Keck/HIRES spectroscopy of V838 Monocerotis in October 2005

V838 Mon erupted at the beginning of 2002 becoming an extremely luminous star. Among various scenarios proposed to explain the nature of the outburst the most promising is a stellar merger event. In this paper we investigate the observational properties of the star and its surroundings in the post outburst phase. We have obtained a high resolution optical spectrum of V838 Mon in October 2005 using the Keck I telescope.We have identified numerous atomic features and molecular bands present in the spectrum and provided an atlas of those features. In order to improve the spectrum interpretation we have performed simple modeling of the molecular bands. Our analysis indicates that the spectrum is dominated by molecular absorption features arising in photospheric regions with temperatures of ~2400 K and in colder outer layers, where the temperature decreases down to ~500 K. A number of resonance lines of neutral alkali metals are observed to show P-Cyg profiles. Particularly interesting are numerous prominent emission lines of [FeII]. All of them show practically the same profile, which can be well described by a Lorentzian profile. In the blue part of the spectrum photospheric signatures of the B-type companion are easily seen. We have fitted the observed spectrum with a synthetic one and the obtained parameters are consistent with the B3V type. We have also estimated radial and rotational velocities of the companion.Comment: accepted to ApJS, 21 pages, 15 figures; a paragraph about photometry has been added, typos corrected

AN EXAMPLE OF ORGANIC SYNTHESIS INDUCED BY LASER IRRADIATION

Apart from certain rare instances, the synthesis of cyclobutane derivatives must be performed photochemically. If, however, acrylonitrile is used as reagent (e.g. for the synthesis of nitrile function terpenes known for their "green notes"), a parasite polymerisation reaction that prevents the intermolecular reaction, is observed. Since the laser is both a powerful and a monochromatic light source, it is a tool of choice for the selective excitation of a chosen substrate molecule

USE OF AN ALIASING ARTEFACT IN FT SPECTROMETRY TO DISTINGUISH BETWEEN PULSED AND CONTINUOUS EMISSIONS OCCURING IN THE SAME SOURCE

Spectral aliasing can be usefully employed to differentiate between emission from pulsed and continuous sources when recording spectra on a continuous scanning Fourier transform spectrometer. Examples are given using a pulsed copper vapour laser to excite fluorescence in the presence of strong blackbody radiation. The continuous emission is sampled at regular optical path differences [MATH] and shows no aliasing in the spectral range [MATH]. The pulsed emission is slaved to the interferometer at a frequency which is half that of the interferometer sampling rate producing a duplicate of the pulsed spectrum [MATH] at [MATH]. The two can thus be distinguished, provided that the ghosts appear in a spectral region which contains no true lines

HIGH SPECTRAL AND TEMPORAL RESOLUTION OF PULSED EMISSIONS BY FOURIER TRANSFORM SPECTROMETRY

By slaving a pulsed laser (a few kHz) to a Fourier transform spectrometer of the "continuous scanning" type [BOMEM DA3], high resolution spectra of the pulsed emission can be obtained in the IR, visible and UV regions. By inserting a fast gated integrator between the detector (PMT) and the amplifier in the sequence of data acquisition elements in the spectrometer, it is possible to record time resolved spectra for which the temporal resolution is imposed by the response time of the detector, typically 10-20 ns

GENERATION OF COHERENT IR, VISIBLE AND UV RADIATIONS BY TWO-PHOTON PUMPING IN ATOMIC BARIUM

Barium atomic vapours were obtained in a cross-shaped heat pipe in the presence of argon. In the temperature range explored (900°-1050°C), the population was ~ 1016 to 1017 cm-3. The transverse and axial (relative to the laser beam) emissions were recorded with the aid of a photomultiplier coupled to an SRS Model 280 boxcar averager. Filters and dichroic mirrors were used to suppress the laser line during axial observations. The dye laser was pumped by a doubled or tripled Nd-YAG laser operating at 10 Hz with 13 ns pulses. The domain explored (725nm > λ > 490nm) correspond to the dyes LDS 698, Rh 590, F548 and C 500. The pulse energies (100-300 µJ) and focussing conditions correspond to an intensity of 100-300 MW/cm2. The dye laser beam was linearly polarised

LASER-INDUCED FLUORESCENCE FROM C 2Π TO X 2Σ+ AND H' 2Ɗ STATES OF BaF ANALYSED BY FOURIER TRANSFORM SPECTROSCOPY

The C2Π state of BaF has been excited by lines of an argon-ion laser. BaF molecules were produced in a heat-pipe in which barium was heated to 1000°C m the presence of argon at a pressure of 1 Torr, fluorine appearing as an impurety. The induced emission was studied m the ranges 8500 to 9500 and 19 400 to 20 300 cm-1. The spectra were recorded on a Fourier transform spectrometer at a resolution of about 0.027 cm-1. In these conditions we observe in emission the C 2Π → X 2Σ+ system in the visible region, and also fluorescence in the infra-red, which is assigned to C2Π → H' 2C. This 2Ɗ state is the third member, now found for the first time, of the d-complex whose other components are A 2Π and B 2Σ+. Until a more rational scheme is introduced, the new state will be labelled H' : the analogous state in BaH is labelled H, but this letter has already been used for a high-lying state in BaF