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J/AJ/153/258    2007.5 to 2010.4 HST astrometry of HD 202206   (Benedict+, 2017)

HD 202206: a circumbinary brown dwarf system. Benedict G.F., Harrison T.E. <Astron. J., 153, 258-258 (2017)> =2017AJ....153..258B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Positional data ; Parallaxes, spectroscopic ; Photometry, UBV ; Proper motions ; Spectral types Keywords: astrometry - binaries: general - brown dwarfs - planetary systems Abstract: Using Hubble Space Telescope Fine Guidance Sensor astrometry and previously published radial velocity measures, we explore the exoplanetary system HD202206. Our modeling results in a parallax, πabs=21.96±0.12 milliseconds of arc, a mass for HD202206B of MB=0.089-0.006^+0.007M, and a mass for HD202206c of Mc=17.9-1.8+2.9MJup. HD202206 is a nearly face-on G + M binary orbited by a brown dwarf. The system architecture that we determine supports past assertions that stability requires a 5:1 mean motion resonance (we find a period ratio, Pc/PB=4.92±0.04) and coplanarity (we find a mutual inclination, Φ=6°±2°). Description: For this study astrometric measurements came from Fine Guidance Sensor 1r (FGS 1r), an upgraded FGS installed in 1997 during the second Hubble Space Telescope (HST) servicing mission. It provided superior fringes from which to obtain target and reference star positions (McArthur et al. 2003hstc.conf..373M). We utilized only the fringe tracking mode (POS mode) in this investigation. POS mode observations of a star have a typical duration of 60s, during which over 2000 individual position measures are collected. The astrometric centroid is estimated by choosing the median measure, after filtering large outliers (caused by cosmic-ray hits and particles trapped by the Earth's magnetic field). The standard deviation of the measures provides a measurement error. We refer to the aggregate of astrometric centroids of each star secured during one visibility period as an "orbit". Because one of the pillars of the scientific method involves reproducibility, we present a complete ensemble of time-tagged HD202206 and reference star astrometric measurements, Optical Field Angle Distortion (OFAD; McArthur et al. 2006hstc.conf..396M) and intra-orbit-drift-corrected, in Table2, along with calculated parallax factors in R.A. and decl. These data, collected from 2007.5 to 2010.4, in addition to providing material for confirmation of our results, might ultimately be combined with Gaia measures, significantly extending the time baseline of astrometry, thereby improving proper motion and perturbation characterization. Our band passes for reference star photometry include: BVRI photometry of the reference stars from the NMSU 1m telescope located at Apache Point Observatory and JHK (from 2MASS; see Cutri et al. 2003, Cat. II/246). Table4 lists the visible and infrared photometry for the HD202206 reference stars. To establish spectral type and luminosity class, the reference frame stars were observed on 2009 December 9 using the RCSPEC on the Blanco 4m telescope at Cerro Tololo Inter-American Observatory (CTIO). We used the KPGL1 grating to give a dispersion of 0.95Å/pix. Classifications used a combination of template matching and line ratios. We determine the spectral types for the higher S/N stars to within ±1 subclass. Classifications for the lower S/N stars have ±2 subclass uncertainty. Table5 lists the spectral types and luminosity classes for our reference stars. Objects: ------------------------------------------------ RA (2000) DE Designation(s) ------------------------------------------------ 21 14 57.77 -20 47 21.15 HD 202206 = HIP 104903 ------------------------------------------------ File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 99 503 HD 202206 field astrometry table3.dat 32 5 Astrometric reference stars table4.dat 72 6 Visible and near-infrared photometry table5.dat 36 4 Astrometric reference star initial spectrophotometric parallaxes table6.dat 47 6 HD 202206 and reference star relative positions table7.dat 52 5 Reference star final proper motions, parallaxes, and absolute magnitudes
See also: B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2012) B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2013) B/hst : HST Archived Exposures Catalog (STScI, 2007) I/322 : UCAC4 Catalogue (Zacharias+, 2012) I/317 : The PPMXL Catalog (Roeser+ 2010) I/305 : The Guide Star Catalog, Version 2.3.2 (GSC2.3) (STScI, 2006) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) I/254 : The HST Guide Star Catalog, Version 1.2 (Lasker+ 1996) J/AJ/152/141 : Solar neighborhood. XXXVII. RVs for M dwarfs (Benedict+, 2016) J/A+A/585/A5 : Exoplanet hosts/field stars age consistency (Bonfanti+, 2016) J/ApJ/795/41 : HD128311 radial velocity and astrometric data (McArthur+, 2014) J/AJ/142/187 : HST observations of 7 Pop.II variable stars (Benedict+, 2011) J/A+A/519/A10 : Radial velocity curve of HD 202206 (Couetdic+, 