Table 2
Spectroscopic properties of HCN transitions.
| HCN transition | Rest frequency(a) | Eup (b) | Aul (b) | SOFIA/4GREAT (c) | Herschel/HIFI (d) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| (v1, v2, v3) | J | Channel | HPBW | ηmb | Factor(e) | Obs. (f) | Band | HPBW | ηmb | Factor(e) | |||
| (GHz) | (K) | (s−1) | (′′) | (Jy K−1) | (′′) | (Jy K−1) | |||||||
| (0,40,0) | 9−8 | 804.7509 | 4226.1 | 2.3 × 10−2 | − | − | − | − | − | 3a | 26.1 | 0.63 | 355 |
| (0,40,0) | 10−9 | 894.4142 | 4269.0 | 3.1 × 10−2 | − | − | − | − | − | 3 b | 23.6 | 0.63 | 353 |
| (1,11e,0)−(0,40,0) | 10−9 | 890.7607 | 4268.8 | … | 4G2 (LSB) | 31.4 | 0.56 | 609 | 1 | 3b | 23.6 | 0.63 | 353 |
| (1,11e,0)−(0,40,0) | 11−10 | 964.3134 | 4315.3 | … | 4G2 (USB) | 28.8 | 0.56 | 599 | 1,2,3,4 | 4 a | 21.8 | 0.64 | 359 |
| (1,11e,0) | 11−10 | 967.9658 | 4315.3 | 4.3 × 10−2 | 4G2 (USB) | 28.8 | 0.56 | 598 | 1,2,3,4 | 4a | 21.7 | 0.64 | 359 |
| (1,11e,0) | 12−11 | 1055.54† | 4365.9 | 5.6 × 10−2 | 4G2 (LSB) | 26.2 | 0.56 | 588 | 1 | 4a/4b | 20.0 | 0.64 | 378 |
Notes. The HCN transitions at 805 and 894 GHz were not observed by SOFIA, as marked by “–” in the corresponding rows. (a) The frequencies of HCN transitions are adopted from Hocker & Javan (1967), with the exception of that of the 1055 GHz line whose frequency is estimated from our detection, labelled by a dagger. (b) The energy of the upper level and the Einstein A coefficient of each transition are adopted from Harris et al. (2006) and Barber et al. (2014), while the Einstein A coefficients for the 891 and 964 GHz lines are not given, labelled as “…”. (c) Reference: Durán et al. (2021). (d) Reference: Shipman et al. (2017). (e) Scaling factors to convert main-beam temperature to flux density. The factors for Herschel/HIFI data are the averages of H and V polarisations. (f) Observed sources at the corresponding transition: (1) IRC+10216; (2) CIT 6; (3) Y CVn; (4) S Cep.
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