EXors are low-mass young stars undergoing a temporary increase of mass accretion rate from the circumstellar disk onto the star. These events lead to brightenings at optical and infrared wavelengths of a few magnitudes, and can last from a few months up to a year. EX Lupi, the prototype of the EXor class, has been observed with various instruments for the past 130 years. Throughout the decades, astronomers have detected dozens of weak (~1 mag) bursts, that are not uncommon in young stellar objects, and two strong (>4 mag), extraordinary and very rare outbursts. In between these categories are the "medium-sized" outbursts with amplitudes of 2-3 mag, which EX Lupi has experienced multiple times in the past century. Based on the powerful outburst of 2008, we know that events like this cause physical, chemical and mineralogical changes to the planet-forming disk surrounding the young star.
But what about the medium outbursts? Can one of these weaker yet more common events cause significant changes in the system? Or can series of them cause cumulative changes?
In this poster we present our search for these answers via our multi-facility multi-wavelength study of the medium-sized outburst that EX Lupi experienced in 2022. We present the results of pre-, during and post-outburst optical and infrared observations with VLT/X-SHOOTER and VLTI/MATISSE, and show how the circumstellar disk of EX Lupi has changed.
In addition, we show the beginnings of our long-term ALMA study to show the chemical evolution of EX Lupi via CO, other small molecules, and methanol. In this poster we summarize the new results and discuss how the new eruption could refine our paradigm of the eruptive phenomenon in young stars, a process that may be part of the early evolution of our Solar System, too.