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http://hdl.handle.net/20.500.12386/34669
Title: | Hunting for brown dwarfs in the globular cluster M4: second epoch HST NIR observations | Authors: | Dieball, A. BEDIN, Luigi Knigge, C. Geffert, M. Rich, R. M. Dotter, A. Richer, H. Zurek, D. |
Issue Date: | 2019 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Number: | 486 | Issue: | 2 | First Page: | 2254 | Abstract: | We present an analysis of the second epoch Hubble Space TelescopeWide Field Camera 3 F110W near-infrared (NIR) imaging data of the globular cluster M 4. The new data set suggests that one of the previously suggested four brown dwarf candidates in this cluster is indeed a high-probability cluster member. The position of this object in the NIR colour-magnitude diagrams (CMDs) is in the white dwarf/brown dwarf area. The source is too faint to be a low-mass main-sequence (MS) star, but, according to theoretical considerations, also most likely somewhat too bright to be a bona-fide brown dwarf. Since we know that the source is a cluster member, we determined a new optical magnitude estimate at the position the source should have in the optical image. This new estimate places the source closer to the white dwarf sequence in the optical-NIR CMD and suggests that it might be a very cool (T<SUB>eff</SUB> ≤ 4500 K) white dwarf at the bottom of the white dwarf cooling sequence in M 4, or a white dwarf/brown dwarf binary. We cannot entirely exclude the possibility that the source is a very massive, bright brown dwarf, or a very low-mass MS star, however, we conclude that we still have not convincingly detected a brown dwarf in a globular cluster, but we expect to be very close to the start of the brown dwarf cooling sequence in this cluster. We also note that the MS ends at F110W ≈ 22.5 mag in the proper-motion cleaned CMDs, where completeness is still high. | URI: | http://hdl.handle.net/20.500.12386/34669 | URL: | http://arxiv.org/abs/1904.02999v1 https://academic.oup.com/mnras/article/486/2/2254/5437690?login=false |
ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stz996 | Bibcode ADS: | 2019MNRAS.486.2254D | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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stz996.pdf | PDF editoriale | 5.09 MB | Adobe PDF | View/Open |
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