SPECKLE OBSERVATIONS OF BINARY STARS WITH THE WIYN TELESCOPE. VII. MEASURES DURING

Transcription

1 C The American Astronomical Society. All rights reserved. Printed in the U.S.A. doi: / /143/1/10 SPECKLE OBSERVATIONS OF BINARY STARS WITH THE WIYN TELESCOPE. VII. MEASURES DURING Elliott P. Horch 1,6,7, Lizzie Anne P. Bahi 1,8, Joseph R. Gaulin 1,9, Steve B. Howell 2, William H. Sherry 3, Roberto Baena Gallé 4,6, and William F. van Altena 5 1 Department of Physics, Southern Connecticut State University, 501 Crescent Street, New Haven, CT 06515, USA; horche2@southernct.edu, bahil1@owls.southernct.edu, jgaulin.jg@gmail.com 2 NASA Ames Research Center, Moffett Field, CA 94035, USA; steve.b.howell@nasa.gov 3 National Optical Astronomy Observatories, 950 North Cherry Avenue, Tucson, AZ 87719, USA; wsherry@noao.edu 4 Observatori Fabra, Reial Acadèmia de Ciències i Arts de Barcelona, Camí de l Observatori s/n, E Barcelona, Spain; rbaena@am.ub.es 5 Department of Astronomy, Yale University, P.O. Box , New Haven, CT 06520, USA; william.vanaltena@yale.edu Received 2011 September 25; accepted 2011 October 31; published 2011 December 8 ABSTRACT Five hundred thirty-one speckle measures of binary stars are reported. These data were taken mainly during the period 2008 June through 2009 October at the WIYN 3.5 m Telescope at Kitt Peak and represent the last data set of single-filter speckle observations taken in the WIYN speckle program prior to the use of the current two-channel speckle camera. The astrometric and photometric precision of these observations is consistent with previous papers in this series: we obtain a typical linear measurement uncertainty of approximately 2.5 mas, and the magnitude differences reported have typical uncertainties in the range of mag. In combination with measures already in the literature, the data presented here permit the revision of the orbit of A 1634AB (= HIP 76041) and the first determination of visual orbital elements for HDS 1895 (= HIP 65982). Key words: binaries: visual techniques: high angular resolution techniques: interferometric techniques: photometric Online-only material: machine-readable and VO tables 1. INTRODUCTION Although long baseline optical interferometers and adaptive optics observations have contributed much to stellar astrophysics in the last decade, speckle imaging remains an important tool in high-resolution survey work, particularly in binary and multiple star observations. The advent of electron-multiplying CCD (EMCCD) detectors has been a particularly fortuitous development for speckle, giving the technique both reasonably good differential photometry and a fainter limiting magnitude than was possible with the previous generation of intensified cameras or normal CCD imagers. The improvement in limiting magnitude is especially important as it allows for studies of binaries farther down the main sequence as well as systems at larger distances. Since its inception in 1997, the WIYN speckle program has produced more than four thousand speckle measures of binary stars using three basic optics packages and four types of detectors. The current optics package, known as the Differential Speckle Survey Instrument (DSSI), is a two-channel instrument that can record speckle patterns in two colors simultaneously. This replaced the RIT-Yale Tip-Tilt Speckle Imager (RYTSI) in DSSI itself is described in (2009), and The WIYN Observatory is a joint facility of the University of Wisconsin Madison, Indiana University, Yale University, and the National Optical Astronomy Observatories. 6 Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation. 7 Adjunct Astronomer, Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA. 8 Current address: People s United Bank, 259 Bull Hill Lane, Orange, CT 06477, USA. 9 Current address: Department of Physics, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747, USA. subsequent observations have been presented in (2011a, 2011b). A description of the RYTSI optics is found in Meyer et al. (2006). Currently, DSSI is used with two Andor ixon EMCCD cameras. However, as DSSI was being finished and before the second EMCCD was purchased, there were four observing runs at WIYN: 2008 June and September, and 2009 June and October. On these runs, we experimented with three different configurations for speckle observing: the RYTSI speckle camera using the first EMCCD as the detector, DSSI in a single-channel mode using the first EMCCD as the detector, and DSSI in dual-channel mode with two large-format CCDs as the detectors. This last configuration is the same as described in the first reference above, but the use of the other two configurations has not been previously reported. However, the DSSI+1EMCCD observations are similar to the two-channel EMCCD mode reported in (2011a), except that the second detector port of the instrument was empty. None of the three configurations represents a data set large enough to determine the statistical properties of the photometry and astrometry obtained with as much precision as one would like. We have therefore decided to analyze all of these mixed configuration observations as one group. While one can anticipate that combining all three data sets in this way will result in slightly lower precision overall due to factors such as uncertainties in scale and detector orientation and differences in the filter center wavelengths, and other details of the filter transmission curves between the RYTSI and DSSI instruments, we judge this as the best way to provide reliable estimates of precision for this time period. 