In this paper we present three new extrasolar planets from the Qatar Exoplanet Survey. Qatar-8b is a hot Saturn, with MP = 0.37 MJ and RP = 1.3 RJ, orbiting a solar-like star every Porb = 3.7 days. Qatar-9b is a hot Jupiter with a mass of MP = 1.2 MJ and a radius of RP = 1 RJ, in an orbit of Porb = 1.5 days around a low mass, M⋆ = 0.7 M⊙, mid-K main-sequence star. Finally, Qatar-10b is a hot, Teq ∼ 2000 K, sub-Jupiter mass planet, MP = 0.7 MJ, with a radius of RP = 1.54 RJ and an orbital period of Porb = 1.6 days, placing it on the edge of the sub-Jupiter desert.

We present the discovery of Qatar-7b-a very hot and inflated giant gas planet orbiting close to its parent star. The host star is a relatively massive main-sequence F-star with mass and radius M-* = 1.41 +/- 0.03 M-circle dot and R-* = 1.56 +/- 0.02 R-circle dot respectively, at a distance d = 726 +/- 26 pc, and an estimated age similar to 1 Gyr. With its orbital period of P = 2.032 days, the planet is located less than five stellar radii from its host star and is heated to a high temperature T-eq 2100 K. From a global solution to the available photometric and radial velocity observations, we calculate the mass and radius of the planet to be M-P = 1.88 +/- 0.25 M-J and R-P = 1.70 +/- 0.03 R-J, respectively. The planet radius and equilibrium temperature put Qatar-7b in the top 6% of the hottest and largest known exoplanets. With its large radius and high temperature, Qatar-7b is a valuable addition to the short list of targets that offer the best opportunity for studying their atmospheres through transmission spectroscopy.

We report the discovery of Qatar-6b, a new transiting planet identified by the Qatar Exoplanet Survey (QES). The planet orbits a relatively bright (V=11.44), early-K main-sequence star at an orbital period of P ∼ 3.506 days. An SED fit to available multi-band photometry, ranging from the near-UV to the mid-IR, yields a distance of d = 101 ± 6 pc to the system. From a global fit to follow-up photometric and spectroscopic observations, we calculate the mass and radius of the planet to be MP = 0.67±0.07 MJ and RP = 1.06±0.07 RJ respectively. We use multi-color photometric light curves to show that the transit is grazing, making Qatar-6b one of the few exoplanets known in a grazing transit configuration. It adds to the short list of targets that offer the best opportunity to look for additional bodies in the host planetary system through variations in the transit impact factor and duration.

We present TSARDI, an efficient rejection algorithm designed to improve the transit detection efficiency in data collected by large scale surveys. TSARDI is based on the Machine Learning clustering algorithm DBSCAN, and its purpose is to serve as a robust and adaptable filter aiming to identify unwanted noise points left over from data detrending processes. TSARDI is an unsupervised method, which can treat each light curve individually; there is no need of previous knowledge of any other field light curves. We conduct a simulated transit search by injecting planets on real data obtained by the QES project and show that TSARDI leads to an overall transit detection efficiency increase of $\sim$11\%, compared to results obtained from the same sample, but using a standard sigma-clip algorithm. For the brighter end of our sample (host star magnitude < 12), TSARDI achieves a detection efficiency of $\sim$80\% of injected planets. While our algorithm has been developed primarily for the field of exoplanets, it is easily adaptable and extendable for use in any time series.

We report the discovery of Qatar-3b, Qatar-4b, and Qatar-5b, three new transiting planets identified by the Qatar Exoplanet Survey (QES). The three planets belong to the hot Jupiter family, with orbital periods of $P_{Q3b}$=2.50792 days, $P_{Q4b}$=1.80539 days, and $P_{Q5b}$=2.87923 days. Follow-up spectroscopic observations reveal the masses of the planets to be $M_{Q3b}$=4.31$\pm0.47$ $M_{\rm J}$, $M_{Q4b}$=6.10$ \pm0.54$ $M_{\rm J}$, and $M_{Q5b}$ = 4.32$ \pm0.18$ $M_{\rm J}$, while model fits to the transit light curves yield radii of $R_{Q3b}$ = 1.096$ \pm0.14$ $R_{\rm J}$, $R_{Q4b}$ = 1.135$ \pm0.11$ $R_{\rm J}$, and $R_{Q5b}$ = 1.107$ \pm0.064$ $R_{\rm J}$. The host stars are low-mass main sequence stars with masses and radii $M_{Q3}$ = 1.145$ \pm0.064$ $M_{\odot}$, $M_{Q4}$ = 0.896$ \pm0.048$ $M_{\odot}$, $M_{Q5}$ = 1.128$ \pm0.056$ $M_{\odot}$ and $R_{Q3}$ = 1.272$ \pm0.14$ $R_{\odot}$, $R_{Q4}$ = 0.849$\pm0.063$ $R_{\odot}$ and $R_{Q5}$ = 1.076$\pm0.051$ $R_{\odot}$ for Qatar-3, 4 and 5 respectively. The V magnitudes of the three host stars are $V_{Q3}$=12.88, $V_{Q4}$=13.60, and $V_{Q5}$=12.82. All three new planets can be classified as heavy hot Jupiters (M > 4 $M_{J}$).

