Related papers: Surface activity of a Rossby sequence of cool Hyad…
The Hyades constitute a homogeneous sample of stars ideal for investigating the dependence of planet formation on the mass of the central star. Due to their youth, Hyades members are much more chromospherically active than stars…
We present first results from a multi-object spectroscopy campaign in IC2602, the Hyades, the Pleiades, and the Coma cluster using VLT/FLAMES. We analysed the data for radial velocity, rotational velocity, and H-alpha activity. Here, we…
Low-mass (< 1.2 Solar mass) main-sequence stars lose angular momentum over time, leading to a decrease in their magnetic activity. The details of this rotation-activity relation remain poorly understood. Using observations of members of the…
We conduct a study of K to M type stars to investigate the activity and the rotation limit in the Hyades. We use a sample of 40 stars in this intermediate-age cluster (~625 Myr) to probe stellar rotation in the threshold region where…
We use the LAMOST spectra of member stars in Pleiades, M34, Praesepe, and Hyades to study how chromospheric activity vary as a function of mass and rotation at different age. We measured excess equivalent widths of H$\alpha$, H$\beta$, and…
Radius inflation continues to be explored as a peculiar occurrence among magnetically active, low-mass stars. Recently Somers et. al. 2017 showed that radius inflation among low-mass stars in the young open cluster M45 (Pleiades Cluster) is…
Magnetic fields of late-type stars are presumably generated by a dynamo mechanism at the interface layer between the radiative interior and the outer convective zone. The Rossby number, which is related to the dynamo process, shows an…
Open clusters are collections of stars with a single, well-determined age, and can be used to investigate the connections between angular-momentum evolution and magnetic activity over a star's lifetime. We present the results of a…
We have examined the relationship between rotation and activity in 14 late-type (M6-M7) M dwarfs, using high resolution spectra taken at the W.M. Keck Observatory and flux-calibrated spectra from the Sloan Digital Sky Survey. Most were…
We derive the effective temperatures and gravities of 461 OB stars in 19 young clusters by fitting the H-gamma profile in their spectra. We use synthetic model profiles for rotating stars to develop a method to estimate the polar gravity…
The relation between the lithium abundance, A_Li, and photospheric activity of solar-type Pleiads is investigated for the first time via acquisition and analysis of B and V-band data. Predictions of activity levels of target stars were made…
We investigate photometric variations due to stellar activity which induce systematic radial-velocity errors (so-called "jitter") for the four targets in the Hyades open cluster observed by the K2 mission (EPIC 210721261, EPIC 210923016,…
Focusing on ROSAT results for clusters in the $\sim 20-600$ Myr range, I first summarize our current understanding of the X-ray activity - rotation - age relationship. Then, the problem of the Hyades K and M dwarfs binaries is addressed: 1.…
As the closest open cluster to the Sun, the Hyades is an important benchmark for many stellar properties, but its members are also scattered widely over the sky. Previous studies of stellar rotation in the Hyades relied on targeted…
We have been using the Keck I High Resolution Spectrograph (HIRES) to search for planetary companions in the Hyades cluster. We selected four stars from this sample which showed significant radial velocity variability on short timescales to…
We revisit the X-ray properties of the main-sequence Hyades members and the relation between X-ray emission and stellar rotation. As input catalog for Hyades members, we combined three recent membership lists derived from Gaia DR2 data…
The connection between stellar rotation, stellar activity, and convective turnover time is revisited with a focus on the sole contribution of magnetic activity to the Ca II H&K emission, the so-called excess flux, and its dimensionless…
X-ray observations of low-mass stars in open clusters are critical to understanding the dependence of magnetic activity on stellar properties and their evolution. Praesepe and the Hyades, two of the nearest, most-studied open clusters, are…
Observations of late-type main-sequence stars have revealed empirical scalings of coronal activity versus rotation period or Rossby number $Ro$ (a ratio of rotation period to convective turnover time) which has hitherto lacked explanation.…
High precision photometry of solar-like members of the open cluster M67 with Kepler/K2 data has recently revealed enhanced activity for stars with a large Rossby number, which is the ratio of rotation period to the convective turnover time.…