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| 2. |
- Larsson, Josefin, et al.
(författare)
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The Matter Beyond the Ring : The Recent Evolution of SN 1987A Observed by the Hubble Space Telescope
- 2019
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 886:2
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Tidskriftsartikel (refereegranskat)abstract
- The nearby SN 1987A offers a spatially resolved view of the evolution of a young supernova (SN) remnant. Here we present recent Hubble Space Telescope imaging observations of SN 1987A, which we use to study the evolution of the ejecta, the circumstellar equatorial ring (ER), and the increasing emission from material outside the ER. We find that the inner ejecta have been brightening at a gradually slower rate and that the western side has been brighter than the eastern side since similar to 7000 days. This is expected given that the X-rays from the ER are most likely powering the ejecta emission. At the same time, the optical emission from the ER continues to fade linearly with time. The ER is expanding at 680 50 km s(-1), which reflects the typical velocity of transmitted shocks in the dense hot spots. A dozen spots and a rim of diffuse H alpha emission have appeared outside the ER since 9500 days. The new spots are more than an order of magnitude fainter than the spots in the ER and also fade faster. We show that the spots and diffuse emission outside the ER may be explained by fast ejecta interacting with high-latitude material that extends from the ER toward the outer rings. Further observations of this emission will make it possible to determine the detailed geometry of the high-latitude material and provide insight into the formation of the rings and the mass-loss history of the progenitor.
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| 3. |
- Larsson, Josefin, et al.
(författare)
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THREE-DIMENSIONAL DISTRIBUTION OF EJECTA IN SUPERNOVA 1987A AT 10,000 DAYS
- 2016
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Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 833:2
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Tidskriftsartikel (refereegranskat)abstract
- Due to its proximity, SN. 1987A offers a unique opportunity to directly observe the geometry of a stellar explosion as it unfolds. Here we present spectral and imaging observations of SN. 1987A obtained similar to 10,000 days after the explosion with HST/STIS and VLT/SINFONI at optical and near-infrared wavelengths. These observations allow us to produce the most detailed 3D map of Ha to date, the first 3D maps for [Ca II] lambda lambda 7292, 7324, [O I] lambda lambda 6300, 6364, and Mg. II lambda lambda 9218, 9244, as well as new maps for [Si I]+[Fe II] 1.644 mu m and He I 2.058 mu m. A comparison with previous observations shows that the [Si I]+[Fe II] flux and morphology have not changed significantly during the past ten years, providing evidence that this line is powered by Ti-44. The time evolution of Ha shows that it is predominantly powered by X-rays from the ring, in agreement with previous findings. All lines that have sufficient signal show a similar large-scale 3D structure, with a north-south asymmetry that resembles a broken dipole. This structure correlates with early observations of asymmetries, showing that there is a global asymmetry that extends from the inner core to the outer envelope. On smaller scales, the two brightest lines, Ha and [Si I]+[Fe II] 1.644 mu m, show substructures at the level of similar to 200-1000 km s(-1) and clear differences in their 3D geometries. We discuss these results in the context of explosion models and the properties of dust in the ejecta.
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| 4. |
- Taddia, Francesco, et al.
(författare)
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Long-rising Type II supernovae from Palomar Transient Factory and Caltech Core-Collapse Project
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 588
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Tidskriftsartikel (refereegranskat)abstract
- Context. Supernova (SN) 1987A was a peculiar hydrogen-rich event with a long-rising (similar to 84 d) light curve, stemming from the explosion of a compact blue supergiant star. Only a few similar events have been presented in the literature in recent decades. Aims. We present new data for a sample of six long-rising Type II SNe (SNe II), three of which were discovered and observed by the Palomar Transient Factory (PTF) and three observed by the Caltech Core-Collapse Project (CCCP). Our aim is to enlarge this small family of long-rising SNe II, characterizing their differences in terms of progenitor and explosion parameters. We also study the metallicity of their environments. Methods. Optical light curves, spectra, and host-galaxy properties of these SNe are presented and analyzed. Detailed comparisons with known SN 1987A-like events in the literature are shown, with particular emphasis on the absolute magnitudes, colors, expansion velocities, and host-galaxy metallicities. Bolometric properties are derived from the multiband light curves. By modeling the early-time emission with scaling relations derived from the SuperNova Explosion Code (SNEC) models of MESA progenitor stars, we estimate the progenitor radii of these transients. The modeling of the bolometric light curves also allows us to estimate other progenitor and explosion parameters, such as the ejected Ni-56 mass, the explosion energy, and the ejecta mass. Results. We present PTF12kso, a long-rising SN II that is estimated to have the largest amount of ejected Ni-56 mass measured for this class. PTF09gpn and PTF12kso are found at the lowest host metallicities observed for this SN group. The variety of early light-curve luminosities depends on the wide range of progenitor radii of these SNe, from a few tens of R-circle dot (SN 2005ci) up to thousands (SN 2004ek) with some intermediate cases between 100 R-circle dot (PTF09gpn) and 300 R-circle dot (SN 2004em). Conclusions. We confirm that long-rising SNe II with light-curve shapes closely resembling that of SN 1987A generally arise from blue supergiant (BSG) stars. However, some of them, such as SN 2004em, likely have progenitors with larger radii (similar to 300 R-circle dot, typical of yellow supergiants) and can thus be regarded as intermediate cases between normal SNe IIP and SN 1987A-like SNe. Some extended red supergiant (RSG) stars such as the progenitor of SN 2004ek can also produce long-rising SNe II if they synthesized a large amount of Ni-56 in the explosion. Low host metallicity is confirmed as a characteristic of the SNe arising from compact BSG stars.
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