Electronic Telegram No. 5568
Central Bureau for Astronomical Telegrams
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GJ 436
     C. M. Lisse, Applied Physical Laboratory, Johns Hopkins University; M. L.
Sitko, Space Science Institute; and G. M. Engh, NASA Infrared Telescope
Facility, report observations of the nearby M3 V red-dwarf star GJ 436 (which
has a well-known transiting, hot-coating Neptune-size planet, GJ 436b) that
reveal the discovery of an Fe I line at 2.31 microns that shows strong
absorption during the "post-transit quadrature" phase that changes to mild
emission during secondary eclipse, and then to red-shifted emission through
transit, when the emission disappears.  The discovery was made using four
timed observations of the GJ 436 system (R.A. = 11h42m11s.09, Decl. =
+26d42'23".7, equinox J2000.0) from 2025 March 14 to 18, taken from with the
3.2-m NASA/IRTF reflector (+ SpeX 0.68- to 5.2-micron spectrometer) atop Mauna
Kea.  Two other excited-state 3d transitions of Na I at 1.14 and 1.27 microns
vary similarly, as does an unidentified line at 2.371 microns, in between
(12)C(16)O-line bandheads.  The phasing behavior of the line structure can be
explained by a long dense "tidal tail" structure trailing the planet by at
least 0.2 day and lasting for at least 0.8 day (as reported by Lavie et al.
2017, A.Ap. 605, L7, for H I) that is rich in Na I and Fe I.  Lisse et al.
suspect that collisions or charge exchange in the tidal tail may be pumping
the phased lines, and models explaining this line behavior need to describe
why other Fe I and Na I lines (like the 2.32-micron Na I doublet) do not show
any phase variability.


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                         (C) Copyright 2025 CBAT
2025 June 13                     (CBET 5568)              Daniel W. E. Green