185

Horizontal Branch stars as AmFm/HgMn stars  

E-print Network

Recent observations and models for horizontal branch stars are briefly described and compared to models for AmFm stars. The limitations of those models are emphasized by a comparison to observations and models for HgMn stars.

G. Michaud; J. Richer

2008-02-12

186

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

187

Neutron Star Compared to Manhattan  

NASA Video Gallery

A pulsar is a neutron star, the crushed core of a star that has exploded. Neutron stars crush half a million times more mass than Earth into a sphere no larger than Manhattan, as animated in this s...

188

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

189

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 Massive Stars Early-type Stars HD 93129 A (O3) M = 94.8 M! L = 1.5e6 L! T = 7.4 T! R = 22.5 R! ·· Produce supernovaeProduce supernovae (neutron stars, black holes)(neutron stars, black holes) ·· Found near birth

Cohen, David

190

~Green Beans ~ Coastal Star  

E-print Network

~Onions ~Green Beans ~Peppers #12;4/13/2011 6 #12;4/13/2011 7 #12;4/13/2011 8 ~ Coastal Star F Si From Siegers... ~Green Towers "Consistent performance in all growing regions" ~Musena "Requires heat heads needed for our CSA. We will start with Cherokee and Magenta, followed by Green Star

Netoff, Theoden

191

Hyperons in neutron stars  

SciTech Connect

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

Glendenning, N.K.

1986-04-01

192

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

193

Rotating hybrid compact stars  

NASA Astrophysics Data System (ADS)

Starting from equations of state of nucleonic and color-superconducting quark matter and assuming a first-order phase transition between these, we construct an equation of state of stellar matter, which contains three phases: a nucleonic phase, as well as two-flavor and three-flavor color-superconducting phases of quarks. Static sequences of the corresponding hybrid stars include massive members with masses of ~2 M? and radii in the range of 13 ? R ? 16 km. We investigate the integral parameters of rapidly rotating stars and obtain evolutionary sequences that correspond to constant rest-mass stars spinning down by electromagnetic and gravitational radiation. Physically new transitional sequences are revealed that are distinguished by a phase transition from nucleonic to color-superconducting matter for some configurations that are located between the static and Keplerian limits. The snapshots of internal structure of the star, displaying the growth or shrinkage of superconducting volume as the star's spin changes, are displayed for constant rest mass stars. We further obtain evolutionary sequences of rotating supramassive compact stars and construct pre-collapse models that can be used as initial data to simulate a collapse of color-superconducting hybrid stars to a black hole.

Ayvazyan, N. S.; Colucci, G.; Rischke, D. H.; Sedrakian, A.

2013-11-01

194

Massive Stars: Stellar Populations  

Microsoft Academic Search

Massive stars dominate the chemical and dynamical evolution of the ISM, and ultimately of their parent galaxy and the universe, because of their fast evolution and intense supersonic winds. Four decades ago, the first rocket UV spectra of massive stars revealed the importance of mass loss and began to change our understanding of their evolution. Recently, advances in stellar modeling,

Luciana Bianchi

2007-01-01

195

Magnetism in Massive Stars  

NASA Astrophysics Data System (ADS)

Stars with mass more than 8 solar masses end their lives as neutron stars, which we mostly observe as highly magnetized objects. Where does this magnetic field come from? Such a field could be formed during the collapse, or is a (modified) remnant of a fossil field since the birth of the star, or otherwise generated by a dynamo during its lifetime in the pre-collapse stages. The answer is unknown, but traditionally magnetic massive stars should not exist since they do not have a convective layer such as the Sun. In the last decade, however, a number of magnetic massive stars have been found, which likely possess a stable field from their birth, and indirect evidence is accumulating that localized fields can indeed be generated during the main-sequence lifetime and beyond. These observational facts opened a new field of research, which is the topic of this review. Among the indirect evidence is a large range of observational phenomena among O and B stars that cannot be explained without the presence of surface magnetic fields. These phenomena include photospheric turbulence, wind clumping, cyclic wind variability observed in UV lines, other types of wind variability in optical lines, anomalous X-ray emission, and non-thermal emission in the radio region. A summary of the properties of observed magnetic massive OB stars is given and the role of magnetic fields in massive stars will be discussed, including how to identify new magnetic candidates.

Henrichs, H. F.

2012-12-01

196

Populations of Carbon Stars  

NASA Astrophysics Data System (ADS)

Carbon stars in the Galaxy do not constitute a single family, but may be divided over several types with distinctive spectroscopic and photometric properties. A subtype of the N stars, characterised by high velocities and weak CN bands, may have been captured by the Milky Way from a cannibalised dwarf galaxy.

Lloyd Evans, T.

2011-09-01

197

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.

198

Boson Stars under Deconstruction  

E-print Network

We study solutions for boson stars in multiscalar theory. We start with simple models with N scalar theories. Our purpose is to study the models in which the mass matrix of scalars and the scalar couplings are given by an extended method of dimensional deconstruction. The properties of the boson stars are investigated by the Newtonian approximation with the large coupling limit.

Nahomi Kan; Kiyoshi Shiraishi

2010-02-03

199

Build Your Own Star  

NSDL National Science Digital Library

This SEED 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.

2007-06-12

200

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

201

Astrophysics. Volume 1 - Stars  

NASA Astrophysics Data System (ADS)

The text is intended for a senior-level or first-year graduate-level course in astrophysics. Volume 1 covers a wide range of subjects in stellar astrophysics. An overview of stellar structure and evolution is provided, taking into account stars, energy transport and generation in stars, stellar time-scales, static configurations (hydrostatic equilibrium), the virial theorem, relativistic effects, star formation, and stellar evolution. Other subjects discussed are related to properties of matter, aspects of observational astronomy, static stellar structure, radiation and energy transport, atomic properties of matter, nuclear energy soruces, the main sequence, evolution away from the main sequence, deviations from quasi-static evolution, the final stages of stellar evolution, weak interactions in stellar evolution, degenerate stars, supernovae, compact stellar and relativistic objects, and close binary systems. Attention is given to neutron stars, gravitational collapse and black holes, white dwarfs, neutrino energy-loss rates, and solar neutrinos.

Bowers, R. L.; Deeming, T.

202

The First Stars  

E-print Network

The formation of the first generations of stars at redshifts z > 15-20 signaled the transition from the simple initial state of the universe to one of increasing complexity. We here review recent progress in understanding the assembly process of the first galaxies, starting with cosmological initial conditions and modelling the detailed physics of star formation. In particular, we study the role of HD cooling in ionized primordial gas, the impact of UV radiation produced by the first stars, and the propagation of the supernova blast waves triggered at the end of their brief lives. We conclude by discussing how the chemical abundance patterns observed in extremely low-metallicity stars allow us to probe the properties of the first stars.

Jarrett L. Johnson; Thomas H. Greif; Volker Bromm

2008-02-01

203

Electrically charged compact stars  

E-print Network

We review here the classical argument used to justify the electrical neutrality of stars and show that if the pressure and density of the matter and gravitational field inside the star are large, then a charge and a strong electric field can be present. For a neutron star with high pressure (~ 10^{33} to 10^{35} dynes /cm^2) and strong gravitational field (~ 10^{14} cm/s^2), these conditions are satisfied. The hydrostatic equation which arises from general relativity, is modified considerably to meet the requirements of the inclusion of the charge. In order to see any appreciable effect on the phenomenology of the neutron stars, the charge and the electrical fields have to be huge (~ 10^{21} Volts/cm). These stars are not however stable from the viewpoint that each charged particle is unbound to the uncharged particles, and thus the system collapses one step further to a charged black hole

Subharthi Ray; Manuel Malheiro; Jose' P. S. Lemos; Vilson T. Zanchin

2006-04-17

204

Extreme Horizontal Branch Stars  

E-print Network

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

Ulrich Heber

2008-04-03

205

Catch a Star!  

NASA Astrophysics Data System (ADS)

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

2006-11-01

206

On stars and Steiner stars. II Adrian Dumitrescu  

E-print Network

On stars and Steiner stars. II Adrian Dumitrescu Csaba D. T´oth Guangwu Xu June 26, 2008 Abstract A Steiner star for a set P of n points in Rd connects an arbitrary center point to all points of P, while a star connects a point p P to the remaining n-1 points of P. All connections are realized by straight

Dumitrescu, Adrian

207

On stars and Steiner stars Adrian Dumitrescu # Csaba D. Toth +  

E-print Network

On stars and Steiner stars Adrian Dumitrescu # Csaba D. Tâ??oth + February 26, 2008 Abstract For a set of n points in the plane, a star connects one of the points (the center) to the other n - 1 points by straight line edges, while a Steiner star connects an arbitrary point in the plane to all n input points

Dumitrescu, Adrian

208

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

209

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.

Duc, P A; Braine, J; Brinks, E; Lisenfeld, U; Charmandaris, V; Duc, Pierre-Alain; Boquien, Meederic; Braine, Jonathan; Brinks, Elias; Lisenfeld, Ute; Charmandaris, Vassilis

2006-01-01

210

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

211

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

212

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

213

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

214

Kepler Star Wheels  

NSDL National Science Digital Library

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

215

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.

216

Lithium in stars with exoplanets  

Microsoft Academic Search

Our recent study of solar-type stars from the HARPS GTO sample provides highly accurate information with regard to Lithium abundances in stars with and without detected planets (Israelian et al. 2009). When the Li abundances of planet bearing stars are compared with the ``single'' stars, we find an excess of Li depletion in planet hosts with effective temperatures in the

Garik Israelian

2010-01-01

217

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

218

Can Boltzmann Soliton Star Exist?  

