We explore several ways to dissect brightest cluster galaxies (BCGs) and their surrounding intracluster light (ICL) using a surface brightness (SB) cut, a luminosity cut, excess light above a de Vaucouleurs profile, or a double Sersic decomposition. Assuming that all light above M{<}-21.85g'mag is attributable to the ICL, we find that an average fraction of f_ICL_^MT^=71+/-22% of all diffuse light centered on the BCG belongs to the ICL. Likewise, if we assume that all light fainter than SB>27g'mag/arcsec^2^ belongs to the ICL, the average ICL fraction is f_ICL_^SB27^=34+/-19% . After fitting a de Vaucouleurs profile to the inner parts of the SB profile, we detect excess light at large radii, corresponding to an average ICL fraction of f_ICL_^DV^=48+/-20% . Finally, by decomposing the SB profile into two Sersic functions, we find an average ICL fraction of f_ICL_^Sx^=52+/-21% associated with the outer Sersic component. Our measured ICL and BCG+ICL luminosities agree well with predictions from high-resolution simulations where the outer Sersic component traces the unrelaxed, accreted stellar material. BCG and ICL properties defined in this way are correlated with cluster parameters to study the coevolution of BCGs, ICL, and their host clusters. We find positive correlations between BCG+ICL brightness and cluster mass, cluster velocity dispersion, cluster radius, and integrated satellite brightness, confirming that BCG/ICL growth is indeed coupled with cluster growth. On average, the ICL is better aligned than the BCG with the host cluster in terms of position angle, ellipticity, and centering. That makes it a potential dark-matter tracer.
Photographic magnitudes are presented for the irregular variable WW Vulpeculae. They were derived from Argelander brightness estimates carried out on N=2774 plates of the Harvard College Observatory Plate Collection. The data set covers the period 1898 to 1966.
We present near-infrared J-band photometric observations of the intermediate polar WX Pyx. The frequency analysis indicates the presence of a period at 1559.2+/-0.2s which is attributed to the spin period of the white dwarf. The spin period inferred from the infrared data closely matches that determined from X-ray and optical observations. WX Pyx is a system whose orbital period has not been measured directly and which is not too well constrained. From the IR observations, a likely peak at 5.30+/-0.02h is seen in the power spectrum of the object. It is suggested that this corresponds to the orbital period of the system. In case this is indeed the true orbital period, some of the system physical parameters may be estimated. Our analysis indicates that the secondary star is of M2 spectral type and the distance to the object is 1.53kpc. An upper limit of 30 for the angle of inclination of the system is suggested. The mass transfer rate and the magnetic moment of the white dwarf are estimated to be (0.95-1.6)x10^-9^M_{sun}/yr and (1.9-2.4)x10^33^G*cm^3^ respectively.
We present new multiband CCD photometry for WZ Cyg made on 22 nights in two observing seasons of 2007 and 2008. Our light-curve synthesis indicates that the system is in poor thermal contact with a fill-out factor of 4.8% and a temperature difference of 1447K. Including our 40 timing measurements, a total of 371 times of minimum light spanning more than 112yr were used for a period study. Detailed analysis of the O-C diagram showed that the orbital period has varied by a combination of an upward parabola and a sinusoid.
X- and gamma-ray fluxes of {gamma}-ray-loud blazars
Short Name:
J/A+A/436/799
Date:
21 Oct 2021
Publisher:
CDS
Description:
We determined the basic parameters, such as the central black hole mass (M), the boosting factor (or Doppler factor) ({delta}) the propagation angle ({Phi}) and the distance along the axis to the site of {gamma}-ray production (d) for 23 {gamma}-ray-loud blazars using their available variability timescales.
In this paper, a sample of 451 blazars (193 flat spectrum radio quasars (FSRQs), 258 BL Lacertae objects) with corresponding X-ray and Fermi {gamma}-ray data is compiled to investigate the correlation both between the X-ray spectral index and the {gamma}-ray spectral index and between the spectral index and the luminosity, and to compare the spectral indexes {alpha}_X_, {alpha}_{gamma}_, {alpha}_X{gamma}_, and {alpha}_{gamma}X{gamma}_ for different subclasses. We also investigated the correlation between the X-ray and the {gamma}-ray luminosity.
Active Galactic Nuclei (AGNs)
are extragalactic objects characterized by extremely complex physical processes
and strong temporal flux variability over almost the whole electromagnetic
spectrum, which play a very important role in studying the formation and
evolution of galaxies, cosmology and many other astrophysical problems.
Flux variability is one of the most remarkable observational characteristics
of AGNs and the variability time scales are from minutes to dozens of years.
Multi-wavelength flux monitoring is the main means to study the nature of AGN flux variability.
In order to systematically study the total flux variability of AGNs in radio band,
we launched a long-term program, which is called the quasi- Simultaneous Multiwavelength
Monitoring of AGNs with the Nanshan 26-m radio telescope of Xinjiang Astronomical Observatory (XAO),
namely SMMAN program. The monitoring data were acquired monthly with the cross-scan mode at
C-band (4.8 GHz) and K-band (23.6 GHz) for a sample of about 100 AGNs selected from Fermi-LAT suvery.
Additionally, we also conducted weekly monitoring observations or Intra-Day Vairibility (IDV)
observations for some of flaring Blazars to reveal their more complex variability time scales.
