We present a new catalogue of blazars based on multi-frequency surveys and on an extensive review of the literature. Blazars are classified as BL Lacertae objects, as flat spectrum radio quasars or ...as blazars of uncertain/transitional type. Each object is identified by a root name, coded as BZB, BZQ and BZU for these three subclasses respectively, and by its coordinates. This catalogue is being built as a tool useful for the identification of the extragalactic sources that will be detected by present and future experiments for X and gamma-ray astronomy, like Swift, AGILE, Fermi-GLAST and Simbol-X. An electronic version is available from the ASI Science Data Center web site at http://www.asdc.asi.it/bzcat
Mkn 421 is a nearby active galactic nucleus dominated at all wavelengths by a very broad non-thermal continuum thought to arise from a relativistic jet seen at a small angle to the line of sight. Its ...spectral energy distribution peaks in the X-ray and TeV gamma-ray bands, where the energy output is dominated by cooling of high-energy electrons in the jet. In order to study the electron distribution and its evolution, we carried out a dedicated multi-wavelength campaign, including extensive observations by the recently launched highly sensitive hard X-ray telescope NuSTAR, between December 2012 and May 2013. Here we present some initial results based on NuSTAR data from January through March 2013, as well as calibration observations conducted in 2012. Although the observations cover some of the faintest hard X-ray flux states ever observed for Mkn 421, the sensitivity is high enough to resolve intra-day spectral variability. We find that in this low state the dominant flux variations are smooth on timescales of hours, with typical intra-hour variations of less than 5%. We do not find evidence for either a cutoff in the hard X-ray spectrum, or a rise towards a high-energy component, but rather that at low flux the spectrum assumes a power law shape with a photon index of approximately 3. The spectrum is found to harden with increasing brightness.
This article describes adherence to a low-fat dietary pattern (less than 20% energy from fat, five or more fruit/vegetable and six or more grain servings daily) in Years 1 and 5 of the Women’s Health ...Initiative Dietary Modification Trial, which was designed to examine the effects of a low-fat dietary pattern on risk of breast and colorectal cancers and other chronic diseases in postmenopausal women. Participants were randomly assigned to a low-fat dietary intervention arm (40%, n=19,542) or a usual diet control arm (60%, n=29,294). Women in the intervention arm completed 18 group sessions during the first year, followed by quarterly annual maintenance sessions. Adherence was assessed as control minus intervention (C−I) group differences in percent total energy from fat as estimated by a food frequency questionnaire. Based on these self-reported dietary data, mean C−I was 10.9 percentage points of energy from fat at Year 1, decreasing to 9.0 at Year 5. Factors associated with poorer adherence were being older, being African American or Hispanic (compared with white), having low income, and being obese. Group session attendance was strongly associated with better dietary adherence. There are many limitations of self-reported dietary data, particularly related to social desirability and intervention-associated bias. Nonetheless, these data indicate that long-term dietary change was achieved in this clinical trial setting and reinforce the potential of the ongoing trial to answer questions of public health importance.
Curved broad-band spectral distributions of non-thermal sources like blazars
are described well by a log-parabolic (LP) law where the second degree term
measures the curvature. LP energy spectra can ...be obtained for relativistic
electrons by means of a statistical acceleration mechanism whose probability of
acceleration depends on energy. In this paper we compute the spectra radiated
by an electron population via synchrotron (S) and Synchro-Self Compton(SSC)
processes to derive the relations between the LP parameters. These spectra were
obtained by means of an accurate numerical code. We found that the ratio
between the curvature parameters of the S spectrum to that of the electrons is
equal to about 0.2 instead of 0.25, the value foreseen in the delta
approximation. Inverse Compton spectra are also intrinsically curved and can be
approximated by a log-parabola only in limited ranges. The curvature parameter,
estimated around the SED peak, may vary from a lower value than that of the S
spectrum up to that of emitting electrons depending on whether the scattering
is in the Thomson or in the Klein-Nishina regime. We applied this analysis to
computing the SSC emission from the BL Lac object Mkn 501 during the large
flare of April 1997. We fit simultaneous BeppoSAX and CAT data and reproduced
intensities and spectral curvatures of both components with good accuracy. The
large curvature observed in the TeV range was found to be mainly intrinsic, and
therefore did not require a large pair production absorption against the
extragalactic background. We regard this finding as an indication that the
Universe is more transparent at these energies than previously assumed by
several models found in the literature. This conclusion is supported by recent
detection of two relatively high redshift blazars with H.E.S.S.
The formation of S{sup +}, S{sup 2+}, S{sup 3+}, and S{sup 4+} is observed following inner-shell photodetachment of S{sup -}. The photodetachment spectra for all possible ionic products are obtained ...over a large region of photon energies covering both the 2p and 2s thresholds (S{sup 5+}, is energetically allowed at the higher photon energies, but not observed), and are placed on an absolute scale. The 2s threshold energy is measured to be 224.6(5) eV, allowing the determination of the neutral atomic S 2s{sup -1}3s{sup 2}3p{sup 5} inner-shell excited state energy for the first time. The S{sup -} 2s{sup -1}3s{sup 2}3p{sup 6} {sup 2}S{sub 1/2} state is observed as a Feshbach resonance 2.3(5) eV below the 2s threshold in the S{sup +}, S{sup 2+}, and S{sup 3+} product channels.
