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We report on the detection of a series of six lines in the ultra-deep Q-band integration toward IRC+10216 carried out with the Yebes 40m telescope, which are in harmonic relation with integer quantum numbers J 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 hydromagnesium cyanoacetylide. The rotational temperature and column density derived for HMgCCCN are 17.1 +/- 2.8K and (3.0 +/- 0.6) e12 cm-2, respectively. The observed abundance ratio between MgCCCN and HMgCCCN is 3. In addition, we report the discovery in space, also toward IRC+10216, of sodium cyanoacetylide, NaCCCN, for which accurate laboratory data are available. For this species we derive a rotational temperature of 13.5 +/- 1.7K and a column density of (1.2 +/- 0.2) e11 cm-2., Comment: Accepted in Astronomy & Astrophysics as Letter to the Editor on April 3rd, 2023

We report the detection of methyl ketene towards TMC-1 with the QUIJOTE line survey. Nineteen rotational transitions with rotational quantum numbers ranging from J = 3 up to J = 5 and Ka ≤ 2 were identified in the frequency range 32.0–50.4 GHz, 11 of which arise above the 3σ level. We derived a column density for CH3CHCO of N = 1.5 × 1011 cm−2 and a rotational temperature of 9 K. Hence, the abundance ratio between ketene and methyl ketene, CH2CO/CH3CHCO, is 93. This species is the second C3H4O isomer detected. The other, trans-propenal (CH2CHCHO), corresponds to the most stable isomer and has a column density of N = (2.2 ± 0.3)×1011 cm−2, which results in an abundance ratio CH2CHCHO/CH3CHCO of 1.5. The next non-detected isomer with the lowest energy is cis-propenal, which is therefore a good candidate for future discovery. We have carried out an in-depth study of the possible gas-phase chemical reactions involving methyl ketene to explain the abundance detected, achieving good agreement between chemical models and observations.

5 pags., 4 figs., 3 tabs., Cyclic C5H (c-C5H), the radical formed by substituting an ethynyl group CCH for the hydrogen atom in the c-C3H radical, has been detected for the first time in the space. The c-C5H species is an isomer of the well-known linear radical l-C5H and is 6 kcal mola 1 less stable. A total of 17 rotational transitions were detected for the c-C5H species in TMC-1 within the 31.0- 50.3 GHz range using the Yebes 40m radio telescope. We derive a column density of (9.0 ± 0.9) a-1010 cma 2 for c-C5H. Additionally, we observed 12 lines for l-C5H and derive a column density for it of (1.3 ± 0.3) a - 1012 cma 2, which results in an abundance ratio c-C5H/l-C5H of 0.069. This is in sharp contrast with the value found for the analogue system c-C3H/l-C3H, whose ratio is 5.5 in TMC-1. We discuss the formation of c-C5H and conclude that this radical is probably formed in the reaction of atomic carbon with diacetylene., We acknowledge funding support from Spanish Ministerio de Ciencia e Innovación through grants PID2019-106110GB-I00, PID2019- 107115GB-C21, and PID2019-106235GB-I00 and from the European Research Council (ERC Grant 610256: NANOCOSMOS).

12 pags., 5 figs., 5 tabs., Using the QUIJOTE line survey in the 32.0-50.4 GHz range, we report the discovery of the molecule CH2CCHC4H towards the prestellar cold core TMC-1 in the Taurus region. We also present a rigorous detection of CH2CCHC3N, along with its detailed analysis. We identified a total of twenty rotational transitions for each one of these molecules. The rotational quantum numbers range from Ju = 17 up to 24 and Ka ≤ 3. The column density for CH2CCHC4H is N = (2.2 ± 0.2) × 10cm, while for CH2CCHC3N, we derived N = (1.2 ± 0.15) × 10cm. The rotational temperature is 9.0 ± 0.5K for both species. The abundance ratiobetween CH2CCHC4H and CH2CCHC3N is 18 ± 4. We also compared the column densities of these species with those of their isomers CH3C6H and CH3C5N, derived from their J = 20-10 up to J = 31-30 rotational transitions observed with the QUIJOTE line survey. The observed abundances for all these species are reasonably well explained by state-of-the-art chemical models of TMC-1. The observed astronomical frequencies were merged with laboratory frequencies from the literature to derive improved spectroscopic parameters., We thank Ministerio de Ciencia e Innovación of Spain (MICIU) for funding support through projects PID2019-106110GB-I00, PID2019-107115GB-C21/AEI/10.13039/501100011033, and PID2019-106235 GB-I00. We also thank ERC for funding through grant ERC-2013-Syg-610256- NANOCOSMOS. M.A. thanks MICIU for grant RyC-2014-16277.

