CC BY
11Peremennye Zvezdy (Variable ¡Stars) 42, No. 11, 2022
Received 5 November; accepted 23 November.
DOI: 10.24412/2221-0474-2022-42-87-105
Long-term Brightness and Color Variations of the Young Variable Star V645 Cyg
S. Yu. Gorda, A. P. Bisyarina, A. M. Sobolev, S. Yu. Parfenov
Kourovka Astronomical Observatory, Ural Federal University, Mira str. 19, Yekaterinburg, 620002 Russia
We presents the results of our 13-year (2009-2022) photometric study of the young variable star V645 Cyg, which is a Herbig Ae/Be object located in a region of active star formation. Observations were carried out in the optical part of the spectrum, in VRI filters. During the observation time interval, we found, along with short-term small-amplitude chaotic brightness changes of V645 Cyg, we found a monotonous increase in the total brightness of the system in the V band by ~ 1m; in R, by ~ 1m4; and in I, by ~ 2m, as well as an increase in the reddening of the system: its V — R color index increased by ~ 0m3, and R — I, by ~ 0m6. Optical brightness variations in the time interval JD 2450000-2456500 are closely followed by variations of the CH3OH maser flux at 6.7 GHz reported in the literature. Absence of strong variations on the time scale of hours suggests that non-stationarity effects in the maser radiation are not significant. The monotonous changes in the brightness and color of V645 Cyg are interpreted as a decrease in the optical depth of the gas-dust cocoon towards the star and corresponding increase in the visibility of regions of the star and its immediate vicinity.
Variability of V645 Cyg was discovered by Hoffmeister et al. (1951). Cohen (1977) found that the position of V645 Cyg coincided, within 5", with a reflection nebula and found three condensations (N0, N1 and N2 in his notation) from spectrophotometry and spectropolarimetry. He came to the conclusion that the star itself, whose radiation is reflected by the condensations, is a young star of the spectral type O and, most likely, is situated between the starlike knot N0 and the knot N1, partially being in a gas-dust cocoon. Further studies of the object V645 Cyg, mainly in the infrared (IR) and radio ranges (Humphreys et al., 1980; Lada et al., 1981; Morris et al., 1982; Torrelles et al., 1983; Goodrich, 1986), revealed bipolar gas outflows, suggestive of the presence of a molecular protoplanetary disk observed in the IR range and in the maser lines of CH3OH and H2O (Valtts et al., 2002). The maser emission in OH transitions was also detected (Morris et al., 1982).
More recent mid-infrared studies of V645 Cyg have shown that N0 is a point source, i.e. a young star, and the nebular component N1, located five arc seconds northwest of N0, is a diffuse nebula, especially since the N0 component is 200 times brighter than N1 (Clarke et al., 2006). Thus, it became clear that N0 was the star V645 Cyg itself, and not just a knot of a reflection nebula such as N1, as it had been previously thought. Various observations show that V645 Cyg is a very complex and interesting object to study, containing a young massive star.
Despite the general opinion that V645 Cyg is a young stellar object, there is still no consensus on its physical parameters. Some authors prefer the classification of an O-type star (e.g., Testi et al., 1998), while others consider it an A-type supergiant (e.g., Bowey et al., 2003). The distance to the object was also ambiguous, ranging from 3 to 6 kiloparsecs (Clarke et al., 2006). The first measurement of trigonometric parallax from H2O maser observations corresponds to a distance of 5.28 kpc (Honma et al., 2007),
but later measurements indicate a smaller value of 4.054-4.15 kpc (Asaki et al., 2014; Quiroga-Nunez et al., 2019).
According to one of the recent studies (Miroshnichenko et al., 2009), V645 Cyg is a young massive B-type main sequence star that has already passed the stage of protostellar accretion and is being released from its gas-dust cocoon. Such young stellar objects are rare because they are quite massive and evolve rapidly. They are usually deeply embedded in the dust shell and their radiation manifests itself only in the IR range (Zinnecker et al., 2007). V645 Cyg is one of the few objects of this class visible in optics. One of the reasons for this is the orientation of the circumstellar disk plane, which practically coincides with the sky plane (Valtts et al., 2002; Miroshnichenko et al., 2009). Optical and IR images of the star contain two bright regions, which are interpreted as radiation from the disk and envelope (Cohen, 1977; Goodrich, 1986).
The angular size of the IR image increases with wavelength in the near- and mid-IR and decreases towards the millimeter range (Quiroga-Nunez et al., 2019; Miroshnichenko et al., 1999). Based on medium-resolution spectroscopy data, Hamann and Persson (1989) suggested that these bright regions could represent reflected light from the disk and bipolar outflows.
The study of the V645 Cyg brightness changes was carried out mainly in the IR range. There are only two series of observations in the optical range, these are the very first photographic observations of Hoffmeister et al. (1951) in the 1950s and photoelectric observations by Shevchenko et al. (1993) in 1985-2000. Miroshnichenko et al. (2019), based on the analysis of the photometric data from Shevchenko et al. (1993) obtained in the UBVR filters at the Maidanak observatory, indicate the possible presence of an 8-year variability period of the star's optical brightness with an average amplitude in the V band ~ 0m6 and a decrease of the IR brightness at time scales of the order of 20 years. Interpreting the speckle interferometry data, Miroshnichenko et al. (2009) subdivided the K-band image of the star into two components. The bright, small ring component (radius r ~ 25 a.u.) is probably the emission from the disk near the sublimation front. The second component (r ~ 250 a.u.) may correspond to the emission of the circumstellar shell's inner part, but the authors emphasize that one cannot exclude, for example, this emission being light reflected off the boundary of the cavity formed by bipolar outflows.
Since photometric observations of V645 Cyg in the optical range were very rare, and the latest of them date back to 2000, new observations are extremely useful, at least in terms of confirming the periodic brightness variation discovered by Miroshnichenko et al. (2009).
Table 1: Designations and coordinates of the observed stars
Name star a(2000) #(2000)
V645 Cyg variable 21h 39m58S3 +50°14' 21" 13m 50
UCAC3 281-203713 comparison 21h 39m52S5 +50° 15' 52" 12m 60
UCAC3 281-203646 check 21h 39m47S6 +50° 17' 01" 12m 22
Our optical photometric observations of V645 Cyg were carried out on 111 nights from May, 2009 to March, 2018 using the AZT-3 reflector (D = 0.45 m, F^ton = 2.0 m) and from December, 2018 to April, 2022, using the AstroSib-500RC Ritchey-Chretien telescope (D = 0.5 m, F = 4.0 m) of the Kourovka Astronomical Observatory (Ural Federal University). Observations were carried out in the VRI filters, reproducing a system close to the Johnson-Cousins system when observing with Apogee Alta U6 CCD
cameras and a Kodak KAF-1001E chip (1024 x 1024, 24 ¡m) and, since 2015, with a PL A230 camera of the company FLI and an E2V 230-42 CCD chip (2048 x 2048, 15 ¡m). Two stars were chosen as a comparison star and a check star in the immediate vicinity of the variable, the data on them are given in Table 1. The coordinates in the Table are based on the Gaia-DR3 catalog.
