Identification of the ~3.55 keV emission line candidate objects across the sky

An emission line at the energy ∼3.55 keV detected in different galaxies and galaxy clusters has caused numerous discussions in high-energy astrophysics and particle physics communities. To reveal the origin of the line, we analyzed publicly-available observations of MOS cameras from XMM-Newton cosmic observatory - the instrument with the largest sensitivity for narrow faint X-ray lines - previously combined in X-ray sky maps. Because an extremely large timescale is needed for detailed analysis, we used the wavelet method instead. Extensive simulations of the central part of the Andromeda galaxy are used to check the validity of this method. The resulting list of wavelet detections now contains 235 sky regions. This list will be used in future works for more detailed spectral analysis

Creation of 2-5 keV and 5-10 keV sky maps using XMM-Newton data

Sky maps are powerful visualisation tools for quicklook analysis of extended sources. The latest sky map in soft X-rays (0.1-2.4 keV) has been created in the 1990's using ROSAT data. By analysing publically available data from XMM-Newton X-ray mission we constructed new sky maps in two energy bands - 2-5 keV and 5-10 keV,complementary to ROSAT data, covering approximately 1% of the sky, and included them in our web-based tool http://skyview.virgoua.org

Chemical freeze-out of light nuclei in high energy nuclear collisions and resolution of the hyper-Triton chemical freeze-out puzzle

Indexación ScopusWe present a summary of the recent results obtained with the novel hadron resonance gas model with the multicomponent hard-core repulsion which is extended to describe the mixtures of hadrons and light (anti-, hyper-)nuclei. A very accurate description is obtained for the hadronic and the light nuclei data measured by STAR at the collision energy The most striking result discussed here is that for the most probable chemical freeze-out scenario for the STAR energy the found parameters allow us to reproduce the values of the experimental ratios S 3 and without fitting. © Published under licence by IOP Publishing Ltd.https://iopscience-iop-org.recursosbiblioteca.unab.cl/article/10.1088/1742-6596/1690/1/01212

Multiwavelength variability of BL Lacertae measured with high time resolution

In an effort to locate the sites of emission at different frequencies and physical processes causing variability in blazar jets, we have obtained high time-resolution observations of BL Lacertae over a wide wavelength range: with the Transiting Exoplanet Survey Satellite (TESS) at 6000–10000 Å with 2 minute cadence; with the Neil Gehrels Swift satellite at optical, UV, and X-ray bands; with the Nuclear Spectroscopic Telescope Array at hard X-ray bands; with the Fermi Large Area Telescope at γ-ray energies; and with the Whole Earth Blazar Telescope for measurement of the optical flux density and polarization. All light curves are correlated, with similar structure on timescales from hours to days. The shortest timescale of variability at optical frequencies observed with TESS is ~0.5 hr. The most common timescale is 13 ± 1 hr, comparable with the minimum timescale of X-ray variability, 14.5 hr. The multiwavelength variability properties cannot be explained by a change solely in the Doppler factor of the emitting plasma. The polarization behavior implies that there are both ordered and turbulent components to the magnetic field in the jet. Correlation analysis indicates that the X-ray variations lag behind the γ-ray and optical light curves by up to ~0.4 day. The timescales of variability, cross-frequency lags, and polarization properties can be explained by turbulent plasma that is energized by a shock in the jet and subsequently loses energy to synchrotron and inverse Compton radiation in a magnetic field of strength ~3 G.Accepted manuscrip

Creation of 2-5 keV and 5-10 keV sky maps using XMM-Newton data

Sky maps are powerful visualisation tools for quicklook analysis of extended sources. The latest sky map in soft X-rays (0.1-2.4 keV) has been created in the 1990's using ROSAT data. By analysing publically available data from XMM-Newton X-ray mission we constructed new sky maps in two energy bands - 2-5 keV and 5-10 keV,complementary to ROSAT data, covering approximately 1% of the sky, and included them in our web-based tool http://skyview.virgoua.org

On separate chemical freeze-outs of hadrons and light (anti)nuclei in high energy nuclear collisions

International audienceThe multiplicities of light (anti)nuclei were measured recently by the ALICE collaboration in Pb+Pb collisions at the center-of-mass collision energy . Surprisingly, the hadron resonance gas model is able to perfectly describe their multiplicities under various assumptions. For instance, one can consider the (anti)nuclei with a vanishing hard-core radius (as the point-like particles) or with the hard-core radius of proton, but the fit quality is the same for these assumptions. In this paper we assume the hard-core radius of nuclei consisting of A baryons or antibaryons to follow the simple law , where Rb is the hard-core radius of nucleon. To implement such a relation into the hadron resonance gas model we employ the induced surface tension concept and analyze the hadronic and (anti)nuclei multiplicities measured by the ALICE collaboration. The hadron resonance gas model with the induced surface tension allows us to verify different scenarios of chemical freeze-out of (anti)nuclei. It is shown that the most successful description of hadrons can be achieved at the chemical freeze-out temperature Th = 150 MeV, while the one for all (anti)nuclei is TA = 168.5 MeV. Possible explanations of this high temperature of (anti)nuclei chemical freeze-out are discussed

AGILE, Fermi, Swift, and GASP/WEBT multi-wavelength observations of the high-redshift blazar 4C +71.07 in outburst

