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- Fridlund, Malcolm, 1952, et al.
(författare)
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Planets observed with CHEOPS: Two super-Earths orbiting the red dwarf star TOI-776
- 2024
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 684
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Tidskriftsartikel (refereegranskat)abstract
- Context. M-dwarf stars are the most common of potential exoplanet host stars in the Galaxy. It is therefore very important to understand planetary systems orbiting such stars and to determine the physical parameters of such planets with high precision. Also with the launch of the James Webb Space Telescope (JWST) the observation of atmospheric parameters of planets orbiting these stars has begun. It is therefore required to determine properties of potential targets. Aims. Two planets around the red dwarf TOI-776 were detected by TESS. The objective of our study was to use transit observations obtained by the CHEOPS space mission to improve the current precision of the planetary radii, as well as additional radial velocity (RV) data in order to improve mass estimates of the two planets. Using these quantities, we wanted to derive the bulk densities of those planets, improving the precision in earlier results, and use this information to put them in context of other exoplanetary systems involving very low mass stars. Methods. Utilizing new transit data from the CHEOPS satellite and its photometric telescope, we obtained very high precision planetary transit measurements. Interpretation of these provides updated planetary radii, along with other system parameters. A concurrent ESO large observing program using the high precision spectrograph HARPS has doubled the available radial velocity data. Calculating the power spectrum of a number of stellar activity indices we update the previously estimated stellar rotation period to a lower value. Results. The CHEOPS data provide precise transit depths of 909 and 1177 ppm translating into radii of Rb = 1.798-0.077+0.078 R⊕ and Rc = 2.047-0.078+0.081 R⊕, respectively. Our interpretation of the radial velocities and activity indicator time series data estimates a stellar rotation period for this early M dwarf of ~21.1 days. A further multi-dimensional Gaussian process approach confirm this new estimate. By performing a Skew-Normal (SN) fit onto the Cross Correlation Functions we extracted the RV data and the activity indicators to estimate the planetary masses, obtaining Mb = 5.0-1.6+1.6 M⊕ and Mc = 6.9-2.5+2.6 M⊕. Conclusions. We improve the precision in planetary radius for TOI-776 b and c by a factor of more than two. Our data and modelling give us parameters of both bodies consistent with mini-Neptunes, albeit with a relatively high density. The stellar activity of TOI-776 is found to have increased by a factor larger than 2 since the last set of observations.
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| 3. |
- Blinov, D., et al.
(författare)
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The RoboPol sample of optical polarimetric standards
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 677
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Tidskriftsartikel (refereegranskat)abstract
- Context. Optical polarimeters are typically calibrated using measurements of stars with known and stable polarization parameters. However, there is a lack of such stars available across the sky. Many of the currently available standards are not suitable for medium and large telescopes due to their high brightness. Moreover, as we find, some of the polarimetric standards used are in fact variable or have polarization parameters that differ from their cataloged values. Aims. Our goal is to establish a sample of stable standards suitable for calibrating linear optical polarimeters with an accuracy down to 10-3 in fractional polarization. Methods. For 4 yr, we have been running a monitoring campaign of a sample of standard candidates comprised of 107 stars distributed across the northern sky. We analyzed the variability of the linear polarization of these stars, taking into account the non-Gaussian nature of fractional polarization measurements. For a subsample of nine stars, we also performed multiband polarization measurements. Results. We created a new catalog of 65 stars (see Table 2) that are stable, have small uncertainties of measured polarimetric parameters, and can be used as calibrators of polarimeters at medium and large telescopes.
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| 5. |
- Abend, Sven, et al.
(författare)
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Terrestrial very-long-baseline atom interferometry : Workshop summary
- 2024
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Ingår i: AVS Quantum Science. - : American Institute of Physics (AIP). - 2639-0213. ; 6:2
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Forskningsöversikt (refereegranskat)abstract
- This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more kilometer--scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions.
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| 7. |
- Anchordoqui, Luis A., et al.
(författare)
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Anomalous U(1) gauge bosons and string physics at the forward physics facility
- 2022
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 832
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Tidskriftsartikel (refereegranskat)abstract
- We show that experiments at the Forward Physics Facility, planned to operate near the ATLAS interaction point during the LHC high-luminosity era, will be able to probe predictions of Little String Theory by searching for anomalous U (1) gauge bosons living in the bulk. The interaction of the abelian broken gauge symmetry with the Standard Model is generated at the one-loop level through kinetic mixing with the photon. Gauge invariant generation of mass for the U(1) gauge boson proceeds via the Higgs mechanism in spontaneous symmetry breaking, or else through anomaly-cancellation appealing to Stuckelberg-mass terms. We demonstrate that FASER2 will be able to probe string scales over roughly two orders of magnitude: 10(5) less than or similar to M-s/TeV less than or similar to 10(7).
