Skip to main content
JSON Notices via Email, Kafka Cron Jobs, Submitter Profile, GCN is Hiring. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
  2. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  3. GRB 240419A: Swift-BAT refined analysis
  4. GRB 240418A: Swift-BAT refined analysis
  5. LXT240402A/GRB240402B: Chandra X-ray detection
  6. LIGO/Virgo/KAGRA S240423br: Retraction of GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  8. GRB 240419A: Possible ATCA radio detection
  9. GRB 240421B: ATCA radio observations
  10. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  11. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  12. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility observations and candidates
  13. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  14. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  15. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  16. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  17. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  18. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  19. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  20. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  21. LIGO/Virgo/KAGRA S240422ed: MeerLICHT and BlackGEM observations report
  22. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  24. LIGO/Virgo/KAGRA S240422ed: Global MASTER-Net observations report
  25. Fermi trigger No 735470374: Global MASTER-Net observations report
  26. GRB 240421A: Glowbug gamma-ray detection
  27. GRB 240414A: radio detection with the VLA
  28. Fermi-LAT gamma-ray observations of IceCube-240419A
  29. GRB 240414A: AMI-LA radio observations
  30. GRB 240414A: LBT optical detection
  31. GRB 240419B : MITSuME Akeno optical upper limits
  32. GRB 240415B: Swift-XRT observations
  33. GRB 240415A: Swift-XRT refined Analysis
  34. Fermi GRB 240422A: Global MASTER-Net observations report
  35. GRB 240421B: AstroSat CZTI detection
  36. GRB 240422A: Fermi GBM Final Real-time Localization
  37. GRB240421B: Zadko Observations
  38. Fermi GRB 240421B: Global MASTER-Net observations report
  39. Swift GRB 240421B: Global MASTER-Net observations report
  40. GRB 240421B: Fermi GBM Observation
  41. GRB 240421B: Swift-XRT refined Analysis
  42. GRB240421B: BOOTES-5/JGT optical upper limit
  43. GRB 240421B: J-band upper limits from WINTER
  44. GRB 240421B: Swift/UVOT Upper Limits
  45. GRB 240421B: Enhanced Swift-XRT position
  46. Fermi GRB 240421A: Global MASTER-Net observations report
  47. EP240417a: no counterpart detection by SOAR
  48. EP240420a: TNT upper limit to its optical counterpart
  49. EP240420a: Xinglong decaying optical counterpart
  50. GRB 240421B: Swift detection of a burst
  51. EP240420a: Nanshan optical counterpart observations
  52. EP240420a: GWAC-F50A optical upper limit
  53. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  54. GRB 240421A: Fermi GBM Final Real-time Localization
  55. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  56. EP240420a: NOT optical counterpart candidate and potential host
  57. Fermi trigger No 735280430: Global MASTER-Net observations report
  58. GRB240419A: Skynet Optical Afterglow Analysis
  59. GRB240418A - Candidate afterglow from NIRES
  60. IceCube Alert 240419.98: Global MASTER-Net observations report
  61. GRB 240419B: Swift/UVOT Upper Limits
  62. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  63. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  64. EP240420a: EP-WXT detection of a fast X-ray transient
  65. GRB 240419A: Swift/UVOT Upper Limits
  66. GRB 240419B: Swift-XRT refined Analysis
  67. GRB 240419B: optical afterglow from the NOT
  68. LIGO/Virgo/KAGRA S240420aw: Retraction of GW compact binary merger candidate
  69. EP240414a: Near-IR observations with NIRES and WINTER
  70. Swift GRB 240419B: Global MASTER-Net observations report
  71. EP240414A: Terskol Zeiss-2000 optical upper limit
  72. GRB 240419B: Enhanced Swift-XRT position
  73. Swift GRB 240419A: Global MASTER-Net observations report
  74. GRB 240418A: Swift/UVOT Upper Limits
  75. GRB 240419A: REM NIR afterglow detection
  76. GRB 240419A: Swift-XRT refined Analysis
  77. GRB 240418A: Swift-XRT refined Analysis
  78. GRB 240419B: Swift detection of a burst
  79. GRB 240411B: Swift/UVOT Detection
  80. EP240417a: YAHPT Optical Upper Limits
  81. GRB240418A: YAHPT Upper Limits
  82. GRB 240419A: VLT/UVES redshift of z = 5.178
  83. GRB 240419A: VLT optical afterglow detection
  84. GRB 240419A: Enhanced Swift-XRT position
  85. Fermi trigger No 735089036: Global MASTER-Net observations report
  86. EP240416a: J-band observations with WINTER
  87. EP240414a: GMG observation
  88. GRB 240419A: Prompt enhanced Swift-XRT position
  89. GRB 240419A: Swift detection of a burst
  90. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  91. GRB 240418A: NOT optical upper limits
  92. GRB 240418A: Enhanced Swift-XRT position
  93. GRB 240418A: AKO Upper Limit
  94. GRB 240411A: GOTO early optical upper limits
  95. Swift GRB240418.85: Global MASTER-Net observations report
  96. GRB 240418A: Swift detection of a burst
  97. EP240417a: EP-WXT detection of a fast X-ray transient
  98. Fermi GRB 240417A: Global MASTER-Net observations report
  99. LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart
  100. EP240416A: Terskol Zeiss-2000 optical upper limit

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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