J/ApJ/885/64 Amplitude of variability for 150 YSOs in Orion (Ellithorpe+, 2019) ================================================================================ The nature of class I sources: periodic variables in Orion. Ellithorpe E.A., Duchene G., Stahler S.W. =2019ApJ...885...64E ================================================================================ ADC_Keywords: YSOs; Stars, pre-main sequence; Infrared Keywords: Circumstellar matter ; Pre-main sequence stars ; Protostars ; Starspots ; T Tauri stars ; Herbig Ae/Be stars Abstract: We present a quantitative, empirically based argument that at least some Class I sources are low-mass, pre-main-sequence stars surrounded by spatially extended envelopes of dusty gas. The source luminosity arises principally from stellar gravitational contraction, as in optically visible pre-main-sequence stars that lack such envelopes. We base our argument on the fact that some Class I sources in Orion and other star-forming regions have been observed by Spitzer to be periodic variables in the mid-infrared, and with periods consistent with T Tauri rotation rates. Using a radiative transfer code, we construct a variety of dust envelopes surrounding rotating, spotted stars, to see whether an envelope that produces a Class I spectral energy distribution at least broadly matches the observed modulations in luminosity. Acceptable envelopes can be either spherical or flattened and may or may not have polar cavities. The key requirement is that they have a modest equatorial optical depth at the Spitzer waveband of 3.6{mu}m, typically {tau}3.6~0.6. The total envelope mass, based on this limited study, is at most about 0.1M{sun}, less than a typical stellar mass. Future studies should focus on the dynamics of the envelope, to determine whether material is actually falling onto the circumstellar disk. Description: We considered the 150 variable objects in Orion that had newly identified periods in Morales-Calderon, 2011, J/ApJ/733/50 (Table 4) to place the amplitude of variability of the Class I sources studied here in their broader context. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table5.dat 47 150 Amplitude of variability for 150 YSOs in Orion -------------------------------------------------------------------------------- See also: VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006) J/ApJS/101/117 : UBVRIJHKLMNQ photometry in Taurus-Auriga (Kenyon+ 1995) J/AJ/130/1145 : YSO near-infrared properties (Doppmann+, 2005) J/AJ/140/1214 : Near-IR spectroscopic survey of class I YSOs (Connelley+,2010) J/ApJ/733/50 : Mid-IR photometric monitoring of ONC (Morales-Calderon+, 2011) J/AJ/144/192 : Spitzer survey of Orion A & B. I. YSO catalog (Megeath+, 2012) J/A+A/570/A29 : TBOSS Survey I: Herschel/PACS (Bulger+, 2014) J/AJ/147/82 : Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014) J/AJ/148/122 : YSOVAR: infrared photometry in Lynds 1688 (Gunther+, 2014) J/AJ/150/118 : YSOVAR IR photometry in IRAS 20050+2720 (Poppenhaeger+, 2015) J/AJ/150/175 : YSOVAR: infrared photometry in NGC 1333 (Rebull+, 2015) J/AJ/150/145 : YSOVAR infrared photometry in GGD12-15 (Wolk+, 2015) J/ApJS/224/5 : The Herschel Orion Protostar Survey: SEDs (Furlan+, 2016) J/ApJ/821/52 : NIR survey of Spitzer YSOs in Orion Mol. Cloud (Kounkel+,2016) J/A+A/590/A33 : Class 0 sources continuum subtracted UV-tables (Persson+,2016) J/ApJ/849/63 : FIR-mm data of YSOs in star-forming regions (Ribas+, 2017) Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 23 A23 --- Star Target name 25- 27 A3 --- Class Classification 29- 33 F5.2 d Period [1.05/24.8] Period 35- 39 F5.2 mag alpha [-0.26/0.39] Amplitude of variation at 3.6micron 41- 45 F5.2 mag error [1.06/15.6] Reduced chi square error 47 A1 --- Note Note (1) -------------------------------------------------------------------------------- Note (1): Notes as follows: a = The object is an eclipsing binary, as identified from its light curve at 3.6microns (2 occurrences). b = Misclassified in Megeath, 2012, J/AJ/144/192. These are Class II Objects, based on their SEDs (2 occurrences). -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Coralie Fix [CDS], 03-Jun-2021