• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-17
Jiayi Sun, Adam K. Leroy, Eva Schinnerer, Annie Hughes, Erik Rosolowsky, Miguel Querejeta, Andreas Schruba, Daizhong Liu, Toshiki Saito, Cinthya N. Herrera, Christopher Faesi, Antonio Usero, Jérôme Pety, J. M. Diederik Kruijssen, Eve C. Ostriker, Frank Bigiel, Guillermo A. Blanc, Alberto D. Bolatto, Médéric Boquien, Mélanie Chevance, Daniel A. Dale, Sinan Deger, Eric Emsellem, Simon C. O. Glover, Kathryn

Using the PHANGS–ALMA CO(2–1) survey, we characterize molecular gas properties on ∼100 pc scales across 102,778 independent sightlines in 70 nearby galaxies. This yields the best synthetic view of molecular gas properties on cloud scales across the local star-forming galaxy population obtained to date. Consistent with previous studies, we observe a wide range of molecular gas surface densities (3.4

更新日期：2020-09-20
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-17
Kishalay De, Michael C. B. Ashley, Igor Andreoni, Mansi M. Kasliwal, Roberto Soria, Gokul P. Srinivasaragavan, Ce Cai, Alexander Delacroix, Tim Greffe, David Hale, Matthew J. Hankins, Chengkui Li, Daniel McKenna, Anna M. Moore, Eran O. Ofek, Roger M. Smith, Jamie Soon, Tony Travouillon, and Shuangnan Zhang

The Galactic magnetar SGR 1935+2154 has been reported to produce the first example of a bright millisecond-duration radio burst (FRB 200428) similar to the cosmological population of fast radio bursts (FRBs). The detection of a coincident bright X-ray burst represents the first observed multiwavelength counterpart of an FRB. However, the search for similar emission at optical wavelengths has been hampered

更新日期：2020-09-20
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-17
Vardan Baghmanyan, Giada Peron, Sabrina Casanova, Felix Aharonian, and Roberta Zanin

We report the analysis of the Fermi-Large Area Telescope data from six nearby giant molecular clouds (MCs) belonging to the Gould Belt and the Aquila Rift regions. The high statistical γ -ray spectra above 3 GeV well described by power laws make it possible to derive precise estimates of the cosmic-ray (CR) distribution in the MCs. The comparison of γ -ray spectra of Taurus, Orion A, and Orion B clouds

更新日期：2020-09-20
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-17
Zhongwei Yang, Ying D. Liu, Andreas Johlander, George K. Parks, Benoit Lavraud, Ensang Lee, Wolfgang Baumjohann, Rui Wang, and James L. Burch

Studies of shocks have long suggested that a shock can undergo cyclical self-reformation on a timescale of ion cyclotron period. This process has been proposed as a primary mechanism for energy dissipation and energetic particle acceleration at shocks. Unambiguous observational evidence, however, has remained elusive. Here, we report direct observations for the self-reformation process of a collisionless

更新日期：2020-09-20
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-17
N. Kanekar, J. X. Prochaska, M. Neeleman, L. Christensen, P. Møller, M. A. Zwaan, J. P. U. Fynbo, and M. Dessauges-Zavadsky

We have used the Atacama Large Millimeter/submillimeter Array (ALMA) to carry out a search for CO (3−2) or (4−3) emission from the fields of 12 high-metallicity ([M/H] ≥ −0.72 dex) damped Ly α absorbers (DLAs) at z ≈ 1.7–2.6. We detected CO emission from galaxies in the fields of five DLAs (two of which have been reported earlier), obtaining high molecular gas masses, ##IMG## [http://ej.iop.org/im

更新日期：2020-09-20
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-15
Lisa Kaltenegger, Ryan J. MacDonald, Thea Kozakis, Nikole K. Lewis, Eric E. Mamajek, Jonathan C. McDowell, and Andrew Vanderburg

The near-term search for life beyond the solar system currently focuses on transiting planets orbiting small M dwarfs, and the challenges of detecting signs of life in their atmospheres. However, planets orbiting white dwarfs (WDs) would provide a unique opportunity to characterize rocky worlds. The discovery of the first transiting giant planet orbiting a WD, WD 1856+534, showed that planetary-mass

更新日期：2020-09-16
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-15
Xingyu Zhu, Jiansen He, Daniel Verscharen, Die Duan, and Stuart D. Bale

