Abstract

The adaptive optics system at the 3.6-m AEOS telescope was used to measure the astrometry and differential magnitude in I band of 56 binary stars in 2002. The astrometric measurements will be of use for future orbital determination, and the photometric measurements will be of use in estimating the spectral types of the component stars. Two candidate companions were detected, but neither is likely to be gravitationally bound. Nine systems had not been observed in over 40 yr. Eight of these are shown to share common proper motion, while HD 182352 is shown to be a background star. One of the two components of the HD 114378 (α Com) is shown to be a variable star of unknown type. In addition, 86 stars were unresolved and the full width at half-maximum of the images are presented.

1 INTRODUCTION

Speckle interferometry has been the dominant technique for observing visual binary stars for the last several decades. There are several groups actively monitoring binary stars with speckle interferometry. One of the longest programmes is that of the US Naval Observatory (Mason, Hartkopf & Wycoff 2010); others include the PISCO programme (Prieur et al. 2010), the WIYN speckle programme (Horch et al. 2010) and that of Docobo and collaborators (Docobo et al. 2010). The main purpose of these observations is measuring the astrometry of the system. These measurements will eventually enable the computation of an orbit for the binary star, which leads to the determination of the dynamical masses of the component stars (Docobo et al. 2010). To compute a high-quality orbit, it requires many epochs of observations over at least one period of the orbit. For some orbits, this may take hundreds of years.

Speckle interferometry systems are relatively inexpensive to build and straightforward to operate. They are able to quickly observe large number of stars; as many as several hundred observations per night. For all of its successes, the technique does have its limitations. It has a fairly low limiting dynamic range. The exact limit depends on the camera used, but it ranges from 3 to 5 mag (Mason 1994). Also, in most cases true images are not created, but instead an autocorrelation, which can lead to quadrant ambiguity where the position of the companion is off by 180° (Bagnuolo et al. 1992). It is also difficult to extract the photometry from speckle interferograms, especially with the commonly used intensified detectors (Roberts 1998).

Adaptive optics (AO) solves many of the problems of speckle interferometry. AO systems sense the phase aberrations in the incoming starlight and correct it in real time. Because the AO system corrects the atmospheric distortion, the images from the science camera have a much higher signal-to-noise ratio and can achieve a dynamic range of 10 mag, though this depends on the separation between the star and the companion (Turner et al. 2008). With coronagraph or image subtraction techniques the achievable dynamic range can be increased dramatically (Oppenheimer & Hinkley 2009). The other great advantage of AO is that it produces a true image of the system. This removes the quadrant ambiguity that is common in speckle interferometry, it also allows for the measurement of the photometry of the individual stars. This information can be used to estimate the spectral type of the companion (ten Brummelaar et al. 2000). This can then be compared to the mass (or mass sum) computed from the orbit. If the observations are made with multiple filters, the components can be put on a colour–colour diagram (Caballero-Nieves et al. 2011) for additional understanding of the system.

Most adaptive optics observations have been focused on specific projects such as multiplicity surveys (e.g. Turner et al. 2008), but there is a great benefit to using AO for long-term monitoring of binary stars. The increased dynamic range of AO allows it to be used in the study of systems that the speckle interferometry has been unable to observe. Many of these systems were discovered decades ago with visual methods (e.g. Burnham 1894) and the published astrometry has large errors.

Between 2001 and 2006, the Advanced Electro-Optical System (AEOS) telescope and AO system (Roberts & Neyman 2002) were used to observe binary stars in I band in order to collect astrometric data to improve orbit determination and to provide photometric data for spectral class determination. This paper presents the measurements from data collected in 2002. The other observations will be presented in subsequent papers.

Most AO systems have science cameras that observe in the near-IR; only a handful of systems have operated in the visible. These include the Mt Wilson system (Shelton et al. 1995) and the systems at the US Air Force telescopes at the Starfire Optical Range (Fugate et al. 1994; Spinhirne et al. 1998) and on Maui (Roberts & Neyman 2002). During the last decade, only the US Air Force's AEOS telescope on Maui was available for astronomical observations and is currently unavailable for astronomical observations. As such, photometric measurements from the AEOS telescope are unique and unlikely to be repeated in the near future. Photometric measurements in the visible are especially useful when combined with near-IR photometric measurements. The addition of visible measurements to near-IR measurements decreases the uncertainty in spectral classification of stars. (Hinkley et al. 2010). Of course, since the binary systems are dynamic, the astrometric measurements cannot be duplicated.

2 OBSERVATIONS

Observations were made using the AEOS 3.6-m telescope and its AO system. The AEOS telescope is located at the Maui Space Surveillance System at the summit of Haleakala (Bradley et al. 2006). The AEOS AO system is a natural guide star system using a Shack–Hartmann wavefront sensor (Roberts & Neyman 2002). The individual subapertures have a diameter of 11.9 cm projected on to the primary. The deformable mirror has 941 actuators. The system's closed-loop bandwidth is adjustable and can run up to 200 Hz, although the normal bandwidth is approximately 50 Hz. In the configuration used for these observations, the light from 500–540 nm is sent to the tip/tilt detector system, the light from 540–700 nm is sent to the wavefront sensor and the light longer than 700 nm is sent to the Visible Imager CCD science camera.

