724 results match your criteria Astrophysical Journal[Journal]


CARINAE'S DUSTY HOMUNCULUS NEBULA FROM NEAR-INFRARED TO SUBMILLIMETER WAVELENGTHS: MASS, COMPOSITION, AND EVIDENCE FOR FADING OPACITY.

Astrophys J 2017 Jun 15;842(2). Epub 2017 Jun 15.

Space Science & Technology Department, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, UK.

Infrared observations of the dusty, massive Homunculus Nebula around the luminous blue variable Carinae are crucial to characterize the mass-loss history and help constrain the mechanisms leading to the Great Eruption. We present the 2.4 - 670 m spectral energy distribution, constructed from legacy ISO observations and new spectroscopy obtained with the Using radiative transfer modeling, we find that the two best-fit dust models yield compositions which are consistent with CNO-processed material, with iron, pyroxene and other metal-rich silicates, corundum, and magnesium-iron sulfide in common. Read More

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http://dx.doi.org/10.3847/1538-4357/aa71b3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7323744PMC

Laboratory Observations of Ultra-Low Frequency Analogue Waves Driven by the Right-Hand Resonant Ion Beam Instability.

Astrophys J Lett 2020 Mar 27;891(1). Epub 2020 Feb 27.

Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.

The Right-Hand Resonant Instability (RHI) is one of several electromagnetic ion/ion beam instabilities responsible for the formation of parallel magnetized collisionless shocks and the generation of ultra-low frequency (ULF) waves in their foreshocks. This instability has been observed for the first time under foreshock-relevant conditions in the laboratory through the repeatable interaction of a preformed magnetized background plasma and a super-Alfvénic laser-produced plasma. This platform has enabled unprecedented volumetric measurements of waves generated by the RHI, revealing filamentary current structures in the transverse plane. Read More

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http://dx.doi.org/10.3847/2041-8213/ab75f4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7119471PMC

Beyond Optical Depth: Future Determination of Ionization History from the Cosmic Microwave Background.

Astrophys J 2020 Feb 30;889(2). Epub 2020 Jan 30.

JHU Department of Physics and Astronomy, 3701 San Martin Drive, Baltimore MD, 21218, USA.

We explore the fundamental limits to which reionization histories can be constrained using only large-scale cosmic microwave background (CMB) anisotropy measurements. The redshift distribution of the fractional ionization () affects the angular distribution of CMB polarization. We project constraints on the reionization history of the universe using low-noise full-sky temperature and E-mode measurements of the CMB. Read More

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http://dx.doi.org/10.3847/1538-4357/ab5fd5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7121248PMC
February 2020

Analytic Calculation of Covariance between Cosmological Parameters from Correlated Data Sets, with an Application to SPTpol.

Astrophys J 2020 Jan 31;888(1). Epub 2019 Dec 31.

Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.

Consistency checks of cosmological data sets are an important tool because they may suggest systematic errors or the type of modifications to ΛCDM necessary to resolve current tensions. In this work, we derive an analytic method for calculating the level of correlations between model parameters from two correlated cosmological data sets, which complements more computationally expensive simulations. This method is an extension of the Fisher analysis that assumes a Gaussian likelihood and a known data covariance matrix. Read More

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http://dx.doi.org/10.3847/1538-4357/ab54ccDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7121275PMC
January 2020

Modeling a Carrington-scale Stellar Superflare and Coronal Mass Ejection from .

Astrophys J 2019 Aug 30;880(2). Epub 2019 Jul 30.

Space Sciences Laboratory, University of California-Berkeley, Berkeley, CA 94720, USA.

Observations from the mission have revealed frequent superflares on young and active solar-like stars. Superflares result from the large-scale restructuring of stellar magnetic fields, and are associated with the eruption of coronal material (a coronal mass ejection, or CME) and energy release that can be orders of magnitude greater than those observed in the largest solar flares. These catastrophic events, if frequent, can significantly impact the potential habitability of terrestrial exoplanets through atmospheric erosion or intense radiation exposure at the surface. Read More

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http://dx.doi.org/10.3847/1538-4357/ab287eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7094772PMC

Particle-in-cell Simulations of the Whistler Heat-flux Instability in Solar Wind Conditions.

Astrophys J Lett 2019 3;882(1). Epub 2019 Sep 3.

Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium.

In collision-poor plasmas from space, e.g., solar wind or stellar outflows, the heat flux carried by the strahl or beaming electrons is expected to be regulated by the self-generated instabilities. Read More

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http://dx.doi.org/10.3847/2041-8213/ab398bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7008930PMC
September 2019
5.339 Impact Factor

Analysis of Small-scale Magnetic Flux Ropes Covering the Whole Mission.

