Examinando por Autor "Beamin, J.C."

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    Discovery of a brown dwarf companion to the A3V star β Circini
    (Oxford University Press, 2015-12) Smith, L.C.; Lucas, P.W.; Contreras Peña, C.; Kurtev, R.; Marocco, F.; Jones, H.R.A.; Beamin, J.C.; Napiwotzki, R.; Borissova, J.; Burningham, B.; Faherty, J.; Pinfield, D.J.; Gromadzki, M.; Ivanov, V.D.; Minniti, D.; Stimson, W.; Villanueva, V.
    We report the discovery of an L dwarf companion to the A3V star β Circini. VVV J151721.49−585131.5, or β Cir B, was identified in a proper motion and parallax catalogue of the VISTA Variables in the Vía Láctea survey as having near-infrared luminosity and colour indicative of an early L dwarf, and a proper motion and parallax consistent with that of β Cir. The projected separation of ∼3.6 arcmin corresponds to 6656 au, which is unusually wide. The most recent published estimate of the age of the primary combined with our own estimate based on newer isochrones yields an age of 370–500 Myr. The system therefore serves as a useful benchmark at an age greater than that of the Pleiades brown dwarfs and most other young L dwarf benchmarks. We have obtained a medium resolution echelle spectrum of the companion which indicates a spectral type of L1.0 ± 0.5 and lacks the typical signatures of low-surface gravity seen in younger brown dwarfs. This suggests that signs of low-surface gravity disappear from the spectra of early L dwarfs by an age of ∼370–500 Myr, as expected from theoretical isochrones. The mass of β Cir B is estimated from the BHAC15 isochrones as 0.056 ± 0.007 M⊙.
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    New VVV Survey Globular Cluster Candidates in the Milky Way Bulge
    (Institute of Physics Publishing, 2017-11) Minniti, D.; Geisler, D.; Alonso-Garcia, J.; Palma, T.; Beamin, J.C.; Borissova, J.; Catelan, M.; Clariá, J.J.; Cohen, R.E.; Ramos, R.C.; Dias, B.; Fernández-Trincado, J.G.; Gómez, M.; Hempel, M.; Ivanov, V.D.; Kurtev, R.; Lucas, P.W.; Moni-Bidin, C.; Pullen, J.; Alegria, S.R.; Saito, R.K.; Valenti, E.
    It is likely that a number of Galactic globular clusters remain to be discovered, especially toward the Galactic bulge. High stellar density combined with high and differential interstellar reddening are the two major problems for finding globular clusters located toward the bulge. We use the deep near-IR photometry of the VISTA Variables in the Via Láctea (VVV) Survey to search for globular clusters projected toward the Galactic bulge, and hereby report the discovery of 22 new candidate globular clusters. These objects, detected as high density regions in our maps of bulge red giants, are confirmed as globular cluster candidates by their color-magnitude diagrams. We provide their coordinates as well as their near-IR color-magnitude diagrams, from which some basic parameters are derived, such as reddenings and heliocentric distances. The color-magnitude diagrams reveal well defined red giant branches in all cases, often including a prominent red clump. The new globular cluster candidates exhibit a variety of extinctions (0.06 < A Ks < 2.77) and distances (5.3 < D < 9.5 kpc). We also classify the globular cluster candidates into 10 metal-poor and 12 metal-rich clusters, based on the comparison of their color-magnitude diagrams with those of known globular clusters also observed by the VVV Survey. Finally, we argue that the census for Galactic globular clusters still remains incomplete, and that many more candidate globular clusters (particularly the low luminosity ones) await to be found and studied in detail in the central regions of the Milky Way.
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    The Emergence of the Infrared Transient VVV-WIT-06
    (Institute of Physics Publishing, 2017-11) Minniti, D.; Saito, R.K.; Forster, F.; Pignata, G.; Ivanov, V.D.; Lucas, P.W.; Beamin, J.C.; Borissova, J.; Catelan, M.; Gonzalez, O.A.; Hempel, M.; Hsiao, E.; Kurtev, R.; Majaess, D.; Masetti, N.; Morrell, N.I.; Phillips, M.M.; Pullen, J.B.; Rejkuba, M.; Smith, L.; Surot, F.; Valenti, E.; Zoccali, M.
    We report the discovery of an enigmatic large-amplitude (ΔKs >10.5 mag) transient event in near-IR data obtained by the VISTA Variables in the Via Lactea (VVV) ESO Public Survey. The object (designated VVV-WIT- 06) is located at R.A.=17:07:18.917, decl.=-39:06:26.45 (J2000), corresponding to Galactic coordinates l=347.14539, b=0.88522. It exhibits a clear eruption, peaking at Ks=9 mag during 2013 July and fading to Ks ∼ 16.5 in 2017. Our late near-IR spectra show post-outburst emission lines, including some broad emission lines (upward of FWHM ∼ 3000 km s-1). We estimate a total extinction of AV = 10-15 mag in the surrounding field, and no progenitor was observed in ZYJHKs images obtained during 2010-2012 (down to Ks > 18.5mag). Subsequent deep near-IR imaging and spectroscopy, in concert with the available multiband photometry, indicate that VVV-WIT-06 may be either: (i) the closest Type I SN observed in about 400 years, (ii) an exotic highamplitude nova that would extend the known realm of such objects, or (iii) a stellar merger. In all of these cases, VVV-WIT-06 is a fascinating and curious astrophysical target under any of the scenarios considered.