Peremennye Zvezdy

Peremennye Zvezdy (Variable Stars) 45, No. 4, 2025

Received 3 January; accepted 30 January.

Article in PDF

DOI: 10.24412/2221-0474-2025-45-45-53

Photometry of the Classical Nova V1112 Per

Igor Volkov

Sternberg Astronomical Institute, Moscow University, Universitetsky Ave., 13, 119992 Moscow, Russia


High precision photometric observations of the bright Nova V1112 Per at early stages after its outburst are presented. We found the time of the star's maximum brightness, estimated its interstellar extinction using empirical formulas. Our data made it possible to determine the mass of white dwarf and the distance to the star kpc. Fast variability at early stages was detected.

1. Introduction

Nova Persei 2020 = V1112 Per = TCP J04291888+4354233 was discovered by Seiji Ueda on 2020 Nov 25.813 UT and classified as a classical nova by Munari et al. (2020). According to the AAVSO light curve, the nova reached its maximum ( , , with ) on JD 2459186.77 and not on JD 2459183.396, as suggested by Chochol et al. (2020): after the proposed date of the outburst, the average brightness of the star definitely increased and reached the absolute maximum on the date we determined, see Fig. 3 below. Our observations started 10 days after the maximum brightness, they include 29 observing nights and cover a time interval of 118 days. The main array of observations was obtained with the 1-m telescope of Simeiz observatory (Institute of Astronomy, Russian Academy of Sciences) in combination with CCD FLI 09000 and Bessel set of filters (Nikolenko et al. 2019). On five nights, observations were carried out in the Johnson-Cousins system with the Zeiss-600 telescope of the same observatory using the VersArray 512UV CCD.

2. Observations and reductions

Magnitudes of the brightest star in the field, HD 276383, were obtained by fitting to the star LD 115 420 = GSC 586 717 from Landolt (2009) using the Zeiss-1000 instrumentation. Although the Landolt standard is equatorial and far from the variable star, our altitude-matched calibration proved very accurate and closely aligned with data in Simbad and APASS catalogues. HD 276383 is located only 27 from the nova and served as a reference star. To study the interstellar absorption in the direction of V1112 Per, magnitudes of stars in its vicinity were measured relative to HD 276383. The results are presented in Table 1 and in Fig. 1. A chart of the area with the numbers of measured stars is shown in Fig. 2. From the two-color diagram in Fig. 1, it is obvious that the region experiences significant interstellar absorption. Magnitudes of HD 276383 in near-infrared bands of the Johnson system can be determined using formulas from Taylor (1986): , .


Table 1. magnitudes of stars in the field of V1112 Per
Star Remark
1 12.015 10.996 9.717 8.922 8.284 1.019 1.279 0.794 0.638 HD276383
0.002 0.002 0.002 0.002 0.002 0.003 0.003 0.003 0.003
3 13.426 13.194 12.422 11.908 11.532 0.232 0.772 0.514 0.376 GSC 2891 2673
0.010 0.002 0.001 0.001 0.001 0.010 0.002 0.001 0.001
4 13.590 13.415 12.632 12.109 11.679 0.175 0.783 0.523 0.430 GSC 2891 2701
0.006 0.015 0.006 0.001 0.001 0.015 0.015 0.006 0.001
5 13.814 13.638 12.781 12.219 11.736 0.176 0.857 0.562 0.483 GSC 2891 2903
0.010 0.012 0.004 0.001 0.001 0.012 0.012 0.004 0.001
6 14.708 13.799 12.434 11.551 10.748 0.909 1.365 0.883 0.803 GSC 2891 2877
0.049 0.077 0.010 0.001 0.001 0.077 0.077 0.010 0.001
7 16.140 15.112 13.713 12.855 12.104 1.028 1.399 0.858 0.751 GSC 2891 2511
0.022 0.032 0.016 0.002 0.002 0.032 0.032 0.016 0.003
8 15.354 14.974 14.436 14.112 13.817 0.380 0.538 0.324 0.295
0.142 0.018 0.007 0.004 0.007 0.142 0.018 0.007 0.008
9 16.031 15.160 13.649 12.733 11.906 0.871 1.511 0.916 0.827 GSC 2891 2691
0.211 0.044 0.010 0.001 0.002 0.211 0.044 0.010 0.002
10 13.321 13.037 12.515 12.185 11.889 0.284 0.522 0.330 0.297 GSC 2891 2677
0.090 0.016 0.001 0.001 0.001 0.090 0.016 0.001 0.001
11 15.201 14.761 13.690 12.993 12.396 0.440 1.071 0.697 0.597
0.034 0.022 0.003 0.002 0.002 0.034 0.022 0.003 0.003
12 16.119 14.713 13.300 12.423 11.664 1.406 1.413 0.877 0.759 GSC 2891 2532
0.310 0.019 0.012 0.001 0.001 0.310 0.019 0.012 0.001
13 14.495 14.217 13.171 12.496 11.891 0.278 1.047 0.675 0.605 GSC 2891 2469
0.007 0.002 0.001 0.001 0.002 0.007 0.002 0.001 0.002
14 15.545 14.675 13.634 12.924 12.407 0.870 1.041 0.710 0.517 GSC 2891 2789
0.017 0.003 0.002 0.001 0.002 0.017 0.004 0.002 0.002

