搜索结果：Eclipses

The eclipses seen in the radio emission of some pulsars can be invaluable to study the properties of the material from the companion stripped away by the pulsar. We present a study of six consecutive eclipses of PSR J0024-7204O in the globular cluster 47 Tucanae as seen by the MeerKAT radio telescope in the UHF (544-1088 MHz) band. A high scintillation state boosted the signal during one of the orbits and allowed a detailed study of the eclipse properties. We measure significant dispersion measure (DM) variations and detect strong scattering that seems to be the dominating mechanism of the eclipses at these frequencies. A complete drop in the linear polarization together with a small increase in the rotation measure suggests the presence of a magnetic field of $\sim 2$ mG. The study of multiple eclipses allowed us to measure difference in the lengths of the eclipses and DM differences of $\sim 0.01$ pc cm$^{-3}$ in consecutive orbits. One orbit in particular shows a delay in recovery of the linear polarization and a visible delay in the arrival of the pulses caused by a stronger scattering event. We suggest that these are caused by a higher variance of density fluctuations during t

This paper presents a comprehensive study of the eclipse properties of the spider millisecond pulsar (MSP) J1908$+$2105, using wide-band observations from the uGMRT and Parkes UWL. For the first time, we observed that this pulsar exhibits extended eclipses up to 4 GHz, the highest frequency band of the UWL, making it one of only three MSPs known to have such high-frequency eclipses. This study reveals synchrotron absorption as the primary eclipse mechanism for J1908$+$2105. We present modeling of synchrotron optical depth with various possible combinations of the parameters to explain the observed eclipsing in this as well as other spider MSPs. Observed eclipses at unusually high frequencies for J1908$+$2105 significantly aided in constraining the magnetic field and electron column density in the eclipse medium while modeling the synchrotron optical depth. Combining our findings with data from other MSPs in the literature, for the first time we note that a higher cutoff frequency of eclipsing, particularly above 1 GHz, is consistently associated with a higher electron column density ($>$ 10$^{17}$ cm$^{-2}$) in the eclipse medium. Additionally, we present the first evidence of l

I conducted photometric observations of the cataclysmic variable LAMOST J035913.61+405035.0 and discovered previously unknown eclipses. During these observations, I recorded 14 eclipses over two groups of nights separated by 13 months. I accurately determined the orbital period of the system to be Porb=0.22834385+\-0.00000021 d. For the eclipses, I derived an ephemeris which is valid for a long time and suitable for studying changes in the orbital period. The out-of-eclipse magnitude of the star varied between 15.32(+\-0.02) and 17.25(+\-0.08) mag. As the brightness decreased, the eclipses became deeper and narrower. The average depth of eclipses was 1.35(+\-0.10) mag, and the average width at half-depth was 16.9(+\-0.7) min. I estimated the range of possible orbital inclinations to be between 72.8 degr and 76.0 degr, and the range of average absolute V-band magnitudes of the disc to be between 5.16(+\-0.15) and 5.44(+\-0.15) mag. Although based on the light curve from the ZTF survey, LAMOST J035913.61+405035.0 showed only small outbursts with amplitudes below 1.5 mag, it should be classified as a dwarf nova because the average disc brightness and mass transfer rate were below the

Eclipses of radio emission have been reported for ~ 58 spider millisecond pulsars (MSP), of which only around 19% have been extensively studied. Such studies at low frequencies are crucial for probing the properties of the eclipse medium, as eclipses are more prominent at such frequencies. This study investigates eclipses in 10 MSPs in compact orbit using wide-bandwidth observations with the upgraded Giant Metrewave Radio Telescope. We report the first evidence of eclipsing for PSR J2234+0944 and J2214+3000 in one epoch, while no evidence of eclipsing was observed in the subsequent two epochs, indicating temporal evolution of the eclipse cutoff frequency in these systems. Constraints on the eclipse cutoff frequency were obtained for PSR J1555-2908, J1810+1744, and J2051-0827. Moreover, for the first time, we detected an eclipse at a non-standard orbital phase (~ 0.5) for PSR J1810+1744, with a duration longer than the eclipse observed at superior conjunction. No eclipses were detected for PSR J0751+1807, J1738+0333, and J1807-2459A at 300-500 MHz and 550-750 MHz, for which we discuss the possible reasons. We calculated the mass loss rates of the companions for PSR J1555-2908 and PS

Eclipses and pulsations are the two primary ways in which the physical properties of stars can be deduced and used to improve our understanding of stellar theory. An obvious idea is to combine these two analyses into the study of pulsating stars in eclipsing binaries. This is the aim of the SWIPE project. This paper summarises the scientific arguments, current status and future plans of the project.

