Search

We report the discovery of a bright, extended X-ray jet in the quasar RGB J1512+020A (z = 0.22). Chandra observations show the X-ray core and 13 arcsec (∼45 kpc projected) extended emission coincident with the radio jet. The jet stands out as one of brightest X-ray jets (LX ∼ 7 × 1043 erg s−1) at low redshift (z < 0.5) discovered so far, with remarkably large X-ray to radio luminosity ratios (LX/Lr up to ∼50). We identified four main components, two unresolved knots and two extended structures, one being the jet brightest feature (JBF). All jet features are also detected in ALMA archival observations. The radio, sub-mm to X-ray spectra of the two knots can be modelled with a single synchrotron component. For the two resolved structures, the ALMA data unveil a turnover of the low-energy continuum at ∼460 GHz. External Comptonization of cosmic microwave background photons can account for the observed X-ray emission if the jet speed remains highly relativistic, with bulk motion Γbulk > 15, up to tens of kiloparsec from the core. However, the comparison with the spectral energy distribution of similar X-ray detected jets shows that the alternative hypothesis of synchrotron emission from an additional population of ultra-high-energy electrons is also possible. We report a tentative (≳2σ) optical detection of the JBF in images of the Dark Energy Camera Legacy Survey. If confirmed, the optical emission should be either the low-energy tail of the radiative component responsible for the X-ray emission or a third, separate component.

The incidence of young but fading radio sources provides important information on the life cycle of radio emission in radio-loud active galactic nuclei. Despite its importance for constraining the models of radio source evolution, there are no systematic studies of remnants in complete samples of young radio sources. We report results on the study of 18 compact steep-spectrum (CSS) radio sources, selected from the statistically complete B3-VLA CSS sample, characterized by a steep optically-thin spectrum (alpha > 1.0) and no core detection in earlier studies. Our deep multi-frequency Very Large Array (VLA), pc-scale Very Long Baseline Array (VLBA), and eMERLIN observations allowed us to locate the core component in 10 objects. In 3 CSS sources there is no clear evidence of present-time active regions, suggesting they are likely in a remnant phase. Among sources with core detection, we find 3 objects that have no clear active regions (hotspots) at the edges of the radio structure, suggesting that the radio emission may have just restarted. Our results support a power-law distribution of the source ages, although the poor statistics prevents us from setting solid constraints on the percentage of remnants and restarted sources in sub-populations of radio sources., 33 pages, 8 figures, 7 tables. Accepted for publication in MNRAS

According to radiative models, radio galaxies and quasars are predicted to produce gamma rays from the earliest stages of their evolution. Exploring their high-energy emission is crucial for providing information on the most energetic processes, the origin and the structure of the newly born radio jets. Taking advantage of more than 11 yr of Fermi-LAT data, we investigate the gamma-ray emission of 162 young radio sources (103 galaxies and 59 quasars), the largest sample of young radio sources used so far for such a gamma-ray study. We separately analyse each source and perform the first stacking analysis of this class of sources to investigate the gamma-ray emission of the undetected sources. We detect significant gamma-ray emission from 11 young radio sources, 4 galaxies, and 7 quasars, including the discovery of significant gamma-ray emission from the compact radio galaxy PKS 1007+142 (z = 0.213). The cumulative signal of below-threshold young radio sources is not significantly detected. However, it is about one order of magnitude lower than those derived from the individual sources, providing stringent upper limits on the gamma-ray emission from young radio galaxies (Fγ < 4.6 × 10−11 ph cm−2 s−1) and quasars (Fγ < 10.1 × 10−11 ph cm−2 s−1), and enabling a comparison with the models proposed. With this analysis of more than a decade of Fermi-LAT observations, we can conclude that while individual young radio sources can be bright gamma-ray emitters, the collective gamma-ray emission of this class of sources is not bright enough to be detected by Fermi-LAT.

We study the multi-phase medium in the vicinity of the active galactic nucleus Centaurus A (Cen A). Combined high-resolution observations with the ALMA and Chandra observatories indicate that the hot X-ray emitting plasma coexists with the warm and cold media in Cen A. This complex environment is a source of CO lines with great impact for its diagnostics. We present the images from the two above-mentioned instruments covering the nuclear region (diameter of 10'' i.e., ~180 pc), and we study the conditions for plasma thermal equilibrium and possible coexistence of cool clouds embedded within the hot X-ray emitting gas. Further, we demonstrate that the multi-phase medium originates naturally by the thermal instability (TI) arising due to the interaction of the high-energy radiation field from the nucleus with the ambient gas and dust. We demonstrate that cold gas clouds can coexist in the mutual contact with hot plasma, but even colder dusty molecular clouds have to be distanced by several hundred pc from the hot region. Finally, we propose a 3-D model of the appearance of the hot plasma and the CO line-emitting regions consistent with the Chandra image and we derive the integrated emissivity in specific molecular lines observed by ALMA from this model. To reproduce the observed images and the CO line luminosity the dusty shell has to be ~420 pc thick and located at ~1000 pc from the centre., 16 pages, 16 figures, Accepted for publication in MNRAS

