Unobscured central broad line regions in Type-1.9 AGN SDSS J1241+2602

Abstract

In this manuscript, strong evidence is reported to support unobscured broad line regions (BLRs) in Type-1.9 AGN SDSS J1241+2602 with reliable broad H$\alpha$ but no broad H$\beta$. Commonly, disappearance of broad H$\beta$ can be explained by the AGN unified model expected heavily obscured BLRs in Type-1.9 AGN. Here, based on properties of two kinds of BH masses, the virial BH mass and the BH mass through the \msig relation, an independent method is proposed to test whether are there unobscured central BLRs in a Type-1.9 AGN. By the reliable measurement of stellar velocity dispersion about 110$\pm$12km/s through the host galaxy absorption features in \obj, the BH mass through the \msig relation is consistent with the virial BH mass $(3.43\pm1.25)\times10^7{\rm M_\odot}$ determined through properties of the observed broad H$\alpha$ without considering effects of obscurations in SDSS J1241+2602. Meanwhile, if considering heavily obscured BLRs in SDSS J1241+2602, the reddening corrected virial BH mass is tens of times larger than the \msig expected value, leading SDSS J1241+2602 to be an outlier in the \msig space with confidence level higher than $5\sigma$. Therefore, the unobscured BLRs are preferred in the Type-1.9 AGN SDSS J1241+2602. The results indicate that it is necessary to check whether unobscured central BLRs are common in Type-1.9 AGN, when to test the AGN unified model of AGN by properties of Type-1.9 AGN.