685 results match your criteria Astrophysical Journal[Journal]


Transition Probabilities of Co ii Weak Lines to the Ground and Low Metastable Levels.

Astrophys J 2018 ;238

National Institute of Standards and Technology, 100 Bureau Dr, Gaithersburg, MD 20899, USA;

New branching fraction (BF) measurements based primarily on data from a cross-dispersed echelle spectrometer are reported for 84 lines of Co ii. The BFs for 82 lines are converted to absolute atomic transition probabilities using radiative lifetimes from laser-induced fluorescence (LIF) measurements on 19 upper levels of the lines. A lifetime of 3. Read More

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http://dx.doi.org/10.3847/1538-4365/aac773DOI Listing
January 2018

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

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
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http://dx.doi.org/10.3847/1538-4357/aaa5a5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6398615PMC
February 2018
4 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

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

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

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

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

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

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
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http://dx.doi.org/10.3847/1538-4357/aadf83DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264787PMC
October 2018

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

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
1 Read

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
1 Read

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

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
1 Read

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
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http://dx.doi.org/10.3847/2041-8213/aad089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120679PMC
July 2018
2 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

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
Publisher Site
http://dx.doi.org/10.3847/1538-4357/aac3d7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120675PMC
June 2018
13 Reads

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
2 Reads

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
5 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

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

Is the gas-phase OH+HCO reaction a source of HCO in interstellar cold dark clouds? A kinetic, dynamic and modelling study.

Astrophys J 2017 Nov 14;850(1). Epub 2017 Nov 14.

Departamento de Química Física Aplicada (UAM), Unidad Asociada IFF-CSIC, Facultad de Ciencias C-XIV, Universidad Autónoma de Madrid, 28049, Madrid, Spain.

Chemical kinetics of neutral-neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T∼10-100K). Scarce kinetic information is currently available for this kind of reactions at T<200 K. In this work we use the CRESU (, which means Reaction Kinetics in a Uniform Supersonic Flow) technique to measure for the first time the rate coefficients () of the gas-phase OH+HCO reaction between 22 and 107 K. Read More

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http://dx.doi.org/10.3847/1538-4357/aa93d9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5988043PMC
November 2017
2 Reads

A Molecular-Line Study of the Interstellar Bullet Engine IRAS05506+2414.

Astrophys J 2017 Nov;850

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

We present interferometric and single-dish molecular line observations of the interstellar bullet-outflow source IRAS05506+2414, whose wide-angle bullet spray is similar to the Orion BN/KL explosive outflow and likely arises from an entirely different mechanism than the classical accretion-disk-driven bipolar flows in young stellar objects. The bullet-outflow source is associated with a large pseudo-disk and three molecular outflows - a high-velocity outflow (HVO), a medium-velocity outflow (MVO), and a slow, extended outflow (SEO). The size (mass) of the pseudo-disk is 10,350 AU×6,400 AU (0. Read More

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http://dx.doi.org/10.3847/1538-4357/aa9273DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5988044PMC
November 2017
2 Reads

First Detection of Interstellar SH.

Astrophys J Lett 2017 Dec;851

Laboratoire d'Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France.

We present the first detection of gas phase SH in the Horsehead, a moderately UV-irradiated nebula. This confirms the presence of doubly sulfuretted species in the interstellar medium and opens a new challenge for sulfur chemistry. The observed SH abundance is ~5×10, only a factor 4-6 lower than that of the widespread HS molecule. Read More

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http://dx.doi.org/10.3847/2041-8213/aaa01bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5975949PMC
December 2017
1 Read

First Laboratory Detection of Vibration-Rotation Transitions of CH and CH and Improved Measurement of their Rotational Transition Frequencies.

Astrophys J 2018 Apr 13;857(1). Epub 2018 Apr 13.

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

The long-searched C-H stretches of the fundamental ions CH and CH have been observed for the first time in the laboratory. For this, the state-dependent attachment of He atoms to these ions at cryogenic temperatures has been exploited to obtain high-resolution rovibrational data. In addition, the lowest rotational transitions of CH, CH and CD have been revisited and their rest frequency values improved substantially. Read More

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http://dx.doi.org/10.3847/1538-4357/aab36aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5975947PMC

The Role of Pickup Ion Dynamics Outside of the Heliopause in the Limit of Weak Pitch Angle Scattering: Implications for the Source of the Ribbon.

Astrophys J 2018 5;855(No 1). Epub 2018 Mar 5.

Southwest Research Institute, San Antonio, TX 78228, USA.

