63 citations · 309 across the 28 of their papers we have counts for
19 papers · 1 filter
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…
On the stellar parameter dependence of the combined Fe I and Fe II chromospheric emission-line in the wings of the Ca II K line
Faiber Rosas-Portilla, Luis Zapata, Klaus-Peter Schröder +3
We present an analysis of the chromospheric emission of Fe I + Fe II in the wing of the Ca II K line of 21 G and K giant stars. Stellar parameters and absolute chromospheric fluxes…
Bright Spectroscopic Binaries: III. Binary systems with orbital periods of P > 500 days
Dennis Jack, Missael Alejandro Hernández Huerta, Faiber Danilo Rosas-Portilla +1
We present an analysis of nine bright spectroscopic binaries (HD 1585, HD 6613, HD 12390, HD 39923, HD 55201, HD 147430, HD 195543, HD 202699, HD 221643), which have orbital period…
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…
On the physical nature of the Wilson-Bappu effect: revising the gravity and temperature dependence
F. Rosas-Portilla, K. -P. Schröder, D. Jack
We present a sample of 32 stars of spectral types G and K, and luminosity classes I to V, with moderate activity levels, covering four orders of magnitude of surface gravity and a…
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…
Bright Spectroscopic Binaries: II. A study of five systems with orbital periods of P < 500 days
Dennis Jack, Missael Alejandro Hernández Huerta, Faiber Danilo Rosas-Portilla +1
We present a detailed analysis of five bright spectroscopic binary systems (HD 18665, HD 27131, HD 171852, HD 215550, HD 217427) that have orbital periods of P < 500 days. We deter…
Connecting the formation of stars and planets. II: coupling the angular momentum of stars with the angular momentum of planets
L. M. Flor-Torres, R. Coziol, K. -P. Schröder +2
A sample of 46 stars, host of exoplanets, is used to search for a connection between their formation process and the formation of the planets rotating around them. Separating our s…
Connecting the formation of stars and planets. I -- Spectroscopic characterization of host stars with TIGRE
L. M. Flor-Torres, R. Coziol, K. -P. Schröder +3
In search for a connection between the formation of stars and the formation of planets, a new semi-automatic spectral analysis method using \textsf{iSpec} was developed for the TIG…
A celestial matryoshka: Dynamical and spectroscopic analysis of the Albireo system
Ronald Drimmel, Alessandro Sozzetti, Klaus-Peter Schroeder +4
We present a spectroscopic characterisation and a new orbital solution for the binary system beta Cyg Aa/Ac (MCA 55), the primary component (beta Cyg A) of the well-known wide doub…
Bright Spectroscopic Binaries: I. Orbital parameters of five systems with periods of P < 365 days
Dennis Jack, Missael Alejandro Hernández Huerta, Klaus-Peter Schröder
In a well-aimed search based on the recently published Gaia~DR2 radial velocity data and performed with the robotic TIGRE telescope, we have discovered 19 bright (~mag) s…
Time series of optical spectra of Nova V659 Sct
Dennis Jack, Klaus-Peter Schröder, Philippe Eenens +4
With our robotic 1.2 m TIGRE telescope, we were able to obtain eight optical spectra with intermediate resolution (R = 20,000) of the Nova V659 Sct during different phases of its o…
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…
Constraint on the axion-electron coupling constant and the neutrino magnetic dipole moment by using the tip-RGB luminosity of fifty globular clusters
Santiago Arceo Díaz, Klaus-Peter Schröder, Kai Zuber +2
The current constraints in the neutrino magnetic dipole moment and axion-electron coupling constant ( and $\mathrm{α_{ae}\leq0.5\times10^{-2…
A catalogue of spectroscopic binary candidate stars derived from a comparison of Gaia DR2 with other radial velocity catalogues
D. Jack
Using the recently published Gaia second data release which includes measurements of the mean radial velocity of about 7.2 million stars, we performed a systematic comparison with…
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…
Habitability around F-type Stars
S. Sato, M. Cuntz, C. M. Guerra Olvera +2
We explore the general astrobiological significance of F-type main-sequence stars with masses between 1.2 and 1.5 Msun. Special consideration is given to stellar evolutionary aspec…
On Silicon Group Elements Ejected by Supernovae Type Ia
Soma De, F. X. Timmes, Themis Athanassiadou +6
There is compelling evidence that the peak brightness of a Type Ia supernova is affected by the electron fraction Ye at the time of the explosion. The electron fraction is set by t…
Theoretical light curves of type Ia supernovae
D. Jack, P. H. Hauschildt, E. Baron
Aims. We present the first theoretical SN Ia light curves calculated with the time-dependent version of the general purpose model atmosphere code PHOENIX. Our goal is to produce li…