REVERBERATION MAPPING OF THE INTERMEDIATE-MASS NUCLEAR BLACK HOLE IN SDSS J114008.71+030711.4

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 (MBH < 10(6) M(circle dot)) 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 (tau) 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 tau to be two days with an upper limit of six days. We estimate the AGN luminosity at 5100 angstrom to be lambda L(5100) approximate to 1.1 x 10(43) erg s(-1) 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 H beta full width at half-maximum of 703 +/- 110 km s(-1) and an upper limit for R(BLR) = 6 light days, we find M(BH) less than or similar to 5.8 x 10(5) M(circle dot) as an upper limit to the BH virial mass in GH08, which implies super-Eddington accretion. Based on our measured MBH we propose that GH08 may be another candidate to add to the very short list of AGNs with M(BH) < 10(6) M(circle dot) determined using RM.