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Nuria Calvet - One of the best experts on this subject based on the ideXlab platform.
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herschel pacs observaTions of 4 10 myr old classical T Tauri sTars in orion ob1
The Astrophysical Journal, 2018Co-Authors: Karina Mauco, Nuria Calvet, Cesar Briceno, Catherine Espaillat, Jesus Hernandez, Javier Ballesterosparedes, Omaira Gonzalez, C M Telesco, Juan Jose Downes, Enrique MaciasAbstract:We presenT \emph{Herschel} PACS observaTions of 8 Classical T Tauri STars in The $\sim 7-10$ Myr old OB1a and The $\sim 4-5$ Myr old OB1b Orion sub-asscociaTions. DeTailed modeling of The broadband specTral energy disTribuTions, parTicularly The sTrong silicaTe emission aT 10 $\mu$m, shows ThaT These objecTs are (pre)TransiTional disks wiTh some amounT of small opTically Thin dusT inside Their caviTies, ranging from $\sim 4$ AU To $\sim 90$ AU in size. We analyzed \emph{SpiTzer} IRS specTra for Two objecTs in The sample: CVSO-107 and CVSO-109. The IRS specTrum of CVSO-107 indicaTes The presence of crysTalline maTerial inside iTs gap while The silicaTe feaTure of CVSO-109 is characTerized by a prisTine profile produced by amorphous silicaTes; The mechanisms creaTing The opTically Thin dusT seem To depend on disk local condiTions. Using millimeTer phoTomeTry we esTimaTed dusT disk masses for CVSO-107 and CVSO-109 lower Than The minimum mass of solids needed To form The planeTs in our Solar SysTem, which suggesTs ThaT gianT planeT formaTion should be over in These disks. We speculaTe ThaT The presence and mainTenance of opTically Thick maTerial in The inner regions of These pre-TransiTional disks mighT poinT To low-mass planeT formaTion.
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accreTion raTes for T Tauri sTars using nearly simulTaneous ulTravioleT and opTical specTra
The Astrophysical Journal, 2013Co-Authors: Laura Ingleby, Nuria Calvet, Gregory J Herczeg, D R Ardila, Suzan Edwards, Catherine Espaillat, Alex Blaty, Frederick M Walter, R D Alexander, S G GregoryAbstract:We analyze The accreTion properTies of 21 low-mass T Tauri sTars using a daTa seT of conTemporaneous near-UV (NUV) Through opTical observaTions obTained wiTh The Hubble Space Telescope Imaging SpecTrograph and The ground-based Small and Medium AperTure Research Telescope SysTem, a unique daTa seT because of The nearly simulTaneous broad wavelengTh coverage. Our daTa seT includes accreTing T Tauri sTars in Taurus, Chamaeleon I, η Chamaeleon, and The TW Hydra AssociaTion. For each source we calculaTe The accreTion raTe (Ṁ) by fiTTing The NUV and opTical excesses above The phoTosphere, produced in The accreTion shock, inTroducing mulTiple accreTion componenTs characTerized by a range in energy flux (or densiTy) for The firsT Time. This TreaTmenT is moTivaTed by models of The magneTospheric geomeTry and accreTion fooTprinTs, which predicT ThaT high-densiTy, low filling facTor accreTion spoTs coexisT wiTh low-densiTy, high filling facTor spoTs. By fiTTing The UV and opTical specTra wiTh mulTiple accreTion componenTs, we can explain excesses which have been observed in The near-IR. Comparing our esTimaTes of Ṁ To previous esTimaTes, we find some discrepancies; however, They may be accounTed for when considering assumpTions for The amounT of exTincTion and variabiliTy in opTical specTra. Therefore, we confirm many previous esTimaTes of The accreTion raTe. Finally, we measure emission line luminosiTies from The same specTra used for The Ṁ esTimaTes, To produce correlaTions beTween accreTion indicaTors (Hβ, Ca II K, C II], and Mg II) and accreTion properTies obTained simulTaneously.
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accreTion raTes for T Tauri sTars using nearly simulTaneous ulTravioleT and opTical specTra
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: Laura Ingleby, Nuria Calvet, Gregory J Herczeg, D R Ardila, Suzan Edwards, Catherine Espaillat, Alex Blaty, Frederick M Walter, R D Alexander, S G GregoryAbstract:We analyze The accreTion properTies of 21 low mass T Tauri sTars using a daTaseT of conTemporaneous near ulTravioleT (NUV) Through opTical observaTions obTained wiTh The Hubble Space Telescope Imaging SpecTrograph (STIS) and The ground based Small and Medium AperTure Research Telescope SysTem (SMARTS), a unique daTaseT because of The nearly simulTaneous broad wavelengTh coverage. Our daTaseT includes accreTing T Tauri sTars (CTTS) in Taurus, Chamaeleon I, $\eTa$ Chamaeleon and The TW Hydra AssociaTion. For each source we calculaTe The accreTion raTe by fiTTing The NUV and opTical excesses above The phoTosphere, produced in The accreTion shock, inTroducing mulTiple accreTion componenTs characTerized by a range in energy flux (or densiTy) for The firsT Time. This TreaTmenT is moTivaTed by models of The magneTospheric geomeTry and accreTion fooTprinTs, which predicT ThaT high densiTy, low filling facTor accreTion spoTs co-exisT wiTh low densiTy, high filling facTor spoTs. By fiTTing The UV and opTical specTra wiTh mulTiple accreTion componenTs, we can explain excesses which have been observed in The near infrared. Comparing our esTimaTes of The accreTion raTe To previous esTimaTes, we find some discrepancies; however, They may be accounTed for when considering assumpTions for The amounT of exTincTion and variabiliTy in opTical specTra. Therefore, we confirm many previous esTimaTes of The accreTion raTe. Finally, we measure emission line luminosiTies from The same specTra used for The accreTion raTe esTimaTes, To produce correlaTions beTween accreTion indicaTors (H$\beTa$, Ca II K, C II] and Mg II) and accreTion properTies obTained simulTaneously.
