Affiliation
American Association of Variable Star Observers (AAVSO)
Sat, 03/14/2015 - 02:25
AAVSO Alert Notice 511 announces a new observing campaign involving dust production in developing planetary systems; Dr. George Rieke is the PI. Please see the Notice for details.
Many thanks and good observing,
Elizabeth Waagen, AAVSO HQ
AAVSO Special Notice #408 reminds observers that the second segment of Dr. George Rieke's campaign on dust production in developing planetary systems is BEGINNING NOW. Please see the notice for details and observing instructions.
Many thanks and good observing,
Elizabeth Waagen, AAVSO HQ
One of the campaign stars, HD 15407A seems accessible to DSLR wide-field photometry. The caveat is that I would not be able to resolve the binary system and would indeed measure HD 15407A and B together. However, since the campaign seems to be mainly about establishing non-variability in V (or T-G) , this might be ok? Anyway there don't seem to be too many observers of HD 15407A reporting at the moment, so maybe this kind of measurement is better than no measurement.
So far measurements seem consistent.
https://www.aavso.org/lcg/plot?auid=000-BKY-015&starname=HD+15407A&last…
https://www.aavso.org/lcg/plot?auid=000-BKY-015&starname=HD+15407A&last…
HB
I think as far as HD 15407A is concerned, the campaign response is problematic. If I get this right, there are three observers currently submitting data more or less on a regular basis.
Because some of them transform the results and others don't you can expect a certain variation in the magnitude reported, but if you look at the light curves of each individual observer, you should see consistent results, but this isn't the case. One observer reports almost constant (within the reported measurement-error) magnitude levels, one observer reports a rather drastic dimming while a third observer reports a significant brightening...all during the same timespan
.
Is there something funny going on with some of the comparison stars? Is it possible that observers get too low an SNR on the comp stars (some use a comp star that is 10 times fainter than the target star)? Saturation issues?
Unless saturation is the issue, I would not advocate changing the setup during the campaign but I think it might be informative to try different comp stars on existing frames.
If anyone with experience on "bright star" (mag 7) photometry wants to join the campaign now (HD 15407A is nicely located near the zenith at around midnight on latitudes of central Europe!) I guess this would be most useful to make this dataset actually useful.
CS
HBE
Occasionally I observe HD 15407A for the campaign but it is more challenging then usual for photometry measurements. In a 30' x 30' frame, there are three ref stars: 95, 96, and 102. 96 is too close to HD 15407A to use. I have tried both 95 and 102 and found that 102 results in a 0.08 V mag increase for HD 15407A compared to 95. Since 95 is brighter, I selected the data for this star to upload to AAVSO.
HD 15407A is much brighter than the ref stars, so some defocusing may be necessary to avoid CCD saturation. If too defocused, the ref stars may be problematic for photometry. Both of these issues may result in an erroneous measurement. I try to set HD 15407A max ADU to just below half of the CCD's full ADU range to maintain linearity.
BPAD
Paul
I've seen your measurements from the spring and current campaign and would really be interested in seeing more of them, to help resolve what is going on.
Because of all the photometry challenges you mentioned for this target, I decided I should try wide-field DSLR photometry on this one, which has its own drawbacks of course. I'm using a vintage Pentax f/2 85 mm lens on my EOS, which gives you all the comparison stars that you want
plus additional variables in that field (I use chart X15363FAW with stars 74 and 85 for comp and check star, resp., much closer to the target's magnitude.). With the current positioin in the sky, differences in air-mass / extinction should not be a problem for wide field photometry I guess. Blending is a problem (the A and B components are not resolved), but since the B component is listed as a potential comp star, I understand it's assumed to be non-variable.
CS
HBE
HD 15407A is in the sweet spot for PEP in V and B. Also may be in reach in H and J for those with an SSP4, which would complement the mid-infrared Spitzer observations. I encourage PEP observers to contribute to this campaign. (No PEP observations to date). Depending on the setup the companion (HD 15407B) may be in the aperture with 15407A (separation is about 20 arc seconds), which should be included in the comments section of any observations. Careful positioning may allow the B component to be excluded.
AUID 000-BBF-155 at 7.4 could be used as a comparison although its B-V of 1.6 is significantly greater than the B-V of the target (~0.5). See chart X15363FAW.
HIP 11796 is relatively close at V of 6.79 and a B-V of 0.4 looks to be a closer match, but is not listed as a comparison star in any sequence. It may be reasonable to use it as a check star. I did a quick search on VSX and did not see this star listed as a variable. I am assuming there is not sufficiently accurate photometry on this star to include it in the sequence. Any comments from the sequence team? It would be great to be able to use this star to help minimize transformation errors.
Jim
During the campaign in 2013 problems with reference star 96 (HD 15407B, AUID 000-BKY-170) surfaced. It should not be used. See Special Notice 373.
https://www.aavso.org/aavso-special-notice-373
Gordon,
If I read the WebObs view of your obervations correctly, you are using the fainter (and less similar in color) of the three reference stars in X15564JO as the comp star and the brightest (and most silimar in color) as check star, is there a reason for this? Would you also get a close to 0.1 mag variability of the target if the measurements were reduced with 000-BKY-169 as the comp star instead?
HBE
HD 15407A campaign & Special Notice 373
Gordon,
Thanks for the reference to SN-373 with regard to modification of the comp stars . The notices for this campaign (Special Notice 408 and Alert Notice 511) referenced Alert Notice 482 which contained the requirement to use Comparison Star label 96 (000-BKY-169, aka HD 15407B) Without your reference to SN-373 I might have used it even though the errors are large since it is the closest to the target and at 35 arcsec separation, if I have done my math correctly, far enough away from the target (47 pixels with my imaging setup) That there should not be serious overlap if the seeing isn’t really bad.
The sequence table I downloaded yesterday still showed the 96 star and the note “Alert Notice 482 Comp.”. I have submitted a CHET report asking for the note and perhaps the star to be removed as a comp provided Alert Notice 373 is valid.
Brad Walter, WBY
[quote=JimK]
I am assuming there is not sufficiently accurate photometry on this star to include it in the sequence. Any comments from the sequence team? It would be great to be able to use this star to help minimize transformation errors.
Jim[/quote]
That one would be great for DSLR wide field as well. It has (as the name already implies) photometry available from the Hipparcos mission, with no evidence of variability detected during the mission and the VT and BT values from the Tycho-2 catalog have error bars that are as good as it gets for that catalog. http://vizier.u-strasbg.fr/viz-bin/VizieR-S?TYC%203691-573-1
Hi All,
I collected a short time series on RZ Psc last night, 50 each of B&V, not transformed. Not knowing the behavior of this system, I let the telescope run while I was working on something else, in hopes of catching a transit event of some sort, or to see if there were observable rapid fluctuations.
There were rapid, tiny fluctuations, but I wouldn't bet my left foot that they were adequately separated from the background noise. Since professionals with much bigger toys will be checking on this system in great detail, I suppose we'll read all about it if they find something interesting.
For whatever they're worth, I submitted them today.
Clear skies,
Brad Vietje
Newbury, VT