Browsing by Author "Baella, Nobar"
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Item Open Access Astrometric observations near the maximun approach of the Potencially Hazardous Asteroid (66391) 1999 KW4(The Astronomer's Telegram, 2019-08-08) Ricra, J.; Zegarra-Valles, M.; Baella, Nobar; Villanueva, R.Our team decided to collaborate with the campaign to observe the maximum approach of the PHA (66391) 1999 KW4, organized by the International Asteroid Warning Network (IAWN). The observations were made from CIEASEST, in the Universidad Nacional San Luis Gonzaga de Ica, Peru (Long. 75 44 12.5 W, Lat. 14 05 21.1 S, Alt. 401 m). A 60 cm Nishimura telescope (f10) and a ZWO ASI 071MC camera were used. The night of the maximum approach (May 25, 2019) we had cloudy skies; however, the night of May 26-27 we had clear skies and we were able to take 147 images with a exposure time of 4 seconds. Dimension 4 software was used to synchronize our time with special purpose Internet Time Servers, ensuring less than one second accuracy. The astrometric measurements were made with the Astrometrica software, using between 15 and 25 stars in the field identified by means of the Gaia DR2 catalog.Item Open Access Astrometric observations of the Potentially Hazardous Asteroid (52768) 1998 OR2 near its maximum approach to earth(The Astronomer's Telegram, 2020-05-13) Villanueva, R.; Ricra, J.; Zegarra-Valles, M.; Baella, Nobar; Santivanez, J.Our team presents astrometric measurements of the PHA (52768) 1998 OR2 obtained close to its maximum approach to Earth. The observations were made from Observatorio Planetario Moche, located in Trujillo, Peru (Long. 79 00 39.2 W, Lat. 08 06 47.9 S, Alt. 48 m), on April 23, 24, 25 and 29, 2020. It is important to note that April 29's measurements were obtained approximately 5 hours before the asteroid's closest approach to Earth. A Celestron NexStar 11 GPS telescope and a ZWO ASI 071MC camera (without filter) were used. In addition, Dimension 4 software was employed to synchronize our time with special purpose Internet Time Servers. A total of 240 images were obtained, of which 19 were selected for presenting better ellipticity and FWHM values. The astrometric measurements were made with the Astrometrica software, using between 13 and 31 field stars identified by means of the Gaia DR1 catalog.Item Open Access Guía del tránsito del planeta Mercurio(Instituto Geofísico del Perú, 2019-11) Baella, Nobar; Quispe, Adita; Ricra, José; Martínez, OrlandoGuía que explica el evento astronómico denominado el "Tránsito de Mercurio" el cual fue observado desde Perú el 11 de noviembre de 2019.Item Open Access High-resolution optical spectroscopic observations of four symbiotic stars: AS 255, MWC 960, RW Hya, and StHα 32(IOP Publishing, 2017-05-23) Pereira, C. B.; Baella, Nobar; Drake, N. A.; Miranda, L. F.; Roig, F.We report on the analysis of high-resolution optical spectra of four symbiotic stars: AS 255, MWC 960, RW Hya, and StHα32. We employ the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG to analyze the spectra. The abundance of barium and carbon was derived using the spectral synthesis technique. The chemical composition of the atmospheres of AS 255 and MWC 960 show that they are metal-poor K giants with metallicities of −1.2 and −1.7 respectively. StHα32 is a CH star and also a lowmetallicity object (−1.4). AS 255 and MWC 960 are yellow symbiotic stars and, like other previously studied yellow symbiotics, are s-process enriched. StHα32, like other CH stars, is also an s-process and carbon-enriched object. RW Hya has a metallicity of −0.64, a value in accordance with previous determinations, and is not s-process enriched. Based on its position in the 2MASS diagram, we suggest that RW Hya is at an intermediate position between yellow symbiotics and classical S-type symbiotics. We also discuss whether the dilution effect was the mechanism responsible for the absence of the s-process elements overabundance in RW Hya. The luminosity obtained for StHα32 is below the luminosity of the asymptotic giant branch (AGB) stars that started helium burning (via thermal pulses) and became self-enriched in neutron-capture elements. Therefore, its abundance peculiarities are due to mass transfer from the previous thermally pulsing AGB star (now the white dwarf) that was overabundant in s-process elements. For the stars AS 255 and MWC 960, the determination of their luminosities was not possible due to uncertainties in their distance and interstellar absorption. AS 255 and MWC 960 have a low galactic latitude and could be bulge stars or members of the inner halo population. The heavy-element abundance distribution of AS 255 and MWC 960 is similar to that of the other yellow symbiotics previously analyzed. Their abundance patterns follow that of the thick disk population for RW Hya and of the halo population for AS 255, MWC 960, and StHα32. We also determined the rotational velocities of these four symbiotic stars and compare our results with those of single field stars.Item Open Access Searching for new yellow symbiotic stars: Positive identification of StHα63(American Astronomical Society, 2016-02-05) Baella, Nobar; Pereira, C. B.; Miranda, L. F.; Alvarez-Candal, A.Yellow symbiotic stars are useful targets to probe whether mass transfer has happened in these binary systems. However, the number of known yellow symbiotic stars is very scarce. We report spectroscopic observations of five candidate yellow symbiotic stars selected by their position in the 2MASS (J-H) vs. (H-Ks) diagram and included in some emission-line catalogs. Among the five candidates, only StHa63 is identified as a new yellow symbiotic star because of its spectrum and its position in the [TiO]1-[TiO]2 diagram that indicates a K4-K6 spectral type. In addition, the derived electron density (10E8.4 cm-3) and several emission line intensity ratios provide further support for that classification. The other four candidates are rejected as symbiotic stars because three of them actually do not show emission lines and the fourth one shows only Balmer emission lines. We also found that the WISE W3-W4 index clearly separates normal K-giants from yellow symbiotic stars and, therefore, can be used as an additional tool to select candidate yellow symbiotic stars.