[vsnet-newvar 2785] Ninety Five Eclipsing Binaries in the MACHO Scutum Fields

Mon Jun 8 05:12:19 JST 2009

Whilst looking for RR Lyrae stars and Cepheids using the MACHO data for the Scutum fields, before learning most of the RRab stars had recenty been published, roughly equal numbers of red variables and eclipsers were found.  As noted in an earlier email on Miras

http://tech.groups.yahoo.com/group/AVSON/message/1746

this was for MACHO fields 301, 302 and 303, including in the end over 700,000 stars with about 200 to 300 true variables from stars with Welch Stetson Index (field rbcross in the MACHO fields' summary data) greater or equal to 3.0, plus via odds and ends of other criteria.

Roughly equal numbers of red variables and eclipsers appear, and odds and ends of others.  There were nearly two dozen various short period pulsators, most already published recently as stated, some known variables, and a few new short period pulsators and about half a dozen or so exotica (one gamma Cassiopeiae variable and some others), most too faint to follow by observers.

And 95 eclipsing binaries of various sorts, there may be more, especially if lower Welch Stetson values and/or single passband data are used.  Again see the Mira email for numerous caveats when it comes to trying to use MACHO data.  For the Sagittarius and Galactic Centre MACHO fields many stars will have already been published, especially the Miras, and especially the eclipsers for those particular fields that overlap with OGLE II Galactic Bulge fields.

All the eclipsers were checked in late February and early March for their variability type, the possibility of finding a period, and their newness.  Twenty were followed to great depth.  These were submitted for publication, but my personal preferences meant I used a much lower precision than preferred by the editors, and although the paper was acceptable, the periods would need redoing and the paper resubmitting.  As the paper is cold to me, several months since I wrote it and looked at the data, and as I have a personal issue with lots of high precision period quoting nowadays, and the oft quoted attendant minuscule errors, and am just generally disinterested in variable star work for various reasons, I can't be bothered to resubmit them.  Yet they are apparently acceptable stars except for the precision, so just deleting them as I have in the past would be a waste.  Possibly.

So, as with the Miras, I present here 95 eclipsing binaries for anyone to use in whatever way, as a public domain submission, as long as the AVSON or VSNET-NEWVAR archived url for this posting is quoted and the source of the objects as eclipsing binaries noted in MACHO data accredited as being John Greaves.  Just a reference and/or acknowledgement in the normal, provenance displaying, way.  Obviously any subsequent analysis and write up will be the sole acceditation, _and _ responsibility, of the person(s) doing it.  They'll need rechecking against any newer variability lists though, as they have not been checked for novelness since late February 2009 and their March submission.

The 95 objects are presented in decreasing Welch Stetson Index Value from 16 to 3.0.  Note that not all stars having values between these ranges were in fact variable, nor were all of them eclipsing binaries.  All the EW stars were checked via folded phaseplot, as the search was intended to look for RRc variables, only one of which was found.  It is possible some of the stars categorised as EW stars by myself are in fact RRc and I just missed them.  EA and EB stars are usually pretty evident from their raw lightcurves, especially in well populated datasets where outliers are less likely to deceive. 

This is an EA star for instance :-

<http://store.anu.edu.au:3001/cgi-bin/clclite?star=302.45762.144&sodset=PhotSS/F_302/sodset_302.45762>

and this an EB (note the different datapoint densities in top and bottom halves of the curve) :-

<http://store.anu.edu.au:3001/cgi-bin/clclite?star=301.45274.8&sodset=PhotSS/F_301/sodset_301.45274>

EW stars are not readily distinguished from RRc stars in raw lightcurves.

EW stars aren't always readily distinguished from RRc stars in folded phaseplots!!!

The period solutions for the first 20 objects can be seen here

http://i41.tinypic.com/4jl3j6.gif

most of the numbers should be still legible.  After creating the merged file into one big image I then discovered tinypic shrinks anything to a maximum of 1600 pixels in either axis, so it got shrunk.   These stars are still in the table below, the first twenty.  Note the bottom right one isn't an error, it was included to illustrate a point: several eclipsers had this artefact, and there is no readily apparent way to separate these data out of the rest of the data from the raw, it's another MACHO data vagary :-

<http://store.anu.edu.au:3001/cgi-bin/clclite?star=301.46780.251&sodset=PhotSS/F_301/sodset_301.46780>

To readily access a MACHO dataset go here

http://store.anu.edu.au:3001//cgi-bin/fts.pl

and input the tripart name, press submit, tick "bundle" at the result, the press the ftp bundle button, press the resulting Download link, or right click save the link underneath to receive a gzipped file, about 50 kb usually.  Columns have headings, rMag and bMag are the instrumental magnitudes (-99 for null observation), date is in MJD (Modified Julian Date) (I think...).

