• P. Marziani

      Articles written in Journal of Astrophysics and Astronomy

    • Measures of the Soft X-ray Excess as an Eigenvector 1 Parameter for Active Galactic Nuclei

      K. Bensch A. del Olmo J. Sulentic J. Perea P. Marziani

      More Details Abstract Fulltext PDF

      We present a preliminary analysis of X-ray data of quasars in the context of the 4D eigenvector 1 parameter space (Sulentic et al. 2000a, b). 4DE1 serves as a surrogate H-R diagram for representing empirical diversity among quasars and identifying the physical drivers of the diversity. The soft X-ray spectral index (𝛤soft) was adopted as one of the key 4DE1 that correlates contrasting extremes in Type 1 properties. 4DE1 motivated the hypothesis of two quasar populations (A and B) divided by 𝐿/𝐿EDD ≈ 0.2. Pop. A is a largely radio-quiet population with FWHM 𝐻𝛽 < 4000 km/s and often showing a soft X-ray excess. Pop. B is a mix of radio-quiet and a majority of RL quasars shows only a hard X-ray power-law SED. The X-ray separation was based upon earlier ROSAT and ASCA data but we now confirm this dichotomy with large samples of X-ray spectra obtained with XMM-Newton and SWIFT. One popular idea connects the soft excess in Pop. A quasars as a signature of thermal emission from a hot accretion disk in sources radiating close to the Eddington limit.

  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.