scholarly journals The results of the photometric optical monitoring of four active galaxies in 2018-2019

2019 ◽  
pp. 42-48
Author(s):  
V. Ponomarenko ◽  
А. Simon ◽  
V. Vasylenko ◽  
I. Izvekova ◽  
О. Baransky
Keyword(s):  
Active Galactic Nuclei ◽  
Total Error ◽  
Galactic Nuclei ◽  
Bl Lacertae ◽  
Flat Field ◽  
National University ◽  
Pixel Scale ◽  
Very High

Active galactic nuclei (AGN) are a source of very high energies. Blazars are a subclass of active galactic nuclei that can be observed in the optical spectral range. The aim of the study is some BL Lacertae type blazars, which are characterized by a non-emission optical spectrum and exhibit brightness variations at all wavelengths. The results of systematical monitoring of selected objects from the CTA (Cherenkov Telescope Array) optical follow up list, started in January 2018 are presented. The observations are carried out with the AZT-8 (D = 70 cm, F = 2.8 m) telescope of the observation station Lisnyky of Taras Shevchenko National University of Kyiv. In 2018 the telescope AZT-8 was included in the list of supporting instruments in the CTA consortium. The AZT-8 equipped with the PL4710-1-BB-E2V CCD (1027×1048 pixels, 13×13 µm/pixel, scale is 0.95 “/pixel, field of view is 16.2 angular minutes) and broadband Johnson/Bessel UBVRI filters. For processing the software Maxim DL was used. During processing accounting of substrate (bias), dark current, flat-field were taken into account. The fluxes of energy from objects of research with the help of standard stars has been turned into visible stellar magnitudes. Light curves for four objects: 1ES 1011+496, PKS 1222+216, 1ES 1426+428, PKS 1510-089 were plotted. Variability of color indexes with time was investigated. In addition, we determined the variability amplitude and tested all these objects for Intraday Variations (IDV), Short (STV) and Long term variability (LTV) where it was possible. A short-term brightness change (STV) with an amplitude of 0.5 to 1 in all filters (UBVRI) of the Johnson/Bessel system for AGN 1ES 1011+496, PKS 1510-089 was determined. For objects 1ES 1426+428 and PKS 1222+216, the brightness variations do not exceed the total error (instrumental and methodical). The total error is ∆Σ ≈ 0.060.1 magnitude.

scholarly journals Monitoring the Extragalactic High Energy Sky

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 9 ◽  
Author(s):  
Jean-Philippe Lenain
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Energy ◽  
Line Of Sight ◽  
Data Sets ◽  
High Energies ◽  
Multi Wavelength ◽  
Rich Data ◽  
Very High

Blazars are jetted active galactic nuclei with a jet pointing close to the line of sight, hence enhancing their intrinsic luminosity and variability. Monitoring these sources is essential in order to catch them flaring and promptly organize follow-up multi-wavelength observations, which are key to providing rich data sets used to derive e.g., the emission mechanisms at work, and the size and location of the flaring zone. In this context, the Fermi-LAT has proven to be an invaluable instrument, whose data are used to trigger many follow-up observations at high and very high energies. A few examples are illustrated here, as well as a description of different data products and pipelines, with a focus given on FLaapLUC, a tool in use within the H.E.S.S. collaboration.

SDSS J154751.94+025550 with double-peaked broad H β but single-peaked broad H α: a candidate for central binary black hole system?

2021 ◽  
Vol 507 (4) ◽  
pp. 5205-5213
Author(s):  
XueGuang Zhang
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Broad Line ◽  
Line Profiles ◽  
Physical Conditions ◽  
Binary Black Hole ◽  
Sinusoidal Function

ABSTRACT In this manuscript, an interesting blue active galactic nuclei (AGNs) SDSS J154751.94+025550 (=SDSS J1547) is reported with very different line profiles of broad Balmer emission lines: double-peaked broad H β but single-peaked broad H α. SDSS J1547 is the first AGN with detailed discussions on very different line profiles of the broad Balmer emission lines, besides the simply mentioned different broad lines in the candidate for a binary black hole (BBH) system in SDSS J0159+0105. The very different line profiles of the broad Balmer emission lines can be well explained by different physical conditions to two central BLRs in a central BBH system in SDSS J1547. Furthermore, the long-term light curve from CSS can be well described by a sinusoidal function with a periodicity about 2159 d, providing further evidence to support the expected central BBH system in SDSS J1547. Therefore, it is interesting to treat different line profiles of broad Balmer emission lines as intrinsic indicators of central BBH systems in broad line AGN. Under assumptions of BBH systems, 0.125 per cent of broad-line AGN can be expected to have very different line profiles of broad Balmer emission lines. Future study on more broad line AGN with very different line profiles of broad Balmer emission lines could provide further clues on the different line profiles of broad Balmer emission lines as indicator of BBH systems.

