Central Bureau for Astronomical Telegrams
IAUC 7659: X-RAY TRANSIENTS IN M31; C/2001 A2
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Circular No. 7659
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)
X-RAY TRANSIENTS IN M31
R. Shirey, University of California at Santa Barbara, on
behalf of the X-Ray Multi-Mirror (XMM) Newton Optical/Ultraviolet
Monitor and the XMM-Newton Survey Science Centre teams, reports the
discovery of two new transient x-ray sources in M31: "The
transients were detected in about 50 000-s exposures with each of
the three EPIC instruments during XMM-Newton observations centered
on June 29.52 UT. One of the transients (XMMU J004308.5+411820),
located at R.A. = 0h43m08s.5, Decl. = +41o18'20" (equinox 2000.0;
about 3" error radius, based on astrometry relative to Chandra
globular-cluster x-ray source positions), exhibits a supersoft
x-ray spectrum (thermal spectrum with kT about 30 eV) with an
observed flux (0.2-2 keV) of 3 x 10**-14 erg s**-1 cm**-2. During
the x-ray observations, the Optical/ultraviolet Monitor (OM)
onboard XMM obtained exposures in three ultraviolet filters. A
faint ultraviolet source is present within 2"-3" of the location of
the supersoft x-ray transient with fluxes of 6 x 10**-17, 5 x
10**-17, and 6 x 10**-17 erg s**-1 cm**-2 A**-1 in UVW1 (245-320
nm), UWM2 (205-245 nm), and UVW2 (180-225 nm) exposures of 5000,
15 000, and 21 000 s, respectively. Shorter B-band and UVW1 OM
exposures (800 and 1200 s) from Dec. 2000 show no such source at
this location. In the MIT/Amsterdam M31 Survey, no source is
catalogued down to B about 21-22 within 5" of the transient
location, while several stars of magnitude I about 19 lie within 4"
of the transient. A second new transient x-ray source (XMMU
J004245.2+411721) is located at R.A. = 0h42m45s.2, Decl. =
+41o17'21" (equinox 2000.0; about 3" error radius) and exhibits a
more typical power-law spectrum (photon index about 1.5) and
observed flux (0.2-10 keV) 1.4 x 10**-13 erg s**-1 cm**-2.
Finally, the near-nuclear x-ray transient discovered with Chandra
in Oct. 1999 (IAUC 7291) and seen to be 'on' by XMM-Newton in June
and Dec. 2000 is no longer detected. Observations of the two new
x-ray transients at other wavelengths are encouraged."
COMET C/2001 A2 (LINEAR)
Total visual magnitude estimates: July 6.05 UT, 5.0 (J.
Kysely, Vlasim, Czech Republic, 7x50 binoculars); 7.98, 5.0 (S.
Baroni, Milan, Italy, 40x80 binoculars; moonlight); 10.89, 5.1 (K.
Hornoch, Lelekovice, Czech Republic, 10x80 binoculars); 12.41, 5.1
(C. S. Morris, Fillmore, CA, 10x50 binoculars; two tails, each at
least 2 deg long).
(C) Copyright 2001 CBAT
2001 July 12 (7659) Daniel W. E. Green
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