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A Re-analysis of Timing Parameters of SGR 1833-0832

ATEL # 2763; A. Baykal (METU), S. Balman (METU), M. Mirac (METU)
on 30 Jul 2010; 14:53 UT
Password Certification: Solen Balman (solen@astroa.physics.metu.edu.tr)

Subjects: X-ray, Gamma Ray, Pulsars, Soft Gamma-ray Repeaters

SGR 1833-0832 is discovered on 2010 March 19 (MJD 55274; GCN #10526) by Swift/BAT and monitored with XMM-Newton, Swift, and RossiXTE. About 90 days after the Swift/BAT event, Esposito et al., 2010, (ATEL #2691) reported the calculation of a second pulse frequency derivative component with respect to the phase-coherent timing solutions previously reported, which included only the period and its first time derivative (ATEL #2550, #2553; Gogus et al. 2010, 718, 311). We re-analyzed the RXTE lightcurve between 55276.64 MJD and 55382.44 MJD with a time span of 106 days (16 days longer than reported in ATEL #2691). Our quadratic fits to the pulse arrival times show that the spin down rate has increased by 39 percent on the average in comparison with Gogus et al. (2010) and reached the value \dot \nu = -10.9(3)E-14 Hz/s. On the other hand, our cubic polynomial fit with a Taylor expansion shows that the value of the second pulse frequency derivative has decreased by a factor of three in comparison with Esposito et al. (2010). Our cubic fit solutions to pulse arrival times for 106 days. (following the Swift/BAT event) are : \nu = 0.13218059(2) Hz, \dot \nu= -8.6(1.6)E-14 Hz/s, and \ddot \nu= -5.6(3.6)E-21 Hz/s^2 . Our initial epoch is 55276.64(5) MJD. We find that the evolution of pulse frequency history of SGR 1833-0832 has variable second pulse frequency derivative which could be part of the red noise process associated with the braking indices of the radio pulsars (see Baykal et al.,1999, MNRAS, 306, 207).


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