Visual photometry of 16 WC8-9 dust-making Wolf-Rayet (WR) stars during 2001--2009 was extracted from the All Sky Automated Survey All Star Catalogue (ASAS-3) to search for eclipses attributable to extinction by dust formed in clumps in our line of sight. Data for a comparable number of dust-free WC6-9 stars were also examined to help characterise the dataset. Frequent eclipses were observed from WR 104, and several from WR 106, extending the 1994-2001 studies by Kato et al. (2002a,b), but not supporting their phasing the variations in WR 104 with its `pinwheel' rotation period. Only four other stars showed eclipses, WR 50 (one of the dust-free stars), WR 69, WR 95 and WR 117, and there may have been an eclipse by WR 121, which had shown two eclipses in the past. No dust eclipses were shown by the `historic' eclipsers WR 103 and WR 113. The atmospheric eclipses of the latter were observed but the suggestion by David-Uraz et al. (2012) that dust may be partly responsible for these is not supported. Despite its frequent eclipses, there is no evidence in the infrared images of WR 104 for dust made in its eclipses, demonstrating that any dust formed in this process is not a significant

Solar eclipses, as rare astronomical events, often evoke a profound sense of wonder and awe within the human spirit. However, for ordinary people, the extremely short preparation time, a few hours of notice from friends or social media, and the lack of observation equipment often hinder safe and effective eclipse viewing. Some individuals directly observe the sun with their naked eyes, risking vision damage. To enable ordinary people to safely observe eclipses in very little preparation and reduce the risk of vision damage, we present a simple and safe method that almost anyone can use under very basic conditions, known as the "Okay" observation method.

We explore 50 Australian Aboriginal accounts of lunar and solar eclipses to determine how Aboriginal groups understood this phenomenon. We summarise the literature on Aboriginal references to eclipses, showing that many Aboriginal groups viewed eclipses negatively, frequently associating them with bad omens, evil magic, disease, blood and death. In many communities, Elders or medicine men were believed to have the ability to control or avert eclipses by magical means, solidifying their role as provider and protector within the community. We also show that many Aboriginal groups understood the motions of the sun-earth-moon system, the connection between the lunar phases and tides, and acknowledged that solar eclipses were caused by the moon blocking the sun.

Over the last decade, the pre-main sequence star KH 15D has exhibited periodic eclipses that are surprisingly deep (~3 mag) and long-lasting (~40% of the 48.4-day period). The cause of the eclipses is unknown, but it could be a feature in a nearly edge-on protoplanetary disk. Here we report on an analysis of archival photographs of KH 15D from the Harvard College Observatory plate collection, most of which were taken during the years 1913-1951. During this time range, the data are consistent with no eclipses; the duty cycle of 1 mag eclipses was less than 20%. The decadal timescale of this change in eclipse behavior is compatible with the expected timescale of protoplanet/disk interactions. Archival images from more recent epochs should reveal the onset of the eclipses.

The double pulsar PSR J0737-3039A/B displays short, 30 s eclipses that arise around conjunction when the radio waves emitted by pulsar A are absorbed as they propagate through the magnetosphere of its companion pulsar B. These eclipses offer a unique opportunity to probe directly the magnetospheric structure and the plasma properties of pulsar B. We have performed a comprehensive analysis of the eclipse phenomenology using multi-frequency radio observations obtained with the Green Bank Telescope. We have characterized the periodic flux modulations previously discovered at 820 MHz by McLaughlin et al., and investigated the radio frequency dependence of the duration and depth of the eclipses. Based on their weak radio frequency evolution, we conclude that the plasma in pulsar B's magnetosphere requires a large multiplicity factor (~ 10^5). We also found that, as expected, flux modulations are present at all radio frequencies in which eclipses can be detected. Their complex behavior is consistent with the confinement of the absorbing plasma in the dipolar magnetic field of pulsar B as suggested by Lyutikov & Thompson and such a geometric connection explains that the observed perio

This article reviews atmospheric changes associated with 44 solar eclipses, beginning with the first quantitative results available, from 1834 (earlier qualitative, accounts also exist). Eclipse meteorology attracted relatively few publications until the total solar eclipse of 16 February 1980, with the 11 August 1999 eclipse producing the most papers. Eclipses passing over populated areas such as Europe, China and India now regularly attract scientific attention, whereas atmospheric measurements of eclipses at remote locations remain rare. Many measurements and models have been used to exploit the uniquely predictable solar forcing provided by an eclipse. In this paper we compile the available publications and review a sub-set of them chosen on the basis of importance and novelty. Beyond the obvious reduction in incoming solar radiation, atmospheric cooling from eclipses can induce dynamical changes. Observations and meteorological modelling provide evidence for the generation of a local eclipse circulation which may be the origin of the "eclipse wind". Gravity waves set up by the eclipse can, in principle, be detected as atmospheric pressure fluctuations, though theoretical predi

The search of a rational explanation of eclipses pervades the beginnings of philosophical and scientific thought. Within this intellectual frame, the knowledge of the "saros cycle" (a cycle of 18 years, 10 or 11 days and 1/3 of a day that separates two successive sun or moon eclipses of similar features), inherited by the Greeks from the Babylonians, favored important theoretical developments in the West. The purpose of this paper is to present, briefly and schematically, a) the ancient theorizations on the causes of eclipses, b) the range of predictability of eclipses in Antiquity, c) the warnings -transmitted by some classical writers- to those who want to observe in naked eyes a solar eclipse, and d) the popular beliefs and social practices upon the occurrence of unexpected eclipses in ancient times.

