Searching for Changing-Look QSOs with PTF
Po-Chieh Yu1*, Chan-Kao Chang1, Matthew J. Graham2, I-Chenn Chen1, Wing-Huen Ip1, PTF Team1,3
1Graduate Institute of Astronomy, National Central University, Taoyuan City, Taiwan
2Center for Advanced Computing Research, California Institute of Technology, Pasadena, USA
3Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, USA
* presenting author:Po-Chieh Yu,
Quasi-stellar objects (QSOs) are powerful radio-loud AGNs, and usually show irregular continuum/line emission variabilities, while changing-look QSOs show decreasing of flux by a factor of 2-3 within 3-5 years at optical band. The broad-line regions (BLRs) disappear in changing-look QSOs with the decreasing of continuum flux. The mechanisms causing the disappearance of BLRs are still unclear. We searched for changing-look QSOs using photometric data of Palomar Transient Factory (PTF), Sloan Digital Sky Survey (SDSS), and Pan-STARRS, along with the spectra of SDSS and LAMOST. In total, 414 QSOs are selected as changing-look QSO candidates on the basis of their decreasing of flux within 3-5 years at either g- or R-band. By comparing the SDSS spectra of earlier epoch with the new spectra of LAMOST and Palomar telescope, we are able to investigate the "changing-look" behavior at different epochs.

Keywords: galaxies: active – galaxies: nuclei– galaxies: QSOs