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publications
Updated census of RR Lyrae stars in the globular cluster ω Centauri (NGC 5139)
Published in Astronomy & Astrophysics, 2015
Navarrete, C., Contreras Ramos, R., Catelan, M., Clement, C. M., Gran, F., Alonso-García, J., Angeloni, R., Hempel, M., Dékány, I., Minniti, D., A&A, 577, 99. ω Centauri (NGC 5139) contains many variable stars of different types and, in particular, more than one hundred RR Lyrae stars. This enabled gathering a homogeneous sample (in terms of instrument, image quality, and time coverage) of high-quality near-infrared (NIR) RR Lyrae light curves by performing an extensive time-series campaign aimed at this object. We have conducted a variability survey of ω Cen in the NIR, using ESO’s 4.1 m Visible and Infrared Survey Telescope for Astronomy (VISTA). This is the first paper of a series describing our results. ω Cen was observed using VIRCAM mounted on VISTA. A total of 42 epochs in J and 100 epochs in KS were obtained, distributed over a total timespan of 352 days. Point-spread function photometry was performed using DAOPHOT in the inner and DoPhot in the outer regions of the cluster. Periods of the known variable stars were improved when necessary using an ANOVA analysis. We collected an unprecedented homogeneous and complete NIR catalog of RR Lyrae stars in the field of ω Cen, allowing us to study for the first time all the RR Lyrae stars associated with the cluster, except for four stars that are located far away from the cluster center. We derived membership status, subclassifications between RRab and RRc subtypes, periods, amplitudes, and mean magnitudes for all the stars in our sample. Additionally, four new RR Lyrae stars were discovered, two of which are very likely cluster members. We also discuss here the distribution of ω Cen stars in the Bailey (period-amplitude) diagram. We provide reference lines in this plane for both Oosterhoff Type I (OoI) and Oosterhoff Type II (OoII) components in J and KS. We clarify the status of many (candidate) RR Lyrae stars that have been reported as unclear in previous studies. This includes stars with anomalous positions in the color-magnitude diagram, uncertain periods or/and variability types, and possible field interlopers. We conclude that ω Cen hosts a total of 88 RRab and 101 RRc stars, which makes for a grand total of 189 probable members. We confirm that most RRab stars in the cluster appear to belong to an OoII component, as previously found using visual data.
The Kapteyn Moving Group Is Not Tidal Debris From ω Centauri
Published in The Astrophysical Journal, 2015
Navarrete, C., Chanamé, J., Ramírez, I., Meza, A., Anglada-Escudé, G., Shkolnik, E., ApJ, 808, 103. The Kapteyn moving group has been postulated as tidal debris from ω Centauri. If true, members of the group should show some of the chemical abundance patterns known for stars in the cluster. We present an optical and near-infrared high-resolution, high-signal-to-noise ratio spectroscopic study of 14 stars of the Kapteyn group, plus 10 additional stars (the ω Cen group) that, while not listed as members of the Kapteyn group as originally defined, have nevertheless been associated dynamically with ω Centauri. Abundances for Na, O, Mg, Al, Ca, and Ba were derived from the optical spectra, while the strength of the chromospheric He i 10830 Å line is studied as a possible helium abundance indicator. The resulting Na–O and Mg–Al patterns for stars of the combined Kapteyn and ω Cen group samples do not resemble those of ω Centauri, and are not different from those of field stars of the Galactic halo. The distribution of equivalent widths of the He i 10830 Å line is consistent with that found among non-active field stars. Therefore, no evidence is found for second-generation stars within our samples, which most likely rules out a globular-cluster origin. Moreover, no hint of the unique barium overabundance at the metal-rich end, well established for ω Centauri stars, is seen among stars of the combined samples. Because this specific Ba pattern is present in ω Centauri irrespective of stellar generation, this would rule out the possibility that our entire sample might be composed of only first-generation stars from the cluster. Finally, for the stars of the Kapteyn group, the possibility of an origin in the hypothetical parent galaxy of ω Centauri is disfavored by the different run of α-elements with metallicity between our targets and stars from present-day dwarf galaxies.
The Discovery of Tidal Tails around the Globular Cluster NGC 7492 with Pan-STARRS1
Published in The Astrophysical Journal Letters, 2017
Navarrete, C., Belokurov, V., Koposov, S. E., ApJL, 841, L23. We report the discovery of tidal tails around the Galactic globular cluster NGC 7492, based on the Data Release 1 of the Pan-STARRS1 survey. The tails were detected using a version of the matched filter technique applied to the (g−r, r) and (g−i, i) color–magnitude diagrams. Tidal tails emerging from the cluster extend at least ∼3.5deg in the north–east to south–east direction, equivalent to ∼1.5 kpc in projected length.
