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M. Ergon,
J. Sollerman,
M. Fraser,
A. Pastorello,
S. Taubenberger,
N. Elias-Rosa,
M. Bersten,
A. Jerkstrand,
S. Benetti,
M. T. Botticella, [......],
A. Howell, E. Kankare,
L. Magill,
S. Mattila,
R. Naves,
P. Ochner,
J. Ruiz,
K. Smith,
L. Tomasella,
M. Turatto
[show abstract]
[hide abstract]
ABSTRACT: We present optical and near-infrared (NIR) photometry and spectroscopy of the
Type IIb supernova (SN) 2011dh for the first 100 days. We complement our
extensive dataset with SWIFT ultra-violet (UV) and Spitzer mid-infrared (MIR)
data to build a UV to MIR bolometric lightcurve using both photometric and
spectroscopic data. Hydrodynamical modelling of the SN based on this bolometric
lightcurve have been presented in Bersten (2012). We find that the absorption
minimum for the hydrogen lines is never seen below ~11000 km/s but approaches
this value as the lines get weaker. This suggests that the interface between
the helium core and hydrogen rich envelope is located near this velocity in
agreement with the Bersten et al. (2012) He4R270 ejecta model. Spectral
modelling of the hydrogen lines using this ejecta model supports the conclusion
and we find a hydrogen mass of 0.01-0.04 solar masses to be consistent with the
observed spectral evolution. We estimate that the photosphere reaches the
helium core at 5-7 days whereas the helium lines appear between ~10 and ~15
days, close to the photosphere and then move outward in velocity until ~40
days. This suggests that increasing non-thermal excitation due to decreasing
optical depth for the gamma-rays is driving the early evolution of these lines.
We also provide and discuss pre- and post-explosion observations of the SN site
which shows a reduction by 60-75 percent in flux at the position of the yellow
supergiant coincident with SN 2011dh. The V band decline between Jan 20 and Apr
14 2013 is 0.76 mag which is consistent with the remaining flux being emitted
by the SN. Hence we find that the star was indeed the progenitor of SN 2011dh
as previously suggested by Maund et al. (2011) and which is also consistent
with the results from the hydrodynamical modelling.
05/2013;
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A. Pastorello,
E. Cappellaro,
C. Inserra,
S. J. Smartt,
G. Pignata,
S. Benetti,
S. Valenti,
M. Fraser,
K. Takats,
S. Benitez, [......],
M. C. Nysewander,
P. Ochner,
Y. -C. Pan,
M. L. Pumo,
D. E. Reichart,
T. G. Tan,
S. Taubenberger,
L. Tomasella,
M. Turatto,
D. Wright
[show abstract]
[hide abstract]
ABSTRACT: We report the results of a 3 year-long dedicated monitoring campaign of a
restless Luminous Blue Variable (LBV) in NGC 7259. The object, named SN 2009ip,
was observed photometrically and spectroscopically in the optical and
near-infrared domains. We monitored a number of erupting episodes in the past
few years, and increased the density of our observations during eruptive
episodes. In this paper we present the full historical data set from 2009-2012
with multi-wavelength dense coverage of the two high luminosity events between
August - September 2012. We construct bolometric light curves and measure the
total luminosities of these eruptive or explosive events. We label them the
2012a event (lasting ~50 days) with a peak of 3x10^41 erg/s, and the 2012b
event (14 day rise time, still ongoing) with a peak of 8x10^42 erg/s. The
latter event reached an absolute R-band magnitude of about -18, comparable to
that of a core-collapse supernova (SN). Our historical monitoring has detected
high-velocity spectral features (~13000 km/s) in September 2011, one year
before the current SN-like event. This implies that the detection of such high
velocity outflows cannot, conclusively, point to a core-collapse SN origin. We
suggest that the initial peak in the 2012a event was unlikely to be due to a
faint core-collapse SN. We propose that the high intrinsic luminosity of the
latest peak, the variability history of SN 2009ip, and the detection of broad
spectral lines indicative of high-velocity ejecta are consistent with a
pulsational pair-instability event, and that the star may have survived the
last outburst. The question of the survival of the LBV progenitor star and its
future fate remain open issues, only to be answered with future monitoring of
this historically unique explosion.
10/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We report the radio detection of supernova 2010P (cf. CBETs 2145, 2149) in Arp 299 in EVLA (8459 MHz) observations from 15th Jun 2011. SN2010P was discovered in near-IR images on 18th Jan 2010, and classified as a Type Ib/IIb SN based on its optical spectrum obtained on 11th Feb 2010 (cf. CBET 2189).
