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Search Results: 1 - 10 of 485770 matches for " A. Carrami?ana "
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A Multiwavelength Cross-Correlation Variability Study of Fermi-LAT Blazars
V. Pati?o-álvarez,A. Carramiana,L. Carrasco,V. Chavushyan
Physics , 2013,
Abstract: We carried out a multiwavelength cross-correlation analysis of a sample of 16 blazars detected by Fermi/LAT. The purpose is to investigate if there exists correlations between the distinct bands we analyze in this work. We searched for cross-correlated delays between emissions in optical, near-infrared and {\gamma}-ray bands for 16 blazars detected by Fermi-LAT, using three methods previously discussed in the literature: the interpolated cross-correlation function, the discrete cross-correlation function and the Z-transformed discrete cross-correlation function. Our results confirm the expectation that in all our sample the four NIR bands vary simultaneously. For three objects of our sample (3C 273, Mrk 501, and PMN J0808-0751), no correlation is found between any of the bands available for this study. For the remaining thirteen, a correlation was found between the V band and the NIR bands, indicating that in most of them the V band and the NIR bands vary simultaneously. For 4 objects (3C 454.3, PKS 0235+164, PKS 1510-089, and PKS 2155-304) a delayed correlation between the {\gamma}-ray emission and the NIR+V bands was found.
An estimate of the temporal fraction of cloud cover at San Pedro Mártir Observatory
E. Carrasco,A. Carramiana,L. J. Sánchez,R. Avila,I. Cruz-González
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.20140.x
Abstract: San Pedro M\'artir in the Northwest of Mexico is the site of the Observatorio Astron\'omico Nacional. It was one of the five candidates sites for the Thirty Meter Telescope, whose site-testing team spent four years measuring the atmospheric properties on site with a very complete array of instrumentation. Using the public database created by this team, we apply a novel method to solar radiation data to estimate the daytime fraction of time when the sky is clear of clouds. We analyse the diurnal, seasonal and annual cycles of cloud cover. We find that 82.4 per cent of the time the sky is clear of clouds. Our results are consistent with those obtained by other authors, using different methods, adding support to this value and proving the potential of the applied method. The clear conditions at the site are particularly good showing that San Pedro M\'artir is an excellent site for optical and infrared observations.
Forjarse mariposa... o la construcción de lo travesti
Claudia Espinoza Carramiana
Ultima Década , 1999,
Abstract:
Searching for Very High Energy Emission from Pulsars Using the High Altitude Water Cherenkov (HAWC) Observatory
C. Alvarez Ochoa,P. M. Saz Parkinson,A. Belfiore,A. Carramiana,C. Rivière,E. Moreno Barbosa,for the HAWC collaboration
Physics , 2015,
Abstract: There are currently over 160 known gamma-ray pulsars. While most of them are detected only from space, at least two are now seen also from the ground. MAGIC and VERITAS have measured the gamma ray pulsed emission of the Crab pulsar up to hundreds of GeV and more recently MAGIC has reported emission at $\sim2$ TeV. Furthermore, in the Southern Hemisphere, H.E.S.S. has detected the Vela pulsar above 30 GeV. In addition, non-pulsed TeV emission coincident with pulsars has been detected by many groups, including the Milagro Collaboration. These GeV-TeV observations open the possibility of searching for very-high-energy (VHE, > 100GeV) pulsations from gamma-rays pulsars in the HAWC field of view.
Weather at Sierra Negra: 7.3-year statistics and a new method to estimate the temporal fraction of cloud cover
E. Carrasco,A. Carramiana,R. Avila,C. Gutiérrez,J. L. Avilés,J. Reyes,J. Meza,O. Yam
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.15163.x
Abstract: Sierra Negra, one of the highest peaks in central Mexico, is the site of the Large Millimeter Telescope. We describe the first results of a comprehensive analysis of the weather data measured in situ from October 2000 to February 2008 to be used as a reference for future activity in the site. We compare the data from two different stations at the summit considering the accuracy of both instruments. We analysed the diurnal, seasonal and annual cycles for all the parameters. The thermal stability is remarkably good, crucial for a good performance of the telescopes. From the solar radiation data we developed a new method to estimate the fraction of time when the sky is clear of clouds. We show that our measurements are consistent with a warm standard atmosphere model. The conditions at the site are benign and stable given its altitude, showing that Sierra Negra is a extremely good site for millimeter and high energy observations.
