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Precise and accurate mass and radius measurements of evolved stars are crucial to calibrating stellar models. Stars in detached eclipsing binaries (EBs) are excellent potential calibrators because their stellar parameters can be measured with fractional uncertainties of a few percent, independent of stellar models. The All-Sky Automated Survey for Supernovae (ASAS-SN) has identified tens of thousands of EBs, >35,000 of which were included in the ASAS-SN eclipsing binaries catalog. Here, we select eight EBs from this sample that contain giants based on their Gaia colors and absolute magnitudes. We use LBT/PEPSI, APF, and CHIRON to obtain multi-epoch spectra of these binaries and measure their radial velocities using two-dimensional cross-correlation methods. We simultaneously fit the ASAS-SN light curves and the radial velocities with PHOEBE to derive accurate and precise masses and radii with fractional uncertainties of $\lesssim 3\%$. For four systems, we also include Transiting Exoplanet Survey Satellite (TESS) light curves in our PHOEBE models, which significantly improves the radius determinations. In seven of our systems, both components have evolved off of the main sequence, and one system has a giant star component with a main sequence, Sun-like companion. Finally, we compare our mass and radius measurements to single-star evolutionary tracks and distinguish between systems that are first ascent red giant branch stars and those that are likely core helium-burning stars., Comment: 25 pages, 18 figures. Submitted to The Open Journal of Astrophysics

Context. In chemically peculiar Ap/Bp stars with large-scale organised magnetic fields with a simple centred dipole configuration, the ratio between the maximum and the minimum of the mean magnetic field modulus is of the order of 1.25. Values of 2 or more are observed only for very few Ap/Bp stars and are indicative of a very unusual magnetic field geometry. Aims. Determining the magnetic field structure of Ap/Bp stars is bound to provide a different insight into the physics and the origin of the magnetic fields in early-type stars. In this respect, the Bp star HD 57372 is of particular interest because strongly variable magnetically split lines are observed in HARPS and APOGEE spectra. Methods. We obtained and analysed measurements of the mean magnetic field modulus and of the mean longitudinal magnetic field using near-infrared spectra and optical polarimetric spectra distributed over the stellar rotation period. Results. The mean magnetic field modulus of HD 57372, as estimated from absorption lines that are split via the Zeeman effect and resolved in both optical and near-infrared spectra, is found to vary by an extraordinary amount of about 10 kG. The exceptional value of 3 for the ratio between the maximum and the minimum of the field modulus is indicative of a very unusual geometry of HD 57372's magnetic field. All observable quantities are found to vary in phase with the photometric period of 7.889 days. This includes the longitudinal magnetic field , which varies from -6 kG up to 1.7 kG in FORS2 spectra as well as the metal line strengths, whose equivalent widths change by up to 50% of their mean values over the course of the rotation period. The B8 temperature class of HD 57372 also places it among the hottest stars known to exhibit resolved, magnetically split lines.

Absorption lines from exoplanet atmospheres observed in transmission allow us to study atmospheric characteristics such as winds. We present a new high-resolution transit time-series of HD 189733b, acquired with the PEPSI instrument at the LBT and analyze the transmission spectrum around the Na D lines. We model the spectral signature of the RM-CLV-effect using synthetic PHOENIX spectra based on spherical LTE atmospheric models. We find a Na D absorption signature between the second and third contact but not during the ingress and egress phases, which casts doubt on the planetary origin of the signal. Presupposing a planetary origin of the signal, the results suggest a weak day-to-nightside streaming wind in the order of 0.7 km/s and a moderate super-rotational streaming wind in the order of 3 - 4 km/s, challenging claims of prevailing strong winds on HD 189733b., Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society

Pulsations of rapidly oscillating Ap stars and their interaction with the stellar magnetic field have not been studied in the near-IR region despite the benefits these observations offer compared to visual wavelengths. The main advantage of the near-IR is the quadratic dependence of the Zeeman effect on the wavelength, as opposed to the linear dependence of the Doppler effect. To test pulsation diagnostics of roAp stars in the near-IR, we aim to investigate the pulsation behaviour of one of the brightest magnetic roAp stars, $\gamma$Equ, which possesses a strong surface magnetic field of the order of several kilogauss and exhibits magnetically split spectral lines in its spectra. Two magnetically split spectral lines belonging to different elements, the triplet Fe I at 1563.63nm and the pseudo-doublet Ce III at 1629.2nm, were recorded with CRIRES+ over about one hour in the H band with the aim of understanding the character of the line profile variability and the pulsation behaviour of the magnetic field modulus. The profile shapes of both studied magnetically split spectral lines vary in a rather complex manner probably due to a significant decrease in the strength of the longitudinal field component and an increase in the strength of the transverse field components over the last decade. A mean magnetic field modulus of 3.9kG was determined for the Fe I, whereas for the Ce III we observe only about 2.9kG. For comparison, a mean field modulus of 3.4kG was determined using the Zeeman doublet Fe II at 6249.25 in optical PEPSI spectra recorded just about two weeks before the CRIRES+ observations. Different effects that may lead to the differences in the field modulus values are discussed. Our measurements of the mean magnetic field modulus using the line profiles recorded in different pulsational phase bins suggest a field modulus variability of 32G for the Fe I and 102G for the Ce III., Comment: Accepted to be published in A&A

Relics of ancient accretion events experienced by the Milky Way are predominantly located within the stellar halo of our Galaxy. However, debris from different objects display overlapping distributions in dynamical spaces, making it extremely challenging to properly disentangle their contribution to the build-up of the Galaxy. To shed light on this chaotic context, we started a program aimed at the homogeneous chemical tagging of the local halo of the Milky Way, focusing on the component in retrograde motion, since this is expected to host a large fraction of stars accreted from past mergers. The A Walk on the Retrograde Side (WRS) project targets retrograde halo stars in the Solar Neighborhood having accurate $6$-D phase space information available, measuring the precise chemical abundance of several chemical elements from high-resolution spectroscopy. In this first paper, we present the project and the analysis of high-resolution spectra obtained with UVES at VLT and PEPSI at LBT for $186$ stars. Accurate radial velocity and chemical abundance of several elements have been obtained for all the target stars. In particular we focus on the chemical composition of a specific subset of substructures identified dynamically in the literature. Our study reveals that two among the more recently discovered structures in the retrograde halo, namely Antaeus / L-RL$64$ and ED-$3$, have identical chemical patterns and similar integrals of motion, suggesting a common origin. In turn, the abundance patterns of this unified system differ from that of Gaia-Enceladus, confirming that it is an independent structure. Finally, Sequoia exhibits a different chemistry with respect to that of Gaia-Enceladus at $\mathrm{[Fe/H]} < -1.5$ dex, showcasing an excess of stars with lower Mg and Ca in the common metallicity range., Comment: 21 pages, 17 figures, accepted for publication in A&A

