SPECKLE INTERFEROMETRY AT THE U.S. NAVAL OBSERVATORY. XVIII

Table 1 presents coordinates and magnitude information from CDS² for four pairs which are measured here for the first time. All were observed as closer components to known systems or pairs in the same field of view. Column 1 gives the coordinates of the primary of the pair. Column 2 is the discoverer designation (where WSI = Washington Stellar Interferometer) number. Columns 3 and 4 give the visual magnitudes of the primary and secondary from Aladin for these pairs, and Column 5 notes the circumstance of the discovery. The mean double star positions (T, θ, and ρ) of these systems are given in Table 2.

Table 2 presents the mean relative position of the members of 1462 systems having no published orbital or rectilinear elements. The first two columns identify the system by providing its epoch-2000 coordinates and discovery designation. Columns 3 through 5 give the epoch of observation (expressed as a fractional Besselian year), the position angle (in degrees), and the separation (in seconds of arc). Note that the position angle has not been corrected for precession and is thus based on the equinox for the epoch of observation. Objects whose measures are of lower quality are indicated by colons following the position angle and separation. These lower-quality observations may be due to one or more of the following factors: close separation, large Δm, one or both components very faint, a large zenith distance, and poor seeing or transparency. They are included primarily due to either the confirming nature of the observation or the number of years since the last measured position. The sixth column indicates the number of independent measurements (i.e., observations obtained on different nights) contained in the mean, and the seventh column flags any notes. The 1462 measurements in Table 2 have a mean separation of 1491 and a median separation of 948.

The most common note indicators are either "C," indicating a confirming observation, or a number (N) indicating the number of years since the system was last measured. This is only given for systems with N ⩾ 50 years. Twenty-three systems are confirmed here. Since priority is given to both unconfirmed systems and to systems not observed recently, the time since the last observation can be surprisingly large; for the systems in Table 2 the average time since the last observation is 11 years (59 years for those measures of reduced accuracy). Twenty systems had not been observed in 50 years or more and twelve had not been observed for at least a century. The maximum such time span was 115 years for SEI1476, SEI1431, and SEI1428 (Scheiner 1908). The long delay in confirming these historic pairs was simply due to poor coordinates—most had only arcminute-precise published coordinates, precessed without proper motion correction from the original coarse epoch-1820 α and δ. Also included in Table 2 are seven measures from 2007. These pairs, originally slated for Mason et al. (2008), were very different from the historical measures and were withheld until those large differences could be verified.

Table 3 presents the mean relative positions for 131 systems with published orbital determinations or linear solutions. The first six columns are identical to the corresponding columns of Table 2. Columns 7 and 8 give O − C residuals (in θ and ρ) to the determination referenced in Column 9. The reference is either to a published orbit or linear calculation. Notes follow in Column 9. The objects in Table 3 tend to be more frequently observed than those in Table 2. Here mean and median separations of 1533 and 2066 are determined, with a mean time interval since the last observation of only 3.6 years. In nine cases, it is not possible to yet ascertain the preferred determination and additional residual lines are provided.

2.3.1. New Linear Elements

In her work as an intern in Summer 2011 one of us (E.A.F.) identified pairs which were possibly linear but for which current data were insufficient for accurate determination (see Friedman et al. 2011, 2012). These objects were flagged for observation and following this observing year additional data now allow these elements to be determined. Their apparent linear relative motions suggest that these pairs are either composed of physically unrelated stars or have very long orbital periods. Linear elements to these doubles are given in Table 4, where Columns 1 and 2 give the WDS and discoverer designations and Columns 3–9 list the seven linear elements: x₀ (zero point in x, in arcseconds), a_x (slope in x, in '' yr⁻¹), y₀ (zero point in y, in arcseconds), a_y (slope in y, in '' yr⁻¹), T₀ (time of closest apparent separation, in years), ρ₀ (closest apparent separation, in arcseconds), and θ₀ (position angle at T₀, in degrees). See Hartkopf & Mason (2011) for a description of all terms. Table 5 gives orbital ephemerides for each pair over the years 2010 through 2035, in five-year increments. Columns 1 and 2 are the same identifiers as in Table 4, while Columns 3 + 4, 5 + 6, etc., through 11 + 12 give predicted values of θ and ρ, respectively, for the years 2010.0, 2015.0, etc., through 2030.0. As an example of these, Figure 1 provides a plot of the new linear solution and data for WDS 00455+1232 = HJ 7. Micrometric observations are indicated by plus signs and asterisks and CCD measures by triangles. "O − C" lines connect each measure to its predicted position along the new linear fit (shown as a thick solid line). The dashed line indicates the time of closest apparent separation. The axis indicates the scale in arcseconds. Direction on the sky and the relative motion of the secondary is indicated at lower right.

Zoom In Zoom Out Reset image size

Table 4. New Rectilinear Elements

WDS	Discoverer	x0	ax	y0	ay	T0	ρ0	θ0
α, δ (2000)	Designation	('')	('' yr−1)	('')	('' yr−1)	(yr)	('')	(deg)
00403+2403	BU 1348 BC	0.790	−0.04503	10.383	0.0034	1316.133	10.413	175.65
00455+1232	HJ 7	2.098	−0.04809	−5.152	−0.0196	1518.825	5.563	22.15
01172+0201	HDO 45	31.333	0.00737	−9.727	0.0237	1234.805	32.808	72.75
01459+7142	HJ 1089 AB	9.221	−0.00644	12.413	0.0048	4708.359	15.463	143.39

Download table as:  ASCIITypeset image

Table 5. Linear Ephemerides

WDS	Discoverer	2010.0	2015.0	2020.0	2025.0	2030.0
α, δ (2000)	Designation	θ ρ	θ ρ	θ ρ	θ ρ	θ ρ
		(○) ('')	(○) ('')	(○) ('')	(○) ('')	(○) ('')
00403+2403	BU 1348 BC	247.3 33.103	247.4 33.189	247.4 33.275	247.5 33.361	247.5 33.446
00455+1232	HJ 7	304.4 26.205	304.4 26.307	304.3 26.408	304.3 26.510	304.2 26.611
01172+0201	HDO 45	103.2 38.071	103.3 38.096	103.4 38.121	103.4 38.146	103.5 38.172
01459+7142	HJ 1089 AB	89.0 26.581	89.0 26.568	89.0 26.555	89.0 26.542	89.0 26.529

Download table as:  ASCIITypeset image

Table 6 presents 13 systems which were observed but not detected. Possible reasons for non-detection include orbital or differential proper motion making the binary too close or too wide to resolve at the epoch of observation, a larger than expected Δm, incorrect pointing, and misprints and/or errors in the original reporting paper. It is hoped that reporting these will encourage other double star astronomers to either provide corrections to the USNO observations or to verify the lack of detection. Notes to some of these pairs, highlighting some possible reasons for non-detection, are appended to the table. In all cases, the position angle, separation, and magnitudes are from the discoverer of the pair.