A public relativistic transfer function model for X-ray reverberation mapping of accreting black holes
Pith reviewed 2026-05-25 19:59 UTC · model grok-4.3
The pith
The reltrans model fits X-ray spectra and lag spectra simultaneously to measure black hole masses and correct prior geometric biases.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
reltrans is a relativistic transfer function model that calculates light-crossing delays and energy shifts experienced by X-ray photons reflecting from an accretion disk, accounting for all general relativistic effects. The model enables simultaneous fitting to spectra and lags, incorporates a self-consistent radial ionization profile, and includes telescope response effects. Fitting to the lag-energy spectrum of Mrk 335 gives a best-fit black hole mass of approximately 7 million solar masses, smaller than the 14-26 million solar masses from prior optical reverberation measurements, while revealing that previous analyses measured artificially low source heights and misestimated lag sizes.
What carries the argument
The reltrans model, a fast relativistic transfer function that computes photon delays, energy shifts, and reflection including general relativity, self-consistent disk ionization, and instrument response.
If this is right
- Simultaneous fitting of the time-averaged spectrum and lag spectra yields tighter constraints on accretion geometry than spectrum fitting alone.
- Black hole masses in both active galactic nuclei and X-ray binaries can be measured directly from X-ray timing data.
- Prior spectral analyses that omitted the radial ionization profile measured source heights that were too low.
- Prior timing analyses that omitted the telescope response underestimated the magnitude of soft lags in AGN and overestimated thermal reverberation lags in X-ray binaries.
Where Pith is reading between the lines
- The lower mass for Mrk 335 may require re-examination of its accretion rate and other derived properties in multi-wavelength studies.
- Applying the same model to additional AGN could resolve systematic differences between X-ray and optical mass estimates across the population.
- Correcting for ionization and response effects in existing archival data might alter interpretations of reflection features in many sources.
Load-bearing premise
The disk ionization parameter varies radially in a way fully determined by the illuminating flux and disk density profile without extra free parameters that would alter the predicted lags.
What would settle it
An independent mass measurement for Mrk 335, such as from optical reverberation mapping or stellar dynamics, that confirms a value of 14-26 million solar masses rather than 7 million would falsify the X-ray lag result.
Figures
read the original abstract
We present the publicly available model \textsc{reltrans} that calculates the light-crossing delays and energy shifts experienced by X-ray photons originally emitted close to the black hole when they reflect from the accretion disk and are scattered into our line-of-sight, accounting for all general relativistic effects. Our model is fast and flexible enough to be simultaneously fit to the observed energy-dependent cross-spectrum for a large range of Fourier frequencies, as well as to the time-averaged spectrum. This not only enables better geometric constraints than only modelling the relativistically broadened reflection features in the time-averaged spectrum, but additionally enables constraints on the mass of supermassive black holes in active galactic nuclei and stellar-mass black holes in X-ray binaries. We include a self-consistently calculated radial profile of the disk ionization parameter and properly account for the effect that the telescope response has on the predicted time lags. We find that a number of previous spectral analyses have measured artificially low source heights due to not accounting for the former effect and that timing analyses have been affected by the latter. In particular, the magnitude of the soft lags in active galactic nuclei may have been under-estimated, and the magnitude of lags attributed to thermal reverberation in X-ray binaries may have been over-estimated. We fit \textsc{reltrans} to the lag-energy spectrum of the Seyfert galaxy Mrk 335, resulting in a best fitting black hole mass that is smaller than previous optical reverberation measurements ($\sim 7$ million compared with $\sim14-26$ million $M_\odot$).
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript introduces the publicly available reltrans model, which computes light-crossing delays and energy shifts for X-ray photons emitted near a black hole, reflected from the accretion disk, and observed after accounting for all general relativistic effects. The model incorporates a self-consistently calculated radial ionization profile of the disk and the effects of telescope response, and is designed to be fit simultaneously to time-averaged spectra and energy-dependent cross-spectra over a range of Fourier frequencies. Application to the lag-energy spectrum of Mrk 335 yields a best-fit black hole mass of approximately 7 million solar masses (smaller than prior optical reverberation estimates of 14-26 million solar masses), with the authors concluding that previous spectral analyses underestimated source heights due to neglecting the ionization profile and that timing analyses have been affected by not accounting for telescope response.