The Astronomer's Telegram. 09/2012; 4432:1.
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[show abstract]
[hide abstract]
ABSTRACT: We present supernova rate measurements at redshift 0.1-1.0 from the Stockholm
VIMOS Supernova Survey (SVISS). The sample contains 16 supernovae in total. The
discovered supernovae have been classified as core collapse or type Ia
supernovae (9 and 7, respectively) based on their light curves, colour
evolution and host galaxy photometric redshift. The rates we find for the core
collapse supernovae are 3.29 (-1.78,-1.45)(+3.08,+1.98) x 10^-4 yr^-1 Mpc^-3
h70^3 (with statistical and systematic errors respectively) at average redshift
0.39 and 6.40 (-3.12,-2.11)(+5.30,+3.65) x 10^-4 yr^-1 Mpc^-3 h70^3 at average
redshift 0.73. For the type Ia supernovae we find a rate of 1.29
(-0.57,-0.28)(+0.88,+0.27) x 10^-4 yr^-1 Mpc^-3 h70^3 at average redshift 0.62.
All of these rate estimates have been corrected for host galaxy extinction,
using a method that includes supernovae missed in infrared bright galaxies at
high redshift. We use Monte Carlo simulations to make a thorough study of the
systematic effects from assumptions made when calculating the rates and find
that the most important errors come from misclassification, the assumed mix of
faint and bright supernova types and uncertainties in the extinction
correction. We compare our rates to other observations and to the predicted
rates for core collapse and type Ia supernovae based on the star formation
history and different models of the delay time distribution. Overall, our
measurements, when taking the effects of extinction into account, agree quite
well with the predictions and earlier results. Our results highlight the
importance of understanding the role of systematic effects, and dust extinction
in particular, when trying to estimate the rates of supernovae at moderate to
high redshift.
06/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We estimate the fraction of core-collapse supernovae (CCSNe) that remain
undetected by optical SN searches due to obscuration by large amounts of dust
in their host galaxies. This effect is especially important in luminous and
ultraluminous infrared galaxies, which are locally rare but dominate the star
formation at redshifts of z~1-2. We perform a detailed investigation of the SN
activity in the nearby luminous infrared galaxy Arp 299 and estimate that up to
83% of the SNe in Arp 299 and in similar galaxies in the local Universe are
missed by observations at optical wavelengths. For rest-frame optical surveys
we find the fraction of SNe missed due to high dust extinction to increase from
the average local value of ~19% to ~38% at z~1.2 and then stay roughly constant
up to z~2. It is therefore crucial to take into account the effects of
obscuration by dust when determining SN rates at high redshift and when
predicting the number of CCSNe detectable by future high-z surveys such as
LSST, JWST, and Euclid. For a sample of nearby CCSNe (distances 6-15 Mpc)
detected during the last 12 yr, we find a lower limit for the local CCSN rate
of 1.5 +0.4/-0.3 x 10^-4 yr^-1 Mpc^-3, consistent with that expected from the
star formation rate. Even closer, at distances less than ~6 Mpc, we find a
significant increase in the CCSN rate, indicating a local overdensity of star
formation caused by a small number of galaxies that have each hosted multiple
SNe.
