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L. Hirsch

Publications and source records attributed to L. Hirsch.

8 recordsLinked to original sources
arXiv2025

PoWER: a new concept for DUNE Phase 2 FD PDS

We propose a novel concept for the future modules of the DUNE Phase 2 Far Detector Photodetection System, namely the Polymer Wavelength shifter and Enhanced Reflection - PoWER. In this concept, the field cage of the LArTPC is entirely covered with polymeric wavelength shifting foils (PolyEthylene Naphthalate - PEN) to convert the liquid argon scintillation light from VUV to visible, and an Enhanced Specular Reflector (ESR) is installed on the membrane aiming to increase the number of reflections and consequently the detection probability. In addition, we use Light Detection Units (LDUs), which are a combination of standard and VUV-sensitive SiPM that can be used as an active veto for events occurring outside the field cage. We present a preliminary study using a Monte Carlo simulation, including a Light Map for photons generated inside the field cage and a demonstration of the active veto.

physics.ins-det↗
arXiv2024

TOI-2266 b: a keystone super-Earth at the edge of the M dwarf radius valley

We validate the Transiting Exoplanet Survey Satellite (TESS) object of interest TOI-2266.01 (TIC 348911) as a small transiting planet (most likely a super-Earth) orbiting a faint M5 dwarf ($V=16.54$) on a 2.33~d orbit. The validation is based on an approach where multicolour transit light curves are used to robustly estimate the upper limit of the transiting object's radius. Our analysis uses SPOC-pipeline TESS light curves from Sectors 24, 25, 51, and 52, simultaneous multicolour transit photometry observed with MuSCAT2, MuSCAT3, and HiPERCAM, and additional transit photometry observed with the LCOGT telescopes. TOI-2266 b is found to be a planet with a radius of $1.54\pm\0.09\,R_\oplus$, which locates it at the edge of the transition zone between rocky planets, water-rich planets, and sub-Neptunes (the so-called M~dwarf radius valley). The planet is amenable to ground-based radial velocity mass measurement with red-sensitive spectrographs installed in large telescopes, such as MAROON-X and Keck Planet Finder (KPF), which makes it a valuable addition to a relatively small population of planets that can be used to probe the physics of the transition zone. Further, the planet's orbital period of 2.33 days places it inside a `keystone planet' wedge in the period-radius plane where competing planet formation scenarios make conflicting predictions on how the radius valley depends on the orbital period. This makes the planet also a welcome addition to the small population of planets that can be used to test small-planet formation scenarios around M~dwarfs.

astro-ph.EP↗
arXiv2021

On the robustness of model-based algorithms for photoacoustic tomography: comparison between time and frequency domains

For photoacoustic image reconstruction, certain parameters such as sensor positions and speed of sound have a major impact in the reconstruction process and must be carefully determined before data acquisition. Uncertainties in these parameters can lead to errors produced by a modeling mismatch, hindering the reconstruction process and severely affecting the resulting image quality. Therefore, in this work we study how modeling errors arising from uncertainty in sensor locations affect the images obtained by matrix model-based reconstruction algorithms based on time domain and frequency domain models of the photoacoustic problem. The effects on the reconstruction performance with respect to the uncertainty in the knowledge of the sensors location is compared and analyzed both in a qualitative and quantitative fashion for both time and frequency models. Ultimately, our study shows that the frequency domain approach is more sensitive to this kind of modeling errors. These conclusions are supported by numerical experiments and a theoretical sensitivity analysis of the mathematical operator for the direct problem.

eess.SP↗
arXiv2020

HAT-P-58b -- HAT-P-64b: Seven Planets Transiting Bright Stars

We report the discovery and characterization of 7 transiting exoplanets from the HATNet survey. The planets, which are hot Jupiters and Saturns transiting bright sun-like stars, include: HAT-P-58b (with mass Mp = 0.37 MJ, radius Rp = 1.33 RJ, and orbital period P = 4.0138 days), HAT-P-59b (Mp = 1.54 MJ, Rp = 1.12 RJ, P = 4.1420 days), HAT-P-60b (Mp = 0.57 MJ, Rp = 1.63 RJ, P = 4.7948 days), HAT-P-61b (Mp = 1.06 MJ, Rp = 0.90 RJ, P = 1.9023 days), HAT-P-62b (Mp = 0.76 MJ, Rp = 1.07 RJ, P = 2.6453 days), HAT-P-63b (Mp = 0.61 MJ, Rp = 1.12 RJ, P = 3.3777 days), and HAT-P-64b (Mp = 0.58 MJ, Rp = 1.70 RJ, P = 4.0072 days). The typical errors on these quantities are 0.06 MJ, 0.03 RJ, and 0.2seconds, respectively. We also provide accurate stellar parameters for each of the hosts stars. With V = 9.710+/-0.050mag, HAT-P-60 is an especially bright transiting planet host, and an excellent target for additional follow-up observations. With Rp = 1.703+/-0.070 RJ, HAT-P-64b is a highly inflated hot Jupiter around a star nearing the end of its main-sequence lifetime, and is among the largest known planets. Five of the seven systems have long-cadence observations by TESS which are included in the analysis. Of particular note is HAT-P-59 (TOI-1826.01) which is within the Northern continuous viewing zone of the TESS mission, and HAT-P-60, which is the TESS candidate TOI-1580.01.

