35 results match your criteria Astronomical Journal[Journal]


The Initial Mass Function of Low-mass Stars and Brown Dwarfs in the W3 Complex.

Astron J 2021 Mar 22;161(3). Epub 2021 Feb 22.

Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA.

We have used archival infrared images obtained with the Wide Field Camera 3 on board the Hubble Space Telescope to constrain the initial mass function of low-mass stars and brown dwarfs in the W3 star-forming region. The images cover 438 arcmin, which encompasses the entire complex, and were taken in the filters F110W, F139M, and F160W. We have estimated extinctions for individual sources in these data from their colors and have dereddened their photometry accordingly. Read More

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Dynamical instabilities in systems of multiple short-period planets are likely driven by secular chaos: a case study of Kepler-102.

Astron J 2020 Sep 4;160(3). Epub 2020 Aug 4.

Lunar and Planetary Laboratory, The University of Arizona, 1629 E University Blvd, Tucson, AZ 85721.

We investigated the dynamical stability of high-multiplicity and planetary systems. Our numerical simulations find instabilities in ~ 20% of the cases on a wide range of timescales (up to 5×10 orbits) and over an unexpectedly wide range of initial dynamical spacings. To identify the triggers of long-term instability in multi-planet systems, we investigated in detail the five-planet Kepler-102 system. Read More

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September 2020

A Census of Star Formation in the Outer Galaxy. II. The GLIMPSE360 Field.

Astron J 2020 Aug 16;160(2). Epub 2020 Jul 16.

Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge MA 02138, USA.

We have conducted a study of star formation in the outer Galaxy from 65°< < 265°in the region observed by the GLIMPSE360 program. This Spitzer warm mission program mapped the plane of the outer Milky Way with IRAC at 3.6 and 4. Read More

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REFINING THE CENSUS OF THE UPPER SCORPIUS ASSOCIATION WITH .

Astron J 2020 Jul 29;160(1). Epub 2020 Jun 29.

Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA.

We have refined the census of stars and brown dwarfs in the Upper Sco association (~ 10 Myr, ~145 pc) by 1) updating the selection of candidate members from our previous survey to include the high-precision astrometry from the second data release of , 2) obtaining spectra of a few hundred candidate members to measure their spectral types and verify their youth, and 3) assessing the membership (largely with astrometry) of 2020 stars toward Upper Sco that show evidence of youth in this work and previous studies. We arrive at a catalog of 1761 objects that are adopted as members of Upper Sco. The distribution of spectral types among the adopted members is similar to those in other nearby star-forming regions, indicating a similar initial mass function. Read More

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A SURVEY FOR NEW STARS AND BROWN DWARFS IN THE OPHIUCHUS STAR-FORMING COMPLEX.

Astron J 2020 Jun 29;159(6). Epub 2020 May 29.

Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802.

We have performed a survey for new members of the Ophiuchus cloud complex using high-precision astrometry from the second data release of , proper motions measured with multi-epoch images from the , and color-magnitude diagrams constructed with photometry from various sources. Through spectroscopy of candidates selected with those data, we have identified 155 new young stars. Based on available measurements of kinematics, we classify 102, 47, and six of those stars as members of Ophiuchus, Upper Sco, and other populations in Sco-Cen, respectively. Read More

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NEW CANDIDATES FOR PLANETARY-MASS BROWN DWARFS IN IC 348.

Astron J 2020 Aug 9;160(2). Epub 2020 Jul 9.

Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802.

We have used infrared images obtained with the Wide Field Camera 3 on board the to search for planetary-mass brown dwarfs in the star-forming cluster IC 348. In those images, we have identified 12 objects that have colors indicative of spectral types later than M8, corresponding to masses of ≲ 30 at the age of IC 348. The four brightest candidates have been observed with spectroscopy, all of which are confirmed to have late types. Read More

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Potential Themis Family Asteroid Contribution to the Jupiter-Family Comet Population.

Astron J 2020 Apr 30;159(4). Epub 2020 Mar 30.