The observing list was created from the Washington Double Star Catalog (WDS) by selecting. All objects had V < 8 and δ > −25°. The list included a number of binary stars with well-measured astrometry, for comparison purposes. These were the stars with the smallest dynamic range in the observing list. It also includes stars with larger dynamic ranges than what speckle interferometry can do. The intent was to gather additional astrometric measurements which could be used for eventual orbit calculation. Special attention was paid to binaries that had no recent published astrometry. Many of these binaries have separations of several arcseconds, but their dynamic range is too large for speckle interferometry observations to detect. AO is well suited to observe these. During testing and characterization of the AO system a number of stars were observed that were not in the WDS. I report on the results of these stars in addition to the observations of the known binaries.

Each data set consists of 250 frames using a Bessel I-band filter. After collection, any saturated frames are discarded and the remaining frames are debiased, dark subtracted and flat fielded. The frames are weighted by their peak pixel, which is proportional to their Strehl ratio and then co-added using a shift-and-add routine. The resulting image is analysed with the program fitstars; it uses an iterative blind-deconvolution that fits the location of delta functions and their relative intensity to the data. The co-adding technique and the analysis with fitstars was presented in ten Brummelaar et al. (1996, 2000). Observations were made in a queue-scheduling mode and as such, observations were made during a wide range of observing conditions.

Error bars on the astrometry and photometry were assigned using the method in Roberts et al. (2005). For the photometry, simulated binary stars were created from observations of single stars. The photometry of these simulated binaries was measured and used to create a grid of measurement errors as a function of separation (ρ) and differential magnitudes. For astrometry, the separation error bar is ±002 arcsec for ρ≤ 1 arcsec, ±001 arcsec for 1 < ρ≤ 4 arcsec and ±002 arcsec for ρ > 4 arcsec. The error in position angle (θ) caused by errors in determining the centroid of the secondary star location will be larger for systems with small separations than wider separations. I have adopted ±2° for ρ < 1 arcsec and ±1° for ρ > 1 arcsec as the position angle error.

3 RESULTS

The astrometry and photometry of all resolved systems are listed in Table 1. For each star, I list the Washington Double Star (WDS) number, the discovery designation, the HD Catalogue number, the Hipparcos Catalogue number, the Besselian date of the observation, the separation in arcseconds, the position angle in degrees and finally the differential magnitude measured in Bessel I band. Since the AEOS telescope is an alt-az design, it requires a Dove prism image derotator in the science camera to keep the orientation of the image fixed. I carried out some tests of the derotator, in which the derotator was turned off. In these cases, it was not possible to make an accurate measurement of the position angle of the stars. The separation and differential magnitude are still published, while the separation will be of marginal value without a position angle, the differential magnitude is still valuable.

Table 1

Resolved binaries.

