An Unusually Fast-Evolving Supernova (2009)
Poznanski, Dovi, Chornock, Ryan, Nugent, Peter E., Bloom, Joshua S., Ganeshalingam, Mohan, Leonard, Douglas C., ...
Analyses of supernovae (SNe) have revealed two main types of progenitors: exploding white dwarfs and collapsing massive stars. We present SN2002bj, which stands out as different from any SN reported...
Seeking Core-Collapse Supernova Progenitors in Pre-Explosion Images (2009)
I summarize what we have learned about the nature of stars that ultimately explode as core-collapse supernovae from the examination of images taken prior to the explosion. By registering...
Research Science and Education: The NSF's Astronomy and Astrophysics Postdoctoral Fellowship (2009)
Norman, Dara, Agueros, Marcel, Brown, Timothy M., Browning, Matthew, Chakrabarti, Sukanya, Cobb, Bethany, ...
The NSF's Astronomy and Astrophysics Postdoctoral Fellowship (AAPF) is exceptional among the available postdoctoral awards in Astronomy and Astrophysics. The fellowship is one of the few that allows...
O/IR Polarimetry for the 2010 Decade (SSE): Science at the Edge, Sharp Tools for All (2009)
Hoffman, Jennifer L., Hines, Dean C., Adamson, Andy, Bjorkman, Karen, Chornock, Ryan, ...
Science opportunities and recommendations concerning optical/infrared polarimetry for the upcoming decade in the fields of stars and stellar evolution. Community-based White Paper to Astro2010 in...
Type II Supernovae as Probes of Cosmology (2009)
Poznanski, Dovi, Baron, Eddie, Blondin, Stephane, Bloom, Joshua S., D'Andrea, Christopher B., Della Valle, Massimo, ...
- Constraining the cosmological parameters and understanding Dark Energy have tremendous implications for the nature of the Universe and its physical laws. - The pervasive limit of systematic...
Leonard, Douglas C., Gal-Yam, Avishay, Fox, Derek B., Cameron, P. B., Johansson, Erik M., Kraus, Adam L., ...
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 or to constrain its...
Improved Standardization of Type II-P Supernovae: Application to an Expanded Sample (2008)
Poznanski, Dovi, Butler, Nathaniel, Filippenko, Alexei V., Ganeshalingam, Mohan, Li, Weidong, Bloom, Joshua S., ...
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 histories and...
Leonard, Douglas C., Gal-Yam, Avishay, Fox, Derek B., Cameron, P. B., Johansson, Erik M., Kraus, Adam L., ...
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 or to constrain its...
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 supernova...
Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen in Nebular Spectra (2007)
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-rich material from...
The Dual-Axis Circumstellar Environment of the Type IIn Supernova 1997eg (2007)
Hoffman, Jennifer L., Leonard, Douglas C., Chornock, Ryan, Filippenko, Alexei V., Barth, Aaron J., Matheson, Thomas
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 circumstellar material...
A High-Resolution Spectrum of the Extremely Metal-rich Bulge G Dwarf OGLE-2006-BLG-265 (2007)
Johnson, Jennifer A., Gal-Yam, Avishay, Leonard, Douglas C., Simon, Joshua D., Udalski, Andrzej, Gould, Andrew
We present an R = 45,000 Keck spectrum of the microlensed Galactic bulge G dwarf OGLE-2006-BLG-265, which has high (~60) signal-to-noise ratio despite its short (15 minute) exposure time, because the...
A High-Resolution Spectrum of the Extremely Metal-Rich Bulge G-Dwarf OGLE-2006-BLG-265 (2006)
Johnson, Jennifer A., Gal-Yam, Avishay, Leonard, Douglas C., Simon, Joshua D., Udalski, Andrzej, Gould, Andrew
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 time because the...
