J/ApJ/935/44 LAT Gamma-ray spectra of RS Oph 2021 nova (Cheung+, 2022)
Fermi LAT Gamma-ray Detection of the Recurrent Nova RS Ophiuchi during its 2021
Outburst.
Cheung C.C., Johnson T.J., Jean P., Kerr M., Page K.L., Osborne J.P.,
Beardmore A.P., Sokolovsky K.V., Teyssier F., Ciprini S., Marti-Devesa G.,
Mereu I., Razzaque S., Wood K.S., Shore S.N., Korotkiy S., Levina A.,
Blumenzweig A.
<Astrophys. J., 935, 44 (2022)>
=2022ApJ...935...44C 2022ApJ...935...44C
ADC_Keywords: Gamma rays; Novae; Spectroscopy
Keywords: Gamma-ray transient sources ; Recurrent novae
Abstract:
We report the Fermi LAT γ-ray detection of the 2021 outburst of
the symbiotic recurrent nova RS Ophiuchi. In this system, unlike
classical novae from cataclysmic binaries, the ejecta from the white
dwarf form shocks when interacting with the dense circumstellar wind
environment of the red giant companion. We find the LAT spectra from
50MeV to ∼20-23GeV, the highest-energy photons detected in some
subintervals, are consistent with π0-decay emission from shocks in
the ejecta as proposed by Tatischeff & Hernanz for its previous 2006
outburst. The LAT light curve displayed a fast rise to its peak >0.1
GeV flux of ∼6x10-6ph/cm2/s beginning on day 0.745 after its
optically constrained eruption epoch of 2021 August 8.50. The peak
lasted for ∼1day and exhibited a power-law decline up to the final LAT
detection on day 45. We analyze the data on shorter timescales at
early times and found evidence of an approximate doubling of emission
over ∼200minutes at day 2.2, possibly indicating a localized
shock-acceleration event. Comparing the data collected by the American
Association of Variable Star Observers, we measured a constant ratio
of ∼2.8x10-3 between the γ-ray and optical luminosities except
for a ∼5xsmaller ratio within the first day of the eruption likely
indicating attenuation of γ rays by ejecta material and lower
high-energy proton fluxes at the earliest stages of the shock
development. The hard X-ray emission due to bremsstrahlung from
shock-heated gas traced by the Swift-XRT 2-10keV light curve peaked at
day ∼6, later than at GeV and optical energies. Using X-ray derived
temperatures to constrain the velocity profile, we find the hadronic
model reproduces the observed >0.1GeV light curve.
Description:
In the context of the hadronic model, we define four emission phases
for spectral study with the >50MeV LAT data the rise from day 0 to
1.0, a peak from day 1.0 to 2.75, decline-a from day 3.0 to 9.0
(2-10xsmaller than the peak), and decline-b from day 9.0 to 46.0. The
aim is to compare the evolution of the flux and spectral properties of
the y-ray emission in defined observation periods that are long enough
to have sufficient statistics to determine accurate values of the
spectral parameters.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
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17 50 13.15 -06 42 28.4 RS Oph 2021 = V* RS Oph
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig5a.dat 47 80 LAT γ-ray spectra
fig5b.dat 19 2468 Best-fit hadronic models
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See also:
IX/67 : Incremental Fermi LAT 4th source cat. (4FGL-DR3) (Fermi-LAT col., 2022)
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
J/ApJS/187/275 : Photometric histories of recurrent novae (Schaefer, 2010)
J/ApJS/247/33 : Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)
Byte-by-byte Description of file: fig5a.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Panel Figure panel (1)
3- 9 F7.1 MeV E [59.7/50825] Energy
11- 16 F6.1 MeV e_E [9/8269] Lower uncertainty in E
18- 23 F6.1 MeV E_E [11/9875] Upper uncertainty in E
25- 31 E7.1 mW/m2 Flux [8e-12/3e-9] Observed flux
33- 39 E7.1 mW/m2 e_Flux [6e-12/2e-9] Lower uncertainty in Flux
41- 47 E7.1 mW/m2 E_Flux [0/7e-10] Upper uncertainty in Flux (2)
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Note (1): Panels as follows:
a = Rise;
b = Peak;
c = Decline-a;
d = Decline-b.
Note (2): An upper uncertainty of zero indicates that the flux is an
upper limit (the lower uncertainty value corresponds to the
arrow drawn in the Figure)
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Byte-by-byte Description of file: fig5b.dat
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Bytes Format Units Label Explanations
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1- 1 A1 --- Panel Figure panel (1)
3- 9 F7.1 MeV E [50.2/60626] Energy
11- 19 E9.3 mW/m2 Flux [1e-12/2e-9] Model flux
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Note (1): Panels as follows:
a = Rise;
b = Peak;
c = Decline-a;
d = Decline-b.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 06-Jun-2024