307 research outputs found
The Simons Observatory: Magnetic Shielding Measurements for the Universal Multiplexing Module
The Simons Observatory (SO) includes four telescopes that will measure the
temperature and polarization of the cosmic microwave background using over
60,000 highly sensitive transition-edge bolometers (TES). These multichroic TES
bolometers are read out by a microwave RF SQUID multiplexing system with a
multiplexing factor of 910. Given that both TESes and SQUIDs are susceptible to
magnetic field pickup and that it is hard to predict how they will respond to
such fields, it is important to characterize the magnetic response of these
systems empirically. This information can then be used to limit spurious
signals by informing magnetic shielding designs for the detectors and readout.
This paper focuses on measurements of magnetic pickup with different magnetic
shielding configurations for the SO universal multiplexing module (UMM), which
contains the SQUIDs, associated resonators, and TES bias circuit. The magnetic
pickup of a prototype UMM was tested under three shielding configurations: no
shielding (copper packaging), aluminum packaging for the UMM, and a
tin/lead-plated shield surrounding the entire dilution refrigerator 100 mK cold
stage. The measurements show that the aluminum packaging outperforms the copper
packaging by a shielding factor of 8-10, and adding the tin/lead-plated 1K
shield further increases the relative shielding factor in the aluminum
configuration by 1-2 orders of magnitude.Comment: 7 pages, 4 figure, conference proceedings submitted to the Journal of
Low Temperature Physic
TESS Asteroseismology of Mensae: Benchmark Ages for a G7 Dwarf and its M-dwarf Companion
Asteroseismology of bright stars has become increasingly important as a
method to determine fundamental properties (in particular ages) of stars. The
Kepler Space Telescope initiated a revolution by detecting oscillations in more
than 500 main-sequence and subgiant stars. However, most Kepler stars are
faint, and therefore have limited constraints from independent methods such as
long-baseline interferometry. Here, we present the discovery of solar-like
oscillations in Men A, a naked-eye (V=5.1) G7 dwarf in TESS's Southern
Continuous Viewing Zone. Using a combination of astrometry, spectroscopy, and
asteroseismology, we precisely characterize the solar analog alpha Men A (Teff
= 5569 +/- 62 K, R = 0.960 +/- 0.016 Rsun, M = 0.964 +/- 0.045 Msun). To
characterize the fully convective M dwarf companion, we derive empirical
relations to estimate mass, radius, and temperature given the absolute Gaia
magnitude and metallicity, yielding M = 0.169 +/- 0.006, R = 0.19 +/- 0.01 and
Teff = 3054 +/- 44 K. Our asteroseismic age of 6.2 +/- 1.4 (stat) +/- 0.6 (sys)
Gyr for the primary places Men B within a small population of M dwarfs
with precisely measured ages. We combined multiple ground-based spectroscopy
surveys to reveal an activity cycle of 13.1 +/- 1.1 years, a period similar to
that observed in the Sun. We used different gyrochronology models with the
asteroseismic age to estimate a rotation period of ~30 days for the primary.
Alpha Men A is now the closest (d=10pc) solar analog with a precise
asteroseismic age from space-based photometry, making it a prime target for
next-generation direct imaging missions searching for true Earth analogs.Comment: Accepted to The Astrophysical Journal; 15 pages, 10 figure
The Simons Observatory microwave SQUID multiplexing detector module design
Advances in cosmic microwave background (CMB) science depend on increasing
the number of sensitive detectors observing the sky. New instruments deploy
large arrays of superconducting transition-edge sensor (TES) bolometers tiled
densely into ever larger focal planes. High multiplexing factors reduce the
thermal loading on the cryogenic receivers and simplify their design. We
present the design of focal-plane modules with an order of magnitude higher
multiplexing factor than has previously been achieved with TES bolometers. We
focus on the novel cold readout component, which employs microwave SQUID
multiplexing (mux). Simons Observatory will use 49 modules containing
60,000 bolometers to make exquisitely sensitive measurements of the CMB. We
validate the focal-plane module design, presenting measurements of the readout
component with and without a prototype detector array of 1728
polarization-sensitive bolometers coupled to feedhorns. The readout component
achieves a yield and a 910 multiplexing factor. The median white noise
of each readout channel is 65 . This impacts the
projected SO mapping speed by , which is less than is assumed in the
sensitivity projections. The results validate the full functionality of the
module. We discuss the measured performance in the context of SO science
requirements, which are exceeded.Comment: Accepted to The Astrophysical Journa