Individual measurements of V1112 Per are presented in the electronic appendix to html version of this article as a zip archive . The first column of the tables gives the Julian Heliocentric Date of mid-exposure minus 2400000, the second column is the stellar magnitude of the object.

After the brightness of V1112 Per became lower, the exposures had to be increased and the star No. 4 from Table 1 was used as a reference object.

Fig. 1. The diagram of V1112 Per and field stars. The red broken line is the novae-giant sequence (Hachisu & Kato 2014). The gray background represents data from the Mermilliod et al. (1997) catalogue. Magenta circles represent field and comparison stars. The red circles show positions of several Novae during the expansion stage of the dense shell, including the object under study. Arrows indicate interstellar reddening lines.

Fig. 2. V1112 Per = No. 2 and local standard stars. The color image was obtained combining frames from the 1-m telescope. The side of the square is . Magnitudes of the stars are presented in Table 1.

3. Basic parameters and classification of V1112 Per

The brightness measurements on each of the observing nights were averaged and are given, together with their errors, in Table 2. The corresponding plots are shown in Figs. 3 and 4. For band , AAVSO measurements are also shown. Comparison of the AAVSO and our graphs shows that the nebular stage of brightness decline occurred around JD 2459270, see Fig. 3. At this point, the graph definitely splits into two. This bifurcation is due to the fact that instrumental systems of AAVSO observers are slightly different from ours and from each other. Thus, when observing stars with emission spectra, some bright spectral lines may be situated at the edge of a given photometric band. In such a case, differences in measured brightness can exceed one stellar magnitude, as it happened, for example, for the slow Nova V475 Sct, in the spectrum of which at the beginning of the nebular stage, very strong emission [OIII] 495.89 nm and 500.69 nm lines had developed. These lines are located just at the edge of the transmission curves of and bands and are responsible for the discrepancy of and magnitudes determined from our observations taken with different instruments (Chochol et al. 2005ab).

Fig. 3. light curves of V1112 Per. - magenta, - blue, - green, - red, - brown filled circles. Small black points are AAVSO data. All magnitudes were increased by . The first black arrow stays for maximum brightness, the second one marks the beginning of nebular stage. Small arrows indicate the influence of the difference in the instrumental systems for photometric measurements during the nebular stage.

Fig. 4. Evolution of color indices of V1112 Per, - magenta, - blue, - green, - red. The downward pointing arrow indicates dust emission. The upward arrow marks the beginning of the nebular stage. Interestingly, dust absorption in is less than in .

The and light curves and AAVSO data were used to find the decline rates = 21 days, = 33.5 days, = 23 days, = 34.5 days. This means that V1112 Per belongs to slow Eddington novae ( days, days), it has a structured light curve with standstill at maximum and dust formation at later stages. It may belong to the Fe II spectroscopic type (Downes & Duerbeck 2000).

