RMxAA: Abstracts of Accepted Papers for Volume 54 Number 1


August 31, 2017

2017: August September October



August 2017


OPTICAL DESIGN OF COATLI: A DIFFRACTION-LIMITED VISIBLE IMAGER WITH FAST GUIDING AND ACTIVE OPTICS CORRECTION

J. Fuentes-Fernández1, S. Cuevas1, and A. M. Watson1

1Instituto de Astronomía, UNAM, México.


jfuentes@astro.unam.mx

Received: January 1 2017
Accepted: August 31 2017

Abstract: We present the optical design of COATLI, a wide-field visible imager for a comercial 50 cm robotic telescope. COATLI will be able to correct guiding errors and atmospheric image motion by means of a tip-tilt mirror for fast guiding, and the static aberrations of the telescope using a deformable mirror for active optics, both mirrors located on two optically transferred pupil planes. The instrument will have two channels separated by a dichroic filter at 550 nm. It will deliver diffraction-limited images (approximately 0.3 arcsec FWHM) in the riz bands, inside a 4.2 arcmin field, and seeing limited images (approximately 0.6 arcsec FWHM) in the B and g bands, inside a 5 arcmin field. The optical design is based on two collimator-camera systems plus a pupil transfer relay, using achromatic doublets of CaF2 and S-FTM16 and one triplet of N-BK7 and CaF2. We discuss the efficiency, tolerancing, thermal behavior and ghosts. COATLI will be installed at the Observatorio Astronómico Nacional in Sierra San Pedro Mártir, Baja California, Mexico, in 2018.




September 2017


THE VARIABLE STAR POPULATION IN THE GLOBULAR CLUSTER NGC 6934

M. A. Yepez1, A. Arellano Ferro1, S. Munner2, and Sunetra Giridhar2

1Instituto de Astronomía, Universidad Nacional Autónoma de México, México.

2Indian Institute of Astrophysics, Bangalore, India.


myepez@astro.unam.mx

Received: June 12 2017
Accepted: September 4 2017

Abstract: We report an analysis of new $V$ and $I$ CCD time-series photometry of the globular cluster NGC 6934. Through the Fourier decomposition of the RR Lyrae light curves, the mean values of [Fe/H] and the distance of the cluster were estimated, we found; [Fe/H]$_{UVES}$=-1.48$\pm$0.14 and $d$=16.03$\pm$0.42 kpc, and [Fe/H]$_{UVES}$=-1.43$\pm$0.11 and $d$=15.91$\pm$0.39 kpc, from the calibrations of RRab and RRc stars respectively. Independent distance estimations from SX Phe and SR stars are also discussed. Individual absolute magnitudes, radii and masses are also reported for RR Lyrae stars. We found 12 new variables: 4 RRab, 3 SX Phe, 2 W Virginis (CW) and 3 semi-regular (SR). The inter-mode or "either-or" region in the instability strip is shared by the RRab and RRc stars. This characteristic, observed only in some OoI clusters and never seen in an OoII, is discussed in terms of mass distribution in the ZAHB.



KIC 9451096: MAGNETIC ACTIVITY, FLARES AND DIFFERENTIAL ROTATION

O. Özdarcan1, E. Yoldaş1, and H. A. Dal1

1Ege University, Science Faculty, Department of Astronomy and Space Sciences, 35100 Bornova, Izmir, Turkey.


orkun.ozdarcan@ege.edu.tr

Received: May 17 2017
Accepted: September 5 2017

Abstract: We present spectroscopic and photometric analysis of KIC\,9451096, where the latter is based on very high precision long cadence photometry obtained by $Kepler$ space craft. Combined spectroscopic and photometric modelling shows that the system is a detached eclipsing binary in a circular orbit and composed of F5V + K2V components. Subtracting the best--fitting light curve model from whole long cadence data reveals additional low (mmag) amplitude light variation in time and occasional flares, suggesting low, but still remarkable level of magnetic spot activity on the K2V component. Analyzing rotational modulation of light curve residuals enables us to estimate differential rotation coefficient of the K2V component as $k = 0.069 \pm 0.008$, which is 3 times weaker compared with the solar value of $k = 0.19$, assuming a solar type differential rotation. We find stellar flare activity frequency for K2V component as 0.000368411 $h^{-1}$ indicating low magnetic activity level.



A COMPARISON OF THE RADIO AND OPTICAL TIME-EVOLUTION OF HH 1 AND 2

L. F. Rodríguez1, A. C. Raga2, A. Rodrí́guez-Kamenetzky1,3 and C. Carrasco-González1

1Instituto de Radioastronomía y Astrofísica, UNAM, México.

2Instituto de Ciencias Nucleares, UNAM, México.