We present the discovery and the subsequent follow up of radio emission from SDSS J130402.36$+$293840.6 (J1304+2938), the candidate host galaxy of the gamma-ray burst GRB~200716C. The galaxy is detected in the RACS (0.89 GHz), the NVSS, the Apertif imaging survey, and the FIRST (1.4 GHz), the VLASS (3 GHz), and in public LOFAR (130-170 MHz), WISE (3.4-22 $\mu$m), and SDSS (z, i, r, g, u filters) data. The luminosity inferred at 1.4 GHz is (5.1$\pm0.2)\times10^{30}$ erg s$^{-1}$ Hz$^{-1}$. To characterise the emission and distinguish between different components within the galaxy, we performed dedicated, high-sensitivity and high-resolution observations with the European VLBI Network + e-MERLIN at 1.6 and 5 GHz. We did not detect any emission from a compact core, suggesting that the presence of a radio-loud AGN is unlikely, and therefore we ascribe the emission observed in the public surveys to star-forming regions within the galaxy. We confirm and refine the redshift estimate, $z=0.341\pm0.004$, with a dedicated TNG spectroscopic observation. Finally, we compiled a list of all the known hosts of GRB afterglows detected in radio and computed the corresponding radio luminosity: if GRB~200716C belongs to J1304+2938, this is the third most radio-luminous host of a GRB, implying one of the highest star-formation rates (SFRs) currently known, namely SFR$\sim$324$\pm$61 M$_{\odot}$ yr$^{-1}$. On the other hand, through the analysis of the prompt emission light curve, recent works suggest that GRB~200716C might be a short-duration GRB located beyond J1304$+$2938 and gravitationally lensed by an intermediate-mass black hole (IMBH) hosted by the galaxy. Neither the public data nor our VLBI observations can confirm or rule out the presence of an IMBH acting as a (milli-)lens hosted by the galaxy, a scenario still compatible with the set of radio observations presented in this work., Comment: 11 pages, 5 figures. Revised manuscript after referee's correction. Accepted for publication in A&A

The radio source 1146+596 is hosted by an elliptical/S0 galaxy NGC\,3894, with a low-luminosity active nucleus. The radio structure is compact, suggesting a very young age of the jets in the system. Recently, the source has been confirmed as a high-energy (HE, $>0.1$\,GeV) $\gamma$-ray emitter, in the most recent accumulation of the {\it Fermi} Large Area Telescope (LAT) data. Here we report on the analysis of the archival {\it Chandra} X-ray Observatory data for the central part of the galaxy, consisting of a single 40\,ksec-long exposure. We have found that the core spectrum is best fitted by a combination of an ionized thermal plasma with the temperature of $\simeq 0.8$\,keV, and a moderately absorbed power-law component (photon index $\Gamma = 1.4\pm 0.4$, hydrogen column density $N_{\rm H}/10^{22}$\,cm$^{-2}$\,$= 2.4\pm 0.7$). We have also detected the iron K$\alpha$ line at $6.5\pm 0.1$\,keV, with a large equivalent width of EW\,$= 1.0_{-0.5}^{+0.9}$\,keV. Based on the simulations of the {\it Chandra}'s Point Spread Function (PSF), we have concluded that, while the soft thermal component is extended on the scale of the galaxy host, the hard X-ray emission within the narrow photon energy range 6.0--7.0\,keV originates within the unresolved core (effectively the central kpc radius). The line is therefore indicative of the X-ray reflection from a cold neutral gas in the central regions of NGC\,3894. We discuss the implications of our findings in the context of the X-ray Baldwin effect. NGC\,3894 is the first young radio galaxy detected in HE $\gamma$-rays with the iron K$\alpha$ line., Comment: Revised version, accepted for publication in the Astrophysical Journal

Powerful radio sources and quasars emit relativistic jets of plasma and magnetic fields that travel hundreds of kilo-parsecs, ultimately depositing energy into the intra- or inter-cluster medium. In the rest frame of the jet, the energy density of the cosmic microwave background is enhanced by the bulk Lorentz factor squared, and when this exceeds the magnetic energy density the primary loss mechanism of the relativistic electrons is via inverse Compton scattering. The microwave energy density is also enhanced by a factor (1+z)^4, which becomes important at large redshifts. We are using Chandra to survey a z>3 sub-sample of radio sources selected with 21 cm wavelength flux density > 70 mJy, and with a spectroscopic redshift. Out of the first 12 objects observed, there are two clear cases of the X-rays extending beyond the detectable radio jet., 6 pages, 4 figures. In proceedings of the IWARA 2018 conference, to be published in Astronomische Nachrichten

[Abridged] Context: We present a systematic X-ray spectral-timing study of the recently discovered, exceptionally bright black hole X-ray binary system MAXI J1820+070. Our analysis focuses on the first part of the 2018 outburst, covering the rise throughout the hard state, the bright hard and hard-intermediate states, and the transition to the soft-intermediate state. Aims: We address the issue of constraining the geometry of the innermost accretion flow and its evolution throughout an outburst. Methods: We employed two independent X-ray spectral-timing methods applied to the NICER data of MAXI J1820+070. We first identified and tracked the evolution of a characteristic frequency of soft X-ray reverberation lags. Then, we studied the spectral evolution of the quasi-thermal component responsible for the observed thermal reverberation lags. Results: The frequency of thermal reverberation lags steadily increases throughout most of the outburst, implying that the relative distance between the X-ray source and the disc decreases as the source softens. However, near transition this evolution breaks, showing a sudden increase (decrease) of lag amplitude (frequency). The temperature of the quasi-thermal component in covariance spectra consistently increases throughout all the analysed observations. Conclusions: The behaviour of thermal reverberation lags near transition might be related to the relativistic plasma ejections detected at radio wavelengths, suggesting a causal connection between the two phenomena. Throughout most of the hard and hard-intermediate states the disc is consistent with being truncated (with an inner radius $R_{\rm in}>\sim 10 R_{\rm g}$), reaching close to the innermost stable circular orbit only near transition., Accepted for publication in Astronomy & Astrophysics, matches published version

