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DOE OSTI2024

Expanded Archaeal Genomes Shed New Light on the Evolution of Isoprenoid Biosynthesis

Isoprenoids and their derivatives, essential for all cellular life on Earth, are particularly crucial in archaeal membrane lipids, suggesting that their biosynthesis pathways have ancient origins and play pivotal roles in the evolution of early life. Despite all eukaryotes, archaea, and a few bacterial lineages being known to exclusively use the mevalonate (MVA) pathway to synthesize isoprenoids, the origin and evolutionary trajectory of the MVA pathway remain controversial. Here, we conducted a thorough comparison and phylogenetic analysis of key enzymes across the four types of MVA pathway, with the particular inclusion of metagenome assembled genomes (MAGs) from uncultivated archaea. Our findings support an archaeal origin of the MVA pathway, likely postdating the divergence of Bacteria and Archaea from the Last Universal Common Ancestor (LUCA), thus implying the LUCA’s enzymatic inability for isoprenoid biosynthesis. Notably, the Asgard archaea are implicated in playing central roles in the evolution of the MVA pathway, serving not only as putative ancestors of the eukaryote- and Thermoplasma-type routes, but also as crucial mediators in the gene transfer to eukaryotes, possibly during eukaryogenesis. Overall, this study advances our understanding of the origin and evolutionary history of the MVA pathway, providing unique insights into the lipid divide and the evolution of early life.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

OGLE-2016-BLG-1227L: A Wide-separation Planet from a Very Short-timescale Microlensing Event

We present the analysis of the microlensing event OGLE-2016-BLG-1227. The light curve of this short-duration event appears to be a single-lens event affected by severe finite-source effects. Analysis of the light curve based on a single-lens single-source (1L1S) model yields very small values of the event timescale, t{sub E}∼3.5 days, and the angular Einstein radius, θ{sub E}∼0.009 mas, making the lens a candidate of a free-floating planet. Close inspection reveals that the 1L1S solution leaves small residuals with an amplitude of ΔI ≲ 0.03 mag. We find that the residuals are explained by the existence of an additional widely separated heavier lens component, indicating that the lens is a wide-separation planetary system rather than a free-floating planet. From Bayesian analysis, it is estimated that the planet has a mass of M{sub p}=0.79{sub −0.39}{sup +1.30} M{sub J} and it is orbiting a low-mass host star with a mass of M{sub host}=0.10{sub −0.05}{sup +0.17} M{sub ⊙} located with a projected separation of a{sub ⊥}=3.4{sub −1.0}{sup +2.1} au. The planetary system is located in the Galactic bulge with a line-of-sight separation from the source star of D{sub LS}=1.21{sub −0.63}{sup +0.96} kpc. The event shows that there is a range of deviations in the signatures of host stars for apparently isolated planetary lensing events and that it is possible to identify a host even when a deviation is subtle.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Identification of Possible Stellar Companions via Speckle Interferometry in a Sample of Be Stars

We present speckle interferometric measurements of Be stars made with the 1.60 m Perkin-Elmer telescope at the Pico dos Dias Observatory of the Laboratório Nacional de Astrofísica in Brazil. Using three different filters (V, R, and I), we obtained astrometric measurements for 23 stars, during three observing runs allocated in 2017 March, 2018 April, and 2019 July. We identified pairs with angular separation ranging from 0.″10 to 6.″69, including six systems with separations smaller than 1.″0. We estimated a mean error in separation of 15 mas, 1.°2 in position angle, and 0.29 mag for the magnitude difference. We discovered three new possible double systems that are not identified in the literature: HD 174886, HD 159032, and HD 168135 with an average angular separation of 0.″20, 3.″23, and 5.″41, respectively. In addition, we identified four new pairs in multiple systems previously known in the Washington Double Star Catalog. However, for 16 stars of our sample, we did not find evidence of binarity, based on the diffraction-limited resolution, the field of view, and/or the sensitivity of our observations. From the cross-match with data from Gaia Data Release 2, we verified the possibility of some of these systems be gravitationally bound or not.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

TOI-677b: A Warm Jupiter (P = 11.2 days) on an Eccentric Orbit Transiting a Late F-type Star

