The origin of the June Bootid outburst in 1998 and determination of cometary ejection velocities

Numerical integrations are used to show that the main contribution to the outburst observed in the June Bootid meteor shower in 1998 was a subset of meteoroids released from the parent comet, 7P/Pons–Winnecke, at its 1825 return. A substantial part of the June Bootid stream is in 2:1 resonance with Jupiter. This inhibits chaotic motion, allowing structures in the stream to remain compact enough over centuries that meteor outbursts can still be produced. Circumstances of ejection in 1825 are calculated that exactly result in orbits capable of producing meteors at the observed time in 1998. Required ejection velocities are  10–20 m s^-1  .     

The 2007 Aurigid meteor outburst

A rare outburst of the Aurigid meteor shower was predicted to occur on 2007 September 1 at 11:36 ± 20 min  ut due to Earth's encounter with the one-revolution dust trail of long-period comet C/1911 N1 (Kiess). The outburst was predicted to last ∼1.5 h with peak zenithal hourly rate of ∼200 h⁻¹, which is ∼20 times higher than the annual Aurigid shower. Three members of Armagh Observatory observed this outburst from the general area of San Francisco, CA, USA, where the shower was anticipated to be best seen. Observed radiant, velocity and activity peak time were consistent with the predictions, whereas the zenithal hourly rate was about half of the predicted value. Five Aurigids were observed by two stations simultaneously, enabling their spatial trajectory to be worked out. The orbits of these double station meteors are in good agreement with that of their parent comet Kiess. The outburst was abundant in bright (−2 to +1 mag) meteors. The first high-altitude Aurigid, with a beginning height of 137.1 km, was recorded.     

The activity of the 2004 Geminid meteor shower from global visual observations

A comprehensive set of 612 h of visual meteor observations with a total of 29 077 Geminid meteors detected was analysed. The shower activity is measured in terms of the Zenithal Hourly Rate (ZHR). Two peaks are found at solar longitudes     and     with  ZHR = 126 ± 4  and  ZHR = 134 ± 4  , respectively. The physical quantities of the Geminid meteoroid stream are the mass index and the spatial number density of particles. We find a mass index of   s ≈ 1.7  and two peaks of spatial number density  234 ± 36  and  220 ± 31  particles causing meteors of magnitude +6.5 and brighter in a volume of 10⁹ km³, for the two corresponding ZHR maxima. There were  0.88 ± 0.08  and  0.98 ± 0.08  particles with masses of 1 g or more in the same volume during the two ZHR peaks. The second of the two maxima was populated by larger particles than the first one. We compare the activity and mass index profiles with recent Geminid stream modelling. The comparison may be useful to calibrate the numerical models.     

Meteor stream activity. III. Measurement of the first in a new series of Leonid outburst

Abstract— In 1994 November, a shower of bright Leonid meteors signaled what is likely the first meteor outburst of Leonids associated with the upcoming return of comet P/Tempel-Tuttle to perihelion. Measurements of meteor activity and the meteor brightness distribution are presented. By comparing the present observation with those of past Leonid returns, a forecast is made of the time, the duration, the intensity, and the mean meteor brightness of Leonid outbursts that may occur if previously observed patterns are repeated in the forthcoming years.     

Taurid resonant-swarm encounters from two decades of visual observations

Enhanced Taurid activity in terms of visual meteor and fireball rates has been found in 1988, 1991, 1995, 1998 and 2005 data. The years of heightened activity are shown to be unequivocally linked to the encounters of swarms of resonantly trapped particles in the Taurid meteoroid stream according to the model proposed by Asher & Clube. While the annual activity level of the Taurid meteor shower in terms of zenithal hourly rate  (ZHR) is 7.8 ± 1.2  , swarm year activity typically reaches ZHRs of 12–17. The annual fraction of fireballs is below 1 per cent; in swarm years, this fraction is as high as 2.4–4.6 per cent near the maximum of the Taurid activity period.     

A micrometeor component of the 1998 Leonid shower

Most astronomers expected a significant meteor shower associated with the Leonid meteoroid stream to appear in 1998 and 1999. An enhanced shower was widely observed in both years, and details can be found in many published articles. In 1998, one remarkable feature was the appearance of a strong component, rich in bright meteors, which appeared about 16 h before the expected maximum of the main shower, but another observed feature was an abnormal peak in the ionosphere characteristic value f _b E _s which was detected about 18 h after the main shower. A very high value of f _b E _s persisted for over an hour. The likely explanation is that the ionosphere was bombarded by an additional swarm of meteoroids, much smaller than those that produce a visible trail or an ionization trail that can be picked up by radio detectors. The different dynamical behaviours between small and large meteoroids are investigated and, in consequence, an explanation for the observed phenomena is offered and 1933 is suggested as being the likely ejection time.     

