We describe a complete volume limited sample of nearby active galaxies selected by their 14?195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow. We also describe a complementary sample of inactive galaxies, selected to match the host galaxy properties. The active sample appears to have no bias in terms of active galactic nucleus (AGN) type, the only difference being the neutral absorbing column, which is two orders of magnitude greater for the Seyfert 2s. In the luminosity range spanned by the sample, ?43.7, the optically obscured and X-ray absorbed fractions are 50%?65%. The similarity of these fractions to more distant spectroscopic AGN samples, although over a limited luminosity range, suggests that the torus does not strongly evolve with redshift. Our sample confirms that X-ray unabsorbed Seyfert 2s are rare, comprising not more than a few percent of the Seyfert 2 population. At higher luminosities, the optically obscured fraction decreases (as expected for the increasing dust sublimation radius), but the X-ray absorbed fraction changes little. We argue that the cold X-ray absorption in these Seyfert 1s can be accounted for by neutral gas in clouds that also contribute to the broad-line region (BLR) emission, and suggest that a geometrically thick neutral gas torus co-exists with the BLR and bridges the gap to the dusty torus.

https://iopscience.iop.org/article/10.1088/0004-637X/806/1/127/pdf

Insights on the Dusty Torus and Neutral Torus From Optical and X-Ray Obscuration in A Complete Volume Limited Hard X-Ray Agn Sample

Analysis of 4662 yellow magnitudes measures, obtained at the Konkoly Observatory on 78 nights in 1958--1962, shows that AC And has its fundamental and first and second overtone radial pulsation modes (periods P$sub 0$=0/sup d/./sub /71124243, P$sub 1$=0/sup d/./sub /52512677, and P$sub 2$ =0/sup d/./sub / 421069) all excited and nonlinearly coupled. Fitting formulae, derived from published pulsation calculations for high-metal-content models (Z=0.044), are given for the direct calculation of mass and radius from observed radial model period pairs. The multimode excitation of 25 Cepheid-strip stars (comprising eight Cepheids, one RR Lyrae star, nine RRs stars, and seven delta Scuti stars) is discussed. AC And is found to have a mass Mapprox. =3.1 M/sub sun/ and to be a high-mass analog of the delta Scuti stars, in the hydrogen-shell-burning and helium-core-contraction stage of evolution. Pulsation theory, evolution theory, and observation seem to be in excellent agreement for AC And and delta Sct. (AIP)

Three radial modes and evolutionary state of AC Andromedae

In this article, we present results based on high-density,
high-precision Wide-Angle Search for Planets (WASP) light
curves supplemented with lower-precision photometry from the
All-Sky Automated Survey (ASAS) for 268 RR Lyrae stars (176
regular, 92 Blazhko). Light curves were Fourier-decomposed and
coefficients from WASP were transformed to the ASAS standard
using 24 common stars. Coefficients were then compared with
similar data from Galactic globular clusters, the Galactic
bulge and the Large and Small Magellanic Clouds (LMC and SMC).
Using Fourier coefficients, we also calculated physical
parameters via standard equations from the literature. We
confirmed the results of previous authors, including lower
amplitudes and longer rise times for Blazhko stars. It was
found that in the R31 versus R21 plot the location of a star
depends mainly on its metallicity and that Blazhko stars prefer
a different location from modulation-free stars. Field and
globular cluster RR Lyrae variables have a different phi21 and
phi31 from stars in the LMC, SMC and Galactic bulge. Although
there are some weak indications that Blazhko stars could tend
towards a slightly lower metallicity and shorter periods, no
convincing proof was found. The most interesting highlight is
the identification of a very recently proposed new group of
metal-rich RR Lyrae type stars. These low-luminosity,
metal-strong variables, comprising both Blazhko and regular
stars, have shorter periods and about 180 K higher temperature
at constant (B-V)0 than the rest of the stars in the sample.

