A survey for variable young stars with small telescopes: VII -- Spot Properties on YSOs in IC5070

TL;DR

This survey analyzes spot properties on 31 young stellar objects using multi-band photometry, revealing diverse spot temperatures and coverage, with implications for stellar activity and accretion processes.

Contribution

It provides the first detailed characterization of spot temperatures and coverage on a sizable sample of YSOs using multi-band data from the HOYS project.

Findings

21 stars have cool spots with temperatures 500-2500 K below T_eff

6 stars exhibit hot spots with temperatures up to 3000 K above T_eff

Large spots are found mainly on cooler stars with T_eff < 4500 K

Abstract

We present measurements of spot properties on 31 young stellar objects, based on multi-band data from the HOYS (Hunting Outbursting Young Stars) project. On average the analysis for each object is based on 270 data points during 80 days in at least 3 bands. All the young low-mass stars in our sample show periodic photometric variations. We determine spot temperatures and coverage by comparing the measured photometric amplitudes in optical bands with simulated amplitudes based on atmosphere models, including a complete error propagation. 21 objects in our sample feature cool spots, with spot temperatures 500 - 2500 K below the stellar effective temperature ($T_{\rm eff}$), and a coverage of 0.05 - 0.4. Six more have hot spots, with temperatures up to 3000 K above $T_{\rm eff}$ and coverage below 0.15. The remaining four stars have ambiguous solutions or are AA Tau-type contaminants. All of the stars with large spots (i.e. high coverage $>0.1$) are relatively cool with $T_{\rm eff} < 4500$ K, which could be a result of having deeper convection zones. Apart from that, spot properties show no significant trends with rotation period, infrared excess, or stellar properties. Most notably, we find hot spots in stars that do not show $K-W2$ infrared excess, indicating the possibility of accretion across an inner disk cavity or the presence of plage.