The puzzling case of the accreting millisecond X-ray pulsar IGR J00291+5934: flaring optical emission during quiescence

Baglio, Maria Cristina; Campana, S.; D’Avanzo, P.; Papitto, A.; Burderi, L.; Salvo, T. Di; Muñoz-Darias, T.; Rea, N.; Torres, D. F.

doi:10.1051/0004-6361/201629524

Cited by 3 publications

(2 citation statements)

References 31 publications

(74 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This optical precursor could have several possible origins: an enhanced mass transfer from the companion star, which would then help triggering the outburst; instabilities in the outer disk, which could lead to heating fronts propagating through the entire disk, that would contribute to igniting the outburst; or changes in the pulsar radiation pressure, the compact object being a millisecond pulsar. Similarly, signatures of enhanced optical activity soon before the onset of an outburst have been suggested also for the NS LMXB IGR J00291+5934, whose optical light curve is dominated by flaring and flickering activity prior to the start of an outburst, completely hiding the sinusoidal modulation of the companion star (Baglio et al 2017).…”

Section: Long-term Optical Monitoringmentioning

confidence: 62%

A Misfired Outburst in the Neutron Star X-Ray Binary Centaurus X-4

Baglio

Saikia²,

Russell³

et al. 2022

ApJ

Self Cite

View full text Add to dashboard Cite

We report on a long-term optical monitoring of the neutron star X-ray binary Centaurus X-4 performed during the last 13.5 yr. This source has been in quiescence since its outburst in 1979. Our monitoring reveals the overall evolution of the accretion disk; we detect short-duration flares, likely originating also in the disk, superimposed with a small-amplitude (<0.1 mag) ellipsoidal modulation from the companion star due to geometrical effects. A long-term (∼2300 days) downward trend, followed by a shorter (∼1000 days) upward one, is observed in the disk light curve. Such a rise in the optical has been observed for other X-ray binaries preceding outbursts, as predicted by the disk instability model. For Cen X-4, the rise of the optical flux proceeded for ∼3 yr, and culminated in a flux increase at all wavelengths (optical–UV–X-rays) at the end of 2020. This increase faded after ∼2 weeks, without giving rise to a full outburst. We suggest that the propagation of an inside-out heating front was ignited due to a partial ionization of hydrogen in the inner disk. The propagation might have stalled soon after the ignition due to the increasing surface density in the disk that the front encountered while propagating outward. The stall was likely eased by the low-level irradiation of the outer regions of the large accretion disk, as shown by the slope of the optical/X-ray correlation, suggesting that irradiation does not play a strong role in the optical, compared to other sources of emission.

show abstract

Section: Long-term Optical Monitoringmentioning

confidence: 62%

A Misfired Outburst in the Neutron Star X-Ray Binary Centaurus X-4

Baglio

Saikia²,

Russell³

et al. 2022

ApJ

Self Cite

View full text Add to dashboard Cite

show abstract

“…This optical precursor can have several possible origins: an enhanced mass transfer from the companion star, which would then help triggering the outburst; instabilities in the outer disc, which could lead to heating fronts propagating through the entire disc, that would contribute to igniting the outburst; changes in the pulsar radiation pressure, the compact object being a millisecond pulsar. Similarly, signatures of enhanced optical activity soon before the onset of an outburst have been suggested also for the NS LMXB IGR J00291+5934, whose optical lightcurve is dominated by flaring and flickering activity prior to the start of an outburst, completely hiding the sinusoidal modulation of the companion star (Baglio et al 2017).…”

Section: Long-term Optical Monitoringmentioning

confidence: 63%

A misfired outburst in the neutron star X-ray binary Centaurus X-4

Baglio,

Saikia,

Russell

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

We report on a long-term optical monitoring of the neutron star X-ray binary Centaurus X-4 performed during the last 13.5 years. This source has been in quiescence since its outburst in 1979. Our monitoring reveals the overall evolution of the accretion disc; we detect short-duration flares, likely originating also in the disc, superimposed with a small-amplitude (<0.1 mag) ellipsoidal modulation from the companion star due to geometrical effects. A long-term (∼2300 days) downward trend, followed by a shorter (∼1000 days) upward one, is observed in the disc light curve. Such a rise in the optical has been observed for other X-ray binaries preceding outbursts, as predicted by the disc instability model. For Cen X-4, the rise of the optical flux proceeded for ∼3 years, and culminated in a flux increase at all wavelengths (optical-UV-X-rays) at the end of 2020. This increase faded after ∼2 weeks, without giving rise to a full outburst. We suggest that the propagation of an inside-out heating front was ignited due to a partial ionization of hydrogen in the inner disc. The propagation might have stalled soon after the ignition due to the increasing surface density in the disc that the front encountered while propagating outwards. The stall was likely eased by the low level irradiation of the outer regions of the large accretion disc, as shown by the slope of the optical/X-ray correlation, suggesting that irradiation does not play a strong role in the optical, compared to other sources of emission.

show abstract

Thermal evolution and quiescent emission of transiently accreting neutron stars

Potekhin

Chugunov

Chabrier

2019

A&A

View full text Add to dashboard Cite

Aims. We study long-term thermal evolution of neutron stars in soft X-ray transients (SXTs), taking the deep crustal heating into account consistently with the changes of the composition of the crust. We collect observational estimates of average accretion rates and thermal luminosities of such neutron stars and compare the theory with observations. Methods. We perform simulations of thermal evolution of accreting neutron stars, considering the gradual replacement of the original nonaccreted crust by the reprocessed accreted matter, the neutrino and photon energy losses, and the deep crustal heating due to nuclear reactions in the accreted crust. We test and compare results for different modern theoretical models. We update a compilation of the observational estimates of the thermal luminosities in quiescence and average accretion rates in the SXTs and compare the observational estimates with the theoretical results.Results. Long-term thermal evolution of transiently accreting neutron stars is nonmonotonic. The quasi-equilibrium temperature in quiescence reaches a minimum and then increases toward the final steady state. The quasi-equilibrium thermal luminosity of a neutron star in an SXT can be substantially lower at the minimum than in the final state. This enlarges the range of possibilities for theoretical interpretation of observations of such neutron stars. The updates of the theory and observations leave unchanged the previous conclusions that the direct Urca process operates in relatively cold neutron stars and that an accreted heat-blanketing envelope is likely present in relatively hot neutron stars in the SXTs in quiescence. The results of the comparison of theory with observations favor suppression of the triplet pairing type of nucleon superfluidity in the neutron-star matter.

show abstract

The puzzling case of the accreting millisecond X-ray pulsar IGR J00291+5934: flaring optical emission during quiescence

Cited by 3 publications

References 31 publications

A Misfired Outburst in the Neutron Star X-Ray Binary Centaurus X-4

A Misfired Outburst in the Neutron Star X-Ray Binary Centaurus X-4

A misfired outburst in the neutron star X-ray binary Centaurus X-4

Thermal evolution and quiescent emission of transiently accreting neutron stars

Contact Info

Product

Resources

About