A sub-Doppler resolution double resonance molecular beam infrared spectrometer operating at chemically relevant energies (~2 eV)

A molecular beam spectrometer capable of achieving sub-Doppler resolution at 2 eV (~18 000 cm^–1) of vibrational excitation is described and its performance demonstrated using the CH stretch chromophore of HCN. Two high finesse resonant power-buildup cavities are used to excite the molecules using a sequential double resonance technique. A v = 0-->2 transition is first saturated using a 1.5 µm color center laser, whereupon a fraction of the molecules is further excited to the v = 6 level using an amplitude modulated Ti:Al2O3 laser. The energy absorbed by the molecules is detected downstream of both excitation points by a cryogenically cooled bolometer using phase sensitive detection. A resolution of approximately 15 MHz (i.e., three parts in 10^8) is demonstrated by recording a rotational line in the v = 6 manifold of HCN. Scan speeds of up to several cm^–1/h were obtained, with signal-to-noise ratios in excess of 100. The high signal-to-noise ratio and a dynamic range of 6×10^4 means that future experiments to study statistical intramolecular vibrational energy redistribution in small molecules and unimolecular isomerizations can be attempted. We would also like to point out that, with improved metrology in laser wavelengths, this instrument can also be used to provide improved secondary frequency standards based upon the rovibrational spectra of molecules

NuSTAR and Swift observations of Swift J1357.2-0933 during an early phase of its 2017 outburst

We present a detailed spectral analysis of Swift and NuSTAR observations of the very faint X-ray transient and black hole system Swift J1357.2-0933 during an early low hard state of its 2017 outburst. Swift J1357.2-0933 was observed at $\sim$0.02% of the Eddington luminosity (for a distance of 2.3 kpc and a mass of 4 M$_{\odot}$). Despite the low luminosity, the broadband X-ray spectrum between 0.3 and 78 keV requires the presence of a disk blackbody component with an inner disk temperature of T$_{\mathrm{in}}$ $\sim$ 0.06 keV in addition to a thermal Comptonization component with a photon index of {\Gamma} $\sim$ 1.70. Using a more physical model, which takes strong relativistic effects into account, and assuming a high inclination of 70$^\circ$, which is motivated by the presence of dips in optical light curves, we find that the accretion disk is truncated within a few RISCO from the black hole, independent of the spin.Comment: 11 pages, 5 figures, accepted for publication in Ap

Peculiar outbursts of an ultra luminous source likely signs of an aperiodic disc-wind

The metal rich globular cluster RZ 2109 in the massive Virgo elliptical galaxy NGC 4472 (M49) harbours the ultra luminous X-ray source XMMU 122939.7+075333. Previous studies showed that this source varies between bright and faint phases on timescales of just a few hours. Here, we report the discovery of two peculiar X-ray bursting events that last for about 8 and 3.5 hours separated by about 3 days. Such a recurring X-ray burst-like behaviour has never been observed before. We argue that type-I X-ray bursts or super bursts as well as outburst scenarios requiring a young stellar object are highly unlikely explanations for the observed light curve, leaving an aperiodic disc wind scenario driven by hyper-Eddington accretion as a viable explanation for this new type of X-ray flaring activities.Comment: 7 pages, 2 figures, accepted by Ap

Curable polyphosphazenes

Class of polyphosphazene polymers can be cured at moderate temperatures by action of moisture. In addition, polymers maintain flexibility when exposed to low temperatures