We report the detection of extended X-ray emission from two high-redshift radio quasars. These quasars, J1405+0415 at $z$=3.208 and J1610+1811 at $z$=3.118, were observed in a Chandra snapshot survey selected from a complete sample of the radio-brightest quasars in the overlap area of the VLA-FIRST radio survey and the Sloan Digital Sky Survey. The extended X-ray emission is located along the line connecting the core to a radio knot or hotspot, favoring the interpretation of X-ray jets. The inferred rest frame jet X-ray luminosities from 2--30 keV would be of order 10$^{45}$ erg~s$^{-1}$ if emitted isotropically and without relativistic beaming. In the scenario of inverse Compton scattering of the cosmic microwave background (CMB), X-ray jets without a coincident radio counterpart may be common, and should be readily detectable to redshifts even beyond 3.2 due to the (1+$z$)$^4$ increase of the CMB energy density compensating for the (1+$z$)$^{-4}$ cosmological diminution of surface brightness. If these can be X-ray confirmed, they would be the second and third examples of quasar X-ray jets without detection of underlying continuous radio jets., 10 pages, 4 figures. Accepted for publication in The Astrophysical Journal

Compact Symmetric Objects (CSOs) show radio features such as jets, lobes, hot spots that are contained within the central 1 kpc region of their host galaxy. Thus, they are thought to be among the progenitors of large-scale radio galaxies. A debate on whether the CSOs are compact primarily because they are young or because they are surrounded by a dense medium impacting their expansion is ongoing. Until now, attempts to discriminate between the environmental and genuine youthfulness scenarios have been inconclusive. We present a study of three CSOs selected on the basis of their puzzling X-ray absorbing properties in prior Beppo-SAX and/or Chandra X-ray Observatory data. Our new XMM-Newton observations unambiguously confirm the nature of their X-ray absorbers. Furthermore, for the first time, our X-ray data reveal the existence of a population of CSOs with intrinsic hydrogen column density $N_H > 10^{23}$ cm$^{-2}$ that is different from the population of X-ray unabsorbed CSOs. The two groups appear to be separated in the linear size vs. radio power plane. This finding suggests that a dense medium in X-ray obscured CSOs may be able to confine the radio jets. Alternatively, X-ray obscured CSOs could be seen as radio brighter than their unobscured counterparts either because they reside in a dense environment or because they have larger jet powers. Our results help constrain the origin of the X-ray emission and the location and size of the X-ray obscurer in CSOs, and indicate that the environment may play a key role during the initial expansion of a radio source., 8 pages, 4 figures, ApJ in press

According to theoretical predictions, young extragalactic radio sources may release a significant fraction of their total radiative power in the high-energy domain. X-ray emission is expected from the central active galactic nucleus (AGN), and from the extended radio components, jet, hot spots, and lobes. The X-rays should also trace the interactions of the radio source with its environment, and reveal to us how the young source clears its way out of the host galaxy and finally reaches the giant stage. Observational campaigns with Chandra and XMM-Newton telescopes have confirmed that young radio sources are indeed relatively X-ray luminous. Recently, efforts have been undertaken to obtain a complete X-ray view of the whole population of young sources, focusing on the youngest and faintest objects. At the same time, the study of the X-ray properties of the samples of quasars and galaxies provides us with clues on the nature of the observed high-energy emission. In specific cases, X-ray and multi-wavelength data allow for a direct test of the different models. A detection in the y-ray band would represent a robust proof of a non-thermal, high-energy component and the launch of the Fermi telescope has opened the hunt to young radio sources in the y-ray window. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present the results from a sensitive X-ray survey of 26 nearby hydrogen-poor superluminous supernovae (SLSNe-I) with Swift, Chandra and XMM. This dataset constrains the SLSN evolution from a few days until ~2000 days after explosion, reaching a luminosity L_x~10^40 erg/s and revealing the presence of significant X-ray emission at the location of PTF12dam. No SLSN-I is detected above L_x~10^41 erg/s, suggesting that the luminous X-ray emission L_x~10^45 erg/s associated with SCP60F6 is not common among SLSNe-I. We constrain the presence of off-axis GRB jets, ionization breakouts from magnetar central engines and the density in the sub-pc environments of SLSNe-I through Inverse Compton emission. The deepest limits rule out the weakest uncollimated GRB outflows, suggesting that IF the similarity of SLSNe-I with GRB/SNe extends to their fastest ejecta, then SLSNe-I are either powered by energetic jets pointed far away from our line of sight theta>30 deg, or harbor failed jets that do not successfully break through the stellar envelope. Furthermore, IF a magnetar central engine is responsible for the exceptional luminosity of SLSNe-I, our X-ray analysis favors large magnetic fields B>2x10^(14) G and ejecta masses M_ej>3 Msun in agreement with optical/UV studies. Finally, we constrain the pre-explosion mass-loss rate of stellar progenitors of SLSNe-I. For PTF12dam we infer Mdot, 12 pages of main text

