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AM Her obs needed - urgent

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weo
weo's picture
AM Her obs needed - urgent

A new observing campaign on the magnetic variable AM Her starts immediately. Filtered photometry is needed to support satellite observations scheduled for APRIL 6; please read AAVSO Alert Notice 517 for details. Many thanks.

Good observing,

Elizabeth Waagen, AAVSO HQ

lmk
lmk's picture
Q

[quote=weo]

A new observing campaign on the magnetic variable AM Her starts immediately. Filtered photometry is needed to support satellite observations scheduled for APRIL 6; please read AAVSO Alert Notice 517 for details. Many thanks.

[/quote]

Hi Elizabeth - a couple questions:

1. Are visual obs of any use to this investigator?

2. Why do your announcements in the forum always appear in duplicate?

Thanks, Mike.

weo
weo's picture
Visual obs for AM Her x-ray campaign? Duplicate postings?

To answer your questions, Mike,

1. Are visual obs of any use to this investigator?  In this particular campaign, visual observations are helpful to know whether AM Her is in its high or low state. However, the behavioral information the astronomers need for more detailed correlation with the x-ray observations requires the higher precision of photometry with S/N~10.

2. Why do your announcements in the forum always appear in duplicate? I assume you mean duplicate as in two emails, not twice in the same forum. When we issue an Alert or Special Notice, we post to the forum to help spread the word. I post to the forums that are appropriate, and that is usually 2 (possibly 3) - the transient or campaign/observation forum and the forum for the type of variable being targeted. I don't usually change the subject line from one forum to another, so it might appear to be a duplication, but it's really two different forums you are hearing from.

Thanks for asking, and Good observing,

Elizabeth

weo
weo's picture
NuSTAR observing AM Her on April 5

The NuSTAR observations of AM Her have been scheduled for 2015 APRIL 5! Please see AAVSO Special Notice #401 for the exact schedule and observing instructions.

Good observing,

Elizabeth Waagen, AAVSO HQ

equinox
equinox's picture
Test

Hi Elizabeth,

I run a test sequence for AM Her yesterday night and have uploaded the file to WebObs right now.

200 pcs of 1-minute exposures (160/1308 APO, ST-10XME, through Bessell-V filter), SNR is 58 (between 25...100), standard deviation is 0.035m, median shift is +0.006m.

What do you think, such a sequence could be useful (if there will not be clouds...)? Sorry for this question;I am not a fully accomplished variable observer...

Attila

HQA
HQA's picture
time series

Hi Atilla,

That time series looks very nice!  It shows the orbital modulation very well.  I think your observations will be fine.  I'd decrease the exposure time to get a 30-second cadence if you can.  They want good time resolution to match the X-ray variability, and so are willing to give up a little signal/noise for the higher cadence.

Continue to observe on the next couple of nights since the two spacecraft observations are split apart in time.

Arne

FJQ
FJQ's picture
time series

I submitted 12, transformed BVI photo-mags of AM Her with an average error (un-transfomred) of 0.006 (V-filter) with 120sec exposure with a 33 Cm apeture scope at F/7.4 with an ST-10XME.    I need to start earlier on AM Her but my east is heavily blocked.

Should I go as short as Attila's recommended exposure of 30 sec to get a better cadence?  (error should go up about +/-0.02 if exposures are 1/4 as long)

James

equinox
equinox's picture
it was cloudy night...

[quote=HQA]

Hi Atilla,

That time series looks very nice!  It shows the orbital modulation very well.  I think your observations will be fine.  I'd decrease the exposure time to get a 30-second cadence if you can.  They want good time resolution to match the X-ray variability, and so are willing to give up a little signal/noise for the higher cadence.

Continue to observe on the next couple of nights since the two spacecraft observations are split apart in time.

Arne

[/quote]

I am very disappointed sad. I spent all my last night in my backyard obsy next to my unlocked and activated "weapon" waiting for clear sky without any result...