Optical Spectrophotometric Monitoring of Fermi/LAT Bright Sources
V. Pati?o-álvarez,V. Chavushyan,J. León-Tavares,J. R. Valdés,A. Carramiana,L. Carrasco,J. Torrealba
Physics , 2013,
Abstract: We describe an ongoing optical spectrophotometric monitoring program of a sample of Fermi/LAT bright sources showing prominent and variable {\gamma}-ray emission, with the 2.1m telescope at Observatorio Astrof\'isico Guillermo Haro (OAGH) located in Cananea, Sonora, M\'exico. Our sample contains 11 flat spectrum radio quasars (FSRQ) and 1 Narrow Line Seyfert 1 (NLSy1) galaxy. Our spectroscopic campaign will allow us to study the spectroscopic properties (FWHM, EW, flux) of broad-emission lines in the optical (e.g. H{\beta}) and mid-UV (e.g. Mg II {\lambda}2800) regimes, depending on the redshift of the source. The cadence of the broad emission lines monitoring is about five nights per month which in turn will permit us to explore whether there is a correlated variability between broad emission line features and high levels of {\gamma}-ray emission.
Astroclimate at San Pedro Mártir I: 2004-2008 Seeing Statistics from the TMT Site Testing Data
L. J. Sánchez,I. Cruz-González,J. Echevarría,A. Ruelas-Mayorga,A. M. García,R. Avila,E. Carrasco,A. Carramiana,A. Nigoche-Netro
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.21527.x
Abstract: We present comprehensive seeing statistics for the San Pedro M\'artir site derived from the Thirty Meter Telescope site selection data. The observations were obtained between 2004 and 2008 with a Differential Image Motion Monitor (DIMM) and a Multi Aperture Scintillation Sensor (MASS) combined instrument (MASS--DIMM). The parameters that are statistically analised here are: whole atmosphere seeing -measured by the DIMM-; free atmosphere seeing --measured by the MASS--; and ground-layer seeing (GL) --difference between the total and free-atmosphere seeing--. We made a careful data coverage study along with statistical distributions of simultaneous MASS--DIMM seeing measurements, in order to investigate the nightly, monthly, seasonal, annual and global behaviour, as well as possible hourly seeing trends. Although this campaign covers five years, the sampling is uneven, being 2006 and 2007 the best sampled years in terms of seasonal coverage. The overall results yield a median seeing of 0.78 (DIMM), 0.37 (MASS) and 0.59 arcsec (GL). The strongest contribution to the whole atmosphere seeing comes, therefore, from a strong ground layer. We find that the best season is summer, while the worst one is winter, in accordance with previous studies. It is worth noting that the best yearly results are correlated with the best sampled years. The hourly analysis shows that there is no statistically significant tendency of seeing degradation towards dawn. The seeing values are slightly larger than those reported before. This may be caused by climate changes.
Flare-like variability of the Mg IIλ2800? emission line in the gamma-ray blazar 3C 454.3
J. León-Tavares,V. Chavushyan,V. Pati?o-álvarez,E. Valtaoja,T. G. Arshakian,L. C. Popovic\altaffilmark,M. Tornikoski,A. Lobanov,A. Carramiana,L. Carrasco,A. L?hteenm?ki,.