After photometric processing, which included subtracting dark frames, dividing into flat-field frames, and determining the brightness of stars by aperture photometry, we obtained 111 night-averaged values of the brightness differences between V645 Cyg and the comparison star in the V filter, 96 values in the R filter, and 58 values in the I filter. The aperture size was chosen to cover the whole radiation associated to V645 Cyg in the given filter (including components N0 and N1). The light curves for V645 Cyg obtained over the 13-year observation period are shown in Fig. 1, Fig. 2 and Fig. 3. Data are given in Tables 2-6.
1 1 1 i ^ A ^^^^ aV = 0.189 ± 0.018
Comp - Check
» * / t / A
/ • .........• * .
** V645Cyg - Comp
• i , i 1,1,1
4500 5500 6500 7500 8500 9500
JD-2450000
Figure 1. The V645 Cyg light curve in the V filter (circles) and the differences in the brightness of the comparison and check stars (triangles). In the upper part of figure, the values of difference between the magnitudes of the comparison star and the check star, averaged over the entire observation period, and the root mean square error are given.
1 1 1 A mm» A ^
Comp - Check aR = 0.500 ± 0.015 " z n
- J
V645Cyg - Comp _
¥, « i , i 1,1,1
4500 5500 6500 7500 8500 9500
JD-2450000
Figure 2. The V645 Cyg light curve in the R filter. Designations are the same as in Fig.1.
As can be seen, a systematic star brightness increase was observed throughout 13 years of our observations along with brightness changes of V645 Cyg with amplitudes from several hundredths to tenths of a magnitude over time intervals from a day to several months. At the same time, the brightness of the comparison star, as can be seen in Fig. 1, Fig. 2 and Fig. 3, remained practically unchanged within the limits of observational errors. Also, the average brightness of V645 Cyg in the V band has increased over 13 years by ~ 1.0m, in the R band by ~ 1.4m, and in the I band by ~ 2.0m.
It can be noted that, along with an increase in brightness, the reddening of the star is also observed, which is clearly seen in the plots of V — R and R — I color indices change over time, shown in Fig. 4 and Fig. 5, respectively. Over the entire observation period, the color index V — R increased by ~ 0.3m, and R — I by ~ 0.6m. A change in the optical brightness within ~ 0.5m was also observed earlier in the data obtained by Shevchenko et al. (1993) (see Miroshnichenko et al., 2009). However, the same paper notes that the color indices V — R, as well as B — V and U — B, remained stable within 0.1m, which is significantly less than the amplitude of the changes in the data obtained from observations at the Kourovka Observatory.
We also did not find any periodicity in the brightness variations of V645 Cyg, especially with a period of 8 years, which was found by Miroshnichenko et al. (2009) in the observations of Shevchenko et al. (1993). Apparently, the periodic change in the optical brightness of this star occurs only during a certain time interval and is not a constant
-2.0
-1.5
< -1.0
-0.5
4500 5500 6500 7500 8500 9500
JD-2450000
Figure 3. The V645 Cyg light curve in the I filter. Designations are the same as in Fig.1. phenomenon.
It is important to note that optical brightness variations in the time interval JD — 2450000 < 6500 are closely followed by the variations of CH3OH maser flux at 6.7 GHz presented by Szymczak et al. (2018). The increase in optical brightness corresponds to the increase of maser brightness and vice versa. Szymczak et al. (2018) found that the maser flux variations were quasi-periodic with a period of 195 days. Based on the observed correspondence between the maser and optical brightness variability, it can be assumed that the optical brightness variations at time scales of the order of 100 days are also quasi-periodic. As shown by Kojima et al. (2018) for the object G33.641-0.228, CH3OH maser bursts can be observed on time scales of the order of several hours. Taking into account that the propagation speed of radiation, which affects the pumping of masers, can be significantly lower than the speed of light (Burns et al., 2020) and that the relaxation time of the CH3OH level populations can be of hours, the interpretation of such maser variability that fast may require to take into account the non-stationary radiation transfer and excitation in the CH3OH transitions. Our data shows that changes in the optical brightness during a night are mostly monotonic (see also Sobolev et al., 2013). Thus, based on our data in the optical range, we can assume that there are no strong sudden changes of CH3OH masers in V645 Cyg on time scales of the order of several hours.
The data obtained by us during thirteen years of photometric observations of the young irregular variable star V645 Cyg are, in essence, the second monitoring series obtained
- 1 1 1 Comp - Check i 1 i 1 i a I = 0.837 ± 0.015 A'^S
- «7 A* -•
f ,«""" t V645Cyg - Comp
m • i i i , i
0.3
0.4
^ 0.5 >
0.6
0.7
4500 5500 6500 7500 8500 9500
JD-2450000
Figure 4. The time dependence of the differences between the V — R color indices of V645 Cyg and the comparison star. Designations are the same as in Fig.1.
in the optical range in the process of studying this star using modern detectors. In this period of observations, in contrast to the results of the earlier optical monitoring of V645 Cyg (see Shevchenko et al., 1993), along with changes in brightness, a significant change in the color indices towards increasing reddening of the star was also observed.
Based on the results of this series of observations, as well as on data obtained at the same time in the IR range (Shenavrin et al., 2011), a number of conclusions can be drawn about the reasons for such changes in the brightness and color of V645 Cyg. These changes can be due to a change in the angle of inclination of the disk plane due to precessional rotation, during which hot structures in the inner region of the disk become more visible to the observer. Another possible scenario explaining the variability in optics and IR can be similar to that presented by Parfenov & Sobolev (2014). In this scenario, a spiral density wave in the inner disk region formed due to multiplicity of the system can propagate up to the radius of the sublimation front. There is a layer of hot gas at the end of the spiral wave near the surface of the star. During rotation, this heated layer is on the line of sight, the hot substance can approach the gas and dust inhomogeneities on the inner boundary of the disk and heat them up. This scenario, however, assumes that the variability of the CH3OH maser flux at 6.7 GHz can be different for different components of the maser spectrum, which are formed in different regions in the vicinity of the star. The observed variability of the maser emission, which is in good agreement
1 • • * J ¿J» \ Comp - At ▲ Check I 1 I 1 aw a(V-R) = -0.311 ± 0.009 -
w \ • \ 4 \ ,1 * 4 r. \ / * \ * •
V645Cyg - Comp ¥ I-"* r 1m.
