Searcharxiv⌕ Search

arXiv subjects

Jarron Leisenring

Publications and source records attributed to Jarron Leisenring.

At least 55 records · Page 3Linked to original sources

JWST NIRCam Defocused Imaging: Photometric Stability Performance and How it Can Sense Mirror Tilts

We use JWST NIRCam short wavelength photometry to capture a transit lightcurve of the exoplanet HAT-P-14 b to assess performance as part of instrument commissioning. The short wavelength precision is 152 ppm per 27 second integration as measured over the full time series compared to a theoretical limit of 107 ppm, after corrections to spatially correlated 1/f noise. Persistence effects from charge trapping are well fit by an exponential function with short characteristic timescales, settling on the order of 5-15 minutes. The short wavelength defocused photometry is also uniquely well suited to measure the realtime wavefront error of JWST. Analysis of the images and reconstructed wavefront maps indicate that two different hexagonal primary mirror segments exhibited "tilt events" where they changed orientation rapidly in less than ~1.4 seconds. In some cases, the magnitude and timing of the flux jumps caused by tilt events can be accurately predicted with a telescope model. These tilt events can be sensed by simultaneous longer-wavelength NIRCam grism spectral images alone in the form of changes to the point spread function, diagnosed from the FWHM. They can also be sensed with the FGS instrument from difference images. Tilt events possibly from sudden releases of stress in the backplane structure behind the mirrors were expected during the commissioning period because they were found in ground-based testing. Tilt events have shown signs of decreasing in frequency but have not disappeared completely. The detectors exhibit some minor (less than 1%) deviations from linear behavior in the first few groups of each integration, potentially impacting absolute fluxes and transit depths on bright targets where only a handful of groups are possible. Overall, the noise is within 50% of the theoretical photon noise and read noise. This bodes well for high precision time series measurements.

astro-ph.IM↗

The JWST Early Release Science Program for the Direct Imaging & Spectroscopy of Exoplanetary Systems

The direct characterization of exoplanetary systems with high contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5$μ$m, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximise the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55-hour Early Release Science Program that will utilize all four JWST instruments to extend the characterisation of planetary mass companions to $\sim$15$μ$m as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative datasets that will enable a broad user base to effectively plan for general observing programs in future cycles.

astro-ph.EP↗

Performance of near-infrared high-contrast imaging methods with JWST from commissioning

The James Webb Space Telescope (JWST) will revolutionize the field of high-contrast imaging and enable both the direct detection of Saturn-mass planets and the characterization of substellar companions in the mid-infrared. While JWST will feature unprecedented sensitivity, angular resolution will be the key factor when competing with ground-based telescopes. Here, we aim to characterize the performance of several extreme angular resolution imaging techniques available with JWST in the 3-5 micron regime based on data taken during commissioning. Firstly, we introduce custom tools to simulate, reduce, and analyze NIRCam and MIRI coronagraphy data and use these tools to extract companion detection limits from on-sky NIRCam round and bar mask coronagraphy observations. Secondly, we present on-sky NIRISS aperture masking interferometry (AMI) and kernel phase imaging (KPI) observations from which we extract companion detection limits using the publicly available fouriever tool. Scaled to a total integration time of one hour and a target of the brightness of AB Dor, we find that NIRISS AMI and KPI reach contrasts of $\sim$7-8 mag at $\sim$70 mas and $\sim$9 mag at $\sim$200 mas. Beyond $\sim$250 mas, NIRCam coronagraphy reaches deeper contrasts of $\sim$13 mag at $\sim$500 mas and $\sim$15 mag at $\sim$2 arcsec. While the bar mask performs $\sim$1 mag better than the round mask at small angular separations $\lesssim$0.75 arcsec, it is the other way around at large angular separations $\gtrsim$1.5 arcsec. Moreover, the round mask gives access to the full 360 deg field-of-view which is beneficial for the search of new companions. We conclude that already during the instrument commissioning, JWST high-contrast imaging in the L- and M-bands performs close to its predicted limits.

