Variable Star Observations: Past, Present and Future

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Variable Star Observations Past, Present and
Future

• 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
• One million observations received yearly
• 15 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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Mission of AAVSO

• Observe and analyze variable stars
• Collect and archive observations for worldwide
  access
• Forge strong Pro-am ties and mentoring
• Promote international collaborations
• Perform educational outreach to the general
  public about variable stars

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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 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 easily
  discernable 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 and pulsating stars
• Observing cataclysmic variables in quiescence and
  outburst
• Long-term monitoring of Mira variables
• Finding unusual objects - gamma-ray bursts,
  microlensing stars, exoplanets
• datamining

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How YOU can contribute

• Studying variable stars is one of the few places
  where amateurs can contribute valuable data
• Visual, PEP, CCD - any observational method works
• Main requirement is to make the observations in a
  scientific manner (training and proper tools)
• You can participate at any level - data
  collection, analysis, research support

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Visual Observing

• Naked eye, binoculars, telescope
• Estimate brightness with respect to other stars
  in field
• AAVSO provides charts and photometric sequences
  (stars over wide range in magnitude)
• Find stars brighter than and fainter than
  variable, interpolate

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Value and Limitations

• Easy to do, cheap, little skill involved
• Typical errors with experience are about 0.2mags.
  Some observers can do 0.1mag or better. Since
  errors random, win when many observers contribute
• Mistakes (wrong identification) difficult to
  trace. Discoveries require confirmation.
• Good for detecting outbursts (CVs) and for stars
  with wide magnitude range (Miras/LPVs)
• Accepted method for long-term monitoring of stars

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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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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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Projects

• Adopt one of the 380 Miras that have long term
  light curves, and continue the tradition into the
  future
• Participate in one of the AAVSO campaigns on CVs,
  watching for outbursts (upcoming HST obs of SDSS
  CVs)

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Project V5558 Sgr
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PEP Observations

• Simple, inexpensive method of precision
  photometry
• Looks at one star at a time
• Requires photometric skies
• Cant go as faint as CCD observing
• Little computer expertise necessary

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SSP-3
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Projects

• Participate in the P Cygni campaign, watching for
  flickering that matches spectroscopic variations
  outbursts
• Participate in the TU Cas campaign
• Next Fall eclipsing systems in Orion zet Aur

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DSLR cameras - 1

• Can use your digital camera (Canon, Nikon) for
  exposures up to 30sec or so
• Precision about 0.1mag, but 3 simultaneous colors
• Can go fainter than visual, permanent record
• Can use the camera for daytime activities

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DSLR cameras - 2

• IR blocker so cant go red
• Monochrome resolution weird (Bayer pattern)
• Can also use color CCD cameras such as DSI-color
  (cheap, but only for astrophotography and not
  vacation photos!)

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DSLR Projects

• Monitoring CVs for outburst
• Monitoring CVs in outburst in multiple passbands
• Monitoring RR Lyr, high-amp delta Sct with
  multiple passbands
• Survey (nova searches)

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CCD Observing

• High precision, very faint, crowded fields,
  multifilter, etc.
• Different price levels (500-50000). Cheaper
  systems usually smaller format, less features
• Requires computer, software, calibration images
  and image processing

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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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Eclipsing Cepheid
Antipin et al. 0705.0605
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AU Peg
PopI/II Cepheid P2.4days, sinusoidal Binary, 53d
period Changing period DMC?
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AU Peg - 2
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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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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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Future

• Surveys, Surveys, Surveys
• More and better equipment and software
• Spectroscopy
• Datamining
• Robotic telescopes

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The XO Project 2x10cm telephoto Lenses with
CCD At Maui, Hawaii. Exoplanet studies
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ASAS
200mm camera lens V-band, nightly Chile, so
southern hemisphere up to 20 Northern
hemisphere system on Maui, not publically
available yet
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PanStarrs
1.8m telescope 1Gpix camera Entire sky visible
from Hawaii every week or so
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Sonoita Research Observatory (SRO)

• Operated by John Gross partners Dirk Terrell,
  Walt Cooney and AAVSO
• C14, Paramount, STL-1001E

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Spectroscopy
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V1280 Sco
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Volunteer work is important, too

• Database (MySQL) programming to give researchers
  access to 200K CCD images, photometry, etc.
• Working on the AAS Pro-Am web page
• Digitization of scans of the 75K Olin Eggen
  observation cards

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Typical Eggen card
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How YOU can get informed

• http//www.aavso.org has manuals, campaigns,
  tutors, maillists
• http//cba.phys.columbia.edu for CVs also CVNET
• http//www.socastrosci.org for CCDs and
  spectroscopy
• RASC, BAA, other organizations have variable-star
  sections and groups
• John Percys new variable star book
• Buils spectroscopy web site http//www.astrosurf
  .com/buil/