Turbulence, a ubiquitous phenomenon in interplanetary space, is crucial for the energy conversion of space plasma at multiple scales. This work focuses on the propagation, polarization, and wave composition properties of the solar wind turbulence within 0.3 au, and its variation with heliocentric distance at magnetohydrodynamic scales (from 10 s to 1000 s in the spacecraft frame). We present the probability

更新日期：2020-09-16
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-15
L. F. Burlaga, N. F. Ness, D. B. Berdichevsky, L. K. Jian, J. Park, and A. Szabo

Voyager 1 (V1) observed q -Gaussian distributions of 1 hr increments of the components the magnetic field ##IMG## [http://ej.iop.org/images/2041-8205/901/1/L2/apjlabb199ieqn1.gif] {${\boldsymbol{B}}$} throughout the very local interstellar medium (VLISM) on scales on the order of 1 year, from 2013 through 2019, excluding the disturbed regions near two shocks. The intermittency of the components of

更新日期：2020-09-16
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-14
Hannah M. Lewis, Borja Anguiano, Keivan G. Stassun, Steven R. Majewski, Phil Arras, Craig L. Sarazin, Zhi-Yun Li, Nathan De Lee, Nicholas W. Troup, Carlos Allende Prieto, Carles Badenes, Katia Cunha, D. A. García-Hernández, David L. Nidever, Pedro A. Palicio, Joshua D. Simon, and Verne V. Smith

Draco C1 is a known symbiotic binary star system composed of a carbon red giant and a hot, compact companion—likely a white dwarf—belonging to the Draco dwarf spheroidal galaxy. From near-infrared spectroscopic observations taken by the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2), part of Sloan Digital Sky Survey IV, we provide updated stellar parameters for the cool, giant component

更新日期：2020-09-15
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-14
Bryce T. Bolin, Christoffer Fremling, Timothy R. Holt, Matthew J. Hankins, Tomás Ahumada, Shreya Anand, Varun Bhalerao, Kevin B. Burdge, Chris M. Copperwheat, Michael Coughlin, Kunal P. Deshmukh, Kishalay De, Mansi M. Kasliwal, Alessandro Morbidelli, Josiah N. Purdum, Robert Quimby, Dennis Bodewits, Chan-Kao Chang, Wing-Huen Ip, Chen-Yen Hsu, Russ R. Laher, Zhong-Yi Lin, Carey M. Lisse, Frank J. Masci

We present time-resolved visible spectrophotometry of 2020 CD 3 , the second known minimoon. The spectrophotometry was taken with the Keck I/Low Resolution Imaging Spectrometer between wavelengths 434 and 912 nm in the B , g , V , R , I , and RG850 filters as it was leaving the Earth–Moon system on 2020 March 23 UTC. The spectrum of 2020 CD 3 resembles V-type asteroids and some lunar rock samples with

更新日期：2020-09-15
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-14
David Kipping

It has been recently claimed that KOIs-268.01, 303.01, 1888.01, 1925.01, 2728.01, and 3320.01 are exomoon candidates, based on an analysis of their transit timing. Here, we perform an independent investigation, which is framed in terms of three questions: (1) Are there significant transit timing variations (TTVs)? (2) Is there a significant periodic TTV? (3) Is there evidence for a nonzero moon mass

更新日期：2020-09-15
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-14
Khai Nguyen, Tamara Bogdanović, Jessie C. Runnoe, Stephen R. Taylor, Alberto Sesana, Michael Eracleous, and Steinn Sigurdsson

We estimate the merger timescale of spectroscopically selected, subparsec supermassive black hole binary (SMBHB) candidates by comparing their expected contribution to the gravitational-wave background (GWB) with the sensitivity of current pulsar timing array (PTA) experiments and in particular, with the latest upper limit placed by the North American Nanohertz Observatory for Gravitational Waves.

