We present new, third-epoch HST H-alpha and [S II] images of three HH jets (HH 1 and 2, HH 34, and HH 47) and compare these images with those from the previous epochs. The high-spatial resolution, coupled with a time-series whose cadence is of order both the hydrodynamical and radiative cooling timescales of the flow allows us to follow the hydrodynamical/magnetohydrodynamical evolution of an astrophysical plasma system in which ionization and radiative cooling play significant roles. Cooling zones behind the shocks are resolved, so it is possible to identify which way material flows through a given shock wave. The images show that heterogeneity is paramount in these jets, with clumps dominating the morphologies of both bow shocks and their Mach disks. This clumpiness exists on scales smaller than the jet widths and determines the behavior of many of the features in the jets. Evidence also exists for considerable shear as jets interact with their surrounding molecular clouds, and in several cases we observe shock waves as they form and fade where material emerges from the source and as it proceeds along the beam of the jet. Fine-structure within two extended bow shocks may result from Mach stems that form at the intersection points of oblique shocks within these clumpy objects. Taken together, these observations represent the most significant foray thus far into the time domain for stellar jets, and comprise one of the richest data sets in existence for comparing the behavior of a complex astrophysical plasma flows with numerical simulations and laboratory experiments.
We present an analysis of four epochs of H$α$ and [S II] $λλ$ 6716/6731 HST images of HH 1. For determining proper motions we explore a new method based on analysis of spatially degraded images obtained convolving the images with wavelet functions of chosen widths. With this procedure we are able to generate maps of proper motion velocities along and across the outflow axis, as well as (angularly integrated) proper motion velocity distributions. From the four available epochs, we find the time evolution of the velocities, intensities and spatial distribution of the line emission. We find that …
We present near-infrared [Fe II] images of four Class 0/I jets (HH 1/2, HH 34, HH 111, HH 46/47) observed with the Hubble Space Telescope Wide Field Camera 3. The unprecedented angular resolution allows us to measure proper motions, jet widths and trajectories, and extinction along the jets. In all cases, we detect the counter-jet which was barely visible or invisible at shorter wavelengths. We measure tangential velocities of a few hundred km/s, consistent with previous HST measurements over 10 years ago. We measure the jet width as close as a few tens of au from the star, revealing high coll…
We present an analysis of the second epoch HST WFC3 F110W near-Infrared (NIR) imaging data of the globular cluster M4. The new dataset suggests that one of the previously suggested four brown dwarf candidates in this cluster is indeed a high-probability cluster member. The position of this object in the NIR colour magnitude diagrams (CMDs) is in the white dwarf/brown dwarf area. The source is too faint to be a low-mass main sequence star, but, according to theoretical considerations, also most likely somewhat too bright to be a bona-fide brown dwarf. Since we know that the source is a cluster …
Aims: for the first time the astrometric capabilities of the Multi-Conjugate Adaptive Optics (MCAO) facility GeMS with the GSAOI camera on Gemini-South are tested to quantify the accuracy in determining stellar proper motions in the Galactic globular cluster NGC 6681. Methods: proper motions from HST/ACS for a sample of its stars are already available, and this allows us to construct a distortion-free reference at the epoch of GeMS observations that is used to measure and correct the temporally changing distortions for each GeMS exposure. In this way, we are able to compare the corrected GeMS …
Accurate determination of the rates of nova eruptions in different kinds of galaxies give us strong constraints on those galaxies' underlying white dwarf and binary populations, and those stars' spatial distributions. Until 2016, limitations inherent in ground-based surveys of external galaxies - and dust extinction in the Milky Way - significantly hampered the determination of those rates and how much they differ between different types of galaxies. Infrared Galactic surveys and dense cadence Hubble Space Telescope (HST)-based surveys are overcoming these limitations, leading to sharply incre…