2. OBSERVATIONS AND DATA REDUCTION In all cases, observations were made at the WIYN 3.5 m Telescope at Kitt Peak National Observatory. The telescope 1

2 Table 1 Observing Dates and Instrument Configurations Run UT Dates Instrument Pixel Scale Offset Angle a Configuration (mas pixel 1 ) ( ) Jun RYTSI+1EMCCD ± ± Sep RYTSI+1EMCCD ± ± Jun DSSI+2CCDs ± b ± 0.35 b Jun DSSI+1EMCCD ± ± Oct 2 7 DSSI+1EMCCD ± ± 0.62 Notes. a Between pixel axes and celestial coordinates. b These values are correct for the DSSI side port. See the discussion in the text for more back port information. has two Nasmyth foci, one of which is reserved for the facility-class multi-object spectrograph (Hydra) and the other which is generally used for imaging and known as the WIYN port. As in our previous work, the speckle instrumentation was mounted to the WIYN port at f/6.28. The speckle optics package then magnified the image to a scale appropriate for high-resolution observations prior to imaging on the detector plane. Table 1 shows the observing runs and instrument configurations covered by the current paper as well as the pixel scales and detector orientation relative to celestial coordinates. For precise scale determination, we have a slit mask which can be mounted on the tertiary mirror baffle support structure. The distance from this point to the telescope focal plane has been determined to high precision by Kitt Peak staff, so that the spacing of the slits on the aperture plane can be determined. When the mask is in place and the telescope is pointed to an unresolved bright star, a pattern of interference fringes can be recorded. In the Fourier plane, these fringes map to well-defined spatial frequencies, which we measure using a least-squares fitting algorithm. By combining the final spatial frequencies with the known slit spacing, filter wavelength, and spectral type of the source, a value of the pixel scale was determined to about 0.2% 0.3% for each instrument configuration. There was no evidence for run-to-run variations in the scale or orientation for any of the instrument configurations used. The orientation of pixels relative to celestial coordinates is determined by taking short exposure images (typically 1 s) of a bright star, and then offsetting the telescope in various directions. As discussed in (2009), there is an apparent misalignment in the DSSI optics package, which has two small effects. The first is that the scale in the back port of the instrument is a function of position angle. This does not appear to affect the side port of the instrument at all, which may suggest that this is introduced by the dichroic beamsplitter, since the back port receives light reflected off this optical element. In any case, it is calibrated out by taking slit mask data at different angles of the WIYN port rotator and fitting those data to a sinusoidal curve. The second effect is that the pixel axes are tilted at approximately a 5 angle relative to celestial coordinates, a much larger value than with the earlier RYTSI optics package. This is most likely due to the fact that one of the galvanometer mirrors inside the DSSI sits on a spindle that has a slight tilt. The data reduction for binary star observations is the same as that documented in previous papers in this series and has four basic steps. (1) The average spatial frequency power spectrum of the speckle data frames is computed. (2) The same is done for a bright point source near in sky position and close in time to the binary star observation. (3) The binary power spectrum is divided by the point source power spectrum and masked based on an estimate of the signal-to-noise ratio of the observation. (4) Finally, a weighted least-squares fit is performed on the resulting function to match the data with a fringe pattern. The binary parameters (position angle, separation, and magnitude difference) are determined from the best-fit model. The typical observation consists of to 50 ms frames of the target, taking approximately 80 s to collect for the EMCCD and 200 s for the large-format CCD detectors. The difference in time is due almost entirely to readout time of the CCDs. This analysis leaves a 180 ambiguity in the position angle determination due to the symmetric nature of the functions involved; this is resolved by computing a diffraction-limited image using low-order subplanes of the image bispectrum (Lohmann et al. 1983). 