19 research outputs found
Photometry of SN 2002ic and Implications for the Progenitor Mass-Loss History
We present new pre-maximum and late-time optical photometry of the Type
Ia/IIn supernova 2002ic. These observations are combined with the published
V-band magnitudes of Hamuy et al. (2003) and the VLT spectrophotometry of Wang
et al. (2004) to construct the most extensive light curve to date of this
unusual supernova. The observed flux at late time is significantly higher
relative to the flux at maximum than that of any other observed Type Ia
supernova and continues to fade very slowly a year after explosion. Our
analysis of the light curve suggests that a non-Type Ia supernova component
becomes prominent days after explosion. Modeling of the non-Type Ia
supernova component as heating from the shock interaction of the supernova
ejecta with pre-existing circumstellar material suggests the presence of a
cm gap or trough between the progenitor system and the
surrounding circumstellar material. This gap could be due to significantly
lower mass-loss years prior to explosion or
evacuation of the circumstellar material by a low-density fast wind. The latter
is consistent with observed properties of proto-planetary nebulae and with
models of white-dwarf + asymptotic giant branch star progenitor systems with
the asymptotic giant branch star in the proto-planetary nebula phase.Comment: accepted for publication in Ap
Chandra's tryst with SN 1995N
We present the spectroscopic and imaging analysis of a type IIn supernova SN
1995N observed with the Chandra X-ray observatory on 2004 March 27. We compare
the spectrum obtained from our Chandra observation with that of the previous
observation with ASCA in 1998. We find the presence of Neon lines in the
Chandra spectrum that were not reported in the ASCA observation. We see no
evidence of Iron in both epochs. The observed absorption column depth indicates
an extra component over and above the galactic absorption component and is
possibly due to a cool dense shell between the reverse-shock and the contact
discontinuity in the ejecta. The ASCA and the ROSAT observations suggested a
non-linear behavior of the X-ray light curve. However, with the higher spatial
resolution and sensitivity of Chandra, we separate out many nearby sources in
the supernova field-of-view that had additionally contributed to the supernova
flux due to the large Point Spread Function of the ASCA. Taking out the
contribution of those nearby sources, we find that the light curves are
consistent with a linear decline profile. We consider the light curve in the
high energy band separately. We discuss our results in the context of models of
nucleosynthesis and the interaction of the shock waves with the circumstellar
medium in core collapse supernovae.Comment: 35 pages, 12 figures, accepted for publication in Astrophysical
Journa
Extraordinary Late-Time Infrared Emission of Type IIn Supernovae
Near-Infrared (NIR) observations are presented for five Type IIn supernovae
(SN 1995N, SN 1997ab, SN 1998S, SN 1999Z, and SN 1999el) that exhibit strong
infrared excesses at late times (t >= 100 d). H- and K-band emission from these
objects is dominated by a continuum that rises toward longer wavelengths. The
data are interpreted as thermal emission from dust, probably situated in a
pre-existing circumstellar nebula. The IR luminosities implied by single
temperature blackbody fits are quite large,> 10^(41 - 42) erg s^-1, and the
emission evolves slowly, lasting for years after maximum light. For SN 1995N,
the integrated energy release via IR dust emission was 0.5 -- 1 * 10^50 erg. A
number of dust heating scenarios are considered, the most likely being an
infrared echo poweredby X-ray and UV emissions from the shock interaction with
a dense circumstellar medium.Comment: 14 Pages, 3 Figures, Accecpted for publication in The Astrophysical
Journa
Massive stars exploding in a He-rich circumstellar medium. I. Type Ibn (SN 2006jc-like) events
We present new spectroscopic and photometric data of the type Ibn supernovae
2006jc, 2000er and 2002ao. We discuss the general properties of this recently
proposed supernova family, which also includes SN 1999cq. The early-time
monitoring of SN 2000er traces the evolution of this class of objects during
the first few days after the shock breakout. An overall similarity in the
photometric and spectroscopic evolution is found among the members of this
group, which would be unexpected if the energy in these core-collapse events
was dominated by the interaction between supernova ejecta and circumstellar
medium. Type Ibn supernovae appear to be rather normal type Ib/c supernova
explosions which occur within a He-rich circumstellar environment. SNe Ibn are
therefore likely produced by the explosion of Wolf-Rayet progenitors still
embedded in the He-rich material lost by the star in recent mass-loss episodes,
which resemble known luminous blue variable eruptions. The evolved Wolf-Rayet
star could either result from the evolution of a very massive star or be the
more evolved member of a massive binary system. We also suggest that there are
a number of arguments in favour of a type Ibn classification for the historical
SN 1885A (S-Andromedae), previously considered as an anomalous type Ia event
with some resemblance to SN 1991bg.Comment: 17 pages including 12 figures and 4 tables. Slightly revised version,
conclusions unchanged, 1 figure added. Accepted for publication in MNRA
Two transitional type~Ia supernovae located in the Fornax cluster member NGC 1404: SN 2007on and SN 2011iv
We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band light curves of SN 2007on and SN 2011iv are characterised by dm_15(B) decline-rate values of 1.96 mag and 1.77 mag, respectively. Although they have similar decline rates, their peak B- and H-band magnitudes differ by ~0.60 mag and ~0.35 mag, respectively. After correcting for the luminosity vs. decline rate and the luminosity vs. colour relations, the peak B-band and H-band light curves provide distances that differ by ~14% and ~9%, respectively. These findings serve as a cautionary tale for the use of transitional SNe Ia located in early-type hosts in the quest to measure cosmological parameters. Interestingly, even though SN 2011iv is brighter and bluer at early times, by three weeks past maximum and extending over several months, its B-V colour is 0.12 mag redder than that of SN 2007on. To reconcile this unusual behaviour, we turn to guidance from a suite of spherical one-dimensional Chandrasekhar-mass delayed-detonation explosion models. In this context, 56Ni production depends on both the so-called transition density and the central density of the progenitor white dwarf. To first order, the transition density drives the luminosity-width relation, while the central density is an important second-order parameter. Within this context, the differences in the B-V color evolution along the Lira regime suggests the progenitor of SN~2011iv had a higher central density than SN~2007on
Robotic Observations of the Sky with TAROT: 2004--2007
International audienceThe TAROTs (Télescopes à Action Rapide pour les Objets Transitoires; Rapid Action Telescopes for Transient Objects) are two fully robotic observatories designed to observe the early transient optical counterpart of gamma-ray bursts (GRBs). As their occurrence is rare, we also use TAROT to observe various other celestial objects: RR Lyrae stars, minor planets and supernovae. In this paper, we describe the telescopes, their networking, and the data-processing methods used