HI emission from the red giant Y CVn with the VLA and FAST

Imaging studies with the VLA have revealed HI emission associated with the extended circumstellar shells of red giants. We analyse the spectral map obtained on Y CVn, a J-type carbon star on the AGB. The HI line profiles can be interpreted with a model of a detached shell resulting from the interaction of a stellar outflow with the local interstellar medium. We reproduce the spectral map by introducing a distortion along a direction corresponding to the star's motion in space. We then use this fitting to simulate observations expected from the FAST radiotelescope, and discuss its potential for improving ourdescription of the outer regions of circumstellar shells.Comment: accepted for publication in RA

Discovery of a Shell of Neutral Atomic Hydrogen Surrounding the Carbon Star IRC+10216

We have used the Robert C. Byrd Green Bank Telescope to perform the most sensitive search to date for neutral atomic hydrogen (HI) in the circumstellar envelope (CSE) of the carbon star IRC+10216. Our observations have uncovered a low surface brightness HI shell of diameter ~1300" (~0.8 pc), centered on IRC+10216. The HI shell has an angular extent comparable to the far ultraviolet-emitting astrosphere of IRC+10216 previously detected with the GALEX satellite, and its kinematics are consistent with circumstellar matter that has been decelerated by the local interstellar medium. The shell appears to completely surround the star, but the highest HI column densities are measured along the leading edge of the shell, near the location of a previously identified bow shock. We estimate a total mass of atomic hydrogen associated with IRC+10216 CSE of M_HI~3x10e-3 M_sun. This is only a small fraction of the expected total mass of the CSE (<1%) and is consistent with the bulk of the stellar wind originating in molecular rather than atomic form, as expected for a cool star with an effective temperature T_eff<~2200 K. HI mapping of a 2 deg x 2 deg region surrounding IRC+10216 has also allowed us to characterize the line-of-sight interstellar emission in the region and has uncovered a link between diffuse FUV emission southwest of IRC+10216 and the Local Leo Cold Cloud.Comment: Accepted to MNRAS. 16 pages. A version with full resolution figures may be found at http://www.haystack.mit.edu/hay/staff/lmatthew/Matthews_etal_IRC+10216.pd

Weak local rules for planar octagonal tilings

We provide an effective characterization of the planar octagonal tilings which admit weak local rules. As a corollary, we show that they are all based on quadratic irrationalities, as conjectured by Thang Le in the 90s.Comment: 23 pages, 6 figure

Efficiency optimization for Atomic Frequency Comb storage

We study the efficiency of the Atomic Frequency Comb storage protocol. We show that for a given optical depth, the preparation procedure can be optimize to significantly improve the retrieval. Our prediction is well supported by the experimental implementation of the protocol in a \TMYAG crystal. We observe a net gain in efficiency from 10% to 17% by applying the optimized preparation procedure. In the perspective of high bandwidth storage, we investigate the protocol under different magnetic fields. We analyze the effect of the Zeeman and superhyperfine interaction

A new root-knot nematode, Meloidogyne moensi n. sp. (Nematoda : Meloidogynidae), parasitizing Robusta coffee from Western Highlands, Vietnam

A new root-knot nematode, parasitizing Robusta coffee in Dak Lak Province, Western Highlands of Vietnam, is described as Meloidogyne moensi n. sp. Morphological and molecular analyses demonstrated that this species differs clearly from other previously described root-knot nematodes. Morphologically, the new species is characterized by a swollen body of females with a small posterior protuberance that elongated from ovoid to saccate; perineal patterns with smooth striae, continuous and low dorsal arch; lateral lines marked as a faint space or linear depression at junction of the dorsal and ventral striate; distinct phasmids; perivulval region free of striae; visible and wide tail terminus surrounding by concentric circles of striae; medial lips of females in dumbbell-shaped and slightly raised above lateral lips; female stylet is normally straight with posteriorly sloping stylet knobs; lip region of second stage juvenile (J2) is not annulated; medial lips and labial disc of J2 formed dumbbell shape; lateral lips are large and triangular; tail of J2 is conoid with rounded unstriated tail tip; distinct phasmids and hyaline; dilated rectum. Meloidogyne moensi n. sp. is most similar to M. africana, M. ottersoni by prominent posterior protuberance. Results of molecular analysis of rDNA sequences including the D2-D3 expansion regions of 28S rDNA, COI, and partial COII/16S rRNA of mitochondrial DNA support for the new species status