Numerous delta Sct and gamma Dor pulsators are identified in the region of the Hertzsprung-Russell diagram that is occupied by chemically peculiar magnetic Ap stars. The connection between delta Sct and gamma Dor pulsations and the magnetic field in Ap stars is however not clear: theory suggests for magnetic Ap stars some critical field strengths for pulsation mode suppression by computing the magnetic damping effect for selected p and g modes. To test these theoretical considerations, we obtained PEPSI spectropolarimetric snapshots of the typical Ap star HD340577, for which delta Sct-like pulsations were recently detected in TESS data, and the gamma Dor pulsator HR8799, which is a remarkable system with multiple planets and two debris disks. Our measurements reveal the presence of a magnetic field with a strength of several hundred Gauss in HD340577. The measured mean longitudinal field would be the strongest field measured so far in a delta Sct star if the pulsational character of HD340577 is confirmed spectroscopically. No magnetic field is detected in HR8799., Comment: 5 pages, 4 figures, accepted for publication as a letter to MNRAS

The identification and characterization of massive ($\gtrsim 0.8~M_\odot$) white dwarfs is challenging in part due to their low luminosity. Here we present two candidate single-lined spectroscopic binaries, Gaia DR3 4014708864481651840 and 5811237403155163520, with K-dwarf primaries and optically dark companions. Both have orbital periods of $P\sim 0.45$ days and show rotational variability, ellipsoidal modulations, and high-amplitude radial velocity variations. Using light curves from the Transiting Exoplanet Survey Satellite (TESS), radial velocities from ground-based spectrographs, and spectral energy distributions, we characterize these binaries to describe the nature of the unseen companion. We find that both systems are consistent with a massive white dwarf companion. Unlike simple ellipsoidal variables, star spots cause the light curve morphology to change between TESS sectors. We attempt to constrain the orbital inclination using PHOEBE binary light curve models, but degeneracies in the light curves of spotted stars prevent a precise determination. Finally, we search for similar objects using Gaia DR3 and TESS, and comment on these systems in the context of recently claimed compact object binaries., Comment: 17 pages, 15 figures. Submitted to MNRAS

We present a magnetic-field surface map for both stellar components of the young visual binary ksi Boo AB (A: G8V, B: K5V). Employed are high resolution Stokes-V spectra obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT). Stokes V line profiles are inverted with our iMAP software and compared to previous inversions. We employed an iterative regularization scheme without the need of a penalty function and incorporated a three-component description of the surface magnetic-field vector. The spectral resolution of our data is 130,000 (0.040-0.055A) and have signal-to-noise ratios (S/N) of up to three thousand per pixel depending on wavelength. A singular-value decomposition (SVD) of a total of 1811 spectral lines is employed for averaging Stokes-V profiles. Our mapping is accompanied by a residual bootstrap error analysis. Magnetic flux densities of the radial field component of up to plus/minus 115 +/- 5 G were reconstructed for ksi Boo A while up to plus/minus 55 +/- 3G were reconstructed for ksi Boo B. ksi Boo A's magnetic morphology is characterized by a very high latitude, nearly polar, spot of negative polarity and three low-to-mid latitude spots of positive polarity while ksi Boo B's morphology is characterized by four low-to-mid latitude spots of mixed polarity. No polar magnetic field is reconstructed for the cooler ksi Boo B star. Both our maps are dominated by the radial field component, containing 86 and 89 percent of the magnetic energy of ksi Boo A and B, respectively. We found only weak azimuthal and meridional field densities on both stars (plus/minus 15-30 G), about a factor two weaker than what was seen previously for ksi Boo A. The phase averaged longitudinal field component and dispersion is +4.5 +/- 1.5G for ksi Boo A and -5.0 +/- 3.0 G for ksi Boo B., Comment: 10 pages, 6 figures, accepted at A&A. arXiv admin note: text overlap with arXiv:1902.11201

Hot giant planets like MASCARA-1 b are expected to have thermally inverted atmospheres, that makes them perfect laboratory for the atmospheric characterization through high-resolution spectroscopy. Nonetheless, previous attempts of detecting the atmosphere of MASCARA-1 b in transmission have led to negative results. In this paper we aim at the detection of the optical emission spectrum of MASCARA-1 b. We used the high-resolution spectrograph PEPSI to observe MASCARA-1 (spectral type A8) near the secondary eclipse of the planet. We cross-correlated the spectra with synthetic templates computed for several atomic and molecular species. We obtained the detection of FeI, CrI and TiI in the atmosphere of MASCARA-1 b with a S/N ~7, 4 and 5 respectively, and confirmed the expected systemic velocity of ~13 km/s and the radial velocity semi-amplitude of MASCARA-1 b of ~200 km/s. The detection of Ti is of particular importance in the context of the recently proposed Ti cold-trapping below a certain planetary equilibrium temperature. We confirm the presence of an the atmosphere around MASCARA-1 b through emission spectroscopy. We conclude that the atmospheric non detection in transmission spectroscopy is due to the high gravity of the planet and/or to the overlap between the planetary track and its Doppler shadow.

Although significant progress has been achieved in recent surveys of the magnetism in massive stars, the origin of the detected magnetic fields remains to be the least understood topic in their studies. We present an analysis of 61 high-resolution spectropolarimetric observations of 36 systems with O-type primaries, among them ten known particle-accelerating colliding-wind binaries exhibiting synchrotron radio emission. Our sample consists of multiple systems with components at different evolutionary stages with wide and tight orbits and different types of interactions. For the treatment of the complex composite spectra of the multiple systems, we used a special procedure involving different line masks populated for each element separately. Out of the 36 systems, 22 exhibit in their LSD Stokes V profiles definitely detected Zeeman features, among them seven systems with colliding winds. For fourteen systems the detected Zeeman features are most likely associated with O-type components whereas for three systems we suggest an association with an early B-type component. For the remaining five systems the source of the field is unclear. Marginal evidence for the detection of a Zeeman feature is reported for eleven systems and non-detection for three systems. The large number of systems with definitely detected Zeeman features presents a mystery, but probably indicates that multiplicity plays a definite role in the generation of magnetic fields in massive stars. The newly found magnetic systems are supreme candidates for spectropolarimetric monitoring over their orbital and rotation periods to obtain trustworthy statistics on the magnetic field geometry and the distribution of field strength., Comment: 21 pages, 2 tables, 9 figures, accepted for publication in MNRAS

We embarked on a high-resolution optical spectroscopic survey of bright Transiting Exoplanet Survey Satellite (TESS) stars around the Northern Ecliptic Pole (NEP), dubbed the Vatican-Potsdam-NEP (VPNEP) survey. Our NEP coverage comprises 1067 stars, of which 352 are bona fide dwarf stars and 715 are giant stars, all cooler than spectral type F0 and brighter than V=8. m 5. Our aim is to characterize these stars for the benefit of future studies in the community. We analyzed the spectra via comparisons with synthetic spectra. Particular line profiles were analyzed by means of eigen-profiles, equivalent widths, and relative emission-line fluxes (when applicable). Two R=200 000 spectra were obtained for each of the dwarf stars with the Vatican Advanced Technology Telescope (VATT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI), with typically three R=55 000 spectra obtained for the giant stars with STELLA and the STELLA Echelle Spectrograph (SES). Combined with V-band magnitudes, Gaia eDR3 parallaxes, and isochrones from the Padova and Trieste Stellar Evolutionary Code, the spectra can be used to obtain radial velocities, effective temperatures, gravities, rotational and turbulence broadenings, stellar masses and ages, and abundances for 27 chemical elements, as well as isotope ratios for lithium and carbon, line bisector spans, convective blue-shifts (when feasible), and levels of magnetic activity from H{\alpha}, H{\beta}, and the Ca ii infrared triplet. In this initial paper, we discuss our analysis tools and biases, presenting our first results from a pilot sub-sample of 54 stars (27 bona-fide dwarf stars observed with VATT+PEPSI and 27 bona-fide giant stars observed with STELLA+SES) and making all reduced spectra available to the community.

