Methanol Masers as Tracers of Circumstellar Disks

We show that in many methanol maser sources the masers are located in lines, with a velocity gradient along them which suggests that the masers are situated in edge-on circumstellar, or protoplanetary, disks. We present VLBI observations of the methanol maser source G309.92+0.48, in the 12.2 GHz transition, which confirm previous observations that the masers in this source lie along a line. We show that such sources are not only linear in space but, in many cases, also have a linear velocity gradient. We then model these and other data in both the 6.7 GHz and the 12.2 GHz transition from a number of star formation regions, and show that the observed spatial and velocity distribution of methanol masers, and the derived Keplerian masses, are consistent with a circumstellar disk rotating around an OB star. We consider this and other hypotheses, and conclude that about half of these methanol masers are probably located in edge-on circumstellar disks around young stars. This is of particular significance for studies of circumstellar disks because of the detailed velocity information available from the masers.Comment: 38 pages, 13 figures accepted by Ap

Pair Creation and an X-ray Free Electron Laser

Using a quantum kinetic equation coupled to Maxwell's equation we study the possibility that focused beams at proposed X-ray free electron laser facilities can generate electric field strengths large enough to cause spontaneous electron-positron pair production from the QED vacuum. Our approach yields the time and momentum dependence of the single particle distribution function. Under conditions reckoned achievable at planned facilities, repeated cycles of particle creation and annihilation take place in tune with the laser frequency. However, the peak particle number density is insensitive to this frequency and one can anticipate the production of a few hundred particle pairs per laser period. Field-current feedback and quantum statistical effects are small and can be neglected in this application of non-equilibrium quantum mean field theory.Comment: 4 pages, LaTeX2

Target Selection for the SDSS-IV APOGEE-2 Survey

APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing roughly 300,000 stars across the entire sky. It is the successor to APOGEE and is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding upon APOGEE's goals of addressing critical questions of stellar astrophysics, stellar populations, and Galactic chemodynamical evolution using (1) an enhanced set of target types and (2) a second spectrograph at Las Campanas Observatory in Chile. APOGEE-2 is targeting red giant branch (RGB) and red clump (RC) stars, RR Lyrae, low-mass dwarf stars, young stellar objects, and numerous other Milky Way and Local Group sources across the entire sky from both hemispheres. In this paper, we describe the APOGEE-2 observational design, target selection catalogs and algorithms, and the targeting-related documentation included in the SDSS data releases.Comment: 19 pages, 6 figures. Accepted to A

The Close Binary Fraction as a Function of Stellar Parameters in APOGEE:A Strong Anti-Correlation With α Abundances

We use observations from the APOGEE survey to explore the relationship between stellar parameters and multiplicity. We combine high-resolution repeat spectroscopy for 41,363 dwarf and subgiant stars with abundance measurements from the APOGEE pipeline and distances and stellar parameters derived using \textit{Gaia} DR2 parallaxes from \cite{Sanders2018} to identify and characterise stellar multiples with periods below 30 years, corresponding to \drvm$\gtrsim$ 3 \kms, where \drvm\ is the maximum APOGEE-detected shift in the radial velocities. Chemical composition is responsible for most of the variation in the close binary fraction in our sample, with stellar parameters like mass and age playing a secondary role. In addition to the previously identified strong anti-correlation between the close binary fraction and \feh\, we find that high abundances of $\alpha$ elements also suppress multiplicity at most values of \feh\ sampled by APOGEE. The anti-correlation between $\alpha$ abundances and multiplicity is substantially steeper than that observed for Fe, suggesting C, O, and Si in the form of dust and ices dominate the opacity of primordial protostellar disks and their propensity for fragmentation via gravitational stability. Near \feh{} = 0 dex, the bias-corrected close binary fraction ($a<10$ au) decreases from $\approx$ 100 per cent at \alh{} = $-$0.2 dex to $\approx$ 15 per cent near \alh{} = 0.08 dex, with a suggestive turn-up to $\approx$20 per cent near \alh{} = 0.2. We conclude that the relationship between stellar multiplicity and chemical composition for sun-like dwarf stars in the field of the Milky Way is complex, and that this complexity should be accounted for in future studies of interacting binaries.Comment: 15 pages, 10 figures, plus appendices; accepted to MNRA

