Search Publications
Reconstruction of the Dark Energy Equation of State from the Latest Observations
Xia, Jun-Qing; Yang, Yang; Dai, Ji-Ping
Since the discovery of the accelerating expansion of our universe in 1998, studying the features of dark energy has remained a hot topic in modern cosmology. In the literature, dark energy is usually described by w ≡ P/ρ, where P and ρ denote its pressure and energy density. Therefore, exploring the evolution of w is the key approach to understand…
On the Full-range β Dependence of Ion-scale Spectral Break in the Solar Wind Turbulence
He, Jiansen; Wang, Xin; Wang, Linghua +1 more
The power spectrum of magnetic fluctuations has a break at the high-frequency end of the inertial range. Beyond this break, the spectrum becomes steeper than the Kolmogorov law f -5/3. The break frequency was found to be associated with plasma beta (β). However, the full-range β dependence of the ion-scale spectral break has not been pr…
A Radio Frequency Study of the Accreting Millisecond X-ray Pulsar, IGR J16597-3704, in the Globular Cluster NGC 6256
Maccarone, T. J.; Altamirano, D.; Degenaar, N. +14 more
We present Karl G. Jansky Very Large Array radio frequency observations of the new accreting millisecond X-ray pulsar (AMXP), IGR J16597-3704, located in the globular cluster NGC 6256. With these data, we detect a radio counterpart to IGR J16597-3704, and determine an improved source position. Pairing our radio observations with quasi-simultaneous…
High-resolution SOFIA/EXES Spectroscopy of SO2 Gas in the Massive Young Stellar Object MonR2 IRS3: Implications for the Sulfur Budget
Montiel, Edward; Neufeld, David A.; Blake, Geoffrey A. +10 more
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 ν 3 rovibrational band o…
Independent Estimation of Black Hole Mass for the γ-ray-detected Archetypal Narrow-line Seyfert 1 Galaxy 1H 0323+342 from X-Ray Variability
Komossa, S.; Jin, Chichuan; Yuan, Weimin +2 more
γ-ray-detected narrow-line Seyfert 1 galaxies (NLS1s) are a newly discovered class of radio-loud active galactic nuclei (AGNs) that launch powerful jets that are generally found only in blazars and radio galaxies. However, their black hole (BH) masses as estimated from their broad emission lines are an order of magnitude or more lower than those i…
Spatial Organization of Seven Extreme Solar Energetic Particle Events
Wang, Haimin; Vainio, Rami; Pohjolainen, Silja +4 more
Emission of relativistic protons and helium responsible for extreme solar particle events (ground level enhancements (GLEs)) is often structured. We investigate its organization depending on the eruption stage characterized by the heliocentric height of associated coronal mass ejections (CMEs). Seven GLEs are considered: events on 1997 November 6,…
NuSTAR Detection of a Hard X-Ray Source in the Supernova Remnant-molecular Cloud Interaction Site of IC 443
Hailey, Charles J.; Mori, Kaya; Zhang, Shuo +10 more
We report on a broadband study of a complex X-ray source (1SAX J0618.0+2227) associated with the interaction site of the supernova remnant (SNR) IC 443 and ambient molecular cloud (MC) using NuSTAR, XMM-Newton, and Chandra observations. Its X-ray spectrum is composed of both thermal and nonthermal components. The thermal component can be equally w…
The Distance to the Galaxy Coma P
Anand, Gagandeep S.; Shaya, Edward J.; Tully, R. Brent +4 more
If the extremely low surface-brightness galaxy Coma P lies at 5.5 ± 0.3 Mpc, as recently proposed, then it would have an extraordinarily deviant peculiar velocity of ∼900 km s-1 at a location where differential velocities between galaxies are low. We have accessed the images from the Hubble Space Telescope (HST) archives used to derive …
Understanding Fundamental Properties and Atmospheric Features of Subdwarfs via a Case Study of SDSS J125637.13-022452.4
Gonzales, Eileen C.; Faherty, Jacqueline K.; Gagné, Jonathan +2 more
We present the distance-calibrated spectral energy distribution (SED) of the sdL3.5 subdwarf SDSS J125637.13-022452.4 (J1256-0224) using its Gaia DR2 parallax. We report the bolometric luminosity and semi-empirical fundamental parameters, as well as updated UVW velocities. The SED of J1256-0224 is compared to field-age and low-gravity dwarfs of th…
Must Star-forming Galaxies Rapidly Get Denser before They Quench?
Morishita, T.; Abramson, L. E.
Using the deepest data yet obtained, we find no evidence preferring compaction-triggered quenching—where rapid increases in galaxy density truncate star formation—over a null hypothesis in which galaxies age at constant surface density ({{{Σ }}}e\equiv {M}* /2π {r}e2). Results from two fully empirical an…