AGN Feedback: Does it work? (2009)
Mathur, Smita, Stoll, Rebecca, Krongold, Yair, Nicastro, Fabrizio, Brickhouse, Nancy, Elvis, Martin
While feedback is important in theoretical models, we do not really know if it works in reality. Feedback from jets appears to be sufficient to keep the cooling flows in clusters from cooling too...
A Search for Oxygen in the Low-Density Lyman-alpha Forest Using the Sloan Digital Sky Survey (2009)
Pieri, Matthew M., Frank, Stephan, Mathur, Smita, Weinberg, David H., York, Donald G., Oppenheimer, Benjamin D.
We use 2167 Sloan Digital Sky Survey (SDSS) quasar spectra to search for low-density oxygen in the Intergalactic Medium (IGM). Oxygen absorption is detected on a pixel-by-pixel basis by its...
Black Hole Masses of Intermediate-Redshift Quasars: Near Infrared Spectroscopy (2009)
Dietrich, Matthias, Mathur, Smita, Grupe, Dirk, Komossa, S.
We present near-infrared spectra of ten luminous, intermediate redshift quasars observed with SofI at the NTT of ESO/La Silla. With these rest-frame optical spectra we probe the Hb -[OIII] emission...
GALEX Measurements of the Big Blue Bump in Soft X-ray Selected AGN (2009)
Atlee, David W., Mathur, Smita
We study the UV properties of Type I AGN from the ROSAT All-Sky Survey that have been selected to show unusually soft X-ray continua. We examine a sample of 54 Seyfert 1 galaxies with detections in...
Metallicity measurements in AGNs (2009)
Measuring metallicity in the nuclear regions of AGNs is difficult because only a few lines are observed and ionization correction becomes a major problem. Nitrogen to carbon ratio has been widely...
Black hole masses of intermediate-redshift quasars: near-infrared spectroscopy (2009)
Dietrich, Matthias, Mathur, Smita, Grupe, Dirk, Komossa, Stefanie
XMM-Newton View of the Multi-Phase Warm Absorber in Seyfert 1 Galaxy NGC985 (2008)
Krongold, Yair, Jimenez-Bailon, Elena, Santos-Lleo, Maria, Nicastro, Fabrizio, Elvis, Martin, Brickhouse, Nancy, ...
We present an analysis of an XMM-Newton observation of the Seyfert 1 Galaxy NGC 985. The EPIC spectra present strong residuals to a single power-law model, indicating the presence of ionized...
Finding Local Low-mass Supermassive Black Holes (2008)
Mathur, Smita, Ghosh, Himel, Ferrarese, Laura, Fiore, Fabrizio
The low-mass end of the supermassive black hole mass function is unknown and difficult to determine. Here we discuss our successful program to find active nuclei of late type "normal" galaxies using...
Detecting Low-Mass Supermassive Black Holes (2008)
Ghosh, Himel, Mathur, Smita, Fiore, Fabrizio, Ferrarese, Laura
We demonstrate the feasibility of uncovering supermassive black holes in late-type, quiescent spiral galaxies by detecting signs of very low-level nuclear activity. We use a combination of x-ray...
The candidate filament close to the 3C295 galaxy cluster: optical and X-ray spectroscopy (2008)
D'Elia, Valerio, Fiore, Fabrizio, Mathur, Smita, Cocchia, Filomena
We present a detailed analysis of the overdensity of X-ray sources colse to the 3C 295 galaxy cluster (z=0.46) to assess whether it is associated with a filament of the large-scale structure of the...
Low-Level Nuclear Activity in Nearby Spiral Galaxies (2008)
Ghosh, Himel, Mathur, Smita, Fiore, Fabrizio, Ferrarese, Laura
We are conducting a search for supermassive black holes (SMBHs) with masses below 10^7 M_sun by looking for signs of extremely low-level nuclear activity in nearby galaxies that are not known to be...
