Ultracompact X-Ray Binaries with Neon-rich Degenerate Donors

Juett, Adrienne M.; Psaltis, Dimitrios; Chakrabarty, Deepto

doi:10.1086/324225

Cited by 103 publications

(195 citation statements)

References 27 publications

(29 reference statements)

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“…Nelson et al 1986;Verbunt 1987; see also Juett et al 2001). The short duration of the X-ray bursts from XB 1745−25 and 4U 1820−30 ( < ∼ 25 s) is consistent with the fuel being only helium (Bildsten 1995).…”

Section: Discussionsupporting

confidence: 52%

Photospheric radius expansion X-ray bursts as standard candles

Kuulkers

Hartog

Zand³

et al. 2003

A&A

373

448

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Abstract. We examined the maximum bolometric peak luminosities during type I X-ray bursts from the persistent or transient luminous X-ray sources in globular clusters. We show that for about two thirds of the sources the maximum peak luminosities during photospheric radius expansion X-ray bursts extend to a critical value of 3.79±0.15×10 38 erg s −1 , assuming the total X-ray burst emission is entirely due to black-body radiation and the recorded maximum luminosity is the actual peak luminosity. This empirical critical luminosity is consistent with the Eddington luminosity limit for hydrogen poor material. Since the critical luminosity is more or less always reached during photospheric radius expansion X-ray bursts (except for one source), such bursts may be regarded as empirical standard candles. However, because significant deviations do occur, our standard candle is only accurate to within 15%. We re-evaluated the distances to the twelve globular clusters in which the X-ray bursters reside.

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Section: Discussionsupporting

confidence: 52%

Photospheric radius expansion X-ray bursts as standard candles

Kuulkers

Hartog

Zand³

et al. 2003

A&A

373

448

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“…These donors, given enough time, may cool down and crystallize, forming a Ne-enriched layer in their interiors (Yungelson et al 2002). The subsequent MT eventually uncovers the deeper layers of the hybrid WD giving rise to a Ne-enriched accretion flow, claimed to be observed in several of the NS UCBs (Juett, Psaltis, & Chakrabarty 2001). As our simulations show, a significant fraction of the NS UCBs have hybrid WD donors.…”

Section: Formation Channelsmentioning

confidence: 57%

Galactic Populations of Ultracompact Binaries

Belczyński

Taam

2004

ApJ

110

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Recent RXTE and Chandra discoveries of low-mass X-ray binaries with ultrashort orbital periods have initiated theoretical work on the origins of these peculiar systems. Using the StarTrack population synthesis code, we analyze the formation and evolution of X-ray ultracompact binaries (UCBs) in the Galactic field. The relative number of UCBs with a neutron star or a black hole accretor populating our Galaxy is predicted. Our results demonstrate that standard evolutionary scenarios involving primordial binaries can be sufficient to produce the UCBs in the Galactic field without requiring additional processes associated with the dense stellar environments in the cores of globular clusters. In contrast to previous studies, we find that the majority of the immediate progenitors of these systems consist of a hydrogen-exhausted donor with an ONeMg white dwarf. The evolution of these systems leads to the accretion-induced collapse of the white dwarf to a neutron star, which can play an important role in the formation of a majority of Galactic UCBs. We predict that with an increase in the number of X-rayactive UCBs hosting neutron stars by an order of magnitude, a system with a black hole accretor may be found.

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“…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. Superbursts are expected to occur only in systems with accretion rates in excess of about 10% of the Eddington rate, i.e., the rate which yields emission at the Eddington limit (Cumming & Bildsten 2001;Strohmayer & Brown 2002).…”

Section: Introductionmentioning

confidence: 90%

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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Ultracompact X-Ray Binaries with Neon-rich Degenerate Donors

Cited by 103 publications

References 27 publications

Photospheric radius expansion X-ray bursts as standard candles

Photospheric radius expansion X-ray bursts as standard candles

Galactic Populations of Ultracompact Binaries

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

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