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IAUC 7276: XTE J1859+226; GM Sgr

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                                                  Circular No. 7276
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
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XTE J1859+226
     P. M. Garnavich and K. Z. Stanek, Harvard-Smithsonian Center
for Astrophysics; and P. Berlind, Fred L. Whipple Observatory
(FLWO), report the detection of an optical counterpart to the new
x-ray transient XTE J1859+226.  CCD images taken on Oct. 12.07 UT
with the FLWO 1.2-m telescope show a bright stellar object not seen
on the second Palomar Sky Survey.  The exact position based on the
HST Guide Star Catalog is R.A. = 18h58m41s.58, Decl. = +22o39'29".4
(equinox 2000.0; estimated uncertainty 0".5).  This is just to the
east of the x-ray error circle given on IAUC 7274 and about 80"
north of a 10th-mag star.  The brightness of the optical transient
is estimated to be R = 15.1, and it appears blue compared to other
stars in the field.  Images taken over a 3.3-hr span show < 0.05
mag variation in brightness.  A faint object (mag about 21) is
visible on the Sky Survey within 1" of the position of the
transient.  The spectrum obtained with the FLWO 1.5-m telescope on
Oct. 12.22 displays a strong blue continuum with weak emission
lines.  H-alpha, with an equivalent width of 0.54 nm, and a
velocity width of 1200 km/s (FWHM), is seen.  He II 468.6-nm is 3
times stronger than H-beta and blended with permitted C III and N
III.  The spectrum is consistent with an x-ray nova in outburst.  A
finder chart may be found at

     R. M. Wagner, Ohio State University, communicates:  "We
obtained a spectrum (range 320-680 nm, resolution 1.5 nm) of GM Sgr
on Sept. 30.13 UT with the MDM Observatory 2.4-m Hiltner telescope
(+ CCDS spectrograph).  The spectrum exhibited relatively strong
Balmer absorption lines visible to the series limit, in addition to
interstellar absorption features at 578.0 and 589.0 (Na D) nm.
Weaker absorption lines of Fe II might also be present.  The Balmer
lines appear to be much stronger than those observed in the later
spectra obtained by Garcia et al. (IAUC 7271), indicating
continuing evolution of the optical spectrum since the outburst.
Equivalent widths were:  H-alpha, 0.81; H-beta, 1.01; H-gamma,
0.87; and H-delta, 0.85 nm.  The FWHM of H-beta absorption was 1.7
nm.  Convolution of the spectrum with broadband filters gives U-B =
+1.8 and B-V = -0.2, although the U measurement might be affected
by differential atmospheric refraction.  The equivalent width of
the 578.0-nm interstellar band was 0.06(1) nm, implying E(B-V) =
0.24 mag."

                      (C) Copyright 1999 CBAT
1999 October 12                (7276)            Daniel W. E. Green

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