Observations of the Geminids and Quadrantids using a stratosphere–troposphere radar

Radar observations of the 1996 Geminid and 1997 Quadrantid showers are reported using the CLOVAR stratosphere–troposphere (ST) radar. A method for determining the limiting sensitivity of a radar system using observed number–amplitude data from a single shower is presented, and the result compared with more conventional measurements. This technique is capable of providing very precise measurement of the mass index for a shower in cases where large numbers of echoes are available. The mass index profiles for both showers are presented and found to be U-shaped with a minimum near the time of peak flux. Peak flux values are found to be 0.19±0.02 meteoroid km⁻² h⁻¹ at 261_.^¡82±0_.^¡2 for the Geminids and 0.14±0.01 meteoroid km⁻² h⁻¹ at 283_.^¡08±0_.^¡08 for the Quadrantids to a limiting radio magnitude of 7.7. The locations of maximum are found to coincide with the visually determined position. No significant difference in the location of maximum is detected for either stream over a range of 2 radio magnitudes or in comparison with the visual results. The Geminid radar flux curve is found to be very broad near maximum with a plateau in activity lasting nearly 2 d, while the visual curve shows a FWHM of 24±4 h and modest asymmetry with a slow build-up to maximum. The Quadrantids are found to have a sharp maximum following a Gaussian profile to first order with a full width to the 1/e flux positions of 12 h.     

Video Observations of the 2006 Leonid Outburst

We carried out double station observations of the Leonid meteor shower outburst, which occurred in the morning hours of November 19, 2006. Using image-intensified cameras we recorded approximately 100 Leonid meteors. As predicted, the outburst was rich especially in fainter meteors. The activity profile shows that the peak of the outburst occurred at 4:40 ± 0:05 UT. The maximum reached flux was 0.03 meteoroids km⁻² hod⁻¹ for meteors brighter than +6.5 magnitude.     

Double station and spectroscopic observations of the Quadrantid meteor shower and the implications for its parent body

Object 2003 EH₁ was recently identified as the parent body of the Quadrantid meteor shower. The origin of this body is still uncertain. We use data on 51 Quadrantid meteors obtained from double-station video observations as an insight on the parent body properties. A data analysis shows that the Quadrantids are similar to other meteor showers of cometary origin in some aspects, but in others to Geminid meteors. Quadrantid meteoroids have partially lost volatile component, but are not depleted to the same extent as Geminid meteoroids. In consideration of the orbital history of 2003 EH₁, these results lead us to the conclusion that the parent body is a dormant comet.     

Leonid outburst activity 1996: A broad structure and a first occurrence of a narrow peak of fainter meteors

Abstract— In 1996, a broad outburst structure of bright Leonid meteors similar to the 1995 and the 1994 displays (Jenniskens, 1996; Langbroek, 1996b) was observed. In addition, a second narrow outburst structure of fainter meteors, which will be reported and discussed in this paper, has with certainty been observed. This observation marks the first detection of such a narrow structure in the new series of Leonid outbursts. It has a similar exponential activity behaviour and similar emphasis on fainter meteors as shown by the 1866 and 1966 Leonid storm structures. Similar narrow peaks have been observed in 1965 and 1969 (Jenniskens, 1995, 1996). The broad 1996 structure of bright meteors peaked at November 17.31 ± 0.04 (λ 235°.28 ± 0.04 (2000.0)). The additional narrow structure peaked at November 17.20 ± 0.01 (λ 235°.172 ± 0.007). The occurrence of the narrow peak can best be explained as a first modest sign of presence of the meteoroid structure that should be responsible for the expected meteor storm activity of the Leonids in 1998–1999. The appearance 0.°085 before the node of 55P/Tempel-Tuttle suggests that the expected 1998–1999 Leonid storms might peak just before passage through the node of the comet.     

Spectroscopic solution of the star QX Cas

High-resolution spectroscopic observations around the Hα line of the binary star QX Cas covering the whole orbital period are presented. Our radial velocity solution, the first ever determined, requires an eccentric orbit with the following orbital parameters: eccentricity,   e = 0.22 ± 0.01  ; longitude of periastron,  ω= 45°± 5°  ; semi-amplitudes of the radial velocity curves of the primary and secondary stars,   K ₁ sin  i = 125.8 ± 0.9 km s⁻¹  and   K ₂ sin  i = 144.8 ± 1.1 km s⁻¹  ; gamma velocity,   V ₀= 65.1 ± 0.5 km s⁻¹  ; and mass ratio,   q = 0.869 ± 0.013  . The corresponding lower limits of the masses of the components and their separation are         , and   a sin  i = 31.34 ± 0.48 R_⊙  .     

