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With the high tempo-spatial Interface Region Imaging Spectrograph 1330 Å images, we find that many bright structures are rooted in the light bridge of NOAA 12192, forming a light wall. The light wall is brighter than the surrounding areas, and the wall top is much brighter than the wall body. The New Vacuum Solar Telescope Hα and the Solar Dynamics Observatory 171 and 131 Å images are also used to study the light-wall properties. In 1330, 171, and 131 Å, the top of the wall has a higher emission, while in the Hα line, the wall-top emission is very low. The wall body corresponds to bright areas in 1330 Å and dark areas in the other lines. The top of the light wall moves upward and downward successively, performing oscillations in height. The deprojected mean height, amplitude, oscillation velocity, and the dominant period are determined to be 3.6 Mm, 0.9 Mm, 15.4 km s⁻¹, and 3.9 minutes, respectively. We interpret the oscillations of the light wall as the leakage of p-modes from below the photosphere. The constant brightness enhancement of the wall top implies the existence of some kind of atmospheric heating, e.g., via the persistent small-scale reconnection or the magneto-acoustic waves. In another series of 1330 Å images, we find that the wall top in the upward motion phase is significantly brighter than in the downward phase. This kind of oscillation may be powered by the energy released due to intermittent impulsive magnetic reconnection.

Solar active region (AR) 12192 of 2014 October hosts the largest sunspot group in 24 years. It is the most prolific flaring site of Cycle 24 so far, but surprisingly produced no coronal mass ejection (CME) from the core region during its disk passage. Here, we study the magnetic conditions that prevented eruption and the consequences that ensued. We find AR 12192 to be "big but mild"; its core region exhibits weaker non-potentiality, stronger overlying field, and smaller flare-related field changes compared to two other major flare-CME-productive ARs (11429 and 11158). These differences are present in the intensive-type indices (e.g., means) but generally not the extensive ones (e.g., totals). AR 12192's large amount of magnetic free energy does not translate into CME productivity. The unexpected behavior suggests that AR eruptiveness is limited by some relative measure of magnetic non-potentiality over the restriction of background field, and that confined flares may leave weaker photospheric and coronal imprints compared to their eruptive counterparts.

We demonstrate that high abundances of water vapor could have existed in extremely low metallicity (10⁻³ solar) partially shielded gas during the epoch of first metal enrichment of the interstellar medium of galaxies at high redshifts.

We present a spectroscopic redshift measurement of a very bright Lyman break galaxy at $z=7.7302\pm 0.0006$ using the Keck/Multi-Object Spectrometer for Infra-Red Exploration. The source was pre-selected photometrically in the EGS field as a robust z ∼ 8 candidate with H = 25.0 mag based on optical non-detections and a very red Spitzer/IRAC [3.6]–[4.5] broad-band color driven by high equivalent width [O iii]+Hβ line emission. The Lyα line is reliably detected at $6.1\sigma$ and shows an asymmetric profile as expected for a galaxy embedded in a relatively neutral intergalactic medium near the Planck peak of cosmic reionization. The line has a rest-frame equivalent width of ${\rm E}{{{\rm W}}_{0}}=21\pm 4$ Å and is extended with ${{V}_{{\rm FWHM}}}=360_{-70}^{+90}$ km s⁻¹. The source is perhaps the brightest and most massive z ∼ 8 Lyman break galaxy in the full CANDELS and BoRG/HIPPIES surveys, having already assembled ${{10}^{9.9\pm 0.2}}\;{{M}_{\odot }}$ of stars at only 650 Myr after the Big Bang. The spectroscopic redshift measurement sets a new redshift record for galaxies. This enables reliable constraints on the stellar mass, star formation rate, and formation epoch, as well as combined [O iii]+Hβ line equivalent widths. The redshift confirms that the IRAC [4.5] photometry is very likely dominated by line emission with EW₀([O iii]+Hβ)$\;=\;720_{-150}^{+180}$ Å. This detection thus adds to the evidence that extreme rest-frame optical emission lines are a ubiquitous feature of early galaxies promising very efficient spectroscopic follow-up in the future with infrared spectroscopy using the James Webb Space Telescope and, later, ELTs.

