Date & Time: 2024/November/15 17:00-18:00, Venue: Zoom TV Conference System. This is an informal seminar on the formation of stars and planets. We welcome anyone interested in the subject.
Abstract:
The dispersal of protoplanetary disks is a crucial factor that constrains planet formation timescales and planetary system architectures, making disk dispersal a central question in planet formation theory. Traditionally, disk lifetimes were estimated to be a few million years, with a mild dependence on the host star’s mass. However, as observational sensitivity and sample sizes increase, this classical view is being re-evaluated. Recent observations suggest a median disk dispersal time of up to 10 Myr for low-mass stars, with significant variability, and dispersal timescales for M-dwarfs and intermediate-mass stars remain uncertain. Addressing these variations requires robust disk-dispersal models, an effort ongoing for over three decades, which has clarified the dominant mechanisms at various stages of disk evolution. Among these, photoevaporation is understood to drive mass loss during the late disk stages, significantly impacting overall disk lifetimes.
Despite extensive numerical modeling, predicted photoevaporative mass-loss rates have varied by orders of magnitude, highlighting a need for improved modeling frameworks. Most studies have focused on solar-type stars, leaving photoevaporation rates in M-dwarfs and intermediate-mass stars largely uncharted. To address this, we developed a generalized analytic model for disk photoevaporation. This model refines estimates of ionization, temperature, and wind velocity profiles as a function of distance from the central star, predicting distinct thermochemical states depending on the luminosity and spectral hardness. For T Tauri stars with moderate extreme-ultraviolet (EUV) luminosities (~10^30 erg s^-1), nonisothermal, ionized disk winds develop, with temperatures lower than classical estimates under soft spectra (average deposited energy < 3.7 eV). Harder spectra yield atomic, isothermal winds at most disk radii, while lower EUV intensities allow atomic winds to emerge at larger disk radii (>10 au) through advection. These predictions align well with radiation hydrodynamics calculations and help resolve the significant discrepancies in mass-loss rates reported in previous literature. This talk will cover these recent findings, along with the latest updates on disk photoevaporation models since the PPVII review.
他、会議報告、速報など、飛び入りも歓迎します。今回もしくは次回以降、話題提供できる方は世話人までメールしていただけましたら幸いです。
Participants: 55, Affiliations: 19
Participants list:
ABC: PD Toshiyuki Mizuki
Hosei: P Tomoaki Matsumoto
Ibaraki: P Toru Turibe
JAMSTEC: Sota Arakawa
Kagoshima: AP Yusuke Tsukamoto, D2 Miyu Kido
Kindai: Masayoshi Kiguchi
Kobe: DA Kenji Kurosaki
Kogakuin: AP Muto
Kurume: L Masanobu Kunitomo
Kyoto: A Yuri Fujii, M2 Wataru Ooyama
Kyushu: P Masahiro Machida, D1 Ayumu Shoshi
Milan: Ryohei Nakatani
Nagoya: P Shu-ichiro Inutsuka, AP Hiroshi Kobayashi, D3 Kanta Kitajima, D2 Tomotaka Nishikawa, D1 Riona Yamada, D1 Izumi Seno, M2 Wataru Takahashi, M2 Kenshin Onogawa, M1 Kota Kobayashi, M1 Yuji Miko, M1 Shusuke Utsumi, B4 Yuki Tamaki
NAOJ: P Eiichiro Kokubo, PD Yuji Matsumoto, PD Yoshiaki Misugi, PD Ayaka Okuya, D1 Gabriel Guimaraes, M1 Naoya Kitade
Osaka: A Shinsuke Takasao
Science Tokyo: P Satoshi Okuzumi, PD Ryosuke Tominaga, D3 Kanon Nakazawa, D3 Yuya Fukuhara, D1 Ryota Yamamuro, D1 Shintaro Taira, M2 Ryo Kato
Shiga medical Univ.: AP Kazutaka Motoyama
Tohoku: PD Daisei Abe, D1 Erika Nishio, M1 Haruki Nabeta
UTokyo: P Takeru Suzuki, P Yuri Aikawa, A Ryo Tazaki, A Shota Notsu, PD Naoto Harada, PD Kensuke Kakiuchi, D3 Ayano Komaki, D1 Yuto Komichi, M1 Yufan Sheng, B4 Taichi Kuriyama
次回：2024/Dec./16 17:00-
連絡世話人：冨永遼佑（東京科学大学） tominaga.r.aa[at]m.titech.ac.jp