Central Bureau for Astronomical Telegrams
IAUC 3306: VARIABLE-EMISSION-LINE STAR IN THE CORE OF M15; V861 Sco
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Read IAUC 3307
Circular No. 3306
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-864-5758
VARIABLE-EMISSION-LINE STAR IN THE CORE OF M15
H. Ford, B. Margon and D. Jenner, University of California at
Los Angeles; and A. Klemola, University of California at Santa Cruz,
write: "Observations have been made of a subgiant star 14" north-east
of the center of M15 that shows strong, variable, Balmer emission
lines. The object is No. 86 in the list of Rosino (1950, Astrophys.
J. 112, 221), where a finding chart may be found. The
star was bright on Kitt Peak H-alpha video camera photographs obtained
on 1977 Dec. 5, and it showed strong H-alpha, H-beta and H-gamma emission lines
in spectra obtained with the Lick Observatory's 305-cm telescope on
1978 Sept. 30 and Oct. 1. The strength of the emission changed by
50 percent on the two successive nights. The emission is entirely
absent on spectra obtained with the Kitt Peak 400-cm telescope on
1978 Oct. 29, 30 and 31. The emission lines are blueshifted 40
km/s relative to the cluster, while the Balmer absorption lines observed
at the end of October have the same radial velocity as the
cluster. The astrometric positions (+/- 0".5 accuracy) of the star,
the cluster center and the planetary nebula K648 (useful as a positional
reference) have been measured from short-exposure Lick refractor
and astrograph plates as:
R.A. (1950) Decl.
Star No. 86 21 27 34.14 +11 56 54.8
Cluster center 21 27 33.30 +11 56 48.4
K648 21 27 34.52 +11 57 16.1
The star is 4" from the center of the 20"-radius SAS-3 error circle
for the x-ray source 4U 2129+12 (Jernigan and Clark, preprint).
Notni and Oleak (1957, Astron. Nachr. 284, 49) note the object to
be variable by 0.9 magnitude (mean V = 14.4) with period 17.1 days,
suggesting a possible interpretation as a long-period Population II
Cepheid; our observed spectral features and color, B-V = +0.7, are
indeed consistent with a W-Vir star. However, the presence of this
large-amplitude spectroscopic and photometric variable in the small
x-ray error box is sufficiently unusual that the alternative interpretation
of a relation to the x-ray source should not be overlooked."
V861 SCORPII
In the table on IAUC 3281 the +/- errors quoted are percentage
errors rather than absolute errors.
1978 November 15 (3306) Brian G. Marsden
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