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"

24848 results found.

  1. GRB 250328A: Swift-XRT refined Analysis
  2. Fermi-LAT gamma-ray observations of IceCube-250330A
  3. SVOM/sb25033102 is a false trigger
  4. GRB 250330A: Fermi GBM Observation
  5. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  6. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  7. GRB 250331C: Swift detection of a burst
  8. GRB 250331B: Swift detection of a burst
  9. GRB 250331A: MAXI/GSC detection
  10. SVOM/sb25033102: SVOM detection of an X-ray transient
  11. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  12. GRB 250330A: Swift/UVOT Upper Limits
  13. GRB 250330A: Swift-XRT afterglow detection
  14. GRB 250328A: 1.6m Mephisto optical observations
  15. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  16. GRB 250330A: VLT/FORS2 Optical Observations
  17. GRB 250329B: Swift-XRT afterglow detection
  18. GRB 250330A: Swift detection of a burst
  19. GRB 250329B: SVOM/C-GFT optical upper limit
  20. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  21. GRB 250329B: SVOM/VT optical upper limit
  22. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  23. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  24. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  25. GRB250329A: REM optical afterglow detection
  26. GRB 250329A: Swift-XRT afterglow detection
  27. GRB 250328A: SVOM/VT optical observation
  28. GRB 250329A: Fading optical counterpart detection by LCO.
  29. GRB 250328A: SVOM/C-GFT optical upper limit
  30. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  31. GRB 250329A: SVOM/VT optical counterpart confirmation
  32. GRB 250329A: SVOM detection of a burst
  33. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  34. GRB 250327B: J-band observations with WINTER
  35. GRB 250327B: LCO optical counterpart detection
  36. GRB 250328A: SVOM detection of a burst
  37. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  38. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  39. GRB 250327B: CrAO and SAO RAS Optical Observations
  40. GRB 250327b: Liverpool Telescope optical observations
  41. GRB 250322A: GRANDMA/TNOT optical upper limits
  42. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  43. GRB 250327A: SVOM/VT upper limits on the XRT position
  44. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  45. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  46. GRB 250327B: Las Cumbres optical counterpart detection
  47. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  48. GRB 250327B: 1.6m Mephisto optical observations
  49. GRB 250327A: Swift-XRT refined Analysis
  50. GRB 250327B: SVOM/VT optically bright counterpart
  51. GRB 250327B: SAO RAS optical candidate
  52. GRB 250327B: SVOM detection of a burst
  53. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  54. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  55. GRB 250327A: J-band observations with WINTER
  56. GRB 250327A: SVOM/VT optical candidate
  57. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  58. GRB 250327A: DDOTI Optical Observations
  59. GRB 250327A: COLIBRÍ optical upper limit
  60. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  61. IPN triangulation of GRB 250322B
  62. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  63. EP250321a: Mondy AZT-33IK Continued Optical Observations
  64. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  65. GRB 250322A: third epoch of NOT optical observations
  66. GRB 250322A: Swift-BAT refined analysis
  67. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  68. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  69. GRB 250322A: further NOT optical observations
  70. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  71. GRB 250322A: Swift/UVOT Upper Limits
  72. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  73. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  74. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  75. GRB 250321B: Swift-XRT observations
  76. GRB 250322A: Swift-XRT refined Analysis
  77. EP250321a: TNOT Observation of Optical Counterpart
  78. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  79. SVOM/sb25032302: SVOM detection of a long X-ray transient
  80. GRB 250322B: AstroSat CZTI detection of a bright long burst
  81. GRB 250322A: VLT optical observations
  82. GRB 250322A: VLT near-infrared observations
  83. FRB 250316A: DDOTI Continued Optical Observations
  84. GRB 250322A: NOT optical upper limits
  85. GRB 250322A: Enhanced Swift-XRT position
  86. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  87. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  88. EP250321a: Liverpool Telescope optical follow-up
  89. EP250321a: Mondy AZT-33IK Optical Observations
  90. GRB 250322A: Swift detection of a short burst
  91. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  92. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  93. EP250321A: COLIBRÍ Continuing Optical Observations
  94. EP250321a: WFST optical observations
  95. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  96. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  97. GRB 250320B: Fermi GBM Observation
  98. EP250321a: Xinglong 216 decaying optical observations
  99. GRB 250321A: Swift-BAT refined analysis
  100. GRB 250321A: Swift-XRT refined Analysis

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