Abstract
We present the on-orbit performance of the Colorado Ultraviolet Transit Experiment (CUTE). CUTE is a 6U CubeSat that launched on 2021 September 27 and is obtaining near-ultraviolet (NUV; ...2480 Å-3306 Å) transit spectroscopy of short-period exoplanets. The instrument comprises a 20 cm × 8 cm rectangular Cassegrain telescope, an NUV spectrograph with a holographically ruled aberration-correcting diffraction grating, and an NUV-optimized CCD detector. The telescope feeds the spectrograph through an 18′ × 60″ slit. The detector is a passively cooled, back-illuminated NUV-enhanced CCD. The spacecraft bus is a Blue Canyon Technologies XB1, which has demonstrated ≤ 6″ jitter in 56% of CUTE science exposures. Following spacecraft commissioning, an on-orbit calibration program was executed to characterize the CUTE instrument’s on-orbit performance. The results of this calibration indicate that the effective area of CUTE is ≈19.0–27.5 cm
2
and that the average intrinsic resolution element is 2.9 Å across the bandpass. This paper describes the measurement of the science instrument performance parameters as well as the thermal and pointing characteristics of the observatory.
Abstract
Atmospheric escape is a fundamental process that affects the structure, composition, and evolution of many planets. The signatures of escape are detectable on close-in, gaseous exoplanets ...orbiting bright stars, owing to the high levels of extreme-ultraviolet irradiation from their parent stars. The Colorado Ultraviolet Transit Experiment (CUTE) is a CubeSat mission designed to take advantage of the near-ultraviolet stellar brightness distribution to conduct a survey of the extended atmospheres of nearby close-in planets. The CUTE payload is a magnifying near-ultraviolet (2479–3306 Å) spectrograph fed by a rectangular Cassegrain telescope (206 mm × 84 mm); the spectrogram is recorded on a back-illuminated, UV-enhanced CCD. The science payload is integrated into a 6U Blue Canyon Technology XB1 bus. CUTE was launched into a polar, low-Earth orbit on 2021 September 27 and has been conducting this transit spectroscopy survey following an on-orbit commissioning period. This paper presents the mission motivation, development path, and demonstrates the potential for small satellites to conduct this type of science by presenting initial on-orbit science observations. The primary science mission is being conducted in 2022–2023, with a publicly available data archive coming online in 2023.
Abstract
Ultraviolet observations of ultrahot Jupiters, exoplanets with temperatures over 2000 K, provide us with an opportunity to investigate if and how atmospheric escape shapes their upper ...atmosphere. Near-ultraviolet transit spectroscopy offers a unique tool to study this process owing to the presence of strong metal lines and a bright photospheric continuum as the light source against which the absorbing gas is observed. WASP-189b is one of the hottest planets discovered to date, with a dayside temperature of about 3400 K orbiting a bright A-type star. We present the first near-ultraviolet observations of WASP-189b, acquired with the Colorado Ultraviolet Transit Experiment (CUTE). CUTE is a 6U NASA-funded ultraviolet spectroscopy mission, dedicated to monitoring short-period transiting planets. WASP-189b was one of the CUTE early science targets and was observed during three consecutive transits in 2022 March. We present an analysis of the CUTE observations and results demonstrating near-ultraviolet (2500–3300 Å) broadband transit depth (
1.08
−
0.08
+
0.08
%
) of about twice the visual transit depth indicating that the planet has an extended, hot upper atmosphere with a temperature of about 15,000 K and a moderate mass-loss rate of about 4 × 10
8
kg s
−1
. We observe absorption by Mg
ii
lines (
R
p
/
R
s
of
0.212
−
0.061
+
0.038
) beyond the Roche lobe at >4
σ
significance in the transmission spectrum at a resolution of 10 Å, while at lower resolution (100 Å), we observe a quasi-continuous absorption signal consistent with a “forest” of low-ionization metal absorption dominated by Fe
ii
. The results suggest an upper atmospheric temperature (∼15,000 K), higher than that predicted by current state-of-the-art hydrodynamic models.
ABSTRACT New deep optical and near-infrared imaging is combined with archival ultraviolet and infrared data for 15 nearby galaxies mapped in the Spitzer Extended Disk Galaxy Exploration Science ...survey. These images are particularly deep and thus excellent for studying the low surface brightness outskirts of these disk-dominated galaxies with stellar masses ranging between 108 and The spectral energy distributions derived from this data set are modeled to investigate the radial variations in the galaxy colors and star formation histories. Taken as a whole, the sample shows bluer and younger stars for larger radii until reversing near the optical radius, whereafter the trend is for redder and older stars for larger galacto-centric distances. These results are consistent with an inside-out disk formation scenario coupled with an old stellar outer disk population formed through radial migration and/or the cumulative history of minor mergers and accretions of satellite dwarf galaxies. However, these trends are quite modest and the variation from galaxy to galaxy is substantial. Additional data for a larger sample of galaxies are needed to confirm or dismiss these modest sample-wide trends.
