DSpace Collection:
http://hdl.handle.net/2445/19703
2024-03-29T01:42:05ZFastIC: a fast integrated circuit for the readout of high performance detectors
http://hdl.handle.net/2445/208558
Title: FastIC: a fast integrated circuit for the readout of high performance detectors
Author: Gomez, Sergio; Alozy, J.; Campbell, Michael; Fernandez-Tenllado, José María; Manera Escalero, R.; Mauricio, J.; Pujol, C.; Sanchez, D.; Sanmukh, A.; Sanuy, A.; Ballabriga,R.; Gascón Fora, David
Abstract: This work presents the 8-channel FastIC ASIC developed in CMOS 65 nm technology suitable for the readout of positive and negative polarity sensors in high energy physics experiments, Cherenkov detectors and time-of-flight systems. The front-end can be configured to perform analog summation of up to 4 single-ended channels before discrimination in view of improving time resolution when segmenting a SiPM. The outputs encode the time-of-arrival information and linear energy measurement which captures the peak amplitude of the input signal in the 5 µA–25 mA input peak current range. Power consumption of the ASIC is 12 mW/ch with default settings. Measurements of single photon time resolution with a red-light laser source and a HPK SiPM S13360-3050CS are ≈140 ps FWHM.2024-03-08T18:24:15ZMultiple Use SiPM Integrated Circuit (MUSIC) for Large Area and High Performance Sensors
http://hdl.handle.net/2445/208497
Title: Multiple Use SiPM Integrated Circuit (MUSIC) for Large Area and High Performance Sensors
Author: Gomez, Sergio; Sanchez, David; Mauricio, Joan; Picatoste Olloqui, Eduardo; Sanuy Charles, Andreu; Sanmukh, Anand; Ribó Gomis, Marc; Gascón Fora, David
Abstract: The 8-channel Multiple Use Silicon Photo-multiplier (SiPM) Integrated Circuit (MUSIC) Application specific integrated circuit (ASIC) for SiPM anode readout has been designed for applications where large photo-detection areas are required. MUSIC offers three main features: (1) Sum of the eight input channels using a differential output driver, (2) eight individual single ended (SE) analog outputs, and (3) eight individual SE binary outputs using a time over threshold technique. Each functionality, summation and individual readout includes a selectable dual-gain configuration. Moreover, the signal sum implements a dual-gain output providing a 15-bit dynamic range. The circuit contains a tunable pole zero cancellation of the SiPM recovery time constant to deal with most of the available SiPM devices in the market. Experimental tests show how MUSIC can linearly sum signals from different SiPMs and distinguish even a few photons. Additionally, it provides a single photon output pulse width at half maximum (FWHM) between 5-10 ns for the analog output and a single-photon time resolution (SPTR) around 118 ps sigma using a Hamamatsu SiPM S13360-3075CS for the binary output. Lastly, the summation mode has a power consumption of approximate to 200 mW, whereas the individual readout consumes approximate to 30 mW/ch.2024-03-07T19:16:57ZThe First Naked-eye Superflare Detected from Proxima Centauri
http://hdl.handle.net/2445/208014
Title: The First Naked-eye Superflare Detected from Proxima Centauri
Author: Howard, Ward S.; Howard, Ward; Tilley, Matt A.; Corbett, Hank; Youngblood, Allison; Loyd, R. O. Parke; Ratzloff, Jeffrey K.; Law, Nicholas M.; Fors Aldrich, Octavi; Ser Badia, Daniel del; Shkolnik, Evgenya L.; Ziegler, Carl; Goeke, Erin E.; Pietraallo, Aaron D.; Haislip, Joshua
Abstract: Proxima b is a terrestrial-mass planet in the habitable zone of Proxima Centauri. Proxima Centauri's high stellar activity, however, casts doubt on the habitability of Proxima b: sufficiently bright and frequent flares and any associated proton events may destroy the planet's ozone layer, allowing lethal levels of UV flux to reach its surface. In 2016 March, the Evryscope observed the first naked-eye-brightness superflare detected from Proxima Centauri. Proxima increased in optical flux by a factor of ∼68 during the superflare and released a bolometric energy of 1033.5 erg, ∼10× larger than any previously detected flare from Proxima. Over the last two years the Evryscope has recorded 23 other large Proxima flares ranging in bolometric energy from 1030.6 to 1032.4 erg; coupling those rates with the single superflare detection, we predict that at least five superflares occur each