Variable x-ray absorption toward the gravitationally-lensed blazar PKS 1830-211 (2008)
Dai, Xinyu, Mathur, Smita, Chartas, George, Nair, Sunita, Garmire, Gordon P.
Restricted Access. Content older than 2 years remains open to all at the journal site(alternative location)
Chandra LETGS spectroscopy of the quasar MR 2251−178 and its warm absorber (2008)
Ramírez, R. M., Komossa, Stefanie, Burwitz, Vadim, Mathur, Smita
CHANDRA LETGS spectroscopy of ionized absorbers: the quasar MR 2251-178 (2008)
Ramírez, J. M., Komossa, Stefanie, Burwitz, Vadim, Mathur, Smita
Chandra Letgs spectroscopy of ionized absorbers: The quasar MR 2251-178 (2008)
J. M. Ramírez, Smita Mathur, Stefanie Komossa, Vadim Burwitz
This flux implies that the nuclear source of MR 2251-178 is in a relatively low state. We did not find evidence for an extra cold material in the line of sight, that would be associated to the giant...
Can Ionized Outflows in AGN Produce Important Feedback Effects? The Case of NGC 4051 (2008)
Elena Jiménez Bailón, Fabrizio Nicastro, Luc Binette, Martin Elvis, Nancy Brickhouse, Smita Mathur, ...
Using a 100 ks XMM-Newton exposure of the Narrow Line Seyfert 1 NGC 4051, we show that the time evolution of the ionization state of the X-ray absorbers in response to the rapid and highly variable...
Missing Baryons and the Warm-Hot Intergalactic Medium (2007)
Nicastro, F., Mathur, Smita, Elvis, Martin
Stars and gas in galaxies, hot intracluster medium, and intergalactic photo-ionized gas make up at most half of the baryons that are expected to be present in the universe. The majority of baryons...
John D. Silverman, Paul J. Green, Dong-woo Kim, Belinda J. Wilkes, Robert A, David Morris, ...
We present X-ray and optical observations of CXOMP J213945.0-234655, a high redshift (z = 4:93) quasar discovered through the Chandra Multiwavelength Project (ChaMP). This object is the most distant...
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio
We search for highly-ionized gas near three AGN host galaxies using the Chandra low-energy transmission grating spectrograph. Strong absorption lines from such gas are seen at z=0, most likely from...
On the nature of the z=0 X-ray absorbers: I. Clues from an external group (2007)
Mathur, Smita, Sivakoff, Gregory R., Williams, Rik J., Nicastro, Fabrizio
Absorption lines of OVII at redshift zero are observed in high quality Chandra spectra of extragalactic sightlines. The location of the absorber producing these lines, whether from the corona of the...
Lost Baryons at Low Redshift (2007)
Mathur, Smita, Nicastro, Fabrizio, Williams, Rik J.
We review our attempts to discover lost baryons at low redshift with ``X-ray forest'' of absorption lines from the warm-hot intergalactic medium. We discuss the best evidence to date along the Mrk...
Variable X-ray Absorption toward Gravitationally-Lensed Blazar PKS1830-211 (2007)
Dai, Xinyu, Mathur, Smita, Chartas, George, Nair, Sunita, Garmire, Gordon P.
We present X-ray spectral analysis of five Chandra and XMM-Newton observations of the gravitationally-lensed blazar PKS1830-211 from 2000 to 2004. We show that the X-ray absorption toward PKS1830-211...
Krongold, Yair, Nicastro, Fabrizio, Elvis, Martin, Brickhouse, Nancy, Binette, Luc, Mathur, Smita, ...
(Abridged) Using a 100 ks XMM-Newton exposure of NGC 4051, we show that the time evolution of the ionization state of the X-ray absorbers in response to the rapid and highly variable X-ray continuum...
HUBBLE SPACE TELESCOPE ULTRAVIOLET SPECTROSCOPY OF 14 LOW-REDSHIFT QUASARS (2007)
Ganguly, Rajib, Brotherton, Michael S., Arav, Nahum, Heap, Sara R., Wisotzki, Lutz, Aldcroft, Thomas L., ...
