Two New Calcium-rich Gap Transients in Group and Cluster Environments
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- California Inst. of Technology (CalTech), Pasadena, CA (United States). Dept. of Astronomy
- California Inst. of Technology (CalTech), Pasadena, CA (United States). Dept. of Astronomy; Univ. of Washington, Seattle, WA (United States). eScience Institute and Astronomy Dept.
- Stockholm Univ. (Sweden). Oskar Klein Centre, Physics Dept.
- Weizmann Inst. of Science, Rehovot (Israel). Benoziyo Center for Astrophysics and the Helen Kimmel Center for Planetary Science
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
- Las Cumbres Observatory Global Telescope Network, Goleta, CA (United States); Univ. of California, Santa Barbara, CA (United States). Dept. of Physics
- Observatories of the Carnegie Institution for Science, Pasadena, CA (United States)
- Univ. of California, Berkeley, CA (United States). Dept. of Astronomy
- Space Telescope Science Inst., Baltimore, MD (United States)
- Stony Brook Univ., NY (United States). Dept. of Physics and Astronomy
- California Inst. of Technology (CalTech), Pasadena, CA (United States). Spitzer Science Center
- California Inst. of Technology (CalTech), Pasadena, CA (United States). Infrared Processing and Analysis Center
- Univ. of California, Berkeley, CA (United States). Dept. of Astronomy; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- National Astronomical Observatory of Japan, Tokyo (Japan). Optical and Infrared Astronomy Division
- California Inst. of Technology (CalTech), Pasadena, CA (United States). Infrared Processing and Analysis Center; California Inst. of Technology (CalTech), Pasadena, CA (United States). Caltech Optical Observatories
We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [Ca ii] emission. A striking feature of both transients is their host environments: PTF12bho is an intracluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset ~150 kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out an underlying host system to a limit of MR > -8.0 mag, while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. Here, we show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for SNe Ia or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require higher kick velocities and/or longer merger times than sGRBs. Finally, we also show that almost all Ca-rich transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intragroup/intracluster light following galaxy-galaxy interactions.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); Gordon and Betty Moore Foundation; National Science Foundation (NSF)
- DOE Contract Number:
- AC02-05CH11231; AST-1211916; AST-313484; 307260; NAS 5-26555; GBMF5076
- OSTI ID:
- 1393615
- Journal Information:
- The Astrophysical Journal (Online), Vol. 836, Issue 1; ISSN 1538-4357
- Publisher:
- Institute of Physics (IOP)
- Country of Publication:
- United States
- Language:
- English
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