Browsing by Author "Elvis, Martin"

Now showing items 1-20 of 42

    • Absorption in X-ray spectra of high-redshift quasars 

      Elvis, Martin S.; Fiore, Fabrizio; Wilkes, Belinda Jane; McDowell, Jonathan Christopher; Bechtold, Jill (IOP Publishing, 1994)
      We present evidence that X-ray absorption is common in high-redshift quasars. We have studied six high-redshift (z approximately 3) quasars with the ROSAT Position Sensitive Proportional Counter (PSPC) of which four are ...

    • ASCA observations of two steep soft X-ray quasars 

      Fiore, F.; Matt, G.; Cappi, M.; Elvis, Martin S.; Leighly, K. M.; Nicastro, F.; Piro, L.; Siemiginowska, Aneta L.; Wilkes, Belinda Jane (Oxford University Press (OUP), 1998)
      Steep soft X-ray (0.1-2 keV) quasars share several unusual properties: narrow Balmer lines, strong FeII emission, large and fast X-ray variability, rather steep 2-10 keV spectrum. These intriguing objects have been suggested ...

    • Atlas of quasar energy distributions 

      Elvis, Martin S.; Wilkes, Belinda Jane; McDowell, Jonathan Christopher; Green, Richard F.; Bechtold, Jill; Willner, Steven P.; Oey, M. S.; Polomski, Elisha; Cutri, Roc (IOP Publishing, 1994)
      We present an atlas of the spectral energy distributions (SEDs) of normal, nonblazar, quasars over the whole available range (radio to 10 keV X-rays) of the electromagnetic spectrum. The primary (UVSX) sample includes 47 ...

    • The Cambridge-Cambridge ROSAT Serendipity Survey - III. VLA observations and the evolution of radio-quiet and radio-loud objects 

      Ciliegi, P.; Elvis, Martin S.; Wilkes, Belinda Jane; Boyle, B. J.; McMahon, R. G.; Maccacaro, T. (Oxford University Press (OUP), 1995)
      We present the results of the VLA radio observations at 1.475 GHz (20 cm) of the active galactic nuclei (AGN) in the Cambridge-Cambridge ROSAT Serendipity Survey (CRSS), a sample of 123 faint X-ray sources with ...

    • The Cambridge-Cambridge ROSAT Serendipity Survey -- IV. The X-ray properties 

      Ciliegi, P.; Elvis, Martin S.; Wilkes, Belinda Jane; Boyle, B. J.; McMahon, R. G. (Oxford University Press (OUP), 1997)
      We present a detailed X-ray spectral analysis in the 0.1–2.4 keV ROSAT band of a complete sample of X-ray-selected AGN using the 80 AGNs in the Cambridge-Cambridge ROSAT Serendipity Survey (68 QSOs and 12 narrow-emission-line ...

    • The Cambridge-Cambridge ROSAT Serendipity Survey -- V. Catalogue and optical identifications 

      Boyle, B. J.; Wilkes, Belinda Jane; Elvis, Martin S. (Oxford University Press (OUP), 1997)
      We report the results of a medium-depth X-ray survey of 20 ROSAT Position Sensitive Proportional Counter (PSPC) fields. 123 X-ray sources were detected down to a flux limit of S(0.5–2 keV) > 2 × 10−14 erg s−1 cm−2 lying ...

    • The Cambridge–Cambridge ROSAT Serendipity Survey – II. Classification of X-ray-luminous Galaxies 

      Boyle, B.J.; McMahon, R.G.; Wilkes, Belinda Jane; Elvis, Martin S. (Royal Astronomical Society, 1995)
      We present the results of an intermediate-resolution (1.5\AA) spectroscopic study of 17 X-ray luminous narrow emission-line galaxies previously identified in the Cambridge-Cambridge {\it ROSAT} Serendipity Survey and the ...

    • Chandra Discovery of a 100 kiloparsec X-Ray Jet in PKS 0637–752 

      Schwartz, D. A.; Marshall, H. L.; Lovell, J. E. J.; Piner, B. G.; Tingay, S. J.; Birkinshaw, M.; Chartas, G.; Elvis, Martin S.; Feigelson, E. D.; Ghosh, K. K.; Harris, D. E.; Hirabayashi, H.; Hooper, E. J.; Jauncey, D. L.; Lanzetta, K. M.; Mathur, S.; Preston, R. A.; Tucker, W. H.; Virani, S.; Wilkes, Belinda Jane; Worrall, Diana M. (IOP Publishing, 2000)
      The quasar PKS 0637-752, the first celestial X-ray target of the Chandra X-Ray Observatory, has revealed asymmetric X-ray structure extending from 3'' to 12'' west of the quasar, coincident with the inner portion of the ...

