New NIR light-curve templates for classical Cepheids.
    Inno L., Matsunaga N., Romaniello M., Bono G., Monson A., Ferraro I.,
    Iannicola G., Persson E., Buonanno R., Freedman W., Gieren W.,
    Groenewegen M.A.T., Ita Y., Laney C.D., Lemasle B., Madore B.F.,
    Nagayama T., Nakada Y., Nonino M., Pietrzynski G., Primas F., Scowcroft V.,
    Soszynski I., Tanabe T., Udalski A.
   <Astron. Astrophys., 576, A30-30 (2015)>
   =2015A&A...576A..30I
ADC_Keywords: Stars, variable; Photometry, infrared

Keywords: stars: variables: Cepheids - stars: distances - stars: oscillations


Abstract:
    We present new near-infrared (NIR) light-curve templates for
    fundamental (FU, J, H, Ks) and first overtone (FO, J) classical
    Cepheids. The new templates together with period-luminosity and
    period-Wesenheit (PW) relations provide Cepheid distances from
    single-epoch observations with a precision only limited by the
    intrinsic accuracy of the method adopted. The templates rely on a very
    large set of Galactic and Magellanic Cloud Cepheids (FU, ∼600; FO,
    ∼200) with well-sampled NIR (IRSF data set) and optical (V, I; OGLE
    data set) light-curves. To properly trace the change in the shape of
    the light-curve as a function of pulsation period, we split the sample
    of calibrating Cepheids into ten different period bins. The templates
    for the first time cover FO Cepheids and the short-period range of FU
    Cepheids (P≤5-days). Moreover, the phase zero-point is anchored to
    the phase of the mean magnitude along the rising branch. The new
    approach has several advantages in sampling the light-curve of bump
    Cepheids when compared with the canonical phase of maximum light. We
    also provide new empirical estimates of the NIR-to-optical amplitude
    ratios for FU and FO Cepheids. We perform detailed analytical fits
    using seventh-order Fourier series and multi-Gaussian periodic
    functions. The latter are characterized by fewer free parameters (nine
    vs. fifteen). The mean NIR magnitudes based on the new templates are
    up to 80% more accurate than single-epoch NIR measurements and up to
    50% more accurate than the mean magnitudes based on previous NIR
    templates, with typical associated uncertainties ranging from 0.015mag
    (J band) to 0.019mag (KS band). Moreover, we find that errors on
    individual distance estimates for Small Magellanic Cloud Cepheids
    derived from NIR PW relations are essentially reduced to the intrinsic
    scatter of the adopted relations. Thus, the new templates are the
    ultimate tool for estimating precise Cepheid distances from NIR
    single-epoch observations, which can be safely adopted for future
    interesting applications, including deriving the 3D structure of the
    Magellanic Clouds.

Description:
    Our analysis is based on the largest available sample of
    fundamental-mode Cepheids with well-covered light-curves in the NIR
    and in optical (V, I) bands. This sample covers a very broad period
    range (1-100 days). We collected J, H, and KS band observations from
    four different data sets: Laney & Stobie (1992A&AS...93...93L, 51) and
    Monson & Pierce (2011ApJS..193...12M, 131) for Galactic Cepheids,
    Persson et al. (2004AJ....128.2239P, 92) for LMC Cepheids, and the
    IRSF survey catalog for ∼500 Small Magellanic Cloud (SMC) Cepheids.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table2.dat       103      275   Pulsation parameters for FU calibrating Cepheids
table3.dat       103       10   Pulsation parameters for FO calibrating Cepheids


See also:
   J/AJ/128/2239 : JHKs photometry of 92 LMC Cepheids (Persson+, 2004)
   J/ApJS/193/12 : JHK photometry of Northern Galactic Cepheids (Monson+, 2011)
   J/AcA/58/163  : VI light curves of LMC classical Cepheids (Soszynski+, 2008)
   J/AcA/60/17   : VI light curves of SMC classical Cepheids (Soszynski+, 2010)


Byte-by-byte Description of file: table2.dat table3.dat

   Bytes Format Units   Label     Explanations

   1-  3  A3    ---     Gal       Galaxy (MW, LMC or SMC)
   5- 13  A9    ---     ID        Primary identification
  15- 19  A5    ---     ---       [OGLE-]
  20- 31  A12   ---     OID       OGLE identification for LMC and SMC Cepheids
                                  (LMC-CEP-NNNN or SMC-CEP-NNNN)
  33- 39  F7.5  [d]     logP      [0.15/1.84] log(Period)
  41- 46  F6.3  mag     <Vmag>    Average V magnitude
  48- 53  F6.3  mag     <Jmag>    ?=- Average J magnitude
  55- 60  F6.3  mag     <Hmag>    ?=- Average H magnitude
  62- 67  F6.3  mag     <Ksmag>   ?=- Average Ks magnitude
  69- 72  F4.2  mag     Vamp      Amplitude of pulsation in V band
  74- 77  F4.2  mag     Jamp      ?=- Amplitude of pulsation in J band
  79- 82  F4.2  mag     Hamp      ?=- Amplitude of pulsation in H band
  84- 87  F4.2  mag     Kamp      ?=- Amplitude of pulsation in Ks band
  89- 99  F11.3 d       JD0       Zero-point, defined as the epoch of the mean
                                  magnitude along the rising branch
 101-103  A3    ---     Sam       Sample designation (1)

Note (1): Sample as follows:
    LS  = Laney and Stobie, 1992A&AS...93...93L
    MP  = Monson and Pierce, 2011ApJS..193...12M, Cat. J/ApJS/193/12
    P04 = Persson et al., 2004AJ....128.2239P, Cat. J/AJ/128/2239
    SMC = IRSF/OGLE sample


History:
    From electronic version of the journal