Skip to main content
Retirement of GCN Classic VOEvent Brokers. See news and announcements

GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. Fermi trigger No 588398821 Global MASTER-Net observations report
  2. LIGO/Virgo S190814bv: MASTER prediscovery and postdiscovery observations DECam candidate DG19wxnjc/AT2019npv field
  3. GRB 190816A: Swift-XRT afterglow detection
  4. LIGO/Virgo S190814bv: No radio counterpart to DG19wxnjc/AT2019npv in ASKAP observations
  5. GRB 190825A: Fermi GBM Final Real-time Localization
  6. GRB 190824A: Swift-XRT refined Analysis
  7. GRB 190824A: Fermi GBM observation
  8. LIGO/Virgo S190814bv: Archival detection of DG19wxnjc/AT2019npv in DES data
  9. Fermi trigger No 588350802 Global MASTER-Net observations report
  10. GRB 190824A: Enhanced Swift-XRT position
  11. Fermi GBM-190816: Updated localization of subthreshold GRB-GW candidate
  12. GRB 190821A: Swift-BAT refined analysis
  13. GRB 190824A: Swift detection of a burst
  14. GRB 190824A: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo S190814bv: Keck NIRES spectroscopy of DG19wxnjc/AT2019npv
  16. LIGO/Virgo S190814bv: Photometric Evolution of DECAM candidates
  17. GRB 190823A: Tiled Swift observations
  18. LIGO/Virgo S190814bv: DESGW photometry of AT2019npv
  19. LIGO/Virgo S190814bv: GROND follow-up observations of AT2019npv
  20. GRB 190823A: MAXI/GSC detection
  21. LIGO/Virgo S190814bv: Further Pan-STARRS z-band observations and AT2019npv photometry
  22. LIGO/Virgo S190814bv: WHT spectroscopy of the host of AT2019npv
  23. Fermi trigger No 588185734 Global MASTER-Net observations report
  24. Fermi GBM-190816: Coverage and upper limits from MAXI/GSC observations
  25. Fermi trigger No 588115134 Global MASTER-Net observations report
  26. GRB 190821A: Swift/UVOT Upper Limits
  27. LIGO/Virgo S190814bv: NIR imaging follow-up of ASKAP transient
  28. GRB 190821A: MASTER VWFC syncronous optical observations
  29. LIGO/Virgo S190814bv: ENGRAVE VLT/HAWK-I observations and archival detection of the CFHT candidate
  30. Fermi GBM-190816: MASTER-Net optical observation report
  31. LIGO/Virgo S190814bv: No radio counterpart detected in ASKAP observations
  32. GRB 190821A: Swift-XRT refined Analysis
  33. LIGO/Virgo S190814bv: a potential faint optical counterpart in CFHT imaging
  34. LIGO/Virgo S190822c: Retraction of GW compact binary merger candidate
  35. LIGO/Virgo S190822c: CLU/NED Galaxies in the 50% Localization Volume
  36. LIGO/Virgo S190822c Global MASTER-Net observations report
  37. LIGO/Virgo S190822c: Upper limits from IceCube neutrino searches
  38. LIGO/Virgo S190814bv: new candidate from DESGW
  39. LIGO/Virgo S190814bv: No Optical Counterpart Candidates in Second-Epoch Lick/KAIT Observations
  40. GRB 190821A: Enhanced Swift-XRT position
  41. GRB 190821A: Fermi GBM observation
  42. Fermi GBM-190816: Upper Limits from Swift/BAT Observations
  43. GRB 190821A: MASTER do not see any afterglow candidate
  44. Fermi GBM-190816: Correction from the Zwicky Transient Facility
  45. GRB 190821A: T60 Les Makes optical detection of the afterglow
  46. Fermi GBM-190816: Four additional candidates from the Zwicky Transient Facility
  47. Swift GRB190821.72 Global MASTER-Net observations report
  48. Fermi trigger No 588100239 Global MASTER-Net observations report
  49. GRB 190821A: Swift detection of a burst
  50. Fermi GBM-190816: No counterpart candidates in Fermi-LAT observations
  51. LIGO/Virgo S190814bv: further candidates from DESGW
  52. Fermi GBM-190816: AGILE in SAA at T0
  53. LIGO/Virgo S190814bv: SOAR spectroscopy of AT2019noq and AT2019ntn
  54. LIGO/Virgo S190814bv: No Counterpart Candidates in Las Cumbres Observatory Galaxy Targeted Search
