Eales, S., Dunne, L., Clements, D., Cooray, A., De Zotti, G., Dye, S., ...
The Herschel ATLAS is the largest open-time key project that will be carried out on the Herschel Space Observatory. It will survey 510 square degrees of the extragalactic sky, four times larger than...
The evolution of the hard X-ray luminosity function of AGN (2009)
Aird, J., Nandra, K., Laird, E. S., Georgakakis, A., Ashby, M. L. N., Barmby, P., ...
We present new observational determinations of the evolution of the 2-10keV X-ray luminosity function (XLF) of AGN. We utilise data from a number of surveys including both the 2Ms Chandra Deep Fields...
Selecting Type-II Seyferts using infrared colours and optical spectroscopy in SWIRE ELAIS-N1 (2009)
Trichas, M., Rowan-Robinson, M., Georgakakis, A., Valtchanov, I., Nandra, K., Farrah, D., ...
We present the largest spectroscopic follow-up performed in SWIRE ELAIS-N1. We were able to determine redshifts for 289 extragalactic sources. The values of spectroscopic redshifts of the latter have...
Testing the starburst/AGN connection with SWIRE X-ray/70 micron sources (2009)
Trichas, M., Georgakakis, A., Rowan-Robinson, M., Nandra, K., Clements, D., Vaccari, M.
We explore the nature of X-ray sources with 70 micron counterparts selected in the SWIRE fields ELAIS-N1, Lockman Hole and Chandra Deep Field South, for which Chandra X-ray data are available. A...
Evolution of the X-ray Luminosity in Young HII Galaxies (2009)
González, D. Rosa, Terlevich, E., Bailón, E. Jiménez, Terlevich, R., Ranalli, P., Comastri, A., ...
In an effort to understand the correlation between X-ray emission and present star formation rate (SFR), we obtained XMM-Newton data to estimate the X-ray luminosities of a sample of actively...
Georgakakis, A., Coil, A. L., Laird, E. S., Griffith, R. L., Nandra, K., Lotz, J. M., ...
We use morphological information of X-ray selected AGN hosts to set limits on the fraction of the accretion density of the Universe at z~1 that is not likely to be associated with major mergers. Deep...
Cosmic Feedback from Supermassive Black Holes (2009)
Fabian, A., Churazov, E., Donahue, M., Forman, W. R., Garcia, M. R., Heinz, S., ...
An extraordinary recent development in astrophysics was the discovery of the fossil relationship between central black hole mass and the stellar mass of galactic bulges. The physical process...
The Growth of Supermassive Black Holes Across Cosmic Time (2009)
Nandra, K., Aird, J. A., Alexander, D. M., Ballantyne, D. R., Barcons, X., Bauer, F. E., ...
One of the main themes in extragalactic astronomy for the next decade will be the evolution of galaxies over cosmic time. Many future observatories, including JWST, ALMA, GMT, TMT and E-ELT will...
Stellar-Mass Black Holes and Their Progenitors (2009)
Miller, J. M., Uttley, P., Nandra, K., Barret, D., Matt, G., Paerels, F., ...
If a black hole has a low spin value, it must double its mass to reach a high spin parameter. Although this is easily accomplished through mergers or accretion in the case of supermassive black holes...
Fundamental Accretion and Ejection Astrophysics (2009)
Miller, J. M., Nowak, M., Nandra, K., Brandt, W. N., Matt, G., Cappi, M., ...
Disk accretion may be the fundamental astrophysical process. Stars and planets form through the accretion of gas in a disk. Black holes and galaxies co-evolve through efficient disk accretion onto...
Spin and Relativistic Phenomena Around Black Holes (2009)
Brenneman, L., Miller, J. M., Nandra, K., Volonteri, M., Cappi, M., Matt, G., ...
Since the seminal work of Penrose (1969) and Blandford & Znajek (1977), it has been realized that black hole spin may be an important energy source in astrophysics. The radio-loud/radio-quiet...
AEGIS: The Clustering of X-ray AGN Relative to Galaxies at z~1 (2009)
Coil, Alison L., Georgakakis, Antonis, Newman, Jeffrey A., Cooper, Michael C., Croton, Darren, Davis, Marc, ...
We measure the clustering of non-quasar X-ray AGN at z=0.7-1.4 in the AEGIS field. Using the cross-correlation of 113 Chandra-selected AGN, with a median log L_X=42.8 erg s^-1, with ~5,000 DEEP2...
Are red 2MASS QSOs young? (2008)
Georgakakis, A., Clements, D. L., Bendo, G., Rowan-Robinson, M., Nandra, K., Brotherton, M. S.
We use photometric data from Spitzer to explore the mid- and far-IR properties of 10 red QSOs (J-K>2, R-K>5) selected by combining the 2MASS in the NIR with the SDSS at optical wavelengths. Optical...
AEGIS-X: The Chandra Deep Survey of the Extended Groth Strip (2008)
Laird, E. S., Nandra, K., Georgakakis, A., Aird, J. A., Barmby, P., Conselice, C. J., ...
We present the AEGIS-X survey, a series of deep Chandra ACIS-I observations of the Extended Groth Strip. The survey comprises pointings at 8 separate positions, each with nominal exposure 200ks,...
