HST/STIS Lyman-α observations of the quiet M dwarf GJ 436 - Predictions for the exospheric transit signature of the hot Neptune GJ 436b

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Table 2

Normalized Lyα and X-ray fluxes of M dwarfs.

Star	Sp. T.	log R_Lyα	log R_X^(*)	σ_{L_X} (dex)	N _X

Lyα from HST
Proxima Cen	M6v	−3.88	−3.58	0.31^†	10
AD Leo	M4.5v	−3.50	−3.12	0.12^†	6
EV Lac	M3.5v	−3.77	−2.70	0.41^†	8
AU Mic	M1v	−3.51	−2.97	0.15^†	3
GJ 436	M2.5v	−4.60	−4.87	0.77^§	3

Lyα from IUE
AX Mic	M0v	−4.22	−5.29	0.14^†	3
DT Vir	M2v	−3.27	−3.15	0.41^†^,^‡	5
GJ 887	M2v	−4.05	−5.13	0.15^†	2
GJ 411	M2v	−4.44	−5.05	0.35^†	4
AD Leo	M4.5v	−3.58	−3.12	0.12^†	6
EV Lac	M3.5v	−2.74	−2.70	0.41^†	8
YZ CMi	M4.5v	−3.21	−3.06	0.03^†^,^‡	2
V1216 Sgr	M3v	−3.34	−4.13	1.10^†^,^‡	3
V998 Ori	M3.5v	−2.95	−3.08	0.18^†	2
Proxima Cen	M6v	−3.58	−3.58	0.31^†	10

Notes.

^(*)

Normalized X luminosities are Rosat values extracted from the Nexxus 2 data base. The dispersion σ_{L_X} is the standard deviation in the N_X measurements found in the Nexxus 2 database. These measurements are derived using (†) Rosat,

^(‡)

XMM-Newton, or (†,‡) both.

^(§)

The dispersion in the case of GJ 436 is obtained as the standard deviation in the three L_X values listed in the text.

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