Articles written in Journal of Astrophysics and Astronomy
Volume 32 Issue 1-2 March 2011 pp 87-90 Part 2. Blazar Observations in Infrared and Optical
The optical variability of 29 flat spectrum radio quasars in SDSS Stripe 82 region are investigated by using DR7 released multi-epoch data. All FSRQs show variations with overall amplitude ranging from 0.24 mag to 3.46 mag in different sources. About half of FSRQs show a bluer-when-brighter trend, which is commonly observed for blazars. However, only one source shows a redder-when-brighter trend, which implies it is rare in FSRQs. In this source, the thermal emission may be responsible for the spectral behaviour.
Volume 32 Issue 1-2 March 2011 pp 197-201 Part 4. Emission Models and Theory
The orientations of the accretion disk of active galactic nuclei (AGN) and the stellar disk of its host galaxy are both determined by the angular momentum of their forming gas, but on very different physical environments and spatial scales. Here we show the evidence that the orientation of the stellar disk is correlated with the accretion disk by comparing the inclinations of the stellar disks of a large sample of Type 2 AGNs selected from Sloan Digital Sky Survey (SDSS, York
Volume 32 Issue 1-2 March 2011 pp 319-321 Part 7. Other Topics
Neutral hydrogen (HI) 21-cm absorption has been detected against very powerful radio jets. In this paper, based on Gupta’s sample (Gupta
Volume 35 Issue 3 September 2014 pp 321-323 Part III: Blazar Observations in High Energy Bands
We present the arcsecond-scale jet structure and related radio properties for a sample of 9 UHBLs selected from Nieppola
Volume 35 Issue 3 September 2014 pp 357-362 Part IV: Emission Models and Theory
We use a sample of radio-loud Active Galactic Nuclei (AGNs) with measured black hole masses to explore the jet formation mechanisms in these sources. We find a significant correlation between black hole mass and the bulk Lorentz factor of the jet components for this sample, while no significant correlation is present between the bulk Lorentz factor and the Eddington ratio. Recent investigations suggested that the most super-massive black holes in elliptical galaxies have on average higher spins than the black holes in spiral galaxies. The correlation between black hole mass and bulk Lorentz factor of the jet components found in this work implies that the motion velocity of the jet components is probably governed by the black hole spin. The faster moving jets are magnetically accelerated by the magnetic fields threading the horizon of more rapidly rotating black holes.
Volume 35 Issue 3 September 2014 pp 369-372 Part IV: Emission Models and Theory
The spectral variability of a sample of 44 Flat-Spectrum Radio Quasars (FSRQs) and 18 Steep-Spectrum Radio Quasars (SSRQs) in SDSS stripe 82 region is investigated. Twenty-five of 44 FSRQs show a bluer-when-brighter trend (BWB), while only one FSRQ shows a redder-when-brighter trend, which is in contrast to our previous results. Eight of 18 SSRQs display a BWB. We found an anticorrelation between the Eddington ratio and the variability amplitude in the 𝑟 band for SSRQs, which is similar to that in radio-quiet AGNs. This implies that the thermal emission from the accretion disk may be responsible for the variability in SSRQs. The spectral variability from SDSS multi-epoch spectroscopy also shows BWB for several SSRQs, which is consistent with that from photometry.
Volume 35 Issue 3 September 2014 pp 477-479 Posters
In a sample of 60 quasars selected from the Sloan Digital Sky Survey (SDSS) with at least six-epoch spectroscopy, we investigated the variability of emission lines and continuum luminosity. In this paper, we present the results of SDSS J030639.57+000343.1. We found a strong anticorrelation between the continuum luminosity at 5100 Å and the spectral index, implying a bluer-when-brighter trend. The luminosity of the broad 𝐻𝛼 line is in proportion to the continuum luminosity at 5100 Å. Correspondingly, we did not find a strong correlation between the equivalent width of broad 𝐻𝛼 and the continuum luminosity, i.e. no Baldwin effect of broad 𝐻𝛼 in this source.
Volume 40 | Issue 5
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