J/ApJ/751/73 Equivalent widths in η Cat in 1998-2012 (Mehner+, 2012)
Secular changes in eta Carinae's wind 1998-2011.
Mehner A., Davidson K., Humphreys R.M., Ishibashi K., Martin J.C.,
Ruiz M.T., Walter F.M.
<Astrophys. J., 751, 73 (2012)>
=2012ApJ...751...73M 2012ApJ...751...73M
ADC_Keywords: Stars, variable ; Equivalent widths
Keywords: circumstellar matter - stars: emission-line, Be -
stars: individual: Eta Car - stars: variables: general -
stars: winds, outflows
Abstract:
Stellar wind-emission features in the spectrum of eta Carinae have
decreased by factors of 1.5-3 relative to the continuum within the
last 10 years. We investigate a large data set from several
instruments (STIS, GMOS, UVES) obtained between 1998 and 2011 and
analyze the progression of spectral changes in direct view of the
star, in the reflected polar-on spectra at FOS4, and at the Weigelt
knots. We find that the spectral changes occurred gradually on a
timescale of about 10 years and that they are dependent on the viewing
angle. The line strengths declined most in our direct view of the
star. About a decade ago, broad stellar wind-emission features were
much stronger in our line-of-sight view of the star than at FOS4.
After the 2009 event, the wind-emission line strengths are now very
similar at both locations. High-excitation He I and N II absorption
lines in direct view of the star strengthened gradually. The terminal
velocity of Balmer P Cyg absorption lines now appears to be less
latitude dependent, and the absorption strength may have weakened at
FOS4. Latitude-dependent alterations in the mass-loss rate and the
ionization structure of eta Carinae's wind are likely explanations for
the observed spectral changes.
Description:
In this paper we analyzed spectral data obtained with several
instruments between 1998 and 2012. We confirmed the spectral changes
in the wind emission lines first reported by Mehner et al.
(2010ApJ...717L..22M 2010ApJ...717L..22M); HST STIS spectra obtained in 2010 August,
∼170 days after the first discovery, are comparable to the
observations in 2010 March. Furthermore, we analyzed the long-term
development of spectral changes in our direct line-of-sight view of
the star, at FOS4 (position FOS4 in the southeast (SE) lobe of the
Homunculus, 4.5" from the star), and at the Weigelt knots.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------
10 45 03.59 -59 41 04.3 eta Carina = HD 93308
-------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 72 235 *Equivalent widths of broad stellar wind-emission
features (1998-2012)
table2.dat 88 270 Equivalent widths of Hα and Hδ
(1998-2012)
--------------------------------------------------------------------------------
Note on table1.dat: Mainly FeII/CrII blends.
--------------------------------------------------------------------------------
See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/A+A/540/A133 : η Car emission spectrum (1700-10400Å) (Zethson+, 2012)
J/other/NewA/15.108 : UBVRIHa of η Car in 2009 (Fernandez-Lajus+ 2010)
J/ApJS/181/473 : Analysis of the spectrum of η Car (Nielsen+, 2009)
J/A+A/493/1093 : BVRI light curves of η Car (Fernandez-Lajus+, 2009)
J/AJ/135/1249 : The early spectra of eta Carinae (Humphreys+, 2008)
J/ApJS/168/289 : NUV spectrum of eta Car in 2003.5 (Nielsen+, 2007)
J/ApJS/163/173 : UV spectrum of eta Car in 2003.5 (Gull+, 2006)
J/ApJS/157/138 : UV spectrum of eta Car (Nielsen+, 2005)
J/AJ/129/2018 : RXTE scaled fluxes of eta Car (Corcoran+, 2005)
J/A+A/419/215 : Emission lines of Sr filament near η Car (Hartman+, 2004)
J/A+A/343/847 : Geneva Photometry of Eta Car (van Genderen+ 1999)
J/A+AS/133/299 : Long-term spectroscopy of eta Carinae (Damineli+ 1998)
