Search Publications
Precise Masses, Ages, and Orbital Parameters of the Binary Systems HIP 11352, HIP 70973, and HIP 72479
Al-Wardat, M. A.; Al-Tawalbeh, Y. M.; Hussein, A. M. +7 more
In this work, the orbital elements are improved and the total masses of the three close visual binary systems CVBSs: HIP 11352, HIP 70973, and HIP 72479 are precisely calculated. The calculations were performed based on an assessment of the latest Gaia DR2 and Hipparcos trigonometric parallax measurements. The morphology and kinematics of orbits a…
Speckle Imaging Characterization of Radial Velocity Exoplanet Systems
Henry, Gregory W.; Kane, Stephen R.; Howell, Steve B. +10 more
We conducted speckle imaging observations of 53 stellar systems that were members of long-term radial velocity (RV) monitoring campaigns and exhibited substantial accelerations indicative of planetary or stellar companions in wide orbits. Our observations were made with blue and red filters using the Differential Speckle Survey Instrument at Gemin…
Modes of a stellar system I: Ergodic systems
Binney, James; Lau, Jun Yan
The excursions of star clusters and galaxies around statistical equilibria are studied. For a stable ergodic model Antonov's Hermitian operator on six-dimensional phase space has the normal modes as its eigenfunctions. The excitation energy of the system is just the sum of the (positive) energies associated with each normal mode. Formulae are give…
GECKO Optical Follow-up Observation of Three Binary Black Hole Merger Events: GW190408_181802, GW190412, and GW190503_185404
Lee, Chung-Uk; Kim, Seung-Lee; Im, Myungshin +12 more
We present optical follow-up observation results of three binary black hole merger (BBH) events, GW190408_181802, GW190412, and GW190503_185404, which were detected by the Advanced LIGO and Virgo gravitational wave (GW) detectors. Electromagnetic (EM) counterparts are generally not expected for BBH merger events. However, some theoretical models s…
From Formation to Disruption: Observing the Multiphase Evolution of a Solar Flare Current Sheet
Chitta, L. P.; Cheng, X.; Priest, E. R.
A current sheet, where magnetic energy is liberated through reconnection and converted to other forms, is thought to play the central role in solar flares, the most intense explosions in the heliosphere. However, the evolution of a current sheet and its subsequent role in flare-related phenomena such as particle acceleration is poorly understood. …
Extreme Variability of the V488 Persei Debris Disk
Rieke, G. H.; Gáspár, András; Melis, Carl +1 more
V488 Persei is the most extreme debris disk known in terms of the fraction of the stellar luminosity it intercepts and reradiates. The infrared output of its disk is extremely variable, similar in this respect to the most variable disk known previously, that around ID8 in NGC 2547. We show that the variations are likely to be due to collisions of …
Multiwavelength investigation of the candidate Galactic PeVatron MGRO J1908+06
Mereghetti, S.; Sidoli, L.; La Palombara, N. +3 more
The candidate PeVatron MGRO J1908+06, which shows a hard spectrum beyond 100 TeV, is one of the most peculiar γ-ray sources in the Galactic plane. Its complex morphology and some possible counterparts spatially related with the very high energy (VHE) emission region, preclude to distinguish between a hadronic and leptonic nature of the γ-ray emiss…
S2D2: Small-scale Significant substructure DBSCAN Detection. I. NESTs detection in 2D star-forming regions
Hacar, Álvaro; Buckner, Anne S. M.; González, Marta +13 more
Context. The spatial and dynamical structure of star-forming regions can offer insights into stellar formation patterns. The amount of data from current and upcoming surveys calls for robust and objective procedures for detecting structures in order to statistically analyse the various regions and compare them.
Aims: We aim to provide the com…
Lower-luminosity Obscured AGN Host Galaxies Are Not Predominantly in Major-merging Systems at Cosmic Noon
Kirkpatrick, Allison; Kocevski, Dale D.; Heckman, Timothy +15 more
For over 60 yr, the scientific community has studied actively growing central supermassive black holes (active galactic nuclei, AGNs), but fundamental questions on their genesis remain unanswered. Numerical simulations and theoretical arguments show that black hole growth occurs during short-lived periods (~107-108 yr) of pow…
New Infrared Spectral Indices of Luminous Cold Stars: From Early K to M Types
Menten, Karl M.; Zhu, Qingfeng; Kudritzki, Rolf-Peter +4 more
We present infrared spectral indices (1.0-2.3 µm) of Galactic late-type giants and red supergiants (RSGs). We used existing and new spectra obtained at resolution power R = 2000 with SpeX on the IRTF telescope. While a large CO equivalent width (EW), at 2.29 µm ([CO, 2.29] ≳ 45 Å) is a typical signature of RSGs later than spectral type…