Proposal Number: 1520017 PI Last Name: Fuerst Title: The magnetic field of EXO 2030+375 Abstract: We propose coordinated INTEGRAL and NuSTAR observations of EXO 2030+375 during one of its next Type I outbursts close to periastron. These observations will allow us to search for a cyclotron line in the hard X-ray spectrum and thereby constrain the magnetic field of the neutron star. Previous INTEGRAL observations found weak evidence for a CRSF around 63 keV. With our proposed observations will be able to confirm (or rule out) this line and at the same time search for lines at lower energies (e.g., around 35 keV, which could be the fundamental line of the claimed feature at 63 keV). Only the combination of NuSTAR and INTEGRAL provide the necessary coverage of the hard X-ray spectrum between 5-200 keV. We will also perform phase-resolved spectroscopy to study the accretion geometry close to the neutron star and search for variability of the CRSF parameters. This will allow us to constrain the magnetic field and emission pattern of EXO 2030+375 better.
Proposal Number: 1540022 PI Last Name: Tsygankov Title: Measuring the High Energy Emission of Millisecond X-Ray Pulsars in Outburst Abstract: We propose to perform two 170 ks INTEGRAL ToO observations of a transient millisecond X-ray pulsar in outburst. To constrain the broadband spectrum we also request one 30 ks simultaneous NuSTAR and two 50 ks XMMNewton observations. The target can be either one of the fifteen known transient accreting millisecond X-ray pulsars (AMXPs) in the case of a new outburst or a "newly" observed object of this class. These observations allow us to study the broad band spectrum in detail from hard to soft X-ray energies as well as the timing properties or eclipsing features of the source during its outburst. The high-statistics spectral information make it possible to disentangle the contributions of soft black body, reflection (if any) and hard Comptonized spectral components. Moreover, we will detect type-I X-ray bursts, and/or for the first time also burst oscillations at high-energy (if present). In particular we will be able to study the energy spectrum in a broad energy range (0.1-300 keV) and with unprecedented high-sensitivity above 20 keV. The INTEGRAL and XMM-Newton observations will also allow a timing analysis to study the pulse profile, time lags and pulsed spectrum, and so will provide important constraints on emission mechanisms.Similar proposals were approved for the INTEGRAL AO2-AO14 cycles, and during these years our ToO has been triggered eight times, i.e., in 2003 we observed XTE J1807-294, in 2004, 2005, 2009, 2011, and 2013 we triggered on newly discovered sources IGR J00291+5934, HETE 1900.1-2455, IGR J17511- 3057, IGR J17498-2921, and IGR J18245-2452, respectively. In 2015, we triggered on IGR J00291+5934 and SAX J1748.5-2021 (data have been made public, because it was not clear whether the source in outburst was the AMXP).
Proposal Number: 1640015 PI Last Name: Kreykenbohm Title: New cyclotron lines in transient pulsars Abstract: We propose a Target of Opportunity observation of a transient accreting X-ray pulsar during a bright outburst for which no cyclotron lines are known so far. We aim to detect cyclotron lines in transient pulsars to extend the list of sources with known cyclotron lines. We propose to perform a 400 ksec long single observation during the peak of the outburst to obtain a spectrum with a very high signal to noise ratio to be able to search also for rather shallow cyclotron lines or CRSFs at energies above 50 keV in the steeply falling part of the continuum. Furthermore we propose to coordinate the INTEGRAL observation with a 20 ksec long NuStar observation to cover also the energy range between 10 keV and 25 keV.
Proposal Number: 1640021 PI Last Name: Alfonso-Garzon Title: Studying the connection between the circumstellar disk and the accretion rate for the Be/XRB system H 1145-619 Abstract: H 1145-619 is a Be/X-ray binary pulsar which displayed frequent, bright outbursts in the 70s to 90s. However, since the advent of modern X-ray astronomy it has remained in a nearly quiescent state. We have compiled the optical and X-ray light evolution of this system, spanning ~40 years, and have found signs of an ongoing replenishment of the Be circumstellar disk. This replenishment suggests that a bright X-ray outburst may happen during the next periastron passages. Therefore, in this proposal we solicit TOO observations of the system in case an X-ray outburst is detected during the 6 April or 9 October 2019 periastron passages. We request to perform one INTEGRAL 170 ks observation during the rising phase of the outburst and one NuSTAR 40 ks observation close to the peak of the outburst, complemented by Swift/XRT monitoring in soft X-rays (seven 1 ks observations every two days). With these observations we expect to model the broad-band spectrum of the source with newly developed physical models and to study the pulse profile variations in different energy bands. We will compare our results with those from previous X-ray outbursts from the 90s, obtained with poorer spectral resolution, and search for cyclotron lines, not detected so far in this system. We will also study the absorption column and spectral variations over the outburst, and determine the orbit elements of the system. The Optical Monitoring Camera (OMC) onboard INTEGRAL will provide simultaneous optical photometry of the source. To complement these observations, we plan to perform simultaneous H-alpha spectroscopy with SALT, to characterize the evolution of the BE disk.
