Multicolor photometry of the GRB970508 optical remnant

We report results of follow-up multicolor photometry of the optical variable source that is a probable remnant of the gamma-ray burst GRB970508 discovered by the BeppoSAX satellite (IAUC 6649). Observations were carried out in Johnson-Kron-Cousins $ BVR_cI_c system with the 1-m and 6-m telescopes of SAO RAS. Between the 2nd and the 5th day after the burst a fading of the remnant is well fitted with an exponential law in all four bands. During this period the `broadband spectrum' of the object was unchanged and can be approximated by a power-law, F_{\nu}\propto\nu^{-1.1}. After the 5th day the decline of brightness is slowed down. In the R_c band until the 32nd day, the light curve can be described by a power-law relation, F_t \propto t^{-1.2}.Comment: 14 pages, Postscript figures, Latex, psfig.sty included, poster to Fourth Huntsville Symposium on Gamma-Ray Burst

Looking for blazars in a sample of unidentified high-energy emitting Fermi sources

Context. Based on their overwhelming dominance among associated Fermi γ-ray catalogue sources, it is expected that a large fraction of the unidentified Fermi objects are blazars. Through crossmatching between the positions of unidentified γ-ray sources from the First Fermi Catalog of γ-ray sources emitting above 10 GeV (1FHL) and the ROSAT and Swift/XRT catalogues of X-ray objects and between pointed XRT observations, a sample of 36 potential associations was found in previous works with less than 15 arcsec of positional offset. One-third of them have recently been classified; the remainder, though believed to belong to the blazar class, still lack spectroscopic classifications. Aims. We study the optical spectrum of the putative counterparts of these unidentified gamma-ray sources in order to find their redshifts and to determine their nature and main spectral characteristics. Methods. An observational campaign was carried out on the putative counterparts of 13 1FHL sources using medium-resolution optical spectroscopy from the Osservatorio Astronomico di Bologna in Loiano, Italy; the Telescopio Nazionale Galileo and the Nordic Optical Telescope, both in the Canary Islands, Spain; and the Observatorio Astronómico Nacional San Pedro Mártir in Baja California, Mexico. Results. We were able to classify 14 new objects based on their continuum shapes and spectral features. Conclusions. Twelve new blazars were found, along with one new quasar and one new narrow line Seyfert 1 (NLS1) to be potentially associated with the 1FHL sources of our sample. Redshifts or lower limits were obtained when possible alongside central black hole mass and luminosity estimates for the NLS1 and the quasar.Fil: Marchesini, Ezequiel Joaquín. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Masetti, Nicola. Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna; ItaliaFil: Chavushyan, V.. Instituto Nacional de Astrofísica, Óptica y Electrónica; MéxicoFil: Cellone, Sergio Aldo. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Andruchow, Ileana. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Bassani, L.. Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna; ItaliaFil: Bazzano, A.. Istituto di Astrofisica e Planetologia Spaziali; ItaliaFil: Jiménez-Bailón, E.. Universidad Nacional Autónoma de México; MéxicoFil: Landi, R.. Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna; ItaliaFil: Malizia, A.. Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna; ItaliaFil: Palazzi, E.. Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna; ItaliaFil: Patiño Álvarez, V.. Instituto Nacional de Astrofísica, Óptica y Electrónica; MéxicoFil: Rodríguez Castillo, G. A.. Osservatorio Astronomico di Roma; ItaliaFil: Stephen, J. B.. Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna; ItaliaFil: Ubertini, P.. Istituto di Astrofisica e Planetologia Spaziali; Itali

Accurate classification of 75 counterparts of objects detected in the 54 month Palermo Swift/BAT hard X-ray catalogue