We report the discovery of TOI-677 b, first identified as a candidate in light curves obtained within Sectors 9 and 10 of the Transiting Exoplanet Survey Satellite (TESS) mission and confirmed with radial velocities. TOI-677 b has a mass of M{sub p} = 1.236{sub −0.067}{sup +0.069} M{sub J}, a radius of R{sub P} = 1.170±0.03 R{sub J}, and orbits its bright host star (V = 9.8 mag) with an orbital period of 11.23660±0.00011 d, on an eccentric orbit with e=0.435±0.024. The host star has a mass of M{sub ⋆} = 1.181±0.058 M{sub ⊙}, a radius of R{sub ⋆} = 1.28{sub −0.03}{sup +0.03} R{sub ⊙}, an age of 2.92{sub −0.73}{sup +0.80} Gyr and solar metallicity, properties consistent with a main-sequence late-F star with T{sub eff}=6295±77 K. We find evidence in the radial velocity measurements of a secondary long-term signal, which could be due to an outer companion. The TOI-677 b system is a well-suited target for Rossiter–Mclaughlin observations that can constrain migration mechanisms of close-in giant planets.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

MCG+07-20-052: Interacting Dwarf Pair in a Group Environment

We present an observational study of the interacting pair of dwarf galaxies, MCG+07-20-052, in the vicinity of Milky Way mass spiral galaxy NGC 2998. MCG+07-20-052 is located at a sky-projected distance of 105 kpc from NGC 2998 and the two have a relative line-of-sight velocity of 60 km s{sup −1}. We observed tidal tail-like extensions on both members (D1 and D2) of the interacting pair MCG+07-20-052. The interacting dwarf galaxies, D1 and D2, have B-band absolute magnitudes of −17.17 and −17.14 mag, respectively, and D2 is significantly bluer than D1. We obtained H i 21 cm line data of the NGC 2998 system using the Giant Metrewave Radio Telescope to get a more detailed view of the neutral hydrogen (H i) emission in the interacting dwarf galaxies and in the galaxy members of the NGC 2998 group. Evidence of a merger between the dwarf galaxies in the MCG+07-20-052 is also present in the H i kinematics and morphology where we find that H i is mostly concentrated around D2, which also shows a higher level of star-forming activity and a bluer g–r color index compared to D1. In addition, we detect extended tenuous H i emission around another member galaxy, NGC 3006, located close to the MCG+07-20-052 pair at a sky-projected distance of 41 kpc. We compare here our results from the MCG+07-20-052 pair NGC 2998 system with other known Large Magellanic Cloud/Small Magellanic Cloud/Milky Way-type systems and discuss the possible origin of the dwarf–dwarf interaction.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Census of the Young Stellar Population in the Galactic H ii Region Sh2-242

We present here identification and characterization of the young stellar population associated with an active star-forming site Sh2-242. We used our own new optical imaging and spectroscopic observational data, as well as several archival catalogs, e.g., Pan-STARRS 1, Gaia DR2, IPHAS, Wide-field InfraRed Camera, 2MASS, and Spitzer. Slit spectroscopic results confirm the classification of the main ionizing source BD+26 980 as an early-type star of spectral type B0.5 V. The spectrophotometric distance of the star is estimated as 2.08 ± 0.24 kpc, which confirms the source as a member of the cluster. An extinction map covering a large area (diameter ∼50′) is generated with H and K photometry toward the region. From the map, three distinct locations of peak extinction complexes (A {sub V} ≃ 7–17 mag) are identified for the very first time. Using the infrared color excess, a total of 33 Class I and 137 Class II young objects are classified within the region. The IPHAS photometry reveals classification of 36 Hα emitting sources, which might be class II objects. Among 36 Hα emitting sources, 5 are already identified using infrared excess emission. In total, 201 young objects are classified toward S242 from this study. The membership status of the young sources is further windowed with the inclusion of parallax from the Gaia DR2 catalog. Using the optical and infrared color–magnitude diagrams, the young stellar objects are characterized with an average age of ∼1 Myr and masses in the range 0.1–3.0 M {sub ☉}. The census of the stellar content within the region is discussed using combined photometric and spectroscopic data.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Radial Star Formation Histories in 32 Nearby Galaxies

