Spectral Characterization of calibration lamps: STIS An improved list of emission lines for STIS Calibration Enhancement Florian Kerber, ST-ECF TIPS Meeting Sept 18th, 2003

TIPS Sept 18th, 2003F. Kerber, ST-ECF 2 Outline  Calibration lamps for HST spectrographs  STIS Calibration Enhancement (STIS-CE)  ST-ECF Lamp Project  Laboratory Work  Results and Outlook

TIPS Sept 18th, 2003F. Kerber, ST-ECF 3 Hollow cathode lamp  Schematic drawing

TIPS Sept 18th, 2003F. Kerber, ST-ECF 4 Pt/Ne hollow cathode lamp (IUE)  Parameters of operation –starting voltage: 300 V; operating voltage: 185 V; current: mA, power consumption: 2 10 mA –dimensions: 19.7 by 4.5 cm; weight: 71 (285) g  Lifetime: > 750 h or years of operation on IUE  Source brightness stability: ~ 5 % after min  Rich emission line spectrum: 115 to 310 nm  Wavelengths for 585 lines; Shenstone (1939)

TIPS Sept 18th, 2003F. Kerber, ST-ECF 5 Hollow cathode lamps - HST (1990)  Goddard High Resolution Spectrograph (GHRS): nm; Pt-Ne ok  Faint Object Spectrograph (FOS): nm –Addition of ~ 10% Cr to cathode extends coverage to 540 nm and Ne has lines up to 800 nm  Space Telescope Imaging Spectrograph (STIS): nm

TIPS Sept 18th, 2003F. Kerber, ST-ECF 6 Ready for Flight / Operations ?  Engineering –for both Pt-Ne and Pt/Cr-Ne thorough characterization of lamps in terms of hardware performance  Science Operations –information on spectral output incomplete and crucial wavelength information based on measurements done in the 1930s (Pt) or absent (Cr) –no spectral characterization of flight hardware

TIPS Sept 18th, 2003F. Kerber, ST-ECF 7 HST Spectrograph Operations  National Institute of Standards and Technology – Pt-Ne lamp atlas nm with ~ 3000 lines (Reader et al., 1990, ApJS 72, 831)

TIPS Sept 18th, 2003F. Kerber, ST-ECF 8 STIS Operations  Pt line list from NIST  Cr lines can not be used because of lack of lab data  1st order long-slit modes have many Pt/Cr blends –wavelengths assigned should be average weighted by line intensity ratios, which are not known  Empirical approach using 2-D polynomial fits for Echelle modes

TIPS Sept 18th, 2003F. Kerber, ST-ECF 9 STIS Calibration Enhancement  Physical Model of STIS –Spectrograph Model  Laboratory Standards –Good line list is required to realize full potential of physical model

TIPS Sept 18th, 2003F. Kerber, ST-ECF 10 ST-ECF Lamp Project  Dedicated ESA funding  Measure spectrum of Pt/Cr-Ne lamp at NIST: nm  Derive an accurate ( < 1/1000 nm) list of wavelengths as input for STIS-CE  Quantify differences between Pt-Ne and Pt/Cr-Ne spectrum  Look into aging effects of hollow cathode lamps

TIPS Sept 18th, 2003F. Kerber, ST-ECF 11 Status of the ST-ECF Lamp Project  First memorandum May 2001  Approved & funded in spring 2002  Contracts to NIST and IST (lamps) issued June 2002  FUV: 5 week measurement campaign Sep/Oct 2002  Intermediate results delivered Nov & Dec 2002  NUV: 6 week campaign in Apr/May 2003  Use within STIS-CE in progress

TIPS Sept 18th, 2003F. Kerber, ST-ECF 12 NIST Eagle vacuum spectrograph  10.7 m focal length, Vacuum UV (VUV) coverage –1.25 m/1 m diameter –13 m long, 15 m 3 –3 chambers  Two 16 in. UV sensitive photographic plates – 750 Å coverage – 0.78 Å/mm resolution

13 NIST Eagle vacuum spectrograph

14 Synchrotron UV Facility (SURF III)  Fourier Transform Spectrograph (FTS 700)

15 Hollow cathode lamp

TIPS Sept 18th, 2003F. Kerber, ST-ECF 16  Measure spectrum of Pt/Cr-Ne lamp at NIST –10.7 m vacuum spectrograph: nm –FTS: nm  Derive an accurate ( < 1/1000 nm) list of wavelengths as input for STIS-CEs –FUV: > 1100 lines total - 95% identified; 235 Cr –NUV: > 3500 lines; ca 50% Cr ST-ECF Lamp Project - Status   in progress 

TIPS Sept 18th, 2003F. Kerber, ST-ECF 17  Quantify differences between Pt-Ne and Pt/Cr-Ne spectrum –addition of Cr changes of line ratios –metal vs gas change as a function of operating current  Aging of lamps –accelerated aging test: 30s on/30s off cycle –vintage flight hardware ST-ECF Lamp Project - Status 1000 h without significant change in progress FOS & GHRS lamps

TIPS Sept 18th, 2003F. Kerber, ST-ECF 18 Mystery feature “Clump” ~1430 Å  Seen in both in FOS and STIS

TIPS Sept 18th, 2003F. Kerber, ST-ECF 19 Chromium “Clump” ~1430 Å Pt/Cr-Ne Cr-Ne Pt-Ne

TIPS Sept 18th, 2003F. Kerber, ST-ECF 20 FUV Spectra: Pt vs Cr Faint Pt-Ne: oldNew CrPt-Ne: old & new

TIPS Sept 18th, 2003F. Kerber, ST-ECF 21 NUV Spectra: Pt vs Cr Pt/Cr-Ne Cr-Ne Pt-Ne

TIPS Sept 18th, 2003F. Kerber, ST-ECF 22 Input for STIS-CE  NUV c : 2843 Å  Lines seen : ~ 450  Pt: ~ 100 lines  Cr: ~ 700 lines known

TIPS Sept 18th, 2003F. Kerber, ST-ECF 23 Open Instrument Surgery

TIPS Sept 18th, 2003F. Kerber, ST-ECF 24 Veteran Space Lamps  After seven years of operation in space back to the lab... FOSGHRS they still work perfectly fine

TIPS Sept 18th, 2003F. Kerber, ST-ECF 25 ST-ECF Lamp Project: Future  NUV FTS data reduction, fall 2003  Return of FOS lamps to museum, Sept 23rd  Paper I, ApJS, Sept 2003 (FUV results)  STIS-CE new dispersion solutions, end 2003  Incorporate into calstis pipeline  STIS calibration proposal #10031 (PI: B. Mobasher)

TIPS Sept 18th, 2003F. Kerber, ST-ECF 26 Lessons learned: Calibration...  requires attention to detail … needs to be an integral part of any science project  requires expertise from different fields  is at the heart of scientific understanding  will give you better results

27 Lessons learned...