From song@astro.UCLA.EDU Tue Sep 17 10:23:56 2002 Date: Mon, 16 Sep 2002 17:20:45 -0700 (PDT) From: Inseok Song To: Mike Bessell Subject: Your ApJ Letters Submission MS# 16698 (fwd) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Virus-Scanned: by amavisd-milter (http://amavis.org/) Content-Length: 7443 X-Status: X-Keywords: X-UID: 558 Dear Dr. Bessell: Hope everything is OK with you. I just got a referee's report and John Stauffer is serving as a referee as I expected. Anyway, please read it and give me your comments, especially on his remark (7). I wonder if you can manage the october observation all by yourself considering your situation. If you want me to come to help you with the observation, I will certainly do that. Just let me know. Best, Inseok ---------- Forwarded message ---------- Date: Mon, 16 Sep 2002 11:32:23 -0400 (EDT) From: apjl@cfa.harvard.edu Reply-To: ApJ-MS16698@mss.uchicago.edu, apjl@cfa.harvard.edu To: song@astro.ucla.edu Cc: ApJ-MS16698@mss.uchicago.edu Subject: Your ApJ Letters Submission MS# 16698 Dear Dr. Song, Following this message I am sending you the referee's report on your paper 'Lithium Depletion Boundary in a Pre-Main Sequence Binary System'. I am willing to consider a revised version for publication in The Astrophysical Journal Letters. Please take care not to exceed the limit of 4 journal pages. To assist us in the rapid processing of your manuscript, please take great care in preparing your revised version. In particular, avoid minor errors that then have to be corrected by us or by you. Yours sincerely, A. Dalgarno Letters Editor AD/rt ======================================= The referee is John Stauffer. I do not require anonymity. I think the results presented in the paper are extremely interesting and deserving of publication in the ApJ Letters. The paper is appropriate in its content and intent to be published in the Letters section, and I believe it is short enough to fit within the page limits. To a large extent, the paper is quite staight-forward. However, there are quite a few places where I think the presentation could be improved to clarify the points the authors want to make. For that reason, I would like to ask the authors to submit a revised version prior to acceptance of the paper for publication. Comments: 1) Intro - p. 2 - 2nd para - 2nd sentence - The LDB method only works up to an age of about 250 Myr. That is the age when an approx. 0.065 Msun star just creeps above the lithium burning temp. For all older clusters, the LDB stays at 0.065 Msun, since that is the mass below which bds never get hot enough to burn lithium. It is at Pleiades age that the LDB is almost at the same mass as the main seq. hydrogen burning mass limit. 2) few sentences later - re: "e.g. luminosity and temperature" - it is really primarily luminosity, simply because the absolute temperature scales still are not nearly as well constrained as are the absolute magnitudes (bolometric corrections). 3) next para - says that both medium and high res. spectra have been obtained - but only the high res. spectra are described in the text. 4) sec. 2.1 - The wavelength region covered, spectral resolution, and S/N (or - easier and perhaps more useful in this case - the counts per pixel) at 6700A for the spectra should be given. 5) sec. 2.2.2 - The Pleiades M dwarfs are also bluer in B-V than one would expect for their V-I or V-K colors (could reference Stauffer et al. 2002 in prep...). This is probably just a feature of young K and M dwarfs. In the text, you should mention that both stars have H alpha in emission with similar strengths (as noted in the table). hence the spectral types should probably be dM4e and dM4.5e (tho a diehard MK spectroscopist would note that the "e" is tradionally meant to indicate CaHK in emission, not H alpha - but any dM stars with H alpha in emission will also have CaHK in emission). 6) last para of this section - "using an empirical temperature calibration" - give reference or provide the calibration used. 7) age from lithium - I think it is possible to derive a consistent age for the two stars and one where the model predicts the right amount of Li for the two stars. I will forward the electronic version of the D'Antona and Mazzitelli 1997 table that I use. I will put a couple small snippets from their table at the bottom of this report. It looks to me that if one chose an age of about 16 Myr, then a 0.35 Msun star would have L ~ -1.28 and < 0.05% Li whereas a 0.3 Msun star would have L ~ -1.38 and some lithium. The table is too coarse to try to pinpoint the exact Li values that are observed, but it certainly looks to me that within the errors one could match the observations. The Teff given by D'Antona and Mazzitelli would not match, but I don't think that is a show stopper. The temperature derived is a strong function of the way D'A&M treat the photosphere (very crudely), whereas the luminosity is much more robust. So, I think one could conclude that the LDB age is ~ 16 Myr, which would then be consistent in saying the LDB age is older than the age derived from other means (the kinematic and isochrone age for the beta pic group), the same result as for the open clusters. 8) sec. 2.2.5 - 2nd sentence - a radial velocity is derived for the primary. You say that the S/N is too poor to derive an rv for the secondary. However, if you can derive a Li abundance for that star, you HAVE TO BE ABLE to derive an rv. Latham derives accurate rv's for late type stars with S/N ~ 1 from echelle spectra! One thing you can easily do is to fit a gaussian to the H alpha profiles (not as accurate in principal as cross correlation, but should be good to 1-2 km/s on the assumption that the resolution is something like 20,000 or better). Also, from the fit to H alpha, you should be able to derive an estimate of the vsini of this star. The text should say how the radial and rotational velocity of the primary (and hopefully secondary) are derived - cross correlation? line fitting? 9) sec. 2.3 - given the results from Fig. 2, I don't understand the last sentence of this section (i.e. the three models disagree considerably, and all seem to indicate age < 10 Myr). 10) table 2 - probably good to add the radial velocity for the two stars to this table. 11) fig.2 - which curve corresponds to which model? ************************************************************* D'Antona and Mazzitelli table: #M/Msun= .300 .020 # N age logL logTe logI_conv logI_tot(1-R_c/Rtot)(1-Mconv)/Ms logX_D/X_Li T_bce rho_bce 249 7.0515 -1.2715 3.5348 53.392 53.392 1.000000 .000000 -8.109 6.557 .971 254 7.1045 -1.3083 3.5342 53.358 53.358 1.000000 .000000 -8.278 6.574 1.022 259 7.1586 -1.3449 3.5339 53.323 53.323 1.000000 .000000 -8.717 6.591 1.073 264 7.2127 -1.3817 3.5334 53.289 53.289 1.000000 .000000 -9.813 6.608 1.125 269 7.2668 -1.4183 3.5330 53.254 53.254 1.000000 .000000 -12.178 6.625 1.177 # #M/Msun= .350 .020 # N age logL logTe logI_conv logI_tot(1-R_c/Rtot)(1-Mconv)/Ms logX_D/X_Li T_bce rho_bce 275 7.0560 -1.1748 3.5453 53.516 53.516 1.000000 .000000 -8.496 6.595 .952 280 7.1096 -1.2118 3.5447 53.482 53.482 1.000000 .000000 -9.247 6.612 1.003 285 7.1628 -1.2483 3.5441 53.448 53.448 1.000000 .000000 -11.050 6.628 1.054 290 7.2159 -1.2851 3.5435 53.414 53.414 1.000000 .000000 -12.199 6.645 1.104 295 7.2712 -1.3219 3.5432 53.379 53.379 1.000000 .000000 -12.199 6.662 1.157