TY  - JOUR
A1  - Oskinova, Lida
A1  - Todt, Helge Tobias
A1  - Ignace, Richard
A1  - Brown, John C.
A1  - Cassinelli, Joseph P.
A1  - Hamann, Wolf-Rainer
T1  - Early magnetic B-type stars X-ray emission and wind properties
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present a comprehensive study of X-ray emission by, and wind properties of, massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three early-type B-type stars, xi(1) CMa, V2052 Oph and zeta Cas, with recently discovered magnetic fields. We report the first detection of X-ray emission from V2052 Oph and zeta Cas. The latter is one the softest X-ray sources among the early-type stars, while the former is one of the X-ray faintest. The observations show that the X-ray spectra of our programme stars are quite soft with the bulk of X-ray emitting material having a temperature of about 1 MK. We compile the complete sample of early B-type stars with detected magnetic fields to date and existing X-ray measurements, in order to study whether the X-ray emission can be used as a general proxy for stellar magnetism. We find that the X-ray properties of early massive B-type magnetic stars are diverse, and that hard and strong X-ray emission does not necessarily correlate with the presence of a magnetic field, corroborating similar conclusions reached earlier for the classical chemically peculiar magnetic Bp-Ap stars.
 We analyse the ultraviolet (UV) spectra of five non-supergiant B stars with magnetic fields (tau Sco, beta Cep, xi(1) CMa, V2052 Oph and zeta Cas) by means of non-local thermodynamic equilibrium (non-LTE) iron-blanketed model atmospheres. The latter are calculated with the Potsdam Wolf-Rayet (PoWR) code, which treats the photosphere as well as the wind, and also accounts for X-rays. With the exception of t Sco, this is the first analysis of these stars by means of stellar wind models. Our models accurately fit the stellar photospheric spectra in the optical and the UV. The parameters of X-ray emission, temperature and flux are included in the model in accordance with observations. We confirm the earlier findings that the filling factors of X-ray emitting material are very high.
 Our analysis reveals that the magnetic early-type B stars studied here have weak winds with velocities not significantly exceeding upsilon(esc). The mass-loss rates inferred from the analysis of UV lines are significantly lower than predicted by hydrodynamically consistent models. We find that, although the X-rays strongly affect the ionization structure of the wind, this effect is not sufficient in reducing the total radiative acceleration. When the X-rays are accounted for at the intensity and temperatures observed, there is still sufficient radiative acceleration to drive a stronger mass-loss than we empirically infer from the UV spectral lines.
KW  - techniques: spectroscopic
KW  - stars: magnetic field
KW  - stars: massive
KW  - stars: mass loss
KW  - X-rays: stars
Y1  - 2011
U6  - https://doi.org/10.1111/j.1365-2966.2011.19143.x
SN  - 0035-8711
VL  - 416
IS  - 2
SP  - 1456
EP  - 1474
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Oskinova, Lida
A1  - Hamann, Wolf-Rainer
A1  - Cassinelli, Joseph P.
A1  - Brown, John C.
A1  - Todt, Helge Tobias
T1  - X-ray emission from massive stars with magnetic fields
JF  - Astronomische Nachrichten = Astronomical notes
N2  - We investigate the connections between the magnetic fields and the X-ray emission from massive stars. Our study shows that the X-ray properties of known strongly magnetic stars are diverse: while some comply to the predictions of the magnetically confined wind model, others do not. We conclude that strong, hard, and variable X-ray emission may be a sufficient attribute of magnetic massive stars, but it is not a necessary one. We address the general properties of X-ray emission from "normal" massive stars, especially the long standing mystery about the correlations between the parameters of X-ray emission and fundamental stellar properties. The recent development in stellar structure modeling shows that small-scale surface magnetic fields may be common. We suggest a "hybrid" scenario which could explain the X-ray emission from massive stars by a combination of magnetic mechanisms on the surface and shocks in the stellar wind. The magnetic mechanisms and the wind shocks are triggered by convective motions in sub-photospheric layers. This scenario opens the door for a natural explanation of the well established correlation between bolometric and X-ray luminosities.
