Search results for "Supernova"
showing 10 items of 330 documents
The r-process in the high entropy bubble
1997
We examined the r-process in the high entropy bubble within a detailed parameter study. Previous investigations ([1,2]) based on realistic supernovae models showed already that this model yields a very good fit to the solar system r-process abundance curve for masses above A = 120. For A < 120 their fit was relatively poor. We are concerned mainly with the question whether it is possible to obtain a good fit in the range below A = 120. Within a simple approach of an adiabatically expanding sphere we analyzed a broad parameter range, independent of specific explosion simulations. We varyied the electron abundance Ye and the entropy S and studied the resulting contributions as a function of t…
Charged-current neutrino-nucleus scattering off 95,97^Mo
2013
Background: Reliable cross sections for the neutrino-nucleus scattering off relevant nuclei for supernova neutrinos are essential for various applications in neutrino physics and astrophysics (e.g., supernova mechanisms). Studies of the nuclear responses for the stable molybdenum isotopes are of great interest for the planned MOON (Mo Observatory of Neutrinos) experiment.Purpose: The purpose of the present work is, thus, to perform a detailed study of the charged-current nuclear responses to supernova neutrinos for the stable odd molybdenum isotopes. A special effort will be devoted to discuss in detail the structures of the most relevant final states in the corresponding proton-odd nucleus…
Estimation of bounds for left-right mixing from nuclear double beta decay processes
1993
Abstract Nuclear matrix elements, extracted from a systematic calculation of neutrinoless double beta decay rates for 0 + g.s →o + g.s transitions in 76 Ge, 82 Se, 128 Te, 130 Te and 136 Xe, have been used to compute bounds on the left-right mixing angle ζ of the weak currents. The parameters of the nuclear model have been fixed by calculating the corresponding two-neutrino double beta decay half lives. The present analysis favours a mixing of the order of |tanξ| −3 which is to be compared with those obtained in muon decay (|tan ξ | ⩽ 0.035) and in supernova (|tan ξ | ⩽ 10 −5 ) analysis. It shows that nuclear structure calculations yield estimates on ξ which complement the existing data.
Neutrino scattering off the stable cadmium isotopes: neutral-current processes
2014
In this work we present computed cross sections for the incoherent neutral-current neutrino scattering off the stable cadmium isotopes. The main focus is on supernova neutrinos. The nuclear states of the even-mass and odd-mass cadmium isotopes have been constructed using the quasiparticle random-phase approximation and the microscopic quasiparticle-phonon model, respectively. The computed cross sections are folded with suitably parametrized Fermi–Dirac distributions of the supernova (anti)neutrinos energies to obtain realistic estimates of the nuclear responses to these neutrinos.
The origin of the Ca–Ti–Cr–Fe–Ni isotopic anomalies in the inclusion EK-1-4-1 of the Allende meteorite
2003
The origin of the correlated Ca-Ti-Cr-Fe-Ni isotopic anomalies in the Ca-Al-rich inclusion of the EK-1-4-1 of the Allende is a longstanding puzzle. The search for a stellar environment which could explain the enrichment of neutron-rich stable Ca-...-Ni isotopes in a self-consistent way requires nuclear physics data far from stability. Recent experimental data have been obtained in the region of the shell closures N = 28 and N = 40, where the possible progenitors of these nuclei are found. Astrophysical network calculations have been updated by including the new beta-decay properties and microscopic predictions of neutron-capture cross sections. Interplay between nuclear structure far from s…
A decade of SN 1993J : discovery of radio wavelength effects in the expansion rate
2009
We studied the growth of the shell-like radio structure of supernova SN 1993J in M 81 from September 1993 to October 2003 with very-long-baseline interferometry (VLBI) observations at the wavelengths of 3.6, 6, and 18 cm. We developed a method to accurately determine the outer radius (R) of any circularly symmetric compact radio structure such as SN 1993J. The source structure of SN 1993J remains circularly symmetric (with deviations from circularity under 2%) over almost 4000 days. We characterize the decelerated expansion of SN 1993J until approximately day 1500 after explosion with an expansion parameter m = 0.845 ± 0.005 (R ∝ tm). However, from that day onwards the expansion differs whe…
Most constraining cosmological neutrino mass bounds
2021
We present here up-to-date neutrino mass limits exploiting the most recent cosmological data sets. By making use of the cosmic microwave background temperature fluctuation and polarization measurements, supernovae Ia luminosity distances, baryon acoustic oscillation observations and determinations of the growth rate parameter, we are able to set the most constraining bound to date, $\ensuremath{\sum}{m}_{\ensuremath{\nu}}l0.09\text{ }\text{ }\mathrm{eV}$ at 95% C.L. This very tight limit is obtained without the assumption of any prior on the value of the Hubble constant and highly compromises the viability of the inverted mass ordering as the underlying neutrino mass pattern in nature. The …
Robust measurement of supernova νe spectra with future neutrino detectors
2017
Measuring precise all-flavor neutrino information from a supernova is crucial for understanding the core-collapse process as well as neutrino properties. We apply a chi-squared analysis for different detector setups to explore determination of $\nu_{e}$ spectral parameters. Using a long-term two-dimensional core-collapse simulation with three time varying spectral parameters, we generate mock data to examine the capabilities of the current Super-Kamiokande detector and compare the relative improvements that gadolinium, Hyper-Kamiokande, and DUNE would have. We show that in a realistic three spectral parameter framework, the addition of gadolinium to Super-Kamiokande allows for a qualitative…
Pair production of helicity-flipped neutrinos in supernovae.
1990
The emissivity was calculated for the pair production of helicity-flipped neutrinos, in a way that can be used in supernova calculations. Also presented are simple estimates which show that such process can act as an efficient energy-loss mechanism in the shocked supernova core, and this fact is used to extract neutrino mass limits from SN 1987A neutrino observations.
GW190521 as a Merger of Proca Stars: A Potential New Vector Boson of 8.7×10−13 eV
2021
Advanced LIGO-Virgo have reported a short gravitational-wave signal (GW190521) interpreted as a quasicircular merger of black holes, one at least populating the pair-instability supernova gap, that formed a remnant black hole of ${M}_{f}\ensuremath{\sim}142\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ at a luminosity distance of ${d}_{L}\ensuremath{\sim}5.3\text{ }\text{ }\mathrm{Gpc}$. With barely visible pre-merger emission, however, GW190521 merits further investigation of the pre-merger dynamics and even of the very nature of the colliding objects. We show that GW190521 is consistent with numerically simulated signals from head-on collisions of two (equal mass and spin) horizonless vecto…