Protostars, nebulas and Brown dwarfs. make-rocky-planets-too-video.html
Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs
description
Transcript of Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs
![Page 1: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/1.jpg)
Prof. Hayashi’s Workon the Pre-Main-Sequence Evolution
and Brown Dwarfs
Takenori NAKANO(Kyoto)
First Star IV May 21, 2012, Kyoto
![Page 2: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/2.jpg)
Prof. Hayashi in early 1961
![Page 3: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/3.jpg)
Hayashi 1961 Publ. Astr. Soc. Japan 13, 450
![Page 4: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/4.jpg)
Hayashi & Nakano 1963 Prog. Theor. Phys. 30, 460
![Page 5: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/5.jpg)
Sandage 1957
HR diagram of star clusters no stars at Teff < several x 103 K (yellowed)
Reason for this unknown in 1950s e.g., Sandage & Schw. 1952
Regarded as peculiar to advanced stage not applicable to pre-main sequence stage e.g., Henyey et al. 1955 Brownlee & Cox 1961
Discovery of the Hayashi Phase
![Page 6: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/6.jpg)
Boundary Conditions at Stellar SurfaceH-ionization zone inside the photosphere in cool stars makes the atmosphere convectively unstable suppresses the decrease of Teff
Hayashi & Hoshi 1961 structure of the atmosphere with H-ioniz. zone ⇒ boundary condition for the internal structure
Previous work neglected the convection induced by H-ioniz. zone
![Page 7: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/7.jpg)
Energy Transport in the star by radiation and convectionConvection occurs where ds/dr < 0 effectively, specific entropy s = const
: radiative zone
: convection zone
Temperature gradient
Convection occurs only whenusuallyfully ioniz. gas with negl. rad. press.H-ionization zone
Convection easily occursdecrease of log T << decrease of log P, log
![Page 8: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/8.jpg)
Hayashi & Hoshi 1961determined by numerical calculation the critical effective temperature Teff (cr) (M★, R★)
Teff = Teff (cr) : Emden solution for a polytrope of N = 1.5 ⇒ fully convective starTeff > Teff (cr) : centrally condensed type sol. for N = 1.5 ρ = ∞, Mr > 0 at r = 0 can be fitted at r > 0 with a regular sol. with N > 1.5 star with convective envelope and radiative coreTeff < Teff (cr) : collapsed type sol.(N=1.5) Mr = 0 at r > 0 can be fitted at Mr > 0 only with a regular core sol. with N < 1.5 Such cores are convectively unstable, N → 1.5 Stars cannot be in hydrostatic equil. with such Teff
polytrope
![Page 9: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/9.jpg)
Hayashi & Hoshi 1961 Publ. Astr. Soc. Japan 13, 442
For each stellar mass the lowest curve is close to Teff
(cr)Comparison with open clusters
![Page 10: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/10.jpg)
Hayashi 1961 Publ. Astr. Soc. Japan 13, 450
Teff (cr) should be applied to any stage of stellar evolution pre-main sequence stage is not an exception
APB : Teff = Teff (cr)
Hayashi lineCPD : Henyey trackAP : Hayashi track Hayashi phaseright side of APB : Hayashi’s forbidden region
on Hayashi track: more luminous, contract faster
![Page 11: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/11.jpg)
Faulkner, Griffiths & Hoyle 1963 MNRAS 126, 1
Mechanisms which can reduce Teff (cr) greatly ?
![Page 12: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/12.jpg)
Pre-main sequence evolution of low-mass starsHayashi & Nakano 1963
As M★ decreases, Teff(cr) decreases.
