Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

45429 results found.

  1. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  2. GRB 250725A: BOOTES-7 early optical detection
  3. GRB 250725A: SVOM/VT optical candidate
  4. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  5. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate (duplicate submission)
  6. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  8. GRB 250725A: Enhanced Swift-XRT position
  9. GRB 250725A: Swift detection of a burst
  10. Swift GRB 250725A: Global MASTER-Net OT detection
  11. GRB 250725A: Fermi GBM Final Real-time Localization
  12. Fermi GRB 250725A: Global MASTER-Net observations report
  13. Swift GRB 250725A: Global MASTER-Net observations report
  14. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  15. SVOM J195836+32283 is not a real source
  16. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  17. SVOM J195836+32283/sb25072103: Second VT observation
  18. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  19. GRB 250723B: Fermi GBM Final Real-time Localization
  20. GRB 250721A: Fermi GBM Observation
  21. GRB 250723A: Fermi GBM Final Real-time Localization
  22. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  23. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  24. Swift-BAT trigger 1334535 is not a GRB
  25. GRB 250721A: Swift-XRT observations
  26. GRB 250722A: Fermi GBM Final Real-time Localization
  27. GRB 250713A : SVOM/ECLAIRs refined analysis
  28. GRB 250717B: SVOM/GRM observation
  29. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  30. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  31. GRB 250721A: Tiled Swift observations
  32. GRB 250721A: MAXI/GSC detection
  33. GRB 250721A: Fermi GBM Final Localization
  34. GRB 250720B: Fermi GBM Final Localization Correction
  35. GRB 250720A: Fermi GBM Final Localization
  36. Fermi trigger No 774730635: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  38. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  39. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  40. GRB 250717B: COLIBRÍ optical upper limit
  41. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  42. GRB 250717B: Swift-XRT observations
  43. GRB 250718B: Fermi GBM Final Localization Correction
  44. GRB 250718B: Fermi GBM Final Real-time Localization
  45. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  46. Swift Trigger 1334535: a possible GRB 250718A
  47. Swift GRB250718.01: Global MASTER-Net observations report
  48. GRB 250717B: Swift ToO observations
  49. GRB 270713A: Kitab and AbAO Optical Observations
  50. GRB 250717B: Fermi GBM Observation
  51. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  52. Konus-Wind detection of GRB 250716A
  53. GRB 250716A: Swift-XRT afterglow detection
  54. GRB 250717B: Fermi GBM Final Real-time Localization
  55. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  56. GRB 250717A: Fermi GBM Final Real-time Localization
  57. GRB 250716A: Swift ToO observations
  58. GRB 250716A: GOTO tentative optical counterpart candidate
  59. GRB 250716A: Fermi GBM Observation
  60. GRB 250714A: SVOM/GRM observation
  61. Fermi GRB 250716A: Global MASTER-Net observations report
  62. GRB 250716A: Fermi GBM Final Real-time Localization
  63. Fermi GRB 250715A: Global MASTER-Net observations report
  64. GRB 250715A: Fermi GBM Final Real-time Localization
  65. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  66. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  67. GRB 250713A: Mephisto optical upper limits
  68. Fermi GRB 250714A: Global MASTER-Net observations report
  69. GRB 250713A: SVOM/VT optical upper limit
  70. GRB 250713A: NOT optical upper limits
  71. GRB 250713A: OHP/T193 upper limit
  72. GRB 250713A: SVOM/C-GFT upper limit
  73. GRB 250714A: Fermi GBM Final Real-time Localization
  74. GRB 250706B/C: 7DT Follow-up Observations
  75. GRB 250713A: Swift-XRT observations
  76. GRB 250713A: EP-FXT counterpart detection
  77. EP250711a: COLIBRÍ continuous optical observations
  78. GRB 250706A: Swift-BAT refined analysis
  79. GRB 250702F: Swift-BAT refined analysis
  80. GRB 250628A: Swift-BAT refined analysis
  81. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  82. GRB 250713A: JinShan optical upper limits
  83. GRB 250713A: SVOM detection of a long burst
  84. EP250711a: Global MASTER-Net observations report
  85. GRB 250711A: DDOTI Optical Upper Limit
  86. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  87. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  88. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  89. GRB 250711A: SVOM/GRM observation
  90. EP250711a: NOT optical counterpart candidate
  91. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  92. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  93. Fermi GRB 250711A: Global MASTER-Net observations report
  94. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  95. GRB 250704A: GRANDMA observations
  96. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  97. GRB 250711A: Fermi GBM Final Real-time Localization
  98. GRB 250704A: SVOM/ECLAIRs refined analysis
  99. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  100. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz

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