Undergraduate
I am currently an undergraduate at the University of Illinois at Urbana-Champaign. I am in the class of 2023, pursuing a double B.S in Astronomy and Physics with a minor in Applied Statistics. I worked with Dr.s Charlie Kilpatrick and Wen-fai Fong on modeling supernova properties to constrain the pathway by which massive stars explode.
The core of a star of at least 8M will catastrophically collapse at the end of its life leading to a supernova (Burrows et al. 1995). Those with hydrogen in their spectra are classified as Type II supernovae, which can then be further classified into Type II-P, Type II-L, and Type IIb based on light curve and spectroscopic properties (Barbon et al.1979; Arcavi 2017). Type II-P supernovae are found to reach maximum brightness and then plateau for approximately 100 days before fading due to radioactive nickel decay. Type II-P supernovae require progenitor stars with massive,extended hydrogen envelopes, suggesting they come from red supergiant (RSG) stars (Arnett 1987; Woosley et al.1987; Falk & Arnett 1973). Observations of RSG stars indicate they range from initial masses of 8–30M(de Jager et al. 1988), but all of the RSG progenitor stars found as counterparts to Type II-P supernovae have initial masses of<17M with no high-mass counterparts to any supernova type found in pre-explosion imaging (the “red supergiant problem”; Smartt 2009, 2015). There is still ambiguity on what the exact distribution of progenitors is and how high the upper mass limit can go, leaving a need for additional Type II progenitor detections and upper limits to constrain the intrinsic distribution. We present SN 2019mhm, a Type II-P supernova discovered in NGC 6753 by Baryon Oscillation Spectroscopic Survey (BOSS) transient survey 2019 Aug 2 13:13:21 (UT; Marples et al. 2019). Here we discuss constraints on its progenitor star using pre- and post-explosion Hubble Space Telescope imaging. The distance assumed for NGC 6753 is 23.44±5.29 Mpc (via the fundamental plane relation (Springob et al. 2014) and a redshift of z= 0.01057. We adopt a host reddening value to be E(B−V) = 0.29±0.17 mag based on the equivalent width of Na I D in the classification spectrum (Chenet al. 2019).
We obtained imaging of NGC 6753 from the Hubble Space Telescope(HST) Mikulski Archive for Space Telescopes.The data were obtained on 2000 June 22 20:26:14 and 2021 April 05 20:07:52 UT. We then ran the files through our HST imaging and photometry pipeline hst123(Kilpatrick et al. 2021) to drizzle the individual images together. Using those combined images we aligned them using TweakReg(Avila et al. 2015) leading to a frame-to-frame alignment precision of 0.027 arcsec in right ascension and 0.020 arcsec in declination. We identified SN 2019mhm in a post-explosion WFC3 F814W image, but did not find any counterpart in pre-explosion WFPC2 F814W imaging within a 3σ alignment precision of the location of SN 2019mhm. Once aligned, we took individual WFC3 and WFPC2 frames and used dolphot(Dolphin 2016) for photometry. Based on the non-detection of a source in the WFPC2 frames, we derived an upper limit on the presence of a counterpart by analyzing sources detected at 3σ significance within 20 arcsec of the location of SN 2019mhm. This gives us a limiting magnitude of mF814W > 24.53 mag(AB). SN 2019mhm itself was 23.28 ±.04 mag(AB) at the time the WFC3 data were obtained 1.6 yr after discovery. Using those values along with the distance modulus, and extinction of the host galaxy we were able to derive a mass limit of < 17.5M by comparing to Mesa Isochrones and Stellar Tracks (MIST) models (Choi et al. 2017).
