We report the deepest radio interferometric observations of the closest Type Ia supernova in decades, SN 2014J, which exploded in the nearby galaxy M 82. These observations
represent, together with radio observations of SNe 2011fe, the most sensitive radio studies of a Type Ia SN ever. We constrain the mass-loss rate from the progenitor system of
SN 2014J lower than 7.0 × 10^(−10) M yr^(−1) (for a wind speed of 100 km s^(−1) ). Our deep upper limits favor a double-degenerate scenario–involving two WD stars–for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast,
most single-degenerate scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to a exploding white dwarf, are ruled out by our observations. The evidence from SNe 2011fe and 2014J points in the direction of a double-degenerate scenario for both

Alberdi, A

Argo, M K

Beswick, Robert

Björnsson, C I

Figueras, F

Fransson, C

Guirado, J C

Hernández-Monteagudo, C

Lundqvist, P

Marcaide, J M M

Martí-Vidal, I

Muxlow, T W B

Paragi, Z

Pérez-Torres, M A

Ros, E

Ryder, S

Trujillo Bueno, J

Valdivielso, L

We report the deepest radio interferometric observations of the closest Type Ia supernova in decades, SN 2014J, which exploded in the nearby galaxy M 82. These observations represent, together with radio observations of SNe 2011fe, the most sensitive radio studies of a Type Ia SN ever. We constrain the mass-loss rate from the progenitor system of SN 2014J lower than 7.0 
7 10^(−10) M yr^(−1) (for a wind speed of 100 km s^(−1) ). Our deep upper limits favor a double-degenerate scenario–involving two WD stars–for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast, most single-degenerate scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to a exploding white dwarf, are ruled out by our observations. The evidence from SNe 2011fe and 2014J points in the direction of a double-degenerate scenario for both

Perez-Torres, Miguel Angel

Lundqvist, P.

Beswick, R. J.

Bjornsson, C. I.

Muxlow, T .W. B.

Paragi, Z.

Ryder, S.

Alberdi, Antxon

Fransson, C.

Marcaide, J. M.

Marti-Vidal, Ivan

Ros, Eduardo

Argo, M. K.

Guirado, J. C.

Chalmers Research

What is the progenitor of the Type Ia SN 2014J?

Perez-Torres, M. A.

Muxlow, T. W. B.

Alberdi, A.

Ros, E.

