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Re: TASSJ165348.7+053411.3



Thanks for the info, as always. I will try to be more precise. Now to your 
questions...

On Sunday, June 9, 2002, at 04:53  PM, aah@nofs.navy.mil wrote:

> Michael K. wrote:
>> Using J2000 this star is GSC 00393 00221. Using JNow it is in the middle
>> of nowhere, so I'm assuming it is the former.
>   The difference between J2000 and current epoch (2002.5 or so) is pretty
> small; can you explain your "middle of nowhere" comment?  I assume
> your "Jnow" means "current epoch" and is not some term used elsewhere?
>

Every program I have lets you display positional information with J1950, 
J200, or JCurrent (JNow). I don't know what this means exactly in terms of 
epoch and equinox. None of these (amateur) programs address both epoch and 
equinox. By "middle of nowhere" I mean that if I use JCurrent there is no 
star within a few arcsecs but with J2000 it is smack on GSC 00393 00221.

>> My unfiltered  magnitude came out to be 12.4 and showed
>> a slight curve as if it was near maximum.
>   There are unfiltered magnitudes, and then there are unfiltered
> magnitudes.  First, what magnitude system did you use for setting
> the zeropoint in your field?  GSC? USNO-Ared? etc.  You should specify
> your magnitudes as "CR" (clear, using R magnitudes for zero point),
> "CV" (clear, using V magnitudes for zero point), etc.  Second, for an LPV,
> it is unlikely that you would see any curvature in a single night's
> observing window, especially with your 0.03mag errors.  Can you
> explain this comment more as well?
>

Well, when Tom said he saw variation I assumed he mean short term 
variation. While this star is near the edge of what I should work on at CV 
 > 12, the change in magnitude looks very non-random, and the comp stars 
are very steady. I have been using GSC for the zeropoint.


>> I'm told my CCD  is probably nearest to R or I than V, so if
>> it was a strong infrared source, you'd think my measurement
>> would be much closer to Tom's I.
>   I don't know of *any* CCD whose unfiltered response is close to Ic.
> The TC237 is probably reasonably close to Rc if you look at my M67 paper.
> Also, I've been pretty lax, but since you are trying to use this
> as a learning experience, please do not use the term "infrared" for
> any CCD filter/bandpass.  The filter is just "Ic" or "far red".
> Infrared means something entirely different to astronomers.  Perhaps
> you really meant astronomical infrared, in which case you might indicate
> your reasoning (did you find it in some IR catalog?).
>

I want to explain my assumption:

Unfiltered = B + V + R + I +/- overlap or gaps, no?

How could unfiltered get less signal than if I had an Ic filter on?

When I said infrared I meant "longer than red". Thank you for the 
clarification, I did not mean astronomically infrared. Apparently the I 
does not stand for infrared?

> John wrote, in response to MK's question:
>> Anything wrong with just writing "possibly associated with 1rxs etc",
>> given a negative result check has been made for any other association, I
>> wonder ?
>   That should be ok, though I would look at the DSS/VizieR and convince 
> myself
> there isn't something else more likely within the 26arcsec error radius.
> It could be an AGN or a multitude of other Xray sources.
>

I did plot this with Aladin and there was nothing close to the supposed 
position of the X-ray source than the star in question. SIMBAD also turns 
up no objects near the star in question except this X-ray source.

Michael Koppelman