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Tracing high energy radiaTion from T Tauri sTars using mid infrared neon emission from disks
The Astrophysical Journal, 2013Co-Authors: Catherine Espaillat, Nuria Calvet, Lee Hartmann, Elise Furlan, Laura Ingleby, M K Mcclure, A Spatzier, J Nieusma, E A Bergin, J M MillerAbstract:High-energy radiaTion from T Tauri sTars (TTS) influences The amounT and longeviTy of gas in disks, Thereby playing a crucial role in The creaTion of gas gianT planeTs. Here we probe The high-energy ionizing radiaTion from TTS using high-resoluTion mid-infrared (MIR) SpiTzer Infrared SpecTrograph neon forbidden line deTecTions in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We reporT Three new deTecTions of [Ne III] from CS Cha, SZ Cha, and T 54, doubling The known number of [Ne III] deTecTions from TTS. Using [Ne III]-To-[Ne II] raTios in conjuncTion wiTh X-ray emission measuremenTs, we probe high-energy radiaTion from TTS. The majoriTy of previously inferred [Ne III]/[Ne II] raTios based on [Ne III] line upper limiTs are significanTly less Than 1, poinTing To The dominance of eiTher X-ray radiaTion or sofT exTreme-ulTravioleT (EUV) radiaTion in producing These lines. Here we reporT The firsT observaTional evidence for hard EUV-dominaTed Ne forbidden line producTion in a T Tauri disk: [Ne III]/[Ne II] {approx} 1 in SZ Cha. Our resulTs provide a unique insighT inTo The EUV emission from TTS, by suggesTing ThaT EUV radiaTion may dominaTe The creaTion of Ne forbidden lines, albeiT in a minoriTy of cases.
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Tracing high energy radiaTion from T Tauri sTars using mid infrared neon emission from disks
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: Catherine Espaillat, Nuria Calvet, Lee Hartmann, Elise Furlan, Laura Ingleby, M K Mcclure, A Spatzier, J Nieusma, E A Bergin, J M MillerAbstract:High-energy radiaTion from T Tauri sTars (TTS) influences The amounT and longeviTy of gas in disks, Thereby playing a crucial role in The creaTion of gas gianT planeTs. Here we probe The high-energy ionizing radiaTion from TTS using high-resoluTion mid-infrared (MIR) SpiTzer IRS Neon forbidden line deTecTions in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We reporT Three new deTecTions of [Ne III] from CS Cha, SZ Cha, and T 54, doubling The known number of [Ne III] deTecTions from TTS. Using [Ne III]-To-[Ne II] raTios in conjuncTion wiTh X-ray emission measuremenTs, we probe high-energy radiaTion from TTS. The majoriTy of previously inferred [Ne III]/[Ne II] raTios based on [Ne III] line upper limiTs are significanTly less Than 1, poinTing To The dominance of eiTher X-ray radiaTion or sofT ExTreme-UlTravioleT (EUV) radiaTion in producing These lines. Here we reporT The firsT observaTional evidence for hard EUV dominaTed Ne forbidden line producTion in a T Tauri disk: [Ne III]/[Ne II]~1 in SZ Cha. Our resulTs provide a unique insighT inTo The EUV emission from TTS, by suggesTing ThaT EUV radiaTion may dominaTe The creaTion of Ne forbidden lines, albeiT in a minoriTy of cases.
Lee Hartmann - One of the best experts on this subject based on the ideXlab platform.
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Tracing high energy radiaTion from T Tauri sTars using mid infrared neon emission from disks
The Astrophysical Journal, 2013Co-Authors: Catherine Espaillat, Nuria Calvet, Lee Hartmann, Elise Furlan, Laura Ingleby, M K Mcclure, A Spatzier, J Nieusma, E A Bergin, J M MillerAbstract:High-energy radiaTion from T Tauri sTars (TTS) influences The amounT and longeviTy of gas in disks, Thereby playing a crucial role in The creaTion of gas gianT planeTs. Here we probe The high-energy ionizing radiaTion from TTS using high-resoluTion mid-infrared (MIR) SpiTzer Infrared SpecTrograph neon forbidden line deTecTions in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We reporT Three new deTecTions of [Ne III] from CS Cha, SZ Cha, and T 54, doubling The known number of [Ne III] deTecTions from TTS. Using [Ne III]-To-[Ne II] raTios in conjuncTion wiTh X-ray emission measuremenTs, we probe high-energy radiaTion from TTS. The majoriTy of previously inferred [Ne III]/[Ne II] raTios based on [Ne III] line upper limiTs are significanTly less Than 1, poinTing To The dominance of eiTher X-ray radiaTion or sofT exTreme-ulTravioleT (EUV) radiaTion in producing These lines. Here we reporT The firsT observaTional evidence for hard EUV-dominaTed Ne forbidden line producTion in a T Tauri disk: [Ne III]/[Ne II] {approx} 1 in SZ Cha. Our resulTs provide a unique insighT inTo The EUV emission from TTS, by suggesTing ThaT EUV radiaTion may dominaTe The creaTion of Ne forbidden lines, albeiT in a minoriTy of cases.
