BOSS Spectrum Models

Module: astra.models.boss

BossVisitSpectrum

An optical BOSS spectrum from a specFull file. A BOSS “visit” is defined as all exposures of a source taken on the same MJD. The wavelengths are in vacuum and shifted to the Solar system barycentric rest frame (not the source rest frame).

There is no BOSS equivalent of apStar in the upstream BOSS pipeline – the BOSS DRP does not stack spectra across multiple nights. Astra fills this gap with the BossCombinedSpectrum model (see MWM Models).

Key Fields

Field	Type	Description
spectrum_pk	ForeignKeyField	Unique spectrum identifier
source	ForeignKeyField	Foreign key to the Source
release	TextField	Data release
run2d	TextField	BOSS reduction pipeline version
fieldid	IntegerField	Field identifier
mjd	IntegerField	Modified Julian Date of observation
catalogid	BigIntegerField	SDSS catalog identifier
telescope	TextField	Telescope used (e.g., "apo25m", "lco25m")
spec_file	TextField	BOSS specFull basename

Spectral data:

Field	Type	Description
wavelength	PixelArray	Wavelength array (vacuum, barycentric frame); derived from loglam as 10**loglam
flux	PixelArray	Flux array
ivar	PixelArray	Inverse variance array
wresl	PixelArray	Wavelength resolution array
pixel_flags	PixelArray	Per-pixel quality flags (from or_mask)

Observing conditions:

Field	Type	Description
snr	FloatField	Signal-to-noise ratio
n_exp	IntegerField	Number of exposures
exptime	FloatField	Total exposure time (seconds)
seeing	FloatField	Seeing (arcseconds)
airmass	FloatField	Airmass
airtemp	FloatField	Air temperature
humidity	FloatField	Humidity

Radial velocity (XCSAO):

Field	Type	Description
xcsao_v_rad	FloatField	Radial velocity from XCSAO (km/s)
xcsao_e_v_rad	FloatField	RV uncertainty from XCSAO (km/s)
xcsao_teff	FloatField	Effective temperature from XCSAO
xcsao_logg	FloatField	Surface gravity from XCSAO
xcsao_fe_h	FloatField	Metallicity from XCSAO
xcsao_rxc	FloatField	Cross-correlation R-value

Warning flags:

Field	Type	Description
zwarning_flags	BitField	BOSS DRP warning flags
flag_sky_fiber	bit 0	Sky fiber
flag_little_wavelength_coverage	bit 1	Too little wavelength coverage
flag_small_delta_chi2	bit 2	Chi-squared too close to second best
flag_unplugged	bit 7	Fiber unplugged or damaged
flag_no_data	bit 9	No data for this fiber
gri_gaia_transform_flags	BitField	Flags for provenance of ugriz photometry

Methods and Properties

path (property)

Returns the file path to the specFull FITS file. The path template depends on the run2d version.

visit = BossVisitSpectrum.get_by_id(1)
print(visit.path)

e_flux (property)

Returns the flux uncertainty array, computed as ivar**-0.5.

field_group (property)

Returns the field group string (e.g., "015XXX" for fieldid 15234), used in the file path.

pad_fieldid (property)

Returns the zero-padded field ID string. Padding rules depend on the run2d version.

isplate (property)

Returns "p" for plate-era run2d versions (v6_0_1 through v6_0_4), or "" otherwise. Used in path construction.