06/2012;
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C. Romero-Canizales,
M. A. Perez-Torres,
A. Alberdi,
M. K. Argo,
R. J. Beswick, E. Kankare,
F. Batejat,
A. Efstathiou,
S. Mattila,
J. E. Conway,
S. T. Garrington,
T. W. B. Muxlow,
S. D. Ryder,
P. Vaisanen
[show abstract]
[hide abstract]
ABSTRACT: The high star formation rates of luminous infrared galaxies (LIRGs) make them
ideal places for core-collapse supernova (CCSN) searches. At radio frequencies,
free from dust extinction, it is possible to detect compact components within
the innermost LIRG nuclear regions, such as SNe and SN remnants, as well as AGN
buried deep in the LIRG nuclei. We studied the LIRG IC883 aiming at: (i)
investigating its (circum-)nuclear regions using the e-EVN at 5GHz, and
e-MERLIN at 6.9GHz, complemented by archival VLBI data; (ii) detecting at radio
frequencies the two recently reported circumnuclear SNe 2010cu and 2011hi,
which were discovered by near-IR (NIR) adaptive optics observations of IC883;
and (iii) further investigating the nature of SN2011hi at NIR by means of
observations with Gemini-North. The circumnuclear regions traced by e-MERLIN at
6.9GHz have an extension of ~1kpc, and show a striking double-sided structure,
which very likely corresponds to a warped rotating ring, in agreement with
previous studies. Our e-EVN observations at 5GHz and complementary archival
VLBI data at 5GHz and 8.4GHz, reveal the presence of various milliarcsec
compact components in the nucleus of IC883. A single compact source, an AGN
candidate, dominates the emission at both nuclear and circumnuclear scales, as
imaged with the e-EVN and e-MERLIN, respectively. The other milliarcsec
components are very suggestive of ongoing nuclear CCSN activity. Our e-EVN
observations also resulted in upper limits to the radio luminosity of the two
SNe in IC883 recently discovered at NIR. We refine the classification of
SN2011hi as a Type IIP SN according to our latest Gemini-North epoch from 2012,
in agreement with a low-luminosity radio SN nature. We estimate a CCSN rate
lower limit of 1.1_{-0.6}^{+1.3} yr^{-1} for the entire galaxy, based on three
nuclear radio SNe and the circumnuclear SNe 2010cu and 2011hi. (abridged)
05/2012;
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E. Kankare,
M. Ergon,
F. Bufano,
J. Spyromilio,
S. Mattila,
N. N. Chugai,
P. Lundqvist,
A. Pastorello,
R. Kotak,
S. Benetti,
M. -T. Botticella,
R. J. Cumming,
C. Fransson,
M. Fraser,
G. Leloudas,
M. Miluzio,
J. Sollerman,
M. Stritzinger,
M. Turatto,
S. Valenti
[show abstract]
[hide abstract]
ABSTRACT: We present an optical and near-infrared photometric and spectroscopic study
of supernova (SN) 2009kn spanning ~1.5 yr from the discovery. The optical
spectra are dominated by the narrow (full width at half-maximum ~1000 km s^-1)
Balmer lines distinctive of a Type IIn SN with P Cygni profiles. Contrarily,
the photometric evolution resembles more that of a Type IIP SN with a large
drop in luminosity at the end of the plateau phase. These characteristics are
similar to those of SN 1994W, whose nature has been explained with two
different models with different approaches. The well-sampled data set on SN
2009kn offers the possibility to test these models, in the case of both SN
2009kn and SN 1994W. We associate the narrow P Cygni lines with a swept-up
shell composed of circumstellar matter and SN ejecta. The broad emission line
wings, seen during the plateau phase, arise from internal electron scattering
in this shell. The slope of the light curve after the post-plateau drop is
fairly consistent with that expected from the radioactive decay of 56Co,
suggesting an SN origin for SN 2009kn. Assuming radioactivity to be the main
source powering the light curve of SN 2009kn in the tail phase, we infer an
upper limit for 56Ni mass of 0.023 M_sun. This is significantly higher than
that estimated for SN 1994W, which also showed a much steeper decline of the
light curve after the post-plateau drop. We also observe late-time
near-infrared emission which most likely arises from newly formed dust produced
by SN 2009kn. As with SN 1994W, no broad lines are observed in the spectra of
SN 2009kn, not even in the late-time tail phase.
05/2012;
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E. Kankare,
S. Mattila,
S. Ryder,
P. Väisänen,
A. Alberdi,
A. Alonso-Herrero,
L. Colina,
A. Efstathiou,
J. Kotilainen,
J. Melinder,
M.-A. Pérez-Torres,
C. Romero-Cañizales,
and A. Takalo
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of two consecutive supernovae (SNe), 2010cu and 2011hi, located at 037 (180 pc) and 079 (380 pc) projected distance, respectively, from the center of the K-band nucleus of the luminous infrared galaxy (LIRG) IC 883. The SNe were discovered in an ongoing near-infrared K-band search for core-collapse SNe in such galaxies using the ALTAIR/NIRI adaptive optics system with laser guide star at the Gemini-North Telescope. These are thus the closest SNe yet discovered to an LIRG nucleus in optical or near-infrared wavelengths. The near-infrared light curves and colors of both SNe are consistent with core-collapse events. Both SNe seem to suffer from relatively low host galaxy extinction suggesting that regardless of their low projected galactocentric distances, they are not deeply buried in the nuclear regions of the host galaxy.
