From kawabata@subaru.naoj.org Tue Oct 29 13:27:51 2002

Dear David,

We will submit our next proposal for Subaru SN observation
in a day.
I would like you to join us again if it is fine with you.

The TeX source is attached below, and its PS-file version
is available at
http://www.astr.tohoku.ac.jp/~kawabata/prop2.ps

I am sorry, but the remaining time is short before deadline.
If you have comments, please tell me within a day.


Sincerely yours,
Koji S. Kawabata

Cc: Nomoto-sama

---
% Template for Subaru proposals (as of S03A)
%
% If you are using LaTeX2e, you should uncomment the \documentclass and
% \usepackage lines and comment the \documentstyle line.
%\documentclass{article}
%\usepackage{subaru}
\documentstyle[subaru,epsf]{article}
\begin{document}
% Set this to the current Subaru semester
\semester{S03A}
% After submitting your proposal electronically, please insert here the
% proposal ID returned by PROMS, so your electronic submission can be
% matched to the hardcopies which arrive in Mitaka.
\proposalid{}
%
% Uncomment this line if this is an Open Use Intensive Program
%\intensive
%
% Enter your title here; it should fit on one line when printed
\title{Polarimetry of Supernovae -- Probing the Origin of Asymmetric Explosions}


% Enter the Principal Investigator's information here
\PIfirstname {Koji}
\PIinitial   {S.}
\PIlastname  {Kawabata}
\PIinstitute {Optical and Infrared Astronomy Division, National
Astronomical Observatory of Japan}
\PIaddress   {Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan}
\PIemail     {koji.kawabata@nao.ac.jp}
\PIphone     {+81-422-34-3533}
\PIfax       {+81-422-34-3545}


% Uncomment ONE of the following lines to indicate the scientific category
%\SolarSystem
%\NormalStars
%\ExtrasolarPlanets
%\StarandPlanetFormation
\CompactObjectsandSNe
%\MilkyWay
%\LocalGroup
%\ISM
%\NearbyGalaxies
%\StarburstGalaxies
%\AGNandQSOActivity
%\QSOAbsorptionLinesandIGM
%\ClustersofGalaxies
%\GravitationalLenses
%\HighzGalaxies
%\DeepSurveys
%\LargeScaleStructure
%\CosmologicalParameters
%\Miscellaneous


% Enter your abstract here. Please ensure it fits in the space provided.
\begin{abstract}
Asymmetry is an important factor in the use of
supernovae as distance indicators because the luminosity can be
view-angle dependent. It provides clues to the physics of supernova
explosions and to the structure of circumstellar matter and hence the
progenitor evolution. Existing SN polarization data
suggested that {\it all} core-collapse SNe (SN II, Ib/c) are
intrinsically polarized at a level of about 1\% and thus pointing to
significant asymmetry. Spectropolarimetry
of two nearby Type Ia
supernovae (SN 2001el and SN 2002bo) have successfully been obtained
both with significant detection of intrinsic polarization.
Our recent success in obtaining polarimetry observations of a
hypernova SN 2002ap using FOCAS proves polarimetry as a unique
tool in probing the structure of supernova ejecta.
We expect SUBARU+FOCAS to play a critical role in
building up a database of well observed nearby supernovae
with spectropolarimetry coverage. Such a database is important
in understanding the complicated physical mechanisms of
supernova explosions on the one hand, and assessing the significance
of systematic effects in using SN Ia as distance indicators
on the other.
\end{abstract}


% Enter name and institution of each Co-I
% e.g., \CoI{I. Newton}{University of Cambridge}
\begin{investigators}
\CoI{K. Nomoto,~K. Maeda,~J. Deng}{\hspace*{4em}Univ. of Tokyo}
\CoI{G. Kosugi,~T. Sasaki}{Subaru Telescope, NAOJ}
\CoI{T. Takata,~K. Aoki}{Subaru Telescope, NAOJ}
\CoI{M. Iye}{Opt.\& IR Astron. Div., NAOJ}
\CoI{D. Baade}{ESO, Germany}
\CoI{L. Wang}{LBNL, USA}
\CoI{P. H\"oflich,~J. C. Wheeler}{Univ. of Texas, USA}
\CoI{D. J. Jeffery}{New Mexico Tech, USA}
\CoI{P. Mazzali}{Trieste Observatory, Italy}
\end{investigators}


