Swift monitoring of the new accreting millisecond X-ray pulsar IGR J17511-3057 in outburst

Bozzo, E.; Ferrigno, C.; Falanga, M.; Campana, S.; Kennea, J. A.; Papitto, A.

doi:10.1051/0004-6361/200913517

Cited by 13 publications

(30 citation statements)

References 22 publications

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“…Under the hypothesis that emission is isotropic, this corresponds to a bolometric luminosity of L x ∼ 1.5 × 10 37 d 2 8 erg s −1 , where d 8 is the distance to the source in units of 8 kpc. We note that an upper limit of 10.6 kpc on the source distance was set by Bozzo et al (2010), by insisting that the burst peak luminosity does not exceed the Eddington limit, while Altamirano et al (2010), from the analysis of the type-I bursts observed by RXTE and Swift found an upper limit of 6.9 kpc. On the basis of the spectral analysis of XMM-Newton data, Papitto et al (2010) also gave a lower limit of 7 kpc, which was, however, based on some assumptions.…”

Section: Derivation Of the Orbital Ephemerismentioning

confidence: 93%

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Timing of the accreting millisecond pulsar IGR J17511-3057

Riggio

Papitto

Burderi

et al. 2011

A&A

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Context. Timing analysis of accretion-powered millisecond pulsars (AMPs) is a powerful tool for probing the physics of compact objects. The recently discovered IGR J17511-3057 was the twelfth discovered of the 13 AMPs known. The Rossi XTE satellite provided an extensive coverage of the 25 days-long observation of the source outburst. Aims. Our goal is to investigate the complex interaction between the neutron star magnetic field and the accretion disk by determining the angular momentum exchange between them. The presence of a millisecond coherent flux modulation allows us to investigate this interaction from the study of pulse arrival times. To separate the neutron star proper spin frequency variations from other effects, a precise set of orbital ephemeris is mandatory. Methods. Using timing techniques, we analysed the pulse phase delays by fitting differential corrections to the orbital parameters. To remove the effects of pulse phase fluctuations, we applied the timing technique that had been already successfully applied to the case of an another AMP, XTE J1807-294. Results. We report a precise set of orbital ephemeris. We demonstrate that the companion star is a main-sequence star. We find pulse phase delay fluctuations on the first harmonic with a characteristic amplitude of about 0.05, similar to those also observed for the AMP XTE J1814-338. For the second time, an AMP shows a third harmonic detected during the entire outburst. The first harmonic phase delays exhibit a puzzling behaviour, while the second harmonic phase delays clearly spin-up. The third harmonic also shows a spin-up, although not highly significant (3σ c.l.). The presence of a fourth harmonic is also reported. If we assume that the second harmonic is a good tracer of the spin frequency of the neutron star, we infer a mean spin frequency derivative for this source of 1.65(18) × 10 −13 Hz s −1 . Conclusions. To interpret the pulse phase delays of the four harmonics, we apply the disk threading model, but obtain different and incompatibleṀ estimates for each harmonic. In particular, the phase delays of the first harmonic are heavily affected by phase noise, and consequently, on the basis of these data, it is not possible to derive a reliable estimate ofṀ. The second harmonic gives aṀ consistent with the flux assuming that the source is at a distance of 6.3 kpc. The third harmonic gives a lowerṀ value, with respect to the first and second harmonic, and this would reduce the distance estimate to 3.6 kpc.

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Section: Derivation Of the Orbital Ephemerismentioning

confidence: 93%

“…An analysis of a Chandra observation by Nowak et al (2009) gave the best source position with an uncertainty of 0.6 . IGR J17511-3057 was observed by Swift and the data analysed by Bozzo et al (2010), which provided a description of the X-ray spectrum. Torres et al (2009) reported a possible near-infrared counterpart.…”

Section: Introductionmentioning

confidence: 99%

Timing of the accreting millisecond pulsar IGR J17511-3057

Riggio

Papitto

Burderi

et al. 2011

A&A

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“…In order to achieve a more physical description of the source X-ray emission, we replaced the cutoff power-law model with the thermal Comptonization model compps, under the assumption of a slab geometry (Poutanen & Svensson 1996). This model has been successfully applied in the past to a number of other AMXPs (see e.g., Gierliński & Poutanen 2005;Falanga et al 2005aFalanga et al ,b, 2007bIbragimov & Poutanen 2009;Bozzo et al 2010;Falanga et al 2011). The new set of model parameters are the absorption column density N H , the plasma temperature of the accretion column kT e , the blackbody temperature kT bb of the soft-seed photons assumed to be injected from the bottom of the slab, the Thomson optical depth τ T across the slab, and the inclination angle θ between the slab normal and the line of sight.…”