Optical study of the anisotropic erbium spin flip-flop dynamics

We investigate the erbium flip-flop dynamics as a limiting factor of the electron spin lifetime and more generally as an indirect source of decoherence in rare-earth doped insulators. Despite the random isotropic arrangement of dopants in the host crystal, the dipolar interaction strongly depends on the magnetic field orientation following the strong anisotropy of the $g$-factor. In Er$^{3+}$:Y$_2$SiO$_5$, we observe by transient optical spectroscopy a three orders of magnitude variation of the erbium flip-flop rate (10ppm dopant concentration). The measurements in two different samples, with 10ppm and 50ppm concentrations, are well-supported by our analytic modeling of the dipolar coupling between identical spins with an anisotropic $g$-tensor. The model can be applied to other rare-earth doped materials. We extrapolate the calculation to Er$^{3+}$:CaWO$_4$, Er$^{3+}$:LiNbO$_3$ and Nd$^{3+}$:Y$_2$SiO$_5$ at different concentrations

HI Observations of the Asymptotic Giant Branch Star X Herculis: Discovery of an Extended Circumstellar Wake Superposed on a Compact High-Velocity Cloud

We report HI 21-cm line observations of the AGB star X Her obtained with the Green Bank Telescope (GBT) and the Very Large Array (VLA). We have detected HI emission totaling M_HI=2.1e-03 M_sun associated with the circumstellar envelope of the star. The HI distribution exhibits a head-tail morphology, similar to those previously observed around Mira and RS Cnc. The tail extends ~6.0' (0.24 pc) in the plane of the sky, along the direction of the star's space motion. We also detect a velocity gradient of ~6.5 km/s across the envelope, consistent with the HI tracing a turbulent wake that arises from the motion of a mass-losing star through the ISM. GBT mapping of a 2x2deg region around X Her reveals that the star lies (in projection) near the periphery of a much larger HI cloud that also exhibits signatures of ISM interaction. The properties of the cloud are consistent with those of compact high-velocity clouds. Using CO observations, we have placed an upper limit on its molecular gas content of N_H2<1.3e20 cm^-2. Although the distance to the cloud is poorly constrained, the probability of a chance coincidence in position, velocity, and apparent position angle of space motion between X Her and the cloud is extremely small, suggesting a possible physical association. However, the large HI mass of the cloud (~>2.4~M_sun) and the blueshift of its mean velocity relative to X Her are inconsistent with an origin tied directly to stellar ejection. (abridged)Comment: Accepted to AJ; 47 pages, 15 figures; version with full resolution figures available at http://www.haystack.mit.edu/hay/staff/lmatthew/matthews_XHer.pd

Bose-enhanced chemistry: Amplification of selectivity in the dissociation of molecular Bose-Einstein condensates

We study the photodissociation chemistry of a quantum degenerate gas of bosonic triatomic $ABC$ molecules, assuming two open rearrangement channels ($AB+C$ or $A+BC$). The equations of motion are equivalent to those of a parametric multimode laser, resulting in an exponential buildup of macroscopic mode populations. By exponentially amplifying a small differential in the single-particle rate-coefficients, Bose stimulation leads to a nearly complete selectivity of the collective $N$-body process, indicating a novel type of ultra-selective quantum degenerate chemistry.Comment: 5 pages, 3 figure

An HI Imaging Survey of Asymptotic Giant Branch Stars

We present an imaging study of a sample of eight asymptotic giant branch (AGB) stars in the HI 21-cm line. Using observations from the Very Large Array, we have unambiguously detected HI emission associated with the extended circumstellar envelopes of six of the targets. The detected HI masses range from M_HI ~ 0.015-0.055 M_sun. The HI morphologies and kinematics are diverse, but in all cases appear to be significantly influenced by the interaction between the circumstellar envelope and the surrounding medium. Four stars (RX Lep, Y UMa, Y CVn, and V1942 Sgr) are surrounded by detached HI shells ranging from 0.36 to 0.76 pc across. We interpret these shells as resulting from material entrained in a stellar outflow being abruptly slowed at a termination shock where it meets the local medium. RX Lep and TX Psc, two stars with moderately high space velocities (V_space>56 km/s), exhibit extended gaseous wakes (~0.3 and 0.6 pc in the plane of the sky), trailing their motion through space. The other detected star, R Peg, displays a peculiar "horseshoe-shaped" HI morphology with emission extended on scales up to ~1.7 pc; in this case, the circumstellar debris may have been distorted by transverse flows in the local interstellar medium. We briefly discuss our new results in the context of the entire sample of evolved stars that has been imaged in HI to date.Comment: Accepted to AJ. A version with full resolution figures is available at http://www.haystack.mit.edu/hay/staff/lmatthew/matthews_HI_survey.pd