Extensive optical and near-infrared (NIR) observations of the type Ib supernova 1999dn are presented, covering the first year after explosion. These new data turn this object, already considered a ...prototypical SNIb, into one of the best observed objects of its class. The light curve of SN 1999dn is mostly similar in shape to that of other SNeIb but with a moderately faint peak M_V=-17.2 mag). From the bolometric light curve and ejecta expansion velocities, we estimate that about 0.11 Msun of 56Ni were produced during the explosion and that the total ejecta mass was 4-6 Msun with a kinetic energy of at least 5x10^{51} erg. The spectra of SN 1999dn at various epochs are similar to those of other Stripped Envelope (SE) SNe showing clear presence of H at early epochs. The high explosion energy and ejected mass, along with the small flux ratio CaII/OI measured in the nebular spectrum, together with the lack of signatures of dust formation and the relatively high-metallicity environment point toward a single massive progenitor (M_ZAMS>=23-25 Msun) for SN 1999dn.
We present densely-sampled ultraviolet/optical photometric and low-resolution optical spectroscopic observations of the type IIP supernova 2013ab in the nearby (\(\sim\)24 Mpc) galaxy NGC 5669, from ...2 to 190d after explosion. Continuous photometric observations, with the cadence of typically a day to one week, were acquired with the 1-2m class telescopes in the LCOGT network, ARIES telescopes in India and various other telescopes around the globe. The light curve and spectra suggest that the SN is a normal type IIP event with a plateau duration of \( \sim80 \) days with mid plateau absolute visual magnitude of -16.7, although with a steeper decline during the plateau (0.92 mag 100 d\( ^{-1} \) in \( V \) band) relative to other archetypal SNe of similar brightness. The velocity profile of SN 2013ab shows striking resemblance with those of SNe 1999em and 2012aw. Following the Rabinak & Waxman (2011) prescription, the initial temperature evolution of the SN emission allows us to estimate the progenitor radius to be \( \sim \) 800 R\(_{\odot}\), indicating that the SN originated from a red supergiant star. The distance to the SN host galaxy is estimated to be 24.3 Mpc from expanding photosphere method (EPM). From our observations, we estimate that 0.064 M\(_{\odot}\) of \(^{56}\)Ni was synthesized in the explosion. General relativistic, radiation hydrodynamical modeling of the SN infers an explosion energy of \( 0.35\times10^{51} \) erg, a progenitor mass (at the time of explosion) of \( \sim9 \) M\(_{\odot}\) and an initial radius of \( \sim600 \) R\(_{\odot}\).
Ultraviolet (UV), optical and near infrared (NIR) observations of the type IIP supernova (SN) 2007od are presented, covering from the maximum light to the late phase, allowing to investigate in ...detail different physical phenomena in the expanding ejecta. These data turn this object into one of the most peculiar IIP ever studied. The early light curve of SN 2007od is similar to that of a bright IIPs with a short plateau, a bright peak (MV = -18 mag), but a very faint optical light curve at late time. However, with the inclusion of mid infrared (MIR) observations during the radioactive decay we have estimate a M(56Ni) ~ 2\times10^-2 M\odot. Modeling the bolometric light curve, ejecta expansion velocities and black-body temperature, we estimate a total ejected mass was 5 - 7.5 M\odot with a kinetic energy of at least 0.5 \times 10^51 erg. The early spectra reveal a boxy H{\alpha} profile and high velocities features of the Balmer series that suggest interaction between the ejecta and a close circum-stellar matter (CSM). SN 2007od may be, therefore, an intermediate case between a Type IIn SN and a typical Type IIP SN. Also late spectra show a clear evidence of CSM and the presence of dust formed inside the ejecta. The episodes of mass loss short before explosion, the bright plateau, along with the relatively small amount of 56Ni and the faint O I observed in the nebular spectra are consistent with a super-asympthotic giant branch (super-AGB) progenitor (M~9.7 - 11 M\odot).
We present photometry and spectroscopy of the type IIP supernova 2009bw in UGC 2890 from few days after the outburst to 241 days. The light curve of SN 2009bw during the photospheric phase is similar ...to that of normal SNe IIP but with brighter peak and plateau (Mmax R = -17.82 mag, Mplateau R = -17.37 mag). The luminosity drop from the photospheric to the nebular phase is one of the fastest ever observed, ~2.2 mag in about 13 days. The radioactive tail of the bolometric light curve indicates that the amount of ejected 56 Ni is \approx 0.022 M\odot. The photospheric spectra reveal high velocity lines of H{\alpha} and H{\beta} until about 105 days after the shock breakout, suggesting a possible early interaction between the SN ejecta and pre-existent circumstellar material, and the presence of CNO elements. By modeling the bolometric light curve, ejecta expansion velocity and photospheric temperature, we estimate a total ejected mass of 8-12M\odot, a kinetic energy of ~0.3 foe and an initial radius of ~ 3.6 - 7 \times 10^13 cm.
