Compact Binaries

A white dwarf accreting material from its companion to form a cataclysmic variable
Artist’s conception of a cataclysmic variable
Image Credit, Dana Berry, STScI

The compact binaries program encompasses a number of scientific cartons, each with its own target selection strategy, organized around the common goal of multi-epoch spectroscopic characterization of known or suspected compact binary systems. Both the BOSS and APOGEE spectrographs are used by this program, depending on the system brightness. Generally, the target selection relies on the expectation that compact binary systems will show an excess in ultraviolet flux contributed by the (optically) unseen compact companion or shows distinctive variability. White dwarf binaries can be selected by a simple linear cut in a UV-optical color magnitude diagram, which is used for both the “gaiagalex” and volume limited “300pc” cartons. Candidate cataclysmic variables were identified from the AAVSO Variable Star Index. Various flavors of “UV-excess” color/magnitude cuts with different UV passbands result in the uvex1 – uvex5 cartons. The uvex1 – uvex4 cartons use the BOSS spectrograph, while uvex5 uses APOGEE.

Cartons

mwm_cb_300pc

This is the plate era carton targeting white dwarf binaries within 300 pc with a simple linear cut in the GALEX FUV and NUV color magnitude diagram. Distances ( rest) come from Bailer-Jones et al. (2018). The selection criteria are:

  • (FUV – 5 * log10(rest/10)) > 14 * (FUV-NUV) – 46
  • rest < 300pc

In the FPS-era, the carton was split into two different cartons that share the same basic selection, but mwm_cb_300pc_apogee limits the H-band magnitude from the 2MASS Point Source Catalog to H < 11 while mwm_cb_300pc_boss requires that the target is detected in Gaia DR2.

Note that an error in the targeting code led to targets being selected in version 0.5.0 with the wrong inequality in the UV color magnitude cut. See Targeting Flags for more information on targeting versions.

All three variations of the carton can be identified with the mwm_cb_300pc alternate carton name.

mwm_cb_cvcandidates

This is the plate era carton of AAVSO cataclysmic variable targets. The “AAVSO catalog” (mos_cataclysmic_variables) was constructed from the VSX catalog, selecting cataclysmic (explosive and novalike) variables (N, NA, NB, NC, NL, NR, SN, SNI, SNII, UG, UGSS, UGSU, UGZ, ZAND) downloaded in summer 2019 and then manually pruned. The mos_catalclysmic_variables catalog can be queried on CasJobs or downloaded from the SAS.

In the FPS-era, the carton was split into two different cartons that share the same basic selection, but mwm_cb_cvcandidates_apogee limits the H-band magnitude from the 2MASS Point Source Catalog to H < 11 while mwm_cb_cvcandidates_boss requires that the target is detected in Gaia DR2.

All three variations of the carton can be identified with the mwm_cb_cvcandidates alternate carton name.

mwm_cb_gaiagalex

This plate era carton combines Gaia DR2 mean photometric G magnitudes with GALEX FUV. White dwarf binaries separate well from the main sequence in absolute FUV vs FUV-G color. Gaia also provides parallax (p) and parallax error (perr). The selection criteria are:

  • p / perr > 3
  • G < 20
  • FUV + 5 * log10(p / 1000) + 5 > 1.5 + 1.28 * (FUV – G)

In the FPS-era, the carton was split into two different cartons that share the same basic selection, but mwm_cb_gaiagalex_apogee limits the H-band magnitude from the 2MASS Point Source Catalog to H < 11 while mwm_cb_gaiagalex_boss requires that the target is detected in Gaia DR2.

All three variations also belong to the mwm_cb_galex alternate carton name, together with some of the UV excess cartons below.

