Abstract
Understanding the physical processes sculpting the appearance of young gas-giant planets is complicated by degeneracies confounding effective temperature, surface gravity, cloudiness, and ...chemistry. To enable more detailed studies, spectroscopic observations covering a wide range of wavelengths are required. Here we present the first L-band spectroscopic observations of HR 8799 d and e and the first low-resolution wide-bandwidth L-band spectroscopic measurements of HR 8799 c. These measurements were facilitated by an upgraded LMIRCam/ALES instrument at the Large Binocular Telescope, together with a new apodizing phase plate coronagraph. Our data are generally consistent with previous photometric observations covering similar wavelengths, yet there exists some tension with narrowband photometry for HR 8799 c. With the addition of our spectra, each of the three innermost observed planets in the HR 8799 system has had its spectral energy distribution measured with integral field spectroscopy covering ∼0.9–4.1
μ
m. We combine these spectra with measurements from the literature and fit synthetic model atmospheres. We demonstrate that the bolometric luminosity of the planets is not sensitive to the choice of model atmosphere used to interpolate between measurements and extrapolate beyond them. Combining luminosity with age and mass constraints, we show that the predictions of evolutionary models are narrowly peaked for effective temperature, surface gravity, and planetary radius. By holding these parameters at their predicted values, we show that more flexible cloud models can provide good fits to the data while being consistent with the expectations of evolutionary models.
This paper presents late-time near-infrared and Spitzer mid-infrared photometric and spectroscopic observations of warm dust in the Type IIn SN 2005ip in NGC 2906. The spectra show evidence for two ...dust components with different temperatures. Spanning the peak of the thermal emission, these observations provide strong constraints on the dust mass, temperature, and luminosity, which serve as critical diagnostics for disentangling the origin and heating mechanism of each component. The results suggest that the warmer dust has a mass of ~5 X 10--4 M , originates from newly formed dust in the ejecta, or possibly the cool, dense shell, and is continuously heated by the circumstellar interaction. By contrast, the cooler component likely originates from a circumstellar shock echo that forms from the heating of a large, pre-existing dust shell ~0.01-0.05 M by the late-time circumstellar interaction. The progenitor wind velocity derived from the blue edge of the He I 1.083 Delta *mm P Cygni profile indicates a progenitor eruption likely formed this dust shell ~100 years prior to the supernova explosion, which is consistent with a Luminous Blue Variable progenitor star.
To characterize the spectrum of Earth viewed as an extrasolar planet, we observed the spatially integrated near-infrared (0.7-2.4 km) reflection spectrum of Earth via the dark side of the Moon ...(earthshine). After contributions from the Sun, Moon, and local atmosphere were removed, the resulting spectrum was fitted with a simple model of the reflectivity of Earth. The best model fit is dominated by the reflection spectrum of the atmosphere above medium-altitude water clouds, with lesser contributions from high-altitude ice clouds and from the ground. The spectral features seen are H sub(2)O (six strong band structures from 0.7 to 2.0 km), CO sub(2) (six moderate-strength features from 1.4 to 2.1 km), O sub(2) (two moderate-strength features at 0.76 and 1.26 km), and several weak CH sub(4) features. Interpreted as a spectrum of an extrasolar planet, we would confidently conclude that this is a habitable planet, based on the presence of strong water bands. Furthermore, the simultaneous presence of oxygen and methane is a strong indicator of biological activity. We might also conclude that the planet is geologically active, based on the presence of CO sub(2), water, and a dynamic atmosphere (inferred from cirrus clouds, cumulus clouds, and clear-air fractions in our model fit). This suggests that it would be valuable for the Terrestrial Planet Finder-Coronagraph (TPF-C) mission to include near-infrared spectroscopy capability. On the basis of the present work, we suggest that future long-term monitoring of the earthshine would allow us to discern how the globally integrated spectrum changes with planet rotation, cloud cover, and seasons.
Abstract
We present the first
L
-band (2.8–4.1
μ
m) spectroscopy of
κ
Andromedae b, a ∼20
M
Jup
companion orbiting at 1″ projected separation from its B9-type stellar host. We combine our Large ...Binocular Telescope (LBT) Arizona Lenslets for Exoplanet Spectroscopy (ALES) integral field spectrograph data with measurements from other instruments to analyze the atmosphere and physical characteristics of
κ
And b. We report a discrepancy of ∼20% (2
σ
) in the
L
′ flux of
κ
And b when comparing to previously published values. We add an additional
L
′ constraint using an unpublished imaging data set collected in 2013 using the LBT Interferometer/LMIRCam, the instrument in which the ALES module has been built. The LMIRCam measurement is consistent with the ALES measurement, both suggesting a fainter
L
-band scaling than previous studies. The data, assuming the flux scaling measured by ALES and LMIRCam imaging, are well fit by an L3-type brown dwarf. Atmospheric model fits to measurements spanning 0.9–4.8
μ
m reveal some tension with the predictions of evolutionary models, but the proper choice of cloud parameters can provide some relief. In particular, models with clouds extending to very low pressures composed of grains ≤1
μ
m appear to be necessary. If the brighter
L
′ photometry is accurate, there is a hint that subsolar metallicity may be required.
