Probing Impacts of Stellar Variability within HST WFC3/STIS and Ariel Tier 2 and Tier 3 Observations with Activity Metrics

Recording: https://www.oact.inaf.it/seminars/

DATE:  Thursday, April 3, 11:00 a.m.

ORGANIZER: INAF-OACT

LOCATION: AULA OVEST (INAF-OACT) + remote

Link for the remote audience:
https://meet.google.com/wvf-uwxo-oyj

SPEAKER: Alexandra Thompson (Department of Physics and Astronomy, University College London)

ABSTRACT:
Stellar activity produces two main diagnostics within low-resolution exoplanet transmission spectra. Its highly chromatic nature imparts trends in the underlying spectrum that become most noticeable at shorter wavelengths due to the increased contrast between the flux from the active regions (i.e. spots and/or faculae) and the quiet photosphere. The second characteristic is that activity is inherently time-variable, predominantly modulated by stellar rotation as active regions rotate into and out of view but also with contributions from longer timescales of evolution/decay and even long-term activity cycles e.g. maxima and minima (although certain configurations e.g. polar spots and active latitudes will be more resistant to this). This variability can reveal itself through subsequent observations of the system and is both useful and challenging; it can further help us to identify and constrain potential contamination but also means that observations at different epochs may require individual corrections before they can robustly be combined and analysed together which will become increasingly difficult for smaller planets as the SNR of each visit progressively decreases. In this seminar I will present how both diagnostics have been used with archival HST WFC3 and STIS datasets to create two new activity metrics that are highly complementary to existing indicators. I will also show preliminary results surrounding how this work is being extended to Tier 2 and Tier 3 Ariel simulations to explore how stellar variability will impact our ability to stack visits to obtain the required SNR for these tiers.

A few rules:
— before joining, make sure you are using your institutional inaf.it account if you have one (otherwise we will grant you permission to join)
— please do not forget to mute your microphone and switch off your webcam when access the virtual room
— for questions leave a message in the chat, the answers at the end of the webinar
— the seminar will be recorded, so if you are interested in it, please contact us to get the link to the registration.