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IAUC 6000: 1993ak; GRS 1915+105

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                                                  Circular No. 6000
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

SUPERNOVA 1993ak IN UGC 8685
     H. Meusinger, Thuringer Landessternwarte, Tautenburg, reports
the discovery of an apparent supernova on a Tautenburg Schmidt plate
taken by F. Borngen on 1993 Mar. 30.1 UT.  The candidate was then at
B = 16.5 and was located 25" east of the center of UGC 8685 = MCG
05-32-074 (R.A. = 13h40m52s.2, Decl. = +30o35'16", equinox 1950.0).
On a second Tautenburg plate taken 1993 Apr. 27.0, SN 1993ak had
dimmed to B = 18.5.  There is no stellar object at this position on
several inspected plates taken before 1977 and after 1994 May 2.9.
Plates taken under good seeing conditions show a relatively bright
diffuse patch in a spiral arm (presumably a giant H II region) at
the position of SN 1993ak.

GRS 1915+105
     P. Durouchoux, S. Corbel, and P. Wallyn, Centre d'Etudes de
Saclay, Service d'Astrophysique; and J. Grindlay, Center for
Astrophysics (CfA), communicate:  "We observed two molecular clouds
in the direction of the hard x-ray transient and possible soft
gamma-ray repeater (SGR) GRS 1915+105 on May 8, via the Swedish-
European Southern Observatory Submillimeter Telescope at La Silla.
Using transitions of 12CO(1-0) at 115 GHz and 13CO(1-0) at 110 GHz,
10x10 grid maps were done centered on the radio counterpart
(discovered by Mirabel et al. 1994, A.Ap. 282, 17) with an angular
resolution of 45", a grid spacing of 45", and 90 s of integration
time per position.  We deduced, from a preliminary analysis, the
following velocities, widths, and implied mean effective column
densities:  first cloud, vLSR = 26 km/s, FWHM about 5 km/s, N(H2)
about 3 x 10E21 cmE-2; second cloud, 59 km/s, 9 km/s, 2 x 10E22
cmE-2.  Both velocities are in good agreement with the previous
Columbia CO survey (Dame et al. 1986, Ap.J. 305, 892) and also
recent observations from the CfA (Grindlay 1994, Ap.J. Suppl., in
press).  This second cloud, with a measured kinematic distance of
about 7.8 kpc, exhibiting a larger line width and a greater column
density (which is in good agreement with the column density deduced
from ROSAT observations by Greiner et al. 1994, AIP Conf. Proc. No.
304, 260), is a good candidate for a possible association with GRS
1915+105.  These results are consistent with the model proposed by
Grindlay (loc. cit.), where SGR sources are due to thermal
instabilities in spherical accretion onto black holes in giant
molecular clouds.  Higher-resolution maps (both radio and
infrared), as well as spectra (to search for x-ray ionization
effects), are needed."

1994 June 3                    (6000)            Daniel W. E. Green

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