Significance. If the implementation and fits prove robust, reltrans represents a useful public tool for joint spectral-timing analysis that can tighten geometric and mass constraints on both supermassive and stellar-mass black holes. The emphasis on self-consistent ionization and proper treatment of instrument response addresses potential systematics in earlier work, and the public release supports reproducibility and community use.
minor comments (3)
- The abstract states that the radial ionization profile is calculated self-consistently from illuminating flux and disk density without additional free parameters, but the manuscript should explicitly state the assumed functional form of the density profile (e.g., in the methods section) to allow readers to assess whether this choice affects the predicted lags.
- The claim that prior spectral analyses measured artificially low source heights would be strengthened by a direct side-by-side comparison (perhaps in a table or figure) of fits with and without the ionization profile for the same dataset.
- The manuscript would benefit from including quantitative benchmarks (e.g., runtime per frequency bin or comparison to existing codes such as relxill) to support the statement that the model is 'fast and flexible enough' for simultaneous fitting.
Simulated Author's Rebuttal
We thank the referee for their positive assessment of the manuscript and for recommending minor revision. The report highlights the utility of reltrans for joint spectral-timing analysis and notes the importance of self-consistent ionization and instrument response. No major comments were raised in the report.
Circularity Check
No significant circularity; forward GR transfer function model
full rationale
The paper constructs reltrans as an explicit forward computation of photon trajectories, light-crossing times, energy shifts and reflection spectra under general relativity, using a self-consistently computed ionization profile derived from illuminating flux and an assumed disk density (no free parameters added to alter lags). The Mrk 335 mass is obtained by fitting this model to observed lag-energy spectra; the output lags are not defined in terms of the fitted mass or height, nor does any equation reduce the result to a prior fit or self-citation. No load-bearing step matches any enumerated circularity pattern.
Axiom & Free-Parameter Ledger
free parameters (2)
- black hole mass =
~7 million solar masses
- source height
axioms (2)
- standard math General-relativistic photon trajectories and energy shifts near a Kerr black hole
- domain assumption Thin accretion disk with radially dependent ionization set by illuminating flux
Reference graph
Works this paper leans on
-
[1]
" write newline "" before.all 'output.state := FUNCTION fin.entry write newline FUNCTION new.block output.state before.all = 'skip after.block 'output.state := if FUNCTION new.sentence output.state after.block = 'skip output.state before.all = 'skip after.sentence 'output.state := if if FUNCTION not #0 #1 if FUNCTION and 'skip pop #0 if FUNCTION or pop #1...
-
[2]
