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IAUC 7816: V838 Mon; 2002ap

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                                                  Circular No. 7816
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     S. Kimeswenger, C. Lederle, and S. Schmeja, University of
Innsbruck, report that this object has increased markedly in
brightness, as seen by their photometry (cf. IAUC 7796):  Feb.
1.8576 UT, B = 12.794, V = 10.708, R = 9.652, I_c = 8.634; 2.7986,
9.607, 8.193, 7.439, 6.657; 2.9132, 9.427, 8.024, 7.276, 6.484.
Spectroscopic follow-up is encouraged.
     Visual magnitude estimates: Jan. 19.137 UT, 10.3 (R. Y. Shida,
Sao Paulo, Brazil); 26.798, 10.8 (A. Pearce, Nedlands, W.
Australia); Feb. 2.803, 8.3 (R. J. Bouma, Groningen, The
Netherlands); 2.847, 8.9 (M. Reszelski, Szamotuly, Poland); 2.843,
8.6 (O. Pejcha, Brno, Czech Rep.).

     S. Smartt and E. Ramirez-Ruiz, Institute of Astronomy,
Cambridge; and P. Vreeswijk, University of Amsterdam, report that
120-s UBVI images of M74 were taken with the Isaac Newton Telescope
(+ Wide Field Camera) in July 2001, as part of the INT Wide Field
Survey.  They detect an object with B = 21.6, V = 21.2, I = 20.5
(uncertainties +/- 0.2 mag) at R.A. = 1h36m24s.00, Decl. =
+15o45'13".6 (equinox 2000.0), which is within 1".3 of a radio
source found on Feb. 1.03 UT
(cf. http://gcn.gsfc.nasa.gov/gcn/gcn3/1237.gcn3; position end
figures 23s.920, 12".87).  This fairly faint object shows some
inconclusive evidence of being extended; at the spatial resolution
of the images (about 50 pc), the object could be an unresolved
small cluster or H II region, or a predominantly bright star on a
variable background.  Assuming that it is a single star, with a
distance modulus of 29.5 to M74, they estimate absolute magnitudes
M_B = -8.2, M_V = -8.5, M_I = -9.1.  The colors B-V = +0.3, V-I =
+0.6, and these absolute magnitudes are consistent with a very
luminous early- to mid-F-type supergiant.  The bolometric
luminosity is approximately 10**5.3 solar luminosities, which would
place the star in the luminous-blue-variable region of the HR
diagram (Humphreys and Davidson 1994, PASP 106, 1025) and suggests
an initial mass of around 40 solar masses.  Smartt et al. add that
any significant extinction would make the star intrinsically bluer
and more luminous.  Further astrometry and image-shape analysis are
required to confirm that the progenitor object is stellar, and
monitoring of SN 2002ap at all wavelengths is encouraged.
     Visual magnitude estimates:  Jan. 31.784 UT, 13.2 (L. Brat,
Pec pod Snezkou, Czech Republic); Feb. 2.776, 12.7 (R. J. Bouma,
Groningen, The Netherlands); 2.783, 12.6 (K. Hornoch, Lelekovice,
Czech Republic).

                      (C) Copyright 2002 CBAT
2002 February 2                (7816)            Daniel W. E. Green

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