H-band Emission Research Articles

Near-infrared Imaging of a Spiral in the CQ Tau Disk

Abstract We present L′-band Keck/NIRC2 imaging and H-band Subaru/AO188+HiCIAO polarimetric observations of the CQ Tau disk with a new spiral arm. Apart from the spiral feature, our observations could not detect any companion candidates. We traced the spiral feature from the r 2-scaled High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) polarimetric intensity image and the fitted result is used for forward modeling to reproduce the ADI-reduced NIRC2 image. We estimated the original surface brightness after throughput correction in the L′ band to be ∼126 mJy arcsec−2 at most. We suggest that the grain temperature of the spiral may be heated up to ∼200 K in order to explain both of the H- and L′-band results. The H-band emission at the location of the spiral originates from the scattering from the disk surface while both scattering and thermal emission may contribute to the L′-band emission. If the central star is only the light source of scattered light, the spiral emission at the L′ band should be thermal emission. If an inner disk also acts as the light source, the scattered light and the thermal emission may equally contribute to the L′-band spiral structure.

Imaging the 44 au Kuiper Belt Analog Debris Ring around HD 141569A with GPI Polarimetry

Abstract We present the first polarimetric detection of the inner disk component around the pre-main-sequence B9.5 star HD 141569A. Gemini Planet Imager H-band (1.65 μm) polarimetric differential imaging reveals the highest signal-to-noise ratio detection of this ring yet attained and traces structure inward to 0.″25 (28 au at a distance of 111 pc). The radial polarized intensity image shows the east side of the disk, peaking in intensity at 0.″40 (44 au) and extending out to 0.″9 (100 au). There is a spiral arm–like enhancement to the south, reminiscent of the known spiral structures on the outer rings of the disk. The location of the spiral arm is coincident with 12CO J = 3–2 emission detected by ALMA and hints at a dynamically active inner circumstellar region. Our observations also show a portion of the middle dusty ring at ∼220 au known from previous observations of this system. We fit the polarized H-band emission with a continuum radiative transfer Mie model. Our best-fit model favors an optically thin disk with a minimum dust grain size close to the blowout size for this system, evidence of ongoing dust production in the inner reaches of the disk. The thermal emission from this model accounts for virtually all of the far-infrared and millimeter flux from the entire HD 141569A disk, in agreement with the lack of ALMA continuum and CO emission beyond ∼100 au. A remaining 8–30 μm thermal excess a factor of ∼2 above our model argues for an as-yet-unresolved warm innermost 5–15 au component of the disk.

A Physical Basis for the H-band Blue-edge Velocity and Light-curve Shape Correlation in Context of Type Ia Supernova Explosion Physics

Abstract Our recent work demonstrates a correlation between the high-velocity blue edge, v edge, of the iron-peak Fe/Co/Ni H-band emission feature and the optical light-curve (LC) shape of normal, transitional and subluminous SNe Ia. We explain this correlation in terms of SN Ia physics. v edge corresponds to the sharp transition between the complete and incomplete silicon burning regions in the ejecta. It measures the point in velocity space where the outer 56Ni mass fraction, X Ni, falls to the order of 0.03–0.10. For a given 56Ni mass, M(56Ni), v edge is sensitive to the specific kinetic energy E kin(M(56Ni)/M WD) of the corresponding region. Combining v edge with LC parameters (i.e., s BV , in B and V) allows us to distinguish between explosion scenarios. The correlation between v edge and light-curve shape is consistent with explosion models near the Chandrasekhar limit. However, the available sub-M Ch WD explosion model based on SN 1999by exhibits velocities that are too large to explain the observations. Finally, the subluminous SN 2015bo exhibits signatures of a dynamical merger of two WDs demonstrating diversity among explosion scenarios at the faint end of the SNe Ia population.

Carnegie Supernova Project-II: Using Near-infrared Spectroscopy to Determine the Location of the Outer 56Ni in Type Ia Supernovae∗

Abstract We present the H-band wavelength region of 37 postmaximum light near-infrared spectra of three normal, nine transitional, and four subluminous type Ia supernovae (SNe Ia), extending from +5 days to +20 days relative to the epoch of B-band maximum. We introduce a new observable, the blue-edge velocity, v edge, of the prominent Fe/Co/Ni-peak H-band emission feature, which is quantitatively measured. The v edge parameter is found to decrease over subtype ranging from around −14,000 km s−1 for normal SNe Ia, to −10,000 km s−1 for transitional SNe Ia, down to −5000 km s−1 for the subluminous SNe Ia. Furthermore, inspection of the +10 ± 3 days spectra indicates that v edge is correlated with the color-stretch parameter, s BV , and hence with peak luminosity. These results follow the previous findings that brighter SNe Ia tend to have 56Ni located at higher velocities as compared to subluminous objects. As v edge is a model-independent parameter, we propose it can be used in combination with traditional observational diagnostics to provide a new avenue to robustly distinguish between leading SNe Ia explosion models.

