Ari Laor
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View article: The CLASS Quasar Catalog: Coronal Line Activity in Type 1 SDSS Quasars
The CLASS Quasar Catalog: Coronal Line Activity in Type 1 SDSS Quasars Open
We conduct the first systematic survey of a total of 11 optical coronal lines (CLs) in the spectra of a large sample of low-redshift ( z < 0.8) Type 1 quasars observed by the Sloan Digital Sky Survey (SDSS). We find that strong CL emission…
View article: Radio emission from absorption-line quasars
Radio emission from absorption-line quasars Open
Absorption Line Quasars (ALQs) generally exhibit significant outflows that may interact with the surrounding medium, resulting in radio emission. We selected a sample of 13 powerful radio-quiet (RQ) ALQs, where the UV outflow kinetic power…
View article: A Dichotomy in the 1–24 GHz Parsec-scale Radio Spectra of Radio-quiet Quasars
A Dichotomy in the 1–24 GHz Parsec-scale Radio Spectra of Radio-quiet Quasars Open
We present the parsec-scale radio spectra of a representative sample of 13 Palomar–Green radio-quiet quasars, based on our new Very Long Baseline Array (VLBA) observations at 8.4 and 23.6 GHz and our earlier VLBA studies at 1.5 and 5.0 GHz…
View article: The CLASS Quasar Catalog: Coronal Line Activity in Type 1 SDSS Quasars
The CLASS Quasar Catalog: Coronal Line Activity in Type 1 SDSS Quasars Open
We conduct the first systematic survey of a total of eleven optical coronal lines in the spectra of a large sample of low redshift (z < 0.8) Type 1 quasars observed by the Sloan Digital Sky Survey (SDSS). We find that strong coronal line e…
View article: Late-time Radio Brightening and Emergence of a Radio Jet in the Changing-look AGN 1ES 1927+654
Late-time Radio Brightening and Emergence of a Radio Jet in the Changing-look AGN 1ES 1927+654 Open
We present multifrequency (5–345 GHz) and multiresolution radio observations of 1ES 1927+654, widely considered one of the most unusual and extreme changing-look active galactic nuclei (CL-AGNs). The source was first designated a CL-AGN af…
View article: Why Are Optical Coronal Lines Faint in Active Galactic Nuclei?
Why Are Optical Coronal Lines Faint in Active Galactic Nuclei? Open
Forbidden collisionally excited optical atomic transitions from high-ionization-potential (IP ≥ 54.8 eV) ions, such as Ca 4+ , Ne 4+ , Fe 6+ , Fe 10+ , Fe 13+ , Ar 9+ , and S 11+ , are known as optical coronal lines (CLs). The spectral ene…
View article: Windy or Not: Radio Parsec-scale Evidence for a Broad-line Region Wind in Radio-quiet Quasars
Windy or Not: Radio Parsec-scale Evidence for a Broad-line Region Wind in Radio-quiet Quasars Open
Does a broad-line region (BLR) wind in radio-quiet (RQ) active galactic nuclei (AGN) extend to parsec scales and produce radio emission? We explore the correlations between a parsec-scale radio wind and the BLR wind in a sample of 19 RQ Pa…
View article: A dichotomy in the 1-24 GHz parsec-scale radio spectra of radio-quiet quasars
A dichotomy in the 1-24 GHz parsec-scale radio spectra of radio-quiet quasars Open
We present the pc-scale radio spectra of a representative sample of 13 Palomar-Green radio-quiet quasars, based on our new Very Long Baseline Array (VLBA) observations at 8.4 and 23.6 GHz and our earlier VLBA studies at 1.5 and 5.0 GHz. Th…
View article: Windy or not: Radio pc-scale evidence for a broad-line region wind in radio-quiet quasars
Windy or not: Radio pc-scale evidence for a broad-line region wind in radio-quiet quasars Open
Does a broad-line region (BLR) wind in radio-quiet (RQ) active galactic nuclei (AGN) extend to pc scales and produce radio emission? We explore the correlations between a pc-scale radio wind and the BLR wind in a sample of 19 RQ Palomar-Gr…
View article: Why are optical coronal lines faint in active galactic nuclei?
