A Survey About Nothing: Monitoring a Million Supergiants for Failed Supernovae (0802.0456v2)

Abstract: Extragalactic transient searches have historically been limited to looking for the appearance of new sources such as supernovae. It is now possible to carry out a new kind of survey that will do the opposite, that is, search for the disappearance of massive stars. This will entail the systematic observation of galaxies within a distance of 10 Mpc in order to watch ~10^6 supergiants. Reaching this critical number ensures that something will occur yearly, since these massive stars must end their lives with a core collapse within ~10^6 years. Using deep imaging and image subtraction it is possible to determine the fates of these stars whether they end with a bang (supernova) or a whimper (fall out of sight). Such a survey would place completely new limits on the total rate of all core collapses, which is critical for determining the validity of supernova models. It would also determine the properties of supernova progenitors, better characterize poorly understood optical transients, such as eta Carina-like mass ejections, find and characterize large numbers of Cepheids, luminous blue variables and eclipsing binaries, and allow the discovery of any new phenomena that inhabit this relatively unexplored parameter space.

• The paper proposes a novel survey monitoring one million supergiants within 10 Mpc to detect failed supernovae by observing star disappearance.
• This method aims to quantify the rate of failed supernovae, providing crucial data to refine models of massive star death and black hole formation.
• The survey dataset helps identify other transients and constrain failed supernova rates, informing future neutrino and gravitational wave searches.

A Survey About Nothing: Monitoring a Million Supergiants for Failed Supernovae

The paper "A Survey About Nothing: Monitoring a Million Supergiants for Failed Supernovae" by Kochanek et al. proposes a novel approach to astrophysical surveys, shifting from traditional methods that focus on the appearance of new astronomical phenomena, such as supernovae (SNe), to those concentrating on the absence or disappearance of stars. This essay will provide a comprehensive overview of the paper, highlighting key aspects and implications of the research.

Overview

The authors introduce a survey aimed at detecting the disappearance of massive stars within a 10 Mpc radius, involving approximately one million supergiants. The objective is to directly observe the final life stages of these stars, whether they culminate in typical supernovae or alternative, less understood events, potentially resulting in black hole (BH) formation without a bright visual explosion. By systematically monitoring these stars using deep imaging and image subtraction techniques, the authors seek to address critical questions concerning the end-of-life stages of massive stars and to validate supernova models more thoroughly.

Scientific Rationale and Methodology

Traditional supernova surveys are predominantly concerned with detecting newly appearing bright sources. However, the fate of many massive stars could be a failed supernova, resulting in direct collapse into a black hole without a significant optical signature. This survey attempts to observe the disappearance of supergiants, potentially indicating such a collapse.

Key aspects of the proposed methodology include:

• Comprehensive Monitoring: Observing galaxies within 10 Mpc to ensure statistical significance, given the core collapse timeframe of approximately 1 million years for each supergiant.
• Detection of Disappearance: Utilizing deep imaging and robust image subtraction to pinpoint faint events or complete disappearances indicative of failed supernovae.
• Sample Size and Frequency: The authors note the importance of covering enough galaxies (about 30 within 10 Mpc) to detect approximately one supernova per year, enhancing the likelihood of identifying both successful and failed supernova events.

Implications and Future Directions

The implications of discovering significant numbers of failed supernovae are profound:

1. Supernova Physics: By quantifying the frequency of failed supernovae, the paper could refine our understanding of stellar evolution and supernova physics, potentially impacting models of element enrichment in galaxies due to fewer explosive events dispersing elements.
2. Black Hole Formation: Determining the occurrence of failed supernovae directly informs models of black hole formation, contributing to a more nuanced understanding of neutron star and black hole populations.
3. Astrophysical Phenomena: The survey would naturally expand knowledge of various transient phenomena, including optical transients, luminous variable stars, and more, providing comprehensive insights into evolved stellar populations.
4. Limits on Failed Supernova Rates: A failure to detect any examples of failed supernovae, on the other hand, would place stringent limits on their rates, influencing the search for neutrino and gravitational wave signatures associated with such events.
5. Additional Discoveries: This research could also uncover previously unknown astrophysical phenomena within a relatively unexplored parameter space of massive star disappearance.

Conclusion

The methodology and proposed implementation outlined in this paper suggest an innovative pathway for astrophysics research. By focusing on the disappearance rather than the emergence of stellar bodies, the survey could yield new insights into stellar lifecycle endpoints and enrich our understanding of both the visible and obscured cosmic events. Additionally, this aligns with broader movements within observational astronomy towards more comprehensive, data-driven approaches to understanding the universe's dynamic processes. As observational technologies advance, such methodologies will become increasingly prevalent, promising to answer fundamental questions about the life cycle of stars and the nature of cosmic transients.