Planetary Science Institute, 1700 East Fort Lowell Rd., Suite 106, Tucson, AZ 85719, USA.

Recent dynamical analyses suggest that some Jupiter family comets (JFCs) may originate in the main asteroid belt instead of the outer solar system. This possibility is particularly interesting given evidence that icy main-belt objects are known to be present in the Themis asteroid family. We report results from dynamical analyses specifically investigating the possibility that icy Themis family members could contribute to the observed population of JFCs. Read More

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Variability in the Massive Open Cluster NGC 1817 from : A Rich Population of Asteroseismic Red Clump, Eclipsing Binary, and Main-sequence Pulsating Stars.

Astron J 2020 Mar 10;159(3). Epub 2020 Feb 10.

San Diego State University, Department of Astronomy, San Diego, CA 92182 USA.

We present a survey of variable stars detected in Campaign 13 within the massive intermediate-age (~1 Gyr) open cluster NGC 1817. We identify a complete sample of 44 red clump stars in the cluster, and have measured asteroseismic quantities ( and/or Δ) for 29 of them. Five stars showed suppressed dipole modes, and the occurrence rates indicate that mode suppression is unaffected by evolution through core helium burning. Read More

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Not a simple relationship between Neptune's migration speed and Kuiper belt inclination excitation.

Astron J 2019 Aug;158(2)

Lunar and Planetary Laboratory, The University of Arizona, 1629 E University Blvd, Tucson, AZ 85721.

We present numerical simulations of giant planet migration in our solar system and examine how the speed of planetary migration affects inclinations in the resulting population of small bodies (test particles) scattered outward and subsequently captured into Neptune's 3:2 mean motion resonance (the Plutinos) as well as the hot classical Kuiper belt population. We do not find a consistent relationship between the degree of test particle inclination excitation and e-folding planet migration timescales in the range 5 - 50 Myr. Our results present a counter-example to Nesvorný (2015)'s finding that the Plutino and hot classical inclinations showed a marked increase with increasing e-folding timescales for Neptune's migration. Read More

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A SURVEY FOR NEW MEMBERS OF TAURUS FROM STELLAR TO PLANETARY MASSES.

Astron J 2019 Aug;158(2)

Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA.

We present a large sample of new members of the Taurus star-forming region that extend from stellar to planetary masses. To identify candidate members at substellar masses, we have used color-magnitude diagrams and proper motions measured with several wide-field optical and infrared (IR) surveys. At stellar masses, we have considered the candidate members that were found in a recent analysis of high-precision astrometry from the mission. Read More

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Instabilities in the Early Solar System due to a Self-gravitating Disk.

Authors:
B Quarles N Kaib

Astron J 2019 Feb;157(2)

HL Dodge Department of Physics & Astronomy, University of Oklahoma, Norman, OK 73019, USA.

Modern studies of the early solar system routinely invoke the possibility of an orbital instability among the giant planets triggered by gravitational interactions between the planets and a massive exterior disk of planetesimals. Previous works have suggested that this instability can be substantially delayed (~100s Myr) after the formation of the giant planets. Bodies in the disk are typically treated in a semi-active manner, wherein their gravitational force on the planets is included, but interactions between the planetesimals are ignored. Read More

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February 2019

OSSOS XV: PROBING THE DISTANT SOLAR SYSTEM WITH OBSERVED SCATTERING TNOS.

Astron J 2019 Jul 2;158(1). Epub 2019 Jul 2.

Institut UTINAM UMR6213, CNRS, Univ. Bourgogne Franche-Comt, OSU Theta F-25000 Besançon, France.

Most known trans-Neptunian objects (TNOs) gravitationally scattering off the giant planets have orbital inclinations consistent with an origin from the classical Kuiper belt, but a small fraction of these "scattering TNOs" have inclinations that are far too large ( 45°) for this origin. These scattering outliers have previously been proposed to be interlopers from the Oort cloud or evidence of an undiscovered planet. Here we test these hypotheses using N-body simulations and the 69 centaurs and scattering TNOs detected in the Outer Solar Systems Origins Survey and its predecessors. Read More

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On the Dynamics of the Inclination Instability.