Astrophys J 2019 13;881(1). Epub 2019 Aug 13.

Department of Space Science, The University of Alabama in Huntsville, Huntsville, AL 35805, USA.

Small-scale magnetic flux ropes in the solar wind have been studied for decades via both simulation and observation. Statistical analysis utilizing various in situ spacecraft measurements is the main observational approach, which helps investigate the generation and evolution of these small-scale structures. In this study, we extend the automated detection of small-scale flux ropes based on the Grad-Shafranov reconstruction to the complete data set of in situ measurements of the spacecraft. Read More

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http://dx.doi.org/10.3847/1538-4357/ab2ccfDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7005604PMC

Octahedron-based Projections as Intermediate Representations for Computer Imaging: TOAST, TEA, and More.

Astrophys J Suppl Ser 2019 Jan;240(2)

American Astronomical Society 1667 K St NW Suite 800 Washington, DC 20006, USA.

This paper defines and discusses a set of rectangular all-sky projections that have no singular points, notably the Tesselated Octahedral Adaptive Spherical Transformation (or TOAST) developed initially for the WorldWide Telescope. These have proven to be useful as intermediate representations for imaging data where the application transforms dynamically from a standardized internal format to a specific format (projection, scaling, orientation, etc.) requested by the user. Read More

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http://dx.doi.org/10.3847/1538-4365/aaf79eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999739PMC
January 2019

Turbulence in the Local Interstellar Medium and the Ribbon.

Astrophys J 2020 Jan;888(1)

Department of Mathematics and Statistics, University of Waikato, Hamilton, New Zealand.

The effects of turbulence in the very local interstellar medium (VLISM) have been proposed by Giacalone & Jokipii (2015) to be important in determining the structure of the () ribbon via particle trapping by magnetic mirroring. We further explore this effect by simulating the motion of charged particles in a turbulent magnetic field superposed on a large-scale mean field, which we consider to be either spatially-uniform or a draped field derived from a 3D MHD simulation. We find that the ribbon is not double-peaked, in contrast to Giacalone & Jokipii (2015). Read More

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http://dx.doi.org/10.3847/1538-4357/ab594dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999793PMC
January 2020

Understanding Heating in Active Region Cores through Machine Learning. I. Numerical Modeling and Predicted Observables.

Astrophys J 2019 Jul;880(1)

NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.

To adequately constrain the frequency of energy deposition in active region cores in the solar corona, systematic comparisons between detailed models and observational data are needed. In this paper, we describe a pipeline for forward modeling active region emission using magnetic field extrapolations and field-aligned hydrodynamic models. We use this pipeline to predict time-dependent emission from active region NOAA 1158 for low-, intermediate-, and high-frequency nanoflares. Read More

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http://dx.doi.org/10.3847/1538-4357/ab290cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6951256PMC

Comet C/2017 S3 (PanSTARRS): Outbursts and Disintegration.

Astrophys J Lett 2019 Oct;884(2)

Dept. of Climate and Space Sciences and Engineering, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143.

The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the SOlar and Heliospheric Observer (SOHO) satellite observed the hydrogen coma of comet C/2017 S3 (PanSTARRS) for the last month of its activity from 2018 July 4 to August 4 and what appears to have been its final disintegration just 11 days before its perihelion on August 15. The hydrogen coma indicated water production had a small outburst on July 8 at a heliocentric distance of 1.1AU and then a much larger one on July 20 at 0. Read More

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http://dx.doi.org/10.3847/2041-8213/ab4887DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6894164PMC
October 2019

Electron Energy Partition across Interplanetary Shocks. I. Methodology and Data Product.

Astrophys J Suppl Ser 2019 Jul;243(1)

University of California Berkeley, Space Sciences Laboratory, Berkeley, CA, USA.

Analyses of 15,314 electron velocity distribution functions (VDFs) within ±2 hr of 52 interplanetary (IP) shocks observed by the spacecraft near 1 au are introduced. The electron VDFs are fit to the sum of three model functions for the cold dense core, hot tenuous halo, and field-aligned beam/strahl component. The best results were found by modeling the core as either a bi-kappa or a symmetric (or asymmetric) bi-self-similar VDF, while both the halo and beam/strahl components were best fit to bi-kappa VDF. Read More

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http://dx.doi.org/10.3847/1538-4365/ab22bdDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6894189PMC

Simulations of ice chemistry in cometary nuclei.

