Improved orbital ephemeris of GRO J1008-57
ATel #4564; M. Kuehnel, S. Mueller, I. Kreykenbohm, J. Wilms (Remeis-Observatory Bamberg), K. Pottschmidt (CRESST-UMBC/NASA-GSFC), F. Fuerst (Caltech-SRL), R. E. Rothschild (UC San Diego), I. Caballero (CEA Saclay), D. Klochkov, R. Staubert, S. Suchy (IAA Tuebingen), P. Kretschmar (ESAC/ESA), C. Ferrigno (ISDC, University of Geneva), J. M. Torrejon and S. Martinez-Nunez (U Alicante)
on 10 Nov 2012; 10:35 UT
Credential Certification: Ingo Kreykenbohm (ingo.ik.kreykenbohm@fau.de)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
The recurrent transient GRO J1008-57 is currently undergoing an unusal
long outburst (ATELs #4561, #4355, #4319). Typically, outbursts of
this system are associated with the periastron passage of the neutron
star.
We have triggered Swift observations of the current outburst (MJD
56197) and furthermore analyzed all available RXTE, Swift, and Suzaku
data of previous outbursts of the system. Using pulse arrival times
we derived an updated solution for the orbital period and the time of
the periastron passage with significantly increased accuracy compared
to the previous solutions of Coe et al. (2007) based on BATSE data and
Levine & Corbet (2006) based on ASM data. We obtain the following
ephemeris:
Porb = 249.46(10) d;
T0 = MJD 54424.6(4) where T0 is the time of periastron passage;
asini = 530(60) lt-sec (Coe et al. 2007);
omega = -26(8) deg (Coe et al. 2007) ;
e = 0.68(2) (Coe et al. 2007).
This new ephemeris allowed us to predict the outburst in April 2011
and this outburst with a precision of 5 days.
Using this updated ephemeris we obtain an orbital phase for the
current re-brightening of GRO J1008-57 of phi = 0.278(4) consistent
with the value of 0.3 found by Nakajima et al. 2012 (ATEL #4561).
