Central Bureau for Astronomical Telegrams
IAUC 6506: MXB 1730-335; C/1996 Q1
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Circular No. 6506
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444 (for emergency use only)
MXB 1730-335
W. H. G. Lewin, D. W. Fox, J. M. Kommers, and E. Morgan,
Massachusetts Institute of Technology; R. E. Rutledge, Max-Planck-
Institut fur Extraterrestrische Physik; L. Bildsten, University of
California, Berkeley; T. Dotani, Institute of Space and
Astronautical Science; L. Lubin, Carnegie Observatories; M. van der
Klis, Astronomical Institute 'Anton Pannekoek', University of
Amsterdam (UA); and J. van Paradijs, University of Alabama in
Huntsville and UA, report: "Following the recurrence of activity
from the rapid burster MXB 1730-335 = X1730-333 (IAUC 6504), we
have carried out a series of observations with the RXTE PCA. On
Nov. 6.8 and 9.0 UT, we made 3000-s observations and detected the
source at a persistent emission level of roughly 160 and 105 mCrab
(2-12 keV), respectively, with no type II x-ray bursts seen. One
burst with type-I characteristics was seen during each observation;
these bursts exhibited a about 3-s rise time and a about 200-s
exponential decay. No significant (3-sigma) coherent or
quasiperiodic oscillations (QPOs) were detected in the persistent
or burst emission between 10 and 2048 Hz; 2-sigma upper limits on
the strength of any 2-10-Hz QPO in the burst decline on those days
are 3 and 5 percent rms, respectively. On Nov. 10.7 (3000-s
observation), 11.9 (2000-s), and 17.0 (3000-s), we detected the
source at fluxes of roughly 90, 80, and 70 mCrab, respectively,
with one small burst of low statistics (and unknown type) seen on
Nov. 11. This behavior is reminiscent of that displayed by the
rapid burster for about 10 days in 1983 Aug. (Kunieda et al. 1984,
PASJ 36, 807), after which it began its usual type-II bursting
behavior. We note that the current active phase of the rapid
burster follows the last one by about 6 months (IAUC 6390, 6409),
strengthening suspicions that this is the recurrence time for the
rapid burster (Lewin and Joss 1983, in Accretion-Driven Stellar X-
ray Sources, Cambridge University Press, p. 41, and references
therein). Sun-angle constraints do not allow us to continue PCA
observations."
COMET C/1996 Q1 (TABUR)
Total visual magnitude estimates by R. J. Bouma, Groningen,
The Netherlands: Nov. 5.75 UT, 9.2 (15x80 binoculars); 8.75, 9.6
(0.25-m reflector); 14.74, 10.4 (0.25-m reflector).
(C) Copyright 1996 CBAT
1996 November 19 (6506) Daniel W. E. Green
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