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Multicolor Photometric Behavior of the Young Stellar Object V1704 Cygni

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Multicolor Photometric Behavior of the Young Stellar Object V1704 Cygni Multicolor photometric behavior of the young stellar object V1704 Cygni Sunay Ibryamov1, Evgeni Semkov2, Stoyanka Peneva2, U˘gur Karadeniz3 1 Department of Physics and Astronomy, University of Shumen, 115, Universitetska Str., 9700 Shumen, Bulgaria 2 Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72, Tsarigradsko Shose Blvd., 1784 Sofia, Bulgaria 3 Department of Physics, Izmir Institute of Technology, Urla, 35430 Izmir, Turkey [email protected] (Submitted on 22.01.2018. Accepted on 20.02.2018) Abstract. Results from BV RI photometric observations of the pre-main sequence star V1704 Cyg collected during the time period from August 2010 to December 2017 are presented. The star is located in the star-forming HII region IC 5070 and it exhibits photometric variability in all optical passbands. After analyzing the obtained data, V1704 Cyg is classified as a classical T Tauri star. Key words: stars: pre-main sequence, stars: variables: T Tauri, star: individual: (V1704 Cyg) 1. Introduction One of the most frequent types of pre-main sequence (PMS) stars are the low-mass (M ≤ 2M⊙) T Tauri stars (TTSs). The first study of the TTSs as a separate class of variables with the prototype star T Tau was made by Joy (1945). These stars show irregular photometric variability and emission spectra. TTSs are divided into two sub-classes: classical T Tauri stars (CTTSs) still actively accreting from their massive circumstellar disks and the weak- line T Tauri stars (WTTSs) without evidence of disk accretion (M´enard & Bertout 1999). According to the classification scheme for the light curves of the CTTSs proposed by Ismailov (2005) we can clearly distinguish five principal types based on the light curve shape: (Type I): constant mean brightness without changes in the amplitude of the rapid brightness variability; (Type II): con- stant mean brightness with changes in the amplitude of the rapid variabil- ity; (Type III): varying mean brightness without changes in the amplitude of the rapid variability; (Type IV): variations of both the mean brightness and the amplitude of the rapid variability; and (Type V): the variable is often bright, and rare brightness decreases are observed. The possible phys- ical mechanisms responsible for the different light curve shapes are given in Ismailov (2005). The long-term multicolor observations are of particular importance to the finding and the classification of PMS stars. The number of the studied PMS stars is not large. Each individual study in this direction is important and contributes to the overall shaping of the scientific ideas about the star formation process. V1704 Cygni (also known as LkHα 155 and [KW97] 50-45) was included in the list of Hα emission-line stars published by Herbig (1958). The spec- trum of the star taken by Mendoza et al. (1990) shows spectral type K3 Bulgarian Astronomical Journal 29, 2018 Multicolor photometric behavior of the YSO V1704 Cygni 11 and strong hydrogen (Wλ(Hα)=98.8 A˚ and Wλ(Hβ)=36.7 A)˚ and forbid- den emission lines. He I (λ 5876 A˚ and λ 7065 A),˚ [O II] (λ 3727-9 A)˚ and [S II] (λ 6717 plus λ 6731 A)˚ emission lines are present. Guieu et al. (2009) included V1704 Cyg in their list of young stellar object candidates. Section 2 in the present paper gives information about the telescopes and cameras used to collect the photometric observations. Section 3 de- scribes the derived results and their interpretation. 2. Observations and Data reduction The BV RI photometric observations of V1704 Cyg were performed from August 2010 to December 2017 with the 2-m Ritchey-Chr´etien-Coud´e(RCC), the 50/70-cm Schmidt and the 60-cm Cassegrain telescopes administered by the Rozhen National Astronomical Observatory in Bulgaria and the 1.3-m Ritchey-Chr´etien (RC) telescope administered by the Skinakas Observa- tory1 of the University of Crete in Greece. The total number of the nights used for observations is 212. The observations were performed with four different types of CCD cam- eras: VersArray 1300B at the 2-m RCC telescope, ANDOR DZ436-BV at the 1.3-m RC telescope, FLI PL16803 at the 50/70-cm Schmidt telescope, and FLI PL09000 at the 60-cm Cassegrain telescope. The