Search Publications
Discovery of Two Small High-velocity Compact Clouds in the Central 10 pc of Our Galaxy
Oka, Tomoharu; Iwata, Yuhei; Nomura, Mariko +2 more
We discovered two small high-velocity compact clouds (HVCCs) in the HCN J = 4-3 and J = 3-2 maps of the central 20 pc of our Galaxy. Both HVCCs have broad velocity widths ({{Δ }}V≳ 40 km s-1) and compact sizes (d∼ 1 {pc}), and originate from the dense molecular clouds in the position-velocity space. One of them has a faint counterpart i…
Detection of Very Low-frequency, Quasi-periodic Oscillations in the 2015 Outburst of V404 Cygni
Kouveliotou, C.; Gehrels, N.; van der Klis, M. +12 more
In 2015 June, the black hole X-ray binary (BHXRB) V404 Cygni went into outburst for the first time since 1989. Here, we present a comprehensive search for quasi-periodic oscillations (QPOs) of V404 Cygni during its recent outburst, utilizing data from six instruments on board five different X-ray missions: Swift/XRT, Fermi/GBM, Chandra/ACIS, INTEG…
The 1600 Å Emission Bump in Protoplanetary Disks: A Spectral Signature of H2O Dissociation
France, Kevin; Roueff, Evelyne; Abgrall, Hervé
The FUV continuum spectrum of many accreting pre-main sequence stars, Classical T Tauri Stars (CTTSs), does not continue smoothly from the well-studied Balmer continuum emission in the NUV, suggesting that additional processes contribute to the short-wavelength emission in these objects. The most notable spectral feature in the FUV continuum of so…
ALMA Multiple-transition Molecular Line Observations of the Ultraluminous Infrared Galaxy IRAS 20551-4250: Different HCN, HCO+, and HNC Excitation, and Implications for Infrared Radiative Pumping
Imanishi, Masatoshi; Izumi, Takuma; Nakanishi, Kouichiro
We present our ALMA multi-transition molecular line observational results for the ultraluminous infrared galaxy IRAS 20551-4250, which is known to contain a luminous buried active galactic nucleus and shows detectable vibrationally excited (v 2 = 1f) HCN and HNC emission lines. The rotational J = 1-0, 4-3, and 8-7 of HCN, {HCO}}+
Testing Metal-Poor Stellar Models and Isochrones with HST Parallaxes of Metal-Poor Stars
McArthur, B. E.; Benedict, G. F.; Sarajedini, A. +7 more
Hubble Space Telescope (HST) fine guidance sensor observations were used to obtain parallaxes of eight metal-poor ([Fe/H] < -1.4) stars. The parallaxes of these stars determined by the new Hipparcos reduction average 17% accuracy, in contrast to our new HST parallaxes, which average 1% accuracy and have errors on the individual parallaxes rangi…
DDO 216-A1: A Central Globular Cluster in a Low-luminosity Transition-type Galaxy
Dolphin, Andrew E.; Skillman, Evan D.; Williams, Benjamin F. +11 more
We confirm that the object DDO 216-A1 is a substantial globular cluster at the center of Local Group galaxy DDO 216 (the Pegasus dwarf irregular), using Hubble Space Telescope ACS imaging. By fitting isochrones, we find the cluster metallicity [M/H] = -1.6 ± 0.2, for reddening E(B-V) = 0.16 ± 0.02 the best-fit age is 12.3 ± 0.8 Gyr. There are ≈ 30…
Shocks and Tides Quantified in the “Sausage” Cluster, CIZA J2242.8+5301 Using N-body/Hydrodynamical Simulations
Broadhurst, T.; Molnar, S. M.
The colliding cluster, CIZA J2242.8+5301, displays a spectacular, almost 2 Mpc long shock front with a radio based Mach number M≃ 5, that is puzzlingly large compared to the X-ray estimate of M≃ 2.5. The extent to which the X-ray temperature jump is diluted by cooler unshocked gas projected through the cluster currently lacks quantification. Here …
On the Origin of the Flare Emission in IRIS’ SJI 2832 Filter:Balmer Continuum or Spectral Lines?
Krucker, Säm; Heinzel, Petr; Kleint, Lucia
Continuum (“white-light,” WL) emission dominates the energetics of flares. Filter-based observations, such as the IRIS SJI 2832 filter, show WL-like brightenings during flares, but it is unclear whether the emission arises from real continuum emission or enhanced spectral lines, possibly turning into emission. The difficulty in filter-based observ…
No Sign of Strong Molecular Gas Outflow in an Infrared-bright Dust-obscured Galaxy with Strong Ionized-gas Outflow
Imanishi, Masatoshi; Toba, Yoshiki; Nagao, Tohru +4 more
We report the discovery of an infrared (IR)-bright dust-obscured galaxy (DOG) that shows a strong ionized-gas outflow but no significant molecular gas outflow. Based on detailed analysis of their optical spectra, we found some peculiar IR-bright DOGs that show strong ionized-gas outflow ([O III] λ5007) from the central active galactic nucleus (AGN…
Evidence for Relativistic Disk Reflection in the Seyfert 1h Galaxy/ULIRG IRAS 05189-2524 Observed by NuSTAR and XMM-Newton
Walton, Dominic J.; García, Javier A.; Harrison, Fiona A. +3 more
We present a spectral analysis of the NuSTAR and XMM-Newton observations of the Seyfert 1h galaxy/ULIRG IRAS 05189-2524 taken in 2013. We find evidence for relativistic disk reflection in the broadband X-ray spectrum: a highly asymmetric broad Fe Kα emission line extending down to 3 keV and a Compton scattering component above 10 keV. Physical mod…