3. RESULTS Table 2 contains our main body of results. Here, the columns give (1) the Washington Double Star (WDS) number (Mason et al. 2001), which also gives the right ascension and declination for the object in coordinates; (2) the Bright Star Catalogue (i.e., Harvard Revised [HR]) number, or if none the Aitken Double Star (ADS) Catalogue number, or if none the Henry Draper (HD) Catalogue number, or if none the Durchmusterung (DM) number of the object; (3) the Discoverer Designation; (4) the Hipparcos Catalogue number (ESA 1997); (5) the Besselian date of the observation; (6) the position angle (θ) of the secondary star relative to the primary, with north through east defining the positive sense of θ; (7) the separation of the two stars (ρ), in arcseconds; (8) the magnitude difference (Δm) of the pair; (9) center wavelength of the filter used; and (10) full width at half-maximum of the filter transmission in nanometers. Position angles have not been precessed from the dates shown and are left as determined by our analysis procedure, even if inconsistent with previous measures in the literature. Twenty-seven of the objects listed in Table 2 have no previous listing in the 4th Catalog of Interferometric Measures of Binary Stars (Hartkopf et al. 2001b); we suggest Discoverer Designations of YSC (Yale-Southern Connecticut) for these. Figure 1 shows the basic properties of the full data set; in Figure 1(a), we plot the magnitude difference obtained as a function of separation, and in Figure 1(b), we plot the magnitude difference as a function of system magnitude Astrometric Accuracy and Precision As in previous papers in this series, we have studied our astrometric accuracy and precision by (1) determining repeatability statistics for objects observed more than once on the same run and (2) studying the residuals of the observations in Table 2 when compared to ephemeris predictions for objects with highquality orbit determinations in the literature. Figure 2 shows the main results of the repeatability study. Here, the standard deviations of the position angle (θ) and separation (ρ) for the repeat observations are plotted as a function of average separation for each object. The average value of the standard deviation in separation was found to be 2.52 ± 0.38 mas. In position angle, the average standard deviation was found to be ± 0. 05, but this value is of course expected to be dependent on separation in the sense that smaller separations will have a larger angle uncertainty if the linear measurement uncertainty is constant. In our plots, the linear measurement uncertainty (as judged from the 2

3 Figure 1. (a) Magnitude difference as a function of separation for the full set of measures described in the text. (b) Magnitude difference as a function of system V magnitude for the same sample. In both plots, the open circles are measures obtained in the bluer filters in Table 2 (i.e., filters with center wavelengths less than 600 nm) and filled circles are measures obtained in redder filters (center wavelengths greater than 600 nm). Table 2 Double Star Speckle Measures WDS HR, ADS Discoverer HIP Date θ ρ Δm λ Δλ (α,δ J2000.0) HD, or DM Designation (2000+) ( ) ( ) (nm) (nm) HD 137 HDS HD 738 HDS ADS 148 BU 1026AB BD HDS HD 2057 HDS 56Aa,Ab HD 2174 HDS HR 101 HDS ADS 449 MCA 1Aa,Ab ADS 490 HO 212AB ADS 520 BU Notes. a Quadrant ambiguous. b Quadrant inconsistent with previous measures in the 4th Interferometric Catalog. c These measures were previously published in (2011b), but the incorrect plate scale was inadvertently applied. Therefore, the values here should replace those. d This measure was published in (2011a) as a non-detection; a reanalysis of this observation gives the values listed at low signal-to-noise ratio. e This measure was published in (2010) at a separation of arcsec; a reanalysis shows that result to have been in error. The values here should replace those. (This table is available in its entirety in machine-readable and Virtual Observatory (VO) forms in the online journal. A portion is shown here for guidance regarding its form and content.) separation coordinate) does appear to be reasonably flat across the range of separations considered here, and therefore, in our case, the angle uncertainty should be given by δθ = arctan (δρ/ρ) 0.14/ρ. (1) This curve is plotted in Figure 2(a) and appears to be consistent with our position angle results. In both plots, the vertical error bars are skewed; this is because the true distribution of the standard deviations is expected to follow this same form. The error bars represent the smallest interval containing 68.3% of the distribution or 1σ. More information on this topic is found in Mendenhall et