technical param- eters and specifications for the cameras used are given in Ibryamov et al. (2015). All frames were taken through a standard Johnson−Cousins BV RI set of filters. The frames are dark (bias) frame subtracted and flat field corrected. The photometric data were reduced using idl based daophot subroutine. As a reference, the BV RI comparison sequence of eleven stars in the field around V2492 Cyg reported in Ibryamov et al. (2018) was used. All data were analyzed using the same aperture, which was chosen to have a 4′′ radius, while the background annulus was taken from 9 to 14′′. The average value of the errors in the reported magnitudes is 0.01−0.02 mag for the I- and R-band data and 0.01−0.03 mag for the V - and B-band data. 3. Results and Discussion V1704 Cyg is located in the field of the Pelican Nebula (IC 5070) at 1′ from the well-studied young star V2492 Cyg. The results from our long-term BV RI photometric monitoring of V1704 Cyg are summarized in Tab. 12. The available photometric data of the star are plotted on Fig. 1. Table 1: Photometric CCD observations of V1704 Cyg. Date J.D. (24...) I [mag] R [mag] V [mag] B [mag] Telescope CCD 26.08.2010 55435.339 14.66 16.24 17.61 19.24 1.3-m AND 1 Skinakas Observatory is a collaborative project of the University of Crete, the Founda- tion for Research and Technology, Greece, and the Max-Planck-Institut f¨ur Extrater- restrische Physik, Germany. 2 The table is available also via CDS Vizier Online Data Catalog. 12 S. Ibryamov et al. Table 1: Continued. Date J.D. (24...) I [mag] R [mag] V [mag] B [mag] Telescope CCD 07.09.2010 55447.457 14.60 16.11 17.20 - Sch FLI 08.09.2010 55448.298 14.57 16.07 17.25 - Sch FLI 09.09.2010 55449.378 14.62 16.14 17.32 - Sch FLI 11.10.2010 55481.316 14.24 15.69 16.92 18.27 1.3-m AND 29.10.2010 55499.210 14.51 15.98 17.20 18.71 2-m VA 30.10.2010 55500.184 14.50 15.98 17.20 18.69 2-m VA 31.10.2010 55501.178 14.46 15.98 - - Sch FLI 31.10.2010 55501.253 14.47 15.97 17.19 18.67 2-m VA 01.11.2010 55502.178 14.48 15.97 17.15 18.57 2-m VA 02.11.2010 55503.188 14.39 15.82 - - Sch FLI 03.11.2010 55504.219 14.41 15.92 - - Sch FLI 04.11.2010 55505.175 14.44 15.98 - - Sch FLI 05.11.2010 55506.206 14.47 15.98 17.18 - Sch FLI 06.11.2010 55507.207 14.50 15.99 - - Sch FLI 01.01.2011 55563.188 14.49 16.04 - - Sch FLI 06.01.2011 55568.169 14.31 15.67 16.62 17.85 2-m VA 08.01.2011 55570.171 14.49 15.93 17.09 18.52 2-m VA 09.01.2011 55571.173 14.34 15.85 16.95 18.30 2-m VA 11.01.2011 55573.215 14.62 16.02 17.18 - 2-m VA 12.01.2011 55574.240 14.59 16.10 17.28 - 2-m VA 07.02.2011 55599.675 14.58 16.12 17.52 - Sch FLI 04.04.2011 55656.484 14.56 16.00 - - Sch FLI 08.04.2011 55659.502 14.37 15.80 - - 2-m VA 21.05.2011 55703.401 14.66 - - - Sch FLI 23.05.2011 55705.398 14.54 - - - Sch FLI 25.05.2011 55707.379 14.63 - - - Sch FLI 08.06.2011 55721.357 14.61 16.07 - - 2-m VA 21.06.2011 55734.405 14.66 - - - Sch FLI 23.06.2011 55736.468 14.72 - - - Sch FLI 16.08.2011 55790.302 14.62 - - - 1.3-m AND 17.08.2011 55791.306 14.68 16.29 17.61 19.14 1.3-m AND 23.08.2011 55797.310 14.64 - - - Sch FLI 10.09.2011 55815.428 14.72 16.33 17.66 19.14 1.3-m AND 11.09.2011 55816.415 14.66 16.22 17.53 - 1.3-m AND 19.09.2011 55824.258 14.55 16.06 17.29 18.69 1.3-m AND 23.09.2011 55828.268 14.57 - - - Sch FLI 07.10.2011 55842.288 14.46 15.88 - - 1.3-m AND 13.10.2011 55848.252 14.67 16.28 17.62 18.94 1.3-m AND 29.10.2011 55864.210 14.70 16.17 17.43 - 2-m VA 31.10.2011 55866.256 14.47 15.93 17.02 18.36 2-m VA 26.11.2011 55892.192 14.35 15.77 16.91 - 2-m VA 29.11.2011 55895.188 14.49 15.92 - - Sch FLI 30.11.2011 55896.201 14.53 15.99 - - Sch FLI 29.12.2011 55925.190 14.52 - - - Sch FLI 01.01.2012 55928.172 14.53 - - - Sch FLI 17.03.2012 56003.552 14.52 - - - Sch FLI 29.03.2012 56015.527 14.57 - - - 2-m VA 15.06.2012 56094.409 14.58 16.07 17.27 - 2-m VA 17.06.2012 56096.374 14.57 16.00 - - Sch FLI 11.07.2012 56120.350 14.62 16.10 17.32 - Sch FLI 12.07.2012 56121.313 14.64 16.17 17.36 - Sch FLI 13.07.2012 56122.375 14.57 16.13 17.25 - Sch FLI 14.07.2012 56123.347 14.56 16.08 17.28 18.64 Sch FLI 01.08.2012 56141.399 14.54 16.02 17.23 - 1.3-m AND 02.08.2012 56142.285 14.53 16.02 17.22 - 1.3-m AND 03.08.2012 56143.269 14.59 16.10 17.23 - 1.3-m AND 12.08.2012 56151.614 14.55 16.05 17.25 - 1.3-m AND Multicolor photometric behavior of the YSO V1704 Cygni 13 Table 1: Continued.
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