Abstract
We present a high-resolution, near-IR spectroscopic study of multiple outflows in the LkH
α
234 star formation region using the Immersion GRating INfrared Spectrometer (IGRINS). Spectral ...mapping over the blueshifted emission of HH 167 allowed us to distinguish at least three separate, spatially overlapped outflows in H
2
and Fe
ii
emission. We show that the H
2
emission represents not a single jet but rather complex multiple outflows driven by three known embedded sources: MM1, VLA 2, and VLA 3. There is a redshifted H
2
outflow at a low velocity,
V
LSR
<+50 km s
−1
, with respect to the systemic velocity of
V
LSR
= −11.5 km s
−1
, that coincides with the H
2
O masers seen in earlier radio observations 2″ southwest of VLA 2. We found that the previously detected Fe
ii
jet with
100 km s
−1
driven by VLA 3B is also detected in H
2
emission and confirm that this jet has a position angle of about 240°. Spectra of the redshifted knots at 14″–65″ northeast of LkH
α
234 are presented for the first time. These spectra also provide clues to the existence of multiple outflows. We detected high-velocity (50–120 km s
−1
) H
2
gas in the multiple outflows around LkH
α
234. Since these gases move at speeds well over the dissociation velocity (>40 km s
−1
), the emission must originate from the jet itself rather than H
2
gas in the ambient medium. Also, position–velocity and excitation diagrams indicate that emission from knot C in HH 167 comes from two different phenomena, shocks and photodissociation.
Mars 2020 Robotic Operations is responsible for the development, planning and Mars execution of robotics aspects of the mission. This includes the Perseverance rover's mobility, manipulation, and ...sampling operations, and the Ingenuity helicopter's flights. As of October 2022 (Martian Solar Day 562, or sol 562), the rover has driven 13,179.5m and collected 15 samples, while the helicopter has logged 32 flights, covering 7281m, with an overall flight time of 3467 seconds. Perseverance and Ingenuity have accomplished several firsts such as coring and caching samples autonomously, and demonstrating powered flight on Mars. Perseverance has also set new planetary rover records such as the longest continuation drive distance (699.9m with no human review), longest single-sol autonomous drive distance (319m), and total autonomously evaluated drive distance (11,594m out of 13,172m total, i.e. 88% of all driving, an order of magnitude more than previous NASA Mars rover missions). This paper presents results from the first year and a half of Mars operations to highlight the operations approach that enabled this success, the challenges encountered, and lessons learned. Challenges include an unexpected reboot while driving that led to the discovery of a race condition in the rover flight software, pebbles unexpectedly interfering with key sampling hardware, the Martian winter temporarily grounding the helicopter, and difficult communication situations between the rover and he-licopter that arise during periods of limited mobility. This paper also describes the sampling sol path, which is used by the operations team to execute sampling activities in a repeatable manner consistent with the goals of the science team and the capabilities of the sampling hardware. Abrading and sampling performance to date is evaluated, with a particular emphasis on changes to operations as a result of the soft rocks encountered in the Delta region on the western border of Jezero Crater.
We have identified two new near-infrared (NIR) emission lines in the spectra of planetary nebulae arising from heavy elements produced by neutron-capture reactions: Te iii 2.1019 m and Br v 1.6429 m. ...Te iii was detected in both NGC 7027 and IC 418, while Br v was seen in NGC 7027. The observations were obtained with the medium-resolution spectrograph Espectrógrafo Multiobjeto Infra-Rojo (EMIR) on the 10.4 m Gran Telescopio Canarias at La Palma, and with the high-resolution Immersion GRating INfrared Spectrometer (IGRINS) on the 2.7 m Harlan J. Smith telescope at McDonald Observatory. New calculations of atomic data for these ions, specifically A-values and collision strengths, are presented and used to derive ionic abundances of Te2+ and Br4+. We also derive ionic abundances of other neutron-capture elements detected in the NIR spectra, and estimate total elemental abundances of Se, Br, Kr, Rb, and Te after correcting for unobserved ions. Comparison of our derived enrichments to theoretical predictions from asymptotic giant branch (AGB) evolutionary models shows reasonable agreement for solar metallicity progenitor stars of ∼2-4 M . The spectrally isolated Br v 1.6429 m line has advantages for determining nebular Br abundances over optical Br iii emission lines that can be blended with other features. Finally, measurements of Te are of special interest because this element lies beyond the first peak of the s-process, and thus provides new leverage on the abundance pattern of trans-iron species produced by AGB stars.
THE ERUPTION OF THE CANDIDATE YOUNG STAR ASASSN-15QI Herczeg(沈雷歌), Gregory J.; Dong, Subo; Shappee, Benjamin J. ...
Astrophysical journal/The Astrophysical journal,
11/2016, Volume:
831, Issue:
2
Journal Article
Peer reviewed
Open access
ABSTRACT Outbursts on young stars are usually interpreted as accretion bursts caused by instabilities in the disk or the star-disk connection. However, some protostellar outbursts may not fit into ...this framework. In this paper, we analyze optical and near-infrared spectra and photometry to characterize the 2015 outburst of the probable young star ASASSN-15qi. The ∼3.5 mag brightening in the V band was sudden, with an unresolved rise time of less than one day. The outburst decayed exponentially by 1 mag for 6 days and then gradually back to the pre-outburst level after 200 days. The outburst is dominated by emission from ∼10,000 K gas. An explosive release of energy accelerated matter from the star in all directions, seen in a spectacular cool, spherical wind with a maximum velocity of 1000 km s−1. The wind and hot gas both disappeared as the outburst faded and the source returned to its quiescent F-star spectrum. Nebulosity near the star brightened with a delay of 10-20 days. Fluorescent excitation of H2 is detected in emission from vibrational levels as high as v = 11, also with a possible time delay in flux increase. The mid-infrared spectral energy distribution does not indicate the presence of warm dust emission, though the optical photospheric absorption and CO overtone emission could be related to a gaseous disk. Archival photometry reveals a prior outburst in 1976. Although we speculate about possible causes for this outburst, none of the explanations are compelling.