% List all relevant publications here.
\begin{publications}
     \normalsize
       Howell, D. A., H\"oflich, P., Wang, L., \& Wheeler, J. C. 2000, ApJ,
        556, 320:
          \footnotesize{Evidence for Asphericity in a Type Ia SN 1999by}
     \smallskip\\
     \normalsize
       Kawabata, K. S., Jeffery, D. J., Iye, M., Ohyama, Y., et al. 2002,
         ApJL, in press:
         \footnotesize{Optical Spectropolarimetry of SN~2002ap: A
          High Velocity Asymmetric Explosion}
     \smallskip\\
     \normalsize
       Maeda, K., Nakamura, T., Nomoto, K., Mazzali, P. A., Patat, F.,
         Hachisu, I. 2002, ApJ, 565, 405:
         \footnotesize{Explosive Nucleosynthesis in Aspherical Hypernova
         Explosions and Late-Time Spectra of SN 1998bw}
     \smallskip\\
     \normalsize
      Mazzali, P. A., Deng, J., Maeda, K., Nomoto, K., et al. 2002,
         ApJ, 572, L61:
          \footnotesize{The Type Ic Hypernova SN 2002ap}
     \smallskip\\
     \normalsize
      Wang, L., H\"oflich, P., Khokhlov, A., Wheeler, J., Baade, D.,
       and the SINS team, ApJ, submitted,
          \footnotesize{The Bipolar Ejecta of Supernova 1987A}
     \smallskip\\
     \normalsize
      Wang, L., Howell, A. D., H\"oflich, P., \& J. C. Wheeler, 2000,
          ApJ, 550, 1030:
          \footnotesize{Polarimetry of Core-collapse Supernovae}
     \smallskip\\
     \normalsize
     Wang, L., \& Wheeler, J. C. 2002, Sky \& Telescope, 103, part no 1, 40:
         \footnotesize{Supernovae are not round}
%    \smallskip\\
\end{publications}


% For each observing run, enter the instrument, number of nights requested,
% lunar phase (Dark/Gray/Bright), preferred dates, acceptable
% dates, and % configuration. Fractional nights are now accepted.
% e.g., \run{IRCS}{1}{Bright}{Dec/early Jan}{Nov--Feb}{K grism}
\begin{observingrun}
%\run{}{}{}{}{}{}
\run{FOCAS}{3}{Gray}{Apr/Sept}{Apr/Sept}{Gr. 300B+SY47 or L600 }


% Enter the minimum acceptable number of nights to achieve your science
% goals. You may leave this empty if you require your full request.
\minnights{2}
\end{observingrun}


% Uncomment the following line if you do not want the technical reviewer
% to see your target names
%\hidetargets
% Enter your targets here: name, RA, dec, equinox, magnitude
% e.g., \target{4C~41.17}{06 50 52.10}{+41 30 30.5}{J2000.0}{$K=19.1$}
\begin{targets}
\target{SN2003XXXX}{00 00 00.00}{+00 00 00.0}{J2000.0}{$V<17$}
\end{targets}

% Explain any scheduling requests noted above.
\scheduling{This is a ToO (Target of Opportunity) observation.
An assignment of a half (or quarter) night is also acceptable
when the target is bright enough.}
%\scheduling{ToO}

% Add any further instrumentation requirements, or details of your own
% instrument.
\instruments{Polarimetry optics are request for this program}