Authors:
Robin T Garrod

Astrophys J 2019 Oct 14;884(1). Epub 2019 Oct 14.

Departments of Astronomy and Chemistry, University of Virginia, Charlottesville, VA 22904.

The first computational model of solid-phase chemistry in cometary nuclear ices is presented. An astrochemical kinetics model, , is adapted to trace the chemical evolution in multiple layers of cometary ice, over a representative period of 5 Gyr. Physical conditions are chosen appropriate for "cold storage" of the cometary nucleus in the outer Solar System, prior to any active phase. Read More

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http://dx.doi.org/10.3847/1538-4357/ab418eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6894404PMC
October 2019

A Kinematically Cold Structure of Candidate Young OB Stars toward the Anticenter.

Astrophys J 2019 Sep;883(1)

Department of Physics, Southern Connecticut State University, 501 Crescent Street, New Haven, CT 06515, USA.

We combine and DR2 catalogs to track star formation in the outskirts of our Galaxy. Using photometry, proper motions, and parallaxes we identify a structure of ~300 OB-type candidates located between 12 and 15 kpc from the Galactic center that are kinematically cold. The structure is located between = 120° and 200°, above the plane up to ~700 pc and below the plane to ~1 kpc. Read More

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http://dx.doi.org/10.3847/1538-4357/ab36b8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6839553PMC
September 2019

Gas Accretion within the Dust Cavity in AB Aur.

Astrophys J Lett 2019 Jul 2;879(1). Epub 2019 Jul 2.

Observatorio Astronómico Nacional (OAN, IGN), Calle Alfonso XII 3 E-28014 Madrid, Spain.

AB Aur is a Herbig Ae star hosting a well-known transitional disk. Because of its proximity and low inclination angle, it is an excellent object to study planet formation. Our goal is to investigate the chemistry and dynamics of the molecular gas component in the AB Aur disk, and its relation with the prominent horseshoe shape observed in continuum mm emission. Read More

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http://dx.doi.org/10.3847/2041-8213/ab289dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6699987PMC

Parallax of the Ribbon Indicates a Spatially-Retained Source.

Astrophys J 2019 Jul 12;879(2). Epub 2019 Jul 12.

Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899, USA.

In 2009, the ( discovered the existence of a narrow "ribbon" of intense energetic neutral atom (ENA) emission projecting approximately a circle in the sky. It is believed that the ribbon originates from outside of the heliopause in radial directions ( ) perpendicular to the local interstellar magnetic field (ISMF), , i.e. Read More

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http://dx.doi.org/10.3847/1538-4357/ab2633DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6687312PMC

Strong Scattering of ~keV Pickup Ions in the Local Interstellar Magnetic Field Draped Around Our Heliosphere: Implications for the Ribbon's Source and .

Astrophys J 2019 May 8;876(2). Epub 2019 May 8.

Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA.

The leading hypothesis for the origin of the "ribbon" of enhanced energetic neutral atoms (ENAs) from the outer heliosphere is the secondary ENA mechanism, whereby neutralized solar wind ions escape the heliosphere and, after several charge-exchange processes, may propagate back toward Earth primarily in directions perpendicular to the local interstellar magnetic field (ISMF). However, the physical processes governing the parent protons outside of the heliopause are still unconstrained. In this study, we compute the "spatial retention" model proposed by Schwadron & McComas (2013) in a 3D simulated heliosphere. Read More

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http://dx.doi.org/10.3847/1538-4357/ab15d6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6662649PMC

Multi-TeV Emission From the Vela Pulsar.

Astrophys J Lett 2018 Dec 11;869(1). Epub 2018 Dec 11.

North-West University, Private Bag X6001, Potchefstroom 2520, South Africa.

Pulsed emission from the Vela pulsar at energies above 3 TeV has recently been detected by the H.E.S. Read More

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http://dx.doi.org/10.3847/2041-8213/aaf3b2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6581446PMC
December 2018
9 Reads

SIFTING FOR SAPPHIRES: SYSTEMATIC SELECTION OF TIDAL DISRUPTION EVENTS IN iPTF.

Astrophys J Suppl Ser 2018 Oct 27;238(2). Epub 2018 Sep 27.

Oskar Klein Centre, Department of Physics, Stockholm University, SE 106 91 Stockholm, Sweden.

