Detection of Near-IR CO Absorption Bands in R Coronae Borealis Stars

R Coronae Borealis (RCB) stars are hydrogen-deficient, carbon-rich pulsating post-AGB stars that experience massive irregular declines in brightness caused by circumstellar dust formation. The mechanism of dust formation around RCB stars is not well understood. It has been proposed that CO molecules play an important role in cooling the circumstellar gas so that dust may form. We report on a survey for CO in a sample of RCB stars. We obtained H- and K-band spectra including the first and second overtone CO bands for eight RCB stars, the RCB-like star, DY Per and the final-helium-flash star, FG Sge. The first and second overtone CO bands were detected in the cooler (T(eff)<6000 K) RCB stars, Z Umi, ES Aql, SV Sge and DY Per. The bands are not present in the warmer (T(eff)>6000 K) RCB stars, R CrB, RY Sgr, SU Tau, XX Cam. In addition, first overtone bands are seen in FG Sge, a final-helium-flash star that is in an RCB-like phase at present. Effective temperatures of the eight RCB stars range from 4000 to 7250 K. The observed photospheric CO absorption bands were compared to line-blanketed model spectra of RCB stars. As predicted by the models, the CO bands are strongest in the coolest RCB stars and not present in the warmest. No correlation was found between the presence or strength of the CO bands and dust formation activity in the stars.Comment: 13 oages, 3 figures, AJ in pres

Site identification in high-throughput RNA-protein interaction data

Motivation: Post-transcriptional and co-transcriptional regulation is a crucial link between genotype and phenotype. The central players are the RNA-binding proteins, and experimental technologies [such as cross-linking with immunoprecipitation-(CLIP-) and RIP-seq] for probing their activities have advanced rapidly over the course of the past decade. Statistically robust, flexible computational methods for binding site identification from high-throughput immunoprecipitation assays are largely lacking however.Results: We introduce a method for site identification which provides four key advantages over previous methods: (i) it can be applied on all variations of CLIP and RIP-seq technologies, (ii) it accurately models the underlying read-count distributions, (iii) it allows external covariates, such as transcript abundance (which we demonstrate is highly correlated with read count) to inform the site identification process and (iv) it allows for direct comparison of site usage across cell types or conditions. © The Author 2012. Published by Oxford University Press. All rights reserved

The L 98-59 System: Three Transiting, Terrestrial-size Planets Orbiting a Nearby M Dwarf

We report the Transiting Exoplanet Survey Satellite (TESS) discovery of three terrestrial-size planets transiting L 98-59 (TOI-175, TIC 307210830)—a bright M dwarf at a distance of 10.6 pc. Using the Gaia-measured distance and broadband photometry, we find that the host star is an M3 dwarf. Combined with the TESS transits from three sectors, the corresponding stellar parameters yield planet radii ranging from 0.8 R ⊕ to 1.6 R ⊕. All three planets have short orbital periods, ranging from 2.25 to 7.45 days with the outer pair just wide of a 2:1 period resonance. Diagnostic tests produced by the TESS Data Validation Report and the vetting package DAVE rule out common false-positive sources. These analyses, along with dedicated follow-up and the multiplicity of the system, lend confidence that the observed signals are caused by planets transiting L 98-59 and are not associated with other sources in the field. The L 98-59 system is interesting for a number of reasons: the host star is bright (V = 11.7 mag, K = 7.1 mag) and the planets are prime targets for further follow-up observations including precision radial-velocity mass measurements and future transit spectroscopy with the James Webb Space Telescope; the near-resonant configuration makes the system a laboratory to study planetary system dynamical evolution; and three planets of relatively similar size in the same system present an opportunity to study terrestrial planets where other variables (age, metallicity, etc.) can be held constant. L 98-59 will be observed in four more TESS sectors, which will provide a wealth of information on the three currently known planets and have the potential to reveal additional planets in the system

C3_3O IN THE CARBON STAR IRC+10216

Author Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721We report the detection of C$_3$O in the circumstellar envelope of IRC+10216. Five rotational lines of this molecule were observed at 2 and 3 mm using the Kitt Peak 12 m telescope of the Arizona Radio Observatory (ARO). The line profiles were U-shaped, indicating that the molecule is present in the outer shell with a source size $\geq$ 81.6''. The derived C$_3$O column density of 1x10$^{12}$ cm$^{-2}$ is two orders of magnitude larger than the value predicted by the most recent chemical model of IRC+10216 (Millar, Herbst \& Bettens 2000). C$_3$O is the sixth oxygen-bearing molecule that has been identified in IRC+10216, and our observations represent the second astronomical detection of C$_3$O

MILLIMETER-WAVE INVESTIGATION OF EVOLVED PLANETARY NEBULAE CHEMISTRY

Author Institution: Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721We report the detection of C$_2$H and c-C$_3$H$_2$ in a number of evolved planetary nebulae. C$_2$H has been detected in NGC 6720 (Ring Nebula), NGC 7293 (Helix Nebula), and NGC 6781 via the two hyperfine components of the N=1$\rightarrow$0, J=3/2$\rightarrow$1/2 transition near 87 GHz, as well as in M4-9 via the two spin-rotation components of the N=3$\rightarrow$2 transition near 262 Ghz. In the Helix Nebula, the J$_{Ka,Kc}$=1$_{2,0}\rightarrow$0$_{1,0}$ and 10$_{1,0}\rightarrow$9$_{2,0}$ transitions of c-C$_3$H$_2$ have been detected near 85 and 105 GHz, respectively. These detections suggest that the molecular complexity in evolved planetary nebulae is higher than previously thought. It appears that as planetary nebulae expand and age, many-atom molecules may be shielded from UV dissociation because they are contained in dense knots of gas and dust. Further investigation of the gas-phase chemistry of evolved planetary nebulae is being conducted using the Arizona Radio Observatory telescopes

A CHEMICAL AND DYNAMICAL MODEL FOR THE OXYGEN-RICH SUPERGIANT VY CMA

Author Institution: UNIVERSITY OF ARIZONA, STEWARD OBSERVATORY, ARIZONA RADIO OBSERVATORY, 933 N CHERRY AVENUE, TUCSON, AZ 85721VY Canis Majoris (VY CMa) is an oxygen-rich supergiant star that is loosing mass at a very high rate ($\sim2\times10^{-4}M_{\odot}yr^{-1}$). A source of OH, H$_2$O, and SiO maser emission, the circumstellar envelope was never thought to be abundant in molecules. Recent observations using the telescope facilities of the Arizona Radio Observatory (ARO) has shown that this source is the most chemically diverse O-rich envelope to date. Seventeen different species have now been found in VY CMa, including exotic compounds such as NaCl and PN. Six carbon-containing molecules have been identified, as well, including CS, HCO$^+$, and HNC. The line profiles vary dramatically from species to species. Modeling of the profiles indicates the presence of a spherical wind, a highly collimated blue-shifted outflow almost directly along the line of sight, and a poorly-collimated red-shifted expansion at a $\sim45^irc$ angle from the line of sight. This model agrees extremely well with Hubble Space Telescope infrared observations and atomic emission/absorption line data. Various chemistries exist in these regions. Sulfur-bearing species such as SO and SO$_2$ are abundant in the collimated outflows, for example, while SiO dominates the spherical wind. The carbon is almost equally shared between CO and HCN in all three regions. Details of this chemistry will be presented, as well as an interpretation of the dynamical structure of VY CMa