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TD1 - TD1 Stellar Ultraviolet Fluxes Catalog

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Overview

The Belgian/UK Ultraviolet Sky Survey Telescope (S2/68) in the ESRO TD1 satellite carried out a controlled scan of the entire sky. It measured the absolute ultraviolet flux distribution between 2740A and 1350A of point sources down to 10th visual magnitude for unreddened early B stars. The S2/68 experiment has been described by Boksenberg et al. (1973MNRAS.163..291B), and the absolute calibration by Humphries et al. (1976A&A....49..389H).

The TD1 Catalog of Stellar Ultraviolet Fluxes represents results from the sky-scan experiment on the TD1 satellite of the European Space Research Organization (ESRO), now part of ESA. It lists the absolute fluxes, in four passbands, for 31,215 stars:

Passband Center:   274.0nm   236.5nm   196.5nm   156.5nm
Effective Width:    31.0nm    33.0nm    33.0nm    33.0nm
The stars have been selected subject to the constraint that the signal-to-noise ratio should be at least 10.0 in any one of the four passbands.

Null values of a flux field and an error field indicate there are no valid data for the star. This usually arises with close pairs of stars whose spectra overlap. Five standard flux error values are greater than 99.99, and were too large for the format of the flux field in the original table. Thus, the flux error values which were greater than 99.99 are given as 99.99.

Many of the fainter stars of spectral type later than A5 do not have significant signals in all of the spectrophotometric channels (particularly the 1565A channel). Consequently, after the removal of the background, they can randomly give rise to small negative values of flux. Those negative values were not suppressed, but are given together with their error, as they can be significant when considered as part of a statistical sample.

Although the sky coverage is essentially complete, the catalog does not contain the fluxes for all stars that fall within the limit of the sensitivity of the instrument. If any star expected to be present is missing, then its signal is probably blended with that of a nearby star, in which case the data have been discarded.


Catalog Bibcode

1978csuf.book.....T

References

Information about TD1 can be found in the published version, "Catalog of Stellar Ultraviolet Fluxes", G.I. Thompson, et.al., The Science Research Council, 1978:
Catalogue of stellar ultraviolet fluxes (TD1):
A compilation of absolute stellar fluxes measured by the Sky Survey
Telescope (S2/68) aboard the ESRO satellite TD-1
     Thompson G.I., Nandy K., Jamar C., Monfils A. Houziaux L.,
     Carnochan D.J., Wilson R.
    <The Science Research Council, U.K. (1978)>

Provenance

The contents of the HEASARC's original TD1 database table originated from a magnetic tape sent to NASA/Goddard Space Flight Center by Dr. G.I. Thompson of the Royal Observatory in Edinburgh, Scotland. The HEASARC recreated this database table in August 2005, based on the CDS table, in an effort to modernize its parameter names and documentation, as well as to add Galactic coordinates.

Parameters

Name
The TD1 Catalog object designation (this does not appear in the printed catalog).

HD_Number
The Henry Draper Catalog number of the star.

UVBS_Flag
This parameter is a flag which is set to 1 to indicate that the object is in the Ultraviolet Bright Star (UVBS) Spectrophotometric Catalog (Jamar et al. 1976, CDS Catalog <III/39>), else is set to 0. The full spectral information for 1356 bright stars has been published in the UBVS Spectrophotometric Catalog.

DM_Name
The Durchmusterung (BD/CD/CPD) designation of the star.

S2_68_Number
The S2/68 Catalog number of the star.

Vmag
The visual magnitude of the star, as listed in the Catalog of Stellar Identifications (CSI: ftp://cdsarc.u-strasbg.fr/pub/cats/V/26/ ).

Spect_Type
The (one-dimensional) spectral type of the star, as listed in the Catalog of Stellar Identifications (CSI: ftp://cdsarc.u-strasbg.fr/pub/cats/V/26/ ).

RA
The Right Ascension of the star in the selected equinox. This was given in 1950 equatorial coordinates in radians to a precision of 1 microradian (0.2 arcseconds) in the original catalog.

Dec
The Declination of the star in the selected equinox. This was given in 1950 equatorial coordinates in radians to a precision of 1 microradian (0.2 arcseconds) in the original catalog.

LII
The Galactic Longitude of the star.

BII
The Galactic Latitude of the star.

Flux_2740_A
The flux F(lambda) of the star in the 2740 Angstrom (274 nm) band, in erg/cm^s/s/A. The fluxes F(lambda), and errors, sigma(lambda), can be transformed to the visual magnitude scale using the absolute calibration of Haynes & Latham (=1975ApJ...197..593H):

                 m(lambda) = -2.5 log10 F(lambda) - 21.175
           sigma_m(lambda) = 1.086  sigma(lambda)/F(lambda)
  
Also, the following other related parameters can be calculated:
    F(nu) = 3.336x10^-19 lambda^2 F(lambda)
    m(nu) = -2.5 log10 F(lambda) - 5 log10 lambda - 18.724
    sigma_m(nu) = 1.086 sigma(lambda)/F(lambda)
    where F(lambda) is in units of erg.cm^-2s^-1A^-1  (mW/m^2/(0.1nm))
    lambda is in Angstroms,  and F(nu) is in units of
    erg.cm^-2s^-1Hz^-1 = mW/m^2/Hz = 10^23 Jy
  

Flux_2740_A_Error
The standard error of the flux in the 2740A band, in erg/cm^2/s/A.

Flux_2365_A
The flux F(lambda) of the star in the 2365 Angstrom (236.5 nm) band, in erg/cm^s/s/A. See the help for the flux_2740_a parameter for more information about the TD1 fluxes.

Flux_2365_A_Error
The standard error of the flux in the 2365A band, in erg/cm^2/s/A.

Flux_1965_A
The flux F(lambda) of the star in the 1965 Angstrom (196.5 nm) band, in erg/cm^s/s/A. See the help for the flux_2740_a parameter for more information about the TD1 fluxes.

Flux_1965_A_Error
The standard error of the flux in the 1965A band, in erg/cm^2/s/A.

Flux_1565_A
The flux F(lambda) of the star in the 1565 Angstrom (156.5 nm) band, in erg/cm^s/s/A. See the help for the flux_2740_a parameter for more information about the TD1 fluxes.

Flux_1565_A_Error
The standard error of the flux in the 1565A band, in erg/cm^2/s/A.

Class
The HEASARC Browse object classification, based on the value of the spect_type parameter.


Contact Person

Questions regarding the TD1 database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 12-Aug-2005