Optical Observations of Core-Collapse Supernovae

I present an overview of optical observations (mostly spectra) of Type II, Ib, and Ic supernovae (SNe). SNe II are defined by the presence of hydrogen, and exhibit a very wide variety of properties. SNe II-L tend to show evidence of late-time interaction with circumstellar material. SNe IIn are distinguished by relatively narrow emission lines with little or no P-Cygni absorption component and (quite often) slowly declining light curves; they probably have unusually dense circumstellar gas with which the ejecta interact. Some SNe IIn, however, might not be genuine SNe, but rather are ``impostors'' --- specifically, super-outbursts of luminous blue variables. SNe Ib do not exhibit the deep 6150 Angstrom absorption characteristic of ``classical'' SNe Ia; instead, their early-time spectra have He I absorption lines. SNe Ic appear similar to SNe Ib, but lack the helium lines as well. Spectra of SNe IIb initially exhibit hydrogen, yet gradually evolve to resemble those of SNe Ib; their progenitors seem to contain only a low-mass skin of hydrogen. Spectropolarimetry thus far indicates large asymmetries in the ejecta of SNe IIn, but much smaller ones in SNe II-P. As one peers deeper into the ejecta of core-collapse SNe, the asymmetry (indicated by the amount of polarization) seems to increase. There is intriguing, but inconclusive, evidence that some peculiar SNe IIn might be associated with gamma-ray bursts. The rates of different kinds of SNe as a function of Hubble type are still relatively poorly known, although there are good prospects for future improvement.Comment: 19 pages, 10 figures. To appear in "Young Supernova Remnants," ed. S. S. Holt (New York: American Institute of Physics), 200

Spectropolarimetry of Core-Collapse Supernovae

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 fundamental result is that asphericity is a ubiquitous feature of young core-collapse SNe. However, the nature and degree of the asphericity vary considerably. The best predictor of core-collapse SN polarization seems to be the mass of the hydrogen envelope that is intact at the time of the explosion: those SNe that arise from progenitors with large, intact envelopes (e.g., Type II-plateau) have very low polarization, while those that result from progenitors that have lost part (SN IIb, SN IIn) or all (SN Ib) of their hydrogen (or even helium; SN Ic) layers prior to the explosion tend to show substantial polarization. Thus, the deeper we probe into core-collapse events, the greater the asphericity seems to be, suggesting a fundamentally asymmetric explosion with the asymmetry damped by the addition of envelope material.Comment: Invited review at Supernovae as Cosmological Lighthouses, 16-19 June, Padua, IT. 6 page

Optical Spectra and Light Curves of Supernovae

I review recent optical observations of supernovae (SNe) conducted by my group. The Lick Observatory Supernova Search with the 0.76-m Katzman Automatic Imaging Telescope is currently the world's most successful search for nearby SNe. We also use this telescope to obtain multicolor light curves of SNe. One of the more interesting SNe we discovered is SN 2000cx, which differs from all previously observed SNe Ia. Another very strange SN Ia that we studied is SN 2002cx, many of whose properties are opposite those of SN 2000cx. Extensive data on SNe II-P 1999em and 1999gi were used to derive distances with the expanding photosphere method. Results from spectropolarimetry suggest that the deeper we peer into the ejecta of core-collapse SNe, the greater the asphericity. We are using Hubble Space Telescope data to identify, or set limits on, the progenitors of core-collapse SNe.Comment: Filippenko, A. V. 2003, in "From Twilight to Highlight: The Physics of Supernovae," ed. W. Hillebrandt and B. Leibundgut (Berlin: Springer-Verlag), 171-18

Probing black hole X-ray binaries with the Keck telescopes

The advent of the large effective apertures of the Keck telescopes has resulted in the determination with unprecedented accuracy of the mass functions and mass ratios of faint (R ~ 21 mag) X-ray transients (GS 2000+25, GRO J0422+32, Nova Oph 1977, Nova Vel 1993), as well as constraining the main-sequence companion star parameters and producing images of the accretion disks around the black holes.Comment: 7 pages, 4 figures, SPIE Symposium 4005, in pres