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Observations of Blazar S5 1803+78 critically needed

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daveh
daveh's picture
Observations of Blazar S5 1803+78 critically needed

Blazar S5 1803+78 is rapidly brightnening. Observers in Spain and Germany have contributed recent observations, but the weather in Europe has been overcast and probably will be until at least this weekend. Observations outside of these areas are encouraged until the weather clears. The next several days may be critical as the blazar seems to be reaching a peak magnitude. Please make observations if possible and upload to light curve for S5 1803+78.

Thanks.

Dave (HDHA)

Bikeman
Bikeman's picture
I'm on it now

Against expectations, the sky cleared up and I'm currently taking frames .. I'm right at the edge of a cloud system ... not sure how long this will last, but the target is still bright so I a meaningful measurement is almost certainly possible already.

Cheers

HB

 

Bikeman
Bikeman's picture
ATEL on Fermi-LAT data

More news on recent gamma ray emission from this source:

http://www.astronomerstelegram.org/?read=13633

CS

HB

CTX
CTX's picture
S5 1803+78

S5 1803+78 Has an Updated & Expanded Sequence, just finished.

Ad Astra & Good Observing,

Tim Crawford, Sequence Team

daveh
daveh's picture
Thanks Tim,

Thanks Tim,

This is good...things are moving very quickly.

Dave

Ccolvin968
Ccolvin968's picture
I'll try to get some tonight.

I'll try to get some tonight.

Will only be Tricolor bands, but it's what I can do. 

Bikeman
Bikeman's picture
It could already be fading

It could already be fading again, last nights measurements were a bit fainter than previously.

Cheers

HB

Bikeman
Bikeman's picture
I'm quite confident I can

I'm quite confident I can take a measurement tonite

Good observing

HB

dam
Confirmation of the discovery

To be honest, Gianpiero Locatelli from Italy was the first to confirm the Blazar explosion.
The next day Jordi Berenguer was from Spain, he confirmed it even more.

I also appreciate the observations of Heinz-Bernd Eggenstein from Germany who also provided this confirmation of the Blazar S5 1803+78 explosion.

I sincerely thank all three for their confirmation and possible monitoring. It is really interesting to watch.

I thank Dave Hinzel for putting this thread in and getting us together so we can get ahead of NASA 4 days before his confirmation on his Atel.

All of this was triggered by a simple observation from David Lane a few days earlier. It had to be confirmed.

Thank you
Adolfo Darriba

Bikeman
Bikeman's picture
Observing now

okish conditions.

Still at around 14.5 mag (V)

CS

HB

Bikeman
Bikeman's picture
Next two nights

It looks like the next two nights will be cloudy for me here, I hope all the others here have better forecasts. We had a wonderful coverage so far

 

HB

Bikeman
Bikeman's picture
Again cloudy

It's again cloudy in Germany. S5 1803+78 seems to be close to it's upper end of quiesence variability now, so a few more days and we'll have concluded the coverage of the flare I guess,

Is anyone else able to observe?

Cheers

HB

daveh
daveh's picture
Again cloudy

I wanted to do some observing but the iTelescope site in Nerpio, Spain has been shut down due to a combination of bad weather and problems of getting people to the site because of the pandemic. So, we might have to sit this one out unless there are observers in other locations that can do observations.

Dave

Bikeman
Bikeman's picture
I took a measurement from

I took a measurement from iTelescope's T11 instrument in New Mexico

Cheers

HB

Bikeman
Bikeman's picture
I made another reservation

I made another reservation for Saturday night/Sunday morning on T21, forecast looks good so far. So if someone else wants to throw in an iTelescope measurement, perhaps take another day to get the best coverage  for the buck.

Cheers

HB

 

Bikeman
Bikeman's picture
ATEL

Here is another ATEL on "our" blazar:

http://www.astronomerstelegram.org/?read=13711

The reoported data points are , IMHO, not as impressive as the light curve that was collected here, so I wonder if this group here should do its own ATELs in the future for similar events. I notified one of the ATEL's authors about the obsevartions collected here, but got no response so far.  

CS

HB

 

Bikeman
Bikeman's picture
I now got a response, the

I now got a response, the team that published the ATEL are now aware of our observations and will contact us if our data poinrts are used in their research. I forwarded a link to this forum discussion to them.

