Peremennye Zvezdy

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:

I present my discovery and CCD observations of three new small-amplitude  Scuti (DSCTC) stars. Two of them demonstrate multiperiodic pulsations. The paper contains detected frequencies, light curves, finding charts, and other relevant information.

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.

Table 1. New Variable Stars
No. Star RA, J2000.0 Dec, J2000.0 G
1 USNO-A2.0 1275-14987520 1307
2 USNO-A2.0 1275-15001392 12.82
3 USNO-A2.0 1275-15124267 13.77

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.

Table 2. Observing sets
No. Telescope CCD Camera
 Interval of  
  JD 245...  
Frames Filter
1 0.3 m, 1/7.8 Apogee Alta U9000 4958 - 4993 630 unfiltered 300
2 0.3 m, 1/7.8 Apogee Alta U9000 5315 - 5450 719 300
3 0.3 m, 1/7.8 Apogee Alta U9000 6586 - 6604 706 300
4 0.25 m, 1/8 SBIG STXL-6303e 9841 - 9948 667 600

For basic reductions for dark current, flat fields, and bias, we used IRAF routines and proprietary software TheSkyXTM 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.

Table 3. Photometric measurements
 Interval of  
  observations JD 245...  
1 4958 - 4993 459 422 630 unfiltered
2 5315 - 5450 190 719 710
3 6586 - 6606 0 615 706
4 9841 - 9948 612 626 667
Total 1261 2382 2713

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

Fig. 1. Phased light curve of 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.

Fig. 2. A finding chart for USNO-A2.0 1275-14987520.

3.2. USNO-A2.0 1275-15001392

Fig. 3. Frequency spectra and light curve of USNO-A2.0 1275-15001392. In the bottom panel, the solid curve is the synthesized light curve and dots are observed data points.

Fig. 4. A finding chart for 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.

Table 4. Detected frequencies of USNO-A2.0 1275-15001392
Frequency, c/d Amplitude, mag
8.4137218 0.173387 0.0128
7.5947267 0.947497 0.0051

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.

Table 5. Detected frequencies of USNO-A2.0 1275-15124267
Frequency, c/d Amplitude, mag
7.3473022 0.911653 0.0220
7.6409009 0.663722 0.0208
7.4684716 0.187621 0.0144

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


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, 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

Fig. 5. Frequency spectra and light curve of USNO-A2.0 1275-15124267. In the bottom panel, the solid curve is the synthesized light curve and dots are observed data points.

Fig. 6. A finding chart for USNO-A2.0 1275-15124267.

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