RadioAstron Space-VLBI observation of SN2014J and the possible AGN in M82
ATel #6197; Kirill V. Sokolovsky (ASC Lebedev/SAI MSU), Petr A. Voytsik (ASC Lebedev), Alexei V. Alakoz (ASC Lebedev), Yoshiharu Asaki (JAXA), Uwe Bach (MPIfR), Roman Feiler (Torun), Marcin P. Gawronski (Torun), Marcello Giroletti (INAF IRA), Mikhail A. Kharinov (IAA), Alexander V. Ipatov (IAA), Alexander M. Kutkin (ASC Lebedev), Ismail A. Rahimov (IAA/Svetloe), Frank K. Schinzel (UNM), Pawel Wolak (Torun)
on 3 Jun 2014; 14:03 UT
Credential Certification: Kirill Sokolovsky (firstname.lastname@example.org)
Subjects: Radio, AGN, Supernova Remnant, Supernovae, Transient
The Type Ia supernova SN2014J (ATel #5786, CBET #3792) appeared in M82
around 2014 January 14.75 UT (Zheng et al., arXiv:1401.7968).
On 2014 March 27 05:20-06:00 UT (71.5d after explosion) it was observed
with the RadioAstron Space-VLBI array consisting of the 10m Space
radio telescope (Kardashev et al., 2013 ARep, 57, 153) operating
simultaneously at 1.6 and 4.8 GHz, the Effelsberg 100m (observing
at 4.8 GHz), Usuda 64m (1.6 GHz), Kalyazin 64m (1.6 and 4.8 GHz),
Torun 32m (1.6 GHz), and Svetloe 32m (4.8 GHz) telescopes.
No radio emission was detected at the position of SN2014J (ATel #5821)
with 7 sigma upper limits on the correlated flux density of
3 mJy (Effelsberg-Svetloe projected baseline of 28 Megawavelength)
17 mJy (Effelsberg-RadioAstron, 2100 Megawavelength, 10.5 Earth diameters)
at 4.8 GHz and 12 mJy (Kalyazin-Torun baseline, 7.2 Megawavelength)
33 mJy (Kalyazin-RadioAstron baseline, 750 Megawavelength) at 1.6 GHz.
This is in agreement with the earlier radio non-detections of SN2014J
reported in ATel #5804, #5812, #6149, #6153 and Perez-Torres et al.
While no radio emission was found from SN2014J, the compact radio source
0951+699 (coinciding with the center of M82) located in the same beam
as the SN is clearly detected on ground-ground baselines with a flux
density of about 12 mJy (Effelsberg-Svetloe) and 62 mJy (Kalyazin-Svetloe;
7.8 Megawavelength) at 4.8 GHz and 90 mJy at 1.6 GHz
(Kalyazin-Torun). The flux density values are similar to the ones obtained
in October 2010 2.3/8.4 GHz VLBI observations by Pushkarev & Kovalev
(2012 A&A, 544, A34; see http://astrogeo.org/vlbi_images/ ).
The source 0951+699 is not detected on space-ground baselines.
Assuming the Gaussian brightness distribution, we use the flux densities
measured at Kalyazin-Svetloe and Effelsberg-Svetloe baselines to estimate
the 4.8 GHz brightness temperature of 0951+699 to be of the order
of 10^11 K in observer's frame. The observed brightness temperature is
consistent with the AGN nature of this source. However, radio supernovae
in the past have shown similar brightness temperature values hundreds of
days past the explosion.
The nearby source 1022+707 was observed by the ground stations only to
set the amplitude scale assuming the source has the flux density of
170 mJy at ground-ground baselines and flat spectrum. Considering
the expected thermal noise level, the estimated coherence loss and
the flux density of 0951+699 consistent with the previous measurements,
we expect the amplitude on baselines with Kalyazin to be accurate to
at least 50% (20% for other baselines).
Since phase referencing is challenging with the space antenna, a direct
fringe detection experiment was attempted with two 20 minute-long scans
on the position of SN2014J utilizing the full scan length for fringe
search. The ground telescopes recorded two 16 MHz-wide sidebands in two
orthogonal circular polarizations with 2-bit sampling at 256 Mbps while
the space telescope utilized 1-bit sampling at 128 Mbps. The correlation
was performed with the RadioAstron-enabled version of DiFX software
correlator (Deller et al., 2011, PASP, 123, 275) developed by
Anderson et al. (in prep.) installed at the ASC. The fringe search
was performed with PIMA ( http://astrogeo.org/pima/ ).
The RadioAstron project is led by the Astro Space Center of the Lebedev
Physical Institute of the Russian Academy of Sciences and the Lavochkin
Scientific and Production Association under a contract with the Russian
Federal Space Agency, in collaboration with partner organizations in
Russia and other countries. This work is based on observations with
the 100-m telescope of the MPIfR at Effelsberg and radio telescopes
of IAA RAS. We thank the RadioAstron mission, Alex Kraus, the PKE for
approving and the staff of participating observatories for performing