Previous observations suggested that Ap and Bp stars exhibit a bimodal distribution of surface magnetic field strengths and that actually only few or no stars exist with magnetic dipole field strengths below 300 G down to a few Gauss. As the number of Ap and Bp stars currently known to possess weak magnetic fields is not large, it is necessary to carry out additional spectropolarimetric studies of Ap and Bp stars to prove whether the assumption of the existence of a critical value for the stability of magnetic fields is realistic. In this study, we present high-resolution HARPSpol magnetic field measurements for a sample of Ap stars with sharp spectral lines with a view to characterize the strengths of their magnetic fields. Out of the studied seven sharp-lined stars, two stars, HD 174779 and HD 203932, exhibit a rather weak longitudinal magnetic field with $\left< B_{\rm z}\right>=-45\pm3$ G and $\left< B_{\rm z}\right>=21\pm4$ G, respectively. Additionally, TESS observations were used to test previous conclusions on the differentiation of rotation periods of Ap and Bp stars. Apart from HD 189832 and HD 203932, all other studied sharp-lined stars have long rotation periods. Since an explanation for the slow rotation of Ap stars is currently missing, additional studies of slowly rotating Ap and Bp stars are necessary to improve our understanding of the formation and evolution of Ap and Bp stars., Comment: 13 pages, 18 figures, 2 tables. Accepted to be published in MNRAS

We present an analysis of the red giant component of the recurrent nova V3890 Sgr, using data obtained before and after its 2019 eruption. Its effective temperature is $T_{\rm eff}=3050\pm$200 K for $\log{g}=0.7$, although there are modest changes in $T_{\rm eff}$. There is an overabundance of both carbon ($0.20\pm0.05$~dex) and sodium ($1.0\pm0.3$~dex) relative to their solar values, possibly the result of ejecta from the 1990 nova eruption being entrained into the red giant photosphere. We find $^{12}$C/$^{13}$C $=25\pm2$, a value similar to that found in red giants in other recurrent novae. The interpretation of the quiescent spectrum in the 5--38$\,mu$m region requires the presence of photospheric SiO absorption and cool ($\sim400$~K) dust in the red giant environment. The spectrum in the region of the Na{\sc i} D lines is complex, and includes at least six interstellar components, together with likely evidence for interaction between ejecta from the 2019 eruption and material accumulated in the plane of the binary. Three recurrent novae with giant secondaries have been shown to have environments with different dust content, but photospheres with similar $^{12}$C/$^{13}$C ratios. The SiO fundamental bands most likely have a photospheric origin in the all three stars., Comment: Accepted for publication in MNRAS on 22 July 2022. 15 pages, 11 figs

We present the results of high-resolution spectropolarimetric observations of the optically dominant component in the rare hydrogen-deficient binary system upsilon Sgr. Only a small number of such systems in a very late phase of helium shell burning are currently known. The mass transfer from the donor star in binary systems usually leads to the stripping of its hydrogen envelope. Consequently, since the mass of the secondary increases, it appears rejuvenated. Using a few ESO FORS1 low-resolution spectropolarimetric observations of this system, Hubrig et al. announced in 2009 the presence of a magnetic field of the order of -70 - -80G. Here we report on more recent high-resolution ESO HARPS spectropolarimetric observations showing that the primary in upsilon Sgr is a spectrum variable star and possesses a weak magnetic field of the order of a few tens of Gauss. The detection of a magnetic field in this rare hydrogen-deficient binary is of particular interest, as such systems are frequently discussed as probable progenitors of core-collapse supernovae and gravitational-wave sources. Future magnetic studies of such systems will be worthwhile to gain deeper insights into the role of magnetic fields in the evolution of massive stars in binary systems., Comment: 7 pages, 2 tables, 2 figures, accepted for publication in ApJ

We report the discovery of a stripped giant + lower giant binary, 2M04123153+6738486 (2M0412), identified during a search for non-interacting compact object-star binaries. 2M0412 is an evolved ($T_{\rm eff, giant}\simeq4000$ K), luminous ($L_{\rm giant}\simeq150~L_\odot$) red giant in a circular $P=81.2$ day binary. 2M0412 is a known variable star previously classified as a semi-regular variable. The cross-correlation functions of follow-up Keck/HIRES and LBT/PEPSI spectra show an RV-variable second component with implied mass ratio $q=M_{\rm giant}/M_{\rm comp}\simeq0.20\pm0.01$. The ASAS-SN, ATLAS, TESS and ZTF light curves show that the giant is a Roche lobe filling ellipsoidal variable with an inclination of $49.4^\circ{}\pm{0.3^{\circ}}$, and a giant mass of $M_{\rm giant}=0.38\pm0.01~ M_\odot$ for a distance of $\simeq3.7$ kpc. The mass of the giant indicates that its envelope has been stripped. The giant companion on the lower red giant branch has a mass of $M_{\rm comp}=1.91\pm0.03~M_\odot$ with $T_{\rm eff, comp}\simeq5000$ K, $L_{\rm comp}\simeq60~L_\odot$ and $R_{\rm comp}\simeq11~R_\odot$. We also identify an orbital phase dependent, broad $\rm H\alpha$ emission line which could indicate ongoing accretion from the stripped red giant onto the companion., Comment: Revised version of the paper following comments from the referee, submitted to MNRAS. arXiv admin note: text overlap with arXiv:2101.02212

The O9.7 V star HD 54879 is currently the only massive magnetic star whose magnetic field geometry and rotation period are not constrained. Over the last three years, we gathered additional observations of this star, obtained using various instruments at several astronomical facilities with, the aim to constrain the rotation period and the magnetic field geometry. The new data include the first full Stokes vector observations with the PEPSI spectropolarimeter, installed at the Large Binocular Telescope. The acquired spectropolarimetric observations show a very slow magnetic field variability related to the extremely slow rotation of HD 54879, which is also indicated in a dynamical spectrum, displaying variability of the H$\alpha$ line. The most intriguing result of our study is the discovery of differences in longitudinal magnetic field strengths measured using different LSD masks containing lines belonging to different elements. It is the first time that such a differential analysis of the field strength in dependence of the used lines is carried out for a magnetic O-type star. Since the LSD Stokes $I$ profiles of the studied O, Si, and He line masks remain stable over all observing epochs, we conclude that the detection of different field strengths using lines belonging to these elements is related to the different formation depths, with the He lines formed much higher in the stellar atmosphere compared to the silicon and the oxygen lines, and NLTE effects. Our numerical magnetospherical model suggests the presence of enhanced gas density that fills the volume inside the field lines close to the star., Comment: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society Published by Oxford University Press on behalf of the Royal Astronomical Society