% Please briefly describe your experience, ability, need of assistance,
% etc. for making observations with Subaru
%
\experience{PI and some Co-Is belong to the FOCAS instrument team and have
sufficient experiences of observations with the FOCAS and the Subaru
telescope. We need only normal assistance by the support astronomer
and by the telescope operator. Our team consists of experienced
observers and theorists in analyzing and modeling
polarimetry data of supernovae. }


% Briefly describe your backup proposal. Please include target names so
% conflicts with accepted proposals can be spotted.
\backup{}


% Put the Observing Method and Technical Details here.
\begin{technicalinfo}
We use the typical long-slit spectroscopic mode ($R\sim 600$) of the FOCAS.
\begin{itemize}
   \item Filter: either Y47 or L600
   \item Grism: 300B
   \item Slit width: 0.8" center/offset slit
   \item Readout mode: whole CCD and normal speed
   \item Necessary S/N: 30
\end{itemize}

For spectropolarimetry, we will use the Wollaston prism
and the half-wave plate. A typical observing sequence
consists of four integrations at the 0, 45, 22.5 and 67.5 degs
positions of the half-wave plate.
\begin{itemize}
   \item Necessary S/N in each integration: 300
\end{itemize}
Note that exposure time varies with the type and brightness
of the SNe. For SN Ia before maximum and $V \sim 13$, we will
target for accuracies around $\Delta P =0.1$--$0.2$ \%/pixel, whereas for
SN II, Ibc, $0.2$--$0.4$ \%/pixel is enough.
The total exposure time of each observation (four integrations) is approximately
\[
   t \simeq 10^{4} \times \frac{0.1 \mbox{ \%}}{\Delta P} \times
   10^{-0.4(V-15)} \mbox{ seconds.}
\]
\end{technicalinfo}


% If this proposal is a continuation of an accepted proposal (or a
% resubmission of one which was weathered out for example), enter the
% proposal ID and title here.
\continuation{}{}


% If these observations are intended to be part of a student's thesis,
% enter the student's name and thesis title.
\thesis{}{}


% Enter your previous Subaru runs from the last 3 years. Enter year/month,
% Proposal ID, PI name, status of data reduction, and status of publications
\begin{previoususe}
%\pastrun{}{}{}{}{}
\pastrun{2001/3}{S00-022}{K. Nomoto}{Data reduced/analyzed}{Paper to appear 
in PASJ}
\pastrun{2002/10-}{S02B-181}{K. Nomoto}{ToO; not yet triggered}{}
\end{previoususe}


% If you have more targets, please uncomment the following 3 lines and
% enter them here, using the same format as above.
%\begin{moretargets}
%\target{}{}{}{}{}
%\end{moretargets}


\scijust
% Enter your scientific justification here (maximum 2 pages, including
% figures and additional references).

SN 1987A represented a breakthrough by
providing the first detailed record of the polarimetric evolution
(Cropper et al. 1988, MNRAS, 231, 695; Mendez et al. 1988, ApJ, 334,
295).  SN 1993J also provided a wealth of data (Trammell, Hines, and
Wheeler 1993, ApJ, 414, L21).  Spectropolarimetry probes the
geometrical structures of the supernova (SN) debris which are closely
related to the explosion mechanisms and the progenitor systems.
Core-collapse SNe are found to be generally more highly polarized than
thermonuclear SNe (SN Ia) (Wang et al. 1996, ApJ, 467, 435; 2001, ApJ,
550, 1030; Howell et al. 2001, ApJ, 556, 302). A peculiar, subluminous
SN Ia was found to be polarized at 1\% level (Howell et al. 2001).
The recent FOCAS observations of the hypernova SN 2002ap shows that
polarimetry can provide unique information on the structure of a
supernova ejecta (Kawabata et al. 2002, ApJ, in press). In particular,
we have identified a high velocity component which may be
associated with a jet produced during the supernova explosion.
The database of supernova polarimetry however are still sparse,
these earlier results should be considered preliminary. It is
the goal of this proposal to obtain a data set that is of sufficient
quantity and quality to address many of the critical issues
on the physics of supernova explosions and the use of them as
standard candles for probing the dark energy content of the universe.