We present a new model of the () ribbon based on the secondary energetic neutral atom (ENA) mechanism, under the assumption that there is negligible pitch angle scattering of pickup ions (PUIs) outside the heliopause. Using the results of an MHD-plasma/kinetic-neutral simulation of the heliosphere, we generate PUIs in the outer heliosheath, solve their transport using guiding center theory, and compute ribbon ENA fluxes at 1 AU. We implement several aspects of the PUI dynamics, including (1) parallel motion along the local interstellar magnetic field (ISMF), (2) advective transport with the interstellar plasma, (3) the mirror force acting on PUIs propagating along the ISMF, and (4) betatron acceleration of PUIs as they are advected within an increasing magnetic field towards the heliopause. Read More

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http://dx.doi.org/10.3847/1538-4357/aaaf6dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5975221PMC

DETERMINING THE ELEMENTAL AND ISOTOPIC COMPOSITION OF THE PRESOLAR NEBULA FROM GENESIS DATA ANALYSIS: THE CASE OF OXYGEN.

Astrophys J Lett 2017 Dec 6;851(No 1). Epub 2017 Dec 6.

Department of Physics, CSUF, Fullerton CA 92831.

We compare element and isotopic fractionations measured in solar wind samples collected by NASA's Genesis mission with those predicted from models incorporating both the ponderomotive force in the chromosphere and conservation of the first adiabatic invariant in the low corona. Generally good agreement is found, suggesting that these factors are consistent with the process of solar wind fractionation. Based on bulk wind measurements, we also consider in more detail the isotopic and elemental abundances of O. Read More

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http://dx.doi.org/10.3847/2041-8213/aa9bf0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5893144PMC
December 2017
1 Read

STAR FORMATION AT = 2.481 IN THE LENSED GALAXY SDSS J1110+6459: STAR FORMATION DOWN TO 30 PARSEC SCALES.

Astrophys J Lett 2017 Jul 6;843(No 2). Epub 2017 Jul 6.

Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA.

We present measurements of the surface density of star formation, the star-forming clump luminosity function, and the clump size distribution function, for the lensed galaxy SGAS J111020.0+645950.8 at a redshift of =2. Read More

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http://dx.doi.org/10.3847/2041-8213/aa7516DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5890445PMC
July 2017
1 Read

CONSTRAINING RELATIVISTIC BOW SHOCK PROPERTIES IN ROTATION-POWERED MILLISECOND PULSAR BINARIES.

Astrophys J 2017 Apr 18;839(No 2). Epub 2017 Apr 18.

Department of Physics and Astronomy, Rice University, Houston, TX 77251, USA.

Multiwavelength followup of unidentified sources has vastly expanded the number of known galactic-field "black widow" and "redback" millisecond pulsar binaries. Focusing on their rotation-powered state, we interpret the radio to X-ray phenomenology in a consistent framework. We advocate the existence of two distinct modes differing in their intrabinary shock orientation, distinguished by the phase-centering of the double-peaked X-ray orbital modulation originating from mildly-relativistic Doppler boosting. Read More

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http://dx.doi.org/10.3847/1538-4357/aa69bfDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5890539PMC
April 2017
1 Read

SUN-TO-EARTH MHD SIMULATION OF THE 14 JULY 2000 "BASTILLE DAY" ERUPTION.

Astrophys J 2018 Mar 27;856(1). Epub 2018 Mar 27.

Predictive Science Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121, USA.

Solar eruptions are the main driver of space-weather disturbances at the Earth. Extreme events are of particular interest, not only because of the scientific challenges they pose, but also because of their possible societal consequences. Here we present a magnetohydrodynamic (MHD) simulation of the 14 July 2000 "Bastille Day" eruption, which produced a very strong geomagnetic storm. Read More

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http://dx.doi.org/10.3847/1538-4357/aab36dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5882495PMC
March 2018
1 Read

STRUCTURE IN THE 3D GALAXY DISTRIBUTION: III. FOURIER TRANSFORMING THE UNIVERSE: PHASE AND POWER SPECTRA.

Astrophys J 2017 Apr 12;839(1). Epub 2017 Apr 12.

Thermo Fisher Scientific, San Jose, CA.

We demonstrate the effectiveness of a relatively straightforward analysis of the complex 3D Fourier transform of galaxy coordinates derived from redshift surveys. Numerical demonstrations of this approach are carried out on a volume-limited sample of the Sloan Digital Sky Survey redshift survey. The direct unbinned transform yields a complex 3D data cube quite similar to that from the Fast Fourier Transform (FFT) of finely binned galaxy positions. Read More

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http://dx.doi.org/10.3847/1538-4357/aa692dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5882497PMC

RELATIVISTIC MR-MP ENERGY LEVELS FOR L-SHELL IONS OF SILICON.

