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Your search keyword '"Angelini L."' showing total 34 results
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34 results on '"Angelini L."'

1. A Search for the 3.5 keV Line from the Milky Way's Dark Matter Halo with HaloSat.

Author

Silich, E. M., Jahoda, K., Angelini, L., Kaaret, P., Zajczyk, A., LaRocca, D. M., Ringuette, R., and Richardson, J.

Subjects
DARK matter, STERILE neutrinos, GALACTIC center, GALACTIC halos, GALACTIC X-ray sources, GALAXY clusters, X-ray detection
Abstract

Previous detections of an X-ray emission line near 3.5 keV in galaxy clusters and other dark-matter-dominated objects have been interpreted as observational evidence for the decay of sterile neutrino dark matter. Motivated by this, we report on a search for a 3.5 keV emission line from the Milky Way's galactic dark matter halo with HaloSat. As a single pixel, collimated instrument, HaloSat observations are impervious to potential systematic effects due to grazing incidence reflection and CCD pixelization, and thus may offer a check on possible instrumental systematic errors in previous analyses. We report nondetections of a ∼3.5 keV emission line in four HaloSat observations near the Galactic center. In the context of the sterile neutrino decay interpretation of the putative line feature, we provide 90% confidence level upper limits on the 3.5 keV line flux for a field centered 18.6 degrees from the Galactic center and the corresponding 7.1 keV sterile neutrino mixing angle: F ≤ 0.077 ph cm−2 s−1 sr−1 and. The HaloSat mixing angle upper limit was calculated using a modern parameterization of the Milky Way's dark matter distribution, and in order to compare with previous limits, we also report the limit calculated using a common historical model. The HaloSat mixing angle upper limit places constraints on a number of previous mixing angle estimates derived from observations of the Milky Way's dark matter halo and galaxy clusters, and excludes several previous detections of the line. The upper limits cannot, however, entirely rule out the sterile neutrino decay interpretation of the 3.5 keV line feature. [ABSTRACT FROM AUTHOR]

Published
2021
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10. Swift Observations of GRB 050128: The Early X-Ray Afterglow.

Author

Campana, S., Antonelli, L. A., Chincarini, G., Covino, S., Cusumano, G., Malesani, D., Mangano, V., Moretti, A., Pagani, C., Romano, P., Tagliaferri, G., Capalbi, M., Perri, M., Giommi, P., Angelini, L., Boyd, P., Burrows, D. N., Hill, J. E., Gronwall, C., and Kennea, J. A.

Published
2005
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11. The Swift Gamma-Ray Burst Mission.

Author

Gehrels, N., Chincarini, G., Giommi, P., Mason, K. O., Nousek, J. A., Wells, A. A., White, N. E., Barthelmy, S. D., Burrows, D. N., Cominsky, L. R., Hurley, K. C., Marshall, F. E., Mészáros, P., Roming, P. W. A., Angelini, L., Barbier, L. M., Belloni, T., Campana, S., Caraveo, P. A., and Chester, M. M.

Published
2004
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12. POSSIBLE DETECTION OF AN EMISSION CYCLOTRON RESONANCE SCATTERING FEATURE FROM THE ACCRETION-POWERED PULSAR 4U 1626–67.

Author

Iwakiri, W. B., Terada, Y., Mihara, T., Angelini, L., Tashiro, M. S., Enoto, T., Yamada, S., Makishima, K., Nakajima, M., and Yoshida, A.

Subjects
CYCLOTRONS, ACCRETION (Astrophysics), PULSARS, STARS, X-ray binaries
Abstract

We present analysis of 4U 1626–67, a 7.7 s pulsar in a low-mass X-ray binary system, observed with the hard X-ray detector of the Japanese X-ray satellite Suzaku in 2006 March for a net exposure of ∼88 ks. The source was detected at an average 10-60 keV flux of ∼4 × 10–10 erg cm–2 s–1. The phase-averaged spectrum is reproduced well by combining a negative and positive power-law times exponential cutoff (NPEX) model modified at ∼37 keV by a cyclotron resonance scattering feature (CRSF). The phase-resolved analysis shows that the spectra at the bright phases are well fit by the NPEX with CRSF model. On the other hand, the spectrum in the dim phase lacks the NPEX high-energy cutoff component, and the CRSF can be reproduced by either an emission or an absorption profile. When fitting the dim phase spectrum with the NPEX plus Gaussian model, we find that the feature is better described in terms of an emission rather than an absorption profile. The statistical significance of this result, evaluated by means of an F test, is between 2.91 × 10–3 and 1.53 × 10–5, taking into account the systematic errors in the background evaluation of HXD-PIN. We find that the emission profile is more feasible than the absorption one for comparing the physical parameters in other phases. Therefore, we have possibly detected an emission line at the cyclotron resonance energy in the dim phase. [ABSTRACT FROM AUTHOR]

Published
2012
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