al. (1990). However, it is important to distinguish between repeatability and true measurement accuracy and precision. The latter will include run-to-run variations in pixel scale and other longterm systematic sources of error. Therefore, wherever possible, we have compared our measures to orbital predictions. For the current study, we consider only Grade 1 or 2 orbits listed in the Sixth Orbit Catalog of Hartkopf et al. (2001a). We also require that the orbital elements have uncertainty estimates, which we can then use to compute uncertainties in the position angle and separation predictions for a given epoch of observation. Table 3 contains the objects and references to the orbits used for this purpose, and Figure 3 shows the residuals we obtain in position angle and separation when compared to results from 3

4 Figure 2. (a) Standard deviation in position angle for objects observed two or more times during the same observing run as a function of average separation. The dashed line is 0.14/ρ, where ρ is in arcseconds. This is the function expected for a linear measurement precision of 2.52 mas. (b) Standard deviation in separation for objects observed two or more times during the same observing run as a function of average separation. The dotted line is drawn at 2.52 mas, the average y-value obtained in the plot. In both plots, open circles indicate systems with two observations while filled circles indicate those with three or more observations. Figure 3. (a) Position angle residuals for objects with Grade 1 or 2 orbits in the Sixth Orbit Catalog. Open circles are those objects with predicted uncertainty <10. 0 and filled circles are those objects with predicted uncertainty <2. 0. The dotted curves indicate the expected uncertainty in θ given a linear measurement precision of 2.7 mas. (b) Separation residuals for objects with Grade 1 or 2 orbit in the Sixth Orbit Catalog. Open circles are those objects with predicted uncertainty <10.0 mas and filled circles are those objects with predicted uncertainty <4.0 mas. The dotted lines here are drawn at ±2.7 mas, the standard deviation of the residuals obtained for the latter objects. Table 3 Orbits Used for the Measurement Precision Study WDS Discoverer Designation HIP Grade Orbit Reference BU 1026AB Hartkopf et al. (1996) HDS Balega et al. (2006) STF 1728AB Muterspaugh et al. (2010) FIN (2011b) BU 612AB Mason et al. (1999) KUI 79AB Hartkopf et al. (1996) COU Hartkopf et al. (1996) A 88AB Hartkopf et al. (1989) A 417AB Hartkopf et al. (1996) MLR Hartkopf et al. (1996) A Docobo & Ling (2009) FIN Mason et al. (2010) A Mason (1997) Table 2. In Table 4, we give the average and standard deviation of residuals for two subsamples defined by the level of the derived uncertainty for each coordinate. In general, the values indicate that the accuracy of the measures is high, since there are no significant offsets in either coordinate, particularly with those orbits with the lowest uncertainties. In addition, the standard deviations decrease for the orbits of smaller uncertainty, indicating that the orbital elements themselves do contribute to 4

5 Figure 4. (a) Magnitude difference residuals as a function of seeing times separation (i.e., the parameter q described in the text). Giants, variables, and triple stars are not considered. Only observations in either the 562 nm or 550 nm filter are shown here. (b) ΔH p vs. the magnitude difference obtained in our observations for objects with uncertainties in ΔH p of less than 0.3 mag. In both plots, filled circles indicate those objects with uncertainties in ΔH p of less than 0.1 mag. Table 4 Measurement Precision Results Data Group Observed Number Average Standard Parameter of Meas. Residual Deviation Grade 1 and 2 with δθ 10 θ ± ± 0. 4 Grade 1 and 2 with δθ 2 θ ± ± 0. 1 Grade 1 and 2 with δρ 10 mas ρ ± 0.9mas 3.6 ± 0.7mas Grade 1 and 2 with δρ 4mas ρ ± 1.0mas 2.7 ± 0.7mas the overall error budget. For the best orbits, the standard deviations are comparable to the values obtained in the repeatability study; we conclude that the repeatability study represents the precision of our measures reasonably well and that there are no measurable systematic effects Photometric Accuracy and Precision We have found in previous studies that the accuracy of magnitude differences obtained with our instrumentation is determined by the degree of correlation between the primary star s speckle pattern and that of the secondary. We characterize this by forming the parameter q for a given observation, which is the seeing value times the separation of the components. Up to a scale factor, this parameter represents a ratio of the separation to the size of the isoplanatic patch, since the latter is inversely related to seeing. Many of the objects in Table 2 have magnitude differences listed in the Hipparcos Catalogue; these values are taken in the H p filter, which has peak