NSVS 2983201 is a binary communication system, notes found

Chart of the sky around NSVS 2983201. The graph is 15 by 15 in size, oriented north-down, east-right. The FOV of the CCD camera is shifted slightly to the east, so that the primary comparison star is not too close to the edge of the frame. Credit: Dębski et al. , 2022.

Polish astronomers have conducted optical observations of a short-period variable star known as NSVS 2983201. They have found that the object is a binary contact system with a mass ratio of about 0.36. The finding was reported in a paper published Dec. 28 in arXiv Prepress warehouse.

The discovery and study of variable stars can provide important clues about aspects of stellar structure and evolution. Investigating variables could also be useful in better understanding the scale of distance in the universe.

NSVS 2983201 (also known as KR00245) was initially identified as a variable with a relatively short orbital period of about 0.286 days, experiencing total eclipses. Follow-up observations for NSVS 2983201 suggested that it may be a contact binary; However, due to very poor light curve coverage and the fact that no numerical modeling analysis was performed for this object, this cannot be confirmed.

Now, a team of astronomers led by Bartomeg Dubski of the Jagiellonian University Astronomical Observatory in Kraków, Poland, has provided observational evidence that confirms the binary contact hypothesis. Their discovery is based on optical data from the Apogee Alta U42 Camera on the astronomical observatory’s Cassegrain Telescope, collected in October 2022.

We took 190 light frames in each filter: B, V, R, and I. The exposure times were: 40 sec, 30 sec, 20 sec, and 20 sec, respectively. Calibration frames were collected on the same day (day-sky Flatframes in each filter). In the evening, while Bias- and Darkframes immediately after the observations, “the researchers explained.

The team applied two methods to obtain the basic parameters for NSVS 2983201. One indicates a distance for this system of about 4,250 light-years, while the other indicates 4,560 light-years. Based on the estimated distance, the absolute magnitude of NSVS 2983201 was found to be 4.71 and 4.56 mag, respectively.

These results, together with a system mass ratio of approximately 0.3585, allowed astronomers to calculate the orbital separation and masses of the two components of NSVS 2983201. Depending on the distance and absolute size, the orbital separation was found to be 2.04 or 2.19 solar radii, which confirmed that it is binary. Contact. If the orbital separation is smaller, the masses of the primary and secondary stars are estimated to be 1.03 and 0.37 solar masses, respectively. In the second scenario, the primary star has a mass of about 1.27 solar masses, while the companion star has a mass of approximately 0.46 solar masses.

The researchers added that the light curve obtained for NSVS 2983201 is burdened by the so-called O’Connell effect – there is a difference between the height of the maximum brightness. This made it possible to identify a large circular star spot that is presumably of magnetic origin and thus visible at visible wavelengths as a bright region on the stellar surface. The paper’s authors hypothesize that this spot belongs to the primary star as it would have a thicker convective envelope.

more information:
Debsky et al., A study of a two-contact system NSVS 2983201, arXiv (2022). doi: 10.48550/arxiv.2212.14085

Journal information:

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