Multiplicity Statistics of Stars in the Sagittarius Dwarf Spheroidal Galaxy: Comparison to the Milky Way

We use time-resolved spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to examine the distribution of radial velocity (RV) variations in 249 stars identified as members of the Sagittarius (Sgr) dwarf spheroidal (dSph) galaxy by Hayes et al (2020). We select Milky Way (MW) stars that have stellar parameters ($log(g)$, $T_{eff}$, and $[Fe/H]$) similar to those of the Sagittarius members by means of a k-d tree of dimension 3. We find that the shape of the distribution of RV shifts in Sgr dSph stars is similar to that measured in their MW analogs, but the total fraction of RV variable stars in the Sgr dSph is larger by a factor of $\sim 2$. After ruling out other explanations for this difference, we conclude that the fraction of close binaries in the Sgr dSph is intrinsically higher than in the MW. We discuss the implications of this result for the physical processes leading to the formation of close binaries in dwarf spheroidal and spiral galaxies

Geometry of the Draco C1 Symbiotic Binary

Draco C1 is a known symbiotic binary star system composed of a carbon red giant and a hot, compact companion -- likely a white dwarf -- belonging to the Draco dwarf spheroidal galaxy. From near-infrared spectroscopic observations taken by the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2), part of Sloan Digital Sky Survey IV, we provide updated stellar parameters for the cool, giant component, and constrain the temperature and mass of the hot, compact companion. Prior measurements of the periodicity of the system, based on only a few epochs of radial velocity data or relatively short baseline photometric observations, were sufficient only to place lower limits on the orbital period ($P > 300$ days). For the first time, we report precise orbital parameters for the binary system: With 43 radial velocity measurements from APOGEE spanning an observational baseline of more than 3 years, we definitively derive the period of the system to be $1220.0^{+3.7}_{-3.5}$ days. Based on the newly derived orbital period and separation of the system, together with estimates of the radius of the red giant star, we find that the hot companion must be accreting matter from the dense wind of its evolved companion.Comment: 8 pages, 4 figures, 1 table. Accepted for publication in ApJ

Does Manual Therapy Provide Additional Benefit To Breathing Retraining In The Management Of Dysfunctional Breathing? A Randomised Controlled Trial

Purpose: Dysfunctional breathing (DB) is associated with an abnormal breathing pattern, unexplained breathlessness and significant patient morbidity. Treatment involves breathing retraining through respiratory physiotherapy. Recently, manual therapy (MT) has also been used, but no evidence exists to validate its use. This study sought to investigate whether MT produces additional benefit when compared with breathing retraining alone in patients with DB. Methods: Sixty subjects with primary DB were randomised into either breathing retraining (standard treatment; n¼30) or breathing retraining plus MT (intervention; n¼30) group. Both the groups received standardised respiratory physiotherapy, which included: DB education, breathing retraining, home regimen, and audio disc. Intervention group subjects additionally received MT following further assessment. Data from 57 subjects were analysed. Results: At baseline, standard treatment group subjects were statistically younger (41.7 + 13.5 versus 50.8 + 13.0 years; p¼0.001) with higher Nijmegen scores (38.6 + 9.5 versus 31.5 + 6.9; p¼0.001). However, no significant difference was found between the groups for primary outcome Nijmegen score (95% CI ( 1.1, 6.6) p¼0.162), or any secondary outcomes (Hospital Anxiety & Depression Score, spirometry or exercise tolerance). Conclusion: Breathing retraining is currently the mainstay of treatment for patients with DB. The results of this study suggest MT provides no additional benefit in this patient group.Juliana Burgess, Dr Robert Wilson, Royal Brompton & Harefield NHS Foundation Trust, and Dr Andy Jones fo

Complete Genome Sequences of Chop, DelRio, and GrandSlam, Three Gordonia Phages Isolated from Soil in Central Arkansas

Chop, DelRio, and GrandSlam are phage with a Siphoviridae morphotype isolated from soil in Arkansas using the host Gordonia terrae 3612. All three are temperate, and their genomes share at least 96% nucleotide identity. These phage are assigned to cluster DI based on gene content similarity to other sequenced actinobacteriophage