NGC 4103 is a young age cluster in the Southern constellation Crux that was discovered in 1826 by James Dunlop. There are 421 probable member stars within the cluster’s angular radius, with 199 within the central part of the cluster. One member of the cluster had been identified as a Be star, which is a part of a heterogeneous set of stars with B spectral types and emission lines. Another member of the cluster is AI Crucis, which is a short-period semi-detached massive close binary star with an orbit period of 1.41771 days. Its orbital period is continuously increasing, being explained by mass transfer from the less massive component to the more massive component, and strong stellar wind from the hot component, with an estimated 4.1 solar mass having been transferred. Currently, no blue stragglers or red giants have been found as members, and the cluster is mostly dominated by stars of the 10th magnitude.

In a recent study,  Li et al (2018) determined that NGC 4103 has an age spread of 2-4 Myr. When compared to other young clusters, such as the Orion Nebula Cluster and W3 Main, it has a relatively average age spread. Some outliers in this data were NGC 3603 YC with an age spread of 0.1 Myr, Antennae Clusters with an age spread of <6 Myr, and NGC 1569A without an observed spread due to it being free of dust extinction.

In order to study NGC 4103 and investigate the relationships between the colors, brightnesses, and the age and chemical composition of the cluster as a whole, I collected 15 images using the Prompt5 telescope located at the Cerro Tololo Inter-American Observatory in Chile. Total exposure durations of 41, 31, and 16 seconds were used for B, V, and R filters, respectively. Each filter was used for 5 images, with an hour between when each image was taken to get more robust data. Additionally, the Max Sun Elevation was set to -15 degrees, Min Target Elevation to 30 degrees, Max Moon Phase to 50%, and Min Moon Separation to 60 degrees, using Skynet. I used Afterglow to align and stack the images taken, and to calibrate the colors. Cluster Astromancer was used to remove field stars, gather data from catalogues, perform Isochrone Matching, and create visual diagrams. This produced the following basic results for NGC 4103:

Proper Motion RA (mas/yr)	Proper Motion Dec (mas/yr)	Distance (kpc)	log(Age(yrs))	Metallicity (solar)	E(B-V)
-6.21	0.19	1.7	7.8	-0.1	0.32

The following diagrams were also created when Isochrone Matching to create a better fit when deciding on the above results:

This data was then used to create a more accurate color image of NGC 4103:

This information shows that NGC 4103 is a young star cluster, with an age of 7.8 log(age(yrs)). It has a much higher absolute RA proper motion than Dec Proper motion, meaning it is moving across the RA more than the Dec. The distance of the cluster is relatively close to us, with an estimated distance of 1.7 kpc. It’s metallicity is -0.1, which implies this cluster has a mix of population I and II stars. The cluster’s interstellar reddening is 0.32, which indicates some interstellar dust.

When observing the Gaia HR diagram, there appears to be 2 stars above the turn-off point, which could be identified as blue stragglers. However, They seem “close enough” to the turn-off point for it to be conclusive. When observing the Gaia HR Diagram, there does not seem to be any white dwarfs within the cluster. There seems to be a bright red star within the colored image near the center, which could indicate a red giant, however the Gaia HR Diagram does not show any indication of red giants within the cluster, so this is also inconclusive. NGC 4103 seems to be primarily dominated by main sequence and pre-main sequence stars.

NGC 4013 was studied by Kharchenko et al (2013), who found the following parameters:

Distance (kpc)	log(Age(yrs))	Metallicity (solar)	E(B-V)
1.659	7.755	N/A	0.302

When plotting the Gaia data using these parameters with Cluster Astromancer, using a value of 0 for metallicity for open clusters, I got the following:

These parameters align better around the turnoff point, but due to not having a metallicity value, the isochrone model is too high for the main sequence area. Adjusting the metallicity to -0.1, and then tweaking the other values gives the best result, which aligns with my own measured parameters. Overall, Kharchenko et al had very close parameters to my own, but the difference with metallicity, as well as the minor changes to distance, age, and reddening, allows for my own analysis to improve on theirs.

Having completed my analysis, this cluster project has improved my knowledge on stellar clusters and created an interest in astronomy that I will continue to pursue.