scholarly journals Can BL Lac Nuclei and Broad Line Regions Coexist? or When is an Object a BL Lac?

1996 ◽  
Vol 175 ◽  
pp. 244-245
Author(s):  
M.J.M. Marchã
Keyword(s):  
Selection Criteria ◽  
Radio Spectrum ◽  
Emission Lines ◽  
Systematic Analysis ◽  
Object A ◽  
Bl Lac ◽  
Optical Continuum ◽  
Common Criterion ◽  
Definition Of ◽  
Bl Lacs

The problem of BL Lac classification is a long standing one and it is mainly due to the subjectiveness of selection criteria used in the definition of BL Lac samples. For instance, an object will undoubtedly be classified as a BL Lac if it shows flat radio spectrum, high optical and radio polarization, featureless optical continuum with weak or absent emission lines, and variable flux and polarization. However, the problem arises when the object shows some but not all of these properties. In face of this difficulty, different authors (Stickel et al. 1991, Stocke et al. 1991) have tried to make a systematic analysis of the data and it has been common to classify as BL Lacs those objects whose strongest emission lines have equivalent width (EW) ≤ 5 Å. Another common criterion is to require the 4000 Å break contrast to be ≤ 0.25. Nevertheless, both of these criteria are rather arbitrary and more directly related to practical observational considerations, than they are to any physical distinction between objects. What is proposed here is a slightly different approach; it is proposed that we take a step back from common classification and that instead of imposing strict selection criteria, we create a multi-observational parameter space to investigate any breaks in the distribution of observed properties that will help clarify the distinction between BL Lacs and other flat radio spectrum sources.

scholarly journals The redshift and the host galaxy of the neutrino candidate 4FGL J0955.1+3551 (3HSP J095507.9+355101)

2020 ◽  
Vol 495 (1) ◽  
pp. L108-L111
Author(s):  
Simona Paiano ◽  
Renato Falomo ◽  
Paolo Padovani ◽  
Paolo Giommi ◽  
Adriana Gargiulo ◽  
...  
Keyword(s):  
Equivalent Width ◽  
Absolute Magnitude ◽  
Emission Lines ◽  
Absorption Lines ◽  
Host Galaxy ◽  
Source Image ◽  
Host Galaxies ◽  
Upper Limit ◽  
Bl Lac ◽  
Bl Lacs

ABSTRACT The BL Lac object 4FGL J0955.1+3551 has been suggested as a possible source of ultra-energetic neutrinos detected by the IceCube observatory. The target was observed in 2020 January at the Large Binocular Telescope. Our spectroscopy (4100–8500 Å) yields a firm redshift z = 0.557 as deduced by the absorption lines of the host galaxy. The upper limit of the minimum equivalent width on emission lines is ∼0.3 Å. From the source image, we are able to resolve the host galaxy for which we measure an absolute magnitude M(R) = −22.9 and Re = 8 kpc, which are values which are typical of the host galaxies of BL Lacs.

scholarly journals Arcsecond Scale Polarization of BL Lac Objects

1996 ◽  
Vol 175 ◽  
pp. 55-56
Author(s):  
C. Stanghellini ◽  
P. Cassaro ◽  
M. Bondi ◽  
D. Dallacasa ◽  
R. Della Ceca ◽  
...  
Keyword(s):  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Radio Spectrum ◽  
Line Of Sight ◽  
Parent Population ◽  
Rapid Variability ◽  
Bl Lac Objects ◽  
Relativistic Jet ◽  
Bl Lac ◽  
Optical Continuum

BL Lac objects are an enigmatic class of active galactic nuclei. They are characterized by high luminosity, a flat radio spectrum that steepens at higher energies, relatively high optical and radio polarization, rapid variability and an optical continuum with weak or absent emission lines (see Urry and Padovani, 1995 for a recent review).These properties have been interpreted in terms of a relativistic jet closely aligned to the line of sight (Blandford and Rees, 1978, Ghisellini et al., 1993). This model, known as the beaming model, implies that there must be a so called “parent population” of radio sources intrinsically identical to BL Lac objects, but with the jets oriented at large angles to the line of sight. Browne (1983) was the first to propose the low luminosity FR I radio galaxies as the most likely candidates for the “parent population” of the core dominated BL Lac objects. An outcome of the beaming model is that all the properties not depending on orientation should be shared by the BL Lac objects and the FR I radio galaxies.