KW  - stars: magnetic fields
KW  - stars: mass-loss
KW  - stars: winds, outflows
KW  - stars: Wolf-Rayet
KW  - techniques: spectroscopic
KW  - X-rays: stars
Y1  - 2011
U6  - https://doi.org/10.1002/asna.201111602
SN  - 0004-6337
VL  - 332
IS  - 9-10
SP  - 988
EP  - 993
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Bonifacio, P.
A1  - Rahmani, H.
A1  - Whitmore, J. B.
A1  - Wendt, Martin
A1  - Centurion, Martin
A1  - Molaro, P.
A1  - Srianand, R.
A1  - Murphy, M. T.
A1  - Petitjean, P.
A1  - Agafonova, I. I.
A1  - Evans, T. M.
A1  - Levshakov, S. A.
A1  - Lopez, S.
A1  - Martins, C. J. A. P.
A1  - Reimers, D.
A1  - Vladilo, G.
T1  - Fundamental constants and high-resolution spectroscopy
JF  - Astronomische Nachrichten = Astronomical notes
KW  - atomic processes
KW  - cosmology: observations
KW  - elementary particles
KW  - line: formation
KW  - quasars: absorption lines
KW  - techniques: spectroscopic
Y1  - 2014
U6  - https://doi.org/10.1002/asna.201312005
SN  - 0004-6337
SN  - 1521-3994
VL  - 335
IS  - 1
SP  - 83
EP  - 91
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Richter, Philipp
A1  - Fox, Andrew J.
A1  - Ben Bekhti, Nadya
A1  - Murphy, M. T.
A1  - Bomans, Dominik J.
A1  - Frank, S.
T1  - High-resolution absorption spectroscopy of the circumgalactic medium of the Milky Way
JF  - Astronomische Nachrichten = Astronomical notes
KW  - Galaxy: halo
KW  - Galaxy: structure
KW  - quasars: absorption lines
KW  - techniques: spectroscopic
Y1  - 2014
U6  - https://doi.org/10.1002/asna.201312013
SN  - 0004-6337
SN  - 1521-3994
VL  - 335
IS  - 1
SP  - 92
EP  - 98
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Aldoretta, E. J.
A1  - St-Louis, N.
A1  - Richardson, N. D.
A1  - Moffat, Anthony F. J.
A1  - Eversberg, T.
A1  - Hill, G. M.
A1  - Shenar, Tomer
A1  - Artigau, E.
A1  - Gauza, B.
A1  - Knapen, J. H.
A1  - Kubat, Jiří
A1  - Kubatova, Brankica
A1  - Maltais-Tariant, R.
A1  - Munoz, M.
A1  - Pablo, H.
A1  - Ramiaramanantsoa, T.
A1  - Richard-Laferriere, A.
A1  - Sablowski, D. P.
A1  - Simon-Diaz, S.
A1  - St-Jean, L.
A1  - Bolduan, F.
A1  - Dias, F. M.
A1  - Dubreuil, P.
A1  - Fuchs, D.
A1  - Garrel, T.
A1  - Grutzeck, G.
A1  - Hunger, T.
A1  - Kuesters, D.
A1  - Langenbrink, M.
A1  - Leadbeater, R.
A1  - Li, D.
A1  - Lopez, A.
A1  - Mauclaire, B.
A1  - Moldenhawer, T.
A1  - Potter, M.
A1  - dos Santos, E. M.
A1  - Schanne, L.
A1  - Schmidt, J.
A1  - Sieske, H.
A1  - Strachan, J.
A1  - Stinner, E.
A1  - Stinner, P.
A1  - Stober, B.
A1  - Strandbaek, K.
A1  - Syder, T.
A1  - Verilhac, D.
A1  - Waldschlaeger, U.
A1  - Weiss, D.