Variability is a defining characteristic of young low-mass stars that are still accreting material from their primordial protoplanetary disk. Here we present the largest \textit{HST} variability study of Classical T Tauri stars (CTTS) to date. For 5 of these objects, we obtained a total of 25 spectra with the Space Telescope Imaging Spectrograph (STIS). Mass accretion rates and the fraction of the star covered by accretion columns (i.e., filling factors) were inferred using 1D NLTE physical models whose parameters were fit within a Bayesian framework. On week long timescales, typical changes i…
We present two new epochs of Hubble Space Telescope/Space Telescope Imaging Spectrograph coronagraphic imaging, along with multi-epoch optical, near-IR, and radio monitoring, of the HD 163296 system. We find ansae features identified in earlier epoch HST imagery are a 4th ring, that resides at a semi-major axis distance of 3.25" (330 au). We determine the scale height of the dust is 64 au at a radial distance of 330 au. We observe surface brightness variations in the 4th ring on <3 month timescales, including large-scale, azimuthally asymmetric changes. This variability resembles earlier studi…
High resolution observations of Young Stellar Object (YSO) jets show them to be composed of many small-scale knots or clumps. In this paper we report results of 3-D numerical simulations designed to study how such clumps interact and create morphologies and kinematic patterns seen in emission line observations. Our simulations focus on clump scale dynamics by imposing velocity differences between spherical, over-dense regions which then lead to the formation of bow shocks as faster clumps overtake slower material. We show that much of the spatial structure apparent in emission line images of j…
Structure and Magnetic Fields in the Precessing Jet System SS433 III. Evolution of the Intrinsic Brightness of the Jets from a Deep Multi-Epoch VLA Campaign
Multi-Epoch Stability in the Rotational Modulation of the Planetary-Mass Companion Ross 458C
AURA for the European Space Agency (ESA), ESA Office, Space Telescope Science Institute（欧洲空间局（ESA）办公室，太空望远镜科学研究所）；Johns Hopkins University（约翰斯·霍普金斯大学）；Centro de Astrobiología, CSIC-INTA（西班牙国家航空航天技术研究所/天文生物中心）；University of Central Florida（中佛罗里达大学）；Bay Area Environmental Research Institute（湾区环境研究所）；NASA Ames Research Center（美国国家航空航天局艾姆斯研究中心）；University of Rochester（罗切斯特大学）；University of Virginia（弗吉尼亚大学）；The University of Arizona（亚利桑那大学）
The JWST Resolved Stellar Populations Early Release Science Program. IX. The RR Lyrae Population in WLM with HST and JWST
Minnesota Institute for Astrophysics, University of Minnesota（明尼苏达大学天体物理研究所）；Department of Astronomy, University of California, Berkeley（加州大学伯克利分校天文学系）；Space Telescope Science Institute（太空望远镜科学研究所）；Department of Physics and Astronomy, Rutgers, the State University of New Jersey（新泽西州立大学罗格斯大学物理与天文系）
Context. To investigate the dynamical properties of protostellar jets. Aims. Determine the proper motion of protostellar jets around Class 0 and Class I sources in an active star forming region in Serpens. Methods. Multi-epoch deep images in the 2.122 $μ$m line of molecular hydrogen, v=1-0 S(1), obtained with the near-infrared instrument NOTCam over a time-scale of 10 years, are used to determine proper motion of knots and jets. K-band spectroscopy of the brighter knots is used to supply radial velocities, estimate extinction, excitation temperature, and H$_2$ column densities towards these kn…
Accreting protoplanets enable the direct characterization of planet formation. As part of a high-contrast imaging search for accreting planets with the Hubble Space Telescope (HST) Wide Field Camera 3, we present H$α$ images of AB Aurigae (AB Aur), a Herbig Ae/Be star harboring a transition disk. The data were collected in two epochs of direct-imaging observations using the F656N narrow-band filter. After subtracting the point spread function of the primary star, we identify a point-like source located at a P.A. of $182.5^{\circ}\pm1.4^{\circ}$ and a separation of $600\pm22$~mas relative to th…
We present a detailed analysis of the protostellar outflow activity in the massive star-forming region NGC 3324, as revealed by new Early Release Observations (ERO) from the James Webb Space Telescope (JWST). Emission from numerous outflows is revealed in narrow-band images of hydrogen Paschen-$α$ (Pa-$α$) and molecular hydrogen. In particular, we report the discovery of 24 previously unknown outflows based on their H$_2$ emission. We find three candidate driving sources for these H$_2$ flows in published catalogs of young stellar objects (YSOs) and we identify 15 IR point sources in the new J…
The Expanding Nebular Remnant of the Recurrent Nova RS Ophiuchi (2006): II. Modeling of Combined Hubble Space Telescope Imaging and Ground-based Spectroscopy