The spatially resolved star formation histories are studied for 32 normal star-forming galaxies drawn from the Spitzer Extended Disk Galaxy Exploration Science survey. At surface brightness sensitivities fainter than 28 mag arcsec{sup −2}, the new optical photometry is deep enough to complement archival ultraviolet and infrared imaging and to explore the properties of the emission well beyond the traditional optical extents of these nearby galaxies. Fits to the spectral energy distributions using a delayed star formation history model indicate a subtle but interesting average radial trend for the spiral galaxies: the inner stellar systems decrease in age with increasing radius, consistent with inside-out disk formation, but the trend reverses in the outermost regions with the stellar age nearly as old as the innermost stars. These results suggest an old stellar outer disk population formed through radial migration and/or the cumulative history of minor mergers and accretions of satellite dwarf galaxies. The subset of S0 galaxies studied here show the opposite trend compared to what is inferred for spirals: characteristic stellar ages that are increasingly older with radius for the inner portions of the galaxies, and increasingly younger stellar ages for the outer portions. This result suggests that either S0 galaxies are not well modeled by a delayed-τ model, and/or that S0 galaxies have a more complicated formation history than spiral galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Accretion Properties of PDS 70b with MUSE

We report a new evaluation of the accretion properties of PDS 70b obtained with the Very Large Telescope/Multi Unit Spectroscopic Explorer. The main difference from the previous studies of Haffert et al. and Aoyama & Ikoma is in the mass accretion rate. Simultaneous multiple line observations, such as Hα and Hβ, can better constrain the physical properties of an accreting planet. While we clearly detected Hα emissions from PDS 70b, no Hβ emissions were detected. We estimate the line flux of Hβ with a 3σ upper limit to be 2.3 × 10{sup −16} erg s{sup −1} cm{sup −2}. The flux ratio F {sub Hβ}/F {sub Hα} for PDS 70b is <0.28. Numerical investigations by Aoyama et al. suggest that F {sub Hβ}/F {sub Hα} should be close to unity if the extinction is negligible. We attribute the reduction of the flux ratio to the extinction, and estimate the extinction of Hα (A {sub Hα}) for PDS 70b to be >2.0 mag using the interstellar extinction value. By combining with the Hα linewidth and the dereddening line luminosity of Hα, we derive the PDS 70b mass accretion rate to be ≳5 × 10{sup −7} M {sub Jup} yr{sup −1}. The PDS 70b mass accretion rate is an order of magnitude larger than that of PDS 70. We found that the filling factor f {sub f} (the fractional area of the planetary surface emitting Hα) is ≳0.01, which is similar to the typical stellar value. The small value of f {sub f} indicates that the Hα emitting areas are localized at the surface of PDS 70b.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Observations of Binary Stars with the Differential Speckle Survey Instrument. IX. Observations of Known and Suspected Binaries, and a Partial Survey of Be Stars

We report 370 measures of 170 components of binary and multiple-star systems, obtained from speckle imaging observations made with the Differential Speckle Survey Instrument at Lowell Observatory’s Discovery Channel Telescope in 2015 through 2017. Of the systems studied, 147 are binary stars, 10 are seen as triple systems, and 1 quadruple system is measured. Seventy-six high-quality nondetections and 15 newly resolved components are presented in our observations. The uncertainty in relative astrometry appears to be similar to our previous work at Lowell, namely, linear measurement uncertainties of approximately 2 mas, and the relative photometry appears to be uncertain at the 0.1–0.15 mag level. Using these measures and those in the literature, we calculate six new visual orbits, including one for the Be star 66 Oph and two combined spectroscopic–visual orbits. The latter two orbits, which are for HD 22451 (YSC 127) and HD 185501 (YSC 135), yield individual masses of the components at the level of 2% or better, and independent distance measures that in one case agrees with the value found in the Gaia DR2 and in the other disagrees at the 2σ level. We find that HD 22451 consists of an F6V+F7V pair with orbital period of 2401.1 ± 3.2 days and masses of 1.342 ± 0.029 and 1.236±0.026 M{sub ⊙}. For HD 185501, both stars are G5 dwarfs that orbit one another with a period of 433.94 ± 0.15 days, and the masses are 0.898 ± 0.012 and 0.876±0.012 M{sub ⊙}. We discuss the details of both the new discoveries and the orbit objects.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

