arXiv subjects

Sunho Jin

Publications and source records attributed to Sunho Jin.

16 recordsLinked to original sources

arXiv2026

SOLO: wide-field asteroid light curve monitoring system for SPHEREx

We present the Solar system Objects Light curve Observatory (SOLO), a wide-field, high-cadence optical survey system designed to obtain absolutely calibrated asteroid light curves, converted to the Gaia G-band photometric system, in support of the SPHEREx Solar System Object Catalog (SSOC). SOLO was installed at the Sierra Remote Observatories (SRO) in California, USA, in July 2025 and is optimized for continuous, multi-night monitoring of asteroid brightness variations. We describe the system configuration, remote operation, and data reduction pipeline, and evaluate its optical and photometric performance using commissioning data. SOLO achieves stable photometric calibration across the 11.6 deg^2 field of view and reaches a 10-sigma limiting magnitude of G ~ 17.5 for a 180 sec exposure. Sample asteroid light curves obtained over multiple nights demonstrate consistent absolute photometry at the same rotational phase, validating the estimated performance. Finally, we outline the planned operational use of SOLO in connection with NASA's SPHEREx mission. Full science operations of SOLO are scheduled to begin in January 2026. Using these data, we aim to obtain on the order of 10^3 absolutely calibrated asteroid light curves per year in the Gaia G-band, which will be used to support the construction and scientific utilization of the SPHEREx SSOC.

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arXiv2026

SQUIDPOL: Seoul National University QUadruple Imaging Device for POLarimetry

We present SQUIDPOL, a low-cost, multi-channel optical imaging polarimeter that performs simultaneous linear polarization measurements using a rotating half-wave plate, a non-polarizing beam splitter, and four wire-grid filters. We show that the off-the-shelf non-polarizing beam splitter introduces measurable polarization-dependent systematics, which can bias polarimetric measurements if left uncorrected. We quantify this effect for both transmitted and reflected beams and incorporate a correction scheme into the data-analysis pipeline. On-sky validation demonstrates stable and reproducible performance, achieving a polarization accuracy of about 0.15 percent for bright polarized standard stars. Mounted on the 60-cm Ritchey-Chretien telescope (focal length 4200 mm, f/7) at the Pyeongchang Observatory of Seoul National University, SQUIDPOL provides an effective common field of view of 13.5 by 8.2 arcminutes with a pixel scale of 0.45 arcseconds per pixel and supports standard B, V, R_C, and I_C filters.

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arXiv2026

Dust Properties of the Interstellar Object 3I/ATLAS Revealed by Optical and Near-Infrared Polarimetry

We present independent polarimetric observations of the interstellar object 3I/ATLAS, including the first near-infrared polarimetric measurements. Using imaging polarimeters, we measured the degree of linear polarization from the visible RC band (0.64 {\mu}m) to the near-infrared KS band (2.25 {\mu}m), and investigated its dependence on solar phase angle (polarization phase curve; PPC) and wavelength (polarization color curve; PCC). We confirm that the PPC of 3I/ATLAS differs significantly from those of typical Solar System comets, showing an unusually large polarization amplitude. This PPC shows no significant change in the RC band across perihelion passage, despite the perihelion lying within the water snow line. This indicates that the unusual polarimetric behavior of 3I/ATLAS is unlikely to be driven by transient volatile activity, but instead reflects intrinsic optical properties of refractory dust particles. The PCC increases with wavelength over 0.6-1.2 {\mu}m and peaks at 1.5-2.0 {\mu}m, suggesting that the dominant scattering units are dust aggregates composed of submicron-sized monomers, broadly consistent with interstellar dust and solar-system cometary aggregates. Taken together, our results indicate that 3I/ATLAS preserves polarimetric properties characteristic of a primitive cometary planetesimal formed in another planetary system, with a refractory dust composition that differs from that typically observed among Solar System comets, despite sharing a similar size scale of the aggregate building blocks.

