TY - JOUR
T1 - The extraordinary outburst in the massive protostellar system NGC 6334 I-MM1
T2 - strong increase in mid-infrared continuum emission
AU - Hunter, T.R.
AU - Brogan, C.L.
AU - De Buizer, J.M.
AU - Towner, A.P.M.
AU - Dowell, C.D.
AU - Macleod, G.C.
AU - Stecklum, B.
AU - Cyganowski, C.J.
AU - El-Abd, S.J.
AU - McGuire, B.A.
N1 - Financial support for this work was provided by NASA through award #07_0156 issued by USRA. Based in part on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO program 089.C-0852(A).
PY - 2021/5/4
Y1 - 2021/5/4
N2 - In recent years, dramatic outbursts have been identified toward massive
protostars via infrared and millimeter dust continuum and molecular
maser emission. The longest lived outburst (>6 yr) persists in NGC
6334 I-MM1, a deeply embedded object with no near-IR counterpart. Using
FORCAST and HAWC+ on SOFIA, we have obtained the first mid-IR images of
this field since the outburst began. Despite being undetected in
pre-outburst ground-based 18 μm images, MM1 is now the brightest region at all three wavelengths (25, 37, and 53 μm),
exceeding the UCHII region MM3 (NGC 6334 F). Combining the SOFIA data
with ALMA imaging at four wavelengths, we construct a spectral energy
distribution of the combination of MM1 and the nearby hot core MM2. The
best-fit Robitaille radiative transfer model yields a luminosity of (4.9
± 0.8) × 104 L⊙. Accounting for an
estimated pre-outburst luminosity ratio MM1:MM2 = 2.1 ± 0.4, the
luminosity of MM1 has increased by a factor of 16.3 ± 4.4. The
pre-outburst luminosity implies a protostar of mass 6.7 M⊙,
which can produce the ionizing photon rate required to power the
pre-outburst HCHII region surrounding the likely outbursting protostar
MM1B. The total energy and duration of the outburst exceed the
S255IR-NIRS3 outburst by a factor of 3, suggesting a different scale of event involving expansion of the protostellar photosphere (to 20 R⊙), thereby supporting a higher accretion rate (0.0023 M⊙ yr−1)
and reducing the ionizing photon rate. In the grid of hydrodynamic
models of Meyer et al., the combination of outburst luminosity and
magnitude (3) places the NGC 6334 I-MM1 event in the region of moderate
total accretion (~0.1–0.3 M⊙) and hence long duration (~40–130 yr).
AB - In recent years, dramatic outbursts have been identified toward massive
protostars via infrared and millimeter dust continuum and molecular
maser emission. The longest lived outburst (>6 yr) persists in NGC
6334 I-MM1, a deeply embedded object with no near-IR counterpart. Using
FORCAST and HAWC+ on SOFIA, we have obtained the first mid-IR images of
this field since the outburst began. Despite being undetected in
pre-outburst ground-based 18 μm images, MM1 is now the brightest region at all three wavelengths (25, 37, and 53 μm),
exceeding the UCHII region MM3 (NGC 6334 F). Combining the SOFIA data
with ALMA imaging at four wavelengths, we construct a spectral energy
distribution of the combination of MM1 and the nearby hot core MM2. The
best-fit Robitaille radiative transfer model yields a luminosity of (4.9
± 0.8) × 104 L⊙. Accounting for an
estimated pre-outburst luminosity ratio MM1:MM2 = 2.1 ± 0.4, the
luminosity of MM1 has increased by a factor of 16.3 ± 4.4. The
pre-outburst luminosity implies a protostar of mass 6.7 M⊙,
which can produce the ionizing photon rate required to power the
pre-outburst HCHII region surrounding the likely outbursting protostar
MM1B. The total energy and duration of the outburst exceed the
S255IR-NIRS3 outburst by a factor of 3, suggesting a different scale of event involving expansion of the protostellar photosphere (to 20 R⊙), thereby supporting a higher accretion rate (0.0023 M⊙ yr−1)
and reducing the ionizing photon rate. In the grid of hydrodynamic
models of Meyer et al., the combination of outburst luminosity and
magnitude (3) places the NGC 6334 I-MM1 event in the region of moderate
total accretion (~0.1–0.3 M⊙) and hence long duration (~40–130 yr).
KW - Protostars
KW - Star formation
KW - Far infrared astronomy
KW - Submilimeter astronomy
KW - Milimeter astronomy
KW - Infrared astronomy
KW - Interstellar masers
KW - Stellar jets
KW - Dust continuum emission
KW - Radio continuum emission
KW - Radio interferometry
KW - Accretion
U2 - 10.3847/2041-8213/abf6d9
DO - 10.3847/2041-8213/abf6d9
M3 - Article
SN - 2041-8205
VL - 912
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L17
ER -