Skip to main content
Circulars over Kafka event name backfill. 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.

Lucene Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

4690 results found.

  1. GRB 250329B: SVOM detection of a faint transient
  2. GRB 250329A: Fading optical counterpart detection by LCO.
  3. GRB 250328A: SVOM/C-GFT optical upper limit
  4. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  5. GRB 250329A: SVOM detection of a burst
  6. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  7. GRB 250327B: J-band observations with WINTER
  8. GRB 250327B: MASTER detection of OT rebrightening
  9. GRB 250327B: LCO optical counterpart detection
  10. GRB 250328A: GWAC-F50A optical upper limit
  11. GRB 250328A: SVOM detection of a burst
  12. FRB 20250316A: FTW optical observations
  13. GRB 250327B: CrAO and SAO RAS Optical Observations
  14. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  15. GRB 250327B: further optical observations by LCOGT
  16. EP250315a: Pan-STARRS r and i-band imaging and photometry
  17. GRB 250327b: Liverpool Telescope optical observations
  18. GRB 250327A: SVOM/VT upper limits on the XRT position
  19. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  20. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  21. GRB 250327B: Las Cumbres optical counterpart detection
  22. GRB 250327B: 1.6m Mephisto optical observations
  23. GRB 250327B: GOTO optical counterpart detection
  24. GRB 250327B: SVOM detection of a burst
  25. GRB 250327A: J-band observations with WINTER
  26. GRB 250327A: SVOM/VT optical candidate
  27. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  28. Fermi GRB 250327A: Global MASTER-Net observations report
  29. Swift GRB 250327A: Global MASTER-Net observations report
  30. GRB 250327A: DDOTI Optical Observations
  31. GRB 250327A: COLIBRÍ optical upper limit
  32. Fermi trigger No 764700395: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  34. EP250321a: Mondy AZT-33IK Continued Optical Observations
  35. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  36. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  37. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  38. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  39. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  40. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  41. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  42. EP250321a: TNOT Observation of Optical Counterpart
  43. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  44. GRB 250322A: Gemini-North redshift of candidate host galaxy
  45. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  46. SVOM/sb25032302: SVOM detection of a long X-ray transient
  47. GRB 250322A: AstroSat CZTI detection of a short burst
  48. GRB 250322B: AstroSat CZTI detection of a bright long burst
  49. GRB 250322A: Gemini-South optical observations
  50. FRB 250316A: DDOTI Continued Optical Observations
  51. GRB 250322A: NOT optical upper limits
  52. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  53. GRB 250322A: MASTER optical observation
  54. EP250321a: Liverpool Telescope optical follow-up
  55. EP250321a: Mondy AZT-33IK Optical Observations
  56. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  57. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP250321A: COLIBRÍ Continuing Optical Observations
  59. GRB 250312A: GECAM-A detection
  60. EP250321a: WFST optical observations
  61. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  62. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  63. EP250321a: Xinglong 216 decaying optical observations
  64. GRB 250321A: Swift-BAT refined analysis
  65. GRB 250321B: SVOM detection of a sub-threshold transient event
  66. EP250321a: SVOM/VT optical observation
  67. EP 250321A: Optical counterpart detection by LCO.
  68. GRB 250320B: SVOM/GRM observation of a long burst
  69. EP250321a: LCO optical counterpart detection
  70. EP250321A: COLIBRÍ Optical Observations
  71. GRB 250320B: AstroSat CZTI detection
  72. Fermi GRB 250320B: Global MASTER-Net observations report
  73. EP250321a: BOOTES-5/JGT optical afterglow detection
  74. EP250321a: Global MASTER-Net observations report
  75. Swift GRB 250321A: Global MASTER-Net observations report
  76. Fermi GRB 250321A: Global MASTER-Net observations report
  77. EP250321a: Einstein Probe detection of an X-ray transient
  78. GRB 250321A: GOTO optical upper limits
  79. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  80. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  81. Fermi GRB 250319B: Global MASTER-Net observations report
  82. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  83. GRB 250313A: GRBAlpha detection
  84. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  85. GRB 250317D: EIRSAT-1 GMOD Detection
  86. EP250302a: VLA observations
  87. GRB 250317B: OHP/T193 continued follow-up
  88. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  89. GRB 250317C: SVOM/GRM observation of a long burst
  90. GRB 250317B: Leavitt Observatory optical upper limit
  91. GRB 250309B/AT2025dws: further ATCA observations
  92. GRB 250317B: Mondy AZT-33IK Optical Observations
  93. GRB 250317C: AstroSat CZTI detection
  94. GRB 250317B: NOT optical observations suggest an optical plateau phase
  95. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  96. GRB 250317C: GECAM-B detection
  97. GRB 250317B: OHP/T193 optical observations
  98. Fermi trigger No 763933627: Global MASTER-Net observations report
  99. GRB 250317B: REM optical/NIR observations
  100. GRB 250316A: AbAO AS-32 Optical Upper Limit

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