arXiv subjects

Silvia Mantovanini

Publications and source records attributed to Silvia Mantovanini.

3 recordsLinked to original sources

arXiv2026

A broadband view of the thermal and non-thermal emission from the embedded massive star cluster RCW 38

Gamma-ray emission has now been detected from a variety of source classes in the Galaxy, including clusters of young massive stars. RCW 38, a very young embedded massive star cluster, is a case of particular interest: its gamma-ray emission detected up to hundreds of GeV, provided the first observational evidence of high-energy particle acceleration powered exclusively by stellar winds. In this work, we aim to characterize the emission mechanisms responsible for the gamma-ray flux in RCW 38 and to provide estimates of the acceleration efficiency, as well as the fraction of accelerated electrons compared to protons, $K_{ep}$. We present the most comprehensive multi-wavelength study of a single star cluster to date. Our analysis ranges from MHz radio observations obtained with the GLEAM-X survey from the Murchison Widefield Array (MWA) to GeV gamma-ray data from Fermi-LAT, and includes GHz and THz measurements from Parkes, Planck, and IRAS. We model the thermal and non-thermal emission of RCW 38 using an eight-parameter model constrained by the Markov chain Monte Carlo method. Our results support an interpretation in which the gamma-ray emission from RCW 38 is produced by hadronic interactions with the host molecular cloud. We derive robust constraints on the electron-to-proton ratio, with $K_{ep} \lesssim 10^{-3}$, and on the acceleration efficiency, estimated to be $\gtrsim$1%, consistent with the values required to explain the cosmic-ray composition, and in particular its $^{22}$Ne anomaly. These results strengthen the idea that stellar clusters play a significant role as contributors to cosmic-ray protons in our Galaxy at least up to energies of a few TeV. Future investigations with the next generation of ground-based detectors will determine whether they also play a relevant role at higher energies, particularly in the context of the cosmic-ray knee.

astro-ph.HE↗

arXiv2025

Low radio frequency detections of known pulsars and identification of new candidates with GLEAM-X: GP

Image-based searches have become a complementary approach for identifying pulsars, particularly at MHz frequencies where scattering and high dispersion measures affect high-time resolution observations. In this work, we searched the Galactic Plane (GP) data release from the GaLactic and Extragalactic All-Sky Murchison Widefield Array eXtended (GLEAM-X) survey, a widefield continuum radio survey covering the 72 - 231 MHz frequency range, at the positions of known pulsars in the ATNF catalogue (version 2.6.2) that lie within its sky coverage. We present the spectral energy distribution for 193 known pulsars located at |b| < 11deg. Notably, 106 of these represent the first detections below 400 MHz. We also cross-match the GLEAM-X: GP compact source catalogue with unassociated sources in the Fermi Large Area Telescope (LAT) catalogue, filtering for gamma-ray spectral and variability properties, as well as coincidence with Active Galactic Nuclei (AGN). We have identified 106 possible pulsar candidates. This work demonstrates the importance of sensitive, low-frequency Galactic plane surveys for detecting emission from known pulsars and presents a potential way of searching for new pulsar candidates that would otherwise be missed by traditional time-domain searches.

astro-ph.GA↗

arXiv2025

Teleios (G305.4-2.2) -- the mystery of a perfectly shaped new Galactic supernova remnant

We present the serendipitous radio-continuum discovery of a likely Galactic supernova remnant (SNR) G305.4-2.2. This object displays a remarkable circular symmetry in shape, making it one of the most circular Galactic SNRs known. Nicknamed Teleios due to its symmetry, it was detected in the new Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) radio-continuum images with an angular size of 1320"x1260" and PA = 0 deg. While there is a hint of possible H$α$ and gamma-ray emission, Teleios is exclusively seen at radio-continuum frequencies. Interestingly, Teleios is not only almost perfectly symmetric, but it also has one of the lowest surface brightnesses discovered among Galactic SNRs and a steep spectral index of $α=-0.6\pm 0.3$. Our estimates from HI studies and the Sigma-D relation place Teleios as a type Ia SNR at a distance of either ~2.2 kpc of ~7.7 kpc. This indicates two possible scenarios, either a young (under 1000 yr) or an older SNR (over 10000 yr). With a corresponding diameter of 14/48 pc, our evolutionary studies place Teleios at the either early or late Sedov phase, depending on the distance estimate. However, our modelling also predicts X-ray emission, which we do not see in the present generation of eROSITA images. We also explored a type Iax explosion scenario that points to a much closer distance of <1 kpc and Teleios size of only ~3.3 pc, which would be similar to the only known type Iax remnant SN1181. Unfortunately, all examined scenarios have their challenges, and no definitive supernova (SN) origin type can be established at this stage. Teleios's symmetrical shape suggests expansion into a rarefied and isotropic ambient medium. The low radio surface brightness and the lack of pronounced polarisation can be explained by a high level of ambient rotation measure (RM), with the largest RM being observed at centre.

astro-ph.HE↗