Browsing by Author "Kunder, A."
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- ItemA 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
- ItemHumps and bumps: the effects of shocks on the optical light curves of fundamental-mode RR Lyrae stars(EDP SCIENCES S A, 2020) Prudil, Z.; Dekany, I.; Smolec, R.; Catelan, M.; Grebel, E. K.; Kunder, A.We present the most extended and homogeneous study carried out so far of the main and early shocks in 1485 RR Lyrae stars in the Galactic bulge observed by the Optical Gravitational Lensing Experiment. We selected nonmodulated fundamental-mode RR Lyrae stars with good-quality photometry. Using a self-developed method, we determined the centers and strengths of main and early shock features in the phased light curves. We found that the positions of both humps and bumps are highly correlated with the pulsation properties of the studied variables. Pulsators with a pronounced main shock are concentrated in the low-amplitude regime of the period-amplitude diagram, while stars with a strong early shock have average and above-average pulsation amplitudes. A connection between the main and early shocks and the Fourier coefficients is also observed. In the color-magnitude diagram, we see a separation between stars with strong and weak shocks. Variables with a pronounced main shock cluster close to the fundamental red edge of the instability strip (IS), while stars with a strong early shock tend to clump in the center and near the fundamental blue edge of the IS. The appearance of shocks and their properties appear to be independent of the direction of evolution estimated from the period change rate of the studied stars. In addition, the differences in the period change rate between the two main Oosterhoff groups found in the Galactic bulge suggest that stars of Oosterhoff type I are located close to the zero-age horizontal branch while Oosterhoff type II variables are on their way toward the fundamental red edge of the instability strip, and have therefore already left the zero-age horizontal branch.
- ItemInterstellar 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.
- ItemMain and Early Shocks in RR Lyrae Photometric Light Curves(2021) Prudil, Z.; Smolec, R.; Catelan, Márcio; Dékány, I.; Grebel, E. K.; Kunder, A.We explore the effect of the main and early shocks (giving rise to the so-called hump and bump features in the light curves, respectively) on the pulsation properties of non-modulated fundamental mode RR Lyrae stars. We utilized I-band photometry from the fourth release of the Optical Gravitational Lensing Experiment (OGLE). We determined the centers and strengths of humps and bumps in the phased light curves of the studied stars. The positions of both shock events in the phased light curves are highly correlated with the amplitudes, pulsation periods, and Fourier coefficients. RR Lyrae stars with prominent humps are located at the low-amplitude regime of the Bailey diagram, while variables with pronounced bumps have average and above average amplitudes. RR Lyrae stars close to the red edge of the instability strip have pronounced humps, while variables with a strong bump are located at the center and close to the blue edge of the instability strip. In general, the effect of the main and early shocks provides a new view on the period-amplitude distribution of fundamental mode RR Lyrae stars....
- ItemThe Horizontal Branch of NGC 1851: Constraints from its RR Lyrae Variables(2013) Kunder, A.; Catelan, Márcio; Amigo Fuentes, Pía
- ItemThe RR Lyrae Instability Strip in the Split Horizontal Branch Globular Cluster NGC 6569(2015) Kunder, A.; Stetson, P. B.; Catelan, Marcio; Walker, A.; Cassisi, S.; Johnson, C.; Soto, M.The first calibrated broadband BVI time-series photometry is obtained for the RR Lyrae variable stars in the split horizontal branch (HB) cluster NGC 6569. As a result, a sizeable population of 27 RR Lyrae variables has been identified. An eclipsing binary in the RR Lyrae instability strip was also found, which is most likely a field star. The 12 fundamental-mode RR Lyrae variables (RR0) have an average period of [P]RR0= 0.57±0.02 d and the 15 first-overtone variables (RR1) have an average period of [P]RR1=0.30±0.01 d. The mean periods of the RR Lyrae stars are consistent with an Oosterhoff I designation, and the number ratio of RR1- to RR0-type variables, N1/NRR=0.56, is more consistent with an Oosterhoff II designation. Compared to the M3 variables, the NGC 6569 RR Lyrae variables are not shifted to a longer periods at a given amplitude, making it unlikely that these stars are He-enhanced. The similarity in the periods and amplitudes between the RR Lyrae stars in NGC 6569 and the bulge field RR Lyrae population may indicate similar formation conditions.
