27 yr of Spaceborne IR Astronomy: An ISO, Spitzer, WISE, and NEOWISE Survey for Large-amplitude Variability in Young Stellar Objects
Year: 2026
Type: article
Abstract: Infrared observations can probe photometric variability across the full evolutionary range of young stellar objects (YSOs), from deeply embedded protostars to pre-main-sequence stars with dusty disks. We present 3–8 μ m light curves extending 27 yr from 1997 to 2024 obtained with three space-based IR telescopes: Infrared Space Observatory, Spitzer, and Wide-field Infrared Survey Explorer (WISE). Although unevenly sampled with large gaps in coverage, these light curves show variability on timescales ranging from days to decades. We focus on the Spitzer-identified YSOs with disks and envelopes that exhibit variations of a factor of two or more in this wavelength range. We identified seven YSOs where the light curves are dominated by bursts of sustained (>5 yr) high flux, including four that show a steep decay ending the burst and three that are ongoing as of the final observation. We find six YSOs that are undergoing declines, which may be the end of bursts that began before 1997. The most common form of variability, exhibited by 26 YSOs in our sample, show variations over time intervals of years to months but do not exhibit sustained bursts or fades. The Spitzer [3.6] – [4.5] and WISE [3.5] – [4.6] colors either increase or remain constant with increasing brightness, inconsistent with dust extinction as being the primary source of the large-amplitude variability.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Awards: G1237781132, G276637519, G5141829021, LOW MASS STAR FORMATION IS A COMPLEX PROCESS INVOLVING THE INTERPLAY OF THE FRAGMENTATION OF FILAMENTARY STRUCTURES THE COLLAPSE OF THE FRAGMENTS THE ACCRETION OF MASS THROUGH DISKS AND THE RESULTING FEEDBACK THROUGH COLLIMATED OUTFLOWS. IT OCCURS IN DIVERSE ENVIRONMENTS WITH ORDER OF MAGNITUDE DIFFERENCES IN THE RATE AND EFFICIENCY OF STAR FORMATION YET RESULTS IN A RELATIVELY INVARIANT IMF. STUDIES OF THE RICH POPULATION OF PROTOSTARS IN THE NEAREST STAR FORMING CLOUDS ARE NOW POSSIBLE DUE TO A REMARKABLE DECADE OF WIDE FIELD SPACED BASED IR ASTRONOMY. WE PROPOSE TO CREATE A DATABASE OF LOW MASS PROTOSTARS WITHIN 500 PC OF THE SUN USING SPITZER HERSCHEL WISE AND NEOWISE TO IDENTIFY PROTOSTARS CONSTRUCT THEIR SPECTRAL ENERGY DISTRIBUTIONS (SEDS) FROM 3.4 TO 500 MICRONS AND STUDY THEIR MID TO FAR-IR VARIABILITY. THIS CENSUS WILL LEVERAGE THE METHODOLOGIES CODE AND EXPERIENCE GAINED IN THE HERSCHEL ORION PROTOSTAR SURVEY OF 321 ORION PROTOSTARS. WE EXPECT TO ALMOST TRIPLE THE NUMBER OF PROTOSTARS WITH WELL DETERMINED SEDS IN THE NEAREST 500 PC MEASURE THE BASIC OBSERVABLES OF THESE PROTOSTARS (BOLOMETRIC LUMINOSITY SED SHAPE AND VARIABILITY) AND ESTIMATE THEIR FUNDAMENTAL PHYSICAL PARAMETERS (TOTAL LUMINOSITY INNER ENVELOPE MASS MASS INFALL RATE) BY PERFORMING FITS TO A GRID OF 30400 SEDS GENERATED FROM ROTATING COLLAPSE MODELS. WITH THESE DATA WE WILL STUDY THE PROCESSES THAT REGULATE MASS ACCRETION ONTO PROTOSTARS THEREBY PUTTING ESSENTIAL CONSTRAINTS ON PROTOSTAR MODELS. USING LUMINOSITIES AND BOLOMETRIC TEMPERATURES WE WILL STUDY THE EVOLUTION OF ACCRETION ONTO PROTOSTARS AS THEIR ENVELOPES DISPERSE THEREBY TESTING MODELS OF MASS INFALL AND THE ORIGIN OF THE IMF. WITH THE MULTI-EPOCH DATA WE WILL ASSESS THE TYPICAL LEVEL OF VARIABILITY AS WELL AS CONSTRAIN THE RATE AND MAGNITUDES OF LUMINOUS OUTBURSTS DRIVEN BY EPISODIC ACCRETION. FINALLY WE WILL LOOK FOR SYSTEMATIC CHANGES IN THE PROTOSTELLAR LUMINOSITY BETWEEN MOLECULAR CLOUDS WHICH WOULD BE EVIDENCE THAT ACCRETION IS STRONGLY AFFECTED BY THEIR FORMATION ENVIRONMENT. THE WIDE SPATIAL AND BROAD WAVELENGTH COVERAGE OF THE SPITZER WISE AND HERSCHEL MISSIONS WILL NOT BE SURPASSED IN THE FORESEEABLE FUTURE AND THE SEDS GENERATED BY THIS PROPOSAL WILL BE THE DEFINITIVE SAMPLE OF MID- TO FAR-IR PROTOSTELLAR SEDS FOR YEARS TO COME. IN ADDITION TO ARCHIVAL DRIVEN SCIENCE THEY WILL BE AN ESSENTIAL RESOURCE FOR PLANNING AND INTERPRETING OBSERVATIONS WITH ALMA SOFIA JWST AND WFIRST.
OpenAlex ID: W7140110257