We present the first short time scale observations of the roAp star gamma Equ in linear polarized light obtained with the PEPSI polarimeter installed at the LBT. These observations are used to search for pulsation variability in Stokes Q and U line profiles belonging to different elements. The atmospheres of roAp stars are significantly stratified with spectral lines of different elements probing different atmospheric depths. roAp stars with strong magnetic fields, such as gamma Equ with a magnetic field modulus of 4kG and a pulsation period of 12.21min, are of special interest because the effect of the magnetic field on the structure of their atmospheres can be studied with greatest detail and accuracy. Our results show that we may detect changes in the transversal field component in Fe I and rare-earth lines possessing large second-order Lande factors. Such variability can be due to the impact of pulsation on the transverse magnetic field, causing changes in the obliquity angles of the magnetic force lines. Further studies of roAp stars in linear polarized light and subsequent detailed modelling are necessary to improve our understanding of the involved physics., Comment: 6 pages, 4 figures, accepted for publication as a letter to MNRAS

We report the discovery of the closest known black hole candidate as a binary companion to V723 Mon. V723 Mon is a nearby ($d\sim460\,\rm pc$), bright ($V\simeq8.3$~mag), evolved ($T_{\rm eff, giant}\simeq4440$~K, and $L_{\rm giant}\simeq173~L_\odot$) red giant in a high mass function, $f(M)=1.72\pm 0.01~M_\odot$, nearly circular binary ($P=59.9$ d, $e\simeq 0$). V723 Mon is a known variable star, previously classified as an eclipsing binary, but its All-Sky Automated Survey (ASAS), Kilodegree Extremely Little Telescope (KELT), and Transiting Exoplanet Survey Satellite (TESS) light curves are those of a nearly edge-on ellipsoidal variable. Detailed models of the light curves constrained by the period, radial velocities and stellar temperature give an inclination of $87.0^\circ{}^{+1.7^{\circ}}_{-1.4^{\circ}} $, a mass ratio of $q\simeq0.33\pm0.02$, a companion mass of $M_{\rm comp}=3.04\pm0.06~M_\odot$, a stellar radius of $R_{\rm giant}=24.9\pm0.7~R_\odot$, and a giant mass of $M_{\rm giant}=1.00\pm0.07~ M_\odot$. We identify a likely non-stellar, diffuse veiling component with contributions in the $B$ and $V$-band of ${\sim}63\%$ and ${\sim}24\%$, respectively. The SED and the absence of continuum eclipses imply that the companion mass must be dominated by a compact object. We do observe eclipses of the Balmer lines when the dark companion passes behind the giant, but their velocity spreads are low compared to observed accretion disks. The X-ray luminosity of the system is $L_{\rm X}\simeq7.6\times10^{29}~\rm ergs~s^{-1}$, corresponding to $L/L_{\rm edd}{\sim}10^{-9}$. The simplest explanation for the massive companion is a single compact object, most likely a black hole in the "mass gap"., Comment: 28 pages, 16 figures. Accepted for publication in MNRAS

NGC 1624-2 is an O7f?p star with a reported probable polar magnetic field strength $\ge$ 20 kG, which is the strongest magnetic field ever measured in an O-type star. We study the variability of the mean longitudinal magnetic field $\langle B_z \rangle$ and the mean field modulus $\langle B \rangle$ to obtain constraints on its field geometry. Only one magnetic pole is observable over the rotation cycle. The approximately sinusoidal variation of $\langle B_z \rangle$ and the ratio of the values of the extrema of $\langle B \rangle$ indicate that there is an important component of the field that is dipolar. The $\langle B_z \rangle$ values measured over the rotation cycle are in the range from $-0.2$ to 4.5 kG, whereas the values for $\langle B \rangle$ vary between 9 and 12 kG. The $\langle B_z \rangle$ values obtained using the O III $\lambda$7455 emission line are in the range from 0.4 to 2.3 kG and show a variability pattern similar to that detected for the absorption lines. The fact that the phase of the $\langle B_z \rangle$ minimum coincides with the phase of the $\langle B \rangle$ maximum, indicates that the field structure must significantly depart from a centred dipole. Further, we discuss the nature of the observed variable Stokes $V$ profiles corresponding to a longitudinal field of negative polarity detected in the emission He I lines and present the first MHD numerical simulations of the gas flow in the magnetosphere of this star., Comment: Accepted to be published in MNRAS

High resolution spectropolarimetric observations of the strongly magnetic, super-slowly rotating rapidly oscillating Ap star HD166473 are used to investigate the implications of the presence of a variable strong magnetic field on the vertical and surface horizontal distribution of various chemical elements. The analysis of the calculated LSD Stokes $I$ and $V$ profiles confirms the previously reported detection of non-uniform horizontal surface distribution of several chemical elements. To test the vertical abundance stratification of iron peak and rare earth elements, magnetic field measurements were carried out using spectral lines of these elements belonging to neutral and ionised stages. We find clear indication of the existence of a relation between the magnetic field strength and its orientation and vertical element stratification: magnetic field values obtained for elements in different stages close to the magnetic equator are rather similar whereas the dispersion in field strengths is remarkably large in the regions close to magnetic field poles. At the phases of negative and positive extrema the mean longitudinal field strength determined from the analysis of the REE lines is usually stronger than when using Fe and Cr. The strongest mean longitudinal magnetic field, up to $-$4160$\pm$226 G, is detected using the La II line list at the negative extremum, followed by the measurements using the Pr III lines with $\langle B_z \rangle$=$-$3740$\pm$343 G and the Ce II lines with $\langle B_z \rangle$=$-$3372$\pm$247 G. The strongest mean longitudinal magnetic field of positive polarity, up to 3584$\pm$354 G is detected using the Pr III lines, followed by the measurement $\langle B_z \rangle$=2517$\pm$249 G using the Ce II lines., Comment: Accepted to be published in MNRAS

High spectral resolution transmission spectroscopy is a powerful tool to characterize exoplanet atmospheres. Especially for hot Jupiters, this technique is highly relevant, due to their high altitude absorption e.g. from resonant sodium (Na I) and potassium (K I) lines. We resolve the atmospheric K I-absorption on HD189733b with the aim to compare the resolved K I -line and previously obtained high resolution Na I-D-line observations with synthetic transmission spectra. The line profiles suggest atmospheric processes leading to a line broadening of the order of 10 km/s for the Na I-D-lines, and only a few km/s for the K I-line. The investigation hints that either the atmosphere of HD189733b lacks a significant amount of K I or the alkali lines probe different atmospheric regions with different temperature, which could explain the differences we see in the resolved absorption lines.