The Astrophysical Journal Letters 12/2011; 744(2):L19. · 5.53 Impact Factor
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A. Pastorello,
M. L. Pumo,
H. Navasardyan,
L. Zampieri,
M. Turatto,
J. Sollerman,
F. Taddia, E. Kankare,
S. Mattila,
J. Nicolas, [......],
G. Cetrulo,
M. Ergon,
L. Germany,
A. Harutyunyan,
S. Howerton,
G. M. Hurst,
F. Patat,
M. Stritzinger,
L. -G. Strolger,
W. Wells
[show abstract]
[hide abstract]
ABSTRACT: In this paper we investigate the properties of SN 2009E, which exploded in a
relatively nearby spiral galaxy (NGC 4141) and that is probably the faintest
1987A-like supernova discovered so far. Spectroscopic observations which
started about 2 months after the supernova explosion, highlight significant
differences between SN 2009E and the prototypical SN 1987A. Modelling the data
of SN 2009E allows us to constrain the explosion parameters and the properties
of the progenitor star, and compare the inferred estimates with those available
for the similar SNe 1987A and 1998A. The light curve of SN 2009E is less
luminous than that of SN 1987A and the other members of this class, and the
maximum light curve peak is reached at a slightly later epoch than in SN 1987A.
Late-time photometric observations suggest that SN 2009E ejected about 0.04
solar masses of 56Ni, which is the smallest 56Ni mass in our sample of
1987A-like events. Modelling the observations with a radiation hydrodynamics
code, we infer for SN 2009E a kinetic plus thermal energy of about 0.6 foe, an
initial radius of ~7 x 10^12 cm and an ejected mass of ~19 solar masses. The
photospheric spectra show a number of narrow (v~1800 km/s) metal lines, with
unusually strong Ba II lines. The nebular spectrum displays narrow emission
lines of H, Na I, [Ca II] and [O I], with the [O I] feature being relatively
strong compared to the [Ca II] doublet. The overall spectroscopic evolution is
reminiscent of that of the faint 56Ni-poor type II-plateau supernovae. This
suggests that SN 2009E belongs to the low-luminosity, low 56Ni mass, low-energy
tail in the distribution of the 1987A-like objects in the same manner as SN
1997D and similar events represent the faint tail in the distribution of
physical properties for normal type II-plateau supernovae.
11/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We present a study of the core-collapse supernova (CCSN) rate in nuclei A and B1, of the luminous infrared galaxy (LIRG) Arp 299, based on ∼11 yr of Very Large Array (VLA) monitoring of their radio emission at 8.4 GHz. Significant variations in the nuclear radio flux density can be used to identify the CCSN activity in the absence of high-resolution very long baseline interferometry (VLBI) observations. In the case of the B1-nucleus, the small variations in its measured diffuse (synchrotron plus free–free) radio emission are below the fluxes expected from radio supernovae (RSNe), thus making it well-suited to detect RSNe through flux density variability. In fact, we find strong evidence for at least three RSNe this way, which results in a lower limit for the CCSN rate (νSN) of >0.28+0.27−0.15 yr−1. This value agrees within the uncertainties with the infrared (IR) luminosity based SN rate estimate, and with previously reported radio estimates. In the A-nucleus, we did not detect any significant variability and found a SN detection threshold luminosity of ≈3.1 × 1028 erg s−1 Hz−1, allowing only the detection of the most luminous RSNe known. Our method is basically blind to normal CCSN explosions occurring within the A-nucleus, which result in too small variations in the nuclear flux density, remaining diluted by the strong diffuse emission of the nucleus itself. Additionally, we have attempted to find near-IR (NIR) counterparts for the earlier reported RSNe in the Arp 299 nucleus A, by comparing NIR adaptive optics images from the Gemini-N Telescope with contemporaneous observations from the European VLBI Network (EVN). However, we were not able to detect NIR counterparts for the reported radio SNe within the innermost regions of nucleus A. While our NIR observations were sensitive to typical CCSNe at ∼300 mas (or 70 pc projected distance) from the centre of the nucleus A, suffering from extinction up to AV∼ 15 mag, they were not sensitive to such highly obscured SNe within the innermost nuclear regions where most of the EVN sources were detected.
