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SOFIA and HST Multi-wavelength study of the Symbiotic Mira HM Sge

SOFIA and HST Multi-wavelength study of the Symbiotic Mira HM Sge

A poster presented at the DELVE: The Death-Throes of Evoled Stars remote conference.

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Steve Goldman

April 19, 2021
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  1. SOFIA and HST Multi-wavelength study of the Symbiotic Mira HM

    Sge Steve Goldman1, Ravi Sankrit1, Nicole Karnath2, Ed Montiel2, Matthew Richter3 1 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 USA 2 SOFIA-USRA, NASA Ames Research Center, MS 232-12, Moffett Field, CA 94035, USA 3 Department of Physics, University of California Davis, Davis, CA, USA References: [1] Dokuchaeva, O. D. 1976, Information Bulletin on Variable Stars, 1189, 1 [2] Goldman S. R., 2020, JOSS, 5(54), 2554 [3] Munari, U., & Whitelock, P. A. 1989, MNRAS, 237, 45P [4] Mürset, U., & Schmid, H. M. 1999, A&AS, 137, 473 Figure 3: The ISO spectrum of HM Sge from 1999 showing strong silicate emission at 10 and 18μm. The spectrum is fit with radiative transfer models using the Dusty Evolved Star Kit [2] (DESK). The FORCAST imaging filters are also shown in gray (orange if profile unavailable) in the top panel. The wavelength range of the proposed grism observations are shown in the green shaded regions. FORCAST (expected 7/21): Photometry and spectroscopy in the mid-IR will allow us to characterize the silicate dust and provide us ionic emission lines to probe the nebular emission (Fig. 3). EXES (expected 12/21): High spectral resolution observations with EXES of the H2O molecular lines will yield the kinematics of the wind and the accretion flow. SOFIA OBSERVATORY (PID: 75_0057) WFC3 (Complete): We have used high angular resolution HST/WFC3 narrowband images in Hα, [N ii] and [O iii] to reveal the morphology of HM Sge’s ionized gas and jet. We have additionally used a longer exposure in the F657N filter to reveal the morphology of the extended nebular emission (Figure 1) . We will examine changes that have occurred since the earlier epochs of observation at sub-arcsecond scales to estimate the velocities of the jet outflow. COS (Complete): Spectroscopy in the UV using COS will target the high ionization lines such as C IV and N V that are crucial probes of the shocked gas. By comparing the UV line strengths obtained with COS to those with IUE, we will track the long-term evolution of the shocks over a time baseline of 28 years. HUBBLE SPACE TELESCOPE (PID: 16492) Figure 1: The IUE spectrum of HM Sge from Murset & Nussbaumer[4]. We have re-observed these lines to study how the shocks have evolved over the past 29 years. Figure 2: New and archival images of HM Sge. HM Sge is a symbiotic system composed of an oxygen-rich AGB star accreting material onto a white dwarf 60 au away. The AGB star has a pulsation period of 527 days [3], an M7 spectral type[4], and is heavily reddened in the near-IR (J − K ∼ 3 mag), all indicative of dust production, high mass loss, and a late stage of AGB evolution. The system is also relaxing from a nova-like outburst that occurred in 1975[1], which drew much attention and has provided a wealth of archival data. As a part of a joint Directors’ Discretionary program, we have been awarded time on four instruments to take advantage of the long baseline of observations, and study the circumstellar dust shell, the molecular flows, and the compact nebula surrounding HM Sge’s central engine. Future Work: We encourage the community to take full advantage of these public datasets. A publication outlining the reduced datasets and current status of the system is forthcoming. It is our hope that these programs anchor future observations of HM Sge, and give us insights into a wide and diverse range of active astrophysical phenomena. 1999 2021 WFPC2/HST NII (F658N) WFC3/HST 1ʺ 1992