 WDS # Discovery designation HD # HIP # Epoch ρ (arcsec) θ (°) ΔI 00554+4023 A 1511 5314 4331 2002.7473 1.21 39.6 2.39 ± 0.01 01060−0840 RST 4165 6514 5154 2002.6244 1.24 44.9 3.92 ± 0.04 01274+0658 A 2006 AB 8849 6788 2002.6245 2.02 276.3 4.39 ± 0.01 01277+4524 BU 999 AB 8799 6813 2002.6052 0.70 325.2 4.7 ± 0.2 01315+1521 BU 506 9270 7097 2002.6052 0.61 292.6 4.46 ± 0.15 01418+4237 MCY 2 10105 7918 2002.7773 0.75 212.0 5.5 ± 0.4 01433+6033 BU 1103 AB 10425 8046 2002.7773 1.61 358.2 4.71 ± 0.09 '' '' '' '' 2005.7727 1.62 359.6 3.8 ± 0.1 01433+6033 New 10425 8046 2002.7773 1.15 340.8 4.99 ± 0.11 '' '' '' '' 2005.7727 1.18 342.2 4.17 ± 0.06 02291+6724 CHR 6 Aa,Ab 15089 - 2002.6053 0.44 238.9 2.86 ± 0.04 02291+6724 STF 262 AB 15089 - 2002.6053 2.70 44.0 2.25 ± 0.03 02449+1007 TOK 1 Aa,Ab 17094 12828 2002.7804 0.21 213.5 3.39 ± 0.20 03027−0741 BU 11 18953 14168 2002.7804 1.37 63.3 3.93 ± 0.04 03524+1836 HDS483 24278 18116 2002.9743 0.63 - 3.25 ± 0.02 04134+6556 HDS536 26221 19710 2002.9743 0.42 - 4.77 ± 0.28 05182+3322 STT 103 34334 24727 2002.9881 4.14 55.3 6.70 ± 0.17 05282−2046 BU 320 AB 36079 25606 2002.7202 2.58 1.4 5.20 ± 0.04 05597+3713 STT 545 AB 40312 28380 2002.7529 3.91 304.9 4.53 ± 0.02 06532+3826 COU 1877 50037 33064 2002.8023 0.27 187.1 1.93 ± 0.03 07176+0918 STT 170 56515 35310 2002.2731 0.35 48.1 0.15 ± 0.02 07518−1354 BU 101 64096 38382 2002.2731 0.14 15.8 0.70 ± 0.03 08122+1739 STF 1196 AB 68257 40167 2002.2731 0.88 70.35 0.26 ± 0.03 08468+0625 SP 1AB 74874 43109 2002.2731 0.24 228.8 1.88 ± 0.03 '' '' '' '' 2002.2732 0.24 226.5 1.91 ± 0.03 08468+0625 STF 1273 AB-C 74874 43109 2002.2731 2.85 293.9 3.87 ± 0.01 '' '' '' '' 2002.2732 2.84 294.5 3.59 ± 0.01 09006+4147 KUI 37 AB 76943 44248 2002.2731 0.71 20.5 1.89 ± 0.03 '' '' '' '' 2002.2732 0.70 20.3 1.89 ± 0.03 '' '' '' '' 2002.2733 0.70 20.1 1.87 ± 0.03 09154+2248 A 2136 79553 45425 2002.1477 1.85 111.8 3.8 ± 0.01 09167−0621 KUI 40 79910 45527 2002.1476 1.44 283.6 6.0 ± 0.2 11182+3132 STF 1523 AB 98230 - 2002.0192 1.75 259.7 0.55 ± 0.01 '' '' '' '' 2002.2731 1.78 259.4 0.61 ± 0.01 11239+1032 STF 1536 AB 99028 55642 2002.1697 1.76 106.5 2.27 ± 0.01 12244+2535 STF 1639 AB 108007 60525 2002.1068 1.72 332.3 0.92 ± 0.01 '' '' '' '' 2002.2731 1.72 322.7 0.92 ± 0.01 12540+5558 BLM 2 112185 62956 2002.2732 0.11 59.9 2.31 ± 0.03 13099−0532 MCA 38 Aa,Ab 114330 64238 2002.4702 0.44 340.0 2.21 ± 0.03 13100+1732 STF 1728 AB 114378 64241 2002.0988 0.19 194.4 0.210 ± 0.04 '' '' '' '' 2002.2731 0.20 190.3 0.49 ± 0.04 13396+1045 BU 612 AB 118889 66640 2002.1069 0.20 179.2 0.20 ± 0.04 '' '' '' '' 2002.2732 0.21 179.5 0.18 ± 0.04 13396+1045 New 118889 66640 2002.1069 3.59 135.9 5.40 ± 0.06 '' '' '' '' 2002.2732 3.61 76.2 5.9 ± 0.06 14118−1901 DON 649 124087 69356 2002.4758 2.19 303.2 4.9 ± 0.03 14148+1006 KUI 66 124679 69612 2002.3502 0.98 106.1 4.2 ± 0.06 14171−1835 HDS 2008 124990 69792 2002.3503 0.67 88.5 5.4 ± 0.45 14227+0216 HDS 2025 143275 78401 2002.5578 0.73 3.1 2.8 ± 0.03 15232+3017 STF 1937 AB 137107 75312 2002.1342 0.61 166.0 0.29 ± 0.03 15576+2653 AGC 7 AB 143107 78159 2002.5797 1.96 9.8 6.44 ± 0.13 16304+4044 HDS 2331 149025 80827 2002.4706 0.56 275.2 3.32 ± 0.07 16492+4559 BU 627 AB 152107 82321 2002.5553 1.79 33.4 3.92 ± 0.04 16492+4559 BU 627 AC 152107 82321 2002.5553 1.95 31.7 3.33 ± 0.04 16492+4559 A 1866 BC 152107 82321 2002.5553 0.15 197.1 0.53 ± 0.04 18000+2449 COU 115 - - 2002.5473 0.28 113.4 0.53 ± 0.04 18272+0012 STF 2316 AB 169985 90441 2002.5611 3.70 318.6 3.42 ± 0.01 18582+1722 HO 91 AB 176155 93124 2002.5611 6.79 143.7 6.33 ± 0.11 19122+3215 HU 941 179708 94350 2002.5803 1.07 145.2 2.890 ± 0.01 19177+2302 BU 248 AB 180968 94827 2002.5803 1.72 127.2 3.57 ± 0.03 19213+5543 A 1395 182352 - 2002.5804 4.02 233.9 2.00 ± 0.01 19244+1656 HDS 2753 Aa,Ab 182490 95398 2002.5802 0.43 138.1 3.44 ± 0.08 19364+5013 BU 1131 AB 185395 96441 2002.6920 2.54 65.8 5.89 ± 0.09 19556+5226 YR 2 Aa,Ab 189037 98055 2002.5805 0.10 77.6 0.66 ± 0.05 19556+5226 STF 2605 AB 189037 98055 2002.5805 2.88 174.1 2.46 ± 0.01 20154+6412 MLR 60 AB 193215 99832 2002.5831 0.19 184.1 0.12 ± 0.04 20176−1230 WZ 15 Aa,Ab 192876 100027 2002.7277 0.82 352.6 6.4 ± 0.6 20569−0942 BU 1034 AB 199345 103401 2002.5857 2.12 164.5 6.15 ± 0.11 21103+1008 KNT 5 AB 201601 104521 2002.5857 0.96 258.0 3.82 ± 0.04 22051+5142 HDS 3134 209870 109015 2002.7470 0.98 352.9 3.05 ± 0.01 22332+3356 HO 293 213745 - 2002.6352 1.51 314.9 2.35 ± 0.01 23300+5833 STT 496 AB 221253 115990 2002.7116 0.78 355.9 3.66 ± 0.05 23355−0709 RST 4726 221823 116426 2002.7117 1.07 277.0 3.71 ± 0.03