transmission at approximately 450 nm and a full width at half-maximum of 221 nm. The transmission is however skewed to the red side of the peak transmission, so that the effective center wavelength is 505 nm. A significant amount of our data in Table 2 was taken in either a 550 or 562 nm filter, the closest matches we have to H p in wavelength. In Figure 4(a), we show the value of Δm ΔH p for these measures as a function of q. As we have seen in previous studies, the average value of this difference is near zero for small values of the q parameter, and systematically above zero for high values of q.thisis the expected signature of speckle decorrelation, since the loss of counts at the binary separation will lead to an overestimate of the speckle magnitude difference. We therefore do not state magnitude differences in Table 2 for observations where the q parameter is greater than 0.6 arcsec squared. After making this data cut to minimize systematic errors, the remaining ΔH p points should have a near-linear relation when plotted as a function of our magnitude difference measures. This is shown in Figure 4(b) (giants, stars indicated as variables in the Hipparcos Catalogue, and stars with B V>0.6 have been removed). In order to study the behavior of our magnitude differences further, we confine our attention to the subsample of data with Δm > 1 mag. We exclude Δm < 1 mag because at small values of Δm, scatter in the data may result in negative magnitude differences. Since observers (including ourselves) typically report such cases as a positive value of the magnitude difference with a quadrant flip, this can lead to a systematically high value in the magnitude difference near Δm = 0, unless one can establish the quadrants unambiguously, which is not generally the case. The mean of all Δm ΔH p values in this magnitude difference range is 0.02 ± 0.03, with a standard deviation of 0.15 ± The average uncertainty in ΔH p of the objects in the plot is 0.05 mag. In principle, these uncertainties should add with those of our photometry in quadrature when forming the residual; if we subtract the 0.05 in quadrature to estimate the uncertainty in our photometry alone, we obtain 0.14 mag, roughly consistent with previous papers in this series (e.g., 2010), but larger than our most recent results obtained with the DSSI ( 2011a). In this discussion, we are combining the data from two filters, 550 nm and 562 nm. Although these center wavelengths are not very different, we have previously seen that magnitude differences obtained in the 550 nm filter are slightly larger than those of Hipparcos leading to a slight positive offset in Δm ΔH p, while the 562 filter for similar data cuts has a value consistent with zero. Therefore, it may be that the filters are measurably different relative to the H p filter, and that this would increase the standard deviation slightly because 5

6 Figure 5. Standard deviation estimates in observed magnitude difference for cases of multiple observations of a target in the similar filter. Open circles are cases where two observations exist in a similar filter in Table 2, and small filled circles are cases where there are three or more observations. The curves are predictions in the uncertainty of the Δm based on the parameterization described in, e.g., (2004). The heavy solid curve represents a typical signal-to-noise ratio for WIYN, and the dotted curves are high and low signal-to-noise ratio curves. The large filled circles are the average of all observed data in the magnitude bins 0 1, 1 2, 2 3, and 3 4. of the combination of data from both filters. Nonetheless, we conclude that for the current data set, mixed though it is, there are no significant discrepancies from previous work in terms of the photometric accuracy and precision. We also can characterize the repeatability of our photometry by considering cases of two or more measures of the same object in the same filter. In previous work, we have shown that the standard deviation of the magnitude differences depends on the magnitude difference itself. At large values of Δm, there is a larger scatter of individual measures, which is easily understood as a loss of signal-to-noise ratio. However, on the small magnitude difference end, our measures have also exhibited an increase in σ (Δm), which we have understood as due to the power spectrum fitting procedure, where the Δm is determined from the depth of fringe minima in the Fourier plane. This is more fully discussed in, e.g., (2004). In Figure 5, we show the current data set together with predicted curves for σ (Δm) based on signal-to-noise ratio. The data here are very similar in terms of repeatability to previous WIYN data sets, indicating average internal precision of approximately 0.1 mag through most of the Δm range in the plot. As in Figure 2, we have drawn skewed error bars following Mendenhall et al. (1990). 