The binary program aims to identify and characterize stellar and substellar companions of stars across the HR diagram. To characterize systems, many epochs of observations are needed to sample the stellar radial velocity over time. This program exclusively uses the APOGEE spectrograph because of its superior spectral resolution. Stellar types explicitly targeted in this program include red giants, subgiants, and M dwarfs.
Program Structure
All stars in the binary program released in DR19 can be identified with the mwm_rv program name in the targeting flags or with the alternate program name bin.
Stars generally fall into one of two targeting categories. Stars with existing multi-epoch observations in legacy APOGEE surveys form the “long baseline” cartons. All of the cartons associated with this strategy can be identified with the alternative carton name mwm_bin_rv_long. Stars with no previous APOGEE observation form the “short baseline” cartons and can be identified with the alternative carton name mwm_bin_rv_short. The “short”/”long” naming convention refers to the total temporal baseline and can seem counterintuitive, since short baseline targets require more epochs of observation during SDSS-V.
In some cartons, stars were priority ranked to increase the representation of certain non-red giant stellar types of interest (since red giants are expected to dominate the short baseline sample) and devalue some classes of main sequence stars (either unsuitable for precise radial velocity measurements or already well studied by most traditional exoplanet surveys).
Cartons
mwm_rv_long-bplates
These targets were observed during the plate era under targeting plan 0.1.0 and belong to the alternate carton mwm_bin_rv_long. Some targets were observed under targeting plan 0.1.4 with the updated carton name mwm_rv_long_bplates drawn from an additional 14 field centers.
Creation of Legacy APOGEE “Merge File”
The long baseline carton selected stars that had been previously observed during the APOGEE-1 and/or APOGEE-2 surveys in at least three separate epochs as of the DR16 data release. They are selected from the mos_sdss_apogeeallstarmerge_r13 table found both on CasJobs and on the SAS. This “allStarmerge” file uses the information in APOGEE DR16’s allStar and allVisit summary files to consolidate duplicate entries of single targets (which occurs when targets are observed in more than field) to facilitate targeting for SDSS-V. The allStarMerge file was constructed as follows:
- Targeting information common to all entries (e.g. APOGEE_ID, coordinates, proper motions, etc.), is directly copied from the first entry for the star in the allStar file, while information that differs (e.g. FIELD) is concatenated in a space-separated string.
- Radial velocity information (VHELIO_AVG, VSCATTER, etc.) were derived or copied (into a space-separated string) from the allVisit entries for a given star.
- ASPCAP-derived stellar parameters (Teff, log g, & metallicity) are averaged (weighted by SNR) from the individual entries for the star in the allStar file. If an entry did not have stellar parameters, it was excluded from the average.
- The text-based TARGFLAGS, STARFLAGS, & ASPCAPFLAGS were concatenated from the star’s individual entries in the allStar file with repeated flags removed.
Selection Criteria
Conditions in bold below are common to all long baseline targets.
- Target exists in the allStarMerge file.
- H < 12.2
- nvisits (in APOGEE-1 and/or 2) > 6
-
TARGFLAGS includes one of the following values:
- APOGEE_SHORT
- APOGEE_INTERMEDIATE
- APOGEE_LONG
- APOGEE2_BIN
- Gaia-based distance
- Targets fall within a list of 20-34 hand selected field centers that are viewable for 6-months during the plate program
mwm_rv_long-fps
These targets were observed during the plate era under targeting plan 0.1.0 and belong to the alternate carton mwm_bin_rv_long.
The selection criteria include the bolded conditions in mwm_rv_long-bplates but with H < 11.5 and nvisits > 3.
mwm_rv_long-rm
These targets were observed during the plate era under targeting plan 0.1.0 and belong to the alternate carton mwm_bin_rv_long.
