Gamma-ray Burst 050709

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:          GCN/HETE BURST POSITION NOTICE
  NOTICE_DATE:    Sun 10 Jul 05 22:00:29 UT
  NOTICE_TYPE:    HETE Ground Analysis
  TRIGGER_NUM:    3862,   Seq_Num: 1
  GRB_DATE:       13560 TJD;   190 DOY;   05/07/09
  GRB_TIME:       81396.70 SOD {22:36:36.70} UT
  TRIGGER_SOURCE: Trigger on the 25-400 keV band.
  SC_-Z_RA:       147 [deg]
  SC_-Z_DEC:       35 [deg]
  SC_LONG:         42 [deg East]
  WXM_CNTR_RA:    345.432d {+23h 01m 44s} (J2000),
                  345.509d {+23h 02m 02s} (current),
                  344.733d {+22h 58m 56s} (1950)
  WXM_CNTR_DEC:   -38.998d {-38d 59' 52"} (J2000),
                  -38.968d {-38d 58' 05"} (current),
                  -39.267d {-39d 16' 00"} (1950)
  WXM_MAX_SIZE:   28.90 [arcmin] diameter
  WXM_LOC_SN:     9 sig/noise (pt src in image)
  WXM_IMAGE_SN:   X= 3.7 Y= 5.6 [sig/noise]
  WXM_LC_SN:      X= 12.6 Y= 11.1 [sig/noise]
  SXC_CNTR_RA:    345.375d {+23h 01m 30s} (J2000),
                  345.452d {+23h 01m 48s} (current),
                  344.676d {+22h 58m 42s} (1950)
  SXC_CNTR_DEC:   -38.976d {-38d 58' 33"} (J2000),
                  -38.946d {-38d 56' 46"} (current),
                  -39.245d {-39d 14' 41"} (1950)
  SXC_MAX_SIZE:   2.67 [arcmin] diameter
  SXC_LOC_SN:     10 sig/noise (pt src in image)
  SUN_POSTN:      109.28d {+07h 17m 08s}  +22.25d {+22d 15' 16"}
  SUN_DIST:       129.70 [deg]
  MOON_POSTN:     149.10d {+09h 56m 24s}  +16.75d {+16d 45' 09"}
  MOON_DIST:      153.61 [deg]
  MOON_ILLUM:     10 [%]
  GAL_COORDS:     358.57,-64.24 [deg] galactic lon,lat of the burst
  ECL_COORDS:     330.23,-29.93 [deg] ecliptic lon,lat of the burst
  COMMENTS:       Definite GRB.
  COMMENTS:       WXM error box is circular; not rectangular.
  COMMENTS:       SXC error box is circular; not rectangular.
  COMMENTS:       Burst_Validity flag is true.
  COMMENTS:       WXM data refined since S/C_Last Notice.
  COMMENTS:       SXC data refined since S/C_Last Notice.
  