We present results from a systematic selection of tidal disruption events (TDEs) in a wide-area (4800 deg), + band, Intermediate Palomar Transient Factory (iPTF) experiment. Our selection targets typical optically-selected TDEs: bright (>60% flux increase) and blue transients residing in the center of red galaxies. Using photometric selection criteria to down-select from a total of 493 nuclear transients to a sample of 26 sources, we then use follow-up UV imaging with the Neil Gehrels Swift Telescope, ground-based optical spectroscopy, and light curve fitting to classify them as 14 Type Ia supernovae (SNe Ia), 9 highly variable active galactic nuclei (AGNs), 2 confirmed TDEs, and 1 potential core-collapse supernova. Read More

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http://dx.doi.org/10.3847/1538-4365/aad8b1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6544052PMC
October 2018
14 Reads

Cloud Coalescence: A Dynamical Instability Affecting Multiphase Environments.

Astrophys J Lett 2019 May 25;876(1). Epub 2019 Apr 25.

Department of Physics & Astronomy, University of Nevada, Las Vegas, NV, USA.

Mass and size distributions are the key characteristics of any astrophysical object, including the densest clumps comprising the cold phase of multiphase environments. In our recent papers, we showed how individual clouds of various sizes form and evolve in active galactic nuclei. In particular, we showed that large clouds undergo damped oscillations as a response to their formation process. Read More

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http://dx.doi.org/10.3847/2041-8213/ab12e8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6520992PMC
May 2019
2 Reads

Hints of the existence of C-rich massive evolved stars.

Astrophys J 2019 May;876(2)

Observatorio Astronómico Nacional (IGN), Alfonso XII, 28014 Madrid, Spain.

We aim at studying the properties of a particular type of evolved stars, the C-rich evolved stars with high expansion velocities. For this purpose we have focused on the two best studied objects within this group, IRC +10401 and AFGL 2233. We focused on determining their luminosity by studying their spectral energy distribution. Read More

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http://dx.doi.org/10.3847/1538-4357/ab133eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6520254PMC
May 2019
3 Reads

Extremely Cr- and Ti-rich presolar oxide grains in a primitive meteorite: Formation in rare types of supernovae and implications for the astrophysical context of solar system birth.

Astrophys J Lett 2018 Apr 18;856(2). Epub 2018 Mar 18.

Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Rd NW, Washington, DC 20015, USA;

We report the identification of 19 presolar oxide grains from the Orgueil CI meteorite with substantial enrichments in Cr, with Cr/Cr ratios ranging from 1.2 to 56 times the solar value. The most enriched grains also exhibit enrichments at mass 50, most likely due in part to Ti, but close-to-normal or depleted Cr/Cr ratios. Read More

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http://dx.doi.org/10.3847/2041-8213/aab61fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6491047PMC
April 2018
3 Reads

Climates of Warm Earth-like Planets I: 3-D Model Simulations.

Astrophys J Suppl Ser 2018 Dec 5;239(2). Epub 2018 Dec 5.

NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY, 10025, USA.

We present a large ensemble of simulations of an Earth-like world with increasing insolation and rotation rate. Unlike previous work utilizing idealized aquaplanet configurations we focus our simulations on modern Earth-like topography. The orbital period is the same as modern Earth, but with zero obliquity and eccentricity. Read More

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http://dx.doi.org/10.3847/1538-4365/aae9e1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6443379PMC
December 2018
3 Reads

Isotopic Dichotomy among Meteorites and Its Bearing on the Protoplanetary Disk.

Astrophys J 2018 Feb 23;854(2). Epub 2018 Feb 23.

Department of Geology, Trinity College, Dublin 2, Ireland.

Whole rock ΔO and nucleosynthetic isotopic variations for chromium, titanium, nickel, and molybdenum in meteorites define two isotopically distinct populations: carbonaceous chondrites (CCs) and some achondrites, pallasites, and irons in one and all other chondrites and differentiated meteorites in the other. Since differentiated bodies accreted 1-3 Myr before the chondrites, the isotopic dichotomy cannot be attributed to temporal variations in the disk. Instead, the two populations were most likely separated in space, plausibly by proto-Jupiter. Read More

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http://stacks.iop.org/0004-637X/854/i=2/a=164?key=crossref.e
Publisher Site
http://dx.doi.org/10.3847/1538-4357/aaa5a5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6398615PMC
February 2018
29 Reads

High-resolution SOFIA/EXES Spectroscopy of SO Gas in the Massive Young Stellar Object MonR2 IRS3: Implications for the Sulfur Budget.

Astrophys J Lett 2018 16;868(1). Epub 2018 Nov 16.

Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands.

