1 Title: Bright Be Stars

1
1 TitleBright Be Stars

• Dietrich Baade
• European Organisation for Astronomical Research
  in the Southern Hemisphere

Gerardo Avila (ESO), Maurizio Baffico (PUC),
Vadim Burwitz(MPE), Carlos Guirao (ESO),
Sebastian Otero (ACS), Stanislav tefl (ESO),
Thomas Rivinius (ESO), Jesus Rodriguez (ESO),
Leonardo Vanzi (PUC), and others
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2 Mottos

• Groundbased To be or not to be (Hamlet)
• Spaceborne To Be or not to Be (Several)

3 Examples

• Not to Be
• To be! (and perhaps even to Be)
• To be and to Be

(All found on the Web and none nearly as serious
as not to be!)
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1st example
(16. June, 2008)
30 Jahre Cordoba sind genug
Cordoba
Burschen, heute könnt ihr Geschichte schreiben!
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2nd example
Yesterday taking effect TODAY!
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3rd example
From the BRITE Constellation Web page
Be
Lets be and Be!
Institute of Communication Networks and Satellite
Communications (Graz) The (BRITE) project is
an offensive programme
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Be stars (a reminder for Be-ginners)

• Emission lines of (classical) Be stars form in
  rapidly rotating circumstellar disks
• Disk built by mass loss (events) from central
  B-type star
• Be stars rotate at gt 90-95 of critical velocity
  (but lt 100)
• Around B2, 15 of all Galactic B stars are Be
  stars (in some clusters total
  fraction 50)
• 1 in 2 broad-lined B stars is a Be star
• Be stars can lose their disk Be ? B ? Be (t
  10 yrs)
• Evolutionary branch or phase of rapidly rotating
  B stars? (Some Be stars were spun up by mass
  transfer in a binary.)

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Absorption line profile variability in Be Stars

• First discovery 30 years ago
• Numerous publications by a variety of observers
• Single-largest database to date in Rivinius et
  al. (2003)
• 27 bright Be stars
• 8 years of spectroscopic monitoring
• 2300 spectra with HEROS and ESO 50-cm Telescope
• 700 spectra with FEROS and ESO 1.5-m Telescope
• From atmospheric cut-off to near-IR
• Resolving power 20,000
• 100 S/N 300

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? CMa
Be stars with low v sin i
Rivinius, Baade, tefl (2003), AA, 411,229
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Be stars with intermediate v sin i
Rivinius, Baade, tefl (2003), AA, 411,229
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Be stars with intermediate to high v sin i
Rivinius, Baade, tefl (2003), AA, 411,229
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Be stars with high v sin i
Rivinius, Baade, tefl (2003), AA, 411,229
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intermediate to high v sin i
low v sin i
intermediate v sin i
high v sin i
One NRP model (l m 2
fitted to ? CMa only) matches 24 out of 27
bright Be stars Only adaptation viewing angle i
(In the other 3 stars, the dominating mode is
probably different)

Rivinius, Baade, tefl (2003), AA, 411,229
? CMa
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• The canonical picture of pulsating Be stars
• Differences in i more relevant than the ones in v
  (had already been inferred
  from circumstellar emission lines)
• Nonradial pulsation (NRP)
• One dominating NRP mode mostly (90) l m 2
• Period 1 day ( Prot)
• g modes?
• Most homogeneous class of early-type (bright)
  pulsating stars
• Additional modes may be present
• In-phase superposition of modes with same l,m may
  trigger mass loss events (replenishment of disk)
• Theory challenge NRP from solar through SMC
  metallicities
• Do Be stars later than B5 pulsate as well?

(Rivinius, Baade, tefl 2003, AA, 411,229)
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Be
?
?
?
?
?
?
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Seismology drivers to Be

• Extreme rotation
• Mode selection (homogeneity)
• (Bi-directional?) interaction between mass loss
  events and pulsation
• Be stars (fast rotation low-order NRP mass
  loss) vs.
• Bn stars (fast rotation high-order NRP)
• g modes vs. p modes
• Limiting Teff values (boundaries of instability
  strip)
• Evolutionary status. Phase or branch?
• Descendents of Be stars
• Broad range in metallicity

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Potential BRITE drivers to Be

• NRP amplitudes not exceeding very few 0.01 mag
• Multi-mode
• Periods near 1 day
• Multiple periods closely spaced (Pbeat weeks to
  months)
• Superimposed irregularities due to mass loss
  events
• About 20 Be stars brighter than mV 4
• Similarities among Be stars may permit first
  meaningful generalizations from as few as 1-2
  stars
• Companion long-term spectroscopic monitoring
  project PUCHEROS

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PUCHEROS

• Decommissioning of ESO 50-cm telescope has
  orphaned HEROS
• Telescope later donated to Santa Martina
  Observatory of Pontificia Universidad Catolica
  (PUC), Santiago
• Joint effort of PUC and ESO staff to build
  fiber-fed spectrograph (PUCHEROS - or is it
  PUC-HEROS?)
• S/N200 _at_ (R20,000, t1200s, V4m)
• Innovative image slicer
• Beginning of operations 2010
• Objectives to Be
• Pulsations
• Mass loss, disk formation (w/ VLTI)
• Photometric support limited to naked-eye
  observations (Sebastian Otero _at_ Buenos Aires
  0.03 mag!)
• High complementarity of BRITE and PUCHEROS
• Conceivably, PUCHEROS can also observe other
  BRITE targets