Optical Modulation in the X-Ray Binary 4U 1543–624 Revisited

Wang, Z.; Tziamtzis, Anestis; Kaplan, David L.; Chakrabarty, Deepto

doi:10.1017/pasa.2015.36

Cited by 9 publications

(6 citation statements)

References 32 publications

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“…The persistent LMXB 4U 1543-624 is an ultra-compact binary with an orbital period of 18.20 ± 0.09 minutes (Wang et al 2015). We used an uncertainty on the orbital period about 7 times larger than the nominal one.…”

Section: U 1543-624mentioning

confidence: 99%

A Deep Pulse Search in 11 Low Mass X-Ray Binaries

Patruno

Messenger

2018

ApJ

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We present a systematic coherent X-ray pulsation search in eleven low mass X-ray binaries (LMXBs). We select a relatively broad variety of LMXBs, including persistent and transient sources and spanning orbital periods between 0.3 and 17 hours. We use about 3.6 Ms of data collected by the Rossi X-Ray Timing Explorer (RXTE) and XMM-Newton and apply a semi-coherent search strategy to look for weak and persistent pulses in a wide spin frequency range. We find no evidence for X-ray pulsations in these systems and consequently set upper limits on the pulsed sinusoidal semi-amplitude between 0.14% and 0.78% for ten outbursting/persistent LMXBs and 2.9% for a quiescent system. These results suggest that weak pulsations might not form in (most) non-pulsating LMXBs.

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Section: U 1543-624mentioning

confidence: 99%

A Deep Pulse Search in 11 Low Mass X-Ray Binaries

Patruno

Messenger

2018

ApJ

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“…4U 1543−624 is a UCXB with an orbital period of 18.2 ± 0.1 minutes (Wang & Chakrabarty 2004;Wang et al 2015) located at a distance between D ∼ 1.4-11.5 kpc (Wang & Chakrabarty 2004;Bailer-Jones et al 2018;Serino et al 2018). The nature of the compact object in 4U 1543−624 is uncertain, but very likely an NS from a tentative association with a Type-1 X-ray burst seen by MAXI (Serino et al 2018) and its radio-X-ray behavior (Ludlam et al 2017b(Ludlam et al , 2019bTetarenko et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous NICER and NuSTAR Observations of the Ultracompact X-Ray Binary 4U 1543–624

Ludlam

Jaodand

García

et al. 2021

ApJ

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We present the first joint NuSTAR and NICER observations of the ultracompact X-ray binary (UCXB) 4U 1543−624 obtained in 2020 April. The source was at a luminosity of L 0.5−50 keV = 4.9(D/7 kpc)2 × 1036 erg s−1 and showed evidence of reflected emission in the form of an O viii line, Fe K line, and Compton hump within the spectrum. We used a full reflection model, known as xillverCO, that is tailored for the atypical abundances found in UCXBs, to account for the reflected emission. We tested the emission radii of the O and Fe line components and conclude that they originate from a common disk radius in the innermost region of the accretion disk (R in ≤ 1.07 R ISCO). Assuming that the compact accretor is a neutron star (NS) and the position of the inner disk is the Alfvén radius, we placed an upper limit on the magnetic field strength to be B ≤ 0.7(D/7 kpc) × 108 G at the poles. Given the lack of pulsations detected and position of R in, it was likely that a boundary layer region had formed between the NS surface and inner edge of the accretion disk with an extent of 1.2 km. This implies a maximum radius of the neutron star accretor of R NS ≤ 12.1 km when assuming a canonical NS mass of 1.4 M ⊙.

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“…By definition, confirmation of J0840 as an UCXB can only be obtained through the measurement of the orbital period. A method that proved to be successful in relatively low-inclination systems has been the detection of a periodic optical modulation in photometric observations (e.g., Zhong & Wang 2011;Wang et al 2015). This arises from X-ray heating of the donor star by the irradiating X-ray source and to the variation of the visible area of the heated face as a function of the orbital phase.…”

Section: Discussionmentioning

confidence: 99%

Multi-band observations of Swift J0840.7-3516: a new transient ultra-compact X-ray binary candidate

Zelati,

Postigo,

Russell

et al. 2021

Preprint

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We report on multi-band observations of the transient source Swift J0840.7−3516, which was detected in outburst in 2020 February by the Neil Gehrels Swift Observatory. The outburst episode lasted just ∼5 days, during which the observed X-ray flux quickly decreased from ∼ 1.8 × 10 −9 erg cm −2 s −1 at peak down to ∼ 1.3 × 10 −13 erg cm −2 s −1 in quiescence (0.3-10 keV). Such a marked and rapid decrease in the flux was also registered at UV and optical wavelengths. In outburst, the source showed considerable aperiodic variability in the X-rays on timescales as short as a few seconds. The spectrum of the source in the energy range 0.3-20 keV was well described by a thermal (blackbody-like) component plus a non-thermal (power law-like) component, and softened considerably as the source returned to quiescence. The spectrum of the optical counterpart in quiescence showed broad emission features associated mainly with ionized carbon and oxygen, superposed on a blue continuum. No evidence for bright continuum radio emission was found in quiescence. We discuss possible scenarios for the nature of this source, and show that the observed phenomenology points to a transient ultra-compact X-ray binary system.

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Optical Modulation in the X-Ray Binary 4U 1543–624 Revisited

Cited by 9 publications

References 32 publications

A Deep Pulse Search in 11 Low Mass X-Ray Binaries

A Deep Pulse Search in 11 Low Mass X-Ray Binaries

Simultaneous NICER and NuSTAR Observations of the Ultracompact X-Ray Binary 4U 1543–624

Multi-band observations of Swift J0840.7-3516: a new transient ultra-compact X-ray binary candidate

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