Sulfur has been observed to be severely depleted in dense clouds leading to uncertainty in the molecules that contain it and the chemistry behind their evolution. Here, we aim to shed light on the sulfur chemistry in young stellar objects (YSOs) by using high-resolution infrared spectroscopy of absorption by the rovibrational band of SO obtained with the Echelon-Cross-Echelle Spectrograph on the Stratospheric Observatory for Infrared Astronomy. Using local thermodynamic equilibrium models we derive physical parameters for the SO gas in the massive YSO MonR2 IRS3. Read More

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http://dx.doi.org/10.3847/2041-8213/aaeda9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6376201PMC
November 2018
5 Reads

The Origins of Young Stars in the Direction of the Leading Arm of the Magellanic Stream: Abundances, Kinematics, and Orbits.

Astrophys J 2019 24;871(1). Epub 2019 Jan 24.

Key Lab of Optical Astronomy, National Astronomical Observatories, CAS, 20A Datun Road, Chaoyang District, 100012 Beijing, China.

We explore the origins of the young B-type stars found by Casetti-Dinescu et al. (2014) at the outskirts of the Milky-Way disk in the sky region of Leading Arm of the Magellanic Stream. High-resolution spectroscopic observations made with the MIKE instrument on the Magellan Clay 6. Read More

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http://dx.doi.org/10.3847/1538-4357/aaf560DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6376199PMC
January 2019
4 Reads

Thermal History of CB Chondrules and Cooling Rate Distributions of Ejecta Plumes.

Astrophys J Lett 2018 Mar 7;855(2). Epub 2018 Mar 7.

Physics, SUNY at Cortland, NY 13045, USA.

It has been proposed that some meteorites, CB and CH chondrites, contain material formed as a result of a protoplanetary collision during accretion. Their melt droplets (chondrules) and FeNi metal are proposed to have formed by evaporation and condensation in the resulting impact plume. We observe that the skeletal olivine (SO) chondrules in CB chondrites have a blebby texture and an enrichment in refractory elements not found in normal chondrules. Read More

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http://dx.doi.org/10.3847/2041-8213/aab15bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6350785PMC
March 2018
1 Read

Double-degenerate Carbon-Oxygen and Oxygen-Neon White Dwarf Mergers: A New Mechanism for Faint and Rapid Type Ia Supernovae.

Astrophys J 2018 Dec 19;869(2). Epub 2018 Dec 19.

Department of Physics, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02740, USA.

Type Ia supernovae (SNe Ia) originate from the thermonuclear explosion of carbon-oxygen white dwarfs (CO WDs), giving rise to luminous optical transients. A relatively common variety of subluminous SNe Ia events, referred to as SNe Iax, are believed to arise from the failed detonation of a CO WD. In this paper, we explore failed detonation SNe Ia in the context of the double-degenerate channel of merging WDs. Read More

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http://dx.doi.org/10.3847/1538-4357/aaedb7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6350549PMC
December 2018
1 Read

CLIMATE MODELING OF A POTENTIAL EXOVENUS.

Astrophys J 2018 Dec 11;869(1). Epub 2018 Dec 11.

NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.

The planetary mass and radius sensitivity of exoplanet discovery capabilities has reached into the terrestrial regime. The focus of such investigations is to search within the Habitable Zone where a modern Earth-like atmosphere may be a viable comparison. However, the detection bias of the transit and radial velocity methods lies close to the host star where the received flux at the planet may push the atmosphere into a runaway greenhouse state. Read More

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http://dx.doi.org/10.3847/1538-4357/aaec68DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6326386PMC
December 2018
1 Read

TOWARD AN UNDERSTANDING OF GRB PROMPT EMISSION MECHANISM: II. PATTERNS OF PEAK ENERGY EVOLUTION AND THEIR CONNECTION TO SPECTRAL LAGS.

Astrophys J 2018 Dec 14;869(2). Epub 2018 Dec 14.

Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.

The prompt emission phase of gamma-ray bursts (GRBs) exhibits two distinct patterns of the peak-energy ( ) evolution; i.e., time-resolved spectral analyses of spectra of broad pulses reveal (1) "hard-to-soft" and (2) "flux-tracking" patterns of evolution in time, the physical origin of which still remains not well understood. Read More

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http://dx.doi.org/10.3847/1538-4357/aaeb30DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7250241PMC
December 2018

Reduction of Thermal Conductive Flux by Non-local Effects in the Presence of Turbulent Scattering.

Astrophys J 2018 Sep 21;865(1). Epub 2018 Sep 21.

