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A stellar census in globular clusters with MUSE. A new perspective on the multiple main sequences of ω Centauri
Dreizler, S.; Latour, M.; Brinchmann, J. +3 more
Context. ω Cen is a rare example of a globular cluster where the iron abundance of the stars spans more than one order of magnitude. Many spectroscopic investigations of its red-giant and sub-giant branches have revealed multiple peaks in the iron abundance distribution. The metallicity distribution of main sequence (MS) stars is not well characte…
Years-delayed X-Ray Afterglows of TDEs Originated from Wind-Torus Interactions
Wang, Wei; Shu, Xinwen; Jiang, Ning +8 more
Tidal disruption events (TDEs) occurring in active galactic nuclei (AGNs) are a special class of sources with outstanding scientific significance. TDEs can generate ultrafast winds, which should almost inevitably collide with the preexisting AGN dusty tori. We perform analytical calculations and simulations on the wind-torus interactions and find …
Mid-infrared reflectance spectroscopy of synthetic glass analogs for Mercury surface studies
Helbert, Joern; Hiesinger, Harald; Weber, Iris +14 more
We have synthesized and analyzed by mid-infrared reflectance spectroscopy silicate glasses that are representative for the glasses on the surface of Mercury. The glass compositions are based on high-pressure laboratory experiments and the resulting compositions of the glass phase. The spectra are of interest for investigating the surface of Mercur…
NGTS 15b, 16b, 17b, and 18b: four hot Jupiters from the Next-Generation Transit Survey
Wheatley, Peter J.; Bayliss, Daniel; Worters, Hannah L. +36 more
We report the discovery of four new hot Jupiters with the Next-Generation Transit Survey (NGTS). NGTS-15b, NGTS-16b, NGTS-17b, and NGTS-18b are short-period (P < 5 d) planets orbiting G-type main-sequence stars, with radii and masses between 1.10 and 1.30RJ and 0.41 and 0.76MJ, respectively. By considering the host star lu…
RR Lyrae stars as seen by the Kepler space telescope
Szabó, Róbert; Plachy, Emese
The unprecedented photometric precision along with the quasi-continuous sampling provided by the Kepler space telescope revealed new and unpredicted phenomena that reformed and invigorated RR Lyrae star research. The discovery of period doubling and the wealth of low- amplitude modes enlightened the complexity of the pulsation behavior and guided …
Broad-line region configuration of the supermassive binary black hole candidate PG1302-102 in the relativistic Doppler boosting scenario
Lu, Youjun; Ge, Junqiang; Ji, Xiang +2 more
PG1302-102 is thought to be a supermassive binary black hole (BBH) system according to the periodical variations of its optical and UV photometry, which may be interpreted as being due to the relativistic Doppler boosting of the emission mainly from the disk around the secondary black hole (BH) modulated by its orbital motion. In this paper, we in…
Class imbalance problem in short-term solar flare prediction
Wan, Jie; Fu, Jun-Feng; Liu, Jin-Fu +3 more
Using data-driven algorithms to accurately forecast solar flares requires reliable data sets. The solar flare dataset is composed of many non-flaring samples with a small percentage of flaring samples. This is called the class imbalance problem in data mining tasks. The prediction model is sensitive to most classes of the original data set during …
Tangent Directions of the Cusp Boundary Derived From the Simulated Soft X Ray Image
Wang, Chi; Sun, Tianran; Wang, Xue
The magnetospheric cusp plays an essential role in mass and energy transportation from the solar wind to the geo space environment. Recent development of the X ray imaging technique makes it possible to study the large scale properties of the cusp region from a global view. As the detected X ray signals will be integrated along the line of sight (…
Magnetic field and activity phenomena of the K2 dwarf V471 Tau
Donati, J. -F.; Klein, B.; Zaire, B.
We analyse spectropolarimetric data of the pre-cataclysmic variable binary system V471 Tau obtained with ESPaDOnS at the Canada-France-Hawaii Telescope in two observational campaigns (in 2004 November/December and 2005 December). Using Zeeman-Doppler imaging, we reconstruct the distribution of brightness map and large-scale magnetic field of the K…
Microlensing predictions: impact of Galactic disc dynamical models
Zang, Weicheng; Mao, Shude; Zhang, Xiangyu +1 more
Galactic model plays an important role in the microlensing field, not only for analyses of individual events but also for statistics of the ensemble of events. However, the Galactic models used in the field vary, and some are unrealistically simplified. Here, we tested three Galactic disc dynamic models; the first is a simple standard model that w…