更新日期：2020-09-15
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-10
Eric R. Coughlin, C. J. Nixon, and Patrick R. Miles

The destruction of a star by the tides of a supermassive black hole (SMBH) powers a bright accretion flare, and the theoretical modeling of such tidal disruption events (TDEs) can provide a direct means of inferring SMBH properties from observations. Previously it has been shown that TDEs with β = r t / r p = 1, where r t is the tidal disruption radius and r p is the pericenter distance of the star

更新日期：2020-09-12
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-10
Natalie R. Hinkel, Hilairy E. Hartnett, and Patrick A. Young

When searching for exoplanets and ultimately considering their habitability, it is necessary to consider the planet’s composition, geophysical processes, and geochemical cycles in order to constrain the bioessential elements available to life. Determining the elemental ratios for exoplanetary ecosystems is not yet possible, but we generally assume that planets have compositions similar to those of

更新日期：2020-09-12
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-10
Jeff J. Andrews

Of the seven known double neutron stars (DNSs) with precisely measure masses in the Milky Way that will merge within a Hubble time, all but one has a mass ratio, q , close to unity. Recently, precise measurements of three post-Keplerian parameters in the DNS J1913+1102 constrain this system to have a significantly non-unity mass ratio of 0.78 ± 0.03. One may be tempted to conclude that approximately

更新日期：2020-09-12
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-10
Masashi Nashimoto, Makoto Hattori, Frédérick Poidevin, and Ricardo Génova-Santos

We have shown that the thermal emission of the amorphous dust composed of amorphous silicate dust (a-Si) and amorphous carbon dust (a-C) provides an excellent fit both to the observed intensity and the polarization spectra of molecular clouds. The anomalous microwave emission (AME) originates from the resonance transition of the two-level systems attributed to the a-C with an almost spherical shape

更新日期：2020-09-12
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-09
Aaron Tran and Lorenzo Sironi

Collisionless shocks heat electrons in the solar wind, interstellar blast waves, and hot gas permeating galaxy clusters. How much shock heating goes to electrons instead of ions, and what plasma physics controls electron heating? We simulate 2D perpendicular shocks with a fully kinetic particle-in-cell code. For magnetosonic Mach number ##IMG## [http://ej.iop.org/images/2041-8205/900/2/L36/apjlabb19cieqn1

更新日期：2020-09-11
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-09
L. E. Rivera Sandoval, T. J. Maccarone, and M. Pichardo Marcano

SDSS J080710+485259 is the longest-period outbursting ultracompact white dwarf binary. Its first-ever detected superoutburst started in 2018 November and lasted for a year, the longest detected so far for any short orbital period accreting white dwarf. Here we show the superoutburst duration of SDSS J080710+485259 exceeds the ∼2 month viscous time of its accretion disk by a factor of about 5. Consequently

更新日期：2020-09-10
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-09
Riccardo Ciolfi and Jay Vijay Kalinani

The observation of a radioactively powered kilonova associated with the first binary neutron star (BNS) merger detected in gravitational waves proved that these events are ideal sites for the production of heavy r -process elements. However, the physical origin of the ejected material responsible for the early (“blue”) and late (“red”) components of this kilonova is still debated. Here, we investigate

更新日期：2020-09-10
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-08
F. Massaro, A. Capetti, A. Paggi, R. D. Baldi, A. Tramacere, I. Pillitteri, and R. Campana

The most elusive and extreme subclass of active galactic nuclei (AGNs), known as BL Lac objects, shows features that can only be explained as the result of relativistic effects occurring in jets pointing at a small angle with respect to the line of sight. A longstanding issue is the identification of the BL Lac parent population with jets oriented at larger angles. According to the “unification scenario”

更新日期：2020-09-10
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-06
A. Palmese, J. deVicente, M. E. S. Pereira, J. Annis, W. Hartley, K. Herner, M. Soares-Santos, M. Crocce, D. Huterer, I. Magaña Hernandez, A. Garcia, J. Garcia-Bellido, J. Gschwend, D. E. Holz, R. Kessler, O. Lahav, R. Morgan, C. Nicolaou, C. Conselice, R. J. Foley, M. S. S. Gill, T. M. C. Abbott, M. Aguena, S. Allam, S. Avila, K. Bechtol, E. Bertin, S. Bhargava, D. Brooks, E. Buckley-Geer, D. L. Burke

We present a measurement of the Hubble constant H 0 using the gravitational wave (GW) event GW190814, which resulted from the coalescence of a 23 M ⊙ black hole with a 2.6 M ⊙ compact object, as a standard siren. No compelling electromagnetic counterpart has been identified for this event; thus our analysis accounts for thousands of potential host galaxies within a statistical framework. The redshift

