Order in the Chaos: Spin-up and Spin-down during the 2002 Outburst of SAX J1808.4-3658

Tiziana Di Salvo, Riggio, Burderi, Menna, Papitto

Risultato della ricerca: Article

46 Citazioni (Scopus)

Abstract

We present a timing analysis of the 2002 outburst of the accreting millisecond pulsar SAX J1808.4-3658. A study of the phase delays of the entire pulse profile shows a behavior that is surprising and difficult to interpret: superposed to a general trend, a big jump by about 0.2 in phase is visible, starting at day 14 after the beginning of the outburst. An analysis of the pulse profile indicates the presence of a significant first harmonic. Studying the fundamental and the first harmonic separately, we find that the phase delays of the first harmonic are more regular, with no sign of the jump observed in the fundamental. The fitting of the phase delays of the first harmonic with a model that takes into account the observed exponential decay of the X-ray flux (and therefore of the mass accretion rate onto the neutron star) gives important information on the torque acting on the neutron star during the outburst. We find that the source shows spin-up in the first part of the outburst, while a spin-down dominates at the end. From these results we derive an estimate of the neutron star magnetic field strength.
Lingua originaleEnglish
pagine (da-a)L133-L136
RivistaTHE ASTROPHYSICAL JOURNAL
Volume653
Stato di pubblicazionePublished - 2006

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chaos
neutron stars
harmonics
profiles
pulses
pulsars
torque
field strength
time measurement
trends
decay
estimates
magnetic fields
x rays

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cita questo

Order in the Chaos: Spin-up and Spin-down during the 2002 Outburst of SAX J1808.4-3658. / Di Salvo, Tiziana; Riggio; Burderi; Menna; Papitto.

In: THE ASTROPHYSICAL JOURNAL, Vol. 653, 2006, pag. L133-L136.

Risultato della ricerca: Article

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title = "Order in the Chaos: Spin-up and Spin-down during the 2002 Outburst of SAX J1808.4-3658",
abstract = "We present a timing analysis of the 2002 outburst of the accreting millisecond pulsar SAX J1808.4-3658. A study of the phase delays of the entire pulse profile shows a behavior that is surprising and difficult to interpret: superposed to a general trend, a big jump by about 0.2 in phase is visible, starting at day 14 after the beginning of the outburst. An analysis of the pulse profile indicates the presence of a significant first harmonic. Studying the fundamental and the first harmonic separately, we find that the phase delays of the first harmonic are more regular, with no sign of the jump observed in the fundamental. The fitting of the phase delays of the first harmonic with a model that takes into account the observed exponential decay of the X-ray flux (and therefore of the mass accretion rate onto the neutron star) gives important information on the torque acting on the neutron star during the outburst. We find that the source shows spin-up in the first part of the outburst, while a spin-down dominates at the end. From these results we derive an estimate of the neutron star magnetic field strength.",
keywords = "Stars: Magnetic Fields, Stars: Neutron, Stars: Pulsars: General, Stars: Pulsars: Individual: SAX J1808.4-3658, X-Rays: Binaries",
author = "{Di Salvo}, Tiziana and Riggio and Burderi and Menna and Papitto",
year = "2006",
language = "English",
volume = "653",
pages = "L133--L136",
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TY - JOUR

T1 - Order in the Chaos: Spin-up and Spin-down during the 2002 Outburst of SAX J1808.4-3658

AU - Di Salvo, Tiziana

AU - Riggio, null

AU - Burderi, null

AU - Menna, null

AU - Papitto, null

PY - 2006

Y1 - 2006

N2 - We present a timing analysis of the 2002 outburst of the accreting millisecond pulsar SAX J1808.4-3658. A study of the phase delays of the entire pulse profile shows a behavior that is surprising and difficult to interpret: superposed to a general trend, a big jump by about 0.2 in phase is visible, starting at day 14 after the beginning of the outburst. An analysis of the pulse profile indicates the presence of a significant first harmonic. Studying the fundamental and the first harmonic separately, we find that the phase delays of the first harmonic are more regular, with no sign of the jump observed in the fundamental. The fitting of the phase delays of the first harmonic with a model that takes into account the observed exponential decay of the X-ray flux (and therefore of the mass accretion rate onto the neutron star) gives important information on the torque acting on the neutron star during the outburst. We find that the source shows spin-up in the first part of the outburst, while a spin-down dominates at the end. From these results we derive an estimate of the neutron star magnetic field strength.

AB - We present a timing analysis of the 2002 outburst of the accreting millisecond pulsar SAX J1808.4-3658. A study of the phase delays of the entire pulse profile shows a behavior that is surprising and difficult to interpret: superposed to a general trend, a big jump by about 0.2 in phase is visible, starting at day 14 after the beginning of the outburst. An analysis of the pulse profile indicates the presence of a significant first harmonic. Studying the fundamental and the first harmonic separately, we find that the phase delays of the first harmonic are more regular, with no sign of the jump observed in the fundamental. The fitting of the phase delays of the first harmonic with a model that takes into account the observed exponential decay of the X-ray flux (and therefore of the mass accretion rate onto the neutron star) gives important information on the torque acting on the neutron star during the outburst. We find that the source shows spin-up in the first part of the outburst, while a spin-down dominates at the end. From these results we derive an estimate of the neutron star magnetic field strength.

KW - Stars: Magnetic Fields

KW - Stars: Neutron

KW - Stars: Pulsars: General

KW - Stars: Pulsars: Individual: SAX J1808.4-3658

KW - X-Rays: Binaries

UR - http://hdl.handle.net/10447/23298

M3 - Article

VL - 653

SP - L133-L136

JO - THE ASTROPHYSICAL JOURNAL

JF - THE ASTROPHYSICAL JOURNAL

SN - 0004-637X

ER -