268 research outputs found
Pod set and Pollen Viability Studies in Yard Long Bean (Vigna unguiculata sub sp. sesquipedalis)
A study was conducted in a yard long bean (Vigna unguiculata sup/ssp. sesquipedalis) hybrid VS 50 (Kakkamoola Local) x VS 26 (Vellayani Jyothika) to assess the percentage fruit set at two time intervals and to identify the best time interval for pollination in yard long bean hybrids. Hand pollination was done using VS 50 as female parent and VS 26 as male parent for seven consecutive days at two time intervals, 6.30 – 7.30 am and 7.30 – 8.30 am. Higher percentage of fruit set (36.8 %) was observed between 6:30 – 7:30 a.m. as compared to the time interval 7:30 – 8:30 am. (23.8%). Pollen viability was determined for the parents VS 50 (Kakkamoola Local) and VS 26 (Vellayani Jyothika) at 6.30, 7.30 and 8.30 am. Highest pollen viability for both the parents VS 50 and VS 26 was observed during 7.30 am. The present study shows that the best time interval for crossing in yard long bean is 6.30- 7.30 a.m
The Luminosities of Protostars in the Spitzer c2d and Gould Belt Legacy Clouds
Motivated by the long-standing "luminosity problem" in low-mass star
formation whereby protostars are underluminous compared to theoretical
expectations, we identify 230 protostars in 18 molecular clouds observed by two
Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We
compile complete spectral energy distributions, calculate Lbol for each source,
and study the protostellar luminosity distribution. This distribution extends
over three orders of magnitude, from 0.01 Lsun - 69 Lsun, and has a mean and
median of 4.3 Lsun and 1.3 Lsun, respectively. The distributions are very
similar for Class 0 and Class I sources except for an excess of low luminosity
(Lbol < 0.5 Lsun) Class I sources compared to Class 0. 100 out of the 230
protostars (43%) lack any available data in the far-infrared and submillimeter
(70 um < wavelength < 850 um) and have Lbol underestimated by factors of 2.5 on
average, and up to factors of 8-10 in extreme cases. Correcting these
underestimates for each source individually once additional data becomes
available will likely increase both the mean and median of the sample by 35% -
40%. We discuss and compare our results to several recent theoretical studies
of protostellar luminosities and show that our new results do not invalidate
the conclusions of any of these studies. As these studies demonstrate that
there is more than one plausible accretion scenario that can match
observations, future attention is clearly needed. The better statistics
provided by our increased dataset should aid such future work.Comment: Accepted for publication in AJ. 21 pages, 10 figures, 4 table
The 69 {}m forsterite band in spectra of protoplanetary disks. Results from the Herschel DIGIT programme
Context. We have analysed far-infrared spectra of 32 circumstellar disks around Herbig Ae/Be and T Tauri stars obtained within the Herschel key programme Dust, Ice and Gas in Time (DIGIT). The spectra were taken with the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory. In this paper we focus on the detection and analysis of the 69 {}m emission band of the crystalline silicate forsterite.
Aims: This work aims at providing an overview of the 69 {}m forsterite bands present in the DIGIT sample. We use characteristics of the emission band (peak position and FWHM) to derive the dust temperature and to constrain the iron content of the crystalline silicates. With this information, constraints can be placed on the spatial distribution of the forsterite in the disk and the formation history of the crystalline grains.
Methods: The 69 {}m forsterite emission feature is analysed in terms of position and shape to derive the temperature and composition of the dust by comparison to laboratory spectra of that band. The PACS spectra are combined with existing Spitzer IRS spectra and we compare the presence and strength of the 69 {}m band to the forsterite bands at shorter wavelengths.
Results: A total of 32 disk sources have been observed. Out of these 32, 8 sources show a 69 {}m emission feature that can be attributed to forsterite. With the exception of the T Tauri star AS 205, all of the detections are for disks associated with Herbig Ae/Be stars. Most of the forsterite grains that give rise to the 69 {}m bands are found to be warm (~{}100-200 K) and iron-poor (less than ~{}2% iron). AB Aur is the only source where the emission cannot be fitted with iron-free forsterite requiring approximately 3-4% of iron.
Conclusions: Our findings support the hypothesis that the forsterite grains form through an equilibrium condensation process at high temperatures. The large width of the emission band in some sources may indicate the presence of forsterite reservoirs at different temperatures. The connection between the strength of the 69 and 33 {}m bands shows that at least part of the emission in these two bands originates fom the same dust grains. We further find that any model that can explain the PACS and the Spitzer IRS observations must take the effects of a wavelength dependent optical depth into account. We find weak indications of a correlation of the detection rate of the 69 {}m band with the spectral type of the host stars in our sample. However, the sample size is too small to obtain a definitive result. Appendix A is available in electronic form at http://www.aanda.or
SOLUTION OF ELD PROBLEM WITH VALVE POINT EFFECTS AND MULTI FUELS USING IPSO ALGORITHM
ABSTRACT: This project presents a novel and improved method for solving the Non Convex Economic Dispatch (ELD) problems with valve-point effects and Multiple Fuels, by integrating the particle swarm optimization (PSO) with the chaotic sequences and Cross over Operations. The results of the IPSO were compared with previous methods and the conventional Genetic Algorithm (GA), revealing that the results clearly show that the proposed IPSO outperforms other state-of-the-art algorithms in solving ELD problems with the valve-point effect
The Rapid Outbursting Star GM Cep: An EX-or in Tr 37?
We present optical, IR and millimeter observations of the solar-type star
13-277, also known as GM Cep, in the 4 Myr-old cluster Tr 37. GM Cep
experiences rapid magnitude variations of more than 2 mag at optical
wavelengths. We explore the causes of the variability, which seem to be
dominated by strong increases in the accretion, being similar to EX-or
episodes. The star shows high, variable accretion rates (up to ~10
Msun/yr), signs of powerful winds, and it is a very fast rotator (Vsini~43
km/s). Its strong mid-IR excesses reveal a very flared disk and/or a remnant
envelope, most likely out of hydrostatic equilibrium. The 1.3 millimeter fluxes
suggest a relatively massive disk (Mdisk~0.1 Msun). Nevertheless, the
millimeter mass is not enough to sustain increased accretion episodes over
large timescales, unless the mass is underestimated due to significant grain
growth. We finally explore the possibility of GM Cep having a binary companion,
which could trigger disk instabilities producing the enhanced accretion
episodes.Comment: 43 pages, including 10 figures, ApJ in pres
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