J/ApJ/812/136 OGLE-2013-BLG-446 photometry (Bachelet+, 2015)
Red noise versus planetary interpretations in the microlensing event
Ogle-2013-BLG-446.
Bachelet E., Bramich D.M., Han C., Greenhill J., Street R.A., Gould A.,
D'ago G., Alsubai K., Dominik M., Jaimes R.F., Horne K., Hundertmark M.,
Kains N., Snodgrass C., Steele I.A., Tsapras Y.,
(the Robonet collaboration), Albrow M.D., Batista V., Beaulieu J.-P.,
Bennett D.P., Brillant S., Caldwell J.A.R., Cassan A., Cole A.,
Coutures C., Dieters S., Dominis Prester D., Donatowicz J., Fouque P.,
Hill K., Marquette J.-B., Menzies J., Pere C., Ranc C., Wambsganss J.,
Warren D., (the Planet collaboration), Andrade De Almeida L., Choi J.-Y.,
Depoy D.L., Dong S., Hung L.-W., Hwang K.-H., Jablonski F., Jung Y.K.,
Kaspi S., Klein N., Lee C.-U., Maoz D., Munoz J.A., Nataf D., Park H.,
Pogge R.W., Polishook D., Shin I.-G., Shporer A., Yee J.C.,
(the µfun collaboration), Abe F., Bhattacharya A., Bond I.A.,
Botzler C.S., Freeman M., Fukui A., Itow Y., Koshimoto N., Ling C.H.,
Masuda K., Matsubara Y., Muraki Y., Ohnishi K., Philpott L.C.,
Rattenbury N., Saito TO., Sullivan D.J., Sumi T., Suzuki D., Tristram P.J.,
Yonehara A., (the Moa collaboration), Bozza V., Calchi Novati S.,
Ciceri S., Galianni P., Gu S.-H., Harpsoe K., Hinse T.C., Jorgensen U.G.,
Juncher D., Korhonen H., Mancini L., Melchiorre C., Popovas A.,
Postiglione A., Rabus M., Rahvar S., Schmidt R.W., Scarpetta G.,
Skottfelt J., Southworth J., Stabile A., Surdej J., Wang X.-B., Wertz O.,
(the Mindstep collaboration)
<Astrophys. J., 812, 136 (2015)>
=2015ApJ...812..136B 2015ApJ...812..136B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry
Keywords: gravitational lensing: micro - planetary systems -
techniques: photometric
Abstract:
For all exoplanet candidates, the reliability of a claimed detection
needs to be assessed through a careful study of systematic errors in
the data to minimize the false positives rate. We present a method to
investigate such systematics in microlensing data sets using the
microlensing event OGLE-2013-BLG-0446 as a case study. The event was
observed from multiple sites around the world and its high
magnification (Amax∼3000) allowed us to investigate the effects of
terrestrial and annual parallax. Real-time modeling of the event while
it was still ongoing suggested the presence of an extremely low-mass
companion (∼3M⊕) to the lensing star, leading to substantial
follow-up coverage of the light curve. We test and compare different
models for the light curve and conclude that the data do not favor the
planetary interpretation when systematic errors are taken into
account.
Description:
Microlensing event OGLE-2013-BLG-0446 (RA=18:06:56.18, DE=-31:39:27.2
(J2000.0); l=0.049°, b=-5.344°) was discovered on 2013 April 6
by the Optical Gravitational Lens Experiment (OGLE) Early Warning
System (Udalski, 2003AcA....53..291U 2003AcA....53..291U) and later alerted by the
Microlensing Observations in Astrophysics (MOA) (Bond et al.,
2001MNRAS.327..868B 2001MNRAS.327..868B). Observations obtained on the rising part of the
light curve indicated that this event could be highly magnified and
might therefore be highly sensitive to planets (Griest & Safizadeh,
1998ApJ...500...37G 1998ApJ...500...37G; Gould et al., 2009, 0910.1832; Yee et al.,
2009ApJ...703.2082Y 2009ApJ...703.2082Y). Follow-up teams, such as µFUN (Gould et al.,
2006ApJ...644L..37G 2006ApJ...644L..37G), PLANET (Beaulieu et al., 2006Natur.439..437B 2006Natur.439..437B),
RoboNet (Tsapras et al., 2009AN....330....4T 2009AN....330....4T), and MiNDSTEp (Dominik
et al., 2008AN....329..248D 2008AN....329..248D), then began observations a few days
before the peak of the event. The peak magnification was ∼3000 and the
peak was densely sampled from different observatories.
The various teams used difference image analysis (DIA) to obtain
photometry: µFUN used pySIS (Albrow et al., 2009MNRAS.397.2099A 2009MNRAS.397.2099A),
with the exception of the Auckland data, which were re-reduced using
DanDIA (Bramich, 2008MNRAS.386L..77B 2008MNRAS.386L..77B; Bramich et al.,
2013MNRAS.428.2275B 2013MNRAS.428.2275B). DanDIA was also used to reduce the RoboNet and
the Danish data sets. PLANET data were reduced online with the WISIS
pipeline, and final data sets were prepared using pySIS.61 OGLE
(Udalski & Szymanski, 2015AcA....65....1U 2015AcA....65....1U) and MOA (Bond et al.,
2001MNRAS.327..868B 2001MNRAS.327..868B) used their own DIA code to reduce their frames.
All other data sets were reduced using pySIS.
A total of 2955 data points from 16 telescopes were used for our
analysis, after problematic data points were masked.
Objects:
----------------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------------
18 06 56.18 -31 39 27.2 OGLE-2013-BLG-446 = EWS 2013-BLG-446
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
photom.dat 42 2955 *Raw photometry
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Note on photom.dat: Data provided are "raw", meaning before error bar rescaling
and systematics corrections (see the publication for more details).
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Byte-by-byte Description of file: photom.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Tel Telescope and filter (TEL_FILT) (1)
12- 17 A6 --- Filt Filter (2)
19- 28 F10.5 d HJD Heliocentric Julian date (HJD-2450000)
30- 35 F6.3 mag mag Magnitude in Filter (3)
37- 42 F6.3 mag e_mag rms uncertainty on mag (3)
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Note (1): List of Telescope and filter:
Auckland_R,
CPTA_i,
CTIO_I and CTIO_V,
Canopus_I,
Danish_z,
LSCA_i and LSCB_i,
MOA_Red,
OGLE_I and OGLE_V,
Possum_N,
SAAO_I,
Salerno_I,
Turitea_R,
Weizmann_I
Note (2): List of filter names:
I = I-band CTIO, Canopus, OGLE, SAAO, Salerno and Weizmann
V = V-band CTIO, OGLE
N = N-band Possum
R = R-band Turitea
Red = Red-band MOA
i+z = i+z-band Danish
SDSS-i = i-band CPTA, LSCA and LSCB
Note (3): The magnitude reported are instrumental, only OGLE photometry is
calibrated (please consult OGLE publications for more details).
Errors on magnitude below 0.001 were artificially set to 0.001.
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Acknowledgements:
Etienne Bachelet, etibachelet(at)gmail.com
(End) Patricia Vannier [CDS] 17-Dec-2015