234 research outputs found
Supernova Classes and Subclasses
The discovery of many objects with unprecedented, amazing observational
characteristics caused the last decade to be the most prolific period for the
supernova research. Many of these new supernovae are transitional objects
between existing classes, others well enter within the defined classes, but
still show unique properties. This makes the traditional classification scheme
inadequate to take into account the overall SN variety and, consequently,
requires the introduction of new subclasses.Comment: 10 pages, 2 figure, review for "Supernova 1987A: 20 Years After:
Supernovae and Gamma-Ray Bursters" AIP, New York, eds. S. Immler, K.W.
Weiler, and R. McCra
Spectral luminosity indicators in SNe Ia - Understanding the R(SiII) line strength ratio and beyond
SNe Ia are good distance indicators because the shape of their light curves,
which can be measured independently of distance, varies smoothly with
luminosity. This suggests that SNe Ia are a single family of events. Similar
correlations are observed between luminosity and spectral properties. In
particular, the ratio of the strengths of the SiII \lambda 5972 and \lambda
6355 lines, known as R(SiII), was suggested as a potential luminosity
indicator. Here, the physical reasons for the observed correlation are
investigated. A Monte-Carlo code is used to construct a sequence of synthetic
spectra resembling those of SNe with different luminosities near B maximum. The
influence of abundances and of ionisation and excitation conditions on the
synthetic spectral features is investigated. The ratio R(SiII) depends
ssentially on the strength of SiII \lambda 5972, because SiII \lambda 6355 is
saturated. In less luminous objects, SiII \lambda 5972 is stronger because of a
rapidly increasing SiII/SiIII ratio. Thus, the correlation between R(SiII) and
luminosity is the effect of ionisation balance. The SiII \lambda 5972 line
itself may be the best spectroscopic luminosity indicator for SNe Ia, but all
indicators discussed show scatter which may be related to abundance
distributions.Comment: 10 pages, 16 figures. Accepted for publication in MNRA
Nomina sunt consequentia rerum. Il problema della definizione di qualità nel caso del vino
ope
Distretto della pesca e filiera ittica: un parallelo con riferimento all’Alto Adriatico
The topic of this thesis was inspired by the question “Can the fishing industry in the province of Ferrara become a district?”, asked by Massimo Buriani in an article published in the 2012 edition of the Socioeconomic Annual Report of Ferrara. Considering the importance of the contribution given by fishing economy to the productivity growth of this country, this work’s main objective is to clarify the differences and analogies between the fishing district and the small- and large-sized fishing industry; moreover, to which extent the notion of “district” can be adapted to the economic reality of the High-Adriatic District, particularly considering the case of Ferrara. Finally, the topic deals with important current issues of European interest related to environmental protection zones fish - district considered: the Marine Strategy , the European Fisheries Fund and the Group of Coastal Action
Signatures of an eruptive phase before the explosion of the peculiar core-collapse SN 2013gc
We present photometric and spectroscopic analysis of the peculiar
core-collapse SN 2013gc, spanning seven years of observations. The light curve
shows an early maximum followed by a fast decline and a phase of almost
constant luminosity. At +200 days from maximum, a brightening of 1 mag is
observed in all bands, followed by a steep linear luminosity decline after +300
d. In archival images taken between 1.5 and 2.5 years before the explosion, a
weak source is visible at the supernova location, with mag20. The
early supernova spectra show Balmer lines, with a narrow (560 km
s) P-Cygni absorption superimposed on a broad (3400 km s)
component, typical of type IIn events. Through a comparison of colour curves,
absolute light curves and spectra of SN 2013gc with a sample of supernovae IIn,
we conclude that SN 2013gc is a member of the so-called type IId subgroup. The
complex profile of the H line suggests a composite circumstellar medium
geometry, with a combination of lower velocity, spherically symmetric gas and a
more rapidly expanding bilobed feature. This circumstellar medium distribution
has been likely formed through major mass-loss events, that we directly
observed from 3 years before the explosion. The modest luminosity
( near maximum) of SN 2013gc at all phases, the very small amount
of ejected Ni (of the order of M), the major
pre-supernova stellar activity and the lack of prominent [O I] lines in
late-time spectra support a fall-back core-collapse scenario for the massive
progenitor of SN~2013gc.Comment: 20 pages, 11 figures, 8 tables, accepted by MNRA
The schmidt 67/92 robotic telescope - roboschmidt user manual
The 67/91 Schmidt telescope is the largest instrument of this type in
Italy. It was officially commissioned in 1966; in 1991
the telescope was moved to mount Ekar, near the Copernico 1.82m
telescope, in order to take advantage of the higher altitude and lower
light pollution.
