Zhang, Ju-JiaJu-JiaZhangWang, Xiao-FengXiao-FengWangSasdelli, MicheleMicheleSasdelliZhang, Tian-MengTian-MengZhangLiu, Zheng-WeiZheng-WeiLiuMazzali, Paolo A.Paolo A.MazzaliMeng, Xiang-CunXiang-CunMengMaeda, KeiichiKeiichiMaedaChen, Jun-ChengJun-ChengChenHuang, FangFangHuangZhao, Xu-LinXu-LinZhaoZhang, Kai-ChengKai-ChengZhangZhai, QianQianZhaiPIAN, ElenaElenaPIANWang, BoBoWangChang, LiangLiangChangYi, Wei-MinWei-MinYiWang, Chuan-JunChuan-JunWangWang, Xue-LiXue-LiWangXin, Yu-XinYu-XinXinWang, Jian-GuoJian-GuoWangLun, Bao-LiBao-LiLunZheng, Xiang-MingXiang-MingZhengZhang, Xi-LiangXi-LiangZhangFan, Yu-FengYu-FengFanBai, Jin-MingJin-MingBai2020-06-222020-06-2220160004-637Xhttp://hdl.handle.net/20.500.12386/26165Photometric and spectroscopic observations of a slowly declining, luminous Type Ia supernova (SN Ia) SN 2011hr in the starburst galaxy NGC 2691 are presented. SN 2011hr is found to peak at {M}<SUB>B</SUB>=-19.84+/- 0.40 {mag}, with a postmaximum decline rate ∆m<SUB>15</SUB>(B) = 0.92 ± 0.03 mag. From the maximum-light bolometric luminosity, L=(2.30+/- 0.90)× {10}<SUP>43</SUP> {erg} {{{s}}}<SUP>-1</SUP>, we estimate the mass of synthesized <SUP>56</SUP>Ni in SN 2011hr to be M{(}<SUP>56</SUP>{Ni})=1.11+/- 0.43 {M}<SUB>☉ </SUB>. SN 2011hr appears more luminous than SN 1991T at around maximum light, and the absorption features from its intermediate-mass elements (IMEs) are noticeably weaker than those of the latter at similar phases. Spectral modeling suggests that SN 2011hr has IMEs of ∼0.07 {M}<SUB>☉ </SUB> in the outer ejecta, which is much lower than the typical value of normal SNe Ia (I.e., 0.3-0.4 {M}<SUB>☉ </SUB>) and is also lower than the value of SN 1991T (I.e., ∼0.18 {M}<SUB>☉ </SUB>). These results indicate that SN 2011hr may arise from a Chandrasekhar-mass white dwarf progenitor that experienced a more efficient burning process in the explosion. Nevertheless, it is still possible that SN 2011hr may serve as a transitional object connecting the SN 1991T-like SNe Ia with a superluminous subclass like SN 2007if given that the latter also shows very weak IMEs at all phases.STAMPAenArticle10.3847/0004-637X/817/2/1142-s2.0-84957954891000369437900031https://iopscience.iop.org/article/10.3847/0004-637X/817/2/1142016ApJ...817..114ZFIS/05 - ASTRONOMIA E ASTROFISICA