Mass distribution of lyrid meteoroids

Long-term visual observations of the Lyrid meteoroid shower have been analyzed to determine the mass distribution of Lyrid meteoroids. The value of the parameter S has been confirmed to be less than 1.8, which is normally assumed for meteoroid streams. The inclination of the descending and ascending branches of the S curve, depending on the longitude of the Sun, does not seem to exceed 3°. Observations carried out from 1987 until 2007 reveal that the minimum value of S corresponding to the longitude of the Sun 32.19 ± 0.04° is equal to 1.54 ± 0.02 (2000.0). The analysis of the S parameter derived from visual observations did not discover any particularities in the mass distribution of the meteoroids in the stream connected with the assumed 12-year enhancement period in the activity of the Lyrids.     

Lyrids 1994 observed by a forward scatter system

Radio observations of the Lyrid meteor shower obtained by a forward scatter radio system (Bologna-Lecce) in 1994 are analysed and discussed. The shower maximum appeared at solar longitude 31.0°(1950.0) and a distinct displacement between the maxima of the short-duration (< 1s) and long-duration ( 1s) echoes is observed. The shower has displayed a high activity, but no exceptional burst similar to that one observed in 1982, was recorded. It has been shown that the shower activity continues down to the smallest particle size of which existence in a meteoroid stream means their recent origin.     

The Lyrid Meteor Stream: Orbit and Structure

A filamentary structure in the Lyrid meteor stream based on photographic orbits available in the IAU Meteor database is identified and studied. About 17 Lyrids are found in the database and the stream mean orbit is derived. The shower radiant is compact, of a size 2° × 1.5°. Applying a stricter limiting value for the Southworth-Hawkins D-criterion, two distinct filaments in the stream, on a short and a long period orbit, are separated. To confirm their consistency as filaments, their orbital evolution over 5,000 years is investigated.     

The 1998 outburst and history of the June Boötid meteor shower

The June Boötid meteor shower (sometimes referred to as the Draconids) surprised a number of regular and casual observers by an outburst with maximum zenithal hourly rates (ZHRs) near 100 on 1998 June 27 after a quiescent period of several decades. A total of 1217 June Boötid meteors were recorded during regular visual meteor observations throughout this outburst. An average population index of r =2.2±0.10 was derived from 1054 shower magnitude estimates. The broad activity profile with ZHR>40 lasting more than 12 h and the large spread of apparent radiants in 1998 resemble the 1916 and 1927 outbursts. The peak time is found to be at about λ _⊙=95°.7 (2000.0); peak ZHRs are of the order of 200, whereas reliable averages reach only 81±7. The period of high ZHRs covered by a single observer implies a full width at half-maximum of 3–4 h. The resulting maximum flux of particles causing meteors brighter than +6.5 mag is between 0.04 and 0.06 km⁻² h⁻¹. The average radiant from photographic, radar and visual records is α =224°.12, δ =+47°.77. The observed activity outbursts in 1916, 1927 and 1998 are not related to the orbital period or the perihelion passages of the parent comet 7P/Pons–Winnecke. These are probably a consequence of the effects of the 2:1 resonance with Jupiter.     

Historical Space Climate Data from Finland: Compilation and Analysis

We have compiled archived geomagnetic observations from the Helsinki magnetic observatory as well as visual sightings of auroral occurrence in Finland. The magnetic database comprises about 2 000 000 observations of H- and D-components measured during 1844–1909 with time resolution of 10 min to 1 h. In addition, magnetic observations carried out in the First and Second Polar Years in Finland have been recompiled. Magnetic activity indices (three-hour K-and daily Ak-figures) have been derived from the magnetic observations. Comparisons between the Finnish indices and simultaneous global aa-index (starting in 1868) show a good mutual correlation. The Helsinki activity index series can be used as a (pseudo) extension of the aa-index series for about two solar cycles 1844d –1868. On the annual level the correlation coefficient is about 0.9 during the overlapped time interval 1868–1897. The auroral database consists of about 20 000 single observations observed in Finland since the year 1748. The database of visual auroras has been completed by auroral occurrence (AO) index data derived from the Finnish all-sky camera recordings during 1973 –1997 at several sites in Lapland. The AO-index reveals both spatial and temporal variations of auroras from diurnal to solar cycle time scales in different space weather conditions.     