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| 8. |
- Antoniadis, A., et al.
(författare)
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A fully polynomial-time approximation scheme for speed scaling with sleep state
- 2015
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Ingår i: Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms. - Philadelphia, PA : Society for Industrial and Applied Mathematics. ; 2015-January:January, s. 1102-
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Konferensbidrag (refereegranskat)abstract
- We study classical deadline-based preemptive scheduling of jobs in a computing environment equipped with both dynamic speed scaling and sleep state capabilities: Each job is specified by a release time, a deadline and a processing volume, and has to be scheduled on a single, speed-scalable processor that is supplied with a sleep state. In the sleep state, the processor consumes no energy, but a constant wake-up cost is required to transition back to the active state. In contrast to speed scaling alone, the addition of a sleep state makes it sometimes beneficial to accelerate the processing of jobs in order to transition the processor to the sleep state for longer amounts of time and incur further energy savings. The goal is to output a feasible schedule that minimizes the energy consumption. Since the introduction of the problem by Irani et al. [17], its exact computational complexity has been repeatedly posed as an open question (see e.g. [2, 9, 16]). The currently best known upper and lower bounds are a 4/3-approximation algorithm and NP-hardness due to [2] and [2, 18], respectively. We close the aforementioned gap between the upper and lower bound on the computational complexity of speed scaling with sleep state by presenting a fully polynomial-time approximation scheme for the problem. The scheme is based on a transformation to a non-preemptive variant of the problem, and a discretization that exploits a carefully defined lexicographical ordering among schedules.
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| 9. |
- Antoniadis, A., et al.
(författare)
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How to pack your items when you have to buy your knapsack
- 2013
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783642403125 ; 8087, s. 62-73
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Konferensbidrag (refereegranskat)abstract
- In this paper we consider a generalization of the classical knapsack problem. While in the standard setting a fixed capacity may not be exceeded by the weight of the chosen items, we replace this hard constraint by a weight-dependent cost function. The objective is to maximize the total profit of the chosten items minus the cost induced by their total weight. We study two natural classes of cost functions, namely convex and concave functions. For the concave case, we show that the problem can be solved in polynomial time; for the convex case we present an FPTAS and a 2-approximation algorithm with the running time of O(n log n), where n is the number of items. Before, only a 3-approximation algorithm was known. We note that our problem with a convex cost function is a special case of maximizing a non-monotone, possibly negative submodular function.
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| 10. |
- Gogas, Helen J., et al.
(författare)
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The role of depression and personality traits in patients with melanoma : a South-European study
- 2017
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Ingår i: Melanoma research. - : LIPPINCOTT WILLIAMS & WILKINS. - 0960-8931 .- 1473-5636. ; 27:6, s. 625-631
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Tidskriftsartikel (refereegranskat)abstract
- We explored the potential association of depression history and personality, evaluated through a robust questionnaire tool, namely the Eysenck Personality Scale, with disease risk and progression among Greek patients. A total of 106 melanoma patients and their 1 : 1 sex-matched controls were interviewed on the basis of a questionnaire comprising phenotypic, sociodemographic, lifestyle and medical history variables, as well as information on history of lifetime major depression. The Eysenck Personality Questionnaire, measuring the four personality dimensions (extraversion, neuroticism, psychoticism, lie), was thereafter completed. Adjusted odds ratios (ORs) for melanoma risk were derived through multiple logistic regression analyses, whereas potential predictors of survival were explored using Cox proportional hazards models. Sun sensitivity score [OR: 1.55, 95% confidence interval (CI): 1.16-2.06] and major depression history (OR: 5.72, 95% CI: 1.38-23.73) were significantly associated with melanoma, whereas inverse associations of extraversion (OR: 0.90, 95% CI: 0.83-0.97) and psychoticism score (OR: 0.88, 95% CI: 0.78-1.00) were noted. These associations were more pronounced and remained solely among female patients; notably, decreased extraversion (OR: 0.86, 95% CI: 0.76-0.98) and psychoticism score (OR: 0.63, 95% CI: 0.43-0.91), as well as increased depression history (OR: 10.69, 95% CI: 1.43-80.03) were evident. Cox-derived hazard ratios showed nonsignificant associations of depression history and personality with disease outcome. Our data support the hypotheses that depression history and personality are associated with melanoma risk. No effect on survival after cancer diagnosis was observed. If confirmed in future studies, these associations may contribute toward better understanding the etiology of melanoma, enhancing health-related quality of life. Copyright (C) 2017 Wolters Kluwer Health, Inc. All rights reserved.
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