-
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;
-
S. Taubenberger, H. Navasardyan,
J. I. Maurer,
L. Zampieri,
N. N. Chugai,
S. Benetti,
I. Agnoletto,
F. Bufano,
N. Elias-Rosa,
M. Turatto,
F. Patat,
E. Cappellaro,
P. A. Mazzali,
T Iijima,
S. Valenti,
A. Harutyunyan,
R. Claudi,
M. Dolci
[show abstract]
[hide abstract]
ABSTRACT: Extensive optical and near-infrared (NIR) observations of the type IIb
supernova 2008ax are presented, covering the first year after the explosion.
The light curve is mostly similar in shape to that of the prototypical type IIb
SN 1993J, but shows a slightly faster decline rate at late phases and lacks the
prominent narrow early-time peak of SN 1993J. From the bolometric light curve
and ejecta expansion velocities, we estimate that about 0.07-0.15 solar masses
of 56Ni were produced during the explosion and that the total ejecta mass was
between 2 and 5 solar masses, with a kinetic energy of at least 10^51 erg. The
spectral evolution of SN 2008ax is similar to that of the type Ib SN 2007Y,
exhibiting high-velocity Ca II features at early phases and signs of
ejecta-wind interaction from H-alpha observations at late times. NIR spectra
show strong He I lines similar to the type Ib SN 1999ex, and a large number of
emission features at late times. Particularly interesting are the strong,
double-peaked He I lines in late NIR spectra, which - together with
double-peaked [O I] emission in late optical spectra - provide clues for
asymmetry and large-scale Ni mixing in the ejecta.
01/2011;
-
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;
-
A. Pastorello,
S. Valenti,
L. Zampieri, H. Navasardyan,
S. Taubenberger,
S. ~J. Smartt,
A. ~A. Arkharov,
O. Barnbantner,
H. Barwig,
S. Benetti, [......],
V. Lorenzi,
J. ~R. Maund,
N. Napoleone,
M. Ragni,
M. Richmond,
C. Ries,
S. Spiro,
S. Temporin,
M. Turatto,
J. ~C. Wheeler
VizieR Online Data Catalog. 11/2010; 739:42266.
-
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;
-
K. Maguire,
E. Di Carlo,
S. J. Smartt,
A. Pastorello,
D. Yu. Tsvetkov,
S. Benetti,
S. Spiro,
A. A. Arkharov,
G. Beccari,
M. T. Botticella, [......],
Gorshanov D,
A. Harutyunyan,
V. M. Larionov, H. Navasardyan,
A. Pietrinferni,
G. Raimondo,
G. Di Rico,
S. Valenti,
G. Valentini,
L. Zampieri
[show abstract]
[hide abstract]
ABSTRACT: We present new optical and near infrared (NIR) photometry and spectroscopy of the type IIP supernova, SN 2004et. In combination with already published data, this provides one of the most complete studies of optical and NIR data for any type IIP SN from just after explosion to +500 days. The contribution of the NIR flux to the bolometric light curve is estimated to increase from 15% at explosion to around 50% at the end of the plateau and then declines to 40% at 300 days. SN 2004et is one of the most luminous IIP SNe which has been well studied, and with a luminosity of log L = 42.3 erg/s, it is 2 times brighter than SN 1999em. We provide parametrised bolometric corrections as a function of time for SN 2004et and three other IIP SNe that have extensive optical and NIR data, which can be used as templates for future events. We compare the physical parameters of SN 2004et with those of other IIP SNe and find kinetic energies spanning the range of 10^50-10^51 ergs. We compare the ejected masses calculated from hydrodynamic models with the progenitor masses and limits derived from prediscovery images. Some of the ejected mass estimates are significantly higher than the progenitor mass estimates, with SN 2004et showing perhaps the most serious mass discrepancy. With current models, it appears difficult to reconcile 100 day plateau lengths and high expansion velocities with the low ejected masses of 5-6 Msun implied from 7-8 Msun progenitors. The nebular phase is studied using very late time HST photometry, along with optical and NIR spectroscopy. The light curve shows a clear flattening at 600 days in the optical and the NIR, which is likely due to the ejecta impacting on the CSM. We further show that the [Oi] 6300,6364 Angstrom line strengths of four type IIP SNe imply ejected oxygen masses of 0.5-1.5 Msun. Comment: 25 pages, 27 figures, submitted to MNRAS
