The present work contains light curve, spectroscopic, and asteroseismic analyses for KIC 04851217 and KIC 10686876. These systems are detached eclipsing binaries hosting a pulsating component of
δ
...Scuti type and have been observed with the unprecedented accuracy of the
Kepler
space telescope. Using ground-based spectroscopic observations, the spectral types of the primary components of the systems were estimated as A6V and A5V for KIC 04851217 and KIC 10686876, respectively, with an uncertainty of one subclass. The present spectral classification, together with literature radial velocity curves, were used to model the light curves of the systems and, therefore, to calculate the absolute parameters of their components with a higher degree of certainty. The photometric data were analysed using standard eclipsing binary modeling techniques, while their residuals were further analysed using Fourier transformation techniques to extract the pulsation frequencies of their host
δ
Scuti stars. The oscillation modes of the independent frequencies were identified using theoretical models of
δ
Scuti stars. The distances of the systems were calculated using the relation between the luminosity and the pulsation period for
δ
Scuti stars. Here, the physical and the oscillation properties of the pulsating components of these systems are discussed and compared with others of the same type. Moreover, using all the currently known cases of
δ
Scuti stars in detached binaries, updated correlations between orbital and dominant pulsation periods and between log
g
and pulsation periods are derived. It can concluded that the proximity of the companion plays significant role in the evolution of the pulsational frequencies.
Context. The present research paper focuses on the eclipsing binary KIC 8553788 which belongs to two different types of binary systems regarding its physical properties. In particular, it is one of ...the 71 oscillating stars of Algol-type that have been discovered so far and one of the six that have been published based on high-cadence photometric data of the Kepler mission. In addition, it is one of the four semi-detached binaries of the group of R CMa-type systems, while its pulsating component has the fourth fastest frequency among the δ Scuti stars-members of semi-detached binaries. Detailed light curves as well as spectroscopic and pulsation analyses are presented, while possible explanation scenarios for the evolution of the system involving past mass transfer, mass loss, and/or angular momentum loss due to the presence of a tertiary component are discussed. Aims. The goal of the study is to extract the pulsational characteristics of the oscillating star of the system, to estimate the absolute parameters of its components, and to provide a possible explanation for its extreme evolutionary status. Methods. Ground-based spectroscopic observations using the 2.3 m “Aristarchos” telescope were obtained and used for the estimation of the spectral type of the primary component and to model the light curves of the system with higher certainty. The short-cadence photometric data provided by the Kepler mission were analysed using standard eclipsing binary modelling techniques, while Fourier analysis was applied on their residuals aiming to reveal the properties of the intrinsic oscillations. The resulting photometric model was combined with a published radial velocity curve to obtain accurate absolute parameters for the components of the system. Results. The results show that the primary component of the system is of A8 spectral type, has a mass of 1.6 M⊙, and a radius of 2 R⊙. It is a relatively fast pulsator of δ Scuti type that oscillates in 89 frequency modes with the dominant one being 58.26 cycles day−1. On the other hand, the secondary component has a mass of only 0.07 M⊙, a radius of 1 R⊙, and a temperature of 4400 K. In addition, it was found to be magnetically active with migrating cool spots on its surface. Conclusions. KIC 8553788, according to its geometrical configuration and its pulsational properties, belongs to the group of oscillating stars of Algol type, while according to its very low mass ratio and its relatively short orbital period belongs also to the group of R CMa stars. If confirmed by radial velocity data of the secondary component, the system would have the lowest mass ratio that has ever been found in semi-detached systems and could therefore be considered as one of the most extreme cases.
Context. This research paper contains light curve modelling, spectroscopy, and detailed asteroseismic studies for four out of a total of five semi-detached eclipsing binaries with a δ Scuti component ...that have been detected to date through Kepler mission; these objects are KIC 06669809, KIC 10581918, KIC 10619109, and KIC 11175495. Aims. The goal is to study the pulsational characteristics of the oscillating stars of the systems and to estimate their absolute parameters and enrich the, thus far, poor sample of such systems. Methods. Ground-based spectroscopic observations provided the means to estimate the spectral types of the primary components and to model the light curves with higher certainty. The photometric data were analysed using eclipsing binary modelling techniques, while Fourier analysis was applied on their residuals to reveal the pulsation frequency modes. Results. The results of analyses show that the primaries are pulsating stars of δ Scuti type and that all systems belong to the group of Algol-type binaries that have an oscillating star (oEA stars). The primaries of KIC 06669809, KIC 10581918, and KIC 10619109 pulsate in three, two, and five frequencies, respectively, and more than 200 others are detected as combination frequencies. The pulsator of KIC 11175495 is the youngest and fastest δ Scuti star that has ever been found in a binary system and oscillates in three main non-radial frequencies and in another 153 dependent frequencies. Moreover, comparisons of the properties of these binaries with other systems of the same type and with theoretical models of pulsating stars are also presented and discussed.
