Towards an informed quest for accretion disc winds in quasars: the intriguing case of Ton 28

We report on the detection of a blueshifted Fe K absorption feature in two consecutive XMM–Newton  observations of the luminous blue quasar Ton 28, at the 4σ cumulative significance. The rest energy of 9.2 keV implies the presence of an accretion disc wind with bulk outflow velocity of ∼0.28c, while the kinetic power is most likely a few per cent of the quasar luminosity. Remarkably, Ton 28 had been specifically selected as an optimal target to reveal an ultra-fast X-ray wind based on its total luminosity (Lbol > 1046 erg s−1) and [O III] λ5007 Å equivalent width (EW < 6 Å), suggestive of high accretion rate and low inclination, respectively. Other peculiar optical/UV emission-line properties include narrow Hβ, strong Fe II, and blueshifted C IV . These are key parameters in the Eigenvector 1 formalism, and are frequently found in active galaxies with ongoing accretion disc winds, hinting at a common physical explanation. Provided that the effectiveness of our selection method is confirmed with similar sources, this result could represent the first step towards the characterization of black hole winds through multiwavelength indicators in the absence of high-quality X-ray spectra

On the 2015 outburst of the EXor variable star V1118 Ori

After a long-lasting period of quiescence of about a decade, the source V1118 Ori, one of the most representative members of the EXor variables, is now outbursting. Since the initial increase of the near-infrared flux of about 1 mag (JHK bands) registered on 2015 September 22, the source brightness has remained fairly stable. We estimate DeltaV about 3 mag with respect to the quiescence phase. An optical/near-IR low-resolution spectrum has been obtained with the Large Binocular Telescope instruments MODS and LUCI2, and compared with a spectrum of similar spectral resolution and sensitivity level taken during quiescence. Together with the enhancement of the continuum, the outburst spectrum presents a definitely higher number of emission lines, in particular HI recombination lines of the Balmer, Paschen, and Brackett series, along with bright permitted lines of several species, forbidden atomic lines, and CO ro-vibrational lines. Both mass accretion and mass loss rates have significantly increased (by to about an order of magnitude, mass accretion rate = 1.2-4.8 10^-8 M_sun/yr, mass loss rate = 0.8-2 10^-9 M_sun/yr) with respect to the quiescence phase. If compared with previous outbursts, the present one appears less energetic. Alternatively, it could already be in the fading phase (with the maximum brightness level reached when the source was not visible), or, viceversa, still in the rising phase.Comment: Accepted ApJ Letter

Hole-depletion of ladders in Sr14_{14}Cu24_{24}O41_{41} induced by correlation effects

The hole distribution in Sr$_{14}$Cu$_{24}$O$_{41}$ is studied by low temperature polarization dependent O K Near-Edge X-ray Absorption Fine Structure measurements and state of the art electronic structure calculations that include core-hole and correlation effects in a mean-field approach. Contrary to all previous analysis, based on semi-empirical models, we show that correlations and antiferromagnetic ordering favor the strong chain hole-attraction. For the remaining small number of holes accommodated on ladders, leg-sites are preferred to rung-sites. The small hole affinity of rung-sites explains naturally the 1D - 2D cross-over in the phase diagram of (La,Y,Sr,Ca)$_{14}$Cu$_{24}$O$_{41}$Comment: 6 pages, 8 figure

Large Binocular Telescope view of the atmosphere of GJ1214b

The atmospheric composition and vertical structure of the super-Earth GJ1214b has been a subject of debate since its discovery in 2009. Recent studies have indicated that high-altitude clouds might mask the lower layers. However, some data points that were gathered at different times and facilities do not fit this picture, probably because of a combination of stellar activity and systematic errors. We observed two transits of GJ1214b with the Large Binocular Camera, the dual-channel camera at the Large Binocular Telescope. For the first time, we simultaneously measured the relative planetary radius $k=R_\mathrm{p}/R_\star$ at blue and red optical wavelengths ($B+R$), thus constraining the Rayleigh scattering on GJ1214b after correcting for stellar activity effects. To the same purpose, a long-term photometric follow-up of the host star was carried out with WiFSIP at STELLA, revealing a rotational period that is significantly longer than previously reported. Our new unbiased estimates of $k$ yield a flat transmission spectrum extending to shorter wavelengths, thus confirming the cloudy atmosphere scenario for GJ1214b.Comment: 11 pages, 5 figures, 3 tables. Published in A&A. Minor changes to reflect the published versio

