2,714 research outputs found
A contracting circumbinary molecular ring with an inner cavity of about 140 AU around Ori 139-409
Sensitive and subarcsecond resolution ( 0.7\arcsec) CHOH(7
6) line and 890 m continuum observations made with the
Submillimeter Array (SMA) towards the hot molecular circumbinary ring
associated with the young multiple star Ori 139-409 are presented. The
CHOH(7 - 6) emission from the ring is well resolved at
this angular resolution revealing an inner cavity with a size of about 140 AU.
A LTE model of a Keplerian disk with an inner cavity of the same size confirms
the presence of this cavity. Additionally, this model suggests that the
circumbinary ring is contracting with a velocity of V 1.5 km
s toward the binary central compact circumstellar disks reported at a
wavelength of 7 mm. {\bf The inner central cavity seems to be formed by the
tidal effects of the young stars in the middle of the ring.} The ring appears
to be not a stationary object. Furthermore, the infall velocity we determine is
about a factor of 3 slower than the free-fall velocity corresponding to the
dynamical mass. This would correspond to a mass accretion rate of about
10 M/yr. We found that the dust emission associated with Ori
139-409 appears to be arising from the circumstellar disks with no strong
contribution from the molecular gas ring. A simple comparison with other
classical molecular dusty rings (e.g. GG Tau, UZ Tau, and UY Aur) suggests that
Ori 139-409 could be one of the youngest circumbinary rings reported up to
date. Finally, our results confirm that the circumbinary rings are actively
funneling fresh gas material to the central compact binary circumstellar disks,
i.e. to the protostars in the very early phases of their evolution.Comment: Accepted by MNRA
Circumbinary Molecular Rings Around Young Stars in Orion
We present high angular resolution 1.3 mm continuum, methyl cyanide molecular
line, and 7 mm continuum observations made with the Submillimeter Array and the
Very Large Array, toward the most highly obscured and southern part of the
massive star forming region OMC1S located behind the Orion Nebula. We find two
flattened and rotating molecular structures with sizes of a few hundred
astronomical units suggestive of circumbinary molecular rings produced by the
presence of two stars with very compact circumstellar disks with sizes and
separations of about 50 AU, associated with the young stellar objects 139-409
and 134-411. Furthermore, these two circumbinary rotating rings are related to
two compact and bright {\it hot molecular cores}. The dynamic mass of the
binary systems obtained from our data are 4 M for 139-409 and
0.5 M for 134-411. This result supports the idea that
intermediate-mass stars will form through {\it circumstellar disks} and
jets/outflows, as the low mass stars do. Furthermore, when intermediate-mass
stars are in multiple systems they seem to form a circumbinary ring similar to
those seen in young, multiple low-mass systems (e.g., GG Tau and UY Aur).Comment: Accepted by Astronomy and Astrophysic
Developed Speculation and Under Developed Markets - The Role of Futures Trading on Export Prices in Less Developed Countries
This paper examines the relationship between New York coffee futures and cash export prices in Guatemala and Honduras . Cointegration tests suggest that the futures market is serving its price discovery function, and provides a vehicle by which to manage the domestic price risk in export countries. However, further analysis finds that as the percent of speculative open interest increases in the coffee futures market, price volatility increases. This suggests that cash market price risk in exporting countries may actually increase as a result of futures trading activity in developed country futures exchanges.
Price Discovery in the World Sugar Futures and Cash Markets: Implications for the Domincan Republic
This paper examines the relationship between #11 sugar futures prices traded in New York and the world cash prices for exported sugar. It was found that the futures market for sugar leads the cash market in price discovery. However, we fail to find evidence that changes in the cash price causes changes in futures price, that is, causality is unidirectional from futures to cash. The finding of cointegration between futures and cash prices suggests that the sugar futures contract is a useful vehicle for reducing overall market price risk faced by cash market participants selling at the world price (i.e., not enjoying favorable trade incentives). Further reliability on the usefulness of the WSF as a price discovery market is found through the impulse response functions; a shock in the futures price innovation generates a quick (one month) and positive response in futures and cash prices; but not vice versa.
Radio Continuum Sources Associated with AB Aur
We present high angular resolution, high-sensitivity Very Large Array
observations at 3.6 cm of the Herbig Ae star AB Aur. This star is of interest
since its circumstellar disk exhibits characteristics that have been attributed
to the presence of an undetected low mass companion or giant gas planet. Our
image confirms the continuum emission known to exist in association with the
star, and detects a faint protuberance that extends about to its
SE. Previous theoretical considerations and observational results are
consistent with the presence of a companion to AB Aur with the separation and
position angle derived from our radio data. We also determine the proper motion
of AB Aur by comparing our new observations with data taken about 17 years ago
and find values consistent with those found by Hipparcos.Comment: 6 pages, 1 figur
Ethnic Identity, Risk, and Protective Factors Related to Substance Abuse Among Mexican American Students
This study examines the relationship between ethnic identity, risk and protective factors for substance use and academic achievement. Risk factors include deviant behavior and susceptibility to peer influence, while the protective factor is self-reported confidence not to use substances. The sample consists of 2,370 Mexican American students enrolled in eighth, ninth, and tenth grades. Results of the analysis (MANOVA) revealed that females had more positive ethnic identity than males. Furthermore, males were significantly more susceptible to peer influence, reported higher levels of deviant behavior, used more substances and had lower grade point averages than females. There was no significant difference in their confidence not to use substances
PRICE DISCOVERY IN THE FUTURES AND CASH MARKET FOR SUGAR
Pricing function using world sugar futures (WSF) has received limited research interest. Findings indicate that WSF and cash prices for the Dominican Republic appears cointegrated with changing relationships. Previous work suggests that futures markets price the cheapest quality of commodities deliverable on contracts. Cointegration results are consistent with this argument.Marketing,
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