Weidong Li

SN 2008S: A Cool Super-Eddington Wind in a Supernova Impostor (2008)

Smith, Nathan, Ganeshalingam, Mohan, Li, Weidong, Chornock, Ryan, Steele, Thea N., Silverman, Jeffrey M., ...

We present visual-wavelength photometry and spectroscopy of SN2008S. Based on the relatively low peak luminosity for a supernova (SN) of M_R = -13.9 mag and moderate outflow speeds of \la 600 km/s...

A Golden Standard Type Ia Supernova SN 2005cf: Observations from the Ultraviolet to the Near-Infrared Wavebands (2008)

Wang, Xiaofeng, Li, Weidong, Filippenko, Alexei V., Foley, R. J., Kirshner, R. P., Modjaz, M., ...

We present extensive photometry at ultraviolet (UV), optical, and near-infrared (NIR) wavelengths, as well as dense sampling of optical spectra, for the normal type Ia supernova (SN Ia) 2005cf. From...

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...

First Results from the Lick AGN Monitoring Project: The Mass of the Black Hole in Arp 151 (2008)

Bentz, Misty C., Walsh, Jonelle L., Barth, Aaron J., Baliber, Nairn, Bennert, Nicola, Canalizo, Gabriela, ...

We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 13 nearby (z < 0.05)...

Coronal lines and dust formation in SN 2005ip: Not the brightest, but the hottest Type IIn supernova (2008)

Smith, Nathan, Silverman, Jeffrey M., Chornock, Ryan, Filippenko, Alexei V., Wang, Xiaofeng, Li, Weidong, ...

We present optical photometry and spectroscopy of SN2005ip for the first 3yr after discovery, showing an underlying Type II-L SN interacting with a steady wind to yield an unusual Type IIn spectrum....

Subaru and Keck Observations of the Peculiar Type Ia Supernova 2006gz at Late Phases (2008)

Maeda, Keiichi, Kawabata, Koji, Li, Weidong, Tanaka, Masaomi, Mazzali, Paolo A., Hattori, Takashi, ...

Recently, a few peculiar Type Ia supernovae (SNe) that show exceptionally large peak luminosity have been discovered. Their luminosity requires more than 1 Msun of 56Ni ejected during the explosion,...

The Rapidly Flaring Afterglow of the Very Bright and Energetic GRB 070125 (2008)

Updike, Adria C., Haislip, Joshua B., Nysewander, Melissa C., Fruchter, Andrew S., Kann, D. Alexander, Klose, Sylvio, ...

We report on multi-wavelength observations, ranging from the X-ray to radio wave bands, of the IPN-localized gamma-ray burst GRB 070125. Spectroscopic observations reveal the presence of absorption...

SN 2006tf: Precursor Eruptions and the Optically Thick Regime of Extremely Luminous Type IIn Supernovae (2008)

Smith, Nathan, Chornock, Ryan, Li, Weidong, Ganeshalingam, Mohan, Silverman, Jeffrey M., Foley, Ryan J., ...

SN2006tf is the third most luminous SN discovered so far, after SN2005ap and SN2006gy. SN2006tf is valuable because it provides a link between two regimes: (1) luminous type IIn supernovae powered by...

Late-time observations of SN2006gy: Still Going Strong (2008)

Smith, Nathan, Foley, Ryan J., Bloom, Joshua S., Li, Weidong, Filippenko, Alexei V., Gavazzi, Raphael, ...

Owing to its extremely high luminosity and long duration, SN2006gy radiated more energy in visual light than any other known SN. Two hypotheses to explain its high luminosity -- that it was powered...

Copolymerization of Ethene and Functionalized Comonomers with Cationic α-Diimine Palladium Catalysts (2008)

Li, Weidong

Polyolefins form a highly important class of materials, with a wide range of applications, which are produced industrially on a huge scale (> 85 Mton per year). By far the largest volume of these...

