NEAR-INFRARED (JHK) PHOTOMETRY OF 131 NORTHERN GALACTIC CLASSICAL CEPHEIDS

Andrew J. Monson; Michael J. Pierce

doi:10.1088/0067-0049/193/1/12

1. INTRODUCTION

In the past decade there have been major improvements constraining the fundamental cosmological parameters of the concordance model (Spergel et al. 2007; Komatsu et al. 2011) and there have been great strides in addressing and reducing the systematic and statistical errors in measurements of the Hubble Constant, H₀ (Freedman et al. 2009; Riess et al. 2009) on which the concordance model greatly depends. Currently, it is the near-infrared (NIR) Cepheid period–luminosity (PL) relation that is being used to determine distances to nearby galaxies which provide the link to farther galaxies in the Hubble flow containing Type Ia supernovae on which the determination of H₀ depends. The NIR PL relation yields less dispersion and fewer systematic errors than the optical PL relation (Madore & Freedman 1991). This has been dramatically shown to be the case for Cepheids in the Large Magellanic Cloud (LMC; Persson et al. 2004) and similarly for a sample of Galactic Cepheids for which NIR photometry currently exist (Fouqué et al. 2007; Gieren et al. 1998).

The uncertainty of the LMC distance and slope of the LMC PL relation are the largest contributors to the total uncertainty in H₀. Despite having an ensemble of distance measurements and a statistical distance uncertainty of less than 5% (Gibson 2000; Freedman et al. 2001), the LMC PL relation is not definitive because the LMC has significantly lower metal abundance than those more luminous galaxies that it is subsequently used to calibrate. On the other hand, the Galactic NIR PL relation would be better suited to calibrate the PL relation. However, due to a small sample size and the uncertainties in the individual distances and extinctions to each Galactic Cepheid, the Galactic NIR PL relation currently has higher dispersion than the LMC NIR PL relation.

One method to reduce the systematic errors on H₀ is to measure Cepheid NIR PL distances to Tully–Fisher/Type Ia calibrating galaxies independent of the LMC. This requires an alternate template PL relation. Riess et al. (2009), using the Hubble Space Telescope (HST) NIR H band, observed Cepheids in the maser galaxy NGC 4258 which has an independent geometrical distance uncertainty of ∼3% (see Riess et al. 2009, and references therein) and has the added benefit of having comparable metal abundance and crowding effects as the calibrating galaxies. Another alternative is to use the Galactic NIR PL relation which offers the possibility of a larger calibrating sample size as more parallaxes become available. The Galactic Cepheids have similar metal abundance to the Tully–Fisher and Type Ia calibrators but require an a priori knowledge of the distance and line-of-sight extinction to each Cepheid. This approach will soon receive a promising reprieve provided by the Global Astrometric Interferometer for Astrophysics (GAIA) astrometric mission, which should obtain high-precision parallaxes to hundreds of Galactic Cepheids. In this scenario, NIR measurements of additional Cepheids will provide the means to statistically reinforce the Galactic NIR PL relation; this was the motivation for this survey.

2. RESEARCH TO DATE

Near-infrared observations of Cepheids have several advantages over the optical; however, to date, NIR observations of Galactic Cepheids are limited mostly to the studies performed by Welch et al. (1984), Laney & Stobie (1992), and Barnes et al. (1997), hereafter collectively referred to as WLB. When combined and limited to known Fundamental Mode Galactic Cepheids (FMGCs), these studies result in a sample of 64 stars. Other Galactic Cepheid studies in the NIR include the work of McGonegal et al. (1982) and Schechter et al. (1992); however these studies were limited to less than five observations per Cepheid and large surveys like Two Micron All Sky Survey (2MASS; Skrutskie et al. 2006) contain even fewer epochs. These measurements often contain too few data to measure an accurate average intensity and were in many cases superseded by the WLB data. Template fitting (Soszynski et al. 2005) is one way to estimate mean magnitudes from sparsely sampled NIR data. A drawback to template fitting is that it requires greater effort and leads to larger uncertainties compared to the direct measurements from well-sampled NIR light curves.

Constructing the Galactic PL relation requires information about the distance and extinction to each Cepheid in the Galactic sample. Fouqué et al. (2007) has compiled the distances to 59 Galactic Cepheids which have NIR data available from the WLB sample. The reddening and distance measurements were compiled from a variety of methods which include: HST parallax measurements (Benedict et al. 2007), revised Hipparcos parallaxes (van Leeuwen et al. 2007), Cepheids in clusters (Turner & Burke 2002), interferometric Baade–Wesselink parallaxes (Lane et al. 2002; Kervella et al. 2004; Mérand et al. 2005), and Barnes–Evans (BE; Barnes et al. 1976) infrared surface brightness (IRSB) parallaxes (Barnes et al. 2005). The latter method makes use of NIR photometry and radial velocity curves to estimate the radii and distances to Cepheids.

Future missions like the GAIA will measure the parallaxes of Galactic Cepheids with superior accuracy and better precision (Lindegren 2005) than ever before. It should therefore be possible for GAIA to obtain unprecedented parallaxes to hundreds of known Galactic Cepheids. With such a large sample of high-precision distances to Galactic Cepheids the major source of uncertainty in the Galactic Cepheid PL relation will be the photometric mean apparent magnitudes derived from their light curves and uncertainties in the line-of-sight extinction.

With the prospect of obtaining Galactic Cepheid parallaxes from GAIA and the advantages of observing in the NIR, calibrating the best possible Galactic PL relation requires additional well-sampled light curves in the NIR of Galactic Cepheids. In this work, we present the mean magnitudes for 131 Northern Galactic Cepheids with the goal of providing a large homogenous sample of accurate mean magnitudes derived from the well-sampled light curves of Galactic Cepheids. When combined with existing data from WLB a set of 186 Galactic Cepheids with full-phase NIR measurements may be used to calibrate the Galactic NIR Cepheid PL relation once distances to these Galactic Cepheids become available.

3. OBSERVATIONS

All observations were obtained during a 10 month span in 2008 at the University of Wyoming Red Buttes Observatory (RBO). Cepheids were observed in 129 fields with the 0.6 m telescope using BIRCAM, a near-infrared imaging camera with a 13 arcmin field of view (Monson & Pierce 2009). The survey was restricted to Fundamental Mode Cepheids in order to avoid contaminating the NIR PL relation with higher-order Cepheid pulsation modes. Figure 1 shows an example of one of the fields observed in this survey.

**Figure 1.**
Finding chart for stars in the SZ AQL field. Numbered objects are presented in Table 2. The finding charts of the other fields are available in the online version. (The complete figure set (129 images) is available in the online journal.)
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3.1. Survey Sample

The sample was chosen from a catalog of 324 FMGCs compiled by Tammann et al. (2003). Stars below a declination of −20° were removed from the sample. The remaining sample was chosen based on brightness, target visibility, and availability. As the survey progressed, fainter stars were rejected in lieu of obtaining well-sampled phase points for stars already included in the sample. The phase of each Cepheid was computed in real-time proceeding and during each night of observing. A spreadsheet was used to graphically illustrate both the real-time phase of each Cepheid as well as the sampling to date. This allowed us to optimize the phase coverage of each variable and minimize any duplication of phase sampling.

A handful of bright Classical Cepheids (i.e., delta CEP) are too bright and were removed from the sample, while a small number of moderately bright Classical Cepheids (i.e., RT AUR) were observed by taking images out of focus. The cluster Cepheids CEa and CEb CAS have an apparent separation of 2 farcs 5 and were observed in the same field as CF CAS, however CEa and CEb CAS were not individually resolved by BIRCAM, thus their light curves are superimposed on each other. The photometric measurements for CEa + CEb CAS is provided in the online data, but no attempt has been made to decouple the individual light curves and no average magnitudes are reported for these two Cepheids.

