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The Hamburg/RASS Catalogue of optical identifications. Northern high-galactic latitude ROSAT Bright Source Catalogue X-ray sources
We present the Hamburg/RASS Catalogue (HRC) of optical identificationsof X-ray sources at high-galactic latitude. The HRC includes all X-raysources from the ROSAT Bright Source Catalogue (RASS-BSC) with galacticlatitude |b| >=30degr and declination delta >=0degr . In thispart of the sky covering ~ 10 000 deg2 the RASS-BSC contains5341 X-ray sources. For the optical identification we used blue Schmidtprism and direct plates taken for the northern hemisphere Hamburg QuasarSurvey (HQS) which are now available in digitized form. The limitingmagnitudes are 18.5 and 20, respectively. For 82% of the selectedRASS-BSC an identification could be given. For the rest either nocounterpart was visible in the error circle or a plausibleidentification was not possible. With ~ 42% AGN represent the largestgroup of X-ray emitters, ~ 31% have a stellar counterpart, whereasgalaxies and cluster of galaxies comprise only ~ 4% and ~ 5%,respectively. In ~ 3% of the RASS-BSC sources no object was visible onour blue direct plates within 40\arcsec around the X-ray sourceposition. The catalogue is used as a source for the selection of(nearly) complete samples of the various classes of X-ray emitters.
| The HRX-BL Lac sample - Evolution of BL Lac objects
The unification of X-ray and radio selected BL Lacs has been anoutstanding problem in the blazar research in the past years. Recentinvestigations have shown that the gap between the two classes can befilled with intermediate objects and that apparently all differences canbe explained by mutual shifts of the peak frequencies of the synchrotronand inverse Compton component of the emission. We study the consequencesof this scheme using a new sample of X-ray selected BL Lac objectscomprising 104 objects with z<0.9 and a mean redshift bar {z} = 0.34.77 BL Lacs, of which the redshift could be determined for 64 (83%)objects, form a complete sample. The new data could not confirm ourearlier result, drawn from a subsample, that the negative evolutionvanishes below a synchrotron peak frequency log nupeak =16.5. The complete sample shows negative evolution at the 2sigma level(< Ve/Va > = 0.42 +/- 0.04). We concludethat the observed properties of the HRX BL Lac sample show typicalbehaviour for X-ray selected BL Lacs. They support an evolutionarymodel, in which flat-spectrum radio quasars (FSRQ) with high energeticjets evolve towards low frequency peaked (mostly radio-selected) BL Lacobjects and later on to high frequency peaked (mostly X-ray selected) BLLacs.Appendix (Tables 8 and 9, Fig. 8) is only available in electronic format http://www.edpsciences.org
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
| M-Type Vega-like Stars
We carried out a search for M-type Vega-like stars by correlating theIRAS Faint Source Catalog with Hipparcos-selected M-type stars. Threestars with apparent IRAS 25 μm excess emission are shown instead tobe non-IR-excess stars from ground-based 11.7 and 17.9 μm photometry.Two stars previously suggested to have Vega-like mid-IR excess are alsoshown to be nonexcess stars. These results imply that other suggestedmid-IR-excess stars in the literature may also be false excess stars.Detection threshold bias is apparently responsible for these bogus IRexcesses. Sixty micron excess emission from a previously known M-typeVega-like star (GJ 803) is identified again.
| High-Resolution Optical Observations of Extreme-Ultraviolet-selected Active Late-type Stars
We present high-resolution optical spectra of EUV-selected late-typestars. We have detected seven new spectroscopic binaries, including apair of F stars and an RS Canum Venaticorum candidate. Many of the starsin our sample show remarkable Hα emission with equivalent widthsup to 8 Å. Several sources show strong He I 5876 Å emission.We use cross-correlation techniques to estimate line-of-sight rotationalvelocities and find that they range from less than 5 to over 80 kms-1. Several of the stars show a strong Li 6707 Å line,which we use to determine their Li abundances. The EUV-to-bolometricluminosity, a measure of the coronal heating efficiency, is as high as10-3. The present sample extends the EUV-selected late-typestars to lower Rossby numbers and makes the coronal saturation boundarybetter pronounced. Our results indicate that there is a drop in the EUVemission from the corona in late M dwarfs possibly because of a changein the nature of the magnetic dynamo in fully convective stars.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| RBSC-NVSS Sample. I. Radio and Optical Identifications of a Complete Sample of 1556 Bright X-Ray Sources
We cross-identified the ROSAT Bright Source Catalog (RBSC) and the NRAOVLA Sky Survey (NVSS) to construct the RBSC-NVSS sample of the brightestX-ray sources (>=0.1 counts s-1~10-12 ergscm-2 s-1 in the 0.1-2.4 keV band) that are alsoradio sources (S>=2.5 mJy at 1.4 GHz) in the 7.8 sr of extragalacticsky with |b|>15deg and δ>-40deg. Thesky density of NVSS sources is low enough that they can be reliablyidentified with RBSC sources having rms positional uncertainties>=10". We used the more accurate radio positions to make reliableX-ray/radio/optical identifications down to the POSS plate limits. Weobtained optical spectra for many of the bright identifications lackingpublished redshifts. The resulting X-ray/radio sample is unique in itssize (1557 objects), composition (a mixture of nearly normal galaxies,Seyfert galaxies, quasars, and clusters), and low average redshift[~0.1].