astro-ph.EP↗

JWST/NIRCam Coronagraphy: Commissioning and First On-Sky Results

In a cold and stable space environment, the James Webb Space Telescope (JWST or "Webb") reaches unprecedented sensitivities at wavelengths beyond 2 microns, serving most fields of astrophysics. It also extends the parameter space of high-contrast imaging in the near and mid-infrared. Launched in late 2021, JWST underwent a six month commissioning period. In this contribution we focus on the NIRCam Coronagraphy mode which was declared "science ready" on July 10 2022, the last of the 17 JWST observing modes. Essentially, this mode will allow to detect fainter/redder/colder (less massive for a given age) self-luminous exoplanets as well as other faint astrophysical signal in the vicinity of any bright object (stars or galaxies). Here we describe some of the steps and hurdles the commissioning team went through to achieve excellent performances. Specifically, we focus on the Coronagraphic Suppression Verification activity. We were able to produce firm detections at 3.35$μ$m of the white dwarf companion HD 114174 B which is at a separation of $\simeq$ 0.5" and a contrast of $\simeq$ 10 magnitudes ($10^{4}$ fainter than the K$\sim$5.3 mag host star). We compare these first on-sky images with our latest, most informed and realistic end-to-end simulations through the same pipeline. Additionally we provide information on how we succeeded with the target acquisition with all five NIRCam focal plane masks and their four corresponding wedged Lyot stops.

astro-ph.IM↗

First Peek with JWST/NIRCam Wide-Field Slitless Spectroscopy: Serendipitous Discovery of a Strong [O III]/H$α$ Emitter at $z=6.11$

We report the serendipitous discovery of an [O III] $λλ$4959/5007 and H$α$ line emitter in the Epoch of Reionization (EoR) with the JWST commissioning data taken in the NIRCam wide field slitless spectroscopy (WFSS) mode. Located $\sim$55" away from the flux calibrator P330-E, this galaxy exhibits bright [O III] $λλ$4959/5007 and H$α$ lines detected at 3.7, 9.9 and 5.7$σ$, respectively, with a spectroscopic redshift of $z=6.112\pm0.001$. The total H$β$+[O III] equivalent width is 664$\pm$98 Å (454$\pm$78 Å from the [O III] $λ$5007 line). This provides direct spectroscopic evidence for the presence of strong rest-frame optical lines (H$β$+[O III] and H$α$) in EoR galaxies as inferred previously from the analyses of Spitzer/IRAC spectral energy distributions. Two spatial and velocity components are identified in this source, possibly indicating that this system is undergoing a major merger, which might have triggered the ongoing starburst with strong nebular emission lines over a timescale of $\sim$2 Myr as our SED modeling suggests. The tentative detection of He II $λ$4686 line ($1.9σ$), if real, may indicate the existence of very young and metal-poor star-forming regions with a hard UV radiation field. Finally, this discovery demonstrates the power and readiness of the JWST/NIRCam WFSS mode, and marks the beginning of a new era for extragalactic astronomy, in which EoR galaxies can be routinely discovered via blind slitless spectroscopy through the detection of rest-frame optical emission lines.

astro-ph.GA↗

L-band nulling interferometry at the VLTI with Asgard/Hi-5: status and plans

Hi-5 is the L'-band (3.5-4.0 $μ$m) high-contrast imager of Asgard, an instrument suite in preparation for the visitor focus of the VLTI. The system is optimized for high-contrast and high-sensitivity imaging within the diffraction limit of a single UT/AT telescope. It is designed as a double-Bracewell nulling instrument producing spectrally-dispersed (R=20, 400, or 2000) complementary nulling outputs and simultaneous photometric outputs for self-calibration purposes. In this paper, we present an update of the project with a particular focus on the overall architecture, opto-mechanical design of the warm and cold optics, injection system, and development of the photonic beam combiner. The key science projects are to survey (i) nearby young planetary systems near the snow line, where most giant planets are expected to be formed, and (ii) nearby main sequence stars near the habitable zone where exozodiacal dust that may hinder the detection of Earth-like planets. We present an update of the expected instrumental performance based on full end-to-end simulations using the new GRAVITY+ specifications of the VLTI and the latest planet formation models.

astro-ph.IM↗

LBT search for companions and sub-structures in the (pre)transitional disk of AB Aurigae