The Broadband and Spectrally Resolved H-band Eclipse of KELT-1b and the Role of Surface Gravity in Stratospheric Inversions in Hot Jupiters

Abstract We present a high-precision H-band emission spectrum of the transiting brown dwarf KELT-1b, which we spectrophotometrically observed during a single secondary eclipse using the LUCI1 multiobject spectrograph on the Large Binocular Telescope. Using a Gaussian-process regression model, we are able to clearly measure the broadband eclipse depth as ΔH = 1418 ± 94 ppm. We are also able to spectrally resolve the H band into five separate wave channels and measure the eclipse spectrum of KELT-1b at R ≈ 50 with an average precision of ±135 ppm. We find that the day side has an average brightness temperature of 3250 ± 50 K, with significant variation as a function of wavelength. Based on our observations and previous measurements of KELT-1b’s eclipse at other wavelengths, we find that KELT-1b’s day side appears identical to an isolated 3200 K brown dwarf, and our modeling of the atmospheric emission shows a monotonically decreasing temperature–pressure profile. This is in contrast to hot Jupiters with similar day-side brightness temperatures near 3000 K, all of which appear to be either isothermal or possess a stratospheric temperature inversion. We hypothesize that the lack of an inversion in KELT-1b is due to its high surface gravity, which we argue could be caused by the increased efficiency of cold-trap processes within its atmosphere.

SPIRAL STRUCTURE AND DIFFERENTIAL DUST SIZE DISTRIBUTION IN THE LkHα 330 DISK

ABSTRACT Dust trapping accelerates the coagulation of dust particles, and, thus, it represents an initial step toward the formation of planetesimals. We report H-band (1.6 μm) linear polarimetric observations and 0.87 mm interferometric continuum observations toward a transitional disk around LkHα 330. As a result, a pair of spiral arms were detected in the H-band emission, and an asymmetric (potentially arm-like) structure was detected in the 0.87 mm continuum emission. We discuss the origin of the spiral arm and the asymmetric structure and suggest that a massive unseen planet is the most plausible explanation. The possibility of dust trapping and grain growth causing the asymmetric structure was also investigated through the opacity index (β) by plotting the observed spectral energy distribution slope between 0.87 mm from our Submillimeter Array observation and 1.3 mm from literature. The results imply that grains are indistinguishable from interstellar medium-like dust in the east side ( ) but are much smaller in the west side , indicating differential dust size distribution between the two sides of the disk. Combining the results of near-infrared and submillimeter observations, we conjecture that the spiral arms exist at the upper surface and an asymmetric structure resides in the disk interior. Future observations at centimeter wavelengths and differential polarization imaging in other bands (Y–K) with extreme AO imagers are required to understand how large dust grains form and to further explore the dust distribution in the disk.

Optical properties of H-band emission in single heterojunctions

The optical properties of n- and p-type, modulation- and delta-doped Al0.35Ga0.65As–GaAs single heterojunctions (SHs) have been studied by means of low-temperature photoluminescence measurement and self-consistent calculation. A very strong, broad, and asymmetric H-band emission was observed only in p-type delta-doped SH. When the optical excitation intensity increases by two orders of magnitude a redshift as large as 27 meV is observed in the H-band emission energy. The large redshift observed is attributed to both inefficiency of screening in the two-dimensional-hole gas and effective band-gap renormalization. It was also observed that the H-band emission strongly depends upon the doping type (n or p type) and doping profile (modulation doping or delta doping).

H-band emission in single heterojunctions

We report on the observation of a very strong, broad and asymmetric H-band photoluminescence (PL) spectrum in silica δ-doped p-type Al0.35Ga0.65As–GaAs heterojunctions (SHs). Doping type (n- or p-type) dramatically changes the H-band PL emission. When optical excitation intensity increases by two orders of magnitude, a redshift of H-band in the δ-doped p-type SH is as large as 27meV. The results of self-consistent calculation of coupled Schrödinger and Poisson equations and PL analysis indicate that the H-band originates from effective band-gap renormalization due to two-dimensional hole-gas.

Impurity-related emission in the photoluminescence from p-type modulation doped Al 1− xGa xAs/GaAs heterostructures

We investigated low-temperature photoluminescence from p-type Al 1− x Ga x As/GaAs heterostructures. Our measurements show that at low laser power the H-band emission disappears and is replaced by a line resulting from the recombination of donor-bound electrons with two-dimensional holes. The properties of both lines are explained based on the results of detailed band structure calculations. Measurements in magnetic fields enabled us to examine the binding energy of donor in parallel electric and magnetic fields.

Investigation of the H-band radiation in GaAs/AlGaAs heterostructures by photoluminescence and optically detected cyclotron resonance measurements

With photoluminescence and optically detected cyclotron resonance measurements, we investigate broad emission bands, so-called H-bands in GaAs/AlGaAs heterostructures. The broad bands are due to the recombination between two-dimensional electrons in the interface notch and spatially separated holes in a GaAs layer. From excitation energy dependence of the radiation intensity of the H-band, transfer of the photoexcited holes from the AlGaAs to the GaAs is found to be important, when the excitation energy exceeds the band-gap energy of the AlGaAs. Under the excitation conditions, the observed peak positions of the H-band are highly dominated by the direct recombination in the real space between the two-dimensional electrons and the holes. By using the optically detected cyclotron resonance measurements, we can assign the H-band emission peak, when the H-band peak overlaps with the other emission peak.