X-ray selected AGN in groups at redshifts z~1 (2008)
Georgakakis, A., Gerke, Brian F., Nandra, K., Laird, E. S., Coil, A. L., Cooper, M. C., ...
We explore the role of the group environment in the evolution of AGN at the redshift interval 0.7
Georgakakis, A., Nandra, K., Laird, E. S., Aird, J., Trichas, M.
We present a new method for determining the sensitivity of X-ray imaging observations, which correctly accounts for the observational biases that affect the probability of detecting a source of a...
AEGIS: Radio and Mid-Infrared Selection of Obscured AGN Candidates (2008)
Park, S. Q., Barmby, P., Fazio, G. G., Nandra, K., Laird, E. S., Georgakakis, A., ...
The application of multi-wavelength selection techniques is crucial for discovering a complete and unbiased set of Active Galactic Nuclei (AGNs). Here, we select a sample of 72 AGN candidates in the...
The role of AGN in the colour transformation of galaxies at redshifts z~1 (2008)
Georgakakis, A., Nandra, K., Yan, R., Willner, S. P., Lotz, J. M., Pierce, C. M., ...
We explore the role of AGN in establishing and/or maintaining the bimodal colour distribution of galaxies by quenching their star-formation and hence, causing their transition from the blue to the...
Modeling of the broad band X-ray spectra of the Seyfert 1 Mrk 841 (2008)
A. L. Longinotti, C. Boisson, G. Matt, G. Ponti, J. Malzac, K. Nandra, ...
The Environment on few Mpc scales of Infrared Luminous Galaxies at Redshifts z~1 (2007)
Marcillac, D., Rieke, G. H., Papovich, C., Willmer, C. N. A., Weiner, B. J., Coil, A. L., ...
We investigate the environment of infrared luminous galaxies (L$_{IR}$[8-1000 $\mu $m$] >10^{11}$L$_{\sun}$). We focus on the redshift range 0.7 $\leq$ z $\leq$ 1, where these galaxies dominate the...
Asca Observations Of The Ionized Gas In The Seyfert Galaxy Ngc 3783 (2007)
I. M. George, T. J. Turner, George Turner Mushotzky, K. Nandra, H. Netzer
We present the results from ASCA observations of NGC 3783 carried out during 1993 and 1996. Variability is observed both between the two epochs and within the individual observations, the latter due...
C. S. Reynolds, A. C. Fabian, K. Nandra, H. Inoue, H. Kunieda, K. Iwasawa
ASCA PV observations of the Seyfert 1 galaxy MCG\Gamma6\Gamma30\Gamma15: rapid variability of the warm absorber.
An XMM-Newton survey of broad iron lines in Seyfert galaxies (2007)
Nandra, K., O'Neill, P. M., George, I. M., Reeves, J. N.
We present an analysis of the X-ray spectra of a sample of 37 observations of 26 Seyfert galaxies observed by XMM-Newton in order to characterize their iron K emission. All objects show evidence for...
Conselice, C. J., Bundy, K., Trujillo, I., Coil, A., Eisenhardt, P., Ellis, R. S., ...
We present the results of a study on the properties and evolution of massive (M_* > 10^11 M_0) galaxies at z~0.4 - 2 utilising Keck spectroscopy, near-Infrared Palomar imaging, and Hubble, Chandra,...
A Compton Thick AGN Powering the Hyperluminous Infrared Galaxy IRAS 00182--7112 (2007)
We present X-ray observations of the Hyperluminous Infrared Galaxy (HLIRG) IRAS 00182--7112 (F00183--7111) obtained using the XMM-Newton EPIC camera. A luminous hard X-ray source co-incident with the...
Relativistic Iron K Emission and absorption in the Seyfert 1.9 galaxy MCG-5-23-16 (2007)
Braito, V., Reeves, J. N., Dewangan, G. C., George, I., Griffiths, R. E., Markowitz, A., ...
We present the results of the simultaneous deep XMM and Chandra observations of the bright Seyfert 1.9 galaxy MCG-5-23-16, which is thought to have one of the best known examples of a...
Unveiling the broad band X-ray continuum and iron line complex in Mkr 841 (2007)
Petrucci, P.O., Ponti, G., Matt, G., Longinotti, A. L., Malzac, J., Mouchet, M., ...
Mkr 841 is a bright Seyfert 1 galaxy known to harbor a strong soft excess and a variable K$\alpha$ iron line. It has been observed during 3 different periods by XMM for a total cumulated exposure...
Unveiling the broad band X-ray continuum and iron line complex in Mkr 841 (2007)
Petrucci, P. O., Ponti, G., Matt, G., Longinotti, A. L., Malzac, J., Mouchet, M., ...
Mkr 841 is a bright Seyfert 1 galaxy known to harbor a strong soft excess and a variable K$\alpha$ iron line. It has been observed during 3 different periods by XMM for a total cumulated exposure...
Le Floc'h, E., Willmer, C. N. A., Noeske, K., Konidaris, N. P., Laird, E. S., Koo, D. C., ...
As part of the All-Wavelength Extended Groth Strip International Survey (AEGIS), we describe the panchromatic characterization of an X-ray–luminous active galactic nucleus (AGN) in a merging galaxy...
The All-Wavelength Extended Groth Strip International Survey (AEGIS) Data Sets (2007)
Davis, M., Guhathakurta, P., Konidaris, N. P., Newman, J. A., Ashby, M. L. N., Biggs, A. D., ...
