Central Bureau for Astronomical Telegrams
IAUC 7336: 1999gn; 1999em; GRS 1915+105
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Circular No. 7336
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)
SUPERNOVA 1999gn IN M61
K. Ayani, Bisei Astronomical Observatory (BAO); and H.
Yamaoka, Kyushu University, report that a wide-band spectrum (range
400-800 nm; resolution 0.6 nm) of SN 1999gn, obtained with the BAO
1.01-m reflector on Dec. 20.8 UT, shows it to be a type-II
supernova in an early phase. It exhibits a blue continuum with a
broad P-Cyg H-alpha profile and H-beta absorption. The expansion
velocity of the supernova, derived from H-alpha absorption minimum
with respect to the narrow H-alpha emission (from the superposed H
II region), is 5300 km/s.
SUPERNOVA 1999em IN NGC 1637
C. K. Lacey, Naval Research Laboratory (NRL); S. D. Van Dyk,
IPAC, California Institute of Technology; K. W. Weiler, NRL; R. A.
Sramek, National Radio Astronomy Observatory (NRAO); and N.
Panagia, Space Telescope Science Institute, report: "Radio
observations with the NRAO Very Large Array on Dec. 1 yield the
detection of a compact radio source at 8.4 GHz (3.6 cm) of 0.19 +/-
0.03 mJy at position R.A. = 4h41m27s.157, Decl. = -2 51'45".83
(equinox 2000.0, uncertainty +/- 0".1) displaced about 1".5 in R.A.
from the precise optical position reported on IAUC 7296. However,
a new measurement of the optical position by Van Dyk from an R-band
image of SN 1999em made with the 0.8-m Katzman Automatic Imaging
Telescope (KAIT) on Nov. 5 UT, and kindly provided by W. D. Li and
A. V. Filippenko, yields optical position end figures 27s.13,
45".4, which agrees to within 0".6 with the radio position. Thus,
this appears to represent a detection of radio emission from the
type-IIP supernova 1999em with an 8.4-GHz spectral luminosity of
1.4 x 10**25 erg s**-1 Hz**-1 for an assumed distance of 7.8 Mpc
(Sohn and Davidge 1998, A.J. 115, 130). On Dec. 13, a new
measurement at 8.4 GHz yields a flux density of 0.22 +/- 0.04 mJy.
The full set of radio measurements, including upper limits reported
earlier on IAUC 7318, is available at
http://rsd-www.nrl.navy.mil/7214/weiler/sne-home.html."
GRS 1915+105
E. B. Waltman, Naval Research Laboratory; and F. D. Ghigo,
National Radio Astronomy Observatory, report: "The Green Bank
Interferometer has observed a flare in the microquasar GRS
1915+105 on Dec. 23. Flux densities reached 0.5 Jy at 2 GHz on
Dec. 23.8 UT, ending the current radio plateau state. The data may
be accessed at http://www.gb.nrao.edu."
(C) Copyright 1999 CBAT
1999 December 23 (7336) Daniel W. E. Green
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