Why are optical coronal lines faint in active galactic nuclei? Open
Forbidden collisionally excited optical atomic transitions from high ionization potential (IP$\geq$54.8\,eV) ions, such as Ca$^{\mathrm{4+}}$, Ne$^{\mathrm{4+}}$, Fe$^{\mathrm{6+}}$, Fe$^{\mathrm{10+}}$, Fe$^{\mathrm{13+}}$, Ar$^{\mathrm{9…
View article: Late-time radio brightening and emergence of a radio jet in the changing-look AGN 1ES 1927+654
Late-time radio brightening and emergence of a radio jet in the changing-look AGN 1ES 1927+654 Open
We present multi-frequency (5-345 GHz) and multi-resolution radio observations of 1ES 1927+654, widely considered one of the most unusual and extreme changing-look active galactic nuclei (CL-AGN). The source was first designated a CL-AGN a…
View article: A Large Jet Narrow-line Seyfert 1 Galaxy: Observations from Parsec to 100 kpc Scales
A Large Jet Narrow-line Seyfert 1 Galaxy: Observations from Parsec to 100 kpc Scales Open
We present new 1.5–8.5 GHz Very Long Baseline Array (VLBA) observations and 0.32–1.26 GHz Giant Meterwave Radio Telescope (GMRT) observations of J0354−1340, which is the only known radio-quiet (RQ) or radio-intermediate (RI) narrow-line Se…
View article: A large jet narrow-line Seyfert 1 galaxy: observations from pc to 100 kpc scales
A large jet narrow-line Seyfert 1 galaxy: observations from pc to 100 kpc scales Open
We present new 1.5-8.5 GHz Very Long Baseline Array (VLBA) observations and 0.32-1.26 GHz Giant Meterwave Radio Telescope (GMRT) observations of J0354-1340, which is the only known radio-quiet (RQ) or radio-intermediate (RI) narrow-line Se…
View article: A Tight Correlation between Millimeter and X-Ray Emission in Accreting Massive Black Holes from <100 mas Resolution ALMA Observations
A Tight Correlation between Millimeter and X-Ray Emission in Accreting Massive Black Holes from <100 mas Resolution ALMA Observations Open
Recent studies have proposed that the nuclear millimeter continuum emission observed in nearby active galactic nuclei (AGNs) could be created by the same population of electrons that gives rise to the X-ray emission that is ubiquitously ob…
View article: The radio emission in radio-quiet quasars: the VLBA perspective
The radio emission in radio-quiet quasars: the VLBA perspective Open
The origin of the radio emission in radio-quiet quasars (RQQ) is not established yet. We present new VLBA observations at 1.6 and 4.9 GHz of ten RQQ (nine detected), which together with published earlier observations of eight RQQ (five det…
View article: A Tight Correlation Between Millimeter and X-ray Emission in Accreting Massive Black Holes from <100 Milliarcsecond-resolution ALMA Observations
A Tight Correlation Between Millimeter and X-ray Emission in Accreting Massive Black Holes from <100 Milliarcsecond-resolution ALMA Observations Open
Recent studies have proposed that the nuclear millimeter continuum emission observed in nearby active galactic nuclei (AGN) could be created by the same population of electrons that gives rise to the X-ray emission that is ubiquitously obs…
View article: Dependence of the Radio Emission on the Eddington Ratio of Radio-quiet Quasars
Dependence of the Radio Emission on the Eddington Ratio of Radio-quiet Quasars Open
Roughly 10% of quasars are “radio-loud,” producing copious radio emission in large jets. The origin of the low-level radio emission seen from the remaining 90% of quasars is unclear. Observing a sample of eight radio-quiet quasars with the…
View article: NGC 3147: a prototypical low-luminosity active galactic nucleus with double-peaked optical and ultraviolet lines
NGC 3147: a prototypical low-luminosity active galactic nucleus with double-peaked optical and ultraviolet lines Open
A previous narrow-slit (0.1 arcsec) Hubble Space Telescope observation unveiled a broad relativistic Hα profile in NGC 3147, a low-luminosity (Lbol ∼ 1042 erg s−1), low-Eddington ratio (Lbol/LEdd ∼ 10−4) active galactic nucleus (AGN), form…
View article: The Nature of Luminous Quasars with Very Large C iv Equivalent Widths
The Nature of Luminous Quasars with Very Large C iv Equivalent Widths Open
We report results for a complete sample of 10 luminous radio-quiet quasars with large C iv equivalent widths (EW ≥ 150 Å). For 8/10 we performed Chandra snapshot observations. We find that, in addition to the enhanced C iv line EW, their H…
View article: Quasi-simultaneous observations of radio and X-ray variability in three radio-quiet Seyfert galaxies
