Variable stars are very common. There are several lists containing hundreds or millions of variable stars just in the Milky Way galaxy. All marked as confirmed or candidates. Because there's many of them to handle, there's no complete list of all known variable stars. Even VSX, which combines the most of verified variable stars, doesn't contain everything we currently discovered. What's more, we are in a moment, when we can start digging around already reported variables instead of searching for new ones to find something worth for further research.
In the topic of planets, comets, asteroids or variable stars, there's always a subject "who was the discoverer". Each of these types work differently. Comets are treated in another way than asteroids. Variable stars are completely different as well. From my look over last years, an arbitrariness about the credit around variables is clearly seen, which leaded to write myself this "short" explaination.
Not everyone puts the discovery credit in a high priority. The majority of astronomers rather look at it differently - who is authored in a paper regarding to the first explaination or conducted follow up of a specific object; where was the paper published and how many citations it got. In general - do you have a paper and does it help much to your career (positions, grants).
And here comes myself - an astronomer amateur working as a dentist. No possibility to access a giant telescope, no availability to write a detailed thirty pages paper about a new finding. Grants? Not applicable, as I don't have a certain position anywhere in academic centers. But still can find something new that is not listed in any catalog of variable stars and (wants to) report with a similar description like many astronomers do especially in larger catalogs. There are also other ways to publish discoveries than putting into the scientific paper. And, the work spent on variable stars means a little for the job (actually, the only thing that binds dentistry and astronomy are black holes!). So why would an amateur even work in finding new variables? Most likely to discover something, report that "there's a new variable I found, maybe it's worth further follow up?". Does it mean anything to astronomers? Do amateurs help them? And how others, also not even involved in astronomy, would say about this situation?
At the beginning an amateur can easily say "I discovered", but when you look at in greater detail, you have more and more doubts if you look at it the same way like others. There's a great definition that sums up the term of discovery in astronomy:
"Discovery is not done by discovery. You find many different things. None of them are discovery until you understand what it is."
The doors are closed when you finally find out someone reported earlier the same thing with a significant detail. So here appears an important determinant - a date when it was done. A lot of things can be hidden behind the word "done", starting from the latest to earliest:
When the journal with your scientific paper got released?
When did your paper appear the earliest to the public (eg. arXiv.org)?
When did you receive a green light by the referee for a submission in the journal?
When did you sent the very first submission of the paper for a check?
When did you start making very first observations of the object you wanted to observe?
When did you notice variability of a certain object for the first time?
Each of these moments most likely have different dates and your work can be put somewhere between above. And not all of them can be applied to each variable star we might be talking about. Variable stars in online lists allow to quickly report that skips many of above that shorten the process. Is that enough? Do you think "you already understand what it is" to claim the discovery credit?
When you look if a specified target is already a known variable, you want to check lists and the literature. You might find out you are indeed the first, but in reality, someone else has seen the variability too, but haven't published it yet. That can be a long project too - someone has observed or analyzed for years and someone suddenly comes up with a submission that took one day. You never know what's behind until the second person (or collaboration) releases their work. You report the discovery and at that moment you're the one containing most detailed information about variability for the public. You discovered, because you reported. And soon you find out that a (most likely) detailed work appears and what you done is more like a summary. So, who is the discoverer? In this sitation an independent discovery credit is reasonable.
Astronomers by profession have no problem about that. Someone else released a paper about the same stars were were working on? No problem - we can write a short sentence that someone else independently worked on the same object and contain similar results. Your paper simply go further and you have another publication into account. The amount of citations or impact factor definitely matters. The discovery credit becomes a secondary or tertiary thing.
As an astronomy amateur, the discovery credit has a much higher importance for my general work in search for new variable stars. This is because my further work is closing only around personally discovered objects, so I have a certain set of objects for follow-up programs. A lot of objects required a discovery credit correction when a previously unchecked database had actually a certain object marked as a known variable. That wasn't a mistake at the beginning - the more you search, the more sources you find that may contain something you discovered. You find a catalog of objects that you haven't seen earlier. Suddenly you find out that one MGAB was flagged as a variable earlier. And now, all stars needs to be rechecked again. What's more, not every catalog is equal to another. Confirmed variable or a candidate. Variability based on the magnitude error or the light curve. Vetted by a human or by an artifical intelligence. Contains details like a period, but may be correct or not. An binary with a known spectroscopic companion and eclipses of that object are just found. At some point even all your discoveries are questionnable, thus for common sense this needs to be sorted. And these are just a few examples that doesn't make the word "discovery" a simple meaning. Dozens of situations that need to be investigated differently.
So, in which cases the discovery credit should be revised?
