The K2 Galactic Caps Project — Going Beyond the textit{Kepler} Field and Ageing the Galactic Disc. (arXiv:1906.07489v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Rendle_B/0/1/0/all/0/1">B.M. Rendle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Miglio_A/0/1/0/all/0/1">A. Miglio</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chiappini_C/0/1/0/all/0/1">C. Chiappini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Valentini_M/0/1/0/all/0/1">M. Valentini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Davies_G/0/1/0/all/0/1">G.R. Davies</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mosser_B/0/1/0/all/0/1">B. Mosser</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Elsworth_Y/0/1/0/all/0/1">Y. Elsworth</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garcia_R/0/1/0/all/0/1">R.A. García</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mathur_S/0/1/0/all/0/1">S. Mathur</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jofre_P/0/1/0/all/0/1">P. Jofré</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Worley_C/0/1/0/all/0/1">C.C. Worley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casagrande_L/0/1/0/all/0/1">L. Casagrande</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Girardi_L/0/1/0/all/0/1">L. Girardi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lund_M/0/1/0/all/0/1">M.N. Lund</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feuillet_D/0/1/0/all/0/1">D.K. Feuillet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gavel_A/0/1/0/all/0/1">A. Gavel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Magrini_L/0/1/0/all/0/1">L. Magrini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Khan_S/0/1/0/all/0/1">S. Khan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodrigues_T/0/1/0/all/0/1">T.S. Rodrigues</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Johnson_J/0/1/0/all/0/1">J.A. Johnson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cunha_K/0/1/0/all/0/1">K. Cunha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lane_R/0/1/0/all/0/1">R.L. Lane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nitschelm_C/0/1/0/all/0/1">C. Nitschelm</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chaplin_W/0/1/0/all/0/1">W.J. Chaplin</a>
Analyses of data from spectroscopic and astrometric surveys have led to
conflicting results concerning the vertical characteristics of the Milky Way.
Ages are often used to provide clarity, but typical uncertainties of $>$ 40,%
restrict the validity of the inferences made. Using the textit{Kepler} APOKASC
sample for context, we explore the global population trends of two K2 campaign
fields (3 and 6), which extend further vertically out of the Galactic plane
than APOKASC. We analyse the properties of red giant stars utilising three
asteroseismic data analysis methods to cross-check and validate detections. The
Bayesian inference tool PARAM is used to determine the stellar masses, radii
and ages. Evidence of a pronounced red giant branch bump and an [$alpha$/Fe]
dependence on the position of the red clump is observed from the radii
distribution of the K2 fields. Two peaks in the age distribution centred at
$sim$5 and and $sim$12 Gyr are found using a sample with $sigma_{rm{age}}$
$<$ 35,%. In a comparison with textit{Kepler}, we find the older peak to be
more prominent for K2. This age bimodality is also observed based on a chemical
selection of low- ($leq$ 0.1) and high- ($>$ 0.1) [$alpha$/Fe] stars. As a
function of vertical distance from the Galactic mid-plane ($|Z|$), the age
distribution shows a transition from a young to old stellar population with
increasing $|Z|$ for the K2 fields. Further coverage of campaign targets with
high resolution spectroscopy is required to increase the yield of precise ages
achievable with asteroseismology.
Analyses of data from spectroscopic and astrometric surveys have led to
conflicting results concerning the vertical characteristics of the Milky Way.
Ages are often used to provide clarity, but typical uncertainties of $>$ 40,%
restrict the validity of the inferences made. Using the textit{Kepler} APOKASC
sample for context, we explore the global population trends of two K2 campaign
fields (3 and 6), which extend further vertically out of the Galactic plane
than APOKASC. We analyse the properties of red giant stars utilising three
asteroseismic data analysis methods to cross-check and validate detections. The
Bayesian inference tool PARAM is used to determine the stellar masses, radii
and ages. Evidence of a pronounced red giant branch bump and an [$alpha$/Fe]
dependence on the position of the red clump is observed from the radii
distribution of the K2 fields. Two peaks in the age distribution centred at
$sim$5 and and $sim$12 Gyr are found using a sample with $sigma_{rm{age}}$
$<$ 35,%. In a comparison with textit{Kepler}, we find the older peak to be
more prominent for K2. This age bimodality is also observed based on a chemical
selection of low- ($leq$ 0.1) and high- ($>$ 0.1) [$alpha$/Fe] stars. As a
function of vertical distance from the Galactic mid-plane ($|Z|$), the age
distribution shows a transition from a young to old stellar population with
increasing $|Z|$ for the K2 fields. Further coverage of campaign targets with
high resolution spectroscopy is required to increase the yield of precise ages
achievable with asteroseismology.
http://arxiv.org/icons/sfx.gif
