Search Publications
A Reverberation Lag for the High-ionization Component of the Broad-line Region in the Narrow-line Seyfert 1 Mrk 335
Skowron, J.; Kochanek, C. S.; Horne, Keith +37 more
We present the first results from a detailed analysis of photometric and spectrophotometric data on the narrow-line Seyfert 1 (NLS1) galaxy Mrk 335, collected over a 120 day span in the fall of 2010. From these data we measure the lag in the He II λ4686 broad emission line relative to the optical continuum to be 2.7 ± 0.6 days and the lag in the H…
The Progenitor of the Type Ia Supernova that Created SNR 0519-69.0 in the Large Magellanic Cloud
Schaefer, Bradley E.; Pagnotta, Ashley; Edwards, Zachary I.
Models for the progenitor systems of Type Ia supernovae can be divided into double-degenerate systems, which contain two white dwarfs, and single-degenerate systems, which contain one white dwarf plus one companion star (either a red giant, a subgiant, or a >1.16 M ⊙ main-sequence star). The white dwarf is destroyed in the supernova …
Measuring the Abundance of Sub-kilometer-sized Kuiper Belt Objects Using Stellar Occultations
Livio, Mario; Nelan, Edmund P.; Gal-Yam, Avishay +6 more
We present here the analysis of about 19,500 new star hours of low ecliptic latitude observations (|b| <= 20°) obtained by the Hubble Space Telescope's Fine Guidance Sensors over a time span of more than nine years, which is in addition to the ~12, 000 star hours previously analyzed by Schlichting et al. Our search for stellar occultations by s…
Systematic Investigation of Solar Modulation of Galactic Protons for Solar Cycle 23 Using a Monte Carlo Approach with Particle Drift Effects and Latitudinal Dependence
Boella, G.; Gervasi, M.; Grandi, D. +8 more
A propagation model of galactic cosmic protons through the heliosphere was implemented using a two-dimensional Monte Carlo approach to determine the differential intensities of protons during solar cycle 23. The model includes the effects due to the variation of solar activity during the propagation of cosmic rays from the boundary of the heliopau…
Galaxy Disks Do Not Need to Survive in the ΛCDM Paradigm: The Galaxy Merger Rate Out to z ~ 1.5 from Morpho-kinematic Data
Flores, H.; Hammer, F.; Puech, M. +5 more
About two-thirds of present-day, large galaxies are spirals such as the Milky Way or Andromeda, but the way their thin rotating disks formed remains uncertain. Observations have revealed that half of their progenitors, six billion years ago, had peculiar morphologies and/or kinematics, which exclude them from the Hubble sequence. Major mergers, i.…
Multi-wavelength Observations of the Radio Magnetar PSR J1622-4950 and Discovery of Its Possibly Associated Supernova Remnant
Esposito, Paolo; Rea, Nanda; Drake, Jeremy J. +29 more
We present multi-wavelength observations of the radio magnetar PSR J1622-4950 and its environment. Observations of PSR J1622-4950 with Chandra (in 2007 and 2009) and XMM (in 2011) show that the X-ray flux of PSR J1622-4950 has decreased by a factor of ~50 over 3.7 years, decaying exponentially with a characteristic time of τ = 360 ± 11 days. This …
On the Occurrence of the Third-order Scaling in High Latitude Solar Wind
Bruno, R.; Carbone, V.; Veltri, P. +3 more
The occurrence and nature of a nonlinear energy cascade within the intermediate scales of solar wind Alfvénic turbulence represents an important open issue. Using in situ measurements of fast, high latitude solar wind taken by the Ulysses spacecraft at solar minima, it is possible to show that a nonlinear energy cascade of imbalanced turbulence is…
Complex Gas Kinematics in Compact, Rapidly Assembling Star-forming Galaxies
Amorín, R.; Pérez-Montero, E.; Vílchez, J. M. +3 more
Deep, high-resolution spectroscopic observations have been obtained for six compact, strongly star-forming galaxies at redshift z ~ 0.1-0.3, most of them also known as green peas. Remarkably, these galaxies show complex emission-line profiles in the spectral region including Hα, [N II] λλ6548, 6584, and [S II] λλ6717, 6731, consisting of the super…
Lyα Dominance of the Classical T Tauri Far-ultraviolet Radiation Field
Herczeg, Gregory J.; Brown, Alexander; France, Kevin +6 more
Far-ultraviolet (FUV) radiation plays an important role in determining chemical abundances in protoplanetary disks. H I Lyman α (Lyα) is suspected to be the dominant component of the FUV emission from Classical T Tauri Stars (CTTSs), but is difficult to measure directly due to circumstellar and interstellar H I absorption. To better characterize t…
The Infrared Eye of the Wide-Field Camera 3 on the Hubble Space Telescope Reveals Multiple Main Sequences of Very Low Mass Stars in NGC 2808
Anderson, J.; Milone, A. P.; Marino, A. F. +9 more
We use images taken with the infrared channel of the Wide Field Camera 3 on the Hubble Space Telescope to study the multiple main sequences (MSs) of NGC 2808. Below the turnoff, the red, the middle, and the blue MS, previously detected from visual-band photometry, are visible over an interval of about 3.5 F160W magnitudes. The three MSs merge toge…