VSX update with ZTF and stars with wrong positions

Affiliation
American Association of Variable Star Observers (AAVSO)
Thu, 10/28/2021 - 02:25

On October 26, we made a very large update of VSX records with information taken from the ZTF Catalog of Periodic Variable Stars (published in 2020).

These revisions are challenging to implement because our goal is not to overwrite existing data with new information that may not be as good as what is currently available.
There are many reasons for this to be a concern, but the main one is that any survey catalogue is based on the results of the data taken from that specific survey. This means, limited time span, limited number of observations and other shortcomings implying that, in a number of cases, the "old" VSX data will be better. This is due to longer time span of the observations, combination of different data sources in complete individual object analysis, etc. So we have to make some comparisons, make some judgements. We do our best although it is impossible to get a perfect result because we have to make some assumptions too (based on survey resolution, quality, etc.) or the task would be neverending. Actually not feasible.

This update was the first one in a number of revisions from the above catalogue that we are going to import to VSX.
A variety of information was revised this time (classifications, amplitudes, periods) but something that we pay special attention to in this first batch was position.
It turns out that the most recent surveys like ZTF have a much better resolution than previous ones (like NSVS, SuperWASP, ASAS-3 or even ASAS-SN), and this allows us to find out that many identifications adopted from those surveys, were plain wrong!
Nearby objects blended with the actual variable star may have been identified as the targets when they are not. Positional offsets may range from a couple of arcseconds to more than an arcminute.
In this update, we corrected identifications for ~2600 stars with positions more than 4" off. 62 objects were more than 30" away from their actual place in the sky, and thus misidentifications when observing them may have been a real issue.

The realization that some of these objects may have been observed by our members using a chart showing the wrong coordinates, led us to start a project to address this problem.
We found that during the VSX lifetime, 233 objects with data in the AAVSO International Database once had a position that was incorrect by more than 30".
We are going to check these cases to rectify potential misidentifications.

You can help us! If you have been observing an object that was supposed to be variable and you saw no variations, or if you are suspicious of any identification, please let us know.
And here, we can help you stop wasting your time looking at the wrong object: below we show you the list of objects (by alphabetical order) that were corrected in VSX.
Maybe you remember some of these ones from the top of your head, maybe they ring a bell, or maybe you want to update your charts.
It is a good example to show that charts should be updated from time to time. And whenever you find an identification change, delete the wrong observations if you are sure of what you observed, or contact us (at vsx@aavso.org) in order to discuss what to do with them (there are cases when observations were just "fainter thans", but other cases where a different star was observed, and that one may turn out to be variable, so it is better if we chat about it before doing anything, if you are not sure).

If you have been observing some of the stars below, you may want to check the new positions in VSX before attempting more observations.

2MASS J00334028+5137302
AB Boo
AG Ori
AI Aql
AL Pic
ASASSN-17mn
AW Aql
BI Ant
BK CMi
BL Sct
CC Cam
CH Car
CP Tri
CPD-59 3095B
CS Peg
CTCV J2056-3014
CX Peg
DH Phe
DN Cap
DN Car
DX Aql
DX Oct
DY Eri
EE Oct
EL Oct
EM Cru
EM CVn
EN Cir
ET Oct
EU Tel
EV Aqr
EV Lup
EZ Vul
FG Mus
FH Car
FS Sgr
FY Com
FZ Cet
GSC 00752-00991
GSC 01643-01527
GSC 02681-00264
GSC 02874-01098
GSC 05938-00301
GSC 05938-00627
HAT 199-13145
HAT-205-0011325
Hen 3-230
HS Leo
HU Cam
IW Peg
KX Nor
KY Ori
LMC V0850
LMC V1512
LMC V1588
LMC V3566
LMC V3773
MC 2
Morel V2 Car
MU Mus
NP Boo
NSV 10167
NSV 11092
NSV 11664
NSV 11948
NSV 12002
NSV 12224
NSV 12228
NSV 12750
NSV 12839
NSV 13000
NSV 13027
NSV 13236
NSV 13562
NSV 13953
NSV 13987
NSV 14284
NSV 14333
NSV 1440
NSV 14420
NSV 14458
NSV 14536
NSV 14580
NSV 14581
NSV 14698
NSV 15170
NSV 3933
NSV 3936
NSV 4168
NSV 4402
NSV 4584
NSV 4618
NSV 4776
NSV 4926
NSV 5031
NSV 5125
NSV 5285
NSV 5472
NSV 5523
NSV 5543
NSV 5725
NSV 6038
NSV 6278
NSV 6282
NSV 6431
NSV 6661
NSV 6808
NSV 6987
NSV 7155
NSV 7284
NSV 751
NSV 7600
NSV 7652
NSV 7724
NSV 8178
NSVS 5733701
OP TrA
OS Aqr
OS Her
OV Lup
OZ Oph
PP Cas
PW Mus
PY Cen
QR Nor
QSO J0050-0929
QT Sct
QW Lup
QY TrA
RR Aps
SN 1964O
SN 1980N
SN 1981D
SN 2011an
SN 2012cd
SN 2016bau
SU Ari
SU Cap
T Boo
TZ Ari
UX Peg
UZ Boo
V0345 Nor
V0357 Tau
V0364 Per
V0368 UMa
V0372 Lyr
V0373 Sge
V0375 Pav
V0384 Car
V0388 Lup
V0390 Nor
V0391 Vir
V0405 Ser
V0409 Nor
V0409 Ser
V0438 Sge
V0442 Hya
V0449 Cas
V0467 Vul
V0493 Aqr
V0508 Cyg
V0548 Pav
V0552 Sco
V0557 Hya
V0577 Cen
V0580 Ser
V0581 Aur
V0583 Ser
V0585 Ser
V0613 Pup
V0614 Ara
V0615 Ser
V0645 Cen
V0645 CrA
V0667 Cen
V0674 Lyr
V0690 Cas
V0703 Cas
V0706 Peg
V0728 Sco
V0737 Cep
V0739 Sgr
V0743 Cep
V0746 Cep
V0755 CrA
V0803 Aql
V0904 Cyg
V0973 Ara
V0979 Sgr
V0985 Ara
V1010 Ara
V1083 Sgr
V1117 Her
V1185 Cas
V1196 Aql
V1208 Cen
V1229 Cyg
V1288 Sgr
V1296 Sgr
V1306 Aql
V1310 Sgr
V1317 Sco
V1341 Cen
V1345 Cen
V1426 Cen
V1472 Ori
V1519 Her
V1531 Her
V1712 Aql
V1721 Sgr
V1730 Cyg
V2533 Sgr
V2677 Oph
V2907 Oph
V3090 Oph
V3918 Sgr
V5810 Sgr
V5829 Sgr
V5832 Sgr
V5842 Sgr
V5843 Sgr
V6346 Sgr
V6504 Sgr
V6564 Sgr
WX Ari
WX Aur
X Col
XO-2
XY Ari
Y CMi
YZ Cam
YZ Sex

But don't worry, we will be checking data and if we need some change to be made from your side, you will get an email and we will be able to discuss each case.

The above facts showcase how one thing leads to another and VSX -and the variable star world in general- is continuously evolving and improving as new and more accurate data become available.

In the months to come we will be working with additional 66,000 objects from that same catalogue to keep revising records, but these ones all have positions less than 6.5" off, so they won't be so problematic regarding identifications!

Thanks for using VSX. We try to offer the best information available to the VS community. This year we are more focused on quality than in quantity :).

Best wishes,
Sebastian and the VSX Team.