| The ROSAT Bright Survey: II. Catalogue of all high-galactic latitude RASS sources with PSPC countrate CR > 0.2 s-1
We present a summary of an identification program of the more than 2000X-ray sources detected during the ROSAT All-Sky Survey (Voges et al.1999) at high galactic latitude, |b| > 30degr , with countrate above0.2 s-1. This program, termed the ROSAT Bright Survey RBS, isto more than 99.5% complete. A sub-sample of 931 sources with countrateabove 0.2 s-1 in the hard spectral band between 0.5 and 2.0keV is to 100% identified. The total survey area comprises 20391deg2 at a flux limit of 2.4 x 10-12 ergcm-2 s-1 in the 0.5 - 2.0 keV band. About 1500sources of the complete sample could be identified by correlating theRBS with SIMBAD and the NED. The remaining ~ 500 sources were identifiedby low-resolution optical spectroscopy and CCD imaging utilizingtelescopes at La Silla, Calar Alto, Zelenchukskaya and Mauna Kea. Apartfrom completely untouched sources, catalogued clusters and galaxieswithout published redshift as well as catalogued galaxies with unusualhigh X-ray luminosity were included in the spectroscopic identificationprogram. Details of the observations with an on-line presentation of thefinding charts and the optical spectra will be published separately.Here we summarize our identifications in a table which contains opticaland X-ray information for each source. As a result we present the mostmassive complete sample of X-ray selected AGNs with a total of 669members and a well populated X-ray selected sample of 302 clusters ofgalaxies with redshifts up to 0.70. Three fields studied by us remainwithout optical counterpart (RBS0378, RBS1223, RBS1556). While the firstis a possible X-ray transient, the two latter are isolated neutron starcandidates (Motch et al. 1999, Schwope et al. 1999).
| Catalogue and bibliography of the UV Cet-type flare stars and related objects in the solar vicinity
This new catalogue of flare stars includes 463 objects. It containsastrometric, spectral and photometric data as well as information on theinfrared, radio and X-ray properties and general stellar parameters.From the total reference list of about 3400 articles, partial listsselected by objects, authors, key words and by any pairs of thesecriteria can be obtained Tables 1, 2 and 3 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Identification of soft high galactic latitude RASS X-ray sources. I. A complete count-rate limited sample
We present a summary of spectroscopic identifications for a completesample of bright soft high galactic latitude X-ray sources drawn fromthe ROSAT All-Sky Survey which have PSPC count-rates CR > 0.5 {ctss}(-1) and hardness ratios HR1 < 0. Of a total of 397 sources, 270had catalogued counterparts although most of these were not previouslyknown as X-ray sources; of the remaining 127 sources neither X-ray noroptical properties were previously known. Of the whole sample of verysoft X-ray sources 155 were also discovered by the Wide-Field-Camera onboard ROSAT. We present spectroscopic identifications of 108 sources andother identifications for further 18 sources; 1 source remainsunidentified so far. In practically all cases a unique opticalcounterpart exists facilitating identification. The largest sourceclasses are AGN, magnetic cataclysmic variables, and hot white dwarfs.Based in part on observations with the ESO/MPI 2.2m telescope at LaSilla, Chile
| An Optical Atlas of Extreme Ultraviolet Explorer (EUVE) Sources
The Extreme Ultraviolet Explorer (EUVE) has been detecting EUV sourcessince its launch in June 1992. Positions of 540 sources have been madeavailable to the community by the EUVE team. We have extracted 7' X 7'images centered on these 540 EUVE sources from the Space TelescopeScience Institute digitized sky archives. We present these images asmosaic finder charts to aid observers trying to identify EUVE sources,or to characterize known sources. (SECTION: Atlases)
| An H-alpha survey of neglected Vyssotsky Catalog stars
Consideration is given to a significant number of Vyssotsky K- andM-dwarfs that have either no published radial velocity (71 stars), or avelocity based on a single measure (22), or with an uncertaintly greaterthan 5 km/s (19). An 'in flare' observation of Vys 250A compared to itsquiescent state, and an example of the double-lined phase of Vys 250Bare illustrated. Mean values from the observations are given in tabularform.
