Started by Pere Blay Jul 20 2011, 15:27
Pere Blay
Moderator
Posts: 7
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Jul 20 2011, 15:27 CET
The classical picture to classify types of ourburts have been proven to be incomplete. We need a refinement on the classification of outburst and a better understanding on their timings and origin. One way out may be seeking for commonalities instead of differences.
A key point is a better knowledge of orbital parameters and see how they relate to the outburst phenomenology.
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Peter Kretschmar
Posts: 3
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Jul 29 2011, 18:14 CET
Having collected data from different instruments on various BeXRB outbursts, some practical questions have appeared:
(1) How do you define the start and end of an outburst?
First of all, instruments different energy bands will have different dates when a flux rise becomes evident. Thus, outburst duration as observed is to some extent a function of energy band used in monitoring.
Second, at the start of an outburst one might have one point significant (by whatever definition), then a few less signficant ones, but all visually part of the outburst. Should one count from the first point or only when a sequence of data points is valid? And how do you handle data gaps? All this makes for significant differences in duration for individual outbursts.
Should one try to fit a smoothed curve to the outburst and use that shape to define duration and other parameters like, e.g., peak height?
(2) How many types of outburst shapes do we have?
Looking at a range of outbursts one sees a great number with the 'expected' shape of faster rise & slower decay. But a rather large fraction is quite symmetrical in shape, some even seem to rise slower than they decay again and some have complex shapes with multiple peaks.
Do we have a good framework to describe this? Should one rather classify or quantify these shapes? Is this always a question of eye-balling?
(3) How do we handle negative fluxes?
It sounds stupid, but the fact is that the typical monitoring instrument does a reconstruction of the source flux and due to uncertain contributions from background and other sources, values below zero are not uncommon and sometimes show visibly a clear evolution.
Should these points still be just ignored? Should one fudge the counts with an offset?
(4) How many energy bands?
While not always immediately available from the Web, the monitor instruments do offer the chance to follow the sources in more than one band per instrument.
One also knows that sources do show spectral evolution during outbursts. But using this ability one looses statistics on the indiivudal measurements.
How many bands and roughly which energy bands make sense to characterize outbursts from weak to giant?
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