461 research outputs found
SN 2006bp: Probing the Shock Breakout of a Type II-P Supernova
HET optical spectroscopy and unfiltered ROTSE-III photometry spanning the
first 11 months since explosion of the Type II-P SN 2006bp are presented. Flux
limits from the days before discovery combined with the initial rapid
brightening suggest the supernova was first detected just hours after shock
breakout. Optical spectra obtained about 2 days after breakout exhibit narrow
emission lines corresponding to HeII 4200, HeII 4686, and CIV 5805 in the rest
frame, and these features persist in a second observation obtained 5 hours
later; however, these emission lines are not detected the following night nor
in subsequent observations. We suggest that these lines emanate from material
close to the explosion site, possibly in the outer layers of the progenitor
that have been ionized by the high energy photons released at shock breakout. A
P-Cygni profile is observed around 4450 A in the +2 and +3 day spectra.
Previous studies have attributed this feature to high velocity H-beta, but we
discuss the possibility that this profile is instead due to HeII 4687. Further
HET observations (14 nights in total) covering the spectral evolution across
the photometric plateau up to 73 days after breakout and during the nebular
phase around day +340 are presented, and expansion velocities are derived for
key features. The measured decay slope for the unfiltered light curve is 0.0073
+/- 0.0004 mag/day between days +121 and +335, which is significantly slower
than the decay of rate 56Co. We combine our HET measurements with published
X-ray, UV, and optical data to obtain a quasi-bolometric light curve through
day +60. We see a slow cooling over the first 25 days, but no sign of an early
sharp peak; any such feature from the shock breakout must have lasted less than
~1 day.[ABRIDGED]Comment: ApJ accepted, 43 page
Photometric Evolution of SNe Ib/c 2004ao, 2004gk and 2006gi
Photometric observations of three core collapse supernovae (SNe 2004ao,
2004gk and 2006gi), covering about 200 days of evolution are presented and
analyzed. The photometric behaviour of the three objects is consistent with
their membership of the envelope-stripped type Ib/c class. Pseudo-bolometric
light curves are constructed. The corresponding measured -folding times are
found to be faster compared to the Co decay (i.e. 111.3 d), suggesting
that a proportion of -rays increasing with time have escaped without
thermalization, owing to the low mass nature of the ejecta. SN 2006gi has
almost identical post maximum decline phase luminosities as SN 1999ex, and
found to be similar to both SNe 1999dn and 1999ex in terms of the
quasi-bolometric shape, placing it among the fast decliner Ib objects. SN
2004ao appears to fit within the slow decliner Ib SNe. SNe 2004ao and 2004gk
display almost identical luminosities in the [50-100] days time interval,
similar to SN 1993J. A preliminary simplified ray deposition model is
described and applied to the computed pseudo-bolometric light curves, allowing
one to find a range in the ejecta and Ni masses. The optical and
quasi-bolometric light curves, and the colour evolution of SN 2004gk are
found to show a sudden drop after day 150. Correlating this fact to dust
formation is premature and requires further observational evidence.Comment: Accepted for publication in The Astrophysical Journal; (11
two-columns Pages, 11 figures, 6 Tables; Scheduled for publication in April
2011
Properties of Newly Formed Dust Grains in The Luminous Type IIn Supernova 2010jl
Supernovae (SNe) have been proposed to be the main production sites of dust
grains in the Universe. Our knowledge on their importance to dust production
is, however, limited by observationally poor constraints on the nature and
amount of dust particles produced by individual SNe. In this paper, we present
a spectrum covering optical through near-Infrared (NIR) light of the luminous
Type IIn supernova (SN IIn) 2010jl around one and half years after the
explosion. This unique data set reveals multiple signatures of newly formed
dust particles. The NIR portion of the spectrum provides a rare example where
thermal emission from newly formed hot dust grains is clearly detected. We
determine the main population of the dust species to be carbon grains at a
temperature of ~1,350 - 1,450K at this epoch. The mass of the dust grains is
derived to be ~(7.5 - 8.5) x 10^{-4} Msun. Hydrogen emission lines show
