| 1. |
- Abdo, A. A., et al.
(författare)
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PULSED GAMMA-RAYS FROM PSR J2021+3651 WITH THE FERMI LARGE AREA TELESCOPE
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 700:2, s. 1059-1066
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Tidskriftsartikel (refereegranskat)abstract
- We report the detection of pulsed gamma-rays from the young, spin-powered radio pulsar PSR J2021+3651 using data acquired with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). The light curve consists of two narrow peaks of similar amplitude separated by 0.468 +/- 0.002 in phase. The first peak lags the maximum of the 2 GHz radio pulse by 0.162 +/- 0.004 +/- 0.01 in phase. The integral gamma-ray photon flux above 100 MeV is (56 +/- 3 +/- 11) x 10(-8) cm(-2) s(-1). The photon spectrum is well described by an exponentially cut-off power law of the form dF/dE = kE(-Gamma)e((-E/Ec)), where the energy E is expressed in GeV. The photon index is Gamma = 1.5 +/- 0.1 +/- 0.1 and the exponential cut-off is E-c = 2.4 +/- 0.3 +/- 0.5 GeV. The first uncertainty is statistical and the second is systematic. The integral photon flux of the bridge is approximately 10% of the pulsed emission, and the upper limit on off-pulse gamma-ray emission from a putative pulsar wind nebula is < 10% of the pulsed emission at the 95% confidence level. Radio polarization measurements yield a rotation measure of RM = 524 +/- 4 rad m(-2) but a poorly constrained magnetic geometry. Re-analysis of Chandra X-ray Observatory data enhanced the significance of the weak X-ray pulsations, and the first peak is roughly phase aligned with the first gamma-ray peak. We discuss the emission region and beaming geometry based on the shape and spectrum of the gamma-ray light curve combined with radio and X-ray measurements, and the implications for the pulsar distance. Gamma-ray emission from the polar cap region seems unlikely for this pulsar.
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| 2. |
- Marcote, B., et al.
(författare)
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A repeating fast radio burst source localized to a nearby spiral galaxy
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 577:7789, s. 190-194
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Tidskriftsartikel (refereegranskat)abstract
- Fast radio bursts (FRBs) are brief, bright, extragalactic radio flashes1,2. Their physical origin remains unknown, but dozens of possible models have been postulated3. Some FRB sources exhibit repeat bursts4–7. Although over a hundred FRB sources have been discovered8, only four have been localized and associated with a host galaxy9–12, and just one of these four is known to emit repeating FRBs9. The properties of the host galaxies, and the local environments of FRBs, could provide important clues about their physical origins. The first known repeating FRB, however, was localized to a low-metallicity, irregular dwarf galaxy, and the apparently non-repeating sources were localized to higher-metallicity, massive elliptical or star-forming galaxies, suggesting that perhaps the repeating and apparently non-repeating sources could have distinct physical origins. Here we report the precise localization of a second repeating FRB source6, FRB 180916.J0158+65, to a star-forming region in a nearby (redshift 0.0337 ± 0.0002) massive spiral galaxy, whose properties and proximity distinguish it from all known hosts. The lack of both a comparably luminous persistent radio counterpart and a high Faraday rotation measure6 further distinguish the local environment of FRB 180916.J0158+65 from that of the single previously localized repeating FRB source, FRB 121102. This suggests that repeating FRBs may have a wide range of luminosities, and originate from diverse host galaxies and local environments.
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| 3. |
- Eftekhari, T., et al.
(författare)
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A Radio Source Coincident with the Superluminous Supernova PTF10hgi : Evidence for a Central Engine and an Analog of the Repeating FRB 121102?
- 2019
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 876:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the detection of an unresolved radio source coincident with the position of the Type I superluminous supernova (SLSN) PTF10hgi (z = 0.098) about 7.5 yr post-explosion, with a flux density of F-nu(6 GHz) approximate to 47.3 mu Jy and a luminosity of L-nu(6 GHz) approximate to 1.1 x 10(28) erg s(-1) Hz(-1). This represents the first detection of radio emission coincident with an SLSN on any timescale. We investigate various scenarios for the origin of the radio emission: star formation activity, an active galactic nucleus, and a non-relativistic supernova blastwave. While any of these would be quite novel if confirmed, none appear likely when considered within the context of the other properties of the host galaxy, previous radio observations of SLSNe, and the general population of hydrogen-poor supernovae (SNe). Instead, the radio emission is reminiscent of the quiescent radio source associated with the repeating FRB 121102, which has been argued to be powered by a magnetar born in a SLSN or long gamma-ray burst explosion several decades ago. We show that the properties of the radio source are consistent with a magnetar wind nebula or an off-axis jet, indicating the presence of a central engine. Our directed search for fast radio bursts from the location of PTF10hgi using 40 minutes of Very Large Array phased-array data reveals no detections to a limit of 22 mJy (10 sigma; 10 ms duration). We outline several follow-up observations that can conclusively establish the origin of the radio emission.
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