IPA: Accretion Rate of a Low-mass Class 0 Protostar, Measured via Mid-IR Fluorescent OH Emission

Abstract The earliest stages of star formation are highlighted by complex interactions between accretion, outflow, and radiative processes, which shape the chemical and physical environment of the emerging protostar. James Webb Space Telescope observations of the low-mass, low-luminosity Class 0 protostar IRAS 16253–2429 (I16253) reveal a central compact source. This object exhibits a rich mid-IR emission spectrum of OH pure rotational lines and CO 2 rovibrational lines. Unusually for a young stellar object, it has no mid-IR line emission from H 2 O to match the other molecules. We demonstrate that the emitting OH molecules arise from UV photodissociation of H 2 O in its second absorption band at λ = 114–145 nm, and that the OH emission is a fluorescent cascade starting with highest-excitation rotational states. This situation offers the opportunity of using the IR OH spectrum to measure the UV flux from the central protostar. Thereby, we determine the disk-to-star accretion rate to be 3 × 10 −10 M ⊙ yr −1 , and demonstrate that the system luminosity arises mostly from the protostar’s photosphere rather than from accretion luminosity. The result is in accord with the measured outflow rate of I16253 and lies within the outflow/accretion-flow rate trend often inferred for protostars, and with episodic accretion as the dominant mechanism by which this protostar has grown.

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Journal
The Astrophysical Journal
Published
2026-03-09
DOI
https://doi.org/10.3847/1538-4357/ae3155
Primary Topic
Astrophysics and Star Formation Studies
Type
article
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article

IPA: Accretion Rate of a Low-mass Class 0 Protostar, Measured via Mid-IR Fluorescent OH Emission

Pooneh Nazari, Riwaj Pokhrel, Robert Gutermuth, Samuel Federman et al.
The Astrophysical Journal
Astrophysics and Star Formation Studies
article

IPA: Accretion Rate of a Low-mass Class 0 Protostar, Measured via Mid-IR Fluorescent OH Emission

Pooneh Nazari, Riwaj Pokhrel, Robert Gutermuth, Samuel Federman, P. Manoj, Nolan Habel, Łukasz Tychoniec, Nashanty G. C. Brunken, Tyler L. Bourke, Prabhani Atnagulov, Thomas Stanke, Caeley V. Pittman, Yao-Lun Yang, James Muzerolle Page, William J. Fischer, Adam E. Rubinstein, D. M. Watson, Leslie W. Looney, David A. Neufeld, Elise Furlan, Rohan Rahatgaonkar, Guillem Anglada, C. M. Lisse, N. Calvet, Nicole Karnath, Catherine Espaillat, K. Slavicinska, Patrick Sheehan, Himanshu Tyagi, Lee Hartmann, Will R. M. Rocha, P. Klaassen, Neal J Evans, Scott Wolk, Mayra Osorio, Alessio Caratti o Garatti, Ewine F. van Dishoeck, Hendrik Linz, Mayank Narang, Joel D. Green, John J. Tobin, Henrik Beuther, S. Thomas Megeath, Amelia M. Stutz
article en

Abstract

Abstract The earliest stages of star formation are highlighted by complex interactions between accretion, outflow, and radiative processes, which shape the chemical and physical environment of the emerging protostar. James Webb Space Telescope observations of the low-mass, low-luminosity Class 0 protostar IRAS 16253–2429 (I16253) reveal a central compact source. This object exhibits a rich mid-IR emission spectrum of OH pure rotational lines and CO 2 rovibrational lines. Unusually for a young stellar object, it has no mid-IR line emission from H 2 O to match the other molecules. We demonstrate that the emitting OH molecules arise from UV photodissociation of H 2 O in its second absorption band at λ = 114–145 nm, and that the OH emission is a fluorescent cascade starting with highest-excitation rotational states. This situation offers the opportunity of using the IR OH spectrum to measure the UV flux from the central protostar. Thereby, we determine the disk-to-star accretion rate to be 3 × 10 −10 M ⊙ yr −1 , and demonstrate that the system luminosity arises mostly from the protostar’s photosphere rather than from accretion luminosity. The result is in accord with the measured outflow rate of I16253 and lies within the outflow/accretion-flow rate trend often inferred for protostars, and with episodic accretion as the dominant mechanism by which this protostar has grown.

The Astrophysical JournalVol. 999(2)
Boston University (US), Tata Institute of Fundamental Research (IN), Leiden University (NL), California Institute of Technology (US), Space Telescope Science Institute (US), Space Science Institute (US), Institute of Astronomy and Astrophysics, Academia Sinica (TW), European Southern Observatory (DE), Jet Propulsion Laboratory (US), Johns Hopkins University (US), University of Illinois Urbana-Champaign (US), University of Concepción (CL), University of Massachusetts Amherst (US), National Radio Astronomy Observatory (US), University of Michigan (US), NASA Exoplanet Science Institute (US), Astronomical Observatory of Capodimonte (IT), Johns Hopkins University Applied Physics Laboratory (US), Max Planck Institute for Extraterrestrial Physics (DE), SKA Observatory (GB), Max Planck Institute for Astronomy (DE), RIKEN (JP), Gemini South Observatory (CL), Center for Astrophysics Harvard & Smithsonian (US), Instituto de Astrofísica de Andalucía (ES), UK Astronomy Technology Centre (GB), University of Rochester (US), University of Baltimore (US), The University of Texas at Austin (US), University of Toledo (US)
Openalex Percentile: Top 31%
Astrophysics and Star Formation Studies
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