On the 2018 Outburst of the Accreting Millisecond X-Ray Pulsar Swift J1756.9–2508 As Seen with NICER

Bult, Peter; Altamirano, D.; Arzoumanian, Zaven; Chakrabarty, Deepto; Gendreau, Keith C.; Guillot, Sebastien; Ho, Wynn C. G.; Jaisawal, Gaurava K.; Lentine, Steven; Markwardt, C. B.; Ngo, Son N.; Pope, J.; Ray, Paul S.; Saylor, M.; Strohmayer, Tod E.

doi:10.3847/1538-4357/aad5e5

Cited by 10 publications

(20 citation statements)

References 38 publications

(50 reference statements)

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“…In this approach we kept the orbital period, P orb , projected semi major axis, a x sin i, fixed at the optimum values given by Patruno et al ( 2010) (see their Table 4). We verified that using updated orbital ephemeris information (Bult et al 2018a) had no impact on the T asc values derived here. The best fit values for ν and T asc along with the validity interval and epoch t 0 for both outbursts separately are listed in Table 3, and are used later in this work in estimating the orbital period derivative combining information from all registered outbursts (see Sect.…”

Section: Nicer Timing Analysis Of the 2018 And 2019 Outburstssupporting

confidence: 70%

“…During the first three recurrent outbursts from 2007 to 2018, the orbital period variation has not been detected (Krimm et al 2007b;Patruno et al 2010;Bult et al 2018a;Sanna et al 2018c). Moreover, the upper limit on the orbital period derivative is | Ṗorb | < 7.4 × 10 −13 s s −1 from the total 11 years span of the observations, consistent with the prediction of a conservative mass transfer in the binary system (Bult et al 2018a). Swift J1756.9−2508 showed long term spin-down behavior with a spin frequency derivative of |ν| 3 × 10 −13 Hz s −1 measured by Patruno et al (2010), |ν| ∼ 7.3 × 10 −16 Hz s −1 by Bult et al (2018a) and a smaller value |ν| ∼ 4.8 × 10 −16 Hz s −1 by Sanna et al (2018c).…”

Section: Introductionmentioning

confidence: 98%

“…Swift J1756.9−2508 showed long term spin-down behavior with a spin frequency derivative of |ν| 3 × 10 −13 Hz s −1 measured by Patruno et al (2010), |ν| ∼ 7.3 × 10 −16 Hz s −1 by Bult et al (2018a) and a smaller value |ν| ∼ 4.8 × 10 −16 Hz s −1 by Sanna et al (2018c). Assuming that the rotational energy loss due to the magnetic dipole emission dominated the spin evolution of Swift J1756.9−2508, the magnetic field strength at the stellar magnetic poles was constrained to the range (3 − 6) × 10 8 G (see, e.g., Patruno et al 2010;Bult et al 2018a;Sanna et al 2018c, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…2018 (Sanna et al 2018c;Bult et al 2018a;Rai & Paul 2019;Chakraborty & Bhattacharyya 2018) and 2019 (Sanna et al 2019). During the first three recurrent outbursts from 2007 to 2018, the orbital period variation has not been detected (Krimm et al 2007b;Patruno et al 2010;Bult et al 2018a;Sanna et al 2018c). Moreover, the upper limit on the orbital period derivative is | Ṗorb | < 7.4 × 10 −13 s s −1 from the total 11 years span of the observations, consistent with the prediction of a conservative mass transfer in the binary system (Bult et al 2018a).…”

Section: Introductionmentioning

confidence: 99%

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Broad-band X-ray spectra and timing of the accretion-powered millisecond pulsar Swift J1756.9$-$2508 during its 2018 and 2019 outbursts

