J/AJ/158/73 Parameters of OB stars & their bow shock nebulae (Kobulnicky+, 2019)
Mass-loss rates for O and early B stars powering bow shock nebulae: evidence
for bistability behavior.
Kobulnicky H.A., Chick W.T., Povich M.S.
<Astron. J., 158, 73-73 (2019)>
=2019AJ....158...73K 2019AJ....158...73K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, early-type ; Stars, OB ; Nebulae ; Spectral types ;
Stars, masses ; Effective temperatures ; Stars, diameters ;
Stars, distances ; Radial velocities ; Spectroscopy
Keywords: H II regions - stars: massive - surveys
Abstract:
Second only to initial mass, the rate of wind-driven mass loss determines
the final mass of a massive star and the nature of its remnant. Motivated
by the need to reconcile observational values and theory, we use a recently
vetted technique to analyze the mass-loss rates in a sample of OB stars
that generate bow shock nebulae. We measure peculiar velocities from new
Gaia parallax and proper motion data and their spectral types from new
optical and infrared spectroscopy. For our sample of 70 central stars in
morphologically selected bow shock nebulae, 67 are OB stars. The median
peculiar velocity is 11 km/s, significantly smaller than classical
"runaway star" velocities. Mass-loss rates for these O and early B stars
agree with recently lowered theoretical predictions, ranging
from ∼10-7 M☉/yr for mid-O dwarfs to 10-9 M☉/yr for
late O dwarfs - a factor of about 2.7 lower than the often-used Vink et al.
(2000A&A...362..295V 2000A&A...362..295V, 2001A&A...369..574V 2001A&A...369..574V) formulation. Our results
provide the first observational mass-loss rates for B0-B3 dwarfs and
giants - 10-9 to 10-8 M☉/yr. We find evidence for an increase
in the mass-loss rates below a critical effective temperature, consistent
with predictions of the bistability phenomenon in the range
Teff=19000-27000 K. The sample exhibits a correlation between modified
wind momentum and luminosity, consistent in slope but lower by 0.43 dex
in magnitude compared to canonical wind-luminosity relations. We identify
a small subset of objects deviating most significantly from theoretical
expectations as probable radiation-driven bow wave nebulae by virtue
of their low stellar-to-nebular luminosity ratios. For these, the inferred
mass-loss rates must be regarded as upper limits.
Description:
We acquired new optical spectra of 15 candidate bow shock stars using
the Double Imaging Spectrograph (DIS) at the Apache Point Observatory
(APO) 3.5 m telescope on the nights of 2018 May 12 and 19, and June 13.
The 1200 line/mm gratings in both the red and blue arms of the spectrograph
yielded reciprocal dispersions of 0.58 and 0.62 Å/pix, respectively,
over wavelength ranges 5700-6900 Å and 4200-5500 Å, respectively.
We observed 25 stars (four of these were also observed with the DIS optical
spectrograph) using the TripleSpec (Wilson et al. 2004SPIE.5492.1295W 2004SPIE.5492.1295W)
infrared cross-dispersed echelle spectrograph at APO on the nights of
2017 July 13, 2017 August 30, 2017 September 1 and 8, 2017 October 9,
2018 May 29, and 2018 June 3 and 24. The spectrograph yields continuous
spectral coverage between 0.95 and 2.4 µm at a resolution of about
R∼3500 (85 km/s) using a 1.1" slit aligned at the parallactic angle.
We have supplemented these new spectroscopic data with 19 stars observed
in the red portion of the optical spectrum with the optical longslit
spectrograph at the Wyoming Infrared Observatory (WIRO; to be reported
in W. T. Chick et al. 2019, in preparation).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 106 70 Measured and adopted parameters for stars
and their bow shock nebulae
table2.dat 78 70 Kinematic data for bow shock stars
table3.dat 100 70 Derived parameters for stars and their bow shock
nebulae
--------------------------------------------------------------------------------
See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars
(Pecaut+, 2013)
J/ApJS/227/18 : Candidate stellar bowshock nebulae from MIR
(Kobulnicky+, 2016)
J/AJ/154/201 : IR properties of stellar bowshock nebulae
(Kobulnicky+, 2017)
J/AJ/157/176 : X-ray emission from Galactic stellar bow shocks
(Binder+, 2019)
J/MNRAS/488/1141 : Milky Way Project DR2 bubbles + bow shocks
(Jayasinghe+, 2019)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/709] Identifier from Kobulnicky et al.
(2016, J/ApJS/227/18)
5 A1 --- n_ID [a] Note on ID (1)
7- 21 A15 --- Alias Common name
23- 39 A17 --- Name Generic identifier in Galactic coordinates
(GLLL.llll+BB.bbbb)
41- 48 A8 --- SpType Spectral classification
50- 54 I5 K Teff [3800/41500] Adopted effective temperature
(2)
56- 59 F4.1 Rsun R* [4.3/50] Stellar radius based on spectral
classification using the theoretical scale
of Martins et al. (2005A&A...436.1049M 2005A&A...436.1049M)
61- 64 F4.1 Msun Mass [1.1/58] Adopted stellar mass
66- 71 F6.1 km/s Vinf [500/3000]? Adopted terminal wind velocity
from Mokiem et al. (2007A&A...473..603M 2007A&A...473..603M)
73- 76 I4 pc Dist [112/5295] Adopted distance (3)
78- 82 F5.1 arcsec R01 [1.9/299] Standoff distance in arcsec
84- 88 F5.3 pc R02 [0.015/1.905] Standoff distance in pc (4)
90- 92 I3 10+7Jy/sr Peak70 [8/764] Peak 70 µm surface brightness
above adjacent background
94- 96 I3 arcsec l [6/277] Angular diameter of the nebula
defined by a chord intersecting the location
of the peak surface brightness
98-100 A3 --- Obs Source(s) of spectroscopy (5)
102-106 I5 --- L*/LIR [0/22422] Ratio of stellar to infrared
nebular luminosity L*/LIR
--------------------------------------------------------------------------------
Note (1): Note as follows:
a = This object was incorrectly identified in Kobulnicky et al. (2016,
J/ApJS/227/18). The star's coordinates and name have been corrected here.
