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PostPosted: 09. February 2008, 14:53:43 PM 
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I have moved down to the H beta line to see if I can get a good measure of the O star RV (RV measurement is something quite new for me. I hope to learn more at Heidelberg) I was hoping to compare my result with the graph fig 1 of the Marchenko paper but that seems to be plotted around a mean of zero and I cannot see a reference to the mean RV of the system. Does anyone know this value?

Thanks
Robin


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PostPosted: 10. February 2008, 16:37:37 PM 
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Hi Robin,
Quote:
I have moved down to the H beta line to see if I can get a good measure
of the O star RV (RV measurement is something quite new for me. I hope
to learn more at Heidelberg) I was hoping to compare my result with the
graph fig 1 of the Marchenko paper but that seems to be plotted around a
mean of zero and I cannot see a reference to the mean RV of the system.
Does anyone know this value?
Why do you think the velocity has been corrected by Marchenko? I assume
they quote heliocentric velocities. Do you find significant disagreement?
Quote:
Thanks
Robin
Best regards,
Otmar


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PostPosted: 10. February 2008, 18:29:59 PM 
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Hi Otmar,
Quote:
Hi Robin,
Why do you think the velocity has been corrected by Marchenko? I assume
they quote heliocentric velocities. Do you find significant disagreement?
If they are absolute heliocentric velocities then it looks like I have to get more practice measuring RV.

If I take my wavelength of 4861.278 A and apply a heliocentric correction of -0.047 A (from VisualSpec) this gives me -0.099 A relative to the rest H beta (4861.33 A) which is -6.1km/s.

If I am reading the graph correctly, at the current phase Marchenko fig 1 gives about +10 km/s for the O star. I had hoped to get closer.

I also measured Deneb on the same night. I will check that against the published figure.

Robin


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PostPosted: 10. February 2008, 18:40:39 PM 
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Hi Robin,
Quote:
I also measured Deneb on the same night. I will check that against
the published figure.
Unfortunately, Deneb shows also radial velocity variations. You should
observe proper radial velocity standards, if you want to check your
spectrograph. See e.g.

http://obswww.unige.ch/~udry/std/std.html
Quote:
Robin
Otmar


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PostPosted: 10. February 2008, 18:44:33 PM 
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Quote:
I also measured Deneb on the same night. I will check that against the published figure.
I get an RV for Deneb of +0.5km/s compared with the published figure of -4.5kms so it does not seem to be a systematic calibration error. Perhaps my SN is just not high enough.

Robin


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PostPosted: 10. February 2008, 18:47:09 PM 
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Quote:
Unfortunately, Deneb shows also radial velocity variations. You should
observe proper radial velocity standards, if you want to check your
spectrograph. See e.g.

http://obswww.unige.ch/~udry/std/std.html
OK Otmar,

Thanks
Robin


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PostPosted: 14. February 2008, 16:26:15 PM 
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Quote:
it does not seem to be a systematic calibration error.
I think I might have found the source of the problem. My neon calibration lines (LHIRES III) are moving 0.5-1 pixel between the start, middle and end of the sets of exposures. (1 pixel = 37km/s) I am not sure if the cause is thermal or mechanical.

Best
Robin

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Ich glaube, ich könnte gefunden haben, die Ursache des Problems. Mein Neon-Kalibrierung Zeilen (LHIRES III) bewegen 0.5-1 Pixel zwischen dem Beginn, Mitte und Ende des Sets von Forderungen. (1 Pixel = 37 km / s) Ich bin mir nicht sicher, ob die Ursache ist, thermische oder mechanische.


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PostPosted: 14. February 2008, 17:33:55 PM 
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Hi Robin,
Quote:
I think I might have found the source of the problem. My neon
calibration lines (LHIRES III) are moving 0.5-1 pixel between the start,
middle and end of the sets of exposures. (1 pixel = 37km/s) I am not
sure if the cause is thermal or mechanical.
You could make a series of exposures without moving the telescopes. Then
you could see if the problem has a mechanical cause.

best regards,
Otmar


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PostPosted: 14. February 2008, 18:59:18 PM 
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Joined: 01. August 2006, 16:08:56 PM
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Location: 68163 Mannheim
Quote:
I think I might have found the source of the problem. My neon calibration lines (LHIRES III) are moving 0.5-1 pixel between the start, middle and end of the sets of exposures. (1 pixel = 37km/s) I am not sure if the cause is thermal or mechanical.
Hello Robin,

such problems i had also with my Lhiress III. There ist a construction problem with the neon lamp in Lhires. The lamp has to be vertical over the slit !!!!!!!
And the flip mechanism has to work reproducible. If there is a hoirzontal shift vertical to the slit of the lamp during flipping, than you get strong mismeasurements in calibration !
Ciao
Lothar


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