5 pags., 1 fig., 4 tabs., We report the first detection in space of the single deuterated isotopologue of methyldiacetylene, CH2DC4H. A total of 12 rotational transitions, with J = 8-12 and Ka = 0 and 1, were identified for this species in TMC-1 in the 31.0-50.4 GHz range using the Yebes 40m radio telescope. The observed frequencies allowed us to obtain, for the first time, the spectroscopic parameters of this deuterated isotopologue. We derived a column density of (5.5 ± 0.2) × 1011 cm-2. The abundance ratio between CH3C4H and CH2DC4H is 24 ± 2. This ratio is similar to that found for the CH3C3N/CH2DC3N analogue system, which is 22 ± 2. We did not detect the deuterated species CH3C4D, which has already been observed in laboratory experiments. The detection of deuterated CH3C4H allows us to extend the discussion on the chemical mechanisms of deuterium fractionation at work in TMC-1 using a new gas-phase chemical model with multiply deuterated molecules. Introducing a possible deuterium exchange reaction between CH3CCH and atomic deuterium allows us to account for the CH3C4H/CH2DC4H abundance ratio., We thank ERC for funding through grant ERC-2013-Syg610256-NANOCOSMOS. The Spanish authors thank Ministerio de Ciencia e Innovación for funding support through projects PID2019-106235GB-I00 and PID2019-107115GB-C21/AEI/10.13039/501100011033. M. A. thanks Ministerio de Ciencia e Innovación for grant RyC-2014-16277. E. R. acknowledges the support of the Programme National ‘Physique et Chimie du Milieu Interstellaire’ (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNES. Several kinetic data we used have been taken from the online databases KIDA (Wakelam et al. (2012), https://kida.astrochem-tools.org/) and UMIST2012 (McElroy et al. (2013), http://udfa.ajmarkwick.net).

6 pags., 2 figs., 3 tabs., We report the detection of the propargyl radical (CH2CCH) in the cold dark cloud TMC-1 in the λ 3 mm wavelength band. We recently discovered this species in space toward the same source at a wavelength of λ 8 mm. In those observations, various hyperfine components of the 20,2-10,1 rotational transition, at 37.5 GHz, were detected using the Yebes 40 m telescope. Here, we used the IRAM 30 m telescope to detect ten hyperfine components of the 50,5-40,4 rotational transition, lying at 93.6 GHz. The observed frequencies differ by 0.2 MHz with respect to the predictions from available laboratory data. This difference is significant for a radio-Astronomical search for CH2CCH in interstellar sources with narrow lines. We thus included the measured frequencies in a new spectroscopic analysis to provide accurate frequency predictions for the interstellar search for propargyl at millimeter wavelengths. Moreover, we recommend that future searches for CH2CCH in cold interstellar clouds be carried out at λ 3 mm rather than at λ 8 mm. The 50,5-40,4 transition is about five times more intense than the 20,2-10,1 one in TMC-1, which implies that detecting the former requires about seven times less telescope time than detecting the latter. We constrain the rotational temperature of CH2CCH in TMC-1 to 9.9 ± 1.5 K, which indicates that the rotational levels of this species are thermalized at the gas kinetic temperature. The revised value of the column density of CH2CCH (including ortho and para species) is (1.0 ± 0.2) × 1014 cm-2, and thus the CH2CCH/CH3CCH abundance ratio is revised slightly higher, approaching one. This study opens the door to future detections of CH2CCH in other cold interstellar clouds, making it possible to further investigate the role of this very abundant hydrocarbon radical in the synthesis of large organic molecules, such as aromatic rings., We acknowledge funding support from Spanish Ministerio de Ciencia e Innovación through grants PID2019-106110GB-I00, PID2019- 107115GB-C21, and PID2019-106235GB-I00 and from the European Research Council (ERC Grant 610256: NANOCOSMOS). M.A. also acknowledges funding support from the Ramón y Cajal programme of Spanish Ministerio de Ciencia e Innovación (grant RyC-2014-16277).

