目录
图像
上传图像
DSS Images Other Images
相关文章
Observation and modelling of main-sequence star chromospheres - XVII. Rotation of dM4 stars
Using two different spectrographs, High Accuracy Radial velocity PlanetSearcher (European Southern Observatory) and SOPHIE (Observatoire deHaute Provence), we have measured v sin i for a sample of 23 dM4 stars.These are the first measurements of v sin i for most of the starsstudied here.We measured v sin i to a precision of 0.3 km s-1 and adetection limit of about 0.5-1 km s-1. All our targets havesimilar (R-I)C colour. This is an advantage and facilitatesthe determination of the narrowest cross-correlation profiles for v sini˜ 0. In our sample, we detected rotation for 21 stars (12 dM4estars and nine dM4 stars) and we did not detect rotation in a furthertwo stars. This result shows that there are many dM4 fast rotators (ofthe order of 5 d), and many more than in the case of dM1 stars.We determined radii and effective temperatures for all our target stars.The effective temperatures were derived using the (R-I)Ccolour and empirical far-red colour-effective temperature correlations.We derived the radii from the standard formulae relatingMbol, bolometric correction (BC) and Teff.We find that the distribution of P/sin i (the projected rotation period)is bimodal with a maximum for slow rotators around 14 d and for fastrotators around 6 d, similar to dM1 stars. The rotation period appearsto decrease with decreasing radius, both among dM4 and dM4e stars. Thesame finding was obtained in our previous study of dM1 stars.
| A Catalog of Rotation and Activity in Early-M Stars
We present a catalog of rotation and chromospheric activity in a sampleof 334 M dwarfs of spectral types M0-M4.5 populating the parameter spacearound the boundary to full convection. We obtain high-resolutionoptical spectra for 206 targets and determine projected rotationalvelocity, vsin i, and H? emission. The data are combined withmeasurements of vsin i in field stars of the same spectral type from theliterature. Our sample adds 157 new rotation measurements to theexisting literature and almost doubles the sample of available vsin i.The final sample provides a statistically meaningful picture of rotationand activity at the transition to full convection in the solarneighborhood. We confirm a steep rise in the fraction of active stars atthe transition to full convection known from earlier work. In addition,we see a clear rise in rotational velocity in the same stars. In veryfew stars, no chromospheric activity but a detection of rotationalbroadening is reported. We argue that all of them are probably spuriousdetections; we conclude that in our sample all significantly rotatingstars are active, and all active stars are significantly rotating. Therotation-activity relation is valid in partially and in fully convectivestars. Thus, we do not observe any evidence for a transition from arotationally dominated dynamo in partially convective stars to arotation-independent turbulent dynamo in fully convective stars;turbulent dynamos in fully convective stars of spectral types around M4are still driven by rotation. Finally, we compare projected rotationalvelocities of 33 stars to rotational periods derived from photometry inthe literature and determine inclinations for a few of them.
| The Search for Super-saturation in Chromospheric Emission
We investigate if the super-saturation phenomenon observed at X-raywavelengths for the corona exists in the chromosphere for rapidlyrotating late-type stars. Moderate resolution optical spectra offast-rotating EUV- and X-ray-selected late-type stars were obtained.Stars in ? Per were observed in the northern hemisphere with theIsaac Newton 2.5 m telescope and Intermediate Dispersion Spectrograph.Selected objects from IC 2391 and IC 2602 were observed in the southernhemisphere with the Blanco 4 m telescope and R-C spectrograph at CTIO.Ca II H and K fluxes were measured for all stars in our sample. We findthe saturation level for Ca II K at log (L CaK/Lbol) = -4.08. The Ca II K flux does not show a decrease as afunction of increased rotational velocity or smaller Rossby number asobserved in the X-ray. This lack of "super-saturation" supports the ideaof coronal stripping as the cause of saturation and super-saturation instellar chromospheres and coronae, but the detailed underlying mechanismis still under investigation.
| Effect of magnetic activity saturation in chromospheric flux-flux relationships
We present a homogeneous study of chromospheric and coronal flux-fluxrelationships using a sample of 298 late-type dwarf active stars withspectral types F to M. The chromospheric lines were observedsimultaneously in each star to avoid spread as a result of long-termvariability. Unlike other works, we subtract the basal chromosphericcontribution in all the spectral lines studied. For the first time, wequantify the departure of dMe stars from the general relations. We showthat dK and dKe stars also deviate from the general trend. Studying theflux-colour diagrams, we demonstrate that the stars deviating from thegeneral relations are those with saturated X-ray emission and we showthat these stars also present saturation in the H? line. Usingseveral age spectral indicators, we show that these are younger starsthan those following the general relationships. The non-universality offlux-flux relationships found in this work should be taken into accountwhen converting between fluxes in different chromospheric activityindicators.
| A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun
Traditionally, runaway stars are O- and B-type stars with large peculiarvelocities. We would like to extend this definition to young stars (upto ?50 Myr) of any spectral type and to identify those present in theHipparcos catalogue by applying different selection criteria, such aspeculiar space velocities or peculiar one-dimensional velocities.Runaway stars are important for studying the evolution of multiple starsystems or star clusters, as well as for identifying the origins ofneutron stars. We compile the distances, proper motions, spectral types,luminosity classes, V magnitudes and B-V colours, and we utilizeevolutionary models from different authors to obtain star ages. We studya sample of 7663 young Hipparcos stars within 3 kpc from the Sun. Theradial velocities are obtained from the literature. We investigate thedistributions of the peculiar spatial velocity and the peculiar radialvelocity as well as the peculiar tangential velocity and itsone-dimensional components and we obtain runaway star probabilities foreach star in the sample. In addition, we look for stars that aresituated outside any OB association or OB cluster and the Galactic planeas well as stars for which the velocity vector points away from themedian velocity vector of neighbouring stars or the surrounding local OBassociation/cluster (although the absolute velocity might be small). Wefind a total of 2547 runaway star candidates (with a contamination ofnormal Population I stars of 20 per cent at most). Thus, aftersubtracting these 20 per cent, the runaway frequency among young starsis about 27 per cent. We compile a catalogue of runaway stars, which isavailable via VizieR.
| Accurate Coordinates and 2MASS Cross Identifications for (Almost) All Gliese Catalog Star
We provide precise J2000, epoch 2000 coordinates, andcross-identifications to sources in the 2MASS Point Source Catalog fornearly all stars in the Gliese, Gliese-Jahreiss, and Woolley catalogs ofnearby stars. The only Gliese objects where we were not successful aretwo Gliese sources that are actually QSOs; two proposed companions tobrighter stars, which we believe do not exist; four stars included inone of the catalogs but identified there as only optical companions; oneprobable plate flaw; and two stars that simply remain unrecovered. Forthe 4251 recovered stars, 2693 have coordinates based on Hipparcospositions, 1549 have coordinates based on 2MASS data, and 9 havepositions from other astrometric sources. All positions have beencalculated at epoch 2000 using proper motions from the literature, whichare also given here.
| UBV(RI)C JHK observations of Hipparcos-selected nearby stars
We present homogeneous, standardized UBV(RI)C photometry forover 700 nearby stars selected on the basis of Hipparcos parallaxes.Additionally, we list JHK photometry for about half of these stars, aswell as L photometry for 86 of the brightest. A number of stars withpeculiar colours or anomalous locations in various colour-magnitudediagrams are discussed.
| Imaging Young Giant Planets From Ground and Space
High-contrast imaging can find and characterize gas giant planets aroundnearby young stars and the closest M stars, complementing radialvelocity and astrometric searches by exploring orbital separationsinaccessible to indirect methods. Ground-based coronagraphs are alreadyprobing within 25 AU of nearby young stars to find objects as small as .This paper contrasts near-term and future ground-based capabilities withhigh-contrast imaging modes of the James Webb Space Telescope (JWST).Monte Carlo modeling reveals that JWST can detect planets with masses assmall as across a broad range of orbital separations. We present newcalculations for planet brightness as a function of mass and age forspecific JWST filters and extending to .
| XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources
The 18,806 ROSAT All Sky Survey Bright Source Catalog (RASS/BSC) X-raysources are quantitatively cross-associated with near-infrared (NIR)sources from the Two Micron All Sky Survey Point Source Catalog(2MASS/PSC). An association catalog is presented, listing the mostlikely counterpart for each RASS/BSC source, the probability Pid that the NIR source and X-ray source are uniquelyassociated, and the probability P no-id that none of the2MASS/PSC sources are associated with the X-ray source. The catalogincludes 3853 high quality (P id>0.98) X-ray-NIR matches,2280 medium quality (0.98 >= P id>0.9) matches, and4153 low quality (0.9 >= P id>0.5) matches. Of the highquality matches, 1418 are associations that are not listed in the SIMBADdatabase, and for which no high quality match with a USNO-A2 opticalsource was presented for the RASS/BSC source in previous work. Thepresent work offers a significant number of new associations withRASS/BSC objects that will require optical/NIR spectroscopy forclassification. For example, of the 6133 P id>0.92MASS/PSC counterparts presented in the association catalog, 2411 haveno classification listed in the SIMBAD database. These 2MASS/PSC sourceswill likely include scientifically useful examples of known sourceclasses of X-ray emitters (white dwarfs, coronally active stars, activegalactic nuclei), but may also contain previously unknown sourceclasses. It is determined that all coronally active stars in theRASS/BSC should have a counterpart in the 2MASS/PSC, and that the uniqueassociation of these RASS/BSC sources with their NIR counterparts thusis confusion limited.
| The effect of activity on stellar temperatures and radii
Context: Recent analyses of low-mass eclipsing binary stars haveunveiled a significant disagreement between the observations andpredictions of stellar structure models. Results show that theoreticalmodels underestimate the radii and overestimate the effectivetemperatures of low-mass stars but yield luminosities that accord withobservations. A hypothesis based upon the effects of stellar activitywas put forward to explain the discrepancies. Aims: In this paper westudy the existence of the same trend in single active stars and providea consistent scenario to explain systematic differences between activeand inactive stars in the H-R diagram reported earlier. Methods: Theanalysis is done using single field stars of spectral types late-K and Mand computing their bolometric magnitudes and temperatures throughinfrared colours and spectral indices. The properties of the stars insamples of active and inactive stars are compared statistically toreveal systematic differences. Results: After accounting for a numberof possible bias effects, active stars are shown to be cooler thaninactive stars of similar luminosity therefore implying a larger radiusas well, in proportions that are in excellent agreement with those foundfrom eclipsing binaries. Conclusions: The present results generalisethe existence of strong radius and temperature dependences on stellaractivity to the entire population of low-mass stars, regardless of theirmembership in close binary systems.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/478/507
| Further observations of Hipparcos red stars and standards for UBV(RI)C photometry
We present homogeneous and standardized UBV(RI)C JHKphotometry for over 100 M stars selected from an earlier paper on thebasis of apparent photometric constancy. L photometry has been obtainedfor stars brighter than about L = 6. Most of the stars have asubstantial number of UBV(RI)C observations and, it is hoped,will prove useful as red supplementary standards. Additionally, we listJHK photometry for nearly 300 Hipparcos red stars not selected asstandards, as well as L photometry for the brightest stars.
