ﻻ يوجد ملخص باللغة العربية
We have conducted a systematic survey for z $<$ 0.04 active Galactic nuclei (AGNs) that may have changed spectral class over the past decade. We use SkyMapper, Pan-STARRS and the Veron-Cetty & Veron (2010) catalogue to search the entire sky for these ``changing-look AGNs using a variety of selection methods, where Pan-STARRS has a coverage of 3$pi$ steradians (sky north of Declination $-30^circ$) and SkyMapper has coverage of $sim$ 21,000$~rm{deg^2}$ (sky south of Declination $0^circ$). We use small aperture photometry to measure how colour and flux have changed over time, where a change may indicate a change in spectral type. Optical colour and flux are used as a proxy for changing H$alpha$ equivalent width, while WISE 3.4 $mu$m flux is used to look for changes in the hot dust component. We have identified four AGNs with varying spectra selected using our optical colour selection method. Three AGNs were confirmed from recent observations with WiFeS on the 2.3 m telescope at Siding Spring and the other was identified from archival spectra alone. From this, we identify two new changing look AGNs; NGC 1346 and 2MASX J20075129-1108346. We also recover Mrk 915 and Mrk 609, which are known to have varying spectra in the literature, but they do not meet our specific criteria for changing look AGNs.
We present a systematic search for changing-look quasars based on repeat photometry from SDSS and Pan-STARRS1, along with repeat spectra from SDSS and SDSS-III BOSS. Objects with large, |Delta g|>1 mag photometric variations in their light curves are
Changing-Look (CL) is a rare phenomenon of Active Galactic Nuclei (AGNs) that exhibit emerging or disappearing broad lines accompanied by continuum variations on astrophysically short timescales ($lesssim$ 1 yr to a few decades). While previous studi
We here report a spectroscopic identification of two new changing-look AGNs (CL-AGNs): SDSS,J104705.16+544405.8 and SDSS,J120447.91+170256.8 both with a turn-off type transition from type 1 to type 1.8/1.9. The identification is arrived by a follow-u
If the disappearance of the broad emission lines observed in changing-look quasars originates from the obscuration of the quasar core by dusty clouds moving in the torus, high linear optical polarization would be expected in those objects. We then me
Changing-look Active Galactic Nuclei (CL-AGNs) are a subset of AGNs in which the broad Balmer emission lines appear or disappear within a few years. We use the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to identify five CL-AGN