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of all the known galactic black holes , grs 1915 + 105 is undoubtedly the most prolific source of state transitions
. discovered as a transient by granat in 1992 ( ( * ? ? ?
* castro - tirado et al . ) ) , it has remained in outburst for the last 18 years and is typically one of the very brightest sources in the x - ray sky .
it is also one of the most variable : its x - ray lightcurve consists of at least 14 different patterns of variability , most of which are high - amplitude and highly - structured ( ( * ? ? ?
* ; * ? ? ?
* ; * ? ? ?
* belloni et al .  2000 ,
klein - wolt et al .
2002 , hannikainen et al .  2005 ) ) .
it is believed that many of these variability classes , which are labeled with greek letters ( ( * ? ? ?
* belloni et al .  2000 ) ) , are limit cycles of accretion and ejection in an unstable disk ( ( * ? ? ?
* ; * ? ? ?
* ; * ? ? ?
* belloni et al .
1997 , mirabel et al .
1998 , tagger et al .  2004 ) ) .    of its many classes of x - ray variability ,
three of the best studied are the @xmath1 state , which produces steady optically thick jets ( see , e.g. ( * ? ? ?
* ; * ? ? ?
* dhawan et al .
2000 , klein - wolt et al .  2002 ) ) , the @xmath2 state , a wild 30-minute cycle with discrete ejection events ( ( * ? ? ?
* mirabel et al .  1998 ) ) , and the @xmath0 state , which is affectionately known as the ` heartbeat ' state for the similarity of its lightcurve to an electrocardiogram ( see figure 1 , right panel ) and which consists of a slow rise followed by a short bright pulse , repeating with a period of roughly 50 s ( ( * ? ? ?
* taam , chen , & swank 1997 , belloni et al .  2000 ) ) . and
while these variability classes have clearly established strong connections between the accretion disk and the jet , the physical processes behind this disk - jet connection have yet to be completely revealed .
in an effort to quantify the physics of these unusual variability classes and the disk - jet connection in grs 1915 + 105 , we recently analyzed @xmath3 years of high - resolution _ chandra _ hetgs observations of this black hole x - ray binary ( ( * ? ? ?
* neilsen & lee 2009 ) ) and performed follow - up with detailed variability analysis ( ( * ? ? ?
* neilsen et al .
2010b ) ) . in our long - term study , we found that during states dominated by jet activity , the x - ray spectra revealed a broad iron emission line , which we argued must originate when the jet illuminates the inner accretion disk .
in contrast , we found that states where the jet is quenched display strong , narrow , blueshifted absorption lines from a highly - ionized accretion disk wind ( see also ( * ? ? ? * miller et al .
we were able to demonstrate that the strength of this wind is anticorrelated with the _ fractional _ hard x - ray flux , which is therefore a useful diagnostic of both the accretion state and outflow physics .
furthermore , we discovered that the wind carries enough matter away from the black hole to suppress the jet , so that mass ejection is regulated in grs 1915 + 105 ( figure 1 , left panel ) .
state from ( * ? ? ?
* neilsen et al .  ( 2010b ) ) , showing strong flux and ionization changes in the disk wind on timescales of 5 seconds .
the x - ray lightcurve , phase - folded over many cycles , is shown for comparison .
since the x - ray luminosity variations are insufficient to produce the observed ionization variability , our phase - resolved spectral analysis requires changes in the structure of the wind on timescales much less than one minute.,title="fig:",scaledwidth=45.0% ] state from ( * ? ? ?
* neilsen et al .  ( 2010b ) ) , showing strong flux and ionization changes in the disk wind on timescales of 5 seconds .
the x - ray lightcurve , phase - folded over many cycles , is shown for comparison .
since the x - ray luminosity variations are insufficient to produce the observed ionization variability , our phase - resolved spectral analysis requires changes in the structure of the wind on timescales much less than one minute.,title="fig:",scaledwidth=47.0% ]    to explore the implications of this result on short timescales and reveal fast ( 1 s ) changes in the accretion flow , we have also performed the very first phase - resolved spectroscopy of the @xmath0 variability class in grs 1915 + 105 ( ( * ? ? ?
* neilsen et al .  2010b ) ) using a joint _ rxte / chandra _ observation .
through a combination of x - ray timing and both broadband and high - resolution x - ray spectroscopy , we show for the first time that changes in x - ray continuum on timescales of seconds ( as probed by _ rxte _ ) are associated with measurable changes in absorption lines ( _ chandra _ hetgs ) from the accretion disk wind ( fig .  1
, right panel ) .
because the x - ray luminosity does not change enough to produce the observed ionization , the density of the disk wind must be modulated periodically on these timescales ( see ( * ? ? ?
* lee et al .  2002 ) for additional evidence of wind structural changes ) .    from our broadband
spectral analysis , we find spectroscopic evidence for a _ local _ eddington limit ( ( * ? ? ?
* ; * ? ? ?
* fukue 2004 , lin et al .
2009 ) ) and the radiation pressure instability in the inner accretion disk ( e.g.  ( * ? ? ?
* ; * ? ? ?
* lightman & eardley 1974 , belloni et al .
our phase - resolved spectral analysis also allows us to detect bremsstrahlung emission from material evaporating from the inner accretion flow ( see also ( * ? ? ?
* janiuk & czerny 2005 ) ) .
follow - up comprehensive analysis of all _ rxte _ observations of the @xmath0 state ( ( * ? ? ?
* neilsen et al .  2010a ) ) suggest that this periodic evaporation process is an essential component of this strange class of variability .
in summary , our combined x - ray timing and spectral analysis probing timescales from 1 second to 10 years reveals new evidence for physical processes that connect the accretion disk , the radio jet , and the accretion disk wind . because the implied mass loss rate in the wind could be much higher than the accretion rate in the inner disk
, we argue that the wind may be massive enough to play an integral role in grs 1915 + 105 , not only in quenching the jet on long timescales , but also in possibly producing or facilitating transitions between classes of x - ray variability ( ( * ? ? ?
* shields et al .
1986 , neilsen & lee 2009 , luketic et al .
2010 , neilsen et al .
2010b ) ) .
we present new insights about accretion and ejection physics based on joint _ 
 rxte/ chandra _ hetgs studies of rapid x - ray variability in grs 1915 + 105 . 
 for the first time , with fast phase - resolved spectroscopy of the @xmath0 state , we are able to show that changes in the broadband x - ray spectrum ( _ rxte _ ) on timescales of seconds are associated with measurable changes in absorption lines ( _ chandra _ hetgs ) from the accretion disk wind . 
 additionally , we make a direct detection of material evaporating from the radiation - pressure - dominated inner disk . 
 our x - ray data thus reveal the black hole as it ejects a portion of the inner accretion flow and then drives a wind from the outer disk , all in a bizarre cycle that lasts fewer than 60 seconds but can repeat for weeks . 
 we find that the accretion disk wind may be sufficiently massive to play an active role in grs 1915 + 105 , not only in quenching the jet on long timescales , but also in possibly producing or facilitating transitions between classes of x - ray variability .