PENELLOPE: The ESO data legacy program to complement the Hubble UV Legacy Library of Young Stars (ULLYSES)

Abstract

The evolution of young stars and disks is driven by the interplay of several processes, notably the accretion and ejection of material. These processes, critical to correctly describe the conditions of planet formation, are best probed spectroscopically. Between 2020 and 2022, about 500orbits of the Hubble Space Telescope (HST) are being devoted in to the ULLYSES public survey of about 70 low-mass (M⋆ ≤ 2 M⊙) young (age < 10 Myr) stars at UV wavelengths. Here, we present the PENELLOPE Large Program carried out with the ESO Very Large Telescope (VLT) with the aim of acquiring, contemporaneously to the HST, optical ESPRESSO/UVES high-resolution spectra for the purpose of investigating the kinematics of the emitting gas, along with UV-to-NIR X-shooter medium-resolution flux-calibrated spectra to provide the fundamental parameters that HST data alone cannot provide, such as extinction and stellar properties. The data obtained by PENELLOPE have no proprietary time and the fully reduced spectra are being made available to the whole community. Here, we describe the data and the first scientific analysis of the accretion properties for the sample of 13 targets located in the Orion OB1 association and in the σ-Orionis cluster, observed in November–December 2020. We find that the accretion rates are in line with those observed previously in similarly young star-forming regions, with a variability on a timescale of days (≲3). The comparison of the fits to the continuum excess emission obtained with a slab model on the X-shooter spectra and the HST/STIS spectra shows a shortcoming in the X-shooter estimates of ≲10%, which is well within the assumed uncertainty. Its origin can be either due to an erroneous UV extinction curve or to the simplicity of the modeling and, thus, this question will form the basis of the investigation undertaken over the course of the PENELLOPE program. The combined ULLYSES and PENELLOPE data will be key in attaining a better understanding of the accretion and ejection mechanisms in young stars.

A survey for variable young stars with small telescopes – V. Analysis of TX Ori, V505 Ori, and V510 Ori, the HST ULLYSES targets in the σ Ori cluster

“…We note that e.g. the Manara et al (2021) accretion rates for V505 Ori are determined from spectroscopy during the faint state and their extinction values are quite small. Furthermore, our assumption that the brightest HOYS magnitude is the extinction free state of the source could be wrong, i.e.…”

“…Main data for the Ori cluster ULLYSES targets. We list the name adopted by us and the ULLYSES project; the coordinates; the parallax values from GaiaEDR3 (Gaia Collaboration 2020); the spectral type, optical extinction, mass and mass accretion rates from Hernández et al (2014) and Maucó et al (2018) (columns labelled 1) and Manara et al (2021) ternational Variable Star Index (Watson et al 2006(Watson et al , 2007Watson 2006Watson , 2012.…”

“…This effort is supported by many other ground-and spacebased programs to complement and extend this data set to other wavelengths and higher spectral resolution. Foremost PENEL-LOPE, a ∼ 250 h Large Program at the ESO Very Large Telescope (VLT) is providing quasi-contemporaneous optical high-resolution (R > 100.000) and medium-resolution flux-calibrated optical and near-infrared (up to 2.5 m, at R > 10.000) spectroscopy (Manara et al 2021).…”

A survey for variable young stars with small telescopes: V - Analysis of TXOri, V505Ori, and V510Ori, the HST ULLYSES targets in the $σ$Ori cluster

“…This effort is supported by many other ground-and spacebased programs to complement and extend this data set to other wavelengths and higher spectral resolution. Foremost PENEL-LOPE, a ∼ 250 h Large Program at the ESO Very Large Telescope (VLT) is providing quasi-contemporaneous optical high-resolution (R > 100.000) and medium-resolution flux-calibrated optical and near-infrared (up to 2.5 𝜇m, at R > 10.000) spectroscopy (Manara et al 2021).…”

“…Main data for the 𝜎 Ori cluster ULLYSES targets. We list the name adopted by us and the ULLYSES project; the coordinates; the parallax values from GaiaEDR3 (Gaia Collaboration 2020); the spectral type, optical extinction, mass and mass accretion rates fromHernández et al (2014) andMaucó et al (2018) (columns labelled 1) andManara et al (2021) (columns labelled 2).…”