Results 31 to 40 of about 4,576 (128)

Variability Time Scales of TeV Blazars Observed in the ASCA Continuous Long-Look X-ray Monitoring [PDF]

, 2001
Three uninterrupted, long (lasting respectively 7, 10, and 10 days) ASCA observations of the well-studied TeV-bright blazars Mrk 421, Mrk 501 and PKS 2155-304 all show continuous strong X-ray flaring. Despite the relatively faint intensity states in 2 of
Kataoka, Jun, Kouda, Manabu, Madejski, Greg M., Madejski, Greg M., Takahashi, Tadayuki, Tanihata, Chiharu, Tashiro, Makoto, Urry, C. Megan, Urry, C. Megan, Wagner, Stefan J., Wagner, Stefan J., 古宇田, 学, 片岡, 淳, 田代, 信, 谷畑, 千春, 高橋, 忠幸   +15 more
core   +2 more sources

The fast UV variability of the active galactic nucleus in Fairall 9

, 2014
We present results from a new optical/UV/X-ray monitoring campaign of the luminous Seyfert galaxy Fairall 9 using the Swift satellite. Using the UV-Optical Telescope (UVOT) on Swift, we find correlated optical/UV variability on all time scales ranging ...
Lohfink, Anne, Miller, Neal, Mushotzky, Richard, Reynolds, Christopher, Vasudevan, Ranjan   +4 more
core   +1 more source

Multiwavelength campaign on Mrk 509. XIII. Testing ionized-reflection models on Mrk 509 [PDF]

, 2014
Active Galactic Nuclei (AGN) are the most luminous persistent objects in the universe. An excess of X-ray emission below about 2 keV, called soft-excess, is very common in Type 1 AGN spectra. The origin of this feature remains debated. Originally modeled
B. De Marco, C. P. de Vries, C. Pinto, E. Behar, E. Costantini, G. A. Kriss, G. Branduardi-Raymont, G. Ponti, J. Ebrero, J. S. Kaastra, K. C. Steenbrugge, M. Cappi, M. Mehdipour, N. Arav, P.-O. Petrucci, S. Bianchi, S. Paltani   +16 more
core   +8 more sources

Chandra Grating Spectroscopy of the Seyfert Galaxy Ton S180 [PDF]

, 2000
This paper presents results from spectral observations of Ton S180 using Chandra and ASCA. The data confirm the presence of the soft excess but the Chandra LETG spectrum reveals it to be broad and smooth, rather than resolved into individual emission ...
Boller T., Brandt W. N., Brandt W. N., Comastri A., D. M. Crenshaw, G. Kriss, I. M. George, J. Wang, K. Nandra, Kaastra J. S., Leahy D. A., Matt G., Pounds K. A., Puchnarewicz E. M., Reynolds C. S., S. Kraemer, T. J. Turner, T. Yaqoob, W. Zheng, Wisotzki A.   +19 more
core   +2 more sources

Spectral monitoring of AGNs: Preliminary results for Ark 564 and Arp 102B

, 2011
We present preliminary results of the long term spectral monitoring of two active galactic nuclei with different broad line shapes: Ark 564 and Arp 102B.
Burenkov, A. N., Chavushyan, V. H., Ilic, D., Kovacevic, A., Kovacevic, J., Popovic, L. C., Shapovalova, A. I.   +6 more
core   +2 more sources

Long-Term X-ray Spectral Variability in Seyfert 1 Galaxies

, 2003
Direct time-resolved spectral fitting has been performed on continuous RXTE monitoring of seven Seyfert 1 galaxies in order to study their broadband spectral variability and Fe K alpha variability characteristics on time scales of days to years ...
A. Markowitz, Fabian A. C., George I. M., Guilbert P., Iwasawa K., Magdziarz P., Matt G., Nandra K., R. Edelson, Reynolds C. S., S. Vaughan, Swank J.   +11 more
core   +1 more source

Discovery of a new Transient X-ray Pulsar in the Small Magellanic Cloud [PDF]

, 2002
Rossi X-Ray Timing Explorer observations of the Small Magellanic Cloud have revealed a previously unknown transient X-ray pulsar with a pulse period of 95s.
Buckley, C. Markwardt, Corbet, Corbet, Corbet, D. Perrodin, Edelson, F. E. Marshall, Finger, Groenewegen, Haberl, Haberl, Jahoda, Kahabka, Kahabka, Lindsay, Lochner, M. J. Coe, Maeder, Meyssonnier, Negueruela, Popov, R. H. D. Corbet, S. Laycock, Santangelo, Stanimirovic, Stavely-Smith, Stella, Swank, Yokogawa   +29 more
core   +2 more sources

A ~4.6 h quasi-periodic oscillation in the BL Lacertae PKS 2155-304?

, 2009
We report a possible detection of an ~4.6-hour quasi-periodic oscillation (QPO) in the 0.3-10 keV emission of the high-energy peaked blazar PKS 2155-304 from a 64 ks observation by the XMM-Newton EPIC/pn detector. We identify a total modulation of ~5% in
A. C. Gupta, Abramowicz, Abramowicz, Aharonian, Aharonian, Balmaverde, Balmaverde, Blandford, Brinkmann, Böttcher, Camenzind, Carini, Chakrabarti, Courvoisier, Dolcini, Dominici, Edelson, Espaillat, Foschini, Foschini, Ghisellini, Gierlinski, Gopal-Krishna, Gupta, H. Gaur, Kolomogorov, Lachowicz, Liu, Mangalam, Marscher, Marshall, P. J. Wiita, P. Lachowicz, Paltani, Perez, Pesce, Pian, Piner, Press, Rani, Remillard, Romero, Rutman, Sakamoto, Schwarzenberg-Czerny, Schwarzenberg-Czerny, Simonetti, Torrence, Urry, Urry, Vaughan, Zhang   +51 more
core   +1 more source

Reverberation Mapping and the Physics of Active Galactic Nuclei [PDF]

, 1997
Reverberation-mapping campaigns have revolutionized our understanding of AGN. They have allowed the direct determination of the broad-line region size, enabled mapping of the gas distribution around the central black hole, and are starting to resolve the
A Robinson, BM Peterson, BM Peterson, BM Peterson, BM Peterson, BM Peterson, BM Peterson, C Done, C Winge, C Winge, D Alloin, D Alloin, D Maoz, D Maoz, D Maoz, D Maoz, DM Crenshaw, E Pérez, FP Pijpers, GA Reichert, GJ Ferland, GM Stirpe, H Netzer, H Netzer, H Netzer, HL Marshall, I Wanders, I Wanders, I Wanders, J Clavel, JH Krolik, JH Krolik, K Horne, KT Korista, M Dietrich, M-H Ulrich, R Edelson, R Warwick, RD Blandford, RJ White, TE Carone, Th Boller, W Romanishin, W Welsh   +43 more
core   +2 more sources

Keeping the dream alive: Managing the Space Station Program, 1982 to 1986 [PDF]

The management is described and analyzed of the formative years of the NASA Space Station Program (1982 to 1986), beginning with the successful initiative for program approval by Administrator James M.
Lewin, Thomas J., Narayanan, V. K.
core   +1 more source