Reactions of Cationic Palladium α-Diimine Complexes with Nitrogen-Containing Olefins: Branched Polyethylene with Carbazole Functionalities (2008)

Li, Weidong, Zhang, Xiaochun, Meetsma, Auke, Hessen, Bart

The reactivity of three nitrogen-containing olefins with a cationic (α-diimine)Pd-Me species was studied to evaluate possibilities for their catalytic copolymerization with ethylene. Allyl dimethyl...

The Detection of a Light Echo from the Type Ia Supernova 2006X in M100 (2007)

Wang, Xiaofeng, Li, Weidong, Filippenko, Alexei V., Foley, Ryan J., Smith, Nathan, Wang, Lifan

We report the discovery of a light echo (LE) from the Type Ia supernova (SN) 2006X in the nearby galaxy M100. The presence of the LE is supported by analysis of both the Advanced Camera for Surveys...

Constraints on Circumstellar Material Around the Type Ia Supernova 2007af (2007)

Simon, Joshua D., Gal-Yam, Avishay, Penprase, Bryan E., Li, Weidong, Quimby, Robert M., Silverman, Jeffrey M., ...

Patat et al. recently inferred the existence of circumstellar material around a normal Type Ia supernova (SN) for the first time, finding time-variable Na I D absorption lines in the spectrum of SN...

Optical and Near-Infrared Observations of the Highly Reddened, Rapidly Expanding Type Ia Supernova 2006X in M100 (2007)

Wang, Xiaofeng, Li, Weidong, Filippenko, Alexei V., Krisciunas, Kevin, Suntzeff, Nicholas B., Li, Junzheng, ...

We present extensive optical (UBVRI), near-infrared (JK) light curves and optical spectroscopy of the Type Ia supernova (SN) 2006X in the nearby galaxy NGC 4321 (M100). Our observations suggest that...

On the Progenitors of Two Type II-P Supernovae in the Virgo Cluster (2007)

Li, Weidong, Wang, Xiaofeng, Van Dyk, Schuyler D., Cuillandre, Jean-Charles, Foley, Ryan J., Filippenko, Alexei V.

Direct identification of the progenitors of supernovae (SNe) is rare because of the required spatial resolution and depth of the archival data prior to the SN explosions. Here we report on the...

SN 2006jc: A Wolf-Rayet Star Exploding in a Dense He-Rich Circumstellar Medium (2006)

Foley, Ryan J., Smith, Nathan, Ganeshalingam, Mohan, Li, Weidong, Chornock, Ryan, Filippenko, Alexei V.

We present optical photometry and spectra of the peculiar Type Ib supernova (SN) 2006jc. Strong and relatively narrow He I emission lines indicate the progenitor star exploded inside a dense...

SN 2006gy: Discovery of the most luminous supernova ever recorded, powered by the death of an extremely massive star like Eta Carinae (2006)

Smith, Nathan, Li, Weidong, Foley, Ryan J., Wheeler, J. Craig, Pooley, Dave, Chornock, Ryan, ...

(abridged) We report our discovery and observations of the peculiar Type IIn supernova SN2006gy in NGC1260, revealing that it reached a peak magnitude of -22, making it the most luminous supernova...

New Hubble Space Telescope Discoveries of Type Ia Supernovae at z > 1: Narrowing Constraints on the Early Behavior of Dark Energy (2006)

Riess, Adam G., Strolger, Louis-Gregory, Casertano, Stefano, Ferguson, Henry C., Mobasher, Bahram, Gold, Ben, ...

We have discovered 21 new Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to trace the history of cosmic expansion over the last 10 billion years. These objects,...

Continuous measurements enhanced self-trapping of degenerate ultra-cold atoms: Nonlinear Quantum Zeno Effect (2006)

Li, WeiDong, Liu, Jie

In the present paper we investigate the influence of measurements on the quantum dynamics of degenerate Bose atoms gases in a symmetric double-well. We show that continuous measurements enhance...

The stationary solutions of G-P equations in double square well (2006)

Li, Weidong

We present analytical stationary solutions for the Gross-Pitaevskii equation (GPE) of a Bose-Einstein condensate (BECs) trapped in a double-well potential. These solutions are compared with those...

