The MAXI/GSC Nova-Alert System and results of its first 68 months

Negoro, H.; Kohama, M.; Serino, M.; Saito, Hiroki; Takahashi, T.; Miyoshi, Seiji; Ozawa, Hiroshi; Suwa, F.; Asada, M.; Fukushima, Kazuki; Eguchi, S.; Kawai, N.; Kennea, J. A.; Mihara, T.; Morii, M.; Nakahira, S.; Ogawa, Y.; Sugawara, A.; Tomida, H.; Ueno, S.; Ishikawa, M.; Isobe, Naoki; Kawamuro, T.; Kimura, Masashi; Masumitsu, T.; Nakagawa, Y. E.; Nakajima, M.; Sakamoto, T.; Shidatsu, M.; Sugizaki, M.; Sugimoto, J.; Suzuki, Kazuhiko; Takagi, T.; Tanaka, Kazuki; Tsuboi, Y.; Tsunemi, H.; Ueda, Yoshihiro; Yamaoka, K.; Yamauchi, M.; Yoshida, A.; Matsuoka, M.

doi:10.1093/pasj/psw016

Cited by 47 publications

(22 citation statements)

References 41 publications

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“…The MAXI transient alert system (Negoro et al 2016) signalled activity from 4U 1608−52 on 19 June 2018 June 19 (MJD 58288; nova ID 8288849999). When MAXI monitoring indicated that 4U 1608−52 had evolved beyond its outburst peak, we started to monitor the source with the X-ray telescope (XRT) aboard the Neil Gehrels Swift observatory (Swift; Gehrels et al 2004).…”

Section: Set Up Of the Observation Programmentioning

confidence: 99%

A strongly changing accretion morphology during the outburst decay of the neutron star X-ray binary 4U 1608−52

Eijnden

Degenaar

Ludlam

et al. 2020

Monthly Notices of the Royal Astronomical Society

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It is commonly assumed that the properties and geometry of the accretion flow in transient low-mass X-ray binaries (LMXBs) significantly change when the X-ray luminosity decays below ∼ 10 −2 of the Eddington limit (L Edd ). However, there are few observational cases where the evolution of the accretion flow is tracked in a single X-ray binary over a wide dynamic range. In this work, we use NuSTAR and NICER observations obtained during the 2018 accretion outburst of the neutron star LMXB 4U 1608−52, to study changes in the reflection spectrum. We find that the broad Fe-Kα line and Compton hump, clearly seen during the peak of the outburst when the X-ray luminosity is ∼ 10 37 erg s −1 (∼ 0.05 L Edd ), disappear during the decay of the outburst when the source luminosity drops to ∼ 4.5 × 10 35 erg s −1 (∼ 0.002 L Edd ). We show that this non-detection of the reflection features cannot be explained by the lower signal-to-noise at lower flux, but is instead caused by physical changes in the accretion flow. Simulating synthetic NuSTAR observations on a grid of inner disk radius, disk ionisation, and reflection fraction, we find that the disappearance of the reflection features can be explained by either increased disk ionisation (log ξ 4.1) or a much decreased reflection fraction. A changing disk truncation alone, however, cannot account for the lack of reprocessed Fe-Kα emission. The required increase in ionisation parameter could occur if the inner accretion flow evaporates from a thin disk into a geometrically thicker flow, such as the commonly assumed formation of an radiatively inefficient accretion flow at lower mass accretion rates.

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Section: Set Up Of the Observation Programmentioning

confidence: 99%

A strongly changing accretion morphology during the outburst decay of the neutron star X-ray binary 4U 1608−52

Eijnden

Degenaar

Ludlam

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Each photon direction typically has errors of 1.5 deg in the scan direction and ∼2 deg in the orthogonal direction at FWHM, corresponding to the point spread function (PSF) of the camera. A nominal GSC camera can detect transient events with a 2-20 keV flux greater than 2 ×10 −9 erg cm −2 s −1 (e.g., Serino et al 2014;Negoro et al 2016) in a scan transit. At the time of the GW170817 observation, seven cameras of ID 0, 2, 3, 4, 5, 6, and 7 were functioning (Mihara et al 2014), and the GSC observed the position using camera ID 2 on the zenith module and using camera ID 4 and 5 on the horizontal module for 10 days after the GW trigger.…”

Section: Instrumentation and Operationmentioning

confidence: 99%

“…Figure 1 shows Xray images of the GSC observation in (a) the first orbit, (b) one day, and (c) ten days with the 90% and 50% probability contours of localization by the LALInference v2 map of GW170817. The MAXI/GSC real-time transient monitor and alert system (novaalert system) is continuously operating (Negoro et al 2016). The nova-alert system detects transient events with fluxes >80 mCrab in a one-orbit scan and sends an alert to the world in less than 30 s after the onboard detection of the transient.…”

Section: Observation Of Gw170817mentioning

confidence: 99%

MAXI upper limits of the electromagnetic counterpart of GW170817

Sugita

Kawai

Nakahira

et al. 2018

Publications of the Astronomical Society of Japan

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We report the MAXI observation of the gravitational-wave (GW) event GW170817 and the electromagnetic counterpart of GW170817. GW170817 is a binary neutron star coalescence candidate detected by the Advanced LIGO and Advanced Virgo detectors, and it is the first event for which the optical counterpart has been discovered. In the MAXI observation, the Gas Slit Camera (GSC) covered approximately 62% of the sky region of the GW event within 90% probability during the first 92 min of orbit after the trigger. No significant X-ray transient was detected in the error region, and the upper limit of the average flux with a significance of 3 σ in the 2-10 keV band was 53/26 mCrab (one-orbit observation/one-day observation). In the optical counterpart of GW170817, the observational window of GSC at the position started at 20 s after the GW trigger, but the high voltage of GSC was unfortunately off at the time because the ISS was entering a high-particle-background region. The first observation of the position by GSC was eventually performed at 16797 sec (4.6 hours) since the GW trigger, yielding the 3 σ upper limit of 8.60×10 −9 erg cm −2 s −1 in the 2-10 keV band, though it was the earliest X-ray observation of the counterpart.

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“…The data from 2009 August 15th to 2011 August 15th are used there. All the data they used were delivered from the MAXI database system [7].…”

Section: Maxi Monitoring Observationsmentioning

confidence: 99%

A Universal Correlation between the Duration and the X-ray Luminosity in Stellar Flares

Tsuboi¹,

Sasaki²,

Sugawara³

et al. 2018

Proceedings of XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop — PoS(MULTIF2017)

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The MAXI/GSC Nova-Alert System and results of its first 68 months

Cited by 47 publications

References 41 publications

A strongly changing accretion morphology during the outburst decay of the neutron star X-ray binary 4U 1608−52

A strongly changing accretion morphology during the outburst decay of the neutron star X-ray binary 4U 1608−52

MAXI upper limits of the electromagnetic counterpart of GW170817

A Universal Correlation between the Duration and the X-ray Luminosity in Stellar Flares

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