We present low-resolution ultraviolet spectra of 14 low-redshift (zem ≤ 0:8) quasars observed with the Hubble Space Telescope STIS as part of a Snapshot project to understand the relationship...
On the faint end of the high redshift AGN luminosity function (2007)
Shankar, Francesco, Mathur, Smita
Using the results of recent optical surveys we conclude that the {\it non}-detection of quasars down to faint magnitudes implies a significant flattening of the high redshift (z~6) optical active...
Time-Evolving Photoionization: the Thin and Compact X-Ray Wind of NGC 4051 (2007)
Nicastro, Fabrizio, Krongold, Yair, Elvis, Martin, Brickhouse, Nancy, Mathur, Smita, Binette, Luc
We discuss the power of time-evolving photoionization as a diagnostic tool to measure the electron density of photoionized gas. We apply this technique to a XMM-Newton observation of the ionized...
Revisiting the Black Hole Masses of Soft X-ray-Selected Active Galactic Nuclei (2006)
Watson, Linda C., Mathur, Smita, Grupe, Dirk
In our previous work, using luminosity and the H-beta FWHM as surrogates for black hole mass (M_BH), we compared the black hole masses of narrow-line Seyfert 1 galaxies (NLS1s) and broad-line Seyfert...
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio, Elvis, Martin
The X-ray bright z=0.116 quasar PKS 2155-304 is frequently observed as a Chandra calibration source, with a total of 483 ksec of Low Energy Transmission Grating (LETG) exposure time accumulated...
The weak absorbing outflow in AGN Mrk 279: evidence of super-solar metal abundances (2006)
Fields, Dale L., Mathur, Smita, Krongold, Yair, Williams, Rik, Nicastro, Fabrizio
We present analysis and photoionization modeling of the Chandra high resolution spectrum of Mrk 279. There is clear evidence of an absorbing outflow which is best fit by a two component model, one...
Hubble Space Telescope Ultraviolet Spectroscopy of Fourteen Low-Redshift Quasars (2006)
Ganguly, Rajib, Brotherton, Michael S., Arav, Nahum, Heap, Sara R., Wisotzki, Lutz, L. Aldcroft, Thomas, ...
We present low-resolution ultraviolet spectra of 14 low redshift (z em < 0.8) quasars observed with HST/STIS as part of a Snap project to understand the relationship between quasar outflows and...
Hubble Space Telescope Ultraviolet Spectroscopy of Fourteen Low-Redshift Quasars (2006)
Ganguly, Rajib, Brotherton, Michael S., Arav, Nahum, Heap, Sara R., Wisotzki, Lutz, Aldcroft, Thomas L., ...
We present low-resolution ultraviolet spectra of 14 low redshift (z
Chandra Observations of Candidate "True" Seyfert 2 Nuclei (2006)
Ghosh, Himel, Pogge, Richard W., Mathur, Smita, Martini, Paul, Shields, Joseph C.
The Unification Model for active galactic nuclei posits that Seyfert 2s are intrinsically like Seyfert 1s, but that their broad-line regions (BLRs) are hidden from our view. A Seyfert 2 nucleus that...
Frank, Stephan, Bentz, Misty C., Stanek, Krzysztof Z., Mathur, Smita, Dietrich, Matthias, Peterson, Bradley M., ...
We examine the recent report by Prochter et al. (2006) that gamma-ray burst (GRB) sight lines have a much higher incidence of strong MgII absorption than quasar sight lines. We propose that the...
XMM-Newton View of the z>0 Warm-Hot Intergalactic Medium Toward Markarian 421 (2006)
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio, Elvis, Martin
The recent detection with Chandra of two warm-hot intergalactic medium (WHIM) filaments toward Mrk 421 by Nicastro et al. provides a measurement of the bulk of the "missing baryons" in the nearby...
