Plant-mediated synthesis of metal oxide nanoparticles is a promising alternative to the traditional method of physical and chemical synthesis. In this paper, we report the green synthesis of zinc oxide nanoparticles (ZnONPs) by a biological method. During the study, Zinc oxide nanoparticles were synthesized by Allium sativum skin (garlic skin) extract. Formation of zinc oxide nanoparticles has ...

The intense, bursting X-ray source in the globular cluster NGC1851 was one of the first cluster sources discovered, but has remained optically unidentified for 25 years. We report here on results from Hubble Space Telescope WFPC2 multicolor images in NGC1851. Our high spatial resolution images resolve ∼200 objects in the 3 radius Einstein X-ray error circle, 40 times as many as in previous grou...

The next generation of gamma-ray telescopes may be able to observe gamma-ray blazars at high redshift, possibly out to the epoch of reionization. The spectrum of such sources should exhibit an absorption edge due to pair-production against UV photons along the line of sight. One expects a sharp drop in the number density of UV photons at the Lyman edge ǫL. This implies that the universe becomes...

We analyze a 137 ks exposure X-ray spectrum of the Seyfert 1 galaxy NGC 5548 obtained with the XMM-Newton Reflection Grating Spectrometer. Due to the long exposure time, the spectrum is of higher statistical quality than the previous observations of this AGN. Therefore, we detect for the first time in NGC 5548 inner-shell transitions from O III to O VI ions, and the Unresolved Transition Array ...

During an XMM-Newton observation, the eclipsing polar UZ For was found in a peculiar state with an extremely low X-ray luminosity and occasional X-ray and UV flaring. For most of the observation, UZ For was only barely detected in X-rays and ∼ 800 times fainter than during a high state previously observed with ROSAT. A transient event, which lasted ∼ 900 s, was detected simultaneously by the X-...

We determine star formation rates (SFRs) in a sample of color-selected, star-forming (sBzK) galaxies (KAB < 21.8) in the Extended Chandra Deep Field-South. To identify and avoid active galactic nuclei, we use X-ray, IRAC color, and IR/radio flux ratio selection methods. Photometric redshift-binned, average flux densities are measured with stacking analyses in Spitzer-MIPS IR, BLAST and APEX/LAB...

The intense, bursting X-ray source in the globular cluster NGC1851 was one of the first cluster sources discovered, but has remained optically unidentified for 25 years. We report here on results from Hubble Space Telescope WFPC2 multicolor images in NGC1851. Our high spatial resolution images resolve ∼200 objects in the 3 radius Einstein X-ray error circle, 40 times as many as in previous grou...

The first generation of stars (commonly known as population III) are expected to form in low-mass protogalaxies in which molecular hydrogen is the dominant coolant. Radiation from these stars will rapidly build up an extragalactic ultraviolet background capable of photodissociating H 2 , and it is widely believed that this background will suppress further star formation in low-mass systems. How...

Benzene molecules, present in the proto-planetary nebula CRL 618, are ionized and dissociated by UV and X-ray photons originated from the hot central star and by its fast wind. Ionic species and free radicals produced by these processes can lead to the formation of new organic molecules. The aim of this work is to study the photoionization and photodissociation processes of the benzene molecule...