Extreme Infrared Variables from UKIDSS - I. A Concentration in Star Forming Regions

Abstract

We present initial results of the first panoramic search for high-amplitude near-infrared variability in the Galactic Plane. We analyse the widely separated two-epoch K-band photometry in the 5th and 7th data releases of the UKIDSS Galactic Plane Survey. We find 45 stars with ΔK > 1 mag, including 2 previously known OH/IR stars and a Nova. Even though the mid-plane is not yet included in the dataset, we find the majority (66%) of our sample to be within known star forming regions (SFRs), with two large concentrations in the Serpens OB2 association (11 stars) and the Cygnus-X complex (12 stars). Sources in SFRs show spectral energy distributions (SEDs) that support classification as Young Stellar Objects (YSOs). This indicates that YSOs dominate the Galactic population of high amplitude infrared variable stars at low luminosities and therefore likely dominate the total high amplitude population. Spectroscopic follow up of the DR5 sample shows at least four stars with clear characteristics of eruptive pre-main-sequence variables, two of which are deeply embedded. Our results support the recent concept of eruptive variability comprising a continuum of outburst events with different timescales and luminosities, but triggered by a similar physical mechanism involving unsteady accretion. Also, we find what appears to be one of the most variable classical Be stars.

26 pages, 16 Figures, accepted for publication in MNRAS

References in corpus (21)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• A Spitzer Survey of Young Stellar Clusters within One Kiloparsec of the Sun: Cluster Core Extraction and Basic Structural Analysis
• The UKIDSS Galactic Plane Survey
• New Grids of ATLAS9 Model Atmospheres
• The WFCAM Science Archive
• The UKIRT Infrared Deep Sky Survey Early Data Release
• The Mid-Infrared Extinction Law in the Ophiuchus, Perseus, and Serpens Molecular Clouds
• The Electron Temperature Gradient in the Galactic Disk
• The IPHAS Catalogue of Halpha Emission Line Sources in the Northern Galactic Plane
• Luminous K-band Selected Quasars from UKIDSS
• IPHAS and the symbiotic stars. I. Selection method and first discoveries
• Warps, bending and density waves excited by rotating magnetized stars: results of global 3D MHD simulations
• The Edge of the Milky Way Stellar Disk Revealed Using Clump Giant Stars as Distance Indicators
• The outburst of the eruptive young star OO Serpentis between 1995 and 2006
• Variable Evolved Stars and YSOs Discovered in the Large Magellanic Cloud using the SAGE Survey
• Deep near-IR variability survey of pre-main-sequence stars in Rho Ophiuchi
• Variability of Be Stars in Southern Open Clusters
• Optical and infrared properties of V1647 Orionis during the 2003-2006 outburst. II. Temporal evolution of the eruptive source
• The B and Be Star Population of NGC 3766
• OB Stars in the Solar Neighborhood I: Analysis of their Spatial Distribution
• Stellar Variability in the VVV survey

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• Quantifying Variability of YSOs in the Mid-IR Over Six Years with NEOWISE
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• Extreme infrared variables from UKIDSS - II. an end-of-survey catalogue of eruptive YSOs and unusual stars
• Short and long term near-infrared spectroscopic variability of eruptive protostars from VVV
• The 2014-2017 outburst of the young star ASASSN-13db: A time-resolved picture of a very low-mass star between EXors and FUors
• Characterising the i-band variability of YSOs over six orders of magnitude in timescale
• Magnetically-activated accretion outbursts of pre-main sequence discs
• Discovery of a mid-infrared protostellar outburst of exceptional amplitude
• High Proper Motion Objects from the UKIDSS Galactic Plane Survey
• YSO jets in the Galactic Plane from UWISH2: IV - Jets and outflows in Cygnus-X
• YSO jets in the Galactic Plane from UWISH2: III - Jets and Outflows in Cassiopeia and Auriga
• A survey for variable young stars with small telescopes: II -- Mapping a protoplanetary disk with stable structures at 0.15 AU
• Accretion and outflow in the proplyd-like objects near Cygnus OB2
• Scientific Goals of the Kunlun Infrared Sky Survey (KISS)
• The VMC Survey - XXXII. Pre-main sequence populations in the Large Magellanic Cloud
• Discovery of a Long-Lived, High Amplitude Dusty Infrared Transient
• The VMC survey -- XXXVI. Young stellar variability in the Large Magellanic Cloud
• New eruptive variable in the massive star-forming region associated with IRAS 18507+0121 source
• Discovery of two infrared objects with strong ice absorption in the AKARI slit-less spectroscopic survey of the Galactic Plane
• Stellar Variability in a Forming Massive Star Cluster
• Discovery of two embedded massive YSOs and an outflow in IRAS 18144-1723
• UGPS J194310+183851: an Unusual Optical and X-ray Faint Cataclysmic Variable?