A significant percentage of OB stars are runaways, so we can expect a similar percentage of their evolved descendants to also be runaways. However, recognizing such stars presents its own set of challenges, as these older, more evolved stars will have drifted farther from their birthplace, and thus their velocities might not be obviously peculiar. Several Galactic red supergiants (RSGs) have be...

The luminous low-mass X-ray binary X2127+119 in the core of the globular cluster M15 (NGC 7078), which has an orbital period of 17 hours, has long been assumed to contain a donor star evolving off the main sequence, with a mass of 0.8 M⊙ (the main-sequence turn-off mass for M15). We present orbital-phase-resolved spectroscopy of X2127+119 in the Hα and He iλ6678 spectral region, obtained with t...

We report the discovery of an unbound hyper-velocity star, US 708, in the Milky Way halo, with a heliocentric radial velocity of +708±15 km s −1. A quantitative NLTE model atmosphere analysis of optical spectra obtained with LRIS at the Keck I telescope shows that US 708 is an extremely helium-rich (N He /N H =10) subluminous O type star with T eff = 44 500 K, log g = 5.23 at a distance of 19 k...

Venemans et al. found evidence for an overdensity of Lyα emission-line galaxies associated with the radio galaxy MRC 0316−257 at z = 3.13 indicating the presence of a massive protocluster. Here, we present the results of a search for additional star-forming galaxies and active galactic nucleus (AGN) within the protocluster. Narrow-band infrared imaging was used to select candidate [O III] emitt...

Star-topology decoupling is a recent search reduction method for forward state space search. The idea basically is to automatically identify a star factoring, then search only over the center component in the star, avoiding interleavings across leaf components. The framework can handle complex star topologies, yet prior work on decoupled search considered only factoring strategies identifying f...

We have used the Owens Valley Radio Observatory Millimeter Array to obtain a map of the J = (1→0) CO emission from the circumstellar shell around HD 179821, a highly evolved G-type star which will probably explode as a supernova in the next 10 5 yr. Very approximately, the gas presents as a circular ring with an inner diameter of 3. ′′ 95, an outer diameter of ∼12 ′′ and with azimuthal variatio...

I review the basic phenomenology and theory of the millisecond brightness oscillations observed during thermonuclear X-ray bursts from 13 of ≈ 70 accreting neutron stars in low-mass X-ray binaries. Compelling observations indicate that the oscillations are produced by surface brightness patterns on the rapidly rotating neutron stars. However, it remains to be understood (1) why the brightness p...

Star-Topology Decoupled Search has recently been introduced in classical planning. It splits the planning task into a set of components whose dependencies take a star structure, where one center component interacts with possibly many leaf components. Here we address a weakness of decoupled search, namely large leaf components, whose state space is enumerated explicitly. We propose a symbolic re...

We study subgroups of Z which possess group theoretic properties analogous to properties introduced by Menger (1924), Hurewicz (1925), Rothberger (1938), and Scheepers (1996). The studied properties were introduced independently by Kočinac and Okunev. We obtain purely combinatorial characterizations of these properties, and combine them with other techniques to solve several questions of Babink...