Central Bureau for Astronomical Telegrams
IAUC 6551: 1997W, 1996bw; BY Dra
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Circular No. 6551
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVAE 1997W AND 1996bw IN NGC 664
P. Berlind, Fred L. Whipple Observatory (FLWO); and P.
Garnavich, Harvard-Smithsonian Center for Astrophysics (CfA),
report their discovery of a second supernova (V = 18.0) in NGC 664
from CCD images obtained with the FLWO 1.2-m telescope on Feb. 1.2
UT by C. Hergenrother. SN 1997W is only 0".7 west and 2".4 south
of SN 1996bw (IAUC 6516), which is currently of comparable
brightness (V = 18.2). The new supernova was identified from
images obtained for the CfA Supernova Photometry program. No
evidence of the new supernova is seen on FLWO images taken on 1996
Dec. 6. Spectra of SN 1997W, obtained with the 1.5-m Tillinghast
telescope on Feb. 3.1, show a broad H-alpha P-Cyg feature on an
otherwise smooth blue continuum, indicating that this is a type-II
supernova caught at an early stage.
BY DRACONIS
R. Mewe and J. Heise, Space Research Organization of the
Netherlands (SRON); J. M. Muller, SRON and BeppoSAX, Rome; A.
Coletta, G. D'Andreta, L. Di Ciolo, G. Spoliti, R. Ricci, and P.
Giommi, BeppoSAX, Rome; and L. Piro, Istituto Astrofisica Spaziale,
Frascati, report: "For 50 min (during an entire orbit of BeppoSAX)
during Jan. 23.863-23.898 UT, the Wide Field Camera 2 (WFC2)
onboard BeppoSax detected a transient x-ray source that was not
seen over 10 hr during immediately-preceding observations of the
same field. The source is located at R.A. = 18h33m.4, Decl. =
+51 46' (equinox 2000.0; error radius 10'), which is 6 deg from the
center of the WFC2 image. Initially, the source flux was 40 mCrab
(8.5 WFC2 counts/s) in the energy band 2-9 keV, decreasing to 14
mCrab towards the end of the observation. At higher energies (up
to 28 keV), no flux was found during the entire observation. In
the next orbit, the 2-9-keV flux had fallen below the sensitivity
limit (over one orbit) of about 10 mCrab. We have identified the
source with the dM0e flare star BY Dra (distance 15.6 pc). No
other sources with a flux > 10 mCrab are present in x-ray
catalogues within 3 deg of the source. We conclude that a giant
stellar flare was detected in x-rays with a remarkably short decay
time. The expected countrates for typical M dwarf flare stars like
BY Dra are of the order of 0.3-1 WFC2 counts/s (during flare), but
the measured countrate (corresponding to an x-ray luminosity of
about 2 x 10E31 erg/s) is exceptionally high -- comparable to the
strongest flare ever seen with the ROSAT PSPC detector."
(C) Copyright 1997 CBAT
1997 February 3 (6551) Daniel W. E. Green
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