UV Excess Cartons

The UV Excess cartons use a common set of astrometric cuts on the closest Gaia cross-match to various UV catalogs, removing objects with small parallaxes and proper motions. Definitions used with the astrometric cuts are:

  • pm: the total proper motion (mas/yr)
  • pmerr: the total error in proper motion (mas/yr)
  • rlo: the lower limit distance (pc) from Bailer-Jones DR2 distance catalog
  • logpmdpm = log10(pm/pmerr)
  • g_vis_per: Gaia DR2 visibility periods used

The selection criteria common to all are:

  • rlo ≤ 1500
  • g_vis_per > 5
  • Neither of the two following conditions are met:
    • (logpmdpm < 0.301) AND (p/perr > -1.4996 * logpmdpm – 4.05) AND (p/perr < 1.4995 * logpmdpm + 4.05)
    • (logpmdpm – 0.301)2/0.397942 + (p/perr)2/4.52 ≤ 1

Additional color cuts are applied to select objects with UV excess between the main sequence and white dwarf sequence.

mwm_cb_uvex1

This carton name was used in both the plate and FPS era, and targets also belong to the mwm_cb_galex alternate carton. The selection criteria rely on 5” cross-match between Gaia and GALEX. The following definitions apply to those criteria

  • NUVerr: Galex NUV magnitude error
  • FUVerr: Galex FUV magnitude error
  • G_AB: Gaia DR2 mean photometric G magnitude, in AB magnitudes
    • G_AB = G – 25.688 + 25.792
  • GBP_AB: Gaia DR2 mean photometric BP magnitude, in AB magnitudes
    • GBP_AB = GBP – 25.351 + 25.386
  • GRP_AB: Gaia DR2 mean photometric RP magnitude, in AB magnitudes
    • GRP_AB = GRP – 24.762 + 25.116
  • MG: absolute Gaia DR2 mean photometric G magnitude
  • GBP: Gaia DR2 mean photometric BP magnitude
  • GRP: Gaia DR2 mean photometric RP magnitude
  • fuvg = FUV – G_AB
  • GMS: Expected MGG for the main sequence defined by the following polynomial
    • x = G – GRP
    • GMS = 0.00206868742x6 + 0.0401594518x5– 0.842512410x4 + 4.89384979x3 – 12.3826637x2 + 17.0197205x – 3.19987835

The bolded criteria below are common to other UV excess cartons that rely on the Gaia GALEX cross-match. The color cuts for this carton rely on both FUV and NUV.

  • NUVerr < 0.2
  • NUV > -100
  • FUVerr < 0.2
  • FUV > -100
  • MG > 4.09 OR MGG > 4.5457 * (GBP – GRP) + 4.0457
  • MG > -1.11749253e-03 * (FUV-NUV)3 + 1.53748615e-02 * (FUV-NUV)2 + 3.66419895e-01 * (FUV-NUV) + 2.20026639)
  • fuvg < 6.08 OR ((fuvg < 11.82 * (GBP_AB – GRP_AB) + 2.58) AND (fuvg < -0.79 * (GBP_AB – GRP_AB) + 9.21))

mwm_cb_uvex2

This carton name was used in both the plate and FPS era, and targets also belong to the mwm_cb_galex alternate carton. The color cuts only rely on NUV data. In addition to the bolded criteria listed for mwm_cb_uvex1, the target selection criteria are:

  • (MGG > 4.09 OR MGG > 4.5457 * (GBP – GRP) + 4.0457)
  • (NUV – G_AB < 2.25) OR ( (NUV – G_AB < 6.725 * (GBP_AB – GRP_AB) – 1.735) AND (NUV – G_AB < -0.983 * (GBP_AB – GRP_AB + 8.24))

mwm_cb_uvex5

This carton name was used in both the plate and FPS era, and targets also belong to the mwm_cb_galex alternate carton. While targets are required to have detections in both NUV and FUV, the color cuts only utilize optical data. In addition to the bolded criteria listed for mwm_cb_uvex1, the target selection criteria are:

