We present the first results from our GALEX program designed to obtain ultraviolet (UV) spectroscopy of nearby core-collapse supernovae (SNe). Our first target, SN 2005ay in the nearby galaxy NGC ...3938, is a typical member of the II-P SN subclass. Our spectra show remarkable similarity to those of the prototypical type II-P event SN 1999em, and resemble also Swift observations of the recent type II-P event SN 2005cs. Taken together, the observations of these three events trace the UV spectral evolution of SNe II-P during the first month after explosion, as required in order to interpret optical observations of high-redshift SNe II-P, and to derive cross-filter K-corrections. While still highly preliminary, the apparent UV homogeneity of SNe II-P bodes well for the use of these events as cosmological probes at high redshift.
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.
We report the first result of a supernova search program designed to measure
the evolution of the supernova rate with redshift. To make the comparison with
local rates more significant we copied, as ...much as possible, the same
computation recepies as for the measurements of local rates. Moreover, we
exploited the multicolor images and the photometric redshift technique to
characterize the galaxy sample and accurately estimate the detection
efficiency.
Combining our data with the recently published meaurements of the SN Ia rate
at different redshifts, we derived the first, direct measurement of the core
collapse supernova rate at z = 0.26 as r_cc = 1.45^{+0.55}{-0.45} h^2 SNu
h=H_0/75. This is a factor three {+/- 50%)} larger than the local estimate.
The increase for a look back time of "only" 2.8 Gyr is more rapid than
predicted by most of the published models of the SN rate evolution.
Core-collapse SN rates measure the death rate of massive star and, because of
the short time scale of evolution, can be translated in a measurement of the
ongoing SFR. Assuming a Salpeter IMF and the standard scenario for
core-collapse progenitors we derived to an estimate of the star formation rate
at redshift 3.1^{+1.1}{-1.0} 10^-2 h^3 M_sun yr^-1 Mpc^{-3} which compare very
well with a recent estimate based on the measurement of the Halpha luminosity
density at the same redshift.
Long-slit echellograms of the high excitation planetary nebula NGC1501, reduced according to the methodology developed by Sabbadin et al. (2000a, b), allowed us to obtain the ``true'' distribution of ...the ionized gas in the eight nebular slices covered by the spectroscopic slit. A 3-D rendering procedure is described and applied, which assembles the tomographic maps and rebuilds the spatial structure. The images of NGC 1501, as seen in 12 directions separated by 15 deg, form a series of stereoscopic pairs giving surprising 3-D views in as many directions. The main nebula consists of an almost oblate ellipsoid of moderate ellipticity (a=44 arcsec, a/b=1.02, a/c=1.11), brighter in the equatorial belt, deformed by several bumps, and embedded in a quite homogeneous, inwards extended cocoon. Some reliability tests are applied to the rebuilt nebula; the radial matter profile, the small scale density fluctuations and the 2-D (morphology) - 3-D (structure) correlation are presented and analysed. The wide applications of the 3-D reconstruction to the morphology, physical conditions, ionization parameters and evolutionary status of expanding nebulae in general (planetary nebulae, nova and supernova remnants, shells around Population I Wolf-Rayet stars, nebulae ejected by symbiotic stars, bubbles surrounding early spectral type main sequence stars etc.) are introduced.
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.
Although there is strong support for the collapsar engine as the power source
of long-duration gamma-ray bursts (GRBs), we still do not definitively know the
progenitor of these explosions. Here we ...review the current set of progenitor
scenarios for long-duration GRBs and the observational constraints on these
scenarios. Examining these, we find that single-star models cannot be the only
progenitor for long-duration GRBs. Several binary progenitors can match the
solid observational constraints and also have the potential to match the trends
we are currently seeing in the observations. Type Ib/c supernovae are also
likely to be produced primarily in binaries; we discuss the relationship
between the progenitors of these explosions and those of the long-duration
GRBs.
An analysis of SNIa events in early type galaxies from the Cappellaro et al (1999) database provides conclusive evidence that the rate of type Ia Supernovae (SNe) in radio-loud galaxies is about 4 ...times higher than the rate measured in radio-quiet galaxies, i.e. SNIa-rate\((radio-loud galaxies) = 0.43^{+0.19}_{-0.14}h^2_{75}\) SNu as compared to SNIa-rate\((radio-quiet galaxies) = 0.11^{+0.06}_{-0.03}h^2_{75}\) SNu. The actual value of the enhancement is likely to be in the range \(\sim 2-7\) (P\(\sim 10^{-4}\)). This finding puts on robust empirical grounds the results obtained by Della Valle & Panagia (2003) on the basis of a smaller sample of SNe. We analyse the possible causes of this result and conclude that the enhancement of SNIa explosion rate in radio-loud galaxies has the same origin as their being strong radio sources, but there is no causality link between the two phenomena. We argue that repeated episodes of interaction and/or mergers of early type galaxies with dwarf companions, on times-scale of about 1 Gyr, are responsible for inducing both strong radio activity observed in \(\sim\)14% of early type galaxies and to supply an adequate number of SNIa progenitors to the stellar population of ellipticals.
We present the reduction and archiving tools developed for our search for
supernovae at intermediate redshifts at ESO as well as the efficiency tests
performed. The data reduction recipes developed ...for the SN candidates selection
are described. All the variable sources detected are stored using a MySQL
database which enables the identification of previously detected variable
sources during past observational runs. Finally, experiments performed with
artificial stars have shown that seeing plays a crucial role for the limiting
magnitude of detection. Crucial is also the detection threshold used by
Sextractor.
Supernova (SN) 2016bdu is an unusual transient resembling SN 2009ip. SN 2009ip-like events are characterized by a long-lasting phase of erratic variability that ends with two luminous outbursts a few ...weeks apart. The second outburst is significantly more luminous (about 3 mag) than the first. In the case of SN 2016bdu, the first outburst (Event A) reached an absolute magnitude M-r approximate to -15.3 mag, while the second one (Event B) occurred over one month later and reached M-r approximate to -18 mag. By inspecting archival data, a faint source at the position of SN 2016bdu is several times in the past few years. We interpret these detections as signatures of a phase of erratic variability, similar to that experienced by SN 2009ip between 2008 and mid-2012, and resembling the currently observed variability of the luminous blue variable SN 2000ch in NGC 3432. Spectroscopic monitoring of SN 2016bdu during the second peak initially shows features typical of an SN IIn. One month after the Event B maximum, the spectra develop broad Balmer lines with P Cygni profiles and broad metal features. At these late phases, the spectra resemble those of a typical Type II SN. All members of this SN 2009ip-like group are remarkably similar to the Type IIn SN 2005gl. For this object, the claim of a terminal SN explosion is supported by the disappearance of the progenitor star. While the similarity with SN 2005gl supports a genuine SN explosion scenario for SN 2009ip-like events, the unequivocal detection of nucleosynthesized elements in their nebular spectra is still missing.
Mon.Not.Roy.Astron.Soc. 336 (2002) 91 Photometric and spectroscopic observations of the peculiar Type Ib Supernova
1991D are presented. SN 1991D was exceptionally bright for a Type Ib supernova.
The ...He I lines were rather weak and the velocity at the photosphere as a
function of time was unusually low. Comparison of the observed and synthetic
spectra indicates that either hydrogen was ejected with a minimum velocity of
12,000 km/s or the spectrum contained features caused by lines of Ne I. Light
curve modelling suggests that the progenitor probably had a very large radius
(~10^14 cm) and that a considerable amount of 56Ni was synthesized during the
explosion (~0.7 Msolar). We suggest a progenitor model of SN 1991D that
involves a binary system.