• red DSS finding chart ps-file
  
  
• GCN notice #3569
  M. Bayliss, J. Haislip, A. Foster, D. Reichart report on behalf of the UNC team of the FUN GRB Collaboration:
  The PROMPT-5 telescope automatically responded to HETE2-SXC alert 3862 for GRB 050709 and imaged the field for 3600s in Rc beginning approximately 27 hours after the time of the GRB. Preliminary analysis reveals no new source down to the limit of the DSS.
  PROMPT is still being built and commissioned.
• GCN notice #3570
  N. Butler, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team;
  M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, J. Kotoku, M. Maetou, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, K. Tanaka, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team;
  G. Crew, J. Doty, G. Prigozhin, R. Vanderspek, J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
  M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team;
  report:
  The HETE FREGATE, WXM, and SXC instruments detected GRB 050709 at 22:36:37 UT (81396.7 SOD) on 9 July 2005. This was a single hard pulse 100ms long, followed about 30s later by a soft, faint, approximately 150s long pulse from the same location. The later pulse was only detected by WXM and SXC, since the spectrum of its emission was confined to below 10 keV.
  The WXM obtained a localization in flight. However, the spacecraft attitude-control system had experienced an upset approximately 19 minutes earlier, so HETE was drifting at the time of the trigger, and real-time aspect information was not available. Consequently, the location was not distributed in real time.
  Ground analysis of the data from the optical cameras has provided reliable aspect despite the issues associated with the high spacecraft drift rate. A GCN Notice was sent out at 22:00:29 UT on 10 July 2005, upon the resolution of spacecraft aspect issues. The 90% confidence region of the WXM location may be expressed as a circle centered at
  R.A. = +23h 01m 44s ; Dec. = -38d 59' 52" (J2000)
  with a radius of 14.5'.
  Ground analysis of the SXC data yields a refined location with a 90% confidence region that may be expressed as a circle centered at
  R.A. = +23h 01m 30s ; Dec. = -38d 58' 33" (J2000)
  with a radius of 1.34'.
  A preliminary spectral analysis based on a fit of a cutoff power-law model to the initial spike indicates that Epk ~ 90 keV. The 30-400 keV fluence is 1.0E-06 erg cm^-2, while the 2-30 keV fluence is 4.0E-07 keV. The enormously softer character of the tail emission suggests that it may be possible to interpret it as the onset of the afterglow of this burst. If this interpretation is correct, then GRB050709 is a localized short hard burst.
  A light curve, skymap, and spectral information for GRB 050709 are provided at the following URL:
  http://space.mit.edu/HETE/Bursts/GRB050709/
• GCN notice #3571
  B. Monard (Bronberg Obs.) reports on behalf of the AAVSO International High Energy Network:
  We observed the localization of the HETE burst GRB050709 (Graziana et al. GCN 3570) with the 30cm telescope of Bronberg Observatory. 532 seconds of stacked unfiltered observations with mipoint at 050711.127 (28.4hrs after the burst) reached a limiting magnitude of CR=20.0. No new object is present in the HETE SXC error box to a limiting magnitude of 19.5R, compared to the DSS-2 red image. The images also covered about 1/2 of the WXM error box.
  The AAVSO thanks the Curry Foundation for their continued support of the AAVSO International High Energy Network.
• GCN notice #3572
  S. Bradley Cenko, Derek B. Fox (Caltech), Edo Berger (Carnegie), and Brian Lee (Toronto) report on behalf of the Caltech-NRAO-Carnegie collaboration:
  We have have obtained two epochs of imaging of the field of GRB 050709 (GCN 3570) with the 40-inch Swope telescope at Las Campanas Observatory. Both epochs consisted of 3 x 600 sec images in the Sloan i' filter. The time of the first epoch was approximately 11 July 2005 4:15 UT (~ 29.6 hours after the burst), while the second epoch was taken 6.3 hours later.
  Image subtraction of the two epochs reveals no variables sources to a limiting magnitude of i' < 20.3 (estimated by comparison with several USNO-B stars in the field).
• GCN notice #3577
  A. Morgan, D. Grupe, C. Gronwall, J. Racusin, A. Falcone (PSU), F. Marshall (GSFC), M. Chester (PSU), and N. Gehrels (GSFC) report on behalf of the Swift UVOT and XRT teams:
  HETE detected GRB 050709 at 22:36:37 UT on 9 July 2005. (Butler et al., GCN 3570). Swift executed a Target of Opportunity observation of the HETE position. The Swift Ultra-Violet/Optical Telescope (UVOT) and X-Ray Telescope (XRT) began observations of GRB 050709 at UT 13:06:53 on 11 July 2005, approximately 38.5 hrs after the HETE detection.
  We detect no new source with either telescope within the 1.34' HETE error circle. In the V filter of the UVOT, we find the following 5 sigma and 3 sigma limiting magnitudes (in 6" radius apertures measured at the HETE position):

  Filter    Lim_Mag      Lim_mag   Exposure time (s)   T_range (hr)
            5sigma       3sigma
  
  V         21.08        21.64        17752            38.50 - 50.27
  

  For XRT data, we assumed a typical spectrum. We find the following 1 sigma and 3 sigma upper limits (in 50" radius apertures measured at the HETE position):

