 Subjects -> ASTRONOMY (Total: 94 journals)
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- The Formation and Eruption of a Sigmoidal Filament Driven by Rotating
Network Magnetic Fields- Authors: Jun Dai; Haisheng Ji, Leping Li, Jun Zhang, Huadong Chen
First page: 66
Abstract: We present the formation and eruption of a sigmoidal filament driven by rotating network magnetic
fields (RNFs) near the center of the solar disk, which was observed by the 1 m aperture New Vacuum
Solar Telescope at the Fuxian Solar Observatory on 2018 July 12. Counterclockwise RNFs twist two
small-scale filaments at their northeastern foot-point region, giving a rotation of nearly 200°
within about 140 minutes. The motion of the RNF has a tendency to accelerate at first and then
decelerate obviously, as the average rotation speed increased from 10 to 150° hr −1 , and then
slowed down to 50° hr −1 . Coalescence then occurs between filaments F1 and F2. Meanwhile the fine
structures in the southwestern region of the filament was involved in another interaction of
coalescence. The subsequent EUV brightening due to plasma heating is observed in the two interaction
regions. These interacting structures, including F1, F2 and the fine structures in the southwestern
re...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abcaf4
Issue No: Vol. 906, No. 2 (2021)
- Escaping Outflows from Disintegrating Exoplanets: Day-side versus
Night-side Escape- Authors: Wanying Kang; Feng Ding, Robin Wordsworth, Sara Seager
First page: 67
Abstract: Ultrahot disintegrating exoplanets have been detected with tails trailing behind and/or shooting
ahead of them. These tails are believed to be made of dust that are formed out of the supersonic
escaping flow that emanated from the permanent day side. Conserving angular momentum, this day-side
escape flux would lead the planet in orbit. In order to explain the trailing tails in observation,
radiation pressure, a repulsive force pushing the escape flow away from the host star, is considered
to be necessary. We here investigate whether escape could be deflected to head away from the host
star by the pressure gradient force. We demonstrate in an idealized framework that escape flux from
the night side can occur, and sometimes, can be even stronger than the escape from the day-side. The
night-side escape infers that escape flow could trail behind the planet in orbit by virtue of
angular momentum conservation even without radiation pressure. We also find analytical
approximations for ...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abcaa7
Issue No: Vol. 906, No. 2 (2021)
- Properties of Galaxies in Cosmic Filaments around the Virgo Cluster
- Authors: Youngdae Lee; Suk Kim, Soo-Chang Rey, Jiwon Chung
First page: 68
Abstract: We present the properties of galaxies in filaments around the Virgo cluster with respect to their
vertical distance from the filament spine using the NASA–Sloan Atlas catalog. The filaments are
mainly composed of low-mass, blue dwarf galaxies. We observe that the g − r color of galaxies
becomes blue and stellar mass decreases with increasing vertical filament distance. The galaxies
were divided into higher-mass ( ##IMG##
[http://ej.iop.org/images/0004-637X/906/2/68/apjabcaa0ieqn1.gif] {${\rm{log}}({h}^{2}{M}_{\ast
}/{M}_{\odot })\gt 8$} ) and lower-mass ( ##IMG##
[http://ej.iop.org/images/0004-637X/906/2/68/apjabcaa0ieqn2.gif] {${\rm{log}}({h}^{2}{M}_{\ast
}/{M}_{\odot })\leqslant 8$} ) subsamples. We also examine the distributions of g − r color, stellar
mass, H α equivalent width (EW(H α )), near-ultraviolet(NUV) − r color, and H i fraction of the two
subsamples with...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abcaa0
Issue No: Vol. 906, No. 2 (2021)
- Does the Disk in the Hard State of XTE J1752–223 Extend to the Innermost
Stable Circular Orbit'- Authors: Andrzej A. Zdziarski; Barbara De Marco, Michał Szanecki, Andrzej Niedźwiecki, Alex Markowitz
First page: 69
Abstract: The accreting black hole binary XTE J1752–223 was observed in a stable hard state for 25 days by the
Rossi X-ray Timing Explorer (RXTE), yielding a 3–140 keV spectrum of unprecedented statistical
quality. Its published model required a single-Comptonization spectrum reflecting from a disk close