We present a high-resolution, near-IR spectroscopic study of multiple outflows in the LkH 234 star formation region using the Immersion GRating INfrared Spectrometer (IGRINS). Spectral mapping over ...the blueshifted emission of HH 167 allowed us to distinguish at least three separate, spatially overlapped outflows in H2 and Fe ii emission. We show that the H2 emission represents not a single jet but rather complex multiple outflows driven by three known embedded sources: MM1, VLA 2, and VLA 3. There is a redshifted H2 outflow at a low velocity, VLSR <+50 km s−1, with respect to the systemic velocity of VLSR = −11.5 km s−1, that coincides with the H2O masers seen in earlier radio observations 2″ southwest of VLA 2. We found that the previously detected Fe ii jet with 100 km s−1 driven by VLA 3B is also detected in H2 emission and confirm that this jet has a position angle of about 240°. Spectra of the redshifted knots at 14″-65″ northeast of LkH 234 are presented for the first time. These spectra also provide clues to the existence of multiple outflows. We detected high-velocity (50-120 km s−1) H2 gas in the multiple outflows around LkH 234. Since these gases move at speeds well over the dissociation velocity (>40 km s−1), the emission must originate from the jet itself rather than H2 gas in the ambient medium. Also, position-velocity and excitation diagrams indicate that emission from knot C in HH 167 comes from two different phenomena, shocks and photodissociation.
We have analyzed the temperature, velocity, and density of H2 gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By observing NGC ...7023 in the H and K bands at R 45,000 with the Immersion GRating INfrared Spectrograph, we detected 68 H2 emission lines within the 1″ × 15″ slit. The diagnostic ratio of 2-1 S(1)/1-0 S(1) is 0.41−0.56. In addition, the estimated ortho-to-para ratio (OPR) is 1.63−1.82, indicating that the H2 emission transitions in the observed region arise mostly from gas excited by UV fluorescence. Gradients in the temperature, velocity, and OPR within the observed area imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H2 from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rotational J levels of = 1, is that the predicted formation temperature for newly formed H2 should be lower than that of the model predictions. To investigate the density distribution, we combine pixels in 1″ × 1″ areas and derive the density distribution at the 0.002 pc scale. The derived gradient of density suggests that NGC 7023 has a clumpy structure, including a high clump density of ∼105 cm−3 with a size smaller than ∼5 × 10−3 pc embedded in lower-density regions of 103-104 cm−3.
ABSTRACT We identify Rb iv 1.5973 and Cd iv 1.7204 m emission lines in high-resolution (R = 40,000) near-infrared spectra of the planetary nebulae (PNe) NGC 7027 and IC 5117, obtained with the ...Immersion GRating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at McDonald Observatory. We also identify Ge vi 2.1930 m in NGC 7027. Alternate identifications for these features are ruled out based on the absence of other multiplet members and/or transitions with the same upper levels. Ge, Rb, and Cd can be enriched in PNe by s-process nucleosynthesis during the asymptotic giant branch stage of evolution. To determine ionic abundances, we calculate Rb iv collision strengths and use approximations for those of Cd iv and Ge vi. Our identification of Rb iv 1.5973 m is supported by the agreement between Rb3+/H+ abundances found from this line and the 5759.55 feature in NGC 7027. Elemental Rb, Cd, and Ge abundances are derived with ionization corrections based on similarities in ionization potential ranges between the detected ions and O and Ne ionization states. Our analysis indicates abundances 2-4 times solar for Rb and Cd in both nebulae. Ge is subsolar in NGC 7027, but its abundance is uncertain due to the large and uncertain ionization correction. The general consistency of the measured relative s-process enrichments with predictions from models appropriate for these PNe (2.0-2.5 M , Fe/H = −0.37) demonstrates the potential of using PN compositions to test s-process nucleosynthesis models.
Abstract
We have analyzed the temperature, velocity, and density of H
2
gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By ...observing NGC 7023 in the
H
and
K
bands at
R
≃ 45,000 with the Immersion GRating INfrared Spectrograph, we detected 68 H
2
emission lines within the 1″ × 15″ slit. The diagnostic ratio of 2-1 S(1)/1-0 S(1) is 0.41−0.56. In addition, the estimated ortho-to-para ratio (OPR) is 1.63−1.82, indicating that the H
2
emission transitions in the observed region arise mostly from gas excited by UV fluorescence. Gradients in the temperature, velocity, and OPR within the observed area imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H
2
from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rotational
J
levels of
ν
= 1, is that the predicted formation temperature for newly formed H
2
should be lower than that of the model predictions. To investigate the density distribution, we combine pixels in 1″ × 1″ areas and derive the density distribution at the 0.002 pc scale. The derived gradient of density suggests that NGC 7023 has a clumpy structure, including a high clump density of ∼10
5
cm
−3
with a size smaller than ∼5 × 10
−3
pc embedded in lower-density regions of 10
3
–10
4
cm
−3
.
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