The surprisingly low carbon mass in the debris disk around HD 32297. (arXiv:1904.07215v4 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Cataldi_G/0/1/0/all/0/1">Gianni Cataldi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wu_Y/0/1/0/all/0/1">Yanqin Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brandeker_A/0/1/0/all/0/1">Alexis Brandeker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ohashi_N/0/1/0/all/0/1">Nagayoshi Ohashi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moor_A/0/1/0/all/0/1">Attila Moór</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Olofsson_G/0/1/0/all/0/1">Göran Olofsson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abraham_P/0/1/0/all/0/1">Péter Ábrahám</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Asensio_Torres_R/0/1/0/all/0/1">Ruben Asensio-Torres</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cavallius_M/0/1/0/all/0/1">Maria Cavallius</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dent_W/0/1/0/all/0/1">William R. F. Dent</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Grady_C/0/1/0/all/0/1">Carol Grady</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henning_T/0/1/0/all/0/1">Thomas Henning</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Higuchi_A/0/1/0/all/0/1">Aya E. Higuchi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hughes_A/0/1/0/all/0/1">A. Meredith Hughes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Janson_M/0/1/0/all/0/1">Markus Janson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kamp_I/0/1/0/all/0/1">Inga Kamp</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kospal_A/0/1/0/all/0/1">Ágnes Kóspál</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Redfield_S/0/1/0/all/0/1">Seth Redfield</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Roberge_A/0/1/0/all/0/1">Aki Roberge</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weinberger_A/0/1/0/all/0/1">Alycia Weinberger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Welsh_B/0/1/0/all/0/1">Barry Welsh</a>
Gas has been detected in a number of debris disks. It is likely secondary,
i.e. produced by colliding solids. Here, we report ALMA Band 8 observations of
neutral carbon in the CO-rich debris disk around the 15–30 Myr old A-type star
HD 32297. We find that C$^0$ is located in a ring at $sim$110 au with a FWHM
of $sim$80 au, and has a mass of $(3.5pm0.2)times10^{-3}$ M$_oplus$.
Naively, such a surprisingly small mass can be accumulated from CO
photo-dissociation in a time as short as $sim$10$^4$ yr. We develop a simple
model for gas production and destruction in this system, properly accounting
for CO self-shielding and shielding by neutral carbon, and introducing a
removal mechanism for carbon gas. We find that the most likely scenario to
explain both C$^0$ and CO observations, is one where the carbon gas is rapidly
removed on a timescale of order a thousand years and the system maintains a
very high CO production rate of $sim$15 M$_oplus$ Myr$^{-1}$, much higher
than the rate of dust grind-down. We propose a possible scenario to meet these
peculiar conditions: the capture of carbon onto dust grains, followed by rapid
CO re-formation and re-release. In steady state, CO would continuously be
recycled, producing a CO-rich gas ring that shows no appreciable spreading over
time. This picture might be extended to explain other gas-rich debris disks.
Gas has been detected in a number of debris disks. It is likely secondary,
i.e. produced by colliding solids. Here, we report ALMA Band 8 observations of
neutral carbon in the CO-rich debris disk around the 15–30 Myr old A-type star
HD 32297. We find that C$^0$ is located in a ring at $sim$110 au with a FWHM
of $sim$80 au, and has a mass of $(3.5pm0.2)times10^{-3}$ M$_oplus$.
Naively, such a surprisingly small mass can be accumulated from CO
photo-dissociation in a time as short as $sim$10$^4$ yr. We develop a simple
model for gas production and destruction in this system, properly accounting
for CO self-shielding and shielding by neutral carbon, and introducing a
removal mechanism for carbon gas. We find that the most likely scenario to
explain both C$^0$ and CO observations, is one where the carbon gas is rapidly
removed on a timescale of order a thousand years and the system maintains a
very high CO production rate of $sim$15 M$_oplus$ Myr$^{-1}$, much higher
than the rate of dust grind-down. We propose a possible scenario to meet these
peculiar conditions: the capture of carbon onto dust grains, followed by rapid
CO re-formation and re-release. In steady state, CO would continuously be
recycled, producing a CO-rich gas ring that shows no appreciable spreading over
time. This picture might be extended to explain other gas-rich debris disks.
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