Probing the origin of UX Ori-type variability in the YSO binary CO Ori with VLTI/GRAVITY

The primary star in the young stellar object (YSO) binary CO Ori displays UX Ori-type variability: irregular, high amplitude optical and near-infrared photometric fluctuations where flux minima coincide with polarization maxima. This is attributed to changes in local opacity. In CO Ori A, these variations exhibit a 12.4 yr cycle. Here, we investigate the physical origin of the fluctuating opacity and its periodicity using interferometric observations of CO Ori obtained using VLTI/GRAVITY. Continuum K-band circum-primary and circum-secondary emission are marginally spatially resolved for the first time while Br$\gamma$ emission is detected in the spectrum of the secondary. We estimate a spectral type range for CO Ori B of K2-K5 assuming visual extinction, $A_{\rm{V}}=2$ and a distance of 430 pc. From geometric modelling of the continuum visibilities, the circum-primary emission is consistent with a central point source plus a Gaussian component with a full-width-half-maximum of 2.31$\pm$0.04 milliarcseconds (mas), inclined at 30.2$\pm$2.2$^{\circ}$ and with a major axis position angle of 40$\pm$6$^{\circ}$. This inclination is lower than that reported for the discs of other UX Ori-type stars, providing a first indication that the UX Ori phenomena may arise through fluctuations in circumstellar material exterior to a disc, e.g. in a dusty outflow. An additional wide, symmetric Gaussian component is required to fit the visibilities of CO Ori B, signifying a contribution from scattered light. Finally, closure phases of CO Ori A were used to investigate whether the 12.4 yr periodicity is associated with an undetected third component, as has been previously suggested. We rule out any additional companions contributing more than 3.6% to the K-band flux within ~7.3-20 mas of CO Ori A.Comment: 7 pages, 4 figures, accepted for publication in MNRA

Assessment of the infrared welding process for a carbon fabric reinforced pps

This study assesses the use of infrared welding for a carbon fabric reinforced polyphenylene sulphide. Infrared light is used in order to melt the thermoplastic matrix of the two components, after which they are joined together under pressure. Welding parameters such as power of the infrared lights, heating time, contact pressure and consolidation time are optimised. Next, a series of joints is fabricated and the interlaminar behaviour of the weld is characterised. For the mode I behaviour, the Double Cantilever Beam test (DCB) is considered, whereas for mode II crack growth, the End Notch Flexure test (ENF) is used. Results are compared to the interlaminar behaviour of the base material. It can be concluded that the infrared process proves very interesting for the material under study and that joints can be manufactured with fracture toughness values equal or higher to the base material, both for mode I and mode II, but that a slightly different failure behaviour manifests itself

Experimental assesment of infrared welded bonds using lapshear, double cantilever beam and end notch flexure tests for a carbon fabric reinforced thermoplastic

High performance composites, such as carbon-fibre reinforced plastics (CFRP), are increasingly being used in high engineering industries. Their wide acceptance introduces an issue regarding the bonding of these materials and their mechanical behaviour. As this reinforced thermoplastic is not easily bonded with adhesives due to the chemical inertness, the fusion bonding process could be used to make a structural bond. In this paper, the interlaminar fracture behaviour of infrared welded bonds was investigated based on experimental analysis. The material used, is a 5-harness satin-weave (5HS) carbon fabric-reinforced polyphenylene sulphide (PPS). Laminates were welded using infrared light and a delamination was introduced by a Kapton film. Welding parameters were first optimized using lapshear tests, then mode I and mode II tests were conducted to determine the fracture toughness behaviour of the welded bonds. Tests under mode I loading were carried out using double cantilever beam (DCB) specimens whereas for mode II loading, three-point end notched flexure (ENF) specimens were considered. Crack growth under mode I and mode II loading conditions was observed to be unstable resulting in a sawtooth like load-displacement response, but nevertheless, values for the fracture toughness were derived

Gas dynamics in the inner few AU around the Herbig B[e] star MWC297: Indications of a disk wind from kinematic modeling and velocity-resolved interferometric imaging

We present near-infrared AMBER (R = 12, 000) and CRIRES (R = 100, 000) observations of the Herbig B[e] star MWC297 in the hydrogen Br-gamma-line. Using the VLTI unit telescopes, we obtained a uv-coverage suitable for aperture synthesis imaging. We interpret our velocity-resolved images as well as the derived two-dimensional photocenter displacement vectors, and fit kinematic models to our visibility and phase data in order to constrain the gas velocity field on sub-AU scales. The measured continuum visibilities constrain the orientation of the near-infrared-emitting dust disk, where we determine that the disk major axis is oriented along a position angle of 99.6 +/- 4.8 degrees. The near-infrared continuum emission is 3.6 times more compact than the expected dust-sublimation radius, possibly indicating the presence of highly refractory dust grains or optically thick gas emission in the inner disk. Our velocity-resolved channel maps and moment maps reveal the motion of the Br-gamma-emitting gas in six velocity channels, marking the first time that kinematic effects in the sub-AU inner regions of a protoplanetary disk could be directly imaged. We find a rotation-dominated velocity field, where the blue- and red-shifted emissions are displaced along a position angle of 24 +/- 3 degrees and the approaching part of the disk is offset west of the star. The visibility drop in the line as well as the strong non-zero phase signals can be modeled reasonably well assuming a Keplerian velocity field, although this model is not able to explain the 3 sigma difference that we measure between the position angle of the line photocenters and the position angle of the dust disk. We find that the fit can be improved by adding an outflowing component to the velocity field, as inspired by a magneto-centrifugal disk-wind scenario.Comment: 15 pages, 13 Figure

A robot swarm assisting a human fire-fighter

Emergencies in industrial warehouses are a major concern for fire-fighters. The large dimensions, together with the development of dense smoke that drastically reduces visibility, represent major challenges. The GUARDIANS robot swarm is designed to assist fire-fighters in searching a large warehouse. In this paper we discuss the technology developed for a swarm of robots assisting fire-fighters. We explain the swarming algorithms that provide the functionality by which the robots react to and follow humans while no communication is required. Next we discuss the wireless communication system, which is a so-called mobile ad-hoc network. The communication network provides also the means to locate the robots and humans. Thus, the robot swarm is able to provide guidance information to the humans. Together with the fire-fighters we explored how the robot swarm should feed information back to the human fire-fighter. We have designed and experimented with interfaces for presenting swarm-based information to human beings