Artículos de conferencia

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A massive binary system can feed Sgr A*
(2017) Calderón Espinoza, Diego Nicolás; Cuadra, Jorge
The enigmatic G2 cloud just passed pericentre around the Galactic Centre super-massive black hole, Sgr A. Despite all theoretical and observational efforts, its nature remains unclear. If purely gaseous, it is possible to explain it as a gas clump formed in a colliding wind binary. Here we study the hypothesis of G2 being one of such clumps ejected from the massive binary IRS 16SW....
Analysis of the velocity data of cluster A562
(2014) Calderón Espinoza, Diego Nicolás; Gómez, P.
We present a recent study of the dynamics of the cluster of galaxies Abell 562 intended to determine if ram pressure is responsible for the jet bending in the Wide-Angle Tailed (WAT) radio source located in the central elliptical galaxy. Given the properties of the jet and of the intra-cluster medium (ICM), a relative velocity between the galaxy and the ICM greater than 800 km/s is needed for this mechanism to bend the WAT jet. We find that the peculiar velocity of the WAT galaxy is 170 ± 140 km/s which is not enough to produce the bending. This is based on the analysis of the velocity of 146 galaxy cluster members obtained with the Gemini Multi-Object Spectrometer (GMOS) at Gemini North. However, our analysis of these velocity data and archival Chandra data suggests that an off-axis merger occurred in this system. This type of merger typically produces bulk flow motions with peak velocities greater than 1000 km/s which should be enough to explain the bending of the jets....
Clump formation through colliding stellar winds in the Galactic Centre
(2017) Calderón Espinoza, Diego Nicolás; Ballone, A.; Cuadra, Jorge; Schartmann, Marc; Burkert, A.; Gillessen, S.
We study the process of clump formation from hydrodynamic instabilities in stellar wind collisions, using analytical and numerical techniques. We show that the cloud G2 in the Galactic Centre could have been formed in this way, with the most promising sources being compact massive binaries, such as IRS 16SW....
CRTS: An Open Optical Transient Survey
(2011) Drake, Andrew J.; Djorgovski, S. G.; Mahabal, A.; Williams, R.; Graham, M. J.; Donalek, C.; Prieto, J. L.; Catelan, Márcio; Beshore, E.; Larson, S.; Christensen, E.
The Catalina Real-time Transient Survey (CRTS) is an open optical transient survey that covers 3/4 of the entire sky in a search of transient astrophysical phenomena occurring on timescales of minutes to years. Observational data is derived from the three telescopes of the Catalina Sky Survey which cover up to 2,500 square degrees of sky each night. CRTS has so far discovered more that 2000 transient sources including 600 supernovae, 500 dwarf novae and more than 100 Blazars and UV Ceti variables. All data is processed within minutes of observation and discoveries are openly distributed using SkyAlert and VOEvent technologies as well as iPhone, html tables, RSS and Twitter feeds. Events are classified utilizing data from virtual observatory enabled archives, machine learning, and collaborative Citizen science....
Disks around young stars with VLTI/MIDI.
(2006) Boekel, Roy van; Lachaume, Regis; Abraham, Peter.; Correia, Serge.; Koter, Alex de; Dominik, Carsten.; Dutrey, Anne.; Henning, Thomas.; Kospal, Agnes.; Leinert, Christoph.; Linz, Hendrik.
Interacting stellar winds: clump formation and accretion onto Sgr A*
(2018) Calderón Espinoza, Diego Nicolás; Schartmann, Marc; Burkert, . Andreas; Cuadra, Jorge
Issues of Temporality - Paradoxes and Challenges of Modern Heritage INTRODUCTION TO THE SESSION
(Wiley, 2008) Torrent, Horacio; VandenHeuvel, D; Mesman, M; Quist, W; Lemmens, B
This article deals with the problem of the imperial intervention of the emperor Constantine in Church matters and proposes a reconsideration of the active measures that he takes to favour the Christian Church. The paper presents a wider scope of the sources: on the one hand it re-examines the Christian ones, but above all, it adds others that, although they are temporally further away from Constantine, give a more complete approach of the role of the Roman emperor as head of the Empire and the specific functions he had to fulfil as pontifex maximus. The first part of the article covers the personal and institutional background of the emperor -that will help to situate him in his particular circumstances- and the second one re-evaluates specific and paradigmatic examples of the problem under consideration.
OHANA and star formation : probing deep into the accretion/ejection mechanism.
(2003) Malbet, Fabien.; Dougados, Catherine.; Lachaume, Regis; Monin, Jean-Louis.; Berger, Jean-Philippe.