Affectus Hispaniae en la historiografía del Alto Imperio
This paper analyses texts written by Greek and Latin High Empire historians dealing with Hispania. Some of the authors have a very positive view (Florus, Iustinus, Appian) while others are clearly negative (Veleius Paterculus, Valerius Maximus) though most of them show little interest, indifference or variety of opinions. When there is interest in the region or praise, it is because the author comes from Hispania or he is trying to please an emperor born in Hispania, but it could also be due to a universal conception of history revealing a critical attitude towards Roman imperialism, as in Appian. The praise found in Iustinus’s epitome should be attributed to the author of the epitome rather than to Pompeius Trogus. This can be taken as evidence for situating Iustinus’s life and work in the 2nd century A.D. Loathing of Hispania seems to have its origins in conservative, ‘optimate’ nationalist circles, who perceive the province as the ‘popular’ region that acclaimed and welcomed ‘seditious’ individuals such as Tiberius Gracchus and Sertorius.Se estudian en este trabajo los textos de historiadores del Alto Imperio, latinos y griegos, que tratan sobre Hispania. En algunos autores encontramos una visión muy positiva (Floro, Justino, Apiano) y en otros claramente negativa (Veleyo Patérculo, Valerio Máximo), aunque en la mayoría de los casos hay escasa atención, indiferencia o diversidad de opiniones. El interés por la región y los elogios pueden estar motivados por el origen hispánico del autor o su voluntad de agradar a algún emperador oriundo de Hispania, pero también por una concepción universal de la historia que denota en ocasiones una posición crítica con el imperialismo romano, como es el caso de Apiano. La alabanza que hallamos en el epítome de Justino creemos que debe atribuirse más al epitomador que a Pompeyo Trogo, lo que apoyaría una datación temprana de la vida y la obra de Justino (s. II d.C.). La aversión hacia Hispania parece haber surgido en medios conservadores, “optimates” nacionalistas, que ven la provincia como el territorio “popular”, que encumbró y acogió a “sediciosos” como Tiberio Graco y Sertorio
The TESS-Keck Survey II: An Ultra-Short Period Rocky Planet and its Siblings Transiting the Galactic Thick-Disk Star TOI-561
We report the discovery of TOI-561, a multi-planet system in the galactic
thick disk that contains a rocky, ultra-short period planet (USP). This bright
() star hosts three small transiting planets identified in photometry
from the NASA TESS mission: TOI-561 b (TOI-561.02, P=0.44 days, ), c (TOI-561.01, P=10.8 days,
), and d (TOI-561.03, P=16.3 days,
). The star is chemically ([Fe/H],
[/H]) and kinematically consistent with the galactic
thick disk population, making TOI-561 one of the oldest (Gyr) and
most metal-poor planetary systems discovered yet. We dynamically confirm
planets b and c with radial velocities from the W. M. Keck Observatory High
Resolution Echelle Spectrometer. Planet b has a mass and density of
and gcm, consistent with
a rocky composition. Its lower-than-average density is consistent with an
iron-poor composition, although an Earth-like iron-to-silicates ratio is not
ruled out. Planet c is and gcm,
consistent with an interior rocky core overlaid with a low-mass volatile
envelope. Several attributes of the photometry for planet d (which we did not
detect dynamically) complicate the analysis, but we vet the planet with
high-contrast imaging, ground-based photometric follow-up and radial
velocities. TOI-561 b is the first rocky world around a galactic thick-disk
star confirmed with radial velocities and one of the best rocky planets for
thermal emission studies.Comment: Accepted at The Astronomical Journal; 25 pages, 10 figure
The Simons Observatory Large Aperture Telescope Receiver
The Simons Observatory (SO) Large Aperture Telescope Receiver (LATR) will be
coupled to the Large Aperture Telescope located at an elevation of 5,200 m on
Cerro Toco in Chile. The resulting instrument will produce arcminute-resolution
millimeter-wave maps of half the sky with unprecedented precision. The LATR is
the largest cryogenic millimeter-wave camera built to date with a diameter of
2.4 m and a length of 2.6 m. It cools 1200 kg of material to 4 K and 200 kg to
100 mk, the operating temperature of the bolometric detectors with bands
centered around 27, 39, 93, 145, 225, and 280 GHz. Ultimately, the LATR will
accommodate 13 40 cm diameter optics tubes, each with three detector wafers and
a total of 62,000 detectors. The LATR design must simultaneously maintain the
optical alignment of the system, control stray light, provide cryogenic
isolation, limit thermal gradients, and minimize the time to cool the system
from room temperature to 100 mK. The interplay between these competing factors
poses unique challenges. We discuss the trade studies involved with the design,
