arXiv subjects

Amaya Moro-Martin

Publications and source records attributed to Amaya Moro-Martin.

At least 19 recordsLinked to original sources

arXiv2025

JWST/NIRSpec Detects Warm CO Emission in the Terrestrial-Planet Zone of HD 131488

We have obtained a high-resolution, JWST NIRSpec $2.87$ -- $5.14$ $μ$m spectrum of the debris disk around HD 131488. We discover CO fundamental emission indicating the presence of warm fluorescent gas within $\sim10$ AU of the star. The large discrepancy in CO's vibrational and rotational temperature indicates that CO is out of thermal equilibrium and is excited with UV fluorescence. Our UV fluorescence model gives a best fit of $1150\,$K with an effective temperature of $450$, $332$, and $125\,$K for the warm CO gas kinetic temperature within $0.5$, $1$, and $10\,$AU to the star and a gas vibrational temperature of $8800\,$K. The newly discovered warm CO gas population likely resides between sub-AU scales and $\sim\,10\,$AU, interior to the cold CO reservoir detected beyond $35\,$AU with HST STIS and ALMA. The discovery of warm, fluorescent gas in a debris disk is the first such detection ever made. The detection of warm CO raises the possibility of unseen molecules (H$_2$O, H$_2$, etc) as collisional partners to excite the warm gas. We estimated a lower mass limit for CO of $1.25\times 10^{-7}\text{M}_{\oplus}$, which is $10^{-5}$ of the cold CO mass detected with ALMA and HST. We demonstrate that UV fluorescence emerges as a promising avenue for detecting tenuous gas at $10^{-7}$ Earth-mass level in debris disks with JWST.

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arXiv2025

Diversity of Exoplanets

This review article delves into the study of low-mass exoplanets: super-Earths, mini-Neptunes and the new categories within and between that we are starting to discover. We provide an overview of current exoplanet observational capabilities, their limitations, and what they are allowing us to learn about low-mass planets. We briefly summarize the most important aspects of planet formation, with an emphasis on processes that may be testable with small exoplanets, in particular those that affect their composition. We also describe the observed compositional diversity of low-mass exoplanets and what it teaches us about planet formation pathways. We finish this review summarizing the study of the composition of small exoplanets during the very last stage of stellar evolution, by studying white dwarfs. This review is written as the JWST is making its first contributions to small planet characterization, rapidly opening new lines of inquiry.

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arXiv2025

Debris disks around M dwarfs: The Herschel DEBRIS survey

The Herschel open-time key program Disc Emission via a Bias-free Reconnaissance in the Infrared and Sub-millimeter (DEBRIS) is an unbiased survey of the nearest ~100 stars for each stellar type A-M observed with a uniform photometric sensitivity to search for cold debris disks around them. The analysis of the Photoconductor Array Camera and Spectrometer (PACS) photometric observations of the 94 DEBRIS M dwarfs of this program is presented in this paper, following upon two companion papers on the DEBRIS A-star and FGK-star subsamples. In the M-dwarf subsample, two debris disks have been detected, around the M3V dwarf GJ581 and the M4V dwarf FomalhautC (LP876-10). This result gives a disk detection rate of 2.1^{+2.7}_{-0.7}% at the 68% confidence level, significantly less than measured for earlier stellar types in the DEBRIS program. However, we show that the survey of the DEBRIS M-dwarf subsample is about ten times shallower than the surveys of the DEBRIS FGK subsamples when studied in the physical parameter space of the disk's fractional dust luminosity versus blackbody radius. Furthermore, had the DEBRIS K-star subsample been observed at the same shallower depth in this parameter space, its measured disk detection rate would have been statistically consistent with the one found for the M-dwarf subsample. Hence, the incidence of debris disks does not appear to drop from the K subsample to the M subsample of the DEBRIS program, when considering disks in the same region of physical parameter space. An alternative explanation is that the only two bright disks discovered in the M-dwarf subsample would not, in fact, be statistically representative of the whole population.

