The case StHA 154

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Francois Teyssier
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The case StHA 154

Post by Francois Teyssier »

Our colleague Keith Shank got a spectrum of StHA 154 and put the finger on an interesting behavior.

StHA 154 = 2MASS J18432793+1930053 in SIMBAD is a poorly studied symbiotic star with 4 references in Simbad.

Keith obtained a spectrum of a red giant, spectral type M7-8 (from TiO1 index) with no emission.
He confirmed the identification taking spectra of the two brightest neighbors of the target. The early type of these two stars excludes that they can be StHa 154.

KS.PNG
(Keith Shank)


Woody Sims and Bob Buchheim confirmed the identification.
Spectra: https://aras-database.github.io/database/stha154.html

StHA 154 was discovered as en emission line star by Stephenson (1986)
Munari & Zwitter (2002) published a spectrum showing a typical symbiotic (nuclear powered) with notably He II, Raman OVI , [OIII]
s2002.png
s2002.png (34.78 KiB) Viewed 3144 times
The coordinates of the various observations (Stepenson, Munari+, Shank+) are consistent. The probability of an error is very low.
We must admit (at a high probability) that this object show a significant variation of its spectrum at a time scale of less than 25 years.
Such variations are well established for accretion powered symbiotics (see e.g. CH Cyg, SU Lyn, ...)
In the case of a classical (nuclear powered symbiotics) this is an atypical behavior. We can find an example with V407 Cyg (symbiotic nova - perhaps recurrent- event in 2010 , showing now only the variations of a classical Mira variable).

After consultation of Dr Rudolf Gàlis, it is proposed a long term monitoring (photometry and low resolution spectroscopy) of this peculiar object over several years in order to detect pulse variations.
The optimal cadency should be a spectrum per 10 days (about 30 spectra for a time scale of 300 days the order of magnitude of mirae periods)


spectra to be send to francoismathieu.teyssier at gmail.com and copy to arasdatabase at gmail.com
Congratulations to Keith for this interesting finding and thanks to Bob and Woody for the confirmation. An excellent collective work!

Best,
François
Francois Teyssier
Posts: 1520
Joined: Fri Sep 23, 2011 1:01 pm
Location: Rouen
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Re: The case StHA 154

Post by Francois Teyssier »

Very interesting and accurate input from Jaroslav Merc.

Once again, congratulations to Keith!
And a thought: do not hesitate to dig in the symbiotic lists http://astronomy.science.upjs.sk/symbiotics/ and have a look to any MIII star in the sky.
Surprises are possible!

François



Jaroslav Merc:

There is indeed something going on, which deserves attention.

I have checked all the available information and observational data on this object. First, let me summarize the limited information in the literature. The first mention of the star is indeed in the list of Halpha emitter of Stephenson (1986). Coordinates point to the object now known as StHa 154. The star is classified there as M2 and neither any information is given about the strength of the Halpha line, nor any comment about other features in the spectrum (it is definitely not mentioned as a possible symbiotic star in the paper). In my opinion, that is strange, given that symbiotics typically have very strong emission lines. For StHa 190, another confirmed symbiotic star Stephenson commented on the other emission lines in the spectrum, for StHa 149 he mentioned 'very strong' Halpha. One should also mention, that the star is just at the magnitude limit of the survey. Therefore I suppose that the spectrum could have a low S/N and maybe even the estimate of the spectral type could be unprecise.

Most of the objects from Stephenson (1986) which are now known as symbiotic stars were confirmed in the scope of the work of Downes and Keyes (1988). The object StHa 154 was unfortunately not observed by them. The star was also not included in the catalog of Belczyński et al. (2000) as at that time there was no suggestion in the literature about the possible symbiotic nature of the star.

There is only one spectrum of StHa 154 suggesting the symbiotic nature presented in the literature. It is in the atlas of Munari and Zwitter (2002). It is a bit intriguing, because they claim in the paper, that they observed the known symbiotic stars from the list of Allen (1984), Belczyński et al. (2000), and SMC objects from Meyssonnier & Azzopardi (1993). In none of these, StHa 154 is listed. The coordinates and cross identification of the star are that of StHa 154, but I am unsure, that the object observed was StHa 154. First, I see no reason why they would observe StHa 154 as it was not suggested as a symbiotic star anywhere in the literature. Secondly, in the paper, it is written that the object was observed on 19.96/04/95. In the figure, it is written that the object was observed on 19.96/04/96. Aside from the uncertain year of observation, the observation took place around midnight (unclear if UT or local, but I assume UT). On April 20, the object rises around 5 AM UT (or 1 AM local), so I don't think it could have been observed. Interestingly, StHa 164, an object classified as a symbiotic star before, was not in the atlas of Munari and Zwitter. This could not be used as final evidence as not all known symbiotic stars were observed for the atlas, but still, I don't see the reason why they would omit StHa 164 and observe StHa 154 instead. After 2002, the object was not analyzed and is included in the list of confirmed symbiotic stars (in Akras et al. catalog and mine Database) only based on the Munari and Zwitter (2002) work.

