J/A+A/318/111       ROSAT Galactic Plane Survey (Motch+ 1997)
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The ROSAT Galactic Plane Survey: analysis of a low latitude sample area in
Cygnus.
       Motch C., Guillout P., Haberl F., Pakull M.W., Pietsch W., Reinsch K.
      
      =1997A&A...318..111M       (SIMBAD/NED BibCode)
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ADC_Keywords: X-ray sources
Mission_Name: ROSAT
Keywords: X-ray: general - X-ray: stars - stars: activity - stars: neutron -
          stars: statistics

Abstract:
    We present the analysis of the point source content of a low galactic
    latitude region selected from the ROSAT all-sky survey. The test field
    is centered at l=90, b=0 and has an area of 64.5deg^2^. A total of 128
    soft X-ray sources are detected above a maximum likelihood of 8.
    Catalogue searches and optical follow-up observations show that in
    this direction of the galactic plane, 85% of the sources brighter than
    0.03PSPC are identified with active coronae. F-K type stars represent
    67% (+/-13%) of the stellar identifications and M type stars account
    for 19% (+/-6%). A small but significant number of X-ray sources are
    associated with A type stars on the basis of positional coincidence.
    These results together with those of similar optical campaigns
    demonstrate that the soft X-ray population of the Milky Way is largely
    dominated by active stars. We show that the density and distribution
    in flux and spectral type of the active coronae detected in X-rays are
    consistent with the picture drawn from current stellar population
    models and age dependent X-ray luminosity functions. The modelling of
    this population suggests that most of the stars detected by ROSAT in
    this direction are younger than 1Gyr. This opens the possibility to
    extract in a novel way large samples of young stars from the ROSAT
    all-sky survey. The small number of unidentified sources at low X-ray
    flux put rather strong constraints on the hypothetical X-ray emission
    from old neutron stars accreting from the interstellar medium. Our
    observations clearly rule out models which assume no dynamical heating
    for this population and a total number of N_ns_=10^9^ neutron stars in
    the Galaxy. If accretion on polar caps is the dominant mode then our
    upper limit may imply N_ns_=~10^8^. Among the non coronal
    identifications are three white dwarfs, a Seyfert 1 active nucleus,
    two early type stars and one cataclysmic variable. We also report the
    discovery of a Me+WD close binary system with P_orb_=~12 .

File Summary:
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  FileName    Lrecl  Records   Explanations
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ReadMe           80        .   This file
table11          82      128   Optical identifications for sources with ML>=8
table12          82       30   Optical identifications for sources with 7>=ML>=8
tables.tex       96      217   LaTeX version of the tables
supertab.sty     76      285   LaTeX utility
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See also:
     IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1996)
     Aug/10

Byte-by-byte Description of file: table11 table12
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   Bytes Format Units   Label     Explanations
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   1-  3  I3    ---     Source    Source index
   5- 19  A15   ---     ROSAT     ROSAT name
  21- 23  A3    ---     Class     Class of the proposed optical counterpart (1)_
      24  A1    ---   u_Class     [?] ? for the more uncertain cases (2)
  26- 31  A6    ---     SpType    Spectral type
  33- 51  A19   ---     IdOpt     Optical identification (2)
      52  A1    ---   u_IdOpt     [?] ? for the more uncertain cases (2)
  54- 58  F5.3  ct/s    Count     Count rate
  60- 64  F5.3  ct/s  e_Count     rms uncertainty on Count
  66- 71  F6.1  ---     MaxLik    Maximun likehood
  73- 76  F4.2  %       PPos      Position probability
      78  A1    ---   l_PCaII     Limit flag on CaII
  79- 82  F4.2  %       PCaII     ? CaII H&K probability (3)
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Note (1):  AC: active corona
          AGN: active galactic nucleus
           CV: cataclysmic variable
           OB: OB star
           WD: White dwarf
           ??: Unknown
Note (2): Proposed counterparts having a probability of identification in the
           range 95% - 98%, These more uncertain cases are marked by a '?' in
           the u_IdOpt column and in the u_Class column
Note (3): Formal probability that if the star is responsible for the X-ray
           emission its chromospheric emission appears fainter or equal to the
           observed value.
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Acknowledgements: Christian Motch 
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(End)                                         Patricia Bauer [CDS]   18-Nov-1996