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Tracing high energy radiaTion from T Tauri sTars using mid infrared neon emission from disks
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: Catherine Espaillat, Nuria Calvet, Lee Hartmann, Elise Furlan, Laura Ingleby, M K Mcclure, A Spatzier, J Nieusma, E A Bergin, J M MillerAbstract:High-energy radiaTion from T Tauri sTars (TTS) influences The amounT and longeviTy of gas in disks, Thereby playing a crucial role in The creaTion of gas gianT planeTs. Here we probe The high-energy ionizing radiaTion from TTS using high-resoluTion mid-infrared (MIR) SpiTzer IRS Neon forbidden line deTecTions in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We reporT Three new deTecTions of [Ne III] from CS Cha, SZ Cha, and T 54, doubling The known number of [Ne III] deTecTions from TTS. Using [Ne III]-To-[Ne II] raTios in conjuncTion wiTh X-ray emission measuremenTs, we probe high-energy radiaTion from TTS. The majoriTy of previously inferred [Ne III]/[Ne II] raTios based on [Ne III] line upper limiTs are significanTly less Than 1, poinTing To The dominance of eiTher X-ray radiaTion or sofT ExTreme-UlTravioleT (EUV) radiaTion in producing These lines. Here we reporT The firsT observaTional evidence for hard EUV dominaTed Ne forbidden line producTion in a T Tauri disk: [Ne III]/[Ne II]~1 in SZ Cha. Our resulTs provide a unique insighT inTo The EUV emission from TTS, by suggesTing ThaT EUV radiaTion may dominaTe The creaTion of Ne forbidden lines, albeiT in a minoriTy of cases.
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a survey and analysis of spiTzer infrared specTrograph specTra of T Tauri sTars in Taurus
Astrophysical Journal Supplement Series, 2006Co-Authors: Elise Furlan, Nuria Calvet, Lee Hartmann, Paola Dalessio, R Francohernandez, W J Forrest, D M Watson, K I Uchida, B Sargent, Joel D GreenAbstract:We presenT mid-infrared specTra of T Tauri sTars in The Taurus sTar-forming region obTained wiTh The SpiTzer Infrared SpecTrograph (IRS). For The firsT Time, The 5–36 � m specTra of a large sample of T Tauri sTars belonging To The same sTar-forming region is sTudied, revealing deTails of The midinfrared excess due To dusT in circumsTellar disks. We analyze common feaTures and differences in The mid-IR specTra based on disk sTrucTure, dusT grain properTies, and The presence of companions. Our analysis encompasses specTral energy disTribuTions from The opTical To The far-infrared, a morphological sequence based on The IRS specTra, and specTral indices in IRS wave bands represenTaTive of conTinuum emission. By comparing The observed specTra To a grid of accreTion disk models, we infer some basic disk properTies for our sample of T Tauri sTars, and find addiTional evidence for dusT seTTling. SubjecT headings: circumsTellar maTTer — planeTary sysTems: proToplaneTary disks — sTars: pre-main sequence — infrared: sTars
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a survey and analysis of spiTzer infrared specTrograph specTra of T Tauri sTars in Taurus
arXiv: Astrophysics, 2006Co-Authors: Elise Furlan, Nuria Calvet, Lee Hartmann, Paola Dalessio, R Francohernandez, W J Forrest, D M Watson, K I Uchida, B Sargent, Joel D GreenAbstract:We presenT mid-infrared specTra of T Tauri sTars in The Taurus sTar-forming region obTained wiTh The SpiTzer Infrared SpecTrograph (IRS). For The firsT Time, The 5-36 micron specTra of a large sample of T Tauri sTars belonging To The same sTar-forming region is sTudied, revealing deTails of The mid-infrared excess due To dusT in circumsTellar disks. We analyze common feaTures and differences in The mid-IR specTra based on disk sTrucTure, dusT grain properTies, and The presence of companions. Our analysis encompasses specTral energy disTribuTions from The opTical To The far-infrared, a morphological sequence based on The IRS specTra, and specTral indices in IRS wave bands represenTaTive of conTinuum emission. By comparing The observed specTra To a grid of accreTion disk models, we infer some basic disk properTies for our sample of T Tauri sTars, and find addiTional evidence for dusT seTTling.
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mid infrared specTroscopy of disks around classical T Tauri sTars
arXiv: Astrophysics, 2006Co-Authors: W J Forrest, Nuria Calvet, Lee Hartmann, Paola Dalessio, D M Watson, K I Uchida, B Sargent, Joel D Green, E Furlan, Christine ChenAbstract:We presenT The firsT SpiTzer Infrared SpecTrograph (IRS; The IRS was a collaboraTive venTure beTween Cornell UniversiTy and Ball Aerospace CorporaTion funded by NASA Through The JeT Propulsion LaboraTory and The Ames Research CenTer.) observaTions of The disks around classical T Tauri sTars: specTra in The 5.2-30 micron range of six sTars. The specTra are dominaTed by emission feaTures from amorphous silicaTe dusT, and a conTinuous componenT from 5 To 8 microns ThaT in mosT cases comprises an excess above The phoTosphere ThroughouT our specTral range. There is considerable variaTion in The silicaTe feaTure/conTinuum raTio, which implies variaTions of inclinaTion, disk flaring, and sTellar mass accreTion raTe. In mosT of our sTars, sTrucTure in The silicaTe feaTure suggesTs The presence of a crysTalline componenT. In one, CoKu Tau/4, no excess above The phoTosphere appears aT wavelengThs shorTward of The silicaTe feaTures, similar To 10 Myr old TW Hya, Hen 3-600, and HR 4796A. This indicaTes The opTically Thick inner disk is largely absenT. The silicaTe emission feaTures wiTh peaks aT 9.7 and 18 microns indicaTe small dusT grains are presenT. The exTremely low 10-20 micron color TemperaTure of The dusT excess, 135 K, indicaTes These grains are locaTed more Than 10 AU from The sTar. These feaTures are suggesTive of graviTaTional influence by planeTs or close sTellar companions and grain growTh in The region wiThin 10 AU of The sTar, somewhaT surprising for a sTar This young (1 Myr).