更新日期：2020-09-08
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-06
S. W. Good, E. K. J. Kilpua, M. Ala-Lahti, A. Osmane, S. D. Bale, and L.-L. Zhao

Magnetic clouds are large-scale transient structures in the solar wind with low plasma- β , low-amplitude magnetic field fluctuations, and twisted field lines with both ends often connected to the Sun. Their inertial-range turbulent properties have not been examined in detail. In this Letter, we analyze the normalized cross helicity, σ c , and residual energy, σ r , of plasma fluctuations in the 2018

更新日期：2020-09-08
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-06
L. M. Ziurys, D. R. Schmidt, and N. J. Woolf

The 12 C/ 13 C ratio has been measured toward a sample of planetary nebulae (PNe) using millimeter observations of CO, HCN, HNC, CN, and other species, conducted with the 12 m antenna and the Submillimeter Telescope of the Arizona Radio Observatory. The observed nebulae spanned the entire lifetime of PNe, from ∼900 to 12,000 yr, and include well-known objects such as NGC 7293 (Helix), NGC 6720 (Ring)

更新日期：2020-09-08
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-06
Jeremy Darling

Axions are a promising dark matter candidate that were motivated to solve the strong charge-parity problem and that may also address the cosmological matter−antimatter asymmetry. Axion−photon conversion is possible in the presence of the strong magnetic fields, and the photon so produced will have energy equal to the axion mass. Here we report new limits on axionic dark matter obtained from radio spectra

更新日期：2020-09-08
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-06
Tobias Felipe, Christoph Kuckein, Sergio Javier González Manrique, Ivan Milic, and C. R. Sangeetha

Oscillations in sunspot umbrae exhibit remarkable differences between the photosphere and chromosphere. We evaluate two competing scenarios proposed for explaining those observations: a chromospheric resonant cavity and waves traveling from the photosphere to upper atmospheric layers. We have employed numerical simulations to analyze the oscillations in both models. They have been compared with observations

更新日期：2020-09-08
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-06
Aditya Chowdhury, Nissim Kanekar, and Jayaram N. Chengalur

We report the discovery of two remarkable high-opacity H i 21 cm absorbers against low-luminosity active galactic nuclei (AGNs), at z = 1.2166 toward J0229+0044 and at z = 1.1630 toward J0229+0053. The absorbers were detected in an unbiased Giant Metrewave Radio Telescope survey for H i 21 cm absorption against radio sources in the DEEP2 survey fields, covering z ≈ 0.73–1.53, and including sources

更新日期：2020-09-08
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-03
David N. Hosking and Lorenzo Sironi

We show that magnetic reconnection in a magnetically dominated fast-cooling plasma can naturally produce bright flares accompanied by rotations in the synchrotron polarization vector. With particle-in-cell simulations of reconnection, we find that flares are powered by efficient particle acceleration at the interface of merging magnetic flux ropes, or “plasmoids.” The accelerated particles stream through

更新日期：2020-09-05
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-03
Zhongwei Yang, Ying D. Liu, Shuichi Matsukiyo, Quanming Lu, Fan Guo, Mingzhe Liu, Huasheng Xie, Xinliang Gao, and Jun Guo

Microinstabilities and waves excited at moderate-Mach-number perpendicular shocks in the near-Sun solar wind are investigated by full particle-in-cell simulations. By analyzing the dispersion relation of fluctuating field components directly issued from the shock simulation, we obtain key findings concerning wave excitations at the shock front: (1) at the leading edge of the foot, two types of electrostatic

更新日期：2020-09-05
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-03
Jane X. Luu, Eirik G. Flekkøy, and Renaud Toussaint

The first known interstellar object, 1I/2017 U1 ’Oumuamua, displayed such unusual properties that its origin remains a subject of much debate. We propose that ’Oumuamua’s properties could be explained as those of a fractal dust aggregate (a “dust bunny”) formed in the inner coma of a fragmenting exo-Oort cloud comet. Such fragments could serve as accretion sites by accumulating dust particles, resulting

更新日期：2020-09-05
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-03
R. A. López, M. Lazar, S. M. Shaaban, S. Poedts, and P. S. Moya

Heat transport in the solar wind is dominated by suprathermal electron populations, i.e., a tenuous halo and a field-aligned beam/strahl, with high energies and antisunward drifts along the magnetic field. Their evolution may offer plausible explanations for the rapid decrease of the heat flux with the solar wind expansion, and self-generated instabilities, or so-called “heat flux instabilities” (HFIs)

