Using the Nanshan One-meter Wide-field Telescope (NOWT), astronomers from China have observed the open cluster NGC 2355 and the surrounding field in search of variable stars. They discovered 72 new variables in this region. The finding is reported in a paper published June 14 on arXiv.org.
Star clusters provide excellent opportunities to study the evolution of stars, as they are collections of stars with similar properties, e.g. age, distance and initial composition. In particular, astronomers often look for: variable stars in young clusters, which could be crucial for advancing the understanding of pre-main sequence stars (PMS), and thus the early stages of stellar evolution†
Recently, a team of astronomers led by Hong Wang of the Xinjiang Astronomical Observatory in Xinjiang, China, conducted an extensive search for variable stars in NGC 2355 using NOWT’s CCD camera. At a distance of about 5,400 light yearsNGC 2355 is a open cluster in the constellation Gemini, estimated to be 900 million years old. To date, only a few variable searches have been performed in this cluster.
“We examined the variable stars in the field around NGC 2355 using photometric observation data from the time series. With the Nanshan One-meter Wide-field Telescope, more than 3,000 CCD frames in the V-band were obtained over 13 nights. .” the researchers wrote in the paper.
All in all, Wang’s team discovered 88 variable stars during 13 nights of photometric observations. It turned out that 72 of the 88 stars are new variables, while the rest are known variables reported from previous observations.
The researchers classified the stars from the sample into different types based on their light curves and derived fundamental parameters. Finally, of all the stars listed in the paper, 52 are pulsating stars, 26 eclipsing binary stars, and four were classified as rotating variables. The other six are variable stars of the unclear type.
“For those variable stars for which no type has been established, we may need more observations later to identify and classify these unknown variable stars,” the researchers said. astronomers wrote.
Of the 52 pulsating stars, 38 were further classified as Delta Scuti variables, nine as RR Lyraes, three as Gamma Doradus variables, and two as Cepheid I-type variable stars. When it comes to the 26 obscuring binaries, 11 are EW type, nine are EA type and the rest are EB type.
The researchers noted that four variable stars listed in the paper are members of NGC 2355, in addition to the 11 previously known variables classified as cluster members by a 2018 study. They are located in the outer region of the cluster and show homogeneity in space positions. and kinematic properties with the TROS members. In addition, the study authors found that NGC 2355 has a metallicity of about -0.07 dex and a redness of 0.24.
Hong Wang et al, Search for variable stars in the open cluster NGC 2355 and the surrounding region. arXiv:2206.06569v1 [astro-ph.SR]† arxiv.org/abs/2206.06569
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