Ar \'e valo P., Uttley P., 2006, @doi [ ] 10.1111/j.1365-2966.2006.09989.x , http://adsabs.harvard.edu/abs/2006MNRAS.367..801A 367, 801
-
[3]
Bardeen J. M., Press W. H., Teukolsky S. A., 1972, @doi [ ] 10.1086/151796 , http://adsabs.harvard.edu/abs/1972ApJ...178..347B 178, 347
-
[4]
Basak R., Zdziarski A. A., Parker M., Islam N., 2017, @doi [ ] 10.1093/mnras/stx2283 , http://adsabs.harvard.edu/abs/2017MNRAS.472.4220B 472, 4220
-
[5]
Bendat J. S., Piersol A. G., 2010, Random Data: Analysis and measurement procedures; 4th edition . Wiley, 2010
work page 2010
-
[6]
Beuchert T., et al., 2017, @doi [ ] 10.1051/0004-6361/201630293 , http://adsabs.harvard.edu/abs/2017A
-
[7]
Testing the X-ray reverberation model KYNREFREV in a sample of Seyfert 1 Active Galactic Nuclei
Caballero-Garcia M. D., Papadakis I. E., Dovciak M., Bursa M., Epitropakis A., Karas V., Svoboda J., 2018, preprint, http://adsabs.harvard.edu/abs/2018arXiv180403503C ( @eprint arXiv 1804.03503 )
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[8]
M., Zoghbi A., Reynolds C., Fabian A
Cackett E. M., Zoghbi A., Reynolds C., Fabian A. C., Kara E., Uttley P., Wilkins D. R., 2014, @doi [ ] 10.1093/mnras/stt2424 , http://adsabs.harvard.edu/abs/2014MNRAS.438.2980C 438, 2980
-
[9]
Caiazzo I., et al., 2019, arXiv e-prints, http://adsabs.harvard.edu/abs/2019arXiv190306760C
work page 2019
-
[10]
Campana S., Stella L., 1995, @doi [ ] 10.1093/mnras/272.3.585 , http://adsabs.harvard.edu/abs/1995MNRAS.272..585C 272, 585
- [11]
-
[12]
Chainakun P., Young A. J., 2015, @doi [ ] 10.1093/mnras/stv1333 , http://adsabs.harvard.edu/abs/2015MNRAS.452..333C 452, 333
-
[13]
Chainakun P., Young A. J., 2017, @doi [ ] 10.1093/mnras/stw2964 , http://adsabs.harvard.edu/abs/2017MNRAS.465.3965C 465, 3965
-
[14]
Chainakun P., Young A. J., Kara E., 2016, @doi [ ] 10.1093/mnras/stw1105 , http://adsabs.harvard.edu/abs/2016MNRAS.460.3076C 460, 3076
-
[15]
W., Falanga M., Fukumura K., Reynolds C
Dauser T., Garcia J., Wilms J., B \"o ck M., Brenneman L. W., Falanga M., Fukumura K., Reynolds C. S., 2013, @doi [ ] 10.1093/mnras/sts710 , http://adsabs.harvard.edu/abs/2013MNRAS.430.1694D 430, 1694
-
[16]
Dauser T., Garc \' a J., Parker M. L., Fabian A. C., Wilms J., 2014, @doi [ ] 10.1093/mnrasl/slu125 , http://adsabs.harvard.edu/abs/2014MNRAS.444L.100D 444, L100
-
[17]
Dauser T., Garc \' a J., Walton D. J., Eikmann W., Kallman T., McClintock J., Wilms J., 2016, @doi [ ] 10.1051/0004-6361/201628135 , http://adsabs.harvard.edu/abs/2016A
-
[18]
De Marco B., Ponti G., Cappi M., Dadina M., Uttley P., Cackett E. M., Fabian A. C., Miniutti G., 2013, @doi [ ] 10.1093/mnras/stt339 , http://adsabs.harvard.edu/abs/2013MNRAS.431.2441D 431, 2441
-
[19]
De Marco B., Ponti G., Mu \ n oz-Darias T., Nandra K., 2015, @doi [ ] 10.1088/0004-637X/814/1/50 , http://adsabs.harvard.edu/abs/2015ApJ...814...50D 814, 50
-
[20]
De Marco B., et al., 2017, @doi [ ] 10.1093/mnras/stx1649 , http://adsabs.harvard.edu/abs/2017MNRAS.471.1475D 471, 1475
-
[21]
M., Chakrabarty D., Harrison F
Degenaar N., Miller J. M., Chakrabarty D., Harrison F. A., Kara E., Fabian A. C., 2015, @doi [ ] 10.1093/mnrasl/slv072 , http://adsabs.harvard.edu/abs/2015MNRAS.451L..85D 451, L85
-
[22]