1) A photometric variability is confirmed based on the light curve or single frames, not by too high magnitude error from the stellar catalog
You can only say that a variable star is variable if you see it's variable. If you have a set of variables that are likely them just because magnitude errors are higher than stars with such brightness tend to have, then no.
2) A variable star is a candidate, but the period (if applicable to a specified variable) is correct.
I am okay with those cases. You haven't confirmed it as a variable, but the periodicity signal is real.
The variable star is deeply examined in a paper (if a paper
A proper classification is given
Now opposite - in which cases the discovery is kept (or is an indepedent discovery)?
Do you consider yourself as a discoverer of a certain variable star, but it is already in the MGAB Variable Star Catalog and already listed as a personal discovery?
Feel free to contact with me if you want this to be corrected (you can find my e-mail in About Me section). It's very likely that I simply missed your report/submission/paper/publication. If I see a date confirming that you have done it earlier and if I easily could have found it when I submitted the variable star (but I didn't know it existed, as it wasn't in my checklist), this can be easily adjusted. It's also possible that I had already noticed, but haven't submitted a revision yet (as those are done in batch). Not for everyone the main goal is to keep variability flags listed in VSX, VizieR or Simbad. If the source is hardly reachable, the chance of being missed increases.
It's possible you might disagree one determination explained above that keeps a certain object as a MGAB variable or independent discoverer(s) are not listed as they should (most likely you will see the same credit in the VSX, as it takes a similar way). Remember that the discovery credit doesn't have a significant scientific importance, especially when there are millions of other variables out there. There are too many variable star catalogs (and reports) out there and it's obvious that conflicts between each other will always be present. A precise term of "who discovered" that covers all unclear situations does not exist. The idea of this Discovery Policy is to organize personal lists and avoid question marks when it comes to note "who was the first to report", so I can be fine with others that indeed should claim the discovery credit. The MGAB catalog is already large enough that is difficult to keep the highest quality. I also had been several moments of disagreement about discovery credit when submitting to the Variable Star Index. Once I couldn't accept submission rejection when it was noted somewhere with very poor variability determination (these have been rejected from the Catalog anyway to avoid further confusion), also once I could add someone else as an independent discoverer, but it wasn't obligatory by the VSX.
MGAB variable stars that later required to correct the discovery credit, will still have original numbers and with the same name still can be found in the VSX. But for those, the Discoverer field and main name are corrected.
There's a plenty of possible details about a new finding, but at what point is that a discovery? A newly reported object can be:
Marked just a possibile variable star candidate without any detailed description what kind of object is it
Reported as a certain variable, but an improper position, classification or period is given
Submitted as a new variable with a correct type, but lack of photometric data disallows to determine fundamental information (eg. an obvious eclipsing white dwarf, but you don't have enough data for a period calculation)
And the object can be reported:
Among other variables in a catalog of variable stars, where you can
Simply put
All ways above can be mixed themselves, giving a specific sitatuion for each of variable star. I have met all
Regarding to variable stars in the MGAB catalog, the answer for specific objects "is that a new discovery?" is not a simple Yes or No. Many of included targets require an extended answer what kind of credit can be given. Still, a detailed answer might not be enough for others that look at the subject differently. Before I start explaining what MGABs mean to scientific astronomy,
The search for variable stars started in 2017 by exploring the neighbourhood of stars hosting an exoplanet transit. More than a hundred of variables were submitted to the Variable Star Index individually using own photometry data combined with survey ones (eg. ASAS-SN Sky Patrol or SuperWASP). A few months later the search changed to data mining using survey data. Because in all cases (dubious variables are never submitted unless there was some kind of a manual error) the photometric data is enough to classify variables, unpublished (missed in catalogs) objects are submitted without any additional observations. This is planned in the last stage, after publication of the paper about MGAB catalog of variable stars.
Variability flags marked as 'true', 'yes', '1' etc. based on RMS are not treated as discoveries and none of these confirm if is indeed variable and contains a bunch of false positives. All MGAB stars are checked manually by eye (even on single images, if needed) to make sure variables are indeed real.
Objects with a general classification by spectroscopy/survey magnitudes are not treated as discoveries. Example: Young Stellar Object (YSO) from SIMBAD based only on IR-excess or H-alpha emission isn't enough to claim if the discovery, as photometric variability was not mentioned.
Variable stars from the ATLAS catalog are treated a discoveries only when are not marked as 'dubious'. Submitted variable stars after the publication date to arXiv with non-dubious code will have their main name & discoverer changed in the VSX database. This is applied to all variable stars except MGAB-V266 (an independent discovery), because of:
Deep eclipses by ATLAS were not mentioned (marked as a pulsator (PULSE) with a doubled period)
We are already observing eclipses of this system extensively for a future publication
All variables previously submitted to the VSX by others are excluded. This also applies to new group of stars, where objects were primarily unknown during the cross-match, but were added to the VSX independently before they are published on this page.