Optical/Near-Infrared Light-Curve Properties of Pulsating Variables in the Cepheid Instability Strip
(2014) Calderón Espinoza, Diego Nicolás; Hajdu, Gergely; Dékány, I.; Catelan, Márcio
Making the distinction between Type I and II Cepheids found in the Vista Variables in the Via Lactea (VVV) ESO Public Survey is crucial for the studies of Galactic structure using these variables. As VVV provides only K_{S}-band light curves, this distinction has to be based on near-IR light-curve properties. Because of their reduced amplitudes in the near-IR, however, it is not immediately obvious whether such a distinction can be unambiguously made. To assess this problem, we have compared the VVV and VVV Templates K_{S}-band light-curve properties of 213 Type I and 215 Type II Cepheids using Fourier decomposition. The Fourier parameters of these types were found to be different enough for the purposes of classification. For example, over most of the Cepheid period range, there is an upper limit for the amplitudes of Type I Cepheids. As 50 percent of the Type II variables lie above this limit, half of the variables that could be confused with Type I Cepheids are sorted out by this simple feature alone, suggesting that the automatic classification schemes under development for the VVV Survey will be able to classify such variables with a high degree of accuracy. We have also found that bump Cepheids can be easily identified using VVV data, as the bump feature also appears in the near-IR light curves. Detailed modeling of the light curves of the bump Cepheids found in the VVV data will provide accurate stellar parameters for these stars....
PEERING THROUGH THE DUST: PRECISE ASTROMETRY IN THE GALACTIC MID-PLANE WITH THE VVV SURVEY
(2015) Lucas, PW; Smart, RL; Jones, HRA; Kurtev, R; Beamin Muhlenbrock, Juan Carlos; Borissova, J.; Gromadzki, Grzegorz; Ivanov, Valentin; Minniti, Dante; Pinfield, DJ
Gaia will see little of the Galactic mid-plane and nuclear bulge due to high extinction at optical wavelengths. To study the structure and kinematics of the inner Galaxy we must look to longer wavelengths. The Vista Variables in the Via Lactea (VVV, Minniti et al. 2010) survey currently provides just over 4 years of observations covering approximately 560 square degrees of the Galactic bulge and plane. Typically each source is observed 50-150 times in the Ks band over this period. Using these data we provide relative proper motions for approximately 200 million unique sources down to Ks similar to 16 with uncertainties approaching 1 mas yr(-1). In addition, we fit a solution of the parallactic motion of all sources with significant proper motion and discover a number of new nearby brown dwarfs. These results will allow us to identify faint common proper motion companions to stars with Gaia parallaxes, increasing the number of brown dwarf benchmark objects. Our absolute astrometric calibration precision is currently similar to 2 mas yr(-1), based on PPMXL. The Gaia absolute astrometric reference grid will allow us to precisely anchor our results and measure the streaming motions of stars in the bulge. Finally, we anticipate that the catalogue could provide kinematic distances to the numerous optically invisible high amplitude variable stars that VVV is discovering.
Probing the inner part of protoplanetary disks with the VLTI.
(2000) Malbet, Fabien.; Lachaume, Regis; Monin, Jean-Louis.; Berger, Jean-Philippe.
Stellar variability in the VVV survey
(2013) Contreras Peña, CarlosEduardo
The Vista Variables in the Via Lactea (VVV) ESO Public Survey is an ongoing time-series, near-infrared (IR) survey of the Galactic bulge and an adjacent portion of the inner disk, covering 562 square degrees of the sky, using ESOs VISTA telescope. The survey has provided superb multi-color photometry in 5 broadband filters ($Z$, $Y$, $J$, $H$, and $K_s$), leading to the best map of the inner Milky Way ever obtained, particularly in the near-IR. The main variability part of the survey, which is focused on $K_s$-band observations, is currently underway, with bulge fields having been observed between 31 and 70 times, and disk fields between 17 and 36 times. When the survey is complete, bulge (disk) fields will have been observed up to a total of 100 (60) times, providing unprecedented depth and time coverage. Here we provide a first overview of stellar variability in the VVV data, including examples of the light curves that have been collected thus far, scientific applications, and our efforts towards the automated classification of VVV light curves....
Stellar variability in the VVV survey: overview and first results
(2013) Contreras Peña, CarlosEduardo
The Vista Variables in the Vía Láctea (VVV) ESO Public Survey is an ongoing time-series, near-infrared (IR) survey of the Galactic bulge and an adjacent portion of the inner disk, covering 562 square degrees of the sky, using ESOs VISTA telescope. The survey has provided superb multi-color photometry in 5 broadband filters (Z, Y, J, H, and K<SUB>s</SUB> ), leading to the best map of the inner Milky Way ever obtained, particularly in the near-IR. The main part of the survey, which is focused on the variability in the K<SUB>s</SUB> -band, is currently underway, with bulge fields observed between 34 and 73 times, and disk fields between 34 and 36 times. When the survey is complete, bulge (disk) fields will have been observed up to a total of 100 (60) times, providing unprecedented depth and time coverage in the near-IR. Here we provide a first overview of stellar variability in the VVV data....
Vista variables in the via lactea (VVV): first results and perspectives
(2011) Saito, R. K.; Minniti, D.; Dekany, I.; Hempel, M.; Alonso-Garcia, J.; Toledo, I.; Beamin Muhlenbrock, Juan Carlos; Angeloni, R.; Lucas, P. W.; Emerson, J. P.
VISTA Variables in the Via Lactea (VVV) is a public ESO near-IR variability survey scanning the Milky Way Bulge and an adjacent section of the mid-plane. The survey will take 1929 hours of observations with the 4 m VISTA telescope during five years (2010-2014), covering similar to 10(9) point sources across an area of 520 deg(2). Here we address the first results obtained from the VVV Survey as well as a glimpse into the possibilities for using a deep near-IR atlas in five passbands and a catalogue of more than 10(6) variable point sources. We expect to use the data to find planetary transits of late-type main-sequence stars. We discuss the planet searches and future follow-ups
VVV IR high proper motion stars
(UNIVERSIDAD NACIONAL AUTONOMA MEXICO INSTITUTO ASTRONOMIA, 2015) Kurtev, R.; Gromadzki, M.; Beamin Muhlenbrock, Juan Carlos; Pena, K.; Folkes, S.; Ivanov, V. D.; Borissova, J.; Kuhn, M.; Villanueva, V.; Minniti, D.; Mendez, R.; Lucas, P.; Smith, L.; Pinfield, D.; Antonova, A.; Vieira, K; VanAltena, W; Mendez, RA
We used the VISTA Variables en Via Lactea (VVV) survey to search for large proper motion (PM) objects in the zone of avoidance in the Milky Way bulge and southern Galactic disk. This survey is multi-epoch and already spans a period of more than four years, giving us an excellent opportunity for proper motion and parallax studies. We found around 1700 PM objects with PM>30 mas yr(-1). The majority of them are early and mid M-dwarfs. There are also few later spectral type objects, as well as numerous new K- and G-dwarfs. 75 of the stars have PM>300 mas(-1) and 189 stars have PM>200 mas(-1). There are only 42 previously known stars in the VVV area with proper motion PM>200 mas(-1). We also found three dM+WD binaries and new members of the immediate solar vicinity of 25 pc. We generated a catalog which will be a complementary to the existing catalogs outside this zone.
Water masers in the ALMA era: an excellent tool to study star formation at sub-arcsecond spatial scales
(2023) de Gregorio-Monsalvo, Itziar; Gil Toriello, Santiago; Santamaría Miranda, Alejandro; Gómez, José Francisco; Pérez Sánchez, Andrés Felipe; Plunkett, Adele; Artur de la Villarmois, Elizabeth; Guzmán Veloso, Viviana Gabriela; Schreiber, Matthias R.
The water molecule is one of the most common compounds in the Universe and it exhibits several maser transitions at submillimeter wavelengths, which can be observed at ALMA. Previous studies have primarily focused on water masers at 22 GHz, which are excited in regions of high density and high temperature. These masers are typically very bright, spectrally narrow, and originate from very compact regions. Consequently, they have been invaluable for studying circumstellar structure and dynamics at sub-arcsecond spatial scales. Different water maser transitions can be pumped over a range of astrophysical conditions. The submillimeter transitions at 321 GHz and 325 GHz, in particular, trace respectively warmer and lower density regions than the 22 GHz transition. They have been identified as tracers of mass-loss phenomena in a limited number of star-forming regions. Conversely, transitions such as the one at 183 GHz, which primarily undergo collisional pumping, can provide valuable insights on the physical conditions of the region where powerful molecular outflows interact with the material from the parental cloud. Observations of different water maser lines need to be used to constrain the physical conditions in the masing region and they constitute excellent tools to study common phenomena associated with the star formation process at sub-arcsecond resolution, if observed with interferometers like ALMA. In this poster we present the results of a survey searching for submillimeter water maser transitions at 321 and 325 GHz complemented with ALMA data at 183 GHz on a sample of young stellar objects spanning a wide range of masses, from high to low-mass.
Weather on other worlds: BD variability and the VVV
(Wiley, 2014) Kurtev, R.; Metchev, S.; Heinze, A.; Gromadzki, M.; Ivanov, V. D.; Minniti, D.; Beamin Muhlenbrock, Juan Carlos; Borissova, J.; Mateus, A; GregorioHetem, J; Fernandes, RC
Various evidences point to the presence of clouds in ultra-cool atmospheres. An important ambiguity remains as to whether all variability in ultra-cool dwarfs is caused by patchy clouds, or other fenomena like magnetic activity and auroras. Simultaneous multi-wavelength photometric and/or spectroscopic monitoring could help to reveal this enigma.
Weather on other worlds: BD variability and the VVV
(UNIVERSIDAD NACIONAL AUTONOMA MEXICO INSTITUTO ASTRONOMIA, 2014) Kurtev, R.; Metchev, S.; Heinze, A.; Gromadzki, M.; Ivanov, V. D.; Minniti, D.; Beamin Muhlenbrock, Juan Carlos; Borissova, J.; Mateus, A; GregorioHetem, J; Fernandes, RC
Various evidences point to the presence of clouds in ultra-cool atmospheres. An important ambiguity remains as to whether all variability in ultra-cool dwarfs is caused by patchy clouds, or other fenomena like magnetic activity and auroras. Simultaneous multi-wavelength photometric and/or spectroscopic monitoring could help to reveal this enigma.

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