Monthly Notices of the Royal Astronomical Society 08/2011; 415(3):2688 - 2698. · 4.90 Impact Factor
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S. Valenti,
M. Fraser,
S. Benetti,
G. Pignata,
J. Sollerman,
C. Inserra,
E. Cappellaro,
A. Pastorello,
S. J. Smartt,
M. Ergon, [......],
R. Kotak,
A. P. LaCluyze,
L. Magill,
S. Mattila,
J. Maza,
P. A. Mazzali,
D. E. Reichart,
S. Taubenberger,
M. Turatto,
L. Zampieri
[show abstract]
[hide abstract]
ABSTRACT: We present an extensive set of photometric and spectroscopic data for SN
2009jf, a nearby Type Ib supernova, spanning from ~20 days before B-band
maximum to one year after maximum. We show that SN 2009jf is a slow evolving
and energetic stripped-envelope SN and is likely from a massive progenitor
(25-30 solar masses). The large progenitor's mass allows us to explain the
complete hydrogen plus helium stripping without invoking the presence of a
binary companion. The supernova occurred close to a young cluster, in a crowded
environment with ongoing star-formation. The specroscopic similarity with the
He-poor Type Ic SN 2007gr suggests a common progenitor for some supernovae Ib
and Ic. The nebular spectra of SN 2009jf are consistent with an asymmetric
explosion, with an off-center dense core. We also find evidence that He-rich Ib
supernovae have a rise time longer than other stripped-envelope supernovae,
however confirmation of this result and further observations are needed.
06/2011;
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[show abstract]
[hide abstract]
ABSTRACT: In this article we present new data of a sample of core-collapse supernovae showing unequivocal evidences of interaction between their ejecta and pre-existing circumstellar matter (CSM). This CSM was produced by the progenitor star through major mass loss episodes during the final stages of its life. The study of the properties of the SN ejecta and the circumstellar environment are crucial to unveil the nature of the progenitors producing interacting supernovae. In this context, the instrumental combination Very Large Telescope (VLT) plus X-shooter provides spectra covering simultaneously the optical and near-infrared domains, and with adequate resolution to constrain the main properties of the supernova and its environment, including its chemical composition, the ejection velocity and the distribution of the emitting gas (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 03/2011; 332(3):266 - 271. · 1.01 Impact Factor
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M. Fraser,
M. Ergon,
J. J. Eldridge,
S. Valenti,
A. Pastorello,
J. Sollerman,
S. J. Smartt,
I. Agnoletto,
I. Arcavi,
S. Benetti, [......],
A. Gal-Yam, E. Kankare,
G. Leloudas,
K. Maguire,
S. Mattila,
J. R. Maund,
F. Salgado,
A. Stephens,
S. Taubenberger,
M. Turatto
[show abstract]
[hide abstract]
ABSTRACT: We present adaptive optics imaging of the core collapse supernova (SN)
2009md, which we use together with archival \emph{Hubble Space Telescope} data
to identify a coincident progenitor candidate. We find the progenitor to have
an absolute magnitude of $V = -4.63^{+0.3}_{-0.4}$ mag and a colour of $V-I =
2.29^{+0.25}_{-0.39}$ mag, corresponding to a progenitor luminosity of log
$L$/L$_{\odot}$ $\sim4.54\pm0.19$ dex. Using the stellar evolution code STARS,
we find this to be consistent with a red supergiant progenitor with $M =
8.5_{-1.5}^{+6.5}$ M$_{\odot}$. The photometric and spectroscopic evolution of
SN 2009md is similar to that of the class of sub-luminous Type IIP SNe; in this
paper we compare the evolution of SN 2009md primarily to that of the
sub-luminous SN 2005cs. We estimate the mass of $^{56}$Ni ejected in the
explosion to be $(5.4\pm1.3) \times 10^{-3}$ M$_{\odot}$\ from the luminosity
on the radioactive tail, which is in agreement with the low $^{56}$Ni masses
estimated for other sub-luminous Type IIP SNe. From the lightcurve and spectra,
we show the SN explosion had a lower energy and ejecta mass than the normal
Type IIP SN 1999em. We discuss problems with stellar evolutionary models, and
the discrepancy between low observed progenitor luminosities (log
$L$/L$_{\odot}$ $\sim4.3-5$ dex) and model luminosities after the
second-dredge-up for stars in this mass range, and consider an enhanced carbon
burning rate as a possible solution. In conclusion, SN 2009md is a faint SN
arising from the collapse of a progenitor close to the lower mass limit for
core-collapse. This is now the third discovery of a low mass progenitor star
producing a low energy explosion and low $^{56}$Ni ejected mass, which
indicates that such events arise from the lowest end of the mass range that
produces a core-collapse supernova (7-8 M$_{\odot}$).
