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HYADESXRAY: Help

HYADESXRAY - ROSAT All-Sky Survey: Hyades Cluster Region


Overview

This catalog contains the results of a complete X-ray survey of the Hyades cluster region using X-ray data from the the ROSAT All-Sky Survey (RASS) that was published by Stern, Schmitt and Kahabka in 1995. The Hyades survey covered over 900 square degrees of the sky. Over 185 optically identified Hyades were detected down to a limiting X-ray luminosity of about 1-2x10^28 ergs/s in the 0.1-1.8keV energy band. Among solar-like stars, i.e., main-sequence stars of spectral type G, the RASS detection rate was about 90%. Stern et al. argue that the presence of many binary systems in the cluster is a key factor influencing the Hyades X-ray luminosity function. Short-period (a few days or less) binaries are anomalously X-ray bright, as might have been expected; however, the X-ray luminosity functions of K and possibly M binary stars of all types are significantly different from their single counterparts, confirming the results of Pye et al. (1994, MNRAS, 266, 798) based on a smaller K star sample drawn from deep ROSAT pointings. Comparison with Einstein Observatory studies of a subset of Hyades stars demonstrates a general lack of significant (> a factor of 2) long-term X-ray variability. Stern et al. suggest that this may be the result of the dominance of a small-scale, turbulent dynamo in the younger Hyades stars compared to the large-scale, cyclic dynamo observed in the Sun.

The HYADESXRAY database consists of X-ray data for 440 probable and possible Hyades members that were included in the Stern et al. survey and were listed in Table 1 of their published paper. The database contains both stars which were detected as X-ray sources and those which were not: for the latter, upper limits to their X-ray emission are provided. For all listed stars, their X-ray luminosities based on a Hyades distance of 45 pc are provided; for some stars, for which individually determined distances from either the Schwan (1991, A&A, 243, 386) or the Hanson (1975, AJ, 80, 379) proper motion surveys are available, their X-ray luminosities based on these alternate distances are also provided. There were 4 stars detected as RASS sources out of over 180 new Hyades candidates listed in the Reid (1992, MNRAS, 257, 257) proper motion survey which were included in Table 2 (but not Table 1) of the Stern et al. paper. These stars are not included in the current database, but are listed in the help section entitled Reid_Stars (q.v.). Similarly, there were 20 stars detected as RASS sources but which were considered by Stern et al. to be non-members of the Hyades which were included in their Table 3 (but not Table 1). These stars are not included in the current database, but are listed in the help section entitled Rejected_Hyades (q.v.).


Catalog Bibcode

1995ApJ...448..683S

References

`ROSAT All-Sky Survey Observations of the Hyades Cluster` by Stern R.A., Schmitt J.H.M.M., and Kahabka P.T. 1995, ApJ, 448, 683.

Provenance

This HEASARC catalog was created in July 1997, derived from CDS Catalog J/ApJ/448/683 obtained from ftp://cdsarc.u-strasbg.fr/cats/J/ApJ/448/683/. Additional information provided in the HEASARC documentation was taken from the original published version of the paper containing this catalog.

Reid Stars

Stars from the Reid (1992, MNRAS, 257, 257) list of candidate Hyades that were detected as X-ray sources in the RASS (Table 2 of Stern et al. paper):

   Name      RA       DEC      Vmag  B-V        PSPC
         h mn sec  d  mn sec                   ct/sec
   -------------------------------------------------------
   RE 12 3 58 35.8 13  6 18.5  8.97 0.66   0.026 +/- 0.009
   RE119 4 15 32.6 20 48 25.3 17.34 1.69   0.056 +/- 0.015
   RE299 4 31 15.7 10 42 15.0 14.91 1.37   0.022 +/- 0.008
   RE391 4 39 51.5 19 39 33.9 16.38 1.90   0.016 +/- 0.007