    • Chandra Study of an Overdensity of X-Ray Sources around Two Distant (z ~ 0.5) Clusters 

      Cappi, M.; Mazzotta, P.; Elvis, Martin S.; Burke, D. J.; Comastri, A.; Fiore, F.; Forman, William R.; Fruscione, Antonella; Green, P.; Harris, D.; Hooper, E. J.; Jones, C.; Kaastra, J. S.; Kellogg, E.; Murray, S.; McNamara, Brian David; Nicastro, F.; Ponman, T. J.; Schlegel, E. M.; Siemiginowska, Aneta L.; Tananbaum, Harvey D.; Vikhlinin, Alexey A.; Virani, S.; Wilkes, Belinda Jane (IOP Publishing, 2001)
      We present results from a Chandra X-Ray Observatory study of the field X-ray source populations in four different observations: two high-redshift (z ~ 0.5) clusters of galaxies 3C 295 and RX J003033.2+261819; and two ...

    • The Complex Optical to Soft X-Ray Spectrum of Low-Redshift Radio-quiet Quasars. II. Comparison with Free-Free and Accretion Disk Models 

      Fiore, Fabrizio; Elvis, Martin S.; Siemiginowska, Aneta L.; Wilkes, Belinda Jane; McDowell, Jonathan Christopher; Mathur, Smita (IOP Publishing, 1995)
      We compare the optical to soft X-ray spectral energy distributions (SEDs) of a sample of bright low-redshift (0.048 < z < 0.155), radio-quiet quasars, with a range of thermal models which have been proposed to explain the ...

    • The complex optical to soft x-ray spectrum of the low-redshift radio-quiet quasars 

      Fiore, Fabrizio; Elvis, Martin S.; McDowell, Jonathan Christopher; Siemiginowska, Aneta L.; Wilkes, Belinda Jane (IOP Publishing, 1994)
      Eight high signal-to-noise ROSAT Position Sensitive Proportional Counter (PSPC) observations of six low-redshift (o.048 less than z less than 0.155) radio-quiet quasars have been analyzed to study ant soft excess. All the ...

    • The Complex X‐Ray Absorbers of NGC 3516 Observed by BEPPOSAX 

      Costantini, E.; Nicastro, F.; Fruscione, Antonella; Mathur, S.; Comastri, A.; Elvis, Martin S.; Fiore, F.; Salvini, C.; Stirpe, G. M.; Vignali, C.; Wilkes, Belinda Jane; O’Brien, P. T.; Goad, M. R. (IOP Publishing, 2000)
      In this paper we present the analysis of two broadband (0.1-150 keV) BeppoSAX observations of the Seyfert 1 galaxy NGC 3516. The two observations were taken 4 months apart, on 1996 November 8 and 1997 March 12. We report ...

    • Discovery of Associated Absorption Lines in an X-Ray Warm Absorber:[ITAL]Hubble Space Telescope[/ITAL] Observations of PG 1114+445 

      Mathur, Smita; Wilkes, Belinda Jane; Elvis, Martin S. (IOP Publishing, 1998)
      The unified picture of X-ray/UV absorbers offers a unique opportunity to probe the nuclear environment of active galactic nuclei. To test the unified absorber scenario and to understand the physical properties of the ...

    • The diversity of soft X-ray spectra in quasars 

      Elvis, Martin S.; Wilkes, Belinda Jane; Tananbaum, Harvey D. (IOP Publishing, 1985)
      Soft X-ray spectra for three quasars obtained with the Einstein Imaging Proportional Counter covering the 0.1-4.0 keV band are reported. Power-law fits to these spectra have best-fit energy indices of 1.2 +0.6 or -0.2, for ...

    • The Far‐Infrared Spectral Energy Distributions of X‐Ray–selected Active Galaxies 

      Kuraszkiewicz, Joanna; Wilkes, Belinda Jane; Eric, undefined; Hooper, J.; McLeod, Kim K.; Wood, Kenneth; Bjorkman, Jon; Delain, Kisha M.; Hughes, David H.; Elvis, Martin S.; Impey, Chris D.; Lonsdale, Carol J.; Malkan, Matt A.; McDowell, Jonathan Christopher; Whitney, Barbara (IOP Publishing, 2003)
      Hard X-ray selection is, arguably, the optimal method for defining a representative sample of active galactic nuclei (AGNs). Hard X-rays are unbiased by the effects of obscuration and reprocessing along the line of sight ...