  Lim_Flux     Lim_Flux   Exposure time (s)   T_range (hr)
  1sigma       3sigma
  
  2e-14        6e-14         15243            38.50 - 50.27
  

  The limiting flux is given in units of erg/s/cm^2. T_range is the range from the HETE detection from the beginning of the first observation to the end of the last.
  The UVOT magnitudes are based on preliminary zero-points, measured in orbit, and will require refinement with further calibration.
  This message may be cited.
• GCN notice #3578
  P. B. Cameron (Caltech) and D. A. Frail (NRAO) report on behalf of the Caltech-NRAO-Carnegie collaboration:
  "We observed the field of GRB050709 (GCN 3570) with the Very Large Array at 8.5 GHz on July 11.51 UT. We detect one known source with Ra=23h01m32.1s Dec=-38d59m27s from the 20-cm NVSS (Condon et al. 1998). There are no new radio sources above 5-sigma in the SXC error region, where sigma=21.5 uJy. Further observations are planned."
• GCN notice #3585
  D.B. Fox (Caltech), D.A. Frail (NRAO), P.B. Cameron (Caltech), and S.B. Cenko (Caltech) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration:
  "We have observed the HETE localization region for GRB050709, a likely short-hard gamma-ray burst (Butler et al., GCN 3570) with the Chandra X-ray Observatory + ACIS, in a single 44 ksec observation beginning at 2005 July 12.2 UT (mean epoch 2.52 days after the burst). Excluding intervals of significant background flares, we retain 38.4 ksec good time. Performing a standard "wavdetect" analysis, we identify three sources within the SXC error circle. The fainter two of these sources are very close to each other and are coincident with the bright radio (NVSS/20-cm and 8.5 GHz) source identified by Cameron & Frail (GCN 3578). The brightest source within the error circle has a total of 49.5 +/- 8.8 counts (0.3-8.0 keV) and is located at:
  RA 23:01:26.96, Dec -38:58:39.5 (J2000),
  where we have made a slight (0.4") adjustment to the native astrometry based on the optical/X-ray coincidence of three other sources in the field, and estimate our positional uncertainty as less than 0.5".
  This position is ~1" distant from an R~20.5 mag point-like object visible in images from the Digitized Sky Survey. Given that our position is marginally consistent with this object, and that we cannot at this time demonstrate significant fading behavior, we caution observers that the source could be revealed to be a coronally-active star or AGN. Nonetheless, we consider it a reasonable afterglow candidate; in particular, the X-ray flux (~8.4E-15 erg/cm2/s, 2-10 keV) is consistent with a ~t**(-1.4) power-law decay from the afterglow peak observed by the SXC (assuming this peak reached ~3E-10 erg/cm2/s, 2-10 keV, at 100 sec after the burst); this flux and decay rate would also be consistent with the Swift XRT non-detection (Morgan et al., GCN 3577).
  A particularly intriguing prospect given observations of the short-hard burst GRB050509B (Barthelmy et al., GCN 3385; Prochaska et al., GCN 3390) is that the DSS object 1" distant from this candidate afterglow may be the burst host galaxy."
• GCN notice #3589
  GRB050709.94 : Chandra source optical counterpart
  B. L. Jensen, U. G. J=C3=B8rgensen, J. Hjorth, J. P. U. Fynbo, D. Watson, J. M. Castro Cer=C3=B3n, K. Pedersen, H. Pedersen, J. Sollerman (DARK Cosmology Centre, Niels Bohr Institute)
  "Using the Danish 1.54m+DFOSC (La Silla), we have obtained R-band images of the field of the SXC-source associated with GRB 050709.94 (Butler et al., GCN#3570) for two nights (July 11.3 and 12.3 UT) under good conditions (0.7" and 1.0" seeing, respectively). At the location of the Chandra source (Fox et al., GCN#3585), we clearly detect the object present on the DSS.
  In the image with the best seeing (the first night), this object resolves into two sources separated by about 1". The 0.5" Chandra error-circle covers the fainter, eastern-most, of these two sources.
  In the image from the second night, the objects are not clearly resolved. Aperture photometry of both objects together in the two epochs (at t+33h and t+56h) do not indicate significant R-band variability.
  Images of the objects are shown at: http://www.astro.ku.dk/~brian_j/grb/grb050709.94/"
• GCN notice #3605
  P.A. Price (IfA, Hawaii), K. Roth (Gemini), and D.W. Fox (Caltech) report on behalf of a larger collaboration:
  We have observed a candidate host galaxy of GRB 050709 with the Gemini North telescope and GMOS spectrograph at 2005 July 13.58 UT. The observations were made under clouds, at high airmass, and with morning twilight interfering with the some of the observations.
  The source acquired is the brighter of the two sources reported by Jensen et al. (GCN #3589; "Source B"). The long slit likely does not cover the position of the fainter of the two sources which is coincident with the Chandra source ("Source A").
  We have reduced 2x900 sec integrations and identify emission lines at approximate observed wavelengths of 7617A and 5810A which we associate with Halpha and [O III]5007 at an approximate redshift of z = 0.16. Fainter emission lines are observed at 5754A and 5641A, corresponding to [O III]4959 and Hbeta, and thus we believe the redshift is secure.
  If source A is the afterglow of GRB 050709, then it is seen in projection about 3 kpc from Source B, suggesting that Source B may be the host galaxy. The similarity of this case with the previous potential association of the short/hard GRB 050509B with a low-redshift galaxy (Bloom et al., GCN #3386) is suggestive. If GRB 050709 is at z = 0.16, then the isotropic-equivalent energy release is about 6 x 10^49 erg (based on Butler et al., GCN #3570).
  A definitive measurement of the distance scale to short/hard GRBs awaits the demonstration of variability of the X-ray or optical emission. We encourage deep observations to ascertain the nature of Source A and, in particular, to search for variability.
  We thank the staff of the Gemini North telescope for outstanding support for these observations.
• GCN notice #3612
  P. A. Price (IfA, Hawaii), B. L. Jensen, U. G. Jargensen, J. Hjorth, J. P. U. Fynbo, D. Watson, J. M. Castro Ceron, K. Pedersen, H. Pedersen, and J. Sollerman (DARK Cosmology Centre, Niels Bohr Institute) report:
  We have performed PSF-matched image subtraction on the images acquired by Jensen et al. (GCN #3589). The images were obtained from the Danish 1.54m+DFOSC at La Silla on 2005 July 11.3 and 12.3 UT.
  PSF-matched image subtraction using the Pan-STARRS Optimal Image Subtraction (POI Sub) code reveals a residual, in the sense that the source fades between the first and the second epochs. The position of the variable source corresponds to the source identified by Jensen et al. (GCN #3589) on the edge of a nearby galaxy (z=0.16; Price, Roth & Fox, GCN #3605) as consistent with the Chandra source (Fox et al., GCN #3585). This detection of optical variability increases the likelihood that this source is the afterglow of the short/hard GRB 050709.
  A figure showing the subtraction is available at http://www.ifa.hawaii.edu/~price/grb050709candidate.jpg
  This message may be cited.
  
