Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

20814 results found.

  1. EP250321A: J band upper limit by SYSU 80cm telescope
  2. EP250404a: Nanshan/HMT optical counterpart detection
  3. EP250404a: Einstein Probe detection of an X-ray transient
  4. GRB 250403A: Swift/UVOT Detection
  5. GRB 250402A: Swift/UVOT Upper Limits
  6. EP250402a: Optical upper limit with Kinder observations
  7. GRB 250403A: REM NIR afterglow detection
  8. GRB 250403A: LCO optical counterpart detection
  9. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  10. GRB 250403A: JinShan optical observations
  11. GRB 250403A: Optical counterpart detection by LCO.
  12. GRB 250322A: 10 GHz VLA radio upper limits
  13. GRB 250403A: GMG Optical Observation
  14. GRB 250403A: 1.6m Mephisto multi-band optical detection
  15. GRB 250403A: SVOM/C-GFT optical observations
  16. GRB 250403A: Fermi GBM Final Real-time Localization
  17. GRB 250225B: VLT host galaxy redshift z = 0.950
  18. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  19. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  20. GRB 250402A: REM optical/NIR upper limits
  21. GRB 250402A: LCO optical counterpart detection
  22. EP250402a: Einstein Probe detection of a fast X-ray transient
  23. GRB 250402A: SVOM/VT optical counterpart
  24. GRB 250402A: SVOM detection of a burst
  25. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  26. GRB 250329B: Swift/UVOT Upper Limit
  27. GRB 250329A: Swift/UVOT Upper Limit
  28. GRB 250327B: Swift/UVOT Detection
  29. GRB 250327A: Swift/UVOT Upper Limits
  30. GRB 250331E: SVOM/GRM observation
  31. GRB 250327B: Kilonova-Catcher Observations
  32. GRB250331D: AbAO optical observations
  33. GRB 250331C: Swift/UVOT Upper Limits
  34. GRB 250331B: Swift/UVOT Upper Limits
  35. GRB 250328A: AbAO AS-32 Optical Observations
  36. GRB 250219A: NOT candidate host galaxy detection
  37. GRB 250331D: Swift-XRT observations
  38. GRB 250322B possible detection by the AstroSat Satellite
  39. GRB 250330B: SVOM/GRM observation of a short burst
  40. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  41. GRB 250331C: Enhanced Swift-XRT position
  42. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  43. GRB 250331B: Enhanced Swift-XRT position
  44. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  45. GRB 250330A: VLT/FORS2 Afterglow Detection
  46. GRB20250327B: 45th Parallel Observatory upper limit
  47. GRB 250328A: Swift/UVOT Detection
  48. GRB 250328A: Swift-XRT refined Analysis
  49. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  50. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  51. GRB 250331C: Swift detection of a burst
  52. GRB 250331B: Swift detection of a burst
  53. GRB 250330A: SVOM/VT optical upper limit
  54. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  55. GRB 250330A: Swift/UVOT Upper Limits
  56. GRB 250330A: Swift-XRT afterglow detection
  57. GRB 250328A: 1.6m Mephisto optical observations
  58. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  59. GRB 250330A: VLT/FORS2 Optical Observations
  60. GRB 250329B: Swift-XRT afterglow detection
  61. GRB 250330A: Swift detection of a burst
  62. GRB 250329B: SVOM/C-GFT optical upper limit
  63. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  64. GRB 250329B: SVOM/VT optical upper limit
  65. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  66. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  67. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  68. GRB250329A: REM optical afterglow detection
  69. GRB 250329B: GWAC-F50A optical upper limit
  70. GRB 250329A: Swift-XRT afterglow detection
  71. GRB 250328A: SVOM/VT optical observation
  72. GRB 250329A: Fading optical counterpart detection by LCO.
  73. GRB 250328A: SVOM/C-GFT optical upper limit
  74. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  75. GRB 250329A: SVOM/VT optical counterpart confirmation
  76. GRB 250329A: SVOM detection of a burst
  77. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  78. GRB 250327B: J-band observations with WINTER
  79. GRB 250327B: LCO optical counterpart detection
  80. GRB 250328A: GWAC-F50A optical upper limit
  81. FRB 20250316A: FTW optical observations
  82. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  83. GRB 250327B: CrAO and SAO RAS Optical Observations
  84. EP250315a: Pan-STARRS r and i-band imaging and photometry
  85. GRB 250327b: Liverpool Telescope optical observations
  86. GRB 250322A: GRANDMA/TNOT optical upper limits
  87. GRB 250327A: SVOM/VT upper limits on the XRT position
  88. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  89. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  90. GRB 250327B: Las Cumbres optical counterpart detection
  91. GRB 250327B: 1.6m Mephisto optical observations
  92. GRB 250327B: SVOM/VT optically bright counterpart
  93. GRB 250327B: SAO RAS optical candidate
  94. GRB 250327B: SVOM detection of a burst
  95. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  96. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  97. GRB 250327A: J-band observations with WINTER
  98. GRB 250327A: SVOM/VT optical candidate
  99. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  100. GRB 250327A: DDOTI Optical Observations

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