At the Edge of NGC 891

I'm currently working on a project to develop a High School research competition based on pulsating variable stars.  This is funded by a NASA Rocky Mountain Space Grant Consortium Mini Grant.  We will provide variable star data to a number of high school teams that will then analyze the data and provide a final report that will be judged.  

We are exploring the changes of Carbon-Monoxide molecular bands over the pulsation cycle of Cepheids variables. The growth of these bands could have an impact on the Hubble Tension. This is done in the Near-IR with the ARC 3.5-m telescope. This allows complete coverage of the phase curve, which is not possible in the Mid-IR (MIR) with systems like the JWST.

We have developed a number of robotic telescope systems on the observation deck of the Eyring Science Center.  These range from 6" and 24".  Most of the systems are currently capable of working the entire night robotically.  We observe transiting planets, eclipsing binary systems, pulsating variables, and other systems that change in brightness. In some cases we really want to process the data as soon as possible to get the data sent to programs like the NASA TESS transit finding program.  With the amount of data generated we just need help in processing the data.  If someone were to work on this program they would get experience over a wide range of objects.

Always looking for new research students on these projects.

The Near-IR is an area that hasn't been extensively explored for pulsating variable stars. We are obtaining NIR spectra of the stars of the instability strip (Cepheids, RR Lyrae, delta Scuti, etc.) to study a number of different issues. This includes looking for cool companion stars, molecular banding structures, line-profile changes over pulsation phases.  Some of these could be related to the Hubble Tension issue.

In general, researchers consider there to be two groups of delta Scuti variables; the High Amplitude delta Scuti (HADS) and the Low Amplitude delta Scuti (LADS). However, the in between realm is interesting. The Medium Amplitide delta Scuti stars seems to show a range of changes in both amplitude and period. This makes them a very interesting group to monitor.

We are now adding some computer modeling to try to better understand these changes.

This is a place where there is always need for additional help.  We will have 6 robotic telescopes running on every clear night by the summer of 2022.  That means a lot of data to process and light curves to be determined.

Traditionally the H-beta index has been used as a reddening free index to measure the surface temperature of stars. Prof. Joner in the department has developed a new H-alpha index that has great promise. We are working together to spectrophotometrically compare the two systems and the application of the system to a number of different types of objects.

To understand the nature of the delta Scuti variables in the instability strip one needs as much information as possible about the stars. However, an examination of the catalog of delta Scuti variables shows a lack of basic information on many of the group. Of the 247 delta Scuti stars visible in the northern hemisphere we currently have spectra of 242 of them. These need to be reduced to provide estimates of some basic stellar properties like [Fe/H], radial velocity, rotational velocity, and perhaps information on any binary companions.

We are currently searching for new low amplitude variable stars in a large sample of open clusters. The clusters cover a wide range of ages and will provide a evolutionary test of how the variable stars change with age. We are also looking for very small eclipses that might be the sign of a planet.