Astronomers from China and Taiwan have observed the nova explosion of V1716 Sco that occurred last year, using various X-ray and gamma-ray space observatories. The results of the observation campaign, presented on June 27 on the preprint server arXivprovide essential information about the evolution of this nova.
A nova is a star that experiences a sudden increase in brightness and slowly returns to its original state, a process that can take many months. Such an explosion is the result of the accretion process in a close binary system containing a white dwarf and its companion.
V1716 Sco, also known as Nova Sco 2023, was discovered when it exploded on April 20, 2023 at magnitude 8.0. Follow-up observations of V1716 Sco spectroscopically confirmed it as a classical (Fe II) nova.
Now, a team of astronomers led by Huihui Wang of Henan University of Science and Technology in Luoyang, China, has probed V1716 Sco in the X-ray and gamma-ray bands. For this purpose, they used NASA’s Swift, NuSTAR and Fermi spacecraft, as well as the Neutron Interior Composition Explorer (NICER) star aboard the International Space Station.
“We performed a joint analysis of NuSTAR, Swift, NICER and Fermi-LAT observations of nova V1716 Sco,” the researchers write in the paper.
The observations revealed that the gamma-ray emission started one day after the optical outburst of V1716 Sco, with a test statistic (TS) value of 70. The duration of this gamma-ray activity with a TS value above 4.0 lasted for 40 days. . Additionally, stronger X-ray emission was also observed by Swift the day after the optical burst.
The findings therefore make V1716 Sco the first classical nova in which Swift’s X-ray detection is simultaneous with gamma-ray emission, and the fourth classical nova to exhibit gamma-ray emission at the same time as the harder emission of X-rays from NuSTAR data.
By analyzing the X-ray spectrum, the researchers found that the hardness ratio decreased rapidly with time, and the observed emission entered the supersoft source (SSS) phase approximately 40 days after the nova explosion. Additionally, the NICER data allowed astronomers to detect a quasi-periodic oscillation (QPO) in the SSS phase with a period of 79.10 seconds.
Trying to explain the origin of the discovered QPO, the authors of the paper emphasize the rotation modulation of the white dwarf as the most plausible hypothesis. However, they observed that the period of the modulations is not stable with time. This could mean that the hot spot region on the white dwarf’s surface could be shifting over time, or the periodic modulation could originate from another mechanism, such as a stellar oscillation.
More information:
H. -H. Wang et al, X-ray and gamma-ray study of the 2023 nova explosion of V1716 Sco, arXiv (2024). DOI: 10.48550/arxiv.2406.19233
Magazine Information:
arXiv
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citation: Nova Eruption of V1716 Sco Inspected in X-rays and Gamma Rays (2024, July 4) Retrieved July 5, 2024 from https://phys.org/news/2024-07-nova-eruption-v1716-sco-rays. html
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