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ABSTRACT: We present optical and near-infrared (IR) photometry and near-IR spectroscopy
of SN 2004am, the only optically detected supernova (SN) in M 82. These
demonstrate that SN 2004am was a highly reddened type II-P SN similar to the
low luminosity type II-P events such as SNe 1997D and 2005cs. We show that SN
2004am was located coincident with the obscured super star cluster M 82-L, and
from the cluster age infer a progenitor mass of 12 +7/-3 Msun. In addition to
this, we present a high spatial resolution Gemini-N K-band adaptive optics
image of the site of SN 2008iz and a second transient of uncertain nature, both
detected so far only at radio wavelengths. Using image subtraction techniques
together with archival data from the Hubble Space Telescope, we are able to
recover a near-IR transient source co-incident with both objects. We find the
likely extinction towards SN 2008iz to be not more than Av ~ 10. The nature of
the second transient remains elusive and we regard an extremely bright
microquasar in M 82 as the most plausible scenario.
07/2012;
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ABSTRACT: Recently there has been mounting observational evidence in favour of Luminous Blue Variables (LBVs) being the ‘direct’ progenitors of some core‐collapse supernovae in stark contrast to theoretical predictions. Here we give an outline of these events and present, possibly, the most convincing evidence to date for LBV supernovae progenitors: the intriguing case of SN 2005 gj. We will connect this to our current understanding of massive star evolution and highlight the potential problems this causes.
AIP Conference Proceedings. 05/2009; 1111(1):311-314.
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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]
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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;
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ABSTRACT: This Letter presents wide-field optical and near-IR (UBVRIHαK') images of the galaxy M74 that were taken between 0.6 and 8.3 yr before the discovery of the Type Ic supernova 2002ap. We have located the position of the supernova on these images with an accuracy of 03. We find no sign of a progenitor object on any of the images. The deepest of these images is the B-band exposure, which has a sensitivity limit corresponding to an absolute magnitude of MB ≤ -6.3. From our observed limits, we rule out as the progenitor all evolved states of single stars with initial masses greater than 20 M☉ unless the W-R phase has been entered. Two popular theories for the origin of Type Ic supernovae are the core collapse of massive stars when they are in the W-R phase or the core collapse of a massive star in an interacting binary that has had its envelope stripped through mass transfer. Our prediscovery images would be sensitive only to the most luminous ~30% of W-R stars, hence leaving a substantial fraction of typical W-R stars as viable progenitors. The energetics measured from modeling the initial light curve and spectral evolution of SN 2002ap suggest an explosion of a 5 M☉ C+O core. While W-R stars generally have measured final masses greater than this, the uncertainties associated with the explosion model, stellar evolutionary calculations, and mass measurements suggest we cannot definitively rule out a W-R star progenitor. The alternative scenario is that the progenitor was a star of initial mass ~20-25 M☉ that was part of an interacting binary and stripped of its hydrogen and helium envelope via mass transfer. We discuss future observations of the supernova environment that will provide further constraints on the nature of the progenitor star.
The Astrophysical Journal 12/2008; 572(2):L147. · 6.02 Impact Factor
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S. Mattila, W. P. S. Meikle,
P. Lundqvist,
A. Pastorello,
R. Kotak,
J. Eldridge,
S. Smartt,
A. Adamson,
C. L. Gerardy,
L. Rizzi,
A. W. Stephens,
S. D. Van Dyk
[show abstract]
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ABSTRACT: We present near- (NIR) and mid-infrared (MIR) photometric data of the Type Ibn supernova (SN) 2006jc obtained with the United Kingdom Infrared Telescope (UKIRT), the Gemini North Telescope and the Spitzer Space Telescope between days 86 and 493 post-explosion. We find that the IR behaviour of SN 2006jc can be explained as a combination of IR echoes from two manifestations of circumstellar material. The bulk of the NIR emission arises from an IR echo from newly condensed dust in a cool dense shell (CDS) produced by the interaction of the ejecta outward shock with a dense shell of circumstellar material ejected by the progenitor in a luminous blue variable (LBV)-like outburst about two years prior to the SN explosion. The CDS dust mass reaches a modest 3.0 × 10−4 M⊙ by day 230. While dust condensation within a CDS formed behind the ejecta inward shock has been proposed before for one event (SN 1998S), SN 2006jc is the first one showing evidence for dust condensation in a CDS formed behind the ejecta outward shock in the circumstellar material. At later epochs, a substantial and growing contribution to the IR fluxes arises from an IR echo from pre-existing dust in the progenitor wind. The mass of the pre-existing circumstellar medium (CSM) dust is at least ∼8 × 10−3 M⊙. This paper therefore adds to the evidence that mass-loss from the progenitors of core-collapse SNe could be a major source of dust in the Universe. However, yet again, we see no direct evidence that the explosion of an SN produces anything other than a very modest amount of dust.