I have checked the recent photometry from the ASAS-SN survey and from the ZTF. Both support the SR pulsations of the giant (on a timescale of about 60 days), therefore I don't think that the giant is pulsating as a Mira pulsator. Moreover, neither the multifrequency SED of the object show IR excess typical for D-type symbiotic stars nor its position in the IR color-color diagram would classify it among D-type symbiotics. Also when I fitted the multifrequency SED I obtained a rather low effective temperature of the star which is more consistent with the estimate from your recent spectra and not with the M2 class obtained by Stephenson (1986).

Comparing the current brightness of the object with some values from the older catalogs (like USNO etc.), there is no indication of significant long-term changes. I searched for them because a star can show prominent emission lines after the symbiotic nova outburst (because of the residual nova burning), but if the giant is later not capable of supplying enough material to the hot component, the shell-burning turns off and the emission lines vanish from the spectrum. However, it seems this is not the case for StHa 154. The example of this scenario is probably the object TYC 1371-69-1 which now looks like an ordinary giant star but in reality, it is a post-symbiotic nova system. One should also mention, that most of the accreting-only symbiotic systems have only weak emission lines, but Halpha is usually present. Only a small fraction of accreting-only objects have absent emission lines.

The outbursts of symbiotic recurrent novae such as RS Oph (also V407 Cyg experienced similar) are very short in duration and only for a very limited time, these objects show emission lines with high ionization potential in their spectra. It is not very probable, that Munari and Zwitter observed the object just in such a short nova outburst, especially without noticing, that the object is much brighter than before. Moreover, SyRNe also shows at least some emission lines in the periods between the outbursts (Balmer lines of H, He I, [O III]).

To sum up what I think about the star:
• coordinates of StHa 154 in Stephenson (1986) are correct, the spectral type given by the author is unprecise because of the faintness of the star
• Munari and Zwitter (2002) probably observed another star but then gave the coordinates and identification of StHa 154
• currently, StHa 154 cannot be classified as a symbiotic star (doesn't fulfill any symbiotic criteria)
• StHa 154 has probably never shown the symbiotic phenomenon (the classification is based only on one spectrum)
• in the case that Munari and Zwitter's spectrum is correct, StHa 154 experienced evolution which I think is unique and not observed in any of the known symbiotic stars
[...]

Once again, thank you very much for pointing this out. It seems that it is very important also to confirm the symbiotic nature of the 'confirmed' symbiotic stars.
Dubreuil Pierre
Posts: 202
Joined: Sat Oct 01, 2011 12:34 pm

StHA 154 with UVEX4

Post by Dubreuil Pierre »

Hello


Last night in the near infrared, With UVEX4 G600tr/mm-750nm, slit=35µ
StHa 154
StHa 154
Spectre StHa154 5725 to 7714.png (112.4 KiB) Viewed 2907 times
Pierre
Christophe Boussin
Posts: 170
Joined: Sun Aug 21, 2016 6:04 pm

Re: The case StHA 154

Post by Christophe Boussin »

Hello all,

Here is my contribution to the monitoring of StHa 154.
I obtained the following spectrum of StHa 154 with a spectral range from 3700 to 7565 A the 2nd of August at 22 h 47 TU with my Alpy 600 (resolution of 536, JJ = 2459794.4494) and an acquisition time of 80 min (8 x 600 s) :
StHa 154 on August 2nd, 2022 (3700-7565 A)
StHa 154 on August 2nd, 2022 (3700-7565 A)
_stha154_20220802_949_Christophe Boussin_3700_7565.png (80.93 KiB) Viewed 2733 times
Clear skies,

Christophe BOUSSIN
CBO (Newton 200 F/5 / Alpy600 / Atik 314L+ / Atik Titan + Mewlon 180 F/12 / LHIRES III 2400 / Atik 460EX / Atik 314 L+) @ ARAS database
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