1 1 t % -*i A 1,1,1
0.3
0.5
0.7
0.9
1.1
1 1 1 ▲ Ml i 1 i '
- Comp - Check a(R-I) = -0.339 ± 0.008
• -
W \
V645Cyg - Comp ^^ \
\ •
4 / >. * -
- I,I i,I,I
4500 5500
6500 7500
JD-2450000
8500 9500
Figure 5. The time dependence of the differences between the R — I color indices of V645 Cyg and the comparison star. Designations are the same as in Fig.1.
with optical brightness variations at time scales of the order of 100 days, is the same in all components of the maser spectrum. Another scenario that can be used to explain the observed variability both in the optical range and in maser lines suggests variations in the accretion rate of matter onto the star, as a result of which the luminosity and temperature of the star change. These changes, in turn, lead to a change of temperature of the dust, radiation of which pumps the CH3OH masers (Sobolev & Deguchi, 1994). This scenario contradicts the conclusion about the absence of accretion made by Miroshnichenko et al. (2009) based on spectroscopic observations of V645 Cyg. However, it can be that the spectroscopic observations of Miroshnichenko et al. (2009) were carried out at the time of a significant drop in the accretion rate. And finally, the fourth reason for the manifestation of the observed changes in the brightness and color of V645 Cyg in the observed time interval may be further dissipation of the gas-dust cocoon surrounding the star and motion of the star out of cocoon which makes radiation from the star and its heated immediate vicinity more visible. This scenario does not allow one to explain optical brightness variations at time scales of the order of 100 days, which can be quasi-periodic, as well as the corresponding variations in the maser flux density. However, this scenario is applicable to explain the observed monotonic variations in brightness and color of V645 Cyg.
Acknowledgments. A.P.B, A.M.S. and S.Yu.P. were supported by the Foundation for the Advancement of Theoretical Physics and Mathematics "BASIS". S.Yu.G was supported by the Ministry of Science and Higher Education of the Russian Federation under contract 075-15-2020-780.
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Bowey , J. E., Adamson A. J., & Yates, J. A., 2003, Mon. Notices Roy. Astron. Soc., 340,1173
Burns, R. A., Sugiyama, K., Hirota, T., et al.,2020, Nature Astronomy, 4, 506 Clarke, A. J., Lumsden, S. L., Oudmaijer, R. D., et al., 2006,Astron. & Astrophys., 457, 183
Cohen, M., 1977, Astrophys. J., 215, 533 Goodrich, R. W., 1986, Astrophys. J., 311, 882
Kojima, Y., Fujisawa, K., & Motogi, K., 2018, Astrophysical Masers: Unlocking the Mysteries of the Universe, Proceedings of the International Astronomical Union, IAU Symposium, 336, 336 Hamann, F. & Persson, S. E., 1989, Astrophys. J., 339, 1078. Hoffmeister, C., Rohlfs, E., & Ahnert, P., 1951, Veroff. ¡Sternwarte Sonneberg, 1, 407 Honma, M., Bushimata, T., Choi, Y. K., et al., 2007, Publ. Astron. Soc. Japan., 59, 889 Humphreys, R. M., Merrill, K. M., & Black, J. H., 1980, Astrophys. J., 237, L17 Lada, C. J., Blitz, L., Reid, M. J., & Moran, J. M., 1981, Astrophys. J., 243, 769 Miroshnichenko, A. S., Hofmann, K.-H., Schertl, D., et al., 2009, Astron. & Astrophys., 498, 115
Miroshnichenko, A., Ivezic, Z., Vinkovic, D., & Elitzur, M., 1999, Astrophys. J., 520, L115
Morris, M. & Kazes, I., 1982, Astron. & Astrophys., 111, 239 Parfenov, S. Yu. & Sobolev, A. M., 2014, Mon. Notices Roy. Astron. Soc., 444, 620 Quiroga-Nunez, L. H., Immer, K., van Langevelde, H. J., et al., 2019, Astron. & Astrophys., 625, id. A70, 12pp. Shenavrin, V. I., Taranova, O. G., & Nadzhip, A. E., 2011, Astronomy Reports., 55, 31 Shevchenko, V. S., Grankin, K. N., Ibragimov, M. A., et al., 1993, Astrophys. Space Sci., 202, 121
Sobolev, A. M. & Deguchi, S., 1994, Astron. & Astrophys., 291, 569 Sobolev, A. M., Gorda, S. Yu., & Davydova, O. A., 2013, Inform. Bull. Var. Stars, No. 6061
Szymczak, M., Olech, M., Sarniak, R., et al., 2018, Mon. Notices Roy. Astron. Soc., 474, 219
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Conference Series, 279, 279 Zinnecker, H. & Yorke, H. W., 2007, Ann. Rev. Astron. Astrophys., 45, 481
Table 2: Night-averaged brightness differences in the V filter of V645 Cyg (AV) and check star (AC) relative to the comparison star
Date (DMY) JD-240000 AF ±a ±a AC ±a ±a N
15.04.
06.05. 13.05. 14.05. 19.05. 20.05. 27.05. 22.07. 23.07. 27.07. 14.09. 15.09.
17.09.
22.10. 16.11.
17.11.
10.12. 21.01. 26.01. 02.02. 06.03. 18.03.
25.03.
08.04.
12.05. 13.05. 21.07.
22.07.
04.08.
05.08.
01.09. 02.09.
22.09.
08.10. 20.10. 02.12. 12.12. 13.12. 08.01. 20.01. 27.04.
28.04.
16.05. 26.09. 27.09.
