A world group of astronomers has employed a set of space telescopes to look at a peculiar nuclear transient often known as AT 2019avd. Outcomes of the observational marketing campaign, introduced in a paper published December 21 on the pre-print server arXiv, ship essential insights into the properties and conduct of this transient.
Nuclear astrophysics is vital to understanding supernova explosions, and particularly the synthesis of the chemical parts that advanced after the Huge Bang. Due to this fact, detecting and investigating nuclear transient occasions may very well be important so as to advance our information on this subject.
At a redshift of 0.028, AT 2019avd is a peculiar nuclear transient found by the Zwicky Transient Facility (ZTF) in 2009. The transient has been detected in varied wavelengths, from radio to tender X-rays, and has just lately exhibited two steady flaring episodes with completely different profiles, spanning over two years.
Earlier research of AT 2019avd have advised, primarily based on its ultra-soft X-ray spectrum and optical spectral strains, that it could be a tidal disruption occasion (TDE). Generally, TDEs happen when a star passes shut sufficient to a supermassive black hole and is pulled aside by the black hole’s tidal forces, inflicting the method of disruption. Nevertheless, two optical flares noticed from this transient turned out to be atypical for TDEs.
As a way to decide the true nature of AT 2019avd, a group of astronomers led by Yanan Wang of the Chinese language Academy of Sciences, has employed NASA’s Swift and Chandra spacecraft, in addition to the Neutron star Inside Composition Explorer (NICER) onboard the Worldwide House Station (ISS) to carry out a monitoring marketing campaign of this transient spanning greater than 1,000 days.
The observations of AT 2019avd have discovered that it reveals excessive X-ray variability on each quick (lasting from lots of to 1000’s of seconds) and lengthy (years) timescales. Furthermore, the monitoring marketing campaign revealed some distinctive properties of this transient.
Initially, a speedy drop in luminosity of AT 2019avd occurred roughly 225 days following the height of X-ray emission, which exceeded two orders of magnitude. This drop in luminosity was accompanied by X-ray spectral hardening and was adopted by the potential ejection of an optically-thick radio outflow.
The observations discovered a softer-when-brighter relation all through the flare because the spectrum hardens because the luminosity decreases. It was additionally discovered that when the luminosity decreases by over one magnitude, the blackbody temperature stays fixed and the photon index decreases with the luminosity.
Based on the research, the fractional root-mean-square (rms) amplitude of the detected X-ray variability is excessive with a median of 43% and its evolution is expounded to spectral state. The astronomers assume that the variability could also be attributed to some intervening clumpy outflows.
The authors of the paper famous that the obtained outcomes don’t enable them to attract closing conclusions on the TDE nature of AT 2019avd. They plan additional monitoring of this transient so as to see whether or not it’s going to finally evolve to the usual exhausting state and the way lengthy it’s going to take to attract a full evolution of the accretion course of.
Extra data:
Yanan Wang et al, Speedy dimming adopted by a state transition: a research of the extremely variable nuclear transient AT 2019avd over 1000+ days, arXiv (2023). DOI: 10.48550/arxiv.2312.13543
Journal data:
arXiv
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