ROSAT Results on Narrow-Line Seyfert 1 Galaxies

The excellent soft X-ray sensitivity of the PSPC detector onboard the ROSAT satellite provided the first chance to study precisely the spectral and timing properties of Narrow-Line Seyfert 1 galaxies. ROSAT observations of Narrow-Line Seyfert 1 galaxies have revealed (1) the existence of a giant soft X-ray excess, (2) a striking, clear correlation between the strength of the soft X-ray excess emission and the FWHM of the H-beta line, (3) the general absence of significant soft X-ray absorption by neutral hydrogen above the Galactic column, (4) short doubling time scales down to about 1000 seconds, (5) the existence of persistent giant (above a factor of 10), and rapid (less than 1 day) X-ray variability in extragalactic sources. The soft X-ray results on Narrow-Line Seyfert 1 galaxies indicate that their black hole regions are directly visible, further supporting the Seyfert 1 nature of these objects. The extreme X-ray properties of Narrow-Line Seyfert 1 galaxies make them ideal objects for understanding many of the problems raised generally by the Seyfert phenomenon.Comment: Invited talk presented at the Joint MPE,AIP,ESO workshop on NLS1s, Bad Honnef, Dec. 1999, to appear in New Astronomy Reviews; also available at http://wave.xray.mpe.mpg.de/conferences/nls1-worksho

Experimental tests of pseudo-complex General Relativity

Based on previous publications exploring pseudo-complex General Relativity (pc-GR) we present a selection of observable consequences of pc-GR and possible ways to experimentally access them. Whenever possible we compare the results to Einstein's GR and differences are worked out in detail. We propose experimental tests to check the predictions of pc-GR for the orbital frequency of test particles, the gravitational redshift effect and the last stable orbit. We will show that the orbital frequency of test particles at a given radius in pc-GR is in general lower compared to standard GR. Also the effect of frame dragging is modified (weakened) in pc-GR. Concerning the gravitational redshift of a radiation emitting object we find that it is also lower in pc-GR than in standard GR. Eventually the classical concept of a last stable orbit has to be modified in pc-GR.Comment: submitted for publication to the Monthly Notices of the Royal Astronomical Societ

XMM-Newton observations of the BL Lac MS 0737+7441

We report on the XMM-Newton observations of the BL Lac object MS 0737.9+7441 during the performance verification phase. A simple power-law fit provides an adequate description of the integrated spectrum in the 0.2-10 keV energy band. The photon index is slightly steeper in the EPIC pn data with 2.38+-0.01 compared to the EPIC MOS data (2.28+-0.01). The difference is most probably due to the present uncertainties in the calibration of the EPIC MOS and EPIC pn data sets. We report evidence for intrinsic absorption in the distant BL Lac above the Galactic column N_H,Gal=3.2*10^20 cm^-2 which is N_H,fit(z=0.315)= (2.70+-0.20)*10^20cm^-2 in the EPIC pn data and N_H,fit(z=0.315)= (3.25+-0.25)*10^20cm^-2 in the EPIC MOS data assuming neutral gas and solar abundances. The flux variations are found to be of the order of 10 %.Comment: 4 pages, 4 Figures, accepted for publication in the special A&A Letters issue for XMM-Newto

Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564. I. ASCA Observations and the Variability of the X-ray Spectral Components

We present a 35 day ASCA observation of the NLS1 Akn 564, which was part of a multiwavelength AGN Watch monitoring campaign. Akn 564 shows a photon index varying across the range 2.45--2.72. The presence of the soft hump component below 1 keV, previously detected in ASCA data, is confirmed. Time-resolved spectroscopy with ~daily sampling reveals a distinction in the variability of the soft hump and power-law components over a timescale of weeks, with the hump varying by a factor of 6 across the 35-day observation compared to a factor 4 in the power-law. Flux variations in the power-law component are measured down to a timescale of ~1000s and accompanying spectral variability suggests the soft hump is not well-correlated with the power-law on such short timescales. We detect Fe Ka and a blend of Fe Kb plus Ni Ka, indicating an origin in highly ionized gas. Variability measurements constrain the bulk of the Fe Ka to originate within a light week of the nucleus. The large EW of the emission lines may be due to high metallicity in NLS1s, supporting some evolutionary models for AGN.Comment: 41 pages, 15 figures. Accepted for publication in the Astrophysical Journal (v3 has final fixes for publication