In this the first of a series of Letters, we present a panchromatic data set in the Extended Groth Strip region of the sky. Our survey, the All-Wavelength Extended Groth Strip International Survey...
An XMM-Newton view of the X-ray flat radio-quiet quasar PG 1416-129 (2007)
Porquet, D., Reeves, J. N., Markowitz, A., Turner, T. J., Miller, L., Nandra, K.
Relativistic inflow in the Seyfert 1 Mrk 335 revealed through X-ray absorption (2007)
Longinotti, A. L., Sim, S., Nandra, K., Cappi, M., O'Neill, P.
An XMM-Newton view of the X-ray flat radio-quiet quasar PG 1416-129 (2006)
Porquet, D., Reeves, J. N., Markowitz, A., Turner, T. J., Miller, L., Nandra, K.
(abridged) The radio-quiet quasar PG1416-129 (z=0.129) exhibits atypical optical and X-ray properties. Between 1990 and 2000, in response to its optical continuum decrease, the ``classical'' broad...
Relativistic inflow in the Seyfert 1 Mrk 335 revealed through X-ray absorption (2006)
Longinotti, A. L., Sim, S., Nandra, K., Cappi, M., O'Neill, P.
The analysis of hard X-ray features in XMM-Newton data of the bright Sy 1 galaxy Mrk 335 is reported here. The presence of a broad, ionised iron K alpha emission line in the spectrum, first found by...
The origin of the strong soft excess and puzzling iron line complex in Mkn 841 (2006)
Petrucci, P. O., Ponti, G., Matt, G., Maraschi, L., Malzac, J., Mouchet, M., ...
Mkn 841 has been observed during 3 different periods (January 2001, January 2005 and July 2005) by XMM-Newton for a total cumulated exposure time of ~108 ks. We present in this paper a broad band...
The X-ray emission of Lyman break galaxies (2006)
Laird, E. S., Nandra, K., Hobbs, A., Steidel, C. C.
We present an analysis of the X-ray emission of a large sample of z∼3 Lyman break galaxies (LBGs), based on Chandra/ACIS observations of several LBG survey fields. A total of 24 LBGs are directly...
An XMM-Newton survey of broad iron lines in AGN (2006)
Nandra, K., O'Neill, P. M., George, I. M., Reeves, J. N., Turner, T. J.
We report on the iron K-alpha line properties of a sample of Seyfert galaxies observed with the XMM-Newton EPIC pn instrument. Using a systematic and uniform analysis, we find that complexity at...
The All-Wavelength Extended Groth Strip International Survey (AEGIS) Data Sets (2006)
Davis, M., Guhathakurta, P., Konidaris, N.P., Newman, J.A., Ashby, M.L.N., Biggs, A.D., ...
Floc'h, E. Le, Willmer, C. N. A., Noeske, K., Konidaris, N. P., Laird, E. S., Koo, D. C., ...
As part of the "All Wavelength Extended Groth Strip International Survey" (AEGIS), we describe the panchromatic characterization of an X-ray luminous active galactic nucleus (AGN) in a merging galaxy...
The X-ray emission of Lyman break galaxies (2006)
Laird, E. S., Nandra, K., Hobbs, A., Steidel, C. C.
We present an analysis of the X-ray emission of a large sample of z~3 Lyman break galaxies (LBGs), based on Chandra/ACIS observations of several LBG survey fields. 24 LBGs are directly detected in...
AEGIS: Host Galaxy Morphologies of X-ray and Infrared-selected AGN at 0.2 < z < 1.2 (2006)
Pierce, C. M., Lotz, J. M., Laird, E. S., Lin, L., Nandra, K., Primack, J. R., ...
We visually and quantitatively determine the host galaxy morphologies of 94 intermediate redshift (0.2 < z < 1.2) active galactic nuclei (AGN), selected using Chandra X-ray and Spitzer mid-infrared...
AEGIS: Chandra Observation of DEEP2 Galaxy Groups and Clusters (2006)
Fang, T., Gerke, B., Davis, D., Newman, J., Davis, M., Nandra, K., ...
We present a 200 ksec Chandra observation of seven spectroscopically selected, high redshift (0.75 < z < 1.03) galaxy groups and clusters discovered by the DEEP2 Galaxy Redshift Survey in the...
The All-wavelength Extended Groth Strip International Survey (AEGIS) Data Sets (2006)
Davis, M., Guhathakurta, P., Konidaris, N., Newman, J. A., Ashby, M. L. N., Biggs, A. D., ...
In this the first of a series of Letters, we present a description of the panchromatic data sets that have been acquired in the Extended Groth Strip region of the sky. Our survey, the All-wavelength...
AEGIS: The color-magnitude relation for X-ray selected AGN (2006)
Nandra, K., Georgakakis, A., Willmer, C. N. A., Cooper, M. C., Croton, D. J., Davis, M., ...
We discuss the relationship between rest-frame color and optical luminosity for X-ray sources in the range 0.6
Georgakakis, A., Nandra, K., Laird, E. S., Cooper, M. C., Gerke, B. F., Newman, J. A., ...
We explore the environment of z~1 AGN using a sample of 53 spectroscopically identified X-ray sources in the All-wavelength Extended Groth strip International Survey. We quantify the local density in...
