Re: Flashers

[Arne Henden <aah@nofs.navy.mil>]

The lack of reasonable explanations is probably due to lack of
reasonable description.
   I would much rather see the original images than light curves.
Automated pipelines have a tendency to create "errors" due to
a variety of reasons.  An ideal image set would contain V&I images
before an event, during the event, and after the event.
   "Flashes" generally implies rapid events, yet you do not tell
us when the previous visit to the field and the subsequent visit
to the field occur, so we cannot judge just how rapid the event was.
Was the level the same in both filters?  You should quote displacements
in pixels, not degrees; it takes time to convert such numbers in my head.
   Doug mentions geosync satellites; there are a couple of problems with
that suggestion.  First, Tom doesn't say whether this occurs only at
one latitude, or throughout his nightly slews.  Second, a geosync flash
right on top of a known star would be extremely rare.  Third, any
such flash would have a finite timespan, and would result in trailing.
Asteroids would be a possibility, but unlikely if Tom has many such
instances.
   Bottom line:  I've looked at hundreds of thousands of images without
seeing many "flashes".  I'm immediately suspicious, and would suspect
hardware, software or data-collection routine before I'd assume a
new class of variable star.
Arne

Tom Droege wrote:
> Well, the lack of any reasonable explanations means that I have to do 
> some work and put up some curves.  I will do this.  It may take a couple 
> of days.  I have been assuming that these were noise or some standard 
> item.  They have been a pain since they show up with high WS statistic 
> and I have to look at all of them to find the other good things.
> 
> Grasping at straws, one could get this type of data by luck and 
> aliasing.  Consider a pulsing star that you happen to measure ten times 
> at it's low value and once (or twice) at it's high value.
> 
> OK, onward to real data, real curves, and stars where the location can 
> be looked up.
> 
> Tom Droege
> 
> At 05:51 AM 5/18/03 +0000, Tom Droege wrote:
> 
>> Are there many stars that flash?  I keep finding stars with one bright 
>> point.  I assume that these are airplanes flying by that happen to 
>> flash on top of a measured star.  This especially if the bright point 
>> is at a slightly different position.  But sometimes the bright point 
>> is at the exact same position as all the others which I think unlikely 
>> for an airplane.
>>
>> Tom Droege
>>
>>
> 
> 
> 
> 
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