Rotation in massive stars:
Progenitors, Core Collapse, and Remnants.

Abstract

This collaborative document has been created for the panel discussion on “Rotation in massive stars” (FOE 2015), held on Thursday 6/4/2015 in Raileigh. All conference participants have been added to the document and can edit / comment / add figures (just drag&drop) / references and even LaTeX equations if needed (check the help page for more info on how to edit the document). Hopefully this will capture the essential ideas and interactions that will stem during and after the discussion. The document can be forked at any time, so that particular discussions can be taken further and potentially lead to active collaborations.

Main Topics


What determines the rotation rates of progenitor stars

  • Single star evolution (hydrodynamic instabilities/circulations, magnetic torques, internal gravity waves, mass loss, etc.)

  • Binary star evolution (mass accretion, tides, mergers, etc.)

How does rotation affect core collapse and the eventual SN/GRB explosion?

  • Typical core-collapse SNe

  • Central engines (GRBs, SLSNe)

How can rotation be inferred from (compact) remnants?

  • White Dwarfs

  • Pulsars

  • X-ray binaries

  • Black Holes

  • SNR

Questions: Stellar Evolution

How reliable are current predictions for the rotational profiles of core collapse progenitors?

a. Within a factor of 2 : 3.03%
b. Within a factor of 10: 50%
c. Within a factor of 100: 27.27%
d. Not at all reliable: 19.70 %
Discussion: Almost half of the audience thinks that stellar evolution models are at least 2 orders of magnitude off when it comes to predictions of final angular momentum content.

66 responses: A: 3.03; B: 50.0; C: 27.27; D: 19.7

Jim Fuller: “Rotation before core collapse”

Is binary interaction the most common reason for very rapid pre-collapse rotation?

a. Yes
b. No
Discussion:

63 Responses: Yes: 84.13 No: 15.87

N.B. May only be for very rare cases!

Is rotation important for enhancing mass loss shortly before core collapse?

a. Yes
b. No
Discussion:

What is the role of large scale magnetic fields for angular momentum transport?

a. They have a negligible effect
b. They enforce rigid rotation
c. They are important only for some progenitors
d. We will never know
Discussion:

Questions: Core Collapse

For which of the following types of supernovae is rotation most important?

a. Type IIp
b. Type Ib/c
c. Type IIn
d. Electron capture SNe
e. None of the above
Discussion: 57 responses: A: 5.26; B: 78.95; C: 0; D: 1.75 (B. Metzger; Crab); E: 14.04

Kei Kotake: “Rotation during core collapse”

Rotation is important during core-collapse because it affects:

a. Convection
b. SASI
c. Others
d. Rotation is not very important during CC
Discussion:

In order for rotation to dramatically effect evolution during the core-collapse phase, NSs would start spinning very fast, which they seem not to.

55 responses: A: 33.33; B: 22.81; C: 33.33; D: 10.53

Replace this text with your caption

Is the rotational axis direction preserved throughout the core-collapse phase?

a. Yes
b. No
c. not certain
Discussion:

55 responses: A: 34.55; B: 27.27; C: 38.18

Very much depends on the amount of initial rotation, if little then likely that instabilities will reset rotation axis. Question is, what level of initial rotation would this transition be at?

Non-rotating cores in CCSNe simulations give  100ms from stochastic variations (http://adsabs.harvard.edu/abs/2013A%26A...552A.126W)

Which central engine model can explain the origin of hypernovae?

a. Collapsar
b. Magnetar
c. Both
d. None of them
Discussion:

52 responses: A: 30.77; B: 17.31; C: 38.46; D: 13.46

How long will it take to make collapsar simulations doable from first principles ?

a. 10 years
b. 20 years
c. 30 years
d. More than 30 years
Discussion:

52 responses: A: 30.77; B: 17.31; C: 38.46; D: 13.46

Questions: Remnants

Tassos Fragkos: “Rotation after core collapse”

Pulsar birth spin periods http://adsabs.harvard.edu/abs/2006MNRAS.372..777L

Black holes formed through fall-back mechanism versus direct-collapse are expected to differ on:

a. Mass
b. Spin
c. Kick
d. All three
e. Other
Discussion:

There are really (at least) three mechanisms.
direct-collapse: core collapses and BH forms before nuclear densities (i.e. failed PISNe).
failed CCSN: core collapses and protoneutron star forms for some period (occurs for any inert iron core collapse), then PNS gravitationally collapse to a BH.
fallback: material falls back after successful explosion, PNS/NS collapses to BH.
62 responses: A: 9.68; B: 6.45; C: 6.45; D: 75.81; E: 1.61

Which compact objects provide the most robust constraints for rotation rates at core collapse?

a. White dwarfs
b. Neutron stars
c. Black holes
d. Other
Discussion:

Voted: 52 a: 23.08%; b: 59.62%; c: 13.46%; d: 3.85%

Pulsar birth spin periods http://adsabs.harvard.edu/abs/2006MNRAS.372..777L

Is there a correlation between the angular momentum content/profile of the pre-core-collapse star and the SN kick that the NS/BH will receive?

a. Yes
b. No
Discussion:

What sets the rotation rate of young neutron stars and black holes?

a. Pre-collapse rotation rate
b. Supernova dynamics (e.g., SASI, kicks, turbulence, fallback, etc.)
c. R-mode instability
d. Other
Discussion:

What future measurements can be used to most strongly constrain the role of rotation in supernovae?

a. Supernovae
b. Compact object rotation rates
c. Gravitational waves
d. Neutrinos
Discussion: