Flags in the SSPP
Because it is important that the SSPP identify situations where the quoted atmospheric parameters or the measured radial velocities may be in doubt, or simply to make the user aware of possible anomalies that might apply to a given star, the SSPP raises a number of flags that serve this purpose. There are two categories of flags. The first one identifies reasons why the reported stellar parameters and radial velocities may not be OK and the second one identifies reasons why a spectrum may need visual inspection.
Flags for Checking Stellar Parameters and Radial Velocities
The SSPP can raise either critical flags and cautionary flags. When a critical flag is raised, the SSPP is set to either ignore the determinations of atmospheric parameters for a given star or forced (in the case of the color flag) to take steps that differ from normal processing in an attempt to rescue this information. Obviously, even when information is salvaged, the presence of a critical flag means the user must be aware that special steps have been taken, and the reported parameters must be viewed with this information in mind. The second category of flags are the cautionary flags, which are provided for user consideration, but are not necessarily cause for concern. Indeed, sometimes these flags are raised because of a peculiarity in the spectrum that is relatively harmless, and which will not unduly influence determination of atmospheric parameters.
The flags are combined into a single set of five letters, the meanings of which are summarized in the following table. The nominal condition for the five letter flag combination is `nnnnn’, which indicates that the SSPP is satisfied that a given stellar spectrum (and its reported g-r colors and S/N) has passed all of the tests that have been performed, and the stellar parameters should be considered well determined.
Position | Flag | Description | Category | Parameters |
---|---|---|---|---|
First | n | Appears normal | …… | Yes |
D | Likely white dwarf | Critical | No | |
d | Likely sdO or sdB | Critical | No | |
H | Hot star with Teff > 10000 K | Critical | No | |
h | Helium line detected, possibly very hot star | Critical | No | |
l | Likely late type solar abundance star | Cautionary | Yes | |
E | Emission lines in spectrum | Critical | No | |
S | Sky spectrum | Critical | No | |
V | No radial velocity information | Critical | No | |
N | Very noisy spectrum | Cautionary | Yes | |
Second | n | Appears normal | …… | Yes |
C | The photometric g-r color may be incorrect | Cautionary | Yes | |
Third | n | Appears normal | …… | Yes |
B | Unexpected Hα strength predicted from Hδ | Cautionary | Yes | |
b | If d or D flag is not raised among stars with B flag | ….. | Yes | |
Fourth | n | Appears normal | …… | Yes |
G | Strong G-band feature | Cautionary | Yes | |
g | Mild G-band feature | Cautionary | Yes | |
Fifth | n | Appears normal | …… | Yes |
B | Too blue g-r < -0.3 to estimate parameters | Critical | No | |
R | Too red g-r > 1.3 to estimate parameters | Critical | No | |
X | No parameters estimate | Critical | No | |
c | Correlation coefficient < 0.4 | Cautionary | Yes | |
T | Difference between adopted Teff and IRFM Teff > 500 K | Cautionary | Yes | |
P | Possible predicted g-r is wrong | Cautionary | Yes | |
RV | NORV | No radial velocity info | ….. | no |
ELRV | Radial velocity from ELODIE template | ….. | Yes | |
BSRV | Radial velocity from spetro1d | …… | Yes | |
RVCAL | Radial velocity calculated from SSPP | …… | Yes |
Flags for visual inspection
The SSPP also has a flag with information useful when visually inspecting spectra for possible issues, including those indicated by the “Critical” and “Cautionary” flags. Those with no flags raised (“nnnnnn”) can be safely assumed to be OK. The definitions for each flag are as follows.
n | Normal |
---|---|
F | Fail: No parameters or radial velocity determined |
T | Temperature difference between Teff(adopted) and IRFM Teff is > 500 K |
t | Temperature difference between Teff(adopted) and spectroscopic-based Teff > 500 K |
M | Adopted [Fe/H] and spectroscopic-based [Fe/H] is > 0.3 dex |
m | Error in adopted [Fe/H] is > 0.3 dex |
C | low confidence: correlation coefficient < 0.4 |