Abstract:Context. V2492 Cyg is a young pre-main sequence star presenting repetitive brightness variations of significant amplitude (∆R ≥ 5 mag) whose physical origin has been ascribed to both extinction (UXor-type) and accretion (EXor-type) variability, although their mutual proportion has not been clarified yet. Recently, V2492 Cyg has reached a level of brightness ever registered in the period of its documented activity. Aims. We aim to derive the variation of the mass accretion rate between low-and high-state and to… Show more
“…First, each line flux was converted into L line by adopting a distance to V1118 Ori of 400 pc (Muench et al 2008). Then, L acc has been estimated together with the visual extinction A V with a recursive fitting method (for a detailed explanation see Giannini et al 2018). The mass accretion rate, Ṁacc , derives from L acc through the formula of Gullbring et al (1998), taking M * = 0.4 M R * = 1.29 R (Hillenbrand 1997, Stassun et al 1999) and a typical disk inner radius R in = 5 R .…”
Section: Mass Accretion Rate and Extinction Variabilitymentioning
Context. V1118 Ori is a classical EXor source whose light curve has been monitored over the past thirty years (although not continuously). It underwent a powerful outburst in 2005, followed by ten years of quiescence and a less intense outburst in 2015. In 2019, a new intense brightness increase was observed (∆g ∼ 3 mag). Aims. This new accretion episode offers the opportunity to compare the photometric and spectroscopic properties of different outbursts of the same source. This allows one to highlight differences and similarities among different events by removing any possible bias related to the intrinsic properties of the star-disk system. Methods. We discovered the 2019 V1118 Ori outburst by examining the g-band light curve acquired by the Zwicky Transient Facility and followed the decreasing phase with the Rapid Eye Mount telescope in the griz bands. Two near-infrared spectra were also acquired at different brightness stages with the Large Binocular Telescope.Results. The last event shows the following characteristics: 1) amplitude similar than in 2015 and lower than in 2005; 2) duration less than one year as in previous events; 3) rise (decline) speed of 0.018 (0.031) mag/day, which is different from previous cases; 4) a gradual blueing of the [g − r] color is observed over time, while the [r − i] color remains roughly unchanged; 5) with few exceptions, the near-infrared lines (mainly H i recombination) are the same observed in 2015; 6) the mass accretion rate peaks atṀ acc ∼ 10 −7 M yr −1 and decreases in about a month down to a few 10 −8 M yr −1 . Conclusions. Our analysis shows that the comparison of data from different outbursts of the same source is a non-trivial exercise, which allows obtaining important clues useful to drive theoretical efforts towards a better understanding of the EXor phenomenon.
“…First, each line flux was converted into L line by adopting a distance to V1118 Ori of 400 pc (Muench et al 2008). Then, L acc has been estimated together with the visual extinction A V with a recursive fitting method (for a detailed explanation see Giannini et al 2018). The mass accretion rate, Ṁacc , derives from L acc through the formula of Gullbring et al (1998), taking M * = 0.4 M R * = 1.29 R (Hillenbrand 1997, Stassun et al 1999) and a typical disk inner radius R in = 5 R .…”
Section: Mass Accretion Rate and Extinction Variabilitymentioning
Context. V1118 Ori is a classical EXor source whose light curve has been monitored over the past thirty years (although not continuously). It underwent a powerful outburst in 2005, followed by ten years of quiescence and a less intense outburst in 2015. In 2019, a new intense brightness increase was observed (∆g ∼ 3 mag). Aims. This new accretion episode offers the opportunity to compare the photometric and spectroscopic properties of different outbursts of the same source. This allows one to highlight differences and similarities among different events by removing any possible bias related to the intrinsic properties of the star-disk system. Methods. We discovered the 2019 V1118 Ori outburst by examining the g-band light curve acquired by the Zwicky Transient Facility and followed the decreasing phase with the Rapid Eye Mount telescope in the griz bands. Two near-infrared spectra were also acquired at different brightness stages with the Large Binocular Telescope.Results. The last event shows the following characteristics: 1) amplitude similar than in 2015 and lower than in 2005; 2) duration less than one year as in previous events; 3) rise (decline) speed of 0.018 (0.031) mag/day, which is different from previous cases; 4) a gradual blueing of the [g − r] color is observed over time, while the [r − i] color remains roughly unchanged; 5) with few exceptions, the near-infrared lines (mainly H i recombination) are the same observed in 2015; 6) the mass accretion rate peaks atṀ acc ∼ 10 −7 M yr −1 and decreases in about a month down to a few 10 −8 M yr −1 . Conclusions. Our analysis shows that the comparison of data from different outbursts of the same source is a non-trivial exercise, which allows obtaining important clues useful to drive theoretical efforts towards a better understanding of the EXor phenomenon.