Chemically peculiar (CP) stars of the upper main sequence are characterised by specific anomalies in the photospheric abundances of some chemical elements. The group of CP2 stars, which encompasses classical Ap and Bp stars, exhibits strictly periodic light, spectral, and spectropolarimetric variations that can be adequately explained by the model of a rigidly rotating star with persistent surface structures and a stable global magnetic field. Using observations from the Kepler K2 mission, we find that the B9pSi star HD 174356 displays a light curve both variable in amplitude and shape, which is not expected in a CP2 star. Employing archival and new photometric and spectroscopic observations, we carry out a detailed abundance analysis of HD 174356 and discuss its photometric and astrophysical properties in detail. We employ phenomenological modeling to decompose the light curve and the observed radial velocity variability. Our abundance analysis confirms that HD 174356 is a silicon-type CP2 star. No magnetic field stronger than 110G was found. The star's light curve can be interpreted as the sum of two independent strictly periodic signals with P1 = 4.04355(5)d and P2 = 2.11169(3)d. The periods have remained stable over 17 years of observations. In all spectra, HD 174356 appears to be single-lined. From the simulation of the variability characteristics and investigation of stars in the close angular vicinity, we put forth the hypothesis that the peculiar light variability of HD 174356 arises in a single star and is caused by rotational modulation due to surface abundance patches (P1) and g mode pulsation (P2)., Comment: 19 pages, 13 figures, 7 tables, accepted by Monthly Notices of the Royal Astronomical Society

The main-sequence mercury-manganese (HgMn) stars are known to exhibit large overabundances of exotic elements and, similar to magnetic Ap/Bp stars, are spectrum variables, implying the presence of an inhomogeneous element distribution over the stellar surface. A number of magnetic field studies have been attempted in the last decades, indicating that magnetic fields in HgMn stars, if they exist, should be rather weak. The presence of tangled magnetic fields was suggested by several authors who detected quadratic magnetic fields using the moment technique. We employ the least-squares deconvolution technique to carry out a sensitive search for weak magnetic fields in spectropolarimetric observations of three HgMn stars, HD221507, HD65949, and HD101189, which have different fundamental parameters and spectral characteristics. A definite weak longitudinal field is discovered in HD221507 and HD65949 on single epochs, while only marginal field detections were achieved for HD101189. The new measurements indicate that the structure of the magnetic fields is probably rather complex: our analysis reveals the presence of reversed Stokes V profiles at the same observational epoch if individual elements are used in the measurements. This is the first observational evidence that individual elements sample distinct local magnetic fields of different polarity across the stellar surface., Comment: 5 pages, 1 table, 3 figures, accepted for publication as MNRAS Letter

Observations of the Earthshine off the Moon allow for the unique opportunity to measure the large-scale Earth atmosphere. Another opportunity is realized during a total lunar eclipse which, if seen from the Moon, is like a transit of the Earth in front of the Sun. We thus aim at transmission spectroscopy of an Earth transit by tracing the solar spectrum during the total lunar eclipse of January 21, 2019. Time series spectra of the Tycho crater were taken with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in its polarimetric mode in Stokes IQUV at a spectral resolution of 130000 (0.06 \AA). In particular, the spectra cover the red parts of the optical spectrum between 7419-9067 \AA . The spectrograph's exposure meter was used to obtain a light curve of the lunar eclipse. The brightness of the Moon dimmed by 10.75 mag during umbral eclipse. We found both branches of the O$_2$ A-band almost completely saturated as well as a strong increase of H$_2$O absorption during totality. The deep penumbral spectra show significant excess absorption from the NaI 5890 \AA doublet, the CaII infrared triplet around 8600 \AA, and the KI line at 7699 \AA in addition to several hyper-fine-structure lines of MnI and even from BaII. The detections of the latter two elements are likely due to an untypical solar center-to-limb effect rather than Earth's atmosphere. The absorption in CaII and KI remained visible throughout umbral eclipse. A small continuum polarization of the O$_2$ A-band of 0.12\% during umbral eclipse was detected at 6.3$\sigma$. No line polarization of the O$_2$ A-band, or any other spectral-line feature, is detected outside nor inside eclipse. It places an upper limit of $\approx$0.2\% on the degree of line polarization during transmission through Earth's atmosphere and magnetosphere., Comment: Accepted for publication in Astronomy & Astrophysics

In recent years Herbig Ae/Be stars receive considerable attention as their disks are believed to be the sites of on-going planet formation. Confirming the presence of magnetic fields in these stars is critical for understanding the transport of angular momentum during the protostellar phase. Furthermore, magnetic fields set the conditions for strongly anisotropic accretion. In this study we present the results of our recent observing campaigns of a sample of Herbig Ae/Be stars aimed at measurements of their magnetic fields applying the Singular Value Decomposition method to high resolution spectropolarimetric observations. The strongest longitudinal magnetic field of 209 G is detected in the Herbig Be star HD 58647, whereas the weakest field of 17 G is measured in the Herbig Ae star HD 190073. A change of polarity is detected for HD 58647 and in the Herbig Be star HD 98922. The obtained results provide further evidence that Herbig Ae/Be stars possess much weaker magnetic fields than their lower mass counterpart T Tauri stars with magnetic fields of kG order., Comment: 6 pages, 3 figures, 1 table, accepted to be published in MNRAS

We present longitudinal magnetic field measurements $\langle B_z \rangle$ for the Herbig Ae primary and the T Tauri secondary in the SB2 system HD 104237. These measurements were carried out using high spectral resolution observations obtained with the High Accuracy Radial velocity Planet Searcher in polarimetric mode, installed at the ESO La Silla 3.6 m telescope. In agreement with previous studies of Herbig Ae stars, the longitudinal magnetic field in the primary is rather weak, ranging from 47 G to 72 G. The secondary component possesses a variable, much stronger magnetic field, up to 600 G, as expected for a magnetically active T Tauri star. We estimated the rotation period of the primary, $P_{\mathrm{rot}}=4.33717\pm0.00316$ d ($=104\pm0.08$ h), from metal line equivalent width variations., Comment: 6 pages, 5 figures, accepted to be published in MNRAS

We present a temperature and a magnetic-field surface map of the K2 subgiant of the active binary II Peg. Employed are high resolution Stokes IV spectra obtained with the new Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT). Our main result is that the temperature features on II Peg closely correlate with its magnetic field topology. We find a warm spot (350K warmer with respect to the effective temperature) of positive polarity and radial field density of 1.1 kG coexisting with a cool spot (780K cooler) of negative polarity of 2 kG. Several other cool features are reconstructed containing both polarities and with (radial) field densities of up to 2 kG. The largest cool spot is reconstructed with a temperature contrast of 550 K, an area of almost 10% of the visible hemisphere, and with a multipolar magnetic morphology. A meridional and an azimuthal component of the field of up to +/-500G is detected in two surface regions between spots with strong radial fields but different polarities. A force-free magnetic-field extrapolation suggests that the different polarities of cool spots and the positive polarity of warm spots are physically related through a system of coronal loops of typical height of approx. 2 Rstar. While the H-alpha line core and its red-side wing exhibit variations throughout all rotational phases, a major increase of blue-shifted H-alpha emission was seen for the phases when the warm spot is approaching the stellar central meridian indicating high-velocity mass motion within its loop. We explain the warm spots due to photospheric heating by a shock front from a siphon-type flow between regions of different polarities while the majority of the cool spots is likely formed due to the expected convective suppression like on the Sun., Comment: 12 pages, 8 figures