Multi-wavelengths high-resolution imaging of protoplanetary disks has revealed the presence of multiple, varied substructures in their dust and gas components which might be signposts of young, forming planetary systems. AB Aurigae bears an emblematic (pre)transitional disk showing spiral structures observed in the inner cavity of the disk in both the sub-millimeter (ALMA; 1.3mm, $^{12}$CO) and near-infrared (SPHERE; 1.5-2.5$μ$m) wavelengths which have been claimed to arise from dynamical interactions with a massive companion. In this work, we present new deep $K_s$ (2.16$μ$m) and L' (3.7$μ$m) band images of AB Aurigae obtained with LMIRCam on the Large Binocular Telescope, aimed for the detection of both planetary companions and extended disk structures. No point source is recovered, in particular at the outer regions of the disk, where a putative candidate ($ρ= 0.681", PA = 7.6^{\circ}$) had been previously claimed. The nature of a second innermost planet candidate ($ρ= 0.16'', PA = 203.9^{\circ}$) can not be investigated by the new data. We are able to derive 5$σ$ detection limits in both magnitude and mass for the system, going from 14 \Mjup at 0.3'' (49 au) down to 3-4 \Mjup at 0.6'' (98 au) and beyond, based on the ATMO 2020 evolutionary models. We detect the inner spiral structures (< 0.5'') resolved in both CO and polarimetric H-band observations. We also recover the ring structure of the system at larger separation (0.5-0.7") showing a clear south-east/north-west asymmetry. This structure, observed for the first time at L'-band, remains interior to the dust cavity seen at ALMA, suggesting an efficient dust trapping mechanism at play in the disk.

astro-ph.EP↗

High contrast imaging with Fizeau interferometry: The case of Altair

The Large Binocular Telescope (LBT) has two 8.4-m primary mirrors that produce beams that can be combined coherently in a "Fizeau" interferometric mode. In principle, the Fizeau PSF enables the probing of structure at a resolution up to three times better than that of the adaptive-optics-corrected PSF of a single 8.4-m telescope. In this work, we examined the nearby star Altair (5.13 pc, type A7V, $\sim$100s Myr to $\approx$1.4 Gyr) in the Fizeau mode with the LBT at Br-$α$ (4.05 $μ$m) and carried out angular differential imaging to search for companions. This work presents the first filled-aperture LBT Fizeau science dataset to benefit from a correcting mirror which provides active phase control. In the analysis of the $λ/D$ angular regime, the sensitivity of the dataset is down to $\approx$0.5 $M_{\odot}$ at 1" for a 1.0 Gyr system. This sensitivity remains limited by the small amount of integration time, which is in turn limited by the instability of the Fizeau PSF. However, in the Fizeau fringe regime we attain sensitivities of $Δm \approx 5$ at 0.2" and put constraints to companions of 1.3 $M_{\odot}$ down to an inner angle of $\approx$0.15", closer than any previously published direct imaging of Altair. This analysis is a pathfinder for future datasets of this type, and represents some of the first steps to unlocking the potential of the first ELT. Fizeau observations will be able to reach dimmer targets with upgrades to the instrument, in particular the phase detector.

astro-ph.IM↗

Resolving Io's Volcanoes from a Mutual Event Observation at the Large Binocular Telescope

Unraveling the geological processes ongoing at Io's numerous sites of active volcanism requires high spatial resolution to, for example, measure the areal coverage of lava flows or identify the presence of multiple emitting regions within a single volcanic center. In de Kleer et al. (2017) we described observations with the Large Binocular Telescope (LBT) during an occultation of Io by Europa at ~6:17 UT on 2015 March 08, and presented a map of the temperature distribution within Loki Patera derived from these data. Here we present emission maps of three other volcanic centers derived from the same observation: Pillan Patera, Kurdalagon Patera, and the vicinity of Ulgen Patera/PV59/N Lerna Regio. The emission is localized by the light curves and resolved into multiple distinct emitting regions in two of the cases. Both Pillan and Kurdalagon Paterae had undergone eruptions in the months prior to our observations, and the location and intensity of the emission is interpreted in the context of the temporal evolution of these eruptions observed from other facilities. The emission from Kurdalagon Patera is resolved into two distinct emitting regions separated by only a few degrees in latitude that were unresolved by Keck observations from the same month.

