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Project Dates

The best dates would be between June 29 and July 7.

Projects Suggestions

HI From MIRA Star Outflows

• Abstract

MIRA-type variable stars typically lose 1 Solar Mass of material during this particular phase of their lifetimes. This amounts to about 1E60 hydrogen atoms. The total mass in HI is roughly M(HI)=0.1 n(HI) r^3(pc) solar masses and with n(HI) = N(HI)/(2 r) we have N(HI)=1e19 M(HI) / r^2(pc). Observations with the GBT would have to take into acount beam dilution (the MIRA shell wouldn't fill the beam) to that N(HI observed) = N(HI) r^2(pc) / [ d^2(pc) (2.6e-3)^2 ] = 1e19 M(HI) / [ d^2(pc) (2.6e-3)^2 ]. For a line-width of 20 km/s this can be converted into an expected line strength of T(line) = M(HI) / [ 2.5 * d(kpc)^2 ]. This makes such shells around MIRA stars detectable with the GBT if they can be separated from the general HI emission from the ISM.

We will identify MIRA with known CO emission. The observations will be done (and reduced) the same way that HI absorption studies are done. This will allow us to isolate the HI associatted with the MIRA stars.

• Sources

Below is a list of the Miras brighter than 7th magnitude in the visual at maximum light that have dec > 0, arranged by dec. I haven't eliminated any by RA yet. If we want to extend the dec range I can add some more to the list.

R Leo and chi Cyg (and omicron Ceti, with negative dec) are all near 100 pc, so most of this list should be stars within about 1 kpc; the K magnitudes would be better indicators of distance, but I'll have to dig a little to get those.

Most of these are well-observed so there will be a lot of other data for comparisons.

Statistically, the longer period stars are younger and more likely to be moving with the disk; the shorter ones are older and more likely to be offset from interstellar H.

The longer period ones also typically have higher mass loss rates and faster outflow speeds; these two factors nearly cancel when used to estimate the mass of H within 10^4 AU. Outflow speeds range from a couple of km/s to 20 km/s or so, with most in the 5 to 15 km/s range. The mass loss rates are variable, however, on time scales from decades to 10^5 years.

Here are some sub-lists that might help in setting priorities.

1. Miras resolved in optical and/or IR interferometric measurements:

IK Tau, R Aur, U Ori, S CMi, R Cnc, R LMi, S CrB, RU Her, U Her, R Aql, chi Cyg, R Aqr and SR variables UU Aur, V Hya and Y CVn.

2. Miras observed by Hipparcos (Whitelock et al., 2000MNRAS_319__728W) - a subset of their Table 1, eliminating faint (distant) ones and very southern ones (below). This does contain some with dec < 0, unlike last night's table. Hipparcos distances to Miras are not very reliable, but this should at least be some rough guide. Generally, stars on two of these 3 lists are high priority and on all three, very high priority.

• LST Range
  • 3:00 to 9:00 or 9:00 to 15:00

• To Do Before Observing Run

One of the following two projects depending on if the weather is good for K-band or not.

A Search For A Relation Between Water And Methanol Masers In Massive Star Formation Regions

• Abstract

It is clear that both water and methanol masers are associated with the earliest stages of massive star formation, with H2O masers thought to arise in outflows from young stellar objects (YSOs). However, few studies have been undertaken to investigate the relationship between H2O and methanol masers in a sample of high-mass YSO candidates. This proposed survey would search for H2O maser emission toward massive YSO candidates with a region already the subject of an unbiased methanol maser survey within the galactic plane. Although the spatial resolution of the GBT is not sufficient for this study to probe the spatial relationship between the two species of maser and the candidate YSO, this study will allow us to conduct a meaningful statistical analysis.

(Allowing a couple of minutes a source this could yield a hundred or so sources, resulting in up 50% new maser detections and pave the way for a much larger survey. Spectra should be quite easy to reduce and analyse.)

• High Risk

This observing involves using a high frequency receiver (K-Band at 22 GHz) during the summer when the atmospheric water content is high which results in large atmospheric opacities. This greatly reduces the chance that this project will have any success.

• Sources

• LST Range
  • 15:00 to 21:00

• To Do Before Observing Run

Mapping The OH In The Giant Atomic Cloud G28.17+0.05

• Abstract

Minter, Lockman, Langston and Lockman (ApJ, 2001, 555, 868) discovered a large atomic cloud containing 100,000 solar masses of atomic hydrogen. This cloud is also know to have at least an equivalent mass of molecular material. The cloud also contains several MSX Dark Clouds and has very few possible young stellar objects. This all suggests that the cloud is in the initial stages of forming and that it will form a stellar cluster in the near future. Minter, et al. also identified OH emission within a large portion of this cloud using archival 140 Foot Telescope data. OH is one of the first molecules to form. With the GBT a higher resolution map of the OH in this cloud could be obtained. A key question to answer is whether the OH is just associatted with the core of the cloud are is the OH dispersed throughout the whole cloud.

• Sources
  • G28.17+0.05 with a size of roughly 2x2 degrees. RA(1950)=18:39:54 Dec(1950)=-04:15:50 or RA(2000)=18 42 32.6 Dec(2000)=-04 12 50.7

• LST Range
  • 15:00 to 21:00

• To Do Before Observing Run
  • Calculate number of pointings in cloud
  • Calculate time per pointing
  • Calculate sensitivity per pointing
  • Define mapped area based on above

-- ToneyMinter - 04 Apr 2006