Department of Physics & Astronomy, Western Kentucky University, Bowling Green, KY 42101, USA;

The heat flux in a plasma is determined by the degree of anisotropy in the particle distribution function, which is in turn driven by gradients in the ambient density and temperature. When the mean free path at the thermal speed is substantially smaller than the scale length associated with the temperature variation, the heat flux simply depends on the local value of the temperature gradient. However, when the temperature scale length and mean free path are comparable, heat conduction becomes substantially non-local in character: the magnitude of the heat flux now depends on the overall temperature profile and is generally smaller than the locally determined value. Read More

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http://dx.doi.org/10.3847/1538-4357/aad961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288677PMC
September 2018
1 Read

Accurate Rotational Rest Frequencies for Ammonium Ion Isotopologues.

Astrophys J 2018 Oct;866(2)

I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany.

We report rest frequencies for rotational transitions of the deuterated ammonium isotopologues NHD, and , measured in a cryogenic ion trap machine. For the symmetric tops NHD and one and three transitions are detected, respectively, and five transitions are detected for the asymmetric top . While the lowest frequency transition of NHD was already known in the laboratory and space, this work enables the future radio astronomical detection of the two other isotopologues. Read More

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http://stacks.iop.org/0004-637X/866/i=2/a=158?key=crossref.e
Publisher Site
http://dx.doi.org/10.3847/1538-4357/aadf83DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264787PMC
October 2018
2 Reads

Identification of Multiple Hard X-Ray Sources in Solar Flares: A Bayesian Analysis of the 2002 February 20 Event.

Astrophys J 2018 Jul 24;862(1). Epub 2018 Jul 24.

Dipartimento di Matematica, Università di Genova, via Dodecaneso 35, I-16146 Genova, Italy.

The hard X-ray emission in a solar flare is typically characterized by a number of discrete sources, each with its own spectral, temporal, and spatial variability. Establishing the relationship among these sources is critical to determining the role of each in the energy release and transport processes that occur within the flare. In this paper we present a novel method to identify and characterize each source of hard X-ray emission. Read More

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http://dx.doi.org/10.3847/1538-4357/aacc27DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6267985PMC
July 2018
3 Reads

Energy Deposition by Energetic Electrons in a Diffusive Collisional Transport Model.

Astrophys J 2018 2;862(2). Epub 2018 Aug 2.

School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.

A considerable fraction of the energy in a solar flare is released as suprathermal electrons; such electrons play a major role in energy deposition in the ambient atmosphere, and hence the atmospheric response to flare heating. Historically, the transport of these particles has been approximated through a deterministic approach in which first-order secular energy loss to electrons in the ambient target is treated as the dominant effect, with second-order diffusive terms (in both energy and angle) being generally either treated as a small correction or neglected. However, it has recently been pointed out that while neglect of diffusion in energy may indeed be negligible, diffusion in angle is of the same order as deterministic scattering and hence must be included. Read More

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http://dx.doi.org/10.3847/1538-4357/aaceaaDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237098PMC
August 2018
2 Reads

In-situ Star Formation in the Outskirts of the Large Magellanic Cloud: DR2 Confirmation.

Astrophys J 2018 Jul;862(1)

Astronomy Department, Yale University, 46 Hillhouse Avenue, New Haven, CT 06511, USA.

We explore the data release 2 (DR2) proper motions of six young, main-sequence stars, members of the Large Magellanic Cloud (LMC) reported by Moni Bidin et al. These stars are located in the outskirts of the disk, between 7° and 13° from the LMC's center where there is very low H I content. DR2 proper motions confirm that four stars formed locally, in situ, while two are consistent with being expelled via dynamical interactions from inner, more gas-rich regions of the LMC. Read More

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http://dx.doi.org/10.3847/2041-8213/aad183DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6208156PMC
July 2018
3 Reads

GALAXY STRUCTURE, STELLAR POPULATIONS, AND STAR FORMATION QUENCHING AT 0.6 ≲ ≲ 1.2.

Astrophys J 2018 Nov;867(2)

Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstrasse 12-14, 69120 Heidelberg, Germany.

We use both photometric and spectroscopic data from the to explore the relationships among 4000 Å break (D4000) strength, colors, stellar masses, and morphology, in a sample of 352 galaxies with log(/) > 9.44 at 0.6 ≲ ≲ 1. Read More

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http://dx.doi.org/10.3847/1538-4357/aae488DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999741PMC
November 2018

RELATIVISTIC MR-MP ENERGY LEVELS FOR L-SHELL IONS OF SULFUR AND ARGON.

Astrophys J Suppl Ser 2018 Oct 23;238(2). Epub 2018 Oct 23.

Physics Division, LLNL, P.O. Box 808, Livermore, CA 94551, USA.

