Model fitting of high-resolution X-ray Spectroscopy of the Planetary Nebula BD+30◦3639 Young Sam Yu, Joel Kastner Rochester Institute of Technology, USA John Houck Massachusetts Institute of Technology, USA Ehud Behar, Raanan Nordon, Noam Soker Technion-Israel Institute of Technology, Israel

Outline What are the Planetary Nebulae(PNe) ? Stellar evolution of Intermediate massive star X-ray emission scenarios in PNe History of X-ray observation of BD+30°3639 Chandra Observation of BD+30°3639 with LETG/ACIS-S Extracted spectra and model fitting Results Interpretation of results Summary

What are planetary nebulae (PNe)? Last stages of evolution for stars of initial mass(1-8M ⊙ ) Unveiled central star has terminated its asymptotic giant branch (AGB) evolution Ejected AGB envelope is ionized by central stellar UV radiation and has yet to disperse entirely The remnant carbon-oxygen core will become a white dwarf

Various morphologies of PNe Optical images in red/green (mostly from HST) X-ray images in blue (XMM & Chandra) X-ray/visual image overlays by M. Guerrero Montage by B. Balick

Stellar evolution along the HR diagram From Herwig (2005, Annu. Rev. Astron. Astrophys.)

X-ray emission from PNe Photoionized gas in PNe is far too cool to emit X-rays The central stars are at best source of very soft X-rays Theorists have long predicted “X-ray emitting gas (hot bubble) comes from wind interactions” Possible scenarios: - Shocked fast wind (~ km/s) from central star rams into the ejected red giant envelope that is coasting outward at ~10km/s - Collimated fast winds or jets blown in conjunction with the companion to the central star (e.g. NGC 7027) => X-ray observations are essential to verify & distinguish scenarios

The planetary nebula BD+30°3639 Top left : Optical (HST WFPC2 in [S III] at 9532A) (Arnaud et al. 1996) Top right : infrared (Gemini at 2.2 microns (K band) ) Bottom left : Chandra Image (ACIS-S3) Bottom right : Chandra spectrum (ACIS- S3) (Kastner et al. 2000) Basic data: Distance from Earth : 1.2 kpc Dimensions: 4 X 5’’ (~0.02 pc) Dynamical age : less than 1000yr Central Star: Carbon-rich Wolf-Rayet type Temp : 30,000K Mass loss rate : ~10 -6 M solar / yr Wind speed: ~700 km/s

Previous results from X-ray CCD spectroscopy: Fitting models to BD+30°3639 spectra * N H constrained by A V for PSPC and SIS model fits telescope (instrument) N H (10 21 cm -2 ) T X (10 6 K)abundancesreference ROSAT (PSPC)1.4*2.5 … Kreysing et al (1992) ASCA (SIS)1.2*3.0 C greatly enhanced; N, Ne enhanced; Fe depleted Arnaud et al. (1996) Chandra (ACIS) C, Ne enhanced; Fe depleted Kastner et al. (2000) Chandra (ACIS) C, Ne greatly enhanced; N, O enhanced; Fe depleted Maness et al. (2003) Chandra (ACIS) SUZAKU No useful constraints! C, N, Ne greatly enhanced; Fe depleted Georgiev et al. (2006) Murashima et al. (2006)

Chandra observation of BD+30°3639 BD+30°3639 is the best target for getting high resolution X-ray grating spectroscopy due to its large X-ray flux at Earth. We decided to use LETG/ACIS-S combination (rather than HETG/ACIS-S) after conducting MARX simulations

Chandra observation of BD+30°3639 Observation ID DateInstrumentExp (ks) 1 st order counts Feb Mar LETG/ACIS-S Dec Dec Dec LETG/ACIS-S Total: We were granted 300ks observing time for Chandra Cycle 6.

High resolution X-ray spectroscopy of BD+30°3639

Extracted spectrum result from 5 split datasets

Model fitting result with APED NeIXFeXVII OVIII OVII CVI

Model fitting result with APED CVI

Results Temperature of shocked plasma: T ~ 2.25x10 6 K Hydrogen column density : log N H (cm -2 ) = 21.4 Plasma abundances, relative to solar: –C/O ~ 49.3 (yes, C is very overabundant!) –Ne/O ~ 4.5 (yes, Ne is overabundant) –Fe/O ~ 0.3 (yes, Fe is quite depleted!) –N/O ~ 0.3 (yes, N is quite depleted)

The inner layers of a highly evolved star From Herwig (2005, Ann. Rev. Astron. Astrophys.) AGB stars are carbon factories!

Interpretation X-ray temperature (T x ) –lower than expected from a simple adiabatic shock model (700 km/s wind should produce a few x 10 million degree plasma) –Possible scenarios Heat conduction moderates T x Shocked wind presently seen in X-rays was ejected at earlier epoch, when the “fast wind” was slower (~400km/s) C/O overabundance –He shell burning and subsequent dredge-up (AGB “third dredge-up”) brings intershell products (C, s-process elements) to the surface Ne/O over abundance –α capture process(α : He) 14 N + α -> 18 O(Burnt in He shell burning) -> 22 Ne 18 F Fe/O, N/O depletion – s-process within pulse-driven convection zone(PDCZ) ), associated He shell burning – 22 Ne is neutron source in s-process and make Fe depletion => non-solar composition of shocked gas originated from intershell region of AGB star

Summary Chandra provides unique means for studying origin of X-ray-emitting gas in Planetary nebulae Sharply non-solar composition of shocked gas originated from intershell region of AGB star Our preliminary results can provide strong constraints on shock and AGB interior models To further understand morphologies and density structures of X-ray-emitting plasmas in PNe, we need to develop 3D volumetric model based on these results

Thank you!!!

Model fitting results wabs(1)*xaped(1) idx param tie-to freeze value min max 1 wabs(1).nH ^22 2 xaped(1).norm xaped(1).temperature e+07 4 xaped(1).density xaped(1).vturb xaped(1).redshift xaped(1).metal_abund xaped(1).Fe xaped(1).Ne xaped(1).O xaped(1).C xaped(1).N xaped(1).Ca

Preliminary results: temperature-sensitive line ratios T ~ 2.8x10 6 K T ~ 2.4x10 6 K Ratio of H-like to He-like resonance lines (from H-like and He-like ions of O and Ne) Ratio of G = (f+i)/r within 22 A triplet line of He-like O VII Models: Astrophysical Plasma Emission (APE) Database and APE Code (Smith et al. 2001, ApJ, 556, L91)