[Astronomy seminar] Astronomy seminar on Friday 17th November

[Astronomy seminar announcements]

Title: Observations of fast-moving structures in the debris disk of AU 
Mic: 3 years of follow-up with SPHERE

Speaker: Anthony Boccaletti (Observatoire de Paris)
Friday 17th of November from 10:30 to 11:30 at FC61.

Abstract:
The instrument SPHERE was installed at the VLT in 2014 and provides a 
significant gain in terms of contrast with respect to the previous 
generation of instruments.
As a result, we now have access to very high contrast in the close 
environment of bright stars in particular the young systems in order to 
search for giant planets and circumstellar disks. During the 
commissioning in Aug 2014, SPHERE has revealed several structures 
(several AU in size) in the form of arches or undulations in the 
midplane of the debris disk around the star AU Microscopii. This disk is 
seen edge on and the system is conveniently close (~10 pc) and young as 
well (~20 Myr). The comparison of these SPHERE observations with the 
ones from STIS/HST 4 years before, not only allowed us to re-identify 
the structures in older data but most importantly led us to conclude 
that these structures were moving outwards in the disk, some with very 
large projected speed (4-10 km/s) hence possibly escaping the system. 
Several assumptions were considered to explain this behaviour, one of 
the them involves a body in Keplerian motion releasing some dust under 
the influence of the star’s activity. Since then, the object is 
regularly observed with SPHERE as part of the GTO and during a 
monitoring program.
After a short introduction on the instrument and its modes as well as 
the achieved performance, I’ll remind the initial results from 2014 
which led to the discovery of these fast-moving structures. Then, I’ll 
present the recent observations obtained from the last 3 years which 
unambiguously confirm the motion of the structures. The hypothesis of a 
parent body emitting an outflow of dust will be discussed in the light 
of these observations.