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MACS: Help

MACS - Magellanic Catalog of Stars


Overview

The Magellanic Catalogue of Stars (MACS) is based on scans of ESO Schmidt plates and contains about 244,000 stars covering large areas around the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The positions refer to the FK5 system via the PPM Catalog. A comparison of positions from different plates ahows internal errors at a level of 0.15 to o.23 arcseconds; the positional accuracy is estimated to be better than 0.5 arcseconds for 99% of the stars. The limiting blue magnitude of the MACS is less than 16.5 magnitudes, but the catalog is not complete to this level, as only those stars are included which are undisturbed by close neighbours as verified by visual (interactive) screening (in order to obtain a clean astrometric reference).

Catalog Bibcode

1996A&AS..119...91T

References

The Magellanic Catalogue of Stars (MACS), Astr. Ap. Suppl., 119, 91. (1996) = ADC/CDS Catalog I/221.

Provenance

This database was created at the HEASARC in June 1998 based on the ADC/CDS Catalog I/221.

Parameters

Name
This parameter is the star name based on the truncated Equinox 2000 position and a running number within an (RA, Declination) box of 1 minute in time x 6 arc minutes. For example, a star with (RA, Declination) = (5 hr 47 min 02.4 sec, -67 deg 12 min 02 sec) would have the designation MACS J0547-672#001, if it were the first star in its box. The positional coding uses in RA the hhmm format and in declination decimal degrees (truncated!), thus defining (in the southern sky) the northwest corner of the box. This format is in agreement with the Rules and Regulations for Nomenclature as defined by IAU Commission 5. Currently, the largest number of stars within a box are 84 and 40 for the LMC and SMC, respectively.

RA
The right ascension of the object in the selected equinox. The original equinox of the MACS in the version as supplied to the CDS was J2000.0 in the FK5/PPM system, notice. The epoch of these positions is the average of the plate epochs, which is around 1989.0. For some SMC fields (28, 50, 51), however, the epoch is 1991.8. This difference matters only for stars of very high proper motion. The internal errors of the positions for 99% of the entries are estimated to be less than or equal to 0.5 arcseconds, and such entries have a value of 0 for the parameter called position_flag; the 2394 (0.99%) of the stars with larger internal errors are flagged with a value of 1 for the position_flag parameter.

Dec
The declination of the object in the selected equinox. The original equinox of the MACS in the version as supplied to the CDS was J2000.0 in the FK5/PPM system, notice. The epoch of these positions is the average of the plate epochs, which is around 1989.0. For some SMC fields (28, 50, 51), however, the epoch is 1991.8. This difference matters only for stars of very high proper motion. The internal errors of the positions for 99% of the entries are estimated to be less than or equal to 0.5 arcseconds, and such entries have a value of 0 for the parameter called position_flag; the 2394 (0.99%) of the stars with larger internal errors are flagged with a value of 1 for the position_flag parameter.

LII
The galactic longitude of the object.

BII
The galactic latitude of the object.

Num_Pos
The number of positions from which the RA, Declination, and instrumental magnitude (int_mag) were computed. This may reach 8 for a fourfold corner overlap; on the average, one MACS position is derived from measurements on 1.8 plates.

Int_Mag
The internal (blue) magnitude of the star; the zero points of this magnitude for the 2 catalog parts (LMC and SMC) are arbitrary, notice. Thus, this parameter should be useful at least for ranking stars by their blue magnitudes, i.e., for relative magnitude information. For stars for which the magnitude measurement procedure failed, a dummy value of 99.0 for this parameter is given. The parameter int_mag_flag is used to indicate stars which have internal errors for int_mag that are larger than a magnitude-dependent limit chosen to select only exceptionally high values: 1248 (0.51%) such stars have int_mag_flag set to 1. Notice that a value of 1 for int_mag_flag may also indicate a large-amplitude photometric variation.

Position_Flag
A flag used to indicate the size of the internal error for the position. The internal errors of the positions for 99% of the entries are estimated to be less than or equal to 0.5 arcseconds, and such entries have a value of 0 for this parameter; in contrast, the 2394 (0.99%) of the stars with larger internal errors have position_flag = 1.

Int_Mag_Flag
A flag used to indicate the size of the internal error for the internal magnitude. Those stars which have internal errors for int_mag that are larger than a magnitude-dependent limit chosen to select only exceptionally high values (there are 1248 such stars or 0.51% of the total) have int_mag_flag set to 1. Notice that a value of 1 for int_mag_flag may also indicate a large-amplitude photometric variation.

Macs_Part
A parameter identifying toward which Magellanic Cloud (LMC or SMC) the particular star lies.

Class
The HEASARC browse classification for the object; all entries in this catalog have been given the same class value of 2900, i.e., unclassified star.


Contact Person

Questions regarding the MACS database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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