On the AGB, low to intermediate mass stars blow away their outer envelopes, forming planetary nebulae. Interaction between the planetary nebula and its central progenitor is poorly understood and even more complex when the central object is a binary star with a magnetically active component, like it is the case for IN Com. We aim to quantify the surface activity of the cool binary component of IN Com and aim to explain its origin. We need a better understanding of how central binary stars in planetary nebulae evolve and how this evolution could develop such magnetically active stars like IN Com. We present 13 Doppler images covering six months in 2017 and use them to measure the surface differential rotation. Hitherto unpublished photometric data from between 1989-2017 are presented. We apply Fourier-transformation to both photometry and spectra. Very high resolution spectra are used to update IN Com's astrophysical parameters by means of spectral synthesis. Doppler images show cool and warm spots coexisting with an average surface temperature contrast of -1000K and +300K with respect to the effective temperature. Approximately 8% of the surface is covered with cool spots and 3% with warm spots. A cool polar spot is seen in all images. We found anti-solar surface differential rotation with a shear coefficient of -0.026+/-0.005 and an equatorial rotation period of 5.973+/-0.008 d. We reconfirm the 5.9-day rotation period of the cool star from photometry, radial velocities, and H alpha line-profile variations. A long-term V-brightness variation with a likely period of 7.2yr is found. It appears in phase with the orbital radial velocity of the binary system in the sense brightest at highest velocity and faintest at lowest velocity. We redetermine [Ba/Fe], [Y/Fe] and [Sr/Fe] ratios and confirm the overabundance of these s-process elements in the atmosphere of IN Com., Comment: accepted for publication in Astronomy & Astrophysics

We present the first temperature surface map of EK Dra from very-high-resolution spectra obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope. Changes in spectral line profiles are inverted to a stellar surface temperature map using our $i$Map code. The long-term photometric record is employed to compare our map with previously published maps. Four cool spots were reconstructed, but no polar spot was seen. The temperature difference to the photosphere of the spots is between 990 and 280K. Two spots are reconstructed with a typical solar morphology with an umbra and a penumbra. For the one isolated and relatively round spot (A), we determine an umbral temperature of 990K and a penumbral temperature of 180K below photospheric temperature. The umbra to photosphere intensity ratio of EK Dra is approximately only half of that of a comparison sunspot. A test inversion from degraded line profiles showed that the higher spectral resolution of PEPSI reconstructs the surface with a temperature difference that is on average 10% higher than before and with smaller surface areas by 10-20%. PEPSI is therefore better suited to detecting and characterising temperature inhomogeneities. With ten more years of photometry, we also refine the spot cycle period of EK Dra to 8.9$\pm$0.2 years with a continuing long-term fading trend. The temperature morphology of spot A so far appears to show the best evidence for the existence of a solar-like penumbra for a starspot. We emphasise that it is more the non-capture of the true umbral contrast rather than the detection of the weak penumbra that is the limiting factor. The relatively small line broadening of EK Dra, together with the only moderately high spectral resolutions previously available, appear to be the main contributors to the lower-than-expected spot contrasts when comparing to the Sun., Comment: Accepted for A&A

Models of magnetically driven accretion reproduce many observational properties of T Tauri stars. For the more massive Herbig Ae/Be stars, the corresponding picture has been questioned lately, in part driven by the fact that their magnetic fields are typically one order of magnitude weaker. Indeed, the search for magnetic fields in Herbig Ae/Be stars has been quite time consuming, with a detection rate of about 7%, also limited by the current potential to detect weak magnetic fields. Over the last two decades, magnetic fields were found in about twenty objects and for only two Herbig Ae/Be stars was the magnetic field geometry constrained. Further, studies were undertaken to investigate the time dependence of spectroscopic tracers of magnetospheric accretion. Overall, it seems that while there is proof that magneospheric accretion is present in some Herbig Ae stars, there is less evidence for the Herbig Be stars., Comment: 9 pages, 3 figures, to appear in "Physics of magnetic stars", 2018 October 1-5, Special Astrophysical Observatory, Russia. arXiv admin note: text overlap with arXiv:1308.6777

Starspots are important manifestations of stellar magnetic activity. By studying their behaviour in young solar analogues, we can unravel the properties of their magnetic cycles. This gives crucial information of the underlying dynamo process. Comparisons with the solar cycle enable us to infer knowledge about how the solar dynamo has evolved during the Sun's lifetime. Here we study the correlation between photometric brightness variations, spottedness and mean temperature in V889 Her, a young solar analogue. Our data covers 18 years of spectroscopic and 25 years of photometric observations. We use Doppler imaging to derive temperature maps from high-resolution spectra. We use the Continuous Period Search method to retrieve mean V-magnitudes from photometric data. Our Doppler imaging maps show a persistent polar spot structure varying in strength. This structure is centered slightly off the rotational pole. The mean temperature derived from the maps shows an overall decreasing trend, as does the photometric mean brightness, until it reaches its minimum around 2017. The filling factor of cool spots, however, shows only a weak tendency to anti-correlate with the decreasing mean brightness. We interpret V889 Her to have entered into a grand maximum in its activity. The clear relation between the mean temperature of the Doppler imaging surface maps and the mean magnitude supports the reliability of the Doppler images. The lack of correlation between the mean magnitude and the spottedness may indicate that bright features in the Doppler images are real., Comment: 9 pages, 7 figures, 4 tables

HD 21190 is a known $\delta$ Scuti star showing Ap star characteristics and a variability period of 3.6 h discovered by the Hipparcos mission. Using Gaia DR1 data for an astrometric analysis, it was recently suggested that HD 21190 forms a physical binary system with the companion CPD -83$^{\circ}$ 64B. An atmospheric chemical analysis based on HARPS observations revealed the presence of overabundances of heavy and rare-earth elements, which are typically observed in chemically peculiar stars with large-scale organized magnetic fields. Previous observations of HD 21190 indicated a magnetic field strength of a few hundred Gauss. The presence of a magnetic field in CPD -83$^{\circ}$ 64B remained unexplored. In this work, we reanalyse this system using Gaia DR2 data and present our search for the magnetic field in both stars based on multi-epoch HARPSpol high-resolution and FORS 2 low-resolution spectropolarimetric observations. The Gaia DR2 results clearly indicate that the two star are not physically associated. A magnetic field detection at a significance level of more than 6$\sigma$ ($\left< B_{\rm z}\right>_{\rm all}=230\pm38$ G) was achieved for the $\delta$ Scuti variable HD 21190 in FORS 2 observations using the entire spectrum for the measurements. The magnetic field appears to be stronger in CPD -83$^{\circ}$ 64B. The highest value for the longitudinal magnetic field in CPD -83$^{\circ}$ 64B, $\left< B_{\rm z}\right>_{\rm all}=509\pm104$ G, is measured at a significance level of 4.9$\sigma$. Furthermore, the high-resolution HARPS\-pol observations of this component indicate the presence of pulsational variability on a time scale of tens of minutes., Comment: MNRAS, accepted

We focus on early-B type stars with helium overabundance, for which the presence of a magnetic field has not previously been reported. The measurements were carried out using high-spectral-resolution spectropolarimetric observations obtained with the High Accuracy Radial velocity Planet Searcher (HARPS) in polarimetric mode, installed at the ESO La Silla 3.6m telescope. For five He-rich stars, the longitudinal magnetic field was detected for the first time. For one target, HD58260, the presence of a longitudinal magnetic field of the order of 1.8 kG has already been reported in the literature, but the magnetic field has remained constant over tens of years. Our measurement carried out using the polarimetric spectra obtained in 2015 March indicates a slight decrease of the longitudinal magnetic field strength compared to measurements reported in previous works. A search for periodic modulation in available photometric data allowed us to confidently establish a period of 2.64119$\pm$0.00420 d in archival ASAS3 data for CPD -27$^{\circ}$ 1791. No period could be determined for the other five stars. The obtained results support the scenario that all He-rich stars are detectably magnetic and form an extension of the Ap star phenomenon to higher temperatures., Comment: Accepted as A&A Letter

