Context.
We analyze the broad H
β
line profile variability of a “changing look” active galactic nucleus (CL-AGN) NGC 3516 over an extensive period of 25 years (from 1996 to 2021). The observed change ...in the broad line profile may indicate a change in the geometry of the broad line region (BLR). The main objective is to follow and understand the change in the BLR over a long period as well as its connection to the CL mechanism.
Aims.
Using spectral line profiles, we aim to explore changes in the kinematics and dimensions of the BLR in NGC 3516. We consider two possible scenarios: the changes in the broad-line emission are either caused by a decrease of ionisation continuum emission or by the BLR obscuration by outer dusty regions. With this investigation, we aim to clarify the CL mechanism of this AGN.
Methods.
We analyzed the spectral band around the H
β
line as well as the broad H
β
line parameters and how they change over time. We modelled the broad-line profiles, assuming that there is an emission from the accretion disc superposed with emission from a surrounding region that is outside the disc.
Results.
We find that in the type 1 activity phase occurring when the strong broad emission lines are observed, the BLR is very complex. There is a clear disc-like BLR that contributes to the broad line wings and an additional intermediate line region (ILR) that contributes to the line core. In the high-activity phase, the ILR emission is close to the center of the line, although in some cases, it is slightly shifted to the red. In the low-activity phase (i.e. type 2 phase), the ILR component has a significant shift to the blue, indicating an outflow.
Conclusions.
We propose that the changing-look mechanism in NGC 3516 is rather connected with the intrinsic effects than with an outer obscuring region. It may still be possible that the dust plays an important role in the low-activity phase when it is coming from within the BLR, leading to a dusty BLR. In this way, it would cause a decrease in the ionisation and recombination rates.
ABSTRACT
We present a study of the nearby low-metallicity dwarf galaxy IC 1613, focusing on the search for massive stars and related feedback processes, as well as for faint supernova remnants (SNR) ...in late stages of evolution. We obtained the deepest images of IC 1613 in the narrow-band H α, He ii and S ii emission lines and new long-slit spectroscopy observations using several facilities (6-m BTA, 2.5m SAI MSU, and 150RTT telescopes), in combination with the multiwavelength archival data from MUSE/VLT, VLA, XMM–Newton, and Swift/XRT. Our deep narrow-band photometry identifies several faint shells in the galaxy, and we further investigate their physical characteristics with the new long-slit spectroscopy observations and the archival multiwavelength data. Based on energy balance calculations and assumptions about their possible nature, we propose that one of the shells is a possible remnant of a supernova explosion. We study five out of eight Wolf–Rayet (WR) star candidates previously published for this galaxy using the He ii emission line mapping, MUSE/VLT archival spectra, and new long-slit spectra. Our analysis discards the considered WR candidates and finds no new ones. We found P Cyg profiles in H α line in two stars, which we classify as Luminous Blue Variable (LBV) star candidates. Overall, the galaxy IC 1613 may have a lower rate of WR star formation than previously suggested.
Introduction. Protocols and guidelines have been improving results of our clinical practice. Sometimes there have been differences between guidelines on the same topic, but they have not been so ...important usually. As far as the start of vitamin K antagonists (VKA) in a non-high risk pulmonary thromboembolism (PTE) patients is concerned, there is global consensus (reflected in all comprehensive guidelines) that it should be on the admission day or a day later. However, there are situations in which this VKA administering from the first (or second) day of hospitalization may actually complicate the treatment. Case report. As an illustration, our female, 71 years old patient with second unprovoked, intermediate-high risk PTE was given low-molecular-weight heparin (LMWH) + VKA from the second day. Due to lack of improvement in symptoms, oxygen saturation and D dimer after 9 days, computed tomography pulmonary angiography (CTPA) was repeated and it confirmed minimal advancement. The patient already had achieved target international normalized ratio (INR) and it complicated proceeding to fibrinolytic therapy. Conclusion. Correction of the therapeutic approach in the PTE treatment may be needed even if the treatment is completely conducted according to the latest guidelines. We recommend postponing VKA from the first (or second) day of hospitalization (as suggested in all available guidelines for non-high risk PTE patients) until satisfying clinical improvement is reached.