 WDS # Discovery designation HD # HIP # Epoch ρ (arcsec) θ (°) ΔI 00554+4023 A 1511 5314 4331 2002.7473 1.21 39.6 2.39 ± 0.01 01060−0840 RST 4165 6514 5154 2002.6244 1.24 44.9 3.92 ± 0.04 01274+0658 A 2006 AB 8849 6788 2002.6245 2.02 276.3 4.39 ± 0.01 01277+4524 BU 999 AB 8799 6813 2002.6052 0.70 325.2 4.7 ± 0.2 01315+1521 BU 506 9270 7097 2002.6052 0.61 292.6 4.46 ± 0.15 01418+4237 MCY 2 10105 7918 2002.7773 0.75 212.0 5.5 ± 0.4 01433+6033 BU 1103 AB 10425 8046 2002.7773 1.61 358.2 4.71 ± 0.09 '' '' '' '' 2005.7727 1.62 359.6 3.8 ± 0.1 01433+6033 New 10425 8046 2002.7773 1.15 340.8 4.99 ± 0.11 '' '' '' '' 2005.7727 1.18 342.2 4.17 ± 0.06 02291+6724 CHR 6 Aa,Ab 15089 - 2002.6053 0.44 238.9 2.86 ± 0.04 02291+6724 STF 262 AB 15089 - 2002.6053 2.70 44.0 2.25 ± 0.03 02449+1007 TOK 1 Aa,Ab 17094 12828 2002.7804 0.21 213.5 3.39 ± 0.20 03027−0741 BU 11 18953 14168 2002.7804 1.37 63.3 3.93 ± 0.04 03524+1836 HDS483 24278 18116 2002.9743 0.63 - 3.25 ± 0.02 04134+6556 HDS536 26221 19710 2002.9743 0.42 - 4.77 ± 0.28 05182+3322 STT 103 34334 24727 2002.9881 4.14 55.3 6.70 ± 0.17 05282−2046 BU 320 AB 36079 25606 2002.7202 2.58 1.4 5.20 ± 0.04 05597+3713 STT 545 AB 40312 28380 2002.7529 3.91 304.9 4.53 ± 0.02 06532+3826 COU 1877 50037 33064 2002.8023 0.27 187.1 1.93 ± 0.03 07176+0918 STT 170 56515 35310 2002.2731 0.35 48.1 0.15 ± 0.02 07518−1354 BU 101 64096 38382 2002.2731 0.14 15.8 0.70 ± 0.03 08122+1739 STF 1196 AB 68257 40167 2002.2731 0.88 70.35 0.26 ± 0.03 08468+0625 SP 1AB 74874 43109 2002.2731 0.24 228.8 1.88 ± 0.03 '' '' '' '' 2002.2732 0.24 226.5 1.91 ± 0.03 08468+0625 STF 1273 AB-C 74874 43109 2002.2731 2.85 293.9 3.87 ± 0.01 '' '' '' '' 2002.2732 2.84 294.5 3.59 ± 0.01 09006+4147 KUI 37 AB 76943 44248 2002.2731 0.71 20.5 1.89 ± 0.03 '' '' '' '' 2002.2732 0.70 20.3 1.89 ± 0.03 '' '' '' '' 2002.2733 0.70 20.1 1.87 ± 0.03 09154+2248 A 2136 79553 45425 2002.1477 1.85 111.8 3.8 ± 0.01 09167−0621 KUI 40 79910 45527 2002.1476 1.44 283.6 6.0 ± 0.2 11182+3132 STF 1523 AB 98230 - 2002.0192 1.75 259.7 0.55 ± 0.01 '' '' '' '' 2002.2731 1.78 259.4 0.61 ± 0.01 11239+1032 STF 1536 AB 99028 55642 2002.1697 1.76 106.5 2.27 ± 0.01 12244+2535 STF 1639 AB 108007 60525 2002.1068 1.72 332.3 0.92 ± 0.01 '' '' '' '' 2002.2731 1.72 322.7 0.92 ± 0.01 12540+5558 BLM 2 112185 62956 2002.2732 0.11 59.9 2.31 ± 0.03 13099−0532 MCA 38 Aa,Ab 114330 64238 2002.4702 0.44 340.0 2.21 ± 0.03 13100+1732 STF 1728 AB 114378 64241 2002.0988 0.19 194.4 0.210 ± 0.04 '' '' '' '' 2002.2731 0.20 190.3 0.49 ± 0.04 13396+1045 BU 612 AB 118889 66640 2002.1069 0.20 179.2 0.20 ± 0.04 '' '' '' '' 2002.2732 0.21 179.5 0.18 ± 0.04 13396+1045 New 118889 66640 2002.1069 3.59 135.9 5.40 ± 0.06 '' '' '' '' 2002.2732 3.61 76.2 5.9 ± 0.06 14118−1901 DON 649 124087 69356 2002.4758 2.19 303.2 4.9 ± 0.03 14148+1006 KUI 66 124679 69612 2002.3502 0.98 106.1 4.2 ± 0.06 14171−1835 HDS 2008 124990 69792 2002.3503 0.67 88.5 5.4 ± 0.45 14227+0216 HDS 2025 143275 78401 2002.5578 0.73 3.1 2.8 ± 0.03 15232+3017 STF 1937 AB 137107 75312 2002.1342 0.61 166.0 0.29 ± 0.03 15576+2653 AGC 7 AB 143107 78159 2002.5797 1.96 9.8 6.44 ± 0.13 16304+4044 HDS 2331 149025 80827 2002.4706 0.56 275.2 3.32 ± 0.07 16492+4559 BU 627 AB 152107 82321 2002.5553 1.79 33.4 3.92 ± 0.04 16492+4559 BU 627 AC 152107 82321 2002.5553 1.95 31.7 3.33 ± 0.04 16492+4559 A 1866 BC 152107 82321 2002.5553 0.15 197.1 0.53 ± 0.04 18000+2449 COU 115 - - 2002.5473 0.28 113.4 0.53 ± 0.04 18272+0012 STF 2316 AB 169985 90441 2002.5611 3.70 318.6 3.42 ± 0.01 18582+1722 HO 91 AB 176155 93124 2002.5611 6.79 143.7 6.33 ± 0.11 19122+3215 HU 941 179708 94350 2002.5803 1.07 145.2 2.890 ± 0.01 19177+2302 BU 248 AB 180968 94827 2002.5803 1.72 127.2 3.57 ± 0.03 19213+5543 A 1395 182352 - 2002.5804 4.02 233.9 2.00 ± 0.01 19244+1656 HDS 2753 Aa,Ab 182490 95398 2002.5802 0.43 138.1 3.44 ± 0.08 19364+5013 BU 1131 AB 185395 96441 2002.6920 2.54 65.8 5.89 ± 0.09 19556+5226 YR 2 Aa,Ab 189037 98055 2002.5805 0.10 77.6 0.66 ± 0.05 19556+5226 STF 2605 AB 189037 98055 2002.5805 2.88 174.1 2.46 ± 0.01 20154+6412 MLR 60 AB 193215 99832 2002.5831 0.19 184.1 0.12 ± 0.04 20176−1230 WZ 15 Aa,Ab 192876 100027 2002.7277 0.82 352.6 6.4 ± 0.6 20569−0942 BU 1034 AB 199345 103401 2002.5857 2.12 164.5 6.15 ± 0.11 21103+1008 KNT 5 AB 201601 104521 2002.5857 0.96 258.0 3.82 ± 0.04 22051+5142 HDS 3134 209870 109015 2002.7470 0.98 352.9 3.05 ± 0.01 22332+3356 HO 293 213745 - 2002.6352 1.51 314.9 2.35 ± 0.01 23300+5833 STT 496 AB 221253 115990 2002.7116 0.78 355.9 3.66 ± 0.05 23355−0709 RST 4726 221823 116426 2002.7117 1.07 277.0 3.71 ± 0.03

