arXiv subjects

J. Núñez

Publications and source records attributed to J. Núñez.

9 recordsLinked to original sources

arXiv2025

Community need for an Astrobiology Sample Repository and Sample Reference Suite

As we prepare for the next planetary mission charged with finding life beyond Earth, the Astrobiology community must continue to improve its understanding of what constitutes a biosignature, through the use of planetary analog samples. The study of these collected and generated samples is expanding our knowledge of what constitutes habitable environments, what life is capable of, and importantly, how to make biosignature detections within compositionally complex samples - aiding in the development of life detection instrumentation. And yet the full potential of these samples remains untapped. While the Astrobiology community possesses an incredible inventory of planetary analog samples, some incredibly precious, these are scattered across the country in individual freezers with varying degrees of documentation, curation practices, and contamination control. We, as a community, need to change the status quo of how we approach planetary analog research. One of the biggest actions we could take over the next 10 years to change that paradigm would be the creation of a sample repository for Astrobiology relevant materials, providing a centralized, well-curated, wealth of precious samples for the community. Such a collection would create a framework for material and meta-data submission that minimizes burden on the individual PIs, satisfying open data requirements; it would facilitate biosignature research, and aid in the creation of a robust life detection framework; support the development of a standardized sample reference suite for life detection instrumentation; and finally, aid in the development of techniques to be used for future sample return endeavors.

astro-ph.IM↗

arXiv2020

Filiform Lie algebras with low derived length

We construct, for any integer n greater than or equal to 5, a family of complex filiform Lie algebras with derived length at most 3 and dimension n. We also give examples of n-dimensional filiform Lie algebras with derived length greater than 3.

math.RA↗

arXiv2018

TFAW: wavelet-based signal reconstruction to reduce photometric noise in time-domain surveys

There have been many efforts to correct systematic effects in astronomical light curves to improve the detection and characterization of planetary transits and astrophysical variability. Algorithms like the Trend Filtering Algorithm (TFA) use simultaneously-observed stars to remove systematic effects, and binning is used to reduce high-frequency random noise. We present TFAW, a wavelet-based modified version of TFA. TFAW aims to increase the periodic signal detection and to return a detrended and denoised signal without modifying its intrinsic characteristics. We modify TFA's frequency analysis step adding a Stationary Wavelet Transform filter to perform an initial noise and outlier removal and increase the detection of variable signals. A wavelet filter is added to TFA's signal reconstruction to perform an adaptive characterization of the noise- and trend-free signal and the noise contribution at each iteration while preserving astrophysical signals. We carried out tests over simulated sinusoidal and transit-like signals to assess the effectiveness of the method and applied TFAW to real light curves from TFRM. We also studied TFAW's application to simulated multiperiodic signals, improving their characterization. TFAW improves the signal detection rate by increasing the signal detection efficiency (SDE) up to a factor ~2.5x for low SNR light curves. For simulated transits, the transit detection rate improves by a factor ~2-5x in the low-SNR regime compared to TFA. TFAW signal approximation performs up to a factor ~2x better than bin averaging for planetary transits. The standard deviations of simulated and real TFAW light curves are ~40x better than TFA. TFAW yields better MCMC posterior distributions and returns lower uncertainties, less biased transit parameters and narrower (~10x) credibility intervals for simulated transits. We present a newly-discovered variable star from TFRM.

astro-ph.IM↗

arXiv2016

Computation of isotopisms of algebras over finite fields by means of graph invariants

In this paper we define a pair of faithful functors that map isomorphic and isotopic finite-dimensional algebras over finite fields to isomorphic graphs. These functors reduce the cost of computation that is usually required to determine whether two algebras are isomorphic. In order to illustrate their efficiency, we determine explicitly the classification of two- and three-dimensional partial quasigroup rings.

math.RA↗

arXiv2015

Isomorphism and isotopism classes of filiform Lie algebras of dimension up to seven

Since the introduction of the concept of isotopism of algebras by Albert in 1942, a prolific literature on the subject has been developed for distinct types of algebras. Nevertheless, there barely exists any result on the problem of distributing Lie algebras into isotopism classes. The current paper is a first step to deal with such a problem. Specifically, we define a new series of isotopism invariants and we determine explicitly the distribution into isotopism classes of $n$-dimensional filiform Lie algebras, for $n\leq 7$. We also deal with the distribution of such algebras into isomorphism classes, for which we confirm some known results and we prove that there exist $p+8$ isomorphism classes of seven-dimensional filiform Lie algebras over the finite field $\mathbb{F}_p$ if $p\neq 2$.