Calculated level energies for valence and K-vacancy states are provided for the ion series S VII - S XIV and Ar IX - Ar XVI. The calculations were performed with the relativistic Multi-Reference Mxller-Plesset Perturbation Theory method (MR-MP). The data set includes all the level energies with configurations 12() , 12() , 12() , 12() , 2() and 2() , where 1 ≤ ≤ 8, ≤ 5 and ≤ 3. Read More

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http://dx.doi.org/10.3847/1538-4365/aae14eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6200352PMC
October 2018
1 Read

Formation and Destruction of SiS in Space.

Astrophys J 2018 Jul;862(1)

Instituto de Física Fundamental, CSIC, C/Serrano 123, E-28006 Madrid, Spain.

The presence of SiS in space seems to be restricted to a few selected types of astronomical environments. It is long known to be present in circumstellar envelopes around evolved stars and it has also been detected in a handful of star-forming regions with evidence of outflows, like Sgr B2, Orion KL and more recently L1157-B1. The kinetics of reactions involving SiS is very poorly known and here we revisit the chemistry of SiS in space by studying some potentially important reactions of formation and destruction of this molecule. Read More

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http://dx.doi.org/10.3847/1538-4357/aaccffDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6122588PMC
July 2018
3 Reads

Discovery of Interstellar Isocyanogen (CNCN): Further Evidence that Dicyanopolyynes are Abundant in Space.

Astrophys J Lett 2018 Jul 13;861(2). Epub 2018 Jul 13.

Instituto de Física Fundamental, CSIC, C/ Serrano 123, 28006 Madrid, Spain.

It is thought that dicyanopolyynes could be potentially abundant interstellar molecules, although their lack of dipole moment makes it impossible to detect them through radioastronomical techniques. Recently, the simplest member of this chemical family, cyanogen (NCCN), was indirectly probed for the first time in interstellar space through the detection of its protonated form toward the dense clouds L483 and TMC-1. Here we present a second firm evidence of the presence of NCCN in interstellar space, namely the detection of the metastable and polar isomer isocyanogen (CNCN). Read More

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http://stacks.iop.org/2041-8205/861/i=2/a=L22?key=crossref.e
Publisher Site
http://dx.doi.org/10.3847/2041-8213/aad089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120679PMC
July 2018
3 Reads

Stability of CHNCO in astronomical ices under energetic processing. A laboratory study.

Astrophys J 2018 Jul 3;861(1). Epub 2018 Jul 3.

Instituto de Estructura de la Materia (IEM-CSIC), Serrano 121-123, 28006 Madrid, Spain.

Methyl isocyanate (CHNCO) was recently found in hot cores and suggested on comet 67P/CG. The incorporation of this molecule into astrochemical networks requires data on its formation and destruction. In this work, ices of pure CHNCO and of CHNCO(4-5%)/HO mixtures deposited at 20 K were irradiated with a UV D lamp (120-400 nm) and bombarded by 5 keV electrons to mimic the secondary electrons produced by cosmic rays (CRs). Read More

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http://dx.doi.org/10.3847/1538-4357/aac826DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120682PMC
July 2018
2 Reads

Binarity and Accretion in AGB Stars: HST/STIS Observations of UV Flickering in Y Gem.

Astrophys J 2018 Jun;860(2)

National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801.

Binarity is believed to dramatically affect the history and geometry of mass loss in AGB and post-AGB stars, but observational evidence of binarity is sorely lacking. As part of a project to search for hot binary companions to cool AGB stars using the GALEX archive, we discovered a late-M star, Y Gem, to be a source of strong and variable UV and X-ray emission. Here we report UV spectroscopic observations of Y Gem obtained with the that show strong flickering in the UV continuum on time-scales of ≲ 20 s, characteristic of an active accretion disk. Read More

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http://stacks.iop.org/0004-637X/860/i=2/a=105?key=crossref.6
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http://dx.doi.org/10.3847/1538-4357/aac3d7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120675PMC
June 2018
46 Reads

Variable Nature of Magnetically-Driven Ultra-Fast Outflows.

Astrophys J Lett 2018 Sep;864(2)

Research Center for Astronomy, Academy of Athens, Athens 11527, Greece.

Among a number of active galactic nuclei (AGNs) that drive ionized outflows in X-rays, a low-redshift ( = 0.184) quasar, PDS 456, is long known to exhibit one of the exemplary ultra-fast outflows (UFOs). However, the physical process of acceleration mechanism is yet to be definitively constrained. Read More

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http://dx.doi.org/10.3847/2041-8213/aadd10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999734PMC
September 2018

VALIDATING FORWARD MODELING AND INVERSIONS OF HELIOSEISMIC HOLOGRAPHY MEASUREMENTS.