The listed astrometry was compared with the latest published astrometry in the WDS. The astrometry for all but two systems was consistent with the published data. The position angle of HD 137107 (WDS 15232+3017) is inconsistent with the orbit of Mason et al. (2006), though the separation appears to be in agreement. The position angle computed from the orbital elements is 85, while I measured it to be 0. The observation is also inconsistent with published observations before and after the AEOS measurement (Bodin 2003; Horch et al. 2008). The position angle for HD 193215 (WDS 20154+6412) also does not match the orbit of Seymour et al. (2002), but again the separation is consistent. The observations of Mason et al. (in preparation) collected in 2007 are consistent with the orbit of Seymour et al. (2002). It seems likely that in both cases the image derotator malfunctioned.

HD 114378 (α Com) consists of an AB pair with an orbital semimajor axis of 067 arcsec (Mason et al. 2006) along with a third star at a separation of over an arcminute. Both of the measurements of the AB pair in this paper are off by 180° from the astrometry computed from the orbit of Mason et al. (2006). Looking at the data collected over the last few decades (Hartkopf, McAlister & Mason 2001), quadrant ambiguity is a fairly common occurrence. In addition, ten Brummelaar et al. (2000) measured the differential magnitude in I band as 0.0 ± 0.03, while the images taken at AEOS clearly show a pair of stars with unequal magnitude. Horch et al. (2010) also shows the differential magnitude varying from 0.0 to 0.66 over the course of a year. The 2002.2731 observation shown in Table 1 is the average of two measurements taken in the same night. The measured differential magnitudes are 0.34 and 0.57. Some of the scatter is caused by relatively small separation of the pair, but the scatter is much higher than the scatter from other stars measured multiple times that same night. The most likely explanation for all of these factors is that one of the components is a variable star with a relatively short period such as a δ Scuti or γ Doradus type.

Nine of the stars were last observed before 1970. The long time period is helpful in determining if the binaries share common proper motion. Table 2 lists the HD Catalogue number of the nine stars, the Besselian date, the change in position angle and separation from their last observation (Mason et al. 2001) and finally the distance the secondary would have moved based on proper motion between the last observation and the one in this paper if it had no proper motion of its own. The proper motion came from either the Hipparcos (Perryman et al. 1997) or Tycho catalogues (Høg et al. 1998). This shows that the companion to HD 182352 = WDS 19213+5543 is a background star, while the other eight systems have common proper motion.

