Association Of Universities For Research In Astronomy Research Articles

Ejection Patterns in the DG Tau Jet over the Last 40 yr: Insights into Mass Accretion Variability* * Based on observations obtained at the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory

We aim to clarify the link between mass accretion and ejection by analyzing DG Tau’s jet observations from optical and near-infrared data spanning 1984–2019, alongside photometric variations between 1983 and 2015. We classified 12 moving knot groups among 17 total knot groups based on their constant proper motions and comparable radial velocities. A strong correlation emerges between the deprojected flow velocities of the knots and the photometric magnitudes of DG Tau. From 1983 to 1995, as the deprojected ejection velocities surged from ∼273 ± 15 to ∼427 ± 16 km s−1, the photometric magnitudes (V) concurrently brightened from 12.3 to 11.4. Notably, when DG Tau became brighter than 12.2 in the V band, its (B − V) color shifted bluer than its intrinsic color range of K5–M0. During this period, the launching point of the jet in the protoplanetary disk moved closer to 0.06 au from the star in 1995. Following a V magnitude drop from 11.7 to 13.4 in 1998, the star may have experienced significant extinction due to a dust wall created by the disk wind during the ejection of the high-velocity knot in 1999. Since then, the magnitude became fainter than 12.2, the (B − V) and (V − R) colors became redder, and the deprojected velocities consistently remained below 200 km s−1. The launching point of the jet then moved away to ∼0.45 au by 2008. The prevailing factor influencing photometric magnitude appears to be the active mass accretion causing the variable mass ejection velocities.

Optimal Observational Scheduling Framework for Binary and Multiple Stellar Systems* *Based in part on observations obtained at the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United

The optimal instant of observation of astrophysical phenomena for objects that vary on human timescales is an important problem, as it bears on the cost-effective use of usually scarce observational facilities. In this paper, we address this problem in the case of tight visual binary systems through a Bayesian framework based on the maximum entropy sampling principle. Our proposed information-driven methodology exploits the periodic structure of binary systems to provide a computationally efficient estimation of the probability distribution of the optimal observation time. We show the optimality of the proposed sampling methodology in the Bayes sense and its effectiveness through direct numerical experiments. We successfully apply our scheme to the study of two visual-spectroscopic binaries and one purely astrometric triple hierarchical system. We note that our methodology can be applied to any time-evolving phenomena, a particularly interesting application in the era of dedicated surveys, where a definition of the cadence of observations can have a crucial impact on achieving the science goals.

Migratory Outbursting Quasi-Hilda Object 282P/(323137) 2003 BM80* * Based on observations obtained at the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council

We report that object 282P/(323137) 2003 BM80 is undergoing a sustained activity outburst, lasting over 15 months thus far. These findings stem in part from our NASA Partner Citizen Science project Active Asteroids (http://activeasteroids.net), which we introduce here. We acquired new observations of 282P via our observing campaign (Vatican Advanced Technology Telescope (VATT), Lowell Discovery Telescope (LDT), and the Gemini South telescope), confirming 282P was active on UT 2022 June 7, some 15 months after 2021 March images showed activity in the 2021–2022 epoch. We classify 282P as a member of the quasi-Hilda objects (QHOs), a group of dynamically unstable objects found in an orbital region similar to, but distinct in their dynamical characteristics to, the Hilda asteroids (objects in 3:2 resonance with Jupiter). Our dynamical simulations show 282P has undergone at least five close encounters with Jupiter and one with Saturn over the last 180 yr. 282P was most likely a Centaur or Jupiter-family comet (JFC) 250 yr ago. In 350 yr, following some 15 strong Jovian interactions, 282P will most likely migrate to become a JFC or, less likely, an outer main-belt asteroid orbit. These migrations highlight a dynamical pathway connecting Centaurs and JFCs with quasi-Hildas and, potentially, active asteroids. Synthesizing these results with our thermodynamical modeling and new activity observations, we find volatile sublimation is the primary activity mechanism. Observations of a quiescent 282P, which we anticipate will be possible in 2023, will help confirm our hypothesis by measuring a rotation period and ascertaining the spectral type.

