Detection of the linear SiC${}_3$ and SiC${}_5$ radicals in IRC\,+10216

Abstract

We detected the linear ${}^3{\Sigma }^{-}$ radicals SiC${}_3$ and SiC${}_5$ toward IRC+10216 using an ultrasensitive line survey gathered with the Yebes 40\,m radio telescope. The derived column densities of $l$-SiC${}_3$ and $l$-SiC${}_5$ are (3.6$\pm$0.4)$\times$10${}^{12}$ cm${}^{-2}$ and (1.8$\pm$0.2)$\times$10${}^{12}$ cm${}^{-2}$, respectively. The linear SiC${}_3$ radical is $\sim$2 times less abundant that its singlet rhomboidal prolate isomer, for which we provide a new analysis based on recent sensitive observations in the Q band (7\,mm), and at 3 and 2\,mm with the IRAM 30m telescope. The emission detected from these species arises from the cool external layers of the circumstellar envelope. We speculate whether ion-neutral routes involving SiC${}_n$H${}_m$${}^{+}$ cations or neutral-neutral reactions involving Si and SiC${}_2$ could efficiently synthesize these species.

Letter accepted for publication in Astronomy & Astrophysics

References in corpus (12)

• Pure hydrocarbon cycles in TMC-1: Discovery of ethynyl cyclopropenylidene, cyclopentadiene and indene
• Discovery of benzyne, o-C6H4, in TMC-1 with the QUIJOTE line survey
• Yebes 40 m radio telescope and the broad band NANOCOSMOS receivers at 7 mm and 3 mm for line surveys
• Discovery of two cyano derivatives of acenaphthylene (C${}_{12}$H${}_8$) in TMC-1 with the QUIJOTE line survey
• Si-bearing molecules towards IRC+10216: ALMA unveils the molecular envelope of CWLeo
• Discovery of the C7N- anion in TMC-1 and IRC+10216
• The magnesium paradigm in IRC+10216: Discovery of MgC${}_4$H${}^{+}$, MgC${}_3$N${}^{+}$, MgC${}_6$H${}^{+}$, and MgC${}_5$N${}^{+}$
• Magnesium radicals MgC${}_5$N and MgC${}_6$H in IRC+10216
• Laboratory and astronomical discovery of magnesium dicarbide, MgC${}_2$
• The complex dust formation zone of the AGB star IRC+10216 probed with CARMA 0.25 arcsec angular resolution molecular observations
• Discovery of two metallic cyanoacetylides in IRC+10216: HMgCCCN and NaCCCN
• Atmospheric molecular blobs shape up circumstellar envelopes of AGB stars

Cited by in corpus (1)

• A quest for sulfur-bearing refractory species. Identification of CaS in the interstellar medium