  Following re-analysis of Hubble Space Telescope observations of primary
transits of the extrasolar planet HD209458b at Lyman-alpha, Ben-Jaffel (2007,
BJ007) claims that no sign of evaporation is observed. Here we show that, in
fact, this new analysis is consistent with the one of Vidal-Madjar et al.
(2003, VM003) and supports the detection of evaporation. The apparent
disagreement is mainly due to the disparate wavelength ranges that are used to
derive the transit absorption depth. VM003 derives a (15+/-4)% absorption depth
during transit over the core of the stellar Lyman-alpha line (from -130 km/s to
+100 km/s), and this result agrees with the (8.9+/-2.1)% absorption depth
reported by BJ007 from a slightly expanded dataset but over a larger wavelength
range (+/-200 km/s). These measurements agree also with the (5+/-2)% absorption
reported by Vidal-Madjar et al. (2004) over the whole Lyman-alpha line from
independent, lower-resolution data. We show that stellar Lyman-alpha
variability is unlikely to significantly affect those detections. The HI atoms
must necessarily have velocities above the escape velocities and/or be outside
the Roche lobe, given the lobe shape and orientation. Absorption by HI in
HD209458b's atmosphere has thus been detected with different datasets, and now
with independent analyses. All these results strengthen the concept of
evaporating hot-Jupiters, as well as the modelization of this phenomenon.
