An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core

(2012)

Authors:

S Gezari, R Chornock, A Rest, ME Huber, K Forster, E Berger, PJ Challis, JD Neill, DC Martin, T Heckman, A Lawrence, C Norman, G Narayan, RJ Foley, GH Marion, D Scolnic, L Chomiuk, A Soderberg, K Smith, RP Kirshner, AG Riess, SJ Smartt, CW Stubbs, JL Tonry, WM Wood-Vasey, WS Burgett, KC Chambers, T Grav, JN Heasley, N Kaiser, R-P Kudritzki, EA Magnier, JS Morgan, PA Price

Ubiquitous equatorial accretion disc winds in black hole soft states

Monthly Notices of the Royal Astronomical Society: Letters 422:1 (2012)

Authors:

G Ponti, RP Fender, MC Begelman, RJH Dunn, J Neilsen, M Coriat

Abstract:

High-resolution spectra of Galactic black holes (GBHs) reveal the presence of highly ionized absorbers. In one GBH, accreting close to the Eddington limit for more than a decade, a powerful accretion disc wind is observed to be present in softer X-ray states and it has been suggested that it can carry away enough mass and energy to quench the radio jet. Here we report that these winds, which may have mass outflow rates of the order of the inner accretion rate or higher, are a ubiquitous component of the jet-free soft states of all GBHs. We furthermore demonstrate that these winds have an equatorial geometry with opening angles of few tens of degrees, and so are only observed in sources in which the disc is inclined at a large angle to the line of sight. The decrease in Fe XXV/Fe XXVI line ratio with Compton temperature, observed in the soft state, suggests a link between higher wind ionization and harder spectral shapes. Although the physical interaction between the wind, accretion flow and jet is still not fully understood, the mass flux and power of these winds and their presence ubiquitously during the soft X-ray states suggest they are fundamental components of the accretion phenomenon. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS.

An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core.

Nature 485:7397 (2012) 217-220

Authors:

S Gezari, R Chornock, A Rest, ME Huber, K Forster, E Berger, PJ Challis, JD Neill, DC Martin, T Heckman, A Lawrence, C Norman, G Narayan, RJ Foley, GH Marion, D Scolnic, L Chomiuk, A Soderberg, K Smith, RP Kirshner, AG Riess, SJ Smartt, CW Stubbs, JL Tonry, WM Wood-Vasey, WS Burgett, KC Chambers, T Grav, JN Heasley, N Kaiser, R-P Kudritzki, EA Magnier, JS Morgan, PA Price

Abstract:

The flare of radiation from the tidal disruption and accretion of a star can be used as a marker for supermassive black holes that otherwise lie dormant and undetected in the centres of distant galaxies. Previous candidate flares have had declining light curves in good agreement with expectations, but with poor constraints on the time of disruption and the type of star disrupted, because the rising emission was not observed. Recently, two 'relativistic' candidate tidal disruption events were discovered, each of whose extreme X-ray luminosity and synchrotron radio emission were interpreted as the onset of emission from a relativistic jet. Here we report a luminous ultraviolet-optical flare from the nuclear region of an inactive galaxy at a redshift of 0.1696. The observed continuum is cooler than expected for a simple accreting debris disk, but the well-sampled rise and decay of the light curve follow the predicted mass accretion rate and can be modelled to determine the time of disruption to an accuracy of two days. The black hole has a mass of about two million solar masses, modulo a factor dependent on the mass and radius of the star disrupted. On the basis of the spectroscopic signature of ionized helium from the unbound debris, we determine that the disrupted star was a helium-rich stellar core.

Impact of Redshift Information on Cosmological Applications with Next-Generation Radio Surveys

ArXiv e-prints (2012)

Authors:

S Camera, MG Santos, DJ Bacon, MJ Jarvis, K McAlpine, RP Norris, A Raccanelli, H Röttgering

Mining the Herschel-ATLAS: submillimeter-selected blazars in equatorial fields

ArXiv e-prints (2012)

Authors:

M López-Caniego, J González-Nuevo, M Massardi, L Bonavera, D Herranz, M Negrello, G De Zotti, FJ Carrera, L Danese, S Fleuren, M Hardcastle, MJ Jarvis, H-R Klöckner, T Mauch, P Procopio, S Righini, W Sutherland, R Auld, M Baes, S Buttiglione, CJR Clark, A Cooray, A Dariush, L Dunne, S Dye, S Eales, R Hopwood, C Hoyos, E Ibar, RJ Ivison, S Maddox, E Valiante