P. Hoêflich

Florida State University

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M. M. Phillips

Las Campanas Observatory

103

C. Ashall

Virginia Tech

E. Y. Hsiao

Florida State University

M. Stritzinger

Aarhus University

L. Galbany

Institut d'Estudis Espacials de Catalunya

C. R. Burns

Carnegie Institution for Science

N. Morrell

Las Campanas Observatory

N. B. Suntzeff

Mitchell Institute

E. Baron

University of Oklahoma

J. C. Wheeler

The University of Texas at Austin

Cooperative Institutions

California Institute of Technology

Centre National de la Recherche Scientifique

National Institute for Astrophysics

University of California, Berkeley

Max Planck Society

Center for Astrophysics Harvard & Smithsonian

Cerro Tololo Inter-American Observatory

The University of Texas at Austin

Lawrence Berkeley National Laboratory

Carnegie Institution for Science

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Non-LTE effects in low-density scattering-dominated photospheres

Astronomy and Astrophysics (1986)

P. Hoêflich R. Wehrsě G. Shaviv

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Carnegie Supernova Project: kinky $i$-band light-curves of Type Ia supernovae

arXiv (Cornell University) (2021)

P. J. Pessi E. Y. Hsiao G. Folatelli J. P. Anderson C. R. Burns

We present detailed investigation of a specific $i$-band light-curve feature in Type Ia supernovae (SNe Ia) using the rapid cadence and high signal-to-noise ratio light-curves obtained by the Carnegie Supernova Project. The feature is present in most SNe Ia and emerges a few days after the $i$-band maximum. It is an abrupt change in curvature in the light-curve over a few days and appears as a flattening in mild cases and a strong downward concave shape, or a "kink", in the most extreme cases. We computed the second derivatives of Gaussian Process interpolations to study 54 rapid-cadence light-curves. From the second derivatives we measure: 1) the timing of the feature in days relative to $i$-band maximum; tdm$_{2}$($i$) and 2) the strength and direction of the concavity in mag d$^{-2}$ ; dm$_{2}$($i$). 76$\%$ of the SNe Ia show a negative dm$_{2}$($i$), representing a downward concavity - either a mild flattening or a strong "kink". The tdm$_{2}$($i$) parameter is shown to correlate with the color-stretch parameter s$_{\mathrm{BV}}$, a SN Ia primary parameter. The dm$_{2}$($i$) parameter shows no correlation with s$_{\mathrm{BV}}$ and therefore provides independent information. It is also largely independent of the spectroscopic and environmental properties. Dividing the sample based on the strength of the light-curve feature as measured by dm$_{2}$($i$), SNe Ia with strong features have a Hubble diagram dispersion of 0.107 mag, 0.075 mag smaller than the group with weak features. Although larger samples should be obtained to test this result, it potentially offers a new method for improving SN Ia distance determinations without shifting to more costly near-infrared or spectroscopic observations.

Flattening

Feature (linguistics)

Cadence

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The SDSS Supernova Survey

American Astronomical Society Meeting Abstracts (2004)

J. Frieman Jennifer Adelman-McCarthy John C. Barentine A. Becker William N. Boroski

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Signatures of Explosion Models for SN ~Ia & Cosmology

arXiv (Cornell University) (2004)

P. Hoêflich

We give an overview of the current understanding of Type Ia supernovae relevant for their use as cosmological distance indicators. We present the physical basis to understand their homogeneity of the observed light curves and spectra and the observed correlations. SNe Ia have been well established as distance indicators on the 10 % level. However, the quest for the nature of the dark energy requires improvements in the accuracy to the 2 to 3 % level, we must understand the diversity within the SNe Ia population, and its evolution with redshift. Based on detailed models for the progenitors, explosions, light curves and spectra, we discuss signatures of thermonuclear explosions, and the implications for cosmology. We emphasize the relation between LC properties and spectra because, for local SNe~Ia, the diversity becomes apparent the combination of spectra and LCs whereas, by enlarge, we have to for high-z objects. At some examples, we show how we can actually probe the properties of the progenitor, its environment, and details of the explosion physics.

