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3Peremennye Zvezdy (Variable ¡Stars) 43, No. 11, 2023 Received 24 November; accepted 12 December.
DOI: 10.24412/2221-0474-2023-43-121-127
Two New 6 Scuti Stars in Hercules
A. Samokhvalov
Surgut, Russia, e-mail: sav@surgut.ru
I present my discovery and CCD observations of two new small-amplitude S Scuti (DSCTC) stars demonstrating multiperiodic pulsations. The paper contains detected frequencies, light curves, finding charts, and other relevant information.
1 Introduction
During observations of a field of the transient 2023lmj in Hercules (see Sokolovsky et al., 2023), I discovered two new small-amplitude 8 Scuti (DSCTC) stars that demonstrate multiperiodic pulsations. 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, see Gaia Data Release 3 (Gaia DR3), Part 4, Variability (2022).
Table 1. New Variable Stars
No. Star RA, J2000.0 Dec, J2000.0 V
1 USNO-A2.0 0975-13540472 18h 54m22.082 +14°55' 53"49 13m27 - 13m32
2 USNQ-A2.0 1050-12146993 18 54 24.577 +15 04 26.11 14. 08 - 14. 19
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 a V filter. A total of 978 images with 600-s exposures were obtained on JD 2460120 - 2460257.
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 & 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 V band, we apply data from the Gaia DR3 catalogue. We use single, relatively bright stars, but with no saturation of pixels for our CCD camera, without
close neighbors, and not demonstrating brightness variations during the time interval of our observations. Detailed information about our calibration stars is collected in Table 2. Uncertainties in the aV column were derives from our photometry; Gaia G, GBP, and Grp magnitudes were drawn from the corresponding catalog. Magnitudes in the Calc. V column were obtained using the equation:
Calc. V = Gaia G - [-0.02704 + 0.01424 x (GBP - GRP) - 0.2156 x (GBP - GRP)2 +
0.01426 x (Gbp - Grp)3], (1)
which is based on table 5.9 of the Gaia Data Release 3, Documentation release 1.2 (https://gea.esac.esa.int/archive/documentation/GDR3/).
Table 2. Magnitudes of calibration stars
GSC ay Gaia Calc. V
G Gbp Grp
01051-01179 0.005 12.7355 12.9894 12.3245 12.8442
01051-01491 0.004 12.0755 12.8689 11.2027 12.6114
01585-00306 0.005 11.9655 12.9243 11.0048 12.6587
01584-00111 0.005 12.2554 12.7376 11.6132 12.5187
01051-01757 0.004 12.1621 12.5855 11.5643 12.3843
01051-00969 0.004 11.8089 12.5785 12.5785 12.3215
To derive periods, we use Period04 software by Lenz & 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 0975-13540472
Observations of this star show rapid variations at a time scale of about 0d05 with a peak-to-peak amplitude about 0m05. 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). Four apparently significant frequencies were detected; their parameters corresponding to the equation:
Am(t) = £ A, sin(2nf + $,)), (2)
determined by least squares, are collected in Table 3.
Table 3. Detected frequencies of USNQ-A2.0 0975-13540472
Frequency, c/d $ Amplitude, mag
fi 18.52586 0.165096 0.0092
f2 18.44123 0.173702 0.0078
fa 16.33431 0.080947 0.0035
f4 19.50166 0.341614 0.0012
Figure 1 presents the amplitude spectrum of USN0-A2.0 0975-13540472 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 P0SS2 red plate is presented in Fig. 2.
USNO-A2.0 0975-13540472
The frequency spectrum
15 16 17 18 19 20 21 22
frequency c/d
Synthesized and observed light curves
0.5 1.0 1.5 2.0 2.5
time(HJD TT) 2460177+
Figure 1. Frequency spectra and light curve of USNO-A2.0 0975-13540472. In the bottom panel, the solid curve is the synthesized light curve and dots are observed data points.
The V-filter phased light curve of USNO-A2.0 0975-13540472 with the following light elements:
Max HJD(TT) = 2460177.2554 + 0d053979 x E is presented in Fig. 3.
3.2 USNO-A2.Q 1050-12146993
Photometric measurements of this star reveal rapid variations at a time scale of about 0d 1 and with a peak-to-peak amplitude about 0m 1. To search for periodic signals in the observations, we applied Period04 software in the frequency range between 3 and 20 cycles per day that had been selected following recommendations by Breger (2000). Three apparently significant frequencies were detected; their parameters, corresponding to Equation 2 determined by least squares, are collected in Table 4.
Table 4. Detected frequencies of USNQ-A2.0 1050-12146993
Frequency, c/d $ Amplitude, mag
fl 9.51668 0.235789 0.0241
f2 5.65634 0.016710 0.0096
f3 6.47599 0.250858 0.0085
USNO-A2.Q 0975-13540472
• ■ ^ • #
■ ■: • • . • •
—i . • ■ • Var . - - * • ♦ • .1 J-/'.
•E ' *—
• • * * . • • 4 F f _ * * ■ ■ ■.. . - * f ■ > , I . - .. • • * r-Vj ' . * • • - ' ■ .
• * -* » - • * • ■ . „ ■ .
STScI POSS2 Red 9.16x 9.16
Figure 2. A finding chart for USNO-A2.0 0975-13540472.
Figure 4 presents the amplitude spectrum of USNO-A2.0 1050-12146993 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. 5. The V-filter phased light curve of USNO-A2.0 1050-12146993 with the following light elements:
Max HJD(TT) = 2460162.4536 + 0d 105079 x E
is presented 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 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., Skrotkiy, S., Potapov, N., et al. 2023, Transient Discovery Report for 2023-06-23
Sokolovsky, K. V. & Lebedev, A. A., 2018, Astron. and Computing, 22, 28
Phased light curve of USNO-A2.0 0975-13540472
13.26
13.27
13.28 ~ 13.29 I 13.30
13.31
13.32
13.33
Figure 3. Phased light curve of USNQ-A2.0 0975-13540472.
Max(HJDTT) = 2460177.2554 + 0.053979xE
Type = DSCT
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00 Phase
USNO-A2.0 1050-12146993
The frequency spectrum
frequency c/d
Synthesized and observed light curves
time(HJD TT) 2460162+
Figure 4. Frequency spectra and light curve of USNO-A2.0 1050-12146993. In the bottom panel, the solid curve is the synthesized light curve and dots are observed data points.
USNQ-A2.0 1050-12146993
' V A ■ • t. » • i • , i • * • v* ' . - ' - . '.
' * • * ■ • ' * ■ v I* , » « * >. • ■ ■ • • Var ' » ■ •- . , ' " '' . i > ' % •
■■ ■ . ■ • , * ' / • ' ' - ■ . - •
V . . . . •■ i V • • * • • » *...*-** 4 '
STScI POSS2 Red 9.16x 9.16
Figure 5. A finding chart for USNO-A2.0 1050-12146993.
Phased light curve of USNQ-A2.0 1050-12146993
14.08 14.10 £ 14.12 E 14.14 14.16 14.18 14.20
Figure 6. Phased light curve of USNO-A2.0 1050-12146993.
Max(HJDTT) = 2460162.4536 + 0.105079xE
Type = DSCT
