x-ray and observational astronomy
DESCRIPTION
X-ray and observational Astronomy. Detection limits for close eclipsing and transiting sub-stellar and planetary companions to white dwarfs in the WASP survey. Francesca Faedi Richard West, Matt Burleigh, Mike Goad, Leslie Hebb. 17 th European White Dwarf Work Shop – 20/08/2010. Outline. - PowerPoint PPT PresentationTRANSCRIPT
X-ray and observational Astronomy
Detection limits for close eclipsing and transiting sub-stellar and planetary companions to white dwarfs in the
WASP survey
Francesca Faedi
Richard West, Matt Burleigh, Mike Goad, Leslie Hebb
17th European White Dwarf Work Shop – 20/08/2010
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
1) Sub-stellar and Planetary companions to WDs
2) Monitoring WD variability with WASP
- Simulation - Detection algorithm- Results from the analysis of 194 WDs in WASP companion’s Frequency
- Photometric variability for our WD sample
Outline
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
The WASP survey
- 8 Canon lenses 200mm f/1.8 - CCD array 20482 13.5μm per pixel - Field of view 7.8 x 7.8 deg2 per camera - magnitude limit V ≈15 - photometric accuracy better than 1% down to V ≈12
42 confirmed transiting planets
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
All stars with mass ≤ 8M will evolve to white dwarfs
What is the fate of known planetary systems?
Motivation
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
Rwd ~ R
Deep transit signals2
WD
pl
R
R
3 < δ < 70 %
Terrestrial companions
δ =100%
BD/Gas Giant
Motivation
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/201017th European White Dwarf Work Shop – 20/08/2010
Parameters: Rpl , RWD , Porb MWD = 0.6M and RWD = 0.013R
Period range2 h – 15 d
WASP data: ~150 days per season 8 min sampling, 30 sec exposure
Companion size~ 0.3 – 12 R
Moon BD/Gas giants
Synthetic dataset
Simulations
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
Orbital Period = 2.52 days
White dwarf MS solar-type star
Gas giant companion
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
transit + Gaussian noise of standard deviation σ
real WASP data
Detection algorithm
Modified Box-Least Square (BLS) +
down weighting
Empirical criteria detection
S/Npeak > 6.3 SDE
PBLS within 0.003d of the corrected (inserted) period
White noise Red noise
Details in Faedi et al. 2010
Results
Our implementationClassic BLS
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
Results for V≈12 Results for V≈15
Results from simulations
Results
see Faedi et al. 2010 for detailed tables on detection limits
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
- Our WD sample consists of 194 stars - WASP multi-season light-curves (2004 - 2008)
€
f = f n 1− f( )N−n N!
n! N −n( )!
No evidence of transiting sub-stellar and planetary companions were found
We use our null result to estimate an upper limit to the frequency of companions to WDs
Data analysis
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
For a perfect survey
Combining the three magnitude-specific maps from simulations into a single averaged map by interpolating/extrapolating according to the magnitude of each object in the sample.
Using our simulations
Limits on companion frequency
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
conclusion
2) Our analysis of 194 WDs found no evidence of companion.
Constraints can only be put on Gas giants and sub-stellar objects in orbits with P< 0.1 − 0.2 days, similar to WD0137−349 (Maxted et al. 2006),
these objects must certainly be rare (∼ < 10%)
Future surveys such as NGTS, Pan-STARRS, LSST, Plato
• Increase sample size • Sampling rate (high cadence)• Baseline
1) My Key result is transits of terrestrial rocky bodies in short period orbits
are detectable in current ground-based photometric surveys such as WASP
none found as yet … !
~1100 WDs 15 <V< 17 McCook & Sion
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
Monitoring WDs variability with WASP
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
Interesting objects
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
X-ray and observational Astronomy
17th European White Dwarf Work Shop – 20/08/2010
Thank you!!