Table 2

Proper motion of neglected binaries.

 HD # Date of last obs Δρ (arcsec) Δθ (°) PM movement (arcsec) 8849 1953.03 0.44 3.3 6.8 8799 1967.387 1.07 206.8 13.45 10425 1934.70 0.38 16.1 1.48 34334 1936.21 0.27 0.9 10.9 79553 1933.30 0.07 10.9 1.35 143107 1965.251 0.14 0.6 3.64 182352 1929.57 3.24 19.6 2.91 185395 1968.723 0.38 5.9 8.9
 HD # Date of last obs Δρ (arcsec) Δθ (°) PM movement (arcsec) 8849 1953.03 0.44 3.3 6.8 8799 1967.387 1.07 206.8 13.45 10425 1934.70 0.38 16.1 1.48 34334 1936.21 0.27 0.9 10.9 79553 1933.30 0.07 10.9 1.35 143107 1965.251 0.14 0.6 3.64 182352 1929.57 3.24 19.6 2.91 185395 1968.723 0.38 5.9 8.9

3.1 Newly discovered components

HD 10425 (WDS 01433+6033). This system is infrequently observed, probably due to its large dynamic range. The central AB pair has only been observed three times since it was discovered in 1889 (Burnham 1894) and it appears to have moved little since then. As shown in Table 2, it is a common proper motion pair. There are also C, D, E components with mean separations of approximately 1, 2 and 3 arcmin, respectively. A new component to this system was observed in 2002. An additional measurement in 2005 confirmed the component. The 2005 observation is shown in Fig. 1. The new component does not appear to form a hierarchical system with the A and B components, as the AB separation of 1.6 arcsec is not 10 times the separation between the A component and the new component or the new component and the B component. As such it was tentatively labelled as F, but if it is found to be bound to the B component, it would be given the designation Bb. Follow-up observations at a current epoch should be able to determine if the new component has the same proper motion as the AB pair.

Figure 1

Image of HD 10425 observed on 2005.7727 showing the AB pair and the newly discovered F component.

Figure 1

Image of HD 10425 observed on 2005.7727 showing the AB pair and the newly discovered F component.

The primary has a spectral class of B8IIIn (Cowley et al. 1969). With only I-band observations it is impossible to tell if either B or F component falls in the main sequence or are also evolved stars.

HD 118889 (WDS 13396+1045). This system already has three known components, a close pair with a separation of several arcseconds and a third component with a separation of several arcminutes. A new component was seen in two observations taken 61 d apart. The position angle of the new component changed substantially between the two observations. It does not appear to be an error in the image derotator, since the two observations of the AB pair are almost identical. The object is either a field object with substantial proper motion or an artefact. These have been seen before in AEOS data, but usually with a much higher dynamic range (Roberts, Turner & ten Brummelaar 2007). It is possible to estimate the companion spectral type assuming it was at the same distance as the primary and in the main sequence using the absolute magnitudes of the MK classification in Cox (2000). Based on the primary's spectral class of an F0V (Royer, Zorec & Gómez 2007), and the differential magnitude in Table 1, the companion would be an early M dwarf.

3.2 Unresolved stars

Observations of stars that did not reveal a companion are detailed in Table 3. The entry for each star lists the WDS number if it has one, the HD Catalogue number, the Hipparcos Catalogue number, the Besselian date of the observation and the full width half-maximum (FWHM) of the image. There are several reasons why known binary stars are not detected. The most common is that the known companion was within the central diffraction core of the image. Second most common is that the companion was outside of the field of view. The Visible Imager camera has a 10-arcsec field of view, but the star was usually not placed at the centre of the image due to a misalignment of the tip/tilt system and the AO system. The offset is usually about 1 arcsec. Sometimes stars with separations of 4–5 arcsec have their companion land outside of the field of view, e.g. HD 159181 (WDS 17304+5218).

Table 3

Unresolved stars.

