Chandra X-Ray Observatory

Joint Chandra/HST Accepted Cycle 4 Targets and Abstracts

Proposals from the following HST scientific categories were accepted by the Cycle 11 HST TAC:

Click on the PI Name for the Proposal Abstract

PI NameTitleChandra timeTargets
Andrew FruchterThe Origin of Gamma-Ray Bursts
100 ks
Paolo PadovaniACS Observations of the Optical Jet of MH 2136-428
10 ks
Optical Jet of MH2136-428
Christopher KochanekThe Host Galaxies of Time Delay Lenses:, An Independent Route to the Hubble Constant
60 ks
B1600+434, B1608+656

Scientific Category: Hot Stars
Title: The Origin of Gamma-Ray Bursts
PI: Andrew Fruchter
Approved Chandra Time (Ksecs): 100


The rapid and accurate localization of gamma-ray bursts (GRBs) promised by a working HETE-2 during the coming year may well revolutionize our ability to study these enigmatic, highly luminous transients. We propose a program of HST and Chandra observations to capitalize on this extraordinary opportunity. We will perform some of the most stringent tests yet of the standard model, in which GRBs represent collimated relativistic outflows from collapsing massive stars. NICMOS imaging and STIS CCD spectroscopy will detect broad atomic features of supernovae underlying GRB optical transients, at luminosities more than three times fainter than SN 1998bw. UV, optical, and X-ray spectroscopy will be used to study the local ISM around the GRB. Chandra spectroscopy will investigate whether the GRB X-ray lines are from metals freshly ripped from the stellar core by the GRB. HST and CTIO infra-red imaging of the GRBs and their hosts will be used to determine whether `dark' bursts are the product of unusually strong local extinction; imaging studies may for the first time locate the hosts of `short' GRBs. Our early polarimetry and late-time broadband imaging will further test physical models of the relativistic blast wave that produces the bright GRB afterglow, and will provide unique insight into the influence of the GRB environment on the afterglow.

Scientific Category: AGN/Quasars
Title: ACS Observations of the Optical Jet of MH 2136-428
PI: Paolo Padovani
Approved Chandra Time (Ksecs): 10


The total number of well-established extragalactic jets is less than twenty, and of these only a handful are blazars. We propose here to use ACS (one orbit) to image in four bands the newly discovered optical jet in the BL Lac object MH 2136-428. This is the first time that an optical jet has been discovered in a completely featureless blazar, that is in an object whose nucleus is particularly highly beamed and/or whose accretion disk power is extremely low. Moreover, our source has a radio flux more than an order of magnitude fainter than those typical of the other blazars with optical jets, allowing us to study an intrinsically weaker jet. Our goals include the study of the jet morphology, its spectral energy distribution, and the relationship between the jet properties in blazar and non-blazar sources, extremely relevant for unified schemes. Only HST can provide the resolution required to study such a faint, narrow feature, close to the bright nucleus. We are also asking for 10ks of Chandra observing time to further constrain the jet spectral energy distribution and its underlying emission processes.

Scientific Category: Cosmology
Title: The Host Galaxies of Time Delay Lenses: , An Independent Route to the Hubble Constant
PI: Christopher Kochanek
Approved Chandra Time (Ksecs): 60


Because of its importance in setting the distance scale, the time scale and in estimating cosmological parameters from the CMB, astronomy needs an estimate of the Hubble constant independent of the local distance scale and its systematic problems. This can be achieved using gravitational lenses with time delay measurements given enough constraints on the gravitational potential of the lens. We will use deep NICMOS observations of the lensed quasar host galaxies in 7 gravitational lenses with time delay measurements to obtain the necessary constraints, determine the dark matter distribution and estimate H_0. Analysis of the existing images and the well-developed theory for analyzing Einstein ring images of host galaxies suggest the new data will break the familiar degeneracies between lens mass distributions and the Hubble constant. We also request 30 ksec Chandra ACIS images for each of the 2 systems lacking them (B1608+656 and B1600+434) to measure the mass in nearby or surrounding groups and clusters.

Last modified: 12/02/10

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