arXiv subjects

Haomiao Huang

Publications and source records attributed to Haomiao Huang.

6 recordsLinked to original sources

arXiv2026

A Stable Mineral Fingerprint in the Fading Warm Debris Disk around HD 15407A

Extreme debris disks provide time-domain probes of rocky planet assembly after giant impacts. We compare Spitzer and JWST spectra of the warm debris disk around HD 15407A, obtained 14.95 yr apart. Across 6-25$\mu$m, the stellar-subtracted mid-infrared excess declined by $14.0\pm1.2$%, while the mineral fingerprint is nearly unchanged. Within the adopted common reduced mineral basis, Mg-rich pyroxene dominates the normalized fitted mineral weights at about 65%, while silica and forsterite contribute about 22-23% and 12-13%, respectively. In both epochs, about 93-94% of the fitted mineral weight is carried by 5.0$\mu$m grains. The fitted optically thin surface-component amplitude drops by 32%, consistent with reduced mineral-emitting flux from the disk surface rather than the appearance of a new dust composition. A simple collisional-cascade guide fitted to the IRAS-to-JWST multi-epoch ratios gives $t_c=87^{+17}_{-12}$ yr, for which the Spitzer-normalized dust-excess ratio reaches 0.5 after one $t_c$. HD 15407A is consistent with an evolved post-impact reservoir with limited recent supply of very small grains: its rocky mineral fingerprint has remained stable since at least 2008, while its warm mineral-emitting flux is gradually fading over several hundred years.

astro-ph.EP↗

arXiv2026

A Search for Variability of Ultracool Dwarfs with the Zwicky Transient Facility

Rotationally modulated photometric variability of ultracool dwarfs encodes key information about cloud structure and temperature contrasts. Large homogeneous optical datasets are crucial for linking atmospheric heterogeneity to fundamental parameters such as rotation, mass, and age. We present a search for rotation periods in ultracool dwarfs using Zwicky Transient Facility (ZTF) optical light curves. By propagating the coordinates to the ZTF epoch and applying Lomb-Scargle analysis, we identified 226 periodic variables, including 32 robust detections and 194 tentative cases. Among the robust detections, 12 have no previously published periods, while 20 have literature counterparts, most of which are consistent with the published values. Most robust detections are M dwarfs, reflecting the optical sensitivity limits of ZTF. We find a trend of decreasing periods toward later spectral types in relatively old dwarfs (> 100 Myr), suggesting faster rotation for late-M types than for mid-M types. The age-period relation of our sample is broadly consistent with angular-momentum-conservation models at higher-mass regime of brown dwarfs, consistent with the M-dwarf bias of our catalog. Many additional candidates remain to be confirmed due to sparse sampling or low S/N. Future high-cadence, multi-wavelength monitoring and systematic mining of ZTF and upcoming surveys will be crucial for validating these periods, extend sensitivity to later (L/T) types, and better connect rotation with cloud physics across the stellar-substellar boundary.

astro-ph.SR↗

arXiv2026

SPHEREx Ultracool Dwarf spectrophotometric Atlas (SUDA): Atmospheric and Fundamental Parameters of Ultracool Dwarfs

We present the SPHEREx Ultracool Dwarf spectrophotometric Atlas (SUDA), a homogeneous sample of 1675 field ultracool dwarfs with continuous 0.75--5~$\mu$m spectrophotometry from SPHEREx Quick Release 2 (QR2). Using the SAND and ATMO2020++ atmospheric grids, we derive atmospheric parameters, compute bolometric luminosities ($L_{\rm bol}$), and combine $T_{\mathrm{eff}}$ and radii with evolutionary tracks to estimate masses, ages, and evolutionary $\log g$. For sources at 1700--2500~K, spectroscopic $\log g$ is systematically lower than evolutionary $\log g$, with a median offset of $\sim$1.05~dex, likely driven primarily by cloud-related model uncertainties. We further construct an empirical atlas by binning the measurements in $T_{\mathrm{eff}}$ and evolutionary $\log g$, producing 57 spectrophotometric templates spanning $T_{\mathrm{eff}}\simeq700$--3000~K. Molecular indices trace a coherent atmospheric sequence: H$_2$O and CH$_4$ indices strengthen toward lower $T_{\mathrm{eff}}$, while CO and CO$_2$ indices increase below $\sim$1500~K and turn over near $\sim$1000~K. Model comparisons indicate that CO$_2$ index is more sensitive to metallicity than gravity at $T_{\mathrm{eff}}\sim800$--1200~K. SUDA provides a reference sample linking 0.75--5~$\mu$m spectrophotometric morphology to atmospheric and evolutionary trends in ultracool dwarfs.

