On the mid-IR variability of candidate eruptive variables (EXors): a comparison between Spitzer and WISE data

Abstract

Aiming to statistically study the variability in the mid-IR of young stellar objects, we have compared the 3.6, 4.5, and 24 um Spitzer fluxes of 1478 sources belonging to the C2D (Cores to Disks) legacy program with the WISE fluxes at 3.4, 4.6, and 22 um. From this comparison we have selected a robust sample of 34 variable sources. Their variations were classified per spectral Class (according to the widely accepted scheme of Class I/flat/II/III protostars), and per star forming region. On average, the number of variable sources decreases with increasing Class and is definitely higher in Perseus and Ophiuchus than in Chamaeleon and Lupus. According to the paradigm Class <=> Evolution, the photometric variability can be considered to be a feature more pronounced in less evolved protostars, and, as such, related to accretion processes. Moreover, our statistical findings agree with the current knowledge of the star formation activity in different regions. The 34 selected variables were further investigated for similarities with known young eruptive variables, namely the EXors. In particular we analyzed : (1) the shape of the spectral energy distribution (SED); (2) the IR excess over the stellar photosphere; (3) magnitude versus color variations; and (4) output parameters of model fitting. This first systematic search for EXors ends up with 11 bona fide candidates that can be considered as suitable targets for monitoring or future investigations.

29 pages, 6 figures, accepted by ApJ; updated version with typos fixed

References in corpus (38)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Spitzer Space Telescope Mission
• The Spitzer c2d Legacy Results: Star Formation Rates and Efficiencies; Evolution and Lifetimes
• Interpreting Spectral Energy Distributions from Young Stellar Objects. II. Fitting observed SEDs using a large grid of pre-computed models
• Interpreting Spectral Energy Distributions from Young Stellar Objects. I. A grid of 200,000 YSO model SEDs
• Dense Cores in Dark Clouds. XIV. N2H+(1-0) maps of dense cloud cores
• From Molecular Cores to Planet-forming Disks: A SIRTF Legacy Program
• 2-D Radiative Transfer in Protostellar Envelopes: I. Effects of Geometry on Class I Sources
• The Spitzer Space Telescope Survey of the Orion A & B Molecular Clouds - Part I: A Census of Dusty Young Stellar Objects and a Study of their Mid-IR Variability
• 2-D Radiative Transfer in Protostellar Envelopes: II. An Evolutionary Sequence
• Properties of the Youngest Protostars in Perseus, Serpens, and Ophiuchus
• Identifying the Low Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores
• A Catalogue of Optically Selected Cores
• YSOVAR: the first sensitive, wide-area, mid-IR photometric monitoring of the ONC
• The Disk Population of the Chamaeleon I Star-Forming Region
• Episodic Accretion on to Strongly Magnetic Stars
• The Spitzer c2d Survey of Large, Nearby, Insterstellar Clouds. IX. The Serpens YSO Population As Observed With IRAC and MIPS
• Current Star Formation in the Perseus Molecular Cloud: Constraints from Unbiased Submillimeter and Mid-Infrared Surveys
• Observations and modeling of the inner disk region of T Tauri stars
• A systematic survey for eruptive young stellar objects using mid-infrared photometry
• Evidence for an FU Orionis-like Outburst from a Classical T Tauri Star
• The outburst and nature of two young eruptive stars in the North America/Pelican Nebula Complex
• New Young Star Candidates in the Taurus-Auriga Region as Selected From WISE
• On the nature of the EXor accretion events: an unfrequent manifestation of a common phenomenology ?
• EX Lupi in quiescence
• Highly Variable Extinction and Accretion in the Jet-driving Class I Type Young Star PTF 10nvg (V2492 Cyg, IRAS 20496+4354)
• A multi-wavelength study of the young star V1118 Orionis in outburst
• X-Ray Spectral Variability During an Outburst in V1118 Ori
• Evidence for T Tauri-like emission in the EXor V1118 Ori from near-IR and X-ray data
• Enhanced X-ray variability from V1647 Ori, the young star in outburst illuminating McNeil's Nebula
• An infrared view of the EXor variables: on the case of V1118 ORI
• Spatially Resolved Mid-IR Imaging of the SR 21 Transition Disk
• Variability at the Edge: Optical Near/IR Rapid Cadence Monitoring of Newly Outbursting FU Orionis Object HBC 722
• A few days before the end of the 2008 extreme outburst of EX Lup : accretion shocks and a smothered stellar corona unveiled by XMM-Newton
• Potential Drivers of Mid-Infrared Variability in Young Stars: testing physical models with multi-epoch near-infrared spectra of YSOs in ρ Oph
• Infrared point source variability between the Spitzer and MSX surveys of the Galactic mid-plane
• Pre-Main Sequence variables in the VMR-D : identification of T Tauri-like accreting protostars through Spitzer-IRAC variability
• WISE photometry of EXor sources and candidates

Cited by in corpus (20)

• Young Stellar Object Variability (YSOVAR): Long Timescale Variations in the Mid-Infrared
• A population of eruptive variable protostars in VVV
• Quantifying Variability of YSOs in the Mid-IR Over Six Years with NEOWISE
• Dust Polarization Toward Embedded Protostars in Ophiuchus with ALMA. III. Survey Overview
• A continuum of accretion burst behavior in young stars observed by K2
• KMOS study of the mass accretion rate from Class I to Class II in NGC 1333
• Extreme infrared variables from UKIDSS - II. an end-of-survey catalogue of eruptive YSOs and unusual stars
• Discovery of a mid-infrared protostellar outburst of exceptional amplitude
• Dissecting the different components of the modest accretion bursts of the very young protostar HOPS 373
• Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants from the VVV survey
• Outbursting Young Stellar Object PGIR 20dci in the Perseus Arm
• The outbursting protostar 2MASS~22352345+7517076 and its environment
• On the incidence of episodic accretion in Class I YSOs from VVV
• The accretion process in the DQ Tau binary system
• DR Tau: Temporal variability of the brightness distribution in the potential planet-forming region
• Photometric and Spectroscopic monitoring of YSOs in nearby star forming regions. I. Eruptive YSOs
• Accretion and extinction variations in the low-mass pre-main sequence binary system WX Cha
• Identification and parameter determination of F-type Herbig stars from LAMOST DR8
• A machine learning approach to estimate mid-infrared fluxes from WISE data
• Automatic Detection of Accretion Bursts in Young Stellar Objects: a New Algorithm for Long--Term Sky Surveys