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XO-7b is a hot Jupiter transiting a V  = 10.52 mag G0V-type star. The planetary system is interesting because the linear slope in the discovery radial-velocity (RV) data indicated a wide-orbit massive companion. In 2020 we started an RV campaign for the system with the main scientific goal to follow-up this linear slope, and to put constraints on the orbital period of the companion. Furthermore, we aimed at refining the system parameters and we wanted to probe transit time variations (TTVs) of XO-7b in order to search for long-term dynamical signs of the companion of XO-7b in the observed-minus-calculated (O-C) data of mid-transit times. Apart from the discovery RVs, we obtained and analysed 20 follow-up RV observations and TESS photometric data. The previously observed significant linear RV slope was not confirmed with the follow-up RV data, where we detected only a marginal linear slope with the opposite trend. If the announced companion really exists, the most convincing explanation is that both RV data sets were collected near its quadrature position. Based on the RVs we estimated the minimum orbital period, which is P orb, min, 3 ≳ 7900 ± 1660 d, and the 'minimum' minimum mass of the companion, which is (M 3sin  i)min = 16.7 ± 3.5 MJup. We did not find significant evidence of the companion of XO-7b in the O-C data set of mid-transit times. We can again conclude that if the announced companion really exists, this is in agreement with previous results that distant companions of exoplanets are only known by RV solutions. [ABSTRACT FROM AUTHOR]

Kepler-13Ab (KOI-13) is an exoplanet orbiting a rapidly rotating A-type star. The system shows a significant spin–orbit misalignment and a changing transit duration most probably caused by the precession of the orbit. Here, we present a self-consistent analysis of the system combining Kepler and Transiting Exoplanet Survey Satellite (TESS) observations. We model the light curves assuming a planet transits a rotating oblate star that has a strong surface temperature gradient due to rotation-induced gravity darkening. The transit chord moves slowly as an emergent feature of orbital precession excited by the oblate star with a decline rate in the impact parameter of d b /d t  = −0.011 yr−1, and with an actual value of b  = 0.19 for the latest TESS measurements. The changing transit duration that was measured from Kepler Q2 and Q17 quarters and the TESS measurements indicates a linear drift of the impact parameter. The solutions for the stellar spin axis suggest a nearly orthogonal aspect, with inclination around 100°. [ABSTRACT FROM AUTHOR]

We present the discovery of a unique object, a chemically peculiar Ap-type star showing δ Scuti pulsations that is bound in an eclipsing binary system with an orbital period shorter than 3 d. HD 99458 is therefore a complex astrophysical laboratory opening doors for studying various, often contradictory, physical phenomena at the same time. It is the first Ap star ever discovered in an eclipsing binary. The orbital period of 2.722 d is the second shortest among all known chemically peculiar (CP2) binary stars. Pulsations of δ Scuti type are also extremely rare among CP2 stars and no unambiguously proven candidate has been reported. HD 99458 was formerly thought to be a star hosting an exoplanet, but we definitely reject this hypothesis using photometric observations from the K2 mission and new radial velocity measurements. The companion is a low-mass red dwarf star (M 2 = 0.45(2) M⊙) on an inclined orbit (i  = 73.2(6) deg) that shows only grazing eclipses. The rotation and orbital periods are synchronized, while the rotation and orbital axes are misaligned. HD 99458 is an interesting system deserving of more intense investigations. [ABSTRACT FROM AUTHOR]

Background A new off-the-shelf, low-cost echelle spectrograph was installed recently on the 0.6-m telescope at the Stará Lesná Observatory (Slovakia). In this paper, we describe in detail the radial velocity (RV) analysis of the first three transiting planetary systems, namely HAT-P-2, WASP-14, and XO-3, observed with this instrument. Materials and Methods First, we reduced and analyzed our RV observations. Subsequently, we compared our data with previously published RV data. We were curious about the precision of our measurements in comparison to that of the RV data achieved with echelle spectrographs of other sub-meter-, meter- and 2-m-class telescopes. Another question was the applicability of our RV data for modeling orbital parameters. For this purpose, the previously published data were analyzed in the same way as our RV data in order to determine and compare the parameters. Finally, we combined and analyzed all used RV data per object. Results The accuracy of our data is well comparable with the average RV scatter achieved with other sub-meter and meter-class telescopes. In comparison with 2-m-class telescopes, our instrumentation gives an RV scatter of about one order greater. On the other hand, our fit results show that RV data obtained with our instrumentation can be used to determine orbital parameters of these objects. Conclusion Based on our results, we can conclude that the spectrograph is a useful instrument for the study of objects with a relatively small RV amplitude. Resulting values are sufficient for exoplanet RV detections and spectroscopic follow-up measurements of massive exoplanets on close-in orbits. [ABSTRACT FROM AUTHOR]

We report results of the first five observing campaigns for the open stellar cluster NGC 7243 in the frame of project Young Exoplanet Transit Initiative (YETI). The project focuses on the monitoring of young and nearby stellar clusters, with the aim to detect young transiting exoplanets and to study other variability phenomena on time-scales from minutes to years. After five observing campaigns and additional observations during 2013 and 2014, a clear and repeating transit-like signal was detected in the light curve of J221550.6+495611. Furthermore, we detected and analysed 37 new eclipsing binary stars in the studied region. The best fit parameters and light curves of all systems are given. Finally, we detected and analysed 26 new, presumably pulsating variable stars in the studied region. The follow-up investigation of these objects, including spectroscopic measurements of the exoplanet candidate, is currently planned. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present a new observational campaign, Dwarf, aimed at detection of circumbinary extrasolar planets using the timing of the minima of low-mass eclipsing binaries. The observations will be performed within an extensive network of relatively small to medium-size telescopes with apertures of ∼20-200 cm. The starting sample of the objects to be monitored contains (i) low-mass eclipsing binaries with M and K components, (ii) short-period binaries with a sdB or sdO component, and (iii) post-common-envelope systems containing a WD, which enable to determine minima with high precision. Since the amplitude of the timing signal increases with the orbital period of an invisible third component, the timescale of the project is long, at least 5-10 years. The paper gives simple formulas to estimate the suitability of individual eclipsing binaries for the circumbinary planet detection. Intrinsic variability of the binaries (photospheric spots, flares, pulsation etc.) limiting the accuracy of the minima timing is also discussed. The manuscript also describes the best observing strategy and methods to detect cyclic timing variability in the minima times indicating the presence of circumbinary planets. First test observations of the selected targets are presented (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]