更新日期：2020-09-05
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-03
Q. Wu, G. Q. Zhang, F. Y. Wang, and Z. G. Dai

Recently, the discovery of Galactic FRB 200428 associated with an X-ray burst (XRB) of SGR 1935+2154 has built a bridge between FRBs and magnetar activities. In this Letter, we assume that the XRB occurs in the magnetar magnetosphere. We show that the observational properties of FRB 200428 and the associated XRB are consistent with the predictions of synchrotron maser emission at ultrarelativistic

更新日期：2020-09-05
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-03
Yajie Yuan, Andrei M. Beloborodov, Alexander Y. Chen, and Yuri Levin

Using numerical simulations we show that low-amplitude Alfvén waves from a magnetar quake propagate to the outer magnetosphere and convert to “plasmoids” (closed magnetic loops) that accelerate from the star, driving blast waves into the magnetar wind. Quickly after its formation, the plasmoid becomes a thin relativistic pancake. It pushes out the magnetospheric field lines, and they gradually reconnect

更新日期：2020-09-05
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-03
Matthew R. Siebert, Georgios Dimitriadis, Abigail Polin, and Ryan J. Foley

We present nebular spectra of the Type Ia supernova (SN Ia) SN 2019yvq, which had a bright flash of blue and ultraviolet light after exploding, followed by a rise similar to other SNe Ia. Although SN 2019yvq displayed several other rare characteristics, such as persistent high ejecta velocity near peak brightness, it was not especially peculiar, and if the early “excess” emission were not observed

更新日期：2020-09-05
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-02
G. Li, L. Zhao, L. Wang, W. Liu, and X. Wu

We examine the release times of energetic electrons in the 2001 April 25 event. An M2.7 flare occurred on 2001 April 25, from AR 09433, located at N18W09. The flare was observed in X-rays by GOES and the Yohkoh spacecraft. The Yohkoh observation also included hard X-ray (HXR) images for all four energy channels: L, M1, M2, and H. We use Yohkoh observation times as a proxy for the release time of energetic

更新日期：2020-09-03
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-02
Parker Brian Crandall, David Müller, Juliette Leroux, Marko Förstel, and Otto Dopfer

Known for their stable structural and thermal properties, diamondoids and particularly their radical cations are viable candidates as carriers for diffuse interstellar bands. While previous research has mainly focused on neutral diamondoids and their derivatives, little is known about their radical cations, which may form in interstellar environments by ionizing radiation. We report the first experimental

更新日期：2020-09-03
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-02
Il-Hyun Cho, Valery M. Nakariakov, Yong-Jae Moon, Jin-Yi Lee, Dae Jung Yu, Kyung-Suk Cho, Vasyl Yurchyshyn, and Harim Lee

Slow magnetoacoustic waves in a static background provide a seismological tool to probe the solar atmosphere in the analytic frame. By analyzing the spatiotemporal variation of the electron number density of plume structure in coronal holes above the limb for a given temperature, we find that the density perturbations accelerate with supersonic speeds in the distance range from 1.02 to 1.23 solar radii

更新日期：2020-09-03
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-02
Hui Fu, R. A. Harrison, J. A. Davies, LiDong Xia, XiaoShuai Zhu, Bo Li, ZhengHua Huang, and D. Barnes

Identifying the source of the material within coronal mass ejections (CMEs) and understanding CME onset mechanisms are fundamental issues in solar and space physics. Parameters relating to plasma composition, such as charge states and He abundance ( A He ), may be different for plasmas originating from differing processes or regions on the Sun. Thus, it is crucial to examine the relationship between

更新日期：2020-09-03
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-02
Zhe Xu, Haisheng Ji, Kaifan Ji, Yi Bi, Bo Yang, Junchao Hong, and Jiayan Yang

In the Sun, the flows of hot plasma drive a dynamo that generates a global magnetic field as well as smaller-scale local fields. The existence of a magnetic field in turn affects the motion of plasma so that complex dynamic characteristics can be observed. In this Letter, we give an analysis on the localized amplification of magnetic fields in front of a moving pore. Moving with the pore, the formation

