Exploring the stellar surface phenomena of WASP-52 and HAT-P-30 with ESPRESSO

We analyse spectroscopic and photometric transits of the hot Jupiters WASP-52b and HAT-P30b obtained with ESPRESSO, Eulercam and NGTS for both targets, and additional TESS data for HAT-P-30. Our goal is to update the system parameters and refine our knowledge of the host star surfaces. For WASP-52, the companion planet has occulted starspots in the past, and as such our aim was to use the reloaded Rossiter-McLaughlin technique to directly probe its starspot properties. Unfortunately, we find no evidence for starspot occultations in the datasets herein. Additionally, we searched for stellar surface differential rotation (DR) and any centre-to-limb variation (CLV) due to convection, but return a null detection of both. This is unsurprising for WASP-52, given its relatively cool temperature, high magnetic activity (which leads to lower CLV), and projected obliquity near 0 degrees (meaning the transit chord is less likely to cross several stellar latitudes). For HAT-P-30, this result was more surprising given its hotter effective temperature, lower magnetic field, and high projected obliquity (near 70 degrees). To explore the reasons behind the null DR and CLV detection for HAT-P-30, we simulated a variety of scenarios. We find that either the CLV present on HAT-P-30 is below the solar level or the presence of DR prevents a CLV detection given the precision of the data herein. A careful treatment of both DR and CLV is required, especially for systems with high impact factors, due to potential degeneracies between the two. Future observations and/or a sophisticated treatment of the red noise present in the data (likely due to granulation) is required to refine the DR and CLV for these particular systems; such observations would also present another opportunity to try to examine starspots on WASP-52.Comment: 11 pages main text, 8 figures; accepted for publication in A&

Exploring the stellar surface phenomena of WASP-52 and HAT-P-30 with ESPRESSO

We analyse spectroscopic and photometric transits of the hot Jupiters WASP-52 b and HAT-P30 b obtained with ESPRESSO, Eulercam and NGTS for both targets, and additional TESS data for HAT-P-30. Our goal is to update the system parameters and refine our knowledge of the host star surfaces. For WASP-52, the companion planet has occulted starspots in the past, and as such our aim was to use the reloaded Rossiter-McLaughlin technique to directly probe its starspot properties. Unfortunately, we find no evidence for starspot occultations in the datasets herein. Additionally, we searched for stellar surface differential rotation (DR) and any centre-to-limb variation (CLV) due to convection, but return a null detection of both. This is unsurprising for WASP-52, given its relatively cool temperature, high magnetic activity (which leads to lower CLV), and projected obliquity near 0° (meaning the transit chord is less likely to cross several stellar latitudes). For HAT-P-30, this result was more surprising given its hotter effective temperature, lower magnetic field, and high projected obliquity (near 70°). To explore the reasons behind the null DR and CLV detection for HAT-P-30, we simulated a variety of scenarios. We find that either the CLV present on HAT-P-30 is below the solar level or the presence of DR prevents a CLV detection given the precision of the data herein. A careful treatment of both DR and CLV is required, especially for systems with high impact factors, due to potential degeneracies between the two. Future observations and/or a sophisticated treatment of the red noise present in the data (likely due to granulation) is required to refine the DR and CLV for these particular systems; such observations would also present another opportunity to try to examine starspots on WASP-52

Agent based modelling helps in understanding the rules by which fibroblasts support keratinocyte colony formation

Background: Autologous keratincoytes are routinely expanded using irradiated mouse fibroblasts and bovine serum for clinical use. With growing concerns about the safety of these xenobiotic materials, it is desirable to culture keratinocytes in media without animal derived products. An improved understanding of epithelial/mesenchymal interactions could assist in this. Methodology/Principal Findings: A keratincyte/fibroblast o-culture model was developed by extending an agent-based keratinocyte colony formation model to include the response of keratinocytes to both fibroblasts and serum. The model was validated by comparison of the in virtuo and in vitro multicellular behaviour of keratinocytes and fibroblasts in single and co-culture in Greens medium. To test the robustness of the model, several properties of the fibroblasts were changed to investigate their influence on the multicellular morphogenesis of keratinocyes and fibroblasts. The model was then used to generate hypotheses to explore the interactions of both proliferative and growth arrested fibroblasts with keratinocytes. The key predictions arising from the model which were confirmed by in vitro experiments were that 1) the ratio of fibroblasts to keratinocytes would critically influence keratinocyte colony expansion, 2) this ratio needed to be optimum at the beginning of the co-culture, 3) proliferative fibroblasts would be more effective than irradiated cells in expanding keratinocytes and 4) in the presence of an adequate number of fibroblasts, keratinocyte expansion would be independent of serum. Conclusions: A closely associated computational and biological approach is a powerful tool for understanding complex biological systems such as the interactions between keratinocytes and fibroblasts. The key outcome of this study is the finding that the early addition of a critical ratio of proliferative fibroblasts can give rapid keratinocyte expansion without the use of irradiated mouse fibroblasts and bovine serum