Astron J 2018 Oct 6;156(4). Epub 2018 Sep 6.

JILA and Department of Astrophysical and Planetary Sciences, CU Boulder, Boulder, CO 80309, USA.

Axisymmetric disks of eccentric Kepler orbits are vulnerable to an instability that causes orbits to exponentially grow in inclination, decrease in eccentricity, and cluster in their angle of pericenter. Geometrically, the disk expands to a cone shape that is asymmetric about the mid-plane. In this paper, we describe how secular gravitational torques between individual orbits drive this "inclination instability". Read More

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October 2018

EMPIRICAL TIDAL DISSIPATION IN EXOPLANET HOSTS FROM TIDAL SPIN-UP.

Astron J 2018 Apr 22;155(4). Epub 2018 Mar 22.

Department of Astrophysical Sciences, Princeton University, 4 Ivy Ln., Princeton, NJ 08544, USA.

Stars with hot Jupiters tend to be rotating faster than other stars of the same age and mass. This trend has been attributed to tidal interactions between the star and planet. A constraint on the dissipation parameter follows from the assumption that tides have managed to spin up the star to the observed rate within the age of the system. Read More

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NEW YOUNG STARS AND BROWN DWARFS IN THE UPPER SCORPIUS ASSOCIATION.

Astron J 2018 Aug 27;156(2). Epub 2018 Jul 27.

Department of Physics, Rockhurst University, 1100 Rockhurst Rd, Kansas City, MO 64110-2508, USA.

To improve the census of the Upper Sco association (~11 Myr, ~145 pc), we have identified candidate members using parallaxes, proper motions, and color-magnitude diagrams from several wide-field imaging surveys and have obtained optical and infrared spectra of several hundred candidates to measure their spectral types and assess their membership. We also have performed spectroscopy on a smaller sample of previously known or suspected members to refine their spectral types and evidence of membership. We have classified 530 targets as members of Upper Sco, 377 of which lack previous spectroscopy. Read More

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Shepherding in a Self-gravitating Disk of Trans-Neptunian Objects.

Astron J 2019 21;157:59. Epub 2019 Jan 21.

Department of Physics, American University of Beirut, PO BOX 11-0236, Riad El-Solh, Beirut 11097 2020, Lebanon;

A relatively massive and moderately eccentric disk of trans-Neptunian objects (TNOs) can effectively counteract apse precession induced by the outer planets, and in the process shepherd highly eccentric members of its population into nearly stationary configurations that are antialigned with the disk itself. We were sufficiently intrigued by this remarkable feature to embark on an extensive exploration of the full spatial dynamics sustained by the combined action of giant planets and a massive trans-Neptunian debris disk. In the process, we identified ranges of disk mass, eccentricity, and precession rate that allow apse-clustered populations that faithfully reproduce key orbital properties of the much-discussed TNO population. Read More

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January 2019

A New, Long-Lived, Jupiter Mesoscale Wave Observed at Visible Wavelengths.

Astron J 2018 Aug 2;156(2). Epub 2018 Aug 2.

Fundació Observatori Esteve Duran, Barcelona, Spain.

Small-scale waves were observed along the boundary between Jupiter's North Equatorial Belt and North Tropical Zone, ~16.5° N planetographic latitude in Hubble Space Telescope data in 2012 and throughout 2015 to 2018, observable at all wavelengths from the UV to the near IR. At peak visibility, the waves have sufficient contrast (~10%) to be observed from ground-based telescopes. Read More

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Jupiter's Mesoscale Waves Observed at 5 m by Ground-based Observations and JIRAM.

Astron J 2018 Aug 26;156(2). Epub 2018 Jul 26.

INAF-Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy.

