相关论文: No "Maunder minimum" candidates in M67: mitigating…

We present the results of a spectroscopic survey of the Ca II H & K core strengths in a sample of 60 solar-type stars that are members of the solar-age and solar-metallicity open cluster M67. We adopt the HK index, defined as the summed H+K…

Activity studies of solar-type stars, especially with reference to the status of our current Sun among them, have exposed the importance of (1) homogeneously selecting the sample stars and (2) reliably evaluating their activities down to a…

HD 166620 was recently identified as a Maunder Minimum candidate based on nearly 50 years of Ca II H & K activity data from Mount Wilson and Keck-HIRES (Baum et al. 2022). These data showed clear cyclic behavior on a 17-year timescale…

We report the results of the analysis of high resolution photospheric line spectra obtained with the UVES instrument on the VLT for a sample of 15 solar-type stars selected from a recent survey of the distribution of H and K chromospheric…

Past UV and optical observations of stars hosting hot Jupiters have shown that some of these stars present an anomalously low chromospheric activity, significantly below the basal level. For WASP-13, observations have shown that the…

We present the results from high-resolution spectroscopic measurements to determine metallicities and activities of bright stars in the southern hemisphere. We have measured the iron abundances ([Fe/H]) and chromospheric emission indices…

We present five decades of chromospheric activity measurements in 59 Sun-like stars as time series. These include and extend the 35 yr of stellar chromospheric activity observations by the Mount Wilson Survey (1966--2001), and continued…

Stars with very low levels of magnetic activity provide an opportunity for a more quantitative comparison with the Sun during its Maunder minimum. We employ spectra from the RAVE survey in a search for particularly low-activity stars with…

The discovery of true solar analogues is fundamental for a better understanding of the Sun and of the solar system. The open cluster M67 offers a unique opportunity to search for solar analogues because its chemical composition and age are…

We have calibrated an extensive set of BVI observations of M67. We have selected stars that are most likely to be single-star members of the cluster using proper motion, radial velocity, and variability information from the literature, and…

As the only known unambiguous star in a Maunder minimum-like chromospheric activity state, the properties of HD 166620 can provide valuable insight into the behaviour of the Sun during the historic extended low-states of its activity cycle.…

The Ca II H & K lines are strong chromospheric diagnostics that can be used to determine the temperature stratification and magnetic structure of the solar atmosphere. The Atacama Large Millimetre/Submillimetre Array (ALMA) offers…

$\require{mediawiki-texvc}$A stellar chromospheric activity database of solar-like stars is constructed based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low-Resolution Spectroscopic Survey (LRS). The database…

The long-term solar magnetic activity and its cyclical behaviour, which is maintained by a dynamo mechanism, are both still challenging for the astrophysics. In particular, an atypical event occurred between 1645 and 1715 when the solar…

One of the most enigmatic phenomena related to solar activity is the so-called Maunder minimum phase. It consists of the lowest sunspot's counting ever registered for the Sun, and never so far confirmed for other stars. Since the…

The open cluster M67 has solar metallicity and an age of about 4Gyr. The turn-off mass is close to the minimum mass for which solar metallicity stars develop a convective core during main sequence evolution as a result of the development of…

It is well known that the magnetic activity of solar type stars decreases with age, but it is widely debated in the literature whether there is a smooth decline or if there is an early sharp drop until 1-2 Gyr followed by a relatively…

Most stars previously identified as Maunder minimum stars are old stars evolved off of the main sequence. Analysis of activity measurements from the California and Carnegie Planet Search program stars and Hipparcos parallaxes implies that…

We present a spectroscopic study at high resolution, R~50,000, of 14 stars located on the main sequence, at the turn-off point and on the early subgiant branch in the cluster M67 in order to investigate its detailed chemical composition,…

An activity indicator, which can provide a robust quantitative mapping between the stellar activity and the physical properties of its atmosphere, is important in exploring the physics of activity across spectral types. But the common…