The 2011 October Draconids outburst – II. Meteoroid chemical abundances from fireball spectroscopy

Abstract

On October 8, 2011 the Earth crossed dust trails ejected from comet 21P/Giacobini-Zinner in the late 19th and early 20 th Century. This gave rise to an outburst in the activity of the October Draconid meteor shower, and an international team was organized to analyze this event. The SPanish Meteor Network (SPMN) joined this initiative and recorded the October Draconids by means of low light level CCD cameras. In addition, spectroscopic observations were carried out. Tens of multi-station meteor trails were recorded, including an extraordinarily bright October Draconid fireball (absolute mag. -10.5) that was simultaneously imaged from three SPMN meteor observing stations located in Andalusia. Its spectrum was obtained, showing a clear evolution in the relative intensity of emission lines as the fireball penetrated deeper into the atmosphere. Here we focus on the analysis of this remarkable spectrum, but also discuss the atmospheric trajectory, atmospheric penetration, and orbital data computed for this bolide which was probably released during 21P/Giacobini-Zinner return to perihelion in 1907. The spectrum is discussed together with the tensile strength for the October Draconid meteoroids. The chemical profile evolution of the main rocky elements for this extremely bright bolide is compared with the elemental abundances obtained for 5 October Draconid fireballs also recorded during our spectroscopic campaign but observed only at a single station. Significant chemical heterogeneity between the small meteoroids is found as we should expect for cometary aggregates being formed by diverse dust components.

Trajectory, orbit, and spectroscopic analysis of a bright fireball observed over Spain on April 13, 2013

“…The planes-intersection method (Ceplecha 1987) was employed to derive the atmospheric trajectory and radiant of the event. This calculation was performed with our AMALTHEA software by following the procedure described in Madiedo et al (2013bMadiedo et al ( , 2013d. When these data were known, the software computed the heliocentric orbit of the parent meteoroid by means of the procedure described in Ceplecha (1987).…”

Analysis of two superbolides with a cometary origin observed over the Iberian Peninsula

“…The observed decrease in the relative intensity of the Na I-1 line could be related to a decrease in the Na content along the atmospheric trajectory of the fireball. This would suggest an early release of Na, a behaviour that has also been found in, for instance, October Draconid meteors (Borovička et al, 2007;Madiedo et al, 2013c). Nevertheless, the calculation of the relative abundances and physical conditions in the meteor plasma is out of the scope of this work.…”

An Earth-grazing fireball from the Daytime ζ-Perseid shower observed over Spain on 2012 June 10

“…In this way, the maximum aerodynamic pressure yields (5.4 ± 0.4)·10 3 dyn cm -2 . As a comparison, since no flares are observed in the lightcurve (which means that the meteoroid did not experience any sudden disruption during its atmospheric path), we can conclude that this particle was tougher that the material forming weak cometary aggregates typical of large October Draconid meteoroids, which exhibit a tensile strength of about 1.4·10 3 dyn cm -2 , or even below (Sekanina 1985;Madiedo et al 2013c). …”