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1.
Comparisons of solar magnetic-field measurements made in different spectral lines are very important, especially in those lines in which observations have a long history or (and) specific diagnostic significance. The spectral lines Fe i 523.3 nm and Fe i 525.0 nm belong to this class. Therefore, this study is devoted to a comprehensive analysis using new high-precision Stokes-meter full-disk observations. The disk-averaged magnetic-field strength ratio R=B(523.3)/B(525.0) equals 1.97±0.02. The center-to-limb variation (CLV) is R=1.74−2.43μ+3.43μ 2, where μ is the cosine of the center-to-limb angle. For the disk center, we find R=2.74, and for near-limb areas with μ=0.3, R equals 1.32. There is only a small dependence of R on the spatial resolution. Our results are rather close to those published three decades ago, but differ significantly from recent magnetographic observations. An application of our results to the important SOHO/MDI magnetic data calibration issue is discussed. We conclude that the revision of the SOHO/MDI data, based only on the comparison of magnetic-field measurements in the line pair Fe i 523.3 nm and Fe i 525.0 nm (increasing by a factor of 1.7 or 1.6 on average according to recent publications) is not obvious and new investigations are urgently needed.  相似文献   

2.
The new spectroscopic observation of MV Sgr obtained at ESO in 1987 July shows enhanced emission lines of He I λ3889, [SII] λ4068 relative to the observations discussed by Jeffreyet al. (1988). The presence of [SII] λ4068 indicates the presence of planetary-nebulae-like envelope around the star. Although the radial velocity of the absorption lines and Fe II emission lines do agree with the velocity given by Jeffreyet al., the [SII] λ4068 and probably He I emission lines appear to behave differently. Based on observations collected at the European Southern Observatory, La Silla, Chile.  相似文献   

3.
Seventeen coudé spectrograms (dispersion 20 A mm–1) of the Lyrae-type eclipsing binary V 367 Cygni (P=18.6 d) have been studied. The observations were made at the Haute Provence Observatory during a period of almost two years (May 1973–March 1975). An anomalous behavior for the radial velocities of the spectrograms taken during one cycle (406) was observed; it is suggested that gas eruption under form of prominences may explain it. The spectrum is dominated by shell lines very similar to those present in the spectrum of the supergiant A9 Ia Aurigae. The underlying stellar spectrum is classified as A5 I on the basis of the intensity of the sole clearly visible stellar line, 4481 MgII, of the wings of the stellar Balmer lines, and an estimate of the intensity of the stellarK line. The radial velocity curves for the shell lines of CaII, HI, metallic ions and neutral iron, as well as the phase dependence of the microturbulence, indicate stratification in the shell.  相似文献   

4.
We examine the XMM X-ray spectrum of the low-ionisation nuclear emission-line region (LINER)-AGN NGC 7213, which is best fit with a power law, Kα emission lines from Fe i, Fe xxv and Fe xxvi and a soft X-ray collisionally ionised thermal plasma with kT = 0.18+0.03−0.01 keV. We find a luminosity of 7× 10−4 LEdd, and a lack of soft X-ray excess emission, suggesting a truncated accretion disc. NGC 7213 has intermediate X-ray spectral properties, between those of the weak AGN found in the LINER M 81 and higher luminosity Seyfert galaxies. This supports the notion of a continuous sequence of X-ray properties from the Galactic Centre through LINER galaxies to Seyferts, likely determined by the amount of material available for accretion in the central regions. This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).  相似文献   

5.
The hydrogen and helium lines are the most prominent lines in the solar prominences spectra. Observations with the SUMER spectrometer onboard SOHO showed that there are weak lines in the blue wings of the Lyman series which affect their profiles. They were all identified as He ii lines in the Lyman series wings, except for the Lα line whose profile was affected by the use of an attenuator. The He ii lines are the even Balmer lines of the He ii system, a set of lines that we complete with the odd ones. We characterize them by comparison with the blue wings of the Lyman series in order to improve the H Lyman series observations and modeling, on one hand and to provide He ii lines observations for further combined H – He i – He ii modeling, on the other hand.  相似文献   

