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<p>Reminder - Sara's seminar in 35 minutes!</p>
<p>Thanks<br>
Chris<br>
</p>
<div class="moz-cite-prefix">On 06/09/2021 12:08, Chris Usher wrote:<br>
</div>
<blockquote type="cite"
cite="mid:97cf33af-a1d2-f2f2-8436-1fafbff6625b@astro.su.se">
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<p>Hello</p>
<p>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.</p>
<p><b>Stellar-mass black holes in young star clusters: exciting
news</b><br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
</p>
<p>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.</p>
Thanks<br>
<p> Chris and Tine</p>
<p>Christopher Usher is inviting you to a scheduled Zoom meeting.
<br>
<br>
Topic: Christopher Usher's Zoom Meeting <br>
Time: Sep 10, 2021 10:30 AM Stockholm <br>
<br>
Join Zoom Meeting <br>
<a class="moz-txt-link-freetext"
href="https://stockholmuniversity.zoom.us/j/63399256477?pwd=U2RPNzY1Ry8wNFU4blFRYWZQeEVYZz09"
moz-do-not-send="true">https://stockholmuniversity.zoom.us/j/63399256477?pwd=U2RPNzY1Ry8wNFU4blFRYWZQeEVYZz09</a>
<br>
<br>
Meeting ID: 633 9925 6477 <br>
Passcode: niChInat </p>
<p><br>
</p>
</blockquote>
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