The selection criteria include the bolded conditions in mwm_rv_long-bplates, but with H < 12.8 and nvisits > 3. These targets were only observed in the Black Hole Mapper RM fields.
mwm_rv_long_fps
These targets were observed during the FPS era under targeting plan 0.50 or 0.5.18 and belong to the alternate carton mwm_bin_rv_long. Beginning in targeting plan 0.5.18, stars were prioritized with the following ranking criteria applied using stellar parameters measured by ASPCAP:
- Low mass dwarfs: Teff < 4500 K and log g ≥ 4.0
- Subgiants: 4.0 < log g < 3.5
- Red Giants: log g > 3.5
- Other/ log g unknown
The selection criteria are the same as mwm_rv_long-fps.
mwm_rv_short-bplates
These targets were observed during the plate era under targeting plan 0.1.0 and belong to the alternate carton mwm_bin_rv_short.
The short baseline cartons selected stars that were never previously observed with APOGEE and applied color magnitude cuts combined with photometric quality cuts to select stars similarly to the earlier APOGEE surveys using both the 2MASS Point Source Catalog and the AllWise Source Catalog. Definitions of the 2MASS photometric flags and quality measurements can be found at the User’s Guide to the 2MASS All-Sky Data Release. The short baseline cartons were more limited in magnitude so that they would not require more than one exposure at each epoch.
Selection Criteria
Conditions in bold below are common to all long baseline targets.
- H < 12.2
- J – Ks – (1.5 * 0.918 * (H – W2 – 0.05)) >= 0.05
- J_msigcom < 0.1
- Ks_msigcom < 0.1
- H_msigcom < 0.1
- W2_sigmpro < 0.12
- 2MASS ph_qual any of the following: AAA, AAB, ABA, BAA, ABB, BAB, BBA, BBB
- 2MASS gal_contam = 0
- 2MASS cc_flg = 0
- 2MASS rd_flg any of the following: 111, 112, 121, 211, 122, 212, 221, 222
- 2MASS prox >= 6
- Gaia DR2 parallax exists
- Does not match a source in the 2MASS extended catalog
- at least 100 other targets matching all above criteria within 3 degrees
mwm_rv_short-fps
These targets were observed during the plate era under targeting plan 0.1.0 and belong to the alternate carton mwm_bin_rv_short.
The selection criteria include the bolded conditions in mwm_rv_short-bplates, but with H < 10.8.
mwm_rv_short-rm
These targets were observed during the plate era under targeting plan 0.1.0 and belong to the alternate carton mwm_bin_rv_short.
The selection criteria include the bolded conditions in mwm_rv_short-bplates, but with H < 12.8. These targets were only observed in the Black Hole Mapper RM fields. [SET LINK]
mwm_rv_short_fps
These targets were observed during the FPS era under targeting plan 0.50 or 0.5.18 and belong to the alternate carton mwm_bin_rv_short. Beginning in targeting plan 0.5.18, stars were prioritized with the following ranking criteria applied using stellar parameters available in the TIC catalog.
- Low mass dwarfs: Teff < 4500 K and log g ≥ 4.0
- Subgiants: 4.0 < log g < 3.5
- Red Giants: log g > 3.5
- Other, or unknown log g or Teff
The selection criteria are the same as mwm_rv_short-fps.
Cadences
During plate operations, the mwm_rv_short-rm and mwm_rv_long-rm cartons were observed exclusively on plates with an RM cadence. The mwm_rv_long-bplates and mwm_rv_short-bplates cartons were observed exclusively on plates with an RV6 or RV12 cadence. All four cartons were observed exclusively with the APOGEE instrument. In contrast, the mwm_rv_long-fps and mwm_rv_short-fps cartons could be observed on any plate with either instrument as “fillers”.
During FPS operations, stars with legacy observations ( mwm_rv_long_fps) can have a variety of cadences depending on the target brightness and how many previous epochs of APOGEE observations exist; however, all targets will obtain at least six new epochs in SDSS-V to take advantage of the improved radial velocity precision. Stars with H > 10.8 require two exposures per epoch to reach the needed S/N for precise radial velocities per epoch. Cadences can include:
- bright_6x1
- bright_6x2
- bright_9x1
- bright_9x2
- bright_12x1
- bright_12x2
- bright_15x1
- bright_15x2
All short baseline targets (mwm_rv_short_fps) are selected to be bright enough to require only a single exposure, and all use the bright_18x1 cadence.