J/ApJ/930/81 Follow-up HST obs. of a strong failed SN cand. (Jencson+, 2022)
An exceptional dimming event for a massive, cool supergiant in M51.
Jencson J.E., Sand D.J., Andrews J.E., Smith N., Pearson J., Strader J.,
Valenti S., Beasor E.R., Rothberg B.
<Astrophys. J., 930, 81 (2022)>
=2022ApJ...930...81J 2022ApJ...930...81J
ADC_Keywords: Stars, giant; Photometry, HST; Infrared sources
Keywords: Red supergiant stars ; Peculiar variable stars ; Stellar mass loss ;
Evolved stars
Abstract:
We present the discovery of an exceptional dimming event in a cool
supergiant star in the Local Volume spiral M51. The star, dubbed
M51-DS1, was found as part of a Hubble Space Telescope (HST) search
for failed supernovae (SNe). The supergiant, which is plausibly
associated with a very young (≲6Myr) stellar population, showed clear
variability (amplitude ΔF814W∼0.7mag) in numerous HST images
obtained between 1995 and 2016, before suddenly dimming by >2mag in
F814W sometime between late 2017 and mid-2019. In follow-up data from
2021, the star rebrightened, ruling out a failed supernova. Prior to
its near-disappearance, the star was luminous and red
(MF814W≲-7.6mag, F606W-F814W=1.9-2.2mag). Modeling of the
pre-dimming spectral energy distribution of the star favors a highly
reddened, very luminous (log[L/L☉]=5.4-5.7) star with
Teff∼3700-4700K, indicative of a cool yellow or post-red supergiant
(RSG) with an initial mass of ∼26-40M☉. However, the local
interstellar extinction and circumstellar extinction are uncertain,
and could be lower: the near-IR colors are consistent with an RSG,
which would be cooler (Teff≲3700K) and slightly less luminous
(log[L/L☉]=5.2-5.3), giving an inferred initial mass of
∼19-22M☉. In either case, the dimming may be explained by a rare
episode of enhanced mass loss that temporarily obscures the star,
potentially a more extreme counterpart to the 2019-2020 "Great
Dimming" of Betelgeuse. Given the emerging evidence that massive
evolved stars commonly exhibit variability that can mimic a
disappearing star, our work highlights a substantial challenge in
identifying true failed SNe.
Description:
We performed image subtraction with the available archival HST
WFC3/UVIS and ACS/WFC images in the F814W filter that overlap with the
footprint of our Cycle 26 program observations. For M51, this includes
ACS/WFC frames taken from 2005 January 12-22 (PI: S. Beckwith;
PID: 10452) and a large campaign consisting of 34 epochs taken between
2016 October 5 and 2017 February 17 to study massive star variability
(PI: C. Conroy; PID: 14704; see Conroy+ 2018, J/ApJ/864/111).
See Section 3.1.
Following our identification of M51-DS1 as a disappearing star and
promising candidate for a failed SN, we began examining the wealth of
multiband, archival HST imaging, including the ACS/WFC F814W images
described above and the complimentary F435W, F555W, and F658N (2005)
and F606W (2016-2017) from the same programs. There is also coverage
with WFC3/IR (0.13"/pixels) in F110W and F128N (Paβ) taken on
2012 September 4 (PI: J. Koda; PID: 12490). Of the available WFC3/UVIS
observations, we use only the 2012 observations in the redder F673N
and F689M filters (PI: K. Kuntz; PID: 12762). Similarly for WFPC2, we
consider only the F814W images from 1995 (PI: R. Kirshner; PID: 5777)
and 2008 (PI: M. Meixner; PID: 11229).
We were also awarded an HST Cycle 28 mid-cycle proposal for additional
deep, optical, and near-IR imaging of the field (PI: J. Jencson;
PID: 16508). The images for this program were obtained with ACS/WFC in
F606W and F814W (total exposure time of 2208s for each filter) on
2021 April 28-29 and with WFC3/IR in F110W and F160W on 2021 June 6
(1200s exposure per filter).
See Section 3.3.