NASA Astrophysics Data System (ADS)

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

Su, Rukeng; Chen, Xuelei; Pan, Rongshi

1992-12-01

219

Hypernuclear Physics for Neutron Stars  

E-print Network

The role of hypernuclear physics for the physics of neutron stars is delineated. Hypernuclear potentials in dense matter control the hyperon composition of dense neutron star matter. The three-body interactions of nucleons and hyperons determine the stiffness of the neutron star equation of state and thereby the maximum neutron star mass. Two-body hyperon-nucleon and hyperon-hyperon interactions give rise to hyperon pairing which exponentially suppresses cooling of neutron stars via the direct hyperon URCA processes. Non-mesonic weak reactions with hyperons in dense neutron star matter govern the gravitational wave emissions due to the r-mode instability of rotating neutron stars.

Jurgen Schaffner-Bielich

2008-01-24

220

Cooling of neutron stars  

NASA Technical Reports Server (NTRS)

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

Pethick, C. J.

1992-01-01

221

Inside a Star . . .  

ERIC Educational Resources Information Center

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

Akerman, Jane; Wentzel, Donat G.

1973-01-01

222

Violent Star Formation  

NASA Astrophysics Data System (ADS)

This volume deals with the most recent theories of violent star formation. It covers the formation and evolution of new stellar clusters, and explores all the possible consequences in a wide variety of objects where massive stellar bursts have occurred. It thus presents an alternative model to that which suggests supermassive black holes are the power houses of active glactic nuclei. In addition, it analyzes the impact of Wolf-Rayet stars, stellar winds and supernovae on their host galaxy, and provides evidence of massive superassociations and of supersonic velocity dispersions that result from photo-ionization by violent star formation. This book gives a valuable overview and a timely update on all aspects of violent star formation for graduate students and researchers in the field.

Tenorio-Tagle, G.

1995-01-01

223

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

224

Neutron stars - thermal emitters  

E-print Network

Confronting theoretical models with observations of thermal radiation emitted by neutron stars is one of the most important ways to understand the properties of both, superdense matter in the interiors of the neutron stars and dense magnetized plasmas in their outer layers. Here we review the theory of thermal emission from the surface layers of strongly magnetized neutron stars, and the main properties of the observational data. In particular, we focus on the nearby sources for which a clear thermal component has been detected, without being contaminated by other emission processes (magnetosphere, accretion, nebulae). We also discuss the applications of the modern theoretical models of the formation of spectra of strongly magnetized neutron stars to the observed thermally emitting objects.

Potekhin, A Y; Pons, J A

2014-01-01

225

Miniature star tracker  

NASA Astrophysics Data System (ADS)

Hughes Danbury Optical Systems, Inc. (HDOS) is developing a new generation of star trackers that combine low-weight and power consumption with high performance, high reliability, and survivability. Our Miniature Star Tracker (MST), Model HD-1003, represents our next step in the evolution of our advanced star tracker (ASTRA) family of CCD-based star trackers and stresses compact packaging to minimize the impact on the spacecraft design. Small size lowers tracker procurement, integration and launch costs, and provides the user with a high degree of flexibility in selecting the optimum attitude sensor suite, especially for small-sats. Weighing less than 6 lbs, our MST incorporates the latest detector, processor, and application- specific integrated circuit (ASIC) electronics technology to provide exceptional accuracy and survivability in the natural, proton-rich space environment.

Cassidy, Lawrence W.

1993-09-01

226

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

2005-10-24

227

Planets Around Evolved Stars  

NASA Astrophysics Data System (ADS)

With searches of planets around evolved pulsating B sub-dwarfs, red giant stars, and white dwarfs underway, it is paramount to advance theoretical research in how stellar evolution affects the architecture of planetary systems. This will not only maximize the discovery potential of said searches, but also aid in the interpretation and understanding of planet formation in a broader context. To acquire a full picture of the planet´s survival process we compute the evolution of the planet´s orbit coupled with the evolution of the star from the main sequence all the way to the white dwarf domain. We explore the range of planetary masses that might survive a common envelope stage during the giant phases of the star and, finally, we investigate how the presence of a planet might influence the evolution of the star itself.

Villaver, Eva; Livio, M.

2011-09-01

228

Catch a Star 2008!  

NASA Astrophysics Data System (ADS)

ESO and the European Association for Astronomy Education have just launched the 2008 edition of 'Catch a Star', their international astronomy competition for school students. Now in its sixth year, the competition offers students the chance to win a once-in-a-lifetime trip to ESO's flagship observatory in Chile, as well as many other prizes. CAS logo The competition includes separate categories - 'Catch a Star Researchers' and 'Catch a Star Adventurers' - to ensure that every student, whatever their level, has the chance to enter and win exciting prizes. In teams, students investigate an astronomical topic of their choice and write a report about it. An important part of the project for 'Catch a Star Researchers' is to think about how ESO's telescopes such as the Very Large Telescope (VLT) or future telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Extremely Large Telescope (E-ELT) could contribute to investigations of the topic. Students may also include practical activities such as observations or experiments. For the artistically minded, 'Catch a Star' also offers an artwork competition, 'Catch a Star Artists'. Last year, hundreds of students from across Europe and beyond took part in 'Catch a Star', submitting astronomical projects and artwork. "'Catch a Star' gets students thinking about the wonders of the Universe and the science of astronomy, with a chance of winning great prizes. It's easy to take part, whether by writing about astronomy or creating astronomically inspired artwork," said Douglas Pierce-Price, Education Officer at ESO. As well as the top prize - a trip to ESO's Very Large Telescope in Chile - visits to observatories in Austria and Spain, and many other prizes, can also be won. 'Catch a Star Researchers' winners will be chosen by an international jury, and 'Catch a Star Adventurers' will be awarded further prizes by lottery. Entries for 'Catch a Star Artists' will be displayed on the web and winners chosen with the help of a public online vote. Detailed entry information and rules can be found at http://www.eso.org/catchastar/cas2008/. The deadline for submitting an entry for the 2008 competition is Friday 29 February 2008, 17:00 Central European Time.

2007-10-01

229

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.

1999-01-01

230

Matter accreting neutron stars  

NASA Technical Reports Server (NTRS)

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

Meszaros, P.

1981-01-01

231

Intergalactic Star Formation  

Microsoft Academic Search

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

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

2006-01-01

232

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

233

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

234

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

235

Holographic Neutron Stars  

E-print Network

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

Jan de Boer; Kyriakos Papadodimas; Erik Verlinde

2009-07-16

236

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

237

MMT Hypervelocity Star Survey  

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

238

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

2008-08-19

239

Quaking Neutron Stars  

NASA Astrophysics Data System (ADS)

Gravitational, magnetic, and superfluid forces can stress the crust of an evolving neutron star. Fracture of the crust under these stresses could affect the star's spin evolution and generate high-energy emission. We study the growth of strain in the crust of a spinning down, magnetized neutron star and examine the initiation of crust cracking (a starquake). In preliminary work in 1998 we studied a homogeneous model of a neutron star. Here we extend this work by considering a more realistic model of a solid, homogeneous crust afloat on a liquid core. In the limits of astrophysical interest, our new results qualitatively agree with those from the simpler model: the stellar crust fractures under shear stress at the rotational equator, matter moves to higher latitudes, and the star's oblateness is reduced. Magnetic stresses favor faults directed toward the magnetic poles. Thus our previous conclusions concerning the star's spin response still hold; namely, asymmetric redistribution of matter excites damped precession, which could ultimately lead to an increase in the spin-down torque. Starquakes associated with glitches could explain the permanent offsets in period derivative observed to follow glitches in at least three pulsars.

Franco, Lucia M.; Link, Bennett; Epstein, Richard I.

2000-11-01

240

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

SciTech Connect

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

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

2011-10-15

241

Magnetic fields in A stars besides Ap stars  

NASA Astrophysics Data System (ADS)

I review ongoing efforts to understand the incidence of magnetism in intermediate-mass stars that are different from the magnetic Ap stars. This includes the search for magnetic fields in chemically peculiar stars of the Am and HgMn types as well as in normal A and late-B stars. I discuss different techniques for detecting weak stellar magnetic fields, and present a critical evaluation of recent magnetic detections in non-Ap stars. Special attention is given to the magnetic status of HgMn stars and to the discovery of weak polarization signatures in Sirius and Vega.

Kochukhov, O.

2014-11-01

242

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

243

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

244

Life Cycle of Stars  

NASA Technical Reports Server (NTRS)

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

1999-01-01

245

A Four-planet System Orbiting The K0V Star HD 141399  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

246

A 4-Planet System Orbiting the K0V Star HD 141399  

E-print Network

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

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

2014-01-01

247

Predicted Colors for Stars in Clusters from 2 to 18 Gyr  

NASA Astrophysics Data System (ADS)

As part of an ongoing project to generate model integrated spectra for star clusters and galaxy nuclei we have calculated new isochrones which cover all phases of stellar evolution from the zero-age main sequence through the asymptotic giant branch. The ages range from 2 to 18 Gyr and the metallicities from [Fe/H] = -2.3 to +0.2. The elemental abundances are in the solar ratio. We have computed synthetic stellar spectra at representative intervals along each of these isochrones and measured their colors via convolution with filter transmission profiles. Various spectral feature indices have been determined in a similar manner. This allows us to directly transform the isochrones into any given color-magnitude or color-color space. By combining the synthetic spectra according to the expected mass function we also produce a synthetic integrated spectrum corresponding to each age and metallicity. In addition, the effect of non-solar abundance ratios is investigated by substituting stellar spectra which have been recomputed using the desired abundances (for example, using enhanced nitrogen and depleted carbon to mimic the mixing of CN-cycled material into the atmospheres). The color systems currently under study include UBVRI, DDO, Stromgren uvby, and Washington. Spectral feature indices such as those on the Lick system are also considered. This work has been supported under NSF grant AST-9122361.

Tripicco, M. J.; Bell, R. A.

