Lambda Boo stars with composite spectra

We examine the large sample of lambda Boo candidates collected in Table 1 of Gerbaldi et al. (2003) to see how many of them show composite spectra. Of the 132 lambda Boo candidates we identify 22 which definitely show composite spectra and 15 more for which there are good reasons to suspect a composite spectrum. The percentage of lambda Boo candidates with composite spectra is therefore > 17 and possibly considerably higher. For such stars the lambda Boo classification should be reconsidered taking into account the fact that their spectra are composite. We argue that some of the underabundances reported in the literature may simply be the result of the failure to consider the composite nature of the spectra. This leads to the legitimate suspicion that some, if not all, the lambda Boo candidates are not chemically peculiar at all. A thorough analysis of even a single one of the lambda Boo candidates with composite spectra, in which the composite nature of the spectrum is duly considered, which would demonstrate that the chemical peculiarities persist, would clear the doubt we presently have that the stars with composite spectra may not be lambda Boo at all.Comment: Accepted for publication by A&A on June 3rd 200

A speckle interferometry survey of lambda Bootis stars

A search for duplicity of lambda Bootis stars has been made by using the speckle camera installed at the Telescopio Nazionale Galileo. The operation mode and the reduction procedure allow one to obtain not only the separation, but also the magnitude difference between the components; the latter parameter is fundamental for determining the degree of contamination from the secondary component of a binary system and thus the importance of the veiling effect that produces absorption lines weaker than normal. Two stars, HD 38545 and HD 290492, are close binaries with values of the separation and of the magnitude difference such that only a composite spectrum can be observed. For another 15 lambda Bootis candidates, observed with negative results, the upper limits of a possible companion separation are given.Comment: A&A in pres

The Solar Photospheric Nitrogen Abundance: Determination with 3D and 1D Model Atmospheres

We present a new determination of the solar nitrogen abundance making use of 3D hydrodynamical modelling of the solar photosphere, which is more physically motivated than traditional static 1D models. We selected suitable atomic spectral lines, relying on equivalent width measurements already existing in the literature. For atmospheric modelling we used the co 5 bold 3D radiation hydrodynamics code. We investigated the influence of both deviations from local thermodynamic equilibrium (non-LTE effects) and photospheric inhomogeneities (granulation effects) on the resulting abundance. We also compared several atlases of solar flux and centre-disc intensity presently available. As a result of our analysis, the photospheric solar nitrogen abundance is A(N) = 7.86 +/- 0.12.Comment: 6 pages, 4 figure

Chemical composition of a sample of bright solar-metallicity stars

We present a detailed analysis of seven young stars observed with the spectrograph SOPHIE at the Observatoire de Haute-Provence for which the chemical composition was incomplete or absent in the literature. For five stars, we derived the stellar parameters and chemical compositions using our automatic pipeline optimized for F, G, and K stars, while for the other two stars with high rotational velocity, we derived the stellar parameters by using other information (parallax), and performed a line-by-line analysis. Chromospheric emission-line fluxes from CaII are obtained for all targets. The stellar parameters we derive are generally in good agreement with what is available in the literature. We provide a chemical analysis of two of the stars for the first time. The star HIP 80124 shows a strong Li feature at 670.8 nm implying a high lithium abundance. Its chemical pattern is not consistent with it being a solar sibling, as has been suggested.Comment: To be published on A

Association of Primary Varicose Veins with Dysregulated Vein Wall Apoptosis

BACKGROUND: Disordered programmed cell death may play a role in the development of superficial venous incompetence. We have determined the number of cells in apoptosis, and the mediators regulating the intrinsic and extrinsic pathways in specimens of varicose vein. METHODS: Venous segments were obtained from 46 patients undergoing surgical treatment for primary varicose veins. Controls samples were obtained from 20 patients undergoing distal arterial bypass grafting surgery. Segments of the distal and proximal saphenous trunk as well as tributaries were studied. Cell apoptoses and mediators of the mitochondrial and trans membrane pathway were evaluated with peroxidase in situ apoptosis detection, Bax and Fas detection, caspase-9 and 8 detection in the medial layer. RESULTS: Disorganised histological architecture was observed in varicose veins. Primary varicose veins also contained fewer peroxidase in situ-positive cells than control veins (2.6% S.D. 0.2% versus 12% S.D. 0.93%, P=.0001, Mann-Whitney u test), fewer Bax positive cells (2.1.% S.D. 0.3% versus 13% S.D. 0.9%, P=.0001) and fewer Caspase 9 positive cells (3.2% S.D. 1% versus 12% S.D. 1.3%, P=.0001). Similar findings were observed in saphenous trunk, main tributaries and accessory veins. In patients with recurrent varicose veins in whom the saphenous trunk had been preserved showed similar findings to primary varicose veins. Residual varicose veins contained fewer peroxidase in situ-positive cells than healthy veins (3.2% S.D. 0.6% versus 11% S.D. 2%, P=.0001), fewer Bax positive cells (2.2% S.D. 0.3% versus 12% S.D. 0.7%, P=.0001) and fewer Caspase 9 positive cells (2.6% S.D. 0.6% versus 12% S.D. 1%, P=.0001). Immunohistochemical detection for Fas and caspase 8 remained equal was the same in the varicose vein and control groups. CONCLUSION: Apoptosis is down regulated in the medial layer of varicose veins. This dysregulation is attributable to a disorder of the intrinsic pathway and involves the great saphenous vein trunk, major tributaries and accessory veins. This process may be among the causes of primary varicose veins