to the innermost stable circular orbit. We studied that model as well as a number of other
single-Comptonization models (yielding similarly low inner radii), but found they violate a number
of basic physical constraints, e.g., their compactness is much above the maximum allowed by pair
equilibrium. We also studied the contemporaneous 0.55–6 keV spectrum from the Swift/X-ray Telescope
and found it well fitted by an absorbed power law and a disk blackbody with the innermost
temperature of 0.1 keV. The normalization of the disk blackbody corresponds to an inner radius of
≳20 gravitational radii and its temperature, to irradiation of the truncated disk by a hot inner
flow. We have also develo...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abca9c
Issue No: Vol. 906, No. 2 (2021)
- Torsional Alfvén Wave Cascade and Shocks Evolving in Solar Jets
- Authors: S. Vasheghani Farahani; S. M. Hejazi, M. R. Boroomand
First page: 70
Abstract: The aim of this study is to model the nature of nonlinear torsional magnetohydrodynamic waves
propagating in solar jets as they are elevated to the outer solar atmosphere. The contribution of
sequential processes to the transfer of energy is taken under consideration: the nonlinear cascade
and shock formation. Thus a straight magnetic cylinder embedded in a plasma with an initial magnetic
field and parallel flow to the cylinder axis is implemented. To resemble a jet where the oscillation
wavelength highly exceeds the radius, the second-order thin flux tube approximation proves adequate.
A Cohen–Kulsrud type equation is presented, and its solution highly depends on the parameter
presented in this study, which itself is constituted of various environmental and equilibrium
conditions that affect the perturbations of the variables as well as the nonlinear forces connected
to Alfvén wave propagation. The shock formation time of torsional waves is inversely proportional to
the density...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abca8c
Issue No: Vol. 906, No. 2 (2021)
- Dust Temperature of Compact Star-forming Galaxies at
z ∼ 1–3 in 3D-HST/CANDELS- Authors: Zuyi Chen; Guanwen Fang, Zesen Lin, Hongxin Zhang, Guangwen Chen, Xu Kong
First page: 71
Abstract: Recent simulation studies suggest that the compaction of star-forming galaxies (SFGs) at high
redshift might be a critical process, during which the central bulge is being rapidly built,
followed by quenching of the star formation. To explore dust properties of SFGs with compact
morphology, we investigate the dependence of dust temperature, T dust , on their size and star
formation activity, using a sample of massive SFGs with ##IMG##
[http://ej.iop.org/images/0004-637X/906/2/71/apjabc9bbieqn1.gif] {$\mathrm{log}({M}_{* }/{M}_{\odot
})\gt 10$} at1
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc9bb
Issue No: Vol. 906, No. 2 (2021)
- Statistical Properties of Superflares on Solar-type Stars: Results Using
All of the Kepler Primary
Mission Data- Authors: Soshi Okamoto; Yuta Notsu, Hiroyuki Maehara, Kosuke Namekata, Satoshi Honda, Kai Ikuta, Daisaku Nogami, Kazunari Shibata
First page: 72
Abstract: We report the latest statistical analyses of superflares on solar-type (G-type main-sequence;
effective temperature is 5100–6000 K) stars using all of the Kepler primary mission data and Gaia
Data Release 2 catalog. We updated the flare detection method from our previous studies by using a
high-pass filter to remove rotational variations caused by starspots. We also examined the sample
biases on the frequency of superflares, taking into account gyrochronology and flare detection
completeness. The sample sizes of solar-type and Sun-like stars (effective temperature is 5600–6000
K and rotation period is over 20 days in solar-type stars) are ∼4 and ∼12 times, respectively,
compared with Notsu et al. As a result, we found 2341 superflares on 265 solar-type stars and 26
superflares on 15 Sun-like stars; the former increased from 527 to 2341 and the latter from three to
26 events compared with our previous study. This enabled us to have a more well-established view on
the statistical ...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc8f5
Issue No: Vol. 906, No. 2 (2021)
- Observational Constraints on the Physical Properties of Interstellar Dust