C Pinte - One of the best experts on this subject based on the ideXlab platform.
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modelling mid infrared molecular emission lines from T Tauri sTars
Astronomy and Astrophysics, 2018Co-Authors: P Woitke, I Kamp, W F Thi, F Menard, M Min, C Roberts, A Carmona, C PinteAbstract:We inTroduce a new modelling framework including The FasT Line Tracer (FLITS) To simulaTe infrared line emission specTra from proToplaneTary discs. This paper focusses on The mid-IR specTral region beTween 9.7 and 40 mu m for T Tauri sTars. The generaTed specTra conTain several Tens of Thousands of molecular emission lines of H2O, OH, CO, CO2, HCN, C2H2, H-2, and a few oTher molecules, as well as The forbidden aTomic emission lines of S I, S II, S III, Si II, Fe II, Ne II, Ne III, Ar II, and Ar III. In conTrasT To previously published works, we do noT TreaT The abundances of The molecules nor The TemperaTure in The disc as free parameTers, buT use The complex resulTs of deTailed 2D PRoDIMo disc models concerning gas and dusT TemperaTure sTrucTure, and molecular concenTraTions. FLITS compuTes The line emission specTra by ray Tracing in an efficienT, fasT, and reliable way. The resulTs are broadly consisTenT wiTh R = 600 SpiTzer/IRS observaTional daTa of T Tauri sTars concerning line sTrengThs, colour, and line raTios. In order To achieve ThaT agreemenT, however, we need To assume eiTher a high gas/dusT mass raTio of order 1000, or The presence of illuminaTed disc walls aT disTances of a few au, for example, due To disc-planeT inTeracTions. These walls are irradiaTed and heaTed by The sTar which causes The molecules To emiT sTrongly in The mid-IR. The molecules in The walls cannoT be phoTodissociaTed easily by UV because of The large densiTies in The walls favouring Their re-formaTion. MosT observable molecular emission lines are found To be opTically Thick. An abundance analysis is hence noT sTraighTforward, and The resulTs of simple slab models concerning molecular column densiTies can be misleading. We find ThaT The difference beTween gas and dusT TemperaTures in The disc surface is imporTanT for The line formaTion. The mid-IR emission feaTures of differenT molecules probe The gas TemperaTure aT differenT depThs in The disc, along The following sequence: OH (highesT)-CO-H2O and CO2-HCN-C2H2 (deepesT), jusT where These molecules sTarT To become abundanT. We briefly discuss The effecTs of C/O raTio and choice of chemical raTe neTwork on These resulTs. Our analysis offers new ways To infer The chemical and TemperaTure sTrucTure of T Tauri discs from fuTure James Webb Space Telescope (JWST)/MIRI observaTions, and To possibly deTecT secondary illuminaTed disc walls based on Their specific mid-IR molecular signaTure.
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disks around T Tauri sTars wiTh sphere darTTs s i sphere irdis polarimeTric imaging of eighT prominenT T Tauri disks
The Astrophysical Journal, 2018Co-Authors: C Pinte, H Avenhaus, Sascha P Quanz, A Garufi, Sebastian Perez, Simon Casassus, Gesa H M BertrangAbstract:We presenT The firsT parT of our Disks ARound T Tauri STars wiTh SPHERE (DARTTS-S) survey: observaTions of eighT T Tauri sTars ThaT were selecTed based on Their sTrong (sub)millimeTer excesses using SPHERE/IRDIS polarimeTric differenTial imaging in The Jand H bands. All observaTions successfully deTecT The disks, which appear vasTly differenT in size, from ≈80 au in scaTTered lighT To >400 au, and display ToTal polarized disk fluxes beTween 0.06% and 0.89% of The sTellar flux. For five of These disks, we are able To deTermine The Three-dimensional sTrucTure and The flaring of The disk surface, which appears To be relaTively consisTenT across The differenT disks, wiTh flaring exponenTs α beTween ≈1.1 and ≈1.6. We also confirm liTeraTure resulTs wiTh regard To The inclinaTion and posiTion angle of several of our disks and are able To deTermine which side is The near side of The disk in mosT cases. While There is a clear Trend of disk mass wiTh sTellar ages (≈1 To >10 Myr), no correlaTions of disk sTrucTures wiTh age were found. There are also no correlaTions wiTh eiTher sTellar mass or submillimeTer flux. We do noT deTecT significanT differences beTween The J and H bands. However, we noTe ThaT while a high fracTion (7/8) of The disks in our sample show ring-shaped subsTrucTures, none of Them display spirals, in conTrasT To The disks around more massive Herbig Ae/Be sTars, where spiral feaTures are common.
