Search Publications
The Changing Fractions of Type Ia Supernova NUV--Optical Subclasses with Redshift
Foley, Ryan J.; Narayan, Gautham; Brown, Peter J. +1 more
Ultraviolet (UV) and optical photometry of Type Ia supernovae (SNe Ia) at low redshift have revealed the existence of two distinct color groups, composed of NUV-red and NUV-blue events. The color curves differ primarily by an offset, with the NUV-blue u-v color curves bluer than the NUV-red curves by 0.4 mag. For a sample of 23 low-redshift SNe Ia…
The Compton hump and variable blue wing in the extreme low-flux NuSTAR observations of 1H0707-495
Harrison, F. A.; Stern, D.; Zhang, W. W. +10 more
The narrow-line Seyfert I galaxy, 1H0707-495, has been well observed in the 0.3-10 keV band, revealing a dramatic drop in flux in the iron Kα band, a strong soft excess, and short time-scale reverberation lags associated with these spectral features. In this paper, we present the first results of a deep 250-ks NuSTAR (Nuclear Spectroscopic Telesco…
Bow Shock Fragmentation Driven by a Thermal Instability in Laboratory Astrophysics Experiments
Hartigan, P.; Frank, A.; Lebedev, S. V. +16 more
The role of radiative cooling during the evolution of a bow shock was studied in laboratory-astrophysics experiments that are scalable to bow shocks present in jets from young stellar objects. The laboratory bow shock is formed during the collision of two counterstreaming, supersonic plasma jets produced by an opposing pair of radial foil Z-pinche…
Measuring Star Formation Rate and Far-infrared Color in High-redshift Galaxies Using the CO(7-6) and [N II] 205 µm Lines
Inami, Hanae; Gao, Yu; Liu, Lijie +13 more
To better characterize the global star formation activity in a galaxy, one needs to know not only the star formation rate (SFR) but also the rest-frame, far-infrared color (e.g., the 60-100 µm color, C(60/100)) of the dust emission. The latter probes the average intensity of the dust heating radiation field and scales statistically with the …
Comparative pick-up ion distributions at Mars and Venus: Consequences for atmospheric deposition and escape
Luhmann, Janet; Curry, Shannon M.; Hara, Takuya +3 more
Without the shielding of a substantial intrinsic dipole magnetic field, the atmospheres of Mars and Venus are particularly susceptible to similar atmospheric ion energization and scavenging processes. However, each planet has different attributes and external conditions controlling its high altitude planetary ion spatial and energy distributions. …
Kinematics of the Outflow from the Young Star DG Tau B: Rotation in the Vicinities of an Optical Jet
Ho, Paul T. P.; Zapata, Luis A.; Rodríguez, Luis F. +4 more
We present 12CO(2-1) line and 1300 µm continuum observations made with the Submillimeter Array of the young star DG Tau B. We find, in the continuum observations, emission arising from the circumstellar disk surrounding DG Tau B. The 12CO(2-1) line observations, on the other hand, revealed emission associated with the d…
Predicting GAIA's Parallax Distance to the Cygnus OB2 Association with Eclipsing Binaries
Kobulnicky, Henry A.; Lundquist, Michael J.; Vargas Álvarez, Carlos A. +2 more
The Cygnus OB2 Association is one of the nearest and largest collections of massive stars in the Galaxy. Situated at the heart of the “Cygnus X” complex of star-forming regions and molecular clouds, its distance has proven elusive owing to the ambiguous nature of kinematic distances along this ℓ ≃ 80° sightline and the heavy, patchy extinction. In…
Using dark energy to suppress power at small scales
Kunz, Martin; Nesseris, Savvas; Sawicki, Ignacy
The latest Planck results reconfirm the existence of a slight but chronic tension between the best-fit cosmic microwave background (CMB) and low-redshift observables: power seems to be consistently lacking in the late universe across a range of observables (e.g. weak lensing, cluster counts). We propose a two-parameter model for dark energy where …
On the Electron-to-Neutral Number Density Ratio in the Coma of Comet 67P/Churyumov-Gerasimenko: Guiding Expression and Sources for Deviations
Edberg, N. J. T.; Vigren, E.; Galand, M. +3 more
We compute partial photoionization frequencies of H2O, CO2, and CO, the major molecules in the coma of comet 67P/Churyumov-Gerasimenko, the target comet of the ongoing ESA Rosetta mission. Values are computed from Thermosphere Ionosphere Mesosphere Energy and Dynamics/Solar EUV Experiment solar EUV spectra for 2014 August 1, …
Organic chemistry in Titan's upper atmosphere and its astrobiological consequences: I. Views towards Cassini plasma spectrometer (CAPS) and ion neutral mass spectrometer (INMS) experiments in space
Sittler, E. C.; Ali, A.; Chornay, D. +2 more
The discovery of carbocations and carbanions by Ion Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard the Cassini spacecraft in Titan's upper atmosphere is truly amazing for astrochemists and astrobiologists. In this paper we identify the reaction mechanisms for the growth of the complex macromolecules…