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Your search keyword '"Grefenstette, B. W."' showing total 6 results
Start Over Author "Grefenstette, B. W." Journal monthly notices of the royal astronomical society
6 results on '"Grefenstette, B. W."'

1. A new transient ultraluminous X-ray source in NGC 7090

Author

Walton, D J, primary, Heida, M, additional, Bachetti, M, additional, Fürst, F, additional, Brightman, M, additional, Earnshaw, H, additional, Evans, P A, additional, Fabian, A C, additional, Grefenstette, B W, additional, Harrison, F A, additional, Israel, G L, additional, Lansbury, G B, additional, Middleton, M J, additional, Pike, S, additional, Rana, V, additional, Roberts, T P, additional, Rodriguez Castillo, G A, additional, Salvaterra, R, additional, Song, X, additional, and Stern, D, additional

Published
2020
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2. Measuring the masses of magnetic white dwarfs: a NuSTAR legacy survey

Author

Shaw, A W, primary, Heinke, C O, additional, Mukai, K, additional, Tomsick, J A, additional, Doroshenko, V, additional, Suleimanov, V F, additional, Buisson, D J K, additional, Gandhi, P, additional, Grefenstette, B W, additional, Hare, J, additional, Jiang, J, additional, Ludlam, R M, additional, Rana, V, additional, and Sivakoff, G R, additional

Published
2020
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3. The soft state of the black hole transient source MAXI J1820+070: emission from the edge of the plunge region?

Author

Fabian, A C, primary, Buisson, D J, additional, Kosec, P, additional, Reynolds, C S, additional, Wilkins, D R, additional, Tomsick, J A, additional, Walton, D J, additional, Gandhi, P, additional, Altamirano, D, additional, Arzoumanian, Z, additional, Cackett, E M, additional, Dyda, S, additional, Garcia, J A, additional, Gendreau, K C, additional, Grefenstette, B W, additional, Homan, J, additional, Kara, E, additional, Ludlam, R M, additional, Miller, J M, additional, and Steiner, J F, additional

Published
2020
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4. A new transient ultraluminous X-ray source in NGC 7090.

Author

Walton, D J, Heida, M, Bachetti, M, Fürst, F, Brightman, M, Earnshaw, H, Evans, P A, Fabian, A C, Grefenstette, B W, Harrison, F A, Israel, G L, Lansbury, G B, Middleton, M J, Pike, S, Rana, V, Roberts, T P, Rodriguez Castillo, G A, Salvaterra, R, Song, X, and Stern, D

Subjects
GALACTIC X-ray sources, X-rays, BLACK holes, ACCRETION (Astrophysics), PULSARS, SIGNAL-to-noise ratio, NEUTRON stars
Abstract

We report on the discovery of a new, transient ultraluminous X-ray source (ULX) in the galaxy NGC 7090. This new ULX, which we refer to as NGC 7090 ULX3, was discovered via monitoring with Swift during 2019–2020, and to date has exhibited a peak luminosity of L X ∼ 6 × 1039 erg s−1. Archival searches show that, prior to its recent transition into the ULX regime, ULX3 appeared to exhibit a fairly stable luminosity of L X ∼ 1038 erg s−1. Such strong long-time-scale variability may be reminiscent of the small population of known ULX pulsars, although deep follow-up observations with XMM–Newton and NuSTAR do not reveal any robust X-ray pulsation signals. Pulsations similar to those seen from known ULX pulsars cannot be completely excluded, however, as the limit on the pulsed fraction of any signal that remains undetected in these data is ≲20 per cent. The broad-band spectrum from these observations is well modelled with a simple thin disc model, consistent with sub-Eddington accretion, which may instead imply a moderately large black hole accretor (M BH ∼ 40 M⊙). Similarly, though, more complex models consistent with the super-Eddington spectra seen in other ULXs (and the known ULX pulsars) cannot be excluded given the limited signal-to-noise ratio of the available broad-band data. The nature of the accretor powering this new ULX therefore remains uncertain. [ABSTRACT FROM AUTHOR]

Published
2021
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6. The soft state of the black hole transient source MAXI J1820+070: emission from the edge of the plunge region?

Author

Fabian, A. C., Buisson, D. J, Kosec, P., Reynolds, C. S., Wilkins, D. R., Tomsick, J. A., Walton, D. J., Gandhi, P., Altamirano, D., Arzoumanian, Z., Cackett, E. M., Dyda, S., Garcia, J. A., Gendreau, K. C., Grefenstette, B. W, Harrison, F. A., Homan, J., Kara, E., Ludlam, R. M., Miller, J. M., and Steiner, J. F.

Subjects
media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, law.invention, Gravitation, Telescope, General Relativity and Quantum Cosmology, law, 0103 physical sciences, Black-body radiation, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Accretion (meteorology), 010308 nuclear & particles physics, Astronomy and Astrophysics, Black hole, Neutron star, Space and Planetary Science, Sky, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The Galactic black hole X-ray binary MAXI J1820+070 had a bright outburst in 2018 when it became the second brightest X-ray source in the Sky. It was too bright for X-ray CCD instruments such as XMM-Newton and Chandra, but was well observed by photon-counting instruments such as NICER and NuSTAR. We report here on the discovery of an excess emission component during the soft state. It is best modelled with a blackbody spectrum in addition to the regular disk emission, modelled either as diskbb or kerrbb. Its temperature varies from about 0.9 to 1.1 keV which is about 30 to 80 per cent higher than the inner disc temperature of diskbb. Its flux varies between 4 and 12 percent of the disc flux. Simulations of magnetised accretion discs have predicted the possibility of excess emission associated with a non-zero torque at the Innermost Stable Circular Orbit (ISCO) about the black hole, which from other NuSTAR studies lies at about 5 gravitational radii or about 60 km (for a black hole mass is 8 M). In this case the emitting region at the ISCO has a width varying between 1.3 and 4.6 km and would encompass the start of the plunge region where matter begins to fall freely into the black hole., Comment: 8 pages, 10 figures, accepted for publication in MNRAS

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