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IAUC 6999: 1SAX J0103.2-7209, AX J0051-722,, XTE J0055-724; 1998dh

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                                                 Circular No. 6999
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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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

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

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