We present the Chandra ACIS-S3 data of the old classical nova RR Pic (1925). The source has a count rate of 0.067 ± 0.002 count s−1 in the 0.3–5.0 keV energy range. We detect the orbital period of the underlying binary system in the X-ray wavelengths. We also find that the neutral hydrogen column density differs for orbital minimum and orbital maximum spectra with values 0.25+0.23−0.18× 1022 and 0.64+0.13−0.14× 1022 cm−2 at 3σ confidence level. The X-ray spectrum of RR Pic can be represented by a composite model of bremsstrahlung with a photoelectric absorption, two absorption lines centered around 1.1–1.4 keV and five Gaussian lines centered at emission lines around 0.3–1.1 keV corresponding to various transitions of S, N, O, C, Ne and Fe. The bremsstrahlung temperature derived from the fits ranges from 0.99 to 1.60 keV and the unabsorbed X-ray flux is found to be 2.5+0.4−1.2× 10−13 erg cm−2 s−1 in the 0.3–5.0 keV range with a luminosity of 1.1 ± 0.2 1031 erg s−1 at 600 pc. We also detect excess emission in the spectrum possibly originating from the reverse shock in the ejecta. A fit with a cooling flow plasma emission model shows enhanced abundances of He, C, N, O and Ne in the X-ray emitting region indicating existence of diffusive mixing. 相似文献
By using high-resolution, low-scan-rate, all-sky CCD cameras, the SPanish Meteor Network (SPMN) is currently monitoring meteor
and fireball activity on a year round basis. Here are presented just a sampling of the accurate trajectory, radiant and orbital
data obtained for meteors imaged simultaneously from two SPMN stations during the continuous 2006–2007 coverage of meteor
and fireball monitoring. Typical astrometric uncertainty is 1–2 arc min, while velocity determination errors are of the order
of 0.1–0.5 km/s, which is dependent on the distance of each event to the station and its particular viewing geometry. The
cameras have demonstrated excellent performance for detecting meteor outbursts. The recent development of automatic detection
software is also providing real-time information on the global meteor activity. Finally, some examples of the all-sky CCD
cameras applications for detecting unexpected meteor activity are given. 相似文献
On December 20, 2004 the Minor Planet Center issued the Minor Planet Electronic Circular (MPEC) 2004-Y25 announcing the discovery of a new Near Earth Asteroid (NEA) with designation 2004 MN4. Only two days later, when the Christmas holidays were about to begin, it was already apparent that this asteroid, currently known as Apophis, would be notorious: our close-approach monitoring system, CLOMON2, was already showing a Virtual Impactor (VI) in 2029 reaching the level 2 in the Torino Scale, the first asteroid to reach that level since our monitoring system had been operational. However, this was just the beginning of what it was to come in the subsequent days. In this paper we will give an overview of the NEODyS-CLOMON2 system and provide the details on how Apophis’ collision scenario evolved, the way NEODyS’ team handled it and the crazy 2004’ Christmas holidays we had due to this unexpected guest. 相似文献
The interaction of carbon dioxide and amorphous water ice at 95 K is studied using transmission infrared spectroscopy. Samples are prepared in two ways: co-deposition of the gases admitted simultaneously or sequential deposition, in which amorphous water ice (ASW) is grown first and CO2 vapor is added subsequently. In either case, a fraction of the CO2 molecules is found to interact with water in a way that gives rise to shifts and splittings in the infrared bands with respect to those of a pure CO2 solid. In co-deposition experiments, a larger amount of carbon dioxide is trapped within the amorphous water than in sequential deposition samples, where a substantial proportion of molecules appears to be trapped in macropores of the ASW. The specific surface area of sequential samples is evaluated and compared to previous literature results. When the sequential samples are heated to 140 K, beyond the onset temperature at which water ice undergoes a phase transition, the CO2 molecules at the pores relocate inside the bulk in a structure similar to that found in co-deposited samples, as deduced by changes in the shape of the CO2 infrared bands. 相似文献
On September 7, 2017, at 23:49 h (local time), a Mw8.2 intermediate-depth normal-fault earthquake occurred in the Gulf of Tehuantepec, 133 km away from Pijijiapan, Chiapas, and about 700 km away from Mexico City. This event caused 95 fatalities and severe damage to different types of structures located close to the epicenter. The main objective of this work is to present observed damages caused in the state of Oaxaca by this earthquake, which were mainly concentrated in self-built houses and historical and ancient buildings. The locations visited by the reconnaissance team of the Institute of Engineering from UNAM in Oaxaca included Salina Cruz, Tehuantepec, Ixtaltepec, Juchitán, Huatulco and La Ventosa.
Natural Hazards - This contribution highlights that the paper presented by Ma et al. (Nat Hazards 89(2):741–756, 2017) presents VIF lower than 1 which does not coincide with the natural... 相似文献
A primary concern of the mining industry is to meet production targets, which are required and defined by customers. Deviations from these targets, in terms of quality and quantity, highly affect the economical aspect. Recently, an efficient resource model updating framework concept has been proposed aiming for the improvement of raw material quality control and process efficiency in any type of mining operation. The concept integrates online sensor measurements, obtained during production, into the resource model. In this way, due to the spatial variability, quality attributes of the blocks that will be produced in the next days or weeks are being updated based on real-time measurements. The concept has been applied in a lignite field with the aim of identifying local impurities in a lignite seam and to improve the prediction of coal quality attributes in neighbouring blocks. This paper investigates the added value of using the resource model updating framework by using the value of information analysis. The expected benefit of additional information (integration of the online sensor measurements into the resource model) is compared to a case where there is no additional information integrated into the process. These benefits are evaluated based on the economic impact determined by applying the resource model updating framework in mine planning.