Multiwavelength Observations of V2775 Ori, an Outbursting Protostar in L 1641: Exploring the Edge of the FU Orionis Regime

TL;DR

This study presents multiwavelength observations of V2775 Ori, a low-luminosity protostar undergoing an FU Orionis-like outburst, revealing insights into episodic accretion processes and their role in protostellar luminosity variation.

Contribution

It provides detailed spectral energy distribution modeling of V2775 Ori before and after outburst, demonstrating a significant increase in accretion rate and confirming low-luminosity FU Orionis events.

Findings

Outburst began between 2005 and 2007.

Accretion rate increased from 2x10^-6 to 10^-5 M_sun/yr.

Post-outburst luminosity is 28 L_sun, the lowest for FU Orionis objects.

Abstract

Individual outbursting young stars are important laboratories for studying the physics of episodic accretion and the extent to which this phenomenon can explain the luminosity distribution of protostars. We present new and archival data for V2775 Ori (HOPS 223), a protostar in the L 1641 region of the Orion molecular clouds that was discovered by Caratti o Garatti et al. (2011) to have recently undergone an order-of-magnitude increase in luminosity. Our near-infrared spectra of the source have strong blueshifted He I 10830 absorption, strong H2O and CO absorption, and no H I emission, all typical of FU Orionis sources. With data from IRTF, 2MASS, HST, Spitzer, WISE, Herschel, and APEX that span from 1 to 70 microns pre-outburst and from 1 to 870 microns post-outburst, we estimate that the outburst began between 2005 April and 2007 March. We also model the pre- and post-outburst spectral energy distributions of the source, finding it to be in the late stages of accreting its envelope with a disk-to-star accretion rate that increased from about 2x10^-6 M_sun/yr to about 10^-5 M_sun/yr during the outburst. The post-outburst luminosity at the epoch of the FU Orionis-like near-IR spectra is 28 L_sun, making V2775 Ori the least luminous documented FU Orionis outburster with a protostellar envelope. The existence of low-luminosity outbursts supports the notion that a range of episiodic accretion phenomena can partially explain the observed spread in protostellar luminosities.