MDia and POTS - The Munich Difference Imaging Analysis for the pre-OmegaTranS Project

We describe the Munich Difference Imaging Analysis pipeline that we developed and implemented in the framework of the Astro-WISE package to automatically measure high precision light curves of a large number of stellar objects using the difference imaging approach. Combined with programs to detect time variability, this software can be used to search for planetary systems or binary stars with the transit method and for variable stars of different kinds. As a first scientific application, we discuss the data reduction and analysis performed with Astro-WISE on the pre-OmegaTranS data set, that we collected during a monitoring campaign of a dense stellar field with the Wide Field Imager at the ESO 2.2m telescope.Comment: 10 pages, 5 figures, accepted for publication in topical issue of Experimental Astronomy on Astro-WISE information syste

Microlensing events from the 11-year observations of the Wendelstein Calar Alto Pixellensing Project

We present the results of the decade-long M31 observation from the Wendelstein Calar Alto Pixellensing Project (WeCAPP). WeCAPP has monitored M31 from 1997 till 2008 in both R- and I-filters, thus provides the longest baseline of all M31 microlensing surveys. The data are analyzed with the difference imaging analysis, which is most suitable to study variability in crowded stellar fields. We extracted light curves based on each pixel, and devised selection criteria that are optimized to identify microlensing events. This leads to 10 new events, and sums up to a total of 12 microlensing events from WeCAPP, for which we derive their timescales, flux excesses, and colors from their light curves. The color of the lensed stars fall between (R-I) = 0.56 to 1.36, with a median of 1.0 mag, in agreement with our expectation that the sources are most likely bright, red stars at post main-sequence stage. The event FWHM timescales range from 0.5 to 14 days, with a median of 3 days, in good agreement with predictions based on the model of Riffeser et al. (2006).Comment: 44 pages, 16 figures, 5 tables. ApJ accepte

Bias-Free Shear Estimation using Artificial Neural Networks

Bias due to imperfect shear calibration is the biggest obstacle when constraints on cosmological parameters are to be extracted from large area weak lensing surveys such as Pan-STARRS-3pi, DES or future satellite missions like Euclid. We demonstrate that bias present in existing shear measurement pipelines (e.g. KSB) can be almost entirely removed by means of neural networks. In this way, bias correction can depend on the properties of the individual galaxy instead on being a single global value. We present a procedure to train neural networks for shear estimation and apply this to subsets of simulated GREAT08 RealNoise data. We also show that circularization of the PSF before measuring the shear reduces the scatter related to the PSF anisotropy correction and thus leads to improved measurements, particularly on low and medium signal-to-noise data. Our results are competitive with the best performers in the GREAT08 competition, especially for the medium and higher signal-to-noise sets. Expressed in terms of the quality parameter defined by GREAT08 we achieve a Q = 40, 140 and 1300 without and 50, 200 and 1300 with circularization for low, medium and high signal-to-noise data sets, respectively.Comment: 19 pages, 8 figures; accepted for publication in Ap

Avoiding the Hermit\u27s Way of Distance Learning: Augmenting Individual Learning With Synchronous Internet Based Seminars

Taking part in professional education is increasingly difficult for highly-skilled employees and executives because they cannot afford to be away from work for the time traditional face-to-face seminars demand. Individual, selfguided learning, on the other hand, lacks the benefits of direct interaction with people interested in the same subject. This calls for a combination of individual and collaborative learning in a virtual setting that preserves the flexibility of individual learning but augments it with virtual seminars that do not necessitate leaving work or travelling for extended periods. In this paper, we present a software environment for such virtual seminars built on widely available technology that provides tools to create a shared context of interaction among the participants and that enables a tutor to structure and facilitate virtual cooperation for learning. This environment was put into practice in an pilot course. Based on this evaluation we survey the fit of the software design for these situations of synchronous, dispersed group work. We particularly explore the role of a tutor or facilitator for successful virtual communication and cooperation. Furthermore, we present first insights into whether virtual seminars could help to improve isolated individual learning through a certain amount of scheduled events and motivating interaction with others. Finally, we describe the information systems community as an ideal test bed for such innovative ways of learning that could help to give IS research a greater bearing on the practice of the field

M31 PAndromeda Cepheid sample observed in four HST bands

Using the M31 PAndromeda Cepheid sample and the HST PHAT data we obtain the largest Cepheid sample in M31 with HST data in four bands. For our analysis we consider three samples: A very homogeneous sample of Cepheids based on the PAndromeda data, the mean magnitude corrected PAndromeda sample and a sample complementing the PAndromeda sample with Cepheids from literature. The latter results in the largest catalog with 522 fundamental mode (FM) Cepheids and 102 first overtone (FO) Cepheids with F160W and F110W data and 559 FM Cepheids and 111 FO Cepheids with F814W and F475W data. The obtained dispersion of the Period-Luminosity relations (PLRs) is very small (e.g. 0.138 mag in the F160W sample I PLR). We find no broken slope in the PLRs when analyzing our entire sample, but we do identify a subsample of Cepheids that causes the broken slope. However, this effect only shows when the number of this Cepheid type makes up a significant fraction of the total sample. We also analyze the sample selection effect on the Hubble constant.Comment: 32 pages, 19 figures, 9 tables, accepted for publication in ApJ, electronic data will be available on CD

Multiband Transit Light Curve Modeling of WASP-4

We report on the simultaneous g′,r′,i′,z′ multiband, high time sampling (18-24s) ground-based photometric observations, which we use to measure the planetary radius and orbital inclination of the extrasolar transiting hot Jupiter WASP-4b. We recorded 987 images during three complete transits with the GROND instrument, mounted on the MPG/ESO-2.2m telescope at La Silla Observatory. Assuming a quadratic law for the stellar limb darkening we derive system parameters by fitting a composite transit light curve over all bandpasses simultaneously. To compute uncertainties of the fitted parameters we employ the Bootstrap Monte Carlo Method. The three central transit times are measured with precision down to 6 s. We find a planetary radius Rp = 1.413 ± 0.020RJup, an orbital inclination i = 88.°57 ± 0.45° and calculate new ephemeris, a period P = 1.33823144 ± 0.00000032 days and reference transit epoch T0 = 2454697.798311 ± 0.000046 (BJD). The analysis of the new transit mid-times in combination with previous measurements imply a constant orbital period and no compelling evidence for TTVs due to additional bodies in the syste

The Impact of the Internet on Telecommunication Architectures

The ever-growing popularity of the Internet is dramatically changing the landscape of the communications market place. The two separate worlds of the Internet and Telecommunications are converging. The respective advantages of the two environments are being integrated to fulfill the promise of the information super-highways. In this paper, we examine the impact of the Internet on the main telecommunication architectures, namely the IN, the TMN and TINA. There are two new tendencies for implementing telephony services in combination with the Internet: running part of the control sys tem over the Internet, or conveying both the user data and the control information over the Internet. We examine these two trends, and elaborate on possible ways of salvaging the best parts of the work achieved by the TINA-Consortium in the Internet context