We present the first in situ observations of turbulence in the local interstellar magnetic field ${\boldsymbol{B}}$, measured by Voyager 1 from 2013.36 to 2014.64. The fluctuations of the components of ${\boldsymbol{B}}$, the rms of the fluctuations of the components of ${\boldsymbol{B}}$, and magnitude of ${\boldsymbol{B}}$ have a Kolmogorov ${{k}^{-5/3}}$ spectrum in the range from $4\times {{10}^{-6}}$ to $3\times {{10}^{-7}}$ Hz. The turbulence is compressible; the variance is primarily along the average magnetic field. The turbulence is weak, the ratio of the turbulent fluctuations to the average field being 0.023. A small linear increase in the azimuthal angle λ of ${\boldsymbol{B}}$ and a small linear decrease in the elevation angle δ were observed during the 468 day interval under consideration, which might be related to magnetic draping.

We report on monitoring observations of the TeV γ-ray binary HESS J0632+057, which were carried out to constrain the interaction between the Be circumstellar disk and the compact object of unknown nature and provide for the first time high-dispersion (R ≳ 50,000) optical spectra in the second half of the orbital cycle, from apastron through periastron. The Hα, Hβ, and Hγ line profiles are found to exhibit remarkable short-term variability for ∼1 month after the apastron (phase 0.6–0.7), whereas they show little variation near the periastron. These emission lines show "S-shaped" variations with a timescale of ∼150 days, which is about twice that reported previously. In contrast to the Balmer lines, no profile variability is seen in any Fe ii emission line. We estimate the radii of emitting regions of the Hα, Hβ, Hγ, and Fe ii emission lines to be ∼30, 11, 7, and 2 stellar radii (${{R}_{*}}$), respectively. The amplitudes of the line profile variations in different lines indicate that the interaction with the compact object affects the Be disk down to, at least, the radius of 7 ${{R}_{*}}$ after the apastron. This fact, together with little profile variability near the periastron, rules out the tidal force as the major cause of disk variability. Although this leaves the pulsar wind as the most likely candidate mechanism for disk variations, understanding the details of the interaction, particularly the mechanism for causing a large-scale disk disturbance after the apastron, remains an open question.

We report our discovery of orbitally modulated γ-ray emission from the black widow system PSR J1311−3430. We analyze the Fermi Large Area Telescope data during the off-pulse phase interval of the pulsar and find the orbital modulation signal at a ∼3σ confidence level. Further spectral analysis shows no significant differences for the spectra obtained during the bright and faint orbital phase ranges. A simple sinusoid-like function can describe the modulation. Given these properties, we suggest that the intrabinary γ-ray emission arises from the region close to the companion and the modulation is caused by the occultation of the emitting region by the companion, similar to that is seen in the transitional millisecond pulsar binary (MSP) PSR J1023+0038. Considering the X-ray detection of intrabinary shock emission from eclipsing MSP binaries recently reported, this discovery further suggests the general existence of intrabinary γ-ray emission from them.

A condensate cloud on Titan identified by its 220 cm⁻¹ far-infrared signature continues to undergo seasonal changes at both the north and south poles. In the north, the cloud, which extends from 55 N to the pole, has been gradually decreasing in emission intensity since the beginning of the Cassini mission with a half-life of 3.8 years. The cloud in the south did not appear until 2012 but its intensity has increased rapidly, doubling every year. The shape of the cloud at the south pole is very different from that in the north. Mapping in 2013 December showed that the condensate emission was confined to a ring with a maximum at 80 S. The ring was centered 4° from Titan's pole. The pattern of emission from stratospheric trace gases like nitriles and complex hydrocarbons (mapped in 2014 January) was also offset by 4°, but had a central peak at the pole and a secondary maximum in a ring at about 70 S with a minimum at 80 S. The shape of the gas emission distribution can be explained by abundances that are high at the atmospheric pole and diminish toward the equator, combined with correspondingly increasing temperatures. We discuss possible causes for the condensate ring. The present rapid build up of the condensate cloud at the south pole is likely to transition to a gradual decline from 2015 to 2016.