The Deep Chandra Survey of the Groth Strip - II. optical identification of the X-ray sources (2006)
Georgakakis, A., Nandra, K ., Laird, E. S., Gwyn, S., Steidel, C. C., Sarajedini, V. L., ...
We discuss the optical and X-ray spectral properties of the sources detected in a single 200ks Chandra pointing in the Groth-Westphal Strip region. Optical identifications and spectroscopic redshifts...
Variable iron-line emission near the black hole of Markarian 766 (2006)
Miller, L., Turner, T. J., Reeves, J. N., George, I. M., Porquet, D., Nandra, K., ...
We investigate the link between ionised Fe X-ray line emission and continuum emission in the bright nearby AGN, Mrk 766. A new long (433 ks) XMM-Newton observation is analysed, together with archival...
On the origin of the Fe K-alpha line cores in Active Galactic Nuclei (2006)
X-ray observations with Chandra and XMM-Newton have shown that there are relatively narrow cores to the iron K-alpha emission lines in active galactic nuclei (AGN). Plausible origins for this core...
XMM-Newton and Chandra observations of SHEEP sources (2006)
Georgantopoulos, I., Nandra, K., Brotherton, M., Georgakakis, A., Papadakis, I. E., O'Neill, P.
We present Chandra and XMM observations of 12 bright (f(2-10 keV) > 10^-13 cgs) sources from the ASCA SHEEP (Search for the High Energy Extragalactic Population) survey. Most of these have been...
The iron emission line complex of MCG-5-23-16: the long XMM-Newton look (2006)
Braito, V., Reeves, J. N., Dewangan, G., George, I., Griffiths, R., Markowitz, A., ...
Energy-shifted lines in XMM-Newton epic spectra of Seyfert galaxies (2006)
Longinotti, A. L., Sim, S., Nandra, K., O'Neill, P. O., Cappi, M.
Variable iron-line emission near the black hole of Markarian 766 (2006)
Miller, L., Turner, T. J., Reeves, J. N., George, I. M., Porquet, D., Nandra, K., ...
Mid-infrared properties of X-ray sources in the Extended Groth Strip (2005)
Barmby, P., Alonso-Herrero, A., Donley, J. L., Egami, E., Fazio, G. G., Georgakakis, A., ...
Mid-infrared observations of Active Galactic Nuclei (AGN) are important for understanding of the physical conditions around the central accretion engines. Chandra and XMM-Newton X-ray observations of...
Energy-shifted lines in XMM-Newton spectra of Seyfert Galaxies (2005)
Longinotti, A. L., Sim, S., Nandra, K., O'Neill, P., Cappi, M.
In the recent literature on AGNs it has been often reported that spectra of Seyfert 1 Galaxies show resonant absorption lines of Fe K which are redshifted from the rest frame position. Such lines are...
Gabel, J. R., Kraemer, S. B., Crenshaw, D. M., George, I. M., Brandt, W. N., Hamann, F. W., ...
We present results on the location, physical conditions, and geometry of the outflow in the Seyfert 1 galaxy NGC 3783 from a study of the variable intrinsic UV absorption. Based on 18 observations...
Weinzirl, Timothy, Brotherton, Mike, Nandra, K., Georgantopoulou, I., Papadakis, I.
Tim Weinzirl is a junior at Drake University, majoring in Physics and Astronomy. He presented this poster session at DUCURS (Drake University Conference on Undergraduate Research in the Sciences)...
The Space Density of Moderate Luminosity Active Galaxies at z=3 (2005)
Nandra, K., Laird, E. S., Steidel, C. C.
We present an estimate of the space density of Active Galactic Nuclei (AGN) at z=3. Combining deep X-ray data with Lyman Break Galaxy (LBG) colour-selection in the rest-frame UV makes for highly...
X-ray properties of UV-selected star forming galaxies at z~1 in the Hubble Deep Field North (2005)
Laird, E. S., Nandra, K., Adelberger, K. L., Steidel, C. C., Reddy, N. A.
We present an analysis of the X-ray emission from a large sample of ultraviolet (UV) selected, star forming galaxies with 0.74
Franceschini, A., Manners, J., Polletta, M., Lonsdale, C. J., Gonzalez-Solares, E., Surace, J., ...
We exploit deep combined observations with Spitzer and Chandra of the SWIRE survey in the ELAIS-N1 region, to investigate the nature of the faint X-ray and IR sources in common, to identify...
Rowan-Robinson, M., Babbedge, T., Surace, J., Shupe, D., Fang, F., Lonsdale, C., ...
We discuss optical associations, spectral energy distributions and photometric redshifts for SWIRE sources in the ELAIS-N1 area and the Lockman Validation Field. The band-merged IRAC (3.6, 4.5, 5.8...
A deep Chandra observation of the Groth Strip. I. The X-ray data (2004)
Nandra, K., Laird, E. S., Adelberger, K., Gardner, J. P., Mushotzky, R. F., Rhodes, J., ...
We present the results of a 200 ks Chandra observation of part of the Groth Strip region, using the ACIS-I instrument. We present a relatively simple method for the detection of point-sources and...
On the variability of the iron line in Mrk 841 (2004)
Longinotti, A. L., Nandra, K., Petrucci, P. O., O'Neill, P. M.
