190 research outputs found
Disentangling the Origin and Heating Mechanism of Supernova Dust: Late-Time Spitzer Spectroscopy of the Type IIn SN 2005ip
This paper presents late-time near-infrared and {\it Spitzer} mid-infrared
photometric and spectroscopic observations of warm dust in the Type IIn SN
2005ip in NGC 2906. The spectra show evidence for two dust components with
different temperatures. Spanning the peak of the thermal emission, these
observations provide strong constraints on the dust mass, temperature, and
luminosity, which serve as critical diagnostics for disentangling the origin
and heating mechanism of each component. The results suggest the warmer dust
has a mass of \msolar, originates from newly formed
dust in the ejecta, or possibly the cool, dense shell, and is continuously
heated by the circumstellar interaction. By contrast, the cooler component
likely originates from a circumstellar shock echo that forms from the heating
of a large, pre-existing dust shell ~\msolar~by the late-time
circumstellar interaction. The progenitor wind velocity derived from the blue
edge of the He 1 1.083 \micron~P Cygni profile indicates a progenitor eruption
likely formed this dust shell 100 years prior to the supernova explosion,
which is consistent with a Luminous Blue Variable (LBV) progenitor star.Comment: 12 pages, 10 figures, Accepted to Ap
Late-Time Circumstellar Interaction in a Spitzer Selected Sample of Type IIn Supernovae
Type IIn supernovae (SNe IIn) are a rare (< 10%) subclass of core-collapse
SNe that exhibit relatively narrow emission lines from a dense, pre-existing
circumstellar medium (CSM). In 2009, a warm Spitzer survey observed 30 SNe IIn
discovered in 2003 - 2008 and detected 10 SNe at distances out to 175 Mpc with
unreported late-time infrared emission, in some cases more than 5 years
post-discovery. For this single epoch of data, the warm-dust parameters suggest
the presence of a radiative heating source consisting of optical/X-ray emission
continuously generated by ongoing CSM interaction. Here we present
multi-wavelength follow-up observations of this sample of 10 SNe IIn and the
well-studied Type IIn SN 2010jl. A recent epoch of Spitzer observations reveals
ongoing mid-infrared emission from nine of the SNe in this sample. We also
detect three of the SNe in archival WISE data, in addition to SNe 1987A,
2004dj, and 2008iy. For at least five of the SNe in the sample, optical and/or
X-ray emission confirms the presence of radiative emission from ongoing CSM
interaction. The two Spitzer nondetections are consistent with the forward
shock overrunning and destroying the dust shell, a result that places upper
limits on the dust-shell size. The optical and infrared observations confirm
the radiative heating model and constrain a number of model parameters,
including progenitor mass-loss characteristics. All of the SNe in this sample
experienced an outburst on the order of tens to hundreds of years prior to the
SN explosion followed by periods of less intense mass loss. Although all
evidence points to massive progenitors, the variation in the data highlights
the diversity in SN IIn progenitor evolution. While these observations do not
identify a particular progenitor system, they demonstrate that future,
coordinated, multi-wavelength campaigns can constrain theoretical mass-loss
models.Comment: 10 pages, 6 figures, accepted to AJ (with comments
PTF11kx: A Type Ia Supernova with Hydrogen Emission Persisting After 3.5 Years
The optical transient PTF11kx exhibited both the characteristic spectral
features of Type Ia supernovae (SNe Ia) and the signature of ejecta interacting
with circumstellar material (CSM) containing hydrogen, indicating the presence
of a nondegenerate companion. We present an optical spectrum at days
after peak from Keck Observatory, in which the broad component of H
emission persists with a similar profile as in early-time observations. We also
present IRAC detections obtained and days after peak,
and an upper limit from ultraviolet imaging at days. We interpret
our late-time observations in context with published results - and reinterpret
the early-time observations - in order to constrain the CSM's physical
parameters and compare to theoretical predictions for recurrent nova systems.
We find that the CSM's radial extent may be several times the distance between
the star and the CSM's inner edge, and that the CSM column density may be two
orders of magnitude lower than previous estimates. We show that the H
luminosity decline is similar to other SNe with CSM interaction, and
demonstrate how our infrared photometry is evidence for newly formed,
collisionally heated dust. We create a model for PTF11kx's late-time CSM
interaction and find that X-ray reprocessing by photoionization and
recombination cannot reproduce the observed H luminosity, suggesting
that the X-rays are thermalized and that H radiates from collisional
excitation. Finally, we discuss the implications of our results regarding the
progenitor scenario and the geometric properties of the CSM for the PTF11kx
system.Comment: 15 pages, 8 figures, 3 tables; submitted to Ap
X-ray Emission from SN 2012ca: A Type Ia-CSM Supernova Explosion in a Dense Surrounding Medium
X-ray emission is one of the signposts of circumstellar interaction in
supernovae (SNe), but until now, it has been observed only in core-collapse
SNe. The level of thermal X-ray emission is a direct measure of the density of
the circumstellar medium (CSM), and the absence of X-ray emission from Type Ia
SNe has been interpreted as a sign of a very low density CSM. In this paper, we
report late-time (500--800 days after discovery) X-ray detections of SN 2012ca
in {\it Chandra} data. The presence of hydrogen in the initial spectrum led to
a classification of Type Ia-CSM, ostensibly making it the first SN~Ia detected
with X-rays. Our analysis of the X-ray data favors an asymmetric medium, with a
high-density component which supplies the X-ray emission. The data suggest a
number density cm in the higher-density medium, which is
consistent with the large observed Balmer decrement if it arises from
collisional excitation. This is high compared to most core-collapse SNe, but it
may be consistent with densities suggested for some Type IIn or superluminous
SNe. If SN 2012ca is a thermonuclear SN, the large CSM density could imply
clumps in the wind, or a dense torus or disk, consistent with the
single-degenerate channel. A remote possibility for a core-degenerate channel
involves a white dwarf merging with the degenerate core of an asymptotic giant
branch star shortly before the explosion, leading to a common envelope around
the SN.Comment: 11 pages, 4 figures. Accepted to MNRA
Rapid formation of large dust grains in the luminous supernova SN 2010jl
The origin of dust in galaxies is still a mystery. The majority of the
refractory elements are produced in supernova explosions but it is unclear how
and where dust grains condense and grow, and how they avoid destruction in the
harsh environments of star-forming galaxies. The recent detection of 0.1-0.5
solar masses of dust in nearby supernova remnants suggests in situ dust
formation, while other observations reveal very little dust in supernovae the
first few years after explosion. Observations of the bright SN 2010jl have been
interpreted as pre-existing dust, dust formation or no dust at all. Here we
report the rapid (40-240 days) formation of dust in its dense circumstellar
medium. The wavelength dependent extinction of this dust reveals the presence
of very large (> 1 micron) grains, which are resistant to destructive
processes. At later times (500-900 days), the near-IR thermal emission shows an
accelerated growth in dust mass, marking the transition of the supernova from a
circumstellar- to an ejecta-dominated source of dust. This provides the link
between the early and late dust mass evolution in supernovae with dense
circumstellar media.Comment: 62 pages, 13 figures, 1 table. Author version of the Letter to
Nature, published online July 9 2014 (Nature, 511, 7509, pp. 326-329 (2014)),
prior to the final editorial changes to conform to Journal style; includes
Methods and Extended Data Figures and the Supplementary Information. See
published version
http://www.nature.com/nature/journal/v511/n7509/full/nature13558.htm
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