We report the detection of weak mean longitudinal magnetic fields in the Herbig Ae double-lined spectroscopic binary AK Sco and in the presumed spectroscopic Herbig Ae binary HD95881 using observations with the High Accuracy Radial velocity Planet Searcher polarimeter (HARPSpol) attached to the European Southern Observatory's (ESO's) 3.6m telescope. Employing a multi-line singular value decomposition (SVD) method, we detect a mean longitudinal magnetic field =-83+-31G in the secondary component of AK Sco on one occasion. For HD95881, we measure =-93+-25G and =105+-29G at two different observing epochs. For all the detections the false alarm probability is smaller than 10^-5. For AK Sco system, we discover that accretion diagnostic Na I doublet lines and photospheric lines show intensity variations over the observing nights. The double-lined spectral appearance of HD95881 is presented here for the first time.

Since its discovery more than half a century ago Przybylski's star (HD101065) continues to excite the astronomical community by the unusual nature of its spectrum, exhibiting exotic element abundances. This star was also the first magnetic chemically peculiar A-type star for which the presence of rapid oscillations was established. Our analysis of newly acquired and historic longitudinal magnetic field measurements indicates that Przybylski's star is also unusual with respect to its extremely slow rotation. Adopting a dipolar structure for the magnetic field and using a sine wave fit to all reported longitudinal magnetic field values over the last 43yr, we find a probable rotation period P_rot ~ 188yr, which however has to be considered tentative as it does not represent a unique solution and has to be verified by future observations. Additionally, based on our own spectropolarimetric material obtained with HARPSpol, we discuss the impact of the anomalous structure of its atmosphere, in particular of the non-uniform horizontal and vertical distributions of chemical elements on the magnetic field measurements and the pulsational variability. Anomalies related to the vertical abundance stratification of Pr and Nd are for the first time used to establish the presence of a radial magnetic field gradient., Comment: 11 pages, 4 tables, 7 figures, accepted for publication in MNRAS

$\xi^{1}$ CMa is a known magnetic star showing rotationally modulated magnetic variability with a period of 2.17937 d. However, recent work based on high-resolution spectropolarimetry suggests that the rotation period is longer than 30 years. We compare our new spectropolarimetric measurements with FORS 2 at the VLT acquired on three consecutive nights in 2017 to previous FORS 1/2 measurements of the longitudinal magnetic field strength. The new longitudinal magnetic field values are in the range from 115 to 240 G and do not support the presence of a long period., Comment: 5 pages, 4 figures, 1 table

We obtained an LBT/PEPSI spectrum with very high resolution and high signal-to-noise ratio (S/N) of the K0V host Kepler-444, which is known to host 5 sub-Earth size rocky planets. The spectrum has a resolution of R=250,000, a continuous wavelength coverage from 4230 to 9120A, and S/N between 150 and 550:1 (blue to red). We performed a detailed chemical analysis to determine the photospheric abundances of 18 chemical elements, in order to use the abundances to place constraints on the bulk composition of the five rocky planets. Our spectral analysis employs the equivalent width method for most of our spectral lines, but we used spectral synthesis to fit a small number of lines that require special care. In both cases, we derived our abundances using the MOOG spectral analysis package and Kurucz model atmospheres. We find no correlation between elemental abundance and condensation temperature among the refractory elements. In addition, using our spectroscopic stellar parameters and isochrone fitting, we find an age of 10+/-1.5 Gyr, which is consistent with the asteroseismic age of 11+/-1 Gyr. Finally, from the photospheric abundances of Mg, Si, and Fe, we estimate that the typical Fe-core mass fraction for the rocky planets in the Kepler-444 system is approximately 24 per cent. If our estimate of the Fe-core mass fraction is confirmed by more detailed modeling of the disk chemistry and simulations of planet formation and evolution in the Kepler-444 system, then this would suggest that rocky planets in more metal-poor and alpha-enhanced systems may tend to be less dense than their counterparts of comparable size in more metal-rich systems., Comment: in press, 11 pages, 3 figures, data available from pepsi.aip.de

We provide a homogeneous library of high-resolution, high-S/N spectra for 48 bright AFGKM stars, some of them approaching the quality of solar-flux spectra. Our sample includes the northern Gaia benchmark stars, some solar analogs, and some other bright Morgan-Keenan (M-K) spectral standards. Well-exposed deep spectra were created by average-combining individual exposures. The data-reduction process relies on adaptive selection of parameters by using statistical inference and robust estimators.We employed spectrum synthesis techniques and statistics tools in order to characterize the spectra and give a first quick look at some of the science cases possible. With an average spectral resolution of R=220,000 (1.36 km/s), a continuous wavelength coverage from 383 nm to 912 nm, and S/N of between 70:1 for the faintest star in the extreme blue and 6,000:1 for the brightest star in the red, these spectra are now made public for further data mining and analysis. Preliminary results include new stellar parameters for 70 Vir and alpha Tau, the detection of the rare-earth element dysprosium and the heavy elements uranium, thorium and neodymium in several RGB stars, and the use of the 12C to 13C isotope ratio for age-related determinations. We also found Arcturus to exhibit few-percent CaII H&K and H-alpha residual profile changes with respect to the KPNO atlas taken in 1999., Comment: in press, 15 pages, 7 figures, data available from pepsi.aip.de

As part of the first Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) key-science project, we aim to provide well-exposed (viz. deep) high-resolution spectra of representative stellar targets. These spectra will be made available in form of (electronic) atlases. The first star in this series of papers is our Sun. It also acts as a system-performance cornerstone. The deep spectra in this paper are the results of combining up to 100 consecutive exposures per wavelength setting and are compared with other solar flux atlases. Our software for the optimal data extraction and reduction of PEPSI spectra is described and verified with the solar data. Three deep solar flux spectra with a spectral resolution of up to 270,000, a continuous wavelength coverage from 383 nm to 914 nm, and a photon signal to noise ratio (S/N) of between 2,000-8,000:1 depending on wavelength are presented. Additionally, a time-series of 996 high-cadence spectra in one cross disperser is used to search for intrinsic solar modulations. The wavelength calibration based on Th-Ar exposures and simultaneous Fabry-Perot combs enables an absolute wavelength solution within 10 m/s (rms) with respect to the HARPS laser-comb solar atlas and a relative rms of 1.2 m/s for one day. For science demonstration, we redetermined the disk-average solar Li abundance to 1.09+/-0.04 dex on the basis of 3D NLTE model atmospheres. We detected disk-averaged p-mode RV oscillations with a full amplitude of 47 cm/s at 5.5 min. Comparisons with two solar FTS atlases, as well as with the HARPS solar atlas, validate the PEPSI data product. Now, PEPSI/SDI solar-flux spectra are being taken with a sampling of one deep spectrum per day, and are supposed to continue a full magnetic cycle of the Sun., Comment: in press, 13 pages, 8 figures, data available from pepsi.aip.de