6.
We have tracked the spectral responsivity of the ultraviolet channels of the UVCS (Ultraviolet Coronagraph Spectrometer) instrument on SOHO by repeated observations of a stable hot star. We demonstrate first that the ultraviolet spectral irradiance of the Be star ζ Tau (HD 37202) for the 100- to 125-nm wavelength range has been sufficiently constant for our purposes when measured periodically over the course of the SOHO mission. We then use ζ Tau as a radiometric transfer standard to determine an average decrease beginning in November of 1998 of 13.0% per year in the responsivity of the UVCS O vi channel for wavelengths near H i Ly α and for a particular UVCS unvignetted aperture used for science observations. The calibration tracking method involves separating two ζ Tau spectral regions that are overlapped on part of the detector. The change in the responsivity of UVCS/SOHO began in late 1998 as determined by comparison of simultaneous observations of the corona carried out with UVCS/SOHO and the freshly-calibrated UVCS instrument on the Spartan 201 satellite in early November of 1998. B. Valcu now at BrainLAB, Inc, 3 Westbrook Corporate Ctr., Tower 3, Suite 400, Westchester, IL 60154, USA, e-mail: bogdan.valcu@brainlab.com or Bogdan_valcu@hotmail.com  相似文献   

7.
Share  G.H.  Murphy  R.J.  Dennis  B.R.  Schwartz  R.A.  Tolbert  A.K.  Lin  R.P.  Smith  D.M. 《Solar physics》2002,210(1-2):357-372
The RHESSI high-resolution spectrometer detected γ-ray lines and continuum emitted by the Earth's atmosphere during impact of solar energetic particles in the south polar region from 16:00–17:00 UT on 21 April 2002. The particle intensity at the time of the observation was a factor of 10–100 weaker than previous events when gamma-rays were detected by other instruments. This is the first high-resolution observation of atmospheric gamma-ray lines produced by solar energetic particles. De-excitation lines were resolved that, in part, come from 14N at 728, 1635, 2313, 3890, and 5106 keV, and the 12C spallation product at ∼ 4439 keV. Other unresolved lines were also detected. We provide best-fit line energies and widths and compare these with moderate resolution measurements by SMM of lines from an SEP event and with high-resolution measurements made by HEAO 3 of lines excited by cosmic rays. We use line ratios to estimate the spectrum of solar energetic particles that impacted the atmosphere. The 21 April spectrum was significantly harder than that measured by SMM during the 20 October 1989 shock event; it is comparable to that measured by Yohkoh on 15 July 2000. This is consistent with measurements of 10–50 MeV protons made in space at the time of the γ-ray observations.  相似文献   

8.
We studied the evolution of a small eruptive flare (GOES class C1) from its onset phase using multi-wavelength observations that sample the flare atmosphere from the chromosphere to the corona. The main instruments involved were the Coronal Diagnostic Spectrometer (CDS) aboard SOHO and facilities at the Dunn Solar Tower of the National Solar Observatory/Sacramento Peak. Transition Region and Coronal Explorer (TRACE) together with Ramaty High-Energy Spectroscopic Imager (RHESSI) also provided images and spectra for this flare. Hα and TRACE images display two loop systems that outline the pre-reconnection and post-reconnection magnetic field lines and their topological changes revealing that we are dealing with an eruptive confined flare. RHESSI data do not record any detectable emission at energies ≥25 keV, and the observed count spectrum can be well fitted with a thermal plus a non-thermal model of the photon spectrum. A non-thermal electron flux F ≈ 5 × 1010 erg cm−2 s−1 is determined. The reconstructed images show a very compact source whose peak emission moves along the photospheric magnetic inversion line during the flare. This is probably related to the motion of the reconnection site, hinting at an arcade of small loops that brightens successively. The analysis of the chromospheric spectra (Ca II K, He I D3 and Hγ, acquired with a four-second temporal cadence) shows the presence of a downward velocity (between 10 and 20 km s−1) in a small region intersected by the spectrograph slit. The region is included in an area that, at the time of the maximum X-ray emission, shows upward motions at transition region (TR) and coronal levels. For the He I 58.4 and O v 62.97 lines, we determine a velocity of ≈−40 km s−1 while for the Fe XIX 59.22 line a velocity of ≈−80 km s−1 is determined with a two-component fitting. The observations are discussed in the framework of available hydrodynamic simulations and they are consistent with the scenario outlined by Fisher (1989). No explosive evaporation is expected for a non-thermal electron beam of the observed characteristics, and no gentle evaporation is allowed without upward chromospheric motion. It is suggested that the energy of non-thermal electrons can be dissipated to heat the high-density plasma, where possibly the reconnection occurs. The consequent conductive flux drives the evaporation process in a regime that we can call sub-explosive.  相似文献   