Near-IR period-luminosity relations for pulsating stars in ω Centauri (NGC 5139)
Published in Astronomy & Astrophysics, 2017
Navarrete, C., Catelan, M., Contreras Ramos, R., Alonso-García, J., Gran, F., Dékány, I., Minniti, D. (2017), A&A, 604, 120. The globular cluster ω Centauri (NGC 5139) hosts hundreds of pulsating variable stars of different types, thus representing a treasure trove for studies of their corresponding period-luminosity (PL) relations. Our goal in this study is to obtain the PL relations for RR Lyrae and SX Phoenicis stars in the field of the cluster, based on high-quality, well-sampled light curves in the near-infrared (IR). Observations were carried out using the VISTA InfraRed CAMera (VIRCAM) mounted on the Visible and Infrared Survey Telescope for Astronomy (VISTA). A total of 42 epochs in J and 100 epochs in KS were obtained, spanning 352 days. Point-spread function photometry was performed using DoPhot and DAOPHOT crowded-field photometry packages in the outer and inner regions of the cluster, respectively. Based on the comprehensive catalog of near-IR light curves thus secured, PL relations were obtained for the different types of pulsators in the cluster, both in the J and KS bands. This includes the first PL relations in the near-IR for fundamental-mode SX Phoenicis stars. The near-IR magnitudes and periods of Type II Cepheids and RR Lyrae stars were used to derive an updated true distance modulus to the cluster, with a resulting value of (m − M)0 = 13.708 ± 0.035 ± 0.10 mag, where the error bars correspond to the adopted statistical and systematic errors, respectively. Adding the errors in quadrature, this is equivalent to a heliocentric distance of 5.52 ± 0.27 kpc.
A fork in the Sagittarius trailing debris
Published in Monthly Notices of the Royal Astronomical Society, 2017
Navarrete, C., Belokurov, V., Koposov, S. E., Irwin, M., Catelan, M., Duffau, S., Drake, A. J. (2017), MNRAS, 467, 1329. We take advantage of the deep and wide coverage of the VLT Survey Telescope (VST) ATLAS survey to study the line-of-sight structure of the Sagittarius (Sgr) stellar stream in the Southern hemisphere, only ∼40° away from the progenitor. We use photometrically selected subgiant branch (SGB) stars to reveal a complex debris morphology of the trailing arm and detect at least two clear peaks in the SGB distance modulus distribution. The separation between the two line-of-sight components is at least 5 kpc at the edge of the VST ATLAS footprint, but appears to change along the stream, which allows us to conclude that these detections correspond to two physically independent stellar structures, rather than a mix of co-distant stellar populations within a single stream. Our discovery of a fork in the Sgr trailing arm is verified using blue horizontal branch stars, and our distance measurements are calibrated using RR Lyrae stars from the Catalina Real-Time Transient Survey. Comparing with numerical simulations of the Sgr dwarf disruption, the more distant of the two components in the fork matches perfectly with the track of the trailing debris. However, no obvious counterpart exists in the simulation for the closer line-of-sight component.
Stellar streams around the Magellanic Clouds in 4D
Published in Monthly Notices of the Royal Astronomical Society, 2019
Navarrete, C., Belokurov, V., Catelan, M., Jethwa, P., Koposov, S. E., Carballo-Bello, J. A., Jofré, P., Erkal, D., Duffau, S., Corral-Santana, J. M. (2019), MNRAS, 483 4160. We carried out a spectroscopic follow-up programme of the four new stellar stream candidates detected by Belokurov & Koposov in the outskirts of the Large Magellanic Cloud (LMC) using FORS2 (VLT). The medium-resolution spectra were used to measure the line-of-sight velocities, estimate stellar metallicities, and classify stars into Blue Horizontal Branch (BHB) and Blue Straggler (BS) stars. Using the 4-D phase-space information, we attribute approximately one half of our sample to the Magellanic Clouds, while the rest is part of the Galactic foreground. Only two of the four stream candidates are confirmed kinematically. While it is impossible to estimate the exact levels of MW contamination, the phase-space distribution of the entire sample of our Magellanic stars matches the expected velocity gradient for the LMC halo and extends as far as 33 deg (angular separation) or 29 kpc from the LMC centre. Our detections reinforce the idea that the halo of the LMC seems to be larger than previously expected, and its debris can be spread in the sky out to very large separations from the LMC centre. Finally, we provide some kinematic evidence that many of the stars analysed here have likely come from the Small Magellanic Cloud.
The 3D kinematics of stellar substructures in the periphery of the Large Magellanic Cloud
Published in Monthly Notices of the Royal Astronomical Society, 2023
Navarrete, C., Aguado, D., Belokurov, V., Erkal, D., Deason, A., Cullinane, L., Carballo-Bello, J. (2023), MNRAS, 523, 4720. We report the 3D kinematics of 27 Mira-like stars in the northern, eastern, and southern periphery of the Large Magellanic Cloud (LMC), based on Gaia proper motions and a dedicated spectroscopic follow-up. Low-resolution spectra were obtained for more than 40 Mira-like candidates, selected to trace known substructures in the LMC periphery. Radial velocities and stellar parameters were derived for all stars. Gaia data release 3 astrometry and photometry were used to discard outliers, derive periods for those stars with available light curves, and determine their photometric chemical types. The 3D motion of the stars in the reference frame of the LMC revealed that most of the stars, in all directions, have velocities consistent with being part of the LMC disc population, out of equilibrium in the radial and vertical directions. A suite of numerical simulations was used to constrain the most likely past interaction history between the Clouds given the phase-space distribution of our targets. Model realizations in which the Small Magellanic Cloud (SMC) had three pericentric passages around the LMC best resemble the observations. The interaction history of those model realizations has a recent SMC pericentric passage (~320 Myr ago), preceded by an SMC crossing of the LMC disc at ~0.97 Gyr ago, having a radial crossing distance of only ~4.5 kpc. The previous disc crossing of the SMC was found to occur at ~1.78 Gyr ago, with a similar radial crossing distance of ~5.6 kpc.
talks
Talk 1 on Relevant Topic in Your Field
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Conference Proceeding talk 3 on Relevant Topic in Your Field
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teaching
Teaching experience 1
Undergraduate course, University 1, Department, 2014
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Teaching experience 2
Workshop, University 1, Department, 2015
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