A1  - Wendt, A.
T1  - An extensive spectroscopic time series of three Wolf-Rayet stars - I. The lifetime of large-scale structures in the wind of WR 134
JF  - Monthly notices of the Royal Astronomical Society
N2  - During the summer of 2013, a 4-month spectroscopic campaign took place to observe the variabilities in three Wolf-Rayet stars. The spectroscopic data have been analysed for WR 134 (WN6b), to better understand its behaviour and long-term periodicity, which we interpret as arising from corotating interaction regions (CIRs) in the wind. By analysing the variability of the He ii lambda 5411 emission line, the previously identified period was refined to P = 2.255 +/- 0.008 (s.d.) d. The coherency time of the variability, which we associate with the lifetime of the CIRs in the wind, was deduced to be 40 +/- 6 d, or similar to 18 cycles, by cross-correlating the variability patterns as a function of time. When comparing the phased observational grey-scale difference images with theoretical grey-scales previously calculated from models including CIRs in an optically thin stellar wind, we find that two CIRs were likely present. A separation in longitude of Delta I center dot a parts per thousand integral 90A degrees was determined between the two CIRs and we suggest that the different maximum velocities that they reach indicate that they emerge from different latitudes. We have also been able to detect observational signatures of the CIRs in other spectral lines (C iv lambda lambda 5802,5812 and He i lambda 5876). Furthermore, a DAC was found to be present simultaneously with the CIR signatures detected in the He i lambda 5876 emission line which is consistent with the proposed geometry of the large-scale structures in the wind. Small-scale structures also show a presence in the wind, simultaneously with the larger scale structures, showing that they do in fact co-exist.
KW  - instabilities
KW  - methods: data analysis
KW  - techniques: spectroscopic
KW  - stars: individual: WR 134
KW  - stars: massive
KW  - stars: Wolf-Rayet
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw1188
SN  - 0035-8711
SN  - 1365-2966
VL  - 460
SP  - 3407
EP  - 3417
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Balthasar, H.
A1  - Gömöry, P.
A1  - González Manrique, Sergio Javier
A1  - Kuckein, Christoph
A1  - Kavka, J.
A1  - Kucera, A.
A1  - Schwartz, P.
A1  - Vaskova, R.
A1  - Berkefeld, T.
A1  - Collados Vera, M.
A1  - Denker, Carsten
A1  - Feller, A.
A1  - Hofmann, A.
A1  - Lagg, A.
A1  - Nicklas, H.
A1  - Suarez, D.
A1  - Pastor Yabar, A.
A1  - Rezaei, R.
A1  - Schlichenmaier, R.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Spectropolarimetric observations of an arch filament system with the GREGOR solar telescope
JF  - Astronomische Nachrichten = Astronomical notes
N2  - Arch filament systems occur in active sunspot groups, where a fibril structure connects areas of opposite magnetic polarity, in contrast to active region filaments that follow the polarity inversion line. We used the GREGOR Infrared Spectrograph (GRIS) to obtain the full Stokes vector in the spectral lines SiI lambda 1082.7 nm, He I lambda 1083.0 nm, and Ca I lambda 1083.9 nm. We focus on the near-infrared calcium line to investigate the photospheric magnetic field and velocities, and use the line core intensities and velocities of the helium line to study the chromospheric plasma. The individual fibrils of the arch filament system connect the sunspot with patches of magnetic polarity opposite to that of the spot. These patches do not necessarily coincide with pores, where the magnetic field is strongest. Instead, areas are preferred not far from the polarity inversion line. These areas exhibit photospheric downflows of moderate velocity, but significantly higher downflows of up to 30 km s(-1) in the chromospheric helium line. Our findings can be explained with new emerging flux where the matter flows downward along the field lines of rising flux tubes, in agreement with earlier results. (C) 2016 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim
KW  - Sun: filaments
KW  - Sun: photosphere
KW  - techniques: polarimetric
KW  - techniques: spectroscopic
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612432
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1050
EP  - 1056
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Gonzalez Manrique, Sergio Javier
A1  - Kuckein, Christoph
A1  - Pastor Yabar, A.
