scholarly journals The Microvariable Activity of BL Lacertae

Galaxies ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 11
Author(s):  
Alberto C. Sadun ◽  
Masoud Asadi-Zeydabadi ◽  
Lauren Hindman ◽  
J. Ward Moody
Keyword(s):  
Intermediate Frequency ◽  
Light Curves ◽  
Optical Observation ◽  
Line Of Sight ◽  
Bl Lacertae ◽  
Moderate Frequency ◽  
Relativistic Beaming ◽  
Bl Lac ◽  
Free Parameters

We report on seven nights of optical observation taken over a two-week period, and the resultant analysis of the intermediate-frequency peaked BL Lac object (IBL), BL Lac itself, at redshift z = 0.069. The microvariable behavior can be confirmed over the course of minutes for each night. A relativistic beaming model was used in our analysis, to infer changes to the line of sight angles for the motion of the different relativistic components. This model has very few free parameters. The light curves we generated show both high and moderate frequency cadence to the variable behavior of BL Lac itself, in addition to the well documented long-term variability.

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 Broadband study of BL Lac during flare of 2020: Spectral evolution and emergence of HBL component

2021 ◽  
Author(s):  
Raj Prince
Keyword(s):  
Time Lag ◽  
Light Curves ◽  
X Rays ◽  
Spectral Evolution ◽  
X Ray ◽  
Bl Lacertae ◽  
Physical Mechanisms ◽  
Broadband Emission ◽  
Bl Lac ◽  
Astrophysical Neutrinos

Abstract BL Lacertae (BL Lac) is categorized as TeV blazar and considered as a possible source of astrophysical neutrinos. In 2020, the brightest X-ray flare ever detected from it. A detailed study can answer many puzzling questions related to multiband emissions and fast-flux variability often seen in this kind of source. We have performed the temporal and spectral analysis of the brightest flare. The variability is characterized by the fractional variability amplitude and the variability time. We found that the source has crossed all its previous limits of flux and reached to a maximum ever seen from it in optical and X-rays. It is highly variable in X-rays with fractional variability above 100 per cent (1.8397±0.0181) and the fastest variability time of 11.28 hours within a day. The broadband light curves correlation with X-ray suggest a time lag of one day. A broadband SED modeling is pursued to understand the possible physical mechanisms responsible for broadband emission. Modeling requires two emission regions located at two different sites to explain the low and high flux states. A significant spectral change is observed in the optical-UV and X-ray spectrum during the high state, which eventually leads to shifts in the location of the synchrotron peak towards higher energy, suggesting an emergence of a new HBL component.

scholarly journals Machine-Learning Assisted Optimisation of Free-Parameters of a Dual-Input Power Amplifier for Wideband Applications

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2831
Author(s):  
Teng Wang ◽  
Wantao Li ◽  
Roberto Quaglia ◽  
Pere L. Gilabert
Keyword(s):  
Power Amplifier ◽  
Power Efficiency ◽  
Average Power ◽  
Long Term Evolution ◽  
Input Power ◽  
Global Optimisation ◽  
Power Ratio ◽  
Term Evolution ◽  
Free Parameters

This paper presents an auto-tuning approach for dual-input power amplifiers using a combination of global optimisation search algorithms and adaptive linearisation in the optimisation of a multiple-input power amplifier. The objective is to exploit the extra degrees of freedom provided by dual-input topologies to enhance the power efficiency figures along wide signal bandwidths and high peak-to-average power ratio values, while being compliant with the linearity requirements. By using heuristic search global optimisation algorithms, such as the simulated annealing or the adaptive Lipschitz Optimisation, it is possible to find the best parameter configuration for PA biasing, signal calibration, and digital predistortion linearisation to help mitigating the inherent trade-off between linearity and power efficiency. Experimental results using a load-modulated balanced amplifier as device-under-test showed that after properly tuning the selected free-parameters it was possible to maximise the power efficiency when considering long-term evolution signals with different bandwidths. For example, a carrier aggregated a long-term evolution signal with up to 200 MHz instantaneous bandwidth and a peak-to-average power ratio greater than 10 dB, and was amplified with a mean output power around 33 dBm and 22.2% of mean power efficiency while meeting the in-band (error vector magnitude lower than 1%) and out-of-band (adjacent channel leakage ratio lower than −45 dBc) linearity requirements.

