- ID:
- ivo://nasa.heasarc/rassdwarf
- Title:
- ROSAT All-Sky Survey: A-K Dwarfs/Subgiants
- Short Name:
- RASS/Dwarf
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog presents X-ray data for all the main-sequence and subgiant stars of spectral types A, F, G, and K and luminosity classes IV and V listed in the Bright Star Catalogue (also known as the HR Catalogue) that have been detected as X-ray sources in the ROSAT All-Sky Survey (RASS). A number of stars in the appropriate spectral type range that do not have assigned luminosity classes have also been included. The catalogue contains 980 such HR stars detected as X-ray sources out of a total of 3054 stars in the HR Catalogue that satisfy the selection criteris, implying an average detection rate of 32%. In addition to the measured ROSAT PSPC count rates, source detection parameters, hardness ratios, and X-ray fluxes, X-ray luminosities derived from Hipparcos parallaxes are also listed. This database was created at the HEASARC in February 1999 based on the ADC/<a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+AS/132/155">CDS Catalog J/A+AS/132/155</a>. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/chasfrxray
- Title:
- ROSAT All-Sky Survey: Chamaeleon Star Forming Region Study
- Short Name:
- RASS/Cham
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog contains a source list derived from observations of the ROSAT all-sky survey (RASS) in the direction of the Chamaeleon star-forming region cloud complex, as well as spectroscopic identifications for the detected X-ray sources. The main purpose of this identification program was the search for low-mass pre-main sequence stars. Sixteen previously known PMS stars were detected with high confidence by ROSAT: eight are classical T Tauri stars and eight are weak-line T Tauri stars. Seventy-seven new weak-line T Tauri stars were identified on the basis of the presence of strong Li 6707 Angstrom absorption, a spectral type later than F0, and chromospheric emission. In addition, 6 new dKe-dMe candidates were found among the RASS sources. Coordinates and count rates are given for all of the X-ray sources. This online catalog was created by the HEASARC in September 1999 based on a machine-readable table obtained from the ADC/CDS data centers (J/A+AS/114/109). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/rasscns3
- Title:
- ROSAT All-Sky Survey: Nearby Stars
- Short Name:
- RASS/CNS3
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog presents X-ray data for all entries in the Third Catalogue of Nearby Stars (CNS3: Gliese and Jahreiss, 1991, ADC/CDS Cat. <V/70>) that have been detected as X-ray sources in the ROSAT All-Sky Survey (RASS). The catalog contains 1252 entries, yielding an average detection rate of 32.9 percent of the 3802 CNS3 stars. In addition to count rates, source detection parameters, X-ray hardness ratios, and X-ray fluxes, X-ray luminosities derived from Hipparcos parallaxes are also listed. For a star to have been considered by the authors to have been detected as an X-ray source in the RASS, an X-ray source with an existence likelihood of 7 or more (equivalent to a source existence probablity of 99.9 percent or more) had to lie within 90 arcseconds of its 1990 epoch CNS3 position. The choice of this cut-off radius was based on a Monte Carlo simulation of about the same number of random positions that were used as input positions. At an offset of 90 arcseconds between the optical and X-ray positions the probability that the X-ray source is attributable to the star and not to a unrelated background object is 50 percent; this probability increases very rapidly for smaller values of the offset, notice. This database was created in June 1999 based on tables provided by the ADC/CDS data centers supplemented by additional tabular material provided to the HEASARC by the author Dr. M. Huensch. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/orionxstar
- Title:
- ROSAT HRI Orion Group 1 Stars
- Short Name:
- ORIONXST
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog presents some of the results from 3 deep ROSAT High Resolution Imager (HRI) observations of the Orion Nebula star-forming region. The fields covered by the X-ray images contain over 1500 catalogued stars in a roughly 0.8 square degree region centered on the Trapezium. In all, 389 distinct X-ray sources were detected, at least two-thirds of which were associated with a single proper-motion cluster member. X-ray emission was detected from stars of all spectral types, from the massive O- and B-type components of the Trapezium to the coolest, low-mass pre-main-sequence (PMS) stars. In the research paper in which these data were presented (Gagne et al. 1995), the authors focussed primarily on X-ray emission from the late-type PMS stars. Of the ~100 late-type cluster members with measured spectral types, approximately three-fourths were detected; the authors derived X-ray luminosity upper limits for the remaining stars. They found that coronal X-ray emission appeared to turn on at around a spectral type of F6, with the upper envelope of activity increasing with decreasing effective temperature. The current database is a representation of Table 6 from Gagne et al. (1995) (notice that the data given in Tables 2 and 3 of this reference is included in the HEASARC database ORIONXRAY, q.v.) which lists X-ray and other data for 175 Orion stars for which spectral types, spectroscopic rotational velocities, and/or spot-modulated photometric rotational periods are available. The X-ray data (either detections or upper limits) are given in the form of X-ray luminosities log Lx and X-ray to bolometric luminosity ratios (log Lx/Lbol). The conversion factor from HRI counts to log Lx was derived for each star based on (i) an assumed 1 keV Raymond and Smith thermal spectrum, (ii) a distance of 440 pc, and (iii) a column density of 2 x 10^21 cm^(-2) per magnitude of visual extinction A(V), where accurate A(V) values are used when available, or otherwise a moderate absorption of 0.25 magnitudes is assumed. Notice that, for stars not identified as candidate optical counterparts in Tables 2 and 3 of Gagne et al. (the HEASARC database ORIONXRAY), the derived upper limit to the X-ray luminosity usually corresponds to the 3 sigma upper limit to the observed count rate. For a handful of stars in the Trapezium region where a star was eliminated as a candidate optical counterpart, despite being within the source search circle, because a more likely counterpart had a smaller position offset, the upper limit corresponds to either half the observed X-ray source count rate or to 3 sigma, whichever is the highest. Such cases are indicated in this database by the presence of the string "NN" in the parameter 'Note'. This is a service provided by NASA HEASARC .