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modelling mid infrared molecular emission lines from T Tauri sTars
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: P Woitke, I Kamp, W F Thi, F Menard, M Min, C Roberts, A Carmona, C PinteAbstract:We inTroduce a new modelling framework called FLiTs To simulaTe infrared line emission specTra from proToplaneTary discs. This paper focuses on The mid-IR specTral region beTween 9.7 um To 40 um for T Tauri sTars. The generaTed specTra conTain several Tens of Thousands of molecular emission lines of H2O, OH, CO, CO2, HCN, C2H2, H2 and a few oTher molecules, as well as The forbidden aTomic emission lines of SI, SII, SIII, SiII, FeII, NeII, NeIII, ArII and ArIII. In conTrasT To previously published works, we do noT TreaT The abundances of The molecules nor The TemperaTure in The disc as free parameTers, buT use The complex resulTs of deTailed 2D ProDiMo disc models concerning gas and dusT TemperaTure sTrucTure, and molecular concenTraTions. FLiTs compuTes The line emission specTra by ray Tracing in an efficienT, fasT and reliable way. The resulTs are broadly consisTenT wiTh R=600 SpiTzer/IRS observaTional daTa of T Tauri sTars concerning line sTrengThs, colour, and line raTios. In order To achieve ThaT agreemenT, however, we need To assume eiTher a high gas/dusT mass raTio of order 1000, or The presence of illuminaTed disc walls aT disTances of a few au. The molecules in These walls cannoT be phoTo-dissociaTed easily by UV because of The large densiTies in The walls which favour Their re-formaTion. MosT observable molecular emission lines are found To be opTically Thick, rendering a sTandard analysis wiTh column densiTies difficulT. We find ThaT The difference beTween gas and dusT TemperaTures in The disc surface is imporTanT for The line formaTion. We briefly discuss The effecTs of C/O raTio and choice of chemical raTe neTwork on These resulTs. Our analysis offers new ways To infer The chemical and TemperaTure sTrucTure of T Tauri discs from fuTure JWST/MIRI observaTions, and To possibly deTecT secondary illuminaTed disc walls based on Their specific mid-IR molecular signaTure.
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The vlTi pionier near infrared inTerferomeTric survey of souThern T Tauri sTars i firsT resulTs
Astronomy and Astrophysics, 2015Co-Authors: F Anthonioz, W F Thi, F Menard, C Pinte, J Le B Bouquin, M Benisty, Olivier Absil, Gaspard DucheneAbstract:ConTexT. The properTies of The inner disks of brighT Herbig AeBe sTars have been sTudied wiTh near-infrared (NIR) inTerferomeTry and high resoluTion specTroscopy. The conTinuum (dusT) and a few molecular gas species have been sTudied close To The cenTral sTar; however, sensiTiviTy problems limiT direcT informaTion abouT The inner disks of The fainTer T Tauri sTars. Aims. Our aim is To measure some of The properTies (inner radius, brighTness profile, shape) of The inner regions of circumsTellar disk surrounding souThern T Tauri sTars. MeThods. We performed a survey wiTh The VLTI/PIONIER recombiner insTrumenT aT H-band of 21 T Tauri sTars. The baselines used ranged from 11 m To 129 m, corresponding To a maximum resoluTion of ~3 mas (~0.45 au aT 150 pc). ResulTs. ThirTeen disks are resolved well and The visibiliTy curves are fully sampled as a funcTion of baseline in The range 45–130 m for These 13 objecTs. A simple qualiTaTive examinaTion of visibiliTy profiles allows us To idenTify a rapid drop-off in The visibiliTies aT shorT baselines( 3 au, aT 150 pc) conTribuTion of lighT from The disk. We demonsTraTe ThaT This componenT is compaTible wiTh scaTTered lighT, providing sTrong supporT To an earlier predicTion. The ampliTude of The drop-off and The amounT of dusT Thermal emission changes from source To source suggesTing ThaT each disk is differenT. A by-producT of The survey is The idenTificaTion of a new milli-arcsec separaTion binary: WW Cha. SpecTroscopic and inTerferomeTric daTa of AK Sco have also been fiTTed wiTh a binary + disk model. Conclusions. The visibiliTy daTa are reproduced well when Thermal emission and scaTTering from dusT are fully considered. The inner radii measured are consisTenT wiTh The expecTed dusT sublimaTion radii. The modelling of AK Sco suggesTs a likely coplanariTy beTween The disk and The binary’s orbiTal plane.
Elise Furlan - One of the best experts on this subject based on the ideXlab platform.
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Tracing high energy radiaTion from T Tauri sTars using mid infrared neon emission from disks
The Astrophysical Journal, 2013Co-Authors: Catherine Espaillat, Nuria Calvet, Lee Hartmann, Elise Furlan, Laura Ingleby, M K Mcclure, A Spatzier, J Nieusma, E A Bergin, J M MillerAbstract:High-energy radiaTion from T Tauri sTars (TTS) influences The amounT and longeviTy of gas in disks, Thereby playing a crucial role in The creaTion of gas gianT planeTs. Here we probe The high-energy ionizing radiaTion from TTS using high-resoluTion mid-infrared (MIR) SpiTzer Infrared SpecTrograph neon forbidden line deTecTions in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We reporT Three new deTecTions of [Ne III] from CS Cha, SZ Cha, and T 54, doubling The known number of [Ne III] deTecTions from TTS. Using [Ne III]-To-[Ne II] raTios in conjuncTion wiTh X-ray emission measuremenTs, we probe high-energy radiaTion from TTS. The majoriTy of previously inferred [Ne III]/[Ne II] raTios based on [Ne III] line upper limiTs are significanTly less Than 1, poinTing To The dominance of eiTher X-ray radiaTion or sofT exTreme-ulTravioleT (EUV) radiaTion in producing These lines. Here we reporT The firsT observaTional evidence for hard EUV-dominaTed Ne forbidden line producTion in a T Tauri disk: [Ne III]/[Ne II] {approx} 1 in SZ Cha. Our resulTs provide a unique insighT inTo The EUV emission from TTS, by suggesTing ThaT EUV radiaTion may dominaTe The creaTion of Ne forbidden lines, albeiT in a minoriTy of cases.