12/2009;
-
D. R. Young,
S. J. Smartt,
S. Valenti,
A. Pastorello,
S. Benetti,
C. R. Benn,
D. Bersier,
M. T. Botticella,
R. L. M. Corradi,
A. H. Harutyunyan,
M. Hrudkova,
I. Hunter,
S. Mattila,
E. J. W. de Mooij, H. Navasardyan,
I. A. G. Snellen,
N. R. Tanvir,
L. Zampieri
[show abstract]
[hide abstract]
ABSTRACT: We present BVRI photometry and optical spectroscopy of two Type Ic supernovae SN 2007bg and SN 2007bi discovered in wide-field, non-targeted surveys and associated with sub-luminous blue dwarf galaxies. Neither SNe 2007bg nor 2007bi were found in association with an observed GRB, but are found to inhabit similar low-metallicity environments as GRB associated supernovae. The radio-bright SN 2007bg is hosted by an extremely sub-luminous galaxy of magnitude MB = -12.4+/-0.6 mag with an estimated oxygen abundance of 12+log(O/H) = 8.18+/-0.17. The lightcurve of SN 2007bg displays one of the fastest post-maximum decline rates of all broad-lined Type Ic supernovae known to date and, when combined with its high expansion velocities, a high kinetic energy to ejected mass ratio (E_K/Mej ~ 2.7). We show that SN 2007bi is possibly the most luminous Type Ic known, reaching a peak magnitude of MR ~ 21.3 mag and displays a remarkably slow decline, following the radioactive decay rate of 56Co to 56Fe throughout the course of its observed lifetime. From a simple model of the bolometric light curve of SN 2007bi we estimate a total ejected 56Ni mass of M_Ni = 3.5 - 4.5 solar masses, the largest 56Ni mass measured in the ejecta of a supernova to date. There are two models that could explain the high luminosity and large ejected 56Ni mass. One is a pair-instability supernova (PISN) which has been predicted to occur for massive stars at low metallicities. We measure the host galaxy metallicity of SN 2007bi to be 12 + log(O/H) = 8.15+/-0.15 which is somewhat high to be consistent with the PISN model. An alternative is the core-collapse of a C+O star of 20 - 40 solar masses which is the core of a star of originally 50 - 100 solar masses. (Abridged) Comment: Minor changes. 19 pages, 21 Figures. Accepted by A&A
10/2009;
-
F. Di Mille,
S. Ciroi, H. Navasardyan,
S. Lepine,
L. Zee von,
K. ~L. Barnes,
D. ~H. Hartmann,
S. ~D. Brittain,
A. ~C. Updike,
A. Kaur,
G. ~G. Williams,
W. Pietsch,
A. Siviero,
T. Saguner,
M. Orio,
P. Rafanelli,
A. Bianchini
The Astronomer's Telegram. 10/2009; 2248:1.
-
The Astronomer's Telegram. 08/2009; 2171:1.
-
A. Pastorello,
S. Valenti,
L. Zampieri, H. Navasardyan,
S. Taubenberger,
S. J. Smartt,
A. A. Arkharov,
O. Bärnbantner,
H. Barwig,
S. Benetti, [......],
V. Lorenzi,
J. R. Maund,
N. Napoleone,
M. Ragni,
M. Richmond,
C. Ries,
S. Spiro,
S. Temporin,
M. Turatto,
J. C. Wheeler
[show abstract]
[hide abstract]
ABSTRACT: We present the results of the one-year long observational campaign of the type II plateau SN 2005cs, which exploded in the nearby spiral galaxy M51 (the Whirlpool galaxy). This extensive data set makes SN 2005cs the best observed low-luminosity, 56Ni-poor type II plateau event so far and one of the best core-collapse supernovae ever. The optical and near-infrared spectra show narrow P-Cygni lines characteristic of this SN family, which are indicative of a very low expansion velocity (about 1000 km s−1) of the ejected material. The optical light curves cover both the plateau phase and the late-time radioactive tail, until about 380 d after core-collapse. Numerous unfiltered observations obtained by amateur astronomers give us the rare opportunity to monitor the fast rise to maximum light, lasting about 2 d. In addition to optical observations, we also present near-infrared light curves that (together with already published ultraviolet observations) allow us to construct for the first time a reliable bolometric light curve for an object of this class. Finally, comparing the observed data with those derived from a semi-analytic model, we infer for SN 2005cs a 56Ni mass of about 3 × 10−3 M⊙, a total ejected mass of 8–13 M⊙ and an explosion energy of about 3 × 1050 erg.