in the Post-Planck Era- Authors: Brandon S. Hensley; B. T. Draine
First page: 73
Abstract: We present a synthesis of the astronomical observations constraining the wavelength-dependent
extinction, emission, and polarization from interstellar dust from UV to microwave wavelengths on
diffuse Galactic sight lines. Representative solid-phase abundances for those sight lines are also
derived. Given the sensitive new observations of polarized dust emission provided by the Planck
satellite, we place particular emphasis on dust polarimetry, including continuum polarized
extinction, polarization in the carbonaceous and silicate spectroscopic features, the
wavelength-dependent polarization fraction of the dust emission, and the connection between optical
polarized extinction and far-infrared polarized emission. Together, these constitute a set of
constraints that should be reproduced by models of dust in the diffuse interstellar medium.
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc8f1
Issue No: Vol. 906, No. 2 (2021)
- Cosmic Inference: Constraining Parameters with Observations and a Highly
Limited Number of
Simulations- Authors: Timur Takhtaganov; Zarija Lukić, Juliane Müller, Dmitriy Morozov
First page: 74
Abstract: Cosmological probes pose an inverse problem where the measurement result is obtained through
observations, and the objective is to infer values of model parameters that characterize the
underlying physical system—our universe, from these observations and theoretical forward-modeling.
The only way to accurately forward-model physical behavior on small scales is via expensive
numerical simulations, which are further “emulated” due to their high cost. Emulators are commonly
built with a set of simulations covering the parameter space with Latin hypercube sampling and an
interpolation procedure; the aim is to establish an approximately constant prediction error across
the hypercube. In this paper, we provide a description of a novel statistical framework for
obtaining accurate parameter constraints. The proposed framework uses multi-output Gaussian process
emulators that are adaptively constructed using Bayesian optimization methods with the goal of
maintaining a low emulation error...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc8ed
Issue No: Vol. 906, No. 2 (2021)
- Waves and Turbulence in the Very Local Interstellar Medium: From
Macroscales to Microscales- Authors: Federico Fraternale; Nikolai V. Pogorelov
First page: 75
Abstract: Voyager 1 ( V1 ) has been exploring the heliospheric boundary layer in the very local interstellar
medium (VLISM) since 2012 August. The measurements revealed a spectrum of fluctuations over a vast
range of space and timescales, but the nature of these fluctuations continues to be an intriguing
question. Numerous manifestations of turbulence cannot be explained using a single phenomenology.
Weak shocks and compressions are the prominent features of the VLISM. We use high-resolution (48 s)
measurements to perform a multiscale analysis of turbulence at V1 between the years of 2013.36 and
2019.0 (124–144 au from the Sun). On relatively large scales, wave trains of mixed
compressible/transverse nature with the correlation scale in the range of 15–100 days dominate the
spectrum of fluctuations. The observed magnetic field profiles are suggestive of a Burgers-like ( f
−2 ) turbulence phenomenology induced by solar activity. We demonstrate that the level of ...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc88a
Issue No: Vol. 906, No. 2 (2021)
- Multiple Stellar Populations along the Red Horizontal Branch and Red Clump
of Globular Clusters- Authors: E. Dondoglio; A. P. Milone, E. P. Lagioia, A. F. Marino, M. Tailo, G. Cordoni, S. Jang, M. Carlos
First page: 76
Abstract: We exploit multiband Hubble Space Telescope photometry to investigate multiple populations (MPs)
along the red horizontal branches (HBs) and red clumps of 14 metal-rich globular clusters (GCs),
including 12 Milky Way GCs and the Magellanic Cloud GCs NGC 1978 and NGC 416. Based on appropriate
two-color diagrams, we find that the fraction of first-generation (1G) stars in Galactic GCs
correlates with cluster mass, confirming previous results based on red-giant branch (RGB) stars.
