arXiv subjects

C. Sigismondi

Publications and source records attributed to C. Sigismondi.

5 recordsLinked to original sources

arXiv2026

GRB 220101A: a most energetic $10^{54}$ erg long GRB triggered by two supernovae 3.5 seconds apart

GRB 220101A is a long GRB, with a total energy exceeding $10^{54}$ erg with a redshift $z = 4.61$ and one of the largest ever high-quality multi-wavelength observational coverage, from a large number of space-based and ground-based telescopes. We interpret this source in a doubly Binary driven peta nova (BdP-N) model. The progenitor is composed of a massive CO core of $\sim 10\,M_\odot$, highly magnetized with $B \sim 10^{6}$ G, associated to a neutron star (NS) and a white dwarf (WD) with orbital periods from minutes to hours. The large GRB luminosity is explained by a sequence of 7 episodes: episode 1 is triggered by a new kind of pair supernova (HB) which originates from the collapse of the strongly magnetized CO core. Accretion of the HB supernova ejecta (the ejecta) onto the white dwarf companion triggers after 3.5 sec the episode 2: the second supernova emitting neutrinos and creating a new neutron star ($ν$NS). The ejecta, interacting with the magnetosphere of the binary NS companion originate the episode 3: the Ultra relativistic Prompt Emission (UPE) emission by far the most energetic episode of this GRB, with the formation of a powerful jet normal to the plane of the GRB. Following the UPE energy loss, the accretion of the ejecta on the NS companion leads to the episode 4: the formation of a black hole (BH) of $2.3 \ M_\odot$ leading to the observed GeV afterglow emission. Further accretion of the ejecta spin up the $ν$NS to a period of $1.3$ ms which gives origin to the episode 5: the birth of a pulsar. The interaction of this milli-second pulsar with the remnants lead to the Episode 6: the synchrotron emission observed in the X-ray, optical and radio, The episode 7 is a 56.7 ms pulsar, as observed $10^{10}$ s after the first burst in the crab nebula.

astro-ph.HE↗

arXiv2025

Selected topics on: 1) proposal of interpreting the Crab supernova with a GRB 2) progress in identifying the seven GRBs episodes 3) the role of Sagittarius A in identifying the dark matter component (the X fermion)

As the fiftieth anniversary of our common effort in the field of relativistic astrophysics is approaching, we offer a new look to some of our acquired knowledge in a more complete view, which evidence previous unnoticed connections. They are gaining due prominence in reaching a more complete picture evidencing the main results. We outline the history of GRB observations along with a summary of the contributions made by our group to develop the BdHN interpreting model. We show the seven Episodes characterizing the most powerful BdHNe I occurred to date: GRB 190114C and GRB 220101A. New inferences for the explanation of the highest energy radiation in the TeV are presented.

astro-ph.HE↗

arXiv2025

ASIACO: Asiago Spectroscopy and Imaging Atlas of COmets

The ASIACO project is an atlas of cometary imaging and spectroscopy obtained from the Asiago Astrophysical Observatory between 2012 and 2024, still ongoing. Up to now, we monitored 41 comets, acquiring broad-band images using the INAF-OAPd 1.82m Copernico and the 0.67/0.92m Schmidt telescopes, as well as low-to-medium resolution spectra with the DFA-UniPd 1.22m Galileo Telescope. Our dataset offers significant scientific potential, enabling studies on the true extent of cometary tails, orientation of nuclei spin axes, retrieval of compositional data, and determination of production rates for key molecular and atomic species. The Atlas will become publicly available for scientific research, and the project remains active, continuously adding monitored comets.

astro-ph.EP↗

arXiv2023

The Great Dimming of the hypergiant star RW Cephei: CHARA Array images and spectral analysis

The cool hypergiant star RW Cephei is currently in a deep photometric minimum that began several years ago. This event bears a strong similarity to the Great Dimming of the red supergiant Betelgeuse that occurred in 2019-2020. We present the first resolved images of RW Cephei that we obtained with the CHARA Array interferometer. The angular diameter and Gaia distance estimates indicate a stellar radius of 900 - 1760 R_sun which makes RW Cep one of the largest stars known in the Milky Way. The reconstructed, near-infrared images show a striking asymmetry in the disk illumination with a bright patch offset from center and a darker zone to the west. The imaging results depend on assumptions made about the extended flux, and we present two cases with and without allowing extended emission. We also present a recent near-infrared spectrum of RW Cep that demonstrates that the fading is much larger at visual wavelengths compared to that at near-infrared wavelengths as expected for extinction by dust. We suggest that the star's dimming is the result of a recent surface mass ejection event that created a dust cloud that now partially blocks the stellar photosphere.

astro-ph.SR↗

arXiv2001

The Observation of Lunar Impacts. Part II

The frequency and the characteristics of lunar impacting meteorites are reconsidered under the general assumption of belonging to the sporadic meteoroids. We develop the model for evaluating the luminous energy detected in the visual band during the impact. The values obtained are consistent with the luminosity of an Earth's meteor as seen at the Moon's distance, although we recover significantly smaller magnitudes for the lunar impacts with respect to other authors.

astro-ph↗