Skip to main content
JSON Notices via Email, Kafka Cron Jobs, Submitter Profile, GCN is Hiring. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32735 results found.

  1. GRB 250813B: Swift/UVOT Upper Limit
  2. IPN triangulation of GRB 250816A (short)
  3. IPN triangulation of GRB 250814C (short)
  4. IPN triangulation of GRB 250804B (short)
  5. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  6. GRB 250818B: Kilonova-Catcher optical afterglow detection
  7. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  8. GRB 250818B: Liverpool Telescope optical detections
  9. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  10. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  11. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  12. GRB 250818A: AstroSat CZTI detection
  13. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  14. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  15. GRB 250818B: Swift/UVOT Detection
  16. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  17. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  18. GRB 250818B: TRT Optical Observation
  19. Fermi GRB 250816A: Global MASTER-Net observations report
  20. GRB 250818B: SAO RAS optical observations
  21. Swift GRB 250818A: Global MASTER-Net observations report
  22. GRB 250818B: NOT optical observations
  23. GRB 250818B: EP-FXT counterpart detection
  24. GRB 250818A: Swift-BAT refined analysis
  25. LIGO/Virgo/KAGRA S250818k: FTW optical and NIR observations of AT 2025ulz
  26. GRB 250818B: Keck redshift of the optical afterglow
  27. GRB 250818B: KAIT optical observations
  28. GRB 250818A: Swift/UVOT Upper Limits
  29. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  30. GRB 250813B: SVOM/ECLAIRs refined analysis
  31. GRB 250818A: Fermi GBM Observation
  32. GRB 250818B: SVOM/VT optical observation
  33. GRB 250814A: Further GRAWITA TNG NIR observations
  34. GRB 250818B: Swift-XRT afterglow detection
  35. GRB 250818B: GOTO optical counterpart candidate
  36. GRB 250818B: SVOM detection of a short burst
  37. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  38. sb25081602: Swift-XRT observations
  39. GRB 250816A: SVOM/GRM observation of a short burst
  40. Fermi GRB 250814B: Global MASTER-Net observations report
  41. GRB 250814A: Swift-BAT refined analysis
  42. GRB 250813B: Liverpool Telescope optical upper limits
  43. GRB 250814A: Further COLIBRÍ optical upper limit
  44. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  45. GRB 250814A: GRAWITA TNG NIR observations
  46. GRB 250812A: SVOM/VT optical continued observation
  47. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  48. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  49. GRB250814A: TRT optical upper limits
  50. GRB 250814B: SVOM/GRM observation
  51. GRB 250813B: SVOM/GRM observation
  52. GRB 250814A: P200/WIRC observations of the afterglow candidate
  53. GRB 250814A: KAIT optical upper limit
  54. GRB 240814A: Fermi GBM Observation
  55. GRB 250814A: Possible afterglow candidate from P200/WIRC
  56. GRB 250813B: Fermi GBM Observation
  57. GRB 250814A: J-band upper limit from WINTER
  58. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  59. GRB 250813B: NOT observations of the optical afterglow
  60. GRB 250813B: SVOM/VT optical observations
  61. Subject GRB 250813B: SVOM/MXT refined analysis
  62. GRB 250814A: COLIBRÍ optical upper limit
  63. GRB 250813A: AstroSat CZTI detection
  64. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  65. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  66. GRB 250814A: DDOTI Optical Upper Limit
  67. GRB 250813B: EP-FXT counterpart detection
  68. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  69. GRB 250813B: Swift-XRT afterglow detection
  70. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  71. GRB 250813B: Ondrejov D50 fast decay
  72. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  73. GRB 250813B: Ondrejov D50 optical afterglow detection
  74. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  75. EP250812a: Nickel optical upper limit
  76. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  77. GRB 250812A: NTT spectroscopic redshift z = 2.57
  78. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  79. EP250812a: NOT, NTT, and GS observations
  80. GRB 250812A: Swift/UVOT Detection
  81. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  82. EP250812a: Liverpool Telescope upper limits
  83. EP250812a: SVOM/VT optical counterpart
  84. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  85. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  86. GRB 250812A: EP-FXT counterpart detection
  87. GRB 250812A: Swift ToO observations
  88. GRB 250807B: Swift-BAT refined analysis
  89. EP 250812a: GOTO optical upper limit
  90. GRB 250812A: Kilonova-Catcher optical afterglow detection
  91. EP250812a: Swift-XRT counterpart detection
  92. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  93. GRB 250812A: SVOM/VT optical afterglow confirmation
  94. GRB 250812A: TRT likely optical counterpart detection
  95. GRB 250809A: Swift-BAT refined analysis
  96. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  97. GRB 250807A: Swift-BAT refined analysis
  98. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  99. GRB 250809A: Swift/UVOT Detection
  100. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate

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