@Arne,

How long will this campaign last exactly?

 

Thanks,

Attila

HQA
HQA's picture
cadence

Hi James,

The request is to obtain optical photometry that is coincident in time with the X-ray observations, to extend the wavelength coverage as widely as possible.  As such, they only need V-band, and want the highest possible cadence.  I'd forego the BVI/transformation route for this particular campaign, and just take high-cadence V-band observations.  Start now, and continue at least a day past the end of the X-ray run if possible.

Pay attention to the details of the request, too.  Because of the strong emphasis on correlation with the X-ray observations, they need very accurate timing.  Be sure that you have some sort of network-served time program running on your computer, such as Dimension4.

Arne

FJQ
FJQ's picture
cadence

To:  Arne,

Will do! Thanks for the clarification.  I've set up my C-11 as far west in my backyard as it will go and will be able to get 1.5 Hrs more observing time on AM Her.  I'll make 2 BI observations at the beginning and end of the run tonight , but will be doing all V filter.  Probably going for 45-sec exposures because the C-11 is much slower than my classical cassegrain (F/10 vs F/7.5).

James

P.s.  I've been using Dim4 since Dr. B. Harris's remarks on time accuracy!

LMA
LMA's picture
AM Her

Elizabeth,

I just submitted a batch of over 200 observations, will have more later this morning when dawn stop my observing. Used a V filter and exposure of 30 sec for a total cycle of about 55 sec.

This is the first time I participate in such campaign, your comments would help to improve the quality of my future data..

Damien

As mentioned above, I have sent a second batch in the morning. But then I realized that I had not erased the log from de first batch. Result, the first 205 observations have been sent twice. Sorry for the extra work, my only excuse is that I am a bit tired.

Damien

 

 

HQA
HQA's picture
slow f/ratio

Hi James,

Thanks for giving me some of your system parameters!  Running D4 is a really good thing, as timing accuracy with these kinds of multiwavelength correlations is extremely important.  For those that have never worked with X-ray satellites, since the fluence is so small, they actually time-tag every photon (something that optical astronomers will do some day!).

Regarding the f/ratio of your telescope:  photometry of stars is very different than imaging of extended objects.  Whether your telescope is f/3, f/7, or f/10, you collect the same number of photons.  As long as the star is unresolved, you won't get higher signal/noise with any focal length.  Usually the choice of focal length (or f/ratio) is due to practical considerations - to achieve ~2 pixels per fwhm, or to have a wide-enough field to find suitable comparison stars.  My recommendation has always been to keep the optical path simple, and if you don't need a focal reducer, don't use one.  The exception is if you are using the focal reducer to also correct optical aberrations - to get a flat field or remove coma, for example.  Then there is the tradeoff of an extra optical element (with absorption and scattering) vs. better quelity images.

Arne

FJQ
FJQ's picture
05Apr15 Results

To:  Arne,

Thanks for your kind advice.  I ended-up taking only 128 x 50 second V-filter images...I started my run 1 hour after AM Her cleared the trees! (Kind of difficult to set-up everything for automated imaging in a brand new area with 40' plus control cables going from house-to-telescope)  My system is a C-11 at F/10.01 (2797mm measured my Pin-point astrometric engine) on a iOptron CEM60.  The C-11 has a rack and pinion focuser with robofocus attached.  This system is controled with MaximDL 5.23 under CCDautopilot 5, which controls the acquisition, scheduling, imaging, focusing, flat-fielding, etc....At least I'm set-up for tomorrow's run with a plate-solved location for AM Her with a nice guide star in my guide-chips' FOV.  I think I'll try 30 sec exposures bin 2x2 and start as soon as AM Her clears the trees to get tighter cadence and maintain low 1/snr.

My V-Mag data compared to other observers V-data looks consistant, but I noticed a set whose profile looks good but is displaced 1 V-magnitude upwards; see portion of graph with red circle: http://www.astroimage.info/images/05Apr15-RunSM.jpg

James

p.s.  I submitted almost 1000 BVRI XZ Ceti transformed photometric data last week form a run I did from in  Sep14-Nov14.  Hope it looks good enough for you to use!