Aim
To assess the efficacy and safety of the novel sodium‐glucose cotransporter 2 (SGLT2) inhibitor empagliflozin compared with placebo or other antidiabetic agents in patients with type 2 diabetes.
...Methods
We conducted a systematic review and meta‐analysis of randomized controlled trials. We searched Medline, Embase and the Cochrane Library through December 2013 and grey literature. Two reviewers working independently extracted relevant data and carried out risk‐of‐bias assessments. We synthesized results using random‐effects models and computed weighted mean differences (WMDs) and odds ratios (ORs).
Results
We included 10 studies with 6203 participants. Compared with placebo, mean changes in haemoglobin A1c were −0.62% 95% confidence interval (CI) −0.68 to −0.57% for empagliflozin 10 mg and −0.66% (−0.76 to −0.57%) for empagliflozin 25 mg. Empagliflozin 25 mg daily had glycaemic efficacy similar to metformin or sitagliptin (WMD −0.11%; 95% CI −0.25 to 0.03%), without increasing risk for hypoglycaemia. It was also associated with body weight loss (WMD −1.84; 95% CI −2.30 to −1.38 kg vs. placebo) and had a favourable effect on blood pressure. Incidence of hypoglycaemia with empagliflozin was similar to placebo (OR 1.10; 95% CI 0.87 to 1.39); nevertheless we noted an increased risk for genital tract infections (OR 3.31; 95% CI 1.55 to 7.09). Findings were similar for the 10‐mg dosing regimen.
Conclusions
Empagliflozin effectively lowers blood glucose and provides additional clinical benefits including body weight and blood pressure reduction. Ongoing trials will elucidate the long‐term safety and effect of empagliflozin on cardiovascular outcomes.
ABSTRACT The detection of periodicity in the broadband non-thermal emission of blazars has so far been proven to be elusive. However, there are a number of scenarios that could lead to quasi-periodic ...variations in blazar light curves. For example, an orbital or thermal/viscous period of accreting matter around central supermassive black holes could, in principle, be imprinted in the multi-wavelength emission of small-scale blazar jets, carrying such crucial information about plasma conditions within the jet launching regions. In this paper, we present the results of our time series analysis of the ∼9.2 yr long, and exceptionally well-sampled, optical light curve of the BL Lac object OJ 287. The study primarily used the data from our own observations performed at the Mt. Suhora and Kraków Observatories in Poland, and at the Athens Observatory in Greece. Additionally, SMARTS observations were used to fill some of the gaps in the data. The Lomb-Scargle periodogram and the weighted wavelet Z-transform methods were employed to search for possible quasi-periodic oscillations in the resulting optical light curve of the source. Both methods consistently yielded a possible quasi-periodic signal around the periods of ∼400 and ∼800 days, the former with a significance (over the underlying colored noise) of . A number of likely explanations for this are discussed, with preference given to a modulation of the jet production efficiency by highly magnetized accretion disks. This supports previous findings and the interpretation reported recently in the literature for OJ 287 and other blazar sources.
We present results of the Near-Earth objects Lunar Impacts and Optical TrAnsients (NELIOTA) campaign for lunar impact flashes observed with the 1.2 m Kryoneri telescope. From August 2019 to August ...2023, we report 113 validated and 70 suspected flashes. For the validated flashes, we calculate the physical parameters (masses, radii) of the corresponding projectiles, the temperatures developed during the impacts, and the expected crater sizes. For the multiframe flashes, we present light curves and thermal evolution plots. Using the whole sample of NELIOTA that encompasses 192 validated flashes in total from 2017, the statistics of the physical parameters of the meteoroids, the peak temperatures of the impacts, and the expected crater sizes has been updated. Using this large sample, empirical relations correlating the luminous energies per photometric band were derived and used to roughly estimate the parameters of 92 suspected flashes of the NELIOTA archive. For a typical value of the luminous efficiency, we found that the majority (>75%) of the impacting meteoroids have masses between 1 and 200 g, radii between 0.5 and 3 cm and produced craters up to 3.5 m. 85% of the peak temperatures of the impacts range between 2000 and 4500 K. Statistics regarding the magnitude decline and the cooling rates of the multiframe flashes are also presented. The recalculation of the appearance frequency of meteoroids (lying within the aforementioned ranges of physical parameters) on the Moon yields that the total lunar surface is bombarded with 7.4 sporadic meteoroids per hour and up to 12.6 meteoroids per hour when the Earth-Moon system passes through a strong meteoroid stream. By extrapolating these rates on Earth, the respective rates for various distances from its surface are calculated and used to estimate the probability of an impact of a meteoroid with a hypothetical infrastructure on the Moon, or with a satellite orbiting Earth for various impact surfaces and duration times of the missions.
