Varkala Beach, India Napa Valley, California Toronto, Canada Kruger National Park, South Africa


Find me

Pupin 1327

marcel at

+1 212 854 6814

+1 212 854 8121

MC 5246
550 W120th St
NY NY 10027

CU astronomy »

I am an observational astronomer with two main research interests. The first is in ordinary stars a bit less massive than the Sun. These, like the Sun, are using the conversion of hydrogen into helium in their cores to prevent gravitational collapse, and are often thought to be pretty boring. But surprisingly little is known about how the basic properties of these stars change after they reach an age of a few hundred million years -- at which point they are still toddlers, since very low-mass stars can live tens of billions of years, and even the (relatively massive) Sun will live about ten billion years! I am therefore measuring and comparing stellar rotation and magnetic activity in a number of stellar clusters of different ages. These clusters have homogeneous, single-aged populations that are the key for calibrating the relationship between stellar age, rotation, and activity. My basic tools include the Palomar Transient Factory to obtain rotational periods, and Columbia's very own (well, co-own) MDM Observatory to obtain spectra, for large numbers of low-mass stars.

I also study white dwarfs and neutron stars, two of the possible endpoints of stellar evolution. In these stars fusion has ended and degeneracy pressure is preventing gravitational collapse. White dwarfs are typically the size of the Earth but two-thirds as massive as the Sun, while neutron stars, city-sized but roughly one and a half times the mass of the Sun, are even more compact. In particular, I am interested in observationally constraining the mass-radius relationship for neutron stars, and in uncovering the expected (but unseen) companions to recently discovered low-mass white dwarfs (which have masses less than one-fifth that of the Sun). Here I rely heavily on data from the Sloan Digital Sky Survey, and occasionally on access to the 3.5 m at Apache Point Observatory.

My work to date has required observations at wavelengths ranging from X-rays to the infrared and the use of large-scale survey data, both photometric and spectroscopic. (You can check my ADS publications for more details.) Using these data has unexpected consequences, like getting an asteroid named after me... an honor I did very little to deserve!