Search Publications
PTF11kx: A Type Ia Supernova with Hydrogen Emission Persisting after 3.5 Years
Fox, O. D.; Filippenko, A. V.; Nugent, P. E. +4 more
The optical transient PTF11kx exhibited both the characteristic spectral features of Type Ia supernovae (SNe Ia) and the signature of ejecta interacting with circumstellar material (CSM) containing hydrogen, indicating the presence of a nondegenerate companion. We present an optical spectrum at 1342 days after peak from Keck Observatory, in which …
Active Longitude and Coronal Mass Ejection Occurrences
Srivastava, A. K.; Erdélyi, R.; Singh, T. +2 more
The spatial inhomogeneity of the distribution of coronal mass ejection (CME) occurrences in the solar atmosphere could provide a tool to estimate the longitudinal position of the most probable CME-capable active regions in the Sun. The anomaly in the longitudinal distribution of active regions themselves is often referred to as active longitude (A…
Near-Infrared Knots and Dense Fe Ejecta in the Cassiopeia A Supernova Remnant
Koo, Bon-Chul; Lee, Jae-Joon; Moon, Dae-Sik +2 more
We report the results of broadband (0.95-2.46 µm) near-infrared spectroscopic observations of the Cassiopeia A supernova remnant. Using a clump-finding algorithm in two-dimensional dispersed images, we identify 63 “knots” from eight slit positions and derive their spectroscopic properties. All of the knots emit [Fe II] lines together with ot…
Absolute Magnitudes of Seismic Red Clumps in the Kepler Field and SAGA: The Age Dependency of the Distance Scale
Zhao, G.; Casagrande, L.; Bovy, J. +4 more
Red clump stars are fundamental distance indicators in astrophysics, although theoretical stellar models predict a dependence of absolute magnitudes with age. This effect is particularly strong below ∼2 Gyr, but even above this limit a mild age dependence is still expected. We use seismically identified red clump stars in the Kepler field for whic…
High-latitude Conic Current Sheets in the Solar Wind
Tokumaru, Munetoshi; Fujiki, Ken'ichi; Malova, Helmi V. +7 more
We provide observational evidence for the existence of large-scale cylindrical (or conic-like) current sheets (CCSs) at high heliolatitudes. Long-lived CCSs were detected by Ulysses during its passages over the South Solar Pole in 1994 and 2007. The characteristic scale of these tornado-like structures is several times less than a typical width of…
Swift, XMM-Newton, and NuSTAR Observations of PSR J2032+4127/MT91 213
Takata, J.; Kong, A. K. H.; Hui, C. Y. +3 more
We report our recent Swift, NuSTAR, and XMM-Newton X-ray and Lijiang optical observations on PSR J2032+4127/MT91 213, the γ-ray binary candidate with a period of 45-50 years. The coming periastron of the system was predicted to be in 2017 November, around which high-energy flares from keV to TeV are expected. Recent studies with Chandra and Swift …
Morphology and the Color-mass Diagram as Clues to Galaxy Evolution at z&approx1
Schawinski, Kevin; Urry, C. Megan; Simmons, Brooke D. +4 more
We study the significance of mergers in the quenching of star formation in galaxies at z∼ 1 by examining their color-mass distributions for different morphology types. We perform two-dimensional light profile fits to GOODS iz images of ∼5000 galaxies and X-ray selected active galactic nucleus (AGN) hosts in the CANDELS/GOODS-north and south fields…
Observational Evidence Linking Interstellar UV Absorption to PAH Molecules
Behar, Ehud; Brosch, Noah; Tielens, Alexander G. G. M. +2 more
The 2175 Å UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs are positively detected by their 3.3, 6.2, 7.7, …
Identification of Faint Chandra X-Ray Sources in the Core-collapsed Globular Cluster NGC 6752
Anderson, Jay; Heinke, Craig O.; Cool, Adrienne M. +2 more
We have searched for optical identifications for 39 Chandra X-ray sources that lie within the 1.‧9 half-mass radius of the nearby (d=4.0 {kpc}), core-collapsed globular cluster, NGC 6752, using deep Hubble Space Telescope ACS/WFC imaging in B 435, {R}625, and Hα. Photometry of these images allows us to classify candidate coun…
No Neon, but Jets in the Remarkable Recurrent Nova M31N 2008-12a?—Hubble Space Telescope Spectroscopy of the 2015 Eruption
Ness, J. -U.; Henze, M.; Shafter, A. W. +14 more
The 2008 discovery of an eruption of M31N 2008-12a began a journey on which the true nature of this remarkable recurrent nova continues to be revealed. M31N 2008-12a contains a white dwarf (WD) close to the Chandrasekhar limit, accreting at a high rate from its companion, and undergoes thermonuclear eruptions that are observed yearly and may even …