The unusual spectral energy distribution of LBQS 0102-2713

We have studied the SED of the quasar LBQS 0102-2713. The available multiwavelength data are one optical spectrum between 3200 and 7400 A, 7 HST FOS spectra between 1700 and 2300 A, one GALEX NUV flux density and a K_S magnitude obtained from NED, and 3 public ROSAT PSPC pointed observations in the 0.1$-$2.4 keV energy band. The alpha_ox values obtained are -2.3 and -2.2, respectively, comparable to BAL quasars. The ROSAT photon index is 6.0+-1.3. The 2500 A luminosity density is about a factor of 10 higher compared to the mean of the most luminous SDSS quasars. We argue that the object might be indicative for a new class of quasars with an unusual combination in their UV-, X-ray, and N_H properties.Comment: 16 pages, 8 figures, accepted by Ap

Correlations among Multi-Wavelength Luminosities of Star-Forming Galaxies

It has been known for two decades that a tight correlation exists between far-infrared (FIR) and radio (1.4 and 4.8 GHz) global fluxes/luminosities from galaxies, which may be explained in terms of massive star formation activities in these galaxies. For this very reason, a correlation might also exist between X-ray and FIR/radio global luminosities of galaxies. We analyze data from {\it ROSAT} All-Sky Survey and {\it IRAS} to show that such correlation does indeed exist between FIR (42.5$-122.5\mu$m) and soft X-ray (0.1$-$2.4keV) luminosities in active star-forming galaxies (ASFGs).In order to establish a physical connection between the L_{\rmX}-L_{\rm FIR} correlation and global star formation rate (SFR) in galaxies, we empirically derive both $L_{\rm X}-L_{\rm B}$ and $L_{\rm FIR}-L_{\rm B}$ relations. Futhermore, we propose a relation between soft X-ray luminosity and SFR in star-forming galaxies. To further understand the $L_{\rm X}-L_{\rm FIR}$ relation, we construct an empirical model in which both FIR and X-ray emissions consist of two components with one being closely associated with star formation and the other not.Comment: 9 pages, 6 figures, accepted by MNRA

Detection of an X-ray periodicity in the Narrow-line Seyfert 1 Galaxy Mrk 766 with XMM-Newton

We have analyzed the timing properties of the Narrow-line Seyfert 1 galaxy Mrk 766 observed with XMM-Newton during the PV phase. The source intensity changes by a factor of 1.3 over the 29,000 second observation. If the soft excess is modeled by a black body component, as indicated by the EPIC pn data, the luminosity of the black body component scales with its temperature according to L ~ T^4. This requires a lower limit 'black body size` of about 1.3*10^25 cm^2. In addition, we report the detection of a strong periodic signal with 2.4*10^-4 Hz. Simulations of light curves with the observed time sequence and phase randomized for a red noise spectrum clearly indicate that the periodicity peak is intrinsic to the distant AGN. Furthermore, its existence is confirmed by the EPIC MOS and RGS data. The spectral fitting results show that the black body temperature and the absorption by neutral hydrogen remain constant during the periodic oscillations. This observational fact tends to rule out models in which the intensity changes are due to hot spots orbiting the central black hole. Precession according to the Bardeen-Petterson effect or instabilities in the inner accretion disk may provide explanations for the periodic signal.Comment: 6 pages, 8 Figures, accepted for publication in the special A&A Letters issue for XMM-Newton; corrections in Section 2.2 require

Soft X-ray spectral variations of the narrow line Seyfert l galaxy Markarian 766

The X-ray variability of the narrow-line Seyfert 1 galaxy Markarian 766 is studied using nine ROSAT PSPC data sets. The spectrum is well described by a power law combined with a blackbody (kT ∼ 70 eV) soft excess. Examination of flux ratio changes and variability amplitude in three X-ray bands shows that the power-law component varies continuously on time-scales of ∼ 5000 s and is steeper when it is brighter. In contrast, variability of the soft excess is not detected. Spectral modelling of 31 spectra from different observations and at a range of count rates is also consistent with a picture in which the power law is steeper when it is brighter, and in which the soft-excess component does not vary. The power-law variability can be explained if the power law is produced by variable thermal or non-thermal Comptonization of soft photons. This behaviour is similar to that of Galactic black hole candidates in the low state. The X-ray and multiwavelength properties of Markarian 766 are shown to be very similar to those of other narrow-line Seyfert 1s. This may mean that the rapid X-ray variability seen in other narrow-line Seyfert 1s may also not originate in their strong soft-excess components