Long-period forcing of Mercury's libration in longitude

Planetary perturbations of Mercury's orbit lead to forced librations in longitude in addition to the 88-day forced libration induced by Mercury's orbital motion. The forced librations are a combination of many periods, but 5.93 and 5.66 years dominate. These two periods result from the perturbations by Jupiter and Venus respectively, and they lead to a 125-year modulation of the libration amplitude corresponding to the beat frequency. Other periods are also identified with Jupiter and Venus perturbations as well as with those of the Earth, and these and other periods in the perturbations cause several arc second fluctuations in the libration extremes. The maxima of these extremes are about 30″ above and the minima about 7″ above the superposed ∼^60″, 88-day libration during the 125-year modulation. Knowledge of the nature of the long-period forced librations is important for the interpretation of the details of Mercury's rotation state to be obtained from radar and spacecraft observations. We show that the measurement of the 88-day libration amplitude for the purposes of determining Mercury's core properties is not compromised by the additional librations, because of the latter's small amplitude and long period. If the free libration in longitude has an amplitude that is large compared with that of the forced libration, its ∼10-year period will dominate the libration spectrum with the 88-day forced libration and the long-period librations from the orbital perturbations superposed. If the free libration has an amplitude that is comparable to those of the long-period forced libration, it will be revealed by erratic amplitude, period and phase on the likely time span of a series of observations. However, a significant free libration component is not expected because of relatively rapid damping.     

Pulsations of the sun and a beat period of 399 days

Measurements of the Doppler effect of the solar photosphere have been carried out at the Crimean Astrophysical Observatory for 37 years, beginning in 1974 (in total, 2188 days or 13 247 h). The measurements use the differential center-to-limb method of registration of line-of-sight velocity with a solar magnetograph (in the iron absorption line λ512.4 nm). As a result of the experiment, two global pulsations of the sun with periods P ₀ = 9600.606(12) and P ₁ = 9597.936(16) s have been discovered. The nature of the periods is unknown. The first pulsation was detected in 1974–1982; the second, during nearly all the 37 years. The 2008–2010 data confirm the stability of the initial phase of the P ₁ pulsation with a mean (differential) amplitude of 0.25 m/s. The fact that the beat period of the two pulsations coincides with the synodic period of Jupiter’s orbital revolution, i.e., 399 days, raises a new, complex problem for solar physics and cosmogony.     

Are Sakurai’s object and Nova Aquilae 1919 recurrent outbursts of classical novae?

It is proposed to interpret the outbursts of Nova Aquilae 1919 (V605 Aql) and the nova-like outburst of Sakurai’s object in 1996 as recurrent outbursts of classical novae of the DQ Her and RR Pic types with recurrence periods of about 1100 and 50,000 years, respectively, and some characteristics of these stars are derived on that basis. Only now has V605 Aql returned to the quiet state, and it has an absolute visual magnitude no fainter than 8^m−9^m. The orbital inclination of the prenova’s binary system is about 90°. The absolute visual magnitude of the prenova of V4334 Sgr is no brighter than 3^m. It is quite possible that the orbital inclination of the prenova’s binary system is close to 0°. The expansion velocities of the shells are 30–40 km/sec in both cases. The structure of the ejection is conserved in the recurrent outbursts. Translated from Astrofizika, Vol. 42, No. 4, pp. 563–570, October–December, 1999.     

