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IAUC 7249: Cas A; N Cir 1999

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                                                  Circular No. 7249
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 617-495-7244/7440/7444 (for emergency use only)

     B. Aschenbach, Max-Planck-Institut fur Extraterrestrische Physik,
Garching, reports: "The analysis of a 180 000-s observation of Cas A taken
with the ROSAT HRI in 1995-96 shows a pointlike source at
R.A. = 23h23m27s.6, Decl. = +58d48'44".0 (equinox 2000.0) that appears to
be the same object reported by Tananbaum et al. from the Chandra First
Light observation (IAUC 7246), because of the small separation of the two
sources (< 2") and the absence of other candidates.  The ROSAT HRI
background-corrected countrate was 0.0015 +/- 0.0003 cts/s.  Correction
for interstellar absorption is highly uncertain because of the large N_H.
However, taking "standard" values of N_H = 1.2 x 10**22 cm-2 and a
distance of 3.4 kpc, the countrate is consistent with blackbody emission
from a 10-km radius neutron star with a temperature of 1.6 MK, and this
supports the view that the object is the Cas A neutron star."

     W. D. Li, University of California at Berkeley, on behalf of the Lick<
Observatory Supernova Search (cf. IAUC 6627, 7126), reports the discovery
with the 0.8-m Katzman Automatic Imaging Telescope (KAIT) of a new nova,
of mag about 17.0, in an unfiltered image of M31 taken on Sept. 2.3 UT.
The nova was confirmed on earlier images taken on Aug. 30.3, 31.3 and Sept.
1.3 at mag about 18.5, 17.8 and 17.0, respectively.  It is located at
R.A. = 0h42m41s.1, Decl. = +41d19'11" (equinox 2000.0), which is about 43"
west and 175" north of the nucleus of M31.  A KAIT image on Aug. 28.3 showed
nothing at the position of the nova (limiting mag 19.0).  A finding
chart can be found at http://astron.berkeley.edu/~bait/1999/n31_3.html.

     Photometry by P. M. Kilmartin and A. C. Gilmore with the 0.6-m
f/16 reflector at Mt. John Observatory: Aug. 26.360 UT, V = 8.49, U-B =
-0.69, B-V = +0.53, V-R = +0.90, V-I = +1.58, airmass = 1.28; 27.387,
9.58, -0.63, +0.47, +1.32, +1.81, 1.35; 31.359, 9.74, -0.50, +0.35, +1.63,
+1.68, 1.31.  Reference stars for Aug. 26 were Cousins' F213 = HD 107547
and F210 = HD 106759.  Nearby reference  stars for Aug. 27 and 31, with
assumed magnitudes and colors, calibrated from Cousins' F-region standards,
were HD 125389 (V = 7.35, U-B = -0.07, B-V = +0.43, V-R = +0.25, V-I
= +0.52) and HD 125605 (9.09, +0.04, +0.56, +0.33, +0.68).  Standard
deviations are 0.01 mag or less.

                      (C) Copyright 1999 CBAT
1999 September 4               (7249)              Brian G. Marsden

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