Recent hydrodynamical and nucleosynthesis studies have suggested binary mergers (NSMs) of double neutron star (and black-hole–neutron-star) systems as major sites of r-process elements in the Galaxy. It has been pointed out, however, that the estimated long lifetimes of neutron star binaries are in conflict with the presence of r-process-enhanced halo stars at metallicities as low as [Fe/H] $\sim -3$. To resolve this problem, we examine the role of NSMs in the early Galactic chemical evolution with the assumption that the Galactic halo was formed from merging sub-halos. We present simple models for the chemical evolution of sub-halos with total final stellar masses between ${{10}^{4}}\;{{M}_{\odot }}$ and $2\times {{10}^{8}}\;{{M}_{\odot }}$. The typical lifetimes of compact binaries are assumed to be 100 Myr (for 95% of their population) and 1 Myr (for 5%), according to recent binary population synthesis studies. The resulting metallicities of sub-halos and their ensemble are consistent with the observed mass–metallicity relation of dwarf galaxies in the Local Group and the metallicity distribution of the Galactic halo, respectively. We find that the r-process abundance ratios [r/Fe] start increasing at [Fe/H] $\leqslant -3$ if the star formation efficiencies are smaller for less-massive sub-halos. In addition, sub-solar [r/Fe] values (observed as [Ba/Fe] $\sim -1.5$ for [Fe/H] $\lt -3$) are explained by the contribution from short-lived (∼1 Myr) binaries. Our results indicate that NSMs may have contributed substantially to the r-process element abundances throughout the history of the Galaxy.

The collisionless dissipation of anisotropic Alfvénic turbulence is a promising candidate to solve the solar wind heating problem. Extensive studies examined the kinetic properties of Alfvén waves in simple Maxwellian or bi-Maxwellian plasmas. However, the observed electron velocity distribution functions in the solar wind are more complex. In this study, we analyze the properties of kinetic Alfvén waves (KAWs) in a plasma with two drifting electron populations. We numerically solve the linearized Maxwell–Vlasov equations and find that the damping rate and the proton–electron energy partition for KAWs are significantly modified in such plasmas, compared to plasmas without electron drifts. We suggest that electron drift is an important factor to take into account when considering the dissipation of Alfvénic turbulence in the solar wind or other $\beta \sim 1$ astrophysical plasmas.

Type Ia SN 2014J exploded in the nearby starburst galaxy M82 = NGC 3032 and was discovered at Earth about seven days later on 2014 January 21, reaching maximum light in V around 2014 February 5. SN 2014J is the closest SN Ia in at least four decades and probably many more. Recent Hubble Space Telescope/WFC3 imaging (2014 September 5 and 2015 February 2) of M82 in the vicinity of SN 2014J reveals a light echo at radii of about 0.6 arcsec from the supernova (SN; corresponding to about 12 pc at the distance of M82). Likely additional light echoes reside at a smaller radii of about 0.4 arcsec The major echo signal corresponds to echoing material about 330 pc in the foreground of SN 2014J and tends to be bright where pre-existing nebular structure in M82 is also bright. The second, likely echo corresponds to foreground distances of 80 pc in front of the SN. Even one year after maximum light, there are indications of further echo structures appearing at smaller radii, and future observations may show how extinction in these affect detected echo farther from the SN, which will affect interpretation of details of the three-dimensional structure of this gas and dust. Given enough data, we might even use these considerations to constrain the near-SN material's shadowing on distant echoing clouds, even without directly observing the foreground structure. This is in addition to echoes in the near future that might also reveal circumstellar structure around SN 2014J's progenitor star from direct imaging observations and other techniques.

Filament eruptions often lead to coronal mass ejections (CMEs), which can affect critical technological systems in space and on the ground when they interact with the geo-magnetosphere at high speeds. Therefore, it is important to investigate the acceleration mechanisms of CMEs in solar/space physics. Based on observations and simulations, the resistive magnetic reconnection and the ideal instability of magnetic flux ropes have been proposed to accelerate CMEs. However, it remains uncertain whether both of them play a comparable role during a particular eruption. It has been extremely difficult to separate their contributions as they often work in a close time sequence during one fast acceleration phase. Here we report an intriguing filament eruption event, which shows two apparently separated fast acceleration phases and provides us an excellent opportunity to address the issue. Through analyzing the correlations between velocity (acceleration) and soft (hard) X-ray profiles, we suggest that the instability and magnetic reconnection make a major contribution during the first and second fast acceleration phases, respectively. Further, we find that both processes have a comparable contribution to the filament acceleration in this event.

We present results from a high-resolution and large-scale hybrid (fluid electrons and particle-in-cell protons) two-dimensional numerical simulation of decaying turbulence. Two distinct spectral regions (separated by a smooth break at proton scales) develop with clear power-law scaling, each one occupying about a decade in wavenumbers. The simulation results simultaneously exhibit several properties of the observed solar wind fluctuations: spectral indices of the magnetic, kinetic, and residual energy spectra in the magnetohydrodynamic (MHD) inertial range along with a flattening of the electric field spectrum, an increase in magnetic compressibility, and a strong coupling of the cascade with the density and the parallel component of the magnetic fluctuations at sub-proton scales. Our findings support the interpretation that in the solar wind, large-scale MHD fluctuations naturally evolve beyond proton scales into a turbulent regime that is governed by the generalized Ohm's law.

We study the stellar angular momentum of thousands of galaxies in the Illustris cosmological simulation, which captures gravitational and gas dynamics within galaxies, as well as feedback from stars and black holes. We find that the angular momentum of the simulated galaxies matches observations well, and in particular two distinct relations are found for late-type versus early-type galaxies. The relation for late-type galaxies corresponds to the value expected from full conservation of the specific angular momentum generated by cosmological tidal torques. The relation for early-type galaxies corresponds to retention of only ∼30% of that, but we find that those early-type galaxies with low angular momentum at z = 0 nevertheless reside at high redshift on the late-type relation. Some of them abruptly lose angular momentum during major mergers. To gain further insight, we explore the scaling relations in simulations where the galaxy formation physics is modified with respect to the fiducial model. We find that galactic winds with high mass-loading factors are essential for obtaining the high angular momentum relation typical for late-type galaxies, while active galactic nucleus feedback largely operates in the opposite direction. Hence, feedback controls the stellar angular momentum of galaxies, and appears to be instrumental for establishing the Hubble sequence.

We investigate Venus Express observations of magnetic field fluctuations performed systematically in the solar wind at 0.72 Astronomical Units (AU), between 2007 and 2009, during the deep minimum of solar cycle 24. The power spectral densities (PSDs) of the magnetic field components have been computed for time intervals that satisfy the data integrity criteria and have been grouped according to the type of wind, fast and slow, defined for speeds larger and smaller, respectively, than 450 km s⁻¹. The PSDs show higher levels of power for the fast wind than for the slow. The spectral slopes estimated for all PSDs in the frequency range 0.005–0.1 Hz exhibit a normal distribution. The average value of the trace of the spectral matrix is −1.60 for fast solar wind and −1.65 for slow wind. Compared to the corresponding average slopes at 1 AU, the PSDs are shallower at 0.72 AU for slow wind conditions suggesting a steepening of the solar wind spectra between Venus and Earth. No significant time variation trend is observed for the spectral behavior of both the slow and fast wind.

