The left panel is a 15′ × 15′ image of
SN 2024abvb constructed using multi Bgr-band Swope images that are mapped to
the blue, green, and red channels of the image, respectively. The right panel
is a 2′ × 2′ cutout with the position of SN 2024abvb marked. The arrow
indicates the host galaxy PSO J011055.760-054416.73. Credit: arXiv (2026). DOI: 10.48550/arxiv.2602.16227
An international team of
astronomers has carried out photometric and spectroscopic observations of SN
2024abvb—a recently discovered supernova of a rare Type Icn. The new
observational campaign yields important information regarding the properties
and nature of this supernova. The study was published February 18 on the arXiv pre-print
server.
Supernovae and their extreme subtype
Supernovae (SNe) are powerful and
luminous stellar explosions. They are important for the scientific community as
they offer essential clues into the evolution of stars and galaxies. In
general, SNe are divided into two groups based on their atomic spectra: Type I
and Type II. Type I SNe lack hydrogen in their spectra, while those of Type II
showcase spectral lines of hydrogen.
Type Icn SNe are an extreme subtype
of interacting stripped-envelope supernovae (SESN). They have strong, narrow
oxygen and carbon lines but weak or absent hydrogen and helium lines,
presenting additional complications to the stripping mechanism. They have
narrow emission features indicative of circumstellar interaction.
Newfound rare Type Icn supernova
So far, only six Type Icn SNe have
been discovered, and SN 2024abvb is the latest addition to this short list. It
was detected on November 22, 2024 by the Asteroid Terrestrial-impact Last Alert
System Project (ATLAS) and was found to be associated with the host galaxy PSO
J011055.760-054416.73, however highly offset from it—about 73,000 light years
from the core of the host.
Recently, a group of astronomers
led by Jennifer Shi of the University of Melbourne in Australia, performed
follow-up monitoring of SN 2024abvb using various ground-based telescopes,
hoping to get more insights into its enigmatic nature.
After explosion
The new observations found that SN
2024abvb reached a peak magnitude of -19.55, which makes it one of the most
luminous Type Icn SNe. It declines at a rate of 0.07 mag/day in the r band,
therefore consistent with other known supernovae of this subclass.
During the first week after
explosion, SN 2024abvb shows evidence of interaction with a
hydrogen/helium-poor, carbon-rich circumstellar medium (CSM) in its optical
spectra. Moreover, the persistent lack of helium emission at late times of
observations indicates a transition from Type Ibn to Icn with low carbon
ionization. This makes SN 2024abvb the first known example of such an event.
Host, progenitor and ejecta mass
When it comes to the host of SN
2024abvb, PSO J011055.760-054416.73, the study found that it is an
intermediate-mass galaxy with a stellar mass of about 6 billion solar masses.
It has an extremely low specific star-formation rate and low metallicity.
According to the astronomers, these
results, together with a large off-set of SN 2024abvb, suggest that the
progenitor of this supernova was a low-mass star stripped by a compact
companion, which then exploded within a dense, hydrogen/helium-poor CSM.
"Based on its spectral
features, local and host environment properties, and host-galaxy offset, we
favor an 8–10 solar masses star that is stripped by a compact companion as the
progenitor that had a sufficient runaway velocity to reach the offset of SN
2024abvb," the researchers conclude.
Regarding the explosion itself, the
results indicate that the ejecta mass of SN 2024abvb was at a level of 2.59
solar masses, interacting with about 0.28 solar masses of CSM material. The
astronomers note that these values are generally larger than other SNe Icn but
consistent with the rapidly evolving SNe Ibn.
Source: Rare Type Icn supernova SN 2024abvb is among the most luminous known
No comments:
Post a Comment