GRB 180418A: A possibly-short GRB with a wide-angle outflow in a faint host galaxy

The authors acknowledge Phil Evans for the useful advice to obtain the full set of X-ray GRB afterglow light curves from the UK Swift Science Data Centre. The authors thank Daniel Perley for his valuable contribution to proposals. The Fong Group at Northwestern acknowledges support by the National Science Foundation under grant Nos. AST-1814782 and AST-1909358. Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Number G08- 19025X issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. P.V. acknowledges support from NASA grants 80NSSC19K0595 and NNM11AA01A. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. Based on observations obtained at the international Gemini Observatory (Program IDs GS-2018A-Q-127, GN-2018A-Q-121, GN-2018B-Q-117), a program of NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigaci´on y Desarrollo (Chile), Ministerio de Ciencia, Tecnolog´ia e Innovaci´on (Argentina), Minist´erio da Ciˆencia, Tecnologia, Inova¸c˜oes e Comunica¸c˜oes (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). This work was enabled by observations made from the Gemini North telescope, located within the Maunakea Science Reserve and adjacent to the summit of Maunakea. We are grateful for the privilege of observing the Universe from a place that is unique in both its astronomical quality and its cultural significance. Observations reported in this paper were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution (Programs 2018C-UAO-G4, UAO-G213-20A, UAO-G4, UAO-G7, UAO-G212-20A, 2018b-UAO-G15). MMT Observatory access was supported by Northwestern University and the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Observations obtained by the United Kingdom Infrared Telescope (UKIRT; program: U/18A/UA01) was supported by NASA and operated under an agreement among the University of Hawaii, the University of Arizona, and Lockheed Martin Advanced Technology Center; operations are enabled through the cooperation of the East Asian Observatory. We thank the Cambridge Astronomical Survey Unit (CASU) for processing the WFCAM data and the WFCAM Science Archive (WSA) for making the data available.

Fully scalable forward model grid of exoplanet transmission spectra (dataset)

Jayesh Goyal and Nathan Mayne are part funded by a Leverhulme Trust Research Project Grant, and in part by a University of Exeter College of Engineering, Mathematics and Physical Sciences PhD studentship. Hannah Wakeford acknowledges funding by Association of Universities for Research in Astronomy (AURA) through a Giacconi Fellowship appointed at Space Telescope Science Institute (STScI). David Sing and Benjamin Drummond acknowledge support from the European Research Council under the European Unions Seventh Framework Programme (FP7/2007-2013)/ ERC grant agreement number 336792. We acknowledge support from the Space Telescope Science Institute (STScI) Research Visitors Program. This work used the DiRAC Complexity system, operated by the University of Leicester IT Services, which forms part of the STFC DiRAC HPC Facility. This work also used the University of Exeter Supercomputer, a DiRAC Facility jointly funded by STFC, the Large Facilities Capital Fund of BIS and the University of Exeter.

Thirty Meter Telescope Detailed Science Case: 2015**Cover image: artist's rendition of the TMT International Observatory on Mauna Kea opening in the late evening before beginning operations.

The TMT Detailed Science Case describes the transformational science that the Thirty Meter Telescope will enable. Planned to begin science operations in 2024, TMT will open up opportunities for revolutionary discoveries in essentially every field of astronomy, astrophysics and cosmology, seeing much fainter objects much more clearly than existing telescopes. Per this capability, TMT's science agenda fills all of space and time, from nearby comets and asteroids, to exoplanets, to the most distant galaxies, and all the way back to the very first sources of light in the universe. More than 150 astronomers from within the TMT partnership and beyond offered input in compiling the new 2015 Detailed Science Case. The contributing astronomers represent the entire TMT partnership, including the California Institute of Technology (Caltech), the Indian Institute of Astrophysics (IIA), the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC), the National Astronomical Observatory of Japan (NAOJ), the University of California, the Association of Canadian Universities for Research in Astronomy (ACURA) and US associate partner, the Association of Universities for Research in Astronomy (AURA).

Optical and Near-Infrared UBVRIJHK Photometry for the RR Lyrae Stars in the Nearby Globular Cluster M4 (NGC 6121)11Based in part on data obtained from the ESO Science Archive Facility under multiple requests by the authors; in part on data obtained from the Isaac Newton Group Archive, which is maintained as part of the CASU Astronomical Data Centre at the Institute