Gaia DR2 variables are all excluded even if their classification is incorrect (eg. DSCT_SXPHE for cataclysmic variables or MIRA for Young Stellar Objects).
RR Lyrae candidates from Pan-STARRS1 are all treated as independent discoveries and both names will be always shown in the VSX. A confirmed part of objects was previously accepted to the Variable Star Index and the rest are treated as candidates. High amplitude variables (with impossible values for RR Lyrae stars) are included with a low RRAB/RRC probability, meaning the machine learning wasn't fully effective or/and the threshold was too low. The search for variables was never based on this catalog.
ZTF variable star candidates from the "A catalog of over ten million variable source candidates in ZTF data release 1" paper are also not treated as discoveries for stars that have been submitted after the publication date. The full discovery credit will be given only to those stars which are validated (dwarf novae and listed short period variables with plotted graphs), as mentioned by authors of the paper. An independent discovery will be considered when the full table will become available in VizieR. A large set of randomly selected stars will be taken for validation to estimate the amount of false positives.
The official ZTF lists (alerce.online & lasair.roe.ac.uk) will not be considered as discoveries unless they are published in other catalogs mentioned above. The discovery date given on sites is the first ever positive detection of the target, not a variability discovery report (eg. MGAB-V301, which has a TNS report by the ZTF more a day later and more than a year before in VSX, so the credit was corrected). Because the paper of ZTF variables is still in development, those sites are treated as experimental before the ZTF's catalog is fully released. So far, variability types are mostly correctly given, so it's worth looking for the paper in the future.
Not all authors of papers submit their findings to SIMBAD, VizieR or even VSX. If a variable star with a reasonable variability explaination in a previously published paper will be found after the submission with MGAB as a main name, it will be corrected.
A proper credit from using datapoints coming from a certain survey in plots is given.
Discovery dates for all objects:
MGAB-V1 to MGAB-V300 - based on submission date to the VSX, except objects from the paper "The discovery of eleven nova-like VY Scl type stars" (Murawski, G.; 2019). Three first objects (MGAB-V195, MGAB-V196 and MGAB-V197) were submitted individually to the VSX in January 2019, but the rest (from V201 to V208) were put to the paper and sent to The Astronomical Reports journal with submission date of 7th February, 2019. The journal had several internal problems, which caused delays and it was finally published on 16th January, 2020. Objects with designations from V201 to V208 were submitted to the VSX earlier (in August 2019) to avoid further problems about the discovery credit. This is explained because of the nova eruption of MGAB-V207, which happened in July 2020, which caught attention. This object was mentioned as a RR Lyrae candidate in the paper "Identification of RR Lyrae stars in multiband, sparsely-sampled data from the Dark Energy Survey using template fitting and Random Forest classification" (Stringer, K. M.; et al., 2019) with a submission date of 1st May, 2019. Because of an earlier submission date (by almost 3 months), object marked as a candidate with an improper classification and late submission to VizieR (in August 2019 the catalog was not present in VizieR to investigate the discovery credit), the variability discovery credit is kept.
MGAB-V301 to MGAB-V550 - 25.09.2019
MGAB-V551 to MGAB-V1120 - 15.10.2019
MGAB-V1121 to MGAB-V1146 - 11.01.2020
MGAB-V1147 - MGAB-V1290 - 27.01.2020
MGAB-V1291 - MGAB-V3361 - 21.02.2020
MGAB-V3362 - MGAB-V3370 - 15.05.2020
MGAB-V3371 - MGAB-V3774 - 20.12.2020 (except MGAB-V3390, MGAB-V3395, MGAB-V3396 - individual submissions to the VSX)
Clarification on discovery, co-discovery, independent discovery counts:
Full discovery - the variability was not confirmed anywhere and the report is the first.
Co-discovery - the submission to the VSX is done with a group of people and is the first that confirms the variability.
Independent discovery - RR Lyrae candidates from Pan-STARRS1, which by usual are correctly identified as variable, but failed to apply a proper classification. If the submission via MGAB catalog was done with a group of people (like a co-discovery), but the target is present in the catalog of RR Lyrae candidates, is also treated as an independent discovery. This is also given if a specified star from the MGAB catalog is the main star topic in a new paper and authors explain that the target was observed for a long time. Additionally, it is applied to MGAB-V266 for reasons explained above.
Total discovery count - is a sum of full discoveries, co-discoveries and independent discoveries.