Carbon Stars in the Hamburg/ESO Survey: Abundances

We have carried out a detailed abundance analysis for a sample of 16 carbon stars found among candidate extremely metal-poor (EMP) stars from the Hamburg/ESO Survey. We find that the Fe-metallicities for the cooler C-stars (Teff ~ 5100K) have been underestimated by a factor of ~10 by the standard HES survey tools. The results presented here provided crucial supporting data used by Cohen et al (2006) to derive the frequency of C-stars among EMP stars. C-enhancement in these EMP C-stars appears to be independent of Fe-metallicity and approximately constant at ~1/5 the solar C/H. The mostly low C12/C13 ratios (~4) and the high N abundances in many of these stars suggest that material which has been through proton burning via the CN cycle comprises most of the stellar envelope. C-enhancement is associated with strong enrichment of heavy nuclei beyond the Fe-peak for 12 of the 16 stars. The remaining C-stars from the HES, which tend to be the most Fe-metal poor, show no evidence for enhancement of the heavy elements. Very high enhancements of lead are detected in some of the C-stars with highly enhanced Ba. (We show that) the s-process is responsible for the enhancement of the heavy elements for the majority of the C-stars in our sample. We suggest that both the s-process rich and Ba-normal C-stars result from phenomena associated with mass transfer in binary systems. This leads directly to the progression from C-stars to CH stars and then to Ba stars as the Fe-metallicity increases. (abridged and slightly edited to shorten)Comment: AJ, in press, submitted 13 Dec, 2005, accepted 21 March 200

Spectroscopic Study of IRAS 19285+0517(PDS 100): A Rapidly Rotating Li-Rich K Giant

We report on photometry and high-resolution spectroscopy for IRAS 19285+0517. The spectral energy distribution based on visible and near-IR photometry and far-IR fluxes shows that the star is surrounded by dust at a temperature of $T_{\rm {d}}$ $\sim$ 250 K. Spectral line analysis shows that the star is a K giant with a projected rotational velocity $v sin i$ = 9 $\pm$ 2 km s$^{-1}$. We determined the atmospheric parameters: $T_{\rm {eff}}$ = 4500 K, log $g$ = 2.5, $\xi_{t}$ = 1.5 km s$^{-1}$, and [Fe/H] = 0.14 dex. The LTE abundance analysis shows that the star is Li-rich (log $\epsilon$(Li) = 2.5$\pm$0.15), but with essentially normal C, N, and O, and metal abundances. Spectral synthesis of molecular CN lines yields the carbon isotopic ratio $^{12}$C/$^{13}$C = 9 $\pm$3, a signature of post-main sequence evolution and dredge-up on the RGB. Analysis of the Li resonance line at 6707 \AA for different ratios $^{6}$Li/$^{7}$Li shows that the Li profile can be fitted best with a predicted profile for pure $^{7}$Li. Far-IR excess, large Li abundance, and rapid rotation suggest that a planet has been swallowed or, perhaps, that an instability in the RGB outer layers triggered a sudden enrichment of Li and caused mass-loss.Comment: To appear in AJ; 40 pages, 9 figure

Evidence of SARS-CoV-2 bacteriophage potential in human gut microbiota

Background: In previous studies we have shown that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replicates in vitro in bacterial growth medium, that the viral replication follows bacterial growth, and it is influenced by the administration of specific antibiotics. These observations are compatible with a 'bacteriophage-like' behaviour of SARS-CoV-2. Methods: We have further elaborated on these unusual findings and here we present the results of three different supplementary experiments: (1) an electron-microscope analysis of samples of bacteria obtained from a faecal sample of a subject positive to SARS-CoV-2; (2) mass spectrometric analysis of these cultures to assess the eventual de novo synthesis of SARS-CoV-2 spike protein; (3) sequencing of SARS-CoV-2 collected from plaques obtained from two different gut microbial bacteria inoculated with supernatant from faecal microbiota of an individual positive to SARS-CoV-2. Results: Immuno-labelling with Anti-SARS-CoV-2 nucleocapsid protein antibody confirmed presence of SARS-CoV-2 both outside and inside bacteria. De novo synthesis of SARS-CoV-2 spike protein was observed, as evidence that SARS-CoV-2 RNA is translated in the bacterial cultures. In addition, phage-like plaques were spotted on faecal bacteria cultures after inoculation with supernatant from faecal microbiota of an individual positive to SARS-CoV-2. Bioinformatic analyses on the reads obtained by sequencing RNA extracted from the plaques revealed nucleic acid polymorphisms, suggesting different replication environment in the two bacterial cultures. Conclusions: Based on these results we conclude that, in addition to its well-documented interactions with eukaryotic cells, SARS-CoV-2 may act as a bacteriophage when interacting with at least two bacterial species known to be present in the human microbiota. If the hypothesis proposed, i.e., that under certain conditions SARS-CoV-2 may multiply at the expense of human gut bacteria, is further substantiated, it would drastically change the model of acting and infecting of SARS-CoV-2, and most likely that of other human pathogenic viruses

Spectropolarimetry of R Coronae Borealis in 1998--2003: Discovery of Transient Polarization at Maximum Brightness

We present an extended optical spectropolarimetry of R CrB from 1998 January to 2003 September. The polarization was almost constant in the phase of maximum brightness, being consistent with past observations. We detected, however, temporal changes of polarization ($\sim 0.5$ %) in 2001 March and August, which were the first detection of large polarization variability in R CrB near maximum brightness. The amplitude and the position angle of the `transient polarization' were almost constant with wavelength in both two events. There was a difference by about 20 degrees in the position angle between the two events. Each event could be explained by light scattering due to short-lived dust puff occasionally ejected off the line of sight. The flatness of the polarization against the wavelength suggests that the scatterer is a mixture of dust grains having various sizes. The rapid growth and fading of the transient polarization favors the phenomenological model of dust formation near the stellar photosphere (e.g., within two stellar radii) proposed for the time evolution of brightness and chromospheric emission lines during deeply declining periods, although the fading timescale can hardly be explained by a simple dispersal of expanding dust puff with a velocity of $\sim 200-350$ km s $^{-1}$. Higher expansion velocity or some mechanism to destroy the dust grains should be needed.Comment: 22 pages, 10 figures, accepted for publication in A