Search Publications
What are the Composition and Power of the Jet in Cyg X-1?
Zdziarski, Andrzej A.; Egron, Elise
We calculate the electron-positron pair production rate at the base of the jet of Cyg X-1 by collisions of photons from its hot accretion flow using the measurement of its average soft gamma-ray spectra by the Compton Gamma Ray Observatory and INTEGRAL satellites. We have found that this rate approximately equals the flow rate of the leptons emitt…
SDSS-IV MaNGA: Cannibalism Caught in the Act-On the Frequency of Occurrence of Multiple Cores in Brightest Cluster Galaxies
Merrifield, Michael; Brownstein, Joel R.; Pan, Kaike +16 more
Although it is generally accepted that massive galaxies form in a two-phased fashion, beginning with a rapid mass buildup through intense starburst activities followed by primarily dry mergers that mainly deposit stellar mass at outskirts, the late time stellar mass growth of brightest cluster galaxies (BCGs), the most massive galaxies in the univ…
Mapping the X-Ray Corona Evolution of IRAS 13224-3809 with the Power Spectral Density
Chainakun, Poemwai; Luangtip, Wasuthep; Jiang, Jiachen +1 more
We develop the power spectral density (PSD) model to explain the nature of the X-ray variability in IRAS 13224-3809, including the full effects of the X-ray reverberation due to the lamppost source. We utilize 16 XMM-Newton observations individually as well as group them into three different luminosity bins: low, medium, and high. The soft (0.3-1 …
AGC 226178 and NGVS 3543: Two Deceptive Dwarfs toward Virgo
Cresci, Giovanni; Cannon, John M.; Haynes, Martha P. +21 more
The two sources AGC 226178 and NGVS 3543, an extremely faint, clumpy, blue stellar system and a low surface brightness dwarf spheroidal, are adjacent systems in the direction of the Virgo cluster. Both have been studied in detail previously, with it being suggested that they are unrelated normal dwarf galaxies or that NGVS 3543 recently lost its g…
Young, Blue, and Isolated Stellar Systems in the Virgo Cluster. II. A New Class of Stellar System
Cresci, Giovanni; Cannon, John M.; Haynes, Martha P. +21 more
We discuss five blue stellar systems in the direction of the Virgo cluster, analogous to the enigmatic object SECCO 1 (AGC 226067). These objects were identified based on their optical and UV morphology and followed up with H I observations with the Very Large Array (and Green Bank Telescope), Multi Unit Spectroscopic Explorer (on the Very Large T…
New Results from the Spectral Observations of Solar Coronal Type II Radio Bursts
Ramesh, R.; Kathiravan, C.; Natarajan, S. Surya
We carried out a statistical study of twenty-six type II radio bursts from the Sun observed with the Gauribidanur Low-frequency Solar Spectrograph in the frequency range 85-35 MHz during the period 2009-2019. Our results indicate that the average instantaneous bandwidth of the type II bursts in the above frequency range correlates with the angular…
Broadband X-Ray Spectral Analysis of the Dual AGN System Mrk 739
Tanimoto, Atsushi; Ueda, Yoshihiro; Ricci, Claudio +4 more
We present the result of a broadband (0.5-70 keV) X-ray spectral analysis of the late-merger galaxy Mrk 739, which contains a dual active galactic nucleus (AGN), Mrk 739E and Mrk 739W, with a separation of ≈3.4 kpc. The spectra obtained with NuSTAR, Chandra, XMM-Newton, and Swift/BAT are simultaneously analyzed by separating the contributions from…
Spectra of Cosmic-Ray Sodium and Aluminum and Unexpected Aluminum Excess
Jóhannesson, G.; Moskalenko, I. V.; Porter, T. A. +11 more
Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, $\bar{p}$ , e ±, and nuclei (H-Si, Fe), which resulted in a number of breakthroughs. The most recent AMS-02 result is the measurement of the spectra of CR sodium and aluminum up to ~2 TV…
Discovery of Year-scale Time Variability from Thermal X-Ray Emission in Tycho's Supernova Remnant
Yamaguchi, Hiroya; Uchida, Hiroyuki; Tsuru, Takeshi Go +2 more
Mechanisms of particle heating are crucial to understanding the shock physics in supernova remnants (SNRs). However, there has been little information on time variabilities of thermalized particles so far. Here, we present a discovery of a gradually brightening thermal X-ray emission found in the Chandra data of Tycho's SNR obtained during 2000-20…
Polarization from Aligned Dust Grains in the β Pic Debris Disk
Hughes, A. Meredith; Hull, Charles L. H.; Le Gouellec, Valentin J. M. +8 more
We present 870 µm Atacama Large Millimeter/submillimeter Array polarization observations of thermal dust emission from the iconic, edge-on debris disk β Pic. While the spatially resolved map does not exhibit detectable polarized dust emission, we detect polarization at the ~3σ level when averaging the emission across the entire disk. The cor…