Aims: MASCARA and bRing are photometric surveys designed to detect
variability caused by exoplanets in stars with mV<8.4. Such variability
signals are typically small and require an accurate calibration algorithm,
tailored to the survey, in order to be detected. This paper presents the
methods developed to calibrate the raw photometry of the MASCARA and bRing
stations and characterizes the performance of the methods and instruments.
Methods: For the primary calibration a modified version of the coarse
decorrelation algorithm is used, which corrects for the extinction due to the
earth's atmosphere, the camera transmission, and intrapixel variations.
Residual trends are removed from the light curves of individual stars using
empirical secondary calibration methods. In order to optimize these methods, as
well as characterize the performance of the instruments, transit signals were
injected in the data. Results: After optimal calibration an RMS scatter of 10
mmag at mV∼7.5 is achieved in the light curves. By injecting transit
signals with periods between one and five days in the MASCARA data obtained by
the La Palma station over the course of one year, we demonstrate that MASCARA
La Palma is able to recover 84.0, 60.5 and 20.7% of signals with depths of 2, 1
and 0.5% respectively, with a strong dependency on the observed declination,
recovering 65.4% of all transit signals at δ>0∘ versus 35.8% at
δ<0∘. Using the full three years of data obtained by MASCARA La
Palma to date, similar recovery rates are extended to periods up to ten days.
We derive a preliminary occurrence rate for hot Jupiters around A-stars of >0.4%, knowing that many hot Jupiters are still overlooked. In the era of
TESS, MASCARA and bRing will provide an interesting synergy for finding
long-period (>13.5 days) transiting gas-giant planets around the brightest
stars.Comment: 18 pages, 17 figures, accepted for publication in A&