Browsing by Author "Rejkuba, M."

Now showing 1 - 20 of 42
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    A colour-excess extinction map of the southern Galactic disc from the VVV and GLIMPSE surveys
    (2019) Soto, M.; Barba, R.; Minniti, D.; Kunder, A.; Majaess, D.; Nilo Castellon, J. L.; Alonso García, J.; Leone, G.; Contreras Ramos, Rodrigo Andrés; Hempel, Maren; Morelli, Lorenzo; Haikala, L.; Firpo, V.; Lucas, P.; Emerson, J. P.; Bidin, C. M.; Geisler, D.; Saito, R. K.; Gurovich, S.; Rejkuba, M.; Barbieri, M.; Román Lopes, A.; Alonso, M. V.; Baravalle, L. D.; Borissova, J.; Kurtev, R.; Milla, F
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    Calcium triplet metallicity calibration for stars in the Galactic bulge
    (2015) Vasquez, S.; Zoccali, Manuela; Hill, V.; Gonzalez, O. A.; Saviane, I.; Rejkuba, M.; Battaglia, G.
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    Comparing the properties of the X-shaped bulges of NGC 4710 and the Milky Way with MUSE
    (2016) Rejkuba, M.; Valenti, E.; Zoccali, Manuela; Coccato, L.; Minniti, D.; Ness, M.; Gonzalez, O.; Gadotti, D.; Debattista, V.
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    Discovery of RR lyrae stars in the nuclear bulge of the Milky Way
    (2016) Minniti, D.; Ramos, R. C.; Zoccali, Manuela; Rejkuba, M.; González, O. A.; Valenti, E.; Gran, F.
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    Discovery of VVV CL001 A low-mass globular cluster next to UKS 1 in the direction of the Galactic bulge
    (EDP SCIENCES S A, 2011) Minniti, D.; Hempel, M.; Toledo, I.; Ivanov, V. D.; Alonso Garcia, J.; Saito, R. K.; Catelan, M.; Geisler, D.; Jordan, A.; Borissova, J.; Zoccali, M.; Kurtev, R.; Carraro, G.; Barbuy, B.; Claria, J.; Rejkuba, M.; Emerson, J.; Moni Bidin, C.
    Context. It is not known how many globular clusters may remain undetected towards the Galactic bulge.
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    FSR 1716: A New Milky Way Globular Cluster Confirmed Using VVV RR Lyrae Stars
    (2017) Hempel, Maren; Catelan, Márcio; Carballo Bello, J. A.; Ramos, R. C.; Gran, F.; Hagdu, G.; Navarrete, C.; Zoccali, Manuela; Minniti, D.; Palma, T.; Dekany, Istvan; Rejkuba, M.; Pullen, J.; Alonso Garcia, J.; Barba, R.; Barbuy, B.; Bica, E.; Borissova, J.; Chene, A. N.; Claria, J. J.; Cohen, R. E.; Dias, B.; Emerson, J.
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    Galactic bulge population II Cepheids in the VVV survey: period-luminosity relations and a distance to the Galactic centre
    (2017) Bhardwaj, A.; Rejkuba, M.; Minniti, D.; Surot, F.; Valenti, E.; Zoccali, Manuela; Gonzalez, O.; Romaniello, M.; Kanbur, S.; Singh, H.
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    Interstellar extinction curve variations towards the inner Milky Way : a challenge to observational cosmology
    (2016) Nataf, D.; Gonzalez, O.; Casagrande, L.; Zasowski, G.; Wegg, C.; Wolf, C.; Kunder, A.; Alonso, J.; Minniti, D.; Zoccali, Manuela; Saito, R.; Valenti, E.; Rejkuba, M.; Poleski, R.; Pietrzynski, G.; Skowron, J.
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    Low-resolution spectroscopy of main sequence stars belonging to 12 Galactic globular clusters I. CH and CN band strength variations
    (2010) Pancino, E.; Rejkuba, M.; Zoccali, M.; Carrera, R.