| Identification of New M Dwarfs in the Solar Neighborhood
We present the results from a spectroscopic study of 1080 nearby activeM dwarfs, selected by correlating the Two Micron All Sky Survey andROSAT catalogs. We have derived the spectral types and estimateddistances for all of our stars. The spectral types range between K5 andM6. Nearly half of our stars lie within 50 pc. We have measured theequivalent width of the Hα emission line. Our targets show anincrease in chromospheric activity from early to midspectral types, witha peak in activity around M5. Using the count rate and hardness ratiosobtained from the ROSAT catalog, we have derived the X-ray luminosities.Our stars display a ``saturation-type'' relation between thechromospheric and coronal activity. The relation is such thatlogLX/Lbol remains ``saturated'' at a value ofapproximately -3 for varying Hα equivalent width. We have found568 matches in the USNO-B catalog and have derived the tangentialvelocities for these stars. There is a slight trend of decreasingchromospheric activity with age, such that the stars with highervtan have lower Hα equivalent widths. The coronalemission, however, remains saturated at a value oflogLX/Lbol~-3 for varying tangential velocities,suggesting that the coronal activity remains saturated with age. We donot find any break in the saturation-type relation at the spectral typeat which stars become fully convective (~M3.5). Most of the stars in oursample show more coronal emission than the dMe stars in the Hyades andPraesepe and have vtan<40 km s-1, suggesting ayoung population.
| The spectroscopic characteristics of intermediate-aged pre-main-sequence stars: the η Chamaeleontis cluster
We present a study of calibrated low-resolution spectra of the 18 knownprimaries of the ~9-Myr-old η Chamaeleontis (η Cha)pre-main-sequence (PMS) star cluster. Using synthetic broad-band coloursand narrow-band continuum-sensitive, temperature-sensitive andgravity-sensitive indices derived from the spectra, we compare the ηCha stars to standard dwarfs. We find that the VRI colours of the PMSstars are indistinguishable from those of main-sequence stars, but thata B-band excess attaining ~0.2 mag for late-M cluster stars is present,which might be an indicator of gravity, metallicity and/or activitydifferences between the two samples of stars. The narrow-band spectralindices for the η Cha stars possibly indicate higher metallicity andstrongly indicate lower surface gravity than the dwarf indices,consistent with the elevated location of the cluster in theHertzsprung-Russell evolutionary diagram. Using the derived syntheticcolours and indices, we adopt spectral types for the late-type η Chastars. We then produce a table of absolute optical magnitudes andcolours representing the cluster isochrone for comparison with PMSevolutionary models. From our results we also conclude that the ηCha stars are unreddened, consistent with the group being a sample ofolder PMS stars distant from obscuring molecular clouds, except for theA1 member HD 75505 for which we confirm AV= 0.4 mag likelydue to the presence of circumstellar material.
| High-energy sources before INTEGRAL. INTEGRAL reference catalog
We describe the INTEGRAL reference catalog which classifies previouslyknown bright X-ray and gamma-ray sources before the launch of INTEGRAL.These sources are, or have been at least once, brighter than ~ 1 mCrababove 3 keV, and are expected to be detected by INTEGRAL. This catalogis being used in the INTEGRAL Quick Look Analysis to discover newsources or significantly variable sources. We compiled several publishedX-ray and gamma-ray catalogs, and surveyed recent publications for newsources. Consequently, there are 1122 sources in our INTEGRAL referencecatalog. In addition to the source positions, we show an approximatespectral model and expected flux for each source, based on which wederive expected INTEGRAL counting rates. Assuming the default instrumentperformances and at least ~ 105 s exposure time for anypart of the sky, we expect that INTEGRAL will detect at least ~ 700sources below 10 keV and ~ 400 sources above 20 keV over the missionlife.The Catalog is available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/411/L59
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| UBV(RI)C photometry of Hipparcos red stars
We present homogeneous and standardized UBV(RI)C photometryfor nearly 550 M stars selected from the Hipparcos satellite data baseusing the following selection criteria: lack of obvious variability (noHipparcos variability flag); δ<+10°(V-I)>1.7 and Vmagnitude fainter than about 7.6. Comparisons are made between thecurrent photometry, other ground-based data sets and Hipparcosphotometry. We use linear discriminant analysis to determine aluminosity segregation criterion for late-type stars, and principalcomponent analysis to study the statistical structure of the colourindices and to calibrate absolute magnitude in terms of (V-I) for thedwarf stars. Various methods are used to determine the mean absolutemagnitude of the giant stars. We find 10 dwarf stars, apparentlypreviously unrecognized (prior to Hipparcos) as being within 25pc,including five within 20pc.
| Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog
We present refined coordinates and proper-motion data for the highproper-motion (HPM) stars in the Luyten Half-Second (LHS) catalog. Thepositional uncertainty in the original Luyten catalog is typicallygreater than 10" and is often greater than 30". We have used the digitalscans of the POSS I and POSS II plates to derive more accurate positionsand proper motions of the objects. Out of the 4470 candidates in the LHScatalog, 4323 objects were manually reidentified in the POSS I and POSSII scans. A small fraction of the stars were not found because of thelack of finder charts and digitized POSS II scans. The uncertainties inthe revised positions are typically ~2" but can be as high as ~8" in afew cases, which is a large improvement over the original data.Cross-correlation with the Tycho-2 and Hipparcos catalogs yielded 819candidates (with mR<~12). For these brighter sources, theposition and proper-motion data were replaced with the more accurateTycho-2/Hipparcos data. In total, we have revised proper-motionmeasurements and coordinates for 4040 stars and revised coordinates for4330 stars. The electronic version of the paper5 contains the updated information on all 4470stars in the LHS catalog.
| 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.
| V857 Centauri
IAUC 7693 available at Central Bureau for Astronomical Telegrams.
| 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 ROSAT all-sky survey catalogue of the nearby stars
We present X-ray data for all entries of the Third Catalogue of NearbyStars \cite[(Gliese & Jahreiss 1991)]{gli91} that have been detectedas X-ray sources in the ROSAT all-sky survey. The catalogue contains1252 entries yielding an average detection rate of 32.9 percent. Inaddition to count rates, source detection parameters, hardness ratios,and X-ray fluxes we also list X-ray luminosities derived from Hipparcosparallaxes. Catalogue also available at CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Galactic Orbits of Nearby UV Ceti Stars
The galactic orbits of 93 UV Ceti stars of the solar neighborhood havebeen numerically integrated. The UV Ceti stars studied are those of theworking list for which Poveda et al. (1996a) determined kinematicproperties and ages. All stars are contained within 25 pc of the Sun(π ≥ 0.04''), and values for their distances, proper motions andradial velocities are available for them (Gliese & Jahreiss 1991).The galactic potential model of Allen & Santillán (1991) wasused, and the orbits were integrated for times similar to the age of theold disk. The galactic orbital parameters are obtained. The orbits areall regular, and the values found for the orbital parameters are similarto those characteristic of the classic young thin disk. The verticalscale height found for the whole sample is 115 pc. However, the orbitalparameters found for the 7 objects with extreme kinematiccharacteristics recognized in Poveda et al. are markedly different fromthose of the rest of the flare stars; in particular, their orbitaleccentricities are larger than 0.3. The vertical scale height of thesample excluding the anomalous objects is just 103 pc. Consequently, wepropose that the anomalous objects belong to the thick disk, which maybe characterized by either e≥ 0.3 or | zmax | > 400 pc.
| 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)
| Astrometric positions of stars with high proper motions in the Southern Hemisphere
Several stars with large proper motions, cited by W.J. Luyten, wereincluded in the preliminary programme for the HIPPARCOS mission. Whenperforming preparatory measurements of plates, difficulties wereencountered in identifying certain of these stars when relying only onpublished coordinates. We have taken advantage of this work whichrelates to the southern sky in order to determine the astrometricposition of the greatest possible number of these objects, even forthose which were not included in the programme. Catalogue 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/Abstract.html
| 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.
| Chromospheric Activity, Stellar Winds and Red Stragglers (Invited Paper)
Not Available
| The Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2799H&db_key=AST
| The Stellar Content of Star Stream I
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1615E&db_key=AST
| 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 general catalogue of trigonometric [stellar] paralaxes
Not Available
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
