Claus Goessl

THE M31 NEAR-INFRARED PERIOD-LUMINOSITY RELATION AND ITS NON-LINEARITY FOR δ Cep VARIABLES WITH 0.5 ≤ log (P) ≤ 1.7

We present the largest M31 near-infrared (F110W (close to J band), F160W (H band)) Cepheid sample so far. The sample consists of 371 Cepheids with photometry obtained from the Hubble Space Telescope PHAT program. The sample of 319 fundamental mode Cepheids, 16 first overtone Cepheids, and 36 type II Cepheids was identified using the median absolute deviation outlier rejection method we develop here. This method does not rely on priors and allows us to obtain this clean Cepheid sample without rejecting a large fraction of Cepheids. The obtained period-luminosity relations (PLRs) have a very small dispersion, i.e., 0.155 mag in F160W, despite using random phased observations. This remarkably small dispersion allows us to determine that the PLRs are significantly better described by a broken slope at 10 days than a linear slope. The use of our sample as an anchor to determine the Hubble constant gives a 3.2% larger Hubble constant compared to the Riess et al. sample.

Commissioning and science verification of the 2m-Fraunhofer Wendelstein Telescope

The commissioning of the telescope and its first instrument, a Nasmyth port mounted 0.5 degree CCD mosaic imager, started in November 2013. We will report about the results of astronomical tests of the integrated system including the achieved optical quality across the field of view, pointing and tracking quality and operational experiences with the observatory system. The special design features of this alt-az telescope are its compactness and the low-ghost wide field optics (0.7o f.o.v. diameter), and we will briefly report on the lessons learned especially for these special features. We will present an outlook on the further commissioning including the additional instruments which are all under construction or already finalized.

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.

Cepheids in M31 : the PAndromeda Cepheid sample.

We present the largest Cepheid sample in M31 based on the complete Pan-STARRS1 survey of Andromeda (PAndromeda) in the r(P1), i(P1), and g(P1) bands. We find 2686 Cepheids with 1662 fundamental-mode Cepheids, 307 first-overtone Cepheids, 278 type II Cepheids, and 439 Cepheids with undetermined Cepheid type. Using the method developed by Kodric et al., we identify Cepheids by using a three-dimensional parameter space of Fourier parameters of the Cepheid light curves combined with a color cut and other selection criteria. This is an unbiased approach to identify Cepheids and results in a homogeneous Cepheid sample. The period-luminosity relations obtained for our sample have smaller dispersions than in our previous work. We find a broken slope that we previously observed with HST data in Kodric et al., albeit with a lower significance.

The Wendelstein three channel imager (3KK): alignment, commissioning, and first results

The Ludwig-Maximilians-Universität München operates an astrophysical observatory on the summit of Mt. Wendelstein which was equipped with a modern 2m-class robotic telescope in 20111-3. One of the two Nasmyth ports is designed to deliver the excellent (< 0.8” median) seeing of the site for a FoV of 60 arcmin2 without any corrector optics at optical and near infrared (NIR) wavebands. This port hosts a three channel imager whose design was already presented in Lang-Bardl et al. 2010.4 It is designed to efficiently support observations of targets of opportunities like Gamma-Ray-bursts or efficient photometric redshift determination of sources identified by surveys like PanSTARS, Planck (SZ) or eROSITA. The covered wavelength range is 340 nm to 2.3 microns. The camera provides standard broadband filters (Sloan, Y, J, H, Ks) and 5 narrowband filters (OI, Hα, SII, H2, Brλ). The narrowband filters will enable deep studies of star forming regions. We present the final design of the camera, the assembly and alignment procedure performed in the laboratory before we transported the instrument to the observatory. We also show first results of the achieved on sky performance concerning image quality and efficiency of the camera in the different filter passbands.