6 pags., 3 figs., 2 tabs., We report the detection in TMC-1 of the cation HCCS+ (X 3Σ-), which is the protonated form of the widespread radical CCS. This is the first time that a protonated radical has been detected in a cold dark cloud. Twenty-six hyperfine components from twelve rotational transitions have been observed with the Yebes 40 m and IRAM 30m radio telescopes. We confidently assign the characteristic rotational spectrum pattern to HCCS+ based on the good agreement between the astronomical and theoretical spectroscopic parameters. The column density of HCCS+ is (1.1 ± 0.1)×1012 cm-2, and the CCS/HCCS+ abundance ratio is 50 ± 10, which is very similar to that of CS/HCS+ (35 ± 8) and CCCS/HCCCS+ (65 ± 20). From a state-of-the-art gas-phase chemical model, we conclude that HCCS+ is mostly formed by reactions of proton transfer from abundant cations such as HCO+, H3O+, and H3+ to the radical CCS., This research has been funded by ERC through grant ERC-2013-Syg-610256-NANOCOSMOS. Authors also thank Ministerio de Ciencia e Innovación for funding support through projects PID2019-106235GBI00 and PID2019-107115GB-C21/AEI/10.13039/501100011033. MA thanks Ministerio de Ciencia e Innovación for grant RyC-2014-16277.

We performed Herschel/HIFI observations of intermediate-excitation molecular lines in the far-infrared/submillimeter range in a sample of ten protoplanetary nebulae and young planetary nebulae. The high spectral resolution provided by HIFI yields accurate measurements of the line profiles. The observation of these high-energy transitions allows an accurate study of the excitation conditions, particularly in the warm gas, which cannot be properly studied from the low-energy lines. We have detected FIR/sub-mm lines of several molecules, in particular of 12CO, 13CO, and H2O. Emission from other species, like NH3, OH, H2^{18}O, HCN, SiO, etc, has been also detected. Wide profiles showing sometimes spectacular line wings have been found. We have mainly studied the excitation properties of the high-velocity emission, which is known to come from fast bipolar outflows. From comparison with general theoretical predictions, we find that CRL 618 shows a particularly warm fast wind, with characteristic kinetic temperature Tk >~ 200 K. In contrast, the fast winds in OH 231.8+4.2 and NGC 6302 are cold, Tk ~ 30 K. Other nebulae, like CRL 2688, show intermediate temperatures, with characteristic values around 100 K. We also discuss how the complex structure of the nebulae can affect our estimates, considering two-component models. We argue that the differences in temperature in the different nebulae can be due to cooling after the gas acceleration (that is probably due to shocks); for instance, CRL 618 is a case of very recent acceleration, less than ~ 100 yr ago, while the fast gas in OH 231.8+4.2 was accelerated ~ 1000 yr ago. We also find indications that the densest gas tends to be cooler, which may be explained by the expected increase of the radiative cooling efficiency with the density., 24 pages, 31 figures

We present Herschel observations of the water molecule in the massive star-forming region W3 IRS5. The o-H17O 110-101, p-H18O 111-000, p-H2O 22 202-111, p-H2O 111-000, o-H2O 221-212, and o-H2O 212-101 lines, covering a frequency range from 552 up to 1669 GHz, have been detected at high spectral resolution with HIFI. The water lines in W3 IRS5 show well-defined high-velocity wings that indicate a clear contribution by outflows. Moreover, the systematically blue-shifted absorption in the H2O lines suggests expansion, presumably driven by the outflow. No infall signatures are detected. The p-H2O 111-000 and o-H2O 212-101 lines show absorption from the cold material (T ~ 10 K) in which the high-mass protostellar envelope is embedded. One-dimensional radiative transfer models are used to estimate water abundances and to further study the kinematics of the region. We show that the emission in the rare isotopologues comes directly from the inner parts of the envelope (T > 100 K) where water ices in the dust mantles evaporate and the gas-phase abundance increases. The resulting jump in the water abundance (with a constant inner abundance of 10^{-4}) is needed to reproduce the o-H17O 110-101 and p-H18O 111-000 spectra in our models. We estimate water abundances of 10^{-8} to 10^{-9} in the outer parts of the envelope (T < 100 K). The possibility of two protostellar objects contributing to the emission is discussed., Accepted for publication in the A&A HIFI special issue

