Period-Luminosity Relation for Type II Cepheids

We have estimated JHKs magnitudes corrected to mean intensity for LMC type II Cepheids found in the OGLE-III survey. Period-luminosity relations (PLRs) are derived in JHKs as well as in a reddening-free VI parameter. The BL Her stars (P<4d) and the W Vir stars (P=4 to 20d) are co-linear in these PLRs. The slopes of the infrared relations agree with those found previously for type II Cepheids in globular clusters within the uncertainties. Using the pulsation parallaxes of V553 Cen and SW Tau, the data lead to an LMC modulus of 18.46+-0.10 mag, uncorrected for any metallicity effects. We have now established the PLR of type II Cepheids as a distance indicator by confirming that (almost) the same PLR satisfies the distributions in the PL diagram of type II Cepheids in (at least) two different systems, i.e. the LMC and Galactic globular clusters, and by calibrating the zero point of the PLR. RV Tau stars in the LMC, as a group, are not co-linear with the shorter-period type II Cepheids in the infrared PLRs in marked contrast to such stars in globular clusters. We note differences in period distribution and infrared colors for RV Tau stars in the LMC, globular clusters and Galactic field. We also compare the PLR of type II Cepheids with that of classical Cepheids.Comment: To appear in the proceedings for the conference "Stellar Pulsation: Challenges for Theory and Observations" held in Santa Fe, US

A lack of classical Cepheids in the inner part of the Galactic disk

Recent large-scale infrared surveys have been revealing stellar populations in the inner Galaxy seen through strong interstellar extinction in the disk. In particular, classical Cepheids with their period-luminosity and period-age relations are useful tracers of Galactic structure and evolution. Interesting groups of Cepheids reported recently include four Cepheids in the Nuclear Stellar Disk (NSD), about 200 pc around the Galactic Centre, found by Matsunaga et al. and those spread across the inner part of the disk reported by Dekany and collaborators. We here report our discovery of nearly thirty classical Cepheids towards the bulge region, some of which are common with Dekany et al., and discuss the large impact of the reddening correction on distance estimates for these objects. Assuming that the four Cepheids in the NSD are located at the distance of the Galactic Centre and that the near-infrared extinction law, i.e. wavelength dependency of the interstellar extinction, is not systematically different between the NSD and other bulge lines-of-sight, most of the other Cepheids presented here are located significantly further than the Galactic Centre. This suggests a lack of Cepheids in the inner 2.5 kpc region of the Galactic disk except the NSD. Recent radio observations show a similar distribution of star-forming regions.Comment: 8 pages, 4 figures, accepted for publication in MNRA

Cepheids and other short-period variables near the Galactic Centre

We report the result of our near-infrared survey of short-period variable stars (P<60d) in a field-of-view of 20'x30' towards the Galactic Centre. Forty-five variables are discovered and we classify the variables based on their light curve shapes and other evidence. In addition to 3 classical Cepheids reported previously, we find 16 type II Cepheids, 24 eclipsing binaries, one pulsating star with P=0.265d (RR Lyr or delta Sct) and one Cepheid-like variable whose nature is uncertain. Eclipsing binaries are separated into the foreground objects and those significantly obscured by interstellar extinction. One of the reddened binaries contains an O-type supergiant and its light curve indicates an eccentric orbit. We discuss the nature and distribution of type II Cepheids as well as the distance to the Galactic Centre based on these Cepheids and other distance indicators. The estimates of R0(GC) we obtained based on photometric data agree with previous results obtained with kinematics of objects around the GC. Furthermore, our result gives a support to the reddening law obtained by Nishiyama and collaborators, A(Ks)/E(H-Ks)=1.44, because a different reddening law would result in a rather different distance estimate.Comment: 13 pages, 10 figures, 7tables, accepted for publication in MNRA

The Cepheid distance to the Local Group Galaxy NGC 6822

Recent estimates of the Cepheid distance modulus of NGC 6822 differ by 0.18 mag. To investigate this we present new multi-epoch JHKs photometry of classical Cepheids in the central region of NGC 6822 and show that there is a zero-point difference from earlier work. These data together with optical and mid-infrared observations from the literature are used to derive estimates of the distance modulus of NGC 6822. A best value of 23.40 mag is adopted, based on an LMC distance modulus of 18.50 mag. The standard error of this quantity is ~0.05 mag. We show that to derive consistent moduli from Cepheid observations at different wavelengths, it is necessary that the fiducial LMC period-luminosity relations at these wavelengths should refer to the same subsample of stars. Such a set is provided. A distance modulus based on RR Lyrae variables agrees with the Cepheid result.Comment: accepted for publication in MNRA

A two-item version of the Japanese Consultation and Relational Empathy measure:A pilot study using secondary analysis of a cross-sectional survey in primary care

BACKGROUND: The Consultation and Relational Empathy (CARE) measure is a patient-reported measure of physician empathy which is widely used internationally. The Japanese version of the CARE measure has very high internal reliability, suggesting that a shorter version may have adequate validity and reliability. OBJECTIVE: To investigate a valid shorter version of the Japanese CARE measure. METHODS: We conducted a pilot study using secondary analysis of previous data obtained from 9 general practitioners and 252 patients and used to develop the Japanese CARE measure. All 1,023 possible combinations of the Japanese CARE items (n = 1–10) were candidates for the short measure. The internal consistency (Cronbach’s alpha) and the correlations between candidate short questionnaires and the original questionnaire were calculated. After selecting the most valid short questionnaire, inter-rater reliability was determined using generalizability theory, and construct validity (Spearman’s rho) was determined using patient satisfaction. RESULTS: Two items were selected for a pilot shorter version: item 6 “Showing care and compassion” and item 9 “Helping you to take control.” These showed high internal consistency and correlations with the 10-item measure (Cronbach’s alpha = 0.920, correlation = 0.979). Forty-five questionnaires per doctor allowed us to reliably differentiate between practitioners. The construct validity for the pilot short measure was high (Spearman’s rho 0.706, P < 0.001). CONCLUSION: We generated a pilot 2-item version of the Japanese CARE measure. This pilot 2-item version provides a basis for future validation studies of short CARE measures in other languages