Rejected Hyades

Stars considered not to be Hyades members that were detected as X-ray sources in the RASS (Table 3 of Stern et al. paper):
   Name            RA       DEC      Vmag  B-V        PSPC
               h mn sec  d  mn sec                   ct/sec
   -------------------------------------------------------------
   L3          3 30 30.3 20  5 54.5 10.78 1.39   0.019 +/- 0.008
   LP413-19    3 37 33.4 17 51 17.9 13.29 1.54   0.145 +/- 0.022
   vB135       3 43 54.3  3 26 45.1  8.99 0.87   0.034 +/- 0.012
   GH8-1       4 14 53.4 27 45 33.4 12.65 1.57   0.038 +/- 0.013
   GH7-152     4 17 50.6 18 28 30.8 13.88 1.57   0.037 +/- 0.011
   GH7-178     4 22 30.3 15 13 11.9 14.64 0.84   0.026 +/- 0.008
   VA247       4 22 39.7 15  3 45.8 15.47 0.95   0.129 +/- 0.020
   vB61        4 25 57.5  5  9  3.6  7.38 0.51   0.112 +/- 0.019
   GH8-46      4 29 54.2 27 38 27.5              0.023 +/- 0.008
   VA751       4 34 42.2 17 44 55.0  7.75 0.65   0.035 +/- 0.012
   VA771       4 35 33.9 12  6  2.0  8.90 0.58   0.224 +/- 0.025
   vB184       4 36  0.1 16 32 26.7 10.83 1.26   0.023 +/- 0.009
   GH82B       4 36 44.9 27  9 53.7 15.94 0.65   0.820 +/- 0.044
   V833Tau     4 36 47.9 27  7 59.5  8.42 1.12   2.613 +/- 0.076
   LP415-1644  4 37 21.8 19 21 17.1 14.65 1.75   0.067 +/- 0.015
   LP476-612   4 47 37.4 10 13 58.5 14.90        0.031 +/- 0.011
   vB165       4 49 48.5 23 23 41.8  8.52 0.63   0.054 +/- 0.013
   BD18:742    4 51 12.8 18 52  0.4 10.40 0.69   0.060 +/- 0.012
   vB152       5 10  0.6 27 38 39.0  9.23 0.93   0.030 +/- 0.011
   AK7-1312    5 11 59.9 20  7  1.9 10.92 0.91   0.015 +/- 0.007

Parameters

Name
The name of the Hyades member star. A table of cross-referenced Hyades members provided by E. Weis was used in selecting the primary designation; for members with multiple designations, the name used was determined by the following order of preference:

      vB   (van Bueren, 1952BAN....11..385V),
      VA   (van Altena, 1969AJ.....74....2V),
      BD   (Bonner Durchmusterung, Cat. <I/122>),
      GH   7 or GH 8 (Giclas, Burnham, & Thomas, 1962LowOB...5..257G),
      L    (Pels et al., 1975A&A....43..423P),
      LP   (Luyten et al., 1981, see Cat. <I/130>),
      H    (Hanson 1975, Cat. <J/AJ/80/379>),
      OS   (Osvald, 1954AN....281..193O),
      AK   (Artyukhina & Khopolov 1975, Trans. Gos. Astron. Inst.
           Sternberg, 46 No. 2, 57 and 1976, Trans. Gos. Astron. Inst.
           Sternberg, 47 ,105)
      HD   or other designation.
  

Vmag
The Visual magnitude.

RA
The Right Ascension of the optical star corrected for proper motion to the epoch 1991.0.

Dec
The Declination of the optical star corrected for proper motion to the epoch 1991.0.

LII
The galactic longitude of the optical star.

BII
The galactic latitude of the optical star.

Xray_Offset
The difference in the X-ray and optical positions in arcseconds.

