Central Bureau for Astronomical Telegrams
IAUC 5142: TRANSIENT X-RAY SOURCES NEAR MX 0836-42
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Circular No. 5142
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
TRANSIENT X-RAY SOURCES NEAR MX 0836-42
F. Makino and the Ginga Team, Institute of Space and Astronautical
Science, telex: "We designate the two transient x-ray sources
that appeared near MX 0836-42 (IAUC 5139) as GS 0836-429 and GS
0834-430, because it is inconclusive that these transients are identical
to MX 0836-42 and GRS 0831-429, respectively. The x-ray fluxes
of GS 0836-429 and GS 0834-430 were 19 and 34 mCrab, respectively,
on Dec. 5.7 UT. Both pulsation and bursting were active. The
following positions(equinox 1950.0) of these new sources were obtained
by cross-scan with the Large Area Proportional Counter aboard Ginga:
GS 0836-429, R.A. = 8h36m.8, Decl. = -42 56' (corners of error
box 8h35m.7, -42 41'; 8h37m.6, -42 56'; 8h37m.9, -43 14'; 8h36m.1,
-42 59').
GS 0834-430, R.A. = 8h34m.9, Decl. = -43 05' (corners of error
box 8h34m.2, -42 52'; 8h35m.5, -43 04'; 8h35m.8, -43 19'; 8h34m.4,
-43 07')."
G. Hasinger, W. Pietsch, and T. Belloni, Max Planck Institute
for Extraterrestrial Physics, communicate: "During its all-sky survey,
ROSAT has scanned the region containing the two transient x-ray
sources MX 0836-42 and GRS 0831-429 (cf. IAUC 5122) in the period
Nov. 14-16, about one week before the recent eruption (cf. IAUC
5139). On top of very bright diffuse emission from the Vela supernova
remnant, which is dominant below about 1 keV, we detected two
x-ray sources with a flux of about 1 mCrab (1-2.4 keV) and relatively
hard spectra (> 1 keV). We have determined the following coordinates
(equinox 1950.0) with an error radius of 50" (90 percent
confidence): northern source, R.A. = 8h35m39s, Decl. = -42 42'.8;
southern source, R.A. = 8h34m11s, Decl. = -43 00'.3. The northern
source is inside the error box of the transient MX 0836-42 (Cominsky
et al. 1978, Ap.J. 224, 46) and about 52' off GRS 0831-429 (IAUC
5122). The southern source is 35' off GRS 0831-429. We have
detected pulsations with a period of 12.3261 +/- 0.0002 s, consistent
with the Ginga observation. However, in contrast to the conclusion
in IAUC 5139, the pulsations occur in the northern source (MX
0836-42). The ratio of second- to first-harmonic is 1.4. We cannot
determine which of the two sources is responsible for the x-ray
bursts observed by Ginga; this requires further x-ray observations."
1990 December 10 (5142) Daniel W. E. Green
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