Detection of the linear SiC₃ and SiC₅ radicals in IRC +10216

2025/08/06 by Cernicharo, José, Pardo, Juan Ramón, Agúndez, Marcelino +6 · 1 citation
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences

paper · doi:10.48550/arxiv.2508.04509

Abstract

We detected the linear ³Σ^- radicals SiC₃ and SiC₅ toward IRC+10216 using an ultrasensitive line survey gathered with the Yebes 40 m radio telescope. The derived column densities of l-SiC₃ and l-SiC₅ are (3.6±0.4)×10¹² cm^-2 and (1.8±0.2)×10¹² cm^-2, respectively. The linear SiC₃ radical is ∼2 times less abundant that its singlet rhomboidal prolate isomer, for which we provide a new analysis based on recent sensitive observations in the Q band (7 mm), and at 3 and 2 mm with the IRAM 30m telescope. The emission detected from these species arises from the cool external layers of the circumstellar envelope. We speculate whether ion-neutral routes involving SiC_nH_m⁺ cations or neutral-neutral reactions involving Si and SiC₂ could efficiently synthesize these species.

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