From: Greg Aldering (aldering@panisse.lbl.gov)
Date: Mon Feb 02 2004 - 10:52:46 PST
Hi Serena,
Echoing Vitaliy, the fitted date of max will depend on the lightcurve
template (among other things Vitaliy listed), and Tonry showed me a number
of fits using different templates; their times of max scattered around by
a few days.
Cheers,
Greg
On Mon, 2 Feb 2004, Serena Nobili wrote:
>
> Dear Vitaliy,
>
> thank you very much for your work. I think we are getting closer to the
> final numbers for 1999Q. What I find annoying however, is the fact that we
> don't get the same tmax as Tonry, given we are using the same data set.
> >From this point of view, Ariel and I have noticed that there are data
> points in the lightcurve you are fitting which are above day 40 (or even
> 50). Those points are certainly worsening your chisq, since they are
> always deviant. As the standard SCP procedure however, is not to include
> points later than 40 days after max in the fit (I believe this was the
> case also for Knop et al.), I think you should try to compute the chisq
> value for all the cases excluding the latest 1 or 2 points.
> Looking at the residuals in your plots, I expect this to give about the
> same chisq in all the cases (except case 1 perhaps). If this is true, and
> we get the same result as Tonry, than we can more easily explain in the
> paper what we did. Thank you again for your help.
> Cheers
>
> Serena
>
>
>
> On Fri, 30 Jan 2004, Vitaliy Fadeyev wrote:
>
> >
> >
> >Hi All,
> >
> >first of all, Serena is right, I made a mistake in inferring the time
> >of maximum from Riess's paper. Riess's JD is ...195.15 and Tonry's ...194.4,
> >i.e. they are fairly similar.
> >
> >I went back and refit the lightcurve while fixing the day of maximum to the Tonry's
> >value. This is case 3 below, the data contain the discovery point. You can see
> >that the Chi^2/#(dof) is really bad. However, previously I did not consider
> >the systematic effects in the photometry. Riess "... conservatively adopted
> >a systematic uncertainty of 0.03 mag in the SN photometry...". I'm not sure
> >what that actually means. Could imagine that a) this is a correlated error
> >for all epics, or b) this is a "random" additional error. It did not seem that
> >either case would change the conclusions. To check that this is true, I followed up
> >with scenario (b). Cases 4 and 5 below repeat cases 2 and 3 with 0.03 mag
> >added to the errors. I think the results with and without systematics
> >are comparable.
> >
> >My conclusion is that the data prefer the earlier day of max that either Riess
> >or Tonry reported. If day of max is ajusted to Tonry's value, then the stretch
> >value is substantially lower (closer to 1).
> >
> >Cases are:
> >1 - HST only
> >2 - HST and discovery point
> >3 - HST and discovery point, maximum fixed to Tonry
> >4 - HST and discovery point, 0.03 mag added to the errors
> >5 - HST and discovery point, 0.03 mag added to the errors, maximum fixed to Tonry
> >
> >SNMINUIT output table:
> >case m_B dm_R m_B_corr dm_B_corr s ds chisq dof m_R kcorr_R kcorr_I tmax dtmax R-I d(R-I)
> >1 22.82 0.06 23.02 0.16 1.117 0.054 5.29 8 22.06 -0.764 -0.310 2451186.54 1.444 -0.054 0.074
> >2 23.14 0.02 23.34 0.07 1.119 0.032 9.95 9 22.24 -0.902 -0.419 2451191.83 0.853 -0.188 0.035
> >3 23.22 0.02 23.31 0.06 1.040 0.022 26.86 10 22.23 -0.987 -0.485 2451194.65 0.000 -0.269 0.031
> >4 23.09 0.03 23.31 0.08 1.131 0.035 7.00 9 22.23 -0.866 -0.390 2451190.94 1.467 -0.153 0.048
> >5 23.23 0.03 23.35 0.07 1.061 0.025 16.00 10 22.26 -0.973 -0.475 2451194.65 0.000 -0.257 0.036
> >
> >The snminuit plots are here:
> >(case 1) http://www-physics.lbl.gov/~fadeyev/snminuit_sn1999q_HSTonly.ps
> >(case 2) http://www-physics.lbl.gov/~fadeyev/snminuit_sn1999q_HSTdisc.ps
> >(case 3) http://www-physics.lbl.gov/~fadeyev/snminuit_sn1999q_fixtmax.ps
> >(case 4) http://www-physics.lbl.gov/~fadeyev/snminuit_sn1999q_HSTdisc_syst.ps
> >(case 5) http://www-physics.lbl.gov/~fadeyev/snminuit_sn1999q_fixtmax_syst.ps
> >
> >Cheers,
> >vitaliy
> >
> >
> >
> >
> >Serena Nobili wrote:
> >
> >> Dear Greg (cc Vitaliy & co.)