Petrucci et al. (2002; hereafter P02) have reported extraordinary behaviour of the iron K alpha line in the type 1 AGN Mrk 841. At the XMM-Newton/EPIC resolution, a narrow line was observed in a...
The HDF-North SCUBA Super-map II: Multi-wavelength properties (2004)
Borys, C., Scott, D., Chapman, S. C., Halpern, M., Pope, A., Nandra, K.
We present radio, optical and X-ray detected counterparts to the sub-mm sources found using SCUBA in the Hubble Deep Field North region (GOODS-N). A new counterpart identification statistic is...
The XMM-Newton iron line profile of NGC 3783 (2004)
Reeves, J.N., Nandra, K., George, I.M., Pounds, Kenneth A., Turner, T.J., Yaqoob, T.
The definitive version of this paper is that available at http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v602n2/58961/58961.html
Waskett, T. J., Eales, S. A., Gear, W. K., McCracken, H. J., Brodwin, M., Nandra, K., ...
We present the X-ray source catalogues for the XMM surveys of the 3-h and 14-h Canada-France Redshift Survey fields (0.5-10 keV flux range ~2E-15 - 1E-13 erg cm^-2 s^-1). We use a subset of the XMM...
Nandra, K., Georgantopoulos, I., Brotherton, M., Papadakis, I. E.
We present followup observations of five hard X-ray sources from the ASCA 5-10 keV SHEEP survey, which has a limiting flux of $\sim 10^{-13}$ erg cm$^{-2}$ s$^{-1}$. Chandra data have been obtained...
The Properties and the Evolution of the Highly Ionized Gas in MR2251-178 (2003)
Kaspi, S., Netzer, H., Chelouche, D., George, I. M., Turner, T. J., Nandra, K.
We present the first XMM-Newton observations of the radio-quiet quasar MR2251-178. We model the X-ray spectrum with two power laws, one at high energies with a slope of \Gamma=1.6 and the other to...
The XMM-Newton Iron Line Profile of NGC 3783 (2003)
Reeves, J. N, Nandra, K., George, I. M., Pounds, K. A., Turner, T. J., Yaqoob, T.
We report on observations of the iron K line in the nearby Seyfert 1 galaxy, NGC 3783, obtained in a long, 2 orbit (240 ks) XMM-Newton observation. The line profile obtained exhibits two strong...
Physical interpretation of the UV/X-ray variability behavior of NGC 7469 (2003)
Petrucci, P. O., Maraschi, L., Haardt, F., Nandra, K.
We present a re-analysis of the simultaneous 30 day IUE/XTE observation of NGC 7469 done in 1996. Our main progress, in comparison to previous spectral analysis, is to adopt and fit directly to the...
Netzer, H., Kaspi, S., Behar, E., Brandt, W. N., Chelouche, D., George, I. M., ...
We present a detailed spectral analysis of the data obtained from NGC 3783 during the period 2000-2001 using Chandra. This analysis leads us to the following results. 1) NGC 3783 fluctuated in...
X-ray fluctuation power spectral densities of Seyfert 1 galaxies (2003)
Markowitz, A., Edelson, R., Vaughan, Simon, Uttley, P., George, I.M., Griffiths, R.E., ...
The definitive version of this paper is available from http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v593n1/56874/56874.html
The complex FeK line of the Narrow-Line Seyfert 1 galaxy IRAS13349+2438 (2003)
Longinotti, A. L., Cappi, M., Nandra, K., Dadina, M., Pellegrini, S.
The observation of the Narrow-Line Seyfert 1 galaxy IRAS13349+2438 performed by XMM-Newton European Photon Imaging Camera between 0.3-10 keV, is presented here. The broadband spectrum of the source...
The long time-scale X-ray variability of the radio-quiet quasar PG 0804+761 (2003)
Papadakis, I. E., Reig, P., Nandra, K.
We present the results from a study of the timing properties and the energy spectrum of the radio-quiet quasar PG0804+761, based on monitoring RXTE PCA observations that lasted for a year. This is a...
Gabel, J. R., Crenshaw, D. M., Kraemer, S. B., Brandt, W. N., George, I. M., Hamann, F. W., ...
We report an intrinsic absorber with decreasing outflow velocity in the Seyfert 1 galaxy NGC 3783. This is the first detection of a change in radial velocity in an outflow associated with a Seyfert...
X-ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies (2003)
Markowitz, A., Edelson, R., Vaughan, S., Uttley, P., George, I. M., Griffiths, R. E., ...
By combining complementary monitoring observations spanning long, medium and short time scales, we have constructed power spectral densities (PSDs) of six Seyfert~1 galaxies. These PSDs span...
X-ray continuum variability of MCG-6-30-15 (2002)
Vaughan, S., Fabian, A. C., Nandra, K.
This paper presents a comprehensive examination of the X-ray continuum variability of the bright Seyfert 1 galaxy MCG-6-30-15. The source clearly shows the strong, linear correlation between rms...
SHEEP: The Search for the High Energy Extragalactic Population (2002)
Nandra, K., Georgantopoulos, I., Ptak, A., Turner, T. J.
We present the SHEEP survey for serendipitously-detected hard X-ray sources in ASCA GIS images. In a survey area of $\sim 40$ deg$^{2}$, 69 sources were detected in the 5-10 keV band to a limiting...