Monthly Notices of the Royal Astronomical Society 04/2009; 394(4):2266 - 2282. · 4.90 Impact Factor
-
M. T. Botticella,
A. Pastorello,
S. J. Smartt,
W. P. S. Meikle,
S. Benetti,
R. Kotak,
E. Cappellaro,
R. M. Crockett,
S. Mattila,
M. Sereno, [......],
K. Maguire,
J. Mendez,
M. Mobberley, H. Navasardyan,
C. Ries,
V. Stanishev,
S. Taubenberger,
C. Trundle,
M. Turatto,
I. M. Volkov
[show abstract]
[hide abstract]
ABSTRACT: We present comprehensive photometric and spectroscopic observations of the faint transient SN 2008S discovered in NGC 6946. SN 2008S exhibited slow photometric evolution and almost no spectral variability during the first nine months, implying a high density CS medium. The light curve is similar in shape to that of SN 1998S and SN 1979C, although significantly fainter at maximum light. Our quasi-bolometric lightcurve extends to 300 days and shows a tail phase decay rate consistent with that of ^{56}Co. We propose that this is evidence for an explosion and formation of ^{56}Ni (0.0015 +/- 0.0004 M_Sun). The large MIR flux detected shortly after explosion can be explained by a light echo from pre-exisiting dust. The late NIR flux excess is plausibly due to a combination of warm newly-formed ejecta dust together with shock-heated dust in the CS environment. We reassess the progenitor object detected previously in Spitzer archive images, supplementing this discussion with a model of the MIR spectral energy distribution. This supports the idea of a dusty, optically thick shell around SN 2008S with an inner radius of nearly 90AU and outer radius of 450AU, and an inferred heating source of 3000 K and luminosity of L ~ 10^{4.6} L_Sun. The combination of our monitoring data and the evidence from the progenitor analysis leads us to support the scenario of a weak electron capture supernova explosion in a super-AGB progenitor star (of initial mass 6-8 M_sun) embedded within a thick CS gaseous envelope. We suggest that all of main properties of the electron capture SN phenomenon are observed in SN 2008S and future observations may allow a definitive answer. Comment: accepted for publication in MNRAS (2009 May 7)
03/2009;
-
I. Agnoletto,
S. Benetti,
E. Cappellaro,
L. Zampieri,
M. Turatto,
P. Mazzali,
A. Pastorello,
M. Della Valle,
F. Bufano,
A. Harutyunyan, H. Navasardyan,
N. Elias-Rosa,
S. Taubenberger,
S. Spiro,
and S. Valenti
[show abstract]
[hide abstract]
ABSTRACT: We present the photometric and spectroscopic study of the very luminous type IIn SN 2006gy for a time period spanning more than one year. The evolution of multiband light curves, the pseudobolometric (BVRI) light curve, and an extended spectral sequence is used to derive constraints on the origin and evolution of the supernova (SN). A broad, bright (MR ~ –21.7) peak characterizes all monochromatic light curves. Afterward, rapid luminosity fading (γ R ~ 3.2 mag(100 days)-1) is followed by a phase of slow luminosity decline (γ R ~ 0.4 mag(100 days)-1) between days ~ 170 and ~ 237. At late phases (>237 days), because of the large luminosity drop (>3 mag), only upper visibility limits are obtained in the B, R, and I bands. In the near-infrared, two K-band detections on days 411 and 510 open new issues about dust formation or infrared echo scenarios. At all epochs, the spectra are characterized by the absence of broad P-Cygni profiles and a multicomponent Hα profile, which are the typical signatures of type IIn SNe. Hα velocities of FWHM 3200 km s-1 and FHWM 9000 km s-1 are measured around the maximum phase for the intermediate and high velocity components, respectively, and they slowly evolve with time. After maximum, spectroscopic and photometric similarities are found between SN 2006gy and bright, interaction-dominated SNe (e.g., SN 1997cy, SN 1999E, and SN 2002ic). This suggests that ejecta-circumsteller material (CSM) interaction plays a key role in SN 2006gy about six to eight months after maximum, sustaining the late-time light curve. Alternatively, the late luminosity may be related to the radioactive decay of ~ 3 M ☉ of 56Ni. Models of the light curve in the first 170 days suggest that the progenitor was a compact star (R ~ (6-8) × 1012 cm, M ej ~ 5-14 M ☉) and that the SN ejecta collided with massive (6-10 M ☉), opaque clumps of previously ejected material. These clumps do not completely obscure the SN photosphere, such that at its peak, the luminosity is due both to the decay of 56Ni and to interaction with CSM. Neither an extraordinarily large explosion energy nor a supermassive star is required to explain the observational data.
