OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. VI. FURTHER OBSERVATIONS FROM TNG, WHT, OAN, SOAR, AND MAGELLAN TELESCOPES

Indexación: Web of ScienceBlazars, one of the most extreme classes of active galaxies, constitute so far the largest known population of.-ray sources, and their number is continuously growing in the Fermi catalogs. However, in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidates of uncertain type (BCUs) for which optical spectroscopic observations are necessary to confirm their nature and their associations. In addition, about one-third of the gamma-ray point sources listed in the Third Fermi-LAT Source Catalog (3FGL) are still unassociated and lacking an assigned lower-energy counterpart. Since 2012 we have been carrying out an optical spectroscopic campaign to observe blazar candidates to confirm their nature. In this paper, the sixth of the series, we present optical spectroscopic observations for 30 gamma-ray blazar candidates from different observing programs we carried out with the Telescopio Nazionale Galileo, William Herschel Telescope, Observatorio Astronomico Nacional, Southern Astrophysical Research Telescope, and Magellan. Telescopes. We found that 21 out of 30 sources investigated are BL Lac objects, while the remaining targets are classified as flat-spectrum radio quasars showing the typical broad emission lines of normal quasi-stellar objects. We conclude that our selection of gamma-ray blazar. candidates based on their multifrequency properties continues to be a successful way to discover potential low-energy counterparts of the Fermi. unidentified gamma-ray sources and to confirm the nature of BCUs.http://iopscience.iop.org/article/10.3847/0004-6256/151/4/95/met

Measurement of the polarizations of prompt and non-prompt J/ψ and ψ (2S) mesons produced in pp collisions at s\sqrt{s} = 13 TeV

The polarizations of prompt and non-prompt J∕ψ and ψ(2S) mesons are measured in proton-proton collisions at √ = 13 TeV, using data samples collected by the CMS experiment in 2017 and 2018, corresponding to a total integrated luminosity of 103.3 fb$^{−1}$. Based on the analysis of the dimuon decay angular distributions in the helicity frame, the polar anisotropy, , is measured as a function of the transverse momentum, $_T$, of the charmonium states, in the 25–120 and 20–100 GeV ranges for the J∕ψ and ψ(2S), respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for T ≳ 25 GeV, the non-prompt J∕ψ and ψ(2S) are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transverse polarizations, even for $_T$ exceeding 30 times the J∕ψ mass, where tends to an asymptotic value around 0.3. Taken together with previous measurements, by CMS and LHCb at √ = 7 TeV, the prompt polarizations show a significant variation with $_T$, at low $_T$

Search for new physics in high-mass diphoton events from proton-proton collisions at √s = 13 TeV

Results are presented from a search for new physics in high-mass diphoton events from proton-proton collisions at sqrt(s) = 13 TeV. The data set was collected in 2016–2018 with the CMS detector at the LHC and corresponds to an integrated luminosity of 138 fb−1 . Events with a diphoton invariant mass greater than 500 GeV are considered. Two diferent techniques are used to predict the standard model backgrounds: parametric fts to the smoothly-falling background and a frst-principles calculation of the standard model diphoton spectrum at next-to-next-to-leading order in perturbative quantum chromodynamics calculations. The frst technique is sensitive to resonant excesses while the second technique can identify broad diferences in the invariant mass shape. The data are used to constrain the production of heavy Higgs bosons, Randall-Sundrum gravitons, the large extra dimensions model of Arkani-Hamed, Dimopoulos, and Dvali (ADD), and the continuum clockwork mechanism. No statistically signifcant excess is observed. The present results are the strongest limits to date on ADD extra dimensions and RS gravitons with a coupling parameter greater than 0.1

Optical Spectroscopic Observations of Gamma-ray Blazar Candidates. XI. Optical Observations from SOAR, Blanco, NTT and OAN-SPM. The Story so Far