Astrophys J Suppl Ser 2018 15;234. Epub 2018 Jan 15.

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

Level energies are reported for Si V, Si VI, Si VII, Si VIII, Si IX, Si X, Si XI and Si XII. The energies have been calculated with the relativistic Multi-Reference Møller-Plesset Perturbation Theory method and include valence and K-vacancy states with up to 5. The accuracy of the calculated level energies is established by comparison with the recommended data listed in the National Institute of Standards and Technology (NIST) on-line database. Read More

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http://dx.doi.org/10.3847/1538-4365/aa94d2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5846692PMC
January 2018

POLYCYCLIC AROMATIC HYDROCARBONS WITH STRAIGHT EDGES AND THE 7.6/6.2 AND 8.6/6.2 INTENSITY RATIOS IN REFLECTION NEBULAE.

Astrophys J 2018 16;854(No 2). Epub 2018 Feb 16.

Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7, Canada.

We have investigated the mid-infrared spectral characteristics of a series of polycyclic aromatic hydrocarbons (PAHs) with straight edges and containing an even or odd number of carbons using density functional theory (DFT). For several even and odd-carbon PAHs, the 8.6/6. Read More

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http://dx.doi.org/10.3847/1538-4357/aaa757DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835977PMC
February 2018
3 Reads

Modifying the Standard Disk Model for the Ultraviolet Spectral Analysis of Disk-dominated Cataclysmic Variables. I. The Novalikes MV Lyrae, BZ Camelopardalis, and V592 Cassiopeiae.

Astrophys J 2017 Sep 31;846(No 1). Epub 2017 Aug 31.

Henry A. Rowland Department of Phyiscs & Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA.

The standard disk is often inadequate to model disk-dominated cataclysmic variables (CVs) and generates a spectrum that is bluer than the observed UV spectra. X-ray observations of these systems reveal an optically thin boundary layer (BL) expected to appear as an inner hole in the disk. Consequently, we truncate the inner disk. Read More

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http://dx.doi.org/10.3847/1538-4357/aa7f71DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5809775PMC
September 2017

Heating and Cooling of Coronal Loops with Turbulent Suppression of Parallel Heat Conduction.

Astrophys J 2018 Jan 15;852(No 2). Epub 2018 Jan 15.

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

Using the "enthalpy-based thermal evolution of loops" (EBTEL) model, we investigate the hydrodynamics of the plasma in a flaring coronal loop in which heat conduction is limited by turbulent scattering of the electrons that transport the thermal heat flux. The EBTEL equations are solved analytically in each of the two (conduction-dominated and radiation-dominated) cooling phases. Comparison of the results with typical observed cooling times in solar flares shows that the turbulent mean free path lies in a range corresponding to a regime in which classical (collision-dominated) conduction plays at most a limited role. Read More

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http://dx.doi.org/10.3847/1538-4357/aa9f29DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5800319PMC
January 2018

Reconnection-Driven Magnetohydrodynamic Turbulence in a Simulated Coronal-Hole Jet.

Astrophys J 2017 Mar 9;837(No 2). Epub 2017 Mar 9.

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

Extreme-ultraviolet and X-ray jets occur frequently in magnetically open coronal holes on the Sun, especially at high solar latitudes. Some of these jets are observed by white-light coronagraphs as they propagate through the outer corona toward the inner heliosphere, and it has been proposed that they give rise to microstreams and torsional Alfvén waves detected in the solar wind. To predict and understand the signatures of coronal-hole jets, we have performed a detailed statistical analysis of such a jet simulated with an adaptively refined magnetohydrodynamics model. Read More

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http://dx.doi.org/10.3847/1538-4357/aa5cb9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5799884PMC
March 2017
1 Read

An Infrared Spectroscopic Study Toward the Formation of Alkylphosphonic Acids and Their Precursors in Extraterrestrial Environments.

Astrophys J Suppl Ser 2018 Jan 12;234(1). Epub 2018 Jan 12.

W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA;

The only known phosphorus-containing organic compounds of extraterrestrial origin, alkylphosphonic acids, were discovered in the Murchison meteorite and have accelerated the hypothesis that reduced oxidation states of phosphorus were delivered to early Earth and served as a prebiotic source of phosphorus. While previous studies looking into the formation of these alkylphosphonic acids have focused on the iron-nickel phosphide mineral schreibersite and phosphorous acid as a source of phosphorus, this work utilizes phosphine (PH), which has been discovered in the circumstellar envelope of IRC +10216, in the atmosphere of Jupiter and Saturn, and believed to be the phosphorus carrier in comet 67P/Churyumov-Gerasimenko. Phosphine ices prepared with interstellar molecules such as carbon dioxide, water, and methane were subjected to electron irradiation, which simulates the secondary electrons produced from galactic cosmic rays penetrating the ice, and probed using infrared spectroscopy to understand the possible formation of alkylphosphonic acids and their precursors on interstellar icy grains that could become incorporated into meteorites such as Murchison. Read More

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http://dx.doi.org/10.3847/1538-4365/aa9183DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6398957PMC
January 2018

Triggered Star Formation inside the Shell of a Wolf-Rayet Bubble as the Origin of the Solar System.