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arXiv2024

MIRI MRS Observations of Beta Pictoris II. The Spectroscopic Case for a Recent Giant Collision

Modeling observations of the archetypal debris disk around $β$ Pic, obtained in 2023 January with the MIRI MRS on board JWST, reveals significant differences compared with that obtained with the IRS on board Spitzer. The bright 5 - 15 $μ$m continuum excess modeled using a $\sim$600 K black body has disappeared. The previously prominent 18 and 23 $μ$m crystalline forsterite emission features, arising from cold dust ($\sim$100 K) in the Rayleigh limit, have disappeared and been replaced by very weak features arising from the hotter 500 K dust population. Finally, the shape of the 10 $μ$m silicate feature has changed, consistent with a shift in the temperature of the warm dust population from $\sim$300 K to $\sim$500 K and an increase in the crystalline fraction of the warm, silicate dust. Stellar radiation pressure may have blown both the hot and the cold crystalline dust particles observed in the Spitzer spectra out of the planetary system during the intervening 20 years between the Spitzer and JWST observations. These results indicate that the $β$ Pic system has a dynamic circumstellar environment, and that periods of enhanced collisions can create large clouds of dust that sweep through the planetary system.

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arXiv2024

A Uniform Analysis of Debris Disks with the Gemini Planet Imager II: Constraints on Dust Density Distribution Using Empirically-Informed Scattering Phase Functions

Spatially-resolved images of debris disks are necessary to determine disk morphological properties and the scattering phase function (SPF) which quantifies the brightness of scattered light as a function of phase angle. Current high-contrast imaging instruments have successfully resolved several dozens of debris disks around other stars, but few studies have investigated trends in the scattered-light, resolved population of debris disks in a uniform and consistent manner. We have combined Karhunen-Loeve Image Projection (KLIP) with radiative-transfer disk forward modeling in order to obtain the highest quality image reductions and constrain disk morphological properties of eight debris disks imaged by the Gemini Planet Imager at H-band with a consistent and uniformly-applied approach. In describing the scattering properties of our models, we assume a common SPF informed from solar system dust scattering measurements and apply it to all systems. We identify a diverse range of dust density properties among the sample, including critical radius, radial width, and vertical width. We also identify radially narrow and vertically extended disks that may have resulted from substellar companion perturbations, along with a tentative positive trend in disk eccentricity with relative disk width. We also find that using a common SPF can achieve reasonable model fits for disks that are axisymmetric and asymmetric when fitting models to each side of the disk independently, suggesting that scattering behavior from debris disks may be similar to Solar System dust.

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arXiv2022

Physical Considerations for an Intercept Mission to a 1I/'Oumuamua-like Interstellar Object

In this paper, we review some of the extant literature on the study of interstellar objects (ISOs). With the forthcoming Vera C. Rubin Telescope and Legacy Survey of Space and Time (LSST), we find that $0.38 - 84$ `Oumuamua-like interstellar objects are expected to be detected in the next 10 years, with 95\% confidence. The feasibility of a rendezvous trajectory has been demonstrated in previous work. In this paper, we investigate the requirements for a rendezvous mission with the primary objective of producing a resolved image of an interstellar object. We outline the rendezvous distances necessary as a function of resolution elements and object size. We expand upon current population synthesis models to account for the size dependency on the detection rates for reachable interstellar objects. We assess the trade-off between object diameter and occurrence rate, and conclude that objects with the size range between a third of the size and the size of `Oumuamua will be optimal targets for an imaging rendezvous. We also discuss expectations for surface properties and spectral features of interstellar objects, as well as the benefits of various spacecraft storage locations.

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arXiv2022

The JWST Early Release Observations

The James Webb Space Telescope (JWST) Early Release Observations (EROs) is a set of public outreach products created to mark the end of commissioning and the beginning of science operations for JWST. Colloquially known as the "Webb First Images and Spectra", these products were intended to demonstrate to the worldwide public that JWST is ready for science, and is capable of producing spectacular results. The package was released on July 12, 2022, and included images and spectra of the galaxy cluster SMACS~J0723.3-7327 and distant lensed galaxies, the interacting galaxy group Stephan's Quintet, NGC 3324 in the Carina star-forming complex, the Southern Ring planetary nebula NGC 3132, and the transiting hot Jupiter WASP 96b. This paper describes the ERO technical design, observations, and scientific processing of data underlying the colorful outreach products.