astro-ph.EP↗

Imaging low-mass planets within the habitable zones of nearby stars with ground-based mid-infrared imaging

Giant exoplanets on 10-100 au orbits have been directly imaged around young stars. The peak of the thermal emission from these warm young planets is in the near-infrared (~1-5 microns), whereas mature, temperate exoplanets (i.e., those within their stars' habitable zones) radiate primarily in the mid-infrared (mid-IR: ~10 microns). If the background noise in the mid-IR can be mitigated, then exoplanets with low masses--including rocky exoplanets--can potentially be imaged in very deep exposures. Here, we review the recent results of the Breakthrough Watch/New Earths in the Alpha Centauri Region (NEAR) program on the Very Large Telescope (VLT) in Chile. NEAR pioneered a ground-based mid-IR observing approach designed to push the capabilities for exoplanet imaging with a specific focus on the closest stellar system, Alpha Centauri. NEAR combined several new optical technologies--including a mid-IR optimized coronagraph, adaptive optics system, and rapid chopping strategy to mitigate noise from the central star and thermal background within the habitable zone. We focus on the lessons of the VLT/NEAR campaign to improve future instrumentation--specifically on strategies to improve noise mitigation through chopping. We also present the design and commissioning of the Large Binocular Telescope's Exploratory Survey for Super-Earths Orbiting Nearby Stars (LESSONS), an experiment in the Northern hemisphere that is building on what was learned from NEAR to further push the sensitivity of mid-IR imaging. Finally, we briefly discuss some of the possibilities that mid-IR imaging will enable for exoplanet science.

astro-ph.IM↗

JWST Noise Floor II: Systematic Error Sources in JWST NIRCam Time Series

JWST holds great promise in characterizing atmospheres of transiting exoplanets, potentially providing insights into Earth-sized planets within the habitable zones of M dwarf host stars if photon-limited performance can be achieved. Here, we discuss the systematic error sources that are expected to be present in grism time series observations with the NIRCam instrument. We find that pointing jitter and high gain antenna moves on top of the detectors' subpixel crosshatch patterns will produce relatively small variations (less than 6 parts per million, ppm). The time-dependent aperture losses due to thermal instabilities in the optics can also be kept to below 2 ppm. To achieve these low noise sources, it is important to employ a sufficiently large (more than 1.1 arcseconds) extraction aperture. Persistence due to charge trapping will have a minor (less than 3 ppm) effect on time series 20 minutes into an exposure and is expected to play a much smaller role than it does for the HST WFC3 detectors. We expect temperature fluctuations to be less than 3 ppm. In total, our estimated noise floor from known systematic error sources is only 9 ppm per visit. We do however urge caution as unknown systematic error sources could be present in flight and will only be measurable on astrophysical sources like quiescent stars. We find that reciprocity failure may introduce a perennial instrument offset at the 40 ppm level, so corrections may be needed when stitching together a multi-instrument multi-observatory spectrum over wide wavelength ranges.

astro-ph.IM↗

JWST Noise Floor I: Random Error Sources in JWST NIRCam Time Series

JWST transmission and emission spectra will provide invaluable glimpses of transiting exoplanet atmospheres, including possible biosignatures. This promising science from JWST, however, will require exquisite precision and understanding of systematic errors that can impact the time series of planets crossing in front of and behind their host stars. Here, we provide estimates of the random noise sources affecting JWST NIRCam time-series data on the integration-to-integration level. We find that 1/f noise can limit the precision of grism time series for 2 groups (230 ppm to 1000 ppm depending on the extraction method and extraction parameters), but will average down like the square root of N frames/reads. The current NIRCam grism time series mode is especially affected by 1/f noise because its GRISMR dispersion direction is parallel to the detector fast-read direction, but could be alleviated in the GRISMC direction. Care should be taken to include as many frames as possible per visit to reduce this 1/f noise source: thus, we recommend the smallest detector subarray sizes one can tolerate, 4 output channels and readout modes that minimize the number of skipped frames (RAPID or BRIGHT2). We also describe a covariance weighting scheme that can significantly lower the contributions from 1/f noise as compared to sum extraction. We evaluate the noise introduced by pre-amplifier offsets, random telegraph noise, and high dark current RC pixels and find that these are correctable below 10 ppm once background subtraction and pixel masking are performed. We explore systematic error sources in a companion paper.

