We present a multi-wavelength compilation of new and previously published photometry for 55 Galactic field RR Lyrae variables. Individual studies, spanning a time baseline of up to 30 years, are self-consistently phased to produce light curves in 10 photometric bands covering the wavelength range from 0.4 to 4.5 microns. Data smoothing via the GLOESS technique is described and applied to generate high-fidelity light curves, from which mean magnitudes, amplitudes, rise times, and times of minimum and maximum light are derived. 60,000 observations were acquired using the new robotic Three-hundred MilliMeter Telescope (TMMT), which was first deployed at the Carnegie Observatories in Pasadena, CA, and is now permanently installed and operating at Las Campanas Observatory in Chile. We provide a full description of the TMMT hardware, software, and data reduction pipeline. Archival photometry contributed approximately 31,000 observations. Photometric data are given in the standard Johnson UBV, Kron-Cousins RCIC, 2MASS JHK, and Spitzer [3.6] and [4.5] bandpasses.

APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing similar to 3. x. 10(5) 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 on 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 and red clump stars, RR Lyrae, lowmass 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.

We present a simple model for low-mass planet formation and subsequent evolution within 'transition' discs. We demonstrate quantitatively that the predicted and observed structures of such discs are prime birthsites of planets. Planet formation is likely to proceed through pebble accretion, should a planetary embryo (M greater than or similar to 10(-4) M-circle plus) form. Efficient pebble accretion is likely to be unavoidable in transition disc dust traps, as the dust particles required for pebble accretion are those which are most efficiently trapped in the transition disc dust trap. Rapid pebble accretion within the dust trap gives rise not only to low-mass planets, but also to a large accretion luminosity. This accretion luminosity is sufficient to heat the disc outside the gravitational influence of the planet and makes the disc locally baroclinic, and a source of vorticity. Using numerical simulations, we demonstrate that this source of vorticity can lead to the growth of a single large-scale vortex in similar to 100 orbits, which is capable of trapping particles. Finally, we suggest an evolutionary cycle: Planet formation proceeds through pebble accretion, followed by vortex formation and particle trapping in the vortex quenching the planetary accretion and thus removing the vorticity source. After the vortex is destroyed, the process can begin anew. This means transition discs should present with large-scale vortices for a significant fraction of their lifetimes, and remnant planets at large 10 au radii should be a common outcome of this cycle.

Zahn first put forward and calculated in detail the torque experienced by stars in a close binary systems due to dynamical tides. His widely used formula for stars with radiative envelopes and convective cores is expressed in terms of the stellar radius, even though the torque is actually being applied to the convective core at the core radius. This results in a large prefactor, which is very sensitive to the global properties of the star, that multiplies the torque. This large factor is compensated by a very small multiplicative factor, E2. Although this is mathematically accurate, depending on the application this can lead to significant errors. The problem is even more severe, since the calculation of E2 itself is non- trivial, and different authors have obtained inconsistent values of E2. Moreover, many codes ( e. g. BSE, STARTRACK, MESA) interpolate ( and sometimes extrapolate) a fit of E2 values to the stellar mass, often in regimes where this is not sound practice. We express the torque in an alternate form, cast in terms of parameters at the envelope- core boundary and a dimensionless coefficient, beta 2. Previous attempts to express the torque in such a form are either missing an important factor, which depends on the density profile of the star, or are not easy to implement. We show that beta 2 is almost independent of the properties of the star and its value is approximately unity. Our formula for the torque is simple to implement and avoids the difficulties associated with the classic expression.

We explore the consequences of dynamical evolution of field binaries composed of a primary black hole (BH) and aWolf-Rayet (WR) star in the context of gravitational wave (GW) source progenitors. We argue, from general considerations, that the spin of the WR-descendent BH will be maximal in a significant number of cases due to dynamical effects. In other cases, the spin should reflect the natal spin of the primary BH which is currently theoretically unconstrained. We argue that the three currently published LIGO systems (GW150914, GW151226, LVT151012) suggest that this spin is small. The resultant effective spin distribution of gravitational wave sources should thus be bi-model if this classic GW progenitor channel is indeed dominant. While this is consistent with the LIGO detections thus far, it is in contrast to the three best-measured high-mass X-ray binary (HMXB) systems. A comparison of the spin distribution of HMXBs and GW sources should ultimately reveal whether or not these systems arise from similar astrophysical channels.

