Suspected/Misclassified Symbiotics: spectra required

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Peter Velez
Posts: 146
Joined: Tue May 12, 2020 7:36 am

Re: Suspected/Misclassified Symbiotics: spectra required

Post by Peter Velez »

V5590 Sgr looks like a symbiotic.

I attach a 70 minute spectrum taken with the UVEX on a PW CDK 12.5. Resolution is reported by ISIS at 1426. SNR for the continuum is very low but the emissions are quite obvious. My measurement of V mag is 14.63 with an error of 0.09 mag. This is worth redoing. The spectrum has been flux calibrated.

My UVEX needs time to cool down and because the roof opening was delayed last night, I didn't get the necessary cool down time. I have manually shifted the spectrum by 4.5 A based on the Ha and Hb lines. I used the wavelength calibration tool in ISIS and assessed the drift in temperature for the target images as well as earlier Are frames. The shift in calibration is quite linear and the line of best fit reconciles with an adjustment of about 4.5A so I'm happy with this.

I've marked the key emissions that I have identified - as always, I will accept any comments/corrections. Ha and Hb are obvious as are [OIII] and HeII. [FeVII] at 5721 and 6087 are also substantial.

This target is worth another look. I plan to try again later in the week.

Spectrum to be sent to Francois for the database

Pete
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v5590_sgr_reg_20211024_408_Peter Velez.png
Terry Bohlsen
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Terry Bohlsen »

Hi Pete
You have observed this before on 4/10/20 and it seems very similar.
https://aras-database.github.io/databas ... 04_433.png

Terry
Terry Bohlsen
Armidale NSW
Australia
Peter Velez
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Peter Velez »

Oh dear. That is embarrassing!

Mind you, I struggle to remember what I did last week.

At least it is consistent with last year’s observation.

Thanks for letting me know

Pete
Peter Velez
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Peter Velez »

Another suspected symbiotic star - AS 280.

Again, only a short exposure time (1 hour 20) with the last few images not producing much as the target slid low in the sky. Imaged with UVEX 600 lines/mm grating on PW CDK 12.5. Simultaneous photometry provides a V mag of 13.03 +/- 0.05. The spectrum has been flux calibrated. The SNR is quite low - around 5 according to ISIS.

Ha and Hb in emission as is He I at 5875. He I at 6678 is also likely in emission but its hard to tell with all the noise.

Pete
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Peter Velez
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Peter Velez »

I managed 30 minutes on AS 280- last night. It was earlier in the evening and I binned my images x2 so the SNR is better than the last attempt.

SNR is about 10 (according to ISIS) with Resolution of 1171. Photometry taken at the end of the imaging run produced B mag 13.7 +-0.04, V mag 13.13 +-0.04, R mag 12.48 +- 0.04 and I mag 12.28 +- 0.15.

I've labelled the main emissions that are markers of a symbiotic - Ha and Hb, He I and He II at 5881. I'm uncertain about [O III] at 4931.

Still not much in the way of continuum.

Pete
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as_280_reg_20211102_384_Peter Velez.png
Hamish Barker
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Hamish Barker »

nice!

any ideas what the bump at 5800 might be?
Peter Velez
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Peter Velez »

Hamish

looking at the .csv files I have, it could be Si II or C IV - but its hard to tell and the spike is quite narrow and well defined which suggests its a dodgy pixel. I have the cosmic rays filter on and the rejection coefficient for optimal binning set to 50 so there shouldn't be pollution of the spectrum from this but has a very short integration time so its possible.

As always, more data is required

Pete
Jaroslav Merc
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Jaroslav Merc »

Dear all,

thank you very much for the data you already obtained.

First of all, Peter, I am not able to find your observations (V618 Sgr, V5590 Sgr, AS280) in the database.

Gaia19dxh, Gaia21dxi (Paolo, Terry) - confirmed as non-symbiotic stars. I think that pulsations triggered the Gaia Science Alert in this case. This is, however, an important result as this confirms that the available data for the Gaia targets (without spectra) would not allow the selection of symbiotic recurrent novae candidates without having the contamination by pulsating giants. It would be great if other targets from the Gaia list would be observed (in their corresponding season), there is no need to reobserve these two.

V917 Sco (Terry) - interesting result. There is no evidence for the symbiotic nature of the object in the spectrum. Previously the spectrum was described as showing strong TiO bands, moderate [Fe VII], and strong OVI (1978MNRAS.184..601A)! Unfortunately, it is not shown in the paper. There might be some confusion about the position in the current databases. If it is really a case, I would do my best to identify the correct target. We would need the B and V band image of the surrounding of the target with a good angular resolution. On the other hand, it is still possible that the object changed its spectroscopic appearance.

V618 Sgr (Peter) - I am bit confused. The target was observed also last year by Terry. The new spectrum is very different from the previous one. I am not sure if the correct target was observed both times. This object would require attention, probably next season.