Characteristics of bright ab-type RR Lyrae stars from the ASAS and WASP surveys


 In this paper, we report on the detection of RRab stars with quasi-identical-shape light curves but period differences as large as 0.05 − 0.21 d using the Galactic bulge data of the OGLE-IV survey. We have examined stars with shorter periods than the Oosterhoff I ridge of the bulge. These stars generally have smaller amplitudes and larger Fourier phase-differences than the typical bulge RRab stars have at the same period. Many of these ”anomalous” stars have good-quality light curves without any sign of the Blazhko modulation. Examining their Fourier parameters revealed that several of these stars show very similar light-curve to the typical bulge RR Lyrae. We found hundreds of quasi-identical-shape light-curve pairs with different periods between the ”anomalous”- and the ”normal”-position RRab stars based on the OGLE I-band data. The OGLE V-band, and the archive VVV and MACHO surveys Ks-, b- and r-band data of these stars were also checked for light-curve-shape similarity. Finally, 149 pairs with identical-shape light curves in each available photometric band were identified. Calculating the physical properties of the variables using empirical formulae, on average, −0.5 dex, −0.13 mag, 0.67, and 165 K differences between the [Fe/H], MV, R/R⊙, and Teff values of the members of the pairs are derived, being the short-period stars less metal-poor, fainter, smaller and hotter than the long-period variables. To explain the existence of variables with different physical properties and pulsation periods but with identical-shape light curves is a challenging task for modelling.

/pdf/rrab-variables-with-identical-light-curve-shapes-at-1bpo093v.pdf

RRab variables with identical light-curve shapes at different pulsation periods

In an extended photometric campaign of RR Lyrae variables of the globular cluster M3, an aberrant-light-curve, non-Blazhko RRab star, V123, was detected. Based on its brightness, colors and radial-velocity curve, V123 is a bona fide member of M3. The light curve of V123 exhibits neither a bump preceding the light minimum, nor a hump on the rising branch, and has a longer than normal rise time, with a convex shape. A similar shape characterizes the mean light curves of some large-modulation-amplitude Blazhko stars, but none of the regular RRab variables with similar pulsation periods. This peculiar object thus mimics Blazhko variables without showing any evidence of periodic amplitude and/or phase modulation. We cannot find any fully convincing answer to the peculiar behavior of V123, however, the phenomenon raises again the possibility that rotation and aspect angle might play a role in the explanation of the Blazhko phenomenon, and that some source of inhomogeneity (magnetic field, chemical inhomogeneity) deforms the radial pulsation of Blazhko stars during the modulation.

/pdf/what-is-the-difference-blazhko-and-non-blazhko-rrab-stars-3coby1pouc.pdf

WHAT IS THE DIFFERENCE? BLAZHKO AND NON-BLAZHKO RRab STARS AND THE SPECIAL CASE OF V123 IN M3

Identifying and characterizing young populations of star-forming regions are crucial to unraveling their properties. In this regard, Gaia-DR3 data and machine-learning tools are very useful for studying large star-forming complexes. In this work, we analyze the ∼7.1 deg2 area of one of our Galaxy’s dominant feedback-driven star-forming complexes, i.e., the region around Trumpler 37. Using the Gaussian mixture and random-forest classifier methods, we identify 1243 highly probable members in the complex, of which ∼60% are new members and are complete down to the mass limit of ∼0.1–0.2 M ⊙. The spatial distribution of the stars reveals multiple clusters toward the complex, where the central cluster around the massive star HD 206267 reveals two subclusters. Of the 1243 stars, 152 have radial velocity, with a mean value of −16.41 ± 0.72 km s−1. We investigate stars’ internal and relative movement within the central cluster. The kinematic analysis shows that the cluster’s expansion is relatively slow compared to the whole complex. This slow expansion is possibly due to newly formed young stars within the cluster. We discuss these results in the context of hierarchical collapse and feedback-induced collapse mode of star formation in the complex.

/pdf/membership-analysis-and-3d-kinematics-of-the-star-forming-2o4q4fax.pdf

P. Prakash

Papers

WHAT IS THE DIFFERENCE? BLAZHKO AND NON-BLAZHKO RRab STARS AND THE SPECIAL CASE OF V123 IN M3

Membership Analysis and 3D Kinematics of the Star-forming Complex around Trumpler 37 Using Gaia-DR3