 WDS # HD # HIP # Epoch FWHM (arcsec) 00542+4318 5178 - 2002.7473 0.26 01100+5202 6843 5468 2002.6245 0.13 01334+5820 9352 7251 2002.7773 0.14 02095+3459 13161 10064 2002.6053 0.13 02130+0851 13611 10324 2002.6053 0.16 02132+4414 13520 10340 2002.6053 0.14 02136+5104 13530 10366 2002.7773 0.19 02171+3413 13974 10644 2002.7773 0.13 02366−1439 16295 12146 2002.7475 0.38 02366+1227 16234 12153 2002.7475 0.16 02424+2001 16811 12640 2002.7804 0.12 02422+4012 16739 12623 2002.7529 0.13 02500+2716 17573 13209 2002.7503 0.24 02543+5246 17879 13531 2002.7503 0.21 03429+4747 22928 17358 2002.7504 0.18 03460+6321 23089 17587 2002.6898 0.11 03492+2403 23850 17847 2002.7504 0.18 03501+4458 23838 17932 2002.9743 0.10 04230+1732 27697 20455 2002.6898 0.13 - 32630 23767 2002.6545 0.10 '' '' '' 2002.7147 0.10 05154+3241 33959 24504 2002.7257 0.11 05251+0621 35468 25336 2002.7393 0.24 05263+2836 35497 25428 2002.7448 0.09 - 39040 27383 2002.0158 0.39 05490+2434 38751 27468 2002.7145 0.16 - 39190 27533 2002.7721 0.35 - 168434 - 2002.7146 0.08 06230+2231 44478 30343 2002.7529 0.11 - 48737 32362 2002.7530 0.13 07269+2015 58579 36156 2002.3334 0.24 08447+1809 74442 42911 2002.3334 0.26 - 86535 48935 2002.1477 0.14 11239+1032 99028 55642 2002.1697 0.17 - 102047 57264 2002.1697 0.41 - 105707 59316 2002.0904 0.11 13022+1058 113226 63608 2002.1069 0.14 13189−2310 115659 64962 2002.0987 0.17 - 123123 68895 2002.1069 0.12 14141+1258 124570 69536 2002.3502 0.14 14157+1911 124897 69673 2002.4757 0.18 15245+3723 137391 75411 2002.4022 0.18 15249+5858 137759 75458 2002.2055 0.10 - 139006 76267 2002.2732 0.12 16003−2237 143275 78401 2002.1262 0.14 16143−0342 146051 79593 2002.4842 0.14 '' '' '' 2002.0987 0.08 16183−0442 146791 79882 2002.1262 0.12 16221+3054 147677 80181 2002.5798 0.14 16254+3724 148283 80460 2002.4706 0.08 - 153210 - 83000 2002.3176 0.13 17003+3056 153808 83207 2002.5553 0.10 17150+2450 156164 84379 2002.5117 0.20 '' '' '' 2002.5552 0.12 17304+5218 159181 85670 2002.3067 0.16 17395+4600 160762 86414 2002.5612 0.12 - 161096 86742 2002.3177 0.12 17566+5129 163967 87833 2002.3203 0.09 - 163917 88048 2002.3204 0.09 - 168411 89140 2002.5446 0.41 18210−2950 168454 89931 2002.4352 0.18 18213−0254 168723 89962 2002.4352 0.14 18280−2525 169916 90496 2002.3998 0.12 18280+0612 170200 90497 2002.5611 0.17 18367+0640 171834 91237 2002.5611 0.12 18426+5532 173524 91755 2002.5611 0.12 18553−2618 175191 92855 2002.3999 0.17 18589+3241 176437 93194 2002.3999 0.11 19054+1352 177724 93747 2002.4518 0.12 19126+6740 180711 94376 2002.4847 0.19 19164+1433 180555 94720 2002.5803 0.14 19180+2012 181025 94847 2002.5804 0.25 19190+3727 181470 94932 2002.5803 0.19 19205−0525 181391 95066 2002.5802 0.13 19463+1037 186791 97278 2002.5503 0.10 19508+0852 187642 97649 2002.5556 0.12 19542+0828 188310 97938 2002.5529 0.19 20143+0803 192366 99740 2002.5830 0.37 20158+2749 192806 99874 2002.5831 0.11 20222+4015 194093 100453 2002.5664 0.18 20349+2833 196198 - 2002.5777 0.12 20414+4517 197345 102098 2002.5637 0.11 20527−0859 198743 103045 2002.5857 0.12 21186+6235 203280 105199 2002.5665 0.16 21567+6338 208816 108317 2002.7058 0.12 21573+5029 208785 108374 2002.7058 0.13 22038+6438 209790 108917 2002.7470 0.14 22236+5214 212496 110538 2002.5586 0.11 22350+6050 214165 111469 2002.6352 0.25
 WDS # HD # HIP # Epoch FWHM (arcsec) 00542+4318 5178 - 2002.7473 0.26 01100+5202 6843 5468 2002.6245 0.13 01334+5820 9352 7251 2002.7773 0.14 02095+3459 13161 10064 2002.6053 0.13 02130+0851 13611 10324 2002.6053 0.16 02132+4414 13520 10340 2002.6053 0.14 02136+5104 13530 10366 2002.7773 0.19 02171+3413 13974 10644 2002.7773 0.13 02366−1439 16295 12146 2002.7475 0.38 02366+1227 16234 12153 2002.7475 0.16 02424+2001 16811 12640 2002.7804 0.12 02422+4012 16739 12623 2002.7529 0.13 02500+2716 17573 13209 2002.7503 0.24 02543+5246 17879 13531 2002.7503 0.21 03429+4747 22928 17358 2002.7504 0.18 03460+6321 23089 17587 2002.6898 0.11 03492+2403 23850 17847 2002.7504 0.18 03501+4458 23838 17932 2002.9743 0.10 04230+1732 27697 20455 2002.6898 0.13 - 32630 23767 2002.6545 0.10 '' '' '' 2002.7147 0.10 05154+3241 33959 24504 2002.7257 0.11 05251+0621 35468 25336 2002.7393 0.24 05263+2836 35497 25428 2002.7448 0.09 - 39040 27383 2002.0158 0.39 05490+2434 38751 27468 2002.7145 0.16 - 39190 27533 2002.7721 0.35 - 168434 - 2002.7146 0.08 06230+2231 44478 30343 2002.7529 0.11 - 48737 32362 2002.7530 0.13 07269+2015 58579 36156 2002.3334 0.24 08447+1809 74442 42911 2002.3334 0.26 - 86535 48935 2002.1477 0.14 11239+1032 99028 55642 2002.1697 0.17 - 102047 57264 2002.1697 0.41 - 105707 59316 2002.0904 0.11 13022+1058 113226 63608 2002.1069 0.14 13189−2310 115659 64962 2002.0987 0.17 - 123123 68895 2002.1069 0.12 14141+1258 124570 69536 2002.3502 0.14 14157+1911 124897 69673 2002.4757 0.18 15245+3723 137391 75411 2002.4022 0.18 15249+5858 137759 75458 2002.2055 0.10 - 139006 76267 2002.2732 0.12 16003−2237 143275 78401 2002.1262 0.14 16143−0342 146051 79593 2002.4842 0.14 '' '' '' 2002.0987 0.08 16183−0442 146791 79882 2002.1262 0.12 16221+3054 147677 80181 2002.5798 0.14 16254+3724 148283 80460 2002.4706 0.08 - 153210 - 83000 2002.3176 0.13 17003+3056 153808 83207 2002.5553 0.10 17150+2450 156164 84379 2002.5117 0.20 '' '' '' 2002.5552 0.12 17304+5218 159181 85670 2002.3067 0.16 17395+4600 160762 86414 2002.5612 0.12 - 161096 86742 2002.3177 0.12 17566+5129 163967 87833 2002.3203 0.09 - 163917 88048 2002.3204 0.09 - 168411 89140 2002.5446 0.41 18210−2950 168454 89931 2002.4352 0.18 18213−0254 168723 89962 2002.4352 0.14 18280−2525 169916 90496 2002.3998 0.12 18280+0612 170200 90497 2002.5611 0.17 18367+0640 171834 91237 2002.5611 0.12 18426+5532 173524 91755 2002.5611 0.12 18553−2618 175191 92855 2002.3999 0.17 18589+3241 176437 93194 2002.3999 0.11 19054+1352 177724 93747 2002.4518 0.12 19126+6740 180711 94376 2002.4847 0.19 19164+1433 180555 94720 2002.5803 0.14 19180+2012 181025 94847 2002.5804 0.25 19190+3727 181470 94932 2002.5803 0.19 19205−0525 181391 95066 2002.5802 0.13 19463+1037 186791 97278 2002.5503 0.10 19508+0852 187642 97649 2002.5556 0.12 19542+0828 188310 97938 2002.5529 0.19 20143+0803 192366 99740 2002.5830 0.37 20158+2749 192806 99874 2002.5831 0.11 20222+4015 194093 100453 2002.5664 0.18 20349+2833 196198 - 2002.5777 0.12 20414+4517 197345 102098 2002.5637 0.11 20527−0859 198743 103045 2002.5857 0.12 21186+6235 203280 105199 2002.5665 0.16 21567+6338 208816 108317 2002.7058 0.12 21573+5029 208785 108374 2002.7058 0.13 22038+6438 209790 108917 2002.7470 0.14 22236+5214 212496 110538 2002.5586 0.11 22350+6050 214165 111469 2002.6352 0.25