Abstract
The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will detect an unprecedentedly large sample of actively accreting supermassive black holes with typical accretion disk ...(AD) sizes of a few light days. This brings us to face challenges in the reverberation mapping (RM) measurement of AD sizes in active galactic nuclei using interband continuum delays. We examine the effect of LSST cadence strategies on AD RM using our metric
AGN
_
TimeLagMetric
. It accounts for redshift, cadence, the magnitude limit, and magnitude corrections for dust extinction. Running our metric on different LSST cadence strategies, we produce an atlas of the performance estimations for LSST photometric RM measurements. We provide an upper limit on the estimated number of quasars for which the AD time lag can be computed within 0 <
z
< 7 using the features of our metric. We forecast that the total counts of such objects will increase as the mean sampling rate of the survey decreases. The AD time lag measurements are expected for >1000 sources in each deep drilling field (DDF; (10 deg
2
)) in any filter, with the redshift distribution of these sources peaking at
z
≈ 1. We find the LSST observation strategies with a good cadence (≲5 days) and a long cumulative season (∼9 yr), as proposed for LSST DDF, are favored for the AD size measurement. We create synthetic LSST light curves for the most suitable DDF cadences and determine RM time lags to demonstrate the impact of the best cadences based on the proposed metric.
Abstract
The AGN STORM 2 Collaboration targeted the Seyfert 1 galaxy Mrk 817 for a year-long multiwavelength, coordinated reverberation mapping campaign including Hubble Space Telescope, Swift, ...XMM-Newton, NICER, and ground-based observatories. Early observations with NICER and XMM revealed an X-ray state 10 times fainter than historical observations, consistent with the presence of a new dust-free, ionized obscurer. The following analysis of NICER spectra attributes variability in the observed X-ray flux to changes in both the column density of the obscurer by at least one order of magnitude (
N
H
ranges from
2.85
−
0.33
+
0.48
×
10
22
cm
−
2
to
25.6
−
3.5
+
3.0
×
10
22
cm
−
2
) and the intrinsic continuum brightness (the unobscured flux ranges from 10
−11.8
to 10
−10.5
erg s
−1
cm
−2
). While the X-ray flux generally remains in a faint state, there is one large flare during which Mrk 817 returns to its historical mean flux. The obscuring gas is still present at lower column density during the flare, but it also becomes highly ionized, increasing its transparency. Correlation between the column density of the X-ray obscurer and the strength of UV broad absorption lines suggests that the X-ray and UV continua are both affected by the same obscuration, consistent with a clumpy disk wind launched from the inner broad-line region.
Abstract
The AGN STORM 2 campaign is a large, multiwavelength reverberation mapping project designed to trace out the structure of Mrk 817 from the inner accretion disk to the broad emission line ...region and out to the dusty torus. As part of this campaign, Swift performed daily monitoring of Mrk 817 for approximately 15 months, obtaining observations in X-rays and six UV/optical filters. The X-ray monitoring shows that Mrk 817 was in a significantly fainter state than in previous observations, with only a brief flare where it reached prior flux levels. The X-ray spectrum is heavily obscured. The UV/optical light curves show significant variability throughout the campaign and are well correlated with one another, but uncorrelated with the X-rays. Combining the Swift UV/optical light curves with Hubble Space Telescope UV continuum light curves, we measure interband continuum lags,
τ
(
λ
), that increase with increasing wavelength roughly following
τ
(
λ
) ∝
λ
4/3
, the dependence expected for a geometrically thin, optically thick, centrally illuminated disk. Modeling of the light curves reveals a period at the beginning of the campaign where the response of the continuum is suppressed compared to later in the light curve—the light curves are not simple shifted and scaled versions of each other. The interval of suppressed response corresponds to a period of high UV line and X-ray absorption, and reduced emission line variability amplitudes. We suggest that this indicates a significant contribution to the continuum from the broad-line region gas that sees an absorbed ionizing continuum.
