2011ApJ...741...66R

We present the results of a reverberation mapping (RM) campaign on the black hole (BH) associated with the active galactic nucleus (AGN) in SDSS J114008.71+030711.4 (hereafter GH08). This object is selected from a sample of 19 candidate intermediate-mass BHs (M_BH< 10⁶ M_{x2609}) found by Greene & Ho in the Sloan Digital Sky Survey. We used the Hobby-Eberly Telescope to obtain 30 spectra over a period of 178 days in an attempt to resolve the reverberation time lag (τ) between the continuum source and the broad-line region (BLR) in order to determine the radius of the BLR (R _BLR) in GH08. We measure τ to be two days with an upper limit of six days. We estimate the AGN luminosity at 5100 Å to be λL₅₁₀₀~ 1.1x10⁴³ erg/s after deconvolution from the host galaxy. The most well-calibrated R_BLR-L relation predicts a time lag that is four times larger than what we measure. Using the measured Hβ full width at half-maximum of 703±110 km/s and an upper limit for R_BLR=6 light days, we find M_BH ≲ 5.8x10⁵ M_{x2609} as an upper limit to the BH virial mass in GH08, which implies super-Eddington accretion. Based on our measured M _BH we propose that GH08 may be another candidate to add to the very short list of AGNs with M_BH< 10⁶ M_{x2609} determined using RM.