The Lockwood photometric system
Basic Reference
Lockwood G.W., 1972, ApJ. Suppl. 24, 375
Abstract
A five-color narrow-band photometric system is described which has been used
for determining magnitudes at 1.04 mu, near-infrared colors, and molecular
band-strength indices for M stars. The system gives accurate spectral types
from M4 to M10 and useful, though less accurate, spectral types from M0 to
M4. Mean 1.04-mu magnitudes, near-infrared colors, and spectral-type indices
are given for photometric and spectroscopic standard stars, and 1795
individual sets of five-color measurements are given for 292 M- and S-type
Mira variables.
The Miras are shown to map out large loops in a diagram of molecular band
strength as a function of color, and large differences of band strength can
occur at a given color and phase in different stars or in the same stars
during different cycles. The Miras with periods less than 300d are warmer
by several hundred degrees at a given spectral type than either the normal
giants used for calibration or the Miras with periods longer than 300d.
The mean phase of earliest spectral type is ~0.03, while maximum light at
1.04 mu occurs at ~0.11. Minimum light at 1.04 mu and latest spectral type
are reached almost simultaneously with minimum visual light.
Content
Access to the data and references
Asiago Database on Photometric System (ADPS)
Indices and Parameters
78-87, 88-87, 87-104, 104, 105-104
Color-free Indices
- TiO strength
- T1 = (78-87) - 0.6 (87-104)
- TiO absorption
- T2 = (88-87) + 0.07 (87-104)
- VO strength
- V1 = (105-104) + 0.1 (87-104)
- Composite index
- D = 0.18 T1 + T2 + V1
Filters
- 78 :
- Peak wavelength: 7818 Å ; Width : 90 Å
- 87 :
- Peak wavelength: 8777 Å ; Width : 82 Å
- 88 :
- Peak wavelength: 8884 Å ; Width : 114 Å
- 104 :
- Peak wavelength: 10351 Å ; Width : 125 Å
- 105 :
- Peak wavelength: 10506 Å ; Width : 100 Å
Photomultiplier
ITT FW-118
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Last update: 21 May 1996