Chalmers Publication Library

	   	  
Highlights	  of	  Spanish	  Astrophysics	  VIII,	  Proceedings	  of	  the	  XI	  Scientific	  Meeting	  of	  the	  Spanish	  Astronomical	  Society	  held	  on	  September	  8–12,	  
2014,	  in	  Teruel,	  Spain.	  A.	  J.	  Cenarro,	  F.	  Figueras,	  C.	  Hernández-­‐Monteagudo,	  J.	  Trujillo	  Bueno,	  and	  L.	  Valdivielso	  (eds.)	  
What is the progenitor of the Type Ia SN 2014J?
M. A. Pe´rez-Torres1,2, P. Lundqvist3,4, R. J. Beswick5, C. I. Bjo¨rnsson3,
T.W.B. Muxlow5, Z. Paragi6, S. Ryder7, A. Alberdi1, C. Fransson3,4, J. M.
Marcaide8, I. Mart´ı-Vidal9, E. Ros8,10, M. K. Argo5 and J. C. Guirado10,11
1 Instituto de Astrof´ısica de Andaluc´ıa, Glorieta de la Astronomı´a, s/n, E-18008 Granada,
Spain.
2 Centro de Estudios de la F´ı´ısica del Cosmos de Arago´n, E-44001 Teruel, Spain.
3Department of Astronomy, Stockholm University, SE-10691, Sweden.
4The Oskar Klein Centre, AlbaNova, SE-10691 Stockholm, Sweden.
5Jodrell Bank Centre for Astrophysics, University of Manchester, Oxford Road, Manchester.
6Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, NL.
7Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670, Australia.
8Depto. de Astronomı´a i Astrof´ısica, Universidad de Valencia, E-46100 Burjassot, Valencia,
Spain.
9Onsala Space Observatory, Chalmers University of Technology, SE-43992 Onsala, Sweden.
10Max-Planck-Institut fu¨r Radioastronomie, D-53121 Bonn, Germany.
11Observatorio Astrono´mico, Universidad de Valencia, E-46980 Paterna, Valencia, Spain.
Abstract
We report the deepest radio interferometric observations of the closest Type Ia supernova
in decades, SN 2014J, which exploded in the nearby galaxy M 82. These observations
represent, together with radio observations of SNe 2011fe, the most sensitive radio studies
of a Type Ia SN ever. We constrain the mass-loss rate from the progenitor system of
SN 2014J to M˙ . 7.0× 10−10 M yr−1 (for a wind speed of 100 km s−1). Our deep upper
limits favor a double-degenerate scenario–involving two WD stars–for the progenitor system
of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast,
most single-degenerate scenarios, i.e., the wide family of progenitor systems where a red
giant, main-sequence, or sub-giant star donates mass to a exploding white dwarf, are ruled
out by our observations. The evidence from SNe 2011fe and 2014J points in the direction
of a double-degenerate scenario for both.
540
M. A. Pe´rez-Torres et al. 541
1 Introduction
Type Ia SNe are the end-products of white dwarfs (WDs) with a mass approaching, or equal
to, the Chandrasekhar limit, which results in a thermonuclear explosion of the star. While it
is well acknowledged that the exploding WD dies in close binary systems, it is still unclear
whether the progenitor system is composed of a C+O white dwarf and a non-degenerate
star (single-degenerate scenario), or both stars are WDs (double-degenerate scenario). In the
single-degenerate scenario, a WD accretes mass from a hydrogen-rich companion star before
reaching a mass close to the Chandrasekhar limit and going off as supernova, while in the
double-degenerate scenario, two WDs merge, with the more-massive WD being thought to
tidally disrupt and accrete the lower-mass WD (see, e.g., [5] and references therein). This
lack of knowledge makes it difficult to gain a physical understanding of the explosions, and
to model their evolution, thus also compromising their use as distance indicators.
Radio and X-ray observations can potentially discriminate between the progenitor mod-
els of SNe Ia. For example, in all single-degenerate (SD) scenarios there is mass transfer from
a companion, a significant amount of circumstellar gas is expected (e.g., [1]), and therefore
a shock is bound to form when the supernova ejecta are expelled. The situation would then
be very similar to circumstellar interaction in core-collapse SNe (see above), where the inter-
action of the blast wave from the supernova with its circumstellar medium results in strong
radio and X-ray emission [2]. On the other hand, the double-degenerate (DD) scenario will
not give rise to any circumstellar medium close to the progenitor system, and hence essen-
