Central Bureau for Astronomical Telegrams

IAUC 8110: V838 Mon; 2003bg; GRB 030329

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                                                  Circular No. 8110
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)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


V838 MONOCEROTIS
     M. Orio, Istituto Nazionale di Astrofisica, Torino, and
University of Wisconsin; S. G. Starrfield, Arizona State University;
and E. Tepedenlegliolu, University of Wisconsin, report that V838
Mon was observed with Chandra (+ ACIS-S) on Feb. 23 for 6800 s, and
it was not detected with a 3-sigma upper limit to the count rate of
approximately 0.04 count/s: "This translates into an upper limit to
the unabsorbed flux in the band 0.2-10 keV of F_x </= 6.5 x 10**-14
erg cm**-2 s**-1, assuming N_H = 4.76 x 10**21 cm**-2 [derived from
E(B-V) = 0.8 mag; Kimesweger et al. 2002, MNRAS 336, L43] and a
plasma emitting at temperature 1 keV, or F_x </= 4.5 x 10**-9 erg
cm**-2 s**-1, assuming instead a blackbody emitting with a
temperature of 30 eV.  Given a distance in the range 2000-6000 pc
(Bond et al. 2003, Nature, in press), the above upper limit to the
x-ray flux rules out that either the central source, or a wind from
it, emits x-ray luminosity at the level observed in symbiotic novae
a year after the outburst (see Muerset et al. 1997, A.Ap. 319, 201).
This is strong evidence against a nova-like thermonuclear runaway
as mechanism for the 2002 outburst of this object."


SUPERNOVA 2003bg IN MCG -05-10-15
     D. Pooley and W. H. G. Lewin, Massachusetts Institute of
Technology, on behalf of a larger collaboration, report the
detection of x-ray emission from SN 2003bg with the Chandra X-ray
Observatory.  A 50500-s ACIS-S3 observation on Mar. 24.49 UT
reveals a 560-count source (0.5-10 keV) at R.A. = 4h10m59s.42,
Decl. = -31o24'50".3 (equinox 2000.0; +/- 0".5 in R.A. and Decl.),
in close agreement with the optical position (cf. IAUC 8082).
Preliminary spectral analysis indicates much low-energy (< 1 keV)
emission, perhaps indicating little absorption.  A power-law fit
gives a photon index of 1.9, but the data are better represented by
hot plasma models (MEKAL models in XSPEC) and are equally well fit
by a two-component MEKAL model with solar elemental abundances
(kT_1 = 0.5 keV; kT_2 = 6.5 keV) or a single MEKAL plasma (kT = 5.7
keV) with significant overabundances of O, Ne, and Ni.  Both models
give an unabsorbed 0.5-10-keV luminosity of about 4 x 10**39 erg/s
(19.1 Mpc, H_0 = 70 km/s/Mpc).  A second Chandra observation is
planned in late May.  Further optical and radio observations are
urged.


GRB 030329
     Additional magnitudes from J. McGaha (cf. IAUC 8107):  Apr.
5.250 UT, R = 18.39; 5.252, V = 18.34; 5.255, B = 18.83; 5.257, I =
17.95.

                      (C) Copyright 2003 CBAT
2003 April 8                   (8110)            Daniel W. E. Green

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