60 citations · 514 across the 29 of their papers we have counts for
29 papers
Six decades of TIGRE and Mount Wilson chromospheric monitoring in the H and K lines: The quest for an understanding of solar-type activity
J. H. M. M. Schmitt, K. -P. Schröder, M. Mittag +3
The combined time series of the consistently calibrated chromospheric activity indicator, the S-index -- derived from Mount Wilson and TIGRE data -- now spans more than five decade…
Relationship between TIGRE solar S-index and USET Ca II K full disk images
G. Vanden Broeck, S. Bechet, F. Clette +3
Full disk observations of the solar chromosphere in the Ca II K line represent a valuable dataset for studies of solar magnetic activity. The S-index is widely used to investigate…
Prominence activation, optical flare, and post-flare loops on the RS Canum Venaticorum star SZ Piscium
Dongtao Cao, Shenghong Gu, Jian Ge +7
We present the results of time-resolved high-resolution spectroscopic observations of the very active RS Canum Venaticorum (RS CVn) star SZ Piscium (SZ Psc), obtained during two co…
Prominence detection and chromosphere feature on the prototype RS CVn of active binary systems
Dongtao Cao, Shenghong Gu, U. Wolter +4
We present a study of high-resolution spectra of RS Canum Venaticorum (RS CVn), a prototype of active binary systems. Our data were obtained from 1998 to 2017 using different teles…
Revisiting the cycle-rotation connection for late-type stars
M. Mittag, J. H. M. M. Schmitt, K. -P. Schröder
We analyse the relation between the activity cycle length and the Rossby number and collected a sample of 44 main sequence stars with well-known activity cycle periods and rotation…
A multi-wavelength view of the multiple activity cycles of ~Eridani
B. Fuhrmeister, M. Coffaro, B. Stelzer +3
Eridani is a highly active young K2 star with an activity cycle of about three years established using Ca II H & K line index measurements (S_MWO). This relatively short cycle…
Chromospheric activity and photospheric variation of Ori during the great dimming event in 2020
M. Mittag, K. -P. Schröder, V. Perdelwitz +2
The so-called great dimming event of alpha Ori in late 2019 and early 2020 sparked our interest in the behaviour of chromospheric activity during this period. To study the timeline…
Eight years of TIGRE robotic spectroscopy: Operational experience and selected scientific results
J. N. González-Perez, M. Mittag, J. H. M. M. Schmitt +4
TIGRE (Telescopio Internacional de Guanajuato Robótico Espectroscópico) has been operating in fully robotic mode in the Observatory La Luz (Guanajuato, Mexico) since the end of 201…
Yet another star in the Albireo system -- The discovery of Albireo Ad
D. Jack, K. -P. Schröder, M. Mittag +1
Context. Albireo is a well-known bright visual double star. It is still unclear if the components A and B form a gravitationally bound system. The component Albireo A is itself a b…
Time evolution of magnetic activity cycles in young suns: The curious case of kappa Ceti
S. Boro Saikia, T. Lueftinger, C. P. Folsom +15
A detailed investigation of the magnetic properties of young Sun-like stars can provide valuable information on our Sun's magnetic past and its impact on the early Earth. We determ…
CARMENES input catalog of M dwarfs VI. A time-resolved Ca II H&K catalog from archival data
V. Perdelwitz, M. Mittag, L. Tal-Or +15
Radial-velocity (RV) jitter caused by stellar magnetic activity is an important factor in state-of-the-art exoplanet discovery surveys such as CARMENES. Stellar rotation, along wit…
The corona -- chromosphere connection studied with simultaneous eROSITA and TIGRE observations
B. Fuhrmeister, J. Robrade, J. N. Gonzalez-Perez +3
Stellar activity is inherently time variable, therefore simultaneous measurements are necessary to study the correlation between different activity indicators. In this study we com…
Magnetic field and chromospheric activity evolution of HD75332: a rapid magnetic cycle in an F star without a hot Jupiter
E. L. Brown, S. C. Marsden, M. W. Mengel +10
Studying cool star magnetic activity gives an important insight into the stellar dynamo and its relationship with stellar properties, as well as allowing us to place the Sun's magn…
An X-ray activity cycle on the young solar-like star
M. Coffaro, B. Stelzer, S. Orlando +7
In 2015 we started the XMM-Newton monitoring of the young solar-like star Epsilon Eridani (440 Myr), one of the youngest solar-like stars with a known chromospheric CaII cycle. By…
The first Doppler imaging of the active binary prototype RS Canum Venaticorum
Yue Xiang, Shenghong Gu, U. Wolter +6
We present the first Doppler images of the prototypical active binary star RS CVn, derived from high-resolution spectra observed in 2004, 2016 and 2017, using three different teles…
Magnetic activity and evolution of the four Hyades K giants
Klaus-Peter Schröder, Marco Mittag, Dennis Jack +2
We determine the exact physical parameters of the four Hyades cluster K giants, using their parallaxes and atmospheric modeling of our red-channel TIGRE high-resolution spectra. Pe…
Magnetic activity of the solar-like star HD 140538
M. Mittag, J. H. M. M. Schmitt, T. S. Metcalfe +2
The periods of rotation and activity cycles are among the most important properties of the magnetic dynamo thought to be operating in late-type, main-sequence stars. In this paper,…
Revisiting the connection between magnetic activity, rotation period, and convective turnover time for main-sequence stars
M. Mittag, J. H. M. M. Schmitt, K. -P. Schröder
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 emi…
Intriguing X-ray and optical variations of the gamma Cas analog HD45314
G. Rauw, Y. Nazé, M. A. Smith +11
A growing number of Be and Oe stars, named the gamma Cas stars, are known for their unusually hard and intense X-ray emission. This emission could either trace accretion by a compa…
The Ca II infrared triplet's performance as an activity indicator compared to Ca II H and K
J. Martin, B. Fuhrmeister, M. Mittag +4
Aims. A large number of Calcium Infrared Triplet (IRT) spectra are expected from the GAIA- and CARMENES missions. Conversion of these spectra into known activity indicators will al…
Coronal X-ray emission and planetary irradiation in HD 209458
S. Czesla, M. Salz, P. C. Schneider +2
HD 209458 is one of the benchmark objects in the study of hot Jupiter atmospheres and their evaporation through planetary winds. The expansion of the planetary atmosphere is though…
Fifteen years in the high-energy life of the solar-type star HD 81809. XMM-Newton observations of a stellar activity cycle
S. Orlando, F. Favata, G. Micela +5
Aims. The data set of the long-term XMM-Newton monitoring program of HD 81809 is analyzed to study its X-ray cycle, to investigate if the latter is related to the chromospheric one…
Carrington cycle 24: The solar chromospheric emission in a historical and stellar perspective
K. -P. Schroder, M. Mittag, J. H. M. M. Schmitt +3
We present the solar S-index record of cycle 24, obtained by the TIGRE robotic telescope facility and its high-resolution spectrograph HEROS (R20,000), which measures the…
Study of the variability of Nova V5668 Sgr, based on high resolution spectroscopic monitoring
D. Jack, J. de J. Robles Pérez, I. De Gennaro Aquino +9
We present results of our dense spectroscopic monitoring of Nova V5668 Sgr. Starting on March 19 in 2015, only a few days after discovery, we have obtained a series of spectra with…