40 research outputs found
The TEXES Survey For H-2 Emission From Protoplanetary Disks
No full textWe report the results of a search for pure rotational molecular hydrogen emission from the circumstellar environments of young stellar objects with disks using the Texas Echelon Cross Echelle Spectrograph (TEXES) on the NASA Infrared Telescope Facility and the Gemini North Observatory. We searched for mid-infrared H-2 emission in the S(1), S(2), and S(4) transitions. Keck/NIRSPEC observations of the H-2 S(9) transition were included for some sources as an additional constraint on the gas temperature. We detected H-2 emission from 6 of 29 sources observed: AB Aur, DoAr 21, Elias 29, GSS 30 IRS 1, GV Tau N, and HL Tau. Four of the six targets with detected emission are class I sources that show evidence for surrounding material in an envelope in addition to a circumstellar disk. In these cases, we show that accretion shock heating is a plausible excitation mechanism. The detected emission lines are narrow (similar to 10 km s(-1)), centered at the stellar velocity, and spatially unresolved at scales of 0.4 '', which is consistent with origin from a disk at radii 10-50 AU from the star. In cases where we detect multiple emission lines, we derive temperatures greater than or similar to 500 K from similar to 1 M-circle plus of gas. Our upper limits for the nondetections place upper limits on the amount of H-2 gas with T > 500 K of less than a few Earth masses. Such warm gas temperatures are significantly higher than the equilibrium dust temperatures at these radii, suggesting that the gas is decoupled from the dust in the regions that we are studying and that processes such as UV, X-ray, and accretion heating may be important.NSF AST 06-07312, AST 07-08074NASA NNG04GG92GAstronom
Design for a near-infrared immersion echelle spectrograph: breaking the R=100,000 barrier from 1.5 to 5 μm
No full textHIGH-RESOLUTION SPECTROSCOPY DURING ECLIPSE OF THE YOUNG SUBSTELLAR ECLIPSING BINARY 2MASS 0535–0546. I. PRIMARY SPECTRUM: COOL SPOTS VERSUS OPACITY UNCERTAINTIES
No full textHigh-resolution Br γ spectro-interferometry of the transitional Herbig Ae/Be star HD 100546 : a Keplerian gaseous disc inside the inner rim
No full textACC acknowledges support from CNPq (grant 308985/2009-5). JDI gratefully acknowledges funding from the European Union FP7-2011 under grant agreement no. 284405. RGV acknowledges the support from FAPESP (grant 2012/20364-4).We present spatially and spectrally resolved Br γ emission around the planet-hosting, transitional Herbig Ae/Be star HD 100546. Aiming to gain insight into the physical origin of the line in possible relation to accretion processes, we carried out Br γ spectro-interferometry using AMBER/VLTI from three different baselines achieving spatial and spectral resolutions of 2-4 mas and 12 000. The Br γ visibility is larger than that of the continuum for all baselines. Differential phases reveal a shift between the photocentre of the Br γ line-displaced~0.6mas (0.06 au at 100 pc) NE from the star-and that of the K-band continuum emission-displaced ~0.3 mas NE from the star. The photocentres of the redshifted and blueshifted components of the Br γ line are located NW and SE from the photocentre of the peak line emission, respectively. Moreover, the photocentre of the fastest velocity bins within the spectral line tends to be closer to that of the peak emission than the photocentre of the slowest velocity bins. Our results are consistent with a Br γ-emitting region inside the dust inner rim (≲0.25 au) and extending very close to the central star, with a Keplerian, disc-like structure rotating counter-clockwise, and most probably flared (~25°). Even though the main contribution to the Br γ line does not come from gas magnetically channelled on to the star, accretion on to HD 100546 could be magnetospheric, implying a mass accretion rate of a few 10-7 M⊙ yr-1. This value indicates that the observed gas has to be replenished on time-scales of a few months to years, perhaps by planet-induced flows from the outer to the inner disc as has been reported for similar systems.Peer reviewe
High-resolution Near-infrared Spectroscopy of HD 100546. II. Analysis of Variable Rovibrational CO Emission Lines
No full textWe present observations of rovibrational CO in HD 100546 from four epochs spanning 2003 January through 2010 December. We show that the equivalent widths of the CO lines vary during this time period with the v = 1–0 CO lines brightening more than the UV fluoresced lines from the higher vibrational states.While the spectroastrometric signal of the hot band lines remains constant during this period, the spectroastrometric signal of the v = 1–0 lines varies substantially. At all epochs, the spectroastrometric signals of the UV fluoresced lines are consistent with the signal one would expect from gas in an axisymmetric disk. In 2003, the spectroastrometric signal of the v = 1–0 P26 line was symmetric and consistent with emission from an axisymmetric disk. However, in 2006 there was no spatial offset of the signal detected on the red side of the profile, and in 2010 the spectroastrometric offset was yet more strongly reduced toward zero velocity. A model is presented that can explain the evolution of the equivalent width of the v = 1–0 P26 line and its spectroastrometric signal by adding to the system a compact source of CO emission that orbits the star near the inner edge of the disk. We hypothesize that such emission may arise from a circumplanetary disk orbiting a gas giant planet near the inner edge of the circumstellar disk. We discuss how this idea can be tested observationally and be distinguished from an alternative interpretation of random fluctuations in the disk emission
Andromeda's Parachute: A Bright Quadruply Lensed Quasar at z = 2.377
No full textWe present Keck Cosmic Web Imager spectroscopy of the four putative images of the lensed quasar candidate J014710+463040 recently discovered by Berghea et al. The data verify the source as a quadruply lensed, broad absorption-line quasar having . We detect intervening absorption in the Fe ii λλ2586, 2600, Mg ii λλ2796, 2803, and/or C iv λλ1548, 1550 transitions in eight foreground systems, three of which have redshifts consistent with the photometric-redshift estimate reported for the lensing galaxy (z L ≈ 0.57). The source images probe these absorbers over transverse physical scales of ≈0.3–22 kpc, permitting assessment of the variation in metal-line equivalent width as a function of sight-line separation. We measure differences in of 50% over the same scales across the majority of sight-line pairs, while C iv absorption exhibits a wide range in differences of ≈5%–80% within transverse distances of lesssim3 kpc. These spatial variations are consistent with those measured in intervening absorbers detected toward lensed quasars drawn from the literature, in which and vary by ≤20% in 35 ± 7% and 47 ± 6% of sight lines separated by 2 quadruply lensed systems for which all four source images are very bright (r = 15.4–17.7 mag) and are easily separated in ground-based seeing conditions. As such, it is an ideal candidate for higher-resolution spectroscopy probing the spatial variation in the kinematic structure and physical state of intervening absorbers
