The Wide-Angle Outflow of the Lensed z = 1.51 AGN HS 0810+2554

We present results from X-ray observations of the gravitationally lensed z = 1.51 AGN HS 0810+2554 performed with the Chandra X-ray Observatory and XMM-Newton. Blueshifted absorption lines are detected in both observations at rest-frame energies ranging between ~1-12 keV at > 99% confidence. The inferred velocities of the outflowing components range between ~0.1c and ~0.4c. A strong emission line at ~6.8 keV accompanied by a significant absorption line at ~7.8 keV is also detected in the Chandra observation. The presence of these lines is a characteristic feature of a P-Cygni profile supporting the presence of an expanding outflowing highly ionized iron absorber in this quasar. Modeling of the P-Cygni profile constrains the covering factor of the wind to be > 0.6, assuming disk shielding. A disk-reflection component is detected in the XMM-Newton observation accompanied by blueshifted absorption lines. The XMM-Newton observation constrains the inclination angle to be < 45 degrees at 90% confidence, assuming the hard excess is due to blurred reflection from the accretion disk. The detection of an ultrafast and wide-angle wind in an AGN with intrinsic narrow absorption lines (NALs) would suggest that quasar winds may couple efficiently with the intergalactic medium and provide significant feedback if ubiquitous in all NAL and BAL quasars. We estimate the mass-outflow rate of the absorbers to lie in the range of 1.5 and 3.4 Msolar/yr for the two observations. We find the fraction of kinetic to electromagnetic luminosity released by HS 0810+2554 is large (epsilon = 9 (-6,+8)) suggesting that magnetic driving is likely a significant contributor to the acceleration of this outflow.Comment: 27 pages, 13 figures, Accepted for publication in Ap

Quasar outflow energetics from broad absorption line variability

Quasar outflows have long been recognized as potential contributors to the co-evolution between supermassive black holes (SMBHs) and their host galaxies. The role of outflows in AGN feedback processes can be better understood by placing observational constraints on wind locations and kinetic energies. We utilize broad absorption line (BAL) variability to investigate the properties of a sample of 71 BAL quasars with P$\thinspace$V broad absorption. The presence of P$\thinspace$V BALs indicates that other BALs like C$\thinspace$IV are saturated, such that variability in those lines favours clouds crossing the line of sight. We use these constraints with measurements of BAL variability to estimate outflow locations and energetics. Our data set consists of multiple-epoch spectra from the Sloan Digital Sky Survey and MDM Observatory. We detect significant (4$\sigma$) BAL variations from 10 quasars in our sample over rest frame time-scales between < 0.2-3.8 yr. Our derived distances for the 10 variable outflows are nominally < 1-10 pc from the SMBH using the transverse-motion scenario, and < 100-1000 pc from the central source using ionization-change considerations. These distances, in combination with the estimated high outflow column densities (i.e. $N_{\textrm{H}}$ > 10$^{22}$ cm$^{-2}$), yield outflow kinetic luminosities between ~ 0.001-1 times the bolometric luminosity of the quasar, indicating that many absorber energies within our sample are viable for AGN feedback.Comment: 19 pages, 3 figures, 4 tables, 1 supplementary figure, accepted to MNRA

Weak magnetic fields in central stars of planetary nebulae?

It is not yet clear whether magnetic fields play an essential role in shaping planetary nebulae (PNe), or whether stellar rotation alone and/or a close binary companion can account for the variety of the observed nebular morphologies. In a quest for empirical evidence verifying or disproving the role of magnetic fields in shaping PNe, we follow up on previous attempts to measure the magnetic field in a representative sample of PN central stars. We obtained low-resolution polarimetric spectra with FORS 2 at VLT for a sample of twelve bright central stars of PNe with different morphology, including two round nebulae, seven elliptical nebulae, and three bipolar nebulae. Two targets are Wolf-Rayet type central stars. For the majority of the observed central stars, we do not find any significant evidence for the existence of surface magnetic fields. However, our measurements may indicate the presence of weak mean longitudinal magnetic fields of the order of 100 Gauss in the central star of the young elliptical planetary nebula IC 418, as well as in the Wolf-Rayet type central star of the bipolar nebula Hen2-113 and the weak emission line central star of the elliptical nebula Hen2-131. A clear detection of a 250 G mean longitudinal field is achieved for the A-type companion of the central star of NGC 1514. Some of the central stars show a moderate night-to-night spectrum variability, which may be the signature of a variable stellar wind and/or rotational modulation due to magnetic features. We conclude that strong magnetic fields of the order of kG are not widespread among PNe central stars. Nevertheless, simple estimates based on a theoretical model of magnetized wind bubbles suggest that even weak magnetic fields below the current detection limit of the order of 100 G may well be sufficient to contribute to the shaping of PNe throughout their evolution.Comment: 16 pages, 11 figures, 3 tables, accepted for publication in A&A; References updated, minor correction