Short period exoplanets are excellent laboratories for understanding processes of mass-loss as their short periods subject them to intense instellation that heats and inflates their atmospheres, ...sometimes driving a hydrodynamic outflow of hydrogen gas and entrapped metals. Ultraviolet transmission spectroscopy can trace the escaping gas, with far-ultraviolet (FUV, λ = 912 – 1700 ˚A) light containing H I Lyα and other chromospheric emission lines, and near-ultraviolet (NUV, λ = 1700 – 4000 ˚A) light containing hundreds of metal resonance lines. This thesis explores the utility of UV transmission spectroscopy for characterizing exoplanet atmospheres balanced by data reduction techniques with The Colorado Ultraviolet Transit Experiment (CUT E). CUT E is a small satellite hosting a near-ultraviolet spectrograph designed to observe these short-period exoplanets with transit spectroscopy and search for signatures of atmospheric inflation and escape. CUT E was developed at the Laboratory for Atmospheric and Space Physics and was launched September 27th 2021. I present the optical calibration for the CUT E instrument for both its component-level testing phase in the laboratory and the final in-flight performance, as well as the spacecraft integration and testing procedures. I describe CUT E’s commissioning activities, in-flight calibration, and data reduction considerations in light of the instrument’s in-flight characteristics. I present new CUT E observations of the ultra-hot Jupiter KELT-9b, the hottest exoplanet discovered to date orbiting an A0 star with a period of 1.481 days, resulting in an equilibrium temperature of Teq = 4566 K. A transmission spectrum made of 25 ˚A-wide bins suggests the detection of metals at altitudes above the planet’s Roche lobe, including which contains the Mg II h and k lines (λ = 2802.7, 2795.5 ˚A). Additional work removing the systematics is required before these detections are finalized.
Abstract We present new near-ultraviolet (NUV, λ = 2479–3306 Å) transmission spectroscopy of KELT-9b, the hottest known exoplanet, obtained with the Colorado Ultraviolet Transit Experiment CubeSat. ...Two transits were observed on 2022 September 28th and September 29th, referred to as Visits 1 and 2 respectively. Using a combined transit and systematics model for each visit, the best-fit broadband NUV light curves are R p / R ⋆ = 0.136 − 0.0146 + 0.0125 for Visit 1 and R p / R ⋆ = 0.111 − 0.0190 + 0.0162 for Visit 2, appearing an average of 1.54× larger in the NUV than at optical wavelengths. While the systematics between the two visits vary considerably, the two broadband NUV light curves are consistent with each other. A transmission spectrum with 25 Å bins suggests a general trend of excess absorption in the NUV, consistent with expectations for ultrahot Jupiters. Although we see an extended atmosphere in the NUV, the reduced data lack the sensitivity to probe individual spectral lines.
Ultraviolet observations of Ultra-hot Jupiters (UHJs), exoplanets with temperatures over 2000 K, provide us with an opportunity to investigate if and how atmospheric escape shapes their upper ...atmosphere. Near-ultraviolet transit spectroscopy offers a unique tool to study this process owing to the presence of strong metal lines and a bright photospheric continuum as the light source against which the absorbing gas is observed. WASP-189b is one of the hottest planets discovered to date, with a dayside temperature of about 3400 K orbiting a bright A-type star. We present the first near-ultraviolet observations of WASP-189b, acquired with the Colorado Ultraviolet Transit Experiment (CU T E). CU T E is a 6U NASA-funded ultraviolet spectroscopy mission, dedicated to monitoring short-period transiting planets. WASP-189b was one of the CU T E early science targets and was observed during three consecutive transits in March 2022. We present an analysis of the CU T E observations and results demonstrating near-ultraviolet (2500-3300 Å) broadband transit depth (1.08 +0.08 −0.08 %) of about twice the visual transit depth indicating that the planet has an extended, hot upper atmosphere with a temperature of about 15000 K and a moderate mass loss rate of about 4 × 10 8 kg s −1. We observe absorption by Mgii lines (R p /R s of 0.212 +0.038 −0.061) beyond the Roche lobe at >4σ significance in the transmission spectrum at a resolution of 10 Å, while at lower resolution (100 Å), we observe a quasicontinuous absorption signal consistent with a "forest" of low-ionization metal absorption dominated by Feii. The results suggest an upper atmospheric temperature (∼ 15000 K), higher than that predicted by current state-of-the-art hydrodynamic models.
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