| PI Name | Title | Chandra time | Targets |
|---|---|---|---|
| Andrew Fruchter | The Origin of Gamma-Ray Bursts | GRB TOO | |
| Paolo Padovani | ACS Observations of the Optical Jet of MH 2136-428 | Optical Jet of MH2136-428 | |
| Christopher Kochanek | The Host Galaxies of Time Delay Lenses:, An Independent Route to the Hubble Constant | B1600+434, B1608+656 |
Scientific Category: Hot Stars
Title: The Origin of Gamma-Ray Bursts
PI: Andrew Fruchter
Approved Chandra Time (Ksecs): 100
Abstract:
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
Abstract:
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
Abstract:
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.