9.
Twenty-five coudé spectrograms (22 with dispersion 12 Å mm–1 and three 7 Å mm–1) of 6 Cassiopeiae (A3 Ia) have been studied. The observations were made at the Haute Provence Observatory. The results of the analysis suggest a correlation between the variations of the equivalent widths, the microturbulence and the radial velocity. The radial velocity and turbulent velocity present a rapid variation with time, even in intervals as short as about an hour. The hydrogen lines are slightly asymmetric but the strongest Feii lines are clearly asymmetric. We found that the amount of asymmetry of the strongest Feii lines (I>6) correlates with the loggf value, with the estimated laboratory intensityI, and with the equivalent widthW .The observations have been made at the Astronomical Observatory of Haute Provence (CNRS). This work has been supported by TUBITAK (Scientific and Technical Research Council of Turkey), and partially by CNR (Consiglio Nazionale delle Ricerche) of Italy.  相似文献   

10.
A survey of the infrared coronal spectrum between 1 and 3 was made from a high altitude aircraft during the 7 March, 1970, solar eclipse. The observations were made with a Fourier transform spectrometer and were confined to the outer chromosphere and inner corona. In addition to well known chromospheric lines of Hi and Hei, nine additional lines were seen. Evidence is presented for the tentative assignment of these lines to forbidden transitions in highly ionized atoms of magnesium, aluminum, silicon, sulphur, and chromium.  相似文献   

11.
We have obtained and analyzed UBVRI CCD frames of the young, 4–10 Myr, open cluster NGC 3293 and the surrounding field in order to study its stellar content and determine the cluster’s IMF. We found significantly fewer lower mass stars, M≤2.5M ⊙, than expected. This is particularly so if a single age for the cluster of 4.6 Myr is adopted as derived from fitting evolutionary models to the upper main sequence. Some intermediate-mass stars near the main sequence in the HR diagram imply an age for the cluster of about 10 Myr. When compared with the Scalo (The stellar initial mass function. ASP conference series, vol. 24, p. 201, 1998) IMF scaled to the cluster IMF in the intermediate mass range, 2.5≤M/M ⊙≤8.0 where there is good agreement, the high mass stars have a distinctly flatter IMF, indicating an over abundance of these stars, and there is a sharp turnover in the distribution at lower masses. The radial density distribution of cluster stars in the massive and intermediate mass regimes indicate that these stars are more concentrated to the cluster core whereas the lower-mass stars show little concentration. We suggest that this is evidence supporting the formation of massive stars through accretion and/or coagulation processes in denser cluster cores at the expense of the lower mass proto-stars. R.W. Slawson and E.P. Horch are guest investigators at the University of Toronto Southern Observatory, Las Campanas, Chile.  相似文献   

12.
The solar UV continuum has been derived from intensity-calibrated observations with the High-Resolution Telescope and Spectrograph - HRTS - on its second rocket flight in 1978. A database has been constructed using the spatially-resolved solar spectrum 1180–1700 Å along a slit extending from near disk center to the solar limb and crossing a sunspot and two active regions. The angular resolution is approximately 1.8″. The data consist of 1772 spectral scans in the full center-to-limb range, including both quiet and active solar regions. The distribution of solar UV intensities has been derived and the center-to-limb variations of the continuum intensities in the quiet Sun are studied. Both quantities show spectral variations, particularly across the Sii continuum edge at 1521 Å. The spectra have been fitted to curves of constant color temperature above and below the Sii edge. The derived center-to-limb variations have been compared to the values of Samain (1979) which are frequently referred to in the literature. A relatively large discrepancy may be explained by the higher spectral and angular resolution of the HRTS as compared to the rocket instrument used by Samain. Comparisons with the VAL III model calculations by Vernazza, Avrett, and Loeser (1981) show discrepancies between the observations and the model predictions, particularly with regard to the sign and amount of the intensity change across the Sii continuum edge. It is noted that some of the results presented, i.e., absolute intensities and brightness temperatures may change, pending confirmation of the SUSIM Spacelab 2 irradiance results (VanHoosieret al., 1988).  相似文献   

