# microlensing-data-challenge/data-challenge-1

Data for the first WFIRST Microlensing Data Challenge
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event_info.txt
lc.tar.gz
wfirst_ephemeris_W149.txt
wfirst_ephemeris_Z087.txt

http://microlensing-source.org/data-challenge/

# Change log

17 August 2018: The event_info.txt file contained incorrect extinction and extinction dispersion values in both bands. The file has been updated and is now correct. Additionally, information about the color-surface brightness relation, which can be used to estimate source angular diameters, has been added to this readme below.

# Lightcurves

Lightcurves are zipped in lc.tar.gz - this will unzip to the directory lc/

Columns: BJD Magnitude Error

# Ephemeris files

There is one ephemeris file for each filter: wfirst_ephemeris_W149.txt and wfirst_ephemeris_Z087.txt. They store the position of WFIRST in the solar system at the times of the observations in each filter. Positions are in units of AU

Columns: BJD X_EQ Y_EQ Z_EQ X_ECL Y_ECL Z_ECL

X,Y,Z_EQ are cartesian coordinates in the J2000 equatorial frame with the solar system barycenter at (0,0,0)

X,Y,Z_ECL are cartesian coordinates in the ICRS ecliptic plane frame with the solar system barycenter at (0,0,0)

Both frames are right handed, the X axis is common to both and increases from the barycenter towards the vernal equinox, Z points towards the north celestial or ecliptic pole, respectively.

# Event Information

There are a few pieces of information that may need to be known for each event that are not in the lightcurve files. These are stored in event_info.txt

Columns: Event_name Event_number RA_(deg) Dec_(deg) Distance A_W149 sigma_A_W149 A_Z087 sigma_A_Z087

Distance, A_W149/Z087 are an estimate of the distance and extinction in each band of the red clump stars. sigma_A_W149/Z087 are dispersions in the extinction.

# Estimating angular diameters of sources

The angular diameter of the source can be estimated from the color-surface brightness relation for dereddened Z087-W149 color:

$\log \theta_{W149=0} = 0.986 + 0.366 (Z087-W149)_0$

where \theta_{W149=0} is the angular diameter at zero apparent W149 magnitude (measured in milli-arcsec) and (Z087-W149)_0 is the dereddened color. The angular diameter is related to the angular diameter at zero magnitude by

$\log \theta_{W149=0} = \log \theta + 0.2 W149_0$

where $\theta$ is the angular diameter (in mas) and $W149_0$ is the dereddened W149 magnitude. See Adams, Boyajian & von Braun (2018) for an overview of such relations, and Yoo et al. 2004 for an example of how they are used to estimate Einstein radii. The above relation is only valid for $-0.3<=(Z087-W149)0<0.6$, and can be assumed to have an intrinsic scatter about the relation of 0.034 in $\log \theta{W149=0}$.

# Problems?

If you spot any problems with the data set, please open an issue on this github repository, or contact Matthew Penny: penny@astronomy.ohio-state.edu as soon as possible.