math.RA↗

arXiv2015

Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

The gamma-ray binary LS I +61 303 is composed of a Be star and a compact companion orbiting in an eccentric orbit. Variable flux modulated with the orbital period of ~26.5 d has been detected from radio to very high-energy gamma rays. In addition, the system presents a superorbital variability of the phase and amplitude of the radio outburst with a period of ~4.6 yr. We present optical photometric observations of LS I +61 303 spanning ~1.5 yr and contemporaneous Halpha equivalent width (EW Halpha) data. The optical photometry shows, for the first time, that the known orbital modulation suffers a positive orbital phase shift and an increase in flux for data obtained 1-yr apart. This behavior is similar to that already known at radio wavelengths, indicating that the optical flux follows the superorbital variability as well. The orbital modulation of the EW Halpha presents the already known superorbital flux variability but shows, also for the first time, a positive orbital phase shift. In addition, the optical photometry exhibits a lag of ~0.1-0.2 in orbital phase with respect to the EW Halpha measurements at similar superorbital phases, and presents a lag of ~0.1 and ~0.3 orbital phases with respect noncontemperaneous radio and X-ray outbursts, respectively. The phase shifts detected in the orbital modulation of thermal indicators, such as the optical flux and the EW Halpha, are in line with the observed behavior for nonthermal indicators, such as X-ray or radio emission. This shows that there is a strong coupling between the thermal and nonthermal emission processes in the gamma-ray binary LS I +61 303. The orbital phase lag between the optical flux and the EW Halpha is naturally explained considering different emitting regions in the circumstellar disk, whereas the secular evolution might be caused by the presence of a moving one-armed spiral density wave in the disk.

astro-ph.HE↗

arXiv2014

Detrending algorithms in large time-series: Application to TFRM-PSES data

Certain instrumental effects and data reduction anomalies introduce systematic errors in photometric time-series. Detrending algorithms such as the Trend Filtering Algorithm (TFA) (Kovács et al. 2004) have played a key role in minimizing the effects caused by these systematics. Here we present the results obtained after applying the TFA, Savitszky-Golay (Savitzky & Golay 1964) detrending algorithms and the Box Least Square phase folding algorithm (Kovács et al. 2002) to the TFRM-PSES data (Fors et al. 2013). Tests performed on this data show that by applying these two filtering methods together, the photometric RMS is on average improved by a factor of 3-4, with better efficiency towards brighter magnitudes, while applying TFA alone yields an improvement of a factor 1-2. As a result of this improvement, we are able to detect and analyze a large number of stars per TFRM-PSES field which present some kind of variability. Also, after porting these algorithms to Python and parallelizing them, we have improved, even for large data samples, the computing performance of the overall detrending+BLS algorithm by a factor of $\sim$10 with respect to Kovács et al. (2004).

astro-ph.IM↗

arXiv2013

Telescope Fabra ROA Montsec: a new robotic wide-field Baker-Nunn facility

A Baker-Nunn Camera (BNC), originally installed at the Real Instituto y Observatorio de la Armada (ROA) in 1958, was refurbished and robotized. The new facility, called Telescope Fabra ROA Montsec (TFRM), was installed at the Observatori Astronòmic del Montsec (OAdM). The process of refurbishment is described in detail. Most of the steps of the refurbishment project were accomplished by purchasing commercial components, which involve little posterior engineering assembling work. The TFRM is a 0.5m aperture f/0.96 optically modified BNC, which offers a unique combination of instrumental specifications: fully robotic and remote operation, wide-field of view (4.4 deg x 4.4 deg), moderate limiting magnitude (V~19.5mag), ability of tracking at arbitrary right ascension and declination rates, as well as opening and closing CCD shutter at will during an exposure. Nearly all kind of image survey programs can benefit from those specifications. Apart from other less time consuming programs, since the beginning of science TFRM operations we have been conducting two specific and distinct surveys: super-Earths transiting around M-type dwarfs stars, and geostationary debris in the context of Space Situational Awareness / Space Surveillance and Tracking (SSA/SST) programs. Preliminary results for both cases will be shown.

astro-ph.IM↗

arXiv2009

The Fabra-ROA Baker-Nunn Camera at Observatori Astronòmic del Montsec: a wide-field imaging facility for exoplanet transit detection

A number of Baker-Nunn Camera (BNC) were manufactured by Smithsonian Institution during the 60s as optical tracking systems for artificial satellites with optimal optical and mechanical specifications. One of them was installed at the Real Instituto y Observatorio de la Armada (ROA). We have conducted a profound refurbishment project of the telescope to be installed at Observatori Astronòmic del Montsec (OAdM). As a result, the BNC offers the largest combination of a huge FOV (4.4$°$x4.4$°$) and aperture (leading to a limiting magnitude of V$\sim$20). These specifications, together with their remote and robotic natures, allows this instrument to face an observational program of exoplanets detection by means of transit technique with high signal-to-noise ratio in the appropiate magnitude range.

astro-ph.EP↗