The radio-loud narrow-line quasar SDSS J172206.03+565451.6 (2006)
Komossa, Stefanie, Voges, Wolfgang, Adorf, Hans-Martin, Xu, Dawei, Mathur, Smita, Anderson, Scott F.
Radio-loud narrow-line type 1 quasars (2006)
Komossa, Stefanie, Voges, Wolfgang, Xu, Dawei, Mathur, Smita, Adorf, Hans-Martin, Lemson, Gerard, ...
Radio-loud narrow-line type 1 quasars (2006)
Komossa, Stefanie, Voges, Wolfgang, Xu, Dawei, Mathur, Smita, Adorf, Hans-Martin, Lemson, Gerard, ...
Chandra Detection of Local Warm-Hot Gas Toward Markarian 279 (2005)
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio
We report the Chandra detection of OVII K\alpha absorption at z=0 in the direction of the z=0.03 Seyfert 1 galaxy Mkn 279. The high velocity cloud Complex C lies along this line of sight, with HI...
Galactic Corona or Local Group Intergalactic Medium? (2005)
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio
Cosmological hydrodynamic simulations predict that the low redshift universe comprises a web of warm-hot intergalactic gas and galaxies, with groups of galaxies and clusters forming at dense knots in...
We re-examine the locus of narrow line Seyfert 1 galaxies on the M_BH--sigma (black hole mass--bulge velocity dispersion) plane in the light of the results from large new optically selected samples....
Probing The Dust-To-Gas Ratio of z > 0 Galaxies Through Gravitational Lenses (2005)
Dai, Xinyu, Kochanek, Christopher S., Chartas, George, Mathur, Smita
We report the detection of differential gas column densities in three gravitational lenses, MG0414+0534, HE1104-1805, and PKS1830-211. Combined with the previous differential column density...
Probing the Local Group Medium Toward Mkn 421 with Chandra and FUSE (2005)
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio, Elvis, Martin, Drake, Jeremy J., Fang, Taotao, ...
We report the detection of highly-ionized gas at z~0 seen in resonant UV and X-ray absorption lines toward the z=0.03 blazar Mkn 421. A total of 13 X-ray and 3 UV lines were measured (or upper limits...
Chandra Detection of the First X-ray Forest along the Line of Sight To Mkn 421 (2005)
Nicastro, Fabrizio, Mathur, Smita, Elvis, Martin, Drake, Jeremy, Fiore, Fabrizio, Fang, Taotao, ...
We present the first >=3.5 sigma (conservative) or >=5.8 sigma (sum of lines significance) detection of two Warm-Hot Intergalactic Medium (WHIM) filaments at z>0, which we find along the line of...
Super-solar Metallicity in the NLS1 Galaxy Markarian 1044 (2005)
Fields, Dale L., Mathur, Smita, Pogge, Richard W., Nicastro, Fabrizio, Komossa, Stefanie, Krongold, Yair
The determination of the bulk metallicity and the abundance mixture of various elements is very difficult in quasars and AGNs because only a few lines are observed and the ionization correction is...
Measured Cosmological Mass Density in the WHIM: the Solution to the 'Missing Baryons' Problem (2005)
Nicastro, Fabrizio, Elvis, Martin, Fiore, Fabrizio, Mathur, Smita
We review the current high-significance X-ray detections of Warm-Hot Intergalactic Medium (WHIM) filaments at z>0 along the lines of sight to the two blazars Mrk 421 (z=0.03) and 1ES 1028+511...
Supersolar N/C in the narrow-line Seyfert 1 galaxy markarian 1044 (2005)
Fields, Dale L., Mathur, Smita, Pogge, Richard W., Nicastro, Fabrizio, Komossa, Stefanie
Supersolar metallicity in the NLS1 galaxy markarian 1044 (2005)
Fields, Dale L., Mathur, Smita, Pogge, Richard W., Nicastro, Fabrizio, Komossa, Stefanie, Krongold, Yair
Black hole growth by accretion (2004)
We show that black holes grow substantially by accretion at close to Eddington rates. Using a complete sample of soft X-ray selected AGNs, Grupe & Mathur (2004) have shown that narrow line Seyfert 1...