tially no prompt radio emission is expected. Nonetheless, we note that the radio emission
increases with time in the DD scenario, contrary to the SD scenario. This also opens the
possibility for confirming the DD channel in Type Ia SNe via sensitive SKA observations of
decades-old Type Ia SNe.
Table 1: Log of radio observations
Starting T a tint Array ν Sνb Lν,23 c M˙−9d
UT day hours GHz µJy
Jan 23.2 8.2 − JVLA 5.50 12.0 1.8 0.7
Jan 24.4 9.4 − JVLA 22.0 24.0 3.5 3.7
Jan 28.8 13.8 13.6 eMERLIN 1.55 37.2 5.5 1.2
Jan 29.5 14.5 14.0 eMERLIN 6.17 40.8 6.0 3.6
Feb 4.0 20.0 11.0 eEVN 1.66 32.4 4.7 1.7
Feb 19.1 35.0 10.0 eEVN 1.66 28.5 4.2 2.9
aMean observing epoch (in days since explosion, assumed to be on Jan 15.0).
b3σ flux density upper limits, in µJy.
cThe corresponding 3σ spectral luminosity, in units of 1023 erg s−1 Hz−1.
dInferred 3σ upper limit to the mass-loss rate in units of 10−9M yr−1, for an
assumed wind velocity of 100 km s−1 and for B = 0.1 (see main text for details).
542 What is the progenitor of the Type Ia SN 2014J?
2 Radio observations of SN 2014J
We observed the type Ia SN 2014J with the electronic Multi Element Radio Interferometric
Network (eMERLIN) at 1.6 and 6.2 GHz, and with the electronic European Very Long
Baseline Interferometry Network (EVN) at a frequency of 1.7 GHz. We observed SN 2014J
several times between 28 January 2014 and 19 February 2014. We show in Table 1 our log
for the radio observations, whose full details are given in [6].
We discuss the radio emission from SNe Ia within a scenario of Type Ib/c SNe (see,
e.g.,[3]) but, since we only have upper limits for the radio emission from SN 2014J, we will
neglect energy losses for the relativistic electrons. The spectrum of the radio emission from
those SNe follows the “Synchrotron Self-Absorption” (SSA) form, i.e., a rising power law with
ν5/2 (low-frequency, optically thick regime), and a declining power law, να (high frequency,
optically thin regime), where α is assumed to be constant. For most well studied SNe,
α ≈ −1 [3]. We assume that electrons are accelerated to relativistic energies, with a power
law distribution, dN/dE = N0E−p; where E = γmec2 is the energy of the electrons and γ
is the Lorentz factor. For synchrotron emission, α = (p − 1)/2, which indicates that p ≈ 3
should be used. We denote B = uB/uth, where uB = B2/(8pi) and uth are the (post-shock)
magnetic and thermal energy densities, respectively; and rel = urel/uth, where urel is the
energy density of the relativistic particles, assumed for simplicity to be electrons. (See [6] for
details of the modelling of the radio emission.)
Fig. 1 shows the predicted radio light curves of SN 2014J in M 82 in the case of a
pre-supernova steady wind (ρCSM ∝ r−2), which is expected in SD scenarios, for B = 0.01
and 0.1. An almost perfect overlap between modeled light curves occurs for the combination
M˙ = 7.0 × 10−10 M yr−1 and B = 0.1, and M˙ = 4.2 × 10−9 M yr−1and B = 0.01. The
values of M˙/vw for SN 2014J in Figure 1 are chosen so that the 5.50 GHz light curves go
through the JVLA 3σ upper limit on day 8.2. The light curves for other frequencies lie below
their corresponding upper limits. The second most constraining limit is from our 1.55 GHz
eMERLIN observation on day 13.8, yielding M˙ <∼ 1.15 (7.0)×10−9 M yr−1 for B = 0.1 (0.01)
and vw = 100 km s−1. We show in Table 1 upper limits for all data points.
3 The progenitor scenarios of Type Ia SNe
The power of radio interferometric observations lies in the fact that they are a perfect tracer
of the mass-loss rate of the pre-supernova wind. In [6], we showed that the optically thin
radio emission from SN 2014J, in the case of a steady wind is approximately
Lν,thin ∝ 1.1B
(
M˙/vw
)1.3
t−1.45
If B is fixed, the luminosity tells us directly what is the value of (M˙/vw). Therefore, if
we plot in a graph M˙ vs. vw, we can constrain the SD progenitors for SN 2014J. This is exactly
the purpose of Figure 2, where we have drawn, schematically, the regions of the (M˙/vw)
parameter space occupied by the most popular SD progenitor scenarios, which include, in
decreasing order of mass-loss rate from the supernova progenitor, symbiotic systems, WDs
M. A. Pe´rez-Torres et al. 543
 1e+22
 1e+23
 1e+24
 1e+25
 10
Lu
m
in
os
ity
 (e
rg 
s−1
 