1993-12-01

248

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

249

Condensate dark matter stars  

E-print Network

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 $M_{crit}\\approx 2(l_a/1fm)^{1/2}(m_{\\chi}/1\\;{\\rm GeV})^{-3/2}M_{\\odot}$ and $R_{crit}\\approx 1.1 \\times 10^6(l_a/1\\;{\\rm fm})^{1/2}(m_{\\chi}/1\\;{\\rm GeV})^{-3/2}$ cm respectively, where $l_a$ and $m_{\\chi}$ are the scattering length and the mass of dark matter particle, respectively.

X. Y. Li; T. Harko; K. S. Cheng

2012-05-14

250

Microlensing Neutron Stars  

E-print Network

We investigate the chances that neutron stars act as the lense in a gravitational microlensing event towards the galactic bulge or a spiral arm. The observation of neutron stars by means of gravitational microlensing would allow the estimation of neutron star masses independently of the property of being a pulsar in a binary system. We estimate the contribution of neutron stars to the optical depth and the lensing rate based on two different models of the pulsar distribution in the galaxy. Since only a small fraction of all neutron stars are pulsars, it is unlikely to find a pulsar that acts as a microlense by chance. A position comparison of known radio pulsars with observed microlensing candidates towards the galactic bulge and spiral arms shows no candidate pair, which is consistent with the theoretical expectation. To improve the probability of microlensing a pulsar, we suggest to search for gravitational microlensing events of known nearby high proper motion pulsars. The pulsar PSR J1932+1059 is a good candidate for an astrometric detection of gravitational lensing.

Dominik J. Schwarz; Dirk Seidel

2002-04-03

251

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

2012-03-05

252

Revised Anatomy of Stars  

E-print Network

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

Maurice Dubin; Robert K. Soberman

1997-04-28

253

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

254

Meet the parents: tracing star formation around the ? Ophiuchi star.  

NASA Astrophysics Data System (ADS)

Understanding the mechanisms that trigger the star formation is of crucial importance both in the solar neighborhood and in more distant places. We propose an XMM-Newton observation to study a possible case of triggered star formation event in the nearby star forming region hosting the Rho Ophiuchi star. The suburbs of Rho Oph star are depleted of dust and are marked by a warm dust ring. Inside the ring, few young stellar objects with disks are found. Through X-rays, we aim to have a complete census of the disk-less stars more evolved than those in the main cloud core. Once knowing the sample of stars with and without disk we can estimate the age and assess the evolutionary stage of this part of the cloud and then trace its star formation history.

Pillitteri, Ignazio

2012-10-01

255

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

E-print Network

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

Bhavya B; Blesson Mathew; Annapurni Subramaniam

2008-04-09

256

General Relativity&Compact Stars  

SciTech Connect

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

Glendenning, Norman K.

2005-08-16

257

Cool Stars in Hot Places  

E-print Network

During the last three decades, evidence has mounted that star and planet formation is not an isolated process, but is influenced by current and previous generations of stars. Although cool stars form in a range of environments, from isolated globules to rich embedded clusters, the influences of other stars on cool star and planet formation may be most significant in embedded clusters, where hundreds to thousands of cool stars form in close proximity to OB stars. At the cool stars 14 meeting, a splinter session was convened to discuss the role of environment in the formation of cool stars and planetary systems; with an emphasis on the ``hot'' environment found in rich clusters. We review here the basic results, ideas and questions presented at the session. We have organized this contribution into five basic questions: what is the typical environment of cool star formation, what role do hot star play in cool star formation, what role does environment play in planet formation, what is the role of hot star winds and supernovae, and what was the formation environment of the Sun? The intention is to review progress made in addressing each question, and to underscore areas of agreement and contention.

S. T. Megeath; E. Gaidos; J. J. Hester; F. C. Adams; J. Bally; J. -E. Lee; S. Wolk

2007-04-08

258

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.

259

Spectropolarimetry of cool stars  

E-print Network

In recent years, the development of spectropolarimetric techniques deeply modified our knowledge of stellar magnetism. In the case of solar-type stars, the challenge is to measure a geometrically complex field and determine its evolution over very different time frames. In this article, I summarize some important observational results obtained in this field over the last two decades and detail what they tell us about the dynamo processes that orchestrate the activity of cool stars. I also discuss what we learn from such observations about the ability of magnetic fields to affect the formation and evolution of Sun-like stars. Finally, I evoke promising directions to be explored in the coming years, thanks to the advent of a new generation of instruments specifically designed to progress in this domain.

P. Petit

2007-03-27

260

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

261

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 starâs 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 monthâs column sheds light on the stars and how astronomers measure distances to these celestial objects.

Riddle, Bob

2009-03-01

262

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

263

How star clusters could survive low star formation efficiencies  

Microsoft Academic Search

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

Michael Fellhauer; Pavel Kroupa

2004-01-01

264

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

265

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

266

The neutron star zoo  

NASA Astrophysics Data System (ADS)

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

Harding, Alice K.

2013-12-01

267

Star cluster dynamics.  

PubMed

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

Vesperini, Enrico

2010-02-28

268

A Real Shooting Star  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

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

2007-01-01

269

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

270

Isolating Triggered Star Formation  

SciTech Connect

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

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

2007-09-12

271

The Neutron Star Zoo  

E-print Network

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

Harding, Alice K

2013-01-01

272

The most magnetic stars  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

273

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

274

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.

275

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 ...

276

Lithium in stars with exoplanets  

E-print Network

We present a comparison of the lithium abundances of stars with and without planetary-mass companions. New lithium abundances are reported in 79 planet hosts and 38 stars from a comparison sample. When the Li abundances of planet host stars are compared with the 157 stars in the sample of field stars of Chen et al. (2001) we find that the Li abundance distribution is significantly different, and that there is a possible excess of Li depletion in planet host stars with effective temperatures in the range 5600--5850 K, whereas we find no significant differences in the temperature range 5850--6350 K. We have searched for statistically significant correlations between the Li abundance of parent stars and various parameters of the planetary companions. We do not find any strong correlation, although there are may be a hint of a possible gap in the Li distribution of massive planet host stars.

Garik Israelian; Nuno Santos; Michel Mayor; Rafael Rebolo

2003-10-14

277

The Austin Energy Star Program  

E-print Network

The Austin Energy Star Program is an Austin-specific energy rating system implemented in July, 1985. Since the first builders joined the program, Energy Star has gone through significant improvements vithout changing the fundamental marketing theme...

Seiter, D. L.

1988-01-01

278

Finding Planets around other stars  

NASA Video Gallery

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

279

Star Formation in Irregular Galaxies.  

ERIC Educational Resources Information Center

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

Hunter, Deidre; Wolff, Sidney

1985-01-01

280

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

281

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

282

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

283

The Neutron Star Laboratory  

Microsoft Academic Search

Neutron stars provide a rich and unique cosmic laboratory for studying fundamental questions in physics and astrophysics, including the effects of superstrong magnetic fields, nuclear deflagration and detonation in dense matter, neutron superfluidity and proton superconductivity, the properties of the nuclear force at high densities, the expected transition to quark matter, and gravitational physics in the strong-field regime. X- and

Frederick K. Lamb

1998-01-01

284

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

285

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

286

Magnetic Dynamos and Stars  

SciTech Connect

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

Eggleton, P P

2007-02-15

287

Magnetic Dynamos and Stars  

Microsoft Academic Search

Djehuty is a code that has been developed over the last five years by the Lawrence Livermore National Laboratory (LLNL), from earlier code designed for programmatic efforts. Operating in a massively parallel environment, Djehuty is able to model entire stars in 3D. The object of this proposal was to continue the effort to introduce magneto-hydrodynamics (MHD) into Djehuty, and investigate

Eggleton

2007-01-01

288

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

289

Bp star magetospheres  

NASA Astrophysics Data System (ADS)

Massive OB stars possess strong stellar winds that are driven by radiation. Through the MiMeS collaboration, an increasing number of these hot stars have been confirmed as having global magnetic fields. Such magnetic fields can have a significant influence on the dynamics of these stellar winds; the latter can be characterized by a single dimensionless parameter, ?_*, the ``wind magnetic confinement'', defined as the ratio of magnetic field to wind kinetic energies. For values of ?_*<1, the influence of the field on the wind is small, but for ?_*>1 the field can alter substantially the wind dynamics, leading to even confinement of the wind. In particular, for chemically peculiar Bp stars, because of the combination of relatively low mass and very high magnetic field (of the order of kG), the values of ?_* are ˜ 10^6, leading to a trapped wind within the magnetosphere. In this presentation, I will discuss how such magnetospheres in massive stars can be modeled numerically.

ud-Doula, A.

2014-11-01

290

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.

291

Specific Star Formation Rates  

E-print Network

We present results from a study to determine how star formation contributes to galaxy growth since redshift z=1.5. Using galaxies from the MUnich Near-Infrared Cluster Survey (MUNICS) and the FORS Deep Field (FDF), we investigate the specific star formation rate (SSFR, star formation rate [SFR] per unit galaxy stellar mass) as a function of galaxy stellar mass and redshift. We test the compatibility of our results with a sample drawn from a larger volume using the Sloan Digital Sky Survey. We find that the SSFR decreases as galaxy stellar mass increases, suggesting that star formation contributes more to the growth of low-mass galaxies than high-mass galaxies at all redshifts in this study. We also find a ridge in the SSFR that runs parallel to lines of constant SFR and decreases by a factor of 10 from z=1 to today, matching the results of the evolution in SFR density seen in the ``Lilly-Madau'' diagram. The ridge evolves independently of galaxy stellar mass to a particular turnover mass at the high mass end. Galaxies above the turnover mass show a sharp decrease in SSFR compared to the average at that epoch, and the turnover mass increases with redshift.

Amanda E. Bauer; Niv Drory; Gary J. Hill

2005-09-02

292

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

293

Written in the Stars  

E-print Network

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

Seager, Sara

294

The Star Formation Camera  

E-print Network

The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, and to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. This program addresses the origins and evolution of stars, galaxies, and cosmic structure and has direct relevance for the formation and survival of planetary systems like our Solar System and planets like Earth. We present the design and performance specifications resulting from the implementation study of the camera, conducted ...