Quasars as standard candles II

A tight non-linear relation between the X-ray and the optical-ultraviolet (UV) emission has been observed in active galactic nuclei (AGN) over a wide range of redshift and several orders of magnitude in luminosity, suggesting the existence of an ubiquitous physical mechanism regulating the energy transfer between the accretion disc and the X-ray emitting corona. Recently, our group developed a method to use this relation in observational cosmology, turning quasars into standardizable candles. This work mainly seeks to investigate the potential evolution of this correction at high redshifts. We thus studied the LX − LUV relation for a sample of quasars in the redshift range 4 <  z <  7, adopting the selection criteria proposed in our previous work regarding their spectral properties. The resulting sample consists of 53 type 1 (unobscured) quasars, observed either with Chandra or XMM-Newton, for which we performed a full spectral analysis, determining the rest-frame 2 keV flux density, as well as more general X-ray properties such as the estimate of photon index, and the soft (0.5–2 keV) and hard (2–10 keV) unabsorbed luminosities. We find that the relation shows no evidence for evolution with redshift. The intrinsic dispersion of the LX–LUV for a sample free of systematics/contaminants is of the order of 0.22 dex, which is consistent with previous estimates from our group on quasars at lower redshift

Bimagnon studies in cuprates with Resonant Inelastic X-ray Scattering at the O K edge. I - An assessment on La2CuO4 and a comparison with the excitation at Cu L3 and Cu K edges

We assess the capabilities of magnetic Resonant Inelastic X-ray Scattering (RIXS) at the O $K$ edge in undoped cuprates by taking La_{2}CuO_{4} as a benchmark case, based on a series of RIXS measurements that we present here. By combining the experimental results with basic theory we point out the fingerprints of bimagnon in the O $K$ edge RIXS spectra. These are a dominant peak around 450 meV, the almost complete absence of dispersion both with $\pi$ and $\sigma$ polarization and the almost constant intensity vs. the transferred momentum with $\sigma$ polarization. This behavior is quite different from Cu $L_3$ edge RIXS giving a strongly dispersing bimagnon tending to zero at the center of the Brillouin zone. This is clearly shown by RIXS measurements at the Cu $L_3$ edge that we present. The Cu $L_3$ bimagnon spectra and those at Cu $K$ edge - both from the literature and from our data - however, have the same shape. These similarities and differences are understood in terms of different sampling of the bimagnon continuum. This panorama points out the unique possibilities offered by O $K$ RIXS in the study of magnetic excitations in cuprates near the center of the BZ

A powerful (and likely young) radio-loud quasar at z=5.3

We present the discovery of PSO J191.05696$+$86.43172 (hereafter PSO J191$+$86), a new powerful radio-loud quasar (QSO) in the early Universe (z = 5.32). We discovered it by cross-matching the NRAO VLA Sky Survey (NVSS) radio catalog at 1.4 GHz with the first data release of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS PS1) in the optical. With a NVSS flux density of 74.2 mJy, PSO J191$+$86 is one of the brightest radio QSO discovered at z$\sim$5. The intensity of its radio emission is also confirmed by the very high value of radio loudness (R>300). The observed radio spectrum of PSO J191$+$86 shows a possible turnover around $\sim$1 GHz (i.e., $\sim$6 GHz in the rest frame), making it a Gigahertz-Peaked Spectrum (GPS) source. However, variability could affect the real shape of the radio spectrum, since the data in hand have been taken $\sim$25 years apart. By assuming a peak of the observed radio spectrum between 1 and 2 GHz (i.e. $\sim$ 6 and 13 GHz in the rest-frame) we found a linear size of the source of $\sim$10-30 pc and a corresponding kinetic age of 150-460 yr. This would make PSO J191$+$86 a newly born radio source. However, the large X-ray luminosity (5.3$\times$10$^{45}$ erg s$^{-1}$), the flat X-ray photon index ($\Gamma_X$=1.32) and the optical-X-ray spectral index ($\tilde{\alpha_{ox}}$=1.329) are typical of blazars. This could indicate that the non-thermal emission of PSO J191$+$86 is Doppler boosted. Further radio observations (both on arcsec and parsec scales) are necessary to better investigate the nature of this powerful radio QSO.Comment: 10 pages, 9 figures, 5 tables, Accepted for publication in A&

Activation of NF-kappaB/Rel transcription factors in human primary peripheral blood mononuclear cells by interleukin 7.

Pathways that regulate the activation of NF-kappaB/Rel transcription factors are known to include signaling through a number of cytokine receptors. Interleukin 7 (IL-7), produced by bone marrow and other stromal cells, is a key factor for differentiation and survival in the lymphoid and other compartments. We found that human recombinant IL-7 induced NF-kappaB/Rel activation, analyzed by electrophoretic mobility shift assay (EMSA), in human peripheral blood T lymphocytes from healthy donors. Induced complexes included p65 and p50 NF-kappaB/Rel subunits. These results demonstrate for the first time that IL-7 can participate in signaling leading to NF-kappaB/Rel activation