Optical spectroscopy of (candidate) ultracompact X-ray binaries: constraints on the composition of the donor stars

Nelemans, G.; Jonker, P. G.; Steeghs, D.

doi:10.1111/j.1365-2966.2006.10496.x

Cited by 94 publications

(138 citation statements)

References 32 publications

(54 reference statements)

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“…Among the possible scenarios of formation and evolution of ultracompact X-ray binaries that we have reported in Sect. 4.1, only an evolved mainsequence companion star is supposed to show hydrogen features in its optical spectrum but they should be detected together with prominent helium lines (Nelemans et al 2006). The detection of H absorption features together with the non-detection of He lines in the spectrum of our source and the absence of variability in the light curve suggests that our candidate is not the quiescent optical counterpart of XTE J1807−294 but more likely an earlytype main-sequence star.…”

Section: A Search For the Optical Counterpart During Quiescencementioning

confidence: 92%

“…4, the detection of hydrogen from one of these systems would be a key discriminant in determining the validity of the first scenario (which involves an evolved main-sequence or a He-burning star) with respect to the second one (white dwarf companion). Optical spectroscopy of XTE J0929−314 carried out during outburst did not reveal any clear evidence of hydrogen or helium lines (Nelemans et al 2006). In addition, we note that, at variance with what is observed for all the compact systems, none of the ultracompact AMXPs showed type-I X-ray bursts.…”

Section: Discussionmentioning

confidence: 99%

“…These authors also report the evidence of an excess in the R and I band in the BVRI broadband spectrum (similar to what observed in SAX J1808.4−3658 and XTE J1814−338), that may be due to synchrotron emission in matter flowing out of the system. The optical spectrum of XTE J0929−314, carried out during outburst, shows a strong feature around 4640 Å, probably due to C or N emission, and no clear evidence for H/He emission or absorption lines (Nelemans et al 2006). During quiescence, XTE J0929−314 was barely 26.9 ± 0.4 0 .28 ± 0.02 12.1 ± 0.4 Values in column three are uncorrected for reddening.…”

Section: Xte J0929−314mentioning

confidence: 99%

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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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Section: A Search For the Optical Counterpart During Quiescencementioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Xte J0929−314mentioning

confidence: 99%

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

D’Avanzo

Campana²,

Casares

et al. 2009

A&A

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“…However, no evidence of He (or H) has been found so far in optical spectra, with rather stringent upper limits: He and/or H are at most present at the 10% level (Werner et al 2006). These spectra suggest the donor star to be a C/O white dwarf (Nelemans et al 2003(Nelemans et al , 2006Werner et al 2006). This seems to be at odds (see Juett et al 2001;Juett & Chakrabarty 2003) with the fact that we see bursts in 4U 0614+091, which are usually understood as being due to unstable ignition of He or H. Moreover, 4U 0614+091 is an interesting case among the sources showing superbursts.…”

Section: Introductionmentioning

confidence: 99%

What ignites on the neutron star of 4U 0614+091?

Kuulkers¹,

Zand

Atteia

et al. 2010

A&A

103

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The low-mass X-ray binary 4U 0614+091 is a source of sporadic thermonuclear (type I) X-ray bursts. We find bursts with a wide variety of characteristics in serendipitous wide-field X-ray observations by the WATCH on EURECA, the ASM on RXTE, the WFCs on BeppoSAX, the FREGATE on HETE-2, the IBIS/ISGRI on INTEGRAL, and the BAT on Swift, as well as pointed observations with the PCA and HEXTE on RXTE. Most of the bursts are bright, i.e., they reach a peak flux of about 15 Crab, but a few are weak and only reach a peak flux below a Crab. One of the bursts shows a very strong photospheric radius-expansion phase. This allows us to evaluate the distance to the source, which we estimate to be 3.2 kpc. The burst durations vary generally from about 10 s to 5 min. However, after one of the intermediate-duration bursts, a faint tail is seen to at least about 2.4 h after the start of the burst. One very long burst was observed, which lasted for several hours. This superburst candidate was followed by a normal type-I burst only 19 days later. This is, to our knowledge, the shortest burst-quench time among the superbursters. The observation of a superburst in this system is difficult to reconcile if the system is accreting at about 1% of the Eddington limit. We describe the burst properties in relation to the persistent emission. No strong correlations are apparent, except that the intermediate-duration bursts occurred when 4U 0614+091's persistent emission was lowest and calm, and when bursts were infrequent (on average roughly one every month to 3 months). The average burst rate increased significantly after this period. The maximum average burst recurrence rate is about once every week to 2 weeks. The burst behaviour may be partly understood if there is at least an appreciable amount of helium present in the accreted material from the donor star. If the system is an ultra-compact X-ray binary with a CO white-dwarf donor, as has been suggested, this is unexpected. If the bursts are powered by helium, we find that the energy production per accumulated mass is about 2.5 times less than expected for pure helium matter.

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“…Because their sizes are comparable to the donor Roche lobe dimension, the most likely Spectra and polametric observations are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A99 companion star candidates for UCXBs are white dwarfs or helium burning stars (Nelson et al 1986). This inference was later confirmed through the observation of strong helium and carbonoxygen lines in their spectra (Schulz et al 2001;Nelemans et al 2004Nelemans et al , 2006.…”

Section: Introductionmentioning

confidence: 70%

Polarimetric and spectroscopic optical observations of the ultra-compact X-ray binary 4U 0614+091

Baglio

Mainetti

D’Avanzo

et al. 2014

A&A

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Aims. We present a polarimetric and spectroscopic study of the persistent ultra-compact X-ray binary 4U 0614+091 aimed at searching for the emission of a relativistic particle jet and at unveiling the orbital period P orb of the system. Methods. We obtained r-band polarimetric observations with the Telescopio Nazionale Galileo (TNG) equipped with the PAOLO polarimeter and with the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument, covering ∼2 h and ∼0.5 h observations, respectively. We carried out low resolution spectroscopy of the system using the ESO Very Large Telescope equipped with FORS1 for ∼1.5 h (16 spectra covering the range 4300−8000 Å).Results. The polarimetric analysis performed starting from the TNG dataset revealed a polarisation degree in the r-band of 3% ± 1%. From the NOT dataset, due to the lower signal-to-noise ratio, we could obtain only a 3σ upper limit of 3.4%. From the joining of a spectroscopic and photometric analysis, through the study of the equivalent width variations of the CII 7240 Å line and the r-band light curve, we could find a hint of a ∼45 min periodicity. Conclusions. A polarisation degree P of ∼3% in the r-band is consistent with the emission of a relativistic particle jet, which is supposed to emit intrinsically linearly polarised synchrotron radiation. Since no variations of P with time have been detected, and the accretion disc of the system does not contain ionised hydrogen, scattering by free electrons in the accretion disc has been rejected. The period of ∼45 min obtained through the analysis of the system light curve and of the equivalent width variations of the selected spectral line is probably linked to the presence of a hot spot or a superhump in the accretion disc, and lead to an orbital period 1 h for the binary system.

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Optical spectroscopy of (candidate) ultracompact X-ray binaries: constraints on the composition of the donor stars

Cited by 94 publications

References 32 publications

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

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

What ignites on the neutron star of 4U 0614+091?

Polarimetric and spectroscopic optical observations of the ultra-compact X-ray binary 4U 0614+091

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