An analysis on the photometric variability of V 1490 Cyg

Variability in Young Stellar Objects (YSOs) is one of their primary characteristics. Long-term, multi-filter, high-cadence monitoring of large samples aids understanding of such sources. Although data from the HOYS citizen science project allows for such monitoring, usage of different filters introduces colour-terms to the photometric data. This thesis outlines the development of a novel colour-term correction method, improving photometric error to within a couple of percent. The corrected light curve for the YSO, V 1490 Cyg, is then discussed in detail. The source is observed to be a quasi periodic dipper with a period of 31.447 ± 0.011 days. Long and short-term variability is observed for B, V, Rc and Ic data, with larger variability on short timescales for U and Hα. U amplitudes were observed to vary on timescales of hours, indicating the source is still accreting. No significant trends were observed in the structure function, with the amount of mass in the occulting structure seen to vary by up to a factor of 10 for both mass increase and decrease. The lower estimate of the typical accretion rate of V 1490 Cyg was found of the order 10^(−10) Mʘ/year, consistent with low levels of accretion as seen in other T-Tauri stars. Investigating the orbiting structure in V vs. V − Ic parameter space suggests low column density material with roughly ISM dust properties. Embedded in this envelope are denser, small-scale structures, most likely composed of larger dust grains. The scattering properties of this material are consistent and do not change over time. An accurate distance to both IC 5070 and V 1490 Cyg of 870 (+70, −55) pc has been determined using Gaia. Literature near-infrared (NIR) and mid-infrared (MIR) data suggest that V 1490 Cyg is most likely a CTTS, with a currently low, but variable accretion rate. It is potentially at the start of the transition into a WTTS or transition disk object. This thesis finds the nature of the variability of the source is most likely attributed to a protoplanet-induced disk warp

A survey for variable young stars with small telescopes: II - mapping a protoplanetary disc with stable structures at 0.15 au

The HOYS citizen science project conducts long term, multifilter, high cadence monitoring of large YSO samples with a wide variety of professional and amateur telescopes. We present the analysis of the light curve of V1490 Cyg in the Pelican Nebula. We show that colour terms in the diverse photometric data can be calibrated out to achieve a median photometric accuracy of 0.02 mag in broadband filters, allowing detailed investigations into a variety of variability amplitudes over timescales from hours to several years. Using Gaia DR2 we estimate the distance to the Pelican Nebula to be 870 +70 −55 pc. V1490 Cyg is a quasi-periodic dipper with a period of 31.447 ± 0.011 d. The obscuring dust has homogeneous properties, and grains larger than those typical in the ISM. Larger variability on short timescales is observed in U and Rc−Hα, with U-amplitudes reaching 3 mag on timescales of hours, indicating the source is accreting. The Hα equivalent width and NIR/MIR colours place V1490 Cyg between CTTS/WTTS and transition disk objects. The material responsible for the dipping is located in a warped inner disk, about 0.15 AU from the star. This mass reservoir can be filled and emptied on time scales shorter than the period at a rate of up to 10−10 M�/yr, consistent with low levels of accretion in other T Tauri stars. Most likely the warp at this separation from the star is induced by a protoplanet in the inner accretion disk. However, we cannot fully rule out the possibility of an AA Tau-like warp, or occultations by the Hill sphere around a forming planet