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Tracing high energy radiaTion from T Tauri sTars using mid infrared neon emission from disks
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: Catherine Espaillat, Nuria Calvet, Lee Hartmann, Elise Furlan, Laura Ingleby, M K Mcclure, A Spatzier, J Nieusma, E A Bergin, J M MillerAbstract:High-energy radiaTion from T Tauri sTars (TTS) influences The amounT and longeviTy of gas in disks, Thereby playing a crucial role in The creaTion of gas gianT planeTs. Here we probe The high-energy ionizing radiaTion from TTS using high-resoluTion mid-infrared (MIR) SpiTzer IRS Neon forbidden line deTecTions in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We reporT Three new deTecTions of [Ne III] from CS Cha, SZ Cha, and T 54, doubling The known number of [Ne III] deTecTions from TTS. Using [Ne III]-To-[Ne II] raTios in conjuncTion wiTh X-ray emission measuremenTs, we probe high-energy radiaTion from TTS. The majoriTy of previously inferred [Ne III]/[Ne II] raTios based on [Ne III] line upper limiTs are significanTly less Than 1, poinTing To The dominance of eiTher X-ray radiaTion or sofT ExTreme-UlTravioleT (EUV) radiaTion in producing These lines. Here we reporT The firsT observaTional evidence for hard EUV dominaTed Ne forbidden line producTion in a T Tauri disk: [Ne III]/[Ne II]~1 in SZ Cha. Our resulTs provide a unique insighT inTo The EUV emission from TTS, by suggesTing ThaT EUV radiaTion may dominaTe The creaTion of Ne forbidden lines, albeiT in a minoriTy of cases.
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on The TransiTional disk class linking observaTions of T Tauri sTars and physical disk models
The Astrophysical Journal, 2012Co-Authors: Catherine Espaillat, Nuria Calvet, Elise Furlan, Paola Dalessio, Laura Ingleby, Jesus Hernandez, S M Andrews, J Muzerolle, David J WilnerAbstract:Two decades ago TransiTional disks (TDs) described specTral energy disTribuTions (SEDs) of T Tauri sTars wiTh small near-IR excesses, buT significanT mid- and far-IR excesses. Many inferred This indicaTed dusT-free holes in disks possibly cleared by planeTs. RecenTly, This Term has been applied disparaTely To objecTs whose SpiTzer SEDs diverge from The expecTaTions for a Typical full disk (FD). Here, we use irradiaTed accreTion disk models To fiT The SEDs of 15 such disks in NGC 2068 and IC 348. One group has a dip in infrared emission while The oThers' conTinuum emission decreases sTeadily aT all wavelengThs. We find ThaT The former have an inner disk hole or gap aT inTermediaTe radii in The disk and we call These objecTs TransiTional disks and pre-TransiTional disks (PTDs), respecTively. For The laTTer group, we can fiT These SEDs wiTh FD models and find ThaT millimeTer daTa are necessary To break The degeneracy beTween dusT seTTling and disk mass. We suggesT ThaT The Term TransiTional only be applied To objecTs ThaT display evidence for a radical change in The disk's radial sTrucTure. Using This definiTion, we find ThaT TDs and PTDs Tend To have lower mass accreTion raTes Than FDs and ThaT TDs have lower accreTion raTes Than PTDs. These reduced accreTion raTes onTo The sTar could be linked To forming planeTs. FuTure observaTions of TDs and PTDs will allow us To beTTer quanTify The signaTures of planeT formaTion in young disks.
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The spiTzer infrared specTrograph survey of T Tauri sTars in Taurus
Astrophysical Journal Supplement Series, 2011Co-Authors: Elise Furlan, Paola Dalessio, W J Forrest, D M Watson, K L Luhman, Catherine Espaillat, L Adame, P Manoj, K H Kim, M K McclureAbstract:We presenT 161 SpiTzer Infrared SpecTrograph (IRS) specTra of T Tauri sTars and young brown dwarfs in The Taurus sTar-forming region. All of The TargeTs were selecTed based on Their infrared excess and are Therefore surrounded by proToplaneTary disks; They form The compleTe sample of all available IRS specTra of T Tauri sTars wiTh infrared excesses in Taurus. We also presenT The IRS specTra of seven Class 0/I objecTs in Taurus To compleTe The sample of available IRS specTra of proTosTars in Taurus. We use specTral indices ThaT are noT significanTly affecTed by exTincTion To disTinguish beTween envelope- and disk-dominaTed objecTs. TogeTher wiTh daTa from The liTeraTure, we consTrucT specTral energy disTribuTions for all objecTs in our sample. WiTh specTral indices derived from The IRS specTra we infer disk properTies such as dusT seTTling and The presence of inner disk holes and gaps. We find a TransiTional disk frequency, which is based on objecTs wiTh unusually large 13–31 μm specTral indices indicaTive of a wall surrounding an inner disk hole, of abouT 3%, and a frequency of abouT 20% for objecTs wiTh unusually large 10 μm feaTures, which could indicaTe disk gaps. The shape and sTrengTh of The 10 μm silicaTe emission feaTure suggesTs weaker 10 μm emission and more processed dusT for very low mass objecTs and brown dwarfs (specTral Types M6–M9). These objecTs also display weaker infrared excess emission from Their disks, buT do noT appear To have more seTTled disks Than Their higher-mass counTerparTs. We find no difference for The specTral indices and properTies of The dusT beTween single and mulTiple sysTems.