• GCN notice #3653
  M. Boer, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team;
  M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, J. Kotoku, M. Maetou, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, K. Tanaka, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team;
  N. Butler, G. Crew, J. Doty, G. Prigozhin, R. Vanderspek, J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
  J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team;
  report:
  We have performed a joint fit to the WXM and FREGATE spectral data for GRB 050709, in order to refine the numbers initially reported in GCN 3570 (Butler et al. 2005) for the short and long pulse components.
  The short pulse is well-fit (chi2/DOF= 35.37/48) by a power-law times exponential model with photon index alpha = -0.7 +/- 0.2 and nu-F_nu peak energy Epeak = 83 +18/-12 keV. The energy fluences of the short pulse are

  S_E(2-30 keV)   = (9.3 +/- 0.9) x 10^(-8) erg cm^-2 and
  S_E(30-400 keV) = (2.9 +/- 0.4) x 10^(-7) erg cm^-2.
  

  The X-ray to gamma-ray fluence ratio is thus 0.32. The t90 duration of the short pulse is 220 +/- 50 ms in the 2-25 keV energy band and 70 +/- 10 ms in the 30-400 keV band. The t90 duration and Epeak of the short pulse are consistent with those found for short/hard GRBs (see, e.g., Ghirlanda, Ghisellini, & Celotti 2004, A&A, 422, L55 for plots of the short/hard GRB Epeak distribution).
  The long pulse is well fit (chi2/DOF = 108.86/138) by a power-law model with photon index beta = -2.2 +0.2/-0.4. The energy fluences of the long pulse are

  S_E(2-30 keV)   = (7.1 +/- 1.5) x 10^(-7) erg cm^-2 and
  S_E(30-400 keV) = (3.9 +4.1/-2.7) x 10^(-7) erg cm^-2.
  