更新日期：2020-09-03
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-09-01
R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, C. Adams, R. X. Adhikari, V. B. Adya, C. Affeldt, M. Agathos, K. Agatsuma, N. Aggarwal, O. D. Aguiar, A. Aich, L. Aiello, A. Ain, P. Ajith, S. Akcay, G. Allen, A. Allocca, P. A. Altin, A. Amato, S. Anand, A. Ananyeva, S. B. Anderson, W. G. Anderson, S. V. Angelova, S. Ansoldi, S. Antier, S. Appert, K. Arai, M. C. Araya, J. S. Areeda, M. Arène

The gravitational-wave signal GW190521 is consistent with a binary black hole (BBH) merger source at redshift 0.8 with unusually high component masses, ##IMG## [http://ej.iop.org/images/2041-8205/900/1/L13/apjlaba493ieqn1.gif] {${85}_{-14}^{+21}$} M ⊙ and ##IMG## [http://ej.iop.org/images/2041-8205/900/1/L13/apjlaba493ieqn2.gif] {${66}_{-18}^{+17}$} M ⊙ , compared to previously reported events, and

更新日期：2020-09-02
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-31
C. J. Nixon, Eric R. Coughlin, and J. E. Pringle

Short gamma-ray bursts (sGRBs) are generally thought to result from the merger of two neutron stars or the merger of a neutron star with a black hole. It is becoming standard practice to model these mergers with hydrodynamical simulations that employ equations of state that are derived, for example, for determining the behavior of matter in core-collapse supernovae, and which therefore make use of

更新日期：2020-09-01
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-31
Ci Xue, Eric R. Willis, Ryan A. Loomis, Kin Long Kelvin Lee, Andrew M. Burkhardt, Christopher N. Shingledecker, Steven B. Charnley, Martin A. Cordiner, Sergei Kalenskii, Michael C. McCarthy, Eric Herbst, Anthony J. Remijan, and Brett A. McGuire

We report an astronomical detection of HC 4 NC for the first time in the interstellar medium with the Green Bank Telescope toward the TMC-1 molecular cloud with a minimum significance of 10.5 σ . The total column density and excitation temperature of HC 4 NC are determined to be ##IMG## [http://ej.iop.org/images/2041-8205/900/1/L9/apjlaba631ieqn1.gif] {${3.29}_{-1.20}^{+8.60}\times {10}^{11}$} cm −2

更新日期：2020-09-01
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-31
Brett A. McGuire, Andrew M. Burkhardt, Ryan A. Loomis, Christopher N. Shingledecker, Kin Long Kelvin Lee, Steven B. Charnley, Martin A. Cordiner, Eric Herbst, Sergei Kalenskii, Emmanuel Momjian, Eric R. Willis, Ci Xue, Anthony J. Remijan, and Michael C. McCarthy

We present an overview of the GBT Observations of TMC-1: Hunting Aromatic Molecules Large Program on the Green Bank Telescope. This and a related program were launched to explore the depth and breadth of aromatic chemistry in the interstellar medium at the earliest stages of star formation, following our earlier detection of benzonitrile ( c -C 6 H 5 CN) in TMC-1. In this work, details of the observations

更新日期：2020-09-01
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-31
E. W. Cliver, F. Mekhaldi, and R. Muscheler

The distribution of the longitudes of solar flares associated with the high-energy proton events called ground level events (GLEs) can be approximated by a Gaussian with a peak at ∼W60, with a full range from ∼E90 to ∼W150. The longitudes of flares associated with the top third (24 of 72) of GLEs in terms of their >430 MeV fluences ( F 430 ) are primarily distributed over E20–W100 with a skew toward

更新日期：2020-09-01
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-26
Wen-Cong Chen, Dong-Dong Liu, and Bo Wang

Ultra-compact X-ray binaries (UCXBs) are low-mass X-ray binaries with ultra-short orbital periods (usually less than 1 hr) and hydrogen-poor donor stars, which are proposed to be potential Laser Interferometer Space Antenna (LISA) sources. In this work, we first employ the Modules for Experiments in Stellar Astrophysics code to examine the parameter space of the progenitors of UCXBs that LISA will

更新日期：2020-08-27
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-26
M. Y. Ge, J. P. Yuan, F. J. Lu, H. Tong, S. Q. Zhou, L. L. Yan, L. J. Wang, Y. L. Tuo, X. F. Li, and L. M. Song