SN 2005bf: A Possible Transition Event Between Type Ib/c Supernovae and Gamma Ray Bursts (2006)

Folatelli, Gaston, Contreras, Carlos, Phillips, M. M., Woosley, S. E., Blinnikov, Sergei, Morrell, Nidia, ...

We present u'g'r'i'BV photometry and optical spectroscopy of the Type Ib/Ic SN 2005bf covering the first ~100 days following discovery. The u'g'BV light curves displayed a double-peaked morphology,...

Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. III. Optical Variability and X-ray/UV/Optical Correlations (2006)

Desroches, Louis-Benoit, Filippenko, Alexei V., Kaspi, Shai, Laor, Ari, Maoz, Dan, Ganeshalingam, Mohan, ...

We present optical observations of the low-luminosity Seyfert 1 nucleus of NGC 4395, as part of a multiwavelength reverberation-mapping program. Observations were carried out over two nights in 2004...

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...

Spectropolarimetry of the Peculiar Type Ia SN 2005hk (2006)

Chornock, Ryan, Filippenko, Alexei V., Branch, David, Foley, Ryan J., Jha, Saurabh, Li, Weidong

We present Keck spectropolarimetry of the unusual type Ia supernova (SN Ia) 2005hk several days before maximum light. An analysis of the high signal-to-noise-ratio total-flux spectrum shows the...

The Type IIn Supernova 2002kg: The Outburst of a Luminous Blue Variable Star in NGC 2403 (2006)

Van Dyk, Schuyler D., Li, Weidong, Filippenko, Alexei V., Humphreys, Roberta M., Chornock, Ryan, Foley, Ryan, ...

We show that Supernova (SN) 2002kg in NGC 2403, initially classified as Type II-narrow (IIn), has photometric and spectroscopic properties unlike those of normal SNe. Its behavior, instead, is more...

A search for core-collapse supernova progenitors in Hubble Space Telescope images (2006)

Van Dyk, Schuyler, Li, Weidong, Filippenko, Alexei

Identifying the massive progenitor stars that give rise to core-collapse supernovae (SNe) is one of the main pursuits of supernova and stellar evolution studies.

Late-Time Spectroscopy of SN 2002cx: The Prototype of a New Subclass of Type Ia Supernovae (2006)

Jha, Saurabh, Branch, David, Chornock, Ryan, Foley, Ryan J., Li, Weidong, Swift, Brandon J., ...

We present Keck optical spectra of SN 2002cx, the most peculiar known Type Ia supernova (SN Ia), taken 227 and 277 days past maximum light. Astonishingly, the spectra are not dominated by the...

Optical Photometry of Type II-P Supernova 2004dj in NGC 2403 (2005)

Zhang, Tianmeng, Wang, Xiaofeng, Li, Weidong, Zhou, Xu, Ma, Jun, Jiang, Zhaoji, ...

We present photometric data of the type II-P supernova (SN) 2004dj in NGC 2403. The multicolor light curves cover the SN from $\sim$ 60 to 200 days after explosion, and are measured with a set of...

The Carnegie Supernova Project: The Low-Redshift Survey (2005)

Hamuy, Mario, Folatelli, Gastón, Morrell, Nidia I., Phillips, Mark M., Suntzeff, Nicholas B., Persson, S. E., ...

Supernovae are essential to understanding the chemical evolution of the Universe. Type Ia supernovae also provide the most powerful observational tool currently available for studying the expansion...

Supernova Cosmology and the ESSENCE project (2005)

Sollerman, Jesper, Aguilera, Claudio, Becker, Andy, Blondin, Stephane, Challis, Pete, Clocchiatti, Alejandro, ...

The proper usage of Type Ia supernovae (SNe Ia) as distance indicators has revolutionized cosmology, and added a new dominant component to the energy density of the Universe, dark energy. Following...

SN 2005bf: A Possible Transition Event Between Type Ib/c Supernovae and Gamma Ray Bursts (2005)

Folatelli, Gaston, Contreras, Carlos, Phillips, M. M., Woosley, S. E., Blinnikov, Sergei, Morrell, Nidia, ...