Proposal Number: 1720024 PI Last Name: Staubert Title: Monitoring the cyclotron line energy in Hercules X-1: search for a turn-up and securing the INTEGRAL calibration Abstract: We propose to continue the study of the long-term evolution of the cyclotron line energy Ecyc in Her X-1. The longterm decay of Ecyc discovered in data taken between 1993 and 2012 had amounted to ~ 5 keV over 20 yrs. The observing campaign in 2016, coordinated between NuSTAR and INTEGRAL, had provided evidence that the decay has ended. This has been confirmed by further NuSTAR observations, showing that the flux corrected cyclotron line energy is very stable at ~37.5 keV - actually since about 2012. It is now the question whether we will (at some time) see a new increase, similar to the one that was observed between 1990 and 1993, due toa possible evolution of the magnetic field configuration at the "accretion mounds" formed by matter accumulated in the polar regions of the neutron star. The remarkable spectral stability shown so far by Her X-1 and its relatively high X-ray flux at high energies during the Main On states, make this source a good calibration target for IBIS/ISGRI, whose performances have recently become more problematic due to the aging of the instrument. In this regard, we have started a collaboration with the INTEGRAL team at ISDC using the Her X-1 data obtained in the previous cycle of observations carried out with INTEGRAL and NuSTAR and we believe it will be useful to continue this effort for a successful future use of IBIS/ISGRI. For both reasons, science and inter-calibration, we therefore propose two further INTEGRAL observations of 200 ks each (about half a year apart) of Her X-1 during AO-17 (with both SPI and IBIS operational), in coordination with observations by NuSTAR.
Proposal Number: 1740029 PI Last Name: La Placa Title: Measuring the High Energy Emission of Millisecond X-Ray Pulsars in Outburst Abstract: We propose to perform two 170 ks INTEGRAL ToO observations of a transient millisecond X-ray pulsar in outburst.To constrain the broadband spectrum we also request one 30 ks simultaneous NuSTAR and two 50 ks XMM-Newton observations. The target can be either one of the eighteen known transient accreting millisecond Xray pulsars (AMXPs) in the case of a new outburst or a "newly" observed object of this class. These observations allow us to study the broad band spectrum in detail from hard to soft X-ray energies as well as the timing properties or eclipsing features of the source during its outburst. The high-statistics spectral information make it possible to disentangle the contributions of soft black body, reflection (if any) and hard Comptonized spectral components. Moreover, we will likely detect type-I X-ray bursts, and/or for the first time also burst oscillations at high-energy (if present). In particular we will be able to study the energy spectrum in a broad energy range (0.1-300 keV) and with unprecedented high-sensitivity above 20 keV. The INTEGRAL and XMM-Newton observations will also allow a timing analysis to study the pulse profile, time lags and pulsed spectrum, and so will provide important constraints on emission mechanisms. Similar proposals were approved for the INTEGRAL AO2-AO16 cycles, and during these years our ToO has been triggered eight times, i.e., in 2003 we observed XTE J1807-294, in 2004, 2005, 2009, 2011, and 2013 we triggered on newly discovered sources IGR J00291+5934, HETE J1900.1-2455, IGR J17511- 3057, IGR J17498-2921, and IGR J18245-2452, respectively. In 2015, we triggered on IGR J00291+5934 and SAX J1748.9-2021, and in 2018 we triggered again on a newly discovered source IGR J17591-2342.
