TESS observations of KIC 7739728 - a new FK Com type star candidate

Ранее по данным наблюдений с космическим телескопом “Kepler” нами было показано, что по своим параметрам KIC 7739728 близка к звездам типа FK Com и может рассматриваться, как потенциальный кандидат для включения в число объектов этого типа. В настоящей работе мы провели анализ всех имеющихся для KIC 7739728 данных в архиве миссии TESS (14 и 26 сектора наблюдений). Показано, что кривая блеска этой звезды ярко проявляет свойства регулярной вращательной модуляции и что в период времени между 14 и 26 секторами произошло явление переключения положений долгот активных областей на поверхности звезды (флип-флоп). Рассматриваются аргументы в пользу возможной принадлежности KIC 7739728 к объектам типа FK Com. Using the observations with the Kepler space telescope we found that parameters of KIC 7739728 are close to that ones of the FK Com type stars and that the object can be considered as a potential candidate for inclusion in the number of objects of this type. In this paper we analysed all available data for KIC 7739728 in the TESS mission archive (14 and 26 sectors). It is shown that the light curve of this star clearly exhibits the properties of regular rotational modulation and that in the time interval between 14 and 26 sectors the phenomenon of switching the positions of the longitudes of the active regions on the surface of the star (flip-flop) occurred. The arguments in favour of the possible relation of KIC 7739728 to objects of the FK Com type are considered.

The roAp Stars Observed by the Kepler Space Telescope

Before the launch of the Kepler Space Telescope, most studies of the rapidly oscillating Ap (roAp) stars were conducted with ground-based photometric B observations, supplemented with high-resolution time-resolved spectroscopy and some space observations with the WIRE, MOST, and BRITE satellites. These modes of observation often only provided information on a single star at a time, however, Kepler provided the opportunity to observe hundreds of thousands of stars simultaneously. Over the duration of the primary 4 year Kepler mission, and its 4 year reconfigured K2 mission, the telescope observed at least 14 new and known roAp stars. This paper provides a summary the results of these observations, including a first look at the entire data sets, and provides a look forward to NASA's TESS mission.

Exomoon candidates from transit timing variations: eightKeplersystems with TTVs explainable by photometrically unseen exomoons

ABSTRACT If a transiting exoplanet has a moon, that moon could be detected directly from the transit it produces itself, or indirectly via the transit timing variations (TTVs) it produces in its parent planet. There is a range of parameter space where the Kepler Space Telescope is sensitive to the TTVs exomoons might produce, though the moons themselves would be too small to detect photometrically via their own transits. The Earth’s Moon, for example, produces TTVs of 2.6 min amplitude by causing our planet to move around their mutual centre of mass. This is more than Kepler’s short-cadence interval of 1 min and so nominally detectable (if transit timings can be measured with comparable accuracy), even though the Moon’s transit signature is only 7 per cent that of Earth’s, well below Kepler’s nominal photometric threshold. Here, we examine several Kepler systems, exploring the hypothesis that an exomoon could be detected solely from the TTVs it induces on its host planet. We compare this with the alternate hypothesis that the TTVs are caused by an non-transiting planet in the system. We examine 13 Kepler systems and find 8 where both hypotheses explain the observed TTVs equally well. Though no definitive exomoon detection can be claimed on this basis, the observations are nevertheless completely consistent with a dynamically stable moon small enough to fall below Kepler’s photometric threshold for transit detection, and these systems warrant further observation and analysis.

K2: Background Survey – the search for undiscovered transients in Kepler/K2 data

ABSTRACT The K2 mission of the Kepler Space Telescope offers a unique possibility to examine sources of both Galactic and extragalactic origin with high-cadence photometry. Alongside the multitude of supernovae and quasars detected within targeted galaxies, it is likely that Kepler has serendipitously observed many transients throughout K2. Such events will likely have occurred in background pixels, coincidentally surrounding science targets. Analysing the background pixels presents the possibility to conduct a high-cadence survey with areas of a few square degrees per campaign. We demonstrate the capacity to independently recover key K2 transients such as KSN 2015K and SN 2018oh. With this survey, we expect to detect numerous transients and determine the first comprehensive rates for transients with lifetimes of ≤1 d.

The Sun is less active than other solar-like stars

The magnetic activity of the Sun and other stars causes their brightness to vary. We investigated how typical the Sun’s variability is compared with other solar-like stars, i.e., those with near-solar effective temperatures and rotation periods. By combining 4 years of photometric observations from the Kepler space telescope with astrometric data from the Gaia spacecraft, we were able to measure photometric variabilities of 369 solar-like stars. Most of those with well-determined rotation periods showed higher variability than the Sun and are therefore considerably more active. These stars appear nearly identical to the Sun except for their higher variability. Therefore, we speculate that the Sun could potentially also go through epochs of such high variability.

Raise Your Glasses to the Skies!

Many exoplanets have been discovered in recent years by searching for regular dips in brightness of a star as a planet passes across its face. NASA’s Kepler Space Telescope was launched to search for exoplanets using this planetary transit method. Kepler monitors 145,000 stars and has so far discovered over 2500 exoplanets. The planetary transit method has also been used to find a family of seven planets around a nearby red dwarf star that has been named TRAPPIST-1.

The Kepler Revolution

The Kepler Space Telescope will soon run out of fuel and end its mission. Here are nine fundamental discoveries about planets aided by Kepler in the 9 years since its launch.

Transit analysis of the exoplanet host Kepler-485

In this study, we present solutions of the transit light curves of the recently discovered exoplanet Kepler-485b observed by the Kepler space telescope. To obtain stellar, planetary, and orbital properties, WINFITTER code was applied to transit light curve data, which are available at the NASA Exoplanet Archive (NEA).