3.2. Observing Strategy

Each Cepheid was observed an average of 22 epochs in the J, H, and K filters. The exposure times varied for each Cepheid based on the Cepheid brightness and the sky background. Because BIRCAM used the (full) K filter, the background was higher and more variable with ambient temperature making the K data noisier than the J. Each observation consisted of a sequence of J, H, and K filtered observations with no fewer than five dithered offsets in each band. As a sequence commenced the next priority target was queued based on visibility and phase priority, as described above, in order to maximize the efficiency of the survey.

At least five measurements were made of standard stars throughout each night to judge quality and calibrate the data. Standards were chosen on the CIT system (Elias et al. 1982) due to available brightness and sky coverage. Sky flats were taken at dusk and dawn when possible, and archival flats were used for partially clear nights. K-band flats were made by differencing sky flats of equal exposure time taken at different ambient temperatures (midnight versus dawn). The difference removed internal thermal scattered light within BIRCAM and left a more uniform sky component for the K-band flat field.

The data were reduced using a pipeline which aligned and co-added individual flat-fielded frames using the IRAF task "XDIMSUM." This task was used to apply a bad-pixel mask for the detector and to perform a background subtraction for each image. Point sources were identified in each image using SExtractor 2.5.0 (Bertin & Arnouts 1996) and astrometric coordinates were found for each object by correlating the sources found to the 2MASS point source catalog (Cutri et al. 2003) using the wcstools 3.7.2 package³ (Mink 2002), more details can be found in Monson (2009).

4. PHOTOMETRIC CALIBRATION

4.1. Aperture Photometry

The BIRCAM images are not perfectly free from aberrations across the field and some Cepheids were observed out of focus; for these reasons, aperture photometry was used to measure stellar fluxes in each field. The raw photometric data were calibrated to the CTIO/CIT system using nightly Elias standards (Elias et al. 1982). The standard star fields are generally free of crowding and an aperture radius of 19 arcsec was used for all standard star measurements since this aperture was large enough to measure essentially all the flux from the standard star. For comparison the average seeing at RBO with BIRCAM was 3–4 arcsec. The photometric parameters for the 88 nights of this survey can be found in Monson (2009). The average rms of the nightly photometric solutions was 0.012, 0.011, and 0.015 for J, H, and K, respectively. These represent the average (systematic/external) uncertainties for each Cepheid observation. The more crowded Cepheid fields required a smaller, default aperture of 7.6 arcsec. This aperture was chosen since in the majority of the fields observed it avoided contamination from nearby stars and it was effective at reducing noise from excess background. An aperture correction was applied based on curve of growth analyses for each frame to correct the aperture photometry to the aperture used for the standard star observations, namely, a radius of 19''. For a small number of very crowded fields, an aperture of 3.8 arcsec was used; again with an aperture correction. There were eight bright Cepheids that were taken out of focus to observe, and an aperture of 26.6 arcsec was used to wholly measure the flux, and thus no aperture correction was applied to these stars.

4.2. Ensemble Photometry

The multi-epoch data for each field were analyzed using the DAOMATCH and DAOMASTER programs provided by P. Stetson (2008, private communication). These routines were used to determine and apply zero-point offsets in each frame based on ensemble photometry of the field stars. Typically, for ensemble photometry of a single field all the frames are referenced to a master frame chosen by some figure of merit. Here, to place all the fields on the same homogeneous photometric system, instead of offsetting all the frames for a field to a single calibrated frame of that field, all offsets were referenced to the average of the calibrated frames of that field. In this way, we attempted to reduce the risk of picking a single discrepant epoch.

Ensemble photometry works by adding offsets which minimize the scatter of as many sources as possible while weighting sources by their brightness. In cases where there are only a few stable field stars, a second iteration of DAOMASTER was necessary where the known Cepheid and other variable star data were flagged by making their magnitude errors artificially high. This effectively removed their variability from the analysis so a stable realistic solution could be found. In some cases it took multiple passes to find and remove all the new variables found; see Section 5.3.

To empirically estimate the (random/internal) photometric error in an individual Cepheid observation, the ensemble variance of field stars was used. This was done since it was not known how reliable the predicted photometric uncertainties were given the effects of crowding and background variability; especially in the K band. Figure 2 shows the photometric error estimates for stars in the SZ AQL field at all observed epochs as well as the final ensemble uncertainty. The latter was fit with the analytic function corresponding to background-limited photometry: σ = a₀ + a₁log(x), in order to provide an empirical estimate of the photometric uncertainty for each Cepheid observation given its measured apparent magnitude. In this fashion, we were able to use empirical data to quantify the internal calibration errors which as can be seen in the figure are in good agreement with the estimated photometric uncertainties for field stars. The final error for each photometric measurement is taken as this (internal) empirical measurement added in quadrature with the average (external) rms of the photometric solutions.

**Figure 2.** Magnitude errors for stars in the field of SZ AQL. The left panels show the calibrated photometric uncertainties for J, H, and K (bottom to top) for all epochs observed. The right panels show the variance of the stars after ensemble photometry has been performed. The variance has been scaled by the root of the number of observations to match more closely the single epoch data. The solid line is a fit to the ccd equation and is used to predict the random error associated with the Cepheid at each epoch, given its apparent magnitude (see the text).
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4.3. Cepheid Light Curves

The light curves for each Cepheid were constructed using the period and epoch of maximum light found in the General Catalog of Variable Stars (GCVS; Samus et al. 2009). In some instances, like SZ AQL, a new period was determined using current and WLB data which provide a long enough baseline to constrain the period. The light curves were interpolated at 50 evenly spaced points using the Gaussian Local Estimation (GLOESS) program provided by B. Madore & C. Burns (2008, private communication). The program interpolates between the data points by fitting a second-order polynomial to the data Gaussian weighted by distance from the fit point. The intensity-weighted mean magnitudes were then calculated from the interpolated light curve. Since the light curves are well sampled, the overall shapes are well constrained and the resulting average should be relatively unaffected by the sampling details. To estimate the random error in the GLOESS interpolation and averaging algorithm, a Monte Carlo analysis was performed.

A simulated light curve was constructed as a sine function with a peak-to-peak amplitude of 0.3 mag. Random phases were selected at uniform probability and the sine function sampled. A random, Gaussian distributed, magnitude error was added to each sampled point according to the ccd equation resulting in a simulated light curve with sampling similar to our survey. The light curve was then input into the GLOESS program and the intensity-weighted average magnitude produced. One hundred simulations run at each magnitude/epoch combination and the results compared with the input sine function. The rms is shown in Figure 3, plotted against the photometric uncertainty of the simulated data. The data are plotted for samples of multiple fit points and were fit by the equation: rms = aσn⁻¹ + bσ + cn⁻², where σ is the photometric uncertainty of the data, n is the number of points used in the fit, and a, b, and c are the coefficients with the values 2.166 ± 0.022, 0.090 ± 0.001, and 0.145 ± 0.005, respectively. For the typical sampling in our survey, the averaging error should be less than 0.005 mag. Although the J-band light curves are not well fit by a simple sine function, we believe this will have a negligible effect given that predicted averaging errors are so small and given that our light curves are relatively well sampled. In any event, the model should be fine for the H- and K-band data. The estimated averaging errors were scaled by the amplitude of each light curve.

**Figure 3.** GLOESS interpolation and averaging error estimates as a function of photometric uncertainty. From top to bottom the groups of data represent the sample size used to compute the mean: 8, 12, 16, 20, 24, 28, and 32 fit points. The solid lines are the fit to the equation in the text and the filled pentagon is the average parameter space filled by this survey. The expected error from fitting and averaging is well less than 0.005 mag.
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5. FINAL RESULTS

5.1. Comparison with Previous Surveys

The field star photometry was compared to the 2MASS catalog to derive the photometric transformation equations between these two systems; see Figure 4. There is a slight difference from the classic CIT to 2MASS equations found in Carpenter (2001).⁴ In the classic CIT equations, there were however only four Elias Standard stars available with colors redder than (J − K) ∼ 1.2 and (J − H) ∼ 0.9 that could be used to derive those relations. Two of them are in the Southern Hemisphere (in the Coal Sack) and were inaccessible for this survey and the other two are carbon stars with very few observations (Elias et al. 1983, and references therein). As can be seen in Figure 4, the current sample extends farther to the red and may offer a alternative solution for highly reddened sources.

