A5044863910- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Nuclear physics research studies
- Particle Accelerators and Free-Electron Lasers
- High-pressure geophysics and materials
- Atomic and Molecular Physics
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Geophysics and Sensor Technology
- Stellar, planetary, and galactic studies
- Methane Hydrates and Related Phenomena
University of Milano-Bicocca
2018-2023
Brera Astronomical Observatory
2020-2023
Ultraluminous X-ray sources (ULX) are extragalactic objects with luminosities above the Eddington limit for a 10 Msun black hole (BH). ULXs may host super-Eddington accreting neutron stars or stellar mass BH, although exact proportion of two populations is not yet known. We investigate properties ULX NGC 4559 X7, which shows flux variability up to factor 5 on months-to-years and hours-to-days timescales. A flaring activity was also observed during source highest epochs. Flares unpredictable,...
The detection and follow-up observations of high-redshift (z>6) gamma-ray bursts (GRBs) provide a unique opportunity to explore the properties distant Universe. Unfortunately, they are rather rare, with only dozen them identified so far. We present here discovery GRB second highest spectroscopic redshift measured date, GRB,240218A at z=6.782, broadband analysis its afterglow. Following by high-energy satellites, we obtained multi-epoch multi-wavelength photometric observations, from 68...
Context. Ultraluminous X-ray sources (ULX) are extragalactic objects with observed luminosities largely above the Eddington limit for a 10 M ⊙ black hole. Currently, it is believed that ULXs host super-Eddington accreting neutron stars or stellar mass holes. However, exact proportion of two populations compact not yet known. Aims. We investigate properties ULX NGC 4559 X7 (hereafter X7), which shows flux variability up to factor five on both long (months years) and short (hours days)...
Context. GRB 211106A and 211227A are two recent gamma-ray bursts (GRBs) whose initial X-ray position enabled us to possibly associate them with bright, low-redshift galaxies ( z < 0.7). The prompt emission properties suggest that is a genuine short-duration short extended emission. Therefore, they likely be produced by compact binary merger. However, classification based solely on the can misleading. Aims. possibility of having GRBs occurring in local Universe makes ideal targets for...
We report on the serendipitous discovery of a new transient in NGC 5907, at peak luminosity 6.4x10^{39} erg/s. The source was undetected previous 2012 Chandra observations with 3 sigma upper limit 1.5x10^{38} erg/s, implying flux increase factor >35. analyzed three recent 60ks/50ks and 50ks XMM-Newton observations, as well all available Swift performed between August 2017/March 2018. Until first half October 2017, do not show any emission from source. entered ULX regime less than two weeks...
Ultraluminous X-ray sources are considered amongst the most extremely accreting objects in local Universe. The recent discoveries of pulsating neutron stars ULXs strengthened scenario highly super-Eddington accretion mechanisms on stellar mass compact objects. In this work, we present first long-term light curve source NGC 4559 X7 using all available Swift, XMM-Newton, Chandra and NuSTAR data. Thanks to high quality 2019 XMM-Newton observations, investigated an unprecedented way spectral...
Abstract Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with luminosities above 10 39 erg s −1 . The ULX population counts several hundred but only fraction well studied. Here we present detailed analysis all ULXs hosted in the galaxy NGC 7456. It was observed X-rays once past (in 2005) by XMM-Newton. observation short and strongly affected high background. In 2018, obtained new, deeper (∼90 ks) XMM-Newton that allowed us to perform characterization galaxy. ULX-1...
The discovery of pulsations in (at least) six ultraluminous X-ray sources (ULXs) has shown that neutron stars can accrete at (highly) super-Eddington rates, challenging the standard accretion theories. M51 ULX-7, with a spin signal $P\simeq2.8$ s, is pulsating ULX (PULX) shortest known orbital period ($P_\mathrm{orb}\simeq2$ d) and been observed multiple times by XMM-Newton, Chandra, NuSTAR. We report on timing spectral analyses three XMM-Newton observations ULX-7 performed between end 2021...
Variability is a powerful tool to investigate properties of X-ray binaries (XRB), in particular for Ultraluminous sources (ULXs) that are mainly detected the band. For most ULXs nature accretor unknown, although few have been confirmed be accreting at super-Eddington rates onto neutron star (NS). Monitoring these particularly useful both detect transients and derive periodicities, linked orbital super-orbital modulations. Here we present results our monitoring campaign galaxy NGC 925,...
ABSTRACT We analyse all the available Chandra observations of Cartwheel galaxy and its compact group, taken between 2001 2008, with main aim addressing variability in X-ray band for this spectacular collisional ring galaxy. focus on study point-like sources, particular we are interested ultraluminous sources (ULXs; LX ≥ 1039 erg s−1), that treat as a class. exploit archival XMM–Newton data to enrich long-term variability, time-scales months years. find total 44 group area, which 37 ULXs...
Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with luminosities above 10$^{39}$ erg s$^{-1}$. The average number ULXs per galaxy is still not well constrained, especially given the uncertainty on fraction ULX transients. Here, we report identification new transient in NGC 55 (which label as ULX-2), thanks to recent XMM-Newton and Neil Gehrels Swift Observatory observations. This object was previously classified source luminosity around few 10$^{38}$ s$^{-1}$...
Context. The discovery of pulsations in (at least) six ultraluminous X-ray sources (ULXs) has shown that neutron stars can accrete at (highly) super-Eddington rates, challenging the standard accretion theories. M51 ULX-7, with a spin signal P ≃ 2.8 s, is pulsating ULX (PULX) shortest known orbital period ( orb 2 d) and been observed multiple times by XMM-Newton , Chandra NuSTAR . Aims. We report on timing spectral analyses three observations ULX-7 performed between end 2021 beginning 2022,...
We analyse all the available Chandra observations of Cartwheel Galaxy and its compact group, taken between 2001 2008, with main aim addressing variability in X-ray band for this spectacular collisional ring galaxy. focus on study point-like sources, particular we are interested Ultraluminous sources (ULXs, Lx >= 10^39 erg/s), that treat as a class. exploit archival XMM-Newton data to enrich long-term variability, timescales months years. find total 44 group area, which 37 ULXs...
Context: GRB 211106A and 211227A are recent gamma-ray bursts (GRBs) with initial X-ray positions suggesting associations nearby galaxies (z < 0.7). Their prompt emission characteristics indicate is a short-duration short extended emission, likely originating from compact binary mergers. However, classifying solely based on can be misleading. Aims: These GRBs in the local Universe offer opportunities to search for associated kilonova (KN) study host galaxy properties detail. Methods: We...
Ultraluminous X-ray sources (ULXs) are extragalactic emitters located off-center of their host galaxy and with a luminosity in excess few ${10^{39}\text{ erg s}^{-1}}$, if emitted isotropically. The discovery periodic modulation revealed that some ULXs the accreting compact object is neutron star, indicating luminosities substantially above Eddington limit. most extreme this respect ${NGC 5907~ULX-1}$ (ULX1), peak 500 times its During Chandra observation to probe low state ULX1, we detected...