Object-X: The Brightest Mid-IR Point Source in M33

We discuss the nature of the brightest mid-IR point source (which we dub Object X) in the nearby galaxy M33. Although multi-wavelength data on this object have existed in the literature for some time, it has not previously been recognized as the most luminous mid-IR object in M33 because it is entirely unremarkable in both optical and near-IR light. In the Local Group Galaxies Survey, Object X is a faint red source visible in VRI and H-alpha but not U or B. It was easily seen at JHK_s in the 2MASS survey. It is the brightest point source in all four Spitzer IRAC bands and is also visible in the MIPS 24-micron band. Its bolometric luminosity is 5x10^5 L_sun. The source is optically variable on short time scales (tens of days) and is also slightly variable in the mid-IR, indicating that it is a star. Archival photographic plates (from 1949 and 1991) show no optical source, so the star has been obscured for at least half a century. Its properties are similar to those of the Galactic OH/IR star IRC+10420 which has a complex dusty circumstellar structure resulting from episodic low velocity mass ejections. We propose that Object X is a M>30 M_sun evolved star obscured in its own dust ejected during episodic mass loss events over at least half a century. It may emerge from its current ultra-short evolutionary phase as a hotter post-RSG star analogous to M33 Var A. The existence and rarity of such objects can be an important probe of a very brief yet eventful stellar evolutionary phase.Comment: 20 pages, 10 figures. Accepted for publication by Ap

Census of Self-Obscured Massive Stars in Nearby Galaxies with Spitzer: Implications for Understanding the Progenitors of SN 2008S-Like Transients

A new link in the causal mapping between massive stars and potentially fatal explosive transients opened with the 2008 discovery of the dust-obscured progenitors of the luminous outbursts in NGC 6946 and NGC 300. Here we carry out a systematic mid-IR photometric search for massive, luminous, self-obscured stars in four nearby galaxies: M33, NGC 300, M81, and NGC 6946. For detection, we use only the 3.6 micron and 4.5 micron IRAC bands, as these can still be used for multi-epoch Spitzer surveys of nearby galaxies (=<10 Mpc). We combine familiar PSF and aperture-photometry with an innovative application of image subtraction to catalog the self-obscured massive stars in these galaxies. In particular, we verify that stars analogous to the progenitors of the NGC 6946 (SN 2008S) and NGC 300 transients are truly rare in all four galaxies: their number may be as low as ~1 per galaxy at any given moment. This result empirically supports the idea that the dust-enshrouded phase is a very short-lived phenomenon in the lives of many massive stars and that these objects constitute a natural extension of the AGB sequence. We also provide mid-IR catalogs of sources in NGC 300, M81, and NGC 6946.Comment: 21 pages, 15 figures, 11 tables. Accepted by ApJ on April 12, 2010. High resolution figures and full length versions of tables 6, 8 and 10 can be accessed at http://www.astronomy.ohio-state.edu/~khan/redstars

Effect of temperature anisotropy on various modes and instabilities for a magnetized non-relativistic bi-Maxwellian plasma

Using kinetic theory for homogeneous collisionless magnetized plasmas, we present an extended review of the plasma waves and instabilities and discuss the anisotropic response of generalized relativistic dielectric tensor and Onsager symmetry properties for arbitrary distribution functions. In general, we observe that for such plasmas only those electromagnetic modes whose magnetic field perturbations are perpendicular to the ambient magneticeld, i.e.,B1 \perp B0, are effected by the anisotropy. However, in oblique propagation all modes do show such anisotropic effects. Considering the non-relativistic bi-Maxwellian distribution and studying the relevant components of the general dielectric tensor under appropriate conditions, we derive the dispersion relations for various modes and instabilities. We show that only the electromagnetic R- and L- waves, those derived from them and the O-mode are affected by thermal anisotropies, since they satisfy the required condition B1\perpB0. By contrast, the perpendicularly propagating X-mode and the modes derived from it (the pure transverse X-mode and Bernstein mode) show no such effect. In general, we note that the thermal anisotropy modifies the parallel propagating modes via the parallel acoustic effect, while it modifies the perpendicular propagating modes via the Larmor-radius effect. In oblique propagation for kinetic Alfven waves, the thermal anisotropy affects the kinetic regime more than it affects the inertial regime. The generalized fast mode exhibits two distinct acoustic effects, one in the direction parallel to the ambient magnetic field and the other in the direction perpendicular to it. In the fast-mode instability, the magneto-sonic wave causes suppression of the firehose instability. We discuss all these propagation characteristics and present graphic illustrations

A PILOT INVESTIGATION INTO ASSOCIATIONS BETWEEN VARIOUS INDOOR AIRBORNE FUNGAL PARTICLES IN TRIPLICANE PUBLIC TOILET OF CHENNAI, TAMIL NADU

Objective: To study and to explore the fungal species present in indoor toilet environment.Methods: Lactophenol cotton blue staining.Results: 5 fungi isolates belonging to 5 genus were identified namely Aspergillus niger, Aspergillus fumigates, Aspergillus flavus, Aspergillus terreus and Rhizopus oryzae.Conclusion: In order to improve the quality of indoor toilet environment regular cleaning and disinfection should be done daily

Population genetic portrait of Pakistani Lahore-Christians based on 32 STR loci.

Phylogenetic relationship and the population structure of 500 individuals from the Christian community of Lahore, Pakistan, were examined based on 15 autosomal short tandem repeats (STRs) using the AmpFℓSTR Identifiler Plus PCR Amplification Kit and our previously published Y-filer kit data (17 Y-STRs) of same samples. A total of 147 alleles were observed in 15 loci and allele 11 at the TPOX locus was the most frequent with frequency value (0.464). The data revealed that the Christian population has unique genetic characteristics with respect to a few unusual alleles and their frequencies relative to the other Pakistani population. Significant deviations from Hardy-Weinberg equilibrium were found at two loci (D13S317, D18S51) after Boneferroni's correction (p ≤ 0.003). The combined power of discrimination, combined power of exclusion and cumulative probability of matching were 0.999999999999999978430815060354, 0.999995039393942 and 2.15692 × 10-17, respectively. On the bases of genetic distances, PCA, phylogenetic and structure analysis Lahore-Christians appeared genetically more associated to south Asian particularly Indian populations like Tamil, Karnataka, Kerala and Andhra Pradesh than rest of global populations