WGR
WGR's picture
AM Her Light Curve last night (Sat)

Hello Elizabeth

It cleared here in NE and got on AM Her about midnight and ran the remainder of the night.  Reduced data and posted with Webobs.  I had looked at the light curve in Maxim6 and deleted some points with high errors. The light curve looked "wonky" (term used by students these days for quasi erratic)   Posted the data, and thought I was seeing double.  BPAD had posted his/her data, and my data posted on top--even with the "wonkyness".  

A shout out to LMA who also posted data, that had the same characteristics, but with an offset from WGR and BPAD.  This star must be very active.  Is this normal for magnetic CV's.  Just printed out the info and will go read it.  

I also deleted some data that had high error bars compared to the 600 or so that I posted.  This happens around JD 2457117.84 and 2457117.86 or so.  Let me know if this high error  bar data might be of use.  I did not want to post it, as I thought it might have been passing clouds.  I will re-examine.  

Will be on it tonight, but weather does not look good.  

WGR

Gary 

pbenni
Transit event detected?

Does this binary system show transits?  There is a U shaped 0.4 mag fade at midpoint ~ JD 2457117.854 detected by at least two observers.

BPAD

Paul

MZK
MZK's picture
Fine Structure

Paul:

The amazing thing is the reproducibility, by three observers, of the magnitude and fine structure at an interval of less than three minutes! I'm running 20 second images with an 8 sec upload. So about a 30 sec cadence. My SNR is 30 so I might try 15s next. (12.5" f/8 scope).  How fast are you running?

Ken

WGR
WGR's picture
Fine Structure

Hello Ken and Paul

I agree, the fine structure is amazing.  Its like you are seeing double when you look at several light curves on top of each other.  I am using the 125 as the ref/comp star.  Using the 131 as the check.  I took 732 images in 400 minutes Sat night, for a cadence of 32.8 seconds.  My exposures were 30 seconds.  I have a very small chip (512x512).  Perhaps those observers with big chips would want to consider sub-framing to reduce the download time, and still keep their exposures closer to 30 seconds.  Its an option to think about.  If you do this, it takes some planning, as you may have to do darks, flats and bias' using the same sub frame.  I think Maxim does this for you, but I have never tried it.  Tonight looks possible here in NE, but clouding in late.  I will give it a go again.  

Great light curve.  

WGR
WGR's picture
Question for Damien

Hello Damien

You have a beautiful light curve on JD 2457117, that duplicates the structure and fine detail from two other observers, but is 1 magnitude brighter.  Then you have a second light curve that matches other observers very well.  Could you have an error in the comp star when doing the reduction of the first half of the light curve?  Did you reduce all the data in one shot?  If so then its not the case.  It would be great if you can check.  

Otherwise, its looks like you might have done a dec flip at the meridian, which can cause offsets in your photometry, but 1 magnitude is pretty large for this effect.  Such a shift can be caused by improper flat fielding,  Did you use twilight flats, or dome flats?  Scattered light issues can also be the culprit.  It was very close to full moon, and that might have put a gradient in your images--but again thats pretty large.  

Its worth a check, as its a very nice light curve, and supports the fine structure from several other observers.  Great Work.

Arne must be grinning from ear to ear when he sees this and realizes that all his hard work on XZ Cet and others is startng to bear fruit in low error photometry for aavso observers.

Gary

LMA
LMA's picture
Question for Damien

Gary,

I am glad you spotted the error. This was my first upload of a file fo WebObs, murphy law jumped on the opportunity to strike :-)

I have been able to duplicate the error by running AIP4WIN on a small sample of images by swapping the Comp and Check star. So, I have rerun this lot of images with the correct Comp and Check.