CCD observations of 68 eclipsing binary systems, candidates for containing δ Scuti components, were obtained. Their light curves are analysed using the period04 software for possible pulsational ...behaviour. For the systems QY Aql, CZ Aqr, TY Cap, WY Cet, UW Cyg, HL Dra, HZ Dra, AU Lac, CL Lyn and IO UMa, complete light curves were observed due to the detection of a pulsating component. All of them, except QY Aql and IO UMa, are analysed with modern astronomical softwares in order to determine their geometrical and pulsational characteristics. Spectroscopic observations of WY Cet and UW Cyg were used to estimate the spectral class of their primary components, while for HZ Dra radial velocities of its primary were measured. O − C diagram analysis was performed for the cases showing peculiar orbital period variations, namely CZ Aqr, TY Cap, WY Cet and UW Cyg, with the aim of obtaining a comprehensive picture of these systems. An updated catalogue of 74 close binaries including a δ Scuti companion is presented. Moreover, a connection between orbital and pulsation periods, as well as a correlation between evolutionary status and dominant pulsation frequency for these systems, is discussed.
We present the technical specifications and first results of the ESA-funded, lunar monitoring project “NELIOTA” (NEO Lunar Impacts and Optical TrAnsients) at the National Observatory of Athens, which ...aims to determine the size-frequency distribution of small near-Earth objects (NEOs) via detection of impact flashes on the surface of the Moon. For the purposes of this project a twin camera instrument was specially designed and installed at the 1.2 m Kryoneri telescope utilizing the fast-frame capabilities of scientific Complementary Metal-Oxide Semiconductor detectors (sCMOS). The system provides a wide field-of-view (17.0′ × 14.4′) and simultaneous observations in two photometric bands (R and I), reaching limiting magnitudes of 18.7 mag in 10 s in both bands at a 2.5 signal-to-noise ratio (S/N) level. This makes it a unique instrument that can be used for the detection of NEO impacts on the Moon, as well as for any astronomy projects that demand high-cadence multicolor observations. The wide field-of-view ensures that a large portion of the Moon is observed, while the simultaneous, high-cadence, monitoring in two photometric bands makes possible the determination of the temperatures of the impacts on the Moon’s surface and the validation of the impact flashes from a single site. Considering the varying background level on the Moon’s surface we demonstrate that the NELIOTA system can detect NEO impact flashes at a 2.5 S/N level of ∼12.4 mag in the I-band and R-band for observations made at low lunar phases (∼0.1). We report 31 NEO impact flashes detected during the first year of the NELIOTA campaign. The faintest flash was at 11.24 mag in the R-band (about two magnitudes fainter than ever observed before) at lunar phase 0.32. Our observations suggest a detection rate of 1.96 × 10−7 events km−2 h−1.
ABSTRACT
Binary and multiple stellar systems are numerous in our solar neighbourhood with 80 per cent of the solar-type stars being members of systems with high order multiplicity. The ...Contact Binaries Towards Merging (CoBiToM) Project is a programme that focuses on contact binaries and multiple stellar systems, as a key for understanding stellar nature. The goal is to investigate stellar coalescence and merging processes, as the final state of stellar evolution of low-mass contact binary systems. Obtaining observational data of approximately 100 eclipsing binaries and multiple systems and more than 400 archival systems, the programme aspires to give insights for their physical and orbital parameters and their temporal variations, e.g. the orbital period modulation, spot activity etc. Gravitational phenomena in multiple-star environments will be linked with stellar evolution. A comprehensive analysis will be conducted, in order to investigate the possibility of contact binaries to host planets, as well as the link between inflated hot Jupiters and stellar mergers. The innovation of CoBiToM Project is based on a multimethod approach and a detailed investigation, that will shed light for the first time on the origin of stellar mergers and rapidly rotating stars. In this work, we describe the scientific rationale, the observing facilities to be used and the methods that will be followed to achieve the goals of CoBiToM Project and we present the first results as an example of the current research on evolution of contact binary systems.
ABSTRACT
Ultra-short orbital period contact binaries (Porb < 0.26 d) host some of the smallest and least massive stars. These systems are faint and rare, and it is believed that they have reached a ...contact configuration after several Gyrs of evolution via angular momentum loss, mass transfer, and mass loss through stellar wind processes. This study is conducted in the frame of the Contact Binaries Towards Merging (CoBiToM) Project and presents the results from light curve and orbital analysis of 30 ultra-short orbital period contact binaries, with the aim to investigate the possibility of them being red nova progenitors, eventually producing merger events. Approximately half of the systems exhibit orbital period modulations, as a result of mass transfer or mass loss processes. Although they are in contact, their fill-out factor is low (less than 30 per cent), while their mass ratio is larger than the one in longer period contact binaries. This study investigates the orbital stability of these systems and examines their physical and orbital parameters in comparison to those of the entire sample of known and well-studied contact binaries, based on combined spectroscopic and photometric analysis. It is found that ultra-short orbital period contact binaries have very stable orbits, while very often additional components are gravitationally bound in wide orbits around the central binary system. We confirmed that the evolution of such systems is very slow, which explains why the components of ultra-short orbital period systems are still Main Sequence stars after several Gyrs of evolution.
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