The topic of this study is the factors that influence the consumption of traditional food products (TFPs) in tourism, as seen from the perspective of management-sector employees in food and beverage ...catering facilities. The paper aims to analyse the economic, environmental, social, and touristic factors that highly influence the consumption patterns of catering facilities which are significant providers of traditional gastronomic experiences in tourism, by using the specially designed TFPct scale. The study was conducted on a sample of 300 catering facilities in AP Vojvodina (the Republic of Serbia). An explanatory factor analysis was used to confirm the key factors that influence the consumption of traditional products used to prepare the meals that are a part of what catering facilities offer. Subsequently, a binary logistics regression model was used to establish which of the indicated factors has a statistically significant effect on the management's decision to purchase these products for their catering facility. The study showed that the TFPct scale is appropriate for this type of research, and that economic factors are key factors in the consumption of traditional products. Moreover, compared with other types of catering facilities, interest in the consumption of these products is clearly expressed by a la carte restaurants.
Purpose
High-fructose consumption and chronic stress are both associated with metabolic inflammation and insulin resistance. Recently, disturbed activity of energy sensor AMP-activated protein kinase ...(AMPK) was recognized as mediator between nutrient-induced stress and inflammation. Thus, we analyzed the effects of high-fructose diet, alone or in combination with chronic stress, on glucose homeostasis, inflammation and expression of energy sensing proteins in the rat liver.
Methods
In male Wistar rats exposed to 9-week 20% fructose diet and/or 4-week chronic unpredictable stress we measured plasma and hepatic corticosterone level, indicators of glucose homeostasis and lipid metabolism, hepatic inflammation (pro- and anti-inflammatory cytokine levels, Toll-like receptor 4, NLRP3, activation of NFκB, JNK and ERK pathways) and levels of energy-sensing proteins AMPK, SIRT1 and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α).
Results
High-fructose diet led to glucose intolerance, activation of NFκB and JNK pathways and increased intrahepatic IL-1β, TNFα and inhibitory phosphorylation of insulin receptor substrate 1 on Ser
307
. It also decreased phospho-AMPK/AMPK ratio and increased SIRT1 expression. Stress alone increased plasma and hepatic corticosterone but did not influence glucose tolerance, nor hepatic inflammatory or energy-sensing proteins. After the combined treatment, hepatic corticosterone was increased, glucose tolerance remained preserved, while hepatic inflammation was partially prevented despite decreased AMPK activity.
Conclusion
High-fructose diet resulted in glucose intolerance, hepatic inflammation, decreased AMPK activity and reduced insulin sensitivity. Chronic stress alone did not exert such effects, but when applied together with high-fructose diet it could partially prevent fructose-induced inflammation, presumably due to increased hepatic glucocorticoids.
Earlier, we suggested the “reload” concept of the polarimetric reverberation mapping of active galactic nuclei (AGN), proposed for the first time more than 10 years ago. We have successfully tested ...this approach of reverberation mapping of the broad emission line on the galaxy Mrk 6. It was shown that such an idea allows one to look at the AGN central parsec structure literally in a new light. However, the method originally assumed the use of spectropolarimetric observations, expensive in terms of telescope time, and implemented on rare large telescopes. Currently, we propose an adaptation of the polarimetric reverberation mapping of broad lines in medium-band filters following the idea of the photometric reverberation mapping, when filters are selected so that their bandwidth is oriented to the broad line and the surrounding continuum near. In this paper, we present the progress status of such monitoring conducted jointly at the Special astrophysical observatory and Asiago Cima Ekar observatory (OAPd/INAF) with support from Rozhen National Astronomical Observatory (NAO), some first results for the most frequently observed AGNs Mrk 335, Mrk 509, and Mrk 817, and the discussion of the future perspectives of the campaign.
The active galactic nuclei (AGN) are among the most powerful sources with an inherent, pronounced and random variation of brightness. The randomness of their time series is so subtle as to blur the ...border between aperiodic fluctuations and noisy oscillations. This poses challenges to analysing of such time series because neither visual inspection nor pre-exisitng methods can identify well oscillatory signals in them. Thus, there is a need for an objective method for periodicity detection. Here we review our a new data analysis method that combines a two-dimensional correlation (2D) of time series with the powerful methods of Gaussian processes. To demonstrate the utility of this technique, we apply it to two example problems which were not exploited enough: damped rednoised artificial time series mimicking AGN time series and newly published observed time series of changing look AGN (CL AGN) NGC 3516. The method successfully detected periodicities in both types of time series. Identified periodicity of ~4 yr in NGC 3516 allows us to speculate that if the thermal instability formed in its accretion disc (AD) on a time scale resembling detected periodicity then AD radius could be ~0.0024 pc.
PDF
