Download detection of transits of extrasolar planets with GAIA

Detection of transits of extrasolar
planets with the GAIA new design
Noël Robichon
DASGAL - CNRS UMR 6633
depth of a transit
m ≈ F/F = (RP/R*)2
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REarth = 0.1 RJup = 0.01 RSun
Earth : m=10-4
Jupiter : m=10-2
HD 209458 : m=1.7 10-2
sG > 10-3  only Jupiter size objects with GAIA
duration of a transit
a
Vcirc = 2pa/P
Dt = 2R*/Vcirc
2R*
( if RP<<R* )
to the
observer
Dt/P = R*/pa = R*/pM*1/3P2/3
Earth : P = 1 yr  Dt/P = 1.5 10-3
Jupiter : P = 11.3 yr  Dt/P = 1.3 10-4
HD 209458 : P = 3.5 days  Dt/P = 3.2 10-2
GAIA : # of observations 150-300  P < 10 days
geometric probability of observation
star
2R*
planet
a
q
cone of transit
visibility
pgeo=p(q<2R*/a)=2sin(R*/2a)
pgeo=R*/a=R*/M*1/3P2/3 (if RP<<R*)
Earth  pgeo = 5 10-3
Jupiter  pgeo = 4 10-4
HD 209458  pgeo = 0.1
 in favor of very short periods
Simulations
• mass-MV and mass-radius relations from litterature
• photometric error sG(G)
• RP=1RJup or 1.3 RJup
Monte Carlo simulation in bins of (b, G, MV, P)
• Galaxy model (Haywood)  N*(b, G, MV)
• scanning law of the satellite  PNobs/transit(b, N)
• probability of having an observable transit star
 Pobs (P, MV) = Pgeo(MV, P) x 0.01 log(P+/P-)/log(10)
• probability of detecting the transit Pdetec(N, G, MV)
less than 10 % of false detection and N>5 or 7 (3 or 4 ≠ epochs)
Number of transited stars if RP = 1.3 RJup
Npts/transits>max(5, N(#false/#true<10%))
# of stars with transiting planet
10 4
1000
MG bins
4
5
6
7
8
9
10
>11
100
10
1
2
4
6
8
Period
10
12
14
16
TOTAL: 29000 stars
Number of transited stars if RP = 1.0 RJup
Npts/transits>max(5, N(#false/#true<10%))
# of stars with transiting planet
10 4
1000
MG bins
4
5
6
7
8
9
10
>11
100
10
1
2
4
6
8
Period
10
12
14
16
TOTAL: 10300 stars
Number of transited stars as a function of G
RP = 1.3 RJup Npts/transits>max(5, N(#false/#true<10%))
# of stars with transiting planet
10 4
MG bins
1000
4
5
6
7
8
9
10
>11
100
10
1
13
14
15
16
G
17
18
19
20
Summary of the results from simulations
RP = 1.0 RJup Npts/transit>5
10300
RP = 1.3 RJup Npts/transit>5
29000
RP = 1.0 RJup Npts/transit>7
5800
RP = 1.3 RJup Npts/transit>7
15500
Conclusions
• simulation predict 5.103 to 30.103 detectable transits
things to improve:
• countings of the Galaxy model -> less transited stars
• better limits in G and MV -> more transited stars
• better precision in AF photometry -> more transited stars
• take account of variable stars: spots, grazing eclipsing binaries...
• detection algorithm
• recovering unbiased planet distribution = f(P, MP, M*…)
unknowns:
• statistics: % of HJ = f(ST)?
• properties of planets: radii? Pmin?…
Photometric precision
sF/F = (RON2+SKY+F)1/2/F
0,1
sG per AF CCD
sG per AF transit (9 CCDs)
smag per MBP transit
(sum of 10 bands + MSM)
G2 star RP=1.3 RJup
0,01
smag
G2 star RP=1 RJup
0.001 mag has been
quadratically added
in the simulation
0,001
0,0001
8
10
12
14
16
G
18
20
22
-0,01
-0,01
-0,005
-0,005
0
0
-0.000572226
-0.000572226
Simulation of HD 209458 for two different TC
0,005
0,005
0,01
0,01
0,015
0,015
0,02
0,02
0
0,2
0,4
0,6
0.802909
0,8
1
0
0,2
0,4
0,6
0.802909
0,8
1
distribution of number of points during a transit
25
P=10.25 days (dt/P = 1.7%)
b = +5° (170 points)
20
percentage
15
P=3 days (dt/P = 3%)
b = +35° (280 points)
10
5
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16
# of points
distribution of periods of known systems
# of stars with planet
20
4 % of stars have
an planetary system
15
 1 % have a planet
with P < 30 days
10
minimum period observed:
3 days
5
0
0,5
1
1,5
2
2,5
log P (days)
3
probability of having N points greater than ps
1
p=1.5
0,01
0,0001
p=2
10 -6
10 -8
p=3
p=2.5
10 -10
0
5
10
N
15
20