The Astrophysical Journal, 646:369Y377, 2006 July 20 # 2006. The American Astronomical Society. All rights reserved. Printed in U.S.A. A SEARCH FOR RADIO EMISSION FROM TYPE Ia SUPERNOVAE Nino Panagia,1, 2 Schuyler D. Van Dyk,3 Kurt W. Weiler,4 Richard A. Sramek,5 Christopher J. Stockdale,6 and Kimberly P. Murata7 Received 2006 February 21; accepted 2006 March 29 ABSTRACT We present and discuss the radio observations of 27 Type Ia supernovae (SNe Ia), observed over two decades with the Very Large Array. No SN Ia has been detected so far in the radio, implying a very low density for any possible circumstellar material established by the progenitor, or progenitor system, before explosion. We derive 2 upper ; À8 À1 limits to a steady mass-loss rate for individual SN systems as low as 3 10 M yr , which argues strongly against white dwarf accretion via a stellar wind from a massive binary companion in the symbiotic star, an example of the ‘‘single-degenerate’’ scenario. However, a white dwarf accreting from a relatively low mass companion via a sufficiently high efficiency (>60%Y80%) Roche lobe overflow is still consistent with our limits. The ‘‘double- degenerate’’ merger scenario also cannot be excluded. Subject headingg: binaries: close — binaries: symbiotic — radio continuum: stars — stars: mass loss — supernovae: general — white dwarfs 1. INTRODUCTION 1984; Webbink 1984) the explosion is triggered by the merger of two degenerate stars, such as WDs or neutron stars. Supernovae (SNe) are among the most energetic events in the The nature of SN Ia progenitors has become even more im- universe. Determining the properties of the progenitor stars or stellar systems remains an important unsolved problem in as- portant in the last decade because of their fundamental impor- tance for cosmology (e.g., Riess et al. 1998; Perlmutter et al. trophysics. Few SNe have had their progenitor stars directly iden- 1999; Perlmutter & Schmidt 2003). Unfortunately, we are in the tified, but the postexplosion radio emission from SNe provides insight into the nature of the progenitor stars and their last stages embarrassing situation that, even as confidence in the astounding new cosmological results increases, we still have little knowledge of evolution. The phenomenon of radio SNe (RSNe) has been of the physical origins of the luminous SN Ia explosions on which best modeled by synchrotron emission resulting from the inter- these results are at least partly based. action of the SN shock with circumstellar material (CSM) estab- Observations of SNe Ia in the radio can provide a powerful lished by pre-SN mass loss from the progenitor system before the constraint on the Chandrasekhar mass explosion mechanism in explosion; likely from the progenitor itself, or possibly from the that the mass exchange required for the single-degenerate sce- progenitor’s companion in the case of a binary system (Chevalier nario should establish an enhanced CSM density, however tenuous, 1982a, 1982b; Sramek et al. 1984; Weiler et al. 1986). near the SN progenitor, while the double-degenerate scenario Although it has been generally accepted that Type Ia SNe should not, unless the two coalescing WDs are in a common (SNe Ia) result from the thermonuclear explosion of a white dwarf (WD) star (e.g., Nomoto et al. 1984; Branch et al. 1985), two fun- envelope (see Livio 2001). Thus, radio detection of the blast wave interaction with the CSM would not only support the single- damental questions remain: (1) Is the exploding WD of Chan- degenerate scenario, but also provide information as to its extent, drasekhar or sub-Chandrasekhar mass? (2) If the former, how density, and structure. does the exploding WD (typically 0.6 M ; e.g., Ritter & Burkert To test the single-degenerate case for a symbiotic star progen- 1986) accumulate enough mass to approach the Chandrasekhar itor system (in which a red giant donates mass to the WD via a limit of 1.4 M prior to explosion? In the so-called single- wind), Boffi & Branch (1995) modeled putative fast-evolving radio degenerate scenario (Nomoto et al. 1984), the source of the ac- light curves for the SN Ia 1986G through analogy with the radio creted material is provided by interaction with a nondegenerate light curves for the SN Ib 1983N (Sramek et al. 1984; Weiler et al. companion, such as a low-mass main-sequence star, a subgiant, 1986). From radio observations of SN 1986G conducted 1 week or a giant star (see the reviews by Branch et al. 1995 and Livio 2001). Under the ‘‘double-degenerate’’scenario (Iben & Tutukov before optical maximum (i.e., early enough to adequately test the Boffi & Branch prediction), Eck et al. (1995) concluded, based on a lack of detected radio emission, that this SN probably did not arise from a symbiotic star system. Eck et al. stressed that fur- 1 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD ther searches for prompt radio emission from other SNe Ia were 21218; [email protected]. 