Swope Supernova Survey 2017a (SSS17a) was discovered as the first optical counterpart to the gravitational wave event GW170817. Although its light curve on the timescale of weeks roughly matches the expected luminosity and red color of an r-process powered transient, the explanation for the blue emission from high velocity material over the first few days is not as clear. Here we show that the power-law evolution of the luminosity, temperature, and photospheric radius during these early times can be explained by cooling of shock-heated material around the neutron star merger. This heating is likely from the interaction of the gamma-ray burst jet with merger debris, the so-called cocoon emission. We summarize the properties of this emission and provide formulae that can be used to study future detections of shock cooling from merging neutron stars. This argues that optical transient surveys should search for such early, blue light if they wish to find off-axis gamma-ray bursts and double neutron star gravitational wave events as soon as possible after the merger.

We present a new method for calculating loops in cosmological perturbation theory. This method is based on approximating a ACDM-like cosmology as a finite sum of complex power-law universes. The decomposition is naturally achieved using an FFTLog algorithm. For power-law cosmologies, all loop integrals are formally equivalent to loop integrals of massless quantum field theory. These integrals have analytic solutions in terms of generalized hypergeometric functions. We provide explicit formulae for the one-loop and the two-loop power spectrum and the one-loop bispectrum. A chief advantage of our approach is that the difficult part of the calculation is cosmology independent, need be done only once, and can be recycled for any relevant predictions. Evaluation of standard loop diagrams then boils down to a simple matrix multiplication. We demonstrate the promise of this method for applications to higher multiplicity/loop correlation functions.

Stellar tidal streams provide an opportunity to study the motion and structure of the disrupting galaxy as well as the gravitational potential of its host. Streams around the Milky Way are especially promising as phase space positions of individual stars will he measured by ongoing or upcoming surveys. Nevertheless, it remains a challenge to accurately assess distances to stars farther than 10 kpc from the Sun, where we have the poorest knowledge of the Galaxy's mass distribution. To address this, we present observations of 32 candidate RR Lyrae stars in the Orphan tidal stream taken as part of the Spitzer Merger History and Shape of the Galactic Halo (SMHASH) program. The extremely tight correlation between the periods, luminosities, and metallicities of RR Lyrae variable stars in the Spitzer IRAC 3.6 mu m band allows the determination of precise distances to individual stars; the median statistical relative distance uncertainty to each RR Lyrae star is 2.5 per cent. By fitting orbits in an example potential, we obtain an upper limit on the mass of the Milky Way interior to 60 kpc of 5.6(-1.1)(+1.2) x 10(11) M-circle dot, bringing estimates based on the Orphan Stream in line with those using other tracers. The SMHASH data also resolve the stream in line-of-sight depth, allowing a new perspective on the internal structure of the disrupted dwarf galaxy. Comparing with N body models, we find that the progenitor had an initial dark halo mass of approximately 3,2 x 10(9) M-circle dot, placing the Orphan Stream's progenitor amongst the classical dwarf spheroidals.

We present nebular-phase spectra of the Type Ia supernova (SN Ia) 2016brx, a member of the 1991bg-like subclass that lies at the faint end of the SN Ia luminosity function. Nebular spectra are available for only three other 1991bg-like SNe, and their Co line centres are all within less than or similar to 500 km s(-1) of each other. In contrast, the nebular Co line centre of SN 2016brx is blue-shifted by >1500 km s(-1) compared to them and by approximate to 1200 km s(-1) compared to the rest frame. This is a significant shift relative to the narrow nebular line velocity dispersion of less than or similar to 2000 km s(-1) of these SNe. The large range of nebular line shifts implies that the Ni-56 in the ejecta of SN 1991bg-like events is off-centre by similar to 1000 km s(-1) rather than universally centrally confined as previously suggested. With the addition of SN 2016brx, the Co nebular line shapes of 1991bg-like objects appear to connect with the brighter SNe Ia that show double-peaked profiles, hinting at a continuous distribution of line profiles among SNe la. One class of models to produce both off-centre and bimodal Ni-56 distributions is collisions of white dwarfs with unequal and equal masses.