Discovery of the Accretion-powered Millisecond Pulsar SWIFT J1756.9-2508 with a Low-Mass Companion

Krimm, H. A.; Markwardt, C. B.; Deloye, Christopher J.; Romano, P.; Chakrabarty, Deepto; Campana, S.; Cummings, J. R.; Galloway, D. K.; Gehrels, N.; Hartman, J. M.; Kaaret, P.; Morgan, E.; Tueller, J.

doi:10.1086/522959

Cited by 72 publications

(106 citation statements)

References 19 publications

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“…( 30 min) have been identified in the Galactic bulge. Third, only three UCXBs with orbital periods between 40 and 55 min, XTE J1807-294 (Markwardt et al 2003), XTE J1751-305 (Markwardt et al 2002) and SWIFT J1756.9-2508 (Krimm et al 2007), are presumably located in the Bulge, based on their positions in the sky, as their distances are not known. As for the predicted ∼1.9 × 10 5 long-period systems, the probable existence of three observed UCXBs with orbital periods shorter than 55 min in the Bulge can be used to calibrate the formation rate of UCXBs, independent of population synthesis.…”

Section: Discussionmentioning

confidence: 99%

Population synthesis of ultracompact X-ray binaries in the Galactic bulge

Haaften

Nelemans

Voss

et al. 2013

A&A

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Aims.We model the present-day number and properties of ultracompact X-ray binaries (UCXBs) in the Galactic bulge. The main objective is to compare the results to the known UCXB population as well as to data from the Galactic Bulge Survey, in order to learn about the formation of UCXBs and their evolution, such as the onset of mass transfer and late-time behavior. Methods. The binary population synthesis code SeBa and detailed stellar evolutionary tracks have been used to model the UCXB population in the Bulge. The luminosity behavior of UCXBs has been predicted using long-term X-ray observations of the known UCXBs as well as the thermal-viscous disk instability model. Results. In our model, the majority of UCXBs initially have a helium burning star donor. Of the white dwarf donors, most have helium composition. In the absence of a mechanism that destroys old UCXBs, we predict (0.2−1.9) × 10 5 UCXBs in the Galactic bulge, depending on assumptions, mostly at orbital periods longer than 60 min (a large number of long-period systems also follows from the observed short-period UCXB population). About 5−50 UCXBs should be brighter than 10 35 erg s −1 , mostly persistent sources with orbital periods shorter than about 30 min and with degenerate helium and carbon-oxygen donors. This is about one order of magnitude more than the observed number of (probably) three. Conclusions. This overprediction of short-period UCXBs by roughly one order of magnitude implies that fewer systems are formed, or that a super-Eddington mass transfer rate is more difficult to survive than we assumed. The very small number of observed longperiod UCXBs with respect to short-period UCXBs, the surprisingly high luminosity of the observed UCXBs with orbital periods around 50 min, and the properties of the PSR J1719−1438 system all point to much faster UCXB evolution than expected from angular momentum loss via gravitational wave radiation alone. Old UCXBs, if they still exist, probably have orbital periods longer than 2 h and have become very faint due to either reduced accretion or quiescence, or have become detached. UCXBs are promising candidate progenitors of isolated millisecond radio pulsars.

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Section: Discussionmentioning

confidence: 99%

Population synthesis of ultracompact X-ray binaries in the Galactic bulge

Haaften

Nelemans

Voss

et al. 2013

A&A

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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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“…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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Discovery of the Accretion-powered Millisecond Pulsar SWIFT J1756.9-2508 with a Low-Mass Companion

Cited by 72 publications

References 19 publications

Population synthesis of ultracompact X-ray binaries in the Galactic bulge

Population synthesis of ultracompact X-ray binaries in the Galactic bulge

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

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

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