We obtained follow-up imaging in the near-IR with the MMT and Magellan
Infrared Spectrograph (MMIRS, 0.2" pixels) on the 6.5m MMT Observatory
telescope on Mt. Hopkins at the Smithsonian's Fred Lawrence Whipple
Observatory. We obtained JHKs imaging over a two-night run on
UT 2021 February 23 and 24. We also obtained J- and Ks-band imaging
with the Near-Infrared Imager (NIRI) on the 8m Gemini-N Telescope on
Maunakea through a Directors Discretionary Time program
(PI: J. Jencson; PID: GN-2021A-DD-101). The images were obtained with
the f/6 camera (0.117" pixels) over multiple nights from 2021 April 1-6.
We also downloaded NIRI JHK images from the Gemini Observatory archive
covering the location of M51-DS1 and taken in a similar manner with
the same camera setup on 2005 June 27 (PI: S. Smartt; PID: GN-2005A-Q-49).
Lastly, near-IR Ks-band observations were obtained on 2022 January 22
at the LBT Observatory. See Section 3.3.2.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
13 29 56.15 +47 11 47.7 NAME M51-DS1 = NAME M51-DS1
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 52 82 HST DOLPHOT photometry
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
II/227 : The Asiago Supernova Catalogue 1999 (Barbon+, 1999)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/A+A/442/281 : Late-type giants BVRIJHKL & Teff (Kucinskas+, 2005)
J/ApJ/671/781 : Red supergiants in Sct-Cru Galactic arm (Davies+, 2007)
J/MNRAS/395/1409 : Type II-P SN progenitor constraints (Smartt+, 2009)
J/AcA/59/239 : VI LCs of LMC long-period variables (Soszynski+, 2009)
J/AJ/142/103 : Cool evolved stars in SAGE-SMC & SAGE-LMC (Boyer+, 2011)
J/A+A/532/A54 : GRAMS carbon-star model grid (Srinivasan+, 2011)
J/ApJ/727/53 : Red supergiant stars in the LMC. I. (Yang+, 2011)
J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)
J/ApJ/754/35 : Red supergiant stars in the SMC. II. (Yang+, 2012)
J/ApJS/215/9 : PHAT X. UV-IR photometry of M31 stars (Williams+, 2014)
J/ApJ/808/42 : CHemical Abundances of Spirals II. M51 (Croxall+, 2015)
J/ApJ/834/107 : Follow-up phot. of M101 OT2015-1 (Blagorodnova+, 2017)
J/ApJ/864/111 : HST/ACS one-year obs. of M51 stars (Conroy+, 2018)
J/MNRAS/478/3138 : Cool supergiants in Magellanic Clouds (Davies+, 2018)
J/ApJ/859/73 : RSGs in M31 from the iPTF survey (Soraisam+, 2018)
J/ApJ/886/40 : Most luminous SPIRITS IR transients (Jencson+, 2019)
J/A+A/629/A91 : A source catalog for the SMC (Yang+, 2019)
J/ApJ/905/34 : 2017-2020 photometry of Betelgeuse (Harper+, 2020)
J/ApJ/889/44 : UKIRT obs. of red supergiants in M31 (Neugent+, 2020)
J/MNRAS/508/5757 : Synthetic sp. of red supergiants (Davies+, 2021)
J/A+A/650/L17 : HERMES spectra of Betelgeuse (Kravchenko+, 2021)
J/AJ/161/79 : Red supergiant stars in M31 and M33 (Massey+, 2021)
J/other/Nat/594.365 : Betelgeuse during its Great Dimming (Montarges+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 yr Obs.Y [1995/2021] UT Year of the observation
6- 8 A3 "month" Obs.M UT Month of the observation
10- 14 F5.2 d Obs.D UT Day of the observation
16- 23 F8.2 d MJD [49732.76/59371.94] Modified Julian date
of observation
25- 33 A9 --- Inst HST instrument ("ACS/WFC", "WFC3/IR", "WFC3/UVIS"
or "WFPC2")
35- 39 A5 --- Band HST photometric band
41 A1 --- l_mag Limit flag on mag (1)
42- 46 F5.2 mag mag [19.48/25.3] Apparent Vega magnitude in Band
48- 52 F5.2 mag e_mag [0.04/0.3]? The 1σ uncertainty in mag
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Note (1): Indicates mag is a limiting magnitude for a non-detection.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Mar-2024