Search for orbital motion of the pulsar 4U 1626–67: Candidate for a neutron star with a supernova fall-back accretion disk

We report here results from a new search for orbital motion of the accretion powered X-ray pulsar 4U 1626–67 using two different analysis techniques. X-ray light curve obtained with the Proportional Counter Array of the Rossi X-ray Timing Explorer during a long observation carried out in February 1996, was used in this work. The spin period and the local period derivative were first determined from the broad 2–60 keV energy band light curve and these were used for all subsequent timing analysis. In the first technique, the orbital phase dependent pulse arrival times were determined for different trial orbital periods in the range of 500 to 10,000 s. We have determined a 3σ upper limit of 13 lt-ms on the projected semimajor axis of the orbit of the neutron star for most of the orbital period range, while in some narrow orbital period ranges, covering about 10% of the total orbital period range, it is 20lt-ms. In the second method, we have measured the pulse arrival times at intervals of 100 s over the entire duration of the observation. The pulse arrival time data were used to put an upper limit on any periodic arrival time delay using the Lomb-Scargle periodogram. We have obtained a similar upper limit of 10 lt-ms using the second method over the orbital period range of 500–10,000 s. This puts very stringent upper limits for the mass of the compact object except for the unlikely case of a complete face-on orientation of the binary system with respect to our line-of-sight. In the light of this measurement and the earlier reports, we discuss the possibility of this system being a neutron star with a supernovae fall-back accretion disk.     

V2213 Cyg is a New W Uma-Type System

V2213 Cyg was discovered as a variable star by Pavlenko (1999) in 1998. We present our photometry of V2213 Cyg from 1998–2003 based on CCD observations with the K-380 Cassegrain telescope of CrAO and the 60 cm Zeiss telescope of SAI. Observations have been carried out mostly in R and sometimes in B and V Johnson system. The total amount of data is 2270 points, covering ∼50 nights. We classify this binary as a W UMa-type contact system. Using all data we determined the orbital period to be 0.350079 ± 0.000007 day. The mean brightness varies between R = 14.35 and 14.05. The mean 1999–2003 orbital light curve has two humps and a primary minimum (I), which is 0.04 mag brighter than the deeper secondary one (II). The mean humps have slightly different height. The difference between two individual maxima varies within 0.1 mag, which may indicate an activity of the components. The highest hump is an asymmetrical one: it has sort of a shoulder at phases 0.75–0.80, before entering the less deep primary minimum (phase 0.0). The system is rather reddened, its colour indices are: B−V ∼ 0.8 and V−R ∼ 0.7, and give a spectral class of V2213 Cyg earlier than K.     

Jupiter approaching asteroids and their possibilities for activity

Jupiter‐family comets (JFCs) may often, closely and/or slowly approach Jupiter. A list of their close approaches within 0.21 AU from Jupiter between 1970 and 2030 is presented to determine the typical changes in some of their orbital elements and their relation to any triggered activity. A few JFCs from the list were temporary satellites of Jupiter. There are also several JFCs which originally had asteroidal provisional designations due to their low activity at discovery. But Jupiter is also approached by asteroids. The presented list of their approaches within 0.60 AU from Jupiter between 1960 and 2040, together with their orbital changes can be compared with the list of comets. Some of the orbital changes are large enough to cause an extremely low or short‐lived activity. Usually, quick and dedicated observations by large‐aperture telescopes are missing to confirm or refute it. Currently, the most important cometary candidate among Jupiter approaching asteroids is 2004 FY140. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Orbital Light Curve of the Peculiar Binary V Sagittae in ExtendedHigh States of Brightness

We have analyzed the orbital modulation of V Sge in two intervals, each several years long, when the long-term light curve was relatively flat, in extended high state of brightness, and displayed just minor fluctuations. We used extensive sets of the visual AAVSO data. The two-sided moving averages with various values of Q were applied to the data folded with the orbital photometric phase – it allowed to pick out the general properties of the orbital component of the variations. We found that the modulation is always present but its shape near the secondary minimum (phase 0.5) remarkably varies for the two respective intervals. The secondary minimum is very prominent in one interval, but is almost absent in other interval. The standard deviation of brightness, computed for each bin of the folded light curve, displays variations through the orbital phase and has its minimum near phase 0.6. All these findings are confirmed for various values of Q. We argue that the source of the scatter of the orbital modulation is located in the lobe of the primary between its center and the L ₁ point, shifted slightly from the line of centers of the stars. This revised version was published online in July 2006 with corrections to the Cover Date.     