2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009
2009
2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 2011 2011 2011 2011 2012 2012 2012
4937.42857 4958.33519 4965.35769 4966.32331 4971.35191 4972.30408 4979.33769 5035.34787 5036.33920 5040.34753 5089.28315 5090.30562 5092.42973 5127.31837 5152.31745 5153.19977 5176.25266 5218.16453 5223.12589 5230.13721 5262.52940 5274.49065 5281.47928 5295.43740 5329.36131 5330.36267 5399.33910 5400.33782 5413.33688 5414.33714 5441.31360 5442.36225 5462.23904 5478.29459 5490.14572 5533.23815 5543.19488 5544.19371 5570.21433 5582.13821 5679.41057 5680.40164 6064.39120 6197.38419 6198.23936
0.683 0.688 0.790 0.759 0.766 0.795 0.716 0.751 0.682 0.726 0.684 0.739 0.717 0.688 0.726 0.654 0.641 0.736 0.708 0.625 0.810 0.937 0.987 1.035 0.947 0.875 0.820 0.813 0.763 0.714 0.796 0.812 0.738 0.941 0.873 0.882 0.859 0.801 0.799 0.758 0.625 0.633 0.824 0.639 0.628
0.005 0.009 0.008 0.010 0.006 0.023 0.015 0.009 0.028 0.012 0.012 0.023 0.015 0.009 0.008 0.017 0.017 0.008 0.011 0.015 0.006 0.011 0.009 0.017 0.009 0.025 0.014 0.015 0.015 0.014 0.009 0.014 0.022 0.010 0.013 0.013 0.018 0.014 0.011 0.013 0.009 0.010 0.015 0.014 0.022
0.001 0.003 0.002 0.002 0.001 0.008 0.003 0.002 0.006 0.002 0.002 0.007 0.003 0.001 0.002 0.003 0.002 0.001 0.002 0.003 0.002 0.004 0.002 0.004 0.002 0.006 0.002 0.002 0.002 0.002 0.002 0.002 0.004 0.001 0.003 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.004 0.004 0.005
0.194 0.196 0.201 0.202 0.190 0.204 0.191 0.199 0.198 0.201 0.201 0.206 0.202 0.207 0.201 0.196 0.201 0.196 0.194 0.198 0.198 0.195 0.199 0.204 0.206 0.208 0.204 0.206 0.211 0.209 0.201 0.201 0.199 0.204 0.214 0.199 0.201 0.199 0.200 0.197 0.200 0.197 0.197 0.205 0.201
0.003 0.007 0.006 0.004 0.005 0.006 0.008 0.004 0.006 0.004 0.003 0.002 0.005 0.007 0.004 0.006 0.005 0.005 0.014 0.006 0.003 0.002 0.005 0.007 0.017 0.005 0.006 0.004 0.006 0.006 0.004 0.004 0.008 0.005 0.006 0.005 0.004 0.006 0.006 0.006 0.004 0.005 0.008 0.006 0.009
0.001 0.002 0.001 0.001 0.001 0.002 0.002 0.001 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.004 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.001 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.002 0.003
10
9
25 25
25 6
22 30 19 47 43 10
26
42 24
43 30
30 22
24 13
7
13 15 19 15 32
43 36
44 43 66
25 79 25 64 70 76 41
31 17
14 11 11
8
Date (DMY) JD-240000 AY ±a ±W AC ±a ±ä N
04.10 10.10 11.10 06.12 07.12 12.12 19.12
17.01
14.02 12.08 10.10 14.07 11.09
15.09 26.04
11.10
05.01 06.01 12.01
16.02 03.04 16.04
26.04
22.05 24.07 19.12 28.01 06.02 12.02 20.02
15.03
06.04 01.04 25.07
19.10
29.11
14.12 29.12 12.02 05.03 23.03
27.03
19.04
.2012 .2012 .2012 .2012 .2012 .2012 .2012 .2013 .2013 .2013 .2013 .2014 .2014 .2015 .2017 .2017 .2018 .2018 .2018 .2018 2018 2018 2018 2018 2018 .2018 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2020 .2020 .2020 .2020 2020
6205.24359 6211.13611 6212.28667 6268.19165 6269.14436 6274.15618 6281.12896 6310.07494 6338.12007 6517.32602 6576.28931 6853.34689 6912.38557 7281.25513 7870.44585 8038.17950 8124.17500 8125.11670 8131.14580 8166.10420 8212.45700 8225.42570 8235.39240 8261.34380 8324.32700 8472.22850 8512.18820 8521.14650 8527.20200 8535.12500 8558.49310 8580.40970 8575.47010 8690.30330 8776.34880 8817.27748 8832.20632 8847.18480 8891.15382 8914.54355 8932.47483 8936.44622 8959.38451
0.610 0.654 0.626 0.584 0.590 0.551 0.539 0.516 0.484 0.656 0.711 0.314 0.451 0.485 0.447 0.324 0.285 0.308 0.341 0.224 0.415 0.400 0.310 0.263 0.151 0.129 0.090 0.177 0.145 0.119 0.126 0.179 0.162 0.296 0.126 0.077 0.030 0.078 0.067 0.117 0.064 0.054 0.003
0.008 0.018 0.010 0.008 0.008 0.011 0.011 0.008 0.003 0.010 0.008 0.013 0.011 0.007 0.012 0.008 0.004 0.006 0.006 0.004 0.007 0.011 0.008 0.006 0.007 0.012 0.012 0.007 0.009 0.005 0.005 0.003 0.003 0.012 0.004 0.004 0.014 0.004 0.005 0.004 0.006 0.005 0.015
0.004 0.005 0.001 0.002 0.002 0.002 0.002 0.003 0.001 0.001 0.001 0.002 0.001 0.001 0.004 0.002 0.001 0.001 0.001 0.001 0.001 0.003 0.002 0.001 0.002 0.003 0.003 0.002 0.003 0.002 0.002 0.001 0.001 0.003 0.001 0.001 0.004 0.001 0.002 0.001 0.002 0.001 0.002
0.208 0.209 0.213 0.208 0.208 0.205 0.206 0.205 0.206 0.204 0.208 0.212 0.189 0.168 0.161 0.181 0.178 0.170 0.176 0.188 0.178 0.178 0.186 0.188 0.183 0.202 0.195 0.199 0.199 0.203 0.193 0.204 0.208 0.202 0.164 0.175 0.175 0.195 0.186 0.159 0.155 0.168 0.172
0.004 0.005 0.004 0.004 0.003 0.004 0.005 0.015 0.003 0.004 0.006 0.008 0.006 0.005 0.004 0.006 0.005 0.005 0.004 0.006 0.007 0.006 0.005 0.007 0.003 0.005 0.004 0.007 0.007 0.008 0.004 0.003 0.003 0.005 0.012 0.017 0.004 0.003 0.007 0.006 0.005 0.004 0.010
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.007 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.002 0.001 0.001 0.002 0.001 0.001 0.001 0.002 0.002 0.004 0.001 0.001 0.001 0.001 0.004 0.003 0.001 0.001 0.003 0.002 0.001 0.001 0.003