astro-ph.IM↗

Searching for Planets Orbiting Alpha Centauri A with the James Webb Space Telescope

Alpha Centauri A is the closest solar-type star to the Sun and offers an excellent opportunity to detect the thermal emission of a mature planet heated by its host star. The MIRI coronagraph on JWST can search the 1-3 AU (1"-2") region around alpha Cen A which is predicted to be stable within the alpha Cen AB system. We demonstrate that with reasonable performance of the telescope and instrument, a 20 hr program combining on-target and reference star observations at 15.5 um could detect thermal emission from planets as small as ~5 RE. Multiple visits every 3-6 months would increase the geometrical completeness, provide astrometric confirmation of detected sources, and push the radius limit down to ~3 RE. An exozodiacal cloud only a few times brighter than our own should also be detectable, although a sufficiently bright cloud might obscure any planet present in the system. While current precision radial velocity (PRV) observations set a limit of 50-100 ME at 1-3 AU for planets orbiting alpha Cen A, there is a broad range of exoplanet radii up to 10 RE consistent with these mass limits. A carefully planned observing sequence along with state-of-the-art post-processing analysis could reject the light from alpha Cen A at the level of ~10^-5 at 1"-2" and minimize the influence of alpha Cen B located 7-8" away in the 2022-2023 timeframe. These space-based observations would complement on-going imaging experiments at shorter wavelengths as well as PRV and astrometric experiments to detect planets dynamically. Planetary demographics suggest that the likelihood of directly imaging a planet whose mass and orbit are consistent with present PRV limits is small, ~5%, and possibly lower if the presence of a binary companion further reduces occurrence rates. However, at a distance of just 1.34 pc, alpha Cen A is our closest sibling star and certainly merits close scrutiny.

astro-ph.IM↗

Thermal Infrared Imaging of MWC 758 with the Large Binocular Telescope: Planetary Driven Spiral Arms?

Theoretical studies suggest that a giant planet around the young star MWC 758 could be responsible for driving the spiral features in its circumstellar disk. Here, we present a deep imaging campaign with the Large Binocular Telescope with the primary goal of imaging the predicted planet. We present images of the disk in two epochs in the $L^{\prime}$ filter (3.8 $μm$) and a third epoch in the $M^{\prime}$ filter (4.8 $μm$). The two prominent spiral arms are detected in each observation, which constitute the first images of the disk at $M^\prime$, and the deepest yet in $L^\prime$ ($ΔL^\prime=$12.1 exterior to the disk at 5$σ$ significance). We report the detection of a S/N$\sim$3.9 source near the end of the Sourthern arm, and, from the source's detection at a consistent position and brightness during multiple epochs, we establish a $\sim$90% confidence-level that the source is of astrophysical origin. We discuss the possibilities that this feature may be a) an unresolved disk feature, and b) a giant planet responsible for the spiral arms, with several arguments pointing in favor of the latter scenario. We present additional detection limits on companions exterior to the spiral arms, which suggest that a $\lesssim$4 M$_{Jup}$ planet exterior to the spiral arms could have escaped detection. Finally, we do not detect the companion candidate interior to the spiral arms reported recently by Reggiani et al. (2018), although forward modelling suggests that such a source would have likely been detected.

astro-ph.SR↗

Astro2020 APC White Paper: The Early Career Perspective on the Coming Decade, Astrophysics Career Paths, and the Decadal Survey Process