The self same data file will be returned via the new VO interface, except as a VOTable, or alternatively via direct access into TOPCAT full version 

http://www.star.bris.ac.uk/~mbt/topcat/

[By heck!  It's British!... faints from the shock...]

This will be the way of it all before long, as VO slowly dominates, folk might as well try it.

Alternatively it may be noticed from the urls given above that the MACHO identity can also be broken up and used in the url template to directly access summary webpages.

Classify the objects, analyse any data to six decimals for the period and it should be publishable, although some venues will also insist on the quoting of some error for the period and epoch, depending on how you convert the magnitudes I suppose.  Or just ignore, it's there for use or none use, but source via myself from this mail's archived link and via MACHO must be acknowledged.  There is too much abuse from all quarters in this area nowadays to not insist on this from some.  For the rest of you though who do play fair, if you want them, enjoy them, 

The following table carries the MACHO identifiers and the MACHO sexagesimal RA and Declination.  The twenty classified objects carry type and period clues at the above url image, which should have just about legible alphanumerically, most of the classifications should be safe.  There looks to be an EW or two that might as readily be called an EB, but that's always somewhat arbitrary re the borderline, or personal preference.  Again, if the identifiers for some are not quite legible, see the table below.  The periods are only for guidance in your own analysis, as they were written on the gif, they're retained, but it should be easy enough to find the periods anyway.

Some may well be bright enough for observers to follow, and the Scutum field suitable enough for both Hemispheres, North and South, and not entirely out of season at the moment.

Finally, for the twenty objects studied in full depth astrometry was more than adequate, however for safety's sake it probably ought to be double checked in each case against CMC14 or 2MASS, where possible, and the same for all objects.

There will be many, many eclipsers and red variables from the unique MACHO Galactic Fields, the data is accessible, despite it's use being nontrivial.  RRab and RS CVn and Cepheids and some other variables have been published by the MACHO team and others, but on the whole some categories have been untouched for nigh on a decade, and present a somewhat sizeable resource for the armchair astronomer interested in doing variable star classification.  It's a good learning ground, specific data accessing and manipulation techniques have to be learnt, some astronomic, some generic, before analysis can even begin.  The fact that data are rarely presented fully conveniently and nuances have to be allowed for is well demonstrated, too.  It's not the worst case scenario, there are even less tractable datasets.  OGLE II Galactic data is the easiest quality epoch photometry data to access and use of any data, but most of the Bulge, and since I highlighted it's much unused existence last year, most of the Disc data therefrom has been analysed (still lots of eclipsers and various odds and ends are left though).  There's a wealth of untouched stuff here, with nice long multiyear runs, just sat, sitting, waiting.  But it takes a lot more to use it.

I'm trying to give up on variable star work.  I've always been very interested in stars, especially stars, and variable stars are an area with the most readily available data, but my old interest in exotica and aperiodic stars cannot be followed to publishing level without much unavailable data.  Maybe in a few years when other more astrophysical data sources come online.  But for people just wanting to start in something like this, MACHO Galactic Fields are a large, albeit tasking, untouched reservoir.

John Greaves

"This post utilizes public domain data originally obtained by the MACHO Project, whose work was performed under the joint auspices of the U.S. Department of Energy, National Nuclear Security Administration by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48, the National Science Foundation through the Center for Particle Astrophysics of the University of California under cooperative agreement AST-8809616, and the Mount Stromlo and Siding Spring Observatory, part of the Australian National University."