28 13 60 22 25 25 25 5 5
55 39
39 62 38
7
25 20
40 20 10
9 20 20 20 13 20 13 10 15 5 10 10 10 20 10 30 15 15 5 11 15 18 10
Table 2: Continued
Date (DMY) JD-240000 AF ±a ±w AC ±a ±W N
13.05.2020 8983.35573 0.019 0.005 0.001 0. 167 0.005 0.001 20
26.09.2020 9119.30094 -0.070 0.007 0.001 0. 163 0.003 0.001 29
02.10.2020 9125.37666 -0.125 0.013 0.003 0. 161 0.010 0.002 20
28.10.2020 9151.33432 -0.193 0.009 0.002 0. 152 0.008 0.002 23
03.11.2020 9157.40251 -0.205 0.006 0.001 0. 158 0.006 0.002 16
10.12.2020 9194.22652 -0.211 0.005 0.001 0. 159 0.003 0.001 25
11.12.2020 9195.22465 -0.200 0.004 0.001 0. 157 0.004 0.001 23
19.12.2020 9203.16506 -0.215 0.004 0.001 0. 156 0.005 0.001 20
18.01.2021 9233.18459 -0.230 0.005 0.001 0. 158 0.006 0.001 12
10.02.2021 9256.12148 -0.143 0.007 0.001 0. 135 0.005 0.001 15
12.04.2021 9317.43391 -0.112 0.005 0.001 0. 174 0.003 0.001 25
16.04.2021 9321.43617 -0.125 0.003 0.001 0. 165 0.003 0.001 17
17.04.2021 9322.38562 -0.072 0.005 0.001 0. 171 0.004 0.001 39
18.04.2021 9323.40756 -0.078 0.004 0.001 0. 173 0.003 0.001 34
13.10.2021 9501.26582 -0.223 0.003 0.001 0. 166 0.003 0.001 18
14.10.2021 9502.35009 -0.252 0.004 0.001 0. 159 0.005 0.001 30
25.12.2021 9574.17410 -0.204 0.008 0.001 0. 153 0.004 0.001 41
12.01.2022 9592.12339 -0.237 0.006 0.001 0. 161 0.007 0.001 20
26.01.2022 9606.13106 -0.257 0.008 0.002 0. 168 0.009 0.002 20
25.03.2022 9664.45067 -0.185 0.004 0.001 0. 174 0.004 0.001 35
11.04.2022 9681.40484 -0.270 0.005 0.001 0. 163 0.006 0.001 20
21.04.2022 9691.39852 -0.166 0.004 0.001 0. 176 0.004 0.001 33
22.04.2022 9692.39289 -0.195 0.006 0.001 -0. 169 0.003 0.001 30
Table 3: Night-averaged brightness differences in the R filter of V645 Cyg (AR) and check star (AC) relative to the comparison star
Date (DMY) JD-240000
AR ±a
±a
AC ±a ±a N
15.04
17.11 21.01 26.01 02.02 06.03 18.03
25.03
08.04
12.05 13.05 21.07
22.07
04.08
05.08
01.09 02.09
22.09
08.10 20.10
02.12 12.12 13.12 08.01 20.01 27.04
28.04
16.05 26.09
27.09
04.10 10.10 11.10 06.12 07.12 12.12 19.12
17.01
14.02 12.08 10.10 14.07 11.09
15.09 26.04
11.10 05.01
2009 .2009 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2010 .2011 .2011 .2011 .2011 .2012 .2012 .2012 .2012 .2012 .2012 .2012 .2012 .2012 .2012 .2013 .2013 .2013 .2013 .2014 .2014 .2015 .2017 .2017 .2018
4937.43140 5153.21515 5218.16560 5223.13941 5230.14237 5262.53163 5274.50131 5281.48204 5295.44222 5329.37148 5330.36559 5399.34054 5400.33931 5413.33720 5414.33911 5441.34618 5442.36419 5462.24106 5478.29670 5490.15031 5533.24075 5543.20149 5544.19296 5570.21428 5582.14021 5679.41259 5680.40578 6064.39120 6197.38655 6198.23906 6205.24509 6211.13493 6212.28589 6268.19709 6269.14649 6274.15831 6281.12896 6310.07528 6338.11821 6517.32602 6576.28931 6853.34795 6912.38674 7281.26488 7870.44698 8038.17950 8124.17500
0.198 0.212 0.271 0.260 0.199 0.353 0.448 0.467 0.484 0.463 0.408 0.364 0.358 0.313 0.271 0.341 0.349 0.317 0.449 0.403 0.425 0.398 0.351 0.343 0.320 0.208 0.216 0.248 0.120 0.127 0.104 0.160 0.139 0.080 0.097 0.055 0.043 0.028 0.001 0.109 0.198 0.293 0.227 0.178 0.305 0.378 0.376
0.004 0.013 0.008 0.012 0.017 0.006 0.005 0.006 0.009 0.007 0.016 0.007 0.008 0.009 0.010 0.015 0.006 0.014 0.009 0.009 0.013 0.017 0.013 0.011 0.013 0.005 0.005 0.014 0.016 0.015 0.005 0.011 0.008 0.007 0.009 0.006 0.010 0.021 0.007 0.006 0.005 0.011 0.005 0.005 0.005 0.008 0.005
0.001 0.002 0.002 0.002 0.004 0.002 0.001 0.002 0.002 0.002 0.004 0.001 0.001 0.001 0.002 0.002 0.001 0.003 0.001 0.002 0.002 0.002 0.002 0.002 0.002 0.001 0.001 0.004 0.006 0.005 0.001 0.003 0.001 0.001 0.002 0.001 0.002 0.010 0.003 0.001 0.001 0.002 0.001 0.001 0.002 0.002 0.001
0.510 0.501 0.499 0.500 0.506 0.507 0.508 0.513 0.518 0.516 0.517 0.515 0.513 0.525 0.524 0.507 0.515 0.505 0.513 0.507 0.500 0.506 0.503 0.505 0.503 0.509 0.506 0.504 0.516 0.511 0.520 0.525 0.522 0.518 0.516 0.515 0.513 0.504 0.527 0.514 0.519 0.517 0.493 0.472 0.464 0.500 0.496
0.004 0.010 0.004 0.004 0.005 0.005 0.005 0.003 0.012 0.010 0.008 0.004 0.005 0.005 0.008 0.008 0.004 0.010 0.004 0.006 0.007 0.006 0.007 0.007 0.007 0.005 0.005 0.008 0.008 0.007 0.003 0.005 0.005 0.006 0.003 0.005 0.006 0.015 0.004 0.006 0.009 0.006 0.006 0.007 0.006 0.009 0.003
0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.003 0.003 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.002 0.002 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.006 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.002 0.001
10 46 29 28 18 13 10 12 18 12 12 32
43
40
44
41 66 22 78 26 65 68 73 40 32 17 16 12 11
8
27
13 61
23 25 25 25
6 6
55 39
45 70
42 8
24 20
Date (DMS) JD-240000
AR ±a
±W
AC ±a ±ä N
06.01. 12.01. 16.02. 03.04. 16.04.
26.04.
22.05. 24.07. 19.12. 28.01. 06.02. 12.02. 20.02.
15.03.
06.04. 01.04. 25.07.
19.10.
29.11.
14.12. 29.12. 12.02. 05.03. 23.03.
27.03.
19.04.
13.05.
26.09.