H
z−
1 )
Time (days)
1.55 GHz
1.66 GHz
5.50 GHz
6.17 GHz
22.0 GHz
Solid: 7.0x10−10 Msun/yr; εrel = 0.1;  εB = 0.1
Dashed: 4.2x10−9 Msun/yr; εrel = 0.1;  εB = 0.01
14J
11fe
Figure 1: Predicted radio light curves of SN 2014J in M 82 for an assumed mass-loss rate of
M˙ = 7.0 × 10−10 M yr−1(solid lines), and for M˙ = 4.2 × 10−9 M yr−1(dashed lines). For
the former we used B = 0.1 and for the latter B = 0.01. The data points (cf. Table 1)
with 3σ upper limits for SN 2014J are in the right part of the figure. Shown in the figure is
also the earliest 5.9 GHz 3σ upper limit for SN 2011fe [4], scaled to its distance of 6.4 Mpc,
together with a dotted line marking the predicted evolution for M˙ = 5.0×10−10 M yr−1(for
B = 0.1). Common parameters in all models are rel = 0.1, p = 3 and vw = 100 km s−1. See
text for further details.
544 What is the progenitor of the Type Ia SN 2014J?
with steady nuclear burning, and recurrent novae.
In a symbiotic system, the WD accretes mass from a giant star. The WD loses this
accreted matter at rates of M˙ & 10−8 M yr−1and vw ≈ 30 km s−1. The radio emission
from those systems should have been detected by our deep sensitive observations. Thus, our
radio non-detection rules out a symbiotic system as the progenitor of SN 2014J (red region
in Figure 2).
Figure 2: Constraints on the parameter space (wind speed vs. mass-loss rate) for SD sce-
narios for SN 2014J (see [6] for details). Progenitor scenarios are plotted as schematic zones,
following [4]. We indicate our 3σ limits on M˙/vw, assuming B = 0.1 (solid line) and the
conservative case of B = 0.01 (dashed line). Mass loss scenarios falling into the gray-shaded
areas should have been detected by the deep radio observations, and therefore are ruled out
for SN 2014J. For a comparison, we have included also the limit on SN 2011fe (dash-dotted
line) for the same choice of parameters as the solid line for SN 2014J, which essentially leaves
only room for quiescent nova emission as a viable alternative among the SD scenarios for
SN 2011fe.
Another possible SD scenario is one where a main sequence, subgiant, helium, or giant
star undergoes Roche lobe overflow onto the WD at rates of 3.1 × 10−7 M yr−1 . M˙ .
M. A. Pe´rez-Torres et al. 545
6.7 × 10−7 M yr−1. At those accretion rates, the WD experiences steady nuclear burning.
For an assumed fraction loss = 0.01 of the transferred mass to be lost from the system, the
mass-loss rate is constrained to 3.1× 10−9 M yr−1 . M˙ . 6.7× 10−9 M yr−1 and typical
speeds of 100 km s−1. vw . 3000 km s−1. At the lower end of M˙ , the mass loss through the
outer Lagrangian points of the system proceeds at speeds up to ∼600 km s−1. Most of the
parameter space for the low-accretion rate scenario is ruled out by our radio observations,
if B ' 0.1 (blue region in Fig. 2). At the upper end of M˙ the winds become optically
thick, limiting the accretion rate to M˙acc ≈ 6 × 10−7 M yr−1 and wind speeds of a few ×
1000 km s−1. Our data essentially rule out completely the high-accretion rate scenario of a
WD with steady nuclear burning (cyan region in Fig. 2).
Finally, another possible SD channel is that of recurrent novae, which lie at the lowest
accretion rate regime among popular SD scenarios. Here, a WD accreting at a rate M˙ ≈
(1 − 3) × 10−7 M yr−1, ejects shells of material at speeds of a few ×1000 km s−1, with
typical recurrence times of a few years. The radio observations in Table 1 probe a radius of
' (0.7− 2.6)× 1016 cm (for s = 2 and B = 0.1), which constrains the presence of shells with
recurrence times of . 1.6 (vshell/2000 km s−1)−1 (rshell/1016 cm) yr. Models of recurrent
novae seem to indicate that as much as ∼15% of the accreted material over the recurrence
time is ejected. For the typical accretion rates above, this implies an ejected shell mass of
≈ (2.4 − 7.1) × 10−8 M, which should have been detected by our sensitive observations
(see yellow region in Fig. 2). Unfortunately, the short duration of the nova radio burst, a
few days at most, may have prevented its detection, so we cannot rule out completely the
possibility of a nova shell ejection. During the quiescent phase between nova shell ejections,
the WD accretes at a rate of M˙ ∼ 1× 10−7 M yr−1, so that the mass-loss wind parameter
is M˙/vw ∼ 1 × 10−9 (loss/0.01)/100 km s−1. If B = 0.1, our observations rule out almost
completely the scenario with WD accretion during the quiescent phase of the star, whereas
the case with B = 0.01 cannot be excluded completely (green region in Fig. 2).
4 Summary
In summary, our observations exclude completely symbiotic systems and the majority of the
parameter space associated with stable nuclear burning WDs, as viable progenitor systems
for SN 2014J. Recurrent novae with main sequence or subgiant donors cannot be ruled out
completely, yet most of their parameter space is also excluded by our observations. Therefore,
our radio non-detections favour the DD scenario for SN 2014J.
Acknowledgments
The European VLBI Network (EVN) is a joint facility of European, Chinese, South African, and other
radio astronomy institutes funded by their national research councils. The electronic Multi-Element
Radio Linked Interferometer Network (eMERLIN) is the UK’s facility for high resolution radio as-
tronomy observations, operated by The University of Manchester for the Science and Technology
Facilities Council (STFC). AA, JCG, JMM, MAPT, ER, and IMV acknowledge support from the
Spanish MICINN through grants AYA2012-38491-C02-01 and AYA2012-38491-C02-02. P.L. acknowl-
546 What is the progenitor of the Type Ia SN 2014J?
edges support from the Swedish Research Council. The research leading to these results has received
funding from the European Commission Seventh Framework Programme (FP/2007-2013) under grant
agreement No 283393 (RadioNet3).
References
[1] Branch, D., Livio, M., Yungelson, L. R. et al. 1995, PASP, 107, 1019
[2] Chevalier, R. A. 1982, ApJ, 259, 302
[3] Chevalier, R. A., Fransson, C., Nymark, T. K. 2006, ApJ, 641, 1029
[4] Chomiuk, L., Soderberg, A. M., Moe, M., et al. 2012, ApJ, 750, 164
[5] Maoz, D., Mannucci, F., Nelemans, G. 2014, ARA&A, 52, 107
[6] Pe´rez-Torres, M. A., Lundqvist, P., Beswick, R. J., et al. 2014, ApJ, 792, 38