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

MACHO ID         COORDS
302.45091.74     18 31  4.410 -14 27 12.10
303.45079.40     18 30 59.640 -15 18  6.75
301.45274.8      18 31 23.602 -13 29 24.50
301.46285.110    18 32 59.677 -13 16 22.59
302.46271.1090   18 32 55.552 -14 13 49.92
303.45419.210    18 31 42.532 -15  1  4.16
301.45275.105    18 31 13.552 -13 23 19.24
301.45269.26     18 31 19.110 -13 48 58.19
301.45782.56     18 32 18.600 -13 11 12.16
301.45950.15     18 32 31.935 -13 11 10.68
301.46780.251    18 33 48.337 -13 53  5.04
302.45431.2663   18 31 31.050 -14 13 56.34
301.46118.63     18 32 50.017 -13 14 10.95
302.46099.350    18 32 39.412 -14 28 29.38
301.45436.100    18 31 39.232 -13 52 33.94
301.46115.239    18 32 39.315 -13 25 57.99
301.46447.456    18 33 25.905 -13 40 44.84
302.45093.308    18 31  4.635 -14 20 46.96
302.45762.144    18 32  8.812 -14 31 58.25
302.46438.372    18 33 26.977 -14 15 23.31
301.45107.80     18 31 11.572 -13 24  0.86
301.45942.561    18 32 24.330 -13 46  0.85
301.45612.194    18 31 55.110 -13 19 29.42
301.45773.228    18 32  5.475 -13 47 41.45
301.46615.657    18 33 27.945 -13 41 58.31
302.45597.140    18 31 55.537 -14 19 18.99
301.45438.240    18 31 37.777 -13 45  2.89
301.45437.135    18 31 36.060 -13 50 37.64
301.45941.716    18 32 20.842 -13 50 52.76
301.46277.399    18 33  5.880 -13 48 54.52
303.45082.28     18 31  0.547 -15  4 22.77
302.44755.97     18 30 32.940 -14 30  6.28
301.46614.401    18 33 42.997 -13 46 27.93
303.44411.331    18 29 49.815 -15  2 55.20
301.45775.377    18 32 16.305 -13 39  3.15
301.45775.220    18 32 10.815 -13 39 53.29
302.45090.327    18 31  8.752 -14 33 53.40
302.45934.766    18 32 27.390 -14 17 50.75
301.45607.33     18 31 48.727 -13 41 48.92
301.45278.52     18 31 15.502 -13 13 37.69
301.46948.34     18 34  2.482 -13 53 11.88
301.45439.274    18 31 29.715 -13 40 49.83
301.46108.128    18 32 48.765 -13 52 31.79
301.45947.259    18 32 33.435 -13 26 54.09
301.46283.374    18 33  4.650 -13 25 21.90
301.45269.635    18 31 12.052 -13 47 27.68
301.45944.290    18 32 23.947 -13 35 16.11
302.44930.54     18 30 42.855 -13 59 40.28
302.45598.289    18 31 57.600 -14 15 29.92
303.44915.172    18 30 41.325 -15  1 21.57
302.45596.172    18 31 56.482 -14 26 42.19
303.44074.130    18 29 29.752 -15  3 30.69
301.45606.365    18 31 47.197 -13 45 39.08
301.45440.172    18 31 40.657 -13 36 42.70
301.45779.114    18 32 18.765 -13 25 31.97
303.45754.433    18 32 15.607 -15  5 56.42
302.44930.647    18 30 41.445 -14  0  3.86
303.44915.120    18 30 39.652 -15  0 57.53
301.45777.1472   18 32 17.737 -13 34 18.32
302.46101.162    18 32 49.815 -14 22 21.47
301.45775.487    18 32  7.290 -13 40 20.50
302.45766.423    18 32 17.130 -14 15 46.81
301.46446.427    18 33 21.202 -13 45 47.13
302.44923.364    18 30 44.707 -14 29 16.94
302.45931.262    18 32 23.355 -14 30 30.20
302.46100.624    18 32 51.307 -14 23  9.02
301.45772.498    18 32 13.102 -13 53 17.02
301.46281.1158   18 32 54.720 -13 34 29.95
301.46451.411    18 33 16.575 -13 26 16.69
302.46098.789    18 32 42.135 -14 33  5.34
301.46616.189    18 33 41.655 -13 36  1.51
302.46267.395    18 32 57.630 -14 28 11.51
303.45587.484    18 31 50.122 -14 59 17.61
303.45750.39     18 32  3.660 -15 19  6.12
302.45091.404    18 31 11.467 -14 27  6.24
302.45428.392    18 31 36.900 -14 25 37.02
301.46285.221    18 33  4.222 -13 16 47.21
303.45586.304    18 31 47.482 -15  4  1.21
302.44925.203    18 30 40.920 -14 21 34.96
303.45588.2685   18 31 55.417 -14 58 46.60
301.46112.395    18 32 41.880 -13 38 42.70
301.46280.316    18 33  6.847 -13 35  6.00
301.46278.60     18 33  8.805 -13 45 41.40
302.44923.114    18 30 40.845 -14 28 48.50
303.45755.445    18 32  5.610 -15  0 57.10
301.45779.145    18 32  5.632 -13 25 38.80
301.46613.1206   18 33 35.677 -13 50 52.90
301.45278.386    18 31 19.297 -13 12 33.40
301.46449.1014   18 33 11.985 -13 32 48.90
301.46446.524    18 33 26.227 -13 43 17.10
301.46783.77     18 33 59.392 -13 40 49.20
302.46435.415    18 33 21.517 -14 27  4.10
302.44757.19     18 30 34.927 -14 22 48.50
302.45259.415    18 31 22.335 -14 27 43.90
302.45597.328    18 31 57.135 -14 21 49.10