Affiliation
Magyar Csillagaszati Egyesulet, Valtozocsillag Szakcsoport (Hungary) (MCSE)
Sat, 02/06/2021 - 08:16
TCP J10203579+3103424
Discovery date: 2021 02 05.9095
Coord.: 10 20 35.79 +31 03 42.4
13.0 R
http://www.cbat.eps.harvard.edu/unconf/followups/J10203579+3103424.html
Also known as: AT 2021bxp
Possible Nova or CV, ~8 mag rise in PS1 source. The transient was discovered on several 120-s survey images (limiting mag about 19.0) taken by Xing Gao using PAT at Xingming Observatory #3 (N88). Images can be found at: http://xjltp.china-vo.org/xm51ht.html
https://www.wis-tns.org/object/2021bxp
TCP J10203579+3103424 200206.2892 12.636V (0.008) FRF
using the T20 telescope at Mayhill, New Mexico, US. (iTelescope.net)
Position end figures: 35.78 (RA), 42.7 (D).
Robert
Thank you for this new deal.
Using VSX (to have a map of the field) I receive the attached map. In red is the position 2021.1 from SkySafari Pro, but with the AAVSO the pointer is in the middle of the map. The two positions are far from each other.
It's not the first time that I observe this difference.
Did you have an explanation ?
Thank you for your help
I think you should use 2000.0 epoch. Probably that is the source of the difference, that you use wrong epoch.
Here you can see the position of TCP J10203579+3103424 in sky-map.org:
Robert
Ok Robert, that's why. I was not expecting to see such a huge difference for only 21 years!
Hello all. I'm Hanjie Tan, one of the discoverers of this transient.
Our latest observation on 2021-02-06.5815 UT show the transient is 12.65 (0.01) V mag, consistent with Fidrich's observation. Its color indices are very blue, B-V = -0.07 mag, g-r = -0.38 mag.
We noticed that this object's last outburst may have been in 2007. It was collected in some QSO catalog, has a redshift (photo z) = 1.25 according to NED(NASA/IPAC EXTRAGALACTIC DATABASE). Further observations especially spectrum are encouraged.
Hello Hanjie,
Why do you say there was a previous outburst? I can't find any previous record of a brightening above its 20-21 quiescent magnitude.
The star is included in many catalogues but always faint.
Also, there are lots of CVs included in those QSO catalogues.
Cheers,
Sebastian
The…
Hello Sebastian,
The outburst was recorded by The Catalina Surveys, you can check it through: http://nunuku.caltech.edu/cgi-bin/getcssconedb_release_img.cgi
Hanjie,
It's been several days since I only get a black screen when trying to retrieve CRTS data.
Are you able to see something?
Cheers,
Sebastian
Yes, maybe you can try different browsers.
Best
-Hanjie
I tried both with Google Chrome and Mozilla Firefox and I always get a black screen...
Cheers,
Sebastian
I just did my first visual estimations of this nova, 12.1 & 12.2 but using Tycho values.
About the estimation did you agree?
Hi Michel,
Using Tycho magnitudes for a 13th mag. object is a bad choice.
When there is no official sequence available, the best choice is using APASS V magnitudes for the comparison stars (for stars fainter than mag. 10). They can be found through VizieR.
This is a consistent catalogue. Tycho-2 barely reaches to mag. 12 but starts having issues at mag. 10 and the few stars that are in Tycho at magnitudes fainter than 12 have a very large error measurement.
So I recommend that you check the APASS magnitudes of your comparison stars and replace the Tycho magnitudes by these ones.
The Sequence Team will surely issue an AAVSO sequence soon.
Cheers,
Sebastian
Indeed thank you Sebastian.
In the dark I used the SkySafari Pro data. This was the Tycho2 for the 2 magnitude 10 stars. In fact after checking the data that I was reading the SkySafari was related to the Gaïa catalog. However I have the Guide9 system too, in this system I have the 3UC data
The comparison stars in Gaïa 12.1 was 11.83 in 3UC, the 12.3 Gaïa was in 3UC 12.07, probably a question of colors (?) So I let my first estimation from Gaïa because this is related to visual magnitude.
Thank you for your help
Hi Michel,
Neither UCAC3 nor Gaia (DR2 or EDR3?) use V filters so they are not good sources of magnitudes unless they are transformed to V. If you do so, that's fine (and Gaia DR2 will be better). The UCAC and Gaia filters are redder than V so they will always be brighter (unless the star is very blue).
That's why you should use APASS (or apply transformations to Gaia DR2).
Cheers,
Sebastian
I don't…
Thanks Sebastian
I don't have the APASS data base, however in the SKySafari Pro the magnitude of Gaïa is labeled "Visual Magnitude". Anyway, I'm waiting for the AAVSO sequence.
Michel
APASS data are available through VizieR, so you can look up the data there.
It is also available through the AAVSO website and VStar.
I do not know if the magnitudes are transformed to V in the SkySafari Pro software but my advice is "never take a piece of software as a mangitude source per se". What matters is the data source. In this case, Gaia. It should be specified if the data came from Gaia DR1, DR2 or EDR3 and from now on we can compare values with the available magnitudes in VizieR.
I would just plot charts with VSP and look up the data in VizieR. Commercial software is a potential source of error and confusion for this specific job that we do.
If you send the coordinates of your comparison stars, we can compare the magnitudes, add APASS V values and come to a transformed V magnitude from Gaia DR2 and UCAC3 that may work as a good exercise.
Cheers,
Sebastian
ATEL 14374: Spectroscopic Classification of the Transient TCP J10203579+3103424 = AT 2021bxp = ZTF21aaherhg as a high-amplitude dwarf nova
Best,
Robert
An official AAVSO sequence has become available through VSP thanks to the Sequence Team.
Please update your charts and use it to submit your observations.
Cheers,
Sebastian
The values given are fully compatible with the "V" Gaia ones from SkySafari, it's also true that for visual observers the precision of 0.01 is not really usefull.
Anyway thank you the Sequence Team for the map, really appreciated.
Out of this sequences values we have to make more stars comparisons and check if those stars are not variable ones.