Search Publications
Update on the X-Ray Variability Plane for Active Galactic Nuclei: The Role of the Obscuration
González-Martín, Omaira
Scaling relations are the most powerful astrophysical tools to set constraints on the physical mechanisms of astronomical sources and to infer properties that cannot be accessed directly. We reinvestigate here one of these scaling relations in active galactic nuclei (AGNs); the so-called X-ray variability plane (or mass-luminosity timescale relati…
Late-time Observations of ASASSN-14lp Strengthen the Case for a Correlation between the Peak Luminosity of Type Ia Supernovae and the Shape of Their Late-time Light Curves
Zurek, David R.; Rest, Armin; Cara, Mihai +5 more
Late-time observations of Type Ia supernovae (SNe Ia), >900 days after explosion, have shown that this type of SN does not suffer an “IR catastrophe” at 500 days as previously predicted. Instead, several groups have observed a slow-down in the optical light curves of these SNe. A few reasons have been suggested for this slow-down, from a changi…
Period Analysis of Seven Field ab-type RR Lyrae Stars Based on O - C Diagrams: Cyclic Variations and Long-term Period Changes
Qian, S. -B.; Zhu, L. -Y.; Li, L. -J.
Using the times of light maximum collected from the GEOS RR Lyrae database and determined from sky surveys, we utilize the O - C method to study the period variations of seven field ab-type RR Lyrae stars. The time coverage of data for most stars is more than 100 years, allowing us to investigate period changes over a large time span. We find that…
Measurement Process and Inversions Using Helioseismic Normal-mode Coupling
Hanasoge, Shravan
Normal modes are coupled by the presence of perturbations in the Sun, providing a novel and underappreciated helioseismic technique with which to image the solar interior. The process of measuring coupling between normal modes is straightforward, much more so when compared with other prevalent helioseismic techniques. The theoretical framework to …
An Empirical Study of Contamination in Deep, Rapid, and Wide-field Optical Follow-up of Gravitational Wave Events
Berger, E.; Rest, A.; Foley, R. J. +10 more
We present an empirical study of contamination in wide-field optical follow-up searches of gravitational wave sources from Advanced LIGO/Virgo using dedicated observations with the Dark Energy Camera. Our search covered ∼56 deg2, with two visits per night, in the i and z bands, followed by an additional set of griz images three weeks la…
Inferring Binary and Trinary Stellar Populations in Photometric and Astrometric Surveys
Leistedt, Boris; Hogg, David W.; Widmark, Axel
Multiple stellar systems are ubiquitous in the Milky Way but are often unresolved and seen as single objects in spectroscopic, photometric, and astrometric surveys. However, modeling them is essential for developing a full understanding of large surveys such as Gaia and connecting them to stellar and Galactic models. In this paper, we address this…
Reverse Current Model for Coronal Mass Ejection Cavity Formation
Li, Hui; Haw, Magnus A.; Wongwaitayakornkul, Pakorn +1 more
We report here a new model for explaining the three-part structure of coronal mass ejections (CMEs). The model proposes that the cavity in a CME forms because a rising electric current in the core prominence induces an oppositely directed electric current in the background plasma; this eddy current is required to satisfy the frozen-in magnetic flu…
Tidal Interactions and Mergers in Intermediate-redshift EDisCS Clusters
Moustakas, John; Aragón-Salamanca, Alfonso; Lotz, Jennifer M. +6 more
We study the fraction of tidal interactions and mergers (TIMs) with well-identified observability timescales (f TIM) in group, cluster, and accompanying field galaxies and its dependence on redshift (z), cluster velocity dispersion (σ), and environment analyzing Hubble Space Telescope/ACS images and catalogs from the ESO Distant Cluster…
Variability-selected Low-luminosity Active Galactic Nuclei Candidates in the 7 Ms Chandra Deep Field-South
Lehmer, B. D.; Brandt, W. N.; Vignali, C. +13 more
In deep X-ray surveys, active galactic nuclei (AGNs) with a broad range of luminosities have been identified. However, cosmologically distant low-luminosity AGN (LLAGN, {L}{{X}}≲ {10}42 erg s-1) identification still poses a challenge because of significant contamination from host galaxies. Based on the 7 Ms Chandra…
The Mass and Absorption Column Densities of Galactic Gaseous Halos. II. The High Ionization State Ions
Bregman, Joel N.; Qu, Zhijie
The high ionization state ions trace the hot gases in the universe, of which gaseous halos around galaxies are a major contributor. Following Qu & Bregman, we calculate the gaseous halo contribution to the observed column density distributions for these ions by convolving the gaseous halo model with the observed stellar mass function. The pred…