Abstract
Because of detailed monitoring of the 22.2 GHz water maser, carried out from 2021 October to 2023 May, a very powerful flare phenomenon was detected in the galactic object W51 near the ...radial velocity of 60 km s
−1
with the amplitude of 140 kJy. A phenomenon of this magnitude was unprecedented in the entire history of observations of the source. Eleven short flares were recorded. The exponential increase and decrease in the flare flux density while reducing in their spectral line widths indicated that water masers were in an unsaturated state during the flares. All flares were located at the top of the less powerful Flare 0 with the amplitude of 13.5 kJy and the spectral line half-width of 3.0 km s
−1
. Such a wide line of the water maser, as well as the amplitude, of the flare phenomenon are so far unique discoveries. The water maser of Flare 0 may have been saturated and created a significant input flux density for other flares of this phenomenon. The extremely high density of maser spots in a cluster led to their partial overlap on the observer’s line of sight. This also confirmed the hypothesis about the need for a significant length of the path along which the generation of maser radiation occurs. New parameters of water masers and the most important physical conclusions have been obtained. The possibility of detecting gravitational waves from massive binary stars at the stage of evolution close to merging is considered for the case of W51 Main.
Powerful bursts of water masers towards G25.65+1.05 Volvach, L N; Volvach, A E; Larionov, M G ...
Monthly notices of the Royal Astronomical Society. Letters,
01/2019, Volume:
482, Issue:
1
Journal Article
Peer reviewed
Open access
ABSTRACT The results of long-term monitoring of the Galactic 22.2 GHz water masers associated with G25.65+1.05 using several telescopes are presented. We report a powerful double flare with peak flux ...densities of ∼60 and 130 kJy in 2017 September and 2017 November, respectively. We propose a linear relationship between the inverse of the square of the line width and the natural logarithm of the flux density of the flaring water maser feature. We infer from this that the flaring feature is unsaturated.
ABSTRACT
As a result of detailed observations of the water vapour maser at the 22-m Simeiz radio telescope from 2017 June to 2019 December, two powerful flares were recorded in the Galactic source ...W49N, which occurred near the high-velocity feature −40 km s−1. The extremely powerful flare had an ultrashort duration of about 2 d and reached a flux density of 110 kJy. An ultrashort flare occurred at the top of a less powerful, but ten times longer one. To our knowledge, a flare of a water maser with such extreme characteristics has never been reported before. A correlation between the exponential increase and decrease in the flare flux density and decrease in line widths with increasing flux density, which is characteristic of an unsaturated maser, is found. The maser of the third flare was in a saturated state and provided a large input flux density 9.5 kJy for the occurrence of two powerful flares, the masers of which were in an unsaturated state. New data have been obtained concerning the physical characteristics of the water maser phenomenon during powerful flares.
Abstract
According to the detailed monitoring of the water maser at a frequency of 22.2 GHz from 2019 to 2021 in IRAS 16293-2422, two powerful phenomena that occurred at radial velocities of about 6 ...and 8 km s
−1
were detected. Each flare phenomenon consisted of several separate flares lasting no more than a month. The existence of the several emitting maser spot configurations with very close radial velocities, located in the line of sight of the observer, were confirmed for the first time. This made possible to demonstrate the plausibility of the water maser activation hypothesis based on an increase in the amplification length of the maser due to several maser condensations. In both cases, powerful short flares were located on the top of less powerful, but more prolonged ones. Their radiation initiated the release of more powerful flares. The broad Doppler spectral lines of less powerful flares indicate that their masers are probably in a saturated state, while more powerful masers are in unsaturated state. New important parameters of water masers have been obtained, including flare amplitudes, maser line widths, H
2
O kinetic temperatures during flares, data on the relaxation time of the maser medium, and the fact of existence of a cascade amplification of the water maser in cases of powerful short flares. The possible localization of water masers at features near 6 and 8 km s
−1
within the young gas and dust complex IRAS 16293-2422 is also discussed in this work.
ABSTRACT
Using long-term monitoring data of water-vapour masers, here we examine a composite powerful flare of extremely short duration (∼12 d), which occurred in IRAS 16293-2422. The most powerful ...part of the flare was located on top of a less strong but more prolonged flare, which in turn is also a composite. The configuration of three radiating maser condensations located on the line of sight to the observer was detected for the first time. This made it possible to confirm one of the hypotheses for the activation of water masers, based on an increase in the maser’s amplification length by the components located in the observer’s line of sight. The unsaturated state of the two most powerful maser flares have been confirmed and some significant water maser parameters were obtained.
ABSTRACT
Blazar S5 0716+714 is well-known for its short-term variability, down to intraday time-scales. We here present the 2-min cadence optical light curve obtained by the TESS space telescope in ...2019 December–2020 January and analyse the object fast variability with unprecedented sampling. Supporting observations by the Whole Earth Blazar Telescope Collaboration in B, V, R, and I bands allow us to investigate the spectral variability during the TESS pointing. The spectral analysis is further extended in frequency to the UV and X-ray bands with data from the Neil Gehrels Swift Observatory. We develop a new method to unveil the shortest optical variability time-scales. This is based on progressive de-trending of the TESS light curve by means of cubic spline interpolations through the binned fluxes, with decreasing time bins. The de-trended light curves are then analysed with classical tools for time-series analysis (periodogram, autocorrelation, and structure functions). The results show that below 3 d there are significant characteristic variability time-scales of about 1.7, 0.5, and 0.2 d. Variability on time-scales $\lesssim 0.2$ d is strongly chromatic and must be ascribed to intrinsic energetic processes involving emitting regions, likely jet substructures, with dimension less than about 10−3 pc. In contrast, flux changes on time-scales $\gtrsim 0.5$ d are quasi-achromatic and are probably due to Doppler factor changes of geometric origin.