**Figure 4.** Transformations and residuals between the current and 2MASS photometric systems. The classic CIT to 2MASS transformation is shown as a dashed line and the current fit is shown as a solid line. The departure from the classic fit in the (J − H) data is discussed in the text.
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The photometric residuals versus color in this study versus the 2MASS catalogs show a dispersion of ≲5%. Our transformations between the CIT system and the 2MASS system are given in Table 1. All photometry presented in this work is reported on the current internal system, which although calibrated to be on the CIT system may be slightly variant (⩽2%) at colors redder than (J − H) ∼ 1 due to a systematic color response from using Elias standards bluer than (J − H) ∼ 1. With the exception of a few phase points for some long-period Cepheids none of the observed Cepheid colors exceeded a (J − H) ∼ 1.

Table 1. Transformation Equations between the 2MASS Photometric System and the CIT and the BIRCAM System

	CIT^a		BIRCAM
Equation	m	b	m	b
Ks_2MASS = K + m(J − K) + b	0.001 ± 0.005	−0.019 ± 0.004	0.008 ± 0.002	−0.042 ± 0.003
(J − H)_2MASS = m(J − H) + b	1.087 ± 0.013	−0.047 ± 0.007	1.050 ± 0.002	−0.038 ± 0.001
(J − Ks)_2MASS = m(J − K) + b	1.068 ± 0.009	−0.020 ± 0.007	1.052 ± 0.002	−0.002 ± 0.001
(H − Ks)_2MASS = m(H − K) + b	1.000 ± 0.023	0.034 ± 0.006	0.993 ± 0.008	0.050 ± 0.001

Notes. ^aCarpenter (2001), updated values obtained from: http://www.astro.caltech.edu/~jmc/2mass/v3/transformations/.

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When previous data from WLB exist for a Cepheid, the residual intensity-weighted mean magnitude compared to the current value was found. In the case of the Barnes et al. (1997) data, mean magnitudes were not available from the original source so the GLOESS algorithm was used to determine the means from the original data. In the case of the Laney & Stobie (1992) data which are on the SAAO system, the data were converted to the CIT system using the transformations from Carter (1990). The residuals between the multiple survey data are shown in Figure 5 and show that there is close agreement between the four surveys within ∼1%. The scatter between these surveys is 0.018, 0.014, and 0.014 at J, H, and K, respectively which if regarded as the sum of calibration errors between the surveys is in good agreement with the calibration errors noted in Section 4.1. The scatter between this and the WLB studies is then a good external measure of the total error in the mean magnitudes and confirms the error estimates used in our sample. The J, H, and K light curves are presented in Figure 6 along with (J − H) and (H − K) color curves. The plots are ordered in increasing period and are on the same scale to emphasize relative changes in shape.

**Figure 5.** Residuals of WLB data compared to the current data for Cepheids in common. The average offsets are shown with the rms scatter. There may be a small systematic offset on the order of 1% in photometry (0.5% in distance), no correction is applied however. If half the rms scatter is attributed to each survey's photometric calibration, then it roughly confirms the photometric calibration errors discussed in Section 4.1.
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Figure 6. — Download figure:
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The light curves are similar to the results found in other surveys in the NIR for Cepheids (Welch et al. 1984; Laney & Stobie 1992; Barnes et al. 1997; Persson et al. 2004). In particular, the H − K color curve is nearly constant through the cycle indicating insensitivity to temperature variations. This feature may provide a method to estimate line-of-sight extinction to each Cepheid. This is a topic of greater discussion in our second paper.

5.2. Photometric Data Summary

The field star photometry is provided in Table 2 which contains 1481 well-observed field stars, 131 Cepheids, and 92 other variables; 82 of which are likely new discoveries. The data include: field identification number, right ascension, and declination (J2000) as adopted from the 2MASS catalog (Cutri et al. 2003), the average J, H, and K magnitudes with internal uncertainty estimates, and the number of observations. Finding charts are provided in Figure 1; the full table and set of charts are available online.⁵ The photometric observations for SZ AQL are given in Table 3; the entire sample is available online as previously noted. The data consist of the name, heliocentric julian date (HJD) of the midpoints of the observing sequence, and corresponding phase relative to maximum light provided in the GCVS. The data provided are the J, H, and K magnitudes on the current system with uncertainties determined from the calibration error and from field star stability; see Section 4. A data flag is also provided indicating that none or some of the data points were rejected when interpolating the light curve. The flag ranges from (0–7) which indicates the data point(s) omitted: 0 = None, 1 = J, 2 = H, 3 = J & H, 4 = K, 5 = J & K, 6 = H & K, and 7 = J, H & K.

Table 2. Photometric Data for Stars in the SZ AQL Field

ID	R.A. (J2000)	Decl. (J2000)	〈J〉 ± σ_J^a	〈H〉 ± σ_H^a	〈K〉 ± σ_K^a	n_obs	(JHK)_2MASS^b	Note
1 SZ AQL	19:04:39.43	+01:18:22.0	5.839 ± 0.018	5.325 ± 0.016	5.158 ± 0.015	24 24 24	5.735 5.333 5.139	Ceph SZ AQL
2 SZ AQL	19:04:39.56	+01:22:18.0	6.999 ± 0.096	5.874 ± 0.101	5.075 ± 0.088	24 24 24	7.140 5.935 5.246	Var V1561 AQL
3 SZ AQL	19:04:50.99	+01:20:27.2	7.610 ± 0.003	6.362 ± 0.005	5.814 ± 0.013	24 24 24	7.635 6.400 5.795
4 SZ AQL	19:04:55.82	+01:21:29.6	8.311 ± 0.107	6.707 ± 0.091	5.539 ± 0.069	24 24 24	8.649 6.970 5.863	Var V1569 AQL
5 SZ AQL	19:04:48.21	+01:15:17.1	8.254 ± 0.009	7.061 ± 0.007	6.642 ± 0.010	24 24 24	8.261 7.085 6.533
6 SZ AQL	19:04:49.64	+01:18:11.2	8.506 ± 0.013	7.262 ± 0.003	6.778 ± 0.004	24 24 24	8.575 7.289 6.691
7 SZ AQL	19:05:01.08	+01:13:54.9	8.243 ± 0.006	7.554 ± 0.005	7.382 ± 0.014	22 22 22	8.237 7.578 7.404
8 SZ AQL	19:04:28.73	+01:19:43.3	8.831 ± 0.007	7.573 ± 0.006	7.127 ± 0.013	24 24 24	8.941 7.645 7.110
9 SZ AQL	19:05:04.61	+01:16:03.5	8.049 ± 0.075	6.905 ± 0.075	6.148 ± 0.087	18 18 18	9.002 7.829 7.019	Var V1570 AQL
10 SZ AQL	19:04:31.87	+01:20:15.5	8.155 ± 0.095	7.721 ± 0.092	7.065 ± 0.089	24 24 24	9.041 7.739 7.045	Unclassified variable
11 SZ AQL	19:04:46.60	+01:21:27.8	7.916 ± 0.004	7.802 ± 0.004	7.696 ± 0.010	24 24 24	7.877 7.797 7.744	HD 177462
15 SZ AQL	19:04:48.38	+01:19:46.6	9.419 ± 0.010	8.221 ± 0.003	7.750 ± 0.009	24 24 24	9.472 8.223 7.721
18 SZ AQL	19:04:35.93	+01:20:25.2	9.846 ± 0.009	8.511 ± 0.009	8.020 ± 0.008	24 24 24	9.911 8.530 7.979
20 SZ AQL	19:05:00.46	+01:17:10.6	10.023 ± 0.016	8.879 ± 0.005	8.506 ± 0.011	24 24 24	10.131 8.989 8.554

Notes. Right ascension and declination are adopted from the 2MASS point source catalog; see the text. The data for all fields are available online; see the text. ^aJ, H, and K photometric uncertainty determined from the data ( $\frac{\rm {\rm {rms}}}{ \sqrt{{n_{\rm obs}}} }$ ). ^bCutri et al. (2003).