We characterize the origin and evolution of a mesoscale wave pattern in Jupiter's North Equatorial Belt (NEB), detected for the first time at 5 m using a 2016-17 campaign of "lucky imaging" from the VISIR instrument on the Very Large Telescope and the NIRI instrument on the Gemini observatory, coupled with -band imaging from Juno's JIRAM instrument during the first seven Juno orbits. The wave is compact, with a 1°.1-1°. Read More

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EXOPLANET MODULATION OF STELLAR CORONAL RADIO EMISSION.

Astron J 2018 Nov 17;156(5). Epub 2018 Oct 17.

Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, Massachusetts, USA.

The search for exoplanets in the radio bands has been focused on detecting radio emissions produced by the interaction between magnetized planets and the stellar wind (auroral emission). Here we introduce a new tool, which is part of our MHD stellar corona model, to predict the ambient coronal radio emission and its modulations induced by a close planet. For simplicity, the present work assumes that the exoplanet is stationary in the frame rotating with the stellar rotation. Read More

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November 2018

Spectroscopic Characterization of Key Aromatic Molecules: A Route toward The Origin of Life.

Astron J 2017 Aug;154(3)

Department of Physics, University of Maryland, College Park, MD 20742, USA.

To gain information on the abiotic synthesis of the building blocks of life from simple molecules, and their subsequent chemical evolution to biological systems, the starting point is the identification of target species in Titan-like planets, i.e., planets that resemble the primitive Earth, as well as in Earth-like planets in the habitable zone of their star, namely planets where life can be already originated. Read More

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FUSE Spectroscopy of the Accreting Hot Components in Symbiotic Variables.

Astron J 2017 Apr 17;153(No 4). Epub 2017 Mar 17.

Department of Physics & Astronomy, Florida Institute of Technology, Melbourne, FL 98195, USA.

We have conducted a spectroscopic analysis of the far ultraviolet archival spectra of four symbiotic variables, EG And, AE Ara, CQ Dra and RW Hya. RW Hya and EG And have never had a recorded outburst while CQ Dra and AE Ara have outburst histories. We analyze these systems while they are in quiescence in order to help reveal the physical properties of their hot components via comparisons of the observations with optically thick accretion disk models and NLTE model white dwarf photospheres. Read More

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Far Ultraviolet Spectroscopy of Old Novae. II. RR Pic, V533 Her, and DI Lac.

Astron J 2017 Mar 15;153(No 3). Epub 2017 Feb 15.

Department of Astrophysics & Planetary Science, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085, USA.

The old novae V533 Her (Nova Her 1963), DI Lac (Nova Lac 1910), and RR Pic (Nova Pic 1891) are in (or near) their quiescent stage, following their nova explosions, and continue to accrete at a high rate in the aftermath of their explosions. They exhibit continua that are steeply rising into the FUV, as well as absorption lines and emission lines of uncertain origin. All three have () spectra that offer not only higher spectral resolution but also wavelength coverage extending down to the Lyman Limit. Read More

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Hubble COS Spectroscopy of the Dwarf Nova CW Mon: The White Dwarf in Quiescence?

Astron J 2017 Aug 13;154(2). Epub 2017 Jul 13.

Department of Physics, University of Warwick, Coventry CV4 7AL, UK.

We present a synthetic spectral analysis of the HST COS spectrum of the U Geminorum-type dwarf nova CW Mon, taken during quiescence as part of our COS survey of accreting white dwarfs in Cataclysmic Variables. We use synthetic photosphere and optically thick accretion disk spectra to model the COS spectrum as well as archival IUE spectra obtained decades ago when the system was in an even deeper quiescent state. Assuming a reddening of E(B-V)=0. Read More

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A SEARCH FOR LOST PLANETS IN THE MULTI-PLANET SYSTEMS AND THE DISCOVERY OF A LONG PERIOD, NEPTUNE-SIZED EXOPLANET KEPLER-150 F.

Astron J 2017 Apr 28;153(No 4). Epub 2017 Mar 28.

Department of Astronomy, Yale University, New Haven, CT 06511 USA.

