Search

Context. Our knowledge of populations and the occurrence of planets orbiting evolved intermediate-mass stars is still incomplete. In 2010 we started a planet search programme among 95 giant stars observed by the Kepler mission to increase the sample of giant stars with planets and with reliable estimates of stellar masses and radii. Aims. We present the two systems from our planet search programme whose companions we were able to characterise: KIC 3526061 and HD 187878. Methods. We used precise stellar radial velocity measurements taken with four different echelle spectrographs to derive an orbital solution. We used Gaia astrometric measurements to obtain the inclination of the HD 187878 system and Kepler photometric observations to estimate the stellar mass and radius. Results. We report the discovery of a sub-stellar companion and a stellar companion around two intermediate-mass red giant branch stars. KIC 3526061 b is most likely a brown dwarf with a minimum mass of 18.15±0.44 MJupiter in a long-period eccentric orbit, with orbital period 3552 135+158 d and orbital eccentricity e = 0.85±0.01. It is the most evolved system found having a sub-stellar companion with such a high eccentricity and wide separation. HD 187878 B has a minimum mass of 78.4±2.0 MJupiter. Combining the spectroscopic orbital parameters with the astrometric proper motion anomaly, we derived an orbital inclination i=9.8 0.6+0.4 deg, which corresponds to the companion's mass in the stellar regime of 0.51 0.02+0.04 M. Conclusions. A sub-stellar companion of KIC 3526061 extends the sample of known red giant branch stars with sub-stellar companions on very eccentric wide orbits, and might provide a probe of the dynamical evolution of such systems over time., SCOPUS: ar.j, info:eu-repo/semantics/published

Context. Hundreds of candidate hybrid pulsators of intermediate type A-F were revealed by recent space missions. Hybrid pulsators allow us to study the full stellar interiors, where both low-order p- and high-order g-modes are simultaneously excited. The true hybrid stars must be identified since other processes, related to stellar multiplicity or rotation, might explain the presence of (some) low frequencies observed in their periodograms. Aims. We measured the radial velocities of 50 candidate δ Scuti -γ Doradus hybrid stars from the Kepler mission with the Hermes and ace spectrographs over a time span of months to years. We aim to derive the fraction of binary and multiple systems and to provide an independent and homogeneous determination of the atmospheric properties and v sin i for all targets. The long(er)-term objective is to identify the (probable) physical cause of the low frequencies. Methods. We computed one-dimensional cross-correlation functions (CCFs) in order to find the best set of parameters in terms of the number of components, spectral type(s), and v sin i for each target. Radial velocities were measured using spectrum synthesis and a two-dimensional cross-correlation technique in the case of double- and triple-lined systems. Fundamental parameters were determined by fitting (composite) synthetic spectra to the normalised median spectra corrected for the appropriate Doppler shifts. Results. We report on the analysis of 478 high-resolution Hermes and 41 ace spectra of A/F-type candidate hybrid pulsators from the Kepler field. We determined their radial velocities, projected rotational velocities, and atmospheric properties and classified our targets based on the shape of the CCFs and the temporal behaviour of the radial velocities. We derived orbital solutions for seven new systems. Three preliminary long-period orbital solutions are confirmed by a photometric time-delay analysis. Finally, we determined a global multiplicity fraction of 27% in our, SCOPUS: ar.j, info:eu-repo/semantics/published

We present an analysis of the first K2 observations of a rapidly oscillating Ap (roAp) star, HD 24355. The star was discovered to be a roAp star by [1], with a frequency of 224.31 d-1 (2596.18 μHz; P = 6.4 min) and an amplitude of 1.51 mmag in SuperWASP broadband photometry. Spectroscopic analysis of low-resolution spectra show the star to be an A5 Vp SrEu star. The high precision K2 data allow us to identify 13 rotationally split sidelobes to the main pulsation frequency. This is the largest number of sidelobes seen in a roAp star to date. We also see an unusual pulsational phase variation as the star rotates, showing this star to be the most distorted quadrupole roAp pulsator yet observed. Modelling of this star confirms its quadrupole nature, and allows us to constrain the magnetic field strength, angle of inclination and the angle of obliquity.

