Discovery of two metallic cyanoacetylides in IRC +10216: HMgCCCN and NaCCCN

Abstract

We report on the detection of a series of six lines in the ultra-deep Q-band integration towards IRC +10216 carried out with the Yebes 40m telescope, which are in harmonic relation with integer quantum numbers J u from 12 to 18. After a detailed analysis of all possible carriers, guided by high-level quantum chemical calculations, we conclude that the lines belong to HMgCCCN, named hydridomagnesium cyanoacetylide. The rotational temperature and column density derived for HMgCCCN are 17.1 ± 2.8 K and (3.0 ± 0.6) × 10 12 cm −2 , respectively. The observed abundance ratio between MgCCCN and HMgCCCN is approximately three. In addition, we report the discovery in space, also towards IRC +10216, of sodium cyanoacetylide, NaCCCN, for which accurate laboratory data are available. For this species we derived a rotational temperature of 13.5 ± 1.7 K and a column density of (1.2 ± 0.2) × 10 11 cm −2 .

The magnesium paradigm in IRC +10216: Discovery of MgC4H+, MgC3N+, MgC6H+, and MgC5N+

“…However, AlCCCN has not yet been detected in our data. NaCCCN has been recently reported by Cabezas et al (2023), but its lines are very weak and its possible isomers have rotational constants that do not agree with those of our series (see Table B.2). Molecules such as CaC 4 H, CaC 3 N, KC 4 H, and KC 3 N produce rotational constants below 1000 MHz (Cabezas et al 2019).…”

“…than three atoms in IRC +10216 is magnesium. These species are MgCCH (Agúndez et al 2014;Cernicharo et al 2019b), HMgNC (Cabezas et al 2013), MgC 4 H, MgC 3 N (Cernicharo et al 2019b), MgC 6 H, MgC 5 N (Pardo et al 2021), HMgCCCN, and NaCCCN (Cabezas et al 2023). The observed abundances for these species are well reproduced adopting the formation mechanism proposed by Dunbar & Petrie (2002).…”

“…The intensity scale used in this work, antenna temperature (T * A ), was calibrated using two absorbers at different temperatures and the atmospheric transmission model ATM (Cernicharo 1985;Pardo et al 2001). Calibration uncertainties were adopted to be 10 % for both the IRAM 30m data and the Yebes 40m data.…”

“…Polyatomic metal-containing molecules are detected only toward the circumstellar envelopes of evolved stars. Diatomic molecules with Al, Na, or K, and a halogen atom have been detected in the prototypical carbon star envelope IRC +10216 (Cernicharo & Guélin 1987). These species are formed in the hot inner parts of the envelope, close to the star.…”

Spectroscopic Study of [Mg, H, N, C, O] Species: Implications for the Astrochemical Magnesium Chemistry

“…Later on, its metastable isomer MgCN and the hydrogenated compound HMgNC were also detected. To date, the molecular inventory detected in the ISM comprises about 30 metal-containing species, and the family of Mg-bearing species (MgNC, MgCN, HMgNC, MgC 3 N, HMgC 3 N, MgC 3 N + , MgC 5 N, MgC 2 , MgC 2 H, MgC 4 H, MgC 6 H) is the most abundant. − It is noteworthy that all these species are detected in the same region of the outer shells of the asymptotic giant branch star IRC+10216, strongly implying the possibility of synthetic connectivity through the reactions of the magnesium atom with other molecules in this region. Models for astrochemical magnesium chemistry propose that gas-phase metals coexist in the neutral (Mg) and ionized (Mg + ) forms due to the readily ionized nature of magnesium, ,,, and photochemical reactions also serve as important driving forces for the production of new molecules. − …”