Ref_Vmag
A code for the reference from which the V magnitude was obtained:

      (1)-(3)   Weis & Hanson, 1988AJ.....96..148W
      (4)-(6)   Upgren et al., 1985AJ.....90.2039U
      (7)       Weis, 1983PASP...95...29W
      (8)-(9)   Weis & Upgren, 1982PASP...94..475W
      (10)      Stauffer, 1982AJ.....87..899S
      (11)      Weis et al., 1979PASP...91..766W
      (12)-(13) Weis, 1992, unpublished photometry;
      (14)      Pels et al., 1975A&A....43..423P
      (15)      Eggen, 1969ApJ...157..287E
      (16)      Morel & Mangnenat, 1978, Cat. <II/7>
      (17)      Schwan, 1991A&A...243..386
      (18)      Reid, 1992, Cat. <J/MNRAS/257/257>
      (19)      Hanson, 1975, Cat. <J/AJ/80/379>
      (20)      Griffin et al., 1988AJ.....96..172G
  

BV_Color
The B-V colour index.

Ref_BV_Color
A code for the reference from which the B-V color index was obtained:

      (1)-(3)   Weis & Hanson, 1988AJ.....96..148W
      (4)-(6)   Upgren et al., 1985AJ.....90.2039U
      (7)       Weis, 1983PASP...95...29W
      (8)-(9)   Weis & Upgren, 1982PASP...94..475W
      (10)      Stauffer, 1982AJ.....87..899S
      (11)      Weis et al., 1979PASP...91..766W
      (12)-(13) Weis, 1992, unpublished photometry;
      (14)      Pels et al., 1975A&A....43..423P
      (15)      Eggen, 1969ApJ...157..287E
      (16)      Morel & Mangnenat, 1978, Cat. <II/7>
      (17)      Schwan, 1991A&A...243..386
      (18)      Reid, 1992, Cat. <J/MNRAS/257/257>
      (19)      Hanson, 1975, Cat. <J/AJ/80/379>
      (20)      Griffin et al., 1988AJ.....96..172G
  

Distance
The individually determined distance to the star, in parsecs, taken either from the Schwan (1991) or the Hanson (1975) proper motion surveys.

Ref_Distance
A reference code for the source of the distance:

       H: Hanson 1975, AJ, 80, 379
       S: Schwan 1991, A&A, 243, 386
  

Binarity
A set of letter code indicating the type of binary system, if any:

      GR: spectroscopic binary as noted in Griffin et al. 1988, AJ, 96, 172
      GP: photometric binary as noted in Griffin et al. 1988, AJ, 96, 172
      GV: visual binary as noted in Griffin et al. 1988, AJ, 96, 172
       B: spectroscopic binary listed in Batten et al. 1989, SB Cat. (CDS <V/64>)
       C: photometric binary from Carney 1982, AJ, 87, 1527
       T: photometric binary as noted by Bettis 1975, PASP, 87, 707
       S: photometric binary as noted by Stauffer 1982, AJ, 87, 899
      UW: photometric binary as noted by Upgren & Weis 1977, AJ, 82, 978
       A: visual binary in ADS catalog
      MD: definite speckle binary in Mason et al. 1993, AJ, 105, 220
      MP: probable speckle binary in Mason et al. 1993, AJ, 105, 220
      MS: suspected speckle binary in Mason et al. 1993, AJ, 105, 220
      SP: spectroscopic binary or triple based on unpublished data
          (Stauffer, private communication).
  

Max_Like
The maximum likelihood ratio for the X-ray source existence. In this survey, the detection threshold was chosen to correspond to a probability of a false detection at a given position of 0.033%, or to a maximum likelihood of 8. Given that about 1000 locations were searched in this survey, this implies that there should be less than 1 false Hyades detection in this catalog.

Flag_Lx_45pc
A flag for the Lx_45pc value which is set to '<' if the quoted value is an upper limit.

Lx_45pc
The derived X-ray luminosity, in units of 10^28 erg/s, based upon an assumed 45pc distance.

Error_Lx_45pc
The rms uncertainty in Lx_45pc.

Flag_Lx_Dpc
A flag for the Lx_Dpc value which is set to '<' if the quoted value is an upper limit.

Lx_Dpc
The derived X-ray luminosity, in units of 10^28 erg/s, based upon the assumed distance listed in the 'Distance' parameter.

Error_Lx_Dpc
The rms uncertainty in Lx_Dpc.

Class
The BROWSE classification type.


Contact Person

Questions regarding the HYADESXRAY database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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