Central Bureau for Astronomical Telegrams
IAUC 6546: NEW X-RAY BURSTER; 1997B
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Circular No. 6546
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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NEW X-RAY BURSTER
T. Boller, F. Haberl, and W. Voges, Max-Planck-Institut fur
Extraterrestrische Physik, Garching; L. Piro, Istituto Astrofisica
Spaziale, CNR, Frascati; and J. Heise, Space Research Organization
of the Netherlands, report: "Within the 10' error box centered on
the BeppoSAX position of the x-ray burst from Jan. 13.295011 UT
(IAUC 6538), we have found the single x-ray source 1RXS
J124938.0-590525, contained in the ROSAT All-Sky Survey Bright
Source Catalogue (IAUC 6420) at the position R.A. = 12h49m38s,
Decl. = -59o05'.4 (equinox 2000.0; estimated 1-sigma error 9"),
which is 5'.6 north of the BeppoSAX position, with a countrate of
4.09 +/- 0.27 counts/s (0.1-2.4 keV) observed during 1991 Aug. 4-5.
During four ROSAT PSPC observations centered on R.A. = 12h47m43s,
Decl. = -59o41'.4, and totalling 12 400 s between 1993 July 11 and
Aug. 27, two sources were detected within the BeppoSax error circle
with the following positions, mean countrates and fluxes (assuming
a power-law model): source 1, R.A. = 12h49m39s, Decl. = -59o05'.2,
2.78 +/- 0.02 counts/s (0.1-2.4 keV), or 1.7 x 10E-10 erg cmE-2
sE-1 [for a power-law-fit value of the hydrogen column density NH =
(2.9 +/- 0.9) x 10E21 cmE-2 and photon index 2.1 +/- 0.2]; source 2,
R.A. = 12h49m27s, Decl. = -59o13'.3 (3'.9 south of the BeppoSAX
position), 0.08 +/- 0.002 counts/s (0.1-2.4 keV) or 2.2 x 10E-12
erg cmE-2 sE-1 [for power-law-fit NH = (0.4 +/- 0.1) x 10E21 cmE-2
and photon index 2.4 +/- 0.3]. Source 2 is probably a foreground
object because of the relatively-low-power-law-fit NH value.
Source 1 shows variability by +/- 20 percent during the pointing.
Source 2 is not detected in the ROSAT all-sky survey. The upper
limit value of 0.03 counts/s implies a change by more than a factor
of 2 between the survey and pointing observations. The ROSAT
source 1 (1RXS J124938.0-590525), as well as the BeppoSAX burster,
are very likely associated with 4U1246-58. Flaring activity from
this source was seen in the past -- but, to our knowledge, a strong
and short burst such as that observed by BeppoSAX (IAUC 6538) was
never reported. The flat-top light curve observed in this event
suggests a type-1 Eddington-limited burst."
SUPERNOVA 1997B IN IC 438
Corrigendum. M. Cavagna and P. Sicoli report that their
measurement on IAUC 6537 was incorrect. The proper position is
refined to read R.A. = 5h53m02s.97, Decl. = -17o52'23".5.
(C) Copyright 1997 CBAT
1997 January 27 (6546) Daniel W. E. Green
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