The Spectroscopic Orbits of Three Double-lined Eclipsing Binaries: I. BG Ind, IM Mon, RS Sgr

We present the spectroscopic orbit solutions of three double-lines eclipsing binaries, BG Ind, IM Mon and RS Sgr. The first precise radial velocities (RVs) of the components were determined using high resolution echelle spectra obtained at Mt. John University Observatory in New Zealand. The RVs of the components of BG Ind and RS Sgr were measured using Gaussian fittings to the selected spectral lines, whereas two-dimensional cross-correlation technique was preferred to determine the RVs of IM Mon since it has relatively short orbital period among the other targets and so blending of the lines is more effective. For all systems, the Keplerian orbital solution was used during the analysis and also circular orbit was adopted because the eccentricities for all targets were found to be negligible. The first precise orbit analysis of these systems gives the mass ratios of the systems as 0.894, 0.606 and 0.325, respectively for BG Ind, IM Mon and RS Sgr. Comparison of the mass ratio values, orbital sizes and minimum masses of the components of the systems indicates that all systems should have different physical, dynamical and probable evolutionary status.Comment: 17 pages, 6 figures and 4 tables, accepted for publication in New Astronom

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

The early-type near-contact binary system V337 Aql revisited

The close binary V337 Aql consists of two early B-type components with an orbital period of 2.7339 d. New multi-band photometric observations of the system together with published radial velocities enabled us to derive the absolute parameters of the components. The simultaneous light and radial velocity curves solution yields masses and radii of M-1 = 17.44 +/- 0.31 M-circle dot and R-1 = 9.86 +/- 0.06 R-circle dot for the primary and M-2 = 7.83 +/- 0.18 M-circle dot and R-2 = 7.48 +/- 0.04 R-circle dot for the secondary component. Derived fundamental parameters allow us to calculate the photometric distance as 1355 +/- 160 pc. The present analysis indicates that the system is a near-contact semi-detached binary, in which a primary star is inside its Roche lobe with a filling ratio of 92% and the secondary star fills its Roche lobe. From O-C data analysis, an orbital period decrease was determined with a rate of -7.6 x 10(-8) yr(-1). Kinematic analysis reveals that V337 Aql has a circular orbit in the Galaxy and belongs to a young thin-disc population. (C) 2013 Elsevier B.V. All rights reserved

TOWARD UNDERSTANDING THE NATURE OF THE YOUNG DETACHED BINARY SYSTEM HD 350731

The young binary system HD 350731 is a noteworthy laboratory for studying early-type binaries with similar components. We present here an analysis of differential multi-color photometric and spectroscopic observations of the double-lined detached system. Accurate absolute parameters were determined for the first time from a simultaneous solution of the light and radial velocity curves. HD 350731 consists of two B8V-type components with masses and radii, respectively, of M-1= 2.91 +/- 0.13 M-circle dot, M-2= 2.80 +/- 0.14 M-circle dot, R-1= 2.11 +/- 0.05 R-circle dot, and R-2= 2.07 +/- 0.05 R-circle dot. The effective temperatures were determined based on analysis of disentangled spectra of the components and were derived to be 12,000 +/- 250 and 11,830 +/- 300 K for the primary and secondary components, respectively. The measured projected rotational velocities, 69.2 +/- 1.5 km s(-1) for the primary and 70.1 +/- 1.7 km s-1 for the secondary, were found to be closer to the pseudo-synchronous velocities of the components. Comparison with evolutionary models suggests an age of 120 +/- 35 Myr. Kinematic analysis of the unevolved binary system HD 350731 revealed that it belongs to the young thin-disk population of the Galaxy