Super-solar N/C in the NLS1 Galaxy Markarian 1044 (2004)
Fields, Dale L., Mathur, Smita, Pogge, Richard W., Nicastro, Fabrizio, Komossa, Stefanie
Narrow-Line Seyfert 1s (NLS1s) are known to have extreme values of a number of properties compared to Active Galactic Nuclei (AGN) as a class. In particular, previous emission-line studies have...
Black Hole Growth & the M_BH--Bulge Relations (2004)
We present the black hole mass--bulge velocity dispersion relation for a complete sample of 75 soft X-ray selected AGNs. We find that the AGNs with highest accretion rates relative to Eddington lie...
The faint X-ray Source Population near 3C 295 (2004)
D'Elia, Valerio, Fiore, Fabrizio, Elvis, Martin, Cappi, Massimo, Mathur, Smita, Mazzotta, Pasquale, ...
We present a statistical analysis of the Chandra observation of the source field around the 3C 295 galaxy cluster (z=0.46) aimed at the search for clustering of X-ray sources. We applied three...
Chandra Observations of X-ray Weak Narrow-Line Seyfert 1 Galaxies (2004)
Williams, Rik J., Mathur, Smita, Pogge, Richard W.
We present Chandra observations of 17 optically-selected, X-ray weak narrow-line Seyfert 1 (NLS1) galaxies. These objects were optically identified by Williams et al. (2002) in the Sloan Digital Sky...
M-BH - sigma relation for a Complete Sample of Soft X-ray Selected AGNs (2003)
We present black hole mass--bulge velocity dispersion relation for a complete sample of 75 soft X-ray selected AGNs: 43 broad line Seyfert 1s and 32 narrow line Seyfert 1s. We use luminosity and...
Chandra discovery of the intracluster medium around UM425 at redshift 1.47 (2003)
Mathur, Smita, Williams, Rik J.
We report on a discovery of a candidate cluster of galaxies at redshift z=1.47 based on Chandra observations in the field of quasars UM425 A & B. We detect with high significance diffuse emission due...
X-ray Observations of the Warm-Hot Intergalactic Medium (2002)
Mathur, Smita, Weinberg, David H., Chen, Xuelei
We present Chandra observations that provide the most direct evidence to date for the pervasive, moderate density, shock-heated intergalactic medium predicted by leading cosmological scenarios. We...
The Ionized Gas and Nuclear Environment in NGC 3783 II. Averaged HST/STIS and FUSE Spectra (2002)
Gabel, Jack R., Crenshaw, D. Michael, Kraemer, Steven B., Brandt, W. N., George, Ian M., Hamann, Frederick W., ...
We present observations of the intrinsic absorption in the Seyfert 1 galaxy NGC 3783 obtained with the STIS/HST and FUSE. We have coadded multiple STIS and FUSE observations to obtain a high S/N...
Narrow-line Seyfert 1 Galaxies from the Sloan Digital Sky Survey Early Data Release (2002)
Williams, Rik J., Pogge, Richard W., Mathur, Smita
We present a sample of 150 narrow-line Seyfert 1s (NLS1s) found within the Sloan Digital Sky Survey Early Data Release (EDR), only two of which were previously identified as such. This substantially...
Mathur, Smita, Weinberg, David, Chen, Xuelei
We present a high resolution (R~500) X-ray spectrum of the bright quasar H1821+643 (z=0.297), obtained in a 470 ksec Chandra observation. We search for X-ray absorption by highly ionized metal...
Warm Absorbers in Active Galactic Nuclei (2002)
Observations of warm absorbers provided new ways to study the nuclear environments of AGNs. I discuss basic properties of warm absorbers and early developments with ROSAT, ASCA and HST observations....
