Possible consequences of a disk around B0656+14 on e–e and near-1 Hz gravitational wave production

Nearby pulsars B0656+14 and Geminga were proposed in the literature as the main sources of cosmic-ray positrons observed near Earth above 10 GeV. B0656+14 has comparable distance from Earth, similar magnetic field and period of Geminga. However, observations in the R and I bands indicate the presence of a disk of approximately 10⁻⁴ M_⊙ around B0656+14. Radio and pulsed γ-ray flux observations from this pulsar are also consistent with supernova fallback material and disk entering the light cylinder and partially quenching the development of electromagnetic showers in the magnetosphere. If this is the case, B0656+14 has unlikely given any contribution to e⁺ and e⁻ observed near Earth. Absolute flux measurements and the level of anisotropy in the high energy electron and positron arrival directions above 50 GeV will help in revealing if none, one of both nearby pulsars are sources of these particles observed near Earth.     

月球粉尘的研究现状

随着我国探月工程的开展,面临着月球粉尘危害性的问题,急需开展月球粉尘的研究。文章在调研的基础上,阐述了目前国外在月球粉尘方面的研究现状,主要是美国"阿波罗"计划中对月尘的特性、危害性、探测和防护方面的研究。     

New insights from cross-correlation studies between solar activity indices and cosmic-ray flux during Forbush decrease events

Observed galactic cosmic ray intensity can be subjected to a transient decrease. These so-called Forbush decreases are driven by coronal mass ejection induced shockwaves in the heliosphere. By combining in situ measurements by space borne instruments with ground-based cosmic ray observations, we investigate the relationship between solar energetic particle flux, various solar activity indices, and intensity measurements of cosmic rays during such an event. We present cross-correlation study done using proton flux data from the SOHO/ERNE instrument, as well as data collected during some of the strongest Forbush decreases over the last two completed solar cycles by the network of neutron monitor detectors and different solar observatories. We have demonstrated connection between the shape of solar energetic particles fluence spectra and selected coronal mass ejection and Forbush decrease parameters, indicating that power exponents used to model these fluence spectra could be valuable new parameters in similar analysis of mentioned phenomena. They appear to be better predictor variables of Forbush decrease magnitude in interplanetary magnetic field than coronal mass ejection velocities.     

First measurements of periodicities and anisotropies of cosmic ray flux observed with a water-Cherenkov detector at the Marambio Antarctic base

A new water-Cherenkov radiation detector, located at the Argentine Marambio Antarctic Base (64.24S-56.62 W), has been monitoring the variability of galactic cosmic ray (GCR) flux since 2019. One of the main aims is to provide experimental data necessary to study interplanetary transport of GCRs during transient events at different space/time scales. In this paper we present the detector and analyze observations made during one full year. After the analysis and correction of the GCR flux variability due to the atmospheric conditions (pressure and temperature), a study of the periodicities is performed in order to analyze modulations due to heliospheric phenomena. We can observe two periods: (a) 1 day, associated with the Earth’s rotation combined with the spatial anisotropy of the GCR flux; and (b) $～$ 30 days due to solar impact of stable solar structures combined with the rotation of the Sun. From a superposed epoch analysis, and considering the geomagnetic effects, the mean diurnal amplitude is $～$ 0.08% and the maximum flux is observed in $～$ 15 h local time (LT) direction in the interplanetary space. In such a way, we determine the capability of Neurus to observe anisotropies and other interplanetary modulations on the GCR flux arriving at the Earth.     

1-D dusty photo-ionization models of WR planetary nebulae NGC 2452 and IC 2003

We report dusty photo-ionization models for two Planetary Nebulae NGC 2452 and IC 2003, which have [WR] type central stars, using 1D photo-ionization code Cloudy17.02. We used the medium resolution optical spectra and archival IRAS photometry to constrain our models. The physical size of the ionized nebula derived using accurate distance measurements and absolute H$\beta$ flux available in the literature were used as additional constrains. We examine the importance of photo-electric heating and found that models with and without considering photo-electric heating do not make significant difference for both PNe for the MRN grain size distribution considered in this study. We derive the nebular elemental abundances of these PNe by the empirical method as well as by making dusty photo-ionization models. The values of N/O ratios for both PNe obtained from our models are lower than their respective values arrived using empirical methods. The central stars are assumed to be black bodies and the photospheric temperatures derived respectively for NGC 2452 and IC 2003 from their best fit models are 182 kK and 155 kK and their respective luminosities are 630$L_{\odot }$ and 1015$L_{\odot }$. We propose that both the PNe were resulted from low-mass progenitors of mass $?$2.8 M_⊙.