Digital transformation is considered as one of the mega-trends in industry and the public sector. One of the sectors with potential for digital transformation is higher education in universities and university colleges. Many universities and schools developed digitization strategies and new kinds of offerings for their traditional target groups and for new, non-traditional target groups. However, digitization and digital strategies often are limited to digitizing the content of lectures and to opening access to education modules by offering them online. We argue that digitization strategies should include a wider focus and propose that enterprise architecture management could provide an important contribution in structuring digitization efforts and that enterprise or knowledge portals could play a role for implementing the strategies.

PURPOSE Basal cell carcinomas (BCCs) are tumors ignored by immune surveillance. Activated Hedgehog (Hh) signaling within primary cilia is a key driver in the pathogenesis of BCCs. We examined immune alterations during treatment with systemic Hh inhibitors. EXPERIMENTAL DESIGN We investigated biopsies from patients with BCC before (23 patients) and after 4 weeks of treatment (5 patients) with Hh signaling inhibitor. Ber-Ep4, BCL-2, Ki-67, CD4, CD8, MHC class I, HLA-DR-class II, and SOX9 were analyzed by immunohistochemistry. Primary cilia were analyzed by double immunofluorescence of acetylated tubulin and SOX9. Differential gene expression for 84 cytokines and chemokines was analyzed in 3 patients. RESULTS After 4 weeks of treatment, we found reduction of Ki-67, SOX9, Ber-EP4, and BCL-2 expression in tumors associated with morphologic signs of squamous differentiation. In addition, the number of cilia-positive BCC cells was significantly decreased. An upregulation of MHC I expression on the cell membranes of residual tumor cells and an influx of CD4(+), HLA-DR-class II(+), and CD8(+) cells with invasion into the tumor cell nests were found. Finally, qPCR arrays showed the differential expression of genes involved in modulating immune responses. CONCLUSIONS We show that Hh pathway inhibitor-induced tumor regression is accompanied by a dynamic change of the microenvironment with a disruption of immune privilege involving an influx of cytotoxic T cells, activation of the adaptive immune functions, and a profound alteration of the local chemokine/cytokine network. Clin Cancer Res; 1-9. ©2015 AACR.

We carried out an extensive observational study of the Slowly Pulsating B (SPB) star, HD 25558. The ≈2000 spectra obtained at different observatories, the ground-based and MOST satellite light curves revealed that this object is a double-lined spectroscopic binary with an orbital period of about nine years. The observations do not allow the inference of an orbital solution. We determined the physical parameters of the components, and found that both lie within the SPB instability strip. Accordingly, both show line-profile variations due to stellar pulsations. 11 independent frequencies were identified in the data. All the frequencies were attributed to one of the two components based on pixel-by-pixel variability analysis of the line profiles. Spectroscopic and photometric mode identification was also performed for the frequencies of both stars. These results suggest that the inclination and rotation of the two components are rather different. The primary is a slow rotator with ≈6 d period, seen at ≈60° inclination, while the secondary rotates fast with ≈1.2 d period, and is seen at ≈20° inclination. Spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field can be detected in the primary. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

The existence of pulsations in HgMn stars is still being debated. To provide the first unambiguous observational detection of pulsations in this class of chemically peculiar objects, the bright star HD 45975 was monitored for nearly two months by the CoRoT satellite. Independent analyses of the light curve provide evidence of monoperiodic variations with a frequency of 0.7572 d-1 and a peak-to-peak amplitude of ~2800 ppm. Multisite, ground-based spectroscopic observations overlapping the CoRoT observations show the star to be a long-period, single-lined binary. Furthermore, with the notable exception of mercury, they reveal the same periodicity as in photometry in the line moments of chemical species exhibiting strong overabundances (e.g. Mn and Y). In contrast, lines of other elements do not show significant variations. As found in otherHgMn stars, the pattern of variability consists in an absorption bump moving redwards across the line profiles. We argue that the photometric and spectroscopic changes are more consistent with an interpretation in terms of rotational modulation of spots at the stellar surface. In this framework, the existence of pulsations producing photometric variations above the ~50 ppm level is unlikely in HD 45975. This provides strong constraints on the excitation/damping of pulsation modes in this HgMn star. © 2013 ESO., SCOPUS: ar.j, info:eu-repo/semantics/published