Monthly Notices of the Royal Astronomical Society 08/2008; 389(1):141 - 155. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: There has been mounting observational evidence in favour of Luminous Blue Variables (LBVs) being the direct progenitors of supernovae. Here we present possibly the most convincing evidence yet for such progenitors. We find multiple absorption component P-Cygni profiles of hydrogen and helium in the spectrum of SN 2005gj, which we interpret as being an imprint of the progenitors mass-loss history. Such profiles have previously only been detected in Luminous Blue Variables. This striking resemblance of the profiles, along with wind velocities and periods consistent with LBV's leads us to connect SN 2005gj to an LBV progenitor. Comment: Accepted as a letter to A&A, 4 pages,3 figures
04/2008;
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S. Mattila, W. P. S. Meikle,
P. Lundqvist,
A. Pastorello,
R. Kotak,
J. Eldridge,
S. Smartt,
A. Adamson,
C. L. Gerardy,
L. Rizzi,
A. W. Stephens,
S. D. Van Dyk
[show abstract]
[hide abstract]
ABSTRACT: We present near- and mid-infrared (IR) photometric data of the Type Ibn supernova (SN) 2006jc obtained with the United Kingdom Infrared Telescope (UKIRT), the Gemini North Telescope, and the Spitzer Space Telescope between days 86 and 493 post-explosion. We find that the IR behaviour of SN 2006jc can be explained as a combination of IR echoes from two manifestations of circumstellar material. The bulk of the near-IR emission arises from an IR echo from newly-condensed dust in a cool dense shell (CDS) produced by the interaction of the ejecta outward shock with a dense shell of circumstellar material ejected by the progenitor in a luminous blue variable (LBV) like outburst about two years prior to the SN explosion. The CDS dust mass reaches a modest 3.0 x 10^(-4) M(solar) by day 230. While dust condensation within a CDS formed behind the ejecta inward shock has been proposed before for one event (SN 1998S), SN 2006jc is the first one showing evidence for dust condensation in a CDS formed behind the ejecta outward shock in the circumstellar material. At later epochs, a substantial and growing contribution to the IR fluxes arises from an IR echo from pre-existing dust in the progenitor wind. The mass of the pre-existing CSM dust is at least ~8 x 10^(-3) M(solar). This work therefore adds to the evidence that mass-loss from the progenitors of core-collapse supernovae could be a major source of dust in the universe. However, yet again, we see no direct evidence that the explosion of a supernova produces anything other than a very modest amount of dust. Comment: 18 pages, 10 figures, accepted to MNRAS
03/2008;
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N. Elias-Rosa,
S. Benetti,
M. Turatto,
E. Cappellaro,
S. Valenti,
A. A. Arkharov,
J. E. Beckman,
A. Di Paola,
M. Dolci,
A. V. Filippenko,
R. J. Foley,
K. Krisciunas,
V. M. Larionov,
W Li, W. P. S. Meikle,
A. Pastorello,
G. Valentini,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: We present VRIJHK photometry, and optical and near-infrared spectroscopy, of the heavily extinguished Type Ia supernova (SN) 2002cv, located in NGC 3190, which is also the parent galaxy of the Type Ia SN 2002bo. SN 2002cv, not visible in the blue, has a total visual extinction of 8.74 +- 0.21 mag. In spite of this we were able to obtain the light curves between -10 and +207 days from the maximum in the I band, and also to follow the spectral evolution, deriving its key parameters. We found the peak I-band brightness to be Imax = 16.57 +- 0.10 mag, the maximum absolute I magnitude to be MmaxI = -18.79 +- 0.20, and the parameter dm15(B) specifying the width of the B-band light curve to be 1.46 +- 0.17 mag. The latter was derived using the relations between this parameter and dm40(I) and the time interval dtmax(I) between the two maxima in the I-band light curve. As has been found for previously observed, highly extinguished SNe Ia, a small value of 1.59 +- 0.07 was obtained here for the ratio Rv of the total-to-selective extinction ratio for SN 2002cv, which implies a small mean size for the grains along the line of sight toward us. Since it was found for SN 2002bo a canonical value of 3.1, here we present a clear evidence of different dust properties inside NGC 3190. Comment: 18 pages, 18 figures. Accepted for publication in MNRAS. Added co-authors