We present u'g'r'i'BV photometry and optical spectroscopy of the Type Ib/Ic SN 2005bf covering the first ~100 days following discovery. The u'g'BV light curves displayed a double-peaked morphology,...

The Light Echo Around Supernova 2003gd in Messier 74 (2005)

Van Dyk, Schuyler D., Li, Weidong, Filippenko, Alexei V.

We confirm the discovery of a light echo around the Type II-plateau Supernova 2003gd in Messier 74 (NGC 628), seen in images obtained with the High Resolution Channel of the Advanced Camera for...

A Complete Survey of the Transient Radio Sky and Implications for Gamma-Ray Bursts, Supernovae, and other Relativistic Explosions (2005)

Gal-Yam, Avishay, Ofek, Eran O., Poznanski, Dovi, Levinson, Amir, Waxman, Eli, Frail, Dale A., ...

We had previously reported on a survey for radio transients, used to set an upper limit on the number of orphan gamma-ray burst (GRB) radio afterglows, and thus a lower limit on the typical GRB...

Identification of the Red Supergiant Progenitor of Supernova 2005cs: Do the Progenitors of Type II-P Supernovae Have Low Mass? (2005)

Li, Weidong, Van Dyk, Schuyler D., Filippenko, Alexei V., Cuillandre, Jean-Charles, Jha, Saurabh, Bloom, Joshua S., ...

The stars that end their lives as supernovae (SNe) have been directly observed in only a handful of cases, due mainly to the extreme difficulty in identifying them in images obtained prior to the SN...

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...

The Calibration of the Swift/UVOT Optical Observations: A Recipe for Photometry (2005)

Li, Weidong, Jha, Saurabh, Filippenko, Alexei V., Bloom, Joshua S., Pooley, David, Foley, Ryan J., ...

Swift/UVOT has the capability to provide critical insight into the physics of the early afterglows of gamma-ray bursts (GRBs). But without precise calibration of the UVOT to standard photometric...

The Progenitor of Supernova 2004dj in a Star Cluster (2005)

Wang, Xiaofeng, Yang, Yanbin, Zhang, Tianmeng, Ma, Jun, Zhou, Xu, Li, Weidong, ...

The progenitor of type II-plateau supernova (SN) 2004dj is identified with a supergiant in a compact star cluster known as "Sandage Star 96" (S96) in the nearby spiral galaxy NGC 2403, which was...

Classifications of the Host Galaxies of Supernovae, Set III (2005)

Bergh, Sidney Van Den, Li, Weidong, Filippenko, Alexei V.

A homogeneous sample comprising host galaxies of 604 recent supernovae, including 212 objects discovered primarily in 2003 and 2004, has been classified on the David Dunlap Observatory system. Most...

Cepheid Calibrations from the Hubble Space Telescope of the Luminosity of Two Recent Type Ia Supernovae and a Re-determination of the Hubble Constant (2005)

Riess, Adam G., Li, Weidong, Stetson, Peter B., Filippenko, Alexei V., Jha, Saurabh, Kirshner, Robert P., ...

We report observations of two nearby Type Ia supernovae (SNe Ia) for which observations of Cepheid variables in the host galaxies have been obtained with the Hubble Space Telescope: SN 1994ae in NGC...

SN 2005bf: A Possible Transition Event Between Type Ib/c Supernovae and Gamma Ray Bursts (2005)

Folatelli, Gaston, Contreras, Carlos, Phillips, M. M., Woosley, S. E., Blinnikov, Sergei, Morrell, Nidia, ...

We present u'g'r'i'BV photometry and optical spectroscopy of the Type Ib/Ic SN 2005bf covering the first ~100 days following discovery. The u'g'BV light curves displayed a double-peaked morphology,...

SN 2005bf: A Possible Transition Event Between Type Ib/c Supernovae and Gamma Ray Bursts (2005)

Folatelli, Gaston, Contreras, Carlos, Phillips, M. M., Woosley, S. E., Blinnikov, Sergei, Morrell, Nidia, ...

