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arXiv · 1005.4618

Dust is forming along the red giant branch of 47 TUC

Livia Origlia·Robert T. Rood·Sara Fabbri·Francesco R. Ferraro·Flavio Fusi Pecci·R. Michael Rich·Emanuele Dalessandro
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Abstract

We present additional evidence that dust is really forming along the red giant branch (RGB) of 47 Tuc at luminosities ranging from above the horizontal branch to the RGB-tip (Origlia et al. 2007). The presence of dust had been inferred from an infrared excess in the (K-8) color, with K measured from high spatial resolution ground based near-IR photometry and "8" referring to Spitzer-IRAC 8 micron photometry. We show how (K-8) is a far more sensitive diagnostic for detecting tiny circumstellar envelopes around warm giants than colors using only the Spitzer-IRAC bands, for example the (3.6-8) color used by Boyer et al. (2010). In addition, we also show high resolution HST-ACS I band images of the giant stars which have (K-8) color excess. These images clearly demonstrate that Boyer et al (2010) statement that our detections of color excess associated with stars below the RGB-tip arise from blends and artefacts is simply not valid.

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Livia Origlia, Robert T. Rood, Sara Fabbri, Francesco R. Ferraro, Flavio Fusi Pecci, R. Michael Rich, Emanuele Dalessandro. 2010-05-25. Dust is forming along the red giant branch of 47 TUC. https://doi.org/10.1088/0004-637x/718/1/522

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