A1  - Collados Vera, M.
A1  - Denker, Carsten
A1  - Fischer, C. E.
A1  - Gömöry, P.
A1  - Diercke, Andrea
A1  - Gonzalez, N. Bello
A1  - Schlichenmaier, R.
A1  - Balthasar, H.
A1  - Berkefeld, T.
A1  - Feller, A.
A1  - Hoch, S.
A1  - Hofmann, A.
A1  - Kneer, F.
A1  - Lagg, A.
A1  - Nicklas, H.
A1  - Orozco Suarez, D.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Verma, Meetu
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Fitting peculiar spectral profiles in He I 10830 angstrom absorption features
JF  - Astronomische Nachrichten = Astronomical notes
N2  - The new generation of solar instruments provides better spectral, spatial, and temporal resolution for a better understanding of the physical processes that take place on the Sun. Multiple-component profiles are more commonly observed with these instruments. Particularly, the He i 10830 triplet presents such peculiar spectral profiles, which give information on the velocity and magnetic fine structure of the upper chromosphere. The purpose of this investigation is to describe a technique to efficiently fit the two blended components of the He i 10830 triplet, which are commonly observed when two atmospheric components are located within the same resolution element. The observations used in this study were taken on 2015 April 17 with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-m GREGOR solar telescope, located at the Observatorio del Teide, Tenerife, Spain. We apply a double-Lorentzian fitting technique using Levenberg-Marquardt least-squares minimization. This technique is very simple and much faster than inversion codes. Line-of-sight Doppler velocities can be inferred for a whole map of pixels within just a few minutes. Our results show sub-and supersonic downflow velocities of up to 32 km s(-1) for the fast component in the vicinity of footpoints of filamentary structures. The slow component presents velocities close to rest. (C) 2016 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim
KW  - Sun: chromosphere
KW  - methods: data analysis
KW  - techniques: spectroscopic
KW  - line: profiles
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201512433
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1057
EP  - 1063
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Verma, Meetu
A1  - Denker, Carsten
A1  - Böhm, F.
A1  - Balthasar, H.
A1  - Fischer, C. E.
A1  - Kuckein, Christoph
A1  - Gonzalez, N. Bello
A1  - Berkefeld, T.
A1  - Collados Vera, M.
A1  - Diercke, Andrea
A1  - Feller, A.
A1  - Gonzalez Manrique, Sergio Javier
A1  - Hofmann, A.
A1  - Lagg, A.
A1  - Nicklas, H.
A1  - Orozco Suarez, D.
A1  - Pator Yabar, A.
A1  - Rezaei, R.
A1  - Schlichenmaier, R.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396
JF  - Astronomische Nachrichten = Astronomical notes
N2  - Improved measurements of the photospheric and chromospheric three-dimensional magnetic and flow fields are crucial for a precise determination of the origin and evolution of active regions. We present an illustrative sample of multi-instrument data acquired during a two-week coordinated observing campaign in August 2015 involving, among others, the GREGOR solar telescope (imaging and near-infrared spectroscopy) and the space missions Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS). The observations focused on the trailing part of active region NOAA 12396 with complex polarity inversion lines and strong intrusions of opposite polarity flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV spectral profiles in the photospheric Si i.1082.7 nm line, the chromospheric He I lambda 1083.0 nm triplet, and the photospheric Ca I lambda 1083.9 nm line. Carefully calibrated GRIS scans of the active region provided maps of Doppler velocity and magnetic field at different atmospheric heights. We compare quick-look maps with those obtained with the " Stokes Inversions based on Response functions" (SIR) code, which furnishes deeper insight into the magnetic properties of the region. We find supporting evidence that newly emerging flux and intruding opposite polarity flux are hampering the formation of penumbrae, i.e., a penumbra fully surrounding a sunspot is only expected after cessation of flux emergence in proximity to the sunspots. (C) 2016 WILEY-VCH Verlag GmbH& Co.KGaA, Weinheim
KW  - Sun: magnetic fields
KW  - sunspots
KW  - methods: data analysis
KW  - techniques: polarimetric
KW  - techniques: spectroscopic
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612447
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1090
EP  - 1098
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Denker, Carsten
A1  - Heibel, C.
