54613553
A search for transit timing variation
Photometric follow-ups of transiting exoplanets (TEPs) may lead to discoveries of additional, less massive bodies in extrasolar systems. This is possible by detecting and then analysing variations in transit timing of transiting exoplanets. In 2009 we launched an international observing campaign, the aim of which is to detect and characterise signals of transit timing variation (TTV) in selected TEPs. The programme is realised by collecting data from 0.6--2.2-m telescopes spread worldwide at different longitudes. We present our observing strategy and summarise first results for WASP-3b with evidence for a 15 Earth-mass perturber in an outer 2:1 orbital resonance.
14633680
Planetary transit observations at the University Observatory Jena: XO-1b and TrES-1
We report on observations of transit events of the transiting planets XO-1b and TrES-1 with a 25 cm telescope of the University Observatory Jena. With the transit timings for XO-1b from all 50 available XO, SuperWASP, Transit Light Curve (TLC)-Project- and Exoplanet Transit Database (ETD)-data, including our own I -band photometry obtained in March 2007, we find that the orbital period is P = (3.941501 ± 0.000001) d, a slight change by ∼3 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we present new R -band photometry of two transits of TrES-1. With the help of all available transit times from literature this allows us to refine the estimate of the orbital period: P = (3.0300722 ± 0.0000002) d. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
117014829
Homogeneous comparison of planet candidates imaged directly until 2008
We present a compilation of the planet candidates currently known from direct imaging. We have gathered available data from the literature and derived the luminosity of all candidates in a homogeneous way using a bolometric correction, the distances and the K band magnitudes of the objects. In a final step we find the masses of the candidates from a comparison of the luminosity or, if not available, an absolute brightness and several well known hot‐start evolutionary models.
118833354
Further deep imaging of HR 7329 A (η Tel A) and its brown dwarf companion B
About 4 arcsec south of the young A0-type star HR 7329, a faint companion candidate was found by Lowrance et al. Its spectral type of M7-8 is consistent with a young brown dwarf companion. Here we report 10 new astrometric imaging observations of the pair HR 7329 A and B, obtained with the Hubble Space Telescope and the Very Large Telescope, aimed at showing a common proper motion with high significance and possible orbital motion of B around A. With 11 yr of epoch difference between the first and our last image, we can reject the possibility by more than 21σ that B would be a non-moving background object unrelated to A. We detect no change in position angle and small or no change in separation (2.91 ± 2.41 mas yr−1), so that the orbit of HR 7329 B around A is inclined and/or eccentric and/or the orbital motion is currently only in the radial direction. If HR 7329 B is responsible for the outer radius of the debris disc around HR 7329 A being 24 au, and if HR 7329 B currently is at its apastron at 200 au (4.2 arcsec at 47.7 pc), we determine its pericentre distance to be 71 au, its semimajor axis to be 136 au, and its eccentricity to be e = 0.47. From the magnitude differences between HR 7329 A and B and the 2MASS magnitudes for the HR 7329 A+B system, we can estimate the magnitudes of HR 7329 B (J = 12.06 ± 0.19, H = 11.75 ±  0.10, Ks = 11.6 ± 0.1, L = 11.1 ± 0.2 mag) and then, with a few otherwise known parameters, its luminosity and mass (20–50 Jupiter masses). In the deepest images available, we did not detect any additional companion candidates up to ≤9 arcsec, but we determined the upper limits in the planetary mass regime.
55951771
Orbital motion of the young brown dwarf companion TWA 5 B
Context. It is difficult to determine masses and test formation models for brown dwarfs, because they are always above the main sequence, so that there is a degeneracy between mass and age. However, for brown dwarf companions to normal stars, such determinations may be possible, because one can know the distance and age of the primary star. As a result, brown dwarf companions are well-suited to testing formation theories and atmosphere models. Aims. With more adaptive optics images available, we aim at detecting orbital motion for the first time in the system TWA 5 A+B. Methods. We measured separation and position angle between TWA 5 A and B in each high-resolution image available and followed their change in time, because B should orbit around A. The astrometric measurement precision is about one milli arcsec. Results. With ten year difference in epoch, we can clearly detect orbital motion of B around A, a decrease in separation by ∼0.0054 �� per year and a decrease in position angle by ∼0.26 ◦ per year. Conclusions. TWA 5 B is a brown dwarf with ∼25 Jupiter masses (Neuhauser et al. 2000), but having large error bars (4 to 145 Jupiter masses, Neuhauser et al. 2009). Given its large projected separation from the primary star, ∼86 AU, and its young age (∼10 Myr), it has probably formed star-like, and would then be a brown dwarf companion. Given the relatively large changes in separation and position angle between TWA 5 A and B, we can conclude that they orbit around each other on an eccentric orbit. Some evidence is found for a curvature in the orbital motion of B around A – most consistent with an elliptic (e = 0.45) orbit. Residuals around the best-fit ellipse are detected and show a small-amplitude (∼18 mas) periodic sinusoid with ∼5.7 yr period, i.e., fully consistent with the orbit of the inner close pair TWA 5 Aa+b. Measuring these residuals caused by the photocenter wobble – even in unresolved images – can yield the total mass of the inner pair, so can test theoretical pre-main sequence models.
15482005
Variability of young stars: determination of rotational periods of weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region
We report on observation and determination of rotational periods of ten weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region. Observations were carried out with the Cassegrain-Teleskop-Kamera (CTK) at University Observatory Jena between 2007 June and 2008 May. The periods obtained range between 0.49 d and 5.7 d, typical for weak-line and post T Tauri stars (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
126009144
Participation of DESY-Zeuthen in the IceCube project