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arXiv2025

SPHEREx Pre-Perihelion Mapping of $\mathrm{H_2O}$, $\mathrm{CO_2}$, and $\mathrm{CO}$ in Interstellar Object 3I/ATLAS

From 01- to 15-Aug-2025UT, the SPHEREx spacecraft observed interstellar object 3I/ATLAS. Using $R=40-130$ spectrophotometry at $\lambda=0.7-5$ $\mu$m, light curves, spectra, and imaging of ATLAS were obtained. From these, robust detections of water gas emission at $2.7-2.8$ $\mu$m and $CO_2$ gas at $4.23-4.27$ $\mu$m plus tentative detections of $^{13}CO_2$ and $CO$ gas were found. A slightly extended $H_2O$ coma was detected, and a huge $CO_2$ atmosphere of extending out to at least $4.2 \times 10^{5}$ km was discovered. Gas production rates and 1$\sigma$ errors for $H_2O$, $^{12}CO_2$, $^{13}CO_2$, and $CO$ were $Q_{gas} = 3.2 \times 10^{26} \pm 20\%$, $1.6 \times 10^{27} \pm 10\%$, $1.3 \times 10^{25} \pm 25\%$, and $1.0 \times 10^{26} \pm 25\%$, respectively. Co-addition of all $\lambda = 1.0-1.5$ $\mu$m scattered light continuum images from produced a high SNR image consistent with an unresolved source. The scattered light lightcurve showed $\lesssim 15\%$ variability over the observation period. The absolute brightness of ATLAS at $1.0-1.5$ $\mu$m is consistent with a $< 2.5$ km radius nucleus surrounded by a 100 times brighter coma. The $1.5-4.0$ $\mu$m continuum structure shows a strong feature commensurate with water ice absorption seen in KBOs and distant comets. The observed cometary behavior of ATLAS, including its preponderance of $CO_2$ emission, lack of $CO$ output, small size, and predominance of large icy chunks of material in a flux-dominant coma is similar to the behavior of short period comet 103P/Hartley 2, the ''hyperactive comet'' flyby target of the NASA Deep Impact extended mission in 2010. This correspondence suggests that ISOs can be significantly thermally processed before ejection into the ISM, and by comparison to 1I and 2I, can be widely variable in their physical outcome.

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arXiv2025

Simulation of Impact-induced seismic shaking on asteroid (25143) Itokawa to address its resurfacing process

The surface of asteroid (25143) Itokawa shows both fresh and mature terrains, despite its short space weathering timescale of approximately 1000 years, as inferred from recent studies. Seismic shaking triggered by the impact that formed the 8-meter Kamoi crater has been proposed as a possible explanation for the diversity. This study aims to examine whether the seismic shaking induced by the impact could account for the observed spatial variations in space weathering and further constrain the internal structure of Itokawa. Assuming that the Kamoi crater was formed by a recent impact, we conducted three-dimensional seismic wave propagation simulations and applied a simplified landslide model to estimate surface accelerations and boulder displacements. Our results show that even a low-energy case (1 % of the nominal seismic energy) produces surface accelerations sufficient to destabilize the surface materials. The simulated boulder displacements are consistent with the observed distribution of space weathering degrees even on the opposite hemisphere. We estimate the seismic diffusivity to be 1000-2000 m2 s-1 and the seismic efficiency to be in the range of 5.0 x 10-8 to 5.0 x 10-7, implying that Itokawa's interior contains blocks tens of meters across and acts as a strongly scattering medium.

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arXiv2025

Optical and Near-Infrared Contemporaneous Polarimetry of C/2023 A3 (Tsuchinshan-ATLAS)

We conducted contemporaneous optical and near-infrared polarimetric and spectroscopic observations of C/2023 A3 (Tsuchinshan-ATLAS, hereafter T-A) from 2024 October 16 to December 17, covering a wide range of phase angles (20-123 deg) and wavelength (0.5-2.3 um). We paid special attention to gas contamination in the dust polarization using these data. As a result, we find the maximum polarization degree $P_max=31.21 +- 0.05 %, 33.52 +- 0.06 %, 35.12 +- 0.01 %, 37.57 +- 0.01 %, and 35.35 +- 0.01 % in the Rc-, Ic-, J-, H-, and Ks-bands, respectively. Although dust polarization shows a red slope at shorter wavelengths and can peak around 1.6 um, the phase angle at which maximum polarization occurs exhibits less dependence on wavelength (alpha_max ~ 90 deg - 95 deg). Although only a few historically bright comets, such as West, Halley, and Hale-Bopp, have undergone such extensive dust-polarization observations, our measurements are generally consistent with those of two comets that possibly originated from the Oort Cloud (West and Halley). From these results, we conjecture that the optical properties and growth processes of dust in the presolar nebula, which formed these cometary nuclei, were likely uniform.

