FAST Team: City University of New York, Hunter College — TDSS

Using TDSS to Examine the Magnetic Variability on the Coolest Stars

FAST advisors: Kelle Cruz and Emily Rice
Students: Jean-Paul Ventura, Aurora Cid
SDSS collaborator: Sarah Schmidt


M and L dwarfs are well known for their magnetic activity, which can be observed at optical wavelengths through rotational/spot modulation, dramatic flare events, and atomic emission (often using the H-alpha emission line). One key element to understanding the formation and evolution of magnetic fields on these dwarfs is their variability, in both photometric and spectroscopic observations. Using data from the Time Domain Spectroscopic Survey (TDSS), we will examine magnetic variability on cool (M) and ultracool (late-M and early-L) dwarfs in two ways.

Each target in the main TDSS survey is selected based on photometric variability criteria, then follow-up spectra are obtained to understand the cause of variability. In the SDSS-III TDSS pilot survey, 1% of the sample (2310 objects) were variable M dwarfs, and those M dwarfs were more likely to show H-alpha in emission. The expansion of the M dwarf sample by an order of magnitude during the SDSS-IV TDSS main survey provides the opportunity to examine the differences between variability-selected and non-variable M dwarfs as a function of spectral type and Galactic height, probing the variability of M dwarfs with respect to both age and mass.

The Few-Epoch Spectroscopy (FES) component of TDSS probes spectroscopic variability through repeat observations of targets with previous spectroscopy. Through TDSS FES, we are obtaining spectra of ~1000 ultracool dwarfs previously observed in DR7 to examine the differences in their chromospheres using the Halpha emission line. Due to the timing of initial SDSS spectroscopy and TDSS, these observations provide a unique opportunity to examine variability on timescales of 1-10 years. Long-timescale variability may trace changes in the underlying magnetic field (similar to the solar cycle), providing constraints on the dynamo operating in these low-mass objects.

Team Bios:

Aurora Cid

Aurora CidI was born and raised in New York City. Currently, I am majoring in Physics with a specialization in astrophysics at CUNY-College of Staten Island. When I eventually apply for a Ph.D. program I hope to specialize in stellar astronomy. My passion for astronomy came during my elementary education; trips to the Rose Center of Earth and Space and viewing the shows at the Hayden Planetarium—both at the American Museum of Natural History. Now, I am back at AMNH working with the Brown Dwarfs New York City (BDNYC) research group. We are utilizing TDSS data to examine the magnetic variability of late-M and early-L dwarfs by analyzing the differences in their chromospheres via the H-alpha emission line.

Jean-Paul Ventura

Jean-Paul VenturaI am a student of the City University of New York at Hunter College and an AstroCom Scholar with the American Museum of Natural History (AMNH). I work with BDNYC, a low-mass star and Brown dwarf research group in collaboration with the SDSS-FAST program. My work is primarily concerned with time domain study of brown dwarf H-alpha emissions as proxy for magnetic variability through use of the Extended Baryon Oscillation Spectroscopic Survey (EBOSS). In school I study both Physics and Earth Science with previous research in both Fluid Dynamics and Geology. My ultimate goal is to use this skill set in the investigation of solar and extrasolar planets and their host stars.

Kelle Cruz

kellecruzAssistant Professor at Hunter College. Her research interests include observational astronomy, optical and near-infrared spectroscopy, low-mass stars and brown dwarfs, and low-mass populations of young moving groups.

Emily Rice

emilyriceProfessor Rice’s research focuses on the astrophysical properties of the lowest mass stars, gas giant planets around nearby stars, and brown dwarfs, which are intermediate between stars and planets. She leads the research group BDNYC (Brown Dwarfs in New York City) with Prof. Kelle Cruz (Hunter College) and Dr. Jackie Faherty (Carnegie & AMNH). Her research methods combine observational and synthetic spectroscopy in order to infer the physical properties of these objects from state-of-the-art atmosphere models.

In addition to research and teaching, Professor Rice is committed to outreach and communicating science to the public. She presents public shows at the Hayden Planetarium at AMNH, organizes Astronomy on Tap (AoT) events at NYC bars, coordinates AoT locations worldwide, and co-founded the astronomy fashion blog STARtorialist. She is also co-author Astronomy Labs: A Concept-Oriented Approach, on a suite of 40 lab activities for introductory astronomy.

Professor Rice grew up in Rochester, NY and attended college at the University of Pittsburgh. She earned her Ph.D. at UCLA with Professor Ian S. McLean and was a postdoctoral researcher for two years with Rebecca Oppenheimer at the American Museum of Natural History before joining the faculty at the College of Staten Island.