“… Figure 2. BVRI light curves of V2492 Cyg for the period 2010 August−2017 December. The circles denote our CCD photometric data (present paper); the empty triangles represent the data from aavso database (); the diamonds represent the photometric data from Munari et al (2010, 2017); the pluses denote the data from Covey et al (2011); the empty squares mark the data from Kóspál et al (2011, 2013); the empty circles represent the data from Hillenbrand et al (2013); the empty diamonds signify the data from Froebrich et al (2017); and the squares represent the data from Giannini et al (2018). …”
Section: Resultsmentioning
confidence: 99%
“…the object passed the recent maximum. Giannini et al (2018) presented optical and NIR photometric and spectroscopic observations of the star, which were obtained during the peak luminosity in 2016–2017. Their combined analysis suggests that the V2492 Cyg variability is a combination of changing extinction and accretion.…”
Results from BV RI photometric observations of the young stellar object V2492 Cyg collected during the period from August 2010 to December 2017 are presented. The star is located in the field of the Pelican Nebula and it was discovered in 2010 due to its remarkable increase in the brightness by more than 5 mag in R-band. According to the first hypothesis of the variability V2492 Cyg is an FUor candidate. During subsequent observations it was reported that the star shows the characteristics inherent to EXor-and UXortype variables. The optical data show that during the whole time of observations the star exhibits multiple large amplitude increases and drops in the brightness. In the beginning of 2017 we registered a significant increase in the optical brightness of V2492 Cyg, which seriously exceeds the maximal magnitudes registered after 2010.
“…The object has been studied by numerous authors in the past, e.g. Kun et al (2011); Aspin (2011); Covey et al (2011); Kóspál et al (2011);Hillenbrand et al (2013); Kóspál et al (2013); ; Giannini et al (2017). It also was subject of many Astronomer's Telegrams, e.g.…”
Variability in Young Stellar Objects (YSOs) is one of their primary characteristics. Longterm, multi-filter, high-cadence monitoring of large YSO samples is the key to understand the partly unusual light-curves that many of these objects show. Here we introduce and present the first results of the HOYS-CAPS citizen science project which aims to perform such monitoring for nearby (d < 1 kpc) and young (age < 10 Myr) clusters and star forming regions, visible from the northern hemisphere, with small telescopes. We have identified and characterised 466 variable (413 confirmed young) stars in 8 young, nearby clusters. All sources vary by at least 0.2 mag in V, have been observed at least 15 times in V, R and I in the same night over a period of about 2 yrs and have a Stetson index of larger than 1. This is one of the largest samples of variable YSOs observed over such a time-span and cadence in multiple filters. About two thirds of our sample are classical T-Tauri stars, while the rest are objects with depleted or transition disks. Objects characterised as bursters show by far the highest variability. Dippers and objects whose variability is dominated by occultations from normal interstellar dust or dust with larger grains (or opaque material) have smaller amplitudes. We have established a hierarchical clustering algorithm based on the light-curve properties which allows the identification of the YSOs with the most unusual behaviour, and to group sources with similar properties. We discuss in detail the light-curves of the unusual objects V2492 Cyg, V350 Cep and 2MASS J21383981+5708470.
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