Magellanic Cloud GCs show higher fractions of 1G stars than Galactic GCs with similar masses, thus
suggesting that the environment affects the MP phenomenon. We compared and combined our population
fractions based on the HB with previous estimates from the MS and RGB, and we used ground-based UBVI
photometry (available for NGC 104, NGC 5927, NGC 6366, and NGC 6838) to extend the investigation
over a wide field of view. All studied GCs are consistent with flat distributions of 1G and
second-generation (2G)...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc882
Issue No: Vol. 906, No. 2 (2021)
- New Horizons Observations of the Cosmic Optical Background
- Authors: Tod R. Lauer; Marc Postman, Harold A. Weaver, John R. Spencer, S. Alan Stern, Marc W. Buie, Daniel D. Durda, Carey M. Lisse, A. R. Poppe, Richard P. Binzel, Daniel T. Britt, Bonnie J. Buratti, Andrew F. Cheng, W. M. Grundy, Mihaly Horányi, J. J. Kavelaars, Ivan R. Linscott, William B. McKinnon, Jeffrey M. Moore, J. I. Núñez, Catherine B. Olkin, Joel W. Parker, Simon B. Porter, Dennis C. Reuter, Stuart J. Robbins, Paul Schenk, Mark R. Showalter, Kelsi N. Singer, Anne J. Verbiscer, Leslie A. Young
First page: 77
Abstract: We used existing data from the New Horizons Long-range Reconnaissance Imager (LORRI) to measure the
optical-band(0.4 ≲ λ ≲ 0.9 μ m) sky brightness within seven high–Galactic latitude fields. The
average raw level measured while New Horizons was 42–45 au from the Sun is 33.2 ± 0.5 nW m −2 sr −1
. This is ∼10× as dark as the darkest sky accessible to the Hubble Space Telescope, highlighting the
utility of New Horizons for detecting the cosmic optical background (COB). Isolating the COB
contribution to the raw total required subtracting scattered light from bright stars and galaxies,
faint stars below the photometric detection limit within the fields, and diffuse Milky Way light
scattered by infrared cirrus. We removed newly identified residual zodiacal light from the IRIS 100
μ m all-sky maps to generate two different estimates for the diffuse Galactic light. Using these
yielded a highly significant detection of the COB in the range 15.9 ± 4...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc881
Issue No: Vol. 906, No. 2 (2021)
- A Two-moment Radiation Hydrodynamics Scheme Applicable to Simulations of
Planet Formation in
Circumstellar Disks- Authors: Julio David Melon Fuksman; Hubert Klahr, Mario Flock, Andrea Mignone
First page: 78
Abstract: We present a numerical code for radiation hydrodynamics designed as a module for the freely
available PLUTO code. We adopt a gray approximation and include radiative transfer following a
two-moment approach by imposing the M1 closure to the radiation fields. This closure allows for a
description of radiative transport in both the diffusion and free-streaming limits, and is able to
describe highly anisotropic radiation transport as can be expected in the vicinity of an accreting
planet in a protoplanetary disk. To reduce the computational cost caused by the timescale disparity
between radiation and matter fields, we integrate their evolution equations separately in an
operator-split way, using substepping to evolve the radiation equations. We further increase the
code’s efficiency by adopting the reduced speed of light approximation (RSLA). Our integration
scheme for the evolution equations of radiation fields relies on implicit-explicit schemes, in which
radiation-matte...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc879
Issue No: Vol. 906, No. 2 (2021)
- On the Occurrence of Type IV Solar Radio Bursts in Solar Cycle 24 and
Their Association with Coronal
Mass Ejections- Authors: Anshu Kumari; D. E. Morosan, E. K. J. Kilpua
First page: 79
Abstract: Solar activities, in particular coronal mass ejections (CMEs), are often accompanied by bursts of