In 2017 the telescope has been considerably refurbished (new CCD
camera, new filters, autoguider) and remotely controlled.
Starting from May, 2020 updates of both hardware and software
allowed the implementation of the fully robotic operational mode .
The observing blocks (OB) are submitted at any time by the PIs of the
proposals or their collaborators. The Robotic System has a
rapid-response capability that allows it to interrupt regular
observations in order to observe transient phenomena with high
priority
SN 1995ah-the first supernova observed in a Blue Compact Dwarf galaxy
We present the properties of the supernova SN 1995ah discovered in a Blue
Compact Dwarf galaxy (BCD) around 10 days after the maximum. This is the first
supernova event observed in a BCD. The photometric and spectroscopic data
suggest that SN 1995ah is a Type II supernova and could belong to the rare
Bright SNII Linear subclass, for which ~=-18.9+-0.6 at maximum
light.Comment: 6 pages, late
The spectacular evolution of Supernova 1996al over 15 years: a low energy explosion of a stripped massive star in a highly structured environment
Spectrophotometry of SN 1996al carried out throughout 15 years is presented.
The early photometry suggests that SN 1996al is a Linear type-II supernova,
with an absolute peak of Mv ~ -18.2 mag. Early spectra present broad,
asymmetric Balmer emissions, with super-imposed narrow lines with P-Cygni
profile, and He I features with asymmetric, broad emission components. The
analysis of the line profiles shows that the H and He broad components form in
the same region of the ejecta. By day +142, the Halpha profile dramatically
changes: the narrow P-Cygni profile disappears, and the Halpha is fitted by
three emission components, that will be detected over the remaining 15 yrs of
the SN monitoring campaign. Instead, the He I emissions become progressively
narrower and symmetric. A sudden increase in flux of all He I lines is observed
between 300 and 600 days. Models show that the supernova luminosity is
sustained by the interaction of low mass (~1.15 Msun) ejecta, expelled in a low
kinetic energy (~ 1.6 x 10^50 erg) explosion, with highly asymmetric
circumstellar medium. The detection of Halpha emission in pre-explosion archive
images suggests that the progenitor was most likely a massive star (~25 Msun
ZAMS) that had lost a large fraction of its hydrogen envelope before explosion,
and was hence embedded in a H-rich cocoon. The low-mass ejecta and modest
kinetic energy of the explosion are explained with massive fallback of material
into the compact remnant, a 7-8 Msun black hole.Comment: 27 pages, 23 figures, Accepted for publication in MNRA
Reflections on Reflexions: II. Effects of Light Echoes on the luminosity and spectra of Type Ia Supernovae
In this paper we present and discuss the effects of scattered light echoes
(LE) on the luminosity and spectral appearance of Type Ia Supernovae (SNe).
After introducing the basic concepts of LE spectral synthesis, by means of LE
models and real observations we investigate the deviations from pure SN
spectra, light and colour curves, the signatures that witness the presence of a
LE and the possible inferences on the extinction law. The effects on the
photometric parameters and spectral features are also discussed. In particular,
for the case of circumstellar dust, LEs are found to introduce an apparent
relation between the post-maximum decline rate and the absolute luminosity
which is most likely going to affect the well known Pskowski-Phillips relation.Comment: 15 pages, 14 figures, submitted to MNRAS. Full resolution version at
http://www.eso.org/~fpatat/science/LE/paperII.pd
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