We present optical and near-infrared UBVRIJHK photometry of stars in the Galactic globular cluster M4 (NGC 6121) based upon a large corpus of observations obtained mainly from public astronomical archives. We concentrate on the RR Lyrae variable stars in the cluster, and make a particular effort to accurately reidentify the previously discovered variables. We have also discovered two new probable RR Lyrae variables in the M4 field: one of them by its position on the sky and its photometric properties is a probable member of the cluster, and the second is a probable background (bulge?) object. We provide accurate equatorial coordinates for all 47 stars identified as RR Lyraes, new photometric measurements for 46 of them, and new period estimates for 45. We have also derived accurate positions and mean photometry for 34 more stars previously identified as variable stars of other types, and for an additional five non-RR Lyrae variable stars identified for the first time here. We present optical and near-infrared color-magnitude diagrams for the cluster and show the locations of the variable stars in them. We present the Bailey (period-amplitude) diagrams and the period-frequency histogram for the RR Lyrae stars in M4 and compare them to the corresponding diagrams for M5 (NGC 5904). We conclude that the RR Lyrae populations in the two clusters are quite similar in all the relevant properties that we have considered. The mean periods, pulsation-mode ratios, and Bailey diagrams of these two clusters show support for the recently proposed “Oosterhoff-neutral” classification.

Understanding the 8 μm versus Paα Relationship on Subarcsecond Scales in Luminous Infrared Galaxies

14 pages, 9 figures, 4 tables.-- Based on observations obtained with T-ReCS instrument at the Gemini South Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: NSF (United States), PPARC (UK), NRC (Canada), CONICYT (Chile) ARC (Australia), CNPq (Brazil), and CONICET (Argentina).-- Also based on observations with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-266555.

Late-Time HST Photometry of SN 1994I: Hints of Positron Annihilation Energy Deposition11Based in part on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555. This research is primarily associated with proposal GO-5777.

ABSTRACTWe present multicolor Hubble Space Telescope (HST) WFPC2 broadband observations of the Type Ic SN 1994I obtained ∼280 d after maximum light. We measure the brightness of the SN and, relying on the detailed spectroscopic database of SN 1994I, we transform the ground-based photometry obtained at early times to the HST photometric system, deriving light curves for the WFPC2 F439W, F555W, F675W, and F814W passbands that extend from 7 days before to 280 days after maximum. We use the multicolor photometry to build a quasi-bolometric light curve of SN 1994I, and compare it with similarly constructed light curves of other supernovae. In doing so, we propose and test a scaling in energy and time that allows for a more meaningful comparison of the exponential tails of different events. Through comparison with models, we find that the late-time light curve of SN 1994I is consistent with that of spherically symmetric ejecta in homologous expansion, for which the ability to trap the γ-rays produced by the radioactive decay of 56Co diminishes roughly as the inverse of time squared. We also find that by the time of the HST photometry, the light curve was significantly energized by the annihilation of positrons.

Optical Sky Brightness at Cerro Tololo Inter‐American Observatory from 1992 to 200611Based in part on observations taken at the Cerro Tololo Inter‐American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation.

ABSTRACTWe present optical (UBVRI) sky brightness measurements from 1992 through 2006. The data are based on CCD imagery obtained with the CTIO 0.9, 1.3, and 1.5 m telescopes. The B‐ and V‐band data are in reasonable agreement with measurements previously made at Mauna Kea, although on the basis of a small number of images per year, there are discrepancies for the years 1992 through 1994. Our CCD‐based data are not significantly different than values obtained at Cerro Paranal. We find that the yearly averages of V‐band sky brightness are best correlated with the 10.7 cm solar flux taken 5 days prior to the sky brightness measurements. This implies an average speed of 350 km s−1 for the solar wind. While we can measure an enhancement of the night‐sky levels over La Serena 10° above the horizon, at elevation angles above 45°, we find no evidence that the night‐sky brightness at Cerro Tololo is affected by artificial light of nearby towns and cities.

The Light Echo around Supernova 2003gd in Messier 7411Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5‐26555.

ABSTRACTWe confirm the discovery of a light echo around the Type II‐plateau supernova 2003gd in Messier 74 (NGC 628), seen in images obtained with the High Resolution Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST) as part of a larger Snapshot program on the late‐time emission from supernovae. The analysis of the echo we present suggests that it is due to the SN light pulse scattered by a sheet of dust grains located ∼113 pc in front of the SN, and that these grains are not unlike those assumed to be in the diffuse Galactic interstellar medium, both in composition and in size distribution. The echo is less consistent with scattering off carbon‐rich grains, and if anything, the grains may be somewhat more silicate rich than the Galactic dust composition. The echo also appears to be more consistent with a SN distance closer to 7 Mpc than to 9 Mpc. This further supports the conclusion we reached elsewhere that the initial mass for the SN progenitor was relatively low (∼8–9 M⊙). The HST should be used to continue to monitor the echo in several bands, particularly in the blue, to better constrain its origin.

