A Multi-Wavelength Study of the Symbiotic Mira HM Sge with SOFIA & HST

We have targeted the dusty symbiotic mira system HM Sge with four instruments from the IR to the UV. We have used these observations along with archival observations to study how the system has been evolving after its 1975 nova-like outburst. We have detected ro-vibrational water emission in a symbiotic system for the first time using new EXES high spectral resolution infrared spectroscopy. The features, detected in emission, have velocities consistent with the systemic velocity but do not show any clear evidence of high velocity outflows. Mid-infrared photometry and grism spectroscopy show that the oxygen-rich Asymptotic Giant Branch (AGB) dust and dust output has shown little to no change over the past 39 years. In the optical/UV, we detect three main [NII] nebular features that were detected 22 years ago. Two of these features show a small amount of movement corresponding to average outflows speeds of 38 kms and 78 kms since they were previously observed; some previously detected [NII] features are no longer visible. New UV spectroscopy has shown that the nebular environment continues to steadily relax after the system's 1975 outburst. The data suggest however, that the hot component has increased in temperature from 200,000 K in 1989 to now greater than 250,000 K. Our new and archival observations suggest that the evolution of the system after its outburst is swift with little to no major changes after a period of a couple years.

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1. A Multi-Wavelength Study of the Symbiotic Mira HM Sge with SOFIA & HST Steven Goldman1,2, Ravi Sankrit1, Ed Montiel2, Sean Garner2, Nathan Wolthius2 , Nicole Karnath2,3,4 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 Space Science Institute, 4765 Walnut St, Suite B Boulder, CO 80301, USA 4 Center for Astrophysics Harvard & Smithsonian, Cambridge, MA 02138, USA Figure 4: New FORCAST photometry and grism spectroscopy of HM Sge, along with archival mid-IR spectra from IRAS and ISO [4]. FORCAST: Photometry and spectroscopy in the mid-IR allow us to characterize the silicate dust. Our new and archival observations suggest that the evolution of the AGB star after its outburst is swift with little to no major changes after a period of a couple years (Fig. 4). SOFIA OBSERVATORY (PID: 75_0057) WFC3: We have used high angular resolution HST/WFC3 narrow- band images in [N ii] and [O iii] to reveal the morphology of HM Sge’s ionized gas and jet. we detect three main [N II] nebular features that were detected 22 years ago (Fig. 2). The movement of these features with respect to comparable data taken in 1999 suggest outflows speeds of 38 km s−1 and 78 km s−1. HUBBLE SPACE TELESCOPE (PID: 16492) Figure 3: Our new COS FUV spectrum of HM Sge Figure 2: HST WFC3 [N II] image of HM Sge and the surrounding nebula artistically enhanced to accentuate features, and an illustration of the system. HM Sge: We have targeted the dusty Symbiotic Mira system HM Sge with four instruments from the IR to the UV using Hubble and SOFIA. We have used these observations along with archival observations to study how the system has been evolving after its 1975 nova-like outburst. TAKE-AWAYS: • Dust production from a Symbiotic Mira returned within a couple years of a novae-like outburst, and remains uninterrupted for the last ~40 years. COS: We have used COS to observe HM Sge in the NUV and FUV (Fig. 3). A rich emission line spectrum is detected, sampling a wide range of ionization states in the gas, from Fe+ and C++ to Ne IV+ and O V+. The presence of highly ionized gas provides evidence of energy input from shocks in addition to photoionization by the hot WD. Comparing this to IUE data from 1989 shows that the nebular environment continues to steadily relax after the system’s 1975 outburst. The data suggest however, that the temperature of the white dwarf has increased from 200,000 K in 1989 to now greater than 250,000 K. EXES: We have detected ro-vibrational water emission in a symbiotic system for the first time using new EXES high spectral resolution infrared spectroscopy. The features, detected in emission over three epochs, have velocities consistent with the systemic velocity but do not show any clear evidence of high velocity outflows. (Fig. 5). Figure 5: Infrared water emission features that probe the kinematics of material around HM Sge. Steve Goldman sgoldman@stsci.edu s-goldman.github.io Figure 1. HST WFC3 [N II] images of HM Sge and its surrounding nebula artistically enhanced to accentuate features, and an illustration of the system. • HM Sge shows complex nebular features and outflows that may be linked to jets as well as multiple previous outbursts. © 2023 Brittany C. Bennett. All rights reserved. Used with permission. References: [1] Dokuchaeva, O. D. 1976, Information Bulletin on Variable Stars, 1189, 1 [2] Eyres et al. 2001, ApJ, 551, 512 [3] Murset, U., & Nussbaumer, H. 1994, A&A, 282,586 [4] Schild et al. 2001, A&A, 378, 146