- ItemThe rr lyrae variables and horizontal branch of NGC 6656 (m22)(2013) Kunder, A.; Stetson, P.; Cassisi, S.; Layden, A.; Bono, G.; Catelan, Márcio; Walker, A.; Paredes Alvarez, L.; Clem, J.; Matsunaga, N.; Salaris, M.; Lee, J.; Chaboyer, B.
- ItemTheoretical modeling of the RR Lyrae variables in NGC 1851(2015) Kunder, A.; Salaris, M.; Cassisi, S.; de Propris, R.; Walker, A.; Stetson, P. B.; Catelan, Marcio; Amigo, P.The RR Lyrae instability strip (IS) in NGC 1851 is investigated, and a model is presented which reproduces the pulsational properties of the RR Lyrae population. In our model, a stellar component within the IS that displays minor helium variations (Y∼0.248-0.270) is able to reproduce the observed periods and amplitudes of the RR Lyrae variables, as well as the frequency of fundamental and first-overtone RR Lyrae variables. The RR Lyrae variables therefore may belong to an He-enriched second generation of stars. The RR Lyrae variables with a slightly enhanced helium (Y∼0.270-0.280) have longer periods at a given amplitude, as is seen with Oosterhoff II (OoII) RR Lyrae variables, whereas the RR Lyrae variables with Y∼0.248-0.270 have shorter periods, exhibiting properties of Oosterhoff I (OoI) variables. %.
- ItemunVEil the darknesS of The gAlactic buLgE (VESTALE)(2018) Bono, G.; Dall'Ora, M.; Fabrizio, M.; Crestani, J.; Braga, V. F.; Fiorentino, G.; Altavilla, G.; Botticella, M. T.; Calamida, A.; Castellani, M.; Catelan, Marcio; Chaboyer, B.; Chiappini, C.; Clarkson, W.; Contreras Ramos, R.; Creevey, O.; da Silva, R.; Debattista, V.; Degl'Innocenti, S.; Ferraro, I.; Gilligan, C. K.; Gonzalez, O.; Hambleton, K.; Iannicola, G.; Inno, L.; Kunder, A.; Lemasle, B.; Magrini, L.; Magurno, D.; Marconi, M.; Marengo, M.; Marinoni, S.; Marrese, P. M.; Martinez-Vazquez, C. E.; Matsunaga, N.; Monelli, M.; Prada Moroni, P. G.; Musella, I.; Navarro, M. G.; Neeley, J.; Nonino, M.; Pietrinferni, A.; Pulone, L.; Rich, M. R.; Ripepi, V.; Sacco, G.; Saha, A.; Salaris, M.; Sneden, C.; Stetson, P. B.; Street, R. A; Szabo, R.; Tantalo, M.; Tognelli, E.; Torelli, M.; Valenti, E.; Walker, A. R.; Zoccali, M.The main aim of this experiment is to provide a complete census of old (t > 10 Gyr, RR Lyrae, type II Cepheids, red horizontal branch), intermediate age (red clump, Miras) and young (classical Cepheids) stellar tracers across the Galactic Bulge. To fully exploit the unique photometric quality of LSST images, we plan to perform a Shallow minisurvey (ugrizy, -20 < l < 20 deg, -15 < b < 10 deg) and a Deep minisurvey (izy, -20 < l < 20 deg, -3 < b < 3 deg). The former one is aimed at constraining the 3D structure of the galactic Bulge across the four quadrants, and in particular, the transition between inner and outer Bulge. The u,g,r,i,z,y LSST bands provide fundamental diagnostics to constrain the evolutionary properties of low and intermediate-mass stars when moving from a metal-poor to a metal-rich regime. The deep minisurvey is aimed at tracing RR Lyrae, Red Clump stars, Miras and classical Cepheids in highly reddened regions of the Galactic center. These images will allow us to investigate the role that baryonic mass and dark matter played in the early formation and evolution of the MW....
- ItemVariable Stars in Large Magellanic Cloud Globular Clusters. III. Reticulum(2013) Kuehn, C. A.; Dame, K.; Smith, H. A.; Catelan, Márcio; Walker, A. R.; Kunder, A.; Pritzl, B. J.; De Lee, N.; Borissova, J.
- ItemVARIABLE STARS IN THE GLOBULAR CLUSTER NGC 2808(2013) Kunder, A.; Catelan, Márcio