Peter Nugent's Publications
Some recent papers of interest. At least interesting to me if you asked me the last time I updated this page...
- Towards a Cosmological Hubble Diagram for Type II-P Supernovae 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 Canada-France-Hawaii Telescope Supernova Legacy Survey and absorption line spectroscopy from the Keck observatory. The method used to measure distances to these supernovae is based on recent work by Hamuy & Pinto (2002) and exploits a correlation between the absolute brightness of SNe II-P and the expansion velocities derived from the minimum of the Fe II 516.9 nm P-Cygni feature observed during the plateau phases. We present three refinements to this method which significantly improve the practicality of measuring the distances of SNe II-P at cosmologically interesting redshifts. These are an extinction correction measurement based on the V-I colors at day 50, a cross-correlation measurement for the expansion velocity and the ability to extrapolate such velocities accurately over almost the entire plateau phase. We apply this revised method to our dataset of high-redshift SNe II-P and find that the resulting Hubble diagram has a scatter of only 0.26 magnitudes, thus demonstrating the feasibility of measuring the expansion history, with present facilities, using a method independent of that based upon supernovae of Type Ia. Nugent et al., ApJ (2006) vol. 645, pg 841.
- Type IIP Supernovae as Cosmological Probes: A Spectral-fitting Expanding Atmosphere Model Distance to SN 1999em Because of their intrinsic brightness, supernovae make excellent cosmological probes. We describe the spectral-fitting expanding atmosphere method (SEAM) for obtaining distances to Type IIP supernovae (SNe IIP) and present a distance to SN 1999em for which a Cepheid distance exists. Our models give results consistent with the Cepheid distance, even though we have not attempted to tune the underlying hydrodynamical model but have simply chosen the best fits. This is in contradistinction to the expanding photosphere method (EPM), which yields a distance to SN 1999em that is 50% smaller than the Cepheid distance. We emphasize the differences between the SEAM and the EPM. We show that the dilution factors used in the EPM analysis were systematically too small at later epochs. We also show that the EPM blackbody assumption is suspect. Since SNe IIP are visible to redshifts as high as z<~6, with the James Webb Space Telescope, the SEAM may be a valuable probe of the early universe. Ed Baron, Peter Nugent, David Branch and Peter Hauschildt, ApJ (2004) vol. 616, pg. 91.
- Could There Be a Hole in Type Ia Supernovae? In the favored progenitor scenario, Type Ia supernovae (SNe Ia) arise from a white dwarf accreting material from a nondegenerate companion star. Soon after the white dwarf explodes, the ejected supernova material engulfs the companion star; two-dimensional hydrodynamic simulations by Marietta et al. (2000) show that in the interaction, the companion star carves out a conical hole of opening angle 30-40 degres in the supernova ejecta. In this paper we use multidimensional Monte Carlo radiative transfer calculations to explore the observable consequences of an ejecta-hole asymmetry. We calculate the variation of the spectrum, luminosity, and polarization with viewing angle for the aspherical supernova near maximum light. We find that the supernova looks normal from almost all viewing angles except when one looks almost directly down the hole. In the latter case, one sees into the deeper, hotter layers of ejecta. The supernova is relatively brighter and has a peculiar spectrum characterized by more highly ionized species, weaker absorption features, and lower absorption velocities. The spectrum viewed down the hole is comparable to those of the class of SN 1991T-like supernovae. We consider how the ejecta-hole asymmetry may explain the current spectropolarimetric observations of SNe Ia and suggest a few observational signatures of the geometry. Finally, we discuss the variety currently seen in observed SNe Ia and how an ejecta-hole asymmetry may fit in as one of several possible sources of diversity. Daniel Kasen, Peter Nugent, Rollin Thomas and Lifan Wang, ApJ (2004), vol. 610, pg. 876.
K-corrections and Extinction Corrections
for Type Ia Supernovae. The measurement
of the cosmological parameters from Type Ia supernovae hinges on our
ability to compare nearby and distant supernovae accurately. Here we
present an advance on a method for performing generalized
K-corrections for Type Ia supernovae that allows us to compare these
objects from the UV to near-IR over the redshift range 0
Here is the data associated with this paper all tar'd and gziped. The
first file has the filters used in
the paper. The second file has for each SN II-P the griz photometry, in the following format:
time (JD), flux (ergs/s/cm^2/Ang), and sigma-flux. The zero point
magnitudes for each filter used in the calculation of the fluxes are
included as well. Note that the zero-points and filters are not an
exact match to those presented in the SNLS First Year Data
Release. The differences, while small (~2%) and included as an
overall calibration uncertainty in this paper, are due to the fact
that SNLS is continuing to improve their calibration of CFHT and
Here is my thesis, The Non-LTE Spectrum Synthesis of Type Ia Supernovae (1997, University of Oklahoma), broken down by chapter. The entire thesis is in one big file at the end. They are all in PostScript format.
- Preface Title, headers, and captions.
- Chapter #1 Introduction
- Chapter #2 SNe Ia 1992A and 1981B
- Chapter #3 Physics and the Hubble Constant
- Chapter #4 A Spectroscopic Sequence Among SNe Ia
- Chapter #5 Hydrodynamic Models of SNe Ia
- Chapter #6 non-LTE vs. LTE
- Appendix #1 Gamma-ray transport in Type Ia Supernovae
- Appendix #2 The Thermalization Parameter
- Whole Thesis