As you guessed, I reduced the data in two shots. In the middle of the night I did a first one for the data between JD 2457117.66067 and 2457117.77190, contained in the file "log-AM Her-20150404_part1".

Later in the morning I computed the remaining data for the night. But then, murphy stroke again, I had not erased the data from the first run. So my second file named "log-AM Her-20150404_part2" actually contained the data for the whole night.

What should I do now? I don't want to generate more confusion. Perhaps the easier way would be that you remove the data from my files "log-AM Her-20150404_part1" and "log-AM Her-20150404_part2", I would then resend a single file for the whole night.

By the way, last night has not been as good as the night before, nonetheless I could go on AM Her for another two hours. The file "logAM Her-20150405" has just been sent

Damien

FJQ
FJQ's picture
1 Mag jump?

To;  Damien,

Was the circled your data? http://www.astroimage.info/images/05Apr15-RunSM.jpg

Here is my secondary set-up of ST-10XME on C-11 scope on a iOptron CEM60 mount about 5 meters WSW of my roll-off roof where my main scopes (13" of CDK17) are located.  This is controlled remotely from my house.http://www.astroimage.info/images/C-11%20on%20CEM60.png

James

 

p.s.  As soon as I started shooting AM Her last night,  a marine layer came in and only left 10% of 300 images usable! :(

WGR
WGR's picture
Circled Data

Hello James

First of all this is Gary.  I wondered about Damien's data--the data that you have circled.  

 

Gary

FJQ
FJQ's picture
Your data?

To:  Gary,

I noted this as an anomaly about 11 posts ago.  Glad someone saw it and is correcting

James

LMA
LMA's picture
Circled data

James,

Yes, I made the error of awapping the Comp (122) and the Check (131). I have rerun the whole lot of picture and will resubmit when I have the OK from headquarter.

Saturday night the sky was one of the best we can get here (Eastern Quebec in Canada). Last night was poor but could spend two hours on AM Her.

Damien

LMA
LMA's picture
Question for Damien, strike two

To Gary and James,

Just to let you know that I have explored AAVSO tools available on the web site and discoreved that I could replace my bad data with newly reduced ones.

Damien

p.s. As you can judge I am still on the learning curve, participating on the forums is a god place to learn

WGR
WGR's picture
Learning Curve

Hello Damien

You are doing great.  Keep up the good observing.  You can get lots of help on the Forums.

Gary

pbenni
Fine Structure

I used comp star 122 for the referece and 125 as the check star.  With my 11" SCT f/7 ST8XME it seems I need to go with 60 sec images to get the ADU to 1000 for this 13-14 mag star.  The moon didnt help on 4/4.  I am also based in NE (Massachusetts).  The weather forecast however doesnt look promising this week...

BPAD

Paul

WGR
WGR's picture
Error in Comp Star

In my post, I said that I used the 125 for comp, that is an error, I used the 122.  It won't let me edit that.

 

Cheers

FJQ
FJQ's picture
Eclipse of bright accreation spot

To:  Paul,

Check this link out for the physical description of AM Her type variable....(RE: Does this binary system show transits) Yes! What were probably seeing is the accreation spot, at maximum, on the white dwarf being briefly eclipsed by the M or K type companion; see: http://www.daviddarling.info/encyclopedia/A/AM_Herculis_star.html

James

p.s.  Ken, I'm going to try for 10-30 second shots  to keep my error (1/snr) from <0.05. 

WGR
WGR's picture
Full Plot of AM Her Data

Hello

I have plotted and Excel sheet, with the low SNR data for AM Her at the end of the run, for your inspection.  I deleted everything with larger that 0.1 error bars.  Typical for the run was .01 mags.  Let me know if you want me to submit this data.  It seems to be corroborated by KRV.  The SNR is 10 or so for this data.

 

Gary

Lew Cook
Lew Cook's picture
Tools to examine observations for clouds

1. Mark 1 eyeball

2. If you were in another part of the world (like Dreamland)  when your photometry system was busily cranking out data, there is always "Lew's AAVSO format Plotting Workbook". It can show you how the clouds (if any) affected your observations. For long runs on a variable, it'll give you the extinction coefficients also.

