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Exoplanet Transits with mini-SONG

Exoplanet Transits with mini-SONG. Licai Deng @ NAOC Presented for the NJU group. mini-SONG. 50cm 2 channel, with dual tube (not really needed, UVI case). 20 ’ x20 ’ FOV (limited by budget). For SONG-north (where photometry will likely be missing (luck imaging)).

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Exoplanet Transits with mini-SONG

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  1. Exoplanet Transits with mini-SONG Licai Deng @ NAOC Presented for the NJU group

  2. mini-SONG • 50cm 2 channel, with dual tube (not really needed, UVI case). • 20’x20’ FOV (limited by budget). • For SONG-north (where photometry will likely be missing (luck imaging)). • Chinese team really want to have that capability for a number of reasons, • And, more importantly, want to make good use of that capability

  3. Do what mini-SONG is really good at ! • There are tons of small telescopes out there with similar or better instruments • What makes mini-SONG unique is the SONG network and the way it schedules observations: • High duty cycle, long time baseline • Identical instruments • Can follow ToOs at any time

  4. Given all these, we should • Stay focus, and just like SONG, stare at only a few targets for the major goals • The targets should contain as many stars as possible to accommodate a variety of interests on stellar variabilities All those made us decided to go for open clusters. (need careful selection)

  5. Searching for transiting planets in open clusters with mini-SONG Hui Zhang & Ji-Lin Zhou College of Astronomy and Space Science Nanjing University

  6. What do we prepare to do? • High accuracy, continual photometry observations in a series of open clusters • Why do we choose stellar clusters? • Stellar members have almost the same age, composition and dynamic environment within a cluster. know one, know all • Stellar members are well studied within a cluster higher certainty of mass, radius, temperature and distance. • Why is the Open Cluster?

  7. Very young stars： • many stars with age of only million years  proto-stellar disk is expected constraint on the life time of protostellar disk • Low metallicity: the least metallicity required by the formation of planet • Diameter < 20’ ,suit for the FOV of mini-SONG 20’x20’ • Stellar density is not too dense nor too low • Characteristics of open cluster：statistical results of 2094 open clusters age：106~1010yr diameter：most< 20 arcmin metallicity：-0.8~0.2

  8. What can we get? – Scientific goals A: Search transiting planets in a series open clusters with varied metallicity The planet frequency as a function of the metallicity of host star B:Search proto-stellar or debris disk in a series open clusters with varied age, mass and metallicity The frequency of debris disk and its life time versus the mass, metallicity of the host star C: Detect the spin of stars by analysis their light curves • The relation between spin, age and mass of star • Higher certainties on the mass, radius of planets in the same cluster

  9. A. Planet frequency VS. Metallicity of host star Lack of planet around low metallicity stars? • Lack of planet around low metallicity stars ： • Observation bias：It is more difficult to detect low mass planet  lack of giant planet around low metallicity star  lack of giant planet around young stars (low metallicity)  time scale required by giant planet formation (agree with the gas accretion time scale？) • Formation mechanism：It is hard to form planet core in a low metallicity proto-stellar disk Prove a core accretion theory?

  10. A. Planet frequency VS. Metallicity of host star Lack of long period planet around low metallicity stars • Lack of long period planet around low metallicity stars ： • Observation bias：It is hard to detect long period planet around young stars (low metallicity and active) • Formation mechanism：Core accretion theory:Metallicity elements tends to condense at the inner part of the proto-stellar disk • Gravitational instability theory:The fragmentation usually happens at the outer part of the disk. Low metallicity makes it even harder.

  11. B. Proto-stellar disk induced light variation Spot-like The problem is how to distinguish the disk AA Tau-like Number VS. Period of two type of disk in NGC2264 The peak at 3~5 days period is coincide with the peak of the hot-Jupiter, the inner boundary of disk? Spot-like AA Tau-like Irregular. The light variation patterns indicate different type of proto-stellar disks. The variation is caused by the warp of inner disk controlled by magnetic field. (Alencar et al. 2010)

  12. C. The spin-age-mass relation of star How to measure the spin of a star? By Meibom, et al. 2011 Sunspot induced light variation (Meibom, et al. 2011) Use the slowing spin rate as a clock to measure the age of a star.

  13. C. The spin-age-mass relation of star By Meibom, et al. 2011 • Light curve  Spin rate of star  Spin ~ age1/2 Law  Age of a star • U-V photometry  Color magnitude Mass of a star • Spin-Age-Mass relation • Appling on other stars with planets in the same cluster  planet frequency VS. age of star  born time and life time of planet

  14. On going projects： Space： • Kepler：NGC 6866, NGC 6811, NGC 6819, NGC 6791 • Corot：NGC2264 Ground： • PISCES: NGC 6791，NGC 2158, NGC 188 • STEPSS: NGC 1245 • MONITOR: ONC， NGC 2362，h & c Per ，IC 4665， NGC 2547，Blanco 1， M50 ，NGC 2516， M34 • EXPLORE-OC: NGC 2660 ， NGC 6208 • Others: M37(Hartman,et al,2007), NGC 7789(Bramich,et al.,2005),NGC 6940(Hood, et al.,2005) A few candidates are found, None of planet is confirmed!

  15. It is probably because: • The sample is too small. The Kepler project suggests the frequency of hot-Jupiter (and Neptune) is around 5%. However only part of stellar members of a open cluster are bright enough to perform high accuracy photometry. • Need deep field observation (10% accuracy at V<20 ). • The continual observation is not long enough: • Peak of period is around 3~5 days • At least 10-days uninterrupted observation Peak at 3-5days

  16. It is probably because: • The dynamic environment of open cluster is not suit for planet formation. • So far, no planet is found in old and high metallicity open cluster as well. • If we really can not find any planet in any open cluster (very hard to believe!) • A great challenge to the planet formation theory!!

  17. Our scheme • 8 open clusters are chosen (preliminary version) Varied age, suitable diameter (20’x20’), has not been observed yet • Observation schedule: 5-minutes exposal V and R band 10-15days uninterrupted observation for a single cluster 50cm aperture 300s exposal Limit magnitude vs. SNR 1” seeing

  18. Targets (preliminary) Increasing age

  19. V band R band Example: NGC 1893 Very young stellar cluster: 10^6.48 yr • total 1483 stars • VRI class 0/I/II: 1068 • VRI diskless: 415 ( 200 V<20 ) • 3-6 candidates expected! 865 V<20 1195 R<20

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