Turner, T. J., Mushotzky, R. F., Yaqoob, T., George, I. M., Snowden, S. L., Netzer, H., ...
We present results from a simultaneous Chandra HETG and XMM-Newton observation of NGC 3516. We find evidence for several narrow components of Fe Kalpha along with a broad line. We consider the...
A long hard look at MCG-6-30-15 with XMM-Newton (2002)
Fabian, A. C., Vaughan, S., Nandra, K., Iwasawa, K., Ballantyne, D. R., Lee, J. C., ...
We present first results from a 325 ks observation of the Seyfert 1 galaxy MCG-6-30-15 with XMM-Newton and BeppoSAX. The strong, broad, skewed iron line is clearly detected and is well characterised...
X-ray properties of Lyman Break Galaxies in the Hubble Deep Field North region (2002)
Nandra, K., Mushotzky, R. F., Arnaud, K. A., Steidel, C. C., Adelberger, K. A., Gardner, J. P., ...
We describe the X-ray properties of a large sample of $z\sim3$ Lyman Break Galaxies (LBGs) in the region of the Hubble Deep Field North, derived from the 1 Ms public Chandra observation. Of our...
Kaspi, S., Brandt, W. N., George, I. M., Netzer, H., Crenshaw, D. M., Gabel, J. R., ...
We present results from a 900 ks exposure of NGC 3783 with the High-Energy Transmission Grating Spectrometer on board the Chandra X-ray Observatory. The resulting X-ray spectrum has the best...
A long hard look at MCG-6-20-15 with XMM-Newton (2002)
Fabian, A.C., Vaughan, Simon A., Nandra, K., Iwasawa, K., Ballantyne, D.R., Lee, J.C., ...
The Effect of Changes in the ASCA Calibration on the Fe-Kalpha Lines in Active Galaxies (2001)
Yaqoob, T., Padmanabhan, U., Dotani, T., Nandra, K.
The ASCA calibration has evolved considerably since launch and indeed, is still evolving. There have been concerns in the literature that changes in the ASCA calibration have resulted in the...
Monitoring RXTE Observations of Markarian 348: the origin of the column density variations (2001)
Akylas, A., Georgantopoulos, I., Griffiths, R. G., Papadakis, I. E., Mastichiadis, A., Warwick, R. S., ...
We analyze 37 RXTE observations of the type 2 Seyfert galaxy Mrk348 obtained during a period of 14 months. We confirm the spectral variability previous reported by Smith et al., in the sense that...
The Density and Location of the X-ray Absorbing Gas in NGC 3516 (2001)
Netzer, H., Chelouche, D., George, I. M., Turner, T. J., Crenshaw, D. M., Kraemer, S. B., ...
A new Chandra observation and archival observations by ASCA are used to investigate spectral variations in the Sy1 galaxy NGC 3516 over a period of 7 years. A large change in flux (factor ~50 at...
The Detection of Circumnuclear X-ray Emission from the Seyfert Galaxy NGC 3516 (2001)
George, I. M., Turner, T. J., Netzer, H., Kraemer, S. B., Ruiz, J., Chelouche, D., ...
We present the first high-resolution, X-ray image of the circumnuclear regions of the Seyfert 1 galaxy NGC 3516, using the Chandra X-ray Observatory (CXO). All three of the CXO observations reported...
Subtleties in Measuring Iron K Lines in AGN (2001)
Yaqoob, T., Padmanabhan, U., Dotani, T., George, I. M., Turner, T. J., Nandra, K.
Chandra and XMM observations are showing that the Fe-K emission lines in type 1 AGN are composite, in general consisting of a narrow and a broad component. We review the latest Chandra HETG results...
Frequency-dependent time lags in the X-ray emission of the Seyfert galaxy NGC 7469 (2001)
Papadakis, I. E., Nandra, K., Kazanas, D.
We report the discovery of time lags in the cross-spectra of the X-ray light curves of the Seyfert galaxy NGC 7469. This behavior is common in Galactic black hole and neutron star binaries, and is in...
Temporal characteristics of the X-ray emission of NGC 7469 (2001)
We present a study of the time variability of NGC 7469, based on a ~30 d RXTE/PCA observation. Variability is seen across the X-ray band, and spectral changes are observed. The softness ratio is...
The X-ray Emission from the Nucleus of the Dwarf Elliptical Galaxy NGC 3226 (2001)
George, I. M., Mushotzky, R. F., Yaqoob, T., Turner, T. J., Kraemer, S., Ptak, A. F., ...
We present the first high resolution X-ray image of the dwarf elliptical galaxy NGC 3226. The data were obtained during an observation of the nearby Seyfert Galaxy NGC 3227 using the Chandra X-ray...
SHEEP: the ASCA 5-10 keV survey (2001)
Georgantopoulos, I., Nandra, K., Ptak, A.
We present the first results of the hard (5-10 keV) ASCA GIS survey SHEEP (Search for the High Energy Extragalactic Population). We have analysed 149 fields covering an area of 39 sq. deg detecting...
X-ray variability of AGN and correlations with spectral properties (2000)
Rapid flux changes in the X-ray emission from active galactic nuclei are commonly observed. The power-density spectra show a pseudo power-law form with a turnover at low frequencies and a high...
