Bibcode
Vivas, A. K.; Olsen, Knut; Blum, Robert; Nidever, David L.; Walker, Alistair R.; Martin, Nicolas F.; Besla, Gurtina; Gallart, C.; van der Marel, Roeland P.; Majewski, Steven R.; Kaleida, Catherine C.; Muñoz, Ricardo R.; Saha, Abhijit; Conn, Blair C.; Jin, Shoko
Bibliographical reference
The Astronomical Journal, Volume 151, Issue 5, article id. 118, 14 pp. (2016).
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5
2016
Citations
45
Refereed citations
39
Description
We report the discovery of one RR Lyrae star in the ultra-faint
satellite galaxy Hydra II based on time series photometry in the g, r
and i bands obtained with the Dark Energy Camera at Cerro Tololo
Inter-American Observatory, Chile. The association of the RR Lyrae star
discovered here with Hydra II is clear because is located at
42\prime\prime from the center of the dwarf, well within its
half-light radius of 102\prime\prime . The RR Lyrae star has
a mean magnitude of i=21.30+/- 0.04 which is too faint to be a field
halo star. This magnitude translates to a heliocentric distance of 151
± 8 kpc for Hydra II; this value is ∼ 13% larger than the
estimate from the discovery paper based on the average magnitude of
several blue horizontal branch star candidates. The new distance implies
a slightly larger half-light radius of {76}-10+12
pc and a brighter absolute magnitude of {M}V=-5.1+/- 0.3,
which keeps this object within the realm of the dwarf galaxies. A
comparison with other RR Lyrae stars in ultra-faint systems indicates
similar pulsational properties among them, which are different to those
found among halo field stars and those in the largest of the Milky Way
satellites. We also report the discovery of 31 additional short period
variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries,
and a likely anomalous cepheid) which are likely not related with Hydra
II.