Toward a cosmological Hubble diagram for Type II-P supernovae (2006)
Nugent, Peter, Sullivan, Mark, Ellis, Richard, Gal-Yam, Avishay, Leonard, Douglas C., Howell, D. Andrew, ...
We present the first high-redshift Hubble diagram for Type II-P supernovae (SNe II-P) based on five events at redshift up to z ~ 0.3. This diagram was constructed using photometry from the...
Towards a Cosmological Hubble Diagram for Type II-P Supernovae (2006)
Nugent, Peter, Sullivan, Mark, Ellis, Richard, Gal-Yam, Avishay, Leonard, Douglas C., Howell, D. Andrew, ...
We present the first high-redshift Hubble diagram for Type II-P supernovae (SNe II-P) based upon five events at redshift up toz~;0.3. This diagram was constructed using photometry from the...
Towards a Cosmological Hubble Diagram for Type II-P Supernovae (2006)
Nugent, Peter, Sullivan, Mark, Ellis, Richard, Gal-Yam, Avishay, Leonard, Douglas C., Howell, D. Andrew, ...
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 from the...
A non-spherical core in the explosion of supernova SN 2004dj (2006)
Leonard, Douglas C., Filippenko, Alexei V., Ganeshalingam, Mohan, Serduke, Franklin J. D., Li, Weidong, Swift, Brandon J., ...
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. Indirect evidence...
Evidence for Spectropolarimetric Diversity in Type Ia Supernovae (2005)
Leonard, Douglas C., Li, Weidong, Filippenko, Alexei V., Foley, Ryan J., Chornock, Ryan
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 exhibit unusually...
Interstellar Polarization and the Position Angle Orientations of Seyfert 1 Galaxies (2005)
Hoffman, Jennifer L., Chornock, Ryan, Leonard, Douglas C., Filippenko, Alexei V.
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 their radio source...
Rajala, Anne M., Fox, Derek B., Gal-Yam, Avishay, Leonard, Douglas C., Soderberg, Alicia M., Kulkarni, S. R., ...
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 photo-typing has...
Spectropolarimetry of Core-Collapse Supernovae (2004)
Leonard, Douglas C., Filippenko, Alexei V.
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) geometry. The...
Fransson, Claes, Challis, Peter M., Chevalier, Roger A., Filippenko, Alexei V., Kirshner, Robert P., Kozma, Cecilia, ...
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 III-IV, as well as...
The type IIn supernova 1994W: evidence for the explosive ejection of a circumstellar envelope (2004)
Chugai, Nikolai N., Blinnikov, Sergei I., Cumming, Robert J., Lundqvist, Peter, Bragaglia, Angela, Filippenko, Alexei V., ...
We present and analyse spectra of the Type IIn supernova 1994W obtained between 18 and 203 days after explosion. During the luminous phase (first 100 d) the line profiles are composed of three major...
Spectropolarimetric Observations of Supernovae (2003)
Filippenko, Alexei V., Leonard, Douglas C.
We briefly review the existing database of supernova spectropolarimetry, concentrating on recent data and on results from our group's research. Spectropolarimetry provides the only direct known probe...
SN 1994W: evidence of explosive mass ejection a few years before explosion (2003)
Chugai, Nikolai N., Cumming, Robert J., Blinnikov, Sergei I., Lundqvist, Peter, Filippenko, Alexei V., Barth, Aaron J., ...
We present and analyse spectra of the Type IIn supernova 1994W obtained between 18 and 202 days after explosion. During the first 100 days the line profiles are composed of three major components:...
Using Multi-Band Photometry to Classify Supernovae (2003)
Poznanski, Dovi, Gal-Yam, Avishay, Maoz, Dan, Filippenko, Alexei V., Leonard, Douglas C., Matheson, Thomas
Large numbers of supernovae (SNe) have been discovered in recent years, and many more will be found in the near future. Once discovered, further study of a SN and its possible use as an astronomical...
