Large-scale changes of the cloud coverage in the $epsilon$ Indi Ba,Bb system. (arXiv:2005.06906v1 [astro-ph.SR])

Large-scale changes of the cloud coverage in the $epsilon$ Indi Ba,Bb system. (arXiv:2005.06906v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hitchcock_J/0/1/0/all/0/1">J. A. Hitchcock</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Helling_C/0/1/0/all/0/1">Ch. Helling</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scholz_A/0/1/0/all/0/1">A. Scholz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hodosan_G/0/1/0/all/0/1">G. Hodosan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dominik_M/0/1/0/all/0/1">M. Dominik</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hundertmark_M/0/1/0/all/0/1">M. Hundertmark</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jorgensen_U/0/1/0/all/0/1">U. G. Jørgensen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Longa_Pena_P/0/1/0/all/0/1">P. Longa-Peña</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sajadian_S/0/1/0/all/0/1">S. Sajadian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Skottfelt_J/0/1/0/all/0/1">J. Skottfelt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Snodgrass_C/0/1/0/all/0/1">C. Snodgrass</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bozza_V/0/1/0/all/0/1">V. Bozza</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burgdorf_M/0/1/0/all/0/1">M. J. Burgdorf</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Campbell_White_J/0/1/0/all/0/1">J. Campbell-White</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jaimes_R/0/1/0/all/0/1">Roberto Figuera Jaimes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fujii_Y/0/1/0/all/0/1">Y. I. Fujii</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haikala_L/0/1/0/all/0/1">L. K. Haikala</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henning_T/0/1/0/all/0/1">T. Henning</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hinse_T/0/1/0/all/0/1">T. C. Hinse</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lowry_S/0/1/0/all/0/1">S. Lowry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mancini_L/0/1/0/all/0/1">L. Mancini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rahvar_S/0/1/0/all/0/1">S. Rahvar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rabus_M/0/1/0/all/0/1">M. Rabus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Southworth_J/0/1/0/all/0/1">J. Southworth</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Essen_C/0/1/0/all/0/1">C. von Essen</a>

We present the results of 14 nights of textit{I}-band photometric monitoring
of the nearby brown dwarf binary, $epsilon$ Indi Ba,Bb. Observations were
acquired over 2 months, and total close to 42 hours of coverage at a typically
high cadence of 1.4 minutes. At a separation of just $0.7”$, we do not resolve
the individual components, and so effectively treat the binary as if it were a
single object. However, $epsilon$ Indi Ba (spectral type T1) is the brightest
known T-type brown dwarf, and is expected to dominate the photometric signal.
We typically find no strong variability associated with the target during each
individual night of observing, but see significant changes in mean brightness –
by as much as $0.10$ magnitudes – over the 2 months of the campaign. This
strong variation is apparent on a timescale of at least 2 days. We detect no
clear periodic signature, which suggests we may be observing the T1 brown dwarf
almost pole-on, and the days-long variability in mean brightness is caused by
changes in the large-scale structure of the cloud coverage. Dynamic clouds will
very likely produce lightning, and complementary high cadence textit{V}-band
and Htextit{$alpha$} images were acquired to search for the emission
signatures associated with stochastic “strikes.” We report no positive
detections for the target in either of these passbands.

http://arxiv.org/icons/sfx.gif