CS

HB

daveh
daveh's picture
Are ATEL and AAVSO normally

Are ATEL and AAVSO normally in communications or is this a one time event? If there is good communications we should use them as much as possible, but if not then an AAVSO "internal ATEL" is a good idea since we published before they did. What do you think?

Bikeman
Bikeman's picture
I think it's not uncommon

I think it's not uncommon that AAVSO amateur observers publish ATELs , e.g. Josch Hambsch  and Tonny Vanmunster  for CVs. I guess the threshold is "would other astronomers find it useful", as when responding to urgent observation requests in other ATELs or when observing something rare or unexpected. Here, the current flare seems to be pretty record-setting, even more than reported in ATEL 13711 because they observed one week after we observed the peak, so if their observations were "good" for an ATEL, I guess our's are even more so :-)

Just my 2 cents.

 

Bikeman
Bikeman's picture
14.44 (V)

Hi!

I've just finished measuring some image form iTel11 in New Mexico *last night* and it was back at 14.44 mag (V) . This night I'm trying to continue observing it from Germany but conditions are not optimal.

For comparison, the brightest V value in the light curve for the recent flare was close to 14.1 , the object made a "V shape recovery" :-) 

CS

HB

 

Bikeman
Bikeman's picture
This source is amazing!

This source is amazing!

It flared up fast to 14.1 ish, dropped quite fast, then continued to rise up again to 14.4 ish and now lingers at 14.5 +/- 0.2 for more than a week !

Is this something that Blazars of this type usually do?

Cheers

HB

 

CrossoverManiac
CrossoverManiac's picture
S5 1803+78 is overlapping a

S5 1803+78 is overlapping a 17.5 magnitude comp star, at least in my image anyway.

The aperture annulus is at 3 pixels with angular resolution of 2.54" per pixel.  I can't separate the two without going to a higher focal length or smaller pixels.  My question is should I just scrap my data? 

Bikeman
Bikeman's picture
FITS image?

Hi

I have a really hard time recognizing the field from your image, The image seems to be blurred or have JPEG artifacts in it, perhaps?

Are you really sure this is infact S5 1803+78? I take images which are a bit oversampled at 0.5" / pixel, so I resampled one of my images to 20% the resolution to simulate a 2.5"/pix resolution, and I get something like the attached image. It should still be possible to avoid overlap with the nearest star that is bright enough to affect the photometry, especially the 17.5 star on AAVSO finder charts (the one I placed in the inner annulus in my simulated image). 

If you like you could upload the FITS image and have us look at it. I really think there is something going wrong here.

CS

HB

CrossoverManiac
CrossoverManiac's picture
I sent the stacked FIT files.

I sent the stacked FIT files.  If you need the unstacked version, let me know.

Bikeman
Bikeman's picture
THX

Ahhh ok, I see. The screenshot was from VPHOT with a single frame, and I got distracted by some bad pixels and mistook them for stars, Sorry for my ignorance,

 

Anyway, this is interesting!

The position that VPHOT tells you is comp star 175 is actually significantly wrong! I guess VPHOT just calculates where the star should be according to the plate solving, and then looks for the nearest centroid, allowing some very generous deviation from the calculated position, and ends up snapping the centroid to our target star (see the end of the post for a fix).

What is worse is that the "Measurement details " that VPHOT optionally displays for each comp star is misleading and wrong:

You get this (I did that for the stacked V image you sent me )

==================

General information:

175

Instr.Mag,:
-2.792

SNR:
51

Error (SNR):
0.021

Airmass:
1.268

FWHM:
2.03

Centroid X:
358.37

Centroid Y:
292.61

RA Catalogue:
270.18780

Decl. Catalogue:
78.46889

RA Estimate:
18:00:45.07117

RA Estimate:
270.18780

Decl. Estimate:
78:28:07.98895

Decl. Estimate:
78.46889

===================

Huh??? Catalog location and estimated position are a perfect match in RA and Decl?? That's suspicious and actually wrong, because if you look it up in the finder chart table, the actual coordinates for 175 are :

000-BNL-903
18:00:41.65 [270.17355347°]
78:28:17.2 [78.47144318°]
175

So...that 175 star really isn't nearly as close to the target star as VPHOT makes you believe, and is indeed easily avoided by chosing the aperture wisely (e.g. radii 4-8-4 in the aperture settings) . That 175 comp star is just too faint to be detectable even in the  stacked V frame (it's kind of visible in the stacked I frame, tho), so VPHOT just tries a bit too hard to identify it in your images and misidentifies it in the process.