In response to the need for the Astro2020 Decadal Survey to explicitly engage early career astronomers, the National Academies of Sciences, Engineering, and Medicine hosted the Early Career Astronomer and Astrophysicist Focus Session (ECFS) on October 8-9, 2018 under the auspices of Committee of Astronomy and Astrophysics. The meeting was attended by fifty six pre-tenure faculty, research scientists, postdoctoral scholars, and senior graduate students, as well as eight former decadal survey committee members, who acted as facilitators. The event was designed to educate early career astronomers about the decadal survey process, to solicit their feedback on the role that early career astronomers should play in Astro2020, and to provide a forum for the discussion of a wide range of topics regarding the astrophysics career path. This white paper presents highlights and themes that emerged during two days of discussion. In Section 1, we discuss concerns that emerged regarding the coming decade and the astrophysics career path, as well as specific recommendations from participants regarding how to address them. We have organized these concerns and suggestions into five broad themes. These include (sequentially): (1) adequately training astronomers in the statistical and computational techniques necessary in an era of "big data", (2) responses to the growth of collaborations and telescopes, (3) concerns about the adequacy of graduate and postdoctoral training, (4) the need for improvements in equity and inclusion in astronomy, and (5) smoothing and facilitating transitions between early career stages. Section 2 is focused on ideas regarding the decadal survey itself, including: incorporating early career voices, ensuring diverse input from a variety of stakeholders, and successfully and broadly disseminating the results of the survey.

astro-ph.IM↗

High Spatial Resolution Thermal-Infrared Spectroscopy with ALES: Resolved Spectra of the Benchmark Brown Dwarf Binary HD 130948BC

We present 2.9-4.1 micron integral field spectroscopy of the L4+L4 brown dwarf binary HD 130948BC, obtained with the Arizona Lenslets for Exoplanet Spectroscopy (ALES) mode of the Large Binocular Telescope Interferometer (LBTI). The HD 130948 system is a hierarchical triple system, in which the G2V primary is joined by two co-orbiting brown dwarfs. By combining the age of the system with the dynamical masses and luminosities of the substellar companions, we can test evolutionary models of cool brown dwarfs and extra-solar giant planets. Previous near-infrared studies suggest a disagreement between HD 130948BC luminosities and those derived from evolutionary models. We obtained spatially-resolved, low-resolution (R~20) L-band spectra of HD 130948B and C to extend the wavelength coverage into the thermal infrared. Jointly using JHK photometry and ALES L-band spectra for HD 130948BC, we derive atmospheric parameters that are consistent with parameters derived from evolutionary models. We leverage the consistency of these atmospheric quantities to favor a younger age (0.50 \pm 0.07 Gyr) of the system compared to the older age (0.79 \pm 0.22 Gyr) determined with gyrochronology in order to address the luminosity discrepancy.

astro-ph.SR↗

A deep search for planets in the inner 15 au around Vega

We present the results of a deep high-contrast imaging search for planets around Vega. Vega is an ideal target for high-contrast imaging because it is bright, nearby, and young with a face-on two-belt debris disk which may be shaped by unseen planets. We obtained $J-$ and $H-$band data on Vega with the coronagraphic integral-field spectrograph Project 1640 (P1640) at Palomar Observatory. Two nights of data were obtained in 2016, in poor seeing conditions, and two additional nights in more favorable conditions in 2017. In total, we obtained 5.5 hours of integration time on Vega in moderate to good seeing conditions (<1.5"). We did not detect any low mass companions in this system. Our data present the most sensitive contrast limits around Vega at very small separations (2-15 au) thus far, allowing us to place new constraints on the companions which may be sculpting the Vega system. In addition to new constraints, as the deepest data obtained with P1640, these observations form the final legacy of the now decommissioned instrument.

astro-ph.EP↗

ALES: Overview and Upgrades

The Arizona Lenslets for Exoplanet Spectroscopy (ALES) is the world's first AO-fed thermal infrared integral field spectrograph, mounted inside the Large Binocular Telescope Interferometer (LBTI) on the LBT. An initial mode of ALES allows 3-4 micron spectra at R~20 with 0.026'' spaxels over a 1''x1'' field-of-view. We are in the process of upgrading ALES with additional wavelength ranges, spectral resolutions, and plate scales allowing a broad suite of science that takes advantage of ALES's unique ability to work at wavelengths >2 microns, and at the diffraction limit of the LBT's full 23.8 meter aperture.

astro-ph.IM↗