Aims. We present a spectroscopic analysis of MWC 314, a luminous blue variable (LBV) candidate with an extended bipolar nebula. The detailed spectroscopic variability is investigated to determine if MWC 314 is a massive binary system with a supersonically accelerating wind or a low-mass B[e] star. We compare the spectrum and spectral energy distribution to other LBVs (such as P Cyg) and find very similar physical wind properties, indicating strong kinship. Methods. We combined long-term high-resolution optical spectroscopic monitoring and V-band photometric observations to determine the orbital elements and stellar parameters and to investigate the spectral variability with the orbital phases. We developed an advanced model of the large-scale wind-velocity and wind-density structure with 3-D radiative transfer calculations that fit the orbitally modulated P Cyg profile of He i λ5876, showing outflow velocities above 1000 km s-1. Results. We find that MWC 314 is a massive semi-detached binary system of ≈1.22 AU, observed at an inclination angle of i = 72.8 with an orbital period of 60.8 d and e = 0.23. The primary star is a low-vsini LBV candidate of m1 = 39.6 M and R1 = 86.8 R. The detailed radiative transfer fits show that the geometry of wind density is asymmetric around the primary star with increased wind density by a factor of 3.3, which leads the orbit of the primary. The variable orientation causes the orbital modulation that is observed in absorption portions of P Cyg wind lines. Wind accretion in the system produces a circumbinary disc. Conclusions. MWC 314 is in a crucial evolutionary phase of close binary systems, when the massive primary star has its H envelope being stripped and is losing mass to a circumbinary disc. MWC 314 is a key system for studying the evolutionary consequences of these effects. © 2013 ESO., SCOPUS: ar.j, info:eu-repo/semantics/published

info:eu-repo/semantics/published

info:eu-repo/semantics/published

Context. Miras are long-period variables thought to be in the asymptotic giant branch (AGB) phase of evolution. In about one percent of known Miras, the pulsation period is changing. It has been speculated that this changing period is the consequence of a recent thermal pulse in these stars. Aims. We aim to clarify the evolutionary state of these stars, and to determine in particular whether or not they are in the thermally-pulsing (TP-)AGB phase. Methods. One important piece of information that has been neglected so far when determining the evolutionary state is the presence of the radio-active s-process element technetium (Tc). We obtained high-resolution, high signal-to-noise-ratio optical spectra of a dozen prominent Mira variables with changing pulsation period to search for this indicator of TPs and dredge-up. We also use the spectra to measure lithium (Li) abundances. Furthermore, we establish the evolutionary states of our sample stars by means of their present-day periods and luminosities. Results. Among the twelve sample stars observed in this programme, five were found to show absorption lines of Tc. BH Cru is found to be a carbon-star, its period increase in the past decades possibly having stopped by now. We report a possible switch in the pulsation mode of T UMi from Mira-like to semi-regular variability in the past two years. R Nor, on the other hand, is probably a fairly massive AGB star, which could be true for all meandering Miras. Finally, we assign RU Vul to the metal-poor thick disk with properties very similar to the short-period, metal-poor Miras. Conclusions. We conclude that there is no clear correlation between period change class and Tc presence. The stars that are most likely to have experienced a recent TP are BH Cru and R Hya, although their rates of period change are quite different. © 2011 ESO., SCOPUS: ar.j, info:eu-repo/semantics/published

The HERMES high-resolution spectrograph project aims at exploiting the specific potential of small but flexible telescopes in observational astrophysics. The optimised optical design of the spectrograph is based on the well-proven concept of white-pupil beam folding for high-resolution spectroscopy. In this contribution we present the complete project, including the spectrograph design and procurement details, the telescope adaptor and calibration unit, the detector system, as well as the optimised data-reduction pipeline. We present a detailed performance analysis to show that the spectrograph performs as specified both in optical quality and in total efficiency. With a spectral resolution of 85 000 (63 000 for the low-resolution fibre), a spectral coverage from 377 to 900 nm in a single exposure and a peak efficiency of 28%, HERMES proves to be an ideal instrument for building up time series of high-quality data of variable (stellar) phenomena. © 2010 ESO., SCOPUS: ar.j, info:eu-repo/semantics/published