Download RIPL Radio Interferometric Planet Search

RIPL
Radio Interferometric
Planet Search
Geoffrey Bower
UC Berkeley
Collaborators: Alberto Bolatto (UMD), Eric Ford (UFL),
Paul Kalas, Anna Treaster, Vince Viscomi (UCB)
MM Wavelength T Tauri Outburst in
Orion
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2nd most luminous stellar radio outburst
Briefly, brightest object in nebula
Required long baselines for detection
Magnetized T Tauri outburst
Contemporaneous with X-ray outburst
Many such objects likely to be found by
CARMA & ALMA
BIMA A configuration images
(Bower, Plambeck, Bolatto, Graham, de Pater, McCrady, Baganoff 2004)
Orion Nebula Parallax
w/Star GMR-A
D=389 pc +/- 5%
<0.1 mas/epoch
Sandstrom, Peek, Bower, Bolatto,
Plambeck 2007
Astro-ph/0706.2361
Planets are Easy to Detect
Companion to GJ 752B Detected
w/Optical Astrometry
Pravdo & Shaklan 2009
White et al
Gudel 2002
Requirements of a Planet Survey
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Low mass, nearby star
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Astrometric displacement ~ 1 mas
Nonthermal radio emission
S ~ 1 mJy
 F ~ GHz
 Positional stability < 0.1 mas
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Stable Image
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Active, but not too active
VLA M dwarf Flux Survey
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174 X-ray selected
nearby M dwarfs
10 minute VLA
observations with 50
microJy rms
40 detections of 29 stars
Rough agreement X-rayradio correlation
No distinction between
early and late types
Bower, Bolatto, Ford, Kalas 2009, ApJ, in press
Stars are Variable
EV Lac
Osten et al 2005
Pilot Survey
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7 stars
3 epochs
< 10 days
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Hipparcos errors ~ 1
mas/y
Error over 10 days < 0.1
mas
Test
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Detectability
Image stability
8000 km baselines
3 cm wavelength
1 mas resolution
Astrometry ~ beam/SNR
Results from Pilot Study:
Apparent Motion of GJ 4247
15 mas
26 March 2006
Comparison of radio positions
(points) with predictions from
Hipparcos astrometry (solid
line) reveal noise-limited rms
residuals ~0.1 milliarcseconds,
approximately 1 stellar
diameter.
Bower, Bolatto, Ford, Kalas 2009, ApJ, in press
25 March 2006
23 March 2006
Pilot Study Results
GJ 4247
GJ 896A
GJ 65B
Residuals are
sensitivity limited
~0.2 mas
VPAS Results
GJ
Detections
Proper Motion
65B
285
896A
4247
412B
803
1224
3/3
2/3
3/3
3/3
0/3
1/2
0/3
Different from Optical
Optical, sensitivity limited
Optical, sensitivity limited
Optical, sensitivity limited
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Agreement with optical
astrometry sets upper limit
on acceleration and
therefore companion
masses
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Mp < 3 – 10 MJup @ 1 AU
Sensitivity is limited by the
short lever arm of VLBA
observations: ~10 days
RIPL will extend this lever
arm by factor of 100
Planet Mass (Mjup)
Results from Pilot Study:
Constraints on Companion Masses
Semi-major Axis (AU)
Bower, Bolatto, Ford, Kalas 2009, ApJ, in press
RIPL
Radio Interferometric Planet Search
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30 stars
12 epochs/4 years
VLBA + GBT
512 Mb/s
2 hours on source + 2
hours calibration
25 microJy rms
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4 x lower than pilot
survey
1392 hours total
Key question: What is fraction
of long-period planets around low
mass stars?
RIPL Sample
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30 Stars
M1 – M8
V = 9.6 – 15.8 mag
S_6cm = 0.1 – 6 mJy
D = 2.7 – 9.5 pc
11 are members of known binary or multiple
systems
Simulated RIPL Results
RIPL Sensitivity
Current Status
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Observing began Oct
2007
 Approximately 4
observations/month
Expected completion in
mid-2011
40% complete
Pipeline processing
underway (see poster by
Vince Viscomi)
All stars detected
 60% of stars detected
in every epoch
Benefits of Astrometric Detection
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Unique method
Breaks degeneracy of RV searches for mass, inclination
angle, and ascending node
Probes low mass, active stars that are difficult to study
with RV method
Planet fraction of low mass stars poorly determined
Detects planets that can be studied with extreme AO
Ties radio and optical astrometric reference frame
RV Search Results
Few M dwarf Hosts
RV Search Results
Most Planets are >10 pc Distant
RV Search Results
What is Mplanet/Mstar?
Microlensing Search Results
What is Mplanet/Mstar?
Microlensing Search Results
Planets are Very Distant
Comparative Sensitivity of Searches
Future Directions for Radio Astrometry
& Planets
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Bandwidth upgrade for
VLBA
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512 Mb/s  8 Gb/s
4 x sensitivity
Calibrator density
increases by 8 x
In-beam calibrators
10 microarcsec accuracy
 Neptune mass planets
Square Kilometer Array
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100 x sensitivity
3000-5000 km baselines
1 microarcsec accuracy 
Earth mass sensitivity
Summary
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Radio astrometry is sensitive to sub-Jupiter mass
planets around M dwarfs
We can already exclude BD companions to three
stars based on only three measurements
RIPL survey will probe low mass, active star
parameter space