Search Publications
Flux emergence and generation of flare-productive active regions
Toriumi, Shin
Solar flares and coronal mass ejections are among the most prominent manifestations of the magnetic activity of the Sun. The strongest events of them tend to occur in active regions (ARs) that are large, complex, and dynamically evolving. However, it is not clear what the key observational features of such ARs are, and how these features are produ…
A Multi-Event Study of Early-Stage SEP Acceleration by CME-Driven Shocks—Sun to 1 AU
Zucca, Pietro; Kozarev, Kamen; Nedal, Mohamed +2 more
The solar corona between below 10 solar radii is an important region for early acceleration and transport of solar energetic particles (SEPs) by coronal mass ejection-driven shock waves. There, these waves propagate into a highly variable dynamic medium with steep gradients and rapidly expanding coronal magnetic fields, which modulates the particl…
A Photometric and Astrometric Study of the Open Clusters NGC 1664 and NGC 6939
Bilir, Selçuk; Yontan, Talar; Paunzen, Ernst +5 more
This study calculated astrophysical parameters, as well as kinematic and galactic orbital parameters, of the open clusters NGC 1664 and NGC 6939. The work is based on CCD ultraviolet, blue, and visual (UBV) and Gaia photometric and astrometric data from ground- and space-based observations. Considering Gaia Early Data Release 3 (EDR3) astrometric …
Parameters of the Galactic Spiral Density Wave from Masers with Parallax Errors Less Than 10\boldsymbol{%}
Bobylev, V. V.; Bajkova, A. T.
We have studied the kinematics of Galactic masers and radio stars with measured VLBI trigonometric parallaxes and proper motions. We have considered masers with relative trigonometric parallax errors less than 10${%}$ and determined the Galactic rotation parameters from them. In particular, the linear rotation velocity of the Galaxy at the solar d…
Intrinsic Shapes of Brightest Cluster Galaxies
Bender, Ralf; Thomas, Jens; Saglia, Roberto P. +5 more
We discuss the statistical distribution of galaxy shapes and viewing angles under the assumption of triaxiality by deprojecting observed surface brightness profiles of 56 brightest cluster galaxies (BCGs) coming from a recently published large deep-photometry sample. For the first time, we address this issue by directly measuring axis ratio profil…
Confirmation and characterisation of three giant planets detected by TESS from the FIES/NOT and Tull/McDonald spectrographs
Bieryla, Allyson; Quinn, Samuel N.; Cochran, William D. +37 more
We report the confirmation and characterisation of TOI-1820 b, TOI-2025 b, and TOI-2158 b, three Jupiter-sized planets on short-period orbits around G-type stars detected by TESS. Through our ground-based efforts using the FIES and Tull spectrographs, we have confirmed these planets and characterised their orbits, and find periods of around 4.9 d,…
AutoSourceID-Light. Fast optical source localization via U-Net and Laplacian of Gaussian
Groot, P. J.; Jóhannesson, G.; Vreeswijk, P. +9 more
Aims: With the ever-increasing survey speed of optical wide-field telescopes and the importance of discovering transients when they are still young, rapid and reliable source localization is paramount. We present AutoSourceID-Light (ASID-L), an innovative framework that uses computer vision techniques that can naturally deal with large amount…
Our Galaxy's youngest disc
Li, Chengdong; Binney, James
We investigate the structure of our Galaxy's young stellar disc by fitting the distribution functions (DFs) of a new family to 5D Gaia data for a sample of $47\, 000$ OB stars. Tests of the fitting procedure show that the young disc's DF would be strongly constrained by Gaia data if the distribution of Galactic dust were accurately known. The DF t…
Magnetic field topology, chemical spot distributions, and photometric variability of the Ap star φ Draconis
Neiner, C.; Kochukhov, O.; Papakonstantinou, N.
The primary component of the multiple star φ Dra is one of the brightest magnetic chemically peculiar stars in the northern sky. Here, we report results of a comprehensive study of the rotational photometric variability, binarity, magnetic field geometry, and surface chemical spot structure for this star. We derived a precise photometric rotationa…
The pre-He white dwarfs in eclipsing binaries - IV. WASP 1814+48 with multiperiodic pulsations
Hong, Kyeongsoo; Lee, Jae Woo; Park, Jang-Ho +1 more
For the EL CVn candidate 1SWASPJ181417.43+481117.0 (WASP 1814+48), we secured the first spectroscopic observations between 2015 April and 2021 March. Using the echelle spectra, the radial velocities (RVs) of the primary star were measured with its atmospheric parameters of Teff, 1 = 7770 ± 130 K and $v$1sin i = 47 ± 6 km s