A deep Chandra observation of the interacting star-forming galaxy Arp 299

We present results from a 90 ks Chandra ACIS-S observation of the X-ray luminous interacting galaxy system Arp 299 (NGC 3690/IC 694). We detect 25 discrete X-ray sources with luminosities above 4.0x10^38 erg s^-1 covering the entire Ultra Luminous X-ray source (ULX) regime. Based on the hard X-ray spectra of the non-nuclear discrete sources identified in Arp 299, and their association with young, actively star-forming region of Arp 299 we identify them as HMXBs. We find in total 20 off-nuclear sources with luminosities above the ULX limit, 14 of which are point-like sources. Furthermore we observe a marginally significant deficit in the number of ULXs, with respect to the number expected from scaling relations of X-ray binaries with the star formation rate (SFR). Although the high metalicity of the galaxy could result in lower ULX numbers, the good agreement between the observed total X-ray luminosity of ULXs, and that expected from the relevant scaling relation indicates that this deficit could be the result of confusion effects. The integrated spectrum of the galaxy shows the presence of a hot gaseous component with kT = 0.72+-0.03 keV, contributing 20% of the soft (0.1-2.0 keV) unabsorbed luminosity of the galaxy. A plume of soft X-ray emission in the west of the galaxy indicates a large scale outflow. We find that the AGN in NGC 3690 contributes only 22% of the observed broad-band X-ray luminosity of Arp 299.Comment: 20 pages, 14 figures, 9 tables. Accepted for publication in MNRA

Effet de l ’inoculum bacterien de la souche IRAT – FA 3 de Bradyrhizobium japonicum sur la croissance et la nodulation de 3 varietes de soja cultivees en Cote d’Ivoire

Le soja a la capacité d’utiliser l’azote atmosphérique grâce à une association symbiotique avec les bactéries du genre Rhizobium. Cette étude a pour objectif de déterminer une dose d’inoculum bactérien qui permet d’améliorer significativement les paramètres de nodulation et de croissance de 3 variétés de soja cultivées en Côte d’Ivoire. L’inoculation des graines a été effectuée avec la souche IRAT-FA3 de Bradyrhizobium japonicum avant le semis selon un dispositif en blocs de Fisher à 5 répétitions. Les résultats obtenus ont montré que la plus grande taille des plants a été observée chez les plants inoculés (54,80 cm) de Tracaja avec 600 g d’inoculum/ha, (46,72 cm) de Doko avec 200 g et (45,68 cm) de Canarana avec 800 g. Les meilleurs rendements de masse sèche racinaire (0,92 t/ha), de biomasse sèche (14,11 t/ha) et le plus grand pourcentage de nodules actifs (68 %) ont été obtenus avec la dose 600 g d’inoculum/ha chez la variété Tracaja. Il ressort de cette étude que l’inoculation a eu un impact positif sur les paramètres de croissance et de nodulation du soja.Mots clés : Soja, Bradyrhizobium japonicum, Canarana, Doko, Tracaja, Côte d’Ivoir

Proving strong magnetic fields near to the central black hole in the quasar PG0043+039 via cyclotron lines

The optical luminous quasar PG0043+039 has not been detected before in deep X-ray observations indicating the most extreme optical-to-X-ray slope index ${\alpha}_{ox}$ of all quasars. This study aims to detect PG0043+039 in a deep X-ray exposure. Furthermore, we wanted to check out whether this object shows specific spectral properties in other frequency bands. We took deep X-ray (XMM-Newton), far-ultraviolet (HST), and optical (HET, SALT telescopes) spectra of PG0043+039 simultaneously in July 2013. We just detected PG0043+039 in our deep X-ray exposure. The steep ${\alpha}_{ox} = -2.37 {\pm} 0.05$ gradient is consistent with an unusual steep gradient $F_{\nu} {\sim} {\nu}^{\alpha}$ with ${\alpha} = -2.67 {\pm} 0.02$ seen in the UV/far-UV continuum. The optical/UV continuum flux has a clear maximum near 2500 {\AA}. The UV spectrum is very peculiar because it shows broad humps in addition to known emission lines. A modeling of these observed humps with cyclotron lines can explain their wavelength positions, their relative distances, and their relative intensities. We derive plasma temperatures of T ${\sim}$ 3keV and magnetic field strengths of B ${\sim}$ 2 ${\times} 10^8$ G for the line-emitting regions close to the black hole.Comment: 4 pages, 3 figures, Astronomy & Astrophysics in pres

SDSSJ143244.91+301435.3 at VLBI: a compact radio galaxy in a narrow-line Seyfert 1