We present DOHA, a new algorithm for cotrending photometric light curves obtained by transiting exoplanet surveys. The algorithm employs a novel approach to the traditional "differential photometry" technique, by selecting the most suitable comparison star for each target light curve, using a two-step correlation search. Extensive tests on real data reveal that DOHA corrects both intra-night variations and long-term systematics affecting the data. Statistical studies conducted on a sample of 9500 light curves from the Qatar Exoplanet Survey reveal that DOHA-corrected light curves show an RMS improvement of a factor of 2, compared to the raw light curves. In addition, we show that the transit detection probability in our sample can increase considerably, even up to a factor of 7, after applying DOHA.

We present the Signal Detection using Random-Forest Algorithm (SIDRA). SIDRA is a detection and classification algorithm based on the Machine Learning technique (Random Forest). The goal of this paper is to show the power of SIDRA for quick and accurate signal detection and classification. We first diagnose the power of the method with simulated light curves and try it on a subset of the Kepler space mission catalogue. We use five classes of simulated light curves (CONSTANT, TRANSIT, VARIABLE, MLENS and EB for constant light curves, transiting exoplanet, variable, microlensing events and eclipsing binaries, respectively) to analyse the power of the method. The algorithm uses four features in order to classify the light curves. The training sample contains 5000 light curves (1000 from each class) and 50 000 random light curves for testing. The total SIDRA success ratio is >= 90 per cent. Furthermore, the success ratio reaches 95-100 per cent for the CONSTANT, VARIABLE, EB and MLENS classes and 92 per cent for the TRANSIT class with a decision probability of 60 per cent. Because the TRANSIT class is the one which fails the most, we run a simultaneous fit using SIDRA and a Box Least Square (BLS)-based algorithm for searching for transiting exoplanets. As a result, our algorithm detects 7.5 per cent more planets than a classic BLS algorithm, with better results for lower signal-to-noise light curves. SIDRA succeeds to catch 98 per cent of the planet candidates in the Kepler sample and fails for 7 per cent of the false alarms subset. SIDRA promises to be useful for developing a detection algorithm and/or classifier for large photometric surveys such as TESS and PLATO exoplanet future space missions.

We present a selection of methods for automatically constructing an optimal kernel model for difference image analysis which require very few external parameters to control the kernel design. Each method consists of two components; namely, a kernel design algorithm to generate a set of candidate kernel models, and a model selection criterion to select the simplest kernel model from the candidate models that provides a sufficiently good fit to the target image. We restricted our attention to the case of solving for a spatially invariant convolution kernel composed of delta basis functions, and we considered 19 different kernel solution methods including six employing kernel regularization. We tested these kernel solution methods by performing a comprehensive set of image simulations and investigating how their performance in terms of model error, fit quality, and photometric accuracy depends on the properties of the reference and target images. We find that the irregular kernel design algorithm employing unregularized delta basis functions, combined with either the Akaike or Takeuchi information criterion, is the best kernel solution method in terms of photometric accuracy. Our results are validated by tests performed on two independent sets of real data. Finally, we provide some important recommendations for software implementations of difference image analysis.

Context. Understanding the source of systematic errors in photometry is essential for their calibration.Aims. We investigate how photometry performed on difference images can be influenced by errors in the photometric scale factor.Methods. We explore the equations for difference image analysis (DIA), and we derive an expression describing how errors in the difference flux, the photometric scale factor and the reference flux are propagated to the object photometry.Results. We find that the error in the photometric scale factor is important, and while a few studies have shown that it can be at a significant level, it is currently neglected by the vast majority of photometric surveys employing DIA.Conclusions. Minimising the error in the photometric scale factor, or compensating for it in a post-calibration model, is crucial for reducing the systematic errors in DIA photometry.

