Central Bureau for Astronomical Telegrams

Central Bureau for Astronomical Telegrams -- Image credits

IAUC 8190: Poss. N IN Sct; CXOU J180951.1-194351 = RXTE J1810-197

The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).

Read IAUC 8189  SEARCH Read IAUC 8191

View IAUC 8190 in .dvi or .ps format.
IAUC number

                                                  Circular No. 8190
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. Nakano, Sumoto, Japan; and H. Sato, National Astronomical
Observatory of Japan (NAOJ), report the discovery of a possible
nova by Hideo Nishimura (Kakegawa, Shizuoka-ken, Japan) on T-Max
films taken on Aug. 28.58 (mag 8.5) and 29.436 UT (mag about 8.4)
with a Pentax 200-mm f/4.0 lens, the position given as R.A. =
18h49m38s, Decl. = -9o33'45" (equinox 2000.0).  T. Nakamura, NAOJ,
reports the following mean precise position end figures by S. Wakuda
(Hamamatsu, Japan) from six CCD images (0.25-m f/5.1 reflector, Aug.
29.354, V = 9.5): 37s.62, 50".3.  H. Yamaoka, Kyushu University,
reports that ASAS-3 images show an object at position end figures
37s.7, 53" with the following V magnitudes:  Aug. 24.105, [14.0;
26.096, 10.15; 28.096, 8.94.  Yamaoka adds that a USNO-A2.0 star of
red mag 16.4 and blue mag 17.2 has position end figures 37s.684,
53".76; this star is also present in the GSC-2.2 and USNO-B1.0
catalogues, and a 2MASS star (J = 14.32, K = 13.82) has position end
figures 37s.70, 54".1.  Visual magnitude estimate by A. Pearce,
Nedlands, W. Australia:  Aug. 30.461, 9.3.

CXOU J180951.1-194351 = RXTE J1810-197
     E. V. Gotthelf and J. P. Halpern, Columbia University; C.
Markwardt, Goddard Space Flight Center (GSFC); A. I. Ibrahim,
George Washington University and GSFC; M. Roberts and S. M. Ransom,
McGill University; and P. Woods, USRA and National Space Science
and Technology Center, on behalf of a larger collaboration, report
a highly significant detection of a pulsed source with a
barycentric period of 5.5391(3) s, from a 2833-s Chandra HRC-I
observation starting Aug. 27.95166 UT.  This source shows a
strongly modulated (52-percent pulsed fraction) sinusoidal pulse
signal with a countrate of 0.917 counts/s in the HRC-I energy band
0.08-10.0 keV.  The pulsar is located at R.A. = 18h09m51s.13, Decl.
= -19o43'51".7 (equinox 2000.0; uncertainty radius of 2".1 at the
off-axis HRC-I position).  This position is offset by 14' from the
centroid reported for the 5.5-s pulsar RXTE J1810-197 (IAUC 8168);
the large offset (6 sigma) is likely due to systematic errors in
the derived RXTE position which are based on scans of the complex
region.  The location of CXOU J180951.1-194351 is consistent with a
source seen in archival ROSAT and ASCA images.  The lack of an
optical counterpart within the 1-sigma Chandra error circle
suggests that CXOU J180951.1-194351 is an isolated neutron star,
one most similar to the transient anomalous x-ray pulsar AX
J1844.8-0256 (cf. Vasisht et al. 2000, Ap.J. 43, L49).

                      (C) Copyright 2003 CBAT
2003 August 30                 (8190)            Daniel W. E. Green

Read IAUC 8189  SEARCH Read IAUC 8191

View IAUC 8190 in .dvi or .ps format.

Our Web policy. Index to the CBAT/MPC/ICQ pages.

Valid HTML 4.01!