Eta-Virginids: another asteroidal meteoroid stream

Abstract

Eta-Virginids is a less-known meteor shower active in March. We investigated the meteoroids of this shower using fireball data from the European Fireball Network supplemented by video data of faint meteors. We first derived the criteria for assigning meteors to this shower. A fragmentation model was then applied to selected shower fireballs with good deceleration data and light curves. Meteoroid fragmentation strengths and bulk densities were derived and compared with three other showers. We have confirmed the four year periodicity in the activity of eta-Virginids and their presence in the 3:1 mean motion resonance with Jupiter. The orbital period of four years was directly measured for the fireballs. Fainter meteors showed somewhat longer periods but the shower is poor in faint meteors. No member fainter than magnitude +1 was observed instrumentally. The physical properties of meteoroids are different from cometary streams and are similar to the Geminids. The limiting fragmentation strength of 0.5 MPa and typical bulk density of cm-sized meteoroids of 1500 kg/m3 suggest that the parent body is a carbonaceous asteroid. Besides Geminids, eta-Virginids is another stream of asteroidal origin. Some small meteoroids have densities around 2500 kg/m3. Three asteroids of the sizes between 40 - 120 meters have been found to have similar orbits but their relation to eta-Virginids remains uncertain.

Figures (14)

• Figure 1: Eta Virginid fireball EN230321_013723 as photographed in constellation of Hercules by DAFO at station Kunžak (panel a) and by radiometers at Kunžak and Kuchařovice (b). The sky was partly hazy that night. The breaks in the fireball image are due to the LCD shutter. One break is intentionally avoided at the beginning of each second. The radiometric light curve from Kuchařovice has been offset by 1000 units for clarity.
• Figure 2: Positions of geocentric radiants located in the Virgo region in equatorial coordinates (panel a) and in Sun-centered ecliptical coordinates (b). The radiants of all fireballs observed by the EN during the month of March in 2017--2025 are plotted as color squares. The radiants of video meteors observed during three nights in March 2025 are plotted as color circles. The radiants of meteor showers active in March according to the IAU MDC are plotted as crosses in panel a. (NVI = Northern March Virginids, SVI = Southern March Virginids, EVI =$\eta$-Virginids, SLE = $\sigma$-Leonids, ABS = April $\beta$-Sextantids) Some showers have multiple solutions in the database and thus more possible radiants. Geocentric velocities are color coded. Stars are plotted as light blue circles. The black line marks the concentration of radiants. Three regions of interest are marked by rectangles in panel b: radiant concentration (A), wider area around the concentration (B) and possible southern branch (C).
• Figure 3: Orbital periods versus solar longitude of meteors with radiants in regions A (blue), B (red), and C (brown). EN fireballs are plotted as squares, video meteors as circles. Video data, generally, have somewhat lower precision. Error bars of orbital periods are indicated (one sigma). The horizontal line corresponds to the 3:1 resonance with Jupiter. The blue rectangle is the region of $\eta$-Virginid fireballs. The dashed blue line indicates possible extension of orbital periods of $\eta$-Virginid video meteors. The fireballs which were subject to fragmentation modeling (see Sect. \ref{['modeling']}) are highlighted by green circle.
• Figure 4: Magnitude distribution of all 130 meteors observed by video cameras during three nights in March 2025 and of four $\eta$-Virginids among them.
• Figure 5: Number of EN fireballs observed in each year. The confirmed $\eta$-Virginids are in blue. Fireballs with radiants in region B and those with radiants in region A but orbital periods incompatible with $\eta$-Virginids are in red. Fireballs with radiants in region C are in brown.