02.10. 28.10.
03.11.
10.12. 11.12. 19.12. 18.01. 10.02. 12.04. 16.04. 17.04. 18.04. 13.10. 14.10. 25.12. 12.01. 26.01.
25.03.
11.04. 21.04. 22.04.
2018 2018 2018 2018 2018 2018 2018 2018 2018 2019 2019 2019 2019 2019 2019 2019 2019 2019 2019 2019
2019
2020 2020 2020 2020 2020 2020 2020 2020 2020 2020 2020 2020 2020 2021 2021 2021 2021 2021 2021 2021 2021 2021 2022 2022 2022 2022 2022 2022
8125.11670 8131.14580 8166.10420 8212.45700 8225.42570 8235.39240 8261.34380 8324.32700 8472.22850 8512.18820 8521.14650 8527.20200 8535.12500 8558.49310 8580.40970 8575.47010 8690.30330 8776.34880 8817.27748 8832.20632 8847.18596 8891.15380 8914.54356 8932.47486 8936.44622 8959.38451 8983.35573 9119.30094 9125.38042 9151.33478 9157.40251 9194.22652 9195.22465 9203.16506 9233.18459 9256.12148 9317.43391 9321.43617 9322.38562 9323.40756 9501.27132 9502.31430 9574.17410 9592.12339 9606.13106 9664.45067 9681.40484 9691.39852 9692.39289
0.332 0.313 0.401 0.175 0.205 0.287 0.350 0.477 0.533 0.603 0.504 0.524 0.546 0.548 0.518 0.501 0.379 0.546 0.628 0.653 0.784 0.774 0.835 0.768 0.765 0.729 0.676 0.817 0.850 0.918 0.940 0.927 0.892 0.913 0.956 0.900 0.886 0.890 0.821 0.849 0.964 0.997 0.934 0.972 0.971 0.918 1.016 0.903 0.929
0.006 0.006 0.007 0.005 0.009 0.007 0.010 0.006 0.007 0.010 0.007 0.007 0.003 0.004 0.007 0.004 0.004 0.005 0.006 0.009 0.007 0.007 0.003 0.007 0.005 0.011 0.005 0.011 0.015 0.011 0.009 0.007 0.007 0.004 0.004 0.006 0.004 0.004 0.005 0.005 0.004 0.011 0.006 0.006 0.016 0.005 0.006 0.005 0.005
0.001 0.001 0.001 0.001 0.003 0.002 0.001 0.002 0.003 0.003 0.002 0.003 0.002 0.002 0.001 0.001 0.003 0.001 0.001 0.002 0.002 0.003 0.001 0.002 0.001 0.004 0.001 0.002 0.004 0.002 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.001 0.001 0.004 0.001 0.001 0.001 0.001
0.490 0.481 0.499 0.487 0.491 0.490 0.502 0.499 0.505 0.497 0.494 0.502 0.507 0.495 0.501 0.504 0.499 0.465 0.477 0.473 0.498 0.473 0.473 0.482 0.497 0.489 0.493 0.488 0.492 0.479 0.488 0.478 0.485 0.477 0.483 0.456 0.494 0.486 0.490 0.493 0.488 0.477 0.471 0.479 0.494 0.493 0.487 0.501 0.491
0.005 0.005 0.006 0.004 0.006 0.006 0.007 0.005 0.008 0.006 0.006 0.005 0.003 0.004 0.007 0.004 0.004 0.005 0.006 0.004 0.004 0.007 0.004 0.007 0.005 0.006 0.007 0.007 0.015 0.010 0.012 0.004 0.004 0.005 0.009 0.007 0.003 0.005 0.005 0.003 0.005 0.006 0.009 0.005 0.010 0.006 0.005 0.005 0.004
0.001 0.001 0.002 0.001 0.001 0.001 0.002 0.001 0.002 0.001 0.002 0.001 0.001 0.001 0.002 0.001 0.001 0.002 0.001 0.001 0.001 0.003 0.001 0.002 0.001 0.002 0.001 0.001 0.003 0.002 0.003 0.001 0.001 0.001 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.001 0.001 0.001 0.001
40 20 10 10 20 20
19 13
20 16 10 15
5 10 10 10 18 10
30 15 15
5 10
15 18 10 20
31 20 23
16 25 23 20 12 15 25
17 39 35
18 30
41 20 20 35 20 33 30
Table 4: Night-averaged brightness differences in the I filter of V645 Cyg (AI) and check star (AC) relative to the comparison star
Date (DMY) JD-240000
AR ±a
±a
AC ±a ±a N
16.05 26.09
27.09
04.10 10.10 11.10 06.12 07.12 12.12 19.12
17.01
14.02 06.01 12.01 16.02 03.04 16.04
26.04
22.05 24.07 19.12 28.01 06.02 12.02 20.02
15.03
01.04 06.04 25.07
19.10
29.11
14.12 29.12 12.02 05.03 23.03
27.03
19.04
13.05 26.09
03.11
10.12 11.12 19.12
.2012 .2012 .2012 .2012 .2012 .2012 .2012 .2012 .2012 .2012 .2013 .2013 .2018 .2018 .2018 .2018 2018 2018 2018 2018 .2018 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2019 .2020 .2020 .2020 .2020 2020 .2020 .2020 .2020 .2020 .2020 .2020
6064.39120 6197.38655 6198.23906 6205.24509 6211.13493 6212.28589 6268.19709
6269.14649 6274.15831 6281.12896 6310.07528 6338.11821 8125.11670 8131.14580 8166.10420 8212.45700 8225.42570 8235.39240 8261.34380 8324.32700 8472.22850 8512.18820
8521.14650 8527.20200 8535.12500 8558.49310 8575.47010 8580.40970 8690.30330 8776.34880 8817.27750 8832.20630 8847.18683 8891.15580 8914.54357 8932.47486 8936.44622 8959.38451 8983.35573 9119.29258 9157.40251 9194.22652 9195.22465 9203.16506
0.328 0.544 0.548 0.585 0.500 0.509 0.607 0.573 0.611 0.635 0.635 0.629 1.211 1.178 1.285 0.932 0.998 1.044 1.134 1.254 1.540 1.631 1.511 1.509 1.543 1.567 1.472 1.504 1.362 1.577 1.661 1.658 1.789 1.763 1.848 1.742 1.753 1.699 1.601 1.864 1.937 1.948 1.904 1.927