We report the discovery of 87 new T dwarfs uncovered with the Wide-field Infrared Survey Explorer (WISE) and 3 brown dwarfs with extremely red near-infrared colors that exhibit characteristics of ...both L and T dwarfs. Two of the new T dwarfs are likely binaries with L7 + or - 1 primaries and mid-type T secondaries. In addition, our follow-up program has confirmed 10 previously identified T dwarfs and 4 photometrically selected L and T dwarf candidates in the literature. This sample, along with the previous WISE discoveries, triples the number of known brown dwarfs with spectral types later than T5. Using the WISE All-Sky Source Catalog we present updated color-color and color-type diagrams for all the WISE-discovered T and Y dwarfs. The substantial increase in the number of known late-type T dwarfs provides a population that will be used to test models of cold atmospheres and star formation. The coolest WISE-discovered brown dwarfs are the closest of their type and will remain the only sample of their kind for many years to come.
Near-infrared photometric observations of the Type IIn supernova (SN) 2005ip in NGC 2906 reveal large fluxes (>1.3 mJy) in the Ks -band over more than 900 days. While warm dust can explain the ...late-time Ks -band emission of SN 2005ip, the nature of the dust heating source is ambiguous. Shock heating of pre-existing dust by post-shocked gas is unlikely because the forward shock is moving too slowly to have traversed the expected dust-free cavity by the time observations first reveal the Ks emission. While an infrared light echo model correctly predicts a near-infrared luminosity plateau, heating dust to the observed temperatures of ~ 1400-1600 K at a relatively large distance from the supernova (1018 cm) requires an extraordinarily high early supernova luminosity (~1 X 1011 L ). The evidence instead favors condensing dust in the cool, dense shell between the forward and reverse shocks. Both the initial dust temperature and the evolutionary trend toward lower temperatures are consistent with this scenario. We infer that radiation from the circumstellar interaction heats the dust. While this paper includes no spectroscopic confirmation, the photometry is comparable to other supernovae that do show spectroscopic evidence for dust formation. Observations of dust formation in supernovae are sparse, so these results provide a rare opportunity to consider supernovae Type IIn as dust sources.
Abstract
Multiwavelength 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 submillimeter (Atacama Large Millimeter/submillimeter Array (ALMA); 1.3 mm,
12
CO) and near-infrared (Spectro-polarimetric High-contrast Exoplanet Research; 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 the L/M-band Infrared Camera 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) had been previously claimed. The nature of a second innermost planet candidate (
ρ
= 0.″16, PA = 203.°9) cannot 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
M
Jup
at 0.″3 (49 au) down to 3–4
M
Jup
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 southeast/northwest 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.
We present 2.9-4.1 m 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. 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 extrasolar 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 0.07 Gyr) of the system compared to the older age ( Gyr) determined with gyrochronology in order to address the luminosity discrepancy.
ABSTRACT In our effort to complete the census of low-mass stars and brown dwarfs in the immediate solar neighborhood, we present spectra, photometry, proper motions, and distance estimates for 42 ...low-mass star and brown dwarf candidates discovered by the Wide-field Infrared Survey Explorer (WISE). We also present additional follow-up information on 12 candidates selected using WISE data but previously published elsewhere. The new discoveries include 15 M dwarfs, 17 L dwarfs, five T dwarfs, and five objects of other types. Among these discoveries is a newly identified "unusually red L dwarf" (WISE J223527.07 + 451140.9), four peculiar L dwarfs whose spectra are most readily explained as unresolved L + T binary systems, and a T9 dwarf (WISE J124309.61 + 844547.8). We also show that the recently discovered red L dwarf WISEP J004701.06 + 680352.1 may be a low-gravity object and hence young and potentially low-mass (< 25 MJup).
We present reliable measurements of the metallicity distribution function (MDF) at different points along the tidal stream of the Sagittarius (Sgr) dwarf spheroidal (dSph) galaxy, based on ...high-resolution, echelle spectroscopy of candidate M giant members of the Sgr system. The Sgr MDF is found to evolve significantly from a median Fe/H similar to -0.4 in the core to similar to - 1.1 dex over a Sgr leading arm length representing similar to 2.5-3.0 Gyr of dynamical (i.e., tidal stripping) age. This is direct evidence that there can be significant chemical differences between current dSph satellites and the bulk of the stars they have contributed to the halo. Our results suggest that Sgr experienced a significant change in binding energy over the past several glgayears, which has substantially decreased its tidal boundary across a radial range over which there must have been a significant metallicity gradient in the progenitor galaxy. By accounting for MDF variation along the debris arms, we approximate the MDF Sgr would have had several gigayears ago. We also analyze the MDF of a moving group of M giants we previously discovered toward the north Galactic cap. These objects have the opposite radial velocities to the infalling Sgr leading arm stars there, and we propose that most of them represent Sgr trailing arm stars overlapping the Sgr leading arm in this part of the sky. If so, these trailing arm stars further demonstrate the strong MDF evolution within the Sgr stream.
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