  55. Fermi GBM-190816: ZTF19abqanpy 10.4m GTC spectroscopy
  56. Fermi-LAT Gamma-ray Observations of IceCube-190819A
  57. LIGO/Virgo S190814bv: AT2019nqq 10.4m GTC spectroscopy
  58. Fermi GBM-190816: One candidate counterpart from the Zwicky Transient Facility
  59. LIGO/Virgo S190814bv: Further Pan-STARRS observations and transient sources
  60. LIGO/Virgo S190814bv: RATIR Optical observations of DECam transients
  61. LIGO/Virgo GBM-190816: no counterpart candidates in the Swift/BAT Observations
  62. Fermi GBM-190816: Upper limits from IceCube neutrino searches
  63. IceCube-190819A: Upper limits from a search for additional neutrino events in IceCube
  64. IceCube-190819A: MASTER analysis
  65. IceCube-190819A - HAWC follow-up
  66. Fermi GBM-190816: No counterpart candidates in HAWC observations
  67. LIGO/Virgo S190814bv: No neutrino candidates at Pierre Auger Observatory
  68. Fermi GBM-190816+LIGO/Virgo : no neutrino counterpart candidate in ANTARES search
  69. Fermi GBM-190816: Location-dependent upper limits from INTEGRAL/SPI-ACS prompt observation
  70. Fermi GBM-190816: A subthreshold GRB candidate potentially associated with a subthreshold LIGO/Virgo compact binary merger candidate
  71. GRB 190816A: Swift-BAT refined analysis
  72. IceCube-190819A: Upper limits from Fermi-GBM Observations
  73. IceCube-190819A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  74. IceCube-190819A - IceCube observation of a high-energy neutrino candidate event
  75. LIGO/Virgo S190814bv: GRAWITA TNG NIR imaging of AT2019nqq and AT2019nqc
  76. LIGO/Virgo S190814bv: No strong counterpart candidates in Swift/XRT observations
  77. GRB 190816A: Swift-XRT observations
  78. LIGO/Virgo S190814bv: DESGW candidate update
  79. LIGO/Virgo S190814bv: No candidates from image subtraction in DCT galaxy targeted search
  80. LIGO/Virgo S190814bv: WIRC NIR imaging follow-up of DECam transients
  81. LIGO/Virgo S190814bv: Keck/MOSFIRE NIR spectroscopy of DG19njmjc (= AT 2019nra)
  82. LIGO/Virgo S190814bv: DG19dnjlc is not offset from its host galaxy
  83. LIGO/Virgo S190814bv: Additional candidates identified in DECam images by the DECam-GROWTH team
  84. LIGO/VIRGO S190814bv: AbAO non-detection of AT2019nme
  85. LIGO/Virgo S190814bv: Prioritization of Counterpart Candidates based on a Photometric Redshift Analysis by the DECam-GROWTH Team
  86. LIGO/Virgo S190814bv: Not observable by CALET
  87. LIGO/Virgo S190814bv: No candidates found in J-GEM follow-up observations
  88. Fermi trigger No 587775150 Global MASTER-Net observations report
  89. GRB 190817A: Fermi GBM Final Real-time Localization
  90. LIGO/Virgo S190814bv: Pan-STARRS imaging indicates DG19sevhc (AT2019npy) is a proper motion star
  91. LIGO/Virgo S190814bv: Fermi-LAT search for a high-energy gamma-ray counterpart
  92. LIGO/Virgo S190814bv : ENGRAVE X-shooter spectra of AT2019nqs and AT2019npy
  93. LIGO/Virgo S190814bv: GRAWITA TNG infrared imaging of desgw-190814e, DG19sevhc and selected galaxies
  94. LIGO/Virgo S190814bv : No Counterpart Candidates in Continued Galaxy Targeted Search with Magellan
  95. LIGO/Virgo S190814bv: No additional candidates from the Zwicky Transient Facility
  96. Baksan Neutrino Observatory Alert 190817.35 Global MASTER-Net observations report
  97. LIGO/Virgo S190814bv: SOAR spectroscopy of 2 DESGW candidates
  98. Baksan Neutrino Observatory Alert 190816.83 Global MASTER-Net observations report
  99. LIGO/Virgo S190814bv: No candidates found in J-GEM follow-up observations
  100. LIGO/Virgo S190814bv: no candidates from optical imaging of selected galaxies at the NOT

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov