06 August 2010

In the framework of the ESO Large Programme "The ground-based counterpart of the CoRoT asteroseismic observations from space" (178.D-0361), time-series of high-resolution (R~48000) spectra have been obtained for the delta Scuti CoRoT target HD 50844 with FEROS@2.2-m ESO/MPI telescope, La Silla, Chile.

Overview

This is the first release of the spectroscopic time-series of the delta Scuti star HD 50844 (V=9.09mag, spectral type A2), obtained in the first semester of the ESO Large Programme 178.D-0361, in the nights of January 1-10, 2007 and January 24-28, 2007. This release contains 232 high-resolution (R~48000) FEROS spectra, covering the spectral range from 3500 to 9200 Angstrom in 39 echelle orders. The following instrumental set-up was used: the object+sky fiber combination, 1x1 binning mode, and the Atmospheric Dispersion Corrector enabled. Exposure times were typically around 900 seconds, resulting in a signal-to-noise ratio (calculated in the regions near 4900 Angstrom and 5700 Angstrom) between 100 and 230. There are 5 spectra are of lower quality (signal-to-noise ratio lower than 80) taken during the 9-10 January night.

Release content

In this release we provide extracted, wavelength calibrated and barycentric corrected 1-dimensional fits spectra (1 fits file for each echelle order), as well as the associated rectified fits spectra (normalized at continuum level 1). We stress that the rectified spectra are provided for quick-look purposes only. Additionally, we provide for each exposure one rectified fits spectrum with the orders merged.

Release Notes

The spectra are reduced using an improved version of the standard FEROS pipeline, written in MIDAS, developed by Rainer (2003, Laurea Thesis, Universita degli Studi di Milano). The main improvements in this pipeline concern the blaze and flat-field correction of the spectra, by using an accurate definition of the blaze function extracted from a well-exposed spectrum of a hot star. The reduced and calibrated spectra were subsequently corrected to the barycentric frame. The rectified spectra were produced by an automated continuum normalisation procedure developed by Bossi (INAF OAB-Merate, Italy). We stress again that the rectified spectra serve only quick-look purposes. Moreover, the merged rectified spectra might show discrepancies in problematic overlap regions. A description of the data can be found in the paper 'HD 50844: a new look at delta Scuti stars from CoRoT space photometry', by Poretti et al., 2009, Astronomy & Astrophysics, 506, 85.

Data format

The data files in this release come in groups of 39: for each exposure we provide 39 fits files, associated to each echelle order, of the 1-dimensional wavelength calibrated and barycentric corrected spectrum. The wavelength step is 0.03 Angstrom. Additionally, we provide for each spectral order the associated 'quick-look' rectified (normalized to continuum level 1) spectrum, as well as a single merged rectified spectrum spanning the full wavelength range, all in fits format. All the relevant parameters (e.g. the barycentric correction used, modified Julian Date (JD - 2400000.5), etc.) are included in the FITS headers. An example of the FITS headers is given below.

The following file naming convention has been adopted for all individual spectra:

ADP.178D0361_HD049434_yyyymmdd_hhxx_zz.fits 1-d fits file
ADP.178D0361_HD049434_yyyymmdd_hhxx_zz_nm.fits 1-d rectified 'quick-look' fits file
ADP.178D0361_HD049434_yyyymmdd_hhxx_nm.fits 1-d rectified merged 'quick-look' fits file

The values yyyymmdd, and hhxx denote the year (yy), month (mm), day (dd), hour (hh) and minutes (xx) of the observation (UT time) at the beginning of the exposure. The echelle order number is indicated by zz. A list of the (approximate) start and end wavelength of the orders is given below.

Example header:

SIMPLE  =                    T / conforms to FITS standard
BITPIX  =                  -64 / array data type
NAXIS   =                    1 / number of array dimensions
NAXIS1  =                  876 / No. of pixels
EXTEND  =                    T / FITS extension may be present
CRPIX1  =                  1.0 / Reference pixel
CRVAL1  =              3586.05 / Coordinate at reference pixel
CDELT1  =                 0.03 / Coord. incr. per pixel (original value)
CTYPE1  = 'Wave    '           / Units of coordinate
CUNIT1  = 'Angstrom'           / Units of data axis 1
BUNIT   = 'Arbitrary units'    / Units of data values
DATAMAX =             24.31857 / Maximum data value
DATAMIN =                  0.0 / Minimum data value
ORIGIN  = 'ESO-MIDAS'          / Written by MIDAS
DATE    = '2007-01-03T02:52:53.751' / [UTC] Date of writing
FILENAME= 'HD050844_20070103_0237_nm.fits' / Original file base-name
MIDASFTP= 'IMAGE   '           / MIDAS File Type
OBJECT  = 'HD050844'           / MIDAS desc.: IDENT(1)
RA      =           103.688176 / MIDAS desc.: O_POS(1)
DEC     =             -1.06706 / MIDAS desc.: O_POS(2)
EQUINOX =               2000.0 / MIDAS desc.: O_POS(3)
RADECSYS= 'FK5     '           / MIDAS desc.: RADECSYS(1)
ERR_TARG= '        '           / Target position error
DATE-OBS= '2007-01-03'         / MIDAS desc.: O_TIME(1)
MJD-OBS =       54103.10962795 / MIDAS desc.: O_TIME(4)
TM-START=    9466.101000000001 / MIDAS desc.: O_TIME(5)
EXPTIME =             899.9999 / MIDAS desc.: O_TIME(7)
TELESCOP= 'MPI-2.2 '           / MIDAS desc.: TELESCOP(1)
INSTRUME= 'FEROS   '           / MIDAS desc.: INSTRUME(1)
OBSTECH = 'Echelle '           / Technique of observation
OBSERVAT= 'ESO-LSO '           / Observatory where the data was obtained
PI-COI  = 'E. Poretti'         / PI of the observation
PROG_ID = 'LP 178.D-0361'      / Proposal ID
FLUXCAL = 'uncalibrated'       / Photometric calibration
SPATCAL = 'uncalibrated'       / Astrometric calibration
FILTER  = '        '           / Filter name
GRISM   = '        '           / Dispersive element
SPECSYS = 'BARYCENT'           / Spectral reference system
BERV    =             1.504187 / Barycentric correction (km/s)
MJDSTART=       54103.10962795 / Start date time (MJD)
MJDEND  =    54103.12004461551 / Stop date time (MJD)
BIBREF  = '2009A&A...506...85' / Bibliographic reference
TLM     = '10:34:34 (28/10/2009)' / UTC time of last modification
HISTORY Extracted, wavelength calibrated and barycentric corrected spectrum
. CHECKSUM= 'EAaWE8XTEAaTE5UT'   / HDU checksum updated 2010-07-23T12:57:37
DATASUM = '3434596670'         / data unit checksum updated 2010-07-23T12:57:37
END

Echelle order definition:

The first column gives the echelle order number. The second and third columns give the (approximate) start and end wavelength of the order.

Data retrieval

Please click on the package name below to request the data set from the ESO science archive.

Acknowledgements

When using spectra provided in this release, we request acknowledgement of the CoRoT ground-based observation project and referring to the publication "HD 50844: a new look at delta Scuti stars from CoRoT space photometry", by Poretti et al., 2009, Astronomy & Astrophysics, 506, 85.

Please also include the following statement in any published material that makes use of these data products: Based on observations made with the 2.2m ESO/MPI telescope at the La Silla Observatory under ESO programme ID 178.D-0361.