Purkinje Cell Activity Determines the Timing of Sensory-Evoked Motor Initiation

Cerebellar neurons can signal sensory and motor events, but their role in active sensorimotor processing remains unclear. We record and manipulate Purkinje cell activity during a task that requires mice to rapidly discriminate between multisensory and unisensory stimuli before motor initiation. Neuropixels recordings show that both sensory stimuli and motor initiation are represented by short-latency simple spikes. Optogenetic manipulation of short-latency simple spikes abolishes or delays motor initiation in a rate-dependent manner, indicating a role in motor initiation and its timing. Two-photon calcium imaging reveals task-related coherence of complex spikes organized into conserved alternating parasagittal stripes. The coherence of sensory-evoked complex spikes increases with learning and correlates with enhanced temporal precision of motor initiation. These results suggest that both simple spikes and complex spikes govern sensory-driven motor initiation: simple spikes modulate its latency, and complex spikes refine its temporal precision, providing specific cellular substrates for cerebellar sensorimotor control

A study of lambda Bootis type stars in the wavelength region beyond 7000A

The group of lambda Bootis type stars comprises late B- to early F-type, Population I objects which are basically metal weak, in particular the Fe group elements, but with the clear exception of C, N, O and S. One of the theories to explain the abundance pattern of these stars involves circumstellar or interstellar matter around the objects. Hence, we have compiled all available data from the literature of well established members of the lambda Bootis group redward of 7000A in order to find evidence for matter around these objects. Furthermore, we present unpublished ISO as well as submillimeter continuum and CO (2-1) line measurements to complete the data set. In total, measurements for 34 (26 with data redward of 20 mu m) well established lambda Bootis stars are available. There is evidence for an infrared excesses in six stars (HD 31295, HD 74873, HD 110411, HD 125162, HD 198160/1 and HD 210111) and two are doubtful cases (HD 11413 and HD 192640) resulting in a percentage of 23% (excluding the two doubtful cases). Dust models for these objects show fractional dust luminosities comparable to the Vega-type stars and slightly higher dust temperatures. ISO-SWS spectroscopy for HD 125162 and HD 192640 resulted in the detection of pure stellar HI lines ruling out an active accretion disk (as found for several Herbig Ae/Be stars) around these objects. The submillimeter measurements gave only upper limits for the line and continuum fluxes.Comment: 16 pages, 5 figures, accepted by A&

The Galactic evolution of phosphorus

As a galaxy evolves, its chemical composition changes and the abundance ratios of different elements are powerful probes of the underlying evolutionary processes. Phosphorous is an element whose evolution has remained quite elusive until now, because it is difficult to detect in cool stars. The infrared weak P I lines of the multiplet 1, at 1050-1082 nm, are the most reliable indicators of the presence of phosphorus. The availability of CRIRES at VLT has permitted access to this wavelength range in stellar spectra.We attempt to measure the phosphorus abundance of twenty cool stars in the Galactic disk. The spectra are analysed with one-dimensional model-atmospheres computed in Local Thermodynamic Equilibrium (LTE). The line formation computations are performed assuming LTE. The ratio of phosphorus to iron behaves similarly to sulphur, increasing towards lower metallicity stars. Its ratio with respect to sulphur is roughly constant and slightly larger than solar, [P/S]=0.10+- 0.10. We succeed in taking an important step towards the understanding of the chemical evolution of phosphorus in the Galaxy. However, the observed rise in the P/Fe abundance ratio is steeper than predicted by Galactic chemical evolution model model developed by Kobayashi and collaborators. Phosphorus appears to evolve differently from the light odd-Z elements sodium and aluminium. The constant value of [P/S] with metallicity implies that P production is insensitive to the neutron excess, thus processes other than neutron captures operate. We suggest that proton captures on 30Si and alpha captures on $27Al are possibilities to investigate. We see no clear distinction between our results for stars with planets and stars without any detected planet.Comment: To be published on A&

Pulsation of the Lambda Bootis star HD 210111

CONTEXT. The Lambda Bootis stars are a small spectroscopic subgroup of Population I A-type stars and show significant underabundances of metals. Many are Delta Scuti pulsators. AIMS. HD 210111 was selected for a detailed multisite pulsation study to determine whether its pulsation properties differ from those of normal A stars. METHODS. 262 hours of high-precision photometry were obtained at the SAAO and SSO observatories. RESULTS. 13 statistically significant pulsation frequencies were detected with very small photometric amplitudes from 1 to 7 millimag in the visual. A comparison with earlier 1994 measurements indicates a small increase in amplitude. As a byproduct, one of the comparison stars, HD 210571, was discovered to be a millimag variable with a frequency of 1.235 c/d and is probably a new Gamma Doradus variable. The observed wide range of excited frequencies from 12 to 30 c/d in HD 210111 can be explained with both the single- and double-star hypothesis. HD 210111 is in a similar evolutionary status to FG Vir, which also shows a wide range of excited frequencies with a similar frequency spacing near 4 c/d. This is interpreted as successive radial orders of the excited nonradial modes. In the double-star hypothesis previously evoked for HD 210111, the low and the high frequencies originate in different stars: here HD 210111 would resemble Theta^2 Tau. CONCLUSIONS. The pulsation of the Lambda Bootis star HD 210111 does not differ from that of normal Delta Scuti stars.Comment: 6 pages, 2 figures, 2 tables, submitted to A&