Search Publications
Proper Motions and Shock Wave Dynamics in the HH 7-11 Stellar Jet
Hartigan, P.; Frank, A.; Holcomb, R.
We have used the Hubble Space Telescope (HST) to acquire new broadband and narrowband images of the optical line emission and red continuum associated with the HH 7-11 stellar jet in the NGC 1333 star formation region. Combining the new narrowband images of Hα, [O I] λ6300, and [S II] λ6716 allows us to measure electron densities and excitations a…
RR Lyrae Stars in the Field of Sagittarius II
Rey, Soo-Chang; Jerjen, Helmut; Cha, Sang-Mok +10 more
We present the detection of RR Lyrae variable stars in the field of the Sagittarius II (Sgr II) ultra-faint dwarf (UFD) galaxy. Using B, V time-series photometry obtained with the Korea Microlensing Telescope Network (KMTNet) 1.6 m telescope at CTIO and G-band data from Gaia Data Release 2 (DR2), we identified and characterized two ab-type and fou…
X-Ray and Radio Variabilities of PSR J2032+4127 near Periastron
Kerr, M.; Wood, K. S.; Gotthelf, E. V. +6 more
We present X-ray and radio monitoring observations of the gamma-ray binary PSR J2032+4127/MT91 213 during its periastron passage in late 2017. Dedicated Chandra, XMM-Newton, NuSTAR X-ray observations, and Very Large Array radio observations of this long orbit (50 yr), 143 ms pulsar/Be star system clearly revealed flux and spectral variability duri…
H I Spectroscopy of Reverberation-mapped Active Galactic Nuclei
Bentz, Misty C.; Courtois, Hélène M.; Johnson, Megan C. +2 more
We present H I 21 cm spectroscopy from the Robert C. Byrd Green Bank Telescope for the host galaxies of 31 nearby active galactic nuclei with direct M BH measurements from reverberation mapping. These are the first published H I detections for 12 galaxies, and the spectral quality is generally an improvement over archival data for the…
Ultraviolet Extinction Properties of the 30 Dor Nebula and Interpreting Observations of Starburst Clusters
Panagia, Nino; De Marchi, Guido
Recent investigations of the extinction law in 30 Dor and the Tarantula Nebula, at optical and near-infrared wavelengths, have revealed a ratio of total to selective extinction R V = A V /E(B - V) of about 4.5. This indicates a larger fraction of big grains than in the Galactic diffuse interstellar medium (ISM). Possible o…
An Ultraviolet-Optical Color-Metallicity Relation for Red Clump Stars Using GALEX and Gaia
Hogg, David W.; Hawkins, Keith; Schiminovich, David +3 more
Although core helium-burning red clump (RC) stars are faint at ultraviolet wavelengths, their ultraviolet (UV)-optical color is a unique and accessible probe of their physical properties. Using data from the Galaxy Evolution Explorer All Sky Imaging Survey, Gaia Data Release 2, and the Sloan Digital Sky Survey Apache Point Observatory Galactic Evo…
A NuSTAR and XMM-Newton Study of the Two Most Actively Star-forming Green Pea Galaxies (SDSS J0749+3337 and SDSS J0822+2241)
Imanishi, Masatoshi; Tanimoto, Atsushi; Ueda, Yoshihiro +4 more
We explore X-ray evidence for the presence of active galactic nuclei (AGNs) in the two most actively star-forming Green Pea galaxies (GPs), SDSS J0749+3337 and SDSS J0822+2241, which have star formation rates (SFRs) of 123 M ⊙ yr-1 and 78 M ⊙ yr-1, respectively. The GPs have red mid-infrared (MIR) spectr…
Signature of Stochastic Acceleration and Cooling Processes in an Outburst Phase of the TeV Blazar ON 231
Gupta, Alok C.; Wiita, Paul J.; Kalita, Nibedita +1 more
We present a detailed spectral and temporal study of the intermediate-type blazar ON 231 during the TeV outburst phase in 2008 June with observations performed by Swift and XMM-Newton. The X-ray flux of the source, which was significantly dominated by the soft photons (below 3-4 keV), varies between 27% and 38% on day timescales, while mild variat…
Long-standing Small-scale Reconnection Processes at Saturn Revealed by Cassini
Coates, A. J.; Krupp, N.; Dougherty, M. K. +12 more
The internal mass source from the icy moon Enceladus in Saturn’s rapidly rotating magnetosphere drives electromagnetic dynamics in multiple spatial and temporal scales. The distribution and circulation of the internal plasma and associated energy are thus crucial in understanding Saturn’s magnetospheric environment. Magnetic reconnection is one of…
Chandra Observations of the Massive Star-forming Region Onsala 2
Skinner, Stephen L.; Güdel, Manuel; Sokal, Kimberly R.
Previous radio and infrared observations have revealed an obscured region of high-mass star formation in Cygnus known as Onsala 2 (ON2). Within this region lies the optically revealed young stellar cluster Berkeley 87, which contains several OB stars and the rare oxygen-type Wolf-Rayet star WR 142. Previous radio studies of ON2 have also discovere…