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arXiv2019

High-Resolution Near-Infrared Polarimetry and Sub-Millimeter Imaging of FS Tau A: Possible Streamers in Misaligned Circumbinary Disk System

We analyzed the young (2.8-Myr-old) binary system FS Tau A using near-infrared (H-band) high-contrast polarimetry data from Subaru/HiCIAO and sub-millimeter CO (J=2-1) line emission data from ALMA. Both the near-infrared and sub-millimeter observations reveal several clear structures extending to $\sim$240 AU from the stars. Based on these observations at different wavelengths, we report the following discoveries. One arm-like structure detected in the near-infrared band initially extends from the south of the binary with a subsequent turn to the northeast, corresponding to two bar-like structures detected in ALMA observations with an LSRK velocity of 1.19-5.64 km/s. Another feature detected in the near-infrared band extends initially from the north of the binary, relating to an arm-like structure detected in ALMA observations with an LSRK velocity of 8.17-16.43 km/s. From their shapes and velocities, we suggest that these structures can mostly be explained by two streamers that connect the outer circumbinary disk and the central binary components. These discoveries will be helpful for understanding the evolution of streamers and circumstellar disks in young binary systems.

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arXiv2019

Increasing Gender Diversity and Inclusion in Scientific Committees and Related Activities at STScI

We present a new initiative by the Women in Astronomy Forum at Space Telescope Science Institute (STScI) to increase gender diversity and inclusion in STScI's scientific committees and the activities they generate. This initiative offers new and uniform guidelines on binary gender representation goals for each committee and recommendations on how to achieve them in a homogeneous way, as well as metrics and tools to track progress towards defined goals. While the new guidelines presented in the paper focus on binary gender representation, they can be adapted and implemented to support all minority groups. By creating diverse committees and making them aware of, and trained on implicit bias, we expect to create a diverse outcome in the activities they generate, which, in turn, will advance science further and faster.

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arXiv2019

Cold Debris Disks as Strategic Targets for the 2020s

Cold debris disks (T$<$200 K) are analogues to the dust in the Solar System's Kuiper belt--dust generated from the evaporation and collision of minor bodies perturbed by planets, our Sun, and the local interstellar medium. Scattered light from debris disks acts as both a signpost for unseen planets as well as a source of contamination for directly imaging terrestrial planets, but many details of these disks are poorly understood. We lay out a critical observational path for the study of nearby debris disks that focuses on defining an empirical relationship between scattered light and thermal emission from a disk, probing the dynamics and properties of debris disks, and directly determining the influence of planets on disks. We endorse the findings and recommendations published in the National Academy reports on Exoplanet Science Strategy and Astrobiology Strategy for the Search for Life in the Universe. This white paper extends and complements the material presented therein with a focus on debris disks around nearby stars. Separate complementary papers are being submitted regarding the inner warm regions of debris disks (Mennesson et al.), the modeling of debris disk evolution (Gaspar et al.), studies of dust properties (Chen et al.), and thermal emission from disks (Su et al.).

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arXiv2019

Debris Disk Composition: A Diagnostic Tool for Planet Formation and Migration

Debris disks are exoplanetary systems containing planets, minor bodies (such as asteroids and comets) and debris dust. Unseen planets are presumed to perturb the minor bodies into crossing orbits, generating small dust grains that are detected via remote sensing. Debris disks have been discovered around main sequence stars of a variety of ages (from 10 Myr to several Gyr) and stellar spectral types (from early A-type to M-type stars). As a result, they serve as excellent laboratories for understanding whether the architecture and the evolution of our Solar System is common or rare. This white paper addresses two outstanding questions in debris disk science: (1) Are debris disk minor bodies similar to asteroids and comets in our Solar System? (2) Do planets separate circumstellar material into distinct reservoirs and/or mix material during planet migration? We anticipate that SOFIA/HIRMES, JWST, and WFIRST/CGI will greatly improve our understanding of debris disk composition, enabling the astronomical community to answer these questions. However, we note that despite their observational power, these facilities will not provide large numbers of detections or detailed characterization of cold ices and silicates in the Trans Neptunian zone. Origins Space Telescope is needed to revolutionize our understanding of the bulk composition and mixing in exoplanetary systems.

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arXiv2019

Probing Unseen Planet Populations with Resolved Debris Disk Structures

Thousands of exoplanets have been found with many widely different from the ones in our own system. Despite the success, systems with planets in wide orbits analogous to those of Jupiter and Saturn, in the critical first several hundred million years of evolution, are virtually unexplored. Where are the low-mass planets that are hidden from our exoplanet detection techniques? Is our Solar System's planetary architecture unique? High-fidelity debris disk images offer an effective method to answer these questions. We can use them to study the formation and evolution of low-mass planets from youth to the age of the Solar System, providing snapshots of the complex processes and valuable insights into the formation and migration history of giant planets at wide orbits. This white paper focuses on resolving debris structures in thermal emission that is applicable to a large unbiased sample. We summarize the properties of the known debris disks and assess the feasibility of resolving them within our current and future infrared and millimeter facilities by adopting uniform criteria. JWST and the 9-m Origins Space Telescope are the most promising missions in the coming decades to resolve almost half of the known disks at high fidelity. Resolved debris structures at multiple wavelengths and at all stages of evolution would reveal the properties of unseen planet populations, enabling a unique demographic study of overall planet formation and evolution.