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

2009-01-01

295

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

2006-10-30

296

Focus on the Stars.  

ERIC Educational Resources Information Center

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

Geary, Pat; And Others

297

Observing Variable Stars  

NASA Astrophysics Data System (ADS)

Foreword; Opening thoughts; Acknowledgments; Part I. Getting To Know The Sky: 1. Beginning with the Big Dipper; 2. Magnitude, color, and distance; 3. A word on binoculars and telescopes; 4. Learning to see; Part II. Getting To Know The Variables: 5. Meeting the family; 6. Getting started with Cepheids; 7. Algol, the demon of autumn; 8. How to estimate a variable; 9. Names and records; 10. Observing hints; 11. Stately and wonderful; 12. Stars of challenge; 13. Bright, easy, and interesting; 14. Betelgeuse: easy and hard; 15. Not too regular; 16. Nova? What nova?; 17. Supernovae; 18. Three stars for all seasons; 19. A nova in reverse; 20. RU Lupi?; 21. Orion, the star factory; 22. Other variable things; 23. The Sun; Part III. Suggested Variables For Observation Throughout The Year: Introduction: January, February, March, April, May, June, July, August, September, October, November, December, Southern sky notes; Part IV. A Miscellany: 24. Stars and people; 25. The next generation; 26. Going further; Glossary and abbreviations; Index.

Levy, David H.; Mattei, Foreword by Janet A.

1998-04-01

298

THE STAR OFFLINE FRAMEWORK.  

SciTech Connect

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

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

2000-02-07

299

White Dwarf Stars  

NSDL National Science Digital Library

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

2007-01-26

300

Energy generation in stars  

E-print Network

It is a current opinion that thermonuclear fusion is the main source of the star activity. It is shown below that this source is not unique. There is another electrostatic mechanism of the energy generation which accompanies thermonuclear fusion. Probably, this approach can solve the solar neutrino problem.

B. V. Vasiliev

2001-10-29

301

Hadrons in compact stars  

E-print Network

We discuss $\\beta$-equilibrated and charge neutral matter involving hyperons and $\\bar K$ condensates within relativistic models. It is observed that populations of baryons are strongly affected by the presence of antikaon condensates. Also, the equation of state including $\\bar K$ condensates becomes softer resulting in a smaller maximum mass neutron star.

Debades Bandyopadhyay

2005-12-28

302

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

303

Division Iv: Stars  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

304

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

305

Infrared Stars. The Interaction between Stars and Interstellar Clouds Produces 'Infrared Stars' of Two Different Kinds.  

National Technical Information Service (NTIS)

Searches for very cool stars have revealed three kinds of objects: very cool Mira stars, perhaps cooler than any of this type previously known; extremely dense interstellar clouds, more dense than any known heretofore; and probably, cool circumstellar clo...

H. L. Johnson

1967-01-01

306

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

307

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

308

The Formation of Massive Stars and Star Clusters  

E-print Network

We model the formation of high-mass stars, specifying the accretion rate in terms of the instantaneous and final mass of the star, the ambient pressure of the star-forming region and the form of polytropic pressure support of the pre-stellar gas core. The high pressures typical of Galactic regions of massive star formation allow a 100 solar mass star to form in ~10^5 years with a final accretion rate ~10^-3 solar masses per year. By modeling protostellar evolution we predict the properties of several nearby massive protostars. We model cluster formation by applying this theory to many stars. We use the observed intensity of outflows from protoclusters to estimate the star formation rate, finding that clusters take at least several free-fall times to form; for a cluster similar to the Orion Nebula Cluster, we predict a formation timescale of ~1x10^6 years.

Jonathan C. Tan; Christopher F. McKee

2002-03-06

309

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

310

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

311

The Formation of Massive Stars  

E-print Network

Massive stars have a profound influence on the Universe, but their formation remains poorly understood. We review the current status of observational and theoretical research in this field, describing the various stages of an evolutionary sequence that begins with cold, massive gas cores and ends with the dispersal and ionization of gas by the newly-formed star. The physical processes in massive star formation are described and related to their observational manifestations. Feedback processes and the relation of massive stars to star cluster formation are also discussed. We identify key observational and theoretical questions that future studies should address.

H. Beuther; E. B. Churchwell; C. F. McKee; J. C. Tan

2006-02-01

312

Star Forming Regions in Cepheus  

E-print Network

The northern Milky Way in the constellation of Cepheus (100 deg 10 deg, 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 each involved in forming stars, like the well known high mass star forming region S140 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.

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

2008-09-27

313

Star Forming Regions in Cepheus  

E-print Network

The northern Milky Way in the constellation of Cepheus (100 deg 10 deg, 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 each involved in forming stars, like the well known high mass star forming region S140 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; Balog, Z

2008-01-01

314

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

315

Disk Dispersal Around Young Stars  

NASA Technical Reports Server (NTRS)

We first review the evidence pertaining to the lifetimes of planet-forming disks of gas and dust around young stars and discuss possible disk dispersal mechanisms: 1) viscous accretion of material onto the central source, 2) close stellar encounters, 3) stellar winds, and 4) photoevaporation caused by the heating of the disk surface by ultraviolet radiation. Photoevaporation is likely the most important dispersal mechanism for the outer regions of disks, and this talk focuses on the evaporation caused by the presence of a nearby, luminous star rather than the central star itself. We also focus on disks around low-mass stars like the Sun rather than high-mass stars, which we have treated previously. Stars often form in clusters and the ultraviolet flux from the most luminous star in the cluster can have a dramatic effect on the disk orbiting a nearby low-mass star. We apply our theoretical models to the evaporating protoplanetary disks (or "proplyds") in the Trapezium cluster in Orion, to the formation of gas giant planets like Jupiter around Sun-like stars in the Galaxy, and to the formation of Kuiper belts around low mass stars. We find a possible explanation for the differences between Neptune and Jupiter, and make a prediction concerning recent searches for giant planets in large clusters. We discuss recent models of the infrared spectra from gaseous disks around young stars.

Hollenbach, David

2004-01-01

316

Activity on young stars.  

NASA Astrophysics Data System (ADS)

Simultaneous photometry and spectroscopy were made of 6 young stars during two observing periods mainly to study short-term variability on time-scales from minutes to a few hours. The material includes two classical T Tauri stars (CTTS): SY Ori and VW Cha; three T Tauri stars with weak emission line spectra (WTTS): San 1, SZ Cha and ADA 481 and one post-T Tauri candidate: HD 70309B. Both UBV and Stroemgren photometry was made. In the visible spectral region we resolved rapid fluctuations - events - with total amplitudes of about 5% (0.05 magnitudes). In the ultraviolet, the corresponding limit of detection was usually <=10%. On the basis of totally about 100 hours of monitoring we conclude that the normal state of these stars is that they are completely constant in brightness or that they vary only slowly with small amplitudes over several hours. Only a few percent of the time, on the average, is a given star caught at brightness changes >=0.2mag. during one night. No event reached a total amplitude of >=0.3mag. VW Cha is the most active star, but no events were seen on SY Ori and HD 70309B. This confirms earlier indications that powerful "flaring" on T Tauri stars is not frequent. We make a detailed study of all events and find two types of slow events, usually with d(U or u)/dt<=0.1mag/hour. One is caused by changes in the continuous emission (the veiling) superimposed on the stellar photospheric spectrum and operates mainly on VW Cha. These events have nothing to do with stellar surface flares of the type observed on flare stars and we suggest that they originate from inhomogeneous mass accretion from a circumstellar disk to the stellar surface. The time-scales support models with magnetically controlled accretion along the stellar dipole field to rings or spots at the stellar surface. The other type of event appears to originate from relatively rapid changes in the opacity of circumstellar dust in the line-of-sight to the star. This effect dominates on SZ Cha, a WTTS surrounded by a substantial dust reservoir. Also for the rapid events we distinguish two types. On two WTTS we detected a few flare-like events produced by a sudden increase in emission in the Balmer continuum and the Balmer lines and no detectable change of the continuum long-ward of the Balmer jump. With only UBV photometry the Balmer flares could erronously been interpreted as very hot blackbody radiators. We suggest that these events are genuine surface flares with total energies of 10^33^ to 10^34^erg, and discuss the implication of energy supply. On ADA 481 we detected 2 flare-like events in white light. If these are due to the ignition of a source of blackbody radiation, the inferred temperature of the flare is low compared to what is normally observed for flare stars. Even though the events are rare and have small total amplitudes in UV, they are extremely powerful, with the same total energies as the largest flares seen on flare stars. The flare stars may show much larger changes in UV, but the difference comes from the lower contrast of the flares on the TTS. If all TTS have surface magnetic activity similar to the flare stars, only the radii being larger, then we conclude that the frequency distribution of the flare-like events on WTTS are similar to flare stars in the field, but much higher than for the dwarfs in the Pleiades. No flare-like event was seen on the CTTS and we discuss possible implications. For the long-term changes (over days) we conclude that very dark spots on the rotating surfaces of SY Ori and San 1 dominates, while VW Cha varies because of variable veiling, but with an uncertain period. For SZ Cha variable circumstellar extinction operates, also in phase with the hydrogen line absorption. The situation for ADA 481 is still unclear. HD 70309B did not vary.

Gahm, G. F.; Loden, K.; Gullbring, E.; Hartstein, D.

1995-09-01

317

Hot Stars in Globular Clusters  

E-print Network

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

S. Moehler

1998-12-08

318

Gaining Insight into Star Formation: Resolved Star Formation Laws  

NASA Astrophysics Data System (ADS)

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

Liebst, Kelley; Scowen, Paul A.