Constraining FeLoBAL outflows from absorption line variability

FeLoBALs are a rare class of quasar outflows with low-ionization broad absorption lines (BALs), large column densities, and potentially large kinetic energies that might be important for `feedback' to galaxy evolution. In order to probe the physical properties of these outflows, we conducted a multiple-epoch, absorption line variability study of 12 FeLoBAL quasars spanning a redshift range between 0.7 and 1.9 over rest frame time-scales of approximately 10 d to 7.6 yr. We detect absorption line variability with greater than 8 sigma confidence in 3 out of the 12 sources in our sample over time-scales of 0.6 to 7.6 yr. Variable wavelength intervals are associated with ground and excited state Fe II multiplets, the Mg II 2796, 2803 doublet, Mg I 2852, and excited state Ni II multiplets. The observed variability along with evidence of saturation in the absorption lines favors transverse motions of gas across the line of sight (LOS) as the preferred scenario, and allows us to constrain the outflow distance from the supermassive black hole (SMBH) to be less than 69, 7, and 60 pc for our three variable sources. In combination with other studies, these results suggest that the outflowing gas in FeLoBAL quasars resides on a range of scales and includes matter within tens of parsecs of the central source.Comment: 21 pages, 6 figures, 2 supplementary figures (attached at the end of the manuscript), accepted to Monthly Notices of the Royal Astronomical Societ

Combined cerebellar and bilateral cervical posterior spinal artery stroke demonstrated on MRI

Combined cerebellar and spinal ischemic stroke is a rare, critical condition. We report a patient with combined cerebellar and bilateral posterolateral cervical spinal cord infarction due to bilateral stenosis of the vertebral arteries. MRI is the method of choice for imaging this condition; diffusion-weighted imaging of the spinal cord gives reliable results

Axions and saxions from the primordial supersymmetric plasma and extra radiation signatures

We calculate the rate for thermal production of axions and saxions via scattering of quarks, gluons, squarks, and gluinos in the primordial supersymmetric plasma. Systematic field theoretical methods such as hard thermal loop resummation are applied to obtain a finite result in a gauge-invariant way that is consistent to leading order in the strong gauge coupling. We calculate the thermally produced yield and the decoupling temperature for both axions and saxions. For the generic case in which saxion decays into axions are possible, the emitted axions can constitute extra radiation already prior to big bang nucleosynthesis and well thereafter. We update associated limits imposed by recent studies of the primordial helium-4 abundance and by precision cosmology of the cosmic microwave background and large scale structure. We show that the trend towards extra radiation seen in those studies can be explained by late decays of thermal saxions into axions and that upcoming Planck results will probe supersymmetric axion models with unprecedented sensitivity.Comment: 16 pages, 7 figures; v2: references added, minor clarifying additions, matches published versio

A High-Velocity Narrow Absorption Line Outflow in the Quasar J212329.46-005052.9

We report on a variable high-velocity narrow absorption line outflow in the redshift 2.3 quasar J2123-0050. Five distinct outflow systems are detected with velocity shifts from -9710 to -14,050 km/s and CIV 1548,1551 line widths of FWHM = 62-164 km/s. These data require five distinct outflow structures with similar kinematics, physical conditions and characteristic sizes of order 0.01-0.02 pc. The most likely location is ~5 pc from the quasar. The coordinated line variations in <0.63 yr (rest) are best explained by global changes in the outflow ionization caused by changes in the quasar's ionizing flux. The absence of strong X-ray absorption shows that radiative shielding is not needed to maintain the moderate ionizations and therefore, apparently, it is not needed to facilitate the radiative acceleration to high speeds. The kinetic energy yield of this flow is at least two orders of magnitude too low to be important for feedback to the host galaxy's evolution.Comment: 20 pages. In press with MNRA

On X-ray pulsations in beta Cephei-type variables

Beta Cephei-type variables are early B-type stars that are characterized by oscillations observable in their optical light curves. At least one Beta Cep-variable also shows periodic variability in X-rays. Here we study the X-ray light curves in a sample of beta Cep-variables to investigate how common X-ray pulsations are for this type of stars. We searched the Chandra and XMM-Newton X-ray archives and selected stars that were observed by these telescopes for at least three optical pulsational periods. We retrieved and analyzed the X-ray data for kappa Sco, beta Cru, and alpha Vir. The X-ray light curves of these objects were studied to test for their variability and periodicity. While there is a weak indication for X-ray variability in beta Cru, we find no statistically significant evidence of X-ray pulsations in any of our sample stars. This might be due either to the insufficient data quality or to the physical lack of modulations. New, more sensitive observations should settle this question.Comment: accepted in A&