Mapping EK Draconis with PEPSI - Possible evidence for starspot penumbrae

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&

PEPSI deep spectra. III. A chemical analysis of the ancient planet-host star Kepler-444

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.d

Warm and cool starspots with opposite polarities. A high-resolution Zeeman-Doppler-Imaging study of II Pegasi with PEPSI

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 figure

Zeeman Doppler Imaging of ksi Boo A and B

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:1902.1120

On a "New" Deformation of GL(2)

We refute a recent claim in the literature of a "new" quantum deformation of GL(2).Comment: 4 pages, LATE

Doppler images and the underlying dynamo. The case of AF Leporis

The (Zeeman-)Doppler imaging studies of solar-type stars very often reveal large high-latitude spots. This also includes F stars that possess relatively shallow convection zones, indicating that the dynamo operating in these stars differs from the solar dynamo. We aim to determine whether mean-field dynamo models of late-F type dwarf stars can reproduce the surface features recovered in Doppler maps. In particular, we wish to test whether the models can reproduce the high-latitude spots observed on some F dwarfs. The photometric inversions and the surface temperature maps of AF Lep were obtained using the Occamian-approach inversion technique. Low signal-to-noise spectroscopic data were improved by applying the least-squares deconvolution method. The locations of strong magnetic flux in the stellar tachocline as well as the surface fields obtained from mean-field dynamo solutions were compared with the observed surface temperature maps. The photometric record of AF Lep reveals both long- and short-term variability. However, the current data set is too short for cycle-length estimates. From the photometry, we have determined the rotation period of the star to be 0.9660+-0.0023 days. The surface temperature maps show a dominant, but evolving, high-latitude (around +65 degrees) spot. Detailed study of the photometry reveals that sometimes the spot coverage varies only marginally over a long time, and at other times it varies rapidly. Of a suite of dynamo models, the model with a radiative interior rotating as fast as the convection zone at the equator delivered the highest compatibility with the obtained Doppler images.Comment: accepted for publication in Astronomy & Astrophysic