| An All-Sky Catalog of Faint Extreme Ultraviolet Sources
We present a list of 534 objects detected jointly in the ExtremeUltraviolet Explorer (EUVE) 100 Angstroms all-sky survey and in theROSAT X-Ray Telescope 0.25 keV band. The joint selection criterionpermits use of a low count rate threshold in each survey. This lowthreshold is roughly 60% of the threshold used in the previous EUVEall-sky surveys, and 166 of the objects listed here are new EUV sources,appearing in neither the Second EUVE Source Catalog nor the ROSAT WideField Camera Second Catalog. The spatial distribution of this all-skycatalog shows three features: an enhanced concentration of objects inUrsa Major, where the Galactic integrated H I column reaches its globalminimum; an enhanced concentration in the third quadrant of the Galaxy(lII from 180 deg to 270 deg) including the Canis Major tunnel, whereparticularly low H I columns are found to distances beyond 200 pc; and aparticularly low number of faint objects in the direction of the fourthquadrant of the Galaxy, where nearby intervening H I columns areappreciable. Of particular interest is the composition of the 166detections not previously reported in any EUV catalog. We offerpreliminary identifications for 105 of these sources. By far the mostnumerous (81) of the identifications are late-type stars (F, G, K, M),while 18 are other stellar types, only five are white dwarfs (WDs), andnone are extragalactic. The paucity of WDs and extragalactic objects maybe explained by a strong horizon effect wherein interstellar absorptionstrongly limits the effective new-source search volume and, thereby,selectively favors low-luminosity nearby sources over more luminous butdistant objects.
| Space Motions of Low-Mass Stars. II: Radial Velocities
Radial velocities are presented for 53 dwarf K and M stars, eight ofwhich are radial velocity standards. This is the second list in aprogram to determine space motions for all of the stars in the McCormicklists of dwarf stars. The observations reported here differ from thoseof the first list in that they were made using the 1.88m David Dunlapreflector. One of the stars varies in radial velocity, consistent with aspectroscopic binary with a period of about 48 days. (SECTION: Stars)
| The Second Extreme-Ultraviolet Explorer Source Catalog
We present the second catalog of extreme-ultraviolet objects detected bythe Extreme-Ultraviolet Explorer. The data include (1) all-sky surveydetections from the initial 6 month scanner-survey phase, (2) additionalscanner detections made subsequently during specially programmedobservations designed to fill in low-exposure sky areas of the initialsurvey, (3) sources detected with deep-survey-telescope observationsalong the ecliptic, (4) objects detected by the scanner telescopesduring targeted spectroscopy observations, and ( 3) other observations.We adopt an innovative source detection method that separates the usuallikelihood function into two parts: an intensity diagnostic and aprofile diagnostic. These diagnostics allow each candidate detection tobe tested separately for both signal-to-noise ratio and conformance withthe known instrumental point-spread function. We discuss the dependenceof the false-alarm rate and the survey's completeness on the survey'ssensitivity threshold. We provide three lists of the EUV sourcesdetected: the all-sky survey detections, the deep-survey detections, andsources detected during other phases of the mission. Each list givespositions and intensities in each wave band. The total number of objectslisted is 734. For approximately 65% of these we also provide plausibleoptical, UV, radio, and/or X-ray identifications.
| The first Extreme Ultraviolet Explorer source catalog
The Extreme Ultraviolet Explorer (EUVE) has conducted an all-sky surveyto locate and identify point sources of emission in four extremeultraviolet wavelength bands centered at approximately 100, 200, 400,and 600 A. A companion deep survey of a strip along half the eclipticplane was simultaneously conducted. In this catalog we report thesources found in these surveys using rigorously defined criteriauniformly applied to the data set. These are the first surveys to bemade in the three longer wavelength bands, and a substantial number ofsources were detected in these bands. We present a number of statisticaldiagnostics of the surveys, including their source counts, theirsensitivites, and their positional error distributions. We provide aseparate list of those sources reported in the EUVE Bright Source Listwhich did not meet our criteria for inclusion in our primary list. Wealso provide improved count rate and position estimates for a majorityof these sources based on the improved methodology used in this paper.In total, this catalog lists a total of 410 point sources, of which 372have plausible optical ultraviolet, or X-ray identifications, which arealso listed.
| Extreme Ultraviolet Explorer Bright Source List
Initial results from the analysis of the Extreme Ultraviolet Explorer(EUVE) all-sky survey (58-740 A) and deep survey (67-364 A) arepresented through the EUVE Bright Source List (BSL). The BSL contains356 confirmed extreme ultraviolet (EUV) point sources with supportinginformation, including positions, observed EUV count rates, and theidentification of possible optical counterparts. One-hundred twenty-sixsources have been detected longward of 200 A.
