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Soam, A.,Kwon, Jugmi,Maheswar, G.,Tamura, Motohide,Lee, Chang Won IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.803 No.2
<P>LDN 328 is cited as an example of a fairly isolated clump contracting to form multiple sub-cores, possibly through gravitational fragmentation. In one of these sub-cores, a proto-brown dwarf (L328-IRS) candidate is in the process of formation through the self-gravitating contraction, similar to the formation scenario of a low-mass star. We present results of our optical and near-infrared polarization observations of regions toward LDN 328. This is the first observational attempt to map the magnetic field geometry of a cloud harboring a proto-brown dwarf candidate associated with a sub-parsec-scale molecular outflow. On a parsec scale, the magnetic field is found to follow the curved structure of the cloud showing a head-tail morphology. The magnetic field is found to be well ordered over a 0.02-0.2 pc scale around L328-IRS. Taking into account the uncertainties in the determination of position angles, the projected angular offset between the magnetic field direction and the outflow axis is found to be in the range of 0 degrees-70 degrees. Considering outflow to be the proxy for the rotation axis, the result obtained in this study implies that the rotation axis in L328 is preferably parallel to the local magnetic field. The magnetic field strength estimated in the close vicinity of L328-IRS is similar to 20 mu G. Results from the present study suggest that the magnetic field may be playing a vital role even in the cores that are forming sub-stellar sources.</P>
Distances to dense cores that contain very low luminosity objects
Maheswar, G.,Lee, C. W.,Dib, S. EDP Sciences 2011 Astronomy and astrophysics Vol.536 No.2
<P>Aims. We estimate the distances to dense molecular cores that harbour very low luminosity objects (VeLLOs) detected by the Spitzer Space Telescope and attempt to confirm their VeLLO nature. Methods. The cloud distances are estimated using a near-IR photometric method. We use a technique that performs a spectral classification of stars lying towards the fields containing the clouds as either main-sequence stars or giants. In this technique, the observed (J H) and (HKs) colours are dereddened simultaneously using trial values of AV and a normal interstellar extinction law. The best fit of the dereddened colours to the intrinsic colours giving a minimum value of χ2 then yields the corresponding spectral type and AV for the star. The main-sequence stars, thus classified, are then utilized in an AV versus distance plot to bracket the cloud distances. The typical error in the estimation of distances to the clouds are found to be ~18%. Results. We estimate distances to seven cloud cores, IRAM?04191, L1521F, BHR?111, L328, L6737, L1014, and L1148 using the above method. These clouds contain VeLLO candidates. The estimated distances to the cores are found to be 127 ±25 pc (IRAM?04191), 136±36 pc (L1521F), 355 ±65 pc (BHR?111), 217 ±30 pc (L328), 240±45 pc (L6737), 258± 50 pc (L1014), and 301± 55 pc (L1148). We re-evaluated the internal luminosities of the VeLLOs discovered in these seven clouds using the distances estimated from this work. Except for L1014 IRS (Lint = 0.15 L<SUB>⊙<SUB>), all other VeLLO candidates are found to be consistent with the definition of a VeLLO (Lint ≤ 0.1 L<SUB>⊙<SUB>). In addition to the cores that harbour VeLLO candidates, we also obtained distances to the clouds L323, L675, L676, CB 188, L1122, L1152, L1155, L1157, and L1158, which are located in the directions of the above seven cores. Towards L1521F and L1148, we found evidence of multiple dust layers.</P>
EXPERIMENTAL INVESTIGATION ON TEMPERATURE SEPARATION OF DUAL FORCED FLOW VORTEX TUBE
G. MARUTHI PRASAD YADAV,P. MALLIKARJUNA REDDY,B. UMA MAHESWAR GOWD 대한설비공학회 2014 International Journal Of Air-Conditioning and Refr Vol.22 No.4
The vortex tube is a device, which emanates hot and cold air streams simultaneously at its two ends from a source of pressurized air: warmer, gas leaves near the periphery at one end as a free vortex and colder, gas leaves via an orifice at the opposite end as a forced vortex. The forced vortex strikes back again by design modifications, result in the formation of one more forced vortex flow. Thus, the modified vortex tube is named as dual forced flow vortex tube (DFFVT). Experimental study is carried on temperature separation of DFFVT for varying pressures, mass flow rates and optimum cold fractions at two ends for efficient temperature drop is revealed. The modified vortex tube yields effectual temperature drop through one end at a lower cold fraction meanwhile providing effective cooling at the other end with higher cold fraction and vice versa.
Magnetic fields in cometary globules – IV. LBN 437
Soam, A.,Maheswar, G.,Bhatt, H. C.,Lee, C. W.,Ramaprakash, A. N. Oxford University Press 2013 Monthly notices of the Royal Astronomical Society Vol.432 No.2
<P>We present results of our R-band polarimetry of a cometary globule, LBN 437 (Gal 96-15, l = 96 degrees, b = -15 degrees), to study the magnetic field geometry of the cloud. We estimated a distance of 360 +/- 65 pc to LBN 437 (also one additional cloud, CB 238) using a near-IR photometric method. The foreground contribution to the observed polarization values was subtracted by making polarimetric observations of stars that are located in the direction of the cloud and with known distances from the Hipparcos parallax measurements. The magnetic field geometry of LBN 437 is found to follow the curved shape of the globule head. This could be due to the drag that the magnetic field lines could have experienced because of the ionization radiation from the same exciting source that caused the cometary shape of the cloud. The orientation of the outflow from the Herbig A4e star, LkH alpha 233 (or V375 Lac), located at the head of LBN 437, is found to be parallel to both the initial (prior to the ionizing source was turned on) ambient magnetic field (inferred from a star HD 214243 located just in front of the cloud) and the Galactic plane.</P>