Unclustered Chandra ACIS-I 2–7 keV image of 2FHL J1745.1–3035. Credit: Marchesi et al., 2024.
Using the XMM-Newton, Chandra and NuSTAR space telescopes, an international team of astronomers explored the nature of a recently detected very high energy source, designated 2FHL J1745.1-3035. Study results, published January 24 on the preprint server arXivsuggested that the source could be a pulsar wind nebula.
The second Fermi-LAT Catalog of High Energy Sources (2FHL) presents the locations, spectra and variability properties of 360 significantly detected sources in the energy range from 50 GeV to 2 TeV in the part of NASA’s Fermi mission. It contains 12 very high energy (VHE) sources in the galactic plane with a gamma photon index less than 1.8, which currently have no association.
One of these unassociated VHE sources is 2FHL J1745.1–3035, located near the galactic center. In gamma rays, this source is the second brightest of the unassociated VHE sources in the 2FHL sample. Previous observations showed that 2FHL J1745.1–3035 had a hard gamma-ray spectrum above 50 GeV and was a TeV emitter.
To better understand the properties and nature of 2FHL J1745.1-3035, a group of astronomers led by Stefano Marchesi of the University of Bologna in Italy, analyzed new archival data from the Chandra and NuSTAR spacecraft of NASA, as well as from ESA’s XMM-Newton satellite.
“We present a multi-epoch, multi-observatory X-ray analysis for 2FHL J1745.1-3035, a recently discovered very high energy galactic source detected by the Fermi Large Area Telescope (LAT) located in close proximity to the galactic center,” the researchers explained.
By analyzing the X-ray and gamma-ray properties of 2FHL J1745.1-3035, astronomers found that the X-ray source is compact, with no evidence of expansion. However, Chandra’s observations allowed researchers to detect significantly extended emission down to a scale of about 5 arcseconds.
The study of the spectral properties of 2FHL J1745.1-3035 shows that the source is very hard at energies below 10 keV, and significantly softer in the higher energy range. According to the study, the source’s broadband X-ray spectrum is best fitted to a broken power law model with a breakdown energy of around 7 keV.
The authors of the paper conclude that the study results suggest that 2FHL J1745.1–3035 is most likely a powerful pulsar wind nebula (PWN). In general, PWNe are nebulae powered by the wind of a pulsar. The pulsar wind is composed of charged particles and when it collides with the pulsar environment, particularly with slowly expanding supernova ejecta, it develops a PWN.
If the PWN scenario for 2FHL J1745.1–3035 is confirmed by further studies, it would be one of the hardest PWNe ever detected in X-rays and the hardest ever detected in gamma rays.
More information:
Stefano Marchesi et al, 2FHLJ1745.1-3035: A powerful, newly discovered candidate for the Pulsar wind nebula, arXiv (2024). DOI: 10.48550/arxiv.2401.13806
Journal information:
arXiv
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