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11Peremennye Zvezdy ( Variable ¡Stars) 43, No. 2, 2023 Received 4 February; accepted 20 February.
DOI: 10.24412/2221-0474-2023-43-14-19
Three new S Scuti stars in Cygnus
A. Samokhvalov
Surgut, Russia, e-mail: sav@surgut.ru
I present my discovery and CCD observations of three new small-amplitude S 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 8 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 G 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.Û 1275-14987520 21h12m19S130 +40°25/52''11 13m 07
2 USNO-A2.Û 1275-15001392 21 12 36.142 +40 41 00.66 12.82
3 USNO-A2.0 1275-15124267 21 15 10.341 +40 37 01.05 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 V 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™ 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 USNQ-A2.0 1275-14987520
Figure 1. Phased light curve of USNQ-A2.0 1275-14987520.
Table 2. Observing sets
No. Telescope CCD Camera Interval of observations JD 245... Frames Filter Exposure, seconds
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 V 300
3 0.3 m, 1/7.8 Apogee Alta U9000 6586 - 6604 706 V 300
4 0.25 m, 1/8 SBIG STXL-6303e 9841 - 9948 667 V 600
Table 3. Photometric measurements
No. Interval of observations JD 245... USNÜ-A2.0 1275-14987520 USNÜ-A2.0 1275-15001392 USNÜ-A2.0 1275-15124267 Filter
1 4958 - 4993 459 422 630 unfiltered
2 5315 - 5450 190 719 710 V
3 6586 - 6606 0 615 706 V
4 9841 - 9948 612 626 667 V
Total 1261 2382 2713
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:
Max HJD(TT) = 2459899.305 + 0d 1302843 x E.
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 USN0-A2.0 1275-14987520 is presented in Fig 1. Its finding chart, based on POSS2 red plate, is shown in Fig. 2.
USNO-A2.Q 1275-14987520
i* ■ * ■ • . * ~ • " : ■ ' " : ■ ■ 4 -J v ■ **Var ' • ' , :•> - V" ' V X ■ E L^" ■ " - v;\ 1 • » , ' ■ ,1 t * • . V -......
* • '.* * • . r. K :
• .... * * r < * ■ •
STScI POSS2 Red 9.16 x 9.16
Figure 2. A finding chart for USNQ-A2.0 1275-14987520.
3.2 USNO-A2.0 1275-15001392
All four observing sets reveal rapid variations at a time scale of about 0d. 1 and with a peak-to-peak amplitude about 0m08. 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
Am(i) = Y, A sin(2n(ftt + $i)),
(1)
USNO-A2.0 1275-15001392
The frequency spectra
Synthesized and observed light curves r™qu«nty at
tlmelHJD TTI 2430554 +
Figure 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.
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 0m 12. 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. Table 4. Detected frequencies of USNO-A2.0 1275-15001392
Frequency, c/d $ Amplitude, mag
fl 8.4137218 0.173387 0.0128
f2 7.5947267 0.947497 0.0051
Table 5. Detected frequencies of USNO-A2.0 1275-15124267
Frequency, c/d $ Amplitude, mag
fl 7.3473022 0.911653 0.0220
f2 7.6409009 0.663722 0.0208
fa 7.4684716 0.187621 0.0144
USNO-A2.Q 1275-15001392
• ■. > , •••*•• •» \ f . ' * ' ,
? •: Var . ■ .
• V*#•'. -* 'T r-i • ' ■ • ■ "E • U . • ' . * * • ; ; • - % ■ . - - • , « *:■*■•' • ' / . * v . . . •* 4
. . * • ' .: , V ' *
•v. \ • * ' '
STScI POSS2 Red 9.16 x 9.16
Figure 4. A finding chart for USNO-A2.0 1275-15001392. 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 Prilozhe-
nie (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. 1.1. 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
USNO-A2.0 1275-15124267
The frequency spectra
^xix
) 5 ID 15 2.5
tlmelHJD TT) Z456595+
Figure 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.
USNO-A2.Q 1275-15124267
- . ' N. •• s. • > • 3 Km
* ■ .. ■ k *,'. ■ • • • • • • .. . v - * * * • * ••. • 1* ■ :* . • . • ■
■ ; . ' • -Vat . : ■ " ■ ' •
. «1 F * —- * 1 ■ • * . • • * • * # »' 4 • — |
' • . * * ■ *. ... - \ ; * ■■ . . y. • v.. ■ i t '» I f
•* .... . • . % , ■ •, V 1 • • * h 1 • • ! * * - * . * *. . .. V • •
t • *f * . t i « • • s, ■ *. • » * •* ■ . ■
STScI POSS2 Red 9.16 x 9.16
Figure 6. A finding chart for USNO-A2.0 1275-15124267.