These measurements are useful for several reasons. For known binaries, they can constrain the orbital solution by providing an upper bound on the orbital separation at a specific time (Hinkley et al. 2010). It also puts an upper limit to the brightness and separation of additional components of a system.

HD 16295 (WDS 02366-1439) has a single unconfirmed observation with a reported differential magnitude of 3.4 in the visible from the Hipparcos satellite (Perryman et al. 1997). The image used in this paper has a fairly low signal-to-noise ratio due to poor AO correction and does not constrain the existence of the purported companion. The observation only rules out additional bright companions.

4 SUMMARY

The AO system at the 3.6-m AEOS telescope was used to measure the astrometry and differential magnitude in I band of 56 binary stars in 2002. The astrometric measurements will be of use for future orbital determination, and the photometric measurements will be of use in estimating the spectral types of the component stars. In addition, 86 stars had no resolved companions, and for these the FWHMs of the images are presented.

In addition, the observations allow for the analysis of specific stars. Through analysis of differential magnitude from AO and speckle interferometry, it was determined that the HD 114378 system contains a variable star with a relatively short period. Follow-up measurements with CCD photometry are needed to determine the exact type of variable star. Simultaneous measurements with AO can be used to identify which component is the variable. The proper motion of nine stars that had not been observed in decades were analysed. HD 182352 was determined to be a background star, while the rest share common proper motion.

Two possible new companions to already known binary stars were detected. A candidate companion to HD 10425 was detected and confirmed with follow-up observations several years later. While the system does not appear hierarchal, it is possible that it is a physical system with a high inclination. Follow-up multifilter near-IR AO observations are needed to determine if it is a physical system through analysis of proper motion and colour photometry. The candidate companion to HD 118889 has a smaller probability of being physical, but follow-up observations are needed to determine if the companion is physical or an artefact.

I thank Kimberly Nguyen for years of love and support. I thank Brian Mason and Bill Hartkopf for providing data from the WDS Catalogue and useful and insightful comments. Also, I thank the numerous staff members of the Maui Space Surveillance System who helped make these data possible. The research in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Additional funding came from AFRL/DE (Contract Number F29601-00-D-0204). This research made use of the Washington Double Star Catalogue maintained at the US Naval Observatory, the SIMBAD data base, operated by the CDS in Strasbourg, France and NASA's Astrophysics Data System.

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