836 research outputs found
Doppler factors, Lorentz factors and viewing angles for quasars, BL Lacertae objects and radio galaxies
We have calculated variability Doppler boosting factors, Lorentz factors, and
viewing angles for a large sample of sources by using total flux density
observations at 22 and 37 GHz and VLBI data. We decomposed the flux curves into
exponential flares and determined the variability brightness temperatures of
the fastest flares. By assuming the same intrinsic brightness temperature for
each source, we calculated the Doppler boosting factors for 87 sources. In
addition we used new apparent jet speed data to calculate the Lorentz factors
and viewing angles for 67 sources. We find that all quasars in our sample are
Doppler-boosted and that the Doppler boosting factors of BL Lacertae objects
are lower than of quasars. The new Lorentz factors are about twice as high as
in earlier studies, which is mainly due to higher apparent speeds in our
analyses. The jets of BL Lacertae objects are slower than of quasars. There are
some extreme sources with very high derived Lorentz factors of the order of a
hundred. These high Lorentz factors could be real. It is also possible that the
sources exhibit such rapid flares that the fast variations have remained
undetected in monitoring programmes, or else the sources have a complicated jet
structure that is not amenable to our simple analysis. Almost all the sources
are seen in a small viewing angle of less than 20 degrees. Our results follow
the predictions of basic unification schemes for AGN.Comment: 12 pages, 14 figures, Accepted for publication in A&
The role of perceived employer obligations in the interpretation of and reaction to expatriate compensation practices
Best Paper Award of EIASM's 3rd Reward Management Conference 2011 (RMC 2011)International audienceIn this paper I examine the relationship between expatriates' perceptions of their compensation package and their affective commitment. The results of this cross-sectional study amongst 263 Finnish expatriates suggest the mediating role of the employee's perceptions of fulfillment of their employer obligations. This leads to the consideration that employees systematically assess their total reward package, interpret and give meaning to these compensation signals in terms of fulfillment of perceived employer obligations and simultaneously re-adapt or adjust their attitudes at any moment thorough their exchange relationship. In addition, this study gives empirical support for some of Rousseau and Ho's (2000) theoretical arguments regarding psychological contract (PC) issues in compensation. Furthermore it provides evidence that three of the PC feature measures for employer obligations developed by Janssens, Sels and Van den Brande (2003) can be replicated. Finally the implications of these findings for future research are discussed
INTERNATIONALISM ANCHOR: CONSTRUCT OPERATIONALIZATION AND SCALE VALIDATION
The internationalism anchor describes individuals who are primarily excited by working in international task environment, who prefer developing their professional competencies in international settings, and search for new experiences by getting to know unfamiliar countries and different cultures (Suutari & Taka, 2004). This anchor is thought to lead the career choices of an increasing number of individuals nowadays. This in-progress research paper presents an operationalization of this construct and examines its validity and correlates.Career Anchor; Internationalism; Expatriates; Self-Initiated Expatriates;
Locating the gamma-ray emission site in Fermi/LAT blazars from correlation analysis between 37 GHz radio and gamma-ray light curves
We address the highly debated issue of constraining the gamma-ray emission
region in blazars from cross-correlation analysis using discrete correlation
function between radio and gamma-ray light curves. The significance of the
correlations is evaluated using two different approaches: simulating light
curves and mixed source correlations. The cross-correlation analysis yielded 26
sources with significant correlations. In most of the sources, the gamma-ray
peaks lead the radio with time lags in the range +20 and +690 days, whereas in
sources 1633+382 and 3C 345 we find the radio emission to lead the gamma rays
by -15 and -40 days, respectively. Apart from the individual source study, we
stacked the correlations of all sources and also those based on sub-samples.
The time lag from the stacked correlation is +80 days for the whole sample and
the distance travelled by the emission region corresponds to 7 pc. We also
compared the start times of activity in radio and gamma rays of the correlated
flares using Bayesian block representation. This shows that most of the flares
at both wavebands start at almost the same time, implying a co-spatial origin
of the activity. The correlated sources show more flares and are brighter in
both bands than the uncorrelated ones.Comment: 15 pages, 8 figures and 4 tables. Published in MNRAS. Online-only
Figure 6 is available as ancillary file with this submissio
Data Congruence in What They Say, Do and Feel: The Role of Researcher's Sensory Processing Sensitivity Trait
This is the author accepted manuscript. The final version is available from Emerald via the DOI in this recordThis chapter focusses on how qualitative research can capture the lived experiences of entrepreneurial individuals by exploring their subjective experiences. Traditional methods of data collection involve listening to what entrepreneurial individuals say and observing their actions, although particular attention to their feelings is often absent. To achieve data congruence and to gain a deeper understanding of their lived experiences, it is crucial to also take into consideration how they feel. This chapter will recount a confessional tale recorded during a recent field study in entrepreneurship that will shed light on the pivotal role that a researcher’s sensory processing sensitivity (SPS) trait can play during qualitative data collection in helping researchers becoming mindful of the feelings of entrepreneurial individuals, even when those feelings are not directly expressed by them. The introduction of the researcher’s SPS trait in promoting data congruence during qualitative data collection will be this chapter’s principal contribution
Perceived uncertainty and behavioral logic: Temporality and unanticipated consequences in the new venture creation process
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.In this study, drawing on effectuation theory, we combine analytical strategies for process data to examine inductively and theorize how founder teams' perceptions of uncertainty and behavioral logics develop during new venture creation processes. The results reveal four phases and suggest a possible evolution from a causal conditional relationship between perceived uncertainty and behavioral logics to an integrative relationship. We bring to light the notion of temporality and unanticipated consequences, discuss their central roles in perceived uncertainty, effectuation, and causation, and offer revelatory insights into why and when effectuation is used in relation to uncertainty and entrepreneurial action
Statistical analyses of long-term variability of AGN at high radio frequencies
We present a study of variability time scales in a large sample of Active
Galactic Nuclei at several frequencies between 4.8 and 230 GHz. We investigate
the differences of various AGN types and frequencies and correlate the measured
time scales with physical parameters such as the luminosity and the Lorentz
factor. Our sample consists of both high and low polarization quasars, BL
Lacertae objects and radio galaxies. The basis of this work is the 22 GHz, 37
GHz and 87 GHz monitoring data from the Metsahovi Radio Observatory spanning
over 25 years. In addition,we used higher 90 GHz and 230 GHz frequency data
obtained with the SEST-telescope between 1987 and 2003. Further lower frequency
data at 4.8 GHz, 8 GHz and 14.5 GHz from the University of Michigan monitoring
programme have been used. We have applied three different statistical methods
to study the time scales: The structure function, the discrete correlation
function and the Lomb-Scargle periodogram. We discuss also the differences and
relative merits of these three methods. Our study reveals that smaller flux
density variations occur in these sources on short time scales of 1-2 years,
but larger outbursts happen quite rarely, on the average only once in every 6
years. We do not find any significant differences in the time scales between
the source classes. The time scales are also only weakly related to the
luminosity suggesting that the shock formation is caused by jet instabilities
rather than the central black hole.Comment: 19 pages, 12 figures, Accepted for publication in A&
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