106 research outputs found
Activity of the Eta-Aquariid and Orionid meteor showers
We present a multi-instrumental, multidecadal analysis of the activity of the
Eta-Aquariid and Orionid meteor showers for the purpose of constraining models
of 1P/Halley's meteoroid streams. The interannual variability of the showers'
peak activity and period of duration is investigated through the compilation of
published visual and radar observations prior to 1985 and more recent
measurements reported in the International Meteor Organization (IMO) Visual
Meteor DataBase, by the IMO Video Meteor Network and by the Canadian Meteor
Orbit Radar (CMOR). These techniques probe the range of meteoroid masses from
submilligrams to grams. The Eta-Aquariids and Orionids activity duration,
shape, maximum zenithal hourly rates (ZHR) values, and the solar longitude of
annual peaks since 1985 are analyzed. When available, annual activity profiles
recorded by each detection network were measured and are compared. Observations
from the three detection methods show generally good agreement in the showers'
shape, activity levels, and annual intensity variations. Both showers display
several activity peaks of variable location and strength with time. The
Eta-Aquariids are usually two to three times stronger than the Orionids, but
the two showers display occasional outbursts with peaks two to four times their
usual activity level. CMOR observations since 2002 seem to support the
existence of an ~12 year cycle in Orionids activity variations; however,
additional and longer term radar and optical observations of the shower are
required to confirm such periodicity.Comment: Accepted for publication in Astronomy & Astrophysics (date of
acceptance: 10/06/2020
Meteor showers of comet C/1917 F1 Mellish
December Monocerotids and November Orionids are weak but established annual
meteor showers active throughout November and December. Analysis of a high
quality orbits subset of the SonotaCo video meteor database shows that the
distribution of orbital elements, geocentric velocity and also the orbital
evolution of the meteors and potential parent body may imply a common origin
for these meteors coming from the parent comet C/1917 F1 Mellish. This is also
confirmed by the physical properties and activity of these shower meteors. An
assumed release of meteoroids at the perihelion of the comet in the past and
the sky-plane radiant distribution reveal that the December Monocerotid stream
might be younger than the November Orionids. A meteoroid transversal component
of ejection velocity at the perihelion must be larger than 100 m/s. A few
authors have also associated December Canis Minorids with the comet C/1917 F1
Mellish. However, we did not find any connection.Comment: 11 pages, 11 figures and 5 table
A retrospective of the GREGOR solar telescope in scientific literature
In this review, we look back upon the literature, which had the GREGOR solar
telescope project as its subject including science cases, telescope subsystems,
and post-focus instruments. The articles date back to the year 2000, when the
initial concepts for a new solar telescope on Tenerife were first presented at
scientific meetings. This comprehensive bibliography contains literature until
the year 2012, i.e., the final stages of commissioning and science
verification. Taking stock of the various publications in peer-reviewed
journals and conference proceedings also provides the "historical" context for
the reference articles in this special issue of Astronomische
Nachrichten/Astronomical Notes.Comment: 6 pages, 2 color figures, this is the pre-peer reviewed version of
Denker et al. 2012, Astron. Nachr. 333, 81
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