We present VLBI observations, carried out with the European Very Long Baseline Interferometry Network (EVN), of SDSSJ143244.91+301435.3, a radio-loud narrow-line Seyfert 1 (RLNLS1) characterized by a steep radio spectrum. The source, compact at Very Large Array (VLA) resolution, is resolved on the milliarcsec scale, showing a central region plus two extended structures. The relatively high brightness temperature of all components (5x10^6-1.3x10^8 K) supports the hypothesis that the radio emission is non-thermal and likely produced by a relativistic jet and/or small radio lobes. The observed radio morphology, the lack of a significant core and the presence of a low frequency (230 MHz) spectral turnover are reminiscent of the Compact Steep Spectrum sources (CSS). However, the linear size of the source (~0.5kpc) measured from the EVN map is lower than the value predicted using the turnover/size relation valid for CSS sources (~6kpc). This discrepancy can be explained by an additional component not detected in our observations, accounting for about a quarter of the total source flux density, combined to projection effects. The low core-dominance of the source (CD<0.29) confirms that SDSSJ143244.91+301435.3 is not a blazar, i.e. the relativistic jet is not pointing towards the observer. This supports the idea that SDSSJ143244.91+301435.3 may belong to the "parent population" of flat-spectrum RLNLS1 and favours the hypothesis of a direct link between RLNLS1 and compact, possibly young, radio galaxies.Comment: 8 pages, 3 figures, accepted for publication in MNRA

A long hard look at the minimum state of PG 2112+059 with XMM-Newton

XMM-Newton successfully detected the minimum state of PG 2112+059 during a short snapshot observation and performed a long follow-up observation. The high signal-to-noise spectra are modelled assuming different emission scenarios and compared with archival spectra taken by XMM-Newton and Chandra. The PG 2112+059 X-ray spectra acquired in May 2007 allowed the detection of a weak iron fluorescent line, which is interpreted as being caused by reflection from neutral material at some distance from the primary X-ray emitting source. The X-ray spectra of PG 2112+059 taken at five different epochs during different flux states can be interpreted within two different scenarios. The first consists of two layers of ionised material with column densities of N_H ~5 x 10^22 cm^-2 and N_H ~3.5 x 10^23 cm^-2, respectively. The first layer is moderately ionised and its ionisation levels follow the flux changes, while the other layer is highly ionised and does not show any correlation with the flux of the source. The spectra can also be interpreted assuming reflection by an ionised accretion disk seen behind a warm absorber. The warm absorber ionisation is consistent with being correlated with the flux of the source, which provides an additional degree of self-consistency with the overall reflection-based model. We explain the spectral variability with light bending according to the models of Miniutti and Fabian and constrain the black hole spin to be a/M > 0.86. Both scenarios also assume that a distant cold reflector is responsible for the Fe K \alpha emission line. Light bending provides an attractive explanation of the different states of PG 2112+059 and may also describe the physical cause of the observed properties of other X-ray weak quasars.Comment: 15 pages, 12 figures, A&A latex, accepted for publication in Astronomy & Astrophysic

The structure of the X-ray absorber in Mrk 915 revealed by Swift

In this paper we present the results obtained with a monitoring programme (23 days long) performed with Swift-XRT on the local Seyfert galaxy Mrk 915. The light-curve analysis shows a significant count rate variation (about a factor of 2-3) on a time-scale of a few days, while the X-ray colours show a change in the spectral curvature below 2 keV and the presence of two main spectral states. From the spectral analysis we find that the observed variations can be explained by the change of the intrinsic nuclear power (about a factor of 1.5) coupled with a change of the properties of an ionized absorber. The quality of the data prevents us from firmly establishing if the spectral variation is due to a change in the ionization state and/or in the covering factor of the absorbing medium. The latter scenario would imply a clumpy structure of the ionized medium. By combining the information provided by the light curve and the spectral analyses, we can derive some constraints on the location of the absorber under the hypotheses of either homogeneous or clumpy medium. In both cases, we find that the absorber should be located inside the outer edge of an extended torus and, in particular, under the clumpy hypothesis, it should be located near, or just outside, to the broad emission line region.Comment: 8 pages, 6 figures, 1 table. Accepted for publication on MNRA

Arp 299: a second merging system with two active nuclei?

Recent BeppoSAX observations of Arp 299, a powerful far-IR merging starburst system composed of IC 694 and NGC 3690, clearly unveiled for the first time in this system the presence of a strongly absorbed active galactic nucleus (AGN). However the system was not spatially resolved by BeppoSAX. Here we present the analysis of archival Chandra and (for the first time) XMM-Newton observations, which allow us to disentangle the X-ray emission of the two galaxies. The detection of a strong 6.4 keV line in NGC 3690 clearly demonstrates the existence of an AGN in this galaxy, while the presence of a strong 6.7 keV Fe-Kalpha line in the spectrum of IC 694 suggests that also this nucleus might harbor an AGN. This would be the second discovery of two AGNs in a merging system after NGC 6240