ГАЗОХРОМАТОГРАФИЧЕСКОЕ ОПРЕДЕЛЕНИЕ ФЕНОЛОВ В ПОВЕРХНОСТНЫХ ВОДАХ С ИСПОЛЬЗОВАНИЕМ ПОЛИОКСИЭТИЛЕН БИС АРСЕНАТА

 Current paper is devoted to the determination of phenols in surface waters using the method of gas-liquid chromatography on the nozzle chromatographic columns with different polarities of sorbents, in the capacity of which silicone elastomers, polyethylene glycol with the molecular weight of 1500, and polyoxyethylene bis arsenate obtained by arsenating polyethylene glycol-1500 were studied. It was shown that positional isomers, para - and meta – cresols, which have almost identical boiling points, were separated on polyoxyethylene bis arsenate and on the standard sorbents (SE-30 and PEG-1000) they practically do not separate and come out with a single peak. The logarithmic retention indexes were determined for the analyzed phenols and chromatographic Rorschneider polarity factors on polyoxyethylene bis arsenate, which are extremely high for ethanol (factor y) and are associated with the formation of an intermolecular hydrogen bond in the sorbate-sorbent system. It was found that polyoxyethylene bis arsenate had a linear dependence of the logarithm of the retention time on their boiling point and dipole moments. In the case of dipole moments, there was a deviation from the specified dependence for o-chlorophenol, obviously as a result of a specific substituent effect (ortho effect). Polyoxyethylene bis arsenate was used to determine phenols in the surface waters of the Kuibyshev reservoir. For this purpose, a sample preparation system based on the conversion of phenols into brominated derivatives, which have high volatility and are fairly well analyzed by gas-liquid chromatography, was used. A comparative characteristic of the limit of detection of phenols for flame ionization and thermionic detectors was given. As a result of the determination of phenols in the surface waters of the Kuibyshev reservoir, a high content of phenols was found, which fluctuates during the different seasons of the year.Keywords: Phenols, gas-liquid chromatography, sorbents, sorbates, polarity factors, polyoxyethylene bis arsenates.DOI: http://dx.doi.org/10.15826/analitika.2020.24.4.001 A.V. Taneeva, A.V. Dmitrieva, V.F. Novikov, V.K. IlyinKazan State Power Engineering University,Krasnoselskaya, 51, Kazan, 420066, Russian FederationВ работе рассмотрены вопросы определения фенолов в поверхностных водах с использованием метода газо-жидкостной хроматографии на насадочных хроматографических колонках с различными по полярности сорбентами, в качестве которых исследованы силиконовые эластомеры, полиэтиленгликоль молекулярной массой 1500, а также полиоксиэтилен бис арсенат, полученный путем арсенирования полиэтиленгликоля-1500. Показано, что на полиоксиэтилен бис арсенате разделяются позиционные изомеры, пара- и мета-крезолы, которые имеют практически одинаковые температуры кипения и на стандартных сорбентах (SE-30 и ПЭГ-1000) практически не разделяются и выходят одним пиком. На полиоксиэтилен бис арсенате определены логарифмические индексы удерживания анализируемых фенолов и хроматографические факторы полярности Роршнайдера, которые экстремально высоки для этанола (фактор у), что связывается с образованием межмолекулярной водородной связи в системе сорбат-сорбент. Установлено, что на полиоксиэтилен бис арсенате наблюдается линейная зависимость логарифма времени удерживания от их температуры кипения и дипольных моментов. При этом в случае дипольных моментов наблюдается отклонение от указанной зависимости для о-хлорфенола, очевидно,  в результате специфического эффекта заместителя (орто-эффект). Полиоксиэтилен бис арсенат использовали для определения фенолов в поверхностных водах Куйбышевского водохранилища. С этой целью проводили  пробоподготовку, основанную на переводе фенолов в бромпроизводные, которые обладают высокой летучестью и достаточно хорошо анализируются методом газо-жидкостной хроматографии. Приведена сравнительная характеристика предела обнаружения фенолов для пламенно-ионизационного и термоионного детекторов.  При использовании  разработанной методики анализа поверхностных вод установлено наличие фенолов в бассейне реки Волга, концентрация которых изменяется в различные периоды времени года.Ключевые слова: фенолы, газо-жидкостная хроматография, сорбенты, сорбаты, факторы полярности.DOI: http://dx.doi.org/10.15826/analitika.2020.24.4.00

B fields in OB stars (BOB): Detection of a magnetic field in the He-strong star CPD-57{\deg} 3509

We report the detection of a magnetic field in the helium-strong star CPD-57 3509 (B2 IV), a member of the Galactic open cluster NGC3293, and characterise the star's atmospheric and fundamental parameters. Spectropolarimetric observations with FORS2 and HARPSpol are analysed using two independent approaches to quantify the magnetic field strength. A high-S/N FLAMES/GIRAFFE spectrum is analysed using a hybrid non-LTE model atmosphere technique. Comparison with stellar evolution models constrains the fundamental parameters of the star. We obtain a firm detection of a surface averaged longitudinal magnetic field with a maximum amplitude of about 1 kG. Assuming a dipolar configuration of the magnetic field, this implies a dipolar field strength larger than 3.3 kG. Moreover, the large amplitude and fast variation (within about 1 day) of the longitudinal magnetic field implies that CPD-57 3509 is spinning very fast despite its apparently slow projected rotational velocity. The star should be able to support a centrifugal magnetosphere, yet the spectrum shows no sign of magnetically confined material; in particular, emission in H{\alpha} is not observed. Apparently, the wind is either not strong enough for enough material to accumulate in the magnetosphere to become observable or, alternatively, some leakage process leads to loss of material from the magnetosphere. The quantitative spectroscopic analysis of the star yields an effective temperature and a logarithmic surface gravity of 23750+-250 K and 4.05+-0.10, respectively, and a surface helium fraction of 0.28+-0.02 by number. The surface abundances of C, N, O, Ne, S, and Ar are compatible with the cosmic abundance standard, whereas Mg, Al, Si, and Fe are depleted by about a factor of 2. This abundance pattern can be understood as the consequence of a fractionated stellar wind. CPD-57 3509 is one of the most evolved He-strong stars known.Comment: 15 pages, 11 figures. Accepted for publication in A&