2 clearly necessary to test this and other models. Istituto Nazionale di Astrofisica ( INAF), Rome, Italy; and Supernova Ltd., Virgin Gorda, British Virgin Islands. Numerous radio observations have been obtained for 27 SNe 8 3 Spitzer Science Center, California Institute of Technology, Pasadena, CA Ia using the Very Large Array (VLA) as part of a SN monitoring 91125; [email protected]. program we have been conducting for more than two decades. In 4 Naval Research Laboratory, Code 7213, Washington, DC 20375-5320; our program we have considered only extragalactic SNe Ia, and [email protected]. 5 National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801; [email protected]. 6 Department of Physics, Marquette University, P.O. Box 1881, Milwaukee, 8 The VLA telescope of the National Radio Astronomy Observatory is op- WI 53201-1881; [email protected]. erated by Associated Universities, Inc. under a cooperative agreement with the 7 9031 Ashmeade Drive, Fairfax, VA 22032; [email protected]. National Science Foundation. 369 370 PANAGIA ET AL. TABLE 1 Observed SNe SN Position Parent Galaxy Date of Optical Magnitude at SN Name Maximuma Maximuma R.A. (J2000.0) Decl. (J2000.0) Name Type (1) (2) (3) (4) (5) (6) (7) 1980N............................ 1980 Dec 11 12.5B 03 22 59.8 Æ 1.3 À37 12 48 Æ 15.0 NGC 1316 S0 1981B............................ 1981 Mar 12 12.0B 12 34 29:57 Æ 0:07 þ02 11 59:3 Æ 1:0 NGC 4536 Sbc 1982E ............................ 1982 Mar 14.0pg 03 26 40:41 Æ 0:54 À21 17 13:8 Æ 8:0 NGC 1332 S0 1983G............................ 1983 Apr 9 12.9B 12 52 21:0 Æ 1:0 À01 12 12 Æ 15:0 NGC 4753 S0 pec 1984A............................ 1984 Jan 16 12.4B 12 26 55:73 Æ 0:06 þ15 03 17:1 Æ 1:0 NGC 4419 SBab 1985A............................ 1985 Jan 14.5pg 09 13 42:43 Æ 0:30 þ76 28 23:8 Æ 1:0 NGC 2748 Sc 1985B............................ 1985 Jan 13.0V 12 02 43:94 Æ 0:07 þ01 58 45:3 Æ 1:0 NGC 4045 Sbc 1986A............................ 1986 Feb 7 14.4B 10 46 36.59 Æ 0.07 +13 45 00.7 Æ 1.0 NGC 3367 SBc 1986G............................ 1986 May 11 12.5B 13 25 36.51 Æ 0.07 À43 01 54.3 Æ 1.0 NGC 5128 S0+Spec 1986O............................ 1986 Dec 20 14.0V 06 25 58.0 Æ 0.58 À22 00 42 Æ 8.0 NGC 2227 SBcd 1987D............................ 1987 Apr 17 13.7B 12 19 41.10 Æ 0.07 +02 04 26.6 Æ 1.0 M+00À32À01 Sbc 1987N............................ 1987 Dec 13.4V 23 19 03.42 Æ 0.07 À08 28 37.5 Æ 1.0 NGC 7606 Sb 1989B............................ 1989 Feb 6 12.5B 11 20 13.93 Æ 0.07 +13 00 19.3 Æ 1.0 NGC 3627 Sb 1989M........................... 1989 Jun 12.1B 12 37 40.75 Æ 0.07 +11 49 26.1 Æ 1.0 NGC 4579 Sab 1990M........................... 1990 Jun 13.4V 14 08 29.3 Æ 0.1 À05 02 36 Æ 1.0 NGC 5493 S0 1991T ............................ 1991 Apr 28.5 11.64B 12 34 10.20 Æ 0.07 +02 39 56.4 Æ 1.0 NGC 4527 Sb 1991bg........................... 1991 Dec 14.7 13.95V 12 25 03.70 Æ 0.07 +12 52 15.6 Æ 1.0 NGC 4374 E1 1992A............................ 1992 Jan 16 12.78V 03 36 27.41 Æ 0.07 À34 57 31.4 Æ 1.0 NGC 1380 S0/Sa 1994D............................ 1994 Mar 22 11.85V 12 34 02.40 Æ 0.007 +07 42 05.7 Æ 0.1 NGC 4526 SAB(s) 1995al............................ 1995 Nov 9 13.25V 09 50 55.97 Æ 0.06 +33 33 09.4 Æ 1.0 NGC 3021 SAbc: 1996X............................ 1996 Apr 18 13.24B 13 18 01.13 Æ 0.06 À26 50 45.3 Æ 1.0 NGC 5061 E0 1998bu........................... 1998 May 21 11.93V 10 46 46.03 Æ 0.03 +11 50 07.1 Æ 0.5 NGC 3368 SABab 1999by........................... 1999 May 10 13.8B 09 21 52.07 Æ 0.04 +51 00 06.6 Æ 1.0 NGC 2841 SA(r)b 2002bo........................... 2002 Mar 23 14.04B 10 18 06.51 Æ 0.03 +21 49 41.7 Æ 0.5 NGC 3190 SA(s)a 2002cv........................... 2002 May 20 14.8J 10 18 03.68 Æ 0.03 +21 50 06.0 Æ 0.5 ..