Skip to main content
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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"

22108 results found.

  1. GRB 250403A: REM NIR afterglow detection
  2. GRB 250403A: LCO optical counterpart detection
  3. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  4. GRB 250403A: JinShan optical observations
  5. GRB 250403A: Optical counterpart detection by LCO.
  6. GRB 250322A: 10 GHz VLA radio upper limits
  7. GRB 250403A: GMG Optical Observation
  8. GRB 250403A: 1.6m Mephisto multi-band optical detection
  9. GRB 250403A: SVOM/C-GFT optical observations
  10. GRB 250403A: Fermi GBM Final Real-time Localization
  11. GRB 250225B: VLT host galaxy redshift z = 0.950
  12. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  13. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  14. GRB 250402A: REM optical/NIR upper limits
  15. GRB 250402A: LCO optical counterpart detection
  16. EP250402a: Einstein Probe detection of a fast X-ray transient
  17. GRB 250402A: SVOM/VT optical counterpart
  18. GRB 250402A: SVOM detection of a burst
  19. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  20. GRB 250329B: Swift/UVOT Upper Limit
  21. GRB 250329A: Swift/UVOT Upper Limit
  22. GRB 250327B: Swift/UVOT Detection
  23. GRB 250327A: Swift/UVOT Upper Limits
  24. GRB 250331E: SVOM/GRM observation
  25. GRB 250327B: Kilonova-Catcher Observations
  26. GRB250331D: AbAO optical observations
  27. GRB 250331C: Swift/UVOT Upper Limits
  28. GRB 250331B: Swift/UVOT Upper Limits
  29. GRB 250328A: AbAO AS-32 Optical Observations
  30. GRB 250219A: NOT candidate host galaxy detection
  31. GRB 250331D: Swift-XRT observations
  32. GRB 250322B possible detection by the AstroSat Satellite
  33. GRB 250330B: SVOM/GRM observation of a short burst
  34. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  35. GRB 250331C: Enhanced Swift-XRT position
  36. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  37. GRB 250331B: Enhanced Swift-XRT position
  38. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  39. GRB 250330A: VLT/FORS2 Afterglow Detection
  40. GRB20250327B: 45th Parallel Observatory upper limit
  41. GRB 250328A: Swift/UVOT Detection
  42. GRB 250328A: Swift-XRT refined Analysis
  43. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  44. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  45. GRB 250331C: Swift detection of a burst
  46. GRB 250331B: Swift detection of a burst
  47. GRB 250330A: SVOM/VT optical upper limit
  48. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  49. GRB 250330A: Swift/UVOT Upper Limits
  50. GRB 250330A: Swift-XRT afterglow detection
  51. GRB 250328A: 1.6m Mephisto optical observations
  52. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  53. GRB 250330A: VLT/FORS2 Optical Observations
  54. GRB 250329B: Swift-XRT afterglow detection
  55. GRB 250330A: Swift detection of a burst
  56. GRB 250329B: SVOM/C-GFT optical upper limit
  57. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  58. GRB 250329B: SVOM/VT optical upper limit
  59. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  60. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  61. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  62. GRB250329A: REM optical afterglow detection
  63. GRB 250329B: GWAC-F50A optical upper limit
  64. GRB 250329A: Swift-XRT afterglow detection
  65. GRB 250328A: SVOM/VT optical observation
  66. GRB 250329A: Fading optical counterpart detection by LCO.
  67. GRB 250328A: SVOM/C-GFT optical upper limit
  68. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  69. GRB 250329A: SVOM/VT optical counterpart confirmation
  70. GRB 250329A: SVOM detection of a burst
  71. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  72. GRB 250327B: J-band observations with WINTER
  73. GRB 250327B: LCO optical counterpart detection
  74. GRB 250328A: GWAC-F50A optical upper limit
  75. FRB 20250316A: FTW optical observations
  76. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  77. GRB 250327B: CrAO and SAO RAS Optical Observations
  78. EP250315a: Pan-STARRS r and i-band imaging and photometry
  79. GRB 250327b: Liverpool Telescope optical observations
  80. GRB 250322A: GRANDMA/TNOT optical upper limits
  81. GRB 250327A: SVOM/VT upper limits on the XRT position
  82. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  83. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  84. GRB 250327B: Las Cumbres optical counterpart detection
  85. GRB 250327B: 1.6m Mephisto optical observations
  86. GRB 250327B: SVOM/VT optically bright counterpart
  87. GRB 250327B: SAO RAS optical candidate
  88. GRB 250327B: SVOM detection of a burst
  89. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  90. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  91. GRB 250327A: J-band observations with WINTER
  92. GRB 250327A: SVOM/VT optical candidate
  93. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  94. GRB 250327A: DDOTI Optical Observations
  95. GRB 250327A: COLIBRÍ optical upper limit
  96. GRB 250327A: Swift detection of a burst
  97. Fermi trigger No 764700395: Global MASTER-Net observations report
  98. Konus-Wind detection of GRB 250322A (short)
  99. IPN triangulation of GRB 250322B
  100. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate

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