내용
사진
사진 업로드
DSS Images Other Images
관련 글
Speckle Observations of Binary Stars with the WIYN Telescope. VII. Measures during 2008-2009
Five hundred thirty-one speckle measures of binary stars are reported.These data were taken mainly during the period 2008 June through 2009October at the WIYN 3.5 m Telescope at Kitt Peak and represent the lastdata set of single-filter speckle observations taken in the WIYN speckleprogram prior to the use of the current two-channel speckle camera. Theastrometric and photometric precision of these observations isconsistent with previous papers in this series: we obtain a typicallinear measurement uncertainty of approximately 2.5 mas, and themagnitude differences reported have typical uncertainties in the rangeof 0.1-0.14 mag. In combination with measures already in the literature,the data presented here permit the revision of the orbit of A 1634AB (=HIP 76041) and the first determination of visual orbital elements forHDS 1895 (= HIP 65982).The WIYN Observatory is a joint facility of the University ofWisconsin-Madison, Indiana University, Yale University, and the NationalOptical Astronomy Observatories.
| Cross-correlation of the 2XMMi catalogue with Data Release 7 of the Sloan Digital Sky Survey
The Survey Science Centre of the XMM-Newton satellite released the firstincremental version of the 2XMM catalogue in August 2008. Containingmore than 220 000 X-ray sources, the 2XMMi was at that time the largestcatalogue of X-ray sources ever published and thus constitutes anunprecedented resource for studying the high-energy properties ofvarious classes of X-ray emitters such as AGN and stars. Thanks to thehigh throughput of the EPIC cameras on board XMM-Newton accuratepositions, fluxes, and hardness ratios are available for a substantialfraction of the X-ray detections. The advent of the 7th release of theSloan Digital Sky Survey offers the opportunity to cross-match two majorsurveys and extend the spectral energy distribution of many 2XMMisources towards the optical bands. This implies building extensivehomogeneous samples with a statistically controlled rate of spuriousmatches and completeness. We here present a cross-matching algorithmbased on the classical likelihood ratio estimator. The method developedhas the advantage of providing true probabilities of identificationswithout resorting to heavy Monte-Carlo simulations. Over 30,000 2XMMisources have SDSS counterparts with individual probabilities ofidentification higher than 90%. At this threshold, the sample has only2% spurious matches and contains 77% of all expected SDSSidentifications. Using spectroscopic identifications from the SDSS DR7catalogue supplemented by extraction from other catalogues, we build anidentified sample from which the way the various classes of X-rayemitters gather in the multi dimensional parameter space can be analysedand later used to design a source classification scheme. We illustratethe interest of this clean source sample by investigating two scientificuse cases. In the first example we show how these multi-wavelength datacan be used to search for new QSO2s. Although no specific range ofobserved properties allows us to efficiently identify Compton ThickQSO2s, we show that the prospects are much better for Compton Thin AGN2and discuss several possible multi-parameter selection strategies. In asecond example, we confirm the hardening of the mean X-ray spectrum withincreasing X-ray luminosity on a sample of over 500 X-ray active starsand reveal that on average X-ray active M stars display bluer g - rcolour indexes than less active ones. Although this catalogue of2XMM-SDSS sources cannot be used directly for statistical studies, itnevertheless represents an excellent starting point to select welldefined samples of X-ray-emitting objects.The corresponding fits file can be downloaded from the XCat-DB home page(http://xcatdb.u-strasbg.fr/).The file also contains line information for all SDSS spectroscopicentries matching a 2XMM source. Results from the cross-correlation withthe 2XMM DR3 are also available at the same location. The 2XMMi/SDSS DR7cross-correlation data file is also available at the CDS via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/527/A126
| Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry
Astrometric surveys provide the opportunity to measure the absolutemagnitudes of large numbers of stars, but only if the individualline-of-sight extinctions are known. Unfortunately, extinction is highlydegenerate with stellar effective temperature when estimated frombroad-band optical/infrared photometry. To address this problem, Iintroduce a Bayesian method for estimating the intrinsic parameters of astar and its line-of-sight extinction. It uses both photometry andparallaxes in a self-consistent manner in order to provide anon-parametric posterior probability distribution over the parameters.The method makes explicit use of domain knowledge by employing theHertzsprung-Russell Diagram (HRD) to constrain solutions and to ensurethat they respect stellar physics. I first demonstrate this method byusing it to estimate effective temperature and extinction from BVJHKdata for a set of artificially reddened Hipparcos stars, for whichaccurate effective temperatures have been estimated from high-resolutionspectroscopy. Using just the four colours, we see the expected strongdegeneracy (positive correlation) between the temperature andextinction. Introducing the parallax, apparent magnitude and the HRDreduces this degeneracy and improves both the precision (reduces theerror bars) and the accuracy of the parameter estimates, the latter byabout 35 per cent. The resulting accuracy is about 200 K in temperatureand 0.2 mag in extinction. I then apply the method to estimate theseparameters and absolute magnitudes for some 47 000 F, G, K Hipparcosstars which have been cross-matched with Two-Micron All-Sky Survey(2MASS). The method can easily be extended to incorporate the estimationof other parameters, in particular metallicity and surface gravity,making it particularly suitable for the analysis of the 109stars from Gaia.
| Observations of Binary Stars with the Differential Speckle Survey Instrument. II. Hipparcos Stars Observed in 2010 January and June
The results of 497 speckle observations of Hipparcos stars and selectedother targets are presented. Of these, 367 were resolved into componentsand 130 were unresolved. The data were obtained using the DifferentialSpeckle Survey Instrument at the WIYN 3.5 m Telescope. (The WIYNObservatory is a joint facility of the University of Wisconsin-Madison,Indiana University, Yale University, and the National Optical AstronomyObservatories.) Since the first paper in this series, the instrument hasbeen upgraded so that it now uses two electron-multiplying CCD cameras.The measurement precision obtained when comparing to ephemeris positionsof binaries with very well known orbits is approximately 1-2 mas inseparation and better than 0fdg6 in position angle. Differentialphotometry is found to be in very good agreement with Hipparcos measuresin cases where the comparison is most relevant. We derive preliminaryorbits for two systems.
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Duplicity in Hubble Space Telescope Guide Stars: Fine Guidance Sensor Serendipitous Survey Results
Data from the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS)interferometers, covering 22 months of guide-star acquisitionoperations, have been analyzed for evidence of stellar duplicity. Thedata comprise a survey of observed guide stars, all of which are takenfrom the HST Guide Star Catalog, ranging in magnitude from 9 to 14. Thesurvey results cover a parameter space for the newly found doubles, forthe fainter stars, which are of smaller limiting angular separationsthan in any previous surveys. The normal HST engineering telemetry datafrom 13,979 acquisitions on 4882 stars have been processed. The FGSguidance data can reveal duplicity with separations ranging fromapproximately 30 mas, for the brighter stars, with small magnitudedifferences, up to the neighborhood of 500 mas, and in some cases to1000 mas. The fraction of guide stars indicating duplicity is a functionof the statistical criteria used but is over 5% at a very high level ofconfidence. It is possible that if some of the brighter and closer pairscould be identified as nearby, then their orbital motions would be rapidenough to allow a mass and distance determination on a timescale of adecade if followed with ground-based interferometric and spectroscopicinstruments. A brief catalog of doubles is given, nearly all of whichare of certain duplicity. Information for accessing on-line catalogs oflarge numbers of stars with lesser, but nevertheless strong,probabilities of duplicity and also for the solutions for duplicity fromall acquisitions is provided.
| Observations of Double Stars. XVIII.
Micrometer observations of 1350 pairs in 1995-1997 are listed.
| New double stars (21st series) discovered at Nice
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1988A&AS...75..163C&db_key=AST
|
새 글 등록
관련 링크
새 링크 등록
다음 그룹에 속해있음:
|
관측 및 측정 데이터
천체목록:
|