The Introduction of Minbenzhuyi and the Return of Its Traditional Chinese Meaning

Cultura ◽  
2019 ◽  
Vol 16 (2) ◽  
pp. 67-88
Author(s):  
Xiaobo LV
Keyword(s):  
Systematic Analysis ◽  
Intellectual Community ◽  
Chinese Context ◽  
Liang Qichao ◽  
Confucian Values ◽  
Chinese Intellectual ◽  
Ancient Literature ◽  
Definition Of ◽  
Chen Duxiu

The concepts of Minben , Minbensixiang , and Minbenzhuyi are rather popular in current Chinese discourse. However, “Minben” was hardly found in Chinese ancient literature as a noun. Around the year of 1916, “Minbenzhuyi” became widely accepted in Japanese intellectual circles, interpreted as one of the Japanese versions of democracy. In 1917, “Minbenzhuyi” was transferred to China as a loanword by Li Dazhao and developed into one of the Chinese definitions of democracy. Nevertheless, Chen Duxiu questioned the meaning of the term in 1919. It was not until 1922 did Liang Qichao bring Minbenzhuyi back into Chinese context and conduct a systematic analysis, which had a lasting impact on Chinese intellectual community. In the following 20 years, Minbenzhuyi was largely accepted in two different senses: 1) interpreted as Chinese definition of democracy; 2) specifically refers to the Confucian idea of “Minshiminting and Minguijunqing (;, ) Gradually, it became evident that Minbenzhuyi in China had grown distant from the meaning of democracy and returned to its traditional Confucian values.

scholarly journals Gaia-assisted discovery of a detached low-ionisation BAL quasar with very large ejection velocities

2020 ◽  
Vol 634 ◽  
pp. A111 ◽  
Author(s):  
J. P. U. Fynbo ◽  
P. Møller ◽  
K. E. Heintz ◽  
J. N. Burchett ◽  
L. Christensen ◽  
...  
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Emission Lines ◽  
Broad Absorption ◽  
Broad Absorption Line ◽  
Red Edge ◽  
First Case ◽  
Bl Lac ◽  
Spatially Extended ◽  
Extended Emission

We report on the discovery of a peculiar broad absorption line (BAL) quasar identified in our Gaia-assisted survey of red quasars. The systemic redshift of this quasar was difficult to establish because of the absence of conspicuous emission lines. Based on deep and broad BAL troughs of at least Si IV, C IV, and Al III, a redshift of z = 2.41 was established under the assumption that the systemic redshift can be inferred from the red edge of the BAL troughs. However, we observe a weak and spatially extended emission line at 4450 Å that is most likely due to Lyman-α emission, which implies a systemic redshift of z = 2.66 if correctly identified. There is also evidence for the onset of Lyman-α forest absorption bluewards of 4450 Å and evidence for Hα emission in the K band consistent with a systemic redshift of z = 2.66. If this redshift is correct, the quasar is an extreme example of a detached low-ionisation BAL quasar. The BALs must originate from material moving with very large velocities ranging from 22 000 km s−1 to 40 000 km s−1. To our knowledge, this is the first case of a systemic-redshift measurement based on extended Lyman-α emission for a BAL quasar. This method could also be useful in cases of sufficiently distant BL Lac quasars without systemic-redshift information.

scholarly journals A Comparison of the X-ray Spectra of Quasars and BL Lac Objects

1989 ◽  
Vol 134 ◽  
pp. 197-198
Author(s):  
D. M. Worrall ◽  
B. J. Wilkes
Keyword(s):  
Power Law ◽  
Radio Spectrum ◽  
Spectral Indices ◽  
Mean Power ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Infrared Frequencies

Quasars with similar core-compact radio properties can be classified by their differences at optical and infrared frequencies. Their X-ray properties might be expected to be similar if the synchrotron self-Compton mechanism relates their radio and X-ray emission. We have compared the 0.2–3.5 keV mean power-law energy spectral indices, , for 4 quasar classes: 12 Highly Polarized QSOs (HPQs), 19 Flat Radio Spectrum, core-compact, low-polarization, QSOs (FRS QSOs), 24 radio-selected BL Lac objects, and 7 X-ray-selected BL Lac objects.

scholarly journals The Environment of OJ 287: Nearby Galaxies and a Long Optical Jet?

1996 ◽  
Vol 175 ◽  
pp. 47-48
Author(s):  
A. Sillanpää ◽  
L. Takalo ◽  
K. Nilsson ◽  
T. Pursimo ◽  
P. Teerikorpi ◽  
...  
Keyword(s):  
Large Scale ◽  
Radio Galaxies ◽  
Trigger Mechanism ◽  
Galaxy Clustering ◽  
Bl Lac Objects ◽  
Close Interaction ◽  
Relativistic Jet ◽  
Bl Lac ◽  
Nearby Galaxies ◽  
Bl Lacs

A widely accepted model for BL Lac objects is that they are radio galaxies with a relativistic jet pointing almost directly towards us. But we need a clear trigger mechanism for these jets. One possibility is the close interaction between the BL Lac host and the closeby galaxies (e.g. Heckman et al. 1986). This interaction has been seen many times in the case of quasars (Hutchings et al. 1989) but not so much is known about the close surroundings of the BL Lac objects although there has been some pioneer work like Stickel et al. (1993). The problem has usually been that the images are not deep enough and that the seeing has not been so good. To clarify the situation we have started an observing program to get very deep images in the sub-arcsecond seeing conditions from the whole 1 Jy sample (Stickel et al. 1991) of BL Lac objects. The aims of this study are: 1. to search for very close companions to the BL Lacs, 2. to study the large scale galaxy clustering around the BL Lacs and 3. to study the BL Lac hosts themselves.