2014-06-01

319

Dead Star Rumbles  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

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

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

2005-01-01

320

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

321

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

322

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

323

Starquakes in Neutron Stars  

NASA Astrophysics Data System (ADS)

The Crab and other pulsars suffer sudden and permanent increases in their spin-down rates in association with glitches, suggesting that the external torque on these objects grows in steps. Here, we describe how torque changes may arise from starquakes, occurring as the star spins down and its rigid crust becomes less oblate. We study the evolution of strain in the crust, the initiation of starquakes, the effects on the magnetic field geometry, and possible observable consequences for neutron star spin down. We find that the stellar crust begins breaking at the rotational equator, forming a fault inclined at an angle to the equator and directed toward the magnetic poles. The resulting asymmetric matter redistribution produces a misalignment of the angular momentum and spin axes. Subsequently, damped precession to a new rotational state increases the angle between rotation and magnetic axes. The change in this angle could increase the external torque, producing a permanent increase in the spin-down rate.

Franco, L. M.; Link, B.; Epstein, R. I.

2000-05-01

324

From stars to planets  

NASA Astrophysics Data System (ADS)

A large program of multi-fibre (FLAMES) spectroscopic observations of the stellar population in two CoRoT/Exoplanet field with the GIRAFFE/VLT, took place in spring 2008. It aims at characterizing the brightest dwarf population and providing the ground for statistical analysis of the planetary population found by CoRoT. To perform such an ambitious analysis, we use an automated software based on the MATISSE algorithm, originally designed for the GAIA/RVS spectral analysis. This software derives the atmospheric stellar parameters: effective temperature, surface gravity and the overall metallicity. Further improvements are foreseen in order to measure also individual abundances. By comparing the main physical and chemical properties of the host stars to those of the stellar population they belong to, this will bring new insights into the formation and evolution of exoplanetary systems and the star-planet connection.

Gazzano, Jean-Christophe; Deleuil, Magali; De Laverny, Patrick; Blanco, Alejandra Recio; Bouchy, François; Gandolfi, Davide; Loeillet, Benoît

2009-02-01

325

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

326

Stars: Interiors Gravitation  

E-print Network

of Earth's age (~ 4.5 x 109 yr). Some other energy source is needed. Assume the Sun contracted from a very Time Evaluate for the Sun. Use -33 mkg104.1 Ã?= hr!5.0ff t Sun is in at least a quasi-equilibrium. There must exist a significant source of internal pressure to support the Sun, and other stars. #12;Virial

Basu, Shantanu

327

Pulsating relativistic stars  

Microsoft Academic Search

In this paper we review the recent developments in the relativistic theory of\\u000astellar pulsations with special emphasis on the spacetime or w-modes. We\\u000adiscuss also the excitation of these modes and the information about the\\u000aneutron star that we will be able to mine from their detection. The paper will\\u000aappear in the Proceedings of the Les Houches School

Kostas D. Kokkotas

1996-01-01

328

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

329

The Star Formation Camera  

Microsoft Academic Search

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

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

2009-01-01

330

Dilepton Measurements at STAR  

NASA Astrophysics Data System (ADS)

In the study of hot and dense nuclear matter, created in relativistic heavy-ion collisions, dilepton measurements play an essential role. Leptons, when compared to hadrons, have only little interaction with the strongly interacting system. Thus, dileptons provide ideal penetrating probes that allow the study of such a system throughout its space-time evolution. In the low mass range (Mll < 1.1 GeV/c2), the dominant source of dileptons originates from the decay of vector mesons which may see effects from chiral symmetry restoration. In the intermediate mass range (1.1 < Mll < 3.0 GeV/c2), the main contributions to the mass spectrum are expected to originate from the thermal radiation of a quark-gluon plasma as well as the decays of charm mesons. In the high mass range (Mll > 3.0 GeV/c2), dilepton measurements are expected to see contributions from primordial processes involving heavy quarks, and Drell-Yan production. With the introduction of the Time-of-Flight detector, the STAR detector has been able to perform large acceptance, high purity electron identification. In this contribution, we will present STAR's recent dielectron measurements in the low and intermediate mass range for RHIC beam energies ranging between 19.6 and 200 GeV. Compared to electrons, muon measurements have the advantage of reduced bremsstrahlung radiation in the surrounding detector materials. With the upcoming detector upgrades, specifically the muon detector (MTD), STAR will be able to include such measurements in its (di-)lepton studies. We will discuss the future dilepton program at STAR and the physics cases for these upgrades.

Geurts, Frank; STAR Collaboration

2013-08-01

331

Which Stars Go BOOM?  

NASA Astrophysics Data System (ADS)

Intermediate mass stars with M = 6 to 10 Msun will end their lives by either losing mass quiescently and forming massive white dwarfs or by exploding as core collapse type II supernovae. The critical mass separating these two stellar evolution channels is not only a fundamental threshold of stellar astrophysics, but is a crucial ingredient to generate reliable galaxy evolution simulations. Given the steepness of the stellar IMF, small changes in the critical mass directly affects chemical evolution scenarios, energetics, and feedback relations. Although most astronomers reference the critical mass at M = 8 Msun, there is a lack of robust theoretical or observational confirmation of this number. We propose to measure the critical mass directly by verifying the end products of stellar evolution in four rich, young, co-eval stellar populations. With ages of 25 to 60 Myr and total stellar masses >10,000 Msun, the Magellanic Cloud globular clusters NGC 1818, NGC 330, NGC 1805, and NGC 2164 have present-day main-sequence turnoff masses of M = 6.2, 7.2, 8.5, and 9.8 Msun, respectively. Existing photometry verifies that each cluster has a rich upper main sequence of massive stars, and therefore would have formed dozen(s) of stars above the present day turnoff. If those stars did not explode as core collapse supernovae, they will populate a clear blue white dwarf cooling sequence. Our experiment uses the full power, wavelength coverage, and resolution of HST/WFC3 to detect these cooling sequences in high-precision, UV-sensitive color-magnitude diagrams.

Kalirai, Jason

2014-10-01

332

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

333

Cosmic Star Formation History  

E-print Network

Over the last decade and a half, an avalanche of new data from multiwavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Making sense of it all and fitting it together into a coherent picture remains one of astronomy's great challenges. Here we review the range of complementary techniques and theoretical tools that are allowing astronomers to map the cosmic history of star formation, heavy element production, and reionization of the universe from the cosmic "dark ages" to the present epoch. A consistent picture is emerging from modern galaxy surveys, whereby the star formation rate density peaked about 3.5 Gyr after the Big Bang, at redshift 1.9, and declined exponentially at later times, with an e-folding timescale of 3.9 Gyr. Half of the stellar mass observed today was formed before redshift 1.3. Less than 1% of today's stars formed during the epoch of reionization, at redshift greater than 6. Under the simple assumption of a universal initial mass func...

Madau, Piero

2014-01-01

334

The Physics of Stars  

NASA Astrophysics Data System (ADS)

John von Neumann speculated that computers might become sufficiently powerful that they could be used to solve analytically intractable problems numerically (he gave turbulence as an example), and that those ``numerical experiments'' could be used to provide the insight necessary to develop analytic solutions. A case study will be presented in which we attempt in this way to use computer simulations of 3D turbulent flow in presupernova stars. We find that we can reproduce the simulations surprisingly well---on average---if we replace the viscous term with an effective damping which turns out to be similar to that inferred by Kolmogorov for a turbulent cascade. Stars are gravitationally-controlled thermonuclear reactors. Abundance change (and hence evolution) occurs because of nuclear burning, and mixing. It is now possible to treat this coupled problem in a self-consistent way, free of astronomically calibrated parameters. Implications for stellar evolution, nucleosynthesis yields, core collapse, supernova explosions, helio-seismology, and solar neutrinos will be discussed. It is argued that advances in the treatment of stellar fluid dynamics, along with new developments in laboratory astrophysics, now allow far more reliable predictions of how stars behave.

Arnett, W. David

2009-05-01

335

Parametrising Star Formation Histories  

E-print Network

We examine the star formation histories (SFHs) of galaxies in smoothed particle hydrodynamics (SPH) simulations, compare them to parametric models that are commonly used in fitting observed galaxy spectral energy distributions, and examine the efficacy of these parametric models as practical tools for recovering the physical parameters of galaxies. The commonly used tau-model, with SFR ~ exp(-t/tau), provides a poor match to the SFH of our SPH galaxies, with a mismatch between early and late star formation that leads to systematic errors in predicting colours and stellar mass-to-light ratios. A one-parameter lin-exp model, with SFR ~ t*exp(-t/tau), is much more successful on average, but it fails to match the late-time behavior of the bluest, most actively star-forming galaxies and the passive, "red and dead" galaxies. We introduce a 4-parameter model, which transitions from lin-exp to a linear ramp after a transition time, which describes our simulated galaxies very well. We test the ability of these paramet...

Simha, Vimal; Conroy, Charlie; Dave, Romeel; Fardal, Mark; Katz, Neal; Oppenheimer, Benjamin D

2014-01-01

336

The STAR offline framework*  

NASA Astrophysics Data System (ADS)

The Solenoidal Tracker At RHIC (STAR) is a large acceptance collider detector which started data taking at Brookhaven National Laboratory in summer 2000. STAR has developed a software framework for simulation, reconstruction and analysis in offline production, interactive physics analysis, and online monitoring. It is well matched both to STAR's present status of transitioning from a Fortran/C++ base to a fully object oriented (OO) base, and to the emerging OO base. This paper presents the results of two years of effort developing a modular C++ framework based on the ROOT package. The framework encompasses both wrapped Fortran components (legacy simulation and reconstruction code) used via IDL-defined data structures, and fully OO components (all physics analysis code) served by a recently developed object model for event data. The framework supports chronologically chained components, which can themselves be composite sub-chains, with components ("makers") managing "data sets" they have created and are responsible for. Makers and data sets inherit from the TDataSet class which supports their organization into hierarchical structures for management. TDataSet also centralizes almost all system tasks such as data set navigation, I/O, database access, and inter-component communication. This paper will present an overview of this system, now deployed and well exercised in production environments with 10 TBytes real and 3 TBytes simulated data, and in an active physics analysis development program.