10.48550/arxiv.astro-ph/0409170

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Carnegie Supernova Project-II: Near-infrared spectral diversity and template of Type Ia Supernovae

arXiv (Cornell University) (2022)

Jing Lü E. Y. Hsiao M. M. Phillips C. R. Burns C. Ashall

We present the largest and most homogeneous collection of near-infrared (NIR) spectra of Type Ia supernovae (SNe Ia): 339 spectra of 98 individual SNe obtained as part of the Carnegie Supernova Project-II. These spectra, obtained with the FIRE spectrograph on the 6.5 m Magellan Baade telescope, have a spectral range of 0.8--2.5 $μ$m. Using this sample, we explore the NIR spectral diversity of SNe Ia and construct a template of spectral time series as a function of the light-curve-shape parameter, color stretch $s_{BV}$. Principal component analysis is applied to characterize the diversity of the spectral features and reduce data dimensionality to a smaller subspace. Gaussian process regression is then used to model the subspace dependence on phase and light-curve shape and the associated uncertainty. Our template is able to predict spectral variations that are correlated with $s_{BV}$, such as the hallmark NIR features: Mg II at early times and the $H$-band break after peak. Using this template reduces the systematic uncertainties in K-corrections by ~90% compared to those from the Hsiao template. These uncertainties, defined as the mean K-correction differences computed with the color-matched template and observed spectra, are on the level of $4\times10^{-4}$ mag on average. This template can serve as the baseline spectral energy distribution for light-curve fitters and can identify peculiar spectral features that might point to compelling physics. The results presented here will substantially improve future SN~Ia cosmological experiments, for both nearby and distant samples.

10.48550/arxiv.2211.05998

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Explosion Physics of Thermonuclear Supernovae and Their Signatures

Springer eBooks (2017)

P. Hoêflich

Thermonuclear Fusion

10.1007/978-3-319-21846-5_56

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Citations (19)

Models for Type Ia Supernovae and Cosmology

arXiv (Cornell University) (1997)

P. Hoêflich

From the spectra and light curves it is clear that SNIa events are thermonuclear explosions of white dwarfs. However, details of the explosion are highly under debate. Here, we present detailed models which are consistent with respect to the explosion mechanism, the optical and infrared light curves, and the spectral evolution. This leaves the description of the burning front and the structure of the white dwarf as the only free parameters. The explosions are calculated using one-dimensional Lagrangian codes including nuclear networks. Subsequently, optical and IR-LCs are constructed. Detailed NLTE-spectra are computed for several instants of time using the density, chemical and luminosity structure resulting from the LCs. Different models for the thermonuclear explosion are discussed including detonations, deflagrations, delayed detonations, pulsating delayed detonations (PDD) and helium detonations. Comparisons between theoretical and observed LCs and spectra provide an insight into details of the explosion and nature of the progenitor stars. We try to answer several related questions. Are subluminous SNe Ia a group different from `normal' SN Ia? Can we understand observed properties of the LCs and spectra?What can we learn from infrared spectra? Can we determine $H_o$ independently from primary distance indicators, and how do the results compare with empirical methods? What do we learn about the progenitor evolution and its metallicity? What are the systematic effects for the determination of the cosmological parameters $\Omega_M$ and $\Lambda$ and how can we recognize this potential 'pitfalls' and correct for evolutionary effects?

Thermonuclear Fusion

Pair-instability supernova

10.48550/arxiv.astro-ph/9709031

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Type Ia supernovae in the age of JWST: Finding the ‘right’ questions and the path to answers

Journal of Physics Conference Series (2024)

P. Hoêflich E. Fereidouni T. Mera

Abstract Understanding the Physics of thermonuclear explosions of a White Dwarf star (WD), so called Type Ia Supernovae (SNe Ia), provide a playground for modern physics, computational methods, and are a key to modern cosmology. We identify new and investigate a variety of observational signatures of underlying physical processes related to the thermonuclear runaway, the flame propagation and the environment. Being intrinsically multi-dimensional phenomena, probing the physics requires multi-dimensional radiation-hydrodynamics and MHD simulations. For this task, we developed and employed methods for photon transport for the X-, gamma- and of low energy and of positrons under non-LTE conditions. We identify signatures in the light curves and spectra, in particular, line profiles and polarization spectra. Consistent treatment of high energy processes is critical. Therefore, our framework and results can be used directly a variety of scenarios for SNe Ia including merging WDs and explosions of sub-Chandrasekhar mass WDs. Current simulations have limitations but, nevertheless, when combined with recent JWST and VLT observations solutions emerge to many of decade old problems on the ignition process, flame physics and thermonuclear explosion.

10.1088/1742-6596/2742/1/012024

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Discovery of Optical Transient TSS J004150.4+404222 in M31

The astronomer's telegram (2006)

R. Quimby F. Castro M. Sellers P. Hoêflich E. L. Robinson

Transient (computer programming)

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Supernova 2001dm in NGC 749

International Astronomical Union Circular (2001)

D. Baade Claes Fransson P. Hoêflich D. A. Howell Peter Lundqvist

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