Dexter J., Agol E., 2009, @doi [ ] 10.1088/0004-637X/696/2/1616 , http://adsabs.harvard.edu/abs/2009ApJ...696.1616D 696, 1616
-
[23]
Done C., Diaz Trigo M., 2010, @doi [ ] 10.1111/j.1365-2966.2010.17092.x , http://adsabs.harvard.edu/abs/2010MNRAS.407.2287D 407, 2287
-
[24]
Done C., Nayakshin S., 2007, @doi [ ] 10.1111/j.1745-3933.2007.00303.x , http://adsabs.harvard.edu/abs/2007MNRAS.377L..59D 377, L59
-
[25]
Done C., Gierlinski M., Kubota A., 2007, @doi [ ] 10.1007/s00159-007-0006-1 , http://adsabs.harvard.edu/abs/2007A
-
[26]
Dovciak M., 2004, PhD thesis
work page 2004
-
[27]
Eardley D. M., Lightman A. P., Shapiro S. L., 1975, @doi [ ] 10.1086/181871 , http://adsabs.harvard.edu/abs/1975ApJ...199L.153E 199, L153
-
[28]
Ellis G. F. R., 2007, @doi [General Relativity and Gravitation] 10.1007/s10714-006-0355-5 , http://adsabs.harvard.edu/abs/2007GReGr..39.1047E 39, 1047
-
[29]
Ellis G. F. R., 2009, @doi [General Relativity and Gravitation] 10.1007/s10714-009-0760-7 , http://adsabs.harvard.edu/abs/2009GReGr..41..581E 41, 581
-
[30]
Emmanoulopoulos D., Papadakis I. E., Dov c iak M., McHardy I. M., 2014, @doi [ ] 10.1093/mnras/stu249 , http://adsabs.harvard.edu/abs/2014MNRAS.439.3931E 439, 3931
-
[31]
Epitropakis A., Papadakis I. E., 2017, @doi [ ] 10.1093/mnras/stx612 , http://adsabs.harvard.edu/abs/2017MNRAS.468.3568E 468, 3568
-
[32]
E., Dov c iak M., Pech \'a c ek T., Emmanoulopoulos D., Karas V., McHardy I
Epitropakis A., Papadakis I. E., Dov c iak M., Pech \'a c ek T., Emmanoulopoulos D., Karas V., McHardy I. M., 2016, @doi [ ] 10.1051/0004-6361/201527748 , http://adsabs.harvard.edu/abs/2016A
-
[33]
Etherington I. M. H., 1933, Philosophical Magazine, http://adsabs.harvard.edu/abs/1933PMag...15..761E 15
work page 1933
-
[34]
Fabian A. C., Rees M. J., Stella L., White N. E., 1989, , http://adsabs.harvard.edu/abs/1989MNRAS.238..729F 238, 729
work page 1989
-
[35]
Fabian A. C., et al., 2009, @doi [ ] 10.1038/nature08007 , http://adsabs.harvard.edu/abs/2009Natur.459..540F 459, 540
-
[36]
Fabian A. C., et al., 2012, @doi [ ] 10.1111/j.1365-2966.2012.21185.x , http://adsabs.harvard.edu/abs/2012MNRAS.424..217F 424, 217
-
[37]
Fender R., et al., 1999, @doi [ ] 10.1086/312128 , http://adsabs.harvard.edu/abs/1999ApJ...519L.165F 519, L165
-
[38]
Galeev A. A., Rosner R., Vaiana G. S., 1979, @doi [ ] 10.1086/156957 , http://adsabs.harvard.edu/abs/1979ApJ...229..318G 229, 318
-
[39]
Garc \' a J., Kallman T. R., 2010, @doi [ ] 10.1088/0004-637X/718/2/695 , http://adsabs.harvard.edu/abs/2010ApJ...718..695G 718, 695
-
[40]
Garc \' a J., Dauser T., Reynolds C. S., Kallman T. R., McClintock J. E., Wilms J., Eikmann W., 2013, @doi [ ] 10.1088/0004-637X/768/2/146 , http://adsabs.harvard.edu/abs/2013ApJ...768..146G 768, 146
-
[41]
Garc \' a J., et al., 2014, @doi [ ] 10.1088/0004-637X/782/2/76 , http://adsabs.harvard.edu/abs/2014ApJ...782...76G 782, 76
-
[42]
Garc \' a J. A., Steiner J. F., McClintock J. E., Remillard R. A., Grinberg V., Dauser T., 2015, @doi [ ] 10.1088/0004-637X/813/2/84 , http://adsabs.harvard.edu/abs/2015ApJ...813...84G 813, 84
-
[43]