HATS-71b: A Giant Planet Transiting an M3 Dwarf Star in TESS Sector 1

We report the discovery of HATS-71b, a transiting gas giant planet on a P=3.7955 day orbit around a G=15.35 mag M3 dwarf star. HATS-71 is the coolest M dwarf star known to host a hot Jupiter. The loss of light during transits is 4.7%, more than in any other confirmed transiting planet system. The planet was identified as a candidate by the ground-based HATSouth transit survey. It was confirmed using ground-based photometry, spectroscopy, and imaging, as well as space-based photometry from the NASA Transiting Exoplanet Survey Satellite mission (TIC 234523599). Combining all of these data, and utilizing Gaia DR2, we find that the planet has a radius of 1.024±0.018 R{sub J} and mass of 0.37 ±0.24 M{sub J} (95% confidence upper limit of <0.80 M{sub J}), while the star has a mass of 0.4861±0.0060 M{sub ⊙} and a radius of 0.4783±0.0060 R{sub ⊙}.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

A Free-floating or Wide-orbit Planet in the Microlensing Event OGLE-2019-BLG-0551

High-cadence observations of the Galactic bulge by the microlensing surveys led to the discovery of a handful of extremely short-timescale microlensing events that can be attributed to free-floating or wide-orbit planets. Here, we report the discovery of another strong free-floating planet candidate, which was found from the analysis of the gravitational microlensing event OGLE-2019-BLG-0551. The light curve of the event is characterized by a very short duration (≲3 days) and a very small amplitude (≲0.1 mag). From modeling of the light curve, we find that the Einstein timescale, t{sub E}=0.381±0.017 day, is much shorter, and the angular Einstein radius, θ{sub E}=4.35±0.34 μas, is much smaller than those of typical lensing events produced by stellar-mass lenses (t{sub E}∼20 days, θ{sub E}∼0.3 mas), indicating that the lens is very likely to be a planetary-mass object. We conduct an extensive search for possible signatures of a companion star in the light curve of the event, finding no significant evidence for the putative host star. For the first time, we also demonstrate that the angular Einstein radius of the lens does not depend on blending in the low-magnification events with strong finite source effects.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Characterization of the Nucleus, Morphology, and Activity of Interstellar Comet 2I/Borisov by Optical and Near-infrared GROWTH, Apache Point, IRTF, ZTF, and Keck Observations

We present visible and near-infrared (NIR) photometric and spectroscopic observations of interstellar object (ISO) 2I/Borisov taken from 2019 September 10 to 2019 December 20 using the GROWTH, the Apache Point Observatory Astrophysical Research Consortium 3.5 m, and the NASA Infrared Telescope Facility 3.0 m combined with pre- and postdiscovery observations of 2I obtained by the Zwicky Transient Facility from 2019 March 17 to 2019 May 5. Comparison with imaging of distant solar system comets shows an object very similar to mildly active solar system comets with an outgassing rate of ∼10{sup 27} mol s{sup −1}. The photometry, taken in filters spanning the visible and NIR range, shows a gradual brightening trend of ∼0.03 mag day{sup −1} since 2019 September 10 UTC for a reddish object becoming neutral in the NIR. The light curve from recent and prediscovery data reveals a brightness trend suggesting the recent onset of significant H{sub 2}O sublimation with the comet being active with super volatiles such as CO at heliocentric distances >6 au consistent with its extended morphology. Using the advanced capability to significantly reduce the scattered light from the coma enabled by high-resolution NIR images from Keck adaptive optics taken on 2019 October 4, we estimate a diameter for 2I’s nucleus of ≲1.4 km. We use the size estimates of 1I/’Oumuamua and 2I/Borisov to roughly estimate the slope of the ISO size distribution, resulting in a slope of ∼3.4 ± 1.2, similar to solar system comets and bodies produced from collisional equilibrium.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