0.006 0.014 0.014 0.007 0.008 0.008 0.006 0.005 0.006 0.007 0.009 0.004 0.008 0.006 0.005 0.007 0.006 0.006 0.010 0.004 0.006 0.014 0.010 0.008 0.008 0.007 0.005 0.007 0.008 0.008 0.007 0.006 0.010 0.006 0.015 0.009 0.017 0.010 0.015 0.017 0.012 0.006 0.009 0.008
0.002 0.005 0.005 0.001 0.002 0.001 0.001 0.001 0.001 0.001 0.004 0.002 0.001 0.001 0.002 0.002 0.001 0.001 0.002 0.001 0.001 0.003 0.003 0.002 0.003 0.002 0.002 0.002 0.002 0.002 0.001 0.001 0.003 0.003 0.004 0.002 0.003 0.004 0.002 0.003 0.003 0.001 0.002 0.002
0.832 0.847 0.848 0.864 0.862 0.861 0.857 0.857 0.854 0.854 0.832 0.855 0.837 0.837 0.851 0.822 0.834 0.854 0.850 0.845 0.847 0.840 0.844 0.834 0.848 0.830 0.843 0.830 0.833 0.791 0.813 0.808 0.839 0.820 0.822 0.830 0.846 0.828 0.836 0.830 0.834 0.825 0.827 0.828
0.009 0.006 0.014 0.005 0.007 0.006 0.006 0.005 0.005 0.007 0.007 0.005 0.005 0.008 0.007 0.004 0.006 0.006 0.008 0.003 0.009 0.009 0.007 0.008 0.005 0.005 0.004 0.008 0.004 0.002 0.007 0.005 0.007 0.009 0.006 0.006 0.006 0.013 0.006 0.013 0.009 0.006 0.010 0.009
0.003 0.002 0.005 0.001 0.002 0.001 0.001 0.001 0.001 0.001 0.003 0.002 0.001 0.002 0.002 0.001 0.001 0.001 0.002 0.001 0.002 0.002 0.002 0.002 0.002 0.002 0.001 0.003 0.001 0.001 0.001 0.001 0.002 0.004 0.002 0.002 0.001 0.004 0.001 0.002 0.002 0.001 0.002 0.002
12
8 9
25 11 61
23 25
24
25
5
6
40 20 10 9 20 20
19 13
20 16 10
15 5
10 10 10
16 10
30 15 15
5 9
15 18 10 20
31
16 25 23 20
Table 4: Continued
Date (DMY) JD-240000 AI ±a ±ä AC ±a ±ä N
18.01.2021 9233.18459 -1.974 0.012 0.004 0.825 0.013 0.004 10
10.02.2021 9256.12148 -1.931 0.011 0.002 0.802 0.014 0.003 15
12.04.2021 9317.43391 -1.926 0.007 0.001 0.845 0.005 0.001 25
16.04.2021 9321.43617 -1.924 0.006 0.001 0.833 0.007 0.001 17
17.04.2021 9322.38562 -1.848 0.008 0.001 0.838 0.008 0.001 39
18.04.2021 9323.40756 -1.892 0.007 0.001 0.842 0.005 0.001 34
13.10.2021 9501.26722 -1.966 0.008 0.001 0.842 0.010 0.002 18
25.12.2021 9574.17410 -1.941 0.008 0.001 0.813 0.013 0.002 41
12.01.2022 9592.12339 -2.003 0.009 0.002 0.827 0.008 0.002 20
26.01.2022 9606.13106 -1.976 0.012 0.003 0.849 0.014 0.003 20
25.03.2022 9664.45067 -1.917 0.006 0.001 0.847 0.006 0.001 35
11.04.2022 9681.40484 -2.009 0.007 0.002 0.833 0.008 0.002 20
21.04.2022 9691.39852 -1.883 0.007 0.002 0.848 0.007 0.001 33
22.04.2022 9692.39289 -1.908 0.006 0.001 0.838 0.006 0.001 30
Table 5: The night-averaged differences between the color indices of V645 Cyg, A(V — R), and the check star, A(V — R)c, relative to the comparison star
Date (DMY) JD-240000 A(V — R) A(V — R)c N
15.04.2009 4937.43140 0.485 -0.316 10
17.11.2009 5153.21515 0.442 -0.305 46
21.01.2010 5218.16560 0.465 -0.303 29
26.01.2010 5223.13941 0.448 -0.306 28
02.02.2010 5230.14237 0.426 -0.308 18
06.03.2010 5262.53163 0.457 -0.309 13
18.03.2010 5274.50131 0.489 -0.313 10
25.03.2010 5281.48204 0.520 -0.314 12
08.04.2010 5295.44222 0.551 -0.314 18
12.05.2010 5329.37148 0.484 -0.310 12
13.05.2010 5330.36559 0.467 -0.309 12
21.07.2010 5399.34054 0.456 -0.311 32
22.07.2010 5400.33931 0.455 -0.307 43
04.08.2010 5413.33720 0.450 -0.314 40
05.08.2010 5414.33911 0.443 -0.315 44
01.09.2010 5441.34618 0.455 -0.306 41
02.09.2010 5442.36419 0.463 -0.314 66
22.09.2010 5462.24106 0.421 -0.306 22
08.10.2010 5478.29670 0.492 -0.309 78
20.10.2010 5490.15031 0.470 -0.293 26
02.12.2010 5533.24075 0.457 -0.301 65
12.12.2010 5543.20149 0.461 -0.305 68
13.12.2010 5544.19296 0.450 -0.304 73
08.01.2011 5570.21428 0.456 -0.305 40
20.01.2011 5582.14021 0.438 -0.306 32
27.04.2011 5679.41259 0.417 -0.309 17
28.04.2011 5680.40578 0.417 -0.309 16
16.05.2012 6064.39120 0.576 -0.307 12
26.09.2012 6197.38655 0.519 -0.311 11
27.09.2012 6198.23906 0.501 -0.310 8
04.10.2012 6205.24509 0.506 -0.312 27
10.10.2012 6211.13493 0.494 -0.316 13
11.10.2012 6212.28589 0.487 -0.309 61
06.12.2012 6268.19709 0.504 -0.310 23
07.12.2012 6269.14649 0.493 -0.308 25
12.12.2012 6274.15831 0.496 -0.310 25
19.12.2012 6281.12896 0.496 -0.307 25
17.01.2013 6310.07528 0.488 -0.299 6
14.02.2013 6338.11821 0.485 -0.321 6
12.08.2013 6517.32602 0.547 -0.310 55
10.10.2013 6576.28931 0.513 -0.311 39
14.07.2014 6853.34795 0.607 -0.305 45
11.09.2014 6912.38674 0.678 -0.304 70
15.09.2015 7281.26488 0.663 -0.304 42
26.04.2017 7870.44698 0.752 -0.303 8
11.10.2017 8038.17950 0.702 -0.319 24
05.01.2018 8124.17500 0.661 -0.318 20
Date (DMY) JD-240000 A(V - R) A(V - R)c N
