================================================================================
     Microlensing optical depth, event rate, and limits on compact objects
             in dark matter based on 20 years of OGLE observations
                         of the Small Magellanic Cloud

      P. Mroz, A. Udalski, M. K. Szymanski, I. Soszynski, P. Pietrukowicz,
  S. Kozlowski, R. Poleski, J. Skowron, D. Skowron, K. Ulaczyk, M. Gromadzki,
               K. Rybicki, P. Iwanek, M. Wrona, and M. Ratajczak

================================================================================

pmroz@astrouw.edu.pl

The directory structure is as follows:

README            - this file

table1.txt        - electronic version of Table 1 (OGLE-IV Fields Toward the
                    Small Magellanic Cloud)
                    
table2.txt        - electronic version of Table 2 (Error Bar Correction
                    Coefficients for the I-band Data)
                    
table4.txt        - electronic version of Table 4 (Detected Microlensing Events)

table6.dat        - electronic version of Table 6 (Number of Microlensing Source
                    Stars Observed in OGLE-IV Fields)

limits.dat        - 95% upper limits on the fraction of dark matter in the form
                    of primordial black holes and other compact objects

phot/             - calibrated I-band photometry of individual events
phot.tar.gz       - gzipped phot/ directory

eff_o3_o4/        - event detection efficiencies in individual fields observed
                    by OGLE-III and OGLE-IV
eff_o3_o4.tar.gz  - gzipped eff_o3_o4/ directory

eff_o4/           - event detection efficiencies in individual fields observed
                    by OGLE-IV only
eff_o4.tar.gz     - gzipped eff_o4/ directory

Format of the photometry files:
------------------------------------------------------------------------
 Bytes  Format Units   Description
------------------------------------------------------------------------
  1- 13 F13.5  HJD     Heliocentric Julian Date
 15- 20 F6.3   mag     I magnitude
 22- 26 F5.3   mag     Magnitude error
------------------------------------------------------------------------

The I-band photometry is calibrated to the standard system. The uncertainties 
were corrected as described in Section 2.3.

Format of the detection efficiency files:
------------------------------------------------------------------------
 Bytes  Format Units   Description
------------------------------------------------------------------------
  1-  4 F4.2   ---     Minimal log(t_E)
  6-  9 F4.2   ---     Maximal log(t_E)
 11- 18 F8.6   ---     Detection efficiency
------------------------------------------------------------------------