Proposal Number: 1740033 PI Last Name: Alfonso-Garzon Title: Studying the connection between the circumstellar disk and the accretion rate for the Be/XRB system H 1145-619 Abstract: H 1145-619 is a Be/X-ray binary pulsar which displayed frequent, bright outbursts in the 70s to 90s. However, since the advent of modern X-ray astronomy it has remained in a nearly quiescent state. We have compiled the optical and X-ray light evolution of this system, spanning ~40 years, and have found signs of an ongoing replenishment of the Be circumstellar disk. This replenishment suggests that a bright X-ray outburst may happen during the next periastron passages. Therefore, in this proposal we solicit TOO observations of the system in case an X-ray outburst is detected during the 6 April or 9 October 2019 periastron passages. We request to perform one INTEGRAL 170 ks observation during the rising phase of the outburst and one NuSTAR 40 ks observation close to the peak of the outburst, complemented by Swift/XRT monitoring in soft X-rays (seven 1 ks observations every two days). With these observations we expect to model the broad-band spectrum of the source with newly developed physical models and to study the pulse profile variations in different energy bands. We will compare our results with those from previous X-ray outbursts from the 90s, obtained with poorer spectral resolution, and search for cyclotron lines, not detected so far in this system. We will also study the absorption column and spectral variations over the outburst, and determine the orbit elements of the system. The Optical Monitoring Camera (OMC) onboard INTEGRAL will provide simultaneous optical photometry of the source. To complement these observations, we plan to perform simultaneous
Proposal Number: 1840002 PI Last Name: Siegert Title: R-Process Elements from Neutron Star Mergers Abstract: The first simultaneous detection of a long-lasting gravitational wave signal (GW170817), together with prompt electromagnetic emission only 1.7 s after (GRB170817A), proved the connection between binary neutron star mergers (NSMs) and short gamma-ray bursts (sGRBs). While the prompt emission is now believed to be fully explained by synchrotron radiation, the delayed emission days to weeks after the merger, is thought to originate from radioactive decays of freshly-produced r-process elements during the NSM. While these "kilonova" signatures have been measured only indirectly at UVOIR wavelengths, the direct proof of radioactivity being the true heating source is still missing. Similar to supernovae, merging NSs produce large amounts of nucleosynthesis products that are ejected into the interstellar medium. Because this environment is neutron-rich, fast neutron capture reactions dominate over beta-decays (r-process), and is expected to form characteristic abundance patterns with three distinct peaks at atomic mass numbers, A, around 80, 130, and 200. The decay of these isotopes happens on a time scale of days to weeks, and the emitted gamma-rays, in the range between ~3 and ~3000 keV, have a high chance to escape the NSM. Only INTEGRAL/SPI and NuSTAR are capable to observe this radiation and to distinguish between individual r-process elements by their characteristic gamma-ray lines. We propose a 1.5 Ms ToO observation with INTEGRAL of a nearby (< 1 Mpc) NSM, together with contemporaneous NuSTAR observations (100 ks), to directly measure r-process element nucleosynthesis.
Proposal Number: 1840005 PI Last Name: Li Title: Measuring the High Energy Emission of Millisecond X-Ray Pulsars in Outburst Abstract: We propose to perform two 170 ks INTEGRAL target of opportunity (ToO) observations of a transient millisecond X-ray pulsar in outburst. To constrain the broadband spectrum we also request one 30 ks simultaneous NuSTAR and two 50 ks XMM-Newton observations. The target can be either one of the nineteen known transient accreting millisecond X-ray pulsars (AMXPs) under going a new outburst, or a "newly" discovered object of this class. These observations will allow us to study the broad band spectrum in detail, from hard to soft X-ray energies, as well as the timing properties or eclipsing features of the source during its outburst. The high signal-to-noise spectral information will make it possible to disentangle the contributions of soft black body, reflection (if any), and hard Comptonized spectral components. Moreover, we may detect type-I X-ray bursts, and/or for the first time also burst oscillations at high-energy (if present). In particular we will be able to study the energy spectrum in a broad energy range (0.1-300 keV) and with unprecedented high sensitivity above 20 keV. The INTEGRAL, NuSTAR, NICER, HXMT and XMM-Newton observations will also allow a timing analysis to study the pulse profile, time lags and pulsed spectrum, and will thus provide important constraints on emission mechanisms. Similar proposals were approved for the INTEGRAL AO2-AO17 cycles, and during these years our ToO has been triggered ten times: in 2003 we observed XTE J1807-294, in 2004, 2005, 2009, 2011, and 2013 we triggered on newly discovered sources IGR J00291+5934, HETE J1900.1-2455, IGR J17511-3057, IGR J17498-2921, and IGR J18245-2452, respectively. In 2015, we triggered on IGR J00291+5934 and SAX J1748.9-2021, and in 2018 we triggered again on a newly discovered source IGR J17591-2342 and Swift J1756.9-2508.
