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AstroSat view of MAXI J1535-571: broad-band spectro-temporal features
UR Rao Satellite Ctr, Space Astron Grp, ISITE Campus,Outer Ring Rd, Bangalore 560037, Karnataka, India.;Indian Inst Sci, Dept Phys, Bangalore 560012, Karnataka, India..
UR Rao Satellite Ctr, Space Astron Grp, ISITE Campus,Outer Ring Rd, Bangalore 560037, Karnataka, India.;Indian Inst Space Sci & Technol, Dept Earth & Space Sci, Thiruvananthapuram 695547, Kerala, India..
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
UR Rao Satellite Ctr, Space Astron Grp, ISITE Campus,Outer Ring Rd, Bangalore 560037, Karnataka, India..
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2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 487, no 1, p. 928-941Article in journal (Refereed) Published
Abstract [en]

We present the results of Target of Opportunity (ToO) observations made with AstroSat of the newly discovered black hole binary MAXI J1535-571. We detect prominent C-type quasi-periodic oscillations (QPOs) of frequencies varying from 1.85 to 2.88 Hz, along with distinct harmonics in all the AstroSat observations. We note that while the fundamental QPO is seen in the 3-50 keV energy band, the harmonic is not significant above similar to 35 keV. The AstroSat observations were made in the hard intermediate state, as seen from state transitions observed by MAXI and Swift. We attempt spectral modelling of the broad-band data (0.7-80 keV) provided by AstroSat using phenomenological and physical models. The spectral modelling using nthComp gives a photon index in the range 2.18-2.37 and electron temperature ranging from 21 to 63 keV. The seed photon temperature is within 0.19 to 0.29 keV. The high flux in 0.3-80 keV band corresponds to a luminosity varying from 0.7 to 1.07 L-Edd assuming the source to be at a distance of 8 kpc and hosting a black hole with a mass of 6 M-circle dot. The physical model based on the two-component accretion flow gives disc accretion rates as high as similar to 1 (m) over dot(Edd) and halo rate similar to 0.2 (m) over dot(Edd), respectively. The near-Eddington accretion rate seems to be the main reason for the unprecedented high flux observed from this source. The two-component spectral fitting of AstroSat data also provides an estimate of a black hole mass between 5.14 and 7.83 M-circle dot.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS , 2019. Vol. 487, no 1, p. 928-941
Keywords [en]
accretion, black hole physics, stars: individual: MAXI J1535-571, X-rays: binaries
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:kth:diva-255481DOI: 10.1093/mnras/stz1327ISI: 000474907100071OAI: oai:DiVA.org:kth-255481DiVA, id: diva2:1352675
Note

QC 20190919

Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-19Bibliographically approved

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Iyer, Nirmal

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