4. ORBIT DETERMINATIONS FOR TWO OBJECTS We have used data in Table 2, combined with other data in the literature, to compute orbital elements for two systems, A 1634AB and HDS For both systems, we have applied the orbit code of MacKnight & Horch (2004). This code can either be used to determine values for all seven of the elements, or, if a spectroscopic solution is known, one can fix the values of P, T 0, e, and ω (which are common with the spectroscopic calculation). Uncertainties are estimated by adding random deviates to the separation and position angle values consistent with a given linear separation error; for the orbits presented here we use 3 mas as the typical linear measurement uncertainty of individual measures, a conservative value for our more than 10 years of data from WIYN and consistent with large-aperture speckle work by other observers over the years A 1634AB Recent measures by our own group (including the three in this paper) and by Docobo et al. (2010) have very large residuals when using the orbit of Hartkopf et al. (1989, hereafter HMF), suggesting that a tune-up is in order for this system. The data available in the 4th Interferometric Catalog date back to a 1921 measure of Merrill using the Mount Wilson stellar interferometer and include visual interferometry and phase grating interferometry in addition to a number of speckle measures. Since the system is a challenging one even for larger apertures, we chose to only include data from telescopes larger than 3 m in diameter, leaving twenty-nine measures that were used for our orbit calculation as well as five non-detections. After calculating a trial orbit, one measure showed particularly large residuals and so was thrown out before computing the final fit. This was the 2004 measure in (2006). It is not clear why this measure would have been problematic, though it does have an anomalously large magnitude difference compared to the other values in the 4th Interferometric Catalog and was just below the diffraction limit. The most likely explanation is that residual atmospheric dispersion was present in the observation, introducing systematic error to the result. The new orbital elements derived for this system are shown in Table 5, and residuals to both the HMF orbit and our own are shown in Table 6. It will be noted there that two of the five non-detections of this system should have been marginally resolvable at the time of observation, but we judge these as minor discrepancies that can be explained by the challenging magnitude difference of the pair when observing at the diffraction limit. Both the HMF orbit and our orbit are shown in Figure 6. 6

7 Table 5 Three Visual Orbits Object HIP P a i Ω T 0 e ω (yr) (mas) ( ) ( ) (yr) ( ) HDS (unconstrained) ±0.049 ±1.4 ±6.9 ±41 ±0.10 ±0.018 ±42 HDS (constrained) ±0.5 ±0.1 ±0.3 A 1634AB ±0.017 ±0.7 ±1.2 ±0.9 ±0.24 ±0.015 ±9. Table 6 Orbital Data and Residuals for A 1634AB HMF This Paper Date θ ρ Δθ Δρ Δθ Δρ Reference (Bess. Yr.) ( ) ( ) ( ) ( ) ( ) (mas) Merrill (1922) Blazit et al. (1977) McAlister (1978a) <0.035 [165.6] [38.8] [157.8] [29.4] a McAlister (1978b) <0.035 [143.4] [29.6] [124.9] [21.6] a Hartkopf & McAlister (1984) <0.030 [263.1] [27.9] [240.9] [29.5] a Hartkopf & McAlister (1984) <0.030 [234.4] [38.2] [221.8] [42.4] a Hartkopf & McAlister (1984) McAlister & Hendry (1982) McAlister et al. (1983) McAlister et al. (1983) Dudinov et al. (1986) McAlister et al. (1983) McAlister et al. (1984) Balega & Ryadchenko (1984) Bonneau et al. (1986) Balega & Balega (1985) McAlister et al. (1987a) Hartkopf et al. (2000) <0.038 [167.9] [40.2] [180.4] [45.7] a McAlister et al. (1987b) McAlister et al. (1987b) Balega et al. (1989) b McAlister et al. (1993) McAlister et al. (1989) McAlister et al. (1990) Hartkopf et al. (1994) Hartkopf et al. (1994) b (2008) b (2010) b (2010) b Docobo et al. (2010) This paper b This paper b This paper Notes. a The bracketed values in this row are the ephemeris values obtained from the orbital elements, indicating the expected position angle and separation for these non-detections. b The quadrant of this observation has been flipped here relative to that appearing in Table 2 or the literature to make a more sensible sequence in position angle prior to calculating the orbit. A 1634AB has a composite spectral type of A5V with magnitude difference approximately 2 mag at 550 nm. At solar metallicity, this would mean perhaps an A4 + F7 pair, and therefore masses of 2.2 and 1.3 M, using information in Schmidt-Kaler (1982). The revised Hipparcos parallax is 8.4 ± 0.77 mas (van Leeuwen 2007). From this parallax and our period and semimajor axis values, we obtain a total mass of 4.8 ± 1.3 M, higher than but marginally consistent with = 3.5 M. This is slightly lower than predicted by the HMF orbit, which has a lower a and lower P; them tot implied in that case is 5.1 ± 1.4 M HDS 1895 HDS 1895 = HIP is a somewhat metal-poor system, with [Fe/H] = 0.46 listed in the Geneva Copenhagen Catalog 7