astro-ph.EP↗
arXiv2018

EPIC229426032 b and EPIC246067459 b: discovery and characterization of two new transiting hot Jupiters from K2

We report the discovery of two hot Jupiters orbiting the stars EPIC229426032 and EPIC246067459. We used photometric data from Campaign 11 and 12 of the Kepler K2 Mission and radial velocity data obtained using the HARPS, FEROS, and CORALIE spectrographs. EPIC229426032 b and EPIC246067459 b have masses of $1.60^{+0.11}_{-0.11}$ and $0.86^{+0.13}_{-0.12}\,M_{\mathrm{Jup}}$, radii of $1.65^{+0.07}_{-0.08}$ and $1.30^{+0.15}_{-0.14}\,R{_\mathrm{Jup}}$, and are orbiting their host stars in 2.18 and 3.20-day orbits, respectively. The large radius of EPIC229426032 b leads us to conclude that this candidate corresponds to a highly inflated hot Jupiter. EPIC2460674559 b has a radius consistent with theoretical models, considering the high incident flux falling on the planet. We consider EPIC229426032 b to be a excellent system for follow-up studies, since not only is it very inflated, but it also orbits a relatively bright star ($V = 11.6$).

astro-ph.EP↗
arXiv2017

HAT-P-67b: An Extremely Low Density Saturn Transiting an F-Subgiant Confirmed via Doppler Tomography

We report the discovery of HAT-P-67b, a hot-Saturn transiting a rapidly rotating F-subgiant. HAT-P-67b has a radius of Rp = 2.085 -0.071/+0.096 RJ,, orbiting a M* = 1.642 -0.072/+0.155 Msun, R* = 2.546 -0.084/+0.099 Rsun host star in a ~4.81-day period orbit. We place an upper limit on the mass of the planet via radial velocity measurements to be Mp < 0.59 MJ, and lower limit of > 0.056 MJ by limitations on Roche lobe overflow. Despite being a subgiant, the host star still exhibits relatively rapid rotation, with a projected rotational velocity of v sin I* = 35.8 +/- 1.1 km/s, making it difficult to precisely determine the mass of the planet using radial velocities. We validated HAT-P-67b via two Doppler tomographic detections of the planetary transit, which eliminated potential eclipsing binary blend scenarios. The Doppler tomographic observations also confirmed that HAT-P-67b has an orbit that is aligned to within 12 degrees, in projection, with the spin of its host star. HAT-P-67b receives strong UV irradiation, and is amongst the one of the lowest density planets known, making it a good candidate for future UV transit observations to search for an extended hydrogen exosphere.

astro-ph.EP↗
arXiv2010

Epitaxial integration of the intrinsic ferromagnetic semiconductor GdN with silicon technology

A major challenge for the next generation of spintronics devices is the implementation of ferromagnetic-semiconductor thin films as spin injectors and detectors. Spin-polarised carrier injection cannot be accomplished efficiently from metals, and coupled with the rarity of intrinsic ferromagnetic semiconductors this has driven intensive study of diluted magnetic semiconductors. Chief among these is the doped III-V compound (Ga,Mn)As. These materials suffer from a number of drawbacks; they (i) require magnetic-ion doping well above the solubility limit, and (ii) must be hole doped to above the degenerate limit, preventing independent control of the carrier concentration and charge sign. Here we demonstrate the first epitaxial growth of a recently-characterised intrinsic ferromagnetic semiconductor, GdN, on silicon substrates, providing an essential step on the way to integrate new spintronics functionalities into Si-based technology. The films have been characterised as regards their growth toward fully relaxed GdN, the density and mobility of their carriers, and their magnetic behaviour.

cond-mat.mtrl-sci↗