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arXiv2019

Multi-epoch Direct Imaging and Time-Variable Scattered Light Morphology of the HD 163296 Protoplanetary Disk

We present H-band polarized scattered light imagery and JHK high-contrast spectroscopy of the protoplanetary disk around HD 163296 observed with the HiCIAO and SCExAO/CHARIS instruments at Subaru Observatory. The polarimetric imagery resolve a broken ring structure surrounding HD 163296 that peaks at a distance along the major axis of 0.65 (66 AU) and extends out to 0.98 (100 AU) along the major axis. Our 2011 H-band data exhibit clear axisymmetry, with the NW- and SE- side of the disk exhibiting similar intensities. Our data are clearly different than 2016 epoch H-band observations from VLT/SPHERE that found a strong 2.7x asymmetry between the NW- and SE-side of the disk. Collectively, these results indicate the presence of time variable, non-azimuthally symmetric illumination of the outer disk. Based on our 3D-MCRT modeling of contemporaneous IR spectroscopic and H-band polarized intensity imagery of the system, we suggest that while the system could plausibly host an inclined inner disk component, such a component is unlikely to be responsible for producing the observed time-dependent azimuthal variations in the outer scattered light disk of the system. While our SCExAO/CHARIS data are sensitive enough to recover the planet candidate identified from NIRC2 in the thermal IR, we fail to detect an object with a corresponding JHK brightness estimated from the atmospheric models of Baraffe et al. 2003. This suggests that the candidate is either fainter in JHK bands than model predictions, possibly due to extinction from the disk or atmospheric dust/clouds, or that it is an artifact of the dataset/data processing. Our SCExAO/CHARIS data lower the IR mass limits for planets inferred at larger stellocentric separations; however, these ALMA-predicted protoplanet candidates are currently still consistent with direct imaging constraints.

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arXiv2018

Subaru/HiCIAO $HK_{\rm s}$ imaging of LkH$α$ 330 - multi-band detection of the gap and spiral-like structures

We present $H$- and $K_{\rm s}$-bands observations of the LkH$α$ 330 disk with a multi-band detection of the large gap and spiral-like structures. The morphology of the outer disk ($r\sim$$0\farcs3$) at PA=0--45$^\circ$ and PA=180--290$^\circ$ are likely density wave-induced spirals and comparison between our observational results and simulations suggests a planet formation. We have also investigated the azimuthal profiles at the ring and the outer-disk regions as well as radial profiles in the directions of the spiral-like structures and semi-major axis. Azimuthal analysis shows a large variety in wavelength and implies that the disk has non-axisymmetric dust distributions. The radial profiles in the major-axis direction (PA=$271^\circ$) suggest that the outer region ($r\geq0\farcs25$) may be influenced by shadows of the inner region of the disk. The spiral-like directions (PA=10$^\circ$ and 230$^\circ$) show different radial profiles, which suggests that the surfaces of the spiral-like structures are highly flared and/or have different dust properties. Finally, a color-map of the disk shows a lack of an outer eastern region in the $H$-band disk, which may hint the presence of an inner object that casts a directional shadow onto the disk.

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arXiv2018

High-contrast Polarimetry Observation of T Tau Circumstellar Environment

We conducted high-contrast polarimetry observations of T Tau in the H-band, using the HiCIAO instrument mounted on the Subaru Telescope, revealing structures as near as 0.$\arcsec$1 from the stars T Tau N and T Tau S. The whole T Tau system is found to be surrounded by nebula-like envelopes, and several outflow-related structures are detected in these envelopes. We analyzed the detailed polarization patterns of the circumstellar structures near each component of this triple young star system and determined constraints on the circumstellar disks and outflow structures. We suggest that the nearly face-on circumstellar disk of T Tau N is no larger than 0.$\arcsec$8, or 117 AU, in the northwest, based on the existence of a hole in this direction, and no larger than 0.$\arcsec$27, or 40 AU, in the south. A new structure "N5" extends to about 0.$\arcsec$42, or 59 AU, on the southwest of the star, believed to be part of the disk. We suggest that T Tau S is surrounded by a highly inclined circumbinary disk with a radius of about 0.$\arcsec$3, or 44 AU, with a position angle of about 30$^\circ$, that is misaligned with the orbit of the T Tau S binary. After analyzing the positions and polarization vector patterns of the outflow-related structures, we suggest that T Tau S should trigger the well-known E-W outflow, and is also likely to be responsible for a southwest precessing outflow "coil" and a possible south outflow.