11/2010;
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S. Taubenberger,
S. Benetti,
M. Childress,
R. Pakmor,
S. Hachinger,
P. A. Mazzali,
V. Stanishev,
N. Elias-Rosa,
I. Agnoletto,
F. Bufano, [......],
H. Navasardyan,
J. Nicolas,
A. Pastorello,
E. Prosperi,
F. Salgado,
J. Sollerman,
M. Stritzinger,
M. Turatto,
S. Valenti,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: SN 2009dc shares similarities with normal Type Ia supernovae, but is clearly
overluminous, with a (pseudo-bolometric) peak luminosity of log(L) = 43.47
[erg/s]. Its light curves decline slowly over half a year after maximum light,
and the early-time near-IR light curves show secondary maxima, although the
minima between the first and second peaks are not very pronounced. Bluer bands
exhibit an enhanced fading after ~200 d, which might be caused by dust
formation or an unexpectedly early IR catastrophe. The spectra of SN 2009dc are
dominated by intermediate-mass elements and unburned material at early times,
and by iron-group elements at late phases. Strong C II lines are present until
~2 weeks past maximum, which is unprecedented in thermonuclear SNe. The ejecta
velocities are significantly lower than in normal and even subluminous SNe Ia.
No signatures of CSM interaction are found in the spectra. Assuming that the
light curves are powered by radioactive decay, analytic modelling suggests that
SN 2009dc produced ~1.8 solar masses of 56Ni assuming the smallest possible
rise time of 22 d. Together with a derived total ejecta mass of ~2.8 solar
masses, this confirms that SN 2009dc is a member of the class of possible
super-Chandrasekhar-mass SNe Ia similar to SNe 2003fg, 2006gz and 2007if. A
study of the hosts of SN 2009dc and other superluminous SNe Ia reveals a
tendency of these SNe to explode in low-mass galaxies. A low metallicity of the
progenitor may therefore be an important pre-requisite for producing
superluminous SNe Ia. We discuss a number of explosion scenarios, ranging from
super-Chandrasekhar-mass white-dwarf progenitors over dynamical white-dwarf
mergers and Type I 1/2 SNe to a core-collapse origin of the explosion. None of
the models seem capable of explaining all properties of SN 2009dc, so that the
true nature of this SN and its peers remains nebulous.
11/2010;
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A. Pastorello,
S. J. Smartt,
M. T. Botticella,
K. Maguire,
M. Fraser,
K. Smith,
R. Kotak,
L. Magill,
S. Valenti,
D. R. Young, [......],
P. A. Price,
P. H. Rhoads,
W. A. Siegmund,
C. W. Stubbs,
W. E. Sweeney,
J. L. Tonry,
R. J. Wainscoat,
M. F. Waterson,
C. Waters,
and C. G. Wynn-Williams
[show abstract]
[hide abstract]
ABSTRACT: Recent searches by unbiased, wide-field surveys have uncovered a group of extremely luminous optical transients. The initial discoveries of SN 2005ap by the Texas Supernova Search and SCP-06F6 in a deep Hubble pencil beam survey were followed by the Palomar Transient Factory confirmation of host redshifts for other similar transients. The transients share the common properties of high optical luminosities (peak magnitudes ~–21 to –23), blue colors, and a lack of H or He spectral features. The physical mechanism that produces the luminosity is uncertain, with suggestions ranging from jet-driven explosion to pulsational pair instability. Here, we report the most detailed photometric and spectral coverage of an ultra-bright transient (SN 2010gx) detected in the Pan-STARRS 1 sky survey. In common with other transients in this family, early-time spectra show a blue continuum and prominent broad absorption lines of O II. However, about 25 days after discovery, the spectra developed type Ic supernova features, showing the characteristic broad Fe II and Si II absorption lines. Detailed, post-maximum follow-up may show that all SN 2005ap and SCP-06F6 type transients are linked to supernovae Ic. This poses problems in understanding the physics of the explosions: there is no indication from late-time photometry that the luminosity is powered by 56Ni, the broad light curves suggest very large ejected masses, and the slow spectral evolution is quite different from typical Ic timescales. The nature of the progenitor stars and the origin of the luminosity are intriguing and open questions.