the final optimization, the construction, and ultimate performance of the
system
The TESS-Keck Survey. XI. Mass Measurements for Four Transiting sub-Neptunes orbiting K dwarf TOI-1246
Multi-planet systems are valuable arenas for investigating exoplanet architectures and comparing planetary siblings. TOI-1246 is one such system, with a moderately bright K dwarf (V=11.6, K=9.9) and four transiting sub-Neptunes identified by TESS with orbital periods of 4.31 d, 5.90 d, 18.66 d, and 37.92 d. We collected 130 radial velocity observations with Keck/HIRES and TNG/HARPS-N to measure planet masses. We refit the 14 sectors of TESS photometry to refine planet radii (2.97±0.06 R⊕,2.47±0.08 R⊕,3.46±0.09 R⊕, 3.72±0.16 R⊕), and confirm the four planets. We find that TOI-1246 e is substantially more massive than the three inner planets (8.1±1.1M⊕, 8.8±1.2M⊕, 5.3±1.7M⊕, 14.8±2.3M⊕). The two outer planets, TOI-1246 d and TOI-1246 e, lie near to the 2:1 resonance (Pe/Pd=2.03) and exhibit transit timing variations. TOI-1246 is one of the brightest four-planet systems, making it amenable for continued observations. It is one of only six systems with measured masses and radii for all four transiting planets. The planet densities range from 0.70±0.24 to 3.21±0.44g/cm3, implying a range of bulk and atmospheric compositions. We also report a fifth planet candidate found in the RV data with a minimum mass of 25.6 ± 3.6 M⊕. This planet candidate is exterior to TOI-1246 e with a candidate period of 93.8 d, and we discuss the implications if it is confirmed to be planetary in nature
The TESS-Keck Survey. XI. Mass Measurements for Four Transiting Sub-Neptunes Orbiting K Dwarf TOI-1246
Multiplanet systems are valuable arenas for investigating exoplanet architectures and comparing planetary siblings. TOI-1246 is one such system, with a moderately bright K dwarf (V = 11.6, K = 9.9) and four transiting sub-Neptunes identified by TESS with orbital periods of 4.31, 5.90, 18.66, and 37.92 days. We collected 130 radial velocity observations with Keck/HIRES and TNG/HARPS-N to measure planet masses. We refit the 14 sectors of TESS photometry to refine planet radii (2.97 +/- 0.06 R (circle plus), 2.47 +/- 0.08 R (circle plus), 3.46 +/- 0.09 R (circle plus), and 3.72 +/- 0.16 R (circle plus)) and confirm the four planets. We find that TOI-1246 e is substantially more massive than the three inner planets (8.1 +/- 1.1 M (circle plus), 8.8 +/- 1.2 M (circle plus), 5.3 +/- 1.7 M (circle plus), and 14.8 +/- 2.3 M (circle plus)). The two outer planets, TOI-1246 d and TOI-1246 e, lie near to the 2:1 resonance (P (e)/P ( d ) = 2.03) and exhibit transit-timing variations. TOI-1246 is one of the brightest four-planet systems, making it amenable for continued observations. It is one of only five systems with measured masses and radii for all four transiting planets. The planet densities range from 0.70 +/- 0.24 to 3.21 +/- 0.44 g cm(-3), implying a range of bulk and atmospheric compositions. We also report a fifth planet candidate found in the RV data with a minimum mass of 25.6 +/- 3.6 M (circle plus). This planet candidate is exterior to TOI-1246 e, with a candidate period of 93.8 days, and we discuss the implications if it is confirmed to be planetary in nature
The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and its Implications for Structure Growth
We present new measurements of cosmic microwave background (CMB) lensing over
sq. deg. of the sky. These lensing measurements are derived from the
Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) CMB dataset, which
consists of five seasons of ACT CMB temperature and polarization observations.
We determine the amplitude of the CMB lensing power spectrum at
precision ( significance) using a novel pipeline that minimizes
sensitivity to foregrounds and to noise properties. To ensure our results are
robust, we analyze an extensive set of null tests, consistency tests, and
systematic error estimates and employ a blinded analysis framework. The
baseline spectrum is well fit by a lensing amplitude of
relative to the Planck 2018 CMB power spectra
best-fit CDM model and relative to
the best-fit model. From our lensing power
spectrum measurement, we derive constraints on the parameter combination
of
from ACT DR6 CMB lensing alone and
when combining ACT DR6 and Planck NPIPE
CMB lensing power spectra. These results are in excellent agreement with
CDM model constraints from Planck or
CMB power spectrum measurements. Our lensing measurements from redshifts
-- are thus fully consistent with CDM structure growth
predictions based on CMB anisotropies probing primarily . We find no
evidence for a suppression of the amplitude of cosmic structure at low
redshiftsComment: 45+21 pages, 50 figures. Prepared for submission to ApJ. Also see
companion papers Madhavacheril et al and MacCrann et a
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