Re: Flashers

[Tom Droege <tdroege2@earthlink.net>]

I like the bad flats best!  ;^)

In all cases, we use lots of reference stars.  It is ensemble 
photometry.  Images range from 1000 to 15000 stars with of order 50 
reference stars per image.  (OK this off the top of my head, I would have 
to do some work to give a good number.)

A satellite glint could do it.

OK, real data is called for, so to work.  I only mentioned these because 
they have become a pain in the neck when I use Welch-Stetson to scan the 
data.  These show up with a high statistic since both the V and I are 
moving together.

Tom Droege

At 04:20 PM 5/18/03 -0500, you wrote:
>Humm; interesting.
>
>bad flats; anything weird can be explained with bad flats
>
>obscuring of the field of view; hence, changing reference stars &/or sky 
>levels
>
>forward scattering of light by a satellite; multiple events seem unlikely;
>ah, unless it geo-synchronous.
>
>I'd insure the steadiness of the reference stars in the same observation;
>ya' want to make sure they're all stable and no drift
>
>just asking the obvious questions;  this is a good one, Tom....
>
>george wm turner
>uits/rats @ indiana university
>812 855 5156
>
>On Sun, 18 May 2003, Tom Droege wrote:
>
> > All my recent data measures a star only once a night.  So why not 
> #3?  With
> > three dual telescopes running, I get everything that transits the meridian
> > once a night in V and I.
> >
> > These are simultaneous brightenings in V and I.  Not necessarily the same
> > change in V and I.
> >
> > These are .2 to 1 mag increases in a star measured many times
> > before.  (Otherwise the WS would not pick it up.) Sometimes I see more 
> than
> > one in the data I have for a star.  In some cases it might be shifted by
> > 0.001 degree.  In others it matches the other measurements to 0.0002 
> degree
> > or better.
> >
> > I have sort of assumed that these are caused by airplane trails or some
> > such.  Cosmic rays cannot do it because of the simultaneous V and I
> > requirement.
> >
> > Tom Droege
> >
> >
> > At 11:35 PM 5/18/03 +0930, Fraser Farrell wrote:
> > >Tom Droege wrote:
> > > > Are there many stars that flash?  I keep finding stars with one bright
> > > > point.
> > >
> > >
> > >TASS Press Release : the Mark IV discovers gravitational lens 
> events....  :-)
> > >
> > >
> > >Three of the four astronomical possibilities that come to mind can all be
> > >dismissed:
> > >
> > >  - Pulsars. Not bright enough (optically), and they would flash many many
> > >times during a single Mark IV exposure.
> > >
> > >  - Gamma ray burst's optical counterpart. This might explain those
> > > occasional
> > >"seen once and never again" stars.
> > >
> > >  - Dwarf novae outbursts typically go on for hours, sometimes days. 
> Lots of
> > >these potentially detectable by TASS. But if you're taking many images per
> > >night of a dwarf nova, you would see it "bright" on several consecutive
> > >images.
> > >
> > >The fourth possibility is red dwarfs that are Flare Stars. These are
> > >detectable as occasional outbursts of light & radio waves that last 10-30
> > >minutes. Proxima Centauri, for example, can brighten from its usual 
> mag 11 up
> > >to mag 9 during a flare. Quite a sight if you're lucky enough to see one!
> > >
> > >
> > >cheers,
> > >
> > >
> > >--
> > >
> > >Fraser Farrell
> > >
> > >----------------------------------
> > >http://astronomy.trilobytes.com.au
> > >----------------------------------
> >
> >
> >