NEW TORQUE REVERSAL AND SPIN-UP OF 4U 1626-67 OBSERVED BY<i>FERMI</i>/GAMMA-RAY BURST MONITOR AND<i>SWIFT</i>/BURST ALERT TELESCOPE

Camero-Arranz, A.; Finger, Mark H.; Ikhsanov, N. R.; Wilson-Hodge, C.; Beklen, E.

doi:10.1088/0004-637x/708/2/1500

Cited by 69 publications

(89 citation statements)

References 39 publications

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“…The strong 48 mHz QPO found consistently during the spin-down phase (Kaur et al 2008), is absent in the power spectrum of the current spin-up phase (Jain et al 2009), although a weak X-ray QPO was reported by Shinoda et al (1990) during the first spin-up epoch. The X-ray spectra are similar during the spin-up eras as against the spin-down era (Camero-Arranz et al 2010). All of these indicate that there are changes in the accretion mode from the inner disc to the neutron star that are associated with the torque reversals (Beri et al 2014).…”

Section: Introductionmentioning

confidence: 79%

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

Raman¹,

Paul²,

Bhattacharya³

et al. 2016

Mon. Not. R. Astron. Soc.

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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.

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Section: Introductionmentioning

confidence: 79%

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

Raman¹,

Paul²,

Bhattacharya³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Then, a pulsed search was made over a narrow frequency band. A detailed explanation of our technique can be found in Finger et al (2009a) and Camero-Arranz et al (2010). The RXTE (Bradt et al 1993) carries three instruments on board.…”

Section: Observations and Analysismentioning

confidence: 99%

X-Ray and Optical Observations of a 0535+26

Camero-Arranz

Finger

Wilson-Hodge

et al. 2012

ApJ

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We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A 0535+26 with the Fermi/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the context of the rich historical data (since ∼1978) and discussed in terms of the neutron-star-Be-disk interaction. The Be circumstellar disk was exceptionally large just before the 2009 December giant outburst, which may explain the origin of the unusual recent X-ray activity of this source. We found a peculiar evolution of the pulse profile during this giant outburst, with the two main components evolving in opposite ways with energy. A hard 30-70 mHz X-ray quasi-periodic oscillation was detected with GBM during this 2009 December giant outburst. It becomes stronger with increasing energy and disappears at energies below 25 keV. In the long term a strong optical/X-ray correlation was found for this system, however in the medium term the Hα equivalent width and the V-band brightness showed an anti-correlation after ∼2002 August. Each giant X-ray outburst occurred during a decline phase of the optical brightness, while the Hα showed a strong emission. In late 2010 and before the 2011 February outburst, rapid V /R variations are observed in the strength of the two peaks of the Hα line. These had a period of ∼25 days and we suggest the presence of a global one-armed oscillation to explain this scenario. A general pattern might be inferred, where the disk becomes weaker and shows V /R variability beginning ∼6 months following a giant outburst.

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“…Meanwhile, the GBM (Gamma-ray Burst Monitor; Meegan et al 2009) onboard the Fermi Gamma-Ray Space Telescope has been monitoring the whole sky in the X-ray to gamma-ray band since 2008. The timing analysis of the GBM data provides us information on the pulsed emission from bright XBPs in our Galaxy (Finger et al 2009;Camero-Arranz et al 2010). Data taken by these two missions for over 6 years satisfy the requirement.…”

Section: Introductionmentioning

confidence: 99%

Correlation between the luminosity and spin-period changes during outbursts of 12 Be binary pulsars observed by the MAXI/GSC and the Fermi/GBM

Sugizaki

Mihara

Nakajima

et al. 2017

Publications of the Astronomical Society of Japan

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To observationally study spin-period changes of accreting pulsars caused by the accretion torque, the present work analyzes X-ray light curves of 12 Be binary pulsars obtained by the MAXI/GSC all-sky survey and their pulse periods measured by the Fermi/GBM pulsar project, both covering more than 6 years from 2009 August to 2016 March. The 12 objects were selected because they are accompanied by clear optical identification, and accurate measurements of surface magnetic fields. The luminosity L and the spin-frequency derivativesν, measured during large outbursts with L > ∼ 1 × 10 37 erg s −1 , were found to approximately follow the theoretical relations in the accretion torque models, represented byν ∝ L α (α ≃ 1), and the coefficient of proportionality betweenν and L α , agrees, within a factor of ∼ 3, with that proposed by Ghosh & Lamb (1979). In the course of the present study, the orbital elements of several sources were refined.

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NEW TORQUE REVERSAL AND SPIN-UP OF 4U 1626-67 OBSERVED BYFERMI/GAMMA-RAY BURST MONITOR ANDSWIFT/BURST ALERT TELESCOPE

Cited by 69 publications

References 39 publications

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

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

X-Ray and Optical Observations of a 0535+26

Correlation between the luminosity and spin-period changes during outbursts of 12 Be binary pulsars observed by the MAXI/GSC and the Fermi/GBM

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