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arXiv2024

New evidence supporting past dust ejections from active asteroid (4015) Wilson-Harrington

Context. (4015) Wilson-Harrington (hereafter, WH) was discovered as a comet in 1949 but has a dynamical property consistent with that of a near-Earth asteroid. Although there is a report that the 1949 activity is associated with an ion tail, the cause of the activity has not yet been identified. Aims. This work aims to reveal the mysterious comet-like activity of the near-Earth asteroid. Methods. We conducted new polarimetric observations of WH from May 2022 to January 2023, reanalyses of the photographic plate images taken at the time of its discovery in 1949, and dust tail simulation modelings, where the dust terminal velocity and ejection epoch are taken into account. Results. We found that this object shows polarization characteristics similar to those of low-albedo asteroids. We derived the geometric albedo ranging from pV = 0.076 +- 0.010 to pV = 0.094 +- 0.018 from our polarimetry (the values vary depending on the data used for fitting and the slope-albedo relationship coefficients). In addition, the 1949 image showed an increase in brightness around the nucleus. Furthermore, we found that the color of the tail is consistent with sunlight, suggesting that the 1949 activity is associated with dust ejection. From the dust tail analysis, ~9 x 10^5 kg of material was ejected episodically at a low velocity equivalent to or even slower than the escape velocity. Conclusions. We conclude that WH is most likely an active asteroid of main belt origin and that the activity in 1949 was likely triggered by mass shedding due to fast rotation.

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arXiv2024

Study of hydrated asteroids via their polarimetric properties at low phase angles

Context. Ch-type asteroids are distinctive among other dark asteroids in that they exhibit deep negative polarization branches (NPBs). Nevertheless, the physical and compositional properties that cause their polarimetric distinctiveness are less investigated. Aims. We aim to investigate the polarimetric uniqueness of Ch-type asteroids by making databases of various observational quantities (i.e., spectroscopic and photometric properties as well as polarimetric ones) of dark asteroids.Methods. We conducted an intensive polarimetric survey of 52 dark asteroids (including 31 Ch-type asteroids) in the R$_\mathrm{C}$-band to increase the size of polarimetric samples. The observed data are compiled with previous polarimetric, spectroscopic, and photometric archival data to find their correlations. Results. We find remarkable correlations between these observed quantities, particularly the depth of NPBs and their spectroscopic features associated with the hydrated minerals. The amplitude of the opposition effect in photometric properties also shows correlations with polarimetric and spectral properties. However, these observed quantities do not show noticeable correlations with the geometric albedo, thermal inertia, and diameter of asteroids. Conclusions. Based on the observational evidence, we arrive at our conclusion that the submicrometer-sized structures (fibrous or flaky puff pastry-like structures in phyllosilicates) in the regolith particles could contribute to the distinctive NPBs of hydrated asteroids.

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arXiv2023

Spectral Type and Geometric Albedo of (98943) 2001 CC21, the Hayabusa2# Mission Target

We conducted optical polarimetry and near-infrared spectroscopy of JAXA's Hayabusa2# mission target, (98943) 2001 CC21, in early 2023. Our new observations indicated that this asteroid has a polarimetric inversion angle of ~21 deg, absorption bands around 0.9 and 1.9 um, and a geometric albedo of 0.285 +- 0.083. All these features are consistent with those of S-type but inconsistent with L-type. Based on this evidence, we conclude that JAXA's Hayabusa2# spacecraft will explore an S-type asteroid with albedo and size (0.42-0.56 km when we assume the absolute magnitude of 18.6) similar to (25143) Itokawa.