J/A+A/304/415 : uvby-Hb photometry of Eta Car 1992-94 (van Genderen+, 1995)
J/ApJS/71/983 : UV spectrum of eta Car (Viotti+ 1989)
http://etacar.umn.edu/ : HST Treasury Program on eta Carinae
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Inst Instrument code (G1)
10- 13 A4 --- Name Name (G2)
15- 25 A11 "YYYY/MMM/DD" Date Observation date
27- 33 F7.1 d MJD Modified Julian Date
35- 39 F5.3 --- Phase [0.03/2.6] Phase in spectroscopic cycle (G3)
41- 45 F5.2 0.1nm EW458 [2.5/17.3]? EW of 4570-4600Å feature (1)
47- 51 F5.3 0.1nm e_EW458 [0/3.4]? EW458 uncertainty (1)
53- 57 F5.2 0.1nm EW463 [0.1/16.2]? EW of 4614-4648Å feature (1)
59- 62 F4.2 0.1nm e_EW463 [0/3.8]? EW463 uncertainty (1)
64- 67 F4.2 0.1nm EW458p [0.3/6.7]? EW of 4570-4600Å feature
at the FOS4 location (1)
69- 72 F4.2 0.1nm e_EW458p [0/1.3]? EW458p uncertainty (1)
--------------------------------------------------------------------------------
Note (1): Integration range as description; continuum was set at 4600-4610Å
and 4740-4744Å. FOS4 is located 4.5arcsec SE from the star.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Inst Instrument code (G1)
10- 13 A4 --- Name Name (G2)
15- 25 A11 "YYYY/MMM/DD" Date Observation date
27- 33 F7.1 d MJD Modified Julian Date
35- 39 F5.3 --- Phase [0/2.6]? Phase in spectroscopic cycle (G3)
41- 46 F6.2 0.1nm EWHa [459/945]? Hα EW of star (1)
48- 52 F5.2 0.1nm e_EWHa [3/83]? EWHa uncertainty (1)
54- 59 F6.2 0.1nm EWHap [26/653]? Hα EW of FOS4 (1)
61- 66 F6.3 0.1nm e_EWHap [0.13/97.38]? EWHap uncertainty (1)
68- 72 F5.2 0.1nm EWHd [14/36]? Hδ EW of star (2)
74- 77 F4.2 0.1nm e_EWHd [0.01/3.02]? EWHd uncertainty (2)
79- 83 F5.2 0.1nm EWHdp [14.95/21.52]? Hδ EW of FOS4 (2)
85- 88 F4.2 0.1nm e_EWHdp [0.17/2.27]? EWHdp uncertainty (2)
--------------------------------------------------------------------------------
Note (1): Integration between 6520 and 6620Å; continuum at 6500-6510 and
6640-6645Å. FOS4 is located 4.5arcsec SE from the star.
Note (2): Integration between 4085 and 4115Å; continuum at 4077-4078 and
4155-4160Å. FOS4 is located 4.5arcsec SE from the star.
--------------------------------------------------------------------------------
Global notes:
Note (G1): Instrument code as follow:
HST/STIS = CCD spectra covering the wavelength region from 1700 to 10000Å
with spectral resolution R∼5000-10000. HST STIS observations in
1998-2004 and then again in 2009-2010.
VLT/UVES = Eta Car was observed with UVES from 2002 to 2009 in the wavelength
range from 3000 to 8500Å using 0.3" and 0.4" wide slits. The
slits were oriented with constant slit position angle of 160°
and placed at two different positions covering the star and FOS4.
The resolving power was R∼80000-110000.
Gem/GMOS = Gemini GMOS spectra of the central object and FOS4 obtained in
2007-2010. The resolving power was R∼3000-6000.
MII/MIKE = Observations with Magellan II MIKE, obtained in 2010 June, covering
a wavelength region between 3200 and 10000Å, with R∼22000-28000,
or about 10km/s near 4600Å.
IdP/B&C = In 2011 February, June, and December we obtained spectra of
η Car and the FOS4 position with the B&C spectrograph at the
Irenee du Pont telescope at Las Campanas Observatory. The spectral
resolution was R∼2000-4000, or about 100km/s at 4600Å.
CTIO/RC = We obtained low-resolution spectra with the RC spectrograph on the
SMARTS 1.5m CTIO telescope in 2004-2012. The wavelength range
covered were 5650-6970Å with spectral resolution R∼2000.
Note (G2): Name as listed on the Eta Carinae Treasury Project site at
http://etacar.umn.edu/
Note (G3): spectroscopic cycle of 5.54years.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 17-Dec-2013