4U 1626-67 - The binary with the smallest known mass function

Levine, A.; Ma, Chung‐Pei; McClintock, Jeffrey E.; Rappaport, S.; Klis, M. van der; Verbunt, F.

doi:10.1086/166230

Cited by 60 publications

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“…The pulsar has a spin period of about 7.7 s with no evidence of pulse arrival time delay due to orbital motion and at the 42 min orbital period measured from an optical sideband by Middleditch et al (1981), the upper limit of the projected semi-major axis is 10 lt-ms (Rappaport et al 1977;Levine et al 1988;Jain et al 2008). Based on these, and faintness of the optical counterpart the neutron star was understood to have an extremely low mass and degenerate companion star (Levine et al 1988;Chakrabarty 1998). It has one of the lowest mass functions of <1.3 x 10 −6 M⊙ (Levine et al 1988) as measured for any X-ray binary.…”

Section: Introductionmentioning

confidence: 98%

“…Based on these, and faintness of the optical counterpart the neutron star was understood to have an extremely low mass and degenerate companion star (Levine et al 1988;Chakrabarty 1998). It has one of the lowest mass functions of <1.3 x 10 −6 M⊙ (Levine et al 1988) as measured for any X-ray binary. A very low inclination or a nearly face on geometry (i<10 • ) allows a higher mass companion although the a priori probability of finding such a system is only 0.015.…”

Section: Introductionmentioning

confidence: 99%

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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: 98%

Section: Introductionmentioning

confidence: 99%

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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“…• ; Levine et al 1988). It is hence classified as an ultra compact X-ray binary (van Haaften et al 2012).…”

Section: Introductionmentioning

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

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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.

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“…| SAS-3 discovered 7.68 s pulsations from 4U 1626-67 in 1977 Rappaport et al 1977 and the optical counterpart was later identi ed to b eKZ TrA McClintock et al 1977 . X-ray timing limits imply an ultracompact binary with an extremely low-mass companion Levine et al 1988, Chakrabarty et al 1997a . There is optical photometric evidence for a 42-min orbital period Middleditch et al 1981 , suggesting a mass of 0:1M for the mass donor.…”

Section: Low-mass Systemsmentioning

confidence: 99%

Observations of accreting pulsars

Prince

Bildsten

Chakrabarty

et al. 1994

AIP Conference Proceedings

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We summarize ve years of continuous monitoring of accretion-powered pulsars with the Burst and Transient Source Experiment BATSE on the Compton Gamma Ray Observatory. Our 20 70 keV observations have determined or re ned the orbital parameters of 13 binaries, discovered 5 new transient accreting pulsars, measured the pulsed ux history during outbursts of 12 transients GRO J1744 28, 4U 0115+634, GRO J1750 27, GS 0834 430, 2S 1417 624, GRO J1948+32, EXO 2030+375, GRO J1008 57, A 0535+26, GRO J2058+42, 4U 1145 619 and A 1118 616 , and also measured the accretion torque history of during outbursts of 6 of those transients whose orbital parameters were also known. We have also continuously measured the pulsed ux and spin frequency for eight persistently accreting pulsars Her X-1, Cen X-3, Vela X-1, OAO 1657 415, GX 301 2, 4U 1626 67, 4U 1538 52, and GX 1+4 . Because of their continuity and uniformity over a long baseline, BATSE observations have provided new insights into the long-term behavior of accreting magnetic stars. We have found that all accreting pulsars show stochastic variations in their spin frequencies and luminosities, including those displaying secular spin-up or spin-down on long time scales, blurring the conventional distinction b e t w een disk-fed and wind-fed binaries. Pulsed ux and accretion torque are strongly correlated in outbursts of transient accreting pulsars, but uncorrelated, or even anticorrelated, in persistent sources. We describe daily folded pulse pro les, frequency, and ux measurements that are available through the Compton Observatory Science Support Center at NASA-Goddard Space Flight Center.

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4U 1626-67 - The binary with the smallest known mass function

Cited by 60 publications

References 0 publications

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

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

Observations of accreting pulsars

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