Only a portion of this table is shown here to demonstrate its form and content. A machine-readable version of the full table is available.

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Table 3. Photometric Observations of SZ AQL

ID	HJD^a	Phase^b	J ± σ_J^c	H ± σ_H^c	K ± σ_K^c
SZ AQL	2454574.919	0.31	5.676 ± 0.013	5.185 ± 0.012	5.006 ± 0.016
SZ AQL	2454577.912	0.48	5.739 ± 0.013	5.209 ± 0.012	4.980 ± 0.016
SZ AQL	2454579.969	0.60	5.836 ± 0.013	5.253 ± 0.012	5.090 ± 0.016
SZ AQL	2454584.920	0.89	6.072 ± 0.013	5.523 ± 0.012	5.355 ± 0.016
SZ AQL	2454585.919	0.95	6.058 ± 0.013	5.568 ± 0.012	5.361 ± 0.016
SZ AQL	2454586.886	0.00	6.070 ± 0.013	5.565 ± 0.012	5.362 ± 0.016
SZ AQL	2454611.902	0.46	5.735 ± 0.013	5.180 ± 0.012	4.971 ± 0.016
SZ AQL	2454627.869	0.40	5.670 ± 0.013	5.153 ± 0.012	4.994 ± 0.016
SZ AQL	2454629.798	0.51	5.746 ± 0.013	5.185 ± 0.012	5.018 ± 0.016
SZ AQL	2454639.727	0.09	5.741 ± 0.013	5.363 ± 0.012	5.231 ± 0.016
SZ AQL	2454641.850	0.21	5.750 ± 0.013	5.295 ± 0.012	5.156 ± 0.016
SZ AQL	2454641.900	0.21	5.754 ± 0.013	5.300 ± 0.012	5.192 ± 0.016
SZ AQL	2454643.964	0.33	5.718 ± 0.013	5.195 ± 0.012	5.074 ± 0.016
SZ AQL	2454667.738	0.72	5.970 ± 0.013	5.352 ± 0.012	5.230 ± 0.016
SZ AQL	2454726.659	0.16	5.717 ± 0.013	5.319 ± 0.012	5.154 ± 0.016
SZ AQL	2454734.664	0.63	5.856 ± 0.013	5.266 ± 0.012	5.117 ± 0.016
SZ AQL	2454735.654	0.68	5.898 ± 0.013	5.311 ± 0.012	5.156 ± 0.016
SZ AQL	2454737.619	0.80	6.033 ± 0.013	5.439 ± 0.012	5.248 ± 0.016
SZ AQL	2454739.590	0.91	6.038 ± 0.013	5.526 ± 0.012	5.367 ± 0.016
SZ AQL	2454740.614	0.97	6.060 ± 0.013	5.543 ± 0.012	5.383 ± 0.016
SZ AQL	2454755.576	0.85	6.056 ± 0.013	5.479 ± 0.012	5.291 ± 0.016
SZ AQL	2454757.608	0.96	6.049 ± 0.013	5.548 ± 0.012	5.295 ± 0.016
SZ AQL	2454762.556	0.25	5.687 ± 0.013	5.288 ± 0.012	5.060 ± 0.016
SZ AQL	2454767.577	0.55	5.787 ± 0.013	5.224 ± 0.012	5.034 ± 0.016

Notes. ^aHeliocentric Julian Date at mid-point of observing sequence. ^bIn most cases the light curve phase was computed from the HJD of the observation and the epoch of maximum light reported in the GCVS. In some cases like SZ AQL a new period was determined by using the multi-epoch data from this and the WLB studies. ^cJ, H, and K photometric uncertainty estimate includes the photometric calibration error and the rms scatter of the local standard stars in the field (see the text). ^dPhotometric flags indicate which, if any, observations were rejected from the light curve construction: 0 = None, 1 = J, 2 = H, 3 = J&H, 4 = K, 5 = J&K, 6 = H&K, and 7 = J, H&K.

Only a portion of this table is shown here to demonstrate its form and content. A machine-readable version of the full table is available.

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The photometric means for the 131 Classical Fundamental Mode Cepheids analyzed in this survey are summarized in Table 4 and also available online as previously noted. The table includes the Cepheid name and the R.A. and decl. (J2000) adopted from the 2MASS catalog (Cutri et al. 2003). The table is sorted by increasing period and includes: the intensity-weighted mean J, H, and K magnitudes along with uncertainty estimates which comprise the photometric calibration error and the GLOESS averaging error. The expected random error from the Monte Carlo simulations is small compared to the total final errors adopted here which indicates that the dominate source of error arises from the absolute photometric calibration.

