FAUST-XXIX. OCS line emission : a new method for measuring the luminosity of embedded protostars in binary systems
Saury, Guillaume (Centre National de la Recherche Scientifique. Université Grenoble Alpes)
Bariosco, Vittorio (Universitat Autònoma de Barcelona. Departament de Química)
Ceccarelli, Cecilia (Centre National de la Recherche Scientifique. Université Grenoble Alpes)
López-Sepulcre, Ana (Institut de Radioastronomie Millimétrique)
Chahine, Layal (Centre National de la Recherche Scientifique. Université Grenoble Alpes)
De Simone, Marta (Osservatorio Astrofisico di Arcetri)
Rimola, Albert (Universitat Autònoma de Barcelona. Departament de Química)
Ugliengo, Piero (Università degli Studi di Torino. Dipartimento di Chimica)
Chandler, Claire J. (National Radio Astronomy Observatory (USA))
Sakai, Nami (RIKEN Cluster for Pioneering Research)
Codella, Claudio (Osservatorio Astrofisico di Arcetri)
Bianchi, Eleonora (Osservatorio Astrofisico di Arcetri)
Boitard-Crépeau, Lise (Centre National de la Recherche Scientifique. Université Grenoble Alpes)
Bouvier, Mathilde (Leiden University. Leiden Observatory)
Le Gal, Romane (Institut de Radioastronomie Millimétrique)
Loinard, Laurent (Harvard University. David Rockefeller Center for Latin American Studies)
Oya, Yoko (Kyoto University. Yukawa Institute for Theoretical Physics)
Podio, Linda (Osservatorio Astrofisico di Arcetri)
Sabatini, Giovanni (Osservatorio Astrofisico di Arcetri)
Vastel, Charlotte (Centre National de la Recherche Scientifique. Université de Toulouse)
Zhang, Ziwei E. (RIKEN Cluster for Pioneering Research)
Yamamoto, Satoshi (SOKENDAI)

Date:	2026
Abstract:	The luminosity of embedded protostars is commonly measured via observations of the dust continuum spectral energy distribution from millimetre to infrared wavelengths. However, this method cannot be applied to embedded protostars in binary or multiple systems, where their components are usually unresolved over this extended wavelength range. We propose a new method, based on the idea that a molecule formed (mainly) on the grain surfaces only emits lines in the region where it thermally sublimates from the grain mantles, heated by the photons emitted by the embedded source. In this respect, carbonyl sulfide (OCS) is an optimal molecule, because of its low binding energy and rotational lines in the millimetre. We apply the method to the protobinary system NGC1333 IRAS4A, using ALMA high-spatial resolution ( ∼50 au) observations of the OCS(19-18) line as part of the ALMA Large Programme FAUST. We also present new quantum mechanics calculations of the OCS binding energy distribution, essential for the application of the method. We found that the two binary components, A1 and A2, have a comparable luminosity within the error bars, 7. 5 ± 2. 5 and 7 ± 1 L , respectively. We discuss the reliability of the estimated luminosities and the potential of this new method for measuring the luminosity of embedded protostars in binary and multiple systems.
Grants:	European Commission 741002 European Commission 811312 European Commission 833460
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Astrochemistry ; Stars: formation ; ISM: molecules ; ISM: individual ; Objects: NGC1333 IRAS4A
Published in:	Monthly Notices of the Royal Astronomical Society, Vol. 545, Num. 3 (January 2026) , art. staf2157, ISSN 1365-2966

DOI: 10.1093/mnras/staf2157

17 p, 2.1 MB

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