Gravitational waves were discovered with the detection of binary black hole mergers and they should also be detectable from lower mass neutron star mergers. These are predicted to eject material rich ...in heavy radioactive isotopes that can power an electromagnetic signal called a kilonova. The gravitational wave source GW170817 arose from a binary neutron star merger in the nearby Universe with a relatively well confined sky position and distance estimate. Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC4993, which is spatially coincident with GW170817 and a weak short gamma-ray burst. The transient has physical parameters broadly matching the theoretical predictions of blue kilonovae from neutron star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 +/- 0.01 Msol, with an opacity of kappa <= 0.5 cm2/gm at a velocity of 0.2 +/- 0.1c. The power source is constrained to have a power law slope of beta = -1.2 +/- 0.3, consistent with radioactive powering from r-process nuclides. We identify line features in the spectra that are consistent with light r-process elements (90 < A < 140). As it fades, the transient rapidly becomes red, and emission may have contribution by a higher opacity, lanthanide-rich ejecta component. This indicates that neutron star mergers produce gravitational waves, radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.
The Public European Southern Observatory Spectroscopic Survey of Transient Objects (PESSTO) began as a public spectroscopic survey in April 2012. We describe the data reduction strategy and data ...products which are publicly available through the ESO archive as the Spectroscopic Survey Data Release 1 (SSDR1). PESSTO uses the New Technology Telescope with EFOSC2 and SOFI to provide optical and NIR spectroscopy and imaging. We target supernovae and optical transients brighter than 20.5mag for classification. Science targets are then selected for follow-up based on the PESSTO science goal of extending knowledge of the extremes of the supernova population. The EFOSC2 spectra cover 3345-9995A (at resolutions of 13-18 Angs) and SOFI spectra cover 0.935-2.53 micron (resolutions 23-33 Angs) along with JHK imaging. This data release contains spectra from the first year (April 2012 - 2013), consisting of all 814 EFOSC2 spectra and 95 SOFI spectra (covering 298 distinct objects), in standard ESO Phase 3 format. We estimate the accuracy of the absolute flux calibrations for EFOSC2 to be typically 15%, and the relative flux calibration accuracy to be about 5%. The PESSTO standard NIR reduction process does not yet produce high accuracy absolute spectrophotometry but the SOFI JHK imaging will improve this. Future data releases will focus on improving the automated flux calibration of the data products.
Gravitational waves were discovered with the detection of binary black-hole mergers1 and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material ...rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova$^{2,3,4,5}$. The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate$^6$. Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short γ-ray burst$^{7,8}$. The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 ± 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 ± 0.1 times light speed. The power source is constrained to have a power-law slope of −1.2 ± 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90–140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.
The most common ecohydrological models start from the water balance equation, a stochastic differential equation constituted by a stochastic part and by a deterministic part. The unknown quantity of ...this equation is the function of the soil moisture, depending both on space and time. The existing solutions in literature have been obtained in a probabilistic framework and under a steady-state condition; even though this last condition allows the analytical handling of the problem, it has considerably simplified the problem by subtracting generalities from it. The steady-state hypothesis, used in the most of ecohydrological works, appears perfectly applicable in arid and semiarid climatic areas like those of African's or middle American's savannas, but it seems to be no more valid in semiarid Mediterranean regimes, like those of south Italy where, notoriously, wet season foregoes growing season, thus recharging the moisture of the soil. For plants physiology, especially for tree vegetation, this initial soil moisture condition has a capital importance by enabling survival in absence of rainfalls during the growing season and, however, keeping low the water stress during his first period. The aim of this paper is to investigate on above topics through a simple non steady numerical ecohydrological model. The proposed model is able to reproduce soil moisture probability density function (pdf) obtained analytically from other authors for different climate and soil conditions in steady-state. The numerical model take in account for initial condition superimposing a value extracted from a Gaussian distribution. This assumption allows to get soil moisture pdf, which can be compared with those obtained in steady-state. Dynamic water stress is computed directly on soil moisture traces, implicitly taking into consideration initial soil moisture condition, without any artifice. The simple numerical model proposed here was applied in the forested river basin of the Euleterio (Sicily, Italy).
