Detection of the 2021 Arid Meteor Shower on Maunakea, Hawai'i

TL;DR

The paper demonstrates the first optical detection of the Arid meteor shower (IAU #1130 ARD) using the Subaru-Asahi StarCam on Maunakea, combining volunteer-based visual inspection with an automated detection pipeline. The observed enhancement of Arid meteors on the predicted peak night, about $6$–$9$ times higher than the background, is supported by trajectory clustering toward a provisional radiant and by dust-trail simulations of Comet 15P/Finlay. The results align with radio observations indicating decayed activity a few hours after the peak, and simulations favor high-velocity dust ejected during the 2014 outburst as the shower’s likely source. This work validates the capability of wide-field, high-sensitivity public cameras for real-time meteor detection and provides empirical support for dust-trail dynamical models of new meteor showers.

Abstract

We report the successful detection of the "Arid" Meteor Shower (IAU\#1130 ARD), predicted to emerge for the first time in 2021, using a publicly accessible YouTube live camera developed by us. This live camera, installed on the Subaru Telescope dome in the summit region of Maunakea, Hawai'i, features a wide field of view (70 deg by 40 deg) and high sensitivity, capable of observing stars fainter than 6th magnitude. Meteor detection was performed in two ways: visual inspection by citizen viewers and subsequent validation through automated detection. As a result, we confirmed that the number of meteors appearing from near the predicted radiant increased by more than six times (~9 sigma) compared to the preceding and following days. Our observation time was 4-5 hours after the predicted peak (solar longitude = 193.9 deg), providing clear data indicating that the activity had not yet declined. Optical observations at this time from the Northern Hemisphere are extremely limited and unique, making our observation point valuable. The meteors are characterized as slow and faint appearance, but several brighter meteors with wakes were also observed. Simulations tracing the dust trails from the parent body, Comet 15P/Finlay, suggest that our detection can be explained by either the dust trails released in 2008 or 2014, both requiring high ejection velocities. However, during the comet's 2008 return, its activity was exceptionally quiet, making a high-velocity dust ejection questionable. On the other hand, multiple large outbursts were observed during the 2014 return, at which time a certain amount of high-velocity dust release is expected. We conclude that the dust source of the meteor shower detected in Hawai'i this time is likely attributable to high-velocity (~67 m s-1) dust ejected during the 2014 outburst.

Figures (9)

• Figure 1: Evaluation of video data (Top) and radiant plot for trajectory determination (Bottom). Note that the bottom figure is expressed as negative images for better visibility. The trajectory diagram is created using the script function of AstroArts' Stellar Navigator Software . The zenith attraction effect is included in the calculation for this plot. Alt text: This figure explains how the volunteers evaluated each meteor if it is the Arids or not.
• Figure 2: The Arids (Top) and sporadic (Bottom) meteor counts from seven volunteer evaluators. The horizontal axis shows time and date in Hawai'i Standard Time (HST) (= UT - 10 hours). Each volunteer was randomly assigned to evaluate a 30-minute window each day, but many went beyond their assignments. Note that sporadic meteor counts for evaluator F are not available. Alt text: This figures are about the result of the eye-ball detection of meteors by volunteers. The individual counts are shown here.
• Figure 3: Final results of the visual Arids detection campaign by volunteers. The plot shows a higher number of Arid candidates on the second day (Oct 7 UT), which was the predicted peak date for the shower. A comparison with sporadic meteors also clearly shows a relative increase in detections on this day. Although one evaluator counted meteors during the 20:30-20:40 HST time slot, this data was not included in the final evaluation. Alt text: This figures are about the final result (after check) of the eye-ball detection of meteors by volunteers.
• Figure 4: This diagram shows the great circles (long lines in green) extending the trajectories of detected meteors (short line segments in red), plotted in horizontal coordinates using a gnomonic projection. From bottom to top, each plot shows the tragectories of meteors detected between 19:00 and 20:30 HST on October 6, 7, and 8, respectively. Alt text: This figure shows the distribution of the grat circle defined by each detected meteor. On 7th UT we can see a concentration of the crossing points of tragectories.
• Figure 5: Relationship between meteor trajectories and the shortest distance to the provisional radiant point. The horizontal axis represents time in UT. The zenith attraction effect was applied to the provisional radiant's position, and the shortest distance vector is considered positive when it lies to the north. A clustering of the Arid meteor candidate near zero for 7th (circled in dashed line) is evident. Alt text: This figure shows the distribution of minimum distance between individual meteor trajectory and tentatively-assigned Arid radiant point.