Search Publications
Bulk Comptonization: new hints from the luminous blazar 4C+25.05
Ghisellini, G.; Behar, E.; Nardini, E. +3 more
Blazars are often characterized by a spectral break at soft X-rays, whose origin is still debated. While most sources show a flattening, some exhibit a blackbody-like soft excess with temperatures of the order of ∼0.1 keV, similar to low-luminosity, non-jetted Seyferts. Here, we present the analysis of the simultaneous XMM-Newton and NuSTAR observ…
A statistical approach to decipher the tectonic control on the geometry of Martian channels: Case study from Pyrrhae Fossae, Noachis Terra, Mars
Kundu, Abhik; Dasgupta, Nilanjan; De, Keyur
Channel networks in the mid-latitude during the late Noachian to early Hesperian Period have invoked opinions in favor of presence of water on Martian surface. Disregarding the controversy of the presence of water, this study aims to probe into the controlling factors involved in the development of the channel pathways. These apparently curvilinea…
Solar EUV Flux Proxy Using Multifrequency Solar Radio Flux
Zhang, Yongliang; Paxton, Larry J.
We report a new solar extreme ultraviolet (EUV; 26-34 nm) proxy using solar radio fluxes at six different frequencies (410; 610; 1,415; 2,695; 4,995; and 8,800 MHz) from ground-based observations. The radio fluxes (2002-2008) are used to estimate the solar EUV flux under nonsolar flare conditions through an artificial neural network trained with c…
A 149 min periodicity underlies the X-ray flaring of Sgr A*
Leibowitz, Elia
In a paper in 2017, I have shown that 39 large X-ray flares of Sgr A* that were recorded by Chandra observatory in the year 2012 are concentrated preferably around tick marks of an equi-distance grid on the time axis. The period of this grid as found in that paper is 0.1033 d. In this work I show that the effect can be found among all the large X-…
The Time Evolution of the HH 1 Jet Modeled as a Variable Outflow
Raga, A. C.; Castellanos-Ramírez, A.; Rodríguez-González, A.
The HH 1 jet is a chain of knots extending out to ∼20″ from the VLA 1 source of the HH 1/2 system. Four epochs of [S II] images obtained with the Hubble Space Telescope over a ∼20 yr period show that these knots have a time-evolving intensity as they travel away from the outflow source. We present an axisymmetric, gas-dynamic simulation of a two-s…
Blue Straggler Stars Beyond the Milky Way. III. Detection of Evolved Blue Straggler Candidates in Large Magellanic Cloud Clusters
Hong, Jongsuk; Deng, Licai; de Grijs, Richard +3 more
We analyze Hubble Space Telescope observations of nine Large Magellanic Cloud star clusters with ages of 1-2 Gyr to search for evolved counterparts of blue straggler stars. Near the red clump regions in the clusters’ color-magnitude diagrams, we find branches of evolved stars that are much brighter than normal evolved stars. We examine the effects…
Stellar Mass and 3.4 µm M/L Ratio Evolution of Brightest Cluster Galaxies in COSMOS since z ∼ 1.0
Kartaltepe, Jeyhan S.; O'Dea, Christopher P.; Moustakas, John +3 more
We investigate the evolution of star formation rates (SFRs), stellar masses, and M/L 3.4 µm ratios of brightest cluster galaxies (BCGs) in the COSMOS survey since z ∼ 1 to determine the contribution of star formation to the growth-rate of BCG stellar mass over time. Through the spectral energy density (SED) fitting of the GALEX, C…
The Isophotal Structure of Star-forming Galaxies at 0.5 < z < 1.8 in CANDELS: Implications for the Evolution of Galaxy Structure
Barro, Guillermo; Hathi, Nimish P.; Koekemoer, Anton M. +15 more
We have measured the radial profiles of isophotal ellipticity (ɛ) and disky/boxy parameter A 4 out to radii of about three times the semimajor axes for ∼4600 star-forming galaxies (SFGs) between redshift 0.5 and 1.8 in the CANDELS/GOODS-S and UDS fields. Based on the average size-mass relation in each redshift bin, we divide our galaxie…
Solar Models with Dynamic Screening and Early Mass Loss Tested by Helioseismic, Astrophysical, and Planetary Constraints
Guzik, Joyce A.; Wood, Suzannah R.; Mussack, Katie
The faint young Sun paradox remains an open question. Presented here is one possible solution to this apparent inconsistency, a more massive early Sun. Based on the conditions on early Earth and Mars, a luminosity constraint is set as a function of mass. We examine helioseismic constraints of these alternative mass-losing models. Additionally, we …
On-ground calibration of the Hitomi Hard X-ray Telescopes
Maeda, Yoshitomo; Ishida, Manabu; Kunieda, Hideyo +46 more
We present x-ray characteristics of the Hard X-ray Telescopes (HXTs) on board the Hitomi (ASTRO-H) satellite. Measurements were conducted at the SPring-8 BL20B2 beamline and the ISAS/JAXA 27-m beamline. The angular resolution defined by a half-power diameter was 1.9‧ (HXT-1) and 2.1‧ (HXT-2) at 8 keV, 1.9‧ at 30 keV, and 1.8‧ at 50 keV. The effect…