NOTcam WFC spectroscopy: first light

For the first-light observations we chose an easy object, meaning lots of photons and clearly identifiable spectral features. On the evening of August 7, 2003, we observed the bright Be star 66 Ophiuchi (B2Ve, V=4.6). Be stars are rapidly rotating main-sequence B stars with strong recombination emission lines arising from a quasi-keplerian circumstellar disk. The origin of the disk is under great debate, but it is clear from abundant observations that the star feeds the disk, i.e. these disks are the opposite of accretion disks. Proposed mechanisms to feed the disk are non-radial pulsations, magnetic fields and stellar wind, all in combination with rapid stellar rotation.

We used baffle-lamp flats for flatfielding and for the creation of a bad-pix map. In H and Ks bands we used the OH sky lines for wavelength calibration. The star was observed in an ABBA nodding pattern for J, H, K', Ks, and K with 20 second exposure time at each telescope position. For correction of telluric lines and fringes we used the F4V star HIP87860 (V=7.6, two offset exposures of 100s each). The spectra were optimally extracted.

 

J band


Dispersed flat field obtained using the baffle lamp. The 5th order runs from the J cut-off around 1330 nm towards shorter wavelength at the top of the image. The 6th order runs from the bottom of the image to the J cut-on at around 1160 nm. The two orders overlap by about 100 pixels.


J band spectrum of 66 Oph (top) and of HIP87860. Flat fielded, bad-pix corrected, and optimally extracted.
Paschen beta 1282.2 nm strongly in emmission in 66 Oph.

 

H band


100 sec H band exposure of HIP87860. Note that the sky lines are bent due to optical distortion. The straight horizontal lines are hot rows.


Result of ABBA nod of 15 arcsec in H band: A + A - B - B. Flatfield and bad-pix corrections have not been applied to this image of 66 Oph.


H band spectrum of 66 Oph with Brackett Series 10-4 to 18-4 indicated. Flat fielded, bad-pix corrected, and optimally extracted. Telluric lines and fringes have been corrected using the spectrum of HIP87860. The wavelength solution was obtained from OH skylines of the exposures of HIP87860.

 

Ks band


Ks band spectrum of HIP87860. Flat fielded, bad-pix corrected, and optimally extracted. The wavelength solution was obtained from OH skylines.


Ks band spectrum of 66 Oph. Flat fielded, bad-pix corrected, and optimally extracted. The wavelength solution was obtained from OH skylines of the exposures of HIP87860. Telluric lines and fringes have been corrected using the spectrum of HIP87860.
Brackett gamma strongly in emmission, and double peaked emission at He I 2058.7 nm.

Last updated Aug 2003
John Telting