Discovery of a High-Latitude Accreting Millisecond Pulsar in an Ultracompact Binary

Galloway, D. K.; Chakrabarty, Deepto; Morgan, E.; Remillard, Ronald A.

doi:10.1086/343841

Cited by 180 publications

(233 citation statements)

References 36 publications

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“…Burgay et al 2003), but, despite the eleven additional systems discovered since (e.g. Galloway et al 2002;Casella et al 2008), we have not obtained a positive result yet.…”

Section: Introductioncontrasting

confidence: 65%

Search for pulsations at high radio frequencies from accreting millisecond X-ray pulsars in quiescence

Iacolina

Burgay

Burderi

et al. 2010

A&A

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Context. It is commonly believed that millisecond radio pulsars have been spun up by transfer of matter and angular momentum from a low-mass companion during an X-ray active mass transfer phase. A subclass of low-mass X-ray binaries is that of the accreting millisecond X-ray pulsars, transient systems that show periods of X-ray quiescence during which radio emission could switch on. Aims. The aim of this work is to search for millisecond pulsations from three accreting millisecond X-ray pulsars, XTE J1751−305, XTE J1814−338, and SAX J1808.4−3658, observed during their quiescent X-ray phases at high radio frequencies (5 ÷ 8 GHz) in order to overcome the problem of the free-free absorption due to the matter engulfing the system. A positive result would provide definite proof of the recycling model, providing the direct link between the progenitors and their evolutionary products. Methods. The data analysis methodology has been chosen on the basis of the precise knowledge of orbital and spin parameters from X-ray observations. It is subdivided in three steps: we corrected the time series for the effects of (I) the dispersion due to interstellar medium and (II) of the orbital motions, and finally (III) folded modulo the spin period to increase the signal-to-noise ratio. Results. No radio signal with spin and orbital characteristics matching those of the X-ray sources has been found in our search, down to very low flux density upper limits. Conclusions. We analysed several mechanisms that could have prevented the detection of the signal, concluding that the low luminosity of the sources and the geometric factor are the most likely reasons for this negative result.

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“…Burgay et al 2003), but, despite the eleven additional systems discovered since (e.g. Galloway et al 2002;Casella et al 2008), we have not obtained a positive result yet.…”

Section: Introductioncontrasting

confidence: 65%

Search for pulsations at high radio frequencies from accreting millisecond X-ray pulsars in quiescence

Iacolina

Burgay

Burderi

et al. 2010

A&A

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“…The measured X-ray mass function ( f X (M) = 2.7 × 10 −7 M ) gives a minimum companion mass of M c = 0.008 M (i = 90 • , M X = 1.4 M ) and implies M c ≤ 0.03 M (95% c.l.) for a uniform a priori distribution of inclination angles (Galloway et al 2002). Chandra observations carried out during the 2002 outburst showed a featureless X-ray spectrum (0.5−8.3 keV) that is well fitted by a power-law + blackbody model with N H consistent to Galaxy line-of-sight values (0.8−1.0) × 10 21 cm −2 (Juett et al 2003).…”

Section: Xte J0929−314mentioning

confidence: 79%

“…This conclusion was further strengthened by the discovery of additional systems in the following years. Eight such systems are now known: SAX J1808.4−3658 (Wijnands & van der Klis 1998; Article published by EDP Sciences Chakrabarty & Morgan 1998); XTE J1751−305 (Markwardt et al 2002); XTE J0929−314 (Galloway et al 2002); XTE J1807−294 (Markwardt et al 2003a); XTE J1814−338 Strohmayer et al 2003); IGR J00291+5934 (Galloway et al 2005); HETE J1900.1-2455 and SWIFT J1756.9-2508 (Krimm et al 2007) 1 . These findings directly confirmed evolutionary models that link the neutron stars of LMXBs to those of millisecond radio pulsars, the former being the progenitors of the latter.…”

Section: Introductionmentioning

confidence: 99%

The optical counterparts of accreting millisecond X-ray pulsars during quiescence