With the 12 year long observations by Fermi-LAT, we discover two pairs of spin-down state transitions of PSR J1124–5916, making it the second young pulsar detected to have such behaviors. PSR J1124–5916 shows mainly two states according to its spin-down rate evolution, the normal spin-down state and the low spin-down state. In about 80% of the observation time, the pulsar is in the normal spin-down

更新日期：2020-08-27
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-25
Luis Preisser, Xóchitl Blanco-Cano, Primoz Kajdič, David Burgess, and Domenico Trotta

Magnetosheath jets and plasmoids are very common phenomena downstream of Earth’s quasi-parallel bow shock. As the increase of the dynamic pressure is one of the principal characteristics of magnetosheath jets, the embedded paramagnetic plasmoids have been considered as an special case of the former. Although the properties of both types of structures have been widely studied during the last 20 years

更新日期：2020-08-26
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-25
Takaaki Tanaka, Hiroyuki Uchida, Hidetoshi Sano, and Takeshi Go Tsuru

We report on results of Chandra X-ray observations of the southwestern part of the supernova remnant (SNR) RX J1713.7−3946. We measure proper motions of two X-ray bright blobs, named Blobs A and B, in regions presumably corresponding to the forward shock of the SNR. The measured velocities are 3800 ± 100 km s −1 and 2300 ± 200 km s −1 for Blobs A and B, respectively. Since a dense molecular clump is

更新日期：2020-08-26
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-24
Xiaoying Pang, Yuqian Li, Shih-Yun Tang, Mario Pasquato, and M. B. N. Kouwenhoven

We identify structures of the young star cluster NGC 2232 in the solar neighborhood (323.0 pc) and a newly discovered star cluster, LP 2439 (289.1 pc). Member candidates are identified using the Gaia DR2 sky position, parallax, and proper-motion data by an unsupervised machine-learning method, S tar GO. Member contamination from the Galactic disk is further removed using the color–magnitude diagram

更新日期：2020-08-26
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-24
Kei E. I. Tanaka, Yichen Zhang, Tomoya Hirota, Nami Sakai, Kazuhito Motogi, Kengo Tomida, Jonathan C. Tan, Viviana Rosero, Aya E. Higuchi, Satoshi Ohashi, Mengyao Liu, and Koichiro Sugiyama

We report results of ##IMG## [http://ej.iop.org/images/2041-8205/900/1/L2/apjlabadfcieqn1.gif] {$0\buildrel{\prime\prime}\over{.} 05$} -resolution observations toward the O-type proto-binary system IRAS 16547–4247 with the Atacama Large Millimeter/submillimeter Array. We present dynamical and chemical structures of the circumbinary disk, circumstellar disks, outflows, and jets, illustrated by multi-wavelength

更新日期：2020-08-26
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-24
Luis F. Rodríguez, Jane Arthur, Gabriela Montes, Carlos Carrasco-González, and Jesús A. Toalá

Wolf–Rayet (WR) stars are evolved massive stars, presumably on their way to becoming supernovae. They are characterized by high luminosities and fast and dense stellar winds. We have detected signs of a radio continuum pinwheel associated with WR 147, a nitrogen-rich WR star with spectral subtype WN8. These structures are known to exist around a handful of late-type carbon-rich WR stars with massive

更新日期：2020-08-26
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-24
W. S. Kurth and D. A. Gurnett

Beginning on 2020 June 19, at a heliocentric distance of 124.2 au, the Voyager 2 Plasma Wave Science instrument began to observe radio emissions followed by electron plasma oscillations in its 3.11 kHz spectrum analyzer channel. Plasma oscillations at this frequency imply an electron density in the range of 0.12 cm −3 ± 15%, although some response in the 1.78 kHz channel near the peak of the plasma

更新日期：2020-08-26
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-19
K. P. Raju

Supergranulation is the horizontal velocity pattern on the solar surface with a typical size of 30,000 km and a lifetime of 24 hr. The network structure seen in chromospheric lines, such as Ca ii K 3934 Å, is the manifestation of supergranulation. The network seen in the extreme-ultraviolet lines like He ii 304 Å is the extension of the chromospheric network into the upper solar atmosphere. We have

更新日期：2020-08-20
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-19
Z. Wang, H. S. Fu, A. Vaivads, J. L. Burch, Y. Yu, and J. B. Cao