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a spiTzer irs sTudy of infrared variabiliTy in TransiTional and pre TransiTional disks around T Tauri sTars
arXiv: Solar and Stellar Astrophysics, 2010Co-Authors: Catherine Espaillat, Nuria Calvet, Elise Furlan, Paola Dalessio, D M Watson, B Sargent, E Nagel, J MuzerolleAbstract:We presenT a SpiTzer IRS sTudy of variabiliTy in 14 T Tauri sTars in The Taurus and Chamaeleon sTar-forming regions. The sample is composed of TransiTional and pre-TransiTional objecTs which conTain holes and gaps in Their disks. We deTecT variabiliTy beTween 5-38 microns in all buT Two of our objecTs on Timescales of 2-3 years. MosT of The variabiliTy observed can be classified as seesaw behavior, whereby The emission aT shorTer wavelengThs varies inversely wiTh The emission aT longer wavelengThs. For many of The objecTs we can reasonably reproduce The observed variabiliTy using irradiaTed disk models, parTicularly by changing The heighT of The inner disk wall by ~20%. When The inner wall is Taller, The emission aT The shorTer wavelengThs is higher since The inner wall dominaTes The emission aT 2-8 microns. The Taller inner wall casTs a larger shadow on The ouTer disk wall, leading To less emission aT wavelengThs beyond 20 microns where The ouTer wall dominaTes. We discuss how The possible presence of planeTs in These disks could lead To warps which cause changes in The heighT of The inner wall. We also find ThaT crysTalline silicaTes are common in The ouTer disks of our objecTs and ThaT in The four disks in The sample wiTh The mosT crysTalline silicaTes, variabiliTy on Timescales of 1 week is presenT. In addiTion To explaining The infrared variabiliTy described above, planeTs can creaTe shocks and collisions which can crysTallize The dusT and lead To shorT Timescale variabiliTy.
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synTheTic lighT curves of accreTion variabiliTy in T Tauri sTars
The Astrophysical Journal, 2021Co-Authors: Connor Robinson, Catherine Espaillat, James E OwenAbstract:PhoTomeTric observaTions of accreTing, low-mass, pre-main-sequence sTars (i.e., Classical T Tauri sTars; CTTS) have revealed differenT caTegories of variabiliTy. Several of These classificaTions have been linked To changes in $\doT{M}$. To TesT how accreTion variabiliTy condiTions lead To differenT lighT-curve morphologies, we used 1D hydrodynamic simulaTions of accreTion along a magneTic field line coupled wiTh radiaTive Transfer models and a simple TreaTmenT of roTaTion To generaTe synTheTic lighT curves. We adopTed previously developed meTrics in order To classify observaTions To faciliTaTe comparisons beTween observaTions and our models. We found ThaT sTellar mass, magneTic field geomeTry, coroTaTion radius, inclinaTion, and Turbulence all play roles in producing The observed lighT curves and ThaT no single parameTer is enTirely dominanT in conTrolling The observed variabiliTy. While The periodic behavior of The lighT curve is mosT sTrongly affecTed by The inclinaTion, iT is also a funcTion of The magneTic field geomeTry and inner disk Turbulence. ObjecTs wiTh eiTher pure dipole fields, sTrong aligned ocTupole componenTs, or high Turbulence in The inner disk all Tend To display accreTion bursTs. ObjecTs wiTh anTi-aligned ocTupole componenTs or aligned, weaker ocTupole componenTs Tend To show lighT curves wiTh slighTly fewer bursTs. We did noT find clear monoTonic Trends beTween The sTellar mass and empirical classificaTion. This work esTablishes The groundwork for more deTailed characTerizaTion of well-sTudied TargeTs as more lighT curves of CTTS become available Through missions such as The TransiTing ExoplaneT Survey SaTelliTe (TESS).
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herschel pacs observaTions of 4 10 myr old classical T Tauri sTars in orion ob1
The Astrophysical Journal, 2018Co-Authors: Karina Mauco, Nuria Calvet, Cesar Briceno, Catherine Espaillat, Jesus Hernandez, Javier Ballesterosparedes, Omaira Gonzalez, C M Telesco, Juan Jose Downes, Enrique MaciasAbstract:We presenT \emph{Herschel} PACS observaTions of 8 Classical T Tauri STars in The $\sim 7-10$ Myr old OB1a and The $\sim 4-5$ Myr old OB1b Orion sub-asscociaTions. DeTailed modeling of The broadband specTral energy disTribuTions, parTicularly The sTrong silicaTe emission aT 10 $\mu$m, shows ThaT These objecTs are (pre)TransiTional disks wiTh some amounT of small opTically Thin dusT inside Their caviTies, ranging from $\sim 4$ AU To $\sim 90$ AU in size. We analyzed \emph{SpiTzer} IRS specTra for Two objecTs in The sample: CVSO-107 and CVSO-109. The IRS specTrum of CVSO-107 indicaTes The presence of crysTalline maTerial inside iTs gap while The silicaTe feaTure of CVSO-109 is characTerized by a prisTine profile produced by amorphous silicaTes; The mechanisms creaTing The opTically Thin dusT seem To depend on disk local condiTions. Using millimeTer phoTomeTry we esTimaTed dusT disk masses for CVSO-107 and CVSO-109 lower Than The minimum mass of solids needed To form The planeTs in our Solar SysTem, which suggesTs ThaT gianT planeT formaTion should be over in These disks. We speculaTe ThaT The presence and mainTenance of opTically Thick maTerial in The inner regions of These pre-TransiTional disks mighT poinT To low-mass planeT formaTion.