Resonant forcing of Mercury's libration in longitude

The period of free libration of Mercury's longitude about the position it would have had if it were rotating uniformly at 1.5 times its orbital mean motion is close to resonance with Jupiter's orbital period. The Jupiter perturbations of Mercury's orbit thereby lead to amplitudes of libration at the 11.86 year period that may exceed the amplitude of the 88 day forced libration determined by radar. Mercury's libration in longitude may be thus dominated by only two periods of 88 days and 11.86 years, where other periods from the planetary perturbations of the orbit have much smaller amplitudes.     

Radar sporadic meteor rates and solar activity

The correlation of sporadic meteor rates from radar observations in January, August, and December non-show-er periods in 1958–2000, and relevant solar activity represented by the solar relative number, R, is investigated. Similar analysis of the December sporadic period was already presented by Simek 1999, and Pecina. Complete analysis indicates high correlation of both phenomena with sporadic meteor counts curve following that of solar activity after 1.5–2 years in the mean eleven year solar cycle with the correlation index exceeding 70%. This result supports the large volume of observing material of the Ondřejov meteor radar in the above mentioned span covering almost four solar cycles. This revised version was published online in July 2006 with corrections to the Cover Date.     

Search for 12.6 millisecond periodicity in TeV gamma rays from Cygnus X-3

Cygnus X-3, an X-ray binary with an orbital period 4.8 hr was seen to be emitting γ-rays with the same period at TeV energies by several groups. In addition the Durham group (Chadwicket al. 1985) published their observations on the existence of a pulsar in the Cyg X-3 system, emitting TeV γ-rays with a periodicity of approximately 12.6 ms. We observed this object during 1986 October-November and did not detect any pulsed emission of TeV γ-rays in the range of periods from 12.5850 to 12.5967 ms.     

Magnetic field structure and accretion regimes of the asynchronous polar by Cam

Series of photometric CCD observations of the asynchronous polar BY Cam in a low accretion state (R = 14^m–16^m) were made on the K-380 telescope at the Crimean Astrophysical Observatory (CrAO) over 100 hours in the course of 31 nights during 2004–2005. A period of P ₁ = 0.137120±0.000002 days was found for the variations in the brightness, along with less significant periods of P ₂ = 0.139759±0.000003 and P₃ = 0.138428±0.000002 days, where P₂ and P₃ are obviously the orbital and rotation periods, while the dominant period P₁ is the sideband period. A modulation in the brightness and an amplitude of 0.137 days in the oscillations at the orbital-rotational beat period (synodic cycle) of 14.568±0.003 day are found for the first time. The profile of the modulation period is four humped. This indicates that the magnetic field has a quadrupole component, which shows up well during the low brightness state. Accretion takes place simultaneously into two or three accretion zones, but at different rates. The times of the times of maxima for the main accretion zone vary with the phase of the beat period. Three types of variation of this sort are distinguished: linear, discontinuous, and chaotic, which indicate changes in the accretion regimes. At synodic phases 0.25 and 0.78 the bulk of the stream switches by 180°, and at phase 0.55, by ∼75°. At phases of 0.25–0.55 and 0.55–0.78, the O-C shift with a period of 0.1384 days, which can be explained by a retrograde shift of the main accretion zone relative to the magnetic pole and/or a change in the angle between the field lines and the surface of the white dwarf owing to the asynchronous rotation. For phases of 0.78–1.25 the motion of the accretion zone is quite chaotic. It is found that synchronization of the components occurs at a rate of less than dP_rot/P_rot∼10⁻⁹ day/day. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 121–137 (February 2006).     

