NuSTAR and XMM–Newton broad-band spectrum of SAX J1808.4–3658 during its latest outburst in 2015

Rosario Iaria, Angelo Francesco Gambino, Tiziana Di Salvo, Riggio, Sanna, Burderi, Papitto, Luciano Burderi

Risultato della ricerca: Article

3 Citazioni (Scopus)

Abstract

The first discovered accreting millisecond pulsar, SAX J1808.4-3658, wentinto X-ray outburst in April 2015. We triggered a 100 ks XMM-Newton ToO, takenat the peak of the outburst, and a 55 ks NuSTAR ToO, performed four days apart.We report here the results of a detailed spectral analysis of both theXMM-Newton and NuSTAR spectra. While the XMM-Newton spectrum appears muchsofter than in previous observations, the NuSTAR spectrum confirms the resultsobtained with XMM-Newton during the 2008 outburst. We find clear evidence of abroad iron line that we interpret as produced by reflection from the inneraccretion disk. For the first time, we use a self-consistent reflection modelto fit the reflection features in the NuSTAR spectrum; in this case we find astatistically significant improvement of the fit with respect to a simpleGaussian or diskline model to fit the iron line, implying that the reflectioncontinuum is also significantly detected. Despite the differences evidentbetween the XMM-Newton and NuSTAR spectra, the smearing best-fit parametersfound for these spectra are consistent with each other and are compatible withprevious results. In particular, we find an upper limit to the inner diskradius of $sim 12~R_g$. In all the cases, a high inclination angle($>50^circ$) of the system is required. This inclination angle, combined withmeasurements of the radial velocity of the optical companion, results in a lowvalue for the neutron star mass ($<0.8,M_odot$), a result that deservesfurther investigation.
Lingua originaleEnglish
pagine (da-a)767-779
Numero di pagine13
RivistaDefault journal
Volume483
Stato di pubblicazionePublished - 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cita questo

NuSTAR and XMM–Newton broad-band spectrum of SAX J1808.4–3658 during its latest outburst in 2015. / Iaria, Rosario; Gambino, Angelo Francesco; Di Salvo, Tiziana; Riggio; Sanna; Burderi; Papitto; Burderi, Luciano.

In: Default journal, Vol. 483, 2019, pag. 767-779.

Risultato della ricerca: Article

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title = "NuSTAR and XMM–Newton broad-band spectrum of SAX J1808.4–3658 during its latest outburst in 2015",
abstract = "The first discovered accreting millisecond pulsar, SAX J1808.4-3658, wentinto X-ray outburst in April 2015. We triggered a 100 ks XMM-Newton ToO, takenat the peak of the outburst, and a 55 ks NuSTAR ToO, performed four days apart.We report here the results of a detailed spectral analysis of both theXMM-Newton and NuSTAR spectra. While the XMM-Newton spectrum appears muchsofter than in previous observations, the NuSTAR spectrum confirms the resultsobtained with XMM-Newton during the 2008 outburst. We find clear evidence of abroad iron line that we interpret as produced by reflection from the inneraccretion disk. For the first time, we use a self-consistent reflection modelto fit the reflection features in the NuSTAR spectrum; in this case we find astatistically significant improvement of the fit with respect to a simpleGaussian or diskline model to fit the iron line, implying that the reflectioncontinuum is also significantly detected. Despite the differences evidentbetween the XMM-Newton and NuSTAR spectra, the smearing best-fit parametersfound for these spectra are consistent with each other and are compatible withprevious results. In particular, we find an upper limit to the inner diskradius of $sim 12~R_g$. In all the cases, a high inclination angle($>50^circ$) of the system is required. This inclination angle, combined withmeasurements of the radial velocity of the optical companion, results in a lowvalue for the neutron star mass ($<0.8,M_odot$), a result that deservesfurther investigation.",
author = "Rosario Iaria and Gambino, {Angelo Francesco} and {Di Salvo}, Tiziana and Riggio and Sanna and Burderi and Papitto and Luciano Burderi",
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TY - JOUR

T1 - NuSTAR and XMM–Newton broad-band spectrum of SAX J1808.4–3658 during its latest outburst in 2015

AU - Iaria, Rosario

AU - Gambino, Angelo Francesco

AU - Di Salvo, Tiziana

AU - Riggio, null

AU - Sanna, null

AU - Burderi, null

AU - Papitto, null

AU - Burderi, Luciano

PY - 2019

Y1 - 2019

N2 - The first discovered accreting millisecond pulsar, SAX J1808.4-3658, wentinto X-ray outburst in April 2015. We triggered a 100 ks XMM-Newton ToO, takenat the peak of the outburst, and a 55 ks NuSTAR ToO, performed four days apart.We report here the results of a detailed spectral analysis of both theXMM-Newton and NuSTAR spectra. While the XMM-Newton spectrum appears muchsofter than in previous observations, the NuSTAR spectrum confirms the resultsobtained with XMM-Newton during the 2008 outburst. We find clear evidence of abroad iron line that we interpret as produced by reflection from the inneraccretion disk. For the first time, we use a self-consistent reflection modelto fit the reflection features in the NuSTAR spectrum; in this case we find astatistically significant improvement of the fit with respect to a simpleGaussian or diskline model to fit the iron line, implying that the reflectioncontinuum is also significantly detected. Despite the differences evidentbetween the XMM-Newton and NuSTAR spectra, the smearing best-fit parametersfound for these spectra are consistent with each other and are compatible withprevious results. In particular, we find an upper limit to the inner diskradius of $sim 12~R_g$. In all the cases, a high inclination angle($>50^circ$) of the system is required. This inclination angle, combined withmeasurements of the radial velocity of the optical companion, results in a lowvalue for the neutron star mass ($<0.8,M_odot$), a result that deservesfurther investigation.

AB - The first discovered accreting millisecond pulsar, SAX J1808.4-3658, wentinto X-ray outburst in April 2015. We triggered a 100 ks XMM-Newton ToO, takenat the peak of the outburst, and a 55 ks NuSTAR ToO, performed four days apart.We report here the results of a detailed spectral analysis of both theXMM-Newton and NuSTAR spectra. While the XMM-Newton spectrum appears muchsofter than in previous observations, the NuSTAR spectrum confirms the resultsobtained with XMM-Newton during the 2008 outburst. We find clear evidence of abroad iron line that we interpret as produced by reflection from the inneraccretion disk. For the first time, we use a self-consistent reflection modelto fit the reflection features in the NuSTAR spectrum; in this case we find astatistically significant improvement of the fit with respect to a simpleGaussian or diskline model to fit the iron line, implying that the reflectioncontinuum is also significantly detected. Despite the differences evidentbetween the XMM-Newton and NuSTAR spectra, the smearing best-fit parametersfound for these spectra are consistent with each other and are compatible withprevious results. In particular, we find an upper limit to the inner diskradius of $sim 12~R_g$. In all the cases, a high inclination angle($>50^circ$) of the system is required. This inclination angle, combined withmeasurements of the radial velocity of the optical companion, results in a lowvalue for the neutron star mass ($<0.8,M_odot$), a result that deservesfurther investigation.

UR - http://hdl.handle.net/10447/350528

UR - http://arxiv.org/abs/1811.00940v1

M3 - Article

VL - 483

SP - 767

EP - 779

JO - Default journal

JF - Default journal

ER -