Evidence of a change in the long-term spin-down rate of the X-ray pulsar 4U 1907+09

Baykal, Altan
Beklen, E.
We analysed RXTE archival observations of 4U 1907+09 between 1996 February 17 and 2002 March 6. The pulse timing analysis showed that the source stayed at almost constant period around 1998 August and then started to spin-down at a rate of (-1.887 -/+ 0.042) x 10(-14) Hz s(-1) which is similar to 0.60 times lower than the long-term (similar to 15 yr) spin-down rate. Our pulse-frequency measurements for the first time resolved significant spin-down rate variations since the discovery of the source. We also presented orbital phase resolved X-ray spectra during two stable spin-down episodes during 1996 November-1997 December and 2001 March-2002 March. The source has been known to have two orbitally locked flares. We found that X-ray flux and spectral parameters except hydrogen column density agreed with each other during the flares. We interpreted the similar values of X-ray fluxes as an indication of the fact that the source accretes not only via transient retrograde accretion disc but also via the stellar wind of the companion, so that the variation of the accretion rate from the disc does not cause significant variation in the observed X-ray flux. Lack of significant change in spectral parameters except hydrogen column density was interpreted as a sign of the fact that the change in the spin-down rate of the source was not accompanied by a significant variation in the accretion geometry.


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İNAM, SITKI ÇAĞDAŞ; Baykal, Altan; Beklen, E. (Oxford University Press (OUP), 2010-03-21)
We present timing and spectral analysis of Rossi X-ray Timing Explorer-Proportional Counter Array observations of SMCX-1 between 1996 January and 2003 December. From observations around 1996 August 30 with a time-span of similar to 6 d, we obtain a precise timing solution for the source and resolve the eccentricity as 0.00089(6). We find an orbital decay rate of (P) over dot(orb)/P(orb) = -3.402(7) x 10(-6) yr(-1) which is close to the previous results. Using our timing analysis and the previous studies, we...
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Baykal, Altan; Beklen, E. (EDP Sciences, 2006-07-01)
The high mass X-ray binary pulsar 4U 1538-52 was observed between July 31 and August 7, 2003. Using these observations, we determined new orbital epochs for both circular and elliptical orbit models. The orbital epochs for both orbit solutions agreed with each other and yielded an orbital period derivative. P/P = (0.4 +/- 1.8) x 10(-6) yr(-1). This value is consistent with the earlier measurement P/P = (2.9 +/- 2.1) x 10(-6) yr(-1) at the 1 sigma level and gives only an upper limit to the orbital period dec...
BAYIN, SS (Springer Science and Business Media LLC, 1992-01-01)
We point out that the conclusions of a recent Letter by Yavuz et al. are based on a misunderstanding of basic perturbation theory.
Discovery of irradiation-induced variations in the light curve of the classical nova V2275 Cyg (N Cyg 2001 No. 2)
Balman, Şölen; Yilmaz, A; Retter, A; Saygac, T; Esenoglu, H (Oxford University Press (OUP), 2005-01-11)
We present charge-coupled device (CCD) photometry, light curve and time-series analysis of the classical nova V2275 Cyg (N Cyg 2001 No. 2). The source was observed for 14 nights in total in 2002 and 2003 using an R filter with the 1.5-m Russian-Turkish joint telescope (RTT150) at the TUBITAK National Observatory in Antalya, Turkey, as part of a large programme on the CCD photometry of cataclysmic variables. We report the detection of two distinct periodicities in the light curve of the nova: (a) P-1 = 0.314...
Arabaci, Mehtap Ozbey; KALEMCİ, EMRAH; Tomsick, John A.; Halpern, Jules; Bodaghee, Arash; Chaty, Sylvain; Rodriguez, Jerome; Rahoui, Farid (American Astronomical Society, 2012-12-10)
We report on the optical spectroscopic follow-up observations of the candidate counterparts to four INTEGRAL sources: IGR J04069+5042, IGR J06552-1146, IGR J21188+4901, and IGR J22014+6034. The candidate counterparts were determined with Chandra, and the optical observations were performed with 1.5 m RTT-150 telescope (TUBITAK National Observatory, Antalya, Turkey) and 2.4 m Hiltner Telescope (MDM Observatory, Kitt Peak, Arizona). Our spectroscopic results show that one of the two candidates of IGR J04069+5...
Citation Formats
A. Baykal and E. Beklen, “Evidence of a change in the long-term spin-down rate of the X-ray pulsar 4U 1907+09,” MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, pp. 1760–1764, 2006, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/44110.