Cool planet mass function
and a fly’s-eye ‘evryscope’
at Antarctica
Philip Yock, Auckland, New Zealand
20th Microlensing Workshop
Institut d'Astrophysique de Paris
13-15 January 2016
Twenty years ago
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Meeting at IAP on gravitational microlensing
Christophe Alard announced DIA
Bohdan Paczynski was present
Would be pleased with results on planets
Pleased with contributions by amateurs
Plea for high magnification
• In the days of Spitzer, K2 and KMTNet
• Hope that high mag events still followed
The mass function
PLANET, Cassan et al,
Nature 48, 167, 2012
OGLE-MOA-WISE
Oct 2015 preprint
MOA
Paris, Jan 2016
The mass function
PLANET, Cassan et al,
Nature 48, 167, 2012
OGLE-MOA-WISE
Oct 2015 preprint
Need more data at low masses
MOA
This meeting
Few detections and low efficiencies at low mass
OGLE-MOA-Wise
(four years)
Single detections
MOA
(6 years)
Nil detections
KMTNet in 2016
KMTNet will detect about 8 lowmass (1 – 10 ME) planets per year
Assumes saturated
Cassan mass function
Calen Henderson et al, ApJ 794, 52, 2014
High magnification technique?
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μFUN technique with 1-2m class telescopes
Monitor FWHM continuously if Amax > 50
Approximately 24 hours per event
Approximately 20 events per year
Reminder: monitor Full Width at Half Max
FWHM
~ 1 day
Follow-up telescopes ignore the wings
Ignore
FWHM
~ 1 day
Ignore
1.5 Earth mass
FWHM
Photometric errors and cadence from the MOA telescope
5.5 Earth masses
Detection efficiency
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u0 : 6 values ± .02, ± .01, ±.005
tE : 3 values 10 days, 20 days, 30 days
ρ :
3 values .0005, .001, .002
q :
5 values 1.5, 2.5, 3.5, 4.5, 5.5 × 10-5
s :
5 values .95, .85, .75, .65, .55
α:
1 value
60⁰ (for 30⁰ < α < 90⁰)
Follow-up data: 1 measurement every .001 day in FWHM at
MOA cadence and precision in fair weather
• Found fraction of events with Δχ2 > 300
F. Abe et al MNRAS 431, 2975, 2013
C. Airey, Doha workshop, 2013
L. Philpott, Santa Barbara, 2014
Detection efficiencies
Planet mass q = 5 × 10-5
Planet distance 0.6 < s < 1.7
Planet angle 30⁰ < α < 150⁰
or 210⁰ < α < 330⁰
Detection efficiency ̴ 75%
Planet mass q = 2 × 10-5
Planet distance 0.8 < s < 1.25
Planet angle 30⁰ < α < 150⁰
or 210⁰ < α < 330⁰
Detection efficiency ̴ 80%
Detection rate
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Assume Cassan mass function
Assume 20 events monitored per year with Amax > 50
Detetct 8 low mass planets (1-6ME) per year
Comparable to KMTNet
Independent sample of events
Could have been done already
Examples: first two high mag planets
OGLE-2005-BLG-071 q = 0.0071 s = 1.29
OGLE-2005-BLG-169 q = 6 × 10-5 s = 1.02
Recent event – OGLE-2015-BLG-0966
Rachel Street et al, arXiv:1508.0702
FWHM (top 0.75 mag)
FWHM
2.2days
modelling? systematics? moon?
Eyeball measurements α and ρ
lens axis
α
source
track
tW
α = tan-1 tEumin/(tp-t0)
= 50⁰
t0
tp
tW≈ 3ρtE (Abe et al)
≈ 0.24 day
ρ ≈ 0.24/3×58
≈ 0.0014
Final measurements of s, q, α, ρ
lens axis
α
source
track
tW
α = tan-1 tEumin/(tp-t0)
= 50⁰
t0
tW≈ 3ρtE
≈ 0.24 day
ρ ≈ 0.24/3×58
≈ 0.0014
tp
The values of s and q cannot
be eyeballed. The shape of
the planetary perturbation
yielded s = 1.115 or 0.909
and q = 1.7 × 10-4
OGLE-2015-BLG-0966
Low mass planets can be found at high mag
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Multiple planets?
Two planet test ̶ OGLE-2012-BLG-0026
Han et al, ApJ 762, L28 (2013)
Follow-up observations by amateurs
OGLE-2012-BLG-0026
Magnification maps, or whatever
OGLE-2012-BLG-0026
Above are Jovian planets
Neptunes more common
Multi-Neptunes?
Triple-Neptune system found by RV
Angelle Tanner et al,
ApJ 800, 115 (2015)
Hunt by microlensing
Summary
• High mag technique sensitive to low-mass planets
• Provides a “snapshot” of a planetary system near
the Einstein ring
• Multi-planets detectable
• Statistics ok
• No problems with low detection efficiencies
• Statistically unbiased and independent sample of
events
Telescopes
• OGLE and MOA survey more than 30 square deg
• Continuous follow-up needed
• Hopefully follow-up telescopes available in Australia
(Tasmania), South Africa (SAAO) and Chile (Danish)
• Some overlap between KMTNet and OGLE/MOA
fields would provide checks
Antarctica – a personal dream for NZ
Excellent seeing, dry atmosphere, long nights, constant air mass
Antarctica – a personal dream for NZ
F
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USA, Australia, Japan, China, France there, but only one NZer
Matthew Freeman at Ridge A in 2015
80⁰S, 4000m, driest & coldest place on Earth
One possibility – the ‘evryscope’
25 telephoto lenses (200mm)
10,000 square degree FOV
Comparable to TESS
Seek transited M dwarfs within 100 lt yr
Microlensing events at < 1 kpc (rE ~ 1 AU)
Chilean Evryscope (Nick Law et al)
Further information: A. Fukui et al ApJ 670, 423 (2007)
S. Gaudi et al ApJ 677, 1268 (2008)
N. Law et al PASP 127, 234 (2015)
Estimated event rate
No. of sources = 4/3π (1000pc3 – 700pc3 ) × 0.01pc-3
= 28 million
Lenses per source = πAU2 × 500pc × 0.1 pc-3
= 4 x10-9
Prob of lensing = 0.12
Event duration = 7 days
Events in 10,000 square degree per winter
= 0.12 × 365/7 × 1/4 × 1/2 = 1 per winter
Probably too few to hunt for planets
F,G