In this Letter, we investigate how galaxy mass assembly mode depends on stellar mass M_* using a large sample of ∼10,000 low-redshift galaxies. Our galaxy sample is selected to have SDSS ${{R}_{90}}\gt 5\buildrel{\prime\prime}\over{.} 0$, which allows the measures of both the integrated and the central NUV–r color indices. We find that in the ${{M}_{*}}$–(NUV–r) green valley (GV), the ${{M}_{*}}\lt {{10}^{10}}\;{{M}_{\odot }}$ galaxies mostly have positive or flat color gradients, while most of the ${{M}_{*}}\gt {{10}^{10.5}}\;{{M}_{\odot }}$ galaxies have negative color gradients. When their central D_n4000 index values exceed 1.6, the ${{M}_{*}}\lt {{10}^{10.0}}\;{{M}_{\odot }}$ galaxies have moved to the UV red sequence, whereas a large fraction of the ${{M}_{*}}\gt {{10}^{10.5}}\;{{M}_{\odot }}$ galaxies still lie on the UV blue cloud or the GV region. We conclude that the main galaxy assembly mode is transiting from "the outside-in" mode to "the inside-out" mode at ${{M}_{*}}\lt {{10}^{10}}\;{{M}_{\odot }}$ and at ${{M}_{*}}\gt {{10}^{10.5}}\;{{M}_{\odot }}$. We argue that the physical origin of this is the compromise between the internal and the external processes that drive the star formation quenching in galaxies. These results can be checked with the upcoming large data produced by the ongoing integral field spectroscopic survey projects, such as CALIFA, MaNGA, and SAMI in the near future.

MHD discontinuities are ubiquitous in the solar wind and are often found at the origin of turbulence intermittency. They may also play a key role in the turbulence dissipation and heating of the solar wind. The tangential discontinuities (TDs) and rotational discontinuities (RDs) are the two most important types of discontinuities. Recently, the connection between turbulence intermittency and proton thermodynamics has been observationally investigated. Here, we present numerical results from a three-dimensional MHD simulation with pressure anisotropy and we define new methods for identifying and distinguishing TDs and RDs. Three statistical results obtained for the relative occurrence rates and heating effects are highlighted: (1) RDs tend to take up the majority of the discontinuities along with time; (2) the thermal states embedding TDs tend to be associated with extreme plasma parameters or instabilities while RDs do not; (3) TDs have a higher average T as well as perpendicular temperature ${{T}_{\bot }}$. The simulation shows that TDs and RDs evolve and contribute to solar wind heating differently. These results will improve our understanding of the mechanisms that generate discontinuities and cause plasma heating.

We report the discovery of an ultra-faint Milky Way satellite galaxy in the constellation of Pegasus. The concentration of stars was detected by applying our overdensity detection algorithm to the SDSS-DR 10 and confirmed with deeper photometry from the Dark Energy Camera at the 4 m Blanco telescope. Fitting model isochrones indicates that this object, Pegasus III, features an old and metal-poor stellar population ([Fe/H] ∼ –2.1) at a heliocentric distance of 205 ± 20 kpc. The new stellar system has an estimated half-light radius of ${{r}_{h}}=78_{-24}^{+30}$ pc and a total luminosity of ${{M}_{V}}\sim -4.1\pm 0.5$ that places it into the domain of dwarf galaxies on the size–luminosity plane. Pegasus III is spatially close to the MW satellite Pisces II. It is possible that the two might be physically associated, similar to the Leo IV and Leo V pair. Pegasus III is also well aligned with the Vast Polar Structure, which suggests a possible physical association.

We present the first photometric observations of trans-Neptunian objects (TNOs) taken with the Kepler space telescope, obtained during the course of the K2 ecliptic survey. Two faint objects have been monitored in specifically designed pixel masks that were centered on the stationary points of the objects, when their daily motion was the slowest. In the design of the experiment, only the apparent path of these objects were retrieved from the detectors, i.e., the costs in terms of Kepler pixels were minimized. Because of the faintness of the targets, we employ specific reduction techniques and co-added images. We measure rotational periods and amplitudes in the unfiltered Kepler band as follows: for (278361) 2007 JJ₄₃ and 2002 GV₃₁, we get ${{P}_{{\rm rot}}}=12.097$ hr and ${{P}_{{\rm rot}}}=29.2$ hr with 0.10 and 0.35 mag for the total amplitudes, respectively. Future space missions, such as TESS and PLATO, are not well suited to this kind of observation. Therefore, we encourage including the brightest TNOs around their stationary points in each observing campaign to exploit this unique capability of the K2 Mission—and therefore to provide unbiased rotational, shape, and albedo characteristics of many objects.