10/2007;
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W. P. S. Meikle,
S. Mattila,
A. Pastorello,
C. L. Gerardy,
R. Kotak,
J. Sollerman,
S. D. Van Dyk,
D. Farrah,
A. V. Filippenko,
P. Höflich,
P. Lundqvist,
M. Pozzo,
J. C. Wheeler
[show abstract]
[hide abstract]
ABSTRACT: We present a new, detailed analysis of late-time mid-infrared (IR) observations of the Type II-P supernova (SN) 2003gd. At about 16 months after the explosion, the mid-IR flux is consistent with emission from 4 x 10^(-5) M(solar) of newly condensed dust in the ejecta. At 22 months emission from point-like sources close to the SN position was detected at 8 microns and 24 microns. By 42 months the 24 micron flux had faded. Considerations of luminosity and source size rule out the ejecta of SN 2003gd as the main origin of the emission at 22 months. A possible alternative explanation for the emission at this later epoch is an IR echo from pre-existing circumstellar or interstellar dust. We conclude that, contrary to the claim of Sugerman et al. (2006, Science, 313, 196), the mid-IR emission from SN 2003gd does not support the presence of 0.02 M(solar) of newly formed dust in the ejecta. There is, as yet, no direct evidence that core-collapse supernovae are major dust factories. Comment: 26 pages, 2 figures, 2 tables, accepted for publication in Astrophysical Journal
05/2007;
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A. Pastorello,
P. A. Mazzali,
G. Pignata,
S. Benetti,
E. Cappellaro,
A. V. Filippenko,
W Li, W. P. S. Meikle,
A. A. Arkharov,
G. Blanc, [......],
J. Rich,
S. D. Ryder,
M. Salvo,
B. P. Schmidt,
V. Stanishev,
P. Szekely,
S. Taubenberger,
S. Temporin,
M. Turatto,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: We present optical and infrared observations of the unusual Type Ia supernova (SN) 2004eo. The light curves and spectra closely resemble those of the prototypical SN 1992A, and the luminosity at maximum (M_B = -19.08) is close to the average for a SN Ia. However, the ejected 56Ni mass derived by modelling the bolometric light curve (about 0.45 solar masses) lies near the lower limit of the 56Ni mass distribution observed in normal SNe Ia. Accordingly, SN 2004eo shows a relatively rapid post-maximum decline in the light curve (Delta m_(B) = 1.46), small expansion velocities in the ejecta, and a depth ratio Si II 5972 / Si II 6355 similar to that of SN 1992A. The physical properties of SN 2004eo cause it to fall very close to the boundary between the faint, low velocity gradient, and high velocity gradient subgroups proposed by Benetti et al. (2005). Similar behaviour is seen in a few other SNe Ia. Thus, there may in fact exist a few SNe Ia with intermediate physical properties.
03/2007;
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W. P. S. Meikle,
S. Mattila,
C. L. Gerardy,
R. Kotak,
M. Pozzo,
S. D. Van Dyk,
D. Farrah,
R. A. Fesen,
A. V. Filippenko,
C. Fransson,
P. Lundqvist,
J. Sollerman,
J. C. Wheeler
[show abstract]
[hide abstract]
ABSTRACT: We present late-time (590-994 d) mid-IR photometry of the normal, but highly-reddened Type IIP supernova SN 2002hh. Bright, cool, slowly-fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star-formation region or molecular cloud along the line-of-sight. We also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly-condensed dust and/or an ejecta/CSM impact but their contributions are likely to be small. For the case of a CSM-IR echo, we infer a dust mass of as little as 0.036 M(solar) with a corresponding CSM mass of 3.6(0.01/r(dg))M(solar) where r(dg) is the dust-to-gas mass ratio. Such a CSM would have resulted from episodic mass loss whose rate declined significantly about 28,000 years ago. Alternatively, an IR echo from a surrounding, dense, dusty molecular cloud might also have been responsible for the fading component. Either way, this is the first time that an IR echo has been clearly identified in a Type IIP supernova. We find no evidence for or against the proposal that Type IIP supernovae produce large amounts of dust via grain condensation in the ejecta. However, within the CSM-IR echo scenario, the mass of dust derived implies that the progenitors of the most common of core-collapse supernovae may make an important contribution to the universal dust content.