  • H < 15
  • FUVerr < 0.2
  • FUV > -100
  • MGG > 4.0866
  • |GMS-MG| ≤ 0.5
  • rest < 0.51 * 10 0.2291G

mwm_cb_uvex3

This carton name was used in both the plate and FPS era, and targets also belong to the mwm_cb_xmmom alternate carton. The selection criteria rely on a 3” cross-match between Gaia DR2 and the XMM-Newton Optical Monitor SUSS Catalog, v4.1 and use the AB magnitude in the XMM UVM2 band (UVM2_AB) and corresponding quality flags (qflag) and detection significance (UVM2signif). They are:

  • The following quality conditions are both NOT met
    • qflag bit 1, 7, 8, or 9 is set
    • qflag bit 2, or 3 is set AND UVM2signif < 10
  • MG > 4.09 OR MGG > 4.5457 * (GBP – GRP) + 4.0457
  • UVM2_AB – G_AB < 2.25 OR [(UVM2_AB – G_AB < 6) AND (UVM2_AB – G_AB < 5.57377 * (GBP_AB – GRP_AB) + 0.2049)]

mwm_cb_uvex4

This carton name was used in both the plate and FPS era, and targets also belong to the mwm_cb_swiftuvot alternate carton. The selection criteria rely on a 3” cross-match between Gaia DR2 and the Swift UVOT catalog. Both the Swift UVOT UVW1 and UVW2 AB magnitudes (UVW1_AB and UVW2_AB) are used to select targets, but only the quality flags and detection significance of UVW2 band (qflag2 and UVW2signif, respectively) are used. The selection criteria are:

  • UVW1_AB > -100
  • UVW2_AB > -100
  • The following quality conditions are both NOT met
    • qflag2 bit 0 or 6 is set
    • qflag2 bit 1, 2, or 5 is set AND UVW2signif < 10
  • MG > 4.09 OR MG > 4.5457 * (GBP – GRP) + 4.0457
  • UVW2_AB – G_AB < 2.25 OR [(UVW2_AB – G_AB < 6) AND (UVW2_AB – G_AB < 5.57377 * (GBP_AB – GRP_AB) + 0.2049)]

Manual Cartons

The targets in these cartons were assembled from various catalogs of binary systems known to or suspected of harboring a neutron star or black hole, including the ATNF pulsar catalog, Mauro Orlandini’s catalog of accreting X-ray binary pulsars, the Ritter and Kolb catalog of low-mass X-ray binaries, the Blackcat catalog of black hole binaries and the Watchdog catalog of black hole binaries. To distinguish these suspected neutron star or black hole systems from the cartons expected to be dominated by white dwarf systems, these targets all use alternate program name nsbh or alternate carton name manual_mwm_nsbh. These cartons were introduced during the FPS-era.

  • manual_nsbh_apogee: requires valid 2MASS H magnitude
  • manual_nsbh_boss: requires valid Gaia DR2 G magnitude

Cadences

During plate operations, the compact binary cartons primarily observed with the BOSS instrument. The exception was mwm_cb_uvex5, which observed with the APOGEE instrument. Compact binary targets could be observed on plates with any cadence except the RM cadence.

In FPS operations, compact binary targets could have a variety of cadences depending on the target brightness and whether multiple epochs of observation are needed to probe for radial velocity variations or optical spectral changes. Cartons that use a single cadence are the mwm_cb_uvex5 carton, which uses the multi-epoch bright_3x1 cadence with APOGEE, and the manual_nsbh_boss carton, which uses the dark_1x1 cadence.

For the remaining cartons, the following rules apply for FPS observations. The single epoch bright_1x1 cadence is used for all cartons that use the APOGEE instrument as well as BOSS observations of UVEX targets with G < 17. BOSS observations of fainter targets in the UVEX cartons use the single epoch dark_1x2 (17 ≤ G < 19) or dark_1x3 (G ≥ 19) cadences. The non-UVEX BOSS cartons (e.g., mwm_cb_300pc_boss) use multi-epoch cadences of either bright_2x1 (for G < 16) or dark_2x1 (G > 16).

Back to Top