2Instituto de Astronomía Teórica y Experimental, (IATE-UNC), Argentina.


l.rodriguez@crya.unam.mx

Received: June 26 2017
Accepted: September 14 2017

Abstract: We present a comparison between the time-evolution over the past $\sim 20$ years of the radio continuum and H$\alpha$ emission of HH~1 and 2. We find that the radio continuum and the H$\alpha$ emission of both objects show very similar trends, with HH~1 becoming fainter and HH~2 brightening quite considerably (about a factor of 2). We also find that the $F_{\rm H\alpha}/F_{ff}$ (H$\alpha$ to free-free continuum) ratio of HH~1 and 2 has higher values than the ones typically found in planetary nebulae (PNe), which we interpret as an indication that the H$\alpha$ and free-free emission of HH~1/2 is produced in emitting regions with lower temperatures ($\sim 2000$~K) than the emission of PNe (with $\sim 10^4$~K).



TESTING THE PLANET-METALLICITY CORRELATION IN M-DWARFS WITH GEMINI GNIRS SPECTRA

M. J. Hobson1, E. Jofré1,2, L. García1, R. Petrucci1,2, and M. Gómez1,2

1Observatorio Astronómico de Córdoba, Argentina.

2CONICET, Argentina.


melissa.hobson@lam.fr

Received: December 15 2016
Accepted: September 18 2017

Abstract: While the planet-metallicity correlation for FGK main-sequence stars hosting giant planets is well established, the results are not so clear for M-dwarf stars, for which precise metallicity measurements are not straightforward. However, new techniques using near infrared spectra show promising results. Using these, we determine stellar parameters and metallicities for a sample of 16 M-dwarf stars, 11 of which host planets, with near-infrared spectra from the Gemini Near-Infrared Spectrograph (GNIRS). We find that M-dwarfs with planets are preferentially metal-rich compared to those without planets. This result, based on GNIRS spectra, is supported by the analysis of a relatively larger sample of M stars with planets (18 in total) and a control sample of 213 M stars without known planets, obtained from the catalogue of Terrien et al. (2015). This, on the one hand, coincides with the trend (not only for M- but also for solar-type stars) reported in the literature and, on the other hand, demonstrates the utility of GNIRS spectra to obtain reliable stellar parameters of M stars. We also find that M dwarfs that harbor giant planets are preferentially more metallic than those associated with low-mass planets (Neptune or super-Earth type). This trend also agrees with that previously reported for solar-type stars. These results would favor the core accretion model for planetary formation.



A STUDY OF THE LONG TERM BEHAVIOR OF THE SX PHE STAR KZ HYA1

J. H. Peña2,3,4, D. S. Piña2,4, A. Rentería2,4, C. Villareal2,4, and J. Calderón2,4

1Based on observations collected at the Tonantzintla and San Pedro Mártir Observatories, México.

2Instituto de Astronomía, Universidad Nacional Autónoma de México, Cd. México, México.

3Observatorio Astronómico Nacional, Tonantzintla, Puebla, México.

4Facultad de Ciencias, Universidad Nacional Autónoma de México, México.


jhpena@astro.unam.mx

Received: May 24 2017
Accepted: September 19 2017

Abstract: From the newly determined times of maximum light of the SX Phe star KZ Hya and others from the literature, as well as from uvby-β photoelectric photometry, we determined the nature of this star and its physical parameters.


October 2017


EMISSION LINE GALAXIES BEHIND THE PLANETARY NEBULA IC 5148: POTENTIAL FOR A SERENDIPITY SURVEY WITH ARCHIVAL DATA

S. Kimeswenger1,2, D. Barria1, W. Kausch2, and D. S. Goldman3

1Instituto de Astronomía, UCN, Antofagasta, Chile.
2Institut f. Astro- und Teilchenphys., Innsbruck, Austria.
3Astrodon Imaging, Roseville, USA.


skimeswenger@ucn.cl

Received: June 5 2017
Accepted: September 10 2017

Abstract: During the start of a survey program using FORS2 long slit spectroscopy on planetary nebulae (PN) and their haloes, we serendipitously discovered six background emission line galaxies (ELG) with redshifts of $z =$ 0.2057, 0.3137, 0.37281, 0.4939, 0.7424 and 0.8668. Thus they clearly do not belong to a common cluster structure. We derived the major physical properties of the targets. Since the used long slit covers a sky area of only 570 arcsec$^2$ ($= 4.3\times10^{-5}$ square degrees), we discuss further potential of serendipitous discoveries in archival data, beside the deep systematic work of the ongoing and upcoming big surveys. We conclude that archival data provide a decent potential for extending the overall data on ELGs without any selection bias.