WASP-131 b with ESPRESSO I : a bloated sub-Saturn on a polar orbit around a differentially rotating solar-type star

In this paper, we present observations of two high-resolution transit datasets obtained with ESPRESSO of the bloated sub-Saturn planet WASP-131 b. We have simultaneous photometric observations with NGTS and EulerCam. In addition, we utilised photometric lightcurves from TESS, WASP, EulerCam and TRAPPIST of multiple transits to fit for the planetary parameters and update the ephemeris. We spatially resolve the stellar surface of WASP-131 utilising the Reloaded Rossiter McLaughlin technique to search for centre-to-limb convective variations, stellar differential rotation, and to determine the star-planet obliquity for the first time. We find WASP-131 is misaligned on a nearly retrograde orbit with a projected obliquity of $\lambda = 162.4\substack{+1.3 \\-1.2}^{\circ }$. In addition, we determined a stellar differential rotation shear of α = 0.61 ± 0.06 and disentangled the stellar inclination ($i_* = 40.9\substack{+13.3 \\-8.5}^{\circ }$) from the projected rotational velocity, resulting in an equatorial velocity of $v_{\rm {eq}} = 7.7\substack{+1.5 \\-1.3}$ km s−1. In turn, we determined the true 3D obliquity of $\psi = 123.7\substack{+12.8 \\-8.0}^{\circ }$, meaning the planet is on a perpendicular/polar orbit. Therefore, we explored possible mechanisms for the planetary system’s formation and evolution. Finally, we searched for centre-to-limb convective variations where there was a null detection, indicating that centre-to-limb convective variations are not prominent in this star or are hidden within red noise

The hot Neptune WASP-166 b with ESPRESSO – I. Refining the planetary architecture and stellar variability

In this paper, we present high-resolution spectroscopic transit observations from ESPRESSO of the super-Neptune WASP-166 b. In addition to spectroscopic ESPRESSO data, we analyse photometric data from TESS of six WASP-166 b transits along with simultaneous NGTS observations of the ESPRESSO runs. These observations were used to fit for the planetary parameters as well as assessing the level of stellar activity (e.g. spot crossings, flares) present during the ESPRESSO observations. We utilize the reloaded Rossiter McLaughlin (RRM) technique to spatially resolve the stellar surface, characterizing the centre-to-limb convection-induced variations, and to refine the star–planet obliquity. We find WASP-166 b has a projected obliquity of λ=−15.52+2.85−2.76∘ and vsin (i) = 4.97 ± 0.09 km s−1 which is consistent with the literature. We were able to characterize centre-to-limb convective variations as a result of granulation on the surface of the star on the order of a few km s−1 for the first time. We modelled the centre-to-limb convective variations using a linear, quadratic, and cubic model with the cubic being preferred. In addition, by modelling the differential rotation and centre-to-limb convective variations simultaneously, we were able to retrieve a potential antisolar differential rotational shear (α ∼ −0.5) and stellar inclination (i* either 42.03+9.13−9.60∘ or 133.64+8.42−7.98∘ if the star is pointing towards or away from us). Finally, we investigate how the shape of the cross-correlation functions change as a function of limb angle and compare our results to magnetohydrodynamic simulations

Alternative methods for skin irritation testing: the current status : ECVAM skin irritation task force report 1

The ECVAM Skin Irritation Task Force was established in November 1996, primarily to prepare a report on the current status of the development and validation of alternative tests for skin irritation and corrosion and, in particular, to identify any appropriate non-animal tests for predicting human skin irritation which were sufficiently well-developed to warrant ECVAM supporting their prevalidation/validation. The task force based its discussions around the proposed testing strategy for skin irritation/corrosion emanating from an OECD workshop held in January 1996. The following have been reviewed: a) structure-activity and structure-property relationships for skin corrosion and irritation, b) the use of pH and acid/alkaline reserve measurements in predicting skin corrosivity; c) in vitro tests for skin corrosion; d) in vitro tests for skin irritation (keratinocyte cultures, organ cultures, and reconstituted human skin models), and e) human patch tests for skin irritation, It was apparent that, although several promising candidate in vitro tests for skin irritation (for example, reconstituted human skin methods, and human and animal skin organ culture methods) were under development and evaluation, a test protocol, a preliminary prediction model and supporting data on different types of chemicals were only available for a method employing EpiDerm™ . Thus, it is proposed that this EpiDerm test undergoes prevalidation during 1998. In addition, since it was felt preferable to be able to include other in vitro tests in such a prevalidation study, it is recommended that a "challenge" be set to anyone interested in taking part. This involves submitting data on ten test chemicals selected by the task force, obtained according to a standard protocol with a preliminary prediction model, for review by the task force by 31 May 1998