scholarly journals ES-1 Clinical results of tumor treating fields in patients with glioblastoma in Japan, compared with global surveillance

2020 ◽  
Vol 2 (Supplement_3) ◽  
pp. ii3-ii3
Author(s):  
Yoshihiro Muragaki ◽  
Masayuki Nitta ◽  
Taiichi Saito ◽  
Shunichi Tutsuki ◽  
Atsushi Fukui ◽  
...  
Keyword(s):  
Side Effects ◽  
Insurance Coverage ◽  
Intermediate Frequency ◽  
Clinical Results ◽  
Tumor Treating Fields ◽  
Post Marketing Surveillance ◽  
Post Marketing ◽  
Us Fda ◽  
Medical University

Abstract INTRODUCTION: The tumor treatment field induces apoptosis of tumor cells by providing a low intensity, intermediate frequency, alternating current electric field via a transducer array. TTFields is based on Phase 3 EF-11 and EF-14 trials for glioblastoma in the US FDA and Japan PMDA. Therefore, I will report the statistics of TTFields use in Japan along with recent papers. METHODS: 410 patients were treated with TTFields in Japan (December 2017-), of which 17 were at Tokyo Women’s Medical University. We also referred to papers about global post-marketing surveillance and recent studies. RESULTS: Of the 410 patients, 409 (99.8%) were diagnosed with ndGBM(male: female, 66.8%: 33.2%). As of June 2020, 222 patients (54.1%) were on treatment and 188 (45.9%) were discontinued. In 17 cases at TWMU, the average age was 46.3 years. The average treatment period was 218 days, with 6 patients (35%) continuing treatment, 6 patients (35%) discontinuing due to patient wishes, and 5 patients (30%) discontinuing treatment due to recurrence. Side effects were contact dermatitis under the array in 9 patients (57%) and mild malaise in 7 patients (43%). We experienced long-term progression-free cases with TTF use of 25 months (survival 30 months after surgery) with a glioma partially resected and 21 months (survival 27 months after surgery) with a biopsied glioma. In the biopsy case, bevacizumab was used in combination during the treatment. Conclusion: In global surveillance, use for rGBM accounts for 39%, but Japan is limited to use for ndGBM due to insurance coverage. In terms of side effects, it showed a good safety profile comparable to previous trials. Long-term progression-free cases have been observed, and it is necessary to examine the characteristics of patients who respond to treatment and the effect of concomitant use with bevacizumab by prospective studies

scholarly journals The challenging SED of AP Librae

2011 ◽  
Vol 7 (S284) ◽  
pp. 411-413 ◽  
Author(s):  
David Sanchez ◽  
Berrie Giebels ◽  
Pascal Fortin ◽  
Keyword(s):  
Spectral Energy Distribution ◽  
Broad Band ◽  
Low Frequency ◽  
Theoretical Models ◽  
Intermediate Frequency ◽  
High Energy ◽  
Spectral Energy ◽  
Broad Band Emission ◽  
Band Emission ◽  
Bl Lac

AbstractMatching the broad-band emission of active galaxies with the predictions of theoretical models can be used to derive constraints on the properties of the emitting region and to probe the physical processes involved. AP Librae is the third low frequency peaked BL Lac (LBL) detected at very high energy (VHE, E>100GeV) by an Atmospheric Cherenkov Telescope; most VHE BL Lacs (34 out of 39) belong to the high-frequency and intermediate-frequency BL Lac classes (HBL and IBL). LBL objects tend to have a higher luminosity with lower peak frequencies than HBLs or IBLs. The characterization of their time-averaged spectral energy distribution is challenging for emission models such as synchrotron self-Compton (SSC) models.

scholarly journals Characterizing the γ-ray long-term variability of PKS 2155−304 with H.E.S.S. and Fermi-LAT

2017 ◽  
Vol 598 ◽  
pp. A39 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Flicker Noise ◽  
High Energy ◽  
Long Term Results ◽  
Noise Power ◽  
Quiescent State ◽  
Physical Processes ◽  
Bl Lac Objects ◽  
Power Spectral ◽  
Bl Lac