2010) J/A+A/390/267 : The CORALIE survey for extrasolar planets VIII (Udry+, 2002) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Set [1/40] Data set (orbit) number (1) 4- 5 I2 --- Star [1/11] Star or reference star number (1=HD202206, 5,6,9,10,11=astrometric reference stars same as Table3) (2) 7- 15 A9 --- HST HST orbit and target identifier 17- 21 F5.2 mag Vmag [8.2/16] Hubble Space Telescope/Fine Guidance Sensor (HST/FGS) V-band magnitude 23- 28 F6.2 deg V3 [0/293] Spacecraft+V3 axis roll angle 30- 39 F10.5 arcsec Xpos [-250/252] Optical Field Angle Distortion (OFAD) X position (3) 41- 50 F10.5 arcsec Ypos [-149/96] Optical Field Angle Distortion (OFAD) Y position (3) 52- 58 F7.5 arcsec e_Xpos [0.0015/0.007] Positional uncertainty in Xpos 60- 66 F7.5 arcsec e_Ypos [0.0014/0.039] Positional uncertainty in Ypos 68- 77 F10.4 d MJD [54285.6/55348.5] Modified Julian Date of observation (JD-2400000.5) 79- 88 F10.7 --- Palpha [-1/1.03] Parallax factor in Right Ascension 90- 99 F10.7 --- Pdelta [-0.31/0.32] Parallax factor in Declination
Note (1): We refer to the aggregate of astrometric centroids of each star secured during one visibility period as an "orbit". Note (2): As defined in Chapter 2, Fine Guidance Sensor Instrument Handbook v.23.0, Nelan 2015, http://www.stsci.edu/hst/fgs/documents/handbooks/instrumenthandbook/fgs_ihb.pdf Note (3): The Optical Field Angle Distortion (OFAD) calibration (McArthur et al. 2006hstc.conf..396M) reduces Hubble Space Telescope (HST) and Fine Guidance Sensors (FGS) as-built optical distortions of the order of 2s of arc to less than one mas in the center of the FGS field of regard. This level of correction persists for average radial distances from the FGS Field Of View (FOV) center <r>≤100'', and is a reason the parallax error for K Pav (±0.28mas, <r> =117'') is over twice that of RR Lyr (±0.13mas, <r> =44'') (Benedict et al. 2011, Cat. J/AJ/142/187).
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Star Reference star number 4- 13 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000) 15- 24 F10.6 deg DEdeg Declination in decimal degrees (J2000) 26- 30 F5.2 --- Vmag [13.9/16] V-band magnitude (2) 32 I1 --- r_DEdeg [1/2] Source of position (1)
Note (2): V magnitude, this paper. Note (1): Position reference is defined as follows: 1 = PPMXL (Roeser et al. 2010, Cat. I/317), J2000; 2 = GSC2.3 (Lasker et al. 2008, Cat. I/305).
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Star Star or reference star number 4- 8 F5.2 mag Vmag V-band magnitude 10- 13 F4.2 mag e_Vmag Error in V-band 15- 18 F4.2 mag B-V The B-V color index 20- 23 F4.2 mag e_B-V Error in B-V 25 A1 --- f_B-V Flag 'a' for B-V estimated from 2MASS photometry 27- 32 F6.3 mag Kmag ? 2MASS K-band magnitude 34- 38 F5.3 mag e_Kmag ? Error in Kmag 40- 44 F5.3 mag J-H ? The 2MASS (J-H) color index 46- 50 F5.3 mag e_J-H ? Error in J-H 52- 56 F5.3 mag J-K ? The 2MASS (J-K) color index 58- 62 F5.3 mag e_J-K ? Error in J-K 64- 67 F4.2 mag V-K ? The (V-K) color index 69- 72 F4.2 mag e_V-K ? Error in V-K
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Star Reference star number 4- 8 A5 --- SpT Spectral type (1) 10- 14 F5.2 mag Vmag [13.9/16] V-band magnitude 16- 18 F3.1 mag VMag [5.1/6.3] Absolute V-band magnitude 20- 23 F4.1 mag m-M [8/10.9] Distance modulus 25- 28 F4.2 mag AV [0/0.06] Interstellar V-band absorption 30- 32 F3.1 mas plx [0.7/2.5] Initial absolute spectrophotometric parallax 34- 36 F3.1 mas e_plx [0.2/0.6] Error in plx
Note (1): Spectral types and luminosity class estimated from classification spectra, colors, and a reduced proper motion diagram (Figures 3 and 4).
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Star Star or reference star number 3 A1 --- f_Star Flag 'b' on Star 9 (R.A.=318.689335, decl.=-20.788494, J2000) 5- 9 F5.2 mag Vmag V-band magnitude 11- 20 F10.5 arcsec ksi Relative position rolled to Right Ascension (ξ) (1) 22- 28 F7.5 arcsec e_ksi Error in ksi 30- 39 F10.5 arcsec eta Relative position rolled to Declination (η) (1) 41- 47 F7.5 arcsec e_eta Error in eta
Note (1): Epoch 2008.4085 (J2000). Roll uncertainty ±.06°.
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Star Reference star number 4- 8 F5.2 mag Vmag V-band magnitude 10- 15 F6.2 mas/yr pmRA Relative proper motion in Right Ascension (3) 17- 20 F4.2 mas/yr e_pmRA Error in pmRA (3) 22- 27 F6.2 mas/yr pmDE Relative proper motion in Declination (3) 29- 32 F4.2 mas/yr e_pmDE Error in pmDE (3) 34- 37 F4.2 mas plx Absolute parallax (3) 39- 42 F4.2 mas e_plx Error in plx (3) 44- 47 F4.2 mag VMag Absolute V-band magnitude (3) 49- 52 F4.2 mag e_VMag The 1σ error in VMag (3)
Note (3): Results of the radial velocity values from Couetdic et al. 2010 (Cat. J/A+A/519/A10) and Hubble Space Telescope (HST) astrometry (Table2) modeling (see Section 2.4 in the paper for additional details).
History: From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 24-Aug-2017
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