A survey for variable young stars with small telescopes – VII. Spot properties on YSOs in IC 5070

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 (Teff), and a coverage of 0.05 – 0.4. Six more have hot spots, with temperatures up to 3000 K above Teff 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 Teff < 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.

Variability of Young Stellar Objects in the Perseus Molecular Cloud

“…We also compared the variability amplitude in g-band with the cool spot models (upper right panel of Figure 14). The comparison indicates that the typical changes in spot coverage of our periodic variables is in the range 30%-40%, and this range is consistent with the cool spot coverage in Cao & Pinsonneault (2022), Herbert et al (2023). For our analysis, we model a single spot on the stellar surface, and the reader is referred to Guo et al (2018) for a discussion about multiple spots configuration.…”

A survey for variable young stars with small telescopes: VI – Analysis of the outbursting Be stars NSW 284, gaia 19eyy, and VES 263

“…The project Hunting Outbursting Young Stars (HOYS) is one of the endeavours designed to overcome this deficit, by collecting observations from a multitude of small telescopes from professional and amateur observatories, all using a pre-defined observing strategy and a specific set of target regions (see overview paper by Froebrich et al 2018). In the first HOYS papers we have, for example, presented a study of rotation in one star forming region (Froebrich et al 2021), a follow-up study of spot properties in the same region (Herbert et al 2023), and an analysis of the variability in a specific source that is caused by eclipses from structures in a protoplanetary disk (Evitts et al 2020), among other findings. In this paper we take a more holistic view -we aim to select prospective young stars in all 25 HOYS target regions, using data from Gaia, collate information about these samples, and study general variability properties among those samples.…”