OBJECTS: Other stars with ISM polarization

UW Astronomer: A. Weitenbeck

Besides the observations which appeared in the WUPPE ISM polarization paper in AJ 112, 2726, Dec 96:
WUPPE obtained observations of several stars which were HUT targets, or which were directly pointed to in a UIT field, or to which WUPPE offset from HUT or UIT pointing coordinates.
These stars are mostly fainter than those chosen to be on the WUPPE ISM polarization target list (in UIT fields there rarely were stars as bright as WUPPE usually tried to observe, since those were too bright for UIT), and the observation was usually shorter than WUPPE needed to obtain very high quality polarimetry (a couple which were usefully long observations are in the AJ Dec 96 paper).
Because of this the observations are generally not as good as those shown in that paper, and interpretation is more difficult. Additionally, since for some we do not have good visual polarization data yet (we planning to acquire new HPOL and southern hemisphere observations), final interepretation of all the observations is impossible now. When we do have complete data, we will look to putting it into a form similar to the earlier AJ paper.
Several stars were given in a poster at the 206th AAS meeting in Minneapolis, BAAS 37, 490 2005:

A slightly reddened B2V in Orion, observed on a HUT program to observe normal stars. A fairly high quality WUPPE observation, but polarization is too low to fit a reliable Serkowski curve with the current HPOL data.

A B2V with Ha emission. This was taken to estimate the ISM polarization in the direction of WUPPE target EZ CMa. The polarization is fairly low, and at dec -24 is also too far south to get highest quality HPOL data. The WUPPE and HPOL data are consistent with small ISM polarization.

NGC 2682 81
A Blue Straggler, B8V, the brightest hot star in M67, a UIT pointing. The WUPPE and HPOL blue grating data now available show measurable polarization when given as one bin. This star is too faint to get high quality HPOL data, but the polarization generally follows a Serkowski curve.

BD+36 367
A Blue Straggler, A0III, in NGC 752, UIT pointing. The HPOL data is good quality polarimetry when expressed as broad band data, but the WUPPE observation is more of an upper limit. This the only example of this type of WUPPE observation (detected, but poor statistics) for which HPOL data can be gotten at PBO.

B9II/III star in the field of globular cluster NGC6752; several UIT pointings were made to this cluster, so the WUPPE observation was long enough to be good quality. We do not have visible polarimetry data for the star itself, but Lupie & Stockman in Polarized Radiation of Circumstellar Origin say the average cluster polarization is .8% at B, .7% in V, at 178 degrees, consistent with the WUPPE data.
This star needs high quality spectropolarimetry from the south (dec -60).

This star was the brightest star in a UIT field; it is relatively faint, and the WUPPE exposure was too short to get high quality data, though it appears that the longer wavelength bin shows polarization. Dec = -36, needs visible light spectropolarimetry.

OBJECTS: Magellanic Cloud targets

UW Astronomer: A. Weitenbeck

WUPPE made several pointings to Magellanic Cloud stars as part of a Guest Investigator project by Geoff Clayton, which appeared in ApJ 460, 313,1996.

Besides these, WUPPE also observed several stars which were HUT targets or in UIT fields. These are generally less highly polarized than the stars chosen by Clayton, the observations are shorter, and some were done during the daytime portion of the orbit (so may be contaminated by scattered light). For these stars we did not have good visible polarimetry beforehand, and we are now attempting to obtain such in order to interpret the data. The WUPPE observations, though not of the best quality, may be useful, if for nothing else, to place upper limits on the UV polarizations of these stars.