Proposal Number: 1840021 PI Last Name: Kreykenbohm Title: Searching For New Cyclotron Lines in Transient Pulsars Title: We propose a Target of Opportunity observation of a transient accreting X-ray pulsar during a bright outburst to study the flux dependency of a newly detected cyclotron line. Using our accepted NuSTAR TOO proposal, we will observe an accreting X-ray pulsar in outburst. If we detect an unknown cyclotron line in that NuSTAR observation, we propose to perform a 400 ksec long INTEGRAL observation during the peak of the outburst coordinated with another 40 ksec NuSTAR observation to obtain a spectrum with a very high S/N. The INTEGRAL and NuSTAR observations together will allow us to constrain the spectral continuum extremely well, permitting us to study any luminosity dependency of the cyclotron line and to find any harmonic line above 50 keV, in the steeply falling part of the continuum.
Proposal Number: 1940020 PI Last Name: Kreykenbohm Title: Searching For New Cyclotron Lines in Transient Pulsars Abstract: We propose a Target of Opportunity observation of a transient accreting X-ray pulsar during a bright outburst to study the flux dependency of a newly detected cyclotron line. Using our NuSTAR TOO proposal, we will observe an accreting X-ray pulsar in outburst. If we detect an unknown cyclotron line in that NuSTAR observation, we propose to perform a 400 ksec long INTEGRAL observation during the peak of the outburst (minimum: 200mCrab) coordinated with another 40 ksec NuSTAR observation to obtain a spectrum with a very high S/N. The INTEGRAL and NuSTAR observations together will allow us to constrain the spectral continuum extremely well, permitting us to study any luminosity dependency of the cyclotron line and to find any harmonic line above 50 keV, in the steeply falling part of the continuum.
Proposal Number: 1940025 PI Last Name: Seigert Title: R-Process Elements from Neutron Star Mergers Abstract: The first simultaneous detection of a long-lasting gravitational wave signal (GW170817), together with prompt electromagnetic emission only 1.7 s after (GRB170817A), proved the connection between binary neutron star mergers (NSMs) and short gamma-ray bursts (sGRBs). While the prompt emission is now believed to be fully explained by synchrotron radiation, the delayed emission days to weeks after the merger, is thought to originate from radioactive decays of freshly-produced r-process elements during the NSM. While these "kilonova" signatures have been measured only indirectly at UVOIR wavelengths, the direct proof of radioactivity being the true heating source is still missing. Similar to supernovae, merging NSs produce large amounts of nucleosynthesis products that are ejected into the interstellar medium. Because this environment is neutron-rich, fast neutron capture reactions dominate over beta-decays (r-process), and is expected to form characteristic abundance patterns with three distinct peaks at atomic mass numbers, A, around 80, 130, and 200. The decay of these isotopes happens on a time scale of days to weeks, and the emitted gamma-rays, in the range between ~3 and ~3000 keV, have a high chance to escape the NSM. Only INTEGRAL/SPI and NuSTAR are capable to observe this radiation and to distinguish between individual r-process elements by their characteristic gamma-ray lines. We propose a 1.5 Ms ToO observation with INTEGRAL of a nearby (< 1 Mpc) NSM, together with contemporaneous NuSTAR observations (100 ks), to directly measure r-process element nucleosynthesis.
Proposal Number: 2040002 PI Last Name: Siegert Title: R-Process Elements From Neutron Star Mergers Abstract: The first simultaneous detection of a long-lasting gravitational wave signal (GW170817), together with prompt electromagnetic emission only 1.7 s after (GRB170817A), proved the connection between binary neutron star mergers (NSMs) and short gamma-ray bursts (sGRBs). While the prompt emission is can be fully explained by synchrotron radiation, the delayed emission days to weeks after the merger, is thought to originate from radioactive decays of freshly-produced r-process elements during the NSM. While these kilonova signatures have been measured only indirectly at UVOIR wavelengths, the direct proof of radioactivity being the true heating source is still missing. Similar to supernovae, merging NSs produce large amounts of nucleosynthesis products that are ejected into the interstellar medium. Because this environment is neutron-rich, fast neutron capture reactions dominate over beta-decays (r-process), and is expected to form characteristic abundance patterns with three distinct peaks at atomic mass numbers, A, around 80, 130, and 200. The decay of these isotopes happens on a time scale of days to weeks, and the emitted gamma-rays, in the range between 3 and 3000 keV, have a high chance to escape the NSM. Only INTEGRAL/SPI, NuSTAR and the future COSI mission are capable to observe this radiation and to distinguish between individual r-process elements by their characteristic gamma-ray lines. We propose a 1.5 Ms ToO observation with INTEGRAL of a nearby (< 1 Mpc) NSM, together with contemporaneous NuSTAR observations (100 ks), to directly measure r-process element nucleosynthesis.
