Two New roAp Stars Discovered with TESS

Rahul Jayaraman,George Ricker,Saul Rappaport,Gerald Handler,Donald W Kurtz

doi:10.3847/2515-5172/ac3a8a

Abstract

Abstract We present two new rapidly oscillating Ap (roAp) stars, TIC 198781841 and TIC 229960986, discovered in TESS photometric data. The periodogram of TIC 198781841 has a large peak at 166.506 day−1 (1.93 mHz), with two nearby peaks at 163.412 day−1 (1.89 mHz) and 169.600 day−1 (1.96 mHz). These correspond to three independent high-overtone pressure modes, with alternating even and odd ℓ values. TIC 229960986 has a high-frequency triplet centered at 191.641 day−1 (2.218 mHz), with sidebands at 191.164 day−1 (2.213 mHz) and 192.119 day−1 (2.224 mHz). This pulsation appears to be a rotationally split dipole mode, with sideband amplitudes significantly larger than that of the central peak; hence, both pulsation poles are seen over the rotation cycle. Our photometric identification of two new roAp stars underscores the remarkable ability of TESS to identify high-frequency pulsators without spectroscopic observations.

Highlights

The Transiting Exoplanet Survey Satellite (TESS; Ricker et al 2015) has revolutionized the field of asteroseismology with its short-cadence observations of over 200 000 stars during its Prime Mission, from 2018 July to 2020 July (Guerrero et al 2021)
We present two new rapidly oscillating Ap stars, TIC 198781841 and TIC 229960986, discovered in TESS photometric data
Our photometric identification of two new rapidly oscillating Ap (roAp) stars underscores the remarkable ability of TESS to identify high-frequency pulsators without spectroscopic observations

Summary

INTRODUCTION

The Transiting Exoplanet Survey Satellite (TESS; Ricker et al 2015) has revolutionized the field of asteroseismology with its short-cadence observations of over 200 000 stars during its Prime Mission, from 2018 July to 2020 July (Guerrero et al 2021). Of particular note are the rapidly oscillating chemically peculiar A (roAp) stars, whose high-frequency pulsations are identified using a continuously-observing, short-cadence space probe like TESS or Kepler that can produce a light curve with a high signal-to-noise ratio. Tens of new roAp stars have been identified from recent large-scale space- and ground-based photometric surveys (see Holdsworth 2021 and references therein). There have been roAp stars discovered that are cooler than the theoretical boundary of the instability strip, along with a pronounced dearth of stars toward the blue (hotter) edge of the instability strip (Cunha et al 2019). By finding more roAp stars, large surveys such as TESS can provide the statistics to determine the underlying cause of this discrepancy – perhaps either from an observational bias or lower amplitudes in the pulsations of hotter stars

OBSERVATIONS AND DATA

MODE IDENTIFICATION

TIC 198781841

TIC 229960986

CONCLUSION