Through an optical campaign performed at 4 telescopes located in the northern and the southern hemispheres, we have obtained optical spectroscopy for 75 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/BAT and listed in the 54 month Palermo BAT catalogue. All these objects have also observations taken with Swift/XRT, ROSAT or Chandra satellites which allowed us to reduce the high energy error box and pinpoint the most likely optical counterpart/s. We find that 69 sources in our sample are Active Galactic Nuclei (AGNs); of them, 35 are classified as type 1 (with broad and narrow emission lines), 33 are classified as type 2 (with only narrow emission lines) and one is an high redshift QSO; the remaining 6 objects are galactic cataclysmic variables (CVs). Among type 1 AGNs, 32 are objects of intermediate Seyfert type (1.2-1.9) and one is Narrow Line Seyfert 1 galaxy; for 29 out of 35 type 1 AGNs, we have been able to estimate the central black hole mass and the Eddington ratio. Among type 2 AGNs, two display optical features typical of the LINER class, 3 are classified as transition objects, 1 is a starburst galaxy and 2 are instead X-ray bright, optically normal galaxies. All galaxies classified in this work are relatively nearby objects (0.006 - 0.213) except for one at redshift 1.137.Comment: 19 pages, 5 figures, 6 tables, accepted for publications on Astronomy and Astrophysics, main journal. arXiv admin note: text overlap with arXiv:1206.509

Performance analysis of a ultra-compact low-power rectenna in paper substrate for RF energy harvesting

In this paper the experimental results of a compact low-power rectenna in paper substrate, designed to operate in the Wi-Fi band, are presented. The complete prototype, based on an annular slot antenna and a single-diode rectifier, features a weight of 1.5 grams and shows an RF-to-dc conversion efficiency in the design band of about 40 % for a -10 dBm available input power, of about 28 % at -15 dBm, and in the range [10, 22] % at -20 dBm, corresponding to an output DC voltage in the order of 320, 240 and 60 mV respectively. Additionally, the rectenna features an efficiency higher then 7 % in the whole band 1.8-2.7 dBm for a power density estimated around 3 μW/cm2.Grant numbers : The work was supported by the EU COST Action IC1301 WiPE (Wireless Power Transmission for sustainable Electronics). © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

VLT observations of GRB 990510 and its environment

We present BVRI photometry and spectrophotometry of GRB990510 obtained with the ESO VLT/Antu telescope during the late decline phase. Between days 8 and 29 after the burst, the afterglow faded from R=24.2 to ~26.4. The spectral flux distribution and the light curve support the interpretation of the afterglow as synchrotron emission from a jet. The light curve is consistent with the optical transient alone but an underlying SN with maximum brightness R>27.4 or a galaxy with R>27.6 (3-sigma upper limits) cannot be ruled out. To a 5-sigma detection threshold of R=26.1, no galaxy is found within 6'' of the transient. A very blue V~24.5 extended object which may qualify as a starburst galaxy is located 12'' SE, but at unknown redshift.Comment: 5 pages A&A Latex, accepted for publication in A&A Letter

Is Venice an ideal habitat for Legionella pneumophila?

Introduction. Legionella bacterium manifests itself in Legion- naire?s disease and Pontiac fever, it is mainly found and trans- mitted by aerosol produced in cooling towers, water distribution plants and medical equipment, and it affects mainly elder persons in poor health. Methods. The population of Venice Local Health Unit was divided in two areas of study and the incidence of legionellosis in residents of Venice historical centre (Distretto Sanitario 1) and in residents of the mainland and coastal areas (Distretti Sanitari 2, 3, 4) was calculated. The cases were those notified to the Public Health Unit by law, and the population of residents was that of the eligible for health care in the archives of the Local Health Unit. Only cases of legionellosis in residents who had not travelled in the 10 days previous of the onset of disease, and not related to nosocomial clusters were considered. The standardized incidence ratio was then calculated and confidence interval were defined by Poisson distribution. Results. Given the population of the two areas, 59801 in Distretto Sanitario 1 and 237555 in Distretti 2, 3, 4, the raw incidence of disease is respectively 87 per 100000 and 20 per 100000 in time 2002-2010. The standardized incidence ratio for the population of Distretto Sanitario 1 vs the remaining population is 4.3. Discussion. The difference in risk of getting the disease in this two residential areas geographically very close, is probably related to the different buildings? characteristics, old and difficult to main- tain in Venice historical centre