13.
As part of a program to estimate the solar spectrum back to the early twentieth century, we have generated fits to UV spectral irradiance measurements from 1 – 410 nm. The longer wavelength spectra (150 – 410 nm) were fit as a function of two solar activity proxies, the Mg ii core-to-wing ratio, or Mg ii index, and the total Ca ii K disk activity derived from ground based observations. Irradiance spectra at shorter wavelengths (1 – 150 nm) where used to generate fits to the Mg ii core-to-wing ratio alone. Two sets of spectra were used in these fitting procedures. The fits at longer wavelengths (150 to 410 nm) were derived from the high-resolution spectra taken by the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) on the Upper Atmospheric Research Satellite (UARS). Spectra measured by the Solar EUV Experiment (SEE) instrument on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite were used for the fits at wavelengths from 1 to 150 nm. To generate fits between solar irradiance and solar proxies, this study uses the above irradiance data, the NOAA composite Mg ii index, and daily Ca ii K disk activity determined from images measured by Big Bear Solar Observatory (BBSO). In addition to the fitting coefficients between irradiance and solar proxies, other results from this study include an estimated relationship between the fraction of the disk with enhanced Ca ii K activity and the Mg ii index, an upper bound of the average solar UV spectral irradiance during periods where the solar disk contains only regions of the quiet Sun, as was believed to be present during the Maunder Minimum, as well as results indicating that slightly more than 60% of the total solar irradiance (TSI) variability occurs between 150 and 400 nm.  相似文献   

14.
Data are presented from a spectral and photometric study of the long-period variable star Y Ori, which we have classified as a type M7IIIe near its brightness minimum. In the blue part of the spectrum, features from a star of an earlier spectral class are superimposed on the spectrum of a cool giant, so that a variable excess emission is observed at wavelengths of 4000–4200 Å. As opposed to the monotonically decreasing intensity of the Balmer lines (EWHα > EWHβ > EWHγ > EWHδ) in normal stars belonging to the earlier spectral classes, a reverse relationship, with EWHγ < EWHδ is detected in Y Ori. Translated from Astrofizika, Vol. 51, No. 4, pp. 567–575 (November 2008).  相似文献   

15.
A comparison is made between Ca xix and Ca xviii line ratios observed in solar flares with the Bent Crystal Spectrometer (BCS) on the Solar Maximum Mission (SMM) satellite and currently available atomic data. Close agreement is found with the excitation rates recently published by Pradhan et al. (1981). The observations show little dependence of line ratios on electron temperature, supporting a further conclusion that cascade contributions to the 23 P and 23 S levels are not significant.  相似文献   

16.
Airborne eclipse observations of the [Six] 1430.5 nm coronal emission line are reviewed, and new ground-based out-of-eclipse coronagraph observations obtained at NSO/Sacramento Peak are reported. We find that the [Six] 1430.5 nm coronal emission line brightness is less than 8 × 10−6 B⊙ in small active region corona which showed [Fexiii] 1074.7 nm emission (corrected for sky background) of about 20 × 10−6 B⊙. Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.  相似文献   

