Optical spectropolarimetry of large C-complex asteroids: polarimetric evidence for heterogeneous surface compositions

This study presents the first optical spectropolarimetric study of large C-complex asteroids. A total of 64 C-complex asteroids of different subclasses are analyzed using archival polarimetric and reflectance data to refine the link between polarimetric parameters and surface properties of the asteroids. We find a consistent difference in the polarization spectra between asteroids containing phyllosilicates and those without, which correlates with the overall morphology of the reflectance spectrum. They exhibit broad similarities in polarization-phase curves; nonetheless, we observe a gradual enhancement of the negative polarization branch in the ascending order of F-B-T-Ch types, along with an increase in reflectance curvature around 500 nm. Our observations suggest at least for large C-complex asteroids a common mechanism underlies the diversity in optical properties. The observed trends would be explained by the surface composition of the asteroids, particularly optical heterogeneity caused by carbon's varying levels of optical influence, primarily regulated by aqueous alteration of the surfaces.Comment: Accepted for publication in Astronomy & Astrophysic

Coma environment of comet C/2017 K2 around the water ice sublimation boundary observed with VLT/MUSE

We report a new imaging spectroscopic observation of Oort-cloud comet C/2017 K2 (hereafter K2) on its way to perihelion at 2.53 au, around a heliocentric distance where H2O ice begins to play a key role in comet activation. Normalized reflectances over 6 500--8 500 AA for its inner and outer comae are 9.7+/-0.5 and 7.2+/-0.3 % (10^3 AA)^-1, respectively, the latter being consistent with the slope observed when the comet was beyond the orbit of Saturn. The dust coma at the time of observation appears to contain three distinct populations: mm-sized chunks prevailing at <~10^3 km; a 10^5-km steady-state dust envelope; and fresh anti-sunward jet particles. the dust chunks dominate the continuum signal and are distributed over a similar radial distance scale as the coma region with redder dust than nearby. they also appear to be co-spatial with OI1D, suggesting that the chunks may accommodate H2O ice with a fraction (>~1 %) of refractory materials. The jet particles do not colocate with any gas species detected. The outer coma spectrum contains three significant emissions from C2(0,0) Swan band, OI1D, and CN(1,0 red band, with an overall deficiency in NH2. Assuming that all OI1D flux results from H2O dissociation, we compute an upper limit on the water production rate Q_H2O of ~7 x 10^28 molec s^-1 (with an uncertainty of a factor of two). the production ratio log[Q_C2/Q_CN] of K2 suggests that the comet has typical carbon-chain composition, with the value potentially changing with distance from the Sun. Our observations suggest that water ice-containing dust chunks (>0.1 mm) near K2's nucleus emitted beyond 4 au may be responsible for its very low gas rotational temperature and the discrepancy between its optical and infrared lights reported at similar heliocentric distances.Comment: Accepted for publication in Astronomy & Astrophysic

On the dust of tailless Oort-cloud comet C/2020 T2 (Palomar)

We report our new analysis of Oort-cloud comet C/2020 T2 (Palomar) (T2) observed at 2.06 au from the Sun (phase angle of 28.5 deg) about two weeks before perihelion. T2 lacks a significant dust tail in scattered light, showing a strong central condensation of the coma throughout the apparition, reminiscent of so-called Manx comets. Its spectral slope of polarized light increases and decreases in the J (1.25 um) and H (1.65 um) bands, respectively, resulting in an overall negative (blue) slope (-0.31+/-0.14 % um^-1) in contrast to the red polarimetric color of active comets observed at similar geometries. The average polarization degree of T2 is 2.86+/-0.17 % for the J and 2.75+/-0.16 % for the H bands. Given that near-infrared wavelengths are sensitive to the intermediate-scale structure of cometary dust (i.e., dust aggregates), our light-scattering modeling of ballistic aggregates with different porosities and compositions shows that polarimetric properties of T2 are compatible with low-porosity (~66 %), absorbing dust aggregates with negligible ice contents on a scale of 10--100 um (density of ~652 kg m^-3). This is supported by the coma morphology of T2 which has a viable beta (the relative importance of solar radiation pressure on dust) range of <~10^-4. Secular evolution of the r-band activity of T2 from archival data reveals that the increase in its brightness accelerates around 2.4 au pre-perihelion, with its overall dust production rate ~100 times smaller than those of active Oort-cloud comets. We also found an apparent concentration of T2 and Manx comets toward ecliptic orbits. This paper underlines the heterogeneous nature of Oort-cloud comets which can be investigated in the near future with dedicated studies of their dust characteristics.Comment: Accepted for publication in Astronomy & Astrophysic

An Update of the Correlation between Polarimetric and Thermal Properties of Cometary Dust