We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10:11:58.6 UTC by ...the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70,000 years. The inferred component black hole masses are \(31.2^{+8.4}_{-6.0}\,M_\odot\) and \(19.4^{+5.3}_{-5.9}\,M_\odot\) (at the 90% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, a mass-weighted combination of the spin components perpendicular to the orbital plane, \(\chi_\mathrm{eff} = -0.12^{+0.21}_{-0.30}.\) This result implies that spin configurations with both component spins positively aligned with the orbital angular momentum are disfavored. The source luminosity distance is \(880^{+450}_{-390}~\mathrm{Mpc}\) corresponding to a redshift of \(z = 0.18^{+0.08}_{-0.07}\). We constrain the magnitude of modifications to the gravitational-wave dispersion relation and perform null tests of general relativity. Assuming that gravitons are dispersed in vacuum like massive particles, we bound the graviton mass to \(m_g \le 7.7 \times 10^{-23}~\mathrm{eV}/c^2\). In all cases, we find that GW170104 is consistent with general relativity.
We report on the first ten identifications of sources serendipitously detected by the NuSTAR to provide the first sensitive census of the cosmic X-ray background (CXB) source population at >10 keV. ...We find that these NuSTAR-detected sources are ~100x fainter than those previously detected at >10 keV and have a broad range in redshift and luminosity (z=0.020-2.923 and L_10-40 keV~4x10^{41}-5x10^{45} erg/s); the median redshift and luminosity are z~0.7 and L_10-40 keV~3x10^{44} erg/s, respectively. We characterize these sources on the basis of broad-band ~0.5-32 keV spectroscopy, optical spectroscopy, and broad-band ultraviolet-to-mid-infrared SED analyzes. We find that the dominant source population is quasars with L_10-40 keV>10^{44} erg/s, of which ~50% are obscured with N_H>10^{22} cm^{-2}. However, none of the ten NuSTAR sources are Compton thick (N_H>10^{24} cm^{-2}) and we place a 90% confidence upper limit on the fraction of Compton-thick quasars (L_10-40 keV>10^{44} erg/s) selected at >10 keV of ~33% over the redshift range z=0.5-1.1. We jointly fitted the rest-frame ~10-40 keV data for all of the non-beamed sources with L_10-40 keV>10^{43} erg/s to constrain the average strength of reflection; we find R<1.4 for \Gamma=1.8, broadly consistent with that found for local AGNs observed at >10 keV. We also constrain the host galaxy masses and find a median stellar mass of ~10^{11} M_sun, a factor ~5 times higher than the median stellar mass of nearby high-energy selected AGNs, which may be at least partially driven by the order of magnitude higher X-ray luminosities of the NuSTAR sources. Within the low source-statistic limitations of our study, our results suggest that the overall properties of the NuSTAR sources are broadly similar to those of nearby high-energy selected AGNs but scaled up in luminosity and mass.
The first observational run of the Advanced LIGO detectors, from September 12, 2015 to January 19, 2016, saw the first detections of gravitational waves from binary black hole mergers. In this paper ...we present full results from a search for binary black hole merger signals with total masses up to \(100 M_\odot\) and detailed implications from our observations of these systems. Our search, based on general-relativistic models of gravitational wave signals from binary black hole systems, unambiguously identified two signals, GW150914 and GW151226, with a significance of greater than \(5\sigma\) over the observing period. It also identified a third possible signal, LVT151012, with substantially lower significance, and with an 87% probability of being of astrophysical origin. We provide detailed estimates of the parameters of the observed systems. Both GW150914 and GW151226 provide an unprecedented opportunity to study the two-body motion of a compact-object binary in the large velocity, highly nonlinear regime. We do not observe any deviations from general relativity, and place improved empirical bounds on several high-order post-Newtonian coefficients. From our observations we infer stellar-mass binary black hole merger rates lying in the range \(9-240 \mathrm{Gpc}^{-3} \mathrm{yr}^{-1}\). These observations are beginning to inform astrophysical predictions of binary black hole formation rates, and indicate that future observing runs of the Advanced detector network will yield many more gravitational wave detections.
Astron.Astrophys.445:843-855,2006 We present a new assessment of the contribution of Blazars to the
extragalactic background radiation across the e.m. spectrum. Our calculations
rely on deep Blazar ...radio counts that we derived combining several
multifrequency surveys. The integrated Blazar emission yields a broad-band
non-thermal background that in some parts of the e.m. spectrum dominates the
extragalactic brightness. Blazars are the main point-like contributors to the
CMB. Their integrated emission causes an apparent T increase of 5-50 muK in the
50-250 GHz range. The CMB fluctuation spectrum is sensibly contaminated at
l>300, for a Poissonian source distribution, or at lower l values if spatial
clustering is present. We estimate that well over 100,000 Blazars will produce
a significant signal in the PLANCK CMB anisotropy maps. Because of the
microwave-Xray flux correlation, these sources are expected to have flux > a
few 10^{-15} erg/s in the soft X-ray band. Thus, a large fraction of the
foreground sources in CMB anisotropy maps could be identified and removed using
a multi frequency approach, provided that a sufficiently deep all sky X-ray
survey will be available. We further show that Blazars are a major constituent
of all high-E extragalactic backgrounds. Their contribution is 11-12% at X-ray
frequencies and possibly 100% in the 0.5-50 MeV band. At E>100 MeV, the Blazar
collective emission, obtained extrapolating their integrated micro-wave flux to
the gamma-ray band using the SED of EGRET detected sources, over-predicts the
extragalactic background by a large factor, implying that Blazars not only
dominate the gamma-ray sky but also that their average duty cycle at these
frequencies must be rather low. We also find that Blazars of the HBL type may
produce a significant amount of flux at TeV energies.