> >>
> >> I am glad you had the possibility to talk directly to Tonry. Reading your
> >> e-mail I went back to Riess et al (2000) to check the date of maximum he
> >> gives. Looking at table 2 of Riess'paper, I get the date of B maximum to
> >> be 51195.15, i.e. only 1 day later than Tonry's value, and not 3 as you
> >> say and, if I am not wrong, Vitaliy was assuming in case 2 of the fit. I
> >> believe the problem comes from column 2 being rest frame, instead of
> >> observed frame, this would give the 3 days difference.
> >>
> >> All of this is suggesting that the time of max given by Tonry and Riess
> >> agree within 1 day. I think we should repeat the lightcurve fit using
> >> Tonry's time of maximum, if we want to use the stretch factor, and refer
> >> to the time of max as private communication (though, it would be nice to
> >> be able to reproduce this fit, since we are using the same data set).
> >> Once we have done this, we can safely include the stretch of 99Q in the
> >> I-band paper. Thank you for your help in solving this problem.
> >> Cheers
> >>
> >> Serena
> >>
> >> On Fri, 30 Jan 2004, Greg Aldering wrote:
> >>
> >> >
> >> >Hi Vitaliy and Serena,
> >> >
> >> >I spoke with John Tonry today concerning 99Q. The photometry he has
> >> >consists of the discovery point and those from the HST images. (This is
> >> >basically the same as in Vitaliy's thrid fit.) The discovery point has I =
> >> >22.3 +/- 0.05 and the fitted date of max is 2451194.4. So, Tonry's date of
> >> >max is 3 days earlier than the one used by Adam, and 2.6 days later than
> >> >your fit using the discovery point (albeit using a larger value for the
> >> >uncertainty).
> >> >
> >> >Tonry said it is possible that Adam might have a "secret stash" of
> >> >additional data points (I found this an odd thing for him to say, but
> >> >apparently they aren't so good about sharing data within their
> >> >collaboration), but this seems unlikely.
> >> >
> >> >So, I think we can safely use 2451194.4, quoting Tonry 2003 & private
> >> >communication, for the time of maximum light. Using this modifed date
> >> >of max isn't enough to alter the maximum restframe I-band brightness
> >> >by more that a few percent. So, it isn't enough to explain why 99Q is
> >> >fainter. However, it does mean that we know that stretch as well
> >> >as the HZSST does.
> >> >
> >> >Looking more carefully, I see that in the uncorrected Hubble diagram 99Q
> >> >is only about 2-sigma too faint using the *inner* error bars. In all
> >> >cases 99Q is beter than 1.5-sigma using the outer error bars (i.e.,
> >> >including intrinsic error).
> >> >
> >> >All of this suggests to me that we may as well show both the uncorrected
> >> >and stretch-corrected results in the I-band paper. It will not be
> >> >controversial, but make the paper clearer and more complete. (Right now
> >> >one wonders about, or is easily confused by, the use of stretch correction
> >> >for the local SNe in the first half of the paper and then skirting of the
> >> >stretch correction in the latter half of the paper.)
> >> >
> >> >Cheers,
> >> >
> >> >Greg
> >> >
> >> >
> >> >
> >
> >
>
> --
>
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