WIYN Open Cluster Study. LXXXI. Caught in the Act? The Peculiar Red Giant NGC 2243-W2135

High-dispersion spectra for giants through turnoff stars in the Li 6708 Å region have been obtained and analyzed in the old, metal-deficient open cluster, NGC 2243. When combined with high-dispersion data from other surveys, the cluster is found to contain a uniquely peculiar star at the luminosity level of the red clump. The giant is the reddest star at its luminosity, exhibits variability at a minimum 0.1 mag level on a timescale of days, is a single-lined, radial-velocity variable, and has vsin i between 35 and 40 km s{sup −1}. In sharp contrast with the majority of the red giant cluster members, the star has a detectable Li abundance, potentially as high or higher than other giants observed to date while at or just below the boundary normally adopted for Li-rich giants. The observed anomalies may be indicators of the underlying process by which the giant has achieved its unusual Li abundance, with a recent mass transfer episode being the most probable within the currently limited constraints.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

HD 191939: Three Sub-Neptunes Transiting a Sun-like Star Only 54 pc Away

We present the discovery of three sub-Neptune-sized planets transiting the nearby and bright Sun-like star HD 191939 (TIC 269701147, TOI 1339), a K {sub s} = 7.18 mag G8 V dwarf at a distance of only 54 pc. We validate the planetary nature of the transit signals by combining 5 months of data from the Transiting Exoplanet Survey Satellite with follow-up ground-based photometry, archival optical images, radial velocities, and high angular resolution observations. The three sub-Neptunes have similar radii (R{sub b}=3.42{sub −0.11}{sup +0.11}, R{sub c}=3.23{sub −0.11}{sup +0.11}, and R{sub d}=3.16{sub −0.11}{sup +0.11} R{sub ⊕}), and their orbits are consistent with a stable, circular, and coplanar architecture near mean-motion resonances of 1:3 and 3:4 (P {sub b} = 8.88, P {sub c} = 28.58, and P {sub d} = 38.35 days). The HD 191939 system is an excellent candidate for precise mass determinations of the planets with high-resolution spectroscopy due to the host star’s brightness and low chromospheric activity. Moreover, the system’s compact and near-resonant nature can provide an independent way to measure planetary masses via transit timing variations while also enabling dynamical and evolutionary studies. Finally, as a promising target for multiwavelength transmission spectroscopy of all three planets’ atmospheres, HD 191939 can offer valuable insight into multiple sub-Neptunes born from a protoplanetary disk that may have resembled that of the early Sun.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Characterization of the Atmosphere of Super-Earth 55 Cancri e Using High-resolution Ground-based Spectroscopy

The nearby super-Earth 55 Cnc e orbits a bright (V = 5.95 mag) star with a period of -18 hr and a mass of -8M {sub ⊕}. Its atmosphere may be water-rich and have a large-scale height; though, attempts to characterize it have yielded ambiguous results. Here we present a sensitive search for water and TiO in its atmosphere at high spectral resolution using the Gemini North telescope and the GRACES spectrograph. We combine observations with previous observations from Subaru and CFHT, improving the constraints on the presence of water vapor. We adopt parametric models with an updated planet radius based on recent measurements, and use a cross-correlation technique to maximize sensitivity. Our results are consistent with atmospheres that are cloudy or contain minimal amounts of water and TiO. Using these parametric models, we rule out a water-rich atmosphere (VMR ≥ 0.1%) with a mean molecular weight of ≤ 15 g mol{sup -1} at a 3σ confidence level, improving on the previous limit by a significant margin. For TiO, we rule out a mean molecular weight of ≤ 5 g mol{sup -1} with a 3σ confidence level for a VMR greater than 10{sup -8}; for a VMR of greater than 10{sup -7}, the limit rises to a mean molecular weight of ≤ 10 g mol{sup -1}. We can rule out low mean-molecular-weight chemical equilibrium models both including and excluding TiO/VO at very high confidence levels (>10σ). Overall, our results are consistent with an atmosphere with a high mean molecular weight and/or clouds, or no atmosphere.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