H2 molecules form in the atmosphere H2-dissociation zone inside the photosphere
makes the atmosphere convectively unstablesuppresses the decrease of Teff
same as H-ioniz. zone
H2-dissociation has great effect a : Hayashi line c : Hayashi line without H2
M★ = 0.2 M☉
![Page 13: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/13.jpg)
Evolutionary paths on the HR diagram
brown dwarfs
For smaller M ★ , longer Hayashi phase shorter Henyey phase
M★ < 0.26 M☉ , no Henyey phasedot : ZAMS
-
![Page 14: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/14.jpg)
ZAMS (zero-age main sequence) the stage at which L★ = LH holds for the first time in the pre-main sequence contraction phase LH : energy released by H-burning per unit time determined by the structure of the central region L★ : energy emitted from the stellar surface per unit time in general, determined by the whole structure of ★ for a fully convective star, determined by the Hayashi line and R★
To determine ZAMS for a given M★, we need both LH and L★ as functions of R★
![Page 15: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/15.jpg)
Determination of ZAMS and bottom of main sequence
Stars of very small mass Electrons degenerate as the star contracts.
Stars of not very small mass
SSK
![Page 16: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/16.jpg)
Evolution of a 0.07 M☉ star
Maximum value of LH / L★ = 0.23 at log R★ / R☉ = -1.09 cannot settle down on the main sequenceLower mass limit to the main sequence ours : between 0.08 and 0.07 M ☉ the newest result (Burrows et al. 1997 ) : between 0.08 and 0.075 M☉
Evolution of brown dwarfs as an example, M★ = 0.05 M☉ (Fig. 2 of HN 1963)
⇐
⇓
![Page 17: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/17.jpg)
Siv S. Kumar 1963, two short papers in Ap.J.
1. “Determined” the lower mass limits to main sequence 0.07 M☉ for Pop. I, 0.09 M☉ for Pop. II “assuming reasonable luminosities for these stars (see the following paper)” detZAMS
2. Simple discussion on the evolution of brown dwarfs time required to contract to some R★ assuming Teff = constant
e.g., Ann. Rev. Astr. Astrophys. Vol.38 (2000) two review articles on brown dwarfs
Kumar 1963a
High reputation for Kumar’s papersdegeneracy ?
![Page 18: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/18.jpg)
IAU Symposium No. 211 “Brown Dwarfs”
Invited talk on history of research on brown dwarfs2002 Hawaii
Chairman of SOC allowed a Japanese participant to give a short talk to introduce HN1963 just before the Summary Talk
A chance was given to me to write a short note on HN1963 in the Proceedings (2003)
![Page 19: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/19.jpg)
Conference Summary by R. F. Jameson
![Page 20: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/20.jpg)
Prof. Hayashi in 2008
![Page 21: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/21.jpg)
After hydrogen is exhausted in the core, Teff continues to decrease.
Discov HP
Sandage & Schwarzschild 1952
![Page 22: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/22.jpg)
Pre-main-sequence evolution on the HR diagram
Discov HP
Brow Cox
Henyey, LeLevier, & Levee 1955
![Page 23: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/23.jpg)
Discov HPBrownlee & Cox 1961
![Page 24: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/24.jpg)
Polytropic stars
Equation of state (polytropic)Change variables
: Lane-Emden eq.
For a given increase of pressure, Δ log P, density increase Δ log ρ is larger for larger N
HH 1961
![Page 25: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/25.jpg)
Fully convective stars (N = 1.5)
Center
sc = sc ( ρc , Tc ) : fn of M★ and R★ Photosphere M★, R★, Teff → ρph sph ( Teff , ρph ) : fn of M★, R★ and Teff increasing fn of Teff for given M★ and R★
For larger s ( higher Teff ), lower ρ for given P ⇒ slower inward decrease of Mr ⇒ finite Mr remains at r = 0 (centrally condensed type)
![Page 26: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/26.jpg)
Kumar 1963a, Ap.J. 137, 1121
Kumar
![Page 27: Prof. Hayashi’s Work on the Pre-Main-Sequence Evolution and Brown Dwarfs](https://reader036.fdocuments.net/reader036/viewer/2022062323/568162b5550346895dd33e62/html5/thumbnails/27.jpg)
Annular Sun cover page