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IAUC 8202: V838 Mon; IGR J17544-2619

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                                                  Circular No. 8202
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)

     R. M. Wagner, LBT Observatory; G. Schwarz, University of
Arizona; S. Starrfield, Arizona State University; U. Munari, E.
Giro, and A. Siviero, Asiago Observatory; A. Henden, USRA and U.S.
Naval Observatory, Flagstaff (USNOFS); P. Szkody, University of
Washington; and H. Bond, Space Telescope Science Institute, write
that optical spectra, obtained with the 6.5-m MMT (range 383-905
nm, resolution 0.6 nm) on Sept. 13.49 UT and with the Asiago 1.82-m
telescope (+ AFOSC) on Sept. 12.13 (range 485-780 nm, resolution
0.8 nm) and Sept. 13.15 (in echelle mode; range 360-860 nm;
resolving power 3800), reveal a dramatic change when compared to
their previous spectra (cf. IAUC 7982, 7992, 8005).  In addition to
the Balmer and He I absorption lines characteristic of a B3 V star
(shortward of 600 nm) and the TiO and VO bands (longward of 600 nm)
that dominated their previous spectra, the spectrum now exhibits
absorption bands of TiO, VO, ZrO, YO, and perhaps CrO, LaO, and ScO
in the region 490-600 nm that were previously absent.  Overlapping
bands make positive identification difficult.  The new spectra
suggest that, while the B3 V star is still visible in the U and B
bands, the O-rich and very cool atmosphere of the outbursting star
is now also dominating the V band (and not only the R and I bands,
as it has been since Oct. 2002).  The changes are accompanied by a
0.5-mag brightening in V, R, and I bands since last May (on Sept.
11-13, V = 15.50, B-V = +1.00, V-R_c = +2.70, R_c-I_c = +3.25;
formal errors 0.01 mag; USNOFS 1.0-m telescope), but with no
appreciable changes in the near-infrared (on Sept. 13.51, J = 6.76,
H = 5.84, K' = 5.10, L' = 3.54; errors 0.03 mag; USNOFS 1.55-m
telescope + ASTROCAM).  Monitoring of the changes in progress is

IGR J17544-2619
     R. Gonzalez-Riestra, M. Santos-Lleo, L. Tomas, and R. Perez-
Martinez, XMM-Newton Science Operations Centre, Madrid, report that
IGR J17544-2619 was clearly detected (countrate 0.41 counts/s;
EPIC-pn + thin filter) in the field-of-view of V4643 Sgr during a
10000-s XMM-Newton observation on Sept. 11.92 UT, five days before
the INTEGRAL discovery (Sunyaev et al.,
http://atel.caltech.edu/?read=190).  The source coordinates are
R.A. = 17h54m25s.7, Decl. = -26o19'58" (equinox 2000.0; uncertainty
about 10"), within the reported INTEGRAL error box.  The spectrum
was consistent with a hydrogen column density of 1.3 x 10**22
cm**-2.  The observed flux in the range 2-10 keV was 4.5 x 10**-12
erg cm**-2 s**-1.

                      (C) Copyright 2003 CBAT
2003 September 19              (8202)            Daniel W. E. Green

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