The optical counterpart of SAX J1808.4 -- 3658, the transient bursting millisecond X-ray pulsar

Giles, A. B.; Hill, K. M.; Greenhill, J.

doi:10.1046/j.1365-8711.1999.02361.x

Cited by 40 publications

(74 citation statements)

References 18 publications

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“…The optical intensity of this source faded as the X-ray source declined, and a 2 hr orbital modulation was marginally detected in the optical flux (Giles, Hill, & Greenhill 1999). This 2 hr optical modu-lation was subsequently confirmed in observations during quiescence (Homer et al 2001).…”

Section: Introductionsupporting

confidence: 61%

“…This is particularly evident in the JKT and Mount Canopus observations on MJD 50,921, which were spaced by half a day but differ by 0.2 mag in V and I. One possible contribution to this discrepancy is the 2 hr orbital flux modulation reported by Giles et al (1999), with an amplitude of Ӎ0.07 mag. To account for this in our fits, we added a systematic uncertainty of this size in quadrature to the statistical uncertainties quoted in Table 1.…”

Section: Observations and Resultsmentioning

confidence: 98%

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The Optical Counterpart of the Accreting Millisecond Pulsar SAX J1808.4−3658 in Outburst: Constraints on the Binary Inclination

Wang

Chakrabarty

Roche

et al. 2001

The Astrophysical Journal

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We present multiband optical/IR photometry of V4580 Sgr, the optical counterpart of the accretion-powered millisecond pulsar SAX J1808.4Ϫ3658, taken during the 1998 X-ray outburst of the system. The optical flux is consistent with emission from an X-ray-heated accretion disk. Self-consistent modeling of the X-ray and optical emission during the outburst yields a best-fit extinction of and an inclination of emission and are too bright to be from either the disk or the companion, even in the presence of X-ray heating.

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Section: Introductionsupporting

confidence: 61%

Section: Observations and Resultsmentioning

confidence: 98%

The Optical Counterpart of the Accreting Millisecond Pulsar SAX J1808.4−3658 in Outburst: Constraints on the Binary Inclination

Wang

Chakrabarty

Roche

et al. 2001

The Astrophysical Journal

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“…On the other hand, with the significant exception of SAX J1808.4−3658 and IGR J00291+5934, their optical/NIR quiescent counterparts are only poorly known. The optical light curve of SAX J1808.4−3658 in outburst and quiescence shows variability modulated at the orbital period, in antiphase with the X-ray light curve (Giles et al 1999;Homer et al 2001;Campana et al 2004;Deloye et al 2008;Wang et al 2009). This is unlike other quiescent transients that normally show a double-humped morphology, due to an ellipsoidal modulation, and indicates that the companion star is exposed to some irradiation.…”

Section: Introductionmentioning

confidence: 94%

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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“…If the persistent spectrum would have been similar to when the persistent flux was measured, the upper limit on the flux would be 3 × 10 −10 erg cm −2 s −1 (in 2-28 keV, for 10 4 s exposures). Figure 2 shows the error regions of all bursts with respect to that of the persistent emission and the optical counterpart (Giles et al 1998). There is no doubt that these bursts are from SAX J1808.4-3658.…”

Section: Observationsmentioning

confidence: 99%

The first outburst of SAX J1808.4-3658 revisited

Zand

Cornelisse

Kuulkers

et al. 2001

A&A

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Abstract. Data of the 1996 outburst of the single-known accreting millisecond pulsar SAX J1808.4-3658, taken with the Wide Field Cameras (WFCs) on BeppoSAX, are revisited with more complete data coverage and more comprehensive analysis techniques than in a previous report. An additional type-I X-ray burst was identified which occurred at a time when the persistent emission is below the detection limit, roughly 30 days after outburst maximum. This burst is three times longer than the first two bursts, and 50% brighter. It is the brightest burst within the ∼1700 type-I bursts detected so far with the WFCs. A spectral analysis of the data reveals a distance to SAX J1808.4-3658 of ∼2.5 kpc. This is an update from a previously reported value of 4 kpc. We present the evidence that we have for the presence of oscillations at the pulsar frequency during part of the newly found burst. Such an oscillation would lend support to the idea that the frequency of millisecond burst oscillations in other objects is very close to the neutron star rotation frequency.

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The optical counterpart of SAX J1808.4 -- 3658, the transient bursting millisecond X-ray pulsar

Cited by 40 publications

References 18 publications

The Optical Counterpart of the Accreting Millisecond Pulsar SAX J1808.4−3658 in Outburst: Constraints on the Binary Inclination

The Optical Counterpart of the Accreting Millisecond Pulsar SAX J1808.4−3658 in Outburst: Constraints on the Binary Inclination

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

The first outburst of SAX J1808.4-3658 revisited

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