We present the first extensive radio to gamma-ray observations of a fast-rising blue optical transient (FBOT), AT2018cow, over its first ~100 days. AT2018cow rose over a few days to a peak luminosity $L_{pk}\sim4\times 10^{44}$ erg/s exceeding those of superluminous supernovae (SNe), before declining as $\propto t^{-2}$. Initial spectra at $\lesssim 15$ days were mostly featureless and indicated large expansion velocities v~0.1c and temperatures reaching 30000 K. Later spectra revealed a persistent optically-thick photosphere and the emergence of H and He emission features with v~sim 4000 km/s with no evidence for ejecta cooling. Our broad-band monitoring revealed a hard X-ray spectral component at $E\ge 10$ keV, in addition to luminous and highly variable soft X-rays, with properties unprecedented among astronomical transients. An abrupt change in the X-ray decay rate and variability appears to accompany the change in optical spectral properties. AT2018cow showed bright radio emission consistent with the interaction of a blastwave with $v_{sh}$~0.1c with a dense environment ($\dot M\sim10^{-3}-10^{-4}\,M_{\odot}yr^{-1}$ for $v_w=1000$ km\s). While these properties exclude Ni-powered transients, our multi-wavelength analysis instead indicates that AT2018cow harbored a "central engine", either a compact object (magnetar or black hole) or an embedded internal shock produced by interaction with a compact, dense circumstellar medium. The engine released $\sim10^{50}-10^{51.5}$ erg over $\sim10^3-10^5$ s and resides within low-mass fast-moving material with equatorial-polar density asymmetry ($M_{ej,fast}\lesssim0.3\,\rm{M_{\odot}}$). Successful SNe from low-mass H-rich stars (like electron-capture SNe) or failed explosions from blue supergiants satisfy these constraints. Intermediate-mass black-holes are disfavored by the large environmental density probed by the radio observations., Comment: 26 pages + tables. Submitted

The energy source powering the extreme optical luminosity of hydrogen-stripped Superluminous Supernovae (SLSNe-I) is not known, but recent studies have highlighted the case for a central engine. Radio and/or X-ray observations are best placed to track the fastest ejecta and probe the presence of outflows from a central engine. We compile all the published radio observations of SLSNe-I to date and present three new observations of two new SLSNe-I. None were detected. Through modeling the radio emission, we constrain the sub-parsec environments and possible outflows in SLSNe-I. In this sample we rule out on-axis collimated relativistic jets of the kind detected in Gamma-Ray Bursts (GRBs). We constrain off-axis jets with opening angles of 5\arcdeg\ (30\arcdeg) to energies of $\rm{E_k, Accepted by ApJ, 14 pages, 6 figures

We present an in-depth study of the large-scale, western jet of the microquasar XTE J1550-564, based on X-ray and radio observations performed in 2002-2003. The jet is spatially resolved in both observing windows. The X-ray jet is expanding in time along the axis of the jet's propagation: we observe the formation of a tail (~2.25"), which appears to extend backwards with an apparent velocity ~-0.10c. The origin of this feature is discussed in the framework of scenarios of energy dissipation. A single power-law adequately describes the broadband spectra, supporting a synchrotron origin of the X-ray emission. However, a spectral break at ~10^{15} Hz is necessary in coincidence with a re-flare at 8.64 GHz in September 2002. This finding may be indicative of emission from newly accelerated low-energy particles. The first detection of the jet is in February 2001 (F_{8.64GHz}=0.25+/-0.09 mJy) in the flux rising phase. A phase of stable emission is followed by a rapid decay (t_{decay}=167+/-5 days). The decay at radio frequencies is significantly shorter than in X-rays (t_{decay}=338+/-14 days). We detected a high fraction (up to ~9%) of linearly polarized radiation at 4.8 GHz and 8.6 GHz. The orientation of the electric vector is consistent with the picture of a shock-compressed magnetic field, and there are hints of variations on month-timescales, possibly connected with the evolution of the jet structure., Accepted for publication in MNRAS

We present the detection of persistent soft X-ray radiation with L_x ~ 10^(41)-10^(42) erg s^(-1) at the location of the extremely luminous, double-humped transient ASASSN-15lh as revealed by Chandra and Swift. We interpret this finding in the context of observations from our multiwavelength campaign, which revealed the presence of weak narrow nebular emission features from the host-galaxy nucleus and clear differences with respect to superluminous supernova optical spectra. Significant UV flux variability on short timescales detected at the time of the rebrightening disfavors the shock interaction scenario as the source of energy powering the long-lived UV emission, while deep radio limits exclude the presence of relativistic jets propagating into a low-density environment. We propose a model where the extreme luminosity and double-peaked temporal structure of ASASSN-15lh is powered by a central source of ionizing radiation that produces a sudden change in the ejecta opacity at later times. As a result, UV radiation can more easily escape, producing the second bump in the light curve. We discuss different interpretations for the intrinsic nature of the ionizing source. We conclude that, if the X-ray source is physically associated with the optical–UV transient, then ASASSN-15lh most likely represents the tidal disruption of a main-sequence star by the most massive spinning black hole detected to date. In this case, ASASSN-15lh and similar events discovered in the future would constitute the most direct probes of very massive, dormant, spinning, supermassive black holes in galaxies. Future monitoring of the X-rays may allow us to distinguish between the supernova hypothesis and the hypothesis of a tidal disruption event.