D’Avanzo

Campana²,

Casares

et al. 2009

A&A

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Context. Eight accreting millisecond X-ray pulsars (AMXPs) are known to date. Although these systems are well studied at high energies, very little information is available for their optical/NIR counterparts. Up to now, only two of them, SAX J1808.4−3658 and IGR J00291+5934, have a secure multi-band detection of their optical counterparts in quiescence. Aims. All these systems are transient low-mass X-ray binaries. Optical and NIR observations carried out during quiescence give a unique opportunity to constrain the nature of the donor star and to investigate the origin of the observed quiescent luminosity at long wavelengths. In addition, optical observations can be fundamental as they ultimately allow us to estimate the compact object mass through mass function measurements. Methods. Using data obtained with the ESO-Very Large Telescope, we performed a deep optical and NIR photometric study of the fields of XTE J1814−338 and of the ultracompact systems XTE J0929−314 and XTE J1807−294 during quiescence in order to look for the presence of a variable counterpart. If suitable candidates were found, we also carried out optical spectroscopy. Results. We present here the first multi-band (VR) detection of the optical counterpart of XTE J1814−338 in quiescence together with its optical spectrum. The optical light curve shows variability in both bands consistent with a sinusoidal modulation at the known 4.3 h orbital period and presents a puzzling decrease of the V-band flux around superior conjunction that may be interpreted as a partial eclipse. The marginal detection of the very faint counterpart of XTE J0929−314 and deep upper limits for the optical/NIR counterpart of XTE J1807−294 are also reported. We also briefly discuss the results reported in the literature for the optical/NIR counterpart of XTE J1751−305. Conclusions. Our findings are consistent with AMXPs being systems containing an old, weakly magnetized neutron star, reactivated as a millisecond radio pulsar during quiescence which irradiates the low-mass companion star. The absence of type I X-ray bursts and of hydrogen and helium lines in outburst spectra of ultracompact (P orb < 1 h) AMXPs suggests that the companion stars are likely evolved dwarf stars.

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“…Since 1998, fourteen such systems have been discovered, with orbital periods in the range of 40 min to 19 h and spin frequencies from 1.7 to 5.4 ms (Wijnands & van der Klis 1998;Chakrabarty & Morgan 1998;Markwardt et al 2002;Galloway et al 2002;Campana et al 2003;Strohmayer et al 2003;Galloway et al 2005;Kaaret et al 2006;Krimm et al 2007;Casella et al 2008;Altamirano et al 2008;Altamirano et al 2010;Papitto et al 2010;Markwardt & Strohmayer 2010;Altamirano et al 2011;Papitto et al 2011). Since they have been spun up by accretion (see, e.g., Falanga et al 2005), their initial mass should have increased by at least 0.1-0.2 M compared to the canonical neutron star mass (e.g., Thorsett & Chakrabarty 1999).…”

Section: Introductionmentioning

confidence: 99%

A search for the near-infrared counterpart of the eclipsing millisecond X-ray pulsar Swift J1749.4–2807

D’Avanzo

Campana

Muñoz-Darias

et al. 2011

A&A

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Context. Swift J1749.4-2807 is a transient accreting millisecond X-ray pulsars and the first to display X-ray eclipses. It therefore holds a strong potential for accurate mass measurements in a low-mass X-ray binary system. Aims. Determining the companion star's radial velocity would make it possible to fully resolve the system and to accurately measure the mass of the neutron star based on dynamical measurements. Unfortunately, no optical or near infrared (NIR) counterpart has been identified to date for this system, whether in outburst or in quiescence.Methods. We performed a photometric study of the field of Swift J1749.4-2807 during quiescence to search for a variable counterpart. The source direction lies on the Galactic plane, making any search for its optical/NIR counterpart challenging. To minimize the effects of field crowding and interstellar extinction, we carried out our observations using the adaptive optics NIR imager NACO mounted at the ESO Very Large Telescope (VLT).Results. From the analysis of public Swift X-ray data obtained during outburst, we derived the most precise (1.6 radius) position for this source. Due to the extreme stellar crowding of the field, 41 sources are detected in our VLT images within the X-ray error circle, with some of them possibly showing variability consistent with the expectations. Conclusions. We carried out the first deep imaging campaign devoted to the search for the quiescent NIR counterpart of Swift J1749.4-2807. Our results allow us to provide constraints on the nature of the companion star of this system. Furthermore, they suggest that future phase-resolved NIR observations (performed with large-aperture telescopes and adaptive optics) covering the full orbital period of the system are likely to identify the quiescent counterpart of Swift J1749.4-2807, through measuring its orbital variability, opening the possibility of dynamical studies of this unique source.

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Discovery of a High-Latitude Accreting Millisecond Pulsar in an Ultracompact Binary

Cited by 180 publications

References 36 publications

Search for pulsations at high radio frequencies from accreting millisecond X-ray pulsars in quiescence

Search for pulsations at high radio frequencies from accreting millisecond X-ray pulsars in quiescence

The optical counterparts of accreting millisecond X-ray pulsars during quiescence

A search for the near-infrared counterpart of the eclipsing millisecond X-ray pulsar Swift J1749.4–2807

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