We present an analysis of the Qatar-1 and TrES-5 transiting exoplanetary systems, which contain Jupiter-like planets on short-period orbits around K-dwarf stars.Our data comprise a total of 20 transit light curves obtained using five medium-class telescopes, operated using the defocussing technique.The average precision we reach in all our data is RMS Q = 1.1 mmag for Qatar-1 (V = 12.8) and RMS T = 1.0 mmag for TrES-5 (V = 13.7).We use these data to refine the orbital ephemeris, photometric parameters, and measured physical properties of the two systems.One transit event for each object was observed simultaneously in three passbands (gri) using the BUSCA imager.The QES survey light curve of Qatar-1 has a clear sinusoidal variation on a period of P ⋆ = 23.697± 0.123 d, implying significant starspot activity.We searched for starspot crossing events in our light curves, but did not find clear evidence in any of the new datasets.The planet in the Qatar-1 system did not transit the active latitudes on the surfaces of its host star.Under the assumption that P ⋆ corresponds to the rotation period of Qatar-1 A, the rotational velocity of this star is very close to the v sin i ⋆ value found from observations of the Rossiter-McLaughlin effect.The low projected orbital obliquity found in this system thus implies a low absolute orbital obliquity, which is also a necessary condition for the transit chord of the planet to avoid active latitudes on the stellar surface.

We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (Mp=1.12MJ, Rp=1.363RJ) orbiting a K2V star, which has a possible gravitationally-bound M-dwarf companion at 0.6 arcsec separation contributing 20 percent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just 40 Myr, assuming a tidal dissipation quality factor of Q'*=10^6. Q'* is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of T_shift 17 seconds after 15 years assuming Q'*=10^6. A shift less than this would place a direct observational constraint on the lower limit of Q'* in this system. We also report a correction to the previously published expected T_shift for WASP-18 b, finding that T_shift=356 seconds after 10 years for Q'*=10^6, which is much larger than the estimated 28 seconds quoted in WASP-18 b discovery paper. We attempted to constrain Q'* via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straight-forward constraints on Q'* will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.

We present a theoretical analysis of the optical light curves (LCs) for short-period high-mass transiting extrasolar planet systems. Our method considers the primary transit, the secondary eclipse, and the overall phase shape of the LC between the occultations. Phase variations arise from (i) reflected and thermally emitted light by the planet, (ii) the ellipsoidal shape of the star due to the gravitational pull of the planet, and (iii) the Doppler shift of the stellar light as the star orbits the center of mass of the system. Our full model of the out-of-eclipse variations contains information about the planetary mass, orbital eccentric- ity, the orientation of periastron and the planet's albedo. For a range of hypothetical systems we demonstrate that the ellipsoidal variations (ii.) can be large enough to be distinguished from the remaining components and that this effect can be used to constrain the planet's mass. As an example we presend KOI-13b (candi- date exoplanet system) included in the September 2011 Kepler data release. The Kepler light curve shows both primary and secondary eclipses, as well as significant out-of-eclipse light curve variations. We model the relative contributions from (i) thermal emission from the companion, (ii) planetary reflected light, (iii) doppler beaming, and (iv) ellipsoidal variations in the host-star arising from the tidal distortion of the host star by its companion. Our analysis, based on the light curve alone, enables us to constrain the mass of the KOI-13.01 companion to be MC = 8.3 ± 1.25 MJ and thus demonstrates that the transiting companion is a planet. The teqnique is useful for current and future space missions such as Kepler and PLATO.

Star formation theory predicts that short-period M-dwarf binaries with highly unequal-mass components are rare. First, the mass ratio of close binary systems is driven to unity due to the secondary preferentially accreting gas with high angular momentum. Secondly, both dynamical decay of multiple systems and interactions with tertiary stars that tighten the binary orbit will eject the lowest mass member. Generally, only the two most massive stars are paired after such interactions, and the frequency of tight unequal-mass binaries is expected to decrease steeply with primary mass. In this paper, we present the discovery of a highly unequal mass eclipsing M-dwarf binary, providing a unique constraint on binary star formation theory and on evolutionary models for low-mass binary stars. The binary is discovered using high-precision infrared light curves from the United Kingdom Infrared Telescope (UKIRT) Wide Field Camera (WFCAM) Transit Survey and has an orbital period of 2.44 d. We find stellar masses of M-1 = 0.53(+/- 0.02) M-circle dot and M-2 = 0.143(+/- 0.006) M-circle dot (mass ratio 0.27), and radii of R-1 = 0.51(+/- 0.01) R-circle dot and R-2 = 0.174(+/- 0.006) R-circle dot. This puts the companion in a very sparsely sampled and important late M-dwarf mass regime. Since both stars will share the same age and metallicity and straddle the theoretical boundary between fully and partially convective stellar interiors, a comparison can be made to model predictions over a large range of M-dwarf masses using the same model isochrone. Both stars appear to have a slightly inflated radius compared to 1 Gyr' model predictions for their masses, but future work is needed to properly account for the effects of star spots on the light-curve solution. A significant, subsynchronous, similar to 2.56 d signal with similar to 2 per cent peak-to-peak amplitude is detected in the WFCAM light curve, which we attribute to rotational modulation of cool star spots. We propose that the subsynchronous rotation is either due to a stable star-spot complex at high latitude on the (magnetically active) primary (i.e. differential rotation), or additional magnetic braking, or interaction of the binary with a third body or circumbinary disc during its pre-main-sequence phase.

