The Excitement of Variable Star Observing

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The Excitement of Variable Star Observing

• Arne Henden
• Director, AAVSO
• arne_at_aavso.org

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American Association of Variable Star Observers

• Founded in 1911
• 3000 total observers in 60 countries
• 900,000 observations received yearly
• 13 million total, on-line, observations
• We provide tutorials, mentoring, workshops,
  connection with professionals, campaigns, etc.
• Website http//www.aavso.org

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AAVSO Headquarters are in Cambridge, MA
USA (about 2km from Harvard College Observatory)
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Typical Visual Observer Albert Jones, NZ 32cm
reflector he built in 1948 He has 500,000
lifetime observations
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Non-typical Observer E.O. Smiths private
Calypso Observatory, a 1.2m scope at Kitt Peak.
He does high-resolution Stellar imaging
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You dont always need fancy personal
equipment Esteve Duran Observatory, a public
observatory In Spain. 60cm telescope and CCD,
studying variable stars
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Not all professional telescopes are huge the
Stare telescope on Tenerife a 12cm aperture with
CCD for exoplanet studies
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The XO Project 2x10cm telephoto Lenses with
CCD At Maui, Hawaii. Exoplanet studies
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The line between amateurs and professionals is
blurring due to high-quality commercial telescopes
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and because of high-quality, inexpensive
commercial cameras
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Variable Stars

• Stars that change in brightness
• Sometimes cyclical sometimes chaotic, sometimes
  just an outburst (or even an explosion,
  destroying the star!)
• About two percent of all stars show some change
  in brightness, including our Sun

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RR Lyr variables in M3 Stanek/CfA
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How Amateurs are contributing to Variable-Star
Studies

• Obtaining light curves and analyzing eclipsing
  binaries
• Observing cataclysmic variables
• Long-term monitoring of Mira variables
• Finding unusual objects - gamma-ray bursts,
  microlensing stars, exoplanets

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Eclipsing Binaries

• - Thousands known
• Light curves give us information about stars
  (mass, size, temperature)
• usually short period, easy to follow

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Observations of HD126080 with 6cm telescope and
CCD Gomez-Forrellad Garcia-Melendo 1997
3 year period eclipse was a month long Terrell
et al. 2003
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Cataclysmic Binaries

• Hundreds known
• Usually faint, go into several-magnitude outburst
  on infrequent basis (weeks/years)
• Interacting binaries - one star is accreting
  matter from the other
• Excellent targets for long-term monitoring and
  short-term campaigns

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SS Cyg, a typical cataclysmic variable light
curve from 1896 to 2004
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Helping astronomers trigger satellite observations
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Pulsating Variables

• Usually periodic, from hours (RR Lyr) to years
  (Miras)
• Amplitude of pulsation from millimag (delta
  Scuti) to many magnitudes (Miras)
• Great long-term monitoring projects to watch for
  evolutionary evidence

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Mira Variables
R And, P 409.33 d
Long-period variables can be some of the
prettiest stars to observe
Typical AAVSO finding chart
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You can observe single pulsation cycles
V Hya
or follow decades-long trends
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Obtaining light curves of microlensing candidates
Credit J. Skowron
Planet Mass 13 ME
Note amateurs discovered closest microlensed
star (Casseopeia) November 2006 8th magnitude at
peak
Credit NASA
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Gamma-ray bursts occur when a massive star
explodes. Detected with satellites, which then
alert ground-based telescopes
Two views of a GRB explosion, from NASA
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Light curve for a bright GRB afterglow, observed
by amateurs
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Transit of mercury - like an exoplanet transit,
it blocks part of the light from our Sun during
its passage across the disk of the Sun
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Two exoplanet transits (much bigger than Jupiter)
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For More Information

• http//www.aavso.org (we have Spanish
  translations of our Visual Observing Manual,
  brochure, press releases)
• http//cba.phys.columbia.edu for CVs
• http//www.socastrosci.org for CCDs