Confirmation of the presence of iron hydride in sunspots and cool stars

A high-resolution sunspot spectrum clearly shows the presence of the 9896 Å and 8691 Å bands of iron hydride (FeH). At least 332 lines of the two bands, accounting for 80% of the lines registered in the laboratory, can be identified with certainty in the spot spectrum; most of these are unblended. Our estimate that the 9896 Å band is 2.0 ± 0.2 times stronger than the 8691 Å band supports the idea, suggested earlier by laboratory deuteride experiments, that the 9896 Å band is the (0, 0) transition. No evidence for FeH is found in the spectrum of the solar disk. Image-tube spectrograms of M dwarfs and S stars have been taken in the near-infrared at 86 Å mm^(-1) to examine the feature which Nordh, Lindgren, and Wing have proposed is due to the 9896 Å band of FeH. At this dispersion enough band structure is evident to confirm the identification in both kinds of stars

First evidence for a gravitational lensing-induced echo in gamma rays with Fermi LAT

Aims. This article shows the first evidence for gravitational lensing phenomena in high energy gamma-rays. This evidence comes from the observation of a gravitational lens induced echo in the light curve of the distant blazar PKS 1830-211. Methods. Traditional methods for the estimation of time delays in gravitational lensing systems rely on the cross-correlation of the light curves of the individual images. In this paper, we use 300 MeV-30 GeV photons detected by the Fermi-LAT instrument. The Fermi-LAT instrument cannot separate the images of known lenses. The observed light curve is thus the superposition of individual image light curves. The Fermi-LAT instrument has the advantage of providing long, evenly spaced, time series. In addition, the photon noise level is very low. This allows to use directly Fourier transform methods. Results. A time delay between the two compact images of PKS 1830-211 has been searched for both by the autocorrelation method and the "double power spectrum" method. The double power spectrum shows a 3 {\sigma} evidence for a time delay of 27.5 $\pm$ 1.3 days, consistent with the result from Lovell et al. (1998). The relative uncertainty on the time delay estimation is reduced from 20% to 5%.Comment: submitted to A&

Dynamic saturation of an intersublevel transition in self-organized InAs/In(x)A(1-x)lAs quantum dots

International audienceWe have observed a dynamic saturation of an intersublevel transition in InAs/InxAl1-xAs quantum dots related to the discrete nature of electron states using midinfrared femtosecond spectroscopy. This dynamic saturation is a consequence of the gradual filling of the discrete quantum-dot electron states due to the capture of electrons injected in the barrier. Our interpretation of the differential transmission experiments is confirmed by a comparison with a rate-equation model with the capture and intersublevel relaxation time as fit parameters yielding 10 ps and 1 ps, respectively. We discuss the mechanism responsible for these relaxation times

Plasma membrane-associated receptor like kinases relocalize to plasmodesmata in response to osmotic stress

Plasmodesmata act as key elements in intercellular communication, coordinating processes related to plant growth, development, and responses to environmental stresses. While many of the developmental, biotic, and abiotic signals are primarily perceived at the plasma membrane (PM) by receptor proteins, plasmodesmata also cluster receptor-like activities; whether these two pathways interact is currently unknown. Here we show that specific PM-located Leucine-Rich-Repeat Receptor-Like-Kinases (LRR-RLKs), QSK1 and IMK2, which under optimal growth conditions are absent from plasmodesmata, rapidly relocate and cluster to the pores in response to osmotic stress. This process is remarkably fast, is not a general feature of PM-associated proteins, and is independent of sterol- and sphingolipid- membrane composition. Focusing on QSK1, previously reported to be involved in stress responses, we show that relocalisation in response to mannitol depends on QSK1 phosphorylation. Loss-of-function mutation in QSK1 results in delayed lateral root (LR) development and the mutant is affected in the root response to mannitol stress. Callose-mediated plasmodesmata regulation is known to regulate LR development. We found that callose levels are reduced in the qsk1 mutant background with a root phenotype resembling ectopic expression of PdBG1, an enzyme that degrades callose at the pores. Both the LR and callose phenotypes can be complemented by expression of wild-type and phosphomimic QSK1 variants, but not by phosphodead QSK1 mutant which fails to relocalise at plasmodesmata. Together the data indicate that re-organisation of RLKs to plasmodesmata is important for the regulation of callose and LR development as part of the plant response to osmotic stress