We present comprehensive observations and analysis of the energetic H-stripped SN 2016coi (a.k.a. ASASSN-16fp), spanning the $\gamma$-ray through optical and radio wavelengths, acquired within the first hours to $\sim$420 days post explosion. Our campaign confirms the identification of He in the SN ejecta, which we interpret to be caused by a larger mixing of Ni into the outer ejecta layers. From the modeling of the broad bolometric light curve we derive a large ejecta mass to kinetic energy ratio ($M_{\rm{ej}}\sim 4-7\,\rm{M_{\odot}}$, $E_{\rm{k}}\sim 7-8\times 10^{51}\,\rm{erg}$). The small [\ion{Ca}{ii}] \lam\lam7291,7324 to [\ion{O}{i}] \lam\lam6300,6364 ratio ($\sim$0.2) observed in our late-time optical spectra is suggestive of a large progenitor core mass at the time of collapse. We find that SN 2016coi is a luminous source of X-rays ($L_{X}>10^{39}\,\rm{erg\,s^{-1}}$ in the first $\sim100$ days post explosion) and radio emission ($L_{8.5\,GHz}\sim7\times 10^{27}\,\rm{erg\,s^{-1}Hz^{-1}}$ at peak). These values are in line with those of relativistic SNe (2009bb, 2012ap). However, for SN 2016coi we infer substantial pre-explosion progenitor mass-loss with rate $\dot M \sim (1-2)\times 10^{-4}\,\rm{M_{\odot}yr^{-1}}$ and a sub-relativistic shock velocity $v_{sh}\sim0.15c$, in stark contrast with relativistic SNe and similar to normal SNe. Finally, we find no evidence for a SN-associated shock breakout $\gamma$-ray pulse with energy $E_{\gamma}>2\times 10^{46}\,\rm{erg}$. While we cannot exclude the presence of a companion in a binary system, taken together, our findings are consistent with a massive single star progenitor that experienced large mass loss in the years leading up to core-collapse, but was unable to achieve complete stripping of its outer layers before explosion., Comment: Submitted to ApJ. Main text: 21 pages; Appendix: 15 pages; 12 figures

We investigated the contribution of the jet to the observed high energy emission in a sample of young and compact radio quasars. For the first time, we compared the Fermi-LAT and Chandra observations of the sample to γ-ray and X-ray luminosities predicted assuming a jet synchrotron and inverse Compton radiative model. The simulations performed for a reasonable set of model parameters and assumptions provide constraints on the minimum jet power (Ljet,kin/Ldisk>0.01), on the contribution of the jet to the X-ray emission, and on the particles to magnetic field energy density ratios.

We present radio, optical/NIR, and X-ray observations of the afterglow of the short-duration 130603B, and uncover a break in the radio and optical bands at 0.5 d after the burst, best explained as a jet break with an inferred jet opening angle of 4-8 deg. GRB 130603B is only the third short GRB with a radio afterglow detection to date, and the first time that a jet break is evident in the radio band. We model the temporal evolution of the spectral energy distribution to determine the burst explosion properties and find an isotropic-equivalent kinetic energy of (0.6-1.7) x 10^51 erg and a circumburst density of 5 x 10^-3-30 cm^-3. From the inferred opening angle of GRB 130603B, we calculate beaming-corrected energies of Egamma (0.5-2) x 10^49 erg and EK (0.1-1.6) x 10^49 erg. Along with previous measurements and lower limits we find a median short GRB opening angle of 10 deg. Using the all-sky observed rate of 10 Gpc^-3 yr^-1, this implies a true short GRB rate of 20 yr^-1 within 200 Mpc, the Advanced LIGO/VIRGO sensitivity range for neutron star binary mergers. Finally, we uncover evidence for significant excess emission in the X-ray afterglow of GRB 130603B at >1 d and conclude that the additional energy component could be due to fall-back accretion or spin-down energy from a magnetar formed following the merger., Submitted to ApJ; emulateapj style; 10 pages, 1 table, 3 figures