We present u'g'r'i'BV photometry and optical spectroscopy of the Type Ib/Ic SN 2005bf covering the first ~100 days following discovery. The u'g'BV light curves displayed a double-peaked morphology,...

The disappearing act of KH 15D: Photometric results from 1995 to 2004 (2005)

Hamilton, Catrina M., Herbst, William, Vrba, Frederick J., Ibrahimov, Mansur A., Mundt, Reinhard, ...

We present results from the most recent (2002-2004) observing campaigns of the eclipsing system KH 15D, in addition to rereduced data obtained at Van Vleck Observatory (VVO) between 1995 and 2000....

On the Progenitor of the Type II Supernova 2004et in NGC 6946 (2004)

Li, Weidong, Van Dyk, Schuyler D., Filippenko, Alexei V., Cuillandre, Jean-Charles

Supernova (SN) 2004et is the eighth historical SN in the nearby spiral galaxy NGC 6946. Here we report on early photometric and spectroscopic monitoring of this object. SN 2004et is a Type II event,...

The late-time light curve of the Type Ia supernova 2000cx (2004)

Sollerman, Jesper, Lindahl, Jan, Kozma, Cecilia, Challis, Peter, Filippenko, Alexei V., Fransson, Claes, ...

We have conducted a systematic and comprehensive monitoring programme of the Type Ia supernova 2000cx at late phases using the VLT and HST. The VLT observations cover phases 360 to 480 days past...

Reading the Spectra of the Most Peculiar Type Ia Supernova 2002cx (2004)

Branch, David, Baron, E., Thomas, R. C., Kasen, D., Li, Weidong, Filippenko, Alexei V.

In spite of the apparent lack of Si II and S II features in its spectra, SN 2002cx was classified as a peculiar Type Ia supernova (SN Ia) on the basis of its overall photometric and spectroscopic...

Examining the Relationships between Ability Conceptions, Intrinsic Motivation, Persistence, and Performance (2004)

Li, Weidong

The purpose of this study was to examine the relationships between ability conceptions, intrinsic motivation, persistence, and performance using an interaction approach. The phase-one study revealed...

Examining the Relationships between Ability Conceptions, Intrinsic Motivation, Persistence, and Performance (2004)

Li, Weidong

The purpose of this study was to examine the relationships between ability conceptions, intrinsic motivation, persistence, and performance using an interaction approach. The phase-one study revealed...

Type Ia Supernova Discoveries at z>1 From the Hubble Space Telescope: Evidence for Past Deceleration and Constraints on Dark Energy Evolution (2004)

Riess, Adam G., Strolger, Louis-Gregory, Tonry, John, Casertano, Stefano, Ferguson, Henry C., Mobasher, Bahram, ...

We have discovered 16 Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to provide the first conclusive evidence for cosmic deceleration that preceded the current...

23 High Redshift Supernovae from the IfA Deep Survey: Doubling the SN Sample at z>0.7 (2003)

Barris, Brian J., Tonry, John, Blondin, Stephane, Challis, Peter, Chornock, Ryan, Clocchiatti, Alejandro, ...

We present photometric and spectroscopic observations of 23 high redshift supernovae spanning a range of z=0.34-1.03, 9 of which are unambiguously classified as Type Ia. These supernovae were...

Observations of Type Ia Supernovae, and Challenges for Cosmology (2003)

Li, Weidong, Filippenko, Alexei V.

Observations of Type Ia supernovae (SNe Ia) reveal correlations between their luminosities and light-curve shapes, and between their spectral sequence and photometric sequence. Assuming SNe Ia do not...

Imaging and Demography of the Host Galaxies of High-Redshift Type Ia Supernovae (2003)

Williams, Benjamin F., Hogan, Craig J., Barris, Brian, Candia, Pablo, Challis, Peter, Clocchiatti, Alejandro, ...

We present the results of a study of the host galaxies of high redshift Type Ia supernovae (SNe Ia). We provide a catalog of 18 hosts of SNe Ia observed with the Hubble Space Telescope (HST) by the...