The X-ray spectrum of the newly discovered accreting millisecond pulsar IGR J17511-3057

Tiziana Di Salvo, Rosario Iaria, Burderi, Menna, Papitto, Riggio, Bozzo

Risultato della ricerca: Article

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Abstract

We report on a 70 ks XMM-Newton Target of Opportunity (ToO) observation of the newly discovered accreting millisecond pulsar, IGR J17511-3057. Pulsations at 244.8339512(1)Hz are observed throughout the outburst with an rms-pulsed fraction of 14.4(3) per cent. Pulsations have been used to derive a precise solution for the Porb = 12487.51(2) s binary system. The measured mass function indicates a main-sequence companion star with a mass between 0.15 and 0.44 Msolar. The XMM-Newton 0.5-11keV spectrum of IGR J17511-3057 can be modelled by at least three components, which we interpret, from the softest to the hardest, as multi-coloured disc emission, thermal emission from the neutron star surface and thermal Comptonization emission. Spectral fit of the XMM-Newton data and of the Rossi X-ray Timing Explorer (RXTE) data, taken in a simultaneous temporal window, well constrain the Comptonization parameters: the electron temperature, kTe = 51+6-4keV, is rather high, while the optical depth (τ = 1.34+0.03-0.06) is moderate. The energy dependence of the pulsed fraction supports the interpretation of the cooler thermal component as coming from the accretion disc, and indicates that the Comptonizing plasma surrounds the hot spots on the neutron star surface, which in turn provides the seed photons. Signatures of reflection, such as a broadened iron Kα emission line and a Compton hump at ~30keV, are also detected. We derive from the smearing of the reflection component an inner disc radius of >~40km for a 1.4 Msolar neutron star, and an inclination between 38° and 68°. XMM-Newton also observed two type I X-ray bursts, whose fluence and recurrence time suggest that the bursts are ignited in a nearly pure helium environment. No photospheric radius expansion is observed, thus leading to an upper limit on the distance to the source of 10kpc. A lower limit of 6.5kpc can be also set if it is assumed that emission during the decaying part of the burst involves the whole neutron star surface. Pulsations are observed during the burst decay with an amplitude similar to the persistent emission. They are also compatible with being phase locked to pre-burst pulsations, suggesting that the location on the neutron star surface where they are formed does not change much during bursts.
Lingua originaleEnglish
pagine (da-a)2575-2588
Numero di pagine14
RivistaMonthly Notices of the Royal Astronomical Society
Volume407
Stato di pubblicazionePublished - 2010

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pulsars
bursts
neutron stars
XMM-Newton telescope
newton
x rays
thermal emission
companion stars
radii
X Ray Timing Explorer
main sequence stars
coolers
accretion disks
outburst
optical thickness
helium
optical depth
inclination
seeds
hot spot

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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The X-ray spectrum of the newly discovered accreting millisecond pulsar IGR J17511-3057. / Di Salvo, Tiziana; Iaria, Rosario; Burderi; Menna; Papitto; Riggio; Bozzo.

In: Monthly Notices of the Royal Astronomical Society, Vol. 407, 2010, pag. 2575-2588.

Risultato della ricerca: Article

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title = "The X-ray spectrum of the newly discovered accreting millisecond pulsar IGR J17511-3057",
abstract = "We report on a 70 ks XMM-Newton Target of Opportunity (ToO) observation of the newly discovered accreting millisecond pulsar, IGR J17511-3057. Pulsations at 244.8339512(1)Hz are observed throughout the outburst with an rms-pulsed fraction of 14.4(3) per cent. Pulsations have been used to derive a precise solution for the Porb = 12487.51(2) s binary system. The measured mass function indicates a main-sequence companion star with a mass between 0.15 and 0.44 Msolar. The XMM-Newton 0.5-11keV spectrum of IGR J17511-3057 can be modelled by at least three components, which we interpret, from the softest to the hardest, as multi-coloured disc emission, thermal emission from the neutron star surface and thermal Comptonization emission. Spectral fit of the XMM-Newton data and of the Rossi X-ray Timing Explorer (RXTE) data, taken in a simultaneous temporal window, well constrain the Comptonization parameters: the electron temperature, kTe = 51+6-4keV, is rather high, while the optical depth (τ = 1.34+0.03-0.06) is moderate. The energy dependence of the pulsed fraction supports the interpretation of the cooler thermal component as coming from the accretion disc, and indicates that the Comptonizing plasma surrounds the hot spots on the neutron star surface, which in turn provides the seed photons. Signatures of reflection, such as a broadened iron Kα emission line and a Compton hump at ~30keV, are also detected. We derive from the smearing of the reflection component an inner disc radius of >~40km for a 1.4 Msolar neutron star, and an inclination between 38° and 68°. XMM-Newton also observed two type I X-ray bursts, whose fluence and recurrence time suggest that the bursts are ignited in a nearly pure helium environment. No photospheric radius expansion is observed, thus leading to an upper limit on the distance to the source of 10kpc. A lower limit of 6.5kpc can be also set if it is assumed that emission during the decaying part of the burst involves the whole neutron star surface. Pulsations are observed during the burst decay with an amplitude similar to the persistent emission. They are also compatible with being phase locked to pre-burst pulsations, suggesting that the location on the neutron star surface where they are formed does not change much during bursts.",
keywords = "stars neutron, X-rays binaries, X-rays individual IGR J17511-3057",
author = "{Di Salvo}, Tiziana and Rosario Iaria and Burderi and Menna and Papitto and Riggio and Bozzo",
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TY - JOUR