You can get it from  http://www.lewcook.com/lewaavsoformatplot.htm  . It works best for non-ensemble photometry.

Gary - you'll need to delete the third (unlabled) column in your spreadsheet before pasting the data. What IS that column, anyway?

Nice data.

Lew

WGR
WGR's picture
Third Column

Hello Lew

The third colum is the JD of the image minus 2457117.6.  Should have used a round number.  This gives the fraction of JD, so that the X axis does not include 6 digits that usually don't matter.  If I delete it, the plot will go away.

 

Gary

weo
weo's picture
AM Her to date

Sincere thanks to all of you who are observing AM Her for this campaign - your photometry is terrific! I know the PI is going to be very appreciative. The second satellite (NuSTAR) observations finish in a few hours, but the PI requested the time series coverage to continue for two nights beyond (Apr 6/7 and Apr 7/8) to give precise context in case the satellite data show something unusual. After that, please go back to nightly snapshots through Apr 15/16.

Many thanks, and keep up the excellent observing!

Elizabeth

WGR
WGR's picture
Wonderful Light Curves

Hello

I have posted a couple of .jpg plots of AM Her for the nights of JD2457117 and 2457118.  The 7117 plot shows observers BPAD, FJQ, HJW, KRV, LMA, and WGR.  The small detail is supported by two observers in most cases.  

The 7118 plot shows similar effects for observers NOT, NIW, LMA, KRV, and COO.  Looks like no offsets between observers.  

This has to warm the Cuckles of Arne's heart.  Great job Observers.

Gary

FJQ
FJQ's picture
Light Curves

Good graphs Gary!

I had more good ones for 06Apr14 than I though (40% of 300).  I got 475 frames last night for 07Apr15.  Will post these when I get home from work.

James

schwope
AAVSO observers supporting the AM Her campaign

I'd like to say a very warm and hearty THANK YOU to all AAVSO observers supporting the XMM-Newton/NuSTAR campaign. I was seeking for ground-based telescopic observations from professional sites as well but was either clouded out or got no data due to technical problems. Thanks to the passion and dedication of the AAVSO amateurs I got a splendid optical light curve that was covering a large fraction of the space-based observations. I'm very much looking forward into the analysis of this very complex and comprehensive dataset. Well done, many thanks! Axel Schwope

FJQ
FJQ's picture
Any more cadence observations needed?

Dr. Schwope,

Thanks for the feedback and kind words towards all observers who supported your AM Her science!  Do you need any more cadence observations for AM Her?  If not we'll turn our attention to other Variables/Pro Astronomer support requests........Guten Tag!

James

sgor
sgor's picture
A day late and a dollar short

Dr. Schwope,

I misread the notice and thought you needed a time series thru the 9th. Maybe what I ran last night will be of some help. Previous to last night I did several series in BVRI to compliment what James and others were doing. Often with CV's information can be gleaned from comparing what is hapening in other bands as well as B-V and V-I. 

All the best,

..george

WGR
WGR's picture
Last Week of AM Her

Hello

I have attached a screen shot of the phase curve for the past 7 days (7117 to 7123).  All data included.  Used VStar an the default period.  The Standard Dev of the Mean (Std Error of Mean) averaged .0070 mags (Note this is the statistical measure to how well the mean was knows using 30 bins and the above data.  The .0070 mag average has a std dev of .0016 mags.  Pretty impressive and very consistant.  Congrats to all.

 

Gary

LMA
LMA's picture
Last Week of AM Her

Gary,

Thank you for the curve, impressive indeed. There is a meeting of our club tonight, I will show it. I am glad I was part of the team.