  These spectral results are preliminary because there is a linear trend in the background that affects the spectral analysis of the long pulse and has not yet been taken into account. The t90 of the long pulse is 130 +/- 7 s in the 2-25 keV energy band.
  Using the redshift of z = 0.16 measured by Price et al. (2005; GCN 3605), the isotropic-equivalent energy of the short pulse in the 1-10,000 keV energy band in the rest frame of the source is
  Eiso (short pulse) = (2.7 +1.1/-0.3) x 10^(49) erg,
  using Omega_M=0.3, Omega_Lambda=0.7, and h=0.65. The Eiso and Epeak values for the short pulse place it well off of the Amati et al. (2002; A&A, 390, 81) relation for long duration GRBs.
  Taking a time interval 0.060 s in the rest frame of the source (corresponding to t90 = 0.07 s in the 30-400 keV energy band in the observer frame) and assuming the same cosmology and energy band as used above for the Eiso determination, the luminosity of the short pulse in the 1-10,000 keV energy band in the rest frame of the source is
  Liso (short pulse) = (5.2 +/- 1.4) x 10^(50) erg s^-1.
  Taking even this short time interval, the Liso and Epeak values for the short pulse place it off the Yonetoku et al. (2004; ApJ, 609, 935) correlation for long duration GRBs.
  A composite lightcurve showing the short and long pulses in both the 2-25 keV and 30-400 keV bands can be found at
  http://space.mit.edu/HETE/Bursts/GRB050709
• GCN notice #3686
  L.A. Antonelli, M.L. Conciatore (INAF/OAR), D. Malesani (SISSA), S. Covino, P. D'Avanzo, S. Campana, G. Tagliaferri (INAF/OABr), M. Della Valle (INAF/OAA), F. Fiore, G.L. Israel, L. Stella (INAF/OAR), G. Chincarini (Univ. Milano-Bicocca), report on behalf of the MISTICI collaboration:
  The Chandra X-ray observatory observed a second time the field of the GRB 050709 (Butler et al., GCN 3570; Boer et al., GCN 3653). The observation, performed with ACIS, started on 2005 Jul 25.86234 UT and ended on 2005 Jul 26.09042, for a total exposure time of 18284 s. The X-ray source reported by Fox et al. (GCN 3585) and coincident with the proposed optical counterpart (Jensen et al., GCN 3589; Price et al., GCN 3612) is still marginally detected in the second epoch.
  We obtained for this source a count rate of (8.4+/-3.5)E-4 cts/s in the (0.3-8.0 keV) band. This count rate compared to the one obtained in the previous observation in the same band (1.2+/-0.2)E-3 cts/s (Fox et al., GCN 3585) does not allow us to firmly establish any variability for the proposed X-ray afterglow.
  This message can be cited.
• GCN notice #3688
  P. B. Cameron (Caltech), F. A. Harrison (Caltech) and D. A. Frail (NRAO) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration:
  "We have observed the HETE localization region for GRB050709 (GCN 3570) with the Chandra X-ray Observatory + ACIS, in a second 18.2 ksec observation beginning at 2005 July 25.86 UT (mean epoch 16.04 days after the burst).
  In contrast to earlier reports by Antonelli et al. (GCN 3686), we find that the X-ray source reported earlier by Fox et al. (GCN 3585) has faded. In reanalyzing both epochs, we measure 10 +/- 3 counts (0.3 - 8.0 keV) for the second epoch, corresponding to a count rate of 5.5 +/- 1.6 e-4 cts/s. This compares to 1.3 +/- 0.2 e-3 cts/s measured for the first epoch, confirming that the source has faded with a decay of t**-0.46 +/- 0.18 since the first Chandra epoch. Although this decay is shallower than typical for an afterglow, the variability implies it is the likely counterpart to the GRB.
  We thank the staff at the Chandra X-ray Center for their execution of this Target of Opportunity observation and rapid processing of the data."
• GCN notice #3702
  J. Haislip, J. Kirschbrown, D. Reichart report on behalf of the UNC team of the FUN GRB Collaboration:
  Under the control of Skynet, PROMPT automatically observed the localization of the probable short-hard GRB 050709 (Butler et al., GCN 3570; Boer et al., GCN 3653) beginning 1.1 days after the burst (Bayliss et al., GCN 3569) and again beginning 8.3 days after the burst.
  3-sigma limiting magnitudes are based on 5 USNO-B1.0 stars:

