Poster Presentation

Changing State Quasar monitor observation

Author(s): Yuto Oikawa, Fumihide Iwamuro

Presenter: Yuto Oikawa (Kyoto University)

Background:
Supermassive black holes (SMBH) are found at the center of the most galaxy, but the evolution process of SMBHs is one of the big questions in astronomy. One way to solve this problem is to understand the broad line region (Broad Line Region), because it is used to estimate the black hole mass. This research focused on quasar, especially Changing-State Quasar (CSQ), which shows broad lines appearing/disappearing in relatively short timescale and much stronger flux variability. It is expected that analyzing the changing process in CSQs allows to understand mechanism of BLR.

Objectives:
To observe changing process, this research tries to find quasars in the early stage of changing state, especially starting to brighten.

Methods:
First, we analyzed light-curves (in recent 2~3 years) of Zwicky Transient Factory Data (ZTF) Release 10 of 2.8 million quasars listed in Million Quasars (MILLIQUAS) Catalog. By the analyses, 4 quasars illustrate brightening 0.5mag/year. The candidates are observed, and one of the candidates kept brightening. Then the object is taken in spectroscopy. Adopting the elliptical disk model to BLR, inner/outer radius, eccentricity, and inclination angle of Hβ(Hα) BLR is estimated.

Results:
Follow-up photometry discovers one of the four candidates is brightening. By observing the object’s spectrum twice, watching the brightening process and comparing with SDSS early prove that inner BLR around the center of the disk is brighter in the changing process.

Conclusion:
It becomes sure that analyzing light curves in ZTF is effective to find CSQ in changing. In addition, detecting brightening quasar enables to see changing process of BLR in brightening.