Note (2): Adopted effective temperature based on spectral classification using
the theoretical scale of Martins et al. (2005A&A...436.1049M 2005A&A...436.1049M) and extrapolated
to early B stars as in Pecaut & Mamajek (2013, J/ApJS/208/9).
Note (3): Adopted distance, from Gaia parallax-based distances estimated by
Bailer-Jones et al. (2018, Cat. I/347).
Note (4): Standoff distance using the adopted distance and angular size adjusted
by a statistical factor of 1.1 for projection effects.
Note (5): Source of spectroscopy as follows:
O = Optical spectroscopy from APO;
I = Infrared spectroscopy from APO;
C = Optical spectra from W. T. Chick et al. (2019, in preparation);
L = Literature spectral classifications.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/709] Identifier from Kobulnicky et al.
(2016, J/ApJS/227/18)
5- 21 A17 --- Name Generic identifier in Galactic coordinates
(GLLL.llll+BB.bbbb)
23- 41 I19 --- Source Gaia DR2 identifier (Cat. I/345)
43- 46 I4 km/s HRV [-108/71]? Heliocentric radial velocity
measured or adopted, as described in
the Appendix
48- 51 I4 mas Plx [148/8910] Gaia DR2 parallax
53- 55 I3 mas e_Plx [26/785] Uncertainty in Plx
57- 61 I5 mas/yr pmRA [-7909/15260] Gaia DR2 proper motion in RA
(pmRA*cosDE)
63- 66 I4 mas/yr e_pmRA [29/1377] Uncertainty in pmRA
68- 73 I6 mas/yr pmDE [-12128/24790] Gaia DR2 proper motion in DE
75- 78 I4 mas/yr e_pmDE [39/1206] Uncertainty in pmDE
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/709] Identifier from
Kobulnicky et al. (2016, J/ApJS/227/18)
5- 19 A15 --- Alias Common name
21- 37 A17 --- Name Generic identifier in Galactic
coordinates (GLLL.llll+BB.bbbb)
39- 46 A8 --- SpType Spectral classification
48- 53 F6.3 10+4Lsun Lum [0.005/87] Stellar luminosity (computed
from the effective temperature and
radius in Table 1)
55- 57 I3 10+2 U [0/338] Dimensionless ratio of the
radiant energy density (in erg/cm3)
from the star to the mean interstellar
radiant energy density estimated by
Mathis et al. (1983A&A...128..212M 1983A&A...128..212M)
59- 61 I3 10-13Jy/sr/cm2 jv [0/302] Dust emission coefficient jv
(in 10-13 Jy/sr/cm2 per nucleon)
following Draine & Li
(2007ApJ...657..810D 2007ApJ...657..810D), after scaling
by the factor fj
63- 66 F4.2 --- fj [1.6/4.48] Scale factor, fj, for dust
emission coefficients on account of the
harder radiation field near OB stars,
as described in the text
68- 71 I4 cm-3 na [4/2111] Computed ambient interstellar
number density, following Equation (5)
of Kobulnicky et al.
(2018ApJ...856...74K 2018ApJ...856...74K)
73- 76 F4.1 km/s Vtot [5/78.1] Peculiar velocity in the star's
local standard of rest (1)
78- 81 F4.1 km/s e_Vtot [0.1/14.3] Uncertainty in Vtot
83- 88 I6 10-10Msun/yr M [3/197923]? Computed mass-loss rate
90- 94 I5 10-10Msun/yr e_M [1/72806]? Uncertainty in M (2)
96-100 F5.2 [-] DlogM [-2.05/4.04]? The base 10 logarithm of
our derived mass-loss rate minus the
logarithm of the theoretical
Vink et al. (2001A&A...369..574V 2001A&A...369..574V)
mass-loss rate, Δlog(M) (3)
--------------------------------------------------------------------------------
Note (1): An arbitrary minimum of 5 km/s has been imposed. Velocities include
only the two plane-of-sky components and not the radial component, as
discussed in the text.
Note (2): Uncertainties do not include the uncertainties on the star's peculiar
velocity and, hence, are lower limits.
Note (3): After correcting the theoretical values downward by 0.12 dex on
account of the revision to the solar abundance scale since that work. For
G012.3407-00.3949, G078.5197+01.0652, G287.4071-00.3593, G288.3138-01.3085,
and G359.9536-00.5088, we have divided the mass-loss rate by a factor of 2 in
order to account for the double nature of these sources. There are certain to
be other unidentified binaries among our sample.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 26-Sep-2019