We report the deepest radio interferometric observations of the closest Type Ia supernova in decades, SN 2014J, which exploded in the nearby galaxy M 82. These observations represent, together with radio observations of SNe 2011fe, the most sensitive radio studies of a Type Ia SN ever. We constrain the mass-loss rate from the progenitor system of SN 2014J to dot{M} ≲ 7.0EE{-10} msunyr (for a wind speed of 100 kms). Our deep upper limits favor a double-degenerate scenario-involving two WD stars-for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast, most single-degenerate scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to a exploding white dwarf, are ruled out by our observations. The evidence from SNe 2011fe and 2014J points in the direction of a double-degenerate scenario for both

The University of Manchester - Institutional Repository

The University of Manchester ResearchWhat is the progenitor of the Type Ia SN 2014J?Link to publication record in Manchester Research ExplorerCitation for published version (APA):Pérez-Torres, M. A., Lundqvist, P., Beswick, R., Björnsson, C. I., Muxlow, T. W. B., Paragi, Z., Ryder, S., Alberdi,A., Fransson, C., Marcaide, J. M. M., Martí-Vidal, I., Ros, E., Argo, M. K., Guirado, J. C., Figueras, F., Hernández-Monteagudo, C., Trujillo Bueno, J., Valdivielso, L., & Cenarro, A. J. (Ed.) (2015). What is the progenitor of the TypeIa SN 2014J? In A. J. Cenarro (Ed.), Highlights of Spanish Astrophysics VIII, Proceedings of the XI ScientificMeeting of the Spanish Astronomical Society (pp. 540-546) http://adsabs.harvard.edu/abs/2015hsa8.conf..540PPublished in:Highlights of Spanish Astrophysics VIII, Proceedings of the XI Scientific Meeting of the Spanish AstronomicalSocietyCiting this paperPlease note that where the full-text provided on Manchester Research Explorer is the Author Accepted Manuscriptor Proof version this may differ from the final Published version. 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Jun. 2022	  	  Highlights	  of	  Spanish	  Astrophysics	  VIII,	  Proceedings	  of	  the	  XI	  Scientific	  Meeting	  of	  the	  Spanish	  Astronomical	  Society	  held	  on	  September	  8–12,	  2014,	  in	  Teruel,	  Spain.	  A.	  J.	  Cenarro,	  F.	  Figueras,	  C.	  Hernández-­‐Monteagudo,	  J.	  Trujillo	  Bueno,	  and	  L.	  Valdivielso	  (eds.)	  What is the progenitor of the Type Ia SN 2014J?M. A. Pérez-Torres1,2, P. Lundqvist3,4, R. J. Beswick5, C. I. Björnsson3,T.W.B. Muxlow5, Z. Paragi6, S. Ryder7, A. Alberdi1, C. Fransson3,4, J. M.Marcaide8, I. Mart́ı-Vidal9, E. Ros8,10, M. K. Argo5 and J. C. Guirado10,111 Instituto de Astrof́ısica de Andalućıa, Glorieta de la Astronomı́a, s/n, E-18008 Granada,Spain.2 Centro de Estudios de la F́ı́ısica del Cosmos de Aragón, E-44001 Teruel, Spain.3Department of Astronomy, Stockholm University, SE-10691, Sweden.4The Oskar Klein Centre, AlbaNova, SE-10691 Stockholm, Sweden.5Jodrell Bank Centre for Astrophysics, University of Manchester, Oxford Road, Manchester.6Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, NL.7Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670, Australia.8Depto. de Astronomı́a i Astrof́ısica, Universidad de Valencia, E-46100 Burjassot, Valencia,Spain.9Onsala Space Observatory, Chalmers University of Technology, SE-43992 Onsala, Sweden.10Max-Planck-Institut für Radioastronomie, D-53121 Bonn, Germany.11Observatorio Astronómico, Universidad de Valencia, E-46980 Paterna, Valencia, Spain.AbstractWe report the deepest radio interferometric observations of the closest Type Ia supernovain decades, SN 2014J, which exploded in the nearby galaxy M 82. These observationsrepresent, together with radio observations of SNe 2011fe, the most sensitive radio studiesof a Type Ia SN ever. We constrain the mass-loss rate from the progenitor system ofSN 2014J to Ṁ . 