A High Angular Resolution Survey of Massive Stars in Cygnus OB2: JHK Adaptive Optics Results from the Gemini Near-Infrared Imager

We present results of a high angular resolution survey of massive OB stars in the Cygnus OB2 association that we conducted with the Near-Infrared Imager camera and ALTAIR adaptive optics system of the Gemini North telescope. We observed 74 O- and early-B-type stars in Cyg OB2 in the JHK infrared bands in order to detect binary and multiple companions. The observations are sensitive to equal-brightness pairs at separations as small as [[Formula]], and progressively fainter companions are detectable out to △K=9 mag at a separation of 2″. This faint contrast limit due to read noise continues out to 10″ near the edge of the detector. We assigned a simple probability of chance alignment to each companion based upon its separation and magnitude difference from the central target star and upon areal star counts for the general star field of Cyg OB2. Companion stars with a field membership probability of less than 1% are assumed to be physical companions. This assessment indicates that 47% of the targets have at least one resolved companion that is probably gravitationally bound. Including known spectroscopic binaries, our sample includes 27 binary, 12 triple, and 9 systems with 4 or more components. These results confirm studies of high-mass stars in other environments that find that massive stars are born with a high-multiplicity fraction. The results are important for the placement of the stars in the Hertzsprung–Russell diagram, the interpretation of their spectroscopic analyses, and for future mass determinations through measurement of orbital motion.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Mathematical Underpinnings of the Multiwavelength Structure of the Tip of the Red Giant Branch

We consider the application of the tip of the red giant branch (TRGB) in the optical and in the near-infrared for the determination of distances to nearby galaxies. We analyze ACS VI (F555W and F814W) data and self-consistently cross-calibrate WFC3-IR JH (F110W and F120W) data using an absolute magnitude calibration of M {sub I} = −4.05 mag as determined in the Large Magellanic Cloud using detached eclipsing binary star geometric parallaxes. We demonstrate how the optical and near-infrared calibrations of the TRGB method are mathematically self-consistent, and illustrate the mathematical basis and relations among these multiwavelength calibrations. We go on to present a method for determining the reddening, extinction, and the true modulus to the host galaxy using multiwavelength data. The power of the method is that with high-precision data, the reddening can be determined using the TRGB stars themselves, and decreases the systematic (albeit generally small) uncertainty in distance due to reddening for these halo stars.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

SCExAO/CHARIS Near-infrared Integral Field Spectroscopy of the HD 15115 Debris Disk

We present new, near-infrared (1.1–2.4 μm) high-contrast imaging of the debris disk around HD 15115 with the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system coupled with the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS). The SCExAO/CHARIS resolves the disk down to ρ ∼ 0.″2 (r {sub proj} ∼ 10 au), a factor of ∼3–5 smaller than previous recent studies. We derive a disk position angle of PA ∼ 279.°4–280.°5 and an inclination of i ∼ 85.°3–86.2.°. While recent SPHERE/IRDIS imagery of the system could suggest a significantly misaligned two-ring disk geometry, CHARIS imagery does not reveal conclusive evidence for this hypothesis. Moreover, optimizing models of both one- and two-ring geometries using differential evolution, we find that a single ring having a Hong-like scattering phase function matches the data equally well within the CHARIS field of view (ρ ≲ 1″). The disk’s asymmetry, well evidenced at larger separations, is also recovered; the west side of the disk appears, on average, around 0.4 mag brighter across the CHARIS bandpass between 0.″25 and 1″. Comparing Space Telescope Imaging Spectrograph (STIS) 50CCD optical photometry (2000–10500 Å) with CHARIS near-infrared photometry, we find a red (STIS/50CCD−CHARIS broadband) color for both sides of the disk throughout the 0.″4–1″ region of overlap, in contrast to the blue color reported at similar wavelengths for regions exterior to ∼2″. Further, this color may suggest a smaller minimum grain size than previously estimated at larger separations. Finally, we provide constraints on planetary companions and discuss possible mechanisms for the observed inner disk flux asymmetry and color.

79 ASTRONOMY AND ASTROPHYSICS↗