A5031697761- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Pulsars and Gravitational Waves Research
- Scientific Research and Discoveries
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Spectroscopy and Laser Applications
- Particle Accelerators and Free-Electron Lasers
- High-pressure geophysics and materials
- Laser Design and Applications
- Solar and Space Plasma Dynamics
- Historical Astronomy and Related Studies
- Atomic and Molecular Physics
- Photocathodes and Microchannel Plates
- CCD and CMOS Imaging Sensors
- Optical Systems and Laser Technology
- Calibration and Measurement Techniques
University of California, Santa Cruz
2015-2024
National Research University Higher School of Economics
2018
Lomonosov Moscow State University
2018
University of California System
2014-2015
The University of Texas at Austin
1983-2013
University of Valparaíso
2011-2013
University of Nebraska–Lincoln
2001-2012
Valparaiso University
2011-2012
University of Michigan–Ann Arbor
1989-2008
Universidad Nacional Autónoma de México
2004-2007
We present photometric and spectroscopic observations of SN 1991bg, a very peculiar Type Ia supernova located in the outskirts E1 galaxy NGC 4374 (M84) Virgo cluster. At maximum brightness 1991bg was 1.6 mag subluminous V 2.5 B, compared with normal SNe Ia. The colors were unusually red, but object not significantly reddened by dust. decline from certainly quite steep; we measure an initial linear fading 0.10 d^-1^ rather than typical value 0.06 for Ia, late- time 0.034 0.026 d^-1^....
view Abstract Citations (566) References (67) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Old stellar populations. I. A spectroscopic comparison of galactic globular clusters, M 31 and elliptical galaxies. Burstein, D. ; Faber, S. M. Gaskell, C. Krumm, N. Integrated 9 A-resolution spectra in the 4000-6300 region are presented for 17 Galactic clusters 19 M31 clusters. Indices 11 molecular bands lines several broadband colors compared between cluster...
view Abstract Citations (502) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steps toward Determination of the Size and Structure Broad-Line Region in Active Galactic Nuclei. I. an 8 Month Campaign Monitoring NGC 5548 with IUE Clavel, J. ; Reichert, G. A. Alloin, D. Crenshaw, M. Kriss, Krolik, H. Malkan, Netzer, Peterson, B. Wamsteker, W. Altamore, Baribaud, T. Barr, P. Beck, S. Binette, L. Bromage, E. Brosch, N. Diaz, Filippenko, V. Fricke,...
view Abstract Citations (386) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Accuracy of Cross-Correlation Estimates Quasar Emission-Line Region Sizes Gaskell, C. Martin ; Peterson, Bradley M. use cross-correlation analyses emission-line and optical continuum fluxes to determine broad-line region (BLR) sizes in low-luminosity quasars is examined detail. Uncertainties associated with this method are discussed, analytic formulas for...
view Abstract Citations (379) References (50) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Line Variations in Quasars and Seyfert Galaxies Gaskell, C. M. ; Sparke, L. S. Quantitative estimates of the sizes broad-line regions three well-studied I galaxies are presented, differences between these previously reported size for NGC 4151 discussed. Both Lick Observatory IUE satellite data on analyzed, it is shown that both consistent with high-ionization...
We present the final results from a high sampling rate, multi-month, spectrophotometric reverberation mapping campaign undertaken to obtain either new or improved Hβ lag measurements for several relatively low-luminosity active galactic nuclei (AGNs). have reliably measured time delay between variations in continuum and emission line six local Seyfert 1 galaxies. These are used calculate mass of supermassive black hole at center each these AGNs. place our context most current calibration...
view Abstract Citations (424) References (51) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A redshift difference between high and low ionization emission-line regions in QSO's-evidence for radial motions. Gaskell, C. M. The discovery of a systematic the redshifts emission lines arising from different zones broad-line quasar clouds is reported. C IV, N V, III], [Fe X], possibly Lyman-α are at lower than 0 1, Mg II, Balmer lines. Comparison with narrow shows...
view Abstract Citations (384) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Old stellar populations. II. an analysis of K-giant spectra. Faber, S. M. ; Friel, E. D. Burstein, Gaskell, C. Eleven strong absorption features are studied in a sample 110 stars, based on spectra taken at 9-A resolution, including such as CN 4170 A, G-band, H-beta, Mg b, MgH, two Fe lines, NaD, and TiO bands. The surface sensitive to gravity determined; it is noted...
view Abstract Citations (302) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steps toward Determination of the Size and Structure Broad-Line Region in Active Galactic Nuclei. II. an Intensive Study NGC 5548 at Optical Wavelengths Peterson, B. M. ; Balonek, T. J. Barker, E. S. Bechtold, Bertram, R. Bochkarev, N. G. Bolte, Bond, D. Boroson, A. Carini, Carone, Christensen, Clements, Cochran, L. Cohen, Crampton, Dietrich, Elvis, Ferguson,...
A detailed analysis of the data from a high sampling rate, multi-month reverberation mapping campaign, undertaken primarily at MDM Observatory with supporting observations telescopes around world, reveals that Hbeta emission region within broad line regions (BLRs) several nearby AGNs exhibit variety kinematic behaviors. While primary goal this campaign was to obtain either new or improved lag measurements for relatively low luminosity (presented in separate work), we were also able...
