Updates to the MGAB variable star catalog

» 28.02.2022

The final release of eclipsing white dwarfs (EA/WDs). After careful analysis, EA/WD variability was confirmed for 56 of previously submitted objects as white dwarfs. Additionally, in collaboration with Adam Nowak and Miłosz Płoszyński, we extended the search for eclipsing white dwarfs and confirmed 37 new targets, which increases the total count in the catalog to 93. Literature check indicates none of those systems were previously known as eclipsers, only a few were found to contain an M dwarf companion via spectroscopy. Two systems were previously listed as RR Lyrae objects (B. Sesar et al. 2017).

37 new EA/WDs have been given three designations that are added to the VSX database: MGAB-V3777 - MGAB-V3813, NADA-V210 - NADA-V246 and PMID-V2 - PMID-V38. The main name used in the VSX corresponds to the first researcher that spotted disappearances of an eclipsing WD candidate.

Out of 93 targets, the period was found for 91 objects. Two remaining EA/WDs are waiting for more data to confirm the variability. Despite numerous epochs observed (MGAB-V3791 with 7 eclipses and MGAB-V3809 with 6 eclipses), none of suggested periods via periodogram could be confirmed. This may suggest the target shows extreme eclipse timing variations up to several minutes (as seen in a few targets in the sample), or (less likely) more than one eclipsing companion. With further releases of photometric data from observatories or individual follow up, the missing data will be filled soon. This is already a large improvement, as previous releases of eclipsing white dwarfs had periods calculated for only a half of targets.

The paper describing discovery of all EA/WD systems (including methods and analysis) is currently in development. Several WDs with substellar companions and binaries with apparent eclipse timing variations are identified. Nowdays, more than half of all known EA/WDs are listed in the MGAB catalog.

A few MGAB targets missing in this list can be found as EA/WD variables in the VSX. These were later excluded, as a different variability (EA/HW or CV) or no variability (CST) was confirmed. Those will be corrected soon among with other stars in further revisions. For a complete list of true EA/WDs in the MGAB catalog, visit the page mentioned above.

» 02.08.2021

A paper about MGAB-V859 variable star has been submitted to arXiv.org. Taichi Kato and Naoto Kojiguchi explained peculiar UGER+UGZ variability (together with another recently found analogue, ZTF18abgjsdg). It is the first paper, where a MGAB variable had it primary name kept (thank you, authors!). It is unusually seen because of two reasons:

• Authors of papers often don't recognize VSX as an important source to check if the variable is known or what are the eventual properties. Despite having a few MGABs found on newly published papers (via coordinates check), usually CTRL+F doesn't find any "VSX" or "MGAB" words in the text, suggesting it wasn't considered to be checked.

• MGAB variables don't have a publication (yet), thus no citation is available. These stars can be found only via Variable Star Index website and this page. That means, in some cases they are considered by authors as "not discovered yet", because they require a publication as a paper.

This does not require to speed up the revision process. Submission dates are from VSX/website dates, meaning discovery dates are 2017-2020 instead of paper publication date (as there are no new variables planned to the paper as a supplement). Mentions about MGAB identifications in papers (even as a secondary name) are just welcome and those will be listed and citated in the paper, when the revision and publication is finished.

There haven't been any update on revisions for a while. This is because I decided to submit all at once instead of doing partially. This is expected to happen in September 2021.

» 29.03.2021

Early revision release of all eclipsing white dwarfs, including new light curves. After checking with latest available ZTF DR4 data, 57 targets were confirmed to be eclipsing white dwarfs (from primary 59) and the orbital period was found in 45 cases.

» 04.01.2021

Variable stars released on 25.09.2019 (from MGAB-V301 to MGAB-V550) have been revised. This is the first part of the second stage, which is about updating all MGAB stars with latest available data.

• Eleven objects have been excluded from being discovered, as they were found to be already known based on Transient Name Server database. These are: V301, V302, V308, V314, V350, V351, V392, V454, V515, V524 and V536. The rest 239 stars (63 are independent discoveries) will appear in the final list of variable star discoveries (independent ones and co-discoveries as well). Already known variables are revised too (including the primary name change in the Variable Star Index database), but in statistics presented below they are excluded.

