Central Bureau for Astronomical Telegrams
IAUC 6999: 1SAX J0103.2-7209, AX J0051-722,, XTE J0055-724; 1998dh
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 7000
.dvi or
.ps format.
Circular No. 6999
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)
1SAX J0103.2-7209, AX J0051-722, AND XTE J0055-724
G. L. Israel and L. Stella, Osservatorio Astronomico di Roma;
S. Campana and S. Covino, Osservatorio Astronomico di Brera; D.
Ricci, SAX Science Data Center; and T. Oosterbroek, Space Science
Department, European Space Agency, on behalf of the BeppoSAX Small
Magellanic Cloud (SMC) Team, report the discovery of a new x-ray
pulsar, designated as 1SAX J0103.2-7209, during a BeppoSAX
observation of the SMC on July 27-28: "The source shows nearly
sinusoidal pulsations at a period of 345.2 +/- 0.1 s. The energy
spectrum is well fitted by a power law with photon index 1.0 +/-
0.1, corresponding to an absorbed flux of 3 x 10E-12 erg sE-1 cmE-2
(energy band 2-10 keV). The BeppoSAX source position (R.A. =
1h03m13s, Decl. = -72o09'.3, equinox 2000.0; estimated error
radius 40") is consistent with the known supernova remnant SNR
0101-724 (Wang and Wu 1992, Ap.J. Suppl. 78, 391) and the Einstein
source 1E 0101.5-7225. The latter source was detected in all
Einstein, ROSAT, and ASCA pointings since 1979 at a flux level of a
few x 10E-13 erg sE-1 cmE-2, while no pulsations were detected.
Multiband optical images obtained with the 1.5-m Danish telescope
at the European Southern Observatory (ESO) on 1998 July 24 show
that the Be star of m_V = 14.8, originally suggested as the optical
counterpart of the Einstein source (Hughes and Smith 1994, A.J.
107, 1363), is the only star that shows strong H-alpha activity in
the BeppoSAX error circle. During a BeppoSAX observation of the
SMC on July 24-25, we detected x-ray pulsations of 90.65 +/- 0.01
and 58.95 +/- 0.01 s from the pulsars AX J0051-722 and XTE
J0055-724, respectively. The spacing of the Nov. 1997 (IAUC 6777),
Mar. 1998 (IAUC 6858), and July 1998 flares observed from AX
J0051-722 further suggests an orbital period of about 120 days.
The inferred period derivative is about -0.3 +/- 0.1 s/yr. The
absorbed flux of XTE J0055-724 is about 7 x 10E-12 erg sE-1 cmE-2
(2-10 keV). Optical spectra (1998 July 27; 1.5-m ESO telescope)
obtained for the second brightest star (R.A. = 0h54m56s, Decl. =
-72o26'47") included in the x-ray error circle of XTE J0055-724
(IAUC 6822) showed strong H-alpha and H-beta emission lines. Also,
a fainter star (R.A. = 0h54m57s, Decl. = -72o26'48") included in
the x-ray error circle of XTE J0055-724 showed an H-alpha emission
line. Further optical and x-ray observations of these pulsars are
encouraged."
SUPERNOVA 1998dh IN NGC 7541
Unfiltered CCD magnitude estimates: Aug. 16.96 UT, 14.5 (L.
Boschini, Miragolo, Bergamo, Italy); 24.04, 14.9 (S. Moretti,
Forli, Italy).
(C) Copyright 1998 CBAT
1998 August 27 (6999) Daniel W. E. Green
Read IAUC 7000
.dvi or
.ps format.
Our Web policy. Index to the CBAT/MPC/ICQ pages.
