DISCOVERY OF A PAIR OF CLASSICAL CEPHEIDS IN AN INVISIBLE CLUSTER BEYOND THE GALACTIC BULGE

ABSTRACT We report the discovery of a pair of extremely reddened classical Cepheid variable stars located in the Galactic plane behind the bulge, using near-infrared (NIR) time-series photometry from the VISTA Variables in the Vía Láctea Survey. This is the first time that such objects have ever bee...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2015-01, Vol.799 (1), p.1-6
Main Authors: Dékány, I., Minniti, D., Hajdu, G., Alonso-García, J., Hempel, M., Palma, T., Catelan, M., Gieren, W., Majaess, D.
Format: Article
Language:English
Subjects:
ACCURACY
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Asymptotic properties
BRIGHTNESS
Cepheid variables
CEPHEIDS
Clusters
DISTANCE
Extinction
Galactic bulge
GALAXIES
Galaxy: stellar content
Galaxy: structure
NEAR INFRARED RADIATION
PHOTOMETRY
Planes
Position (location)
STAR CLUSTERS
stars: variables: Cepheids
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Summary:ABSTRACT We report the discovery of a pair of extremely reddened classical Cepheid variable stars located in the Galactic plane behind the bulge, using near-infrared (NIR) time-series photometry from the VISTA Variables in the Vía Láctea Survey. This is the first time that such objects have ever been found in the opposite side of the Galactic plane. The Cepheids have almost identical periods, apparent brightnesses, and colors. From the NIR Leavitt law, we determine their distances with precision and accuracy. We find that they have a same total extinction of mag, and are located at the same heliocentric distance of kpc, and less than 1 pc from the true Galactic plane. Their similar periods indicate that the Cepheids are also coeval, with an age of Myr, according to theoretical models. They are separated by an angular distance of only 18 3, corresponding to a projected separation of ∼1 pc. Their position coincides with the expected location of the Far 3 kpc Arm behind the bulge. Such a tight pair of similar classical Cepheids indicates the presence of an underlying young open cluster that is both hidden behind heavy extinction and disguised by the dense stellar field of the bulge. All our attempts to directly detect this "invisible cluster" have failed, and deeper observations are needed.
ISSN:2041-8205
2041-8213
2041-8213
DOI:10.1088/2041-8205/799/1/L11