SAX J1808.4−3658, an accreting millisecond pulsar shining in gamma rays?

Wilhelmi, E. de Oña; Papitto, A.; Li, J.; Rea, N.; Torres, D. F.; Burderi, L.; Salvo, T. Di; Iaria, R.; Riggio, A.; Sanna, A.

doi:10.1093/mnras/stv2695

Cited by 20 publications

(10 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Among previous searches for γ-ray emission from neutron star X-ray binaries (e.g., Xing & Wang 2013;de Oña Wilhelmi et al 2016), Li et al (2012) have provided a very similar case to GRO J1008−57 by justifying that the γ-ray transients GRO J1036−55 and AGL J1037−5708 are associated with the HMXB 4U 1036−56. The likely association indicates that the HMXB only had occasional (detectable) γ-ray emission during several days.…”

Section: Discussionmentioning

confidence: 99%

The Likely Fermi Detection of the Be X-Ray Binary GRO J1008-57

Xing

Wang

2019

ApJ

View full text Add to dashboard Cite

In our search for γ-ray emission from Be X-ray binaries from analysis of the data obtained with the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope, we find likely detection of GRO J1008−57. The binary has an orbital period of 249.48 days, and it is only significantly detected in its orbital phase 0.8-0.9 (> 4σ). Further light curve analysis indicates that the detection is probably largely due to an emitting event in one orbital cycle around year 2012-2013, following a giant X-ray outburst of the source. This property of having occasional γ-ray emitting events is similar to that seen in another high-mass X-ray binary 4U 1036−56. However, models considering possible γ-ray emission from an accreting neutron star have difficulty in explaining the observed ∼ 10 34 erg s −1 luminosity of the source, unless the distance was largely over-estimated. Further observational studies are required, in order to more clearly establish the high-energy emission properties of GRO J1008−57 or similar high-mass X-ray binaries and find clues for understanding how γ-ray emission is produced from them.

show abstract

Section: Discussionmentioning

confidence: 99%

The Likely Fermi Detection of the Be X-Ray Binary GRO J1008-57

Xing

Wang

2019

ApJ

View full text Add to dashboard Cite

show abstract

“…The proposed mechanism to expel the accreting matter from the system involves radiation pressure of the magneto-dipole rotator that should power the NS during quiescence phases (see e.g., Burderi et al 2003;Di Salvo et al 2008). Over the years several indirect hints that in SAX J1808.4-3658 the radio pulsar mechanism turns on during quiescence phases have been collected, e.g., the presence of an over-luminous optical counterpart of the source (Homer et al 2001) interpreted by Burderi et al (2003) as the spin-down luminosity of the magneto-dipole rotator reprocessed by the companion star; the secular spin-down evolution of the NS spin showing derivative values typical of millisecond radio pulsars (Hartman et al 2009b;Patruno et al 2012); detection of a possible gamma-ray counterpart of the source as observed by Fermi-LAT during the quiescence phases of SAX J1808.4-3658 (de Oña Wilhelmi et al 2016;Xing et al 2015). Nonetheless, although carefully searched (Burgay et al 2003;Patruno et al 2016), no direct observation of the radio pulsar activity of the source has been observed to date (at this moment the only known AMXP observed as rotation-powered pulsar is IGR J18245-2453, Papitto et al 2013).…”

Section: Radio-ejection Mechanismmentioning

confidence: 99%

On the timing properties of SAX J1808.4−3658 during its 2015 outburst

Sanna

Salvo

Burderi

et al. 2017

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

We present a timing analysis of the 2015 outburst of the accreting millisecond Xray pulsar SAX J1808.4-3658, using non-simultaneous XMM-Newton and NuSTAR observations. We estimate the pulsar spin frequency and update the system orbital solution. Combining the average spin frequency from the previous observed, we confirm the long-term spin down at an average rateν SD = 1.5(2) × 10 −15 Hz s −1 . We also discuss possible corrections to the spin down rate accounting for mass accretion onto the compact object when the system is X-ray active. Finally, combining the updated ephemerides with those of the previous outbursts, we find a long-term orbital evolution compatible with a binary expansion at a mean rateṖ orb = 3.6(4) × 10 −12 s s −1 , in agreement with previously reported values. This fast evolution is incompatible with an evolution driven by angular momentum losses caused by gravitational radiation under the hypothesis of conservative mass transfer. We discuss the observed orbital expansion in terms of non-conservative mass transfer and gravitational quadrupole coupling mechanism. We find that the latter can explain, under certain conditions, small fluctuations (of the order of few seconds) of the orbital period around a global parabolic trend. At the same time, a non-conservative mass transfer is required to explain the observed fast orbital evolution, which likely reflects ejection of a large fraction of mass from the inner Lagrangian point caused by the irradiation of the donor by the magneto-dipole rotator during quiescence (radio-ejection model). This strong outflow may power tidal dissipation in the companion star and be responsible of the gravitational quadrupole change oscillations.

show abstract

“…In recent works, Xing et al (2015) and de Oña Wilhelmi et al (2016)identified a possible gamma-ray counterpart of SAX J1808.4−3658, and spectral modeling of the Fermi Large Area Telescope (FERMI/LAT) data impliesthat (if the counterpart is confirmed) about 30% of the spin-down energy is transformed into gammarays, providing further evidence in favor of this scenario, although no gamma-ray pulsations have been found so far.…”

Section: Introductionmentioning

confidence: 98%

Radio Pulse Search and X-Ray Monitoring of SAX J1808.4−3658: What Causes Its Orbital Evolution?

Patruno

Jaodand

Kuiper

et al. 2017

ApJ

View full text Add to dashboard Cite

The accreting millisecond X-ray pulsar SAX J1808.4−3658 shows a peculiar orbital evolution that proceeds at a very fast pace. It is important to identify the underlying mechanism responsible for this behavior because it can help to understand how this system evolves and which physical processes (such asmass loss or spin-orbit coupling) are occurring in the binary. It has also been suggested that, when in quiescence, SAX J1808.4−3658 turns on as a radio pulsar, a circumstance that might provide a link between accreting millisecond pulsars and black-widow (BW) radio pulsars. In this work, we report the results of a deep radio pulsation search at 2 GHz using the Green Bank Telescope in 2014 August and an X-ray study of the 2015 outburst with Chandra, SwiftXRT, and INTEGRAL. In quiescence, we detect no radio pulsationsand place the strongest limit to date on the pulsed radio flux density of any accreting millisecond pulsar. We also find that the orbit of SAX J1808.4−3658 continues evolving at a fast pace. We compare the orbital evolution of SAX J1808.4−3658 to that of several other accreting and nonaccreting binaries, including BWs, redbacks, cataclysmic variables, black holes, and neutron stars in lowmass X-ray binaries. We discuss two possible scenarios: either the neutron star has a large moment of inertia and is ablating the donor, generating massloss with an efficiency of 40%, or the donor star has a strong magnetic field of at least 1 kG and is undergoing quasi-cyclic variations due to spin-orbit coupling.

show abstract

SAX J1808.4−3658, an accreting millisecond pulsar shining in gamma rays?

Cited by 20 publications

References 49 publications

The Likely Fermi Detection of the Be X-Ray Binary GRO J1008-57

The Likely Fermi Detection of the Be X-Ray Binary GRO J1008-57

On the timing properties of SAX J1808.4−3658 during its 2015 outburst

Radio Pulse Search and X-Ray Monitoring of SAX J1808.4−3658: What Causes Its Orbital Evolution?

Contact Info

Product

Resources

About