The vast majority of the 4700 confirmed planets and planet candidates discovered by the space telescope were first found by the pipeline. In the pipeline, after a transit signal is found, all data points associated with those transits are removed, creating a "Swiss cheese"-like light curve full of holes, which is then used for subsequent transit searches. These holes could render an additional planet undetectable (or "lost"). Read More

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TRITON'S EVOLUTION WITH A PRIMORDIAL NEPTUNIAN SATELLITE SYSTEM.

Astron J 2017 Nov 6;154(5). Epub 2017 Nov 6.

Southwest Research Institute, Boulder, Colorado 80302, USA.

The Neptunian satellite system is unusual. The major satellites of Jupiter, Saturn and Uranus are all in prograde, low inclination orbits. Neptune on the other hand, has the fewest satellites and most of the system's mass is within one irregular satellite, Triton. Read More

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November 2017

SNaX: A Database of Supernova X-Ray Light Curves.

Astron J 2017 Jun 9;153(6). Epub 2017 May 9.

Astronomy and Astrophysics, University of Chicago, 5640 S Ellis Avenue, ERC 569, Chicago, IL 60637, USA.

We present the Supernova X-ray Database (SNaX), a compilation of the X-ray data from young supernovae (SNe). The database includes the X-ray fluxes and luminosities of young SNe, from days to years after outburst. The original goal and intent of this study was to present a database of Type IIn SNe (SNe IIn), which we have accomplished. Read More

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Second Epoch VLBA Calibrator Survey Observations - VCS-II.

Astron J 2016 May;151(6)

National Science Foundation, Washington, DC,

Six very successful VLBA calibrator survey campaigns were run between 1994 and 2007 to build up a large list of compact radio sources with positions precise enough for use as VLBI phase reference calibrators. We report on the results of a second epoch VLBA Calibrator Survey campaign (VCS-II) in which 2400 VCS sources were re-observed at X and S bands in order to improve the upcoming third realization of the International Celestial Reference Frame (ICRF3) as well as to improve their usefulness as VLBI phase reference calibrators. In this survey, some 2062 previously detected sources and 324 previously undetected sources were detected and revised positions are presented. Read More

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Far Ultraviolet Spectroscopy of Old Novae I. V603 Aquila.

Astron J 2015 Jul 7;150(No 1). Epub 2015 Jul 7.

Astrophysics & Planetary Science, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085, USA.

We present the results of a synthetic spectral analysis of the far ultraviolet archival IUE, HST and FUSE observations of the fast old nova V603 Aql, obtained some 90 years after its 1918 nova outburst. Our analysis utilizes the new Hubble FGS parallax distance for this nearly face-on old nova, a high white dwarf mass and a low reddening. Our analysis includes non-truncated optically thick accretion disks since V603 Aql is neither a polar nor an intermediate polar. Read More

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2MASS J035523.37+113343.7: A YOUNG, DUSTY, NEARBY, ISOLATED BROWN DWARF RESEMBLING A GIANT EXOPLANET.

Astron J 2013 20;2. Epub 2012 Nov 20.

Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034.

We present parallax and proper motion measurements, near-infrared spectra, and WISE photometry for the low surface gravity L5 dwarf 2MASSJ035523.37+113343.7 (2M0355). Read More

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November 2012

DISCOVERY OF TWO VERY WIDE BINARIES WITH ULTRACOOL COMPANIONS AND A NEW BROWN DWARF AT THE L/T TRANSITION.

Astron J 2012 ;144(6)

Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 53, Valparaíso, Chile.

We present the discovery and spectroscopic follow-up of a nearby late-type L dwarf (2M0614+3950), and two extremely wide very-low-mass binary systems (2M0525-7425AB and 2M1348-1344AB), resulting from our search for common proper motion pairs containing ultracool components in the Two Micron All Sky Survey (2MASS) and the Wide-field Infrared Survey Explorer (WISE) catalogs. The near-infrared spectrum of 2M0614+3950 indicates a spectral type L9 ± 1 object residing at a distance of 26.0 ± 1. Read More

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January 2012