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Transients and Stellar Activity as Revealed by Ultraviolet Diagnostic Tracers
Richard de Grijs, Martin A. Barstow, Deepak Chahal +5
Ultraviolet (UV) observations offer unique insights into transient and variable astrophysical phenomena, from the Sun and nearby stars to supernovae and star-forming galaxies. Here…
Optical spectroscopic signatures of the red giant evolutionary state
Ella Xi Wang, Melissa Ness, Thomas Nordlander +17
Modern spectroscopic surveys output large data volumes. Theoretical models provide a means to transform the information encoded in these data to measurements of physical stellar pr…
Photometric activity cycles in fast-rotating stars: Revisiting the reality of stellar activity cycle branches
Deepak Chahal, Devika Kamath, Richard de Grijs +2
We aim to detect activity cycles in young main-sequence stars, analogous to the 11-year solar cycle, using combined photometric survey data. This research will enhance our understa…
The Origin of Young Stellar Populations in NGC 1783: Accretion of External Stars
Li Wang, Licai Deng, Xiaoying Pang +4
The presence of young stellar populations in the Large Magellanic Cloud cluster NGC 1783 has caught significant attention, with suggestions ranging from it being a genuine secondar…
The VMC Survey -- L. Type II Cepheids in the Magellanic Clouds
Teresa Sicignano, Vincenzo Ripepi, Marcella Marconi +9
Type II Cepheids (T2C) are less frequently used counterparts of classical Cepheids which provide the primary calibration of the distance ladder for measuring in the local Uni…
Extended Main Sequences in Star Clusters
Chengyuan Li, Antonino P. Milone, Weijia Sun +1
Extended main sequences (eMSs) and extended main-sequence turnoffs (eMSTOs) are fascinating phenomena that are routinely observed in star clusters. These phenomena strongly challen…
The role of tidal interactions in the formation of slowly rotating early-type stars in young star clusters
Chenyu He, Chengyuan Li, Weijia Sun +9
The split main sequences found in the colour-magnitude diagrams of star clusters younger than ~600 Myr are suggested to be caused by the dichotomy of stellar rotation rates of uppe…
Unravelling the Period Gap using LAMOST Chromospheric Activity Indices
Deepak Chahal, Devika Kamath, Richard de Grijs +2
In our recent catalogue of BY Draconis (BY Dra) variables based on Zwicky Transient Facility data, we found traces of a period gap in the period-colour diagram. We combined our BY…
Precise Empirical Determination of Metallicity Dependence of Near-infrared Period-Luminosity Relations for RR Lyrae Variables
Anupam Bhardwaj, Marcella Marconi, Marina Rejkuba +9
RR Lyrae variables are excellent population II distance indicators thanks to their well-defined period-luminosity relations (PLRs) at infrared wavelengths. We present results of ne…
Hubble Space Telescope survey of Magellanic Cloud star clusters. Photometry and astrometry of 113 clusters and early results
A. P. Milone, G. Cordoni, A. F. Marino +29
In the past years, we have undertaken an extensive investigation of LMC and SMC star clusters based on HST data. We present photometry and astrometry of stars in 101 fields observe…
The role of binarity and stellar rotation in the split main sequence of NGC 2422
Chenyu He, Weijia Sun, Chengyuan Li +8
In addition to the extended main-sequence turnoffs widely found in young and intermediate-age (~ 600 Myr-2 Gyr-old) star clusters, some younger clusters even exhibit split main seq…
Double Mode Cepheids from the Zwicky Transient Facility Survey
Vishwangi Shah, Xiaodian Chen, Richard de Grijs
Multi-mode Cepheids pulsate simultaneously in more than one mode of oscillation. They provide an independent means to test stellar models and pulsation theories. They can also be u…
Statistics of BY Draconis Chromospheric Variable Stars
Deepak Chahal, Richard de Grijs, Devika Kamath +1
We present an extensive catalogue of BY Draconis (BY Dra)-type variables and their stellar parameters. BY Dra are main-sequence FGKM-type stars. They exhibit inhomogeneous starspot…
Exploring the stellar rotation of early-type stars in the LAMOST Medium-Resolution Survey. II. Statistics
Weijia Sun, Xiao-Wei Duan, Licai Deng +1
Angular momentum is a key property regulating star formation and evolution. However, the physics driving the distribution of the stellar rotation rates of early-type main-sequence…
Exploring the stellar rotation of early-type stars in the LAMOST Medium-Resolution Survey. I. Catalog
Weijia Sun, Xiao-Wei Duan, Licai Deng +3
We derive stellar parameters and abundances (`stellar labels') of 40,034 late-B and A-type main-sequence stars extracted from the Large Sky Area Multi-Object Fiber Spectroscopic Te…
The GALAH+ Survey: A New Library of Observed Stellar Spectra Improves Radial Velocities and Hints at Motions within M67
Tomaž Zwitter, Janez Kos, Sven Buder +25
GALAH+ is a magnitude-limited survey of high resolution stellar spectra obtained by the HERMES spectrograph at the Australian Astronomical Observatory. Its third data release provi…
Star clusters: Anything but simple
Richard de Grijs
The heated debate on the importance of stellar rotation and age spreads in massive star clusters has just become hotter by throwing stellar variability into the mix.
The VMC survey - XXIII. Model fitting of light and radial velocity curves of Small Magellanic Cloud classical Cepheids
Marcella Marconi, Roberto Molinaro, Vincenzo Ripepi +7
We present the results of the chi2 minimization model fitting technique applied to optical and near-infrared photometric and radial velocity data for a sample of 9 fundamental and…
Variability in the Milky Way: Contact binaries as diagnostic tools
Richard de Grijs, Xiaodian Chen, Licai Deng
We used the 50 cm Binocular Network (50BiN) telescope at Delingha Station (Qinghai Province) of Purple Mountain Observatory (Chinese Academy of Sciences) to obtain simultaneous …
The radial distributions of the two main-sequence components in the young massive star cluster NGC 1856
Chengyuan Li, Richard de Grijs, Licai Deng +1
The recent discovery of double main sequences in the young, massive star cluster NGC 1856 has caught significant attention. The observations can be explained by invoking two stella…
Stellar populations in star clusters
Chengyuan Li, Richard de Grijs, Licai Deng
Stellar populations contain the most important information about star clus- ter formation and evolution. Until several decades ago, star clusters were believed to be ideal laborato…
Physical parameter study of eight W Ursae Majoris-type contact binaries in NGC 188
Xiaodian Chen, Licai Deng, Richard de Grijs +10
We used the newly commissioned 50 cm Binocular Network (50BiN) telescope at Qinghai Station of Purple Mountain Observatory (Chinese Academy of Sciences) to observe the old open clu…
First Observational Signature of Rotational Deceleration in a Massive, Intermediate-age Star Cluster in the Magellanic Clouds
Xiaohan Wu, Chengyuan Li, Richard de Grijs +1
While the extended main-sequence turn-offs (eMSTOs) found in almost all 1--2 Gyr-old star clusters in the Magellanic Clouds are often explained by postulating extended star-formati…
The VMC Survey. XVIII. Radial dependence of the low-mass, 0.55--0.82 stellar mass function in the Galactic globular cluster 47 Tucanae
Chaoli Zhang, Chengyuan Li, Richard de Grijs +12
We use near-infrared observations obtained as part of the {\sl Visible and Infrared Survey Telescope for Astronomy} (VISTA) Survey of the Magellanic Clouds (VMC), as well as two co…