Skip to main content
Updated Client Credential Expiration Policy. 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"
  1. Swift GRB 250103B: Global MASTER-Net observations report
  2. GRB 250103A: SVOM/VT optical counterpart confirmation
  3. EP250101a: Liverpool Telescope optical upper limit
  4. GRB 250103A: Swift ToO observations
  5. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  6. GRB 250101a: Liverpool Telescope optical follow-up
  7. GRB 250103B: SVOM detection of a long burst
  8. GRB 250103B: Swift detection of a burst
  9. GRB 250103A: Xinglong 2.16m Optical Candidate
  10. Fermi GRB 250102A: Global MASTER-Net observations report
  11. GRB 250101B: SVOM/GRM observation
  12. GRB 250103A: GOTO optical upper limit
  13. GRB 250103A: SVOM/C-GFT optical upper limit
  14. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  15. IceCube Alert 250102.58: Global MASTER-Net observations report
  16. EP241231b: optical upper limit with the Liverpool Telescope
  17. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  18. GRB 250103A: SVOM detection of a long burst
  19. EP250101a: Xinglong optical upper limit
  20. GRB 250102A: Fermi GBM Final Real-time Localization
  21. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  22. GRB 250101A: Swift-BAT refined analysis
  23. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 250101A: further SAO RAS optical observations
  25. GRB 250101A: LCO optical counterpart detection
  26. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  27. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  28. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  29. GRB 250101A: Swift/UVOT Detection
  30. GRB 250101A: 1.6m Mephisto multi-band optical followup
  31. GRB 250101A: Swift-XRT refined Analysis
  32. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  33. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  34. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  35. GRB 250101A: LCOGT optical afterglow detection
  36. GRB 250101A: OASDG optical observations
  37. Fermi GRB 250101B: Global MASTER-Net observations report
  38. GRB 250101B: Fermi GBM Final Real-time Localization
  39. GRB 250101A: SAO RAS observations of optical brightening
  40. GRB 250101A: BOOTES-4/MET optical afterglow detection
  41. GRB 250101A: AKO Optical Afterglow Detection
  42. GRB 250101A: SAO RAS optical observations
  43. GRB 250101A: Enhanced Swift-XRT position
  44. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  45. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  46. GRB 250101A: SVOM/C-GFT early optical observations
  47. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  48. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  49. GRB 250101A: Nanshan/HMT optical observations
  50. GRB 250101A : GIT optical detection
  51. GRB 250101A: GMG Optical Observation
  52. GRB 250101A: Swift detection of a burst with an optical counterpart
  53. Swift GRB250101.56: Global MASTER-Net observations report
  54. GRB 241217a/EP241217b: ATCA Radio Detection
  55. EP241217a: VLA Radio Detection

  56. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  57. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  58. GRB 241229B: Continued CrAO ZTSh observations
  59. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  60. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  61. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  62. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  63. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  64. GRB 241229A: EP-FXT X-ray afterglow confirmation
  65. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  66. GRB 241229B: SVOM/GRM observation
  67. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  68. EP241217A: J band upper limit by SYSU 80cm telescope
  69. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  70. GRB 241229B: SAO RAS optical upper limit
  71. GRB 241228B: SAO RAS optical observations
  72. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  73. GRB 241229A: SAO RAS optical observations
  74. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  75. GRB 241229B: SVOM/VT optical candidate
  76. GRB 241229A: Swift-XRT observations
  77. Konus-Wind detection of GRB 241228A
  78. GRB 241229A: EP-FXT afterglow candidates
  79. EP240702a: 7DT Optical upper limits
  80. GRB 240606B: 7DT Optical upper limits
  81. Fermi trigger No 757231333: Global MASTER-Net observations report
  82. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  83. GRB 241229B: Swift-BAT refined analysis
  84. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  85. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  86. Fermi Gamma-ray Burst Monitor trigger 757207662/241229978 (GRB 241229C) is not a GRB
  87. GRB241229B: UVOT upper limits
  88. GRB 241229C: Fermi GBM Final Real-time Localization
  89. GRB 241228B: D50 optical detection
  90. GRB 241228B: Fermi GBM Observation
  91. GRB 241228B: Swift-XRT afterglow detection
  92. GRB 241229B: Fermi GBM Observation
  93. GRB 241229A: Swift ToO observations
  94. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  95. GRB 241228A: Mondy optical afterglow observations
  96. GRB 241229B: Swift-XRT refined Analysis
  97. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  98. Swift GRB 241229B: Global MASTER-Net observations report
  99. GRB 241229A: GOTO optical upper limits
  100. GRB 241228B: VLT/X-shooter redshift of z = 2.674

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