AM CVn systems are a select group of ultracompact binaries with the shortest orbital periods of any known binary subclass; mass transfer is likely from a low-mass (partially-) degenerate secondary onto a white dwarf primary, driven by gravitational radiation. In the past few years, the Sloan Digital Sky Survey (SDSS) has provided five new AM CVns. Here we report on two further candidates selected from more recent SDSS data. SDSS J1208+3550 is similar to the earlier SDSS discoveries, recognized as an AM CVn via its distinctive spectrum which is dominated by helium emission. From the expanded SDSS Data Release 6 (DR6) spectroscopic area, we provide an updated surface density estimate for such AM CVns of order 10(-3.1)-10(-2.5) deg(-2) for 15 < g < 20.5. In addition, we present another new candidate AM CVn, SDSS J2047+0008, which was discovered in the course of follow-up of SDSS-II supernova candidates. It shows nova-like outbursts in multi-epoch imaging data; in contrast to the other SDSS AM CVn discoveries, its (outburst) spectrum is dominated by helium absorption lines, reminiscent of KL Dra, and 2003aw. The variability selection of SDSS J2047+0008 from the 300 deg(2) of SDSS Stripe 82 presages further AM CVn discoveries in future deep, multicolor, and time-domain surveys such as the Large Synoptic Survey Telescope (LSST). The new additions bring the total SDSS yield to seven AM CVns thus far, a substantial contribution to this rare subclass, versus the dozen previously known.

ABSTRACTThis poster presents a customizable round-tripping UML class diagram plug-in for Eclipse called Green. While this tool was developed primarily with students and instructors in introductory OO computer science courses in mind, its extensible architecture makes it potentially useful to others.Green is a flexible tool: each binary class relationship is implemented as a separate plug-in to the basic tool. The set of relationships supported is therefore easily tailored to the needs of the user. More importantly, the semantics of the relationships can be defined to suit the user. The tool can therefore adapt to the needs of its users.

UML class diagrams are used quite commonly in CS1-CS2 courses and textbooks. The benefits of using these diagrams include providing a programming-language independent way of communicating program design, in an industry standard language. While drawing diagrams by hand is in itself useful, beginning students do not always perceive the benefit of designing before coding, and create these diagrams only if they have to, and then only as an afterthought.We have found that students are much more receptive to using UML class diagrams as an integral part of their development if they see immediate benefits from doing so. This paper describes Green , a simple to use yet flexible and extensible UML class diagramming tool. Green (an Eclipse plug-in) provides complete round-tripping between code and class diagram. This capability makes it easy for students to alternate between a detailed code-level view and a more abstract design view of their projects. With this capability students see creating class diagrams not as a separate and tedious activity, but as an easy way to turn designs into code and to discover the design of existing code.Green's distinguishing features when compared to similar tools are that it has been developed to meet the needs of CS1-CS2 students, the semantics of its relationships are customizable, additional class relationships can be defined and it is integrated with Eclipse, a mature development environment.