06.01.2018 8125.11670 0.640 -0.320 40
12.01.2018 8131.14580 0.654 -0.305 20
16.02.2018 8166.10420 0.625 -0.311 10
03.04.2018 8212.45700 0.590 -0.309 10
16.04.2018 8225.42570 0.605 -0.313 20
26.04.2018 8235.39240 0.597 -0.304 20
22.05.2018 8261.34380 0.613 -0.314 19
24.07.2018 8324.32700 0.628 -0.316 13
19.12.2018 8472.22850 0.662 -0.303 20
28.01.2019 8512.18820 0.693 -0.302 16
06.02.2019 8521.14650 0.681 -0.295 10
12.02.2019 8527.20200 0.669 -0.303 15
20.02.2019 8535.12500 0.665 -0.304 5
15.03.2019 8558.49310 0.674 -0.302 10
06.04.2019 8580.40970 0.697 -0.297 10
01.04.2019 8575.47010 0.663 -0.296 10
25.07.2019 8690.30330 0.675 -0.297 18
19.10.2019 8776.34880 0.672 -0.301 10
29.11.2019 8817.27748 0.705 -0.302 30
14.12.2019 8832.20632 0.683 -0.298 15
29.12.2019 8847.18596 0.706 -0.303 15
12.02.2020 8891.15380 0.707 -0.307 5
05.03.2020 8914.54356 0.718 -0.314 10
23.03.2020 8932.47486 0.704 -0.327 15
27.03.2020 8936.44622 0.711 -0.329 18
19.04.2020 8959.38451 0.726 -0.319 10
13.05.2020 8983.35573 0.695 -0.327 20
26.09.2020 9119.30094 0.747 -0.326 31
02.10.2020 9125.38042 0.725 -0.331 20
28.10.2020 9151.33478 0.725 -0.327 23
03.11.2020 9157.40251 0.735 -0.330 16
10.12.2020 9194.22652 0.716 -0.319 25
11.12.2020 9195.22465 0.692 -0.328 23
19.12.2020 9203.16506 0.698 -0.321 20
18.01.2021 9233.18459 0.726 -0.325 12
10.02.2021 9256.12148 0.757 -0.321 15
12.04.2021 9317.43391 0.774 -0.320 25
16.04.2021 9321.43617 0.765 -0.321 17
17.04.2021 9322.38562 0.749 -0.319 39
18.04.2021 9323.40756 0.771 -0.320 35
13.10.2021 9501.27132 0.741 -0.322 18
14.10.2021 9502.31430 0.745 -0.318 30
25.12.2021 9574.17410 0.730 -0.318 41
12.01.2022 9592.12339 0.735 -0.318 20
26.01.2022 9606.13106 0.714 -0.326 20
25.03.2022 9664.45067 0.733 -0.319 35
11.04.2022 9681.40484 0.746 -0.324 20
21.04.2022 9691.39852 0.737 -0.332 33
22.04.2022 9692.39289 0.734 -0.322 30
Table 6: The night-averaged differences between the color indices of V645 Cyg, A(R — I), and the check star, A(R — I)C, relative to the comparison star
Date (DMY) JD-240000 A(R — I) A(R — I )c N
16.05.2012 6064.39120 0.576 -0.328 12
26.09.2012 6197.38655 0.664 -0.331 8
27.09.2012 6198.23906 0.675 -0.337 9
04.10.2012 6205.24509 0.689 -0.344 25
10.10.20012 6211.13493 0.660 -0.337 11
11.10.2012 6212.28589 0.648 -0.339 61
06.12.2012 6268.19709 0.687 -0.339 23
07.12.2012 6269.14649 0.670 -0.341 25
12.12.2012 6274.15831 0.666 -0.339 24
19.12.2012 6281.12896 0.678 -0.341 25
17.01.2013 6310.07528 0.663 -0.328 5
14.02.2013 6338.11821 0.628 -0.328 6
06.01.2018 8125.11670 0.879 -0.327 40
12.01.2018 8131.14580 0.865 -0.336 20
16.02.2018 8166.10420 0.884 -0.332 10
03.04.2018 8212.45700 0.757 -0.315 9
16.04.2018 8225.42570 0.793 -0.323 20
26.04.2018 8235.39240 0.757 -0.344 20
22.05.2018 8261.34380 0.784 -0.328 19
24.07.2018 8324.32700 0.777 -0.326 13
19.12.2018 8472.22850 1.007 -0.342 20
28.01.2019 8512.18820 1.028 -0.343 16
06.02.2019 8521.14650 1.007 -0.350 10
12.02.2019 8527.20200 0.985 -0.332 15
20.02.2019 8535.12500 0.997 -0.341 5
15.03.2019 8558.49310 1.019 -0.335 10
01.04.2019 8575.47010 0.971 -0.342 10
06.04.2019 8580.40970 0.986 -0.326 10
25.07.2019 8690.30330 0.983 -0.334 16
19.10.2019 8776.34880 1.031 -0.326 10
29.11.2019 8817.27750 1.033 -0.336 30
14.12.2019 8832.20630 1.005 -0.335 15
29.12.2019 8847.18683 1.005 -0.341 15
12.02.2020 8891.15580 0.989 -0.347 5
05.03.2020 8914.54357 1.013 -0.349 9
23.03.2020 8932.47486 0.974 -0.348 15
27.03.2020 8936.44622 0.988 -0.349 18
19.04.2020 8959.38451 0.969 -0.338 10
13.05.2020 8983.35573 0.924 -0.342 20
26.09.2020 9119.29258 1.046 -0.341 31
03.11.2020 9157.40251 0.997 -0.345 16
10.12.2020 9194.22652 1.031 -0.347 25
11.12.2020 9195.22465 1.012 -0.342 23
19.12.2020 9203.16506 1.014 -0.351 20
Table 6: Continued
Date (DMY) JD-240000 A(R - I) A(R - I)c N
18.01.2021 9233.18459 1.018 -0.342 10
10.02.2021 9256.12148 1.031 -0.346 15
12.04.2021 9317.43391 1.044 -0.352 25
16.04.2021 9321.43617 1.034 -0.347 17
17.04.2021 9322.38562 1.027 -0.348 39
18.04.2021 9323.40756 1.043 -0.349 34
13.10.2021 9501.26722 1.002 -0.354 18
25.12.2021 9574.17410 1.007 -0.342 41
12.01.2022 9592.12339 1.031 -0.348 20
26.01.2022 9606.13106 1.005 -0.355 20
25.03.2022 9664.45067 0.999 -0.350 35
11.04.2022 9681.40484 0.993 -0.346 20
21.04.2022 9691.39852 0.980 -0.347 33
22.04.2022 9692.39289 0.979 -0.347 30
