Bridging between type IIb and Ib supernovae: SN IIb 2022crv with avery thin Hydrogen envelope
Anjasha Gangopadhyay
Assistant Professor
Hiroshima Astrophysical Science Center, Hiroshima University, JapanIn Collaboration with : Keiichi Maeda, Avinash Singh, Nayana AJ, Koji S Kawabata, Tatsuya Nakaoka, Kenta Taguchi,
Masayuki Yamanaka, Miho Kawabata, Takashi Moriya, Masaomi Tanaka & Collaborators from India

Seimei Users Meeting

The extragalactic transient space
Perley etal. 2020

Continuityof outerenvelope??

Ho et al. 2021

Are the classes distinct or linked by a outer layer ?
● Spectroscopically, SNe IIb are differentiated from SNe Ib by the presence of Hα, which●●●

gradually diminishes over time, and He I feature takes over.
From their synthetic spectra, (Hachinger et al. 2012) concluded that even 0.025 − 0.033
M⊙ can produce strong Hα absorption feature, suggesting that there is a blending
between SNe IIb and SNe Ib.
Prentice & Mazzali (2017) created two further SE-SNe subcategories: the SNe IIb(I),having moderate H-rich spectra in which the Hα P-Cygni profile is dominated by theabsorption component relative to the emission profile, and the Ib(II), whose having
residual weak Hα, but, no other Balmer lines more energetic than Hα.
Thus, findings by Prentice & Mazzali (2017) along with Hachinger et al. (2012) indicatethat SNe IIb and SNe Ib are linked more physically than thought before.

SN 2022crv : Discovery
SN 2022crv was first discovered
as a SN Ib by Dong et al. 2022
on 19th February. The
classification spectrum wastaken by Andrews, Jennifer etal.2022.
Ryder et al. 2022 reported the radio
detection at 5.5 and 9 GHz using Australia
Telescope Compact Array and reported flux
densities of 0.7 mJy and 0.5 mJy at 9.0 and
5.5 GHz respectively.

The dip at 6200
Ang andinteraction inradio???

Observing run of SN 2022crv:
Photometriccoverage:-8 day to 86 day post
maximaSpectroscopic
coverage:-15 day to 33 day post
maximaPhotometric observations(Optical and Near-Infrared)

1m Sampurnanand
Telescope, 1.3m Devasthal
Fast Optical Telescope, 1.5m
Kanata Telescope, 2m
Himalayan Chandra
Telescope, 3.6m Devasthal
Optical Telescope & 3.8m
Seimei TelescopeRadio observations

Spectroscopic
observations (Optical)

RadioObservations:uGMRT:
upgraded GiantMeter Radiowave
Telescope (4epochs in 0.7 and1.37 GHz
respectively).
Archival ATCA
points added.

Spectral Evolution:● The absorption at 6250 Ang is moving with a
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velocity of 18,000 km s−1 showing a highvelocity ejecta.
Fe multiplets could be seen.
The spectra also shows a “W” shaped
absorption feature centered around 5000
Ang.
Mazzali et al. (2008) explains the origin of
these features due to Fe ii complexes,
whereas Silverman et al. (2009) consider
that the features arise due to a combinationof Ciii, N iii and O iii and their high velocities.
We also see prominent lines of He I 5876,6678 and 7065 Ang appearing with time.

Velocity evolution:● The absorption at 6250 Ang is moving

●
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with a velocity of 19,000 km s−1
showing a high-velocity ejecta.
If the feature is due to Si II, the velocities
are less than the photospheric velocities.
So, the feature is likely due to thecombination of Halpha + Si II.
We also see prominent lines of He I5876, 6678 and 7065 Ang appearingwith time.
The velocities are consistent with Hevelocities.

SYNAPPS:●For generating the absorption dip in the−9.7 d spectrum, a combination of Hα andSi ii were used. For modelling SN 2022crv
spectra, we used H i, He i, O i, Mg ii, Ca ii,Fe ii and Sc ii species. The maximum
velocity for all the ions from the fitting is
30,000 km s−1.