Table 4. Final Summary of Observed Cepheids and their Observed NIR Magnitudes

ID	R.A. (J2000)	Decl. (J2000)	log P	〈J〉	〈H〉	〈K〉	n_obs
S VUL	19:48:23.80	+27:17:11.4	1.8385	5.410 ± 0.012	4.806 ± 0.011	4.586 ± 0.015	34
GY SGE	19:35:13.64	+19:12:08.6	1.7138	5.530 ± 0.012	4.827 ± 0.011	4.546 ± 0.015	36
V1467 CYG	20:04:02.17	+32:27:02.4	1.6866	8.150 ± 0.013	7.278 ± 0.012	6.961 ± 0.016	26
SV VUL	19:51:30.90	+27:27:36.8	1.6553	4.552 ± 0.012	4.051 ± 0.011	3.905 ± 0.016	32
V0396 CYG	20:16:12.67	+42:06:31.5	1.5218	6.031 ± 0.012	5.037 ± 0.011	4.619 ± 0.016	27
V0609 CYG	21:26:56.03	+54:29:29.2	1.4924	6.800 ± 0.013	6.108 ± 0.012	5.817 ± 0.016	20
T MON	06:25:13.00	+07:05:08.4	1.4319	4.077 ± 0.014	3.610 ± 0.012	3.496 ± 0.017	17
OT PER	04:38:37.93	+47:44:24.9	1.4165	8.712 ± 0.013	7.899 ± 0.012	7.598 ± 0.016	22
BM PER	04:29:39.40	+48:25:19.1	1.3608	6.656 ± 0.013	5.991 ± 0.012	5.741 ± 0.016	26
WZ SGR	18:16:59.71	−19:04:32.9	1.3394	5.258 ± 0.013	4.740 ± 0.012	4.573 ± 0.016	22
VX CYG	20:57:20.82	+40:10:38.9	1.3039	6.689 ± 0.012	6.065 ± 0.011	5.875 ± 0.016	24
KX CYG	20:24:19.34	+40:33:40.0	1.3020	6.838 ± 0.013	5.980 ± 0.011	5.621 ± 0.016	25
RU SCT	18:41:56.37	−04:06:38.3	1.2946	5.886 ± 0.013	5.274 ± 0.012	5.069 ± 0.016	21
YZ AUR	05:15:21.98	+40:04:41.0	1.2599	7.484 ± 0.013	6.892 ± 0.011	6.705 ± 0.016	24
CP CEP	21:57:52.70	+56:09:49.9	1.2519	7.330 ± 0.012	6.711 ± 0.011	6.511 ± 0.016	22
AA SER	18:41:21.75	−01:06:40.3	1.2340	7.544 ± 0.012	6.758 ± 0.011	6.491 ± 0.015	21
SZ AQL	19:04:39.43	+01:18:22.0	1.2340	5.839 ± 0.012	5.325 ± 0.011	5.158 ± 0.016	24
CD CYG	20:04:26.55	+34:06:44.0	1.2323	6.351 ± 0.012	5.830 ± 0.011	5.684 ± 0.016	27
RW CAM	03:54:21.79	+58:39:12.0	1.2152	5.819 ± 0.012	5.276 ± 0.011	5.113 ± 0.016	21
ER AUR	05:13:09.96	+41:59:25.8	1.1956	9.069 ± 0.012	8.589 ± 0.011	8.447 ± 0.015	20
SV MON	06:21:26.31	+06:28:12.5	1.1828	6.260 ± 0.013	5.817 ± 0.011	5.704 ± 0.016	24
SZ CYG	20:32:54.28	+46:36:04.5	1.1793	6.515 ± 0.012	5.944 ± 0.011	5.745 ± 0.015	33
CH CAS	23:22:28.41	+62:45:25.7	1.1786	7.321 ± 0.013	6.673 ± 0.011	6.420 ± 0.015	21
RW CAS	01:37:14.01	+57:45:33.0	1.1701	6.836 ± 0.013	6.354 ± 0.011	6.212 ± 0.016	21
UZ SCT	18:31:22.36	−12:55:43.4	1.1686	7.395 ± 0.012	6.735 ± 0.011	6.496 ± 0.015	21
TX CYG	21:00:06.36	+42:35:51.2	1.1676	5.312 ± 0.013	4.616 ± 0.011	4.341 ± 0.015	22
CY CAS	23:29:12.74	+63:22:27.5	1.1577	7.850 ± 0.013	7.160 ± 0.012	6.938 ± 0.016	22
CY AUR	04:57:40.07	+46:05:33.1	1.1414	8.580 ± 0.013	7.945 ± 0.012	7.744 ± 0.016	21
TT AQL	19:08:13.73	+01:17:55.1	1.1384	4.642 ± 0.013	4.162 ± 0.012	4.035 ± 0.016	26
V0916 AQL	19:10:00.42	+12:32:11.7	1.1284	7.362 ± 0.012	6.751 ± 0.011	6.551 ± 0.015	25
V1364 CYG	20:07:29.43	+35:20:46.9	1.1132	9.088 ± 0.013	8.337 ± 0.011	8.089 ± 0.016	19
GX SGE	19:31:10.48	+19:15:25.5	1.1106	8.261 ± 0.012	7.561 ± 0.011	7.310 ± 0.015	27
Z SCT	18:42:57.27	−05:49:15.3	1.1106	6.954 ± 0.013	6.465 ± 0.011	6.300 ± 0.015	19
GQ VUL	19:47:58.00	+26:00:00.1	1.1019	8.669 ± 0.013	7.919 ± 0.011	7.643 ± 0.015	22
AS VUL	19:47:44.47	+27:55:05.6	1.0872	8.374 ± 0.012	7.715 ± 0.011	7.489 ± 0.015	32
RY CAS	23:52:07.03	+58:44:30.2	1.0841	7.063 ± 0.012	6.537 ± 0.011	6.347 ± 0.015	24
EZ CYG	19:57:49.02	+30:15:57.1	1.0667	8.192 ± 0.013	7.655 ± 0.011	7.496 ± 0.015	20
RX AUR	05:01:23.18	+39:57:37.5	1.0653	5.741 ± 0.012	5.346 ± 0.011	5.250 ± 0.015	22
AA GEM	06:06:34.94	+26:19:45.1	1.0532	7.646 ± 0.012	7.189 ± 0.011	7.086 ± 0.016	23
HZ PER	04:25:37.29	+45:37:12.9	1.0523	9.127 ± 0.013	8.324 ± 0.012	8.035 ± 0.016	22
V0438 CYG	20:18:54.30	+40:03:52.3	1.0496	6.764 ± 0.012	6.060 ± 0.011	5.757 ± 0.015	27
SV PER	04:49:47.94	+42:17:22.9	1.0465	6.798 ± 0.012	6.342 ± 0.011	6.214 ± 0.016	20
TY SCT	18:42:07.91	−04:17:36.5	1.0435	7.226 ± 0.013	6.620 ± 0.011	6.400 ± 0.015	22
VX PER	02:07:48.48	+58:26:36.8	1.0370	6.886 ± 0.012	6.427 ± 0.011	6.277 ± 0.015	21
Z LAC	22:40:52.12	+56:49:46.0	1.0369	6.221 ± 0.013	5.792 ± 0.011	5.668 ± 0.016	19
Y SCT	18:38:03.30	−08:22:08.0	1.0146	6.456 ± 0.012	5.881 ± 0.011	5.663 ± 0.015	22
AN AUR	04:59:41.53	+40:50:09.6	1.0124	7.932 ± 0.013	7.434 ± 0.011	7.274 ± 0.016	20
SY AUR	05:12:39.22	+42:49:54.5	1.0062	6.925 ± 0.012	6.514 ± 0.011	6.386 ± 0.015	20
BZ CYG	20:45:59.79	+45:18:25.0	1.0061	6.751 ± 0.012	6.134 ± 0.011	5.899 ± 0.015	29
CN SCT	18:42:30.48	−04:19:50.4	0.9997	7.821 ± 0.012	7.055 ± 0.011	6.730 ± 0.015	23
DD CAS	23:57:34.95	+62:43:05.7	0.9918	7.533 ± 0.012	7.055 ± 0.011	6.924 ± 0.015	26
YZ SGR	18:49:28.60	−16:43:22.9	0.9802	5.378 ± 0.012	4.989 ± 0.011	4.878 ± 0.015	24
CN CEP	23:25:34.79	+64:47:25.4	0.9778	8.316 ± 0.012	7.627 ± 0.011	7.367 ± 0.015	21
FN AQL	19:12:47.31	+03:33:26.4	0.9769	5.947 ± 0.012	5.473 ± 0.011	5.328 ± 0.015	19
TX MON	06:50:52.27	−01:25:45.3	0.9396	8.576 ± 0.012	8.102 ± 0.011	7.959 ± 0.015	22
AC MON	07:00:59.81	−08:42:32.3	0.9039	7.579 ± 0.012	7.054 ± 0.011	6.885 ± 0.015	22
BK AUR	05:10:40.19	+49:41:15.3	0.9032	7.302 ± 0.013	6.873 ± 0.011	6.749 ± 0.015	19
DL CAS	00:29:58.58	+60:12:43.1	0.9031	6.556 ± 0.012	6.089 ± 0.011	5.929 ± 0.015	21
U VUL	19:36:37.73	+20:19:58.6	0.9026	4.515 ± 0.012	4.074 ± 0.011	3.928 ± 0.015	19
W GEM	06:34:57.44	+15:19:49.6	0.8984	5.133 ± 0.013	4.757 ± 0.012	4.671 ± 0.016	17
RX CAM	04:04:58.44	+58:39:35.4	0.8983	5.169 ± 0.013	4.714 ± 0.011	4.577 ± 0.015	19
VY CYG	21:04:16.63	+39:58:20.1	0.8953	7.005 ± 0.012	6.536 ± 0.011	6.374 ± 0.015	26
GH CYG	19:59:10.79	+29:27:02.7	0.8931	7.256 ± 0.012	6.787 ± 0.011	6.614 ± 0.015	18
CD CAS	23:45:02.59	+63:00:13.9	0.8921	7.631 ± 0.012	7.077 ± 0.011	6.896 ± 0.015	25
