MAXI observations of long-term variations of Cygnus X-1 in the low/hard and the high/soft states

Sugimoto, J.; Mihara, T.; Kitamoto, Shunji; Matsuoka, M.; Sugizaki, M.; Negoro, H.; Nakahira, S.; Makishima, Kazuo

doi:10.1093/pasj/psw004

Cited by 19 publications

(15 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the MAXI satellite continues to furnish long-term X-ray monitoring coverage of bright X-ray binaries in a similar manner to the RXTE/ASM (e.g. Sugimoto et al 2016), including SMC X-1 itself (Sugimoto et al 2014). Therefore, we anticipate X-ray monitoring of further superorbital period excursions of SMC X-1 will allow triggering of observational campaigns to measure P spin evolution coincident with further large changes in P sup .…”

Section: No Relation Between the Spin-and Superorbital Behavioursmentioning

confidence: 99%

Longterm properties of accretion discs in X-ray Binaries - III. A search for spin-superorbital correlation in SMC X-1

Dage

Clarkson

Charles

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Thanks to long-term X-ray monitoring, a number of interacting binaries are now known to show X-ray periodicities on timescales of tens to hundreds of binary orbits. In some systems, precession of a warped accretion disc is the leading model to explain the superorbital modulation. The High Mass X-ray Binary SMC X-1 showed two excursions in superorbital period (from ∼60 d to ∼45 d) during the 1996-2011 interval, suggesting that some characteristic of the accretion disc is varying on a timescale of years. Because its behaviour as an X-ray pulsar has also been intensively monitored, SMC X-1 offers the rare chance to track changes in both the accretion disk and pulsar behaviours over the same interval. We have used archival X-ray observations of SMC X-1 to investigate whether the evolution of its superorbital variation and pulse period are correlated. We use the 16-year dataset afforded by the RXTE All-Sky Monitor to trace the behaviour of the warped accretion disc in this system, and use published pulse-period histories to trace the behaviour of the pulsar. While we cannot claim a strong detection of correlation, the first superorbital period excursion near MJD 50,800 does coincide with structure in SMC X-1's pulse period history. Our preferred interpretation is that the superorbital period excursion coincides with a change in the long-term spin-up rate of the SMC X-1 pulsar. In this scenario, the pulsar and the accretion disc are both responding to a change in the accretion flow, which the disc itself may regulate.

show abstract

Section: No Relation Between the Spin-and Superorbital Behavioursmentioning

confidence: 99%

Longterm properties of accretion discs in X-ray Binaries - III. A search for spin-superorbital correlation in SMC X-1

Dage

Clarkson

Charles

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Negoro et al 2010), showing that there is a non-negligible fraction of the accretion power which is not dissipated in the thin disk. This could mean that Cyg X-1 never quite makes a full transition, so that the accretion disk never quite reaches down to the last stable circular orbit, and/or that the coronal emission is fed directly from the stellar wind rather than via the accretion disk (Sugimoto et al 2016). This latter idea might explain its rather different X-ray variability power spectra compared to high/soft states with similarly strong tails in the transients (Done & Gierliński 2005).…”

Section: Introductionmentioning

confidence: 99%

Black hole spin of Cygnus X-1 determined from the softest state ever observed

Kawano

Done

Yamada

et al. 2017

Publications of the Astronomical Society of Japan

View full text Add to dashboard Cite

We show the softest ever spectrum from Cyg X-1, detected in 2013 with Suzaku. This has the weakest high energy Compton tail ever seen from this object, so should give the cleanest view of the underlying disk spectrum, and hence the best determination of black hole spin from disk continuum fitting. Using the standard model of a disk with simple non-thermal Comptonisation to produce the weak high energy tail gives a high spin black hole. However, we get a significantly better fit by including an additional, low temperature thermal Comptonisation component, which allows a much lower black hole spin. Corroboration of the existence of an additional Compton component comes from the frequency dependent hard lags seen in the rapid variability in archival high/soft state data. These can not be explained if the continuum is a single non-thermal Comptonisation component, but are instead consistent with a radially stratified, multi zone Comptonisation spectrum, where the spectrum is softer further from the black hole. A complex multi-zone Comptonisation continuum is required to explain both spectra and timing together, and this has an impact on the derived black hole spin.

show abstract

“…1 The MAXI flare lasted for two days. A re-brightening of the source was detected by MAXI/GSC on 2015 October 6 (ATel 8143; Sugimoto et al 2015), and a peak flux of 16(5) mCrab was reached on 2015 October 7 in the 2-20 keV band. Again, the flare lasted for two days in the MAXI energy band.…”

Section: Introductionmentioning

confidence: 99%

MAXI J1957+032: An Accreting Neutron Star Possibly in a Triple System

Ravi

2017

ApJ

View full text Add to dashboard Cite

I present an optical characterization of the Galactic X-ray transient source MAXI J1957+032. This system flares by a factor of 10 4 every few hundred days, with each flare lasting ∼5days. I identify its quiescent counterpart to be a late-K/early-M dwarf star at a distance of 5±2 kpc. This implies that the peak 0.5 10 keV -luminosity of the system is 10 36.4 0.4  erg s −1 . As found by Mata Sanchez et al. the outburst properties of MAXI J1957+032 are most consistent with the sample of accreting millisecond pulsars. However, the low inferred accretion rate, and the lack of evidence for a hydrogen-rich accretion flow, are difficult to reconcile with the late-K/early-M dwarf counterpart being the mass donor. Instead, the observations are best described by a low-mass hydrogen-and possibly heliumpoor mass donor, such as a carbon-oxygen white dwarf, forming a tight interacting binary with a neutron star. The observed main-sequence counterpart would then likely be in a wide orbit around the inner binary.

show abstract

MAXI observations of long-term variations of Cygnus X-1 in the low/hard and the high/soft states

Cited by 19 publications

References 48 publications

Longterm properties of accretion discs in X-ray Binaries - III. A search for spin-superorbital correlation in SMC X-1

Longterm properties of accretion discs in X-ray Binaries - III. A search for spin-superorbital correlation in SMC X-1

Black hole spin of Cygnus X-1 determined from the softest state ever observed

MAXI J1957+032: An Accreting Neutron Star Possibly in a Triple System

Contact Info

Product

Resources

About