Chandra Grating Spectroscopy of the Seyfert Galaxy Ton S180 (2000)
Turner, T. J., George, I. M., Yaqoob, T., Kriss, G., Crenshaw, D. M., Kraemer, S., ...
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...
Yaqoob, T., George, I. M., Nandra, K., Turner, T. J., Serlemitsos, P. J., Mushotzky, R. F.
We report the detection of a narrow Fe-K emission line in the Seyfert 1 galaxy NGC 5548 with the Chandra High-Energy Transmission Gratings. In the galaxy frame we measure a center energy of 6.40 \pm...
Iron K line emission in AGN: observations (2000)
Iron K-alpha lines are key diagnostics of the central regions of AGN. Their profiles indicate that they are formed deep in the potential well of the central black hole, where extreme broadening and...
The Origin of the X-ray and Ultraviolet Emission in NGC 7469 (2000)
Nandra, K., Le, T., Edelson, R. A., George, I. M., Mushotzky, R. F., Peterson, B. M., ...
We present a spectral analysis of a 30d, near-continuous observation of the Seyfert 1 galaxy NGC 7469 with RXTE. Daily integrations show strong spectral changes during the observation. Ourmain result...
X-ray Observations of Optically-Selected, Radio-Quiet Quasars I: The ASCA results (1999)
George, I. M., Turner, T. J., Yaqoob, T., Netzer, H., Laor, A., Mushotzky, R. F., ...
We present the result of 27 ASCA observations of 26 radio-quiet quasars (RQQs) from the PG survey. All the RQQs were detected except 2 BALQSOs. We find the variability characteristics of the sources...
A Highly Doppler Blueshifted Fe-K Emission Line in the High-Redshift QSO PKS 2149-306 (1999)
Yaqoob, T., George, I. M., Nandra, K., Turner, T. J., Zobair, S., Serlemitsos, P. J.
We report the results from an \asca observation of the QSO PKS 2149-306 (z=2.345). We detect an emission line centered at $\sim 17$ keV in the quasar frame. Line emission at this energy has not been...
X-ray dependencies on luminosity in AGN (1999)
Several X-ray properties of active galactic nuclei depend, or appear to depend, on their luminosity. It has long been suggested that alpha o-x, the X-ray ``loudness'' decreases with luminosity. There...
The properties of the relativistic iron K-line in NGC 3516 (1999)
Nandra, K., George, I. M., Mushotzky, R. F., Turner, T. J., Yaqoob, T.
We present an analysis of the relativistic iron K-alpha line in the Seyfert 1 galaxy NGC 3516, based on a continuous, five-day ASCA observation. The broad profile which has been found in several...
On X-ray Variability in Seyfert Galaxies (1999)
Turner, T. J., George, I. M., Nandra, K., Turcan, D.
This paper presents a quantification of the X-ray variability amplitude for 79 ASCA observations of 36 Seyfert 1 galaxies. We find that consideration of sources with the narrowest permitted lines in...
ASCA and ROSAT observations of NGC5548: discrepant spectral indices (1999)
Iwasawa, K., Fabian, A. C., Nandra, K.
We report on simultaneous ASCA and ROSAT observations of the Seyfert galaxy NGC5548 made during the ASCA Performance Verification phase. Spectral features due to a warm absorber and reflection are...
A Peculiar Emission Line Feature in the X-ray Spectrum of the Quasar PKS 0637-752 (1998)
Yaqoob, T., George, I. M., Turner, T. J., Nandra, K., Ptak, A., Serlemitsos, P. J.
We report the results from an ASCA observation of the high-luminosity, radio-loud quasar PKS 0637-752 (redshift 0.654), covering the 0.8-15 keV band in the quasar-frame. We find the source to have a...
X-ray Observations of the Seyfert galaxy LB 1727 (1H 0419-577) (1998)
Turner, T. J., George, I. M., Nandra, K., Remillard, R. A., Leighly, K. M., Marshall, H. L., ...
We discuss the properties of the Seyfert 1.5 galaxy LB 1727, also known as 1H 0419-577, from X-ray observations obtained by ASCA and ROSAT along with optical observations from earlier epochs. ASCA...
The X-ray Spectral Variability of the Seyfert Galaxy NGC 3227 (1998)
George, I. M., Mushotzky, R. F., Turner, T. J., Yaqoob, T., Ptak, A., Nandra, K., ...
(Abridged) We present the results from {\it ASCA} observations of NGC 3227 along with those from a {\it ROSAT} observation. The 0.6--10 keV continuum is consistent with a powerlaw with $\Gamma \sim...
X-ray Signatures of an Ionized Reprocessor in the Seyfert galaxy Ton S 180 (1998)
Turner, T. J., George, I. M., Nandra, K.
We discuss the hard X-ray properties of the Seyfert galaxy Ton S 180, based upon the analysis of ASCA data. We find the X-ray flux varied by a factor ~2 on a time scale of a few thousand seconds. The...
Nandra, K., Clavel, J., Edelson, R. A., George, I. M., Malkan, M. A., Mushotzky, R. F., ...
We have undertaken near-continuous monitoring of the Seyfert 1 galaxy NGC 7469 in the X-ray with RXTE over a ~30d baseline. The source shows strong variability with a root-mean-square (rms) amplitude...
