Time filter

Source Type

Szombathely, Hungary

Shporer A.,California Institute of Technology | Shporer A.,Jet Propulsion Laboratory | O'Rourke J.G.,California Institute of Technology | Knutson H.A.,California Institute of Technology | And 15 more authors.
Astrophysical Journal | Year: 2014

Kepler-13Ab (= KOI-13.01) is a unique transiting hot Jupiter. It is one of very few known short-period planets orbiting a hot A-type star, making it one of the hottest planets currently known. The availability of Kepler data allows us to measure the planet's occultation (secondary eclipse) and phase curve in the optical, which we combine with occultations observed by warm Spitzer at 4.5 μm and 3.6 μm and a ground-based occultation observation in the Ks band (2.1 μm). We derive a day-side hemisphere temperature of 2750 ± 160 K as the effective temperature of a black body showing the same occultation depths. Comparing the occultation depths with one-dimensional planetary atmosphere models suggests the presence of an atmospheric temperature inversion. Our analysis shows evidence for a relatively high geometric albedo, A g = . While measured with a simplistic method, a high A g is supported also by the fact that the one-dimensional atmosphere models underestimate the occultation depth in the optical. We use stellar spectra to determine the dilution, in the four wide bands where occultation was measured, due to the visual stellar binary companion 1.″15 ± 0.″05 away. The revised stellar parameters measured using these spectra are combined with other measurements, leading to revised planetary mass and radius estimates of Mp = 4.94-8.09 M J and Rp = 1.406 ± 0.038 R J. Finally, we measure a Kepler midoccultation time that is 34.0 ± 6.9 s earlier than expected based on the midtransit time and the delay due to light-travel time and discuss possible scenarios. © 2014. The American Astronomical Society. All rights reserved.. Source

Molnar L.,Hungarian Academy of Sciences | Pal A.,Hungarian Academy of Sciences | Pal A.,Eotvos Lorand University | Plachy E.,Hungarian Academy of Sciences | And 7 more authors.
Astrophysical Journal | Year: 2015

We present the first observations of extragalactic pulsating stars in the K2 ecliptic survey of the Kepler space telescope. The variability of all three RR Lyrae stars in the dwarf spheroidal galaxy Leo IV was successfully detected, at a brightness of Kp ≈ 21.5 mag, from data collected during Campaign 1. We identified one modulated star and another likely Blazhko candidate with periods of 29.8 ± 0.9 days and more than 80 days, respectively. EPIC 210282473 represents the first star beyond the Magellanic Clouds for which the Blazhko period and cycle-to-cycle variations in the modulation were unambiguously measured. The photometric [Fe/H] indices of the stars agree with earlier results that Leo IV is a very metal-poor galaxy. Two out of the three stars blend with brighter background galaxies in the K2 frames. We demonstrate that image subtraction can be reliably used to extract photometry from faint confused sources, which will be crucial not only for the K2 mission but also for future space photometric missions. © 2015. The American Astronomical Society. All rights reserved.. Source

Pal A.,Hungarian Academy of Sciences | Pal A.,Eotvos Lorand University | Szabo R.,Hungarian Academy of Sciences | Szabo Gy.M.,Hungarian Academy of Sciences | And 8 more authors.
Astrophysical Journal Letters | Year: 2015

We present the first photometric observations of trans-Neptunian objects (TNOs) taken with the Kepler space telescope, obtained during the course of the K2 ecliptic survey. Two faint objects have been monitored in specifically designed pixel masks that were centered on the stationary points of the objects, when their daily motion was the slowest. In the design of the experiment, only the apparent path of these objects were retrieved from the detectors, i.e., the costs in terms of Kepler pixels were minimized. Because of the faintness of the targets, we employ specific reduction techniques and co-added images. We measure rotational periods and amplitudes in the unfiltered Kepler band as follows: for (278361) 2007 JJ43 and 2002 GV31, we get Prot = 12.097 hr and Prot = 29.2 hr with 0.10 and 0.35 mag for the total amplitudes, respectively. Future space missions, such as TESS and PLATO, are not well suited to this kind of observation. Therefore, we encourage including the brightest TNOs around their stationary points in each observing campaign to exploit this unique capability of the K2 Mission - and therefore to provide unbiased rotational, shape, and albedo characteristics of many objects. © 2015. The American Astronomical Society. All rights reserved. Source

Pal A.,Hungarian Academy of Sciences | Pal A.,Eotvos Lorand University | Kiss C.,Hungarian Academy of Sciences | Muller T.G.,Max Planck Institute for Extraterrestrial Physics | And 9 more authors.
Astronomical Journal | Year: 2016

We present the first comprehensive thermal and rotational analysis of the second most distant trans-Neptunian object (TNOs) (225088) 2007 OR10. We combined optical light curves provided by the Kepler Space Telescope-K2 extended mission and thermal infrared data provided by the Herschel Space Observatory. We found that (225088) 2007 OR10 is likely to be larger and darker than derived by earlier studies: we obtained a diameter of d = 1535+75 -225 kmwhich places (225088) 2007 OR10 in the biggest top three TNOs. The corresponding visual geometric albedo is Pv =0.089+0.031 -0.009. The light-curve analysis revealed a slow rotation rate of Prot = 44.81 0.37 hr, superseded by very few objects. The most likely light-curve solution is double-peaked with a slight asymmetry; however, we cannot safely rule out the possibility of having a rotation period of Prot = 22.40 0.18 hr, which corresponds to a single-peaked solution. Due to the size and slow rotation, the shape of the object should be a MacLaurin ellipsoid, so the light variation should be caused by surface inhomogeneities. Its newly derived larger diameter also implies larger surface gravity and a more likely retention of volatiles - CH4, CO, and N2 - on the surface. © 2016. The American Astronomical Society. All rights reserved. Source

Szabo G.M.,ELTE Gothard Astrophysical Observatory | Szabo G.M.,Hungarian Academy of Sciences | Szabo G.M.,Gothard Lendulet Research Team | Simon A.,Hungarian Academy of Sciences | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

Kepler-13b is a most intriguing exoplanet system due to the rapid precession rate, exhibiting several exotic phenomena.We analysed Kepler short cadence data up to Quarter 14, with a total time-span of 928 d, to reveal changes in transit duration, depth, asymmetry and identify the possible signals of stellar rotation and low-level activity.We investigated long-term variations of transit light curves testing for duration, peak depth and asymmetry. We also performed cluster analysis on Kepler quarters. We computed the autocorrelation function of the out-oftransit light variations. Transit duration, peak depth and asymmetry evolve slowly, due to the slowly drifting transit path through the stellar disc. The detected transit shapes will map the stellar surface on the time-scale of decades. We found a very significant clustering pattern with 3-orbit period. Its source is very probably the rotating stellar surface, in the 5:3 spin- orbit resonance reported in a previous study. The autocorrelation function of the out-of-transit light variations, filtered to 25.4 h and harmonics, shows slow variations and a peak around 300-360 d period, which could be related to the activity cycle of the host star. © 2013 The Authors. Source

Discover hidden collaborations