J/ApJ/694/1115 Modulation in the X-ray binary SAX J1808.4-3658 (Wang+, 2009)
An accurate determination of the optical periodic modulation in the X-ray
binary SAX J1808.4-3658.
Wang Z., Bassa C., Cumming A., Kaspi V.M.
<Astrophys. J., 694, 1115-1120 (2009)>
=2009ApJ...694.1115W 2009ApJ...694.1115W
ADC_Keywords: Binaries, X-ray ; Photometry, SDSS
Keywords: binaries: close - stars: individual (SAX J1808.4-3658) -
stars: neutron - X-rays: binaries
Abstract:
We report on optical imaging of the X-ray binary SAX J1808.4-3658 with
the 8m Gemini South Telescope. The binary, containing an
accretion-powered millisecond pulsar, appears to have a large periodic
modulation in its quiescent optical emission. In order to clarify the
origin of this modulation, we obtained three time-resolved r'-band
light curves (LCs) of the source over five days. The LCs can be
described by a sinusoid, and the long time-span between them allows us
to determine optical period P=7251.9s and phase 0.671 at MJD 54599.0
(TDB; phase 0.0 corresponds to the ascending node of the pulsar
orbit), with uncertainties of 2.8s and 0.008 (90% confidence),
respectively. This periodicity is highly consistent with the X-ray
orbital ephemeris.
Description:
To determine the periodicity in the source's optical emission
accurately, three Gemini queue mode observations of J1808.4 were
carried out over five days, on 2008 May 11, 12, and 15. The starting
time of each observation was approximately 06 hour (UTC) each day,
resulting in a time span of ∼4 days between the first and third
observations.
Objects:
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RA (2000) DE Designation(s)
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18 08 27.5 -36 58 44 SAX J1808.4-3658 = V* V4580 Sgr
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 21 108 Photometry of SAX J1808.4-3658
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See also:
V/106 : Catalogue of X-ray binaries (Liu+ 2001)
J/A+A/469/807 : Catalogue of Galactic low-mass X-ray binaries (Liu+, 2007)
J/A+A/472/705 : BeppoSAX WFC X-ray source catalogue (SAXWFC) (Verrecchia+,
2007)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 F8.6 d MJD Modified Julian Date minus 54597.0
10- 15 F6.3 mag r'mag The r' band magnitude
17- 21 F5.3 mag e_r'mag The 1σ uncertainty in rmag resulting
from PSF fitting
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Mar-2011