A tale of 115 photons: a new, faint population of X-ray transients

as presented at Journal Club on 14 April 2017

Transcript

1. “A New, Faint Population of X-ray Transients” (Bauer et al. 2017) Anna Ho Journal Club 14 April 2017 1 A tale of 115 photons: (±10)
2. 2 “A New, Faint Population of X-ray Transients” (Bauer et al. 2017)
3. 3 “Discovery of a New Kind of Explosive X-Ray Transient Near M86” (Jonker et al. 2013) “Two fast X-ray transients in archival Chandra data” (Glennie et al. 2015) “Ultraluminous X-ray bursts in two ultracompact companions to nearby elliptical galaxies” (Irwin et al. 2016, Nature) “A New, Faint Population of X-ray Transients” (Bauer et al. 2017)
4. 4 “Discovery of a New Kind of Explosive X-Ray Transient Near M86” (Jonker et al. 2013) “Two fast X-ray transients in archival Chandra data” (Glennie et al. 2015) “Ultraluminous X-ray bursts in two ultracompact companions to nearby elliptical galaxies” (Irwin et al. 2016, Nature) Ariel V (Pye & McHardy 1983) “A New, Faint Population of X-ray Transients” (Bauer et al. 2017) HEAO-1 (Ambruster et al. 1986) Einstein (Gotthelf et al. 1996) ROSAT (Greiner et al. 1999) WATCH (Castro-Tirado et al. 1999) BeppoSAX (Heise et al. 2001) MAXI (Serino et al. 2014)
5. “A New, Faint Population of X-ray Transients” (Bauer et al. 2017) 1. Context and the discovery 2. Temporal properties (light curve) 3. Spectral properties (spectrum) 4. Multi-wavelength imaging (host, transient counterpart) 5. Archival search and rate estimate 6. Physical possibilities 7. Next steps
6. Context: “fast X-ray transients” vary on timescales from seconds to hours. 6
7. Context: “fast X-ray transients” vary on timescales from seconds to hours. 6 Stellar flares X-ray binaries Galactic sources:
8. Context: “fast X-ray transients” vary on timescales from seconds to hours. 6 Stellar flares X-ray binaries Galactic sources: Extragalactic sources: Gamma-ray burst (GRB), X-Ray Flash (XRF) Tidal disruption event (TDE) Supernova shock breakout (SBO)
9. The Bauer burst was detected in the Chandra Deep Field-South (CDF-S). 7 0.3-1 keV 1-2 keV 2-7 keV
10. There were 115 photons measured in the 0.3-10 keV spectral range. 8 Figure adapted from Bauer et al. (2017) Counts 30 20 10 0 ~2 mins ~7 hours
11. There were 115 photons measured in the 0.3-10 keV spectral range. 9 Figure adapted from Bauer et al. (2017) Counts 30 20 10 0 ~2 mins ~7 hours F / t 1.53 peak flux: 5 x 10-12 erg/s/cm2
12. 10 Figure adapted from Bauer et al. (2017) log(counts/s/keV) 0 -1 -2 0.5 keV -3 -4 -5 1 keV 2 keV 5 keV There were no clear spectral variations over the course of the detection. early late complete
13. 11 Figure adapted from Bauer et al. (2017) log(counts/s/keV) 0 -1 -2 0.5 keV -3 -4 -5 The spectrum can be fit with an absorbed power law. 1 keV 2 keV 5 keV dN/dE / E = 1.43+0.26 0.15
14. 12 Figure adapted from Bauer et al. (2017) Counts 30 20 10 ~2 mins ~7 hours Hardness 1 0 -1 There is no significant evolution of the hardness ratio (HR). HR = (H-S) / (H+S), H: 2-7 keV, S: 0.3-2 keV
15. Imaging shows a likely mR = 27.5 mag counterpart 13 Figure adapted from Bauer et al. (2017) Chandra detection HST GOODS HST CANDELS
16. Imaging shows a likely mR = 27.5 mag host galaxy 14 Figure adapted from Bauer et al. (2017) Chandra detection HST GOODS HST CANDELS It has zphot ~ 2.2. Assuming that redshift*, an SED fit suggests a dwarf galaxy with MR = -17.3 mag. *the 1-sigma range on zphot is 1.57-2.81, the 3-sigma range is 0.39-3.21
17. There was no transient counterpart detected in optical, near-IR, or radio follow-up imaging. 15 Figure adapted from Bauer et al. (2017) VLT, T+0 VLT, T+18d GMOS T+27d HST T+111d Australian Telescope Compact Array (T+7d), 2-19 GHz neither Swift nor Fermi were looking
19. 16 1. Detection of the transient
20. 16 1. Detection of the transient 2. Temporal properties (light curve)