Astrophys J 2017 Dec 22;851(2). Epub 2017 Dec 22.

Department of Physics and Astronomy, Clemson University, Clemson, SC, 29634-0978, USA;

A critical constraint on solar system formation is the high Al/Al abundance ratio of 5 × 10 at the time of formation, which was about 17 times higher than the average Galactic ratio, while the Fe/Fe value was about 2 × 10, lower than the Galactic value. This challenges the assumption that a nearby supernova (SN) was responsible for the injection of these short-lived radionuclides into the early solar system. We show that this conundrum can be resolved if the solar system was formed by a triggered star formation at the edge of a Wolf-Rayet (W-R) bubble. Read More

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http://dx.doi.org/10.3847/1538-4357/aa992eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6430574PMC
December 2017
1 Read

Photochemistry of coronene in cosmic water ice analogs at different concentrations.

Astrophys J 2017 Oct;848(No 2)

NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035-1000, USA.

This work presents the photochemistry of ultraviolet (UV) irradiated coronene in water ices at 15 K, studied using mid-infrared Fourier transform (FTIR) spectroscopy for CH:HO at concentrations of (1:50), (1:150), (1:200), (1:300) and (1:400). Previous UV irradiation studies of anthracene:HO, pyrene:HO and benzo[ghi]perylene:HO ices at 15 K have shown that aromatic alcohols and ketones, as well as CO and HCO are formed at very low temperatures. Like-wise, here, in addition to the coronene cation, hydroxy-, keto-, and protonated coronene (coronene-H) are formed. Read More

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http://dx.doi.org/10.3847/1538-4357/aa8c71DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5688519PMC
October 2017

Accurate Frequency Determination of Vibration-Rotation and Rotational Transitions of SiH.

Astrophys J 2017 Jan;849

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

The fundamental SiH ion has been characterized in a collaborative work, utilizing a hollow-cathode-discharge laser-spectrometer and a cryogenic ion trap spectrometer. Twenty-three vibration-rotation transitions around 4.75 m have been detected with high accuracy. Read More

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http://dx.doi.org/10.3847/1538-4357/aa8fcaDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5683345PMC
January 2017

The Planetary Nebula Survey (HerPlaNS): A Comprehensive Dusty Photoionization Model of NGC6781.

Astrophys J Suppl Ser 2017 Aug 18;231(2). Epub 2017 Aug 18.

Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium.

We perform a comprehensive analysis of the planetary nebula (PN) NGC 6781 to investigate the physical conditions of each of its ionized, atomic, and molecular gas and dust components and the object's evolution, based on panchromatic observational data ranging from UV to radio. Empirical nebular elemental abundances, compared with theoretical predictions via nucleosynthesis models of asymptotic giant branch (AGB) stars, indicate that the progenitor is a solar-metallicity, 2.25-3. Read More

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http://dx.doi.org/10.3847/1538-4365/aa8175DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619666PMC
August 2017
3 Reads

X-Rays from the Location of the Double-humped Transient ASASSN-15lh.

Astrophys J 2017 Feb 6;836(1). Epub 2017 Feb 6.

Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA.

We present the detection of persistent soft X-ray radiation with ~ 10-10 erg s at the location of the extremely luminous, double-humped transient ASASSN-15lh as revealed by and . We interpret this finding in the context of observations from our multiwavelength campaign, which revealed the presence of weak narrow nebular emission features from the host-galaxy nucleus and clear differences with respect to superluminous supernova optical spectra. Significant UV flux variability on short timescales detected at the time of the rebrightening disfavors the shock interaction scenario as the source of energy powering the long-lived UV emission, while deep radio limits exclude the presence of relativistic jets propagating into a low-density environment. Read More

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http://dx.doi.org/10.3847/1538-4357/836/1/25DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619250PMC
February 2017
2 Reads

Probing the Cold Dust Emission in the AB Aur Disk: A Dust Trap in a Decaying Vortex?

Astrophys J Lett 2017 Sep 28;846(1). Epub 2017 Aug 28.