Confirmation of the presence of iron hydride in sunspots and cool stars

A high-resolution sunspot spectrum clearly shows the presence of the 9896 Å and 8691 Å bands of iron hydride (FeH). At least 332 lines of the two bands, accounting for 80% of the lines registered in the laboratory, can be identified with certainty in the spot spectrum; most of these are unblended. Our estimate that the 9896 Å band is 2.0 ± 0.2 times stronger than the 8691 Å band supports the idea, suggested earlier by laboratory deuteride experiments, that the 9896 Å band is the (0, 0) transition. No evidence for FeH is found in the spectrum of the solar disk. Image-tube spectrograms of M dwarfs and S stars have been taken in the near-infrared at 86 Å mm^(-1) to examine the feature which Nordh, Lindgren, and Wing have proposed is due to the 9896 Å band of FeH. At this dispersion enough band structure is evident to confirm the identification in both kinds of stars

A High-Resolution Atlas of Uranium-Neon in the H Band

We present a high-resolution (R ~ 50 000) atlas of a uranium-neon (U/Ne) hollow-cathode spectrum in the H-band (1454 nm to 1638 nm) for the calibration of near-infrared spectrographs. We obtained this U/Ne spectrum simultaneously with a laser-frequency comb spectrum, which we used to provide a first-order calibration to the U/Ne spectrum. We then calibrated the U/Ne spectrum using the recently-published uranium line list of Redman et al. (2011), which is derived from high-resolution Fourier transform spectrometer measurements. These two independent calibrations allowed us to easily identify emission lines in the hollow cathode lamp that do not correspond to known (classified) lines of either uranium or neon, and to compare the achievable precision of each source. Our frequency comb precision was limited by modal noise and detector effects, while the U/Ne precision was limited primarily by the signal-to-noise ratio (S/N) of the observed emission lines and our ability to model blended lines. The standard deviation in the dispersion solution residuals from the S/N-limited U/Ne hollow cathode lamp were 50% larger than the standard deviation of the dispersion solution residuals from the modal-noise-limited laser frequency comb. We advocate the use of U/Ne lamps for precision calibration of near-infrared spectrographs, and this H-band atlas makes these lamps significantly easier to use for wavelength calibration.Comment: 23 pages, 7 figures, submitted and accepted in ApJSS. Online-only material to be published online by ApJS

Optical properties of self-assembled InAs quantum islands grown on InP(001) vicinal substrates

International audienceWe have investigated the effect of misorientated InP001 substrates on the optical properties of InAs quantum islands QIs grown by molecular-beam epitaxy in the Stranski-Krastanow regime. Detailed temperature-dependent photoluminescence PL, excitation density PL, and polarization of photoluminescence PPL are studied. PPL shows a high degree of linear polarization near 40% for the nominally oriented substrate n and for the substrate with 2° off miscut angle toward the 110 direction (2° F), while it is near 15% for the substrate with 2° off miscut angle towards 010 direction (2° B), indicating the growth of InAs quantum wires on nominal and 2° F substrates and of InAs quantum dots on 2° B substrate. These island shapes are confirmed by morphological investigations performed by atomic force microscopy. The integrated PL intensity remains very strong at room temperature, as much as 36% of that at 8 K, indicating a strong spatial localization of the carriers in the InAs QIs grown on InP001

Solar abundance corrections derived through 3D magnetoconvection simulations

We explore the effect of the magnetic field when using realistic three-dimensional convection experiments to determine solar element abundances. By carrying out magnetoconvection simulations with a radiation-hydro code (the Copenhagen stagger code) and through a-posteriori spectral synthesis of three Fe I lines, we obtain evidence that moderate amounts of mean magnetic flux cause a noticeable change in the derived equivalent widths compared with those for a non-magnetic case. The corresponding Fe abundance correction for a mean flux density of 200 G reaches up to ~0.1 dex in magnitude. These results are based on space- and time-averaged line profiles over a time span of 2.5 solar hours in the statistically stationary regime of the convection. The main factors causing the change in equivalent widths, namely the Zeeman broadening and the modification of the temperature stratification, act in different amounts and, for the iron lines considered here, in opposite directions; yet, the resulting $|\Delta\log\epsilon_{\odot}(Fe)|$ coincides within a factor two in all of them, even though the sign of the total abundance correction is different for the visible and infrared lines. We conclude that magnetic effects should be taken into account when discussing precise values of the solar and stellar abundances and that an extended study is warranted.Comment: ApJ accepte