One can estimate the absolute magnitudes of V1112 Per at maximum , using the MMRD (Magnitude at Maximum – Rate of Decline) relations:

(1) absolutely calibrated relation (Della Valle & Livio 1995):

(1)

.

(2) relation (Downes & Duerbeck 2000):

(2)

.

(3) empirical relation (Downes & Duerbeck 2000). The cited authors found that Novae 15 days after maximum had similar absolute magnitudes :

(3)

.

(4) The relations (Pfau 1976; Livio 1992):

(4)

.

(5) empirical relation (Pfau 1976):

(5)

.

The unweighted mean absolute magnitudes: , .

The calculated intrinsic color index at maximum light, = 0.16, is close enough to that derived by Downes & Duerbeck (2000) for the intrinsic colors of novae at maximum, , and this implies . Since the accuracy of the maximum brightness estimate in the band is significantly higher than for the band, the maximum value in the band can be accepted as the average of the two estimates, .

Using the derived and the formula given by Livio (1992):

(6)

we can estimate the mass of the white dwarf in V1112 Per as .

The interstellar extinction of the Nova can be derived:

(1) from the comparison of the observed index at maximum , affected by extinction, to the intrinsic color index , ;

(2) by comparison of the and indices during the opaque shell stage in the diagram to the novae-giant sequence according to Hachisu & Kato (2014). This gives , see Fig. 1. To demonstrate this method, some other Novae measured by us at the same stages were placed on the diagram, see Fig. 1. The stars CT Tri (Chochol et al. 2009), V529 Dra (Katysheva et al. 2013), V466 And (Chochol et al. 2010) experience little or no absorption, while the star V475 Sco (Chochol et al. 2005b) experiences significant absorption. for V339 Del (Chochol et al. 2014), and it fits better into the supergiant sequence;

(3) from the relation of van den Bergh & Younger (1987), who found that novae two magnitudes below maximum have an unreddened color index

(7)

The observed color of V1112 Per two magnitudes below maximum is , which thus yields ;

(4) from the relation suggested by Miroshnichenko (1988) who developed the photometric method to determine interstellar extinction towards Novae. He found that during "stability stage", which occurs not very long after maximum, when both and indices do not change systematically, the color excess is given by:

(8)

where is the mean color index during the stability stage. For V1112 Per, the stability stage lasted from JD 2,459,190 to JD 2,459,207. For , we find a corresponding .

The mean reddening found from the data mentioned above is . This value is higher than follows from data in Green et al. (2015) for this region and the distance of 6 kpc or more (piercing the Galaxy's disk through and through), . Multicolor photometry of other objects under study, such as V2544 Cyg (Volkov et al. 2017) and V839 Cep (Volkov et al. 2024), has already shown significant excesses of interstellar extinction compared to survey data.

The corresponding absorption in and bands is and . The resulting distance moduli of V1112 Per are and , corresponding to a distance of  kpc.