Resonant Absorption in the AGN spectra emerging from photoionized gas: differences between steep and flat ionizing continua

We present photoionization models accounting for both photoelectric and resonant absorption. Resonance absorption lines from C, O, Ne, Mg, Si S and Fe between 0.1 and 10 keV are treated. In particular we consider the complex of almost 60 strong Fe L absorption lines around 1 keV. We calculate profiles, intensities and equivalent widths of each line, considering both Doppler and natural broadening mechanisms. Doppler broadening includes a term accounting for turbulence of the gas along the line of sight. We computed spectra transmitted by gas illuminated by drastically different ionizing continua and compared them to spectra observed in flat X-ray spectrum, broad optical emission line type 1 AGN, and steep X-ray spectrum, narrow optical emission line type 1 AGN. We show that the $\sim 1$ keV absorption feature observed in moderate resolution X-ray spectra of several Narrow Line Seyfert 1 galaxies can be explained by photoionization models, taking into account for resonance absorption, without requiring relativistic outflowing velocities of the gas, if the physical properties of these absorbers are close to those found in flat X-ray spectrum Seyfert 1 galaxies.Comment: 22 pages, 10 figures. Accepted for publication on Ap

Manejos para redução de perdas em pré-colheita de canola sob elevada pluviosidade

Canola stands out as an important economic alternative as it is a source for the production of oil for human consumption, and in its use for the production of biodiesel. However mechanized harvesting is an obstacle to the expansion of the cultivation of this brassicaceae that need to be solved. The objective of this work was to evaluate five canola mechanized harvesting management systems, with or without the application of a sealant, compared to losses of preharvest and harvest, grain yield and water content in the grains. The canola hybrid Hyola 61 was used, being seeded with row spacing of 0.45 meters, and density of 40 viable seeds m-2. The treatments resulted from the combination of different management processes combined with a sealant. The adopted managements were: M1- harvesting with cut straight to the natural maturation point (untreated); M2 - previous chemical desiccation with diquat; M3 - previous chemical desiccation with ammonium glufosinate; M4 - cut-windrowing, and M5 - ethefom application. The harvest managements with cut-windrowing, previous chemical desiccation, and applying etefom, singly or in combination to sealant, reduced the grain losses in the harvest allowing higher yields to be obtained, and also reducing the water content in the grains, under conditions of excessive rainfall.A canola destaca-se como importante alternativa econômica, pois constitui matéria prima na produção de óleo para o consumo humano, como para produção de biodiesel. No entanto a operação de colheita é um entrave à ampliação do cultivo desta brassicácea que necessita ser solucionado. O objetivo do trabalho foi avaliar cinco sistemas de manejo de colheita mecanizada de canola, com ou sem a aplicação de um adesionante, em relação às perdas de pré-colheita e colheita, rendimento de grãos e teor de água nos grãos colhidos. O híbrido de canola utilizado foi o Hyola 61, sendo semeado com espaçamento entrelinhas de 0,45 m, e com densidade de 40 sementes viáveis m-2. Os tratamentos resultaram das combinações entre diferentes manejos da colheita e uso de um adesionante. Os manejos adotados foram: M1 - colheita com corte direto no ponto de maturação natural (testemunha); M2 - dessecação química prévia com diquat; M3 - dessecação química prévia com glufosinato de amônio; M4 - corte-enleiramento, e M5 - aplicação de etefom. Os manejos da colheita com corte-enleiramento, dessecação química prévia, e aplicação de etefom, isoladamente ou combinados ao adesionante, reduzem as perdas na colheita e permitem obter maiores rendimentos de grãos de canola, além de reduzirem o teor de água nos grãos colhidos, sob condições de pluviosidade excessiva