Search Publications
An HST/STIS view of protoplanetary discs in Upper Scorpius: observations of three young M stars
Kalas, Paul; Carpenter, John; Ren, Bin +2 more
We present observations of three protoplanetary discs in visible scattered light around M-type stars in the Upper Scorpius OB association using the Space Telescope Imaging Spectrograph (STIS) instrument on the Hubble Space Telescope (HST). The discs around stars 2MASS J16090075-1908526, 2MASS J16142029-1906481, and 2MASS J16123916-1859284 have all…
Star formation around three co-moving HAeBe stars in the Cepheus Flare
Saha, P.; Maheswar, G.; Kamath, U. S. +1 more
Context. The presence of three more Herbig Ae/Be (HAeBe) candidates in the Cepheus Flare within a 1.5° radius centered on HD 200775 suggests that star formation is prevalent in a wider region of the LDN 1147/1158, LDN 1172/1174, and LDN 1177 clouds. A number of young stellar objects (YSOs) are found to be distributed toward these cloud complexes a…
Evaluation of Stellar Parameters and Calibrating the Surface Gravity log g for LAMOST-II Median Resolution Survey
Luo, A. -Li; Li, Yin-Bi; Zhang, Shuo +8 more
The LAMOST II survey began in the fall of 2018, and LAMOST formally released the obtained medium-resolution spectra (MRS) as well as catalogs of stellar parameters and radial velocities (RV) derived from the MRS in the seventh LAMOST data release (DR7). Compared with the RVs and parameters from high-resolution SDSS14/APOGEE spectra, nearly no RV d…
The angular-momentum flux in the solar wind observed during Solar Orbiter's first orbit
Verscharen, Daniel; Bruno, Roberto; Maksimovic, Milan +20 more
Aims: We present the first measurements of the angular-momentum flux in the solar wind recorded by the Solar Orbiter spacecraft. Our aim is to validate these measurements to support future studies of the Sun's angular-momentum loss.
Methods: We combined 60-min averages of the proton bulk moments and the magnetic field measured by the Sol…
A Case for a Small to Negligible Influence of Dust Charging on the Ionization Balance in the Coma of Comet 67P
Rubin, M.; Vigren, E.; Eriksson, A. I. +3 more
A recent work aided by Rosetta in situ measurements set constraints on the dust-to-gas mass emission ratio and the size distribution of dust escaping the nucleus of comet 67P/Churyumov-Gerasimenko near perihelion. Here we use this information along with other observables/parameters as input into an analytical model aimed at estimating the number d…
Investigating variable stars in the open cluster NGC 1912 and its surrounding field
Zhang, Yu; Esamdin, Ali; Chen, Li +6 more
In this work, we studied the variable stars in the open cluster NGC 1912 based on the photometric observations and Gaia DR2 data. More than 3600 CCD frames in B, V, R filters were reduced, and we obtained the light curves that span about 63 hours. By analyzing these light curves, we detected 24 variable stars, including 16 periodic variable stars,…
Investigation of the subsurface structure of a sunspot based on the spatial distribution of oscillation centers inferred from umbral flashes
Chae, Jongchul; Cho, Kyuhyoun; Madjarska, Maria S.
The subsurface structure of a solar sunspot is important for the stability of the sunspot and the energy transport therein. Two subsurface structure models have been proposed, the monolithic and cluster models, but no clear observational evidence supporting a particular model has been found to date. To obtain clues about the subsurface structure o…
Pairing function of visual binary stars
Chulkov, Dmitry
An all-sky sample of 1227 visual binaries based on Washington Double Star catalogue is constructed to infer the initial mass function (IMF), mass ratio, and projected distance distribution with a dedicated population synthesis model. Parallaxes from Gaia DR2 and Hipparcos are used to verify the distance distribution. The model is validated on the …
Chemodynamics of metal-poor wide binaries in the Galactic halo: Association with the Sequoia event
Hansen, Camilla Juul; Peñarrubia, Jorge; Lépine, Sebastien +4 more
Recently, an increasing number of wide binaries has been discovered. Their chemical and dynamical properties are studied through extensive surveys and pointed observations. However, the formation of these wide binaries is far from clear, although several scenarios have been suggested. In order to investigate the chemical compositions of these syst…
The origin of X-ray emission in 3CRR sources: Hints from mid-infrared Spitzer observations
Li, Shuang-Liang; Gu, Minfeng
Aims: Whether X-ray emission in radio-loud (RL) active galactic nuclei (AGNs) originates from disk coronae or jets is still under debate. For example, the positive relationships in radio-quiet AGNs (such as the optical to X-ray spectral index αOX and Eddington ration λO as well as the X-ray photon index Γ and λO