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RASSGIANT - RASS Giants & Supergiants Cat.

HEASARC
Archive

Overview

The ROSAT All-Sky Survey Catalogue of Optically Bright Late-Type Giant and Supergiant Stars contains X-ray data for all late-type (spectral types of A through M, inclusive) giants and supergiants (luminosity classes of I through III-IV, inclusive) listed in the Bright Star Catalogue (BSC) that have been detected in the ROSAT All-Sky Survey. The RASS giants and supergiants catalog contains 450 entries of X-ray emitting, evolved late-type stars, which corresponds to an average detection rate of 11.7 percent. For each star, the ROSAT PSPC count rate, the hardness ratio, the apparent X-ray flux (calculated using an individual energy-conversion-factor based on the hardness ratio), and the ratio of X-ray to bolometric flux are given. The full details of the data selection, the source detection criteria, etc., are given in the paper by Huensch, Schmitt and Voges (1998, A&AS, 127, 251) describing this catalog; essentially for a star to be identified as an X-ray source, the X-ray source had to have at least a 99.9 percent existence probability, corresponding to a likelihood of greater than or equal to 7, and lie within 90 arcseconds of the optical position. Given the number of sky locations examined and the total number of RASS sources, it is expected that of order 27.4 of the 450 claimed associations in this catalog will be chance coincidences.

Catalog Bibcode

1998A&AS..127..251H

References

The ROSAT All-Sky Survey Catalogue of Optically Bright Late-Type Giant and Supergiants, Huensch, M., Schmitt, J.H.M.M., and Voges, W., Astron. Ap. Suppl., 127, 251. (1998) = ADC/CDS Catalog J/A+AS/127/251.

Provenance

This database was created at the HEASARC in July 1998 based on the ADC/CDS Catalog J/A+AS/127/251.

Parameters

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

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.

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.

LII
The galactic longitude of the star.

BII
The galactic latitude of the star.

HD
The HD number of the star.

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).

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

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.

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" separation is known)
      SB: spectroscopic binary (as given in the BSC)
      RS: RS CVn system (usually also SB)
       B: other binary (composite spectrum)
      CV: cataclysmic companion (HR 4765 = 4 Dra)
    SYMB: symbiotic star (HR 8992 = R Aqr)
  

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

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. Given the 150,000 total number of RASS X-ray sources and the 3839 positions of BSC giants and supergiants examined, 27.4 out of the 450 `detections' listed here are expected to be chance coincidences. If a maximum offset of 60 arcseconds is permitted, the number of chance coincidences drops to 12.2.

Hardness_Ratio
The hardness ratio HR for the PSPC X-ray source, where HR = (H-S)/(H+S), H is the source counts in the hard (0.5 - 2.0 keV) passband of the PSPC, and S is the 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 passband, the hardness ratio is is set to +1.0 by definition.

Hardness_Ratio_Error
The error E(HR) in the hardness ratio HR for the PSPC X-ray source, calculated from the expression:

   E(HR) = 2 * (S+H)**-1.5 * (S*H)**0.5
  

Flux
The apparent X-ray flux in the full (0.1 - 2.4 keV) PSPC bandpass in units of erg s**-1 cm**-2.

Log_Xray_Bol
The logarithm of the X-ray to bolometric flux ratio.

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


Contact Person

Questions regarding the RASSGIANT database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Monday, 08-Nov-2004 11:26:57 EST