130 research outputs found
Correlation of the rate of Type Ia supernovae with the parent galaxy properties: Light and shadows
The identification of the progenitors of Type Ia Supernovae (SNIa) is
extremely important in several astrophysical contexts, ranging from stellar
evolution in close binary systems to evaluating cosmological parameters.
Determining the distribution of the delay times (DTD) of SNIa progenitors can
shed light on their nature. In this paper we investigate on the diagnostic
capabilities on the DTD of the correlation between the SNIa rate and the parent
galaxy properties by examining its systematics with the various parameters at
play: simple stellar population models, the adopted description for the star
formation history in galaxies, and the way in which the masses of the galaxies
are evaluated. We compute models for the correlations of the SNIa rate with the
parent galaxy color and specific star formation rate for a variety of input
ingredients, and for a few astrophysically motivated DTD laws. The models are
compared to the results of three independent observational surveys. We find
that the scaling of the SNIa rate with the properties of the parent galaxy is
sensitive to all input ingredients mentioned above. This is a severe limitation
on the possibility to discriminate alternative DTDs. In addition, current
surveys show some discrepancies for the rate measured in the reddest and bluest
galaxies, likely due to limited statistics and inhomogeneity of the
observations. For galaxies with intermediate colors the rates are in agreement,
leading to a robust determination of the productivity of SNIa from stellar
populations of 0.8 events per 1000 \msun. Large stastistics of SNIa
events along with accurate measurements of the star formation history in the
galaxies are required to derive firm constraints on the DTD. LSST will achieve
these results by providing the homogeneous, unbiased and vast database on both
SNIa and galaxies.Comment: Astronomy and Astrophysics in press. Includes one more figure in the
appendix. Notice the slight change of titl
The evolution of the cosmic SN rate
We briefly review the contribution of SN rate measurements to the debate on
SN progenitor scenarios. We find that core collapse rates confirms the rapid
evolution of the star formation rate with redshift. After accounting for the
dispersion of SN Ia measurements and uncertainty of the star formation history,
the standard scenarios for SN Ia progenitors appear consistent with all
observational constraints.Comment: 8 pages, to appear in the AIP conference proceedings of "Supernova
1987A: 20 Years after Supernovae and Gamma-Ray Bursters", Feb 19-23, 2007,
Aspen, C
Why Are Radio-Galaxies Prolific Producers of Type Ia Supernovae?
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 SNu as compared to SNIa-rate SNu. The actual value of the
enhancement is likely to be in the range (P). 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 14% of early type galaxies and to
supply an adequate number of SNIa progenitors to the stellar population of
ellipticals.Comment: 26 pages+6 figures, ApJ, in pres
An empirical limit on the kilonova rate from the DLT40 one day cadence Supernova Survey
Binary neutron star mergers are important to understand stellar evolution,
the chemical enrichment of the universe via the r-process, the physics of short
gamma-ray bursts, gravitational waves and pulsars. The rates at which these
coalescences happen is uncertain, but it can be constrained in different ways.
One of those is to search for the optical transients produced at the moment of
the merging, called a kilonova, in ongoing SN searches. However, until now,
only theoretical models for kilonovae light curve were available to estimate
their rates. The recent kilonova discovery AT~2017gfo/DLT17ck gives us the
opportunity to constrain the rate of kilonovae using the light curve of a real
event. We constrain the rate of binary neutron star mergers using the DLT40
Supernova search, and the native AT~2017gfo/DLT17ck light curve obtained with
the same telescope and software system. Excluding AT~2017gfo/DLT17ck due to
visibility issues, which was only discovered thanks to the aLIGO/aVirgo
trigger, no other similar transients detected during 13 months of daily cadence
observations of 2200 nearby (40 Mpc) galaxies. We find that the rate
of BNS mergers is lower than 0.47 - 0.55 kilonovae per 100 years per
(depending on the adopted extinction distribution). In volume,
this translates to <0.99\times
10^{-4}\,_{-0.15}^{+0.19},\rm{Mpc^{-3}}\,\rm{yr^{-1}}(SNe Ia-like extinction
distribution), consistent with previous BNS coalescence rates. Based on our
rate limit, and the sensitivity of aLIGO/aVirgo during O2, it is very unlikely
that kilonova events are lurking in old pointed galaxy SN search datasets.Comment: 3 figures, 2 table
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
The discovery of the electromagnetic counterpart of GW170817: kilonova AT 2017gfo/DLT17ck
During the second observing run of the Laser Interferometer gravitational-
wave Observatory (LIGO) and Virgo Interferometer, a gravitational-wave signal
consistent with a binary neutron star coalescence was detected on 2017 August
17th (GW170817), quickly followed by a coincident short gamma-ray burst trigger
by the Fermi satellite. The Distance Less Than 40 (DLT40) Mpc supernova search
performed pointed follow-up observations of a sample of galaxies regularly
monitored by the survey which fell within the combined LIGO+Virgo localization
region, and the larger Fermi gamma ray burst error box. Here we report the
discovery of a new optical transient (DLT17ck, also known as SSS17a; it has
also been registered as AT 2017gfo) spatially and temporally coincident with
GW170817. The photometric and spectroscopic evolution of DLT17ck are unique,
with an absolute peak magnitude of Mr = -15.8 \pm 0.1 and an r-band decline
rate of 1.1mag/d. This fast evolution is generically consistent with kilonova
models, which have been predicted as the optical counterpart to binary neutron
star coalescences. Analysis of archival DLT40 data do not show any sign of
transient activity at the location of DLT17ck down to r~19 mag in the time
period between 8 months and 21 days prior to GW170817. This discovery
represents the beginning of a new era for multi-messenger astronomy opening a
new path to study and understand binary neutron star coalescences, short
gamma-ray bursts and their optical counterparts.Comment: ApJL in press, 4 figure
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