Authors: Cernicharo, J.; Cabezas, C.; Pardo, J. R.; Agundez, M.; Roncero, O.; Tercero, B.; Marcelino, N.; Guelin, M.; Endo, Y.; de Vicente, P.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/04/21

DOI: 10.1051/0004-6361/202346467

Abstract: We found four series of harmonically related lines in IRC +10216 with the Yebes 40 m and IRAM 30 m telescopes. The first series corresponds to a molecule with a rotational constant, B, of 1448.5994 +/- 0.0013 MHz and a distortion constant, D, of 63.45 +/- 1.15 Hz and covers upper quantum numbers from J(u) = 11 up to 33 (B1449). The second series is fitted with B = 1446.9380 +/- 0.0098 MHz and D = 91 +/- 23 Hz and covers upper quantum numbers from J(u) = 11 up to 17 (B1447). The third series is fitted with B = 598.7495 +/- 0.0011 MHz and D = 6.13 +/- 0.43 Hz and covers quantum numbers from J(u) = 26 up to 41 (B599). Finally, the frequencies of the last series of lines can be reproduced with B = 594.3176 +/- 0.0026 MHz and D = 4.92 +/- 1.16 Hz (B594). The large values of D point toward four metal-bearing carriers. After exploring all plausible candidates containing Na, Al, Mg, and other metals, our ab initio calculations indicate that the cations MgC4H+, MgC3N+, MgC6H+, and MgC5N+ must be the carriers of B1449, B1447, B599, and B594, respectively. These cations could be formed by the radiative association of Mg+ with C4H, C3N, C6H, and C5N, respectively. We calculated the radiative association rate coefficient of Mg+ with C4H, C3N, C6H, and C5N and incorporated them in our chemical model. The results confirm that the Mg-bearing cations can be formed through these radiative association reactions in the outer layers of IRC +10216. This is the first time that cationic metal-bearing species have been found in space. These results provide a new paradigm on the reactivity of ionized metals with abundant radicals and open the door for further characterization of similar species in metal-rich astrophysical environments.

Authors: Cabezas, C.; Pardo, J. R.; Agundez, M.; Tercero, B.; Marcelino, N.; Endo, Y.; de Vicente, P.; Guelin, M.; Cernicharo, J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/04/21

DOI: 10.1051/0004-6361/202346462

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 40 m 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) x 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) x 10(11) cm(-2).

Authors: Ruiz-Lapuente, P.; Hernandez, J. I. Gonzalez; Cartier, R.; Boutsia, K.; Figueras, F.; Canal, R.; Galbany, L.

Journal: ASTROPHYSICAL JOURNAL

Publication date: 2023/04/01

DOI: 10.3847/1538-4357/acad74

Abstract: We use the Gaia EDR3 to explore the Galactic supernova remnant (SNR) G272.2-3.2, produced by the explosion of a Type Ia supernova (SN Ia) about 7500 yr ago, to search for a surviving companion. From the abundances in the SNR ejecta, G272.2-3.2 is a normal SN Ia. The Gaia parallaxes allow us to select the stars located within the estimated distance range of the SNR, and the Gaia proper motions allow us to study their kinematics. From the Gaia EDR3 photometry, we construct the H-R diagram of the selected sample, which we compare with the theoretical predictions for the evolution of possible star companions of SNe Ia. We can discard several proposed types of companions by combining kinematics and photometry. We can also discard hypervelocity stars. We focus our study on the kinematically most peculiar star, Gaia EDR3 5323900215411075328 (hereafter MV-G272), an 8.9 sigma outlier in proper motion. It is of M1-M2 stellar type. Its trajectory on the sky locates it at the center of the SNR, 6000-8000 yr ago, a unique characteristic among the sample. Spectra allow a stellar parameter determination and a chemical abundance analysis. In conclusion, we have a candidate to be the surviving companion of the SN Ia that resulted in SNR G272.2-3.2. It is supported by its kinematical characteristics and its trajectory within the SNR. This opens the possibility of a single-degenerate scenario for an SN Ia with an M-type dwarf companion.

