Speckle interferometry at SOAR in 2019

The results of speckle interferometric observations at the 4.1 m Southern Astrophysical Research Telescope (SOAR) in 2019 are given, totaling 2555 measurements of 1972 resolved pairs with separations from 15 mas (median 0.21") and magnitude difference up to 6 mag, and non-resolutions of 684 targets. We resolved for the first time 90 new pairs or subsystems in known binaries. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. We give a list of 127 orbits computed using our latest measurements. Their quality varies from excellent (25 orbits of grades 1 and 2) to provisional (47 orbits of grades 4 and 5).Comment: Accepted by The Astronomical Journal. 10 pages, 5 Figures. Measurements and non-resolutions, published electronically, are available from the first author. arXiv admin note: substantial text overlap with arXiv:1905.1043

Speckle interferometry at SOAR in 2015

The results of speckle interferometric observations at the SOAR telescope in 2015 are given, totalling 1303 measurements of 924 resolved binary and multiple stars and non-resolutions of 260 targets. The separations range from 12 mas to 3.37" (median 0.17"); the maximum measured magnitude difference is 6.7 mag. We resolved 27 pairs for the first time, including 10 as inner or outer subsystems in previously known binaries, e.g. the 50-mas pair in Epsilon Cha. Newly resolved pairs are commented upon. We discuss three apparently non-hierarchical systems discovered in this series, arguing that their unusual configuration results from projection. The resolved quadruple system HIP 71510 is studied as well.Comment: 10 pages, 8 figures. Accepted for publication in AJ. The online tables are not included, available from Tokovinin on request. arXiv admin note: text overlap with arXiv:1506.0571

The Nature of Radio Continuum Emission in the Dwarf Starburst Galaxy NGC 625

We present new multi-frequency radio continuum imaging of the dwarf starburst galaxy NGC 625 obtained with the Very Large Array. Data at 20, 6, and 3.6 cm reveal global continuum emission dominated by free-free emission, with only mild synchrotron components. Each of the major HII regions is detected; the individual spectral indices are thermal for the youngest regions (showing strongest H Alpha emission) and nonthermal for the oldest. We do not detect any sources that appear to be associated with deeply embedded, dense, young clusters, though we have discovered one low-luminosity, obscured source that has no luminous optical counterpart and which resides in the region of highest optical extinction. Since NGC 625 is a Wolf-Rayet galaxy with strong recent star formation, these radio properties suggest that the youngest star formation complexes have not yet evolved to the point where their thermal spectra are significantly contaminated by synchrotron emission. The nonthermal components are associated with regions of older star formation that have smaller ionized gas components. These results imply a range of ages of the HII regions and radio components that agrees with our previous resolved stellar population analysis, where an extended burst of star formation has pervaded the disk of NGC 625 over the last ~ 50 Myr. We compare the nature of radio continuum emission in selected nearby dwarf starburst and Wolf-Rayet galaxies, demonstrating that thermal radio continuum emission appears to be more common in these systems than in typical HII galaxies with less recent star formation and more evolved stellar clusters.Comment: ApJ, in press; 27 pages, 5 figures. Full-resolution version may be obtained at http://www.astro.umn.edu/~cannon/n625.vla.p

Is secure coding education in the industry needed? An investigation through a large scale survey

The Department of Homeland Security in the United States estimates that 90% of software vulnerabilities can be traced back to defects in design and software coding. The financial impact of these vulnerabilities has been shown to exceed 380 million USD in industrial control systems alone. Since software developers write software, they also introduce these vulnerabilities into the source code. However, secure coding guidelines exist to prevent software developers from writing vulnerable code. This study focuses on the human factor, the software developer, and secure coding, in particular secure coding guidelines. We want to understand the software developers' awareness and compliance to secure coding guidelines and why, if at all, they aren't compliant or aware. We base our results on a large-scale survey on secure coding guidelines, with more than 190 industrial software developers. Our work's main contribution motivates the need to educate industrial software developers on secure coding guidelines, and it gives a list of fifteen actionable items to be used by practitioners in the industry. We also make our raw data openly available for further research.info:eu-repo/semantics/acceptedVersio

kHz Quasi Periodic Oscillations in Low Mass X-ray Binaries as Probes of General Relativity in the Strong Field Regime

We consider the interpretation of a pair of kHz Quasi Periodic Oscillations (QPOs) in the Fourier spectra of two Low Mass X-Ray Binaries, Sco X-1 and 4U1608-52, hosting an old accreting neutron star. The observed frequency difference of these QPOs decreaseas as their frequency increases, contrary to simple beat frequency models, which predict a constant frequency difference. We show that the behaviour of these QPOs is instead well matched in terms of the fundamental frequencies (in the radial and azimuthal directions) for test particle motion in the gravitational field of the neutron star, for reasonable star masses, and nearly independent of the star spin. The radial frequency must be much smaller than the azimuthal one, testifying that kHz QPOs are produced close to the innermost stable orbit. These results are not reproduced through the post--Newtonian (PN) approximation of General Relativity (GR). kHz QPOs from X-ray binaries likely provide an accurate laboratory for strong field GR.Comment: to appear in Physical Review Letters, PRL Latex plus 2 figures in standard PostScript forma

Galactic Kinematics Towards the South Galactic Pole. First Results from the Yale-San Juan Southern Proper-Motion Program

The predictions from a Galactic Structure and Kinematic model code are compared to the color counts and absolute proper-motions derived from the Southern Proper-Motion survey covering more than 700 $\deg^2$ toward the South Galactic Pole in the range $9 < B_{\rm J} \le 19$. The theoretical assumptions and associated computational procedures, the geometry for the kinematic model, and the adopted parameters are presented in detail and compared to other Galactic Kinematic models of its kind. The data to which the model is compared consists of more than 30,000 randomly selected stars, and it is best fit by models with a solar peculiar motion of +5 km s$^{-1}$ in the V-component (pointing in the direction of Galactic rotation), a large LSR speed of 270 km s$^{-1}$, and a (disk) velocity ellipsoid that always points towards the Galactic center. The absolute proper-motions in the U-component indicate a solar peculiar motion of $11.0 \pm 1.5$ km s$^{-1}$, with no need for a local expansion or contraction term. The fainter absolute motions show an indication that the thick-disk must exhibit a rather steep velocity gradient of about -36 km s$^{-1}$ kpc$^{-1}$ with respect to the LSR. We are not able to set constraints on the overall rotation for the halo, nor on the thick-disk or halo velocity dispersions. Some substructure in the U & V proper-motions could be present in the brighter bins $10 < B_{\rm J} < 13$, and it might be indicative of (disk) moving groups.Comment: 24 double-column pages, 12 tables, AAS Latex macros v4.0, 19 B&W figures, 1 color figure. Accepted for publication on The Astronomical Journa