Effect of Method of Defining the Active Patient Population on Measured Immunization Rates in Predominantly Medicaid and Non-Medicaid Practices

PEDIATRICS ◽  
2000 ◽  
Vol 106 (Supplement_1) ◽  
pp. 171-176
Author(s):  
Ardythe L. Morrow ◽  
R. Clinton Crews ◽  
Henry J. Carretta ◽  
Mekibib Altaye ◽  
Albert B. Finch ◽  
...  
Keyword(s):  
Selection Criteria ◽  
Immunization Practice ◽  
Immunization Rate ◽  
The Past ◽  
Immunization Rates ◽  
Patient Selection Criteria ◽  
Definition Of ◽  
Practice Assessment ◽  
Active Patients

Objective. To examine the effect of patient selection criteria on immunization practice assessment outcomes. Methods. In 3 high- (50%–85%) and 7 low- (<25%) Medicaid pediatric practices in urban eastern Virginia, we assessed immunization rates of children 12 and 24 months old comparing thestandard criteria (charts in the active files excluding those that documented the child moved or went elsewhere) with 3 alternative criteria for selecting active patients: 1)follow-up: the chart contained a complete immunization record or the patient was found to be active in the practice through follow-up contact by phone or mail; 2) seen in the past year: the chart indicated that the patient was seen in the practice in the past year; 3) consecutive: patients that were seen consecutively for any reason. Results. Of the 1823 charts assessed in the high- and low-Medicaid practices, follow-up identified 61% and 83% as active patients; 78% and 95% were ever seen in the past year. At 24 months, mean practice immunization rates were lower for standard (70%) than all 3 alternative criteria (78%–86%). Immunization rate differences between standard and alternative criteria were greater in high- (17%–23%) than low-Medicaid practices (5%–13%). Conclusion. The standard for practice assessment should be based on a consistent definition of active patients as the immunization rate denominator.

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 When is a Learning Object not an Object: A first step towards a theory of learning objects

2002 ◽  
Vol 3 (2) ◽  
Author(s):  
Mike Sosteric ◽  
Susan Hesemeier
Keyword(s):  
Economies Of Scale ◽  
Learning Objects ◽  
Short Term ◽  
Object A ◽  
Smart Learning ◽  
Smart Learning Environments ◽  
Adequate Definition ◽  
Definition Of ◽  
Conceptual Confusion

<p> For some, “learning objects" are the “next big thing” in distance education promising smart learning environments, fantastic economies of scale, and the power to tap into expanding educational markets. While learning objects may be revolutionary in the long term, in the short term, definitional problems and conceptual confusion undermine our ability to understand and critically evaluate the emerging field. This article is an attempt to provide an adequate definition of learning objects by (a) jettisoning useless theoretical links hitherto invoked to theorize learning objects, and (b) reducing the definition of learning objects to the bare essentials. The article closes with suggestions for further research and further refinement of the definition of learning objects. </P>

scholarly journals Systemic approach to the choice of optical methods of forensic examination of micro-objects

2021 ◽  
Vol 39 (69) ◽  
pp. 564-580
Author(s):  
Liudmyla Havryliuk ◽  
Valentyna Drozd ◽  
Olena Nenia ◽  
Anatolii Kyslyi ◽  
Andrii Niebytov
Keyword(s):  
Systematic Approach ◽  
Systemic Approach ◽  
Optical Methods ◽  
Structural Method ◽  
Systematic Analysis ◽  
Holistic View ◽  
Legal Method ◽  
Logical Method ◽  
Examination Methods ◽  
Definition Of

The aim of the article is to analyze theoretical and methodological provisions related to the definition of directions and principles of implementation of a systematic approach to the use of optical research methods, in particular micro-objects. Subject of research is substantiation and formulation of the classification characteristics of such systematic approach, considering the requirements of forensic techniques. Methodology: The study applies such methods of scientific knowledge as dialectical method, system and structural method, logic and legal method, methods of systematic analysis, logical method. Research results: The article studies the problematic issues of a systematic approach to the choice of scientific and technical methods and means for micro-object examination. Practical consequences: The authors argue that optical methods of the micro-object examination require classifying and systematizing to provide a holistic view of their potentials, as well as the nature of the information that can be obtained about the object being examined. Value / originality: The analysis of clarified classification characteristics and requirements for examination methods in forensic science enables to propose the algorithm of the systemic approach to the creation of the open system classification of methods of micro-object examination and to make justified conclusions.

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