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24th of June 2016
ATCA maps molecules in η Carina
by Laurent Loinard (UNAM)
η Carinae is one of the most massive stellar sources in the Milky Way. It entered the Hall of Fame of astronomy in the mid 19th century when it underwent a major outburst, temporarily becoming the second brightest star at visible wavelengths in the entire sky. Known as the Great Eruption, this event led to the ejection of at least ten solar masses of material now distributed in a bipolar, vaguely anthropomorphic, nebula called the Homunculus. Using the Australia Telescope Compact Array (ATCA), we have mapped the distribution of the hydrogen cyanide molecule (HCN) in the innermost circumstellar environment around η Carinae. Given the extent and location of this molecular material, we associate it with the complex of dusty arcs and knots seen in mid-infrared emission along the equatorial plane of the Homunculus nebula. The dust located in the central few arcseconds around η Carinae and the molecular component described here have most likely formed in situ, out of material expelled by the central stars in the system over the 180 years that elapsed since the Great Eruption of the 1840s. Thus, Carinae offers us a rare glimpse on the processes leading to the formation of dust and molecules around massive stars that are so relevant to the interpretation of dust and molecule detections at high redshift. The successful calibration of these ATCA data was only possible thanks to the expert help received during the ATNF data reduction workshop organized in May 2016.

Reference: L. Loinard, T., Kaminski, P. Serra, K. Menten, L. Zapata, L. Rodriguez 2016, ApJ, submitted

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