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arXiv2022

Spectral evolution of dark asteroid surfaces induced by space weathering over a decade

The surface of airless bodies like asteroids in the Solar System are known to be affected by space weathering. Experiments simulating space weathering are essential for studying the effects of this process on meteorite samples, but the problem is that the time spent to reproduce space weathering in these experiments is billions of times shorter than the actual phenomenon. In December 2010, the T-type asteroid 596 Scheila underwent a collision with a few-tens-of-meters impactor. A decade later, there is an opportunity to study how the surface layer of this asteroid is being altered by space weathering after the impact. To do so, we performed visible spectrophotometric and near-infrared spectroscopic observations of 596 Scheila. The acquired spectrum is consistent with those observed shortly after the 2010 impact event within the observational uncertainty range. This indicates that the surface color of dark asteroids is not noticeably changed by space weathering over a 10-year period. This study is the first to investigate color changes due to space weathering on an actual asteroid surface in the Solar System. Considering that fresh layers are regularly created on asteroid surfaces by collisions, we suggest a genetic link between D/T-type and dark (low albedo) X-complex asteroids and very red objects such as 269 Justitia, 732 Tjilaki (and 203 Pompeja). New observations show that 203 Pompeja has a X-type-like surface, with some local surface areas exhibiting a very red spectrum.

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arXiv2022

Estimation of space weathering timescale on (25143) Itokawa: Implications on its rejuvenation process

Context. The space weathering timescale of near-Earth S-type asteroids has been investigated by several approaches (i.e., experiments, sample analyses, and theoretical approaches), yet there are orders of magnitude differences. Aims. We aim to examine the space weathering timescale on a near-Earth S-type asteroid, Itokawa using Hayabusa-AMICA images and further investigate the evolutional process of the asteroid. Methods. We focused on bright mottles on the boulder surfaces generated via impacts with interplanetary dust particles (IDPs). We compared the bright mottle size distribution with an IDP flux model to determine the space weathering timescale. Results. As a result, we found that the space weathering timescale on Itokawa's boulder surfaces is 10$^3$ years (in the range of 10$^2$-10$^4$ years), which is consistent with the timescale of space weathering by light ions from the solar wind. Conclusions. From this result, we conclude that Itokawa's surface has been weathered shortly in 10$^3$ years but portions of the surface are exposed via seismic shaking triggered by a recent impact that created the Kamoi crater.

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arXiv2022

(3200) Phaethon Polarimetry in the Negative Branch: New Evidence for the Anhydrous Nature of the DESTINY+ Target Asteroid

We report on the first polarimetric study of (3200) Phaethon, the target of JAXA's DESTINY$^+$ mission, in the negative branch to ensure its anhydrous nature and to derive an accurate geometric albedo. We conducted observations at low phase angles (Sun-target-observer angle, alpha = 8.8-32.4 deg) from 2021 October to 2022 January and found that Phaethon has a minimum polarization degree $P_{min}$ = -1.3 +- 0.1 %, a polarimetric slope h = 0.22 +- 0.02 % deg$^{-1}$, and an inversion angle alpha$_0$ = 19.9 +- 0.3 deg. The derived geometric albedo is $p_V$ = 0.11 (in the range of 0.08-0.13). These polarimetric properties are consistent with anhydrous chondrites, and contradict hydrous chondrites and typical cometary nuclei.

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arXiv2021

A polarimetric study of asteroids in comet-like orbits

Context. Asteroids in comet-like orbits (ACOs) consist of asteroids and dormant comets. Due to their similar appearance, it is challenging to distinguish dormant comets from ACOs via general telescopic observations. Surveys for discriminating dormant comets from the ACO population have been conducted via spectroscopy or optical and mid-infrared photometry. However, they have not been conducted through polarimetry. Aims. We conducted the first polarimetric research of ACOs. Methods. We conducted a linear polarimetric pilot survey for three ACOs: (944) Hidalgo, (3552) Don Quixote, and (331471) 1984 QY1. These objects are unambiguously classified into ACOs in terms of their orbital elements (i.e., the Tisserand parameters with respect to Jupiter $T_\mathrm{J}$ significantly less than 3). Three ACOs were observed by the 1.6 m Pirka Telescope from UT 2016 May 25 to UT 2019 July 22 (13 nights). Results. We found that Don Quixote and Hidalgo have polarimetric properties similar to comet nuclei and D-type asteroids (optical analogs of comet nuclei). However, 1984 QY1 exhibited a polarimetric property consistent with S-type asteroids. We conducted a backward orbital integration to determine the origin of 1984 QY1, and found that this object was transported from the main belt into the current comet-like orbit via the 3:1 mean motion resonance with Jupiter. Conclusions. We conclude that the origins of ACOs can be more reliably identified by adding polarimetric data to the color and spectral information. This study would be valuable for investigating how the ice-bearing small bodies distribute in the inner Solar System.

