Two new delta Scuti stars in Auriga Текст научной статьи по специальности «Физика»

Peremennye Zvezdy ( Variable ¡Stars) 43, No. 3, 2023 Received 10 April; accepted 27 April.

DOI: 10.24412/2221-0474-2023-43-20-26

Two new ô Scuti stars in Auriga

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 that demonstrate multiperiodic pulsations. The paper contains detected frequencies, light curves, finding charts, and other relevant information.

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 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. New Variable Stars

No. Star RA, J2000.0 Dec, J2000.0 V Rc

1 TYC 2414-127-1 05h58m16.689 +35011'20''15 11m 81 - 11m 85 11m 72 - 11m 75

2 USNO-A2.0 1200-04164745 05 59 34.451 +35 11 15.38 15.18 - 15.28 14.78 - 14.90

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 V and Rc filters. Information about the observing sets is given in Table 2.

Table 2. Observing sets

No. Interval of observations JD 245... Frames Filter Exposure, seconds

1 9257 - 9305 356 Rc 300

2 9875 - 9987 1156 V 600

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.

For magnitude calibration in the V band, we use data of the Tycho2 catalogue, and in the Rc 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 av and aRc columns were obtained from our photometry; Tycho B, Tycho V, Gaia G, GBP, and Grp were drawn from the corresponding catalogues. Magnitudes in the Calc. V column were obtained using the equation:

Calc. V = Tycho V - 0.09 x (Tycho B - Tycho V), (1)

described in eq. 1.3.20 in Hipparcos and Tycho Catalogue (ESA, 1997). To calculate magnitudes in the Calc. Rc column, we use the equation:

Calc. Rc = Gaia G - 0.02275 + 0.3961 x (GBP - GRP) - 0.1243 x (GBP - GRP)2 -

0.01396 x (GBP - Grp)3 + 0.003775 x (GBP - GRP)4, (2)

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

Table 3. Magnitudes of calibration stars

Tycho name ay aRc Tycho Calc. V Gaia Calc. Rc

B V G Gbp Grp

TYC-2414-97-1 0.004 0,004 13.272 12.331 12.246 12.6844 12.7066 12.1160 12.5190

TYC-2414-128-1 0.006 0.005 13.511 12.258 12.145 12.0363 12.4114 11.4907 11.8079

TYC-2427-89-1 0.006 0.005 11.980 11.703 11.678 11.9705 12.1948 11.5968 11.8033

TYC-2427-185-1 0.007 0.005 12.371 11.784 11.731 11.5736 11.8105 11.1838 11.3998

TYC-2427-495-1 0.006 0.005 12.521 11.910 11.855 11.5991 11.9529 11.0720 11.3766

TYC-2427-497-1 0.006 0.006 13.176 12.830 12.799 12.1947 12.5411 11.6725 11.9742

TYC-2427-623-1 0.006 0.005 12.212 11.994 11.974 11.7696 12.0481 11.3194 11.5741

TYC-2427-1263-1 0.006 0.004 12.460 11.896 11.845 11.9711 12.1749 11.6178 11.8138

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.

Table 4. Number of photometric measurements

No. Interval of observations JD 245... TYC 2414-127-1 USNO-A2.0 1200-04164745 Filter

1 9257 - 9305 355 355 Rc

2 9875 - 9987 1155 1155 V

Total 1510 1510

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

TYC 2414-127-1

The frequency spectrum

h X /f3

J

0.008 s 0.006

0.002 0.000

-0.02 -0.01

g1 0.00 E

22

frequency c/d

Synthesized and observed light curves

1.2 1.4

time(HJD TT) 2459957+

Figure 1. Frequency spectrum and light curve of TYC 2414-127-1. In the bottom panel, the solid curve is the synthesized light curve and dots are observed data points.

Observations of this star show rapid variations at a time scale of about 0d05 with a peak-to-peak amplitude about 0m04. 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:

Am(i) = £ A, sin(2nf + $,)), (3)

determined by least squares, are collected in Table 4.