7.0× 10−10 M yr−1 (for a wind speed of 100 km s−1). Our deep upperlimits favor a double-degenerate scenario–involving two WD stars–for the progenitor systemof SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast,most single-degenerate scenarios, i.e., the wide family of progenitor systems where a redgiant, main-sequence, or sub-giant star donates mass to a exploding white dwarf, are ruledout by our observations. The evidence from SNe 2011fe and 2014J points in the directionof a double-degenerate scenario for both.540M. A. Pérez-Torres et al. 5411 IntroductionType Ia SNe are the end-products of white dwarfs (WDs) with a mass approaching, or equalto, the Chandrasekhar limit, which results in a thermonuclear explosion of the star. While itis well acknowledged that the exploding WD dies in close binary systems, it is still unclearwhether the progenitor system is composed of a C+O white dwarf and a non-degeneratestar (single-degenerate scenario), or both stars are WDs (double-degenerate scenario). In thesingle-degenerate scenario, a WD accretes mass from a hydrogen-rich companion star beforereaching a mass close to the Chandrasekhar limit and going off as supernova, while in thedouble-degenerate scenario, two WDs merge, with the more-massive WD being thought totidally disrupt and accrete the lower-mass WD (see, e.g., [5] and references therein). Thislack of knowledge makes it difficult to gain a physical understanding of the explosions, andto model their evolution, thus also compromising their use as distance indicators.Radio and X-ray observations can potentially discriminate between the progenitor mod-els of SNe Ia. For example, in all single-degenerate (SD) scenarios there is mass transfer froma companion, a significant amount of circumstellar gas is expected (e.g., [1]), and thereforea shock is bound to form when the supernova ejecta are expelled. The situation would thenbe very similar to circumstellar interaction in core-collapse SNe (see above), where the inter-action of the blast wave from the supernova with its circumstellar medium results in strongradio and X-ray emission [2]. On the other hand, the double-degenerate (DD) scenario willnot give rise to any circumstellar medium close to the progenitor system, and hence essen-tially no prompt radio emission is expected. Nonetheless, we note that the radio emissionincreases with time in the DD scenario, contrary to the SD scenario. This also opens thepossibility for confirming the DD channel in Type Ia SNe via sensitive SKA observations ofdecades-old Type Ia SNe.Table 1: Log of radio observationsStarting T a tint Array ν Sνb Lν,23 c Ṁ−9dUT day hours GHz µJyJan 23.2 8.2 − JVLA 5.50 12.0 1.8 0.7Jan 24.4 9.4 − JVLA 22.0 24.0 3.5 3.7Jan 28.8 13.8 13.6 eMERLIN 1.55 37.2 5.5 1.2Jan 29.5 14.5 14.0 eMERLIN 6.17 40.8 6.0 3.6Feb 4.0 20.0 11.0 eEVN 1.66 32.4 4.7 1.7Feb 19.1 35.0 10.0 eEVN 1.66 28.5 4.2 2.9aMean observing epoch (in days since explosion, assumed to be on Jan 15.0).b3σ flux density upper limits, in µJy.cThe corresponding 3σ spectral luminosity, in units of 1023 erg s−1 Hz−1.dInferred 3σ upper limit to the mass-loss rate in units of 10−9M yr−1, for anassumed wind velocity of 100 km s−1 and for εB = 0.1 (see main text for details).542 What is the progenitor of the Type Ia SN 2014J?2 Radio observations of SN 2014JWe observed the type Ia SN 2014J with the electronic Multi Element Radio InterferometricNetwork (eMERLIN) at 1.6 and 6.2 GHz, and with the electronic European Very LongBaseline Interferometry Network (EVN) at a frequency of 1.7 GHz. We observed SN 2014Jseveral times between 28 January 2014 and 19 February 2014. We show in Table 1 our logfor the radio observations, whose full details are given in [6].We discuss the radio emission from SNe Ia within a scenario of Type Ib/c SNe (see,e.g.,[3]) but, since we only have upper limits for the radio emission from SN 2014J, we willneglect energy losses for the relativistic electrons. The spectrum of the radio emission fromthose SNe follows the “Synchrotron Self-Absorption” (SSA) form, i.e., a rising power law withν5/2 (low-frequency, optically thick regime), and a declining power law, να (high frequency,optically thin regime), where α is assumed to be constant. For most well studied SNe,α ≈ −1 [3]. We assume that electrons are accelerated to relativistic energies, with a powerlaw distribution, dN/dE = N0E−p; where E = γmec2 is the energy of the electrons and γis the Lorentz factor. For