Physics , 2013, DOI: 10.1088/2041-8205/763/2/L36
Abstract: We report the detection of a statistically significant flare-like event in the Mg II\lambda 2800\AA\ emission line of 3C 454.3 during the outburst of autumn 2010. The highest levels of emission line flux recorded over the monitoring period (2008 - 2011) coincide with a superluminal jet component traversing through the radio core. This finding crucially links the broad-emission line fluctuations to the non-thermal continuum emission produced by relativistically moving material in the jet and hence to the presence of broad-line region clouds surrounding the radio core. If the radio core were located at several parsecs from the central black hole then our results would suggest the presence of broad-line region material outside the inner parsec where the canonical broad-line region is envisaged to be located. We briefly discuss the implications of broad-emission line material ionized by non-thermal continuum on the context of virial black hole mass estimates and gamma-ray production mechanisms.
The host-galaxy of the gamma-ray Narrow-line Seyfert 1 galaxy 1H~0323+342
J. León-Tavares,J. Kotilainen,V. Chavushyan,C. A?orve,I. Puerari,I. Cruz-González,V. Pati?o-álvarez,S. Antón,A. Carramiana,L. Carrasco,J. Guichard,K. Karhunen,A. Olguín-Iglesias,J. Sanghvi,J. R. Valdes
Physics , 2014, DOI: 10.1088/0004-637X/795/1/58
Abstract: We present optical and near infrared (NIR) imaging data of the radio-loud Narrow-line Seyfert 1 galaxy 1H 0323+342, which shows intense and variable gamma-ray activity discovered by the Fermi satellite with the Large Area Telescope. NIR and optical images are used to investigate the structural properties of the host galaxy of 1H 0323+342; this together with optical spectroscopy allowed us to examine its black hole mass. Based on the 2D multiwavelength surface brightness modeling, we find that, statistically, the best model fit is a combination of a nuclear component and a S\'ersic profile (n~2.8). However, the presence of a disc component (with a small bulge n~1.2) remains also a possibility and cannot be ruled out with the present data. Although at first glance a spiral-arm like structure is revealed in our images, a 2D Fourier analysis of the imagery suggests that such structure corresponds to an asymmetric ring, likely associated to a recent violent dynamical interaction. We discuss our results on the context of relativistic jets production and galaxy evolution.
Brote por Salmonella enteritidis en una residencia de ancianos
Yá?ez Ortega,Jose Luis; Carramiana Martínez,Isabel; Bayona Ponte,Mercedes;
Revista Espa?ola de Salud Pública , 2001, DOI: 10.1590/S1135-57272001000100010
Abstract: background: an outbreak of gastroenteritis caused by salmonella enteritidis (se), phagotype 1, reported at a senior citizen living facility in burgos on november 15, 1999 is discussed. the objective of the research of this outbreak was that of ascertaining the source of infection, the mechanism by which it was transmitted and to propose the suitable measures for preventing any recurrence of this problem. methods: an observational retrospective cohort study has been made by surveying 106 of a total of 119 residents and 9 employees at the center in question. the relative risk of being affected by this disorder has been estimated in terms of the intake of different foods. logic regression was employed for calculating the odds ratio adjusted by age, sex and by the intake of foods and wine. the concordance of the clinical diagnosis with the coproculture diagnosis was studied using the cohen's kappa index of agreement. results: a total of 42 individuals reported symptoms (37 residents and 5 employees). the clinical attack rate was 36.5%. forty-five (45) of the 91 coprocultures performed (82 on residents and 9 on employees) were positive (41 in residents and 4 in employees). the attack rate for cases confirmed by coproculture was 49.5% among those investigated. fried breaded milk and flour batter sweets was the food product implicated epidemiologically with the onset of the outbreak: rr 3.25 (c.i at 95% 1.10-9.59). the protective effect of the wine (odds ratio: 0.68) was not high enough to be statistically significant (p=0.36). the kappa index was 0.43 (p<0.001), which reveals very little agreement between the clinical diagnosis and the coproculture diagnosis. conclusions: epidemiological evidence exists of the intake of fired breaded milk and flour batter sweets having been the mechanism for the transmission of the infection, and the food product in question having been stored at room temperature having been the determining contributing factor in the start of the outbreak
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