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"

32739 results found.

  1. GRB 250902A: MSU cubesats detection
  2. GRB 251005C: Fermi GBM Observation
  3. Swift GRB 251005A: Global MASTER-Net observations report
  4. GRB 251005C: GOTO optical upper limits
  5. GRB 251002A: Mondy/AZT-33IK optical observations
  6. GRB 251002A: Insight-HXMT detection
  7. GRB 251002A: Insight-HXMT detection
  8. GRB 251003A: J-band detection with WINTER
  9. GRB 251002A: NIR observations with WINTER
  10. Fermi GBM Sub-Threshold Detection of GRB 250910A
  11. GRB 251003A: Swift-BAT refined analysis
  12. GRB 251001B: NIR observations with WINTER
  13. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  14. GRB 251003A: Swift/UVOT Upper Limits
  15. GRB 251002A: Swift/UVOT detection
  16. GRB 251001A: AstroSat CZTI detection
  17. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  18. GRB 251003A: COLIBRÍ photometric redshift
  19. GRB 251003A: GOTO detection of the optical counterpart
  20. GRB 251002A: Fermi GBM Observation
  21. GRB 251002A: GOTO detection of optical counterpart
  22. GRB 251001C: SVOM/GRM observation
  23. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  24. GRB 251002A: AKO Early Optical Afterglow Detection
  25. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  26. GRB 251003A: Kilonova-Catcher optical afterglow detection
  27. GRB 251002A: Swift-XRT afterglow detection
  28. GRB 251001B: AbAO optical upper limit
  29. GRB 251002A: Kilonova-Catcher optical afterglow detection
  30. GRB 251002A: AbAO optical observations
  31. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  32. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  33. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  34. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  35. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  36. GRB 251002A: EP-FXT counterpart detection
  37. GRB 251003A: LCOGT Optical Detection
  38. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  39. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  40. GRB 251002A: BOOTES-6 early optical detection
  41. GRB 251002A: SAO RAS optical observations
  42. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  43. GRB 251002A: FRAM-ORM afterglow detection
  44. GRB 251002A: LCO optical observation
  45. GRB 251002A: SVOM/VT optical observation
  46. GRB 251001B: Swift-BAT refined analysis
  47. GRB 251001A: SVOM/GRM observation
  48. GRB 251001A: Insight-HXMT detection
  49. GRB 251001B: Swift/UVOT Detection
  50. GRB 251001B: COLIBRÍ optical observations
  51. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  52. GRB 251001B: SVOM/VT optical observation
  53. GRB 251001B: NOT optical observations
  54. Swift GRB 251001B: Global MASTER-Net observations report
  55. GRB 251001B: Fermi GBM Observation
  56. GRB 251001B: Further GOTO observations of optical counterpart.
  57. GRB 251001B: LCOGT Optical Observations
  58. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  59. GRB 251001B: GOTO optical counterpart detection
  60. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  61. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  62. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  63. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  64. GRB 250925A: MAO/AZT-22 optical observations
  65. Fermi GRB 250929A: Global MASTER-Net observations report
  66. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  67. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  68. GRB 250925A: Mondy I-band optical observations
  69. GRB 250916A: SVOM/VT optical observation
  70. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  71. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  72. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  73. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  74. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  75. GRB 250924A: SVOM/GRM observation
  76. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  78. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 250926A: Insight-HXMT detection
  80. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  81. GRB 250926A: AstroSat CZTI detection
  82. GRB 250925A: Swift/UVOT Upper Limits
  83. GRB 250925A: Swift-BAT refined analysis
  84. GRB 250925A: Mondy and AbAO optical observations
  85. GRB 250925A: COLIBRÍ photometric redshift
  86. GRB 250925A: SVOM/GWAC-F60A upper limit
  87. GRB 250925A/EP250925a: EP-WXT detection
  88. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  89. GRB 250925A : MITSuME Akeno optical upper limits
  90. GRB 250925A: JinShan optical observations
  91. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  92. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  93. Fermi GRB 250926A: Global MASTER-Net observations report
  94. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  95. GRB250925A: Liverpool Telescope optical observations
  96. GRB 250925A: NOT optical afterglow candidate
  97. GRB 250925A: Leavitt Observatory optical upper limit
  98. GRB 250924A: Swift-BAT refined analysis
  99. GRB 250925A: GROWTH-India Telescope Upper Limits
  100. GRB 250922A: SVOM/GRM observation

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