We present results of an intensive 2 month campaign ground-based spectrophotometric monitoring the Seyfert 1 galaxy NGC 7469, with a temporal resolution ≲ day. The broad Hα and Hβ emission lines respond to ~35% ultraviolet continuum variations amplitude ~10% time delays 5.6 ± 1.3 days 5.4 0.8 days, respectively. interpret this as evidence variable Balmer line gas ~5-6 light from central source in object, widely believed be supermassive black hole. virial mass implied by widths is ~106-107...
An 8 month monitoring campaign on the Seyfert 1 galaxy Fairall 9 has been conducted with International Ultraviolet Explorer in an attempt to obtain reliable estimates of continuum-continuum and continuum-emission-line delays for a high-luminosity active galactic nucleus (AGN). While results this are more ambiguous than those previous campaigns lower luminosity sources, we find general agreement earlier results: (1) there is no measurable lag between ultraviolet continuum bands, (2) measured...
view Abstract Citations (180) References (64) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multiwavelength Observations of Short-Timescale Variability in NGC 4151. IV. Analysis Continuum Edelson, R. A. ; Alexander, T. Crenshaw, D. M. Kaspi, S. Malkan, Peterson, B. Warwick, Clavel, J. Filippenko, V. Horne, K. Korista, Kriss, G. Krolik, H. Maoz, Nandra, O'Brien, P. Penton, Yaqoob, Albrecht, Alloin, Ayres, Balonek, Barr, Barth, Bertram, Bromage, E. Carini,...
From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored Seyfert 1 galaxy NGC 7469 continuously in an attempt measure time delays between continuum and emission-line fluxes. delays, one can estimate size of region dominating production UV emission lines this source. We find strong respond variations with about 23-31 for Lyα, 27 C IV λ1549, 19-24 N V λ1240, 17-18 Si λ1400, 07-10 He II λ1640. The most remarkable result, however, is detection apparent different bands. With...
We present extinction curves derived from the broad emission lines and continua of large samples both radio-loud radio-quiet AGNs. The are significantly flatter in UV than for local ISM. reddening LBQS quasars slightly steeper those UV, probably because additional by dust further out host galaxies former. AGNs very flat. This is explicable with slight modifications to standard MRN models: there a relative lack small grains nuclear dust. Our continuum broad-emission line agree shape...
view Abstract Citations (131) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Type Ib Supernovae 1983n and 1985f: Oxygen-rich Late Time Spectra Gaskell, C. M. ; Cappellaro, E. Dinerstein, H. L. Garnett, D. R. Harkness, P. Wheeler, J. Spectroscopic observations of SN obtained on February 28 March 1, 1984 (8 mo after maximum light) 1985f 25, 1985 (25 d discovery), both using the IDS spectrograph 2.7-m telescope at McDonald Observatory, are...
Context.Spectropolarimetry of AGNs is a powerful tool for studying the structure and kinematics inner regions quasars.
We present the first results from a high sampling rate, multimonth reverberation mapping campaign undertaken primarily at MDM Observatory with supporting observations telescopes around world. The primary goal of this was to obtain either new or improved Hβ lag measurements for several relatively low luminosity active galactic nuclei (AGNs). feature NGC 4051 here because, until now, object has been significant outlier AGN scaling relationships, e.g., it previously ∼2–3σ on relationship...
We discuss the use of Sloan Digital Sky Survey (SDSS) ugriz point-spread function (PSF) photometry for setting zero points UBVRI CCD images. From a comparison with Landolt (1992, AJ, 104, 340) standards and our own we find that there is fairly abrupt change in B, V, R, I around g, r, i ∼ 14.5, U point at u 16. These changes correspond to where significant interpolation due saturation SDSS PSF fluxes. There also seems be another, much smaller systematic effect stars r ≳ 19.5. The latter...
We present the results of extensive multi-frequency monitoring radio galaxy 3C 120 between 2002 and 2007 at X-ray, optical, wave bands, as well imaging with Very Long Baseline Array (VLBA). Over 5 yr observation, significant dips in X-ray light curve are followed by ejections bright superluminal knots VLBA images. Consistent this, flux 37 GHz anti-correlated leading variations. This implies that, this galaxy, radiative state accretion disk plus corona system, where X-rays produced, has a...
Low-redshift active galactic nuclei (AGNs) with extremely blue optical spectral indices are shown to have a mean, velocity-averaged, broad-line Hα/Hβ ratio of ≈2.72 ± 0.04, consistent Baker-Menzel Case B value. Comparison wide range properties the very bluest AGNs those luminosity-matched subset Dong et al. AGN sample indicates that only difference is internal reddening. Ultraviolet fluxes brighter for by an amount flat reddening curve Gaskell The lack significant in GALEX...
ABSTRACT We derive a mean attenuation curve out to the rest-frame extreme ultraviolet (EUV) for ‘BAL dust’ – dust causing additional extinction of active galactic nuclei (AGNs) with broad absorption lines (BALQSOs). In contrast normal, relatively flat, AGN curve, BAL is well fit by steeply rising, SMC-like curve. confirm shape theoretical Weingartner & Draine SMC 700 Angstroms but drop in at still shorter wavelengths less than predicted. The similar low-ionization BALQSOs (LoBALs) does...
view Abstract Citations (164) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steps toward Determination of the Size and Structure Broad-Line Region in Active Galactic Nuclei. V. Variability Ultraviolet Continuum Emission Lines NGC 3783 Reichert, G. A. ; Rodriguez-Pascual, P. M. Alloin, D. Clavel, J. Crenshaw, Kriss, Krolik, H. Malkan, Netzer, Peterson, B. Wamsteker, W. Altamore, Altieri, Anderson, K. S. Blackwell, H., Jr. Boisson, C. Brosch,...