synchrotron emission, α = (p − 1)/2, which indicates that p ≈ 3should be used. We denote εB = uB/uth, where uB = B2/(8π) and uth are the (post-shock)magnetic and thermal energy densities, respectively; and εrel = urel/uth, where urel is theenergy density of the relativistic particles, assumed for simplicity to be electrons. (See [6] fordetails of the modelling of the radio emission.)Fig. 1 shows the predicted radio light curves of SN 2014J in M 82 in the case of apre-supernova steady wind (ρCSM ∝ r−2), which is expected in SD scenarios, for εB = 0.01and 0.1. An almost perfect overlap between modeled light curves occurs for the combinationṀ = 7.0 × 10−10 M yr−1 and εB = 0.1, and Ṁ = 4.2 × 10−9 M yr−1and εB = 0.01. Thevalues of Ṁ/vw for SN 2014J in Figure 1 are chosen so that the 5.50 GHz light curves gothrough the JVLA 3σ upper limit on day 8.2. The light curves for other frequencies lie belowtheir corresponding upper limits. The second most constraining limit is from our 1.55 GHzeMERLIN observation on day 13.8, yielding Ṁ <∼ 1.15 (7.0)×10−9 M yr−1 for εB = 0.1 (0.01)and vw = 100 km s−1. We show in Table 1 upper limits for all data points.3 The progenitor scenarios of Type Ia SNeThe power of radio interferometric observations lies in the fact that they are a perfect tracerof the mass-loss rate of the pre-supernova wind. In [6], we showed that the optically thinradio emission from SN 2014J, in the case of a steady wind is approximatelyLν,thin ∝ ε1.1B(Ṁ/vw)1.3t−1.45If εB is fixed, the luminosity tells us directly what is the value of (Ṁ/vw). Therefore, ifwe plot in a graph Ṁ vs. vw, we can constrain the SD progenitors for SN 2014J. This is exactlythe purpose of Figure 2, where we have drawn, schematically, the regions of the (Ṁ/vw)parameter space occupied by the most popular SD progenitor scenarios, which include, indecreasing order of mass-loss rate from the supernova progenitor, symbiotic systems, WDsM. A. Pérez-Torres et al. 543 1e+22 1e+23 1e+24 1e+25 10Luminosity (erg s−1 Hz−1 )Time (days)1.55 GHz1.66 GHz5.50 GHz6.17 GHz22.0 GHzSolid: 7.0x10−10 Msun/yr; εrel = 0.1;  εB = 0.1Dashed: 4.2x10−9 Msun/yr; εrel = 0.1;  εB = 0.0114J11feFigure 1: Predicted radio light curves of SN 2014J in M 82 for an assumed mass-loss rate ofṀ = 7.0 × 10−10 M yr−1(solid lines), and for Ṁ = 4.2 × 10−9 M yr−1(dashed lines). Forthe former we used εB = 0.1 and for the latter εB = 0.01. The data points (cf. Table 1)with 3σ upper limits for SN 2014J are in the right part of the figure. Shown in the figure isalso the earliest 5.9 GHz 3σ upper limit for SN 2011fe [4], scaled to its distance of 6.4 Mpc,together with a dotted line marking the predicted evolution for Ṁ = 5.0×10−10 M yr−1(forεB = 0.1). Common parameters in all models are εrel = 0.1, p = 3 and vw = 100 km s−1. Seetext for further details.544 What is the progenitor of the Type Ia SN 2014J?with steady nuclear burning, and recurrent novae.In a symbiotic system, the WD accretes mass from a giant star. The WD loses thisaccreted matter at rates of Ṁ & 10−8 M yr−1and vw ≈ 30 km s−1. The radio emissionfrom those systems should have been detected by our deep sensitive observations. Thus, ourradio non-detection rules out a symbiotic system as the progenitor of SN 2014J (red regionin Figure 2).Figure 2: Constraints on the parameter space (wind speed vs. mass-loss rate) for SD sce-narios for SN 2014J (see [6] for details). Progenitor scenarios are plotted as schematic zones,following [4]. We indicate our 3σ limits on Ṁ/vw, assuming εB = 0.1 (solid line) and theconservative case of εB = 0.01 (dashed line). Mass loss scenarios falling into the gray-shadedareas should have been detected by the deep radio observations, and therefore are ruled outfor SN 2014J. For a comparison, we have included also the limit on SN 2011fe (dash-dottedline) for the same choice of parameters as the solid line for SN 2014J, which essentially leavesonly room for quiescent nova emission as a viable alternative among the SD scenarios forSN 2011fe.Another possible SD scenario is one where a main sequence, subgiant, helium, or giantstar undergoes Roche lobe overflow onto the WD at rates of 3.1 × 10−7 M yr−1 . Ṁ .M. A. Pérez-Torres et al. 5456.7 × 10−7 M yr−1. At those accretion rates, the WD experiences steady nuclear burning.For an assumed fraction εloss = 0.01 of the transferred mass to be lost from the system, themass-loss rate is constrained to 3.1× 10−9 M yr−1 . Ṁ . 