Optical light curves of FUor and FUor-like objects
aa r X i v : . [ a s t r o - ph . S R ] D ec Astroinformatics 2016Proceedings IAU Symposium No. 325, 2017M. Brescia, G. Djorgovski, E. Feigelson, G. Longo & S. Cavuoti,eds. c (cid:13) Optical light curves of FUor and FUor-likeob jects
Evgeni Semkov , Stoyanka Peneva and Sunay Ibryamov , Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy ofSciences, Sofia, Bulgariaemail: [email protected] Department of Theoretical and Applied Physics, University of Shumen, Shumen, Bulgaria
Abstract.
Using recent data from photometric monitoring and data from the photographic platearchives we aim to study, the long-term photometric behavior of FUors. The construction of thehistorical light curves of FUors could be very important for determining the beginning of theoutburst, the time to reach the maximum light, the rate of increase and decrease in brightness,the pre-outburst variability of the star. Our CCD photometric observations were performedwith the telescopes of the Rozhen (Bulgaria) and Skinakas (Crete, Greece) observatories. Mostsuitable for long-term photometric study are the plate archives of the big Schmidt telescopes,as the telescopes at Kiso Observatory, Asiago Observatory, Palomar Observatory and others.In comparing our results with light curves of the well-studied FUors, we conclude that everynew FUor object shows different photometric behavior. Each known FUor has a different rateof increase and decrease in brightness and a different light curve shape.
Keywords. stars: pre–main-sequence, stars: individual (V2493 Cyg, V582 Aur, V900 Mon)
1. Introduction
The young eruptive objects such as FU Orionis (here after FUor) are very rare, butwith a significant role in the stellar evolution. All known FUors share the same definingcharacteristics: a ∆ V ≈
2. Observations
Our CCD photometric observations of FUor objects were performed with the 2 mRCC, the 50/70 cm Schmidt, and the 60 cm Cassegrain telescopes of the National Astro-1 Evgeni Semkov, Stoyanka Peneva & Sunay Ibryamovnomical Observatory Rozhen (Bulgaria) and with the 1.3 m RC telescope of the SkinakasObservatory † of the Institute of Astronomy, University of Crete (Greece). The techni-cal parameters for the CCD cameras used, observational procedure and data reductionprocess are described in Ibryamov et al. (2015).The only possibility for long-time photometric study is a search in the photographicplate archives at the astronomical observatories around the world. Most suitable for thispurpose are the plate archives of the big Schmidt telescopes that have a large field of view.In this paper we present photometric data obtained from the photographic plate archivesof the 105/150 cm Schmidt telescope at the Kiso Observatory (Japan) and the 67/92 cmSchmidt telescope at the Asiago Observatory (Italy). We also used the digitized platesfrom the Palomar Schmidt telescope, available via the website of the Space TelescopeScience Institute.
3. Results and discussion
In this section we present results from the long-term photometric study of three FUorobjects. All three objects were discovered recently and the available data for their pho-tometric behavior are still incomplete.3.1.
V2493 Cyg
The outburst of V2493 Cyg was discovered during the summer of 2010 (Semkov et al.2010; Miller et al. 2011) in the dark clouds between NGC 7000 and IC 5070 (so-called”Gulf of Mexico”). Subsequent photometric and spectral observations (K´osp´al et al. 2011;Semkov et al. 2012; Baek et al. 2015) indicate that the object can be definitely assigned tothe class of FUors. The
BV RI light curves of V2493 Cyg from the collected photometricdata are plotted in Fig. 1. The filled diamonds represent our CCD observations fromRozhen and Skinakas observatories, the filled circles CCD observations from the 48 inchSamuel Oschin telescope at Palomar Observatory (Miller et al. 2011), the open diamondsphotographic data from the Asiago Schmidt telescopes, the open squares photographicdata from the Palomar Schmidt telescope, the filled squares photographic data from theByurakan Schmidt telescope and the open circles photographic data from the Rozhen2-m RCC telescope.The photometric observation obtained before the outburst displayed only small am-plitude variations in all pass-bands typical of T Tauri stars. Acoording to our data theoutburst started sometime before May 2010, and reached the first maximum value at theperiod September - October 2010. Since October 2010, a slow fading was observed andup to May 2011 the star brightness decreased by 1.4 mag. ( V ). Since the autumn of 2011,another light increase occurred and the star became brighter by 1.8 mag. ( V ) until April2013. From the spring of 2011 up to now the star keeps its maximum brightness showinga little bit fluctuations around it. Therefore, we have observed a classical outburst fromFUor type, which should continue over the next few decades.3.2. V582 Aur
The discovery of V582 Aur was reported by the amateur astronomer Anton Khruslov.The star is located in a region of active star formation near Auriga OB2 association.According to Samus (2009) the increase in brightness of the star started between 1982and 1986. Munari et al. (2009) obtained the first spectrum of V582 Aur, which confirms † Skinakas Observatory is a collaborative project of the University of Crete, the Foundationfor Research and Technology - Hellas, and the Max-Planck-Institut f¨ur Extraterrestrische Physik. ptical light curves of FUor and FUor-like objects λ BV RI light curves of V582 Aurfrom all available photometric observations are plotted in Fig. 2. On the figure, the filleddiamonds represent our CCD observations from Rozhen end Skinakas observatories, thefilled circles photographic data from the Asiago Schmidt telescope, the filled trianglesphotographic data from the Kiso Schmidt telescope, and the filled squares photographicdata from the Palomar Schmidt telescope.The results of lasted for six years photometric monitoring of V582 Mon show extremelystrong variability that is not seen in other FUor objects. We suggest that the strongphotometric variability can be explained by 1) time-variable extinction or 2) changes inaccretion rate from the circumstellar disk onto the stellar surface. During the large dropsin brightness, an appearance of dust particles in the immediate circumstellar environmentof the star and change of the shape of basic spectral lines from absorption to emissionwas registered (Semkov et al. 2013).3.3.
V900 Mon
The variability of V582 Aur was discovered by the amateur astronomer Jim Thommes.Based on detailed multi-wavelength study of the star Reipurth et al. (2012) reach theconclusion that V582 Aur belongs to the group of FUor objects. According to the authorsthe outburst of the star occurred between 1953 and 2009. Recently Varricatt et al. (2015)registered a rise in the brightness of V900 Mon in the infrared.Our photometric monitoring of V900 Mon during the period from 2011 to 2016 showsa gradual increase in the brightness (Fig. 3). Our search in the Digitized Sky Surveysshows that the star was registered at minimum light on the photographic plates obtainedon 8 Jan. 1989 ( R ) and 10 Feb. 1985 ( I ). Hence the rise in the brightness of V900 Monbegan after 1985 and continued in the recent years. References
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Figure 1.
Historical
BV RI light curves of V2493 Cyg for the period September 1973 -November 2016
Evgeni Semkov, Stoyanka Peneva & Sunay Ibryamov
Figure 2.
Historical
BV RI light curves of V582 Aur for the period December 1954 − October2016
Figure 3.
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