astro-ph.SR↗

arXiv2025

A Morpho-kinematic Study of Galactic High-ADF PNe Based on the VLT/UVES Deep Spectroscopy

We report detailed analyses of deep, high-resolution spectra of three Galactic planetary nebulae (PNe) with high abundance discrepancy factors (ADFs), Hf2-2, M1-42 and NGC6153, obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES) on the 8.2m Very Large Telescope (VLT). These spectra were carefully reduced, including rigorous absolute flux calibration, yielding detections of ~410-800 emission lines in each PN. Plasma diagnostics and abundance calculations were critically performed using nebular lines. In all three PNe, the electron temperatures derived using the collisionally excited lines (CELs) are higher than those yielded by the HI Balmer and Paschen jumps, while the temperatures yielded by the OII and NII optical recombination lines (ORLs) are very low, <2000 K, indicating that the heavy-element ORLs probe cold nebular regions. The ORL abundances of N, O and Ne are systematically higher than the corresponding CEL values, confirming high ADFs in the three objects. Position-velocity (PV) diagrams were created, and spatio-kinematical studies show that CELs come from the outer nebular regions, while the ORL-emitting regions are close to nebular center. Additionally, the velocity indicated by CEL line-splitting decreases with ionization potential, which was not obvious in ORLs. These spatial and kinematic differences support two distinct components of ionized gas: a cold, metal-rich component and a warmer component with normal metallicity. Heavy elements are strongly enriched in the cold gas, while its H^+ fraction is low but still produces significant HI emission, affecting CEL abundance estimates.

astro-ph.SR↗

arXiv2025

GTC/OSIRIS Deep Spectroscopy of Galactic Compact Planetary Nebulae: PNG048.5+04.2 and PNG068.7+14.8

We report deep long-slit spectroscopy of two Galactic compact planetary nebulae (PNe), PNG048.5+04.2 and PNG068.7+14.8, obtained using the 10.4m Gran Telescopio Canarias (GTC). These spectra cover a broad wavelength range of ~3630-10370 A, enabling detection of numerous emission lines critical for nebular analysis, including [O II] 3727 and [O III] 4363 in the blue and [S III] 6312,9069 in the red. Also detected in the spectrum of PNG068.7+14.8 are broad C III and C IV lines probably due to stellar emission, indicating that the central star of this PN is [WC]-type. These GTC optical-IR spectra were analyzed in details in conjunction with the archival Spitzer/IRS mid-IR spectra, and elemental abundances of the two PNe determined. Photoionization models were established for the two PNe using CLOUDY, based on the ratios of line fluxes measured from the GTC optical-NIR spectra. Our best photoionization modeling, in combination with state-of-the-art post-AGB evolutionary model tracks, shows that both PNe evolved from low-mass progenitors (<2 M_sun) with relatively young ages (<3 Gyr), although their central cores are probably in different evolutionary stages - the central star of PNG068.7+14.8 is still in the process of heating up, while that of PNG048.5+04.2 has already entered the white dwarf cooling track. A comparison with AGB model predictions also constrains the progenitors of both PNe to be of low masses. Moreover, the two PNe are in line with the radial oxygen gradients exhibited by the Galactic PN populations, using the most up-to-date distances.

astro-ph.GA↗

arXiv2024

GTC Spectroscopic Surveys of Planetary Nebulae in the Milky Way and M31

We report spectroscopic surveys of planetary nebulae (PNe) in the Milky Way and Andromeda (M31), using the 10.4-m Gran Telescopio Canarias (GTC). The spectra are of high quality and cover the whole optical range, mostly from 3650 Å to beyond 1 micron, enabling detection of nebular emission lines critical for spectral analysis as well as photoionization modeling. We obtained GTC spectra of 24 compact (angular diameter <5 arcsec) PNe located in the Galactic disk, ~3-20 kpc from the Galactic centre, and can be used to constrain stellar evolution models and derive radial abundance gradients of the Milky Way. We have observed 30 PNe in the outer halo of M31 using the GTC. These halo PNe are uniformly metal-rich and probably all evolved from low-mass stars, consistent with the conjecture that they all formed from the metal-rich gas in M31 disk but displaced to their present locations due to galaxy interactions.

astro-ph.GA↗