Proposal Number: 2040026 PI Last Name: Fiocchi Title: INTEGRAL-NuSTAR observation of an Ultra Compact X-ray Binaries in outburst Abstract: The study of accretion onto neutron stars and black holes provides a unique window on the physics of strong gravity and dense matter. After the first detection of Gravitational Waves, a renewed interest has grown for the UltraCompact X-ray Binaries (UCXBs), which are likely sources of mHz gravitational waves. We request an INTEGRAL and NuSTAR ToO observation of an UCXB in outburst in a low/hard state (taken from a list of UCXB simultaneously visible by both satellite), for an exposure time of 300 ks and 25 ks for INTEGRAL and NuSTAR, respectively. Observations will be triggered following criteria based on hard X-ray brightening as detected by satellites in operation such as SWIFT, ASTROSAT, HXMT and INTEGRAL. Furthermore, in case of trigger we will also request Swift/XRT and Radio data from available facilities to follow the evolution in the soft X-ray and radio energy bands.The aim of this proposal is to identify the emission of each component as the accretion disk, the corona and the jet and to probe the physical parameters describing these emission components. These results together with comparison of previous data, will be a substantial building block for the improvement in our understanding of the UCXB properties and evolution. The previous spectral analysis and simulated spectra in a broad energy band has demonstrated that only combining Swift, INTEGRAL and NuSTAR instruments, we can discriminate the accretion disc, corona and jet emissions and monitor the physical parameters and timing behavior of a UCXB.
Proposal number: 2140005 PI last name: Fiocchi Title: INTEGRAL-NuSTAR observation of an Ultra Compact X-ray Binaries in outburst Abstract: The study of accretion onto neutron stars and black holes provides a unique window on the physics of strong Gravity and dense matter. After the first detection of Gravitational Waves, a renewed interest has grown for the Ultra-Compact X-ray Binaries (UCXBs), which are likely sources of mHz gravitational waves. We request an INTEGRAL and NuSTAR ToO observation of an UCXB in outburst in a low/hard state (taken from a list of UCXB simultaneously visible by both satellite), for an exposure time of 300 ks and 25 ks for INTEGRAL and NuSTAR, respectively. Observations will be triggered following criteria based on hard X-ray brightening as detected by satellites in operation such as SWIFT, ASTROSAT, HXMT and INTEGRAL. Furthermore, in case of trigger we will also request Swift/XRT and Radio data from available facilities to follow the evolution in the soft X-ray and radio energy bands. The aim of this proposal is to identify the emission of each component as the accretion disk, the corona and the jet and to probe the physical parameters describing these emission components. These results together with comparison of previous data, will be a substantial building block for the improvement in our understanding of the UCXB properties and evolution. The previous spectral analysis (e.g. for 1RXS J180408.9-342058 and 4U 1543-624) and simulated spectra in a broad energy band has demonstrated that only combining Swift, INTEGRAL and NuSTAR instruments, we can discriminate the accretion disc, corona and jet emissions and monitor the physical parameters and timing behavior of a UCXB. This observing AO21 proposal is an updated version of the approved and no-triggered proposal in previous AO20.
Proposal number: 2140012 PI last name: Kreykenbohm Title: Searching For New Cyclotron Lines in Transient Pulsars Abstract: We propose a Target of Opportunity observation of a transient accreting X-ray pulsar during a bright outburst to look for new or unknown harmonic cyclotron lines. We propose to perform a 400 ksec long INTEGRAL observation during the peak of the outburst coordinated with a 40 ksec NuSTAR observation to obtain a spectrum from .5 keV to &100 keV with a very high S/N: while NuSTAR is the perfect choice below .50 keV, INTEGRAL will considerably extend the spectral coverage to higher energies. The INTEGRAL and NuSTAR observations together will therefore allow us to constrain the spectral continuum extremely well, which is crucial to find also a shallow harmonic line in the NuSTAR energy range or a line above 50 keV in the exponentially falling part of the continuum which would not be possible with NuSTAR or INTEGRAL alone.
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