[Astronomy seminar] Astronomy Department Seminar - September 10th Sara Saracino

[Astronomy seminar announcements]

Hello

On Friday the 10th we have the second astronomy seminar of the year with 
Sara Saracino (Liverpool John Moores University) speaking via Zoom at 10:30.

*Stellar-mass black holes in young star clusters: exciting news*

Black holes (BHs) are among the most mysterious and elusive objects in 
the Universe. The recent discovery through gravitational waves of very 
massive BHs has challenged our understanding of stellar evolution in 
massive stars, moving the focus to high-density environments like star 
clusters, where merger cascades are most likely to happen. In this 
context, a systematic search for stellar mass BHs in star clusters would 
be crucial to add important pieces of information in this complicated 
puzzle.

Exploiting the technique developed by Giesers et al. 2018, 2019, we have 
recently started a large spectroscopic campaign with MUSE, to search for 
these objects in clusters of different ages. For two very young clusters 
in the Large Magellanic Clouds (NGC 1850, ~100Myr and NGC1846, ~1.5Gyr) 
we have recently secured ~15 epochs of observations spanning almost 2 
years. First results show that a fair amount of stars in the clusters 
are in binary systems, with some of them showing evidence of orbit 
around BHs.

I will spend some time discussing the first BH directly detected in NGC 
1850, which is in a binary system with a B main sequence star. The 
simultaneous modelling of both radial velocity and OGLE light curves 
allowed us to derive the main physical properties of the system, as well 
as a first BH mass measurement.

Such a detection is very important for clusters as young as 100 Myr, as 
this is the first step in constructing the initial mass function of BHs, 
which represents a long standing open question in astrophysics.

We are trying something new this year with leaving the Zoom call open 
after the formal hour of the seminar is up to allow the speaker, if they 
wish, to chat informally with anyone who is interested.

Thanks

Chris and Tine

Christopher Usher is inviting you to a scheduled Zoom meeting.

Topic: Christopher Usher's Zoom Meeting
Time: Sep 10, 2021 10:30 AM Stockholm

Join Zoom Meeting
https://stockholmuniversity.zoom.us/j/63399256477?pwd=U2RPNzY1Ry8wNFU4blFRYWZQeEVYZz09 


Meeting ID: 633 9925 6477
Passcode: niChInat


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