Context. The flat-spectrum radio quasar 4C +71.07 is a high-redshift (z = 2.172), γ-loud blazar whose optical emission is dominated by thermal radiation from the accretion disc. Aims. 4C +71.07 has been detected in outburst twice by the AGILE γ-ray satellite during the period from the end of October to mid-November 2015, when it reached a γ-ray flux of the order of F(E > 100 MeV)=(1.2 ± 0.3)×10 photons cm s and F(E > 100 MeV)=(3.1 ± 0.6)×10 photons cm s, respectively, allowing us to investigate the properties of the jet and the emission region. Methods. We investigated its spectral energy distribution by means of almost-simultaneous observations covering the cm, mm, near-infrared, optical, ultraviolet, X-ray, and γ-ray energy bands obtained by the GASP-WEBT Consortium and the Swift, AGILE, and Fermi satellites. Results. The spectral energy distribution of the second γ-ray flare (whose energy coverage is more dense) can be modelled by means of a one-zone leptonic model, yielding a total jet power of about 4 × 10 erg s. Conclusions. During the most prominent γ-ray flaring period our model is consistent with a dissipation region within the broad-line region. Moreover, this class of high-redshift, flat-spectrum radio quasars with high-mass black holes might be good targets for future γ-ray satellites such as e-ASTROGAM. © ESO 2019.AGILE is an ASI space mission developed with programmatic support by INAF and INFN. We acknowledge partial support through the ASI grant no. I/028/12/0. SV and PR acknowledge contract ASI-INAF I/004/11/0 and INAF/IASF Palermo where most of the work was carried out. SV acknowledges financial contribution from the agreement ASI-INAF no. 2017-14-H.0. Part of this work is based on archival data, software, or online services provided by the ASI SPACE SCIENCE DATA CENTER (ASI-SSDC). SV and PR thank Leonardo Barzaghi and Sara Baitieri for useful discussions. The Osservatorio di Torino team acknowledges the financial contribution from the agreement ASI-INAF No. 2017-14-H.0 and from the contract PRIN-SKA-CTA-INAF 2016. OMK acknowledges financial support from the Shota Rustaveli National Science Foundation under contract FR/217950/16 and grants NSFC11733001, NSFCU1531245. IA acknowledges support from a Ramón y Cajal grant of the Ministerio de Economía y Compet-itividad (MINECO) of Spain. The research at the IAA–CSIC was supported in part by the MINECO through grants AYA2016–80889–P, AYA2013–40825–P, and AYA2010–14844, and by the regional government of Andalucía through grant P09–FQM–4784. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Calar Alto Observatory is jointly operated by the MPIA and the IAA-CSIC. This research was partially supported by the Bulgarian National Science Fund of the Ministry of Education and Science under grant DN 08-1/2016. The St. Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. AZT-24 observations are made within an agreement among the Pulkovo, Rome, and Teramo observatories. GD and OV gratefully acknowledge the observing grant support from the Institute of Astronomy and Rozhen National Astronomical Observatory, Bulgaria Academy of Sciences, via bilateral joint research project “Observations of ICRF radio-sources visible in optical domain” (PI G. Damljanovic). This work is a part of Project No. 176011 (“Dynamics and kinematics of celestial bodies and systems”), No. 176004 (“Stellar physics”) and No. 176021 (“Visible and invisible matter in nearby galaxies: theory and observations”) supported by the Ministry of Education, Science, and Technological Development of the Republic of Serbia. The Maidanak Observatory team acknowledges support from Uzbekistan Academy of Sciences grants No. F2-FA-F027 and F.4-16.Peer Reviewe

Multiwavelength Variability of BL Lacertae Measured with High Time Resolution

© 2020. The American Astronomical Society. All rights reserved.. In an effort to locate the sites of emission at different frequencies and physical processes causing variability in blazar jets, we have obtained high time-resolution observations of BL Lacertae over a wide wavelength range: with the Transiting Exoplanet Survey Satellite (TESS) at 6000-10000 Å with 2 minute cadence; with the Neil Gehrels Swift satellite at optical, UV, and X-ray bands; with the Nuclear Spectroscopic Telescope Array at hard X-ray bands; with the Fermi Large Area Telescope at γ-ray energies; and with the Whole Earth Blazar Telescope for measurement of the optical flux density and polarization. All light curves are correlated, with similar structure on timescales from hours to days. The shortest timescale of variability at optical frequencies observed with TESS is ∼0.5 hr. The most common timescale is 13 ± 1 hr, comparable with the minimum timescale of X-ray variability, 14.5 hr. The multiwavelength variability properties cannot be explained by a change solely in the Doppler factor of the emitting plasma. The polarization behavior implies that there are both ordered and turbulent components to the magnetic field in the jet. Correlation analysis indicates that the X-ray variations lag behind the γ-ray and optical light curves by up to ∼0.4 day. The timescales of variability, cross-frequency lags, and polarization properties can be explained by turbulent plasma that is energized by a shock in the jet and subsequently loses energy to synchrotron and inverse Compton radiation in a magnetic field of strength ∼3 G

Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

In 2015 July 29-September 1, the satellite XMM-Newton pointed at the BL Lac object PG 1553+133 six times, collecting data for 218 h. During one of these epochs, simultaneous observations by the Swift satellite were requested to compare the results of the X-ray and optical-UV instruments. Optical, near-infrared and radio monitoring was carried out by the Whole Earth Blazar Telescope (WEBT) collaboration for the whole observing season. We here present the results of the analysis of all these data, together with an investigation of the source photometric and polarimetric behaviour over the last 3 yr. The 2015 EPIC spectra show slight curvature and the corresponding light curves display fast X-ray variability with a time-scale of the order of 1 h. In contrast to previous results, during the brightest X-ray states detected in 2015 the simple log-parabolic model that best fits the XMM-Newton data also reproduces reasonably well the whole synchrotron bump, suggesting a peak in the near- UV band. We found evidence ofa wide rotation of the polarization angle in 2014, when the polarization degree was variable, but the flux remained almost constant. This is difficult to interpret with deterministic jet emission models, while it can be easily reproduced by assuming some turbulence of the magnetic field.Peer reviewe

Multi-messenger Observations of a Binary Neutron Star Merger

International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta