X. Huang, G. Á. Bakos and J. A. Hartman Xuhuang@Princeton.Edu

Using Kepler as a Calibrator

X. Huang, G. Á. Bakos and J. A. Hartman [email protected]

PROBLEM OBSERVATION The HATNet project is a wide-field ground-based search for transiting planets around moderately bright stars. Like other wide-field ground-based transit sur- veys, HATNet is primarily sensitive to gas giant planets with orbital periods less than 10 days. The detection of smaller and longer period planets are difficult because of the fol- lowing aspects.

1. Large gap in time series, either due to rotation of earth, or inclement weather conditions. 2. Data quality is highly variable due The Kepler field was observed by HAT- period smaller than 20 days and size bigger to changing extinction, clouds, back- Net prior to the launch of the mission. The than Neptune in the center field G154. We ground, seeing, etc. whole Kepler field is overlapped with five use this sample to calibrate a new transit de- 3. The per-point photometry precision is HATNet fields in total. We select Kepler tection pipeline. worse compare to space based obser- planet candidates (Batalha et al.(2013)) with vations. The high quality light curves from Kepler mission provide a valuable opportunity for EXAMPLE HAT LIGHT CURVES RESULT us to improve our yield of smaller and longer We yield robust detections for Kepler period planets. -0.01 HAT1998264, unbinned candidates that were previously not selected HAT1998264, binned average -0.005 KOI12.01, binned average by HATNet (for instance, see the exam- 0

mag ple light curves of KOI12.01,KOI18.01 and METHOD 6 0.005 0.01 KOI98.01).

0.015 We search the HATNet light curves based -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 HATNet field G154 has 52 Kepler can- Orbital phase on our previous experience on Kepler data -0.01 didates with period shorter than 20 days HAT1998264, binned average, dip significance=9.5 KOI12.01, binned average, P=17.8day,Rp/Rstar=0.09 (Huang et al. (2013)). We use a method that -0.005 and size bigger than Neptune. Consider- includes: 0 ing that the signal-to-noise of a transit de- mag 6 0.005 pends on both the period and the radius ra- 1. Initial de-trending of the data; 0.01 tio between the planet and the star, we ap- -0.04 -0.02 0 0.02 0.04 −0.5 2 2. The reconstructive Trend Filtering Al- Orbital phase ply a selection cut with P (Rp/Rstar) . > −0.5 HAT15527847, unbinned −3 gorithm (TFA, Kovács et al. (2005)); -0.04 HAT15527847,binned average 2 × 10 Day (Jupiter size planet around KOI18.01,binned average 3. The Box Least Squares (BLS, Kovács et -0.02 solar type star with a period of 20 Day) for 0 mag al. (2002)) method; 6 our sample of study. We detect 17 of the 29 0.02 4. A phase space transit fitting method. 0.04 planet candidates satisfying this threshold, -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 besides the known HAT planets in the Ke- Orbital phase -0.02 The reconstructive TFA is an iterative noise HAT15527847, binned average, dip significance=7.0 pler field (HAT-P-7b and HAT-P-11b). -0.015 KOI18.01,binned average, P=3.548, Rp/Rstar=0.078 filtering algorithm making use of the infor- -0.01 We show the BLS spectrum of one of the -0.005 0 mation obtained from BLS. We include pos- mag smallest planets in this analysis here, the real 6 0.005 sible transit signals as an additional template 0.01 signal is selected among the best five BLS 0.015 0.02 besides the typical sets of templates from -0.1 -0.05 0 0.05 0.1 peaks in the spectrum: Orbital phase stars in the same fields. This would allow -0.01 HAT1546994, unbinned 2 HAT1546994, binned average BLS spectrum of HAT1546994 (KOI98.01) (Rp/Rstar) =3.7mmag the correction of systematics along with pre- -0.005 KOI98.01, binned average 2.5e-07 2.5e-07 serving the transit signal. 0

mag 2e-07 6 The phase space transit ﬁtting method is 2e-07 1.5e-07

0.005 SR 1e-07 aimed to separate the contribution to the sig- KOI98.01 P=6.79 day 0.01 5e-08 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 nal due to a single outlier from that of a Orbital phase 1.5e-07 1 2 3 4 5 6 7 8 9 10 Period(day) SR -0.004 HAT1546994, binned average, dip significance=6.8 real transit, and then enhancing the signal- KOI98.01, binned average, P=6.79, Rp/Rstar=0.056 -0.002 to-noise of the real transit by allowing for 1e-07 0 mag transit timing variations. 6 0.002 0.004 5e-08 0.006 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 6.6 6.7 6.8 6.9 7 7.1 Orbital phase Period(day) REFERENCES

[1] Batalha, N. M., Rowe, J. F., Bryson, S. T., et al. 2013, ApJS, 204, 24 FUTURE DIRECTIONS [2] Huang, X., Bakos, G. Á., & Hartman, J. D. 2013, MN- We expect similar planet distributions in the neighboring fields of Kepler field (i.e. G115, RAS, 429, 2001 G153, G155 and G198). By applying our new pipeline to the observations in these four fields, [3] Kovács, G., Zucker,S., & Mazeh, T. 2002, A&A, 391, we’ll be able to yield detections of known Kepler planets as well as new discoveries that are 369 not covered by the Kepler field. If extrapolating the result from field G154, we expect more [4] Kovács, G., Bakos, G.,& Noyes, R. W. 2005, MNRS, than twenty new planet candidates lie in the parameter range with period between 10-20 day, 356, 557 with at least one super-Neptune size planet per field.