Various observatories around the globe started regular full-disk imaging of the solar atmosphere in the Ca II K line in the early decades of the 20th century. The archives made by these observations ...have the potential of providing far more detailed information on solar magnetism than just the sunspot number and area records to which most studies of solar activity and irradiance changes are restricted. We evaluate the image quality and contents of three Ca II K spectroheliogram time series, specifically those obtained by the digitization of the Arcetri, Kodaikanal, and Mt Wilson photographic archives, in order to estimate their value for studies focusing on timescales longer than the solar cycle. We analyze the quality of these data and compare the results obtained with those achieved for similar present-day observations taken with the Meudon spectroheliograph and with the Rome-PSPT. We also investigate whether image-segmentation techniques, such as those developed for identification of plage regions on present-day Ca II K observations, can be used to process historic series. We show that historic data suffer from stronger geometrical distortions and photometric uncertainties than similar present-day observations. The latter uncertainties mostly originate from the photographic calibration of the original data and from stray-light effects. We also show that the image contents of the three analyzed series vary in time. These variations are probably due to instrument changes and aging of the spectrographs used, as well as changes of the observing programs. The segmentation technique tested in this study gives reasonably consistent results for the three analyzed series after application of a simple photographic calibration. Although the plage areas measured from the three analyzed series differ somewhat, the difference to previously published results is larger.
The paper presents an analysis of a series of observations of the full H-alpha line profile in the solar chromosphere. The analysis is based on data from the spectroheliograph patrol telescope ...developed at the Kislovodsk Mountain Astronomical Station, which has been in operation since 2015. The telescope conducts continuous observations with a scanning time of the entire solar disk of about 1 min. The problem of measurement of the parameters of the H-alpha line with various methods of profile approximation is considered. The possibility of determining the Doppler shift in the H-alpha line with the use of a convolutional, artificial neural network has been studied. Also considered are the characteristic forms of the H-alpha profile in active regions of the Sun and the evolution of the line profile and Doppler velocities during the formation of a solar flare on the example of an X-class flare.
Abstract
We report the discovery and multicolour (VRIW) photometry of the rare explosive star MASTER OT J004207.99+405501.1 – a luminous red nova – in the Andromeda galaxy M31N2015–01a. We use our ...original light curve acquired with identical MASTER Global Robotic Net telescopes in one photometric system: VRI during the first 30 d and W (unfiltered) during 70 d. Also, we added published multicolour photometry data to estimate the mass and energy of the ejected shell and we discuss the likely formation scenarios of outbursts of this type. We propose an interpretation of the explosion that is consistent with an evolutionary scenario where the merging of stellar components or the disruption of the common envelope of a close binary can explain some luminous red novae. Radiative hydrodynamic simulations of a luminous red nova were carried out in extended parameter space to fit its light curves. We find that the multicolour passband light curves of the luminous red nova are consistent with an initial common envelope radius of 10 R⊙, a merger mass of 3 M⊙ and an explosion energy of 3 × 1048 erg. As a result, the phenomenon of novae consists of two classes: classical nuclear novae and more rare events (red novae) connected with the loss of compact common envelopes.
We present the earliest astronomical observation of a high-energy neutrino error box of which the variability was discovered after high-energy-neutrino detection. The one robotic telescope of the ...MASTER global international networks automatically imaged the error box of the very high-energy-neutrino event IceCube-170922A. Observations were carried out in minutes after the IceCube-170922A neutrino event was detected by the IceCube observatory at the South Pole. MASTER found the blazar TXS 0506+056 to be in the off-state after one minute and then switched to the on-state no later than two hours after the event. The effect is observed at a 50 significance level. We also present own a unique 16 yr light curve of blazar TXS 0506+056 (518 data set).
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The solar activity at different latitudes is analyzed based on daily observations at Kodaikanal, Mount Wilson, Sacramento Peak, and Meudon observatories in the CaIIK line. Activity elements of ...various sizes, from the elements of the chromospheric network to the flocculi, are identified. A joint database of observation results that provides information on solar activity for 1905–2018 is created. Bright elements at middle and high latitudes are distinguished in the CaIIK line in daily images, in addition to the low-latitude activity that accompanies the appearance of sunspots. The activity can be represented as a single process that begins at high latitudes during the decline phase of the previous solar cycle and continues at low latitudes as sunspot activity. The activity-drift pattern is studied for Cycles 14–24. It is more consistent with the hypothesis of an extended solar cycle than the concept of two activity waves from the midlatitudes to poles and equator obtained from the processing of faculae in white light.
