Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9-2021

Tiziana Di Salvo, Rosario Iaria, Burderi, D'Aí, Riggio, Pintore, Sanna, Scarano, Del Santo

Risultato della ricerca: Article

19 Citazioni (Scopus)

Abstract

We analysed a 115-ks XMM-Newton observation and the stacking of 8 d of INTEGRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during the XMM-Newton observation, and for this reason we studied separately the persistent and burst epochs. We described the persistent emission with a combination of two soft thermal components, a cold thermal Comptonization component (~2 keV) and an additional hard X-ray emission described by a power law (Γ ~ 2.3). The continuum components can be associated with an accretion disc, the neutron star (NS) surface and a thermal Comptonization emission coming out of an optically thick plasma region, while the origin of the high-energy tail is still under debate. In addition, a number of broad (σ = 0.1-0.4 keV) emission features likely associated with reflection processes have been observed in the XMM-Newton data. The estimated 1.0-50 keV unabsorbed luminosity of the source is ~5 × 1037 erg s-1, about 25 per cent of the Eddington limit assuming a 1.4 M⊙ NS. We suggest that the spectral properties of SAX J1748.9-2021 are consistent with a soft state, differently from many other accreting X-ray millisecond pulsars which are usually found in the hard state. Moreover, none of the observed type-I burst reached the Eddington luminosity. Assuming that the burst ignition and emission are produced above the whole NS surface, we estimate an NS radius of ~7-8 km, consistent with previous results.
Lingua originaleEnglish
pagine (da-a)2988-2998
Numero di pagine11
RivistaMonthly Notices of the Royal Astronomical Society
Volume457
Stato di pubblicazionePublished - 2016

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pulsars
spectral analysis
neutron stars
spectrum analysis
bursts
XMM-Newton telescope
newton
broadband
x rays
luminosity
M stars
thermal emission
accretion disks
ignition
stacking
outburst
erg
time measurement
continuums
power law

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cita questo

Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9-2021. / Di Salvo, Tiziana; Iaria, Rosario; Burderi; D'Aí; Riggio; Pintore; Sanna; Scarano; Del Santo.

In: Monthly Notices of the Royal Astronomical Society, Vol. 457, 2016, pag. 2988-2998.

Risultato della ricerca: Article

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title = "Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9-2021",
abstract = "We analysed a 115-ks XMM-Newton observation and the stacking of 8 d of INTEGRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during the XMM-Newton observation, and for this reason we studied separately the persistent and burst epochs. We described the persistent emission with a combination of two soft thermal components, a cold thermal Comptonization component (~2 keV) and an additional hard X-ray emission described by a power law (Γ ~ 2.3). The continuum components can be associated with an accretion disc, the neutron star (NS) surface and a thermal Comptonization emission coming out of an optically thick plasma region, while the origin of the high-energy tail is still under debate. In addition, a number of broad (σ = 0.1-0.4 keV) emission features likely associated with reflection processes have been observed in the XMM-Newton data. The estimated 1.0-50 keV unabsorbed luminosity of the source is ~5 × 1037 erg s-1, about 25 per cent of the Eddington limit assuming a 1.4 M⊙ NS. We suggest that the spectral properties of SAX J1748.9-2021 are consistent with a soft state, differently from many other accreting X-ray millisecond pulsars which are usually found in the hard state. Moreover, none of the observed type-I burst reached the Eddington luminosity. Assuming that the burst ignition and emission are produced above the whole NS surface, we estimate an NS radius of ~7-8 km, consistent with previous results.",
keywords = "Accretion; Accretion discs -X-rays; Binaries - X-rays; Galaxies -X-rays; Individual; SAX J1748.9-2021; Space and Planetary Science; Astronomy and Astrophysics",
author = "{Di Salvo}, Tiziana and Rosario Iaria and Burderi and D'A{\'i} and Riggio and Pintore and Sanna and Scarano and {Del Santo}",
year = "2016",
language = "English",
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pages = "2988--2998",
journal = "Monthly Notices of the Royal Astronomical Society",
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TY - JOUR

T1 - Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9-2021

AU - Di Salvo, Tiziana

AU - Iaria, Rosario

AU - Burderi, null

AU - D'Aí, null

AU - Riggio, null

AU - Pintore, null

AU - Sanna, null

AU - Scarano, null

AU - Del Santo, null

PY - 2016

Y1 - 2016

N2 - We analysed a 115-ks XMM-Newton observation and the stacking of 8 d of INTEGRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during the XMM-Newton observation, and for this reason we studied separately the persistent and burst epochs. We described the persistent emission with a combination of two soft thermal components, a cold thermal Comptonization component (~2 keV) and an additional hard X-ray emission described by a power law (Γ ~ 2.3). The continuum components can be associated with an accretion disc, the neutron star (NS) surface and a thermal Comptonization emission coming out of an optically thick plasma region, while the origin of the high-energy tail is still under debate. In addition, a number of broad (σ = 0.1-0.4 keV) emission features likely associated with reflection processes have been observed in the XMM-Newton data. The estimated 1.0-50 keV unabsorbed luminosity of the source is ~5 × 1037 erg s-1, about 25 per cent of the Eddington limit assuming a 1.4 M⊙ NS. We suggest that the spectral properties of SAX J1748.9-2021 are consistent with a soft state, differently from many other accreting X-ray millisecond pulsars which are usually found in the hard state. Moreover, none of the observed type-I burst reached the Eddington luminosity. Assuming that the burst ignition and emission are produced above the whole NS surface, we estimate an NS radius of ~7-8 km, consistent with previous results.

AB - We analysed a 115-ks XMM-Newton observation and the stacking of 8 d of INTEGRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during the XMM-Newton observation, and for this reason we studied separately the persistent and burst epochs. We described the persistent emission with a combination of two soft thermal components, a cold thermal Comptonization component (~2 keV) and an additional hard X-ray emission described by a power law (Γ ~ 2.3). The continuum components can be associated with an accretion disc, the neutron star (NS) surface and a thermal Comptonization emission coming out of an optically thick plasma region, while the origin of the high-energy tail is still under debate. In addition, a number of broad (σ = 0.1-0.4 keV) emission features likely associated with reflection processes have been observed in the XMM-Newton data. The estimated 1.0-50 keV unabsorbed luminosity of the source is ~5 × 1037 erg s-1, about 25 per cent of the Eddington limit assuming a 1.4 M⊙ NS. We suggest that the spectral properties of SAX J1748.9-2021 are consistent with a soft state, differently from many other accreting X-ray millisecond pulsars which are usually found in the hard state. Moreover, none of the observed type-I burst reached the Eddington luminosity. Assuming that the burst ignition and emission are produced above the whole NS surface, we estimate an NS radius of ~7-8 km, consistent with previous results.

KW - Accretion; Accretion discs -X-rays; Binaries - X-rays; Galaxies -X-rays; Individual; SAX J1748.9-2021; Space and Planetary Science; Astronomy and Astrophysics

UR - http://hdl.handle.net/10447/209930

UR - http://mnras.oxfordjournals.org/

M3 - Article

VL - 457

SP - 2988

EP - 2998

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

ER -