  This paper presents a study of the accretion properties of 19 very low mass
objects (Mstar .01-0.1 Msun) in the regions Chamaeleon I and rho-Oph For 8
objects we obtained high resolution Halpha profiles and determined mass
accretion rate Macc and accretion luminosity Lacc. Pabeta is detected in
emission in 7 of the 10 rho-Oph objects, but only in one in Cha I. Using
objects for which we have both a determination of Lacc from Halpha and a Pabeta
detection, we show that the correlation between the Pabeta luminosity and
luminosity Lacc, found by Muzerolle et al. (1998) for T Tauri stars in Taurus,
extends to objects with mass approx 0.03 Msun; L(Pab) can be used to measure
Lacc also in the substellar regime. The results were less conclusive for
Brgamma, which was detected only in 2 objects, neither of which had an Halpha
estimate of Macc. Using the relation between L(Pab) and Lacc we determined the
accretion rate for all the objects in our sample (including those with no
Halpha spectrum), more than doubling the number of substellar objects with
known Macc. When plotted as a function of the mass of the central object
together with data from the literature, our results confirm the trend of lower
Macc for lower Mstar, although with a large spread. Some of the spread is
probably due to an age effect; our very young objects in rho-Oph have on
average an accretion rate at least one order of magnitude higher than objects
of similar mass in older regions. As a side product, we found that the width of
Halpha measured at 10% peak intensity is not only a qualitative indicator of
accretion, but can be used to obtain a quantitative estimate of Macc over a
large mass range, from T Tauri stars to brown dwarfs. Finally, we found that
some of our objects show evidence of mass-loss.