SN 2019mhm can be added to the current sample of 26 direct detections and upper limits that are used to con-strain the Type II supernova progenitor mass function (Smartt 2015).The spectral emission lines help confirm that SN 2019mhm had a RSG as a progenitor star, mostly demonstrated by the broadness of the Hα line. Based on the methods described above, we derived a mass limit of 17.5M. This further constrains the mass threshold at whichType II-P supernovae can explode from RSGs as likely being below 18M. By analyzing every example of supernovae possible, it helps build up statistics that can shed light onto whether or not the red supergiant problem is caused by more than just a lack of observable supernovae (Smartt 2015). Another possible solution to the RSG problem is that dust shells surrounding these stars obscure them, and as a result their luminosities and masses are severely underestimated. However, it was shown that the luminosities of these progenitors in the x-ray were not high enoughto prove this was the case (Dwarkadas 2014). The conclusion that dust obscuration significantly lowers the inferred luminosities of these red supergiants assumes that the circumstellar material is extended around the progenitor star, whereas some Type II progenitors are known to have compact circumstellar shells (Kilpatrick & Foley 2018).
Acknowledgements This material is based upon work supported by the National Science Foundation under grant No. AST-1757792, a Research Experiences for Undergraduates (REU) grant awarded to CIERA at Northwestern University.Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) anddo not necessarily reflect the views of the National Science Foundation.
Adams, S. M., Kochanek, C. S., Gerke, J. R., Stanek, K. Z.,& Dai, X. 2017, MNRAS, 468, 4968
Arcavi, I. 2017, Hydrogen-Rich Core-Collapse Supernovae,ed. A. W. Alsabti & P. Murdin, 239
Arnett, W. D. 1987, ApJ, 319, 136
Avila, R. J., Hack, W., Cara, M., et al. 2015, inAstronomical Society of the Pacific Conference Series,Vol. 495, Astronomical Data Analysis Software anSystems XXIV (ADASS XXIV), ed. A. R. Taylor &E. Rosolowsky, 281
Barbon, R., Ciatti, F., & Rosino, L. 1979, A&A, 72, 287
Beasor, E. R., & Davies, B. 2016, Monthly Notices of theRoyal Astronomical Society, 463, 1269.https://doi.org/10.1093/mnras/stw2054
Burrows, A., Hayes, J., & Fryxell, B. A. 1995, ApJ, 450, 830
Chen, P., Holoien, T. W. S., & Dong, S. 2019, Transient Name Server Classification Report, 2019-1444, 1
Choi, J., Conroy, C., & Byler, N. 2017, ApJ, 838, 159
de Jager, C., Nieuwenhuijzen, H., & van der Hucht, K. A.1988, A&AS, 72, 259
Dolphin, A. 2016, DOLPHOT: Stellar photometry, , ,ascl:1608.013
Dwarkadas, V. V. 2014, Monthly Notices of the RoyalAstronomical Society, 440, 1917.https://doi.org/10.1093/mnras/stu347
Falk, S. W., & Arnett, W. D. 1973, ApJL, 180, L65
Kilpatrick, C. D., & Foley, R. J. 2018, MNRAS, 481, 2536
Kilpatrick, C. D., Drout, M. R., Auchettl, K., et al. 2021,MNRAS, 504, 2073
Marples, P., Bock, G., & Pearl, P. 2019, Transient Name Server Discovery Report, 2019-1393, 1
O’Connor, E., & Ott, C. D. 2011, ApJ, 730, 70
Smartt, S. J. 2009, ARA&A, 47, 63—. 2015, PASA, 32, e016
Smith, N., Li, W., Filippenko, A. V., & Chornock, R. 2011,Monthly Notices of the Royal Astronomical Society, 412,1522. https://doi.org/10.1111/j.1365-2966.2011.17229.x
Springob, C. M., Magoulas, C., Colless, M., et al. 2014,MNRAS, 445, 2677
Woosley, S. E., Pinto, P. A., Martin, P. G., & Weaver,T. A. 1987, ApJ, 318, 664
Woosley, S. E., & Weaver, T. A. 1986, ARA&A, 24, 205
Jason Vazquez
Department of Astronomy
UIUC
Urbana-Champaign, IL 61801
email : jasonv3 [at] illinois dot edu