8 Figure 6. (a) The orbit of HMF (1989) together with the astrometry shown in Table 6. Observations in 2007 (Docobo et al. 2010; 2010), 2009, and 2010 (this paper), drawn as filled circles, exhibit large residuals. (b) The orbit revision presented here together with the same data. Table 7 Orbital Data and Residuals for HDS 1895 Unconstrained Orbit Constrained Orbit Date θ ρ Δθ Δρ Δθ Δρ Reference (Bess. Yr.) ( ) ( ) ( ) (mas) ( ) (mas) <0.03 [210.1] [58.7] [229.7] [57.9] a B. D. Mason et al. (in preparation) Jao et al. (2009) <0.054 [309.6] [41.3] [293.3] [32.3] a Hartkopf & Mason (2009) (2011b) (2010) Tokovinin et al. (2010) Tokovinin et al. (2010) Tokovinin et al. (2010) This paper This paper This paper (2011a) Note. a The bracketed values in this row are the ephemeris values obtained from the orbital elements, indicating the expected position angle and separation for these non-detections. (Nordström et al. 2004; Holmberg et al. 2009). No mass ratio is listed there, but the system does have a single-lined spectroscopic orbit due to Torres et al. (2002). The composite spectrum is G9V, according to both the Hipparcos Catalogue and SIMBAD 10. In addition to the three points in Table 2, there are eight other data points appearing in the Fourth Interferometric Catalog, as well as two non-detections. Given the spectroscopic orbit, we have approached this system by calculating two different orbits, one as if the spectroscopic orbit did not exist and the other fixing the four orbital elements in common between the spectroscopic solution and the visual solution to be the values found in the spectroscopic orbit. We will refer to these as the unconstrained and constrained solutions, respectively. Orbital elements for both the unconstrained and constrained orbits are shown in Table 5, and residuals for both orbits are found in Table 7. Visual representations of the orbits are shown in Figure 7. In both cases, the Hipparcos data point has not been used. The orbital period is of the order of the Hipparcos mission, and so the Hipparcos value does not represent reliable 10 astrometry even in an average sense in this case. The period and time of periastron passage of the unconstrained solution are consistent with the spectroscopic elements of Torres et al. (2002), but the eccentricity of our orbit is lower than the Torres et al. value (0.558 ± versus ± 0.027). The spectroscopic value for ω is 1.27σ away from the unconstrained value, using our error bar. Together with the revised Hipparcos parallax of ± 2.01 mas (van Leeuwen 2007), this orbit gives a mass sum of 2.4 ± 0.5 M, which would seem to be slightly higher than expected given that the magnitude difference is approximately 1.5 at 550 nm. One might expect a G8+K4 pair in this case, which at solar metallicity would yield masses of M and 0.7 M, and therefore a total of M. At sub-solar metallicity, the result is expected to be somewhat smaller for the same spectral type. On the other hand, if one uses the constrained orbit to compute the total mass, a value of M tot = 1.9 ± 0.4 M is obtained, owing primarily to the smaller value of the semimajor axis. This is also high, but almost certainly within 2σ of the expected value of this system, even given the metallicity. To improve upon this situation, the real solution in our view would be a 8

9 Figure 7. Preliminary orbits for HDS (a) Unconstrained visual orbit. (b) Orbit obtained after fixing the elements available from the spectroscopic orbit of Torres et al. (2002). In both plots, the filled circles are those measures appearing in Table 2. simultaneous spectroscopic/visual orbit fit; however, without more astrometric data, the spectroscopic data would dominate such a fit and not be much more useful than the constrained orbit presented here. Therefore, the time for that will be in a few years when there is more relative astrometry data in the literature. In the meantime, we encourage other observers to obtain data on this system, for which purpose the constrained orbit here should serve well enough as a source of ephemeris positions. The two non-detections for this system are results of B. D. Mason et al. (in preparation) and Hartkopf & Mason (2009). The Hartkopf and Mason point would have been below the stated detection limit. However, both the unconstrained and constrained orbital elements predict that the Mason et al. point should have been resolvable with a separation of 59 mas, nearly double the stated resolution limit (30 mas). However, it is worth noting that the Mason et al. observation was quite close in time to the predicted periastron passage at which time our orbit predicts that the system would have a relative separation below 30 mas. So, this discrepancy could potentially be resolved with even a small revision of the time of periastron passage in the future, given the rapid change in separation at that point in the orbit. 