Blazars represent about 62% of the sources in the ?-ray Fermi-LAT catalog, and about 80% of the ?-ray sources associated with a lower-energy counterpart, dominating the ?-ray sky. In particular, about 42% of the ?-ray blazars are classified as Blazars Candidates of Uncertain type (BCUs) for which spectroscopic observations are mandatory to confirm their blazar nature. Here we report the spectra of 64 targets observed as part of our follow-up optical spectroscopic campaign. This sample includes 62 sources classified in Fermi-LAT catalog as BCUs, one source classified as a generic active galactic nucleus, and one source classified as a BL Lac in Fermi-LAT and as blazar of uncertain type in the Roma-BZCAT catalog. We confirm the blazar nature of all BCUs. We classify 33 of them as BL Lacs, 11 as Flat Spectrum Radio Quasars, and 18 as blazars with nonnegligible host-galaxy emission. We also classify the generic active galactic nucleus as a BL Lac. Finally, we confirm the classification of the BL Lac. We also reported a lower limit redshift for 43 sources. For 20 sources, we got redshift measurements consistent with the literature values. For the other 21 sources, we obtained their first spectroscopic redshift measurement; while, for two sources, we provide lower limits on the redshift. With the upcoming release of the sixth edition of the Roma-BZCAT Multifrequency Catalog of Blazars, we take the opportunity in the present work to present the collective results of the first phase of our optical spectroscopic follow-up campaign

Optical spectroscopic observations of low-energy counterparts of Fermi -LAT γ -ray sources

Context. A significant fraction of all γ-ray sources detected by the Large Area Telescope aboard the Fermi satellite is still lacking a low-energy counterpart. In addition, there is still a large population of γ-ray sources with associated low-energy counterparts that lack firm classifications. In the last 10 years we have undertaken an optical spectroscopic campaign to address the problem of unassociated or unidentified γ-ray sources (UGSs), mainly devoted to observing blazars and blazar candidates because they are the largest population of γ-ray sources associated to date. Aims. Here we describe the overall impact of our optical spectroscopic campaign on sources associated in Fermi-LAT catalogs, coupled with objects found in the literature. In the literature search we kept track of efforts by different teams that presented optical spectra of counterparts or potential counterparts of Fermi-LAT catalog sources. Our summary includes an analysis of additional 30 newly collected optical spectra of counterparts or potential counterparts of Fermi-LAT sources of a previously unknown nature. Methods. New spectra were acquired at the Blanco 4 m and OAN-SPM 2.1 m telescopes, and those available in the Sloan Digital Sky Survey (data release 15) archive. Results. All new sources with optical spectra analyzed here are classified as blazars. Thanks to our campaign, altogether we discovered and classified 394 targets with an additional 123 objects collected from a literature search. We began our optical spectroscopic campaign between the release of the second and third Fermi-LAT source catalogs (2FGL and 3FGL, respectively), classified about 25% of the sources that had uncertain nature and discovered a blazar-like potential counterpart for ∼10% of UGSs listed therein. In the 4FGL catalog, about 350 Fermi-LAT sources have been classified to date thanks to our campaign. Conclusions. The most elusive class of blazars are found to be BL Lacs since the largest fraction of Fermi-LAT sources targeted in our observations showed a featureless optical spectrum. The same conclusion applied to the literature spectra. Finally, we confirm the high reliability of mid-IR color-based methods to select blazar-like candidate counterparts of unassociated or unidentified γ-ray sources

Electron Transfer and Electrocatalytic Properties of the Immobilized Met80Ala Cytochrome c Variant in DMSO

The electrode-immobilized Met80Ala variant of yeast iso-1 cytochrome c in mixed water/dimethylsulfoxide (DMSO) solutions up to 60 % v/v DMSO shows thermodynamic and kinetic parameters of electron exchange and electrocatalytic properties towards O2 reduction fully comparable to those in water. This is the result of moderate protein conformational changes thanks to immobilization that, to a certain extent, preserves protein structure, possibly due to the constraints on protein mobility/flexibility induced by the electrostatic interactions with the electrode-coating SAM. Upon increasing the DMSO content of the mixed solution beyond 60 %, a much larger perturbation occurs that leads to the progressive loss of the electrocatalytic ability. Therefore, under these conditions, the organic solvent remarkably affects the structure and properties of the protein probably involving major conformational changes or even the replacement of the 6th axial hydroxide ligand of the heme iron with a strong protein ligand, possibly a lysine residue