[vsnet-alert 1856] XTE J2012+381 (Garcia)

[Taichi Kato <tkato>]

Date: Wed, 3 Jun 1998 17:27:30 -0400
From: garcia@cfa219.harvard.edu (Mike Garcia)
Message-ID: <vsnet-alert1856@hoge.baba.hajime.jp>
To: BAILYN@astro.yale.edu, ajct@laeff.esa.es, chaswell@star.maps.susx.ac.uk,
        e.kuulkers1@physics.oxford.ac.uk, fghigo@nrao.edu,
        garcia@head-cfa.harvard.edu, guy@mrao.cam.ac.uk,
        ewaltman@rsd.nrl.navy.mil, jem@head-cfa.harvard.edu,
        lewin@space.mit.edu, marshall@milkyway.gsfc.nasa.gov,
        pac@astro.ox.ac.uk, rhjellmi@aoc.nrao.edu, rmw@lowell.Lowell.Edu,
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        starrfie@hydro.la.asu.edu, stroh@pcasun1.gsfc.nasa.gov,
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        vsnet-alert@kusastro.kyoto-u.ac.jp
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Subject: [vsnet-alert 0] IAUC submittion on XTE J2012+381
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Dear Colleagues - We have submitted the following for inclusion
in the next IAUC.

-----------------------
M.R. Garcia, J.E. McClintock, E. Barton, 
(Center for Astrophysics)
P. Callanan (University College, Cork, Ireland), report:


On Jun 1.45 UT, we obtained an optical spectrum of the star
USNO1275.13846761 201237.796 +381100.57 (2000.0) (r=17.5, b=19.3)
which is within ~1.3" of the variable radio source (IAUC 6924, 6926),
which in turn may be related to the x-ray transient XTE J2012+381
(IAUC 6920, 6922).  Preliminary reduction of the 20 minute exposure
with the Whipple Observatory 1.5m and FAST spectrograph (0.3 nm
resolution, covering 400 nm to 700 nm) shows a nearly featureless red
continuum.  The only clearly identifiable lines are H-beta, H-gamma,
and NaD in absorption; a strong night sky line at H-alpha makes it
difficult to determine the intrinsic H-alpha profile.  The upper limit
to the equivalent width of any possible HeII 468.4 nm emission is
about 0.1 nm.  A cross-correlation with the Jacoby stellar atlas
indicates a spectral type of F3 +/- 3 subclasses for a dwarf, or F0
+/- 6 subclasses for a giant.  Photometry with the Whipple Observatory
1.2m and CCD camera on May 28.31 determines B=19.35 +/- 0.1, V=18.1
+/- 0.1, indicating (B-V) = 1.25.

The photometry and spectroscopy are consistent with an absorption A(v)
= 2.8, and a F3 dwarf at about 3 kpc or an F0 giant at about 6 kpc.

These results neither confirm nor refute the possible association of
this star with the x-ray nova. If this star is the counterpart it
could be similar to the F giant companion of Cyg X-2, which shows weak
(EW ~ 0 to 3 Angstroms) and variable He II 468.6 emission, and
sometimes an absence of H-Balmer emission.  Alternatively, the star
could be a chance co-incidence along the line of sight, similar to the
case of GX17+2.

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