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A decade of SN 1993J : discovery of radio wavelength effects in the expansion rate

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A decade of SN 1993J : discovery of radio wavelength effects in the expansion rate

dc.contributor.author	Marcaide Osoro, Juan María
dc.contributor.author	Martí Vidal, Iván
dc.contributor.author	Alberdi, A.
dc.contributor.author	Pérez Torres, Miguel Ángel
dc.contributor.author	Ros Ibarra, Eduardo
dc.contributor.author	Diamond, P. J.
dc.contributor.author	Guirado Puerta, Jose Carlos
dc.contributor.author	Lara, L.
dc.contributor.author	Shapiro, I.I.
dc.contributor.author	Stockdale, C.J.
dc.contributor.author	Weiler, K. W.
dc.contributor.author	Mantovani, F.
dc.contributor.author	Preston, R.A.
dc.contributor.author	Schilizzi, R. T.
dc.contributor.author	Sramek, R.A.
dc.contributor.author	Trigilio, C.
dc.contributor.author	Van Dyk, S. D.
dc.contributor.author	Whitney, A. R.
dc.date.accessioned	2010-06-21T10:46:13Z
dc.date.available	2010-06-21T10:46:13Z
dc.date.issued	2009
dc.identifier.citation	Marcaide Osoro, Juan María, et al. (2009): A decade of SN 1993J : discovery of radio wavelength effects in the expansion rate, Astronomy and Astrophysics, vol. 505, núm. 3, pp. 927-945	en
dc.identifier.uri	http://hdl.handle.net/10550/13041
dc.description.abstract	We studied the growth of the shell-like radio structure of supernova SN 1993J in M 81 from September 1993 to October 2003 with very-long-baseline interferometry (VLBI) observations at the wavelengths of 3.6, 6, and 18 cm. We developed a method to accurately determine the outer radius (R) of any circularly symmetric compact radio structure such as SN 1993J. The source structure of SN 1993J remains circularly symmetric (with deviations from circularity under 2%) over almost 4000 days. We characterize the decelerated expansion of SN 1993J until approximately day 1500 after explosion with an expansion parameter m = 0.845 ± 0.005 (R ∝ tm). However, from that day onwards the expansion differs when observed at 6 and 18 cm. Indeed, at 18 cm, the expansion can be well characterized by the same m as before day 1500, while at 6 cm the expansion appears more decelerated, and is characterized by another expansion parameter, m6 = 0.788 ± 0.015. Therefore, since about day 1500 onwards, the radio source size has been progressively smaller at 6 cm than at 18 cm. These findings differ significantly from those of other authors in the details of the expansion. In our interpretation, the supernova expands with a single expansion parameter, m = 0.845 ± 0.005, and the 6 cm results beyond day 1500 are caused by physical effects, perhaps also coupled to instrumental limitations. Two physical effects may be involved: (a) a changing opacity of the ejecta to the 6 cm radiation; and (b) a radial decrease of the magnetic field in the emitting region. We also found that at 6 cm about 80% of the radio emission from the backside of the shell behind the ejecta is absorbed (our average estimate, since we cannot determine any possible evolution of the opacity), and the width of the radio shell is (31 ± 2)% of the outer radius. The shell width at 18 cm depends on the degree of assumed absorption. For 80% absorption, the width is (33.5 ± 1.7)%, and for 100% absorption, it is (37.8 ± 1.3)%. A comparison of our VLBI results with optical spectral line velocities shows that the deceleration is more pronounced in the radio than in the optical. This difference might be due to a progressive penetration of ejecta instabilities into the shocked circumstellar medium, as also suggested by other authors.	en
dc.language.iso	en	en
dc.subject	Galaxies : clusters : individual : M 81; Radio continuum : stars; Supernovae : general; Supernovae : individual : SN 1993J; Techniques : interferometric	en
dc.title	A decade of SN 1993J : discovery of radio wavelength effects in the expansion rate	en
dc.type	journal article	es_ES
dc.subject.unesco	UNESCO::ASTRONOMÍA Y ASTROFÍSICA::Cosmología y cosmogonia::Galaxias	en
dc.subject.unesco	UNESCO::ASTRONOMÍA Y ASTROFÍSICA::Cosmología y cosmogonia::Estrellas	en
dc.identifier.doi	10.1051/0004-6361/200912133	en
dc.type.hasVersion	VoR	es_ES
dc.identifier.url	http://www.aanda.org/index.php?option=article&access=doi&doi=10.1051/0004-6361/200912133	en