    • Infrared to x-ray spectral energy distributions of high redshift quasars 

      Bechtold, Jill; Elvis, Martin S.; Fiore, Fabrizio; Kuhn, Olga; Cutri, Roc M.; McDowell, Jonathan Christopher; Rieke, Marcia; Siemiginowska, Aneta L.; Wilkes, Belinda Jane (IOP Publishing, 1994)
      We have observed 14 quasars with z greater than 2.8 with the ROSAT-PSPC, and detected 12 of them, including the z=4.11 quasar 0000-263. We present the first x-ray spectrum of a radio quiet quasar with z greater than 3, ...

    • Is optical Fe II emission related to the soft X-ray properties of quasars? 

      Wilkes, Belinda Jane; Elvis, Martin S.; McHardy, Ian (IOP Publishing, 1987)
      Radio-quiet quasars generally show broad, blended multiplets of Fe II emission in their optical and UV spectra. Radio-loud quasars also show UV Fe II emission, but their optical Fe II emission is generally weaker. No ...

    • Mid-Infrared-Selected Quasars. I. Virial Black Hole Mass and Eddington Ratios 

      Dai, Y. Sophia; Elvis, Martin S.; Bergeron, Jacqueline; Fazio, Giovanni Gene; Huang, Jia-Sheng; Wilkes, Belinda Jane; Willmer, Christopher N. A.; Omont, Alain; Papovich, Casey (IOP Publishing, 2014)
      We provide a catalog of 391 mid-infrared-selected (MIR; 24 μm) broad-emission-line (BEL; type 1) quasars in the 22 deg2 SWIRE Lockman Hole field. This quasar sample is selected in the MIR from Spitzer MIPS with S 24 > 400 ...

    • Multiple Velocity Components in the C iv Absorption Line of NGC 5548 

      Mathur, Smita; Elvis, Martin S.; Wilkes, Belinda Jane (IOP Publishing, 1999)
      We have observed the much-studied Seyfert 1 galaxy NGC 5548 with the Goddard High-Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). Our 14 ks observation covers the C IV emission line at a resolution of ...

    • The Nuclear Spectroscopic Telescope Array (NuSTAR) High-Energy X-Ray Mission 

      Harrison, Fiona A.; Craig, William W.; Christensen, Finn E.; Hailey, Charles J.; Zhang, William W.; Boggs, Steven E.; Stern, Daniel; Cook, W. Rick; Forster, Karl; Giommi, Paolo; Grefenstette, Brian W.; Kim, Yunjin; Kitaguchi, Takao; Koglin, Jason E.; Madsen, Kristin K.; Mao, Peter H.; Miyasaka, Hiromasa; Mori, Kaya; Perri, Matteo; Pivovaroff, Michael J.; Puccetti, Simonetta; Rana, Vikram R.; Westergaard, Niels J.; Willis, Jason; Zoglauer, Andreas; An, Hongjun; Bachetti, Matteo; Barrière, Nicolas M.; Bellm, Eric C.; Bhalerao, Varun; Brejnholt, Nicolai F.; Fuerst, Felix; Liebe, Carl C.; Markwardt, Craig B.; Nynka, Melania; Vogel, Julia K.; Walton, Dominic J.; Wik, Daniel R.; Alexander, David M.; Cominsky, Lynn R.; Hornschemeier, Ann E.; Hornstrup, Allan; Kaspi, Victoria M.; Madejski, Greg M.; Matt, Giorgio; Molendi, Silvano; Smith, David M.; Tomsick, John A.; Ajello, Marco; Ballantyne, David R.; Baloković, Mislav; Barret, Didier; Bauer, Franz E.; Blandford, Roger D.; Brandt, W. Niel; Brenneman, Laura W.; Chiang, James; Chakrabarty, Deepto; Chenevez, Jerome; Comastri, Andrea; Dufour, Francois; Elvis, Martin S.; Fabian, Andrew C.; Farrah, Duncan; Fryer, Chris L.; Gotthelf, Eric V.; Grindlay, Jonathan E.; Helfand, David J.; Krivonos, Roman; Meier, David L.; Miller, Jon M.; Natalucci, Lorenzo; Ogle, Patrick; Ofek, Eran O.; Ptak, Andrew; Reynolds, Stephen P.; Rigby, Jane R.; Tagliaferri, Gianpiero; Thorsett, Stephen E.; Treister, Ezequiel; Urry, C. Megan (IOP Publishing, 2013)
      The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates in the band from 3 to 79 keV, extending the sensitivity of ...