ABSTRACT
We report the earliest detection of the 19.967-GHz transition 21–30E (t = 0) methanol maser associated with the massive star-forming region G358.93–0.03. The flare was detectable from 2019 ...January 23 to March 5, for only 44 d. It turned out to be the most powerful 19.967-GHz maser in the Galaxy in the entire history of observations, taking into account the 104-Jy flux from it on the Earth’s surface and the distance to the source, 6.75 kpc. The 19.967-GHz maser flared contemporaneously with the first of two flares detected in associated 20.971-GHz methanol masers. We estimated that the ratio of flux densities between these two transitions is F20.971/F19.967 = 14 ± 4, increasing to >520 in the second flare. We discuss the differences between the two flares in the 20.971-GHz methanol masers and the consequence thereof.
Flaring water masers associated with W49N Volvach, L. N.; Volvach, A. E.; Larionov, M. G. ...
Astronomy and astrophysics (Berlin),
08/2019, Volume:
628
Journal Article
Peer reviewed
Open access
Aims. We present our monitoring observations and analysis of water masers associated with W49N taken in 2017 and 2018. A significant flare occurred during these observations. Methods. We used ...ground-based radio telescopes in Simeiz (RT-22), Torun (RT-32), Medicina (RT-32), Effelsberg (RT-100) with broadband spectrometers. Observational data were collected and processed automatically. Results. We report a powerful flare of the v = +6 km s−1 water maser feature; it increased in over ten months to S1.3 cm = 84 kJy in 2017 December, then decayed to the pre-flare quiescent value of S1.3 cm = 8.7 kJy in 2018 August. We infer that this flaring feature is unsaturated based on the relationship between line width and flux density.
We report new data on AO 0235+164, obtained under the program of long-term multifrequency monitoring of active galactic nuclei (AGNs). A model is proposed for finding the parameters of close binary ...systems of supermassive black holes (SMBHs) by using only observational data in the radio range. The methodology for determining the physical characteristics of the SMBHs includes harmonic and wavelet analyses as well as the assessment of the masses of the satellites and their orbital characteristics. It is shown that AO 0235+164 can be a very massive and close binary system containing companions with similar masses. The presence of an orbital period and a multiple half-period indicates the absence of noticeable eccentricity in the system. Estimates show that, along with such AGNs as 3C 454.3 and OJ 287, AO 0235+164 can be a high-power gravitational wave (GW) emitter accessible for detection by gravitational wave detectors such as the International Pulsar Timing Array (IPTA).
Context. The BL Lac object 3C 371 was observed by the Transiting Exoplanet Survey Satellite (TESS) for approximately a year, between July 2019 and July 2020, with an unmatched two-minute imaging ...cadence. In parallel, the Whole Earth Blazar Telescope (WEBT) Collaboration organized an extensive observing campaign, providing three years of continuous optical monitoring between 2018 and 2020. These datasets allow for a thorough investigation of the variability of the source. Aims. The goal of this study is to evaluate the optical variability of 3C 371. Taking advantage of the remarkable cadence of TESS data, we aim to characterize the intra-day variability (IDV) displayed by the source and identify its shortest variability timescale. With this estimate, constraints on the size of the emitting region and black hole mass can be calculated. Moreover, WEBT data are used to investigate long-term variability (LTV), including in terms of the spectral behavior of the source and the polarization variability. Based on the derived characteristics, we aim to extract information on the origin of the variability on different timescales. Methods. We evaluated the variability of 3C 371 by applying the variability amplitude tool, which quantifies variability of the emission. Moreover, we employed common tools, such as ANOVA (ANalysis Of VAariance) tests, wavelet and power spectral density (PSD) analyses to characterize the shortest variability timescales present in the emission and the underlying noise affecting the data. We evaluated the short- and long-term color behavior to understand its spectral behavior. The polarized emission was analyzed, studying its variability and possible rotation patterns of the electric vector position angle (EVPA). Flux distributions of the IDV and LTV were also studied with the aim being to link the flux variations to turbulent and/or accretion-disk-related processes. Results. Our ANOVA and wavelet analyses reveal several entangled variability timescales. We observe a clear increase in the variability amplitude with increasing width of the time intervals evaluated. We are also able to resolve significant variations on timescales of as little as ∼0.5 h. The PSD analysis reveals a red-noise spectrum with a break at IDV timescales. The spectral analysis shows a mild bluer-when-brighter (BWB) trend on long timescales. On short timescales, mixed BWB, achromatic and redder-when-brighter signatures can be observed. The polarized emission shows an interesting slow EVPA rotation during the flaring period, where a simple stochastic model can be excluded as the origin with a 3 σ significance. The flux distributions show a preference for a Gaussian model for the IDV, and suggest it may be linked to turbulent processes, while the LTV is better represented by a log-normal distribution and may have a disk-related origin.
PDF