Authors: Ruiz-Lapuente, Pilar

Journal: FRONTIERS IN ASTRONOMY AND SPACE SCIENCES

Publication date: 2023/03/16

DOI: 10.3389/fspas.2023.1112880

Abstract: At the 450 years anniversary of its observation, the supernova named after Tycho Brahe, SN 1572, can be explained in the terms used nowadays to characterize Type Ia supernovae (SNe Ia). By assembling the records of the observations made in 1572-74 and evaluating their uncertainties, it is possible to recover the light curve and the color evolution of this supernova. It is found that, within the SNe Ia family, the event should have been a SN Ia with a normal rate of decline. Concerning the color evolution of SNe Ia, the most recently recovered records reaffirm previous findings of its being a normal SN Ia. The abundance studies from X-ray spectroscopy of the whole remnant point to a nuclear burning of the kind of a delayed detonation explosion of a Chandrasekhar-mass white dwarf. A tentative single degenerate path to explosion was suggested from the exploration of the stars in the field of SN 1572. Though, the origin in a double degenerate is being considered as well. Tycho Brahe’s supernova, being the first supernova studied by astronomers, is still the subject of very intensive debates nowadays.

Authors: Fuentetaja, R.; Bermudez, C.; Cabezas, C.; Agundez, M.; Tercero, B.; Marcelino, N.; Pardo, J. R.; Margules, L.; Motiyenko, R. A.; Guillemin, J. -C.; de Vicente, P.; Cernicharo, J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/03/03

DOI: 10.1051/0004-6361/202245732

Abstract: 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 K-a <= 2 were identified in the frequency range 32.0-50.4 GHz, 11 of which arise above the 3 sigma level. We derived a column density for CH3CHCO of N=1.5 x 10(11) 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)x10(11) 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.

Authors: Mebel, Alexander M.; Agundez, Marcelino; Cernicharo, Jose; Kaiser, Ralf I.

Journal: ASTROPHYSICAL JOURNAL LETTERS

Publication date: 2023/03/01

DOI: 10.3847/2041-8213/acbf41

Abstract: The recent astronomical detection of ethynylbutatrienylidene (HCCCHCCC)-a high-energy isomer of triacetylene (HCCCCCCH) and hexapentaenylidene (H2CCCCCC)-in TMC-1 puzzled the laboratory astrophysics community since proposed reaction pathways could not synthesize the ethynylbutatrienylidene (HCCCHCCC) under cold molecular cloud conditions. Exploiting a retrosynthesis coupled with electronic structure calculations and astrochemical modeling, we reveal that observed fractional abundance of ethynylbutatrienylidene (HCCCHCCC) of 1.3 +/- 0.2 x 10(-11) can be quantitatively replicated though the barrierless and exoergic reaction of tricarbon (C-3) with the resonantly stabilized propargyl radical (C3H3) after a few 10(5) yr-typical ages of cold molecular clouds. Our study provides persuasive evidence that previously assumed dead reactants such as tricarbon (C-3) and the propargyl radical (C3H3) provide fundamental molecular building blocks in molecular mass growth processes leading to exotic, high-energy isomers of hydrocarbons: ethynylbutatrienylidene (HCCCHCCC).

Authors: Cernicharo, J.; Pardo, J. R.; Cabezas, C.; Agundez, M.; Tercero, B.; Marcelino, N.; Fuentetaja, R.; Guelin, M.; de Vicente, P.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/02/15

