Browsing by Author "Bachetti, Matteo"

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    An extremely luminous and variable ultraluminous X-ray source in the outskirts of circinus observed with nustar
    (2013) Walton, D. J.; Fürst, F.; Harrison, F. A.; Stern, D.; Bachetti, Matteo; Barret, Didier; Bauer, Franz Erik; Boggs, S. E.
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    PHASE-RESOLVED NuSTAR AND SWIFT-XRT OBSERVATIONS OF MAGNETAR 4U 0142+61
    (2015) Tendulkar, Shriharsh P.; Hascoeet, Romain; Yang, Chengwei; Kaspi, Victoria M.; Beloborodov, Andrei M.; An, Hongjun; Bachetti, Matteo; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Guiilot, Sebastien; Hailey, Charles A.; Harrison, Fiona A.; Stern, Daniel; Zhang, William
    We present temporal and spectral analysis of simultaneous 0.5-79 keV Swift-XRT and Nuclear Spectroscopic Telescope Array observations of the magnetar 4U 0142+61. The pulse profile changes significantly with photon energy between 3 and 35 keV. The pulse fraction increases with energy, reaching a value of approximate to 20%, similar to that observed in 1E 1841-045 and much lower than the approximate to 80% pulse fraction observed in 1E 2259+586. We do not detect the 55 ks phase modulation reported in previous Suzaku-HXD observations. The phase-averaged spectrum of 4U 0142+61 above 20 keV is dominated by a hard power law (PL) with a photon index Gamma(H) similar to 0.65, and the spectrum below 20 keV can be described by two blackbodies, a blackbody plus a soft PL, or by a Comptonized blackbody model. We study the full phase-resolved spectra using the e(+/-) outflow model of Beloborodov. Our results are consistent with the parameters of the active j-bundle derived from INTEGRAL data by Hascoet et al. We find that a significant degeneracy appears in the inferred parameters if the footprint of the j-bundle is allowed to be a thin ring instead of a polar cap. The degeneracy is reduced when the footprint is required to be the hot spot inferred from the soft X-ray data.
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    The high energy X-ray probe (HEX-P): Resolving the nature of Sgr A* flares, compact object binaries and diffuse X-ray emission in the Galactic center and beyond
    (2024) Mori, Kaya; Ponti, Gabriele; Bachetti, Matteo; Bodaghee, Arash; Grindlay, Jonathan; Hong, Jaesub; Krivonos, Roman; Kuznetsova, Ekaterina; Mandel, Shifra; Rodriguez, Antonio; Stel, Giovanni; Zhang, Shuo; Bao, Tong; Bauer, Franz; Clavel, Maica; Coughenour, Benjamin; Garcia, Javier A.; Gerber, Julian; Grefenstette, Brian; Jaodand, Amruta; Lehmer, Bret; Madsen, Kristin; Nynka, Melania; Predehl, Peter; Salcedo, Ciro; Stern, Daniel; Tomsick, John
    HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10 '' FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far superior to current facilities' (including XMM-Newton and NuSTAR). These capabilities will enable revolutionary new insights into a variety of important astrophysical problems. We present scientific objectives and simulations of HEX-P observations of the Galactic Center (GC) and Bulge. We demonstrate the unique and powerful capabilities of the HEX-P observatory for studying both X-ray point sources and diffuse X-ray emission. HEX-P will be uniquely equipped to explore a variety of major topics in Galactic astrophysics, allowing us to 1) investigate broad-band properties of X-ray flares emitted from the supermassive black hole (BH) at Sgr A* and probe the associated particle acceleration and emission mechanisms; 2) identify hard X-ray sources detected by NuSTAR and determine X-ray point source populations in different regions and luminosity ranges; 3) determine the distribution of compact object binaries in the nuclear star cluster and the composition of the Galactic Ridge X-ray emission; 4) identify X-ray transients and measure fundamental parameters such as black hole spin; 5) find hidden pulsars in the Galactic Center; 6) search for BH-OB binaries and hard X-ray flares from young stellar objects in young massive clusters; 7) measure white dwarf (WD) masses of magnetic CVs to deepen our understanding of CV evolution and the origin of white dwarf magnetic fields; 8) explore primary particle accelerators in the GC in synergy with future TeV and neutrino observatories; 9) map out cosmic-ray distributions by observing non-thermal X-ray filaments; 10) explore past X-ray outbursts from Sgr A* through X-ray reflection components from giant molecular clouds.