Peremennye Zvezdy (Variable Stars) 43, No. 2, 2023 Received 4 February; accepted 20 February.	Article in PDF
	DOI: 10.24412/2221-0474-2023-43-14-19

Three new Scuti stars in Cygnus

A. Samokhvalov

Surgut, Russia, e-mail: sav@surgut.ru

1. Introduction

During observations of a field in Cygnus, Kryachko et al. (2010) discovered several new variable stars. Here I report three additional new small-amplitude  Scuti (DSCTC) stars in the same field. The new variable stars are listed in Table 1. Their coordinates were drawn from the Gaia DR3 catalog (Gaia Collaboration, 2022). None of these stars are currently contained in the AAVSO Variable Star Index (VSX). However, they are marked VARIABLE in the Gaia DR3 catalog. Table 1 also presents mean Gaia DR3  magnitudes; they are needed for reference because our light curves (see below) are plotted in magnitude differences.

2. Observations

Our observations were carried out at the Astrotel-Caucasus observatory using the 0.3-m Ritchey-Chretien telescope, equipped with an Apogee Alta U9000 CCD camera, and at the Caucasian Mountain Observatory (CMO) of M.V. Lomonosov Moscow State University, see Shatsky et al. (2020), using the 0.25-m remote controlled Ritchey-Chretien telescope, equipped with a SBIG STXL-6303e CCD camera and a filter. The detailed information about observing sets is given in Table 2.

For basic reductions for dark current, flat fields, and bias, we used IRAF routines and proprietary software TheSkyX^TM by Software Bisque Inc. For photometry of new pulsating stars, we applied VaST software by Sokolovsky and Lebedev (2018). All times in this paper are expressed in terrestrial time in accordance with IAU recommendations (resolution B1 XXIII IAU GA), with heliocentric corrections applied. Detailed information about photometrical measurements of each star is given in Table 3.

To derive periods, we use Period04 software by Lenz and Breger (2005) that implements discrete Fourier transform and is very suitable for analysis of sine-shaped light curves of multiperiodic pulsating variable stars.

3. Results

3.1. USNO-A2.0 1275-14987520

Observations of this star show changes in the level of maximum brightness. To clarify the star's variability features, we obtained additional observations at the Astrotel Caucasus observatory and, after its closure, at the Caucasian Mountain observatory. In total, we collected only 1261 observations between JD 2454958 and JD 2459948, because this star was outside the field of view during our observing set No. 3 (see Table 3). All these observations have sufficient accuracy for period analysis. Using Period04 software, we derived the following light elements:

Unfortunately, we were not able to detect multiperiodicity, possibly because the secondary oscillation's amplitude is within the accuracy of our photometry. The phased light curve of USNO-A2.0 1275-14987520 is presented in Fig 1. Its finding chart, based on POSS2 red plate, is shown in Fig. 2.

3.2. USNO-A2.0 1275-15001392

All four observing sets reveal rapid variations at a time scale of about and with a peak-to-peak amplitude about . We searched for periodic signals in the observations using Period04 software in the frequency range between 3 and 20 cycles per day that was selected following recommendations by Breger (2000). Two apparently significant frequencies were detected; their parameters corresponding to the equation

determined by least squares, are collected in Table 4.

Figure 3 presents the amplitude spectrum of USNO-A2.0 1275-15001392 and its theoretical light curve (solid curve) with superposed data points corresponding to individual observations. Light curve variations are easy to notice, they are reproduced with the model rather well. The finding chart based on POSS2 red plate is presented in Fig. 4.

3.3. USNO-A2.0 1275-15124267

The set of observations obtained for this star demonstrates rapid variations with an amplitude not exceeding . The sufficient number of available measurements and relatively high amplitude made it possible to identify three frequencies, presented in Table 5, with notation corresponding to eq. 1. Fig. 5 presents the amplitude spectrum of USNO-A2.0 1275-15124267 and its theoretical light curve (solid curve) with superposed data points corresponding to individual observations. The finding chart, based on POSS2 red plate, is shown in Fig. 6.

Acknowledgements: I would like to thank N.N. Samus for helpful discussion.

References:

Breger, M., 2000, ASP Conference Series, 210, 3

Gaia Collaboration, Vallenari, A., Brown, A. G. A., et al., 2022, ArXiv:2208.00211

Kryachko, T., Samokhvalov, A., Satovskiy, B., Denisenko, D., Peremennye Zvezdy Prilozhenie (Variable Stars Supplement), 2010, 10, No. 10

Lenz, P., Breger, M., 2005, Comm.in Asteroseismology, 146, 53

Shatsky, N., Belinski, A., Dodin, A., et al. 2020, in Ground-Based Astronomy in Russia. 21st Century, ed. I. I. Romanyuk, I. A. Yakunin, A. F. Valeev, & D. O. Kudryavtsev, pp. 127-132

Sokolovsky, K. V., Lebedev, A. A., 2018, Astron. and Computing, 22, 28

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