A Caltech Library Service

Discovery of hard phase lags in the pulsed emission of GRO J1744-28

D'Aì, A. and Burderi, L. and Di Salvo, T. and Iaria, R. and Pintore, F. and Riggio, A. and Sanna, A. (2016) Discovery of hard phase lags in the pulsed emission of GRO J1744-28. Monthly Notices of the Royal Astronomical Society: Letters, 463 (1). L84-L88. ISSN 1745-3925. doi:10.1093/mnrasl/slw112.

[img] PDF - Submitted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We report on the discovery and energy dependence of hard phase lags in the 2.14 Hz pulsed profiles of GRO J1744−28. We used data from XMM–Newton and NuSTAR. We were able to well constrain the lag spectrum with respect to the softest (0.3–2.3 keV) band: the delay shows increasing lag values reaching a maximum delay of ∼12 ms, between 6 and 6.4 keV. After this maximum, the value of the hard lag drops to ∼7 ms, followed by a recovery to a plateau at ∼9 ms for energies above 8 keV. NuSTAR data confirm this trend up to 30 keV, but the measurements are statistically poorer, and therefore, less constraining. The lag-energy pattern up to the discontinuity is well described by a logarithmic function. Assuming this is due to a Compton reverberation mechanism, we derive a size for the Compton cloud Rcc ∼ 120 Rg, consistent with previous estimates on the magnetospheric radius. In this scenario, the sharp discontinuity at ∼6.5 keV appears difficult to interpret and suggests the possible influence of the reflected component in this energy range. We therefore propose the possible coexistence of both Compton and disc reverberation to explain the scale of the lags and its energy dependence.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
D'Aì, A.0000-0002-5042-1036
Additional Information:© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 June 1. Received 2016 June 1; in original form 2016 March 31. Published: 17 June 2016. The High-Energy Astrophysics Group of Palermo acknowledges support from the Fondo Finalizzato alla Ricerca (FFR) 2012/13, project N. 2012-ATE-0390, founded by the University of Palermo. AR gratefully acknowledges the Sardinia Regional Government for the financial support (P.O.R. Sardegna F.S.E. Operational Programme of the Autonomous Region of Sardinia, European Social Fund 2007–2013 – Axis IV Human Resources, Objective l.3, Line of Activity l.3.1). The Palermo and Cagliari University groups acknowledge financial contribution from the agreement ASI-INAF I/037/12/0.
Subject Keywords:line: formation – line: identification – stars: individual: (GRO J1744−28) – X-rays: binaries – X-rays: general
Issue or Number:1
Record Number:CaltechAUTHORS:20160603-084223310
Persistent URL:
Official Citation:A. D'Aì, L. Burderi, T. Di Salvo, R. Iaria, F. Pintore, A. Riggio, A. Sanna; Discovery of hard phase lags in the pulsed emission of GRO J1744−28, Monthly Notices of the Royal Astronomical Society: Letters, Volume 463, Issue 1, 21 November 2016, Pages L84–L88,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67639
Deposited By: Joy Painter
Deposited On:03 Jun 2016 16:15
Last Modified:11 Nov 2021 03:52

Repository Staff Only: item control page