Reverberation Mapping of a Low-mass Black Hole in a Narrow-line Seyfert 1 Galaxy

We present results of a reverberation mapping (RM) campaign on the low black hole mass narrow-line Seyfert 1 (NLS1) galaxy SDSS J113913.91+335551.1 (hereafter SL01). Using the H beta measurements, we find a time lag tau = 12.5(-11)(+0.5) days and a broad-line velocity width of 1450 km s(-1) which implies a black hole mass of 3.8(-2.8)(+0.6) x 10(6) M-circle dot. To further bolster our time lag results, we employ a secondary method based on the multivariate correlation function as described in Chelouche & Zucker, in which case we obtain consistent lags for the Balmer lines, yet without the need to spectrally deconvolve line from continuum emission processes. Given SL01's luminosity (L-bol approximate to 7 x 10(43) erg s(-1)), we estimate an Eddington ratio (L-bol/L-Edd) of similar to 0.18. This fairly low-mass determination and rather high L-bol/L-Edd is consistent with the current paradigm that the nuclei of NLS1 galaxies host small black holes (as low as 10(6) M-circle dot) with high accretion rates. SL01 is one of only a few NLS1s to date with robust RM results.