A1  - Rendtel, J.
A1  - Arlt, K.
A1  - Balthasar, H.
A1  - Diercke, Andrea
A1  - Gonzalez Manrique, Sergio Javier
A1  - Hofmann, A.
A1  - Kuckein, Christoph
A1  - Önel, H.
A1  - Valliappan, Senthamizh Pavai
A1  - Staude, J.
A1  - Verma, Meetu
T1  - Solar physics at the Einstein Tower
JF  - Astronomische Nachrichten = Astronomical notes
KW  - history and philosophy of astronomy
KW  - Sun: photosphere
KW  - Sun: magnetic fields
KW  - techniques: spectroscopic
KW  - telescopes
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612442
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1105
EP  - 1113
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Gimenez-Garcia, Ana
A1  - Shenar, Tomer
A1  - Torrejon, J. M.
A1  - Oskinova, Lida
A1  - Martinez-Nunez, S.
A1  - Hamann, Wolf-Rainer
A1  - Rodes-Roca, J. J.
A1  - González-Galan, A.
A1  - Alonso-Santiago, J.
A1  - González-Fernández, C.
A1  - Bernabeu, Guillermo
A1  - Sander, Andreas Alexander Christoph
T1  - Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in supergiant fast X-ray transient and classical supergiant X-ray binaries
JF  - Siberian Mathematical Journal
N2  - Aims. To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J175442619 (SFXT) and Vela X-1 (SGXB). We analyze the spectra of each star in detail and derive their stellar and wind properties. As a next step, we compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. Methods. We use archival infrared, optical and ultraviolet observations, and analyze them with the non-local thermodynamic equilibrium (NLTE) Potsdam Wolf-Rayet model atmosphere code. We derive the physical properties of the stars and their stellar winds, accounting for the influence of X-rays on the stellar winds. Results. We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). The distance to the sources have been revised and also agree well with the estimations already available in the literature. In IGR J17544-2619 we are able to narrow the uncertainty to d = 3.0 +/- 0.2 kpc. From the stellar radius of the donor and its X-ray behavior, the eccentricity of IGR J17544-2619 is constrained to e < 0.25. The derived chemical abundances point to certain mixing during the lifetime of the donors. An important difference between the stellar winds of the two stars is their terminal velocities (v(infinity) = 1500 km s(-1) in IGR J17544-2619 and v(infinity) = 700 km s(-1) in Vela X-1), which have important consequences on the X-ray luminosity of these sources. Conclusions. The donors of IGR J17544-2619 and Vela X-1 have similar spectral types as well as similar parameters that physically characterize them and their spectra. In addition, the orbital parameters of the systems are similar too, with a nearly circular orbit and short orbital period. However, they show moderate differences in their stellar wind velocity and the spin period of their neutron star which has a strong impact on the X-ray luminosity of the sources. This specific combination of wind speed and pulsar spin favors an accretion regime with a persistently high luminosity in Vela X-1, while it favors an inhibiting accretion mechanism in IGR J17544-2619. Our study demonstrates that the relative wind velocity is critical in class determination for the HMXBs hosting a supergiant donor, given that it may shift the accretion mechanism from direct accretion to propeller regimes when combined with other parameters.
KW  - accretion, accretion disks
KW  - methods: observational
KW  - techniques: spectroscopic
KW  - stars: atmospheres
KW  - X-rays: binaries
KW  - stars: winds, outflows
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527551
SN  - 1432-0746
VL  - 591
PB  - EDP Sciences
CY  - Les Ulis
ER  -