• There are 96 revisions of variability types out of 239 stars, where:

  • 30 are UGSU to UGSU: changes (due to a new standard that SU Ursae Majoris cannot be confirmed without superhumps observed despite superoutbursts observed (higher amplitude and longer duration than normal outbursts seen in the curve)

  • 10 are uncertainity mark removal (the variability type is confirmed, eg. UGZ: to UGZ)

  • 46 are changes in the type, including promotions (eg. from UG to UG+E, or CV to AM) and degradations (eg. from UGSS to UGSS:, or UGSU to UG)

• 125 out of 239 stars have their magnitude range values changed.

• Gaia EDR3 position has been applied to 238 objects (MGAB-V407 is the only one that appears in Gaia DR2, but is missing in Gaia EDR3).

• 4 objects have a new period & epoch value (eclipsing dwarf novae and one IBWD) and 1 object (MGAB-V545) a new, more accurate value.

Similar to above, Transient Name Server was also checked for MGAB variables in range V3371-V3774. 29 variable stars have their discovery credit corrected.

Additional changes:

• Added the Variable Star Discovery Policy page, which explains how discovery credit was given for catalogued objects.

• The Variable Stars Discovery Count list has been cleared and shows only confirmed discoveries based on revisions from the second stage. It also contains an information about the count of discoveries, co-discoveries and independent discoveries.

• Added a separate pages for lists (each one has 500 instead of 1000). Old URLs still exist, but only new ones will receive an update (and doesn't contain old, not revised yet variables). More objects will be added after each revision. It doesn't make any changes f For full lists, please search for "MGAB%" using the VSX.

» 20.12.2020

Variables MGAB-V3371 - MGAB-V3774 are now in the VSX. During preparing of this set, two of variables turned out to be submitted before they appeared in the Variable Star Index:

• MGAB-V3528 = TCP J06515141-0310267 (17 XII 2020, date from Transient Name Server)

• MGAB-V3551 = Gaia20frm (11 XII 2020, date from Gaia Alerts)

The status of both stars has been updated to "non-discovery" (N) in the table.

» 17.12.2020

New variable stars with identifications starting from MGAB-V3371 to MGAB-V3774. The set contains hundreds of cataclysmic variables, eclipsing white dwarfs and hot subdwarfs and WDs showing rotation or reflection effect. The table of variables uses Gaia EDR3 positions and contains information if the finding is a discovery, co-discovery or an independent discovery.

Note: There's a new catalog of ZTF variables and many of new findings might have been already included there. These objects were mentioned as 'variable candidates' in the paper and no classification was done for them, except several dozens of cataclysmic variables. Codes (D/ID/N) will be updated after the submission of the catalog in VizieR and the proper discovery (or independent discovery) credit will be given afterwards.

» 15.05.2020

9 new variable stars have been added to the MGAB catalog (V3362 - V3370). Eight of them are new eclipsing white dwarfs and one is a short period cataclysmic variable.

» 21.02.2020

2071 new variable stars with names starting from MGAB-V1291 to MGAB-V3361 have been published! These are objects with high infrared excess, mostly Young Stellar Objects (YSOs) and Mira stars. The selection was done with a large caution, to avoid false positives (AGNs, blends) and non-variable stars (scatter).

» 27.01.2020

Release of new variable stars with names MGAB-V1147 - MGAB-V1290. Most of these targets are periodic high amplitude variables with low color indexes (reflection effect, eclipsing binaries, HADS and SXPHE stars). A few cataclysmic variables from ZTF DR2 data were also added.

» 11.01.2020

New variable stars MGAB-V1121 - MGAB-V1146 have been published! These are mostly (24 out of 26) new eclipsing binaries around white dwarfs (EA/WDs). All these stars show almost constant brightness during maximum (only a slight reflection effect might be noticeable) and show sudden dimmings with amplitudes 2 mag and above in optical band. Most of them don't have their orbital periods determined and require photometric follow-up observations.

» 15.10.2019

Release of new cataclysmic variables and YSOs (Young Stellar Objects) with names MGAB-V551 - MGAB-V1120.

» 25.09.2019

Release of new cataclysmic variables and a few YSOs (Young Stellar Objects) with names MGAB-V301 - MGAB-V550.