The Astrophysical Journal Letters 10/2010; 724(1):L16. · 5.53 Impact Factor
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S. Gezari,
A. Rest,
M. E. Huber,
G. Narayan,
K. Forster,
J. D. Neill,
D. C. Martin,
S. Valenti,
S. J. Smartt,
R. Chornock, [......],
J. S. Morgan,
P. M. Onaka,
P. A. Price,
P. H. Rhoads,
W. A. Siegmund,
C. W. Stubbs,
J. L. Tonry,
R. J. Wainscoat,
M. F. Waterson,
and C. G. Wynn-Williams
[show abstract]
[hide abstract]
ABSTRACT: We present the early UV and optical light curve of Type IIP supernova (SN) 2010aq at z = 0.0862, and compare it to analytical models for thermal emission following SN shock breakout in a red supergiant star. SN 2010aq was discovered in joint monitoring between the Galaxy Evolution Explorer (GALEX) Time Domain Survey (TDS) in the NUV and the Pan-STARRS1 Medium Deep Survey (PS1 MDS) in the g, r, i, and z bands. The GALEX and Pan-STARRS1 observations detect the SN less than 1 day after the shock breakout, measure a diluted blackbody temperature of 31, 000 ± 6000 K 1 day later, and follow the rise in the UV/optical light curve over the next 2 days caused by the expansion and cooling of the SN ejecta. The high signal-to-noise ratio of the simultaneous UV and optical photometry allows us to fit for a progenitor star radius of 700 ± 200R ☉, the size of a red supergiant star. An excess in UV emission two weeks after shock breakout compared with SNe well fitted by model atmosphere-code synthetic spectra with solar metallicity is best explained by suppressed line blanketing due to a lower metallicity progenitor star in SN 2010aq. Continued monitoring of PS1 MDS fields by the GALEX TDS will increase the sample of early UV detections of Type II SNe by an order of magnitude and probe the diversity of SN progenitor star properties.
The Astrophysical Journal Letters 08/2010; 720(1):L77. · 5.53 Impact Factor
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M. T. Botticella,
C. Trundle,
A. Pastorello,
S. Rodney,
A. Rest,
S. Gezari,
S. J. Smartt,
G. Narayan,
M. E. Huber,
J. L. Tonry, [......],
J. S. Morgan,
P. M. Onaka,
P. A. Price,
P. H. Rhoads,
W. A. Siegmund,
W. E. Sweeney,
R. J. Wainscoat,
C. Waters,
M. F. Waterson,
and C. G. Wynn-Williams
[show abstract]
[hide abstract]
ABSTRACT: We present photometric and spectroscopic observations of a luminous Type IIP Supernova (SN) 2009kf discovered by the Pan-STARRS 1 (PS1) survey and also detected by the Galaxy Evolution Explorer. The SN shows a plateau in its optical and bolometric light curves, lasting approximately 70 days in the rest frame, with an absolute magnitude of M V = –18.4 mag. The P-Cygni profiles of hydrogen indicate expansion velocities of 9000 km s-1 at 61 days after discovery which is extremely high for a Type IIP SN. SN 2009kf is also remarkably bright in the near-ultraviolet (NUV) and shows a slow evolution 10-20 days after optical discovery. The NUV and optical luminosity at these epochs can be modeled with a blackbody with a hot effective temperature (T ~ 16,000 K) and a large radius (R ~ 1 × 1015 cm). The bright bolometric and NUV luminosity, the light curve peak and plateau duration, the high velocities, and temperatures suggest that 2009kf is a Type IIP SN powered by a larger than normal explosion energy. Recently discovered high-z SNe (0.7 < z < 2.3) have been assumed to be IIn SNe, with the bright UV luminosities due to the interaction of SN ejecta with a dense circumstellar medium. UV-bright SNe similar to SN 2009kf could also account for these high-z events, and its absolute magnitude M NUV = –21.5 ± 0.5 mag suggests such SNe could be discovered out to z ~ 2.5 in the PS1 survey.