How to fix this? Fortunately VPHOT allows you to configure the way it tries to identify stars on the frame ==> Tools ==> Settings > Centroid Determination,

When I went there, "it displayed Search-radius in Pixels" : 5  and "Initial FWHM (pixels)" : 5

Because your plate scale of 2.54" / pixel is a bit on the coarse end, 5 pixels is a bit too generous. If you try setting both to 3, then when you load the comp stars from the AAVSO, VPHOT will no longer even give you the 175 star because it fails to identify it on your frame with sufficient SNR, and this is the right thing to do. Because the limits for trying to identify the star near it's computed position are now less generous, VPHOT will no longer mistake the target star for star 175.

So mystery and (perceived) problem solved I guess, You can do photometry and submit it all right, just don't include the 175 star or configure VPHOT in the described way so VPHOT won't misidentify it.

The whole thing is captured in the attached screenshot. It shows the stacked I-filter frame you sent me.

I put a crosshair to the right of the 175 star to highlight it, I made the aperture avoid that star, and in the right top corner you see the config dialog that lets you pick the parameters for identifying stars in VPHOT.

Hope this helps,

HBE

 

File upload: 
daveh
daveh's picture
I believe the AAVSO criteria

I believe the AAVSO criteria for good data is as follows:

Star SNR >= 10 (which your measurement is).

Magnitude estimate error <0.05 good; <= 0.015 excellent; 0.05 to 0.100 still worth reporting to AAVSO; >0.100 probably shouldn't report.

Hope this helps.

Dave

Bikeman
Bikeman's picture
More than two month after

More than two month after what must have been one of the brightest recorded flares of S5 1803+78, it still refuses to go back to its optical pre-flare state (at around 16.5 mag (V) ).

The weather is horrible in Germany now (I should not complain tho, the rain is much needed after a record braking dry spring). Even some iTelescope New Mexico observation was cancelled because of high winds :-( . I hope others have more luck, I'm sure the data will be useful .

CS

HB

Bikeman
Bikeman's picture
again at ca 14.7 - 14.8

Hi all,

 

Just now taking frames but I can already tell that S5 1803+78 is again at 14.7 .. 14.8 which I guess again qualifies as a flare?

CS

HB

 

 

Bikeman
Bikeman's picture
Fermi gamma ray light curve

Fermi gamma ray light curve for comparison...no flare there (yet).

https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/S5_1803p78

CS

HB

 

Bikeman
Bikeman's picture
Gamma ray activity

Meanwhile there is a clear signal in the gamma ray lightcurve (the link above is for a daily updated lc), It shows some day to day variability so I guess it will be interesting for scientists later to compare the optical and gamma ray lightcurves ==> let's keep observing this one.

foudastro
S5 1803+78 observation submission question

Hi all,

I'm new to this group and I have questions regarding the submission of observation to the AAVSO database. My setup is a 14" RC scope with STX16803 CCD camera in Spain.

I took an image of S5 1803+78 with a Luminance filter (I don't have photometric filters) and I am not sure what to do next. I navigated to the AAVSO "enter observations individually" page. Is it where to submit the observation? Do I need to stack multiple images or are you looking for a single image? Calibrated or not?...

Thanks!

Francois

Bikeman
Bikeman's picture
Welcome! That is some

Welcome! That is some impressive equipment, I'm sure this will be useful! Even without photometric filters, you can still submit datapoints for observations thru a clear filter (or no filter).

I see you already have an observer code...so you are good to go.