Garc \' a J. A., Fabian A. C., Kallman T. R., Dauser T., Parker M. L., McClintock J. E., Steiner J. F., Wilms J., 2016, @doi [ ] 10.1093/mnras/stw1696 , http://adsabs.harvard.edu/abs/2016MNRAS.462..751G 462, 751
-
[44]
The Problem of the High Iron Abundance in Accretion Disks around Black Holes
Garc \' a J. A., Kallman T. R., Bautista M., Mendoza C., Deprince J., Palmeri P., Quinet P., 2018, preprint, http://adsabs.harvard.edu/abs/2018arXiv180500581G ( @eprint arXiv 1805.00581 )
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[45]
C., et al., 2016, in Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray
Gendreau K. C., et al., 2016, in Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray. p. 99051H, @doi 10.1117/12.2231304
-
[46]
George I. M., Fabian A. C., 1991, , http://adsabs.harvard.edu/abs/1991MNRAS.249..352G 249, 352
work page 1991
-
[47]
Gilfanov M., Churazov E., Revnivtsev M., 2000, @doi [ ] 10.1046/j.1365-8711.2000.03686.x , http://adsabs.harvard.edu/abs/2000MNRAS.316..923G 316, 923
-
[48]
Grier C. J., et al., 2012, @doi [ ] 10.1088/2041-8205/744/1/L4 , http://adsabs.harvard.edu/abs/2012ApJ...744L...4G 744, L4
-
[49]
Haardt F., Maraschi L., 1991, @doi [ ] 10.1086/186171 , http://adsabs.harvard.edu/abs/1991ApJ...380L..51H 380, L51
-
[50]
Harrison F. A. e. a., 2013, @doi [ ] 10.1088/0004-637X/770/2/103 , http://adsabs.harvard.edu/abs/2013ApJ...770..103H 770, 103
-
[51]
Heida M., Jonker P. G., Torres M. A. P., Chiavassa A., 2017, @doi [ ] 10.3847/1538-4357/aa85df , http://adsabs.harvard.edu/abs/2017ApJ...846..132H 846, 132
-
[52]
Ichimaru S., 1977, @doi [ ] 10.1086/155314 , http://adsabs.harvard.edu/abs/1977ApJ...214..840I 214, 840
-
[53]
Ingram A., van der Klis M. v. d., 2013, @doi [ ] 10.1093/mnras/stt1107 , http://adsabs.harvard.edu/abs/2013MNRAS.434.1476I 434, 1476
-
[54]
Ingram A., van der Klis M., 2015, @doi [ ] 10.1093/mnras/stu2373 , http://adsabs.harvard.edu/abs/2015MNRAS.446.3516I 446, 3516
-
[55]
Ingram A., Maccarone T. J., Poutanen J., Krawczynski H., 2015, @doi [ ] 10.1088/0004-637X/807/1/53 , http://adsabs.harvard.edu/abs/2015ApJ...807...53I 807, 53
-
[56]
Ingram A., van der Klis M., Middleton M., Done C., Altamirano D., Heil L., Uttley P., Axelsson M., 2016, @doi [ ] 10.1093/mnras/stw1245 , http://adsabs.harvard.edu/abs/2016MNRAS.461.1967I 461, 1967
-
[57]
Ingram A., van der Klis M., Middleton M., Altamirano D., Uttley P., 2017, @doi [ ] 10.1093/mnras/stw2581 , http://adsabs.harvard.edu/abs/2017MNRAS.464.2979I 464, 2979
-
[58]
Jansen F., et al., 2001, @doi [ ] 10.1051/0004-6361:20000036 , http://adsabs.harvard.edu/abs/2001A
-
[59]
W., 2019, arXiv e-prints, http://adsabs.harvard.edu/abs/2019arXiv190401674J
Jiang Y.-F., Blaes O., Stone J., Davis S. W., 2019, arXiv e-prints, http://adsabs.harvard.edu/abs/2019arXiv190401674J
work page 2019
-
[60]
Kalberla P. M. W., Burton W. B., Hartmann D., Arnal E. M., Bajaja E., Morras R., P \"o ppel W. G. L., 2005, @doi [ ] 10.1051/0004-6361:20041864 , http://adsabs.harvard.edu/abs/2005A
-
[61]
Kammoun E. S., Dom c ek V., Svoboda J., Dov c iak M., Matt G., 2019, @doi [ ] 10.1093/mnras/stz408 , http://adsabs.harvard.edu/abs/2019MNRAS.485..239K 485, 239
-
[62]
