Flags in the SSPP - SSPP

Introduction

As it is important that the SSPP be able to identify situations where the quoted atmospheric parameters or the measured radial velocites 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. Basically, there are two categories of the flags. The first one is to check if the determined stellar parameters and the measured radial velocites are reasonably OK, whereas the other one is to check if a spectrum is needed for visual inspection.

Flags for checking the stellar parameters and radial velocites

There are two primary categories of flags -- 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 it is 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 estimated parameters must be viewed with this knowledge in mind.

The second category of flags are the cautionary flags, which are provided for user consideration, but are not necessarily cause for undue concern. Indeed, sometimes these flags are raised when all is in fact OK, but the flag has been raised due to a peculiarity in the spectrum that is relatively harmless, and which will not unduly influence determination of atmospheric parameters. The user should nevertheless be aware of the existence of these flags. 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 T_eff > 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 T_eff and g-z color-based T_eff > 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

A flag based on a six letter combination is, since the DR7, added to speed up the visual inspection of the stellar spectra. Those spectra where one or more of these flags are raised are visually inspected, while 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 T_eff(adopted) and g-z color-based T_eff is > 500 K
t	Temperature difference between T_eff(adopted) and spectroscopic-based T_eff > 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