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Improved Standardization of Type II-P Supernovae: Application to an Expanded Sample
Dovi Poznanski, Nathaniel Butler, Alexei V. Filippenko +16
In the epoch of precise and accurate cosmology, cross-confirmation using a variety of cosmographic methods is paramount to circumvent systematic uncertainties. Owing to progenitor…
An Upper Mass Limit on a Red Supergiant Progenitor for the Type II-Plateau Supernova SN 2006my
Douglas C. Leonard, Avishay Gal-Yam, Derek B. Fox +5
We analyze two pre-supernova (SN) and three post-SN high-resolution images of the site of the Type II-Plateau supernova SN 2006my in an effort to either detect the progenitor star…
GALEX Spectroscopy of SN 2005ay suggests a UV spectral uniformity among type II-P supernovae
A. Gal-Yam, F. Bufano, T. Barlow +24
We present the first results from our GALEX program designed to obtain ultraviolet (UV) spectroscopy of nearby core-collapse supernovae (SNe). Our first target, SN 2005ay in the ne…
The type IIb SN 2008ax: the nature of the progenitor
R. M. Crockett, J. J. Eldridge, S. J. Smartt +9
A source coincident with the position of the type IIb supernova (SN) 2008ax is identified in pre-explosion Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observations i…
A Supernova Riddle
Douglas C. Leonard
Analysis of the polarization of light from supernovae can reveal the shape and distribution of matter ejected from exploding stars. Here we review the young field of Type Ia supern…
Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen in Nebular Spectra
Douglas C. Leonard
Despite intense scrutiny, the progenitor system(s) that gives rise to Type Ia supernovae remains unknown. The favored theory invokes a carbon-oxygen white dwarf accreting hydrogen-…
The Dual-Axis Circumstellar Environment of the Type IIn Supernova 1997eg
Jennifer L. Hoffman, Douglas C. Leonard, Ryan Chornock +3
We present multi-epoch spectral and spectropolarimetric observations of the Type IIn supernova (SN) 1997eg that indicate the presence of a flattened disk-like concentration of circ…
Detection of circumstellar material in a normal Type Ia Supernova
F. Patat, P. Chandra, R. Chevalier +19
Type Ia supernovae are thought to be thermonuclear explosions of accreting white dwarfs that reach a critical mass limit. Despite their importance as cosmological distance indicato…
Preliminary Results from the Caltech Core-Collapse Project (CCCP)
Avishay Gal-Yam, S. B. Cenko, D. B. Fox +4
We present preliminary results from the Caltech Core-Collapse Project (CCCP), a large observational program focused on the study of core-collapse SNe. Uniform, high-quality NIR and…
A High-Resolution Spectrum of the Extremely Metal-Rich Bulge G-Dwarf OGLE-2006-BLG-265
Jennifer A. Johnson, Avishay Gal-Yam, Douglas C. Leonard +3
We present an R=45,000 Keck spectrum of the microlensed Galactic bulge G-dwarf OGLE-2006-BLG-265, which has a high (~60) signal-to-noise ratio despite its short (15 min) exposure t…
The gamma-ray burst GRB060614 requires a novel explosive process
A. Gal-Yam, D. Fox, P. Price +26
Over the past decade our physical understanding of gamma-ray bursts (GRBs) has progressed rapidly thanks to the discovery and observation of their long-lived afterglow emission. Lo…
On the progenitor of SN 2005gl and the nature of Type IIn supernovae
Avishay Gal-Yam, D. C. Leonard, D. B. Fox +8
We present a study of the type IIn supernova (SN) 2005gl, in the relatively nearby (d~66 Mpc) galaxy NGC 266. Photometry and spectroscopy of the SN indicate it is a typical member…
Towards a Cosmological Hubble Diagram for Type II-P Supernovae
Peter Nugent, Mark Sullivan, Richard Ellis +13
We present the first high-redshift Hubble diagram for Type II-P supernovae (SNe II-P) based upon five events at redshift up to z~0.3. This diagram was constructed using photometry…
A non-spherical core in the explosion of supernova SN 2004dj
Douglas C. Leonard, Alexei V. Filippenko, Mohan Ganeshalingam +9
An important and perhaps critical clue to the mechanism driving the explosion of massive stars as supernovae is provided by the accumulating evidence for asymmetry in the explosion…
Hubble Space Telescope and Ground-Based Observations of Type Ia Supernovae at Redshift 0.5: Cosmological Implications
A. Clocchiatti, B. Schmidt, A. Filippenko +26
We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshift z~0.5. They were discovered in early 1999 with the 4.0~m Blanco telescope…
The afterglow and elliptical host galaxy of the short gamma-ray burst GRB 050724
E. Berger, P. A. Price, S. B. Cenko +21
Despite a rich phenomenology, gamma-ray bursts (GRBs) are divided into two classes based on their duration and spectral hardness -- the long-soft and the short-hard bursts. The dis…
Evidence for Spectropolarimetric Diversity in Type Ia Supernovae
Douglas C. Leonard, Weidong Li, Alexei V. Filippenko +2
We present single-epoch, post-maximum spectropolarimetry of four Type Ia supernovae (SNe Ia) that span a range of spectral and photometric properties: SN 2002bf and SN 2004dt exhib…
Interstellar Polarization and the Position Angle Orientations of Seyfert 1 Galaxies
Jennifer L. Hoffman, Ryan Chornock, Douglas C. Leonard +1
We comment on recent spectropolarimetric studies that compare the observed polarization position angles (PAs) of Seyfert 1 galaxies near H alpha with the observed orientations of t…
A Definitive Measurement of Time Dilation in the Spectral Evolution of the Moderate-Redshift Type Ia Supernova 1997ex
R. J. Foley, A. V. Filippenko, D. C. Leonard +3
We have obtained high-quality Keck optical spectra at three epochs of the Type Ia supernova 1997ex, whose redshift z is 0.361. The elapsed calendar time between the first two spect…
An HST Search for Supernovae Accompanying X-ray Flashes
A. M. Soderberg, S. R. Kulkarni, D. B. Fox +24
We present the results from an Hubble Space Telescope/ACS search for supernovae associated with X-ray flashes 020903, 040701, 040812 and 040916. We find strong evidence that XRF 02…
Photometric Typing Analyses of Three Young Supernovae with the Robotic Palomar 60-Inch Telescope
Anne M. Rajala, Derek B. Fox, Avishay Gal-Yam +6
We present photometric typing analyses of three young supernovae observed with the Robotic 60-inch Telescope at Palomar Observatory (P60). This represents the first time that such…
The Caltech Core-Collapse Project (CCCP)
A. Gal-Yam, S. B. Cenko, D. W. Fox +4
The cosmological utility of type Ia Supernovae (SNe) prompted numerous studies of these events, and they are now well characterized observationally, both as individual objects and…
Spectropolarimetry of Core-Collapse Supernovae
Douglas C. Leonard, Alexei V. Filippenko
We briefly review the young field of spectropolarimetry of core-collapse supernovae (SNe). Spectropolarimetry provides the only direct known probe of early-time supernova (SN) geom…
Hubble Space Telescope and Ground-Based Observations of SN 1993J and SN 1998S: CNO Processing in the Progenitors
Claes Fransson, Peter M. Challis, Roger A. Chevalier +13
Ground-based and Hubble Space Telescope observations are presented for SN 1993J and SN 1998S. SN 1998S shows strong, relatively narrow circumstellar emission lines of N III-V and C…