T1 - The X-ray spectrum of the newly discovered accreting millisecond pulsar IGR J17511-3057

AU - Di Salvo, Tiziana

AU - Iaria, Rosario

AU - Burderi, null

AU - Menna, null

AU - Papitto, null

AU - Riggio, null

AU - Bozzo, null

PY - 2010

Y1 - 2010

N2 - We report on a 70 ks XMM-Newton Target of Opportunity (ToO) observation of the newly discovered accreting millisecond pulsar, IGR J17511-3057. Pulsations at 244.8339512(1)Hz are observed throughout the outburst with an rms-pulsed fraction of 14.4(3) per cent. Pulsations have been used to derive a precise solution for the Porb = 12487.51(2) s binary system. The measured mass function indicates a main-sequence companion star with a mass between 0.15 and 0.44 Msolar. The XMM-Newton 0.5-11keV spectrum of IGR J17511-3057 can be modelled by at least three components, which we interpret, from the softest to the hardest, as multi-coloured disc emission, thermal emission from the neutron star surface and thermal Comptonization emission. Spectral fit of the XMM-Newton data and of the Rossi X-ray Timing Explorer (RXTE) data, taken in a simultaneous temporal window, well constrain the Comptonization parameters: the electron temperature, kTe = 51+6-4keV, is rather high, while the optical depth (τ = 1.34+0.03-0.06) is moderate. The energy dependence of the pulsed fraction supports the interpretation of the cooler thermal component as coming from the accretion disc, and indicates that the Comptonizing plasma surrounds the hot spots on the neutron star surface, which in turn provides the seed photons. Signatures of reflection, such as a broadened iron Kα emission line and a Compton hump at ~30keV, are also detected. We derive from the smearing of the reflection component an inner disc radius of >~40km for a 1.4 Msolar neutron star, and an inclination between 38° and 68°. XMM-Newton also observed two type I X-ray bursts, whose fluence and recurrence time suggest that the bursts are ignited in a nearly pure helium environment. No photospheric radius expansion is observed, thus leading to an upper limit on the distance to the source of 10kpc. A lower limit of 6.5kpc can be also set if it is assumed that emission during the decaying part of the burst involves the whole neutron star surface. Pulsations are observed during the burst decay with an amplitude similar to the persistent emission. They are also compatible with being phase locked to pre-burst pulsations, suggesting that the location on the neutron star surface where they are formed does not change much during bursts.

AB - We report on a 70 ks XMM-Newton Target of Opportunity (ToO) observation of the newly discovered accreting millisecond pulsar, IGR J17511-3057. Pulsations at 244.8339512(1)Hz are observed throughout the outburst with an rms-pulsed fraction of 14.4(3) per cent. Pulsations have been used to derive a precise solution for the Porb = 12487.51(2) s binary system. The measured mass function indicates a main-sequence companion star with a mass between 0.15 and 0.44 Msolar. The XMM-Newton 0.5-11keV spectrum of IGR J17511-3057 can be modelled by at least three components, which we interpret, from the softest to the hardest, as multi-coloured disc emission, thermal emission from the neutron star surface and thermal Comptonization emission. Spectral fit of the XMM-Newton data and of the Rossi X-ray Timing Explorer (RXTE) data, taken in a simultaneous temporal window, well constrain the Comptonization parameters: the electron temperature, kTe = 51+6-4keV, is rather high, while the optical depth (τ = 1.34+0.03-0.06) is moderate. The energy dependence of the pulsed fraction supports the interpretation of the cooler thermal component as coming from the accretion disc, and indicates that the Comptonizing plasma surrounds the hot spots on the neutron star surface, which in turn provides the seed photons. Signatures of reflection, such as a broadened iron Kα emission line and a Compton hump at ~30keV, are also detected. We derive from the smearing of the reflection component an inner disc radius of >~40km for a 1.4 Msolar neutron star, and an inclination between 38° and 68°. XMM-Newton also observed two type I X-ray bursts, whose fluence and recurrence time suggest that the bursts are ignited in a nearly pure helium environment. No photospheric radius expansion is observed, thus leading to an upper limit on the distance to the source of 10kpc. A lower limit of 6.5kpc can be also set if it is assumed that emission during the decaying part of the burst involves the whole neutron star surface. Pulsations are observed during the burst decay with an amplitude similar to the persistent emission. They are also compatible with being phase locked to pre-burst pulsations, suggesting that the location on the neutron star surface where they are formed does not change much during bursts.

KW - stars neutron, X-rays binaries, X-rays individual IGR J17511-3057

UR - http://hdl.handle.net/10447/52708

UR - http://adsabs.harvard.edu/abs/2010MNRAS.407.2575P

M3 - Article

VL - 407

SP - 2575

EP - 2588

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

ER -