| Photometry of dwarf K and M stars
An observational program using UBVRI photometry is presented for 688stars from among the dwarf K and M stars already found spectroscopicallyby Vyssotsky (1958). Of these, 211 have not been observedphotometrically. These observations were obtained over a period ofseveral years at the Kitt Peak National Observatory using a GaAsphotomultiplier with an 0.9 m reflector. Based on night-to-nightvariations in the measures of individual stars, the internal errors maybe estimated to be roughly 0.01 mag for the colors and 0.015 for the Vmagnitudes. The photometric parallaxes reported for each star werecomputed in the manner discussed by Weis (1986).
| An optical Atlas of ROSAT Wide Field Camera EUV sources
The ROSAT Wide Field Camera has been detecting EUV sources since itslaunch in June 1990. A preliminary list of 384 bright sources has beensupplied by the Wide Field Camera team to the EUVE Guest ObserverCenter, and to the astronomical community. We have extracted 5.4 x 5.4arcmin images of all 384 WFC sources from the Space Telescope ScienceInstitute digitized sky archives. These images are presented asmosaicked finder charts for observers trying either to identify WFCsources or to characterize known sources.
| The ROSAT Wide Field Camera all-sky survey of extreme-ultraviolet sources. I - The Bright Source Catalogue
First comprehensive results from an initial processing of the ROSAT WideField Camera all-sky survey for cosmic sources of extreme-ultravioletradiation are presented. The reduction of the survey data has yielded acatalog of 383 relatively bright EUV sources, forming the WFC BrightSource Catalogue. Details of the EUV source positions and count ratesare given, as are optical identifications where known. It is found thatthe log N-log S distributions are unusually flat for the white dwarfstars, but almost Euclidean for the nearby main-sequence late-typestars. The sky distribution of identified white dwarfs is highlynonuniform, suggesting gross variations in the opacity of theinterstellar medium within about 100 pc.
| Parallaxes and proper motions from the McCormick Observatory - List 46
Trigonometric parallaxes and relative proper motions are presented for26 late-type stars observed with the Leander McCormick rafractor.Eighteen stars have no previously published parallaxes. Sixteen starsare K and M dwarfs identified by Vyssotsky and his collaborators. Thelist includes three probable Hyades cluster members, two subdwarfs, andan M dwarf at a distance of about 10 pc. New BVRI photometry has beenobtained for most stars on the list.
| H-alpha photometry of dwarf K and M stars - Chromospheric activity
H-alpha photometry of 118 K and M dwarfs are presented, with H-alphaequivalent width measures accurate to about 0.05 A. The data arecombined with the spectroscopic surveys of Stauffer and Hartmann (1986)and Fleming et al. (1988) to study the main features of thechromospheric activity versus mass relation for low-mass stars. An upperbound to the H-alpha equivalent width is found to be a function of themass relation (R-I). H-alpha luminosities and surface fluxes arecalculated for active stars, showing that both quantities generallydecline with R-I. The upper bound to the fraction of a star's bolometricluminosity, however, is independent of R-I. The results suggest that thechromospheres of most dMe stars with R-I less than 1.1 are in anactivity-saturated state. Also, H-alpha variability, probably due toflares, is detected in several stars.
| Dwarf K and M stars of high proper motion found in a hemispheric survey
A recently completed visual/red spectral region objective-prism surveyof more than half the sky found some 2200 dwarf K and M stars ofnegligible proper motion (Stephenson, 1986). The present paper adds the1800-odd spectroscopically identified dwarfs that did prove to havesignificant proper motions. About half of these had previous spectralclassifications of some sort, especially by Vyssotsky (1952, 1956). Forthe great majority, the present coordinates are more accurate thanprevious data. The paper includes about 50 stars with unpublishedparallaxes, likely to have parallaxes of 0.05 arcsec or more. Combiningthe present data with the first paper suggests that the number oflow-proper-motion stars in that paper was not unreasonable.
| Photovisual magnitudes of 418 dwarf M stars and 34 parallax stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..219S&db_key=AST
| Dwarf M stars found spectrophotometrically .
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..201V&db_key=AST
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| קבוצת-כוכבים: | נחש |
| התרוממות ימנית: | 15h21m52.93s |
| סירוב: | +20°58'39.9" |
| גודל גלוי: | 10.087 |
| מרחק: | 11.391 פארסק |
| תנועה נכונה: | 80.1 |
| תנועה נכונה: | 128.7 |
| B-T magnitude: | 11.884 |
| V-T magnitude: | 10.236 |
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