Discovery of the New X-Ray Transient MAXI J1807+132: A Candidate of a Neutron Star Low-mass X-Ray Binary

Shidatsu, M.; Tachibana, Y.; Yoshii, T.; Negoro, H.; Kawamuro, T.; Iwakiri, W.; Nakahira, S.; Makishima, Kazuo; Ueda, Yoshihiro; Kawai, N.; Serino, M.; Kennea, J. A.

doi:10.3847/1538-4357/aa93f0

Cited by 12 publications

(5 citation statements)

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“…We also note that Armas Padilla et al (2013b); Shidatsu et al (2017); Degenaar et al (2017) suggested the possible origin of the observed thermal emission in the X-ray spectra to be neutron star surface or the accretion disc. From Table 3, we observe that the obtained values of blackbody radius (2-3 kpc) are very similar to that have been found in other systems that are either proposed to be NS or are confirmed NS systems.…”

Section: Discussionmentioning

confidence: 71%

Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-xrt

Beri

Altamirano

Wijnands

et al. 2019

Monthly Notices of the Royal Astronomical Society

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MAXI J1957+032 is a transient Low-mass X-ray binary (LMXB) that underwent four short outbursts in 1.5 years since its discovery in 2015. The nature of the compact object in MAXI J1957+032 is not clear, but it was proposed to be a neutron star based on the short-duration of its outbursts. Here, we report the results obtained after performing spectral analysis using data obtained with the X-ray telescope aboard the Neil Gehrels Swift satellite. When describing the spectrum with an absorbed power law, we found that the spectra softens (the power-law index increases from ∼ 1.8 to 2.5) as the luminosity decreases. Near the end of its outbursts the observed value of power-law index (Γ) is ∼ 2.5. To identify the nature of the compact object in this system, we used Γ as a tracer of the spectral evolution with luminosity. We found that for the distance of 4 kpc, our results suggest that the source harbours a neutron star.

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Section: Discussionmentioning

confidence: 71%

Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-xrt

Beri

Altamirano

Wijnands

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Following previous works (e.g., Shidatsu et al 2017), we fixed r irr and f in , which were unconstrained with our data, at default values, 1.1 and 0.1, respectively, which are appropriate for the low/hard state spectra (Poutanen et al 1997). The other parameters were left as free parameters.…”

Section: Analysis Of Multi-wavelength Sedsmentioning

confidence: 99%

X-Ray, Optical, and Near-infrared Monitoring of the New X-Ray Transient MAXI J1820+070 in the Low/Hard State

Shidatsu

Nakahira

Yamada

et al. 2018

ApJ

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We report X-ray, optical, and near-infrared monitoring of the new X-ray transient MAXI J1820+070 discovered with MAXI on 2018 March 11. Its X-ray intensity reached ∼ 2 Crab in 2-20 keV at the end of March, and then gradually decreased until the middle of June. In this period, the X-ray spectrum was described by Comptonization of the disk emission, with a photon index of ∼1.5 and an electron temperature of ∼50 keV, which is consistent with a black hole X-ray binary in the low/hard state. The electron temperature and the photon index were slightly decreased and increased with increasing flux, respectively. The source showed significant X-ray flux variation on timescales of seconds. This shortterm variation was found to be associated with changes in the spectral shape, and the photon index became slightly harder at higher fluxes. This suggests that the variation was produced by a change in the properties of the hot electron cloud responsible for the strong Comptonization. Modeling a multi-wavelength SED around the X-ray flux peak at the end of March, covering the near-infrared to X-ray bands, we found that the optical and near-infrared fluxes were likely contributed substantially by the jet emission. Before this outburst, the source was never detected in the X-ray band with MAXI (with a 3σ upper limit of ∼0.2 mCrab in 4-10 keV, obtained from the 7-year data in 2009-2016), whereas weak optical and infrared activity was found at their flux levels ∼3 orders of magnitude lower than the peak fluxes in the outburst.

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“…MAXI J1807+132 (hereafter MAXI J1807) was first discovered by the nova-alert system of the Monitor of All-sky X-ray Image Gas Slit Camera (MAXI /GSC; Matsuoka et al 2009;Mihara et al 2011) during its 2017 outburst (Negoro et al 2017). This detection was followed up with The Neil Gehrels Swift Observatory (Swift; Gehrels 2004) X-Ray Telescope (XRT; Burrows et al 2003) observations, spectral analysis of which suggested a LMXB with a NS primary (Shidatsu et al 2017). Further X-ray studies with XMM-Newton's European Photon Imaging Camera (EPIC;Strüder et al 2001) and ground-based optical telescopes supported the NS identification, although the possibility of a BH primary could not be ruled out (Jiménez-Ibarra et al 2019).…”

Section: Introductionmentioning

confidence: 98%

Discovery of thermonuclear Type-I X-ray bursts from the X-ray binary MAXI J1807+132

Albayati

Altamirano

Jaisawal

et al. 2020

Monthly Notices of the Royal Astronomical Society

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MAXI J1807+132 is a low-mass X-ray binary (LMXB) first detected in outburst in 2017. Observations during the 2017 outburst did not allow for an unambiguous identification of the nature of the compact object. MAXI J1807+132 was detected in outburst again in 2019 and was monitored regularly with NICER. In this paper we report on five days of observations during which we detected three thermonuclear (Type-I) X-ray bursts, identifying the system as a neutron star LMXB. Time-resolved spectroscopy of the three Type-I bursts revealed typical characteristics expected for these phenomena. All three Type-I bursts show slow rises and long decays, indicative of mixed H/He fuel. We find no strong evidence that any of the Type-I bursts reached the Eddington Luminosity; however, under the assumption that the brightest X-ray burst underwent photospheric radius expansion, we estimate a <12.4 kpc upper limit for the distance. We searched for burst oscillations during the Type-I bursts from MAXI J1807+132 and found none ($<10\%$ amplitude upper limit at 95% confidence level). Finally, we found that the brightest Type-I burst shows a ∼ 1.6 sec pause during the rise. This pause is similar to one recently found with NICER in a bright Type-I burst from the accreting millisecond X-ray pulsar SAX J1808.4–3658. The fact that Type-I bursts from both sources can show this type of pause suggests that the origin of the pauses is independent of the composition of the burning fuel, the peak luminosity of the Type-I bursts, or whether the NS is an X-ray pulsar.

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Discovery of the New X-Ray Transient MAXI J1807+132: A Candidate of a Neutron Star Low-mass X-Ray Binary

Cited by 12 publications

References 53 publications

Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-xrt

Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-xrt

X-Ray, Optical, and Near-infrared Monitoring of the New X-Ray Transient MAXI J1820+070 in the Low/Hard State

Discovery of thermonuclear Type-I X-ray bursts from the X-ray binary MAXI J1807+132

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