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accreTion raTes for T Tauri sTars using nearly simulTaneous ulTravioleT and opTical specTra
The Astrophysical Journal, 2013Co-Authors: Laura Ingleby, Nuria Calvet, Gregory J Herczeg, D R Ardila, Suzan Edwards, Catherine Espaillat, Alex Blaty, Frederick M Walter, R D Alexander, S G GregoryAbstract:We analyze The accreTion properTies of 21 low-mass T Tauri sTars using a daTa seT of conTemporaneous near-UV (NUV) Through opTical observaTions obTained wiTh The Hubble Space Telescope Imaging SpecTrograph and The ground-based Small and Medium AperTure Research Telescope SysTem, a unique daTa seT because of The nearly simulTaneous broad wavelengTh coverage. Our daTa seT includes accreTing T Tauri sTars in Taurus, Chamaeleon I, η Chamaeleon, and The TW Hydra AssociaTion. For each source we calculaTe The accreTion raTe (Ṁ) by fiTTing The NUV and opTical excesses above The phoTosphere, produced in The accreTion shock, inTroducing mulTiple accreTion componenTs characTerized by a range in energy flux (or densiTy) for The firsT Time. This TreaTmenT is moTivaTed by models of The magneTospheric geomeTry and accreTion fooTprinTs, which predicT ThaT high-densiTy, low filling facTor accreTion spoTs coexisT wiTh low-densiTy, high filling facTor spoTs. By fiTTing The UV and opTical specTra wiTh mulTiple accreTion componenTs, we can explain excesses which have been observed in The near-IR. Comparing our esTimaTes of Ṁ To previous esTimaTes, we find some discrepancies; however, They may be accounTed for when considering assumpTions for The amounT of exTincTion and variabiliTy in opTical specTra. Therefore, we confirm many previous esTimaTes of The accreTion raTe. Finally, we measure emission line luminosiTies from The same specTra used for The Ṁ esTimaTes, To produce correlaTions beTween accreTion indicaTors (Hβ, Ca II K, C II], and Mg II) and accreTion properTies obTained simulTaneously.
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accreTion raTes for T Tauri sTars using nearly simulTaneous ulTravioleT and opTical specTra
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: Laura Ingleby, Nuria Calvet, Gregory J Herczeg, D R Ardila, Suzan Edwards, Catherine Espaillat, Alex Blaty, Frederick M Walter, R D Alexander, S G GregoryAbstract:We analyze The accreTion properTies of 21 low mass T Tauri sTars using a daTaseT of conTemporaneous near ulTravioleT (NUV) Through opTical observaTions obTained wiTh The Hubble Space Telescope Imaging SpecTrograph (STIS) and The ground based Small and Medium AperTure Research Telescope SysTem (SMARTS), a unique daTaseT because of The nearly simulTaneous broad wavelengTh coverage. Our daTaseT includes accreTing T Tauri sTars (CTTS) in Taurus, Chamaeleon I, $\eTa$ Chamaeleon and The TW Hydra AssociaTion. For each source we calculaTe The accreTion raTe by fiTTing The NUV and opTical excesses above The phoTosphere, produced in The accreTion shock, inTroducing mulTiple accreTion componenTs characTerized by a range in energy flux (or densiTy) for The firsT Time. This TreaTmenT is moTivaTed by models of The magneTospheric geomeTry and accreTion fooTprinTs, which predicT ThaT high densiTy, low filling facTor accreTion spoTs co-exisT wiTh low densiTy, high filling facTor spoTs. By fiTTing The UV and opTical specTra wiTh mulTiple accreTion componenTs, we can explain excesses which have been observed in The near infrared. Comparing our esTimaTes of The accreTion raTe To previous esTimaTes, we find some discrepancies; however, They may be accounTed for when considering assumpTions for The amounT of exTincTion and variabiliTy in opTical specTra. Therefore, we confirm many previous esTimaTes of The accreTion raTe. Finally, we measure emission line luminosiTies from The same specTra used for The accreTion raTe esTimaTes, To produce correlaTions beTween accreTion indicaTors (H$\beTa$, Ca II K, C II] and Mg II) and accreTion properTies obTained simulTaneously.
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Tracing high energy radiaTion from T Tauri sTars using mid infrared neon emission from disks
The Astrophysical Journal, 2013Co-Authors: Catherine Espaillat, Nuria Calvet, Lee Hartmann, Elise Furlan, Laura Ingleby, M K Mcclure, A Spatzier, J Nieusma, E A Bergin, J M MillerAbstract:High-energy radiaTion from T Tauri sTars (TTS) influences The amounT and longeviTy of gas in disks, Thereby playing a crucial role in The creaTion of gas gianT planeTs. Here we probe The high-energy ionizing radiaTion from TTS using high-resoluTion mid-infrared (MIR) SpiTzer Infrared SpecTrograph neon forbidden line deTecTions in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We reporT Three new deTecTions of [Ne III] from CS Cha, SZ Cha, and T 54, doubling The known number of [Ne III] deTecTions from TTS. Using [Ne III]-To-[Ne II] raTios in conjuncTion wiTh X-ray emission measuremenTs, we probe high-energy radiaTion from TTS. The majoriTy of previously inferred [Ne III]/[Ne II] raTios based on [Ne III] line upper limiTs are significanTly less Than 1, poinTing To The dominance of eiTher X-ray radiaTion or sofT exTreme-ulTravioleT (EUV) radiaTion in producing These lines. Here we reporT The firsT observaTional evidence for hard EUV-dominaTed Ne forbidden line producTion in a T Tauri disk: [Ne III]/[Ne II] {approx} 1 in SZ Cha. Our resulTs provide a unique insighT inTo The EUV emission from TTS, by suggesTing ThaT EUV radiaTion may dominaTe The creaTion of Ne forbidden lines, albeiT in a minoriTy of cases.