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RASSCNS3 - ROSAT All-Sky Survey: Nearby Stars

HEASARC
Archive

Overview

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.


Catalog Bibcode

1999A&AS..135..319H

References

Huensch M., Schmitt J.H.M.M., Sterzik M.F., Voges W. Astron. Astrophys. Suppl. Ser. 135, 319 (1999)

Provenance

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.

Parameters

Name
The designation of the star, with the original Gliese (GL), Gliese and Jahreiss (GJ), and Woolley designations preferred. Stars lacking these designations are given their Henry Draper (HD), Giclas (G), Luyten Half-Second (LHS), Durchmusterung (BD or CD), or various other (LTT, LP, GR, STEPH, ROB, BPM, or AC) designations, in that order of preference. In a very few cases, where the authors could find no common designation, a name based on the approximate celestial co-ordinates was used.

RA
The right ascension in the default equinox of the X-ray source that has been associated with the specified CNS3 star. This parameter was not in the published version of this catalog but was provided for the HEASARC version by the authors. The original equinox of the position as supplied to the HEASARC was 2000.

Dec
The declination in the default equinox of the X-ray source that has been associated with the specified CNS3 star. This parameter was not in the published version of this catalog but was provided for the HEASARC version by the authors. The original equinox of the position as supplied to the HEASARC was 2000.

LII
the galactic longitude of the X-ray source.

BII
The galactic latitude of the X-ray source.

RA_Optical
The right ascension at a fixed 2000 equinox of the specified CNS3 star, i.e, the optical RA, for the epoch 1990, i.e., including proper motion to that date, obtained by the authors using the information on positions in CNS3. This parameter was not in the published version of this catalog but was provided for the HEASARC version by the authors. Notice that the CNS3 only provides the RA to an accuracy of 1 second.

Dec_Optical
The declination at a fixed 2000 equinox of the specified CNS3 star, i.e, the optical declination, for the epoch 1990, i.e., including proper motion to that date, obtained by the authors using the information on positions in CNS3. This parameter was not in the published version of this catalog but was provided for the HEASARC version by the authors. Notice that the CNS3 only provides the declination to an accuracy of 0.1 arcminutes.

Vmag
The V magnitude of the star taken from the CNS3.

BV_Color
The B-V colour index of the star taken from the CNS3.

Spect_Type
The MK or other spectral classification of the star taken from the CNS3.

Distance
The distance to the star in parsecs obtained from the Hipparcos parallax.

Exposure
The effective ROSAT PSPC exposure time, in seconds.

Count_Rate
The mean PSPC count rate, in counts per second (cps).

Count_Rate_Error
The error in the mean PSPC count rate, in cps.

Likelihood
The likelihood of existence Li of the X-ray source, as expressed by the relation Li = -ln(1-P), where is the probablility of existence. All X-ray sources in this catalog have a likelihood of 7 or greater. A value of 999 for this parameter has been given to all hources having a likelihood of greater than or equal to 999.

Offset
The offset in arcseconds between the optical and X-ray positions.

Hardness_Ratio
The hardness ratio HR defined by the relation HR =(H-S)/(H+S) where H and S denote the source counts in the hard (0.5-2.0 keV) and soft (0.4 keV) bandpasses of the ROSAT PSPC detector, respectively.

Hardness_Ratio_Error
The error in the hardness ratio.

Flux
The apparent X-ray flux fx in the full 0.1-2.4 keV bandpass, in units of erg/sec/cm^2, using an energy conversion factor (ECF) to convert the count rate in this bandpass to an X-ray flux calculated using the formula ECF = (5.30 x HR + 8.31) x 10^-12 erg/cm^2/ct.

Log_Lx
The logarithm of the X-ray luminosity Lx in the 0.1-2.4 keV bandpass, in units of erg/sec, calculated from the X-ray flux and the Hipparcos-derived distance D using the standard relation, Lx = 4 x pi x D^2 x fx.

Class
The browse classification, derived from the spectral type parameter.


Contact Person

Questions regarding the RASSCNS3 database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Monday, 08-Nov-2004 11:26:51 EST