Continued cooling of the accretion-heated neutron star crust in the X-ray transient IGR J17480–2446 located in the globular cluster Terzan 5

Ootes, L. S.; Vats, Smriti; Page, Dany; Wijnands, Rudy; Parikh, A. S.; Degenaar, N.; Wijngaarden, M. J. P.; Altamirano, D.; Bahramian, A.; Cackett, E.; Heinke, Craig; Homan, J.; Miller, J. M.

doi:10.1093/mnras/stz1406

Cited by 15 publications

(14 citation statements)

References 68 publications

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“…We therefore hypothesise that the presence of pasta (in an NS with either a cold or a hot core) would not explain the decay and subsequent rise in our observed kT ∞ eff evolution because this would only produce a decay in the cooling curve and no subsequent rise. Cooling-curve modelling including a pasta layer has previously been carried out for several crustcooling sources (MXB 1659−29, MAXI J0556−332, and Terzan 5 X-3;Horowitz et al 2015;Parikh et al 2017;Ootes et al 2019) which showed the expected behaviour we hypothesised for XTE J1701−462 and EXO 0748−676 here.…”

Section: Nuclear Pastasupporting

confidence: 71%

Unexpected late-time temperature increase observed in the two neutron star crust-cooling sources XTE J1701−462 and EXO 0748−676

Parikh

Wijnands

Homan

et al. 2020

A&A

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Transient low-mass X-ray binaries (LMXBs) that host neutron stars (NSs) provide excellent laboratories for probing the dense matter physics present in NS crusts. During accretion outbursts in LMXBs, exothermic reactions may heat the NS crust, disrupting the crust-core equilibrium. When the outburst ceases, the crust cools to restore thermal equilibrium with the core. Monitoring this cooling evolution allows us to probe the dense matter physics in the crust. Properties of the deeper crustal layers can be probed at later times after the end of the outburst. We report on the unexpected late-time temperature evolution (≳2000 days after the end of their outbursts) of two NSs in LMXBs, XTE J1701−462 and EXO 0748−676. Although both these sources exhibited very different outbursts (in terms of duration and the average accretion rate), they exhibit an unusually steep decay of ∼7 eV in the observed effective temperature (occurring in a time span of ∼700 days) around ∼2000 days after the end of their outbursts. Furthermore, they both showed an even more unexpected rise of ∼3 eV in temperature (over a time period of ∼500–2000 days) after this steep decay. This rise was significant at the 2.4σ and 8.5σ level for XTE J1701−462 and EXO 0748−676, respectively. The physical explanation for such behaviour is unknown and cannot be straightforwardly be explained within the cooling hypothesis. In addition, this observed evolution cannot be well explained by low-level accretion either without invoking many assumptions. We investigate the potential pathways in the theoretical heating and cooling models that could reproduce this unusual behaviour, which so far has been observed in two crust-cooling sources. Such a temperature increase has not been observed in the other NS crust-cooling sources at similarly late times, although it cannot be excluded that this might be a result of the inadequate sampling obtained at such late times.

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Section: Nuclear Pastasupporting

confidence: 71%

Unexpected late-time temperature increase observed in the two neutron star crust-cooling sources XTE J1701−462 and EXO 0748−676

Parikh

Wijnands

Homan

et al. 2020

A&A

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“…IGR J17480-2446 also displayed a clear evidence of a fast-moving disk wind with ejection velocity up to ∼3000 km s −1 , a rare feature in NSs hosted in LMXB and much more common in systems harboring accreting BHs (Miller et al, 2011). In addition, the source endured an extremely high level of crustal heating during the outburst, which did not seem to have cooled completely even 5.5 years since the end of the outburst (Degenaar et al, 2011(Degenaar et al, , 2013Ootes et al, 2019).…”

Section: Thermonuclear Type-i X-ray Burstsmentioning

confidence: 99%

The INTEGRAL view of the pulsating hard X-ray sky: from accreting and transitional millisecond pulsars to rotation-powered pulsars and magnetars

Papitto¹,

Falanga

Hermsen

et al. 2020

New Astronomy Reviews

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In the last 25 years, a new generation of X-ray satellites imparted a significant leap forward in our knowledge of X-ray pulsars. The discovery of accreting and transitional millisecond pulsars proved that disk accretion can spin up a neutron star to a very high rotation speed. The detection of MeV-GeV pulsed emission from a few hundreds of rotation-powered pulsars probed particle acceleration in the outer magnetosphere, or even beyond. Also, a population of two dozens of magnetars has emerged. INTEGRAL played a central role to achieve these results by providing instruments with high temporal resolution up to the hard X-ray/soft γ-ray band and a large field of view imager with good angular resolution to spot hard X-ray transients. In this article, we review the main contributions by INTEGRAL to our understanding of the pulsating hard X-ray sky, such as the discovery and characterization of several accreting and transitional millisecond pulsars, the generation of the first catalog of hard X-ray/soft γ-ray rotation-powered pulsars, the detection of polarization in the hard X-ray emission from the Crab pulsar, and the discovery of persistent hard X-ray emission from several magnetars.

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“…The thermal relaxation of the crust is still not fully understood. In particular, the interpretation of the cooling data requires the existence of some unknown heat sources in the shallow layers of the crust [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], as summarized in Table I. In most cases, the extra heat, typically released in the outer crust at densities below about 10 10 g cm −3 , amounts to about 1-2 MeV per accreted nucleon with the notable exceptions of MAXI J0556−332 and Aql X-1.…”

Section: Introductionmentioning

confidence: 99%

Experimental constraints on shallow heating in accreting neutron-star crusts

et al. 2020

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The observed thermal relaxation of transiently accreting neutron stars during quiescence periods in low-mass x-ray binaries suggests the existence of unknown heat sources in the shallow layers of neutron-star crust. Making use of existing experimental nuclear data, we estimate the maximum possible amount of heat that can be deposited in the outer crust of an accreting neutron star due to electron captures and pycnonuclear fusion reactions triggered by the burial of x-ray burst ashes.

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Continued cooling of the accretion-heated neutron star crust in the X-ray transient IGR J17480–2446 located in the globular cluster Terzan 5

Cited by 15 publications

References 68 publications

Unexpected late-time temperature increase observed in the two neutron star crust-cooling sources XTE J1701−462 and EXO 0748−676

Unexpected late-time temperature increase observed in the two neutron star crust-cooling sources XTE J1701−462 and EXO 0748−676

The INTEGRAL view of the pulsating hard X-ray sky: from accreting and transitional millisecond pulsars to rotation-powered pulsars and magnetars

Experimental constraints on shallow heating in accreting neutron-star crusts

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