This will be the first observation you submit? I guess then this is a good starting point, it covers every aspect from taking the images to reducing the data to magnitude values to submitting to the AAVSO:

https://www.aavso.org/ccd-camera-photometry-guide

Note that if you are an AAVSO member, you can use the online tool VPHOT for reduction :

https://www.aavso.org/vphot

CS

HBE

 

 

foudastro
Thanks for your message. I am

Thanks for your message. I am familiar with the raw images calibration process and also with photometry of exoplanet transits as I have observed over 40 such events as part of the Exoclock program. My question is not so much about how to reduce the raw images and what photometry is about but rather in the specific case of Blazar observation submission:

Whether you want to see raw images, calibrated or not

If images should be stacked to reach a specific S/N ratio 

Thanks!

François

Bikeman
Bikeman's picture
Ah sorry, from your AAVSO

Ah sorry, from your AAVSO database record and your message it wasn't quite clear to me what your level of experience is. All the better that you are already familiar with the technique.

> Whether you want to see raw images, calibrated or not

That's usually not done here unless the result is so unusual that people want to investigate what could have caused the deviation. Just submitting the results to the DB is fine.

> if images should be stacked to reach a specific S/N ratio

I guess with a scope like yours, you'll need (say) just a few minutes of total exposure to get a good SNR ( say, 100), stacked or single frame. Runs of time series (as with exoplanet research but nowhere near the SNR needed for exoplanet transits, SNR 100 is good enough) might even be useful to capture variations on the timescales of minutes to hours.

CS

HB

Bikeman
Bikeman's picture
Almost as bright as in April now (V)

My latest measurement has the V magnitude very close to the peak in April again (!!!)

The weather here is Germany is not good at the moment and using iTelescope is getting a bit expensive, I hope others have a clear sky to observe this new (re)brightening. I think this prolonged period of activity with now 3 distinct flares in a relatively short time is quite unprecedented in the data for this source.

weo
weo's picture
AAVSO Alert Notice 717 on S5 1803+78

AAVSO Alert Notice 717 reports on the recent and current flaring activity of the blazar S5 1803+78. Please see the notice for details and observing instructions.

Many thanks, and Good observing,

Elizabeth O. Waagen, AAVSO HQ

foudastro
File submission

Hi

I attempted to upload a .fit file to the database but I cannot figure out how.

I went to: https://www.aavso.org/webobs/file but it looks the expected format is a text file.

Can someone explain the process?

Thanks!

Francois

Bikeman
Bikeman's picture
Indeed, the webobs->Upload

Indeed, the webobs->Upload page iis for uploading AAVSO report files, text files containing the reduced magnitudes. The format is explained here:

https://www.aavso.org/aavso-extended-file-format

put many photometry software packages can generate the files for you.

Which software are you using for the reduction?

If you arfe an AAVSO member, you can use VPHOT

https://www.aavso.org/vphot

as already mentioned, and there you can indeed upload a FITS file and perform the reduction in a web interface. There is no need (or storage) to upload FITS file for permanent archival, only the measurements are going to the database.

Does that answer your questions?

CS

HB

Bikeman
Bikeman's picture
For ca past 160 days, S5 1803

For ca past 160 days, S5 1803+78 has shown a roller coaster ride between multiple flare events, but never actually returned to its pre-flare level.

A week or so ago it looked like it was finally taking a dive, and maybe observers are now getting a bit of fatigue from this object (plus observers in California are having a hard time with fires and smoke at the moment.....) BUT observers should really try to stick to this object because .... it is now more or less stable again around 15.1 +/- 0.1 mag for the last 4 days or so. Hmm....what will it do next?

The AAVSO now has a very dense lightcurve for those last 160 days of activity, it would be great if we could keep it well sampled until it finally goes back to 16.5 ish or so.

P.S.: And as a reminder, BL Lac is also still having a flare!

CS

HB

Bikeman
Bikeman's picture
one more time

It seems that S5 1803+78 is doing "it" again. 

Both optical and gamma ray activity are on the rise again! Let's keep an eye on this.

I might have one or two good nights coming up after a long stretch of clouds and rain.

CS

HB

 

Bikeman
Bikeman's picture
Bummer ... I had hoped to get

Bummer ... I had hoped to get new data last night from an iTelescope, but it had a slight pointing error ... actually one hour in RA :-( .

Please, anybody who has a clear sky, have a look at S5 1803+78. The Fermi gamma ray Light curve indicates renewed activity as well and a full rebrightening in the next few days is a possibility , if the past light curve is any indication of the current behavior.

CS

HB

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