Consistent with the SN IIb with athin H envelope (along with Si II)
which vanished with time.

What makes this SN interesting?
●The +8.3 d spectrum of SN 2022crv shows avery small absorption dip at the Halpha position.

●At similar epochs all other SN IIb shows aprominent Halpha as seen in the Figure.

●The Halpha dip of most SN IIb shows aprominent dip almost ~40-50 days postmaximum.

This makes us suggest that thisis a SN IIb which retained a verythin H envelope!!!

Also validated from Equivalent width plot:● Initially, the EW of Hα+Si II issimilar to all other SNe IIb.
● As time progresses, theequivalent width of Hα+Si IIdecreases and the feature
becomes equal to a SN Ib andmuch lesser than SN IIb.

Apparent magnitude light curves andcolor curves of SN 2022crv

Gangopadhyay,Maeda, Singh et al.
2023, ApJ,underrevisionAbsolute magnitude & Bolometric light curves:●The V-band absolute magnitude of the SESNe group typically lies between −16.5 mag to−19.5 mag. Our obtained Mv =-17.82±0.17
mag are consistent with SN IIb (−17.40±0.55mag), but are brighter than the average SNIb (−17.07±0.56 mag).

Bolometriclight curvemodelling :Estimating radius-mass limits of the progenitor space:●Ouchi & Maeda (2017) calculated a grid of binary evolution
models for a SNe IIb that have extended progenitors. They
derived an observational relation between the progenitor radii andestimated the envelope mass as a consequence of nonconservative mass transfer in the final phase of progenitor
evolution.

●We used the Nagy and Vinko model to estimate an allowed rangeof radius for which we could estimate the envelope masses. We
found that our progenitor is quite compact with the limits on theRenv , Menv to be 3 R⊙, 0.05 M⊙ respectively. However, we want toremark that this estimates are limits because large uncertainty isinvolved in the first point. The low-estimated value of Hydrogenenvelope mass suggests that even Hydrogen is present for thisSN in the early times, it was thin and quickly diminished thanother SNe IIb.

Radio observations:●uGMRT observations werecarried out.The observations

were done in band-3(250−500 MHz),band-4(550−950 MHz) and band-5(1050−1450 MHz).

The near-simultaneous spectral indices between 1.37 and 0.69 GHz are 1.38±0.50, 1.45±0.29 and 2.15±0.23 at t ∼ 120, 197 and 305 days, respectively. These are flatter than (5/2), indicating inhomogeneties
in the magnetic field or relativistic electron distribution in the emitting region.

An adaptation from Maeda et al. 2015

Comparatively compact progenitor
Fairly luminous
We see a fairly compact progenitor
Bridging the gap ???

Mass-loss rates ~Summary● SN IIb with very thin Halpha, prominent Halpha changing to Helium within fewdays.
● A very compact progenitor, with a upper limit of 3 Msun.
● LInked by a continuity of hydrogen layer.
● No interaction signatures in optical, while radio detection is seen.
Why ??? The possible answers to this question could be:● If the CSM is present but not super dense, then signatures in optical become challenging todiscern, or it shows up at later stages due to inhomogeneities.
● The interaction signatures in thin less dense shell will be absorbed completely in optical,● The estimated mass loss rate from radio observation is 10−5, which is also not so high.
● At the same time, we see that the optical light curves are highly powered by the radioactive decayof Iron group elements synthesized in the explosion.
● Moreover, the star must have been massive and compact if the optical luminosity isoverwhelmingly dominated by radioactive decay.

Future work with Seimei: (In collaboration
with Avinash Singh, Miho Kawabata,
Kenta Taguchi,
Masayuki Yamanaka)● Estimating
Metallicities ofHost
Environments ofCore-Collapse
Supernovae

A glimpseof people
at work
duringKanataMirroralumnizing
work!

The picture perfect Hiroshima
Courtesy : https://www.thetravel.com/pics-of-what-hiroshima-looks-like-today/

Questions, Suggestions are welcome !!!