Zobrazeno 1 - 10
of 411
pro vyhledávání: '"Alston, W."'
Autor:
Walton, D. J., Bachetti, M., Kosec, P., Furst, F., Pinto, C., Roberts, T. P., Soria, R., Stern, D., Alston, W. N., Brightman, M., Earnshaw, H. P., Fabian, A. C., Harrison, F. A., Middleton, M. J., Sathyaprakash, R.
We present a series of five new broadband X-ray observations of the ultraluminous X-ray source Holmberg IX X-1, performed by $XMM$-$Newton$ and $NuSTAR$ in coordination. The first three of these show high soft X-ray fluxes but a near total collapse o
Externí odkaz:
http://arxiv.org/abs/2409.12241
Active Galactic Nuclei are powered by accretion of matter onto a supermassive black hole (SMBH) of mass Mbh ~ 10^{5}-10^{9} Msun. The accretion process is indeed the most efficient mechanism for energy release we currently know of, with up to ~30-40%
Externí odkaz:
http://arxiv.org/abs/2206.11790
Autor:
Mallick, L., Fabian, A. C., García, J. A., Tomsick, J. A., Parker, M. L., Dauser, T., Wilkins, D. R., De Marco, B., Steiner, J. F., Connors, R. M. T., Mastroserio, G., Markowitz, A. G., Pinto, C., Alston, W. N., Lohfink, A. M., Gandhi, P.
The standard alpha-disc model predicts an anti-correlation between the density of the inner accretion disc and the black hole mass times square of the accretion rate, as seen in higher mass ($M_{\rm BH}>10^{6} M_{\odot}$) active galactic nuclei (AGNs
Externí odkaz:
http://arxiv.org/abs/2203.04522
Autor:
Parker, M. L., Alston, W. N., Härer, L., Igo, Z., Joyce, A., Buisson, D. J. K., Chainakun, P., Fabian, A. C., Jiang, J., Kosec, P., Matzeu, G. A., Pinto, C., Xu, Y., Zaidouni, F.
We examine archival XMM-Newton data on the extremely variable narrow-line Seyfert 1 (NLS1) active galactic nucleus (AGN) 1H 0707-495. We construct fractional excess variance (Fvar) spectra for each epoch, including the recent 2019 observation taken s
Externí odkaz:
http://arxiv.org/abs/2108.10167
Autor:
D'Aì, A., Pinto, C., Del Santo, M., Pintore, F., Soria, R., Robba, A., Ambrosi, E., Alston, W., Barret, D., Fabian, A. C., Fürst, F., Kara, E., Kosec, P., Middleton, M., Roberts, T., Rodriguez-Castillo, G., Walton, D. J.
Soft Ultra-Luminous X-ray (ULXs) sources are a subclass of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a few systems
Externí odkaz:
http://arxiv.org/abs/2108.09221
Autor:
Walton, D. J., Balokovic, M., Fabian, A. C., Gallo, L. C., Koss, M., Nardini, E., Reynolds, C. S., Ricci, C., Stern, D., Alston, W. N., Dauser, T., Garcia, J. A., Kosec, P., Reynolds, M. T., Harrison, F. A., Miller, J. M.
We present the first high signal-to-noise broadband X-ray spectrum of the radio-quiet type-2 Seyfert ESO 033-G002, combining data from $XMM$-$Newton$ and $NuSTAR$. The nuclear X-ray spectrum is complex, showing evidence for both neutral and ionised a
Externí odkaz:
http://arxiv.org/abs/2107.10278
Autor:
Robba, A., Pinto, C., Walton, D. J., Soria, R., Kosec, P., Pintore, F., Roberts, T. P., Alston, W. N., Middleton, M., Cusumano, G., Earnshaw, H. P., Fuerst, F., Sathyaprakash, R., Kyritsis, E., Fabian, A. C.
Publikováno v:
A&A 652, A118 (2021)
It is thought that ultraluminous X-ray sources (ULXs) are mainly powered by super-Eddington accreting neutron stars or black holes as shown by recent discovery of X-ray pulsations and relativistic winds. This work presents a follow up study of the sp
Externí odkaz:
http://arxiv.org/abs/2106.04501
Autor:
Alston, W. N., Pinto, C., Barret, D., D'Ai, A., Del Santo, M., Earnshaw, H., Fabian, A. C., Fuerst, F., Kara, E., Kosec, P., Middleton, M. J., Parker, M. L., Pintore, F., Robba, A., Roberts, T. P., Sathyaprakash, R., Walton, D., Ambrosi, E.
Most ultraluminous X-ray sources (ULXs) are believed to be stellar mass black holes or neutron stars accreting beyond the Eddington limit. Determining the nature of the compact object and the accretion mode from broadband spectroscopy is currently a
Externí odkaz:
http://arxiv.org/abs/2104.11163
Autor:
Pinto, C., Soria, R., Walton, D., D'Ai, A., Pintore, F., Kosec, P., Alston, W. N., Fuerst, F., Middleton, M. J., Roberts, T. P., Del Santo, M., Barret, D., Ambrosi, E., Robba, A., Earnshaw, H., Fabian, A.
Most ULXs are believed to be powered by super-Eddington accreting neutron stars and, perhaps, black holes. Above the Eddington rate the disc is expected to thicken and to launch powerful winds through radiation pressure. Winds have been recently disc
Externí odkaz:
http://arxiv.org/abs/2104.11164
Autor:
Härer, L., Parker, M. L., Joyce, A., Igo, Z., Alston, W. N., Fürst, F., Lobban, A. P., Matzeu, G. A., Reeves, J. N.
We present an improved model for excess variance spectra describing ultra-fast outflows and successfully apply it to the luminous (L ~ 10^47 erg/s) low-redshift (z = 0.184) quasar PDS 456. The model is able to account well for the broadening of the s
Externí odkaz:
http://arxiv.org/abs/2011.06472