Kara E., Fabian A. C., Cackett E. M., Uttley P., Wilkins D. R., Zoghbi A., 2013, @doi [ ] 10.1093/mnras/stt1055 , http://adsabs.harvard.edu/abs/2013MNRAS.434.1129K 434, 1129
-
[63]
Kara E., et al., 2015, @doi [ ] 10.1093/mnras/stv304 , http://adsabs.harvard.edu/abs/2015MNRAS.449..234K 449, 234
-
[64]
Kara E., Alston W. N., Fabian A. C., Cackett E. M., Uttley P., Reynolds C. S., Zoghbi A., 2016, @doi [ ] 10.1093/mnras/stw1695 , http://adsabs.harvard.edu/abs/2016MNRAS.462..511K 462, 511
-
[65]
Kara E., et al., 2019, @doi [ ] 10.1038/s41586-018-0803-x , http://adsabs.harvard.edu/abs/2019Natur.565..198K 565, 198
-
[66]
Keek L., Ballantyne D. R., 2016, @doi [ ] 10.1093/mnras/stv2882 , http://adsabs.harvard.edu/abs/2016MNRAS.456.2722K 456, 2722
-
[67]
Kolehmainen M., Done C., D \' az Trigo M., 2014, @doi [ ] 10.1093/mnras/stt1886 , http://adsabs.harvard.edu/abs/2014MNRAS.437..316K 437, 316
-
[68]
Kotov O., Churazov E., Gilfanov M., 2001, @doi [ ] 10.1046/j.1365-8711.2001.04769.x , http://adsabs.harvard.edu/abs/2001MNRAS.327..799K 327, 799
-
[69]
Laor A., 1991, @doi [ ] 10.1086/170257 , http://adsabs.harvard.edu/abs/1991ApJ...376...90L 376, 90
-
[70]
Lightman A. P., Rybicki G. B., 1980, @doi [ ] 10.1086/157820 , http://adsabs.harvard.edu/abs/1980ApJ...236..928L 236, 928
-
[71]
Lindquist R. W., 1966, @doi [Annals of Physics] 10.1016/0003-4916(66)90207-7 , http://adsabs.harvard.edu/abs/1966AnPhy..37..487L 37, 487
-
[72]
A Physical Model for the Spectral-Timing Properties of Accreting Black Holes
Mahmoud R. D., Done C., 2018, preprint, http://adsabs.harvard.edu/abs/2018arXiv180304811M ( @eprint arXiv 1803.04811 )
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[73]
Mahmoud R. D., Done C., De Marco B., 2018, preprint, http://adsabs.harvard.edu/abs/2018arXiv181106911M ( @eprint arXiv 1811.06911 )
-
[74]
Markoff S., Nowak M. A., Wilms J., 2005, @doi [ ] 10.1086/497628 , http://adsabs.harvard.edu/abs/2005ApJ...635.1203M 635, 1203
-
[75]
Martocchia A., Matt G., 1996, @doi [ ] 10.1093/mnras/282.4.L53 , http://adsabs.harvard.edu/abs/1996MNRAS.282L..53M 282, L53
-
[76]
Mastroserio G., Ingram A., van der Klis M., 2018, @doi [ ] 10.1093/mnras/sty075 , http://adsabs.harvard.edu/abs/2018MNRAS.475.4027M 475, 4027
-
[77]
C., Piro L., 1991, , http://adsabs.harvard.edu/abs/1991A
Matt G., Perola G. C., Piro L., 1991, , http://adsabs.harvard.edu/abs/1991A
work page 1991
-
[78]
McHardy I. M., Papadakis I. E., Uttley P., Page M. J., Mason K. O., 2004, @doi [ ] 10.1111/j.1365-2966.2004.07376.x , http://adsabs.harvard.edu/abs/2004MNRAS.348..783M 348, 783
-
[79]
Black hole spin: theory and observation
Middleton M., 2016, in Bambi C., ed., Astrophysics and Space Science Library Vol. 440, Astrophysics of Black Holes: From Fundamental Aspects to Latest Developments. p. 99 ( @eprint arXiv 1507.06153 ), @doi 10.1007/978-3-662-52859-4_3
work page internal anchor Pith review Pith/arXiv arXiv doi:10.1007/978-3-662-52859-4_3 2016
-
[80]
Miller J. M., 2007, @doi [ ] 10.1146/annurev.astro.45.051806.110555 , http://adsabs.harvard.edu/abs/2007ARA
work page internal anchor Pith review Pith/arXiv arXiv doi:10.1146/annurev.astro.45.051806.110555 2007
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