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arXiv2018

Kuiper Belt Analogues in Nearby M-type Planet-host Systems

We present the results of a Herschel survey of 21 late-type stars that host planets discovered by the radial velocity technique. The aims were to discover new disks in these systems and to search for any correlation between planet presence and disk properties. In addition to the known disk around GJ 581, we report the discovery of two new disks, in the GJ 433 and GJ 649 systems. Our sample therefore yields a disk detection rate of 14%, higher than the detection rate of 1.2% among our control sample of DEBRIS M-type stars with 98% confidence. Further analysis however shows that the disk sensitivity in the control sample is about a factor of two lower in fractional luminosity than for our survey, lowering the significance of any correlation between planet presence and disk brightness below 98%. In terms of their specific architectures, the disk around GJ 433 lies at a radius somewhere between 1 and 30au. The disk around GJ 649 lies somewhere between 6 and 30au, but is marginally resolved and appears more consistent with an edge-on inclination. In both cases the disks probably lie well beyond where the known planets reside (0.06-1.1au), but the lack of radial velocity sensitivity at larger separations allows for unseen Saturn-mass planets to orbit out to $\sim$5au, and more massive planets beyond 5au. The layout of these M-type systems appears similar to Sun-like star + disk systems with low-mass planets.

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arXiv2017

The Fundamental Stellar Parameters of FGK Stars in the SEEDS Survey

Large exoplanet surveys have successfully detected thousands of exoplanets to-date. Utilizing these detections and non-detections to constrain our understanding of the formation and evolution of planetary systems also requires a detailed understanding of the basic properties of their host stars. We have determined the basic stellar properties of F, K, and G stars in the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) survey from echelle spectra taken at the Apache Point Observatory's 3.5m telescope. Using ROBOSPECT to extract line equivalent widths and TGVIT to calculate the fundamental parameters, we have computed Teff, log(g), vt, [Fe/H], chromospheric activity, and the age for our sample. Our methodology was calibrated against previously published results for a portion of our sample. The distribution of [Fe/H] in our sample is consistent with that typical of the Solar neighborhood. Additionally, we find the ages of most of our sample are $< 500 Myrs$, but note that we cannot determine robust ages from significantly older stars via chromospheric activity age indicators. The future meta-analysis of the frequency of wide stellar and sub-stellar companions imaged via the SEEDS survey will utilize our results to constrain the occurrence of detected co-moving companions with the properties of their host stars.

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arXiv2017

SONS: The JCMT legacy survey of debris discs in the submillimetre

Debris discs are evidence of the ongoing destructive collisions between planetesimals, and their presence around stars also suggests that planets exist in these systems. In this paper, we present submillimetre images of the thermal emission from debris discs that formed the SCUBA-2 Observations of Nearby Stars (SONS) survey, one of seven legacy surveys undertaken on the James Clerk Maxwell telescope between 2012 and 2015. The overall results of the survey are presented in the form of 850 microns (and 450 microns, where possible) images and fluxes for the observed fields. Excess thermal emission, over that expected from the stellar photosphere, is detected around 49 stars out of the 100 observed fields. The discs are characterised in terms of their flux density, size (radial distribution of the dust) and derived dust properties from their spectral energy distributions. The results show discs over a range of sizes, typically 1-10 times the diameter of the Edgeworth-Kuiper Belt in our Solar System. The mass of a disc, for particles up to a few millimetres in size, is uniquely obtainable with submillimetre observations and this quantity is presented as a function of the host stars' age, showing a tentative decline in mass with age. Having doubled the number of imaged discs at submillimetre wavelengths from ground-based, single dish telescope observations, one of the key legacy products from the SONS survey is to provide a comprehensive target list to observe at high angular resolution using submillimetre/millimetre interferometers (e.g., ALMA, SMA).

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