VERITAS OBSERVATIONS OF RELATIVISTIC OUTFLOWS IN LOW- AND INTERMEDIATE-FREQUENCY-PEAKED BL LAC OBJECTS

2014 ◽  
Vol 28 ◽  
pp. 1460178
Author(s):  
◽  
HEIKE PROKOPH
Keyword(s):  
Gamma Ray ◽  
Intermediate Frequency ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Bl Lacs ◽  
Gamma Ray Telescopes ◽  
Very High

The majority of blazars detected at very high energies (VHE; E > 100 GeV) are high-frequency-peaked BL Lac objects (HBLs). Low- and intermediate-frequency-peaked BL Lacs (LBLs/IBLs with synchrotron-peak frequencies in the infrared and optical regime) are generally more powerful, more luminous, and have a richer jet environment than HBLs. However, only a handful of these IBL and LBLs have been detected by ground-based gamma-ray telescopes, typically during high-flux states. The VERITAS array has been monitoring five known VHE LBLs/IBLs since 2009: 3C 66A, W Comae, PKS 1424+240, S5 0716+714 and BL Lacertae, with typical exposures of 5-10 hours per year. The results of these long-term observations are presented, including a bright, subhour-scale VHE flare of BL Lacertae in June 2011, the first low-state detections of 3C 66A and W Comae, and the detection and characterization of the IBL B2 1215+30.

scholarly journals Active Galactic Nuclei in the Extreme Ultraviolet

1996 ◽  
Vol 152 ◽  
pp. 27-36
Author(s):  
Arieh Königl
Keyword(s):  
Active Galactic Nuclei ◽  
Extreme Ultraviolet ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Potential Usefulness ◽  
Spectral Features ◽  
Bl Lacertae Objects ◽  
Spectroscopic Measurements ◽  
Bl Lacertae ◽  
Unique Information

EUV observations could provide valuable and unique information about the nature of active galactic nuclei. I discuss their potential usefulness and review some of the main results obtained so far with the ROSAT WFC and the EUVE instruments. About three dozen sources, mostly Seyfert galaxies and BL Lacertae objects, have already been identified, and spectroscopic measurements of several of them have yielded a number of surprises. However, more observations are clearly needed to confirm some of the reported spectral features and to validate their interpretation.

scholarly journals Localization of binary black hole mergers with known inclination

2019 ◽  
Vol 488 (3) ◽  
pp. 4459-4463 ◽  
Author(s):  
K Rainer Corley ◽  
Imre Bartos ◽  
Leo P Singer ◽  
Andrew R Williamson ◽  
Zoltán Haiman ◽  
...  
Keyword(s):  
Black Hole ◽  
Binary System ◽  
Active Galactic Nuclei ◽  
Prior Information ◽  
Galactic Nuclei ◽  
Electromagnetic Emission ◽  
Accretion Discs ◽  
Host Galaxies ◽  
Binary Black Hole

ABSTRACT The localization of stellar-mass binary black hole mergers using gravitational waves is critical in understanding the properties of the binaries’ host galaxies, observing possible electromagnetic emission from the mergers, or using them as a cosmological distance ladder. The precision of this localization can be substantially increased with prior astrophysical information about the binary system. In particular, constraining the inclination of the binary can reduce the distance uncertainty of the source. Here, we present the first realistic set of localizations for binary black hole mergers, including different prior constraints on the binaries’ inclinations. We find that prior information on the inclination can reduce the localization volume by a factor of 3. We discuss two astrophysical scenarios of interest: (i) follow-up searches for beamed electromagnetic/neutrino counterparts and (ii) mergers in the accretion discs of active galactic nuclei.

scholarly journals The Compact Magnetic Field Structures of AGN from Space VLBI Polarization Observations

2001 ◽  
Vol 205 ◽  
pp. 134-135
Author(s):  
D.C. Gabuzda ◽  
J.L. Gómez
Keyword(s):  
Magnetic Field ◽  
Active Galactic Nuclei ◽  
Linear Polarization ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Emission Mechanism ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Optical Line

BL Lacertae objects are active galactic nuclei with weak, sometimes undetectable, optical line emission and strong variability in total intensity and linear polarization over a broad range of wavelengths from ultraviolet to radio. It is believed that synchrotron radiation is the dominant emission mechanism virtually throughout the spectrum. Their strong linear polarization makes BL Lac objects prime targets for space VLBI polarization observations.

scholarly journals A possible γ-ray quasi-periodic oscillation of ∼314 days in the blazar OJ 287

2020 ◽  
Vol 499 (1) ◽  
pp. 653-658
Author(s):  
Pankaj Kushwaha ◽  
Arkadipta Sarkar ◽  
Alok C Gupta ◽  
Ashutosh Tripathi ◽  
Paul J Wiita
Keyword(s):  
Light Curve ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Periodic Oscillation ◽  
Large Area ◽  
Quasi Periodic Oscillation ◽  
Bl Lacertae ◽  
Emission Models ◽  
Γ Ray ◽  
Blazar Oj 287

