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SUMMARY:Distinct Rotational Evolution of Giant Planets and Brown Dwarf Com
 panions
DTSTART:20260504T124500Z
DTEND:20260504T130000Z
DTSTAMP:20260509T024800Z
UID:indico-event-1814@indico.dfa.unipd.it
DESCRIPTION:Speakers: Ilaria Giovannini (INAF - Università degli Studi di
  Padova)\n\nWe present a rotational velocity ( vsini ) survey of 32 stel
 lar/substellar objects and giant planets using Keck/KPIC high-resolution s
 pectroscopy\, including 6 giant planets (2─7 MJup) and 25 substellar/ste
 llar companions (12─88 MJup). Adding companions with spin measurements f
 rom the literature\, we construct a curated spin sample for 43 benchmark s
 tellar/substellar companions and giant planets and 54 free-floating brown 
 dwarfs and planetary mass objects. We compare their spins\, parameterized 
 as fractional breakup velocities at 10 Myr\, assuming constant angular mom
 entum evolution. We find the first clear evidence that giant planets exhib
 it distinct spins versus low-mass brown dwarf companions (10─40 MJup) at
  4─4.5σ significance assuming inclinations aligned with their orbits\, 
 while under randomly oriented inclinations the significance is at 1.6─2.
 1σ. Our findings hold when considering various assumptions about planets\
 , and the mass ratio below 0.8% gives a clean cut for rotation between gia
 nt planets and brown dwarf companions. The higher fractional breakup veloc
 ities of planets can be interpreted as less angular momentum loss through 
 circumplanetary disk braking during the planet formation phase. Brown dwar
 f companions exhibit evidence of slower rotation compared to isolated brow
 n dwarfs\, while planets and planetary mass objects show similar spins. Fi
 nally\, our analysis of specific angular momentum versus age of 221 stella
 r/substellar objects below 0.1 M⊙ with spin measurements in the literat
 ure indicates that the substellar objects of 5─40 MJup retain much high
 er angular momenta compared to stellar and substellar objects of 40─100 
 MJup after 10 Myr\, when their initial angular momenta were set.\n\n\nhttp
 s://indico.dfa.unipd.it/event/1814/
LOCATION:Aula Rosino (Dipartimento di Fisica e Astronomia - Edificio ex-Ri
 zzato)
URL:https://indico.dfa.unipd.it/event/1814/
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