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IAUC 5949: N Sgr 1994 = LUMINOUS RED Var IN Sgr

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IAUC number

                                                  Circular No. 5949
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505

     A. Tomaney and R. M. Rich, Columbia University; R. M. Wagner,
Ohio State University; and M. Della Valle, Padua University, report:
"Spectra obtained on Mar. 4.54 (IAUC 5944) and 9.54 UT at the Perkins
1.8-m telescope (range 450-570 nm, resolution 0.5 nm) and on Mar.
7.2 at La Silla (IAUC 5945) reveal narrow Balmer emission lines and
TiO absorption bands superimposed on a strong red continuum,
characteristic of an M giant star.  Comparison of the Mar. 4 and 9 spectra
shows an evolution from an M0- to an M5-type spectrum associated with
more than a magnitude decline in flux.  Based on the evolution toward
later spectral type and the lack of any emission lines other than
the Balmer lines, we propose that this object bears a striking
resemblence to a unique superluminous outburst observed in M31 in
1988 (Rich et al. 1989, Ap.J. 341, L51; Mould et al. 1990, Ap.J. 353,
L35; Tomaney and Shafter 1992, Ap.J. Suppl. 81, 683).  This object
brightened by > 5 mag over 2 yr and was discovered at Mbol = -10.
After the outburst, it faded rapidly, while also changing from M0 to
M9; when last detected, the M31 variable was brightest in the
infrared L band, and it never showed an obvious nebular-phase
spectrum characteristic of a classical nova outburst, suggesting a
large ejected mass.  Infrared observations (1-10 microns) are
urgently required; based on the behavior of the M31 variable, we
predict that this new object will rapidly fade in the visible but
remain bright in the infrared.  The M31 outburst showed dramatic
changes in the continuum and emission lines over a few nights.  If
this outburst is associated with a close binary system, it may
exhibit possible pronounced radial-velocity variations associated
with the common phase.  Higher resolution spectra (resolution 0.1
nm) obtained on Mar. 7.2 and 8.2 at La Silla with the New Technology
Telescope (+ EMMI) reveal that H-alpha exhibits an inverse P-Cyg
line profile (correcting the remark on IAUC 5945, line 9).  The
infall velocity is on the order of 150 km/s (computed from the
minimum of the absorption component), and the full width at half-
maximum of H-alpha emission corresponds to about 300 km/s."
     Further photoelectric photometry by A. C. Gilmore (cf. IAUC
5944) at Mt. John Observatory: Mar. 7.71 UT, V = 9.82, B-V = +1.97,
V-R = +1.07, V-I = +2.27; 8.70, 10.29, +1.94, +1.20, +2.59; 10.71,
11.18, +1.85, +1.32, +3.09.

1994 March 12                  (5949)            Daniel W. E. Green

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