Chandra Detection of Highest Redshift (z~6) Quasars in X-rays (2002)
Mathur, Smita, Wilkes, Belinda, Ghosh, Himel
We report on Chandra observations of three quasars SDSSP J083643+005453, SDSSP J103027+052455, and SDSSP J130608+035626 at redshifts 5.82, 6.28 and 5.99 respectively. All the three sources are...
Recent Chandra Results on AGNs & Future Prospects (2001)
I review Chandra's achievements in the last two years in AGN research. I concentrate on some topics of my interest; some others are reviewed in an accompanying article by K. Nandra. I comment briefly...
HST STIS Observations of PG 0946+301: the Highest Quality UV Spectrum of a BALQSO (2001)
Arav, Nahum, De Kool, Martijn, Korista, Kirk T., Crenshaw, D. Michael, Van Breugel, Wil, Brotherton, Michael, ...
We describe deep (40 orbits) HST/STIS observations of the BALQSO PG 0946+301 and make them available to the community. These observations are the major part of a multi-wavelength campaign on this...
The z=5.8 Quasar SDSSp J1044-0125: A Peek at Quasar Evolution? (2001)
The newly discovered z=5.8 quasar SDSSp J104433.04-012502.2 was recently detected in X-rays and found to be extremely X-ray weak. Here we present the hardness ratio analysis of the XMM-Newton...
Supersolar metal abundances and the Broad Line Region of Narrow-line Seyfert 1 galaxies (2001)
Komossa, Stefanie, Mathur, Smita
Narrow-line Seyfert 1 galaxies (NLSy1) are intriguing due to their extreme continuum and emission line properties which are not yet well understood. This paper is motivated by the recent suggestion...
A Chandra Survey of Broad Absorption Line Quasars (2001)
Green, Paul J., Aldcroft, Thomas L., Mathur, Smita, Wilkes, Belinda J., Elvis, Martin
We have carried out a survey with the Chandra X-ray Observatory of a sample of 10 optically bright broad absorption line (BAL) QSOs. Eight out of ten sources are detected. The 6 brightest X-ray...
Evolution of Active Galaxies: Black-hole Mass - Bulge relations for Narrow Line Objects (2001)
Mathur, Smita, Kuraszkiewicz, Joanna, Czerny, Bozena
Mathur (2000) has proposed that the narrow line Seyfert 1 galaxies (NLS1s) are likely to be the active galaxies in early stage of evolution. To test this hypothesis, we have calculated the black hole...
BeppoSAX Observations of the Maser Sy2 Galaxy: ESO103-G35 (2000)
Wilkes, Belinda J., Mathur, Smita, Fiore, Fabrizio, Antonelli, Angelo, Nicastro, Fabrizio
We have made BeppoSAX observations of the Seyfert 2/1.9 galaxy ESO103-G35, which contains a nuclear maser source and is known to be heavily absorbed in the X-rays. Analysis of the X-ray spectra...
150 keV Emission from PKS2149-306 with BeppoSAX (2000)
Elvis, Martin, Fiore, Fabrizio, Siemiginowska, Aneta, Bechtold, Jill, Mathur, Smita, McDowell, Jonathan
A BeppoSAX observation of the z=2.34 quasar PKS2149-306 produced a strong signal in the high energy PDS instrument up to a maximum observed energy of nearly 50 keV, 150 keV in the quasar frame. The...
New Insights Into The Narrow-Line Seyfert 1 Phenomenon (2000)
I briefly review the X/UV absorber models and show that the observations of NLS1s are generally consistent with the models. The covering factor of absorbers in NLS1s is likely to be high and there is...
Narrow Line Seyfert 1 Galaxies and the Evolution of Galaxies & Active Galaxies (2000)
Narrow Line Seyfert 1 galaxies (NLS1s) are intriguing due to their continuum as well as emission line properties. The observed peculiar properties of the NLS1s are believed to be due to accretion...
Acculturation among Indian immigrants : a study of ethnic identification and mate-selection / (2000)
Photocopy.