V5590 Sgr (Peter) - symbiotic star, very strong [Fe VII] in the spectrum. Peter, this is not anyhow embarrassing, that you reobserved the target, actually, this was great that you did it! [Fe VII] lines in your spectrum from last year were rather weak, so only the spectrum obtained now undoubtedly confirms symbiotic nature.

AS 280 (Peter) - the emission line at 5876A is neutral helium. I would suggest observing the region covering the ionized helium line at 4686A, which is the strongest in the spectrum.

Here I repeat the list of targets from my previous post, which needs observations (of course, when they will be observable, just not to lose them in the thread):
  • V618 Sgr (V ~ 10) - see above.
    ASAS J174600-2321.3 (Sgr, V ~ 13)
    TYC 1371-69-1 (Gem, V ~ 10)
    V917 Sco (V ~ 15; very crowded region) - after solving the possible confusion in the position given in the current databases.
    AS 280 (Sgr, V ~ 13) - see above.
    V850 Aql (Mira variable with V ~ 14 - 16; period of 390 d; now relatively faint, next maximum in April 2022)
    V1290 Aql (Mira variable with V ~ 14 - 16; period of 280d; now faint, next maximum in March 2022, then second half of December 2022)
    Gaia19dpl (Cen, G ~ 12.1; RA 13:12:12.26, DEC -48:58:38.71)
    Gaia20fut (Vel, G ~ 13.1; RA 08:51:30.36, DEC -44:40:09.91)
    Gaia18ctm (Mus, G ~ 13.6; RA 13:47:13.51, DEC -70:10:12.76)
    Gaia18cwv (Sco, G ~ 13.7; RA 17:52:47.77, DEC -34:31:21.83)
    Gaia18bec (Scu, G ~ 14.0; RA 18:33:42.40, DEC -14:13:52.03)
    Gaia18cfh (Sgr, G ~ 14.1; RA 17:44:15.19, DEC -25:15:40.64)
    Gaia21axn (Sgr, G ~ 14.9; RA 18:05:44.31, DEC -24:33:32.44)
Jaroslav
Jaroslav Merc
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Jaroslav Merc »

I would like to add one more target to the list. I received some data from colleagues from Hungary this week. They study young stellar objects, but this one might be a symbiotic star. We already have two low-res optical spectra, one medium-res spectrum covering Halpha, IR spectra, but to confirm either similarity to BX Mon or symbiotic nova nature, we need:

a) low-res optical spectrum covering as wide range of wavelengths as possible
b) low-res spectrum going to near-UV to see if the Balmer jump is in emission or in absorption
c) spectra with higher resolution of Halpha to study the profiles (spectrum which we already have shows emission line with strong absorption component)

The target is:
  • Gaia19bpg (Cyg, G ~ 14; RA 21:41:50.43, DEC +51:55:45.48)
Jaroslav
Peter Velez
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Re: Suspected/Misclassified Symbiotics: spectra required

Post by Peter Velez »

Jasolav

first up, my apologies - I have yet to share my .fits files with Francois for the database. I was tinkering with wavelength registration before submitting and then life got in the way - as it tends to do. I'll send them to Francois shortly.

On V618 Sgr. I've considered my guider image for this target and plate solved it. I am certain it is the correct star. I can share this with you if it assists.

You mentioned in your request last year that the star may be brighter than ~15.3. It certainly was. I measured its V mag at around 9.3. ASAS-SN reported its g mag at between 9.65 and 10.0 on the same day so we are in the ball park. When Terry took his spectrum last year, the ASAS-SN g mag was around 12.4. I attach the ASAS-SN light curve for the last 2 years.

Simbad records V618 Sgr as a R CrB star - the dip in brightness and subsequent climb in the lightcurve is consistent with that. Terry's spectrum was taken as the star had not yet hit its minimum brightness while my spectrum was taken as it was nearing its normal brightness. There are no emissions. I've had a stab at identifying the absorption lines in the attached plot. If you disregard the continuum, the closest analog I could find was a late G star - again consistent with the R CrB identification which generally presents as an F or G supergiant.

The continuum is a distracting element of my spectrum. It was taken late in the season. I managed 2 exposures of 10 minutes with the target at airmass 2.6 at the beginning of the run. The reference star was a bit higher at airmass 2.3. Clearly there is atmospheric differential refraction at work here. I attach a plot comparing this spectrum to a MILES G8I star and its a reasonable match but for the dodgy continuum.

Please feel free to correct or comment. Irrespective of whether this hypothesis is correct, it will certainly on my list of targets for next year when it returns to the night sky.

Pete
Attachments
v618_sgr_reg_20211105_409_Peter Velez.png
light_curve_1f6899d4-041d-4b17-8424-108a76920477.png
v618_sgr_reg_alt_20211105_409_Peter Velez_compare.png
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