Quasi-simultaneous observations of radio and X-ray variability in three radio-quiet Seyfert galaxies Open
Radio variability in some radio-quiet (RQ) active galactic nuclei suggests emission from regions close to the central engine, possibly the outer accretion disc corona. If the origins of the radio and the X-ray emission are physically relat…
View article: Hard-X-ray-selected active galactic nuclei – II. Spectral energy distributions in the 5–45 GHz domain
Hard-X-ray-selected active galactic nuclei – II. Spectral energy distributions in the 5–45 GHz domain Open
A wide-frequency radio study of active galactic nuclei (AGN) is crucial to evaluate the intervening radiative mechanisms responsible for the observed emission and relate them with the underlying accretion physics. We present wide-frequency…
View article: Radio spectra of narrow-line Seyfert 1 galaxies observed with Australia Telescope Compact Array and Very Large Array Sky Survey
Radio spectra of narrow-line Seyfert 1 galaxies observed with Australia Telescope Compact Array and Very Large Array Sky Survey Open
We present radio spectral analyses for a sample of 29 radio-quiet (RQ) and three radio-loud (RL) narrow-line Seyfert 1 galaxies (NLS1s) detected with the Australia Telescope Compact Array at both 5.5 and 9.0 GHz. The sample is characterize…
View article: A New Iron Emission Template for Active Galactic Nuclei. I. Optical Template for the Hβ Region*
A New Iron Emission Template for Active Galactic Nuclei. I. Optical Template for the Hβ Region* Open
We present a new empirical template for iron emission in active galactic nuclei (AGNs) covering the 4000–5600 Å range. The new template is based on a spectrum of the narrow-line Seyfert 1 galaxy Mrk 493 obtained with the Hubble Space Teles…
View article: A New Iron Emission Template for Active Galactic Nuclei. I. Optical Template for the H$\beta$ region
A New Iron Emission Template for Active Galactic Nuclei. I. Optical Template for the H$\beta$ region Open
We present a new empirical template for iron emission in active galactic nuclei (AGN) covering the $4000-5600$ A range. The new template is based on a spectrum of the narrow-line Seyfert 1 galaxy Mrk 493 obtained with the Hubble Space Tele…
View article: The PG-RQS survey. Building the radio spectral distribution of radio-quiet quasars. I. The 45-GHz data
The PG-RQS survey. Building the radio spectral distribution of radio-quiet quasars. I. The 45-GHz data Open
The origin of the radio emission in radio-quiet quasars (RQQs) remains unclear. Radio emission may be produced by a scaled-down version of the relativistic jets observed in radio-loud (RL) AGN, an AGN-driven wind, the accretion disc corona…
View article: Radiation pressure confinement – V. The predicted free–free absorption and emission in active galactic nuclei
Radiation pressure confinement – V. The predicted free–free absorption and emission in active galactic nuclei Open
The effect of radiation pressure compression (RPC) on ionized gas in active galactic nuclei (AGNs) likely sets the photoionized gas density structure. The photoionized gas free–free absorption and emission are therefore uniquely set by the…
View article: Hubble Space Telescope Ultraviolet Spectroscopy of 14 Low-Redshift Quasars
Hubble Space Telescope Ultraviolet Spectroscopy of 14 Low-Redshift Quasars Open
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View article: The aox--HeII EW Connection in Radio-Loud Quasars
The aox--HeII EW Connection in Radio-Loud Quasars Open
Radio-loud quasars (RLQs) are known to produce excess X-ray emission, compared to radio-quiet quasars (RQQs) of the same luminosity, commonly attributed to jet-related emission. Recently, we found that the HeII EW and $α_{\rm{ox}}$ in RQQs…
View article: What controls the UV-to-X-ray continuum shape in quasars?
What controls the UV-to-X-ray continuum shape in quasars? Open
We present an investigation of the interdependence of the optical-to-X-ray spectral slope (αox), the He ii equivalent-width (EW), and the monochromatic luminosity at 2500 Å (L2500). The values of αox and He ii EW are indicators of the stre…
View article: The aox--HeII EW Connection in Radio-Loud Quasars
The aox--HeII EW Connection in Radio-Loud Quasars Open
The catalog and research note presenting the X-ray and HeII EW properties of Radio-loud quasars. Our results indicate that the X-ray emission from typical RLQs largely originates in the corona and not from a jet-linked component.