Accurate Fitting of High Magnification PSPL Events

Noise model and accurate fitting of high magnification PSPL events Pascal Fouqué

Alerts from OGLE-III and MOA-II in 2008 • 912 alerts (647 OGLE, 475 MOA) • OGLE: Feb. 23 - Nov. 3 • MOA: Feb. 9 - Oct. 21 • 176 possibleanomalies (including HME) • 97 followed by microFUN • 78 RoboNet-II / LCOGT • 78 PLANET • 74 MindStep

29 announced as possible HME • KB08022 • OB08013 = KB08032 • KB08044 = OB08054 • KB08054 • KB08087 • KB08096 • OB08140 = KB08115 • KB08105 • OB08199 = KB08144 • OB08209 = KB08155 • OB08210 = KB08177 • OB08215 = KB08161 • KB08149 • KB08151 • KB08159 • KB08198 • OB08279 = KB08225 • OB08303 = KB08267 • OB08426 • KB08310 • KB08311 • KB08349 = OB08509 • KB08383 • KB08384 • KB08402 • KB08415 • OB08580 • KB08428 • KB08453

First impressions • More MOA than OGLE announcements • Not all of them were HME • Some present further anomalies • Not all announced: • OB08155 = KB08137 • OB08290 = KB08241 • OB08307 = KB08215 • OB08349 = KB08261 • OB08358 = KB08264 • OB08367 = KB08269 • KB08307 = OB08448 • KB08325 • KB08352 • KB08356 • OB08506 • OB08513 = KB08401

A posteriori • Difficult to predict Amax from few points • Include priors as in BAP (M. Albrow) • Even when finished, accurate parameters are difficult to measure: • Combining several telescopes • MOA only events • Blending • Noise model

Analysis • plens fitting program: K. Horne, used by RoboNet/LCOGT • Noise model: 3 components: • Bright or HM events: errors down to 1 mmag: add percent systematic error: 2 to 5 mmag • Baseline: add flux accuracy due to faint background stars; larger for fainter stars: 0 to 0.1 mag • Rescale error bars: for OGLE, 0.8 - 2.0

Modelling parameters • Fit: 4 (t0, tE, u0, m0): no blending • 5: blending grid: parameters vs b = fb/fs • 6: 0 (baseline flux accuracy in mag) • 7: f (error bar scaling factor) • Grid 0 vs. f

Example of OB08279: blend ratio grid

Example of OB08279: noise model grid

Real HME events • Definition: Amax > 40 (4 mag) • About 16: 2% of all events • Retained (11 MOA, 5 OGLE): • KB08087 (60) • KB08096 (300) • KB08149 (600) • KB08151 (300) • KB08198 (40) • KB08310 (ext src) • KB08311 (200) • KB08383 (ext src) • KB08415 (130) • KB08428 (100) • KB08453 (100) • OB08013 (44) • OB08199 (44) • OB08279 (4000) • OB08290 (ext src) • OB08303 (55) • Extended source effects in some: O279?

OB08279 = KB08225 • Highly blended event: b = 40 • tE = 130 days, u0 = 2 10-4 (OGLE only) • OGLE, MOA, FUN, Canopus, RoboNet-II/LCOGT • Marginal extended source effect:  = u0 • Extended source: 2= 60 • Fix LLD for 5000 K dwarf • Andy’s sfit program, Yoo approx.: • u0 = 4.3 10-4 -> 5.7 10-4 and  = 5.9 10-4

PSPL ESPL

OB08290 = KB08241 • Clear extended source effect: ~ 60 |u0| • tE = 16.5 days • 12 telescopes: OGLE, MOA, FUN (4), LCOGT/RoboNet (3), PLANET (3) • Negligible blending • V, R, I, clear: fit LLD • Andy’s sfit program, Yoo approx. •  = 0.0220

OB08290 = KB08241 • V=0.72, =0.45 ≈ EROS 2000-BLG-5 -> K3 III • Target in 2MASS but blended: IRSF separates components • Estimate of extinction: isochrones fit • Bonatto et al. (2004) isochrones for 2MASS photometric system • IRSF images (S. Nishiyama) • Aks=0.44, Aj=2.5 Aks, Ah=1.7 Aks, =14.4 • J0=13.85, H0=13.17, Ks0=13.01: K4 III • CTIO V - I CMD: V0=16.10, I0=14.73: K3 III • Martin’s galactic model: disk lens (2/3-1/3), M=0.3 Msun at 5.8 kpc

Reddening law and extinction corrections • Sumi (2004) gives E(V-I) for each OGLE-II field • Ai = 0.964 E(V-I), Av = 1.964 E(V-I) • What to do when OGLE-III event not in OGLE-II field? • Once OGLE-III calibrated, use RGC: clump measured color gives E(V-I) (assume source and clump equally extincted) • Ai: three routes: use Sumi’s Ri (or other value), use clump measured magnitude and assumed distance (depends on bar geometry) • Third route: use near-infrared extinction maps, but which ratio E(V-I)/Aks ? • Near-infrared ( > 0.8 m): power-law: • E(-Ks)/E(J-Ks) = a - + b • Cardelli et al. (1989):  = 1.61 • He et al. (1995):  = 1.73 • Nishiyama et al. (2006):  = 1.99 • I adopt Av/Aks=10, E(V-I)/Aks=4.4

New IRSF work • Nishiyama et al. (2008): compare OGLE-II and IRSF for Udalski’s A region (l = 0, b = -2) • Aj/Av = 0.187 +- 0.009 • Similarly, Aj/Ai = 0.392 +- 0.004 • Gives Ri = Ai/E(V-I) = 0.91 +- 0.13 • Nice confirmation of Sumi’s result 0.930 +- 0.006 • Extrapolating to E(V-I)/Aks ? Not same region • If correct: Av/Aks=16.2 +- 0.8, E(V-I)/Aks = 8.5 +- 0.8

Isochrone fits • 2MASS images not deep enough • Needs IRSF images • Nishiyama uses (H-Ks)0 = 0.07 + his reddening law: • Aj=3.0 Aks, Ah=1.73 Aks • Example of OB08290: gives Aks=0.48 but bad fit • I get 0.42 with Aj=2.6 Aks and same Ah/Aks • Proves that reddening law depends on direction

Accurate Fitting of High Magnification PSPL Events

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