Spectral,Photometric, and Dynamic Analysis of Eight Draconid Meteors

A Draconid meteor shower outburst was observed from on board two scientific aircraft deployed above Northern Europe on 8th October 2011. The activity profile was measured using a set of photographic and video cameras. The main peak of the activity occurred around 20:15 ± 0:0.5 UT which is consistent with the model prediction as well as with the IMO network visual observations. The corrected hourly rates reached a value of almost 350. The brighter meteors peaked about 15–20 min earlier than the dimmer ones. This difference can be explained by different directions of the ejection of the meteoroids from the parent comet. One of the instruments was even able to detect meteors connected with the material ejected from the parent comet before 1900 and thus confirmed the prediction of the model, although it was based on uncertain pre-1900 cometary data. Another small peak of the activity, which was caused by material ejected during the 1926 perihelion passage of the parent comet, was detected around 21:10 UT. The mass distribution index determined using the narrow field-of-view video camera was 2.0 ± 0.1. This work shows that the observation of meteor outbursts can constrain the orbital elements, outgassing activity and existence of jets at the surface of a comet.     

The dipole anisotropy of the 2 Micron All-Sky Redshift Survey

We estimate the acceleration on the Local Group (LG) from the 2 Micron All-Sky Redshift Survey (2MRS). The sample used includes about 23 200 galaxies with extinction-corrected magnitudes brighter than   K _s= 11.25  and it allows us to calculate the flux-weighted dipole. The near-infrared flux-weighted dipoles are very robust because they closely approximate a mass-weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. This is combined with the redshift information to determine the change in dipole with distance. The misalignment angle between the LG and the cosmic microwave background (CMB) dipole drops to  12°± 7°  at around  50  h ⁻¹ Mpc  , but then increases at larger distances, reaching  21°± 8°  at around  130  h ⁻¹ Mpc  . Exclusion of the galaxies Maffei 1, Maffei 2, Dwingeloo 1, IC342 and M87 brings the resultant flux dipole to  14°± 7°  away from the CMB velocity dipole. In both cases, the dipole seemingly converges by  60  h ⁻¹ Mpc  . Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters  Ω^0.6_m/ b _L= 0.40 ± 0.09  .     

BF Eridani: a cataclysmic variable with a massive white dwarf and an evolved secondary

We present high- and medium-resolution spectroscopic observations of the cataclysmic variable BF Eridani (BF Eri) during its low and bright states. The orbital period of this system was found to be 0.270881(3) d. The secondary star is clearly visible in the spectra through the absorption lines of the neutral metals Mg  i , Fe  i and Ca  i . Its spectral type was found to be K3±0.5. A radial velocity study of the secondary yielded a semi-amplitude of   K ₂= 182.5 ± 0.9 km s⁻¹  . The radial velocity semi-amplitude of the white dwarf was found to be   K ₁= 74 ± 3 km s⁻¹  from the motion of the wings of the Hα and Hβ emission lines. From these parameters, we have obtained that the secondary in BF Eri is an evolved star with a mass of  0.50–0.59 M_⊙  , whose size is about 30 per cent larger than a zero-age main-sequence single star of the same mass. We also show that BF Eri contains a massive white dwarf  ( M ₁≥ 1.2 M_⊙)  , which allows us to consider the system as a Type Ia supernova progenitor. BF Eri also shows a high γ-velocity  (γ=−94 km s⁻¹)  and substantial proper motion. With our estimation of the distance to the system  ( d ≈ 700 ± 200 pc)  , this corresponds to a space velocity of ∼350 km s⁻¹ with respect to the dynamical local standard of rest. The cumulative effect of repeated nova eruptions with asymmetric envelope ejection might explain the high space velocity of the system. We analyse the outburst behaviour of BF Eri and question the current classification of the system as a dwarf nova. We propose that BF Eri might be an old nova exhibiting 'stunted' outbursts.     

A southern hemisphere survey of meteor shower radiants and associated stream orbits using single station radar observations

The 33.2 MHz interferometric meteor radars located at Davis Station, Antarctica and Darwin, Australia typically detect around 15 000 specular underdense meteor echoes every day. While the angle of arrival of the scattered radio wave can be inferred using phase differences between receive antennae, the direction of individual meteors is not known beyond a plane of ambiguity perpendicular to the angle of arrival. Using the great circle mapping technique with a Jones & Jones type weighting function, 37 meteor shower systems were detected in data collected at both locations over 2006–2007, including nine undocumented showers. The orbital elements of the parent debris streams were then calculated for the 31 showers where sufficiently precise measurements were available.     