We report early optical linear polarization observations of two gamma-ray bursts made with the MASTER robotic telescope network. We found the minimum polarization for GRB 150301B to be 8 per cent at ...the beginning of the initial stage, whereas we detected no polarization for GRB 150413A either at the rising branch or after the burst reached the power-law afterglow stage. This is the earliest measurement of the polarization (in cosmological rest frame) of gamma-ray bursts. The primary intent of the paper is to discover optical emission and publish extremely rare (unique) high-quality light curves of the prompt optical emission of gamma-ray bursts during the non-monotonic stage of their evolution. We report that our team has discovered the optical counterpart of one of the bursts, GRB 150413A.
In this paper we studied long-term variations in the areas of coronal holes (CHs) reconstructed on the basis of synoptic Hα charts for the period 1887–2016 and occurrences of magnetic storms with ...gradual commencements. It was found that the temporal variations in mean yearly values of the CH areas in the northern and southern hemispheres are characterized by a pronounced ∼11-year periodicity, but they differ markedly on a multidecadal time scale. The wavelet spectra of the CH areas in the southern hemisphere, unlike those of the northern one, demonstrate persistent periodicities of ∼30–35 years, which are also observed in geomagnetic activity and climatic characteristics. The results of cross-wavelet analysis revealed a link between annual occurrences of magnetic storms with gradual commencements and variations in CH areas in both hemispheres. The obtained results allow us to conclude that the evolution of solar coronal holes may be considered as a possible factor of the formation of multidecadal cycles in geomagnetic activity, as well as climatic cycles.
A comparative analysis of sunspot sizes in sunspot groups was performed. For this analysis, we used the database of characteristics of individual sunspots and pores according to observations at the ...Kislovodsk Mountain Astronomical Station (KMAS) and the photoheliographic data from the Debrecen Heliographical Observatory, Hungary (DPD). We found agreement in the full area index for sunspot groups. However, in the DPD data for 1974–2018, the number of groups is ~50% higher than that for the KMAS data. The difference is that there are a large number of groups in the DPD data with an area of 1 mdp or less. We also found a significant difference in the properties of spots and pores of different types within the group. A significant difference in the distribution pattern of the sunspot area, which is the largest in the group S
max
and other spots S
nomax
, was detected. There are two local maxima,
~ 8–10 mdp and
~ 130–180 mdp, in the area distribution of the largest sunspot S
max
in the group. The first maximum is associated with the existence of pores and transition spots in which the penumbra is at the formation stage. The second maximum S
max
in the distribution is associated with the existence of regular spots. For the remaining spots S
nomax
in the group, the area distribution function monotonically decreases with increasing area.
An analysis of the relative number of groups in cycles 21–24 based on the digitization of observations of sunspots at the Locarno Observatory (Locarno, Switzerland) was performed. In the Zurich ...classification of sunspot groups, there are classes from A to J. The classes correspond to the process of development and decay of sunspot groups. Class A and B groups correspond to single pores or small pore clusters (class A) and bipolar group (class B). For the reconstruction of solar indices, the relative number of groups (A + B) is of great importance. We found significant variations in the relative number of spot groups (A + B) in the activity cycles. If the relative number of groups (A + B) at the activity minima is 45–50%, then a decrease to 25–30% at the activity cycle maxima is observed. In the original spot index
R
, proposed by R. Wolf, pores were not considered, and many cores united by one penumbra were counted as one spot. After 1893, at the suggestion of A. Wolfer, the method of calculating the sunspot index changed. The pores and all individual cores in the spots began to be considered – this index is denoted by
Rz
. It is believed that between the spot indices of the Wolf (
R
) and Wolfer (
Rz
), there is a constant transition coefficient close to
R
/
Rz
= 0.6. We found that this assumption is incorrect, and
R
/
Rz
depends on the amplitude of the activity cycle, varying for the N19 cycle
R
19
~ 0.34, and for the period of the grand minimum
R
MM
~ 0.64.
We present a model for the propagation of coronal mass ejections (CMEs) based on the interaction of CMEs with the solar wind through aerodynamic drag. The parameters of the solar wind are calculated ...based on observational data of the STOP magnetograph. The CME parameters, namely, the velocity vector and the estimated density at the initial stage of propagation, can be determined from the data of patrol telescopes. In the model, we consider a CME in the form of a cloud, represented by a set of points, and we track the trajectory of the motion of each point in the heliosphere. The simulation data can be used to estimate the geoefficiency of coronal mass ejections.
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