Peter Höflich - Academia.edu (original) (raw)

Papers by Peter Höflich

We report the results of a coherent study of three chemically anomalous metal-poor ([Fe/H] ~ -2) ... more We report the results of a coherent study of three chemically anomalous metal-poor ([Fe/H] ~ -2) stars. These objects exhibit unusually low abundances of Mg, Si, Ca (alpha-elements) and Sr, Y, and Ba (neutron-capture elements). Our analyses confirm and expand upon earlier reports of atypical abundances in BD+80~245, G4-36, and CS22966-043. We also find that the latter two stars exhibit

The early discovery of soft and hard X-rays as well as of gamma-ray line emission from supernova ... more The early discovery of soft and hard X-rays as well as of gamma-ray line emission from supernova 1987A indicates that radioactive 56Co has been mixed from the deep interior of the exploding star into the hydrogen-rich envelope. This paper reports numerical simulations of the mixing process by modeling the supernova explosion using a 3-d explicit Eulerian hydrodynamic code.

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Astrophysical Journal, 2004

We report a subtle error in the normalization of the absolute flux published in our original arti... more We report a subtle error in the normalization of the absolute flux published in our original article (hereafter HWK98), and some minor updates. The normalization problem is related to the post-processing. As a consequence, the reported line fluxes are too large at early times. Note that Figure 1 of P. Höflich (ApJ, 492, 228 [1998]) has been transferred from HWK98.

Astrophysical Journal, 2006

We present the spectral evolution, light curve, and corresponding interpretation for the ``normal... more We present the spectral evolution, light curve, and corresponding interpretation for the ``normal-bright'' Type Ia supernova 2005cg discovered by ROTSE-IIIc. The host is a low-luminosity (Mr=-16.75) blue galaxy with strong indications of active star formation and an environment similar to that expected for SNe Ia at high redshifts. Early-time (t~-10 days) optical spectra obtained with the HET reveal an asymmetric,

Astrophysical Journal, 2007

HET optical spectroscopy and unfiltered ROTSE-III photometry spanning the first 11 months since e... more HET optical spectroscopy and unfiltered ROTSE-III photometry spanning the first 11 months since explosion of the Type II-P SN 2006bp are presented. Flux limits from the days before discovery combined with the initial rapid brightening suggest the supernova was first detected just hours after shock breakout. Optical spectra obtained about 2 days after breakout exhibit narrow emission lines corresponding to

Astrophysical Journal, 2007

We present unfiltered photometric observations with ROTSE-III and optical spectroscopic follow-up... more We present unfiltered photometric observations with ROTSE-III and optical spectroscopic follow-up with the HET and Keck of the most luminous supernova yet identified, SN 2005ap. The spectra taken about 3 days before and 6 days after maximum light show narrow emission lines (likely originating in the dwarf host) and absorption lines at a redshift of z=0.2832, which puts the peak

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Astrophysical Journal, 1997

We present broad band and spectropolarimetry of the Type Ia SN 1996X obtained on April 14, 1996 (... more We present broad band and spectropolarimetry of the Type Ia SN 1996X obtained on April 14, 1996 (UT), and broad band polarimetry of SN 1996X on May 22, 1996 (UT), when the supernova was about a week before and 4 weeks after optical maximum, respectively. The Stokes parameters derived from the broad band polarimetry are consistent with zero polarization. The

Astrophysical Journal, 1999

The recent discovery of the unusual supernova SN 1998bw and its apparent correlation with the gam... more The recent discovery of the unusual supernova SN 1998bw and its apparent correlation with the gamma-ray burst GRB 980425 has raised new issues concerning both gamma-ray bursts and supernovae. Although the spectra of SN 1998bw resemble those of Type Ic supernovae (SNe Ic), there are distinct differences. At early times the expansion velocities inferred by the Doppler shift of (unidentified)

Astrophysical Journal, 2001

We present polarization spectra near maximum light for the strongly subluminous Type Ia supernova... more We present polarization spectra near maximum light for the strongly subluminous Type Ia supernova 1999by that show that the supernova is intrinsically polarized. SN 1999by has an observed, overall level of polarization of ~0.3 to 0.8%, a rise of the polarization P redward of 6500 A, and a change in polarization across the Si II 6150 A feature of about

Astrophysical Journal, 2003

High-quality spectropolarimetry (range 417-860 nm; spectral resolution 1.27 nm and 0.265 nm pixel... more High-quality spectropolarimetry (range 417-860 nm; spectral resolution 1.27 nm and 0.265 nm pixel-1) of the Type Ia supernova (SN Ia) 2001el was obtained with the ESO Very Large Telescope Melipal (+FORS1) at five epochs. The spectra a week before maximum and around maximum indicate photospheric expansion velocities of about 10,000 km s-1. Prior to optical maximum, the linear polarization of

Astrophysical Journal, 2000

We outline the possible physical processes, associated timescales, and energetics that could lead... more We outline the possible physical processes, associated timescales, and energetics that could lead to the production of pulsars, jets, asymmetric supernovae, and weak gamma-ray bursts in routine circumstances and to a 1016 G magnetar and perhaps stronger gamma-ray burst in more extreme circumstances in the collapse of the bare core of a massive star. The production of a LeBlanc-Wilson MHD