The spectra of BL Lac objects and Fanaroff-Riley I radio galaxies are commonly explained by the one-zone leptonic synchrotron self-Compton (SSC) model. Spectral modeling of correlated multiwavelength data gives the comoving magnetic field strength, the bulk outflow Lorentz factor and the emission region size. Assuming the validity of the SSC model, the Hillas condition shows that only in rare cases can such sources accelerate protons to much above 10^19 eV, so > 10^20 eV ultra-high-energy cosmic rays (UHECRs) are likely to be heavy ions if powered by this type of radio-loud active galactic nuclei (AGN). Survival of nuclei is shown to be possible in TeV BL Lacs and misaligned counterparts with weak photohadronic emissions. Another signature of hadronic production is intergalactic UHECR-induced cascade emission, which is an alternative explanation of the TeV spectra of some extreme non-variable blazars such as 1ES 0229+200 or 1ES 1101-232. We study this kind of cascade signal, taking into account effects of the structured extragalactic magnetic fields in which the sources should be embedded. We demonstrate the importance of cosmic-ray deflections on the gamma-ray flux, and show that required absolute cosmic-ray luminosities are larger than the average UHECR luminosity inferred from UHECR observations and can even be comparable to the Eddington luminosity of supermassive black holes. Future TeV gamma-ray observations using the Cherenkov Telescope Array and the High Altitude Water Cherenkov detector array can test for UHECR acceleration by observing >25 TeV photons from relatively low-redshift sources such as 1ES 0229+200, and > TeV photons from more distant radio-loud AGN., 14 pages, 9 figures, 2 tables, accepted for publication in ApJ, references and discussions added

We present the X-ray analysis of a deep (~200 ks) Chandra observation of the compact steep spectrum radio-loud quasar 3C 186 (z = 1.06) and investigate the contribution of the unresolved radio jet to the total X-ray emission. The spectral analysis is not conclusive on the origin of the bulk of the X-ray emission. In order to examine the jet contribution to the X-ray flux, we model the quasar spectral energy distribution, adopting several scenarios for the jet emission. For the values of the main physical parameters favored by the observables, a dominant role of the jet emission in the X-ray band is ruled out when a single-zone (leptonic) scenario is adopted, even including the contribution of the external photon fields as seed photons for inverse Compton emission. We then consider a structured jet, with the blazar component that—although not directly visible in the X-ray band—provides an intense field of seed synchrotron photons Compton-scattered by electrons in a mildly relativistic knot. In this case, the whole X-ray emission can be accounted for if we assume a blazar luminosity within the range observed from flat spectrum radio quasars. The X-ray radiative efficiency of such a (structured) jet is intimately related to the presence of a complex velocity structure. The jet emission can provide a significant contribution in X-rays if it decelerates within the host galaxy on kiloparsec scales. We discuss the implications of this model in terms of jet dynamics and interaction with the ambient medium.

In this paper we investigate q 2 /4-sets of type (0, q /4, q /2) in projective planes of order q ≡0(mod 4). These sets arise in the investigation of regular triples with respect to a hyperoval. Combinatorial properties of these sets are given and examples in Desarguesian projective planes are constructed.

NGC 6251 is a luminous radio galaxy ~104 Mpc away that was detected significantly with the Fermi Gamma-ray Space Telescope, and before that with EGRET (onboard the Compton Gamma-ray Observatory). Different observational constraints favor a nuclear origin for the gamma-ray emission. Here we present a study of the spectral energy distribution (SED) of the core of NGC 6251, and give results of modeling in the one-zone synchrotron/SSC framework. The SSC model provides a good description of the radio to gamma-ray emission but, as for other misaligned sources, predicts a lower Lorentz factor (\Gamma~2.4) than typically found when modeling blazars. If the blazar unification scenario is correct, this seems to point to the presence of at least two emitting regions in these objects, one with a higher and one with a lower Lorentz factor. The solution of a structured jet, with a fast moving spine surrounded by a slow layer, is explored and the consequences of the two models for the jet energetics and evolution are discussed., Comment: 11 pages, 4 figures, accepted for publication in Astronomy & Astrophysics

El PDF auto-archivado en Digital.CSIC es el PRE-PRINT del autor.-- arXiv:1007.1624. -- 28 páginas, 8 figuras, 2 tablas. -- Autores: Abdo, Aous A. ... [et al.], Analysis is presented for 15 months of data taken with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope for 11 non-blazar active galactic nuclei (AGNs), including seven FRI radio galaxies and four FRII radio sources consisting of two FRII radio galaxies and two steep spectrum radio quasars. The broad line FRI radio galaxy 3C 120 is reported here as a γ-ray source for the first time. The analysis is based on directional associations of LAT sources with radio sources in the 3CR, 3CRR, and MS4 (collectively referred to as 3C-MS) catalogs. Seven of the eleven LAT sources associated with 3C-MS radio sources have spectral indices larger than 2.3 and, except for the FRI radio galaxy NGC 1275 that shows possible spectral curvature, are well described by a power law. No evidence for time variability is found for any sources other than NGC 1275. The γ-ray luminosities of FRI radio galaxies are significantly smaller than those of the BL Lac objects detected by the LAT, whereas the γ-ray luminosities of the FRII sources are quite similar to those of FSRQs, which could reflect different beaming factors for the γ-ray emission. A core dominance (CD) study of the 3CRR sample indicates that sources closer to the jet axis are preferentially detected with the Fermi LAT, insofar as the γ-ray-detected misaligned AGNs have larger CD at a given average radio flux. The results are discussed in view of the AGN unification scenario.

We present here the first Simbol‐X simulations of the extended components, lobes and hot spots, of the radio galaxies. We use the paradigmatic case of Pictor A to test the capabilities of Simbol‐X in this field of studies. Simulations demonstrate that Simbol‐X will be able not only to perform spatially resolved studies on the lobes of radio galaxies below 10 keV but also to observe, for the first time, hard X‐ray emission from the hot spots. These extremely promising results show the considerable potentiality of Simbol‐X in studying interaction phenomena between relativistic plasma and surrounding environment.

