Discovery of a deep Seyfert-2 galaxy at z = 0.222 behind NGC 300

We report on the unveiling of the nature of the unidentified X-ray source 3XMM J005450.3-373849 as a Seyfert-2 galaxy located behind the spiral galaxy NGC 300 using Hubble Space Telescope data, new spectroscopic Gemini observations and available XMM-Newton and Chandra data. We show that the X-ray source is positionally coincident with an extended optical source, composed by a marginally resolved nucleus/bulge, surrounded by an elliptical disc-like feature and two symmetrical outer rings. The optical spectrum is typical of a Seyfert-2 galaxy redshifted to z=0.222 +/- 0.001, which confirms that the source is not physically related to NGC 300. At this redshift the source would be located at 909+/-4 Mpc (comoving distance in the standard model). The X-ray spectra of the source are well-fitted by an absorbed power-law model. By tying $N_\mathrm{H}$ between the six available spectra, we found a variable index $\Gamma$ running from ~2 in 2000-2001 years, to 1.4-1.6 in the 2005-2014 period. Alternatively, by tying $\Gamma$, we found variable absorption columns of N_H ~ 0.34 x $10^{-22}$ cm$^{-2}$ in 2000-2001 years, and 0.54-0.75 x $10^{-22}$ cm$^{-2}$ in the 2005-2014 period. Although we cannot distinguish between an spectral or absorption origin, from the derived unabsorbed X-ray fluxes, we are able to assure the presence of long-term X-ray variability. Furthermore, the unabsorbed X-ray luminosities of 0.8-2 x 10$^{43}$ erg s$^{-1}$ derived in the X-ray band are in agreement with a weakly obscured Seyfert-2 AGN at $z \approx 0.22$.Comment: MNRAS, accepte

Phosphoproteomics data classify hematological cancer cell lines according to tumor type and sensitivity to kinase inhibitors

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Disorder-induced double resonant Raman process in graphene

An analytical study is presented of the double resonant Raman scattering process in graphene, responsible for the D and D$^{\prime}$ features in the Raman spectra. This work yields analytical expressions for the D and D$^{\prime}$ integrated Raman intensities that explicitly show the dependencies on laser energy, defect concentration, and electronic lifetime. Good agreement is obtained between the analytical results and experimental measurements on samples with increasing defect concentrations and at various laser excitation energies. The use of Raman spectroscopy to identify the nature of defects is discussed. Comparison between the models for the edge-induced and the disorder-induced D band intensity suggests that edges or grain boundaries can be distinguished from disorder by the different dependence of their Raman intensity on laser excitation energy. Similarly, the type of disorder can potentially be identified not only by the intensity ratio $I_{\mathrm{D}}/I_{\mathrm{D}^{\prime}}$, but also by its laser energy dependence. Also discussed is a quantitative analysis of quantum interference effects of the graphene wavefunctions, which determine the most important phonon wavevectors and scattering processes responsible for the D and D$^{\prime}$ bands.Comment: 10 pages, 4 figure

Direct and Heterodyne Detection of Microwaves in a Metallic Single Wall Carbon Nanotube

This letter reports measurements of microwave (up to 4.5 GHz) detection in metallic single-walled carbon nanotubes. The measured voltage responsivity was found to be 114 V/W at 77K. We also demonstrated heterodyne detection at 1 GHz. The detection mechanism can be explained based on standard microwave detector theory and the nonlinearity of the DC IV-curve. We discuss the possible causes of this nonlinearity. While the frequency response is limited by circuit parasitics in this measurement, we discuss evidence that indicates that the effect is much faster and that applications of carbon nanotubes as terahertz detectors are feasible

Optical and near-infrared observations of the microquasar V4641 Sagittarii during the 1999 September outburst

We present photometric and spectroscopic optical and near-infrared (NIR) observations (Based on observations collected at the European Southern Observatory, Chile (ESO ID 63.H-0493 and 64.H-0382)) taken during the outburst of the microquasar V4641 Sgr = SAX J1819.3-2525 (in'tzand et al., 2000) in September 1999. We observed an increase in the J-Ks colour between 5 and 8 days after the outburst, which we interpret as likely evidence for the presence of dust around the source. We also observed an extraordinarily strong, broad and variable H_alpha line, with a velocity width of 4560 km/s suggesting the presence of a high-velocity outflow component. We constrain the distance of the system between 3 and 8 kpc, locating it further away than previously derived from radio observations (Hjellming et al., 2000), but consistent with Orosz et al. (2001). We then discuss the nature of this system, showing that the companion star is either a B3-A2 main sequence star, or a B3-A2 sub-giant crossing the Hertzsprung gap. The system is therefore an Intermediate or High Mass X-ray Binary System (IMXB or HMXB). The distance derived by these optical/NIR observations implies that the jets observed by Hjellming et al. (2000) would then exhibit apparent velocities of ~ 10 c. We finally discuss the possibility of an interaction between the jets and surroundings of the source, and also of this source being a ``microblazar''.Comment: 7 pages, 6 figures, accepted for publication in MNRA