Central Bureau for Astronomical Telegrams
IAUC 5104: GX 1+4, KS 1731-260, GRS 1741.9-2853, A1524-62
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 5105
Circular No. 5104
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
GX 1+4, KS 1731-260, GRS 1741.9-2853, A1524-62
R. Sunyaev, on the behalf of the Granat team (Space Research
Institute, Moscow; Centre d'Etude Spatiale des Rayonnements,
Toulouse; Service d'Astrophysique, Centre d'Etudes Nucleaires de
Saclay, Gif sur Yvette), reports: "The field of the well-known
pulsar GX 1+4 was observed with the Granat observatory on Aug. 23.
The pulsations with period 114.60 +/- 0.05 s (at solar barycenter)
were detected both by ART-P (2-60 keV) and SIGMA (> 35 keV)
instruments. Comparison with the Mir-Kvant measurements in 1988
yields the following value of the average spindown rate during the
elapsed period: P-dot/P = 1.0 x 10E-2 yrE-1. This value is
remarkably lower than that observed with Ginga and Kvant in 1987-
1988 (P-dot/P = 1.3 x 10E-2 yrE-1). The source luminosity (3-20
keV) was found to be (2.3 +/- 0.2) x 10E36 erg/s (for distance 8.5
kpc).
In the same field, ART-P detected the transient x-ray burster
KS 1731-260 (IAUC 4839), with the 3- to 20-keV luminosity being
1.2 x 10E37 erg/s (for distance 8.5 kpc). During these observations,
the source was two times weaker than during Apr. 4 Granat
observations (the 3- to 20-keV luminosity being 2.1 x 10E37 erg/s)
and similar to that observed in 1989 Aug.-Sept. by Mir-Kvant (the
3- to 20-keV luminosity being 1.5 x 10E37 erg/s).
Further analysis of 1990 Mar. 24 and Apr. 8 observations of
the Galactic Center by ART-P (IAUC 5032) improves the error box
of x-ray source to within 10' of Sgr A. Previously this source
was tentatively identified with 1E 1741.7-2850. Now the 99-percent-
confidence error circle (1'.6 radius) does not overlap with error
boxes of 1E 1741.7-2850 and GS 1741.2-2859/GS 1741.6-289. The
coordinates of the new transient x-ray source GRS 1741.9-2853 (GRanat
Source) are: R.A. = 17h41m52s, Decl. = -28 52'55" (equinox 1950.0).
The 4- to 20-keV averaged luminosity of this source was 1.3 x 10E36
erg/s (for distance 8.5 kpc). A bremsstrahlung fit to the spectrum
gives a temperature of 8 keV.
During the Aug. 27-28 observations, the SIGMA telescope detected
a hard x-ray source whose 2' error box contains the soft x-ray
transient A1524-62. The 30- to 100-keV luminosity was 2.5 x 10E35
erg/s (for a distance of 2 kpc). This result implies the presence
of a hard component in the source spectrum, like that observed for
GS 2000+25 and A0620+00."
1990 September 27 (5104) Daniel W. E. Green
Read IAUC 5105
Our Web policy. Index to the CBAT/MPC/ICQ pages.
