v473 Lyr

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v473 Lyr

Postby Peter Somogyi » Mon Mar 11, 2019 9:28 pm

Hello,

There is an ongoing research about v473 Lyr in the past years, and nowadays speculated that X-ray outbursts are happening at a certain period.
XMM-Newton is scheduled at MAR-17 daytime (star taken on the list a bit late).
There's an ongoing alert for variable observers too, between from MAR-11 to MAR-22. Amateur high res. spectra in this period would be also welcome.
Requirement for spectroscopy is to have roughtly like a 1 km/s accuracy (still negotiating, my knowledge about LHires is only 2 km/sec). Measurement method is cross correlation, spectral region is not clearly defined (my guess from arxiv should be 6100-6250 Fe absorptions and other metallic lines).
v473 Lyr is observable at my location ~2 hours before sunrise.
0.5-1 hour observation (depending on scope) for multiple days should be welcome (the star having a 1.5 day period).

SASER for U Tra has had a similar success extending profs data with a high resolution spectra here: https://arxiv.org/abs/1612.06722 (amateurs acknowledged).

Amateurs with high resolution could proving important coverage here.
There have been no time for any official alert, I've been approached by local profs - specialists for this star - and suspect that my future observation alone could be too few (weekend oriented).

Further readings:
http://adsabs.harvard.edu/full/1998A%26A...329..599A
https://arxiv.org/abs/1406.0494
https://arxiv.org/abs/1206.4282
https://arxiv.org/abs/1612.06722

Cheers,
Peter
Peter Somogyi
 
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Re: v473 Lyr

Postby Peter Somogyi » Tue Mar 12, 2019 8:44 pm

Update: the max RV accuracy of the LHires (roughly 2 km/sec) is OK.
A good quality telluric removal should be also necessary for the cross correlation practice.
Continuum will be normalized, so no need to any ref.star (but I would shoot a Vega for checking the tellurics removal).
Calibration frame should be taken before and after (indeed, I usually take it per every exposure).

2-3 spectra from amateurs spread across multiple days could be enough, I'd attempt one of these during the weekend...

- Peter
Peter Somogyi
 
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Re: v473 Lyr

Postby James Foster » Thu Mar 14, 2019 5:51 pm

To: Peter,

This probably requires the 2400 l/mm grating? Vega area is tough for my roll-off roof observatory because I have trees on my east that go up to almost 60 degrees
above the horizon!

From where my C-11 is placed, 20ft further west on my property, I can see this area just before dawn, so maybe I should try photometry.

James
James Foster
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope,
LISA IR/Visual Spectroscope (IR Configured Presently)
Alpy 600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
James Foster
 
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Re: v473 Lyr

Postby Peter Somogyi » Thu Mar 14, 2019 6:47 pm

Hello James,

In this special case when measuring RV with cross-correlation, down to R~10.000 the resolution should be convertible to wavelength range somewhat. Just the calibration errors become more disturbing (tellurics, flat, RV).
So in case you have the 1800/mm grating in there, that should be also useable.
There is also no real hard limit for the RV accuracy, but we should do our best - pulsation amplitude in RV is roughly 25 km/sec (Fig.8: https://arxiv.org/abs/1612.06722), that's what needed to be fit across multiple days, close to 17-MAR.

I am fine any other bright A or B type star with a smooth continuum you can easily shoot just before the target, at a similar altitude. This is only for checking RV and the later tellurics removal.
Actually, these recommendations coming from myself, being precautious to prove our data validity that always come at a later time... in case being confident with other methods, feel free to discuss.

Photometry coverage may also be important in this case, however I'm not the contact person for this (special requests are in place - e.g. bright target at a given high accuracy).

Cheers,
Peter
PS.: weather is bad here, only Sunday morning looks promising at this moment...
Peter Somogyi
 
Posts: 380
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Re: v473 Lyr

Postby Peter Somogyi » Thu Mar 14, 2019 9:48 pm

James,

Re-reading past mails, your geographic location should have importance, also with photometry.
Johnosson V or B was requested by the local observer team, and they look for observers from other continents. Aavso also has this star being tracked.
Amplitude is 0.05-0.1 mag, and the minimal required accuracy must be 0.01mag.
Period determination of this star is very tricky, night availability also short around 17-MAR +/- 6 days, this is why spectroscopy also requested.

Peter
Peter Somogyi
 
Posts: 380
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Re: v473 Lyr

Postby James Foster » Fri Mar 15, 2019 9:13 am

Thanks a lot Peter!

On examining this on its AASVO chart I see that I cannot do adequate photometry on this object for the following:
1.) Too bright at 5.99-6.35 mag, even if I bin 1x1, my exposure time need to be no more than 1-3 sec of I and 5-10 sec for B.
2.) There are no comparison stars in the FOV (18') for my C-11 at F/6.3

I'll switch over to the 2400 l/mm Grat and try to shoot on the weekend. Thanks again for all the great feedback!