RS ORI	06:22:13.18	+14:40:41.2	0.8789	6.411 ± 0.012	6.009 ± 0.011	5.898 ± 0.015	24
V1344 AQL	19:11:59.16	+04:21:17.6	0.8738	5.184 ± 0.012	4.720 ± 0.011	4.573 ± 0.015	20
TZ MON	06:58:00.93	−00:22:33.4	0.8709	8.454 ± 0.012	7.993 ± 0.011	7.832 ± 0.015	19
CK SCT	18:41:00.66	−06:05:49.9	0.8701	7.380 ± 0.012	6.806 ± 0.011	6.627 ± 0.015	19
V0336 AQL	19:01:19.73	+00:08:49.2	0.8635	7.155 ± 0.012	6.676 ± 0.011	6.521 ± 0.015	17
V0459 CYG	21:10:54.36	+49:08:31.4	0.8604	7.601 ± 0.012	7.058 ± 0.011	6.883 ± 0.015	19
V0600 AQL	19:20:56.08	+08:33:22.1	0.8596	6.961 ± 0.012	6.435 ± 0.011	6.242 ± 0.015	22
AK CEP	22:28:50.06	+58:12:39.3	0.8593	8.404 ± 0.012	7.884 ± 0.011	7.740 ± 0.015	21
TW CMA	07:22:02.37	−14:19:05.5	0.8448	7.579 ± 0.012	7.167 ± 0.011	7.046 ± 0.015	26
AO AUR	05:47:45.05	+32:00:52.7	0.8301	8.640 ± 0.013	8.188 ± 0.011	8.064 ± 0.015	21
U SGR	18:31:53.32	−19:07:30.1	0.8290	4.516 ± 0.013	4.088 ± 0.011	3.949 ± 0.016	24
V0495 CYG	20:15:58.32	+35:00:52.9	0.8276	7.105 ± 0.012	6.526 ± 0.011	6.287 ± 0.015	23
AY SGR	18:23:19.15	−18:34:29.2	0.8175	7.122 ± 0.012	6.518 ± 0.011	6.299 ± 0.015	25
AW PER	04:47:46.32	+36:43:22.1	0.8105	5.225 ± 0.012	4.821 ± 0.011	4.695 ± 0.015	24
RR LAC	22:41:26.53	+56:25:58.1	0.8073	6.982 ± 0.012	6.609 ± 0.011	6.506 ± 0.015	23
X VUL	19:57:28.60	+26:33:23.3	0.8007	5.915 ± 0.012	5.412 ± 0.011	5.231 ± 0.015	27
RS CAS	23:37:16.04	+62:25:44.3	0.7991	6.767 ± 0.012	6.212 ± 0.011	6.004 ± 0.015	21
CR CEP	22:46:24.79	+59:26:31.8	0.7947	6.641 ± 0.012	6.084 ± 0.011	5.909 ± 0.015	22
VV CAS	01:51:07.01	+59:53:17.6	0.7929	8.325 ± 0.013	7.868 ± 0.011	7.734 ± 0.015	21
V0538 CYG	21:37:28.12	+51:45:44.8	0.7867	7.795 ± 0.012	7.294 ± 0.011	7.136 ± 0.015	23
FM AQL	19:09:15.98	+10:33:08.8	0.7863	5.664 ± 0.012	5.198 ± 0.011	5.044 ± 0.015	23
MW CYG	20:12:22.83	+32:52:17.9	0.7749	6.692 ± 0.012	6.194 ± 0.011	6.021 ± 0.018	23
FM CAS	00:14:28.23	+56:15:10.5	0.7641	7.141 ± 0.012	6.736 ± 0.011	6.619 ± 0.015	23
RZ GEM	06:02:36.57	+22:14:02.9	0.7427	7.607 ± 0.012	7.153 ± 0.011	6.987 ± 0.015	25
X LAC	22:49:03.17	+56:25:41.5	0.7408	6.506 ± 0.012	6.128 ± 0.011	6.007 ± 0.015	21
SW CAS	23:07:10.07	+58:33:15.0	0.7357	7.410 ± 0.012	6.971 ± 0.011	6.838 ± 0.015	22
CV MON	06:37:04.84	+03:03:50.2	0.7307	7.313 ± 0.012	6.768 ± 0.011	6.565 ± 0.015	22
V1162 AQL	19:52:20.99	−11:22:00.6	0.7305	6.150 ± 0.012	5.802 ± 0.011	5.701 ± 0.015	21
BG LAC	22:00:25.15	+43:26:43.3	0.7269	7.022 ± 0.012	6.638 ± 0.011	6.511 ± 0.015	22
CR SER	18:10:02.13	−13:32:45.4	0.7244	7.335 ± 0.012	6.746 ± 0.011	6.520 ± 0.015	20
V0386 CYG	21:14:40.42	+41:42:58.7	0.7208	6.359 ± 0.012	5.793 ± 0.011	5.560 ± 0.015	18
BR VUL	19:46:35.18	+22:53:23.2	0.7158	7.713 ± 0.012	7.209 ± 0.011	7.042 ± 0.015	28
V0514 CYG	20:46:12.53	+45:28:43.1	0.7075	7.637 ± 0.012	6.998 ± 0.011	6.737 ± 0.015	24
V LAC	22:48:37.98	+56:19:17.4	0.6975	7.049 ± 0.013	6.656 ± 0.011	6.569 ± 0.015	21
AS PER	04:19:46.84	+48:57:11.7	0.6966	6.934 ± 0.013	6.465 ± 0.011	6.295 ± 0.015	18
CF CAS	23:58:17.96	+61:13:15.8	0.6880	8.595 ± 0.012	8.114 ± 0.011	7.937 ± 0.015	34
VZ CYG	21:51:41.43	+43:08:02.6	0.6870	7.202 ± 0.013	6.841 ± 0.011	6.737 ± 0.015	20
RY CMA	07:16:37.64	−11:29:14.3	0.6701	6.379 ± 0.012	6.031 ± 0.011	5.912 ± 0.015	28
TV CMA	07:09:15.41	−13:47:09.9	0.6693	8.028 ± 0.012	7.570 ± 0.011	7.401 ± 0.015	26
WW MON	06:33:37.18	+09:12:12.7	0.6686	9.971 ± 0.014	9.495 ± 0.012	9.370 ± 0.016	17
XY CAS	00:49:53.26	+60:07:38.4	0.6534	7.746 ± 0.012	7.325 ± 0.011	7.194 ± 0.015	19
V0402 CYG	20:09:07.76	+37:09:07.1	0.6400	7.811 ± 0.012	7.400 ± 0.011	7.285 ± 0.015	23
Y LAC	22:09:02.92	+51:02:45.0	0.6359	7.631 ± 0.012	7.299 ± 0.011	7.219 ± 0.015	21
SX PER	04:17:06.06	+41:43:54.5	0.6325	8.767 ± 0.013	8.335 ± 0.011	8.205 ± 0.015	24
EP CYG	19:45:03.68	+31:19:50.9	0.6323	10.120 ± 0.013	9.675 ± 0.012	9.520 ± 0.016	18
RZ CMA	07:21:21.58	−16:39:35.8	0.6289	7.545 ± 0.012	7.167 ± 0.011	7.005 ± 0.015	25
X SCT	18:31:19.75	−13:06:29.4	0.6230	7.387 ± 0.013	6.940 ± 0.011	6.805 ± 0.015	19
V0508 MON	06:47:09.40	+03:58:01.3	0.6163	8.643 ± 0.012	8.266 ± 0.011	8.174 ± 0.015	18
MM PER	03:45:23.34	+48:05:00.6	0.6147	8.666 ± 0.012	8.249 ± 0.011	8.124 ± 0.015	23
V0495 MON	06:37:03.38	−02:49:26.6	0.6124	9.834 ± 0.012	9.339 ± 0.011	9.222 ± 0.015	24
SY CAS	00:15:09.81	+58:25:27.3	0.6097	7.830 ± 0.012	7.438 ± 0.011	7.325 ± 0.015	27
ST TAU	05:45:03.16	+13:34:34.9	0.6058	6.283 ± 0.013	5.893 ± 0.011	5.784 ± 0.016	18
TY MON	06:56:39.79	+00:11:24.1	0.6045	9.310 ± 0.012	8.853 ± 0.011	8.705 ± 0.015	18
AA MON	06:57:23.77	−03:50:35.9	0.5953	9.729 ± 0.013	9.186 ± 0.012	8.989 ± 0.015	22
CS ORI	06:07:25.46	+11:09:07.1	0.5899	9.344 ± 0.013	8.943 ± 0.011	8.828 ± 0.016	25
Y AUR	05:28:39.23	+42:26:15.8	0.5865	7.664 ± 0.012	7.276 ± 0.011	7.151 ± 0.015	29
SU CYG	19:44:48.73	+29:15:52.8	0.5850	5.652 ± 0.012	5.380 ± 0.011	5.307 ± 0.015	32
AD GEM	06:43:07.51	+20:56:20.9	0.5784	8.468 ± 0.012	8.140 ± 0.011	8.066 ± 0.015	24
RT AUR	06:28:34.06	+30:29:35.1	0.5713	4.246 ± 0.012	3.977 ± 0.011	3.920 ± 0.015	23
SS SCT	18:43:43.50	−07:43:52.0	0.5648	6.299 ± 0.012	5.918 ± 0.011	5.818 ± 0.015	22
AV TAU	05:45:44.91	+27:04:04.5	0.5582	9.195 ± 0.013	8.635 ± 0.011	8.441 ± 0.015	22
V0335 AUR	05:42:29.25	+37:38:46.9	0.5332	9.869 ± 0.013	9.386 ± 0.012	9.232 ± 0.016	22
AX AUR	05:46:50.81	+31:35:52.4	0.4838	9.936 ± 0.012	9.479 ± 0.011	9.320 ± 0.015	18
BV MON	06:56:51.09	+04:30:58.3	0.4792	9.016 ± 0.013	8.572 ± 0.011	8.458 ± 0.016	17
V0465 MON	07:08:09.31	−00:03:56.5	0.4335	8.770 ± 0.012	8.429 ± 0.011	8.354 ± 0.015	22
BE MON	06:40:05.59	+07:36:21.0	0.4322	8.267 ± 0.012	7.842 ± 0.011	7.714 ± 0.016	19

