Detection of Additional Periodicities in RXTE ASM Light Curves
ATel #940; Alan M. Levine (MIT MKI) and Robin Corbet (NASA/GSFC and USRA)
on 9 Nov 2006; 15:49 UT
Credential Certification: Alan M. Levine (aml@space.mit.edu)
Subjects: X-ray, Binary, Black Hole, Neutron Star, Pulsar
Referred to by ATel #: 1995
We have detected periodicities in the Rossi X-ray Timing Explorer (RXTE) All-sky Monitor (ASM) X-ray light curves beyond those reported
by Wen et al. (2006, ApJS, 163, 372). We analyzed data accumulated
over nearly 10 years (1996 March through 2005 November) from some 450
sources. Several weighting and filtering techniques not used by Wen et
al. were applied previous to the Fourier analysis in order to reduce
noise levels. We have searched for both known and previously unknown
periods; the signal strengths required for detection in the two cases
are quite different. One periodicity, i.e., that of GRO J1008-57, was
found by visual identification of periodically occurring outbursts
rather than via the power density spectrum. Our results are listed
below.
| Source | Period | Comments |
|---|
| X1145-619 | ÃÅ870 s | alias of 290 s pulse period |
| X1820-303 | 685.01117 ñ 0.0005 s |
| X1323-619 | 2.94192 ñ 0.00004 h |
| X1636-536 | 3.79315 ñ 0.00006 h |
| X1254-690 | 3.93336 ñ 0.00006 h
or 3.93995 ñ 0.00006 h |
two nearly equally likely values |
| GX9+9 | 4.19344 ñ 0.00007 h | also see ATEL #839 |
| X1746-370 | 5.16329 ñ 0.00016 h |
| X1957+115 | 9.3175 ñ 0.0005 h | marginal detection |
| GX339-4 | 1.7563 ñ 0.0003 d | not a strong detection |
| GRO J1655-40 | 2.621 ñ 0.007 d | not a strong detection |
| V4641 Sgr | 2.8019 ñ 0.0002 d | not a strong detection |
| LMC X-1 | 3.9081 ñ 0.0015 d | see below |
| SS433 | 13.075 ñ 0.017 d | see below |
| IGR J18483-0311 | 18.55 ñ 0.03 d | new periodicity |
| X1417-62 | 42.12 d | period from Bildsten et al. 1997 |
| X1845-024 | 242.18 d | period from Finger et al. 1999 |
| GRO J1008-57 | 248.9 ñ 0.5 d | see text below |
Periodicities with periods close to those in the above table have
been previously reported in all cases except that of IGR J18483-0311.
In an least one power spectrum for GX339-4, the highest power
occurs at the frequency corresponding to the 1.7 d period reported by
Hynes et al. (2003, ApJL, 583, L95). The magnitude of this power is
not so high that the detection is completely secure. However, given
the number of frequency bins, and the fact that we do not find high
values of power at the frequencies corresponding to the 0.62 d period
reported by Callanan et al. (1992, MNRAS, 259,395) or to the 0.7 d
period reported by Cowley et al. (2002, ApJ, 123, 1741), we believe
that this result confirms the Hynes et al. result.
To our knowledge, this is the first detection of the orbital period
of LMC X-1 in X-rays. Hutchings et al. (1983, ApJL, 275, L43) and
Hutchings et al. (1987, AJ, 94, 340) reported periods of LMC X-1 based
on radial velocities. We find a highly significant peak at a period
of 3.9081 ñ 0.0015 d that is nearly exactly the first of
several possible values given by Hutchings et al. (1983).
Gies et al. (2002, ApJ, 566, 1069) have previously reported the
detection in ASM data of the 13.075 d orbital period of SS433.
The orbital periods of X1417-62 and X1845-024 were determined much
more accurately via pulse timing analyses by Bildsten et al. (1997,
ApJS, 113, 367) and Finger et al. (1999, ApJ, 517, 449), respectively,
than in our work.
Previous estimates regarding the period of GRO J1008-57 may be
found in Schrader et al. (1999, ApJ, 512, 920) and references
therein.
