What are Supernovae?

Supernovae are among the most energetic events in the universe, marking the end of a star’s life. They appear as sudden, brilliant flashes in the sky.These explosions are categorized into two main types, based on the mass of the star that created them.

Thermonuclear Supernovae

Thermonuclear supernovae occur in stars with initial masses under eight times that of our Sun. These stars evolve into white dwarfs-dense remnants that no longer generate heat through nuclear fusion. If a white dwarf exists in a binary system, it can accrete matter from its companion star. This added mass increases internal pressure until the white dwarf explodes.

Core-Collapse Supernovae

Core-collapse supernovae involve stars exceeding eight solar masses. These stars fuse progressively heavier elements in their cores until they reach a point where further fusion is impossible. The core then collapses under its own gravity, triggering a massive explosion.

The Importance of Early Detection

The initial hours and days following a supernova explosion are critical for understanding the event. Early data provides direct clues about the progenitor system, allowing astronomers to distinguish between competing explosion models, estimate key parameters, and study the surrounding surroundings. Historically, obtaining this early data was challenging, as supernovae were often discovered days or weeks after the explosion.

Modern wide-field, high-cadence sky surveys are changing this, enabling discoveries within hours or days. these surveys repeatedly scan large areas of the sky, quickly identifying new transient events.

The Pilot Study and Methodology

Lluís Galbany of the Institute of Space Sciences (ICE-CSIC) in Barcelona and his colleagues developed a methodology to obtain early spectra of supernovae. Their pilot study, published in the Journal of Cosmology and Astroparticle Physics (JCAP), tested this protocol using observations from the Gran Telescopio de canarias (GTC).

The protocol involves a two-step process:

1. Candidate Search: Identify potential supernovae candidates based on two criteria: the object must not have been present in previous night’s images, and it must reside within a galaxy.
2. Spectroscopic Confirmation: If both criteria are met,the team uses the OSIRIS instrument on the GTC to obtain a spectrum.

the study analyzed ten supernovae-five thermonuclear and five core-collapse-most observed within six days of the estimated explosion, with two observed within 48 hours.

Decoding the Spectra

A supernova’s spectrum provides vital facts about its nature. Such as, the presence of hydrogen indicates a core-collapse supernova. Early spectra also allow astronomers to search for additional data, such as photometry from the Zwicky Transient Facility (ZTF) and the Asteroid Terrestrial-impact Last alert System (ATLAS).

Analyzing light curves-graphs of brightness over time-can reveal subtle features, such as bumps, that might indicate interactions with a companion star.

Future Implications

The success of this pilot study demonstrates that rapid-response spectroscopic programs are feasible and can realistically collect spectra within a day of a supernova explosion. This paves the way for systematic studies in upcoming large surveys, such as the La silla Southern Supernova Survey (LS4) and the Legacy Survey of Space and Time (LSST) in chile.