    Context. Globular clusters show star-to-star abundance variations for light elements that are not yet well understood. The preferred explanation involves a self-enrichment scenario, within which two subsequent generations of stars co-exist in globular clusters. Observations of chemical abundances in the main sequence and sub-giant branch stars allow us to investigate the signature of this chemically processed material without the complicating effects caused by stellar evolution and internal mixing.
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    Mapping the Milky Way bulge at high resolution : the 3D dust extinction, CO, and X factor maps
    (2014) Schultheis, M.; Chen, B.Q.; Jiang, B.W.; Gonzalez, O.A.; Enokiya, R.; Fukui, Y.; Torii, K.; Rejkuba, M.; Minniti, D.
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    Mapping the stellar age of the Milky Way bulge with the VVV I. The method
    (2019) Surot, F.; Valenti, E.; Hidalgo, S.L.; Zoccali, Manuela; Sokmen, E.; Rejkuba, M.; Minniti, D.; Gonzalez, O.A.; Cassisi, S.; Renzini, O.; Weiss, A.
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    Mapping the stellar age of the Milky Way bulge with the VVV II. Deep JKs catalog release based on PSF photometry
    (2019) Surot, F.; Valenti, E.; Hidalgo, S. L.; Zoccali, M.; Gonzalez, O. A.; Sokmen, E.; Minniti, D.; Rejkuba, M.; Lucas, P. W.
    Context. The bulge represents the best compromise between old and massive Galactic components, and as such its study is a valuable opportunity to understand how the bulk of the Milky Way formed and evolved. In addition, being the only bulge in which we can individually resolve stars in all evolutionary sequences, the properties of its stellar content provide crucial insights into the formation of bulges.
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    Microlensing Constraints on the Mass of Single Stars from HST Astrometric Measurements
    (2017) Kains, N.; Calamida, A.; Sahu, K.; Casertano, S.; Anderson, J.; Udalski, A.; Zoccali, Manuela; Bond, H.; Albrow, M.; Bond, I.; Brown,T.; Dominik, M.; Fryer, C.; Livio, M.; Mao, S.; Rejkuba, M.
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    Milky Way demographics with the VVV survey I. The 84-million star colour-magnitude diagram of the Galactic bulge
    (EDP SCIENCES S A, 2012) Saito, R. K.; Minniti, D.; Dias, B.; Hempel, M.; Rejkuba, M.; Alonso Garcia, J.; Barbuy, B.; Catelan, M.; Emerson, J. P.; Gonzalez, O. A.; Lucas, P. W.; Zoccali, M.
    Context. The Milky Way (MW) bulge is a fundamental Galactic component for understanding the formation and evolution of galaxies, in particular our own. The ESO Public Survey VISTA Variables in the Via Lactea is a deep near-IR survey mapping the Galactic bulge and southern plane. Particularly for the bulge area, VVV is covering similar to 315 deg(2). Data taken during 2010 and 2011 covered the entire bulge area in the JHKs bands.
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    Milky Way demographics with the VVV survey: III. Evidence for a great dark lane in the 157 million star bulge color-magnitude diagram
    (2014) Minniti, D.; Saito, R.; Gonzalez, O.; Zoccali, Manuela; Rejkuba, M.; Alonso-Garcia, J.; Benjamin, R.; Catelan, Márcio; Dekany, Istvan; Emerson, J.; Hempel, M.; Lucas, P.; Schultheis, M.
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    Near-infrared observations of RR Lyrae and Type II Cepheid variables in the metal-rich bulge globular cluster NGC 6441
    (2022) Bhardwaj, A.; Kanbur, S. M.; Rejkuba, M.; Marconi, M.; Catelan, Márcio; Ripepi, V.; Singh, H. P.