6.7× 10−9 M yr−1 and typicalspeeds of 100 km s−1. vw . 3000 km s−1. At the lower end of Ṁ , the mass loss through theouter Lagrangian points of the system proceeds at speeds up to ∼600 km s−1. Most of theparameter space for the low-accretion rate scenario is ruled out by our radio observations,if εB ' 0.1 (blue region in Fig. 2). At the upper end of Ṁ the winds become opticallythick, limiting the accretion rate to Ṁacc ≈ 6 × 10−7 M yr−1 and wind speeds of a few ×1000 km s−1. Our data essentially rule out completely the high-accretion rate scenario of aWD with steady nuclear burning (cyan region in Fig. 2).Finally, another possible SD channel is that of recurrent novae, which lie at the lowestaccretion rate regime among popular SD scenarios. Here, a WD accreting at a rate Ṁ ≈(1 − 3) × 10−7 M yr−1, ejects shells of material at speeds of a few ×1000 km s−1, withtypical recurrence times of a few years. The radio observations in Table 1 probe a radius of' (0.7− 2.6)× 1016 cm (for s = 2 and εB = 0.1), which constrains the presence of shells withrecurrence times of . 1.6 (vshell/2000 km s−1)−1 (rshell/1016 cm) yr. Models of recurrentnovae seem to indicate that as much as ∼15% of the accreted material over the recurrencetime is ejected. For the typical accretion rates above, this implies an ejected shell mass of≈ (2.4 − 7.1) × 10−8 M, which should have been detected by our sensitive observations(see yellow region in Fig. 2). Unfortunately, the short duration of the nova radio burst, afew days at most, may have prevented its detection, so we cannot rule out completely thepossibility of a nova shell ejection. During the quiescent phase between nova shell ejections,the WD accretes at a rate of Ṁ ∼ 1× 10−7 M yr−1, so that the mass-loss wind parameteris Ṁ/vw ∼ 1 × 10−9 (εloss/0.01)/100 km s−1. If εB = 0.1, our observations rule out almostcompletely the scenario with WD accretion during the quiescent phase of the star, whereasthe case with εB = 0.01 cannot be excluded completely (green region in Fig. 2).4 SummaryIn summary, our observations exclude completely symbiotic systems and the majority of theparameter space associated with stable nuclear burning WDs, as viable progenitor systemsfor SN 2014J. Recurrent novae with main sequence or subgiant donors cannot be ruled outcompletely, yet most of their parameter space is also excluded by our observations. Therefore,our radio non-detections favour the DD scenario for SN 2014J.AcknowledgmentsThe European VLBI Network (EVN) is a joint facility of European, Chinese, South African, and otherradio astronomy institutes funded by their national research councils. The electronic Multi-ElementRadio Linked Interferometer Network (eMERLIN) is the UK’s facility for high resolution radio as-tronomy observations, operated by The University of Manchester for the Science and TechnologyFacilities Council (STFC). AA, JCG, JMM, MAPT, ER, and IMV acknowledge support from theSpanish MICINN through grants AYA2012-38491-C02-01 and AYA2012-38491-C02-02. P.L. acknowl-546 What is the progenitor of the Type Ia SN 2014J?edges support from the Swedish Research Council. The research leading to these results has receivedfunding from the European Commission Seventh Framework Programme (FP/2007-2013) under grantagreement No 283393 (RadioNet3).References[1] Branch, D., Livio, M., Yungelson, L. R. et al. 1995, PASP, 107, 1019[2] Chevalier, R. A. 1982, ApJ, 259, 302[3] Chevalier, R. A., Fransson, C., Nymark, T. K. 2006, ApJ, 641, 1029[4] Chomiuk, L., Soderberg, A. M., Moe, M., et al. 2012, ApJ, 750, 164[5] Maoz, D., Mannucci, F., Nelemans, G. 2014, ARA&A, 52, 107[6] Pérez-Torres, M. A., Lundqvist, P., Beswick, R. J., et al. 2014, ApJ, 792, 38

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What is the progenitor of the Type Ia SN 2014J?

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