ABSTRACT We report the detection of a probable γ-ray quasi-periodic oscillation (QPO) of around 314 d in the monthly binned 0.1–300 GeV γ-ray Fermi-Large Area Telescope light curve of the well-known BL Lacertae blazar OJ 287. To identify and quantify the QPO nature of the γ-ray light curve of OJ 287, we used the Lomb–Scargle periodogram (LSP), REDFIT, and weighted wavelet Z-transform (WWZ) analyses. We briefly discuss possible emission models for radio-loud active galactic nuclei that can explain a γ-ray QPO of such a period in a blazar.

scholarly journals Polarization Distributions in Compact Radio Sources

1986 ◽  
Vol 119 ◽  
pp. 141-147
Author(s):  
David H. Roberts ◽  
John F. C. Wardle
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Bl Lacertae ◽  
The Galaxy ◽  
5 Ghz

We present milliarcsecond-resolution 5 GHz polarization maps of several active galactic nuclei: one epoch each for the quasar 3C345, the galaxy 3C120, and the BL Lacertae object 0735+178, and two epochs for the BL Lacertae object OJ287.

scholarly journals A patient with severe rhabdomyolysis and high levels of creatinine kinase had renal functions fully recovered after haemodialysis: a case report

2019 ◽  
Vol 48 (4) ◽  
pp. 030006051988810 ◽  
Author(s):  
Shang-Feng Tsai ◽  
Jun-Li Tsai ◽  
Cheng-Hsu Chen
Keyword(s):  
Renal Function ◽  
Serum Creatinine ◽  
Predictive Power ◽  
Kidney Injury ◽  
Blood Biomarkers ◽  
History Of ◽  
Very High ◽  
Current Report

Rhabdomyolysis is diagnosed based on the levels of blood biomarkers such as creatine kinase (CK), but the use of CK levels to predict long-term renal function remains controversial. This current report presents a case with a very high CK level with the presentation of acute kidney injury (AKI) who regained full renal function. A 29-year-old man, in a manic mood and presenting with dyspnoea, was admitted to hospital following an episode of ketamine use along with a history of drug abuse. The laboratory analyses identified rhabdomyolysis (CK, 35 266 U/l) and AKI (serum creatinine, 3.96 mg/dl). Despite treatment with intravenous normal saline (4000 ml/day), his CK level reached at least 300 000 U/l. He underwent 13 sessions of haemodialysis and his renal function fully recovered. The final measurements were serum creatinine 1.0 mg/dl and CK 212 U/l. These findings support the view that the predictive power of CK level on AKI is limited, especially regarding long-term renal function. Close follow-up examinations of renal function after haemodialysis are mandatory for patients with rhabdomyolysis.

scholarly journals APASL HCV guidelines of virus-eradicated patients by DAA on how to monitor HCC occurrence and HBV reactivation

2019 ◽  
Vol 13 (6) ◽  
pp. 649-661 ◽  
Author(s):  
Tatsuo Kanda ◽  
George K. K. Lau ◽  
Lai Wei ◽  
Mitsuhiko Moriyama ◽  
Ming-Lung Yu ◽  
...  
Keyword(s):  
Hbv Dna ◽  
Hbv Reactivation ◽  
Close Attention ◽  
Short Term ◽  
Direct Acting Antiviral ◽  
B Virus ◽  
Direct Acting ◽  
Very High

Abstract In the direct-acting antiviral (DAA) era for hepatitis C virus (HCV) infection, sustained virological response (SVR) is very high, but close attention must be paid to the possible occurrence of hepatocellular carcinoma (HCC) and reactivation of hepatitis B virus (HBV) in patients with co-infection who achieved SVR in short term. HCC occurrence was more often observed in patients with previous HCC history. We found occurrence of HCC in 178 (29.6%) of 602 patients with previous HCC history (15.4 months mean follow-up post-DAA initiation) but, in contrast, in only 604 (1.3%) of 45,870 patients without previous HCC history (18.2 months mean follow-up). Thus, in these guidelines, we recommend the following: in patients with previous HCC history, surveillance at 4-month intervals for HCC by ultrasonography (US) and tumor markers should be performed. In patients without previous HCC history, surveillance at 6- to 12-month intervals for HCC including US is recommended until the long-term DAA treatment effects, especially for the resolution of liver fibrosis, are confirmed. This guideline also includes recommendations on how to follow-up patients who have been infected with both HCV and HBV. When HCV was eradicated in these HBsAg-positive patients or patients with previous HBV infection (anti-HBc and/or anti-HBs-positive), it was shown that HBV reactivation or HBV DNA reappearance was observed in 67 (41.4%) of 162 or 12 (0.9%) of 1317, respectively. For these co-infected patients, careful attention should be paid to HBV reactivation for 24 weeks post-treatment.

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