CC BY
0Peremennye Zvezdy (Variable ¡Stars) 44, No. 1, 2024 Received 1 January; accepted 26 January.
DOI: 10.24412/2221-0474-2024-44-1-5
Photometry of Transient 2023lmj, an UGSU Cataclysmic Variable Star
A. Samokhvalov
Surgut, Russia, e-mail: sav@surgut.ru
I present a photometric study of the new UGSU cataclysmic variable star discovered as the transient 2023lmj. 160 V-band observations of the object were obtained on JD 2460120-2460142. The period of superhumps is found to be 0? 06033. An overall light curve and average superhump profile are shown.
1 Introduction
The optical transient 2023lmj was detected on JD 2460119 (Sokolovsky et al., 2023). Several days later, Zhao & Gao (2023) obtained the spectrum of the transient and classified it as a cataclysmic variable star.
On the next night after discovering, I started my observations 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. A total of 978 images of the field with 600-second exposures were obtained on JD 2460120-2460257, but the star is visible only on 163 images, obtained on JD 2460120-2460142.
2 Primary reduction and magnitude calibration
For basic reductions for dark current, flat fields, and bias, we used IRAF routines and proprietary software TheSkyX™ by Software Bisque Inc. For calibration, each observing night we obtained 16 bias frames, 16 dark frames, 16 flat fields, plus 16 dark frames corresponding to flat fields.
For photometry of the cataclysmic variable star, 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 plotting light curves, we used our own routines, written in Python 3 programming language using NumPy (Harris et al., 2020) and Matplotlib (Hunter, 2007) libraries.
For magnitude calibration in V band, we use data of the GAIA DR3 catalogue. We restrict ourselves to single, relatively bright stars, with no saturation of pixels for our CCD camera, no close neighbors, and demonstrating no brightness variations during the time interval of our observations. Detailed information about our calibration stars is collected in Table 1. Uncertainties in the oV 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)
based on Table 5.9 of the Gaia Data Release 3, Documentation release 1.2 (https://gea.esac.esa.int/archive/documentation/GDR3/).
Table 1. Magnitudes of calibration stars
GSC name 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
3 Results
14.0
14.5
> O)
2 15.0
15.5
16.0
Figure 1. The superoutburst of 2023lmj: overall light curve.
Superoutburst of 2023lmj
Type = UGSU
> %
\
\ 1
1 1
1
0 5 10 15 20
HJD(TT) 2460120+
Observations of this star demonstrate rapid variations at a time scale of about 0d06 with a peak-to-peak amplitude about 0m 12 on each observing night and with average level decreasing from 13m70 (V) on JD 2460120 to 16m05 (V) on JD 2460142. This photometric behavior is typical of cataclysmic variable stars of the UGSU subtype. Note that super-humps were already observed on the first night after the superoutburst, JD 2460120 (see
the top light curve in Fig. 2). Unfortunately, because of the weather conditions, observations were interrupted after JD 2460142 and resumed on JD 2460159, when nothing brighter than 19m3 (V) was visible at the position of the star.
Using Peranso software by Paunzen and Vanmunster (2016), we performed a period analysis with discrete Fourier transform, very suitable for analyzing sine-shaped super-hump profiles of cataclysmic variable stars. The best period of superhumps is 0d06033, typical of UGSU variable stars. The average superhump profile with the following light elements:
Max HJD(TT) = 2460120.455 + 0d06033 x E in filter V is presented in Fig. 3.
Acknowledgements: I would like to thank N.N. Samus, S.V. Antipin, K.V. Sokolovsky, and S.A. Korotkii for helpful discussion.
References:
Hunter, J. D., 2007, Computing in Science & Engineering, 9, No. 3, 90 Harris, C. R., Millman, K. J., van der Walt, S. J., et al., 2020, Nature, 585, Issue 7825, 357
Gaia Collaboration, Vallenari, A., Brown, A. G. A., et al., 2022, ArXiv:2208.00211 Paunzen, E. & Vanmunster, T., 2016, Astron. Nachr., 337, Issue 3, 239 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, p. 127
Sokolovsky, K., Korotkiy, S., Potapov, N., et al., 2023, Transient Discovery Report for 2023-06-23
Sokolovsky, K. V., Lebedev, A. A., 2018, Astron. & Computing, 22, 28 Zhao, J. & Gao, X., 2023, XOSS Transient Classification Report for 2023-06-25
Figure 2. Superhumps
of 2023lmj at different stages of the superoutburst.
Average superhump profile of 2023lmj
Max{HJDTT) = 2460120.455 + 0.06033xE Type = UGSU
-0.075 -0.050 -0.025 H
I o.ooo -...........j......
0.025 H 0.050
» M...........•.....:'
*
• .
. • *
« w..........•.....r
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
Phase
Figure 3. The average superhump profile of 2023lmj.