06/2006;
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ABSTRACT: We present optical and infrared (IR) observations of the Type II SN 2002hh from 3 to 397 d after explosion. The optical spectroscopic (4–397 d) and photometric (3–278 d) data are complemented by spectroscopic (137–381 d) and photometric (137–314 d) data acquired at IR wavelengths. This is the first time L-band spectra have ever been successfully obtained for a supernova (SN) at a distance beyond the Local Group. The VRI light curves in the first 40 d reveal SN 2002hh to be an SN IIP (plateau) – the most common of all core-collapse SNe. SN 2002hh is one of the most highly extinguished SNe ever investigated. To provide a match between its early-time spectrum and a coeval spectrum of the Type IIP SN 1999em, as well as maintaining consistency with K i interstellar absorption, we invoke a two-component extinction model. One component is due to the combined effect of the interstellar medium (ISM) of our Milky Way Galaxy and the SN host galaxy, while the other component is due to a ‘dust pocket’ where the grains have a mean size smaller than in the ISM. The early-time optical light curves of SNe 1999em and 2002hh are generally well matched, as are the radioactive tails of these two SNe and SN 1987A. The late-time similarity of the SN 2002hh optical light curves to those of SN 1987A, together with measurements of the optical/IR luminosity and [Fe ii] 1.257 μm emission indicate that 0.07 ± 0.02 M⊙ of 56Ni was ejected by SN 2002hh. However, during the nebular phase the HKL′ luminosities of SN 2002hh exhibit a growing excess with respect to those of SN 1987A. We attribute much of this excess to an IR-echo from a pre-existing, dusty circumstellar medium. Based on an IR-echo interpretation of the near-IR (NIR) excess, we deduce that the progenitor of SN 2002hh underwent recent mass-loss of ∼0.3 M⊙. A detailed comparison of the late-time optical and NIR spectra of SNe 1987A and 2002hh is presented. While the overall impression is one of similarity between the spectra of the two events, there are notable differences. The Mg i 1.503 μm luminosity of SN 2002hh is a factor of 2.5 greater than in SN 1987A at similar epochs, yet coeval silicon and calcium lines in SN 2002hh are fainter. Interpreting these differences as being due to abundance variations, the overall abundance trend between SN 1987A and 2002hh is not consistent with explosion model predictions. It appears that during the burning to intermediate-mass elements, the nucleosynthesis did not progress as far as might have been expected given the mass of iron ejected. Evidence for mixing in the ejecta is presented. Pronounced blueshifts seen in the more isolated lines are attributed to asymmetry in the ejecta. However, during the time-span of these observations (∼1-yr post-explosion) we find no evidence of dust condensation in the ejecta such as might have been revealed by an increasing blueshift and/or attenuation of the red wings of the emission lines. Nevertheless, the clear detection of first overtone CO emission by 200 d and the reddening trend in (K−L′)0 suggest that dust formation in the ejecta may occur at later epochs. From the [O i]λλ6300, 6364 Å doublet luminosity we infer a 16–18 M⊙ main-sequence progenitor star. The progenitor of SN 2002hh was probably a red supergiant with a substantial, dusty wind.