Fine, V.; Fisyak, Y.; Perevoztchikov, V.; Wenaus, T.

2001-10-01

337

Photoevaporating Disks Around Young Stars  

NASA Technical Reports Server (NTRS)

Ultraviolet radiation from the central star or from a nearby massive star heats the surfaces of protoplanetary disks and causes the outer, less gravitationally bound part of the disks, to photoevaporate into interstellar space. Photoevaporation is likely the most important dispersal mechanism for the outer regions of disks. We focus in this talk on disks around low-mass stars like the Sun rather than high-mass stars, which we have treated previously. Stars often form in clusters and the ultraviolet flux from the most luminous star in the cluster can have a dramatic effect on the disk orbiting a nearby low-mass star. We apply our theoretical models to the evaporating protoplanetary disks (or "proplyds") in the Trapezium cluster in Orion, to the formation of gas giant planets like Jupiter around Sun-like stars in the Galaxy, and to the formation of Kuiper belts around low mass stars. We discuss recent models of the effects of the radiation from the central low mass star including both the predicted infrared spectra from the heated disks as well as preliminary results on the photoevaporation rates.

Hollenbach, David

2004-01-01

338

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

339

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

340

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

341

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 t...

Efremov, Yu N

2005-01-01

342

Massive stars in starbursts. Proceedings.  

NASA Astrophysics Data System (ADS)

This book reviews the importance of massive stars in several areas of astrophysics. Massive stars are objects that are 10 - 100 times the mass of our Sun. Above ten solar masses, loss through stellar winds begins to have a major impact on the evolution of a star. The upper limit of 100 solar masses is derived from observations. Significant progress has now been achieved in massive star research. New models, along with high quality observations, have improved our understanding of the formation, structure, atmosphere and evolution of these massive objects. They are formed in violent bursts of star formation and are probably related to the phenomena observed in active galactic nuclei. The workshop at the Space Telescope Science Institute examined the interplay between the astrophysics of massive stars and their location in extragalactic starburst regions. The workshop was conceived not merely as a review of the pertinent fields but as a dynamical contribution toward future research.

Leitherer, C.; Walborn, N. R.; Heckman, T. M.; Norman, C. A.

343

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.

344

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

345

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

346

Measuring Proper Motion of Barnard's Star  

Microsoft Academic Search

Stars of the night sky are generally considered to be fixed points, not changing noticeably over generations of observations. While most stars seem to appear in the same place year after year, some change location noticeably, the best example being Barnard's Star. Barnard's star is closer to Earth than any other star except Proxima Centauri. It also appears to move

Katrina Wiechmann; Tom Michalik

2009-01-01

347

Elemental Abundances as Tracers of Star Formation  

E-print Network

have Z Cycle of GAS and STARS in Galaxies Gas is transformed into stars Each star into the interstellar gas at the end of the star's life Through winds and supernovae explosions Some fractionElemental Abundances as Tracers of Star Formation S. Veilleux (U. Maryland) (Tremonti+04) Three

Veilleux, Sylvain

348

Abundances in stars with exoplanets  

E-print Network

Extensive spectroscopic studies of stars with and without planets have concluded that stars hosting planets are significantly more metal-rich than those without planets. More subtle trends of different chemical elements begin to appear as the number of detected extrasolar planetary systems continues to grow. I review our current knowledge concerning the observed abundance trends of various chemical elements in stars with exoplanets and their possible implications.

Garik Israelian

2003-10-14

349

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

350

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

351

The Spacelab IPS Star Simulator  

NASA Technical Reports Server (NTRS)

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

Wessling, Francis C., III

1993-01-01

352

The Spacelab IPS Star Simulator  

NASA Technical Reports Server (NTRS)

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

Wessling, Francis C., III

1993-01-01

353

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

354

Interferometric observations of hot stars.  

E-print Network

??Accurate determination of fundamental stellar properties is crucial in understanding and testing models of stellar structure and evolution. To date, most stars with independent determinations… (more)

Maestro, Vicente

2014-01-01

355

Excavation of the first stars  

E-print Network

The external pollution of the first stars in the Galaxy is investigated. The first stars were born in clouds composed of the pristine gas without heavy elements. These stars accreted gas polluted with heavy elements while they still remained in the cloud. As a result, it is found that they exhibit a distribution with respect to the surface metallicity. We have derived the actual form of this distribution function. This metallicity distribution function strongly suggests that the recently discovered most metal-deficient star HE0107-5240 with [Fe/H]=-5.3 was born as a metal-free star and accreted gas polluted with heavy elements. Thus the heavy elements such as Fe in HE0107-5240 must have been supplied from supernovae of later generations exploding inside the cloud in which the star had been formed. The elemental abundance pattern on the surface of stars suffering from such an external pollution should not be diverse but exhibit the average pattern of numerous supernovae. Future observations for a number of metal-deficient stars with [Fe/H]<-5 will be able to prove or disprove this external pollution scenario. Other possibilities to produce a star with this metallicity are also discussed.

Toshikazu Shigeyama; Takuji Tsujimoto; Yuzuru Yoshii

2003-02-17

356

Population synthesis of massive stars  

NASA Astrophysics Data System (ADS)

This review deals with massive star population synthesis with a realistic population of binaries. We focus on the comparison between observed star numbers (as a function of metallicity) and theoretically predicted numbers of stellar populations in regions of continuous star formation and in starburst regions. Special attention is given to the O-type/WR/red supergiant stellar population, the population of blue supergiants, the pulsar and binary pulsar population, and the supernova rates. Finally, we consider massive double compact star mergers and the link with gravitational wave sources (the advanced LIGO II) and r-process element production sites.

Vanbeveren, Dany

2014-09-01

357

Accretion Onto Magnetic Degenerate Stars  

NASA Technical Reports Server (NTRS)

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

Frank, Juhan

2000-01-01

358

Photometry of astrometric reference stars  

NASA Technical Reports Server (NTRS)

UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral types and luminosity classifications made from the colors are used to determine their spectroscopic parallaxes. In this paper, colors for 309 stars in 25 regions are given, and classifications for 210 stars have been made. These stars form reference frames in the Allegheny Observatory Multichannel Astrometric Photometer astrometric program, and in the Praesepe cluster reduced by Russell (1976). It is found that the present photometric spectral types are reliable to within 2.5 spectral subclasses.

Castelaz, Michael W.; Persinger, Tim; Stein, John W.; Prosser, James; Powell, Harry D.

1991-01-01

359

Polyelectrolyte stars in planar confinement  

E-print Network

We employ monomer-resolved Molecular Dynamics simulations and theoretical considerations to analyze the conformations of multiarm polyelectrolyte stars close to planar, uncharged walls. We identify three mechanisms that contribute to the emergence of a repulsive star-wall force, namely: the confinement of the counterions that are trapped in the star interior, the increase in electrostatic energy due to confinement as well as a novel mechanism arising from the compression of the stiff polyelectrolyte rods approaching the wall. The latter is not present in the case of interaction between two polyelectrolyte stars and is a direct consequence of the impenetrable character of the planar wall.

Martin Konieczny; Christos N. Likos

2006-03-28

360

The Elements: Forged in Stars  

NSDL National Science Digital Library

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

2011-03-28

361

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.

362

Gravitational Condensate Stars  

NASA Astrophysics Data System (ADS)

The issue of the final state of the gravitational collapse will be addressed. Ishall present physical arguments to the effect that the remnant of the gravitationalcollapse of super-massive stars is a cold and dark super-dense object which isthermodynamically and dynamically stable: a Gravitational Condensate Star orQuasi Black Hole (QBH). A QBH is characterized by a huge, but not an infinite,surface redshift. This surface redshift depends universally on the total mass of aQBH and the proper thickness of a thin shell of an exotic matter described bythe Zel'dovich equation of state p = c2 . The velocity of sound in a thin shell isequal to the velocity of light. Hence, this thin shell replaces the event horizon of amathematical black hole ( = 0). Inside a thin shell the zero entropy gravitationalcondensate characterized by the cosmological equation of state p = -c2 resides.A QBH is described by a new static and spherically symmetric solution of Ein-stein's equations supplemented with the proper boundary conditions based on mi-crophysics considerations. The new solution has no singularities and no eventhorizons. Its entropy is maximized under small fluctuations and is given by thestandard hydrodynamic entropy of the thin shell which is proportional to the to-tal mass instead of the Bekenstein-Hawking entropy which is proportional to thesquare of the total mass. This resolves the paradox of an excessively high en-tropy of black holes as compared to their progenitors. The formation of such acold gravitational condensate stellar remnant very likely would require a violentcollapse process with an explosive output of energy. Some observational conse-quences of the formation of gravitational condensate stars will be described.

Mazur, P.; Mottola, E.

