We analyze sparsely-sampled near-infrared (JHK s ) light curves of a sample of 1781 Mira variable candidates in M33, originally discovered using I-band time-series observations. We extend our single-band semi-parametric Gaussian process modeling of Mira light curves to a multi-band version and obtain improved period determinations. We use our previous results on near-infrared properties of candidate Miras in the LMC to classify the majority of the M33 sample into Oxygen-or Carbon-rich subsets. We derive Period-Luminosity relations for O-rich Miras and determine a distance modulus for M33 of 24.80 ± 0.06 mag.

We have conducted a near-infrared monitoring campaign at the UK Infrared Telescope, of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. In this second paper of the series, we construct the birth mass function and hence derive the star formation history. The star formation rate has varied between ∼0.002 and 0.007 M yr −1 kpc −2 . We give evidence of two epochs of a star formation rate enhanced by a factor of a few -one that happened ≥6 Gyr ago and produced ≥80 per cent of the total mass in stars, and one around 250 Myr ago that lasted ∼200 Myr and formed ≤6 per cent of the mass in stars. We construct radial and azimuthal distributions in the image plane and in the galaxy plane for populations associated with old first-ascent red giant branch (RGB) stars, intermediate-age asymptotic giant branch (AGB) stars and young (massive) blue and red supergiants. We find that the RGB stars follow an spheroidal distribution, while younger stars follow a flat-disc distribution. The intermediate-age population displays signs of a pseudo-bulge or possibly a bar. The inner spiral arm pattern as recorded in mid-19th-century drawings is confirmed. We interpret our findings as evidence for an old, pressure-supported component and a younger disc formed 6 Gyr ago, with an accretion event occurring 250 Myr ago giving rise to the compact nucleus in M33. Our study provides support for recent Padova stellar evolution models except that super-AGB stars likely reach low temperatures and thus high mass-loss rates, supporting the super-AGB nature of the progenitors of dust-enshrouded supernovae such as SN 2008S.

We present the first reconstruction of the star formation history (SFH) of the Large and Small Magellanic Clouds (LMC and SMC) using Long Period Variable stars. These cool evolved stars reach their peak luminosity in the near-infrared; thus, their K-band magnitudes can be used to derive their birth mass and age, and hence the SFH can be obtained. In the LMC, we found a 10-Gyr old single star formation epoch at a rate of ∼ 1.5 M ⊙ yr −1 , followed by a relatively continuous SFR of ∼ 0.2 M ⊙ yr −1 , globally. In the core of the LMC (LMC bar), a secondary, distinct episode is seen, starting 3 Gyr ago and lasting until ∼ 0.5 Gyr ago. In the SMC, two formation epochs are seen, one ∼ 6 Gyr ago at a rate of ∼ 0.28 M ⊙ yr −1 and another only ∼ 0.7 Gyr ago at a rate of ∼ 0.3 M ⊙ yr −1 . The latter is also discernible in the LMC and may thus be linked to the interaction between the Magellanic Clouds and/or Milky Way, while the formation of the LMC bar may have been an unrelated event. Star formation activity is concentrated in the central parts of the Magellanic Clouds now, and possibly has always been if stellar migration due to dynamical relaxation has been effective. The different initial formation epochs suggest that the LMC and SMC did not form as a pair, but at least the SMC formed in isolation.

We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M 33 (Triangulum). On the basis of their variability, we have identified stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. In this fifth paper of the series, we construct the birth mass function and hence derive the star formation history across the galactic disc of M 33. The star formation rate has varied between ∼ 0.010 ± 0.001 (∼ 0.012 ± 0.007) and 0.060±0.005 (0.052±0.009) M ⊙ yr −1 kpc −2 statistically (systematically) in the central square kiloparsec of M 33, comparable with the values derived previously with another camera. The total star formation rate in M 33 within a galactocentric radius of 14 kpc has varied between ∼ 0.110 ± 0.005 (∼ 0.174 ± 0.060) and ∼ 0.560 ± 0.028 (∼ 0.503 ± 0.100) M ⊙ yr −1 statistically (systematically). We find evidence of two epochs during which the star formation rate was enhanced by a factor of a few -one that started ∼ 6 Gyr ago and lasted ∼ 3 Gyr and produced ≥ 71% of the total mass in stars, and one ∼ 250 Myr ago that lasted ∼ 200 Myr and formed ≤ 13% of the mass in stars. Radial star formation history profiles suggest that the inner disc of M 33 was formed in an inside-out formation scenario. The outskirts of the disc are dominated by the old population, which may be the result of dynamical effects over many Gyr. We find correspondence to spiral structure for all stars, but enhanced only for stars younger than ∼ 100 Myr; this suggests that the spiral arms are transient features and not part of a global density wave potential.

Objective. Febrile seizures are the most common type of convulsion in children. The identification of influencing factors on incidence of the first febrile seizures is of prime priority. The aim of this study was to identify the risk factors of the first febrile seizures in Iranian children. Methods. In this case-control study 80 children aged 9 month to 5 years with their first febrile seizures were compared with 80 children with fever without seizure based on different risk factors in 2007. Results. There was significant difference between two groups regarding the gender, family history of febrile seizures, breast-feeding duration, and the body temperature (P < .05). Conclusion. Our study showed that factors including the gender, family history of febrile seizures, breast-feeding duration, and the body temperature are among the risk factors in occurrence of the first febrile seizure. Preventive measures to remove such risk factors could lead to lower the incidence of febrile seizures.