We present a possible correlation between the properties of scattered and thermal radiation from dust and the principal dust characteristics responsible for this relationship. To this end, we use the NASA/PDS archival polarimetric data on cometary dust in the Red (0.62--0.73 $\mu$m) and K (2.00--2.39 $\mu$m) domains to leverage the relative excess of the polarisation degree of a comet to the average trend at the given phase angle ($P_{\rm excess}$) as a metric of the dust's scattered light characteristics. The flux excess of silicate emissions to the continuum around 10 $\mu$m ($F_{\rm Si}/F_{\rm cont}$) is adopted from previous studies as a metric of the dust's MIR feature. The two metrics show a positive correlation when $P_{\rm excess}$ is measured in the K domain. No significant correlation was identified in the Red domain. The gas-rich comets have systematically weaker $F_{\rm Si}/F_{\rm cont}$ than the dust-rich ones, yet both groups retain the same overall tendency with different slope values. The observed positive correlation between the two metrics indicates that composition is a peripheral factor in characterising the dust's polarimetric and silicate emission properties. The systematic difference in $F_{\rm Si}/F_{\rm cont}$ for gas-rich versus dust-rich comets would rather correspond with the difference in their dust size distribution. Hence, our results suggest that the current MIR spectral models of cometary dust should prioritise the dust size and porosity over the composition. With light scattering being sensitive to different size scales in two wavebands, we expect the K-domain polarimetry to be sensitive to the properties of dust aggregates, such as size and porosity, which might have been influenced by evolutionary processes. On the other hand, the Red-domain polarimetry reflects the characteristics of sub-$\mu$m constituents in the aggregate.Comment: 11 pages, 11 figures, accepted to A&A on 26 May, 202

Monitoring Observations of the Jupiter-Family Comet 17P/Holmes during 2014 Perihelion Passage

We performed a monitoring observation of a Jupiter-Family comet, 17P/Holmes, during its 2014 perihelion passage to investigate its secular change in activity. The comet has drawn the attention of astronomers since its historic outburst in 2007, and this occasion was its first perihelion passage since then. We analyzed the obtained data using aperture photometry package and derived the Afrho parameter, a proxy for the dust production rate. We found that Afrho showed asymmetric properties with respect to the perihelion passage: it increased moderately from 100 cm at the heliocentric distance r_h=2.6-3.1 AU to a maximal value of 185 cm at r_h = 2.2 AU (near the perihelion) during the inbound orbit, while dropping rapidly to 35 cm at r_h = 3.2 AU during the outbound orbit. We applied a model for characterizing dust production rates as a function of r_h and found that the fractional active area of the cometary nucleus had dropped from 20%-40% in 2008-2011 (around the aphelion) to 0.1%-0.3% in 2014-2015 (around the perihelion). This result suggests that a dust mantle would have developed rapidly in only one orbital revolution around the sun. Although a minor eruption was observed on UT 2015 January 26 at r_h = 3.0 AU, the areas excavated by the 2007 outburst would be covered with a layer of dust (<~ 10 cm depth) which would be enough to insulate the subsurface ice and to keep the nucleus in a state of low activity.Comment: 25 pages, 6 figures, 2 tables, ApJ accepted on December 29, 201

Risk of all-cause and cause-specific mortality associated with immune-mediated inflammatory diseases in Korea

ObjectiveImmune-mediated inflammatory disease (IMID) is associated with an increased risk of mortality. It is unclear whether the higher mortality is attributable to the IMIDs themselves or to the higher prevalence of comorbidities in IMIDs. We aimed to investigate whether IMIDs per se confer a higher risk of mortality.MethodsFrom the Korean National Health Insurance Service-National Sample Cohort database, this population-based cohort study included 25,736 patients newly diagnosed with IMIDs between January 2007 and December 2017, and 128,680 individuals without IMIDs who were matched for age, sex, income, hypertension, type 2 diabetes, dyslipidemia, and the Charlson comorbidity index. All individuals were retrospectively observed through December 31, 2019. The outcomes included all-cause and cause-specific mortalities. Adjustments for age, sex, and comorbidities were performed using multivariable Cox proportional hazard regression analyses, and adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs) for the outcomes were estimated.ResultsThe adjusted risk of all-cause mortality was significantly lower in patients with IMIDs than that in those without (aHR, 0.890; 95% CI, 0.841–0.942). Regarding cause-specific mortality, cancer-specific (aHR, 0.788; 95% CI, 0.712–0.872) and cardiovascular disease-specific (aHR, 0.798; 95% CI, 0.701–0.908) mortalities were the two causes of death that showed significantly lower risks in patients with IMIDs. A similar trend was observed when organ based IMIDs were analyzed separately (i.e., gut, joint, and skin IMIDs).ConclusionAfter adjusting for comorbidities, IMIDs were associated with a lower risk of all-cause mortality compared to those without IMIDs. This was attributable to the lower risks of cancer-and cardiovascular disease-specific mortalities

Systemic chemotherapy with doxorubicin, cisplatin and capecitabine for metastatic hepatocellular carcinoma