The Astrophysical Journal 02/2009; 691(2):1348. · 6.02 Impact Factor
-
S. Valenti,
N. Elias-Rosa,
S. Taubenberger,
V. Stanishev,
I. Agnoletto,
D. Sauer,
E. Cappellaro,
A. Pastorello,
S. Benetti,
A. Riffeser, [......],
V. Lorenzi,
F. Patat,
M. Turatto,
R. Barbon,
S. Ciroi,
F. Di Mille,
S. Frandsen,
J. P. U. Fynbo,
P. Laursen,
and P. A. Mazzali
[show abstract]
[hide abstract]
ABSTRACT: The first 2 months of spectroscopic and photometric monitoring of the nearby Type Ic SN 2007gr are presented. The very early discovery (less than 5 days after the explosion) and the relatively short distance of the host galaxy motivated an extensive observational campaign. SN 2007gr shows an average peak luminosity but unusually narrow spectral lines and an almost flat photospheric velocity profile. The detection of prominent carbon features in the spectra is shown and suggests a wide range in carbon abundance in stripped-envelope supernovae. SN 2007gr may be an important piece in the puzzle of the observed diversity of CC SNe.
The Astrophysical Journal 12/2008; 673(2):L155. · 6.02 Impact Factor
-
U. Munari,
A. Siviero,
A. Henden,
G. Cardarelli,
G. Cherini,
S. Dallaporta,
G. Dalla Via,
A. Frigo,
R. Jurdana-Sepic,
S. Moretti,
P. Ochner,
S. Tomaselli,
S. Tomasoni,
P. Valisa, H. Navasardyan,
M. Valentini
[show abstract]
[hide abstract]
ABSTRACT: AIMS: Nova Cyg 2006 has been intensively observed throughout its full outburst. We investigate the energetics and evolution of the central source and of the expanding ejecta, their chemical abundances and ionization structure, and the formation of dust. METHOD: We recorded low, medium, and/or high-resolution spectra (calibrated into accurate absolute fluxes) on 39 nights, along with 2353 photometric UBVRcIc measures on 313 nights, and complemented them with IR data from the literature. RESULTS: The nova displayed initially the normal photometric and spectroscopic evolution of a fast nova of the FeII-type. Pre-maximum, principal, diffuse-enhanced, and Orion absorption systems developed in a normal way. After the initial outburst, the nova progressively slowed its fading pace until the decline reversed and a second maximum was reached (eight months later), accompanied by large spectroscopic changes. Following the rapid decline from second maximum, the nova finally entered the nebular phase and formed optically thin dust. We computed the amount of formed dust and performed a photo-ionization analysis of the emission-line spectrum during the nebular phase, which showed a strong enrichment of the ejecta in nitrogen and oxygen, and none in neon, in agreement with theoretical predictions for the estimated 1.0 Msun white dwarf in Nova Cyg 2006. The similarities with the poorly investigated V1493 Nova Aql 1999a are discussed. Comment: in press in Astronomy and Astrophysics
10/2008;
-
I. Agnoletto,
S. Benetti,
E. Cappellaro,
L. Zampieri,
M. Turatto,
P. Mazzali,
A. Pastorello,
M. Della Valle,
F. Bufano,
A. Harutyunyan, H. Navasardyan,
N. Elias-Rosa,
S. Taubenberger,
S. Spiro,
S. Valenti
[show abstract]
[hide abstract]
ABSTRACT: We present an optical photometric and spectroscopic study of the very
luminous type IIn SN 2006gy for a time period spanning more than one year. In
photometry, a broad, bright (M_R~-21.7) peak characterizes all BVRI light
curves. Afterwards, a rapid luminosity fading is followed by a phase of slow
luminosity decline between day ~170 and ~237. At late phases (>237 days),
because of the large luminosity drop (>3 mag), only upper visibility limits are
obtained in the B, R and I bands. In the near-infrared, two K-band detections
on days 411 and 510 open new issues about dust formation or IR echoes
scenarios. At all epochs the spectra are characterized by the absence of broad
P-Cygni profiles and a multicomponent Halpha profile, which are the typical
signatures of type IIn SNe. After maximum, spectroscopic and photometric
similarities are found between SN 2006gy and bright, interaction-dominated SNe
(e.g. SN 1997cy, SN 1999E and SN 2002ic). This suggests that ejecta-CSM
interaction plays a key role in SN 2006gy about 6 to 8 months after maximum,
sustaining the late-time-light curve. Alternatively, the late luminosity may be
related to the radioactive decay of ~3M_sun of 56Ni. Models of the light curve
in the first 170 days suggest that the progenitor was a compact star (R~6-8
10^(12)cm, M_ej~5-14M_sun), and that the SN ejecta collided with massive
(6-10M_sun), opaque clumps of previously ejected material. These clumps do not
completely obscure the SN photosphere, so that at its peak the luminosity is
due both to the decay of 56Ni and to interaction with CSM. A supermassive star
is not required to explain the observational data, nor is an extra-ordinarily
large explosion energy.