Optical Photometry and Spectroscopy of the SN 1998bw-like Type Ic Supernova 2002ap (2003)
Foley, Ryan J., Papenkova, Marina S., Swift, Brandon J., Filippenko, Alexei V., Li, Weidong, Mazzali, Paolo A., ...
We present optical photometric and spectral data of the peculiar Type Ic SN 2002ap. Photometric coverage includes UBVRI bands from 2002 January 30, the day after discovery, through 2002 December 12....
The Cepheid Distance to NGC 1637: A Direct Test of the EPM Distance to SN 1999em (2003)
Leonard, Douglas C., Kanbur, Shashi M., Ngeow, Choong C., Tanvir, Nial R.
Type II-plateau supernovae (SNe II-P) are the classic variety of core-collapse events that result from isolated, massive stars with thick hydrogen envelopes intact at the time of explosion. Their...
Evidence for Extremely High Dust Polarization Efficiency in NGC 3184 (2002)
Leonard, Douglas C., Filippenko, Alexei V., Chornock, Ryan, Li, Weidong
Recent studies have found the Type II-plateau supernova (SN) 1999gi to be highly polarized (p_max = 5.8%, where p_max is the highest degree of polarization measured in the optical bandpass; Leonard &...
Leonard, Douglas C., Filippenko, Alexei V., Li, Weidong, Matheson, Thomas, Kirshner, Robert P., Chornock, Ryan, ...
We present optical spectra and photometry sampling the first six months after discovery of supernova (SN) 1999gi in NGC 3184. SN 1999gi is shown to be a Type II-plateau event with a photometric...
Leonard, Douglas C., Filippenko, Alexei V., Chornock, Ryan, Foley, Ryan J.
The early-time optical spectrum of the Type Ic supernova (SN) 2002ap was characterized by unusually broad features, leading some authors to designate it a "hypernova." We present optical...
Not Color Blind: Using Multiband Photometry to Classify Supernovae (2002)
Poznanski, Dovi, Gal-Yam, Avishay, Maoz, Dan, Filippenko, Alexei V., Leonard, Douglas C., Matheson, Thomas
Large numbers of supernovae (SNe) have been discovered in recent years, and many more will be found in the near future. Once discovered, further study of a SN and its possible use as an astronomical...
A Hubble Space Telescope Snapshot Survey of Nearby Supernovae (2002)
Li, Weidong, Filippenko, Alexei V., Van Dyk, Schuyler D., Hu, Jingyao, Qiu, Yulei, Modjaz, Maryam, ...
We present photometry of 12 recent supernovae (SNe) recovered in a {\it Hubble Space Telescope} Snapshot program, and tie the measurements to earlier ground-based observations, in order to study the...
The Distance to SN 1999em in NGC 1637 from the Expanding Photosphere Method (2001)
Leonard, Douglas C., Filippenko, Alexei V., Gates, Elinor L., Li, Weidong, Eastman, Ronald G., Barth, Aaron J., ...
We present 30 optical spectra and 49 photometric epochs sampling the first 517 days after discovery of supernova (SN) 1999em, and derive its distance through the expanding photosphere method (EPM)....
BVRI Photometry of Supernovae (2001)
Ho, Wynn C. G., Van Dyk, Schuyler D., Peng, Chien Y., Filippenko, Alexei V., Leonard, Douglas C., Matheson, Thomas, ...
We present optical photometry of one Type IIn supernova (1994Y) and nine Type Ia supernovae (1993Y, 1993Z, 1993ae, 1994B, 1994C, 1994M, 1994Q, 1994ae, and 1995D). SN 1993Y and SN 1993Z appear to be...
Fransson, Claes, Chevalier, Roger A., Filippenko, Alexei V., Leibundgut, Bruno, Barth, Aaron J., Fesen, Robert A., ...
Optical and ultraviolet observations of the Type IIn supernova 1995N at epochs between 321 and 1799 days after the explosion show three distinct velocity components. The narrow lines come from...
