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RASSDWARF - RASS A-K Dwarfs/Subgiants Catalog

HEASARC
Archive

Overview

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.

Catalog Bibcode

1998A&AS..132..155H

References

The ROSAT All-Sky Survey Catalogue of Optically Bright Main-Sequence Stars and Subgiant Stars, Huensch M., Schmitt H.H.M.M., Voges W., Astron. Astrophys. Suppl. Ser. 132, 155 (1998) = 1998 A&AS..132..155H (SIMBAD/NED BibCode)

Provenance

This database was created at the HEASARC in February 1999 based on the ADC/CDS Catalog J/A+AS/132/155.

Parameters

HR
The HR number of the star in the Bright Star Catalog.

RASS_Note
This parameter is set to 'X' for objects that have been observed later than the original All-Sky Survey phase, in the course of the so-called "survey repair". Their X-ray data were acquired in February 1997, whereas the major part of the survey was carried out in 1990 and 1991.

RA
The right ascension of the star in the selected equinox, i.e., the optical position. This information was not in the original version of this catalog but was added by the HEASARC using the co-ordinates listed in the online version of the Bright Star Catalog (BSC5P).

Dec
The declination of the star in the selected equinox, i.e., the optical position. This information was not in the original version of this catalog but was added by the HEASARC using the co-ordinates listed in the online version of the Bright Star Catalog (BSC5P).

LII
The galactic longitude of the star, i.e., the optical position.

BII
The galactic latitude of the star, i.e., the optical position.

HD
The HD number of the star in the Henry Draper Catalog.

Name
The commonly used constellation-based (Bayer or Flamsteed) name for the star, if one exists.

Vmag
The Johnson V magnitude of the star (taken from the BSC by the catalog authors).

BV_Color
The Johnson (B-V) color index of the star (taken from the BSC by the catalog authors).

Spect_Type
The spectral classification (spectral type + luminosity class) of the star, usually on the MK system (a few of the entries are on the old Harvard system where lower case 'g' means giant luminosity class), as taken from the BSC.

Distance
The distance to the star in parsecs, as derived from its Hipparcos trigonometrical parallax.

Binary_Flag
A flag indicating the binary status of the star, using the following categories:

            S: Single star
           VB: Visual binary (if a companion within 90 arcsecs is known)
           SB: Spectroscopic binary (as given in the BSC)
            B: Other binary (composite spectrum)
  

Exposure_Time
The effective exposure time in seconds for the X-ray measurement.

Count_Rate
The mean PSPC count rate in counts per second.

Count_Rate_Error
The error in the mean PSPC count rate in counts per second.

Likelihood
The likelihood significance Li for the existence of the X-ray source: Li = -ln(1-P), where P is the existence probability. The minimum likelihood for sources in the current catalog is 7, corresponding to P = 99.9 percent.

Offset
The offset in arcseconds between the X-ray and optical positions. The maximum offset accepted in the current catalog is 90 arcseconds, based on a Mpnte Carlo simulation that implied that there is a 50% probablility that an X-ray source offset by 90 arcseconds from a star position is actually attributable to the star. Since the total search area examined around the 3054 late-type main-sequence and subgiant stars in the BSC was 6 square degrees or 0.0145% of the sky, and the total number of RASS sources amounts to about 150,000, 21.8 (2.2%) out of the 980 `detections' listed here are expected to be chance coincidences.

Hardness_Ratio
The hardness ratio HR for the PSPC X-ray source, where HR = (H-S)/(H+S), H is the number of source counts in the hard (0.5 - 2.0 keV) passband of the PSPC, and S is the number of source counts in the soft (0.1 - 0.4 keV) passband of the PSPC. For a few sources which were not detected in the soft or the hard passband, the hardness ratio is is set to +1.0 or -1.0, respectively, by definition.

Hardness_Ratio_Error
The error E(HR) in the hardness ratio HR for the PSPC X-ray source.

Flux
The apparent X-ray flux in the full (0.1 - 2.4 keV) PSPC bandpass in units of erg s**-1 cm**-2. This was calculated from the count rate CR using the formula flux = CR * ECF, where ECF is an individual energy-conversion factor based on the hardness ratio HR of the source given by:

        ECF = (5.30 * HR + 8.31) * 10**-12 erg cm**-2 cts**-1
  

Log_Lx
The logarithm (base 10) of the X-ray luminosity in erg/sec, derived from the X-ray flux fx and the listed distance D to the star using the standard formula log Lx = 4 * pi * D**2 * fx.

Class
The HEASARC browse classification for the star, as constructed from its spectral classification (the parameter spect_type).


Contact Person

Questions regarding the RASSDWARF database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 8-Nov-2004