Search Publications
The Secret Lives of Cepheids: Evolution, Mass-Loss, and Ultraviolet Emission of the Long-period Classical Cepheid
Guinan, Edward F.; Engle, Scott G.; Neilson, Hilding R. +2 more
The classical Cepheid l Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive (M ≥ 8 M ⊙) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of …
A Chandra Study of Temperature Distributions of the Intracluster Medium in 50 Galaxy Clusters
Hu, Dan; Xu, Haiguang; Zhu, Zhenghao +10 more
To investigate the spatial distribution of the intracluster medium temperature in galaxy clusters in a quantitative way and probe the physics behind it, we analyze the X-ray spectra from a sample of 50 clusters that were observed with the Chandra ACIS instrument over the past 15 years and measure the radial temperature profiles out to 0.45r50…
The Binary Black Hole Model for Mrk 231 Bites the Dust
Gallagher, Sarah C.; Terndrup, Donald M.; Leighly, Karen M. +1 more
Mrk 231 is a nearby quasar with an unusually red near-UV-to-optical continuum, generally explained as heavy reddening by dust. Yan et al. proposed that Mrk 231 is a milliparsec black hole binary with little intrinsic reddening. We show that if the observed FUV continuum is intrinsic, as assumed by Yan et al., it fails by a factor of about 100 in p…
Eta Carinae's Thermal X-Ray Tail Measured with XMM-Newton and NuSTAR
Hamaguchi, Kenji; Corcoran, Michael F.; Russell, Christopher M. P. +12 more
The evolved, massive highly eccentric binary system, η Car, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission …
The Tale of the Two Tails of the Oldish PSR J2055+2539
De Luca, Andrea; Caraveo, Patrizia; Marelli, Martino +3 more
We analyzed a deep XMM-Newton observation of the radio-quiet γ-ray PSR J2055+2539. The spectrum of the X-ray counterpart is nonthermal, with a photon index of Γ = 2.36 ± 0.14 (1σ confidence). We detected X-ray pulsations with a pulsed fraction of 25% ± 3% and a sinusoidal shape. Taking into account considerations on the γ-ray efficiency of the pul…
Genesis of Interplanetary Intermittent Turbulence: A Case Study of Rope&enrope Magnetic Reconnection
Miranda, Rodrigo A.; Chian, Abraham C. -L.; Muñoz, Pablo R. +5 more
In a recent paper, the relation between current sheet, magnetic reconnection, and turbulence at the leading edge of an interplanetary coronal mass ejection was studied. We report here the observation of magnetic reconnection at the interface region of two interplanetary magnetic flux ropes. The front and rear boundary layers of three interplanetar…
The First High-phase Observations of a KBO: New Horizons Imaging of (15810) 1994 JR1 from the Kuiper Belt
Olkin, Cathy B.; Stern, S. Alan; Young, Leslie A. +12 more
NASA’s New Horizons spacecraft observed (15810) 1994 JR1, a 3:2 resonant Kuiper belt object (KBO), using the LOng Range Reconnaissance Imager (LORRI) on 2015 November 2 from a distance of 1.85 au and again on 2016 April 7 from a distance of 0.71 au. These were the first close observations of any KBO other than Pluto. Combining ground-ba…
Survival of Pure Disk Galaxies over the Last 8 Billion Years
Sachdeva, Sonali; Saha, Kanak
Pure disk galaxies without any bulge component, I.e., bulges that are neither classical nor pseudo, seem to have escaped the effects of merger activity that are inherent to hierarchical galaxy formation models as well as strong internal secular evolution. We discover that a significant fraction (∼15%-18%) of disk galaxies in the Hubble Deep Field …
Suprathermal Electrons at Saturn's Bow Shock
Coates, A. J.; Dougherty, M. K.; Fujimoto, M. +4 more
The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach numb…
The Candidate Cluster and Protocluster Catalog (CCPC) of Spectroscopically Identified Structures Spanning 2.74 < z < 3.71
Franck, J. R.; McGaugh, S. S.
We developed a search methodology to identify galaxy protoclusters at z\gt 2.74 and implemented it on a sample of ∼14,000 galaxies with previously measured redshifts. The results of this search are recorded in the Candidate Cluster and Protocluster Catalog (CCPC). The catalog contains 12 clusters that are highly significant overdensities ({δ }