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

One serious challenge for planet formation is the rapid inward drift of pebble-sized dust particles in protoplanetary disks. Dust trapping at local maxima in the disk gas pressure has received much theoretical attention but still lacks observational support. The cold dust emission in the AB Aur disk forms an asymmetric ring at a radius of about 120 au, which is suggestive of dust trapping in a gas vortex. Read More

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http://dx.doi.org/10.3847/2041-8213/aa8558DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5609659PMC
September 2017
1 Read

Identification of PAH Isomeric Structure in Cosmic Dust Analogues: the AROMA setup.

Astrophys J 2017 Jul;843(1)

Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysique et Planétologie, 9 avenue du Colonel Roche, 31028 Toulouse Cedex 4 (France).

We developed a new analytical experimental setup called AROMA (Astrochemistry Research of Organics with Molecular Analyzer) that combines laser desorption/ionization techniques with ion trap mass spectrometry. We report here on the ability of the apparatus to detect aromatic species in complex materials of astrophysical interests and characterize their structures. A limit of detection of 100 femto-grams has been achieved using pure polycyclic aromatic hydrocarbon (PAH) samples, which corresponds to 2x10 molecules in the case of coronene (CH). Read More

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http://dx.doi.org/10.3847/1538-4357/aa73ddDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5564497PMC
July 2017
4 Reads

Exploring the SDSS Dataset with Linked Scatter Plots: I. EMP, CEMP, and CV Stars.

Astrophys J Suppl Ser 2017 Feb 9;228(2). Epub 2017 Feb 9.

NASA Ames Research Center, NASA Advanced Supercomputing Facility, Moffett Field, CA, 94035-1000, USA.

We present the results of a search for EMP, CEMP, and cataclysmic variable stars using a new exploration tool based on linked scatter plots (LSPs). Our approach is especially designed to work with very large spectrum data sets such as the SDSS, LAMOST, RAVE, and Gaia data sets and can be applied to stellar, galaxy, and quasar spectra. As a demonstration, we conduct a search for EMP, CEMP, and cataclysmic variable stars in the SDSS DR10 data set. Read More

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http://dx.doi.org/10.3847/1538-4365/228/2/19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5495198PMC
February 2017

Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C.

Astrophys J 2017 Feb 24;835(2). Epub 2017 Jan 24.

Space Radiation Laboratory, California Institute of Technology, 1200 E California Boulevard, MC 249-17, Pasadena, CA 91125, USA.

We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays ~40 keV. SN 2014C shows ordinary explosion parameters ( ~ 1. Read More

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http://dx.doi.org/10.3847/1538-4357/835/2/140DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5495200PMC
February 2017
1 Read

IMPROVED Cr II log( ) VALUES AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937.

Astrophys J Suppl Ser 2017 Jan 20;228(1). Epub 2017 Jan 20.

Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, USA.

New emission branching fraction (BF) measurements for 183 lines of the second spectrum of chromium (Cr II) and new radiative lifetime measurements from laser-induced fluorescence for 8 levels of Cr are reported. The goals of this study are to improve transition probability measurements in Cr II and reconcile solar and stellar Cr abundance values based on Cr I and Cr II lines. Eighteen spectra from three Fourier Transform Spectrometers supplemented with ultraviolet spectra from a high-resolution echelle spectrometer are used in the BF measurements. Read More

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http://stacks.iop.org/0067-0049/228/i=1/a=10?key=crossref.4f
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http://dx.doi.org/10.3847/1538-4365/228/1/10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5455792PMC
January 2017
3 Reads

The Photodissociation of HCN and HNC: Effects on the HNC/HCN Abundance Ratio in the Interstellar Medium.

Astrophys J 2017 Mar 21;838(1). Epub 2017 Mar 21.

Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, Cantoblanco 28049, Spain.

The impact of the photodissociation of HCN and HNC isomers is analyzed in different astrophysical environments. For this purpose, the individual photodissociation cross section of HCN and HNC isomers have been calculated in the 7-13.6 eV photon energy range for a temperature of 10 K. Read More

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http://dx.doi.org/10.3847/1538-4357/aa63eeDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5433558PMC

A Supernova at 50 pc: Effects on the Earth's Atmosphere and Biota.

Astrophys J 2017 May 12;840(2). Epub 2017 May 12.

Department of Science and Mathematics, MidAmerica Nazarene University, Olathe, KS 66062, USA.

Recent Fe results have suggested that the estimated distances of supernovae in the last few million years should be reduced from ∼100 to ∼50 pc. Two events or series of events are suggested, one about 2.7 million years to 1. Read More

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http://dx.doi.org/10.3847/1538-4357/aa6c57DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6052450PMC