year. Simultaneous high-resolution High Accuracy Radial velocity Planet Searcher (HARPS) spectroscopy during the Evryscope superflare constrains the superflare's UV spectrum and any associated coronal mass ejections. We use these results and the Evryscope flare rates to model the photochemical effects of NOx atmospheric species generated by particle events from this extreme stellar activity, and show that the repeated flaring may be sufficient to reduce the ozone of an Earth-like atmosphere by 90% within five years; complete depletion may occur within several hundred kyr. The UV light produced by the Evryscope superflare would therefore have reached the surface with ∼100× the intensity required to kill simple UV-hardy microorganisms, suggesting that life would have to undergo extreme adaptations to survive in the surface areas of Proxima b exposed to these flares.2024-02-23T18:04:48ZTFAW: Wavelet-based signal reconstruction to reduce photometric noise in time-domain surveys
http://hdl.handle.net/2445/208020
Title: TFAW: Wavelet-based signal reconstruction to reduce photometric noise in time-domain surveys
Author: Ser Badia, Daniel del; Fors Aldrich, Octavi; Núñez de Murga, Jorge, 1955-
Abstract: Context. 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 such as the trend filtering algorithm (TFA) use simultaneously-observed stars to measure and remove systematic effects, and binning is used to reduce high-frequency random noise. Aims: We present TFAW, a wavelet-based modified version of TFA. First, TFAW aims to increase the periodic signal detection and second, to return a detrended and denoised signal without modifying its intrinsic characteristics. Methods: We modified 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-based filter was added to TFA's signal reconstruction to perform an adaptive characterization of the noise- and trend-free signal and the underlying 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. Results: TFAW improves the signal detection rate by increasing the signal detection efficiency (SDE) up to a factor ̃2.5× for low S/R light curves. For simulated transits, the transit detection rate improves by a factor ̃2 - 5× in the low-S/R regime compared to TFA. TFAW signal approximation performs up to a factor ̃2× better than bin averaging for planetary transits. The standard deviations of simulated and real TFAW light curves are ̃40% better compared to TFA. TFAW yields better MCMC posterior distributions and returns lower uncertainties, less biased transit parameters and narrower (by approximately ten times) credibility intervals for simulated transits. TFAW is also able to improve the characterization of multiperiodic signals. We present a newly-discovered variable star from TFRM.2024-02-23T17:55:41ZOptical Photometric Monitoring of LS i +61 303
http://hdl.handle.net/2445/208013
Title: Optical Photometric Monitoring of LS i +61 303
Author: Paredes Fortuny, Xavier; Ribó Gomis, Marc; Fors Aldrich, Octavi; Núñez de Murga, Jorge, 1955-; Bosch i Ramon, Valentí
Abstract: Three gamma-ray binaries, namely PSR B1259 63, HESS J0632+057 and LS I +61 303, contain compact objects orbiting around massive Be stars. Around periastron passage the compact objects should produce significant changes in the structure of the Be disks due to gravitational forces and eventually by ram pressure from the putative pulsar wind. Indeed, variability in the Hα emission line has been detected in all these systems, and optical periodic variability has been detected in one of them. However, there is lack of a systematic monitoring with accurate photometry, which could be used to constrain the shape of the disk during the periastron passage. This information is important to build accurate physical models to explain the broadband spectral energy distribution of these sources. Here we present an ongoing program to monitor the optical photometry of gamma-ray binaries and show preliminary results for the case of LS I +61 303.2024-02-23T17:51:31ZTelescope Fabra ROA Montsec: a new robotic wide-field Baker-Nunn facility
http://hdl.handle.net/2445/207998
Title: Telescope Fabra ROA Montsec: a new robotic wide-field Baker-Nunn facility
Author: Fors Aldrich, Octavi; Núñez de Murga, Jorge, 1955-; Muiños, J.L.; Montojo, F.J.; Baena Gallé, Roberto; Boloix, J.; López-Morcillo, R.; Merino, M.T.; Downey, E.; Mazur, M.J.
