Search Publications
Evidence of Multiple Slow Acoustic Oscillations in the Stellar Flaring Loops of Proxima Centauri
Srivastava, A. K.; Pandey, J. C.; Lalitha, S.
We present the first observational evidence of multiple slow acoustic oscillations in the post-flaring loops of the corona of Proxima Centauri using XMM-Newton observations. We find the signature of periodic oscillations localized in the decay phase of the flare in its soft (0.3-10.0 keV) X-ray emissions. Using the standard wavelet tool, we find m…
A Low-metallicity Molecular Cloud in the Lower Galactic Halo
Lockman, Felix J.; Wakker, Bart P.; Benjamin, Robert A. +5 more
We find evidence for the impact of infalling, low-metallicity gas on the Galactic disk. This is based on FUV absorption line spectra, 21 cm emission line spectra, and far-infrared (FIR) mapping to estimate the abundance and physical properties of IV21 (IVC135+54-45), a galactic intermediate-velocity molecular cloud that lies ~300 pc above the disk…
HST/WFC3 Near-infrared Spectroscopy of Quenched Galaxies at z ~ 1.5 from the WISP Survey: Stellar Population Properties
Scarlata, C.; Malkan, M.; Hathi, N. P. +15 more
We combine Hubble Space Telescope (HST) G102 and G141 near-IR (NIR) grism spectroscopy with HST/WFC3-UVIS, HST/WFC3-IR, and Spitzer/IRAC [3.6 µm] photometry to assemble a sample of massive (log (M star/M ⊙) ~ 11.0) and quenched (specific star formation rate <0.01 Gyr-1) galaxies at z ~ 1.5. Our sample of 4…
Pulse-phase-dependent Variations of the Cyclotron Absorption Features of the Accreting Pulsars A0535+26, XTE J1946+274, and 4U 1907+09 with Suzaku
Maitra, Chandreyee; Paul, Biswajit
We have performed a detailed pulse-phase-resolved spectral analysis of cyclotron resonant scattering features (CRSFs) of the two Be/X-ray pulsars A0535+26 and XTE J1946+274 and the wind accreting HMXB pulsar 4U 1907+09 using Suzaku observations. The CRSF parameters vary strongly over the pulse phase and can be used to map the magnetic field, and a…
Extraordinary Luminous Soft X-Ray Transient MAXI J0158-744 as an Ignition of a Nova on a Very Massive O-Ne White Dwarf
Sakamoto, T.; Mihara, T.; Sugizaki, M. +29 more
We present the observation of an extraordinary luminous soft X-ray transient, MAXI J0158-744, by the Monitor of All-sky X-ray Image (MAXI) on 2011 November 11. This transient is characterized by a soft X-ray spectrum, a short duration (1.3 × 103 s < ΔTd < 1.10 × 104 s), a rapid rise (<5.5 × 103 …
The Pulsation Mode of the Cepheid Polaris
Kovtyukh, V. V.; Usenko, I. A.; Turner, D. G. +1 more
A previously derived photometric parallax of 10.10 ± 0.20 mas, d = 99 ± 2 pc, is confirmed for Polaris by a spectroscopic parallax derived using line ratios in high dispersion spectra for the Cepheid. The resulting estimates for the mean luminosity of langMV rang = -3.07 ± 0.01 s.e., average effective temperature of langT eff…
Evolution of the Global Temperature Structure of the Solar Corona during the Minimum between Solar Cycles 23 and 24
Jin, Meng; Huang, Zhenguang; Vásquez, Alberto M. +3 more
The combination of differential emission measure tomography with extrapolation of the photospheric magnetic field allows determination of the electron density and electron temperature along individual magnetic field lines. This is especially useful in quiet-Sun (QS) plasmas where individual loops cannot otherwise be identified. In Paper I, this ap…
A State Transition of the Luminous X-Ray Binary in the Low-metallicity Blue Compact Dwarf Galaxy I Zw 18
Feng, Hua; Kaaret, Philip
We present a measurement of the X-ray spectrum of the luminous X-ray binary in I Zw 18, the blue compact dwarf galaxy with the lowest known metallicity. We find the highest flux yet observed, corresponding to an intrinsic luminosity near 1 × 1040 erg s-1 establishing it as an ultraluminous X-ray source (ULX). The energy spect…
Direct Detections of Young Stars in Nearby Elliptical Galaxies
Bregman, Joel N.; Ford, H. Alyson
Small amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identi…
Water Maser Survey on AKARI and IRAS Sources: A Search for "Low-velocity" Water Fountains
Kwok, Sun; Yung, Bosco H. K.; Nakashima, Jun-ichi +3 more
We present the results of a 22 GHz H2O maser survey toward a new sample of asymptotic giant branch (AGB) and post-AGB star candidates. Most of the objects are selected for the first time based on the AKARI data, which have high flux sensitivity in the mid-infrared ranges. We aim at finding H2O maser sources in the transient p…