Four candidates of eclipsing multiples, based on new extraneous eclipses found on Kepler binary light curves, are presented and studied. KIC 7622486 is a double eclipsing binary candidate with orbital period of 2.2799960 days and 40.246503 days. The two binary systems do not eclipse each other in the line of sight, but there is mutual gravitational influence between them which leads to the small but definite eccentricity 0.0035(0.0022) on the short 2.2799960 days period orbit. KIC 7668648 is hierarchical quadruple system candidate, with two sets of solid 203(+-5) days period extraneous eclipses and another independent set of extraneous eclipses. A clear and credible extraneous eclipse is found on the binary light curve of KIC 7670485 which made it a triple system candidates. Two sets of extraneous eclipse of about 390 days and 220 days period are found on KIC 8938628 binary curves, which not only confirms the previous conclusion of $388.5(+-0.3) triple system, but also proposed a new additional objects that make KIC 8938628 a hierarchical quadruple system candidates. It is wished that the four candidates here will make some contributions to the field of eclipsing multiples.

This paper centers on the collection of accounts on solar eclipses from the era of the Aztecs in Mesoamerica, about 1300 to 1550 AD. We present a list of all eclipse events complying with the topological visibility from the capital Tenochtitlan. Forty records of 23 eclipses entered the various Aztec manuscripts (codices), usually those of large magnitude. Each event is discussed with regard to its historical context, as we try to comprehend the importance the Aztecs gave to the phenomenon. It seems that this culture paid noticeably less attention to eclipses than the civilisations in the "Old World". People did not understand the cause of it and did not care as much about astronomy as in Babylonia and ancient China. Furthermore, we discuss the legend on the comet of Moctezuma II. It turns out that the post-conquest writers misconceived what the sighting was meant to be.

We present photometry obtained during the 2012 May and September outbursts of the frequently outbursting dwarf nova, V1227 Her. Superhumps were present in both cases with a peak-to peak amplitude of up to 0.28 mag, showing these events to be superoutbursts. We show for the first time that the system undergoes small eclipses with a depth of up to 0.08 mag, lasting 11 to 14 min, which are likely to be grazing eclipses of the accretion disc. The September outburst was the better observed of the two and lasted at least 14 days with an outburst amplitude of approximately 4 magnitudes. The mean superhump period was Psh = 0.065103(20) d. Analysis of eclipse times of minimum gave an orbital period Porb = 0.064419(26) d, although there is some ambiguity due to the relatively short time over which the eclipses were observed. The fractional superhump period excess, epsilon, was 0.0106(7).

A double planet system or planet binary undergoes eclipses that modify the reflective light curve. In the time domain, the eclipse events are fast and weak. This would make their signal difficult to find and recognize in the phase light curve, even for small inclinations when eclipses happen frequently. However, due to the quasiperiodic nature of the phenomenon, the Fourier transform of the direct reflection signal consists of a double sum of sharp peaks. These peaks can be resolved for large close binaries and sufficiently long observation times with a star coronagraph. Eclipses modulate the phase curve, having an orbital period $2π/ω$, with a contribution from the relative motion in the binary plane of a period $2π/Ω$. This leads to a spectral structure with basis frequencies $ω$ and $Ω$. We aim to characterize these spectra. We studied the regime of short eclipses that occur when the planet radii are small compared to the planet separation. We derived formulas for the peak amplitudes applicable to homogeneous (Lambertian) planet binaries in circular orbit with small inclination. The effects of an eclipse and of double reflection appear as first- and second-order contributions (i

We present a comparative study of the low-frequency eclipses of spider (compact, irradiating binary) PSRs B1957+20 and J1816+4510. Combining these data with those of three other eclipsing systems we study the frequency dependence of the eclipse duration. PSRs B1957+20 and J1816+4510 have similar orbital properties, but the companions to the pulsars have masses that differ by an order of magnitude. A dedicated campaign to simultaneously observe the pulsed and imaged continuum flux densities throughout the eclipses reveals many similarities between the excess material within the two binaries, irrespective of the companion star properties. The observations show that the pulsar fluxes are removed from the line of sight throughout the main body of the eclipses. For PSR J1816+4510 we present the first direct evidence of an eclipse mechanism that transitions from one that removes the pulsar flux from the line of sight to one that merely smears out pulsations, and claim that this is a consequence of scattering in a tail of material flowing behind the companion. Inferred mass loss rates from the companion stars are found to be $\dot{M}_{\text{C}} \sim 10^{-12}~M_\odot$~yr$^{-1}$ and $\dot{M

We searched for eclipses of two millisecond pulsars, PSR J1807-2459 and PSR B1908+00. These pulsars are in very low mass binary systems with orbital parameters similar to those of eclipsing binaries. Observations were made with the GBT at frequencies as low as 575 MHz. No eclipses were detected in either system. Observations of well-established eclipsing binary J2051-0827 found eclipses to be substantially weaker than previously seen, with the pulsar detected throughout the eclipse region at 575 MHz and with an electron column density an order of magnitude smaller than previously measured.