    Context. NGC 6441 is a bulge globular cluster (GC) with an unusual horizontal branch morphology and a rich population of RR Lyrae (RRL) and Type II Cepheid (T2C) variables that is unexpected for its relatively high metallicity. Aims: Our goal is to characterize the pulsation properties of the population II RRL and T2C variables in this metal-rich GC and compare them with a sample of variables in more metal-poor clusters, as well as with theoretical predictions. Methods: We present JHKs time-series observations of 42 RRLs, eight T2Cs, and ten eclipsing binary candidate variables in NGC 6441 . The multi-epoch observations were obtained using the FLAMINGOS-2 instrument on the 8-m Gemini South telescope. Multiband data are used to investigate pulsation properties of the RRL and T2C variables, including their light curves, instability strip, period-amplitude diagrams, and period-luminosity and period-Wesenheit relations (PLRs and PWRs) in the JHKs filters. Results: The near-infrared (NIR) pulsation properties of RRL variables are well fitted with theoretical models that have canonical helium content and the mean-metallicity of NGC 6441 ([Fe/H] = −0.44 ± 0.07 dex). The helium-enhanced RRL models predict brighter NIR magnitudes and bluer colors than the observations of RRL in the cluster. We find that the empirical slopes of the RRL PLRs and PWRs in NGC 6441 are statistically consistent with those of RRLs in more metal-poor GCs, as well as the theoretical models. Therefore, we use theoretical calibrations of RRL period-luminosity-metallicity (PLZ) relations to simultaneously estimate the mean reddening, E(J − Ks)=0.26 ± 0.06 mag, and the distance, d = 12.67 ± 0.09 kpc, to NGC 6441. Our mean reddening value is consistent with an independent estimate from the bulge reddening map based on red clump stars. The RRL-based distance agrees well with similar literature measurements based on the PLZ relations, and the Gaia and other independent methods. Our distance and reddening values provide a very good agreement between the PLRs of T2Cs in NGC 6441 and those for RRLs and T2Cs in Galactic GCs that span a broad range of metallicity. Conclusions: We conclude that the NIR colour-magnitude diagrams, pulsation properties, and PLRs for RRLs and T2Cs in NGC 6441 are in good agreement with the predictions of RRL pulsation models with canonical helium content. This suggests that these population II variables are either not significantly helium enhanced, as previously thought, or the impact of such enhancement is smaller in NIR than the predictions of the pulsation models. Full Table 2 is only available at the CDS via anonymous ftp to https://cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/668/A59...
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    New candidate hypervelocity red clump stars in the inner Galactic bulge
    (2024) Luna, A.; Marchetti, T.; Rejkuba, M.; Leigh, N. W. C.; Alonso-Garcia, J.; Navarro, A. Valenzuela; Minniti, D.; Smith, L. C.
    We search for high-velocity stars in the inner region of the Galactic bulge using a selected sample of red clump stars. Some of those stars might be considered hypervelocity stars (HVSs). Even though the HVSs ejection relies on an interaction with the supermassive black hole (SMBH) at the centre of the Galaxy, there are no confirmed detections of HVSs in the inner region of our Galaxy. With the detection of HVSs, ejection mechanism models can be constrained by exploring the stellar dynamics in the Galactic centre through a recent stellar interaction with the SMBH. Based on a previously developed methodology by our group, we searched with a sample of preliminary data from version 2 of the Vista Variables in the Via Lactea (VVV) Infrared Astrometric Catalogue (VIRAC2) and Gaia DR3 data, including accurate optical and near-infrared proper motions. This search resulted in a sample of 46 stars with transverse velocities larger than the local escape velocity within the Galactic bulge, of which four are prime candidate HVSs with high-proper motions consistent with being ejections from the Galactic centre. Adding to that, we studied a sample of reddened stars without a Gaia DR3 counterpart and found 481 stars with transverse velocities larger than the local escape velocity, from which 65 stars have proper motions pointing out of the Galactic centre and are candidate HVSs. In total, we found 69 candidate HVSs pointing away from the Galactic centre with transverse velocities larger than the local escape velocity.
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    New variable stars towards the Galactic Bulge - I. The bright regime
    (2019) Kains, N.; Calamida, A.; Rejkuba, M.; Bhardwaj, A.; Inno, L.; Sahu, K.C.; Zoccali, Manuela; Bono, G.; Surot, F.; Anderson, J.; Casertano, S.
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    Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud. II. The extended sample
    (2007) Borissova, J.; Minniti, Dante; Rejkuba, M.; Alves, D.