10/2008;
-
S. Taubenberger,
S. Hachinger,
G. Pignata,
P. A. Mazzali,
C. Contreras,
S. Valenti,
A. Pastorello,
N. Elias-Rosa,
O. Bärnbantner,
H. Barwig, [......],
W. Krzeminski,
N. Morrell, H. Navasardyan,
S. E. Persson,
M. M. Phillips,
C. Ries,
M. Roth,
N. B. Suntzeff,
M. Turatto,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: Optical observations of the Type Ia supernova (SN Ia) 2005bl in NGC 4070, obtained from −6 to +66 d with respect to the B-band maximum, are presented. The photometric evolution is characterized by rapidly declining light curves [Δm15(B)true= 1.93] and red colours at peak and soon thereafter. With MB,max=−17.24 the SN is an underluminous SN Ia, similar to the peculiar SNe 1991bg and 1999by. This similarity also holds for the spectroscopic appearance, the only remarkable difference being the likely presence of carbon in pre-maximum spectra of SN 2005bl. A comparison study among underluminous SNe Ia is performed, based on a number of spectrophotometric parameters. Previously reported correlations of the light-curve decline rate with peak luminosity and (Si) are confirmed, and a large range of post-maximum Si iiλ6355 velocity gradients is encountered. 1D synthetic spectra for SN 2005bl are presented, which confirm the presence of carbon and suggest an overall low burning efficiency with a significant amount of leftover unburned material. Also, the Fe content in pre-maximum spectra is very low, which may point to a low metallicity of the precursor. Implications for possible progenitor scenarios of underluminous SNe Ia are briefly discussed.
Monthly Notices of the Royal Astronomical Society 03/2008; 385(1):75 - 96. · 4.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present photometric and spectroscopic data of the peculiar SN 2005la, an object which shows an optical light curve with some luminosity fluctuations and spectra with comparably strong narrow hydrogen and helium lines, probably of circumstellar nature. The increasing full-width-half-maximum velocity of these lines is indicative of an acceleration of the circumstellar material. SN 2005la exhibits hybrid properties, sharing some similarities with both type IIn supernovae and 2006jc-like (type Ibn) events. We propose that the progenitor of SN 2005la was a very young Wolf-Rayet (WN-type) star which experimented mass ejection episodes shortly before core collapse. Comment: 9 pages, including 6 figures and 4 tables. Minor corrections, 1 figure added. Accepted for publication in MNRAS
01/2008;
-
A. Pastorello,
S. Mattila,
L. Zampieri,
M. Della Valle,
S. J. Smartt,
S. Valenti,
I. Agnoletto,
S. Benetti,
C. R. Benn,
D. Branch, [......],
P. Milne, H. Navasardyan,
E. O. Ofek,
E. Pian,
O. Shemmer,
S. Spiro,
R. A. Stathakis,
S. Taubenberger,
M. Turatto,
H Yamaoka
[show abstract]
[hide abstract]
ABSTRACT: 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 MNRAS
01/2008;
-
The Astronomer's Telegram. 12/2007; 1325:1.
-
A Pastorello,
S J Smartt,
S Mattila,
J J Eldridge,
D Young,
K Itagaki,
H Yamaoka, H Navasardyan,
S Valenti,
F Patat, [......],
V Lorenzi,
P A Mazzali,
X Meng,
S Nakano,
T B Nielsen,
J V Smoker,
V Stanishev,
M Turatto,
D Xu,
L Zampieri
[show abstract]
[hide abstract]
ABSTRACT: The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars. The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf-Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60-100 solar masses, but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf-Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf-Rayet star exploding as SN 2006jc, could explain the observations.
Nature 07/2007; 447(7146):829-32. · 36.28 Impact Factor