The Astrophysical Journal Letters 06/2010; 717(1):L52. · 5.53 Impact Factor
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A. Pastorello,
M. T. Botticella,
C. Trundle,
S. Taubenberger,
S. Mattila, E. Kankare,
N. Elias-Rosa,
S. Benetti,
G. Duszanowicz,
L. Hermansson,
J. E. Beckman,
F. Bufano,
M. Fraser,
A. Harutyunyan,
H. Navasardyan,
S. J. Smartt,
S. D. Van Dyk,
J. S. Vink,
R. M. Wagner
[show abstract]
[hide abstract]
ABSTRACT: We present new photometric and spectroscopic observations of an unusual luminous blue variable (LBV) in NGC 3432, covering three major outbursts in October 2008, April 2009 and November 2009. Previously, this star experienced an outburst also in 2000 (known as SN 2000ch). During outbursts the star reached an absolute magnitude between -12.1 and -12.8. Its spectrum showed H, He I and Fe II lines with P-Cygni profiles during and soon after the eruptive phases, while only intermediate-width lines in pure emission (including He II 4686A were visible during quiescence. The fast-evolving light curve soon after the outbursts, the quasi-modulated light curve, the peak magnitude and the overall spectral properties are consistent with multiple episodes of variability of an extremely active LBV. However, the widths of the spectral lines indicate unusually high wind velocities (1500-2800 km/s), similar to those observed in Wolf-Rayet stars. Although modulated light curves are typical of LBVs during the S-Dor variability phase, the luminous maxima and the high frequency of outbursts are unexpected in S-Dor variables. Such extreme variability may be associated with repeated ejection episodes during a giant eruption of an LBV. Alternatively, it may be indicative of a high level of instability shortly preceding the core-collapse or due to interaction with a massive, binary companion. In this context, the variable in NGC 3432 shares some similarities with the famous stellar system HD 5980 in the Small Magellanic Cloud, which includes an erupting LBV and an early Wolf-Rayet star. Comment: 22 pages, 13 Figures; accepted for publication in MNRAS
06/2010;
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M. T. Botticella,
C. Trundle,
A. Pastorello,
S. Rodney,
A. Rest,
S. Gezari,
S. J. Smartt,
G. Narayan,
M. E. Huber,
J. L. Tonry, [......],
J. S. Morgan,
P. M. Onaka,
P. A. Price,
P. H. Rhoads,
W. A. Siegmund,
W. E. Sweeney,
R. J. Wainscoat,
C. Waters,
M. F. Waterson,
C. G. Wynn-Williams
[show abstract]
[hide abstract]
ABSTRACT: We present photometric and spectroscopic observations of a luminous type IIP Supernova 2009kf discovered by the Pan-STARRS 1 (PS1) survey and detected also by GALEX. The SN shows a plateau in its optical and bolometric light curves, lasting approximately 70 days in the rest frame, with absolute magnitude of M_V = -18.4 mag. The P-Cygni profiles of hydrogen indicate expansion velocities of 9000km/s at 61 days after discovery which is extremely high for a type IIP SN. SN 2009kf is also remarkably bright in the near-ultraviolet (NUV) and shows a slow evolution 10-20 days after optical discovery. The NUV and optical luminosity at these epochs can be modelled with a black-body with a hot effective temperature (T ~16,000 K) and a large radius (R ~1x10^{15} cm). The bright bolometric and NUV luminosity, the lightcurve peak and plateau duration, the high velocities and temperatures suggest that 2009kf is a type IIP SN powered by a larger than normal explosion energy. Recently discovered high-z SNe (0.7 < z < 2.3) have been assumed to be IIn SNe, with the bright UV luminosities due to the interaction of SN ejecta with a dense circumstellar medium (CSM). UV bright SNe similar to SN 2009kf could also account for these high-z events, and its absolute magnitude M_NUV = -21.5 +/- 0.5 mag suggests such SNe could be discovered out to z ~2.5 in the PS1 survey. Comment: Accepted for publication in APJL
01/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present the results of an eight-year long monitoring of the radio emission from the Luminous Infrared Galaxy (LIRG) NGC 7469, using 8.4 GHz Very Large Array (VLA) observations at 0.3'' resolution. Our monitoring shows that the late time evolution of the radio supernova SN 2000ft follows a decline very similar to that displayed at earlier times of its optically thin phase. The late time radio emission of SN 2000ft is therefore still being powered by its interaction with the presupernova stellar wind, and not with the interstellar medium (ISM). Indeed, the ram pressure of the presupernova wind is \rho_w v_w^2 \approx 7.6E-9 dyn/cm^2, at a supernova age of approximately 2127 days, which is significantly larger than the expected pressure of the ISM around SN 2000ft. At this age, the SN shock has reached a distance r_{sh \approx 0.06 pc, and our observations are probing the interaction of the SN with dense material that was ejected by the presupernova star about 5820 years prior to its explosion. From our VLA monitoring, we estimate that the swept-up mass by the supernova shock after about six years of expansion is \approx 0.29 M_sun, assuming an average expansion speed of the supernova of 10000 km/s. We also searched for recently exploded core-collapse supernovae in our VLA images. Apart from SN 2000ft (S_\nu \approx 1760 microJy at its peak, corresponding to 1.1E28 erg/s/Hz, we found no evidence for any other radio supernova (RSN) more luminous than \approx 6.0E26 erg/s/Hz, which suggests that no other Type IIn SN has exploded since 2000 in the circumnuclear starburst of NGC 7469. Comment: 10 pages, 5 figures, accepted for publication in MNRAS
07/2009;
