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The Value of Visual Observations of Variable Stars

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Provide systematic observing program of variable stars to serious amateur astronomers worldwide ... Why is it important AMATEURS observe variables? ... – PowerPoint PPT presentation

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Title: The Value of Visual Observations of Variable Stars


1
The Value of Visual Observations of Variable Stars
  • Elizabeth O. Waagen
  • AAVSO
  • 25 Birch Street
  • Cambridge, MA 02138
  • eowaagen_at_aavso.org
  • AAVSO Workshop for Visual Observing,
  • 15 October 2005, Newton, MA

2
What is a visual variable star observation?
  • the estimation by an observer of the brightness
    of a variable star at a given date and time,
  • using the eye by itself, or with binoculars or a
    telescope
  • example
  • 213843 SS CYG 2453289.7901 8.0 WEO
  • Star identification date time mag
    observer

3
How is a visual observation made?
  • Compare the brightness of the variable star to
    the brightnesses of nearby stars of known
    brightness (comparison stars).

4
Purpose of AAVSO
  • Provide systematic observing program of variable
    stars to serious amateur astronomers worldwide
  • Make the resulting observations useful and
    available to the professional astronomer,
    educator, and student

5
Why is it important AMATEURS observe variables?
  • Professionals cannot observe variables night
    after night
  • do not have the time or equipment
  • too many stars for them to monitor
  • time better spent analyzing data, theorizing

6
Why is it important AMATEURS observe variables?
  • Amateurs can observe night after night
  • They have the time and equipment
  • They have the expertise
  • They have the necessary enthusiasm and
    persistence
  • Careful, longterm observing yields data the
    professional can use to correlate his/her special
    observations

7
Visual observations are essential!
  • What for?
  • - Satellite observations schedule observing run,
    simultaneous monitoring, TOO trigger

8
Visual observations are essential!
  • What for?
  • - Satellite observations schedule observing run,
    simultaneous monitoring, TOO trigger
  • Correlation of multiwavelength space- and
    ground-based data

9
Visual observations are essential!
  • What for?
  • - Satellite observations schedule observing run,
    simultaneous monitoring, TOO trigger
  • Correlation of multiwavelength space- and
    ground-based data
  • Analysis of long term behavior (stellar
    evolution)

10
Visual observations are essential!
  • What for?
  • - Satellite observations schedule observing run,
    simultaneous monitoring, TOO trigger
  • Correlation of multiwavelength space- and
    ground-based data
  • Analysis of long term behavior (stellar
    evolution)
  • Testing theoretical models

11
Visual observations are essential!
  • What for?
  • - Satellite observations schedule observing run,
    simultaneous monitoring, TOO trigger
  • Correlation of multiwavelength space- and
    ground-based data
  • Analysis of long term behavior (stellar
    evolution)
  • Testing theoretical models
  • Furthering understanding of many/most subclasses
    of pulsating, eruptive, and extrinsic variables,
    esoteric high-energy objects

12
Visual observations are essential!
  • What for?
  • - Satellite observations schedule observing run,
    simultaneous monitoring, TOO trigger
  • Correlation of multiwavelength space- and
    ground-based data
  • Analysis of long term behavior (stellar
    evolution)
  • Testing theoretical models
  • Furthering understanding of many/most subclasses
    of pulsating, eruptive, and extrinsic variables,
    esoteric high-energy objects
  • Applications we havent even dreamed of yet!

13
Examples of How Visual Observations Are Valuable
14
Observing LPVs with HST
  • AAVSO observations help astronomers schedule
    observations of pulsating stars with HST by
    providing the phase of variability and magnitude.
  • Observations of Mira (omicron Ceti)


AAVSO visual light curve of Mira 1994-1997 HST
observation made December 11, 1995, is marked.
Each dot is one observation.
HST images of Mira (left) and close companion VZ
Cet taken December 11, 1995 (M.
Karovska,Harvard-Smithsonian Center for
Astrophysics, and NASA).
15
Modeling Pulsating Variables
  • AAVSO data on hundreds of stars covering many
    decades are a treasure-trove for theoreticians!
  • AAVSO observations provide astronomers with phase
    of variation and magnitude for correlating visual
    data with UV, optical (spectroscopic and
    photometric), IR, and radio data in theoretical
    research on
  • ? Mechanism and mode of pulsation
  • ? Composition and motion of atmosphere
  • ? Radius, luminosity, mass, temperature,
  • and other properties
  • ? Correlations among parameters

Evolutionary models link stars in different
evolutionary states as well as relating stellar
properties and (occasionally) rates of change of
those properties. (L. A. Willson, 1997, JAAVSO,
25, 99, Figure 4)
16
  • AAVSO long term visual light curve
  • Mira, 1835-2000

