We construct spectra of supernovae interacting strongly with a circumstellar medium (CSM) by adding SN templates, a black-body continuum and an emission-line spectrum. In a Monte Carlo simulation we ...generate more than 800 spectra, distribute them to 10 different classifiers and study how the different simulation parameters affect the appearance of the spectra. SNe IIn showing some structure over the continuum were characterized as SNe IInS. We demonstrate that the flux ratio of the underlying SN to the continuum fv is the most important parameter determining the spectral classification. Thermonuclear SNe get progressively classified as Ia-CSM, IInS and IIn as fv decreases. The transition between Ia-CSM and IInS occurs at fv~0.2-0.3. It shown that SNe Ia-CSM are found at the magnitude range -19.5> M >-21.6, in good agreement with observations, and that the faintest SN IIn that can hide a SN Ia has M = -20.1. The sample of SNe Ia-CSM shows an association with 91T-like SNe Ia. Our experiment does not support that this association is due to a luminosity bias (91T-like being brighter than normal Ia). We therefore conclude that this association has real physical origins and we propose that 91T-like explosions result from single degenerate progenitors. Despite the similarities between SNe Ibc and SNe Ia, the number of misclassifications between these types was small and mostly at low S/N. Combined with the luminosity function needed to reproduce the observed SN Ia-CSM luminosities, it is unlikely that SNe Ibc constitute an important contaminant within this sample. We show how Type II spectra transition to IIn and how the Ha profiles vary with fv. SNe IIn fainter than M = -17.2 are unable to mask SNe IIP brighter than M = -15. A simulation including radiative transfer shows that our simplified model is a good first order approximation. The spectra obtained are in good agreement with real data.
The wavelength-dependence of the extinction of Type Ia SN2014J in the nearby galaxy M82 has been measured using UV to near-IR photometry obtained with the Hubble Space Telescope, the Nordic Optical ...Telescope, and the Mount Abu Infrared Telescope. This is the first time that the reddening of a SN Ia is characterized over the full wavelength range of \(0.2\)-\(2\) microns. A total-to-selective extinction, \(R_V\geq3.1\), is ruled out with high significance. The best fit at maximum using a Galactic type extinction law yields \(R_V = 1.4\pm0.1\). The observed reddening of SN2014J is also compatible with a power-law extinction, \(A_{\lambda}/A_V = \left( {\lambda}/ {\lambda_V} \right)^{p}\) as expected from multiple scattering of light, with \(p=-2.1\pm0.1\). After correction for differences in reddening, SN2014J appears to be very similar to SN2011fe over the 14 broad-band filter light curves used in our study.
We present ultraviolet (UV) observations of six nearby Type~Ia supernovae
(SNe~Ia) obtained with the Hubble Space Telescope, three of which were also
observed in the near-IR (NIR) with Wide-Field ...Camera~3. UV observations with
the Swift satellite, as well as ground-based optical and near-infrared data
provide complementary information. The combined data-set covers the wavelength
range $0.2$--$2~\mu$m. By also including archival data of SN 2014J, we analyse
a sample spanning observed colour excesses up to $E(B-V)=1.4~$mag. We study the
wavelength dependent extinction of each individual SN and find a diversity of
reddening laws when characterised by the total-to-selective extinction $R_V$.
In particular, we note that for the two SNe with $E(B-V)\gtrsim1~$mag, for
which the colour excess is dominated by dust extinction, we find
$R_V=1.4\pm0.1$ and $R_V=2.8\pm0.1$. Adding UV photometry reduces the
uncertainty of fitted $R_V$ by $\sim50\,$% allowing us to also measure $R_V$ of
individual low-extinction objects which point to a similar diversity, currently
not accounted for in the analyses when SNe~Ia are used for studying the
expansion history of the universe.
We report on the discovery of SN2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova over a wide range of the electromagnetic ...spectrum. The first set of optical, near-IR and mid-IR observations of SN2014J, orchestrated by the intermediate Palomar Transient Factory (iPTF), show that SN2014J is a spectroscopically normal Type Ia supernova, albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the lightcurve rise. Similarly to other highly reddened Type Ia supernovae, a low value of total-to-selective extinction, Rv < 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from HST with special emphasis on the sources nearest to the SN location.
We present ultraviolet (UV) observations of six nearby Type~Ia supernovae (SNe~Ia) obtained with the Hubble Space Telescope, three of which were also observed in the near-IR (NIR) with Wide-Field ...Camera~3. UV observations with the Swift satellite, as well as ground-based optical and near-infrared data provide complementary information. The combined data-set covers the wavelength range \(0.2\)--\(2~\mu\)m. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to \(E(B-V)=1.4~\)mag. We study the wavelength dependent extinction of each individual SN and find a diversity of reddening laws when characterised by the total-to-selective extinction \(R_V\). In particular, we note that for the two SNe with \(E(B-V)\gtrsim1~\)mag, for which the colour excess is dominated by dust extinction, we find \(R_V=1.4\pm0.1\) and \(R_V=2.8\pm0.1\). Adding UV photometry reduces the uncertainty of fitted \(R_V\) by \(\sim50\,\)% allowing us to also measure \(R_V\) of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe~Ia are used for studying the expansion history of the universe.
During a core-collapse supernova (SN), axionlike particles (ALPs) could be produced through the Primakoff process and subsequently convert into γ rays in the magnetic field of the Milky Way. We do ...not find evidence for such a γ-ray burst in observations of extragalactic SNe with the Fermi Large Area Telescope (LAT). The SN explosion times are estimated from optical light curves and we find a probability of about ∼ 90 % that the LAT observed at least one SN at the time of the core collapse. Under the assumption that at least one SN was contained within the LAT field of view, we exclude photon-ALP couplings ≳ 2.6 × 10−12 GeV−1 for ALP masses ma ≲ 3 × 10−10 eV, improving previous limits from SN1987A by a factor of 2.
Strong lensing by galaxy clusters can be used to significantly expand the survey reach, thus allowing observation of magnified high-redshift supernovae that otherwise would remain undetected. Strong ...lensing can also provide multiple images of the galaxies that lie behind the clusters. Detection of strongly lensed Type Ia supernovae (SNe Ia) is especially useful because of their standardizable brightness, as they can be used to improve either cluster lensing models or independent measurements of cosmological parameters. The cosmological parameter, the Hubble constant, is of particular interest given the discrepancy regarding its value from measurements with different approaches. Here, we explore the feasibility of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) of detecting strongly lensed SNe in the field of five galaxy clusters (Abell 1689 and Hubble Frontier Fields clusters) that have well-studied lensing models. Considering the 88 systems composed of 268 individual multiple images in the five cluster fields, we find that the LSST will be sensitive to SNe Ia (SNe IIP) exploding in 41 (23) galaxy images. The range of redshift of these galaxies is between 1.01<z<3.05. During its 10 years of operation, LSST is expected to detect 0.2±0.1 SN Ia and 0.9±0.3 core collapse SNe. However, as LSST will observe many more massive galaxy clusters, it is likely that the expectations are higher. We stress the importance of having an additional observing program for photometric and spectroscopic follow-up of the strongly lensed SNe detected by LSST.
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