Notes. Right ascension and declination are adopted from the 2MASS point source catalog, see the text. The quoted errors include the photometric calibration uncertainty and the estimated GLOESS averaging error.

Download table as: ASCIITypeset images: 1 2

5.3. Serendipitous Variables

Although the field of view of BIRCAM was only 13 arcmin, there were a number of variables within the fields that were simultaneously observed with the Cepheids. Some were previously classified variables in the GCVS but most are new and unclassified (i.e., not in SIMBAD database⁶). The periods of most of these variables are longer than the duration of the BIRCAM survey and as a result the periods are unconstrained. We suspect that the majority are long-period variables. Subjective estimates of the periods were made by constructing rough light curves and likely represent lower limits. A total of 82 variables were found that were unclassified and are serendipitous discoveries. For previously identified variables, periods were taken from the literature. In the case of QX Cas (16 CF Cas in this survey), no variability was detected which may confirm recent findings (Bonaro et al. 2009) that it is no longer eclipsing. The data for these variables are available online and are summarized in Tables 5 and 6.

Table 5. Summary of Serendipitous Variables

BIRCAM Field ID	Other ID	R.A. (J2000)	Decl. (J2000)	Period (days)	Period Ref.
2 SZ AQL	V1561 AQL	19:04:39.56	+01:22:18.0	290.0	1
4 SZ AQL	V1569 AQL	19:04:55.82	+01:21:29.6	413.0	1
9 SZ AQL	V1570 AQL	19:05:04.61	+01:16:03.5	260.3	1
10 SZ AQL	...	19:04:31.87	+01:20:15.5	⩾350
5 FM AQL	...	19:09:31.36	+10:35:07.7	⩾400
15 FM AQL	...	19:09:03.41	+10:32:29.3	∼223
22 FM AQL	...	19:09:34.51	+10:30:21.7	⩾300
22 V0336 AQL	...	19:01:20.65	+00:04:33.3	⩾320
7 V0600 AQL	...	19:21:09.68	+08:32:02.4	⩾250
10 V0600 AQL	...	19:20:56.08	+08:33:22.1	⩾400
17 V0600 AQL	...	19:21:00.21	+08:30:34.9	⩾220
5 V0916 AQL	...	19:10:19.34	+12:34:01.3	⩾450
6 V1344 AQL	V1426 AQL^a	19:12:12.01	+04:23:41.5	1.175147	2
7 V1344 AQL	...	19:12:13.21	+04:16:54.5	⩾450
12 V1344 AQL	...	19:11:54.89	+04:25:22.8	⩾220
32 V1344 AQL	...	19:12:20.96	+04:17:49.3	⩾450
3 AO AUR	Kiso C2-66^b	05:48:03.07	+32:03:19.6	∼150
16 CF CAS	QX CAS^c	23:58:43.16	+61:09:39.5	6.004709	3
5 RS CAS	...	23:37:41.62	+62:21:18.8	55
8 FM CAS	...	00:14:46.95	+56:11:32.0	⩾320
1 SU CYG	...	19:45:02.09	+29:15:06.3	∼160
20 SU CYG	...	19:45:18.23	+29:13:09.7	∼216
26 SU CYG	...	19:44:54.74	+29:20:29.8	∼350
1 VZ CYG	V0673 CYG	21:51:37.74	+43:09:58.6	325.5	4
6 EZ CYG	V2222 CYG	19:57:52.75	+30:11:53.9	176
18 EZ CYG	...	19:57:49.62	+30:18:18.3	⩾281
1 GH CYG	...	19:59:35.96	+29:26:31.3	⩾240
11 GH CYG	...	19:59:18.67	+29:22:51.5	⩾240
3 KX CYG	...	20:24:16.34	+40:38:04.6	⩾200
7 MW CYG	...	20:12:32.33	+32:49:03.8	⩾240
3 V0438 CYG	...	20:19:16.66	+40:04:04.7	⩾270
28 V0438 CYG	...	20:19:15.18	+40:03:57.3	⩾350
11 V0495 CYG	...	20:16:11.19	+35:01:39.5	⩾270
1 V1364 CYG	V1422 CYG	20:07:52.84	+35:18:57.4	⩾120
4 V1467 CYG	...	20:04:05.74	+32:29:28.3	⩾230
14 V1467 CYG	...	20:04:05.94	+32:25:55.8	⩾220
80 SV MON	V0615 MON	06:21:53.85	+06:26:27.1	∼127
11 AC MON	BB MON^a	07:01:16.48	−08:41:42.5	1.4654	2
11 WZ SGR	...	18:17:29.32	−19:07:25.5	⩾215
74 WZ SGR	...	18:16:54.43	−19:01:30.5	⩾250
77 WZ SGR	...	18:17:17.68	−19:00:02.5	⩾250
2 AY SGR	...	18:23:41.67	−18:39:20.9	⩾215
110 AY SGR	...	18:23:35.30	−18:36:37.3	⩾215
29 AY SGR	...	18:23:23.41	−18:38:42.2	⩾230
505 AY SGR	...	18:23:06.14	−18:36:39.0	∼190
168 AY SGR	...	18:23:36.73	−18:34:48.6	∼118
29 X SCT	...	18:31:29.13	−13:11:14.9	⩾200
37 X SCT	...	18:31:41.59	−13:10:48.1	⩾350
56 X SCT	...	18:31:31.56	−13:10:33.4	⩾320
60 X SCT	...	18:31:16.55	−13:11:59.2	⩾400
77 X SCT	...	18:31:47.20	−13:06:19.7	∼230
6 Y SCT	...	18:38:15.54	−08:18:22.8	⩾400
7 Y SCT	...	18:37:54.36	−08:17:40.8	⩾400
18 Y SCT	...	18:38:07.98	−08:24:32.6	⩾200
25 Y SCT	...	18:37:54.89	−08:17:06.9	⩾400
35 Y SCT	...	18:38:31.16	−08:19:09.2	⩾500
37 Y SCT	...	18:38:31.14	−08:23:17.8	⩾320
60 Y SCT	...	18:37:55.13	−08:20:27.9	⩾500
73 Y SCT	...	18:38:02.34	−08:24:03.1	⩾400
4 Z SCT	StRS 248	18:43:19.31	−05:50:02.4	⩾200	5
6 Z SCT	...	18:43:20.93	−05:51:25.7	⩾400
13 Z SCT	...	18:42:52.35	−05:46:26.6	74.65
17 Z SCT	...	18:43:12.12	−05:44:16.3	⩾400
19 Z SCT	...	18:43:19.23	−05:47:19.8	⩾500
34 Z SCT	...	18:42:44.47	−05:44:50.2	⩾500
73 Z SCT	...	18:43:06.24	−05:51:11.5	⩾500
99 Z SCT	...	18:42:50.37	−05:54:09.1	⩾300
2 RU SCT	...	18:41:52.63	−04:07:24.2	⩾350
6 SS SCT	...	18:44:05.02	−07:44:50.9	⩾400
28 SS SCT	...	18:44:03.84	−07:38:33.8	⩾350
51 SS SCT	...	18:43:35.38	−07:47:35.0	⩾300
4 UZ SCT	...	18:31:18.58	−12:57:18.6	⩾400
6 UZ SCT	...	18:31:30.38	−12:51:36.7	⩾400
10 UZ SCT	...	18:31:12.85	−12:51:34.1	⩾320
34 UZ SCT	...	18:31:19.93	−12:59:20.1	⩾350
7 CK SCT	...	18:40:46.68	−06:04:14.9	⩾220
9 CK SCT	...	18:40:47.76	−06:06:55.0	⩾400
10 CK SCT	...	18:41:07.90	−06:05:26.1	⩾220
13 CK SCT	...	18:41:25.27	−06:03:16.2	⩾220
17 CK SCT	...	18:41:18.03	−06:09:17.7	⩾350
25 CK SCT	...	18:41:18.33	−06:08:19.0	⩾300
28 CK SCT	...	18:40:51.59	−06:02:47.0	⩾400
42 CK SCT	...	18:41:20.47	−06:01:37.9	⩾400
43 CK SCT	...	18:40:47.18	−06:08:36.1	⩾200
46 CK SCT	...	18:41:20.38	−06:11:46.9	⩾500
52 CK SCT	...	18:41:03.94	−06:09:05.8	⩾300
60 CK SCT	...	18:41:07.28	−06:08:35.6	⩾200
61 CK SCT	...	18:41:27.45	−06:07:15.9	⩾200
22 AA SER	...	18:41:17.74	−01:07:05.1	⩾300
5 CR SER	...	18:10:30.51	−13:31:53.1	⩾220
2 X VUL	...	19:57:52.59	+26:31:00.6	⩾300
8 AS VUL	...	19:47:47.48	+27:53:23.7	⩾202
8 BR VUL	...	19:46:40.09	+22:53:27.7	246