James
James Foster
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope,
LISA IR/Visual Spectroscope (IR Configured Presently)
Alpy 600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
James Foster
 
Posts: 316
Joined: Sun Jan 24, 2016 7:14 am

Re: v473 Lyr

Postby Peter Somogyi » Sun Mar 17, 2019 3:35 pm

Till this morning, I've taken 14 x 600 sec exposures (300/1200 Newton + 2.66x APM Barlow, internal cal.lamp, 35 micron slit, ATIK 428EXm, bin2x2).
Did take calibration between each exposures (15 sec, + 15sec waiting guide to settle, all automatic).
Calibration: brightest Neon line went up to 22000 ADU, in overall used 7 weak Ar lines + 4 stronger Ne lines.
v473 ADUs varied from 2200 ADU to 4000 ADU when it came higher in the sky.
Tellurics not removed, as did not find any in my range (Vega: before/after).

Did take 45 Dra (+1 mag brighter, matching F8Ib-II spectral type!, known RV), for an easy RV match (allows cross-checking the absolute RV).
Taking 45 Dra (1 x 10 minute, 8000 ADU) has become even more important, when I realized Vega did not show any telluric line in my range (6103-6222A).
It also allows a quick evaluation (matching all the light projection - no need to build an artifical F8 type from library), adding its absolute RV from Simbad (-12.32 km/sec):
v473Lyr_fxcor_isis_rv.png
RV + AG Dra measured with both ISIS and IRAF/fxcor
v473Lyr_fxcor_isis_rv.png (14.21 KiB) Viewed 949 times

This graph contain error information from fxcor, and filled a constant 0.5 km/sec for ISIS (no error estimate other than the graph it produces).
By text, the ISIS fitted CCF peak output (JD-MID, Vrad diff to 45 Dra in km/sec, error):
JD-MID RV diff
============ =======
2458559.5811 -2.090
2458559.5886 -1.632
2458559.5961 -1.759
2458559.6036 -1.804
2458559.611 -1.751
2458559.6185 -1.662
2458559.626 -1.600
2458559.6335 -1.191
2458559.6409 -1.454
2458559.6484 -1.322
2458559.6559 -1.447
2458559.6634 -1.241
2458559.6708 -1.075
2458559.6783 -1.084
2458559.6858 -0.738

Sum: within this ~2.5 hour, RV increased by roughly 0.7-1 km/s (min. 0.5). If can trust 45 Dra (Simbad), absolute Vrad is provided on the graph. Otherwise, need to find artifical spectral type from somewhere.

I will ask profs soon how the XMM-Newton is going and how much further spectra required.

Cheers,
Peter
Peter Somogyi
 
Posts: 380
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Re: v473 Lyr

Postby James Foster » Mon Mar 18, 2019 11:07 am

To: Robin,

Nice RV work! I found out I can (barely) get non-saturated exposures if I use 2,5,10 sec 1x1 bin with IVB photometric filters on my C-11 at F/6.3; shooting it starting tonight.
I'll have to wait 3-5 weeks before this object clears the trees to do spectro work on it with my larger scope.

James
James Foster
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope,
LISA IR/Visual Spectroscope (IR Configured Presently)
Alpy 600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
James Foster
 
Posts: 316
Joined: Sun Jan 24, 2016 7:14 am

Re: v473 Lyr

Postby Peter Somogyi » Mon Mar 18, 2019 7:54 pm

Thank you James. Currently we are waiting for the XMM-Newton data to be evaluated, any further requests and priorities depending on its outcome.
Peter
Peter Somogyi
 
Posts: 380
Joined: Sun Jul 13, 2014 8:56 am

Re: v473 Lyr

Postby Peter Somogyi » Sat Mar 30, 2019 10:18 am

Summary
========
XMM-Newton has made a non-detection.

Only I was doing RV spectroscopy during this campaign, there was no professional followup.

Showing on this illustration containing my 2nd day of observation (2019.03.24 morning as green, the red what was already published):
v473Lyr_period1_5_XmmBlueDot.png
the start of the period is self chosen (arbitraty)
v473Lyr_period1_5_XmmBlueDot.png (13.29 KiB) Viewed 809 times

Used IRAF/fxcor output here, all telling RV error was between 0.55 - 0.8 km/sec.
Template star I've been using: 45 Dra of both night. Unfortunately, found 1.1 km/s shift between the 2 night's 45 Dra.
3 possibilities for this error (I'm uncertain which can be):
- real RV shift
- error of 45 Dra measurement itself
- error that is correcting optical path difference, so it fixes shifts for target star (= my wishful thinking)
A 2nd way of processing using synthetic spectrum would be another choice - but having no others spectrum to confirm, so skipping this for now. I believe at least, the relative RV accuracy of 0.55-0.8 km/sec within 1 night should be OK (valuable as a gradient).
The curve was drawn by me (bezier curve) by free hand as a speculative illustration - using the average RV (~ roughly -15 km/s) information from earlier papers.
Blue line is representing the real XMM-Newton coverage (I've extracted from the public log), where there was no outburst (told me by profs).
Photometry was also collected from others, that is still under evaluation by professional - independently from this assessment.
We are looking for the next campaign, possibly trying to avoid this period.

- Peter
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Posts: 380
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