HST and ground-based eclipse observations of V2051 Ophiuchi: binary parameters

We report on high-speed eclipse photometry of the dwarf nova V2051 Oph while it was in a low brightness state, at B  ≃ 16.2 mag. In comparison with the average IUE spectra, the ultraviolet continuum and emission lines appear reduced by factors of, respectively, ≃ 4 and ≃ 5. Flickering activity is mostly suppressed and the light curve shows the eclipse of a compact white dwarf at the disc centre which contributes ≃ 60 per cent of the total light at 3900–4300 Å. We use measurements of contact phases in the eclipse light curve to derive the binary geometry and to estimate masses and relevant dimensions. We find a mass ratio of q  = 0.19 ± 0.03 and an inclination of i  = 83 ± 2°. The masses of the component stars are M ₁ = 0.78 ± 0.06 M⊙ and M ₂ = 0.15 ± 0.03 M⊙. Our photometric model predicts K ₁ = 83 ± 12 km s⁻¹ and K ₂ = 436 ± 11 km s⁻¹. The predicted value of K₁ is in accordance with the velocity amplitude obtained from the emission lines after a correction for asymmetric line emission in the disc is made. The secondary of V2051 Oph is significantly more massive than the secondaries of the other ultrashort period dwarf novae. V2051 Oph is probably a relatively young system, with a secondary star that has not had enough time to evolve out of thermal equilibrium.     

A research of the Orionid meteor shower by television observations in 2006–2008

The results of observations of the Orionid meteor shower are given in the period from 2006 to 2008. Observations were carried out using a highly sensitive camera FAVOR (FAst Variability Optical Registrator) a limiting magnitude of above +11.0^m (for stars) and a field of view of 18° × 20°. Over the period of the shower from October 2 to November 7, 2006–2008, there were 3713 meteors. 449 of these meteors were associated with the Orionid meteor shower. The distributions of Orionid meteors by the stellar magnitude is presented. It turned out that most of meteors (65%) of this shower have a brightness of +5.0^m-+7.0^m. On each night of observation the index of meteor activity was calculated for Orionids.     

Periodicities in the high-mass X-ray binary system RX J0146.9+6121/LS I+61°235

The high-mass X-ray binary RX J0146.9+6121, with optical counterpart LS I+61°235 (V831 Cas), is an intriguing system on the outskirts of the open cluster NGC 663. It contains the slowest Be type X-ray pulsar known with a pulse period of around 1400 s and, primarily from the study of variation in the emission line profile of Hα, it is known to have a Be decretion disc with a one-armed density wave period of approximately 1240 d. Here we present the results of an extensive photometric campaign, supplemented with optical spectroscopy, aimed at measuring short time-scale periodicities. We find three significant periodicities in the photometric data at, in order of statistical significance, 0.34, 0.67 and 0.10 d. We give arguments to support the interpretation that the 0.34 and 0.10 d periods could be due to stellar oscillations of the B-type primary star and that the 0.67 d period is the spin period of the Be star with a spin axis inclination of  23⁺¹⁰₋₈  degrees. We measured a systemic velocity of  −37.0 ± 4.3 km s⁻¹  confirming that LS I+61°235 has a high probability of membership in the young cluster NGC 663 from which the system's age can be estimated as 20–25 Myr. From archival RXTE All Sky Monitor (ASM) data we further find 'super' X-ray outbursts roughly every 450 d. If these super outbursts are caused by the alignment of the compact star with the one-armed decretion disc enhancement, then the orbital period is approximately 330 d.     

The continuing saga of Sakurai's object (V4334 Sgr): dust production and helium line emission

We report further UKIRT spectroscopic observations of Sakurai's object (V4334 Sgr) made in 1999 April/May in the 1–4.75 μm range, and find that the emission is dominated by amorphous carbon at T _d~600 K. The estimated maximum grain size is 0.6 μm, and the mass lower limit is 1.7±0.2×10⁻⁸ M_⊙ to 8.9±0.6×10⁻⁷ M_⊙ for distances of 1.1–8 kpc. For 3.8 kpc the mass is 2.0±0.1×10⁻⁷ M_⊙.
We also report strong He  i emission at 1.083 μm, in contrast to the strong absorption in this line in 1998. We conclude that the excitation is collisional, and is probably caused by a wind, consistent with the P Cygni profile observed by Eyres et al. in 1998.     

Meteoric activities during the 11th century

We have analysed the meteor records in the chronicles that describe the era of the Song dynasty ( ad 960–1279). The data are complementary to the record-vacant 10th century of the Koryo dynasty ( ad 918–1392). The annual activity of sporadic meteors analysed shows a generic sinusoidal behaviour as in modern observations. In addition, we have also found that there are two prominent meteor showers, one in August and the other in November, appearing on the fluctuating sporadic meteors. The date of occurrence of the August shower indicates it to be the Perseids. By comparing the date of occurrence of the November shower with those of the Leonid showers of the Koryo dynasty, recent visual observations and the world-wide historical meteor storms, we conclude that the November shower is the Leonids. The regression rate of the Leonids is obtained to be     days per century, which agrees with recent observations.