Peremennye Zvezdy (Variable Stars) 43, No. 3, 2023 Received 10 April; accepted 27 April.	Article in PDF
	DOI: 10.24412/2221-0474-2023-43-20-26

Two new Scuti stars in Auriga

A. Samokhvalov

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

1. Introduction

During observations of a field in Auriga, Kryachko et al. (2011) discovered several new variable stars. Here I report two 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.

2. Observations and magnitude calibration

Our observations were carried out 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 with and filters. Information about the 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.

For magnitude calibration in the band, we use data of the Tycho2 catalogue, and in the band, Gaia DR3. We use single, relatively bright stars that do not produce saturation of pixels of our CCD camera, have no close neighbors, and do not demonstrate variability on the time interval of our observations. Detailed information about calibration stars is given in Table 3. Values in the and columns were obtained from our photometry; Tycho , Tycho , Gaia , , and were drawn from the corresponding catalogues. Magnitudes in the Calc. column were obtained using the equation:

described in eq. 1.3.20 in Hipparcos and Tycho Catalogue (ESA, 1997).

To calculate magnitudes in the Calc. column, we use the equation:

based on Table 5.9 of the Gaia Data Release 3, Documentation release 1.2
(https://gea.esac.esa.int/archive/documentation/GDR3/).

Information on photometric measurements available for the two variable stars is given in Table 4. An archive of all observations is available online in the html version of this paper.

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. TYC 2414-127-1

Observations of this star show rapid variations at a time scale of about 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, selected following recommendations by Breger (2000). Three apparently significant frequencies were detected; their parameters corresponding to the equation:

determined by least squares, are collected in Table 4.

Figure 1 presents the amplitude spectrum of TYC 2414-127-1 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. 2.

The phased light curve of TYC 2414-127-1 with the following light elements:

in the and filters is presented in Fig. 3.

3.2. USNO-A2.0 1200-04164745

Both observing sets reveal rapid variations at a time scale of about and with a peak-to-peak amplitude about . In Gaia DR3, Part 4, Variability by Gaia Collaboration (2022), the variability type specified for this star is RS, but this object is not present in the X-Ray 1RXS catalogue, see Voges at al. (1999). Based on our photometry, we assume the DSCT type of variability. To search for periodic signals in our observations, we use the Period04 software in the frequency range between 3 and 20 cycles per day, selected following recommendations by Breger (2000). Two apparently significant frequencies were detected; their parameters corresponding to Equation 3, determined by least squares, are collected in Table 5.

Figure 4 presents the amplitude spectrum of USNO-A2.0 1200-04164745 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 Figure 5. The phased light curve of USNO-A2.0 1200-04164745 with the following light elements:

in the and filters is presented in Fig. 6.

4. Conclusions

I have found two small-amplitude  Scuti (DSCT) variables in a field in Auriga, earlier studied by Kryachko et al. (2011). The first of them, TYC 2414-127-1, turns out to be multiperiodic, with three detected frequencies. For the second one, USNO-A2.0 1200-04164745, I found two frequencies. Finding charts and light curves are presented for both stars.

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

References:

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

ESA, 1997, The Hipparcos and Tycho Catalogues, ESA SP-1200, Vol. 1 (ESA97)

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

Kryachko, T., Samokhvalov, A., Satovskiy, B., Peremennye Zvezdy Prilozhenie (Variable Stars Supplement), 2011, 11, No. 4

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

Voges, W., Aschenbach, B., Boller, Th., et al. 1999, Astron. & Astrophys., 349, 389

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