Search results for "Techniques: photometric"
showing 10 items of 14 documents
Long-term optical and X-ray variability of the Be/X-ray binary H 1145-619: Discovery of an ongoing retrograde density wave
2017
Multiwavelength monitoring of Be/X-ray binaries is crucial to understand the mechanisms producing their outbursts. H 1145-619 is one of these systems, which has recently displayed X-ray activity. We investigate the correlation between the optical emission and the X-ray activity to predict the occurrence of new X-ray outbursts from the inferred state of the circumstellar disc. We have performed a multiwavelength study of H 1145-619 from 1973 to 2017 and present here a global analysis of its variability over the last 40 years. We have used optical spectra from the SAAO, SMARTS and SALT telescopes and optical photometry from INTEGRAL/OMC and ASAS. We also used X-ray observations from INTEGRAL/…
Euclid preparation. XII. Optimizing the photometric sample of the Euclid survey for galaxy clustering and galaxy-galaxy lensing analyses
2021
Pocino, A., et al. (Euclid Collaboration)
Photospheric response to an ellerman bomb-like event—an analogy of Sunrise/IMaX observations and MHD simulations
2017
S. Danilovic et. al.
ELDAR, a new method to identify AGN in multi-filter surveys: the ALHAMBRA test case
2017
We present ELDAR, a new method that exploits the potential of medium- and narrow-band filter surveys to securely identify active galactic nuclei (AGN) and determine their redshifts. Our methodology improves on traditional approaches by looking for AGN emission lines expected to be identified against the continuum, thanks to the width of the filters. To assess its performance, we apply ELDAR to the data of the ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift Astronomical) survey, which covered an effective area of 2.38 deg2 with 20 contiguous medium-band optical filters down to F814W ≃ 24.5. Using two different configurations of ELDAR in which we require the detection of at lea…
A Precise Photometric Ratio via Laser Excitation of the Sodium Layer II: Two-photon Excitation Using Lasers Detuned from 589.16 nm and 819.71 nm Reso…
2020
This article is the second in a pair of articles on the topic of the generation of a two-color artificial star (which we term a "laser photometric ratio star," or LPRS) of de-excitation light from neutral sodium atoms in the mesosphere, for use in precision telescopic measurements in astronomy and atmospheric physics, and more specifically for the calibration of measurements of dark energy using type Ia supernovae. The two techniques respectively described in both this and the previous article would each generate an LPRS with a precisely 1:1 ratio of yellow (589/590 nm) photons to near-infrared (819/820 nm) photons produced in the mesosphere. Both techniques would provide novel mechanisms f…
Correcting the effect of stellar spots on ARIEL transmission spectra – II. The limb-darkening effect
2021
This paper is part of an effort to correct the transmission spectra of a transiting planet orbiting an active star. In Paper I (Cracchiolo et al. 2020) we have demonstrated a methodology to minimize the potential bias induced by unocculted star spots on the transmission spectrum, assuming a spot model parameterized by filling factor and temperature. In this work we introduce the limb darkening effect, therefore the position of the spot in the stellar disk and the impact parameter of the transiting planet now play a key role. The method is tested on simulations of planetary transits of three representative kinds of planetary systems, at ARIEL resolution. We find that a realistic treatment of…
Flux and color variations of the quadruply imaged quasar HE 0435-1223
2011
aims: We present VRi photometric observations of the quadruply imaged quasar HE 0435-1223, carried out with the Danish 1.54m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time. methods: We monitored the object during two seasons (2008 and 2009) in the VRi spectral bands, and reduced the data with two independent techniques: difference imaging and PSF (Point Spread Function) fitting.results: Between these two seasons, our results show an evident decrease in flux by ~0.2-0.4 magnitudes of the four lensed components in the three filters. We also found a significant increase (~0.05-0.015) in their V-R …
A precise photometric ratio via laser excitation of the sodium layer - I. One-photon excitation using 342.78 nm light
2020
The largest uncertainty on measurements of dark energy using type Ia supernovae is presently due to systematics from photometry; specifically to the relative uncertainty on photometry as a function of wavelength in the optical spectrum. We show that a precise constraint on relative photometry between the visible and near-infrared can be achieved in upcoming surveys (such as in LSST at the Vera C. Rubin Observatory) via a mountaintop-located laser source tuned to the 342.78 nm vacuum excitation wavelength of neutral sodium atoms. Using a high-power (500 W) laser modified from laser guide star studies, this excitation will produce an artificial star (which we term a "laser photometric ratio s…
A New Look at Spitzer Primary Transit Observations of the Exoplanet HD 189733b
2014
Blind source separation techniques are used to reanalyse two exoplanetary transit lightcurves of the exoplanet HD189733b recorded with the IR camera IRAC on board the Spitzer Space Telescope at 3.6$\mu$m during the "cold" era. These observations, together with observations at other IR wavelengths, are crucial to characterise the atmosphere of the planet HD189733b. Previous analyses of the same datasets reported discrepant results, hence the necessity of the reanalyses. The method we used here is based on the Independent Component Analysis (ICA) statistical technique, which ensures a high degree of objectivity. The use of ICA to detrend single photometric observations in a self-consistent wa…
The large trans-Neptunian object 2002 TC 302 from combined stellar occultation, photometry, and astrometry data
2020
All authors: Ortiz, J. L.; Santos-Sanz, P.; Sicardy, B.; Benedetti-Rossi, G.; Duffard, R.; Morales, N.; Braga-Ribas, F.; Fernández-Valenzuela, E.; Nascimbeni, V.; Nardiello, D.; Carbognani, A.; Buzzi, L.; Aletti, A.; Bacci, P.; Maestripieri, M.; Mazzei, L.; Mikuz, H.; Skvarc, J.; Ciabattari, F.; Lavalade, F. Scarfi, G.; Mari, J. M.; Conjat, M.; Sposetti, S.; Bachini, M.; Succi, G.; Mancini, F.; Alighieri, M.; Dal Canto, E.; Masucci, M.; Vara-Lubiano, M.; Gutiérrez, P. J.; Desmars, J.; Lecacheux, J.; Vieira-Martins, R.; Camargo, J. I. B.; Assafin, M.; Colas, F.; Beisker, W.; Behrend, R.; Mueller, T. G.; Meza, E.; Gomes-Junior, A. R.; Roques, F.; Vachier, F.; Mottola, S.; Hellmich, S.; Campo …