Inherently, magnetic reconnection—the process responsible for stellar flares and magnetospheric substorms—is very dynamic in space, owing to magnetic fluctuations and unsteady inflows. However, this process was always explained as a static picture in spacecraft measurements, neglecting the temporal evolution. This picture is not correct. Here we provide the first dynamic picture of magnetic reconnection

更新日期：2020-08-20
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-19
Kai Liao

Due to the finite size of the disk and the temperature fluctuations producing the variability, microlensing changes the actual time delays between images of strongly lensed active galactic nuclei on the ∼day(s) light-crossing timescale of the emission region. This microlensing-induced time delay depends on the disk model, primarily the disk size R disk , which has been found to be larger than predicted

更新日期：2020-08-20
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-18
Víctor M. Rivilla, Jesús Martín-Pintado, Izaskun Jiménez-Serra, Sergio Martín, Lucas F. Rodríguez-Almeida, Miguel A. Requena-Torres, Fernando Rico-Villas, Shaoshan Zeng, and Carlos Briones

One of the proposed scenarios for the origin of life is the primordial RNA world, which considers that RNA molecules were likely responsible for the storage of genetic information and the catalysis of biochemical reactions in primitive cells, before the advent of proteins and DNA. In the last decade, experiments in the field of prebiotic chemistry have shown that RNA nucleotides can be synthesized

更新日期：2020-08-19
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-18
J. Liu, S. T. Yao, Q. Q. Shi, X. G. Wang, Q. G. Zong, Y. Y. Feng, H. Liu, R. L. Guo, Z. H. Yao, I. J. Rae, A. W. Degeling, A. M. Tian, C. T. Russell, Y. T. Zhang, Y. X. Wang, L. D. Woodham, Z. Y. Pu, C. J. Xiao, S. Y. Fu, and B. L. Giles

Particle energization and energy dissipation in electromagnetic environments are longstanding topics of intensive research in space, laboratory, and astrophysical plasmas. One challenge is to understand these conversion processes at smaller and smaller spatial/temporal scales. In this Letter, with very high cadence measurements of particle distributions from the Magnetospheric Multiscale spacecraft

更新日期：2020-08-19
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-18
Monica Gallegos-Garcia, Blakesley Burkhart, Anna L. Rosen, Jill P. Naiman, and Enrico Ramirez-Ruiz

Intermediate and massive stars drive fast and powerful isotropic winds that interact with the winds of nearby stars in star clusters and the surrounding interstellar medium (ISM). Wind–ISM collisions generate astrospheres around these stars that contain hot T ∼ 10 7 K gas that adiabatically expands. As individual bubbles expand and collide they become unstable, potentially driving turbulence in star

更新日期：2020-08-19
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-18
G. Zhou, H.-Q. He, and W. Wan

The correlation scale and the Taylor scale are evaluated for interplanetary magnetic field fluctuations from two-point, single time correlation function using the Advanced Composition Explorer (ACE), Wind, and Cluster spacecraft data during the time period from 2001 to 2017, which covers over an entire solar cycle. The correlation scale and the Taylor scale are respectively compared with the sunspot

更新日期：2020-08-19
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-18
Ben Margalit, Paz Beniamini, Navin Sridhar, and Brian D. Metzger

A luminous radio burst was recently detected in temporal coincidence with a hard X-ray flare from the Galactic magnetar SGR 1935+2154 with a time and frequency structure consistent with cosmological fast radio bursts (FRBs) and a fluence within a factor of ≲10 of the least energetic extragalactic FRB previously detected. Although active magnetars are commonly invoked FRB sources, several distinct mechanisms

更新日期：2020-08-19
• Astrophys. J. Lett. (IF 8.198) Pub Date : 2020-08-18
Katherine A. Suess, Mariska Kriek, Sedona H. Price, and Guillermo Barro

This Letter examines how the sizes, structures, and color gradients of galaxies change along the quiescent sequence. Our sample consists of ∼400 quiescent galaxies at1.0 ≤ z ≤ 2.5 and ##IMG## [http://ej.iop.org/images/2041-8205/899/2/L26/apjlabacc9ieqn1.gif] {$10.1\leqslant \mathrm{log}{M}_{* }/{M}_{\odot }\leqslant 11.6$} in three CANDELS fields. We exploit deep multi-band Hubble Space Telescope imaging

更新日期：2020-08-19
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