* Astronomy

Blobrana · L

RE: MAXI J1659-152

Blobrana · L

Black hole-star pair orbiting at dizzying speed

ESA's XMM-Newton space telescope has helped to identify a star and a black hole that orbit each other at the dizzying rate of once every 2.4 hours, smashing the previous record by nearly an hour.
The black hole in this compact pairing, known as MAXI J1659-152, is at least three times more massive than the Sun, while its red dwarf companion star has a mass only 20% that of the Sun. The pair is separated by roughly a million kilometres.
Read more

Blobrana · L

Title: MAXI J1659-152: The shortest orbital period black-hole transient in outburst
Authors: E. Kuulkers, C. Kouveliotou, T. Belloni, M. Cadolle Bel, M. Diaz Trigo, J. Homan, A. Ibarra, J.A. Kennea, T. Munoz-Darias, J.-U. Ness, A.N. Parmar, A.M.T. Pollock, E.P.J. van den Heuvel, A.J. van der Horst

MAXI J1659-152 is a bright X-ray transient black-hole candidate binary system discovered in September 2010. We report here on MAXI, RXTE, Swift, and XMM-Newton observations during its 2010/2011 outburst. We find that during the first one and a half week of the outburst the X-ray light curves display drops in intensity at regular intervals, which we interpret as absorption dips. About three weeks into the outbursts, again drops in intensity are seen. These dips have, however, a spectral behaviour opposite to that of the absorption dips, and are related to fast spectral state changes (hence referred to as transition dips). The absorption dips recur with a period of 2.414±0.005 hrs, which we interpret as the orbital period of the system. This implies that MAXI J1659-152 is the shortest period black-hole candidate binary known to date. The inclination of the accretion disk with respect to the line of sight is estimated to be 65-80 degrees. We suggest the companion to the black-hole candidate to be an M5 dwarf star, with a mass and radius of about 0.2-0.3 solar masses and 0.2-0.25 solar radii, respectively. We find that the companion had an initial mass of about 1.5 solar masses, which evolved to its current mass in about 5-6 billion years. The system is rather compact (orbital separation of about 1.33 solar radii), and is located at a distance of about 8.6 kpc, with a height above the Galactic plane of about 2.4 kpc. The characteristics of short orbital period and high Galactic scale height are shared with two other transient black-hole candidate X-ray binaries, i.e., XTE J1118+480 and Swift J1735.5-0127. All three are kicked out of the Galactic plane into the halo, rather than being formed in a globular cluster.

Read more (611kb, PDF)

Blobrana · L

Title: The black hole candidate MAXIJ1659-152 in and towards quiescence in X-ray and radio
Authors: Peter G. Jonker, James C.A. Miller-Jones, J. Homan, J. Tomsick, R.P. Fender, P. Kaaret, S. Markoff, E. Gallo

In this paper we report on Expanded Very Large Array radio and Chandra and Swift X-ray observations of the outburst decay of the transient black hole candidate MAXI J1659-152 in 2011. We discuss the distance to the source taking the high inclination into account and we conclude that the source distance is probably 6±2 kpc. The lowest observed flux corresponds to a luminosity of 2x10^31 (d/6 kpc)^2 erg/s This, together with the orbital period of 2.4 hr reported in the literature, suggests that the quiescent X-ray luminosity is higher than predicted on the basis of the orbital period -- quiescent X-ray luminosity relationship. The relation between the accretion and ejection mechanisms can be studied using the observed correlation between the radio and X-ray luminosities as these evolve over an outburst. We determine the behaviour of MAXI J1659-152 in the radio -- X-ray diagram at low X-ray luminosities using the observations reported in this paper and at high X-ray luminosities using values reported in the literature. At high X-ray luminosities the source lies closer to the sources that follow a correlation index steeper than 0.6-0.7. However, when compared to other sources that follow a steeper correlation index, the X-ray luminosity in MAXI J1659-152 is also lower. The latter can potentially be explained by the high inclination of MAXI J1659-152 if the X-ray emission comes from close to the source and the radio emission is originating in a more extended region. However, it is probable that the source was not in the canonical low-hard state during these radio observations and this may affect the behaviour of the source as well. At intermediate X-ray luminosities the source makes the transition from the radio underluminous sources in the direction of the relation traced by the 'standard' correlation similar to what has been reported for H1743-322.

Read more (501kb, PDF)

Blobrana · L

Title: Combined Spectral and Timing Analysis of the Black Hole Candidate MAXI J1659-152 Discovered by MAXI and Swift
Authors: Kazutaka Yamaoka, Ryan Allured, Philip Kaaret, Jamie A. Kennea, Toshihiro Kawaguchi, Poshak Gandhi, Nicholai Shaposhnikov, Yoshihiro Ueda, Satoshi Nakahira, Taro Kotani, Hitoshi Negoro, Ichiro Takahashi, Atsumasa Yoshida, Nobuyuki Kawai, Satoshi Sugita

