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Sökning: WFRF:(Jencson J. E.) > (2017)

  • Resultat 1-3 av 3
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  • Kasliwal, M. M., et al. (författare)
  • Illuminating gravitational waves : A concordant picture of photons from a neutron star merger
  • 2017
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 358:6370, s. 1559-
  • Tidskriftsartikel (refereegranskat)abstract
    • Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.
  • Blagorodnova, N., et al. (författare)
  • 2017
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 834:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results of optical, near-infrared, and mid-infrared observations of M101 OT2015-1 (PSN J14021678+ 5426205), a luminous red transient in the Pinwheel galaxy (M101), spanning a total of 16 years. The light curve showed two distinct peaks with absolute magnitudes M-r <= -12.4 and M-r similar or equal to -12, on 2014 November 11 and 2015 February 17, respectively. The spectral energy distributions during the second maximum show a cool outburst temperature of approximate to 3700 K and low expansion velocities (approximate to -300 km s(-1)) for the H I, Ca II, Ba II, and K I lines. From archival data spanning 15-8 years before the outburst, we find a single source consistent with the optically discovered transient, which we attribute to being the progenitor; it has properties consistent with being an F-type yellow supergiant with L similar to 8.7 x 10(4) L-circle dot, T-eff approximate to 7000. K, and an estimated mass of M1= 18 +/- 1 M-circle dot. This star has likely just finished the H-burning phase in the core, started expanding, and is now crossing the Hertzsprung gap. Based on the combination of observed properties, we argue that the progenitor is a binary system, with the more evolved system overfilling the Roche lobe. Comparison with binary evolution models suggests that the outburst was an extremely rare phenomenon, likely associated with the ejection of the common envelope of a massive star. The initial mass of the primary fills the gap between the merger candidates V838 Mon (5-10 M-circle dot) and NGC. 4490-OT. (30M(circle dot)).
  • Johansson, Joel, et al. (författare)
  • Spitzer observations of SN 2014J and properties of mid-IR emission in Type Ia supernovae
  • 2017
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 466:3, s. 3442-3449
  • Tidskriftsartikel (refereegranskat)abstract
    • SN 2014J in M 82 is the closest Type Ia supernova (SN Ia) in decades. The proximity allows for detailed studies of supernova physics and provides insights into the circumstellar and interstellar environment. In this work, we analyse Spitzer mid-infrared (mid-IR) data of SN 2014J in the 3.6 and 4.5 mu m wavelength range, together with several other nearby and well-studied SNe Ia. We compile the first composite mid-IR light-curve templates from our sample of SNe Ia, spanning the range from before peak brightness well into the nebular phase. Our observations indicate that SNe Ia form a very homogeneous class of objects at these wavelengths. Using the low-reddening supernovae for comparison, we constrain possible thermal emission from circumstellar dust around the highly reddened SN 2014J. We also study SNe 2006X and 2007le, where the presence of matter in the circumstellar environment has been suggested. No significant mid-IR excess is detected, allowing us to place upper limits on the amount of pre-existing dust in the circumstellar environment. For SN 2014J, M-dust less than or similar to 10(-5) M-circle dot within r(dust) similar to 10(17) cm, which is insufficient to account for the observed extinction. Similar limits are obtained for SNe 2006X and 2007le.
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  • Resultat 1-3 av 3

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