To assess ambulatory surgery practices in France, make an inventory of projects for the creation of ambulatory structures and analyze the perception of different hospital personnel of ambulatory surgery.A questionnaire was sent to 541 public hospitals with a surgery unit in France. The first part of the questionnaire was used to record current activity and existing projects for ambulatory surgery. The questionnaire also collected opinions concerning the analysis of difficulties encountered and possibilities offered by ambulatory surgery.Overall participation rate was 59%. Ambulatory surgery was practised in 81% of the hospitals. Sixty-six percent had a projects under consideration, including several at the decision making stage (17%). 1550 ambulatory surgery clinics could be created by the year 2000. In 66% of the cases, the future facility would be integrated into the traditional surgery unit. There was favorable opinion concerning the development of ambulatory surgery clinics in public hospitals in 83% of the cases. Inconveniences suggested generally involved organizational aspects, particularly concerning medical organization. Foreseen obstacles to the development of ambulatory surgery clinics were regulatory procedures, unfavorable exchange rate, insufficient investment funds and the lack of a policy favoring their development.The development of ambulatory surgery clinics in public hospitals in France can be expected in the near future. Budgeting and regulatory procedures must however be adapted to promote implementation of the existing projects.

Fournier's syndrome, characterised by anaerobic necrotising cellulitis of the soft tissues situated below the diaphragm, is a serous disease with an unpredictable course. From 1978 to 1991, we treated 24 men with a mean age of 57 years (27 to 90 years). Following the diagnosis of this disease, rigorous treatment was instituted immediately, consisting of a triple antibiotic combination, repeated surgical exposure, debridement and drainage with a frequent, almost systematic indication for faecal diversion (n = 16), hyperbaric oxygen therapy and classical intensive care measures. The mean interval between the first clinical signs and the diagnosis was 7.4 days. The lesions were limited to the perineum in 11 cases and extended to the abdomen, thighs and/or loins in 13 cases. The microorganisms responsible for the infection were identified in 19 cases and blood cultures were positive in 5 cases. This infection was of coloproctological origin in 12 cases, urogenital origin in 4 cases and postoperative in 2 cases, while no aetiology could be identified in 6 patients. There were 6 deaths and 18 cures without sequelae. 1. The prognosis of this disease is better in younger subjects (under the age of 60 years) with a localised clinical form, with no deterioration in the general status, sterile blood cultures and treated by a diversion colostomy. 2. A detailed aetiological work-up must be performed, looking for local or regional infection, cancer, haematological malignancy or arterial disease.

The risk of contracting infective diseases, which may be potentially lethal, from transfused blood has led to a necessary critical review of the transfusion practice. Autologous transfusion eliminates such risk and appears as an ideal procedure for a pre-hospital donation program particularly useful in elective surgery. To determine the extent to which predeposited autologous blood is used in patients undergoing elective surgery and to assess whether predonation decreases the use of homologous blood and the demand of blood supply, the Authors studied 261 patients submitted to elective surgery from October 1986 to October 1989. In the Authors' opinion a predeposit autotransfusion program is cost-effective, practical and nondisruptive. Therefore, it should be considered as a necessary and standard medical practice by clinicians and patients.

By combining gel filtration on Sephadex G-15 and G-10 and ion exchange chromatography on Cellex CM, 6 different peaks of physiological activity were separated from aqueous extracts of Periplaneta americana corpora cardiaca. The following physiological activities were assayed on the fractions; heart accelerating (HA), hyperglycaemic (HG), and increasing the frequency of the spontaneous firing recorded from nerves leaving the 6th abdominal ganglion (SFI). The 6 peaks had the following activities; (1) HA and SFI (2) HA, SFI and HG (3) HG and SFI (4) SFI (5) HA and (6) HA. Each was inactivated by treatment with trypsin. Analogies with physiologically active factors separated by other authors from similar tissue extracts are discussed, e.g. the possible identity of the active material present in peak 1 with neurohormone D of Unger and with factor P1 of Brown. None of the peaks of activity corresponds to the elution characteristics of a pure sample of 5-hydroxy-tryptamine.

Extracts of Periplaneta americana corpora cardiaca were subjected to separation procedures on columns. The eluates were assayed biologically on the cockroach for heart accelerating and hyperglycaemic action. In order to determine the exact location of the peaks, the recovery with respect to the crude extract, and the degree of purification obtained, quantitative assays were done on the basis of arbitrarily established activity units. Gel filtration through columns of Sephadex G-25 was found to separate the hyperglycaemic from the heart-accelerating activity in two distinct peaks, located in the zone expected for peptides. Reasonably good recoveries were obtained with respect to the activity of the crude extract. No activity was found in the zone where a pure sample of 5-hydroxytryptamine was found to emerge. The hyperglycaemic material recovered from this column could be separated in two different peaks by chromatography on a column of SE-Sephadex C-50. An extract of whole cockroach heads was fractionated by gel filtration first on a column of Bio-gel P-10, then on a column of Sephadex G-25. As a result of this procedure the hyperglycaemic activity was purified 61 times, and the heart accelerating activity 98 times with respect to the crude extract (purification was estimated from increase in activity units/mg of protein). Gel filtration through Sephadex G-25 was employed to fractionate an extract of whole heads of Apis mellifica . The higher molecular weight material showed both hyperglycaemic and heart-accelerating activity on cockroach preparations.

