Fading into Darkness: A Weak Mass Ejection and Low-efficiency Fallback Accompanying Black Hole Formation in M31-2014-DS1

March 2026 • 2026ApJ...999L..25D

Authors • De, Kishalay • MacLeod, Morgan • Jencson, Jacob E. • Lau, Ryan M. • Antoni, Andrea • Colmenares, María José • Huang, Jane • Masterson, Megan • Karambelkar, Viraj R. • Kasliwal, Mansi M. • Loeb, Abraham • Panagiotou, Christos • Quataert, Eliot

Abstract • Stellar-mass black holes (BHs) can form from the near-complete collapse of massive stars, causing them to abruptly disappear. The star M31-2014-DS1 in the Andromeda galaxy was reported to exhibit such a disappearance between 2014 and 2022, with properties consistent with the failed explosion of an ≍12─13 M_⊙ yellow supergiant leading to the formation of an ≍5 M_⊙ BH. We present mid-infrared (MIR) observations of the remnant obtained with the James Webb Space Telescope (JWST) and X-ray observations from the Chandra X-ray Observatory in 2024. The JWST Mid-infrared Instrument/NIRSpec data reveal an extremely red source, showing strong blueshifted absorption from molecular gas (CO, CO₂, H₂O, SO₂) and deep silicate dust features. Modeling the dust continuum confirms continued bolometric fading of the central source to log(L/L⊙)≍3.88 (≍7%─8% of the progenitor luminosity), surrounded by a dust shell spanning ≍40─200 au. Modeling of the molecular gas indicates ∼0.1 M_⊙ of gas expanding at ≍100 km s⁻¹ near the inner edge of the dust shell. No X-ray source is detected down to a luminosity limit of L_X ≲ 1.5 × 10³⁵ erg s⁻¹. We show that the panchromatic observations are explained by (i) a low-energy (≍10⁴⁶ erg) ejection of the outer H-rich progenitor envelope and (ii) a fading central BH powered by inefficient (∼0.1% in mass) accretion of loosely bound fallback material. The analysis robustly establishes the bolometric fading of M31-2014-DS1 following its >30 yr archival record of constant optical/infrared brightness, and provides the first cohesive insights into BH formation via low-energy explosions and long-term fallback.

Links

• PDF https://iopscience.iop.org/article/10.3847/2041-8213/ae468d/pdf
• PREPRINT http://arxiv.org/abs/2601.05774
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2026ApJ...999L..25D
• DATA https://doi.org/10.17909/c3sv-qh71
• DATA https://doi.org/10.25574/cdc.538
• ELECTR https://doi.org/10.3847/2041-8213/ae468d