5. CONCLUSIONS We have presented 531 speckle observations of binary stars taken during 2008 and 2009 at the WIYN Telescope at Kitt Peak. The astrometric and photometric data quality is consistent with previous papers in this series. Using our data on two systems together with other measures in the literature, we have revised orbital elements for A 1634AB and determined visual orbital elements of HDS 1895 for the first time. The period and other elements obtained in the latter case from the astrometry alone are reasonably consistent with the spectroscopic orbit obtained by Torres et al. (2002). It is a pleasure to thank all of the outstanding staff at WIYN for their continued assistance and support at the telescope, especially Bill Binkert, Karen Butler, Charles Corson, Jenny Power, Krissy Reetz, Dave Summers, and George Will. This work was funded by NSF Grant AST It made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory and the SIMBAD database, operated at CDS, Strasbourg, France. REFERENCES Balega, I. I., Balega, Y. Y., Hoffmann, K.-H., et al. 2006, A&A, 448, 703 Balega, I. I., Balega, Y. Y., & Vasyuk, V. A. 1989, Astrofiz. Issled. Izv. Spets. Ast. Obs., 28, 107 Balega, Y. Y., & Balega, I. I. 1985, Sov. Astron. Lett., 11, 47 Balega, Y. Y., & Ryadchenko, V. P. 1984, Sov. Astron. Lett., 10, 95 Blazit, A., Bonneau, D., Koechlin, L., & Labeyrie, A. 1977, ApJ, 214, L79 Bonneau, D., Balega, Y., Blazit, A., et al. 1986, A&AS, 65, 27 Docobo, J. A., & Ling, J. F. 2009, AJ, 138, 1159 Docobo, J. A., Tamazian, V. S., Balega, Y. Y., & Melikian, N. D. 2010, AJ, 140, 1078 Dudinov, V. N., Kuz menkov, S. G., Konichek, V. V., et al. 1986, SvA, 30, 359 ESA 1997, The Hipparcos and Tycho Catalogues (ESA SP 1200; Noordwijk: ESA) Hartkopf, W. I., & Mason, B. D. 2009, AJ, 138, 813 Hartkopf, W. I., Mason, B. D., & McAlister, H. A. 1996, AJ, 111, 370 Hartkopf, W. I., Mason, B. D., McAlister, H. A., et al. 2000, AJ, 199, 3084 Hartkopf, W. I., Mason, B. D., & Worley, C. E. 2001a, AJ, 122, 3472 Hartkopf, W. I., & McAlister, H. A. 1984, PASP, 96, 105 Hartkopf, W. I., McAlister, H. A., & Franz, O. G. 1989, AJ, 98, 1014 (HMF) Hartkopf, W. I., McAlister, H. A., & Mason, B. D. 2001b, AJ, 122, 3480 Hartkopf, W. I., McAlister, H. A., Mason, B. D., et al. 1994, AJ, 108, 2299 Holmberg, J., Nordström, B., & Andersen, J. 2009, A&A, 501, 941 Horch, E. P., Falta, D., Anderson, L. M., et al. 2010, AJ, 139, 205 Horch, E. P., Franz, O. G., & van Altena, W. F. 2006, AJ, 132, 2478 Horch, E. P., Gomez, S. C., Sherry, W. H., et al. 2011a, AJ, 141, 45 Horch, E. P., Meyer, R. D., & van Altena, W. F. 2004, AJ, 127, 1727 Horch, E. P., van Altena, W. F., Cyr, W. M., et al. 2008, AJ, 136, 312 Horch, E. P., van Altena, W. F., Howell, S. B., Sherry, W. H., & Ciardi, D. R. 2011b, AJ, 141, 180 Horch, E. P., Veillette, D. R., Baena Gallé, R., et al. 2009, AJ, 137, 5057 Jao, W.-C., Mason, B. D., Hartkopf, W. I., Henry, T. J., & Ramos, S. N. 2009, AJ, 137, 3800 Lohmann, A. W., Weigelt, G., & Wirnitzer, B. 1983, Appl. Opt., 22, 4028 MacKnight, M., & Horch, E. P. 2004, BAAS, 36, 788 Mason, B. D. 1997, AJ, 114, 808 Mason, B. D., Douglass, G. G., & Hartkopf, W. I. 1999, AJ, 117, 1890 Mason, B. D., Hartkopf, W. I., & Tokovinin, A. 2010, AJ, 140, 735 Mason, B. D., Wycoff, G. L., Hartkopf, W. I., Douglass, G. G., & Worley, C. E. 2001, AJ, 122, 3466 McAlister, H. A. 1978a, ApJ, 225, 932 McAlister, H. A. 1978b, PASP, 90, 288 McAlister, H. A., Hartkopf, W. I., & Franz, O. G. 1990, AJ, 99, 965 McAlister, H. A., Hartkopf, W. I., Hendry, E. M., Gaston, B. J., & Fekel, F. C. 1984, ApJS, 54, 251 9

10 McAlister, H. A., Hartkopf, W. I., Hutter, D. J., & Franz, O. G. 1987a, AJ, 93, 688 McAlister, H. A., Hartkopf, W. I., Hutter, D., Shara, M., & Franz, O. 1987b, AJ, 93, 183 McAlister, H. A., Hartkopf, W. I., Sowell, J. R., Dombrowski, E. G., & Franz, O. G. 1989, AJ, 97, 510 McAlister, H. A., & Hendry, E. M. 1982, ApJS, 49, 267 McAlister, H. A., Hendry, E. M., Hartkopf, W. I., Campbell, B. G., & Fekel, F. C. 1983, ApJS, 51, 309 McAlister, H. A., Mason, B. D., Hartkopf, W. I., & Shara, M. M. 1993, AJ, 106, 1639 Mendenhall, W., Wackerly, D. D., & Scheaffer, R. L. 1990, Mathematical Statistics with Applications (4th ed.; Boston, MA: PWS-Kent) Merrill, P. W. 1922, ApJ, 56, 40 Meyer, R. D., Horch, E. P., Ninkov, Z., van Altena, W. F., & Rothkopf, C. A. 2006, PASP, 118, 162 Muterspaugh, M. W., Hartkopf, W. I., Lane, B. F., et al. 2010, AJ, 140, 1623 Nordström, B., Mayor, M., Andersen, J., et al. 2004, A&A, 419, 989 Schmidt-Kaler, T. 1982, in Landolt-Börnstein New Series, Group 6, Vol. 2b, Stars and Star Clusters, ed. K. Schaefers & H.-H. Voigt (Berlin: Springer), 1 Tokovinin, A., Mason, B., & Hartkopf, W. 2010, AJ, 139, 743 Torres, G., Boden, A. F., Latham, D. W., Pan, W., & Stefanik, R. P. 2002, AJ, 124, 1716 van Leeuwen, F. 2007, A&A, 474,