The Unique Type Ia Supernova 2000cx in NGC 524 (2001)
Li, Weidong, Filippenko, Alexei V., Gates, Elinor, Chornock, Ryan, Gal-Yam, Avishay, Ofek, Eran O., ...
We present extensive photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2000cx in the S0 galaxy NGC 524, which reveal it to be peculiar. Photometrically, SN 2000cx is...
Spectropolarimetry of the Type II Supernovae 1997ds, 1998A, and 1999gi (2001)
Leonard, Douglas C., Filippenko, Alexei V.
We present single-epoch spectropolarimetry of the Type II supernovae (SNe II) 1997ds, 1998A, and 1999gi. SN 1997ds and SN 1998A were both observed during the early photospheric phase, while...
Optical Spectroscopy of Type Ib/c Supernovae (2001)
Matheson, Thomas, Filippenko, Alexei V., Li, Weidong, Leonard, Douglas C., Shields, Joseph C.
We present 84 spectra of Type Ib/c and Type IIb supernovae (SNe), describing the individual SNe in detail. The relative depths of the helium absorption lines in the spectra of the SNe Ib appear to...
Is it Round? Spectropolarimetry of the Type II-P Supernova 1999em (2000)
Leonard, Douglas C., Filippenko, Alexei V., Ardila, David R., Brotherton, Michael S.
We present the first multi-epoch spectropolarimetry of a type II plateau supernova (SN II-P), with optical observations of SN 1999em on days 7, 40, 49, 159, and 163 after discovery. These data are...
Optical Spectra of Type Ia Supernovae at z=0.46 and z=1.2 (2000)
Coil, Alison L., Matheson, Thomas, Filippenko, Alexei V., Leonard, Douglas C., Tonry, John, Riess, Adam G., ...
We present optical spectra, obtained with the Keck 10-m telescope, of two high-redshift type Ia supernovae (SNe Ia) discovered by the High-z Supernova Search Team: SN 1999ff at z=0.455 and SN 1999fv...
The Subluminous Type Ia Supernova 1998de in NGC 252 (2000)
Modjaz, Maryam, Li, Weidong, Filippenko, Alexei V., King, Jennifer Y., Leonard, Douglas C., Matheson, Thomas, ...
We present spectroscopic and extensive photometric observations of supernova (SN) 1998de in the S0 galaxy NGC 252, discovered during the course of the Lick Observatory Supernova Search. These data,...
Detailed Analysis of Early to Late-Time Spectra of Supernova 1993J (2000)
Matheson, Thomas, Filippenko, Alexei V., Ho, Luis C., Barth, Aaron J., Leonard, Douglas C.
We present a detailed study of line structure in early to late-time spectra of Supernova (SN) 1993J. Spectra during the nebular phase, but within the first two years after explosion, exhibit...
Helium Emission in the Type Ic SN 1999cq (2000)
Matheson, Thomas, Filippenko, Alexei V., Chornock, Ryan, Leonard, Douglas C., Li, Weidong
We present the first unambiguous detection of helium emission lines in spectra of Type Ic supernovae (SNe Ic). The presence of He I lines, with full width at half maximum ~ 2000 km/s, and the...
Probing the Geometry of Supernovae with Spectropolarimetry (1999)
Leonard, Douglas C., Filippenko, Alexei V., Matheson, Thomas
We present results from a spectropolarimetric survey of young supernovae completed at the Keck Observatory, including at least one example from each of the major supernova types: Ia (1997dt), Ib...
Evidence for Asphericity in the Type IIn Supernova 1998S (1999)
Leonard, Douglas C., Filippenko, Alexei V., Barth, Aaron J., Matheson, Thomas
We present optical spectropolarimetry obtained at the Keck-II 10-m telescope on 1998 March 7 UT along with total flux spectra spanning the first 494 days after discovery (1998 March 2 UT) of the...