Table 4. Detected frequencies of TYC 2414-127-1

15

16

17

18

19

20

21

0.2

0.4

0.6

1.0

Frequency, c/d $ Amplitude, mag

fi 18.612620 0.348661 0.0081

f 18.807620 0.416727 0.0045

f3 18.706380 0.779225 0.0038

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: Max HJD(TT) = 2459937.367 + 0d053727 x E in the V and Rc filters is presented in Fig. 3.

TYC 2414-127-1

•

• N •

• * t •

s • • •

* • • . t *

«p *• • • • *

\*ir

t

i ■ .*. • §

E 1 * * • • »—r ' • •

• * ... . ^ • * ** (

* ■ • ■ • • + • ■ "

STScI POSS2 Red 9.16 x 9.16

Figure 2. A finding chart for TYC 2414-127-1. 3.2 USNO-A2.0 1200-04164745

Both observing sets reveal rapid variations at a time scale of about 0d08 and with a peak-to-peak amplitude about 0m 1. 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.

Table 5. Detected frequencies of USNO-A2.0 1200-04164745

Frequency, c/d $ Amplitude, mag

fi 12.50865 0.655434 0.0180

f2 11.92780 0.015228 0.0087

Figure 4 presents the amplitude spectrum of USN0-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 P0SS2 red plate is presented in Figure 5. The phased light curve of USN0-A2.0 1200-04164745 with the following light elements:

Max HJD(TT) = 2459899.4356 + 0d0799447 x E in the V and Rc filters is presented in Fig. 6.

0.00 0.25 0.50 0.75 1.00 1.25 1.50

Max(HJDTT) = 2459937.367 + 0.053727 xE Filter \Rc

; • • • • !• • • . • • •

« J : * , .. :.....•«:.....»V i* J I * % I : V > • • ■■ s ii . . . \ ;. . •: m• a \ | f ■ .. ••• . " ■ ...» . v >• « , ■• • ; Î A * * • i » *. ' « . i t -•

i • • ; * a* * » • • . S • * •: C. • •-•'it " * • • • •• •• •' •• .•..•• . ? v -v -jy" • f.' : ••• ••

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1 •

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11.72 -........... ;....... 1

11.73 - '

Ol

is E

2.00 phase

Figure 3. Phased light curves of TYC 2414-127-1.

4 Conclusions

I have found two small-amplitude 8 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 120004164745, 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. 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

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

0.0025 -0.0000 -

01 IS

E

USNO-A2.0 1200-04164745

The frequency spectrum

~T 14

~T 16

Synthesized and observed light curves

~T 18

~T 20

frequency c/d

timefHJD TT) 2459956+

Figure 4. Frequency spectrum and light curve of USNO-A2.0 1200-04164745. In the bottom panel, the solid curve is the synthesized light curve and dots are observed data points.

USNQ-A2.0 1200-04164745

N * '

• ■ • » * * * • * •

• * - + . • *•

♦ # • * *

• Var i ■ ■

* *

E 1 • * 1 •*

4 •

• - • •

• • • •

* , $

# . *

STScI POSS2 Red 9.16 x 9.16

Figure 5. A finding chart for USNO-A2.0 1200-04164745.

Phased light curves of USNO-A2.0 1200-04164745

Max(HJDTT) = 2459899.4356 + 0.0799447 xE Filter \V

Max(HJDTT) = 2459899.4356 + 0.0799447 xE Filter \Rc

2.00 phase

14.78 -14.80 -14.82

D>

£ 14.84 14.86 14.88 -14.90 -

• * ' v'J ".•".!. ' ••• y*

'• K-v.....- • • ......... •......'.............. ......-......:......V - • ; .•.........•.....1.....................*.......:.".....%

^...................:......*. -y.:. .»;':•». . ......../.♦.......;.................;.....'* •.»•„•:. ••;•». ........;

.......*...........*•/*'. '' •*' i....... ......«...........•' * ' ^ ^.......

2.00 phase

Figure 6. Phased light curves of USNQ-A2.0 1200-04164745.