A photometric study of the ULLYSES/PENELLOPE T Tauri star sample in Ori OB1 and 𝛔Ori: the accretion process at the highest time resolution The ULLYSES/PENELLOPE project on YSO accretion • A legacy spectroscopy survey of accreting pre-main sequence stars, including ~70 T Tauri stars • Synchronized HST COS/STIS as well as VLT UVES/ ESPRESSO/X-Shooter observing campaigns; for a few sources multiepoch observations • ULLYSES (Roman-Duval et al. 2020): accretion and ejection tracers at ultraviolet/optical wavelengths; ODYSSEUS (Espaillat et al. 2022): archive research to model and interpret the HST spectral observations; PENELLOPE (Manara et al. 2021): stellar parame- ters; interstellar extinction, veiling; disk wind and jets; • Unique and contemporaneous UV, optical, and near- infrared legacy dataset of a large YSO sample, covering all evolutionary stages from full disk to transitional disks and Class III disk-less objects The Orion sample • 10 stars in Ori OB1, 3 stars in σ Ori • Sp. type: K6-M3.5, Mass: 0.25-1.1 M⊙ • Distance ~400 pc • CVSO 17, CVSO 36, CVSO 58, CVSO 90, CVSO 104, CVSO 107, CVSO 109, CVSO 146, CVSO 165, CVSO 176, SO 518, SO 583, SO 1153 • ULYSSES/PENELLOPE papers: Manara et al. (2021, survey presentation), Frasca et al. (2021, CVSO104), Espaillat et al. (2022, CVSO109), Froebrich et al. (2022, σ Ori), Pittman et al. (submitted, Ori OB1) • Our goals: (1) extend the project in the time domain; (2) put the spectroscopic results into variability context; (3) identify the underlying physical processes Accretion rates estimated from optical photometry • The X-Shooter UV-optical-infrared spectra were fitted with a model composed of a stellar photospheric template and a slab of gas to simulate the accretion hot spot (Manara et al. 2021) • Adopting stellar and extinction parameters from the X-Shooter model, slab models were fitted to optical broad-band photometry from Konkoly Observatory. We assigned chi2-based probability to each fit, and determined the most likely accretion rate value and its uncertainty at each epoch (left figure) Typical accretion rates: ~10-8 M⊙/yr; variation ⪅3 Variability timescales • The observed timescales of variability are related to the physical processes causing the flux changes • Accretion rate (left) and TESS magnitude (right) differences vs. Δt between any two measurements: • Variability amplitudes steadily increase up to ~2 days, and level off afterward Probably related to rotational timescales Hot accretion spots, funnel flows Does this pattern changes on yearly timescales? References Cody et al., AJ 147, id.82 (2014); De et al., PASP 132, id.025001 (2020); Espaillat et al., AJ 163, id.114 (2022); Frasca et al., A&A 656, id.A138 (2021); Froebrich et al., MNRAS 510, 2883 (2022); Manara et al., A&A 650, id.A196 (2021); Roman-Duval et al., RNAAS 4, id.205 (2020) Acknowledgement This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme under grant agreement No 716155 (SACCRED). Observations • BVr’i’ images from Konkoly Observatory, Hungary, 2020 Nov 5 – Dec 26 • BVRCICz’ images from OACt, Catania, Italy, 2020 Nov 25 – Dec 16 • BVr’i’ images, AAVSOnet, 2020 Nov 8 – Dec 19 • J-band images, GATTINI survey (De et al. 2020), 2020 Oct 29 – Jan 2 • g-band photometry, ASAS-SN survey • TESS white light (~i-band), 2020 Nov 20 – Dec 16, 10-min cadence TESS (credit: NASA) Characterization of the light curves Left: Example multi-wavelength light curves of CVSO 146. Middle: Distribution of the T Tauri stars in the QM parameter space (based on Cody et al. 2014) • Variability amplitudes: typically ΔV=0.3-0.7 mag, up to 2 mag. Usually decrease with wavelength • Two-parameter description (Cody et al. 2014): degree of periodicity (Q) and flux asymmetry (M), computed from the TESS light curves • QM distribution: three light curves are periodic or quasi- periodic, the remaining ones are close to aperiodic • Most light curv