IGR J19294+1816: a new Be-X ray binary revealed through infrared spectroscopy

The aim of this work is to characterize the counterpart to the INTEGRAL High Mass X-ray Binary candidate IGR J19294+1816 so as to establish its true nature. We obtained H band spectra of the selected counterpart acquired with the NICS instrument mounted on the Telescopio Nazionale Galileo (TNG) 3.5-m telescope which represents the first infrared spectrum ever taken of this source. We complement the spectral analysis with infrared photometry from UKIDSS, 2MASS, WISE and NEOWISE databases. We classify the mass donor as a Be star. Subsequently, we compute its distance by properly taking into account the contamination produced by the circumstellar envelope. The findings indicate that IGR J19294+1816 is a transient source with a B1Ve donor at a distance of $d = 11 \pm 1$ kpc, and luminosities of the order of $10^{36-37}$ erg s$^{-1}$, displaying the typical behaviour of a Be X-ray binary.Comment: 8 pages, 6 figures, accepted to be published in MNRA

The Highly Eccentric Pre-Main Sequence Spectroscopic Binary RX J0529.3+1210

The young system RX J0529.3+1210 was initially identified as a single-lined spectroscopic binary. Using high-resolution infrared spectra, acquired with NIRSPEC on Keck II, we measured radial velocities for the secondary. The method of using the infrared regime to convert single-lined spectra into double-lined spectra, and derive the mass ratio for the binary system, has been successfully used for a number of young, low-mass binaries. For RX J0529.3+1210, a long- period(462 days) and highly eccentric(0.88) binary system, we determine the mass ratio to be 0.78+/-0.05 using the infrared double-lined velocity data alone, and 0.73+/-0.23 combining visible light and infrared data in a full orbital solution. The large uncertainty in the latter is the result of the sparse sampling in the infrared and the high eccentricity: the stars do not have a large velocity separation during most of their ~1.3 year orbit. A mass ratio close to unity, consistent with the high end of the one sigma uncertainty for this mass ratio value, is inconsistent with the lack of a visible light detection of the secondary component. We outline several scenarios for a color difference in the two stars, such as one heavily spotted component, higher order multiplicity, or a unique evolutionary stage, favoring detection of only the primary star in visible light, even in a mass ratio ~1 system. However, the evidence points to a lower ratio. Although RX J0529.3+1210 exhibits no excess at near-infrared wavelengths, a small 24 micron excess is detected, consistent with circumbinary dust. The properties of this binary and its membership in Lambda Ori versus a new nearby stellar moving group at ~90 pc are discussed. We speculate on the origin of this unusual system and on the impact of such high eccentricity on the potential for planet formation.Comment: 4 Figure

Experimental investigation of critical Casimir forces in binary liquid mixtures by blinking optical tweezers

We investigate, for the first time and by blinking optical tweezers, the effects of critical Casimir forces (CCFs) on the free dynamics of a pair of spherical colloidal particles, immersed in binary liquid mixtures upon approaching their critical points. © 2017 OSA

Optical spectra of selected Chamaeleon I young stellar objects

We present optical spectra of eight candidate brown dwarfs and a previously known T Tauri star (Sz 33) of the Chamaeleon I dark cloud. We derived spectral types based on the strength of the TiO or VO absorption bands present in the spectra of these objects as well as on the PC3 index of Martin et al. (1999). Photometric data from the literature are used to estimate the bolometric luminosities for these sources. We apply D'Antona & Mazzitelli (1997) pre-main sequence evolutionary tracks and isochrones to derive masses and ages. Based on the presence of Halpha in emission, we confirm that most of the candidates are young objects. Our sample however includes two sources for which we can only provide upper limits for the emission in Halpha; whereas these two objects are most likely foreground/background stars, higher resolution spectra are required to confirm their true nature. Among the likely cloud members, we detect one new sub-stellar object and three transition stellar/sub-stellar sources.Comment: 22 pages - manuscript forma

Microscopic engine powered by critical demixing

We propose a new type of engine that is powered by the local, reversible demixing of a critical binary liquid. A microscopic particle is optically trapped and performs revolutions due to the emergence of diffusiophoresis. © 2017 OSA

Pulsation in the atmosphere of the roAp star HD 24712. I. Spectroscopic observations and radial velocity measurements

We have investigated the structure of the pulsating atmosphere of one of the best studied rapidly oscillating Ap stars, HD 24712. For this purpose we analyzed spectra collected during 2001-2004. An extensive data set was obtained in 2004 simultaneously with the photometry of the Canadian MOST mini-satellite. This allows us to connect directly atmospheric dynamics observed as radial velocity variations with light variations seen in photometry. We directly derived for the first time and for different chemical elements, respectively ions, phase shifts between photometric and radial velocity pulsation maxima indicating, as we suggest, different line formation depths in the atmosphere. This allowed us to estimate for the first time the propagation velocity of a pulsation wave in the outer stellar atmosphere of a roAp star to be slightly lower than the sound speed. We confirm large pulsation amplitudes (150-400 m/s) for REE lines and the Halpha core, while spectral lines of the other elements (Mg, Si, Ca, and Fe-peak elements) have nearly constant velocities. We did not find different pulsation amplitudes and phases for the lines of rare-earth elements before and after the Balmer jump, which supports the hypothesis of REE concentration in the upper atmosphere above the hydrogen line-forming layers. We also discuss radial velocity amplitudes and phases measured for individual spectral lines as tools for a 3D tomography of the atmosphere of HD 24712.Comment: accepted by A&