Miras

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Miras Janet

• Prepared for the meeting in remembrance of Janet
  A. Mattei
• Held in Waltham, MA on October 29, 2004

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Where were headed

• 471 papers (at least one, however, written by
  Jean-Luc Mattéi)
• Of these, approximately 70 had to do with Miras,
  semi-regular (SR) red variables, or Symbiotic
  Systems (with or without Mira components)

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Miras by decade - context

• 1903-13 Establishment of AAVSO
• 1913-53 Hot Topic

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Miras by decade - context

• 1903-13 Establishment of AAVSO
• 1913-53 Hot Topic
• 1953-73 A few observers and almost no theory
• 1973-83 Shocks evolutionary status internal
  models( IUE CO radio lines. (Wood, Hill,
  Hinkle, Ostlie,..)
• 1983-93 IRAS, Hipparcos
• 1993-2003 HST, 2-MASS, Macho, Ogle,

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Miras - Janet, by decade

• 1973-1983
• 1978 eclipse of R Aqr (Garnavich, Willson)
• Small amplitude red variables (Percy)
• 1983-93
• Hipparcos (Foster, Mennessier)
• Chaos studies (Cannizzo, Cadmus, ..)
• 1993-2003
• Symbiotics, Miras, HST (Karovska, ..)
• Multi-P and changing P (Hawkins, Hazen,
  Templeton)

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About R Aqr
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A BIG change in the flux we see
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A picture? of the system
X? a mira
Orbit (here seen nearly edge-on) may be eccentric
Eclipsing body needs to be at least as large as
the mira, and almost completely opaque
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R Aquarii - surrounding gas
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Fundamental problems in Mirology

• How big what pulsation mode?
• Until 2004, angular diameters gt from gt1 to gt2
  AU gt F or 1O or both???
• Shock amplitudes of 25-35 km/s gt high escape
  velocity gt small gt F mode
• Evolutionary status and significance?
• 1977 Wood/Cahn Tip of the AGB
• 1991 Bowen/Willson They are the stars that mark
  the onset of the Superwind.

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The Evolutionary Context - 1977
Wood, Cahn from N(P) and evolutionary models
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The evolutionary context - 2004
This is a lemming diagram
Bowen and Willson 1991
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Figure from Wood 2000 based on MACHO data
Miras
Log(P in days)
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Small(er) Amplitude Red Variables
Not a very satisfactory classification scheme!

• Miras Very cool giants, emission lines,
  visual amplitude gt2.5 mag, relatively regular
  variation
• SR classes
• SRa Smaller amplitude than Miras
• SRb Less regular than Miras
• SRc Supergiants, not just giants (higher mass
  and/or luminosity)
• SRd Warmer than Miras

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Miras - large amplitudeand regular!
Omicron Ceti Mira, long term AAVSO light curve
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SR Variable Betelgeuse
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How good are visual observations of SR stars?
Support for the Hipparcos mission included
predicting brightness for these stars
Grant Foster JAM demonstrated that the AAVSO
light curves contained the essential information
to recover the light curve and make predictions
even where the amplitude is small and the
variation less regular
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From a Sky and Telescope article on Amateurs and
Hipparcos
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M, S, or C from the light curve?
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M, S, or C from the light curve?
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M, S, or C from the light curve?
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Towards an understanding of less regular variables

• Collaboration with Cannizzo, Cadmus,
• Mode switching and other signatures of
  (mathematical) Chaos
• Collaboration with Mennessier, Classification
  of SR variables revisited using statistical
  methods

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Mode switching?
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Mode switching?
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Search for Chaos in 3 Miras
And the answer is No, for R Leo, Mira and V Boo
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Back to Symbiotic Systems

• (At least) Two types
• Dusty, with Miras, wide separation
• S, with non-Miras, often eclipsing (gt close,
  with notable exception)
• Three examples
• R Aqr (already discussed)
• CH Cygni
• o Ceti

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CH Cygni
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o Ceti (Mira) - an almost-symbiotic system
from Karovska et al.
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Long-term light curve R Aql
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Trend T Umi (Templeton 2003)
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Anomalies What causes P to vary?
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Miras are the key to learning the ultimate fate
of the Earth

• Mass loss determines how bright the Sun will get
  gt how hot Earth will be
• Mira radii tell us how big the Sun will become gt
  whether Earth ends up inside
• Pre-Mira mass loss determines whether Earth gets
  away or not

But thats another lecture altogether, not today!
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The End