Astrophys J 2018 Aug;863(1)

NorthWest Research Associates, 3380 Mitchell Lane, Boulder, CO 80301, USA.

Here we use synthetic data to explore the performance of forward models and inverse methods for helioseismic holography. Specifically, this work presents the first comprehensive test of inverse modeling for flows using lateral-vantage (deep-focus) holography. We derive sensitivity functions in the Born approximation. Read More

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http://dx.doi.org/10.3847/1538-4357/aacffdDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999794PMC

Thermal Jeans Fragmentation within ~ 1000 AU in OMC-1S.

Astrophys J 2018 Mar;855(1)

École Normale Supérieure de Lyon, CRAL, UMR CNRS 5574, Université Lyon I, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.

We present subarcsecond 1.3 mm continuum ALMA observations towards the Orion Molecular Cloud 1 South (OMC-1S) region, down to a spatial resolution of 74 AU, which reveal a total of 31 continuum sources. We also present subarcsecond 7 mm continuum VLA observations of the same region, which allow to further study fragmentation down to a spatial resolution of 40 AU. Read More

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http://dx.doi.org/10.3847/1538-4357/aaad03DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6071874PMC
March 2018
4 Reads

Young Accreting Compact Objects in M31: The Combined Power of , and .

Astrophys J 2018 Jul;862(1)

Department of Physics and Astronomy, Box 41051, Science Building, Texas Tech University, Lubbock, TX 79409, USA.

We present 15 high-mass X-ray binary (HMXB) candidates in the disk of M31 for which we are able to infer compact object type, spectral type of the donor star, and age using multiwavelength observations from , , and the . The hard X-ray colors and luminosities from permit the tentative classification of accreting X-ray binary systems by compact object type, distinguishing black hole from neutron star systems. We find hard-state black holes, pulsars, and non-magnetized neutron stars associated with optical point-source counterparts with similar frequency. Read More

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http://dx.doi.org/10.3847/1538-4357/aacb2aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6800711PMC

Discovery of the Ubiquitous Cation NS in Space Confirmed by Laboratory Spectroscopy.

Astrophys J Lett 2018 Jan;853

IRAP, Université de Toulouse, CNRS, UPS, CNES, Toulouse, France.

We report the detection in space of a new molecular species which has been characterized spectroscopically and fully identified from astrophysical data. The observations were carried out with the 30m IRAM telescopea. The molecule is ubiquitous as its =2→1 transition has been found in cold molecular clouds, prestellar cores, and shocks. Read More

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http://dx.doi.org/10.3847/2041-8213/aaa83aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6031291PMC
January 2018
6 Reads

The Maser Emitting Structure and Time Variability of the SIS Lines = 14 - 13 and 15 - 14 in IRC+10216.

Astrophys J 2018 Jun;860(2)

Departamento de Astrofísica Teórica, Instituto de Astronomía, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Mexico City (Mexico).

We present new high angular resolution interferometer observations of the = 0 = 14 - 13 and 15 - 14 SiS lines towards IRC+10216, carried out with CARMA and ALMA. The maps, with angular resolutions of reveal (1) an extended, roughly uniform, and weak emission with a size of (2) a component elongated approximately along the East-West direction peaking at at both sides of the central star, and (3) two blue- and red-shifted compact components peaking around to the NW of the star. We have modeled the emission with a 3D radiation transfer code finding that the observations cannot be explained only by thermal emission. Read More

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http://dx.doi.org/10.3847/1538-4357/aac5e3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6029660PMC
June 2018
1 Read

Carbon Chemistry in IRC+10216: Infrared Detection of Diacetylene.

Astrophys J 2018 Jan 9;852(2). Epub 2018 Jan 9.

Astronomy Dept., University of Texas, Austin, TX 78712 (USA).

We present the detection of CH for first time in the envelope of the C-rich AGB star IRC+10216 based on high spectral resolution mid-IR observations carried out with the Texas Echelon-cross-Echelle Spectrograph (TEXES) mounted on the Infrared Telescope Facility (IRTF). The obtained spectrum contains 24 narrow absorption features above the detection limit identified as lines of the ro-vibrational CH band The analysis of these lines through a ro-vibrational diagram indicates that the column density of CH is (2.4 1. Read More

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http://dx.doi.org/10.3847/1538-4357/aa9ee0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5988042PMC
January 2018
1 Read