ASCA Observations of the Ionized Gas in the Seyfert Galaxy NGC 3783 (1998)
George, I. M., Turner, T. J., Mushotzky, R. F., Nandra, K., Netzer, H.
We present the results from ASCA observations of NGC 3783 carried out during 1993 and 1996. Variability is observed both between the two epochs and within the individual observations, the latter due...
Wanders, I., Peterson, B.M., Alloin, D., Ayres, T.R., Clavel, J., Crenshaw, D.M., ...
From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line...
Yaqoob, T., McKernan, B., Ptak, A., Nandra, K., Serlemitsos, P. J.
We present a new, simple method for analysing gapped time-series which is particularly suited to probe the X-ray power spectra of active galactic nuclei (AGN).The method is applied to a four-day...
ASCA observations of type-2 Seyfert Galaxies. III. Orientation and X-ray Absorption (1997)
Turner, T. J., George, I. M., Nandra, K., Mushotzky, R. F.
We discuss the spectral properties of a sample of type-2 Seyfert galaxies based upon the analysis of \asca data. In this paper we consider the sources for which the X-ray spectra appear to be...
George, I. M., Turner, T. J., Netzer, Hagai, Nandra, K., Mushotzky, R. F., Yaqoob, T.
(Abridged) We present the results from a detailed analysis of the 0.6 - 10 keV spectra of 23 ASCA observations of 18 objects. We find that in most cases the underlying continuum can be...
On the dependence of the iron K-line profiles with luminosity in Active Galactic Nuclei (1997)
Nandra, K., George, I. M., Mushotzky, R. F., Turner, T. J., Yaqoob, T.
We present evidence for changes in the strength and profile of the iron K-alpha line in Active Galactic Nuclei (AGN), based on X-ray observations with ASCA. There is a clear decrease in the strength...
Evidence for Absorption due to Highly-Ionized Gas in the Radio-quiet Quasar PG 1114+445 (1997)
George, I. M., Nandra, K., Laor, A., Turner, T. J., Fiore, F., Netzer, H., ...
We present results on the X-ray spectrum of the quasar PG 1114+445 from an ASCA observation performed in 1996 June, and a ROSAT observation performed 3 years earlier. We show good agreement between...
Turner, T. J., George, I. M., Nandra, K., Mushotzky, R. F.
We discuss the importance of X-ray scattering and Compton reflection in type-2 Seyfert galaxies, based upon the analysis of ASCA observations of 25 such sources. Consideration of the iron Kalpha, [O...
ASCA observations of Seyfert 1 galaxies: I. Data Analysis, Imaging and Timing (1996)
Nandra, K., George, I. M., Mushotzky, R. F., Turner, T. J., Yaqoob, T.
We present the first in a series of papers describing the X-ray properties of a sample of 18 Seyfert 1 galaxies, using data obtained by \asca. The imaging data reveal a number of serendipitous hard...
Variability of the iron K-emission line in the Seyfert 1 galaxy NGC 3516 (1996)
Nandra, K., Mushotzky, R. F., Yaqoob, T., George, I. M., Turner, T. J.
We present strong evidence for variability of the flux of the iron K$\alpha$ emission line in the Seyfert 1 galaxy, NGC 3516. Two ASCA observations, separated by $\sim 1$~yr, showed a marked decrease...
ASCA observations of Seyfert 1 galaxies: II. Relativistic Iron K-alpha emission (1996)
Nandra, K., George, I. M., Mushotzky, R. F., Turner, T. J., Yaqoob, T.
We present evidence for widespread relativistic effects in the central regions of active galactic nuclei. In a sample of 18 Seyfert 1 galaxies observed by \asca, 14 show an iron K$\alpha$ line which...
The variable iron K emission line in MCG-6-30-15 (1996)
Iwasawa, K., Fabian, A. C., Reynolds, C. S., Nandra, K., Otani, C., Inoue, H., ...
We report on the variability of the iron K emission line in the Seyfert 1 galaxy MCG--6-30-15 during a four-day ASCA observation. The line consists of a narrow core at an energy of about 6.4 keV, and...
On broad iron K-alpha lines in Seyfert 1 galaxies (1995)
Fabian, A. C., Nandra, K., Reynolds, C. S., Brandt, W. N., Otani, C., Tanaka, Y., ...
The X-ray spectrum obtained by Tanaka et al from a long observation of the active galaxy MCG$-6-30-15$ shows a broad iron K$\alpha$ line skewed to low energies. The simplest interpretation of the...
Reynolds, C. S., Fabian, A. C., Nandra, K., Inoue, H., Kunieda, H., Iwasawa, K.
We present a detailed re-analysis of the two {\it ASCA} Performance Verification observations of the nearby Seyfert 1 galaxy MCG-6-30-15. Confirming the results of Fabian et al. (1994), we find...
Detection of broad iron K lines in active galaxies (1995)
Mushotzky, R F, Fabian, A C, Iwasawa, K, Kunieda, H, Matsuoka, M, Nandra, K, ...
Brandt, W. N., Fabian, A. C., Nandra, K., Reynolds, C. S., Brinkmann, W.
We present spatial, temporal and spectral analyses of ROSAT Position Sensitive Proportional Counter (PSPC) observations of the Seyfert 1 galaxies Ark 564, NGC 985, Kaz 163, Mrk 79 and RX...