Table 2. magnitudes of V1112 Per
JD
2 400 000 +
59196.3199 9.928 10.355 9.600 8.499 - 7.848 -
0.002 0.001 0.001 0.001 - 0.002 -
59197.2814 9.884 10.295 9.526 8.474 - 7.846 -
0.007 0.004 0.004 0.002 - 0.002 -
59198.5451 9.830 10.301 9.479 8.467 - 7.831 -
0.005 0.005 0.004 0.003 - 0.003 -
59206.1970 10.542 10.948 10.203 9.017 - 8.435 -
0.000 0.009 0.003 0.003 - 0.004 -
59207.2274 10.571 10.957 10.225 9.040 - 8.455 -
0.016 0.003 0.003 0.002 - 0.003 -
59210.1605 10.665 11.146 10.450 9.197 - 8.610 -
0.000 0.004 0.003 0.002 - 0.000 -
59212.2962 10.705 11.096 10.383 9.209 - 8.638 -
0.005 0.003 0.003 0.002 - 0.002 -
59214.5913 10.852 11.279 10.575 9.358 - 8.776 -
0.005 0.005 0.004 0.003 - 0.003 -
59215.5722 10.965 11.371 10.695 9.420 - 8.822 -
0.004 0.002 0.003 0.003 - 0.004 -
59216.5966 11.163 11.517 10.862 9.533 - 8.912 -
0.009 0.004 0.003 0.002 - 0.002 -
59217.1714 11.136 11.518 10.915 9.608 - 8.987 -
0.003 0.003 0.002 0.001 - 0.001 -
59219.5394 11.132 11.472 10.787 9.695 - 9.101 -
0.015 0.002 0.002 0.002 - 0.002 -
59221.3016 11.935 12.203 11.507 10.220 - 9.569 -
0.004 0.002 0.002 0.001 - 0.001 -
59230.1971 14.644 15.567 14.270 12.275 11.702 - 10.266
0.012 0.011 0.004 0.005 0.002 - 0.002
59232.2420 - 16.388 14.901 12.608 - 11.574 -
- 0.100 0.050 0.050 - 0.070 -
59234.2201 - - 15.150 12.770 - 11.720 -
- - 0.009 0.003 - 0.004 -
59246.2820 15.949 16.590 15.652 13.549 - 12.756 -
0.026 0.020 0.020 0.002 - 0.004 -
59256.2049 16.190 16.883 15.837 14.148 13.692 - 12.715
0.000 0.040 0.008 0.007 0.003 - 0.007
59262.2287 - 16.631 15.972 - - - -
- 0.050 0.050 - - - -
59265.2024 16.165 16.472 16.008 14.491 14.094 - 13.362
0.050 0.017 0.009 0.008 0.005 - 0.013
59268.4040 16.026 16.661 16.088 14.548 14.159 - 13.511
0.210 0.081 0.022 0.015 0.013 - 0.023
59272.2774 16.497 16.459 15.993 14.508 14.133 - 13.591
0.082 0.024 0.013 0.006 0.007 - 0.008
59273.2132 16.517 16.506 15.737 14.423 - 14.383 -
0.075 0.024 0.021 0.007 - 0.007 -
59274.2073 16.646 16.521 15.690 14.413 - 14.388 -
0.034 0.011 0.002 0.005 - 0.007 -
59276.4121 16.339 16.724 15.743 14.373 - 14.477 -
0.210 0.019 0.054 0.009 - 0.021 -
59279.2216 16.604 16.471 15.531 14.280 - 14.298 -
0.039 0.009 0.005 0.003 - 0.006 -
59293.2183 16.389 16.051 15.056 13.925 - 13.975 -
0.105 0.001 0.035 0.006 - 0.010 -
59294.3818 - 16.057 14.988 13.830 - 13.739 -
- 0.063 0.080 0.021 - 0.100 -
59314.2565 15.870 15.493 14.352 13.432 - 13.578 -
0.076 0.005 0.005 0.004 - 0.012 -

4. Fast variability

We examined our data for early periodic variability. For this purpose, observations with dates after JD 2 459 230 were corrected for trends and brought to the same level. The periods were searched in the interval from 002 to 52. The algorithm suggested by Volkov (2022) was used. This program is well suited for searching for small-amplitude oscillations of arbitrary shape, it uses the sliding average algorithm. The period 0054 produces a small peak on the periodogram in the photometric band. For the remaining photometric bands, traces of oscillations were not found. This period does not coincide with that suggested by Schmidt (2021), 00927 day. A plot of data phased with our period is presented in Fig. 5.

Fig. 5. Our observations after JD 2,459,230 phased with the period 0054. Data points circled with red are individual nights 2,459,230 and 2,459,314. The dark sine-shaped curve is for the sliding mean.

Acknowledgements.

This study has made use of the SIMBAD database of the Strasbourg Astronomical Data Center (France).

The study was conducted under the state assignment of Lomonosov Moscow State University.

I would like to express my sincere gratitude to the editor of the journal, Prof. N.N. Samus, for his fruitful discussions of the manuscript and for introducing important editorial improvements.

References:

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