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New possible variable star for VSX?

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Trygve Prestgard
New possible variable star for VSX?

Hi all,

Having been searching recently for unknown variable stars in DSS images, I stumbled upon this faint candidate in Vulpecula that had many POSS images available. All POSS images (including POSSII-IR) showed the star to fluctuate noticeably in brightness over time (see attachement).

The object did not appear in the VSX, or in any variable star catalog suggested by Vizier, and it wasn't listed by NSVS (taking into account the uncertainties and magnitudes). I wasn't able to access ASAS data however, so I can't be sure on that.

I have read all VSX information concerning reporting variable stars, but knowing that I'm rather new to variable star observing, I thought it would probably be better getting an opinion before going on to reporting.

I'm registered to VSX and have signed up for the VSX yahoo discussion group, but I'm not able to post anything there (at least for now), so I decided to post here first.

Thanks for your help and corrections if possible,

Best regards,

Trygve

Regarding the variable star, here's all the information I've got on it:

The object is catalogued as 2MASS 20060630+2213287 (IR source), USNO-A2 1050-16403172 (+15.8 mag star acc. to wikisky), USNO-B1 1122-0534439, AllWISEJ200606.30+221328.7. The J2000.00 coordinates are: 20:06:06.302 +22:13:28.76.

If I have not mistaken, it appears USNO has based the magnitudes of their objects on their appearance in the DSS1 and 2 plates. If that's the case, then:

POSSI-E Red (1951-07-13): Red mag: +13.19  /  POSS-I O (1951-07-13): Blue mag: +16.83

POSS-II Red (1991-09-08): Red mag: +13?     /   POSSII Blue(1988-06-14): Blue mag: +18.5?

POSS-II Red (1992-09-19) Red mag: +15.66?  /   POSSII Blue(1990-07-26): Blue mag +18.5?

POSS-II N (1994-06-15) Near-IR mag: +12.82? /  POSS-II N (1995-07-19): Near-IR mag: +12?

It is likely that I've got some of the magnitudes wrong. Alot of these are estimated based on comparisons in other images and to other neighbouring stars.

2MASS band magnitudes:    J: +9.378    H: +8.401     K: +7.888

WISE band magnitudes:  W1: +7.257   W2: +6.989    W3: +6.215   W4: +5.754

Unfortunately, with only these POSS images it seems impossible to give the period of this variable.

I also don't know what kind of variable it could be, but I assume it's something like a Mira type variable (based on its brightness in the near-mid IR especially) and the rather significant changes in luminosity it displays. But I can't actually be sure.

BPO
BPO's picture
New possible variable star

Hi Trygve,

I've imaged this star for a couple of hours and it is varying. The star wasn't visible in V, but did show up in SI (sloan) at around mag 13, I will later today ask the chart team for some comps for the field to get an accurate measurement, and when you get your star acknowledged in VSX I will upload to the DB.

Congrats on your new star!

Regards,
Douglas

Trygve Prestgard
New possible variable star

Hi Douglas,

Wow that's great news, thank very much for observing this star for me! Can't wait for the next results on it. I'll let you know when the vsx is out for this one.

Best regards,

Trygve

 

Sebastian Otero
Sebastian Otero's picture
VSX submission

Hello Trygve,

Your analysis is basically okay.
The star is not in ASAS-3 because it is too faint and also close to a 14th mag. star.
No survey data to use unfortunately.
However, we can confirm its variability with data derived from CMC15 (V= 15.2) and GSC2.3 (V= 16.6).
The GSC2.3 zero point might be a couple of tenths too bright and the CMC15 mags are usually within 0.1 mag. when transformed to V.
The DSS images also show evident variability as you said.
The 2MASS colors are typical of a red variable and yes, this could be a mira from its amplitude.

A submission to VSX for this one will be accepted even when no standard (i.e.: a light curve) supporting evidence can be uploaded. You can upload your DSS image comparison. Include the range I gave you (with > and < symbols for the magnitudes) and all the information regarding cross-IDs and position.
The submission should be straightforward. So give it a try. I will help you if something is wrong.

Cheers,
Sebastian

----------------------

Sebastian Otero

VSX Team

American Association of Variable Star Observers

 

Trygve Prestgard
VSX Submission

Hello Sebastian,

Thanks for your help! I've finished submitting the star through VSX (wizard form), including the information you gave. Hopefully it should all (or at least mostly) be good. Main designation: 2MASS 20060630+2213287.

Best regards,

Trygve

Trygve Prestgard
2MASS J20060630+2213287 accepted into VSX

Thanks again to Sebastian for adding the star so quickly to the VSX! Thanks to Douglas again for keeping me update with the follow-ups from the chart team.

Trygve

 

BPO
BPO's picture
First data uploaded

Hi Trygve,

The chart team have provided 7 comps in the field now. I've uploaded ob's from three nights and
the lightcurve shows that the star is fading. Hopefully it can be followed through to
the minimum and rise to max..

Douglas

Trygve Prestgard
First data

Hi Douglas, 

Thank you for keeping me updated and uploading the data and thanks to the chart team for already spending so much time observing this star! Would definitely be great if they could observe the star long enough to make a good light curve out of the data. 

I really appreciate all the efforts put in to studying and gaining more information on this object.

Best regards,

Trygve

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