wavelength-dependent absorption, which provides a good estimate on the typical
size of the newly formed dust grains (~0.1 micron, and most likely <~0.01
micron). We attribute the dust grains to have been formed in a dense cooling
shell as a result of a strong SN-circumstellar media (CSM) interaction. The
dust grains occupy ~10% of the emitting volume, suggesting an inhomogeneous,
clumpy structure. The average CSM density is required to be >~3 x 10^{7}
cm^{-3}, corresponding to a mass loss rate of >~0.02 Msun yr^{-1} (for a mass
loss wind velocity of ~100 km s^{-1}). This strongly supports a scenario that
SN 2010jl and probably other luminous SNe IIn are powered by strong
interactions within very dense CSM, perhaps created by Luminous Blue Variable
(LBV)-like eruptions within the last century before the explosion.Comment: 18 pages, 11 figures. Accepted by ApJ on 30 July 2013. The accepted
version was submitted on 8 July 2013, and the original version was submitted
on 3 March 201
Disappearance of the Progenitor of Supernova iPTF13bvn
Supernova (SN) iPTF13bvn in NGC 5806 was the first Type Ib SN to have been
tentatively associated with a progenitor candidate in pre-explosion images. We
performed deep ultraviolet (UV) and optical Hubble Space Telescope (HST)
observations of the SN site 740 days after explosion. We detect an object in
the optical bands that is fainter than the pre-explosion object. This dimming
is likely not produced by dust absorption in the ejecta; thus, our finding
confirms the connection of the progenitor candidate with the SN. The object in
our data is likely dominated by the fading SN, which implies that the pre-SN
flux is mostly due to the progenitor. We compare our revised pre-SN photometry
with previously proposed progenitor models. Although binary progenitors are
favored, models need to be refined. In particular, to comply with our deep UV
detection limit, any companion star must be less luminous than a late-O star or
substantially obscured by newly formed dust. A definitive progenitor
characterization will require further observations to disentangle the
contribution of a much fainter SN and its environment.Comment: 8 pages, 3 tables, 3 figures. Accepted for publication in ApJ
Light Curve Modeling of Superluminous Supernova 2006gy: Collision between Supernova Ejecta and Dense Circumstellar Medium
We show model light curves of superluminous supernova 2006gy on the
assumption that the supernova is powered by the collision of supernova ejecta
and its dense circumstellar medium. The initial conditions are constructed
based on the shock breakout condition, assuming that the circumstellar medium
is dense enough to cause the shock breakout within it. We perform a set of
numerical light curve calculations by using a one-dimensional multigroup
radiation hydrodynamics code STELLA. We succeeded in reproducing the overall
features of the early light curve of SN 2006gy with the circumstellar medium
whose mass is about 15 Msun (the average mass-loss rate ~ 0.1 Msun/yr). Thus,
the progenitor of SN 2006gy is likely a very massive star. The density profile
of the circumstellar medium is not well constrained by the light curve modeling
only, but our modeling disfavors the circumstellar medium formed by steady mass
loss. The ejecta mass is estimated to be comparable to or less than 15 Msun and
the explosion energy is expected to be more than 4e51 erg. No 56Ni is required
to explain the early light curve. We find that the multidimensional effect,
e.g., the Rayleigh-Taylor instability, which is expected to take place in the
cool dense shell between the supernova ejecta and the dense circumstellar
medium, is important in understanding supernovae powered by the shock
interaction. We also show the evolution of the optical and near-infrared model
light curves of high-redshift superluminous supernovae. They can be potentially
used to identify SN 2006gy-like superluminous supernovae in the future optical
and near-infrared transient surveys.Comment: 18 pages, 19 figures, 2 tables, accepted by Monthly Notices of the
Royal Astronomical Societ
Interaction-powered supernovae: Rise-time vs. peak-luminosity correlation and the shock-breakout velocity
Interaction of supernova (SN) ejecta with the optically thick circumstellar
medium (CSM) of a progenitor star can result in a bright, long-lived shock
breakout event. Candidates for such SNe include Type IIn and superluminous SNe.