Section: Spectral Analysismentioning

confidence: 99%

The 2015 outburst of the accretion-powered pulsar IGR J00291+5934: INTEGRAL andSwiftobservations

Falco

Kuiper

Bozzo

et al. 2017

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The pulsar IGR J00291+5934 is the fastest-known accretion-powered X-ray pulsar, discovered during a transient outburst in 2004. In this paper, we report on INTEGRAL and Swift observations during the 2015 outburst, which lasts for ∼ 25 d. The source has not been observed in outburst since 2008, suggesting that the long-term accretion rate has decreased by a factor of two since discovery. The averaged broad-band (0.1 -250 keV) persistent spectrum in 2015 is well described by a thermal Comptonization model with a column density of N H ≈ 4 × 10 21 cm −2 , a plasma temperature of kT e ≈ 50 keV, and a Thomson optical depth of τ T ≈ 1. Pulsations at the known spin period of the source are detected in the INTEGRAL data up to the ∼ 150 keV energy band. We also report on the discovery of the first thermonuclear burst observed from IGR J00291+5934, which lasts around 7 min and occurs at a persistent emission level corresponding to roughly 1.6% of the Eddington accretion rate. The properties of the burst suggest it is powered primarily by helium ignited at a depth of y ign ≈ 1.5 × 10 9 g cm −2 following the exhaustion by steady burning of the accreted hydrogen. The Swift/BAT data from the first ∼ 20 s of the burst provide indications of a photospheric radius expansion phase. Assuming this is the case, we infer a source distance of d = 4.2 ± 0.5 kpc.

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“…The measured pulsar mass function indicated a mainsequence companion star with a mass between 0.15 and 0.44 M ⊙ (Papitto et al 2010). At discovery, 18 type-I Xray bursts were observed from the pulsar (Altamirano et al 2010;Bozzo et al 2010;Papitto et al 2010;Falanga et al 2011). Evidence of photospheric radius expansion was not displayed by any of these bursts, and an upper limit to the source distance (6.9 kpc) was provided by Altamirano et al (2010).…”

Section: Introductionmentioning

confidence: 93%

“…IGR J17511-3057 was discovered by INTEGRAL during an outburst in September 2009 (Baldovin et al 2009;Bozzo et al 2010). The detection of 4.1 ms coherent pulsations in the Rossi X-ray Timing Explorer light curve allowed the identification of the source as an AMSP in a binary system with a 3.47 hr orbital period (Markwardt et al 2009).…”

Section: Introductionmentioning

confidence: 99%

The 2015 outburst of the accreting millisecond pulsar IGR J17511–3057 as seen by INTEGRAL,Swift, andXMM-Newton

Papitto¹,

Bozzo²,

Sánchez–Fernández³

et al. 2016

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We report on INTEGRAL, Swift and XMM-Newton observations of IGR J17511-3057 performed during the outburst that occurred between March 23 and April 25, 2015. The source reached a peak flux of 0.7(2) × 10 −9 erg cm −2 s −1 and decayed to quiescence in approximately a month. The X-ray spectrum was dominated by a power-law with photon index between 1.6 and 1.8, which we interpreted as thermal Comptonization in an electron cloud with temperature > 20 keV . A broad (σ ≃ 1 keV) emission line was detected at an energy (E = 6.9 +0.2 −0.3 keV) compatible with the K-α transition of ionized Fe, suggesting an origin in the inner regions of the accretion disk. The outburst flux and spectral properties shown during this outburst were remarkably similar to those observed during the previous accretion event detected from the source in 2009. Coherent pulsations at the pulsar spin period were detected in the XMM-Newton and INTEGRAL data, at a frequency compatible with the value observed in 2009. Assuming that the source spun up during the 2015 outburst at the same rate observed during the previous outburst, we derive a conservative upper limit on the spin down rate during quiescence of 3.5 × 10 −15 Hz s −1 . Interpreting this value in terms of electromagnetic spin down yields an upper limit of 3.6 × 10 26 G cm 3 to the pulsar magnetic dipole (assuming a magnetic inclination angle of 30 • ). We also report on the detection of five type-I X-ray bursts (three in the XMM-Newton data, two in the INTEGRAL data), none of which indicated photospheric radius expansion.

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Swift monitoring of the new accreting millisecond X-ray pulsar IGR J17511-3057 in outburst

Cited by 13 publications

References 22 publications

Timing of the accreting millisecond pulsar IGR J17511-3057

Timing of the accreting millisecond pulsar IGR J17511-3057

The 2015 outburst of the accretion-powered pulsar IGR J00291+5934: INTEGRAL andSwiftobservations

The 2015 outburst of the accreting millisecond pulsar IGR J17511–3057 as seen by INTEGRAL,Swift, andXMM-Newton

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