Browsing by Author "Buchner, J."

Now showing 1 - 11 of 11
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    A search for a surviving companion in SN 1006
    (2018) Kerzendorf, W. E.; Strampelli, G.; Shen, K. J.; Schwab, J.; Pakmor, R.; Do, T.; Buchner, J.; Rest, A.
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    Cosmic evolution and metal aversion in superluminous supernova host galaxies
    (2018) Schulze, Steve; Krühler, T.; Leloudas, G.; Gorosabel, J.; Mehner, A.; Buchner, J.; Kim, Sam; Ibar, Edo; Amorín, Ricardo; Herrero Illana, Rubén; Anderson, Joseph; Bauer, Franz Erik
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    Galaxy gas as obscurer - I. GRBs x-ray galaxies and find an NH^3 propto M_{star} relation
    (2017) Buchner, J.; Schulze, S.; Bauer, Franz Erik
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    Low-frequency View of GW170817/GRB 170817A with the Giant Metrewave Radio Telescope.
    (2018) Resmi, L.; Sam, Kim.; Schulze, Steve.; Ishwara-Chandra, C. H.; Misra, K.; Buchner, J.; Pasquale, M. de; Sánchez-Ramírez, R.; Klose,Sylvio; Tanvir, N. R.; O’Brien, P. T.
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    New spectral model for constraining torus covering factors from broadband X-ray spectra of active galactic nuclei
    (2018) Baloković, M.; Brightman, M.; Harrison, F.A.; Comastri, A.; Ricci, Claudio; Buchner, J.; Gandhi, P.; Farrah, D.; Stern, D.
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    Quantifying the Bayesian Evidence for a Planet in Radial Velocity Data
    (2020) Nelson, B. E.; Ford, E. B.; Buchner, J.; Cloutier, R.; Diaz, R. F.; Faria, J. P.; Hara, N. C.; Rajpaul, V. M.; Rukdee, Surangkhana
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    SPIDERS: selection of spectroscopic targets using AGN candidates detected in all-sky X-ray surveys
    (OXFORD UNIV PRESS, 2017) Dwelly, T.; Salvato, M.; Merloni, A.; Brusa, M.; Buchner, J.; Anderson, S. F.; Boller, Th.; Brandt, W. N.; Budavari, T.; Clerc, N.; Coffey, D.; Del Moro, A.; Georgakakis, A.; Green, P. J.; Jin, C.; Menzel, M. L.; Myers, A. D.; Nandra, K.; Nichol, R. C.; Ridl, J.; Schwope, A. D.; Simm, T.
    SPIDERS (SPectroscopic IDentification of eROSITA Sources) is a Sloan Digital Sky Survey IV (SDSS-IV) survey running in parallel to the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected active galactic nuclei (AGN) and galaxy cluster members detected in wide-area eROSITA, XMM-Newton and ROSAT surveys. We describe the methods used to choose spectroscopic targets for two sub-programmes of SPIDERS X-ray selected AGN candidates detected in the ROSAT All Sky and the XMM-Newton Slew surveys. We have exploited a Bayesian cross-matching algorithm, guided by priors based on mid-IR colourmagnitude information from the Wide-field Infrared Survey Explorer survey, to select the most probable optical counterpart to each X-ray detection. We empirically demonstrate the high fidelity of our counterpart selection method using a reference sample of bright welllocalized X-ray sources collated from XMM-Newton, Chandra and Swift-XRT serendipitous catalogues, and also by examining blank-sky locations. We describe the down-selection steps which resulted in the final set of SPIDERS-AGN targets put forward for spectroscopy within the eBOSS/TDSS/SPIDERS survey, and present catalogues of these targets. We also present catalogues of similar to 12 000 ROSAT and similar to 1500 XMM-Newton Slew survey sources that have existing optical spectroscopy from SDSS-DR12, including the results of our visual inspections. On completion of the SPIDERS programme, we expect to have collected homogeneous spectroscopic redshift information over a footprint of similar to 7500 deg(2) for > 85 per cent of the ROSAT and XMM-Newton Slew survey sources having optical counterparts in the magnitude range 17 < r < 22.5, producing a large and highly complete sample of bright X-ray-selected AGN suitable for statistical studies of AGN evolution and clustering.
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    X-Ray Bolometric Corrections for Compton-thick Active Galactic Nuclei
    (2017) Brightman, M.; Balokovic, M.; Ballantyne, D. R.; Bauer, Franz Erik; Boorman, P.; Buchner, J.; Brandt, W. N.; Comastri, A.; Del Moro, A.; Ricci, Claudio
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    X-ray constraints on the fraction of obscured active galactic nuclei at high accretion luminosities
    (OXFORD UNIV PRESS, 2017) Georgakakis, A.; Salvato, M.; Liu, Z.; Buchner, J.; Brandt, W. N.; Ananna, T. Tasnim; Schulze, A.; Shen, Yue; LaMassa, S.; Nandra, K.; Merloni, A.; McGreer, I. D.
    The wide-area XMM-XXL X-ray survey is used to explore the fraction of obscured active galactic nuclei (AGNs) at high accretion luminosities, L-X(2-10 keV) greater than or similar to 10(44) erg s(-1), and out to redshift z approximate to 1.5. The sample covers an area of about 14 deg(2) and provides constraints on the space density of powerful AGNs over a wide range of neutral hydrogen column densities extending beyond the Compton-thick limit, N-H approximate to 10(24) cm(-2). The fraction of obscured Compton-thin (N-H = 10(22) - 10(24) cm(-2)) AGNs is estimated to be approximate to 0.35 for luminosities L-X(2-10 keV) > 10(44) erg s(-1), independent of redshift. For less luminous sources, the fraction of obscured Compton-thin AGNs increases from 0.45 +/- 0.10 at z = 0.25 to 0.75 +/- 0.05 at z = 1.25. Studies that select AGNs in the infrared via template fits to the observed spectral energy distribution of extragalactic sources estimate space densities at high accretion luminosities consistent with the XMM-XXL constraints. There is no evidence for a large population of AGNs (e.g. heavily obscured) identified in the infrared and missed at X-ray wavelengths. We further explore the mid-infrared colours of XMM-XXL AGNs as a function of accretion luminosity, column density and redshift. The fraction of XMM-XXL sources that lie within the mid-infrared colour wedges defined in the literature to select AGNs is primarily a function of redshift. This fraction increases from about 20-30 per cent at z = 0.25 to about 50-70 per cent at z = 1.5.
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    XZ: Deriving redshifts from X-ray spectra of obscured AGN
    (2018) Simmonds, C.; Buchner, J.; Salvato, M.; Hsu, L-T; Bauer, Franz Erik