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arXiv2021

Polarimetric Properties of the Near--Sun Asteroid (155140) 2005 UD in Comparison with Other Asteroids and Meteoritic Samples

The investigation of asteroids near the Sun is important for understanding the final evolutionary stage of primitive solar system objects. A near-Sun asteroid, (155140) 2005 UD, has orbital elements similar to those of (3200) Phaethon (the target asteroid for the JAXA's $DESTINY^+$ mission). We conducted photometric and polarimetric observations of 2005 UD and found that this asteroid exhibits a polarization phase curve similar to that of Phaethon over a wide range of observed solar phase angles ($ α= 20 - 105^\circ $) but different from those of (101955) Bennu and (162173) Ryugu (asteroids composed of hydrated carbonaceous materials). At a low phase angle ($α\lesssim 30^\circ$), the polarimetric properties of these near-Sun asteroids (2005 UD and Phaethon) are consistent with anhydrous carbonaceous chondrites, while the properties of Bennu are consistent with hydrous carbonaceous chondrites. We derived the geometric albedo, $ p_\mathrm{V} \sim 0.1 $ (in the range of 0.088-0.109); mean $ V $-band absolute magnitude, $ H_\mathrm{V} = 17.54 \pm 0.02 $; synodic rotational period, $ T_\mathrm{rot} = 5.2388 \pm 0.0022 $ hours (the two-peaked solution is assumed); and effective mean diameter, $ D_\mathrm{eff} = 1.32 \pm 0.06 $ km. At large phase angles ($ α\gtrsim 80^\circ$), the polarization phase curve are likely explained by the dominance of large grains and the paucity of small micron-sized grains. We conclude that the polarimetric similarity of these near-Sun asteroids can be attributed to the intense solar heating of carbonaceous materials around their perihelia, where large anhydrous particles with small porosity could be produced by sintering.

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arXiv2021

Implications of High Polarization Degree for the Surface State of Ryugu

The asteroid exploration project "Hayabusa2" has successfully returned samples from the asteroid (162173) Ryugu. In this study, we measured the linear polarization degrees of Ryugu using four ground-based telescopes from 2020 September 27 to December 25, covering a wide-phase angle (Sun-target-observer's angle) range from 28$^\circ$ to 104$^\circ$. We found that the polarization degree of Ryugu reached 53$\%$ around a phase angle of 100$^\circ$, the highest value among all asteroids and comets thus far reported. The high polarization degree of Ryugu can be attributed to the scattering properties of its surface layers, in particular the relatively small contribution of multiply-scattered light. Our polarimetric results indicate that Ryugu's surface is covered with large grains. On the basis of a comparison with polarimetric measurements of pulverized meteorites, we can infer the presence of submillimeter-sized grains on the surface layer of Ryugu. We also conjecture that this size boundary represents the grains that compose the aggregate. It is likely that a very brittle structure has been lost in the recovered samples, although they may hold a record of its evolution. Our data will be invaluable for future experiments aimed at reproducing the surface structure of Ryugu.

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arXiv2019

The Geometric Albedo of (4179) Toutatis Estimated from KMTNet DEEP-South Observations

We derive the geometric albedo of a near-Earth asteroid, (4179) Toutatis, to investigate its surface physical conditions. The asteroid has been studied rigorously not only via ground-based photometric, spectrometric, polarimetric, and radar observations but also via \textit{in situ} observation by the Chinese Chang'e-2 space probe; however, its geometric albedo is not well understood. We conducted V-band photometric observations when the asteroid was at opposition in April 2018 using the three telescopes in the southern hemisphere that compose the Korea Microlensing Telescope Network (KMTNet). The observed time-variable cross section was corrected using the radar shape model. We find that Toutatis has a geometric albedo $p_\mathrm{V} = 0.185^{+0.045}_{-0.039} $, which is typical of S-type asteroids. We compare the geometric albedo with archival polarimetric data and further find that the polarimetric slope--albedo law provides a reliable estimate for the albedo of this S-type asteroid. The thermal infrared observation also produced similar results if the size of the asteroid is updated to match the results from Chang'e-2. We conjecture that the surface of Toutatis is covered with grains smaller than that of the near-Sun asteroids including (1566) Icarus and (3200) Phaethon.

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