modelling of w uma -type variable stars
DESCRIPTION
Modelling of W UMa -type Variable Stars. Patricia Skelton MSc UNISA Prof. Derck Smits SKA Postgraduate Bursary Conference The Wallenberg Centre, sti s 1 – 5 December 2008. Over-Contact System. Properties of W UMa-type Stars. Overcontact binary: Common Envelope binary - PowerPoint PPT PresentationTRANSCRIPT
Modelling of W UMa-type Modelling of W UMa-type Variable StarsVariable Stars
Patricia SkeltonPatricia Skelton
MScMSc
UNISAUNISA
Prof. Derck SmitsProf. Derck Smits
SKA Postgraduate Bursary ConferenceSKA Postgraduate Bursary Conference
The Wallenberg Centre, stiThe Wallenberg Centre, stiss
1 – 5 December 20081 – 5 December 2008
Over-Contact SystemOver-Contact System
Properties of W UMa-type StarsProperties of W UMa-type Stars
Overcontact binary:Overcontact binary: Common Common Envelope binaryEnvelope binary Period < 1 dayPeriod < 1 day Spectral Range: A - K Spectral Range: A - K ΔΔT approximately a few hundred T approximately a few hundred degreesdegrees Subclasses : A-Type and W-TypeSubclasses : A-Type and W-Type
ASASASAS Las Campanas Observatory, ChileLas Campanas Observatory, Chile 7cm aperture telescope7cm aperture telescope Observe once every 1 – 3 daysObserve once every 1 – 3 days 50,000+ variable stars discovered50,000+ variable stars discovered Over 5000 are EW starsOver 5000 are EW stars
SuperWASPSuperWASP
Monitor sky for planetary transitsMonitor sky for planetary transits Two robotic observatories:Two robotic observatories:
North: La Palma, South: SAAONorth: La Palma, South: SAAO Eight wide angle cameras. Camera Eight wide angle cameras. Camera
aperture 11.1cmaperture 11.1cm Observe on a daily basisObserve on a daily basis
ASAS
WASP
PHOEBEPHOEBE
Stars Of InterestStars Of Interest
Stars that display period changesStars that display period changes Stars that may be magnetically Stars that may be magnetically
active: Search for radio emissionactive: Search for radio emission Previous surveys for radio emission Previous surveys for radio emission
used distance as a search criterion. used distance as a search criterion. Flare detected from VW Cep.Flare detected from VW Cep.
Goal: Evidence for magnetic activity Goal: Evidence for magnetic activity in light curves.in light curves.
The O’Connell EffectThe O’Connell Effect
Maxima Different HeightMaxima Different Height Magnetic Activity: SpotsMagnetic Activity: Spots
Flux ChangesFlux Changes
8.3
8.35
8.4
8.45
8.5
8.55
8.6
8.65
1750 1950 2150 2350 2550 2750 2950 3150 3350 3550 3750
HJD ( + 2450000)
Mag
nit
ud
e
ASAS 133246-1745.5
10.4
10.5
10.6
10.7
10.8
10.9
11
11.1
1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800
HJD ( + 2450000)
Mag
nit
ud
e
ASAS 062426-2044.9
Decrease in flux
Increase in flux
Flux ChangesFlux Changes
9.7
9.8
9.9
10
10.1
10.2
10.3
10.4
1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800
HJD ( + 2450000)
Mag
nit
ud
e
9.8
9.9
10
10.1
10.2
10.3
10.4
10.5
3850 3900 3950 4000 4050 4100
HJD ( + 2450000)
Mag
nit
ud
e
ASAS 002328-2041.8ASAS 002328-2041.8
ASAS dataASAS data
WASP dataWASP data
Combined increase & decrease in flux
Interesting starInteresting star
ASAS 002328-2041.8
Period ChangesPeriod Changes
ASAS Data
WASP Data
Unanswered QuestionsUnanswered Questions
EW stars: How do they form and EW stars: How do they form and what do they become?what do they become?
Complex pattern of period changesComplex pattern of period changes Common Envelope: Uniform Common Envelope: Uniform
temperature. Why?temperature. Why?
Future ResearchFuture Research
Period changes: O-C diagramPeriod changes: O-C diagram APT observationsAPT observations Radial velocity measurements: Mass Radial velocity measurements: Mass
ratiosratios Surveys for radio emission from Surveys for radio emission from
spots: VLA, SKAspots: VLA, SKA
Image adapted from Binary Maker 3