NICER and Fermi GBM Observations of the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

Wilson-Hodge, C.; Malacaria, C.; Jenke, P.; Jaisawal, Gaurava K.; Kerr, M.; Wolff, M. T.; Arzoumanian, Zaven; Chakrabarty, Deepto; Doty, J.; Gendreau, Keith C.; Guillot, Sebastien; Ho, Wynn C. G.; LaMarr, Beverly; Markwardt, C. B.; Özel, Feryal; Prigozhin, G.; Ray, Paul S.; Ramos-Lerate, M.; Remillard, Ron; Strohmayer, Tod E.; Vezie, Michael; Wood, K. S.

doi:10.3847/1538-4357/aace60

Cited by 126 publications

(132 citation statements)

References 57 publications

(78 reference statements)

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“…The PF of > 50 % was detected at > ∼ 1 keV in NGC300 ULX1 and two observations of Swift J0243.6+6124 showed the PF of ≫ 50 %. In addition, it was reported that the PF depends on the photon energy (see e.g., Bachetti et al 2014;Wilson-Hodge et al 2018). The energy dependence of the PF and the high PF (≫ 50 %) might be resolved by the thermal and bulk Comptonization, which are not taken into account in the present study.…”

Section: Conclusion and Discussionmentioning

confidence: 75%

“…This implies that the magnetic axis is not drastically misaligned with the rotation axis and that observer's viewing angle is relatively small in most ULXPs, since the sinusoidal pulse has been detected (see e.g., Bachetti et al 2014;Fürst et al 2016;Israel et al 2017aIsrael et al , 2017b). An exceptional object is Swift J0243.6+6124 of which the pulse has a secondary peak (Wilson-Hodge et al 2018). Thus, θ obs > 70 • or θB > 70 • might be realized in this object.…”

Section: Conclusion and Discussionmentioning

confidence: 97%

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Pulsed fraction of super-critical column accretion flows on to neutron stars: Modeling of ultraluminous X-ray pulsars

Inoue

Ohsuga

Kawashima

2020

Publications of the Astronomical Society of Japan

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We calculate the pulsed fraction (PF) of the super-critical column accretion flows onto magnetized neutron stars (NSs), of which the magnetic axis is misaligned with the rotation axis, based on the simulation results by Kawashima et al.(2016, PASJ, 68, 83). Here, we solve the geodesic equation for light in the Schwarzschild spacetime in order to take into account the light bending effect. The gravitational redshift and the relativistic doppler effect from gas motions of the accretion columns are also incorporated. The pulsed emission appears since the observed luminosity, which exceeds the Eddington luminosity for the stellar-mass black holes, periodically changes via precession of the column caused by the rotation of the NS. The PF tends to increase as θ obs approaching to θ B , where θ obs and θ B are the observer's viewing angle and the polar angle of the magnetic axis measured from the rotation axis. The maximum PF is around 50 %. Also, we find that the PF becomes less than 5 % for θ obs < ∼ 5 • or for θ B < ∼ 5 • . Our results are consistent with observations of ultraluminous X-ray pulsars (ULXPs) with few exceptions, since the ULXPs mostly exhibit the PF of < ∼ 50 %. Our present study supports the hypothesis that the ULXPs are powered by the super-critical column accretion onto NSs.

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Section: Conclusion and Discussionmentioning

confidence: 75%

Section: Conclusion and Discussionmentioning

confidence: 97%

Pulsed fraction of super-critical column accretion flows on to neutron stars: Modeling of ultraluminous X-ray pulsars

Inoue

Ohsuga

Kawashima

2020

Publications of the Astronomical Society of Japan

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“…The expected counts λ j arise from folding a model for the jth source through the instrument response to predict the counts in bin i, including the effects of varying exposure. If these bins are taken to be so small that n i ∈ (0, 1), this becomes the "unbinned" likelihood (Tompkins 1999),…”

Section: General Formalismmentioning

confidence: 99%

“…Generally, the power spectrum is unchanged in regions where the window function is minimal (exposure variations washed out), but substantially improved near problematic frequencies. This approach is critical in the analysis of strongly pulsed sources; see, e.g., the analysis of an ultraluminous X-ray pulsar (Wilson-Hodge et al 2018).…”

