Workshop at STScI, 2011 June 28-30
“Intermediate-Luminosity Red Transients”
K. Davidson
Workshop at STScI, 2011 June 28-30
“Intermediate-Luminosity Red Transients”
K. Davidson
Diverse aspects of the
Physics of Eruptions,
especially those propelled by Eddington.
or,
F
Excerpts from The Missing Manual.
E
Part the first: Radiation temperature.
What does an eruption look like when
it is visually most spectacular ?
How big and how hot is the UV-to-far-red
photosphere ?
Question:
Suppose that a stellar wind or eruptive outflow is
dense enough to be opaque. Then, WHAT IS THE
RELATION BETWEEN APPARENT RADIATIVE
TEMPERATURE AND MASS-LOSS RATE ?
Caveat
Tc = APPARENT temperature or
CHARACTERISTIC temperature.
EFFECTIVE temperature is ill-defined!
A LATE-NEOLITHIC CALCULATION …
Fair approximation:
1. Solve spherical scattering problem with F ~ 1/r2,
opacity = scattering + absorption, mostly scattering.
2. Assume T(r) = radiation-density temperature.
3. Temperature of escaping radiation
= approximately T(thermalization depth).
Of course varying degrees of better approximation
can be arranged.
( Another story: The elusive
“Modified Eddington Limit” )
-- FROM THE 1987 PAPER -LIKE THE PREVIOUS FIGURE, AXES INTERCHANGED
Note: No need for spherical symmetry, steady flow, etc.
Can be an outburst, a bipolar thing, etc.
7000 K* IS A SPECIAL TEMPERATURE
IN THE H-R DIAGRAM.
* (Really meaning 6000—8000 K.)
7000 K IS A SPECIAL TEMPERATURE
IN THE H-R DIAGRAM.
NATURAL LIMIT FOR MASSIVE OUTFLOWS:
-- SNae; LBV’s; Novae; Eta Car; Impostors; … ? --
7000 K IS A SPECIAL TEMPERATURE
IN THE H-R DIAGRAM.
NATURAL LIMIT FOR MASSIVE OUTFLOWS:
-- SNae; LBV’s; Novae; Eta Car; Impostors; … ? -Analogous to the Hayashi Limit at 3000 K …
7000 K IS A SPECIAL TEMPERATURE
IN THE H-R DIAGRAM.
NATURAL LIMIT FOR MASSIVE OUTFLOWS:
-- SNae; LBV’s; Novae; Eta Car; Impostors; … ? -Analogous to the Hayashi Limit at 3000 K …
Moreover, B.C. Is close to zero at 5500--7500 K;
allowing visually bright stars.
( memo ) Shaviv plural & novae,
same problem.
SUPER – EDDINGTON FLOWS (CONTINUUM DRIVEN WIND)
Observed characteristics of Eta Car 1836—1858 event:
-----
L roughly 2—5 times Eddington for 5—20 years
Ejected mass 10—20 Msun
Radiated energy
Kinetic energy
Observed characteristics of Eta Car 1836—1858 event:
-----
L roughly 2—5 times Eddington for 5—20 years
Ejected mass 10—20 Msun
Radiated energy
Kinetic energy
Set up normal equations, try to make it work.
Observed characteristics of Eta Car 1836—1858 event:
-----
L roughly 2—5 times Eddington for 5—20 years
Ejected mass 10—20 Msun
Radiated energy
Kinetic energy
Set up normal equations, try to make it work.
Doesn’t work; ejects too much mass, too fast .
Quoting Shaviv...
Quoting Shaviv...
Typo above! Read “sonic radius”, not “shock”
“POROSITY”
(N. Shaviv)
Quoting Shaviv...
Result:
Can simulate Eta Car Great Eruption, Novae.
More or less.
Tired old joke:
Theorist, “assume a spherical cow...”
Tired old joke:
Theorist, “assume a spherical cow...”
21st century version:
Theorist, “assume a homogeneous cow...”
- Granulation with
various size scales –
Equatorial Skirt
Which
are the TRANSFER
dense places –
RADIATIVE
Bright
or dark?
PROBLEM
SN 2010da: X-rays and He II 4687 ??
-- 30 --
He II 4687
ETA CAR
“EVENT”
2009
2-10 keV
X-rays
He II
4687
Refs. for physics of He II 4687, soft X-rays,
and shock breakup:
J. Martin et al, ApJ 640, 474 (2006)
Soker & Behar, ApJ 652, 1563 (2006)
A. Mehner et al, new astro-ph