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Green, Joel D.,Evans II, Neal J.,Jørgensen, Jes K.,Herczeg, Gregory J.,Kristensen, Lars E.,Lee, Jeong-Eun,Dionatos, Odysseas,Yildiz, Umut A.,Salyk, Colette,Meeus, Gwendolyn,Bouwman, Jeroen,Visser, Ruu IOP Publishing 2013 The Astrophysical journal Vol.770 No.2
<P>We present 50-210 mu m spectral scans of 30 Class 0/I protostellar sources, obtained with Herschel-PACS, and 0.5-1000 mu m spectral energy distributions, as part of the Dust, Ice, and Gas in Time Key Program. Some sources exhibit up to 75 H2O lines ranging in excitation energy from 100 to 2000 K, 12 transitions of OH, and CO rotational lines ranging from J = 14 -> 13 up to J = 40 -> 39. [O I] is detected in all but one source in the entire sample; among the sources with detectable [O I] are two very low luminosity objects. The mean 63/145 mu m [O I] flux ratio is 17.2 +/- 9.2. The [O I] 63 mu m line correlates with L-bol, but not with the time-averaged outflow rate derived from low-J CO maps. [C II] emission is in general not local to the source. The sample L-bol increased by 1.25 (1.06) and T-bol decreased to 0.96 (0.96) of mean (median) values with the inclusion of the Herschel data. Most CO rotational diagrams are characterized by two optically thin components (< N > = ( 0.70 +/- 1.12) x 10(49) total particles). N-CO correlates strongly with L-bol, but neither T-rot nor N-CO(warm)/N-CO(hot) correlates with L-bol, suggesting that the total excited gas is related to the current source luminosity, but that the excitation is primarily determined by the physics of the interaction (e.g., UV-heating/shocks). Rotational temperatures for H2O (< T-rot > = 194 +/- 85 K) and OH (< T-rot > = 183 +/- 117 K) are generally lower than for CO, and much of the scatter in the observations about the best fit is attributed to differences in excitation conditions and optical depths among the detected lines.</P>
Green, Joel D.,Yang, Yao-Lun,II, Neal J. Evans,Karska, Agata,Herczeg, Gregory,Dishoeck, Ewine F. van,Lee, Jeong-Eun,Larson, Rebecca L.,Bouwman, Jeroen American Astronomical Society 2016 The Astronomical journal Vol.151 No.3
<P>We present the COPS-DIGIT-FOOSH (CDF) Herschel spectroscopy data product archive, and related ancillary data products, along with data fidelity assessments, and a user-created archive in collaboration with the Herschel-PACS and SPIRE ICC groups. Our products include datacubes, contour maps, automated line fitting results, and best 1D spectra products for all protostellar and disk sources observed with PACS in RangeScan mode for two observing programs: the DIGIT Open Time Key Program (KPOT_nevans_1 and SDP_nevans_1; PI: N.. Evans), and the FOOSH Open Time Program (OT1_jgreen02_2; PI: J. Green). In addition, we provide our best SPIRE-FTS spectroscopic products for the COPS Open Time Program (OT2_jgreen02_6; PI: J. Green) and FOOSH sources. We include details of data processing, descriptions of output products, and tests of their reliability for user applications. We identify the parts of the data set to be used with caution. The resulting absolute flux calibration has improved in almost all cases. Compared to previous reductions, the resulting rotational temperatures and numbers of CO molecules have changed substantially in some sources. On average, however, the rotational temperatures have not changed substantially (<2%), but the number of warm (T-rot similar to 300 K) CO molecules has increased by about 18%.</P>
Green, Joel D.,Robertson, Paul,Baek, Giseon,Pooley, David,Pak, Soojong,Im, Myungshin,Lee, Jeong-Eun,Jeon, Yiseul,Choi, Changsu,Meschiari, Stefano IOP Publishing 2013 The Astrophysical journal Vol.764 No.1
<P>We present the detection of day-timescale periodic variability in the r-band lightcurve of newly outbursting FU Orionis-type object HBC 722, taken from >42 nights of observation with the CQUEAN instrument on the McDonald Observatory 2.1 m telescope. The optical/near-IR lightcurve of HBC 722 shows a complex array of periodic variability, clustering around 5.8-day (0.044 mag amplitude) and 1.28-day (0.016 mag amplitude) periods, after removal of overall baseline variation. We attribute the unusual number of comparable strength signals to a phenomenon related to the temporary increase in accretion rate associated with FUors. We consider semi-random 'flickering,' magnetic braking/field compression and rotational asymmetries in the disk instability region as potential sources of variability. Assuming that the 5.8-day period is due to stellar rotation and the 1.28-day period is indicative of Keplerian rotation at the inner radius of the accretion disk (at 2 R-star), we derive a B-field strength of 2.2-2.7 kG, slightly larger than typical T Tauri stars. If instead the 5.8-day signal is from a disk asymmetry, the instability region has an outer radius of 5.4 R-star, consistent with models of FUor disks. Further exploration of the time domain in this complicated source and related objects will be key to understanding accretion processes.</P>