Context: HD 54879 (O9.7 V) is one of a dozen O-stars for which an organized atmospheric magnetic field has been detected. To gain insights into the interplay between atmospheres, winds, and magnetic fields of massive stars, we acquired UV and X-ray data of HD 54879 using the Hubble Space Telescope and the XMM-Newton satellite. In addition, 35 optical amateur spectra were secured to study the variability of HD 54879. A multiwavelength (X-ray to optical) spectral analysis is performed using the Potsdam Wolf-Rayet (PoWR) model atmosphere code and the xspec software. Results: The photospheric parameters are typical for an O9.7 V star. The microturbulent, macroturbulent, and projected rotational velocities are lower than previously suggested (<4 km/s). An initial mass of 16$\,M_\odot$ and an age of 5 Myr are inferred from evolutionary tracks. We derive a mean X-ray emitting temperature of $\log T_{\rm X} = 6.7\,$[K] and an X-ray luminosity of $\log L_\text{X} = 32\,$[erg/s]. Short- and long-scale variability is seen in the H-alpha line, but only a very long period of $P \approx 5\,$yr could be estimated. Assessing the circumstellar density of HD 54879 using UV spectra, we can roughly estimate the mass-loss rate HD 54879 would have in the absence of a magnetic field as $\log \dot{M}_{B=0}\approx -9.0\,[{M_\odot}/{\rm yr}]$. The magnetic field traps the stellar wind up to the Alfv\'en radius > $12\,R_\odot$, implying that its true mass-loss rate is $\log \dot{M}< -10.2\,[{M_\odot}/{\rm yr}]$. Hence, density enhancements around magnetic stars can be exploited to estimate mass-loss rates of non-magnetic stars of similar spectral types, essential for resolving the weak wind problem. Conclusions: Our study confirms that strongly magnetized stars lose little or no mass, and supplies important constraints on the weak-wind problem of massive main sequence stars., Comment: Accepted for publication in A&A on Aug. 9, 2017, 12 + 1 pages, 15 figures. Paper replaced due to typos and missing acknowledgments

The magnetic field of CPD -57 3509 was recently detected in the framework of the BOB (B fields in OB stars) collaboration. We acquired low-resolution spectropolarimetric observations of CPD -57 3509 with FORS2 and high-resolution UVES observations randomly distributed over a few months to search for periodicity, to study the magnetic field geometry, and to determine the surface distribution of silicon and helium. We also obtained supplementary photometric observations at a timeline similar to the spectroscopic and spectropolarimetric observations. A period of 6.36d was detected in the measurements of the mean longitudinal magnetic field. A sinusoidal fit to our measurements allowed us to constrain the magnetic field geometry and estimate the dipole strength in the range of 3.9-4.5kG. Our application of the Doppler imaging technique revealed the presence of He I spots located around the magnetic poles, with a strong concentration at the positive pole and a weaker one around the negative pole. In contrast, high concentration Si III spots are located close to the magnetic equator. Further, our analysis of the spectral variability of CPD -57 3509 on short time scales indicates distinct changes in shape and position of line profiles possibly caused by the presence of beta Cep-like pulsations. A small periodic variability in line with the changes of the magnetic field strength is clearly seen in the photometric data., Comment: 11 pages, 5 tables, 7 figures, accepted for publication in MNRAS

Although pulsations of $\delta$ Scuti type are not expected among Ap stars from a theoretical point of view, previous observations of the known $\delta$ Scuti star HD21190 indicated a spectral classification F2 III SrEuSi:, making it the most evolved Ap star known. Our atmospheric chemical analysis based on recent HARPS observations confirms the presence of chemical peculiarities in HD21190. This star is also the only target known to host a magnetic field along with its $\delta$ Scuti pulsation properties. Using an astrometric analysis, we show that HD21190 forms a physical binary system with the companion CPD -83$^{\circ}$ 64B. The presented astrometric and spectroscopic study of the binary components is important to understand the complex interplay between stellar pulsations, magnetic fields, and chemical composition., Comment: 16 pages, 9 figures, 4 tables

A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, recently announced the discovery of two rare rigidly rotating magnetosphere stars, HD345439 and HD23478. Near-infrared spectra of these objects revealed emission-line behavior identical to that previously discovered in the helium-strong star sigma Ori E, which has a strong magnetic field and rotates fast. A single spectropolarimetric observation of HD345439 with FORS2 at the VLT in 2014 over 88min indicated that HD345439 may host a strong, rapidly varying magnetic field. In this work, we present the results of our spectropolarimetric monitoring of this star with FORS2, which revealed the presence of a strong longitudinal magnetic field dominated by a dipolar component. The analysis of spectral variability indicates an opposite behaviour of He and Si lines, which is usually attributed to differences in the distribution of surface He and Si abundance spots., Comment: 5 pages, 1 table, 6 figures, accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:1702.01063

A longitudinal magnetic field with a strength of 5.2kG was recently detected in CPD -62 2124, which has a fractional main-sequence lifetime of about 60%. Strongly magnetic early-B type chemically peculiar stars in an advanced evolutionary state are of special interest to understand the evolution of the angular momentum and spin-down timescales in the presence of a global magnetic field. We exploited 17 FORS2 low-resolution spectropolarimetric observations and 844 ASAS3 photometric measurements for the determination of the rotation period, pulsations, and the magnetic field geometry of the star. We calculated periodograms and applied phenomenological models of photometric, spectral and spectropolarimetric variability. We found that all quantities studied, specifically equivalent widths, the mean longitudinal magnetic field , and the flux in the V filter, vary with the same period P = 2.628d, which was identified as the rotation period. The observed variations can be fully explained by a rigidly rotating main-sequence star with an uneven distribution of chemical elements, photometric spots, and a stable, nearly dipolar magnetic field with a polar field strength of about 21kG, frozen into the body of the star. The magnetic field of CPD -62 2124 is tilted to the rotation axis by beta=28+-7deg, while the inclination of the rotation axis towards the line of sight is only i=20+-5deg. In the acquired FORS2 spectra, we detect short-term line profile variations indicating the presence of beta Cephei type pulsations. As of today, no other pulsating star of this type is known to possess such a strong magnetic field., Comment: 9 pages, 3 tables, 9 figures, accepted for publication in MNRAS

RZ Psc is an isolated high-latitude post-T Tauri star that demonstrates a UX Ori-type photometric activity. The star shows very weak spectroscopic signatures of accretion, but at the same time possesses the unusual footprints of the wind in Na I D lines. In the present work we investigate new spectroscopic observations of RZ Psc obtained in 2014 during two observation runs. We found variable blueshifted absorption components (BACs) in lines of the other alcali metals, K I 7699 \AA\ and Ca II IR triplet. We also confirmed the presence of a weak emission component in the H$\alpha$ line, which allowed us to estimate the mass accretion rate on the star as $\dot{M}\leq$ $7 \cdot 10^{-12}$Msun yr$^{-1}$. We could not reveal any clear periodicity in the appearance of BACs in sodium lines. Nevertheless, the exact coincidence of the structure and velocities of the Na I D absorptions observed with the interval of about one year suggests that such a periodicity should exist.