The Masses of the B Stars in the High Galactic Latitude Eclipsing Binary IT Librae11Based on observations made at the 2.1 m Otto Struve Telescope of McDonald Observatory operated by the University of Texas at Austin and also at the 2.1 m telescope at Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities

ABSTRACTA number of blue stars that appear to be similar to Population I B stars in the star‐forming regions of the Galactic disk are found more than 1 kpc from the Galactic plane. Uncertainties about the true distances and masses of these high‐latitude B stars have fueled a debate as to their origin and evolutionary status. The eclipsing binary IT Lib is composed of two B stars, is approximately 1 kpc above the Galactic plane, and is moving back toward the plane. Observations of the light and velocity curves presented here lead to the conclusion that the B stars in this system are massive young main‐sequence stars. While there are several possible explanations, it appears most plausible that the IT Lib system formed in the disk about 30 million years ago and was ejected on a trajectory taking it to its present position.

A Search for Core‐Collapse Supernova Progenitors in Hubble Space Telescope Images11Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive of the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5‐26555.

ABSTRACTIdentifying the massive progenitor stars that give rise to core‐collapse supernovae (SNe) is one of the main pursuits of supernova and stellar evolution studies. Using ground‐based images of recent, nearby SNe obtained primarily with the Katzman Automatic Imaging Telescope, astrometry from the Two Micron All Sky Survey, and archival images from the Hubble Space Telescope, we have attempted the direct identification of the progenitors of 16 Type II and Type Ib/c SNe. We may have identified the progenitors of the Type II SNe 1999br in NGC 4900, 1999ev in NGC 4274, and 2001du in NGC 1365 as supergiant stars with M0V ≈ -6 mag in all three cases. We may have also identified the progenitors of the Type Ib SNe 2001B in IC 391 and 2001is in NGC 1961 as very luminous supergiants with M0V ≈ -8 to −9 mag, and possibly the progenitor of the Type Ic SN 1999bu in NGC 3786 as a supergiant with M0V ≈ -7.5 mag. Additionally, we have recovered at late times SNe 1999dn in NGC 7714, 2000C in NGC 2415, and 2000ew in NGC 3810, although none of these had detectable progenitors on pre‐supernova images. In fact, for the remaining SNe only limits can be placed on the absolute magnitude and color (when available) of the progenitor. The detected Type II progenitors and limits are consistent with red supergiants as progenitor stars, although possibly not as red as we had expected. Our results for the Type Ib/c SNe do not strongly constrain either Wolf‐Rayet stars or massive interacting binary systems as progenitors.

A Hubble Space Telescope Snapshot Survey of Nearby Supernovae11Partially based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5‐26555.

ABSTRACTWe present photometry of 13 recent supernovae (SNe) recovered in a Hubble Space Telescope Snapshot program and tie the measurements to earlier ground‐based observations in order to study the late‐time evolution of the SNe. Many of the ground‐based measurements are previously unpublished and were made primarily with a robotic telescope, the Katzman Automatic Imaging Telescope. Evidence for circumstellar interaction is common among the core‐collapse SNe. Late‐time decline rates for Type IIn SNe are found to span a wide range, perhaps because of differences in circumstellar interaction. An extreme case, SN IIn 1995N, declined by only 1.2 mag in V over about 4 yr following discovery. Template images of some SNe must therefore be obtained many years after the explosion if contamination from the SN itself is to be minimized. Evidence is found against a previous hypothesis that the Type IIn SN 1997bs was actually a superoutburst of a luminous blue variable star. The peculiar SN Ic 1997ef, a “hypernova,” declined very slowly at late times. The decline rate of the SN Ia 2000cx decreased at late times, but this is unlikely to have been caused by a light echo.

Johns Hopkins site of Space Institute

The Space Telescope Science Institute (STSI) will be located on the Homewood Campus of the Johns Hopkins University, Baltimore, Maryland. The institute will perform critical mission science activity for the forthcoming space telescope mission. The 13.1‐m spacecraft is to be placed into a 600‐k‐high orbit by the space shuttle, and it will perform scientific investigations for at least 15 years.The Association of Universities for Research in Astronomy (AURA), a consortium of 14 universities, has been selected for final negotiation of a contract to establish, operate, and maintain STSI for the space telescope scheduled for launch in early 1985 on the space shuttle. The contractor's estimated cost for the initial 5‐year contract is approximately $24 million. Additional funding will be required in support of a guest observer and archival research program, as it develops. The contract will contain options for three additional 5‐year extensions.