21. 16 1. Detection of the transient 2. Temporal properties (light curve) fast (~100s rise time), t -1.5 decay
22. 16 1. Detection of the transient 2. Temporal properties (light curve) 3. Spectral properties (spectrum, hardness) fast (~100s rise time), t -1.5 decay
23. 16 1. Detection of the transient 2. Temporal properties (light curve) 3. Spectral properties (spectrum, hardness) fast (~100s rise time), t -1.5 decay no spectral variation, index 1.43
24. 16 1. Detection of the transient 2. Temporal properties (light curve) 3. Spectral properties (spectrum, hardness) 4. Counterparts at other wavelengths (or lack thereof) fast (~100s rise time), t -1.5 decay no spectral variation, index 1.43
25. 16 1. Detection of the transient 2. Temporal properties (light curve) 3. Spectral properties (spectrum, hardness) 4. Counterparts at other wavelengths (or lack thereof) fast (~100s rise time), t -1.5 decay no spectral variation, index 1.43 associated m=27.5 galaxy, z=2.2
26. 16 1. Detection of the transient 2. Temporal properties (light curve) 3. Spectral properties (spectrum, hardness) 4. Counterparts at other wavelengths (or lack thereof) fast (~100s rise time), t -1.5 decay no spectral variation, index 1.43 —> ultraluminous transient L~1046 erg/s associated m=27.5 galaxy, z=2.2
27. 16 1. Detection of the transient 2. Temporal properties (light curve) 3. Spectral properties (spectrum, hardness) 4. Counterparts at other wavelengths (or lack thereof) 5. Archival search and rate estimate 6. Physical possibilities 7. Next steps fast (~100s rise time), t -1.5 decay no spectral variation, index 1.43 —> ultraluminous transient L~1046 erg/s associated m=27.5 galaxy, z=2.2
28. 17 A Chandra archival search turned up zero candidates “comparable” to this event. “comparable”: 1) no counterpart in 2MASS or WISE, outside Galactic plane 2) similar variability (non-recurrent, similar rise time and decay index) 3) similar spectra (hardness ratio, spectral slope) 4.2+9.7 3.4 The implied rate is events per deg2 per year.
29. 18 Potential interpretations include GRBs, shock breakout, TDEs, and something of Galactic origin.
30. 18 Stellar flares Galactic sources: Potential interpretations include GRBs, shock breakout, TDEs, and something of Galactic origin.
31. 18 Stellar flares Galactic sources: Potential interpretations include GRBs, shock breakout, TDEs, and something of Galactic origin. Extragalactic sources: Gamma-ray burst (GRB), X-Ray Flash (XRF) Tidal disruption event (TDE) Supernova shock breakout (SBO)
32. 19 Stellar flares A stellar flare is unlikely because of the coincident host and the implied luminosity.
33. 20 Extragalactic interpretations include GRBs, TDEs, and shock breakout. Extragalactic sources: Gamma-ray burst (GRB), X-Ray Flash (XRF) Tidal disruption event (TDE) Supernova shock breakout (SBO) lGRB afterglow or flare sGRB
34. 21 The rest-frame LC is most comparable to GRBs, but with different rising behavior. log trest (days) Figure adapted from Bauer et al. (2017) 2 1 -4 -3 log(Luminosity [erg/s]) 40 42 44 46 48 50 52 750 Swift/BAT X-ray GRB afterglows TDE XRF XRF SBO
35. Assuming the event is unique in the dataset, the implied rate is events deg-2 yr-1, roughly comparable to the GRB family 22 Volumetric Rate 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Redshift 4.2+9.7 3.4 Beamed lGRBs Unbeamed lGRBs Supernova shock breakout TDE Beamed sGRBs Unbeamed sGRBs Figure adapted from Bauer et al. (2017)
36. • could these be consistent with the MAXI Unidentified Short Soft Transients (MUSSTs) or with any of the other mysterious short soft transients detected by other wide-field x-ray missions? 23 • tabulate “fast” x-ray transients, cross-match against catalogs, check rates thank you to: Vikram Ravi, Shri Kulkarni, Matthew Graham Next steps?