Abstract: 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 0.5 m 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 × 4°.4), moderate limiting magnitude (V ∼ 19.5 mag), ability of tracking at arbitrary right ascension (α) and declination (δ) rates, as well as opening and closing CCD shutter at will during an exposure. Nearly all kinds 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.2024-02-23T17:32:28ZEvryFlare. III. Temperature Evolution and Habitability Impacts of Dozens of Superflares Observed Simultaneously by Evryscope and TESS
http://hdl.handle.net/2445/207398
Title: EvryFlare. III. Temperature Evolution and Habitability Impacts of Dozens of Superflares Observed Simultaneously by Evryscope and TESS
Author: Howard, Ward S.; Corbett, Hank; Law, Nicholas M.; Ratzloff, Jeffrey K.; Galliher, Nathan; Glazier, Amy L.; Gonzalez, Ramses; Vasquez Soto, Alan; Fors Aldrich, Octavi; Ser Badia, Daniel del; Haislip, Joshua
Abstract: Superflares may provide the dominant source of biologically relevant UV radiation to rocky habitable-zone M-dwarf planets (M-Earths), altering planetary atmospheres and conditions for surface life. The combined line and continuum flare emission has usually been approximated by a 9000 K blackbody. If superflares are hotter, then the UV emission may be 10 times higher than predicted from the optical. However, it is unknown for how long M-dwarf superflares reach temperatures above 9000 K. Only a handful of M-dwarf superflares have been recorded with multiwavelength high-cadence observations. We double the total number of events in the literature using simultaneous Evryscope and Transiting Exoplanet Survey Satellite observations to provide the first systematic exploration of the temperature evolution of M-dwarf superflares. We also increase the number of superflaring M dwarfs with published time-resolved blackbody evolution by ∼10×. We measure temperatures at 2 minutes cadence for 42 superflares from 27 K5–M5 dwarfs. We find superflare peak temperatures (defined as the mean of temperatures corresponding to flare FWHM) increase with flare energy and impulse. We find the amount of time flares emit at temperatures above 14,000 K depends on energy. We discover that 43% of the flares emit above 14,000 K, 23% emit above 20,000 K and 5% emit above 30,000 K. The largest and hottest flare briefly reached 42,000 K. Some do not reach 14,000 K. During superflares, we estimate M-Earths orbiting <200 Myr stars typically receive a top-of-atmosphere UV-C flux of ∼120 W m−2 and up to 103 W m−2, 100–1000 times the time-averaged X-ray and UV flux from Proxima Cen.2024-02-09T17:49:37ZEvryscope and K2 Constraints on TRAPPIST-1 Superflare Occurrence and Planetary Habitability
http://hdl.handle.net/2445/207397
Title: Evryscope and K2 Constraints on TRAPPIST-1 Superflare Occurrence and Planetary Habitability
Author: Glazier, Amy L.; Howard, Ward S.; Corbett, Hank; Law, Nicholas M.; Ratzloff, Jeffrey K.; Fors Aldrich, Octavi; Ser Badia, Daniel del
Abstract: The nearby ultracool dwarf TRAPPIST-1 possesses several Earth-sized terrestrial planets, three of which have equilibrium temperatures that may support liquid surface water, making it a compelling target for exoplanet characterization. TRAPPIST-1 is an active star with frequent flaring, with implications for the habitability of its planets. Superflares (stellar flares whose energy exceeds 1033 erg) can completely destroy the atmospheres of a cool star's planets, allowing ultraviolet radiation and high-energy particles to bombard their surfaces. However, ultracool dwarfs emit little ultraviolet flux when quiescent, raising the possibility of frequent flares being necessary for prebiotic chemistry that requires ultraviolet light. We combine Evryscope and Kepler observations to characterize the high-energy flare rate of TRAPPIST-1. The Evryscope is an array of 22 small telescopes imaging the entire Southern sky in g' every two minutes. Evryscope observations, spanning 170 nights over 2 yr, complement the 80 day continuous short-cadence K2 observations by sampling TRAPPIST-1's long-term flare activity. We update TRAPPIST-1's superflare rate, finding a cumulative rate of 4.2−0.2+1.9 superflares per year. We calculate the flare rate necessary to deplete ozone in the habitable-zone planets' atmospheres, and find that TRAPPIST-1's flare rate is insufficient to deplete ozone if present on its planets. In addition, we calculate the flare rate needed to provide enough ultraviolet flux to power prebiotic chemistry. We find TRAPPIST-1's flare rate is likely insufficient to catalyze some of the Earthlike chemical pathways thought to lead to ribonucleic acid synthesis, and flux due to flares in the biologically relevant UV-B band is orders of magnitude less for any TRAPPIST-1 planet than has been experienced by Earth at any time in its history.2024-02-09T17:43:31ZEvryFlare. II. Rotation Periods of the Cool Flare Stars in TESS across Half the Southern Sky