17
  • AAVSO long term visual light curve
  • R Aquarii 1810-2000

18
  • AAVSO long term visual light curve
  • V Hya 1884-2000

19
  • AAVSO longterm visual light curve
  • V Hya 1913-2003

20
Amateurs Assist Hipparcos
  • AAVSO data were crucial to success of
    observations of Long Period Variables with the
    ESA High-Precision Parallax Collecting Satellite
    (1989-1997)
  • Pre-launch
  • ? 1 million AAVSO observations provided
    before satellite launch to determine and test
    methods of predicting long period variable (LPV)
    behavior during mission (illustration below,
    left)
  • During mission
  • ? Real-time observations (70,000 per year)
    provided monthly to
  • ? refine LPV predictions
    (illustration below, left)
  • ? calibrate aging satellite optics
    (esp. for observing red stars)
  • ? 245 LPVs successfully observed through
    this collaboration

AAVSO light curve with successive fittings of
Hipparcos prediction algorithm to data dashed
line is final fit
21
Light curves from Hipparcos and Tycho Catalogues,
Vol. 12 (ESA 1997) Smoothed curves fitted to
AAVSO observations (left) Hipparcos photometry
on transformed-AAVSO smoothed curves (right)
  • Amateurs Assist Hipparcos

Post-mission ? Hipparcos precision
photometry superimposed on AAVSO light curves for
optimal interpretation of photometry
(illustration below, middle) ? Combined
light curves published in The Hipparcos and Tycho
Catalogues, Vol. 12 - Hipparcos Variability
Annex Light Curves (illustration below,
right) Good agreement of fit between Hipparcos
and AAVSO data shows the high quality of AAVSO
data
22
Visual Observations Contribute to High-Energy
Cataclysmic Variable Research
  • Amateur astronomers worldwide have helped
  • ? to obtain the first detection of X-ray emission
    from several members of each cataclysmic variable
    category
  • ? to obtain the first detection of soft X-ray
    pulsations from astrophysical sources such as
    dwarf novae
  • ? to obtain the first multi-wavelength spectra of
    dwarf novae
  • ? in the discovery that 70 of cataclysmic
    variables emit X-rays (information that is vital
    in testing theories for high-energy emission in
    compact systems)
  • ? in the discovery of stellar winds during the
    outburst of some dwarf novae
  • ? in the discovery of a delay during outburst
    between optical, ultraviolet, far ultraviolet,
    extreme ultraviolet, and X-ray emission in some
    dwarf novae
  • ? in discovering that the EUV soft X-ray flux
    initially tracks the optical flux, but then falls
    quickly during the decline from outburst in some
    dwarf novae

23
  • ? in discovering that during the rise to optical
    outburst, the hard X-ray flux rises, followed by
    a fast decline, with a subsequent rise in the EUV
    flux? in discovering that the hard X-ray flux
    remains suppressed throughout the outburst but
    recover suddenly at the end of the optical
    outburst
  • ? in discovering novae and supernovae? in
    triggering multi-wavelength observations at the
    onset of an outburst, which is crucial in
    understanding the nature and origin of
    outbursts? in providing a continuous record of
    the behavior of cataclysmic variables to
    correlate multi-wavelength observations and
    theories? in furthering our understanding of
    compact binaries, the nature of the white dwarf
    and the secondary component, accretion disks, and
    the nature and origin of outbursts.

24
Amateurs Keep Astronauts Pointing with Astro-1
and Astro-2
  • In 1990 and 1995, AAVSO observers assisted in
    space shuttle-based observing programs
  • Astro-1 (1990, 9-day mission)
  • AAVSO observers monitored 19 cataclysmic
    variables
  • and active galactic nuclei for outbursts,
    reporting activity to Headquarters
  • Unique, excellent far-UV spectra on Z Cam
    obtained using Hopkins Ultraviolet Telescope on
    Astro-1 less than 48 hours after first detection
    of outburst by amateur astronomer
  • Astro-2 (1995, 16-day mission)
  • Satellite observations were scheduled based on
    information provided by AAVSO (often every 8
    hours, around the clock) thanks to dedicated
    AAVSO observers worldwide
  • ? Results Excellent data obtained on 17
    cataclysmic variables

25
  • AAVSO longterm data on RX And part 1

26
AAVSO longterm data on RX And part 2
27
AAVSO longterm data on GK Per 1904-2003
28
AAVSO longterm data on Z And 1913-2003
29
AAVSO longterm data on R CrB 1905 - 2003
30
Z Cha(P. Wheatley C. Mauche)10/13/05
31
U Gem (Smak Waagen 2004)AAVSO light curve and
residuals
32
AAVSO visual observations continue to helpbreak
new ground in variable star astronomy!
33
  • Visual observations
  • Are enormously valuable

34
  • Visual observations
  • are enormously valuable
  • and
  • They always will be!

35
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