Water is a key molecule in the star formation process, but its spatial distribution in star-forming regions is not well known. We study the distribution of dust continuum and H2O and 13CO line emission in DR21, a luminous star-forming region with a powerful outflow and a compact HII region. Herschel-HIFI spectra near 1100 GHz show narrow 13CO 10-9 emission and H2O 1(11)-0(00) absorption from the dense core and broad emission from the outflow in both lines. The H2O line also shows absorption by a foreground cloud known from ground-based observations of low-J CO lines. The dust continuum emission is extended over 36" FWHM, while the 13CO and H2O lines are confined to ~24" or less. The foreground absorption appears to peak further North than the other components. Radiative transfer models indicate very low abundances of ~2e-10 for H2O and ~8e-7 for 13CO in the dense core, and higher H2O abundances of ~4e-9 in the foreground cloud and ~7e-7 in the outflow. The high H2O abundance in the warm outflow is probably due to the evaporation of water-rich icy grain mantles, while the H2O abundance is kept down by freeze-out in the dense core and by photodissociation in the foreground cloud., Comment: Accepted by A&A Letters (Herschel special issue); 4 pages, 4 figures

We derive the dense core structure and the water abundance in four massive star-forming regions which may help understand the earliest stages of massive star formation. We present Herschel-HIFI observations of the para-H2O 1_11-0_00 and 2_02-1_11 and the para-H2-18O 1_11-0_00 transitions. The envelope contribution to the line profiles is separated from contributions by outflows and foreground clouds. The envelope contribution is modelled using Monte-Carlo radiative transfer codes for dust and molecular lines (MC3D and RATRAN), with the water abundance and the turbulent velocity width as free parameters. While the outflows are mostly seen in emission in high-J lines, envelopes are seen in absorption in ground-state lines, which are almost saturated. The derived water abundances range from 5E-10 to 4E-8 in the outer envelopes. We detect cold clouds surrounding the protostar envelope, thanks to the very high quality of the Herschel-HIFI data and the unique ability of water to probe them. Several foreground clouds are also detected along the line of sight. The low H2O abundances in massive dense cores are in accordance with the expectation that high densities and low temperatures lead to freeze-out of water on dust grains. The spread in abundance values is not clearly linked to physical properties of the sources., Comment: 8 pages, 5 figures, accepted for publication the 15/07/2010 by Astronomy&Astrophysics as a letter in the Herschel-HIFI special issue

Spectra, taken with the heterodyne instrument, HIFI, aboard the Herschel Space Observatory, of O-rich asymptotic giant branch (AGB) stars which form part of the guaranteed time key program HIFISTARS are presented. The aim of this program is to study the dynamical structure, mass-loss driving mechanism, and chemistry of the outflows from AGB stars as a function of chemical composition and initial mass. We used the HIFI instrument to observe nine AGB stars, mainly in the H2O and high rotational CO lines We investigate the correlation between line luminosity, line ratio and mass-loss rate, line width and excitation energy. A total of nine different molecules, along with some of their isotopologues have been identified, covering a wide range of excitation temperature. Maser emission is detected in both the ortho- and para-H2O molecules. The line luminosities of ground state lines of ortho- and para-H2O, the high-J CO and NH3 lines show a clear correlation with mass-loss rate. The line ratios of H2O and NH3 relative to CO J=6-5 correlate with the mass-loss rate while ratios of higher CO lines to the 6-5 is independent of it. In most cases, the expansion velocity derived from the observed line width of highly excited transitions formed relatively close to the stellar photosphere is lower than that of lower excitation transitions, formed farther out, pointing to an accelerated outflow. In some objects, the vibrationally excited H2O and SiO which probe the acceleration zone suggests the wind reaches its terminal velocity already in the innermost part of the envelope, i.e., the acceleration is rapid. Interestingly, for R Dor we find indications of a deceleration of the outflow in the region where the material has already escaped from the star., Comment: 6 Figures in the main paper + 12 further figures in the appendix (to be printed in electronic form) Accepted for publication by A&A