radiation at meter wavelengths. Some of these bursts have a long duration and extend over a wide
frequency band, namely, type IV radio bursts. However, the association of type IV bursts with CMEs
is still not well understood. In this article, we perform the first statistical study of type IV
solar radio bursts in solar cycle 24. Our study includes a total of 446 type IV radio bursts that
occurred during this cycle. Our results show that a clear majority, ∼81% of type IV bursts, were
accompanied by CMEs, based on a temporal association with white-light CME observations. However, we
found that only ∼2.2% of the CMEs are accompanied by type IV radio bursts. We categorized the type
IV bursts as moving or stationary based on their spectral characteristics and found that only ∼18%
of the total type IV bursts in this study were moving type IV bursts. Our study suggests that type
IV bursts ...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc878
Issue No: Vol. 906, No. 2 (2021)
- The CARMA-NRO Orion Survey: Filament Formation via Collision-induced
Magnetic Reconnection—the Stick
in Orion A- Authors: Shuo Kong; Volker Ossenkopf-Okada, Héctor G. Arce, John Bally, Álvaro Sánchez-Monge, Peregrine McGehee, Sümeyye Suri, Ralf S. Klessen, John M. Carpenter, Dariusz C. Lis, Fumitaka Nakamura, Peter Schilke, Rowan J. Smith, Steve Mairs, Alyssa Goodman, María José Maureira
First page: 80
Abstract: A unique filament is identified in the Herschel maps of the Orion A giant molecular cloud. The
filament, which we name the Stick, is ruler-straight and at an early evolutionary stage. Transverse
position–velocity diagrams show two velocity components closing in on the Stick. The filament shows
consecutive rings/forks in C 18 O (1−0) channel maps, which is reminiscent of structures generated
by magnetic reconnection. We propose that the Stick formed via collision-induced magnetic
reconnection (CMR). We use the magnetohydrodynamics code Athena++ to simulate the collision between
two diffuse molecular clumps, each carrying an antiparallel magnetic field. The clump collision
produces a narrow, straight, dense filament with a factor of>200 increase in density. The
production of the dense gas is seven times faster than freefall collapse. The dense filament shows
ring/fork-like structures in radiative transfer maps. Cores in the filament are confined by surface
magnetic pr...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc687
Issue No: Vol. 906, No. 2 (2021)
- Lorentz–Lorenz Coefficient of Ice Molecules of Astrophysical Interest: N
2 , CO 2 , NH 3 , CH 4 , CH
3 OH, C 2 H 4 , and C 2 H 6- Authors: M. Domingo; R. Luna, M. Á. Satorre, C. Santonja, C. Millán
First page: 81
Abstract: This work calculates the Lorentz–Lorenz coefficient with the refractive index and density values of
various molecules in their solid phase measured in our laboratory under astrophysical conditions.
This was completed for a range of temperatures from 13 K to close to the sublimation temperature for
each molecule. The studied molecules were N 2 , CO 2 , NH 3 , CH 4 , CH 3 OH, C 2 H 4 , and C 2 H 6
. For CO 2 , our results match those found in the unique similar previous work in the literature.
The results obtained for NH 3 and CH 3 OH are relevant because they confirm that the procedure
adopted is applicable also to polar molecules. The study presented here updates the previous work on
these molecules by focusing on their solid states under astrophysical conditions and at a range of
temperatures. The knowledge of the Lorentz–Lorenz coefficient in a specific temperature rang...
Citation: The Astrophysical Journal
PubDate: 2021-01-11T00:00:00Z
DOI: 10.3847/1538-4357/abc5c5
Issue No: Vol. 906, No. 2 (2021)
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