DOI: 10.1051/0004-6361/202245816

Abstract: We report on the discovery of the C7N- anion towards the starless core TMC-1 and towards the carbon-rich evolved star IRC +10216. We used the data of the QUIJOTE (Q-band Ultrasensitive Inspection Journey to the Obscure TMC-1 Environment) line survey towards TMC-1 and found six lines in perfect harmonic frequency relation from J = 27 26 up to J = 32 31. The frequency of the lines can be reproduced with a rotational constant and a distortion constant of B = 582.68490 +/- 0:00024 MHz and D = 4.01 +/- 0.13 Hz, respectively. The standard deviation of the fit is 4 kHz. Towards IRC +10216, we identify 17 lines from J = 27 26 up to J = 43 42; their frequencies are also in harmonic relation, providing B = 582.6827 +/- 0.00085 MHz and D = 3.31 +/- 0.31 Hz. The nearly exact coincidence of the rotational and distortion constants in both sources points unambiguously to a common molecular carrier. Taking into account the chemical peculiarities of both sources, the carrier could be a radical or an anion. The radical can be discarded, as the observed lines belong to a singlet species. Hence, the most plausible carrier is an anion. High-level ab initio calculations indicate that C7N, for which we compute a rotational constant of B = 582.0 MHz and a dipole moment of 7.5 D, is the carrier of the lines in both sources. We predict the neutral C7N to have a ground electronic state(2)Pi and a dipole moment of similar to 1 D. Because of this low value of mu and to its much larger rotational partition function, its lines are expected to be well below the sensitivity of our data for both sources.

Authors: Fuente, A.; Riviere-Marichalar, P.; Beitia-Antero, L.; Caselli, P.; Wakelam, V.; Esplugues, G.; Rodriguez-Baras, M.; Navarro-Almaida, D.; Gerin, M.; Kramer, C.; Bachiller, R.; Goicoechea, J. R.; Jimenez-Serra, I.; Loison, J. C.; Martin-Domenech, R.; Ivlev, A.; Spezzano, S.; Roncero, O.; Munoz-Caro, G.; Cazaux, S.; Marcelino, N.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2023/02/15

DOI: 10.1051/0004-6361/202244843

Abstract: Context. Gas phase Elemental abundances in molecular CloudS (GEMS) is an IRAM 30-m Large Program aimed at determining the elemental abundances of carbon (C), oxygen (O), nitrogen (N), and sulfur (S) in a selected set of prototypical star-forming filaments. In particular, the elemental abundance of S remains uncertain by several orders of magnitude, and its determination is one of the most challenging goals of this program. Aims. This paper aims to constrain the sulfur elemental abundance in Taurus, Perseus, and Orion A based on the GEMS molecular database. The selected regions are prototypes of low-mass, intermediate-mass, and high-mass star-forming regions, respectively, providing useful templates for the study of interstellar chemistry. Methods. We have carried out an extensive chemical modeling of the fractional abundances of CO, HCO+, HCN, HNC, CS, SO, H2S, OCS, and HCS+ to determine the sulfur depletion toward the 244 positions in the GEMS database. These positions sample visual extinctions from A(V) similar to 3 mag to >50 mag, molecular hydrogen densities ranging from a few x 10(3) cm(-3) to 3 x 10(6) cm(-3), and T-k similar to 10-35 K. We investigate the possible relationship between sulfur depletion and the grain charge distribution in different environments. Results. Most of the positions in Taurus and Perseus are best fitted assuming early-time chemistry, t = 0.1 Myr, zeta(H2) similar to (0.5-1) x 10(-16) s(-1), and [S/H] similar to 1.5 x 10(-6). On the contrary, most of the positions in Orion are fitted with t = 1 Myr and zeta(H2) similar to 10(-17) s(-1). Moreover, similar to 40% of the positions in Orion are best fitted assuming the undepleted sulfur abundance, [S/H] similar to 1.5 x 10(-5). We find a tentative trend of sulfur depletion increasing with density. Conclusions. Our results suggest that sulfur depletion depends on the environment. While the abundances of sulfur-bearing species are consistent with undepleted sulfur in Orion, a depletion factor of similar to 20 is required to explain those observed in Taurus and Perseus. We propose that differences in the grain charge distribution might explain these variations. Grains become negatively charged at a visual extinction of A(V) similar to 3.5 mag in Taurus and Perseus. At this low visual extinction, the S+ abundance is high, X(S+) > 10(-6), and the electrostatic attraction between S+ and negatively charged grains could contribute to enhance sulfur depletion. In Orion, the net charge of grains remains approximately zero until higher visual extinctions (A(V) similar to 5.5 mag), where the abundance of S+ is already low because of the higher densities, thus reducing sulfur accretion. The shocks associated with past and ongoing star formation could also contribute to enhance [S/H].