If some of these SNe are powered by interaction, then there should be a
relation between their peak luminosity, bolometric light-curve rise time, and
shock-breakout velocity. Given that the shock velocity during shock breakout is
not measured, we expect a correlation, with a significant spread, between the
rise time and the peak luminosity of these SNe. Here, we present a sample of 15
SNe IIn for which we have good constraints on their rise time and peak
luminosity from observations obtained using the Palomar Transient Factory. We
report on a possible correlation between the R-band rise time and peak
luminosity of these SNe, with a false-alarm probability of 3%. Assuming that
these SNe are powered by interaction, combining these observables and theory
allows us to deduce lower limits on the shock-breakout velocity. The lower
limits on the shock velocity we find are consistent with what is expected for
SNe (i.e., ~10^4 km/s). This supports the suggestion that the early-time light
curves of SNe IIn are caused by shock breakout in a dense CSM. We note that
such a correlation can arise from other physical mechanisms. Performing such a
test on other classes of SNe (e.g., superluminous SNe) can be used to rule out
the interaction model for a class of events.Comment: Accepted to ApJ, 6 page
Evidence for a Compact Wolf-Rayet Progenitor for the Type Ic Supernova PTF 10vgv
We present the discovery of PTF 10vgv, a Type Ic supernova (SN) detected by the Palomar Transient Factory, using the Palomar 48 inch telescope (P48). R-band observations of the PTF 10vgv field with P48 probe the SN emission from its very early phases (about two weeks before R-band maximum) and set limits on its flux in the week prior to the discovery. Our sensitive upper limits and early detections constrain the post-shock-breakout luminosity of this event. Via comparison to numerical (analytical) models, we derive an upper-limit of R ≾ 4.5 R_☉ (R ≾ 1 R_☉) on the radius of the progenitor star, a direct indication in favor of a compact Wolf-Rayet star. Applying a similar analysis to the historical observations of SN 1994I yields R ≾ 1/4 R_☉ for the progenitor radius of this SN
Hydrogen-poor superluminous stellar explosions
Supernovae (SNe) are stellar explosions driven by gravitational or
thermonuclear energy, observed as electromagnetic radiation emitted over weeks
or more. In all known SNe, this radiation comes from internal energy deposited
in the outflowing ejecta by either radioactive decay of freshly-synthesized
elements (typically 56Ni), stored heat deposited by the explosion shock in the
envelope of a supergiant star, or interaction between the SN debris and
slowly-moving, hydrogen-rich circumstellar material. Here we report on a new
class of luminous SNe whose observed properties cannot be explained by any of
these known processes. These include four new SNe we have discovered, and two
previously unexplained events (SN 2005ap; SCP 06F6) that we can now identify as
members. These SNe are all ~10 times brighter than SNe Ia, do not show any
trace of hydrogen, emit significant ultra-violet (UV) flux for extended periods
of time, and have late-time decay rates which are inconsistent with
radioactivity. Our data require that the observed radiation is emitted by
hydrogen-free material distributed over a large radius (~10^15 cm) and
expanding at high velocities (>10^4 km s^-1). These long-lived, UV-luminous
events can be observed out to redshifts z>4 and offer an excellent opportunity
to study star formation in, and the interstellar medium of, primitive distant
galaxies.Comment: Accepted to Nature. Press embargoed until 2011 June 8, 18:00 U
Galaxy Zoo Supernovae
This paper presents the first results from a new citizen science project:
Galaxy Zoo Supernovae. This proof of concept project uses members of the public
to identify supernova candidates from the latest generation of wide-field
imaging transient surveys. We describe the Galaxy Zoo Supernovae operations and
scoring model, and demonstrate the effectiveness of this novel method using
imaging data and transients from the Palomar Transient Factory (PTF). We
examine the results collected over the period April-July 2010, during which
nearly 14,000 supernova candidates from PTF were classified by more than 2,500
individuals within a few hours of data collection. We compare the transients
selected by the citizen scientists to those identified by experienced PTF
scanners, and find the agreement to be remarkable - Galaxy Zoo Supernovae
performs comparably to the PTF scanners, and identified as transients 93% of
the ~130 spectroscopically confirmed SNe that PTF located during the trial
period (with no false positive identifications). Further analysis shows that
only a small fraction of the lowest signal-to-noise SN detections (r > 19.5)
are given low scores: Galaxy Zoo Supernovae correctly identifies all SNe with >
8{\sigma} detections in the PTF imaging data. The Galaxy Zoo Supernovae project
has direct applicability to future transient searches such as the Large
Synoptic Survey Telescope, by both rapidly identifying candidate transient
events, and via the training and improvement of existing machine classifier
algorithms.Comment: 13 pages, 10 figures, accepted MNRA
The Palomar Transient Factory photometric catalog 1.0
We construct a photometrically calibrated catalog of non-variable sources
from the Palomar Transient Factory (PTF) observations. The first version of
this catalog presented here, the PTF photometric catalog 1.0, contains
calibrated R_PTF-filter magnitudes for about 21 million sources brighter than
magnitude 19, over an area of about 11233 deg^2. The magnitudes are provided in
the PTF photometric system, and the color of a source is required in order to
convert these magnitudes into other magnitude systems. We estimate that the
magnitudes in this catalog have typical accuracy of about 0.02 mag with respect
to magnitudes from the Sloan Digital Sky Survey. The median repeatability of
our catalog's magnitudes for stars between 15 and 16 mag, is about 0.01 mag,
and it is better than 0.03 mag for 95% of the sources in this magnitude range.
The main goal of this catalog is to provide reference magnitudes for
photometric calibration of visible light observations. Subsequent versions of
this catalog, which will be published incrementally online, will be extended to
a larger sky area and will also include g_PTF-filter magnitudes, as well as
variability and proper motion information.Comment: 6 pages, 6 figures, PASP in pres
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