Section: Pulse Profilesmentioning

confidence: 99%

Multiscale Time- and Frequency-domain Likelihood Analysis with Photon Weights

Kerr

2019

ApJ

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We present an unbinned likelihood analysis formalism employing photon weights-the probabilities that events are associated with a particular source. This approach is applicable to any photon-resolving instrument, and thus well suited to high-energy observations; we focus here on GeV γ-ray data from the Fermi Large Area Telescope. Weights connect individual photons to the outputs of a detailed, expensive likelihood analysis of a much larger data set. The weighted events can be aggregated into arbitrary time spans ranging from microseconds to years. Such retrospective grouping permits timeand frequency-domain analysis over a wide range of scales and enables characterization of disparate phenomena like blazar flares, γ-ray bursts, pulsar pulses, novae, γ-ray binaries, and other variable sources. To demonstrate the formalism, we incorporate photon weights into the Bayesian blocks algorithm and perform a hierarchical time scale analysis of 3C 279 activity. We analyze pulsar pulse profiles and estimate the unpulsed emission level and the optimal division of the data into on-and offpulse intervals. We extend the formalism to Fourier analysis and derive estimators for power spectra, used to search for and characterize periodic sources. We show how the Fast Fourier transform can be used to probe orbital periods as short as a minute and we discuss mitigation of spurious signals. Our final example combines time-and frequency-domain analysis to jointly characterize the flares and orbital modulation of Cygnus X-3, yielding the strongest detection of the orbital signal (>13σ) to date. Finally, we discuss extensions of the work to other GeV sources and to X-ray and TeV observations.

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“…The ULX population consists of several hundreds sources in nearby galaxies (e.g. , and they are usually extragalactic (although see Wilson-Hodge et al 2018), off-nuclear and point-like objects. Nowadays, they are believed to be mostly stellar mass BHs or neutron stars (NSs) accreting well above the Eddington limit rather than sub-Eddington accreting intermediate mass BHs (10 2 − 10 5 M ; e.g.…”

Section: Introductionmentioning

confidence: 99%

The Ultraluminous X-Ray Sources Population of the Galaxy NGC 7456

Pintore

Marelli

Salvaterra

et al. 2020

ApJ

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Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with X-ray luminosities above 10 39 erg s −1 . The ULX population counts several hundreds objects but only a minor fraction is well studied. Here we present a detailed analysis of all ULXs hosted in the galaxy NGC 7456. It was observed in X-rays only once in the past (in 2005) by XMM-Newton but the observation was short and strongly affected by high background. In 2018, we obtained a new, deeper (∼ 90 ks) XMM-Newton observation that allowed us to perform a detailed characterization of the ULXs hosted in the galaxy. ULX-1 and ULX-2, the two brightest objects (L X ∼ 6 − 10 × 10 39 erg s −1 ), have spectra that can be described by a two-thermal component model as often found in ULXs. ULX-1 shows also one order of magnitude in flux variability on short-term timescales (hundreds to thousand ks). The other sources (ULX-3 and ULX-4) show flux changes of at least an order of magnitude, and these objects may be candidate transient ULXs although longer X-ray monitoring or further studies are required to ascribe them to the ULX population. In addition, we found a previously undetected source that might be a new candidate ULX (labelled as ULX-5) with a luminosity of ∼ 10 39 erg s −1 and hard power-law spectral shape, whose nature is still unclear and for which a background Active Galactic Nucleus cannot be excluded. We discuss the properties of all the ULXs in NGC 7456 within the framework of super-Eddington accretion onto stellar mass compact objects. Although no pulsations were detected, we cannot exclude that the sources host neutron stars.

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NICER and Fermi GBM Observations of the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

Abstract: Swift J0243.6+6124 is a newly discovered Galactic Be/X-ray binary, revealed in late September 2017 in a giant outburst with a peak luminosity of 2 × 10 39 (d/7 kpc) 2 erg s −1 (0.

Cited by 126 publications

References 57 publications

Pulsed fraction of super-critical column accretion flows on to neutron stars: Modeling of ultraluminous X-ray pulsars

Pulsed fraction of super-critical column accretion flows on to neutron stars: Modeling of ultraluminous X-ray pulsars

Multiscale Time- and Frequency-domain Likelihood Analysis with Photon Weights

The Ultraluminous X-Ray Sources Population of the Galaxy NGC 7456

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