363

Supermassive monopole stars  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

364

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

365

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

366

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

367

Star Forming Galaxy Models: Blending Star Formation into TREESPH  

E-print Network

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

Chris Mihos; Lars Hernquist

1994-06-14

368

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

369

STAFF APPRECIATION AND RECOGNITION (STAR) Berkeley STAR Nomination Form  

E-print Network

1 STAFF APPRECIATION AND RECOGNITION (STAR) Berkeley STAR Nomination Form Name of Nominee: Employee ID: Job Title: Job Title Code: Unit/Department Name: Type of Award: Achievement Award Spot Award and has no outstanding disciplinary actions. Nominator Name: Signature: Date: mm/dd/yyyy (For Achievement

Sanders, Seth

370

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

371

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

372

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

2008-03-11

373

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

374

Recovery Ship Freedom Star  

NASA Technical Reports Server (NTRS)

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

1998-01-01

375

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

376

Stars and Planets  

NASA Astrophysics Data System (ADS)

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

Neta, Miguel

2014-05-01

377

Rotating relativistic neutron stars  

NASA Astrophysics Data System (ADS)

Models of rotating neutron stars are constructed in the framework of Einstein's theory of general relativity. For this purpose a refined version of Hartle's method is applied. The properties of these objects, e.g., gravitational mass, equatorial and polar radius, eccentricity, red- and blueshift, quadrupole moment, are investigated for Kepler frequencies of 4000/s less than OmegaK less than 9000/s. Therefore a self-consistency problem inherent in the determination of OmegaK must be solved. The investigation is based on neutron star matter equations of state derived from the relativistic Martin-Schwinger hierarch of coupled Green's functions. By means of introducing the Hartree, Hartree-Fock, and ladder (Lambda) approximations, models of the equation of states are derived. A special feature of the latter approximation scheme is the inclusion of dynamical two-particle correlations. These have been calculated from the relativistic T-matrix applying both the HEA and Bonn meson-exchange potentials of the nucleon-nucleon force. The nuclear forces of the former two treatments are those of the standard scalar-vector-isovector model of quantum hadron dynamics, with parameters adjusted to the nuclear matter data. An important aspect of this work consists in testing the compatibility of different competing models of the nuclear equation of state with data on pulsar periods. By this the fundamental problem of nuclear physics concerning the behavior of the equation of state at supernuclear densities can be treated.

Weber, F.; Glendenning, N. K.

1991-07-01

378

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

379

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

380

Star formation in the multiverse  

NASA Astrophysics Data System (ADS)

We develop a simple semianalytic model of the star formation rate as a function of time. We estimate the star formation rate for a wide range of values of the cosmological constant, spatial curvature, and primordial density contrast. Our model can predict such parameters in the multiverse, if the underlying theory landscape and the cosmological measure are known.

Bousso, Raphael; Leichenauer, Stefan

2009-03-01

381

A Handbook of Double Stars  

NASA Astrophysics Data System (ADS)

Preface; Part I. Historical, and Descriptive of Instruments and Methods: 1. Historical introduction; 2. The Equatorial: its construction and adjustments; 3. Some account of the Equatorials which have been used by double-star observers; 4. The micrometer; 5. Methods of observing double stars; Part II. On the Calculation of the Orbit of a Binary Star: 1. Introduction; 2. Example of an orbit worked by a graphical method; 3. Dr. Doberck's example of an orbit worked by analytical methods; 4. On relative rectilinear motion; 5. On the effect of proper motion and parallax on the observed position angles and distance of an optically double star; 6. On the errors of observation and the combination of observations; Part III. The Catalogue and Measures: Introductory remarks; A catalogue of binary and other double starts deserving of attention; Lists of measures, with historical notes, etc.; Supplementary list of measures; Appendix; Additional notes to measures; Binary stars classified; Note on systematic errors in the measures of angle and distance of double stars; Part IV. Bibliography: A. Some of the most important works and papers on double stars; B. Some papers on the micrometer; C. Some papers on the colours of double stars; Additional notes; Corrections 1880.

Crossley, Edward; Gledhill, Joseph; Wilson, James M.

2011-11-01

382

Magnetic fields in O stars  

NASA Astrophysics Data System (ADS)

During the last decade, large-scale, organized (generally dipolar) magnetic fields with strengths between 0.1 and 20 kG have been detected in dozens of OB stars. This contribution reviews the impact of such fields on the stellar winds of O-type stars, with emphasis on variability and X-ray emission.

Nazé, Y.

2014-11-01

383

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

384

Coronal Structures in Cool Stars.  

National Technical Information Service (NTIS)

We have extended our study of the structure of coronas in cool stars to very young stars still accreting from their surrounding disks. In addition we are pursing the connection between coronal X-rays and a powerful diagnostic line in the infrared, the He ...

R. Oliversen, A. K. Dupree

2005-01-01

385

Kinesthetic Life Cycle of Stars  

Microsoft Academic Search

We present a kinesthetic approach to learning about the life cycle of stars. Using a simplified two-layer model for stellar structure, learners recreate kinesthetically the birth, life, and death of low- and high-mass stars. Examples of how this activity has been used in several settings outside school time provide additional resources for extending student learning about this topic.

Erika L. Reinfeld; Mark A. Hartman

2008-01-01

386

Stars, brown dwarfs and planets  

Microsoft Academic Search

There is both observational and theoretical evidence for the occurrence of an embedded stage in the evolution of a stellar cluster during which the density of normal stars can be as high as a few times 104 stars pc-3, although usually somewhat lower than this. During this final stage of cluster development, when the gas density is higher and the

S. Oxley; M. M. Woolfson

387

Fate of most massive stars  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

388

Deformation of relativistic magnetized stars  

E-print Network

We formulate deformation of relativistic stars due to the magnetic stress, considering the magnetic fields to be perturbations from spherical stars. The ellipticity for the dipole magnetic field is calculated for some stellar models. We have found that the ellipticity becomes large with increase of a relativistic factor for the models with the same energy ratio of the magnetic energy to the gravitational energy.

Konno, K; Kojima, Y

1999-01-01

389

WhiteStar user's guide  

SciTech Connect

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

Ezell, T.F.

1990-08-01

390

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

391

Dust near luminous ultraviolet stars  

NASA Technical Reports Server (NTRS)

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

Henry, Richard C.

1993-01-01

392

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

393

Effective Dynamics for Boson Stars  

E-print Network

We study solutions close to solitary waves of the pseudo-relativistic Hartree equation describing boson stars under the influence of an external gravitational field. In particular, we analyze the long-time effective dynamics of such solutions. In essence, we establish a (long-time) stability result for solutions describing boson stars that move under the influence of an external gravitational field.

Juerg Froehlich; B. Lars G. Jonsson; Enno Lenzmann

2006-05-17

394

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

395

Comparable Habitable Zones of Stars  

NASA Video Gallery

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

396

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

397

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

398

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

399

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.

400

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

SciTech Connect

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

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

1994-03-02

401

Complexity and neutron stars structure  

E-print Network

We apply the statistical measure of complexity introduced by Lopez-Ruiz, Mancini and Calbet to neutron stars structure. Neutron stars is a classical example where the gravitational field and quantum behavior are combined and produce a macroscopic dense object. Actually, we continue the recent application of Sanudo and Pacheco to white dwarfs structure. We concentrate our study on the connection between complexity and neutron star properties, like maximum mass and the corresponding radius, applying a specific set of realistic equation of states. Moreover, the effect of the strength of the gravitational field on the neutron star structure and consequently on the complexity measure is also investigated. It is seen that neutron stars, consistent with astronomical observations so far, are ordered systems (low complexity), which cannot grow in complexity as their mass increases. This is a result of the interplay of gravity, the short-range nuclear force and the very short-range weak interaction.

K. Ch. Chatzisavvas; V. P. Psonis; C. P. Panos; Ch. C. Moustakidis

2009-05-27

402

IUE observations of Hyades stars  

SciTech Connect

The authors have obtained short wavelength, low dispersion ultraviolet spectra of seven of the brightest X-ray emitting stars in the Hyades cluster with the IUE observatory. Four of the stars show evidence of emission lines characteristic of transition region temperatures (about 30,000 - 2000,000 K): for the remaining three stars, we derive upper limits for emission line fluxes. In addition, observed were three of the above stars with the long wavelength spectrograph on IUE at high dispersion and find evidence for chromospheric emission from the MG II h and k lines for two of these objects. Combining the IUE results with X-ray observations from the survey of the Hyades with the Einstein Observatory. The author estimated the differential emission measure function for each of the above stars. They derived constraints on stellar atmospheric parameters (chromospheric pressure, coronal temperature and filling factor), and discussed the implications of the results for models of stellar chromospheres and coronae.

Zolcinski, M.S.; Antiochos, S.K.; Stern, R.A.; Walker, A.B.C.

1982-01-01

403

Stable phases of boson stars  

NASA Astrophysics Data System (ADS)

We analyze the physical properties of boson stars, which possess counterparts in flat space-time, Q-balls. Applying a stability analysis via catastrophe theory, we show that the families of rotating and nonrotating boson stars exhibit two stable regions, separated by an unstable region. Analogous to the case of white dwarfs and neutron stars, these two regions correspond to compact stars of lower and higher densities. Moreover, the high density phase ends when the black hole limit is approached. Here another unstable phase is encountered, exhibiting the typical spiralling phenomenon close to the black hole limit. When the interaction terms in the scalar field potential become negligible, the properties of mini-boson stars are recovered, which possess only a single stable phase.

Kleihaus, Burkhard; Kunz, Jutta; Schneider, Stefanie

2012-01-01

404

Toward Understanding Massive Star Formation  

E-print Network

Although fundamental for astrophysics, the processes that produce massive stars are not well understood. Large distances, high extinction, and short timescales of critical evolutionary phases make observations of these processes challenging. Lacking good observational guidance, theoretical models have remained controversial. This review offers a basic description of the collapse of a massive molecular core and a critical discussion of the three competing concepts of massive star formation: - monolithic collapse in isolated cores - competitive accretion in a protocluster environment - stellar collisions and mergers in very dense systems We also review the observed outflows, multiplicity, and clustering properties of massive stars, the upper initial mass function and the upper mass limit. We conclude that high-mass star formation is not merely a scaled-up version of low-mass star formation with higher accretion rates, but partly a mechanism of its own, primarily owing to the role of stellar mass and radiation pressure in controlling the dynamics.