We report the discovery of 16 detached M-dwarf eclipsing binaries with J < 16 mag and provide a detailed characterisation of three of them, using high-precision infrared light curves from the WFCAM Transit Survey (WTS). Such systems provide the most accurate and model-independent method for measuring the fundamental parameters of these poorly understood yet numerous stars, which currently lack sufficient observations to precisely calibrate stellar evolution models. We fully solve for the masses and radii of three of the systems, finding orbital periods in the range 1.5 < P < 4.9 days, with masses spanning 0.35 0.50M⊙ and radii between 0.38 0.50R⊙, with uncertainties of � 3.5 6.4% in mass and � 2.7 5.5% in radius. Close-companions in short-period binaries are expected to be tidally-locked into fast rotational velocities, resulting in high levels of magnetic activity. This is predicted to inflate their radii by inhibiting convective flow and increasing star spot coverage. The radii of the WTS systems are inflated above model predictions by � 3 12%, in agreement with the observed trend, despite an expected lower systematic contribution from star spots signals at infrared wavelengths. We searched for correlation between the orbital period and radius inflation by combining our results with all existing M-dwarf radius measurements of comparable precision, but we found no statistically significant evidence for a decrease in radius inflation for longer period, less active systems. Radius inflation continues to exists in non-synchronised systems indicating that the problem remains even for very low activity M-dwarfs. Resolving this issue is vital not only for understanding the most populous stars in the Universe, but also for characterising their planetary companions, which hold the best prospects for finding Earth-like planets in the traditional habitable zone.

We report on the current status of the Holomon Variable Star and Exoplanets Survey. Two northern (Lacerta and Andromeda) FOVs approximately 3.5×2.5 deg were observed in July 2009 (trial session) and August 2010. Based on simulations on the basis of the Tycho catalogue both fields have a better than 75% probability for detection of at least one transiting hot Jupiter. The observations were analysed with an upgraded version of ThReT pipeline, using new cutting edge algorithms for de-trending and detection. We present the basic parameters of thirty six new (lacking bibliographic reference) variable stars. 1 Target field selection and observations method We used a hot Jupiter detection probability map [1] in order to select the most promising areas on the sky. For the testing phase we observed one of these areas at Lacerta (Ra: 22 53 40 Dec: +44 44 55) and for the first run a target field in Andromeda (Ra: 00 08 00 Dec: +33 30 00). We used 60 sec exposures with no filter in order to be able to detect, with good signal to noise ratio, stars with magnitude range between 12 and 15 mag . After the analysis of the testing phase data, we decided that it would be better to use a Bessel R filter for the measurements. In order to remain in the same star magnitude range, in the first run, 120 sec exposures were taken. Also to achieve good time resolution we used 2×2 binning so the download time was 60 sec. The time between two exposures was 180 sec. The observations were undertaken between Jul 22, 2010 and Aug 10, 2010. The weather conditions were good and the average seeing was calculated about 0.72 arcsec. The observations started at 00:00 U.T. and ended at 04:30 U.T.. As a result we have 690 image frames with ∼ 7500 stars and photometric precision less than 1% for the 10% of the sample (Fig.1c&d). 2 Data analysis The data from the testing phase were analysed with the ThReT v0.5 pipeline [2]. After the de-trending of the time series with the application of the TFA algorith [3], selection criteria were implemented in order to flag potential variable stars, namely j-index [4] above 0.6 and pulsation parameter [5] above 2.5. Figure 1(a&b) corresponds to two subgroups of 3.5σ and 7σ deviation for j-index and pulsation parameter values respectively. In order to overcome some problems in data analysis the ThReT pipeline was upgraded to v1.0. It consists of fifteen c-shell and python scripts in order to perform bias and dark current correction along with flat-fielding. The photometric astrometry phase utilises the Daophot and Extractor packages within Starlink. The very large FoV of the observation images involves a variety of trends which are the result of the atmospheric turbulence or inhomogeneous illumination of the celestial sphere. Therefore we need a sensitive and reliable de-trending method in order to detect transit-like signals and variable stars. The pipeline uses a fast de-trend algorithm, which was developed by us, in order to determine some statistics about the data i.e. the rms vs magnitude of the light curves. Such