Multiple Velocity Components in the CIV Absorption Line of NGC5548 (1999)
Mathur, Smita, Elvis, Martin, Wilkes, Belinda
We have observed the much studied Seyfert 1 galaxy NGC5548 with the GHRS spectrometer on HST. Our 14ksec observation covers the CIV emission line at a resolution of >20,000. Our purpose was to study...
NGC 7582: The Prototype Narrow-Line X-ray Galaxy (1998)
Schachter, Jonathan F., Fiore, Fabrizio, Elvis, Martin, Mathur, Smita, Wilson, Andrew S., Morse, Jon A., ...
NGC 7582 is a candidate prototype of the Narrow Line X-ray Galaxies (NLXGs) found in deep X-ray surveys. An ASCA observation shows the hard (> 3 keV) X-ray continuum of NGC 7582 drops 40% in ~6 ks,...
Mathur, Smita, Wilkes, Belinda, Elvis, Martin
The unified picture of X-ray/UV absorbers offers an unique opportunity to probe the nuclear environment of AGNs. To test the unified absorber scenario and to understand the physical properties of the...
Comments On The Intrinsic X-ray/UV Absorbers In AGN (1997)
This talk discusses the unified X-ray/UV absorption models in AGN. I will first review the models and discuss how they offer an unique opportunity to probe the near nuclear environment of AGNs....
X-ray Absorption Towards The Einstein Ring Source PKS1830-211 (1997)
PKS1830-211 is an unusually radio-loud gravitationally lensed quasar. In the radio, the system appears as two compact, dominant features surrounded by relatively extended radio emission which forms...
Evidence Against BALS in the X-ray Bright QSO PG1416-129 (1997)
Green, Paul J., Aldcroft, Thomas L., Mathur, Smita, Schartel, Norbert
Recent results from the ROSAT All Sky Survey, and from deep ROSAT pointings reveal that broad absorption line quasars (BALQSOs) are weak in the soft X-ray bandpass (with optical-to-X-ray spectral...
The X-ray Warm Absorber in NGC3516 (1996)
Mathur, Smita, Wilkes, Belinda J., Aldcroft, Thomas
The Seyfert 1 galaxy, NGC3516 has been the subject of many absorption line studies at both ultraviolet and X-ray wavelengths. In the UV, strong, broad, variable associated metal line absorption with...
Associated Absorption at Low and High Redshift (1996)
Elvis, Martin, Mathur, Smita, Wilkes, Belinda J., Fiore, Fabrizio, Giommi, Paolo, Padovani, Paolo, ...
Combining information on absorbing material in AGN from X-ray and the UV creates a powerful investigative tool. Here we give examples from both low and high redshift.
The Evolving XUV Absorber in NGC3516 (1996)
Mathur, Smita, Wilkes, Belinda, Aldcroft, Thomas
For NGC3516 we find that the X-ray warm absorption and the broad UV associated absorption features can be produced by the same absorbing material. We argue that the evolution of the XUV absorber from...
Broad Absorption Line QSOs Observed by the ROSAT PSPC (1995)
Recent results from the ROSAT All-Sky Survey (RASS) have shown that broad absorption line (BAL) QSOs are either highly absorbed or underluminous in the soft X-ray bandpass. Here, we extend this work...
Optical Detection of the Hidden Nuclear Engine in NGC~4258 (1995)
Wilkes, Belinda J., Schmidt, Gary D., Smith, Paul S., Mathur, Smita, McLeod, Kim K.
The sub-parsec masing disk recently found to be orbiting a central mass of $\sim3.6\times10^7$~\msun\ in the Seyfert/LINER galaxy NGC~4258 provides the most compelling evidence to date for the...
Strong X-ray Absorption in a BALQSO: PHL5200 (1995)
Mathur, Smita, Elvis, Martin, Singh, K. P.
We present $\it {ASCA}$ observations of the z=1.98 prototype BALQSO: PHL5200. The source was detected in both SIS and GIS. A power-law spectrum ($\alpha_E = 0.6^{+0.9}_{-0.6}$) with large intrinsic...