Monthly Notices of the Royal Astronomical Society 05/2006; 368(3):1169 - 1195. · 4.90 Impact Factor
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N. Elias-Rosa,
S. Benetti,
E. Cappellaro,
M. Turatto,
P. A. Mazzali,
F. Patat, W. P. S. Meikle,
M. Stehle,
A. Pastorello,
G. Pignata,
R. Kotak,
A. Harutyunyan,
G. Altavilla,
H. Navasardyan,
Y Qiu,
M. E. Salvo,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: We present optical and near-infrared photometry and spectroscopy of the Type Ia SN 2003cg, which exploded in the nearby galaxy NGC 3169. The observations cover a period between -8.5 and +414 days post-maximum. SN 2003cg is a normal but highly-reddened Type Ia event. Its B magnitude at maximum B_max = 15.94+/-0.04 and Delta m_15(B)_obs = 1.12+/-0.04 (Delta m_15(B)_intrinsic = 1.25+/-0.05). Allowing R_v to become a free parameter within the Cardelli et al. (1989) extinction law, simultaneous matches to a range of colour curves of normal SNe Ia yielded E(B-V) = 1.33+/-0.11, and R_v = 1.80+/-0.19. While the value obtained for R_v is small, such values have been invoked in the past, and may imply a grain size which is small compared with the average value for the local ISM. Comment: 28 pages, 21 figures. Accepted for publication in MNRAS. Minor changes following the referee suggestions
03/2006;
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[show abstract]
[hide abstract]
ABSTRACT: We present optical and infrared (IR) observations of the type IIP SN2002hh from 3 to 397 days after explosion. The optical spectroscopic (4-397d) and photometric (3-278d) data are complemented by spectroscopic (137-381d) and photometric (137-314d) data acquired at IR wavelengths. This is the first time L-band spectra have ever been successfully obtained for a supernova at a distance beyond the Local Group. The VRI light curves in the first 40 days reveal SN2002hh to be a SN IIP (plateau) - the most common of all core-collapse supernovae. SN2002hh is one of the most highly extinguished supernovae ever investigated. To provide a good match between its early-time spectrum and a coeval spectrum of the Type IIP SN1999em, as well as maintaining consistency with KI interstellar absorption, we invoke a 2-component extinction model. One component is due to the combined effect of the interstellar medium of our Milky Way Galaxy and the SN host galaxy, while the other component is due to a "dust pocket" where the grains have a mean size smaller than in the interstellar medium. The early-time optical light curves of SNe 1999em and 2002hh are generally well-matched, as are the radioactive tails of these two SNe and SN1987A. The late-time similarity of the SN2002hh optical light curves to those of SN1987A, together with measurements of the optical/IR luminosity and [FeII] 1.257mu emission indicate that 0.07 +- 0.02 Msun of Ni 56 was ejected by SN2002hh. [... ABRIDGED...] From the [OI] 6300,6364 A doublet luminosity we infer a 16-18 Msun main-sequence progenitor star. The progenitor of SN2002hh was probably a red supergiant with a substantial, dusty wind. Comment: 32 pages, 30 figures, accepted for publication in MNRAS
02/2006;
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[show abstract]
[hide abstract]
ABSTRACT: Using a combination of high resolution optical spectroscopy and
near-infrared photometry, we show that the circumstellar medium (CSM) of
SN 2002ic consists of a slow-moving, dense, dusty outflow.
11/2005; 342:264.
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M. A. Hendry,
S. J. Smartt,
J. R. Maund,
A. Pastorello,
L. Zampieri,
S. Benetti,
M. Turatto,
E. Cappellaro, W. P. S. Meikle,
R. Kotak, [......],
P. G. Jonker,
L. Vermaas,
R. F. Peletier,
H. van Woerden,
K. M. Exter,
D. L. Pollacco,
S. Leon,
S. Verley,
C. R. Benn,
G. Pignata
[show abstract]
[hide abstract]
ABSTRACT: We present photometric and spectroscopic data of the type II-P supernova 2003gd, which was discovered in M74 close to the end of its plateau phase. SN 2003gd is the first type II supernova to have a directly confirmed red supergiant progenitor. We compare SN 2003gd with SN 1999em, a similar type II-P supernova, and estimate an explosion date of 18th March 2003. We determine a reddening towards the supernova of E(B-V) = 0.14+/-0.06, using three different methods. We also calculate three new distances to M74 of 9.6+/-2.8 Mpc, 7.7+/-1.7 Mpc and 9.6+/-2.2 Mpc. The former was estimated using the Standardised Candle Method (SCM), for type II supernovae, and the latter two using the Brightest Supergiants Method (BSM). When combined with existing kinematic and BSM distance estimates, we derive a mean value of 9.3+/-1.8 Mpc. SN 2003gd was found to have a lower tail luminosity compared to other ``normal'' type II-P SNe bringing into question the nature of this supernova. We present a discussion concluding that this is a ``normal'' type II-P supernova which is consistent with the observed progenitor mass of 8(+4/-2) Mo. Comment: 23 pages, 24 figures to appear in MNRAS
01/2005;
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[show abstract]
[hide abstract]
ABSTRACT: We present results from the first high-resolution, high signal-to-noise ratio spectrum of SN 2002ic. The resolved Hα line has a P Cygni-type profile, clearly demonstrating the presence of a dense, slow-moving (∼100 km s−1) outflow. We have additionally found a huge near-infrared excess, hitherto unseen in Type Ia supernovae. We argue that this is due to an infrared light-echo arising from the pre-existing dusty circumstellar medium. We deduce a circumstellar medium mass probably exceeding 0.3 M⊙ produced by a mass-loss rate greater than several times 10−4 M⊙ yr−1. For the progenitor, we favour a single-degenerate system where the companion is a post-asymptotic giant branch star. As a by-product of our optical data, we are able to provide a firm identification of the host galaxy of SN 2002ic.