  Mean Time 	Integration 	Filter 	Limiting 	Telescope
  Since GRB 	Time 			Magnitude
  
  1d 5h 36m 	82 x 80s 	Rc 	21.6 		PROMPT-5
  8d 9h 3m 	136 x 80s 	Rc 	21.6 		PROMPT-5
  

  We detect the host galaxy (Fox et al., GCN 3585; Price et al., GCN 3612) in both epochs and measure its brightness to be Rc = 21.16 +/- 0.26 and Rc = 21.06 +/- 0.21, respectively. PSF-matched image subtraction using ISIS2 (Alard 2000) does not reveal the afterglow (Price et al., GCN 3612).
  PROMPT is still being built and commissioned.
  Alard, C. 2000, A&AS, 114, 363
• astro-ph/0601670 from 30 Jan 2006
  Zou: Tail emission from a ring-like jet: its application to shallow decays of early afterglows and to GRB 050709
  Similar to the pulsar, the magnetic axis and the spin axis of the gamma-ray burst source may not lie on the same line. This may cause a ring-like jet. We analyze the tail emission from such a jet, and find that it has a shallow decay phase with temporal index equal to -1/2 if the Lorentz factor of the ejecta is not very high. This phase is consistent with the shallow decay phase of early X-ray afterglow detected by SWIFT. The ring-like jet has a tail cusp with sharp rising and very sharp decay. This effect can provide an explanation to the brightening and sharp decay of the X-ray afterglow of GRB 050709.
• astro-ph/0604153 from 7 Apr 2006
  Watson: Are short gamma-ray bursts collimated? GRB050709, a flare but no break
  From the small sample of afterglow lightcurves of short duration gamma-ray bursts (GRBs), the decays are rapid, roughly following a power-law in time. It has been assumed that the afterglow emission in short GRBs is collimated in jets in the same way as in long GRBs. An achromatic break in a short GRB afterglow lightcurve would therefore be strong evidence in favour of collimation in short GRBs. We examine the optical lightcurve of the afterglow of the short GRB050709, the only short GRB where a jet break has been claimed. We show that (1) the decay follows a single power-law from 1.4 to 19 days after the burst and has a decay index alpha = 1.76 (-0.04, +0.11), (2) that an optical flare at ~10 days is required by the data, roughly contemporaneous with a flare in the X-ray data, and (3) that there is no evidence for a break in the lightcurve. This means that so far there is no direct evidence for collimation in the outflows of short GRBs. The available limits on the collimation angles in short GRBs now strongly suggest much wider opening angles than found in long GRBs.
• 1603.07869 from 28 Mar 16
  Zhi-Ping Jin et al.: The 050709 macronova and the GRB/macronova connection
  We reanalyzed the publicly-available optical/near-infrared afterglow observations of GRB 050709, the first short GRB from which an optical afterglow was detected. The $I$-band/F814W-band light curve is significantly shallower than the $R$-band light curve. This additional low-luminosity soft component can be a signature of a Li-Paczy\'{n}ski macronova (also known as kilonova) arising from $\sim 0.05~M_\odot$ r-process material launched by a compact binary merger. As macronovae are relatively weak and soft they can be identified only within the afterglows of relatively nearby ($z<0.4$) bursts that have sufficient near-infrared/optical data. There are five such events: GRBs 050709, 060505, 060614, 061201 and 130603B. However, the redshift of 061201 is unclear and there is doubt concerning the origin of GRB 060505. Remarkably, evidence for a macronova signature is found in the afterglow of each one of the remaining three events. This demonstrates that macronovae are ubiquitous. The significant mass ejection supports the suggestion that these events are significant and possible main sites of heavy r-process nucleosynthesis. The identification of two of the three macronova candidates in the $I$-band implies a more promising detection prospect for the ground-based survey.