A statistical study bearing upon othe fall of blood pressure concomitant with the setting of peridural anaesthesia was carried out upon an homogeneous series of patients over 75 belonging to groups III and IV of the A S A classification for interventions seating below the IXth metamere. From this study, it seems to follow that: - for starting maximum arterial tensions over 180 mm/Hg, pressure falls are virtually constant in absolute value; - the most important variations in pressure falls are to be found in abdominal surgery; - the lowest figure in blood pressure which accompanies the achievement of surgical analgesia takes place about the 24 th minute whatever the type of surgery can be; - no significant link can be evidence between the importance of the fall in blood pressure and the consumption of the mixture required for surgical analgesia.

Lesions of the main hepatic veins constitute a special entity in the field of liver trauma. Their originality resides: in their immediate severity (difficulty of hemostasis) and secondary consequences (disturbance of the venous blood flow), in their frequent association with other traumatic lesions, The serious consequences of partial emergency hepatectomy which is the usual treatment. There are a number of factors which permit one to propose in a certain number of favourable cases, treatment of the wound or disinsertion of a hepatic vein by vascular ligature, or, preferably, reinsertion on the inferior vena cava after prior suture, associated with conservation of the hepatic parenchyma affected by the vascular lesion. This method seems to us particularly justified when there exist accessory hepatic veins undamaged during the trauma. The possibility of secondary complications cannot be excluded, but in the special case of severe multiple trauma, the immediate vital prognosis is more important than the risk of secondary complications and the difficulty of possible reoperation. Favoured by modern means of vascular exclusion of the liver, conservative treatment may have a place in lesions of the hepatic veins where emergency partial hepatectomy cannot be undertaken without a risk to life.

Continuous peridural analgesia took a long time to be accepted in current practice in surgery of the elderly, owing to the apprehensions for the possible cardiovascular consequences and also, the difficulty in using this form of anaesthesia in the elderly. The experience of more than 300 cases, collected in the Nice department of Anesthetics and Intensive Care, has shown that: 1--technical failures are exceptional with routine use of prior epidurography; 2--its indications depend on the site and type of surgery and on the clinical conditions of the patient; 3--until now, there have been no severe complications due to this method whatever the degree and number of morbid conditions; 4--in the elderly subject, the importance of problems of pre and post-operative analgesia have led us to enlarge the indications for long-term peridural analgesia. Peridural anesthesia may be used as a routine when the site of the operation involves areas situated below the IXth metamere. This shows its importance in surgery in the elderly.

The authors present a series of 30 cases of acute supra- and inframesocolic peritonitis which, in addition to the treatment of their organic causes, benefitted from medical treatment by noxythioline, used as a peritoneal lavage, an irrigation with aspiration, or an instillation. A marked amelioration in the postoperative course was noted, particularly in those cases with infra-mesocolic peritonitis, with the absence of adhesions and suppurative collections on reintervention, and a rapid return to negativity of the positive bacteriological investigations performed systematically on the pe ritoneal fluid and on the drainage.

The radiographic opacification of the peridural space was carried out prior to any injection of anaesthetic solution, both in the interest of security and to maximize the chances of success, on a homogeneous series of patients of more than 75 years of age, benefiting from continuous peridural analgesia. The following observations are made: - the direction of the catheter is ascending in 94 p. 100 of the cases, - the frequency of malpositions seems to increase with the lenght of the catheter introduced into the space, - the images obtained by injections of the radio-opaque agent are sufficiently specific to allow verification of the extra-dural situation of the apex of the catheter, - the permeability of the intervertebral foramina is found in 36 p. 100 of the cases, - the unilateral blocks appear to be exceptional, the technical difficulties inherent in the effects of aging on the vertebral system being compensated for by the constant success whenever the peridural space is reached.

Partial occlusion of inferior vena cava with clip of Adams De Weese is now currently performed in cavo-iliac thrombosis. The authors recall technical modalities for inserting clip and they try to bring to light the indications of each modality according to following parameters: upper level thrombosis, state of abdominal cavity, general condition of the patient and researched result: temporary or definitive artial oclusion, with or without associated thrombectomy. In localizations under renal veins, a definitive partial occlusion is indicated by sub-mesocolic way, eventually retro-peritoneal way in case of poor risk; it is a fact that associated thrombectomy will be realized easily, only by transmesenteric and submesocolic way. In localizations above renal veins, the authors think that transpericardiac way which allow temporary occlusion and thrombectomy of retro-hepatic part of vena cava is indicated.

In the two cases reported, pulmonary oedema developed immediately following revascularisation of the lower limbs after prolonged ischaemia. Without it being possible to formally exclude the possible role of a haemodynamic factor, the authors suggest the hypothesis of a predominantly lesional mechanism. The "reconnection to the circuit" is the provoking factor in this oedema, the alveolo-capillary membrane being previously altered by the prolonged ischaemia, infection and massive transfusion. The pulmonary manifestations would seem to enter within the classification of somatolysis.