Damien

WGR
WGR's picture
Refining the Analysis

Hello All

I extended the data set from 2457116 to 2457124 (Present Sat AM).  ReRan the period.  Got 0.12882741 versus the .12919974 from the previous  analysis.  This suggested some period change.  More on that later.  

I optomized the bin count to 15 and got the average Standard Error of the Mean down to .0050 mags with a one sigma of .0007.  (Previously reported .0070 mags average and a std dev of .0016).  This is much better.  Plot attached.

The period change suggested that a Wavelet Analysis might be able to show this.  Attached is a plot showing the period vs time.  I wonder if the cycle shown continues?  

All analysis done in VStar.  What a great program.  If you have not taken the course in VStar, I strongly suggest it.

Gary

 

FJQ
FJQ's picture
AM Her Comp Star 118 Variable?

I was going over my last run of AM Her last night and noticed a distinct upward trend in comp star 118 V-magnitude.  Actually, it looked like it started out dim, with a V-mag as low as 11.874 (+/-0.031) and gradually got to its normal V-mag of 11.765 towards the end of the almost 5 hour run I made (561 frames). 

While my 15sec exposures have loussey SNR, I saw a definite trend in the MaximDL photometric graph when using the other comp stars with their standard referenced magnitudes; see http://www.astroimage.info/images/AM%20Her%20Comp118varSM.jpg

When I saw this, I decided NOT to use 118 as a comp star.  While doing my 11Apr15 run my air mass changed from 1.540 to 1.038.   There was some haze during the run, but it didn't seem to affect the other comp stars. Comp star 118 has a B-V of 0.928, but comp star 135 has a larger B-V (1.036) and didn't seem to have an upward trend in V-mag.  Should we exclude 118 as a proper comp star?

James

schwope
Comp 118

Hello James,

I suggest using star 122. Its very nearby and should be in the field of view even when CCDs were windowed. There should be many measurements of star 118 around from the recent days. If someone finds the time he/she might be looking into its variability.

Axel

 

Tonisee
Comp star 118

[quote=schwope]

I suggest using star 122. Its very nearby and should be in the field of view even when CCDs were windowed. There should be many measurements of star 118 around from the recent days. If someone finds the time he/she might be looking into its variability.

[/quote]

I used star 122 as comparison and 118 and 13* as check stars. During my 6.22 hour long high-cadence time series, star 118 shows just random scatter:

AM Her comp star 118 light curve

Corresponding airmass change is from 2.3 to 1.08, SNR changed from 133 to 156.

FJQ
FJQ's picture
comp 118

To Tonisee,

Thanks for looking at your data for comp 118.  I hope I  wrong about this because if I'm correct, many observations of AM Her done over the last week will have to be re-submitted because of the use of one errant comp star.  I think I'll do mine over as suggested by the Principal Observer (Axel Schwope) so we will have the best quality ground support data for his space based X-ray set.

James

 

 

 

 

 

 

 

 

 

 

 

FJQ
FJQ's picture
Comp 118

Thanks for the suggestion Dr Schwope.  I show more concern about this because many observers, including myself, used 118 as their principal (bright) comp star.  I wonder how this variability would affect all the thousands of time series submitted for the Nu-Starrs and Newton observations of AM Her.

I think I'm going to delete all my data on AM Her data that used this 118 comp star and resubmit using only the remaining comps.  I'd rather have less data of higher accuracy than more data with a comp star of suspicious behavior.

James

 

 

 

 

 

 

 

schwope
stability of the period

Hello Gary,

the orbital period of AM Her is quite stable and known to be linear over several decades now. Difficult to imagine that the period is variable over a few days only. The bright orbital hump we are seeing is a combination of beamed cyclotron radiation from the accretion plasma and recombination radiation from the gas stream between the two stars (plus some weaker components from the white dwarf and the mass donating stars, all variable due to temperature inhomogeneities). Accretion is highly dynamic and we might be seeing an apparent period change mimicked to forward/backward migration of the accretion spot or similar. Nevertheless, very interesting result. 

Cheers

Axel

 

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