We present spectral energy distribution modelling of 6875 stars in \omega Centauri , obtaining stellar luminosities and temperatures by fitting literature photometry to state-of-the-art marcs stellar models .
By comparison to four different sets of isochrones , we provide a new distance estimate to the cluster of 4850 \pm 200 ( random error ) \pm 120 ( systematic error ) pc , a reddening of E ( B - V ) = 0.08 \pm 0.02 ( random ) \pm 0.02 ( systematic ) mag and a differential reddening of \Delta E ( B - V ) < 0.02 mag for an age of 12 Gyr .
Several new post-early-AGB candidates are also found .
Infra-red excesses of stars were used to measure total mass-loss rates for individual stars down to \sim 7 \times 10 ^ { -8 } M _ { \odot } yr ^ { -1 } .
We find a total dust mass-loss rate from the cluster of 1.3 \pm ^ { 0.8 } _ { 0.5 } \times 10 ^ { -9 } M _ { \odot } yr ^ { -1 } , with the total gas mass-loss rate being > 1.2 \pm ^ { 0.6 } _ { 0.5 } \times 10 ^ { -6 } M _ { \odot } yr ^ { -1 } .
Half of the cluster ’ s dust production and 30 % of its gas production comes from the two most extreme stars – V6 and V42 – for which we present new Gemini/T-ReCS mid-infrared spectroscopy , possibly showing that V42 has carbon-rich dust .
The cluster ’ s dust temperatures are found to be typically { { { { \mathrel { \mathchoice { \lower 2.0 pt \vbox { \halign { \cr } $ \displaystyle \hfil > $ \cr$% \displaystyle \hfil \sim$ } } } { \lower 2.0 pt \vbox { \halign { \cr } $ \textstyle \hfil > $ \cr% $ \textstyle \hfil \sim$ } } } { \lower 2.0 pt \vbox { \halign { \cr } $ \scriptstyle \hfil > $ \cr% $ \scriptstyle \hfil \sim$ } } } { \lower 2.0 pt \vbox { \halign { \cr } $ \scriptscriptstyle% \hfil > $ \cr$ \scriptscriptstyle \hfil \sim$ } } } } 550 K. Mass loss apparently does not vary significantly with metallicity within the cluster , but shows some correlation with barium enhancement , which appears to occur in cooler stars , and especially on the anomalous RGB .
Limits to outflow velocities , dust-to-gas ratios for the dusty objects and the possibility of short-timescale mass-loss variability are also discussed in the context of mass loss from low-metallicity stars .
The ubiquity of dust around stars near the RGB-tip suggests significant dusty mass loss on the RGB ; we estimate that typically 0.20–0.25 M _ { \odot } of mass loss occurs on the RGB .
From observational limits on intra-cluster material , we suggest the dust is being cleared on a timescale of { { { { \mathrel { \mathchoice { \lower 2.0 pt \vbox { \halign { \cr } $ \displaystyle \hfil < $ \cr$% \displaystyle \hfil \sim$ } } } { \lower 2.0 pt \vbox { \halign { \cr } $ \textstyle \hfil < $ \cr% $ \textstyle \hfil \sim$ } } } { \lower 2.0 pt \vbox { \halign { \cr } $ \scriptstyle \hfil < $ \cr% $ \scriptstyle \hfil \sim$ } } } { \lower 2.0 pt \vbox { \halign { \cr } $ \scriptscriptstyle% \hfil < $ \cr$ \scriptscriptstyle \hfil \sim$ } } } } 10 ^ { 5 } years .