http://hdl.handle.net/2445/207422
Title: EvryFlare. II. Rotation Periods of the Cool Flare Stars in TESS across Half the Southern Sky
Author: Haislip, Joshua; Howard, Ward S.; Corbett, Hank; Law, Nicholas M.; Ratzloff, Jeffrey K.; Galliher, Nathan; Glazier, Amy; Fors Aldrich, Octavi; Ser Badia, Daniel del
Abstract: We measure rotation periods and sinusoidal amplitudes in Evryscope light curves for 122 two-minute K5–M4 TESS targets selected for strong flaring. The Evryscope array of telescopes has observed all bright nearby stars in the south, producing 2-minute cadence light curves since 2016. Long-term, high-cadence observations of rotating flare stars probe the complex relationship between stellar rotation, starspots, and superflares. We detect periods from 0.3487 to 104 days and observe amplitudes from 0.008 to 0.216 <em>g</em>' mag. We find that the Evryscope amplitudes are larger than those in TESS with the effect correlated to stellar mass (<em>p</em>-value = 0.01). We compute the Rossby number (<em>Ro</em>) and find that our sample selected for flaring has twice as many intermediate rotators (0.04 < <em>Ro</em> < 0.4) as fast (<em>Ro</em> < 0.04) or slow (<em>Ro</em> > 0.44) rotators; this may be astrophysical or a result of period detection sensitivity. We discover 30 fast, 59 intermediate, and 33 slow rotators. We measure a median starspot coverage of 13% of the stellar hemisphere and constrain the minimum magnetic field strength consistent with our flare energies and spot coverage to be 500 G, with later-type stars exhibiting lower values than earlier-type stars. We observe a possible change in superflare rates at intermediate periods. However, we do not conclusively confirm the increased activity of intermediate rotators seen in previous studies. We split all rotators at <em>Ro</em> ∼ 0.2 into bins of <em>P</em>Rot < 10 days and <em>P</em>Rot > 10 days to confirm that short-period rotators exhibit higher superflare rates, larger flare energies, and higher starspot coverage than do long-period rotators, at <em>p</em>-values of 3.2 × 10−5, 1.0 × 10−5, and 0.01, respectively.2024-02-09T17:35:15ZRobotilter: an automated lens/CCD alignment system for the Evryscope
http://hdl.handle.net/2445/207421
Title: Robotilter: an automated lens/CCD alignment system for the Evryscope
Author: Ratzloff, Jeffrey K.; Law, Nicholas M.; Corbett, Henry T.; Fors Aldrich, Octavi; Ser Badia, Daniel del
Abstract: Camera lenses are increasingly used in wide-field astronomical surveys due to their high performance, wide field-of-view (FOV) unreachable from traditional telescope optics, and modest cost. The machining and assembly tolerances for commercially available optical systems cause a slight misalignment (tilt) between the lens and CCD, resulting in point spread function (PSF) degradation. We have built an automated alignment system (Robotilters) to solve this challenge, optimizing four degrees of freedom¿two tilt axes, a separation axis (the distance between the CCD and lens), and the lens focus (the built-in focus of the lens by turning the lens focusing ring, which moves the optical elements relative to one another) in a compact and low-cost package. The Robotilters remove tilt and optimize focus at the sub-10-μm level, are completely automated, take ≈2 h to run, and remain stable for multiple years once aligned. The Robotilters were built for the Evryscope telescope (a 780-MPix 22-camera array with an 8150-sq. deg FOV and continuous 2-min cadence) designed to detect short-timescale events across extremely large sky areas simultaneously. Variance in quality across the image field, especially the corners and edges compared to the center, is a significant challenge in wide-field astronomical surveys like the Evryscope. The individual star PSFs (which typically extend only a few pixels) are highly susceptible to slight increases in optical aberrations in this situation. The Robotilter solution resulted in a limiting magnitude improvement of 0.5 mag in the center of the image and 1.0 mag in the corners for typical Evryscope cameras, with less distorted and smaller PSFs (half the extent in the corners and edges in many cases). We describe the Robotilter mechanical and software design, camera alignment results, long-term stability, and image improvement. The potential for general use in wide-field astronomical surveys is also explored.2024-02-09T17:27:28Z