Hale Cyclicity of Solar Activity and Its Relation to Climate Variability

The periodicity of climatic processes along the Russian Arctic Ocean coast has been studied by analyzing the tree-ring chronologies for the regions close to the northern timberline. The wavelet analysis of annual series of conifer tree rings for the period 1458–1975 has revealed climatic oscillations with periods of 20–25 years. The amplitudes and periods of climatic oscillations in the region of Russian Arctic Ocean proved to exhibit appreciable changes. Especially strong climatic variations in comparison with the recent ones were found to occur during the Maunder minimum epoch when the period of oscillations increased from 22–23 years to 24–29 years, and oscillations with periods of 15 years appeared. After the Maunder minimum, the periods of oscillations and their amplitudes again decreased, and the 15–16-year maximum disappeared. Analysis of solar activity based on of radiocarbon (¹⁴C) concentration in annual tree rings has revealed a similar pattern in changes of periodicity before, during, and after the Maunder minimum. This suggests that quasi-bidecadal climatic oscillations and variations in solar activity can be connected with each other. A possible solar forcing of periodic climatic processes and its nonlinear influence on the atmosphere-ocean-continental system are discussed. The intense quasi-bidecadal climatic oscillations can be, in all probability, interpreted as resulting from amplification of a weak solar signal in the atmosphere-ocean system that has its own noises whose frequencies are close to the 22–23-year solar cycles.     

Orbit Determination of Binary Asteroids

In addition to the detection of an asteroid moon or a binary asteroid, the knowledge of the satellite’s true orbit is of high importance to derive fundamental physical parameters of the binary system such as its mass and to shed light on its possible formation history and dynamical evolution (prograde/retrograde orbit, large/small eccentricity or inclination, etc.). A new methodology for preliminary orbit determination of binary asteroids – and visual binaries in general – is proposed. It is based on Thiele–Innes method combined with a ‘trial and error’ Monte-Carlo technique. This method provides the full set of solutions (bundle of orbits, with the 7 orbital elements) even for a reduced number of observations. The mass is a direct by-product of this orbit determination, from which one can next infer the bulk-density and porosity. In addition to the bundle of orbits, the method provides the marginal probability densities of the foreseen parameters. Such error analysis – since it avoids linear approximation – can be of importance for the prediction of the satellite’s position in the plane-of-sky during future stellar occultations or subsequent observations, but also for the analysis of the orbit’s secular evolution. After briefly describing the method, we present the algorithm and its application to some practical cases, with particular emphasis on asteroids binaries and applications on orbital evolution.     

First CCD photometry for the contact binary VZ Trianguli

First CCD photometry is presented for the eclipsing binary VZ Trianguli, observed at the Sheshan Station of Shanghai Astronomical Observatory in 2008. Using the Wilson–Devinney Code, the photometric solution of VZ Tri was first deduced from the R-band observations. The results show that VZ Tri is an A-subtype late-type contact binary, with a mass ratio of q=0.350(±0.004) and a low contact degree of f=27.9%(±1.0%). Based on all available light minimum times covering over 40 years, it is found that the orbital period shows a long-term decrease at a rate of dP/dt=−1.52(±0.03)×10⁻⁷ d yr⁻¹, suggesting that VZ Tri is undergoing mass transfer from the more massive component to the less massive component, accompanied with angular momentum loss. With period decreasing, the inner and outer critical Roche lobes will shrink, and then cause the contact degree to increase. Therefore, the weak-contact binary VZ Tri with decreasing period may evolve into a deep-contact configuration.     

Photometric Evolution of the Orbital Light Curves of the Slow Nova V723 Cas

UBVRI photoelectric and CCD photometry of the slow nova V723 Cas obtained in the years 1995–2003 is presented. The evolution of light curves in 1-year intervals, folded with the orbital period 0.69326 days, shows an increase of the amplitude of the wave-like variations from 0.07 to 1.3 mag during the years 1997–2003. The fact that the shape and amplitude of the orbital light curves does not depend on wavelength is most probably related to the geometry of eclipses combined with the distribution of circumstellar matter in the system.