We report on X-ray spectral and timing results of the new black hole candidate (BHC) MAXI J1659-152 with the orbital period of 2.41 hours (shortest among BHCs) in the 2010 outburst from 65 Rossi X-ray Timing Explorer (RXTE) observations and 8 simultaneous Swift and RXTE observations. According to the definitions of the spectral states in Remillard & McClintock (2006), most of the observations have been classified into the intermediate state. All the X-ray broadband spectra can be modelled by a multi-colour disk plus a power-law with an exponential cutoff or a multi-colour disk plus a Comptonisation component. During the initial phase of the outburst, a high energy cutoff was visible at 30-40 keV. The innermost radius of the disk gradually decreased by a factor of more than 3 from the onset of the outburst and reached a constant value of 35 d_10 cos i^-½ km, where d_10 is the distance in units of 10 kpc and i is the inclination. The type-C quasi-periodic oscillation (QPO) frequency varied from 1.6 Hz to 7.3 Hz in association with a change of the innermost radius, while the innermost radius remained constant during the type-B QPO detections at 1.6-4.1 Hz. Hence, we suggest that the origin of the type-B QPOs is different from that of type-C QPOs, the latter of which would originate from the disk truncation radius. Assuming the constant innermost radius in the latter phase of the outburst as the innermost stable circular orbit, the black hole mass in MAXI J1659-152 is estimated to be 3.6-8.0 solar masses for a distance of 5.3-8.6 kpc and an inclination angle of 60-75 degrees.

Read more (1255kb, PDF)

Blobrana · L

Title: Swift Observations of MAXI J1659-152: A Compact Binary with a Black Hole Accretor
Authors: J.A. Kennea, P. Romano, V. Mangano, A.P. Beardmore, P.A. Evans, P.A. Curran, H.A. Krimm, C.B. Markwardt, K.Yamaoka

We report on the detection and follow-up high cadence monitoring observations of MAXI J1659-152, a bright Galactic X-ray binary transient with a likely black-hole accretor, by Swift over a 27 day period after its initial outburst detection. MAXI J1659-152 was discovered almost simultaneously by Swift and MAXI on 2010 Sept 25, and was monitored intensively from the early stages of the outburst through the rise to a brightness of ~0.5 Crab by the Swift XRT, UVOT, and BAT. We present temporal and spectral analysis of the Swift observations. The broadband light-curves show variability characteristic of black-hole candidate transients. We present the evolution of thermal and non-thermal components of the 0.5-150 keV combined X-ray spectra during the outburst. MAXI J1659-152 displays accretion state changes typically associated with black-hole binaries, transitioning from its initial detection in the Hard State, to the Steep Power-Law State, followed by a slow evolution towards the Thermal State, signified by an increasingly dominant thermal component associated with the accretion disk, although this state change did not complete before Swift observations ended. We observe an anti-correlation between the increasing temperature and decreasing radius of the inner edge of the accretion disk, suggesting that the inner edge of the accretion disk in-falls towards the black-hole as the disk temperature increases. We observed significant evolution in the absorption column during the initial rise of the outburst, with the absorption almost doubling, suggestive of the presence of an evolving wind from the accretion disk. We detect quasi- periodic oscillations that evolve with the outburst, as well as irregular shaped dips that recur with a period of 2.42±0.09 hours, strongly suggesting an orbital period that would make MAXI J1659-152 the shortest period black-hole binary yet known.

Read more (86kb, PDF)

Blobrana · L

Title: The identification of MAXI J1659-152 as a black hole candidate
Authors: M. Kalamkar, J. Homan, D. Altamirano, M. van der Klis, P. Casella, M. Linares
(Version v2)

We report on the analysis of all 65 pointed Rossi X-ray Timing Explorer observations of the recently discovered soft X-ray transient MAXI J1659-152 (initially referred to as GRB 100925A). The source was studied in terms of its evolution through the hardness-intensity diagram (HID) as well as its X-ray variability properties. MAXI J1659-152 traced out an anti-clockwise loop in the HID, which is commonly seen in transient low-mass X-ray binaries. The variability properties of the source, in particular the detection of type-B and type-C low-frequency quasi-periodic oscillations, and the way they evolve along the HID track, indicate that MAXI J1659-152 is a black hole candidate. The spectral and variability properties of MAXI J1659-152 imply that the source was observed in the hard and soft intermediate states during the RXTE observations, with several transitions between these two states.

Read more (83kb, PDF)

Blobrana · L

Title: The identification of MAXI J1659-152 as a black hole candidate
Authors: M. Kalamkar, J. Homan, D. Altamirano, M. van der Klis, P. Casella, M. Linares

We report on the analysis of all 65 pointed Rossi X-ray Timing Explorer observations of the recently discovered soft X-ray transient MAXI J1659-152 (initially referred to as GRB 100925A). The source was studied in terms of its evolution through the hardness-intensity diagram (HID) as well as its X-ray variability properties. MAXI J1659-152 traced out an anti-clockwise loop in the HID, which is commonly seen in transient low-mass X-ray binaries. The variability properties of the source, in particular the detection of type-B and type-C low-frequency quasi-periodic oscillations, and the way they evolve along the HID track, indicate that MAXI J1659-152 is a black hole candidate. The spectral and variability properties of MAXI J1659-152 imply that the source was observed in the hard and soft intermediate states during the RXTE observations, with several transitions between these two states.

Read more (78kb, PDF)