Hans Zinnecker; Harold W. Yorke

2007-07-09

405

Quadrupole moments of rotating neutron stars and strange stars  

NASA Astrophysics Data System (ADS)

We present results for models of neutron stars and strange stars constructed using the Hartle-Thorne slow-rotation method with a wide range of equations of state, focusing on the values obtained for the angular momentum J and the quadrupole moment Q, when the gravitational mass M and the rotational frequency ? are specified. Building on previous work, which showed surprising uniformity in the behaviour of the moment of inertia for neutron-star models constructed with widely different equations of state, we find similar uniformity for the quadrupole moment. These two quantities, together with the mass, are fundamental for determining the vacuum space-time outside neutron stars. We study particularly the dimensionless combination of parameters QM/J2 (using units for which c = G = 1). This quantity goes to 1 in the case of a Kerr-metric black hole and deviations away from 1 then characterize the difference between neutron-star and black hole space-time. It is found that QM/J2 for both neutron stars and strange stars decreases with increasing mass, for a given equation of state, reaching a value of around 2 (or even less) for maximum-mass models, meaning that their external space-time is then not very far from that of the Kerr metric. If QM/J2 is plotted against R/2M (where R is the radius), it is found that the relationship is nearly unique for neutron-star models, independent of the equation of state, while it is significantly different for strange stars. This gives a new way of possibly distinguishing between them.

Urbanec, M.; Miller, J. C.; Stuchlík, Z.

2013-08-01

406

Infrared Stars: The interaction between stars and interstellar clouds produces "infrared stars" of two different kinds.  

PubMed

Our searches for very cool stars have revealed three kinds of objects: very cool Mira stars, perhaps cooler than any of this type previously known; extremely dense interstellar clouds, more dense than any known heretofore; and, probably, cool circumstellar clouds that may be planetary systems in an early stage of formation. PMID:17792840

Johnson, H L

1967-08-11

407

StarFISH: For Inferring Star-formation Histories  

NASA Astrophysics Data System (ADS)

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

Harris, Jason; Zaritsky, Dennis

2012-04-01

408

Profiling young massive stars  

NASA Astrophysics Data System (ADS)

We present the results of spectral energy distribution analysis for 162 of the 405 sources reported in the SIMBA survey of Hill et al. (2005). The fits reveal source specific parameters including: the luminosity, mass, temperature, H2 number density, the surface density and the luminosity-to-mass ratio. Each of these parameters are examined with respect to the four classes of source present in the sample. Obvious luminosity and temperature distinctions exist between the mm-only cores and those cores with methanol maser and/or radio continuum emission, with the former cooler and less luminous than the latter. The evidence suggests that the mm-only cores are a precursor to the methanol maser in the formation of massive stars. The mm-only cores comprise two distinct populations distinguished by temperature. Analysis and conclusions about the nature of the cool-mm and warm-mm cores comprising the mm-only population are drawn.

Hill, Tracey; Burton, M. G.; Cunningham, M. R.; Minier, V.

2007-03-01

409

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.

410

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

411

Binary Neutron Star Mergers  

E-print Network

We review the current status of studies of the coalescence of binary neutron star systems. We begin with a discussion of the formation channels of merging binaries and we discuss the most recent theoretical predictions for merger rates. Next, we turn to the quasi-equilibrium formalisms that are used to study binaries prior to the merger phase and to generate initial data for fully dynamical simulations. The quasi-equilibrium approximation has played a key role in developing our understanding of the physics of binary coalescence and, in particular, of the orbital instability processes that can drive binaries to merger at the end of their lifetimes. We then turn to the numerical techniques used in dynamical simulations, including relativistic formalisms, (magneto-)hydrodynamics, gravitational-wave extraction techniques, and nuclear microphysics treatments. This is followed by a summary of the simulations performed across the field to date, including the most recent results from both fully relativistic and micro...

Faber, Joshua A

2012-01-01

412

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

413

Radio Emission from Massive Stars  

NASA Astrophysics Data System (ADS)

I will report on two projects: The COBRaS E-Merlin survey of Cygnus OB2 and the BOSS search for bow shocks around massive stars. The Cygnus OB2 association is a nearby (1.2-1.8 kpc) young (~2-3 Myr) massive star cluster, that is tremendously rich in massive stars with strong stellar winds. The region will be studied using e-MERLIN as part of the COBRaS (Cygnus OB2 Radio Survey) project. The COBRaS project will enable studies of this region in areas of 1) mass-loss from massive stars, 2) radio astrometry yielding information on cluster dynamics, 3) binarity and colliding stellar winds and 4) ongoing and triggered star formation. The BOw Shock Survey (BOSS) is a multiwavelength search for bow shocks around massive stars. I will briefly discuss this project and present results with the VLA and GMRT on one particular object, which is a runaway star from Cyg OB2.

Brookes, Diane

2011-07-01

414

A-V Licks An Impossible Situation  

ERIC Educational Resources Information Center

An extensive multi-media program designed and developed by teachers and inmates at the Atlanta Federal Penitentiary has proven highly successful in providing students hands-on vocational education experiences necessary to equip them with job-entry skills. (EA)

Pounds, Jerry

1974-01-01

415

Do Massive Stars Have Planets?  

NASA Astrophysics Data System (ADS)

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

Barber, Sara; Kilic, Mukremin; Leggett, Sandy

2012-12-01

416

Neutron star moments of inertia  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

417

Differential Seismic Modeling of Stars  

NASA Astrophysics Data System (ADS)

CoRoT (Convection Rotation and planetary Transits) observations provide the opportunity to study a large sample of stars ranging from the Main Sequence (MS) to the Red Giant Branch. With the large increase in the number of stars showing solar-like oscillations, we intend to extract as much information as possible from a low signal-to-noise ratio (SNR) oscillation spectrum, benefiting from comparison with a reference star having similar seismic and fundamental parameters. We propose a differential method to determine stellar properties of solar-like oscillations which we call “differential seismology of stellar twins”.

Ozel, N.; Mosser, B.; Dupret, M.-A.; Bruntt, H.; Barban, C.; Deheuvels, S.; García, R. A.; Michel, E.; Samadi, R.; Baudin, F.; Régulo, C.; Auvergne, M.; Baglin, A.; Catala, C.; Morel, P.; Pichon, B.

2013-12-01

418

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

419

Oscillations on the star Procyon  

E-print Network

Stars are sphere of hot gas whose interiors transmit acoustic waves very efficiently. Geologists learn about the interior structure of Earth by monitoring how seismic waves propagate through it and, in a similar way, the interior of a star can be probed using the periodic motions on the surface that arise from such waves. Matthews et al. claim that the star Procyon does not have acoustic surface oscillations of the strength predicted. However, we show here, using ground-based spectroscopy, that Procyon is oscillating, albeit with an amplitude that is only slightly greater than the noise level observed by Matthews et al. using spaced-based photometry.

Francois Bouchy; Andre Maeder; Michel Mayor; Denis Megevand; Francesco Pepe; Danuta Sosnowska

2005-10-11

420

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

421

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

422

Soliton stars at finite temperature  

NASA Astrophysics Data System (ADS)

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

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

1991-09-01

423

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

2005-08-03

424

The STAR experiment's data acquisition system  

Microsoft Academic Search

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

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

2000-01-01

425

The STAR experiment's data acquisition system  

Microsoft Academic Search

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

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

1999-01-01

426

Terrestrial planet formation surrounding close binary stars  

Microsoft Academic Search

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

Elisa V. Quintana; Jack J. Lissauer

2006-01-01

427

Homogeneous Star Products Louis Boutet de Monvel  

E-print Network

1 were studied in [3], under the name "graded star products" (with a somewhat narrow symmetryHomogeneous Star Products Louis Boutet de Monvel Abstract: We give short proofs of results concerning homogeneous star products, of which S. Gutt's star product on the dual of a Lie algebra

Boutet de Monvel, Louis

428

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

429

"The Stars Tonight" LIVE Planetarium Show  

E-print Network

"The Stars Tonight" LIVE Planetarium Show Theme: The Stars Tonight Program is built around how The Stars Tonight and its associated classroom extensions meet specific national standards of learning (SoL's). The Stars Tonight takes its audience on a tour of the night sky, free from cloudy skies

Mathis, Wayne N.

430

WIMP Annihilation and Cooling of Neutron Stars  

E-print Network

We study the effect of WIMP annihilation on the temperature of a neutron star. We shall argue that the released energy due to WIMP annihilation inside the neutron stars, might affect the temperature of stars older than 10 million years, flattening out the temperature at $\\sim 10^4$ K for a typical neutron star.

Chris Kouvaris

2007-08-17

431

An Observational Look at Rotating Stars  

E-print Network

An Observational Look at Rotating Stars Stellar Structure and Evolution Rachel Matson ASTR 8100 #12;I. Introduction Rotational velocities of stars provide important clues to how stars form and evolve have been implemented to determine the rotational velocities of various types of stars, in order

Wiita, Paul J.

432

Spectral analyses of three carbonenhanced metalpoor stars  

E-print Network

Spectral analyses of three carbon­enhanced metal­poor stars N. T. Behara ab , P. Bonifacio abc , H% of very metal­poor stars ([Fe/H] +1.0). Such stars are referred to as carbon­enhanced metal­poor (CEMP) stars. A vari­ ety of abundance patterns are found among

Recanati, Catherine

433

X-ray Emission from Massive Stars  

E-print Network

X-ray Emission from Massive Stars David Cohen Department of Physics and Astronomy Swarthmore College http://astro.swarthmore.edu/~cohen Hot, massive stars are among the brightest objects be related to the production of X-rays on massive stars. If so, massive stars' X-rays are much different than

Cohen, David

434

The Stars behind the Curtain  

NASA Astrophysics Data System (ADS)

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

2010-02-01

435

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.

436

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.

437

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

with the American Russian Young Artists Orchestra Chamber Music Ensemble Amirus with performances at the Tatar, Eddie Lewis & Living Rhythms, and the Houston Professional Musician's Union All-Star Big Band featuring) Saturday, October 16 @ 12 noon Kemah, Texas PANtagonists STEEL DRUM BAND 4th Annual Pan Jam Festival Blake

Azevedo, Ricardo

438

Middle Level Activities Programs: Helping Achieve Academic Success.  

ERIC Educational Resources Information Center

The middle school athletic program should be based on the same philosophy governing academics and nonathletic activities. Essential criteria include total participation, no emphasis on winning, administrative and staff encouragement, short athletic sessions providing several choices, no tournaments or co