Timing the Pulsations of the Accreting Millisecond Pulsar SAX J1808.4–3658 during Its 2019 Outburst

Bult, Peter; Chakrabarty, Deepto; Arzoumanian, Zaven; Gendreau, Keith C.; Guillot, Sebastien; Malacaria, C.; Ray, Paul S.; Strohmayer, Tod E.

doi:10.3847/1538-4357/ab9827

Cited by 30 publications

(77 citation statements)

References 55 publications

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“…Similarly rapid orbital evolution has been observed in a number of other AMXPs and LMXBs Di Salvo & Sanna 2020). In a few particularly well sampled sources, most notably SAX J1808.4-3658 (Bult et al 2020a), the advancing T asc shows complex residuals, suggesting that the orbital period evolution is modulated (quasi-) periodically over decades. In IGR J17062, such modulation is not apparent in the data.…”

Section: Binary Evolutionsupporting

confidence: 52%

“…We find that these latter two criteria are often too conservative when applied to the observations of IGR J17062. Following Bult et al (2020a), we first smoothed the overshoot light curve using 5-second windows to reduce noise and then only retained those epochs when the absolute rate was less than 1.5 ct/s/detector and increased the scaling factor of the cor sax expression filter from 1.52 to 2.0. The undershoot filter was only an issue in data groups 3,4,5, and 8.…”

Section: Observations and Data Processingmentioning

confidence: 99%

“…In all cases these derivatives were measured by modelling the quadratic drift in pulse phase. However, flux-dependent timing noise can bias such phase measurements, making it difficult to disentangle what part of the observed phase drift is intrinsic to the pulsar rotation and what part is instead due to accretion driven variability in the hot spot (Patruno et al 2009;Bult et al 2020a). Our spin frequency derivative measurement for IGR J17062 does not suffer from this ambiguity: the spin change is directly visible in frequency space.…”

Section: Long-term Spin Upmentioning

confidence: 99%

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Long-term coherent timing of the accreting millisecond pulsar IGR J17062-6143

Bult,

Strohmayer,

Malacaria

et al. 2021

Preprint

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We report on a coherent timing analysis of the 163 Hz accreting millisecond X-ray pulsar IGR J17062-6143. Using data collected with the Neutron Star Interior Composition Explorer and XMM-Newton, we investigated the pulsar evolution over a timespan of four years. We obtained a unique phase-coherent timing solution for the stellar spin, finding the source to be spinning up at a rate of (3.77 ± 0.09) × 10 −15 Hz/s. We further find that the 0.4 − 6 keV pulse fraction varies gradually between 0.5% and 2.5% following a sinusoidal oscillation with a 1210 ± 40 day period. Finally, we supplemented this analysis with an archival Rossi X-ray Timing Explorer observation, and obtained a phase coherent model for the binary orbit spanning 12 years, yielding an orbital period derivative measurement of (8.4 ± 2.0) × 10 −12 s/s. This large orbital period derivative is inconsistent with a binary evolution that is dominated by gravitational wave emission, and is suggestive of highly non-conservative mass transfer in the binary system.

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Section: Binary Evolutionsupporting

confidence: 52%

Section: Observations and Data Processingmentioning

confidence: 99%

Section: Long-term Spin Upmentioning

confidence: 99%

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Long-term coherent timing of the accreting millisecond pulsar IGR J17062-6143

Bult,

Strohmayer,

Malacaria

et al. 2021

Preprint

Self Cite

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“…3) cannot be explained by a bias model containing a bolometric flux dependent term (see e.g. Patruno et al 2009) which otherwise works well for such instances as the ToA modelling of the 2019 outburst of SAX J1808.4-3658 (see Bult et al 2020, for a flux-adjusted phase model).…”

Section: Discussionmentioning

confidence: 99%

High-energy characteristics of the accretion-powered millisecond pulsar IGR J17591−2342 during its 2018 outburst

Kuiper

Tsygankov

Falanga

et al. 2020

A&A

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IGR J17591−2342 is an accreting millisecond X-ray pulsar, discovered with INTEGRAL, which went into outburst around July 21, 2018. To better understand the physics acting in these systems during the outburst episode, we performed detailed temporal-, timing-, and spectral analyses across the 0.3–300 keV band using data from NICER, XMM-Newton, NuSTAR, and INTEGRAL. The hard X-ray 20–60 keV outburst profile covering ∼85 days is composed of four flares. Over the course of the maximum of the last flare, we discovered a type-I thermonuclear burst in INTEGRAL JEM-X data, posing constraints on the source distance. We derived a distance of 7.6 ± 0.7 kpc, adopting Eddington-limited photospheric radius expansion and assuming anisotropic emission. In the timing analysis, using all NICER 1–10 keV monitoring data, we observed a rather complex set of behaviours starting with a spin-up period (MJD 58345–58364), followed by a frequency drop (MJD 58364–58370), an episode of constant frequency (MJD 58370–58383), concluded by irregular behaviour till the end of the outburst. The 1–50 keV phase distributions of the pulsed emission, detected up to ∼120 keV using INTEGRAL ISGRI data, was decomposed in three Fourier harmonics showing that the pulsed fraction of the fundamental increases from ∼10% to ∼17% going from ∼1.5 to ∼4 keV, while the harder photons arrive earlier than the soft photons for energies ≲10 keV. The total emission spectrum of IGR J17591−2342 across the 0.3–150 keV band could adequately be fitted in terms of an absorbed COMPPS model yielding as best fit parameters a column density of NH = (2.09 ± 0.05) × 1022 cm−2, a blackbody seed photon temperature kTbb, seed of 0.64 ± 0.02 keV, electron temperature kTe = 38.8 ± 1.2 keV and Thomson optical depth τT = 1.59 ± 0.04. The fit normalisation results in an emission area radius of 11.3 ± 0.5 km adopting a distance of 7.6 kpc. Finally, the results are discussed within the framework of accretion physics- and X-ray thermonuclear burst theory.

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“…So far, only IGR J00291+5934 has shown a doublepeaked outburst (Lewis et al, 2010;Hartman et al, 2011), while a few other AMSPs have undergone "reflares" toward the later stages of the return to quiescence. The mechanism(s) driving these re-brightening episodes is still a matter of debate (see, e.g., Patruno et al, 2016;Bult et al, 2019, and references therein). The typical luminosity at which the re-flares occur is close to the detection limit for both IBIS/ISGRI and JEM-X and thus these events are hardly observable by INTEGRAL.…”

Section: The X-ray Light Curvesmentioning

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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Timing the Pulsations of the Accreting Millisecond Pulsar SAX J1808.4–3658 during Its 2019 Outburst

Cited by 30 publications

References 55 publications

Long-term coherent timing of the accreting millisecond pulsar IGR J17062-6143

Long-term coherent timing of the accreting millisecond pulsar IGR J17062-6143

High-energy characteristics of the accretion-powered millisecond pulsar IGR J17591−2342 during its 2018 outburst

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

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