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SUMMARY:Stellar Evolution and Mass Transfer from a Star to a Supermassive 
 Black Hole [HYBRID]
DTSTART:20260408T113000Z
DTEND:20260408T123000Z
DTSTAMP:20260429T030400Z
UID:indico-event-24822@indico.gsi.de
CONTACT:t.neff@gsi.de
DESCRIPTION:Speakers: Andrey Sandomirsky (Hebrew University of Jerusalem\,
  Israel)\n\nSupermassive black holes (SMBHs) reside in the centers of most
  galaxies and are surrounded by millions of stars that orbit them. LISA wo
 uld be able to detect emission of gravitational waves (GWs) from stars orb
 iting close enough to the SMBH\, with orbital periods of order an hour. At
  such a period\, mass transfer would take place from the star into the SMB
 H. We show that in the case of orbital angular momentum conservation\, mas
 s transfer is likely to be stable. For stable systems\, evolution of the s
 emi-major axis of the orbit of the star and the frequency of the emitted G
 Ws\, depends on the mass-radius relation of the star as it loses mass. We 
 use MESA code to study the mass-radius relation of a massive star that sta
 rts transferring mass while on the main sequence (MS). We show that stars\
 , above about 2 solar masses\, remain in the MS as their mass shrinks. Onc
 e below approximately 2 solar masses\, the GW timescale is too short to al
 low heat transfer to adjust the stellar structure and the star evolves adi
 abatically (each mass element preserves its entropy) off the MS. We find t
 hat contrary to previous estimates\, such stars shrink\, rather than expan
 d. We show analytically\, that this discrepancy stems from the structure o
 f a two solar mass star as a dense core containing most of the mass surrou
 nded by a low density envelope which occupies most of the volume with negl
 igible mass. We discuss the evolution of the resulting GW signal.\n\nhttps
 ://indico.gsi.de/event/24822/\n\nZoom: https://gsi-fair.zoom.us/j/92473872
 583
LOCATION:KBW 2.27 (GSI)
URL:https://indico.gsi.de/event/24822/
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