Monthly Notices of the Royal Astronomical Society 09/2004; 354(2):L13 - L17. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present late-time near-infrared (NIR) and optical observations of the type IIn SN 1998S. The NIR photometry spans 333-1242 days after explosion, while the NIR and optical spectra cover 333-1191 days and 305-1093 days respectively. The NIR photometry extends to the M'-band (4.7 mu), making SN 1998S only the second ever supernova for which such a long IR wavelength has been detected. The shape and evolution of the H alpha and HeI 1.083 mu line profiles indicate a powerful interaction with a progenitor wind, as well as providing evidence of dust condensation within the ejecta. The latest optical spectrum suggests that the wind had been flowing for at least 430 years. The intensity and rise of the HK continuum towards longer wavelengths together with the relatively bright L' and M' magnitudes shows that the NIR emission was due to hot dust newly-formed in supernovae may provide the ejecta and/or pre-existing dust in the progenitor circumstellar medium (CSM). [ABRIDGED] Possible origins for the NIR emission are considered. Significant radioactive heating of ejecta dust is ruled out, as is shock/X-ray-precursor heating of CSM dust. More plausible sources are (a) an IR-echo from CSM dust driven by the UV/optical peak luminosity, and (b) emission from newly-condensed dust which formed within a cool, dense shell produced by the ejecta shock/CSM interaction. We argue that the evidence favours the condensing dust hypothesis, although an IR-echo is not ruled out. Within the condensing-dust scenario, the IR luminosity indicates the presence of at least 0.001 solar masses of dust in the ejecta, and probably considerably more. Finally, we show that the late-time intrinsic (K-L') evolution of type II supernovae may provide a useful tool for determining the presence or absence of a massive CSM around their progenitor stars. Comment: 23 pages, 15 figures, to be published in MNRAS
04/2004;
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[show abstract]
[hide abstract]
ABSTRACT: A handful of nearby supernovae (SNe) with visual extinctions of a few magnitudes have recently been discovered. However, an undiscovered population of much more highly extinguished (A(V) > 10) core-collapse supernovae (CCSNe) is likely to exist in the nuclear (central kpc) regions of starburst galaxies. The high dust extinction means that optical searches for such SNe are unlikely to be successful. Here, we present preliminary results from our ongoing near-infrared Ks-band search programme for nuclear SNe in nearby starburst galaxies. We also discuss searches for SNe in Luminous and Ultraluminous Infrared Galaxies. Comment: 8 pages, in "Supernovae and dust" (Paris, May 2003), eds. F. Combes, A.-L. Melchior. To be published by New Astronomy
10/2003;
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A. Pastorello,
L. Zampieri,
M. Turatto,
E. Cappellaro, W. P. S. Meikle,
S. Benetti,
D. Branch,
E. Baron,
F. Patat,
M. Armstrong,
G. Altavilla,
M. Salvo,
M. Riello
[show abstract]
[hide abstract]
ABSTRACT: In this paper we present spectroscopic and photometric observations for four core collapse supernovae (SNe), namely SNe 1994N, 1999br, 1999eu and 2001dc. Together with SN 1997D, we show that they form a group of exceptionally low-luminosity events. These SNe have narrow spectral lines (indicating low expansion velocities) and low luminosities at every phase (significantly lower than those of typical core-collapse supernovae). The very low luminosity during the ^{56}Co radioactive decay tail indicates that the mass of ^{56}Ni ejected during the explosion is much smaller (M(Ni) ~ 2-8 x 10^{-3} Mo) than the average (M(Ni) ~ 6-10 x 10^{-2} Mo). Two supernovae of this group (SN 1999br and SN 2001dc) were discovered very close to the explosion epoch, allowing us to determine the lengths of their plateaux (~ 100 days) as well as establishiing the explosion epochs of the other, less-completely observed SNe. It is likely that this group of SNe represent the extreme low-luminosity tail of a single continuous distribution of SN II-P events. Their kinetic energy is also exceptionally low. Although an origin from low mass progenitors has also been proposed for low-luminosity core-collapse SNe, recent work provides evidence in favour of the high mass progenitor scenario. The incidence of these low--luminosity SNe could be as high as 4-5$ $ of all type II SNe. Comment: 23 pages, 26 figures, accepted for publication in MNRAS
09/2003;
