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22Peremennye Zvezdy (Variable ¡Stars) 42, No. 12, 2022
Received 1 December; accepted 16 December.
DOI: 10.24412/2221-0474-2022-42-106-110
Four High-amplitude 6 Scuti Stars from the ZTF Survey
A. M. Zubareva1'2, S. V. Antipin2, N. P. Ikonnikova2, A. A. Belinskii2, A. V. Samokhvalov3
1 Institute of Astronomy of the Russian Academy of Sciences, Pyatnitskaya str., 48, 119017 Moscow, Russia
2 Sternberg Astronomical Institute, Lomonosov Moscow University, Universitetsky Ave., 13, 119234 Moscow, Russia
3 Surgut, Russia
We report the results of our CCD photometry of several variable stars. As a result, we are able to confirm that four stars from the ZTF survey that were classified uncertainly are indeed highamplitude S Scuti stars. Periods, epochs of maximum light, magnitudes at maximum and minimum, phased light curves are presented.
1 Introduction
While preparing a paper on the discovery of a bimodal high-amplitude 8 Scuti star (HADS) that will be published elsewhere, we have checked whether the star is now contained in the VSX database1. We found out that our object is listed in the VSX among a group of cases with the same common feature. Several dozens of variables from the ZTF catalog of periodic variable stars (Chen et al., 2020) have ambiguous classification (HADS: | EW). In our attempt to find several multiperiodic HADS stars or at least to distinguish between two types of variability, HADS and W UMa (EW) with a twice longer period, we carried out CCD photometry of selected stars from this particular group of VSX-listed stars.
2 Observations and Analysis
We observed several targets in constellations Aquila, Cygnus, and Vulpecula, which are easily observable in July with the Zeiss-600 telescope of the Crimean Astronomical Station (P.K. Sternberg Astronomical Institute, M.V. Lomonosov Moscow State University). Additional data were collected at the Caucasus Mountain Observatory (CMO) of M.V. Lomonosov Moscow State University with two Ritchey-Chretien telescopes: the 60-cm RC600 telescope (Berdnikov et al., 2020) and the 25-cm Astrosib telescope (F = 200 cm). The detailed information about observing runs is given in Table 12.
We picked stars brighter than 17m in the Rc filter that can be reliably measured with a good signal-to-noise ratio. The images were reduced in the standard manner comprising bias, dark and flat-field frames. To perform aperture photometry and magnitude calibration, we used VaST3 software (Sokolovsky and Lebedev, 2018). Information on R
1 www.aavso.org/vsx
2A.M.Z. is for A. M. Zubareva; N.P.I. for N. P. Ikonnikova; A.V.S. for A. V. Samokhvalov.
3 scan.sai.msu.ru/vast
Table 1: Log of observations
Telescope CCD camera JD2459... Number Filter Exposure, Observer
diameter, cm of nights seconds
Zeiss-600 (60) Kepler KL400 775-789 11 Rc 120, 180 A.M.Z.
RC600 (60) Andor iKon-L DZ936N-BV 872-925 17 Rc 120 N.P.I.
Astrosib (25) SBIG STXL 6303E 898-915 5 Rc 600 A.V.S.
magnitudes of field stars was extracted from the GAIA DR3 catalog (GAIA Collaboration et al., 2022) for calibration purposes. To derive periods, we applied WinEfk software4. The package allows us to implement calculations with the Deeming method (Deeming, 1975) that is very suitable for analysis of smooth sine-like light curves of variable stars, especially for pulsating variables.
3 Results
3.1 ZTF J195936.84+365219.3
The first observational set for ZTF J195936.84+365219.3 was carried out from July, 14 to July, 16, 2022 with the Zeiss-600 telescope, exposure times being 120 seconds. After analyzing the light curve of ZTF J195936.84+365219.3 more thoroughly, we found changes in the level of maximum brightness. To confirm or to discard possible bimodality of ZTF J195936.84+365219.3, we decided to continue observations of the star with the two CMO telescopes (see Table 1). In total, we collected 1023 individual measurements on 25 individual runs between July, 14 and December, 11, 2022. We derive the following light elements:
HJD Max = 2 459 776.356 + 0d 181237 x E.
The phased light curve is presented in Fig. 1. The brightness in maximum is Rc = 14m86 and in minimum, Rc = 15m09; thus, the peak-to-peak amplitude is 0m23. After performing periodogram analysis of the combined photometry from three telescopes, we did not detect any signal implying a second periodicity.
3.2 Three Confirmed HADS Variables
The summary results concerning the three observed stars are presented in Table 2.
Table 2: The data on three observed high-amplitude 6 Scuti stars
Name JD2459... No. of Exp, No. of HJD Max P, d Max Min
nights s obs.
ZTF J190321.93-011900.0 787-789 3 180 238 2459788.335 0.1814 15.93 16.35
ZTF J192734.17+233948.7 782-784 3 120 362 2459782.454 0.1775 13.78 14.00
ZTF J204838.44+413414.7 780-781 2 120 278 2459781.514 0.1724 14.90 15.23
4 http://www.vgoranskij.net/software/
ZTF J195936.84+365219.3
c
14,80 14,85 14,90 14,95 15,00 15,05 15,10 15,15
-0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2
phase
Figure 1. Phased light curve for ZTF J195936.84+365219.3.
The corresponding phased light curves are presented in Figs. 2-4. The rapid rise to maximum brightness and resulting asymmetry of the light curves, the amplitudes and the periods for all four objects in the section are typical of high-amplitude 5 Scuti stars.
4 Conclusions
Unfortunately, we did not succeed in our attempts to find multiperiodicities in the course of analyzing our CCD photometry of ZTF J190321.93-011900.0, ZTF J192734.17+233948.7, ZTF J195936.84+365219.3, and ZTF J204838.44+413414.7. However, these variables can be classified as assured high-amplitude 5 Scuti stars.
References:
Berdnikov, L. N., Belinskii, A. A., Shatskii, N. I., et al., 2020, Astron. Rep., 64, 310 Chen, X., Wang, S., Deng, L., et al., 2020, Astron. J. Suppl. Ser., 249, id. 18 Deeming, T. J., 1975, Astrophys. and Space Sci., 36, 137
Gaia Collaboration, Vallenari, A., Brown, A. G. A., Prusti, T., et al., 2022, Gaia Data
Release 3: Summary of the content and survey properties, arXiv:2208.00211 Sokolovsky, K. V., Lebedev, A. A., 2018, Astron. and Computing, 22, 28
ZTF J190321.93-011900.0
c
15,8 16,0 16,2 16,4 16,6
-0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2
phase
Figure 2. Phased light curve for ZTF J190321.93-011900.0.
13.8
13.9 14,0
-0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2
phase
Figure 3. Phased light curve for ZTF J192734.17+233948.7.
ZTF J192734.17+233948.7
ZTF J204838.44+413414.7
с
14,9
15.0
15.1
15.2
15.3
-0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2
phase
Figure 4. Phased light curve for ZTF J2G4838.44+413414.T.