Notes. Right ascension and declination are adopted from the 2MASS point source catalog, see the text. ^aEclipsing binary. ^bCarbon star. ^cQX Cas, an eclipsing binary. No variability was detected in this work. References. (1) Rosino et al. 1997; (2) Pojmanski et al. 2006; (3) Kjurkchieva et al. 2007; (4) Samus et al. 2009; (5) Stephenson 1992.

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Table 6. Photometric Data for Serendipitous Variables

BIRCAM Field ID	HJD	J ± σ_J^a	H ± σ_H^a	K ± σ_K^a
10 SZ AQL	2454574.919	9.226 ± 0.018	7.750 ± 0.014	7.020 ± 0.017
10 SZ AQL	2454579.969	9.227 ± 0.018	7.748 ± 0.014	7.060 ± 0.017
10 SZ AQL	2454585.919	9.150 ± 0.018	7.713 ± 0.014	7.044 ± 0.017
10 SZ AQL	2454611.902	9.036 ± 0.017	7.702 ± 0.014	7.071 ± 0.017
10 SZ AQL	2454629.798	9.035 ± 0.017	7.717 ± 0.014	7.121 ± 0.017
10 SZ AQL	2454641.850	9.066 ± 0.017	7.744 ± 0.014	7.148 ± 0.017
10 SZ AQL	2454643.964	8.994 ± 0.017	7.693 ± 0.014	7.122 ± 0.017
10 SZ AQL	2454726.659	8.186 ± 0.015	6.850 ± 0.012	6.227 ± 0.016
10 SZ AQL	2454735.654	8.135 ± 0.014	6.824 ± 0.012	6.260 ± 0.016
10 SZ AQL	2454739.590	8.114 ± 0.014	6.798 ± 0.012	6.260 ± 0.016
10 SZ AQL	2454755.576	8.148 ± 0.014	6.826 ± 0.012	6.159 ± 0.016
10 SZ AQL	2454762.556	8.173 ± 0.015	6.887 ± 0.012	6.268 ± 0.016

Notes. The data for all observed variables are available online; see the text. ^aJ, H, and K photometric uncertainty determined from the data ( $\frac{\rm {\rm {rms}}}{ \sqrt{{n_{\rm obs}}} }$ ).

Only a portion of this table is shown here to demonstrate its form and content. A machine-readable version of the full table is available.

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6. CONCLUDING REMARKS

One hundred twenty-nine fields containing Galactic Cepheids were synoptically observed over the course of 10 months at the University of Wyoming 0.6 m telescope at Red Buttes Observatory. These data represent a significant change from previous studies of Galactic Cepheids in that the photometric data were obtained using ensemble aperture photometry over a calibrated 10 arcmin field of view using differential measurements from local standards. The NIR light curves for 131 Cepheids were interpolated to obtain the intensity-weighted mean magnitudes. The final results are in agreement with previous studies and triple the number of FMGCs with accurate NIR photometry.

When combined with radial velocity measurements, these new data will allow the determination of radii and distances, via the Barnes–Evans IRSB technique. As distances and radii become available for this sample, it will possible to accurately and precisely construct a statistically robust Galactic NIR PL relation and period–radius relation. With an accurate Galactic NIR PL relation at hand, it will be possible to calibrate the distance to calibrating galaxies in the NIR using HST/JWST and bypass the LMC. This has the benefit of avoiding the systematic uncertainty in the LMC distance and it mitigates the complication of any PL slope dependence on metal abundance.

In this survey, 82 previously unclassified but probable long-period variables were discovered. It is clear that the discovery of these variables was made possible by synoptic observations of the Galactic disk at NIR wavelengths. Given the areal coverage and depth of the BIRCAM survey in the Galactic Plane, a long-term synoptic observing program in the NIR of the entire Galactic disk would likely reveal tens of thousands of long-period variables currently hidden behind several magnitudes of optical extinction.

The authors express their appreciation to the support received at Red Buttes Observatory by Ron Canterna, Chris Rodgers, and Vanessa Bailey who have helped make this research possible. In this research, we have used and acknowledge with thanks, data from the General Catalog of Variable Stars. This publication makes use of the data products from the 2MASS project as well as the SIMBAD database, Aladin, and Vizier catalogue operation tools (CDS Strabourg, France). The Two Micron All Sky Survey is a joint project of the University of Massachusetts and the Infrared Processing Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. BIRCAM was developed with support from a grant from the Astronomical Science Division of the National Science Foundation (NSF/MRI 0421507).

NEAR-INFRARED (JHK) PHOTOMETRY OF 131 NORTHERN GALACTIC CLASSICAL CEPHEIDS

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ABSTRACT

1. INTRODUCTION

2. RESEARCH TO DATE