Studying the temporal variability of BL Lac objects at the highest energies provides unique insights into the extreme physical processes occurring in relativistic jets and in the vicinity of super-massive black holes. To this end, the long-term variability of the BL Lac object PKS 2155−304 is analyzed in the high (HE, 100 MeV < E < 300 GeV) and very high energy (VHE, E > 200 GeV) γ-ray domain. Over the course of ~9 yr of H.E.S.S. observations the VHE light curve in the quiescent state is consistent with a log-normal behavior. The VHE variability in this state is well described by flicker noise (power-spectral-density index βVHE = 1.10+0.10-0.13) on timescales larger than one day. An analysis of ~5.5 yr of HE Fermi-LAT data gives consistent results (βHE = 1.20+0.21-0.23, on timescales larger than 10 days) compatible with the VHE findings. The HE and VHE power spectral densities show a scale invariance across the probed time ranges. A direct linear correlation between the VHE and HE fluxes could neither be excluded nor firmly established. These long-term-variability properties are discussed and compared to the red noise behavior (β ~ 2) seen on shorter timescales during VHE-flaring states. The difference in power spectral noise behavior at VHE energies during quiescent and flaring states provides evidence that these states are influenced by different physical processes, while the compatibility of the HE and VHE long-term results is suggestive of a common physical link as it might be introduced by an underlying jet-disk connection.

scholarly journals CCD Observations and Analysis of the W UMA Type Binary SS Arietis

1998 ◽  
Vol 11 (1) ◽  
pp. 382-382
Author(s):  
Wonyong Han ◽  
Chun-Hwey Kim ◽  
Jae Woo Lee ◽  
Ho-Il Kim ◽  
Woo-Baik Lee
Keyword(s):  
Period Change ◽  
Light Curves ◽  
Period Variation ◽  
Light Elements ◽  
Astronomy Observatory ◽  
Third Body ◽  
Convective Envelope ◽  
Ccd Observations ◽  
The Times

The BVR CCD observations of W UMa-type eclipsing binary SS Arietis were made for ten nights from November 1996 to December 1996 at the Sobaeksan Astronomy Observatory. From the observed light curves, nine new times of minimum lights were derived from the Kwee and van Woerden’s method. Improved light elements for this system were determined from these minimum lights with all the published minima. The analysis of the times of minima of SS Ari confirms that the orbital period of SS Ari has been suffering from a sinusoidal variation as the suggestions of other previous investigators (Kaluzny & Pojmanski 1984, Demircan & Selam 1993). The calculation shows that the cyclic period change has a period of about 56.3yrs with an amplitude of about 0.d052. The period variation has been discussed in terms of two potential mechanisms: 1) the light-time effect due to a hypothetical third body and 2) deformations in the convective envelope of a magnetically active component. The BVR light curves of SS Ari observed for about one month showed the existence of cycle to cycle light variations. Long-term light changes of SS Ari are discussed in terms of the period variation of the binary system.

scholarly journals Long-term Photometric Monitoring of FUor and FUor-like Objects

2018 ◽  
pp. 240-248
Author(s):  
E. Semkov ◽  
S. Ibryamov ◽  
S. Peneva ◽  
A. Mutafov
Keyword(s):  
Light Curve ◽  
Significant Role ◽  
Stellar Evolution ◽  
Photographic Plate ◽  
Light Curves ◽  
Curve Shape ◽  
Rate Of Increase ◽  
Fu Ori ◽  
Photometric Monitoring

A phenomenon with a significant role in stellar evolution is the FU Orionis (FUor) type of outburst. The first three (classical) FUors (FU Ori, V1515 Cyg and V1057 Cyg) are well-studied and their light curves are published in the literature. But recently, over a dozen new objects of this type were discovered, whose photometric history we do not know well. Using recent data from photometric monitoring and data from the photographic plate archives we aim to study, the long-term photometric behavior of FUor and FUor-like objects. The construction of the historical light curves of FUors could be very important for determining the beginning of the outburst, the time to reach the maximum light, the rate of increase and decrease in brightness, the pre-outburst variability of the star. So far we have published our results for the light curves of V2493 Cyg, V582 Aur, Parsamian 21 and V1647 Ori. In this paper we present new data that describe more accurate the photometric behavior of these objects. In comparing our results with light curves of the well-studied FUors (FU Ori, V1515 Cyg and V1057 Cyg), we conclude that every object shows different photometric behavior. Each known FUor has a different rate of increase and decrease in brightness and a different light curve shape.

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