The spectroscopic and spectropolarimetric variability of the peculiar variable V838 Monocerotis during the brighter phases of its multiple outbursts in 2002 is presented. Significant line profile variability of H and Si ii 6347.10 and 6371.36 Å occurred in spectra obtained between 2002 February 5 and March 14, and a unique secondary absorption component was observed near the end of this time period. Our observations also suggest that multiple shifts in ionization states occurred during the outbursts. Spectropolarimetric observations reveal that V838 Mon exhibited both intrinsic and interstellar polarization components during the initial stages of the second outburst, indicating the presence of an asymmetric geometry; however, the intrinsic component had declined significantly by February 14. We determine the interstellar polarization to be P max ¼ 2:746% AE 0:011%, max ¼ 5790 AE 37 G, and P:A: ¼ 153=43 AE 0=12, and we find the integrated intrinsic V-band polarization on February 5 to be P ¼ 0:983% AE 0:012% at a position angle of 127=0 AE 0=5. The implications of these observations for the nature of V838 Monocerotis, its distance, and its ejecta are discussed.

One of the major challenges of modern cosmology is the detection of B-mode polarization anisotropies in the Cosmic Microwave Background. These originate from tensor fluctuations of the metric produced during the inflationary phase. Their detection would therefore constitute a major step towards understanding the primordial Universe. The expected level of these anisotropies is however so small that it requires a new generation of instruments with high sensitivity and extremely good control of systematic effects. We propose the QUBIC instrument based on the novel concept of bolometric interferometry, bringing together the sensitivity advantages of bolometric detectors with the systematics effects advantages of interferometry. The instrument will directly observe the sky through an array of entry horns whose signals will be combined together using an optical combiner. The whole set-up is located inside a cryostat. Polarization modulation will be achieved using a rotating half-wave plate and the images of the interference fringes will be formed on two focal planes (separated by a polarizing grid) tiled with bolometers. We show that QUBIC can be considered as a synthetic imager, exactly similar to a usual imager but with a synthesized beam formed by the array of entry horns. Scanning the sky provides an additional modulation of the signal and improve the sky coverage shape. The usual techniques of map-making and power spectrum estimation can then be applied. We show that the sensitivity of such an instrument is comparable with that of an imager with the same number of horns. We anticipate a low level of beam-related systematics thanks to the fact that the synthesized beam is determined by the location of the primary horns. Other systematics should be under good control thanks to an autocalibration technique, specific to our concept, that will permit the accurate determination of most of the instrumental parameters that would otherwise lead to systematics. (C) 2011 Elsevier B.V. All rights reserved

We examine constraints from Big Bang nucleosynthesis on type II Randall-Sundrum brane cosmologies with both a dark radiation component and a quadratic term that depends on the 5dimensional Planck mass, M5. Using limits on the abundances of deuterium and helium-4, we calculate the allowed region in the M5-dark radiation plane and derive the precise BBN bound on M5 alone with no dark radiation: M5 > 13 TeV.

In this paper, we describe QUBIC, an experiment that will observe the polarized microwave sky with a novel approach, which combines the sensitivity of state-of-the-art bolometric detectors with the systematic effects control typical of interferometers. QUBIC’s unique features are the so-called “self-calibration”, a technique that allows us to clean the measured data from instrumental effects, and its spectral imaging power, i.e., the ability to separate the signal into various sub-bands within each frequency band. QUBIC will observe the sky in two main frequency bands: 150 GHz and 220 GHz. A technological demonstrator is currently under testing and will be deployed in Argentina during 2019, while the final instrument is expected to be installed during 2020.

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