Claes Fransson
Stockholm University, Department of Astronmy, Faculty Member
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After nearly two decades at least five emission mechanisms can be found in SN 1987A. The ejecta continue to glow as a result of the radioactive decay of long-lived nuclei (mostly 44Ti), but is fading continuously because of the expansion... more
After nearly two decades at least five emission mechanisms can be found in SN 1987A. The ejecta continue to glow as a result of the radioactive decay of long-lived nuclei (mostly 44Ti), but is fading continuously because of the expansion and the reduced opacity. The nearly stationary rings around SN 1987A are still fluorescing from the recombination of matter originally excited by the soft X-ray emission from the shock breakout at explosion. The supernova shock reached the inner circumstellar ring about ten years ago and the forward shock is moving through the inner ring and leaves shocked material behind. This material is excited and accelerated. The reverse shock illuminates the fast-moving supernova ejecta as it catches up. And, finally light echoes in nearby interstellar matter can still be observed. We present here high resolution spectroscopy in the optical and integral-field spectroscopy in the near infrared of SN 1987A and its rings.
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The narrow emission lines from the inner ring around SN 1987A during the first $\sim 2000$ days are modeled. The analysis extends that in Lundqvist & Fransson (1991) to include an improved description for the geometry, a multi-density... more
The narrow emission lines from the inner ring around SN 1987A during the first $\sim 2000$ days are modeled. The analysis extends that in Lundqvist & Fransson (1991) to include an improved description for the geometry, a multi-density structure of the emitting gas, results from improved calculations for the evolu- tion of the EUV radiation from the outburst, and updated atomic data. The ring has to be optically thick to the ionizing radiation, as is the case for a ring geometry, but not for a spherical shell. The density of the observed gas in the ring ranges from $(6.0\pm1.0)\EE{3} \cm3$ to $3.3\EE{4} \cm3$. The early ($t \lesssim 410$ days) UV line emission is dominated by the gas with the high- est density. Gas of lower density than $\sim 6\EE{3} \cm3$ may be present in the ring, but will not dominate the emission until after $\sim 2000$ days. The ionized mass observed up to day 1882 is $\sim 4.5\EE{-2} \Msun$. The He/H ratio is $0.25\pm0.05$, and the overall abundance of C, N and O is $0.30\pm0.05$ times solar with relative abundances ${\rm N/C} = 5.0\pm2.0$ and ${\rm N/O} = 1.1\pm0. 4$. The peak effective temperature of the burst is in the range $(5-8)\EE{5}$ K. The corresponding color temperature is $(1.0-1.5)\EE6$ K. To model the $\NV$~ $\lambda$1240 light curve, resonance scattering in a medium external to the ring is needed. It is shown that the $\NV$ line scattering can be used to discrimi- nate between models for the formation of the inner ring and the extended nebula.
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... Schuyler D. Van Dyk2, Chien Y. Peng3, Aaron J. Barth4, and Alexei V. Filippenko Department of Astronomy, University of California, Berkeley, CA 94720-3411 ... SN 1979C is also a bright late-time radio source (Weiler et al. 1986,... more
... Schuyler D. Van Dyk2, Chien Y. Peng3, Aaron J. Barth4, and Alexei V. Filippenko Department of Astronomy, University of California, Berkeley, CA 94720-3411 ... SN 1979C is also a bright late-time radio source (Weiler et al. 1986, 1991). ...
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ABSTRACT We report spectroscopic and imaging observations of rotational transitions of cold CO and SiO in the ejecta of SN1987A, the first such emission detected in a supernova remnant. In addition to line luminosities for the CO J=1-0,... more
ABSTRACT We report spectroscopic and imaging observations of rotational transitions of cold CO and SiO in the ejecta of SN1987A, the first such emission detected in a supernova remnant. In addition to line luminosities for the CO J=1-0, 2-1, 6-5, and 7-6 transitions, we present upper limits for all other transitions up to J=13-12, collectively measured from the Atacama Large Millimeter Array (ALMA), the Atacama Pathfinder EXperiment (APEX), and the Herschel Spectral and Photometric Imaging REceiver (SPIRE). Simple models show the lines are emitted from at least 0.01 solar masses of CO at a temperature > 14 K, confined within at most 35% of a spherical volume expanding at ~ 2000 km/s. Moreover, we locate the emission within 1'' of the central debris. These observations, along with a partial observation of SiO, confirm the presence of cold molecular gas within supernova remnants and provide insight into the physical conditions and chemical processes in the ejecta. Furthermore, we demonstrate the powerful new window into supernova ejecta offered by submillimeter observations.
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Astrophys Space Sci (2006) 303:6984 DOI 10.1007/s10509-005-9012-9 ... The Need for Ultraviolet to Understand the Chemical Evolution ... Willem Wamsteker · Jason X. Prochaska · Luciana Bianchi · Dieter Reimers · Nino Panagia · Andrew C.... more
Astrophys Space Sci (2006) 303:6984 DOI 10.1007/s10509-005-9012-9 ... The Need for Ultraviolet to Understand the Chemical Evolution ... Willem Wamsteker · Jason X. Prochaska · Luciana Bianchi · Dieter Reimers · Nino Panagia · Andrew C. Fabian · Claes Fransson · Boris M. ...