CO in Protostars (COPS): <i>Herschel</i>-SPIRE Spectroscopy of Embedded Protostars
Yang, Yao-Lun,Green, Joel D.,Evans II, Neal J.,Lee, Jeong-Eun,Jørgensen, Jes K.,Kristensen, Lars E.,Mottram, Joseph C.,Herczeg, Gregory,Karska, Agata,Dionatos, Odysseas,Bergin, Edwin A.,Bouwman, Jeroe American Astronomical Society 2018 The Astrophysical journal Vol.860 No.2
<P>We present full spectral scans from 200 to 670. mu m of 26 Class 0+I protostellar sources obtained with Herschel-SPIRE as part of the 'COPS-SPIRE' Open Time program, complementary to the DIGIT and WISH Key Programs. Based on our nearly continuous, line-free spectra from 200 to 670. mu m, the calculated bolometric luminosities (L-bol) increase by 50%. on average, and the bolometric temperatures (T-bol) decrease by 10%. on average, in comparison with the measurements without Herschel. Fifteen protostars have the same class using Tbol and L-bol/L-smm. We identify rotational transitions of CO lines from J = 4 -> 3to J = 13 -> 12, along with emission lines of (CO)-C-13, HCO+, H2O, and [C I]. The ratios of (CO)-C-12 to (CO)-C-13 indicate that (CO)-C-12 emission remains optically thick for J(up) < 13. We fit up to four components of temperature from the rotational diagram with flexible break points to separate the components. The distribution of rotational temperatures shows a primary population around 100 K with a secondary population at similar to 350 K. We quantify the correlations of each line pair found in our data set and find that the strength of the correlation of CO lines decreases as the difference between J levels between two CO lines increases. The multiple origins of CO emission previously revealed by velocity-resolved profiles are consistent with this smooth distribution if each physical component contributes to a wide range of CO lines with significant overlap in the CO ladder. We investigate the spatial extent of CO emission and find that the morphology is more centrally peaked and less bipolar at high-J lines. We find the CO emission observed with SPIRE related to outflows, which consists of two components, the entrained gas and shocked gas, as revealed by our rotational diagram analysis, as well as the studies with velocity-resolved CO emission.</P>
HIGH RESOLUTION OPTICAL AND NIR SPECTRA OF HBC 722
Lee, Jeong-Eun,Park, Sunkyung,Green, Joel D.,Cochran, William D.,Kang, Wonseok,Lee, Sang-Gak,Sung, Hyun-Il IOP Publishing 2015 The Astrophysical journal Vol.807 No.1
<P>We present the results of high resolution (R >= 30,000) optical and near-IR spectroscopic monitoring observations of HBC 722, a recent FU Orionis object that underwent an accretion burst in 2010. We observed HBC 722 in the optical/near-IR with the Bohyunsan Optical Echelle Spectrograph, Hobby-Eberly Telescope-HRS, and Immersion Grating Infrared Spectrograph, at various points in the outburst. We found atomic lines with strongly blueshifted absorption features or P Cygni profiles, both evidence of a wind driven by the accretion. Some lines show a broad double-peaked absorption feature, evidence of disk rotation. However, the wind-driven and disk-driven spectroscopic features are anti-correlated in time; the disk features became strong as the wind features disappeared. This anti-correlation might indicate that the rebuilding of the inner disk was interrupted by the wind pressure during the first 2 years. The half-width at half-depth of the double-peaked profiles decreases with wavelength, indicative of the Keplerian rotation; the optical spectra with the disk feature are fitted by a G5 template stellar spectrum convolved with a rotation velocity of 70 km s(-1) while the near-IR disk features are fitted by a K5 template stellar spectrum convolved with a rotation velocity of 50 km s(-1). Therefore, the optical and near-IR spectra seem to trace the disk at 39 and 76 R-circle dot, respectively. We fit a power-law temperature distribution in the disk, finding an index of 0.8, comparable to optically thick accretion disk models.</P>
L1448-MM OBSERVATIONS BY THE <i>HERSCHEL</i> KEY PROGRAM, “DUST, ICE, AND GAS IN TIME” (DIGIT)
Lee, Jinhee,Lee, Jeong-Eun,Lee, Seokho,Green, Joel. D.,Evans II, Neal J.,Choi, Minho,Kristensen, Lars,Dionatos, Odysseas,Jørgensen, Jes K. IOP Publishing 2013 The Astrophysical journal, Supplement series Vol.209 No.1