Spectral and temporal changes associated with flux enhancement in 4U 1626−67

Jain, Chetana; Paul, Biswajit; Dutta, A.

doi:10.1111/j.1365-2966.2009.16170.x

Cited by 25 publications

(39 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We used a canonical model which allowed us to compare our spectral study with previous works (Angelini et al 1995;Pravdo et al 1979;Orlandini et al 1998;Krauss et al 2007;Jain et al 2010, among others) and update the longterm X-ray flux history of 4U 1626-67 relative to the flux measured by HEAO 1 (Chakrabarty et al 1997;Krauss et al 2007;Camero-Arranz et al 2010). …”

Section: Resultsmentioning

confidence: 99%

4U 1626–67 as seen bySuzakubefore and after the 2008 torque reversal

Camero-Arranz¹,

Pottschmidt²,

Finger³

et al. 2012

A&A

View full text Add to dashboard Cite

Aims. The accretion-powered pulsar 4U 1626-67 experienced a new torque reversal at the beginning of 2008, after about 18 years of steadily spinning down. The main goal of the present work is to study this recent torque reversal that occurred in February 2008. Methods. We present a spectral analysis of this source using two pointed observations performed by Suzaku in March 2006 and in September 2010. Results. We confirm with Suzaku the presence of a strong emission-line complex centered on 1 keV, with the strongest line being the hydrogen-like Ne Lyα at 1.025(3) keV. We were able to resolve this complex with up to seven emission lines. A dramatic increase in the intensity of the Ne Lyα line after the 2008 torque reversal occurred, with the equivalent width of this line reaching almost the same value measured by ASCA in 1993. We also report on the detection of a cyclotron line feature centered at ∼37 keV. In spite of the increase in the X-ray luminosity (0.5−100 keV) of a factor of ∼2.8 that occurred between these two observations, no significant change in the energy of the cyclotron line feature was observed. However, the intensity of the ∼1 keV line complex increased by an overall factor of ∼8. Conclusions. Our results favor a scenario in which the neutron star in 4U 1626-67 accretes material from a geometrically thin disk during both the spin-up and spin-down phases.

show abstract

Section: Resultsmentioning

confidence: 99%

4U 1626–67 as seen bySuzakubefore and after the 2008 torque reversal

Camero-Arranz¹,

Pottschmidt²,

Finger³

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…This was associated with a possible warp in the accretion disc. Detailed observations in the last four decades have indicated change in accretion mode associated with change in accretion torque (Jain et al 2009;Beri et al 2014). In this paper we investigate the optical temporal characteristics of 4U 1626-67 after the second torque reversal, when it is in a spin-up phase to re-examine various features like the relative pulse amplitudes in X-rays and optical, the strength of the previously reported orbital sidebands and the pulse profile evolution.…”

Section: Introductionmentioning

confidence: 95%

SALT observation of X-ray pulse reprocessing in 4U 1626−67

Raman¹,

Paul²,

Bhattacharya³

et al. 2016

Mon. Not. R. Astron. Soc.

Self Cite

View full text Add to dashboard Cite

We investigate optical reprocessing of X-rays in the LMXB pulsar 4U 1626-67 in its current spin-up phase using observations with Southern African Large Telescope (SALT), nearsimultaneous observations with Swift-XRT and non-simultaneous RXTE-PCA observations and present the results of timing analysis. Using SALT observations carried out on 2014, March 5 and 6, we detect some interesting reprocessing signatures. We detect a weak optical Quasi Periodic Oscillation (QPO) in the power density spectrum on March 5 at 48 mHz with a fractional rms of 3.3% in spite of the fact that source shows no corresponding X-ray QPO in the spin-up phase. In the light curve obtained on March 5, we detect a coherent pulsation at the spin period of ∼7.677 s. A previously known, slightly down-shifted side-band is also detected at 129.92 mHz. The frequency spacing between main pulse and this side-band is different from earlier observations, though the statistical significance of the difference is limited. The light curve of March 6 displays short time-scale variability in the form of flares on time-scales of a few minutes. Folded pulse profiles resulting from data of this night show an interesting trend of pulse peak drifting. This drift could be due to i) rapid changes in the reprocessing agent, like orbital motion of an accretion disc warp around the neutron star or ii) intrinsic pulse phase changes in X-rays. We also examine some X-ray light curves obtained with RXTE-PCA during 2008-2010 for pulse shape changes in short time-scales during X-ray flares.

show abstract

“…Jain et al 2010;Camero-Arranz et al 2012). According to Camero-Arranz et al (2012), the spectra in both phases can be fitted with a model composed of a blackbody and a cutoff power law, and their difference is in the blackbody component, whose temperature is ∼ 0.5 keV in the spin-up phase and ∼ 0.2 keV in the spin-down phase.…”

Section: Estimation Of Bolometric Fluxmentioning

confidence: 99%

Application of the Ghosh & Lamb relation to the spin-up/down behavior in the X-ray binary pulsar 4U 1626−67

Takagi

Mihara

Sugizaki

et al. 2016

Publications of the Astronomical Society of Japan

View full text Add to dashboard Cite

We analyzed continuous MAXI/GSC data of the X-ray binary pulsar 4U 1626-67 from 2009 October to 2013 September, and determined the pulse period and the pulse-period derivative for every 60-d interval by the epoch folding method. The obtained periods are consistent with those provided by the Fermi/GBM pulsar project. In all the 60-d intervals, the pulsar was observed to spin up, with the spin-up rate positively correlated with the 2-20 keV flux. We applied the accretion torque model proposed by Ghosh & Lamb (1979, ApJ, 234, 296) to the MAXI/GSC data, as well as the past data including both spin-up and spin-down phases. The Ghosh & Lamb relation was confirmed to successfully explain the observed relation between the spin-up/down rate and the flux. By comparing the model-predicted luminosity with the observed flux, the source distance was constrained as 5-13 kpc, which is consistent with that by Chakrabarty (1998, ApJ, 492, 342). Conversely, if the source distance is assumed, the data can constrain the mass and radius of the neutron star, because the Ghosh & Lamb model depends on these parameters. We attempted this idea, and found that an assumed distance of, e.g., 10 kpc gives a mass in the range of 1.81-1.90 solar mass, and a radius of 11.4-11.5 km, although these results are still subject to considerable systematic uncertainties other than that in the distance.

show abstract

Spectral and temporal changes associated with flux enhancement in 4U 1626−67

Cited by 25 publications

References 36 publications

4U 1626–67 as seen bySuzakubefore and after the 2008 torque reversal

4U 1626–67 as seen bySuzakubefore and after the 2008 torque reversal

SALT observation of X-ray pulse reprocessing in 4U 1626−67

Application of the Ghosh & Lamb relation to the spin-up/down behavior in the X-ray binary pulsar 4U 1626−67

Contact Info

Product

Resources

About