# The complex phenomena of YSOs revealed by their X-ray variability

## TL;DR

This paper reviews recent X-ray observations of Young Stellar Objects, highlighting complex phenomena and physical processes involved in star-disk interactions, based on large datasets from multiple space telescopes.

## Contribution

It presents new insights from analyzing large flare datasets and coordinated multi-wavelength observations, advancing understanding of YSO X-ray variability.

## Key findings

- Large flares observed with Chandra COUP reveal complex phenomena.
- Systematic analysis of flares from NGC 2264 enhances understanding of YSO activity.
- Simultaneous XMM-Newton and NuSTAR data provide new insights into Class I/II YSOs.

## Abstract

X-ray observations of Young Stellar Objects (YSOs) have shown several complex phenomena at work.In recent years a few X-ray programs based on long, continuous and, sporadically, simultaneous coordinated multi-wavelengths observations have paved the way to our current understanding of the physical processes at work, that very likely regulates the interaction between the star and its circumstellar disk. We will present and discuss some recent results based on a novel analysis of few selected very large flares observed with the Chandra Orion Ultradeep Pointing (COUP), on the systematic analysis of a large collection of flares observed with the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) as well as on the Class I/II YSO Elias 29, in the rho Oph star forming region, whose data have been recently gathered as part of a joint simultaneous XMM-Newton and NuSTAR large program.