- The paper demonstrates that M31-2014-DS1, a massive hydrogen-depleted supergiant, collapsed directly into a black hole without a classic supernova explosion.
- It employs extensive multi-wavelength and archival photometry to document dramatic luminosity drops and other quantitative changes over roughly 1000 days.
- The findings support a fallback model where a weak shock partially ejects the stellar envelope, leading to dust formation and a failed supernova event.
Observational Signature of Black Hole Birth in Andromeda
The paper discusses the study of M31-2014-DS1, a massive hydrogen-depleted supergiant in the Andromeda Galaxy, which provides compelling evidence for the direct formation of stellar-mass black holes (BHs) from stripped massive stars. This work reveals the detailed constraints based on extensive multi-wavelength observations, leading to the understanding of the object's disappearance linked with black hole formation.
Key Observations and Analysis
The subject of this research, M31-2014-DS1, was initially identified due to an infrared brightening observed by NEOWISE starting in 2014. After a period of increasing luminosity over approximately 1000 days, the object's total and optical luminosity declined dramatically by ≳10× and ≳100× respectively, rendering it invisible in the following deep optical observations. Archival data suggested a consistent identification with a luminous and cool supergiant enshrouded by a dust shell.
Utilizing various models incorporating enhanced wind mass loss, the progenitor star was deduced to have an initial mass of ≈20 solar masses (M⊙), reaching the terminal nuclear burning phase with a mass of ≈6.7 M⊙ and a thin hydrogen envelope. The observational constraints were reinforced by deep space-based photometry, showing a remnant markedly obscured by dust and severely reduced in both luminosity and effective radius relative to the progenitor.
The observations and subsequent analysis suggest a black hole formation event characterized by the fallback of the stellar envelope moderated by a weak shock. The emergent theoretical model postulates an energy injection into the outer stellar envelope leading to partial ejection and dust shell formation at the condensation radius. This model is supported by the absence of a substantial optical outburst, indicating a 'failed supernova' where the stellar core collapses directly into a black hole without a discernible supernova explosion. The paper quantitatively constrains the mass of the ejected hydrogen-rich material and corroborates the majority of the stellar mass collapsing into the core, consistent with the formation of a black hole exceeding the mass threshold of a neutron star.
Comparative Analysis
This study draws parallels with another similar candidate, NGC 6946-BH1, and provides a unified model framework for black hole formation from such progenitors. The work recognizes the differences in evolutionary endpoints and attributes the non-detection of traditional electromagnetic and neutrino emission from newly formed black holes to the enshrouding by thick circumstellar material.
This research highlights the significance of long-term and multi-wavelength monitoring of potential supernova progenitors and their eventual collapse. With the proximity of M31 being a substantial advantage, further electromagnetic observations, X-ray studies, and potential gravitational-wave detections are anticipated avenues to explore these challenging cosmic events.
Conclusions
The findings from this study significantly contribute to the stellar evolution field, offering empirical insight into the lifecycle of massive stars culminating in black hole formation. These results not only fill a critical gap in understanding massive star deaths but also support the theoretical predictions regarding the chaotic relationship between progenitor stars and their end-state compact remnants. Future studies, facilitated by the growing capabilities of astronomical instruments and surveys, are expected to broaden our knowledge in this domain extensively.