Li,

Kuiper,

Falanga

et al. 2021

Preprint

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The accreting millisecond X-ray pulsar Swift J1756.9−2508 went into outburst in April 2018 and June 2019, 8.7 yr after the previous activity period. We investigated the temporal, timing and spectral properties of these two outbursts using data from NICER, XMM-Newton, NuSTAR, INTEGRAL, Swift and Insight-HXMT. The two outbursts exhibited similar broad-band spectra and X-ray pulse profiles. For the first time, we report the detection of the pulsed emission up to ∼ 100 keV observed by Insight-HXMT during the 2018 outburst. We also found the pulsation up to ∼ 60 keV observed by NICER and NuSTAR during the 2019 outburst. We performed a coherent timing analysis combining the data from two outbursts. The binary system is well described by a constant orbital period over a time span of ∼ 12 years. The time-averaged broad-band spectra are well fitted by an absorbed thermal Comptonization model compps in a slab geometry with the electron temperature kT e = 40-50 keV, Thomson optical depth τ ∼ 1.3, blackbody seed photon temperature kT bb,seed ∼0.7-0.8 keV and hydrogen column density of N H ∼ 4.2 × 10 22 cm −2 . We searched the available data for type-I (thermonuclear) X-ray bursts, but found none, which is unsurprising given the estimated low peak accretion rate (≈ 0.05 of the Eddington rate) and generally low expected burst rates for hydrogen-poor fuel. Based on the history of four outbursts to date, we estimate the long-term average accretion rate at roughly 5 × 10 −12 M yr −1 for an assumed distance of 8 kpc. The expected mass transfer rate driven by gravitational radiation in the binary implies the source can be no closer than 4 kpc. Swift J1756.9−2508 is the third low mass X-ray binary exhibiting "double" outbursts, separated by much shorter intervals than usual, and likely resulting from interruption of the accretion flow from the disk onto the neutron star. Such behavior may have important implications for the disk instability model.

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Section: Nicer Timing Analysis Of the 2018 And 2019 Outburstssupporting

confidence: 70%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Broad-band X-ray spectra and timing of the accretion-powered millisecond pulsar Swift J1756.9$-$2508 during its 2018 and 2019 outbursts

Li,

Kuiper,

Falanga

et al. 2021

Preprint

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Accretion Powered X-ray Millisecond Pulsars

Salvo

Sanna

2021

Astrophysics and Space Science Library

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Indications of non-conservative mass transfer in AMXPs

Marino

Salvo

Burderi

et al. 2019

A&A

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Context. Since the discovery of the first Accreting Millisecond X-ray Pulsar SAX J1808.4-3658 in 1998, the family of these sources kept growing on. Currently, it counts 22 members. All AMXPs are transients with usually very long quiescence periods, implying that mass accretion rate in these systems is quite low and not constant. Moreover, for at least three sources, a non-conservative evolution was also proposed. Aims. Our purpose is to study the long term averaged mass-accretion rates in all the Accreting Millisecond X-ray Pulsars discovered so far, to investigate a non-conservative mass-transfer scenario. Methods. We calculated the expected mass-transfer rate under the hypothesis of a conservative evolution based on their orbital periods and on the (minimum) mass of the secondary (as derived from the mass function), driven by gravitational radiation and/or magnetic braking. Using this theoretical mass-transfer, we determined the expected accretion luminosity of the systems. Thus, we achieved the lower limit to the distance of the sources by comparing the computed theoretical luminosity and the observed flux averaged over a time period of 20 years. Then, the lower limit to the distance of the sources has been compared to the value of the distance reported in literature to evaluate how reasonable is the hypothesis of a conservative mass-transfer. Results. Based on a sample of 18 sources, we found strong evidences of a non-conservative mass-transfer for five sources, for which the estimated distance lower limits are higher than their known distances. We also report hints for mass outflows in other six sources. The discrepancy can be fixed under the hypothesis of a non-conservative mass-transfer in which a fraction of the mass transferred onto the compact object is swept away from the system, likely due to the (rotating magnetic dipole) radiation pressure of the pulsar.

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On the 2018 Outburst of the Accreting Millisecond X-Ray Pulsar Swift J1756.9–2508 As Seen with NICER

Cited by 10 publications

References 38 publications

Broad-band X-ray spectra and timing of the accretion-powered millisecond pulsar Swift J1756.9$-$2508 during its 2018 and 2019 outbursts

Broad-band X-ray spectra and timing of the accretion-powered millisecond pulsar Swift J1756.9$-$2508 during its 2018 and 2019 outbursts

Accretion Powered X-ray Millisecond Pulsars

Indications of non-conservative mass transfer in AMXPs

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