Exploring Wind Episodes in BZ Cam at Indiana University
A study conducted by collaborators at Indiana University delves into wind episodes in BZ Cam, a Nova-like CV, revealing variability, optical characteristics, and orbital ephemeris challenges. Spectral analysis, duty cycles, and episodic properties are explored, providing insight into the nature of wind features in this celestial phenomenon.
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Wind Episodes in BZ Cam Kent Honeycutt Indiana University COLLABORATORS: Stella Kafka, Spitzer Jeff Robertson, ATU Arne Henden, AAVSO Daniel Proga, UNLV Spectra from KPNO,CTIO,WIYN,MMT
BZ Cam (Nova-like CV) Surrounded by faint bow-shaped nebulae, likely related to the wind. P = 221 min i < 40 Wind features in BZ Cam spectra are known to be quite variable (e.g. Ringwald & Naylor 1998; Prinja et al. 2000), but the character of the changes remain poorly defined. BZ Cam is part of program to study CV winds in the optical: 9 spectral runs on BZ Cam, covering many orbits. This is a preliminary analysis of the BZ Cam (and some related) spectra. Photo from Greiner et al. 2001
Optical Study of CV Winds, with emphasis on variability Survey of ~80 mostly northern NL CVs, V < 17.5 Obtain spectral sequences when found active At least two time scales for variability are found: Active/Inactive; time scales of weeks/years? Wind episodes lasting 20-90 min Episodes are mostly resolved using 3-5 min exps mostly spectrally resolved at 3 Ang resolution Episode properties similar from star-to-star, but some systematic differences star-to-star Duty cycle of episodes can differ greatly from star-to-star BZ Cam has very frequent episodes, but (in our preliminary analysis) its other episode properties appear similar to those of other CVs
BZ Cam Ephemeris Good orbital ephemeris needed for two purposes: Correct RVs of wind features for orbital motion Check for any orbital phase dependence of the wind Existing spectroscopic periods of 0.1535d (Lu & Hutchings 1985) and 0.1533d (Patterson et al. 1996) have accumulated too much phase error. Our spect. data: Sequences (averaging 3 hr in length) on 9 nights over 11 months 2005-06. Orbital RV analysis known to be difficult in BZ Cam: confirmed. Different lines have differing RV curves Only the em core of HeI 5876 gave good periodgram results Still had significant gamma changes night-to-night: prewhitening required.
Folded BZ Cam RV Curves for the emission core of HeI 5876 T0 = 2453654.008(2) + 0.15353(4)*E, for to + crossing of gamma by emission core. K = 84(5) km s-1
Movie format for time-lapse images of the changes in 3 spectral lines
BZ Cam Spectral Sequence 17b 2005-Oct-11(UT) KPNO 2.1-m + GoldCam 3A resolution, 3 min exps 40 exp sequence over ~2.6 hrs (Note occasional redshifted emission in H
BZ Cam Spectral Sequence 18 2005-Oct-12(UT) KPNO 2.1-m + GoldCam 3A resolution, 3 min exps 60 exp sequence over ~4.3 hrs
TT Ari Spectral Sequence 28 2005-Oct-27(UT) WIYN 3.5-m + Hydra/MOS 3A resolution, 3 min exps 50 exp sequence over ~4.8 hr (Note redshifted H emission up to 2000 km s-1)
HL Aqr Spectral Sequence 16 2005-Oct-27(UT) WIYN 3.5-m + Hydra/MOS 3A resolution, 5 min exps 36 exp sequence over ~3.8 hr USNO/FS 1-m Photometry
BZ Cam Spectral Sequence 22 2005 Feb-21(UT) WIYN 3.5-m + Hydra/MOS 3A resolution, 5 min exps 42 exp sequence over ~5.2 hrs (considerable clouds)
BZ Cam Spectral Sequence 20 2006-Jan-11(UT) KPNO 4-m + RC 3A resolution, 3 min exps 70 exp sequence over ~2.6 hrs
QUALITATIVE SYSTEMATICS (dominant behaviors/trends, but not without exceptions) He I 5876 (triplet) and H have similar blue absorption velocities from wind He I 6678 (singlet) never has P Cygni profile Typical abs profile starts broad and shallow, evolving to more narrow abs, with lower velocity Blue shifted emission is common, esp in H Red shifted emission sometimes occurs in H , (This is relatively rare in BZ Cam but is common in Q Cyg and is sometimes present in TT Ari (as seen in the movie), and in V795 Her, V592 Cas, and HL Aqr)
EXTRACTING PRELIMINARY QUANTITATIVE SYSTEMATICS Correct RVs for orbital motion Measure strengths and velocities of line components vs time Fit multi-component line profiles Advantage: provides parameters for shapes as well as EW and RV Disadvantages: Must choose number of components Correlations among parameters Measure EW and centroid RV for C.M rest frame window -750 to -2500 km s-1, for em and abs, using direct integration Advantages: -- Fewest assumptions needed -- Errors easier Disadvantages: No shape parameter Central em line can contribute Both fits and integration measures avail: Will discuss only some of the direct integration results today.
Examples of Inactive and active (time scales of days/months) Sequences for BZ Cam MMT 2006-Sep 17 (UT) [Inactive] WIYN 2006-Feb21 (UT) [Active]
Two Examples of Isolated Wind Episodes in BZ Cam KPNO 2.1-m 2005-Oct-11 (UT) KPNO 2.1-m 2005-Oct-12 (UT)
QUANTITATIVE SYSTEMATICS (dominant behaviors/trends, but not without exceptions) Isolated P Cygni abs events start simul. in H and He I, but events last significantly longer in He I. Velocity evolution is same (to within errors) in H and in He I blue abs, declining from -2000 to - 1000 km s-1 during most isolated events (6 of 7 for BZ Cam) H blue emission begins after and peaks after blue absorption events. (Some anticorrelation expected due to EW technique in which both abs and em EWs are extracted from the same spectral window)
Orbital Phase Dependence of the EW of the blue shifted He I 5876 absorption in BZ Cam Most of the variability at a given phase is due to episodes, but there does appear to be some orbital dependence as well. Prinja, Knigge, Witherick, Long, Bammer 2004 reported similar results for V592 Cas, including progression of abs vel from more negative to less negative during episodes.
Resonance line profiles computed as a function of orbital inclination. Proga, Kallman, Drew, Hartley 2002. Unsteady disk outflow in wind simulations of Proga, Stone, Drew 1999. Time scales for filaments are similar to those seen observationally ~500 s However, inhomogeneities are mostly near disk plane, at low velocities
Nature of Wind and Wind Episodes Models of outflows due to radiation pressure are promising but may need to be customized for these kinds of spectra: Non-resonance scattering Time dependent line profiles Are episodes due to lifting (and fall-back) of random wind-driven filaments, or to ballistic-like events? Or from a combination of the two? Random wind-driven filaments will be different front/back while an M-dot initiated ejection event might affect both front and back. The high vel red emission that sometimes appears must be (for low i systems) the backside outflow. If we see both front and backside spectral signatures, are they correlated with each other? or correlated with M-dot? Provides leverage for distinguishing random filaments from ejection common to both front and back? Key may be continuum light from M-dot Correlation with continuum flickering implies initiation of an episode by M-dot.
Simultaneous photometry and spectroscopy 7 partially-successful attempts on 4 different systems; 3 are BZ Cam Many (but not all) were compromised in various ways, such as wind being weak or absent. But BZ Cam has large 0.4 mag flickering in 1 good phot/sp run. KPNO 2.1-m spectra. Tenagra photometry. 2005-Oct-12 (UT)
