Rachel Street. K2/Campaign 9: Microlensing

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1 C2 C9 C7 Rachel Street K2/Campaign 9: Microlensing

2 Probing Cool Planets

3 Value of probing colder population Rocky planets Icy planets Gas giants Beyond snowline: Giant planet formation(?) Icy planets/planetesimals Source of water From: Ida, Lin & Nagasawa, 2013.

4 Planet Detection by Microlensing Microlensing sensitivity From the ground From space Extreme magnification can be produced, allowing even low-mass planets to be detected from the ground. Opportunity to probe low-mass cool planets in complementary regime. Photometry ~few to tens of millimag precision (limited by seeing/blending) Cadence ~mins or lower

5 Free-floating/wide-separation planet population Planets widely-separated from host stars? At least some are likely to be free-floating planets. Tough to study Sumi et al announced the discovery of 11 short timescale microlensing events

6 Planet Detection by Microlensing Extreme magnifications can result from trajectories passing close to alignment ground-based detection possible probes snowline region with just a few weeks' observations Alignments rare need to observe dense starfields

7 Characterizing Lensing Systems Ang. Einstein radius To measure MLens, we need: - the parallax, πe - the angular source size, ΘE 2 c AU Θ E M Lens = 4G π E Parallax (if measured)

8 Microlensing Parallax how we normally measure it Wait for Earth to move (long events only) Simultaneous observations (high mag events only) E.g. Gould et al. 2009

9 Parallax from Space how we'd like to measure it Pros: Measures parallax for almost all events Can detect planets independently Gould & Horne 2013b, Fig 1 Event seen from Earth Event seen from Sun Cons: [until recently...] Requires a wide field space telescope well separated from Earth

10 Parallax from Space Pathfinder work with Spitzer From Udalski et al And Calchi Novati et al single lens events Shvartzvald, Y. et al massive remnant in binary Zhu et al binary lensing events ++ From Street et al See talk by W. Zhu

11 K2/Campaign 9 Region of highest microlensing rate (Almost) unblinking stare ideal to find free-floating planet candidates See talk by C. Henderson

12 Space-based Parallax from Kepler Earth-trailing orbit ~0.5AU from Earth Gal. Bulge visibility overlaps well with Earth...if it points in +VV direction Kepler + Earth-based observers will measure parallax

13 Predicted Yield Based on frequency of events in region from previous observations ~85 events within footprint/time window Comparing survey with MOA to estimate FFP events ~6 events

14 Ground-based Campaign Challenges Continuous optical/nir photometry for ~80d 24/7 coverage multiple sites 1-2m class telescopes with good resolution (<0.5 /pix) Ideally wide-field imagers

15 Ground-based Campaign Microlensing surveys: 24/7 coverage Good resolution Good S/N WISE All optical no NIR None US-based KMTNet

16 Ground-based Campaign Why NIR? Need to measure source flux in NIR during event in order to subtract it from later AO Optical + NIR photometry delivers more accurate estimate of stellar radius Need 2+ datapoints per star per night for whole campaign

17 Ground-based Campaign Coordinated proposals submitted for optical/nir: DECam CFHT WIYN VST Liverpool Telescope IRTF CTIO 1.3m Keck Collaborative efforts with: VVV Skymapper Photo by Hideaki Fujiwara

18 Ground-based Campaign AO Imaging Prompt AO in NIR: - Distinguish free-floating/wideseparated planets by ruling out most stellar hosts Late-time AO: - Distinguish light from the lens by PSF elongation - Probe for dynamical companions

19 K2 Pixel Selection Superstamp region: Cannot target known events on alerts from the ground Short mid-campaign break for downlink 3.8 sq. deg survey N Events / field N RedClumpStars N Stars See work by Radek Poleski

20 K2 Crowded Field Photometry Challenges 5x5' image of OGLE-2014-BLG-1186 LCOGT-Chile 1m, /pixel Severe blending K2 PRF variable Detrending Rapid brightness changes Same image, resampled to K2 pixel scale 3.98 /pixel

21 K2 Crowded Field Photometry Challenges Severe blending K2 PRF variable Detrending Rapid brightness changes 14 Kepler pixels 14 Kepler pixels 14 Kepler pixels Bryson et al., 2010, Fig. 1 Kepler pixel response functions at different points in the focal plane

22 K2 Crowded Field Photometry Challenges Community already exploring multiple approaches [Penny, Bond, Street, Hogg, Foreman-Mackey] DIA analysis Detrending variation due to pointing variation due to movement of blended lensed star Forward-modeling based on high-resolution ground-based data Modeling of K2 PSF as a function of temperature, time and position on CCD based on existing K2 data See talk by M. Penny

23 Data Archiving K2 data public K2/C9 GO strongly encourages teams to make public their data products Support from NASA Exoplanet Database Community feedback to optimize ExoFOP: would like OGLE-III catalog data in archive with extraction/analysis tools extract source (blend) positions and associate with K2 objects Color-mag diagram analysis

24 K2 Microlensing Science Team Cycle 3 GO selected a team to coordinate with the community the execution of Campaign 9 the ground-based campaign US-based community is small but strong links with teams worldwide aim to expand US community ahead of WFIRST benefit from expertise overseas

25 Summary K2/C9 is a unique opportunity! will measure and characterize a large sample of lenses Only chance to measure masses for free-floating Jovian planets (WFIRST-AFTA may measure free-floating terrestrial planets) Selection biases well understood population analysis Science return impossible without simultaneous ground-based coverage K2 crowded field photometry challenging...but not impossible. Community-wide coordination