Related papers: High-redshift Narrow-line Seyfert 1 Galaxies: A Ca…
Gamma-ray emitting narrow-line Seyfert 1 ($\gamma$-NLS1) galaxies possibly harbour relatively low-mass black holes (10$^6$-10$^8$ M$_{\odot}$) accreting close to the Eddington limit, and share many characteristics with their sibling…
1H0323+342 is one of narrow-line radio-loud Seyfert 1 galaxies (RL-NLS1), which is a new class of gamma-ray emitting AGNs. Narrow-line Seyfert 1 galaxies (NLS1) have a small-mass black hole, but its mass accretion rate is almost as high as…
We present a comprehensive spectroscopic and variability-based characterisation of a sample of low-luminosity active galactic nuclei (AGNs) hosting low mass black holes, identified by $H\beta$ full width at half maximum (FWHM) $< 2200$ km…
Narrow-line Seyfert 1 (NLS1) galaxies are peculiar active galactic nuclei (AGN). Most of them do not show strong radio emission, but recently seven radio-quiet (or -silent) NLS1s have been detected flaring multiple times at 37 GHz by the…
Line profiles can provide fundamental information on the physics of active galactic nuclei (AGN). In the case of narrow-line Seyfert 1 galaxies (NLS1s) this is of particular importance since past studies revealed how their permitted line…
We present Chandra observations of 17 optically-selected, X-ray weak narrow-line Seyfert 1 (NLS1) galaxies. These objects were optically identified by Williams et al. (2002) in the Sloan Digital Sky Survey Early Data Release, but were not…
In a single optical spectrum, the quasar narrow-line region (NLR) reveals low density, photoionized gas in the host galaxy interstellar medium, while the immediate vicinity of the central engine generates the accretion disk continuum and…
In this letter we present clear evidence that Mrk 573 is an obscured Narrow-Line Seyfert 1 (NLSy1) and not an archetypal Seyfert 2, as it has been classified until now. Only three galaxies have been proposed as members of this class, prior…
Near-Eddington accretion rates onto low-mass black holes are thought to be a prime driver of the multi-wavelength properties of the narrow-line Seyfert 1 (NLS1) population of active galactic nuclei (AGN). Orientation effects have repeatedly…
We report the optical spectroscopy of four young radio sources which are observed with the Lijiang 2.4m telescope. The Eddington ratios of these sources are similar with those of narrow-line Seyfert 1 galaxies (NLS1s). Their Fe {\sc ii}…
We present the detection of compact radio structures of fourteen radio-loud narrow line Seyfert 1 (NLS1) galaxies from Very Long Baseline Array observations at 5 GHz, which were performed in 2013. While 50\% of the sources of our sample…
Studying large-scale environments of narrow-line Seyfert 1 (NLS1) galaxies gives a new perspective on their properties, particularly their radio loudness. The large-scale environment is believed to have an impact on the evolution and…
The excellent soft X-ray sensitivity of the PSPC detector onboard the ROSAT satellite provided the first chance to study precisely the spectral and timing properties of Narrow-Line Seyfert 1 galaxies. ROSAT observations of Narrow-Line…
We revisit the possibility of redshift evolution in the $M_{\rm{BH}}-\sigma_*$ relation with a sample of 22 Seyfert 1 galaxies with black holes (BHs) in the mass range $10^{6.3}-10^{8.3}~M_\odot$ and redshift range $0.03<z<0.57$ with…
Narrow-line Seyfert 1 galaxies (NLSy1s) are a subclass of active galactic nuclei (AGNs), commonly associated with rapidly accreting, relatively low-mass black holes ($10^6$ - $10^8 M_\odot$) hosted in spiral galaxies. Although typically…
Narrow-line Seyfert 1 galaxies (NLS1s) are a class of active galactic nuclei (AGN) which are known to be one of the few sources of $\gamma$ rays, which originate in a relativistic beamed jet. Becuase of their relatively large distance, a…
Narrow-line Seyfert 1 (NLSy1) galaxies are an enigmatic class of active galactic nuclei (AGN) that exhibit peculiar multiwavelength properties across the electromagnetic spectrum. For example, these sources have allowed us to explore the…
Optical spectra of 14 emission-line galaxies representative of the 1999 NICMOS parallel grism Ha survey of McCarthy et al. are presented. Of the 14, 9 have emission lines confirming the redshifts found in the grism survey. The higher…
Narrow Line Seyfert 1 galaxies (NLS1) are generally believed to host "under-massive" black holes with respect to the predictions from the host galaxy -- black hole mass scale relations. Black hole masses in NLS1 are estimated from the…
Controversy regarding whether Narrow Line Seyfert 1 galaxies (NLS1s) follow the same black hole --- galactic bulge relation as normal galaxies has been raised by Mathur et al. (2001) and Ferrarese et al. (2001). In this paper, the…