17.
Nine high- and low-resolution IEU spectra at different orbital phases during different cycles, of the hydrogen-poor single-lined spectroscopic binary KS per (HD 30353) have been studied. The near-UV spectrum is characterized by the presence of several lines of once ionized metals which show the same orbital RV shifts observed in the visual range. The MgII resonance lines present a sharp interstellar + circumstellar core and an emission peak at about 83 and 92 km s–1. The far UV spectrum is characterized by the presence of strong absorptions of the resonance lines ofNV,CIV, SiIV, SiIII.Direct determination of the IS extinction from the 2200 Å feature givesE(B-V)=0.33. A comparison of corrected logarithmic continuous energy distribution with the theoretical models by Kurucz, indicates that the companion is a hot star,T e=15000 K; logg=4. A comparison with the recent UV work ofv Sgr, shows that, KS Per is very similar tov Sgr.Based on observations by the International Ultraviolet Explorer (IUE) collected at the Villafrance Satellite Tracking Station and obtained from the IUE data bank.  相似文献   

18.
We present a new method to reconstruct the solar spectrum irradiance in the Ly α – 400 nm region, and its variability, based on the Mg ii index and neutron-monitor measurements. Measurements of the solar spectral irradiance available in the literature have been made with different instruments at different times and different spectral ranges. However, climate studies require harmonised data sets. This new approach has the advantage of being independent of the absolute calibration and aging of the instruments. First, the Mg ii index is derived using solar spectra from Ly α (121 nm) to 410 nm measured from 1978 to 2010 by several space missions. The variability of the spectra with respect to a chosen reference spectrum as a function of time and wavelength is scaled to the derived Mg ii index. The set of coefficients expressing the spectral variability can be applied to the chosen reference spectrum to reconstruct the solar spectra within a given time frame or Mg ii index values. The accuracy of this method is estimated using two approaches: direct comparison with particular cases where solar spectra are available from independent measurements, and calculating the standard deviation between the measured spectra and their reconstruction. From direct comparisons with measurements we obtain an accuracy of about 1 to 2%, which degrades towards Ly α. In a further step, we extend our solar spectral-irradiance reconstruction back to the Maunder Minimum introducing the relationship between the Mg ii index and the neutron-monitor data. Consistent measurements of the Mg ii index are not available prior to 1978. However, we remark that over the last three solar cycles, the Mg ii index shows strong correlation with the modulation potential determined from the neutron-monitor data. Assuming that this correlation can be applied to the past, we reconstruct the Mg ii index from the modulation potential back to the Maunder Minimum, and obtain the corresponding solar spectral-irradiance reconstruction back to that period. As there is no direct measurement of the spectral irradiance for this period we discuss this methodology in light of the other proposed approaches available in the literature. The use of the cosmogenic-isotope data provides a major advantage: it provides information about solar activity over several thousands years. Using technology of today, we can calibrate the solar irradiance against activity and thus reconstruct it for the times when cosmogenic-isotope data are available. This calibration can be re-assessed at any time, if necessary.  相似文献   

19.
We explore the hard X-ray source distributions of an C1.1 flare occurred on 14 December 2007. Both Hinode/EIS and RHESSI observations are used. One of EIS rasters perfectly covers the double hard X-ray footpoints, where the EUV emission appears strong from the cool line of He ii (log T=4.7) to the hot line of Fe xvi (log T=6.4). We analyze RHESSI X-ray images at different energies and different times before the hard X-ray maximum. The results show a similar topology for the time-dependent source distribution (i.e. at 14:14:35 UT) as that for energy-dependent source distribution (i.e. at a given energy band of 6 – 9 keV) overlapped on EUV bright kernels, which seems to be consistent with the evaporation model.  相似文献   

20.
During the total solar eclipse at Akademgorodok, Siberia, Russia, on 1 August 2008, we imaged the flash spectrum with a slitless spectrograph. We have spectroscopically determined the duration of totality, the epoch of the second and third contacts and the duration of the flash spectrum. Here we compare the 2008 flash spectra with those that we similarly obtained from the total solar eclipse of 29 March 2006, at Kastellorizo, Greece. Any changes of the intensity of the coronal emission lines, in particularly those of Fe x and Fe xiv, could give us valuable information about the temperature of the corona. The results show that the ionization state of the corona, as manifested especially by the Fe xiv emission line, was much weaker during the 2008 eclipse, indicating that following the long, inactive period during the solar minimum, there was a drop in the overall temperature of the solar corona.  相似文献   

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