BACKGROUND: Although numerous chemotherapeutic agents have been tested, the role of systemic chemotherapy for hepatocellular carcinoma (HCC) has not been clarified. New therapeutic strategies are thus needed to improve outcomes, and we designed this study with new effective drug combination. METHODS: Twenty-nine patients with histologically-confirmed, metastatic HCC received a combination chemotherapy with doxorubicin 60 mg/m(2 )and cisplatin 60 mg/m(2 )on day 1, plus capecitabine 2000 mg/m(2)/day as an intermittent regimen of 2 weeks of treatment followed by a 1-week rest. RESULTS: The median age was 49 years (range, 32–64) and 19 patients were hepatitis B virus seropositive. Child-Pugh class was A in all patients and 4 had Zubrod performance status of 2. The objective response rate was 24% (95% CI 9–40) with 6 stable diseases. The chemotherapy was generally well tolerated despite one treatment-related death. CONCLUSION: Combination chemotherapy with doxorubicin, cisplatin and capecitabine produced modest antitumor activity with tolerable adverse effects in patients with metastatic HCC

Association of immune-mediated inflammatory diseases with depression and anxiety in patients with type 2 diabetes: A nationwide population-based study

ObjectivePatients with type 2 diabetes (T2DM) are at a high risk of developing depression and anxiety. To better stratify the risk, we aimed to assess whether the presence of immune-mediated inflammatory diseases (IMIDs) confers a higher risk of depression and anxiety in these patients.MethodsPatients with T2DM without prior depression or anxiety who underwent national health examination between 2009 and 2012 (n = 1,612,705) were enrolled from the nationwide health check-up data from Korean National Health Insurance Service. The outcome events were incident depression and anxiety, defined as International Classification of Diseases, 10th Revision codes F32–F33 and F40–F41, respectively. Multivariable Cox proportional hazard regression analyses were conducted to estimate the adjusted hazard ratio (aHR) and 95% confidence interval (CI) according to the existence of IMIDs.ResultsOver an average follow-up time of 6.4 years, existence of gut IMIDs was associated with a higher risk of depression (aHR: 1.28 [95% CI: 1.08–1.53]) and anxiety (1.22 [1.06–1.42]). Existence of joint IMIDs was associated with a higher risk of depression (1.34 [1.31–1.37]) and anxiety (1.31 [1.29–1.34]). Existence of skin IMID was associated with a higher risk of depression (1.18 [1.14–1.23]) and anxiety (1.13 [1.09–1.16]). The effect sizes of IMIDs on depression and anxiety were larger in those with ≥ 2 IMIDs (1.42 [1.19–1.69] and 1.49 [1.29–1.72], respectively) than in those with one IMID (1.30 [1.27–1.32] and 1.26 [1.24–1.28], respectively).ConclusionIn patients with T2DM, presence of IMIDs was associated with a higher risk of depression and anxiety. More stringent attention and screening for anxiety and depression should be encouraged in patients with T2DM and comorbid IMIDs due to clinical implications of psychological distress on patient-reported outcomes and prognosis

The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms−1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule

Probing the surface environment of large T-type asteroids

International audienceContext. The thermal and radiative environments encountered by asteroids have shaped their surface features. Recent observations have focused on asteroids in the main belt and showed indications for ices and organics in the interiors of the asteroids that were likely significant on prebiotic Earth. They stand out in reflectance spectra as darker, redder colours than most colocated asteroids. Aims: We probe the surface environment of large (>80km in diameter) T-type asteroids. This taxonomic type is relatively ill-constrained as an independent group. We discuss their place of origin based on our probing. Methods: We performed spectroscopic observations of two T-type asteroids, (96) Aegle and (570) Kythera, over the L band (2.8-4.0 µm) using the Subaru telescope. The spectra of other T-type asteroids are available in the literature, as are survey datasets. Based on this, we strove to find commonalities and global trends in this group. We also used the archival polarimetric data of the asteroids and meteorite spectra from laboratory experiments to constrain their surface texture and composition. Results: Our targets exhibit red L-band continuum slopes, (0.30±0.04) µm−1 for (96) Aegle and (0.31 ± 0.03) µm−1 for (570) Kythera, that are similar to those of (1) Ceres and 67P/Churyumov-Gerasimenko, and have an OH-absorption feature with band centres Conclusions: The 2.9 µm band depths of large T-type asteroids suggest that they might have experienced aqueous alteration comparable to Ch-type asteroids, but that it was more intense than for most of the main-belt asteroids. The polarimetric phase curve of the T-type asteroids is well described by a particular surface structure. The 0.5−4.0 µm reflectance spectra of large T-type asteroids appear most similar to those of CI chondrites with grain sizes of ~25−35 µm. Taken as a whole, we propose that large T-type asteroids may have been dislodged roughly around 10 au in the early Solar System