{\bf 1. Thermonuclear Explosions (Type Ia)}


Type Ia SNe are crucial for determining cosmological distance scales
and the dynamics of the Universe.  Significant asymmetries would mean
the luminosity to be dependent on the viewer aspect angle which could
make a SN less reliable as a distance calibrator.  Polarization data
are therefore of fundamental importance as a self-consistency check
for SNe as distance calibrators, and to understand the remaining 10\%
luminosity scatter of stretch-corrected SNe Ia to determine H$_0$ and
the dark energy content.  Our collaborator have observed successfully three
pre-maximum SN Ia (SN 2001V, SN 2001el and SN 2002bo) using the
ESO+VLT.  All three SNe are polarized before optical maximum. The
polarization of SN 2001el diminished post-maximum.  Most SN Ia
have small polarization.


The polarization can be modeled and gives clues to the physics of the
deflegation of the white dwarf (Wang, Wheeler, \& H\"oflich 1997, ApJ,
476, L27). The observations will be used to test SN Ia models based on a
close binary system involving a white dwarf (WD) and a main sequence,
subgiant or red giant star as the progenitor of SN Ia. According to
recent calculations of Marietta, Burrows, and Fryxell (ApJS, 128, 615,
2000) the impact of the SN ejecta with the secondary star creates a
hole in the SN debris with an angular size of $\sim 30^{\circ}$ in the
ejecta which corresponds to 7\%-12\% of the ejecta's surface. Such a
hole, if it exists, is expected to produce average polarizations of
around 1\%.  A low observed degree of polarization therefore implies
that either the hole is very close to the line of sight (in front of
or behind the WD), or the models have to be modified. The spectral
profiles would also be tests for such models when viewed at different
angles.  Asymmetry probes also the complicated explosion mechanisms of
SN Ia.  Recently, Livne (ApJL, 527, 97, 1999) pointed out that the
deflagration/detonation transition may be aspherical.  Polarimetry will
provide the necessary guidance for these and many other complicated
models. It thus seems that the low observed degree of polarization of
SN Ia in previous studies is by no means a final answer to
polarimetry properties of this group of SNe.


These data are important for using SN Ia as distance calibrators.
To test the effect of asymmetry on the
luminosity of SN Ia, SNe in the smooth Hubble flow are required,
which are usually too faint for small telescopes but can be comfortably
observed by SUBARU telescope.
Polarimetry will be combined with photometric data to study the effect
of asymmetry on distance calibrations using SN Ia. Time evolution is
critical. We would like to know at which phase an SN Ia shows lower
degrees of polarization so that it can be a 'better' calibrator.


{\it We require the large aperture of the SUBARU to make careful
measurements of the polarization of more SN Ia to determine their origin
and whether asymmetry could affect distance estimates.}


{\bf 2. Core-collapse Supernovae}


Earlier studies are suggestive that core-collapse SNe show higher
polarizations for events with smaller envelope mass and that the
polarization increases with time as we see to greater depth in a
single event.  (Wang et al. 2001, ApJ, 550, 1035; Leonard et al. 2001,
ApJ, 553, 8611).  This suggests that the core collapse process may be
intrinsically asymmetric and that the asymmetry is damped by an
extensive envelope. The data on Type Ic SN 1997X showed strong
polarization, well in excess of 1 \%.  This is an especially exciting
observation because SN 1997X must have occurred in a nearly naked,
non-degenerate, carbon/oxygen core.  There is little mass to diffuse
an asymmetrical explosion and render it more spherical.  There is thus
the tantalizing expectation that in SN 1997X we may be seeing the
direct effects of a strongly asymmetric explosion.


SN polarimetry is still an under-cultivated field which promises rich
and interesting scientific returns, and surprises. The
hypernova SN~2002ap serves as a nice example as shown in Figure 1.
The degree of
polarization is nearly 1\%, which is among the average values for SN
II events. The polarizations and their time evolution will allow us to
study the geometry of different chemical layers.  The positive
detection of polarization features across spectral lines implies that
the ejecta are asymmetric. In particular, the data are suggestive of
a high velocity jet material.
\begin{figure}
   \begin{flushleft}
   \epsfysize=9cm
   \epsfbox{sn02apb.eps}
   \caption{FOCAS spectropolarimetry of SN 2002ap}
   \end{flushleft}
\end{figure}

Many questions can be asked of these canonical events.  Is the progenitor
in a binary system ? Is the asymmetry due to external circumstellar
material or is it from deep inside the stellar core ?  If the origin
of the asymmetry is from near the stellar center and the symmetry axis
is constant, as is consistent with the observed polarimetry evolution,
the central engine for the explosion must be highly aspherical and
co-aligned so that the asymmetry can still influence the outermost
part of the ejecta.  We need SUBARU data to follow a number of
core-collapse events to late times to determine if the polarization
anti-correlates with envelope mass and luminosity and how it varies
with time.
  The SUBARU data will help to establish whether or not the the
core-collapse process is intrinsically strongly asymmetric and the
nature of the asymmetry, eg, jet-like.


This program aims to make use of the SUBARU telescope
to obtain high quality spectropolarimetric data on 3-6 SNe brighter
than V=16 mag. Because the current data are sparse and every new SN
adds to our understanding of SN asymmetry, we will observe all types
of SNe that are available.  We will observe Type Ia SNe down to a
noise level $\sim$ 0.2\%, with a spectral coverage from 4100 to 8600
\AA.  To probe core collapse, it is important to monitor asymmetries
as the SN fades and the photosphere recedes, so these events need to
be followed to faint epochs, outside the reach of 4-m telescopes.
The data will be used to study both the properties of the SNe and of
the interstellar dust in the host galaxies of the SNe.  Some immediate
applications include:


{\bf (a)} Polarimetry data base.
With this data we will expand the statistical base, the time coverage,
and the quality of the data.  We will attempt to test our hypothesis
that Type Ib/c are systematically more polarized than Type II.  We
will attempt to study the geometry of the ejecta and correlate it with
the observed luminosity.  The data will be used to isolate different
mechanisms to produce polarization and to constrain physical
mechanisms of core collapses.  We will seek to determine the
frequency, amplitude and cause of the polarization of Type Ia, and
determine the effect of asymmetry on the luminosity of an SN Ia.


{\bf (b)} Models.
We will explore multi-dimensional physical models of thermonuclear
explosions in Type Ia and core collapse in Type II and Ib/c to
understand the origin and nature of asymmetries.  Some asymmetry is
expected in the turbulent burning of a white dwarf in a Type Ia, but
large polarizations may require an external influence such as a
companion or an accretion disk.  We will be able to test dynamical
models of core collapse that generate jets to determine the degree of
fundamental asymmetry in the explosion necessary to imprint a certain
polarization in the homologously expanding ejecta.  We will also
compute multi-dimensional radiative transfer to determine the
predicted polarization spectrum to compare to the observations.


{\bf (c)} Dust properties.
This program yields the wavelength dependence of the degree of
polarization of the ISM as a by-product.  The ISM data gives the
wavelength of the maximum polarization which is a sensitive diagnostic
of the reddening coefficient $R_V\ =\ A_V/E(B-V)$.  Our preliminary
result is that the reddening coefficient is different for the host
galaxy of every SN and the result can deviate substantially from the
canonical value of $R_{V}=3.1$.  We will continue a systematic study of the
interstellar polarization.



{\it The large aperture of SUBARU provides the almost unique means to lead
the small sample of SNe with spectropolarimetry out of statistical
meaninglessness. This concerns especially studies of individual
spectral features, which are crucial for all types of SNe and would be
wiped out by strong binning, and the follow-up into advanced stages of
core-collapse SNe, when the inner layers of the progenitor become
accessible and so come closer to the zone of origin of the asymmetry. }
\end{document}